# PNM email 12-8-10.txt

RE: Questions on CD contract dates, cost of electricity, and implosion

study

Norem, Nancy

to:

Joe Kordzi

12/08/2010 01:54 PM

Cc: "Gannon, Maureen", mack.mcguffey, "Alvidrez, Richard (Miller)", "Fischer,

Diane M.", "Lucas, Kyle J.", "Williams, Mark A."

Show Details

History: This message has been replied to and forwarded.

Joe,

Attached is the response to the questions you sent on November 12, 2010.

Nancy

From: Kordzi.Joe@epamail.epa.gov [mailto:Kordzi.Joe@epamail.epa.gov]

Sent: Friday, November 12, 2010 10:36 AM

To: Norem, Nancy

Cc: Gannon, Maureen

Subject: Questions on CD contract dates, cost of electricity, and

implosion study

Hi Nancy,

I wanted to followup on a few remaining questions.

Have you been able to locate the dates of the contracts for the consent

decree work? Can you provide the current cost to PNM to produce electricity (busbar

cost)?

Can you provide the implosion study, which was part of the boiler

stiffening study?

Regards,

Joe

" ... and miles to go before I sleep."

-- Robert Frost

Page 1

# Response to Question 1 in email dated November 12, 2010:

PNM has undertaken a more detailed review of the project design records for the boiler

stiffening work previously performed at SJGS as part of the installation of baghouses in

compliance with the 2005 Consent Decree. Although the following provides additional

clarification of our prior res ponses, it does not alter the reco mmendation of PNM’s experts that

additional boiler stiffening will be needed as part of any plan to install SCR at SJGS.

As an initial matter, PNM must correct its prior response to your que stions, in which we

indicated that SJGS only complied with the 2004 version of the National Fire Protection

Association (NFPA) Code 85 during the installati on of the pollution control equipment required

by the Consent Decree. On the contrary, SJGS did in fact consider the newer 2007 version of

NFPA 85 when it completed th e Consent Decree work.

The confusion was caused in part by the structure of NFPA 85 itself. NFPA 85 contains a broad,

generally-applicable standard that requires all bo ilers with downstream fans to be capable of

withstanding a pressure differen tial of +/- 35 inches w.g. (or the maximum capability of the fans,

whichever is less; in this case, +/ - 35 inches is less than the capabi lity of the fans). Because this

standard is applicable to a wi de range of boilers, and does not take into account site-specific

circumstances, it is designed to be relatively conservative, particular ly given the catastrophic

consequences and safety concerns associated with a boiler impl osion or explosion. However,

recognizing that the safety concer ns underlying the “one -size-fits-all” standa rd can be addressed

by other means in some instances, NFPA 85 allo ws “[a] designer capable of applying a more

complete and rigorous analysis to special or unusual problems [to] have latitude in the

development of [boiler] designs.” NFPA 85 S ection 1.2.3.1. In essence, boiler owners have two

methods of complying with NFPA 85 – implement the generally-ap plicable standard of +/- 35

inches w.g., or conduct “a more complete and rigorous analysis ” to determine whether other

safety precautions and specifications will suffice.

In light of the latitude allowed by NFPA 85, th e engineers hired by PNM to help complete the

SJGS Consent Decree work, Sargent & Lundy (S &L), asked boiler designer Babcock and

Wilcox (B&W) to determine whether SJGS could su fficiently protect its bo ilers without meeting

the generally-applicable NFPA 85 standard of +/- 35 inches w.g. B&W in turn asked TRAX

Corporation to develop implosion studies (attached) to determine the best means of protecting

the boiler. Those studies required a rigorous , time-consuming analysis that cost over $300,000,

not including costs associated with the review and approval of those studies.

With the implosion studies, PNM’ s experts were able to demonstr ate that the SJGS boilers would

be adequately protected from implosion during a master fuel trip if stiffened to withstand

negative pressure differentials of 15 inches w.g. (for Units 3 and 4) and 12 inches w.g. (for Units

1 and 2), instead of the generally applicable N FPA 85 standard of +/- 35 w.g. These conclusions

were provided to the insurance carrier for SJGS , FM Global, as eviden ce of compliance with

NFPA 85. However, FM Global required PNM to be more conservative and stiffen the boilers

further so that all four units would be able to withstand a negative pressure differential of up to

18 inches w.g. PNM complied with that request and stiffened the boi lers to that specification.

# Although SJGS fully complied with NFPA 85 (2007) during the Consent Decree work, the

installation of SCR at the pl ant will place increased implosion potential on the boilers by

increasing the negative pressure on the draft system by 10 more inches w.g. As a result, a

requirement to install SCR at SJGS will trigge r the need to once again perform a costly, timeconsuming analysis to determine whether PNM w ill qualify for an exception from the generallyapplicable implosion protection st andard of NFPA 85. To date, neither PNM nor its consultants

have attempted to determine whether an altern ative to the +/- 35 inch es w.g. standard would

suffice following installation of an SCR, due to the significant amount time and expense that

would be associated with that analysis. Howe ver, based on the information that is currently

available, and the added pressures associated with an SCR, PNM’s expert Black and Veatch

remains concerned that it may not be possible to successfully develop other means for protecting

the boilers without stiffening them to the N FPA 85 standard. As such, Black and Veatch

recommends stiffening the boile rs to +/- 35 inches w.g.

Without a successful demonstrati on that the boilers could be adequately protected without

stiffening them to the NFPA 85 standard (and ap proval of that approach by PNM’s insurance

carrier), PNM cannot assume that additional bo iler stiffening will not be required. Quite the

opposite, PNM must instead assume that s tiffening will be required unless (and until)

demonstrated otherwise. The mere existen ce of a possible exception from the generally

applicable NFPA 85 standard, even if successfully obtained in the past, does not change the fact

that PNM’s experts currently believe significant boiler stiffening will be necessary to protect the

boilers from implosion followi ng installation of an SCR.

Response to Question 1 in email dated November 12, 2010:

PNM’s average cost of generation is $47.83/MWh.

Response to Question 3 in email dated November 12, 2010:

The implosion studies are attached.

# Public Service Company of New Mexico

San Juan Generating Station Units 1 & 2

Furnace Draft Analysis



# FINAL REPORT FINAL REPORT

Report Number EA0711



# – 0103



# March 27, 2008 Prepared by:

107 Vista Centre Drive Forest, Virginia 24551

Voice: 434.385.7250 Fax: 434.385.8233

www.traxcorp.com

# PUBLIC SERVICE COMPANY OF NEW MEXICO

SAN JUAN GENERATING STATION UNITS 1 & 2

FURNACE DRAFT ANALYSIS



# FINAL REPORT

Prepared for:



# The Babcock & Wilcox Company

P.O. No. BAX080393



# Report Number EA0711–0103

Prepared by:

Satish Perivilli, Simulation Engineer

Engineering Applications Business Unit

Reviewed by Kent Kozak, Senior Engineer



# TRAX, LLC

107 Vista Centre Drive Forest, VA 24551

Voice: (434) 385-7250, Ext. 271 Fax: (434) 385-8233

Email: sperivilli@traxcorp.com

Approved by:

Gregory M. Kosowski, Vice President

# TRAX, LLC shall not be liable for any losses or for damages resulting from the use of any

information, apparatus, method, or pr ocess disclosed in this report.

Copyright © TRAX LLC , 2007. All rights reserved.

ProTRAX is a trademark of TRAX, LLC.

All other brand and product names are tr ademarks or registered trademarks

of their respective companies.

# PNM – San Juan Generating Station Unit 1 Page i

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# TABLE OF CONTENTS

LIST OF FI GURES.......................................................................................................... ii

LIST OF TABLES .......................................................................................................... iv

EXECUTIVE SU MMARY ................................................................................................ v

1.0 INTRODUCTION.................................................................................................. 1

2.0 NOMENCLAT URE ............................................................................................... 3

3.0 EXISTING CONFIGURATION MO DEL AND VALI DATION ................................ 4

3.1 Existing Configurati on Process Model..................................................... 4

3.2 Existing Configurati on Control Model ...................................................... 5

3.3 Steady-State Conditi ons ............................................................................ 6

3.3.1 Full Load Steady -State ....................................................................... 6

3.3.2 Low Load Steady -State ...................................................................... 9

3.3.3 Validation Load St eady-State ........................................................... 11

3.4 Transient Va lidation ................................................................................. 13

3.4.1 Unit 1 MFT Procedur e ...................................................................... 13

3.4.2 Unit 1 Validati on Parame ters............................................................ 13

3.4.3 Unit 1 Validati on Results .................................................................. 14

3.5 Validation C onclusion.............................................................................. 16

4.0 FUTURE CONFIGURATION MODEL AND TRANSIENT TESTING ................. 17

4.1 Future Configuratio n Process M odel...................................................... 17

4.2 Future Configuration Control M odel....................................................... 18

4.3 Steady -State Conditi ons .......................................................................... 20

4.3.1 Full Load Steady -State ..................................................................... 20

4.3.2 Low Load Steady -State .................................................................... 22

4.4 Transient Events an d Mitigations ........................................................... 23

4.4.1 T1: Full Lo ad MFT ............................................................................ 24

4.4.2 T2: Full Load All Boos ter Fans Trip .................................................. 28

4.4.3 T3: Full Load Both FD Fans Trip ...................................................... 35

4.4.4 T4: Low Load Two Booste r Fans R unaway...................................... 38

4.4.5 T5: Full Load All Fans Trip................................................................ 41

4.4.6 T6: Full Load Single B ooster Fan Trips ............................................ 45

4.4.7 T7: Full Load Baghouse Clean ing System Failure............................ 50

4.5 Transient Events Summary Table........................................................... 54

5.0 CONCLUSIONS AND RE COMMENDAT IONS.................................................. 55

# PNM – San Juan Generating Station Unit 1 Page ii

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# LIST OF FIGURES

Figure 1 Unit 1 Pressure Profile at Full Loa d............................................................ 8

Figure 2 Unit 1 Pressure Profile at Low Load ......................................................... 10

Figure 3 Unit 1 Pressure Profile at Validation Point (97.2% Load)........................ 12

Figure 4 San Juan Future Configur ation................................................................. 18

Figure 5 Booster Fan IGV C ontrols.......................................................................... 19

Figure 6 Steady-St ate Pressure Profile for 100% Load.......................................... 21

Figure 7 Steady-St ate Pressure Profile for 30% Load............................................ 23

Figure 8 T1 Un it Pressu res....................................................................................... 25

Figure 9 T1 Fan Inlet Guide Vane Positi ons............................................................ 26

Figure 10 T1 Baghouse and Scrubber Pressure s................................................... 27

Figure 11 T1 Flows.................................................................................................... 28

Figure 12 T2 Un it Pressu res..................................................................................... 29

Figure 13 T2 Fan Inlet Guide Vane Positi ons.......................................................... 30

Figure 14 T2 Fan Speed s .......................................................................................... 30

Figure 15 T2 Baghouse and Scrubber Pressure s................................................... 31

Figure 16 T2 Flows.................................................................................................... 32

Figure 17 T2 and MT2 Transi ent Maximum Pressu re Profile................................. 33

Figure 18 T2 and MT2 Furna ce Pressure Co mparis on........................................... 33

Figure 19 MT2 and MT2A Transi ent Maximum Pressu re Profile ........................... 34

Figure 20 MT2 and MT2A Fur nace Pressure Comparis on ..................................... 35

Figure 21 T3 Un it Pressu res..................................................................................... 36

Figure 22 T3 Fan Inlet Guide Vane Positi ons.......................................................... 36

Figure 23 T3 Baghouse and Scrubber Pressure s................................................... 37

Figure 24 T3 Flo ws.................................................................................................... 38

Figure 25 T4 Un it Pressu res..................................................................................... 39

Figure 26 T4 Fan Inlet Guide Vane Positi ons.......................................................... 39

Figure 27 T4 Baghouse and Scrubber Pressure s................................................... 40

Figure 28 T4 Flows.................................................................................................... 41

Figure 29 T5 Un it Pressu res..................................................................................... 42

Figure 30 T5 Fan Speed s .......................................................................................... 42

Figure 31 T5 Fan Inlet Guide Vane Positi ons.......................................................... 43

# PNM – San Juan Generating Station Unit 1 Page iii

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Figure 32 T5 Baghouse and Scrubber Pressure s................................................... 44

Figure 33 T5 Flows.................................................................................................... 45

Figure 34 T6 Un it Pressu res..................................................................................... 46

Figure 35 T6 Fan Speed s .......................................................................................... 47

Figure 36 T6 Baghouse and Scrubber Pressure s................................................... 47

Figure 37 T6 Flows.................................................................................................... 48

Figure 38 T6 Fan Inlet Guide Vane Positi ons.......................................................... 48

Figure 39 T6 Transient Maximum Pressure Profile ................................................ 49

Figure 40 T6 Furnace Pressure Comp arison .......................................................... 50

Figure 41 T7 Un it Pressu res..................................................................................... 51

Figure 42 T7 Baghouse and Scrubber Pressure s................................................... 52

Figure 43 T7 Fan Inlet Guide Vane Positi ons.......................................................... 52

Figure 44 T7 Flows.................................................................................................... 53

# PNM – San Juan Generating Station Unit 1 Page iv

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# LIST OF TABLES

Table 1 List of Transi ents ........................................................................................... 2

Table 2 Unit 1 Critical Plant Parameters at Ful l Load ( 100%) .................................. 7

Table 3 Stack Calculat ions ......................................................................................... 9

Table 4 Unit 1 Critical Plant Parameters at Lo w Load (55.5%) .............................. 10

Table 5 Unit 1 Critical Plant Parameters at Validation Point (97.2% Load) .......... 12

Table 6 100% Load Init ial Condition Pa ramete rs.................................................... 21

Table 7 30% Load Initia l Condition Pa ramete rs...................................................... 22

Table 8 Transi ent Descrip tions ................................................................................ 24

Table 9 Transient E vent Summary Table ................................................................ 54

Table 10 Transient E vent Summary Table .............................................................. 54

Table 11 Ki ck Values................................................................................................. 56

# PNM – San Juan Generating Station Unit 1 Page v

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# EXECUTIVE SUMMARY

TRAX, LLC has been retained by The Babc ock and Wilcox Company (B&W) to perform a

furnace draft analysis for the Public Servi ce Company of New Mexi co (PNM) San Juan

Generating Station Units 1 and 2. This study analyzed the eff ect of ductwork and equipment

changes related to the addition of environmental equipment. These modifications included the

addition of a baghouse and relate d ductwork, the replacement of ex isting booster fans with new

upgraded booster fans, and the re direction all the flue gas flow through the baghouse, the booster

fans, and the scrubbers before entering the st ack. The primary goal of this study was to

determine the effects of these plant modificatio ns on pressures and flows throughout the furnace

draft system during normal and abnormal operation.

In the initial phase of this analysis, a model of the existing plant conf iguration for Unit 1 was

built. The plant model was validated against plant data to ensure accuracy and to establish a

baseline for the subsequent investigation of the equipment addition. The validation effort

consisted of running the Unit 1 m odel through a severe transien t similar to one previously

experienced at the plant, and comparing the model results to historical plant data. The results

from this validation were delivered in Validation Report EA0711–0101, dated September 25,

2007.

The existing configuration was then modified to the future configuration by making process and

control changes as necessitated by the additional equipment. The future configuration model

was then tested through seven severe transients . TRAX implemented the basic proposed control

logic for the new environmental equipment as pr ovided by PNM. This control logic was then

enhanced by tuning the controllers and adding mitigating measures to improve the control

system performance and protect the equipment during pressure excursions.

The results obtained duri ng the transient analysis of the fu ture configuration are summarized

below:

• Holding the booster fan kicker circuit for 15 seconds following a master fuel trip (MFT)

promoted stable process and c ontrol behavior during recovery.

Furnace Pressure

• During a full load MFT, the quick adjustment of booster fan inlet guide vanes (IGV) via a

kicker circuit was essential to preven t further furnace pressure excursions.

• Prior to applying any mitigating measures, the “Full Load All Booster Fans Trip,” “Full

Load Single Booster Fan Trips,” and “Full Load Baghouse Cleaning System Failure”

transients resulted in positive furnace pressure excursions, while all the other transients

resulted in negative furnace pressure excursions.

• Prior to applying any mitigating measures, the “Full Load Single Booster Fan Trips” and

the “Full Load All Booster Fans Trip” tran sients caused the highest positive furnace

pressure excursions of +21.1 in wc and +18.6 inwc respectively.

# PNM – San Juan Generating Station Unit 1 Page vi

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# − Reduction of mass flow through the system via a runback from 100% to 70%, at a

rate of 30 MW/min, mitigated the furnace pressure to a maximum of +17.4 inwc

during the “Full Load Single Boos ter Fan Trips” transient.

− Tripping both forced draf t (FD) fans on a high pressure limit following the MFT

mitigated the furnace pressure to a maximu m of +15.1 inwc during the “Full Load All

Booster Fans Trip” transient. Note that th e +15 inwc high pressu re limit caused the

FD fan trip to occur 59 seconds after the MFT.

− Tripping both FD fans immedi ately following the MFT mitigat ed the furnace pressure

to a maximum of +9.9 inwc during the “Full Load All Booster Fans Trip” transient.

Note that this transient was run to compar e the results of an immediate FD fan trip

with the results of a delayed FD fan trip, as described above.

• The “Full Load Both FD Fans Trip” tran sient caused the lowest furnace pressure

excursion of –6.9 inwc.

• The overriding booster fan runback controlle r was responsible for limiting the furnace

pressure to only –3.7 inwc during the “Low Load Two Booster Fans Runaway” transient.

Booster Fan Inlet Pressure

• Prior to applying any mitigating measures, the “Full Load All Booster Fans Trip”

transient caused the highest booster fan inlet pressure excursion of +8.3 inwc, while the

“Full Load Baghouse Cleaning System Failure” transient caused th e lowest booster fan

inlet pressure excu rsion of –14.7 inwc.

− Tripping both FD fans on a high pressu re limit following the MFT mitigated the

booster fan inlet pressure to a maximum of +5.5 inwc during the “Full Load All

Booster Fans Trip” transient.

Air Heater Gas Outlet Pressure

• Prior to applying any mitigating measures, the “Full Load All Booster Fans Trip”

transient caused the highest air heater gas outlet pressure excursion of +14.6 inwc, while

the “Full Load Both FD Fans Trip” transi ent caused the lowest air heater gas outlet

pressure excursion of –7.7 inwc.

− Tripping both FD fans on a high pressure limit following MFT mitigated the air

heater gas outlet pressure to a maximum of +11.4 inwc during the “Full Load All

Booster Fans Trip” transient.

Based on the results of the transient runs, TR AX recommends the following control strategies

and mitigating measures be implemented in the future plant configuration controls:

1. During normal operation, the booster fan IGV should be controlled by a feed-forward

signal from the FD fan IGV added to a trim control that monitors air heater gas outlet

pressure.

2. A kicker circuit should be us ed to immediately run back boos ter fan inlet guide vanes for

15 seconds following an MFT.

# PNM – San Juan Generating Station Unit 1 Page vii

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 3. An overriding booster fan runback controller should be used to help mitigate negative

furnace pressure excursions during MFT and fan transients.

4. If all operating booster fans ar e tripped, immediately trigge ring an MFT, then both FD

fans should also be tripped to avoid high furnace pressure excursions.

5. In the event of a single booster fan trip at full load, the lo ad should be reduced in order to

avoid high positive furnace pressure excursions.

The model construction, validation, transient testing, results, and conclusions are detailed in the

following report. The transient anal ysis modeling selected as descri bed in this report was used to

estimate the magnitude of possible events. Some of the cases modeled are worst-case scenarios

that have a low probability of occurrence. This report does not attempt to predict the likelihood

of any of these events occurring.

# PNM – San Juan Generating Station Unit 1 Page 1 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 1.0 INTRODUCTION

TRAX, LLC has been retained by The Babcock & Wilcox Company to pe rform an engineering

analysis on Units 1 and 2 at the Public Service Company of New Mexico San Juan Generating

Station. This study analyzed the effect of propo sed plant modifications, which included addition

of a baghouse and related ductwork changes and re placement of existing booster fans with new

upgraded booster fans while allowing no bypass flow directly to the stack.

The primary goal of the study was to he lp answer the following questions:

1. What is the impact of the process modifi cations on furnace and ductwork pressure

excursions during normal and abnormal plant operation?

2. How does the proposed control system design be have during severe pressure excursions?

3. What, if any, corrective actions are necessary?

The approach used in this study cons isted of the following basic steps:

1. A dynamic model of Unit 1 in its existing co nfiguration was constr ucted and validated

against historical plant data.

2. A baghouse was added, booster fans were up graded, and ductwork was modified to

represent the plant in it s future configuration.

3. The future configuration model was run th rough selected transients, and pressure

excursions in the furnace and ductwork were recorded.

4. The results were analyzed, and mitigating measures designed to minimize pressure

excursions were identified and tested.

The existing furnace draft system for San Juan Unit 1 was modeled using ProTRAX , a

commercially available dynamic simulation system. The ProTRAX system is based on modular

components, allowing interconnecting of modules representing furnaces, fans, dampers, ducts,

etc., into any physically realis tic configuration. A ll of the module formulations are based on

first-principle conservation rela tions, the Second Law of Therm odynamics, and well-established

constitutive relations for heat tr ansfer and fluid mechanics. The resulting executable models are

operated from a graphics-based environment that provided extensive capability for controlling

the models and displaying the results in various formats.

B&W, PNM, and TRAX selected a total of seven transients to be tested with the new plant

configuration. The goal was to identify conditions that would create large pressure excursions in

the furnace and ductwork. Each transient consiste d of an initial event followed by the response

of the controls, which could eventua lly lead to a master fuel trip a nd/or individual fan trips. The

transients selected for the study are shown in Table 1.

# PNM – San Juan Generating Station Unit 1 Page 2 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 No. Transient Name

T1 Full Load MFT

T2 Full Load All Booster Fans Trip

T3 Full Load Both FD Fans Trip

T4 Low Load Two Booster Fans Runaway

T5 Full Load All Fans Trip

T6 Full Load Single Booster Fan Trips

T7 Full Load Baghouse Cleaning System Failure

Table 1 List of Transients



# This report describes the results of these transien t runs. A Reference Sec tion is provided at the

end of this report containing sche matics, plots for validation runs , and plots for transient runs

pertinent to each named transient.

# PNM – San Juan Generating Station Unit 1 Page 3 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 2.0 NOMENCLATURE

The naming convention used throughout th is report is described below:

1 st 

# Quadrant Fan Operation

Fan operation where the fan has flow in the dir ection of fan suction to discharge, with a

discharge pressure grea ter than the suction pressure. Op eration in this region is governed

by manufacturers’ fan curves (developed head versus volumetric flow).

2 nd 

# Quadrant Fan Operation

Flow through the fan has reversed and is now from discharge to suction. Head is positive

with the discharge pressure greater than the su ction pressure. In this quadrant the fan is

acting as a resistance with flow from higher (discharge) to lower (suction) pressure.

Operation in this region starts at the fan d ead head pressure (zer o flow) and is based on

an assumed flow resistance. Fan operation in the 2 nd 

# quadrant typically occurs during fan

trips or other equipment malfunctions.

4 th 

# Quadrant Fan Operation

Flow is in the direction of fan suction to di scharge with a discharge head less than the

suction head (i.e., the pressure drops across the fan rather than rising). Operation in this

region is governed by the run out portion of the fan curve and assumed flow resistance

behavior. Typically, fan operation in the 4 th 

# quadrant occurs during a fan trip.

MFT

Master fuel trip (MFT) is the procedure in whic h all fuel to the furnace is completely shut

off.

Water Seal Venting

Water seal venting refers to the water seal at the bottom of the furnace. At sufficiently

low furnace pressure (–28 inwc below ambient), the water seal can rupture, allowing

ambient air into the furnace. This additiona l flow of ambient ai r into the furnace will

help minimize any negative furnace pressure transient.

# PNM – San Juan Generating Station Unit 1 Page 4 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 3.0 EXISTING CONFIGURATION MODEL AND VALIDATION

TRAX, PNM, and B&W worked together to analyze plant historian data, equipment

configurations, and control sc hemes to determine if Unit 1 and Unit 2 required separate

validations. It was determined by the project team that the simulation of Unit 1 was sufficient to

represent both Unit 1 and Unit 2. All subsequent references to Unit 1 should be considered

representative of Unit 1 or Unit 2.

The dynamic model representing San Juan Genera ting Station Unit 1 consisted of a process

model, which simulated the existing process conf iguration; and a controls model, which was

built from a subset of existing plant controls. TRAX prepared the process model based on

drawings provided by PNM, a plant walkdown, a nd discussions with plant personnel. The

process and control model configuration drawi ngs were reviewed and approved by B&W and

PNM.

Validation is the process of comparing steady-st ate and dynamic model predictions with plant

data. The process and controls models were r un to full and low load st eady-state conditions, and

the results were compared with plant data. Fo r this study, an MFT event was picked as the

validation transient, and the San Juan Unit 1 mode l was run to a steady-stat e at this load. The

model was run through the event, and the results were compared with plant data provided.

3.1 Existing Configuration Process Model

The process model included the following components:

• Air path through and including FD fans, air heaters, and furnace

• Fuel (coal) and primary air path including primary air (PA) fans, pulverizers, and feeders

• Flue gas path from the furnace including supe rheaters, reheaters, economizer, air heaters,

booster fans, and stack

• Pollution control systems including precipita tor and flue gas desulphurization (FGD)

equipment

As the focus of the study involve d relatively fast furnace pressu re transients, slower steam-side

components, such as steam drums and desuperheat ers, were not modeled. Only the metal mass

for the walls and heated surfaces was modeled, al ong with the energy stored in the metal during

the transient.

Centrifugal fan operation was modeled by incorporat ing the actual fan head curves. In addition,

shutdown flow effects (4 th 

# quadrant behavior) were simulate d and combined th e run-out portion

of the fan curve, and assumed flow resistance behavior.

Pulverized coal combustion was simulated in the furnace module. Coal combustion was

represented as a two-stage reaction, with the fi rst stage being the rapid devolatilization of the

coal particles, and the second stage being the combustion of the remaining coal char. Char

# PNM – San Juan Generating Station Unit 1 Page 5 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# combustion was a function of temperature, partic le size, and availabili ty of oxygen. The amount

and size of the char particles woul d strongly affect the rate of fireball collapse during a fuel trip.

The furnace module calculated the ex iting flue gas composition based on the rate of fuel and air

flow into the furnace, the chemistry of combustion, and furnace leakage.

3.2 Existing Configuration Control Model

As the controls for a unit play an important role in the behavior of the plant through any

transient, a detailed model of the San Juan Unit 1 control system was also constructed. Note that

only those portions of the controls that affect a ny of the final control elements in the model were

included in the control system simulation. Control loops for th e existing configuration plant

model included:

• Furnace pressure

• Primary air heater (PAH) air outlet pressure

• Primary air heater air outlet temperature

• Secondary airflow

• Economizer excess air

• Fuel flow

• Pulverizer coal air temperature

• Pulverizer primary airflow

• Stack flue gas temperature

• Master fuel trip

These control loops manipulated the following fina l control elements (not necessarily in the

order listed above):

• FD fan IGV demand

• PA fan IGV demand

• Booster fan IGV demand

• Feeder speed

• Primary air control dampers

• Hot air dampers

• Tempering air dampers

• PAH gas inlet dampers

# PNM – San Juan Generating Station Unit 1 Page 6 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 3.3 Steady-State Conditions

An overall heat balance is achieved and the mode ls are parameterized to a full load condition.

The process and control models ar e then integrated and run to a steady-state condition to observe

stability within the models. The three steady-state conditions used to ensure model stability are:

1. Full load steady-state

2. Low load steady-state

3. Validation load steady-state

The steps must be completed in the above order, as each step was dependent upon the successful

completion of the previous step. All three st eps involved a comparis on of model output with

plant data, and the combination of all three comp arisons resulted in a high level of confidence

that the model provided reliable predictions for the current plan t configuration.

The following sections describe the steps used fo r the validation of the Sa n Juan Unit 1 model.

3.3.1 Full Load Steady-State

Each furnace draft component was simulated and connected in the same configuration as the

plant using ProTRAX modules. Where there were parallel co mponents in the plant, such as FD

fans, each fan was modeled separately to assure any effects of multiple component operations

were incorporated in the study. This was the “configuration” process.

The physical characteristics of each component were input through fill-in-the-blank forms in the

modeling system. This included data such as damper sizes, fan head curves, and physical

dimensions of ducts, stacks, and vessels. This was the “parameterization” process. The

parameterization process also included operating data based on a full load heat balance created

from plant data, manufacturer’s heat balances, discussions with plant personnel, and visual

observations during the plant walkdo wn. Where plant data was not available, such as pressure

profiles through the convection pass of the furnace, estimates of pressure drops were made based

on the physical drawings showing tube dens ities, flow cross sectional areas, and gas

temperatures. Plant data itself is generally not sufficient due to instrumentation errors and

unavailable signals. Therefore, the full load heat balance data comes from a variety of sources

and is adjusted to ensure mass and energy balance.

At this point, the model had the thre e requirements of a high-fidelity model:

• Module equations were based on conserva tion of mass, energy, momentum, and wellaccepted correlations for heat transfer and mass flow.

• The configuration of the model was the same as the plant based on the scope of this

study.

• The physical characteristics of each component were programmed into the corresponding

modules.

# PNM – San Juan Generating Station Unit 1 Page 7 of 57

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# Step 1 was performed at full load, as most desi gn data required for model parameterization was

available at that load. Most dampers and fans were operated at known design conditions at full

load. This helped to determine the size and performance of these components, and thereby

identified inherent plant operational limits su ch as fan runout and damper flow limits.

The full load model was run at steady-state for several minutes and test ed for stability and

accuracy. That is, the model was initialized to full load conditions, and then allowed to run to

equilibrium. If properly parameterized, the model should show little or no movement from the

parameterization point and should co me to a solid, steady-state in ju st a few seconds. Since all

the module equations calculated an absolute heat balance at steady-state, any deviation from the

full load conditions by the m odel would be immediately obvious and indicate an error in

parameterization of the model. Once the model ha d demonstrated a reliable, stable match to the

plant data at full load, it was rea dy to run to a lower load condition.

In this case, at the full load steady-state point the San Juan Unit 1 model was immediately stable

and no further corrections were required. Criti cal parameters for the full load steady-state are

listed in Table 2. The corresponding model pressure profile at full load for Unit 1 is shown in

Figure 1.

Parameter Plant Data Model Unit

Gross Load 360 360 MW

Load Level 100 100 Percent

Heat Rate 9,033 9,033 BTU/kWh

Coal Flow Rate 346 342 kpph

Number of Mills Grinding 3 3

Economizer Oxygen 3.2–3.5 3.33 % By Vol.

Total Secondary Air Flow 2,393 2,462 kpph

Pulverizer Air Flow 178 178 kpph

FD Fan Discharge Pressure +22.8 +22.8 inwc

PA Fan Discharge Pressure +74.3 +76.6 inwc

Primary Air Duct Pressure +72.2 +72.2 inwc

Windbox Pressure +15.1 +15.1 inwc

Furnace Pressure +10.2 +10.2 inwc

Ambient Air Temperature 73 70 °F

Primary Air Heater Air Inlet Temperature 138 139 °F

Secondary Air Heater Air Inlet Temperature 110 110 °F

Coal Air Temperature 157 157 °F

Primary Air Heater Air Outlet Temperature 505 505 °F

Secondary Air Heater Air Outlet Temperature 514 514 °F

Table 2 Unit 1 Critical Plant Parameters at Full Load (100%)

# PNM – San Juan Generating Station Unit 1 Page 8 of 57

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Project Number EA0711 Figure 1 Unit 1 Pressure Profile at Full Load



# Stack Calculations

Pressure difference along the height of the stack is made up of three parts:

• Density head of the column of flue gas

• Fluid frictional losses

• Exit losses due to unrecoverable kinetic energy (flue gas velocity) at the stack exit

Table 3 summarizes these calculations for the full load plant configuration.

Having demonstrated a reliable, stable match to the plant data at full load, the San Juan Unit 1

model was ready to run to the lower load condition.

# PNM – San Juan Generating Station Unit 1 Page 9 of 57

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Project Number EA0711 Description Value

Plant Load 100%

Gauge Pressure at the Stack Base –0.53 inwc

Ambient Gauge Pressure at the Top of the Stack –4.57 inwc

Elevation Difference: Stack Breeching to Top of Stack 309 ft

Flue Gas Temperature Entering Stack 135.4 °F

Density Head of Flue Gas 3.55 inwc

Fluid Frictional Losses 0.09 inwc

Kinetic Energy (Exit) Losses 0.40 inwc

Total Pressure Difference: Botto m to Top of Stack 4.04 inwc

Table 3 Stack Calculations



# Note that the total stack draft loss is the sum of the fricti onal and kinetic energy losses.

3.3.2 Low Load Steady-State

The control system was used to run the plant model down in load. Pu lverizers and/or other

equipment were turned off as necessary to repr esent the plant condition at the lower load. The

model was then tested at this lower load for st ability and accuracy. Typically, the primary causes

of variations at this poi nt would be the following:

1. Missing, incomplete, or erroneous data

2. Different operational procedures of the model compared to the plant

3. Fouling and soot buildup on various surf aces that alter pressure distribution

4. Significantly different conditions at the plant during the low load compared to the full

load data set (e.g., winter versus summer operation)

For Unit 1, the low load data available from the plant was at 200 MW duri ng plant start-up. All

the control setpoints were applied as observed from the historian data for a 55.5% load. The

number of pulverizers operating was reduced from three to two, the excess oxygen percentage

was adjusted to 4.1%, and the model was run to a steady-state. A compar ison of model and plant

parameters for the lower load steady-state is shown in Table 4. The corresponding model

pressure profile at full load for Unit 1 is shown in Figure 2.

# PNM – San Juan Generating Station Unit 1 Page 10 of 57

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Project Number EA0711 Parameter Plant Data Model Unit

Gross Load 200 200 MW

Load Level 55.5 55.5 Percent

Heat Rate 9,375 9,375 BTU/kWh

Coal Flow Rate 194 194 kpph

Number of Mills Grinding 2 2

Economizer Oxygen 4.0–4.3 4.11 % By Vol.

Total Secondary Air Flow 1,320 1,425 kpph

Pulverizer Air Flow 185 185 kpph

FD Fan Discharge Pressure +7.4 +7.7 inwc

PA Fan Discharge Pressure +62.0 +62.6 inwc

Primary Air Duct Pressure +60.8 +60.2 inwc

Windbox Pressure +5.0 +5.0 inwc

Furnace Pressure +4.0 +3.4 inwc

Ambient Air Temperature 86 86 °F

Primary Air Heater Air Inlet Temperature 156 143 °F

Secondary Air Heater Air Inlet Temperature 127 127 °F

Coal Air Temperature 154 154 °F

Primary Air Heater Air Outlet Temperature 422 422 °F

Secondary Air Heater Air Outlet Temperature 467 455 °F

Table 4 Unit 1 Critical Plant Parameters at Low Load (55.5%)

Figure 2 Unit 1 Pressure Profile at Low Load

# PNM – San Juan Generating Station Unit 1 Page 11 of 57

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Project Number EA0711 

# The Unit 1 model was stable and accurate at low load condition, and no further actions were

required.

3.3.3 Validation Load Steady-State

As a part of the dynamic testing, it was importa nt to establish a steady-state condition at the

validation load. Normally, a MFT would be the best choice for dynamic testing, provided that

the trip was not caused by a component failure in the gas path such as a fan or damper. Multiple

events made it more difficult to identify and duplic ate the actual driving forces on the plant, and

hence the model. A transient th at was both severe enough to te st the model, yet had only one

cause was selected. It was also important to begin the transient at a high load when most plant

equipment was operational.

B&W provided TRAX with historian spreadsheet exports of two MFT events. TRAX chose the

validation event based on the following criteria:

• Near full load condition

• Steady state condition prior to the trip

• Single event as the cause of the trip

• Normal operation of components in the flue gas path

• Adequate data during the trip from the plant historian

The event data selected by TRAX to validate models against was fr om an MFT that occurred on

February 25, 2006 at 9:48 a.m. with a unit load of 97.2%. The historian data was provided in 10

second intervals.

The validation load model was run at steady-state for several minutes and tested for stability and

accuracy. Critical plant paramete rs obtained at this steady state were compared with plant data

as shown in Table 4.

# PNM – San Juan Generating Station Unit 1 Page 12 of 57

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Project Number EA0711 Parameter Plant Data Model Unit

Gross Load 350 350 MW

Load Level 97.2 97.2 Percent

Heat Rate 9,028 9,028 BTU/kWh

Coal Flow Rate 350 335 kpph

Number of Mills Grinding 3 3

Economizer Oxygen 2.8–3.9 3.05 % By Vol.

Total Secondary Air Flow 2,307 2,313 kpph

Pulverizer Air Flow 182 183 kpph

FD Fan Discharge Pressure +19.8 +19.7 inwc

PA Fan Discharge Pressure +76.7 +79.0 inwc

Primary Air Duct Pressure +74.4 +73.8 inwc

Windbox Pressure +13.2 +13.0 inwc

Furnace Pressure +9.3 +8.7 inwc

Ambient Air Temperature 36 36 °F

Primary Air Heater Air Inlet Temperature 113 123 °F

Secondary Air Heater Air Inlet Temperature 113 106 °F

Coal Air Temperature 155 155 °F

Primary Air Heater Air Outlet Temperature 481 464 °F

Secondary Air Heater Air Outlet Temperature 486 498 °F

Table 5 Unit 1 Critical Plant Parame ters at Validation Point (97.2% Load)



# The model pressure profile generated from the st eady-state at validation load for Unit 1 is shown

in Figure 3.

Figure 3 Unit 1 Pressure Profile at Validation Point (97.2% Load)

# PNM – San Juan Generating Station Unit 1 Page 13 of 57

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# 3.4 Transient Validation

To perform the transient validation, the model was first moved to the steady-state operating point

corresponding to 97.2% load to be consistent with the plant data. The tr ansient event was then

initiated and all known plant variables, (i.e. damper positions, fan and feeder speeds) were

maneuvered by the control system to mimic plant movements as closely as possible based on the

available plant data.

The behavior of a number of va riables during this transient was analyzed and compared to the

plant data, over a period of 120 seconds, for vali dation. One of the major variables of interest

was the furnace pressure. In comparing the mode l response to the plant, the criterion was the

time required for the furnace pressure to reach a minimum, the magnitude of the minimum, and

the rate of decrease of the fu rnace pressure. The most importa nt factors that affected these

results were:

• Timing and speed of fuel shutoff to the furnace

• Control of airflow to the furnace

A significant level of effort was invested to assure that the timing of movement for the burner

coal valves, fan inlet vane position, and the s hutdown of pulverizers, PA fans, and feeders was

duplicated as closely as possible.

3.4.1 Unit 1 MFT Procedure

During the MFT, the following control elements we re driven as described based on the historian

data:

• All pulverizers and associat ed feeders were tripped

• Burner coal valves for al l pulverizers were closed

• Primary air shutoff and control damp ers for each pulverizer were closed

• Hot air dampers and tempering air dampers were closed

• FD fan inlet guide vanes were frozen in place

• Both PA fans were tripped and their inlet guide vanes were closed

• All three booster fans were tripped

All other control elements remained in auto for the duration of the MFT event.

3.4.2 Unit 1 Validation Parameters

To validate the models, TRAX compared the model-generated values for the following

parameters to plant data as recorded by the historian:

• Furnace pressure

• Windbox pressure

# PNM – San Juan Generating Station Unit 1 Page 14 of 57

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# • Coal feeder flow

• Secondary airflow

• FD fan discharge pressure

• PA fan discharge pressure

• Economizer oxygen

3.4.3 Unit 1 Validation Results

Validation comparisons of the ProTRAX Unit 1 model versus plan t data are shown in the

Reference Section.

Furnace Pressure

The Unit 1 model was initialized to the validation condition load (350 MW) and allowed to run

for 10 seconds to ensure steady-state operation. At 10 seconds, an MFT was initiated by tripping

all pulverizers, associated feed ers, and both PA fans. As a result of the MFT, controls

instantaneously set the PA fan guide vanes to zero and fully closed the PA control dampers,

burner coal valves, pulver izer hot air dampers, and tempering air damper for each pulverizer.

Although all dampers in the primary air path associated with each pulverizer were closed, it was

the fast-acting burner coal valve (with a seven- second stroke time) that decided the magnitude

and timing of the furnace pressure minimum by stopping fuel flow to the furnace.

Upon loss of the PA fans, the amount of pulverized coal being transported to the burners began

to drop rapidly due to the decreas ing primary air flow. When th e burner coal valves closed

completely at 17 seconds, the fireball collapse be gan due to the fuel being shut off and furnace

pressure dropped to its minimum of –0.15 inwc on ce the available fuel was totally consumed.

The furnace then began to res pond to the additional inflow of air caused by the continuous

operation of the FD fans, and recovered to +7.3 inwc by 120 seconds.

The plant data, as shown in the furnace pressure plot, indicated a maximu m pressure drop of only

+1.5 inwc and an eventual steady-state recovery pr essure. Since an MFT is a fast transient, and

the fuel is rapidly cut off due to the coal valve shutoff, the fireba ll collapse is usually severe and

a much greater drop in furnace pressure was expected. PNM indicated that this data behavior

was likely the result of a partially plugged tap that did not respond to the expected pressure dip.

This lack of response is further illustrated by th e windbox pressure plot, which is discussed in the

following section.

Windbox Pressure

The windbox pressure at the beginning of the tran sient was +13.0 inwc. The fireball collapse led

windbox pressure to decrease to a minimum of +6.6 inwc at 17 seco nds. Freezing the FD fan

guide vanes while they remained in operation caused the pressure to increase to +13.1 inwc by

the end of the transient.

# PNM – San Juan Generating Station Unit 1 Page 15 of 57

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# The windbox pressure plot illust rates that the windbox pressure minimum predicted by the model

was +3.3 inwc lower than the corresponding plant measurement. However, the shape of the

plant data curve indicates th at the minimum windbox pressure probably occurred between

recorded measurements and was likely lower than the given +9.9 inwc. Since furnace and

windbox pressures generally behave in accordance with one another, this reinforces the

probability of a plugged furnace pressu re tap, as discussed above.

Coal Feeder Flow

Prior to the MFT, a total of 335 kpph of coal wa s supplied to the furnace through the feeders.

During the MFT, the coal feeders were tripped and fuel flow stopped. The plot of coal flow into

the mills agrees well with the plant data.

Secondary Airflow

Prior to the MFT, 2,313 kpph of se condary air was flowing into the furnace through the flow

control sleeves and registers. Following the MFT, the controls froze both FD fan inlet vanes.

The increased pressure differential between the FD fans and the furnace (due to the drop in

furnace pressure) led to an increase in the s econdary airflow to a maximum of 2,954 kpph by 23

seconds. As the system pressures stabilized, th e secondary air flow dropped slightly to a steady

value of approximately 2,776 kpph. The secondary ai rflow plot shows a cl ose match in shape,

magnitude, and timing between the model and plant data.

The sharp increase in airflow was not seen in the plant data most likely because of the ten second

historian frequency and signal filtering.

FD Fan Discharge Pressure

The FD fan discharge pressure was steady at +19.7 inwc at the begi nning of the transient. Upon

initiation of the MFT, the controls locked both FD fan inlet vanes and all secondary air dampers

in place. The 8.85 inwc drop in furnace pressu re during the MFT only caused a 2.8 inwc drop in

FD fan discharge pressure because of the resistan ce of the secondary air heaters and registers.

The minimum FD fan discharge pressure corres ponds to the minimum furnace pressure during

the fireball collapse. As the furnace pressure re covered, the FD fans’ discharge pressure reached

a steady value of +22.3 inwc by the end of the tran sient. The FD fans’ discharge pressure plot

illustrates a close match between the model and the plant historian data.

PA Fan Discharge Pressure

The PA fans were operating steadi ly with a discharge pressure of +79.0 inwc prior to the MFT.

The loss of primary air due to the PA fan trip and shutoff during the MFT resulted in a decrease

of discharge pressure, as illustrated by the PA fan discharge pressure plot. As the system

pressures recovered, the PA fa n discharge pressure recovere d to +21.0 by 120 seconds. The

decay in discharge pressure as predicted by the model matched the plant data well.

Economizer Oxygen

A range for economizer oxygen was established by two corresponding measurements (2.8% and

3.9%) provided by the historian for this particular transient. Based on the plant controls, a value

for economizer oxygen (within this range) that provided the closest match to the historian

secondary air flow was determined. This value wa s established as 3.05% for the validation case.

# PNM – San Juan Generating Station Unit 1 Page 16 of 57

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Project Number EA0711 

# The complete loss of fuel due to the MFT re sulted in an increase of economizer oxygen, as

illustrated by the corresponding plot. The plan t economizer oxygen measurements do not show

this significant increase from thei r steady-state values. This indicates significant filtering in the

oxygen transmitter signals. Filtered model data, re presented by the dashed line in the plot, shows

a closer agreement with the plant data.

3.5 Validation Conclusion

A dynamic model of the Unit 1 furnace draft system was constructed. Controls were installed on

the process model consistent with existing plant logic. The process plus control system model

was tested for both steady state and dynamic accurac y. Dynamic testing consisted of running the

model through a severe furnace pressure excursi on and comparing the model generated data to

historical plant data. This comparison of data showed that the model generated data matched

both the timing and magnitude of the plant data. Therefore, the Unit 1 model is considered

sufficiently accurate to provide a m eaningful basis for further draft analysis. Note that the model

can also provide excellent relative results, which are particularly important in the planned study.

# PNM – San Juan Generating Station Unit 1 Page 17 of 57

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Project Number EA0711 

# 4.0 FUTURE CONFIGURATION MO DEL AND TRANSIENT TESTING

The existing process and controls models were updated to reflect the changes necessary for the

addition of the environmental equipment. Note that while the existing controls scheme was

retained for the most part, modifications were made as necessary. These controls may change as

a part of the proposed mitigations. The models were then run to obtain full and low load steadystate initial conditions. Once the steady-state co nditions were obtained, the future configuration

model was run through the seven selected transients and the results were analyzed. The selected

transients were run at their respective operating conditions and any controls mitigations

necessary to limit extreme pressure excursions through the system were tested.

4.1 Future Configur ation Process Model

The proposed future configuration process model included all of the components in the San Juan

Unit 1 process models, plus the proposed environm ental equipment. Modifications to represent

the future configuration included:

• Addition of a baghouse and related controls

• Replacement of existing booster fans with new upgraded booster fans

• Related ductwork changes

• Elimination of bypass flow direct ly to the stack; that is, the total flue gas flow from the

air heaters will pass through the new baghouse, new booster fans, and scrubbers before

reaching the stack

Parameterization data for the new process equipm ent such as fan head curves, pressure drops,

etc. was based on proposed design informa tion provided by B&W and PNM. The proposed

configuration schematics for the process model are given in the Reference Section. A block

diagram of the future confi guration is shown in Figure 4.

# PNM – San Juan Generating Station Unit 1 Page 18 of 57

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Project Number EA0711 Figure 4 San Juan Future Configuration



# 4.2 Future Configurat ion Control Model

The control logic for the new equi pment included various control l oops for the booster fans. In

the booster fan IGV control loop, an error signal was calculated by compari ng the air heater gas

outlet duct pressure to a setpoint . The controller output was then added to a characterized feedforward signal from the FD fan inlet guide vane demand and a kicker circuit signal activated for

15 seconds upon initiation of an MFT. The sum of these outputs was then used to adjust booster

fan inlet guide vanes’ demand. This control sche me also included an overriding controller that

would cause the booster fan inlet guide vanes to run back in an attempt to maintain a furnace

pressure of +1 inwc if the furnace pressure dropped below –1 inwc or an MFT occurred. A

functional diagram of this control loop is shown in Figure 5. Flue Gas from

Primary Air

Heaters

Flue Gas from

Secondary Air

Heaters Baghouse Booster Fan A

Booster Fan B

Booster Fan C Scrubber A

Scrubber B

Scrubber C StackPNM – San Juan Generating Station Unit 1Page 19 of 57Furnace Draft Analysis – Final Report3/27/2008Project Number EA0711Figure 5 Booster Fan IGV Controls

# PNM – San Juan Generating Station Unit 1 Page 20 of 57

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Project Number EA0711 

# In addition, the following controls logic was used:

• When the furnace pressure dropped below –7 inwc for three seconds, a low furnace

pressure MFT was triggered.

• During an MFT, no FD fans or booster fans we re tripped by the controls unless specified

as a failed component for transient testing.

• During transient testing, the booster fan inle t guide vanes’ stroke time was 17 seconds.

The proposed configuration sche matics for the contro ls model are given in the Reference

Section.

Several other control solutions were developed to mitigate the severity of pressure excursions.

These measures are discussed in Section 4.4.

4.3 Steady-State Conditions

All transient runs were initiated with the model at a steady-state condition, with all pressures,

flows, temperatures, and controlle d variables constant. While ther e were seven transient events

tested during this phase, there were only two unique in itial conditions:

• Full load (100%)

• Low load (30%)

The models were run to steady-st ates corresponding to these loads to establish initial conditions

for the transient runs.

4.3.1 Full Load Steady-State

The model was re-parameterized at full load to account for the addition of the environmental

equipment and associated ductwork changes. While the parameterization of most of the modules

was retained from the existing configuration, only the necessary change s as required by the

addition of the new equipment were made. Criti cal parameters for the steady-state condition at

full load are shown in Table 6. Figure 6 graphica lly shows the steady-stea dy pressure profiles.

# PNM – San Juan Generating Station Unit 1 Page 21 of 57

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Project Number EA0711 Parameter 100% Load Unit

Gross Load 360 MW

Load Level 100 Percent

Heat Rate 9,033 BTU/kWh

Coal Flow Rate 342 kpph

Number of Mills Grinding 3

Economizer Oxygen 3.33 % By Vol.

Total Secondary Air Flow 2,460 kpph

Pulverizer Airflow 178 kpph

FD Fan Discharge Pressure +22.4 inwc

PA Fan Discharge Pressure +76.4 inwc

Primary Air Duct Pressure +71.9 inwc

Windbox Pressure +14.7 inwc

Furnace Pressure +9.9 inwc

Ambient Air Temperature 70 °F

Primary Air Heater Air Inlet Temperature 139 °F

Secondary Air Heater Air Inlet Temperature 110 °F

Coal Air Temperature 157 °F

Primary Air Heater Air Outlet Temperature 500 °F

Secondary Air Heater Air Outlet Temperature 509 °F

Table 6 100% Load Initial Condition Parameters

Figure 6 Steady-State Pressure Profile for 100% Load

# PNM – San Juan Generating Station Unit 1 Page 22 of 57

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Project Number EA0711 

# 4.3.2 Low Load Steady-State

The model was then used to generate a low lo ad steady-state condition. The operation of the

plant on two pulverizers and two booster fans with both FD fans in operation was simulated for

this load condition. Critical parameters for th e steady-state condition at low load are shown in

Table 7. Figure 7 graphically shows the steady-steady pressure profiles.

Parameter 30% Load Unit

Gross Load 108 MW

Load Level 30 Percent

Heat Rate 10,516 BTU/kWh

Coal Flow Rate 120 kpph

Number of Mills Grinding 2

Economizer Oxygen 9.21 % By Vol.

Total Secondary Air Flow 1,315 kpph

Pulverizer Airflow 148 kpph

FD Fan Discharge Pressure +5.8 inwc

PA Fan Discharge Pressure +53.9 inwc

Primary Air Duct Pressure +53.0 inwc

Windbox Pressure +3.6 inwc

Furnace Pressure +2.2 inwc

Ambient Air Temperature 70 °F

Primary Air Heater Air Inlet Temperature 141 °F

Secondary Air Heater Air Inlet Temperature 115 °F

Coal Air Temperature 157 °F

Primary Air Heater Air Outlet Temperature 492 °F

Secondary Air Heater Air Outlet Temperature 454 °F

Table 7 30% Load Initial Condition Parameters

# PNM – San Juan Generating Station Unit 1 Page 23 of 57

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Project Number EA0711 Figure 7 Steady-State Pressure Profile for 30% Load



# The combination of both comparisons resulted in a high level of confidence that the model

provided reliable predictions for th e future plant c onfiguration.

4.4 Transient Events and Mitigations

To evaluate the performance of th e plant in its new configuration, seven transients were run with

the new control logic and the results analyzed. This process consisted of the following steps:

• Initially run the selected transients with the new control logic to obtain baseline

(unmitigated) results for analysis

• Analyze the baseline results and find areas that need improvement (typically pressures,

flows, and fan IGV)

• Go through each transient and determine process/controls mitigations required for

individual transients

• Implement the mitigations for all transients

The goal in selecting the transients was to defi ne conditions that would create large pressure

excursions in the furnace and ductwork. Transi ent descriptions are li sted in Table 8.

# PNM – San Juan Generating Station Unit 1 Page 24 of 57

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Project Number EA0711 No. Transient Name Unit

Load Description

T1 Full Load MFT 100% With the unit at full load, an operator initiates an MFT. All controls

remain in auto.

T2 Full Load All Booster

Fans Trip 100% With the unit at full load, all three booster fans trip and immediately

trigger an MFT.

T3 Full Load Both FD Fans

Trip 100% With the unit at full load, both FD fans trip and immediately initiate

an MFT. All three booster fans w ill run back, but no booster fan will

be tripped.

T4 Low Load Two Booster

Fans Runaway 30% With the unit at low load, the inlet guide vanes on both operating

booster fans will ramp open.

T5 Full Load All Fans Trip 100% With the unit at full load, an electrical bus failure causes all fans to

trip. An MFT is immediately initiat ed. All controls remain in auto.

T6 Full Load Single

Booster Fan Trips 100% With the unit at full load, a single booster fan is tripped. A 30-

second stroke time is assumed for the booster fan inlet damper.

The tripped fan is isolated and the unit continues to operate at full

load on the remaining two booster fans. All controls remain in auto.

T7 Full Load Baghouse

Cleaning System

Failure 100% With the unit at full load, the baghouse cleaning system failure

increases the baghouse differential pressure from 10 inwc to 14

inwc over a period of one minute. All controls remain in auto.

Table 8 Transient Descriptions



# As part of this study, TRAX proposed and tested several mitigating measures to help control the

extent of furnace and ductwork pressure excursi ons. Mitigating measures added to the control

model included:

• If all the three operating booster fans trippe d at full load operation, the controls should

wait 20 seconds following the MFT and the FD fans should be tripped once the furnace

pressure reached +15 inwc.

• On a single booster fan trip, the load should be run back from 100% to 70% to avoid

severe pressure excursions in the furnace.

The graphs, presented under each transient headi ng, are results obtained from the unmitigated

runs. Any results obtained from mitigated tran sient runs are presented under the mitigations

subsection of each transient. All the graphs are shown in th e Reference Section. Among the

plots shown for each transient is a graphical profile of the maximum and minimum pressure

measurements at various positions along the air-gas path. Points on each maximum and

minimum profile did not necessarily occur at the same time.

The baseline transient runs are designated with a “T” and are then given sequential numbers

according to their order in Table 8. Each m itigated run designation matches the corresponding

baseline transient designation, but is preceded by an “M.”

4.4.1 T1: Full Load MFT

This transient consisted of the following steps:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

# PNM – San Juan Generating Station Unit 1 Page 25 of 57

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# • MFT initiated by an operator at 10 seconds

• All controls remained in au to throughout the transient

The control system triggered a series of even ts immediately following the MFT. The control

actions are listed below:

• Froze FD inlet guide vanes at their curre nt position

• Tripped pulverizers and their feeders

• Shut coal valves

• Tripped, shut off, and isolated PA fans

• Closed hot air, tempering air, and primary air control dampers

• Booster fan IGV demand controlled by a kicker circuit for 15 seconds following the MFT

• Transferred control of the booster fan IGV de mand to a runback co ntroller from 25

seconds to the end of the transient

The Unit 1 model was initialized to the full load condition (360 MW) and allowed to run for 10

seconds to ensure steady-state operation. At 10 seconds, an operator init iated an MFT, which

shut down the coal valves and shut off the pul verizer feeders, causing the amount of pulverized

coal being transported to the burne rs to drop rapidly. Due to this rapid fuel shutoff, the fireball

collapsed and the furnace pressure dropped to a minimum of –1.2 inwc upon total consumption

of available fuel, as shown in Figure 8. The co ntinuous operation of the FD fans and the action

of the booster runback control l ogic triggered at 25 seconds led furnace pressure recovery to

reach +3.2 inwc by 120 seconds.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### FD Discharge Furnace Air Heater Gas Outlet



# Figure 8 T1 Unit Pressures

# PNM – San Juan Generating Station Unit 1 Page 26 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# During this and all the other transients, a kick er circuit for controlling the booster fan IGV was

active for 15 seconds following an MFT signal. It is important to include this kicker circuit in

the controls in order to prevent more severe negative furnace pressure excursions during an

MFT. As an example, the furnace pressure wo uld have dropped by an a dditional 9 inwc in the

absence of the kicker circuit during this transien t. The kicker was held active until after the

completion of the fireball collapse and into the be ginning of furnace pressure recovery to provide

a more stable and over-dampened response when the booster fan IGV control was transferred to

the runback logic.

The booster fan IGV closed from 64% open (initi al condition) to 18% open in eight seconds

during this transient, as shown in Figure 9. For the rema ining seven seconds of the kicker

operation, the IGV position remained constant with only a minor adjustment from the air heater

gas outlet pressure controller. At 25 seconds, the kicker was re leased and the r unback controller

opened the booster fan IGV in an attempt to maintain a +1 inwc furnace pressure.

0 10 20 30 40 50 60 70 80 90 100

0 20 40 60 80 100 120

Time (seconds)Position (percent open) 

### FD Fans Booster Fans



# Figure 9 T1 Fan Inlet Guide Vane Positions

# PNM – San Juan Generating Station Unit 1 Page 27 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Figure 10 shows the baghouse, FGD, and booster fa n inlet pressures during the transient. The

baghouse inlet pressure d ecreased from +0.1 inwc to –3.2 inwc during the fireball collapse.

Following the rise in furnace pressure after the MFT, the baghouse inlet pressure increased to

–1.0 inwc at 25 seconds, and eventually decreased to –4.8 inwc as the booster fan IGV continued

to open because of the ru nback controller action.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 10 T1 Baghouse and Scrubber Pressures



# The immediate impact of closing the booster fan IGV during the fire ball collapse can be seen on

the booster fan inlet pressure plot. The reducti on in flow being transported across the booster

fan, due to the closing of its IGV, led to an in crease of the inlet pressu re from an initial –11.0

inwc to –3.8 inwc while the kicker was active. Following the opening of the booster fan IGV,

the booster fan inlet pressure decreased to –14.5 inwc by the end of the transient.

Also, during the closing of booster fan IGV fr om 10 seconds to 18 seconds, the FGD inlet

pressure dropped by 11.4 inwc due to reduction in flow being transported across it. The FGD

inlet pressure then remained nearly constant at around +2.5 inwc (for seven seconds) while the

booster fan IGV was held in place by the kicker circ uit. Following the tran sfer of control to the

booster fan runback logic, the FGD inlet pressu re started increasing and eventually reached

+12.3 inwc by the end of the transient.

Flows corresponding to the FD fans, furnace exha ust, and FGD inlet are shown in Figure 11.

The rapid fuel shutoff, combined with loss of pr imary air due to the MFT, led to a 43% decrease

in furnace exhaust flow in seven seconds, and a corresponding decrease in FGD inlet flow.

During this time, the FD fans’ IGVs were frozen in place while the fans continued to operate.

The increased differential between the FD discha rge and furnace pressures led to the increased

transportation of air, as shown in Figure 11. The total FGD inlet flow remained nearly constant

# PNM – San Juan Generating Station Unit 1 Page 28 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# from 18 seconds to 25 seconds, during which the FGD inlet pressure remained nearly constant.

The loss of primary air and fuel (due to th e MFT) caused the furnace exhaust and FGD inlet

flows to steady out at values lowe r than their initial conditions.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 20 40 60 80 100 120

Time (seconds)Flow (kpph) 

### Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 11 T1 Flows



# Mitigations

During this transient, process pressures did not reach values that required additional control

mitigations. Since the booster fans did not tri p, the mitigations listed on page 24 had no effect on

this transient.

4.4.2 T2: Full Load All Booster Fans Trip

This transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Tripped all three operating boos ter fans, immediately causi ng an MFT and associated

control actions as li sted in Section 4.4.1

• All controls remained in au to throughout the transient

# PNM – San Juan Generating Station Unit 1 Page 29 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Following the MFT initiated by the loss of all boos ter fans, the furnace pressure dropped to a

minimum of +1.8 inwc by 18 seconds. This fall in furnace pressure was not as great as in the

“Full Load MFT” transient because of the reduc tion in furnace exhaust flow due to the booster

fans’ trip. This behavior was reflected in the FD discharge and air heater gas outlet pressures, as

shown in Figure 12, which were also measured upstream of the tripped booster fans.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### FD Discharge Furnace Air Heater Gas Outlet



# Figure 12 T2 Unit Pressures



# Following the kicker release at 25 seconds, the booster fan IGV opened up continuously, as

shown in Figure 13. Despite the opening IGV positi on, the tripped booster fans operated only at

constantly decreasing speeds, as shown in Figure 14. The re duction in flow through the tripped

booster fans resulted in inadequate relief of pres sures upstream, and the furnace, FD discharge,

and air heater gas outle t pressures increased correspondingly upon comple tion of the fireball

collapse. The rate of increase of these pressures slowed with time, as shown in Figure 12, once

the booster fan IGV was completely open.

# PNM – San Juan Generating Station Unit 1 Page 30 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 0 10 20 30 40 50 60 70 80 90 100

0 20 40 60 80 100 120

Time (seconds)Position (percent open) FD Fans Booster Fans



# Figure 13 T2 Fan Inlet Guide Vane Positions

0 200 400 600 800 1000 1200 1400

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Speed (rpm) FD Fans Booster Fans



# Figure 14 T2 Fan Speeds



# While the booster fan IGVs were closing (due to the kicker action from 10 seconds to 25

seconds), the baghouse inlet pre ssure increased by about 1.8 inwc. The inadequate pressure

relief provided by the tripped booster fans resulted in a baghouse inlet pressu re increase to +13.9

inwc by the end of the transient. The booster fan inlet pressure increased during the fireball

collapse, as shown in Figure 15, and continued to increase at a lesser rate following the opening

of booster fan IGV.

# PNM – San Juan Generating Station Unit 1 Page 31 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 15 T2 Baghouse and Scrubber Pressures



# The FGD inlet pressure dropped by about 13.2 inwc during the fireball collapse, and stayed

nearly constant from 17 seconds to 25 seconds as the booster fan IGV was held constant by the

kicker. The pressure started to increase followi ng the transition of cont rols to the booster fan

runback controller, and eventually steadied out at 48% of the initial cond ition. Figures 12 and 15

show that, compared to their initial values, th e pressures upstream of the tripped booster fans

recovered to a higher value while the downstrea m pressures approached a lower value.

Figure 16 shows the behavior of th e flows during this transient. The total FD fan flow increased

by only 2% during the fireball collapse, and decreas ed to 83% of the initial value by the end of

the transient. This was a result of the cont inuous operation of the FD fans, even though the

booster fans were tripped. Follow ing the fireball colla pse, the FGD inlet fl ow fell to about 1,570

kpph, from an initial value of 3,823 kpph. The flow stayed constant for a bout eight seconds, due

to the constant FGD inlet pressure during this time. The tripped booster fans did not transport as

much air, which resulted in FGD inlet flow recove ry to only 73% of the in itial flow by the end of

the transient.

# PNM – San Juan Generating Station Unit 1 Page 32 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Flow (kpph) 

### Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 16 T2 Flows



# Mitigations

MT2: Mitigated Full Load All Booster Fans Trip– Delayed FD Trip

The high positive pressures obtained during this tr ansient were prevented by tripping the FD fans

simultaneously with the operating booster fans. For this mitigation, the MFT was allowed to

continue for 20 seconds, and the FD fans were tripped once the furnace pressure exceeded +15

inwc. The results of the mitigated transient ar e presented in the Reference Section. Figure 17

shows a comparison of the maximum system pre ssures obtained with and without mitigations,

showing an improvement of all pressures upstream of the booster fan outlets.

# PNM – San Juan Generating Station Unit 1 Page 33 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -4.6 +2.9 +14.9 +17.6

0.0 +8.3 +9.0 +14.6 +18.6 +24.9 +30.5

+29.2

+23.1

+16.9

+13.9

-0.3 +5.5 +6.2 +10.7 +11.4 +13.5 +14.2 +15.1 +20.3 +22.4 +27.3 +28.8

-40 -30 -20 -10

0 +10 +20 +30 +40

Ambient FD Fan

O

u tle

t S AH

Ai

r I

n l e t SAH Air Outlet Win

d b o x Furnace Ec

o nomiz

e r O

u tle

t Pre

c ip

Ou

t l e t SAH Gas Outlet Ba

g h o u se

Inl

e t Ba

g h o u se

Ou

t l e t Booste

r Fan Inlet

Bo

o st er

F a n O

u tle

t Scr

u bber Outlet Sta

c k B

a se

T op of StackPressure (inwc) 

### Maximum (Unmitigated) Maximum with FD Fan Trip (Mitigated)



# Figure 17 T2 and MT2 Transient Maximum Pressure Profile



# Figure 18 shows a comparison of the mitigated and unmitigated furnace pressures. For this

mitigation, both FD fans were tripped at about 59 seconds, when the furnace pressure reached

+15 inwc. The mitigated furnace pressure recovered to about 18.6 inwc lower than the

unmitigated pressure at the end of this transient.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) Furnace (Unmitigated) Furnace with FD Fan Trip (Mitigated)



# Figure 18 T2 and MT2 Furnace Pressure Comparison

# PNM – San Juan Generating Station Unit 1 Page 34 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# MT2A: Mitigated Full Load All Boost er Fans Trip – Immediate FD Trip

During discussion between members of the project team, the merits of immediately tripping the FD

fans were considered. It was agreed that the “Full Load All Booster Fans Trip” transient should

be tested to compare a delayed FD fan trip ag ainst an immediate FD fan trip. Letter Report

0817-0101, which contains a comparison of the “MT2 : Mitigated Full Load All Booster Fans

Trip – Delayed FD Trip” and “MT2A: Mitigated Full Load All Booster Fans Trip – Immediate

FD Trip” transients, is include d in the Reference Section. Fi gure 19 shows a comparison of the

maximum system pressures obtained with th e delayed and immediate FD fan trips.

0.0 +28.8 +27.3

+22.4

+20.3

+15.1 +14.2 +13.5

+11.4 +10.7

+6.2 +5.5 +14.9

+2.9

-0.3

-4.6 0.0 +22.4 +20.9

+16.6

+14.7

+9.9

+7.5 +6.1

+1.5 +0.2 -0.7 +14.9

-0.7 -0.5

-40 -30 -20 -10

0 +10 +20 +30 +40

Am

b i e nt FD Fa

n O

u tlet SA

H

A ir

I n let SA

H

A ir Outlet

Wi

n dbox Fur

n ac

e Eco

no

m iz e r Outl

e t Precip Outlet SA

H

Ga

s Outlet

B ag

h ouse

I nle

t Bag

h ouse

Ou

t l e t Boost

er

Fa

n I nle

t B oo

s ter Fan Outl

e t Scrubber Out

l et St

ac

k Base Top of

St

a ckPressure (inwc) 

### Maximum with MT2 Maximum with MT2A



# Figure 19 MT2 and MT2A Transient Maximum Pressure Profile



# Figure 20 shows a comparison of the furnace pre ssures for the MT2 and MT2A runs. At 10

seconds, an MFT occurred and fuel was shut off to the furnace. The resulting fireball collapse

caused a sharp drop in furnace pressure. Pressure for the MT2A run continued to drop as the FD

fans were immediately tripped a nd reduced mass flow into the furnace. Furnace pressure for run

MT2A eventually reached a minimum of -3.3 inwc. Conversely, pressure for the MT2 run began

to rise at about 20 seconds as the FD fans continued to run and pressurize the furnace.

Eventually, furnace pressure rose above +15 inwc at about 60 seconds and the FD fans tripped.

Furnace pressure for both transients then tren ded to ambient as the FD fans spun down.

# PNM – San Juan Generating Station Unit 1 Page 35 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### MT2 Furnace MT2A Furnace



# Figure 20 MT2 and MT2A Furnace Pressure Comparison



# 4.4.3 T3: Full Load Both FD Fans Trip

This transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Tripped both operating FD fans immediatel y causing an MFT and associated control

actions as listed in Section 4.4.1.

• All controls remained in au to throughout the transient

Figure 21 shows the FD discharge, furnace, and air heater gas outlet pressures during this

transient. At 10 seconds, an MFT was initiat ed following the loss of both FD fans. Reduced

airflow through the tripped FD fans resulted in a reduction in FD disc harge pressure by about

21.6 inwc in 18 seconds following the MFT. The furnace pressure decreased by 16.8 inwc to a

minimum of –6.9 inwc and recovered to –2.2 inwc by the end of the transient. The recovery of

the furnace pressure was limited by the la ck of flow through the FD fans.

# PNM – San Juan Generating Station Unit 1 Page 36 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) FD Discharge Furnace Air Heater Gas Outlet



# Figure 21 T3 Unit Pressures



# Following the MFT at 10 seconds, the booster fans’ inlet guide vanes closed from 64% to 12%

over nine seconds, as shown in Figure 22. In the next six seconds, the active kicker circuit

further reduced the position to 7%, after which the control was transferred to the booster fan

runback logic. At this point, the booster fan IGV closed furthe r in an attempt to bring the

furnace pressure up to its setpoint of +1 inwc. The FD fan IGVs froze in place following

initiation of the MFT at 10 seconds.

0 10 20 30 40 50 60 70 80 90 100

0 20 40 60 80 100 120

Time (seconds)Position (percent open) FD Fans Booster Fans



# Figure 22 T3 Fan Inlet Guide Vane Positions

# PNM – San Juan Generating Station Unit 1 Page 37 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# The baghouse inlet pressure decreased by about 8 inwc following the MFT and eventually

recovered to 3.2 inwc lower than its initial value by the e nd of the transient. The reduction in air

being transported through the FD fans, combined with the closing of booster fan IGV (triggered

at 25 seconds), led to lower baghous e inlet pressure at the end of the transient. Corresponding to

the movement of the fan IGV position, the booster fan inlet pressure increased from 10 seconds

to 19 seconds, and then increased gradually over the remainder of the transient.

The FGD inlet pressure fell from an initial value of +14.5 inwc to +0.6 inwc ove r nine seconds

following the MFT at 10 seconds. The pressure th en remained nearly constant for six seconds,

as shown in Figure 23, due to the restricted moveme nt of the booster fan IGV. Further closing of

the booster fan IGV led the FGD inle t pressure to stabilize at a pr essure lower than the initial

condition by the end of the transient.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 23 T3 Baghouse and Scrubber Pressures

# PNM – San Juan Generating Station Unit 1 Page 38 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Following the MFT at 10 seconds, furnace exhaust flow dropped by 40% in ei ght seconds, as shown

in Figure 24. The loss of the FD fans resulted in a gradual decrease of the flow tr ansported through

the fans, and this loss of airflow, combined with th e loss of fuel due to th e MFT, caused the furnace

exhaust flow to drop from an init ial value of 3,263 kpph to 1,000 kpph by the en d of the transient.

Closing the booster fan IGV caused th e decrease in FGD flow. The rate of decrease of the FGD inlet

flow was similar to the FGD inlet pressure, as was the case in the previous transients.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Flow (kpph) Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 24 T3 Flows



# Mitigations

During this transient, process pressures did not reach values that required additional control

mitigations. Since the booster fans did not tri p, the mitigations listed on page 24 had no effect on

this transient.

4.4.4 T4: Low Load Two Booster Fans Runaway

This transient consisted of the following steps and control actions:

• Initialized the model to the 30% load conditi on (only two booster fa ns were in operation

at this load)

• Ran the model for 10 seconds to establish steady-state conditions

• Manually opened the inlet guide vane s of the two operating booster fans

• All controls remained in au to throughout the transient

Following the opening of the booster fan IGV at 10 seconds, the furn ace pressure decreased to a

minimum of –3.7 inwc at 27 seconds, as shown in Figure 25. By 17 seconds, the furnace

pressure decreased below –1 inwc , triggering the runback contro ller, which ramped back the

inlet guide vanes on both operating booster fans. The booster fan IGV position changed from an

# PNM – San Juan Generating Station Unit 1 Page 39 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# initial 37% at 10 seconds to 79% at 18 seconds, a nd then closed to 49% at 25 seconds due to the

runback controller, as shown in Figure 26. The FD fan IGV gradually closed during the course

of the transient to facilitate transport of less ai r due to the closing of the booster fan IGV. As a

result, the unit pressures did not recover to their ini tial values, even though the booster fan IGV

recovered to nearly the initial valu e at the end of the transient.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) FD Discharge Furnace Air Heater Gas Outlet



# Figure 25 T4 Unit Pressures

0 10 20 30 40 50 60 70 80 90 100

0 20 40 60 80 100 120

Time (seconds)Position (percent open) FD Fans Booster Fans



# Figure 26 T4 Fan Inlet Guide Vane Positions

# PNM – San Juan Generating Station Unit 1 Page 40 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Figure 27 shows the baghouse and scrubber pressures during this transient. The booster fans’

runaway at 10 seconds caused an immediate decrease in the baghouse inlet pressure by 5.6 inwc

in eight seconds. The baghouse inlet pressure reached –4 inwc after the booster fans’ IGVs

closed due to the runback control action initia ted at 18 seconds (and maintained throughout the

transient).

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 27 T4 Baghouse and Scrubber Pressures



# A qualitatively similar behavior was observed in the booster fa n inlet pressure profile. In

summary, the booster fans’ runaway at 10 seconds caused an immediate decrease in pressures

upstream of the booster fans, as reflected in th e baghouse and booster fan inlet pressures. The

combined effect of the booster fan IGVs closi ng to their initial value and the FD fan IGVs

closing caused the baghouse and boos ter fan inlet pressures to drop lo wer than their initial values

by the end of the transient.

Figure 27 also shows the close correspondence of th e FGD inlet pressure to the booster fans’ IGV

position. As the inlet guide vanes opened from 10 seconds to 18 seconds, thereby transporting

more flow, the FGD inlet pressure increased by 10.1 inwc. The F GD inlet pressure then fell by

7.7 inwc in the next seven seconds due to the clos ing of IGV caused by the runback controller.

The booster fans transported more flow into th e scrubbers as they opened, which reflected an

increase of the total FGD inlet flow from 2,031 kpph to 2,960 kpph in a pe riod of eight seconds

following the runaway at 10 seconds , as shown in Figure 28. Once the runback controller took

over at 18 seconds, the flow decreased to 2,319 kpph by 25 seconds, which corresponded to the

closing of the booster fan IGV. While the boos ter fan IGVs opened, the decrease in furnace

pressure led to a 14% increas e in furnace exhaust flow.

# PNM – San Juan Generating Station Unit 1 Page 41 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Flow (kpph) 

### Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 28 T4 Flows



# Mitigations

During this transient, process pressures did not reach values that required additional control

mitigations. It is, however, important to realize that the transfer of the booster fans’ IGV control

to the runback controller at 18 seconds was essential in prev enting further negative furnace

pressure excursions. In the case of no runback controller or IGV runawa y caused by an actuator

failure, the continuous opening of the booster fans’ IGV would ha ve resulted in a further

decrease of upstream pressures an d could have led to a possible low pressure MFT. Since the

booster fans did not trip, the mitigations liste d on page 24 had no effect on this transient.

4.4.5 T5: Full Load All Fans Trip

This transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Manually tripped both operating FD fans and all three operating booster fans immediately

causing an MFT and associated contro l actions as liste d in Section 4.4.1.

• All controls remained in au to throughout the transient

The furnace pressure reached a minimum of –3.3 in wc at about 21 seconds before recovering to

–0.3 inwc at the end of the transi ent. Figure 29 shows that the FD discharge and air heater gas

outlet pressures also recovered to values less than their initial values. This occurred because the

# PNM – San Juan Generating Station Unit 1 Page 42 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# air pushed by the FD fans decreased with time, since the tripped FD fans operated at decreasing

speeds, which in turn reduced the downstream pr essures, as shown in Figure 30. A comparison

of Figures 29 and 21 revealed that the final pres sures were higher than those in the “Full Load

Both FD Fans Trip” transi ent due to the additional tripping of booster fans.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### FD Discharge Furnace Air Heater Gas Outlet



# Figure 29 T5 Unit Pressures

0 200 400 600 800 1000 1200 1400

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Speed (rpm) 

### FD Fans Booster Fans



# Figure 30 T5 Fan Speeds

# PNM – San Juan Generating Station Unit 1 Page 43 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Following the MFT at 10 seconds, the booster fans’ IGVs closed from 64% to 17% in eight

seconds, as shown in Figure 31. In the next se ven seconds, the active ki cker circuit further

reduced the position to 14%, after wh ich control was transferred to th e booster fan runback logic.

The later movement in the booster fans’ IGV po sition was a result of the runback controller

attempting to attain the furnace pressure setpoint of +1 inwc. The FD fan IGV froze in place

following the MFT.

0 10 20 30 40 50 60 70 80 90 100

0 20 40 60 80 100 120

Time (seconds)Position (percent open) FD Fans Booster Fans



# Figure 31 T5 Fan Inlet Guide Vane Positions



# The baghouse inlet pressure decreased by 4.2 inwc in 10 seconds, following the loss of the FD

fans at 10 seconds, before recovering to a value closer to its initial condition. The booster fan

inlet pressure increased by 6.3 inwc during the 15 seconds of kicker circuit operation. A

comparison of Figures 32 and 15 re veals that the magnitude of incr ease was less for this transient

than the “Full Load All Booster Fans Trip” transi ent because of the simultaneous trip of the FD

fans. The FGD inlet pressure, as shown in Fi gure 32, decreased from +14.5 inwc to +0.3 inwc

by 18 seconds. As the rate of change in the booster fans’ IGV slowed down, the inlet pressure

remained nearly constant over the next seven s econds before eventually steadying out at -0.7

inwc by the end of the transient.

# PNM – San Juan Generating Station Unit 1 Page 44 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 32 T5 Baghouse and Scrubber Pressures



# By 18 seconds, the furnace exhaust flow decreased to about 34% of its in itial value during the

fireball collapse associated with the MFT. As shown in Figure 33, the flow continued to

decrease further, due to the loss of air from the FD fans and fuel flow caused by the MFT, and

reached about 11% of its initial value by the e nd of the transient. A similar behavior was

observed in the total flow to the FGD inlet during this transient. The tr ipped FD fans continued

to transport air at a lesser rate due to thei r decreasing speed. This resulted in a continuous

decrease of the total air pushed by th e FD fans throughout the transient.

# PNM – San Juan Generating Station Unit 1 Page 45 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Flow (kpph) 

### Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 33 T5 Flows



# Mitigations

During this transient, process pressures did not reach values that required additional control

mitigations. Since the booster fans did not tri p, the mitigations listed on page 24 had no effect on

this transient.

4.4.6 T6: Full Load Single Booster Fan Trips

This transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Manually tripped an operating booster fan

• Isolated the tripped booster fan by closing the associated inlet and outlet dampers

• All controls remained in au to throughout the transient

• MFT was not triggered during this event

• Booster fan runback control did not occur as the furnace pressure never reached -1 inwc

during the transient

Note that this transient alone was tested for a period of 300 seconds to capture all events.

# PNM – San Juan Generating Station Unit 1 Page 46 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Figure 34 shows the FD discharge, fu rnace, and air heater gas outlet pressures during this transient.

The loss of a single booster fan at 10 seconds led to an incr ease in pressures upstream of the

booster fans. By 40 seconds, the furnace pressure increased by 7.5 inwc from its initial value. At

this point, the gradual reduction of the tripped fan’ s speed, combined with th e continuous operation

of the remaining two boosters, as shown in Figu re 35, caused pressures to steady out. All the

pressures upstream of the booster fans recovered to values higher than their initial values.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 50 100 150 200 250 300

Time (seconds)Pressure (inwc) 

### FD Discharge Furnace Air Heater Gas Outlet



# Figure 34 T6 Unit Pressures



# Figure 35 also shows the speed profile of the tripped booster fan (Booster Fan A). In addition to

being tripped during this transient, Booster Fan A was isolated by closing the associated inlet and

outlet dampers. The inertial losses resulted in a rapid decrease of speed by 47% in the first 15

seconds of the transient. As the flow through th e fan went to zero due to its isolation, the work

done by the fan went to zero, resulti ng in a sudden change in direc tion of the Booster Fan A speed

at 25 seconds. The frictional losses in the fan caus ed a more gradual decrease of speed thereafter,

and the operating speed of the tripped booster fan decreased to about 115 rpm by 300 seconds.

# PNM – San Juan Generating Station Unit 1 Page 47 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 0 200 400 600 800 1000 1200 1400

0 50 100 150 200 250 300

Time (seconds)Speed (rpm) FD Fans Booster Fan A Booster Fans B & C



# Figure 35 T6 Fan Speeds



# The effect of a single booster fan loss on the upst ream pressures was also reflected in the baghouse

and booster fan inlet pressures, as shown in Figure 36. The baghouse inlet pressure increased by 9

inwc in the first 30 seconds, and eventually steadied out at +10.7 inwc by the en d of the transient.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 50 100 150 200 250 300

Time (seconds)Pressure (inwc) Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 36 T6 Baghouse and Scrubber Pressures



# The booster fan inlet pressure similarly recovered to 10.6 inwc higher than the initial value. The FGD

inlet pressure increased by 77% by 40 seconds and attained almost tw ice the initial va lues by the end

of the transient. Th e isolation of the tri pped booster fan and subs equent redistribution of the total flue

gas flow to two scrubber s resulted in steady, but higher, pressure s at the end of the transient.

# PNM – San Juan Generating Station Unit 1 Page 48 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# At 10 seconds, tripping and isol ating a single booster fan led to a sudden 17% decrease in FGD

inlet flow in the first 15 second s of the transient. As the IGVs of the remaining two booster fans

opened in an effort to decrease furnace pressure, th e flow was redistributed to the two scrubbers in

operation and eventually recovered to the initial valu e, as shown in Figure 37. The reduction in the

total flow through the FD fans at the start of the transient resulted in a decrease of the oxygen

percentage at the economizer outlet, which caused the FD fan IGV to open, as shown in Figure 38.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 50 100 150 200 250 300

Time (seconds)Flow (kpph) Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 37 T6 Flows

0 10 20 30 40 50 60 70 80 90 100

0 50 100 150 200 250 300

Time (seconds)Position (percent open) FD Fans Booster Fans



# Figure 38 T6 Fan Inlet Guide Vane Positions

# PNM – San Juan Generating Station Unit 1 Page 49 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# MT6: Mitigated Full Load Single Booster Fan Trips

The high positive pressures measured throughout the system could be prevented by reducing the

mass flowing through the system via a runback. For this mitigation, TRAX tested a load

reduction from 100% to 70% at the rate of 30 MW/mi n. This rate was obtained from the original

control logic supplied to TRAX. The time taken for the desired load reduction at the specified

rate was calculated to be appr oximately 216 seconds (3.6 minutes). Thus it was necessary to run

the transient, with and wit hout mitigations, for 300 seconds to allow additional time for

stabilization. The results of the mitigated tran sient are presented in the Reference Section.

Figure 39 shows a comparison of the maximum sy stem pressures obtained with and without

mitigations. There is an improvement in a ll pressures upstream of the stack base.

-4.6 +11.5 +17.4 +25.9 +32.1 +33.6

+27.8

+21.1

+12.9

+2.2

+0.2 0.0 +18.8 +30.0

+3.5

+1.0 +9.1 +28.9 +27.5

+23.4

+21.7

+17.4 +15.4

+14.2 +10.3 +28.0

+3.2 -0.4

-0.6

-40 -30 -20 -10

0 +10 +20 +30 +40

Ambient F D Fan Outlet SAH A

i r Inlet

SAH

A i r O

u tl e t Windbox F u rnace Econo

m i zer

O ut l et Precip O

ut l et SAH

G as

O utlet Baghouse Inlet B a ghou

se

O ut

l e t Boo

s ter

F an I

nl et Booster Fan Ou

t le t Scrubber Outlet S t a c k B

ase

T op of

St

a c kPressure (inwc) 

### Maximum (Unmitigated) Maximum with Load Runback (Mitigated)



# Figure 39 T6 Transient Maximum Pressure Profile



# A comparison of the mitigated and unmitigated furnace pressures is shown in Figure 40. The

mitigated value of the maximum furnace pressure was 3.7 inwc lower than the case without

mitigation. The furnace pressure following the mitigation recovered to about 15.3 inwc lower

than the unmitigated pressure at the end of this transient.

# PNM – San Juan Generating Station Unit 1 Page 50 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 50 100 150 200 250 300

Time (seconds)Pressure (inwc) Furnace (Unmitigated) Furnace with Load Runback (Mitigated)



# Figure 40 T6 Furnace Pressure Comparison



# 4.4.7 T7: Full Load Baghouse Cleaning System Failure

This transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Increased the pressure drop across the baghouse by 4 inwc, from 9.7 inwc to 13.7 inwc,

in 10 seconds to simulate its cleaning system failure (for testing a severe transient)

• All controls remained in au to throughout the transient

• MFT was not triggered during this event

• Booster fan runback control did not occur as the furnace pressure never reached -1 inwc

during the transient

At 10 seconds, the pressure drop across the baghouse was increased by 4 inwc to begin the

transient. This led to an increase in pressures upstream of the baghouse to allow for more flow

through the system. This increase in pressure was small in magnitude compared to the other

transients. Also, the rise in pressure due to increased baghouse pressure differential was more

prominent closer to the baghouse, and the effect grew less pronounced away from it, as shown in

Figure 41. The air heater gas outlet pressure increased by about 1.3 inwc, while the FD fan

discharge pressure increased by 0.7 inwc by 20 se conds. The rate at which the upstream pressures

increased gradually slowed over the next 40 seconds before the pressures eventually recovered to

their initial values. The rate of change for these pressures was dependent on their relative position

with respect to the baghouse. The pressures else where in the system responded proportionately, as

shown in Figure 42.

# PNM – San Juan Generating Station Unit 1 Page 51 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### FD Discharge Furnace Air Heater Gas Outlet



# Figure 41 T7 Unit Pressures



# The baghouse inlet pressure increased by 1.5 inwc fr om 10 seconds to 20 seconds, and gradually

increased through the next 40 seco nds, before recovering to its in itial value by th e end of the

transient, as shown in Figure 42. As show n in Figure 43, the booster fan IGV opened by 8%

during the first 40 seconds of the transient and subsequently remain ed nearly constant at this

position to support the additional flow transporte d by the increased baghouse differential. The

opening of the IGV corresponded w ith an initial 1.3 inwc decrea se of the booster fan inlet

pressure for the first 10 seconds of the transient. Boos ter fan inlet pressure eventually settled at

about 3.6 inwc lower than the in itial value. The movement of the booster fan IGV, followed by

the adjustment in booste r fan inlet pressures, led to a nearly consta nt FGD inlet pressure

throughout the transient. Overall, the booster fan IGV movement wa s able to compensate for the

additional 4 inwc pressure drop across the baghouse.

# PNM – San Juan Generating Station Unit 1 Page 52 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 -40 -30 -20 -10

0 +10 +20 +30 +40

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Pressure (inwc) 

### Baghouse Inlet Booster Fan Inlet FGD Inlet



# Figure 42 T7 Baghouse and Scrubber Pressures

0 10 20 30 40 50 60 70 80 90 100

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Position (percent open) 

### FD Fans Booster Fans



# Figure 43 T7 Fan Inlet Guide Vane Positions



# No significant changes were obser ved in the flows of interest as the pressures measured at the

FD outlet, furnace, and FGD inlet remained nearly constant throughout the transient, as shown in

Figure 44.

# PNM – San Juan Generating Station Unit 1 Page 53 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0

Time (seconds)Flow (kpph) 

### Total FD Fans Furnace Exhaust Total FGD Inlet



# Figure 44 T7 Flows



# Mitigations

During this transient, process pressures did not reach values that required additional control

mitigations. Since the booster fans did not tri p, the mitigations listed on page 24 had no effect on

this transient.

# PNM – San Juan Generating Station Unit 1 Page 54 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 4.5 Transient Events Summary Table

A summary of the unmitigated transi ent results is shown in Table 9.

Furnace

Pressure

(inwc) Air Heater

Gas Outlet

Duct (inwc) Booster Fan

Inlet (inwc) No. Transient Name No. of

Booster

Fans in

Service Gross

Load

% Min Max Min Max Min Max

T1 Full Load MFT 3 100 -1.2 +9.9 -3.6 +1.5 -14.4 -3.8

T2 Full Load All Booster Fans Trip 3 100 +1.8 +18.6 +0.4 +14.6 -11.0 +8.3

T3 Full Load Both FD Fans Trip 3 100 -6.9 +9.9 -7.7 +1.5 -11.0 -4.4

T4 Low Load Two Booster Fans Runaway 2 30 -3.7 +2.2 -6.8 +0.0 -12.1 -3.5

T5 Full Load All Fans Trip 3 100 -3.3 +9.9 -4.0 +1.5 -11.0 -0.7

T6 Full Load Single Booster Fan Trips 2 100 +9.9 +21.1 +1.5 +12.9 -11.0 +0.2

T7 Full Load Baghouse Cleaning System Failure 3 100 +9.5 +11.5 +1.4 +3.1 -14.7 -11.0

Table 9 Transient Event Summary Table



# A summary of the mitigated transient results is shown in Table 10.

Furnace

Pressure

(inwc) Air Heater

Gas Outlet

Duct (inwc) Booster Fan

Inlet (inwc) No. Transient Name No. of

Booster

Fans in

Service Gross

Load

% Min Max Min Max Min Max

MT2 Mitigated Full Load All Booster Fans Trip –

Delayed FD Trip 3 100 -0.0 +15.1 -0.3 +11.4 -11.0 +5.5

MT2A Mitigated Full Load All Booster Fans Trip –

Immediate FD Trip 3 100 -3.3 +9.9 -4.0 +1.5 -11.0 -0.7

MT6 Mitigated Full Load Single Booster Fan

Trips 2 100* +1.2 +17.4 -3.4 +10.3 -11.0 -0.6

Table 10 Transient Event Summary Table

*As a part of the mitigated run, the load changed from 100% to 70%.

# PNM – San Juan Generating Station Unit 1 Page 55 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 5.0 CONCLUSIONS AND RECOMMENDATIONS

During transient testing, unmitigated furnace pressu res were held within the range of –6.9 inwc

to +21.1 inwc. The “Full Load All Booster Fans Trip” and “Full Load Single Booster Fan Trips”

transients led to high furnace pressure maximums of +18.6 inwc and +21.1 inwc respectively. A

delayed trip of the FD fans mitigated the furn ace pressure to a maximum of +15.1 inwc for the

former transient, and an immediate trip of th e FD fans mitigated the furnace pressure to a

maximum of +9.9 inwc, but a furnace pressure minimum of -3.3 inwc was experienced.

Reducing the load from 100% to 70%, at a rate of 30 MW/min, mitigated the maximum furnace

pressure to +17.4 inwc for the “Full Load Single Booster Fan Trips” transient. The remaining

transients led to negative furnace pressure excursions, with the most severe being –6.9 inwc

measured during the “Full Load Both FD Fans Trip” transient.

The rapid movement of the booster fan inlet guide vanes to prevent furnace pressure excursions

often caused sharp downstream pressure excursions . The booster fans’ in let pressure was found

to vary within -14.7 inwc and +8.3 inwc for a ll the transients. Again, the indicated maximum

pressure was obtained for the “Full Load All Booster Fans Trip” transient. The proposed

mitigation of tripping both the FD fans when all booster fans trip mitigated the booster fan inlet

pressure to a maximum of +5.5 inwc.

Pressure excursions at the flue gas outlet of the air heaters were within –7.7 inwc and +14.6

inwc. The indicated maximum air heater gas out let pressure was obtained during the “Full Load

All Booster Fans Trip” transient. Tripping both the FD fans on a high pressure limit following

the MFT mitigated the air heat er gas outlet pressure to a maximum of +11.4 inwc.

During the “Full Load MFT” transient, the fireba ll collapse resulted in the furnace pressure

dropping by 11.1 inwc in about eight seconds. Du ring this period of time, closing booster fan

inlet guide vanes by 46% reduced flow to the scr ubbers and caused inlet pr essure to the FGD to

drop by about 12.6 inwc. Over a pe riod of 15 seconds following the release of the kicker at 25

seconds, the FGD inlet pressure improved by 7.2 inwc while the boosters opened by 24%.

The fast-adjusting booster fan inle t guide vanes were a key fact or in moderating the furnace

pressure drop associated with a MFT fireball colla pse. On an MFT, controls closed the burner

shutoff valves, which rapidly cut off fuel to the furnace and caused a sharp fireball collapse.

With the FD fan IGV frozen in place, the only response available to the controls was to cut

furnace exhaust by decreasing the flow transpor ted by the downstream booster fans. The 17

second full stroke time of the booster fan inlet guide vanes enab led controls to reduce furnace

exhaust by 43% in seven seconds. This flow reduction limited the nega tive furnace pressure

excursion during the fireball collapse.

# PNM – San Juan Generating Station Unit 1 Page 56 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# Because the MFT fireball collapse happened so quickly, a kicker circuit was necessary to

reduce the booster fan in let guide vane position demand. Th e air heater gas outlet pressure

controls alone were not fast enough to close booster fan inlet guide vanes to achieve the 43%

reduction in furnace ex haust necessary to mitigate the MFT. Upon initiation of an MFT, a

kicker circuit immediat ely reduced demand to th e booster fan inlet guid e vanes by 46%. This

quick change in demand closed the booster fan inlet guide vanes sufficiently to reduce the

furnace exhaust flow and hold the furnace pressu re excursion to –1.2 inwc during a full load

MFT.

A fast-acting booster fan runback control was crit ical to mitigating the “Low Load Two Booster

Fans Runaway” transient. When the furnace pressure dropped below –1 inwc, the booster fan

runback controller overrode no rmal controls and adjusted boos ter fan inlet guide vanes to

maintain +1 inwc furnace pressure. During the “Low Load Two B ooster Fans Runaway”

transient, the booster fan runback controls be gan to decrease booster fan inlet guide vane

positions after the runaway had opened the vanes to 79%. If the booster fan inlet guide vanes

had driven full open, the furnace pressure excursi on would have been more severe than the –3.7

inwc measured during the transient.

Based on the results of the transient runs, TR AX recommends the following control strategies

and mitigating measures be implemented in the future plant configuration controls:

1. During normal operation, adjust the booster fan in let guide vanes via a control that uses

an FD inlet guide vane demand feed-forward, a dded to a trim controller that monitors air

heater gas outlet pressure.

2. For mitigating MFT events, a kicker circuit should be used to immediately run back

booster fan inlet guide vanes. The kicker would be activated by the MFT circuit and

should last 15 seconds. The kick value is a function of a feed forward signal of the FD

fan demand and the relation is shown in Table 10.

FD Fan Feed-Forward Signal (%) Kick Value (%)

0 0

50 –20

100 –60

Table 11 Kick Values



# The extent of the booster fan runback should be load dependent—i.e. at lower loads, the

extent of the booster fan runb ack would be less than a ru nback during an MFT at full

load.

3. An overriding booster fan runback controller should be used to help mitigate negative

furnace pressure excursions. The runback controller should take precedence over normal

controls and operator auto/manual stations. When active, the runba ck controller would

adjust booster fan inlet guide vanes to maintain a positive furnace pressure. The

controller should go ac tive if furnace pressure drops below –1 inwc without an MFT

occurrence.

# PNM – San Juan Generating Station Unit 1 Page 57 of 57

Furnace Draft Analysis – Final Report 3/27/2008

Project Number EA0711 

# 4. On an all booster fan trip, there are two alte rnate control strategies that have merit for

mitigating positive and negative pressure excursions:

a. Trip FD fans on a high furnace pressure limit

b. Trip FD fans immediately

Tripping both FD fans if the furnace pre ssure exceeded +15 inwc prevented overpressurizing the furnace following an MFT. However, by immediat ely tripping the FD

fan, high positive pressures were avoided, but a furnace pressure minimum of –3.3 inwc

was experienced. Note that tripping the FD fans immediately upon loss of all booster

fans is in compliance with a strict interpretation of the NFPA guidelines.

5. If a single booster fan is tripped, the mass flowing through the system should be reduced

in order to prevent over-pressurize the furnace via a runback. A load reduction from

100% to 70% at a rate of 30 MW/min reduced the maximum furnace pressure value by

3.7 inwc as compared to the unmitigated transient.

# REFERENCE SECTION

This Reference Section is a supplement to the San Juan Generating Station Units 1 & 2 Final

Report Number EA0711-0103.

The following additional reference information is provided in this sectio n, subdivided into the

following categories, each cont aining a list of contents:

1. Schematics

2. Validation Runs

3. Transient Runs

4. Letter Report

# 1. SCHEMATICS

The Unit 1 Process Schematics contain the following pages:

• INDEX 1–1

• FANS AND AIR HEATERS 2–1

• FURNACE 3–1

• PULVERIZERS A–D 1–2

• BAGHOUSE AND BOOSTER FANS 2–2

• SCRUBBERS AND STACK 3–21122334455667788AABBCCDDPrepared bySVPDrawing No.EA0711.02 - 01 - 001 page 1-1Date26 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft Analysis Process Model - Proposed ConfigurationPROCESS MODELSAN JUAN GENERATING STATION UNIT 1FURNACE DRAFT ANALYSIS2-2Key:ProTRAX Module NameModule IDFlow Stream IDFSIDFSIDConnectorCoordinates of matching connector on page p-pPage number of matching connectorp-p (xy)'MID'FANPUBLIC SERVICE COMPANY OF NEW MEXICO1-1INDEX1-2PULVERIZERS A-D2-1FANS ANDAIR HEATERS3-1FURNACEBAGHOUSE ANDBOOSTER FANS3-2SCRUBBERS ANDSTACK1122334455667788AABBCCDDPrepared bySVPDrawing No.EA0711.02 - 01 - 001 page 2-1Date26 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft Analysis Process Model - Proposed ConfigurationLB_1EPS_1EPS2_1LB2_1EPAHLB_1EPAHB_1LPSCAHB_1EBPAHB_1EPAHLA_1EPAHA_1LPSCAHA_1EBPAHA_1LSOFA_1LOFA_1ESAHLA_1ESAHA_1LBSAHA_1GLSAHB_1ESAHLB_1ESAHB_1LBSAHB_1ETDD_1ETDC_1ETDB_1ETDA_1LTA2_1LTA_1

E T A 2

_ 1LPAOSB_1ETA_1

L P A O S A

_ 1ESOFA_1EOFA_1EBSAHA_1EBSAHB_1EFDOSA_1LFDA_1LDWB_1LDWA_1

E P A G C D B _ 1EPAB_1LFDXO_1EFDXO_1LPAHB_1LPAHLB_1LPAGSOB_1 GLPAHB_1GEPAHB_1EDWA_1LSCASO_1

L S C B S O _ 1

L S A H B

_ 1EHPAH1_1LPAHA_1LPAGSOA_1GLPAHA_1EPAGCDA_1GEPAHA_1

E S B G S O

_ 1GESAHB_1GESAHA_1ESAGSO_1LSAHA_1EDWB_1GLSAHA_1

E F D B _ 1

EF D A_ 1LPAB_1

L F D B_ 1LPAA_1EPAA_1LPAHLA_1LSAHLB_1LSAHLA_1EPAOSB_1

E P A O S A _ 1EFDOSB_1LFDOSB_1LFDOSA_13-2 (D7)To StackFANS AND AIR HEATERSDAMPER'FDOSA_1''J5_1'DAMPER'FDOSB_1''J11_1'DAMPER'PAOSA_1'FD Fan A'J12_1'DAMPER'PAOSB_1'Primary Air Fan A1-2 (B2)1-2 (B2)1-2 (D2)1-2 (C2)3-1 (B5)From ESP3-1 (B5)3-2 (D7)3-2 (B7)3-1 (C1)SCAHSAH BOutletShutoffAtmosphereAtmosphereTo Furnace'J16_1''J17_1'DUCT'TA_1'OutletShutoffDUCT'SAHLA_1'DUCT'SAHLB_1'3-2 (A7)To Stack3-2 (C7)DUCT'PAHLA_1'3-1 (A5)3-2 (C7)From ESPFrom ESPPAH BTo Booster FansTo Booster FansPrimary Air Fan BOutletShutoffDUCT'DWA_1'FD Fan BFANTAB'PAA_1'FANTAB'FDA_1'FANTAB'FDB_1'FANTAB'PAB_1'BC'BCA_1'BC'BCB_1'RHTRFD'PAHA_1'RHTRFD'SAHA_1'RHTRFD'SAHB_1' PLNMRV 'PN20_1'DAMPRN'SAF_1'1-2 (C1)Air Sleeves & RegistersDUCT'DWB_1'

PLNMRV 'PN29_1'SCAHDAMPER'SCASO_1'DAMPER'SAGSO_1'DAMPER'SCBSO_1'DAMPER'SBGSO_1'DAMPER'PAGCDA_1'DAMPER'PAGSOA_1'DUCT'PSCAHA_1'Temp Air to Pulverizer BTemp Air to Pulverizer ATemp Air to Pulverizer DTemp Air to Pulverizer C'JHP_1'Hot Primary Air toPulverizers A,B,C, DSAH ATo StackDAMPRN'OFA_1'NOX PortsRHTRFD'PAHB_1'DUCT'PSCAHB_1'3-2 (C7)DAMPER'PAGSOB_1'DAMPER'PAGCDB_1'3-2 (B7)DUCT'PAHLB_1'PAH LkgPAH A

DAMPER 'FDXO_1'3-1 (A5)From ESPREF :Stearns-Roger L-22325'JA21_1''J4_1'BANK'BSAHB_1'BANK'BSAHA_1''J32_1''J33_1'DUCT'TA2_1' PLNMRV 'PN1_1''J22_1''J23_1'3-1 (B1)To FurnaceBANK'BPAHA_1''J24_1'BANK'BPAHB_1''J25_1'PAH LkgTo Stack'J29_1''J30_1'OutletShutoffSAH LkgSAH Lkg1122334455667788AABBCCDDPrepared bySVPDrawing No.EA0711.02 - 01 - 001 page 3-1Date26 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft Analysis Process Model - Proposed ConfigurationLBSOD_1LBSOC_1LBSOB_1LBSOA_1LOFA_1LSOFA_1EPSH_1ESHDIV_1LUEDPR_1LUECON_1

L F S H _ 1LRHDPR_1LRH_1ERH_1EECON_1

E F S H _ 1LPSH_1EPAGCDB_1

L B C DBC'BCD_1'FURNMF'FRN_1'LECON_1LESPA_1EPAGCDA_1ESAGSO_1ESBGSO_1LESPB_1LLKOUT_1ELKOUT_1LFRND_1LFRN_1LBRN_1LSEAL_1ELKIN_1LLKIN_1BANK'PSH_1'BANK'CONVSH_1'BANK'RH_1'BC'SEAL_1'Water SealPendantSuperheaterConvSuperheaterReheaterUpperEconomizer BANK

'ECON_1'LowerEconomizerFURNACEFurnaceFurnaceIn-Leakage

DUCT

'LKIN_1' BCATM

'LKBC_1'DUCT'FRND_1' PLNMRV 'PLK_1'BC'L2BC_1'DUCT'LKOUT_1'AtmosphereFurnaceOut-LeakageDUCT'ESPB_1'

PLNMRV

'ESPR_1'Hot-SidePrecipitator2-1 (C5)To SecondaryAir Heater A2-1 (A5)To SecondaryAir Heater B2-1 (D6)To PrimaryAir Heater ADUCT'ESPA_1' PLNMRV

'PL1_1'EESPA_1EESPB_1BURNMF'BRN_1'2-1 (C6)To PrimaryAir Heater B'JFB1''JFB2'REF :Stearns-Roger L-22325DAMPRN'RHDPR_1'DAMPRN'UEDPR_1'BANK'UECON_1'BANK'SHDIV_1'Division walls2-1 (B7)2-1 (A7)From Windbox1-2 (D7)From WindboxPrim Air & CoalFrom Pulverizer A1-2 (C8)1-2 (B8)1-2 (A8)From Pulverizer BFrom Pulverizer CFrom Pulverizer D1122334455667788AABBCCDDPrepared bySVPDrawing No.EA0711.02 - 01 - 001 page 1-2Date26 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft Analysis Process Model - Proposed ConfigurationLBSOD_10 W334.6 P157.4 T19.57 HLBSOC_1LBSOB_1LBSOA_1EBSOD_1EHDD_1ETDD_1EPASOD_1EPACD_1LHDD_1LTDD_1LPACD_1EPVD_1LPVD_1LPVC_1EPVC_1EPVB_1LPACC_1LPACB_1 E P V A _ 1LPACA_1EHPAH1_1LHAH1_1EPASOC_1EPASOB_1EPACC_1EPACB_1EPACA_1EPASOA_1EHDC_1EHDB_1EHDA_1ETDC_1ETDA_1ETDB_1LHDA_1LTDA_1LPVA_1EBSOA_1LTDB_1LHDB_1LTDC_1LHDC_1LPVB_1EBSOC_1EBSOB_1PULVBR'PVA_1'2-1 (D8)DAMPER'TDA_1'DAMPER'HDA_1''JBA_1''JCA_1'DAMPRC'BSOA_1'Tempering DamperHot Air DamperDAMPER'TDB_1'DAMPER'HDB_1''JBB_1'PULVBR'PVB_1''JCB_1'DAMPRC'BSOB_1'DAMPER'TDC_1'DAMPER'HDC_1''JBC_1''JCC_1'DAMPRC'BSOC_1'2-1 (D8)Temp Air fromPA PlenumTemp Air fromPA PlenumTemp Air fromPA PlenumPulverizer APulverizer BPulverizer CPULVERIZERS A - D PLNMRV 'HP1_1'2-1 (D7)2-1 (C8)Hot Air fromPrimary Air HeaterDAMPER'PASOA_1'DAMPER'PACA_1'DAMPER'PASOB_1'DAMPER'PACB_1'DAMPER'PASOC_1'DAMPER'PACC_1'Primary AirShutoff DamperPrimary AirControl DamperBurner Coal ValvesDUCT'HPAH1_1'Hot Primary AirHeader A'JDA_1''JDB_1''JDC_1'PULVBR'PVC_1'REF :Stearns-Roger L-22325Primary AirShutoff DamperPrimary AirControl DamperDAMPER'TDD_1'DAMPER'HDD_1''JBD_1''JCD_1'DAMPRC'BSOD_1'2-1 (C8)Temp Air fromPA PlenumDAMPER'PASOD_1'DAMPER'PACD_1'Burner Coal Valves'JDD_1'PULVBR'PVD_1'Pulverizer D3-1 (D1)To Furnace3-1 (C1)3-1 (C1)3-1 (C1)To FurnaceTo FurnaceTo Furnace1122334455667788AABBCCDDPrepared bySVPDrawing No.EA0711.02 - 01 - 001 page 2-2Date26 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft Analysis Process Model - Proposed ConfigurationLBHBPD_1EBHBPD_1LEBFD_1LEBFJ_1LBHOLD_1LBHPL_1LBHD_1LBHILD_1EBHILD_1LDBBH_1

L B B H P L _ 1

LSADB_1 L S A D A

_ 1LBFODC_1LBFODB_1LBFODA_1LBFA_1LBFB_1EBFODC_1LBFC_1EBFODB_1EBFODA_1EBFC_1

E B F B _ 1EBFA_1LBFIDC_1

L B F I D B _ 1LBFIDA_1

E B F I D C

_ 1 EBFIDA_1 E B F I D B _ 1BAGHOUSE AND BOOSTER FANS PLNMRV 'EBFPL_1'DAMPER'BFIDA_1'FANTAB'BFA_1'DAMPER'BFODA_1'DAMPER'BFIDB_1'FANTAB'BFB_1'DAMPER'BFODB_1'DAMPER'BFIDC_1'FANTAB'BFC_1'DAMPER'BFODC_1'Booster Fan ABooster Fan BBooster Fan C'BFDJ_1''BFEJ_1''BLCJ_1''BOAJ_1''BOBJ_1''BOCJ_1'REF: B&W 561902E-Rev. CB&W 561905E-Rev. CB&W 81126J-Rev. 01B&W 521137E3-2 (C1)3-2 (B1)3-2 (A1)To Scrubber ATo Scrubber C3-2 (D4)3-2 (A4) PLNMRV 'BBHPL_1'DUCT'DBBH_1''BBHJ_1'DAMPER'BHILD_1'DAMPER'BHOLD_1'DUCT'BHD_1' PLNMRV 'BHPL_1''EBFJ_1'To Scrubber BDUCT'EBFD_1'DAMPER'BHBPD_1'BaghouseBaghouseInlet DamperBaghouseOutlet DamperBaghouseBypass DamperFrom SAH BFrom SAH A1122334455667788AABBCCDDPrepared bySVPDrawing No.EA0711.02 - 01 - 001 page 3-2Date26 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft Analysis Process Model - Proposed ConfigurationLSBC4C_1LBFODC_1LBFODB_1LBFODA_1LFE_1LFGDPL_1

L S A D B _ 1

L S A D A _ 1LFGDBD_1 ESTK_1ED121_1 LSBDB_1

L S B D A

_ 1LSTK_1LPAHLB_1LPAGSOB_1LPAGSOA_1GLSAHB_1GLSAHA_1ESBDB_1ESBDA_1LPAHLA_1LSAHLB_1LSAHLA_1ESADB_1 E S A D A _ 1LPB_1EPB_1LPA_1EPA_1LSBC3C_1LSBC2C_1LSBC1C_1LWWBCC_1LSBC4B_1LSBC3B_1LSBC2B_1LSBC1B_1LWWBCB_1LSBC4A_1LSBC3A_1LSBC2A_1LSBC1A_1LWWBCA_1 L F G D C D

_ 1

L F G D A D _ 1FGDSCB'FGDC_1'FGDSCB'FGDB_1'FGDSCB'FGDA_1'LFGDC_1

L F G D B _ 1LFGDA_1

EF G D C _ 1

E F G D B _ 1

E F G D A _ 1BC'ATMSK'Stack'BFCJ_1''BFBJ_1''BFAJ_1' PLNMRV 'FGDPL_1'DUCT'FGDAD_1'DUCT'FGDBD_1'DUCT'FGDCD_1'BC'WWBCA_1'BC'SBC1A_1'BC'SBC2A_1'BC'SBC3A_1'BC'SBC4A_1'BC'WWBCB_1'BC'SBC1B_1'BC'SBC2B_1'BC'SBC3B_1'BC'SBC4B_1'WashWaterSlurryEnteringSlurryEnteringBC'WWBCC_1'BC'SBC1C_1'BC'SBC2C_1'BC'SBC3C_1'BC'SBC4C_1'SlurryEntering2-1 (B3)2-1 (D4)2-1 (A4)'J411_1''J412_1''J413_1' DUCT 'PA_1' DUCT

'PB_1'DUCT'SADA_1'DUCT'FE_1'DUCT'SADB_1'From SecondaryAir Heater AFrom SecondaryAir Heater BFrom PrimaryAir Heater A2-1 (B3)LeakageFrom SecondaryAir Heater A2-1 (A3)LeakageFrom SecondaryAir Heater B2-1 (D3)LeakageFrom PrimaryAir Heater A

DAMPER

'SBDA_1' DAMPER 'SBDB_1'Scrubber Module AScrubber Module BScrubber Module C2-1 (C4)From PrimaryAir Heater B2-1 (C4)STACK'STK_1''J44_1'

DUCT 'D121_1'REF: B&W 521137E2-2 (D1)2-2 (B1)To BaghouseTo BaghouseWashWaterWashWaterSCRUBBERS AND STACK2-2 (D8)2-2 (C8)2-2 (B8)From Booster Fan AFrom Booster Fan BFrom Booster Fan CLeakageFrom PrimaryAir Heater B

# The Unit 1 Controls Schematics contain the following pages:

• INDEX 1–1

• LEGEND 2–1

• SEC AIR CNTRL & OXYGEN TRIM 3–1

• FD DEMAND 4–1

• PRIMARY AIR PRESSURE 5–1

• MASTER FUEL TRIP 6–1

• EQUIPMENT SHUTDOWN 7–1

• BOOSTER FANS 8–1

• PULVERIZER/COMPARTME NT A CONTROLS 1–2

• PULVERIZER/COMPARTME NT B CONTROLS A 2–2

• PULVERIZER/COMPARTME NT C CONTROLS 3–2

• PULVERIZER/COMPARTME NT D CONTROLS 4–2

• AIR HEATER INLET DAMPERS 5–2

• PRIMARY AIR SHUTOFF DAMPERS 6–2

• BAGHOUSE DAMPERS 7–2

• FD FAN TRIPS 1–31122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 1-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration FD DEMANDPRIMARY AIRPRESSUREMASTER FUELTRIPLEGENDPULVERIZER/COMPARTMENT ACONTROLSINDEX1-11-22-23-2CONTROLS MODEL2-1PULVERIZER/COMPARTMENT BCONTROLSPULVERIZER/COMPARTMENT CCONTROLSPULVERIZER/COMPARTMENT DCONTROLS4-23-14-1 5-1SEC AIR CNTRL &OXYGEN TRIM6-1EQUIPMENTSHUTDOWN7-1SAN JUAN GENERATING STATION UNIT 1FURNACE DRAFT ANALYSISPUBLIC SERVICE COMPANY OF NEW MEXICOBOOSTER FANS8-1AIR HEATERINLET DAMPERSPRIMARY AIRSHUTOFF DAMPERS5-2 6-2FD FAN TRIPS1-3BAGHOUSEDAMPERS7-21122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 2-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration LEGENDPROCESS VARIABLE FROMFIELD TRANSMITTERLEAD-LAGLIMIT HIGHValve DetailsCYxyz= Valve Demandxyz = Valve PositionModule IDYOUTPUT TOFINAL CONTROL ELEMENTPROCVAR*ID*IDVALVE*IDSUM*IDTRANSFERDIFFERENCEDIVIDEDERIVATIVEBIASBIAS*IDd*IDdt*IDf(x)*ID~1 + ks*ID1 - 2s*ID>*ID> <LIMIT HIGH LOW*ID<LIMIT LOWX*IDMULTIPLYOR*IDLOGIC ORNOT*IDLOGIC NOTK/S/D*IDPID CONTROLLERK*IDPROPORTIONAL*IDRAMP>*ID<*IDHIGH SELECTLOW SELECTAMANUAL ANALOG SETMANUAL INTEGER/DISCREET SET*IDSQUARE ROOTf(t)*IDdoTIME DELAY*IDANDLOGIC AND*IDAUTO MANUAL STATIONFUNCTION GENERATORVELOCITY LIMITER*IDV<K/S*IDFLIP FLOPPI CONTROLLERACCUM1*IDINTEGRATORACCUM2*ID2-INPUT INTEGRATORWITH LIMITSH/*ID*IDH/L/L*IDHIGH SIGNAL MONITORHIGH/LOW SIGNAL MONITORLOW SIGNAL MONITORMEM2DIGITAL OUT WHEN INPUTIS ABOVE SETPOINTDIGITAL OUT WHEN INPUTIS BELOW SETPOINTDIGITAL OUT WHEN INPUTIS ABOVE HIGH SETPOINTOR BELOW LOW SETPOINTORAN*IDAVERAGE0 = Auto1 = Manual1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 3-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration AVGPVDMDTOTFUELTOTFUELHL2VH2HL1VH1DB11LP46_OUTLIMBFDIFFLIMFUELMB1_2B9BSPAIRWAIRLIMB5FUEL_MULTPIB5DB5MB1_2BTUCSTMFLSPAIRWAIRSCAT421SUM51DB10SPVDMDPIB11FMSTRFGB9BLIMFUELDLAIRLIMAIRLIMAIRAIRMINFUELBIASAIRBIASGENDMDGENDMDWEPVDWEPVCSUM51EBI51AFX51CBLRDMDWEDWBWEDWAWEPVBWEPVAECONO2O2TRIMKS51BE51BKS51AE51AMULT51AWAIRTOTAIRSUM51AFuel Demand'SUM51A''SUM51C'Primary Air Flowf(x)'FX51A'X'MUL51A''E51A'K/S'KS51A''SUM51D'

4-1 (D1) PROCVAR

'ECONO2''E51B'K/S'KS51B''LIM51B'><Pulverizer DemandFlue Gas O2Airflow Demandto FD Fans

3-1 (C6)SEC AIR CNTRL & OXYGEN TRIM1-2 (D1)4-2 (D1)2-2 (D1)3-2 (D1) PROCVAR

'WEPVA' PROCVAR

'WEPVB' PROCVAR

'WEPVC' PROCVAR

'WEPVD''SUM51E'

PROCVAR

'WLDWA' PROCVAR

'WLDWB'Secondary Air Flow 4-1 (C3)f(x)'FX51C'BIAS'BI51A'Firing Demand0-2885(KPPH)(0-100%)FD Fan MasterREF : FOXBORO DRAWING NO00F72719-FD-0010-Rev. 0200F72719-FD-0017-Rev. 0200F72719-FD-0026-Rev. 0200F72719-FD-0029-Rev. 023-1 (D3)6-1 (C1)Total AirflowBIAS'AIRBIAS'BIAS'FUELBIAS'>'LIMAIR'<'LIMFUEL' 7-2 (D2)Total AirflowAFiring RateDemand>'LIMAIR1't-to'DTIM'B5B6-3B7B8-1B10B10B10B10B9-1B9-2B9-1B9-2B23AB24ATotal Fuel Flow(Add All Fuel to Pulverizers)(0-100 %)K/S'FMSTR''B10S'f(x)'FGB9B'B9BB10B10B10B10Average PulverizerDemandK/S'PIB11'Integral OnlyB11B11'LIMB11'> <B11B6B6B6B40.8 to 1.230%'LIMB10'>'LIM51A'>102OUT00100INPROCVAR'STMFL'f(x)'BTUC''DB5'X'MB1_2'K/S'PIB5''LIMB5'> <BTU CompensatorIntegral OnlyB5B5B5LOOPA'LOOP45'LOOPA'LOOP46'f(x)'B9B''FDIFF''DB11'AAPROCVAR'PTOTFUEL' PROCVAR

'PAVGDMD'1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 4-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration LIMB11ALP2_OUTFDTVFDTSCYFDOSACYFDOSBFX31DCYFDBTR31BTR31ATR31BLP1_OUTTR31ALIMB18LIMB18SA31BSI31BTR31BBI31BAUT31BLIMB11ALIMB14LIMB14FX31CCYFDATR31ALIMB11AKS31ASCAT421FDAVGDMDGROSS_MWGENDMDBLRDMDGENDMDAUT31AFDB_TRPFDA_TRPNFDSFDANFDANFDSFDBNFDBBI31ASA31ASI31AE31A'E31A'K/S'KS31A'BIAS'BI31A''TR31A'ACYFDAFD Fan AInlet Guide Vanes PROCVAR

'GENDMD'Firing Rate DemandAA'TR61A'A'TR61B'FD Fan A SpeedFD Fan B Speed1-3 (D3)1-3 (B3)'AUT31A'Firing Demand

3-1 (D8)f(x)'FX31B'1180 RPMf(x)'FX31C'CYFDOSAFD Fan AOutlet Shutoff Damperf(x)'FX31B1'FD Fan ADemand4-1 (D2)FD Fan ADemand'FDAVGDMD'

4-1 (B2) 4-1 (A6)FD Fan BDemand

3-1 (A6)AirflowDemandB8-2B11B11B14B14B14B151000100050OutInFD FAN SPEEDREF : FOXBORO DRAWING NO00F72719-FD-0026-Rev. 0200F72719-FD-0027-Rev. 02'LIMB11A'> <'LIMB14'> <f(x)'FX120A'B14f(x)'FX120C'BIAS'B131B''TR31B'ACYFDBFD Fan BInlet Guide Vanes'AUT31B'f(x)'FX31D'CYFDOSBFD Fan BOutlet Shutoff Damper4-1 (D2)FD Fan BDemandB18B18B18B151000100050OutIn'LIMB18'> <f(x)'FX120B'B18f(x)'FX120D'LOOPA'LOOP1'LOOPA'LOOP2'AFD DEMAND8-1 (C1)FD Fan DemandTo Booster Fan1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 5-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration PFURNACEPFURNACEMAXPVDMDB511FX41ANPANPACYPAOSBTR41HCYPAOSATR41GCYPABTR41BTR41BTR41BCYPAATR41ATR41ATR41ALP4_OUTTR41BLP3_OUTTR41APADIFPLPAHKS41ASI41DSA41DAUT41DFX41DSI41CSA41CAUT41CFX41CKS41BKS41BAUT41BAUT41AAVE41ATRPPABPABZERONPABTRPPAAPAAZERONPAASI41BSA41BSI41ASA41AE41BE41A

PROCVAR

'PV41A'Pri Air Duct PressHighestFeederDemandf(x)'FX41A''E41A'K/S'KS41A''E41B'K/S'KS41B'N'AVE41A''TR41A''TR41B'AACYPAACYPABPA FAN SPEED'TR41D'A'TR41F'A'AUT41A''AUT41B''TR41G'ACYPAOSA'AUT41C'f(x)'FX41C''TR41H'ACYPAOSB'AUT41D'f(x)'FX41D'1790 RPMPA Fan AInlet Guide Vanes10001000501000100050B3B4B45-1 (D3)5-1 (D4)

5-1 (A2) 5-1 (A5)Integral OnlyB5B5B8B9B11B12'PADIF'Furnace PressureOutInOutInLOOPA'LOOP3'LOOPA'LOOP4'REF : FOXBORO DRAWINGNO 00F72719-FD-0030-Rev. 02f(x)'FX121A'f(x)'FX121B'f(x)'FX121C'f(x)'FX121D'ABIAS'B511'PRIMARY AIR PRESSURE PROCVAR

'PMAXPVDMD'

PROCVAR

'PFURNACE'PA Fan AOutlet Shutoff DampersPA Fan BInlet Guide VanesPA Fan BOutlet Shutoff Dampers8-1 (B8)PA Fan B SpeedPA Fan A SpeedPA Fan Inlet Guide Vane Demand1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 6-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration PFURNACEPFURNACETRIP_PA_FANSTRIP_ALL_BFDHBDPBHDELPHBHDPMFTFCLSPULDMPRWAIT8MFTWAIRRHTBLKMFTBA6TD61ANO_PA_FANSMFTWAIT7FREEZE_FD_IGVWAIT6FEEDER_TRIPMFTMFTMFTMFTMFTFDR_NOSTOPMFTCNO_FD_FANSMFTFMFTELO61APLPAHWAIT5CLOSE_COAL_VALVESWAIT1TRIP_PULVWAIT2WAIT3IGNITOR_TRPMFTALO61BHI61AMFTDLO61CMFTSETMFTRESET'A1'AND'A2'AND'A3'AND'A5'ANDPROCVAR'PV61A'PROCVAR'PV61C'OR'OR61A'/L'LO61B'f(t)pu'TD61B'PROCVAR'PV61B'H/'HI61A'< -7 inwcf(t)pu'TD61C'OR'SMFT2'3 sPrimary Air Duct PressureFurnace Pressure< 25%3 sf(t)pu'TD61A'< +47.7 inwc5 s/L'LO61C'> +34.4 inwc3 sf(t)pu'TD61D'Secondary Air FlowMEM3'MMFT'Both PA fans tripped/L'LO61A'Loss of FD fansMFT Emerg. PBf(t)pu'TD61E'0 s'A6'ANDPROCVAR'PV61F'All Feeders Not StoppedReheater BlockedIgnitor Fuel TripPulverizer Trip'A7'ANDClose BurnerCoal ValvesFeeder Trip'A8'ANDFreeze FD IGVREF : Currently the MFT logic comes from the logic for Unit 4.TRAX expects the MFT logic to be similar to Unit 4 logic3-1 (C6)'A9'ANDClose Pulverizer AirShutoff Damper7-2 (D2)To Baghouse Dampers9-2 (B5)H/'HI61A1'> +14.0 inwcBaghouse DPf(t)pu'TD61C1'5 s7-2 (C7)Trip All Booster FansMASTER FUEL TRIP7-1 (B1)PA Fan Trip5-1 (D2)1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 7-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration TRIP_PA_FANSFDB_TRPFDA_TRPPAB_TRPTRIP_PA_FANSPAA_TRPYBSOYBSOYBSOYBSONPULVNPULVNPULVNPULVTRPPULVTRPPULVTRPPULVTRPPULVNPVANPVBNPVCNPVDTRPVATRPVBTRPVCTRPVDSA71BSA71CSA71DSA71FSI71FSI71DSI71CSI71BCYBSOACYBSOBCYBSOCCYBSODAA'TRPA15''TRPA16'ABURNER COAL VALVES'TRPA17'A'TRPA18'AA'TPVA''TPVB''TPVC''TPVD'PULVERIZERSAMFT6-1 (D8)OR'OR41A'FD Fan A trippedMFT6-1 (D8)OR'OR41B'FD Fan B trippedPA Fan B tripped1-3 (D3)1-3 (B3)PA FANSEQUIPMENT SHUTDOWNPA Fan A trippedPulverizer ASpeedCYBSOACYBSOBCYBSOCCYBSODNPVA NPVB NPVC NPVDPulverizer BSpeedPulverizer CSpeedPulverizer DSpeedBurner ACoal ValveBurner DCoal ValveBurner CCoal ValveBurner BCoal Valve1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 8-1Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration FDFFSKICKTFFMPULFDFFSKICKBFRBYBFAPFURNACEMFTPFURNACEMPULMFTS332S332S332BFRBPSAD

F D F S SMFTLIMB11ALIMB11ABFRBBFRBBFRBPIBFPIBFPIBFCYBFACYBFBCYBFCAUT81AAUT81BAUT81CD312FDFFSV_0_AV_100_APID331_LOCLAMPPID331_HICLAMPFDFFSPSADNORMMPULKICKTFFKVALSPT_BFRBACKDF331TP6NT6IR333MAND7BFLPPID331PIBFNT8NT7BTRKO67BFRBRSTRB

Y B F A'TR81A'CYBFABooster Fan AInlet Guide Vanes'TR81B'CYBFB'TR81C'CYBFC'AUT81A''AUT81B''AUT81C'Normally in Auto 9-2 (B6)'D331'Airheater GasOutlet Duct Pressure (inwc)K/S/D'PID331''S332'4-1 (C2)K'PP332'From FD DemandSetpoint0.0 inwcFD Feed ForwardX 1.0'D502''D503'AAHigh and Low Clamps for PID3318-1 (C4)'MAND6'ANDf(x)'FX41A1'ANormally in AutoNormally in Auto6-1 (D6)'TR333'A'PUL'f(x)'FX41A2'MFT Kicker CircuitMFT20 s'S333'8-1 (C3)Normally Zero 5-1 (D2)'DF331'AK/S/D'PIBF'6-1 (D6)f(t)pu'TP6'8-1 (D3)NOT'NT6'NOT5-1 (D2)6-1 (D6)NOT'MAND7'ANDNOT'NT7'OR'O67'8-1 (A6)/L'BFLP' 8-1 (B4)8-1 (C8)NOTNOT'NT8'8-1 (A8)8-1 (A8)8-1 (A8)8-1 (C8)8-1 (C8)8-1 (C8)8-1 (D4)5 s< -1 inwcMFT inProgressBF KickerActiveFurnacePressureMFT inProgressBooster Fan RunbackController ActiveFurnacePressure-1 inwcBooster FanPosition FeedbackBooster FanRunback ControllerActiveTracking SignalTracking Switch

8-1 (C3)'D811'8-1 (C8)Tracking SignalBF RunbackController ActiveMEM2'MRB'P = 1I = 10 sX Y0 050 -20100 -60X Y0 0100 50P = 10I = 1 sPROCVAR'P1'Booster FanDemand OverrideBOOSTER FANSBooster Fan BInlet Guide VanesBooster Fan CInlet Guide Vanes8-1 (C6)MFT Impulse8-1 (D6)Booster Kicker8-1 (D6)FD Feed ForwardFD Feed ForwardMFT ImpulseBooster Fan AIGV Position1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 1-2Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration LDGAIN12FX12ADIV12WEPVADIV12ALDLAG12CYTDATR12DKS12CCYHDATR12CCYPACATR12BNFPVATR12AKS12CKS12CLIM12ACASPTTLPVAPVDMDLIM12ASUM12AKS12BBI12AE12BSI12CSA12C S I 1 2 D

S A 1 2 DSA12ASI12ASI12BSA12BPV12BE12APROCVAR'PV12E'PROCVAR'PV12D''E12B''TR12C'ACoal AirTemperaturePulverizer ATempering Air DamperCYHDA'TR12D'ACYTDAPROCVAR'PV12B'Pulverizer BiasFeeder Demand'SUM12A''TR12A'NFPVAAK/S'KS12B''TR12B'ACYPACAPulverizer APrimary AirControl DamperFeeder ASpeed Control PROCVAR

'PV12C''E12A'BIAS'BI12A'f(x)'FX12A'K/S'KS12C'Pulverizer AHot Air Damper'LIM12A'> <3-1 (A4)Air Flow STPT0100OUTIN0100B6B6B11B11B13B135-2 (D2)Temp ControlOutputFeeder AREF : FOXBORO DRAWING NO 00F72719-FD-0020-Rev. 02f(x)'FXSPD2A'f(x)'FX108'f(x)'FX104A'f(x)'FX104B'~1 + ks'LDLAG12'1 - 2s'DIV12A'B7B2AB9K'K12'PULVERIZER/COMPARTMENT A CONTROLSCoal Air SetpointNormally 160 FPulverizer APA Air FlowTypical For Pulverizer B-D1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 5-2Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration LH3B1CYPAGCDBTRGID1CYPAGCDATRGIDSI41D2SA41D2LH3B2KS7B1DIFB8TLAHBLH3BSA41D1SI41D1KS7BDIFBCLH3BKS3BDIF3BSETPAMAXPAKS12CKS42CKS32CKS22CTLAHAPROCVAR'TLAHA'Primary AirHeater AAir Out Temp'DIFB7' 1-2 (C6) 2-2 (C6) 3-2 (C5) 4-2 (C5)Temp ControlOutputFeeder ATemp ControlOutputFeeder BTemp ControlOutputFeeder CTemp ControlOutputFeeder D>'MAXPA''DIF3B'A80%K/S'KS3B''LH3B'> <Integral OnlyK/S'KS7B''LH3B1'> <'TRGID'APROCVAR'TLAHB''DIFB8'K/S'KS7B1''LH3B2'> <'TRGID1'APrimary AirHeater BAir Out TempCYPAGCDAPrimary Air Heater AGas Inlet DamperCYPAGCDBPrimary Air Heater BGas Inlet DamperB1B3B3B3B7B7B7B10B10B10f(x)'FX88'f(x)'FX87'REF : FOXBORO DRAWING NO 00F72719-FD-0043-Rev. 02Hi Lim 600 FLo Lim 350 FAIR HEATER INLET DAMPERS1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 6-2Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration CYPASOCYPASOCYPASOLB103LB102LB101LB100CYPASORU190CSRU190CVCYPASOCCYPASODRU190DSRU190DVCYPASOBRU190BSRU190BVCYPASOARU190ASRU190AV'RU190A'ACYPASOAPrimary Air ShutoffDamper A'RU190B'ACYPASOB'RU190C'ACYPASOC'RU190D'ACYPASODPROCVAR'P11'BIAS'B100'BIAS'B101'BIAS'B102'BIAS'B103'Primary Air ShutoffDamper BPrimary Air ShutoffDamper CPrimary Air ShutoffDamper DPRIMARY AIR SHUTOFF DAMPERSPrimary AirShutoff DamperSetpoint1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 7-2Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration TLPJFFMFTFOR431OR431GENDMDCYBHBPDST431HIACTIS431OPENBYPIS432OPENINLST432AST432CYBHOLDST431AIS430TRIP_ALL_BFPEBFLLIMBFLIMLOWBFPOR431TRBFOK_TO_TRIPTRIP_ON_LOW_FURNACEWAIT9'TR431'CYBHBPDBaghouse Bypass Damper9-2 (C5)H/'SH431'MEM2'OPENBYP'OR'OR431'Temperature ofFlue Gas LeavingBaghouseResetCloseCYBHOLDBaghouseOutlet DamperMEM2'OPENINL'Set'TR432'ACloseA> 345 FAOpenAOpenMEM2'OPENBYP1'Reset1-3 (C1)Trip all Booster Fans/L'BFL'PROCVAR'P721'PROCVAR'P722'f(x)'FX2'Load-Based Trip (Normally Disabled)BF InletPressureADAPT'ADP'OR'OR432'6-1 (B5)'A821'ANDLow Furnace Pressure MFTUnit LoadX Y30 -9.4100 -22.1PROCVAR'P2'BAGHOUSE DAMPERS1122334455667788AABBCCDDPrepared byMGDrawing No.EA0711.02 - 01 - 002 page 1-3Date18 Sep 2007No.DateByDescriptionRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 1 Furnace Draft AnalysisControls Model - Proposed Configuration ONBFTPLDWBWAIT11TRIP_ALL_BFFDB_TRPFDA_TRPPLDWATLSAHAHI31ATLSAHBHI31BHI31DTRFDFDA_TRP_PBFDB_TRP_PBHI31CONBFTPROCVAR'PV31A'Secondary Air A DuctPressurePROCVAR'PV31B'Secondary Air A TempH/'HI31A'> +47.7 inwcH/'HI31B'> 620 FOR'OR31A'FD Fan A trippedPROCVAR'PV31C'Secondary Air B DuctPressurePROCVAR'PV31D'Secondary Air B TempH/'HI31C'> +47.7 inwcH/'HI31D'> 620 FOR'OR31B'FD Fan B trippedPROCVAR'PV31E'FD Fan A Operator TripPROCVAR'PV31F'FD Fan B Operator Trip'AD1'ANDf(t)pu'DL1'7-2 (C7)15 sTrip all Booster FansFrom Baghouse DampersFD FAN TRIPS

# 2. VALIDATION RUNS

The Unit 1 Validation Runs c ontain the following graphs:

• Furnace Pressure

• Windbox Pressure

• Coal Flow

• Secondary Airflow

• FD Fans Discharge Pressure

• PA Fans Discharge Pressure

• Economizer OxygenFurnace Pressure-50+5+10+15+20+250 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

Pressure (inwc)ModelFURNACE PRESSWindbox Pressure0+5+10+15+20+250 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

Pressure (inwc)ModelWINDBOX PRESSCoal Flow0204060801001201400 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

Flow (kpph)Model (per pulverizer)COAL FEEDER 1A FLOWCOAL FEEDER 1B FLOWCOAL FEEDER 1C FLOWCOAL FEEDER 1D FLOWSecondary Airflow020040060080010001200140016000 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

Flow (kpph)Model (Draught Side A)SEC AIR FLOW 1ASEC AIR FLOW 1BFD Fans Discharge Pressure0+5+10+15+20+250 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

Pressure (inwc)ModelFD FAN 1A DISCH PRESSFD FAN 1B DISCH PRESSPA Fans Discharge Pressure0+10+20+30+40+50+60+70+80+900 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

Pressure (inwc)ModelPA FAN 1A DISCH PRESSPA FAN 1B DISCH PRESSEconomizer Oxygen05101520250 10 20 30 40 50 60 70 80 90 100 110 120Time (seconds)

0 2 (percent)ModelModel with filteringECON FLUE 1A OXYGENECON FLUE 1B OXYGEN

# 3. TRANSIENT RUNS

Transient No. 1: “Full Load MFT” contains the following graphs:

• Transient Max/Min Pressure Profile (Unmitigated)

• Unit Pressures (Unmitigated)

• Baghouse and Scrubber Pressures (Unmitigated)

• Flows (Unmitigated)

• Fan Inlet Guide Vanes (Unmitigated)

• Fan Speeds (Unmitigated)Full Load MFT (Unmitigated)Transient Max/Min Pressure Profile-4.6+2.9+14.9+7.50.0-0.0-3.8-3.4+1.5+9.9+16.7+22.8+21.3+14.8+6.1+0.1-1.4-0.7+1.9-14.4-13.2-4.8-3.6-1.9-1.7-1.2+6.8+9.9+16.8+18.8-40-30-20-100+10+20+30+40 

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Pressure (inwc)MaximumMinimumFull Load MFT (Unmitigated)Unit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load MFT (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load MFT (Unmitigated)Flows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load MFT (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansFull Load MFT (Unmitigated)Fan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# Transient No. 2: “Full Load All Booster Fa ns Trip” contains the following graphs:

• Transient Max/Min Pressure Profile (Unmitigated)

• Unit Pressures (Unmitigated)

• Baghouse and Scrubber Pressures (Unmitigated)

• Flows (Unmitigated)

• Fan Inlet Guide Vanes (Unmitigated)

• Fan Speeds (Unmitigated)

• Mitigated Transient Max/Min Pressure Profile

• Mitigated Unit Pressures

• Mitigated Baghouse and Scrubber Pressures

• Mitigated Flows

• Mitigated Fan Inlet Guide Vanes

• Mitigated Fan Speeds

• Furnace Pressure Comparison

• Transient Max/Min Pressu re Profile ComparisonFull Load All Booster Fans Trip (Unmitigated)Transient Max/Min Pressure Profile-4.6+13.9+16.9+23.1+29.2+30.5+24.9+18.6+14.6+9.0+8.3-0.30.0+17.6+14.9+2.9+20.4+18.5+12.1+9.2+1.8+1.4+1.2+0.4+0.1-9.5-11.0+1.4-0.8-1.4-40-30-20-100+10+20+30+40 

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Pressure (inwc)MaximumMinimumFull Load All Booster Fans Trip (Unmitigated)Unit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load All Booster Fans Trip (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load All Booster Fans Trip (Unmitigated)Flows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load All Booster Fans Trip (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansFull Load All Booster Fans Trip (Unmitigated)Fan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster FansMitigated Full Load All Booster Fans TripTransient Max/Min Pressure Profile-4.6+10.7+13.5+20.3+27.3+28.8+22.4+15.1+11.4+6.2+5.5-0.30.0+14.2+14.9+2.9+0.5+0.4 +0.2+0.2-0.0-0.1-0.2-0.3-0.3-9.5-11.0-0.5-0.8-1.4-40-30-20-100+10+20+30+40 

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Pressure (inwc)MaximumMinimumMitigated Full Load All Booster Fans TripUnit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletMitigated Full Load All Booster Fans TripBaghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletMitigated Full Load All Booster Fans TripFlows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletMitigated Full Load All Booster Fans TripFan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansMitigated Full Load All Booster Fans TripFan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster FansFull Load All Booster Fans TripFurnace Pressure Comparison-40-30-20-100+10+20+30+40020406080100120Time (seconds)

Pressure (inwc)Furnace (Unmitigated)Furnace with FD Fan Trip (Mitigated)Full Load All Booster Fans TripTransient Max/Min Pressure Profile Comparison-4.6+2.9+14.9+17.60.0+8.3+9.0+14.6+18.6+24.9+30.5+29.2+23.1+16.9+13.9-0.3+5.5+6.2+10.7+11.4+13.5+14.2+15.1+20.3+22.4+27.3+28.8-40-30-20-100+10+20+30+40 

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Pressure (inwc)Maximum (Unmitigated)Maximum with FD Fan Trip (Mitigated)

# Transient No. 3: “Full Load Both FD Fa ns Trip” contains the following graphs:

• Transient Max/Min Pressure Profile (Unmitigated)

• Unit Pressures (Unmitigated)

• Baghouse and Scrubber Pressures (Unmitigated)

• Flows (Unmitigated)

• Fan Inlet Guide Vanes (Unmitigated)

• Fan Speeds (Unmitigated)Full Load Both FD Fans Trip (Unmitigated)Transient Max/Min Pressure Profile-4.6+0.1+6.1+14.7+20.9+22.4+16.6+9.9+1.5-4.2-4.4-0.50.0+7.5+14.9+2.9-0.3-0.6-2.4-3.6-6.9-7.2-7.4-7.7-8.0-9.5-11.0+0.4-1.0-1.5-40-30-20-100+10+20+30+40 

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Pressure (inwc)MaximumMinimumFull Load Both FD Fans Trip (Unmitigated)Unit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load Both FD Fans Trip (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load Both FD Fans Trip (Unmitigated)Flows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load Both FD Fans Trip (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansFull Load Both FD Fans Trip (Unmitigated)Fan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# Transient No. 4: “Low Load Two Booster Fa ns Runaway” contains the following graphs:

• Transient Max/Min Pressure Profile

• Unit Pressures

• Baghouse and Scrubber Pressures

• Flows

• Fan Inlet Guide Vanes

• Fan SpeedsLow Load Two Booster Fans Runaway (Unmitigated)Transient Max/Min Pressure Profile-4.6+2.0+18.7+1.70.0-0.1-3.5-3.0+0.0+2.2+4.1+5.8+5.4+3.6+1.3-0.4-1.1+0.2+6.7-12.1-11.3-7.3-6.8-5.0-4.5-3.7-2.2-1.6-0.2+0.2-40-30-20-100+10+20+30+40 

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Pressure (inwc)MaximumMinimumLow Load Two Booster Fans Runaway (Unmitigated)Unit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletLow Load Two Booster Fans Runaway (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletLow Load Two Booster Fans Runaway (Unmitigated)Flows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletLow Load Two Booster Fans Runaway (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansLow Load Two Booster Fans Runaway (Unmitigated)Fan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# Transient No. 5: “Full Load All Fans Trip” contains the following graphs:

• Transient Max/Min Pressure Profile (Unmitigated)

• Unit Pressures (Unmitigated)

• Baghouse and Scrubber Pressures (Unmitigated)

• Flows (Unmitigated)

• Fan Inlet Guide Vanes (Unmitigated)

• Fan Speeds (Unmitigated)Full Load All Fans Trip (Unmitigated)Transient Max/Min Pressure Profile-4.6+0.2+6.1+14.7+20.9+22.4+16.6+9.9+1.5-0.7-0.7-0.50.0+7.5+14.9+2.9+0.0-0.0-0.5-0.9-3.3-3.6-3.7-4.0-4.1-9.5-11.0-0.6-1.1-1.5-40-30-20-100+10+20+30+40 

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Pressure (inwc)MaximumMinimumFull Load All Fans Trip (Unmitigated)Unit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load All Fans Trip (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load All Fans Trip (Unmitigated)Flows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load All Fans Trip (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansFull Load All Fans Trip (Unmitigated)Fan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# Transient No. 6: “Full Load Single Booster Fan Trips” contains the following graphs:

• Transient Max/Min Pressure Profile (Unmitigated)

• Unit Pressures (Unmitigated)

• Baghouse and Scrubber Pressures (Unmitigated)

• Flows (Unmitigated)

• Fan Inlet Guide Vanes (Unmitigated)

• Fan Speeds (Unmitigated)

• Mitigated Transient Max/Min Pressure Profile

• Mitigated Unit Pressures

• Mitigated Baghouse and Scrubber Pressures

• Mitigated Flows

• Mitigated Fan Inlet Guide Vanes

• Mitigated Fan Speeds

• Furnace Pressure Comparison

• Transient Max/Min Pressu re Profile ComparisonFull Load Single Booster Fan Trips (Unmitigated)Transient Max/Min Pressure Profile-4.6+11.5+17.4+25.9+32.1+33.6+27.8+21.1+12.9+2.2+0.2-0.40.0+18.8+30.0+3.5+22.4+20.9+16.6+14.7+9.9+7.5+6.1+1.5+0.1-9.5-11.0+14.9+1.7-0.9-40-30-20-100+10+20+30+40 

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Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load Single Booster Fan Trips (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 50 100 150 200 250 300Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load Single Booster Fan Trips (Unmitigated)Flows0100020003000400050006000700080009000100000 50 100 150 200 250 300Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load Single Booster Fan Trips (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 50 100 150 200 250 300Time (seconds)

Position (percent open)FD FansBooster FansFull Load Single Booster Fan Trips (Unmitigated)Fan Speeds02004006008001000120014000 50 100 150 200 250 300Time (seconds)

Speed (rpm)FD FansBooster Fan ABooster Fans B & CMitigated Full Load Single Booster Fan TripsTransient Max/Min Pressure Profile-4.6+3.2+28.0+15.40.0-0.4-0.6+1.0+10.3+17.4+23.4+28.9+27.5+21.7+14.2+9.1-0.9+0.9+12.3-11.0-9.7-4.2-3.4-0.8-0.1+1.2+3.6+4.5+6.6+7.3-40-30-20-100+10+20+30+40 

### A mb

i ent F

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AH Air I nlet S

AH Air Ou

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urn

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agho u se

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agho u se

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cru

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t a ck Ba s e T

op

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Pressure (inwc)MaximumMinimumMitigated Full Load Single Booster Fan TripsUnit Pressures-40-30-20-100+10+20+30+400 50 100 150 200 250 300Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletMitigated Full Load Single Booster Fan TripsBaghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 50 100 150 200 250 300Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletMitigated Full Load Single Booster Fan TripsFlows0100020003000400050006000700080009000100000 50 100 150 200 250 300Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletMitigated Full Load Single Booster Fan TripsFan Inlet Guide Vanes01020304050607080901000 50 100 150 200 250 300Time (seconds)

Position (percent open)FD FansBooster FansMitigated Full Load Single Booster Fan TripsFan Speeds02004006008001000120014000 50 100 150 200 250 300Time (seconds)

Speed (rpm)FD FansBooster Fan ABooster Fans B & CFull Load Single Booster Fan TripsFurnace Pressure Comparison-40-30-20-100+10+20+30+40050100150200250300Time (seconds)

Pressure (inwc)Furnace (Unmitigated)Furnace with Load Runback (Mitigated)Full Load Single Booster Fan TripsTransient Max/Min Pressure Profile Comparison-4.6+11.5+17.4+25.9+32.1+33.6+27.8+21.1+12.9+2.2+0.20.0+18.8+30.0+3.5+1.0+9.1+28.9+27.5+23.4+21.7+17.4+15.4+14.2+10.3+28.0+3.2-0.4-0.6-40-30-20-100+10+20+30+40 

### Ambie n t FD Fa

n Out l et SAH Air Inlet SAH Air Outlet W

in

db

o x Fu

r nace Ec

o

no

m

izer Ou t le

t Precip Outlet SAH Gas O u t le

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ou

s e Outlet Boo s ter Fa

n Inlet Boo s ter Fa

n Outlet

Sc

r ubber O

utlet St

a c k Base To

p

o f

Stack

Pressure (inwc)Maximum (Unmitigated)Maximum with Load Runback (Mitigated)

# Transient No. 7: “Full Load Baghouse Cleaning Sy stem Failure” contains the following graphs:

• Transient Max/Min Pressure Profile (Unmitigated)

• Unit Pressures (Unmitigated)

• Baghouse and Scrubber Pressures (Unmitigated)

• Flows (Unmitigated)

• Fan Inlet Guide Vanes (Unmitigated)

• Fan Speeds (Unmitigated)Full Load Baghouse Cleaning System Failure (Unmitigated)Transient Max/Min Pressure Profile-4.6+1.7+7.7+16.5+22.8+24.3+18.4+11.5+3.1-9.5-11.0-0.50.0+9.1+15.5+3.0+21.7+20.3+16.1+14.3+9.5+7.3+5.9+1.4-0.1-13.2-14.7+14.7+2.8-0.5-40-30-20-100+10+20+30+40 

### A mb

i ent F

D F a

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AH Air I nlet S

AH Air Ou

tle

t Wi

ndbox F

urn

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ce E

conom i ze

r O

ut

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AH Ga s

O

ut

l e t

B

agho u se

I nle

t B

agho u se

O

ut

l e t

B

oost e r Fan I nle

t

B

oost e r Fan O

ut

l e t

S

cru

b ber O u tlet S

t a ck Ba s e T

op

o

f Sta ck

Pressure (inwc)MaximumMinimumFull Load Baghouse Cleaning System Failure (Unmitigated)Unit Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load Baghouse Cleaning System Failure (Unmitigated)Baghouse and Scrubber Pressures-40-30-20-100+10+20+30+400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load Baghouse Cleaning System Failure (Unmitigated)Flows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load Baghouse Cleaning System Failure (Unmitigated)Fan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position (percent open)FD FansBooster FansFull Load Baghouse Cleaning System Failure (Unmitigated)Fan Speeds02004006008001000120014000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# 4. LETTER REPORT

Letter Report—EA-0817-0101 contai ns the following sections:

• Introduction

• Model Construction

• Model Validation

• Future Configuration Model

• Initial Conditions

• Transient Testing: MT2 Full Load All B ooster Fans Trip – Delayed FD Trip

• Transient Testing: MT2A Full Load All B ooster Fans Trip – Immediate FD Trip

• Results

• Transient Events Summary Table

• Conclusions and Recommendations

# PNM, San Juan Generating Station Units 1 & 2 Page 1 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Letter Report

To: Public Service Company of New Mexi co/The Babcock and Wilcox Company

From: Satish Perivilli/TRAX LLC

Date: 4 March 2008

Subject: San Juan Generating Station Units 1 & 2/Furnace Draft Analysis

Introduction

TRAX, LLC has been retained by The Babc ock and Wilcox Company (B&W) to perform a

furnace draft analysis for Units 1 & 2 of Public Service Company of New Mexico’s (PNM) San

Juan Generating Station. This study analyzed the effect of ductwork and equipment changes

related to the addition of environmental equipmen t. These modifications included the addition of

a baghouse and related ductwork, the replacement of existing booster fans with new upgraded

booster fans, and the redirection of all the flue gas flow through the baghouse, the booster fans,

and the scrubbers before enteri ng the stack. The study was base d on the assumption that San

Juan Generating Station Units 1 and 2 are id entical in construction and operation.

The primary goal of this study was to determin e the effects of these plant modifications on

pressures and flows throughout the furnace draft system during normal and abnormal operation.

To accomplish this, TRAX built a model of the exis ting process and control system for San Juan

Station Unit 1. This model was validated against plant data and then modified to represent the

future plant configuration by adding the new equipment and making the corresponding changes

to the controls model. The future configura tion model was then tested through seven severe

transients. The results of these transient r uns were presented in Preliminary Report EA0711-

0102 dated December 12, 2007.

During the transient runs, the exis ting controls did not trip the forced draft (FD) fans during a

booster fan trip, which led to high furnace pressure during the transient. To mitigate this furnace

pressure excursion, TRAX suggested tripping the FD fans based on high furnace pressure

following a booster fan trip and resulting master fuel trip (MFT). During discussion between

members of the project team, the merits of imme diately tripping the FD fa ns vs. a delayed trip

were discussed. It was agreed that a single tran sient should be tested to compare a delayed FD

fan trip against an immediate FD fan trip. The tr ansient selected to test these alternative control

strategies was the “Full Load All Booster Fans Tr ip” transient. This letter report presents the

results of these transient runs.

# PNM, San Juan Generating Station Units 1 & 2 Page 2 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Model Construction

The dynamic model representing San Juan Station Unit 1 consisted of a process model, which

simulated the existing process configuration; and a controls model, which was built from a

subset of existing plant controls. TRAX prepar ed the process model based on drawings provided

by PNM and discussions with plant personnel. The process and control model configuration

drawings were reviewed by B&W and PNM. Th e model was parameterized to a full load

steady-state condition based on plant data provided from Unit 1.

Model Validation

Validation is the process of comparing steady-st ate and dynamic model predictions with plant

data. The process and controls models were run to high (360 MW) and low (200 MW) load

steady-state conditions, and the resu lts were compared with plant data. The model was then run

through an MFT transient similar to one that occurred at the plant and the dynamic data

generated by the model was compared to the dyna mic plant data. The steady state and transient

comparisons were documented and presented to PNM and B&W in Preliminary Report EA0711-

0102 dated December 12, 2007.

Future Configuration Model

The validated process and contro l system models were then modified to reflect the plant

configuration with the new equipmen t. These modifications included:

• Addition of a baghouse and related controls

• Replacement of existing booster fans with new upgraded booster fans

• Related ductwork changes

• Elimination of bypass flow di rectly to the stack. All flue gas flow from the air heaters

will pass through the new baghouse, new booster fans, and scrubbers before reaching the

stack

A schematic diagram of the proposed plan t configuration is shown in Figure 1.

Figure 1 Proposed Plant Configuration Flue Gas from

Primary Air

Heaters

Flue Gas from

Secondary Air

Heaters Baghouse Booster Fan A

Booster Fan B

Booster Fan C Scrubber A

Scrubber B

Scrubber C Stac k

# PNM, San Juan Generating Station Units 1 & 2 Page 3 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Initial Conditions

The transient run was initiated with the model at a full load, steady-s tate condition, with all

pressures, flows, temperatures, and controlled variables constant. The full load, steady-state

pressure profile for this initial condition is shown in Figure 2.

Figure 2 Initial Condition Pressure Profile for Full Load



# Transient Testing: MT2 Full Load All Booster Fans Trip – Delayed FD Trip

This full load transient run (MT2 ) tripped all of the booster fans, but delayed the FD fan trip for

20 seconds. After that delay, a high furnace pre ssure FD fan trip was enabled and would be

triggered if furnace pressure rose above +15 inwc.

This transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Tripped all three operating booster fans, imme diately causing an MFT and the following

associated control actions:

− Froze FD inlet guide vanes at their curre nt position

− Tripped pulverizers and their feeders

− Shut coal valves

− Tripped, shut off, and isolated primary air (PA) fans

# PNM, San Juan Generating Station Units 1 & 2 Page 4 of 13

Letter Report—EA-0817-0101 3/4/2008 

# − Closed hot air, tempering air, and primary air control dampers

− Booster fan IGV demand is controlled by a kicker circuit for 15 seconds after the

initiation of the MFT. Control of the IGVs is then transferred to a runback controller

through the end of the transient

− Waited 20 seconds following the MFT, th en enabled the +15 inwc high furnace

pressure FD fan trip

• All controls remained in au to throughout the transient

The model was run for 120 seconds and data was saved. Results are presented below.

Transient Testing: MT2A Full Load All B ooster Fans Trip – Immediate FD Trip

This full load transient run (MT2A) tripped al l of the booster fans and immediately tripped all

FD fans. The transient consisted of the following steps and control actions:

• Initialized the model to the 100% load condition

• Ran the model for 10 seconds to establish steady-state conditions

• Tripped all three operating booster fans, imme diately causing an MFT and the following

associated control actions:

− Froze FD inlet guide vanes at their curre nt position

− Tripped pulverizers and their feeders

− Shut coal valves

− Tripped, shut off, and isolated PA fans

− Closed hot air, tempering air, and primary air control dampers

− Booster fan IGV demand is controlled by a kicker circuit for 15 seconds after the

initiation of the MFT. Control of the IGVs is then transferred to a runback controller

through the end of the transient

− Tripped the FD fans immediately

• All controls remained in au to throughout the transient

The model was run for 120 seconds and data was saved. Results are presented below.

# PNM, San Juan Generating Station Units 1 & 2 Page 5 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Results

Figure 3 shows a comparison of the furnace pre ssures for the MT2 and MT2A runs. At 10

seconds, an MFT occurred and fuel was shut off to the furnace. The resulting fireball collapse

caused a sharp drop in furnace pressure. Pressure for the MT2A run continued to drop as the FD

fans were immediately tripped and reduced mass flow into the furnace. Furnace pressure for run

MT2A eventually reached a minimum of -3.3 inwc. Conversely, pressure for the MT2 run began

to rise at about 20 seconds as the FD fans c ontinued to run and pressurize the furnace.

Eventually, furnace pressure rose above +15 inwc at about 60 seconds and the FD fans tripped.

Furnace pressure for both transients then tren ded to ambient as the FD fans spun down.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 20 40 60 80 100 120

Time (seconds)Pressure (inwc) 

### MT2 Furnace MT2A Furnace



# Figure 3 T2 Furnace Pressure Comparison

# PNM, San Juan Generating Station Units 1 & 2 Page 6 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Figure 4 shows system pressures for the two runs. Pr essures at the FD fan discharge and air

heater gas outlet followed predicable paths as th e transient proceeded. Pressures for the MT2 run

initially dropped due to the MFT, and then increas ed as the FD fans continued to push air into

the draft system. The pressure plots remained approximately the same distance apart until 60

seconds, indicating a relatively cons tant flow of air into the syst em. Pressures dropped after 60

seconds as the fans tripped and spun down.

Pressures for the MT2A run, with the immediate FD fan trip, also followed expected paths as

they quickly dropped as the fireball collapsed due to the MFT. The pressures then trended

together and approached ambient as the booster and FD fans spun down.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 20 40 60 80 100 120

Time (seconds)Pressure (inwc) 

### MT2 FD Discharge MT2 Furnace MT2 Air Heater Gas Outlet

MT2A FD Discharge MT2A Furnace MT2A Air Heater Gas Outlet



# Figure 4 T2 Unit Pressures

# PNM, San Juan Generating Station Units 1 & 2 Page 7 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Figure 5 shows the guide vane position for the boos ter and FD fans. For both transients, the FD

fan vane positions were frozen in place after the trip at 10 seconds, and so remained constant

throughout both runs.

The booster fan guide vanes were used to contro l pressure at the rege nerative air heater gas

outlet. Plots of the booster fan guide vane positi ons showed an initial steep ramp downward as

the kicker circuit reduced the guide vane posit ion immediately after the booster fan trip. At

about 18 seconds, the two plots diverged due to the differences in air heater gas outlet pressure

for the two runs (see Figure 4). At 25 seconds, th e kicker circuit was released and control of the

booster fan guide vanes was transf erred to the runback controller , which attempted to control

furnace pressure at +1 inwc. After 25 seconds, furnace pressure was only slightly negative for

transient MT2A (since the FD fans had alread y tripped), so the booster fan guide vanes only

needed to increase to about 25% to bring furnace pressure back to setpoint. For transient MT2,

after the release of the kicker circuit, the booster fan guide vanes ramped full open in an attempt

to control furnace pressure, which had steadily rise n above +10 inwc. Afte r the FD fans tripped

at 60 seconds, furnace pressure began to decr ease, and the booster fan guide vane positions

decreased.

0 10 20 30 40 50 60 70 80 90 100

0 20 40 60 80 100 120

Time (seconds)Position (percent open) 

### MT2 FD Fans MT2 Booster Fans

MT2A FD Fans MT2A Booster Fans

MT2 FD Fans and MT2A FD Fans are identical



# Figure 5 T2 Fan Inlet Guide Vane Positions

# PNM, San Juan Generating Station Units 1 & 2 Page 8 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Figure 6 shows the FD and booster fan speeds during this transien t. For both runs, the booster

fans tripped at 10 seconds and immediately be gan coasting down. The FD fans tripped at 10

seconds during transient MT2A, and immediat ely begin coasting down; whereas during run

MT2, the FD fans did not trip until 60 s econds and then began coasting down.

0 200 400 600 800 1000 1200 1400

0 20 40 60 80 100 120

Time (seconds)Speed (rpm) MT2 FD Fans MT2 Booster Fans

MT2A FD Fans MT2A Booster Fans



# Figure 6 T2 Fan Speeds

# PNM, San Juan Generating Station Units 1 & 2 Page 9 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Figure 7 shows back end pressures at the baghouse, booster fan, and scrubber. Pressures for run

MT2A were consistent with the other plots as pressures trended towards ambient immediately

after the FD and booster fan trips. The pressure s for run MT2 also trended as expected, slowly

rising until 60 seconds when the FD fans trippe d and system pressures slowly dropped down to

ambient.

-40 -30 -20 -10

0 +10 +20 +30 +40

0 20 40 60 80 100 120

Time (seconds)Pressure (inwc) MT2 Baghouse Inlet MT2 Booster Fan Inlet MT2 FGD Inlet

MT2A Baghouse Inlet MT2A Booster Fan Inlet MT2A FGD Inlet



# Figure 7 T2 Baghouse and Scrubber Pressures

# PNM, San Juan Generating Station Units 1 & 2 Page 10 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Figure 8 shows the system flows during this transient. Flows for run MT2A dropped off

immediately as the FD and booster fans trip ped and spun down. Furnace and FGD flows

dropped more sharply due to the MFT, while the FD fan flow dropped more slowly as flow was

still being transported by the decelerating fans. For run MT2, FD flow initi ally increased due to

the lower pressure in the furnace after the MFT. Flows at the back end initially dropped due to

the kicker circuit, then increased after the kicker circuit released. Flows steadied out until about

60 seconds, at which time the FD fans tripped a nd flows slowly decreased as pressures dropped

to ambient.

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0 20 40 60 80 100 120

Time (seconds)Flow (kpph) 

### MT2 Total FD Fans MT2 Furnace Exhaust MT2 Total FGD Inlet

MT2A Total FD Fans MT2A Furnace Exhaust MT2A Total FGD Inlet



# Figure 8 T2 Flows

# PNM, San Juan Generating Station Units 1 & 2 Page 11 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Figure 9 shows the maximum pressures experienced during these two transien ts at various points

in the flue gas path. As expected, front end pres sures for run MT2A were lower, as the FD fans

had tripped. Back end pressures for the two runs were similar, as the booster fans tripped in both

cases. Note that draft system pressures for eith er of the transients as shown in Figure 9 do not

necessarily occur at the same time.

0.0 +28.8 +27.3

+22.4

+20.3

+15.1 +14.2 +13.5

+11.4 +10.7

+6.2 +5.5 +14.9

+2.9

-0.3

-4.6 0.0 +22.4 +20.9

+16.6

+14.7

+9.9

+7.5 +6.1

+1.5 +0.2 -0.7 +14.9

-0.7 -0.5

-40 -30 -20 -10

0 +10 +20 +30 +40

Am

b i e nt FD Fa

n O

u tlet SA

H

A ir

I n let SA

H

A ir Outlet

Wi

n dbox Fur

n ac

e Eco

no

m iz e r Outl

e t Precip Outlet SA

H

Ga

s Outlet

B ag

h ouse

I nle

t Bag

h ouse

Ou

t l e t Boost

er

Fa

n I nle

t B oo

s ter Fan Outl

e t Scrubber Out

l et St

ac

k Base Top of

St

a ckPressure (inwc) 

### Maximum with MT2 Maximum with MT2A



# Figure 9 T2 Transient Maximum Pressure ProfilePNM, San Juan Generating Station Units 1 & 2Page 12 of 13Letter Report—EA-0817-01013/4/2008Transient Events Summary TableA summary of the maximum andminimum pressures at various locations in the system are shown in Table 1. All thepressures are unfiltered values. Notethat the pressures in any row do notnecessarily occur at the same time.FurnacePressure(inwc)Air HeaterGas OutletDuct (inwc)Booster FanInlet (inwc)No. Transient NameNo. ofBoosterFans inServiceGrossLoad%Min Max Min Max Min MaxMT2 Full Load All Booster Fans Trip – DelayedFD Trip 3 100 -0.0 +15.1 -0.3 +11.4 -11.0 +5.5MT2A Full Load All Booster Fans Trip – Immediate FD Trip 3 100 -3.3 +9.9 -4.0 +1.5 -11.0 -0.7Table 1 Transient Event Summary Table

# PNM, San Juan Generating Station Units 1 & 2 Page 13 of 13

Letter Report—EA-0817-0101 3/4/2008 

# Conclusions and Recommendations

Based on this transient analysis, th e following conclusions can be made:

• The delayed trip of the FD fans results in a furnace pressure that reached a positive value

of +15.1 inwc.

• By immediately tripping the FD fan, high pos itive furnace pressures were avoided, but a

furnace pressure minimum of -3.3 inwc was experienced.

• Tripping the FD fans immediately upon loss of all booster fans is in compliance with a

strict interpretation of the NFPA guidelines.

# P P u u b b l l i

i c

c S S e e r r v

v i i c

c e e C C o o m m p p a a n n y y o o f f N N e e w w M M e e x x i i c

c o o

S S a a n n J J u u a a n n G G e e n n e e r r a

a t t i

i n

n g g S S t t a

a t t i

i o

o n n U U n n i i t

t s

s 3 3 & & 4 4

I I m

m p p l l o

o s s i i o

o n n S S t t u

u d d y y



# F F I I N

N A A L L R R E E P P O O R R T T

Prepared for:

The Babcock & Wilcox Company

P.O. NO.: BAX067843

Report Number EA0624-0301

July 10, 2007

# Public Service Company of New Mexico

San Juan Generating Station Units 3 & 4

Implosion Study



# FINAL REPORT

Prepared for:

The Babcock & Wilcox Company

P.O. NO.: BAX067843

Report Number EA0624-0301

Prepared by:

Kent Kozak, Senior Engineer



# TRAX, LLC

107 Vista Centre Drive Forest, VA 24551

Voice: (434) 385-7250, Ext. 228 Fax: (434) 385-8233

Email: kmkozak@traxcorp.com

Approved by:

Gregory M. Kosowski, Vice President Prepared by:

Kent Kozak, Senior Engineer



# TRAX, LLC

107 Vista Centre Drive Forest, VA 24551

Voice: (434) 385-7250, Ext. 250 Fax: (434) 385-8233

Email: kmkozak@traxcorp.com

Approved by:

Gregory M. Kosowski, Vice President

# TRAX shall not be liable for any losses or for dam ages resulting from the use of any information,

apparatus, method, or process disclosed in this report.

Copyright © TRAX, LLC , 2007. All rights reserved.

ProTRAX is a trademark of TRAX, LLC.

All other brand and product names are trademarks or registered

trademarks of their respective companies.

# PNM, San Juan Generating Station Units 3 & 4 Page i of iii

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# TABLE OF CONTENTS

LIST OF A PPENDICES ................................................................................................... I

EXECUTIVE SU MMARY ................................................................................................ II

1.0 INTRODUCTION.................................................................................................. 1

2.0 NOMENCLAT URE ............................................................................................... 3

3.0 DYNAMIC MODEL CONSTRUCTION ................................................................. 4

4.0 VALIDATION OF EXISTING CONFIGURATION MODEL................................... 7

5.0 TRANSIENT EVENT TESTIN G.......................................................................... 14

6.0 CONCLUSIONS................................................................................................. 24

LIST OF APPENDICES

APPENDIX A Model Process Schematics

APPENDIX B Model Control Schematics

APPENDIX C Validation Results

APPENDIX D Full Load MFT

APPENDIX E Full Load All Booster Fans Trip

APPENDIX F Full Load Both FD Fans Trip

APPENDIX G Low Load Two Booster Fans Runaway

APPENDIX H Full Load All Fans Trip

# PNM, San Juan Generating Station Units 3 & 4 Page ii of iii

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# EXECUTIVE SUMMARY

TRAX, LLC has been retained by The Babcoc k & Wilcox Company (B&W) to perform an

implosion study for San Juan Generating Station Units 3 and 4. This study analyzed the effect of

ductwork and equipment changes related to the addition of a baghouse. Model simulation

performed as part of this study predicted the behavi or of the units in their future configuration,

and determined the extent of furnace and ductw ork pressure excursions through several severe

transient events.

In the initial phase of this project, the project team analyzed plant data to determine the

differences between Units 3 and 4. Following this analysis, the team agr eed that the two units

are almost identical. For the purposes of this report, all references to Unit 4 apply equally to

Unit 3.

After determining a single unit was sufficient to represent both Units 3 a nd 4, a model of the

current plant configuration for Unit 4 was built. The plant m odel was validated against plant

data to ensure accuracy and to establish a baseline for the investigation of the subsequent flue gas

desulphurization (FGD) changes. The validatio n effort consisted of running the Unit 4 model

through a severe transient similar to one previous ly experienced at the pl ant, and comparing the

model results to historical plant data. The re sults from this validation were delivered in

Validation Report EA0624-0401, dated November 6, 2006.

Following the validation of the Unit 4 current c onfiguration model, ductw ork was modified and

emission controls equipment was added to represen t the plant in its future configuration. These

modifications included addition of a baghouse, replacement of existing booster fans with new

upgraded booster fans, removal of the existing stack dampers and air heater gas outlet to stack

breaching ducts, and de-energizing (but not rem oving) the existing hot-side precipitator. The

future configuration model was then te sted through five severe transients.

TRAX implemented the basic proposed control logic for the new environmental equipment as

provided by PNM. This control logic was then enhanced by tuni ng the controllers and adding

mitigating measures to improve the control system performance and protect the equipment

during pressure excursions.

The results obtained during the st udy are summarized below:

• The controls as designed were able to mitigate all negative furnace pressure excursions to

within -11 inwc.

• During transient testing, pressure excursions downstream of the flue gas outlet of the air

heaters were within +25 inwc and -20 inwc.

• The “Full Load Both FD Fans Trip” tran sient caused the lowe st furnace pressure

excursions. During this transient, furn ace pressures decreased to -10.3 inwc.

• The lowest booster fan inlet duct pressures m easured were during the “Full Load MFT”

transient. The inlet pressure dropped to -19.9 inwc during this transient.

# PNM, San Juan Generating Station Units 3 & 4 Page iii of iii

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Project Number EA0624 

# • The highest pressure excursi ons occurred during the “Full Load All Booster Fans Trip”

transient. Following the booster fans trip, th e lack of exhaust capab ility caused furnace

pressure to rise to +24.8 in wc, and booster fan inlet pressure to rise to +21.0 inwc.

Tripping both forced draft (FD) fans on a high furnace pressure limit following the

master fuel trip (MFT) easily mitigated the high pressures.

• During a full load MFT, the quick adjustment of booster fan inlet guide vanes via the

kicker circuit prevented an additional 7 inwc of furnace pressure excursion.

• Holding the booster fan kicker circuit for 20 seconds during an MFT promoted stable,

over-dampened process and control behavi or during furnace pressure recovery.

• The overriding booster fan runback controlle r was responsible for limiting the furnace

pressure excursion to only -3.2 inwc during the “Low Load Two Booster Fans Runaway”

transient.

Based on the results of the transient runs, TR AX recommends the following control strategies

and mitigating measures be implemented in the future plant configuration controls:

1. During normal operation, the booster fan inlet guide vanes should be controlled by a

feed-forward signal from the FD inlet guide va nes, added to a trim control that monitors

air heater gas outlet pressure.

2. For mitigating MFT events, a kicker circuit should be used to immediately run back

booster fan inlet guide vanes.

3. An overriding booster fan runback controller should be used to help mitigate negative

furnace pressure excursions during MFT and fan transients.

4. During an MFT, if both booster fans are trip ped, both FD fans should be tripped if the

furnace pressure exceeds a high furnace pressure limit. This will help prevent overpressurizing the furnace.

5. Should the booster fan runback controller fa il to mitigate a booster fan runaway event,

the controls should trip the fan. One such m easure would be to trip the booster fans on a

load-indexed, low booster fan inlet pressure.

The model construction, validation, transient testing, results, and conclusions are detailed in the

following report. The transient anal ysis modeling selected as descri bed in this report was used to

estimate the magnitude of possible events. Some of the cases modeled are worst-case scenarios

that have a low probability of occurrence. This report does not attempt to predict the likelihood

of any of these events occurring.

# PNM, San Juan Generating Station Units 3 & 4 Page 1 of 25

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Project Number EA0624 

# 1.0 INTRODUCTION

TRAX, LLC has been retained by The Babcoc k & Wilcox Company to perform an implosion

study for San Juan Generating Station Units 3 and 4. This study analyzed the effect of proposed

plant modifications related to the addition of a new baghouse. These modifications included

addition of a baghouse, replacement of existing booster fans with new upgraded booster fans,

removal of the existing stack dampers and air heater gas outlet to stack breaching ducts, and deenergizing (but not removing) th e existing hot-side precipitator.

The primary goals of the study were to help answer the following questions:

1. What is the impact of the process modi fications on furnace and ductwork pressure

excursions during normal and abnormal plant operation?

2. How does the proposed control system design be have during severe pressure excursions?

3. What, if any, corrective actions are necessary?

The approach used in this study cons isted of the following basic steps:

1. Compare data for Units 3 and 4 to determine if a single model would be sufficient to

represent both units.

2. A dynamic model of Unit 4 in its existing co nfiguration was constr ucted and validated

against historical plant data.

3. A baghouse was added, booster fans were up graded, and ductwork was modified to

represent the plant in its fu ture configuration.

4. The future configuration model was run th rough selected transients, and pressure

excursions in the furnace and ductwork were recorded.

5. The results were analyzed, and mitigating measures designed to minimize pressure

excursions were identified and tested.

The existing furnace draft system for San Juan Unit 4 was modeled using ProTRAX , a

commercially available dynamic simulation system. The ProTRAX system is based on modular

components, allowing interconnecting of modules representing furnaces, fans, dampers, ducts,

etc., into any physically realis tic configuration. A ll of the module formulations are based on

first-principle conservation rela tions, the Second Law of Therm odynamics, and well-established

constitutive relations for heat tr ansfer and fluid mechanics. The resulting executable models are

operated from a graphics-based environment that provided extensive capability for controlling

the models and displaying the results in various formats.

A workgroup with representatives from Babc ock & Wilcox, Sargent and Lundy (S&L), and

TRAX selected a total of five transients to be tested with the new plan t configuration. The goal

was to identify conditions that would create la rge pressure excursions in the furnace and

ductwork. Each transient consisted of an initia l event followed by the response of the controls,

which could eventually lead to a master fuel trip and/or individual fan trips. The transients

selected for the study are s hown below in Table 1.

# PNM, San Juan Generating Station Units 3 & 4 Page 2 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 No. Transient Name

1 Full Load MFT

2 Full Load All Booster Fans Trip

3 Full Load Both FD Fans Trip

4 Low Load Two Booster Fans Runaway

5 Full Load All Fans Trip

Table 1 List of Transients



# This report describes the resu lts of these transient runs.

# PNM, San Juan Generating Station Units 3 & 4 Page 3 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# 2.0 NOMENCLATURE

The naming convention used throughout this report is described below:

1 st 

# Quadrant Fan Operation

Fan operation where the fan has flow in the dire ction of fan suction to discharge, with a

discharge pressure grea ter than the suction pressure. Op eration in this region is governed

by manufacturers fan curves (developed head versus volumetric flow).

2 nd 

# Quadrant Fan Operation

Flow through the fan has reversed and is now from discharge to suction. Head is positive

with the discharge pressure greater than the su ction pressure. In this quadrant the fan is

acting as a resistance with flow from higher (discharge) to lower (suction) pressure.

Operation in this region starts at the fan d ead head pressure (zer o flow) and is based on

an assumed flow resistance. Fan operation in the 2 nd 

# quadrant typically occurs during fan

trips or other equipment malfunctions.

4 th 

# Quadrant Fan Operation

Flow is in the direction of fan suction to di scharge with a discharge head less than the

suction head (i.e., the pressure drops across the fan rather than rising). Operation in this

region is governed by the run out portion of the fan curve and assumed flow resistance

behavior. Typically, fan operation in the 4 th 

# quadrant occurs during a fan trip.

MFT

Master fuel trip (MFT) is the procedure in whic h all fuel to the furnace is completely shut

off.

Water Seal Venting

Water seal venting refers to the water seal at the bottom of the furnace. At sufficiently

low furnace pressure (-19 inwc below ambient), the water seal can rupture allowing

ambient air into the furnace. This additiona l flow of ambient ai r into the furnace will

help minimize any negative furnace pressure transient.

# PNM, San Juan Generating Station Units 3 & 4 Page 4 of 25

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Project Number EA0624 

# 3.0 DYNAMIC MODEL CONSTRUCTION

3.1 Existing Configuration Model

The dynamic model representing San Juan Unit 4 consisted of a process model, which simulated

the existing process configuration; and a controls model, which was built from a subset of

existing plant controls.

TRAX prepared the process model based on draw ings provided by PNM, a plant walkdown, and

discussions with plant personnel. The process and control model confi guration drawings were

reviewed and approved by B&W, S&L, and PNM.

During the initial phase of the pr oject, the project team compared process and controls data for

both Unit 3 and Unit 4. It was determined, during the comparison of data between the units, that

there were only subtle differences between the overall process and controls systems for Units 3

and 4. The team determined that a single model would be sufficient to accurately represent the

two units as they are almost identical. For the purposes of this report all references to Unit 4

apply equally to Unit 3.

3.1.1 Existing Configur ation Process Model

The process model for each of the units included the following components:

• Air path through and including FD fans, air heaters, and furnace

• Fuel (coal) and primary air path incl uding PA fans, pulverizers, and feeders

• Flue gas path from the furnace includi ng superheaters, reheaters, economizer, air

preheater, and stack

• Pollution control systems including precipitator and FGD equipment

As the focus of the study involved relatively fast furnace pressure transients, slower steam-side

components, such as steam drums and desuperheat ers, were not modeled. Only the metal mass

for the walls and heated surfaces was modeled, al ong with the energy stored in the metal during

the transient.

Centrifugal fan operation was modeled by incorporat ing the actual fan head curves. In addition,

shutdown flow effects (4 th 

# quadrant behavior) were simulate d and combined th e run-out portion

of the fan curve, and assumed flow resistance behavior.

Pulverized coal (PC) combustion was simulated in the furnace. Coal combustion was

represented as a two-stage reaction, with the fi rst stage being the rapid devolatilization of the

coal particles, and the second stage being the combustion of the remaining coal char. Char

combustion was a function of temperature, partic le size, and availabili ty of oxygen. The amount

and size of the char particles woul d strongly affect the rate of fireball collapse during a fuel trip.

The furnace calculated the exit ing flue gas composition based on the rate and chemistry of

combustion and furnace leakage.

# PNM, San Juan Generating Station Units 3 & 4 Page 5 of 25

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Project Number EA0624 

# 3.1.2 Existing Configuration Control Model

Note that only those portions of the controls that affected any of the final control elements in the

model were included in the control system simulation. Control loops for the existing

configuration plant model included:

• Secondary air duct pressure

• Primary air heater (PAH) air outlet pressure

• Secondary airflow

• Economizer excess air

• Fuel flow

• Pulverizer coal air temperature

• Pulverizer primary airflow

• Stack flue gas temperature

• Master fuel trip

3.2 Future Configuration Model

3.2.1 Future Configur ation Process Model

The proposed future configuration process model included all of the components in the San Juan

process models, plus the proposed emission control equipment. Modifications to represent the

future configuration included:

• Addition of a baghouse

• Replacement of existing booster fans with new upgraded booster fans

• Removal of the existing stack dampers and ai r heater gas outlet stack breeching ducts

• De-energizing (but not removing) the existing hot-side precipitator

Parameterization data for the new process equipment such as fan head curves, vessel volumes,

pressure drops, etc. was based on proposed de sign information provided by B&W, S&L, and

PNM.

3.2.2 Future Configur ation Control Model

The control logic for the new equi pment included various control l oops for the booster fans. In

the booster fan control loop, an error signal was calc ulated by comparing th e air heater gas outlet

duct pressure to a setpoint, which remained constant for all loads. The controller output was then

added to a characterized feed-forward signal, wh ich was developed from the FD fan inlet guide

van demand. The total was then used to adju st booster fan inlet guide vane demand. A

functional diagram of this control loop is shown in Figure 1.

# PNM, San Juan Generating Station Units 3 & 4 Page 6 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 Figure 1 Booster Fan Inlet Guide Vane Controls



# This control scheme also included overriding cont rollers to protect the furnace and associated

ductwork. The booster fan runback controller s uperseded any booster fan demand by adjusting

booster fan inlet guide vane to maintain a -1 inwc furnace pressure. Either of the following

activated the override:

• A MFT was in progress for at least five seconds and the bo oster fan kicker circuit was

completed

• A MFT was not in progress and the furnace pressure had dropped below -1 inwc

# PNM, San Juan Generating Station Units 3 & 4 Page 7 of 25

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Project Number EA0624 

# 4.0 VALIDATION OF EXISTING CONFIGURATION MODEL

Model validation is the process of running the m odel through a transient and comparing the data

produced by the model to data gathered from the plant for a similar transient event.

There are three basic steps to validating a dynamic model for an implosion study:

1. Configure and parameterize the process model at full load

2. Run the model to a lower load and compare to plant data

3. Compare model to plant data during a severe transient

These steps must be completed in the above orde r, as each step is dependent upon the successful

completion of the previous step. All three step s involve a comparison of model output with plant

data, and the combination of all three comparisons result in a high level of confidence that the

model provides reliable predic tions for current and future plant configurations.

The following sections describe the steps used fo r the validation of the Sa n Juan Unit 4 model.

Step 1: Configure and Para meterize Model at Full Load

Each furnace draft component in the plant was simulated and connected in the same

configuration as the plant using ProTRAX modules. Where there are parallel components in the

plant, such as FD fans, each fan was modeled separately to ensure any effects of multiple

component operations were incorpor ated in the study. This was the “configuration” process.

The physical characteristics of each component were input through fill-in-the-blank forms in the

modeling system. This included data such as damper sizes, fan head curves, and physical

dimensions of ducts, stacks, and vessels. This was the “parameterization” process. The

parameterization process also included operati ng data based on a full load heat balance

performed by TRAX using plant da ta, manufacturer’s heat bala nces, discussions with plant

personnel, and visual observat ions during the plant walkdow n. Where plant data was not

available, such as pressure profiles through the convection pass of the furnace, estimates of

pressure drops were made based on the physical drawings showing tube densities, flow cross

sectional areas, and gas temperatures. Plant da ta itself is generally not sufficient due to

instrumentation errors and unavaila ble signals. Therefore, the full load heat balance data comes

from plant and design data, and is adjusted to ensure mass and energy balance.

At this point, the model had the thre e requirements of a high-fidelity model:

• Module equations were based on conserva tion of mass, energy, momentum, and wellaccepted correlations for heat transfer and mass flow.

• The configuration of the model was the same as the plant for the scope under consideration.

• The physical characteristics of each component were programmed into the corresponding

modules.

# PNM, San Juan Generating Station Units 3 & 4 Page 8 of 25

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Project Number EA0624 

# Model parameterization was performed at full loa d, as most design data was available at that

point and not at other points. Also, at full lo ad most plant equipment is in service and is

operating at a substantial load where losses a nd inefficiencies play a minor role in the

component’s performance.

The full load model was run at steady-state for several minutes and test ed for stability and

accuracy. That is, the model was initialized to full load conditions, and then allowed to run to

equilibrium. If properly parameterized, the mo del should show little or no movement from the

parameterization point and should come to a solid, steady state in just a few seconds. Since all

the module equations calculate an absolute heat ba lance at steady-state, any deviations from the

full load conditions by the model are immediately obvious and indicate an error in

parameterization of the model. If there are in stabilities, the model will not reach a smooth

steady-state, and the model must be corrected.

In this case, at the full load steady-state point the San Juan Unit 4 model was immediately stable

and no further corrections were required. Criti cal parameters for the full load steady-state are

listed in Table 2.

Parameter Plant Data Model Unit

Gross Load 550 550 MW

Load Level 100 100 Percent

Coal Flow Rate 552 552 kpph

Number of Mills Grinding 6 6

Total Secondary Airflow 4,400 4,400 kpph

Total Compartmental Airflow 3,700 3,700 kpph

Pulverizer Airflow (per mill) 190 190 kpph

FD Fan Discharge Pressure 30 30 inwc

PA Fan Discharge Pressure 74 74 inwc

Secondary Air Heater Air Outlet Pressure 25 25 inwc

Primary Air Heater Air Outlet Pressure 70 70 inwc

Secondary Air Duct Pressure 23 23 inwc

Furnace Pressure 10.2 10.1 inwc

Secondary Air Heater Gas Outlet Pressure 0.7 0.5 inwc

Economizer Gas Outlet Temperature 704 696 Degree F

Table 2 Unit 4 Critical Plant Parameters at Full Load (100%)



# Having demonstrated a reliable, stable match to the plant data at full load, the San Juan Unit 4

model was ready to run to the lower load condition.

Step 2: Run Model to Lower Load and Compare to Plant Data

The control system was used to run the plant model to a lower load. The model was tested at this

lower load for stability and accuracy . Typically, the primary causes of variations at this point are

the following:

1. Missing, incomplete or erroneous da ta for full load parameterization

2. Different operation of the model compared to the plant

# PNM, San Juan Generating Station Units 3 & 4 Page 9 of 25

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Project Number EA0624 

# 3. Fouling and soot buildup on various surf aces that alter pressure distribution

4. Significantly different conditions at the plan t during the low load compared to the full

load data set (e.g., winter versus summer operation)

For Unit 4, the low load data available from the plant was at 300 MW. All the control setpoints

were applied as observed from the historian data for a 54.5% load. The number of mills

operating was reduced from six to four, excess oxygen trim percentage was increased from

2.03% to 6.3%, and the model was run to a stea dy-state. A comparison of model and plant

parameters for the lower load st eady state is shown in Table 3.

Parameter Plant Data Model Unit

Gross Load 300 300 MW

Load Level 54.5 54.5 Percent

Coal Flow Rate 341 341 kpph

Number of Mills Grinding 4 4

Total Secondary Airflow 3,400 3,320 kpph

Total Compartmental Airflow 2,500 2,500 kpph

Pulverizer Airflow (per mill) 186 186 kpph

FD Fan Discharge Pressure 22 23 inwc

PA Fan Discharge Pressure 72 72 inwc

Secondary Air Heater Air Outlet Pressure 19 20 inwc

Primary Air Heater Air Outlet Pressure 70 70 inwc

Secondary Air Duct Pressure 18 19 inwc

Furnace Pressure 5.0 4.0 inwc

Secondary Air Heater Gas Outlet Pressure 0.1 -0.7 inwc

Economizer Gas Outlet Temperature 570 587 Degree F

Table 3 Unit 4 Critical Plant Parameters at Low Load (54.5%)



# The Unit 4 model was stable and accurate at low load condition, and no further actions were

required.

Step 3: Compare Model to Plant Data/Historical Data During Severe Transient

The first two steps in the vali dation process addressed the st eady-state characterization and

operation of the model. The third step addres ses the dynamic behavior. Step 3 cannot begin

without the successful completion of the first two st eps. The third step is the focus and essence

of the validation report, and is th erefore described in more detail than the previous two steps.

It is important to select a transient for validation that is both severe enou gh to test the model, yet

has only one cause. In most cases, a master fuel trip (MFT) is the best choice providing that the

trip was not caused by a component failure in the gas path such as a fan or damper. Multiple

failures make it more difficult to identify and duplicate the actual driving forces on the plant and

the model.

To perform the validation, the mode l was first moved to a steady-st ate operating point consistent

with the plant data for the select ed event. The control system was again used to run the plant

model to this load, and the model was allowed to reach a steady-state. A short run of ten seconds

was made at the beginning of th e transient to show that the models were at the proper steady-

# PNM, San Juan Generating Station Units 3 & 4 Page 10 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# state. The MFT was initiated and all known pl ant variables, (i.e. damper positions, feeder

speeds, etc.) were maneuvered by the control syst em to mimic plant movements as closely as

possible based on the available plant data.

The primary variable of interest in model validation was the furnace pressure. The model

furnace pressure was compared to plant furnace pressure for a period of one minute. In

comparing the model response to the plant, the criter ion was the time required for the furnace

pressure to reach a minimum, the magnitude of the minimum, and the rate of decrease of the

furnace pressure. The most important factors that affected results were:

• Timing and speed of fuel shutoff to the furnace

• Control of airflow to the furnace

A significant level of effort was invested to as sure the timing of movement for the burner coal

valves, fan inlet vane position, and the shutdown of pulverizers, PA fans, and feeders were

duplicated as closely as possible.

4.1.1 Unit 4 Initial Conditions

PNM provided TRAX with plant historian data for an MFT at 98% load. The MFT occurred

May 4, 2006 at 11:39 a.m. Although the historian data had a five second sampling rate, TRAX

identified that in every 15 seconds of data, tw o measurements were id entical, leading to the

conclusion that the data was actually recorded at 10 second intervals. TRAX took this into

account during the model validation, by tuning the model to produce a slightly more

conservative estimate of system pressures during the transient. The larger the time span between

recorded data, the more likely stored data missed the furnace pressure minimum.

Critical plant parameters for the 98% load at the beginning of the MFT are listed in Table 4.

Parameter Plant Data Model Unit

Gross Load 539 539 MW

Load Level 98 98 Percent

Coal Flow Rate 524 526 kpph

Number of Mills Grinding 6 6

Total Secondary Air Flow 4,300 4,300 kpph

Total Compartmental Airflow 3,400 3,500 kpph

Pulverizer Airflow (per mill) 193 195 kpph

FD Fan Discharge Pressure 28.0 27.5 inwc

PA Fan Discharge Pressure 72 74 inwc

Secondary Air Heater Air Outlet Pressure 24 23 inwc

Primary Air Heater Air Outlet Pressure 70 70 inwc

Secondary Air Duct Pressure 21 21 inwc

Furnace Pressure 9.6 9.4 inwc

Secondary Air Heater Gas Outlet Pressure 0.8 0.4 inwc

Economizer Gas Outlet Temperature 670 691 Degree F

Table 4 Unit 4 Critical Plant Para meters at Validation Point (98% Load)

# PNM, San Juan Generating Station Units 3 & 4 Page 11 of 25

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Project Number EA0624 

# At steady-state conditions, a pressure profile plot for the air/gas path from the FD fan inlet to the

stack outlet was generated for Unit 4, and compar ed with the available historian data for the

validation case. Model pressure profile at validation condition for Unit 4 is shown in Figure 2.

Figure 2 Unit 4 Pressure Profile at Validation Conditions (98% Load)



# 4.1.2 Unit 4 MFT Procedure

During the MFT, the following control elements were driven as described based on historian data:

• All pulverizers, associated feeder s and both PA fans were tripped

• Burner coal valve for all pulverizers were closed

• Primary air shutoff and control damp ers for each pulverizer were closed

• Hot air dampers were closed and temp ering air dampers were opened fully

• All secondary air dampers were locked in place

• FD fan inlet vanes were frozen in place

• Booster fan inlet guide vane control remained in manual

# PNM, San Juan Generating Station Units 3 & 4 Page 12 of 25

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Project Number EA0624 

# 4.1.3 Unit 4 Validation Parameters

To validate the models, TRAX selected several critical parameters that were measured and

archived in plant data. The model results were then compared to plant historical data for the

selected MFT. The following measured values were selected for comparison:

• Furnace pressure

• Total secondary airflow

• FD fan discharge pressure

• Primary air heater air outlet pressure

4.1.4 Unit 4 Validation Results

Validation comparisons of the ProTRAX Unit 4 model versus plant data are shown in Appendix C.

Furnace Pressure

The Unit 4 model was initialized to the validati on condition load (536 MW) and allowed to run

for ten seconds to ensure steady-state opera tion. At 10 seconds, an MFT was initiated by

tripping all pulverizers, associated feeders and bot h PA fans. As a result of the MFT, controls

instantaneously closed the PA shutoff damper s, PA control dampers, burner coal valves,

pulverizer hot air dampers, and opened the temp ering air damper fully for each pulverizer.

Although all dampers in the primary air path associated with each pulverizer were closed, it was

the fast acting burner coal valve (with a 14 second stroke time) that decided the magnitude and

the timing of furnace pressure minimum.

Upon loss of the PA fans, the amount of pulverized coal being transported to the burners began

to drop rapidly due to the decreasing primary ai rflow. When the burner coal valves closed

completely at 24 seconds, the fireball collapse d and furnace pressure dropped to its minimum of

+1.9 inwc. The furnace then began to respond to the additional air flowing in, and consequently

furnace pressure began to increase and recovered to +5.6 inwc by 80 seconds.

The furnace pressure plot illustrates that the furnace pressure minimum predicted by the model

was +1.4 inwc lower than the corresponding plant m easurement. However, from the shape of the

plant data curves, it is likely that the mini mum furnace pressure occurred between recorded

measurements and was likely lower than 3 inches.

Total Secondary Airflow

Prior to the master fuel trip, 4,300 kpph of sec ondary air was flowing into the furnace through

overfire air dampers and six windbox compartments . Following the MFT, the controls froze

both FD fan inlet vanes and all secondary air dampers in place. The drop in furnace pressure

increased the differential pressure between the FD fans and the furnace, which led to an increase

in the secondary airflow up to a maximum of 5,110 kpph by 26 seconds. As the system

pressures stabilized, the secondary airflow dropped slig htly to a steady value of approximately

5,000 kpph. This increased airflow helped the furn ace pressure recover from its minimum. The

Total Secondary Airflow plot shows a close matc h in shape, magnitude, and timing between the

model and plant data.

# PNM, San Juan Generating Station Units 3 & 4 Page 13 of 25

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Project Number EA0624 

# FD Fan Discharge Pressure

Prior to the MFT, the FD fans were controlling sec ondary air duct pressure at +21 inwc and

hence the FD fan discharge pressure was steady at +27.5 inwc. Upon init iation of the MFT, the

controls locked both FD fan inlet vanes and all secondary air dampers in place. The 7.5 inwc

drop in furnace pressure resulting from the MFT only caused a 1.0 inwc drop in FD fan

discharge pressure because of the resistance of the secondary air heaters and secondary air

dampers. As the furnace pressure recovered, the FD fans discharge pressure reached a steady

value of +29.2 inwc by 50 seconds. The FD Fans Discharge Pressure pl ot illustrates a close

match between the model and the plant historian data.

Primary Air Heater Air Outlet Pressure

The PA fan inlet dampers were controlling the primary air heater air outlet pressure at +70 inwc

before the MFT was triggered. Immediately fo llowing the MFT, the cont rols tripped both PA

fans and locked both PA fan inlet dampers in pla ce. This caused the prim ary air heater air outlet

pressure to drop from +70 inwc to +35.8 inwc by 80 seconds. Th e plot of primary air heater

outlet pressure in Appendix C shows a close match between the model and historian data.

4.3 Validation Conclusion

A dynamic model of the San Juan Unit 4 furnace draft process equipment was constructed.

Controls were installed on the pr ocess model consistent with exis ting plant logic. The models

were tested for both steady state and dynamic accuracy. Dynamic testing consisted of running

the model through a severe furnace pressure excu rsion, and comparing the model-generated data

to plant historian data. This comparison show ed that the model data matched both the timing

and magnitude of the plant data to a high degr ee of accuracy. Therefore, the San Juan Unit 4

model is considered sufficiently accurate to provid e a meaningful basis for further draft analysis.

Note that the model can also provide excellent re lative results, which are particularly important

in the planned study.

# PNM, San Juan Generating Station Units 3 & 4 Page 14 of 25

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Project Number EA0624 

# 5.0 TRANSIENT EVENT TESTING

This section describes the transient testing proce dure and analyzes the resu lts of that testing in

detail.

5.1 Initial Conditions

All transient runs were initiated with the model at a steady-stat e condition, with all pressures,

flows, temperatures, and controlle d variables constant. While ther e were five transient events

tested during this phase, there were only two unique initial conditions.

• 100% Load – Unit 4 was operating at base load with 7 pulverizers active. Three booster

fans were in operation.

• 30% Unit – Unit 4 was operating at 30% load with 2 pulverizers active. Two booster

fans were in operation.

Critical parameters for the initia l conditions listed above are show n in Table 5. Figures 3 and 4

graphically show the steady- steady pressure profiles.

Parameter 100%

Load 30%

Load Unit

Gross Load 550 165 MW

Load Level 100 30 Percent

Coal Flow Rate 552 191 kpph

Number of Mills Grinding 6 2

Total Secondary Airflow 4,401 2,107 kpph

Economizer Oxygen 5.5 9.2 % Vol

Pulverizer Airflow (Per Mill) 190 197 kpph

FD Fan Discharge Pressure 30.0 16.6 inwc

PA Fan Discharge Pressure 73.9 70.7 inwc

Secondary Air Heater Air Outlet Pressure 25.0 15.4 inwc

Primary Air Heater Air Outlet Pressure 70.0 70.0 inwc

Secondary Air Duct Pressure 23.0 15.0 inwc

Furnace Pressure 9.6 1.9 inwc

Secondary Air Heater Gas Outlet Pressure 0.0 0.0 inwc

Baghouse Differential Pressure 11.6 2.5 inwc

Number of Booster Fans in Service 3 2

Booster Fan Pressure Rise 33.6 9.3 inwc

Booster Fan Inlet Guide Vane Position 100 29 Percent

Table 5 100% and 30% Load Initial Condition Parameters

# PNM, San Juan Generating Station Units 3 & 4 Page 15 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 Figure 3 100% Load Initial Condition Pressure Profile

Figure 4 30% Load Initial Condition Pressure Profile

# PNM, San Juan Generating Station Units 3 & 4 Page 16 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# 5.2 Transient Events

To evaluate the performance of the plant in its new configuration and with the new control logic,

as described in Section 3.2.1 “Future Configur ation Process Model” and Section 3.2.2 “Future

Configuration Control Model,” five transients were run and the results analyzed. The goal in

selecting the transients was to de fine conditions that would create large pressure excursions in

the furnace and ductwork. Transient descriptions fo r each of the five runs are listed in Table 6.

No. Transient name Unit Load Description

1 Full Load MFT 100% With the unit at full load, an MFT is initiated manually.

All controls remain in auto.

2 Full Load All Booster Fans Trip 100% With the unit at full load, a ll three-booster fans trip

and immediately trigger an MFT.

3 Full Load Both FD Fans Trip 100% With the unit at full load, both FD fans trip and

immediately initiate an MFT. All three booster fans

will runback, but no booster fans will be tripped.

4 Low Load Two Booster Fans

Runaway 30% With the unit at low load, the inlet guide vanes on

both operating booster fans ramp open.

5 Full Load All Fans Trip 100% With the unit at full load, an electrical bus failure

causes all fans to trip. An MFT is immediately

initiated. All controls remain in auto.

Table 6 Transient Descriptions



# Transient results are shown in Appendices D through H. Among the plots shown for each

transient is a graphical profile of maximum a nd minimum pressure measurements at various

positions along the air-gas path. Points on each maximum and minimum profile did not

necessarily occur at the same time.

5.2.1 Full Load MFT

This transient consisted of the following steps:

• Initialize the model to the 100% lo ad condition, as shown in Figure 3

• Run the model for five seconds to establish steady-state conditions

• Manually initiate an MFT

• All controls remain in au to throughout the transient

Transient results are presented in Appendix D.

Unit 4

At five seconds an MFT was initia ted on Unit 4. Rapid fuel shutoff via burner coal valves led to

a quick fireball collapse. Eleven seconds fo llowing the MFT, the furnace pressure dropped 11.1

inwc to a minimum value of -1.7 inwc. Furn ace pressure recovered to 2.0 inwc by 27 seconds,

and slowly decreased to +1.2 inwc by the end of the transient.

# PNM, San Juan Generating Station Units 3 & 4 Page 17 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# At 5 seconds, the kicker circuit reduced the de mand to the booster fan in let guide vanes by 43%.

The subsequent inlet guide vane movement brought about a 25% decrease in furnace exhaust

flow. It is important to include the kicker ci rcuit in the controls be cause without the kicker

circuit movement of the booster fan inlet guide vanes, furnace pressure would have dropped

another 7 inwc duri ng the transient.

To promote process stability, the kicker ci rcuit was active for 20 seconds. The runback

controller was tuned aggressively, and during initial testing, it wa s found that a kicker circuit

duration less than 20 seconds caused oscillator y behavior during furnace pressure recovery.

Holding the kicker circuit until after the comp letion of the fireball collapse and into the

beginning seconds of furnace pressure recovery led to more stable over-dampened process

response when the booster fan runback controller became active.

During the MFT, the inlet guide vanes on the FD fans were held in place to maintain airflow to

the furnace. FD fans were not tripped during the transient.

It took roughly 11 seconds for the booster fan inlet guide vanes to close from 100% to 36%. For

the remaining nine seconds of the kicker circu it, the kicker circuit demand remained constant

with only a 1% adjustment of the booster fan in let guide vanes from th e air heater gas outlet

pressure controller.

At 25 seconds into the transient, the kicker circuit was released, and the booster fan runback

controller attempted to maintain a +1 inwc furn ace pressure. In the first two seconds of the

transfer, the booster fan runback controller ope ned inlet guide vanes by 8% to 43%, keeping

furnace pressure at about +2 inwc. The slope of the furnace pressure curve flattened near this

point, and for the remainder of the transient, the runback controller gr adually increased the

booster fan inlet guide vane opening to bring furnace pressure to setpoint.

Baghouse and Scrubbers

During the fireball collapse in Unit 4, baghouse in let pressure decreased by 4.5 inwc, from -2.8

inwc to -7.5 inwc. As furnace pres sure rose following th e fireball collapse, baghouse inlet pressure

recovered to -4.1 inwc by 27 seconds. As the booster fan ru nback controller opened booster fan

inlet guide vanes, pressure at the baghouse inlet gradually decreased to -8.5 inwc by 120 seconds.

Booster fan inlet pressure rose 5.4 inwc during the fireball collapse as the rapid closing of

booster fan inlet guide vanes results in a 2,230 kpph (or 35%) drop in flow through the fans.

After 27 seconds, the booster fan runback contro ller opened booster fa n inlet guide vanes,

resulting in higher flows transporte d by the fans and a decrease in booster fan inlet pressure to

-20 inwc by the end of the transient.

The rapid closing of booster fan inlet guide va nes lessened furnace exhaust to limit the furnace

pressure excursion, but caused a 35% drop in FGD inlet flow and a corresponding 11.7 inwc

drop of FGD inlet pressure. This was the larges t pressure excursion e xperienced during the MFT

transient. From 16 to 25 seconds, the FGD inlet pressure remained nearly constant at +5.8 inwc

while the booster fan inlet guide vanes were held near 36%. FGD inlet pressure increased to

14.2 inwc by transient end as flows gr adually rose through the scrubbers.

# PNM, San Juan Generating Station Units 3 & 4 Page 18 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# Mitigation

Though the results indicate no immediate need fo r mitigation, some measures may be taken to

increase downstream pressures during MFT recovery. Either the setpoint of the furnace pressure

runback control could be increased, or the contro l system could revert back to air heater gas

outlet pressure contro l after 40 seconds.

5.2.2 Full Load All Booster Fans Trip

This transient consisted of the following steps:

• Initialize the model to the 100% lo ad condition, as shown in Figure 3

• Run the model for five seconds to establish steady-state conditions

• Manually trip all three operating booster fans

• Immediately initiate an MFT

• All controls remain in au to throughout the transient

Transient results are presented in Appendix E. In order for pressu res to come to a steady-state,

this transient was conducted for a longer test period of 360 seconds.

Unit 4

Following the trip of all three operating booster fa ns at five seconds, the controls immediately

initiated an MFT. Furnace pressure dropped to +6.5 inwc, 8.2 inwc less change than that

measured during the “Full Load MFT” transient. Tripping the booster fa ns increased pressures

upstream of the booster fan, which helped to offset the fireball collaps e. This can be seen in the

air heater gas outlet pressure. In the “Full Load MFT” transient, the air heater gas outlet pressure

had dropped to -6 inwc by 16 seconds, while in this transient, the air heat er gas outlet pressure

increased to +4 inwc over the same period.

After the completion of the fireball collapse at roughly 17 seconds, the lack of furnace exhaust

capability led to a furnace mass imbalance that caused furnace pressure to ramp up from +4.2

inwc to +19.6 inwc by 60 seconds.

After 120 seconds, as the imbalance between furn ace airflow and exhaust became less, the rate

of furnace pressure rise slowed. In the remaini ng 240 seconds of the transient, furnace pressure

only increased an additional 3.4 inwc to +26.9 inwc. The +26.9 inwc furnace pressure was the

highest measured during transient testing.

Both FD fans remained in operation throughout the transient. However, the increase in

downstream pressures led to a 33% drop in FD fan throughpu t by 90 seconds. From 4,000 kpph,

flow continued a gradual decrease, reaching 57% of the initial flow, or 3,390 kpph, by 360

seconds.

# PNM, San Juan Generating Station Units 3 & 4 Page 19 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# Baghouse and FGD

By 15 seconds, the trip of all booster fans, comb ined with the MFT kicker circuit movement of

the booster fan inlet guide vanes, caused total FGD inlet flow to drop by 39% from 6,280 kpph to

3,820 kpph. Following a 15 second, 500-kpph flow depr ession, FGD inlet flow decreased at a

slower rate over the next 300 seconds and reache d 3,320 kpph (50%) by the end of the transient.

The decrease in flow through the FGD led to incr easing pressures upstream of the booster fans.

Baghouse inlet pressure increased from -2.8 inwc at the beginning of the transient to +24.8 inwc

by transient end. Likewise, booster fan inlet pressu re increased from -16 inwc to +21 inwc as

flow through the fans decreased.

Even though the booster fans had tripped, they were still able to transport flue gas for about 30

seconds as they spun down from 890 to 330 rpm. As the fan speed decreased, the fans no longer

put work into the flue gas, but instead became a resistive element. The fans eventually slowed

down to about 65 rpm by 330 seconds.

Mitigations

The high positive pressures measured throughout the process could be prevented by eventually

following the booster fan trips with th e tripping of both FD fans. In th is transient, th e tripping of

all booster fans led to an immediate MFT. Mitig ations that tripped FD fans following the MFT

and after reaching a high furnace pressure lim it were tested. Tripping following the MFT

allowed airflow from the FD fans to at least partially purge combustib les throughout the fireball

collapse and into furnace pressure recovery. For Unit 4, the controls should wait 20 seconds

following an MFT prior to enabling a high furnace pressure trip of FD fans. For testing

purposes, the FD fan trip limit was set to +15 in wc. The improvement in furnace pressure is

shown on the Furnace Pressure plot.

When this FD tripping scheme was tested, both FD fans were tripped at 38 seconds when the

furnace pressure reached +15 inwc. The furnace pr essure reached a maximum pressure of +15.3

inwc, 11.7 inwc lower that without the FD fans tr ip. As shown in the transient maximum profile

plot, improvements were observed on all pr essures upstream of the scrubbers.

5.2.3 Full Load Both FD Fans Trip

This transient consisted of the following steps:

• Initialize the model to the 100% lo ad condition, as shown in Figure 3

• Run the model for five seconds to establish steady-state conditions

• Manually trip both operating FD fans

• Immediately initiate an MFT

• Inlet guide vanes on all booster fans were r un back, but none of the booster fans tripped

• All controls remain in au to throughout the transient

Transient results are pres ented in Appendix F.

# PNM, San Juan Generating Station Units 3 & 4 Page 20 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# Unit 4

During the MFT, furnace pressure dropped from + 9.6 inwc to -10.3 inwc, the lowest furnace

pressure measured during transient testing, and 8.6 inwc lower than measured during the “Full

Load MFT” transient. While the MFT booster fa n kicker circuit reduced furnace exhaust flow

by 2,000 kpph, any improvement to the furnace pressu re excursion was offset by the tripping of

both FD fans. Tripping the FD fans decreased flow to the furnace by 1,120 kpph. Despite the

FD fans tripping, the controls were able to ad just the booster fan inle t guide vanes to keep

furnace exhaust flow below total FD fan flow throughout the transient. This enabled furnace

pressure to recover to 0 inwc following the fireball collapse.

Though the FD fans tripped, the FD fans con tinued to transport air while coasting down

throughout the transient, though at a decreasing flow rate. In the first 15 seconds following the

FD fans trip, FD fan speed reduced 256 rpm to 453 rpm. Correspondingly, FD fan discharge

pressure dropped from +30 inwc to +9.2 inwc. However, total FD fan flow only decreased by

17% over the same period, and the slope of the total FD fan flow measurement flattened between

10 and 16 seconds. The flattening slope was due to the collapse of the fireball lowering furnace

pressure to maintain a 20 inwc differential betw een FD fans and furnace. As furnace pressure

recovered following the completion of the fire ball collapse at 18 se conds, the differential

between FD fans and furnace dropped, aiding in a sh arper decrease in total FD fan flow rate.

Between 20 and 40 seconds, the FD fans coaste d down another 153 rpm, which reduced FD fan

flow by an additional 22% (or 1,650 kpph). Duri ng this period, total FD fan flow exceeded

furnace exhaust by an average of roughly 800 kpph, which enabled the furnace pressure to

recover to -1 inwc by 40 seconds.

By the end of the transient, unit pressures were approaching +1 inwc as total FD fan flow and

furnace exhaust flow were at 9% of the initial flows. FD fan speed decreased from 300 rpm to

125 rpm over the last 80 sec onds of the transient.

Baghouse and Scrubbers

Immediately following initiation of the MFT, the kicker circuit reduced booster fan inlet guide

vane demand by 64%. By 18 seconds, total FGD in let flow reduced to approximately 50% of the

initial flow. In turn, FGD inlet pressure droppe d to +1.5 inwc, 16 inwc lower than that at the

beginning of the transient. At the same time, pressure at the baghous e inlet dropped from -2.8

inwc to -13.9 inwc, and booster fan inlet pressure dropped 2.7 inwc to -18.8 inwc.

Following the conclusion of the fireball coll apse at 18 seconds, the booster fan runback

controller continued to cl ose booster fan inlet guide vanes and decrease flow to the scrubbers.

By 113 seconds, booster fan inlet gu ide vanes were fully closed w ith a total FGD inlet flow of

550 kpph, roughly one-tenth of the starting total flow.

Mitigations

During this transient, process pressures did not reach values that required additional control

mitigations.

# PNM, San Juan Generating Station Units 3 & 4 Page 21 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# 5.2.4 Low Load Two Booster Fans Runaway

This transient consisted of the following steps, and the transient results are presented in

Appendix G:

• Initialize the model to the 30% load condition, as shown in Figure 4. Note that at low

load only two booster fans are in operation.

• Run the model for five seconds to establish steady-state conditions

• Manually open the inlet guide vanes for the two operating booster fans

• When the furnace pressure decreased below -1 inwc, the booster fan runback controller

began to runback the inlet guide va nes on the two operating booster fans

• When the furnace pressure dropped below -2 inwc for 3 seconds, a low furnace pressure

MFT was initiated by the controls

• All controls remain in au to throughout the transient

Unit 4

At five seconds into the transi ent, the booster fan in let guide vanes for operating Fan A and Fan

B began to ramp open from 29%. This caused furnace exhaust flow to increase by 300 kpph, or

roughly 10%. By 9 seconds, the imbalance in furnace draft caused furnace pressure to decrease

below -1 inwc, triggering operation of the booster fan runback controller, which began to close

the booster fans blades. Furnace pressure contin ued to drop until the minimum of -3.2 inwc was

reached at 12 seconds.

Furnace pressure stayed below -2 inwc for three seconds, which triggered a lower furnace

pressure MFT. Because of the lower load and the booster fan runback controller actions, only a

slight effect of the fireball co llapse associated with MFT was obs erved in furnace pressure from

13 to 20 seconds. By 60 seconds, the booster fan runback controller was able to maintain

furnace pressure near its +1 inwc setpoint, and he ld it near setpoint for the remainder of the

transient.

Baghouse and FGD

During the booster fans runaway, total FGD inle t flow increased from 3,000 kpph to 4,140 kpph.

This burst of flow caused FGD inlet pressure to rise 7.4 inwc to +13.2 inwc, and booster fan inlet

pressure to decrease 7 inwc to -10.7 inwc. At nine seconds, the booster fan runback controller

began to ramp back the inlet gui de vanes on both booster fans. This decrease in booster fan inlet

guide vane position dropped total FGD inlet fl ow to 1,470 kpph by 27 seconds. By the end of

the transient, as the booster fan runback controller steadied inlet guide van adjustment, total flow

to the FGD stabilized at 2,580 kpph and baghouse and booster fan inlet pressures approached

pre-transient values.

Because of the action of the booster fan runback c ontroller, none of the FD or booster fans were

tripped during this transient.

# PNM, San Juan Generating Station Units 3 & 4 Page 22 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# Mitigation

The booster fan runback controlle r overriding adjustment of the inlet guide vanes on all booster

fans was critical to mitigating the furnace pressure excursion during this transient. After nine

seconds into the transient, if the booster fan inlet guide vanes continued to ramp open, the

negative furnace pressure excursion would have been more severe. The last line of defense for

this transient was to trip the fan(s) that are running away. TRAX recommends using a booster

fan-tripping scheme based upon low inlet duct pressu re with a load-indexed limit. At 30% load,

the booster fans could be tripped if fan inlet pr essures dropped below -18 inwc. At higher loads,

the trip limit would decrease, at lo wer loads the trip would increase.

5.2.5 Full Load All Fans Trip

This transient consisted of the following steps:

• Initialize the model to the 100% lo ad condition, as shown in Figure 3

• Run the model for five seconds to establish steady-state conditions

• Manually trip both operating FD fans, and all three operating booster fans

• Immediately initiate an MFT

• Controls continued to modulate the booster fan inlet guide vanes

• All controls remain in au to throughout the transient

Transient results are pres ented in Appendix H.

Unit 4

During the MFT, furnace pressure dropped from + 9.6 to -1.3 inwc, 0.5 inwc less excursion than

measured during the “Full Load MFT” transient. The tripping of booster fans, combined with

the action of the MFT kicker circuit, led to a 50% reduction in furn ace exhaust flow by 20

seconds. This large reduction in furnace exhaust helped to mitigate the effect of the fireball

collapse. On the other hand, the loss of 35% of flow through the FD fans offset some of the

change in furnace exhaust. However, the net flow favored airflow to the furnace, and furnace

pressure recovered to +1 inwc by 60 seconds. By 120 seconds, the lack of airflow led furnace

pressure to decrease back to ambient pressure.

Baghouse and Scrubbers

Following the conclusion of the fireball collapse at 17 seconds, the runback furnace pressure

controller adjusted booster fan inlet guide vane s, which reduced flow through the scrubbers.

After 60 seconds, the controls gradually closed th e booster fan inlet guide vanes, but all the fans

had decelerated so that flows through the system had reduced. By the end of the transient, FGD

inlet flow had decreased to roughly 12% of that measured at the star t of the transient.

Mitigations

During this transient, process pressures did not reach values that required additional control

mitigation measures.

# PNM, San Juan Generating Station Units 3 & 4 Page 23 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# 5.3 Transient Events Summary Table

A summary of the unmitigated runs is shown in Table 7 below.

Furnace

Pressure

(inwc) Airheater

Gas Outlet

Duct (inwc) Booster

Fan Inlet

(inwc) Case # Transient Name No. of

Booster

Fans in

Service Gross

Load

%

Min Max Min Max Min Max

1 Full Load MFT 3 100 -1.7 +9.6 -6.1 0.0 -19.9 -10.4

2 Full Load All Booster Fans Trip 3 100 +6.5 +26.9 0.0 +24.8 -16.1 +21.0

3 Full Load Both FD Fans Trip 3 100 -10.3 +9.6 -13.1 +0.7 -18.9 +0.4

4 Low Load Two Booster Fans

Runaway 2 30 -3.2 +2.0 -5.7 +0.6 -10.7 -0.7

5 Full Load All Fans Trip 3 100 -1.3 +9.6 -2.7 +0.7 -16.1 -0.3

Table 7 Unmitigated Transient Event Summary Table



# A summary of the mitigated run is shown in Table 8 below.

Furnace

Pressure

(inwc) Airheater

Gas Outlet

Duct (inwc) Booster

Fan Inlet

(inwc) Case # Transient Name No. of

Booster

Fans in

Service Gross

Load

%

Min Max Min Max Min Max

2 Full Load All Booster Fans Trip 3 100 -0.5 +15.3 -0.7 +11.9 -16.1 +6.1

Table 8 Mitigated Transient Event Summary Table

# PNM, San Juan Generating Station Units 3 & 4 Page 24 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# 6.0 CONCLUSIONS

During transient testing, furnace pressures were held to within the range of +27 inwc to -11 inwc.

Only the “Full Load All Booster Fans Trip” tran sient led to high furnace pressures, but tripping

the FD fans easily mitigated the high +26.9 inwc measured at the furnace. The remaining

transients led to negative furnace pressure excu rsions, with the most severe being -10.3 inwc

measured during the “Full Load All FD Fans Trip” transient.

Pressure excursions downstream of the flue gas outlet of the air heaters were within +25 inwc

and -20 inwc. The rapid movement of booster fan inlet guide vanes to prevent furnace pressure

excursions often caused sharp downstream pressure excursions. For example, during the “Full

Load MFT” transient, furnace pressure changed by 11.1 inwc (from +9.6 inwc to -1.7 inwc).

During the transient, closing booster fan inlet guid e vanes by 64% reduced flow to the scrubbers

and caused inlet pressure to the FGD to drop 11.7 inwc.

The fast-adjusting booster fan inle t guide vanes were a key fact or in moderating the furnace

pressure drop associated with a MFT fireball co llapse. On an MFT, controls closed burner

shutoff valves that rapidly cut o ff fuel to the furnace and caused a sharp fireball collapse. With

FD fan dampers frozen in place (per NFPA requ irements), the only res ponse available to the

controls was to cut furnace exhaust by decreasing the flow transported by the downstream

booster fans. The 17 second full stroke time of th e booster fan inlet guide vanes enabled controls

to reduce furnace exhaust by 20% in 10 seconds. This flow reduction prevented 7 inwc of

additional furnace pressure excursion during the fireball collapse.

Because the MFT fireball collapse was a short duration event, a ki cker circuit was necessary to

reduce the booster fan inlet guide vane position demand. At full load, the fireball collapse was

complete 12 seconds after MFT ini tiation. The air heater gas outlet pressure controls alone were

not fast enough to close booster fan inlet guide vanes to achieve the 20 % reduction in furnace

exhaust necessary to mitigate the MFT. Upon initi ation of an MFT, a kicker circuit immediately

reduced demand to the booster fan inlet guide vanes by 43%. This quick change in demand

drove close booster fan inlet guide vanes sufficien tly reduced furnace exhaust flow and held the

furnace pressure excursion to -1.7 inwc during a full load MFT.

A fast acting booster fan runback control was crit ical to mitigating the “Low Load Two Booster

Fans Runaway” transient. When the furnace pr essure dropped below -1 inwc, the booster fan

runback controller overrode no rmal controls and adjusted boos ter fan inlet guide vanes to

maintain +1 inwc furnace pressure. During the “Low Load Two B ooster Fans Runaway”

transient, the booster fan runback controls be gan to decrease booster fan inlet guide vane

positions after the runaway had opened the vanes to 53%. If the booster fan inlet guide vanes

had driven full open, the furnace pressure excursion would have been more severe than the -3.2

inwc measured during the transient.

# PNM, San Juan Generating Station Units 3 & 4 Page 25 of 25

Implosion Study – Final Report 7/10/2007

Project Number EA0624 

# Based on the results of the transient runs, TR AX recommends the following control strategies

and mitigating measures be implemented in the future plant configuration controls:

1. In normal operation, adjust booster fan inlet guide vanes via a control th at uses a FD inlet

guide vane demand feed-forward, added to a trim controller that monitors air heater gas

outlet pressure.

2. For mitigating MFT events, a kicker circuit should be used to immediately run back

booster fan inlet guide vanes. The kicker would be activated by the MFT circuit and

should last 20 seconds. The extent of the booster fan runback should be load

dependent—i.e. at lower loads the extent of the booster fan runback would be less than a

runback during a MFT at full load.

3. An overriding booster fan runback controller should be used to help mitigate negative

furnace pressure excursions. The runback c ontroller should take precedence over normal

controls and operator auto ma nual stations. When active, the runback controller would

adjust booster fan inlet guide vanes to maintain a positive furnace pressure. The

controller would go active when the furnace pressure dropped below -1 inwc and if the

furnace MFT kicker circuit was not active.

4. If the booster fans are tripped, both FD fans should be tripped if the furnace pressure

exceeds a high furnace pressure limit to pr event over-pressurizing the furnace following

an MFT.

# APPENDIX A

Model Process Schematics1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 1-1Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed ConfiguraionPROCESS MODELSAN JUAN GENERATING STATION UNIT 4BOILER IMPLOSION STUDY3-2BAGHOUSE ANDBOOSTER FANSKey:ProTRAX Module NameModule IDFlow Stream IDFSIDFSIDConnectorCoordinates of matching connector on page p-pPage number of matching connectorp-p (xy)'MID'FANPUBLIC SERVICE COMPANY OF NEW MEXICO1-1INDEX1-2PULVERIZERS A-C2-2PULVERIZERS D-F2-1FANS ANDAIR HEATERS3-1FURNACE4-2SCRUBBERS ANDSTACK1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 2-1Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed ConfiguraionEDWA_4LSCASO_4ERF_4LSAF_4ERD_4LSAD_4ERC_4LSAC_4ERB_4LSAB_4ERA_4LSAA_4LOFA_4EOFA_4ETA_4LSCBSO_4LSAHB_4EHPAH2_4EHPAH1_4LPAH_4EPSCAH_4EPAH_4LPAGSO_4GLPAH_4EPAGCD_4GEPAH_4ESBGSO_4GESAHB_4GESAHA_4ESAGSO_4LSAHA_4ESAHB_4ESCAHB_4ESAHA_4ESCAHA_4LDWB_4EDWB_4LRF_4LRE_4LRD_4LRB_4LRC_4LRA_4EWBDK_4LWBDK_4ESAF_4ESAE_4ESAD_4ESAC_4ESAB_4ESAA_4LSAE_4ERE_4LDWA_4LPAOSB_4GLSAHB_4GLSAHA_4EFDB_4EFDA_4LPAB_4EPAB_4LFDB_4LFDA_4LPAA_4EPAA_4EPAHLA_4LPAHLA_4LSAHLB_4ESAHLB_4LSAHLA_4ESAHLA_4LPAOSA_4ETDA_4ETDB_4ETDC_4ETDD_4ETDE_4ETDF_4EPAOSB_4EPAOSA_4EFDOSB_4EFDOSA_4LFDOSB_4LFDOSA_4LTA_44-2 (C8)Sec. AH LeakageFANS AND AIR HEATERS'J4_4'DAMPER'FDOSA_4''J5_4'DAMPER'FDOSB_4''J11_4'DAMPER'PAOSA_4'Forced DraftFan AOutletShutoff'J12_4'DAMPER'PAOSB_4'Primary Air Fan A PLNMRV 'PN1_4'2-2 (B3)2-2 (C3)2-2 (D2)1-2 (B2)1-2 (C2)1-2 (D2)Temp Air to Pulverizer F3-1 (B5)From ESP3-1 (B5)4-2 (D8)4-2 (B8)3-1 (C1)SCAH(Out of Service)Sec. Air Heater BOutletShutoffAtmosphereAtmosphereTo Furnace

PLNMRV 'PN2_4''J16_4''J17_4'DUCT'TA_4'OutletShutoffDUCT'SAHLA_4'DUCT'SAHLB_4'4-2 (A8)To Flue Gas Duct4-2 (B8)DUCT'PAHLA_4'Pri. AH Leakage3-1 (A5)4-2 (C8)From ESPFrom ESPPri. Air HeaterPrimary Air Fan BOutletShutoffDUCT'DWA_4'Forced DraftFan BFANTAB'PAA_4'FANTAB'FDA_4'FANTAB'FDB_4'FANTAB'PAB_4'BC'BCA_4'BC'BCB_4'RHTRFD'PAH_4'RHTRFD'SAHA_4'RHTRFD'SAHB_4' PLNMRV 'PN20_4'DAMPRN'SAA_4'DUCT'WBDK_4''JEW_4'DAMPRN'RA_4'DAMPRN'SAB_4'DAMPRN'RB_4'DAMPRN'SAC_4'DAMPRN'RC_4'DAMPRN'SAD_4'DAMPRN'RD_4'DAMPRN'SAE_4'DAMPRN'RE_4'

PLNMRV 'CE_4'DAMPRN'SAF_4'DAMPRN'RF_4'1-2 (C1)'JFB'CompartmentsDUCT'DWB_4'

PLNMRV 'PN29_4'RegistersSCADSDUCT'SCAHA_4'SCAH(Out of Service)DUCT'SCAHB_4'DAMPER'SCASO_4'DAMPER'SAGSO_4'DAMPER'SCBSO_4'DAMPER'SBGSO_4'DAMPER'PAGCD_4'DAMPER'PAGSO_4'SCAH(Out of Service)DUCT'PSCAH_4'Temp Air to Pulverizer ATemp Air to Pulverizer BTemp Air to Pulverizer CTemp Air to Pulverizer DTemp Air to Pulverizer E'JHP_4'2-2 (C1)Hot Primary Air toPulverizers A,B,CHot Primary Air toPulverizers D,E,FSec. Air Heater ADAMPRN'OFA_4'OFA

PLNMRV 'CA_4'

PLNMRV 'CB_4'

PLNMRV 'CC_4'

PLNMRV 'CD_4'

PLNMRV 'CF_4'PXMTRP'PT408F'PXMTRP'PT408E'PXMTRP'PT439A'WXMTRF'WLSAA'WXMTRF'WLSAB'WXMTRF'WLSAC'WXMTRF'WLSAD'WXMTRF'WLSAE'WXMTRF'WLSAF'TXMTRT'TSAHA'TXMTRT'TSAHB'WXMTRF'WEDWA'WXMTRF'WEDWB'To Flue Gas DuctTo Flue Gas DuctWindboxTo Flue Gas DuctTo Flue Gas DuctTo Flue Gas DuctPXMTRP'PEFDA_4'PXMTRP'PLFDA_4'PXMTRP'PESAHA_4'PXMTRP'PLSAHA_4'PXMTRP'PESAA_4'PXMTRP'PGLSAHA_4'1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 3-1Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed Configuraion

L B C DBC'BCD_4'FURNMF'FRN_4'LSECSH_4LECON_4LESPA_4EPAGCD_4ESAGSO_4ESBGSO_4LESPB_4LWBDK_4LLKOUT_4ELKOUT_4ESHPL_4LFRND_4LFRN_4LBNRD_4LBRN_4LSEAL_4ELKIN_4LLKIN_4LRH_4LSHPL_4LPSH_41-2 (A8)Primary Air &Coal Pulv A-FBANK'SHPL_4'BANK'SECSH_4'BANK'RH_4'BANK'PSH_4'BC'SEAL_4'Water SealSecondary PlatenSuperheaterSecondarySuperheaterReheaterPrimarySuperheaterBANK'ECON_4'EconomizerFrom WindboxesFURNACEFurnaceFurnaceIn-Leakage

DUCT

'LKIN_4' BCATM

'LKBC_4'DUCT'FRND_4' PLNMRV 'PLK_4'BC'L2BC_4'DUCT'LKOUT_4'AtmosphereFurnaceOut-Leakage2-1 (B8)DUCT'ESPB_4'

PLNMRV

'ESPR_4'Hot-SidePrecipitator2-1 (C5)To SecondaryAir Heater A2-1 (A5)To SecondaryAir Heater B2-1 (D6)To PrimaryAir HeaterDUCT'ESPA_4' PLNMRV

'PL1_4'EESPA_4EESPB_4BURNMF'BRN_4'PXMTRP'PFURN'(De-energized)PXMTRP'PLECON_4'PXMTRP'PESAGSO_4'1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 1-2Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed ConfiguraionLPVC_4EPVC_4EPVB_4LPACC_4LPACB_4EPVA_4LPACA_4LBSOF_4EHPAH1_4LHAH1_4EPASOC_4EPASOB_4EPACC_4EPACB_4EPACA_4EPASOA_4EHDC_4EHDB_4EHDA_4ETDC_4LBNRD_4EBNRD_4ETDA_4ETDB_4LBSOD_4LBSOE_4LBSOB_4LBSOC_4LHDA_4LTDA_4LPVA_4EBSOA_4LTDB_4LHDB_4LTDC_4LHDC_4LPVB_4EBSOC_4EBSO2_4LBSOA_4PULVBR'PVA_4'2-1 (C8)DAMPER'TDA_4'DAMPER'HDA_4''JBA_4''JCA_4'DAMPRC'BSOA_4'Tempering DamperHot Air DamperDAMPER'TDB_4'DAMPER'HDB_4''JBB_4'PULVBR'PVB_4''JCB_4'DAMPRC'BSOB_4'DAMPER'TDC_4'DAMPER'HDC_4''JBC_4''JCC_4'DAMPRC'BSOC_4'2-1 (C8)'JC15_4'2-2 (D8)2-2 (C8)3-1 (D1)To BurnerTemp Air fromPA PlenumTemp Air fromPA PlenumTemp Air fromPA PlenumFrom Pulverizer EPulverizer APulverizer BPulverizer CDUCTC'BNRD_4'PULVERIZERS A - C PLNMRV 'HP1_4'2-1 (D7)2-1 (D8)Hot Air fromPrimary Air HeaterDAMPER'PASOA_4'DAMPER'PACA_4'DAMPER'PASOB_4'DAMPER'PACB_4'DAMPER'PASOC_4'DAMPER'PACC_4'Primary AirShutoff DamperPrimary AirControl DamperBurner Coal ValvesDUCT'HPAH1_4'From Pulverizer D2-2 (B8)From Pulverizer FHot Primary AirHeader A'JDA_4''JDB_4''JDC_4'TXMTRT'TPVA'TXMTRT'TPVB'TXMTRT'TPVC'WXMTRF'WEPVA'WXMTRF'WEPVB'WXMTRF'WEPVC'PULVBR'PVC_4'1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 2-2Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed ConfiguraionLPVF_4EPVF_4LPVE_4EPVE_4LPVD_4EPVD_4LPACF_4LPACE_4LPACD_4EHPAH2_4EHDF_4EHDE_4EHDD_4LHAH2_4ETDD_4LTDD_4LBSOD_4EBSOD_4LHDD_4EPACD_4EPASOD_4EPASOF_4EPASOE_4EPACF_4EPACE_4ETDF_4ETDE_4EBSOF_4LHDF_4LTDF_4EBSOE_4LTDE_4LHDE_4LBSOE_4LBSOF_4DAMPER'TDE_4'DAMPER'HDE_4''JBE_4''JCE_4'DAMPRC'BSOE_4'Tempering DamperHot Air DamperDAMPER'TDF_4'DAMPER'HDF_4''JBF_4''JCF_4'DAMPRC'BSOF_4'2-1 (D8)2-1 (D8)1-2 (A6)1-2 (A6)Temp Air fromTemp Air fromPA PlenumPA PlenumTo BurnerTo BurnerPulverizer EPulverizer FPULVERIZERS D - FDAMPER'PASOE_4'DAMPER'PACE_4'DAMPER'PASOF_4'DAMPER'PACF_4'Primary AirShutoff DamperPrimary AirControl DamperDAMPER'TDD_4'DAMPER'HDD_4''JBD_4''JCD_4'DAMPRC'BSOD_4'2-1 (D8)Temp Air fromPA PlenumPulverizer DDAMPER'PASOD_4'DAMPER'PACD_4'1-2 (A6)To BurnerDUCT'HPAH2_4' PLNMRV 'HP2_4'2-1 (D7)Hot Air fromPrimary Air HeaterHot Primary AirHeader BBurner Coal Valves'JDD_4''JDE_4''JDF_4'TXMTRT'TPVD'TXMTRT'TPVE'TXMTRT'TPVF'WXMTRF'WEPVD'WXMTRF'WEPVE'WXMTRF'WEPVF'PULVBR'PVD_4'PULVBR'PVE_4'PULVBR'PVF_4'1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 3-2Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed ConfiguraionEBFIDC_4EBFIDA_4EBFIDB_4LFFOD_4LSADB1_4ESADB1_4LSADB_4LSADA1_4ESADA1_4LSADA_4EFFOD_4LBHOLD_4LBYBH_4EBYBH_4EBHILD_4LFFID_4

E F F I D _ 4LBHILD_4 E B H O L D _ 4 E S A D A _ 4ESADB_4LBFODC_4LBFODB_4LBFODA_4LPJFF_4EBFODC_4LBFC_4EBFODB_4LBFB_4EBFODA_4LBFA_4EBFC_4EBFB_4EBFA_4LBFIDC_4LBFIDB_4LBFIDA_4BAGHOUSE AND BOOSTER FANS

PLNMRV 'EBFPL_4'DAMPER'BFIDA_4'FANTAB'BFA_4'DAMPER'BFODA_4'DAMPER'BFIDB_4'FANTAB'BFB_4'DAMPER'BFODB_4'DAMPER'BFIDC_4'FANTAB'BFC_4'DAMPER'BFODC_4'Booster Fan N'BFAJ_5''BFBJ_5''BFCJ_5''BOAJ_4''BOBJ_4''BOCJ_4'DUCT'SADA_4'DUCT'SADB_4'DUCT'PJFF_4' PLNMRV 'BHPL_4'BaghouseDAMPER'BYBH_4'4-2 (C1)4-2 (B1)4-2 (A1)4-2 (A6)4-2 (D6)PXMTRP'PT439A1'DAMPER'BHOLD_4'BaghouseOutlet DamperBaghouse Emergency BypassDamperDAMPER'BHILD_4'BaghouseInlet DamperBooster Fan PBooster Fan RDUCT'FFID_4'DUCT'FFOD_4''BHJ1_4''BHJ2_4'

PLNMRV

'SAAPL_4' PLNMRV

'SABPL_4'DUCT'SADA1_4'DUCT'SADB1_4' PLNMRV 'BFPL_4'Flue Gas FromAirheatersFlue Gas FromAirheatersTo Scrubber NTo Scrubber PTo Scrubber RPXMTRP'PT439A2'PXMTRP'PT439A3'PXMTRP'PT439A4'PXMTRP'PLBHOLD_4'PXMTRP'PLBFA_4'1122334455667788AABBCCDDPrepared byJBDrawing No.EA0624.01 - 04 - 001 page 4-2Date04 Oct 2006No.123Date25 Oct 200612 Nov 200601 Mar 2007BySPSPKMKDescriptionIncorporated client's commentsAdded Baghouse and Upgraded the Booster FansFinal ConfigurationRevision HistoryNo.DateByDescriptionTRAX LLC, Forest,Virginiafor Public Service Company of New MexicoPublic Service Company - San Juan Unit 4Boiler Implosion StudyProcess Model - Proposed ConfiguraionESADB_4LSAHLB_4GLSAHB_4LPB_4FGDSCB'FGDC_4'ESADA_4LBFODC_4LBFODB_4LBFODA_4LPAGSO_4GLSAHA_4LPAHLA_4LSAHLA_4LFE_4EFE_4EPB_4LPA_4EPA_4LSBC4C_4LSBC3C_4LSBC2C_4LSBC1C_4LWWBCC_4LSBC4B_4LSBC3B_4LSBC2B_4LSBC1B_4LWWBCB_4LSBC4A_4LSBC3A_4LSBC2A_4LSBC1A_4LWWBCA_4LFGDCD_4LFGDBD_4LFGDAD_4FGDSCB'FGDB_4'FGDSCB'FGDA_4'LFGDC_4LFGDB_4LFGDA_4EFGDC_4EFGDB_4

E F G D A _ 4LSTK_4ESTK_4

DUCTDW 'STK_4'BC'ATMSK'Stack'BFCJ_4''BFBJ_4''BFAJ_4' PLNMRV 'FGDPL_4'DUCT'FGDAD_4'DUCT'FGDBD_4'DUCT'FGDCD_4'BC'WWBCA_4'BC'SBC1A_4'BC'SBC2A_4'BC'SBC3A_4'BC'SBC4A_4'BC'WWBCB_4'BC'SBC1B_4'BC'SBC2B_4'BC'SBC3B_4'BC'SBC4B_4'Wash WaterSlurryEnteringWash WaterSlurryEnteringBC'WWBCC_4'BC'SBC1C_4'BC'SBC2C_4'BC'SBC3C_4'BC'SBC4C_4'Wash WaterSlurryEntering2-1 (C3)2-1 (D4)2-1 (A3)'J411_4''J413_4' DUCT 'PA_4' DUCT

'PB_4'DUCT'FE_4'From SecondaryAir Heater AFrom SecondaryAir Heater BFrom PrimaryAir Heater2-1 (B1)LeakageFrom SecondaryAir Heater A2-1 (B1)LeakageFrom SecondaryAir Heater B2-1 (D2)LeakageFrom PrimaryAir HeaterScrubber Module NScrubber Module PScrubber Module RPLNMRV'STKPL_4'

T XMTRT 'TESTK'3-2 (C8)3-2 (B8)3-2 (A8)3-2 (A8)3-2 (D7)SCRUBBERS AND STACKFlue Gas toBaghouse InletFlue Gas toBaghouse InletFlue GasFrom Booster Fan AFlue GasFrom Booster Fan BFlue GasFrom Booster Fan CPXMTRP'PT408E1'PXMTRP'PT408E2'PXMTRP'PLFGDA_4'PXMTRP'PESTK_4'PXMTRP'PLSTK_4''J412_4'

# APPENDIX B

Model Control Schematics1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 1-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration INDEX1-1PULVERIZER /1-22-23-2CONTROLS MODEL2-1COMPARTMENT ACONTROLSPULVERIZER /COMPARTMENT BCONTROLSPULVERIZER /COMPARTMENT CCONTROLSPULVERIZER /4-2 5-26-2COMPARTMENT DCONTROLSPULVERIZER /COMPARTMENT ECONTROLSPULVERIZER /COMPARTMENT FCONTROLS3-14-1 5-1SEC AIR CNTRL &6-1MASTER FUEL7-1EQUIPMENTSAN JUAN GENERATING STATION UNIT 4BOILER IMPLOSION STUDYPUBLIC SERVICE COMPANY OF NEW MEXICOLEGENDOXYGEN TRIMTRIPSHUTDOWN8-1BOOSTER FANSCONTROLPRIMARY AIRPRESSUREWINDBOXPRESSURE7-2PRIMARY AIRSHUTOFF DAMPERSBAGHOUSEDAMPERS8-2FD FANS TRIPS1-31122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 2-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration LegendLEGENDPROCESS VARIABLE FROMFIELD TRANSMITTERLEAD-LAGLIMIT HIGHValve DetailsCYxyz= Valve Demandxyz = Valve PositionModule IDYOUTPUT TOFINAL CONTROL ELEMENTPROCVAR*ID*IDVALVE*IDSUM*IDTRANSFERDIFFERENCEDIVIDEDERIVATIVEBIASBIAS*IDd*IDdt*IDf(x)*ID~1 + ks*ID1 - 2s*ID>*ID> <LIMIT HIGH LOW*ID<LIMIT LOWX*IDMULTIPLYOR*IDLOGIC ORNOT*IDLOGIC NOTK/S/D*IDPID CONTROLLERK*IDPROPORTIONAL*IDRAMP>*ID<*IDHIGH SELECTLOW SELECTAMANUAL ANALOG SETMANUAL INTEGER/DISCREET SET*IDSQUARE ROOTf(t)*IDdoTIME DELAY*IDANDLOGIC AND*IDAUTO MANUAL STATIONFUNCTION GENERATORVELOCITY LIMITER*IDV<K/S*IDFLIP FLOPPI CONTROLLERACCUM1*IDINTEGRATORACCUM2*ID2-INPUT INTEGRATORWITH LIMITSH/*ID*IDH/L/L*IDHIGH SIGNAL MONITORHIGH/LOW SIGNAL MONITORLOW SIGNAL MONITORMEM2DIGITAL OUT WHEN INPUTIS ABOVE SETPOINTDIGITAL OUT WHEN INPUTIS BELOW SETPOINTDIGITAL OUT WHEN INPUTIS ABOVE HIGH SETPOINTOR BELOW LOW SETPOINTORAN*IDAVERAGE0 = Auto1 = Manual1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 3-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration FDTSFDTVGROSS_MWGENDMDSA31DSI31DCYFDOSBAUT31DFX31DKS31AKS31ASI31CSA31CCYFDOSAAUT31CFX31CKS31ABLRDMDGENDMDAUT31AAUT31BKS31AFDB_TRPFDA_TRPNFDFX31ASLO31AGENDMDPLDWBPLDWASFDANFDANFDSFDBNFDBBI31ABI31BCYFDACYFDBSA31ASI31ASA31BSI31BE31A'E31A'K/S'KS31A'BIAS'BI31A''TR31A'ACYFDAFD Fan AInlet Guide VanesBIAS'BI31B''TR31B'ACYFDBFD Fan BInlet Guide VanesWINDBOX PRESSUREf(x)'FX31A'

PROCVAR

'WBOXPA' PROCVAR

'WBOXPB' PROCVAR

'GENDMD'Firing Rate DemandAA'TR61A'A'TR61B'FD Fan A SpeedFD Fan B Speed<'SLO31A'1-3 (D3)1-3 (B3)REF : FOXBORO 04F465609-FD-4049 Rev. 3B&WD8071960A Sht 1D8071960CSht 2D8071960ASht 3'AUT31A''AUT31B'Boiler Demand

5-1 (D2)f(x)'FX31B'709 RPMf(x)'FX31C''AUT31C''TR31C'ACYFDOSAFD Fan AOutlet Shutoff Damperf(x)'FX31D''AUT31D''TR31D'ACYFDOSBFD Fan BOutlet Shutoff Damperf(x)'FX31B1'Secondary Air Duct PressAX Y0 0100 90X Y0 0100 550P = 1.0I = 10 SecX Y0 0100 100X Y0 0100 100X Y0 030 1554.55 19100 231122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 4-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration BI41A

P L P A HSI41DSA41DCYPAOSBAUT41DFX41DKS41BSI41CSA41CCYPAOSAAUT41CFX41CKS41BPVDMDFX41BKS41AKS41BKS41BAUT41BAUT41AAVE41A

A V E 4 1 AYPABYPAACNPAALOTRPPABPABZEROCNPABHIPABSELNPABPABSPDCNPABLOTRPPAAPAAZERONPAAPAASPDCNPAAHIPAASELCYPABCYPAASI41BSA41BSI41ASA41AE41BE41AFX41APRIMARY AIR PRESSURE

PROCVAR

'PV41A'Pri Air Duct PressCoal Demandf(x)'FX41A'BIAS'BI41A''E41A'K/S'KS41A''E41B'K/S'KS41B'N'AVE41A''TR41A''TR41B'AACYPAAPA Fan ACYPABPA Fan BAPA FAN SPEED'TR41C''TR41D'AHi SpdLo SpdSpeed SelectorA'TR41E'A'TR41F'AHi SpdLo SpdSpeed SelectorA

PROCVAR

'YPAA_4' PROCVAR

'YPAB_4''AUT41A''AUT41B'f(x)'FX41B'PA Fan Inlet Guide Vane Position

5-1 (A1)'TR41G'ACYPAOSAPA Fan AOutlet Shutoff Damper'AUT41C'f(x)'FX41C''TR41H'ACYPAOSBPA Fan BOutlet Shutoff Damper'AUT41D'f(x)'FX41D'Normal 1182 RPMNormal 1182 RPM887 RPM887 RPMREF : FOXBORO 04F465609-FD-4037 Rev. 304F465609-FD-4038 Rev. 3B&WD8071959A Sht 1D8071959DSht 2D8071959BSht 3Inlet DamperInlet DamperP = 1.0I = 10 SecX Y0 0100 100P = 0.5I = 20 SecX Y0 032.8 100X Y0 032.8 1001122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 5-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration WAIRSUM51ESUM51BBI51AFX51CBLRDMDWEDWBWEDWAWEPVFWEPVEWEPVDWEPVCWEPVBWEPVAPVDMDBLRDMDBLRDMDBLRDMDSEHI51AECONO2TOTFUELDIV51APV51ANUMOFPULVO2TRIMKS51BE51BFX51BKS51ASUM51DE51AMUL51AWAIRTOTAIRSCAT421SUM51A

PROCVAR

'TOTFUEL'Total Fuel Flow(Add All Fuel To Pulverizers)Boiler Demand'SUM51A''SUM51B''SUM51C'Primary Air Flowf(x)'FX51A'X'MUL51A''E51A'K/S'KS51A''SUM51D''LIM51A'> < 1-2 (D6)f(x)'FX51B' PROCVAR

'ECONO2''E51B'K/S'KS51B''LIM51B'><f(x)'PV51A'A'DIV51A'Number ofPulverizersPulverizer Demandf(x)'PV51B'>'SEHI51A'Flue Gas O2(0.7 - 1.3)Sec. Air Trim

3-1 (C3)SEC AIR CNTRL & OXYGEN TRIM

4-2 (D1)( 0-100 % ) PROCVAR

'WEPVA' PROCVAR

'WEPVB' PROCVAR

'WEPVC' PROCVAR

'WEPVD' PROCVAR

'WEPVE' PROCVAR

'WEPVF'Primary Air Flow'SUM51E'

PROCVAR

'WLDWA' PROCVAR

'WLDWB'Secondary Air Flow 3-1 (C3)f(x)'FX51C'BIAS'BI51A'Firing Demand( KPPH )( 0-100 % )Air Flow MasterREF : FOXBORO 04F465609-FD-4040 Rev. 304F465609-FD-4041 Rev. 304F465609-FD-4042 Rev. 3B&WD8071956A Sht 1D8071956ASht 2D8071956ASht 36-1 (C1)X Y0 027.0 191,00049.0 360,00074.7 460,00090.0 552,200X Y0 092033.3 80P = 0.1I = 100 SecX Y0 02474 274998 80P = 1I = 10 SecX Y20 1049.1 6.874.7 5.890.0 5.5X Y0 090 11122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 6-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration TRIP_ALL_BFDHBDPHBHDPBHDELPCLSPULDMPRWAIT8MFTWAIRRHTBLKMFTBA6TD61ANO_PA_FANSMFTWAIT7FREEZE_FD_IGVWAIT6FEEDER_TRIPMFTMFTMFTMFTMFTFDR_NOSTOPMFTCNO_FD_FANSMFTFMFTEPFURNACEPFURNACELO61APLPAHWAIT5CLOSE_COAL_VALVESWAIT1TRIP_PULVTRIP_PA_FANSWAIT2WAIT3IGNITOR_TRPMFTALO61BHI61AMFTDLO61CMFTSETMFTRESET'A1'AND'A2'AND'A3'AND'A5'ANDMASTER FUEL TRIPPROCVAR'PV61A'PROCVAR'PV61C'OR'OR61A'PROCVAR'PV61E'/L'LO61B'f(t)pu'TD61B'PROCVAR'PV61B'H/'HI61A'< -2 inwcf(t)pu'TD61C'OR'SMFT2'3 SecPrimary Air Duct PressureFurnace Pressure< 25%3 Secf(t)pu'TD61A'< +47.7 inwc5 Sec/L'LO61C'> +34.4 inwc3 Secf(t)pu'TD61D'Secondary Air FlowMEM3'MMFT'Both PA fans tripped/L'LO61A'Loss of FD fansMFT Emerg. PBf(t)pu'TD61E'0 Sec'A6'ANDPROCVAR'PV61F'All Feeders Not StoppedReheater BlockedIgnitor Fuel TripPulverizer TripPA Fans Trip'A7'ANDClose Burner Coal ValvesFeeder Trip'A8'ANDFreeze FD IGVREF : Forney Technical Manual; Unit 4Section 8 March 1981San Juan Generating Station Unit 4Operating Procedures Volume IXU4P-73, Date 11-6-845-1 (C5)'A9'ANDClose Pulverizer AirShutoff Damper9-2 (B5)H/'HI61A1'> +14.0 inwcBaghouse DPf(t)pu'TD61C1'5 Sec8-2 (D7)Trip All Booster Fans1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 7-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration TRIP_ALL_BFTRIP_ALL_BFTRIP_ALL_BFSBCSBBSBANBFCNBFBNBFANBFNBFNBFTRIP_PA_FANSFDB_TRPFDA_TRPPAB_TRPTRIP_PA_FANSPAA_TRPYBSOYBSOYBSOYBSOYBSONPULVNPULVNPULVNPULVNPULVNPULVTRPPULVTRPPULVTRPPULVTRPPULVTRPPULVTRPPULVNPVANPVBNPVCNPVDTRPVATRPVBTRPVCTRPVDNPVENPVFTRPVETRPVFSA71BSA71CSA71DSA71FSA71GSA71HSI71HSI71GSI71FSI71DSI71CSI71BCYBSOACYBSOBCYBSOCCYBSODCYBSOECYBSOFYBSOEQUIPMENT SHUTDOWNAA'TRPA15''TRPA16'ABURNER COAL VALVES'TRPA17'A'TRPA18'A'TRPA19'A'TRPA20'AA'TPVA''TPVB''TPVC''TPVD'PULVERIZERSA'TPVE''TPVF'6-1 (D7)OR'OR41A'FD Fan A trippedPA Fan A tripped6-1 (D7)OR'OR41B'FD Fan B trippedPA Fan B tripped1-3 (D3)1-3 (B3)PA FANSTrip PA FansTrip PA FansAA'TR61A1'A'TR61B1'Booster Fan A SpeedBooster Fan B Speed890 RPMA'TR61B2'Booster Fan C Speed8-2 (D7)1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 8-1Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration  Y B F ARSTRBBFRBO67BFRBBTRK

F D F F SNT7YBFABFRBBFRBBFRBPIBFPIBFPIBFBFRBNT8PIBFPID331MFTBFLPPFURNACEMAND7IR333MFTNT6MPULMFTTP6DF331PFURNACESPT_BFRBACKKVALKS31A T F FTFFKICKFDFFSKICKMPULNORMPSADSPSAD

S 3 3 2S332S332FDFFKS31APID331_HICLAMPPID331_LOCLAMPV_100_AV_0_AFDFFSD312AUT81CAUT81BAUT81ACYBFCCYBFBCYBFA'TR81A'CYBFABooster Fan AInlet Guide Vanes'TR81B'CYBFBBooster Fan BInlet Guide Vanes'TR81C'CYBFCBooster Fan CInlet Guide VanesBOOSTER FANS CONTROL'AUT81A''AUT81B''AUT81C'Normally in Auto 9-2 (B6)'D331'Airheater GasOutlet Duct Pressure (inwc)K/S/D'PID331''S332'3-1 (B2)K'PP332'FD Fan DemandFrom Airflow ControlsSetpoint0.0 inwcFeed ForwardX 1.0'D502''D503'AAHigh and Low Clamps for PID3318-1 (C3)'MAND6'ANDf(x)'FX41A1'ANormally in AutoNormally in Auto6-1 (D6)'TR333'A'PUL'f(x)'FX41A2'MFT Kicker CircuitMFT20 Sec'S333'8-1 (D2)Normally Zero 9-2 (C1)'DF331'AK/S/D'PIBF'6-1 (D6)f(t)pu'TP6'8-1 (D2)NOT'NT6'NOT9-2 (C1)6-1 (D6)NOT'MAND7'ANDNOT'NT7'OR'O67'8-1 (A7)/L'BFLP' 8-1 (B4)8-1 (C8)NOTNOT'NT8'8-1 (A8)8-1 (A8)8-1 (A8)8-1 (C8)8-1 (C8)8-1 (C8)8-1 (D4)5 Seconds< -1 inwcMFT inProgressBF KickerActiveFurnacePressureMFT inProgressBooster FanRunback ControllerActiveFurnacePressure-1 inwcBooster FanPosition FeedbackBooster FanRunback ControllerActiveTracking SignalTracking SwitchBooster FanDemand Override

8-1 (C3)'D811'8-1 (C8)Tracking SignalTracking SwitchMEM2'MRB'P = 1I = 10 SecX Y0 050 -20100 -60X Y0 0100 50P = 10I = 1 SecPROCVAR'P1'1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 1-2Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration TSATRKACASPTTLPVAWMILLASUM12DPVDMDPVDMDPVDMDLIM12ASUM12AKS12BKS12BKSD12AKSD12AE12CFX12FSA12GSCAT421BI12ASI12FSA12FSI12ESA12ECYSAA2CYSAA1WEPVAWLSAABI12DBI12CMUL12ASUM12CSUM12CKS12CFX12DE12BFX12ASI12CSA12CCYHDASI12DCYTDASA12DSA12ASI12ANFPVASI12BSA12BCYPACAPV12BFX12EWEPVAFX12BE12APROCVAR'PV12E'PROCVAR'PV12D''E12B''TR12C'APulv A Coal AirTemperatureCoal Air SetpointNormally 160 FPulverizer ATempering Air DamperCYHDA'TR12D'ACYTDAPROCVAR'PV12B'PulverizerBiasFeeder Demand'SUM12A''TR12A'NFPVAFeeder "A"AK/S'KS12B''TR12B'ACYPACAPulverizer APrimary AirControl DamperPULVERIZER/COMPARTMENT A CONTROLSSpeed Controlf(x)'FX12E'

PROCVAR

'PV12C'f(x)'FX12B''E12A'BIAS'BI12A'f(x)'FX12A'Pulverizer APA Air FlowK/S'KS12C'f(x)'FX12D''SUM12C'Pulverizer AHot Air DamperFeeder "A" Demand 5-1 (A4)Sec. Air TrimX'MUL12A''SUM12D''SUM12E'

PROCVAR

'PV12G' PROCVAR

'PV12H'Sec Airflow'E12C'BIAS'BI12C'BIAS'BI12D''TR12E'ACYSAA1SCAD'TR12F'ACYSAA2Pulverizer APA Air FlowPulverizer AAf(x)'FX12F'K/S/D'KSD12A''LIM12A'> <5-1 (A1) 5-1 (A1)Typical For Pulverizer B-FAir Flow Setpoint0100OUTIN0100BiasREF : FOXBORO 04F465609-FD-4019 Rev. 404F465609-FD-4020 Rev. 304F465609-FD-4043 Rev. 3B&WD8071957B Sht 1D8071957BSht 2D8071957CSht 3SCADAX Y0 0100 100X Y0 0190,000 80P = 0.5I = 180 SecP = 1.5I = 77 SecX Y0 0100 50X Y0 100100 0P = 1.0I = 20 SecX Y0 080 8074651122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 7-2Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration CYPASOFRU190FSRU190FVLB105RU190ESRU190EVCYPASOELB104 C Y P A S OCYPASOCYPASOCYPASOCYPASOLB103LB102LB101LB100CYPASORU190CSRU190CVCYPASOCCYPASODRU190DSRU190DVCYPASOBRU190BSRU190BVCYPASOARU190ASRU190AV'RU190A'ACYPASOAPrimary Air Shut OffDamper A'RU190B'ACYPASOB'RU190C'ACYPASOC'RU190D'ACYPASODPROCVAR'P11'BIAS'B100'BIAS'B101'BIAS'B102'BIAS'B103''RU190B1'ACYPASOE'RU190C1'ACYPASOFBIAS'B104'BIAS'B105'Primary Air Shut OffDamper BPrimary Air Shut OffDamper CPrimary Air Shut OffDamper DPrimary Air Shut OffDamper EPrimary Air Shut OffDamper FPRIMARY AIR SHUT OFF DAMPERS1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 8-2Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration WAIT9TRIP_ON_LOW_FURNACEOK_TO_TRIPMFTFTRBF

O R 4 3 1LOWBFPBFLIMLLIMGENDMDPEBFTRIP_ALL_BFIS430TLPJFFOR431ST431ACYBHOLDST432ST432AOPENINLOR431IS432OPENBYPIS431HIACTST431CYBPASS'TR431'CYBPASSBaghouse EmergencyBypass Damper9-2 (C5)H/'SH431'MEM2'OPENBYP'OR'OR431'Temperature ofFlue Gas LeavingBaghouse (oF)ResetCloseCYBHOLDBaghouseOutlet DamperMEM2'OPENINL'Set'TR432'ACloseA> 345 Deg FAOpenAOpenBAGHOUSE DAMPERSMEM2'OPENBYP1'Reset7-1 (A8)Trip all Booster Fans/L'BFL'PROCVAR'P721'PROCVAR'P722'f(x)'FX2'Load-Based Trip (Normally Disabled)BF Inlet PressureADAPT'ADP'OR'OR432'6-1 (B3)'A821'ANDLow Furnace Pressure MFTUnit LoadX Y30 -9.4100 -22.1PROCVAR'P2'1122334455667788AABBCCDDPrepared byCUDrawing No.EA0624.01 - 04 - 002 page 1-3Date04 Oct 2006No.1234Date25 Oct 200613 Nov 200601 Mar 200710 Jul 2007BySPSPKMKSJDescriptionIncorporated client's commentsUpdated Booster Fan control logicFinal ConfigurationDisplayed Tuning Parameters and Function GeneratorsRevision HistoryNo.DateByDescriptionTRAX LLC., Forest, VAfor Public Service of New MexicoPNM - San Juan Generating Station Unit 4 Boiler Implosion StudyControls Model - Proposed Configuration WAIT11ONBFTONBFT

H I 3 1 CFDB_TRP_PBFDA_TRP_PBTRFDTRIP_ALL_BFHI31DHI31BFDB_TRPTLSAHBPLDWBFDA_TRPHI31ATLSAHAPLDWAPROCVAR'PV31A'Secondary Air A Duct PressPROCVAR'PV31B'Secondary Air A TempH/'HI31A'> +47.7 inwcH/'HI31B'> 620 FOR'OR31A'FD Fan A trippedPROCVAR'PV31C'Secondary Air B Duct PressPROCVAR'PV31D'Secondary Air B TempH/'HI31C'> +47.7 inwcH/'HI31D'> 620 FOR'OR31B'FD Fan B trippedPROCVAR'PV31E'FD Fan A Operator tripPROCVAR'PV31F'FD Fan B Operator tripFD FANS TRIPS'AD1'ANDf(t)pu'DL1'8-2 (D7)15 Sec9-2 (B4)

# APPENDIX C

Unit 4 Validation ResultsFurnace Pressure02468101214160 10 20 30 40 50 60 70 80Time (Seconds)

Pressure (inwc)A1574 FURNACE PRESSModelTotal Secondary Airflow01000200030004000500060000 10 20 30 40 50 60 70 80Time (Seconds)

Flow (kpph)PlantModelFD Fans Discharge Pressure051015202530350 10 20 30 40 50 60 70 80Time (Seconds)

Pressure (inwc)A1501 FD FAN A DISCHARGE PRESSA1503 FD FAN B DISCHARGE PRESSModelPrimary Air Heater Air Outlet Pressure01020304050607080901000 10 20 30 40 50 60 70 80Time (Seconds)

Pressure (inwc)A1531 PRI AH AIR OUT PRESSModel

# APPENDIX D

Full Load MFTFull Load MFTTransient Max/Min Pressure ProfileWithout Mitigations-6.20.0+31.0+29.8+25.0+23.0+9.6+7.0+5.30.0-9.6-10.4+17.4+1.8+0.5+23.0-2.8+28.2+26.9+21.2+18.3+18.3-1.7-2.8-3.6-6.1-8.5-18.4-19.9+5.7-0.8-1.3-40-35-30-25-20-15-10-50+5+10+15+20+25+30+35+40 

### Ambie n t FD Fa

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Pressure (inwc)MaximumMinimumFull Load MFTUnit Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load MFTBaghouse and Scrubber Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load MFTFlows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load MFTFan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position ( percent open)FD FansBooster FansFull Load MFTFan Speeds010020030040050060070080090010000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# APPENDIX E

Full Load All Booster Fans

TripFull Load All Booster Fans TripTransient Max/Min Pressure ProfileWithout Mitigations-6.2+24.2+32.6+0.5+1.8+17.4+21.0+21.4+24.8+26.1+26.5+26.9+32.6+33.5+35.4+35.80.0-1.6-1.2+2.9-16.1-14.4-2.80.0+5.2+5.7+6.5+22.8+22.8+25.0+29.0+30.0-40-35-30-25-20-15-10-50+5+10+15+20+25+30+35+40 

### Ambie n t FD Fa

n Out l et SAH Air Inlet SAH Air Outlet Sec. Air Duct W

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Pressure (inwc)MaximumMinimumFull Load All Booster Fans TripUnit Pressures-30-20-100102030400 40 80 120 160 200 240 280 320 360Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load All Booster Fans TripBaghouse and Scrubber Pressures-30-20-100102030400 40 80 120 160 200 240 280 320 360Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load All Booster Fans TripFlows0100020003000400050006000700080009000100000 40 80 120 160 200 240 280 320 360Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load All Booster Fans TripFan IGV01020304050607080901000 40 80 120 160 200 240 280 320 360Time (seconds)

Position ( percent open)FD FansBooster FansFull Load All Booster Fans TripFurnace Pressure-30-20-100102030400 40 80 120 160 200 240 280 320 360Time (seconds)

Pressure (inwc)Furnace (Unmitigated)Furnace With FD Fan Trip (Mitigated)Full Load All Booster Fans TripTransient Maximum Pressure Profile-6.20.0+35.8+35.4+33.5+32.6+26.9+26.5+26.1+24.8+21.4+21.0+17.4+1.8+0.5+32.6+24.20.0+34.0+33.2+29.4+27.6+27.6+15.3+14.6+13.9+11.9+10.9+6.6+6.1-10-50+5+10+15+20+25+30+35+40 

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n Out l et SAH Air Inlet SAH Air Outlet Sec. Air Duct W

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Pressure (inwc)Maximum (Unmitigated)Maximum With FD Fan Trip (Mitigated)Full Load All Booster Fans TripFan Speeds010020030040050060070080090010000 40 80 120 160 200 240 280 320 360Time (seconds)

Speed (rpm)FD FansBooster Fans

# APPENDIX F

Full Load Both FD Fans

TripFull Load Both FD Fans TripTransient Max/Min Pressure ProfileWithout Mitigations-6.2+0.6+23.0+0.5+1.8+17.4+0.4+0.50.0+5.3+7.0+9.6+23.0+25.0+29.0+30.00.0-2.2-2.2-2.0-18.9-18.2-14.0-13.1-11.5-11.0-10.3+1.0+1.0+1.0+1.1+1.1-40-35-30-25-20-15-10-50+5+10+15+20+25+30+35+40 

### Ambie n t FD Fa

n Out l et SAH Air Inlet SAH Air Outlet Sec. Air Duct W

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Pressure (inwc)MaximumMinimumFull Load Both FD Fans TripUnit Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load Both FD Fans TripBaghouse and Scrubber Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load Both FD Fans TripFlows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load Both FD Fans TripFan IGV01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position ( percent open)FD FansBooster FansFull Load Both FD Fans TripFan Speeds010020030040050060070080090010000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# APPENDIX G

Low Load Two Booster

Fans RunawayLow Load Two Booster Fans RunawayTransient Max/Min Pressure ProfileWithout Mitigations-6.2+0.3+17.5-0.90.0+13.6-0.7-0.50.0+1.1+1.5+2.0+17.5+18.0+19.0+19.30.0-1.9-1.8-0.3-10.7-10.0-6.5-5.7-4.3-3.8-3.2+13.6+13.6+14.1+15.2+15.5-40-35-30-25-20-15-10-50+5+10+15+20+25+30+35+40 

### Ambie n t FD Fa

n Out l et SAH Air Inlet SAH Air Outlet Sec. Air Duct W

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Pressure (inwc)MaximumMinimumLow Load Two Booster Fans RunawayUnit Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletLow Load Two Booster Fans RunawayBaghouse and Scrubber Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletLow Load Two Booster Fans RunawayFlows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletLow Load Two Booster Fans RunawayFan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position ( percent open)FD FansBooster FansLow Load Two Booster Fans RunawayFan Speeds010020030040050060070080090010000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans

# APPENDIX H

Full Load All Fans TripFull Load All Fans TripTransient Max/Min Pressure ProfileWithout Mitigations-6.20.0+23.0+0.5+1.8+17.4-0.3-0.20.0+5.3+7.0+9.6+23.0+25.0+29.0+30.00.0-2.2-2.1-1.8-16.1-14.4-3.2-2.7-1.9-1.7-1.3+0.8+0.8+0.9+1.0+1.0-40-35-30-25-20-15-10-50+5+10+15+20+25+30+35+40 

### Ambie n t FD Fa

n Out l et SAH Air Inlet SAH Air Outlet Sec. Air Duct W

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Pressure (inwc)MaximumMinimumFull Load All Fans TripUnit Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)FD DischargeFurnaceAir Heater Gas OutletFull Load All Fans TripBaghouse and Scrubber Pressures-30-20-100102030400 20 40 60 80 100 120Time (seconds)

Pressure (inwc)Baghouse InletBooster Fan InletFGD InletFull Load All Fans TripFlows0100020003000400050006000700080009000100000 20 40 60 80 100 120Time (seconds)

Flow (kpph)Total FD FansFurnace ExhaustTotal FGD InletFull Load All Fans TripFan Inlet Guide Vanes01020304050607080901000 20 40 60 80 100 120Time (seconds)

Position ( percent open)FD FansBooster FansFull Load All Fans TripFan Speeds010020030040050060070080090010000 20 40 60 80 100 120Time (seconds)

Speed (rpm)FD FansBooster Fans