April 1 5 , 2013

Mr. Arthur Hofmeister Via Email EPA Region 4 Hofmeister.Art@epa.gov Air Permits Section 61 Forsyth St. S.W. Atlanta, GA 30303

– 8960

Re: Tampa Electric Company Polk Power Station Polk 2 Combined Cycle GHG PSD Permit

Dear Mr. Hofmeister,

During a call on Thursday April, 4 2013, EPA had several questions regarding the GHG PSD permit application submitted by Tampa Electric Company ( TEC ) for the Polk 2 Combined Cycle Project. Our responses to these questions are provided below.

Question 1: What is TEC’s justification for having an annual 3

– hou r test certified by the CEMS for the following modes of operation, combined cycle on fuel oil, simple cycle on natural gas, and simple cycle on fuel oil?

Operation on fuel oil is expected to be infrequent for both combined and simple cycle modes of operat ion since natural gas is significantly lower in cost and is expected to remain lower for the foreseeable future. In addition, the draft Florida Department of Environmental Protection (FDEP) air construction permit for the Polk 2

- 5 Conversion Project contai ns limits on fuel oil operating hours; i.e., no more than 750 hours per year per CT (8.5% of the available hours in a year) of which no more than 375 hours per year per CT (4.3% of the available hours in a year) may be in simple cycle mode. Accordingly, it is expected that use of fuel oil will be limited to periods when natural gas is unavailable and brief periods for routine maintenance and readiness testing.

Following the conversion to combined cycle mode, operation in simple cycle mode will also be infr equent due to the higher fuel costs associated with simple cycle operation. The revised draft
FDEP air construction permit limits simple cycle hours to no more than 900 hours per year (10.3% of the available hours in a year) with a special one

- time allocat ion of 3,480 hours for periods when the combined cycle system is unavailable. Operation in simple cycle mode will generally be limited to periods when the combined cycle HRSG units and/or common steamturbine generator are inoperative due to planned outage s or equipment malfunctions and power

cannot be provided by other more efficient units in Tampa Electric’s fleet of generating units.

Since use of fuel oil and simple cycle mode will be infrequent, it is not possible to predict with certainty under what c onditions ( e.g. loads and ambient temperature) the CTs will operate during these infrequent events. For this reason, the proposed GHG BACT limits for the infrequent events are referenced to ISO conditions with compliance confirmed on an annual 3

- hour test basis using CO 2 CEMS and Part 98 emission fact ors for CH 4 and N

2 O.

Question 2: What is the agreement between FDEP and TEC for simple cycle hours of operation? Also, what is the justification for the agreed upon hours?

The permit condition that was agreed upon between FDEP and TEC regar ding simple cycle hours of operation is below. TEC has agreed that this condition allows for maximum flexibility to operate the units as required to be able to provide power for our customer s in any circumstance that it is needed.

“c. Simple Cycle Operation: Beginning the first full calendar year (CY

- 1) after demonstrating initial compliance in combined cycle mode, the group of four CTGs shall operate in simple cycle mode for no more than an average of 900 hours per calendar year per CT G (avg. hours/CY/CTG) except that:
During CY

- 1, a one

- time special allocation of 3,480 avg. hours/CTG shall be available for use by the permittee to provide for events when the steam turbine

- electric generator is unavailable, including but not limited to planned outages, forced outages and derates;

If the one

- time special allocation of 3,480 avg. hours/CTG is not fully used in CY

- 1, the balance may be carried over into CY

- 2;
If the annual allocation of 900 avg. hours/CTG is not fully used in CY

- 1, the re mainder may be added to the year

- end balance of the special allocation carried over from CY

- 1 and up to 3,480 avg. hours/CTG may be carried over into CY

- 2; and
If the annual allocation of 900 avg. hours/CTG is not fully used in CY

- 3, CY

- 4, CY

- 5, CY

- 6, etc ., the remainder may be added to the year

- end balance of the special allocation carried over from the previous year and up to 3,480 avg. hours/CTG may be carried over into subsequent CY

- 4, CY

- 5, CY

- 6, CY

- 7, etc., respectively.

d. Fuel Oil Usage

– CTGs 2A, 2B, 2C and 2D: CTGs 2A

, 2B

, 2C and 2D shall use ULSD fuel oil for no more than 750 avg. hours/CY/CTG of which no more than 375 hours/CY/CTG may be in simple cycle mode. The CTGs shall fire ULSD fuel oil no more than 48 hours per day. [Rules 62

- 210.200(PT E) and 62

- 212.400(BACT), F.A.C.]”

Tampa Electric is an investor owned electric utility regulated by the Florida Public Service Commission and subject to the requirements of Chapter 366 of the Florida Statues which include an obligation to provide electric service in a reliable and cost eff ective manner. The request for allowable hours of operation contained in the permit application is based upon these requirements and necessary to ensure that TEC is in a position to provide the electric service should a problem arise with the combined cycl e operation necessitating the operation of the units in simple cycle mode for an extended period. Although TEC can agree that this contingencymay not be likely to occur for an extended period, there are many types of possible failures and

TEC cannot elimi nate the possibility that they may occur. TEC and its customers are making a significant investment in the damper system to allow flexible use of the CT’s to meet our customers’ needs and are seeking to permit a flexible and environmentally sustainable mod e of operation.

As included in the technical evaluation and preliminary determination , 1050233

– 034

– AC, by FDEP, it was agreed between both parties that simple cycle is intended to be a backup mode of operation and that TEC would run in combined cycle u nless TEC has the need for peaking service or the steam turbine

– electric generator is derated, in a forced outage, or in a planned outage.

TEC needs these simple cycle hours for the following reasons:

 TEC has a statutory obligation to provide electric service in a reliable and cost effective

manner

 TEC customers could be subjec t to significant cost increases due to the possibility of having to buy outside power if simple cycle hours on TEC’s system are not avail able.

 The scenarios requiring > 900 hours of simple cycle operation are possible so they must be accommodated.

 Air quality modeling by ECT and FDEP indicate no significant contribution to non

attainment is occurring from the project with any requested mode of operation

FDEP requested that we describe the plausibility of the operating scenario that could interfere with the service to our customers. During the past two years, PPS Units 2

- 5 have averaged over
900 hours per year per CT and may need to continue utilizing the units in this manner depending on the load profile. Figure 1 depicts the actual hours of operation for these units during 2012.

Figure 1

– 2012 Cumulative Operating Hours

– PPS 2

- 5 Simple Cycle Operation

0 200 400 600 800 1000 1200 Hours/year 

## PPS Units 2

- 5 2012 Operating Hours

2

3

4

5 Limit in FDEP Revised Draft PermitThis operating profile is a reasonable estimate of required simple cycle operation needs after

completion of the combined cycle portion of the system. This is supported by considering Progress Energy’s 4

- on

- 1 Bartow combined cycle plant with alternative simple cycle operation, which has utilized equivalent simple cycle hours when their combined cycle operation did not
meet their needs.

If a failure preventing combined cycle operation occurred mid

- year or later with a limited amount simple cycle hours , TEC would not have any simpl e cycle operating time available and would be required to go through the process of requesting permission to operate in simple cycle
mode. Such a process presents uncertainty in terms of time required to go through the process and outcome. These factors would necessitate TEC taking action to secure purchased power very quickly after such a failure to ensure power availability to customers. This can and should be
addressed at this time to avoid this result.

TEC has also looked into the possibility of a steam turbine failure, as seen below.

There are many different failure risks and failure rates associated with steam turbines, including (from Steam Turbine Risk Assessment; Christ et al 1 ):

 Fatigue

 Thermal fatigue

 Ero sion

 Stress Corrosion

 Cracking

 Rubbing/distortion

 Overload

 Material Defect

 Foreign Object Damage

 Wear

 Fretting

 Corrosion

 Electric Discharge

 Creep

 Fouling

 Improper Installation

Many different parts of a turbine could be subject to these failure modes. Most parts of a turbine are subject to more than one failure mode. For example, a plug could be subject to erosion, fouling, material defect, rubbing distortion, or wear.Table 1 d escribes the top 16 failure modes. The ranks of these failure modes were determined by

industry experts. These failure modes account for 50% of the basic risk.

Table 1

– Top 16 Steam Turbine Failure Modes

Subcomponent Failure Mechanism When Failure Occur s Rank Labyrinth seal fixed/rotating Rubbing/Distortion Test & Startup 1 Casing Erosion Outage 2 Labyrinth seal fixed/rotating Rubbing/Distortion Run 3 Stator blading (reaction) Fouling Run 4
Rotor Rubbing/Distortion Test & Startup 5 Stationary Diaphragms Fouling Run 6
Shroud/bands Fatigue Run 7 Blade foils Fouling Run 8 Casing Erosion Run 9 Blade foils Rubbing/Distortion Test & Startup 10
Tenons Fatigue Run 11 Bushings Fouling Run 12 Coupling gear teeth Fouling Run 13 Casing bottling Overload Test & Startup 14
Thrust collar Overload Test & Startup 15 Turbine split line Improper Installation Test & Startup 16

Ancillary equipment such as the generator step up (GSU) transformer can also fail or be damaged as a result of extreme weather, rendering the steam turbine generator unavailable. A GSU repair can take up to one year to complete.

Steam turbine failures a re not common but there are local examples. Big Bend had a forced steam turbine outage in summer 2009 resulting from unavoidable failure. The steam turbine tripped during shut down, auxiliary power failed, oil pressure dropped, and the rotor lost

pressur e. The rotor kept spinning as the unit was coming down and destroyed the bearings. Overspeed damage can also cause an outage of up to a year or more. Seminole’s Midulla plant in Hardee County had a steam turbine and generator failure in 2007 that took ov er one year to repair.

As described above, there are many incidents that could prevent the use of the preferred combined cycle mode of operation and TEC is requesting the use of the permit condition that was approved by FDEP for simple cycle operation.

1 Christ, Timothy J; Drosjack , Michael J; Tanner, G. Mark; “Steam Turbine Risk Assessment

– A Tool To Assist In Optimizing Inspection And Overhauls Of Industrial Steam Turbines”; Proceedings of the 26 th Turbomachinery SymposiumQuestion 3: Why are the calendar year (CY) allocation s of combined and simple cycle

hours appropriate?

For the purpose of conservatively estimating potential annual emission rates, the PSD application submitted to FDEP used operating scenarios based on 1 00% loads and ISO conditions (i.e., at 59 o F). This is considered appropriate for estimating annual potential emission rates since emission rates will be lower at lower loads and higher ambient temperatures.

However, the 100% load scenarios represent the most eff icient load for power generation and therefore these loads are not suitable for determining a GHG BACT limit in units of lb CO 2 e/MWh on a 12

– month rolling average basis using CO 2 CEMS monitoring data if actual operating loads will be lower.

Acc ordingly, the calendar year allocation of operating scenarios identified for combined cycle natural gas

– firing represents the expected actual use of the combined cycle system and resulting in power generation efficiencies; i.e., actual combined cycle mod e heat rates.

Due to the language that was agreed upon between TEC and FDEP a rolling average is inappropriate. As part of the agreement, TEC will get an annual allocation of 900 simple cycle hours, which includes both fuel oil and natural gas operation. This annual allocation occurs the first calendar year after TEC begins operation in combined cycle mode. In addition, TEC will
receive a one

– time allocation of 3,480 hours to be used when the steam turbi ne is derated or in a planned or forced outage. TEC will then be able to bank left ove r hours of the 900 hours that

are not used at the end of each calendar year . However, the one

– time allocation bank will

never exceed 3,480 h hours at any time. An exampl e of how this agreement will work can be seen below.

Year Annual

Allocation at Beginning of CY One

- Time

Allocation at Beginning of CY Annual Allocation

Used One

– Time

Allocation Used

CY

– 1 900 3,480 500 1,000
CY

– 2 900 2,880 500 1

, 000 CY

– 3 900 2,280 500 1

, 000

A rolling limit for hours will not allow for the banking concept, to build back up the one

– time allocation, that FDEP and TEC agreed upon. In addition, this will not provide the operational flexibility that TEC requires to provide reliable electricity to our customers.

Question 4: Why does TEC have a combined GHG limit for all 4 turbines on combined cycle operation and a separate GHG limit for each turbine on simple cycle operation?

TEC has proposed a GHG limit for the entire 4

– on

– 1 combined cycle system instead of a per unit basis because it is more accurate. The steam turbine (ST) only has one meter associated with measuring the megawatts ( MW s) that the ST is generating at any time and this allows for only one ST number for all 4 combustion turbines. A mathematically derived number for allocating the ST MWs to each combustion turbine would be inaccurate because sometimes notall four units are running and during a startup scenario steam from a HRSG unit could be vented

and th e ST bypassed until the steam is hot enough

.

Question 5: Explain the margin used for the proposed GHG BACT limits?

A heat input margin of 10 percent was used in developing the proposed GHG BACT limits in units of lb CO2e/MWh, gross. This margin is approximately the same as the margin previously used to develop GHG BACT limits in units of Btu/kWh, net with the differenc e due to expressing the GHG BACT limit on a gross rather than net power generation basis.

Also, attached is the corrected proposed GHG BACT emission limits.

Please contact myself, 813

– 228

– 4740, or Byron Burrows, 813

– 228

– 1282 if there are any ad ditional questions that arise.

Thank you,

(No Signature Required)

Lyndsey Baldyga Engineer

– Air Programs Environmental Health & Safety Tampa Electric Company

EHS/iym/LMB 127 Polk 2 Combined Cycle GHG PSD Application EPA Questions