### Selective Catalytic Reduction (SCR) Technical Feasibility For M.R. Young Station

1. 

### Introduction

On July27, 2006 a Consent Decree was entered by the United States District Court for the District ofNorth Dakota for Civil Action No.1 :06-CY-034, United States ofAmerica and the State of North Dakota versus Minnkota Power Cooperative, Inc. and Square Butte Electric Cooperative. The Consent Decree resolved alleged violations ofthe Federal Clean Air Act and the North Dakota Air Pollution Control Rules (NDAC 33-15) including the Prevention of Significant Deterioration Rules (NDAC 33-15-15). Section Y, Paragraph 65, ofthe Consent Decree required Minnkota Power Cooperative and Square Butte Power Cooperative (hereafter Minnkota) to submit to the Department for review and approval, a nitrogen oxides (NOx) topdown BestAvailable Control Technology (BACT) analysis for the two existing units atthe M.R. Young Station. The Consent Decree required Minnkota to evaluate various technologies including selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), over-fire air (OFA) and rich reagent injection (RRI). Minnkota must also submit any additional information requested by the Department or the U.S. Environmental Protection Agency (hereafter EPA) which is pertinent to the BACT determination. On October9, 2006, the Departmentreceivedtherequired BACT analyses.

### Under Section III, paragraphs 23 and 24 ofthe Consent Decree, the BACT analysis must be made in accordance with the provisions ofChapter B ofEPA's New Source Review Workshop Manuat9 (hereafterNSR Manual). As discussed in the NSR Manual, the steps for conducting a BACT analysis using the "top down" approach are as follows:
Step 1: IdentifyAll Control Technologies.

Listis comprehensive.
Potentiallyapplicable control alternatives canbe categorizedinthree ways.

• Inherently Lower-Emitting Processes/Practices, including the use of materials and production processes and work practices that prevent emissions and result in lower "production-specific" emissions; and

• Add-on Controls, such as scrubbers, fabric filters, thermal oxidizers and other devices thatcontrol andreduce emissions afterthey areproduced.

• Combinations of Inherently Lower Emitting Processes and Add-on Controls. For example, the application of combustion and post-combustion controls to reduce NOx 

### emissions at agas-firedturbine.

2

### The top-down BACT analysis should considerpotentially applicable control techniques from all three categories. Lower-polluting processes shouldbe consideredbased on demonstrations made
on the basis of manufacturing identical or similar products from identical or similar raw materials or fuels. Add-on controls, on the other hand, should be considered based on the physical and chemical characteristics ofthe pollutant-bearing emission stream. Thus, candidate add-on controls may have been applied to abroad range ofemission unit types that are similar, insofaras emissions characteristics, to the emissions unitundergoing BACTreview.
Step2: EliminateTechnically Infeasible Options.

A demonstration of technical infeasibility should be clearly documented and should show, based on physical, chemical, and engineering principles, that technical difficulties would preclude the successful use ofthe control option on the emissions unitunderreview.

The NSR Manua19 

### provides guidance for determining whether a control option is technically infeasible. Two concepts are important in making this determination, "availabilityll and "applicabilityll. A technology is considered "availablell ifit can be obtained through commercial channels or is otherwise available within the common sense meaning ofthe word. An available technology is "applicablell ifit can reasonably be installed and operated on the source type under consideration. Atechnologythatis available and applicable is considered technically feasible.
Regarding "availability" theNSRManuat9 states:
3

### "A control technique is considered available, within the contextpresented above, ifithas reached the licensing and commercial sales stage ofdevelopment. A source would notbe required to experience extended time delays orresource penalties to allow research to be conducted on anew technique. Neither is it expected that an applicant would berequired to experience extended trials to learn how to apply a technology on a totally new and dissimilar source type. Consequently, technologies in a pilot scale testing stages of developmentwould notbe considered available for BACTreview."

Withrespectto "applicability" theNSRManual9 

### states:

"Technical judgment on the part of the applicant and the review authority is to be exercised in determining whether a control alternative is applicable to the source type under consideration. In general, a commercially available control option will be presumed applicable ifithas been oris soonto be deployed (e.g., is specified in apermit)
on the same or a similar source type. Absent a showing ofthis type, technical feasibility would be based on examination of the physical and chemical characteristics of the pollutant-bearing gas stream and comparison to the gas stream characteristics of the
source types to which the technology had been applied previously. Deployment ofthe control technology on an existing source with similar gas stream characteristics is generally sufficient basis for concluding technical feasibility barring a demonstration to the contrary.

4

### Step 3: Forprocess-type control alternatives the decision ofwhether or not it is applicable to the
source in question would have to be based on an assessment of the similarities and differences between the proposed source and other sources to which the process technique had been applied previously. Absent an explanation ofunusual circumstances by the applicant showing why aparticularprocess cannotbeused on the proposed source thereview authoritymaypresumeitis technically feasible.

In practice, decisions about technical feasibility are within the purview ofthe review authority. Further, a presumption oftechnical feasibility may be made by the review authority based solely on technology transfer. For example, in the case of add-on controls, decisions ofthis type would be made by comparing the physical and chemical characteristics ofthe exhaust gas stream from the unit under review to those ofthe unit from which the technology is to be transferred. Unless significant differences between
source types exist that are pertinent to the successful operation ofthe control device, the control option is presumed to be technically feasible unless the source can present informationto the contrary."

RankRemaining Control Technologies By Control Effectiveness

This includes:

control effectiveness (percentpollutantremoved); expectedemissionrate (tons peryear);
5

### Step 4:

Step 5: expected emissionreduction (tons per year);

.energyimpacts (Btu, KW-hr); environmental impacts (othermedia andthe emissions oftoxic and hazardous air emissions); and economic impacts (total costeffectiveness and incremental cost effectiveness).

Evaluate MostEffective Controls and DocumentResults
Case-by-case consideration ofenergy, environmental, and economic impacts. Ifthemosteffective option is not selected as BACT, evaluate nextmosteffective control option.

SelectBACT

Most effective option notrejected is BACT and establish emission limitorwork practice standard.

The Department solicited public comments on its preliminary BACT detennination for nitrogen oxides (NOx) 

### controls at the M.R. Young Station (MRYS). Comments from the Environmental Protection Agency and several environmental groups disagreed with the conclusion that high dust SCR (HDSCR), low dust SCR (LDSCR) and tail end SCR (TESCR) were technically infeasible. Comments from other parties agreed with the Department's preliminary detennination. The Department has evaluated the comments and has reaffinned its preliminary
6detennination that HDSCR is technically infeasible. However, the Department now believes LDSCR andTESCR are technically feasible.

This document explains the Department's current views on technical feasibility. This document does not represent a final Department action. The Department will make its final BACT detennination after the remaining steps for conducting a BACT analysis have been completed. Minnkota will be required to submit additional infonnation necessary for the Department to make its final BACT detennination including an evaluation ofthe cost ofLDSCR and TESCR.

II. High Dust Selective Catalytic Reduction (HDSCR)
HDSCR, or conventional SCR, refers to an SCR system that is installedpriorto any airpollution control equipment and usually between the economizer outlet and air heater inlet. HDSCR has been installed on many pulverized coal and cyclone boilers firing bituminous and subbitiminous coal inthe United States.

A. Public Comments

1. NDDH's Technical FeasibilityAnalysis ofHigh Dust SCR is Incorrect and Based Upon Flawed Data

The NSR Manual states "A demonstration oftechnical infeasibility is based on a technical assessment considering physical, chemical and engineering principles,
7

### and/or empirical data showing that the technology would not work on the emissions unit under review, or that unresolvable technical difficulties would precludethe successful deploYment ofthetechnique."

The Department asked EPA's consultant, Mr. Roger Christmann, ifhe was aware ofany installation in the world where HDSCR had been applied to a facility with
as high of sodium loading as at MRYS. Mr. Christmann indicated no. This indicates that there has never been a design established for a flue gas with the chemical characteristics found at MRYS. Simple mathematics prepared by the Department shows that the flue gas at MRYS is muchhigher in sodium and other catalyst deactivation chemicals than otherpower plant flue gases. EPA seems to ignore the fact that the sodium at MRYS is the soluble form (organically associated) which is a more potent catalyst deactivation chemical than the insoluble (inorganically associated) form found in other coals. EPA tries to dismiss this showing by ratioing the loading of Powder River Basin (PRB) subbituminous coal to bituminous coal without indicating the actual loading. The Department showed the actual loading (lb/dscfand lb/wscf) as well as the ratio to other facilities. When you start out with avery small loading, as is the case with bituminous coal, a large ratio for subbituminous coal also gives you small loading. As EPA's own consultant points out, SCR has never been applied to sodiumloading as high as atMRYS.

8

### Minnkota and its consultants have documented very well the effect of soluble sodium on an SCR catalyst. Although the Coyote testing did not provide any deactivation rate data for high soluble sodium North Dakota lignite, it did show that an HDSCR design for subbituminous coal will probably not work successfully with North Dakota lignite. As Sargent and Lundy pointed out, there is no known solution for the soluble alkalis such as the soluble sodium and potassium found in North Dakota lignite. EPA ignores the chemical differences betweenTexas lignite andNorth Dakotalignite.

With respect to the catalyst vendor "guarantees", all ofthe vendors that Minnkota contacted indicated that pilot scale testing was either required or should be done priorto applying high dust SCRtechnology to aNorth Dakotalignite-firedboiler. Minnkotahas provided informationthatindicates the potential for greatly reduced catalyst life due to the chemical characteristics ofthe flue gas. Although two vendors indicated a catalyst life which the Department would consider as a "successful application" of HDSCR technology at MRYS, others did not give such an indication. All vendors indicated the flue gas temperature problems (too hot or too cold) must be resolved for the application ofHDSCR to be successful. No solution to this problem has been found at this time. EPA has indicated that
some ofthe vendors may have been prompted by Minnkota, orits consultants, to indicate that pilot testing should be done. Even ifsome vendors may have been "prompted" to make these statements, it is irrelevant sincethe vendors couldhave chosennotto makethe statement.
9

### Although the Texas CEQ has determined that HDSCR is technically feasible for Texas lignite, the chemical constituents ofNorth Dakota lignite that affect the feasibility of HDSCR are quite different. The State of Louisiana recently determinedthat HDSCRwas nottechnically feasible for an activated carbonplant becauseofthe flue gas characteristics ofthe ligniteusedinthe process.
The NSR Manual9 

### indicates that an add-on control technology is only technically feasible ifit can lead to "successful operation" or "successful deployment." The Department has indicated that anything less than 10,000 hours of catalyst life would not be successful operation of the SCR system and thus technically infeasible. Kling et. al? conducted pilot and bench sale testing ofSCR catalysts when subjected to flue gas from the combustion ofbiomass. The testing was conducted using three different types ofcatalyst. Catalyst Type A was typical of that used for coal-fired boilers, Type B was a "bio-optimized" catalyst with an increased vanadium content and Type C had a very high vanadium content. Kling2
, 

### and laterZheng et. al3
, 

### have concludedthat itis the alkali aerosols that are less than or equal to 0.1 micrometers that cause most ofthe catalyst deactivation. InNorthDakotalignite, the alkali metals are generally associated withthe organic matter ofthe lignite while in other coals the alkaline constituents are associated with the inorganic portion of the coal (e.g. clays). The combustion of the organically associated alkaline elements causes them to vaporize; when they condense, they form submicron aerosols. The combustion of inorganically
10

### associated alkalis causes only a small portion to vaporize. Minnkotahas supplied infonnation that indicates these condensed alkali aerosols have a mass mean diameter of approximately 0.1 micrometers. Therefore, 50% of the aerosols would be less than 0.1 micrometers in size on amass basis. The average mass of sodiumoxide andpotassiumoxide emitted from the MRYS boilers was calculated at 3.05 x lO-

### s lb/dscf (524 mgiNm3) 

### and 9.01 x 10-6 

### lb/dscf (155 mgiNm\ respectively.
Crespi6

### has provided datathat suggests potassium oxide is approximatelytwice as potent a catalyst deactivation chemical on a molar basis (1.3 times on a mass basis) than sodium oxide. The equivalent potassium oxide emission rate for MRYS based on this data wouldbe 558 mgiNm3

. 

### The aerosols are most likely in the sulfate fonn.s This would lead to an equivalent potassium sulfate emission rate of1034mgiNm3• 

### Kling2 

### found a deactivation rate of21-52% over 1500 hours for fuel made up of tree bark and 30% demolition wood waste. This fuel has a potassium chloride loading of 16.7 mgiNm3 

### and 

### a sodium chloride loading of 5.8 mgiNm3• 

### The Kling2 

### results were for aerosols with an aerodynamic diameter ofless than 0.1 micrometers. Ifall ofthe sodium and potassium in lignite vaporizes, 50% ofthe total loading would be less than or equal to 0.1 micrometers or 517mgiNm3 

### of equivalent potassium sulfate. Zheng3 

### has suggested that potassium chloride is two and one halftimes more potent catalystpoison than potassium sulfate (0.4%
11

### perday versus 1% 

### perday). An equivalentloading ofsodium andpotassium for a HDSCR at MRYS as potassium chloride would be 207 mglNm3

. 

### This loading is nearly 10 times that ofthe Kling2 

### testing. The Kling2 

### results suggest 2,885-7,140

.hours until 100% deactivation. The higher loading at the North Dakota facilities

suggests amuch higherdeactivationrate and ashortercatalystlife.
Zheng et. al. 3 

### found a catalyst deactivation rate of0.4% per day for a potassium sulfate. The testing was conducted using a concentration of20-30 mglNm3 

### of potassium sulfate with amass mean diameterof0.55 micrometers. Although data is not available to determine the loading ofaerosols with adiameterless than 0.55 micrometers, a comparison to the fraction less than 0.1 micrometers indicates a concentration 17-26 times larger than the concentration in Zheng's tests. The 0.4% deactivation rate per day is equivalent to 6000 hours at 100% deactivation. For a HDSCR, the flue gas from the MRYS would likely produce a higher deactivationrate.

The recent testing by Kling2 

### and Zheng3 

### indicate that it is unlikely that a HDSCR will achieve 10,000 hours of catalyst life when combusting Center lignite at MRYS. In fact, the catalyst life couldbe only a few thousand hours as suggested bythepilot scale testing atthe Coyote Station.

122. MRYS Temperature Variation Issue Relatedto HDSCR

EPAhas indicated thetemperatureproblems with HDSCR canberesolved.

Mr. Steve Moorman ofBabcock and Wilcox in a July 18, 2007 email stated the resolution of the temperature problem would require a technical feasibility analysis of a "very complex nature" to determine ifboiler modifications could bring furnace exit gas temperatures into the range needed for compatibility with operation of HDSCR. Modifications outside of the boiler may solve the temperature problem; however, a study would be required. EPA's statement that the technical issues with the temperature issue can be resolved appears to be premature.

The email also states "Ourbudget estimate to complete this study is $275,000 to $400,000 including the performance test, project management costs and travel expenses. We projectthe study will require 20 to 24 weeks to complete including the time to run the performance tests." The NSR Manual9 states: "A control technique is considered available, within the context presented above, ifit has reached the licensing and commercial sales stage of development. A source would not be required to experience extended time delays or resource penalties to allow research to be conducted on anew technique. Neither is it expected that an applicant would be required to experience extended trials to learn how to apply a technology on a totally new and dissimilar source type. Consequently,
13

### technologies in the pilot scale testing stages of development would not be considered available for BACT review." The Department considers the time and money necessary to detennine ifthe temperature problems canbe overcometo be excessive.

3. EPA's ConclusiononHDSCR

When considering application of HDSCR to a cyclone boiler burning North Dakota lignite, the MRYS is considered a new source type. In the past, EPA has recognized cycloneboilers, and more generally slag tap furnaces, thatbum lignite from North Dakota, South Dakota and Montana as a separate source category for NOx 

### emissions in the New Source Perfonnance Standards, Subparts D and Da. This separate category was established primarily based on the use ofhigh sodium lignite. Not until EPA developed a fuel and furnace neutral standard was this categoryreplaced. The replacement ofthis category was apparently done without
an evaluation ofthe flue gas characteristics ofNorth Dakota lignite. The NSR Manual9 

### states "Add-on controls, on the other hand, should be considered based
on the physical and chemical characteristics of the pollutant-bearing emission stream. Thus, candidate add-on controls may have been applied to abroad range ofemission unit types that are similar, insofar as emissions characteristics, to the emission unit undergoing BACT review." (NSR Manual, Chapter B, Section IV.A).

14Minnkotahas demonstrated thatthe flue gas characteristics atMRYS are different from other coal-fired boilers where HDSCR has been applied. The NSR Manual states "A source would not be required to experience time delays or resource penalties to allow research to be conducted on a new technique. Neither is it expected that an applicant wouldbe requiredto experience extendedtrials to learn how to apply a technology on atotally new and dissimilar source type." (Chapter B, Section IV.B). Minnkota is not required to conduct extensive and expensive feasibility analyses for modifying the boiler to correct temperature problems that make HDSCRinfeasible.

EPA has indicated that catalyst regeneration is a viable option (that is currently used in practice) for restoring catalyst life either in-situ, on-site, or off-site water washing. EPA cites aPowerPoint presentation at the 2007 NOxRound Table and Expo by Reinhold Environmental Limited as evidence that this technique is available. 

### DOl's consultant, Mr. Hans Hartenstein, also made a presentation at the referenced Expo. In Mr. Hartenstein's presentation the following statement is made "Regeneration 

### = Removal of catalyst poisons plus restoration of catalytically active ingredients

- can typically not be done in-situ or on-site, but should be done off-site to ensure required close process control." EPA may be referring to "rejuvenation" of a catalyst for which Mr. Hartenstein states "Removal of catalyst poisons without the need for replenishing catalytically active compounds

- can sometimes [emphasis added] be done in-situ, but is most commonly done either on-site or off-site." These statements were also made by
15

### Ehrnschwender and Holsccher at the February 2008 Expo (Considerations for CatalystDeactivation and Regeneration When Firing Biomass). Minnkota and its consultants**hav~** 

### addressed this issue by stating "Regarding the contention of Hartenstein, there is extremely limited experience with in-situ catalystcleaningon coal-fired units. ENBW in Germany developed this technique, but it has never had a commercial success. It 

### has also neverbeen used for blinded or chemically poisoned catalyst, but only for mechanically plugged catalyst." There is no evidence regarding the effectiveness ofwashing to rejuvenate an SCR catalyst on the MRYS. Pilot scale testing would be necessary to determine the feasibility of this catalystmaintenancetechnique.

4. The NDDH BACT Determination Incorrectly Applies the Concept of Pilot Testing in EPA's NSRManual to Concludethat SCRis notTechnicallyFeasible

EPA states that "For determining whether a control option is available, EPA's NSR Manual does not describe the comparison of gas stream characteristics betweenthe sourceunderreview and other sources."

There has never been SCR technology applied to a boiler that combusts North Dakota lignite. EPA has recognized in the past, that cyclone boilers, such as those at Minnkota, that bum lignite from North Dakota is a separate source category for NOx 

### emission limits under the New Source Performance Standards, Subpart D and Da. Chapter B, Section IV.A, Identify Alternative Emission
16

### Control Techniques (Step 1) 

### [emphasis added] states "The top-down BACT analysis should consider potentially applicable control techniques from all three categories. Lower polluting processes should be considered based on demonstrations made on the basis ofmanufacturing identical or similarproducts

. from identical or similar raw materials or fuels. Add-on controls, on the other

hand, should be considered based on the physical and chemical characteristics of the pollutant-bearing emission stream. Thus, candidate add-on controls may have been applied to a broad range of emission unit types that are similar, insofar as emissions characteristics, to the emissions unit undergoing BACT review." 

### [emphasis added] Clearly, identification of control options under Step 1 musttake into account the flue gas characteristics. If the flue gas characteristics can be shown to prevent successful application ofthe technology to the source under view, the technology is not identified as "potentially applicable" to the source in Step 1 and is therefore not commercially available under Step 2. Minnkotahas shown that the flue gas characteristics for a HDSCR at MRYS are different from that at any other coal-fired power plant where SCR has been installed. Mr. Roger Christmann, EPA consultant, stated thathe was not aware ofanypowerplant where HDSCRhadbeen applied with as high ofsodium loading as MRYS.

HDSCR technology designed for othercoal-firedpowerplants is not applicable to
a North Dakota lignite-fired unit and there is no commercially available design. Pilot scale testing would be necessary to show whether HDSCR can work
17successfully. As Sargent and Lundy (S&L) pointed out, there are no known solutions for the catalyst surface masking and catalyst deactivation caused by the soluble alkalis (Na20 and K20) found in North Dakota lignite. S&L indicated that somethresholds orlimits are yetto be defined for HDSCRinvolving ash with greater than 2% Na20 and greater than 1% K2 0. Ash from MRYS contains an average 4.4% Na20 and 1.3% K20. TheNa20 canbe as high as 13% and K20 as high as 7%. Any pilot scale testing would be used to obtain data on the soluble alkalis and ash characteristics and compare the findings with experience on PowderRiverBasin Coal.

The pilot scale testing for a HDSCR would not be for optimizing an existing applicable control technology. It would be for researching solutions for the high soluble alkalis and possibly designing anew SCR system for anew and dissimilar
source category.

5. The NDDH BACT Determination Frustrates the Technology Forcing Function of the BACTthatwas Intendedby Congress.

MRYS is a different source category based on its flue gas characteristics at a HDSCR location. The Department has taken the position that the flue gas characteristics at the MRYS would preclude the successful application ofexisting HDSCR technology. Decisions regarding technical feasibility are based on the flue gas characteristics, not whether it has been applied to a coal-fired boiler or
18some other general source category. We believe Congress never intended forcing
a technology on a source when there is a low probability of successful deployment ofthattechnology.

B. Conclusions

Recent testing by Kling2 and Zheng3 suggest a low probability ofachieving successful application ofHDSCR technology by MRYS. The high concentration of sodium and potassium in the flue gas will rapidly deactivate the catalyst. The results suggest much less than 10,000 hours ofcatalyst life which the Department believes is necessary for successful application ofHDSCR.

Minnkotahas supplied data indicating temperature problems (both too high and too low) at the location ofHDSCR which will affect the catalyst life. Babcock and Wilcox has estimatedthat a study ofthe temperature problems could take up to 24 weeks and costup to $400,000. The NSR manual indicates that a company is not expected to experience extendedtrials to learnhow to apply atechnology.

Based on the flue gas characteristics at the location of the high dust SCR and the temperature problems (both too high and too low), the Department does not consider HDSCRto betechnically feasible for MRYS.

19

### III. Tail End SCR and Low Dust SCR

A. 

### Introduction

SCR systems placed between the particulate control device and sulfur dioxide control equipment are called low dust SCR (LDSCR). Systems that are placed downstream of the particulate matter (PM) and sulfur dioxide (S02) control systems are generally referred to as tail end SCR (TESCR). This is in contrast to a HDSCR location where
none ofthe particulate matter and sulfur dioxide has been removed from the flue gas. LDSCR and TESCR systems have been used on coal-fired and biomass fired boilers in the United States as well as other countries. However, no SCR system including a low dust or tail end SCR has everbeen operated on aboiler firing North Dakota lignite. The flue gas produced by the combustion of North Dakota lignite contains high concentrations of alkali aerosols (primarily sodium and potassium). Cyclone boilers, such as the two units at the M.R. Young Station, produce higher concentrations of submicron aerosols than conventional pulverized or fluidized bed boilers. The higher temperature in the cyclone boilers vaporizes the organically associated sodium and potassium in North Dakota lignite. When these elements condense, they form submicron aerosols. Minnkota1 

### (p. 12) 

### has indicated that the condensed vapors have a mean diameter ofapproximately 0.1 

### micrometers. Papers by Kling2and Zheng3

### have indicated that the aerosols with a diameter less than or equal to 0.1 

### micrometers cause the greatest catalystdeactivation.

20

### The NSR Manua1 9 

### states that decisions regarding technically feasibility are made by comparing the physical and chemical characteristics ofthe exhaust gas stream from the unit under review to those ofthe unit from which the technology is being transferred. Unless significant differences between the source types exist that are pertinent to the successful operation of the control device, the control option is presumed to be technicallyfeasible unless the source canpresentinformationto the contrary.

Sinceno LDSCR orTESCR systemhas everbeen applied to aboilerthatcombusts North Dakotalignite, an evaluation ofthe flue gas characteristics was madeto determine ifthey
were substantially different from facilities thathave successfully applied SCRtechnology
orto determine ifempirical data would indicate whether low dust or tail end SCR canbe successfully applied.

B.Flue Gas Characteristics

At the MRYS, both units use an electrostatic precipitator (ESP) to control PM emissions. Unit 2is equipped with awet scrubberto control S02 emissions while awet scrubberwill be constructed for Unit 1. Minnkota4 

### (p.20) has provided an analysis ofthe particulate matter emitted from Unit 2 which can be used for evaluation ofTESCR. The analysis indicated the PM was 6.56% sodium (Na), 2.26% potassium (K), 5.71% sulfur (S), 57.52% oxygen (0) and theremaining other elements.

21

### The sodium and potassium after the ESP and wet scrubberis most likely in sulfate forms (p.32). If all ofthe sodium and potassium is in the sulfate form, sodium sulfate and potassium sulfate would comprise approximately 25% ofthe total particulate matter emitted from Unit 2 (see Appendix A). Minnkota has indicated that the sample ofthe particulate matter that was analyzed was obtained while some flue gas was bypassing the S02 scrubber. The amount ofsodium, potassium and/or sulfur in the sample could be biased high when compared to a sample when all flue gas passes through the wet scrubber.

Areview ofthe latest PM stack tests at M.R. Young Unit 2 (8/07 and 5/08) indicated an average PM emission rate of 10.61 milligrams per normal cubic meter (mg/Nm3 

### at 6% 02

- see Appendix B). Based on 25% ofthePM being sodium and potassium sulfate, the combined emission rate ofthese two compounds is approximately 2.7 mg/Nm3

. 

### This indicates asodium and potassiumremoval efficiency ofgreaterthan 99% bythe ESP and wet scrubber.

Minnkota has submitted data from a study by Markowskis (p.3l) which indicated that approximately 81 % ofthe sulfate emitted after the Unit 2 wet scrubber is less than 1.1 micrometers in size and approximately 36% is less than 6.26 micrometers in size. Based
on the latest stack tests and the Markowski data, the submicron sodium sulfate plus potassium sulfate emission rate would be less than 2.2 mgiNm3 

### and the emission rate of sodium and potassium sulfate less than 0.26 micrometers in size would be approximately

22

### 1.0 mg/Nm3

. 

### These values are similar to those Markowski reported which were 1.335 mg/m3 

### and 0.602 mg/m3

### respectively.

C. 

### CatalystDeactivation

The two primary flue gas constituents that will cause SCR catalyst deactivation in a low dust or tail end configuration are sodium and potassium, most likely in sulfate formS (p.32-35). Crespi et.a1.6, 

### in their paper regarding the Arnager Station, presented a graph which shows the effect ofvarious poisons on the activity ofvanadia

- titania catalysts. Minnkotal 

### (page 21) provided similarinformation thatindicates that

### potassiu~ oxide is a more potent catalystpoison on amolarbasis than sodium oxide. Although no actual data is supplied, analysis ofthe graph indicates thatpotassium oxide is 1.77

- 

### 2.08 

### times more potent catalyst poison than sodium oxide (on a molar basis) up to a poison to vanadium/titanium ratio of0.5 (see Appendix C). 

### Because potassium oxide has a larger molecularweightthan sodium oxide, the poisoningratio is 1.1

- 1.3 on amass basis.

As indicated earlier, Kling2 

### and Zheng3 

### have indicated thatthe aerosols less than or equal to 0.1 micrometers cause the catalystdeactivation. Data are not available to calculate the portions of the PM emissions from Unit 2 that would be less than or equal to 0.1 micrometers. A conservative assumption is that all ofthe sodium and potassium sulfate less than 0.26 micrometers is less than or equal to 0.1 micrometers. Based on this assumption and the PM analysis data, the total emission rate forsodiurn and potassium

23

### sulfate combined that is less than or equal to 0.1 micrometers is size is estimated at 0.98 mg/Nm3 

### ofwhich 0.78 mg/Nm3 

### is sodium sulfate.
KlingZ

### has provided catalyst deactivationrates for various biomass fuels whichproduce a flue gas that contains sodium and potassium aerosols. The testing was conducted using different types ofhoneycomb 

### WzOs/TiOz SCR catalyst. Type A catalyst was catalyst typically applied at coal-fired powerplants, Type B was a "bio-optimized" catalyst with increasedvanadium content, and Type Chad an evenhighervanadium content.

For a mixture ofpeat and 15% wood, the flue gas contained 4.4 mg/Nm3 

### ofpotassium and 0.8 mg/Nm3 

### ofsodium aerosols with an aerodynamic particle diameter less than 0.1 micrometers.

Potassium (mg/Nm3) 

### Sodium (mg/Nm3) 

### Peat

### + 15% Wooda



### 4.4 0.8 CenterLigniteb



### 0.20 0.78

a b 

### As chloride As sulfate

The maximum deactivation rate was 12% in 768 hours using Type A catalyst. Another result indicated 15% deactivation in 1488 hours using Type B catalyst. The shorter test
24result on peat plus 15% wood indicates 6400 hours to 100% deactivation while the longer test result indicates 9920 hours to 100% deactivation. Regarding the deactivation rates, Kling et.ae stated "Exposure ofthis kind of short samples gives a larger deactivation compared to a full-length catalyst [1, 4] thatis mainly a consequence ofturbulence ofthe inletofthe catalyst, beforelaminarflow is attained."

The sodium concentration in the flue gas after the wet scrubber from Center lignite is similar to that of the peat plus 15% wood; however, the potassium content is approximately 17 times lower. It appears the catalyst life for an SCR at M.R. Young Station shouldbe substantiallylongerthan that estimated forpeatplus 15% wood.
Zheng et.a!.3 found a deactivation rate of 0.4% per day for potassium sulfate or 6000 hours to 100% deactivation. The testing was conducted at a loading of20-30 mglNm3

. The aerosols varied in size from 0.07 micrometers to 1.05 micrometers with amass mean diameter of0.55 micrometers. The Markowski data indicates that approximately 53% of outlet sulfate was less than or equal to 0.52 micrometers. Based on the latest stack tests at M.R. Young Unit 2, this equates to·a total emission rate ofapproximately 1.4 mglNm3 for those sodium and potassium sulfate aerosols less than 0.52 micrometers. The Minnkotaemissionrate is substantiallyless (14-21 times) than the Zhengtesting.

The above results do not consider the fact that potassium is amore potent catalystpoison than sodium and chlorides are more potent than sulfates. These facts make it even more likely that the catalyst life will be longer than the testing indicated by Kling2 and Zheng3
25since Center lignite combustion at MRYS produces primarily sodium sulfate aerosols whilebiomass combustionproduces primarilypotassium chloride aerosols.

For a LDSCR application, the only airpollution control device priorto SCR will be adry electrostatic precipitator (ESP). Stacktest results from the FINE Particles

- Technology, Environmental and Health Technology Programme13 suggests that an ESP on a biomass boiler will have a control efficiency ofgreater than 90% for submicron particles and can achieve greater than 96% for particles less than 0.1 micrometers in size. This is consistent with AP_42 12 data for Kraft recovery boilers which indicates an ESP can remove more than 98% ofthe submicron particulate matter in the flue gas which is primarily sodium sulfatel4

. Similarresults are reported for coal-firedlbiomass boilers by Mohrl5
, Lindl6 and the Power Station Emissions Handbook17

. This indicates that most of the submicron sodium and potassium aerosols, including those aerosols less than 0.1 micrometers in size, will beremovedbythe electrostaticprecipitators atMRYS.

Minnkota has submitted data on the ash composition that accumulated on the electrodes ofthe Power Span ECO electrodes during apilottestll (p. 26). The data suggests thatthe sodium and potassium concentration in the particulate matter downstream ofthe Unit I ESP is higher than the concentration in the particulate matter downstream ofthe Unit II wet scrubber. However, the concentration is less than a factor oftwo higher. The total loading ofsodium and potassium, as indicatedby the data submittedby Minnkota, would still be considerably less than the loadings in the Kling2 and Zheng3 tests. This suggests

26that the catalyst deactivation rate of a LDSCR at MRYS should be lower than in the referenced tests.

D. Vendor Information

The U.S. Department of Justice, through their contractor Mr. Hans Hartenstein, has provided emails from various catalyst and SCR system providerslO (Appendix D). Each ofthe responses from the vendors indicated that tail end SCR is technically feasible for the Milton R. Young Station.

The Department contacted three ofthe vendors, Ceram Environmental, Haldor Topsoe and BabcockPower. The companies generally confirmedthe information inthe emails to Mr. Hartenstein. Babcock Power indicated they had no worries about getting 10,000 hours ofcatalyst life at the M.R. Young Station. However, they recommended "coupon" testing prior to design ofthe SCR. Ceram was convinced it was technically feasible; however, their representative did acknowledge that ifthe sodium and potassium aerosols
are making it through the ESP and wet scrubber, catalyst deactivation could be a problem. HaldorTopsoe indicatedthat the catalystdeactivation at M.R. Young wouldbe manageable ifthe catalyst is kept dry during outages. Although no written guarantees have been provided by the vendors, it appears that vendors are willing to provide them for atail end SCR atthe M.R. Young Station.

27E. Biomass Facilities using LDSCRJTESCR

There are no boilers that combust North Dakota lignite and are equipped with SCR technology. LDSCR and TESCR has been applied to coal-fired boilers in Europe, Asia and the United States. However, in general, other U.S. coals are much lower in the organically associated alkalis that cause SCR catalyst deactivation. Biomass fired boilers have flue gas characteristics that more closely approximate those from North Dakota lignite. At least four biomass boilers that are equipped with tail end or low dust SCR are currentlyin operation in the United States. Theboilers are spreader stokerdesign anduse
an electrostatic precipitator as the primary particulate matter control device. These include:

• Whitefield Power & Light, New Hampshire

- Boiler uses whole tree chips and has operated since October2004.

• Bridgewater Power, New Hampshire

- Boiler uses whole tree chips and has operated since October2007.

• PineTree Power, New Hampshire

- Biomass combustion.

• Boralex Stratton, Maine

- Boiler uses whole tree chips, waste wood, and construction and demolition waste. The boiler has operated since December 2004.
28

### The Department is also aware of proposed TESCR or LDSCR installations at the Burlington Electric Plant in Vermont, Synterprise Global Solutions in Tennessee and the Amager Heat and Power Plant near Copenhagen, Denmark. The Amager Station is also allowed to bum coal and may not be required to operate the TESCR when combusting biomass.
Although there are boilers that combust 100% biomass and utilize LDSCR for NOx 

### control, there is no information about the actual loading of potassium and sodium aerosols at the inlet to the SCR. The New Hampshire Department of Environmental Services (NHDES) was contacted regarding the biomass boilers that use LDSCR. The Whitefield Power Plant is a 16 MWe spreader stoker that is equipped with a multiclone and electrostatic precipitator for particulate matter control. The NHDES confirmed the boiler had been operating for approximately four years. NHDES was not aware ofany catalyst**dea~tivation** 

### problems at this facility. The plant has a NOx 

### emission limit of 0.075 Ibll06

### Btu. The other facilities in New Hampshire are similar; however, theyhave not operated as long. No data was available regarding the loading of potassium and sodium atthe inletofthe SCR.

F. Conclusions

In the June 2008 Preliminary Best Available Control Technology Determination for Control ofNitrogen Oxides for M.R. Young Station Units 1 and 2, the Department 

### 29concluded that an SCR system must have a catalyst life ofat least 10,000 hours before SCR technology could be deemed successfully applied to the source. The life ofthe catalyst will depend on many factors including the reduction efficiency required, the allowable ammonia slip, the volume ofcatalyst used, the plant load variability, the coal flue gas characteristics, the makeup ofthe catalyst (e.g. high vanadium catalyst will last longer than a catalyst with a lower vanadium content), the design ofthe reactor system, the number of catalyst layers, the catalyst management plan, and other factors. The catalyst could be replaced when deactivation has reached 50% or less or it could be replaced at a higher deactivation point depending on the system's ability to meet the regulatoryrequirements for the NOxemissionrate and/or ammonia slip rate.

No data has been found from an actual operating facility which has similar flue gas characteristics to M.R. Young Station that use high dust, low dust or tail end SCR. However, experimental and pilot scale testing by Kling2 and Zheng3 provides empirical data for comparison. The total sodium and potassium loading ofaerosols less than 0.1 micrometers expected at the inlet ofa TESCR at M.R. Young Station is expectedto be at least 5 times less than found in the Kling tests on peat plus 15% wood. Kling's data indicated up to 9920 hours before 100% deactivation for catalyst type B. Zheng's3 data suggested 6,000 hours before 100% deactivation when exposed to potassium sulfate aerosols with an mean diameter of0.55 micrometers at a concentration which is 14-21 times higher than the concentration of sodium and potassium aerosols of this size expected after awet scrubber at M.R. Young Station. The loading at a low dust location would also be substantially less than the loading in the Kling or Zheng tests. Kling2 also
30pointed out that the testing probably over estimates the deactivation rate because of turbulence in the pilot scale inlet ofthe catalyst which would be more laminar in a full scale SCR.
Existing biomass boilers are using LDSCR successfully. Although the boilers are not cyclone fired units, the New Hampshire units use similar PM control devices as M.R. Young Station (i.e. ESP). The potassium chloride emitted from the biomass boilers is a much more potent catalyst poison than the sodium sulfate emitted at the MRYS. The Whitefield Plant has operated for more than four years without deactivation problems. Kling2 has referred to "bio-optimized" catalyst and higher vanadium catalysts that appears to have a longer life than the typical coal-fired boiler SCR catalyst for a given concentration of sodium and potassium aerosols. A bio-optimized catalyst (high vanadium content) will be installed at the Amager Station6 (p. 13). Vendors believe that TESCRis technicallyfeasible and canbe successfully applied atM.R. Young Station.

Based on the empirical data available at that time, vendor information that TESCR is feasible at the M.R. Young Station and the use oflow dust SCR onbiomass fired boilers, the Department concludes that tail end and low dust SCR appear to be technically feasible atM.R. Young Station.

31

### References
1. MinnkotaPower Cooperative; 2008 Comments and Responses to NDDH Regarding U.S. EPA Region 8's July 31,2008 Comments and Plains Justice July 30, 2008 Comments for NDDH Preliminary NOx BACT Determination for Milton R. Young Station (MRYS) September22,2008. 2. Kling, Asa; Andersson, Chester; Myringer, Ase; Eskilsson, David; Jaras, Sven G.; Alkali deactivation ofhigher dust SCR catalysts used for NOx reduction exposed to flue gas from 100 MW-scale biofuel and peat fired boilers: Influence offlue ga;s composition; Applied Catalysis; 2007. 3. Zheng, Yuanjing; Jensen, Anker Dega; Johnsson, Jan Erik; Thogersen, Jaokim Reimer; Deactivation of V205

- W03

- Ti02 SCR catalyst at biomass fired power plants; Elucicdation ofmechanisms by lab

- and pilot-scale experiments; Applied Catalysis; 2008. 4. 

### Minnkota Power Cooperative, Inc. and Square Butte Electric Cooperative; Responses to NDDH and EPA Comments Regarding SCR Technical Feasibility and Non-SCR concerns, Milton R. Young Station Unit 1 and Unit 2 NOx BACT Analysis Study; April 18,2007. 5. Minnkota Power Cooperative, Inc.; Supplemental Information for Consideration Regarding NOx BACT for M.R. Young Station Units 1 and 2: Technical Feasibility Issues forTESCR and LDSCR Retrofit; February 20,2009. 6. 

### Crespi, Mario; Porle, Magnus; Larsson, Dr. Ann

- Charlotte; La Civita, Raffaela; Nielsen, Anders Rooma; The influence of biomass burning in the design of an SCR installation. 7. Hartenstein, Hans; Hans Hartenstein's Thoughts on Klingpaper; April 9, 2009. 8. NDDH, Analysis ofthepotency ofpotassium oxide versus sodiumoxide; May 1,2009. 9. EPA, 1990 New Source Review Workshop Manual, Preventing SignificantDeterioration and Non-attainment Area Permitting, Office of Air Quality Planning and Standards, ResearchTrianglePark, NC 27711. 10. Hartenstein, Hans; Feasibility ofSCR Technology for NOx 

### Control Technology for the Milton R. Young Station, Center, North Dakota; July 2008. 32

### 11. Minnkota Power Cooperative; Comments and Responses to NDDH Regarding U.S. EPA Region 8's July 31, 2008 Comments and Plains Justice July 30, 2008 Comments on NDDH Preliminary NOx 

### BACT Determination for Milton R. Young Station (MRYS); September22,2008. 12. EPA, 1995 Compilation ofAir Pollution Emission Factors Volume 1: Stationary Point and Area Sources, Office ofAir QualityPlanning and Standards, ResearchTriangle Park, NC 27711. 13. Ohlstrom, Mikael; Jokinieme, Jorma; Hokkinen, Joumi; Makkonen, Pasi; Tissari, Jakko; Combating Particulate Emissions in Energy Generation and Industry; VTT Technical Research Centre ofFinland; 2006. 14. Lind, T., Hokkinen, J.; Jokiniemi, J.K.; HiIlano; R; Makkonen, U; Raukola, A.; Rintamen, J; Saviharju, K; Electrostatic Precipitator Performance and Trace Element Emissions from Two Kraft Recovery Boilers; Environmental Science and Technology; January 15, 2006. 15. Mohr, Martin; Yiatalo, Ni; Klippel, E.!.; Kauppinen, O. Riccius; Burtscher, H.; Submicron Flay Ash Penetration Through Electrostatic Precipitators at Two Coal Power Plants, Aerosol Science andTechnology, 1996. 16. Lind, Terttaliisa; Hokkinen, Joumi; Jokinemi; Jonna K; Electrostatic Precipitator Collection Efficiency and Trace Element Emissions from Co-Combustion of Biomass and Recovered Fuel in Fluidized Bed Combustion; Environmental Science and Technology; 2003. 17. Power Station Emissions Handbook; www.ccsd.biz/PSE Handbook/5/6/5 index.efrn

33Appendix A Analysis ofUnit II

StackTest Filter

34

## MINNKOTA UNIT 2 FILTERANALYSIS

ELEMENT % OF ELEMENT MOLECULAR MOLES a ON FILTER WEIGHT Na 6.56 23.0 0.285 K 2.26 39.1 0.058 S 5.71 32.1 0.178 0 57.52 16.0 3.595

a BASED ON 100 GRAMS OFPM

0.285 MOLES OF SODIUM AVAILABLE

. . NEED (0.285/2)*(1) MOLES OF SULFUR 

## =0.142 MOLES NEED (0.285/2)*(4) MOLES OF OXYGEN 

## =0.570 MOLES TOTAL

### wr. Na2S04 

### = (23)(0.285) 

### + (32.1)(.142) 

### + (16)(.570) 

### =20.2 grams POTENTIAL Na2S04 

### =20.2 g/100 g *100% == 20.2%

0.058 MOLES OF POTASSIUM AVAILABLE NEED (0.058/2)(1) MOLES OF SULFUR 

## =0.029 MOLES NEED (0.058/2)(4) MOLES OF OXYGEN 

## =0.116 MOLES TOTAL WEIGHT K 2 S04

### =(39.1)(.058) 

### + (0.029)(32.1)

### + (16)(.116) 

### =5.05 grams POTENTIAL K 2

S04= 5.05%the strands. These particles are rich in sodium and sulfuras comparedto the filtermaterials. Figure 18 shows a regionofthe filter that was notexposedto flue gas andthe fiber stands do nothave particles bondedto the sUrfaces. Table5. Morphologicalanalysis results for filtersample001. Results·expressedas**wei~ht** percenton an elemental basis. Fig. J;»tI**Ar.~a ~escription**  Na Mg Al Si S Cl .K Ca Ti Fe Ba 0

14 " 1* Overallarea,-lOOx 5.98 1.83 2.62 to.85 3.80 0.00 2.29 lUO 0.00 2.31 0.00 59.21 2* Overall area- lOOx 5.95 2.40 2.82 lO.93 5.42 0.00 2.25 11.30 0.40 2.46 0.00 56.07 3* Overallarea-lOOx 7.311.992.238.737.380.002.289.860.001.11 0.0059.10 4* Overall area- lOOx 5.66 2.54 2.20 9.47 5.27 0.00 2.54 10.08 0,00 3.05 1.65 57.56 5 Lightparticle 1.21 3.33 5.47 7.65 1.38 0.00 1.40 13.44 0.00 6.76 1.85 57.52· 6 Darkparticle 6.40 9.79 1.47 10.75.6.24 0.00 3.76 7.84'**O~OO** ·1.96 0.00 52.68 7 Lightparticle 0.57 3.99 7.49 8.94 1.74 0.19 U5 15.670.43 3.83 0.00 56.01' 8 Ovenill area- 100x 8.50 2.62 2.45 10.04 6.81 0.00 2.12 9.26 .0.50 2.40 0.00 55.30 9 Overall area- lOOx 5.95 1.97 2.64 11.03 5.58 0.00 .2.09 10.21 0,86 1.78 0.00 57.90 10 Lightparticle**0~78** 4.20 6.78 11.26 0.00 0.00 1.24 15.37 0.00 3.70 5.10 51.56 11* Blankedgeoffilter 0.00 0.93 5.11 20.20 0.00 0.00·0.93 13.83 (}.OO ·,().OO 0.00 59.00· 12* Blankeqgeoffilter 0.00 1.19 4.95 19.69 0.00 0:00 i.l6 16.52 0.00 0.59 0:00 55.91

. 15 13 Small, lightparticles 3.00 3.30 3.10 7.72 2.91 0.00 1.40 1"1.02 0.00' 3.49 1.89 62.18 14 SmaIlbondedparticles 2.93 1.25 1.02 10.04 6.99 0.00 4.0629.33 0.00 5.38 2.93 36.08 15 Largedarkpartic1e 10.25 9.68 0.00 1.41 22.60 0.00 3.74 2.16 0.00 0.00 0.00 50.15

. 16 Large darkparticles 13.40 11.82 0.00 1.30 10.30 0.00 2.28 0.96 0.00 2,17 0.00 57.78

17 Smallbondedparticles 4.39 3.56 2.17 10.95 6.88 0.00 2.77 14.020.51 2.83 0.00 51.92 18 Smllilbondedparticles 1.49 2.82 5.86 10.45 4.93 0.00 3.19 26.01 1.19 8.23 0.00 35.84 Overallareas 6.56 2.23 2.49 10.17 5.71 0.00 2.26 10.30 0.29 2.18 0.27 57.52 Light"particles 1.39 3.71 5.71 8.89 1.51 0.05 1.30 13.88 0.11 4.442.21 56.82 Average Dark**particl~** 10.0210.43 0.49 4.49 13."OS**O~OO** :t26 3.65 0.00 1.08 0.00 53.54 Smallbondedparticles 2.94 Z.54 3.02 10.48 6.27 0.00 3.34 23.12 0.57 5.48 0.98 41.28 Filteredge 0.00 1.06 5.03 19.94 0.00 0.00 1.04 15.18 0.00 0.30 0.00 57.46 

## * = areas notspeCifically noted orshown in electronmicrographFigure 14.

Minnkota PowerCooperative, Inc. 

### 20 Bums & McDonnellAppendix B Calculation ofEmissions Rate For M.R. Young Station



### 35

### MINNKOTA STACKTEST RESULTS

UNIT DATE OFTEST PM OXYGEN PM PM PM EMISSION.RA TE CONTENT EMISSION RATE EMISSION RATE EMISSION RATE (gr/dscf) (%) (mg/m3) (mg/Nm3) • (mg/Nm3) at 6%02 1 6/9/2008 0.0026 8.6 5.95 6.39 7.74 1 8/29/2007 0.0031 5.9 7.09 7.61 7.56 AVERAGE 0.00285 7.25 6.52 7.00 7.65 2 5/7/2008 0.0042 7.4 9.61 10.32 11.38 2 08/28/2007 0.0039 6.4 8.92 9.58 9.84 AVERAGE 0.00405 6.9 9.27 9.95 10.61

a ADJUSTED TO 0 0 C TAILENDSCR

FROM FILTER ANALYSIS Na =6.56% OF PM AND K=2.26%. IF ALL Na AND KIS SULFATE FORM, Na2S04 =20.2% AND K 2 S04=5.05% OF PM. UNIT DATE OFTEST POTENTIAL Na2S04 POTENTIAL K2 S04 EQ. K2 S04 b EQ. K2 S04 b,c EQ. KCI c,d EMISSION RATE EMISSION RATE EMISSION RATE EMISSION RATE EMISSION RATE (mg/Nm3) (mg/Nm3) (mg/Nm3) < 0.52 um < 0.26 um (mg/Nm3) (mg/Nm3) 1 6/9/2008 1.56 0.39 1.59 0.85 0.23 8/29/2007 1.53 0.38 1.56 0.83 0.23 AVG. 1.55 0.39 1.57 0.84 0.23

2 5/7/2008 2.30 0.57 2.34 1.24 0.34 2 08/28/2007 1.99 0.50 2.03 1.08 0.30 AVG. 2.14 0.54 2.19 1.16 0.32
b BASED ONCRESPIDATA INDICA TINGPOTASSIUMIS1.3 TIMESMOREPOTENTCATALYSTPOISON THANSODIUM ONA MASSBASIS. C BASED ONMARKOWSKIDATA THATINDICATES53.1% OFSULFATEISLESS THAN0.52 urnAND36.5% ISLESS THAN0.26urn. d BASED ONZHENG'SDATA THATINDICATEDA DEACTIVA TIONRA TEOF1% PER DA YFOR KCfAND 0.4% PERDA YFOR K2 SO4' ZHENG TO MINNKOTA LOADING RATIO = (20-30 mg/Nm3)/(1.16 mg/Nm3) = 17.2 TO 25.9 KUNG (PEAT+ 15% WOOD) TO MINNKOTA LOADING RATIO = (4.4 + 0.8/1.3 mg/Nm3)/(O.32 mg/NmJ) 

## =15.7 NOTE: THISISCONSERVATIVESINCELESS THAN36.S% OFSULFATEATMINNKOTA WILL PROBABLY HAVEA DIAMETER OF0.1 urn ORLESS.

## MINNKOTA POWER COOP. UNIT 2 HIGH DUST SCR

AVG. EMISSION RATE (Ib/dscf)

AVG. EMISSION RATE (mg/Nm3) Na20

3.051E-05

524 K20

9.014E-06

155 EO. K20 a

3.248E-05

558 EO. K2S04 b

6.013E-05

1034 EO. KCI C

2.405E-05

413 EQ.KCL d 

## « 0.1 urn)

1.203E-05

207

i1 BASED ONCRESPIDATA WHICHINDICATESK20IS1.3 TIMESMOREPOTENTCATALYSTPOISON THATNa20 ONA MASSBASIS. /, BASED ONA MOLECULAR WEIGHTOF94FORK20AND174FORK2S04 ANDASSUMINGALL Na & KISINSULFATEFORM. C BASED ONZHENG'SDATA THATINDICATEDA DEACTIVATIONRA TEOF1% PERFORDAYFORKCf AND 0.4% PERDA YFORK2S04' d BASED OONSO% OF AEROSOLSLESS THAN0.1 MICRONSINSIZE. MINNKOTA TOZHENGLOADINGRATIO

## =(1034mg/Nm3)*0.50/(20-30mg/Nm3 ) 

## =25.9 TO 17.2 MINNKOTA TO KLINGLOADINGRATIO (BARK+ 30% DEMOLITION WOOD) = (207mg/Nm3 ) / (16.7+ 5.8/1.3) =..£6Appendix C Analysis ofNazO and 

### KzO Poisoning Potency

36

### DEPARTMENT ANALYSIS Na20 and K 2

0 DEACTIVATION POTENCY



## 100

80,



### 20

0.5 1 1.5 Me: V molar ratio 

## 2

CONTAMINANT RELATIVE MOLAR Na20jK2O ACTIVITY RATIO MOLAR RATIO Na20 30% 0.55 2.20 K

2 0 30% 0.25 Na20 40% 0.42 2.00 K

2 0 40% 0.21 Na20 60% 0.25 1.79 K

20 60% 0.14 AVERAGE 2.00Appendix D Vendor Infonnation Tail End SCR

37

### Appendix B: SCRVendor Query Correspondence 1. Vendor Correspondencewith SCR system suppliers 1.1 E-Mail correspondencewith Clay Erickson, Babcock Power(SCR System Vendor

- extensive tail-end SCRexperience) From: cerickson@babcockpower.com [mailto:cerickson@babcockpower.com] Sent: Thursday, June 19, 2008 15:59 To: Hans Hartenstein· Cc: jlangone@babcockpower.com; tlicata@babcockpower.com Subject: Re: Tail-end SCR Hans, Babcock Power has reviewed the Milton Young plant in the past, based on these reviews Babcock Powerfinds o A tail-end SCR is technically and commercial feasible o Babcock Power does not recommend or require additional pilot testing only proper flue gas characterization as with any SCR system per performed o Will provide commercial guarantees forthe SCR and catalyst performance (activity, pressure drop and SOz/S03conversion rate) and lifetime
. Babcock Power has the largest SCR experience list in the world; from this experience we are completely confident in the application ofa tail end system at Milton Young. Ifyou have further questions please let me know. With best regards, Clay Clayton Erickson, PhD Director, Process Engineering Babcock Power Inc. 5 Neponset Street Worcester, MA01606 T: 508-854-4039 F: 508-854-1177 M: 508-245-2383

From: "HansHartenstein"<Hans.Hartenstein@Evonik-EnergyServices.us>

. Sent: 06/18/2008 12:16 To: <cerickson@babcockpower.com> Subject: Tail-end SCR Clay, As discussed during our phone conversation today, during which you stated that Babcock Power considers a high-dust SCR principally, technically feasible even though notwithout technically resolvable challenges for Minnkota's Milton R. Young Station, I would also be interested in Babcock Power's position'on the technical feasibility ofa tail-end SCR (downstream of a wet scrubber including A- 57flue gas reheat) Given your knowledge about the plant (cyclone-fired B&W boilers, ESP, wet scrubber) and the fuel (NO lignite), would Babcock Power: Considera tail-end SCR technically feasible? Recommend or require additional pilot testing? Be willing to provide commercial guarantees for catalyst performance (activity, pressure drop and S02/S03 conversion rate) and lifetime? Ifso what would these be? Given the fact that tail-end SCRs in Germany including the ones built by your licensor Fisia Babcock (most ofwhich are on wet bottom boilers) went into operation in the late 1980s and most ofthem still operate on the initial fill ofcatalyst afteralmost 20 years and up to 130,000 operating hours, I would assume that Babcock Power 1Fisia Babcock has sufficient confidence in yourtail-end SCR experience to competently respond to these questions. Please let me know ifyou have any additional questions. Thanks. Best regards, Hans Hartenstein 1.2 E-Mail Correspondencewith Don TODn, Babcock & Wilcox (SCR System Vendor

- no tail-end SCR experience) From: Tonn, Donald P [mailto:dptonn@babcock.com] sent: Monday, June 23,2008 16:06 To: Hans Hartenstein Subject: RE: Tail-end SCR Hans: Please note my responses to your questions in the referenced email below. Regards, Donald P. Tonn Babcock &Wilcox Power Generation Group

.AQCS Technology Phone 330-860-1986 Cell 330-289-7795

From: Hans Hartenstein [mailto: Hans.Hartenstein@Evonik-Energy5ervices.us] sent: Wednesday, June 18, 2008 13:25 To: Tonn, Donald P Subject: Tail-end SCR Don, As discussed during our phone conversation today, during which you stated that Babcock & Wilcox considers atail-end SCR (downstream of a wet scrubber including flue gas reheat) principally technically feasible for Minnkota's Milton R. Young Station, I would be interested in Babcock & Wilcox's position on the following questions. Given your knowledge about the plant (cyclone-fired B&W boilers, ESP, wet scrubber) and the fuel (NO lignite), would Babcock & Wilcox: Considera tail-end SCR technically feasible? Yes Recommend or require additional pilot testing? Requires further discussion with catalyst suppliers. A- 58Be willing to provide commercial guarantees for catalyst performance (activity, pressure drop and S02/S03 conversion rate) and lifetime? If so what would these be? While B&W has considered tail-end SCR systems on other projects we have not had these commercial guarantee discussions with the catalyst suppliers forthe North Dakota lignite application. Before consideration of providing these guarantees a comfort level would be required after obtaining guarantees from catalyst suppliers. Given the fact that tail-end SCRs in Germany went into operation in the late 1980s and most ofthem still operate on the initial fill of catalyst afteralmost 20 years and up to 130,000 operating hours, I would assume that Babcock & Wilcox has sufficient confidence in tail-end SCR systems to competently respond to these questions. Please let me know ifyou have any additional questions. Thanks. Best regards, Hans Hartenstein
2. VendorCorrespondencewith SCR CatalystManufacturers 2.1 E-Mail Correspondencewith Cindy Khalaf, Argillon (CataiystManufacturerextensive tail-end SCRexperience) From: Khalaf Cindy R [mailto:cindy.khalaf@argillon.com] Sent: Tuesday, June 24 2008 14:15 To: Hans Hartenstein Subject: Re: Argillon Tail-end SCR No problem. Regards, Cindy

From: Hans Hartenstein <Hans.Hartenstein@Evonik-EnergyServices.us> Sent: Tuesday, June 24,2008, 16:45 To: Khalaf Cindy R SUbject: RE: Argillon Tail-end SCR Cindy, Thanks a bunch fortaking the time to respond. I greatly appreciate your answer. I'll keep you posted where this thing is going. Best regards, Hans Hartenstein http://www.evonik-energyservices.us

From: Sadler Randy (mailto:randy.sadler@argillon.comJ Sent: Tuesday, June 24,200808:15 AM 

### A-59To: Hans Hartenstein Cc: Khalaf Cindy R Subject: Argillon Tail-end SCR Importance: High On behalfof Cindy Khalaf - Hans, Furtherto our phone call, as far as I know, Argillon has moretail end experience than any other SCR catalyst manufacturerand, as you noted, we also have experience with high dust, German lignite SCRs. Argillon also won the first US lignite SCR catalyst project (Luminant Oak Grove 1 & 2) and provided commercial guarantees. These units are not in service yet. So, yes, we consider ourselves able to answerthese questions competently. Consideratail-end SCR technically feasible? Yes, we considerthis configuration to betechnically feasible. As you know, tail end SCRs are often used when there are significant catalyst poisons in aflue gas stream. A wet scrubber can remove most ofthese poisons, resulting in very low catalyst deactivation. Recommend or.require additional pilot testing? Fora high dust configuration, we would say definitely. Fora tail-endconfiguration, We would say no. We would only like to see a flue gas analysis for conditions atthe inlet to the SCR in orderto predict deactivation rate. Be willing to provide commercial guarantees for catalyst performance (activity, pressure drop and S02/S03 conversion rate) and lifetime? Ifso what would these be? Generally speaking, yes, we would provide guarantees for DeNOx & slip as specified (not to exceed 90% or2 ppm), 24k hours life, S02 conversion rate - low but value TBD, pressure drop - value TBD. Of course we would have to see the technic,al specifications before being more specific. In addition, tail-end SCRs perform much longer, so depending on the application specifics, customer, etc., we may decide to extend the operating life guarantees. This is a commercial decision and will be reviewed on a case-by case basis.
. Ifyou have any more questions, please let me know. Regards, Cindy Cindy R. Khalaf Argilloil LLC President Tel: 678.341.7520 Mobile: 770.331.9571 FAX: 678.341.7509 Email: cindy.khalaf@argillon.com 5895 Shiloh Road, Ste. 101 Alpharetta, GA 30005 From: Hans Hartenstein [mailto:Hans.Hartenstein@Evonik-EnergvServices.usJ Sent: Thursday, June 19, 2008 16:29 A- 60To: KhalafCindy R Subject: Tail-end SCR Cindy, As discussed during our phone conversation today, during which you stated thatArgillon considers a high-dust SCR principally technically, feasible based on your high-dust SCR experience with lignite fired units in Europe even though not without technically resolvable challenges for Minnkota's Milton R. Young Station, I would also be interested in Argillon's position on the technical feasibility ofa tail-

. end SCR (downstream of a wet scrubber including flue gas reheat). Given your knowledge about the

plant (cyclone-fired B&W boilers, ESP,wet scrubber) and the fuel (ND lignite), would Argillon: Considera tail-end SCR technically feasible? Recommend or require additional pilottesting? Be willing to provide commercial guarantees for catalystperformance (activity, pressure drop and S02/S03 conversion rate) and lifetime? If so what would these be? Given the fact that tail-end SCRs in Germany including the ones equipped with Argillon catalyst went into operation in the late 1980s and most ofthem still operate on the initial fill ofcatalyst afteralmost 20 years and up to 130,000 operating hours, I would assume thatArgillon has sufficient confidence in yourtail-end SCR experience to competently respond to these questions. Please let me know ifyou bave any additional questions. Thanks. Best regards,
. Hans Hartenstein 2.2 E-Mail Correspondence with John Cochran, CERAM Environmental (Catalyst Manufacturer

- extensive tail-end SCRexperience) From: John Cochran [mailto:John.Cochran@ceram-usa.com] Sent: Wednesday, June 25,200815:14 To: Hans Hartenstein Cc: Greg Holscher; Noel Rosha; OrehovskyKurt Subject: RE: Request for Information Hans, CERAM certainly considers the use of atail"end SCR on applications such as the Milton R. Young Station as technically feasible provided a proper design approach is used. CERAM has the experience from more than 100tail-end and low dust applications dating from 1988 that would substantiate ouropinion. For atail-end approach we see no need for additional pilottesting. As such, we can provide full commercial guarantees for catalyst performance (activity or lifetime, conversion rate, pressure drop, etc.). The choice between high dust and tail-end processes certainly should consider capital costs, operating costs and process risk. Based on our experience certainly process riskwould favor atailend approach, but albeit for most circumstances at a higher "all-in" cost. Should very high retrofit factors be present for a high dust arrangement then the relative economicfactors may even favor a tail-end approach. I hope this information is useful to your evaluation. Please advise should you have anyfurther A- 61questions or information needs. Thanks. Best Regards, John Cochran CERAM Environmental, Inc. wwwJrauenthal.net 913.239.9896 (phone) 913.205.5615 (cell) This e-mailandanyattachmentsare confidential. If youhave received this electronictransmission in error, pleasereplyto thesender regarding the errorandpermonently. delete the originalmessage andanyattachments.**~------------------------------------------------------------------------------------------------------------------------------------** From: Hans Hartenstein [mailto:Hans.Hartenstein@Evonik-EnergyServices.us] sent: Tuesday, June 17, 2008 7:20 To: John Cochran Subject: Request for Information John, As discussed during our phone conversation today, during which you stated that CERAM considers a high-dust SCR principally technically, feasible even though notwithout technically resolvable challenges forMinnkota's Milton R. Young Station, I would also be interested in CERAM's position on the technical feasibility ofa tail-end SCR (downstream ofawet scrubber including flue gas reheat) Given your knowledge about the plant (cyclone-fired B&W boilers, ESP, wet scrubber) and the fuel (ND lignite), wouid CERAM: Considera tail-end SCR technically feasible? Recommend or require additional pilot testing? Be willing to provide commercial guarantees for catalyst performance (activity, pressure drop and S02/S03 conversion rate) and lifetime? Ifso what would these be? Given the fact that tail-end SCRs in Germany including the ones equipped with·CERAM catalyst (Herne 1, 2 and 3, Voerde (West) 1 and 2, LOnen 10 and 11 - all ofwhich are wet bottom boilers) went into operation in the late 1980s and most ofthem still operate onthe initial fill ofcatalyst after almost 20 years and up to 130,000 operating hours, I would assume that CERAM has sufficient confidence in yourtail-end SCR experience to competently respond to these questions. Please let me know ifyou have any additional questions. Thanks. Best regards, Hans Hartenstein 2.3 E-Mail Correspondencewith ScotPritchard, Cormetech (Catalyst Manufacturer

- no tail-end SCRexperience)
From: Pritchard, Scot G. [mailto:PritchardSG@Cormetech.com] Sent: Thursday, June 19, 2008 17:41 To: Hans Hartenstein Subject: RE: Tail-end SCR Hans, A- 62I was thinking of ifyou put a coupon in the tailend location and it showed something weird then you would have to do something more elaborate Le. A slipstream with longer hours, etc
.. We do not anticipate this - in fact you could probably do without the coupon test as well since I don't see any reason why this system would be any differentthe primary tail end experience Le. Unlikely any nasties make itthrough the lowertemperature environment and scrubber process. The coupon is OK but I really don't expect to see much. Finally, we have not done any specific coupon tests (because slipstream has been the primaryway to evaluate) so we would need to think through the bestway to do it - Le. holder, mounting arrangement, test method, hours ofexposure, etc. Ifyou already have something in mind please let uS know. Hope that helps with the clarification. Scot
From: "Hans Hartenstein" <Hans.Hartenstein@Evonik-EnergyServices.us> Sent: thursday, 6/19/08 4:26 pm To: "Pritchard, ScotG." <PritchardSG@Cormetech.com> Subject: RE: Tail-end SCR Scot, Thanks for the input from Cormetech, which is greatly valued. One question forclarification purposes only, though. Coupon tests and/orflue gas analysis would only be performed in orderto characterize the flue gas going into the tail-end SCR as is needed for the design of anyAPC equipment. Obviously, nobody could offerany performance guarantees concerning what's coming out ofa tail-end SCR without knowing. what's going into it. You state that in case coupon tests would show a significant accumulation of catalyst poisons, a subsequent slip stream test, which is unquestionably more accurate and representative of a full scale - in this case tail-end - SCR, would berecommended. Stating this, do I understand you right that you would recommend this slip stream testing mainlyfor the purpose of properly characterizing the flue gas composition at the inletto the tail-end SCR in orderto provide a reliable basis forcorrect catalyst design? Do I assume correctly, that you would not require extensive and long-term (12 - 24 months) pilot testing with a slip stream reactor because you have serious doubts about the principal technical feasibility of a tail-end SCR forthis application? Please clarify. Thanks.
. Best regards, Hans Hartenstein From:Pritehard, ScotG. [mailto:PritchardSG@Cormetech.com] Sent: Thursday, June 19, 2008 12:15 To: Hans Hartenstein Subject: RE: Tail-end SCR Hans, Please see my input below.' As discussed during our phone conversation today, during which you stated that Cormetech considers a high-dust SCR principally technically, feasible even though not without technically resolvable challenges for Minnkota's Milton R. Young Station, I would also be interested in Cormetech's position on the technical feasibility ofa tail-end SCR (downstream ofawet scrubber including flue gas reheat) Given your knowledge about the plant (cyclone-fired B&W boilers, ESP, wet scrubber) and the fuel (NO lignite), would Cormetech: Considera tail-end SCR technically feasible? - yes A- 63Recommend or require additional pilottesting? - We generally do not considercoupon testing an accurate representation ofan SCR, however in orderto minimize cost and provide basic screening information we would suggest the potential use ofa coupon sample test. Ifthe coupon shows significant accumulation ofcatalyst poisons, a subsequent slipstream type test which is more representative of a full scale SCR i.e match velocity, AVs, etc. would be recommended. Be willing to provide commercial guarantees for catalyst performance (activity, pressure drop and SOiS03 conversion rate) and lifetime? Ifso what would these be? Presuming the coupon test does not sholN anything unusual (which we do not expect to see anything unusual) we would be willing to provide commercial guarantees for a low dust application. Basic guarantees would be associated with life (this would not include specific Ko and KlKo as guarantees - the guarantee would be an efficiency and slip guarantee at a certain number ofoperating hours ), S02 conversion, pressure loss. As discussed, the high dust application needs additional due diligence testing (slipstream, ash testing, etc.) as well as the practicality ofthe applicable operating temperature to establish the commercial stance fora high dust application on North Dakota Lignite. We have done such work forTexas lignite as well as other coal sources and otherfuels/applications in the past and would expect to be able to achieve the same forthis application. The economics forany given application would be considered on a case by case basis: Let me know ifyou have any questions. Also I would appreciate anything ofthe final document that you can share. Thank you and regards, Scot Pritchard VP, Sales & Marketing Cormetech 919-595-87080 919-815-2380 c Frain: Hans Hartenstein [mailto:Hans.Hartenstein@Evonik-EnergyServices.us] sent: Thursday, June 19, 2008 11:35 AM To: Pritchard, Scot G. Subject: Tail-end SCR Scot, As discussed during our phone conversation today, during which you stated that Cormetech considers a high-dust SCR principallytechnically, feasible even though not without technically resolvable challenges for Minnkota's Milton R.Young Station, I would also be interested in Cormetech's position on the technical feasibility of a tail-end SCR (downstream ofa wet scrubber inclUding flue gas reheat) Given your knowledge about the plant (cyclone-fired B&W boilers, ESP, wet scrubber) and the fuel (NO lignite), would Cormetech:
. Consider a tail-end SCR technically feasible? Recommend or require additional pilot testing? Be willing to provide commercial guarantees for catalyst performance (activity, pressuredrop and SOiS03 conversion rate) and lifetime? Ifso whatwould these be? Given the fact that tail-end SCRs in Germany (most ofwhich are on wet bottom boilers) went into operation in the late 1980s and most ofthem still operate on the initial fill ofcatalyst afteralmost 20 years and up to 130,000 operating hours, I would assume that Cormetech has sufficient confidence in tail-end SCR systems to competently respond to these questions. Please let me know ifyou have any additional questions. Thanks. A- 64Best regards, Hans Hartenstein 2.4 E-Mail Correspondencewith Flemming Hansen, HaldorTopsoe (Catalyst Manufacturer

- extensive tail-end SCRexperience) From: Flemming Hansen [mailto:FGH@topsoe.com] sent: Friday, June 27, 2008 12:56 To: Hans Hartenstein Subject: RE: Tail-end SCR Hans, Your understanding is what I meant to say. Thanks Flemming G. Hansen ManagerSCR DeNOx Catalyst HaldorTopsoe, Inc. 281-228-5120 (office) 281-228-5129 (fax) 281-684-8820 (cell) FGH@Topsoe.com www.topsoe.com

"Hans Hartenstein"<Hans.Hartenstein@EvonikEnergySerifices.us> 06/24/200804:16 PM
Flemming, To "Flemming Hansen" <FGH@topsoe.com> cc Subject RE: Tail-end SCR

Thanks for your note. Just to make sure that I understand you correctly. Is it correct to state that HaldorTopsoe feels fully confident that atail-end SCR is technically feasible and would not experience any accelerated catalyst deactivation? Therefore, you would be willing to guarantee catalyst performance (NOx removal efficiency, pressure drop, S02/S03 conversion rate and catalyst lifetime) without any need forfurther pilot testing. Please confirm. Thanks. Best regards, Hans Hartenstein
From: Flemming Hansen [mailto:FGH@topsoe.com] Sent: Dienstag, 24. Juni 200816:44 To: Hans Hartenstein A- 65Subject: Re: Tail-end SCR Hans, Like you describe we have had very good operating experience with SCR in the clean environment aftera scrubber or bag filter. There appears to be practically no catalyst deactivation and with the low amount of particulate the catalyst pitch can be small, which both leads to a compact SCR as compared toa high dust SCR. Based on theclean flue gas afterthe FGD we would not require any further testing in orderto guarantee a catalyst performance. The actual guarantees would be as normally applied in a high dust installation and depend on the catalyst volume and operating conditions. At the low operating temperature expected at the tail-end position the S02 oxidation will be negligible. I hope this confirmation will have yourapproval. Flemming G. Hansen Manager SCR DeNOx Catalyst HaldorTopsoe, Inc. 281-228-5120 (office) 281-228-5129 (fax) 281-684-8820 (cell) FGH@Topsoe.com www.topsoe.com

"Hans Hartenstein" <Hans.Hartenstein@EvonikEnergyServices.us> 06/24/2008 10:24AM Flemming, To <fgh@topsoe.com> cc Subject Tail-end SCR
As discussed during our phone conversation today, during which you stated that HaldorTopsoe considers a high-dust SCR principallytechnically, feasible even though not without technically resolvable challenges for Minnkota's Milton R. Young Station. I would also be interested in Haldor Topsoe's position onthe tecRl"licalfeasibilityofatail-em.l-SGR (downstream of awet scrubber including flue gas reheat) Given your knowledge about the plant (cyclone-fired B&W boilers, ESP. wet scrubber) and the fuel (NO lignite), would HaldorTopsoe: Considera tail-end SCR technically feasible? Recommend or require additional pilot testing? Be willing to provide commercial guarantees forcatalyst performance (activity, pressure drop and S02/S03 conversion**rat~)** and lifetime? Ifso whatwould these be? Given the fact that tail-end SCRs in Germany including the ones equipped with yourcatalyst have been in operation since the late 1980s and most ofthem still operate on the initial fill ofcatalyst after almost 20 years and up to 130,000 operating hours, I would assume that HaldorTopsoe has sufficient confidence in yourtail-end SCR experience to competently respond to these questions. Please let me know ifyou have any additional questions. Thanks. Best regards, Hans Hartenstein A- 66