DEI'ARTME T OF ENVmONMENTAL QUALITY

DIVISION OF AIR QUALITY

Permit Application Analysis, NSR-AP-C92

April 24, 2002

COMI)ANV:

FACILITY:

FACILITY LOCATION:

TYPE OF FACILITY:

RESPONSIBLE OFFICIAL:

COMPANY REI)RESF:NTATIVE:

MAILING ADDIU:SS:

I~EVIEWEO BY:

1'11HI'OSF: OF AI'!'I.IC'ATION:

Black I-II lis Corporation

WYOEN2

13151 Highway 51

Gillette. WY

Section 27, T50N, R71W

Campbell County, Wyoming

Coal Fired Steam Electric Generating Plant

Tom Ohlmachcr

Senior V,P. Power Supply and Operations

Fred Carl

Environmental ("oordlnator

P.O. Box 1400

Rapid City, SO 57709-1400

Stewart Grmer, Air Quailly Engmeer

Ken Raingh, AIr Quality Engmeer/Modeler

Bllll.:k Hills Corpuratmll submlllcd an appllcatlun tu wnslrUCI a 500 megawall (MW) pulvcrli"cd coal

(PC') fired electnc generatmg faCIlity to be known as WYGE r 2. '111c proposed facilIty consists of one

1'(' builer bummg coal from the nearby Wyodak coal mme wIth assocIated CO:J1 and [unc handlmg and

nuc gas dcsulfufl7...atlon (FGD) waste product handling. !'arametcrs used for deSIgn values, based on coal

frol11lhc Wyodak mme. mclude a deSign heat content of7,950 Btullb and a maximum sulfur content of

1.2%. The maximum deSIgn he:lllnpllt 10 Ihe faCIlIty will be 5,145.7 MMBlu/hr.

The appllcanl Idcntllicd Ihc followlIlg emIssion sources in thc pCIll1it appllcatlon:
Black JiJlls CorporatIon (WYGEN 2)

Permit ApplictJllOn Analysis. NSR-AP-C92

Page 4

3) An Increment consumption analysis IS required for regulated pollutants based on allowable

emissIOn rates as well as increment consuming emissions from other sources in the region. The

lotal deterioration determined from this analysis must comply with the allowable increments

established for PM ,o, S02' and NO. for the classification of the area (i.e. Class I or Class U) in

which the Increment consumption is predicted.

4) An analysis IS required to assess the Impairment to viSibility, soils, and vegetation resulting from

the facihty and general commercial, residential, industrial, and other growth associated with the

faelilly.

BEST ,\VAILABLE CONTROL TECHNOLOGY (BACT):

A best available control technology (BACI) analysis for NOx• 502, PMlPM IO, CO, VQC, H2SO., and

nuonde is reqUIred because each of these pollutants is emitted above PSO significant emission rates.

Additionally, a BACf analySIS is required for beryllium and mercury under Chapter 6, Section 4(a)(x.xi)

of the \VAQSR. The BACf analySIS for each emission source is presented in the following sections:

I. 500 MW PC Uoilcr - NO, Control

Black Ililis Corpor:ltion proposed low NOx burners and SCR wllh an cmlSSlOn 1Imlt ofO.09lb/MMBtu

as BACT The DIVISion reviewed the RACf/BACT/LAER C'leannghouse (RBLC) and information from

EPA Regional offices to find permitted or proposed PC uulny boilers With NO, emiSSions equal or lower

than 0.09 IblMMBtu as shown m the following table:

Facilny Statc Sizc Control NOx Emissions Status

(MW) Device (Ib/MMBlu)

Kal1s:ls City Power & Light Co. - MO 570 SCI( O.OX (30 day)' Opcrtllional

Ilawthomc Stat lOll May 200!

0.12 Ib/MMl3tu (30 day) hmit for first 3 years, Lhen 0.08Ib/MMBtu Ifdemonstrated fC3!'ilb1c. Accordlllg

to Missoun DNR. Hawthorne StatIon is currently meeting the 0.08 Ib/MMBtu limIt.

•

(irca! Plall1s Powcr - Weston Bcnd

(jencralll1g Slat Ion MO H20 SCI( O.OX (30 day) Proposed

EmiSSion Control Technologies

Black I!Ills CorporatIon conSIdered thc followmg controls for NOx reductIOn:

COmbll,\f;O/l tollfrols - Low NOx humcrs (LNB). ovcrfirc lIlr (OFA). and advanced gas rebum (AOR) all

serve \() rcduce JX'ak cnmbustulIllcmpcratures thus lowcnng NOx cmlSSlOns. Although nonc ofthese

C0l1lrols com Jchlc\c Crnl~S1tl11 Icvcb comparable 10 pUSI comhusllon controls. they do prevcnt somc of

the Illltla] li)nnal1tlll Ilf NU>... 1.31ack II dis Corpor.Jllon ~clt:l':h:J 10\\ NOx burners 11\ combmatlon wtlh

1)(ISI-comhu..Il1111 ctllliruis hCC:lu<;c thc l<m cr emlSSlOllS gClll'r<ltcd n:<;ult In 10\\ cr caplinI cost and reagent

usc
lack 111115 Corporallon (WYGEN 2)

?enrut Application AnalYSis, NSR·AP-C92

?age 5

Selective Coralytic Reduction (SCR) - SCR is a post combustion control techmque in which the flue gas

IS combined with vaporized ammonia in the presence ofa catalyst and NO~ is reduced to nitrogen and

water. Black Hills Corporation evaluated SCR at emission levels of0.06, 0.08, and 0.091b1MMBtu.

Selective Non-Catalytic Reductio" (SNCR) • SNCR is SImilar to SCR in that it involves the injection of a

reducmg agent such as ammoma or urea into the flue gas stream. The reduction chemistry, however,

tnkes place Without the aid of a catalyst. SNCR systems rely on appropriate injection temperatures,

pror>cl' reagent/gas mixing and prolonged retcntion time in place of the catalyst. SN R systems are very

sl.:nsitive to temperature changcs and typically have lower emissions reduction (up to fifty or sixty

percent) and higher ammonia slip. Black Hills Corporation did nOI further consider SNCR because ofthe

lower emissions reduction and the lack of any operational advantage over SCR.

JJyhrid SNCRJCatalysl System. These systems were developed to combine the relatively low capital COSI

and high ammonia slip associated with SNCR with the high reduction potential and low ammonia slip

!Oherent to SCR. '1l1C first part of the system is a typical SNCR system with increased reagent now for

additional NOx reduction. A small catalyst follows to reduce ammoma slip and poSSibly achieve

addItIonal Ox reduchon. This system requires more ammonia but uses a smaller catalyst. Black Hills

Corporation did not further conSider a hybnd system because of poSSible problems achlevmg adequatc

dlstnbutlon of ammoma and because there is no operatIOnal or ClnlSSlOn reduction advantagc over SCR.

I:nergy and EnVironmental Evaluation

Black Ihils Corporation evaluated the energy and environmental considerations for SCR. An SCR

1>ystem consumes electncal energy for ammonia transport and vaponzallon and for incremental fan

ucmand to overcome pressure drop across the catalyst.

EnVironmental callSlllcrallons mcludc ammOOlil slip. a slight IIlcrcase in SOl emiSSions, a possible slight

mcn:aSl: In PM lo ellllSSlons. and ammonia handlmg and storage. Ammoni,1 sl1p emissions of2 to 5 ppm

and tl I (02 pcn;cnl lllcrcasc 1n SOl emISSIons are cxpech.:d. Unrcaclcd allllllOllla ,md SOl can react to

form <lmtllOnla hisLJIfate and amtllOlll(l Slllfale >;.ills It1 Ihe form of PM III ellllSSlons. Allllllon ia is a

ha/.anJolls Illtltenal and adequate design prcc,llltions nrc necessary for bandllllg and ~torage.

b.:onOIllIC bvaluatlOl1 of Alternatives

l3Iack IlIlIs CorporJ.tlOn evaluated the combmation of Low NOx burners and SCR at emiSSIon levels of

0.06,0.08, and 0.09Ib/MMBtu. An cconoml7.cr bypass IS required to keep temperatures m the opllmum

range m order to meet the 0.06 or 0.08 IbIMMl3tu emiSSion limits at 50% load. Consequently, the

mcremental cost IS higher from 0.09 Ib/MMBtu to 0.08 IbII\lMBtu than from O.09Ib/MMB1U to le"els

lower than 0.08 IblMM Rtu. The results are shown III the followmg table:
Black Ilil1s Corporation (WYGEN 2)

Pemut Application Analysis, NSR-AP-C92

Page 6

Annual Emissions

EmiSSions ReductIOn

Total Annualized Cost

Total Cost Effectiveness

Incremcntal Reduction·

Incremenlal Annualized

Cost

Incremental Cost

Effectiveness

Baseline

0.25 IblMMBtu

5,635tpy

Baselinc

Baseline

Baseline

LNB/SCR LNB/SCR LNB/SCR

0.091b1MMBtu 0.08 Ib/MMBtu 0.061b1MMBtu

2.028 tpy 1,803 tpy 1,352tpy

3,606tpy 3,832 tpy 4,283 tpy

$12,563,000 515,582,000 $17,798,000

53,484/to" S4,067/to" $4,1 561ton

Baseline 225 tpy 676tpy

Baseline 53,019,000 55,235,000

Baseline 513,395/too $7,7421ton

• 11lc DIvision calculatcd incremental coslo; based on a 0.09 Ib/MMBtu baseline for both 0.08 and 0.06

Ib/MMBtu becausc an economizer bypass is required 10 achieve either 0.08 or 0.061b1MMBlu.

Black IIt lis Corporation chose 0.091b/MMHtu as BACT because they consIdered the Incrcmental cost

effectiveness to be unreasonable for the lower emISSion levels and because they were unablc to find an

Issued permit With a [1I1l\t less than 0.12 IblMMBtu for a PC boiler. (Note thai the Ilawthomc Station

boder III MISSOUri has a lImit ofO.12lbfMMBtu for 3 years and then a limit ofO.081b1MMBtu unlcss the

penlllltec can demonstrate th:lt 0.08 IbfMMBtu is not feasible.) According to Missouri DNR, Hawthome

StatIon IS mcctlllg the 0.08 [bfMMBtu limIt. Missouri DNR IS also working on a pcrmlt for Greal Plallls

Power WIth a proposcd llllllt ofO.08IbfMMlltu. Although Grcat Plall1s Power requested 3 years 10

detl:rmlne If they can comply with the limit as allowed in the Hawthorne Stallon penllit, Missoun DNR

IIldlcaled that they do !lot pl:lll to issue the permit with any execpllons 10 Ihe O.08Ib/MMBtu hmlt.

The l)IVI:-:lon CvUlll:Lted the control effiCIency requIred to mcctltmlts 01'0.09, 0.08, and O.061b/MMBtl,J

llStng a baseline of 0.25 Ib/MMBtu ns shown In the followll1g tnblc:

EmISSion Levcl

(lblMMBtu)

0.09

0.08

0.06

Control Efficll:!lcy

(%)

64

68

76

rhese cffiClcncles sccm low based on mfomlalton that vendors arc deslgmng and provldmg guarantee...

ror SCI{ systems \\'Ith at lcasl9011 0 control efficlcncles. For example. Montour Steam Elec,;tnc Slatum III

AlIcntown. PA rl'lrufllted 1\\'0 750 fl,IW coal fired hollers \\llh SCR systems deSigned for 90% control

cfliclclley und 1).1)" Ib fl,1fI,lBtu USl11g castcrn bltUtnlllOm, coal It .!>hould be noted that Ihese arc deSign

levels tn mcet aCIl! ram rcqUlrcmcnts and there arc no penlllt Ilmlls rcqulfIng thIS level ofrcduC\lon.
Black Jlllls Corporation (WYGEN 2)

Permit Application Analysis, NSR4AP..c92

Page 7

The BACI' analysis indIcates that 0.06lb1MMBtu is technically feasible and the Division considers the

total and incremental cost effectiveness to be reasonable. Note that the incremental cost effectiveness is

much lower when conSIdering emission limits less than 0.08 IblMMBtu because an economizer bypass is

required to achieve emission limits ofO.08lb1MMBtu or less. Although the BACT analysis indicates an

emission level ofO.06Ib1MMBtu, Black Hills Corporation has expressed uncertainty about meeting 0.06

IbIMMBtu on a continuous basis. The Division and Black Hills Corporation discussed various options

for dealing with this uncertainty while setting an appropriate BACT level. One option discussed was

0.06 Ib/MMBtu annual average and 0.08 IblMMBtu 30 day average. This option still len Black Hills

Corporation with a measure of uncertainty in regards to meeting Ihe annual limit and they requested that

the O.06Ib/MMBtu limit not become effective until issuance ofthe Title V operating pennit in order to

allow additional time to demonstrate compliance. Even with the additional time for compliance, Black

Hills Corporation expressed concern about meeting a 0.061b/MMBtu limit and discussed options if they

could not meet the limit. Upon further discussion, the Division and Black Hills Corporation agreed that a

30 day limit ofO.071blMMBlu would be more stringent than any existing limit for an operating PC

boiler and could be met Without additional time to demonstrate compliance. The Division concludes that

Low NOx. burners and SCR with an emission limit ofO.07lb1MMBtu pO day rolTmg average) represent

BACT. -

II. 500 MW PC Boiler 4 SO, Control

Black 1II1Is Corporation proposed a seml-dry lime spray dryer absorber with emiSSion hmlts of 0.15

Ib/MMBtu (30 day average) and 0.17 Ib/MMBtu (2 hour block). 'me Division reviewed the

RACr/BACrfLAER Cleannghouse (RBLC) and mfonnatlon from EPA Regional offices 10 find

pennitted or proposed PC utility boilers with 502 emiSSIOns lower than 0.15 IbIMMBtu as shown in the

followmg table: