One Source...Many Solutions...One PurposeWhat’s New inSCRsLisauskasMay 16, 2006Clay Erickson, Ph.DRobert Lisauskas, Ph.DAnthony LicataDOE’sEnvironmental Control ConferenceSCR Technology•System uses NH3or urea injected into the flue gasupstream of active reduction catalyst•In the catalyst, NOx is reduced selectively by the NH3toproduce N2, & H20•Catalyst reduces temperature for reduction reaction to~600F•Catalyst requires proper temperature, homogeneousNOx/ NH3mixture, homogeneous temperature, anduniform flow distribution atits inlet to perform properly–Catalyst typically is honeycomb or plateconfiguration–Life is dependent on poisons present in flue gas;typically 8,000 to 24,000 hours of operationOperating History of SCR Retrofits in US•Before 1998 < 1,000 MW•By 2005≈85,000 MW•By 2009 140,000 MW• NOxremoval–85 –92%•Availability–>99%Technological Challenges•Currently most SCRsoperate during ozoneseason 5 months per year•Under new CAIR rulesNOx control will berequired 12 months peryear–Catalyst management–Outage schedulingCAIR Retrofit Cost Challenges•High Cost Low RevenueUnits– OlderUnits–Smaller Units–Peaking Units–High Heat Rate Units•High Retrofit Cost– Tail-endSCRs– MarginalCost•Boiler ModificationsCAIR Retrofit Challenges•Fuel flexibility–Catalysts are a componentof fuel cost–Poisons, NOx compliance–PRB proliferation•Shorter emissionaveraging times• Mercury,SO3–Higher S fuels–New catalystNew SCR Challenges•Most new SCR will not be built withbypass system–Lower capital and maintenance cost–May limit fuels burned–Need improved catalystmanagement/fuel use strategy– SO3conversion•Future value of NOx and SO2credits–Banking, availability, $$ Impact of 600 MW SCR OperationsIncreasedSCRPerformance Over80%Efficiency02004006008001,00078%80%82%84%86%88%90%92%94%NOx Removal(%)

N o r m ali z ed N O x R e mo ved (T on s )0.00.51.01.52.02.53.03.5 N o r m ali z ed N O x C r ed it s ( M illion $)SCR Options•“Full” SCR System•Compact In-Duct SCR Reactor•Hybrid SNCR/ In-Duct SCR System(“Cascade®”)•Tail-end SCR systems (RSCR)Full SCR SystemEconomizer By-passEconomizer OutletCrossMixersIn Duct SCRHybrid Project Overview•BPE has been selected to provide a hybridSNCR/In-Duct SCR to coal-fired plant•Fuel Tech to supply Noxoutreagent, storage,injection and controls•BPE to provide static mixers to homogenizethe flow and excess slip, SCR reactor, andcontrols•Unit will be in operation 5/2006•Overall NOx reduction of ~ 65% requiredTail-End SCR Systems•Installed upstream of stack, downstream of particulate removal–Clean gas–Low temperature gas (~300F)•Only practical SCR solution forWFB, WTE plants (catalystpoisoning issues) space limitations –Mercer Station•Erected, then tied in; minimal disruption to operations•Requires energy input/heat recovery to minimize operating costs•Typical tail-end unit consists of:–Heat exchanger–Duct burners–Ammonia injection–SCR reactor–Booster fans•NOx reductions 60-90%; energy efficiency ~70%; high $/KWSlide 14Self Tuning SCR•170 MW Gas Plant with Single FeedForward/Feed Back Control•Two Injection Points with Delta Wings•Modified with Additional Outlet NOx Meter ForTwo Feed Back Loops•Installed in Summer 2005•Extended Time Between Injection Point ‘TuneUps’Slide 15Trends in SCR Specifications Requirements•Lower Specified SO2Conversion Rates–Industrial Experience–Anticipating the Use of Higher Sulfur Fuel –Scrubbers•Higher Removal Efficiencies ( 91% to 92%)–>10 Units with > 90% Removal•‘Pre-Engineered’ Large Particle Ash Removal Screens•Year Round Operation–Units without SCR Bypasses•No Clear Winner on Reagent–Anhydrous, Aqueous, or Urea•High Ash Loading CriteriaSCR Effect on WFGD Mercury CaptureSCR –Effect on Mercury Capture•Reaction Hg + 2Cl -> HgCl2Downstream Wet FGDCapture•Full Scale Bituminous Test Results–Mg-Enhanced Lime, Lime Venturi, Limestone ForcedOxidation–Hg Capture Efficiency of 80% to >90%•Some indication that catalyst Hg Oxidation deactivationsimilar to DeNoxDeactivation•No affect on PRB coals to assist in Hg capture–Lack of chlorineLarge Particle Ash Design•LPA Properties–Size >4.0 mm–Density 0.7 to 1.25 g/cc–Sphericity0.7 to 0.99–Coefficient of Restitution 0.15 to 0.2•Screen Design Important•Pluggage• ErosionLarge Particle Ash Design•Design and Modeling–CFD Modeling–Industry Coated Screens–Experience From Past•Soot Blowers• LowVelocity•Low Pressure LossStart Up and Availability•Clean Tuning and Start Up Over the Load Range•No Gross Difference in Reliability of DifferentAmmonia Systems–Urea , anhydrous, or aqueous system•Overall system AvailabilityOne Source...Many Solutions...One PurposeThe CascadeThe Cascade®SystemHybrid NOxControl System“Cascade®”123456789101112131415I.D.FAN(S)ESP(S)FLYASHF.D.FAN(S)AIRPREHEATER(S)ECONOMIZERBYPASS623 MWSTEAMTURBINEUREASTORAGESNCRFLGR/SNCRCOALBOILERPRIMARY AIRPULVERIZER(S)SCR MODULECATALYSTTRAYSGASECONOMIZERLOWNOxBURNERS• SNCR(using urea)•Compact In-duct SCR• SNCRslipconsumedin SCR•Up to 80% overallNOxreduction•Low capital costsCascade®Process•System Description–The Combination of In-Furnace SNCR withdownstream Selective Catalytic Reduction (SCR) toExtend the NOx Reduction Capability of SNCR,Improve Overall SNCR Reagent Utilization andMitigate Downstream Balance of Plant Impacts•ARedesigned SNCR system with SCR• HigherNOxreduction and utilization than SNCR•Lower capital costs than full-scale SCR•Greater operational flexibility• SeasonalNOxemission limitsCascade Process Application and Limitations•Single Layer of Catalyst (SCR Requirements)–Space Restrictions, 16 –20 fps face velocity– NH3Scrubber vs. Significant NOx Reduction•No Requirements for new fans–Utilize existing fans or re-tip–Deploy in conjunction with backend APC equipmentsuch as new scrubbers/baghouses which may requirenew fans•Limited Structural Steel Modifications•No New Foundation Requirements• NoNH3Injection Grid RequiredSummary of Cascade®Process•Cascade Performance Ranges from 55 to 80% NOxReduction–NH3 “Mop” vs. NOx Reduction•1/4 to 1/2 Capital Cost of Full SCR System•Improved Chemical Utilization over SNCR System•Shorter Boiler Outage Requirement•Single Layer of Catalyst; Easy Removal and Replacement•Staged Installation; SNCR 1stFollowed by Compact SCRLaterSummary•SCR options exist to reduce NOx to meet requirements•More expensive systems than SNCR and/or low-NOxburners•Removal efficiencies much higher than SNCR/burners•Higher performance than needed to meet permit cangenerate revenues from NOx credits•Unique mixing technology enables in-duct, and hybridsystems–Lower capital costs than conventional SCR–Greatly reduced installation costs–Performance comparable to full SCR obtainedSCR System Performance0.0000.1000.2000.3000.4000.5000.6000.7000.8000.9001.0001.100 1 / 1/ 03 1 / 29/ 03 2 / 26/ 03 3 / 26/ 03 4 / 23/ 03 5 / 21/ 03 6 / 18/ 03 7 / 16/ 03 8 / 13/ 03 9 / 10/ 03 10 / 8 / 0 3 11 / 5 / 0 3 12 / 3 / 0 3 12 / 3 1/ 0 3

% Load0.0000.1000.2000.3000.4000.5000.6000.700Stack Gross Load(MWg)24HrRollingNOx EmissionRate(lb/mmBTU)24HrRollingNOx EmissionRate(lb/mmBTU)30 Day Rolling NOx Emi s si on Rat e ( l b/ mmBTU)00.0050.010.0150.020.0250.030.0350.040.0450.0512345678910111213141516171819202122232425Lowest Outlet NOx UnitsSource USEPAResults –Unit Size•19 units between 90 and 1,300 MWachieving above 90%•34 units between 200 and 1,300 MWachieving 87% to 90% (19,757 MW)•44 units between 200 and 1,300 MWachieving 80% to 86% (26,205 MW)•33 units between 150 and 1,300 MWachieving 70% to 80% (15,043 MW)•Availability not sensitive to unit size0.600.650.700.750.800.850.900.951.00 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77

NOx Removal Efficiency (fraction)Results –Catalyst TypeCorrugatedHoneycombPlate0.600.650.700.750.800.850.900.951.00 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85

NOx Removal Efficiency (fraction)Urea Based SystemsAqueous AmmoniaAnhydrous AmmoniaResults –Ammonia Type0.600.650.700.750.800.850.900.951.00 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115

NOx Removal Efficiency (fraction)Tail EndLow DustHigh DustResults –Arrangement Type0.600.650.700.750.800.850.900.951.001234567891011121314151617181920212223242526272829303132333435

NOx Removal Efficiency (fraction)Results –SCR SupplierData Analysis•90% NOx removal achieved by ~10,000 MW•Outlet emissions on less than 0.05 lbs/mmBtuachieved by multiple units•Availability insensitive to catalyst type, alltypes have achieved 90%•Availability insensitive to ammonia type, alltypes have achieved 90%•Arrangement type appears to affect, mostlydue to sample sizeData Source•Data downloaded from–Acid Rain/OTC Program HourlyEmission Data–www.epa.gov/airmarkets/emissions/raw•Analysis period year 2004•Ozone season June 1stto September 30th–Some states had one month start delay•Single stack only data, common stacksremoved