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Impact of SOx, NOx and Mercury Controlson ESP PerformanceWPCA MeetingNovember 29, 2007Sam KumarManager, Particulate Control

U.S. Coal-Fired Power PlantsThere are about 530power plants with 305GW of capacity thatconsist of about 1,300units.Coal plants generate thevast majority of powersector emissions:• 100% Hg• 95% SO 2• 90% of NO X© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.1

More than 70% of Coal-Fired units use ESPsBoilers and FuelsAPCD Configuration No. of Units (Year 2000)Boilers (1140)•PC fired-979ESP787•Cyclone-87• Fluid Bed- 42• Stoker- 32Coals and Fuels• Bituminous• Subbituminous•Lignite•MixturesSCRESP(or FF)Wet FGDScrubber“Other” units -143122© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.2

There is interest in making existing ESPswork – avoid new fabric filters• Utilities have invested heavilyin LNBs, SCRs and FGD systems• Utilities looking for means to benefitfrom these SOx, NOx retrofits formercury and particulate control• Additional new fabric filtersare expensive• Avoid high FF capital costs– 100 to 200 USD/kW• Are there means to manage ESP impactsfrom SOx, NOx and mercury control?© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.3

Changes to ESP Inlet Loading from…SOxNOxHgControl• There is interplay among SO 3 levels,carbon injection and mercury control• Attempts to mitigate SO 3 could have particulateemission impacts• Activated Carbon Injection ( ACI) for mercurycontrol may also have particulate emission impacts© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.4

Chlorine vs. Mercury Speciation100%Elemental Mercury Into ESPc versus ChlorinePercent of Total Inlet Hg as Hg o90%80%70%60%50%40%30%20%10%Note: these three subbituminousdata pointsare from a boiler thathad recently firedbituminous coalBitBit-Coke blendSubBit-Sub blendLignite0%10 100 1,000 10,000Coal Chlorine, ppmCoal Chlorine, ppmICR data for Hg 0 at ESP inlet• Hg 0 oxidation appears to be enhanced by chlorine• Effect of chlorine is significant for all coal types• Other important factors: temperature, carbon in fly ash© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.5

Sorbent Injection for Mercury ControlSorbent InjectionCoalESPFly Ash + Sorbent• ACI is injected upstream of the ESP© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.6

Mercury Reduction Trends with ACI onFF’s and ESPs;100FF's BIT, PRB, PRB/SDA9080Mercury Removal (%)706050403020ESP's PRB No SO 3ESP's LS BITPRB & LS Bit with SO 3ESP's HS BITESPs, S> ~ 3.5 %FF BITFF PRBSDA FF PRBESP PRB U1ESP PRB U2ESP PRB U3ESP PRB U4ESP BIT1000 5 10 15 20Sorbent Injection Concentration (lb/MMacf)Source: ADA ES© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.7

Co-Injection with Alkaline Sorbents;10090Hg Removal (%)8070605040302010Merrimack,Hg-LHMerrimack,Hg-LH + TronaShawvilleShawville,Hg + Lime00 2 4 6 8 10Injection Concentration (lb/MMacf)Source: ADA ES© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.8

Mercury Control through ACI• Powdered activated carbon increases particulateloading into the ESP• Type of carbon and degree of mercury controldetermines solids injection rate for a given coal• Low chlorine PRB coals may not require much higherinjection rates than Eastern bituminous coals!• SCR enhances mercury oxidationand control on PRB coals• SO 3 affects mercury capture by ACI• Some eastern coals generate high levels of SO 3• Additional increases in SO 3 due to SCR© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.9

SCR ImpactsIncreased SO 2 to SO 3 ConversionBoilerNH 3FeedNO XSO 2H 2SO 4Acid Mist(“Blue Plume”)N 2NH 3 SlipH 2 OSO 3SCRSO 2to SO 3ConversionAirHeaterPotentialAmmonium BisulfateDeposit/plugging[Excess NH 3+ SO 3]ESPSO 3 + H 2 SO 4WetFGDStack© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.10

Sulfur Trioxide Issues• Sulfur trioxide (SO 3 or acid mist)corrodes flues, air heatersand other equipment• SO 3 forms sulfuric acid mist aerosolin a wet scrubber which contributesto a visible, trailing plume• Wet FGDs collect very littleacid mist: 10 to 30%• There can be more acid mistthan dry particulate in manywet scrubber stacks• Acid mist is PM2.5• SO 3 affects mercury capture by ACI© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.11

Wet FGD Stack Particulate EmissionsIncludes:• Flyash• Gypsum carryover• H 2 SO 4• Permitted emissionand opacity limitswill drive technology© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.12

SO 3 ControlInjection Options:• Sorbent injection (calcium, magnesium, or sodiumcompounds), typically in furnace, after the SCR,or upstream of the particulate collection device• Ammonia injection upstream of the Dry ESPvs.Hardware Solution:• Wet ESP© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.13

Sorbent Injection for SO X ControlSorbent InjectionCoalESPFly Ash + Sorbent• Sorbent is injected upstream of the ESP• Trona, lime magnesium and ammonia known to remove SO 3• Sorbents affect ESP ash and performance• Dry sorbent injection with trona used for SO 2 control© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.14

Key Factors Affecting ESP PerformanceESP Inlet Loading & Flyash Size Distribution• Increase in fines and loading canimpair performanceFlyash Resistivity• Increase in resistivity can criticallyhurt performanceFlyash Cohesivity• Increase in ash cohesivityis beneficial to controllingre-entrainment• Needs management to preventperformance damaging build-ups© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.15

Implications on Sorbent Injection with Dry ESPsSodium Based Sorbent for SO x Control• Decrease in flyash resistivity from 10*12 to 10*11 ohm.cm• Increased ESP Performance / Decreased PM emissionsup to 30% SO 2control in several plants• Sorbent loading and fines increase – and may impose performance limits• Hotside ESP experience is more promising: no loading effectsup to 80% SO 2control• Higher SO 2removals maycontribute to NO 2plume© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.16

Implications on Sorbent Injection with Dry ESPsAmmonia Based Sorbent for SO 3 Control• No resistivity impact seen on several high S applications• Increased fines• Ash may get too sticky• Hopper evacuation issues• Electrode design is important to preserve emissionsperformanceLime/ MgO for SOx Control• Increased resistivity.• Decreased ESP Performance /Increased PM Emissions• ESP performance enhancementmay be necessary© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.17

Dry ESPs on more than 70% of boilers in USPrinciple• Ash particles charged, collected toplates then rapped off into hoppersFeatures• Top rapped or tumbling hammer• Wires, Rigid DEs or rigid frame• Variable CP spacing to 400 mm(15.75 in)A. Precipitator ControlsB. High Voltage Support SystemC. Inlet Flow Distribution DevicesD. High Voltage Discharge ElectrodesE. Collecting Plate RappersF. Discharge Electrode RappersG. Collecting Plates© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.18

Sorbent Injection for Mercury ControlSorbent InjectionCoalESPFly Ash + Sorbent• ACI is injected upstream of the ESP• In some plants, heavy ESP sparking noticed: Insulators getting coated?• Some indications of heightened peak opacity while average opacity ispreserved: re-entrainment and electrical effects• There will be upper limits to injection rate before opacity shows increase• ESP enhancement techniques may be needed© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.19

Upgrades/Enhancements canrestore ESP Performance• Replace worn out, corroded internals• Increase electrical sectionalization• Improve flow quality• Install optimal rigid discharge electrodes• Upgrade HV power supplies• Increase treatment time• Raise roof to put in taller electrodes• Add a field© 2007 The Babcock & Wilcox Company. All rights reserved. Proprietary and ConfidentialB&W Presentation for WCPA – S. Kumar.20

Thank You.Impact of SOx, NOx and Mercury Controlson ESP PerformanceWPCA MeetingNovember 29, 2007Sam KumarManager, Particulate Control