COAL-FIRED POWER PLANTS: OPPORTUNITIES FOR BETTER POLLUTANT CONTROL

Transcription

1 COAL-FIRED POWER PLANTS: OPPORTUNITIES FOR BETTER POLLUTANT CONTROL Frank Princiotta, Director Air Pollution Prevention and Control Division National Risk Management Research Laboratory September 17, 2003

2 What We ll Cover Today... Health and environmental impacts of pollutants Pollutant emissions Regulatory overview Control technologies 2

3 Health and Environmental Impacts NOx: ground level ozone; acid deposition; formation of PM-2.5 SO2: respiratory illness; aggravation of cardiovascular disease; acid deposition Mercury: fish advisories; neurodevelopmental effects to children exposed in utero; cardiovascular concerns PM-2.5: respiratory distress; cardiac arrhythmia; higher death rates from respiratory and cardiovascular diseases; reduced visibility (haze) 3

4 NOx Sources Mobile sources 12,405,000 tons 55.5% Industrial processes 1,031,000 tons 4.6% Electric utilities 4,891,000 tons 21.9% Miscellaneous area and point 314,000 tons 1.4% Industrial and other combustion 3,708,000 tons 16.6% 4

5 Existing NOx Regulations Title IV regulations to address acid deposition Phase I: starting January 1, 1996, affected sources nationwide with emission limits for Group 1 boilers; basis: low NO x burners; NOx reduction: 340,000 tons/yr Phase II: starting January 1, 2000, affected sources nationwide with revised limits for Group 1 boilers and emission limits for Group 2 boilers; basis combustion controls, SCR, NGR; NOx reduction: about 2 million tons/yr NOx SIP Call NO x budgets for 19 States & DC, starting May ; assumes reductions primarily from large sources in a cap and trade program; EGUs (average rate) = 0.15 lb/10 6 Btu; Non-EGU: 60% control level; basis: a variety of NO x controls, but extensive use of SCR on utility boilers; NOx reduction: 1 million tons/yr by

6 Sources of SO2 Electric utilities 10,821,000 tons 68.5% Industrial processes 1,447,000 tons 9.2% Mobile sources 701,000 tons 4.4% Miscellaneous area and point 10,000 tons 0.1% Industrial and other combustion 2,811,000 tons 17.8% 6

7 Existing SO2 Regulations Title IV of the Clean Air Act Amendments of 1990 required SO 2 reductions to address acid rain (deposition) SO2 reduction via a cap-and-trade program Phase I, : 445 units, Phase II, : >2000 units, 7

8 Title IV SO2 Program 8

9 Sources of Mercury Top five anthropogenic sources (1999) Utility coal tons (39.8%) Industrial boilers - 12 tons (10%) HWI tons (5.5%) Chlorine production tons (5.4%) MWC tons (4.2%) Natural sources Volcanoes - annual tonnage not quantified Forest fires - annual tonnage not quantified 9

10 Clean Air Act Section 112 HAP Rule Best of the best for new sources Average of the top performing 12 percent for existing sources defines the floor emission limit Recent court decisions relating to how floors, subcategorization, etc. are handled will be examined Emissions standard applicable to each source Section 112 does not allow trading between facilities to meet the standard Averaging among units at a given facility will be considered 10

11 Mercury MACT Plans/ Schedule Under settlement agreement, proposal of MACT rule on or before December 15, 2003 UNLESS multipollutant legislation enacted before then that amends CAA and eliminates MACT requirement Expect a lot of comments Promulgation on or before December 15, 2004 Litigation expected Expect requests for a 1-year extension to the statutory 3-year compliance schedule (normally December 15, 2007) 11

12 PM Sources and Sinks 12

13 Sources of Fine Particles SULFATE from SO2 (Power Plants and Coal & Oil-fired Boilers) NITRATE from NOx (Cars, Trucks, Power Plants & Heavy Equipment) CRUSTAL MATERIAL (Roads, Construction & Field Dust) ELEMENTAL CARBON (Diesel Engines, Heavy Equipment, Highway Vehicles) ORGANICS (Wildland Fires, Waste Burning, Heavy Equipment Engines, Cars & Trucks) Typical Western City Typical Eastern City 13

14 Current Attainment with the Fine Particle (PM2.5) Standard ( ) Legend <= ug/m3 Number of Counties 160 There are 129 counties nationwide (114 counties in the East) that are likely to exceed the annual fine particle standard of 15 µ/m million people (43 million people in the East) live in counties that would not meet this standard ug/m3 22 Hawaii Alaska ug/m3 41 PM2.5 standard = 15 µ/m ug/m3 34 >= ug/m

15 Multipollutant Reduction Two mechanisms: Clear Skies Act Legislation that addresses transported air pollution from power plants in addition to other environmental concerns (e.g., mercury). Transport Rule Regulatory approach that uses existing CAA mechanisms to address transported air pollution from all potential transport sources. 15

16 Clear Skies Reduce air pollution from electricity generators and, thereby, improve air quality throughout the country Emissions Reductions: NOx by 67 percent, SO2 by 73 percent, and mercury by 69 percent Timing: Emission reductions phased-in from Regulatory approach: phase-in of cap and trade program 16 9

17 Widespread improvement expected in attaining NAAQS Current mobile rules/clear Skies (or Transport Rule) Counties Exceeding the Annual Fine Particle Standard in 2001 Remaining Counties Likely to Exceed the Annual Fine Particle Standard with Clear Skies in 2020 (18 Counties) Hawaii Alaska Hawaii Alaska Note: This analysis shows the counties that would come into attainment due to Clear Skies alone in Additional federal and state programs are designed to bring all counties into attainment by 2017 at the latest. Widespread PM 2.5 attainment in 2020: Tier 2, HD Diesel, NOx SIP call, other programs Projected regional SOx/NOx reductions from Clear Skies Act, or regional transport rule/regional haze programs Doesn t include SIP local/regional measures 17

18 PM Transport Rulemaking Plan to address SO2 & NOx. Analyze sources of SO2 (for PM2.5) and NOx (for PM2.5 and ozone). Determine whether there is a significant contribution from individual states. Controls effective 2009/2010 at the earliest. EPA develops an emissions budget for each state. States have discretion in deciding which sources to control to meet the budget. Plan to propose an optional cap-and-trade program similar to Acid Rain and NOx SIP call. 18

19 Pollutant Reduction Multipollutant reductions possible through: Emissions control technologies Advanced power generation technologies Power plant upgrading options Focus on emissions control technologies 19 3

20 Reburning Superheaters Reburn air Reburn fuel Main fuel and air Main fuel and air Flue gas Reburn zone Burning zone Reburn fuel (natural gas, coal, other fuels) is injected to provide 15-25% of total heat input >50% NOx reduction, mercury and SO2 reduction Low capital costs Fuels costs, availability of adequate residence time Applications: cyclone, wall, tangential; MWe 20 15

21 SCR NH3 injection, generally between o C More than 90 % reduction is possible Capital intensive, space requirements, NH3 slip, SO3 emissions, catalyst deactivation Applications: More than 75 boilers; cyclone, wall, tangential; MW 21 17

22 Capacity (MWe) Equipped with FGD Technology United States Abroad World Wet 82, , ,892 Dry 14,081 10,654 24,735 Regenerable 2,798 2,394 5,192 Total FGD 98, , ,819 22

23 Performance 100 Design SO2 Removal Efficiency, % Wet Limestone Spray Drying Median s 1980s 1990s 23

24 Existing Mercury Controls Post-comb ust ion Co ntro l Strat egy PM Control Only Post-comb ust ion Emi ssion Co ntro l Dev ice Co nfigura tion Ave rage Merc ury Capt ure by Control Conf igurat ion Coal Burned i n Pulver ize d-coal-fire d Boiler Un it Bituminous Coal Su bbi tuminous Coal Lignite CS-ESP 36 % 9 % 1 % HS-ESP 14 % 7 % not tested FF 90 % 72 % not tested PS not tested 9 % not tested PM Co ntrol A nd Spray Dryer Adsorber SDA+ESP not tested 43 % not tested SDA+FF 98 % 25 % 2 % SDA+FF+SCR 98 % not tested not tested PM Co ntrol A nd We t F GD System(a) PS +FGD 12 % 10 % not tested CS-ESP+FGD 81 % 29 % 48 % HS-ESP+FGD 46 % 20 % not tested FF +FGD 98 % not tested not tested 24

25 SCR and Mercury Interactions Speciation influences emissions control Ionic Hg 2+ is removed easily by wet scrubbers Volatile elemental Hg 0 is difficult to capture SCR units are being used extensively to meet current NOx regulations SCR can convert elemental mercury in coal combustion flue gas into the ionic form Limited field data in Europe and U.S. Increase in Hg 2+ across SCR reactor 25

26 PM Control Technologies for Power Plants Electrostatic precipitators (ESPs) 72% of U.S. coal-fired boilers, total PM up to 99.9%, fine PM 80-95% Baghouses 14% of U.S. coal-fired boilers, total PM up to 99.9%, fine PM % PM scrubbers 2% of U.S. coal-fired boilers, total PM 95-99%, fine PM 30-85% 26

27 Emerging Technologies Reduce costs Increase performance Increase flexibility Multipollutant control 27 18

28 Sorbent Injection The extent of capture depends on: Inlet mercury concentration Sorbent Injection Sorbent characteristics (particle size distribution, porosity, capacity at different gas temperatures) Residence time in the flue gas Type of PM control (FF vs. ESP) Concentrations of SO 3 and other contaminants Flue Gas ESP or FF Ash and Sorbent 28 9

29 Mercury Removal Trends with ACI Mercury Removal (%) Gaston Brayton Point PPPP Injection Concentration (lb/mmacf) Source: ADA Environmental Solutions (2003) 29

30 Advanced Dry FGD Process hydrated lime slurry, contained in a circulating fluidized bed absorber, reacts with exhaust gases to capture SO 2, SO 3, HCl, and mercury Increased gas-solid mixing resulting in reduced absorber residence time and recycle loop enhances lime utilization Circulating Dry Scrubbing (Lurgi), Gas Suspension Absorbers (FLS Miljo), Reflux Circulating Fluidized Bed (WULFF Gmbh), Rapid Absorption Process (Beaumont Environmental) Status Commercial technologies; installations in the U.S. and abroad Capable of up to 90+% SO2 reductions % mercury capture has been reported; limited data 30 8

31 ESFF Electrostatically Stimulated Fabric Filtration (ESFF)--developed by EPA Pulsejet fabric filter with high voltage electrodes centered between groups of four bags Pilot-scale performance data: PM2.5 with ESFF=0.14 mg/m3 PM2.5 without ESFF=0.51 mg/m3 PM1 with ESFF=0.05 mg/m3 PM1 without ESFF=0.17 mg/m3 BHA Group, Inc. licensee has developed preliminary commercial design 31

32 Development of Multipollutant Sorbents Capture Capacity of Various Sorbents Amount Adsorbed 160 A-Clay 140 K-Clay 120 Act C Lime 100 ox-csh NO2 SO2 Hg Pollutant NO2 and SO2 capacity given as mg/g adsorbed in 1 hr at 80 C; Hg 0 capacity given as µg/g adsorbed in 1 hr at 80 C Sorbent Development Synthesis, Characterization, Evaluation & Optimization Relate structure and chemical nature to adsorption characteristics Types of Sorbents Being Studied Sorbents synthesized using industrial by-products Modified carbon-type sorbents Surface modified Calcium Silicate Hydrate (C-S-H) Multipollutant sorbents that also have adsorptive capacity for 32

33 Our Current Efforts Investigation of SCR and mercury interactions Bench-, pilot-, and full-scale efforts Development of a multipollutant scrubbing system Development of multipollutant sorbents Participation in DOE- and EPRI-sponsored technology development activities Technical guidance to EPA program offices 33