Mercury Capture in Conventional APC Technologies

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1 Mercury Capture in Conventional APC Technologies STAPPA/ALAPCO Workshop October 27, 2004 Coeur d Alene, ID Sean Black Marketing Manager - ECS ALSTOM Power, Inc. (865) sean.black@power.alstom.com

2 MACT Analysis is Based Upon 1999 Data on Hg Removal with Existing Equipment not Designed to Remove Mercury Controls Bituminous PM Only CS-ESP 46% HS-ESP 12% FF 83% PM Scrubber 14% Dry FGD SDA + ESP SDA + FF 98% Wet FGD CS-ESP+Wet FGD 81% HS-ESP+Wet FGD 55% FF+Wet FGD 96% Subbituminous 16% 13% 72% 0% 38% 25% 35% 33%

3 Conventional AQCS Plant Arrangements PC SCR AH FF/ESP ID FAN WFGD WESP STACK 1 PC SCR AH FF/ESP ID FAN WFGD STACK 2 PC SCR AH SDA-DFGD FF/ESP ID FAN STACK 3 PC SCR AH FDA-DFGD FF/ESP ID FAN STACK 3 CFB AH FDA-DFGD FF/ESP ID FAN STACK 1 CFB AH FF/ESP ID FAN STACK 2 Typical ~NOx Typical ~SO2 Typical Typical ~SO2 ~H2SO4 Typical Boiler Cooling PM GasFlow Other Discharge 1 Max Multi-Control (NOx + SOx + H 2 SO 4 ) burning high sulfur fuel 2 NOx + SOx Control burning mid-level sulfur fuel (~2%) 3 NOx + SOx + H 2 SO 4 Control burning mid/low sulfur fuel (2% & lower) 4 What is best for PAC injection for Mercury Control?

4 Primary Capture Technologies Available to Reduce Mercury Emissions 1. Flue Gas Desulfurization (FGD) Scrubbers. Capture Oxidized Mercury in Flue Gas 2. Particulate Matter (PM) Collection Devices Capture Sorbed Mercury on Fly Ash Capture Sorbed Mercury on Injected Sorbents

5 Mercury Speciation & Emissions Control Mercury Downstream ofthe Boiler Particulate Mercury: collected ESP and FF. Oxidized Mercury (Hg ++, HgCl 2,): Demonstrated high net capture efficiency for oxidized mercury in full-scale installations. Elemental mercury (Hg 0 ): not captured by scrubbers Some re-emission of elemental mercury in scrubbers

6 Enhancing Capture of Hg in FGD Scrubbers: Increase Amount of Oxidized Hg Oxidizing Catalysts FGD Scrubber SCR for NOx Coal Electrostatic Precipitator Oxidizing Chemicals

7 Status of Technologies for Oxidizing Mercury SCR (Co-Benefits of DeNOx and Hg Oxidation): Demonstrated performance on full-scale installations. Further enhancements at various stages of demonstration. Low-Temperature Oxidizing Catalysts: SCR Catalyst and Palladium on Alumina. Demonstrated in pilot-scale testing.

8 Simultaneous SCR Reactions: DeNO x and Hg Oxidation NOx NH 3 and Optional Cl Injection NOx+NH3 SCR Catalyst N2+H2O Hg + Cl Hg + Cl HgCl 2 DeNOx and Mercury Oxidation Reactions NO + NH 3 + 1/4 O 2 N 2 + 3/2 H 2 O (DeNO x Reaction) Hg + 2 HCl + 1/2 O 2 HgCl 2 + H 2 O (Hg Oxidation) Inhibition of Hg Oxidation by Ammonia HgCl 2 + NH 3 + 1/4 O 2 Hg + 2 HCl + ½ N 2 + ½ H 2 O

9 EPA Lab Tests: SCR Works for PRB with Enough Cl Simulated PRB Flue Gas 100% Elemental Hg at SCR Inlet HCl Injection Level 0 ppm 8 ppm Hg Oxidation over SCR Catalyst 4 % 97 %

10 Enhanced SCR Approaches - Estimated Hg Reductions Hg Capture (tons/year) Without Cl Injection Hg Capture (tons/year) With Cl Injection Enhanced SCR Option Bituminous PRB Bituminous PRB Option 1 - Operate SCR Units Year-Round Option 2 - Add Extra Layer of SCR Catalyst Option 3 - Combo 1 & 2, With NH3 Year-Round Option 4 - Combo 1&2, No NH3 October to May Enhanced Hg Capture Would be Beyond Incidental Co-Benefits Analysis is only for Units with SCR + Wet FGD Projected in 2010

11 Hg Control Enhancements with SCR Add an Extra SCR Layer Effective at Low NH3 Location Inject Chlorinating Agent Especially for Low-Rank Coals (e.g. PRB) Makes Hg Oxidation Thermodynamically Favorable SCR Catalyst Makes the Reaction Proceed Run SCR Units Year-Round More than Doubles Hg Oxidation and Capture Very Effective in Non-Ozone Season (Not Injecting NH3 for DeNOx) Optimize Catalyst Formulations for Hg Oxidation Low-Temperature SCR for Hg Oxidation

12 Sorbent Injection Upstream of a Wet Scrubber Injection of AC and capture in ESP will provide an additional mechanism to reduce mercury emissions. Oxidation of mercury produced by carbon could enhance capture in wet scrubber. Decreased mercury levels in scrubber could reduce potential for reemission of elemental mercury from scrubber. Too much PAC carryover to scrubber will impact gypsum quality; important for modern designs that re-sell their gypsum

13 Control of Mercury with Sorbent Injection Technology Powdered Activated Carbon (PAC) Sorbent. Demonstrated high net capture efficiency for elemental and oxidized mercury in full-scale installations. Other sorbents are under development. Effective on bituminous, subbituminous, and lignite coals.

14 Selected European Experience With Control of Mercury Emissions Commercialized mercury removal technology for the European WtE industry Sorbent injection upstream of dedicated HRFF Installed 19 systems during early 1990s Utilize activated carbon/coke ALL have operated reliably for more than 10 years ALL achieve between 80-90% mercury removal ALL capture both elemental and oxidized mercury Additional experience with sorbent injection upstream of DFGD systems Data from US utility pilots validates performance curves from European WtE industry

15 Mercury Removal Across Filsorption System ALSTOM data from WtE experience demonstrates: High mercury removal efficiency achieved at inlet conditions and mercury concentrations similar to coal-fired boilers Achieved high removal of both oxidized & elemental mercury 19 units in operation with consistent results achieved Units average over 10 years operating experience with demonstrated high availability levels Representative Data Oxidized Elemental Total (µg/nm 3 ) (µg/nm 3 ) (µg/nm 3 ) Filsorption Inlet Filsorption Outlet % Reduction >85% >90% >91%

16 Chemical Additives at Holcomb Station Hg Removal (%) FGD SDA In FGD + KNX FGD + ADA-632 FGD, no SDA* * DOE Results 1997 Comanche Station PRB Coal Injection Concentration (lb/mmacf at ~ 290 o F)

17 Decisions on Mercury Control with Flexibility in Achieving Reductions The cost of mercury control technology is independent of the amount of mercury controlled SCR/FGD and ACI costs are only proportional to the size of the plant treated For the same sized plant, the cost of mercury control for a given percentage removal is the same whether 2 lbs, 20 lbs, or 200 lbs per year are controlled. Utilities would have a significant economic incentive to put mercury control on units that are: Higher emitters Larger plants Therefore, a flexible approach would result in the greatest reduction in total mercury emissions while minimizing costs

18 Environmental Benefits of a Flexible Regulation 1. Greater reduction in mercury emissions achievable without impacting generation 2. Emission reductions could be achieved sooner 3. Higher emission sources will be targeted and reduced 4. Future improvements in control technology could be applied to provide even greater emission reductions 5. More new plants could be brought on-line that operate at higher efficiency (reduced CO2) and lower emissions