The Cost of Mercury Removal in an IGCC Plant

Transcription

1 The Cost of Mercury Removal in an IGCC Plant M.D. Rutkowski, M.G. Klett, R.C. Maxwell October 1, 2002 Washington, D.C.

2 Acknowledgments Gary J. Stiegel James R. Longanbach David L. Denton U.S. DOE/NETL U.S. DOE/NETL Eastman Chemical Company

3 Background EPA Announced It Will Regulate Mercury and Other Air Toxics from Coal-Burning Utilities Two EPA reports to Congress ( ) Mercury is toxic of greatest concern Coal-fired plants largest source of mercury 43 tons of mercury per year

4 Background Proposed EPA Regulations to Control Mercury Emissions from Coal-Burning Utilities Regulations to be proposed by December 2003 Regulations to be promulgated by December 2004 Utility compliance by December 2007

5 Mercury Removal from Conventional Power Plants Based on 1997 EPA Report to Congress Activated carbon injection with and without spray cooling Activated carbon bed 90% removal from stack gas $1.43/MWh to $3.10/MWh $17,400/lb Hg to $37,800/lb Hg Amounts to nearly 10% of COE

6 The Eastman Chemical Approach Eastman has been removing vapor phase mercury for 20 years Activated carbon beds Located upstream of AGR process Bed changeout every 18 to 24 months 90 to 95% mercury removal ~20-second gas residence time in vessel

7 Tennessee Eastman, Kingsport, TN Gasification Area EASTMAN

8 Chemicals from Coal Final Products Coal Acetic Anhydride Acetic Acid EASTMAN

9 Environmentally Friendly Process Sulfur removal is > 99.9% (with Rectisol) Eastman has a patented sulfur-free startup process (available for license) NOx is not an issue with chemical production operations Eastman has practiced vapor-phase mercury removal from syngas since initial plant startup EASTMAN

10 Eastman Vapor-Phase Mercury Removal Process Oxygen Shift Reaction: CO + H2O CO2 + H2 Hg Removal 1300 ton/day Coal Water Rod Mills Steam Dry Shifted Gas Hg Removal Scrubber Slurry Pump Slag NG Steam Quench Water Blowdown, Clarification, And Recycle Dry Unshifted Gas EASTMAN Preheating Gasifier

11 Vapor-Phase Mercury Removal Process and Performance Sulfur-impregnated activated carbon beds ~30 C and psig dry syngas feed ~15-20 seconds contact time (based on total packed volume) >90-95% mercury removal (based on Radian International study) >12-18 month lifetime of carbon beds (limited by pressure drop or shift catalyst changeouts, not mercury breakthrough) EASTMAN

12 Mercury Removal Beds EASTMAN

13 Mercury Removal Bed EASTMAN

14 Activated Carbon to Remove Mercury from IGCC Calgon type HGR granules Best temperature is 100 F No moisture condensation Sulfided carbon Adsorbs and converts Hg to HgS Stable compound for landfill or recovery

15 Mercury Removal from IGCC Syngas at high pressure Low volumetric gas flow Moderate temperatures Particulate-free Moderate humidity

16 Flow Diagram Showing Locations for Mercury Removal Fuel Gas Scrubber 410 F COS Hydrolysis Fuel Gas Cooling & Knockout 103 F Mercury Removal MDEA Unit Gas Turbine Combustor 450 F Coal Water Texaco Gasifier & Fuel Gas Cooling Slag Sour Water Sour Water Stripper Claus Plant Oxidant Acid Gas Sulfur Claus Plant Flue Gas 1131 F HRSG Gasifier Oxidant Air to ASU ASU Water Recycle to Gasifier Tail Gas Treatment Unit 280 F Stack Gas Vent Gas Claus Plant Oxidant Vent Gas to Incinerator

17 Mercury Removal Process Design 250 MW net IGCC plant Texaco radiant cooler gasifier GE 7FA gas turbine 80% plant capacity factor Mercury removal located upstream of AGR 20-second gas residence time Low humidity gas 103 F operating temperature

18 Activated Carbon Bed Design Cylindrical bed configuration Operating pressure Pressure drop through bed Mercury concentration inlet Mercury concentration outlet Carbon loading, mercury Initial carbon charge Carbon replacement rate Two vessels, 7.3 ft diameter x 20.2 ft high 378 psia 10 psi 52 ppbw 5 ppbw 0.4% 25 tons 17 tons/year

19 Mercury Removal Cost Basis Purchased equipment Installation Indirects 25% contingency Total capital cost Capital 15% $407,000 $203,500 $122,100 $101,750 $834,350 ($3.34/kW) $125,153/year Other O&M costs O&M labor Power penalty $6.43/pound Total O&M $59,242/year $7,446/year $36,792/year $217,203/year $320,683/year

20 Cost of Mercury Removal Total $/year Total $/MWh $445,836/year $0.254/MWh Mercury reduction, lb/year Mercury, $/lb 131 lb/year $3,412/lb

21 Compared with Conventional Power Plants using Carbon Beds Removal location Relative volumetric gas flow Cost of removal, $/MWh Fraction of COE Cost of removal, $/pound Syngas ahead of AGR 1.0 $0.254/MWh < 1% $3,412/pound Stack gas 160 $3.10/MWh ~ 9% $37,800/pound

22 Sensitivity to Capital Cost Factor Sensitivity of Key Parameters on Mercury Removal Costs $0.400 $0.350 Cost of Mercury Removal, $/MWh $0.300 $0.250 $0.200 $0.150 $0.100 $0.050 $ Relative Capital Cost Factor = 0.5, 1.0, 2.0

23 Sensitivity to Carbon Cost Sensitivity of Key Parameters on Mercury Removal Costs $0.400 $0.350 Cost of Mercury Removal, $/MWh $0.300 $0.250 $0.200 $0.150 $0.100 $0.050 $ Relative Carbon Cost Factor = 0.5, 1.0, 2.0

24 Sensitivity to Carbon Life Factor Sensitivity of Key Parameters on Mercury Removal Costs $0.450 $0.400 Cost of Mercury Removal, $/MWh $0.350 $0.300 $0.250 $0.200 $0.150 $0.100 $0.050 $ Carbon Replacement Time (months) = 9, 18, 36

25 Amount of Mercury Removal Sensitivity of Key Parameters on Mercury Removal Costs $0.450 $0.400 Cost of Mercury Removal, $/MWh $0.350 $0.300 $0.250 $0.200 $0.150 $0.100 $0.050 $ Amount of Mercury Removal (%) = 90, 99+

26 Conclusions The cost of mercury removal from an IGCC plant is reduced by locating the carbon bed in the pressurized syngas stream. This stream is characterized as having a greatly reduced volumetric gas flow relative to that of stack gas by a factor of nearly 200 for the same size plant. The size of equipment, number of beds, and consequent costs are much less than treating for mercury removal in the stack gas of a PC or IGCC plant. The estimated cost of $0.254 per MWh and $3,412 per pound of mercury from an IGCC plant is shown to be significantly lower than costs of mercury removal from PC power plants. The capital cost estimate of $3.34 per kw for removal from the IGCC plant represents less than 0.3 percent of the total IGCC plant capital. The small increase in cost of electricity of $0.254 per MWh due to adding the mercury removal system represents an increase in the overall cost of electricity from the plant of less than 1 percent.