COAL-BIOMASS COFIRING

Transcription

1 COAL-BIOMASS COFIRING PRACTICAL CONSIDERATIONS Larry Felix Slide 1 DOE Cooperative Agreement No. DE-FC26-00NT40895

2 Why Biomass Cofiring? Cofiring Helps to Reduce SO 2 and NO X Emissions Legislatively Targeted for Reduction Renewable Energy may be Mandated at a percentage of a Utilities Energy Output U.S. Tax Advantages for the Production of Energy from Renewable Fuels Climate Protection Global Warming Slide 2

3 US Consensus The addition of biomass has been shown to reduce NO X emissions in most commercial facilities, usually beyond the reductions expected because of a lower overall fuel-bound nitrogen content. The high volatiles content of biomass can effectively establish a fuel-rich zone early in the flame that can reduce NO X emissions. Adding biomass can reduce flame temperatures, leading to lower levels of thermal NO X. The high moisture content of some biomass may also be effective for NO X reduction at full-scale. 1 1 Dayton, David, A Summary of NO X Emissions Reduction from Biomass Cofiring, DOE Contract DE-AC36-99-GO10337, NREL/TP , National Renewable Energy Laboratory, Golden CO, May, 2002, p.3 Slide 3

4 Full-Scale Experience in the US Plant Biomass % NO X Result Reference Hammond Wood 13 No effect Boylan, et al., 1992 Kraft Wood 0-30 Reduced > fuel N Boylan, et al., 1994 Greenidge Station Dry wood 10 No effect Prinzing et al, 1996 Greenidge Station Wet wood 10 Reduced Prinzing et al, 1996 Madison Gas & Electric Switchgrass 14 No to slight effect Ragland et al, 1996 Allen Fossil Plant Wood 0-20 Reduced > fuel N Tillman et al, 1996 Sandia Pilot Wood, switchgrass 0-66 Reduced to fuel N Baxter and Robinson, 1999 Seward, Allen, Michigan City Wood 0-20 Reduced < fuel N on average Tillman, Plasynski, and Hughes, 1999 Gadsden Switchgrass 10 No effect Boylan, 2001 Colbert Wood 1-5 Up to 16% Increase Dayton, 2002 Slide 4

5 US Results Mass Basis (Dayton NREL, May 2002) Slide 5

6 At the Pilot Scale Slide 6

7 Combustion Research Facility All testing conducted at the SRI/SCS 6.0 MMBtu/hr Combustion Research Facility (at 3.5 MMBtu/hr) Continuous measurement and logging of ~ 200 pertinent process parameters In-situ testing for mass emissions, particle size, char, pyrometry, ash resistivity, gases (O 2 at furnace exit and at CEM location, CO, CO 2, SO 2, NO X, NH 3, H 2 O, HCl). On-site wet chemical flue gas and ash analyses, CHN (for carbon in ash), fuel heat value measurement Instrumented CE-Raymond Model 352 Deep Bowl mill Slide 7

8 Slide 8

9 Pilot-Scale Test Facility Furnace Convective Section Heat Exchangers Pulse-Jet Baghouse Packed- Column Scrubber Burner Pulverized Fuel Bin Coal Feeder Electrostatic Precipitator Slide 9

10 Locations for Biomass Injection Slide 10

11 Percent NO X Reduction COMILLED CENTER SIDE 15% Overfire Air - 3.5% Furnace Exit O 2 10% SAWDUST 20% SAWDUST 10% SWITCHGRASS 15% SWITCHGRASS 20% SWITCHGRASS Slide 11

12 Milling Coal and Biomass SRI / SCS CE-Raymond Model 352 Deep Bowl Mill Slide 12

13 Analyses of Fuels ANALYSIS PROXIMATE (As Received) MOISTURE, % ASH, % VOLATILE, % FIXED CARBON, % SULFUR, % HEAT VALUE, Btu/lb ULTIMATE (Dry) CARBON, % HYDROGEN, % NITROGEN, % SULFUR, % ASH, % OXYGEN, % (DIFF) CHLORINE, % COAL Eastern hv bit. Pratt Seam BIOMASS Switchgrass Field Chopped Sawdust Red Oak Slide 13

14 MILLING COAL AND BIOMASS-1 COAL SAWDUST SWITCHGRASS MILLING RATES UNIT Pratt Seam 10% 20% 15% 20% Net Coal Added to Bins lb/h Coal Burned lb/h Fuel Heat Value Btu/lb Mill Output lb/hr Mill Rejects lb/h Slide 14

15 MILLING COAL AND BIOMASS - 2 COAL SAWDUST SWITCHGRASS AVERAGES UNIT Pratt Seam 10% 20% 15% 20% Mill Current Amps Drying Natural Gas scfh Mill Inlet Temperature F Mill Outlet Temperature F Mill Exit Gas Flow ACFM Mill Exit Gas Flow SCFM P at Mill Inlet in. H2O O 2 at Mill Inlet % Mill Spring Pressure, West lbs Mill Spring Pressure, East lbs Journal Lift, West in Journal Lift, East in Hardgrove Grindability no unit 49.0 N/A N/A N/A N/A Slide 15

16 MILLING COAL AND BIOMASS - 3 COAL SAWDUST SWITCHGRASS CALCULATED ENERGY USAGE UNIT Pratt Seam 10% 20% 15% 20% Fuel Heat Value Btu/lb Mill Output MBtu/hr Specific Grinding Energy, gross kw/ton Specific Grinding Energy, net kw/ton Specific Drying Energy Btu/lb Specific Grinding Energy, gross kwh/mbtu Specific Grinding Energy, net kwh/mbtu Specific Drying Energy Btu/MBtu Hardgrove Grindability no unit 49.0 N/A N/A N/A N/A Slide 16

17 Biomass Comilled with HV Bituminous Coal Percent of 100% Coal Value Net Specific Grinding Energy, kw/ton Switchgrass Sawdust Mill Output, lb/h Slide % Biomass

18 Size Distributions Slide 18

19 80% Pratt Seam Coal - 20% Sawdust Cumulative Percent Coal & Sawdust RR Fit Coal RR Fit Sawdust RR Fit Coal +Sawdust Data Coal Data Sawdust Data Particle Size, microns Slide 19

20 Is it the Biomass OR Does Coal Particle Size Affect NO X and/or UBC Emissions? Slide 20

21 Regular Grind (70% < 200 mesh) and Fine Grind Coal Cumulative Percent Mill PC Sample - Reg. Grind Finely Gound Coal - CFD Samplel Regular Grind Coal - CFD Sample Fine Coal Fit Reg. Grind Coal B Reg. Grind B Fit Particle Size, microns Slide 21

22 Pratt Seam Coal - Baseline Injection Configuration Effect of Normal and Fine Coal Grind NOx Performance in the Pilot-Scale Combustor Dependence on Furnace Exit Oxygen NO x Conc., ppmv at 3% O 2 dry % Overfire Air 15% Overfire Air Normal Coal Grind Fine Coal Grind Previous Testing NO x Emissions, lb/10 6 Btu Furnace Exit O 2, % Wet Slide 22

23 Pratt Seam Coal - Comilling Configuration Effect of Normal and Fine Coal Grind Unburned Carbon Performance in the Pilot-Scale Combustor Fly Ash Unburned Carbon, % % Overfire Air Test 10, Normal Grind Test 10, Fine Coal Grind Test 6, Norm al Coal Grind Test 5, Norm al Grind Test 1, Norm al Grind Furnace Exit O 2, % Wet Slide 23

24 With Comilling, NO X and UBC Emissions are Apparently Unaffected by More Finely Ground Coal ~90% <200 mesh Slide 24