DEC 7, 2012 Biomass Project Partnership Part 5 Fuel Yard / Project Website / Regulatory Issues Biomass / Coal Fuel & Boiler Considerations Photo credit: Ferman Milster
Fuel Yard UI Main Power Plant on constricted site. Campus and city have grown up around us. No UI-controlled coal or biomass long-term fuel storage. Coal supply located in Muscatine IA, 60-miles away. Regional supply opportunity to other coal boilers? Fuel yard provides facility to blend, size, densify, and store biomass and coal. Business model yet to be developed. Likely opportunity for 3 rd party contracted operation. 2
UI Main Power Plant 3
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Project Website http://sustainability.uiowa.edu/biomass/ 5
Regulatory Issues Need to discuss if a material is classified as a hazardous waste, what are the implications when burned for energy recovery. 40 CFR 261. Boiler 11 90% sulfur removal 6
Biomass/Coal Fuel Comparison Proximate As Received Moisture Ash Volatile Fixed Carbon Btu/lb Sulfur Poplar wood chips 46.78% 1.11% 46.02% 6.08% 4,547 0.06% Miscanthus grass 9.70% 2.70% 75.54% 12.06% 6,870 0.05% Reed canary grass 8.91% 7.67% 67.04% 16.38% 7,092 0.18% Reed canary grass 23.53% 7.16% 5,885 0.11% Corn Seeds 11.59% 0.83% 78.62% 8.96% 6,957 0.10% Soy Bean Seeds 12.91% 5.21% 74.42% 7.46% 8,910 0.36% Cardboard sludge 53.13% 7.52% 2,824 0.05% Oat Hulls 10.03% 4.62% 72.23% 13.13% 7,240 0.07% Stoker Coal 13.61% 5.72% 35.01% 45.67% 11,617 1.21% Washed Bituminous 13.26% 8.39% 36.37% 41.98% 11,130 2.95% Wood Chips 34.68% 0.46% 57.30% 7.56% 5,552 0.02% Corn Stover 10.00% 6.18% 7,620 0.06% Brush 27.24% 18.46% 4,427 0.06% Sludge 7
Biomass/Coal Fuel Comparison Biomass has: Less energy density (Btu/lb) More moisture content. Moisture in fuel must be evaporated in the combustion process, and is not available to produce steam in the boiler (1,061 Btu/lb) More oxygen, compared to coal More volatile content As the fuel heats in the furnace, the volatiles turn to gas and burn quickly Less sulfur content, and sulfur dioxide emissions are greatly reduced Typically produces more ash, for a given amount of energy burned Typically does not have heavy metals (e.g. Hg) in stack emissions and ash 8
Fuel Btu/lb Tons for 2020 (assuming all additional renewable energy comes from this one source) Poplar wood chips 4,547 153,948 Miscanthus grass 6,870 101,892 Reed canary grass 7,092 98,703 Reed canary grass 5,885 118,946 Corn Seeds 6,957 100,618 Soy Bean Seeds 8,910 78,563 Cardboard sludge 2,824 247,875 Oat Hulls 7,240 96,685 Stoker Coal 11,617 60,257 Washed Bituminous 11,130 62,893 Wood Chips 5,552 126,081 Corn Stover 7,620 91,864 Brush 4,427 158,121 Assuming the amount of energy we consume in 2020 is the same as 2010, we will need 1.6 million MMBtu of additional renewable energy to reach our goal of 40% renewable. 9
Fuel Energy Density Fuel Density (lbs/ft 3 ) Energy Content (Btu/lb) Energy Density (Btu/ft 3 ) Bituminous Coal 55 11,500 632,500 Energy Pellets 50 11,300 565,000 Corn Seeds 45 7,000 315,000 Switchgrass pellets 50 6,000 300,000 Paper Sludge 50 3,556 177,800 Lignin 50 3,307 165,350 Wood Chips (dry) 12 6,000 72,000 Miscanthus Grass 8 7,600 60,800 Wood Chips (green) 14 4,000 56,000 Energy density has an influence on transportation cost. Typically, the lower the density, the more expensive to transport the fuel, per unit of distance. High volume semi-trailers help mitigate energy density influence. 10
Stoker Boiler Fuel burns on traveling grate Boiler capacity limited by: Grate heat release rate (how much burning fuel you can put on the grate) Fuel feeder volumetric capacity Gas burners will assure combustion stability and full boiler capacity 11
Boiler 10 Fuel Feeder Limits Feeder Volumetric Flow Required (ft 3 /hr) Biomass Density 15 lbs/ft 3 Biomass HHV (Btu/lb) Percent Biomass 4,000 5,000 6,000 7,000 8,000 0% 70 70 70 70 70 10% 129 116 107 101 96 20% 189 162 145 132 122 30% 249 209 182 163 149 40% 308 255 220 194 175 50% 368 301 257 225 201 60% 428 348 294 256 228 70% 488 394 332 288 254 80% 547 441 369 319 281 90% 607 487 407 350 307 100% 667 533 444 381 333 Feeder Volumetric Flow Required (ft 3 /hr) Biomass Density 30 lbs/ft 3 Biomass HHV (Btu/lb) Percent Biomass 4,000 5,000 6,000 7,000 8,000 0% 70 70 70 70 70 10% 96 89 85 82 79 20% 122 109 100 94 89 30% 149 129 115 106 99 40% 175 148 131 118 108 50% 201 168 146 130 118 60% 228 188 161 142 128 70% 254 208 176 154 138 80% 281 227 192 166 147 90% 307 247 207 178 157 100% 333 267 222 190 167 Feeder Volumetric Flow Required (ft 3 /hr) Biomass Density 20 lbs/ft 3 Biomass HHV (Btu/lb) Percent Biomass 4,000 5,000 6,000 7,000 8,000 0% 70 70 70 70 70 10% 113 103 96 91 88 20% 156 136 122 113 106 30% 199 169 149 134 124 40% 242 202 175 156 142 50% 285 235 201 178 160 60% 328 268 228 199 178 70% 371 301 254 221 196 80% 414 334 281 242 214 90% 457 367 307 264 232 100% 500 400 333 286 250 Feeder Volumetric Flow Required (ft 3 /hr) Biomass Density 40 lbs/ft 3 Biomass HHV (Btu/lb) Percent Biomass 4,000 5,000 6,000 7,000 8,000 0% 70 70 70 70 70 10% 95 90 86 84 82 20% 120 110 103 98 95 30% 145 130 120 112 107 40% 170 150 136 127 120 50% 195 170 153 141 132 60% 220 190 170 155 145 70% 245 210 186 170 157 80% 270 230 203 184 170 90% 295 250 220 198 182 100% 320 270 236 212 195 12
Circulating Fluidized Bed Boiler Fuel burns in suspension of circulating material Need ash and limestone, or other inert material, to maintain bed integrity Permit requires 90% removal of potential SO 2 emissions Lower combustion temperature, compared to Stoker (less NO x ) 13