EFFICIENT AND ECONOMICAL ENERGY RECOVERY FROM WASTE BY COFIRING WITH COAL

Cofiring fuels derived from municipal and nonhazardous industrial wastes with coal in industrial and utility boilers is an efficient and cost-effective method of energy recovery from wastes in many cases. Waste fuels such as scrap tires, tire-derived fuel, refuse-derived fuel, paper mill sludge, sewage sludge, sawdust, wood, and industrial waste can be cofired with coal in many stoker, pulverized coal, cyclone, and fluidized bed boilers with only minimal modifications and with minimal impacts on environmental emissions and plant safety. Waste cofiring with coal usually exhibits a higher waste-to-energy conversion efficiency than 100 percent waste firing in dedicated waste-to-energy plants, because coal-fired plants typically operate at higher steam pressures and temperatures and therefore higher steam-cycle and thermal efficiencies than dedicated plants. In addition, waste cofiring generally requires a much lower incremental capital investment than waste firing in a dedicated waste-to-energy facility. Both factors can contribute to a lower breakeven waste disposal cost or tipping fee for waste fuel cofiring with coal than for dedicated plants. This economic advantage should be highest for low-volume, low heating-value fuels, such as municipal solid waste and sewage sludge, and lowest for high-volume, higher quality fuels, such as scrap tires.