Evaluation of Switchgrass Co-firing for Utility Boiler Applications --For Presentation at the American Society of Mechanical Engineers International Joint Power Generation Conference New Orleans, Louisiana June 4-7,2001

摘要

A study is being conducted by Southern Company, Southern Research Institute, EPRI and the US Department of Energy to evaluate the feasibility, costs, and benefits of co-firing switchgrass with coal in existing coal-fired power plants. Switchgrass is a highly productive prairie grass native to the United States. The grass can be grown on marginal land, requires little fertilization and weed control, and can be maintained and harvested with standard farm equipment. Energy production from a renewable biomass fuel offers reduced emissions, including CO2, NOx, and SO2, as well as agri-business benefits. The program includes farm, pilot-scale combustor, and full-scale power plant studies. Three hundred acres of Alabama farmland have been planted with switchgrass, and costs and techniques of grass production, harvesting options, handling, and preparation are being evaluated. To evaluate the possibility of co-milling coal and grass, studies were conducted at Southern Company's pilot combustion facility to investigate the milling properties of the mixtures. Combustion studies, also conducted at the pilot facility, measured the effects of co-firing methods and quantities on emissions, combustion stability, unburned carbon, and slagging and fouling. Results have been obtained on field processing and handling issues, as well as farm production costs. Pilot-scale tests of co-milling and combustion of blends of switchgrass with coal have been successfully completed. An additional phase of work yet to be completed is full-scale testing of switchgrass co-firing in a 60 MW power plant boiler. For these tests, a pneumatic injection system was designed and constructed at the site. In on-going testing, switchgrass is being conveyed at up to 10% of the total heat input through this system and introduced into the boiler separately from the coal. Testing is scheduled to be completed by mid-2001.