CHARACTERIZATION AND USE OF FLUIDIZED-BED-COMBUSTION COAL ASH

Fluidized-bed-combustion (FBC) technology will become more common as coal-combustion systems are retrofitted to meet air-emissions standards mandated by the 1991 Clean Air Act. FBC ash will present new challenges for coal-combustion by-product management. Calcium-based sorbents added to the combustion system of FBC make the properties of the resulting ash different from electric-utility fly ash. Rccycling options, used to divert electric-utility ash from landfills, will have to be reevaluated for FBC ash. FBC ash from Central Soya Company's circulating FBC boiler, previously located in Chattanooga, Tennessee, was sampled over a 2-year period. The ash was analyzed for chemical and physical properties and evaluated as a concrete admixture. Results show that concrete strength and long-term durability are compromised by substituting FBC ash for portland cement. The high pozzolanic activity of the ash and the decrease in leach-ability of some constituents with increasing ash content in concrete suggest that FBC ash has potential to be a good material for hazardous-waste solidification and stabilization.