Demonstration of pelletized fly ash reinjection for reduction of limestone consumption and ash disposal

The Energy and Environmental Research Center (EERC) has successfully demonstrated a technology conceived by Community Energy Alternatives Incorporated (CEA) for reducing limestone consumption and solid waste disposal requirements from a circulating fluidized-bed combustor (CFBC) operating on fluid petroleum coke. The testing was designed to investigate the potential for reduced limestone usage through pelletization of the collected fly and subsequent recycle to the CFBC. To produce representative results, fluid petroleum coke and limestone from one of CEA`s GWP Power Systems Corporation plants were used as feedstock for the EERC 1-MW{sub th} CFBC. All of the fly ash generated from operation of the CFBC was collected, pelletized, and recycled to the combustor to enhance sorbent utilization. Testing proceeded through five cycles using pellets made from fly ash generated from the preceding test. Limestone usage was reduced approximately 24% from the baseline, limestone-only test, to the fifth cycle at similar sulfur capture efficiencies and total calcium-to-sulfur ratios. Calcium utilization increased from 30.7% during the baseline test to 38.5% for the fifth cycle. Other advantages demonstrated include improved carbon burnout, higher boiler efficiencies, and lower emissions of NO{sub x}, N{sub 2}O, and CO{sub 2}.