Combustion of waste sludge with oxygen and carbon dioxide at a circulating fluidized bed

Cold bed and pilot bed tests using circulating fluidized bed (CFB) were conducted to apply oxy-fuel technology for waste sludge combustion as a carbon capture and storage technology. In preliminary, the hydrodynamics of circulating fluidized bed was observed in the cold-bed setup to simulate the 30KW_th CFB oxy-fuel pilot test bed, in which the superficial velocity for fast fluidization was determined over than 2.5m/s. The minimum fluidization velocity (U_mf) was estimated as 0.104 m/s. In the pilot test, air and oxy-fuel combustion experiments for waste sludge and biomass were conducted with a flue-gas recirculation unit. The oxygen injection rate for oxy-fuel combustion was optimized from 21% to 25%. In 15% of flue-gas recirculation rate, carbon dioxide concentration in flue-gas was achieved over 90% of purity, which verified the possibility of oxy-fuel technology as CCS ready technology in a CFB combustion system for burning waste sludge and biomass.