The experimental study of fly ash decarbonization on a circulating fluidized bed combustor

Fly ash is a by-product of coal-fired power plants, whose production is huge. As the coal resources are in short supply in recent years, most circulating fluidized bed (CFB) boilers in China burn hard coals, thus, the carbon content in the fly ash is much higher than expected. The high carbon content in the fly ash limits the potential utilization as building materials. At present, the decarbonization method of high carbon content CFB fly ash is mainly fly ash recirculation combustion (FARC). Because of the huge difference between original boiler operating conditions and fly ash ideal combustion state, the decarbonization effect is disappointed. Therefore, a series of fly ash decarbonization experiments were carried out on a bench-scale CFB combustor designed on fluidization properties of fly ash, and the decarbonization characteristics were discussed. Results show that fly ash requires a minimum sectional thermal load of 0.42 MW/m2 for continuous and stable combustion in test combustor, corresponding to the critical carbon content in the fly ash is 18%. The maximum decarbonization efficiency of the test CFB combustor is approximately 75%, which is much higher than that of FARC.