Chemical looping combustion of coal in interconnected fluidized bed with NiO/Al₂O₃ oxygen carrier

The chemical looping combustion of coal with NiO/Al₂O₃ oxygen carrier was experimentally investigated in a 1 kW_th interconnected fluidized bed. The carbon conversion η_C,coal, the conversion of gaseous products, the carbon capture efficiency η_C,cap and the coal combustion efficiency η_combust were calculated and discussed. Several influencing factors including the temperature t_FR, excess air coefficy α, the ratio of steam flow rate in the loopseal to the feed coal S_LS/C, the ratio of steam flow rate in the fuel reactor to the feed coal S_FR/C were examined. The results indicate that the increase in either t_FR or S_LS/C is favorable for increasing η_C,coal and the conversion of gas products from coal gasification. A larger α can also give a higher η_C,coal. With the S_FR/C increasing from 0.8 to 1.6, η_C,coal first increases and then decreases with the maximum at S_FR/C=1.2. η_combust has the same trends as η_C,coal; it is mainly affected by the loss of carbon in the fly ash. Contrary to α or S_LS/C, increasing T_FR can give a higher η_C,cap.