Attrition and sulfation of calcium sorbent and solids circulation rate in an internally circulating fluidized bed

In this study, an attempt was made to use internally circulating fluidized bed (ICFB) as a desulfurization reactor. One of the special features of the ICFB is high attrition of the particles in the bed, which would remove the product layer of sulfation and increase the utilization of the calcium sorbent. The other features are easy control of the solids circulation rate and gas residence time in the bed by individually adjusting the gas velocity in the annulus and the draft tube, which would increase the efficiency of the desulfurization. process. The effects of the operating parameters including relative humidity, the particle size of calcium sorbent, superficial gas velocity in the draft tube, total superficial gas velocity in the bed and inlet concentration Of SO2 on attrition rate, calcium sorbent conversion and solids circulation rate in the ICFB were investigated. It was found that a higher relative humidity had a higher calcium sorbent conversion and a lower solids circulation rate. A smaller particle size of calcium sorbent had a higher attrition rate and a higher solids circulation rate. In addition, a higher superficial gas velocity in the draft tube at the same total superficial gas velocity in the bed had a lower calcium sorbent conversion. However, the solids circulation rate might have a maximum value with respect to the gas velocity in the draft tube. A higher total superficial gas velocity in the bed had a higher attrition rate and a higher solids circulation rate, but had a lower calcium sorbent conversion. Moreover, the effect of the inlet concentration of SO2 was negligible from 200 to 500 ppm. Finally, an attrition rate model proposed in this study could predict the elutriation rate satisfactorily. (C) 2002 Elsevier Science B.V. All rights reserved.