An investigation of CaO sulfation mechanisms in boiler sorbent injection

A laboratory differential reactor study was conducted at temperatures of 975–1,275 K to investigate CaO sulfation mechanisms with calcine (CaO) samples derived from pulverized limestones and dolomites, and hydrated limes. The limestones had 8–115 μm mean particle sizes, a range applicable for boiler sorbent injection for SO2 control. Under conditions applicable for boiler sorbent injection, the sorbent performance, in terms of initial reaction rate and saturation utilization, was limited by the SO2 pore diffusion rate and by premature pore mouth plugging by CaSO4 product and, thus, depended on CaO particle size and pore size. Hydrated lime and Na2CO3‐promoted limestones showed performance superior to that of limestones, because they produced calcines with larger pores. Intrinsic reaction rate as reported by Borgwardt and Bruce (1986) was observed at temperatures below 1, 100 K.