Performance study on Ca-based sorbents for sequential CO2 and SO2 capture in a bubbling fluidised bed.

High temperature CO 2 and SO 2 sequential capture in a bubbling fluidised bed was investigated using a natural limestone and synthetic composite pellets. Calcination was conducted under oxy-combustion conditions, while carbonation and sulphation occurred in an air-combustion atmosphere. The goal of sequential capture of CO 2 /SO 2 is to desulphurise the flue gas first, followed by cyclic carbonation and calcination. Here, fresh sorbent is first used in the cyclic calcination/carbonation process and then the spent sorbent is sent for sulphation. The pellet carrying capacity is 0.29 g CO 2 /g sorbents for the first cycle, while that of natural limestone is about 0.45 g CO 2 /g sorbents. The carrying capacity first fell and then finally plateaued around 0.10 and 0.12 g CO 2 /g sorbents for limestone and pellets respectively. The SO 2 carrying capacity for limestone and pellets after 20 cycles of CO 2 capture was 0.17 and 0.22 g SO 2 /g sorbents respectively. This indicates that the sorbent spent in CO 2 capture can be effectively reused for SO 2 removal. Abrasion was observed to be the main mode of attrition, but some agglomeration was also found with increasing number of cycles and this may be a concern in the use of Ca-based sorbent for CO 2 or SO 2 fluidised bed capture. • Sequential capture of carbon and sulphur was investigated with a natural and synthetic limestone pellets. • Pellets performed better cyclic activity over a large number of cycles. • Experienced some weak agglomeration which can be destroyed by gently shaking or stirring. • Intensified attrition created cracks on the surface of limestone, however smoother surface on the pellets. [ABSTRACT FROM AUTHOR]