CO2 sorbent attrition testing for fluidized bed systems

The extent and causes of attrition for three possible carbon dioxide capture sorbents for fluidized bed systems were investigated. The sorbents were crushed limestone, lime-based pellets containing calcium aluminate cement binder, and the same pellets coated by mesoporous silica without a binder. An air-jet apparatus based on the ASTM D5757 standard, with several improvements in testing capabilities, was used to conduct experiments for varying attrition periods, gas velocities, temperatures, relative humidities and initial particle sizes. The results indicate that the cement-bound pellets suffered similar or worse attrition than crushed limestone, and were highly sensitive to humidity because of the hygroscopic cement and formation of calcium hydroxide. The silica-coated pellets were found to have high attrition resistance in dry air at 500 °C. After 24 h of operation, compared to the coated sorbents, the lime mean diameter reduction and Air Jet Index were greater by factors of 2.4 and 3.4, respectively.