CALCINATION OF PULVERIZED LIMESTONE PARTICLES UNDER FURNACE INJECTIONCONDITIONS

The calcination behaviour of limestone particles (6-90 mu m) under fur nace injection conditions (1073-1673 K) was determined. Scanning elect ron microscopic analysis of partially calcined particles revealed that calcination occurred over the total (internal and external) surface a rea with different calcination rates at different locations. A model c onsistent with experimental rate data indicated that the calcination r ate was influenced by heat transfer, mass transfer and chemical kineti cs. Internal temperature and CO2 partial pressure gradients produced a location-dependent calcination rate. For particles > 20 mu m and gas temperatures > 1473 K, external heat transfer and pore diffusion of CO 2 offered the major resistances to calcination. For particles < 10 mu m and gas temperatures < 1073 K, chemical kinetics were rate-controlli ng.