Calcination of pulverized limestone particles under furnace injection conditions

The calcination behaviour of limestone particles (6-90 mu m) under furnace injection conditions (1073-1673 K) was determined. Scanning electron microscopic analysis of partially calcined particles revealed that calcination occurred over the total (internal and external) surface area with different calcination rates at different locations. A model consistent with experimental rate data indicated that the calcination rate was influenced by heat transfer, mass transfer and chemical kinetics. 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 CO2 offered the major resistances to calcination. For particles < 10 mu m and gas temperatures < 1073 K, chemical kinetics were rate-controlling.