Pulverized coal, air, and sorbent are injected tangentially toward the wall through tubes in the annular region of the combustor to cause cyclonic action. In this manner, coal-particle combustion takes place in a swirling flame in a region favorable to particle retention in the combustor.
Secondary air is used to adjust the overall combustor stoichiometry.
The ceramic liner is cooled by the secondary air and maintained at a temperature high enough to keep the slag in a liquid, free-flowing state. The secondary air is preheated by the combustor walls to attain efficient combustion of the coal particles in the fuel-rich combustor. Fine coal pulverization allows combustion of most of the coal particles near the cyclone wall. The combustor was designed to retain a high percentage of the ash and sorbent fed to the combustor as slag. For NO x control, the combustor is operated fuel rich, with final combustion taking place in the boiler furnace to which the combustor is attached.