Drying Brown Coal in Steam-Heated, Steam-Fluidized Beds

Removal of moisture in steam-fluidized, mainly steam-heated, fluidized beds makes possible significant energy savings over conventional forms of large-scale drying. The systems are described and their application to brown coal is reviewed. In this application the use of the system to permit meeting diurnal variation in power-station output, and the use of triple-effect drying to minimise coal usage and to avoid the necessity of recovering in the turbines the energy in the steam from the last dryer are discussed. Moisture-equilibrium of brown coal in superheated steam is reported. To facilitate the rapid adoption of the systems proposed, studies are being made of heat-transfer to dried coal, of moisture equilibrium in pressurized and vacuum systems, and of the use of carrier solids for drying lump materials.