Flash Drying Characteristics with Sub-Bituminous Coals in a Pressurized Micro-Riser Reactor

Clean coal technologies, such as pressurized fluidized bed combustion, integrated gasification combined cycle, and so on, have been widely adopted due to higher efficiencies and superior environmental performance in the long term. Also, the usage of low grade coals with high moisture content has increased in the world because of its abundance and relatively inexpensiveness. However, technical issues such as pre-drying or dewatering low grade coals should be solved to develop cost competitive systems since advanced systems generally operate under high pressure. In this study, the flash drying characteristics of 2 different types of coals (moisture contents: 14.7wt% and 18.1wt%) were determined in a micro-riser. The micro-riser consisted of M.F.C., disk type feeder, rolled tube with oven(tube length: 2m, 4m, 6m), cyclone, back filter and back pressure regulator. The effect of operation conditions, such as pressure(up to 40bar), drying temperature (up to 600^oC), and residence time (up to 1sec), on drying ratio were investigated. As drying temperature and pressure increased, drying ratios increased from 25% to 73%.