Combined Removal of Surface Moisture and Dust from Feed Coal for Coal Dry Cleaning with an Air-solid

Dec.2005J. China Univ. of Mining Tech (English Edition)Combined removal of surface moisture andDust from Feed Coal for Coal Dry Cleaningwith an Air-solid fluidized bedYANG Guo-hua, ZHAO Yue-min, Chen Qing-ruI Ningbo University, Ningbo, Zhejiang 315211, ChinaSchool of Chemical Engineering and Technology, China University of Mining Technology, Xuzhou, Jiangsu 221008, ChinaAbstract: A demonstration plant and a commercial plant employing coal dry cleaning technology with an air-solidfluidized bed were built in China. The operation practice of these two plants shows that the surface moisture and thefines or dust of feed coal must be well controlled as low as possible. For this purpose, a new process of combinedremoval of surface moisture and dust from feed coal using a vibrated fluidized bed dryer was investigated in a batch testapparatus and a pilot test system. A mathematical model on drying kinetics of coal surface moisture was developed andthree empirical formulas of the model coefficient involving the main operating variables were determined based on theest results from the batch test apparatus. The mathematical model shows that the surface moisture retained in coduring drying decreases exponentially with drying time. According to this model, a new divisional heat supply mode, intemperature into the rear part of the dryer, was employed in the pilot test system. The pilot tests show that 1)the newdivisional heat supply mode is effective for lowering down the average temperature and reducing the total heat loss ofthe outlet gas off the dryer, 2)the moist coal of about 60 g/kg surface moisture contentcan be dried to about 10 g/kg, andsimultaneously the fines(