Combined process of air classification and coal cleaning with air-solid fluidized bed

A force balance or motion equation of a particle in air-solid fluidized bed was set up and analyzed. An appropriate size fraction which could be effectively separated in air-solid fluidized bed was determined by theoretical analysis and tests. The problems in controlling upper size and lower size of feed into an air-solid fluidized bed were discussed, and then an air classification technology of moist raw coal was introduced. Pilot Test results show that 1) the air flow has a good 'dust-washing' effect on the surfaces of coarse coal particles in air classification, and nearly all coal dusts smaller than 1 mm were washed off from the coarse particles by air flow. As a result, the coal dust content is as low as 0.2% in the coarse particle product. This is very favorable for stabilizing the fluidized bed density and reducing the burden of medium purification; 2) air classification has a 'clean' effect on fines product. As far as the treated coal is concerned, the ash of fines product obtained by air classification is 1.7% lower than the ash of the same size fraction in feed, and 7.5% less than the feed ash because of the density difference between the clean and the waste. A combined process of air classification and coal cleaning with air-solid fluidized bed is put forward, which can optimize coal dry cleaning process, and then reduce the construction and operation costs by more than 50%.