In recent years, at China, the coal washing rate has increased rapidly, but the processing and recycling method is very extensive. Actually, while coal washing, here will produce many byproducts: middings coals, coal slime and coal gangue etc. Among them, coal slime has high water content, high viscosity and low calorific value, so it always is regarded as waste. Just last year, 200 million tons of slime were wasted.
Since the slime particles are very fine, so the dewatering is very difficult. After the plate and frame filter press, the cake moisture will be about 25% (chamber filter press). Once it is dried, it will fly everywhere, and once rain, it will flow everywhere, so it's a serious pollution source. Additionally at present, a large part of coal tailing is mixed into the coal concentrate for sale. Actually this greatly reduces the washing effect of raw coal. Beside that, some are used for power plants, but it might reduce the thermal efficiency of the boiler and pollute the air. In fact, the slime can be turned from a wast into a treasure.
At present, here is a good solution to solve the problem, namely via deep dewatering, make the coal tailing become a fuel with easy transportation and storage. The complete technology is called “large-scale cyclone depolymerization coal slime hot air drying process”. It can solve the problems of uneven drying, coal flying and high cost in the traditional process, and can avoids the secondary pollution from the source. With this new technology, the final cake moisture can reduce by 14-25%, and the calorific value can increases by 25%-35%.