The fundamental requirements of a coal washing plant are to recover the raw coal and produce waste that may be safely dumped with no risk of long-term pollution or combustion.
Coal slurries (slimes) with a grain size below 1 mm are generated during coal washing in coal preparation plants. They are separated during dewatering of the washed coal products and then, after slime thickening, can be either a commercial product or go to settling ponds etc. as a waste product. This depends mainly on their quality parameters. Provided the quality parameters (ash, sulphur content and calorific value) are favourable, the slurries are blended with fine coal, creating a mixture for power generation.
In the past, the majority of slimes were accumulated in settling ponds and treated as waste from the coal washing process as they were of little use to commercial users. In reality many of these wastes can now be used as fuel for the power generation.
The other main benefit of the thickening & removal the slimes is that the settled water can then be reused in the washing process helping to keep down the cost of bringing in fresh water 🙂
http://www.solidliquid-separation.com/Thickeners/thickener.htm
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