Читать книгу Coal-Fired Power Generation Handbook - James Speight G., James G. Speight - Страница 71

The water clarification plant receives all the slurry from the washing plant, separates the -48 mesh fraction for cleaning, and returns the water for reuse. The 48 mesh fraction flows to froth flotation cells, where it is mixed thoroughly with a reagent (light oil). The coal accepts a coating of oil and floats off the top of the liquid to a disc filter, where the excess water is drawn through a fabric by a vacuum. The water is recirculated to the washer, and the fine coal is transported to loading or to a dryer.

The refuse does not accept the oil coating and sinks, to be removed with most of the incoming water to a static thickener. The thickener is a large, circular, open tank, which retains the water long enough to permit the particles of refuse to sink to the bottom. Clarified water is removed from the surface by “skimming troughs” around the perimeter of the tank and is recirculated to the cleaning plant.

The tank is equipped with a rotating rake, which rakes the fine refuse from the bottom of the tank to the center of the tank, where it is collected by a pump and transferred to a disc filter. The filter removes part of the water for recirculation and discharges the solids as refuse.