Definition - What does Coal Washing mean?
Coal washing is a process that is undertaken in a coal washery or coal preparation plant (CPP) where coal is refined or cleaned of impurities. Coal washing involves using water, mechanical techniques and relies on gravity and the difference of density between coal and it's impurities which are usually more densely packed due to the fact that they are inorganic.
Safeopedia explains Coal Washing
Coal is a type of sedimentary rock that is formed by buried vegetation that is transformed by pressure and heat over long periods of time. Coal will eventually turn into diamond formations with enough time, pressure and heat. Impurities include slate and other non-organic rocks etc.. Washing coal increases its efficiency and quality, therefore increasing its price. It can also help to reduce emissions from burning.