The modern foundry producer is interested in the production of the best quality product without compromise - wetting can be a cause of some problems in the metals casting process.
Coal as mined is not a worthy material for modern combustion, owing to its large quantity of sulfur compounds amongst others. When burned, these release toxic gases. Coal washing reduces the amount of these gases released on burning - by helping to remove them from the coal. The addition of zinc chloride to a coal beneficiation process can lead to the production of activated carbon products.
Foundry burn on is a name given to a wide variety of surface defects that are produced at high heat during the metal sand casting process. Carbonaceous materials in the mold, such as high-anthracite coal dust can prevent such defects from forming.
Bentonite is a form of clay that has found numerous uses over its thousands of years of use - but perhaps most notably in foundries from the 1900’s onwards, alongside powdered coal.
Anthracite is one of the hardest forms of coal and is known for its high carbon content. Aside from as a fuel, anthracite finds use in high temperature applications - especially when calcined - due to its relatively high resistance to thermal shock, strength and chemical inertness.