Coal Gangue is a kind of solid waste discharged from coal mining and coal washing. It is also a kind of black-gray rock with lower carbon content and harder than coal. Its main components are Al2O3 and SIO2. In addition, it contains various amounts of Fe2O3, Cao, MgO, Na2O, K2o, P2O5, SO3 and traces rare elements (gallium, vanadium, titanium ...Web