Cement mill - WikipediaPortland clinker is the main constituent of most cements. In Portland cement, a little calcium sulfate (typically 3-10%) is added in order to retard the hydration of tricalcium aluminate. The calcium sulfate may consist of natural gypsum, anhydrite, or synthetic wastes such as flue-gas desulfurization gypsum. In addition, up to 5%.how many types of cement mill in cement plant,Cement Plant Equipment - Cement Ball MillsWe are the leading manufacturer and exporter of cement plant equipment includes cement ball mills, material handling equipment, feeders, classifiers, belt conveyor, cyclones, rotary vane feeders, static classifiers, open circuit ball mills, equipment for cement industry, . Open circuit mills - Continuous gravity discharge type.