Coal assay Coal assay Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel. Coal comes in four main types or ranks: lignite or brown coal, bituminous coal or black coal, anthracite and graphite. Each type of coal has a certain set of physical parameters which are mostly controlled by moisture, volatile content (in terms of aliphatic or aromatic hydrocarbons) and carbon content. Moisture is an important property of
Coal breaker screen (e.g., was of acceptable steam size or smaller). Raw coal often contains impurities such as slate, sulphur, ash (or "bone"), clay, or soil, which requires that it be cleaned before shipment to market. Mine workers sampled the coal as it came out of the mine to determine whether the level of impurity recommended washing (if washing was available). Slate, sulphur, and ash have a higher relative density than coal, and will sink in agitated water. Passing the coal through the tipple was an essential pre-treatment process for coal washing, however, because the impure coal must be of similar sized