Steam boiler can be classified by fuel. One of them is solid fuel which contains coal as fuel in steam boiler. Coal can be classified based on percentage of volatile matter, ash, fixed carbon and moisture (see table 1). Based on these matter coal can be named as peat coal, bituminous coal (1), bituminous coal (2) and anthracite.
|Table 1: Classification Coal in Steam Boiler|
Source: The Boiler Operators Handbook - graham & Trotman
Percentage of volatile matter can be defined as percentage of coal component exclude moisture, which is heated until temperature 905 C, then measure the weight loss. Percentage of moisture is percentage of wetness content or condensed liquid in coal which can be dried on temperature 105 C. Percentage of fixed carbon is percentage of carbon content when volatile matter is driven off. Percentage of ash is a residue from firing coal which can be burned.
High percentage of volatile matter will make coal can be burned quickly and more generate smoke and low percentage of volatile matter coal can be burned slower and produce less smoke.