Steam boiler can be classifiedbase on fuel. One of them is solid fuel such as bagasse, wood and coal. Methods to burning coal can be distinguished by underfeed stoker, overfeed stoker and pulverized coal firing. Pulverized coal firing is generally used for bigger scale of power plant than use stoker firing. The best classification of coal to be used in this method is bituminous type.
The size of coal to be burned should be small and ground so grinding step must be performed by pulverizes coal. Pulverized coal will make combustion occur easily and fast when reach ignition temperature. Pulverized coal should be designed dry by use warm air. Warm Air and pulverized coal are mixed flow though exhauster to furnace and to be burned on temperature about 3000 F. Warm air is taken from heat exchanger process in air heater. Primary air is supplied by force draft fan into pulverizer while secondary fan flow through winbox.