The coal feeder feeds the coal to the coal chute and then the coal enters to the hearth. The air required by the boiler combustion is supported by the primary air and secondary air fan. The air sent by primary air fan  is preheated by the primary  air preheater and then is introduced to the water-cooling air chamber under the boiler via the air duct at the left and right sides, and then it enters the combustion chamber through air hood on the water-cooling air distribution board. The air sent by secondary  air fan is preheated by the secondary air preheater and is sprayed to the hearth through the spraying holes on the front and the back wall of the hearth, then is supplemented with air to strengthen the disturbance and mixing. Fuel and air are mixed and burned in fluidized state in hearth, and exchange heat with the heating surface. The fume inside the hearth(carrying a lot of unburnt carbon particles) burns ad releases heat on the upper part of the hearth. The fume leaving from the hearth and carrying a large number of materials is separated by the volute steam cooled cyclone separator, most of the materials are separated out, then they are returned to the hearth via the return feeder, thus realizing circulating combustion. The fume separated is exhausted to the bag filter for dedusting and exhausting by the tail flue via the steering chamber, high temperature superheater, low temperature superheater, economizer, the primary and secondary air preheater by tail flue bag filter for dust removing the back out into the electricity.