Zhundong coal circulating fluidized bed boiler

The invention provides a Zhundong coal circulating fluidized bed boiler. A heating surface comprises a buried pipe and a membrane-type wall, a hearth comprises a three-return-stroke flue gas channel,the cross section of the channel comprises a front membrane-type wall, a rear membrane-type wall, a left membrane-type wall, a right membrane-type wall and a middle membrane-type wall and is in the shape which is the same as or similar to that of the Chinese character 'ri' or 'yue', a U-shaped flue gas channel is formed between the first return stroke and the second return stroke, and a U-shaped flue gas channel is formed between the second return stroke and the third return stroke. Secondary air is prepared. A cyclone separator is arranged outside the hearth, the convection heating surfaces of a tail shaft flue are arranged in a large pitch row by row, and the fluidization speed of a dense-phase region of the hearth is 3-4m/s, the combustion temperature is 850-900 DEG C, and the inlet flue gas temperature of conv