This boiler adopts the high-temperature volute declining cyclone separator; the separator is arranged on the furnace exit. The separator inlet smoke temperature is about 850～1000℃. The separator lower is equipped with the back-feeding device. The separated flying-ash should be sent back to the furnace for burning through the back-feeding device. The back-feeding pore is about 1200mm far away from the air hood on the height direction. To adjust the air volume, the back-feeding air should connect to the air door and the flow meter. Starts from the separator outlet shell, the separated smoke flows across the horizontal flue and then it enters into the tail flue to heat the tail heating surface.