Why do circulating fluidized bed boilers use slag coolers?

Circulating fluidized bed boiler is the most industrialized clean coal combustion technology. Circulating fluidized bed boiler adopts fluidized combustion, and its main structure includes combustion chamber (including dense phase zone and dilute phase zone) and circulating furnace (including high temperature gas-solid separator and material return system). Compared with bubbling fluidized bed combustion technology, the biggest difference is that the running wind speed is high, which strengthens the heterogeneous reaction processes such as combustion and desulfurization, and the boiler capacity can be expanded to a large capacity (above 600MW) acceptable to the power industry. At present, the circulating fluidized bed boiler has well solved the basic problems of heat, mechanics, materials science and engineering problems such as expansion, wear and overheating, and has become a kind of flame-retardant solid fuel (such as coal gangue, oil shale, municipal garbage, sludge and other wastes).