Air preheater is a kind of heat exchange equipment. There is a large heat difference between the two media to recover heat. Generally, high temperature flue gas and air are used for heat exchange as combustion air to improve the thermal efficiency of the boiler. Usually, the air preheater is one of the parts of the waste heat boiler. It is generally arranged on the heating surface of the tail of the flue gas, which can solve the problem of low temperature and corrosion of the air inlet, and is w