Air preheater, which use the high-temperature smoke gas after reaction or combustion to preheat the low-temperature air participates in reaction or combustion, can improve heat exchange efficiency and reduce energy consumption. As the gas-air heat exchanger, it can not only reduce the high-temperature smoke gas to the specified temperature, but also use the recovered heat to preheat the low-temperature air. Air preheater is one of the core equipment of energy recovery and utilization in chemical production, so it is widely used in high energy consuming processes such as carbon black production, coal gasification, solid waste treatment, metallurgy, etc.