The waste heat boiler mainly adopts the flue pipe heat exchange during the working process, and the temperature of the lower wall surface of the metal heating surface and the discharge temperature of the hot fluid are roughly in a multiple relationship. Regarding the smoke tube heat exchanger, if the metal heating surface wall temperature is required to be no less than 150°C, the exhaust gas temperature is usually not less than 300°C, otherwise it will cause low-temperature condensation and corrosion.

　　In its low-temperature operating conditions, the exhaust gas temperature of the waste heat boiler is not lower than 450°C based on the safety factor of 1.5 times. At this time, the waste heat boiler can recover about 0.5 tons of heat, and the recovery efficiency is still very low. In addition, the temperature at this time is only a check temperature. When the operating conditions need to be adjusted due to operating requirements, there is no way to directly stop the adjustment and control of the wall temperature.

　　When the temperature of the metal wall on the heating surface of the tail is lower than the condensation point of sulfuric acid vapor during operation, liquid sulfuric acid will be formed on the surface. For a long time, corrosion caused by condensation on the heating surface of the tail of the heat exchange equipment has often occurred. As a result, in the design of waste heat boilers, it is necessary to increase the exhaust gas temperature or use non-metallic materials with poor heat transfer to reduce the occurrence of condensation and corrosion, but the problem is still not basically solved. Even so, the waste heat recovery equipment will often show corrosion after one to two years of operation until it is perforated.

　　It can apply its isothermal heat transfer to reduce the exhaust gas temperature, but the lower wall temperature of the heated surface of its tail will still be lower than the acid dew point temperature, and corrosion caused by condensation cannot be allowed, and heat pipes are generally produced and accumulated without condensation. The gradual aging of the gas and the effect of gravity cause the uneven thickness of the heat transfer liquid film to cause unstable heat transfer.