Waste heat boiler refers to a boiler that uses waste heat from various industrial processes, waste materials or waste heat and the heat generated by the combustion of combustible substances to heat water to a certain temperature. The waste heat boiler can produce hot water or steam for use in other sections through waste heat recovery. Fuel, gas, and coal are burned to produce high-temperature flue gas to release heat. The high-temperature flue gas first enters the furnace, then enters the waste heat recovery device of the front smoke box, then enters the pyrotechnic pipe, and finally enters the waste heat recovery device in the flue of the rear smoke box. The flue gas becomes low-temperature flue gas and is discharged into the atmosphere through the chimney. Because the waste heat boiler greatly improves the utilization rate of the heat released by fuel combustion, this kind of boiler is very energy-saving.