Objective The aim is to solve problems such as the rise of the process gas outlet temperature of the waste heat boiler, the increase of the system pressure difference and the forced shutdown of the sulfur furnace due to the fouling and blockage of the process gas side of the waste heat boiler during the operation of the sulfur recovery unit.

Method The gray-white powdery blockage scale found after the shutdown inspection was analyzed, and the source of impurity elements was systematically analyzed.

Result Laboratory analysis revealed that the main components of the blockage scale were oxides of two kinds of impurity elements, iron and silicon. It was determined that the impurity elements entered the acid water stripping mainly through the atmospheric and vacuum sewage, and then entered the sulfur furnace from the ammonia-containing acid gas of acid water stripping. After the above impurity elements entered the sulfur furnace, they were dehydrated and oxidized to form their oxides attached to the inner wall of the waste heat boiler tube bundle, which caused the blockage of the tube bundle over time.

Conclusion In order to prevent impurities from entering the sulfur furnace, the fouling problem of the sulfur furnace was effectively solved by reducing the temperature of ammonia-containing acid gas, strengthening the dehydration of ammonia-containing acid gas and reforming the process of atmospheric and vacuum sewage, so as to ensure the long-term stable operation of the sulfur recovery unit.