Objective A large number of black sediment appeared in the liquid sulfur of the sulfur recovery unit of a high-sulfur natural gas, which led to a series of problems such as the pump shaft stuck of the liquid sulfur storage tank, the blockage of the filter screen, and the performance degradation of the sulfur granulation unit, which seriously affected the normal production of sulfur particles. It is necessary to investigate the causes and develop corresponding countermeasures.

Methods The formation causes of the black sediment were analyzed through elemental composition measurement, overall process analysis, and field experiment.

Results The analysis results showed that the black sediment originate from the injection of liquid sulfur degassing catalyst, and the smolder of the liquid sulfur tank pump accelerates the formation of black sediment.

Conclusions By optimizing the operating parameters of liquid sulfur treatment, improving the liquid sulfur degassing process, replacing the liquid catalyst, and introducing the solid catalyst degassing technology, the black sediment can be eliminated from the source, which can provide the operation and adjustment reference for solving the problems of sulfur production on site.