Cause Analysis and Prevention Measures of Fire and Explosion Caused by Sulfur Corrosion

Abstract With the rapid development of the petrochemical industry, sulfur-related devices are increasing. In this paper, a fire accident occurred in a petrochemical storage tank of a petrochemical enterprise. Through analysis, we found that the direct cause of the accident was the spontaneous combustion of ferrous sulfide (FeS), which caused the explosion of the oil and gas mixture between the floating disk and the tank top. In addition, we analyzed the corrosion of aluminum floating plates in oil tanks by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). The analyses showed that although AlMn1Cu aluminum alloy has high corrosion resistance, the material composition contains impurity elements such as silicon and iron, which weakens the corrosion resistance of aluminum alloy, and the intergranular corrosion and corrosion effects such as pitting corrosion cause cracks to form in the floating disk. The oil and gas that volatilize in the oil tank diffuse through the pores between the floating plate and the top of the tank to form an explosive mixture of oil gas and air. Next, the corrosion products of the manhole cover and the edge of the floating plate were sampled and were analyzed the sulfur and iron contents by elemental analysis. The results showed that the sulfur content in the sample of the manhole of the No. 1 tank was 25.04wt%, and the sulfur content in the sample at the edge of the floating plate was 7.49 wt%. This was owing to the manhole at the bottom of tank No. 1 is not in contact with air. The edge of the floating plate of tank No. 1 has a low sulfur content due to the long-term contact with air and the burning process during an accident. Using Fault Tree Analysis (FTA), we conclude that the necessary conditions for the accident are appropriate heat storage conditions. The key factors are bad desulfurization effect on the refining process, sulfur in the crude oil, nonresistance of the tank material to corrosion and presence of S2- in the tank. Finally, corresponding countermeasures are proposed.