Experiment Investigation on Spontaneous Combustion of Iron Sulfides’ in Oil Tank

With sulfur-contained oil tanks undergoing chemical corrosions, the corresponding products (i.e. rust, mainly comprising of Fe2O3, Fe3O4 and Fe (OH)3) would react with hydrogen sulfide, sulfur, mercaptan sulfur and other active sulfur contained in the oil to produce highly oxidizing iron sulfide, which is liable to cause fire and explosions upon exothermic reactions. In this paper, the corrosion induced by low-temperature wet H2S and natural oxidations of corresponding products within the sulfur-contained oil tanks are simulated. An analysis is also made on the temperature changing patterns during the sulfidation of Fe2O3, Fe3O4, Fe (OH) 3, and their mixtures as well as in the natural oxidation process of sulfide. Research results indicate that due to the strong oxidation tendency revealed by ferrous sulfide generated from reactions between Fe2O3, Fe3O4, Fe (OH) 3, and their mixtures with wet H2S under anaerobic conditions, it can react with oxygen in the natural air violently to release a lot of heat. The higher the content of Fe2O3 and Fe3O4, the greater the risk of spontaneous combustion would be. Moreover, the oxidation of iron sulfide undergoes three phases in natural environment, i.e. oxidation induction, oxidation incubation, and oxidation acceleration.