Oxidizing-gas-based passivation of pyrophoric iron sulfides

Iron sulfides, as a class of common pyrophoric materials, are widely formed and deposited on the internal surface of transportation, storage, and refinery equipment in oil, petrochemical, and chemical industries. To reduce the self-heating risk from iron sulfides, this paper proposes a practicable method for inhibiting pyrophoric iron sulfides. Unlike existing inhibition methods, an oxidative gas mixture with a limited oxygen concentration and flow rate was employed in this study. The limited oxygen concentration and flow rate were determined using the following: (i) a combination of a trial-and-error method with a model developed through an experimental study and (ii) the support vector machine (SVM). In our experiments, the sulfurization and oxidation apparatus described in a previous study was improved, and then, the effects of mass deposition, concentration, and flow rate of oxygen on the self-heating property of pyrophoric iron sulfides were investigated. The results showed that the tendencies of the maximum oxidation temperature of pyrophoric iron sulfide versus the mass per unit area and oxygen concentration exhibited an approximate logistic fit, and for the oxygen flow rate, the tendency followed a log-normal fit. The developed SVM-based model is highly reliability in predicting the maximum oxidation temperature. Accordingly, a set of procedures for suppressing pyrophoric iron sulfide was given and explained by its implementation in a distillation column. Our proposed method was confirmed to be more effective, economic, and cleaner for the inhibition of pyrophoric iron sulfides.