Investigation of the pyrophoric tendency of the powder of corrosion products in an oil tank

Abstract The pyrophoric tendency of the powder of corrosion products and deposits in oil tanks was investigated by performing several series of tests in a modified self-heating experimental apparatus based on the crossing point temperature method. Three samples of the powder of corrosion products and deposits in oil tanks as well as a ferrous sulfide were used as test samples. The corresponding apparent activation energies ( E a s) were obtained: 26.1 kJ mol −1 for the corrosion products of a crude oil storage tank, 27.2 kJ mol −1 for the middle distillate oil storage tanks, and 43.5 kJ mol −1 for ferrous sulfide; the unexposed cross-point for deposits of a crude oil storage tank was at a temperature below 250 °C. Those values of E a s indicated that the corrosion products of the two oil storage tanks showed a stronger pyrophoric tendency than did the deposits of the crude oil storage tanks and ferrous sulfide. Furthermore, the E a values were similar to those of reactions reported for the incomplete oxidation of hydrogen sulfide (H 2 S), thus supporting the viewpoint that H 2 S may be considered the intermediate product for accelerating the self-heating and self-ignition of sulfide at temperatures below 250 °C and may play a major role in inducing fires and explosions in storage oil tanks. In addition, possible sources of H 2 S in self-heating of the corrosion product were largely caused by thermochemical sulfate reduction or thermal decomposition of the organic matter of oil tanks.