Investigation of Self-Ignition Risks of Iron Sulfides in the Sour Crude Oil Storage

The sour crude oil and its evaporation react with corrosion and bio-corrosion products of the storage equipment to form iron sulfides.  The pyrophoric nature of iron sulfides leads them to ignite spontaneously and ignite oil and flammable substances.  Self-ignition of iron sulfides can cause serious problems during storage of the sour crude oil.  To investigate the cause of the thermal reaction and the thermal hazard of self-ignition, different kinds of iron sulfides were heated at different heating rates and in different atmosphere.  The reaction heat, onset and peak temperatures, other thermodynamics and kinetics characteristics of iron sulfides in different conditions are analyzed.  It is demonstrated that the presence of oxygen atmosphere seems to be the most important factor to induce the self-ignition.  Moreover, the results showed that the smaller the diameter of iron sulfide is, the lower the onset temperature of self-ignition is.  The injection or supplying with nitrogen into the oil storage equipment should be a feasible approach to prevent the self-ignition.