Evaluation of the pyrophoric risk of sulfide mineral in storage

Spontaneous combustion of the sulfide mineral is one of the major challenge during the sulfide mineral storage and transportation. To evaluate the pyrophoric risk of the sulfide mineral, the thermo-gravimetry and differential scanning calorimetry (TG-DSC) technique were employed to evaluate the thermal behavior of the sulfide concentrate sample. The samples were heated from ambient temperature to 1000 °C at four heating rates. The thermodynamic parameters were obtained from the experimental data. Based on Semenov model, the self-accelerating decomposition oxidation temperature (SADT) and temperature of no return (TNR) were calculated. Assuming that the sulfide stockpile is under quasi adiabatic condition, the auto ignition delay time (AIDT) of the sulfide stockpile was predicted. Results indicate that the oxidation of sulfide concentrate sample under different heating rates undergoes a similar process: an initial physical absorption stage, a subsequent chemical absorption stage and a final reaction stage. The thermal behavior of the sulfide mineral at different heating rates indicates that the more rapid the heating rate, the higher the onset and peak temperature. As the heating rate increases, the AIDT decreases from approximately 20 to 12 days under a given set of conditions. The information obtained in the present study is useful for mitigating hazards due to the spontaneous combustion of a large pile of sulfide mineral in storage.