Self-heating: Estimation of the heat release coefficient QA for Ni- and Cu-concentrates and sulphide mixtures

•The self-heating heat release rate QA (J g−1 min−1) for sulphide materials were determined.•The QA for sulphide concentrates were higher than those of sulphide mixtures.•No clear relationship was found between the energy of activation (Ea) and QA.•The (Ea) and QA should be used to classify self-heating sulphides.

The self-heating heat release rate coefficient QA (J g−1 min−1) for Ni- and Cu-concentrates and sulphide mixtures has been determined. The QA for the concentrates were higher than those of the sulphide mixtures. This difference in QA between the materials, for which the reaction causing self-heating is surmised to be the same, may be attributed to differences in specific heat capacity Cp, a steric effect, and in the case of the mixtures, a galvanic effect. The lack of clear relationship between QA and the energy of activation Ea suggests at least both be measured to characterize the self-heating of sulphide materials.