Galvanic interaction in self-heating of sulphide mixtures

CIM Journal, Vol. 3, No. 3, 2012
R. Payant, F. Rosenblum, J. E. Nesset, and J. A. Finch Department of Mining and Materials Engineering, McGill University, Montréal, QC
Abstract
Under certain conditions of moisture and oxygen, sulphides can
spontaneously self-heat. We tested a hypothesis that galvanic interaction
between some sulphides can promote self-heating. Galvanic interaction is
controlled by the rest potential difference between sulphides and particle size.
A series of binary sulphide mixtures was tested. Individual sulphides and
mixtures with low rest potential difference did not self-heat, but mixtures of
high rest potential difference did. When testing pyrite-sphalerite mixtures,
self-heating increased inversely with particle size, with the fineness of the
pyrite governing self-heating, indicating the rate-limiting step is the
reduction reaction. The results support the hypothesis that galvanic interaction
contributes to sulphide self-heating. A possible mechanism based on hydrogen
sulphide as an intermediate product is proposed. The understanding gained will
be of interest to those involved in storage, shipping, and disposal of
sulphides.

 
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