Abstract
Previous work has shown that sulphide self-heating occurs in three distinct stages, referred to as Stage A, Stage B and Stage C. In this publication, the focus is the transition from Stage A to Stage B which occurs at ca. 100 °C. Background literature hints that the transition corresponds to the transformation of the rhombic form of elemental sulphur to the more reactive monoclinic form that occurs at 96 °C. A test apparatus is modified for adiabatic heating to track the transition. The results support this transformation of sulphur as being key to the transition, and the transition temperature is thus modified to 96 °C. Variations in a sample’s response under adiabatic conditions are observed and possible reasons are discussed. Testing in adiabatic mode provides new insights into the sulphide self-heating process that complements the test designed to identify propensity to self-heat.
Highlights
Some materials, when exposed to ambient conditions, can exhibit a rise in temperature without requiring an external heat source
The higher values exhibited by rod mill discharge (RMD) are attributed to the fact that after the initial 10 weathering cycles there was more elemental sulphur present compared with the Ni Con sample (Figure 6)
The original hypothesis was that transition from Stage A to Stage B occurs at 100 ◦ C; that Stage A
Summary
Some materials, when exposed to ambient conditions, can exhibit a rise in temperature without requiring an external heat source. Referred to as pyrophoric or self-heating substances, they pose a challenge to the safe handling of materials in storage and transportation. Numerous substances self-heat, ranging from wood chips and powdered milk to coal and sulphide minerals [1,2]. Combinations of sulphide minerals, most notably those containing the iron sulphide pyrrhotite (Fe(1−x) S), commonly encountered in the extraction of base metals (e.g., copper, zinc, lead, and nickel), are prone to self-heating [3,4]. Sulphide self-heating can lead to work disruptions, loss of infrastructure, delays in operations and in some severe cases, loss of life [5]. Dramatic examples include in-situ smelting of ores and resultant fires [5,6] and loss of a ship transporting
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