Emissions in Shinas due to sulphide combustion

MUSCAT: Experts from the Earth Science Research Centre at Sultan Qaboos University (SQU) have come up with a scientific explanation for the smoke emissions from a closed copper mine in Shinas in North Al Batinah Governorate. Rumours had been spreading through the social media about hot gas emissions from the closed copper mine.
Prof Sobhy Nasr, Director of the Earth Science Research Centre, said the smoke in the area was caused by the burning of sulphides in the closed mine due to humidity of the atmosphere, oxygen uptake and other natural conditions.
Prof Nasr said that several previous studies about copper sulphide mine residues, such as those found in Shinas, have shown that moisture in the air and ambient temperature can increase due to self-combustion of the sulphides in such mines. Quoting earlier studies, Prof Nasr said that humidity of air and ambient temperature can increase self-heating of sulphides.
Self-heating of sulphides may increase the temperature and may lead to spontaneous combustion, which is particularly difficult to control. Active ores that were left in underground mines for a prolonged duration oxidised rapidly and self-heated. Problems are also encountered during crushing and handling processes, where sulphide ores are commonly introduced to humid air and oxygen, promoting self-heating.
Self-heating of sulphides was also periodically reported during storage and transportation. Self-heating is an exothermic oxidation reaction. A material is self-heating when heat generated within the material, without external heat input, is greater than the heat being dissipated to the surroundings.
Pyrrhotite and pyrite have been reported as the most reactive and prone to self-heating out of other sulphide minerals due to the high iron-deficiency.
Numerous factors account for sulphides to become self-heating in nature. Some of the major factors are humidity of the atmosphere, moisture content, oxygen uptake, particle size, pyrrhotite content, ambient temperature and pH.
– ONA