Understanding, Managing and Preventing Spontaneous Combustion
There is a good deal of confusion in the mining industry regarding the key causes of Spontaneous Combustion, and just as much uncertainty around effective management and prevention strategies. The uncertainty is primarily a result of the distinctly different forms that the issue displays. Conventional rapid sulfide oxidation can often go unnoticed for many years. Visual cues could include steam vents, surficial native sulfur deposits or vegetation dieback zones across mine waste rock piles, but it also passes unnoticed at many sites. If sulfide oxidation, which normally generates acid and metalliferous drainage (AMD), proceeds very rapidly in the presence of a secondary fuel such as some reactive form of carbon in the mine wastes, the results are generally more obvious, challenging and disturbing.
Coal, bituminous shales or graphitic shales have the potential to auto-ignite at the high temperatures generated by some sulfide oxidation processes. Smoke discharging from waste rock piles is the most obvious indicator of carbon combustion generated by sulfide oxidation. Once ignited, carbon sources within mine wastes are difficult to extinguish. Fortunately, limiting air entry to mine wastes is important for decreasing both the potential for ongoing rapid sulfide oxidation, as well as retarding carbon oxidation.
Many operations cannot resist the impulse to dowse their smoking rock piles with water. In many instances, it is strongly recommended that you resist the urge (see information sheet). Since both sulfide and carbon oxidation processes require oxygen to proceed, the most appropriate course of action is to identify air-entry locations and isolate the reactive wastes from the air. This is often more straightforward than it sounds, particularly in end-dumped waste rock piles.
If you are concerned about the potential for Spontaneous Combustion, or worried about how best to deal with it, please call Earth Systems. We specialise in the prediction, identification and prevention of Spontaneous Combustion and its impacts. We have been working to prevent, minimise, control and treat AMD, Spontaneous Combustion and related issues at over 100 mine sites across the globe for more than 20 years.
For more information, refer to our specialists services for Spontaneous Combustion Management