Underground » Detection and Prevention of Fires and Explosions
The aim of this project was to improve the ability to detect spontaneous combustion and to be able to monitor the changes in intensity of any spontaneous combustion event.
Large scale testing of 5 coal samples (16 tonne) lead to successful self heatings on two occasions.
Some of the key findings from the project were:
- Heatings can develop and worsen in confined areas involving a few tonnes of coal. These heatings will be difficult to identify remotely due to dilution effects.
- For pillar heatings infrared cameras and thermography will be more sensitive than gas detection.
- The further away from the heating monitoring is carried out, the more dilute or mixed with other gas streams the products of oxidation become, the less reliable is the ability to identify the heating.
- The best indicators of spontaneous combustion are those that are independent of the air flow ie. CO make and Graham's ratio, but even these have grave limitations and we should be aware of what they can and cannot do.
- Using standard CO make values as action levels is meaningless. As soon as the CO make significantly exceeds the background level investigation should begin. Current trigger levels correspond to large scale heatings too late to treat.
- Monitor comprehensively and accurately.
Prevention is better than cure so more emphasis needs to be placed on:
- The use of inertisation technology to remove oxygen, and thus the potential for spontaneous combustion of goafs.
- Where pillar heatings are possible, the use of sealants to eliminate oxygen coal interaction should be undertaken.
- Ventilation must be better controlled, leakage minimised.
- Mine design should include the evaluation of pressure differences and leakage to identify the potential hotspots for spontaneous combustion.
The report goes on to make recommendations for further research into spontaneous combustion.