Many coals, especially lower rank coals, have a tendency to self-heat. Spontaneous combustion is a risk to health and safety on site, and a source of uncontrolled pollution (including greenhouse gases). It can lead to a significant amount of lost stock and lost working days.
This new report for the IEA Clean Coal Centre by Dr Lesley Sloss, Assessing and managing spontaneous combustion of coal, reviews the recent advances in testing methods for both coals and coal pile emissions, and covers all the options to predict and prevent spontaneous combustion. Legislation and guidelines, including spontaneous combustion management plans, are included.
Spontaneous combustion can happen at almost any stage in the coal chain, from mining through to stockpiling. Incidents can be kept to a minimum by improved management and monitoring techniques. Successful approaches include:
• Analysis of coals and predictive modelling of heating behaviour.
• Real-time monitoring and measurement of changes in coal characteristics.
• Techniques and technologies to control and contain self-heating events.
Advances in measurement techniques have improved the control and prevention of spontaneous combustion. Coal can be analysed to identify each coal’s self-inherent heating property. This information can be used in models to predict a coal’s behaviour in different mining, transport and storage situations. Gas emissions and temperature changes can be monitored at all stages of the coal chain to provide an early warning of heating activity. Visible signs, such as glowing embers and smoke emissions, can be a final indication that spontaneous combustion is imminent. By combining coal analysis with advanced mathematical and modelling techniques, coal users can now understand the conditions most appropriate to control self-heating in individual coals. So mining and handling systems can be fine-tuned to each coal type and to each location to provide the safest work environment possible.
Spontaneous combustion management plans (SCMP) and trigger action response plans (TARP) can be fine-tuned to different coals and working locations. SCMP are becoming increasingly common, especially in Australia. SCMP aim to:
• minimise the risk of spontaneous combustion
• manage any occurrence of spontaneous combustion effectively and efficiently
• minimise off-site impacts of any incidents
• minimise impacts to personnel on site.
Technologies for heat suppression and control are also advancing. For example, air flow control or the application of chemical suppressants can be very successful in controlling fire events.
Despite this progress, spontaneous combustion incidents still occur. Fire suppressant treatment may be needed or even site evacuation. As part of an SCMP, these events must be monitored and audited afterwards to provide feedback to update or even re-write the SCMP to prevent reoccurrence. Records are kept of accidents and also of potential areas of concern where additional monitoring may be needed. This means many SCMPs are ‘live’ documents and are frequently updated.
In severe combustion incidents, the monitoring equipment may be destroyed. Unless appropriate recordings are made beforehand, there is no way of understanding what occurred or how to avoid it ever happening again. SCMPs and the associated testing and monitoring skills have changed the coal industry significantly in recent years and will continue to do so in future.
The report Assessing and managing spontaneous combustion of coal CCC/259 by Dr Lesley Sloss,
ISBN: 978-92-9029-582-2, 55 pp, October 2015 2015 is available for download from the IEA Clean Coal Centre Bookshop http://bookshop.iea-coal.org.uk/site/uk/clean-coal-technology-research-reports. Residents of member countries and employees of sponsoring organisations can download the report at no charge after a one-off registration.
For more information contact: Deborah Adams, [email protected]