Completed last month, bench-scale tests in the latest ACARP project on gel-fire suppressants have identified anionic polyacrylamide (HPAM Al-13+) gel as the most favourable to suppress underground coal heatings because of its relatively high thermal stability, low cost and easy preparation.

CSIRO Exploration & Mining Research Team Leader Dr Sheng Xue told International Longwall News the next step will be large-scale trials and development of suitable injection systems.

“It is a very important and necessary step for the techniques to be practically used for controlling or extinguishing underground spontaneous combustion and it will depend upon further ACARP funding,” he said.

On implementing the new technology at longwall mines, Xue said no major operational changes are likely to result from using the new generation of gel-fire suppressants at sites, except that a new system will be available to safeguard mine operators against possible spontaneous combustion.

Looking at when the changes could take place, Xue said it depends upon further recommended work.

“If an extension of the project is granted [from ACARP], and it may take about two more years to complete, then it is expected that mine operators will make the changes to incorporate the new mobile gel-preparation and injection system.”

While gels are already used to control underground spontaneous combustion, Xue noted the progress from the recent research.

“Major issues with the gels are cost, toxicity, and control of gelling time. With the development of the new gels through the ACARP project, these issues are basically addressed,” he said.

Xue confirmed that with further research the aim was to form a new industry-accepted system for this area of safety and that there would be new equipment on the cards to deliver the gel fire-suppressants.

Spontaneous heating or combustion from the natural oxidation of coal and other carbon material is not only a safety concern, but can also cause production delays, and property and coal resource damage.