Coal bed temperature change and the variation of gas concentrations in coal bed indicated that the gel barrier was effective not only for preventing oxygen ingress to the hot spot but also for sealing the leakage of the toxic and combustible gases.
The hydrogen level after applying gel can be higher than the lower explosive limit of hydrogen for a short period of time and then quickly dropped to very low levels. This hydrogen generation was caused by insufficient oxygen supply after applying gels and presence of coal moisture rather than the use of gel.
Guidelines for the selection of gel systems suitable for particular types of heatings and the operating procedures for delivering gel forming mixtures to heatings occurred in goaf, pillar and coal roof layer through injection and/or spray have been developed.
Though the CMC-Al3+ gel system can be readily applied in operating coal mines, the guidelines and operating procedures are of the pilot-scale nature, not standard operating procedures used in coal mines, and would require substantial field-based testing and modifications for mine site applications.
The pilot scale test work conducted in this project has demonstrated the effectiveness of CMC-Al3+ gel system. Applications of the gel technique at mine sites will require further developments of field-based approaches and equipment, according to ACARP.
