Underground » Ventilation, Gas Drainage and Monitoring
This project investigated the variability of gas content results across three laboratories processing mine gas content using the new quick crushing or fast desorption method.
In this study some 10 horizontal boreholes were drilled into coal seams from newly developed roadways at five mines in NSW. There were 37 suitable cores generating 106 samples, which were distributed to three laboratories using different types of coal crushers with different sample sizes and sample to volume ratios. Coal seams contained CH4 or CO2 or both gases.
The results of gas content comparison showed that the maximum cross-laboratory variability could be as high as 17% of the average gas content. On a 2-laboratory comparison basis, the maximum variability was found to be higher at 20% of the mean gas content results of the two laboratories. In analysing the data no measurement value was rejected and all gas content results were included in the study.
Possible reasons for this variability are discussed including the gas collection system, dissolution of CO2 in water, the partial pressure of the seam gas in the crusher, temperature rise in the crusher and the time before crushing, all of which can affect both the gas content and the gas composition.
Accurate and reliable gas content results are particularly vital for safe mining in mines prone to gas outbursts. An average variability of 17% could have serious implications for those mines with gas contents close to the threshold limits. Some recommendations are suggested to decrease the variability across the gas laboratories.