Ventilation and Gas Extraction Techniques of High Gas Seams in Kazakhstan

The execution of gas drainage techniques to degas the high methane content seams, and to allow their safe working, is influenced by the low permeability of the coal seams. The extraction techniques of coal degasification employed are; mining the underlying thin seam before extracting the main thicker target seam; pre-drainage of the target seam, from surface in conjunction with in-seam drainage, both using vacuum extraction and; taking a top lift of the very thick seams. A significant proportion of the liberated gas is also extracted from the goaf area. Several special techniques are employed in managing the goaf gas, including gas extraction from surface boreholes, bleeder drivages and gas drainage from roadways constructed above the extraction seam. Methane removal levels of 60% are achieved through effective methane gas drainage management and control in coal production. These practical measures contributed to increase in methane gas volume available for utilisation to 120 m3/min.