Methane drainage from roof strata using an overlying drainage gallery

• The design of methane drainage system with overlying drainage gallery.
• The principle of determination of gas desorption zone in overburden.
• Indicated desorption zone enabling the design of methane drainage system.
• The practical drainage system in Longwall panel B-11.
• The influence of variance factors on drainage efficiency.

Methane drainage is conducted in Polish coal mines to reduce mine methane emissions and to keep methane concentrations in mines within safety limits.This article describes a method of methane drainage conducted during mining in Polish coal mines. The method is based on driving a drainage gallery into a coal seam situated above or below the worked seam prior to its extraction by a longwall method.This article shows the influence of a typical ventilation system on the drainage efficiency at longwall panel B-11 in seam 348 with an overlying drainage gallery. At this longwall, measurements of the methane emissions and efficiency of the methane capture were conducted. These measurements consisted of gauging the methane concentration, air velocity, absolute air pressure and the amount of methane captured by the drainage system. The experimental data were used to estimate the variations in the total methane release, methane release into the ventilation system and – most importantly – the efficiency of methane drainage. The results obtained were analysed statistically, and the influence of different factors on the total methane release and the amount of methane captured into the drainage system were determined.