Significant improvement in effectiveness of nitrogen infusion technology for control of fire by dynamic balancing of pressure - A case study of powered support longwall face

A large number of powered supports and other equipment costing millions of rupees were trapped due to sudden loading and collapse of part of the roof of longwall panel No. 3 in Samla Seam (R III / II) of Kottadih colliery, Ra niganj coalfields, India. In fact 55 out of 83 chock shields were badly dam aged and subsequently healing was detected in the panel which quickly aggra vated, leading to sealing of the panel Therefore, at that stage, the most urgent need was to bring the fire under control as quickly as possible, preferably within three weeks lime, and wit hout allowing the temperature to exceed 50 degrees C at the face, as it cou ld have caused heavy leakage of hydraulic fluid due to failure of the "O" r ings of the powered supports. Both the aforesaid objectives were achieved by nitrogen infusion along with dynamic balancing of pressure. liquid and gaseous nitrogen were infused in the affected panel through boreholes and pipes already laid in the mine. T he panel was then successfully reopened after 19 days of sealing, and it wa s possible to keep the temperature of the face below 40 degrees C throughou t the operation. This, therefore, paved the way for safe recovery of all th e healthy supports and other equipment worth over Rs 400 million. In essence, the paper briefly highlights salient features of the fire probl em, and the results oiinvesligations undertaken before and after implementa tion of various control measures adopted in the mine. Successful control of fire even under critical gee-mining conditions has led to the conclusion t hat liquid nitrogen (LN2) in conjunction with dynamic balancing of pressure has the potential to control underground mine fire quickly and safely.