Of India’s 204.65 billion tonne coal reserves, around 20% is amenable to open-cast mining. In a technical paper, Dr SK Das, associate professor at the Department of Mining Engineering, Indian Institute of Technology Kharagpur, described longwall mining in India.
The first mechanised powered supports were introduced in 1978 at the Moondih mine. Before that some 17 caved longwall faces using individual friction props under a depth of 220m to 400m were worked out at the mine.
Out of the total 28 mechanized longwalls installed in India employing powered roof supports there are currently around 20 longwalls operating. Twelve of these are owned by the state-owned Coal India (CIL). A further nine longwalls are believed to be in the pipeline. Because of the high cost of longwall equipment in India, and the comparatively poor production results, Coal India has opted for a Risk-Gain type arrangement with its equipment suppliers.
Under this arrangement, the equipment supplier has to give minimum production guarantees per face and operates the face for five years. If the production is less than the minimum guaranteed production, the supplier’s payment is deducted. If production exceeds the minimum production guarantee then the profit is shared when the coal is sold.
SCCL, under the State Government of Andhra Pradesh, runs a further eight longwall faces and the company plans to install another three faces in the near future. SCCL has made significant operational changes which are delivering better results.
Among the difficulties faced by India’s longwall producers are strata control problems, inadequate underground clearance equipment, prohibitive cost of capital, poor development drivage rates, and lack of planning. One of the most serious problems revolves around equipment and the lack of availability of spare parts and suitable workshop facilities for overhauls. On the manpower side a lack of training and education, and a work culture not endemic to highly mechanized, high production longwalls has contributed to low productivity.
The present focus is on shortwall and miniwall faces utilising single entry retreat system. Two mechanized shortwalls employing shearer and powered roof supports are currently being operated efficiently by CIL and SCCL. Despite the fact that highly mechanised longwall systems have not delivered high productivity rates in India, many remain convinced that it remains the best among all other systems presently available.