In India, technology penetration in mine planning and operations continues to be lower than that in many leading economies. However, the country’s mining industry is heading towards a technology-driven optimisation process and envisages the use of progressively bigger-sized equipment. Difficult geology of mines (frequent faults, shallow and thick deposits), surface constraints, law and order problems, challenges due to forest permissions, etc. have further necessitated the use of more advanced technologies. The introduction of global high capacity technology will facilitate the exploitation of these reserves and result in an increase in production.
Primarily, there are two types of mining techniques – surface/opencast mining and underground mining. Surface mining is more prevalent and produces most of the metallic ores and minerals (excluding petroleum and natural gas) in the country while the share of underground mining has been declining owing to huge capital requirements, long gestation periods, high manpower costs and the non-availability of indigenous equipment.
In this segment, there has been a gradual move towards high capacity, mechanised drilling technologies to enhance the pace of exploration. Technologies like 2D and 3D seismic surveys and other advanced geophysical techniques are finding wider applications. Recently, the central government introduced the National Mineral Exploration Policy which is aimed at accelerating exploration activity through the enhanced participation of the private sector. Under the policy, the Ministry of Mines will provide world-standard baseline geoscientific data in the public domain, gathered through quality research carried out via public-private partnerships. The ministry will also take special initiatives for finding deep-seated, concealed deposits, and will undertake aero-geophysical surveys of the country. Such policy moves are expected to push the demand for advanced exploration equipment.
Surface mining techniques
Surface mining has contributed to global mineral production in a big way in the past four and a half decades and is the predominant technology choice for mining activities. A blast-free method, it is expected to continue to remain the mainstay of mining operations. Further, it does not require multiple operations, deploys less people, offers improved operations as well as works well for selective mining. It is a proven technology for soft rocks, though it may be unsuitable for hard rocks.
The use of surface miners is gaining widespread acceptance in opencast mines as it leads to selective mining as well as enhanced output. This equipment is increasingly finding its way in today’s marketplace, especially in applications where drilling and blasting is either prohibited or uneconomical. At the Gevra coal mine (Korba district, Chhattisgarh) the largest opencast mine in Asia, about 66 per cent of the coal production is through surface miners and 34 per cent using the conventional drilling/blasting method.
Surface mining is the dominant contributor in the overall output as it is environment friendly and requires minimum manpower at the mine face during machine operations. Surface miners reduce the cost of transportation of minerals by belt conveyors/dumpers. The inbuilt water spraying system suppresses dust which is generated during coal cutting. In addition, there are very low chances of fire in the coal face.
In-pit crushing and conveying
In a fully mobile in-pit crushing and conveying system, an excavator located on the muck pile loads the material directly on to the hopper of a mobile crushing plant, instead of feeding a dump truck. Crushed rock is then transported to an in-pit belt conveyor via mobile conveyors. This conveyor carries the crushed rock from the mobile crusher to the fixed secondary crushing plant for further processing, thus eliminating the need for dump trucks. This process reduces operational costs and lowers emissions. When blasting is done, the mobile primary crusher and the mobile conveyors move away to a safe distance. After the blasting is over, a wheelloader cleans the floor and the crusher moves to a new muck pile thus resuming operations with minimal downtime. In-pit solutions are applicable both to greenfield projects and mine expansion projects.
A continuous miner is a machine designed to remove coal and other soft minerals from the face of the mine and load it on to cars or conveyors continuously, without the use of cutting machines, drills or explosives. Continuous mining is characterised by higher productivity as no drilling or blasting is required. Though there are many variations in design, continuous miners mostly comprise five main elements – a central body to carry the other components mounted on a drive mechanism to provide mobility (most commonly, caterpillar tracks), a cutting head (usually rotating drums and/or chains with cutting picks attached), a loading mechanism to pick up the cut mineral and deliver it to the central part of the machine, a conveying system (usually a chain conveyor running in a steel trough from the front to the rear of the miner), and a rear jib section capable of a certain degree of vertical and horizontal movement to enable the ore to be delivered into a transport vehicle or loaded at the desired point.
Though longwall is an old technology, it is now being reinvented in India. Longwall mining involves the full extraction of coal from a section of the seam or face using mechanical shearers. The coal seam can vary in length from 100 metres to 350 metres. Self-advancing, hydraulically powered supports hold up the roof temporarily while the coal is extracted. When the coal has been fully extracted from the area, the roof is allowed to collapse. Over 75 per cent of the coal in a deposit can be extracted from the coal panels that can extend 3 km through the coal seam.
Longwall mining, after having witnessed failure in a number of projects, is now receiving interest from the industry, given a few recent successful projects (Adriyala mines). Also, future extraction is likely to be from deeper locations (300-600 metres) which can only be achieved through the use of longwall technology.
Underground mining techniques
In a scenario where there is an urgent need to augment domestic output, the declining trend of underground production is a matter of serious concern. It is pertinent to mention here that the share of underground mines in other major coal producing countries like China, the US and Australia are 95 per cent, 30 per cent and 25 per cent respectively. In India, efforts are under way to step up production from underground mines by introducing mass production techniques.
To achieve higher production from underground mines, stress is being laid on introducing mechanisation, wherever geotechnical conditions permit. Further, efforts are being made to identify suitable prospective sites for highwall mining, which is a method to extract the mineral from an exposed seam at the terminating line of an opencast mine or at project sites which are amenable to neither opencast nor underground mining exclusively. Based on geological conditions, longwall or continuous miner technologies are also being adopted.
The way forward
India produces 89 types of minerals and in terms of the quantity produced, over 80 per cent is coal. The increase in coal production envisaged in the next five years necessitates the adoption of appropriate technologies and requires support in terms of supply and maintenance of equipment, as well as skill management. To ensure high performance, there is a need for the introduction of mechanised surface mining systems with large-sized equipment, switching from diesel-powered equipment to more energy efficient equipment and the introduction of total mine management systems with truck dispatcher systems. In addition, equipment manufacturers will have to closely associate themselves with coal companies to understand and guide the development of large-sized, more efficient mining operations in both opencast and underground mines with improved production, productivity and safety.
In sum, the timely adoption of technology in the right mix is the need of the hour for mining companies to remain competitive in the volatile market. In addition, advanced technologies will lead to the optimum and balanced exploitation of mineral reserves, thus resulting in operational and financial efficiency. However, tough investment decisions must be made to achieve this end.