Evolving Methods: Making headway towards better extraction techniques

Making headway towards better extraction techniques

Mining is one of the core sectors driving the growth of the economy and acts as a catalyst for the growth of other core sectors such as power, steel and cement. The choice of mining methods is largely determined by factors such as depth, geology of the mineral deposit and cost of equipment. The Indian mining industry continues to depend on opencast mining technology for excavation of precious minerals such as coal, iron ore or non-ferrous metals such as bauxite, copper, chrome and nickel. Coal India Limited (CIL), the dominant player in the market, produced about 94 per cent of raw coal through this technology in 2017-18, thus highlighting its dominance. In contrast, the contribution of underground or deep mining in total production remains subdued. Two commercial miners — CIL and Singareni Collieries Company Limited (SCCL) — produced only 6 per cent (39 million tonnes [mt]) of coal using the underground mining technology in 2017-18. This is primarily because the technology is more expensive as compared to opencast mining and is geotechnically complex.

Enhancing output from underground mining

Since the near-surface coal deposits are being exhausted at an alarming rate, augmenting production from underground coal mines has become inevitable, given the Ministry of Coal’s target of 1.5 billion tonnes (bt) of coal production by 2022. Currently, underground mining in the country accounts for only 10 per cent of the total coal production, as against 90 per cent and 33 per cent in China and the US respectively. Therefore, there lies significant untapped opportunity in underground mines translating into demand for side discharge loaders, load haul dumpers, continuous miners and equipment for longwall mining.

In India, there has been high deployment of continuous miners. Going forward, underground mining equipment is likely to witness wider applications including advanced strata control equipment, mechanised drifting, gas chromatographs, lightweight cap lamps, continuous coal cutting technologies, etc.

To maintain production levels (or to achieve higher levels), mining companies need to carry out deeper excavations in their mining operations. As the depth of the deposits increases, it becomes more difficult to mine them without heavy equipment. Thus, this also becomes a major growth driver for the increased use of equipment in the sector. As mine life matures, the pit becomes deeper and waste dumps become bigger, resulting in increased truck haul cycles, which require additional trucks to maintain production rates. This pushes up the cost of haulage. To counter this, continuous in-pit crushing and conveying systems are gaining traction as these offer numerous advantages over traditional truck haulage systems.

Use of heavy equipment

Over the past decade, mining equipment has steadily increased in size and complexity due to growing mechanisation. With infrastructure development at the forefront and CIL’s target of 1 bt of coal production by 2020, mining operations are bound to increase in terms of both number and scale. With regard to equipment, mining companies are steadily moving towards large-size equipment to expand their scale of operations and to overcome shortage of manpower. For instance, large capacity bucket wheel excavators are used for lignite mining and dump trucks of about 400 tonne payload capacity are being designed for enhanced mining operations. For opencast mining, two types of mining equipment – surface miners and shovel and dumper combination – are preferred as they are highly efficient and cost-effective. CIL, for example, produced about 47 per cent of its coal (266 mt) using surface miners in 2017-18. Draglines and dozers are other equipment deployed to remove overburden earth in surface mining.

New mining techniques

New and cutting-edge mining techniques such as digital mining and hybrid mining are gradually emerging to combat the issues associated with traditional mining techniques.

  • Digital mining: Wi-Fi-enabled underground mines are being developed in advanced economies. Wi-Fi helps track underground equipment, execute remote operation of loaders, automate auxiliaries such as pumping stations and ventilation shafts, and undertake VoIP-based communication with workers, thus ensuring their safety. Miners are embedding digital thinking in the core processes of mine operations. Location-aware machinery is being used for mining and drones are being used for stack and remote inspection. Companies are also using wearable devices to track humans and equipment. They are innovating new digital points of view (PoVs) to digitise the mining value chain. A digital PoV is a digital canvas which digitally maps productivity throughout the mining process and increases operational effectiveness.
  • Using trackless equipment and drones: Trackless equipment is being increasingly used by miners to promote safety and increase efficiency at their mines. This equipment uses proximity detection and collision avoidance systems to operate equipment which does not require any human intervention. Moreover, drones are being increasingly used to undertake mine site planning and health/compliance checks at the mines aerially. During the operations stage, this helps reduce any slippages and enables better monitor mining operations. It can also be used for carrying and detonating explosives. The process of using drones for digital mapping and visualisation involves obtaining XYZ coordinates for every surface point for mine planning, using the coordinates for 3D modelling, visualising and estimating possible resource extraction, assisting in planning and positioning utilities and equipment, and visualising the entire mine using drone-based mapping.
  • Hybrid mining: This mining method is generally used for extraction of precious metals such as platinum. Under this method, conventional underground mining methods are used along with conventional manual methods for extraction using hand-held equipment in addition to machines. This method is useful also for mines where the topography does not permit the extensive use of machines.
  • Micro-explosives: They can be used to avert the risk of fire caused by blasting of hard rocks using explosives. Micro-explosives, when deployed with computer-assisted design and timing, help control the fragment size, thus ensuring time and cost savings.
  • Automated drill rigs: They are a good solution for excavation involving hard rocks. In particular, battery-operated drill rigs are noteworthy as they are faster and more precise as compared to manually operated equipment. They also incur lower maintenance costs provided they are supplemented with rapid chargers or replaceable batteries. They do not generate toxic fumes and are efficient at drilling blast patterns and can make cutting easier when coupled with the latest cutters or preconditioning equipment.
  • Self-driving ore carriers: Ore carriers like above-ground earthmovers and underground ore carriers have the capability of working through the day. Thus, people can be eliminated from dangerous sites and these carriers can be used instead. When fitted with radar and laser scanners they can even navigate their way around dark areas. Further development of electric vehicles that run on batteries can help in mining above as well as below ground. A case in point is Rio Tinto which is in the process of developing automated ore trains.

The way forward: Sustainable mining techniques

Given the increasing global concern with regard to reducing the carbon footprint of mining activities, there has been much focus on this in the country’s mining industry. For instance, CIL is in advanced stages of implementing clean coal technologies including coal bed methane (CBM) and underground coal gasification (UCG). India needs to tie up with foreign mining firms for clean coal technologies such as carbon sequestration, under which waste carbon dioxide is captured and sequestered away from the atmosphere.

Moreover, other technologies such as converting coal into oil and using it thereafter, as adopted in South Africa, must be explored. With the government opening up the coal sector for commercial mining, private players can explore the use of Australian clean coal technologies such as coal mine methane, CBM, UCG, safety improvements, reclamation of mined out areas, etc., to help reduce carbon emissions. Alternatives to blasting such as the use of a terminator impact hammer or selective/smart blast design technology can be effective in curbing greenhouse gas emissions. Global mining companies are moving ahead with their plans to become energy efficient, and India too is attempting to catch up.