Mining methods in India

Draglines are by far the most commonly used overburden-removal equipment in surface coal mining. A dragline sits on the top of the overburden, digs the overburden material directly in front of it, and disperses the material over greater distances than a shovel. Compared with shovels, draglines provide greater flexibility, work on higher benches, and move more material per hour. The largest dragline in operation has a bucket capacity of 170 cubic metres. OPERATION In a typical cycle of excavation, the bucket is positioned above the material to be excavated. The bucket is then lowered and the dragrope is then drawn so that the bucket is dragged along the surface of the material. The bucket is then lifted by using the hoist rope. A swing operation is then performed to move the bucket to the place where the material is to be dumped. The dragrope is then released causing the bucket to tilt and empty. This is called a dump operation. The bucket can also be 'thrown' by winding ...

Longwall mining is a highly productive underground coal mining technique.  Longwall mining machines consist of multiple coal shearers mounted on a series of self-advancing hydraulic ceiling supports.  The entire process is mechanized.  Longwall mining machines are about 800 feet (240 meters) in width and 5 to 10 feet (1.5 to 3 meters) tall.  Longwall miners extract "panels" - rectangular blocks of coal as wide as the mining machinery and as long as 12,000 feet (3,650 meters). Massive shearers cut coal from a wall face, which falls onto a conveyor belt for removal.  As a longwall miner advances along a panel, the roof behind the miner's path is allowed to collapse.

BACKGROUND & HISTORICAL TRENDS Construction and mining equipment cover a variety of machinery such as hydraulic excavators, wheel loaders, backhoe loaders, bull dozers, dump trucks, tippers, graders, pavers, asphalt drum / wet mix plants, breakers, vibratory compactors, cranes, fork lifts, dozers, off-highway dumpers (20T to 170T), drills, scrapers, motor graders, rope shovels etc. They perform a variety of functions like preparation of ground, excavation, haulage of material, dumping/laying in specified manner, material handling, road construction etc. These equipments are required for both construction and mining activity. With a wide production capacity base, India is perhaps the only developing country, which is totally self-reliant in such highly sophisticated equipment. India has only a few, mainly medium and large companies in the organized sector who manufacture these. The technology barriers are high, especially with respect to mining equipment and therefore the role of SM...

Q-1. Which subsidiary of CIL has not a single UG mine ? (A) NCL (B) MCL (C) SECL (D) All Q-2. CIL has bagged two nos. virgin coal blocks in ...................... ? (A) Indonesia (B) Mozambique (C) Australia (D) Africa Q-3. Which Indian state has largest reserve of coking coal ? (A) Chhattisgarh (B) Jharkhand (C) Madhya Pradesh (D) Maharashtra Q-4. Which company in India is the largest producer of lignite ? (A) GMDCL (B) NLC (C) GPCL (D) RSMML Q-5. Which state in India produces coking coal ? (A) Jharkhand (B) Chhattisgarh (C) Madhya Pradesh (D) All Q-6. Which Indian state is the largest producer of coking coal ? (A) Jharkhand (B) Chhattisgarh (C) Madhya Pradesh (D) West Bengal Q-7. Which state had highest pit head stock of raw coal during 2008-09 ? (A) Chhattisgarh (B) Orissa (C) Jharkhand (D) Maharashtra Q-8. Which company had highest pit head stock of raw coal as on 31.03.2009 ? (A) CCL (B) BCCL (C) SECL (D) MCL Q-9. What is the import duty on coking ...

India's coal reserves are vastly overstated, says a policy paper by The Energy Research Institute, casting doubts on the estimates of the extractable resources. Demolishing the myth that the country has plenty of coal, a TERI (The Energy Research Institute) Policy Brief says that India may be living in a fool's world. It has less coal than it thinks. The coal that can be extracted — taking into account the geological, technical and economic aspects — is only a small per cent of the total coal inventory, without considering the no-go areas where mining may not be permitted, according to Mr R.K. Batra and Mr S.K. Chand, authors of the paper titled "India's coal reserves are vastly overstated". The issue of coal availability assumes significance because the commodity accounts for more than half of the country's energy mix. To sustain the growth rate of 8-9 per cent over the next few decades, the country has invariably to depend on coal. Demand for coal from the p...

Coal can be readily converted into a variety of fuels, with a number of key advantages: • Coal-derived fuels are sulphur-free, low in particulates, and low in nitrogen oxides. • With carbon capture and storage, life cycle CO2 emissions can be reduced by as much as 20% compared to conventional oil products. • Coal is available worldwide enabling countries to access domestic coal reserves and decrease reliance on oil imports – improving energy security. • Coal liquids can be used for transport, cooking, stationary power generation, and in the chemicals industry. Increasing vehicle traffic, particularly in developing countries, is driving oil demand. Alternative fuels such as CTL may have significant benefits for local air quality. South Africa has been producing coal-derived fuels since 1955 and has the only commercial coal to liquids (CTL) industry in operation today. Currently around 30% of the country’s gasoline and diesel needs are produced from indigenous coal. The t...

Methane (CH4) is a gas formed as part of the process of coal formation. When coal is mined this gas is released from the coal seam and the surrounding disturbed strata. It is also the major component of natural gas. Methane is highly combustible – its release can therefore have serious implications for the safety of mine operations. Methane is also a potent greenhouse gas – 21 times more harmful than carbon dioxide. Utilising Methane Methane is a valuable product – it can be used for power generation or domestic cooking and heating. Utilising the gas can have significant benefits – safety, environmental and economic. There are two ways that the methane can be recovered: • Coal Mine Methane (CMM) • Coal Bed Methane (CBM) CBM and CMM operations are taking place all over the world - including Australia, China, Ukraine and the USA. Coal Mine Methane CMM captures the methane that is released or will be released during coal mining activities. CMM is recovered using gas drainage systems, whic...

A number of options for the storage of CO2 are being researched at the present time, including geological storage and mineral carbonation. Geological Storage – Injection of CO2 into the earth's subsurface offers potential for the permanent storage of very large quantities of CO2 and is the most comprehensively studied storage option. The CO2 is compressed to a dense state, before being piped deep underground into natural geological 'reservoirs'. Provided the reservoir site is carefully chosen, the CO2 will remain stored (trapped in the bedrock or dissolved in solution) for very long periods of time and can be monitored. The options for geological storage include: • Deep saline aquifers • Depleted oil and gas reservoirs • Operational oil and gas reservoirs • Unmineable coal seams Deep Saline Aquifers – Storing large amounts of CO2 in deep water-saturated porous rock offers great potential. A number of projects are already being conducted including one major project by th...

Underground Coal Gasification (UCG) is a method of converting unmined coal into combustible syngas – a combination of hydrogen and carbon monoxide. This syngas can be used for industrial heating, power generation or the manufacture of hydrogen, synthetic fuels or other chemicals. The gas can be processed to remove its CO2 content, thereby providing a source of clean energy with minimal greenhouse gas emissions. UCG uses a similar process to surface gasification. The main difference between both gasification processes is that in UCG the cavity itself becomes the reactor so that the gasification of the coal takes place underground instead of at the surface. UCG Process The basic UCG process involves drilling two wells into the coal, one for injection of the oxidants (water/air or water/oxygen mixtures) and another well some distance away to bring the product gas to the surface. The coal at the base of the first well is then heated to temperatures that would normally cause the coal to...

Integrated Gasification Combined Cycle (IGCC) produces electricity by first gasifying coal. Coal is gasified through a controlled shortage of air or oxygen in a pressurised reactor - ‘gasifier’ - to create a syngas. This syngas – a mixture of hydrogen (H2) and carbon monoxide (CO) – is first cooled and cleaned of impurities such as sulphur, then combusted with air or oxygen to drive a gas turbine. The exhaust gases are heat exchanged with water/steam to generate a superheated steam, which drives a steam turbine. By adding a ‘shift’ reaction indroducing steam between the cooler and the gas clean-up, additional hydrogen can be produced and the carbon monoxide can be converted to CO2 which can be captured and stored. IGCC offers efficiencies up to 50%, with a potential of 56% in the future – significantly improving the environmental performance of coal. Pollutant emissions are also significantly reduced – even compared to advanced conventional technologies: • 33% less NOx • 75% less ...

Supercritical & Ultra-supercritical Supercritical (SC) and ultra-supercritical (USC) power plants operate at temperatures and pressures above the critical point*. This results in higher efficiencies – up to 46% for supercritical and 50% for ultra-supercritical – and lower emissions than traditional coal-fired plant. Temperatures and pressures for different types of plant using bituminous coal: Temperature (°C) Pressure (bar) Subcritical 538 167 Supercritical 540 - 566 250 Ultra-supercritical 580 - 620 270 - 285 One feature helping with the deployment of supercritical power plants is their similarities with conventional power plants. This allows supercritical plants to be constructed and operated without significant retraining, enabling faster deployment. More than 240 high efficiency ‘supercritical’units are in operation worldw...

Fluidised Bed Combustion (FBC) is a very flexible method of electricity production – most combustible material can be burnt including coal, biomass and general waste. FBC systems improve the environmental impact of coal-based electricity, reducing SOx and NOx emissions by 90%. In fluidised bed combustion, coal is burned in a reactor comprised of a bed through which gas is fed to keep the fuel in a turbulent state. This improves combustion, heat transfer and recovery of waste products. The higher heat exchanger efficiencies and better mixing of FBC systems allows them to operate at lower temperatures than conventional pulverised coal combustion (PCC) systems. By elevating pressures within a bed, a high-pressure gas stream can be used to drive a gas turbine, generating electricity. FBC sys...