Continuous Miners or
Continuous Mining Machines have revolutionized the underground mining of coal
and other minerals. These machines have been used in the mining industry for
over a century, and they have played an essential role in making mining faster,
safer, efficient and environment-friendly.
With the increase in coal
demand and growing awareness towards sustainable development, the coal industry
has drawn a consensus over the need for increased production of coal from
underground coal mines. India has huge untapped potential for underground mining,
with extractable reserves beyond 300 m depth. Around 70% of the country's coal
reserves are amenable to underground mining, which delivers several advantages.
Underground coal is superior in quality compared with open cast and reduces the
import burden for higher grades of coal. Underground mining is minimally
invasive on land, detours land acquisition, avoiding its degradation,
environmentally clean, and is society friendly.
Underground mining can only
bridge the demand and supply gap with decent quality and quantity, provided
proper technique is used for mass production from underground mines. Continuous
Miner Technology (CMT) is one of the best underground coal mining methods over
conventional or partial mechanised ones with a high rate of safe extraction.
Its high productivity, the highest level of safety, eliminating blasting
vibration, eliminating the occurrence of noxious gases generated after blasting
and restricting the deployment of the workforce directly under the exposed roof
attracts the mine operator to choose this method.
The Continuous miner
technology in board and pillar mining is the best option, which does not
require virgin areas, whereas it can also be applied where development has
already been done. Since board and pillar system is a well-proven technology in
India, this technology helps in achieving high production and faster rate of
extraction with safety.
The continuous miner
technology is being adopted extensively in underground coal mines globally as
Mass Production Technology (MPT). This technology potentially eliminates the
two-unit operating, namely the drilling and blasting. This elimination helps
for better strata control and avoids the drillers working in unsafe conditions,
maybe under the loose coal roof. This CMT improves the quality of the coal
extracted and increases the output per man shift (OMS) by reducing the
deployment of face crew. It also reduces the accident as it is operated by
remote and workforce exposure to faces is limited. The method also helps for
better roof and side control, thus preventing side and roof fall danger. With
the changing time now, continuous miners of different heights are available,
which helps for optimum use of technology to mine out varying insitu height of
coal seam.
Continuous mining
technology utilizes a continuous miner machine with a large rotating steel drum
equipped with tungsten carbide picks that scrape coal from the seam. Operating
in a "room and pillar", also known as "board and pillar"
system, where the mine is divided into a series of rooms or work areas cut into
the coal bed. Standard continuous miners can extract coal at a rate of up to 38
tons a minute depending upon the seam thickness. New, more powerful continuous
miners are highly productive and are remotely controlled being designed for a
variety of seams and mining conditions. These make possible even fuller
recovery of the available coal, while removing the machine operator further
from the working area. Continuous miners provide mining companies with
countless benefits. In fact, almost 45% of the coal mined worldwide comes from
the efforts of a continuous mining technology.
The deployment of
continuous miner is dictated by a host of factors such as (i) gallery width
(not less than 5.5m), height (not less than 3m) for the standard height
continuous miner, (ii) ground condition (iii) power (iv) adequate ventilation
system (sufficient to remove the coal dust and other noxious gases) (v)
transport system -preferably belt conveyor (vi) pumping arrangements (vii)
adequate filtered water for dust suppression and roof bolting.
There are various
continuous miner manufacturers in the world, and they supply almost the same
outfit of machines. The primary difference is the capacity and operational
output and its size. Though there are many variations in design, continuous
miners mostly consist of five main elements:
A
Central Body
The central body of the
continuous miner houses all the components mounted on the drive mechanism,
including the cutter. It permits mobility during industrial mineral mining
applications below the mine roof.
A
Cutting Head
The cutting head features a
metallic rotating drum. Sharp cutter picks attach to the head and extract coal
from the coal seam, working within the machine's minimum and maximum cutting
height.
Some models have a dual
gathering head system to increase development rates. Both single and double
cutter head systems lift to reach their maximum cutting height. After doing so,
internal mechanisms enable the cutters to lower back to their minimum cutting
height.
A
Loading Mechanism
The loading mechanism
harvests the coal and conveys it to a central area within the equipment.
Depending upon the automated sequences used by the continuous mining system,
the machine may then use conveyors to move coal out of the mine.
A
Conveying System
Usually a chain conveyor
running in a steel trough from front to rear of the miner.
A
Jib Section
A continuous miner machine
typically has a jib at the rear. Operators can move this jib vertically and
horizontally during operation. The position of the jib allows for easy coal
loading and delivery throughout the system.
Robotic continuous miners are now being developed for more automatic operations. These offer a vision of what could become the standard coal mining method of the not too distant future: ‘Intelligent’ mining machines completely controlled by computers, with sensors that pinpoint the positions of all moveable parts, and on-board control systems that run the equipment and collect data on the coal seam. A robotic miner would have its own navigation and guidance systems, as well as internal diagnostics to spot problems and video equipment to allow continuous monitoring of the mining operation by highly trained personnel located in a safe position either underground or on the surface. Fully automated versions of the mining system make it easier to cut coal in hard-to-mine seams, lowering the risks of operating a continuous miner.
