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Optimising underground coal mining

South African based Magatar Mining has developed a Linear Continuous Mining (LCM) methodology to increase the output and productivity of underground coal mines without having to increase the amount of capital used.

Phillip Venter

Phillip Venter, managing
director of Magatar Mining

Phillip Venter, who is managing director of Magatar Mining, says that while bord-and-pillar and longwall mining methods have become industry standards in coal mining, they are not optimal in respect of resource utilisation, efficiency, flexibility and safety.

Hence he and his partners saw scope for the LCM methodology that Magatar has developed to optimise the mining process. The LCM methodology uses a similar continuous miner equipment set as used in bord-and-pillar underground mining, but changes the way the equipment is assembled, operated and sequenced.

It allows for cutting machine utilisation to be increased from about 30% to above 60% depending on mining conditions. Importantly, the 100% increase in coal production can be achieved for the same installed power.

While the LCM methodology entails the use of a continuous miner, the traditional shuttle car/battery haulage system is replaced with a simple haulage system that transfers coal to the section conveyor belt on a continuous basis. This eliminates the need to disengage the cutting system.

With this system the cutting sequences have been modified so that most of the mining is done in retreat mode instead of advance mode. As the production cycle takes place in retreat and continuously moves away from the danger area, this system is inherently safer than traditional continuous mining methods.

Using the LCM methodology, roof-bolters and rib-bolters form part of the continuous mining machine. This allows mining and roof- or rib-bolting to take place at the same time as the cutting process, which allows for high utilisation ratios.

Explaining some of the thinking that has seen the evolution of the LCM process over the past six years, Venter says, “The methodology has its roots in both longwall and continuous mining and best practises and equipment from both were used when developing the LCM system.”

As a result of Magatar’s thinking, features of the LCM methodology, which has been patented in South Africa, include reduced levels of required maintenance and safer and more harmonious movement of equipment as opposed to the use of batching systems.

It is a totally mechanised system that also works for lower seam deposits, down to 1.5 metres. In fact for lower seam deposits, such as those in the 1.5 to two metre thickness range, Venter says it is possible for the LCM methodology to increase productivity by as much as three times.

“The top 10% of high seam coal operations are achieving about a 30% plus utilisation of the continuous miner, and with our system we can get to about 50%. In lower seam operations the ratio is different and we can take them from about 12% to over 30%.

“Lower seam operations have lower utilisation rates because the logistics in these operations increase exponentially. One has to advance twice as fast to take out the same tonnage from a 1.5 m seam when compared to a three metre seam.”

Venter says the main differences in comparison with other methods is that with the LCM methodology there is less moving equipment, the equipment is moving in one direction for most of the time, and it avoids the need to change places with the cutting machine. The latter is a big inhibitor of efficiency in continuous mining operations.

He says that Magatar provides a contract mining service, where it provides its own equipment and operational personnel and delivers coal to the mine owner on a rand per tonne basis. Contracts should ideally be a minimum of five years in order to pay back capital equipment while keeping the contract rand per tonne rates competitive.

Venter is careful to point out that the methodology is applied on a horses for courses basis. “Every site is different owing to geology and other mining conditions and equipment, procedures, sequences and production output will differ from site to site.”

Regardless of the above Venter says it is a package system that can be rolled out rapidly. It means the window period from getting a contract to implementing it is in the order of a maximum of 12 months.

Though, developed in South Africa, the LCM methodology was first implemented in Australia at the Cook colliery in Queensland, in early 2008. Magatar is now looking to introduce the methodology in South Africa.

Magatar Mining

Magatar Mining uses a similar continuous miner equipment set to that utilised in bord-and-pillar underground mining, but changes the way the equipment is assembled, operated and sequenced.

While there has been a lot of interest in South Africa, mining companies are often reluctant to be the first to try a new technology. In this case it is really existing, proven equipment assembled and operated in a different way to free up additional production time. Venter says, however, that the LCM methodology will give groups an edge in terms of accessing lower seam resources.

A few months ago advanced negotiations were underway with South African operations. Magatar has been undertaking feasibility studies for two major underground mining projects in the country. In both cases, Magatar would be responsible for all underground mining activities, with the clients handling the transportation, beneficiation and marketing of the coal.