Mining and construction services provider Wirtgen South Africa has successfully finalised trials of its 2200 SM surface miner at three coal mines in Mpumalanga, where the capabilities of the machine were tested under local mining conditions, proving that it is a viable alternative to opencast mining methods.
There is local demand for surface mining machines as most of the country’s coal is left unmined at borders of properties that are too close to villages, pipelines or highways, Wirtgen Group subsidiary Wirtgen SA sales executive Mike Newby tells Mining Weekly.
With conventional mining, drilling and blasting, it is dangerous to exceed certain parameters of the property, but surface miners can go right to the edge of the property without risking safety, he says.
Mining professionals and contractors were impressed with the results of the machines, exceeding the company’s expectations with their reactions, reveals Newby.
However, the challenge in South Africa, he says, is convincing about 30 boardroom executives to adopt the technology. “Everyone has to agree to the decision – miners, contractors, consultants and their superiors. Marketing surface miners to operational mines is difficult, since money has already been spent on drilling, blasting, cutting, crushing, separating and washing the coal with various equipment, which can all be replaced with one machine.”
Wirtgen SA took delivery of the 2200 SM surface miner in time for its opening in February 2016. The first trial took place at coal miner Wescoal’s Intebane opencast coal mine and the second trial took place at coal miner Mbyelo’s Vlakvarkfontein coal mine, both in Ogies, within two months.
The sites were prepared by cleaning out 50 m × 100 m blocks directly on the coal seam, after which the 2200 SM cut and crushed coal and loaded it directly onto the mine’s 40 t articulated dump trucks for hauling to the final stockpile.
The surface miner’s average production rate was more than 400 t/h, including standard production stoppages and delays.
Wirtgen SA’s final trial of the 2200 SM took place later in 2016 at coal miner Universal Coal’s Kangala opencast coal mine, in Delmas, with the primary objective to improve the yield of the operation’s production plant. At the end of the trial, about 96% of the mined material was cut below 53 mm and the fines content was less than 14%.
“The 2200 SM surface miner is designed for selective mining, separating coal from waste and ensuring that good, clean coal is mined with minimal contamination and no primary crushing is required,” notes Newby.
The machine can separate thin coal seams and cut, crush and load coal ore in one operation. “This allows for delivery of a final, saleable product without the need to drill and blast, with reduced washing costs and processes, and significantly improved product yields.”
Newby adds that the challenge in South Africa is to mine cleanly. Once the most easily mined, economical coal is removed, mines are left with thinner coal seams. “If they do drill and blast the seams, the coal will mix with waste, resulting in unusable or low-quality coal, owing to a high ash content. This is why the 2200 SM is attractive. It offers the opportunity to mine coal cleanly and efficiently that would otherwise be uneconomical.”
Germany-based Wirtgen Group started developing surface miners from road milling technology in 1970 and has four surface miners on the market – the 2200 SM, 2500 SM and 2200 SM, with 3.8 m drum, as well as the larger 4200 SM. The number in the model name refers to the width of the drum – for example, the 2200 SM has a 2.2-m-wide cutting drum. Each machine has a different cutting drum width to suit client requirements with regard to production rate and cutting depth. The 4200 SM, for example, can cut up to 83 cm deep, and has a production rate of up to 3 000 t/h.
The surface miners run on four tracks, with a cutting drum in the centre. As the machine moves, the drum rotates and cuts into the ore. The crushed material moves onto the machine’s transfer and a conveyor belt discharges the material onto a truck.
Newby likens the operation of the machine to that of an excavator – essentially, one person can operate the machine after having undergone training. “We find that it takes about two weeks for drivers to become proficient in operating the machine. Many of the controls and functions are automated, while the 2200 SM also includes a safety system that reduces the possibility of it tilting during operation, owing to steep slopes.”
Wirtgen SA has supplied surface miners to Vale’s Moatize coal mine, in Mozambique, gypsum mining company Saint Gobain’s operation in Bushmanland, in the Northern Cape, natural sodium products producer Botash, in Sua Pan, and diamond miner Debswana Mining’s Letlhakane diamond mine, both in Botswana.
Worldwide there are more than 500 Wirtgen surface miners in operation, in various commodities, such as coal, gypsum, limestone, bauxite, salt, iron-ore, kimberlite, phosphate and oil sands in countries in North America, Europe, South America and Africa.