Mine excursion
Technology adds value
Berger adds that instead of a drum spiral cyclone module typically used in coal processing plants, the plant at Khanye will make use of large coal dense medium separators( Larcodems). Larcodems are cylinder cyclones designed to beneficiate feed material sized from 0.5mm to a top size of 150mm. The Larcodems are gravity fed and, unlike cyclones, introduce the medium and the coal separately.“ That enables us to dry transport the coal to the top with a conveyor into a bin and, in turn, into the Larcodems, which treats all the different size fractions,” says Berger. This is unlike a typical plant where a certain size fraction has to be put through the drum, a certain fraction through the cyclone, and the fines through the spirals. In the Larcodems, it is split at once and then screened into the different size fractions at the other side.
“ The coal at Khanye is slightly more brittle than usual and we need to reduce the handling that results in unnecessary breakage. Trying to put coal through a pump and then get it up to a cyclone will result in fracturing, and the Larcodems process eliminates that risk. In the design we have also allowed for a second Larcodems that will be able to split smaller fractions,” says Berger.
To keep the revenue flowing, some of the run of mine( ROM) being stockpiled at Khanye before the processing plants are commissioned( first the interim and then the main plant), will be transported to the Phalanndwa plant near Delmas, where it will be washed. The construction of the two plants will take, according to Mabbett, at least another three to four months to complete.
A unique partnership
Although Isimilo can be regarded as a contractor, the company is really part of the Canyon Coal stable. However, Berger says that in a unique partnership, Isimilo can also undertake contract work at other mining sites. The long-term vision at Canyon Coal is that they will eventually undertake all work in-house, although they are still using Koza as a mining contractor at Khanye.“ At Khanye, we need six teams of equipment— a team meaning an excavator, articulated dump trucks( ADTs), and all the other equipment associated with it. Four teams are Canyon’ s own teams and two will be
Khoza’ s teams,” says Mabbett. A team consists of a supervisor and a number of operators.
In total, there will be six excavators, three or four ADTs per excavator( thus 24 ADTs), and several pieces of ancillary equipment like dozers and graders. Currently, the mine is using an 870 Hitachi excavator, Bell B40 ADTs, Komatsu dozers, a Bell 770 grader, and two 23 000-litre Bell water bowsers.
Geology presents challenges
Hallatt says the three seams at Khanye differ in quality and, depending on the customer requirements, the product will have to be a blend of all three seams.“ The upper seam disappears in certain areas, which then leaves us with only the middle and lower seams( or 1 and 2 seams),” says Hallatt.
The deepest part of the opencast mine at Kanye will be about 76m; however, due to the seam thickness, it will still be mined economically.“ Where we have started mining now, the pit will only be about 45m deep, with an extremely low stripping ratio. The overall project strip ratio is 2:1. However, there are a few areas in the pit where the seam dips down to about 70m, and that will naturally increase the stripping ratio,” says Hallatt. When the mine reaches full production, there will be two pits, namely a northern and a southern pit. The northern pit currently consists of two box cuts. These two box cuts will eventually merge into one big pit.
Hallatt mentions that there are a few geological challenges in the pit, but nothing that cannot be overcome.“ For example, there is a geological occurrence( basement high) between the northern and southern pits where the coal was never formed. We have done extensive drilling and determined that the middle section( the dead spot) is a geological anomaly, so we have delineated the potential problem areas adequately,” says Mabbett. The other challenge will be to control the strip ratio where the seams dip to 70m below surface.
Canyon Coal has firmly established itself as a significant mid-tier player in the coal mining industry of South Africa and is set to make further inroads in the future. Be sure to scribble down the name as competition in the South African coal sector heats up. b
[ 14 ] MINING MIRROR MAY 2018