Mining journal. - 1990. -¹32. - p.8
Translation of article into Russian
Design and construction work is currently underway for a high-capacity overland belt conveyor system to transport crushed coal over undulating terrain from the mine to a hydrogenation plant some 20 km away. The installation is for Sasol Mining (Pry) Ltd's Secunda Collieries in the Transvaal. Consultant for the project is Keeve Steyn Inc. and the contractor Krupp Industrietechnik GmbH, Duisburg, F.R.G. The system is scheduled to commence operation in summer 1991 and is expected to set new standards as regards advanced minerals handling systems over long distances.
Sasol, the South African oil-from-coal concern required some 7 Mt/y of pre-crushed coal of maximum lump size 100 mm to be transported under conditions of high product protection, high reliability and low operating costs. Environmental factors were of considerable importance as the conveyor route is over undulating farmland; it was also specified that the conveyor be completed within 18 months. Another important consideration was that powdery or fine ñîal could not be tolerated in the hydro-genation process, and thus minimizing degradation during transport was essential.
There are a number of innovative features in the conveyor, such as a minimum number of transfer points which must also be of special design to protect the coal being handled. The total 20 km-plus distance will be traversed by three belts: the first - a relatively short 375 m - is the accelerator belt running at 2 m/s and is 2.1 in wide. The second and third are the long-distance belts of width 1.2 m, speed -4 m/s, capacity 2,000 t/h and respectively 8.7 km and 12.3 km long. The second belt will follow a straight line while the No.3 belt will be carved in order to circumvent certain obstacles. Having a curved belt dispenses with the need for an intermediate transfer station: the actual shape of the curve, with a 6,000 m radius, was determined using advanced computer-based design techniques.
The extremely long belt transfer station between belts 2 and 3 is said to be based on a novel design concept: during transfer, the coal is prevented from falling and impacting on the next belt, which would cause degradation. Shortly after being ejected from the respective head drum the coal is caught in a tube-like chute (which incorporates a 90° curve) and guided through a gentle curve on to the next belt.
The two long-distance belts are driven at both ends by 450 kW squirrel-cage motors with fluid couplings giving precisely-controllable, jerk-free starting. This type of coupling also allows the belt to be run at creep speed for maintenance purposes. Depending on operating conditions -- e.g. starting, normal operation, braking, idling, etc. - drive torque and belt tension have to be carefully controlled. These values are monitored by special measuring facilities and adjusted by programmable controllers. The idle roller stations in horizontal curves are pitched at different angles to suit the terrain, the data required for this being determined by computer simulation.
The conveyor line will run mainly at ground level, its supports standing on precast concrete sleepers. Accessways will be provided for local traffic and animals, and the conveyor plus coal will be protected from the elements by continuous covers supported at one side. Contact Krupp Industrietechnik GmbH, P.O. Box 141960, Duisburg-Rhein-hausen 14, D-4100 F.R.G., phone 2135 780, telex 8554860, fax 2135 75191.