Mining equipment and service provider Sandvik Mining Systems is providing coal miner Sasol Mining with an end-to-end bulk materials handling solution for its new Shondoni Colliery in Secunda, Mpumalanga.

Work is under way to provide one of the world’s largest and most challenging single- drive conveyors as a complete integrated mining system to convey materials from the mining face to the company’s coal-to-liquid facility, on the other side of town.

Apart from the distances, such as 21 km overland, and the high volumes of run-of-mine coal required, the conveyor also has to span several waterways and skirt roads and populated areas, without impacting on either. As a result, the solution from Sandvik Mining Systems had to be innovative to meet and exceed all the design briefs.

Sandvik Mining Systems market development and sales manager Rudi Pieterse says the company’s design incorporates a single-drive system to reduce power consumption and precludes the need for a midway transfer point and associated infrastructure and manpower.

It also reduces coal degradation, as Sasol Synfuels, one of the operations of energy and chemicals company Sasol, requires relatively high-grade coal from the mine, with large lump sizes and minimal fines.

“Our successful bid was based on a combination of providing a sound technical solution with a proven execution philosophy and a balanced cost ratio between initial capex and opex expenditure,” Pieterse says.

He explains that the project begins underground with a shaft incline conveyor to transport coal from the mine’s main ore pass to the surface. A bunker conveyor lifts the material to the main bunker, where a tripper uses a bifurcated chute to evenly distribute materials across the surface area and reduce drop forces to prevent degradation of the material. Coal drawn from the main bunker is then transported to the main overland conveyor.

While maintaining the same capacity as the previous conveyor, 5 MW installed drives – four at the head and a single drive at the tail – to move the coal over the required 21 km. Its trajectory requires five horizontal curves, 6 000 m in radius, to guide it through an existing corridor.

Numerous water crossings, with the longest one spanning 700 m, as well as road crossings and the close proximity of human settlements, require the belt to be completely spill free and sealed over these sensitive areas.

An 80 t counterweight provides the required tension to keep the belt operating trouble-free and without slippage at either end. At landfall, the conveyor feeds several ancillary belts and a distribution bunker to ensure coal is delivered where it is required throughout Sasol’s Synfuels plant.

“Our proactive approach to minimise maintenance and enhance the efficiency and reliability of the system also necessitated the use of mechanical luffing chutes instead of vibrating chutes, which enable us to reduce moving parts and, therefore, reduce energy consumption and maintenance requirements.

“We also used discreet element modelling methods to optimise all the flows and ensure transfer chutes were optimally designed for the high speed of the main belts at 6 m/s. In this way, we are able to deliver a high-performance solution that sets the benchmark for perform- ance in the bulk materials handling industry,” Pieterse concludes.