Sandvik Mining Systems has pulled out all the stops to provide Sasol Mining with an end-to-end bulk materials handling solution for its new Shondoni Colliery in Secunda.

Work is currently underway on the project 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 (21km overland) and high volumes of run-of-mine coal required, the conveyor also needs to span a number of waterways, roads and skirt 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.

Engineered solution

“Our state-of-the-art design incorporates a single drive system to reduce power consumption and preclude the need for a mid-way transfer point and associated infrastructure and manpower. It also minimises coal degradation as Sasol Synfuels require relatively high grade coal from the mine, with large lump sizes and minimal fines,” says Rudi Pieterse, market development and sales manager for Sandvik Mining Systems.

“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 provide even distribution of materials across the surface area and minimise drop forces (to prevent degradation of the material). Coal drawn from the main bunker then makes its way to the main overland conveyor.

Sensitive areas

While maintaining the same capacity as the previous conveyor, it takes a massive 5 megawatts of installed drives (four at the head and a single drive at the tail) to move the coal over the required 21km. Complicating the overland journey, its trajectory requires five horizontal curves (6000m radius) to guide it through an existing corridor.

Numerous sensitive water crossings, with the longest one spanning 700m, 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. A massive 80 ton counter weight provides the required tension to keep the belt operating trouble-free and without slippage at either end. At landfall the conveyor feeds a number of 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 in place of vibrating chutes that allowed us to minimise moving parts and so cut energy consumption and slash maintenance requirements.”

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

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