The CSD debottlenecking project at Assmang Chrome’s Machodorp Works in South Africa is intended to improve the production process and increase profitability. LogiProc, an engineering services company, is responsible for designing and constructing the upgrade.
Material being conveyed in the crushing and screening plant is high carbon ferrochrome with a chrome solid density of up to 7.1 t/m3 and a total bulk density of 2.45 t/m3. The particle size distribution is minus 260 up to minus 3 mm. To reduce wear, LogiProc decided to introduce Weba Chute Systems and these were installed in 2009 in the bin feed, crushing and screening sections of the plant. Custom designed for the transfer point served, each Weba Chute System is configured to control the direction, flow and velocity of the calculated volume and type of material processed in a particular application.
At Machodorp, the chute in the bin feed section is fed by a front end loader and from there the material is conveyed to the crusher building. This chute is more robust in construction to facilitate the impact of the loader bucket while discharging the material. According to Weba Chute Systems’ Ted Cruikshank, the chutes are designed using a “supertube” or cascade effect where 95% of the moving material runs on a bed of similar material at any one time.
Cruikshank explained, when viewed in slow motion, the bottom layer of particles in the product screen is seen to move in a tumbling motion rather than gliding down the chute. “This motion creates significantly reduced wear and, in many cases, the lip remains completely covered by material and never needs replacement. This manner of controlling material movement is taken a step further by designing the internal angle of the transfer chute to match the product with the belt speed and in doing so, spillage is either completely eliminated or greatly reduced.”
Six more Weba Chutes will be installed in the crusher building with the balance of nine chutes being installed in the screening plant.