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Bokamoso Pellet Plant uses waste to reduce energy consumption, GHG emissions and costs

The Bokamoso pelletising and sintering plant located at the Wonderkop operations takes waste material from mines and agglomerates it into pellets which are then used to heat its furnaces.

In 2004, Xstrata Alloys began to explore alternative supplies of chrome ore and means to improve the efficiency of the older and less efficient furnaces. A study regarding the use Outokumpu technology was conducted, a process that takes the fine ore waste material from the chrome mining operations, including the UG2 chrome tailings from the platinum mines, and uses a chemical process to agglomerate it into spherical pellets.

Following the successful outcome of the study, construction began in May 2005 on a mega chrome ore pelletising and sintering plant at the Xstrata-Merafe Chrome Venture’s Wonderkop operations. The Bokamoso plant became operational in July 2007 and is now at full production, producing 1.2 million tonnes of chrome ore pellets annually, which are used to heat the furnaces at the smelters on the Western Limb.

The Bokamoso plant has substantially increased furnace efficiency. Annually, the pellets are used to produce 522,000 tonnes of ferrochrome. To achieve this level of production, 30% less ore is now required to fuel the furnace, there has been a subsequent 17% reduction in the amount of electricity used by the smelters and 42% less slag is produced. The reduced electricity consumption translates to a saving of 165,913 tonnes of coal and over 390,000KL of water.

The lifespan of the chrome mines has been extended, as 1.2 million tonnes of saleable ore per annum, equivalent to 2 million tonnes run of mine, has been replaced by the fine ore waste material. Approximately 40% less waste is being discarded annually due to the reduction in chrome mining, which has led to reduced levels of dust, fugitive emissions and reductants from the process. There has also been a 40% reduction of Cr6+ in furnace off-gas. Overall, the Bokamoso plant has cut CO₂ emissions by over 300,000 tonnes per annum and has decreased the release of ash by 88 tonnes, SO₂ by over 2,700 tonnes and NOx by over 1,200 tonnes per annum.

The fine ore material, now used in the Bokamoso plant, was previously stockpiled and this initiative has reduced the waste and working capital employed in storing the material. As the Bokamoso plant is located next to the fine ore platinum tailings, the compressed pellets are now transported to the smelters rather than previous wet material, which is heavier and of a greater volume, leading to a saving of approximately 170,000 litres of diesel per year.

Jurg Zaayman, Group Technical Manager for Xstrata Alloys said: “The Bokamoso plant has brought us a number of advantages and we are very pleased with the contribution the plant has made towards improving efficiency across the Group. With the recent power crisis in South Africa, responsible energy use is even more important to both the country and our operations and we are doing everything we can to reduce our power consumption further.”

Xstrata Alloys’ target of improving energy and greenhouse gas intensity across all of its operations by 5% while also reducing greenhouse gas emissions is being supported by the Bokamoso plant.