Red mud is the waste product generated by what is known as the Bayer Process when refining bauxite to produce alumina (aluminum oxide). Via a purification process, alumina can be refined to produce aluminum. However, bauxite—which is the most important ore available for producing aluminum—may contain only 30-60% aluminum oxide. The remaining composition consists of silica, iron and other various metals and oxides.
Considering the worldwide demand for aluminum and the amount of bauxite that has been processed to extract alumina, there are vast pools of red mud being held in containment areas across the globe. Obviously, this is a major environmental problem—because of the high alkalinity of the sludge—that requires new ideas that can be used to process the waste stream.
One idea is to pre-process the bauxite through a dry separation process that can concentrate the alumina and reduce the iron, clays (kaolinite) and other inerts before it goes through the Bayer Process. This process reduces the amount of reactive silica in the bauxite fed to the Bayer process, as well as removing a percentage of the inerts (such as iron) that contribute to red mud generation. The result is a higher yield of alumina from the bauxite, lower consumption of caustic soda, and lower volumes of red mud generated. The remaining low alumina bauxite materials can then be used in the production of cement and for highway construction projects.
ST Equipment & Technology’s proprietary triboelectrostatic belt separator provides a low energy, low cost solution to reduce red mud generation. Our process is effective at separating minerals and metal ores that have only been achievable previously through flotation (wet) techniques. The different grades of materials produced can be a major economic resource for mining operations currently producing or processing bauxite. The STET is low operating cost, high rate and entirely water and chemical free, making it very environmentally friendly.
Our separators can also be used on-site at mining operations, eliminating the need (and cost) for transportation of low grade bauxite. The high-efficiency, multi-stage process can handle a high volume of material without using a lot of energy, providing our clients with a reduction in toxic and potentially dangerous materials (red mud), a greater output of valuable materials that have been previously overlooked, and low operating/overhead costs.
STET is proud to contribute an efficient and high-value answer to the world’s ever-increasing red mud problem while also providing extreme environmental stewardship. Let’s keep working together to make the world a better place for everyone.