:: Mintek Develops More Cost-Effective Grinding Media

Mintek, specialists in mineral and metallurgical research and development (R&D), technology transfer and beneficiation, in association with industry and university partners, has begun a major project to develop a more cost-effective type of grinding ball for the minerals industry.

With a budget of R5-million spread over three years, the project is funded by the National Research Foundation’s (NRF) Innovation Fund. Anglo Platinum, the University of Pretoria, and Prima Industrial Holdings are Mintek’s project partners.

The programme will initially focus on developing a grinding ball for the platinum-group metals (PGM) industry, which could later be expanded to include other sectors. "Grinding, including the energy input, typically constitutes about fifty per cent of the total costs of metallurgical processing", said Dr Jones Papo, head of Base Metals in Mintek’s Advanced Materials Division (AMD). "South Africa’s PGM industry consumes more than 70 000 tons of grinding media each year, at an annual cost of about R500-million. If a ball can be developed that exceeds the performance of current products at a more competitive price, it would result in a significant reduction in processing costs. A high quality product such as this would also create an excellent export opportunity."

Mintek has been involved in R&D on grinding media, including quality control work for producers and consumers, for more than twenty years. During this time, a large amount of information has been built up on the effects of different compositions, microstructures, and heat treatments on grinding ball performance.

For the current project, five promising alloy compositions have been selected for initial investigations. Samples produced in laboratory-scale melts are undergoing screening for their mechanical and metallurgical characteristics, and their microstructures will be optimised for the best combination of impact and wear resistance. Balls cast from the three most promising materials will then be evaluated through Mintek’s own quality control system.

In the subsequent stages of development, pilot-scale batches of balls will undergo marked-ball tests in an industrial mill, to compare their wear rates with those of commercial grinding media. For the final evaluation, full-charge performance trials will be undertaken on one or more milling circuits over a period of about nine months.