The chrome mine faced various risks in disposing of its tailings and approached Multotec for a solution.
According to Khathutshelo Mutshinyalo, senior process engineer at Multotec Process Equipment, the chrome operation was aware of the challenges that a traditional tailings storage facility (TSF) could create. These include the large footprint of a tailings dam, the expense of lining the tailings dam and the environmental and social impacts.
"The mine management was keen to conserve scarce water resources by avoiding evaporation," said Mutshinyalo. "They also wanted to prevent any potential groundwater contamination that might result from solution seepage. There was also the local community to consider, to which a normal TSF could present a risk."
Multotec was able to explore the full range of its dewatering solutions before recommending the most suitable one for this application, he said.
The filter press technology was the chosen option, as it was shown to meet the duty requirements in the most cost-effective manner. As a mechanical dewatering strategy, the filter press was able to immediately recover about 80% of the clean water in the slurry.
"The cake that is left from the tailings after water removal is then easily moved by conveyor to a dump area," Mutshinyalo explained. "This dump is much simpler and safer to manage than a tailings dam."
The solution facilitates short cycle times, less wear on consumables and lower power consumption. The cakes are also easily released from the cloth and leave little residue behind on the cloth. He highlighted that the process of reaching the selected solution was driven by thorough investigation, extensive test work and many years of experience in the field. He noted that it always begins with a detailed understanding of the conditions that exist at the site, as well as the customer's priorities.
"With the support of the research team at our testing facilities in Spartan, we were able to test the behaviour of the customer's slurry samples with various Multotec solutions," said Mutshinyalo. "This allowed us to confirm not only the best technology for the application, but also to innovate our equipment for optimal results."
In this case, the abrasive impact of the tailings material was one of the key factors to be accommodated. While the filter press was proven to be the most effective solution, there was still considerable wear experienced by the filter cloth in the press.
"Combining our field experience and metallurgical expertise, we looked more closely at possible innovations for this aspect of the equipment," he said. "We developed an improvement that would better protect the high-wearing areas of the filter cloth and deliver longer wear life."
The detailed preparation behind this solution, and Multotec's practical expertise in installing and maintaining its equipment, meant that final commissioning on site could be done without delay.
Mutshinyalo noted that another recent application of filter press technology was in coal tailings, this time for a coal mine in the Mpumalanga area. Test work was again effectively used to find the solution best suited to the application.
"Here, we needed the filter press to operate in demanding conditions including a high tonnage throughput," he said. "Once again, the focus was on innovation where we customised the filter cloth to improve its rigidity and life."
The result was that the cycle life per cloth was doubled based on typical tailings applications - a considerable improvement in the wear life. Apart from the robustness of the filter press, the feed arrangement and process control were optimised to suit the process.
In addition to these applications, Multotec has also applied filter press solutions to copper sulphide, copper oxide and gold sludge applications. The company's range of equipment and depth of technical expertise allows turnkey solutions which include the various items of auxiliary equipment around the filter press.
"Our branch infrastructure and network around the country gives us a quick response capability with our customers," concluded Mutshinyalo. "We are always mindful that - alongside the optimal solution - customers need quick action by all partners to keep operations running smoothly."