South African mining products provider Fraser Alexander Tailings has partnered with mineral process solutions provider Multotec to develop a tailings deposition solution for the global mining industry that will increase cost savings, productivity and site safety, and reduce environmental impact, presenting a viable alternative to traditional methods.

Fraser Alexander Tailings has already deployed 12 of these new track-mounted, self-propelled cyclone units (SPCUs) into the field at a tailings dam in Stilfontein and has placed an order for a further 12 units with Multotec for a tailings dam in Brakpan.

Fraser Alexander Tailings operations director Aidan Götz says the new units are site specific. “The units have been developed to tackle the particular issues associ- ated with high-tonnage tailings dams. For example, we have deployed the first units at a tailings dam with a tonnage of around 1.8-million tons a month.

“Tailings deposition methods affect how the tailings deposit and settle within the impoundment. Up until now, when cyclones have been harnessed in tailings deposition, this has typically been approached using a multideposition point method, where the cyclones operate in banks. A typical challenge associated with this method, however, is moving the numerous cyclones around the site,” he notes.

Further, he says cyclone deposition can also take place through a single deposition point, where a cluster of cyclones is deployed at a certain spot, operating to uniformly produce the geotechnical specifications required by the engineer. The challenge in this method is that the massive cyclone cluster still needs to be moved around the site.

“These challenges prompted us to investigate the possibility of building an SPCU to overcome the mobility question and suitable for large tailings dams, where the cyclone multideposition point method would be complex. We solved this with the already developed, track-mounted hydraulic mining gun,” he adds.

Fraser Alexander Tailings had started a full tailings dam cyclone study and Multotec was one of the companies contributing to the study. The two companies engaged in talks about the possibility of codeveloping a track-mounted cyclone unit and Fraser Alexander later officially appointed Multotec to put together a set of cyclones to produce the required geotechnical specifications from certain tailings. The company then had to design and manufacture a cluster cyclone assembly to be mounted onto a diesel or electrical self-propelled track chassis developed by Fraser Alexander.

“We needed Multotec’s input to work out how to combine their cyclone technology onto the unit we had conceptualised. The resulting prototype was put to work in an exacting field trial for about nine months and the result exceeded our expectations. Although the original unit is still evolving in terms of minor modifications, Multotec gave us a well-designed cyclone assembly that clearly exemplifies the company’s experience in this arena,” Götz says.

He notes there is a definite trend in the local mining industry that is seeing clients move to the larger, super-tailings dams. Up until now, many mines have run tailings strategies on multiple structures, that is, limiting the size of their tailings dams, but these multiple structures have both cost and environmental implications.

The introduction of the SPCU opens up an alternative to companies producing high tonnages of tailings. In addition to the cost benefits associated with building bigger tailings dams, the remotely controlled SPCU helps to create a safer environment for operational personnel, while having a single point of deposition makes for a far better geotechnical output, compared with a multi- stage approach at this level of tonnage.

“We are currently showcasing the SPCU to clients and are finding that there is a definite appetite out there for this pioneering alternative,” he adds.

Multotec’s Ian du Plessis comments that the productivity levels of the new SPCU are quite high, with a single SPCU with four 420 mm cyclones capable of achieving the same output as 16 conventional 250 mm cyclones.

“We are excited about the part we have played in the development of this unit, proving that we are able to partner with clients to meet their requirements and, at the same time, come up with technological innovations that will benefit the entire industry,” he concludes.