DRF assists production of guar-based depressants

THE MERGER between local depressant supplier, ChemQuest – African Products, and APX Guar will lead to the resumption of full-scale production of guar-based depressants in South Africa. This recent announcement was made at the third Annual Colloquium of UCT's Depressant Research Facility (DRF).

According to Dr Dee Bradshaw, Manager of the DRF, it is hoped that, with continued development by the facility, the resumed production will lead to a product range for international consumption.

Polymeric depressants, derived from starches, plant fibres (especially cotton) and the guar bean are important reagents in the flotation of ores to recover nickel and copper and, especially, the platinum group metals (PGMs).

The guar bean is a traditional peasant crop, with the bulk of the world's supply coming from the Indian subcontinent, where supply and the price are subject to the vagaries of the monsoon climate.

A series of bad harvests in the 1990s coupled with the weak Rand, pushed the raw material price of guar out of reach of the South African industry and led to the closure of local manufacture.

Bradshaw explained that at the same time efforts were being made to grow guar beans in Africa and southern Africa. “It was reasoned that the chances of major crop failure, simultaneously, on two continents, would be reduced and that this would smooth the supply to world markets, so limiting price fluctuations.

“Equally important, a home grown source of raw material would remove the exposure to exchange rate movements,” she added.

Trial quantities of depressants manufactured from the locally grown material have been evaluated by the DRF and have been shown to be as good as the previous commercial product.

The DRF was established in 1999 by the main PGM producers, namely Anglo Platinum, Impala Platinum, and Lonmin, who fund the facility's ongoing research programmes. The international mining group Rio Tinto and the Canadian nickel producer, Falconbridge, have since joined them.

Other work is undertaken for depressant manufacturing companies (many of them South African), including the Dutch AKZO and North American Cytec companies.

The DRF's Annual Colloquium attracted 52 delegates and participants, including 13 representatives of industrial depressant users and 15 manufacturers.

The eight technical presentations covered all aspects of the current work being undertaken within the facility. These addressed various issues, including:

• the influence of changes in depressant characteristics on overall flotation performance;
• the behaviour and response to depressants of specific minerals; and
• novel methodologies and tools for testing and the evaluation of results.

The DRF is situated within UCT's Department of Chemical Engineering, where work has began to construct a new building to house the department.

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