:: New Pressure Jig Plant Revitalises Tanzanian Diamond-Mines Output

Australian specialist in the design of mineral processing equipment that focuses on gravity separation solutions, Gekko Systems, in collaboration with the team at Williamson and DeBeers technical services arm, has commissioned a 600t/h InLine Pressure Jig plant at the Williamson Diamond Mine, Tanzania.

The mine, located south of Lake Victoria has been operating for over 60 years, with the management of the mine currently performed by diamond mining giant De Beers.

Over the past two years, the recovered diamond grade at mine has been reducing.

This led to the mine being placed in a marginal position, providing an interesting challenge to mine manager John Acland, and the team at Williamson. Extra diamonds were required to increase revenue. However, this had to be achieved at a low capital cost and without a significant increase in operating costs.

The mine had completed a conceptual design of a conventional diamond treatment plant including feed preparation and a dense media separation (DMS) circuit. No scrubbing or crushing was required, as the material has already been treated through an old DMS circuit before being deposited on the tailings dump. The conventional plant proved to be too costly.

Jigs with hutch water pipes installed

The InLine Pressure Jigs changed all that, as Gekko Systems offered a cheap and reliable method of concentrating diamondiferous material prior to the final concentrating process of the DMS, explains Senior Mining Engineer Jonny Velloza. The InLine Pressure Jigs changed all that, as Gekko Systems offered a cheap and reliable method of concentrating diamondiferous material prior to the final concentrating process of the DMS, explains Senior Mining Engineer Jonny Velloza.

Williamson had heard that Debtech and Gekko Systems had been successfully performing trials, using the InLine Pressure Jig for shell removal on the marine vessels and identified the possibility of using the Jigs on their tailings material.

The Jig was installed in July last year at Williamson and a series of tests were completed on the viability of recovering diamonds from the tailings.

The first round of tests made use of tracers, with exceptionally good results being achieved, and the second round produced the first diamonds, enthuses Williamson Metallurgist Danna Myburgh.

The InLine Pressure Jig concentrated the diamonds by a factor of ten times at an operating cost of less than US$0,02/tonne treated. A bulk sample program was carried out and numerous diamonds were recovered.

The InLine Pressure Jig used during the test was able to recover fine diamonds, which is where the revenue lies in the dumps that we have targeted. The jig was also able to recover flat diamonds, says Velloza.

A complete conceptual and detailed design of the plant was performed on site with significant input from Nigel Grigg, Gekko Systems and the De Beers research unit, Debtech in South Africa.

The plant is designed to treat 4,2 million tons a year of old DMS tailings material that was deposited on large waste dumps, created between 1958 and 1974. The resource that is being targeted is some 20 million tons in extent. The plant treats 600t/h of between 1,5mm and 25mm material treated by six InLine Pressure Jigs. The IPJ's have allowed us to reduce the overall cost per ton treated, with a low associated capital cost. They have also reduced the power consumed per ton treated and the water consumed during the treatment of the dump material has also been reduced, says Velloza.

The InLine Pressure Jigs

The whole project was performed within a year, although we have not yet reached full production capacity the indications are that we should be able to sustain the designed throughput within eight weeks of putting the first ground through the plant, he says.

We are very happy with the performance of the IPJ units and, in fact, we are in the process of investigating the introduction of the units into the main treatment plant, which treats normal run-of-mine material.