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MEI Online: Commodities: Non-Metallic Ores: Diamond: Latest News: May 30th 2007


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:: Demonstration Diamond-rock Sorter

A demonstration facility, based on a revolutionary new technology for the detection, imaging and sorting of diamonds in kimberlite, is being commissioned at the University of the Witwatersrand, Johannesburg, South Africa, supported by Wits Commercial Enterprise (Pty) Ltd, the university’s commercialisation company, in partnership with Bateman Engineering.

The facility will be used in tests to reveal whether positron emission tomography (PET) can be applied in practice to separate diamond-bearing rock from waste material. It comprises a conveyor and detection system that can be applied to generate the design data needed for the design of a commercial pilot-scale unit.

The conveyor belt will pass a bed of crushed rock, some pieces of which will be spiked with traces of g-ray emitting radioactive sodium-22 (22Na), through the detection system. By varying the speed of the conveyor, it will be possible to determine the detection limits and the viability of this technology.

The use of spiked rock pieces instead of diamond-bearing ore will defer the need to obtain a linear accelerator to irradiate the ore, as the emissions from 22Na are identical to those from diamonds that have been irradiated by a beam of photons.

The software for a fast, real-time computer algorithm to identify diamondiferous kimberlite has also been developed.

This demonstration facility will permit the level of the likely background emissions to be determined and the height above this level that will be required to detect diamonds efficiently, enabling the specification of an appropriate linear-accelerator and detector system to irradiate and detect the diamonds.

Proven technologies are being adapted. The first is PET, used in hospitals for medical diagnoses. However, as detailed images are not required for diamond identification, the processing times will be reduced considerably. The demonstration facility will explore how fast the data can be processed in a simulated mineral-processing environment.

The second is linear-accelerator irradiation. Its wide use in medical applications has led to significant improvements in the capacity to build the required type of machine. This will not necessarily reduce the capital-cost requirements of the project, as a specialised unit will have to be custom made if the project proceeds to the pilot-plant stage. A benefit will be that the much reduced power requirements for diamond identification will greatly reduce the safety measures that are required in hospitals by medical PET systems.

The potential of a technology to quickly locate concentrations of carbon within the rock, and therefore to identify the presence of diamonds, was first identified by (the late) Professor Friedel Sellschop at the University of Witwatersrand. The implications for the diamond industry are significant. A recovery facility would have to handle only a small fraction of the material it now has to process and permit the immediate disposal of the barren material, either underground or on surface. The technology has appropriately been named Diamond-PET.

This project commenced in January 2006 (see Bateman Globe, No. 49, January 2006) and it is anticipated that it will be possible to make a decision about proceeding to the pilot-plant stage after the middle of 2007.




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