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Simplified processes, suitable technologies key to success – diamond miners told

24th March 2017

By: Ilan Solomons

Creamer Media Staff Writer

     

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Historically, diamond plants were designed on the basis of process engineering excellence. However, this focused excessively on ensuring maximum diamond liberation and recovery, rather than on the defining of the optimal mix of technical and financial solutions.

This is according to project management and engineering company Paradigm Project Management (PPM) MD Jeremy Clarke, who was speaking at an event hosted by the Southern African Institute of Mining and Metallurgy Johannesburg Branch, last month.

He proposed that diamond miners should instead design plants to ensure “business excellence”. Clarke said that, for this to be achieved, diamond producers would have to introduce appropriate modern technologies and simplify their workflow processes.

He commented that one of the technologies that diamond miners should introduce was autogenous milling as it provided a number of business advantages, such as the fact that it combined several unit processes into one including scrubbing, secondary crushing, high-pressure grinding roll (HPGR) recrush crushing, HPGR disagglomeration and recovery plant feed preparation.

Clarke noted that autogenous milling also provided for improved diamond liberation; reduced diamond breakages; removed circulating loads within the plant; generated a high percentage of fine, discard material; reduced downstream unit processes’ required capacities; effectively undertook preliminary waste sorting and treated weathered kimberlite, thereby ensuring easier downstream materials handling.

Further, he highlighted that autogenous milling could have a “significant impact” on the upstream mining processes.

“It can handle less ‘well shaped’ material than conventional crushing. Therefore, it allows for the use of primary jaw crushers rather than the more expensive gyratory crushers or mineral sizers,” Clarke stated.

He said that it also handled fine, sticky material well, allowing for mining finer blasting. “Finer blasting reduces overall mine operating costs, can increase diamond liberation and decrease diamond breakages,” Clarke commented.

Additionally, he recommended that diamond miners use X-ray transmission (XRT) technology as it combined the diamond concentration and recovery process. Clarke remarked that this enabled high-capacity sorting, owing to the system’s increase in computer processing power.

He pointed out that XRT technology could sort materials ranging in size from 150 mm to about 12 mm, with capacities of up to 150 t/h, while concentrates were sent directly to the sort house. Clarke added that XRT technologies also replaced the need for dense-media separation (DMS) technologies in the treatment of materials of 12 mm and larger, thereby further reducing operational costs (opex).

Moreover, waste sorting, combined with autogenous milling, provided for a number of advantages, he said.

“Autogenous milling of kimberlite effectively concentrates waste in the mill recycle load. Historically, this has been crushed, often using expensive HPGRs prior to returning to the mill feed. Waste sorting can remove a very high percentage of the basalt and granite in this stream, potentially up to 80% of the mill recycle load,” Clarke remarked.

He noted that this ensured that diamond miners could lower their power consumption, decrease diamond breakage, lower opex, reduce downstream unit processes’ capacity requirements and reduce wear and maintenance costs.

Clarke averred that XRT technologies were developing rapidly and would eventually be able to treat all required size fractions down to sizes as small as 2 mm. He added that XRT technology would, in time, remove the need for X-ray machines to recovery diamonds from the coarse DMS concentrates.

“In the medium term, XRT technologies will be applied to the recovery plant X-ray machines to improve selectivity and reduce yields. Additionally, laser Raman diamond sorters will become more common as they generate a process stream containing up to 90% diamond,” Clarke stated.

Further, he mentioned that size frequency distribution analysis machines would be installed in diamond recovery plants to provide online information for metallurgical accounting and process management and that secure packaging systems would also become more prevalent to reduce diamond processing risks.

Clarke, moreover, emphasised that security of the diamonds would have to be “fully integrated” into the metallurgical process, as he felt it had traditionally been a neglected consideration in the diamond process engineering design.

Meanwhile, he said that PPM was of the view that the principles of simplicity which have proven to be successful in the diamond industry could be applied to other commodity types.

“This is considered to be an essential part of the necessary move towards a more profitable global mining industry and one that is significantly more environment friendly,” Clarke concluded.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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