Engineering & Mining Journal

AUG 2018

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Page 97 of 107

96 E&MJ • AUGUST 2018 PROCESSING SOLUTIONS Afrox, owned by industrial gas and engi- neering supplier Linde Group, said it has developed a unique, fully integrated end- to-end product service offering (PSO) for the global gold mining industry to optimize metallurgical gold leach using oxygen. The Linde Group is a major provider of technology for generation of low-pu- rity (90%-95%) oxygen through the use of its proprietary Vacuum Pressure Swing Adsorption (VPSA) technology. As a mem- ber of the Linde Group, Afrox said it can provide accurate guidance to gold mines regarding their oxygen requirements for both new and existing leach plants. Understanding oxygen demand is ab- solutely critical to ensuring successful metallurgical gold leach optimization, said Rob de Zoeten, metallurgist at Afrox. "The importance of accurately estab- lishing total oxygen requirement is often overlooked and unfortunately in many cases undersized on-site oxygen plants are installed that cannot produce suffi - cient oxygen to optimize the leach." Linde Engineering's oxygen VPSA sys- tem is claimed to enable gold mines to achieve improved gold recoveries, higher plant productivity and throughput, great- er energy effi ciency, and superior environ- mental performance. VPSA is an ambient temperature technology that takes advantage of the different binding capabilities of various gas molecules to a solid, porous material such as zeolites. The VPSA process cycles between adsorption and desorption of impurities as the feed gas fl ows through adsorber vessels in order to produce a continuous high-purity product gas. Be- cause heating or cooling is not required, cycle time can be short, usually less than a minute, which results in a long lifetime for the adsorbent material. Recent advances in adsorption tech- nology and system design by Linde Engi- neering have enabled oxygen VPSA plants to become less expensive, more power-ef- fi cient and smaller in size. The result, said the company, is that an oxygen VPSA system offers a very cost-competitive, fl exible oxygen supply solution, which has demonstrated excellent results. For low-purity applications with fl ow rates from 10 metric tons per day (mt/d) to 342 mt/d — typical requirements for gold mining applications — VPSA has proven to be the most cost-effective solution, ac- cording to Afrox, which also listed other benefi ts. For example, VPSA plants have a low specifi c-energy consumption and operate at low pressure, with booster com- pression to achieve customer pressure de- mands. They offer competitive capital and operating cost per ton of oxygen produced. VPSA plants provide oxygen on demand with easy turndown from 0%-100%, have high availability, are fully automatic, and can be remote controlled and monitored. The Afrox PSO, called Goldox, provides: • An oxygen demand test program for speci- fying oxygen demand requirements; • The supply of oxygen using Linde Engi- neering's proprietary state-of-the-art on- site vacuum pressure swing adsorption (VPSA) technology; • Supply, installation, and commissioning of the oxygen reticulation network, fl ow control panels with safety interlocks and the oxygen injection system; • Ongoing maintenance and downstream oxygen control management if required; and • Provision of a fl exible commercial struc- ture for the supply of oxygen to the mine over an agreed period. As part of the Goldox PSO, Afrox said it can also offer a downstream oxygen management service in which Afrox op- erates and maintains the oxygen injection equipment to achieve the desired dis- solved oxygen (DO) levels in the leach as required, freeing up plant metallurgists to concentrate on managing the gold plant. "The supply of oxygen to the gold leach needs to be supplemented by an effi cient injection system to ensure opti- mum oxygen utilization in the slurry, oth- erwise the benefi t of the oxygen injection may be limited," explained de Zoeten. Afrox will also, through Linde Engi- neering, manufacture, supply, deliver, install and commission plants throughout Africa and will operate and maintain these plants to supply oxygen to its customers. Ore Analyzer Uses MRI Approach Copper miners may be able to reduce en- ergy and water consumption for every ton of metal produced by using an ore sorting analyzer developed by CSIRO. Employing magnetic resonance tech- nology, the analyzer rapidly identifi es ore grade so that large volumes of waste rock, or gangue, can be rejected before entering the plant, signifi cantly reducing the amount of energy and water needed for processing, according to the Australian scientifi c and industrial research organization. The analyzer is available to the inter- national copper market through NextOre, a new company created by RFC Ambrian, Advisian Digital and CSIRO. "NextOre has identifi ed 59 mature cop- per mine sites where the analyzer could be applied to extend their life, capturing 35% New Service and Supply Package for Oxygen-leached Gold Operations VPSA plants, according to Afrox, are standardized and feature modular design, thus requiring less construction and commissioning time.

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