Engineering & Mining Journal

DEC 2018

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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FLOTATION DECEMBER 2018 • E&MJ 53 www.e-mj.com HydroFloats Running at Cadia By Jaisen Kohmuench, Eric Wasmund, Eriez Flotation Division; and Brigitte Seaman, Luke Vollert, Newcrest Mining In the December 2017 issue of E&MJ, Eriez reported on the eco- nomic benefits and preliminary metallurgical results of coarse particle flotation using the patented HydroFloat separator. 1 The major benefits include the ability to increase grind size, resulting in less grinding energy per ton of processed ore. A result of this is that the concentrator tailing stream is coarser, making it easier to de-water and more useful as a building material. The out- come is improved global recovery while reducing energy costs or increasing concentrator throughput while maintaining the same recovery prior to the increase in grind size. A number of pilot campaigns and engineering studies have considered the benefits of adding a coarse particle flotation mod- ule using HydroFloat technology in either the mill circuit or to scavenge tails. A comparison study based on ore from Capstone's Cozamin mine quantitatively showed the benefits of using a HydroFloat on mill ore versus tails scavenging. 2 While there is greater benefit to placing the HydroFloat in the mill flowsheet, this approach is more challenging for an existing installation. For a brownfield installation, coarse particle flotation technology can be used to re-process the concentrator tailing stream, allowing for the capture of coarse values that were not recovered from the primary flotation circuit. A benefit of this approach is that it can be un-coupled and operated independently from the rest of the plant. Rio Tinto Kennecott ran a HydroFloat-based pilot plant at the tailing facility for their Copperton concentrator. They report- ed an additional recovery of 70% copper and 90% molybdenum of the coarse fraction was achieved by simply scavenging their tailings stream before final impoundment. 3 Newcrest in Australia — a pioneer in coarse particle flota- tion — reported the benefits of this technology, as presented by Brigitte Seaman and Luke Vollert in their paper presented in Vancouver at World Gold 2017. 4 In their manuscript, Newcrest showed that high recoveries of gold were realized for multiple test campaigns — including those conducted at a lab-scale — in ad- dition to pilot work conducted on and off site. This work showed gold recoveries ranging between 80% and 95% were achieved for particles nominally 600 x 150 micron. This abundance of test- ing has helped to de-risk the technology for sulfides. In fact, as reported last December, Newcrest is building a plant for treating tails from their Cadia concentrator in New South Wales, Australia. Cadia's Coarse Ore Flotation plant for treating tailings was re- cently commissioned and is now being optimized, as announced in their recent investor day presentation. This module is based on two major proprietary unit operations developed and sold by Eriez: CrossFlow and HydroFloat. The Eriez CrossFlow is a fluid- ized-bed classifier used to coarsen feed for the second unit op - eration. The HydroFloat Separator uses an aerated, dense-phase fluidized bed to float liberated and semi-liberated particles at a much coarser size than that which can be achieved using con- ventional flotation. An explanation of how the HydroFloat works can be found below. 1, 2 The installation consists of two modules, each made up of two CrossFlows and one HydroFloat. A photo of a similar installation is shown as Figure 1. A good illustration, which explains Newcrest's value propo- sition, reproduced from Newcrest's Investor Day Briefing Book, is included. 5 The accompanying chart shows two global recovery curves, includ- ing one when coarse ore flo- tation is used and one when it is not. The x-axes repre- sent the energy c o n s u m p t i o n required to achieve a given gold recovery and the 80 % passing size (P 80 ) of the ore produced by the primary mill. These results illustrate quan- titatively the expected ben- efit of coarse particle flota- tion in allowing a coarser grind size (less grind- ing energy and installed capacity) for the same recovery. Be- sides the benefits of lower grinding requirements, other benefits include the production of coarser tails, which are suitable for building impoundment walls or other structures. Newcrest's forward-thinking mindset and transformative vision made this innovative application possible, through collaboration with engineers and vendors and quick adoption of technology. A number of other important mining companies are at dif- ferent stages of evaluating and implementing the HydroFloat technology for improving plant economics and reducing the environmental footprint of their operations. Anticipated bene- fits include reduced energy demand, better water recovery, im- proved overall recovery and coarser tails. References 1. Walker, S., "Squeezing the stone, Improving recovery," En- gineering and Mining Journal , December 2017, pp 44-51 2. Wasmund E., "It's all in the flotation," Mining Mirror, Sep- tember 2017, pp 18-22 3. Eriez/Rio Tinto Press release, 2017, available at www.eriez- flotation.com/news/2017/20/ 4. Seaman, B.A. and Vollert, L., "Recovery of Coarse Liberat- ed Gold Particles Using Pneumatically Assisted Fluidized Bed Flotation," Proceedings of World Gold Conference, Vancouver, 2017. 5. Newcrest Mining Ltd., 2018 Newcrest Investor Day Mar- ket Release, electronically published October 25, 2018, and Investor Day Briefing Book published by the Newcrest Investor Relations Department, October 2018, www.new- crest.com.au, pp. 30, 37,55, 56 58, 60,61,64. Figure 1—This installation consists of two modules, each made up of two CrossFlows and one HydroFloat.

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