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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Page 54 of 115

FLOTATION DECEMBER 2018 • E&MJ 53 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- 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,, 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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