Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng Breakage and liberation characteristics of low grade sulphide gold ore blends A. Wikedzi a,b, ⁎ , M.A. Arinanda c , T. Leißner a , U.A. Peuker a , T. Mütze a a Technische Universität Bergakademie Freiberg, Institute of Mechanical Process Engineering and Mineral Processing, Agricolastraße 1, 09599 Freiberg, Germany b Department of Chemical and Mining Engineering, University of Dar es Salaam, P.O. Box 35131, Dar es Salaam, Tanzania c University of Liège - GeMMe, Laboratory of Minerals Engineering and Recycling, Sart-Tilman Campus - Building B52, 4000 Liège, Belgium ARTICLE INFO Keywords: Grinding kinetics Bond test Mineral liberation Sulphide gold ore ABSTRACT Within the scope of the evaluation and optimization of a grinding circuit, the breakage and mineral liberation characteristics of three low grade sulphide gold ore blends have been investigated by Bond tests, batch grinding tests, and mineral liberation characterization. The tests were conducted in a size range from 0.063 to 2 mm. It was found that the breakage of all blends follows a first-order behaviour for all feed sizes. The work index was correlated with the quartz content and the breakage rate deceleration parameter, which both showed a linear relationship. The correlation between breakage function fineness parameter and first-order rate constant also satisfied a linear relationship .The breakage parameters established from batch grinding and grindability studies indicate differences in the breakage behaviour of the three ore blends. However, the mineral liberation prop- erties of the valuable phase in three blends show minor differences. 1. Introduction In the minerals industry, it is important to understand how mills will respond to variations in the grindability of ores coming from different parts of a deposit. It is based on the fact that comminution accounts for approximately 65–85% of all energy used for processing ore (Deep level mining consumes the major part in some mines) and that only 1–2% of the supplied energy is translated to the creation of new surface area (Tromans, 2008). Nevertheless, comminution circuits determine the success of overall mineral processing plants; sufficient comminution products are the basis of good results in beneficiation, extraction and recovery stages, and vice versa (Wills and Finch, 2016). The main purpose of comminution is to liberate valuable minerals from the gangue prior to subsequent beneficiation processes such as flotation or leaching. However, the performance of comminution circuits is typi- cally modelled, designed or assessed based on product size reduction rather than liberation. In order to properly design, diagnose, monitor and optimize comminution processes, the liberation characteristics of ore minerals have to be of equal interest and should not be ignored. If such aim is achieved, not only is energy saved by size reduction pro- cesses, but also, any subsequent separation stage becomes easier and cheaper to operate. One of the main challenges in mineral liberation is the changing grinding and liberation behaviour of the material as the mineralogical composition of the feed varies with time. Therefore, the ability to predict how minerals act during grinding will be important for two reasons: (1) the output of processing plant can be projected based on present condition, and (2) further actions can be taken in order to meet the target product size. The grinding result is determined by two components, the circuit or equipment on one side and the material itself on the other. Studies on the correlation between mineralogical composition of the material and the grinding properties of blends, ores or pure minerals provide in- formation about the integral or individual liberation characteristics. Thus, it becomes possible to estimate and predict the liberation based on mineralogical data of a deposit, even before a mine is in operation. Another approach in studying the grinding behaviour is by de- termination of Bond’s work index (Bond and Maxson, 1943). This is the comminution parameter which expresses the resistance of material to crushing and grinding. It is derived from the Bond grindability test, which is a dry laboratory simulation of closed circuit grinding. Apart from Bond’s work index, selection and breakage functions are used to describe the grinding kinetics. This is based on the theory of commi- nution that considers the process as being represented by two events (Kelly and Spottiswood, 1990): (1) the fracture event, where a particle is selected for breakage (represented by the selection function), and (2) http://dx.doi.org/10.1016/j.mineng.2017.10.009 Received 26 May 2017; Received in revised form 6 October 2017; Accepted 7 October 2017 ⁎ Corresponding author at: Technische Universität Bergakademie Freiberg, Institute of Mechanical Process Engineering and Mineral Processing, Agricolastraße 1, 09599 Freiberg, Germany. E-mail address: alphonce-wendelin.wikedzi@mvtat.tu-freiberg.de (A. Wikedzi). Minerals Engineering 115 (2018) 33–40 Available online 17 October 2017 0892-6875/ © 2017 Elsevier Ltd. All rights reserved. MARK