Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng Breakage characterization of gold ore components A. Wikedzi a,b, ⁎ , S. Saquran a , T. Leißner a , U.A. Peuker a , T. Mütze a a TU 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 ARTICLE INFO Keywords: Breakage Breakage energy Breakage probability Breakage function Selection function Work index Ore components ABSTRACT In the comminution of heterogeneous bulk mixtures, the comminution behavior of the individual components plays a major role. The present study discusses the linkage between breakage of single ore components and their influence to the breakage characteristics of a defined bulk mixture. Thus, five components were identified from a heterogeneous gold ore material from Buzwagi Gold Mine in Tanzania by washing and manual sorting. The components were characterized in terms of particle size by sieving and composition by XRD. The breakage properties were determined by standard Bond test, batch grinding, and single particle tests. The breakage characteristics were linked to the composition of the components and the bulk sample. The study reveals dif- ferences in breakage behaviour of the components as well as their influence in the breakage characteristics of a heterogeneous bulk mixture. 1. Introduction Most of the fundamental studies for size reduction and modelling of comminution processes are based on a homogeneous ore material (i.e. single ore component). However, particles in real comminution systems are heterogeneous in composition and physical properties (i.e. shape, size) and have high differences in grindability (Bueno et al., 2010; Csőke et al., 2013; Kapur and Fuerstenau, 1988; Wedekind and Schubert, 1984). Distinguishing between heterogeneous ore compo- nents has benefits which include; designing milling circuits to treat ores based on a single or a group of valuable components, adjusting process parameters in favour of only the mineral phase of interest (selective grinding), and as a base for development of sensor based pre-con- centration techniques (gangue minimization before milling stage). In SAG mill operation for example, the hard component is found to dominate the mill throughput and content, and therefore the mill throughput can be unexpectedly sensitive to a small change of this fraction in the feed. Also the mill power prediction is affected when the feed has components with different specific gravities (Bueno et al., 2010; Napier-Munn et al., 1996). In the literature, still little is reported in terms of ore components breakage. The present work gives the linkage between breakage of single ore components and their influence on the breakage behaviour of a defined bulk mixture. Thus, five components were identified in a heterogeneous gold ore from Buzwagi Gold Mine in Tanzania by washing and manual sorting. The components were characterized for size by sieving and composition by XRD. The breakage properties were determined by single particle breakage tests (i.e. compression) for selected fractions, as well as standard Bond test and batch grinding tests. 2. Theory 2.1. Grinding kinetics It is generally accepted that the rate of breakage of particles of a certain size is proportional to the amount of that size present. The as- sumption is known as first-order breakage law and results in a similarity between milling and chemical reactions (Reid, 1965). The rate of breakage of a material in the top size interval 1 can be expressed as (Austin, 1972): − = dw dt Sw t () 1 1 1 (1) S 1 is the specific rate of breakage (time -1 ), w t () 1 is the weight fraction of the material at time t. If S 1 does not change with time (i.e. first-order breakage process), Eq. (1) integrates to: = − = w t w St () exp( · ) t 1 0 1 (2) The following model was used by Austin and co-workers (Austin et al., 1984) to express the effect of particle size on the specific rate of breakage: https://doi.org/10.1016/j.mineng.2020.106314 Received 12 December 2018; Received in revised form 20 February 2020; Accepted 1 March 2020 ⁎ Corresponding author at: Department of Chemical and Mining Engineering, University of Dar es Salaam, P.O. Box 35131, Dar es Salaam, Tanzania. E-mail address: awikedzi@udsm.ac.tz (A. Wikedzi). Minerals Engineering 151 (2020) 106314 0892-6875/ © 2020 Elsevier Ltd. All rights reserved. T