Modeling ore degradation during handling using continuum damage mechanics ☆ Luís Marcelo Tavares ⁎, Rodrigo M. de Carvalho Department of Metallurgical and Materials Engineering, COPPE, Universidade Federal do Rio de Janeiro – UFRJ. Cx. Postal 68505, CEP 21941-972, Rio de Janeiro, RJ, Brazil abstract article info Article history: Received 22 February 2010 Received in revised form 29 June 2010 Accepted 10 July 2010 Available online 16 April 2012 Keywords: Degradation Handling Modeling Particle breakage Degradation of steelmaking materials during handling causes a significant economic impact, given the higher prices achieved by lump ore in comparison to finer products. It is relevant to model the amenability of ores to degradation, since it may be used to simulate the response of ores to different sequences of handling and transportation events from mine to port. The paper presents a mechanistic model to describe degradation caused by transfers and drops of particulate materials. The model is based on damage mechanics and the dis- tribution of fracture energies of the original particles, using data collected in impact load cell and tumbling tests. This model, which is capable of predicting the proportion of particles broken and the entire size distri- bution resulting from any sequence of drops, has been validated at a preliminary level using data from drop tests of a Brazilian iron ore. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Ores undergo significant degradation during mining as a result of blasting, mechanical handling by shovels and crushing in order to produce a size distribution that is capable of meeting specifications that are set by customers and the market. Such degradation is partic- ularly relevant in the case of steelmaking materials. Degradation of lump ores, such as coal, iron and manganese ores into fines is often undesirable because lumps have premium prices when com- pared to fines. However, the relationship between the proportion of lump ore and fines that is produced in a given processing plant is co- determined by the ore's mechanical strength and the nature of the crushing and handling processes (Dukino et al., 1995). In addition to that, between the mine and the end user, the lump material is subject to a number of mechanical actions which cause degradation. These include at the mine site: crushing and screening, conveying, stockpiling and rail wagon load- ing; and at the port: rail wagon unloading, conveying, drops at transfer points, screening, stockpiling, reclaiming and ship loading (Sahoo, 2007). A number of experimental studies have been conducted to inves- tigate ore degradation during handling. Some of the conclusions of these studies may be summarized as: • Degradation during handling results predominantly from impact from drops and, to a minor extent, also from abrasion due to gravity flow through bins (Fagerberg and Sandberg, 1973); • Degradation varies with particle size, with coarser particles suffering a greater degradation effect than finer ones (Fagerberg and Sandberg, 1973; Waters et al., 1987); • Greater fines generation is associated to handling weaker ores than tougher ones (Fagerberg and Sandberg, 1973; Norgate et al., 1986; Sahoo, 2007); • Impact surface influences the level of degradation upon impact, and a cushioning effect occurs as the percentage of initial fines increases (Fagerberg and Sandberg, 1973; Norgate et al., 1986; Sahoo, 2007); • Norgate et al. (1986) stated that a drop height of large magnitude will cause more degradation earlier in a handling system rather than later, because of the conditioning of the ore, which removes the weaker particles; • Degradation is significantly reduced by using drop heights below about 1 to 3 m (Fagerberg and Sandberg, 1973; Norgate et al., 1986; Waters and Mikka, 1989). Prediction of the amenability of ores to degradation is relevant, since it can be used to investigate the response of ores to different sequences of handling and transportation events from mine to port. This can be a useful tool to assess the effectiveness of measures taken to minimize degradation during handling. A number of attempts have been made in the last couple of decades to describe quantitatively this phenomenon (Norgate et al., 1986; Teo et al., 1990; Dukino et al., 2000; Weedon and Wilson, 2000; Baxter et al., 2004; Sahoo, 2007), without any particular model finding wide acceptance or being able to describe in great detail the response of the material during the handling processes. The paper presents a simulation procedure that describes degra- dation caused by transfers and drops of the particulate material. It is based on data collected from drop weight, impact load cell tests and tumbling tests, a model from damage mechanics and the distribution of strengths in the original material. International Journal of Mineral Processing 112–113 (2012) 1–6 ☆ A publishers' error resulted in this article appearing in the wrong issue. The article is reprinted here for the reader's convenience and for the continuity of the special issue. For citation purposes, please use the original publication details; International Journal of Mineral Processing, 101(1-4), pp. 21-27. **DOI of original item: doi:10.1016/j.minpro.2010.07.008. DOI of original article: 10.1016/j.minpro.2010.07.008. ⁎ Corresponding author. E-mail address: Tavares@metalmat.ufrj.br (L.M. Tavares). 0301-7516/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.minpro.2010.07.011 Contents lists available at SciVerse ScienceDirect International Journal of Mineral Processing journal homepage: www.elsevier.com/locate/ijminpro