Abstract

Mine planning in open pit operations defines the material to be extracted, when it will be extracted and its final destination. Conventional scheduling usually considers block values based on geological parameters such the grade of the metal of interest, its mineralogy, and parameters external to geology. The latter parameters correspond, for example, to economic parameters, opportunity costs, types of plant and plant processes. The scope of this research is to include geometallurgical constraints into the optimization problem known in mine planning as the constrained pit-limit problem. In recent years, numerous works have proven that clays have a strong on the flotation recovery process for chalcopyrite or bornite minerals. This impact generates operational problems that, if not controlled, can decrease metallurgical recovery. For example, clays are usually soft rocks and hence the grinding time is modified, thus affecting the operational performance and final recovery. In addition, clays increase the costs associated with water input as they require additional consumption to obtain the expected recovery. All these factors can be handled when they are incorporated in medium to long-term plans, but they are challenging in short-term planning and make most projects uneconomical. In this work, we propose a methodology which adds a homogeneity condition to the optimization problem. The condition is that minerals with similar geometallurgical properties (in this case, the estimated clay content) should be extracted in each period so that the operational mineral processing parameters would remain relatively similar. The algorithm was applied to a case study where zones with different levels of alteration and clay content were modelled. The valuation used standard mining industry economic parameters.