Determination of optimised cut-off grade utilising non-linear programming
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ORIGINAL PAPER
Determination of optimised cut-off grade utilising non-linear programming Amir Bijan Yasrebi & Andy Wetherelt & Patrick Foster & Gareth Kennedy & Dariush Kaveh Ahangaran & Peyman Afzal & Ahmad Asadi
Received: 25 August 2014 / Accepted: 10 December 2014 # Saudi Society for Geosciences 2015
Abstract One of the most fundamental problems in a mining operation is how to recognise an optimum cut-off grade, which defines the grade for discriminating between ore and waste in an ore body, including ore that is extracted at different periods over a mine life period. Therefore, the identification of an optimised cut-off grade (COG) is a crucial function which has to be monitored during the mine life. The main aim of this study is to propose a modified optimum COG model in order to maximise the profit value (PV) for mining projects. Maximising the PV of a mining operation, which is a nonlinear programming, is subject to different constraints involving a general grade distribution within a deposit and three stages of production namely mining, concentrating and refining. The proposed computer-based model is more effective in long-term planning of the open pit mines. To provide a better understanding of the algorithm efficiency, a numerical example is given and subsequently solved based on the Lane algorithm. In order to achieve this, the LINGO software was employed.
Keywords Cut-off grade (COG) . Profit value (PV) . Non-linear programming . Lane algorithm
A. B. Yasrebi (*) : A. Wetherelt : P. Foster : G. Kennedy : D. Kaveh Ahangaran : P. Afzal Camborne School of Mines, University of Exeter, Penryn, UK e-mail: [email protected] D. Kaveh Ahangaran : P. Afzal : A. Asadi Department of Mining Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran
Introduction A cut-off grade (COG) represents the grade which distinguishes between the ore and waste within an ore deposit. Identification of an optimised cut-off grade plays a significant role during the mine life since the optimisation of cut-off grade is one of the fundamental aspects for open pit mine design and planning (Lane 1964; Lane 1988; Osanloo and Ataei 2003; Yasrebi et al. 2011) since elemental concentrations above and below the COG are moved to different destinations, namely processing plant and waste stockpile (Osanloo et al. 2008). In order to achieve this, Lane (1964) created an algorithm for cutoff grade optimisation in ore deposits as the most frequently utilised methods; in order to recognise COG optimisation to maximise the total profit of the mining project (regardless of the money time value), maximise the net present value (NPV) and maximise the project profit at the time equal to zero (Bascetin 2007; Yingliang et al. 2008). However, this contribution has been developed in the recent years to demonstrate a proper techno-economic in regard to increase NPVs of mining projects, especially in multiple metal deposits (Asad et al. 2005a, b; Asad 2007; Dagdelen et al. 2007). In addition, some other methods based on the Lane algorithm
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