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Abstract UG2 is a low grade PGM ore, with value concentration in the range of 1–2 ppm. In this paper, we aim to determine whether the PGM values in the UG2 ore are associated with a soft or hard mineral phase. The anticipated benefits of determining which mineral phase the PGMs are associated with is that such knowledge may be very useful in the efficient processing of the ore. We developed and successfully applied a simple model in order to achieve our objective. The development of our model is from fundamental first principles, in which we mathematically manipulate the component mass fraction ratio of a hard component in the ore to develop an expression that we used to predict the mass fraction of the hard component in UG2 ore remaining in the largest size class material after a specified milling duration. Our results show that as the mass fraction of the tracer element retained in the largest size class increases with grinding time, so does the predicted mass fraction of the hard component. This similarity in grinding behaviour and the linear relationship that exists between the tracer element and the hard component theoretically supports that the PGMs in the UG2 ore are associated with the hard mineral phase.

Abstract In this article, the breakage behavior of a bed of silica particles is tested to identify optimum operating parameters to get products in three different previously defined particle size classes. This is done by drop weight tests with steel balls of different sizes (10, 20 and 30 mm) from different heights (up to 2.0 m). Many different techniques have been adopted in comminution in order to find ways of optimizing energy consumption in the size reduction process. In this paper, we apply one such method called the Attainable Region (AR) analysis technique to optimize the impact energy on a bed of silica particles. The attainable region is a fundamental approach that is equipment-independent and can be used to analyze breakage processes. The AR is defined as a set of all possible outcomes, for the system under consideration that can be achieved using fundamental processes operating within the system. The main finding of the article is that the 20 mm steel ball leads to a maximum yield in the intermediate size class.

Abstract In this work, we apply the attainable region (AR) method to laboratory data in order to optimize the milling and leaching processes of a low grade gold ore. To date, no research has been published on the application of the AR optimization technique on combined milling and leaching processes. The advantage of the AR approach lies in its ability to simplify the optimization problem, as searching over a defined space for the maximum of an objective function is a fairly standard procedure. The objective function we selected in this investigation was that of optimizing a linear function of the value of the recovered material minus the cost of both milling and leaching. Using the three variables (milling time, leaching time and recovery), we constructed a 3D plot and used it to obtain all the possible recoveries from the different milling and leaching times. The optimum for our chosen objective was then found by overlaying a contour plot of the objective function on the 3D plot. Our results show that the optimum was obtained at 90% recovery with a profit value of $600, milling time of 30 min and a leaching time of 1750 min.