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By L. Wade

Laboratory testing of the self-heating propensity of coal, using crossing-point temperature and differential thermal analysis techniques, involves the frequent recording of several temperatures. The volume of data and the desire for high accuracy of measurements motivates an automated recording system. The data which are recorded must be adjusted for calibration factors and the results presented in both graphical and tabular form. The paper describes hardware and software features of a computerised system which is being used to establish the relative propensity to self-heating of a wide variety of coals.

Jan 1, 1987

By A. C. Wingrove

The paper outlines the selection of a dewatered tailings backfill system for the Johannesburg Consolidated Investment Gold Division, and covers the following aspects: (i) 16 Shaft pilot testwork; (ii) engineering design problems relating to the Cooke 3 Shaft backfill operation; (iii) in-line mixing - applications with respect to the Randfontein Estates Gold Mine and Western Areas Gold Mine backfill operations; and (iv) pipeline friction losses.

Jan 1, 1988

By J. Githiria, C. Musingwini

"Cut-off grade is a decision-making criterion often used for determining the quantities of material (ore and waste) to be mined, ore processed, and saleable product. It therefore directly affects the cash flows from a mining operation and the net present value (NPV) of a mining project. A series of different cut-off grades that are applied over the life of mine (LOM) of an operation defines a cut-off grade policy. Due to the complexity of the calculation process, previous work on cut-off grade calculation has mostly focused on deterministic approaches. However, deterministic approaches fail to capture the uncertainty inherent in input parameters such as commodity price and grade-tonnage distribution. This paper presents a stochastic cut-off grade optimization model that extends Lane’s deterministic theory for calculating optimal cut-off grades over the LOM. The model, code-named ‘NPVMining’, uses realistic grade-tonnage realizations and commodity price distribution to account for uncertainty. NPVMining was applied to a gold mine case study and produced an NPV ranging between 7% and 186% higher than NPVs from deterministic approaches, thus demonstrating improved project value from using stochastic optimization approaches. Background on cut-off grade calculation and optimizationCut-off grade is a decision-making criterion that is generally used in mining to distinguish ore from waste material. Consequently, it is used to determine the quantities of material (ore and waste) to be mined, ore processed, and saleable product. A series of different cutoff grades that are applied over the life-ofmine (LOM) of a mining operation defines the cut-off grade policy for that particular operation. The cut-off grade therefore directly affects the cash flows to be produced and the net present value (NPV) of a project at the mine planning or feasibility study stage."

Mar 1, 2019

To determine the characteristics of a mineral deposit, the usual practice is to take samples, analyse the properties of those samples and infer the characteristics of the deposit from these properties. This analysis can be done using statistical methods. In the present work we are concerned with two types of statistical approaches, classical statistics and spatial statistics. If one uses classical statistics to represent the properties of the sample values, the assumption is made that the values are realizations of a random variable. The relative positions of the samples are ignored, and it is assumed that all sample values in the mineral deposit have an equal probability of being selected. The likely presence of trends, zones of enrichment, or pay shoots in the mineralization, is ignored. The fact that two samples taken close to each other are more likely to have similar values than if taken far apart is also not taken into consideration. In contrast, spatial statistics will be used if one chooses to consider that the sample values are realizations of random functions. On this hypothesis, the value of a sample is a function of its position in the mineralization of the deposit, and the relative position of the samples is taken into consideration. The similarity between sample values is quantified as a function of the distance between samples and this relationship represents the foundation of spatial statistics. There are few situations where classical statistics can be used. The assumption that all sample values in the mineral deposit have an equal likelihood of being represented will be satisfied only if the sample values are randomly distributed, or if the sample positions are random. Sample values are in fact never randomly distributed within a mineral deposit. Further- more, geologists usually avoid taking samples at random (random sampling), as it is correctly accepted that samples located on a regular grid, or approximately on a regular grid, give more information than randomly located samples. In practice, classical statistics should be used only in the early stages of exploration, when the number of samples available is relatively small and the distances between samples are large. In these circumstances, and whenever the information available is not sufficient to permit the use of spatial statistics, application of the methods described in this chapter is justified.

Jan 1, 1978

By M. Izadi Yazdan-Abadi, S. H. Amiri, M. Ramezanizadeh, M. Bazmandeh

Iron ore concentrate is used as the fresh feed of pelletising plants. The green pellet properties depend on iron concentrate characteristics such as particle size distribution (PSD), specific surface area (Blaine value), iron grade, moisture content and grinding methods. The grinding methods affects particle size distribution and Blaine value. To find out the effects of grinding methods on pelletising process, green pellets were produced with concentrates that were reground by means of HPGR (high pressure grinding rolls) and ball mill. The Blaine values of ground concentrates in both types of milling were approximately 1400, 1600 and 1800 cm2/gr. The results of green pelletising tests on a pilot plant scale showed that at the same Blaine values, drop numbers of green pellets produced by ground concentrate inside HPGR were higher than the green pellets produced by ground concentrate inside a ball mill. Also, reground concentrates by means of HPGR, in comparison with ball mill, caused the production of green pellets, at higher wet and dry compression strengths. As a result, it was found that preparing the pelletising feed by means of HPGR led to more positive effects on the properties of green pellets. Keywords: Ball mill, HPGR, green pellet, drop number, wet and dry compression strengths

Jan 1, 2020

By I. O. Flores, A. Anani, H. Li

Current technological advancement has increased the exploitation of deeper ore bodies using underground methods. In certain cases, the mineral deposit starts near the surface and continues deep within the earth's crust. Such deposits are best mined with both underground and surface methods. Two main techniques are used to determine the optimal transition depth from surface to underground - a disintegrated approach and an integrated approach. Both methods have limitations in their use to determine the optimal transition depth. The objective of this research is to investigate the conditions in which an integrated approach to the transition depth problem is superior to a disintegrated approach. Three binary integer linear programming models are developed for this purpose: a surface and underground model for the disintegrated instance and an integrated model. A case study is performed to validate the models, with a comparative sensitivity analysis to obtain operational insights.

Sep 1, 2021

By N. A. Chapman

The effect of using conventional crushing and HPGR in combination with dry or wet milling was investigated using a base metal sulphide (sphalerite), and a PGM (platinum group minerals) ore in order to determine how these different processes affect the flotation performance. In the case of sphalerite, irrespective of the crushing procedure (HPGR or conventional), dry milling resulted in the highest grades and recoveries of zinc. Conversely, in the case of PGMs, a similar treatment produced the poorest results. The results were investigated further by comparing the relative effects of factors such as percentage liberation, particle size, and surface properties of the samples produced by the different milling procedures as well as the concentrates and tailings obtained from the flotation tests.

Jan 1, 2013

By B. P. Watson

The Bushveld platinum group metal deposits in South Africa are the largest in the world. These deposits occur as two distinct stratiform tabular ore bodies and strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2300 m. The mining method is a variation of planar open stoping. Crush pillars are widely used to support the open stopes. These pillars are designed to fail and the residual strength provides the required support resistance to stabilize the stoping excavations. This paper describes the in situ measurement, of stress within a Merensky pillar from Impala Platinum. These measurements were used to derive a stress-strain curve that includes pre and post failure behaviour. 2D FLAC modelling, with strain softening, was done to investigate how damage expands into the hanging- and/or footwall. Although the so-called ?squat? effect is always present, the modelling suggests that it does not dominate the pillar system behaviour at larger width to height ratios. Punching of the pillar into the hanging- and/or footwall increasingly controls the pillar system behaviour with larger width to height ratios. The paper investigates the behaviour of a system that incorporates the immediate hanging- and footwall, as well as the pillar itself.

Jan 1, 2009

By S. K. Mahata, P. G. Suresh Kumar, B. B. Singh

Improvement of post tap hole practices is achievable by mechanized handling of melt during the production of Ferro Chrome, resulting in higher recovery of chromium. The paper deals with modern practices adopted in the production of ferro-chrome since past two decades. The methods and practices deal with various areas : a) Improved method of operating the tap hole by selection of right quality of refractory to maintain the life of tap hole. b) Collection of melt in different types of receptacles like refractory brick lined mild steel ladles, cast steel ladles, cast iron pans being chosen for cost effective and efficient handling. c) Separation of slag and metal, casting of metal, crushing, sizing and stock piling etc. d) Slag disposal and recovery of entrapped metal. The drive behind the above development is continuous improvement, which results in higher chromium recovery and reduces loss of metal in slag by completely mechanized method so as to be at the same level with producers of ferro-chrome in other advanced countries , in the emerging global economy.

Jan 1, 2007

By G. Sánchez, S. Seiler, B. Klein, T. Cebeci, P. Bradshaw

The Decar Nickel District is a greenfield discovery by FPX Nickel Corp., of nickel mineralisation located in central British Columbia (BC), Canada. The Baptiste deposit is part of the Decar Nickel District and is a unique deposit containing a nickel-iron alloy mineral called awaruite, with over 2-billion tonnes of inferred resource grading 0.12% Davis Tube Recoverable (DTR) nickel. This deposit represents a significant nickel resource. Awaruite is a high density and ferromagnetic mineral, which could be recovered, along with magnetite that is also present in the samples, using magnetic separation. However, there is still a lack of understanding of the properties of the awaruite and its metallurgical response. This information is imperative for the set-up of the variables involved in its concentration. The aim of this paper is to show and discuss the effect of magnetic field strength for the recovery of nickel from Baptiste deposit samples. Magnetic separation at bench and pilot scale with different magnetic field strengths is evaluated as a concentration method for awaruite. Mineralogical information is provided to support the results and also to briefly assess the variability of DTR nickel within the deposit. The Baptiste deposit is unique and will benefit from a sound scientific understanding of the process solution as well as other ongoing work. If successful, the outcome will lead to the development of a mine. With greater than 2-billion tonnes of inferred resource, the mine would represent a significant new source of nickel globally. Keywords: Nickel ore processing, magnetic separation , awaruite, magnetite

Jan 1, 2020

By Y. Yang, M. Zhang, X. Xia, S Shi, Z. Shen

A stepwise arrangement of flotation cells is the most common layout of a flotation circuit in the mineral processing industry. In such a design, slurry flows from upstream to downstream by means of gravity, and the middling products are returned to previous stages by pumps. This paper will introduce an alternative solution in which the forced-air and slurry-induced flotation cells are adopted so that all the flotation cells can be placed on the same horizontal platform and no pumps will be needed for middling product transferring. The technology of the forced-air and slurry-induced flotation cell will be described in detail, including unique features, the working principle and the related fundamental problems. The comparison of capital investment, operating cost and metallurgical performance will be made between the conventional stepwise arrangement and the samelevel arrangement technology based on industrial practice. Keywords: Forced-air and slurry-induced flotation cell, same-level arrangement, stepwise

Jan 1, 2020

By S. M. Brabyn

The wear in mild steel pipelines used to convey rod-milled waste backfill was determined and then compared with that obtained using a laboratory rig designed to simulate the wear condition in slurry pipelines. The relative importance of corrosion and abrasion was investigated under various conditions of water quality and particle size distribution. The laboratory rig was then used to evaluate other possible materials of construction for backfill pipelines. A preliminary assessment of the economic viability of pipelines made of alternative materials is included.

Jan 1, 1988

By R. P. King

A class of gravity separation unit operations in ore-dressing relies for its operation on the production of a stratified bed. Heavier material gravitates downwards, and separation is achieved by splitting the ore horizontally, with the recovery of a dense stream and a lighter stream. The important ore-dressing unit operations that fall in this class are the jig, the Reichert cone and the pinched sluice. A new quantitative model based on Mayer's potential theory is developed here. This model is developed completely for the simple case of binary mono-size particulate materials, but the extension to units operating with feed material distributed over particle size and density is discussed in principle. The model can be used to predict the performance of these units and is very suitable for simulation. The model is tested successfully against experimental data obtained from a batch jig and a Reichert cone.

Jan 1, 1987

By S. Duma

The main sulphide zone (MSZ) of the Great Dyke is cryptic and without obvious stratigraphic markers. Although there are trends in the dimensions of the PGE and base metal profiles across the Hartley Complex, the profiles are invariant within a particular mining area. Ratios derived from these profiles are used to interpret diamond drill cores drilled ahead of underground development. Detailed logging of oriented core shows the exact position and attitude of intersected faults. Metal ratios are used to estimate fault throw to within 25 cm. It is possible to draw detailed sections showing the extent of ground disturbance well ahead of mining. The method has been confirmed by mining and by drilling inclined holes through the fault blocks. Keywords: main sulphide zone, Hartley Complex, Great Dyke, Zimbabwe, platinum, Palladium, Nickel.

Jan 1, 2004

By U. König, N. Norberg

Ore mineralogy defines the properties during processing and metal extraction. Fast and frequent monitoring of the mineral content and related process parameters brings value to the mining operation and material processing. Decreasing ore qualities and increasing prices for raw materials require a better control of processed ore and a more efficient use of energy. Traditionally quality control in mining industries has relied on time consuming wet chemistry or the analysis of the elemental composition. The mineralogy that defines the physical properties is often monitored infrequently, if at all. The use of highspeed detectors has turned X-ray diffraction (XRD) into an important tool for fast and accurate process control. XRD data and their interpretation make the difference in the identification of minerals, in describing their distribution in ore bodies and in their beneficiation during processing. The use of statistical techniques such as Partial Least-Squares Regression (PLSR) or Principal Component Analysis (PCA) on XRD raw data has been successfully trialled to determine raw materials and processed ores, in addition to well established methods for mineral identification and quantification. PLSR can be used to correlate process parameters directly from the XRD pattern without investigating the mineral content. Hidden information present in the XRD pattern but not determined with traditional methods can be used to improve the characterisation of the analysed materials. The practical use for the direct determination of process relevant parameters during exploration and ore beneficiation will be illustrated in several case studies from mining and ore processing. Keywords: Geometallurgy, mineral monitoring, X-ray diffraction, process efficiency

Jan 1, 2020

While some of the practical details of ilmenite smelting are not well documented, there is a substantial body of literature on the principles of ilmenite smelting, and the behaviour of solidified titania slag. This information is summarized, focusing on the basic reactions, departure from equilibrium, the behaviour of impurities, and reactions of solidified slag. The emphasis is on the South African operations.

Jan 1, 2007

A dual rate kinetic model consisting of differential equations is used to describe the kinetics of the adsorption of gold cyanide on activated carbon. The partial differential equation describing the material balance in the liquid phase is written for the special case of a fixed bed system. It is shown that an isotherm for the case of a closed system is required to yield accurate simulations of the equilibrium in a column of activated carbon. Whereas the equilibrium loading of gold cyanide is influenced by the free access of oxygen to the system, the traditional open batch stirred tank experiments, which are used to estimate parameters for the calculation of breakthrough curves for organic solutes, cannot be used here. The program solves this model at incremental heights in the column at a specific future point in time. Runge-Kutta and backwards- difference methods are used in the numerical solution. A Von Neumann method is used to show that the solution is stable. Kinetic parameters can be estimated either from batch experiments or from short column runs. In the latter method the column should not be long enough to contain the concentration wavefront for the system of interest. Results obtained from bench scale continuous column experiments were used to verify the computer model. Pure gold solutions as well as real leach liquor were used in both short column and countercurrent moving bed experiments.

Jan 1, 1987

By E. M. Sacris

The semi-autogenous grinding mill is the bottleneck whenever treating hard and finely fragmented ore at Benguet Corporation's Kaline Concentrator. Low milling rates result from very high and fluctuating mill power draw. Attempts to use a mill horsepower control loop to regulate feed rate were unsuccessful because of operational upsets caused by fluctuations in feed rate on downstream operations. The objective of the computer control was to maximize tonnage throughput by stabilizing the power draw at a high but safe level without upsetting subsequent operations. The semi-autogenous mill is operated in closed circuit with a stationary screen. Instrumentation consists of a feed weightometer, a power transmitter to measure mill load, a headwater flowmeter and an ultrasonic level sensor to measure the mill discharge sump level. A 64 k-byte FOX-3 Foxboro computer processes field data from various sensors and manipulates the input control variables. These variables are the fresh feed rate and the headwater flowrate. Feed rate is controlled through a supervisor-type computer program aimed at maximizing and stabilizing power draw. The control scheme was according to how the operators responded during an operator-directed automatic control mode. Mill dilution is similarly controlled. Results achieved reflect a 3% increase in tonnage milled because of the reduction in control variability that ensued.

Jan 1, 1987

By M. Saghaeian, R. Hejazi, V. Sheikhzadeha, A. H. Baladastian, A. Dehghani Ahmadabadi

This paper describes research done to remove apatite (phosphorus) from hematite ultrafine (70% finer than 25 micron) concentrate, recovered by electromagnetic separators at the FST Tailing Recovery Plant located in Chadormalu Iron Ore Complex through reverse froth flotation. As a result, iron and phosphorus content in magnetic concentrate (flotation feed) were 53.52% and 0.58%, respectively. Therefore, to increase the Fe content and decrease the P content of the sample, reverse flotation tests were applied. Chemical reagents used in this research consisted of sodium silicate as a depressant, sodium hydroxide and sodium carbonate as pH regulators, Alke & Dirol as fatty acid collectors and MIBC as frother. Process parameters including dosages of collectors, depressant and frother, preparation times of depressant and collectors, steps and time of frothing and pH range were selected. After doing flotation tests, in optimum condition, dosages of collectors were 1200 g/t, depressant 1200 g/t, pH in the range of 9.5 to 10, preparation time of collectors in the first step was eight minutes and at the other steps, four minutes; the number of frothing steps 4 and frothing time in each stage was three minutes. In this case, it was observed that the amount of phosphorus in the final concentrate was reduced to 0.05%, the Fe content increased from 53.52% to 61.66% and the Fe recovery achieved was 82.21%. Keywords: Iron ore, hematite ultrafine concentrate, iron and phosphorus content

Jan 1, 2020

PREFACE During the past year, considerable effort was devoted to the implementation of the strategic plan that was adopted by the SAIMM in 1986. Good progress was made in a number of areas, while in others the foundation was laid for future progress. Key Objective of the Institute The key objective of the SAIMM is as follows: To identify the needs of its members and to initiate and give effect to the means whereby the requirements for technology and scientific knowledge of the minerals and metals section of the South African economy are satisfied; and to represent and promote the interests of its members.

Jan 1, 1987