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By D. Saramak, T. Gawenda, A. Stempkowska, Z. Naziemiec

The aim of the paper is to discuss the possibility of producing aggregates with an increased content of regular particles, as well as to present a method of aggregate production which has not previously been used in the industry. Traditional aggregate production circuits require the application of three or four grinding stages (depending on the particle size of the feed), but for fine particle fractions of aggregates, irregular grains occur on average with a content of 10%. The innovative technological circuit can produce the aggregates with the content below 3%, even in a single- or two-stage crushing circuit. Downstream jig beneficiation of such prepared material results in higher separation sharpness, lower probable error index (Ep) and imperfection (I). Keywords: Aggregate production, jig beneficiation, mineral processing, raw materials

Jan 1, 2020

By N. D. Fernandes

Labour-intensive narrow reef stoping, as traditionally practised in South African gold and platinum mines, is almost unique in the modern first-world mechanized mining environment. Shortcomings of the system include the ever increasing cost of labour, a cap on achievable productivity and a poor safety record, particularly in the field of rock-related accidents. In the absence of sustainable alternative technologies, the South African mining industry has spent millions of rands improving the present system, focusing on improving workplace safety. This paper details the changes to stope support at Impala Platinum?s Rustenburg operations, and the impact on rock-related safety performance. Keywords Stope panel support, narrow reef stoping, improving workplace safety.

Jan 1, 2011

By G. Mucsi, F. Kristály, R. Szabó

Kaolin is one of the most important ingredients in porcelain manufacturing. Its main phase is clay mineral containing aluminum hydrosilicate, namely kaolinite. Beside kaolinite it also contains quartz, illite and feldspars, which impair its applicability. Kaolin is a non-reactive material, but metakaolin can be produced by heat treatment (calcination) of kaolin, which is also used by the cement and concrete industry due to its latent hydraulic (pozzolanic) properties. Beside thermal activation, reactive materials can also be produced by mechanochemical activation in general. This paper deals with the mechanochemical activation of kaolin. The raw material was classified into various size fractions, then ground in a batch stirred media mill under varying circumstances (residence time, circumferential velocity). After grinding, the structural changes of the products were investigated by X-ray diffractometry (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). In addition, the particle size distribution of the ground material was determined by laser scattering. As a result of the grinding experiments and analytical measurements of the products, it can be clearly seen that reactivity of kaolin can be improved significantly by mechanical activation in a stirred media mill, but due to its high energy density the circumstances were optimised carefully to avoid aggregation. Keywords: Kaolin, grinding, stirred media mill, mechanical activation, material structure

Jan 1, 2020

By H. Zhong, S. Wang, Q. Lin

To improve the flotation performance of chalcopyrite collector, 2-(tert-butoxy)ethyl xanthate (TBEX) and its derivative O-(2-(tert-butoxy)ethyl)-N-ethyl-thionocarbamate (TBEETC) were designed and prepared by the introduction of a 2-(tert-butoxy) ethyl group into xanthate and thionocarbamate. TBEX and TBEETC were both prepared via the one-pot method with superior efficiency, which has significant commercial implications. The micro-flotation tests demonstrated that compared with sodium isobutyl xanthate (SIBX) and O-isopropyl-N-ethyl-thionocarbamate (Z-200), TBEX and TBEETC both possessed better collecting ability and selectivity for chalcopyrite. DFT calculations and XPS were utilised to investigate the flotation mechanism involving TBEX or TBEETC and chalcopyrite. The results demonstrate that although 2-(tert-butoxy) ethyl group does not interact with minerals directly, its introduction reduces the energy of HOMO, so that they can better accept electrons instead of donating electrons which leads to better interaction with copper atoms rather than iron atoms. Keywords: Chalcopyrite, flotation, thionocarbamate, xanthate, synthesis

Jan 1, 2020

By M. Gomo, L. S. Mokhahlane

"Underground coal gasification (UCG) is an unconventional mining method that converts coal in situ into a fuel gas that can be used for electricity generation. Residue products from UCG have the potential to leach into surrounding groundwaters. The geochemistry and leaching dynamics of these products are explored in this study. The products include char, ash, and the heat-affected zone in the surrounding rocks. Core samples from the pilot plant at Majuba are the first ever to be recovered from a UCG cavity in Africa, and they give key insights into the geochemistry of the gasification zone. Mineralogical and chemical analyses were performed on the samples, and acid-base accounting (ABA) was used to predict the acid-producing capacity of the gasification zone, particularly for char samples. Some of the char contained pyrite, although not all samples were acid-producing as determined by the ABA analysis. The ABA results showed that some of the unburned coal has moderate levels of sulphur, which could be the driving medium for acidic conditions. The ABA analysis indicated that water in contact with the gasification zone would eventually have a pH lower than 7, which could lead to acid rock drainage. These results form part of a preliminary investigation into the geochemistry of the reaction zone, post gasification. IntroductionUnderground coal gasification (UCG) is an unconventional mining method that converts coal in situ into a fuel gas that can be used for industrial purposes, including electricity generation. The gasification process leads to the formation of a cavity composed of char, rubble, and void space (Bhutto, Bazmi, and Zahedi, 2013). Residue products from UCG have the potential to leach into groundwater. These products include char (devolatilized coal), which can generate acid rock drainage (ARD). ARD is caused by the oxidation of sulphide minerals, which acidifies the leachate, thus increasing the solubility of some environmentally toxic metals (As, Cd, Hg, Pb, Zn, etc.) (Bouzahzah et al., 2015).The main source of ARD is oxidation of sulphide-bearing minerals due to interactions with oxygen, water, and microorganisms (Simate and Ndlovu, 2014; Kefeni, Msagati, and Mamba, 2017; Bouzahzah et al., 2015). Although ARD occurs naturally, it can be enhanced by mining activities that escalate exposure of sulphide minerals to water, air, and bacteria (Simate and Ndlovu, 2014). At the Majuba pilot plant, the unburned coal remaining in the cavity has been in contact with groundwater since the gasifier was shut down in 2013. It is possible that in a commercial UCG plant, most of the coal will be consumed and no unburnt coal will be left in the cavity. Most of the sulphur will be converted to H2S during the gasification process and transported with the syngas to surface, where it can be removed and captured as elemental sulphur."

Oct 1, 2018

By S. Liaghat, J. Rosenkranz, P. Semsari Parapari, S. Chehreh Chelgani, A. Tohry

It is commonly accepted that the energy consumption for comminution within mineral processing is responsible for around 3% of the global electrical energy usage. However, it was clearly noted that inside mills, less than 1% of this energy efficiency is actually consumed for particle size reduction. Therefore, monitoring of grinding parameters and modelling of product particle size distribution (e.g. characterised by the 80% passing size P80) play an essential role in operating costs of a mineral processing plant. Several empirical models have been introduced for the prediction of the P80. Since in the industrial scale usually a few numbers of grinding variables are monitored, these models cannot identically be used in plants. In addition, these empirical models do not always indicate the magnitude of correlations between milling variables. This study proposes to introduce the Hilbert-Schmidt independence criterion (HSIC) as an intelligent model for exploring linear and nonlinear relationships between grinding variables and P80 for an industrial scale data assessment. HSIC can rank variables based on their importance and help to select the most effective one for the generation of predictive models. HSIC modelling through various monitored grinding variables (ball charge, feed input rate, F80, power draw and work index) of an industrial plant indicated that F80 as a feed property has the highest effect on P80 of the ball mill products. Modelling results highlighted that the P80 can be accurately predicted, based on effective variables by using a HSIC model. These outcomes showed that HSIC as a powerful modelling tool can assess the relationships between monitored grinding parameters, select the most effective grinding parameters and satisfactorily predict the P80. Keywords: Product particle size, variable importance measurement, Hilbert-Schmidt independence criterion, mill charge

Jan 1, 2020

By B. k. Kenzhaliyev, M. A. Naimanbayev, Zh. A. Baltabekova, N. G. Lokhova

In research various desorbents were used to desorb the following rare-earth metals from Purosorb 140 cation exchanger, i.e. ammonium chloride; ammonium sulfate; a mixture of nitric acid and ammonium nitrate; a mixture of hydrochloric acid and ammonium chloride; a mixture of sulfuric acid and ammonium sulfate. It was established that a solution containing 30 g/dm3 of H2SO4 + 300 g/dm3 of (NH4) 2SO4 is the most optimal desorbing solution to desorb REMs from macroporous Purosorb 140 cation exchanger impregnated with rare-earth metals from industrial dihydrate wet-process phosphoric acid. It was established that the residual REM content in the cation exchanger decreased from 0.89 to 0.10 wt. % with an increase in the ammonium sulfate concentration from 10 to 400 g/dm3. Technological desorption regimes for rare-earth metals from cation exchanger were developed. The optimal conditions were determined to desorb rare-earth metals from the Purosorb 140 cation exchanger, particularly temperature 25°C; L:S ratio = (0.8 ÷ 1.1):1; duration = 1.0-1.5 hours. Keywords: Rare elements, sorption, cation exchangers, wet-process phosphoric acid, desorption

Jan 1, 2020

By M. R. L. Blackwell

Over the period 1964 to 1969 Conzinc Riotinto of Australia undertook and completed an evaluation of a large low-grade copper orebody on Bougainville Island in the Territory of Papua and New Guinea. From the outset it was clear that the geographic, climatic and topographic characteristics of the area would necessitate a heavy capital outlay on production and support facilities. Both the physical problems and the magnitude of the investment amplified the need for a thorough and rigorous evaluation of the various strategies for exploiting the orebody. In view of the number of independent and inter-related variables and the flow of new data, a computer-based evaluation process extended the scope and depth of the analysis considerably. The system used permitted an iterative assessment and re-assessment of the various strategies with the results becoming increasingly refined with time. This process encompassed the modelling of the orebody, the simulation of alternative operating strategies and the determination of the financial profitability of the project,

Jan 1, 2014

By S. Langea, H. Lieberwirth

Impact crushers are common machines in comminution plants. Their high size-reduction ratio and relatively simple design, make them a preferred tool even when subjected to harsh wear, and producing a large quantity of fines in some applications. Until now the alignment of the operational parameters was an operator’s responsibility. Due to the random process characteristic this is mostly done based on empirical values and sensor data, such as power consumption. This paper describes a new approach for online process monitoring of the horizontal-shaft-impact crusher. The application of robust, low-cost acceleration sensors enables the permanent observation of the process characteristics. The operational and evaluation methods are determined on the basis of experiments. Subsequently the recorded measurements are analysed in regards of throughput, rotational speed and product particle size distribution. Occurring signal characteristics are described based on physical and technical principles. The measured data of the acceleration sensors at varying operation conditions provide insight in the course of process. The accurate utilisation yields the determination of the preferential process conditions providing the best balance between the pros and cons of an impact crusher. Both the experimental method and the data processing is discussed from a scientific perspective, displaying a completely new approach for the operation of impact crushers. Keywords: Impact crusher, acceleration sensors, data processing, particle size

Jan 1, 2020

By P. G. Toledo, R. I. Jeldres, G. R. Quezada

Chile is the main producer of copper in the world and lately the mining industry has suffered challenges due to the lack of water in the north of the country, along with the new policies of not using fresh water for the industry. This has prompted the use of seawater as an alternative source for mining. Several studies have been driven due to this new scenario, which have shown that seawater can be beneficial, if certain ions are removed from the process. This is the Mg that generates precipitates at high pH, that have been shown to make mining operations difficult. In particular, thickening operations are impaired by the presence of Mg ions, where aggregate formation and sedimentation decreases substantially. Our studies suggest the competence of the precipitates in adhering to the polyacrylamide (HPAM) flocculant and not towards the surface of the quartz minerals. This motivates the present work to use molecular dynamics to study the adsorption of a HPAM molecule on quartz surfaces and the surfaces formed by Mg precipitates. The surfaces are immersed in a saline solution or seawater that includes the HPAM molecule. Results are obtained by measure the adsorption frequency and duration. We obtained that the HPAM molecules are preferably absorbed on the surfaces of magnesium hydroxide. This gives us a good agreement with what is observed experimentally and strengthens the premise of the competition of hydroxide with the flocculant. Keywords: Molecular dynamics, adsorption, tailing flocculation, magnesium removal

Jan 1, 2020

By J. Engelbrecht

Understanding the deportment of minerals in size fractions has already led to improvements in the flow sheets for platinum minerals beneficiation. There are, however, more potential changes in the flow sheets that may improve the recovery of platinum group metals or reduce the costs of beneficiation before refining. Based on known technology of pre-concentration, milling, gravity concentration, flotation, and magnetic separation a number of potential alterations or additions can be considered and motivated based on the mineral deportment in size fractions.

Jan 1, 2012

By M. Ericsson

?Rare earths ?will not be bargaining instruments?? was stated in a headline in China Daily of 29 October 2010. The Chinese government is trying to fend off the persistent accusations from Japan, the USA, and Europe that it is manipulating the supply of these so called ?critical? metals to gain political and economic advantages. The critics maintain that China has taken the rest of the world hostage by controlling 97% of the resources of rare earths. These elements are crucial in a number of high-tech applications. They are not impossible to substitute, but difficult to do so effectively. The name ?rare earth? is a misnomer, as even the least abundant is 200 times more common in the Earth?s crust than gold. They are, however, difficult to find in economic concentrations. The Chinese near-monopoly over the rare earths, together with China?s scramble for other resources in Australia, Africa, and elsewhere around the world, is seen as an example of a Chinese strategy to take control of vital metal resources. The Chinese are also accused of using unfair and sometimes illegal business practices in this fight for resources. Practices which, critics claim, put the Chinese interests above the interests of the host countries, in particular in Africa.

Jan 1, 2011

By Y. Cao, C. Li, A. Song

Bubble size plays a key role in determining flotation efficiency. Bubbles can be formed by passing air through pores. Bubble detachment from a pore is driven by lifting forces including buoyancy force and momentum force. Enhancing the momentum force is the key to accelerate bubble detachment and to minimise bubble size. Recent studies show that replacing steady air with oscillatory air supply could significantly decrease bubble size by enhancing the momentum force. To date, the underlying mechanism for the improved momentum force with oscillatory air supply is not yet clear. This work, for the first time, developed a qualitative model for the momentum force as a function of frequency, on/off time ratio and gas flow rate. It was found that the momentum force was positively correlated with the frequency as well as the air flow rate, and was negatively related to the on/off time ratio. The relation between bubble size and these operating parameters was also investigated. Keywords: Flotation, bubble size, momentum force, modelling, oscillatory air supply

Jan 1, 2020

By D Olivier

De Beers' Finsch Mine is situated in the Northern Cape province, 170 km northwest of Kimberley. The concentrator facility, designed and constructed by Bateman Engineering, was commissioned in 1967 and upgraded in 1979 using diamond liberation and extraction technology available at the time of design. Since then significant advances in diamond processing and technology have been made and these -have been incorporated into the new main treatment plant and recovery plant flowsheets, making diamond liberation and recovery from the Pre-1979 dumps a viable economic option at Finsch."

Jan 1, 2010

By J. D. T. Steyl, G. B. Grobbelaar

Two examples are presented to show how first-principles – physical-dynamic, here termed behavioural modelling, is used to build digital twins of unit processes or plant sections. A digital twin equips the metallurgist, engineer, or manager with a powerful tool to conduct model-based design, solve process problems and improve operations. It is particularly relevant in the metallurgical industry where plant behaviour is highly integrated, rates respond to particle dynamics in complicated ways and mineral flows across flowsheet boundaries are variable. The two examples used to illustrate the behavioural modelling methodology are 1) a flotation column unit block and 2) a multi-compartment pressure oxidation (POX) autoclave. It simultaneously accounts for the causality of material and heat flow, takes care of mineral particle dynamics, physical and chemical reaction rates, the plant control system behaviour and operating heuristics. The basic modelling building blocks are briefly reviewed to show how the behavioural modelling attributes constrain the mass and heat flow dynamics to physically realistic values. This is the key aspect that allows project value to be created with minimal input data. Behavioural modelling is especially valuable where the process dynamics are poorly understood or controlled, where data-driven models fail to cope with complex and highly integrated plant behaviour, where quality data is lacking or limited funds are available to generate the data required to fill all the knowledge gaps. The paper uses the flotation column example to show how behavioural modelling and simulation can be used to optimise plant performance, while the multi-compartment POX autoclave model shows how it can be used to diagnose process problems. It also provides a solid basis to add a data-driven component – in other words, it makes a strong case for a hybrid first-principle– data-driven approach to solve process problems, especially where microscopic-level understanding is poor. Keywords: Digital twin, behavioural modelling, simulation, flotation column, pressure oxidation

Jan 1, 2020

By L. Gutierrez, R. Yepsena

Enargite in porphyry copper deposits is an important mineral as it displays good floatability under the presence of the collectors usually used in the flotation of copper sulfides. As a result, copper concentrates grades are reduced. As scarcity of water resources is a problem relevant to Chilean mining, the use of seawater is a feasible solution. The behaviour of copper sulfides and molybdenite in the process of flotation in seawater was previously studied but not for enargite. The objective of this research is to study the behaviour of the enargite in different conditions of electrochemical potential during the process of flotation using seawater. The study was carried through micro-flotation tests using pure samples of enargite, at Eh values ranging from -300 to 500 mV(SHE), both in seawater and aqueous solutions containing calcium and magnesium. The results show that at pH 10.5 in seawater, the enargite and chalcopyrite recoveries are reduced throughout the whole range of Eh studied. At pH 9 in seawater, enargite and chalcopyrite are depressed under reducing and slightly oxidising conditions. The recovery of both minerals drastically decreases at Eh values lower than -100 mV and greater than 400 mV. The behaviour of enargite in seawater flotation differs from that observed in conventional water, since in the latter case the recovery of enargite decreases at higher potentials close to 500 mV. Keywords: Enargite, flotation, seawater, redox potential

Jan 1, 2020

By A. Melkumyan, M. Balamurali, J. Zigman

Understanding the contribution of geophysical variables is vital for identifying ore indicator regions. Both magnetometry and gamma-rays are used to identify the geophysical signatures of the rocks. Density is another key variable for tonnage estimation in mining, and needs to be re-estimated in areas of change when a boundary update has been conducted. Modelling these geophysical variables in 3D will enable investigation of the properties of the rocks and improve our understanding of the ore. The Gaussian Process (GP) was previously used to generate 3D spatial models for grade estimation using geochemical assays. This study investigates the influence of the following two factors on the GP-based autonomously generated 3D geophysical models: the resolution of the input data, and the number of nearest samples used in the training process. A case study conducted on a typical Hammersley Ranges iron ore deposit using geophysical logs, including density, collected from the exploration holes, is examined in this paper.

Sep 1, 2021

By K. C. Corin, M. S. Manono

The drive to reduce water usage globally has led to the mining industry reassessing its water usage - owing to past environmental degradation due to effluent discharge, tailings disposal and process water seepage into the water-table (Haggard et al., 2015). Factors such as water scarcity and environmental restrictions have created the necessity for recycling of process water in mining and other industries. Water recycling, however, causes an accumulation of ions in the process water, which may affect the strength of reagent action on the target mineral and in turn critical aspects of flotation may be impacted. Prior studies have shown that certain ions have specific effects on flotation: for example, calcium and copper have been found to enhance the adsorption of depressant onto gangue (Feng et al., 2013, Wang et al., 2016). Calcium and sulfate ions have been seen to give a higher concentrate grade than other ions present in process water (Manono et al., 2012). An increase in ion concentration will increase the mineral grade due to a decrease in entrainment (Corin et al., 2011). This study considers the impact of ion accumulation on reagent action and flotation response. Keywords: Flotation chemistry, water quality, ionic strength

Jan 1, 2020

By M. Seerane, R. Machaka, P. Ndlangamandla

"Metal injection moulding (MIM) is a near-net-shaping powder metallurgy technique suitable for the cost-effective mass production of small and complex components. In this paper, the effects of the metal powder particle size on the final properties of 17-4 PH stainless steel are reported. Three different particle sizes (d50 33.0, 7.91 and 4.04 µm) were used to prepare the injectable MIM feedstocks using a CSIR-developed wax-based binder system at a fixed solids loading of 60 vol.%. The distribution slope parameter and the rheological flow index behaviour were used to predict the flowability of the feedstocks. The effects of the particle size on MIM products were established. The results are discussed in terms of the subsequent microstructural and mechanical properties of MIM 17-4 PH stainless steel against the established MPIF Standard 35. IntroductionMetal injection moulding (MIM) is a near-netshape manufacturing process established as an alternative to produce complex small-tomedium shaped components that were previously fabricated by conventional methods at higher costs (Attia and Alcock, 2011; Todd and Sidambe, 2013).Although recent advances in micromanufacturing (mainly machining and electrodeposition-based) have enabled the fabrication of complex micro-size geometries directly into miniaturized parts, these processes are generally neither routine nor easily accessible at present (Attia and Alcock, 2011).Typically, the MIM process consists of four steps: mixing, injection moulding, debinding and sintering. Mixing involves blending of the desired metal powder composition with carefully selected multicomponent organic binders at the right proportion. This mixture, which is called feedstock, is then injected into a mould of a required shape to form a ‘green part’. Debinding is the removal of the binders by chemical, thermal, or catalytic means while maintaining the shape of the part. Finally, the debound part is sintered to a full or near-full density part (Sotomayor, Varez and Levenfeld, 2010). The MIM process is essentially a combination of plastic injection moulding with conventional powder metallurgy technologies."

Jan 1, 2016

By T. Wajima

Recovery of precious metals from hydrochloric solution using sulfur-impregnated carbonaceous adsorbent was examined. Sulfur-impregnated adsorbent with adsorption abilities of precious metals can be prepared from activated carbon using pyrolysis at 600 oC under 10 % H2S gas flow, and the adsorbed Au and Pd were precipitated as metal phase on the surface of the adsorbent. The adsorbents after precious metals adsorption were burned at 700 oC to obtain the residue mainly containing precious metals. The adsorbent was found to be highly efficient and selective for the uptake of precious metals, especially Au, in the presence of excess base metal ions from simulated spent automotive catalyst eluted solution using a column pack test. Keywords: Gold, platinum, palladium, reduction precipitation

Jan 1, 2020