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By D. F. Caicedo, I. A. Brum, L. A. Betancourt

Ferricyanide ()()*is one of the most stable cyanometallic complexes present in the gold mining effluents. This cyanocomplex is hard to degrade by natural attenuation and generates a negative impact on aquatic environments. Although free cyanide (CN-) can be obtained by acidifying the solution, the CN- is lethal for all forms of life. The oxidation of ()()* in a typical photocatalitic system was evaluated with the addition of H2O2. To verify the degradation, chemical parameters, such as free cyanide, the formation of ammonia, nitrate, and total iron were analysed at the end of the process. The degradations obtained were up to 70% in a heterogeneous photocatalysis system with TiO2, and a low rate of dissociation was observed by photolysis. The best result was achieved with the H2O2 and TiO2 photocatalytic system, and the stoichiometric concentration was about 2.5 times less than the peroxide used in the real gold mining industry, reaching 83% degradation. The photocatalytic process obtained less toxic byproducts than the original synthetic ferricyanide used as mining wastewater. Keywords: Cyanide, heterogeneous photocatalysis, titanium dioxide, UV radiation, gold wastewater

Jan 1, 2020

By M. Smit, N. C. J. Dempers, S. Lunkov, C. Saguru, J. Nel

A common method for the recovery of copper is by heap leaching, solvent extraction, and electrowinning. During solvent extraction, the solution is continuously recycled, and it is necessary to remove impurities that build up in the raffinate. For the process investigated in this study, the main impurities include Fe, Co, As, and Zn. Recovery of these impurities can provide economic benefits while adhering to legal and environmental constraints. Such impurities are often removed by precipitation utilizing a neutralizing agent, such as limestone or lime, but it is also possible to remove the impurities by sulfide precipitation. Sodium hydrosulfide (NaHS) is used to selectively precipitate copper, arsenic, and zinc from a solvent-extraction raffinate stream. The resulting sulfide precipitate is bagged and sent to a roaster for further treatment. The design of the sulfide precipitation was investigated to optimize the processing conditions (including temperature, pressure, and residence time), the materials of construction, and the toxicity and explosive nature of the hydrogen sulfide gas produced

Jan 1, 2023

By L. Kühnel, H. Lieberwirth

Confined bed comminution in High Pressure Grinding Rollers (HPGR) and Vertical Roller Mills (VRM) is gaining substantial attention in many applications. Previously used mainly for milling coal or construction materials, HPGR and VRM have started to complement or even replace tumbling mills in ore beneficiation. Materials like coal or clinker are relatively homogenous, however, in comparison to metal ores and wall rocks. This characteristic poses a new challenge to the confined bed comminution but also an opportunity. Fuerstenau and Abouzeid have investigated the selectivity in comminution of a mixture of particles of different strength in a particle bed. The median particle size and particle size distribution (PSD) of the two constituents used were kept constant. Only the proportion of the two constituents was modified. The competence of a material is, however, also a function of particle size. Smaller particles tend to be more competent than larger ones of the same material. If selective comminution is applied on ores, this size influence has to be understood. The paper presents research results on this topic based on experimental investigations with model materials as well as with natural particles, which were stressed in a piston-die press. It appeared that the comminution result depends substantially on the material characteristics and the composition of the mixture. Conclusions will be drawn for the application in future applications of selective comminution in mineral processing. Keywords: Confined bed comminution, HPGR, VRM, piston die press, particle size

Jan 1, 2020

By J. O. Mogalanyane, N. Naudé, A. M. Garbers-Craig

The fines produced is not suitable as feed material for the subsequent rotary kiln and the electrical arc furnace. The need for briquetting the ferronickel ore is premised on the minimisation of fine particles in the rotary kiln as well as improving charge permeability in the furnace, and improving overall process safety. Briquetting may be defined as an agglomeration method in which fine particles are compressed under pressure. It consists of three different technologies: vibropressing, roller pressing and stiff extrusion. The current study focuses on evaluating the performance of ferronickel briquettes generated, using roller-pressing technology. Physical properties, chemical properties and metallurgical properties of the briquettes were used to evaluate their performance and quality. Standard ISO tests for iron ore pellets were used. Size degradation as a result of reduction was measured using the ISO 4696-1 test. The decrepitation of the briquettes at the point of entry into the rotary kiln was evaluated using the ISO 8371 test method at a temperature of 700oC. The degree of reduction was evaluated using the ISO 4695 test procedure. Average green briquette compressive strength of 559 N was reported at a moisture content of 16% with an average drop number of 19.1. Increasing the moisture content has a detrimental effect on both the compressive strength and the green briquette yield. The drop number is expressed as the number of drops until breakage, when a briquette is dropped from a 1 m height, decreased with an increase in moisture content. At a moisture content of 16% an average green briquette yield of 85.1% was reported. Keywords: Ferronickel briquettes, moisture content, curing conditions, physical properties, chemical properties

Jan 1, 2020

By X. Zhang, E. Li, Y. Xiao, Z. Yu, H. Han, J. Xie, J. Tian, W. Sun, K. Hong

In a pulp environment, the surface properties of magnesite and dolomite tend to be similar, due to the re-adsorption of dissolved calcium species, which makes the flotation separation difficult. In this paper, the chelating reagent EDTA is introduced to eliminate the adverse influence of the calcium species and to restore the selectivity of magnesite-dolomite separation using sodium hexametaphosphate (SHMP) as a depressant. Flotation experiments confirm that the recovery of magnesite improves significantly in the presence of EDTA. Zeta potential experiments confirm that the negatively charged EDTA4+ and HEDTA3+ species can form soluble and stable chelates with positively charged Ca2+ and Ca(OH)+ species preventing their adsorption on the magnesite surface. Adsorption measurements prove the addition of EDTA can decrease the adsorption of depressant SHMP on the magnesite surface. X-ray photoelectron spectroscopy (XPS) measurements further confirm the transformation from the surface of magnesite to dolomite in the presence of calcium ions, and the possible adsorption mechanism of EDTA and SHMP on the magnesite and dolomite surface. Key words: Magnesite; Dolomite; Surface dissolution; Flotation separation

Jan 1, 2020

By K. C. Corin, M. Tadie, R. M. Manenzhe

The near depletion of high-grade ores, among other factors, has necessitated the consideration of alternative PGM sources. Various factors in the metallurgical processing of ores result in valuable minerals being lost to the tailings, and hence, PGM tailings are a possible alternative PGM source. However, as the value residing in PGM tailings remains unquantified and uncharacterised, there is a challenge in knowing the recoverable fraction of value contained in PGM wastes. This paper outlines the in-situ techniques of oxygen uptake and EDTA extraction for their possible use for determining the recoverable value in PGM tailings. Both methods have shown efficiency in determining the weathering of sulphide minerals and sulphide-bearing ores. Keywords: PGM tailings, tailing retreatment, oxidation, oxygen decay, EDTA

Jan 1, 2020

By D. Yu Pleev, V. G. Krivolapov

Mines of Southern Kuzbass working out, basically, coal formations of flat seams. Seams, as a rule, are inclined to self-ignition. Detection at early stages of the centers of endogenous underground fires has great value for safe conducting mountain works. One of methods of detection of an early stage of underground fires in the worked out space is the method of superficial radon survey. In the report the method is de-scribed and examples of superficial radon survey on concrete layers are given.

Jan 1, 2003

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 T. Scheldt, M. Lu, A. Myrvang

Abstract: In this paper both continuous and discontinuous modelling are utilised in order to analyze the stability of the Gjøvik Olympic Mountain Hall. The large span cavern (62 m) was built for the 1994 Winter Olympic Games at Lillehammer, and is a unique case study because of the large amount of available input data, through a comprehensive pre-investigation, stress and deformation monitoring program before, during and after the excavation. Phase2, a two-dimensional non-linear finite element program, and the Discontinuous Deformation Analysis (DDA) are used as representative tools for continuous and discontinuous modelling, respectively. The analysis results are compared and discussed taking the reliability of the models, time-consumption and costs into consideration. Some guidelines for the total modelling process, from field measurements to final results, are also presented. Zusammenfassung: In diesem Artikel werden sowohl kontinuierlich als auch diskontinuierlich Modellierung verwendet, um die Stabilität, der in den Berg gebauten Olympiahalle in Gjøvik zu analysieren. Die Olympiahalle wurde 1994 zu den Olympische Spielen in Lillehammer errichtet. Ihr Dach erstreckt sich über eine Breite von zweiundsechzig Meter. Für den Bau wurden umfangreiche Daten durch Voruntersuchungen, und Überwachung von Gebirgsspannungen und Deformationen bevor, während und nach Exkavation eingesammelt. Auf Grund dieser großen Datenmenge stellt die Olympiahalle ein herausragendes Beispiel für den Bau ähnlicher Projekte dar. Für die kontinuierlichen Modellierungen wurde „Phase2“, ein zwei-dimensionales, nicht lineares „endlich Element“ Rechnerprogramm angewandt. Die diskontinuierlichen Modellierungen erstellte man mit Hilfe von der „Diskontinuierliche Deformations Analyse“ (DDA). Die Analysenergebnisse sind mit Rücksicht auf die Zuverlässigkeit der Modelle, Zeitverbrauch und Kosten verglichen und diskutiert worden. Im Artikel werden Richtlinien für den Modellierungsprozess von Dateneinsammlung bis Schlussfolgerung gegeben. Résumé: Dans cet article la modélisation continue et discontinue sont utilisés pour analyser la stabilité de Gjøvik Olympic Mountain Hall. Cette caverne de grande portée (62 m) a été construite pour les Jeux Olympiques d’Hiver de 1994 à Lillehammer, et est une étude de cas unique grâce à la grande quantité de données disponibles, de par un programme de pré-investigation compréhensive, monitorage des contraintes et déformations avant, pendant et après l'excavation. Phase2, un code d’éléments finis non linéaire à deux dimensions, et l’Analyse en Déformations Discontinues (DDA) sont utilisés comme outils représentatifs de la modélisation continue et discontinue, respectivement. Les résultats d'analyses sont comparés et sont discutés, prenant en compte la fiabilité des modèles, la consommation en temps de calcul et les coûts. Quelques indications pour le procédé total de modélisation, des mesures sur place aux résultats finaux, sont aussi présentées.

Jan 1, 2003

By E. J. Y., G. J. McLachlan, E. Amini, Koha

Inferring individual component flotation rates from recovery-time data of ore complexes is important in optimising and designing minerals processing plants. However, existing two-component first-order flotation models are computationally intensive to solve using conventional non-linear least squares regression. In this paper, a Convolutional Neural Network (CNN) is used to approximate the inverse function which predicts the two-component first-order model parameters using recovery-time data. This paper compares the accuracy and computation speed of the proposed CNN against traditional non-linear least squares regression on 1 million generated data based on a known two-component firstorder kinetic model. It is shown that using a CNN is possible to approximate the inverse function for the non-invertible two-component model with recovery-time as an input matrix for convolution operations. The CNN method is 450 times faster to compute than the Trust-Region (TR) non-linear least squares regression algorithm. However, the CNN model is less accurate compared to the TR algorithm overall. Keywords: Flotation kinetics, convolutional neural network, inverse problem, modelling and simulations

Jan 1, 2020

By N. Sacks, N. B. S. Magagula, I. Botef

"Low-pressure cold gas dynamic spraying was used to deposit WC-4wt%Ni and WC-4wt%Ni-1wt%Mo coatings onto mild steel. Dense coatings with very low porosities were produced. No decarburization occurred during deposition and no deleterious phases were formed. The coatings were subjected to standardized material characterization tests, as well as slurry abrasion testing to assess their wear behaviour. The wear tests were conducted in synthetic minewater-silica slurries, while distilled watersilica slurries were used as a control. The hardness of the coatings, 512HV0.3 and 458HV0.3 for WC-4wt%Ni and WC-4wt%Ni-1wt%Mo respectively, are comparable to those achieved using high-temperature coating processes. The abrasion wear rates for both coatings were less than 5 mg/min and 10 mg/min in the distilled water-silica and synthetic mine water-silica slurries respectively. The approximately 50% increase in wear rate in the synthetic minewater slurry is attributed to a synergistic corrosive wear mechanism. The predominant wear mechanisms were identified as binder smearing and delamination, with carbide grain fracture and pull-out. IntroductionSlurry abrasion is a common phenomenon in mining operations, particularly in pipelines transporting, for example, sand-water slurries. This type of wear can cause pipeline fracture, shortened operational lifetimes, and impede pipeline efficiency. To reduce or limit abrasion, thermally sprayed tungsten-carbide-based coatings are often used as pipe linings (Kanchan et al., 2010). This is due to their attractive mechanical properties, which include high wear resistance, stiffness, hardness, compressive strength, and tensile strength. These properties are provided by the coating microstructure and composition, which is a blend of hard, wear-resistant tungsten carbide (WC) particles embedded in a fracture-tough metallic binder phase (Brookes, 1997). Cobalt (Co) is the most commonly used binder due to its excellent wetting of the WC phase and moderate mechanical properties; however, its application is limited to non-corrosive environments as it has a low corrosion and oxidation resistance (Andren, 2001). Nickel (Ni) may also be used as a binder, and has been shown to have superior oxidation and corrosion resistance, but in some applications may not have the required mechanical properties (Kim et al., 2006)."

Jan 1, 2016

By A. J. S. Spearing, M. Sharifzadeh, K. V. Jessu

Empirical pillar design methods are commonly used in the mining industry. The parameters within which these methods are valid are frequently unknown to the user or ignored. In addition, empirical design may not consider essential parameters such as blasting effects, orebody dip and the presence of geological structures, which all adversely affect the stability of the pillars. This can result in potentially serious pillar design strength over-estimates. Although the commonly based tributary area method is generally conservative, as the spans are seldom that large relative to the depth, failing to consider other relevant parameters can result in errors. Problems associated with an under-designed pillar can range from a local pillar collapse to a catastrophic chain reaction collapse (or run). Over-designed pillars are generally safe but reduce the extraction of the orebody, thus adversely affecting the profitability of the mining operation. We used laboratory tests and numerical modelling to understand the effects of pillar orientation, blasting and the presence of discontinuities on pillar strength. Reduction factors were developed with these models to be implemented in conjunction with the existing empirical pillar design methods. For any pillar or mine design, once it is implemented, the actual performance of the system must be checked regularly by observation and monitoring and adjusted if needed. The pillar design approach outlined in this paper can better optimize the pillar mining method by considering other generally ignored but important parameters, thus improving safety, productivity, and economic aspects.

Oct 1, 2022

By A. Muller

The magnesia-carbon refractories used in the ConArc process experience severe wear as a result of the varying slag composition during the blowing phase. This work determines the basicity range in which minimum as well as maximum refractory wear was experienced by the magnesia-carbon refractories during service. In order to determine an optimum slag composition, the crucible test in an induction furnace was used. The magnesia-carbon refractory bricks were cut into cylindrical crucibles to which a synthetic slag in the form of pellets was added. The basicity (B2) of the slag was varied from 0.5 to 3. Tests were done at 1 600°C for one hour. Apart from the crucible test in an induction furnace, visual inspection and SEM analysis were also done to investigate the corrosion mechanism. FACTSage® predictions about the interaction between refractories and slag were also done. These predictions were compared to the actual results attained. It was found that the extent of corrosion by slag attack decreases as the basicity increases. The most severe corrosion of the MgO-C refractories occurred at a basicity of 0.5 whereas the optimum basicity is above 2.0. SEM analysis indicated severe slag attack at the lower basicities with no visible refractory-slag interaction at higher basicities. TheFACTSage® predictions supported most of the actual findings. Keywords Magnesia-carbon, ConArc, blowing phase, slag resistance, induction furnace, crucibles.

Jan 1, 2011

By A. Mainza, I. Govender, Elbasher M. E. Ahmed

A mechanistic description of axial segregation in rotating drum flows remains an open question. Consequently, optimal mixing of grinding balls and rocks for efficient breakage, maximum production of fines, and slurry transport is seldom achieved. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. We present a practical model of the axial free surface profile by linking it to readily-derived geometric features of the cross-sectional S-shaped free surface profile. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends.

May 1, 2021

"Chairman: Prof A. E. H. BLEKSLEY Rapporteur: Prof J. ELBRONDPanel Members: Prof J. C. Griffiths, Prof T. E. Hawkins, Mr A. C. Langton, Mr M. Splaine, Mr A. WeissThe reasons for failure of computer applications in the mineral industry and the direction of future developments.The Chairman opened the discussion by elaborating on the disappointment felt by some authorities with the lack of progress in the application of computers in the mineral industry during the last ten years, and posed the question to the panel : 'Do you agree that the computer age has not come up to expectations?'Mr Langton said that although there seemed to be a tremendous amount of brainpower applied to the theoretical side, he thought that the production men had not got all the help from computers that could have been given to them. The computer, said Prof Griffiths, is as yet a new tool which should not be used to do old things in old ways. To learn to use the computer will take time. After all, he said, it had taken 400 years after the introduction of the printing press to achieve general literacy, and perhaps it will take 40 years after the introduction of the computer to achieve `numeracy'.In Mr Weiss' view, the reason for the feeling of disappoint¬ment lay in the focussing of attention on the computer. The blame, if any, lay with the people surrounding the computer, that is, the analysts and programmers, to whom the emphasis should be shifted.Prof Hawkins said that he thought that some applications of the computer in the mineral industry had been successful, such as, for example, the compilation of payrolls. Reasons for failures in other areas were to be sought in the fact that the people connected with computers had failed to realise that they were merely part of a system. They had not understood the power structure of the organization which their work tended to change, and were therefore not prepared for the inevitable conflict with the production men.In Mr Splaine's view the production man had not received the assistance he could have had from the computer people because he may possibly not have allowed this to happen.Prof Bleksley concluded from these opinions that the promise which computers had ton years ago had not been fulfilled and added that the opinions expressed by the panel had intruded on his next question which was: 'Is the reason for this that people are involved?Prof Hawkins elaborated on his previous theme, namely, that of computer people in relation to management. Com-puter people, he said, were trying to impose change on management but were not prepared to share the responsibility for these changes. In fact, they wanted their work to be distinct and separate, and, as far as management was concerned, changes would be made when management believed that these would be less agonizing than no change at all."

Jan 1, 2014

By R. Kumar, N. R. Mandre

"The beneficiation of iron ore slimes by selective flocculation was studied. Polyacrylamide (PAM) and guar gum were used as flocculant, along with sodium hexametaphosphate (SHMP) as a dispersant. The samples collected were initially subjected for chemical and mineralogical studies. The mineralogical studies indicated the presence of haematite and goethite as the principal iron-bearing minerals, with quartz and kaolinite as gangue minerals. The selective flocculation tests showed that the Fe grade can be enhanced from 58.24% to 64.60% Fe at a recovery of 66.33% using polyacrylamide as the flocculant. A Fe grade of 63.20% at a recovery of 68.04% was obtained using guar gum as flocculant. The efficacy of the studies was analysed using a separation index, which indicated that the higher separation index was obtained with the tests employing polyacrylamide as the flocculant. IntroductionIndia is endowed with huge reserves of highgrade iron ore and is one of the prominent producers in the world. As the high-grade iron ores have been exhaustively mined, it has become imperative to use low-grade iron ores, fines, and slimes to meet the growing demand. Also, generation of fines and slimes during mining and processing contributes to loss of minerals to the extent of 30% of the total value (Mandre and Panigrahi, 1997). These fines/slimes are often discarded as waste into tailing ponds, containing considerable amounts of iron. Therefore beneficiation of tailings/slimes has become necessary for optimal utilization of the resources.In recent years, interest in recovery of valuable minerals from low-grade ores, slimes, and tailings has increased worldwide. These activities are initiated not only to recover minerals but also to address various environmental issues associated with fine particle treatment. The literature reveals that several technologies have been employed in this regard, including flotation, advanced gravity separation, and high-intensity magnetic separation. However, these processes are found to be ineffective for fine particle treatment due to lower collision probability in flotation, decreased gravitational effect in gravity separation, and reduced drag force in magnetic separation, among other factors (Batisteli and Peres, 2008; Das et al., 2007; Dworzanowski, 2012; Rocha, Caneado, and Peres, 2010). Therefore, it is in this regard that selective flocculation has gained importance in treating slimes in recent years."

Jan 1, 2017

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 J. Bullón, A. Pérez

Some years ago, Ferroatlantica developed a new type of electrode known as the ELSA electrode. In this electrode there is a central graphite core that provides support, surrounded by an annulus of Søderberg paste that gets baked during operation. This technology has been implemented on several silicon furnaces around the world, and was reported on during the previous Infacon conference. In all electrodes, but particularly in the ELSA electrode, the quality and consistency of the paste are important for correct operation. As the type of paste varies between customers and between countries, Ferroatlantica has developed a quality control procedure for their customers of this technology. This procedure is geared to the point of view of the customer rather than the paste producer. The analysis is based on the desired flow pattern of the raw paste and on the desired mechanical and electrical properties of the baked paste, as experience has shown that these are the most important parameters to monitor in order to avoid having problems with the resulting electrodes. This paper discusses these methods of paste analysis in the light of complementary studies that have been done when there has been an electrode breakage in the different plants.

Jan 1, 2007

By F. Nakhaei, A. Noury, S. Ghodrati

To achieve maximum efficiency in any purification stage, the flotation should be continued until the concentrate grade reaches the feed grade. During sampling from rougher cells of the Iranian Sarcheshmeh copper concentrator plant 1, it was revealed that the concentrate grade of the last five cells of rougher circuit was close to feed grade. Therefore, it was suggested that the concentrate of the aforementioned cells be mixed with rougher feed. In this study, one of eight rougher circuit rows was selected and evaluated. The floatability tests were performed to compare the flotation behaviour of rougher feed and mixture of concentrate of the last five cells with rougher feed in the laboratory scale by a tree analysis process. The results showed that mixing of rougher last five cell concentrate with feed has a detrimental effect on flotation efficiency that leads to a 3% decrease in recovery. It was also observed that with grinding of this concentrate, recovery can be improved. Keywords: Efficiency, flotation, rougher, tree analysis, floatability, concentrate, mixing

Jan 1, 2020

By and M. V Roper, H. N. Engelbrecht

Quality control interventions emanate from process upsets and trends that move product quality beyond the natural variation expected in a stable process. The ability to detect upset conditions and react in an effective manner protects both resource utilisation and compliance to specifications. Product quality control on coal processing plants traditionally relies on the reference (combined sampler and laboratory) system to measure product qualities. The introduction of online analyser (OA) technology, applied in different configurations, creates a second source of measurement information for control decision making. The case study was done on the primary sample stream of the final product stream at Exxaro’s GG7 and 8 plants, part of the Grootegeluk complex. It explores the OLA system’s ability to meet the OEM performance guarantee, perform equally to the reference system without analytical delay time, and assesses the effort to achieve this performance in a by-line analyser (BLA) configuration. In the paper, a conceptual comparison of the two measurement systems is done and the theoretical and practical comparison of measurement performance is discussed. Results demonstrate that the OA outperformed the OEM’s performance guarantee and achieved similar levels of performance to the reference system without the response delay. Keywords: Online analyser (OLA), by-line analyser (BLA), coal quality measurement, measurement performance

Jan 1, 2020