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By A. Chieregati

"A heterogeneity study was conducted at Erdenet Copper Mine in Erdenet, Mongolia, to determine the fundamental sampling error associated with blasthole sampling. Using a custom designed sector sampler, six large blasthole samples were collected to perform the test that was developed by Pierre Gy, to estimate the constitutional heterogeneity factor for several types of ore. The study investigated the entire sampling protocol, from mine site to analytical laboratory, and quantified the contributions to fundamental sampling error (FSE) of the various stages of sampling and sample preparation. The total relative standard deviation (RSD) of sampling error was determined to be ±32% and ±49.4% for copper and molybdenum respectively. A classical statistics analysis conducted on the data confirmed the level of RSD. About 95% of the sampling error was produced from only one step in the sampling protocol: when the 1 kg sample was reduced to 50 g sample for chemical analysis. Therefore, it is recommended that the 1 kg sample be reduced to 50g using a slightly different protocol to minimize the FSE. The 1 kg sample should be first crushed to 0.2cm size. A 250g split should then be taken and fine ground. A 50g split should then be taken from the 250g fine ground split. These two simple steps will reduce the FSE to ±7.9% and ±17% for copper and molybdenum respectively. The modified sampling protocol effectively reduces the probability of misclassification of low grade ore to zero. INTRODUCTION The Erdenet copper-molybdenum open pit mine is located in Erdenet, in Orkhon province, Mongolia. The Erdenetiin-Ovoo copper-molybdenum deposit is between 1.5 and 3 km wide, and about 25 km in length (Erdenet Mining Corporation, 2016). Chalcopyrite, bornite covellite and chalcocite are among the major minerals found in the deposit. The mine processes approximately 26 million tons of ore annually. A study was conducted to evaluate the fundamental error associated with the blasthole cuttings and sampling protocol at the mine. The open pit mine uses 215mm diameter Russian drills to drill 17.5m holes for 15m benches. The total weight of blasthole cuttings for a 215mm diameter hole and 15m bench height is between 1.5 and 2 tonnes. This amount of sample is difficult and time consuming to collect and analyze. Therefore, a sector sampler was designed for the Russian drills to collect large samples that were representative of the blasthole cuttings (Ganguli et al., 2016). In order to eliminate the delimitation and the extraction errors, researchers consider sector samplers to be ideal for sampling blastholes (Pitard, 2008; Chieregati and Pitard, 2009). This method was intentionally more rigorous than the blasthole sampling protocol at the mine to ensure that the blasthole cuttings were properly sampled. This study was part of a broader study that also looked at the relationship between particle size and grade. The samples collected by the custom designed sector sampler were very large (195 kg on average), and therefore, sufficient for both studies. The relationship between particle size and grade has been reported in Ganguli et al. (2016)."

Jan 1, 2017

By A. Chieregati

"A heterogeneity study was conducted at Erdenet Copper Mine in Erdenet, Mongolia, to determine the fundamental sampling error associated with blasthole sampling. Using a custom-designed radial sector sampler , six large blasthole samples were collected to perform the test developed by Pierre Gy to estimate the constitutional heterogeneity factor for several types of ore. The study investigated the entire sampling protocol, from mine site to analytical laboratory, and quantified the contributions to total fundamental sampling error (FSE) of the various stages of sampling and sample preparation. The total relative standard deviation (RSD) of sampling error was determined to be ±32 percent and ±49 percent for copper and molybdenum, respectively. A classical statistical analysis conducted on the data confirmed the level of RSD native to the mine. About 95 percent of the sampling error was produced from one step in the sampling protocol, that of reducing the 1-kg (2.2-lb) sample to a 50-g (0.1-lb) sample for chemical analysis. To minimize the FSE, the use of a slightly different protocol is recommended. The 1-kg sample (2.2-lb) should first be crushed to a 0.2 cm (0.08 in.) particle size. A 250-g (0.5-lb) split should then be taken and finely ground, from which a 50-g (0.1-lb) split should then be taken. These simple steps will reduce the FSE to ±7.9 percent and ±17 percent for copper and molybdenum, respectively. The modified sampling protocol effectively reduces to zero the probability of misclassification of low-grade ore. IntroductionThe Erdenet copper-molybdenumopenpit mine is located in Erdenet in Orkhon province, Mongolia. The Erdenetiin-Ovoo copper-molybdenum deposit is 1.5 to 3 km (0.9 to 1.8 miles) wide and about 25 km (16 miles) long (Erdenet Mining Corp., 2016). Chalcopyrite, bornite covellite and chalcocite are among the major minerals found in the deposit. The mine processes approximately 26 Mt/a (29 million stpy) of ore."

Jan 11, 2017

Based on experimental and computer simulation results from our group, we report a systematic, atomic level analysis of carbon dissolution from carbonaceous materials in molten iron. Experimental results on graphite / Fe-C-S system were obtained using carbon dissolution studies, XRD and FESEM investigations and were supplemented with Monte Carlo simulations. Three basic mechanisms, namely carbon atom dissociation rate, interfacial phenomena and mass transfer in the melt were found to be responsible for the overall dissolution process. While mass transfer in the melt is governed by the concentration gradients, melt composition and temperature; impurities present in ash play a significant role in the interfacial phenomena. For less ordered forms of carbonaceous materials, carbon atom dissociation rate depends strongly on the degree of long-range order and is an important rate controlling mechanism in the overall dissolution process. A systematic comparison of dissolution rates for a variety of coal-chars, natural and synthetic graphites has been carried out in an attempt to identify rate-controlling mechanisms. The structure of the carbonaceous material appears to be an important underlying factor in the carbon dissolution process.

Jan 1, 2003

Based on experimental and computer simulation results from our group, we report a systematic, atomic level analysis of carbon dissolution from carbonaceous materials in molten iron. Experimental results on graphite/Fe-C-S system were obtained using carbon dissolution studies, XRD and FESEM investigations and were supplemented with Monte Carlo simulations. Three basic mechanisms, namely carbon atom dissociation rate, interfacial phenomena and mass transfer in the melt were found to be responsible for the overall dissolution process. While mass transfer in the melt is governed by the concentration gradients, melt composition and temperature; impurities present in ash play a significant role in the interfacial phenomena. For less ordered forms of carbonaceous materials, carbon atom dissociation rate depends strongly on the degree of long-range order and is an important rate controlling mechanism in the overall dissolution process. A systematic comparison of dissolution rates for a variety of coal-chars, natural and synthetic graphites has been carried out in an attempt to identify rate-controlling mechanisms. The structure of the carbonaceous material appears to be an important underlying factor in the carbon dissolution process.

Jan 1, 2003

The SART (sulfidisation, acidification, recycle, and thickening) process is an effective way to separate copper and cyanide from each other in the waste stream of gold processing plants using cyanidation. Factorial experimentation has been conducted to create models of copper recovery, cyanide recovery, acid addition, and oxidation I reduction potential during SART. Economic analysis of the resultant models showed that SART is best operated with a sulfide to copper molar ratio of around 0.56, a pH of 4, and a minimised cyanide to copper molar ratio. The experiments also showed that thickening time may have drastic impacts on SART performance.

Jan 1, 2011

By O Ignatenko, A van Schaik

Environmental legislation for the process and manufacturing industries is frequently formulated without considering the fundamental limits of physics, chemistry and thermodynamics within process technology. Recycling of end-of-life goods is used in this paper to show how the limits can be evaluated on the basis of the theory of minerals processing and metallurgical engineering. This theory has been applied on European Union level to re-examine the legislation for automobile recycling in a recent stakeholder discussion involving the automotive industry (http://www.assurre.org). This theory and our models are finding their way into the computer aided design (CAD) tools of the automotive industry, developments that form part of a project to design the super light car of the future (http://www.superlightcar.com). Only such fundamental approaches will in future be able to provide the basis to argue and define realistic and sensible environmental legislation.

Jan 1, 2006

By M. Brennan, A. Majumder

"The mineral processing research community has devoted enormous efforts to the modelling of mineral separators over the last 50 years. While many efforts have been made to use only fundamental physics as a basis for the models, fluid flow patterns in separators are not simple while the motion of particle swarms through fluids is extremely complex.One of the simplest separators is the sluice, in which separation takes place in a flowing film a few millimetres thick. The particles are suspended by turbulent eddies and motion relative to the fluid takes place in so-called hindered settling mode.In an effort to test the extent to which fundamental fluid mechanics can provide a prediction of particle separation, a study on a simple parallel-sided sluice has been carried out using glass beads at various particle concentrations and flow rates.The actual particle separation taking place was compared to predictions made by first describing the fluid flow by a modified ‘law of the wall’ model.Particle concentration distributions were described using Hunt’s sediment transport model, assuming the particle eddy diffusion coefficient to be the same as that for the water. Settling velocities were calculated using either the Richardson and Zaki or Brauer and Thiele models. The latter takes into account particle size and density distributions and solids volumetric concentration.The resulting predictions of particle separation are remarkably good, even though the model does not model the local settling velocity in the slurry."

Jan 1, 2003

By Martin McKinnon, Guy Reed, Russell Frith

"It is arguable that the development of reinforcing roof bolting systems has largely stagnated in recent times, primarily due to the prevailing industry view that few, if any, further improvements can be made to what currently exists. However, this paper contends that reinforcing roof bolting systems can be further refined by considering both the specific manner by which horizontally bedded roof strata loses its natural self-supporting ability and the specific means by which reinforcing roof bolts act to promote or retain this natural self-supporting ability. The Australian coal industry insists on minimising bolt-hole diameter to maximise load transfer and on targeting full-encapsulation by any means necessary. This has led to a significant, albeit unintended, consequence in terms of overall roof bolting effectiveness, namely increased resin pressures during bolt installation and the associated potential for opening bedding planes that may have, otherwise, remained closed during the bolt installation process. Given that the natural self-supporting ability of roof strata is strongly linked to whether bedding planes are open or closed, logically, minimising resin pressures should be a significant benefit. This paper focuses primarily on three key issues that relate directly to the function of the roof bolting system itself: (i) the importance of proper resin mixing in the context of maximising load transfer strength and stiffness, (ii) the importance of minimising resin pressures developed during bolt installation, and (iii) the importance of maximising the effectiveness of the available bolt pre-tension. All mine operators should be invested in improving the individual effectiveness of each installed roof bolt, even by relatively small incremental amounts, so this is an important topic for discussion within the mining community."

Jan 1, 2017

By Pekka Taskinen

The converter-less nickel matte smelting technology (DON) adopted more than 20 years ago in Boliden Harjavalta smelter has been since that applied successfully to the processing of large number of nickel sulphide concentrates of various Ni-to-Cu ratios and MgO contents. The operational point of the technology is far from the conventional primary nickel smelting in the smelting-converting route. Therefore, a careful scouting of distribution equilibria of the base and trace elements in the smelting conditions of DON process has been conducted, in order to obtain quantitative information about the equilibria and thermodynamic properties of the nickel mattes at low iron concentrations, less than 10 wt% [Fe] in matte. The series of investigations has included novel experimental and analytical techniques for increasing the reliability and sensitivity of the phase equilibria as well as the element distribution observations carried out in typical high-grade nickel matte smelting conditions.

By Janusz S. Laskowski

The flotation-related properties of hexanol derivatives and mono-alkyl ethers of propylene oxide, which include many important flotation frothers (e.g. MIBC, DF-200, DF-250, DF-1012, etc.) have been studied. The obtained results show that the DFI (Dynamic Foamability Index) - CCC (Critical Coalescence Concentration) plot can be used to classify flotation frothers. The frothers characterized by low CCC and high DFI values have properties of strong flotation frothers, while those with high CCC and low DFI values are more selective. The proposed frother classification system, based on simple CCC and DFI measurements, provides, for the first time, a solid ground-work for characterization of the flotation frothers.

Jan 1, 2003

By J S. Laskowski

Froth flotation process requires the use of frothers. These important flotation agents are commonly characterised as either æselectiveÆ or æpowerfulÆ and are chosen following general guidelines and verification by laboratory and/or pilot plant tests. Fundamental properties of the flotation frothers have been extensively studied over the last few years. These studies have led to the development of standardised procedures to characterise frothers in terms of their ability to reduce bubble size and to increase foam stability. In this research project, the performance of five frothers in flotation of coal is evaluated and related to the fundamental properties of these agents. Since the recovery of water in the concentrate is closely related to the non-selective transport of solid particles by entrainment, the tested frothers are also assessed in terms of their ability to promote the transport of water towards the froth collection zone, both in absence and in presence of solids.

Jan 1, 2005

By Hirohide Kamada, Gustavo Scarpim

The increase in industrial demand is responsible for a consequent evolution in the process of injection of aluminum under pressure (Die Casting) to achieve requirements such as; greater geometric complexity of injected parts, larger dimensions, hard-filled cavities, thin walls, and more refined mechanical and aesthetic requirements. Thus, the industries have searched for sensible increases in pressure and injection speed, always combining the best resistance and performance of the wells submitted to the new process conditions. The need for more aggressive applications for the cavities means that there is a constant evolution of the entire production chain in the manufacture of molds, passing through several processes, among them; machining, designs with complex engineering solutions, refining in the process of heat treatments and surface treatments. Allied to these needs, high performance steels manufactured by differentiated processes with high fracture resistance, hot strength and wear must be selected. This work aims to present the main factors considered in the development of high performance molds, the engineering of materials involved, technological trends and technical engineering solutions for the different variables of the die casting process.

Nov 22, 2018

By N Schofield

For the sampling of particulate materials in mineral exploration and mining, the fundamental sampling error (FSE) introduced by Gy is a measure of the constitutional heterogeneity of the sample lot and is expressed as the relative standard deviation of subsample grades of a particular mass. The FSE is presently regarded as an important indicator of quality for samples used in resource estimation. Constitutional heterogeneity describes an ideal state of heterogeneity with respect to all constituents of the lot such that the fundamental error among subsamples of a particular mass is minimised.In this paper, the term ‘sampling precision’ used in relation to mineral resource sampling usually refers to a statistic based on the assay results drawn from pairs of separate subsample splits of multiple sample lots. The pairs of splits are extracted after the lots have been prepared by crushing and pulverising to meet specified criteria of grain size and subsample mass. There is presently no generally accepted method of calculating the ‘sampling precision’ from such paired data but some form of the relative standard deviation that is consistent with definition of the FSE is preferred here. The work of Thompson and Howarth in the 1970s on geochemical analytical precision, which has been subjected to extensive examination and criticism by Stanley and Lawie (2007), and that of Francois-Bongarçon since the 1990s forms the background to the discussion in the paper.A significant aspect of the application of Gy’s sampling theory to sampling in gold deposits is the requirement that the fundamental error be maintained at less than ±20 per cent. The most important reason for this is to ensure that the effects of other sampling errors such as the grouping and segregation, and increment delimitation which can cause local and global biases in sampling are kept as small as possible. This paper is focused mainly on the quality of sampling in gold deposits and looks at an alternative to the use of a constant sampling precision applied to a collection of lots with varying average grade. A theoretical model for the FSE based on duplicate sampling is presented and the simulated results of the model are compared to practical outcomes of real duplicate pairs drawn from multiple sample lots. The goal of the work is to present a more informative analysis of duplicate sample data from multiple lots which may allow a more informed view of the potential for bias generating errors during sample preparation and processing.

Aug 22, 2011

By G Reynolds, N A. Ware, L Lu

Queensland Pacific Metals (QPM) is progressing its Townsville Energy Chemicals Hub (TECH) project to produce nickel and cobalt sulfates for advanced battery materials. Apart from the nickel and cobalt sulfates, the process also generates a hematite by-product (~640 ktpa). The hematite byproduct precipitated from the process, hereafter ‘hematite precipitate’, is high in Fe and particularly low in impurities. However, it is a fine <20 μm crystalline, hydrometallurgical precipitate and is produced as a filter cake containing a high moisture content of about 15 per cent. This is considerably different from natural hematite ore and is expected to change its performance during sintering. In the present study, laboratory scale sintering tests were undertaken to evaluate the potential impacts of substitution of the hematite precipitate for traditional magnetite concentrates and further for Australian hematite-goethite ores in a simulated industry base blend. Substitution of hematite precipitate for magnetite concentrates was found to slightly increase the sintering temperature required to achieve the strength of laboratory sinters. However, further substitution of hematite precipitate for Australian hematite-goethite ores slightly reduced the sintering temperature required to achieve the laboratory sinter strength. These results reflect the reduction in Al2O3 contents of the blends and are consistent with the trend observed in industry and pilot scale facilities. The reduction in sintering temperature generally correlates to a reduction in fuel rate in the larger scale sintering process. The pore structure of selected laboratory sinters was further examined and discussed in conjunction with sinter strength. The pore structure images highlighted the relative difference between the blends with the most obvious difference being seen at 1290°C which correlates well with the laboratory tumble index (TI). The laboratory sinter samples showed an increase in porosity and irregularity of pore shape, as hematite substitution increased demonstrating the correlation between a more porous structure and a lower TI.

Sep 18, 2023

By D. B. Dreisinger, M. Mokmeli, B. Wassink

Dissemination of selenium and tellurium in sulphide minerals results in the contamination of pregnant leach solutions and electrolytes in the hydrometallurgical treatment of sulphide ores and residues. The selenium and tellurium content of the copper sulphate-sulfuric acid solution may be reduced into insoluble precipitates of copper selenides and tellurides using cuprous ion. This study presents the use of the thermodynamics and kinetics for the removal process of selenium and tellurium in real life application. Dominant species of selenium and tellurium in acidic copper sulfate solutions were identified and the reduction rates of species were compared. The findings were applied to industrial conditions by modeling the Vale’s CRED (Sudbury, Canada) plant’s selenium and tellurium purification circuit. Rate reducing factors on selenium and tellurium removal were identified and discussed.

Jan 1, 2014

By G. P. Wong

"In the Inco matte separation process, a slow-cooled converter matte is separated into three main discrete mineral phases: chalcocite (Cc), heazlewoodite (Hz) and a Cu-Ni-Fe alloy. After magnetic removal of the alloy, Cc and Hz are separated by flotation at pH>12 with diphenyl guanidine (DPG) as both collector and frother. High selectivity is achieved in rougher flotation. However, in later flotation stages such as in the middlings circuit, as oxidation takes place, Hz becomes highly floatable, resulting in a very poor separation between Cc and Hz.Starch and dextrin as Hz depressants were evaluated on the middlings circuit feed and showed no positive impact on Cc/Hz separation selectivity. Ethylene diamine tetra-acetic acid (EDTA) extraction showed the existence of abundant surface Cu and Ni ions. The use of triethylene triamine (TETA) or EDTA in flotation did not improve Cc/Hz separation selectivity. Microflotation tests were carried out on pure synthetic Cc and Hz minerals. It was found that Hz did not float in the presence of DPG. However, Hz conditioned with either copper sulfate solution or in contact with Cc floated readily in the presence of DPG. It is concluded that the major reason for Hz flotation in the middlings circuit is due to Cc oxidation releasing Cu ions that adsorb on the Hz surface making it reactive with DPG thus rendering the Hz floatable."

Jan 1, 2003

By Jian Li, Robbie McDonald, David Robinson

"The pressure oxidation of sulfide minerals at temperatures above 200°C enables the extraction of base metals, improves the extractability of gold from refractory ores, enables solubilisation of PGEs and can be used to hydrothermally upgrade base metal-containing feeds. Fundamental studies reveal that the solution chemistry (and mineralogy of the solids) during pressure oxidation can be manipulated with outcomes that include (1) increased leaching rates, (2) lower oxygen requirements and (3) the formation of chemically more stable residues. This paper presents examples describing how these outcomes might be achieved based upon fundamental investigations.INTRODUCTION The application of pressure oxidation to the processing of gold ores and concentrates dates back several decades and continues to be the process of choice at operations such as Pueblo Viejo (pyritic gold) which host the largest autoclave of its kind in the world (Barrick Gold Corporation, 2016). Commercial application to the processing of base metals and PGMs resides with long established processes such as the Sherritt process, ore specific applications such as by Noril’sk, at Sepon etc. or has not proceeded to date beyond pilot scale testing (e.g. Phelps Dodge, CESL, Activox, Platsol). Recently there has been significant interest in hydrothermal upgrading options for concentrates including the NONOX and Toowong processes (Rohner et al., 2016; Weidenbach et al., 2016). The latter options suggest directions where sound knowledge of the underlying fundamentals enables novel outcomes and efficiencies to be obtained. It comes as no surprise that investigations similar to those underpinning these developing processes can be traced back several decades. It is not the subject of this paper to provide a historical perspective of the relevant autoclave chemistries but rather, to present some potential opportunities suggested by studies in our laboratories. Topics to be discussed in this paper include (1) control of metal extraction rates, (2) control of iron-residue composition and (3) control of sulfur oxidation and hence acid generation and oxygen requirements. The work described will focus upon the pressure oxidation of a nickel concentrate."

Jan 1, 2017

By Yoshiaki Numata

It is a matter of importance to use the lower alkyl monoethers of propylene glycol (polyPGME) as a frother in sulfide mineral flotation, for their compounds are highly soluble in water and are surface active frothers to some extent. The purpose of this study is to clarify fundamental roles of frothers in sulfide mineral flotation by investigating the effects of polyPGME on the floatability of galena with xanthate and adsorption property those ethers at the liquid/air interface. Fundamental investigation on the flotation of sulfide minerals using o,o-dialkyl dithiophosphates has been carried out through galena floatability tests in the following two cases:(l)single use of dithiophosphate for sulfide mineral collection and (2) joint use of dithiophosphates for its collection.

Jan 1, 1991

By H. Jiang, S. Yang

"The main processes for nickel metallurgy in China consist of electric arc furnace smelting to produce low grade nickel matte and converter to high grade nickel matte, grinding and flotation to separate nickel sulfide from copper sulfide and direct electrolysis of nickel matte. Systematic studies on the properties of electric furnace slag, smelting process for nickel matte, anodic process of nickel matte, cathodic process of nickel electrolysis have been done in our labs. In addition, an approach to a new hydrometallurgy process for nickel matte has been done. The feature of the new process is one stage acidic leaching of high grade nickel matte. The leaching solution could be purified by deposition way or by solvent extraction way. There are two leaching rate-determing steps, chemistry reaction-determing one at temperatures below 600C and diffusion-determing one at temperatures higher than 600 c. The acidic leaching fraction reacted dvaties with leaching time t according to the equation 1-(1- a ) 1/3=kt. The experimental data also show that the leaching reaction rate varies with concentrations of H+, Cl-, and it is also effected by copper sulfide and Cu++. The Cu++ ion can retard the leaching reaction due to forming a copper sulfide layer on the matte surface and the equation 1- 2/3 a. - (1- a: ) 2/3 akt can be used for the case. However the copper sulfide added into nickel matte can facilitate the leaching process. The research work for nickel metallurgy done by others in China has also been mentioned in this paper.Large scale production of nickel in China started in 1960s.The main processes consist of electric arc furnace smelting to produce low grade nickel matte and converter to high grade nickel matte grinding and floatation to separate copper sulfide from nickel sulfide and direct electrolysis of nickel matte.To reduce nickel loss in slag a reseaech group organized by Jinchuan Company and Central South Institute of Mining and Metallurgy (now the Central South University of Technology) measured the viscosity surface tention density conductance melting point and structure of the slag(I).lt has been found that the physico-chemical properties of the slag depend on the components SiO2 ,MgO and FeO but FeO in the slag is too high and the statistic analysis of data from industry gave an equation to correlate the content of Ni in slag with the content of Ni in matte and the composition of slag again it was pointed out that the content of FeO in slag effected the loss of Ni in slag very much (2). The ratio (FeO+MgO) to SiO2shouid be less than 1.13 and the content of Fe3O4should be as low as possible but the reaction"

Jan 1, 1988

By T Takayama, R Muroi, M Matsumura

The steel industry occupies 14 per cent of CO2 emissions in Japan, and the sintering process is one of the major emitters. Since most of CO2 released from the sintering process comes from coke fine combustion, replacement of coke fines with biomass char as bonding agent is a potential countermeasure. In order to explore the effective use of biomass char, we chose char made from Palm Kernel Shell (PKS) as a sample. First, the char’s combustion behaviour was examined with varying the char’s particle size by means of admixing the char in alumina ball packed bed placed in an electric furnace. As a result, the finer the PKS char the faster the burning rate and reaching a higher temperature compared to coke fine. In addition, it is also concluded that the optimum size of PKS char was larger than coke fines. Next, the effect of different heat profiles on sinter structure was examined by sintering tablet made of chemical reagents. In this experiment, the chemical composition is designed based on sinter composition. By this sintering test, even at high temperature, rapid cooling is effective to make fine sinter matrix and fine pores, which has possibility for high sinter reducibility. Based on these two experiments, using PKS char as a sinter fine source has the possibility to improve sinter reducibility.

Nov 8, 2021