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By E. Guerrini, M. Maccagni, J. Nielsen

"The solution for the treatment of the EAFD has not yet been fully achieved. Some of this dust has still not found an appropriate final destination. Large consortium treatment plants are quite expensive both in terms of investment and operating cost. Meanwhile, the tolling expenses for steel production companies are becoming very important, causing them to look for alternatives. Some steel plants are looking to close their production loop by internal treatment of their dust. Some years ago, Engitec began studying the coupling of the EZINEX® Process, an ammonium chloride electrolysis to recover the zinc contained in the EAFD, with the INDUTEC® Process, a pyro process based on an induction furnace that can convert EAFD into a C.Z.O. similar to the Waelz oxide. The combination of these two processes provides an alternative to the existing treatment options and is particularly interesting for relatively small capacities. In this paper, we would like to give the latest update about these two processes and their possible integration INTRODUCTION Zinc is contained in numerous wastes and secondary raw materials that can be thought of as high zinc concentrate mines. This is a very interesting source of Zn that is typically easily exploitable. Unfortunately, only a portion of these materials are currently processed to recover the metal value, while stabilized or unstabilized landfilling is often the final destination. Pyrometallurgical processes are mainly used to convert the zinc into crude zinc oxide (CZO). The various processes are very similar and characterized by the fact that the zinc bearing materials are usually submitted to a thermal treatment [1] in which the zinc is reduced, vaporized and re-oxidized producing CZO. This material not only contains zinc oxide, but also relatively high concentrations of heavy metals. Many potential CZO sources, such as electric arc furnace dust (EAF), galvanizing ashes, brass foundry and converters fumes also contain chlorides, fluorides and alkali metals that will transfer to the CZO. The classic example is the Waelz oxide [2]. This CZO is an intermediate product that must be transformed into zinc salts or zinc metal. Until now, the conversion to zinc metal is done through two main processes: the sulphate leaching and electrowinning system and the Imperial Smelting Process (ISP). ISP is facing a crisis for technical and economic reasons that has led to the closing of most of the existing plants. In any case, before being fed to one of these two processes, the CZO must be treated to eliminate or reduce some of the contained impurities. In particular, the halides are most harmful to these processes."

Jan 1, 2018

By E. Guerrini, M. Maccagni, J. Nielsen

"The solution for the treatment of the EAFD has not yet been fully achieved. Some of this dust has still not found an appropriate final destination. Large consortium treatment plants are quite expensive both in terms of investment and operating cost. Meanwhile, the tolling expenses for steel production companies are becoming very important, causing them to look for alternatives. Some steel plants are looking to close their production loop by internal treatment of their dust. Some years ago, Engitec began studying the coupling of the EZINEX® Process, an ammonium chloride electrolysis to recover the zinc contained in the EAFD, with the INDUTEC® Process, a pyro process based on an induction furnace that can convert EAFD into a C.Z.O. similar to the Waelz oxide. The combination of these two processes provides an alternative to the existing treatment options and is particularly interesting for relatively small capacities. In this paper, we would like to give the latest update about these two processes and their possible integration INTRODUCTION Zinc is contained in numerous wastes and secondary raw materials that can be thought of as high zinc concentrate mines. This is a very interesting source of Zn that is typically easily exploitable. Unfortunately, only a portion of these materials are currently processed to recover the metal value, while stabilized or unstabilized landfilling is often the final destination. Pyrometallurgical processes are mainly used to convert the zinc into crude zinc oxide (CZO). The various processes are very similar and characterized by the fact that the zinc bearing materials are usually submitted to a thermal treatment [1] in which the zinc is reduced, vaporized and re-oxidized producing CZO. This material not only contains zinc oxide, but also relatively high concentrations of heavy metals. Many potential CZO sources, such as electric arc furnace dust (EAF), galvanizing ashes, brass foundry and converters fumes also contain chlorides, fluorides and alkali metals that will transfer to the CZO. The classic example is the Waelz oxide [2]. This CZO is an intermediate product that must be transformed into zinc salts or zinc metal. Until now, the conversion to zinc metal is done through two main processes: the sulphate leaching and electrowinning system and the Imperial Smelting Process (ISP). ISP is facing a crisis for technical and economic reasons that has led to the closing of most of the existing plants. In any case, before being fed to one of these two processes, the CZO must be treated to eliminate or reduce some of the contained impurities. In particular, the halides are most harmful to these processes."

Jan 1, 2018

By Susanna A. C. Stadler, Chris Aldrich, Jacques J. Eksteen

Slag foaming occurs in several pyrometallurgical processes. These processes include steelmaking in basic oxygen steelmaking furnaces and electric arc furnaces as well as various non-ferrous operations like sulphide smelting/converting and base metal slag cleaning. Although slag foaming in steelmaking processes has been extensively researched, little attention has been given to slag foaming in non-ferrous operations. Slag foaming phenomena are complex because often the system consists of three or more phases. With this in mind, factors previously identified as influencing slag foaming were investigated. These include the slag basicity, physical properties of the slag, namely viscosity, surface tension and density, the formation of particles due to undercooling of the slag and the FexO concentration in the slag. The effect of increasing FexO concentration was found to decrease the foam index due to lower viscosities, but higher surface tension depression appears to have led to increased foam index values at high FexO concentrations. The foaming index decreases with increasing basicity, until precipitation of solids occurs. After this point, the foaming index was found to increase with increasing basicity due to increased solids precipitation. In general, increasing amounts of slag-wettable solids led to higher foam indices, but the precise nature of the effect on slag foaming was dependant on the nature of the solid precipitate.

Jan 1, 2003

By R. ?. Shishmarjov, Yu. ?. Davidenko, S. V. Bukhalov, ?. S. Baksheev, M. S. Shkirya, N. ?. Aikasheva, D. V. Bogdanovich, ?. Yu. Faustova

"The goal of prospecting operations in the Republic of Altay was to locate gold-sulfide-quartz mineralization. For this purpose we applied the technology of electromagnetic sounding and induced polarization (EMS-IP). These operations resulted in localizing promising sites with presence of sulfidization. The EMS-IP method proved to be highly efficient amongst other prospecting methods targeted at recognizing zones of sulfide mineralization making up 91%, considering that in more than half cases the ore intervals were the case. In the Yakutian diamondiferous province the EMS-IP technology was approbated during three field seasons to accomplish the assignments on searching for kimberlite bodies under conditions of various geological types. As a result, the reference objects were distinguished, and geoelectric parameters of kimberlite pipes of explosion were defined.INTRODUCTION In the time span 2015-2016 in Gorny Altay the EMS-IP technology was approbated in the Novokuznetsk area. The on-land areal geophysical survey was performed by EMS-IP method applied to identify, outline and locate promising sites with Au-Ag-bearing polymetallic mineralization within surveyed areas. Compared to the hosting rocks, the sulfides contained in polymetallic mineralization are typified by low specific electrical resistivity (SER) and high polarization. The areal survey conducted via EMS-IP method provided spatial characteristics of searched object. From July 2016 to August 2017 our expedition group carried out serial test works and laboratory investigations intending to define performance capabilities of EMS-IP technology in searching for kimberlite bodies under conditions of diverse geological types. The prerequisites for serial work were operations accomplished at the «Listvenichny» site lying 35 km away from Mirny town in the Sakha Republic (Yakutia), where the EMS-IP technology was probed for locating position and measuring geoelectric parameters of tuff pipe «Buardakhsky». After successful completion of operations it was decided to evaluate geoelectric parameters of kimberlite pipes of explosion."

Jan 1, 2018

By Vinay Jain

Beneficiation of alumina rich iron ore slimes is a major challenge for the Indian iron ore industry. One of the methods by which this problem might be addressed is by design/screening of suitable reagents (flocculants/depressants/collectors) which act selectively towards either aluminum containing minerals (gibbsite and kaolinite) or iron bearing minerals (hematite and goethite) in order to separate them. Our earlier work indicates that separation of iron oxide minerals from gibbsite is relatively more difficult than from kaolinite. Accordingly, our research work has been focused on finding selective reagents for iron oxide ? gibbsite separation. We have performed density functional theory (DFT) computations to evaluate the interaction energies of seven different reagent groups - carboxylic acid, flotol, hydroxamic acid, phosphonic acid, iminobismethyl phosphoric acid, xanthate and starch with hematite and gibbsite surfaces. The objective was to identify if any of these groups show selective adsorption towards one of the mineral surfaces. Among all these reagents, starch exhibits the highest selectivity towards the hematite surface with a difference in interaction energy of ~63 kcal/mol between hematite and gibbsite surfaces. This is consistent with experimental findings at our laboratories on slime samples from Noamundi mines wherein it is being observed that usage of starch as a flocculant does lead to an improvement in the final grade of the ore with significant reduction in the Al-content. A binuclear complexation mechanism based on affinity between Fe and Ostarch atoms combined with a geometrical templating effect, arising out of a close correspondence between Fe-Fe distance on the hematite surface and O-O distance in starch, is proposed to explain the strong adsorption of starch on hematite surface. Keywords: slimes, iron ore, alumina, hematite, gibbsite, DFT, adsorption, flocculants

Sep 1, 2012

By Bertil I. Pålsson, Sture V. Persson, Kent T. Tano

"Grinding is one of the most energy consuming unit operations and is also a very inefficient and costly process. Therefore, it is of great importance to run the grinding process as efficiently as possible. The most common way today to control grinding processes is by measuring the power draw of the mill and try to keep it at a maximum level. However, some studies (Kawatra, 1989, Koivistoinen, 1989, Moys, 1989) have shown that this measurement doesn.t reflect everything that takes place inside a mill. Among other parameters like slurry rheology, temperature and charge behaviour, the volumetric filling of a grinding mill seems to have a large influence on the grinding efficiency (Herbst, 1988, Koivistoinen, 1992, Vermeulen, 1988). A problem in attempting to measure those parameters has been to get a sensor that is both robust and sensitive enough for continuous on-line measurement.This paper presents a method for the measurement of the apparent filling level in a pilot ball mill equipped with the Metso Continuous Charge Measurement system (CCM). In this technique a strain gauge sensor is mounted on a flat steel spring which is fitted into a recess underneath a lifter bar. In addition, a conductivity probe, the Boliden Grinding Measurement System (GMS), is mounted in another lifter bar with the purpose of comparing the two measurements. To visualise the behaviour of the charge a DEM modelling technique is used.The results indicate that the system is capable of following the normal variation that occurs in the mill. The signal also very well reflect changes in operating variables such as ball charge level, pulp density and rotational speed. By studying the nature and different features of the signal one can get a better understanding of milling circuit dynamics. Another feature of the technique is the possibility for an operator to continuously follow the grinding process and thereby run the process under optimal conditions."

Jan 1, 2003

By F. Ngoroma

Concentrators processing PGM bearing ores make use of polysaccharide depressants to reduce the recovery of the undesired naturally floatable gangue minerals, mainly silicates, present in the ore. Recent work has shown that high depressant dosages can completely depress naturally floatable gangue and thus prevent it from reporting to the concentrate. These high depressant dosages can, however, have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the effects of depressant addition, frothers are added. It is, however, preferable to maintain independent control over bubble size and froth stability which is difficult to achieve with only one frother. An alternative strategy is, to use a blend of frothers, e.g. a weaker frother in combination with a stronger frother. Such a system allows an additional degree of freedom: changing the ratio of the two frothers, that would provide more independent control of bubble size and froth stability. This study demonstrates, through the use of batch flotation tests, how blending low molecular weight alcohols with commercially available frothers impact the solids and water recovery, as well as the valuable mineral recovery and concentrate grade in different PGM ores. Higher water and solids recoveries together with higher valuable mineral recoveries (>90% copper and >70% nickel) were obtained from tests using frother blends.

Sep 1, 2012

By Yuemin Zhao

Pre-combustion cleaning of coal plays a key role in the process of efficient and clean utilization of coal resources. Recently, wet beneficiation of coal is predominant around the world. Nevertheless, wet beneficiation processes are limited by the increasingly serious problem of worldwide shortage of water, especially in China. Thus, it is imperative to develop efficient dry coal beneficiation techniques. Currently, several technologies such as air dense medium fluidized bed, compound dry cleaning and air jigging have successfully achieved high-efficiency separation of 50~6 mm coal. However, in recent years, a large amount of fine coal is generated as the mechanized mining technology has been progressively deployed in coal sector. Thus, it is necessary to develop efficient dry beneficiation techniques for fine coal. In recent years, many countries including China, India, Canada, Germen, and Australia have carried out many research works on fine coal dry beneficiation techniques. China University of Mining and Technology has carried out systematic researches on the introduction the vibrated energy to traditional air dense medium fluidized bed for fine coal beneficiation. This paper studied air dense medium vibrated fluidized beds (ADMVFB) for fine coal dry beneficiation. The experimental results show that the coal of <6 mm size can be beneficiated in an ADMVFB efficiently with the E value of 0.065~0.085, the separating density can be adjusted in the range of 1.45~2.2 g/cm3, and the lower limit of beneficiation can reach to 0.5 mm. Keywords: fine coal, air dense medium vibrated fluidized bed, coal separation, dry separation

Sep 1, 2012

By Georges Delemontex, Nigel Grigg

"Pre-concentration of precious metal and base metal ore types is becoming more relevant with the discovery, development and operation of many lower grade deposits around the world. The fluctuations in metal prices and currencies expose many mines to risks especially dealing with low and variable ore grades. Pre-concentration, the process of concentrating the valuable metal into a smaller mass yield, effectively results in the introduction of higher feed grades to milling circuits. Gangue rejection, the removal of lower S.G. waste rock from the circuit, not only results in higher downstream grades but also potentially removes harder, non-valuable mineral, providing significant power savings within the circuit. The pre-concentration or ‘gangue rejection’ process offers a number of benefits when considering the treatment of marginal ore deposits, especially if it can be performed at a coarse crush size; these benefits include a reduction of the operating costs and the feed of more metal units to the mill. Gekko Systems has effectively utilized the Inline Pressure Jig (IPJ) to pre-concentrate the valuable metal, achieving high primary recoveries into a range of mass yields resulting in upgrade ratios between 2 and 10 times. This paper explores: the benefits of pre-concentrating ‘marginal’ ore deposits prior to the milling circuit; the selective rejection of ore types that may affect either the recovery or comminution process; and also looks into the potential to effectively reduce the ‘cut-off’ grade when considering the mine planning process. Case studies of projects using the IPJ to pre-concentrate and reject gangue are also included. Pre-concentration and gangue rejection provide the potential to develop marginal ore deposits, thus providing higher grades, less gangue and more metal at a lower operating cost to producers."

Jan 1, 2014

By G. Alfano

We have investigated the breakage actions of solid particles observed in a new generation fluid energy micronizer being set up at our laboratories. The attention has been focussed in particular on breakage caused by interparticle collision, particle impact against a fixed surface, interparticle attrition and particle against wall of jet mill attrition. We have also studied the influence of grain size distribution, maximum particle size, flow rate and characteristics of the solid to be processed, as well as of flow rate and pressure of injected air on the above mechanism. Lastly, the operating parameters of a dynamic air classifier in closed circuit with the micronizer for recovering the fine fraction and automatically recycling the oversize, have been optimized. The findings of this investigation have been used to design, build and fine tune a micronizer capable of controlling the top size of a product having average particle size that meets market requirements for fine powders, while keeping power consumption relatively low.

Jan 1, 2014

By U. M. J. Boin, W. L. Dalmijn, T. P. R. de Jong

"This paper explores the complex interrelationship between the resource cycle, recycling and metal production as a function of economics, environmental legislation, and product design. It is argued that central to optimising this resource cycle lies the control in particular of physical separation plants by the application of advanced sensor technology and sorting equipment, as well as suitable control and sampling algorithms supported by optimising mass balance models.Metals are produced through a long chain of processes. For primary resources, metals production goes through mining, mineral processing, ore smelting, conversion and refining steps or via low temperature hydrometallurgical processes, or a combination of both pyro- and hydrometallurgical operations. For the recycling of resources, metals are separated and recovered from metal scrap, which plays an increasingly important role in the world. Metals after being produced, either from primary or recycling resources, have to be further refined or manufactured into various types of alloys and finally shaped into different products for the end-users. Since the end-user discards products the contained materials find their way back into the resource cycle as scrap. Therefore, controlling the metallurgical reactors also controls, in a much broader sense, the material quality in the complete metals cycle, from the production phase, to the end-use phase, up to the recycling phase (Reuter et al., 2003). The recycling phase includes separation of materials into saleable intermediate products, which are reintroduced into the production phase as a recycling resource. Therefore, the metallurgical processes in each unit operation in the metals production and processing chain have to be controlled, so as to achieve optimal performance of high product quality, low energy and materials consumption, and low environmental impact."

Jan 1, 2003

By Paul W. Weiblen, Louis J. Cabri, Rolando Lastra

"Preliminary tests were done to determine whether comminution by electric-pulse disaggregation, or E-PD (cf. Rudashevsky et al; 1995), was more effective than using conventional crushing for Merensky Reef ore. A hand sample of the Merensky Reef was sawn in two: then one sub-sample was comminuted to .2 mm using E-PD at the University of Minnesota, and the other sub-sample was crushed to .2 mm using a conventional jaw crusher at CANMET.The products of the electric-pulse disaggregation and jaw crusher were fractionated by sieving and by a separation using a heavy liquid with a specific gravity of 3.3, because the proportion of platinum-group minerals (PGM) and sulphides to silicate minerals is very low. Thus, four mineral separates were produced: .2000 + 833 µm, -833 +208 µm, -208-µm float and -208-µm sink. All the mineral separates were studied by image analysis (Lastra et al; 1998). The main objective was to determine the liberation of gangue (silicate minerals), chromite, pyrrhotite, chalcopyrite, pentlandite and PGM. In the case of the PGM, a specific image analysis program was written to search and measure these minerals.The results show that the liberation obtained for gangue was similar (~99%) using either method of comminution. However, the liberation obtained for chromite (~89% vs. ~38%), pentlandite (~50% vs. 1%), pyrrhotite (~56% vs. ~38%), and PGM (~56% vs. ~1%) by E-PD was higher than that obtained by conventional jaw crusher, whereas the liberation obtained for chalcopyrite (~20% vs. ~71%) by E-PD was lower. Nevertheless, the image analysis of the products also showed that the PGM are strongly associated with pentlandite. Thus, for the Merensky Reef, liberation of pentlandite from the gangue minerals and chromite is important to recover more of the PGM. This maybe be significant because, in addition to increased recovery of platinum-group minerals (PGM), Merensky Reef pentlandite also contains significant quantities of valuable platinum-group elements like Pd and Rh (Cabri, 1981; Cabri 1988, Kinloch 1982, Peyerl 1983). Hence, the results indicate that for the Merensky Reef, electric-pulse disaggregation would represent a better comminution operation than a conventional jaw crusher would. In addition, the greatly improved liberation for chromite may find application for the PGM-rich UG2 chromitite."

Jan 1, 2003

By P. Gao, J. W. Yu

"Pre-concentration is a necessary step for upgrading low-grade iron ores, and its aim is to remove gangue minerals for improving efficiency of downstream separation process. The most important pre-concentration technique for iron ores, including hematite, siderite and limonite, is magnetic separation based on the appreciable differences between the desired iron minerals and gangue minerals in magnetic susceptibility. In this paper, the separation efficiency of one-stage low-intensity magnetic roughing combined with two-stage high-gradient magnetic scavenging for the pre-concentration of a low-grade hematite from Donganshan was investigated. It is a BIF type of ore containing hematite, magnetite and a bit of siderite, and an average content of Fe is about 34.6%. The effects of grinding fineness and magnetic field intensity for scavenging I and II were studied and optimized. The results showed that a magnetic preconcentrate assaying 42.7% with a recovery of 95.4% was obtained under the conditions of ore grinding fineness of -74 µm 70%, magnetic field intensity of 300 mT and 800 mT for scavenging I and II, respectively. Over 20% of the feed was rejected as the final tailings assaying 6.4% Fe. Meanwhile, the XRD, iron chemical phase and SEM analyses of different stage products revealed that hematite, magnetite and siderite could be recovered successfully by magnetic separation. However, some ultra-fine hematite particles (-10 µm) were difficult to be captured by magnet, and lost in the final tailing, resulting in lower iron recovery.INTRODUCTION Donganshan iron ore belongs to sedimentary-metamorphic iron formation called banded iron formation (BIF), which is formed in the Precambrian with a layered structure composed of ore bodies (Shen, 2012). Such type of iron deposit contains various iron-bearing minerals like hematite, magnetite, and siderite, suggesting it may be amenable to pre-concentration with magnetic separation. The pre-concentration process is effectively applied in recovering hematite, magnetite and siderite from iron ore, due to its benefits of further upgrading iron ore and improving separation efficiency. The most important pre-concentration technique for iron ore is magnetic separation, including low-intensity magnetic separation and high-gradient magnetic separation, based on the fact that there are appreciable differences between the desired hematite, magnetite or siderite and the gangue minerals in magnetic susceptibility."

Jan 1, 2018

By S. Banisi, A. R. Ghasemi, M. Maleki-Moghaddam

Direct observation of the charge shape and its motion in industrial mills are not possible, it is then customary to use transparent end, small-scale mills (i.e., model mills) to determine the charge trajectory directly by visualization methods. Because of a short length of the model mills, the end-wall effects could introduce a significant bias on the observed charge trajectories and shape. The shorter the mill, the stronger the bias. This could be due to some material bridging between the end walls. In this research, the end-wall effects were investigated by gradually increasing the model mill length and analysing the charge trajectory and shape variation at a given operating conditions (i.e., ball filling, mill speed, liner type). The unbiased mill length was assumed to be beyond the mill length where no significant change observed in the charge trajectory and shape. For all tests, the torque of the charge was also measured by a torque sensor. The special design of the model mill with the diameter of 100 cm made possible to increase the mill length in steps of 3.6 cm up to 21.6 cm. Four types of liners, five steel ball fillings (10, 15, 20, 25, 30% v/v) and three mill speeds (55, 70, 85% of critical speed) were tested. The ball sizes ranged from 4 to 12 mm. The results indicated that when the mill length was below 10.8 cm the end walls prevented the charge from free falling. This resulted in lower impact point angles and lower power draws compared with the case of no end-wall effects. When the same experiments were performed using an iron ore instead of balls with the same size range, the impact of end-wall effects was more pronounced. For an increase of 30% in the speed (from 55 to 85%), the torque due the change in the charge shape decreased by 41% (from 3.7 to 2.2 kgf.m) when mill filling was 30%. At the same operating conditions when steel balls used the torque decreased only by 19% (from 9 to 7.2 kgf.m). This was expected due to irregular shapes of the ore particles which facilitated bridging. Three-dimensional DEM simulations also resulted in the similar conclusions.

Jan 1, 2014

By B. A. Kutlin

29% of the total ore mined in the Russian Federation for copper production is finely disseminated copper-zinc-pyrite ores of the Ural Region. Physical and chemical characteristics of pyrite copper-zinc ores make for difficulties in obtaining high indices during processing. At present, the authors have elaborated the technology to improve the quality of copper concentrates up to 20.0% for the ones obtained during pyrite copper-zinc ore processing (based on the example of the ore mining and processing enterprise ?Uchalinsky GOK?, Russian Federation). There are examples of use of fair-sized pneumo-mechanical flotation machines by modernization of processing plants. Keywords: copper-zinc-pyrite ores, Ural region Russian, selective flotation, pneumo- mechanical flotation machines

Sep 1, 2012

By Ying Gu

Automated mineralogy methods and tools, such as the Mineral Liberation Analyzer (MLA) and the QEMSCAN, are now widely used for ore characterization, process design and optimization. Several case studies published recently demonstrate that large gains can be obtained through grinding and flotation optimization guided by automated mineralogy data. However, since automated mineralogy can only provide the information pointing to where the process gains can be made, it does not directly impact the production gain. Thus, a question is often asked: how to value the contribution of automated mineralogy to process improvement of a particular plant. This appears to be a difficult question. On close examination however, it is found that this is essentially a question of the value of information and it is reasonably well documented in various other industries. Hubbard (2010), in chapter 7 ?Measuring the Value of Information?, dealt with exactly this type of problem. The value of information is the reduced risk of an investment and opportunity loss. The methods Hubbard developed can be applied to estimate the value of automated mineralogy, as well as metallurgical test work, which also produces information that reduces the risk of investment. This paper first introduces Hubbard?s theory on the value of information and how to measure it. It then applies his methods to estimate the value of automated mineralogy, using Anglo Platinum?s fine grinding project as an example. In this case, the value of automated mineralogy includes the reduction in investment risk worth US$ 62.5million, in project rejection worth US$197 million and in opportunity loss worth US$320 million. In the end, a general model is developed to allow the simulation of the value of automated mineralogy in different mining operations constrained by different parameters.

Sep 1, 2012

By K. D. Mehta

Copper concentrate containing complex sulphides of Cu-Ni with 14.13% Cu and 10.04% Ni besides impurities such as 0.33% Co and 0.71% Mo, is not acceptable to the copper smelters due to the smelting problems. Selective bioleaching of nickel from the concentrate can be considered an an option to make it suitable for copper smelter. Effect of elemental sulphur and pyrite on the bioleaching of Ni and Co has been investigated using a mixed culture of Acidithiobacillus ferrooxidans (A.f.) and Acidithiobacillus thiooxidans (A.t.). Parameters such as pH, temperature, particles, size etc. were optimised to understand the role of additives in the bioleaching. With 2% S at 308K, 2.0 pH, 5% pulp density and 200µm size particles while shaking at 100 rpm, 79% Ni, 41% Co and 5% Cu were bioleached as compared to the leaching of 81% Ni and 45% Co in presence of 10 wt% pyrite in 60 days; 27% Ni, 24% Co and 4% Cu were recovered in sterile experiment. The selective dissolution of nickel and cobalt as compared to copper may be explained by galvanic interaction between chalcopyrite: pentlandite / pyrrhotite. Bioleaching was facilitated by strong oxidizing conditions due to higher Fe3+/Fe2+ ratio/redox potential (ESCE) as a result of improved interaction of minerals through biooxidation of sulphur and accelerated galvanic interaction by pyrite. The mechanism of selective leaching of Ni and Co was established by XRD phase identification.

Sep 1, 2012

By A. Koizhanova

Kumistinskoye gold- and silver bearing ores (Republic of Kazakhstan) as well as standardized test solutions containing gold, silver, copper, zinc and iron were studied. The best results in silver and gold recovery from Kumistinskoye gold- and silver bearing ores were achieved through use of complex cyanide-thiosulfate solutions as compared to individual cyanide solutions and thiosulfate solutions. It was found that such complex solutions substantially step up leaching process herewith increasing precious metals recovery rates. Thermodynamics of studied chemical processes was calculated. Reaction order, kinetic constant and activation energy of gold leaching process through use of cyanide-thiosulfate solutions were identified. We managed to prove that the sorption rates and holding capacity in process of gold anions recovery with anionite AM-2B are comparable to sorption characteristics for cyanide solutions. Keywords: gold, silver, copper, zinc, iron, cyanide-thiosulfate solutions, anionite AM-2B

Sep 1, 2012

By Yongfu Yu, Xiaotie Wang, Fuguang Zhang, Liping Che

"The flotation process of native Rare Earth minerals such as bastnasite, monazite, mixed minerals of bastnasite and monazite, using the new effective collector Dh was studied in this paper, respectively, and the flotation properties are described. The good qualities of the new collector Dh were revealed through comparing with other collector of Rare Earth minerals. The test results of different ore samples show that at moderate pulp pH (8.5-9.5), Rare earth minerals can be effectively separated from barium, calcium and silicon bearing intergrowth minerals (barite, calcite and silicate minerals) and high quality Rare Earth concentrates can be obtained successfully by the new collector Dh, acid silica gel, turpentine and reagents fitting together rationally. In order to determine optimum technical conditions, the effect of pulp pH, pulp temperature, pulp density and the effect of dosage of reagents (Dh and acid silica gel) on the flotation were investigated in the test.Simultaneously, the paper explores the mechanism of the flotation of Rare Earth minerals from intergrowth minerals. The infrared spectra for Dh and Rare Earth cation by analysis in theory shows that Dh formed chelate complex with Rare Earth cation and were adsorbed on the surfaces of Rare Earth minerals. The mechanism of the intergrowth minerals depressed by acid silica gel can be explained as gummy colloid hydrolyzed from acid silica gel which are selectively absorbed on the gangue minerals, making them hydrophilic and depressed, with pulp pH value of alkalescent."

Jan 1, 2003

By Rogerio C. Guimarães, Antonio E. C. Peres

The production of phosphate concentrates (phosphate rock) from slimes represents a challenge to the phosphate industry worldwide. In Brazil, this challenge is particularly relevant due to the consistently low P2O5 grades and the igneous origin. The first industrial experiences of producing phosphate rock from slimes (-44µm or -325#) fraction started at Arafertil, currently Bunge Fertilizantes SA, in Araxá, in the 1980.s. This production corresponds, nowadays, to 35% of the total production of concentrates in the company (830,000t/year) in a circuit consisting of desliming in 40mm microcyclones and concentration in flotation columns, corn starch and fatty acids being utilised as reagents. The performance of slimes flotation and the process control, at Bunge´s concentrator, were improved after the introduction of column flotation technology, in the first half of the nineties. The column flotation technology for slimes recovery was expanded to other Brazilian concentrators still in the nineties: Ultrafértil (Catalão - GO), Bunge (Cajati - SP), Fosfértil (Tapira - MG) and Copebrás (Catalão - GO). At present the Brazilian production of phosphate rock is approximately 4.5Mt/year, with a strong trend for a market increase. Genuinely Brazilian technology is utilised for the processing of slimes, the concentrates representing 11 to 13% of the overall production. The production of apatite concentrates from slimes was relevant to increase phosphate recovery and reduce costs, contributing to the growth of the fertilisers industry.

Jan 1, 2003