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By Danfeng Xu

The majority of the world?s nickel (Ni) resources occur as laterite ores, which are exceptionally complex, lower grade (<1.5% Ni) and expensive to treat using conventional smelting and high temperature/pressure autoclave methods. Heap leaching is a promising, less costly, alternative technology for processing low grade nickel laterite ores. However, significant technical challenges remain with Nickel laterite heap leaching, preventing its general adoption. This paper presents some highlights of laboratory column leaching studies undertaken to characterise, evaluate and optimise sulphuric acid leaching behaviour of Nickel laterite agglomerates. They provide basic but valuable information regarding Nickel laterite agglomerate structure stability and leaching performance under industrially-relevant, continuous acid irrigation conditions. In particular, Nickel and other key metals? (e.g. Co, Fe, Al and Mn) extraction rates, free acid concentration, bed slump and structural changes were determined at a given acid percolation rate as a function of time. Potential implications of the findings, for devising strategies for improved Nickel laterite plant heap leach operations are discussed. Keywords: nickel laterite, column leaching, agglomerates, leaching kinetics, acid consumption

Sep 1, 2012

By Shobha Kumari

Coal is the prime source of energy in India. It now contributes to about 55% of the total power generation and will continue to have its major share in the energy mix of the country in the foreseeable future. Thermal coals of India, known for their wide variations in nature and categorized as difficult to wash due to their typical mineral matter association with the organic matrix, need suitable beneficiation technique for quality upgrade for improving the overall economics, efficiency and pollution free power generation. A non-coking high-ash coal, collected from Vasundhara open cast mine of the Ib Valley Coalfield, Orissa, has been characterized along with its different fractions obtained in the process of beneficiation for distribution of minerals using FTIR, XRD and ash analysis. The raw coal was fractionated by size as well as by density. It has been observed that ash yields and mineralogical composition (found to be mainly kaolinite and quartz) have no appreciable change in different size fractions, indicating homogeneous distribution of minerals in the coal matrix. However, for the different density fractions the mineral composition and ash yield have significant variations. The quartz content of the beneficiated coal visualized with 34% ash yield, as mandated by the Ministry of Environment and Forest (MOEF) for the use of coal in power plants is reduced to half of that of the raw coal. As quartz is the most abrasive mineral in coal, reduction of its proportion obviously signifies considerable reduction of wear of power plant machinery when beneficiated coal is fed to utility boiler for generation of power. The composition of the major minerals quartz and kaolinite as determined, also favors formation of ash of refractory nature during combustion. Keywords: IB valley coal, beneficiation characteristics,

Sep 1, 2012

By Jochen Petersen, David G. Dixon

"Although heap leaching may be perceived as a somewhat low-tech route for the extraction of low-grade minerals, the underlying physical, chemical and biological processes are in fact extremely complex. There has been increased interest in heap leaching of sulphide minerals in recent years with the advent of controlled bio-heap leaching, and the need to mine more marginal ore deposits.A detailed investigation into the dynamics of heap leach processes has provided much insight into the underlying complexities, and has led to the development of a sophisticated modelling tool. Some of the features include mineral kinetics, particle level effects, bacterial growth, oxidation and adsorption, gas adsorption, pore diffusion, bulk advection, gas balance and heat conservation.Two case studies are presented which illustrate specific features of the model for different applications and how these have helped to identify key areas of concern. In each case the model has proved as an invaluable tool either for the improvement of existing heap leach practice or for the development and assessment of novel applications."

Jan 1, 2003

By A. A. Sirkeci

In the scope of this investigation comparison between impact breakage and compression breakage were carried out for the separation efficiency of minerals using a chromite ore sample. The ore sample was broken below 1 mm employing a laboratory type roll crusher and an impact crusher. Concentration tests were conducted on -1+0.5 mm, -0.5+0.2 mm and -0.2 mm size fractions using a Wilfley type shaking table. Test results showed a remarkable difference between two types of breakage. Both concentrate grade and recovery was in the favour of impact crushing. Furthermore, the shape of the broken particles also showed differences such that in the case of impact breakage they were more spherical compared to compressive crushing. The results of the shaking table con-centration tests showed that a concentrate assaying 48.4% Cr2O3 were obtained with 78.5% recovery in the case of impact breakage. On the other hand the concentrate grade and recovery values were 48.8% Cr2O3and 52.4% respectively in the case of compression crushing. The losses in the tailings were also in favour of impact breakage proving that differential breakage occurred between chromite and gangue minerals.

Jan 1, 2014

By T. V. Chnyrenkova, J. Troncoso, V. A. Luganov, G. P. Kluev

"Arsenic-gold bearing ores are used as flux in smelting or are leached to extract gold. The main aim is to decrease the arsenic content in processed materials and to break up the ore lattice, thus liberating the gold. Some regulations were established by authorities for sulfidizing of arsenic bearing compounds in a presence of pyrite and for oxidation of ores and concentrates in the presence of soda.This article analyses the results of laboratory and pilot plant testing of dissociating and oxidizing roasting of gold-arsenic bearing concentrates. During the dissociation roasting under vacuum, arsenic is sublimated into elemental and sulfide forms. This process allows for the minimization of the negative influence on the environment, but requires costly engineering solutions. Roasting in a limited quantity of oxygen in the gaseous phase makes it possible to sublimate arsenic in the form of oxides and sulfides and it may be carried out in fluid bed furnaces.Oxidizing roasting of the concentrates in the presence of soda results in formation of water-soluble compounds and forces practically all arsenic and sulfur to remain in the cinder."

Jan 1, 2003

By Arman Ehsani, Ersin Yazici, Haci Deveci

The downstream treatment of chloride leach solutions of WPCB for recovery of base and precious metals by a combination of adsorption and precipitation processes were carried out. A synthetic leach solution (1 M HCl, 116.5 g/L Cl-, 30 g/L Cu2+, 2.5 g/L Fe3+, 5 mg/L Au3+, 10 mg/L Ag+ and 20 mg/L Pd2+), which was prepared based on the composition of the pregnant leach solution obtained in the previous study was used in the tests. The leach solution was initially subjected to activated carbon (AC) adsorption (20 g/L AC, 80°C) in which gold was selectively recovered over silver and palladium i.e., 88% Au recovery at 0.5 h (92% at 3.5 h) compared with only 3-6% for Ag/Pd. Copper and iron were also observed to adsorb on AC as indicated by 1.4% and 17% decline, in their respective concentrations. Following the adsorption and filtration stage, metallic copper was added into the gold-barren solution to allow reduction of Cu2+ to Cu+, and to cement Pd on metallic copper. Over the mixing period (1 h), 93% of the Pd was recovered while only 1.4% of silver was cemented onto metallic copper. Subsequently, the leach solution was gradually neutralised by NaOH to pH 4, 7.5 and 9.5 for the precipitation of copper as cuprite (Cu2O). It was found that 41% and 46% of Cu and Ag, respectively, were precipitated at pH 4 at which iron was almost totally (99.8%) removed from solution. Precipitation of copper and silver was increased further at high pHs. At pH 9.5, cumulative recoveries for copper and silver were 91% and 85%, respectively. XRD analysis of the precipitates confirmed the presence of cupric copper oxides/hydroxides and revealed that copper losses occurred at pH 4 was due to the undesired presence of cupric copper in the solution.

Jan 1, 2014

By H. Z. Liu

An extra-refractory gold ore in China belongs to Carlin Type Gold Ore which is not only submicroscopic but also rich in arsenic and organic carbon. They have been proved that its floatability is not good enough and the gold in the ore could not be leached almost if it was not pretreated. The tests for the ore were carried out in accordance with flotation-concentrate preoxidation-cyanidation(or CIL) processes in order to exploit the mine. Two new depressants were discovered in the flotation tests and improved concentrate grades from about 20g/t to 32~50g/t. The methods of the concentrate preoxidation tests were alkaline atmospheric oxidation, acidic atmospheric oxidation, acidic pressure oxidation, roasting oxidation?biooxidation. The cyanidation tests after the concentrate preoxidation have proved the gold extraction of the pressure oxidation to be the highest(92.5%) and that of roasting secondary(89.3%). After fuller techno-economic comparison, it is suggested that the flotation-pressure oxidation or roasting-CIL process should be the most optimal for treating the ore. The gold recoveries of the ore were 83% for the pressure oxidation and 80% for the roasting respectively.

Jan 1, 2014

By S. M. Viduka

This paper presents a numerical investigation of solid separation in jigging device, which is a gravity separation method widely used in ore processing. Separation is recognized as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile on jigging performance. Modelling of the liquid-solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A variety of jigging profiles are implemented in jigging. The saw tooth pulsation profile is selected with three variations in both amplitude and frequency. The performance of each profile variant is compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system.

Sep 1, 2012

By W. Rubarth

The kaolin losses in hydrocyclone classification are determined by the fines, which are discharged together with the water to the underflow. This paper presents an improved technique of water injection to the conical part of the cyclone applied especially for small cyclones in kaolin preparation. In small hydrocyclones water, injection is a sensitive process. Therefore, the process was stabilized by controlled water injection dependent on the measurement of the underflow shape. Three applications of this innovation are presented. In the first case, the water injection is applied for the separation stage in dilute suspension where the final product is produced in the overflow of a 50mm hydrocyclone. The underflow contains sand and residual kaolin. For a higher kaolin recovery, the underflow is usually treated downstream in washing cyclones. The wash water injection results in a 45 ? 50% - reduction of the kaolin fraction <25µm in the underflow. Thus, water injection to the classifying cyclone leads to a separation comparable with a downstream washing stage. An additional hydrocyclone stage can be deleted. The second application refers to a classification in dense suspension. Here, the underflow of the last hydrocyclone stage was directed to a washing in a 50mm hydrocyclone. The additional injection of 3L/min water in to the conical part of the cyclone reduced the kaolin losses by half.The third application was executed in the washing stage equipped with 75mm hydrocyclones where the underflow is directed to flotation. Using the water injection the kaolin recovery in this stage was increased by approximately 20%. Keywords: hydrocyclone, classification, kaolin beneficiation, water injection, underflow washing

Sep 1, 2012

By G. M. Wolfaardt, B. C. Qi

"From a lifecycle point of view, biologically digested sludge is a valuable product that should be reused if possible. Sludge may be applied to agricultural land for further sludge treatment and improvement of the characteristics of the soil. The characteristics of sludge that affect its applicability for soil conditioning include moisture content, pathogens, nutrients and metals. In this paper, the use of solid anaerobic digestion sludge of the lignocellulosic residues to condition soil was investigated in regards to nutrient composition, water content/retention capacity, hygienic quality (contamination of pathogenic bacteria) and heavy metal adsorbing/releasing characteristics of the sludge.It was found that the digested sludge had approximately 44.5% free and immobilized water and 46.9% bound water. The water-holding capacity of the sludge was high. This was a merit to apply the sludge to agriculture in dry areas. Anaerobic digestion under thermophilic conditions showed a promising disinfecting effect to the sludge, in contrast to the landfill digestion. The anaerobic digestion sludge could be considered as a humus-rich hygienic product that improves soil fertility and water holding capacity, nourishes plants and immobilizes heavy metals in the environment"

Jan 1, 2003

By R. K. Rath

The low-grade iron ore sample contains both lumps and fines. It is mostly hematitic iron ore and considerable amount of goethitic/limonitic material is present in it. The major impurities present were quartz and clay. It is observed that the iron bearing phases are poorly liberated above 300 µm and the liberation improves below 300 µm. More than 80% liberation is achieved below 106 µm. Based on the liberation data, the feed for the different beneficiation methods was prepared by stage crushed the ROM followed by grinding passing to 106µm and the ground material (-106µm) was deslimed. The underflow was subjected to various beneficiation techniques such as tabling, enhanced gravity separator (EGS), wet high intensity magnetic separation (WHIMS), and flotation and the results are discussed. All the methods studied could able to produce pellet grade concentrate with iron content of 64.5%, however, a marginal higher yield was observed for WHIMS (81%). Keywords: beneficiation, gravity, magnetic, enhanced gravity separation, flotation, low-grade iron ore, desliming

Sep 1, 2012

By R. ?. Sherembayeva, ?. ?. ?uktybayeva, ?. B. Rakhimbekova, N. ?. ?m?rova

"Studying the interaction of the phosphorus-containing flotation reagent with the components of the flotation system ""liquid-gas-solid"" during flotation of non-ferrous metal ores allows regulating the enrichment process. The phosphorus-containing reagent-collector anabasinium-O,O-dimethyl-thiophosphate has beensynthesized under laboratory conditions and the concentrated aqueous solution of anabasin hydrochloride and the 40% solution of sodium hydroxide have been used as the raw material. The phosphorus-containing reagent has been obtained by interaction of the anabasine base, sulfur and dimethyl phosphite, due to sulfur and nitrogen atoms it can form complex compounds with heavy metal ions.Studying flotation of copper-sulfide ore of the Sayak field with the use of the phosphorus-containing reagent-collector anabasinium has been performed in the open and closed cycles. The degree of ore grinding was 60- 62% of the class -0.074 mm. There has been established the dependence of the ore flotation parameters on: a) pH of the pulp; b) the consumption of the reagent-collector anabasinium.The effect of the pulp pH on the technological parameters of copper ore flotation has been carried out with a reagent regulator that increases the difference in the surface properties of the minerals to be separated.There has been used lime as the regulator of the medium, the consumption of which varied from 750 to 1500 g/t; the consumption of the reagent-collector anabasinium was 10, 15, 20 and 25 g/t.It has been found that when flotation of copper ore without the use of lime at pH equal to 7.8 and at the reagent consumption, g/t: anabasinium - 25, T-92 - 55, copper recovery in the concentrate is 92.72%, the quality of concentrate is 7, 1%.In flotation according to the factory mode (the consumption of xanthate is 44 g/t, T-92 is 55 g/t, pH = 7.8 (without lime)) of copper ore, copper recovery in the concentrate is 87.38%, the concentrate quality is 7, 97%, with reducing the xanthate consumption to 25 g/t copper recovery is reduced to 83.39%, the quality of the concentrate is up to 6.69%.In the experiments using the factory reagent mode in the closed cycle, with the xanthate mass consumption of 44 g/t, T-92 blowing agent of 55 g/t, the third recleaning concentrate contained 19.13% copper with recovery of 86.89%.Using a phosphorus-containing reagent instead of xanthate with the same flow rate, the third recleaning concentrate with the mass fraction of copper of 19.82% has beenobtained with recovery of 87.77%."

Jan 1, 2018

By Shugang Hu

According to XRD, DTA and SEM detections, the hydration products of blast furnace slag (BFS) based cementing material SL, SLG. were studied in different age periods. The XRD analysis of cementing material SL hydration products showed that the composition of hydration products were mainly amorphous substances, few crystalline substances. Characteristic peak of ettringite hadn?t been found in the spectral line of DTA, and it hadn?t been found in the figures of SEM, either, which was accordant with the conclusion that the cementing performance of SL mainly coming from gel of hydrated calcium silicate (CSH) and hydrated calcium aluminate. However, the main hydration products of SLG are Aft, CSH, and AFm, which are similar to Portland cement. All results suggest that BFS is a suitable base material for cementation. Keywords: blast furnace slag, backfilling cementing material, hydration products, cementing performance

Sep 1, 2012

By Z. C. Shen

As core part of flotation column, aerator has been always priority research. A new type of porous aerator made of stainless sintered microcellular material is designed , which diameter is between 20µm to 40µm. High bubble surface area flux is obtained at low air pressure 20kPa by this type of aerator in water. In order to extend its applied range ,experiments were carried out in alkali slurry (pH=12) , resulting with porous aerator clogged after working 20 days . Sampling the cross-section of aerator detected by microscope and X-ray diffraction ,the reason clogging was found. Then plugging aerator was reactivated after putting it in acidic liquor treated by ultrasonic for about ten minutes. On-line aerator maintenance can be done in no down time , and it can be repetitive-used after recovered ,so reduced capital costs.

Jan 1, 2014

By Peter Kondos

The need for a sustainable development of ore deposits makes it imperative to be innovative and mindful in creating an economically and environmentally viable operation, while maintaining a good working relationship with the various stakeholders involved in developing and operating a large and complex mining project. This is becoming immensely important as gold ore deposits are becoming more mineralogically complex along with lower grades presenting both metallurgical and environmental challenges that need to be addressed in mitigating risks and improving project economics. This paper presents Barrick?s approach to development of strategic technologies for our long-term sustainable growth through conversion of valuable resources into reserves for both our green-field development projects and the expansion of our existing mining operations. Some of the key strategic solutions, including mineral processing, metallurgical and energy technologies, developed by Barrick and their impact on some of our complex gold and copper-gold ores will also be discussed in this paper. Keywords: gold ores, copper-gold ores, processing, breakthrough technologies

Sep 1, 2012

By P. Prusti

An air dense medium fluidised bed separator (ADMFBS) is the efficient process for dry beneficiation of coal. Magnetite powder is used as medium to make required pseudo-fluid density in the fluidised bed. The dynamics behavior of coal particle with reference to its position changes from ideal solution to pseudo-fluid condition in different bed densities depending on its shape, size and density. In this study, three set of projected areas of coal particles were taken. Each set contains four different shapes i.e., cubical, rectangular prism, spherical and triangular prism with different density starting from 1.3 to 1.8 gm/cc. It is observed that coal particles having density less than the bed density, floats in different positions in the dense medium fluidised bed. Higher projected area particles float in deeper height in comparison with smaller projected area. The difference in position of coal particles in the bed increases (nearly 1 to 4 cm) as the coal density approaches towards bed density irrespective of the different shapes. Different shapes of coal particles behave in different ways based on the operating parameters like bed density, coal density and projected area of coal particle. Empirical model equations are proposed to predict the position of coal particle of each shape in the air dense medium fluidised bed system. Keywords: ADMFBS, particle dynamics, projected area, shape

Sep 1, 2012

By Kyoungkeun Yoo

A citric acid leaching test after heavy medium separation process was performed to remove the heavy metal contaminat such as Pb, Cu, and Zn from contaminated soil. The lead component was removed from soil by heavy medium separation whereas zinc component shows 0 % - 37.9 % removal ratio with particle size. The citric acid leaching was conducted to remove the remained zinc component. The removal ratio of Zn reached to more than 95 % under the conditions; 10 % in pulp density, 200 rpm in agitation speed, 50 °C, 2 mol/L in citric acid concentration at 2 hrs in leaching time. These results suggest that the heavy medium separation method followed by citric acid leaching is effective for treatment of soil contaminated with various chemical forms of heavy metal. Keywords: metal contaminated soil, citrate, heavy medium separation, zinc

Sep 1, 2012

By M. Tang

The phosphate ore sample was taken from the iron tailings after recovering most of magnetite by magnetic separation in Longlin, Yunnan Province of China. Batch flotation tests had been conducted to upgrade the phosphate concentrate by conventional fatty acids reagents under 70% -75 µm of the particle size; however, the unsatisfied results (P2O5 grade of 27.84% and recovery of 49.25%) were obtained. Also there are a large amount of slimes trapped in the concentrate and high-dosages consumption of reagents, for example, more than15 kg/t soda ash and 2 kg/t sodium silicate at only one-staged roughing. Based on the analysis of X-ray diffraction (XRD) for the sample, most of gangues are clay, quartz, and chlorite, which may easy to over-grind and deteriorate the flotation process either on reagents consumption or slurry fluidity or viscosity. A hydro-cyclone had been introduced to pre-concentrate the phosphate ore by scrubbing the slime before flotation, which can result obviously in reducing the dosages of soda ash from 15 Kg/t to 4 Kg/t, and raising the grade of P2O5 in the concentrate from 27.84% to 36.13% at the expense of about 4% recovery of P2O5. They also substantially reduced the time of sedimentation of concentrate after flotation from ~10 to ~1 min. In this paper, the effects on the recovery of P2O5 by the different dosages of flotation reagents with or without de-sliming were studied, with the objective of determining the different effects on the functions of flotation reagents by slime during flotation. Keywords: de-sliming, phosphate, soda ash, flotation

Sep 1, 2012

By M. K. Aydogan

Today, arsenic has become a much greater problem than before because of the limitations introduced by WHO and USEPA that are lowered from 0.05 ppm to 0.01 ppm. In the nature Arsenic is mostly found as inorganic compounds in the forms of arsenite (As+3) and arsenate (As+5) in aqueous solutions. Arsenic contamination in ground and surface waters has been encountered in almost every country. This element has a carcinogenic effect and can occur in natural sources and anthropogenic sources such as metal mining, groundwater usage and industrial activities. In this study adsorbing colloid flotation was applied in the presence of aluminum sulfates. In the experiments SDS and K-Oleate were used as collectors while MIBC was the frother employed. The effects of collectors and aluminum/arsenic ratios on the removal of arsenic were examined under various pH values. It was found that arsenic removal enhanced with increasing aluminum concentration. Furthermore, it was observed that pH was a very critical parameter in all experiments. The best results were obtained when initial As: SDS: Al concentrations were 10:40:40 ppm at pH 5.5. At this concentration, the efficiency of arsenic removal found to be 99.9%. Keywords: arsenic, adsorbing colloid flotation, aluminum sulfate

Sep 1, 2012

By T. Wallmach, S. B. Blancher, A. Delaporte, P. Goncalves

"Fe-Ti oxides concentrates produced from heavy mineral sand deposits are widely used for the production of titanium dioxide pigments that are critical components of white paint, plastics and paper. According to mining industry, the Fe-Ti concentrates mostly consists of three phases: ilmenite, leucoxene and rutile. However, a few mineralogical studies have shown that the variety of Fe-Ti oxides found in sand deposits is far more complex, mostly due to alteration processes. The aim of this contribution is to characterize in detail by means of Qemscan analyses the mineralogy of the three main concentrates (ilmenite, leucoxene and rutile) produced by the Grande Côte Operation (GCO) mineralurgical plant in Senegal. The ultimate goal is to characterize the different products and textures formed during the natural ilmenite alteration processes, to localize the phases carrying the main impurities (Cr and P), and finally to determine the physical properties of each mineral component to improve metal recoveries. Along alteration processes, Ti content increase. Ilmenite (FeTiO3) is progressively transformed into pseudorutile (Fe2Ti3O9) particles which could also be altered and transformed into hydroxylian pseudorutile [FeTi6O12(OH)3.3H2O] or complex blends of anatase microcrystals (TiO2). These transformations are accompanied by significant changes in particle textures. Microporosity and fractures appear and the impurity content also increases. Anatase rich microcrystal assemblages, so far described as Leucoxene, could be identified to consist of grains with higher porosities, water contents and higher intrapore impurities. These particles are the main carriers of chromium and phosphorus. The observed mineral transition textures have a significant impact on the ore dressing processes. During these transformations, the physical properties of these phases change, the magnetic susceptibility as well as densities decreases, due to the increase in porosity. The separation of particles, especially those with high porosity will help improving the GCO mineralurgical plant performance and to reduce the impurity contents in finals products."

Jan 1, 2018