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By D. W. Feng

Thiosulfate as an alternative lixiviant for gold has received much attention in recent years due to the growing environmental concerns over the use of cyanide. Cu(II) is used to catalyze the oxidation of gold and ammonia is to stabilize Cu(II) in alkaline solution. However, the presence of Cu(II) enhances the oxidative degradation of thiosulfate. The high consumption of reagents has made thiosulfate leaching uneconomical to date, in comparison with cyanide leaching. Therefore, further investigations are required to leaching under low reagent concentrations over extended periods where reagent consumption is low and gold leaching rate is low as well. It is thus necessary to find additives to enhance gold dissolution in the thiosulfate leaching system. Electrochemical studies using rotating gold disc showed that the oxidation of gold in ammoniacal thiosulfate solution increased significantly in the presence of a small amount of thiourea and the beneficial effect increased with an increase in the thiourea concentration up to 7.2 mM. Thiourea improved gold extraction in the thiosulfate leaching of gold from a sulfide ore under low reagent concentrations. Excessive addition of thiourea inhibited the leaching of the gold ore. The decomposition of thiosulfate was reduced with the presence of thiourea. X-ray Photoelectron Spectroscopy (XPS) results indicated that thiou-rea likely decomposed to sulfide and formed gold sulfide species at the gold surface.

Jan 1, 2014

By Alejandro Yañez, Martta Nousiainen, Rodrigo Grau

"Gas dispersion plays a fundamental role in froth flotation. Gas dispersion in flotation is quantified by using four properties: gas velocity, bubble size, gas hold-up and bubble surface area flux. Gas dispersion measurements were conducted in three flotation cells: TankCell 1, TankCell e300 and TankCell e500. The measurements reported in this paper were carried out exclusively in two-phase systems using only water and air at frother dosages exceeding the Critical Coalescence Concentration (CCC) in order to prevent bubbles from coalescing. The measurements conducted in TankCell 1 and TankCell e500 were conducted by Outotec specialists, whereas the characterization of TankCell e300 had been conducted earlier in 2008 by a team from McGill University. When working in two-phase systems and under non-coalescing conditions, gas dispersion characteristics measured in different scales can be compared directly. The measurements conducted in TankCell e300 are taken as a base line in order to compare the performance of TankCell e500, whereas TankCell 1 is a pilot-scale flotation cell which is used in rotor testing. The gas dispersion properties in TankCells were found to be affected by the air flow rate and rotor tip speed. Bubble sizes (d32) measured on the three-size scale seem to be within the same range of 0.6 mm to 1.6 mm. It was noted that the bubble size was influenced by rotor tip speed and gas velocity. In general, as the rotor tip speed increased, the bubble size decreased and as the gas velocity increased, so did the bubble size. The rotor tip speed also has an impact on the hold-up; in general, as the rotor tip speed increased the gas hold-up also increased but the influence of air flow rate on gas hold-up was greater. Bubble surface area flux was found to vary between 40 and 85 1/s. As the gas velocity increased, the bubble surface area flux also increased."

Jan 1, 2014

By P. K. Rozakeas

It has been experimentally demonstrated that the application of electrokinetic techniques in the continuous flow of coal-water suspensions within a helical anode-cathode pipe geometry effectively causes a significant reduction in the wall shear stress. This reduction in the frictional force at the cathodic pipe wall surface is attributed to a decrease in the concentration of coal particles in this flow region caused by the migration of negatively charged coal particles towards the anodic surface(s). The disadvantage of flow-intrusive geometries is the reduction in effective flow area as well as an increase in frictional surface area caused by the placement of the anode(s) within the flow region. Experimental data is presented for a non-intrusive helical anode-cathode geometry embedded in the pipe wall which shows that a reduction in pumping energy of approximately an order of magnitude is possible. A sample of sub-bituminous black coal fines having a mean particle size of approximately 17 microns was used to prepare coal-water suspensions with a solids concentration of 50%(w/w). The practical and economic implications of this work relate to an enhanced method of long distance transportation of slurries in pipes as well as an alternative technique for continuously separating solid-liquid suspensions.

Jan 1, 2014

By G. Unland

The sizing of crushers depends on the expected crushing forces. However, the crushing forces develop differently with every individual rock while it is compressed by the working surfaces of the crusher. For sizing, this compression process has to be characterized by the maximum crushing force. The maximum crushing force depends on the strength, shape and size of the rock, the amount and velocity of the imposed displacement of the working surfaces of the crusher on the rock and the conditions of the contact surfaces. From experience it is known that the strength of the material and, therefore, the crushing forces depend on the size of the specimen. This dependence is the so called size effect. The determination is based on compression tests. The force development is recorded during the compression of the specimen and for every individual test the maximum force is determined. The occurring maximum crushing forces of several rocks with the same diameter comminuted under the same conditions can be assessed by a mean value and a variance. The relationship between the mean values of the cross section related maximum crushing forces FAmax and the corresponding sizes d of the specimens can then be described by mathematical functions. They are derived from different approaches (phenomenological, statistical and statistical-physical methods). The phenomenological methods are subjective and yield functions depending on the assumptions of a person, whereas the statistical and statistical-physical methods are based on an evaluated function and the optimization of the parameters.

Jan 1, 2014

By Thi Hien Tran, Ngoc Anh Tran, Thi Thu Hien-Dinh, Duy Anh Dao

"Natural graphite exists mainly in three types of amorphous graphite, flakes graphite and lump graphite. Graphite from Bao Ha mine, Lao Cai province is with 11.8 carbon-graphite %, forms in flakes and dense crystals. The paper presents the comparison among enrichment of Bao Ha’s graphite by two types of froth flotation with 90 g/t kerosene oil as collector, 50 g/t montanol 800 as frother, in natural pH, and at 20 wt.% of solid. The differences among three flow charts indicated that using middling flotation and re-middling flotation for the cleaning tails and the scavenger concentrates, the final concentrate was improved and containing up to 94 carbon-graphite % of flakes graphite, up to 82 carbon-graphite % of fine graphite with 93.48 % total recovery, moreover, carbon-graphite in the final tail is 0.86 % with 6.52 % recovery. However, a refining mill and a classification stage were applied before doing the middling flotation stages.1. INTRODUCTIONGraphite (black lead or plumbago) is used in many industrial applications due to its high electrical and thermal conductivity, lubricity, and chemical inertness. High quality graphite can be used in metallurgy, molding, brake linings, batteries, and fuel cells. Graphite, composed exclusively of the element Carbon, is rather common mineral, but fine crystals are rare. Graphite is soft (hardness: 0.5-1 Mohs scale); has a layered, planar structure; occurs in platy or acicular (occasionally) morphology (Minerals.net; Pierson, 1993).USGS (2017) reported, global consumption of natural graphite continuing increase in the period of 2012-2016. In 2016, China used up 35% while produced 66% of the world’s graphite. Graphite mining are being developed in Madagascar, Mozambique, Namibia and Tanzania, but production reduced in Canada from 2015. Based on the statistic of Statista.com shows from 2011 to 2014 and a forecast to 2020, the global graphite demand is mostly in refractories, batteries, others, lubricant/crucible, foundry and pencil, and that is increase every year.Graphite Vietnam lies on the fault of the Red river from Yen Bai to Lao Cai, the reserves is estimated around 29.3 million ton and mostly in Lao Cai province where has Nam Thi graphite mine and Bao Ha graphite mine (MOIT, 2008). Vietnamese graphite products could reached to ~92% graphite carbon (Cg) (Tran Thi Hien et al., 2008). Studied samples was collected in Bao Ha graphite mine, is located in Lao Cai province. Graphite Bao Ha exists in two types as graphite flakes and amorphous (Hoang Thi Minh Thao et al., 2017)."

Jan 1, 2018

By P. Spolaore

In the frame of Bioshale FP6 project, the bioprocessing of a polymetallic and polymineral concentrate produced in an industrial operation in Lubin, Poland, was assessed. Following successful batch culture tests, processing in continuous conditions was tested to determine the main specifications for the application of the stirred-tank technology to this sulphide concentrate from black shale ores. The experimental work was carried out in a laboratory-scale unit consisting of 3 stirred tanks (50L or 20L) using an acidophilic and moderate thermophilic bacterial population. Different configurations of the unit and key operating parameters were tested (nutrient medium composition, solids concentration, rates of agitation and aeration). Scientific and technical approaches, such as bacterial community structure and mineralogical analysis were implemented in order to better understand the chemical and biochemical reactions occurring in the system. Using the data produced during the continuous operation, downstream processing assessment for both copper and silver recovery was also carried out. The best copper recovery obtained in the continuous operation was 92% and a hot brine leaching of the bioleach residue (PLINT process) allowed to recover 92% of the silver. A preliminary tech-no-economic evaluation of Lubin concentrate bioprocessing including bioleaching, copper and silver recoveries demonstrated the potential economic feasibility. Recovery of silver plays an important role in the economy of the process. This study presents promising values to further investigate this bioprocessing option.

Jan 1, 2014

By Hideki Yamamoto, Norihiro Murayama, Junji Shibata

"Hydrothermal syntheses of zeolite from coal fly ash were carried out by using various alkali sources. NaOH, Na2CO3, KOH, K2CO3 and their mixture were applied for an alkali source of zeolite synthesis. The various physical properties of the reaction product, such as the kind of zeolite crystal, cation exchange property, surface texture and so on, was investigated through the zeolitization reaction from fly ash. The mechanism of zeolitization reaction was considered from these results.Zeolite P(NaP), hydroxysodalite(HS) and chabazite(K-CHA) are synthesized as zeolite species, when fly ash hydrothermally reacts in various alkali solutions at 393K. The crystal structure of the products obtained in NaOH solutions for 3h changes from NaP to HS with increasing NaOH concentration. K-CHA formation in KOH solutions needs 10h of reaction time, which is longer than that of NaP or HS.Dissolution, condensation and crystallization steps exist in the zeolitization reaction from fly ash, and the particle surface of products remarkably changes in each step. The fly ash is spherical particles and the surface is smooth(Fig.1(a)). The dissolution of fly ash occurs in the heating process until 393K, and the particle surface changes like unevenness(Fig.1(b)). In case of NaP, the condensation of aluminosilicate ions takes place at 373-393K, and the amorphous aluminosilicate is deposit on the unreacted fly ash(Fig.1(c)). The crystallization of NaP already begins to occur at 393K and the surface is covered with fine zeolite crystals for 24h(Fig.1(d))."

Jan 1, 2003

By Q. Huo

The alumina production might not continue when the sulfur content of bauxite was too high. In order to bring down the sulfur content in bauxite, we studied on the bauxite desulfurization by bacteria screened from the acid mine drainage at mines of high sulfur content. The screened bacteria were domesticated by the high sulfur content bauxite. The experiments of bauxite desulfurization were carried out under the conditions of 5% pulp density, temperature of 30?, rotate speed of 120rpm. Bacterial desulfurization for 30 days, the sulfur content of the bauxite was reduced from 5.73% to 1.55% and the desulfurization percent was 72.9%. The recovery percent of alumina was 94.3%. The study showed that it was feasible to bring down the sulfur content of bauxite by bioleaching and this technique might make full use of the low grade bauxite.

Jan 1, 2014

Pyrite and Chalcocite have different crystal lattice, with different dissolution rate in the same ac-id solution, the dissolution rate of which is accelerated with increasing redox potential, they are leached simultaneously at high redox. In present work, some methods are adopted to inhibition the bioleaching of the pyrite by controlling the redox potential. Shake flask experiment shows that the dissolution of pyrite and chalcocite is slow as redox potential <700mV(Eh), but the dissolution in-creases exponentially as redox potential>800mV(Eh), they have good selectivity at redox potential between 700mV and 760mV(Eh).

Jan 1, 2014

By C. Çelik

Nowadays the optical sorting of industrial minerals is one of the most important processing methods which has cost efficient production possibilities. This method is used for industrial and raw materials that have different colour and brightness features. Initially this technology is used for sorting of foodstuffs and recovered glass, but for a long time also as physical mineral processing method for both industrial minerals like: limestone, marble, talc, basalt, flint, quartz and secondary raw materials like: building rubble, refractory materials, glass, plastic and household waste. In this study via optical sorting the separation of quartz out of a flint mix, which consists of the particles with different colors and brightness, is aimed. Experiments are performed on an optical sorting machine named CombiSense® 1200 at the institute of ?Aufbereitung mineralischer Rohs-toffe? RWTH Aachen. This automatic picking device was developed by the company ?Separation Systems Engineering (SSE), Wedel?. Hand picking method is used for product analysis and the efficiency tables are prepared on every step accordingly. This process enables to reach quartz products with purity up to 100%.

Jan 1, 2014

By Xiaoming Wang

This paper describes a new magnetic separator integrating dynamic permanent magnetic force, gravity and flow dynamics to enhance the quality of the iron concentration. This equipment can increase the grade of concentrate by controlling the formation of magnetic agglomerations to reject most gangue. Test results indicates that the compound force field separator can be applied in improving the quality of iron concentrate and has a wide range of potential market applications. Keywords: magnetic separator, compound force field, rotating magnetic system, magnetite concentration

Sep 1, 2012

By J. Y. P. Leite

In a small-scale mining in Brazil?s northeast, scheelite were exploited since 1940?s using a traditional gravity concentration flowchart (composed by jigs and shacking tables) that operates with low efficient for fine particles. Tailing of this plant was submitted to chemical, mineralogical and size characterization. Results pointed 50% smaller than 74µm with a grade of 0.11% WO3. The particle?s size is an important operational variable to heighten recuperation by shacking tables. Tests using Falcon SB40 centrifuge concentrators and shacking table were realized, optimizing their operational variables. Based on the tests results a new flowchart was proposed for concentrating and tailings recovery.

Sep 1, 2012

By V. V. Lodeischikov

This paper covers some problems of treatment of complex gold ores and concentrates containing copper, lead, zinc, antimony and uranium. All these metals may present in ores both as major and associated components. The paper suggests recommendations for early determination of relative value of the metals in ores, which largely contribute to the selection of concentration and metallurgical flow sheets. The focus of this work is on treatment of complex ores in gold plants. The metal extraction technologies used by such gold plants are typically aimed at maximum gold recovery. Therefore, production of base metals as by-products requires significant updating of the existing process flow sheets based on economic, environmental and other considerations. At the same time, cooperation between gold plants and base-metal plants is of great importance. This paper provides an overview of worldwide existing and innovative processes of base metals extraction from complex and refractory gold ores.

Jan 1, 2014

By P. A. Bepswa

A numerical study done to test the efficacy of heuristics developed for the design of measurement networks for high precision metallurgical accounting is presented in this paper. The heuristics considered were designed to maximise variance reduction of terminal stream measurements through data reconciliation for observable linear flow systems. A complex metallurgical process flow sheet from the mineral sands industry was used as a case study. Monte Carlo type simulations coupled with a non-linear programming based steady state data reconciliation algorithm were used as tools to investigate the heuristics. The results obtained suggested a close correlation between magnitudes of measured variances and the respective levels of variance reduction obtained through data reconciliation for both internal and terminal streams. It was observed that variance reduction through data reconciliation was maximised for terminal stream measurements in networks characterised by high precision measurement of internal streams and/or in flow sheets characterised by high ?stream to node ratios?. Terminal streams attached to highly interconnected parent nodes were observed to experience higher reductions in variance compared to terminal streams attached to less interconnected parent nodes. The results generally highlight the additional benefits of highly interconnected flow sheets and high precision internal stream measurement regimes on the maximisation of variance reduction of terminal stream measurements through data reconciliation. These findings are significant to metallurgical accounting and to process accounting applications in general in that they provide a conceptual basis for design decision making regarding the construction of measurement networks aimed at maximising variance reduction of targeted streams through data reconciliation.

Jan 1, 2014

By Gökçe Törenli, Okay Tutar

"Predicting the performance of plant-scale comminution circuits is essential to monitor the energy use and product size distribution, allowing us to control and optimize the whole process. In the light of this issue, with the assist of recent technologies, simulation techniques utilize the chance of putting the theory into practice in the most accurate way. For this purpose, this study aims to evaluate and optimize the efficiency of a plant-scale ball mill circuit by using perfect-mixing ball mill model on a simulation environment. The comminution circuit is selected from a specific copper-ore processing plant in Turkey. The essential parameters which are required for this study such as fresh feed Bond work index, size distribution etc. are determined by laboratory experiments. The forecasted data which are calculated by third-party software will be compared by the industrial operating data, in order to determine the performance of comminution circuit. In addition to that, this methodology provides a greater ability to analyse, optimize and understand the comminution circuit of ore treatment plant. The authors believe this work will provide supplementary data for further studies on simulation and subsequent optimization of comminution circuits.INTRODUCTION By the assist of mathematical models of the grinding mills and classifiers, simulation of the grinding circuits become more common in comminution because it is relatively economical and able to consider many variables simultaneously. It’s proceeds depends on the accuracy of the models and capability of reflect real operations. Computer-based simulation studies would provide the quantified information about the effects of the proposed changes on the comminution circuit performance in terms of size distribution, mass flow rates, equipment efficiency etc. Then the mentioned data used in order to check the suitability of the current equipment to the modified conditions, and for equipment selection. The outputs of circuit could also be used to estimate downstream flotation circuit performance because the general aim in this study is to The aim of the study is to investigate optimum operating variables and achieve p(80) size of 57 µm and 64 % of -36 µm particle in hydrocyclone overflow stream, which is optimum for that porphyritic copper ore for best concentrate recovery after flotation process in specific copper ore comminution circuit by using modelling and simulation techniques. Sampling survey was carried on the fine ore bin in order to perform Bond work index test and determine work index value (Wi). Thereafter mass balancing, using the size distribution data and tonnages, models for ball mills and hydrocyclone were developed. Finally, the circuit performance were investigated by computer simulations via JKSimMet software."

Jan 1, 2018

By Liang Dianyin

In this paper, the molybdenite flotation tailing of cleaner-scavenger bank which has a mass of very fine particles has been taken as raw ore to be processed by flotation with/without ultrasonic. The effect of ultrasonic frequency, intensity, processing time and uploading location on molybdenite flotation efficiency is investigated by four-factor three-level orthogonal experiment, and the effect significances of these ultrasonic variables to molybdenite flotation efficiency have also been evaluated. Single-factor analysis of variance is conducted to investigate whether the effect of ultrasonic on molybdenum ore flotation efficiency is significant or not. The samples extracted from different ore species in different time have been mixed to analyze the particle size. The results show that the particle size of +38µm in concentrate obviously increases while the particle size of -25µmobviouslydecreaseswith ultrasonic, which means that ultrasonic is good for flotation due to sludge removing effect. Keywords: ultrasonic, flotation efficiency, sulfide ore, tailing, grade, sludge removing

Sep 1, 2012

By Carlos Gualdron, Elizabeth Gomez, Rafael Bolivar

The productivity index of the Coopracarcegua Ltda., a mid-size coal mining company of Norte de Santander, Colombia, was related absenteeism using accident, productivity and profit data four years. The analysis was based on type, severity and frequency of accidents, number of absentee days; price per metric ton, and other relevant parameters. The enterprise is formed by 5 different mines of thermic coal, each one with different exploitation technologies and different productivity. Each mine was analysed separately and the loss of profit due to absenteeism was calculate for each one. The study showed that the foregone earnings due to absenteeism in terms of the whole productivity of the enterprise was about of 6.6% of the total profit average the 4 years, with calculated values of 14.7%, 3.5%, 8.4% and 4% per year in the evaluated period. The study identified that the most important cause of absenteeism was "General Disease". The foregone earnings in 2009, the highest loss for the analysed period, was about US$ 0.937 million and during the whole evaluated period was US$ 2.46 million.

Jan 1, 2014

By O. A. Bascur

"In recent years, metal producing companies have increased their investment in automation and technological innovation, embracing new opportunities to enable transformational change. Internet of Things (IoT) is one of many transformational initiatives, which can fundamentally revolutionize how industrial complexes operate. Whatever the issue, the answer is in the abundant and growing quantity of real time data and events collected in the grinding and flotation circuits in a mineral processing plant. Based on earlier work, today a grade recovery model permits identifying the best operating conditions in real time. We will review the strategy for increasing the value of the abundance instrumentation in current plants. An optimal Gaudin size distribution model provides augmented information from traditional sensors to find the optimal grind cut to reduce metal losses in the flotation circuits. The large amount of sensors in a flotation circuits permits to estimate the recovery and to find the optimal froth depth and aeration using an air holdup flotation model. The paper will describe the strategy of classifying data for on line generation of insights to using operational intelligence tools. We will discuss the implementation Recovery/Grind strategy with industrial examples in non-ferrous mineral processing and iron beneficiation.INTRODUCTIONThe declining supplies of high grade ores and increasing consumption of mineral and metal products have demanded higher operational efficiencies with minimum capital investments. The objective of copper flotation objectives are based on maximizing the dollars return on the concentrate produced. The economic efficiency is maximized by manipulating the circuit along the grade/recovery curve relationship. To achieve such objective improved stabilization of the grinding and flotation circuits are required (Oosthuizen, Craig, and Jamsa-Jounela, 2017)."

Jan 1, 2018

The energy dispersion X-ray fluorescence (EDXRF) analysis technique is a rapid and accurate method for describing sample?s element component and percentage composition. On the base of profound research for the national and international development and research condition, the author researched the EDXRF analyze technique and the EDXRF analyzer?s principle in depth, the difficulties and the key points for research and development of EDXRF analyzer; gave a scheme for re-search of bench EDXRF analyzer; researched some algorithms used in energy spectrum analysis; developed the energy spectrum analysis software based on the Visual C++ 6.0; together with the energy spectrum analysis software, the author designed and processed the structural of the bench XRF analyzer and integrated the import X-ray tube, thermoelectrically cooled Si-PIN photodiode X-ray detector and pulse amplitude analyzer as a model machine. The result shows: The model machine can be used in multi-element analysis at the same time for different types of dry mineral samples, with fast analysis speed, accurate model and high stability.

Jan 1, 2014

By U. S. Chattopadhyay

The estimated requirement of the nation by the year 2020 is approx. 80 Mt of steel and more than 0.2 million MW installed capacity of the electricity, thereby increasing the consumption of the coking and non-coking coal, which is expected to be in tune of about 75 Mt & 500 Mt respectively. One of the major deleterious factors in achieving the goal is the deteriorating quality of the feed coal used in both steel and power industries. Indian coking coals, in general, are typified by high ash, high inert (both organic and inorganic), low rank, low reactive macerals content, heterogeneous petrographic make-up, inferior coking properties and poor amenability to washing, thereby necessitating suitable washing measure. Coke-based steel industries in India require washed coking coal containing ash % varying between 17-19. The situation demands taking on immediate challenges to fill up the gap between the requirements and supply of coking coal. This paper reviews the R&D attempts in this laboratory and throws light on the key measures as long-term solution to the problem. Search for alternative source of coking coal, like LVC coal and their judicious preparation technology. The low volatile coking coal (LVCC) constitutes about 50% of the total coking coal reserves in India. These coals are characterized by high raw coal ash content (37 to 40%) and very difficult washability potential. If these coals are treated in the existing washeries, which are generally 2 or 3-product systems, the cost of clean coal is high as the byproduct sale value is low. It has been proposed to produce a new type of by product, which enjoys high demand and good coking properties.

Sep 1, 2012