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By John A. Herbst

Professor A.M. Gaudin and his students at MIT were dedicated to understanding the fundamentals of mineral processing and as a consequence were constantly searching for better quantatative descriptions of size reduction, liberation and mineral separations. I have had the good fortune of meeting Professor Gaudin and working with many the modeling pioneers who followed him. I have observed first hand the refinement of mineral processing models as they increased in realisticness moving up the steps of the pyramid (see figure below) from pure empiricism to the current pinacle of physics based models. During this journey our industry benefited significanbtly as model prediction errors were reduced from ± 20% to ± 1%. Unit operation and plant simulations improved in accuracy and speed of calculations.

Sep 1, 2012

By P. K. Fedotov

Centrifugal separation opens its new application fields in the Mining Industry. The up-to-date equipment for ultra-fine ore and concentrates grinding allows an efficient use of centrifugal concentration for micronic gold grains recovery. Moreover, advanced centrifugal concentrators are presented on the market: concentrators with continuous concentrate discharge designed both for ore and non-metallic minerals concentration process. The conducted tests proved the centrifugal concentration to be efficient process for gold recovery from finely ground concentrates and ores (less than 20 µm). Knelson concentrator application for such a fine material in different process circuits makes possible to raise the total gold recovery level of plants. In the circuits of coal plants and in course of coal slimes treatment the centrifugal concentration may be used before flotation in order to improve process performances. A centrifugal concentrator KC-CVD with continuous concentrate discharge working on 0.3 (0.5)mm fraction before flotation is

Jan 1, 2014

By N. Naudé

The theory on particles displacement subjected to upwards and settling movements in water, using a water pulse, is described in literature, but very little experimental data is available to verify these theoretical ideas. The aim of this research work was to visualize the displacement of solid particles in a mixture of water and solid particles created with the aid of water pulses in the Mineral Density Separator. From the literature it is known that lighter particles are subjected to higher levels of displacement than heavier particles, and when the particles then settled down, layers of material are formed ac-cording to the densities of the material. By removing the individual material layers, the materials can then be separated according to their densities. During this study the individual material layers were investigated regarding the density and size distribution in that specific density layer. It is important for this project to have a statistical prediction of the ?real? flow of the particles with different density and size distribution, inside the Mineral Density Separator. The information gathered during this study will be used to show the correlation between a two dimensional model of the particle flow and that of the real three dimensional flow inside the Mineral Density Separator.

Jan 1, 2014

By L. Kuzev

Unknown and unpopular vibrational grinding mills possibilities to horizontal working chambers have been discussed. They can be realized under normal conditions with the typical values of vibrations applied with vibrational grinding which are: vibration frequency from 15 Hz to 50 Hz, vibration amplitude to 6 mm and vibration geometry. These possibilities constantly increase involving new raw materials and processes. Vibration grinding is possible with other technological process accompanied by intensified technological processing, while the process decreases. In many cases these technological decisions are original.

Jan 1, 2014

By N. A. Dementyeva

To improve gold recovery from preg-robbing carbonaceous ores a technology including gravity, flotation, recleaning of the flotation concentrate, intensive cyanidation of the gravity concentrate and carbon-in-leach (CIL) process for intensive cyanidation tailings and the recleaned concentrate was developed. The final flotation tailings are shipped to tailings disposal. Total gold recovery by the proposed technology from the ore with the head grade of 0.8 g/t was 83.9%. The gold loading onto the activated carbon from CIL process was 6.5 g/kg.

Jan 1, 2014

By N. Tsoni

The separation and recovery of fine and ultra-fine particles during the processing of mineral commodities by conventional separation methods is difficult and inefficient. This is due to the problems posed by the very small size of the mineral particles. The fine and ultra-fine mineral particles are either generated during size reduction processes or are necessitated by liberation size. This problem is expected to deteriorate, as deposits of even lower grade are processed. The inefficiency of the conventional separation methods with regards to the processing of very fine particles leads to the loss of considerable quantities of mineral commodities to the tailings. Novel methods and techniques as well combinations of known methods have been tested over the years. Among them, selective aggregation, along or in combination with flotation, has been given much attention. This study deals with the application of hydrophobic agglomeration as a separation method for very fine particles. The selected mineral system is magnesite/quartz, due to its sensitivity to physi-cochemical separation methods. The aim was the selective agglomeration of magnesite using sodium oleate. Tests on single minerals revealed that separation seems feasible and efficient. The parameters examined were: pH, quantity of sodium oleate, conditioning time, and, finally, settling time. Tests carried out on artificial mixtures of the two minerals, under various proportions, confirmed the results obtained from single mineral tests but they were slightly inferior. Finally, hydrophobic ag-glomeration tests were carried out on single and artificial mixtures of minerals using sodium oleate and petroleum as reagents. The results show that the addition of petroleum improves the results. In conclusion, hydrophobic agglomeration can be applied successfully even for fine particles of difficult-to-be-separated systems such as magnesite and quartz.

Jan 1, 2014

By P. Braga, A. Chaves, S. França, A. Luz

"In Brazil, there are no official reserves of molybdenum, and the unofficial reserves are modest. Therefore, the molybdenum ore (molybdenite) produced as a co-product or by-product of emerald mining in the region of Campo Formoso, BA, has arisen as the only economic option. The flotation process is commonly used in Brazil for the recovery of molybdenite from emerald mining tailings, but it produces low-content molybdenite concentrates, thereby resulting in a product with low economic value. The molybdenite concentrate produced in Campo Formoso contains 83.5% MoS2 (50% Mo), which is less than the international standard product that contains > 90% MoS2 (54% Mo).This low value is due to the presence of talc, which is a naturally hydrophobic mineral that is also floated with the molybdenite during the flotation process. Separability studies were done in a Partridge-Smith cell using dextrin and quebracho as a molybdenite depressor in solution at different concentrations and pH values to produce a technical-grade concentrate (i.e., 90% MoS2). These basic studies were accompanied by measurements of the zeta potential and contact angle, which was determined by the capillary rise method. The results of these floatability studies were used in bench flotation tests, which were performed in a Denver laboratory flotation cell. A molybdenite concentrate of 93.4% MoS2 was obtained when dextrin was used at a concentration of 100 g/t."

Jan 1, 2014

By S. V. Petrov

In recent years, heap leaching of gold is becoming wide spread due to low capital and operational costs that allows economically feasible processing of low-grade and cut-off grade ores. Currently, over 30 heap leach projects are operated in Russia. Some of the deposits treated by heap leach methods are almost depleted. Therefore, they will soon require spent heaps detoxification and reclamation. Traditionally, spent heaps are detoxified by chemical treatment. This process is characterized by relatively high kinetics and requires expensive reagents and additional equipment. The main disadvantage of this process is secondary contamination of the solutions by products of detoxification reactions and impurities contained in reagents. If there is enough time, spent heaps can be detoxified by natural degradation. The advantages of the proposed method are low operational costs due to use of existing heap leaching facilities and eliminating the need for chemicals for spent heaps detoxification. Residual concentrations of cyanides and thyocyanates in liquid phase (wet ore) of spent gold ore heaps after detoxification were 0.2~0.3 mg/L. Heavy metals were almost completely removed. The method was successfully used for detoxification of spent heaps at two gold mines.

Jan 1, 2014

By W. X. Yin

Electrowinning of lead from aqueous solution of PbCl2 and electrowinning of manganese dioxide from aqueous solution of MnCl2 are two research focuses in hydrometallurgy. This paper investigated a new process of simultaneous electrowinning of lead and manganese dioxide in chloride medium. The simultaneous electrowinning process in chloride solution not only can prevent chloride from liberating at anodes but also obtain two electrolysis products and decrease electric energy consumption. Diaphragm cell is used in the simultaneous electrowinning process to form separate anode and cathode compartment. The effects of temperature, HCl concentration in anolyte, NaCl concentration in catholyte and electrolysis time on current efficiency and cell voltage are studied. The results indicate that current efficiency of anode and cathode for 5 hours is 99% and 96% respectively, average cell voltage is 1. 701V, the weight ratio of lead and manganese dioxide produced at electrodes is 2. 39:1 under the optimum conditions. As anode products, manganese dioxide is ??MnO2, content of which in the products is more than 92%.

Jan 1, 2014

By Luis Cáceres, Genny Leinenweber

"We have designed a planar perpendicular flow cell for electrochemical measurement of a mineral available as a fine powder. The working electrode consisting of mineral powder supported on a carbon paste surface as a 4 mm diameter disk, was concentrically positioned inside a vertical tubular reactor. The counter electrode was a 316L tube embedded in the body cell. The supportive media was a 1.2:1 mixture of candle wax and graphite powder respectively, which is a good electrical conductor. The concentrate electrode as a film attached on a carbon paste disk was prepared rubbing the surface carbon paste against dried powdered mineral. An Ag/AgCl 1 M KCl cell as a reference electrode was attached to the body cell by using a fast coupling fitting. A stable flow rate was achieved using a frequency inverter to drive the pump motor. The flow through the cell verified to be laminar due to the Reynolds number in the cell flow passage. Cyclic voltammetry from - 1200 a 600 mVSAgE were measured using a carbon paste with and without mineral attached to the surface. The main findings of this work were: a). Electrochemical measurement of mineral powder in contact with flowing samples was easily achieved using ground mineral. This is important where massive samples are not available. b). The voltammetric curve features of ground mineral coincided with reported data. c). The working electrode could be quickly replaced while maintaining very good reproducibility."

Jan 1, 2014

By M. Evertsson, M. Johansson

"In minerals processing control is vital to increasing performance and output of a plant. Model predictive control (MPC) is one of the most effective control strategies used in process industry. Sbárbaro (Sbárbaro and Del Villar, 2010), Asbjörnsson (Asbjörnsson, 2015), and Légaré (Légaré et al., 2016) have for example highlighted the possibility to simulate, develop and tune control systems using plant simulators within minerals processing. In more recent years the use of model predictive controllers have increased, and many process industries now utilize more advanced control methods to regulate their processes, raising the question regarding how to, build, test and verify a proposed control solution successfully. In this research, a linear model predictive controller is formulated and applied to a simulator of an existing tertiary crushing circuit. The circuit has in previous work by Johansson (Johansson, 2017) been modeled in MATLAB Simulink and calibrated relative plant data to an average error of less than 10% over 8 hours of production. The work demonstrates how to formulate the controller model structure to describe conveyor belts, storage components, screens, crushers, and control objectives for a minerals processing circuit. The work illustrates how to apply and successfully evaluate possible upsides in a circuit. The advantage of a crushing circuit simulator is that it can be configured, tuned and modified in any possible way, which is of great benefit to developers and engineers. Additionally, examples of how to use estimated measures to improve the performance of the plant are demonstrated. The control performance is finally evaluated for three different controller configurations."

Jan 1, 2018

By V. F. Petrov, E. P. Olberg, S. V. Petrov

"The study was carried out using process solutions produced during cyanidation of gold-bearing concentrates from a gold-processing plant. It was found that the water contained a significant portion of thiocyanate (7910.0 mg/L), cyanide was virtually not present. The metals occurred primarily as iron (355.0 mg/L) in the form of ferrocyanide. Cyanide recovery was conducted using an ozone treatment process with reactors developed by the Environmental Department of Irgiredmet. The process design ensured complete utilization (100%) of O3, thus equipment operation safety increased.The recovery of free cyanide from thiocyanate was 76.6%, which corresponded to 5.12 kg of NaCN (100%) per 1 m3 of solution. Recovered NaCN can be used for recycling in hydrometallurgical processes.The operating costs estimation showed that the production cost of a tonne of recovered cyanide was US$1288.7, considering the prices of energy and commercial sodium cyanide in Russia in 2017, i.e. recovered cyanide is cheaper than commercial cyanide by 55.8%.INTRODUCTION Depletion of oxidized gold-bearing ores readily amenable to cyanidation has shifted focus to large-scale processing of primary ores with high sulphide content. Primary ores processing flow sheets involve gravitational and/or flotation concentration with subsequent treatment of produced gold-bearing concentrates. Typically, concentrates reporting to cyanidation contain considerable amounts of sulphur that can interact with CN- and further formation of SCN-. The use of refractory gold liberation methods (bacterial liberation, ultra-fine grinding) provides activation of this side reaction up to complete consumption of free cyanide in a short period. This makes water recycling unviable and impractical.The interaction of the sulphur content in concentrates and cyanide contributes substantially to consumption of NaCN required for efficient gold recovery. Inappropriate consumption of the main reagent achieves dozens of kilogram per tonne of material to cyanidation, and reaches approximately 100% when gold is recovered from activated sulphide-containing products (e.g. by ultra-fine grinding)."

Jan 1, 2018

By S. Gaydardzhiev

Initial experiments towards preparation of hollow ceramic microtubes by dip-coating of fibrous plants with water based alumina gel-casting slurries using hemp and coconut fibres as templates have been done. It has been found that the wettability of fibres and accordingly the stability of the developed ceramic layer on their surface during slurry gelation varied significantly within the different fibre types. Good correlation between the diameters of the template fibres and the resulting channels has been found at the level of solids loadings used, 31 %. Hemp fibres used as bundles have led to formation of multi channel patterns while the coconut fibres-templated process resulted in uniform monochannel materials. The micro tubes have show good mechanical handling.

Jan 1, 2014

By Gabriel Barrios, Juan Pérez-Prim, Marcelo Tavares

"The application of High Pressure grinding Rolls (HPGR) has been growing in the mining industry for the last 10 to 15 years. The major benefits generally supporting this trend are better energy efficiency, improved grinding capacity, less sensitivity to ore grindability variations and higher metal recovery in downstream processes such as heap leaching and flotation. The HPGR machine comprises a pair of counter-rotating rolls mounted in a sturdy frame. One roll is fixed in the frame, while the other is allowed to float on rails and is positioned using pneumohydraulic springs. The feed material is introduced in the gap between the rolls and is crushed by the mechanism of interparticle breakage. Comminution performance is largely determined by the pressure exerted on the bed of particles by the floating roll hydraulic system. The operating bed pressure depends on the hydraulic system start-up parameters and the loading response of the feed material. The work describes how the coupling of the multi-body dynamic simulation with Discrete Element Method in which particle breakage is described using the particle replacement method, can be effectively used to predict the performance of the HPGR. The model considers important variables as the HPGR rolls geometry and design, the hydraulic spring system start-up parameters and the material loading response, to describe operational key outputs as material throughput, operating gap and roller pressure distribution. The preliminary version of the model has been used to predict the effect of material properties on the operating gap and the load distribution on the surface of the rolls, demonstrating that it can describe qualitatively the HPGR operation, indicating that the model will be a power full tool for the simulation and selection of industrial HPGR units."

Jan 1, 2014

By W. S. Eu

Thermal treatment of mineral ores can initiate thermal phase transformations which can affect either their activation or deactivation, subsequently influencing their ability to dissolve in a leaching reagent. The formation of rutile and hematite from ilmenite minerals, for example, has been suggested to occur through a series of reduction and segregation reactions. This process has been used in beneficiating low-grade weathered ilmenite ores to higher grade rutile. Despite decades of re-search, the mechanism of this process is not well understood, because dissolved intermediates are poorly crystalline and are difficult to quantify, with the exception of the final rutile products. Previous studies have shown that disrupted intermediate phases, by thermal treatment, are most susceptible to reagent attack and can often demonstrate ?activation? effects. In this study, synchrotron based X-ray diffraction method was used to investigate in-situ and in real-time the transformation of ilmenite minerals to rutile and hematite during calcination. The rate of formation and disappearance of specific Bragg peaks during the reaction and thermal decomposition of the mineral were used to derive an understanding of the solid-state reactions. The effects of the mineral transformation were validated by laboratory based batch calcination and leaching in sulphuric acid. The results suggest that transformation of major mineral phases occurs within of specific window of operation and thermal treatment appears to influence the extent of activation and leachability of ilmenite minerals.

Jan 1, 2014

By J. W. Ahn

Calcined calcium oxide from limestone is hydrated to manufacture calcium hydroxide, and then precipitated calcium carbonate is synthesized from calcium hydroxide. Precipitated calcium carbonate of various morphologies is obtained by controlled conditions of each step and characteristics of limestone, calcium oxide and calcium hydroxide. Especially characteristics of calcium hydroxide have the most influence on morphology of precipitated calcium carbonate character. In this study, therefore, it is investigated the specific surface area of calcium hydroxide and morphology of precipitated calcium carbonate according to hydration temperature. Calcium hydroxide hydrated at high initial temperature has larger particle size than that hydrated at low initial temperature. And formation yield of aragonite precipitated calcium carbonate has improved by using calcium hydroxide had larger particle size (hydrated at high initial temperature).

Jan 1, 2014

By Jia Ma, Zhi-Chao Liu, Kang Liu, Chun-Feng Li, Bao-Bin Tang

"The geological environment of the certain uranium-molybdenum deposit is very complicated. While the study of process mineralogy is relatively few, which restricting the processing and leaching effect of ores. According to reaserch on process mineralogy of this mine, the basis of ore processing can be provided. The main contents of research are the uranium occurrence state and the influence of H2O2 in acid leaching. By various methods and experiments, the process of uranium mineralogical characteristics in this deposit are systematically studied. The results show that the uranium is mainly in the form of independent uranium minerals. The structures of these uranium minerals are venous and disseminated in mineral fissures, or microgranular inclusions in quartz and feldspar. It is not appropriate to concentrate the uranium minerals by flotation beneficiation because that the loss rate of target metals via water leaching process is very high. The ores are suitable for being acid leaching directly with 6% – 8% of H2O2, and the maximum leaching rate of uranium can be 96.88%. INTRODUCTION The uranium ores with associated elements have a large proportion in uranium resources (Lei, et al., 2014, Xing, et al., 2006; Ritchy and Wong, 1985). The uranium and molybdenum are easy to be paragenesis in nature enviroment because of their similar chemical properties. Therefor the uranium-molybdenum associated deposits are widely existing, such as the sedimentary sandstone uranium deposit in American with vanadium and molybdenum, the sedimentary sandstone uranium deposits in French with vanadium (Chen, et al., 2014; Lounis, 1997). A certain epithermal porphyry uranium-molybdenum deposit in China is mainly controlled by the subrhyolite- porphyry and the fault zone (Lv, 2012; Rui, 2010; Liu, et al., 2010). The ore properties of this deposit are complex, which include the high alteration degree, and the fine grain size of the target minerals (Ma, et al., 2013). The ore properties and occurrence state are quite different during each mining stage. As a consequence, the consumption of reagent increased and the leaching rate declined as long as the continuously mining. The author explored the best leaching rate of target elements According to the basic research on process mineralogy of present ores, experimental study of water leaching and oxidizing acid leaching on different particle sizes."

Jan 1, 2018

By Petrus van Staden, Dragan Milanovic, Francisco Sánchez, Eero Kolehmainen, Carlos Frias

"Currently there is no economical and viable process for on-site metal extraction from Low Grade, Complex or Poly-metallic deposits, and even more, there is not any industrial process or technology able to deal with polymetallic or bulk concentrates containing Cu+Zn+Pb base metals and also precious metals. Traditionally, metals recovery from polymetallic sulfide deposits is performed by mining, selective flotation to separate Cu, Pb and Zn concentrates, and finally, smelting/refining of those concentrates to obtain the refined metals. In many cases, selective flotation of that kind of complex ores produces low metals recovery and low concentrate quality containing impurities such as Hg, As, Bi, etc., which results in high penalties in treatment and refining charges, and consequently, worsening the economy of the mining business. Recovery of the valuable metals from Polymetallic, Complex or Low Grade ores could then be maximised by producing bulk concentrates or middling flotation products to feed novel hydrometallurgical processes, like the integral metallurgical system that is currently under development within the INTMET project. For example, producing bulk concentrates would increase more than 100% Cu+ Zn+Pb cumulative recovery versus conventional selective flotation. Founded by the Horizon-2020 EU Programme, the INTMET Project was started in February 2016 and will be running over three years. The INTMET consortium is led by Cobre Las Cruces (Spain) and integrates twelve partners from seven EU countries, and including Serbia and South Africa as well. The INTMET project represents a challenging opportunity to develop suitable technological solutions to deal efficiently with difficult, polymetallic and complex sulphide ores that are abundant in Europe and worldwide. Main activities carried out during the first 18 months of the INTMET project development includes: (i) An atmospheric leaching pilot plant having a capacity of 300 kg/h bulk concentrate which has been installed and operated continuously for nine months at the Las Cruces mine; (ii) Pressure leaching test work developed by Outotec; (iii) Bioleaching test work performed by Mintek in collaboration with MMI Bor. Prior test work was applied on bulk concentrate samples supplied from Spain, Portugal and Serbia. Some of the results of these technological developments have been very positive and are presented in this paper."

Jan 1, 2018

By I. L. Grigorova

As a result of the main processes of the limestone treatment ? sawing, buffing and polishing, a technological waste is usually obtained. These final tailings consist of a water suspension with highly variable solid phase content and granulometric composition. Since the waste is conducted to a tailing pool or another place, this leads to environment pollution. In this work the slurry waste generated during the limestone processing in a Bulgarian limestone manufacturing company was characterized. The chemical composition, particle size distribution, solid phase content, whiteness, yellowness, abrasion, specific surface and density were determined. The possibility of obtaining building/construction materials from limestone processing waste was studied in a laboratory scale. The technological tests included thickening, filtration and drying of waste products. Continuous operation laboratory thickener was used. Coagulant Accepta® 8302 (aluminum sulphate solution) and anionic flocculant Magnafloc® 155 were found to be the most effective in the sedimentation of the products. Filtration tests were performed using a laboratory pressure filter. Drying tests were carried out in laboratory facilities using the direct heating method. On the basis of the laboratory results a technology for limestone treatment waste was developed. A production line for building materials from limestone slurry was set up. As a result the manufacturing company has a possibility to use circulating water.

Jan 1, 2014

By Georg Unland, Thomas Wegner

"Different types of impact crushers use the physical effect of impact to crush rocks. The rocks can vary from soft to hard and from ductile to brittle but they should never be abrasive. Since the principles of impact crushing of larger rocks are hardly investigated these crushers are still sized rather by empirical than by scientific approaches.In order to investigate the principles of comminution by impact of large rocks a test rotor was developed and rocks of different dimensions were tested. The integrated measuring devices of the rotor enable the recording of impact forces and of absorbed impact energy with high resolution during the contact time.Since impact crushers stress the rock particles with a defined velocity the main crushing properties are gained as a function of the applied velocity and the particle size of the rock: likelihood of breakage, contact time, maximum crushing force, mass specific crushing work, surface related crushing ratio and crushed fragment shape distribution."

Jan 1, 2003