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It is well known that the crushing and grinding steps in the mineral processing of ores represent a substantial proportion of total energy, cost and carbon emission in mining. For instance a recent study calculated that 36% of the energy consumed by gold and copper producing mines in Australia was attributable to comminution (Ballantyne et al, 2012). Understanding this component of a business is essential in a world seeking to lower production costs, improve earnings and reduce its carbon footprint. The issue commands the attention and support of industry leaders in the mining sector, government, equipment manufacture, engineering design and research organizations. Furthermore, several researchers have often stated that globally, comminution processes consume between 3-4% of the world?s electrical energy production (Daniel and Lewis-Gray, 2011). In 2009-10, Australia?s Federal Government Energy Efficiency Opportunity (EEO) participants in the mining sector used 336.5 PJ, representing approximately 6 percent of Australia's total energy use. It is evident that the current practices of breaking rocks in tumbling mills are relatively inefficient (Fuerstenau and Abouzeid, 2002). Research and improved engineering design has established that a range of improved blasting, crushing and grinding techniques and flow sheets may lower project costs and carbon footprint. These include relatively simple process flow sheet strategies such as gangue rejection or pre-concentration prior to size reduction, a better combination of grinding technologies (both current and new systems), and selection of coarser grind sizes where ore and waste mineralogy allow. Yet, despite this systematic and detailed research, the industry remains somewhat reluctant to implement these strategies. CEEC (Coalition for Eco-Efficient Comminution) was established in 2011 to support knowledge sharing and change in an area of high-energy consumption for the global mineral industry. CEEC is a not-for-profit industry company, funded by grants from world wide industry companies, whose mission is to accelerate knowledge and technology transfer in the field of energy-efficient comminution. The key benefit to the mining sector arising from CEEC?s activities will be an increase in the rate at which more energy-efficient comminution data sets, processes, and technologies are developed, demonstrated, shared and applied. This will contribute directly to the industry?s target of reducing operating costs and carbon emissions. CEEC International Ltd and JKTech Pty Ltd teamed together to facilitate the inaugural CEEC Workshop, in June 2012. The purpose of the workshop was to produce a roadmap to provide guidelines for how (1) operations can achieve best EEC practice in the short to medium term, in collaboration with vendors, engineering companies and other service providers, and (2) what R&D is needed to achieve paradigm change in EEC in the medium to long term, e.g. 75% reduction in comminution energy in 10 years.

Sep 1, 2012

By J. Faitli, I. Tarján

One of the basic processes of process engineering is the production of dense suspensions. The major two equipment of this task are the periodically operating propeller mixer, and the continuously operating mixer tank based on the flow principle. In the laboratory of the Department of Process Engineering at the University of Miskolc, laboratory scale experimental setups had been built of both types of mixers in the frame of the FKFP 0504/1999 signed research project, supported by the Hungarian Ministry of Education. By these experimental setups many systematical experimental series had been carried out by test materials of water as the dispersing media and sand, power plant fly ash and magnetite as the granular solids. On the basis of the literature and these experimental investigations, scale-up methods had been developed for both types of mixers for the determination of the main technical parameters of industrial size equipment.

Jan 1, 2003

By R. Marandi

The effective removal of heavy metals from aqueous wastes is among the most important issues for many industrialized countries, How ever biosorption, i.e. the uptake of heavy metals by non- living biomass, has gained increased credibility during recent years. Biosorption of Cr(VI) from aqueous solution, on pretreated and immobilized Aspergillus niger was investigated in a batch and countinuous reactors. A.niger biomass pretreated by boiling in 0.5 N NaOH solution for 15 min, exhibited higher Cr(VI) removal capacity than autoclaved biomass. The optimum adsorption pH value observed for Cr(VI) ions was 2. The Cr(VI)removal rate increased with a decrease in pH. The influence of contact time, pH, Cr(VI) concentration, biomass concentration and temperature on Cr(VI) removal were also evaluated. Biosorption of Cr(VI) on pretreated biomass followed the Freundlich and Langmuir adsorption models.In this study A.niger biomass was immobilized in Na-alginate matrix. The biomass beads packed in a column were able to remove metal ions.In this study we used two different flow rate in a column, 1.5 mL/min and 3 mL/min.The breakthrough data obtained for Cr(VI) was adequately by the Thomas and Yan models and the adsorption capacity of the biomass was found to less than the adsorption capacity obtaind in the batch study. When the beads containing biomass become saturated with metal ions, the adsorbed metals were eluted using 0.5 N NaOH solution. Therefor nearly 90% of Cr(VI) was desorbed by NaOH solution.

Jan 1, 2014

By R. Imhof, S. E. Sánchez-Pino, H. Sprenger, S. A. Sánchez-Baquedano

"In 1992, Ingeniería de Minerales started with the introduction of pneumatic flotation technology in Chile and South America. This technology consists of vertical cells and gyratory cells, used mainly under actual operational conditions, with pilot units directly installed in the concentrator circuits of the industrial process. Successful industrial applications have been observed at Los Pelambres, in the molybdenum plant; at Codelco Andina in the molybdenum plant as pre-rougher to produce directly a final concentrate; in the copper circuit at Las Luces as pre-rougher producing final concentrate using sea water; at Minera Valle Aconcagua where a full automatic plant produces pre-concentrate from fresh tailings as feed; at the silica and silicate reverse flotation circuit of Compañía Minera del Pacífico; in cleaning the final concentrate of Zn by reverse flotation removing ultrafine carbonate; and in a plant that reprocesses fresh tailings from a copper slag flotation process. Positive operational changes in the design of the flotation circuit have been seen in plants using G-cells and V-cells, improving the performance of flotation circuits and the quality of final products. The high concentration of bubbles and micro turbulence produced by the pneumatic aeration units provide a high probability of collision and attachment, reducing dramatically the residence time. Though it is a pneumatic flotation, no compressed air is needed, and the equipment is characterized by low maintenance costs, full automation, savings in investment and energy."

Jan 1, 2014

By G. S. Zeng

The mechanism of cobalt removal from zinc sulfate solution with zinc dust is still not understood well. The experiments in this paper were carried out by zinc dust from zinc sulfate solution with high cobalt to study the mechanism of cobalt removal. Residues after the cementation process from zinc sulfate solution were analyzed by SEM and Electron probe micro-analysis (EPMA) to investigate the morphology of products. Different temperature will cause different structure of particles. With the increasement of temperature, cobalt removal can be improved considerably. The mechanism of cobalt removal by zinc dust is thought as follows: firstly, the cobalt ion forms Co-Zn alloy with zinc particles, and the reaction reaches equilibrium quickly; secondly, the Co-Zn alloy continues reacting to Co with Co2+, which is the control procedure of the whole reaction.

Jan 1, 2014

By Kyle Bartholomew, Robert McIvor

"Functional performance analysis of closed circuit grinding provides valuable insight into the two components of ball mill circuit grinding efficiency: classification system efficiency and mill grinding efficiency. Classification system efficiency isolates the combined effect of classifier performance and circulating load ratio from other circuit variables, such as ore grindability and the mill grinding environment. Optimization of classification system efficiency ensures grinding energy is applied to particles needing further size reduction and not to overgrinding. Entirely based on size distribution data, classification system efficiency precisely distinguishes subtle changes in classification system performance. Use of the functional performance equation to isolate mill grinding efficiency allows for proper optimization of the mill grinding environment by isolating confounding effects of changes in classification and ore grindability. Variables such as mill percent solids and grinding media selection can be optimized using the mill grinding efficiency subcomponent of functional performance. First published by McIvor in 1988, the functional performance equation provides a set of standardized, quantitative optimization criteria, simple and powerful, which link circuit performance to plant design and operating variables that can be manipulated. Functional performance optimization has been applied in numerous mineral processing plants globally and continues to gain acceptance as a practical means for grinding circuit optimization. In this paper, examples of derivation and industrial application demonstrate the means by which functional performance analysis dissects grinding circuit efficiency into its subcomponents allowing the reader to apply this straightforward, powerful optimization methodology at their mineral processing operation."

Jan 1, 2014

By Dongyun Liang

Process mineralogy focuses on the chemical components and mineral composition of ore, dissemination size of valuable minerals, the occurrence of valuable and detrimental elements as well as the behavior of each mineral in the process. Through determining process mineralogy parameters and analyzing the characteristics of minerals, the results of process mineralogy study can provide mineralogy data for making a reasonable mineral processing technology program and optimizing the process. A detailed process mineralogy study is carried out for a complex rare metal ore in this paper and the results show that niobium mainly exists in the form of ferrocolumbite as well as nioboaeschynite and zirconium primarily occurs as zircon. The valuable minerals including Th-nioboaeschynite, ferrocolumbite, zircon, etc. have the characteristics of fine dissemination size, wide size range, complex chemical composition and variable physical properties, which mean it is a refractory ore. According to the results of mineral composition of ore, chemical composition of minerals, dissemination size of minerals, magnetism ranges of minerals and the distribution of niobium and zirconium, the process of ?desliming-Nb-Zr bulk flotation? is designed for this ore and the niobium-zirconium bulk rough concentrate with the grade of Nb2O5 9.43%, ZrO2 24.95%, Ta2O5 0.36% and the recovery of Nb2O5 77.66%, ZrO2 76.70%, Ta2O5 75.13% to crude ore can be obtained in the whole process closed-circuit test.

Sep 1, 2012

By Rod Hocking, Nenad Djordjevic, Randolph A. Pax

"Semi Autogenous (SAG) mills exhibit complex interactions between the competing processes occurring inside them. Traditional practice is to measure the operation of the SAG mill at an operating point in terms of its load, power draw, steel load, ore throughput rate, water addition rate and more recently the feed size distribution. However significant departures from standard operating conditions can occur due to changes, for example, in ore hardness, the quest for higher throughputs and mill internal geometry.Fundamental to SAG mill operation are the internal processes that ensure that a given ore throughput and discharge grind size are obtained and maintained. These processes can be measured using non-contact acoustic emissions from the SAG mills which utilise the information rich noise that is generated by the grinding, flow and charge movement inside a mill. Non-contact acoustic in-mill measurements can be used for the validation of discrete element modelling (DEM). The approach being reported in this paper is to model the individual physical processes and then to simulate the assemblage of a physical mill.By modelling the assemblage of steel balls in a 1 m pilot mill and duplicating the experimental arrangement exactly with the PFC3D model, it was possible to replicate the pattern of falling balls in the experimental mill. Furthermore, the key features of the acoustic emission spectrum that was calculated compared favourably to the measured spectrum at low frequencies. The experimental spectrum is shown in Figure 1."

Jan 1, 2003

By T. Bhambhani

Research at Cytec over the past two decades has shown that the traditional approach for ore metallurgical characterization (typically conducted via laboratory-scale batch flotation tests), which involves changing reagents and conditions one-factor-at-a-time, leads to several pitfalls. The chemical solution thus selected has a narrow un-optimized window of performance and will likely fail in the plant. A holistic approach, called the Flotation Matrix 100? process for ore metallurgical characterization, was developed at Cytec about a decade ago and has been successfully used to develop robust reagent solutions for several operations around the world. The premise for the approach is that flotation outcome from ores is variable and is determined by complex interactions between various physical, chemical and operational factors. A key component of the process is the use of efficient multivariate designs focused on the chemistry aspects (reagents and pulp chemistry), which helps identify the best processing conditions for each ore type, as well as the conditions resulting in poor performance. It also includes advanced statistical methods for dealing with the complexity and variability of experimental data. The holistic approach is illustrated in this paper with a case study on Pb/Zn ores. Using just 18 carefully designed batch tests, it is possible to partially simulate the behavior of each ore type in the plant. The best conditions for each ore type, along with the conditions to avoid, are identified. Along with this, insights are obtained into the reasons for high reagent dosages for certain ore types, and interactions between variables. Keywords: flotation, holistic approach, metallurgical characterization, multivariate experimental designs, base and precious metals recovery, sulfide collectors and modifiers, Pb/Zn sequential flotation

Sep 1, 2012

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisinger

"INTRODUCTIONThe objective of this work was to deport silver into a residue suitable for subsequent extraction without compromising the high base metal extraction during the pressure oxidation.RESULTS AND DISCUSSIONThe complex sulphide from the tailing pond of Cannington mine, Australia, was re-grounded and a bulk concentrate was recovered by flotation. The major economic sulphides are galena and sphalerite. The chemical analyses revealed 17.22% Fe; 4.88% Zn; 8.22% Pb; 9.49% S2- and 422 g/t Ag. The baseline cyanidation yielded 36.60% of silver at high cyanide consumption (24.17 kg/t NaCN). Pressure oxidation at 150°C (in the absence of iodide), followed by cyanidation of the residue yielded 8% silver extraction. Pressure oxidation was carried out at 110-150°C in sulphate media with additions of potassium iodide and the resulting residue was subjected to cyanidation. High recovery of silver was achieved because its incorporation into lead-hydronium jarosite during the pressure oxidation was minimised, while its deportment into the cyanide-soluble silver iodide was favoured (Figure 1). Silver recovery decreased slightly at high temperatures (140° and 150°C) because of the enhanced stability and kinetics of leadhydronium jarosite, but this could be overcome by increasing acidity and iodide concentration of the slurry."

Jan 1, 2003

By K. W. Stöckelhuber, A. Wenger, H. J. Schulze

"An important elementary step of the flotation process is the forming, drainage and rupture of a thin intervening liquid film between bubble and mineral particle.After the encounter of the bubble with the solid surface a wetting film is formed. The initial thinning of this film is driven by the capillary pressure inside the bubble. When the film has reached a certain thickness rupture can take place.There are two possible mechanisms describing this process:-, Growing fluctuation waves (spinodal dewetting) on fluid interfaces under the influence of any kind of attractive forces (electrostatic, van der Waals). -, Nucleation inside the film.Metastable wetting films on negatively charged, hydrophobic glass surfaces (gaseous phase methylated), or on hydrophilic, positively charged glass surfaces (with Al3+ ions), have been analysed by means of the kinetics of film thinning according to the Reynolds law. These experiments demonstrate that both mechanisms can be responsible for the rupture of a thin wetting film. In the case of hydrophobic surfaces the nucleation mechanism is preferred; in the case of opposite charged silica surface the capillary waves mechanism due to an attractive electrostatic double layer force between silica and air bubble takes place.Hereby the existence of a long range hydrophobic force. on a hydrophobic surface can be excluded. The apparent interaction can be explained by the presence of gas nuclei formed on heterogeneous surface sites. The results provide deeper insight into the mechanisms of wetting film stability, adhesion process in flotation and droplet coalescence."

Jan 1, 2003

By Chen Shuwen, Yao Zhihua

In the process of thickening dewatering_the motion state of two- phase flow in a thickener has a very great influence on thickening efficiency. The investigation was made using copper mill tailings. In this investigation the authors explored the formation conditions and motion range of density current in the thickening process by model experiments, and analyzed the influence of density current on thickening efficiency. The results have shown that the formation of density current has relations with the structure parameters of a thickener and thickening process. The density current and its forming location affect thickener’s working efficiency. The author measured the motion state of two- phase flow in a 53-m dial. thickener for copper mill tailings under its operation conditions and analyzed the density distribution and motion state of two-phase flow in the thickener. The results obtained by the industry tests have shown that the motion state of two- phase flow in the thickener can be greatly improved by modification of its structure, achieving a great improvement in its thickening efficiency. It is concluded that, a thickener’s working efficiency depends on the formation and motion range of density current in it, which is of great importance to designing and establishment of thickener’s working parameters.

Jan 1, 2003

By N. P. Haran

A detailed study was undertaken to beneficiate sub-grade iron ore sample from Kenojhar District, Orissa, India containing 57% Fe (T), 7.7% SiO2, 4.8% Al2O3, 4 % L.O.I. 0.4% TiO2,1.3 % Mn and traces of S(T) to make it suitable for the user industry. The mineralogical study indicated that it predominantly consists of haematite with subordinate amounts of goethite and clay. Quartz, Cryptomelane / Psilomelane, Pyrolusite, Gibbsite, Feldspar and Muscovite mica were present in very minor to trace amounts. The Denver grind ability tests indicated, that the sample could be categorized as ?medium soft to medium.? The Bond ball mill work index was determined to be 14.19 kwh per short ton. The beneficiation process involved classification followed by tabling of the classified sand, ground to minus 48 mesh size. The table slimes were subjected to Wet High Intensity Magnetic Separator (WHIMS). The developed process yielded a composite concentrate from tabling and WHIMS operations assaying 65% Fe(T), 2% SiO2, 1.8% Al2O3, 2% Mn and 0.9% LOI with a recovery of 60.1% Fe (T), amounting to 52.5 wt.% yield. To meet the size specifications for pellet making, it was further ground. Dewatering studies were also carried out on the ground combined concentrate and rejects. The thickener area of ground combined concentrate using 0.02 kg/t of Sufloc A 1115 flocculant was 0.02 m2/tonne of dry solids per 24 h. And for the combined rejects using 0.12 kg/t of flocculant, it was 0.035 m2/tonne of dry solids per 24 h. The moisture content, in the pressure filtration cake, in the ground combined concentrate product was 10.0%, and productivity was 506.7 kg/m2h. Thus, by thickening and filtration of process products, 90% of water used in the process could be recovered. The study highlights the development of a simple and cost effective flowsheet with almost complete water recovery for a subgrade iron ore sample. Keywords: tabling, WHIMS, thickener, filtration

Sep 1, 2012

By Long Han, Jianyuan Liu, Ping Ying

"Particle-bed compressive stressing is the main work mechanism of comminution by high pressure grinding rolls(HPGR). An experimental study on comminution and mineral liberation of two copper sulfide ores was carried out using a piston-die compressive stressing rig to simulate the situation of comminution with HPGR as the final-grinding device. The tests carried out include compressive comminution tests on particle-bed with narrow-size feed, and the locked-cycle comminution test on particle-bed with broad-size feed, which was then compared to a corresponding locked-cycle test of ball-mill grinding. The narrow-size feed is made up of particles in the size range 2.36~3.35 mm, whereas the broad-size feed of particles in the size range 0~3.35 mm. The liberation analysis for copper-mineral in the comminution products was accomplished using BPMA system – an automatic mineral liberation analyzer developed by BGRIMM. The influences of the stressing intensity and the method of comminution on the copper mineral liberation are discussed in terms of product size distribution, copper-metal deportation among size fractions, distribution of copper mineral among particle-size and particle-grade classes, degree of mineral liberation in size class as well as degree of mineral liberation overall.INTRODUCTION Traditionally, comminution process commonly applied in mineral processing is a flowsheet consisting of crushing of crude ore with conventional crushers, followed by grinding of the crushed ore in tumbling mills. In last decades, the energy-efficient HPGR (high-pressure grinding rolls) has found its application in mineral processing, mostly as tertiary or quaternary crusher to generate a fine-crushed product either as feed to subsequent grinding or as feed to a pre-beneficiation process before further grinding. Compared with the process of conventional crushing followed by grinding in ball mill, this mode of HPGR-application can achieve energy saving to some extent by reducing particle size of the feed to ball milling, and by reducing amount of the feed to ball milling if a significant portion of tailings in relatively coarse particle-size range can be discarded at the pre-beneficiation stage. In recent years, the approaches of letting HPGR take more comminution work from ball mill by applying it in semi-finish grinding mode or even finish grinding mode have been discussed (Burchardt, 2014). Although HPGR finish-grinding has been successfully applied in the cement industry for grinding of cement clinker and raw materials, this mode of HPGR application has yet rarely been implemented in mineral processing, despite the advantage of more energy-saving and other potential benefits such as preferential breakage, internal damage of particles and enhanced mineral liberation which may lead to a better downstream processing performance. The reasons for the retardation of the progress of this kind of HPGR-application in the mineral industry lies not only in that a finish-grinding with HPGR has to be operated in dry condition whereas most of ore-beneficiation processes like flotation are operated in wet condition, but also in that there are large variety of ore materials with various complexity of processing technology, which need to be addressed on a case-by-case basis with a lot of test work, in order to evaluate the potential advantages or disadvantages of this application."

Jan 1, 2018

By J. Drzymala

Ores and raw materials are subjected to mineral processing operations to increase the content of their useful components. Upgrading of these materials can proceed with different selectivity and therefore, there is a need to know and monitor the separation results of the process. The separation results can be evaluated using tables and graphs called upgrading curves. The course of lines in the upgrading curves is usually complex and depends on the graph type and process parameters. The Halbich grade vs. recovery plot is frequently used because is practical and it indicates several characteristic features of separation results. Separations by means of flotation of several different shale, dolomite and sandstone copper ores were performed along with determination of their mineral composition, copper content, liberation degree, and the maximum theoretical copper content in the first concentrate. These data, plotted as the Halbich upgrading curves, allowed to find other characteristic points such as practical maximum copper content in the first concentrate, maximum curvature coexisting with the liberation degree, maximum recovery of ore valuable components, and the slope the recovery-grade line at high recoveries as a measure of liberation. Correlations between theoretical and practical maximum copper contents in the first concentrate as well liberation degree and maximum curvature were also presented. They show that the ore type significantly influences the shape of the Halbich curve and its characteristic points.

Sep 1, 2012

By Ana C. C. Pacheco, Maurício L. Torem

"The aim of this work was the study of the effect of the type (Fe3+, Al3+ and Fe3+ and Al3+ mixture) and of the coprecipitant concentration on As5+ removal by ACF. Removal of As5+ using sodium dodecyl sulfate (SDS) as a collector was studied by Adsorbing Colloid Flotation (ACF) at laboratory scale. The morphology of the precipitate retained in the foam was analyzed by Scanning Electron Microscopy (SEM/EDS).In order to investigate the effect of the initial concentration of Fe3+ on As removal, sets of experiments were performed with a concentration of Fe3+ in the proper range of pH (5,0 – 6,0) previously observed in the coprecipitation tests. As removal improves significantly as the concentration of the coprecipitant agent increases from 60 mg.L-1 (77,4%) to 80 mg.L-1 (99,7%). This is probably due to the higher concentration of ferric hydroxide (Fe(OH)3) which provides a larger surface area available for adsorption of As. From the initial coprecipitant concentration of 80 mg.L-1, As removal has shown to be rather high (? 99,7%), with the maximum being (99,9%) by using a Fe3+ concentration of 160 mg.L-1. Therefore, for a maximum As removal, under these test conditions, the optimum concentration of Fe3+ is 160mg.L-1.This paper also shows the effect of the initial concentration of Al3+ on As removal at a suitable range of pH (7,0 – 8,0). A very significant increase on As removal was found to occur as the initial concentration of coprecipitant was increased from 60 mg.L-1 (35,7%) to 80 mg.L-1 (97,7%) and a decrease in As floatability (43,7% - 54,5%) was found to occur from that Al3+ concentration amount. Based upon those results, the optimum Al3+ concentration so as to remove As under these test conditions is 80 mg.L-1."

Jan 1, 2003

By T. Tumidajski

The purpose of the separation processes in coal processing is obtaining products of certain ash contents. In the most of cases it is assumed that the separation process is described by one, selected parameter, which usually is grain size or material density. The separation may be described by means of statistical distributions of random variables, what allows forecasting the separation results of certain enrichment method. There are very well known the applications of approximations of Tromp separation curves or distribution functions of Erasmus, Meloy or Weibull. It is necessary to say that if the fitness of the approximation more suitable, then the characteristics of the process itself is also better. In purpose of obtaining more appropriate results, these methods were modified by application the mathematical functions, as i.e. hyperbolic tangens function. Furthermore, on the basis of empirical data, so-called interpolations may be performed in purpose of getting more appropriate results of approximation. One of the most known techniques of interpolation is Hughes method. This method for interpolating standard data involves breaking down each interval into a number of smaller sub-intervals. The results of such one-dimensional approach not always contain the full in-formation of the searched distribution. It happens because such interpretation of the problem is not completely correct. In practice, the separation process depends not only on the one parameter (i.e. grain size), but also on many other features characterizing certain material (i.e. its density). It seems then that in some cases the application of multidimensional grain characteristics distributions will be more appropriate. In this paper, the technique of joining the distributions of grain size and density by means of so-called Morgenstern distributions is shown. The general form of these distributions is as following:

Jan 1, 2014

By U. A. Peuker, T. Mütze, F. Shayo, A. Wikedzi

"Buzwagi Gold Mine (BGM) is operated by Acacia Mining and located in the Lake Victoria Goldfields of central Tanzania. The mine treats a sulphide copper-gold ore to produce gold in form of doré bars and a concentrate containing gold, copper and silver. The BGM comminution circuit includes a primary crushing stage with a gyratory crusher and two grinding circuits using a Semi-Autogenous Grinding (SAG) mill and a ball mill. Currently, the grinding circuits are inefficient in achieving the aspired product fineness of xP,80 = 125 µm even at low to normal throughputs (450-600 t/h). An optimization study of the circuit performance was conducted to improve product fineness through circuit surveys, experimental lab work and simulations. The analysis of survey data revealed inefficient grinding operation characterized by ball mill product (xP,80 > 400 µm) coarser than designed and higher hydrocyclone cut sizes (xT > 200 µm), too. In MODSIM several options were simulated such as reduction of vortex finder and apex diameters, reduction of SAG screen aperture, and modification of cyclone feed density. An improvement of product fineness could be achieved by simulation of the cumulative changes but it was also concluded that the current equipment cannot achieve the target. Further simulations showed that a second ball mill might help to achieve the desired fineness as well as an increase of grinding throughput by up to 26 %. INTRODUCTION Simulation of comminution, particularly grinding and classification, has received great attention for many years, due to the fact that the unit operation is by far the most important both in terms of energy consumption as well as overall plant performance (King, 2001; Wills et al., 2006). The use of simulation is advantageous due to low cost as well as its ability to consider many variables simultaneously. Moreover, there are some benefits for optimizing grinding operations by simulation like decreased unit operating costs, increased capacity, and improved performance of downstream processes due to improved feed size distribution. This paper presents an optimization study for the grinding efficiency at Buzwagi Gold Mine. This was achieved through three full scale circuit surveys, lab work and simulations with MODSIM."

Jan 1, 2018

By S. L. Zheng

The compound material of Nano-TiO2 Supported on the diatomite was prepared by the hydrolytic method with purified diatomite and TiCl4. The compound material was characterized by SEM, XRD, TEM, EDX, XPS, and the application test of the compound material was studied. The characterization test results showed that the Nano-TiO2 was coated on the surface of diatomite, the crystal of TiO2 is anatase, and the average crystal size is 12 nm. The pore diameter was reduced, but pore volume and surface area of the compound material are increased after Nano-TiO2 Supported on the diatomite. The application test results for treating coking waste water and formaldehyde gas show that the compound material of Nano-TiO2 / diatomite has adsorption and photo-catalytic function and strong degradation performance for phenol and formaldehyde.

Jan 1, 2014

By E. Pourjenaei, P. Ghobadi

High Pressure Grinding Roll (HPGR) is efficient equipment in comminution process. HPGR could be a good option for preparing ball mill feed at the first stage of grinding due to its high efficiency and low energy consumption. Closing with a screen, these mills are utilizing as one of the principle parts in mineral processing industries, especially for iron ores. Recently, HPGRs are working as primary mills at 4 developing lines in Gol-e-Gohar Iron Ore Processing Complex, Iran. Different mechanism of particle crushing in compare to the other tumbling mills makes the HPGR as certain equipment with its own particular controlling parameters. Hydraulic pressure, roller speed and level of material inside feeding hopper are the most important variables influencing grinding efficiency of the HPGR. To figure out how they impress the process and operation situation, different industrial tests were carried out and the best result (d80 about 8 mm for HPGR discharge) was achieved at 180-190 bar pressure (P), 300 rpm speed (S) and 50% of hopper level (L). It is worth noting that this finding has been observed through past pilot test too. We also used design expert method (DX7 software) to develop the best design and analysis the test results, as well. According to the mechanical restriction of HPGR and process limitation in the plant (based on the industrial results), we adjusted value of each parameter in a logical range. Therefore, 20 industrial tests were conducted, as DX7 recommended, and the various impacts of the parameters and their interaction were identified based on statistical analysis. As the authors expected, it was revealed that after presser, roller speed is a critical variable because of its significant role in residence time of the particles between the rollers. The function below has been determined to explain the relation between different parameters and the response.

Jan 1, 2018