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By V. E. Vigdergauz

The work presented shows results of electrochemical study of pyrite hydrophobicity evaluated by air bubble induction time (IT) measurements. On the basis of measured IT?s an average thickness of the thin liquid film prior to its rupture has been evaluated, which confirms long-range character of the interactions between air bubbles and hydrophobic surfaces. Obtained data are discussed in the frame of recent studies of structures of solid-liquid interface based on molecular dynamics simulations and results of surface force measurements.

Jan 1, 2014

By John A. Rumball, Martin R. Houchin

Data from autogenous and semi-autogenous tests in a 1.67m diameter mill have been analysed in terms of a new model for rock abrasion. This model defines specific rate as the rate of production of fines (material less than 13mm) per unit mass of rock, where the term “rock” is applied to all ore pieces of ore coarser than the grate size. In most cases, an allowance for preliminary rounding and cleavage was made. A method has been developed to analyse steady-state data, using piecewise fitting to the cumulative size distributions. The model was compared to the well-established models, which are based on the population balance method. The specific rate increased for all rock sizes as the volume of 100mm balls in the mill was increased. Tests using a coarser feed and smaller balls provided further evidence that once rocks are rounded, abrasion is due to localised surface damage, caused by impacts, rather than rotational shear. An allowance for rapid rounding of jagged rocks, followed by less rapid abrasion of rounded pebbles was also tested, but the analysis was not conclusive. The average specific rate is a useful measure of the capacity of a primary mill. The effect of power intensity (kW/t of ore) was also investigated as a means of extrapolating the pilot-plant data to large production mills.

Sep 29, 2003

By A. F. Usov

The paper is concerned with an analysis of the experience gained in development of special electro-technical installations applied in electric-pulse destruction of materials. A principle scheme of an electric electric-pulse installation is given, and electric circuit variants of its blocks made on various element bases are discussed. Also assessed are some ideas to further improve the technical and economic characteristics of the equipment.

Jan 1, 2014

By Jia Ma, Lu-De Qiang, Zhi-Chao Liu, Chun-Feng Li, Guang Li, Bao-Bin Tang

"At present, research on the surface chemical properties of uranium minerals is very scanty, which restricts the research progress of uranium ore flotation process research. The research aimed at exploring the surface characteristics of two common uranium minerals and providing basis for flotation process to enrich uranium minerals in ore. This paper selected pitchblende and uraninite as the object of study, which are widely distributed in uranium deposits. We chose out the pure minerals of pitchblende and uraninite from different ores collected from different uranium deposits. By means of Zeta potential test and X-ray photoelectron spectroscopy (XPS) test, a preliminary study on surface characteristics of the pure minerals of pitchblende and uraninite was conducted. And the significance of the change of Zeta potential, the elements composition and valence state on the minerals surface for flotation was discussed. The research shows that, the Zeta potentials of pitchblende and uraninite in pure water are negative mainly when the pH value varies from 2 to 11, which maybe a result of the difference of ionization capacity between two kinds of oxy-compounds on the surface of minerals. On the surface of pitchblende and uraninite, the metal elements are mainly U, Th and Pb. U is mainly in the form of UO2, Th is mainly in the form of ThO2, and Pb is mainly in the form of Pb and PbO. Based on the surface characteristics of pitchblende and uraninite, we can select process and reagents appropriately in uranium ore flotation.INTRODUCTION Globally, the major challenges associated with exploitation of low grade ores are about finding economically feasible processes for reducing the mass of gangue minerals (Filippov et al., 2012). Among the beneficiation technologies of low grade uranium ores with complex minerals assemblage, flotation is the common process which is used to reduce production cost and eliminate the acid-consuming minerals (Li et al., 2016; Liu et al., 2015)."

Jan 1, 2018

By Fuqiang Zheng, Shuai Wang, Feng Chen, Yufeng Guo, Guanzhou Qiu, Tao Jiang

"The direct reduced iron powder and Ti-V-rich material was prepared from vanadium titanomagnetite concentrate by solid-state reduction-magnetic separation. The result indicated that under the studied conditions, adding KS can effectively improve the metallization rate of pellets. 2% KS was well mixed with vanadium titanomagnetite concentrate to make the pellets. The green pellet was preheated at 900 ? for 6 min. The preheated pellet was reduced at 1050 ? for 100 min, then crushed and ground to more than 80% was below 0.045 mm. The direct reduced iron powder and Ti-V-rich material were separated from the slurry by wet magnetic separation at 800Gs. The TFe content of magnetic material was 90.63%, and the Fe recovery rate reached 96.53%. The TiO2 and V2O5 contents of Ti-V-rich material were 28.40 % and 1.64 %, respectively. The TiO2 and V2O5 recovery rates were 69.05% and 96.82%, respectively. 1. Introduction The ilmenite and rutile are the main titanium resources which can be used in the present technical level and economic conditions[1,2]. However, with the rapid development of China’s economy, the market demand of titanium products is increasing sharply. The current supply of ilmenite and rutile cannot meet the needs of chemical industry[3]. China is rich in vanadium titanomagnetite concentrate which contains abundant titanium and vanadium resources. The TiO2 and V2O5 content of vanadium titanomagnetite concentrate are usually about 7% and 0.3%, respectively[4]. Because the TiO2 and V2O5 grades are low, it generally requires pre-concentrated to Ti-V-rich material before extracting the titanium and vanadium. Therefore, it is vital to find effective processes for pre-concentrating the titanium and vanadium in vanadium titanomagnetite concentrate. There are many methods[5-13] developed or under development to pre-concentrate Ti-V-rich material from vanadium titanomagnetite concentrate, including the blast furnace process, pre-reduction electric furnace process, to utilized vanadium titanomagnetite concentrate are direct reduction-electric furnace smelting, sodium salt roasting-direct reduction-electric furnace smelting and direct reduction-magnetic separation and so on. The blast furnace process and other methods cannot effectively utilize the titanium and vanadium resource due to the technical or environmental problems[9]. In this study, the vanadium titanomagnetite concentrate was obtained from Panxi region of China, the reserves of which account for 11.6% of vanadium and 35.17% of titanium all over the world[3]. The preparation of direct reduced iron powder and Ti-V-rich material based on reduction-magnetic separation is proposed. The process utilizes a new catalyst for titanium ore reduction in rotary kiln followed by magnetic separation. Using this novel technology, the titanium-vanadium and iron are successfully separated. Compared to the traditional reduction of Ti-bearing ore, the reduction temperature reduced to 1050 ?, leading to higher efficiency, lower energy consumption and investment, and broader applications."

Jan 1, 2018

By Marko Hilden

"A stochastic model of mineral texture is discussed and used to demonstrate that grain association within the intact texture has a significant effect on the liberation characteristics of breakage products. The majority of previous models have simulated texture and liberation of binary systems. This new model is able to simulate complex multi-component (multi-mineral) aggregate textures and their breakage products. Grain size distributions can be defined for each of several minerals. Mineral-mineral associations can be controlled by inserting mineral grains within grains of another mineral. Repeated Monte Carlo sampling of the aggregate is used and the liberation properties of the fragments are calculated. These are analysed to generate data in a similar form as reported by mineral liberation analysis systems, including density distributions, liberation distributions, and particle class distributions. Simulations results are presented where the model has been fitted to complex sulphide ores with four minerals. Comparison of the simulated particles and experimental data show that the model is able to reproduce similar particle class distributions as measured by QEMSCAN. The texture of real complex ores can be simulated and fitted to conventional mineral liberation analysis data. The model should provide a useful and practical means of modelling the effects of mineral texture on separation processes and in geometallurgical models."

Jan 1, 2014

By Francisca San Martín, Martin Rudolph, Willy Kracht, Tomás Vargas

It has been shown that bacteria Acidithiobacillus ferrooxidans can be used to depress pyrite in seawater flotation at natural pH, which opens the possibility for its use as an alternative to lime to depress pyrite in copper sulfide flotation. In order to have a better understanding of the mechanisms involved in pyrite depression with A. ferrooxidans, an exploratory experimental campaign was carried out, including attachment density and contact angle measurements, and the effect of adding bacteria before or after collector. Biodepression of pyrite improves when increasing pH from 3 to 8, with a decrease in recovery from 92% to 36%. This increase in depressing capability is accompanied by an increase in attachment density, from 2.58×108 bacteria/g to 1.99×109 bacteria/g at pH 3 and 8, respectively, suggesting that the mechanism of depression is related to the attachment of bacteria to the pyrite surface. It was observed that the conditioning sequence with collector and bacteria influences the biodepression capacity of A. ferrooxidans. Having as a reference a value of pyrite recovery equal to 97%, when using only xanthate in seawater flotation at pH 8, the effect of both conditioning with bacteria-followed-by-xanthate and xanthate-followed-by-bacteria were assessed. When bacteria were added before the collector, the recovery of pyrite decreased to 36%. On the other hand, when bacteria were added after collector, the recovery was 64%, showing that biodepression of pyrite with Acidithiobacillus ferrooxidans is more efficient when the conditioning is carried out first with bacteria. The contact angle values show that there is little effect of the second component added to the system, i.e., if pyrite is first conditioned with bacteria, the contact angle does not change significantly once the xanthate is added (bacteria-followed-by-xanthate). The same was observed when the conditioning sequence was xanthate-followed-by-bacteria.

Jan 1, 2018

By Rolf Lauten, Yongjun Peng, Yufan Mu

"Biopolymers, produced from cellulosic biomass, have promising prospects of application as depressants in mineral processing. In this study, three different types of biopolymers (i.e., DP-1775, DP-1777 and DP-1778) were used to study the effect of polymer structure on flotation of un-activated pyrite, copper activated pyrite and chalcopyrite. It was found that the depressing effect of DP-1775 and DP-1778 was much stronger than that of DP-1777, and pyrite was depressed to a greater content than chalcopyrite with the same biopolymer at the same dosage. The biopolymer concentration played a vital role in determining the degree of depression. For each biopolymer, the higher the concentration, the greater the minerals were depressed. The mechanism underpinning the depressing effect of these biopolymers was explored in this paper. The concentration of biopolymers could determine the properties of the adsorption layer and the confirmation of biopolymer chains on mineral surfaces. The biopolymer molecules may aggregate when polymer concentration was over a critical value. Molecular weight and functional groups of biopolymers were the key factors characterizing the depressing capability of different biopolymers. Differences between the tested biopolymers and features of the adsorbed layer might account for the observed trends in ability to depress pyrite and chalcopyrite flotation. The greater depressing effect of biopolymers on pyrite over chalcopyrite might result from the preferential adsorption of biopolymers on pyrite over chalcopyrite."

Jan 1, 2014

Goethite ore are the third most abundant source of iron. The overwhelming part of these ore is represented by low-grade varieties which cannot be used in iron and steel industry without preliminary beneficiation. Biomass is a renewable solid fuel, which is feasible for the substitution of coke and coal in the manufacturing due to its lower contents of harmful elements and abundant raw material sources. Utilization of biomass in iron ore sintering process as heating agent and reducing agent contributes to energy conservation and emission reduction. The biomass was mixed together with goethite ore for roasting process to investigate the effects of reduction roasting. The results show that the goethite ore is dramatically reduced and magnetized into maghemite by biomass with the biomass dosage less than 20% and the roasting temperature below 650 oC. When the goethite ore roasted with biomass, the magnetization values could be enhanced more than two orders of magnitude, meets the standard of magnetic separation, which could significantly reduce the iron beneficiation cost. Keywords: biomass, goethite, reduction, magnetization, roasting

Sep 1, 2012

By T. Gong

Often plans to increase plant throughput provide an opportunity for optimising plant equipment and operating methods. This was the case in 2005 at TISCO Jianshan Iron Mine, when an increase in production was planned. The thickening circuit had presented a limitation to the plant throughput and operation with poor overflow clarity and underflow density. Following a course of test work by Outotec, a 53m diameter Supaflo® High Rate Thickener (HRT) was selected for the duty. From early stages of operation of the new thickener, the benefits have been dramatic, including: ? Improved tailings underflow density by 9% ? Improved Overflow clarity to less than 150ppm ? Considerably decreased the water and energy consumption as well as operation cost ? Stable and reliable operation This paper looks at this installation as a case study and compares the previous thickener installa-tion performance with the performance of the single 53m HRT.

Jan 1, 2014

By R. C. Miranda

Artificial vision systems are increasingly used to assist humans to perform different tasks in different areas. These systems are able to recognize patterns in complex images, which can provide multiple data. Currently, vision systems are used in both; monitoring traffic - which uses radars for vehicular plate recognition- as in metallurgical and food industries for strict quality inspections. Their use in mining occurs in measuring the speed of froth over the lip of a cell, in determining the shape and size of pellets, in obtaining from the tendency of mineral content and as a replacement for laboratory analysis of particle size. With this advanced tool, it is possible to achieve significant improvements in quality, productivity, and especially in reducing costs in pelletizing plant of iron ore. The objective of this paper is to contemplate the current situation of image analysis in the pelleting plants and glimpse at the potential applications that are being developed. This paper also presents the conception and implementation of an automatic control system of the pellets size distribution applied on a pelletizing plant of iron ore. The article demonstrates the strategy used for measuring the size distribution of the iron ore pellets, based on image analysis and the strategy implemented on advanced process control, which shows substantial gain on plant performance.

Sep 1, 2012

By M. Panayotova

Most of the quantity of the water soluble xanthates, used in mineral flotation, is consumed in the process. However, the residue amounts are water contaminants downstream the mineral processing operations and can be toxic to aquatic biota at concentrations of 1 mg/L. In order to be able to discharge water from tailing ponds to natural water bodies the concentration of xanthates has to be decreased. The present paper studies the uptake of potassium ethyl xanthate by directly modified with copper and lead ions natural zeolitic rock, without passing through zeolite transformation into homoionic form. Modified zeolite exhibits high, comparable with powdered activated carbon of chemical purity grade, capacity to remove potassium ethyl xanthate from model wastewater, with pH in the range of 7?9 and pollutant concentration in the range of 10-150 mg/L. The pollutant immobilization is fast. Both Cu and Pb modified zeolite behave as selective with respect to xanthate in the model wastewater, and Cu-modified zeolite possesses higher selectivity. The equilibrium is best described by the Freundlich equation. Keywords: xanthate, wastewater, modified zeolite

Sep 1, 2012

By A. Y. Senchenko, S. G. Rybkin, A. V. Aksenov

"Oxidized nickel ores are important source for nickel production in Russia. Considerable explored reserves of oxidized nickel ores with relatively low nickel content, about 0.6-1.4%, are concentrated in the Ural region of Russia. Conventional process flowsheet with the use of blast matte smelting, applied in particularly by JSC “Ufaleynickel”, proves itself as extremely low-margin technology. This paper will examine development of a new more cost-efficient process involving integrated treatment of oxidized nickel ores using the ore from Serovskoye deposit as an example. Target products of this process are hydrate residues containing up to 15 % of nickel and 0.3 % of cobalt, as well as saleable salts of magnesium sulphate and ammonium suplphate. This innovative process includes roasting of a mixture composed of ground ore and sulphuric acid at 650 °?. Sulphate roasted product is then leached in a weak sulphuric acid solution with the following separation of liquid from insoluble solids. Sulphate solution is neutralized by aqua ammonia in two stages until media pH is 3.0-3.5 and 7.5-8.0 with detachment of iron- and nickel-bearing hydrate residues respectively. The mother solution is boiled out resulting in salt crystals which are then dried and roasted at 500-600 °? to obtain magnesium sulphate. The gases generated during salts roasting are captured with production of ammonium sulphate. The developed technology demonstrates higher potential in terms of its economics and eco-efficiency comparing with the conventional process. This innovative technology for integrated process of oxidized nickel ores was patented in Russia.INTRODUCTION Development and industrial implementation of efficient technologies to process oxidized nickel ores is a very important task for non-ferrous metallurgy of Russia. The main reasons for the required technical upgrade of the plants processing oxidized nickel ores is depletion of rich ores, increase of energy resources costs, amplification of environmental and production standards. Due to this, transition from conventional pyrometallurgy to cost-effective hydrometallurgical technologies of ore liberation and solutions processing is logical and corresponds to the worldwide practice of Ni production from oxidized nickel ores."

Jan 1, 2018

By M. Saghaeian, R. Hejazi, H. Abedini, M. Zare

Water recovery in mineral processing plants is one of the most important subjects because water supply is a critical matter economically and environmentally, especially in desert areas. In this paper, the filtration behaviour of two iron ore tailing sample has been investigated using laboratory scale vacuum and pressure filtration units. These samples including tailing from Sirjan and Zarand concentrate production plants with the d80 of 94 and 41 micron, respectively. The results show that by using vacuum filtration the cake moisture content of Sirjan sample would be about 24%. But the filtration time is too long and vacuum belt filter cannot be used in industrial scale. Adding about 40 g/ton of flocculant would decrease the filtration time by about 30% and make the vacuum belt filter appropriate for dewatering of this sample. For Zarand tailing sample, the vacuum filtration would produce a wet cake by about 31% moisture content. Filtration time is too long and adding flocculant would not improve the results very much. So pressure filtration must be used for dewatering of this sample. The results of laboratory tests show that using pressure filter would reduce the cake moisture content to 21%. The filtration time is logical, so this process can be used for Zarand tailing dewatering.

Jan 1, 2014

By G. Venkateswara Rao

The jigging of ferrous ore to produce higher-grade products has been practiced for many decades. This is due to easy separation, a beneficial trade- off between operating cost and reduced yield relative to Dense Media Separation (DMS). Jigging becomes prominent for beneficiation of iron ores in the coarser size range. At present drive is towards the use of under bed air pulsed jigs for the beneficiation of ferrous ores. The main advantage is that the under bed air pulsed jigs are capable of generating the large pulse of amplitudes required to fluidize a deep bed of heavy ores particularly lump iron ore up to 40mm size. The major jig parameters effecting the jigging operation are bed height, shape of the pulse, residence time, operating pressure, valve cycle time and water flow rate. With the pulse shape set correctly for optimum stratification rate, even it is still necessary to provide enough residence time, to ensure the difficult material will take time to migrate to the expected layer in the bed. In order to find the Jig Stratification Index (JIS) parameters like bed height, operating pressure, water flow rate, cycle valve time and shape of the pulse were optimized first by conducting various tests. Typical Iron ore samples from Odisha (both lump and fines) were subjected to stratification studies at residence time of 1, 5 and 15 minutes. Jig Stratification Index (JSI) for both lump (0.30) and fines (0.20) were determined by using APIC Jig. The maximum possible JSI was calculated by using heavy liquid separation test (0.42 for lump and 0.24 for fines). It is found that the jig bed JSI is less than the Heavy liquid JSI for both lump and fines. The ratio of Jig bed JSI to the heavy liquid JSI is 0.83 for lump and 0.71 for fines. The JSI and ratio of Jig bed JSI to Heavy liquid JSI are low for fines due to fluid turbulences causing some degree of remixing in the jig bed. The fluid turbulences are more for fines than lump, hence jigging of fines is difficult and challenging. Keywords: sub grade iron ore, gravity separation, jigging, apic jig, stratification, residence time, jig stratification index

Sep 1, 2012

By Kang N. Zhong, Hui H. Luo, Yi H. Wei, Yu L. Wang

"More than 85% of phosphorous reserves in China occur as middle-low grade phosphate of sedimentary origin. The main gangues are dolomite, quartz, silicates, and clays. The characteristics of minerals are finely disseminated. Flotation results have shown that the floatability of apatite of this kind of ore is much worse than that of igneous and metasedimentary origin because of its high specific surface area. Although some effective depressants, such as naphthalene sulfonate and phenanthrene sulfonate, are used to decrease the MgO content in the P2O5 concentrate, its presence is still high (about 2%) in the Chinese concentrates. Meanwhile, the wastewater may cause some environmental problems. Batch flotation results and measurements of specific surface area and CO3 2- have revealed that there is a relationship between the floatability of apatite and the surface area.A two-stage flotation flowsheet, which includes a combination of direct and reverse flotation, was developed for beneficiating sedimentary phosphate ores. The direct flotation was conducted in an alkaline medium and most of the apatite and carbonate minerals floated leaving quartz and siliceous gangue in the sink. In the reverse flotation circuit, the floated product was further beneficiated in an acidic medium to eliminate the carbonate as a float product. Apart from the high quality of concentrate, the two-stage flotation also facilitated the treatment and the recycling of wastewater. A wastewater recycling procedure was developed and tested in a continuous flotation process. The key factor was the careful selection of effective and non-toxic reagents."

Jan 1, 2003

By J. Temuujin

Mongolia has some of the world?s largest coal reserves with an estimated total coal reserve of over 150 billion tonnes. At present, over 90% of Mongolian electricity is produced by combined heat and thermal power stations. The main coal deposits used for Central power system's power stations are Baganuur, Shivee-ovoo lignite type coal and Shariin gol bituminous coal. In Mongolia almost 600,000 tonnes of coal combustion by-products are disposed of in waste ponds. In this research, we have thoroughly characterized Mongolian coal combustion by-products including fly ashes sourced directly from thermal power stations and ash retrieved from ponds. It was determined that fly ashes generated from Baganuur and Shivee-ovoo coal deposits are class C, while ash from Shariin gol coal is class F (according the ASTM C618). All ash products were characterized by chemical, mineralogical, granulometrical, porosity, FE-SEM and radiation methods. Fly ashes sourced directly from power stations were found to be more suitable for manufacture of geopolymers for building materials application and zeolite synthesis than ashes retrieved from ash ponds. The adsorption and porous properties of zeolitic compounds were measured and found to be suitable for adsorption of Cr6+ from simulated tannery waste water. Keywords: coal, coal combustion by products, synthesis, geopolymers, zeolitic compound

Sep 1, 2012

By John Ralston, Jona Addai-Mensah, Patience Mpofu

The flocculation and dewatering behaviour of kaolinite (non swelling) and smectite (swelling) clay dispersions has been investigated using hydrolysable metal ions Mn(II) and Ca(II) and anionic polyacrylamide-acrylate copolymer (PAM) at pH 7.5 and 10.5. A pH-dependent, specific metal ion adsorption behaviour, accompanied by a marked reduction in particle zeta potential and slurry shear yield stress, was observed to have a profound influence on the colloid stability of both types of clays. Due to the differences in the cation exchange capacity, the smectite clay dispersion required a higher amount of metal ions than kaolinite dispersion to produce similar effects. The adsorption density of the anionic PAM at the negatively charged clay particle surfaces correlated well with metal ion hydrolysis and adsorption behaviour, all of which had a strong effect on slurry settling rate and extent of consolidation. At pH 7.5 where Mn(II) ions hydrolyse, metal ion and flocculant adsorption densities were both greater in the presence of Mn(II) than Ca(II) ions. At pH 10.5, however, where Ca(II) ions begins to hydrolyse, higher adsorption densities were observed for Ca(II) ions in comparison with Mn(II) ions, as the latter hydrolysed completely and precipitated. The metal ion mediated flocculant adsorption led to improved hydrogen bond driven particle bridging and facilitated charge neutralisation flocculation mechanisms which significantly enhanced the dewaterability of both clay dispersions.

Jan 1, 2003

By I. Silin, H. Wotruba, J. Huben, A. Ognyanova

"With increasing shortage of raw materials, the beneficiation of ultra-fine ores will play a larger role in the near future. Many established process technologies do not yield satisfactory separation results for ultra-fine materials. Without selectivity, high-grade concentrates cannot be produced. The material at hand is a taconite which had to be ground to d(90) = 25 µm to guarantee liberation of the iron oxides. The comminution was done by High Pressure Grinding Roll (HPGR) and resulted in smooth surfaces and clear grain boundaries. This is an indication of selective grinding and mineral liberation. Further processing steps included selective desliming, magnetic separation as well as reverse flotation. INTRODUCTION During the last centuries, the processing of iron ores became increasingly important. The coarse-grained, so-called lump ores that are ready for direct usage in blast furnaces without further processing are becoming gradually less abundant. The processing of ultra-fine-grained ores, which in addition require a complex ore beneficiation due to the composition of the material, will progressively gain relevance with increasing resource shortages in the future (Arvidson, 2013). The term “ultra-fine” does not hold a precise definition in mineral processing. In this paper, “ultra-fine-grained” ores are defined by the required grind size for full liberation smaller than 20 µm. Many established mineral processing technologies do not yield satisfactory separation results for ultra-fine materials. Thus, they are limited in their application to produce high-grade concentrates suitable for sintering and pelletizing for direct reduction processes. The production of a high-grade iron concentrate (over 68% Fe) with low silica content (under 2.5% SiO2) is possible from both magnetite and hematite containing ore. In addition to the mineral processing technologies (magnetic and gravity separation, flotation), technologies for the liberation of fine-grained iron ores need to be developed and improved. In contrast to the conventional wet grinding circuit by means of tumbling mills, several future trends in dry and wet grinding and regrinding are already in use. These include technologies such as vibration mills (Palla®Mill), stirred media mills (Vertimill®), vertical roller mills (Loesche) and high-pressure grinding rolls (HPGR) (Jankovic, 2015). This study preliminary investigated the mineral processing of a low-grade, ultra-fine-grained, complex iron ore in a laboratory scale after dry grinding by HPGR to 90% < 25 µm without consideration of the grinding, milling, energy and classification cost."

Jan 1, 2018

By L. Burdukova

"In flotation, depressants are used to reduce the amount of gangue that reports to the concentrate and hence increase the selectivity of the flotation process. At the University of Cape Town extensive batch flotation tests are carried out to evaluate industrial depressants and standard procedures have been developed over the years.This study was conducted in order to develop an improved method for comparing depressants using machine vision as an aid. The modified method of batch flotation involved a test with prolonged intervals between scraping to allow more time for the froth to build up and mature.This method of testing showed increased differences between the flotation performance obtained as represented by grade recovery curves for carboxymethyl cellulose and guar depressants when compared to the standard method of testing with shorter scraping intervals. The improvement was attributed to reduced entrainment resulting from longer drainage time in the froth and therefore yielded a better test for comparing depressants on the basis of true gangue flotation with minimized entrainment. As expected, the sulphide recoveries were unaffected by the change in method. The machine vision system also added to the information obtained during these tests by recording bubble size trends throughout the tests which were later analyzed and related to the amount of flotable gangue in the froth. Modifications are recommended to improve the usefulness of machine vision in batch flotation."

Jan 1, 2003