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By L. Bbosa

Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to investigate Power Draw in a laboratory scale tumbling mill. The mill is run dry in batch mode at different speeds using mono-size charge of glass beads, and is mounted along with a torque transducer to measure power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behavior, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz-Mindlin contact model. For PEPT and DEM data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all tests. Spatial distributions plotted from this approach highlight the regions of the mill that draw the greatest power. A second technique to obtain Power Draw from DEM data which sums particle forces against the mill geometry is similarly found to accurately predict mill power with lower statistical error. Keywords: Power Draw, PEPT, DEM

Sep 1, 2012

By Xiqing Wu, Tao Yue

"Magnetic seeding co-agglomeration, i.e. adding magnetic seeds, organic depressant (such as the starch), and pre-magnetization for co-agglomeration, was applied in the reverse flotation for hematite ore slimes. Samples of the hematite ore slimes and the pure hematite fines were investigated by the co-agglomeration, respectively. Flotation tests suggest that the depressing effect of starch in the flotation was further enhanced with the addition of magnetic seeds and the pre-magnetization. Following the laser size analysis and flotation tests, TOC adsorption analysis, VSM, surface charge measurement, AFM, FTIR study, and SEM imaging have been utilized to understand the depressing mechanism. Based on the results it was demonstrated that with the addition of magnetic seeds and the low field pre-magnetization, the adsorption of starch onto hematite minerals was strengthened through the magnetic seeding co-agglomeration. The co-agglomeration improved the flotation performance by introducing the magnetic interactions and acting the bridging adsorption of starch between fine hematite and magnetic seeds in a suspension, and then resulting in an intensified coverage of the starch onto hematite particles and positive action in the coagglomeration under the pre-magnetization.INTRODUCTIONFlotation is undoubtedly the most important and versatile mineral processing technique, and both its use and application are continually being expanded to treat greater tonnages and to cover new area. However, its influence was limited to a relatively narrow particle size range of 5–300 µm (Wills and Napier-Munn, 2006). The main reason behind this limitation lies in that fine particles have high specific surface area, so need relatively high dosage of reagents (collectors or depressants), and exhibit poor flotation performance while intermediate or properly-sized particles produce high flotation kinetics and need low consumption of reagents. In order to increase the recovery of fine particles, quite a few of flotation techniques have been investigated. Most of them are based on particle aggregation, namely, by enlarging the apparent particle size, such as carrier flotation (Valderrama and Rubio, 1998; Zhu et al., 2009), shear flocculation (Duzyola and Ozkan, 2010; Yin et al., 2011), selective polymer flocculation (Rubio et al., 2007; Song et al., 2012; Ng et al., 2015), oil agglomeration (Laskowski and Lopez- Vladivieso, 2004; Forbes, 2011), temperature responsive polymer flocculation flotation (Forbes et al, 2011), and etc. However, these techniques above-mentioned are mainly studied for the direct flotation of fine minerals, and most of these techniques have not found applications for iron ore slimes especially recovered by the reverse cationic or anionic flotation."

Jan 1, 2018

By M. Roy

Coke combustion during sintering process is significantly governed by coke breeze size distribution, which in turn affect sinter quality i.e. sinter granulometry, Tumbler index, Reduction Degradation Index and Reducibility Index of sinter. To know the effect of microfines of coke breeze on sintering process parameters, pot sintering tests were conducted and it was found that when microfines are eliminated and optimum coke size (1-3mm) is used yield of sinter increased by more than 7%. Similarly productivity increased by 9%, the strength of sinter i.e. ISO Tumbler Index increased by 2.3% and +10mm sinter size increased by 5.5%. Controlling of microfines during crushing and by improving crushing index will result in improved quality and productivity of sinter with lesser amount of coke breeze. This paper describes that how to optimize solid fuel i.e. coke breeze consumption in sintering process through granulometry control. Keywords: iron ore sintering, coke breeze granulometry, productivity of sinter, quality of sinter

Sep 1, 2012

By Kamalendu Bhunia

With the progressive depletion of known resources of good quality coal and minerals as well as the increasing demand of these minerals by different user industries, the emphasis has been shifted all over the world from selective mining to bulk mining followed by up- gradation to obtain the required quality of concentrate. The column flotation cell is one of the alternatives to reduce the gangue content of fines because of its inherent characteristics viz. easier to operate, low space required, no moving parts etc. A laboratory flotation column is used to conduct experiment. Present work has been undertaken to observe the effect of process variables (gas flow rate, feed/slurry flow rate, and frother concentration) on gas dispersion parameters (gas holdup, bubble surface area flux) in collection zone and to explore the effect of feed (slurry) inlet orientations and gas flow rate on column?s metallurgical performance. The effects of solid particle concentration, size and type (hydrophobic and hydrophilic) of solid on gas dispersion parameters have also been investigated. Test work has been performed in a continuously operating Perspex column (10 cm in diameter and 168 cm in height) using coal, sphalerite and dolomite as solid. Gas hold-up has been measured by phase separation method and mean bubble sizes are estimated from a drift flux analysis. The influence of operating parameters on bubble surface area flux has been discussed. It is observed that gas holdup in collection zone is affected by air as well as feed flow rates and also solid?s type. It is also found that addition of solid decreases the gas holdup and rate of decrease in gas holdup increases when solid concentration increases and particle size increases. Increase in gas flow rate increases recovery in collection zone due to increase in number of bubbles per unit volume of the column. From the experimental results it is evident that cross-current orientation of feed inlet shows slightly better metallurgical performance compared to other orientations. Keywords: column flotation, gas holdup, drifts flux, bubble size, bubble surface area flux, hydrophobicity, and recovery

Sep 1, 2012

By A. I. Urvanzev, N. V. Shikhov

"In this paper, we present the study’s results of electrical separation processes on the basis of new separator designs, new technological solutions, and newly discovered effects. We considered the options of enrichment by magnet separation of magnetite and titanomagnetite ores, ores and products containing chromium and manganese, ores of non-ferrous and precious metals. During pneumo-electric separation of mixed iron ore of SMPC, 43.3% of the output of the concentrate with an iron content of 61.7% was obtained in one step, with extraction of 70.5%. The paper also presents the results of the finalization on the air-electric separator of the magnetic fraction when separating oxidized ores of MPPOO (mining and processing plant of oxidized ores) on the Jans polygrade magnetic separator. A concentrate was obtained with an iron content of 65.1% with the extraction of 95.0% and tails with an iron content of 13.0%. The possibility of obtaining low-silica concentrates from these ores with an iron content of 67.15 and a quartz of 2.88% is shown. Also, the results of tests on the enrichment of chromite ores on the firing-magnetic scheme with corona-electrostatic separation are considered. On the initial ore of the Don MPP (mining and processing plant), a concentrate with a content of 61.8% Cr2O3 was obtained with a quartz content of ~ 1.0%. The results of pneumo-electric separation with triboelectric charge of the separated particles are presented. The results of the tests indicate a principal possibility of enriching chromite ores without costly high-temperature roasting. Dry technology of enrichment of manganese ores with the use of electrical separation increases the quality of the oxidized concentrate to the first grade and raises the total extraction by 2 times. For the Chineya deposit of titanomagnetite ores with copper impurities, electroseparation operations were carried out on two samples with a Cu content of 1.93 and 3.75%, respectively. For a sample with a Cu content of 6.02%, a copper concentrate output of 24.42% was obtained with a Cu content of 23.82% and the extraction of 94.88%. The results of enrichment by electroseparation of gold-containing sulfide ores can have the practical importance. For ores of the Berezovskoye deposit, a pyritic concentrate containing 100 g / t of gold was obtained after two or three operations of IES (integrated energy systems)."

Jan 1, 2018

By L. J. Li, Q. Zhang, Z. H. Liu, Q. L. Chen

Phosphogypsum (PG) is an industrial waste from the production of phosphate fertilizer. The utilization of PG is restricted by its containing impurities, and the pretreatment is crucial to eliminating these impurities. The purpose of the research is to recycle pretreatment PG as raw material for preparation of a-calcium sulfate hemihydrate (a-HH) by salt solution method. The effect of pretreatment technologies of lime neutralization and washing on dehydration rate, phase composition and morphology evolution of a-HH were investigated by crystal water content analysis, XRD and SEM. Furthermore, the change of pH in the reaction process was also discussed in detail. The results show that the dehydration rate of conversion PG to a-HH increases and the corresponding induction period, crystal growth period and total time decrease with an increase in CaO dosage from 0.2% to 0.6%. In the presence of 0.4% CaO or 0.6% CaO, the a-HH presents a long hexagon-prism-shaped crystal with a purity of 94%, and the end face of a-HH presents polyhedron. The system pH sharply decreases with the reaction time under different CaO dosage, and the pH variation from the initial alkalinity to acidity. The main reason is that as the co-crystallized phosphorus dissolved and released HPO42-, and with the pH decreasing to 4-5, HPO42- transformed into H2PO4-. The dehydration rate of washing PG is lower than that of original PG. Compared with the original PG, a-HH with the larger width and smaller aspect ratio can be achieved from the pretreatment PG subjected to lime neutralization and washing, meanwhile the crystal surface is more smooth.

Jan 1, 2018

By A. A. Rogozhin, E. G. Likhnikevich, S. I. Anufrieva, A. V. Kurkov

"Russia is among the nations holding the world's largest lithium ore reserves. Lithium is of key importance for the global economy. Therefore, it is important to review the current state of technology research aimed at finding the most effective solutions for the recovery of lithium from promising reserves in Russia. In Russia, a number of process solutions for the flotation of spodumene into salable concentrate (5% Li2O) have been implemented at the earlier existing complex low-grade ore concentration project. By applying these solutions, a sample of high-grade spodumene ore (4.7% Li2O) of the Greenbushes deposit was processed into a spodumene concentrate (7.5% Li2O) at a high recovery (~93%) of lithium. In Australia and Canada, new processes have been developed for the recovery of high-grade spodumene concentrates from high-grade ores using dense medium separation and flotation. For the recovery of mica lithium concentrates from low-grade ore, a flotation process was developed in Russia using the cationic collector ANP-2 and Oxifos-B as an additional collector. Low-grade ore containing 0.14% of lithium oxide was processed into a 2.7% Li2O concentrate. New hydrometallurgical lithium concentrate and ore processes are developed to avoid high-temperature (>1000 °C) roasting. The Sileach process (Australia) includes leaching of lithium ore with sulfuric acid in the presence of a halogen-containing component at a temperature of 95-115 °C. In the Russian process, lithium is recovered into an alkaline solution from low-grade spodumene ore in a pressure alkaline leaching environment (250 °C, NaOH concentration > 300 g/l). The developed concentration and hydrometallurgical methods will allow to design on their basis efficient processes for recovering salable products for hi-tech industries from lithium ores.INTRODUCTION Lithium has many unique and important properties. It is the least dense hard metal. Its alloys have some of the highest strength-to-weight ratios. Lithium has the lowest melting point of all known solid elements and is used as a highly-effective heat transfer medium. The high demand for lithium is due primarily to its unique electrochemical potential and low thermal expansion coefficient. It is used in the production of glass and ceramics, in petrochemicals, metals, medical and other industries. Since the late 20th century, the electronics industry has been the largest consumer of lithium. In recent years, lithium has attracted much attention also as an important component of ultra-lightweight electronic devices. It is also the preferred metal for electric batteries used in mobile electronic devices, vehicles, household power generators, making it an important resource for the development of environmentally friendly technology. Leading automotive brands have ambitious plans for the production of electric cars — Tesla Motors, VW, Toyota, GM, BYD Auto. It is expected that the production of electric vehicles alone will triple the demand for lithium by 2025. A sharp increase in the production of lithium is expected. Lithium has all the prerequisites to become a strategic resource of the 21st century. (Deutsche Bank, 2016; Bradley et al, 2017)"

Jan 1, 2018

By Bo Feng

The development of surface charge of serpentine mineral and implications for sulphide ?otation have been studied through flotation tests, sedimentation tests, zeta potential measurements and optical microscope photos. The results show that the serpentine mineral was positively charged at an extensive pH range, with an isoelectric point (IEP) of 11.9. The magnitude and sign of the pyrite particles were pH dependent and were negative for pH values above 2. At pH value 9, where ?otation of nickel sul?de ores is routinely performed, serpentine and pyrite particles attract through an electrostatic mechanism. Slime coatings of serpentine adhere to the surface of pyrite, reducing pyrite flotation recovery. The removal of magnesium ions from the serpentine surface by acid leaching results in a decrease of serpentine IEP and eliminates the adverse effect of serpentine on pyrite flotation. Therefore, it has been clearly established that the surface charge value developed in the serpentine/aqueous electrical interface is a function of the serpentine surface incongruently dissolution. As a result of hydroxyl dissolution, the magnesium ions are left in serpentine surface, which is responsible for serpentine surface charge. The methods, which can remove magnesium ions from serpentine surface, can be used to eliminate the adverse effect of serpentine on pyrite flotation.

Sep 1, 2012

By S. K. Kawatra, T. C. Eisele

"Coal-fired electrical power generation plants produce 56% of all the electricity in the U.S., burning approximately 860 million tons of coal annually. This results in the production of 58 million tons of fly-ash; 19 million tons of bottom ash and boiler slag, and 23 million tons of desulfurization sludge.s annually. These are a considerable disposal problem, and it would therefore be very valuable to be able to sell these residues and by-products as useful materials, rather than paying to dispose of them in landfills. However, utilization rates are currently very low, below 32% even for the most thoroughly commercialized combustion byproduct (fly-ash). This poor utilization rate is a result of the high impurity content of combustion byproducts, which makes them unsuitable for existing markets.Mineral processing techniques are useful for upgrading and utilizing combustion by-products. Fly-ash can be processed to remove unburned carbon, or utilized as a binder component in ore pelletization and agglomeration processes; bottom ash can be processed to produce certain aggregate grades; CO2 emissions can be sequestered using modified leaching techniques; and many scrubber sludge’s require processing before they can be used for producing gypsum products.The experiments described in this paper were carried out to study the application of mineral processing techniques to upgrading combustion by-products, particularly flue-gas scrubber sludge. A process was developed for upgrading unoxidized Flue-Gas Desulfurization (FGD) sludge’s by removing the primary impurity (unreacted limestone). A combination of hydrocycloning followed by froth flotation reduced the limestone concentration to as little as 1.7%, while recovering 66% of the sludge weight as a clean product. The recovered limestone was sufficiently concentrated that it could be recycled to the scrubber for more complete utilization."

Jan 1, 2003

By Ata Akcil, Z. B. Karshigina, Ye. G. Bochevskaya, E. A. Sargelova, Z. S. Abisheva

Phosphorus slag is one of the most large-tonnage of yellow phosphorus production waste, which for decades stored in the slag disposal, by polluting the environment and creating environmental problems in the regions. Phosphorus slags from the processing of Karatau phosphorites are a very promising source of raw materials not only for silicon compounds but also rare earth metals (REM). Among the REM, yttrium, neodymium, europium and lutetium predominate, which are relevant to high-tech industries. The report presents technological scheme of complex processing of slags of phosphoric production with obtaining of REM concentrate and precipitated silicon dioxide ("white soot"). The regime parameters of the main operations of the technology are determined: I stage- leaching of slag with nitric acid solution; extraction of the REM-containing solution with tributyl phosphate and stripping of the REM with water; settling of solution of salts of oxalic acid, calcining the precipitate to obtain a concentrate S REM oxides and II stage of leaching silicon cake to obtain "white soot". Recovery of S REM from slags of phosphoric production on various redistribution has made, %: leaching – 95.0; extraction - 90.2; extraction on the average ~ 93.2; the production of a concentrate of REM oxide is 93.9. A concentrate containing 17.3 % of REM oxides was obtained. According to X-ray analysis it contains the following phases: calcium oxide, portlandite2, gadolinium oxide and yttrium, gadolinium oxide, gadolinium oxide and cerium, neodymium oxide, neodymium oxide and cerium. Thus, the concentrate can serve as a raw material for the production of individual rare-earth metals like gadolinium, cerium, yttrium and neodymium. After performing the II stage of leaching siliceous cake with nitric acid the samples of "white soot" were obtained. Its chemical composition corresponds to the state standard and has a specific surface area equal to 180 - 200 m2/g. The technology has been tested in a large-scale laboratory scale and will solve the problem of complex processing of phosphorus raw materials and import substitution in Kazakhstan. The end-to-end recovery of S REM oxides and silicon into concentrate and product from their initial content in slags is ~ 75.0 and 98.0 %, respectively.

Jan 1, 2018

By D. Moradkhani

The objective of this research was, to evaluate the hazard of heavy metals in the soil around the National Iranian Lead & Zinc (NILZ) Company. In this study, 38 samples of soil around the NILZ factory were collected using standard sampling method, so that, the heavy metals Pb, Zn, Cd and Cr have been evaluated. The concentration of heavy metals were measured and compared with standard limits. The results show that the hazard of heavy metals in soil is not so serious and the content of Pb in just 5 percent of samples, and the content of Zn in just 3 percent of samples were above standard limits and the concentration of Cd and Cr were under the standard limits. Average, variance and standard deviation of the elements are calculated and with due attention to the standard deviation, Pb and Zn are seen to be more distributed than Cd and Cr. Also the isograde curve of heavy metals was drawn using software called Surfer. These curves showed that the heavy metals are concentrated at particular distances from the factory. Keywords: heavy metals, remote sensing, sampling method, isograde curve, Surfer software

Sep 1, 2012

By John Starkey

"The development of the Minnovex SAG Power Index (SPI) Test in Canada has created a new and accurate way to measure ore hardness in a SAG environment. Coupled with the standard Bond Ball Mill Work Index Test it is now possible to determine from these two relatively inexpensive laboratory tests, the amount of energy required to grind an ore from the primary crushed size to the desired liberation size. By testing multiple samples to discover where the hard and soft ore zones are located, the representative hardness distribution for the ore body can be determined and grinding equipment selected that is capable to meet production targets for all mining areas of the deposit.In the last century, it was deemed prudent to select up to 50-tonne samples of ore for Semi Autogenous Grinding (SAG) pilot plant tests and a second 5-tonne sample for metallurgical pilot plant work. The methods outlined in this paper show how the 50-tonne sample is no longer required for SAG design because it is better to measure the representative hardness distribution of the ore body than the hardness of a “chosen” representative sample. This is demonstrated to be true by the fact that the lower horizons of an ore zone cannot initially be accessed to recover 150mm pieces, and the bulk samples taken, rarely represent the desired design hardness of the ore. Median hardness will not yield a good result in most cases and a clear understanding of the location and extent of the hardest zones is imperative to achieve a truly successful grinding circuit design.This paper discusses two plants (Kubaka and Agnico Eagle) that have been designed using SPI and Bond with no pilot plant test backup. Both have been very successful in that they can grind design tonnage on the hardest ores in the mine. This guarantees that the mine’s profitability is protected in any mining sequence. It also allows the extra power to be converted to higher throughput on softer ores if additional cash flow is needed. The advantages from the owner’s point of view are dramatic. This procedure will be attractive as well when considering the costs for test work, and the samples for testing. Existing diamond drill core is normally used and this allows the inclusion of data from the deepest regions of the mine. In addition, it is also clear that the decision to use a crusher can now be made at the design stage of a project based on measured parameters and the estimated capital costs of alternative designs."

Jan 1, 2003

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 Mojtaba Ghorbannezhad, Abbas Sam, Soroush Arabzadeh

One of the dewatering methods in mineral processing plant is filtration system. Disk filters are included the porous surface with pressure drop on both sides, Water in the pulp passes through the surface and solid particles remain as a cake on it. Wet concentrate production of magnetite processing plant at Golgohar Mining and Industrial Company with solid tonnage of 160 ton per hour and 49% solid amount contains 166 m3/h of water. In the present study, in addition to studying disc filter performance, the effective parameters on cake moisture were studied using Vacuum Bottom-Feed Leaf method (in the laboratory scale). Optimization was performed using the Taguchi method. The results showed that the cake moisture is reduced by increasing particle size and solid percentage (because of specific resistivity reduction), while the rate of cake formation and its thickness are increased. Also, it was found that by increasing pressure, the cake moisture is reduced and cake formation rate and its thickness are increased. In this study, the effect of fabric texture was also examined. Lowest cake moisture was obtained in condition of using compressed plain fabric with mono-multi filament fibres, pressure at 75kPa, solid percentage of 65 to 70, particle size (D80) equivalent to 123µm and disk rotation speed of 1.25 rpm.

Jan 1, 2014

By D. Saramak

The comminution technology based on High-Pressure Grinding Rolls presses (HPGR) application is currently one of the most efficient methods of hard ore comminution from the scope of the energy consumption and the development of industrial HPGR applications in ore preparation circuits is presently the world trend. However, even though the technology is already in use in many countries, which are the leaders in application of modern mining technology, there is still lack of base investigations over the HPGR performance. Throughput and energetic models of HPGR performance are quite well developed, but technological models predicting the comminution effects still needs an in-depth research. In the paper authors present the method of modeling of HPGR products? particle size distribution with using of suitable mathematical models. A basis of the HPGR performance assessment and HPGR-based crushing circuits design is a product?s particle size distribution. In order to precisely determine the particle size distribution of a HPGR product, parameters of product?s particle size distributions should be conditional on the main technical parameters of the roller press like operating pressure and the speed of rolls. The most accurate approximation of a distribution of size particle d appeared the Weibull?s truncated distribution and it is possible to obtain significant relationships between the approximation formula and the value of operating pressure, or feed characteristics. It makes possible a determination of mass recoveries of the product?s respective size fractions and the productivity planning. Instead of pressure (P), the other HPGR operating parameters can be applied, but the P value appears to produce the most relevant relationship. Keywords: HPGR, comminution, particle size distribution, ore processing

Sep 1, 2012

This article takes the OMRON C200HE PLC for example introducing its application in mica-paper production equipment, including style selection, address assignment of I/O point, and programming for different function. In the transformation process of simulated data and digit data, the corresponding relations between two data and so on are also discussed.

Jan 1, 2014

By S. Z. Shafaei

An experimental investigation has been carried out using a laboratory scale Denver flotation cell. For evaluation of cokeable coal of Alborze Sharghi coal washing plant, the full factorial method was used to statistically design and analyse the experiments. The 2 factorial interaction model were developed for combustible recovery and ash content as response and diesel dosage, conditioning time, feed percent solids and rotor speed as factors. Model validation and residual analysis were con-ducted and results indicated that the fitness, predictability power and residual distributions of models were good. The effect of parameters and interactions were examined and it has been demonstrated that rotor speed, solid percent and interaction between diesel dosage and solid percent were more important terms of all responses. A product with approximately 78% combustible recovery and 10% ash content was obtained at 4000gr/ton diesel fuel oil (high level), 30 sec conditioning time (low level), feed percent solids of 15% (low level) and 800 rpm rotor speed in appropriate condition.

Jan 1, 2014

By Xin Tan

In this paper, two types of low-grade complex zinc oxide ores (sandstone and limestone ores) from Yunnan province, China were investigated. A large number of argillaceous and alkaline gangue makes it infeasible to treat the ores with heap leaching. Although wet metallurgy can be considered, the lower efficiency of liquid-solid separation, the high cost, and low revenue limit this technology to be put into practice in large-scale. In order to solve this problem, a new technology combining mineral processing method with metallurgy technique is studied to process this refractory ore that consists of sandstone ore with 5.84 per centZn and limestone ore with 6.50 per centZn. The results of the tests showed that zinc can effectively be recovered from two types of the ores by using the new technology, and the acid consumption can be remarkably reduced. For sandstone sample, 82.96 per cent Zn was recovered by flotation and final Zn recovery by flotation+ hydro-metallurgy can be up to 78.17 per cent from the ore. In addition, for sandstone, acid consumption can be reduced from 270kg/t by direct acid, leaching to 76.92kg/t by flotation + hydrometallurgy combination. For limestone sample, 85.90 per centZn was recovered by flotation and totally 80.95 per cent Zn can be recovered by new technology which is a combination of mineral processing and metallurgy. Besides, H2SO4 consumption can be reduced from 450kg/t for sandstone originally to113.79kg/t after using new technology. One merit of this new process technology is that the zinc sulfides and oxides can be recovered without desliming in the flotation cells at the different stage and make sure the concentrate products as a good feed for hydrometallurgical technology. This study provided pretty good technical support for tapping low-grade refractory zinc oxide ores. Keywords: low-grade zinc oxide ores, limonite, non-desliming beneficiation, flotation + hydrometallurgy combination

Sep 1, 2012

By S. Q. Zhu

Coal Water Mixtures (CWMs) are densed suspensions of coal particles in water. Viscosity is one of the most important rheological properties of CWMs and it is desired to be as low as possible. The slurry viscosity was influenced significantly by additive formation, the particle size distribution and the ash content of the coal. However, the influence of dispersants is most obvious. At present, there are several kinds of dispersants such as polymeric styrene sulfuric sodium, lignin sulfonate, humate, polycarboxy salt, ethylene epoxide surfactant. In this paper, a newly synthesized CWM dispersant has been reported, which is an efficient anionic surfactants of polycarboxylic acid type. The synthesis process includes three steps. At the beginning, the polyglycol acetate ester has been performed by acetic acid and polyethylene glycol (PEO) on the condition of acetic-acid/PEO ratio 1:1.1, at 368~373K for 30 minutes. Then the macro-monomer is prepared through the esterification of 85.71% acrylic and 14.29% polyglycol acetate ester, at 368~373K for 10 minutes. After that, the polycarboxylic acid CWM dispersant is polymerized using proper proportion macro-monomer, acrylic (AA) and sulfonic styrol sodium, at 368~373K for 1 hour. This new dispersants are used in the coal water mixtures formulation. Four kinds of coal used in the experiment are Shuang Yashan, Tunliu, Luning, Changcun samples. ? The highest concentration for shuanyashan coal is 70% when the dosage of dispersant is 0.4%, and the content of -200 meshes particles is 75.53%. As the dosage of dispersant de-creases to 0.25%, the Shangyashan CWM concentration is 67%. ? For Tunliu coal CWM concentrations are in the range of 76% to 75% when dosage of the dispersant changes from 0.4% to 0.25% at the same particle size distribution of 83.5% minus 200 meshes. ? The highest concentration for Luning coal is 69% when dosage of the dispersant is 0.4%, and the content of -200 meshes particles is 88.86%. ? For Changcun sample, the coal concentration of CWM is 73%~75% when dosage range of the dispersant is 0.35%~0.5%. The experiments show that the synthesied dispersant is quite promising for some coals CWM preparation, but a little bit coal-dependent. The Proximate and Ultimate analysis, surface characteristic measurement have been made to investigate the interactions between coal and additives.

Jan 1, 2014

By G. X. Du

Improving reaction effectiveness of asbestos tailings and acid is main means to increase the productivity of magnesium hydroxide and amorphous silica and to reduce production costs. In this paper, the process optimization of acid-leaching reaction process of asbestos tailings is reported. Through the orthogonal experiments of four influence factors, such as acid consumption, reaction temperature, reaction time and initial acid concentration in the leaching reaction. The experiment results indicated that the optimal process parameters were as follows: reaction temperature was 95?, reaction time was 1.5h, acid consumption was 218.9g hydrochloric acid(37%) per 100g asbestos tailings and initial acid concentration was about 25%. The influence significance sequence of the four factors was as follows: reaction temperature > reaction time > mass concentration of hydrochloric acid > hydrochloric acid consumption. Under the optimum process conditions, the leaching rate of MgO was 97.3%, total iron 98.15% and Al2O3 57.9%.

Jan 1, 2014