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By Harshad Bhagwat

The objective of this work is to investigate the inadequacies of current CFD based methodologies of model development for predicting combustion behavior of pulverized coal in furnaces. In the present paper, a steady state CFD model was used for in-depth analysis of pulverized coal combustion. The model accounts for turbulence, coal combustion, convective and radiative heat transfer and motion of coal particles. It also uses coal combustion models to account for important processes such as devolatilization, combustion of char and the evolution of fuel nitrogen during coal combustion. The model predicts fluid flow, heat transfer, progress of combustion and pollutant formation (NOx, etc.). The model uses several parameters, which need to be tuned with experimental data, which is not only limited in quantity but also insufficient in detail. Various existing methodologies like part calibration method for tuning of the parameters are discussed. In the present work, the parameters associated with coal combustion models were tuned and validated with published data obtained from an experimental furnace using one such part calibration methodology. The results clearly show that the model predictions differed with the experimental data not only quantitatively but also qualitatively. These discrepancies were attributed to part calibration methodology. A detailed parametric study was carried out to demonstrate the importance of parameters from various classes, namely, combustion kinetics, heat transfer, process and geometry parameters, and CFD model parameters. This investigation clearly indicates that parameters from different classes have significant effect on combustion behavior. The discrepancies in current methodology are discussed and a need for comprehensive methodology is highlighted. Keywords: pulverized coal combustion, computational fluid dynamics (CFD), pollutant formation (NOx), mathematical modeling

Sep 1, 2012

By M. Kinnunen

Handling of municipal solid waste (MSW) and control of its potential resources is becoming increasingly important in modern society. The OECD (Organization for Economic Co-operation and Development) average on municipal waste produced in 2003 was that of around 570 kg per inhabitant. In European Union countries around half amount is of MSW landfilled. In Finland still 88% of MSW was landfilled in 2004. Since incineration reduces MSW volume significantly while producing heat energy, it has become one of the most common waste handling techniques. The shortcoming of incineration is however, that incinerated MSW is often not pre-sorted and it produces slags and ashes as side streams from which recovery of metals is difficult. This paper looks into possibilities of scrap metal recovery for recycling from municipal solid waste incineration (MSWI) bottom ash. In order to do that, a flow sheet of physical separation methods was developed and tested with Finnish rotary furnace MSWI bottom ash. In addition, an empirical model for estimation of the recoveries of scrap metals with physical separation methods for treatment of MSWI bottom ash was developed. According to the results of this study, for 1 Mt of incinerated MSW with 30% mass reduction, a minimum resource potential of 100 kt for magnetic metal scrap of roughly 24 % grade and about 19 kt of non-magnetic metal scrap of roughly 65 % grade. In other words, 57 kg magnetic scrap and 12 kg non-magnetic scrap per inhabitant at the mentioned grades, respectively. Although wide variations of parameters affect the MSWI bottom ash quality, it can be said that a considerable amount of metals is drained into MSWI bottom ash. Results of this study show that from MSWI bottom ash significant material streams metal scrap can be reintroduced into the resource cycle which would otherwise be lost.

Jan 1, 2014

By E. Gock

Based on the scientific investigations on mechanochemical synthesis of metal sulphides from metals or metal compounds and sulphur or sulphur compounds, the article describes the industrial production of nanoscale metal sulphides. Special operational conditions such as inert atmosphere, size and type of the grinding balls, grinding time and specific energy input are taken into consideration. A system configuration for the manufacturing of sulphides at a capacity of 100 kg/h is presented.

Jan 1, 2014

By B. Y. Tuo

This article presents results of studies performed to determine the feasibility of using low-grade limonite ores from Yunnan deposit. Laboratory tests and commercial trials have shown that the magnetic separation can be performed with a high high-grade concentrates. The quality of the preparation concentration meets the requirements for blast-furnace smelting. The results as a whole demonstrate the feasibility of utilizing bank limonite ore. Yunnan limonite?s magnetic separation, roasting magnetic separation and flotation experimental study shows that grade of the ore grade can been from 32.91% heighten to 58.64%, a recovery of iron is 90.87%, productive rate is 51% through orthogonal test optimization; roasting magnetic separation can obtain that the grade of iron preparation concentrate is 61.16%, recovery is 67.39%, productive rate is 36%. As far as economy and enviormental protection is concerned, strong mag-netic suggested a more appropriate process. Keywords: Limonite; Roast; Magnetic separation

Jan 1, 2014

By R. Venugopal

Hydrocyclones have been used extensively for more than 100 years to classify mineral slurries for recirculation in grinding circuits. Sometimes hydrocyclone classification is carried out in more than one stage to improve the efficiency of classification. Factors affecting separation efficiency include fluid velocity, density, and viscosity as well as the mass, size, and density of the particles. The geometric configuration also affects its efficiency; it includes parameters like cyclone diameter, underflow and overflow diameter, position of vortex finder, height of the cyclone, feed inlet geometry, and diameter etc. Besides changes in the basic parameters some modifications in cyclone has also been introduced from time to time which have affected its efficiency, some of these are :-(i).Introduction of magnetic force along with the centrifugal and drag force to control the flow of the magnetic particles inside the chamber.(ii). Introduction of sparger, air is introduced in the chamber in the form of bubbles, to control the flow of fine particles and hydrophobic particles. (iii). Introduction of dilution technologies for the dilution of thickened underflow. (iv).Introduction of new model. In spite of wide use and simple geometry, the real working principle of hydrocyclone chamber is extremely complex because of the swirling turbulent flow inside the device. In order to get more knowledge about hydrocyclones and to increase its efficiency, past 10-15 years simulation techniques are being developed. The simulation models also enabled a deeper insight into the static and dynamic behavior of hydrocyclones. Therefore, more emphasis on simulations by methods like Computational Fluid Dynamics (CFD), Finite Element method (FEM) is given. Overall, a status review of the work carried out on the analysis of hydrocyclone performance, modeling approaches and its contribution in the efficiency of mineral processing operation is highlighted.

Sep 1, 2012

By N. I. Tyushkova

This is a brief survey of the technological solutions for deep cleaning of baddeleyite?s concen-trate. Baddeleyite is part of kamaphorite of composite apatite-magnetite ore in alkaline-ultrabasic mountain range of Kola Peninsula. Baddeleyite?s concentrate, which is being produced by Kovdorsky GOK (ore mining and processing enterprise) contains 97.5%~98.5% (Zr?2 + ?f?2) and also scandium oxide (0.05%). It is usually used without any chemical processing. World demand for zirconium oxide is constantly on the rise. Its consumption grows in ceramic industry and in high-tech spheres. That?s why the demand for its purity is very important nowadays (additional cleaning from phosphorus, silicon, iron, aluminium). The mechanism and kinetics of interaction of activated bad-deleyite with sulphuric acid has been studied as well. While applying method of mathematical mod-eling it was confirmed that the mechanical activation is effective for the intensification of sulphation process of baddeleyite?s concentrate with the aim of purifying it from dirt. The use of the calculated optimal regimes allows to reduce such technological operation factors as: temperature, the du-ration of process, the sulphuric acid consumption. It also allows to determine the conditions of anticipatory abstraction of scandium and main dirt in solution in comparison with zirconium oxide.

Jan 1, 2014

By David G. Hulbert, Daniël J. Oosthuizen, Bernard Muller, Daniël de V. van der Spuy

"Expert Online is a software system that makes use of novel artificial intelligence technology, known as the Interpreting Expert System (IES), to mimic an informed expert on a minerals processing plant. Previous implementations of the IES were only capable of explaining the controller actions. Expert Online will also take on the more difficult task of explaining the complex process behaviour to the operator in simple language.The primary functions of Expert Online are to serve as a training tool and an online assistant to operators. However, it is also expected to be of value to supervisors and plant managers.A number of additional features are envisaged, including different operating modes, fault detection, speech synthesis and advanced message filtering. Expert Online will increase the operator’s knowledge of the process and his/her understanding and acceptance of the complex control systems. Users would be supplied with relevant and timeous information required to make informed decisions to ensure smooth plant operation.This paper discusses the structural design of Expert Online for implementation on the latest version of MINTEK’s open control platform, PlantStar, as well as several advances and additions since the previous implementations of the Interpreting Expert System."

Jan 1, 2003

By Antony Amberg, Gonzalo Saldías, Romke Kuyvenhoven, Catherine Souza, Heriban Soto, Francisco Soto

"Vizcachitas is an advanced stage copper–molybdenum porphyry deposit, fully owned by Los Andes Copper and located in Central Chile. The property contains an indicated resource of 1,038 million tonnes grading 0.37% Cu and 0.012% Mo, and an inferred resource of 318 million tonnes grading 0.345% Cu and 0.013% Mo (Coffey & Alquimia, 2014). The deposit occurs in the same geological belt as several other giant copper-molybdenum porphyry deposits including Río Blanco-Los Bronces, Los Pelambres-Pachon and El Teniente. In 2018, the original Preliminary Economic Assessment (PEA) study from 2014 was updated; this paper presents the geometallurgical testwork that was performed to support that update. The testwork focused on the metallurgical characterization of 40 DDH samples and the development of a more profound orebody knowledge by relating geological features with metallurgical performance. The scope of work included complete chemical and mineralogical QemSCAN characterization; SAG, ball mill and abrasion testing; complete rougher and cleaner kinetics including locked-cycle-test; environmental ABA and settling tests on rougher tailings. The results show that the ore can be classified as medium-hard, with a hardness that is slightly below the average for large Cu/Mo deposits in the region. A good correlation was found between lithology and breakage characteristics, implying that the specific energy consumption (kWh/t) is well correlated to rock type. The results of the flotation tests were very encouraging and did not show significant variability. An overall Cu recovery of 91% can be expected for the flotation circuit. The use of a relatively coarse primary grind size gave good final recovery and grade for both Cu and Mo, and deserves further attention in future work, as this impacts positively both energy consumption and water recovery.INTRODUCTION Los Andes Copper Ltd. is a Canadian exploration and development company focused on the acquisition, exploration and development of advanced stage copper deposits in Latin America. The company owns 100% of the Vizcachitas project in Chile, the largest copper deposit in the Americas not controlled by the majors. Vizcachitas is a copper-molybdenum porphyry deposit, located 120 km north of Santiago, in an area of very good infrastructure."

Jan 1, 2018

By Z. F. Dai

The Thompson Nickel Belt, located in Northern Manitoba, Canada, contains more than 400 million tonnes of ultramafic low-grade nickel mineralization in 9 deposits. One of these, the Pipe deposit, was mined between 1971 and 1983 producing a Ni concentrate of 9% to 11% grade at 73% recovery. The operation was terminated because the poor recovery, low Ni grade and high MgO con-tent of the concentrate made processing this ore uneconomical at the metal prices prevailing at that time. Vale Inco is now re-evaluating these deposits with the intent of providing a new source of concentrate for its Thompson integrated processing facility. It is known that serpentine slimes coating on the sulphide surfaces are responsible for the poor metallurgy. Various desliming methods were tested including settling, elutriating, tabling and hydrocycloning. Hydrocycloning has proven to be the most effective means of desliming. With a feed assaying 0.70% Ni and 33% MgO, a rougher flotation concentrate assaying 22.7% Ni and 4.8% MgO was produced at a Ni recovery of 62.5% (relative to the feed to grinding), with no utilization of slimes dispersants. Another 16.6% Ni recovery was achieved in scavenger flotation resulting in a total Ni recovery of 79.1%. Batch flotation tests using various flowsheet configurations to optimize the grinding, desliming, reagentizing and flotation conditions are in progress.

Jan 1, 2014

By Y. Q. He

The dynamic behaviors of the air bubbles in the dense gas-solid fluidized bed have a significant effect on the performance of dry coal separation. The combined method of experimental measurement and numerical simulation were conducted to conduct the research of the mean diameters and rising velocities of the bubbles in the fluidized bed. The calculation models of mean diameter and rising velocity of the single bubble were proposed. The results indicate that the models of the mean diameter raised by Rowe (1976) and the rising velocity raised in this work could be used to predict the bubble dynamic parameters in gas-solid fluidized bed. With the Geldart B type of magnetite powder as the medium solids and while the gas velocity of 1.5Umf=U=2.2Umf, the mean bubble diameter along the bed height is 36mm<Db<45mm, and the mean rising velocity of the single bubble is distributed in 40~65cm/s. The results of experimental measurement, numerical simulation and model predication provide well agreements finally. Based on the uniform fluctuations of air bubbles diameters and their rising velocities, the separation experiments of 50~6mm dry coal using the mixture of 0.3~0.15mm magnetite powder and <1mm fine coal as medium solids were carried out. The results show that the probable error, E is 0.06, which indicates a good separation performance by using the gas-solid fluidized bed. Keywords: dense gas-solid fluidized bed, bubble dynamic behaviors, numerical simulation, separation performance

Sep 1, 2012

By Indrajit Paul, Atanu Pal, Kapil Modi, Sanjay Chandra, Chandra Sekhar, Srinivas Dwarapudi

"High alumina content in the Indian iron ore fines (2.5% Al2O3) resulted in poor quality pellets at the recently commissioned 6 MTPA pelletizing plant and a study was under taken to establish suitable pellet chemistry through proper fluxing agents. Limestone fluxed pellets were prepared at varying basicity (0 to 0.8) and pyroxenite fluxed pellets at varying MgO contents (0 to 3%) to study their effect on the metallurgical properties. Fired pellets were tested for their strength, RDI, reducibility and swelling. Microstructural studies, optical and SEM-EDS, were carried out to quantify different phases and their chemistry. Acid pellets exhibited poor quality whereas limestone pellets at 0.8 basicity and pyroxenite pellets at 1.5% MgO exhibited optimum metallurgical quality. Formation of widely distributed silicate melt in limestone pellets and high melting point slag & magnesioferrite in pyroxenite pellets found to improve their quality. However during commercial production of MgO bearing pyroxenite pellets, their room temperature and low temperature properties found to be inferior, but exhibited better high temperature properties, viz. softening-melting behavior. Contrary to this, commercially produced limestone pellets, comprising CaO, exhibited better strength and RDI but showed poor high temperature properties. To yield the benefits of both CaO (for good strength and RDI) and MgO (for low swelling and high softening), a dual flux combination was established by using both limestone and pyroxenite/olivine together that resulted in optimum metallurgical properties. Coke rate at the blast furnaces found to be reduced by 1kg for every1% increase of dual flux pellets in the burden.INTRODUCTION Iron ore agglomerate quality plays a vital role in decreasing the reducing agent consumption and increasing the productivity of blast furnace. In most of the integrated steel works, the burden mix for blast furnace is decided as per the availability of the iron ore agglomerates like sinter and pellets. More attention has been given in recent years to the use of fluxed pellets in blast furnace due to their good strength and improved reducibility, swelling and softening melting characteristics. Generally, quality of pellets is influenced by the nature of ore or concentrate, associated gangue, type and amount of fluxes added and their subsequent treatment to produce pellets. These factors in turn result in the variation of physicochemical properties of the coexisting phases and their distribution during pellet induration. Hence properties of the pellets are largely governed by the form and degree of bonding achieved between ore particles and the stability of these bonding phases during reduction of iron oxides (Panigraphy et al., 1990). It is important to note that conditions and parameters of pelletizing are specific to given ore or concentrate; the present study is undertaken for typical Indian hematite ore fines high in alumina. Except authors earlier work on quality of pellets from Indian iron ore (Dwarapudi et al., 2008, 2010), there is no considerable literature reported on the effect of pellet basicity and MgO content in the basicity range of 0 to 0.8 for Indian hematite ore."

Jan 1, 2018

By B. A. Kutlin, S. A. Ropeyko, N. A. Yurlova

"The aim of NPO RIVS research and practice activities is to minimize impact of the mineral processing plants (MPP) on environment by using new concentration methods, high-technology equipment, implementation of engineering solutions directed to reduce emission of polluting substances (PS) into atmosphere, application of low-waste technologies, decrease of water withdrawal from a surface water or groundwater source for process needs. In our studies environmental safety of mineral flotation is provided through technologies using highly selective chemicals, that leads not only to reducing reagent consumption, and production of saleable products of high content of extracted minerals, but also to reducing pollutant emissions, decreasing supply of surfactants (SAA) in natural geosystems, primarily, in ground and surface waters. Decrease of water withdrawal from a surface water or groundwater sources for process needs can be achieved by using closed circuits and waste water treatment for further use in process operations, recycled water conditioning to obtain optimum quality parameters for process operations of concentration. Concentration in water (wet processing), tailings dewatering and semidry and dry (filtration cake) stockpiling in tailing ponds, efficient dust-collecting systems contribute to pollutant emission reduction. Use of mineral wastes – concentration tailings as a source of valued components, facilitates efficient use of natural resources and reduces wastes and its impact on natural ecosystems due to smaller areas of damaged lands during waste products disposal. Process and engineering solutions of NPO RIVS that allow diminishing impact of MPP on natural environment (NE) have been implemented in mining and processing complexes of Russia, Kazakhstan, Ukraine, Kirghizia and Mongolia. Compliance with environmental safety requirements contributes to enhancement of mineral processing and sustainable mineral development.INTRODUCTION Mining and processing complexes have a significant impact on environment as a result of extraction and recovery of mineral resources, landscape changes, waste disposal and, as a consequence, pollution of soils, surface and underground water sources. Therefore, the aim of the operation of the mineral processing enterprises in its research and practical activities is to reduce impact on environment due to new beneficiation technologies, high-technology equipment, implementation of engineering solutions directed to reduce emissions of polluting substances (PS) into atmosphere, use of low-waste technologies, decrease of water withdrawal from a surface water or groundwater source for process needs. Compliance with the requirements of environmental safety encourages advancement of mineral processing technologies and sustainable mineral development. Concentration in water, tailings dewatering and semidry and dry (filtration cake) stockpiling in tailing ponds, efficient dust-collecting systems contribute to pollutant emission reduction. Use of mineral wastes – concentration tailings as a source of valued components, facilitates efficient use of natural resources and minimizes waste formation and its impact on natural ecosystems due to reduction of damaged land areas during waste disposal."

Jan 1, 2018

By Duong Huu Hoang, Nathalie Kupka, Urs A. Peuker, Martin Rudolph

"The froth ability, froth stability and the froth structure are strong influences in flotation process i.e. on water recovery, bubble size, entrainment of gangue particle, flotation rate constants, grade and recovery. The labscale flotation of rich apatite ore with a high mass pull leads to significant changes in pulp and froth properties over time. The froth stability decreases with increasing the flotation time. These changes can be related to different solid contents, reagent concentration, froth heights and bubble size distributions. This study presents the results from froth studies and discussions on the particle size of fully liberated silicates and degree of entrainment based on automated mineralogy size-by-size analysis. The change of entrainment in a rich apatite ore batch flotation with time will describe more precisely by measuring froth properties using a Dynamic Foam Analyzer. It is concluded that the degree of entrainment is not only dependent on particle size but also the pulp density due to its effect on particle settling and also froth properties in varying resistance to particle drainage. Furthermore, entrainment models are applied to predict the effect of size, flotation time on entrainmentINTRODUCTIONFroth flotation belongs to the group of heterocoagulation separation techniques. Froth flotation is classically divided into two active zones, the pulp zone (where particle collection occurs) and the froth zone. A schematics drawing of the interaction between both zones is plotted in Figure 18 (Yianatos and Contreras, 2010). In froth flotation, the collision probability in the collection zone is governed by the physics of the process or hydrodynamics (Wills and Finch, 2016). The true flotation event in the pulp occurs when the hydrophobic valuable mineral particles collide with bubbles and formation of a stable particle-bubble aggregates moving upwards against gravity to the froth phase (Yianatos et al., 2009)."

Jan 1, 2018

By Z. H. Wang

The internal parameters of ball mill are very important in the grinding process and have significant impact on the grinding results. Accurate measurement of the internal parameters of ball mill is crucial and indispensable for optimization and control of grinding process. In this paper, a novel tri-sensor measurement method was used to measure the external signals (i.e., bearing pressure, sound intensity and power consumption) of ball mill. Mathematical models, which link the external signals of ball mill with its internal parameters, were established to predict the internal parameters of ball mill. Experimental results showed that the mathematical models could directly predict the internal parameters of ball mill once the external signals were obtained. The tri-sensor measurement method and the mathematical models proposed in this paper provided a new way and solid basis for optimization and control of ball milling.

Jan 1, 2014

By T. X. Hu

Pyrite ore is one of the main raw materials in the production of sulfuric acid. For a long time, the raw material containing the pyrite, which is used to produce sulfuric acid, generally contains S only 32%~45%. A plenty of residue from the sulfuric acid production contains 40%~50% Fe and 1%~2% S. Some of the residue also contains Cu, Pb, Zn and other harmful elements like As, thus it pollutes environment seriously and is solid waste. The research on comprehensive utilization of the residue has been made by many scholars. Through the study, the residue can only be used to pro-duce iron concentrate and the iron oxide red pigment. But because of the complex techniques, the low recovery, the low grade of iron concentrate , high sulfur in iron concentrate, causing second waste residue and the environmental pollution, the residue is mainly used as an accessory material in the production of cement, and is of a low value. Therefore, the iron resource in pyrite has not been used efficiently until now. In the paper, the flotation condition test, the flotation open circuit test and the flotation closed circuit test to produce high-purity pyrite concentrate with the low-grade pyrite ore in oceanic ore deposit have been carried on. Flotation reagent scheme of sulfuric acid used as activator and butyl xanthate as collector is determined. After four times depth cleaning, high-purity pyrite concentrate containing 52.82% S, 44.29% Fe, and only 2.89% impurities has been obtained. The S recovery is 99.13%, and the Fe recovery is 96.00% in the high-purity pyrite concentrate. The oxidizing roasting depth desulfurization experiment of the high-purity pyrite concentrate has been conducted. The results show that the Fe grade in the residue obtained is 68.58%, the content of S is 0.25%, the content of P is 0.0084%, the content of As is 0.0065%. The residue is a kind of high-quality iron-smelting raw material. Based on the above experiments, the industrial experiments on producing high-purity pyrite concentrate with the low-grade pyrite ore, and producing sulfuric acid and iron concentrate with high-purity pyrite concentrate have been done. The results indicate that the high-purity pyrite concentrate with the S grade of 51.24%, the Fe grade of 44.15% has been obtained. The iron concentrate obtained with 65.73% Fe and 0.23% S is a sort of high-quality iron-smelting raw material applied to the production of steel and iron smelting. Through the experimental study, the sulfur and iron resources in the pyrite ore have been recovered and utilized efficiently.

Jan 1, 2014

By H. D. Yu

In this paper, an evaluation about the process mineralogy of the rich iron mine in Mongolia with comprehensive methods is given; this provides foundation of the comprehensive recovery of iron and cobalt in the ore. The research shows that the iron?s grade is 61.23%, Co?s grade is 0.02%, the ore is rich iron ore and its Co content also reaches border mining grade. For the ore, if want get high grade iron concentrate powder, must identify the mineral composition and the occurrence of iron and take into ac-count the recovery of Co content as associated resources. Chemical phase analysis results show that 86.35% of iron exists in magnetite, which means that the theoretical recovery ratio of iron is close to 86%. Minerals spectrum analysis confirmed that the magnetite containing a small amount of Mg, Al, and other impurities, the actual iron minerals to 70.28%, which means that theoretically iron grade iron concentrate only close to 70.28%. Based on the result of iron chemical phase analysis, by investigating the liberation of sulfide minerals and gangue, the recovery index of iron can be forecasted, when grinding fineness is 35%, 45%, 55% and 65% bellow 0.074mm,theoretical content of Fe in iron concentrate separately is 67.71%,67.88%,68.78%,and 69.43%,accordingly the theoretical recovery of Fe is 87.38%,87.05%,86.92% and 86.63%. From the perspective of process mineralogy, the forecast mineral beneficiation indicators show that the ore is easy sorting ore, iron processing operations have higher recovery rate, but wants sorting of high-grade iron ore concentrate still need appropriate grinding fineness. Furthermore, associated element Co, existing mostly in pyrite and pyrrhotite, is valuable in the ore. Pyrite and pyrrhotite have ideal liberation under grinding, so cobalt can be easily enriched in sulfide concentrate.

Jan 1, 2014

By ?. S. Potokin

"In general the electric pulse treatment is composed from two processes – electric pulse grinding and electric explosive (electric discharging) activation. The electric pulse grinding with the effect of selective destruction refers to a major slag fraction, more that 2-5 mm, when a one can see a physical prerequisites for electrical breakdown of the slag particles. The electric pulse treatment of slag is considered as an additional operation in the technological scheme extraction of non-ferrous metals from copper smelting slags in addition with mechanical grinding, flotation enrichment and acid leaching. Studies of the reprocessability of pelletized slag have shown the possibility of higher extracting non-ferrous metals via flotation after electric pulse disintegration (EPD) treatment. By using EPD of slag pellets, it is possible to increase the non-ferrous metal yield to concentrate by 18-24%.INTRODUCTION The use of the explosive effect of the plasma discharge channel at electrical breakdown of a solid at a pulsed high voltage is the physical basis of the electric pulse method of destruction of geomaterials (Vorobiev et al., 1971; Andres, 1995; Semkin et al., 1995). The flowing of a pulsed current in the discharge channel is accompanied by a sharp increasing of plasma’s temperature and pressure, leading to a supersonic expanding of the discharge channel, the formation in the solid of intensive mechanical tension field, spreading of cracks, and eventually, to the destruction of the solid. Fragmentation and grinding of ore and mineral aggregates by electric pulse method due to a number of specific physical mechanisms of power load and crack formation, belonging only to this method, is different by high selectivity of destruction. This ensures better liberation of grains of individual minerals and their better preservation from destruction and less formation of a slurry output. These features creates the prerequisites for a more complete extraction of a useful mineral in the concentrate during ore dressing, to improve the quality of concentrate. In contradistinction to mechanical methods, electric pulse technology does not contaminate the product with instrumental metal, material of lining and grinding bodies. The possibility simply and in a wide range to change the dynamic load character allows to regulate the granulometric composition of the product of grinding, to obtain a narrower class of product size than is possible with mechanical grinding. The product of electric pulse grinding is characterized by less roundness and large specific surface area of grains due to the trait, that a new surface is formed in the process of splitting during the expanding of cracks. The degradation product has increased sorption and reactivity in chemical reactions. Liberation of the mineral inclusions particle better corresponds to their initial natural state in the rock and this is the great importance for the study of mineral raw materials."

Jan 1, 2018

By M. J. Lottering

Gold deposits in South Africa are invariably associated with uranium bearing minerals. Although it is low grade uranium by international standards, averaging around 0.3 kg U3O8 per ton of ore, recovery of uranium as a by-product improves the overall economics of gold extraction. Moreover, the current high uranium prices as well as increased demand due to renewed interest in nuclear power provide significant incentives for dedicated uranium production. An understanding of the uranium leaching response to changes in operating conditions is an important first step to-wards optimisation of uranium recoveries. In South African acid leaching plants, uranium dissolutions higher than 90% are difficult to achieve, and the chemical origin of this limit is not clear. To study leaching behaviour, an important consideration is the mineralogical characteristics of the ores. Typically, a diagnostic leaching approach can be followed. In this paper, a mineralogy-leachability explanation is presented to rationalise the difficulty in exceeding 90% dissolution from low grade uranium ores on the basis of a simple diagnostic leaching method. It was found that brannerite was the main reason for the existence of a dissolution limit in Witwatersrand ore and that chemical liberation was more effective to increase end dissolution compared to physical liberation. The findings from these investigations will form guidelines for developing economically viable flow sheets for improved uranium recovery, at least in a South African (Witwatersrand) context.

Jan 1, 2014

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 X. Cui

Hydrocyclone is widely used in closed-circuit grinding process. However, in the first classification operation of coarse particles with high pulp density, the shortcomings of traditional cyclone are that the grinding cycle load is much high, the apex of cyclone is easily to be blocked and classification efficiency is less. Specifically, the problems of traditional cyclone used in grinding process are as follows: (1) Mill utilization factor is low and its handling capacity is small. (2) Coarse particles mixing in cyclone overflow affects the following separation process and fine particles mixing in underflow causes over-grinding, which affects the total recovery rate of valuable minerals. (3) High grinding cycle load leads to large amount of high-density slurry pumping, which causes high energy consumption and severe wear of cyclones, pipelines and pumps. The applications of new type pre-classification hydrocyclone with centrifugal volute in the first classification process of Iron Mine Mill are introduced in the paper. Pulp particles fed in the centrifugal volute were arranged in advance, so that coarse particles can be far away from the overflow pipe, which can reduce the short circuit current to avoid coarse particles entering overflow and improve classification efficiency and accuracy of cyclone. The strong points of the new cyclone in the coarse classification operation are as follows: (1) finer overflow and less fine particles mixing in underflow improves classification efficiency more than 10%; (2) lower ball mill load cycle improves ball capacity more than 10%;(3) grinding energy consumption reduces by more than 20% and cyclone feed pump reduces energy consumption by more than 12%. In short, new type pre-classification cyclone with centrifugal volute solves the problems of fine particles mixing in underflow, high grinding cycle load and less classification efficiency in the coarse classification operation. Therefore, it has broad application prospects in ferrous metal and non-ferrous metal ore dressing plant.

Sep 1, 2012