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By M. T. Spyridopolous, S. J. Neethling

"There has been a significant research interest in the stability of single thin films, including prediction of their failure based on disjoining pressure and film thickness experiments and DLVO theory. It is, however, notoriously difficult to correlate information on the failure of a single thin film with measurements of foam stability. This is particularly true for the prediction of dynamic foam stability indicators, such as equilibrium froth height and surface bubble size.An alternative experimental approach to studying single thin film failure for predicting foam stability is to measure directly the coalescence probability between two approaching bubbles in a surfactant solution. These experiments can be performed under different chemical and physical conditions by using a micromanipulator that allows variation of bubble size, surfactant concentration, approach velocity and stationary position. The interface radius of curvature, the time to coalescence and the film area between the bubbles can be measured directly using image analysis.In a foam, the force exerted on the thin film separating two bubbles depends on the local radius of curvature of the Plateau borders and vertices, which depends in turn on the local liquid content. Results from different bubble sizes in the micromanipulator therefore translate into regions of different liquid content in the foam. Small bubbles, having a high radius of curvature correspond to the low-liquid content (Polyhederschaum) region higher in the foam, and large bubbles to the wetter (Kugelschaum) region closer to the liquid-foam interface. Experiments with different holding distances between the bubbles correspond to differences in bubble size in the foam, as the size of the film between the bubbles varies."

Jan 1, 2003

By Kal Sastry, Anshuman Prasad

"Agglomeration of fine iron ore concentrates is carried out in two steps:Balling, which refers to the production of green pellets by tumbling moist fines powders in drums, discs, or cones, and Induration, which refers to the subsequent thermal treatment of the green pellets in straight grate or grate-kiln systems.This paper addresses computer simulation of balling or green pelletization step. The process of agglomeration from a mechanistic point of view can be described as the transformation of moist feed to well-formed species or pellets. The moist feed is composed of fines of infinitesimal size while well-formed species are of finite size and number. These well-formed species undergo changes in their size and number through different mechanisms of agglomerate formation and growth. Nucleation, coalescence and layering are the three main mechanisms that describe the formation and growth of granules during an agglomeration process. A population balance equation enables quantitative description of the evolution of agglomerate size distribution due to the occurrence of each of the mechanisms.A numerical solution for the population balance model is necessary and is obtained by the use of a sizediscretization approach. The numerical solutions provide a suitable basis for the analysis of the agglomeration process. Also a coalescence kernel has been introduced that is capable of describing the simultaneous occurrence of nucleation, coalescence and layering mechanisms. The effect of feed moisture has been described using a moisture factor with an exponential functional dependence on the moisture content. The effect of the feed to seed ratio is modelled by the introduction of a crowding factor. It was assumed that only the feed particles which are much more in number experience a crowding or restricted in space interactions effect. A computer simulation program has been developed with MATLAB as the simulation language."

Jan 1, 2003

By S. J. Neethling

"Flotation is a complex process with many factors that influence the performance of a cell. This paper examines the impact of several key variables on the performance of flotation cells. The study makes use of a simulator for the froth phase of the flotation vessel, as the main purpose of this study is to separate the impact of different variables from one another.In experiments it is very difficult to separate the effect of variables from one another as a change in a singe input parameter, such as air rate, invariably also affects many of the other key variables, such as bubble size and bubble bursting rates. This interaction between variables makes it very hard to experimentally separate the impact of, for instance, the air rate from that of bubble size or bursting rate. In the simulator, though, it easy to make independent changes to these variables.In order to achieve this a base case simulation that is typical of many of the rougher cells found in sulphide flotation circuits was carried out. Four key variables, air rate, incoming bubble size, surface bubble size and the fraction of the bubbles flowing out of the cell unburst, were varied in order to obtain the system’s response.The most significant results were obtained when the bubble size was varied. An increase in the incoming bubble size has the effect of reducing the pulp zone recovery, but increases the froth zone recovery. If it were possible to vary the incoming bubble size without influencing the overflowing bubble size, the impact of the change would be unclear because of these two competing effects. The effect of a change in the overflowing bubble size has an opposite effect on the froth recovery, with larger bubbles resulting in lower froth recoveries."

Jan 1, 2003

By Briony C. Ruse, David V. Boger, Fiona Sofra1

"The sustainability of the mining industry must be addressed through improving tailings management. The use of thickened tailings and pastes stems from a paradigm shift towards designing tailings disposal sites to suit their surrounding environment, rather than manipulating the environment to accommodate the tailings. Thickened tailings and pastes usually exhibit non-Newtonian behaviour, so a thorough understanding of the rheological characteristics of the material is required in order to determine the disposal plant operating conditions.As environmental factors translate into economic issues, minimising waste production using dry disposal methods is gaining popularity. The use of rheological information is of high importance in evaluating the spreading characteristics, the transportation and the dewatering of thickened mineral tailings. The principles outlined may be applied to many industries encompassing a wide range of waste materials. The main obstacle to the widespread implementation of dry disposal methods has been the high initial capital cost of the methods due to the dewatering step, and the high cost of pumping thick suspensions across any great distance. Proper and thorough costing of tailings disposal activities combined with an accounting approach that shows closure and post-closure care costs on a per tonne basis of tailings disposed throughout the life of the tailings facility will show that dry disposal methods are more favourable than they might seem on initial appraisal."

Jan 1, 2003

By Genrich A. Denisov

Principles of ecologically friendly geo-technologies construction are formulated on the basis of the works of the leading scientists in the field of rational processing of mineral resources of the Russian Academy of Sciences. One of these concepts is a new direction in rotational disintegration of mineral and technogenic raw material with the purpose of effective subsequent enrichment. A large amount of practical experience has been accumulated in the industry on selective destruction by application of vibrational method on initial material with consideration of its physical-mechanical properties and mineral structure. This method is successfully realised in a conic inertial pulverisation devices constructed by Mekhanobr Institute (St.-Petersburg). A new construction of conical-inertial pulverisation with a modification of disintegration force has been developed recently at Mekhanobr Institute. It allows, in some cases, to increase selectivity of subdivision and to avoid over-disintegration. Advantages of “wet” subdivision methods in conic inertial disintegration devices are proved. The efficiency of such subdivision can be increased due to rational use of the phenomenon of a dislocation-dynamic diffusion. Its advantage is proved by the effect on disintegrated material by frequency-modulated variable electrical fields of low power. It was shown in industrial conditions, that the productivity of the spherical mill can be increased by 10 %, and that it also prevents ecologically harmful surface active substances (SAS) in milling zone and it reduces the dust content in the air. The techniques of tentative estimation of efficiency of various proceedings technogenic materials and their classification are created. The scientific fundaments of rational, ecologically friendly technology of processing and regeneration of various kinds of technogenic raw material are developed. A number of effective technologies on processing of wastes is developed and inculcated in concentration factories and metallurgical factories.

Jan 1, 2003

By Jian Zhang, Yongfu Yu, Fuguang Zhang, Liping Che

There is one large-scaled iron ore deposit in Inner Mongolia of China, but it is very complex which includes about 170 types of minerals and 71 elements. The hematite, magnetite are mainly iron ores. It is difficult that the iron mineral can be separated efficiently by common dressing methods due to the complexity, and the iron concentrates in the mineral processing factory contains many foreign substance such as K, Na and Si so that the process in iron mill is influenced because of the foreign substance, so it is vital reducing the foreign substance.

Jan 1, 2003

By Chen Shuwen, Yao Zhihua

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

Jan 1, 2003

By Ronald Smeink, Ton de Gouw

"Reagents are an important cost-factor in the flotation of minerals. The mechanism of collectors and frothers has been studied extensively, but on depressants – probably the biggest cost-factor in the reagent suite – very little is actually known. Theories are frequently faced with the bare facts, pointing in another direction. Fundamental research is complicated by the fact that the amount of possible interactions in the flotation cell is almost unlimited and makes “change-one-parameter-at-a-time” experiments questionable and at least difficult to interpret. Also, the adsorption of depressants on the ore is very strong and desorption merely impossible. Detection methods therefore tend to be indirect and – therefore - non-specific about the location of the depressant on the ore.Depressants are supposed to adsorb selectively on gangue minerals; not on the valuable minerals in the froth. In order to be able to develop better and ‘’smarter’’ depressants, an analytical method is therefore required that will enable to detect which (=qualitatively) depressant, in which concentration (=quantitatively) sits where exactly (= selectively) on the mineral surface. (Answering the question: ‘’ Which minerals is located direct under the depressant?’’)And also: does the depressant compete with other reagents for that location? (like collectors) This analytical method is under development. The actual status of the method is promising and the results will be shown."

Jan 1, 2003

By John Ralston, Jonas 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 Yongfu Yu, Xiaotie Wang, Fuguang Zhang, Liping Che

"Rare Earth water dregs is the drained waste dregs, which contains over 0.2 percent thorium dioxide and about 6-10 percent di-Rare Earth trioxide, which is beyond the standard of draining off that China governments set, so that the Rare Earth water leach dregs must be sacked and laid down in storehouse, which costs lots of money. It is a pity that the RE and thorium compounds very useful elements in industry are discarded. A lot of work must be carried out so that this resource was fully developed.In this paper, four separation techniques of recovery Rare Earth minerals and enrichment thorium element and reduction thorium content of drained dreg for the different test samples of Rare Earth water leach dregs which is radioactive waste dregs got from diverse locus are studied, respectively, and the separation characteristic and the separation process are described, using several combination processes of classification and gravity and flotation separation which were prepared according to the characteristic of test samples and technology. The test results show that the combination processes are the more remarkable separation techniques and the flotation reagents used in test can be applied to utilizing synthetically radioactive waste dregs. Through the combined technique process, three parts of products were obtained, namely, Rare Earth concentrate collected, the thorium product enriched and a large amount of the waste dregs product that can be directly drained and the total quantity is 50%-60%. In order to determine optimum technical condition, the effect factors of separation process were investigated in the test."

Jan 1, 2003

By Patrick A. Turner, Timothy J. Olson, Abraham J. Schutte, Roman van Ommen

"The use of classifying devices in grinding circuits dates back to the early 1900’s when classifiers were installed to close ball mills. The search for ways to further improve grinding circuits led to the use of hydrocyclones in place of mechanical classifiers in South Africa in the early 1950’s. Today Hydrocyclones are considered as the best classifying devices to close grinding circuits. After 50 years of development the hydrocyclone has changed significantly when compared to the designs of the early days, but the focus to circuit optimization must be expanded to an understanding of the integral system consisting of mill, cyclone feed pump and cyclone.The key to good cyclone circuit design and operation in primary grinding circuits will be discussed including individual cyclone design features such as cone angle or materials of construction, as well as orientation and manifold configuration.Cyclone performance issues as well as maintenance considerations will be detailed in an effort to achieve consistent cyclone operation with minimal coarse solids in the overflow. “The importance of constant cyclone feed conditions is unquestioned today. The challenge of Cyclone sizing is a large number of not fully known variables prior to startup. The most significant unknown variable is slurry viscosity. Because of this, engineers often specify a conservative cyclone system that produces a finer than required separation. However, this approach often leads to higher circulating loads and a higher overflow density in order to produce the required separation. The higher cyclone overflow density results in a less efficient cyclone separation. The average concentrator can pick up 2-4% finer overall grind by having a more aggressive cyclone operation.”"

Jan 1, 2003

By Rebecca Hope, Derick Moolman, Frikkie Malan

"Despite the lip service that has been paid to pro-active plant maintenance processes over recent years, a significant portion of maintenance in industry is still reactive. The business driving force to prevent expensive production opportunity costs arising from “break-down maintenance” is obvious. Various benefits can be derived from successfully deploying remote equipment diagnosis technology and associated business processes.From an end-client’s viewpoint these include the ability to predict and take actions to prevent equipment breakdowns, increasing the lifetime of equipment by responding to appropriate operating instructions and therefore improving the return on capital expenditure. Better planning and scheduling of maintenance priorities and resources with performance measures like an Equipment Health Index are also possible. The knowledge that a qualified supplier engineer is constantly in touch with the operating conditions of their equipment, albeit remotely, is more than a comfort, and can be translated into quantifiable cost savings and improved supplier service levels."

Jan 1, 2003

By Daniela Venter, Stephen Chryssoulis, Ken Stowe

"A sampling campaign was conducted at Kemess in order to identify and assess the chemical and physical factors, which control free gold flotation kinetics in the rougher and cleaner circuits. The rationale behind this approach was that accurate knowledge of the parameters affecting free gold flotation kinetics, can be used to determine how to accelerate free gold flotation. Collected samples were composites of 5-6 cuts over a four-hour period, at steady plant conditions.In the rougher circuit, coarser equidimensional gold particles floated ahead of the finer grained and the flaky gold. Sulphur followed by molybdenum and to a lesser extent silver enhanced gold flotation kinetics, while hydroxyl followed by carbonate ions induced depression."

Jan 1, 2003

By G. Demi, G. Belardi, N. Shehu, S. Cico

The physico-chemical interaction between minerals such as olivine, chromite and serpentine and the ions most commonly present in solution, like Ca and Mg and flotation reagents such as EDTA and oleic acid was investigated. The study was conducted via release tests, electrophoretic measurements and microflotation of selected minerals coming from the Kukes deposit (Albania).

Jan 1, 2003

By Shenxu Bao, Ying Bian, Xiang Liu, Liuyi Ren, Yimin Zhang, Chun Liu

Efficient enrichment of high-carbon low-grade mica stone coal containing vanadium is a key problem in the mineral processing field, and the mature beneficiation process is yet to be developed and applied. In this paper, a special mineral mica type of stone coal containing vanadium from Tongshan, Hubei Province, China was selected as the research object. Chemical analysis results show that this mineral contains V2O5 0.71%, SiO2 49.28%, C 13.44%, and CaO 6.26%. Scanning electron microscope (SEM) shows that vanadium generally exists in all kinds of mica minerals in 20 µm to 50 µm fractions. Mica stone coal containing vanadium must be ground to a particular fineness (approximately 45 µm). To reduce acid consumption during vanadium extraction from stone coal through acid leaching, a pretreatment process was proposed to enrich micas by using shaking table and flotation methods. A new combined technology process was implemented, resulting in a 0.96% improvement in the vanadium grade of raw materials in the succeeding process. Vanadium losses were controlled to 4.57% through the pre-concentration process, which reduced the burden of the subsequent procedure. The content of high acid consuming minerals was also diminished, such that approximately 6612 CNY was saved from producing 1 t V2O5. Therefore, stone coal containing vanadium should be pre-concentrated by using an appropriate combined process to reduce costs.

Jan 1, 2014

By Dominic Howarth, Diana Drinkwater, Don McKee

"The pressures on mining and minerals education at the tertiary level are well known. Within Australia, for example, the number of undergraduate mining engineering courses with 30 or more students in each year has reduced to three (University of Queensland, University of New South Wales and Curtin University). Similar declines in both student numbers and participating institutions are evident in many other parts of the world, and notably in USA and most countries in Europe.An in depth study of the Australian sector was conducted in 1997/1998, resulting in the Back from the Brink report (Carter 1998). The Australian situation was summarised as follows.Australia’s minerals education system, in its current form, is fragile and is in no position to seize the opportunity (i.e. world leadership in minerals education) and is more likely to succumb to the threat.Current trends include:- an acute shortage of talented academic staff, as a result of University remuneration packages having become hopelessly uncompetitive with those in the minerals industry;- small student populations and high relative costs, making mineral specific courses vulnerable to closures, when Universities are under extreme cost pressures; this situation will be exacerbated if enrolments drop in response to, say, a cyclical down turn in the industry; and- under-resourcing of minerals departments because of their comparatively small size, making these departments incapable of delivering top class teaching in all aspects of their courses, despite being excellent in some areas.Most of the Australian issues identified above have direct parallels in other countries.The most common response of institutions to the threats is to seek strength, and in some cases survival, through various forms of linkages and networks. A number of these associations, which are frequently defensive in nature, are outlined in the paper."

Jan 1, 2003

By Jing Zhou

2-hydroxy-3-naphthoy hydroxamic acid code name F203 is a good collector of cassiterite, 1-hydroxy-2-naphthoy hydroxamic acid code name ZJ-3. F203 and ZJ-3 are similar series of isomers. They have similar naphthye, and similar series of functional OH and ?CONHOH, but the seat of OH and ?CONHOH group are different, on the F203 is 2.3; on the ZJ-3 is 1.2, ortho position too. According to Isomeric principle ZJ-3 is a good collector of cassiterite slime too. Using ZJ-3 as collector flotation -10µm occupies 90%, grade 1.16% Sn cassiterite slime of Da Chang Chehe concentration plant, pass one coursing flotation, two cleaning and one scarenging flotation, and obtains grand 18.26% Sn, recovery 92.68% cassiterite concentrate. The result proves the Isomeric principle of flotation reagents is correct again. This principle may supply to synthetize new flotation reagents reference. Keywords: F2O3, ZJ-3, cassiterite flotation, Isomeric principle, Isomeric principle of flotation reagents

Sep 1, 2012

By F. Y. Kang

There are rich resources of natural graphite in China. It would be a good opportunity to upgrade national graphite industry if natural graphite with modification is used in lithium ion battery. Micro-crystalline graphite in high purity was coated with a carbon film on the surface. The initial cycle efficiency was improved to be 89.9% and cycle stability was remarkably improved. The experiments proved that microcrystalline graphite with carbon coating have excellent electrochemical performances at low cost as anode materials for lithium-ion battery. In addition, H2SO4-GIC technique was used to prepare the natural flake graphite powders with mild-exfoliation. Sub-micro and nano pores were found in the graphite samples. In correspondence the reversible capacity, rate capacity and cycle life were improved, which would meet the demand of high-power lithium-ion battery. Natural graphite is the most promising anode material for large-scale lithium-ion batteries. The demand of modified graphite grows up greatly in the market. Microcrystalline graphite with surface coating and flake graphite with mild-exfoliation are the promising commercial anode materials for the industry of lithium ion battery.

Jan 1, 2014

By F. B. Waanders

Coal, as energy resource, possesses numerous characteristics and properties which all have an influence on its gasification behaviour. The two properties considered as critically important when evaluating a coal source for gasification is its mineral content and slagging behaviour. Research has indicated that slagging formation can be inhibited or even prevented by the addition of a fluxing agent. It is thus of great importance to understand the mineral interaction during gasification in order to select a suitable fluxing agent for the prevention of slagging and clinker formation in the gasifier. The aim of the present project is to evaluate the effect of iron as a fluxing agent and study the transformation of the mineral and added iron during gasification. A pre-determined amount of pure elemental iron (between 2wt% and 20wt%) was added to a base case coal sample in order to study the effect of the addition of iron to the coal. The transformation of the iron in conjunction with the possible iron containing minerals present in the coal was studied by means of Mössbauer analyses. Typical characterisation techniques included proximate analyses, ultimate analyses and ash composition analyses. The ash fusion temperature analyses (AFT) were used to study and predict the slagging behaviour of the iron-spiked coal samples. Even though AFT analyses only provide an average flow property, it gives a good indication of the changes that the iron addition induces on coal properties. FactSage modelling was carried out in conjunction with the Mössbauer and AFT analyses. From the proximate, ultimate and ash composition analyses it was clear that the coal used con-formed to the average characteristics measured over an extended time period. From the AFT values it was seen that an increase in the flow temperature occurred with the addition of pure elemental iron to the coal, which can be of importance for operational purposes as to raise the gasifier temperature and not to have slagging problems to occur in the gasifier. The Mössbauer data show that he-matite is the main Fe-component that forms from the pyrite originally present and from the added iron to the coal, consistent with FactSage modelling, which shows that the partial oxygen pressure determines which mineral species will form. This study opens up new possibilities when considering operational problems experienced in in-dustrial gasifiers. Successful completion of this study and a study to look at reducing conditions in the gasifier will also add to the knowledge that already exists regarding fluxing agents.

Jan 1, 2014

By S. M. Javad Koleini

Processing of phosphate ore sample was investigated for increasing phosphate content and reduction of its gangue minerals such as carbonates and silicates. Experimental designs were per-formed using Taguchi method. Different flotation methods were investigated for Moundon phosphate ore sample and three methods were used as follow: direct cellophane flotation, reverse calcite flotation and reverse quartz flotation. Because of the sensitivity of cellophane flotation to slime content, prior desliming was carried out before the experiments. Direct flotation experiments carried out and a concentrate contained 23.80% P2O5, 6.88% SiO2 and 72.33% recovery were produced. The achieved P2O5 content in the produced concentrate from reverse flotation of calcite was 26.44% and the recovery was 82.56%. The concentrate products obtained at optimum conditions by direct flotation of phosphate and indirect flotation of calcite were subjected to indirect flotation of calcite and direct flotation of appetite and final concentrates with P2O5 grade of the order of 24.19% and 26.96% were obtained, respectively. It was concluded that one stage direct flotation is unavoidable to achieve a product with low SiO2 content.

Jan 1, 2014