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By Anatoly F. Usov, Vyacheslav A. Tsukerman

"The Russian scientists have developed a new energy saving method for an efficient destruction of the sturdy and hard materials (rocks, ores, frozen soils, concrete blocks ets.) - the Electric Pulse Discharge method of materials destruction (EPD). The detailed researches of a broad circle of problems connected to development EPD-disintegration of materials of a various nature and area of use are executed. The electrical and power characteristics of process, physical fundamentals of selectivity of a breakdown and destruction are investigated, the means of electric pulse splitting and refinements of materials are developed, the technological efficiency of disintegration of industrial minerals estimated.One of the most important characteristics of the EPD-disintegration of ores is the high selectivity of destruction, which provides a large ratio of useful minerals' grains opening, and at the same time, it destroy them less. This ensures in the subsequent stages of beneficiation of ores considerable increase of the extraction and improving the quality of concentrates.The technological tests of various industrial minerals have shown a possibility the EPD-disintegration, as a process that provides the best efficiency of disclosure of useful minerals in all types of ores. Technological and economic efficiency of the method of ore beneficiation is the highest for difficult beneficiated ores with rather low extraction by existing methods. The increase of extraction in this case can reach several percents. As a rule, at a EPD-disintegration the disclosure of mineral grains happens in earlier stages of material comminution than at a mechanical comminution, and with less damage of products. This promotes a simplifying the process of ore preparation and for reducing the power consumption."

Jan 1, 2003

By J. Broadhurst

"A number of metal supplying industries have in recent years seen the compilation of life cycle inventories (LCIs) and life cycle assessments (LCAs). The activity has largely been driven by the interest of ultimate metal users, such as the automotive industry, in the interest of designing more sustainable products. Often, the compilation of such inventories has been little more than an auditing exercise. However, the process of conducting an LCA can have more value, guiding designers and operators to points within the technology train where significant emissions and impacts originate. The LCA product can thus be used to inform on-site environmental management, and, where process data is used to construct dynamic operational models, to support strategic decision making in the realm of project planning and technology selection. LCA thus serves as a valuable tool to support the industry’s drive to support the sustainable development of the societies in which it operates.This paper reviews and compares the priorities of environmental and closure planning in the design phase, with environmental management and auditing during operation, and with green procurement of minerals and metals products. It shows how life cycle assessments of various complexities can be used to reconcile these various objectives, ensuring that the latter, critical to business success, can be addressed from the outset in a new project. The paper then reviews a case study of the use of LCA in the base & precious metals industry, where the complexity of the operation disallowed the simpler auditing process so that a detailed process understanding had to be built up in order to compile a meaningful life cycle inventory."

Jan 1, 2003

By Derek Caizergues, Hurman Eric

The principle of carbothermic reduction has been around for many years. In principle it is a simple process, yet with a multitude of problems. The temperature required to affect reduction is in the region of 2200ºC and results in aluminium oxy-carbide formation rather than metallic aluminium. From a thermodynamic point of view, reducing the temperatures of reaction which would suppress oxy-carbide formation would only be possible by lowering the total pressure of the system. A decrease in thermodynamic activity of product aluminium by dissolving it in another phase would also help preventing the formation of oxy-carbides and would also increase the yield of the reduction reaction. Thus experiments have been conducted at around 1700ºC to determine the possibility of carbothermic reduction of alumina under the presence of a metallic solvent. Total pressure of the system was reduced to around 30kPa and metallic nickel, iron, copper and tin were selected as the solvent. The highest recovery of aluminium was achieved with the nickel solvent followed by iron, copper and tin. This ranking for the first three was also in accord with the extent of negative deviation form ideality in the respective binary solutions of these solvents with aluminium. The tin-aluminium system displays positive deviation form ideality. The rate and extent of reduction was found to be highly dependent on temperature and pressure. The pseudo first order reaction rate was found to be applicable to the process in all the solvents used. Rate constants were calculated and it is also suggested that the reduction was controlled primarily by the chemical reaction rate.

Jan 1, 2003

By Slobodan B. Vujic

"Some twenty years ago, during construction of flotation in the “Veliki Krivelj” copper and non-metallic mine Bor, a computer supported system for remote controle of technological process was installed. Nowadays, the major part of equipment of this system is worn-out and technically old-fashioned. Having this in mind a decision was made to design a new computer supported information-management system for Flotation. The paper presents a concept and features of project solutions.For the requirements of remote monitoring and management of technological process in Flotation of “Veliki Krivelj”, Copper and non-metallic minerals mine in Bor, Yugoslavia (hereinafter: CNM Bor), a measuring-regulation equipment was implemented and a computer control system, adjusted for that time, built some twenty years ago. The major part of this equipment is today worn out and technically out of date.Having estimated that production and business activities could hardly be more efficient, operative and successful on one hand, and available mineral and other resources rationally exploited, the CNM Bor made a decision in 1999 to improve information-management function of Flotation. The idea was that the set task be realized through development and introduction into practice up-to-date integrated and computer-supported production-business information-management system. The first logic step in completion of this task refers to engineering-creative determination of information management system (hereinafter: IMS), namely to project elaboration.When considering the real system from technical, technological, organization, monitoring-management, logistic and business aspects, the Project on IMS of Flotation, should provide a rational, modern and, for the real system conditions, complete solution. The Project solutions should be based on the most recent knowledge from computer and measuring-regulation technics as well as from CIM concept (Computer Integrated Manufacturing)."

Jan 1, 2003

By Barbara Peszko, Tadeusz Tumidajski

"Various methods are used to identify the grain composition of fine-grained materials because so far the best notion of the grain size has not found and there is no single method to define grain size. In practice the most important are the following grain sizes: sieve diameter dt, effective diameter de, substitute diameter d2 and statistical diameter dst. The mentioned sizes are connected with the methods of analyses. Methods are correct but measure of different diameters of grain and their results are different.The most important methods of granulometric composition analyses are the following: the sieve analysis, the sedimentation method and the conductometric (Coulter-Counter) methods. In each of these methods various physical features connected with the grain size are measured.Sizes of grains defined by different formulas or measurement methods are associated mutually by dependencies, which are results of differences in their determination or calculation ways.In order to determine principles of results comparison the classification analysis results on linearly or non-linearly connected was made. Analyses which results demonstrate the same type of grain size distribution are treated as linearly connected. It is based on the general formulae which determines the probability density function of random variable which is the function of another random variable having the known density function.In order to show the difference in the grain composition of the same material qualified by different methods, three methods of investigations were distinguished. They are: the sieve analysis performed on precise sieves, the sedimentation analysis performed by means of a sedimentation balance “Sartorius” and the microscopic analysis performed after preparing a microscopic slide where the grain size was measured by the Martin’s method.The materials selected for the analysis were quartzite and glass, which are the material of high purity.The obtained results of mentioned above three types of analyses were approximated by distribution function of four distributions: Weibull, log-normal, cut Weibull and Gaudin-Schuhman."

Jan 1, 2003

By Jean-Paul Franzidis, Robert G. Coleman, Emmy V. Manlapig

"The Floatability Characterisation Test Rig (FCTR) is a self-contained, highly instrumented mobile pilot flotation plant developed by the Julius Kruttschnitt Mineral Research Centre, the Mineral Processing Research Unit of the University of Cape Town and EIMCO, as part of the Australian Minerals Industries Research Association (AMIRA) P9 Project. Apart from being a fully operational pilot plant, the FCTR was designed to determine flotation model parameters and to develop and validate flotation plant modelling, scale-up and simulation methodologies.The FCTR was installed at WMC’s Kambalda Nickel Operation where circuit modelling, simulation and scale-up test work was performed using the AMIRA P9 flotation model as the basis of the analysis. The model parameters were obtained through metallurgical sampling, batch flotation tests and gas dispersion characterisation around the FCTR. Model parameters were determined for four FCTR circuits, each of increasing complexity. The circuits ranged from a simple rougher-cleaner configuration with no recycle streams, to a more complex rougher-cleaner-recleaner configuration with two recycle streams.Using the P9 modelling methodology, the system was analysed using four mineral species: nickel sulphide, iron sulphide, copper sulphide and non-sulphide gangue. The floatability of each mineral was analysed as two floating species (fast and slow) and a non-floating species. Mass balanced data from all four FCTR circuits were regressed simultaneously together with data from 47 batch flotation tests. Nonlinear regression was used to determine the solution. The model fit was found to be accurate with most data points predicted within experimental standard deviations. A Monte Carlo sensitivity analysis was also performed to establish the stability of the regressed parameters.Using the P9 simulation methodology, simulations of five FCTR circuits (different from the previous four) were performed. The FCTR was also operated in these five circuit configurations to obtain experimental data to validate the simulated predictions. The simulations were found to predict the recovery and grade of nickel sulphide and copper sulphide within experimental standard deviations. The prediction of recovery and grade of iron sulphide and non-sulphide gangue was less accurate. Overall the FCTR simulations predicted the changes in circuit configuration well."

Jan 1, 2003

By Markus A. Reuter, Jacques J. Eksteen

"The modelling of bath type furnaces tends to be either fundamental in nature or total empirical ""black box models"". While models of the first kind are robust, they tend to lack accuracy, in cases where they are to be used for process control, and may take an overly long in development time. On the other hand, black box models tend to lack robustness of prediction for all circumstances and tend to be limited to interpolate based on historical data. While this may very often provide short-term accuracy, the models may have problems with stability in the long term. Moreover, the model structure may not reflect any of the fundamental properties of the system and remains opaque to fundamental analysis. The aim of the model development is in obtaining a model that have robustness, high accuracy, a short development time and which is adaptive to a changing environment. The models are specifically developed for on-line decision support or control of furnaces. The modelling approach is evaluated for a chromite bath smelting furnace. The role of systems analysis, mass balance smoothing, thermodynamic analysis are integrated into one generic algorithm for bath type furnaces. Not only are fundamental process relationships such the mass and energy balances satisfied through a scientific method of data reconciliation; the proposed modelling approach allows adaptive prediction, the first step towards predictive control or metallurgical decision support.It is shown that neither an ARMAX model only, nor a purely equilibrium model only, could predict the dynamics of the process very well. However, a combination of the two approaches more than doubled the accuracy as measured by the R2. It was noted for carbon dissolved in the alloy, that the improvement in R2 in using a hybrid modelling approach was more than the sum of the R2 of the individual traditional approaches. Similar improvements in modelling performance were noted for all other species.It shows further that process dynamics may totally overshadow the effect of thermochemical equilibrium (even when the thermochemical equilibrium prediction includes the recycled alloy and slag heels as additional feeds). The exclusion of process dynamics therefore leads to erroneous results."

Jan 1, 2003

By Markus A. Reuter, Albert Scholte, Ewoud V. Verhoef, Gerard P. J. Dijkema

"A dynamic, interactive map has been developed of the life cycle of a number of metals, from mining through to minerals processing, metal production, product manufacturing, recovery and waste management. Whilst the existing metal process network and waste management infrastructure provide substantial scope for (product) design, these also limit change because of the strong path dependency of industry and infrastructure development. The metal production network is complex, as it consists of an interconnected and integrated system that incorporates multiple production routes for a spectrum of metals. More often than not, the production or recovery of a single metal is related to or dependent on the generation or recovery of another. The effects of these other metals is of great importance. In order to realize the potential economic importance of impurities, research and development have integrated the processes of copper production with those of lead and zinc, and connected the processes to those of among others silver, bismuth, tin and platinum group metals (PGMs), for example. The recovery of these elements from the interconnected circuits is extremely complex, as most of the elements must be circulated between two or more circuits before they are concentrated enough to make their extraction possible, and their recovery as a compound profitable.From such a system’s perspective, it can easily be seen that a complication for solid waste management has arisen through the development of products (consumer goods) that bring together metals that are not linked in natural resources. As a consequence, many of these materials are not compatible with any process in the metals production network that was developed for the processing of primary, natural resources, optimized for the processing not only of the primary metal but also for all mineralogically associated minor valuable and harmful elements. The formation of large or complex residue streams or undesired harmful emissions then inhibits processing and recovery of said products at their end-of-life. Another complication is that any change to the system (in metal production, SWM or product design) affects the system configuration. Due to the changing demands for metals as a result from the changing products made from the metals for example, the relationships between the processes in the interconnected metal production systems change. This affects both the demand for old scrap (required amount and grade) from waste management, and the environmental profile of the metals. Preferably, therefore, product designers, waste processors and metal producers must cooperate to realize optimal metal recovery in processing discarded consumer products."

Jan 1, 2003

By Vincent C. Smith, Agit Singh, Daniel de V. van der Spuy, Bernard Muller

"Process control in the minerals industry is made difficult by factors such as the multivariable nature of the processes, noise, many disturbances, the changing nature of the processes, nonlinearities, process constraints, slow responses and large deadtimes. A good example of such a process is a milling circuit, where all these problems are experienced. Since model predictive control (MPC) effectively handles most of these difficulties, Mintek decided to develop, customise and test an MPC controller for milling control.Conventional MPC uses a dynamic model of the plant to calculate the future (predicted) plant outputs based on the movements of the manipulated variables in the past. The future moves of the manipulated variables can then be calculated using an optimisation algorithm that will minimise the difference between the setpoints and the predicted outputs. The least squares optimisation method is the quickest, but it does not cater for process constraints. Constraints can, however, be handled explicitly by using a quadratic programming optimisation method. This method ensures that the variables stay within the constraints at all times, but the calculation procedure is much more computationally intensive.• modifying MPC for the Minerals Processing IndustryIt was found that in order to obtain good, robust control using MPC in the minerals processing industry, the conventional MPC algorithm had to be adapted. The MPC controller was first tested on an extensive milling simulator, which was specifically developed for that purpose. Problem areas were identified and the MPC controller was specially adapted to accommodate for these difficulties. Some of the adaptations to the conventional MPC algorithm and special features added were as follows:Since milling plants contain many integrating processes (e.g. sumps), and integrating errors can cause offsets and poor control, it was essential that integrators be handled explicitly. This problem was solved by adapting the algorithm and also using an integrating error portion to compensate for integrating errors.Constraints on the inputs and outputs adversely affected the control. The controller using simple least squares optimisation was tuned with the constraints in place, while the maximum expected setpoint changes were made. This ensured that the process would be able to handle most setpoint changes up to these expected values without violating the constraints. A later improvement on this method was the incorporation of a quadratic programming algorithm to perform the optimisation. This method handles limits explicitly and was shown to perform better than the least squares methods (at the expense of a much higher computational cost)"

Jan 1, 2003

By H. Pearce, A. E. Lewis, A. Ochieng

"Hydrodynamics and mixing are fundamental to the operation of mineral process systems such as flotation cells and metal precipitation reactors. Hydrodynamic conditions influence phase mixing and mass transfer in a multiphase system, and these affect the overall performance of such a system. Detailed information on the effects of the hydrodynamics on the performance of agitated systems is still required for the design and optimal operation of hydrometallurgical systems, which are always multiphase. Computational fluid dynamics (CFD) techniques have been employed to study the hydrodynamics and mixing, most of which have focussed on the performance of axial and radial pumping impellers in agitated tanks. However, very little has been reported on the influence of a draft tube on the flow profile in such systems.CFD simulation of a stirred vessel centres on the way the impeller is modelled. Some of the most recent approaches to modelling an impeller are impeller boundary condition (IBC), snap shot, sliding grid (SG), multiple frame of reference (MFR) and inner outer (IO). The accuracy, with which these models predict experimental results and the corresponding computational demands, form the basis upon which the choice of an approach is made. Most of these approaches (IO, SG and MFR) address the key problem of the stirred tank modelling, namely, the simultaneous meshing of the rotating impellers and the stationary baffles. The MFR is computationally cheap and has been found to give predictions that compare well with experimental data.The CFD technique (code CFX4.4) has been employed in the present work to study the hydrodynamics in a mixing vessel stirred with either a Rushton turbine or a pitched blade impeller. The multiple frame of reference (MFR) approach has been used to model both impellers. A draft tube was used only in the Rushton turbine stirred vessel. The flow profiles for the impellers have been studied in three regions; below the impeller tip, at the middle of the tank, and near the liquid surface. The simulation results were compared with literature data obtained using a laser Doppler velocimetry in the three regions of the vessel, and it was found that the model predictions were better in the impeller region. There was a poor prediction of the experimental results in the region closer to the liquid surface; however, this was improved when the turbulence parameter (C2) in the k-e model was set to a higher value. The value of the impeller clearance at which the Rushton turbine generates an axial impeller type flow has been determined and it has been shown that, at this clearance, a draft tube can be used to enhance axial flow in a Rushton turbine stirred reactor."

Jan 1, 2003

By Tim Suljada, Mary Stewart, Jim G. Petrie, Damien Giurco

"The minerals industry is being challenged to reduce the amount of virgin ore that is mined, and to replace this material through the recycling of used commodity items and scrap, or by the reprocessing of waste materials. It is argued here that the existing technology base of minerals processing and refining offers real potential for handling these secondary resources. The challenge is to develop tools by which the most preferable recycling routes (both economically and environmentally) can be identified from a list of feasible alternatives, taking into account any operational constraints of these technologies.This paper describes an heuristic approach to developing the family of all technically feasible flowsheets to address this challenge, from which a preferred option may be selected according to a set of decision criteria (economic and environmental). Our approach uses conventional flowsheeting techniques of selecting flow variables and splitter functions, supported by design performance information for each unit operation. This set of design decision variables is augmented by knowledge of the suitability of a particular waste or scrap stream for a given unit operation within a flowsheet. We achieve this by comparing the composition of the scrap stream with the range of mineral streams for which the unit operation was designed initially. This is inspired by the “overlap” approach proposed by Legarth, where an “overlap” of 1 would suggest that there is high degree of compatibility between a given secondary resource stream and a primary mineral stream as inputs to a specific technology. The “overlap” concept has been extended to include information about the physical characteristics of secondary resource streams, as well as information relating to synergistic / antagonistic influences of minor elements present in the waste stream. A flowsheet which delivers a product of acceptable quality from a given secondary resource material is built up from a progression of unit technologies. The exercise is repeated to generate the family of all feasible flowsheets from combinations of acceptable unit technologies."

Jan 1, 2003

By Markus A. Reuter, Bernardete Castro, Antoinette van Schaik, Han Remmerswaal

"INTRODUCTIONThis paper describes the inseparable relation between product design, liberation, and metallurgical recovery in the optimisation of the recycling of passenger vehicles. This is illustrated by the use of an optimisation model that uses among others a material combination matrix based on metallurgical process data, which depicts the consequences of the quality of intermediate recycling products on the metallurgical material recovery and final alloy metal quality. Various simulations will illustrate the effect of changes in product design and hence liberation on the recycling of end-of-life vehicles. Although this paper focuses on cars, the discussion is equally valid for any end-of-life product. Calibration of the model will be discussed with reference to experiments carried out in order to study the optimal recovery of aluminium applications used in passenger vehicles.OPTIMISATION MODEL FOR LINKING DESIGN TO RECYCLINGImproving the efficiency of the material cycle of the car is essential to ensure a sustainable development of our society as well as e.g. to comply with the recycling targets imposed by EU legislation. In the design of the car various materials are combined and connected in many different ways, making up the complex 'mineralogy' of the car and its components, which is changing rapidly and continuously over time. The liberation of materials during shredding plays an important role in the composition (and quality) of the intermediate recycling streams. In order to include the influence of product design (mineralogy), liberation, and particle composition (quality of the intermediate recycling streams) in the optimisation of the recycling of end-of-life vehicles, a systems engineering tool for optimisation of the recycling of end-of-life vehicles was developed, including a liberation model. The optimisation model predicts the recovery rate as a function of product design (in this case a car), liberation, efficiency of the different process steps, economy and legislation based on a developed recycling flow sheet for end-of-life vehicles. Optimisation can only be achieved through the combination of the knowledge areas of product design, shredding, mechanical separation technology linked to pyro- and hydrometallurgy, composing a complex interconnected network of unit operations."

Jan 1, 2003

By Georg Unland, Thomas Wegner

"Impact crushers are widely used in different industries to crush materials which can vary from soft to hard and from ductile to brittle. However, the sizing of impact crushers is still based rather on empirical than on scientific approaches. Therefore, a test rotor was developed in order to investigate the principles of comminution by impact. Rocks of diabase with different diameters were used to gain the crushing properties with the following results:RESISTANCE AGAINST CRUSHINGLikelihood of BreakageThe likelihood of breakage is a function of the impact velocity and the particle diameter. The likelihood increases with higher velocities and larger diameters. Maximum Crushing ForceThe crushing force is related to the area of projection of the rock. The smaller the particles and the higher the velocities the larger are the maximum related contact forces.Contact TimeThe contact time increases with the rock diameter whereas the influence of the impact velocity is neglectable.Mass Specific Crushing WorkThe mass specific crushing work decreases with the particle diameter and increases with the impact velocity."

Jan 1, 2003

By D. P. Hatfield, G. de Jager

"Recent developments in image analysis techniques and the power of computer hardware have spurred international interest in the potential uses of image analysis techniques in a range of industrial applications. One of these applications is the control of the complex flotation process. Despite years of work, the flotation process is still poorly understood. Current attempts to control flotation cells focus on consistently duplicating the control achieved by human operators.In human control of flotation two of the dominant visual cues are the froth flow speed and the froth stability. These two factors can be measured and inferred respectively from image analysis of video of the froth surface. Two important hydrodynamic variables for control of the flotation process are the air addition rate and the level of the froth pulp interface.The current work focuses on the relationship between froth flow speed and the rate of recovery of concentrate from a flotation cell. Results are presented that show a strong relationship between flow speed and concentrate yield. These results include tests where the conditions in the cell were not changed, as well as tests involving changes to the cell level and air addition rate. Preliminary results are presented which show a correlation between froth stability and froth percent solids.Future developments of the system will include comprehensive froth texture typing, colour space and stability analyses."

Jan 1, 2003

By Paul W. Cleary

"Particle scale simulation of industrial particle flows using DEM (Discrete Element Method) offers the opportunity for better understanding the flow dynamics leading to improvements in equipment design and operation that can potentially lead to large increases in efficiency, throughput or product quality. DEM has been used for modelling many industrial applications, particularly milling. This includes ball and rock motions and power consumption in ball mills, AG and SAG mills, vibrational segregation, flows in rotating drums, operation of dragline excavators and hopper flows. In mineral processing, DEM has been concentrated on mills because of their critical importance. However DEM also offers the opportunity to improve many other parts of mineral processing operations. These areas often do not receive the attention that the key comminution equipment commands, but can become critical when they fail or under-perform. Importantly their assessment/improvement using DEM is often much more feasible because of smaller problem sizes and the absence of poorly understood physics such as breakage. In this paper we describe DEM simulations of four important pieces of non-comminution equipment that are commonly found in or near mineral processing plants (these are shown in Figure 1):"

Jan 1, 2003

By Katarina Theander, Robert J. Pugh

In the flotation process, control of the stability of the froth is extremely critical. In the case where the froth is too stable then mechanical entrainment of particles can occur but in the opposite case, where the froth is too unstable and difficult to skimm-off, then a reduction in recovery can result. In minerals and deinking flotation, commercial fatty acids are used and may act as both both collectors and frothers. However, frequently the fatty acids are mixed with nonionic ethoxylated surfactants to give more effective froth control and increase the flotation performance. It is of interest to note from the surface chemistry literature, that such mixtures may cause synergistic effects in surface activity which may explain changes in bubble size, foaming and carry over of particles. In the present study, we have carried out foaming and drainage experiment with oleic acid and model nonionic surfactants; hexa(ethylene glycol) mono-dodecyl ether, C12E6 and tetra (ethylene glycol) mono-dodecyl ether, C12E4 both in separate and mixed systems. Frothing was carried out in a column, equipped with a series of conductivity electrodes which enabled the water content of the froth to be measured along the length of the column, during various stages of the drainage process. The variation in water content of the froth enabled the process to be characterised by distinct three stages; (a) an entrainment state where the water transfer from the bulk phase to the froth was dominant (b) a steady state when entrainment and drainage are balanced and no water is transferred to or from the froth and (c) the drainage step when drainage predominates and the volume of the bulk phase increases. We also carried out surface tension measurements on the oleic acid/ nonionic systems and related the results to the frothing and drainage performance. From the surface tension data, the adsorption interaction parameter of the mixed systems at the air/solution interface could be calculated and was found to depend on the oleate/ nonionic surfactant ratio. This value was related to the frothing performance and the results indicated a positive interaction parameter for the mixed surfactant systems which could explained the synergistic effects in frothing performance.

Jan 1, 2003

By Thomas Pretz, Alexandra Pehlken

Sampling of municipal solid waste is known to be difficult to sample if it has to be representative. When dealing with municipal solid waste, the usual method is to study separately waste material below 40 mm and particles bigger than 40 mm. The material < 40 mm cannot be sorted manual and is termed the “fine fraction”. The particles > 40 mm can be separated manually and are usually sorted into pre-defined groups of materials. These groups can be defined depending on the demand of quality assurance. But standardisation of procedures is not far progressed, even for the widely practised sorting methods.

Jan 1, 2003

By Caibin Wu, Ali Lei, Ningning Liao, Jingsheng Ye

"The particle size distribution characteristics of ground product can influence the quality of the classification overflow and the next beneficiation indexes in an ore concentrator. Usually, the size distribution of ground product is considered to be determined by that of new ball mill feed. However, based on large amounts of data from industrial grinding circuit surveys, this paper has clearly shown that the size distribution of ground product should be determined by the size characteristics from classification underflow unless the circulating load was small, because the new feed is an important component and occupy a dominant position of mixed ore from belt feed and classification underflow. On the other hand, the correlation coefficient of the size distribution between ground product and classification underflow can be more than 0.99 when the relevance principle and its method are used. Meanwhile, their P80 value also keeps a synchronous correlation. The greater the capacity of classification underflow is, the higher the correlation of size distribution between the ground product and the mixed feed is. Furthermore, the correlation coefficient of the size distribution between ground product and classification overflow which is from primary or secondary can be 0.96. It is another discovery that the correlation coefficient is related to the type of classifier. The coefficient of size distribution of overflow and underflow from hydrocyclone is superior to that of spiral classifier, which can explain the reason why the hydrocyclone is widely used to replace the spiral classifier in concentrator.INTRODUCTION It is well knows that ball mill circuits closed with cyclones or spiral classifier such as a primary grinding circuit, a secondary grinding circuit and SAB mill have become an industry standard. Which grinding process employed will be determined by the P80 value of ground products. When the primary closed circuit ball mill or SAB that it is different throughout between the two processes was employed, a grinding fineness with -200mesh under 68% will be available. However, the secondary grinding circuit with the fineness of -200mesh above 80% can be conducted. Of course, the grinding fineness is determined by the grain size characteristics of the mineral."

Jan 1, 2018

By A. Collings, A. Farmer

"Power ultrasound may be used in the processing of mineral suspensions to clean the particle surfaces of oxidation products and fine coatings, mainly through the large, but very localised forces, produced by cavitation, which is the formation and sudden collapse of bubbles in a fluid. Cavitation occurs preferentially at solid surfaces in a liquid: at container walls, inserted objects or suspended particles. When the cavitational bubbles collapse near a solid they do so by forming a very high energy jet directed from the point on the bubble furthest from, and directed towards, the surface of the solid, in effect micro jet blasting.This paper highlights some of the major mineral processes where ultrasonics is beneficial namely: Surface cleaning of detrital mineral particles, where container quality glass sand was upgraded to tableware quality and up to 20% improvements in the sharpness of high tension separation of mineral sands was achieved"

Jan 1, 2003

By Peter Ay, Elena Geldt, Satyanarayana Narra, Claudia Glaser

"As part of an extensive research and development project, the technical and technological implementation of the patents DE 10 358 245 B4 and WO/2006/056172 was developed with the goal to present a system for the innovative roll- agglomeration method exhibiting a) a modular setup, b) high productivity and c) suitability for the use of fibres of different applications and product qualities (high technical availability). The processability of the rarely adapted raw fibre materials into high-value intermediates brings forward their application in various processing industries dealing with the production of fibre reinforced plastic composites, heat and sound insulation materials as well as with the gas and liquid cleaning systems. The innovative fibre agglomeration presented in this work is performed by a combination of rolling and pressing the fibres inside a geometrically pre-defined roller table, in which the fibres are forced to bound through entanglement / interlocking and develop into agglomerate. The agglomeration process is carried out in a circular roller path with a rectangular cross-section. For improving the adhesive properties, and thus the quality of the agglomerates, the boundary surfaces can be covered / patterned / lined / coated with various materials. The resulting roll-agglomerates are characterized by different quality parameters such as mass, shape, porosity and stability. The properties of the agglomerates can be modified based on the end-product requirements by slightly modifying the process parameters such as filling ratio, residence time, roll-geometry, procurement of the boundary surfaces, etc. as well as the input material properties such as fibre type, fibre fineness, fibre length, etc. This work carries extensive work on the roll-agglomeration system to assess the effectiveness and the variability based on the product specifications. Agglomerates were produced with wide variations of system parameters with varying roller table liners and based on evaluation of the produced agglomerates with respect to their mass, the geometrical dimensions, their porosity and stability."

Jan 1, 2014