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By H. Lieberwirth, M. Hesse

"Selective comminution (SC) is beneficial for the treatment of primary raw materials, especially if it is utilized in the pre-concentration process. Pre-concentration processes are applied in mineral processing to relieve subsequent processes and to achieve a higher efficiency. SC is also a promising method for the treatment of low-grade ores and waste dumps. With SC, various components can be separated such as valuable minerals from waste, ore from wall rock and different ore varieties within a deposit. SC is a property of a comminution system and leads either to a preferred crack propagation in one component (called preferential breakage) or to a preferred crack propagation along the grain boundaries (called interfacial breakage). SC results from different comminution behavior of various components in the feed material. For mechanical comminution, the preferential breakage seems to be the most important case of SC. Hereby SC generates only the difference in the particle size which can finally be used as a sorting parameter. A sorting process which uses SC depends on three parts: the feed material, the comminution machine and the separation machine. The feed material defines the potential for SC. Differences in properties like strength, toughness and density which are related to comminution are often used. The comminution machine has to exploit this potential. The extent of the exploitation can be influenced by the machine design, material and operational parameters. After SC, the various components are still combined in the product. So ultimately, a separation machine is needed. At preferential breakage, a simple screening machine can be used. The basics about SC will be presented at first. This contains relationships between material properties, the kind of loading in the comminution machine and the SC effect. These basics can be used for example to exploit a potential to SC for a pre-concentration step or to avoid the SC for a higher efficiency of subsequent processes. Based on recent investigations with impact load, the influence of the important parameters compressive strength, density, particle size and impact velocity to the SC will be shown, using examples of lead-zinc ore comminution and fluorspar processing."

Jan 1, 2018

By F. S. Hoseinian, K. Filho, D. Deglon, T. Souza, M. Safari

"This paper investigates the reverse flotation of hematite in three laboratory flotation cells with very different contacting environments. The main objectives are to investigate the recovery of coarse quartz by flotation and fine hematite by entrainment. The laboratory flotation cells used were the mechanical, oscillating grid and pneumatic cells. The effect of froth height and solid concentration were investigated in the mechanical and pneumatic cells. The effect of impeller speed and energy input were investigated in the mechanical and oscillating grid cells. Froth height results show that coarse quartz particle recovery decreases almost linearly with increasing froth height due to increased detachment of coarse quartz particles in the froth. Fine hematite particle recovery also decreases almost linearly with increasing froth height due to decreased water recovery and associated entrainment. Agitation/energy input results show that coarse quartz particle recovery increases with increasing impeller speed to an optimum, after which this decreases dramatically. The increase is due to improved gas dispersion, generation of smaller bubbles and increased bubble-particle collision and attachment. The decrease is due to significantly increased bubble-particle detachment at higher impeller speeds. The recovery of coarse quartz particles in the OGC is higher than that in the mechanical cell with an optimum at a much lower energy input. Solids concentration results show that both mass recovery and water recovery increase with increasing solid concentrations. The pneumatic cell achieves higher mass recoveries and lower water recoveries than those in the mechanical cell at equivalent solids concentrations and operating conditions. INTRODUCTIONFlotation is a selective process for separating different minerals from each other. The flotation separation efficiency depends on the recoveries of the mineral species by both true flotation and entrainment (Neethling and Cilliers 2009; Wang et al. 2015). Both chemical variables and hydrodynamic conditions within the flotation cell affect the recovery and selectivity of the flotation process. Cationic reverse flotation of hematite is a common method for selective separation of quartz from iron ores to produce pellet feed. The presence of coarse quartz particles in the tailings and fine hematite particles in the concentrate are two major challenges in the reverse flotation of hematite (Vieira and Peres 2007)."

Jan 1, 2018

By S. P. Das

Tumbling mill is an important unit operation in a mineral processing industry whose operation needs to be understood to make it an energy efficient unit. One of the important mill parameters is the impact spectra generated by collision of the moving charge mass on the mill shell. This process also generates mechanical vibration on the mill shell and propagates to the plumber block of the mill. In this work, we tried to understand the impact spectra by using different minerals such as Banded Hematite Quartzite (BHQ), Hematite and Quartz as mill feed of a semi-autogenous (SAG) mill. The said mill is of 1000 mm diameter and fitted with a force sensor on the mill shell and a vibration sensor on the plumber block. The analysis of the impact spectra was done by taking into consideration the peak impact force above a certain threshold value. It clearly shows that the impact force decreases as the particle size become finer irrespective of the mill feed material. This can be used as an effective tool by the mill operators to have an understanding of the mill product size reduction. The mechanical vibration tapped by a tri-axial accelerometer was analyzed by power spectral density analysis. The vibration signal analysis shows the variation in the power spectrum magnitude both at lower and higher frequency. It also shows inconsistency in case of BHQ where it shows a significant decrease in vibration at lower frequency and increase in vibration at higher frequency. Therefore, the impact spectra analysis is a better method compared to vibration analysis in understanding the mill product size reduction.

Sep 1, 2012

By J. R. Cui

The production of electric and electronic equipment (EEE) is one of the fastest growing areas. This development has resulted in an increase of waste electric and electronic equipment (WEEE). In view of the environmental problems involved in the management of WEEE, many counties and organizations have drafted national legislation to improve the reuse, recycling and other forms of recovery of such wastes so as to reduce disposal. Recycling of WEEE is an important subject not only from the point of waste treatment but also from the recovery of valuable materials. Consumer electronic equipment (brown goods), such as television sets (TV), radio sets, and video recorders, are most common. However, recent work on recycling of waste electric and electronic equipment (WEEE) primarily focused on personal computer and printed circuit boards scraps. Based on a detailed characterization study of consumer electronic scraps, recycling of TV scraps oriented to recovery of metals is highlighted by utilizing air table separation, eddy current separation, and optical (metal) sorting process. The result indicates that a high recovery of copper could be obtained by utilizing an effective gravity separation process. The separation results reveal that air table separation is an effective technology to recover metals from consumer electronic scraps. By using a DGS table, approximately 90% of non-ferrous metals were recovered in the heavy product with a purity of 40%. Printed circuit boards and cables in TV scrap cause metals loss due to the fact that metals in printed circuit boards and cables are not liberated from plastics and ceramic materials. The study shows that eddy current separation and optical (metal) sorting process provide alternatives for recovery of metals from shredded TV scraps.

Jan 1, 2014

By R. Shiva Kumar, G. Sreedhar, S. Sharma

Some of the Indian origin iron ore deposits located in Bellary, Karnataka province are having peculiar characteristics of Iron ore deposits (Hematite) having Iron above 64% and 30-40% lump (-30+6mm) recovery which are not suitable to use in blast furnace due to not meeting the specification of Tumbler Index and Abrasion Index. In general for high grade Iron ores, process flow sheet involves crushing and screening (dry/wet). In the contest of high grade Iron ores located at Bellary sector of Karnataka state in India, lump generated from this process could not attain the required physical properties (Tumbler Index, Abrasion Index) and metallurgical properties , even though the grade of the lump ore is above 64% Fe. Washing techniques like Drum scrubber and Log washer play major role in improving the metallurgical properties of Iron ore lumps by removing the light and hard layers of clay, silica coated over the lumps. In this study the effects were compared of drum scrubbing and log washing on iron ore lumps. It is found that by incorporating simple washing technique i.e. drum scrubbing or log washing, Tumbler Index of Iron ore Lumps could be increased from 74% to 78% which is acceptable for use in Blast furnace. From the Drum scrubber and Log washer tests, it is clear that Log washers have an edge over Drum scrubber in removing hard coated clay on surface of Lumps. This simple washing technique facilitate us to utilize the lumps directly in blast furnace and eliminate the unnecessary crushing and grinding of the ore so as to meet the specifications of Sinter fines and pellet feed.

Jan 1, 2014

By Sunil Tripathy, Y. Rama, Srinivasulu. A., Amit Ranjan

Process improvements in an operating plant are always challenging. Mineral beneficiation plants based on gravity concentration techniques need continuous evaluation and monitoring of its processes for getting maximum recovery and better grades. But, in an operating plant it is very difficult to control all the parameters due to numerous reasons such as unsteady operation, fluctuation in the quality of run-off-mine ore, overall flow rate etc. For better understanding of the beneficiation circuit, it is necessary to evaluate the critical operating parameters which affect the performance in terms of grade, recovery and throughput including losses of valuable materials into tailing. Accurate data collection and proper data interpretation followed by making necessary change which is implementable in an operating plant play very critical role in performance of the circuit. In case of gravity operated beneficiation circuits of chrome ores where the quality of the feed and physical parameters varies continuously, the operators are required to modify the critical operating process parameters on continuous basis which is very difficult and tiresome. There are many causes of the data variability, including both error (sampling and assay), and real variation in performance due to changes in ore mineralogy, operating conditions and other factors. In this article, attempts made to evaluate the performance of ultra-fine beneficiation circuit in terms of silica reduction in the concentrate of chrome ore beneficiation plant (COB), India are discussed. The approach adopted and practical problems encountered during the study were also discussed. Results obtained from plant audit based on the above methodology has shown that SiO2 content in the concentrate can be reduced to <4%.

Jan 1, 2014

By I. N. Babich

"Complex technological problems associated with the processing of mineral raw materials require the search and development of new means and ways of thinking. At present, computer cognitive graphics (CCG) are one of the most actively developing areas of new information technologies. The aim of the study was to optimize the cycle of technological evaluation of ores at all stages of geological exploration of deposits on the basis of analysis of geological sampling data using CCG. A new approach has been developed that facilitates optimization of the whole cycle of subsoil exploration. At the gold ore deposit, the results of the geological sampling data were processed by the method of constructing the CCG in the form of a histogram showing the frequency of gold extraction and the average amount of its content. Significant peaks of the metal content in the ore, exceeding the level of the average content in the ore by tens of times, have been revealed. Graphical interpretation of the parameters of mineralization reflects the uneven nature of its variability, which indicates the presence of large, rarely occurs of gold in the ore and the need to conduct studies on a sample of ore of greater mass than for ores with tiny gold. On a sample of 50 kg gold-quartz ore studies were carried out on gravity enrichment. The maximum size found in the gold concentrate was 0.07 mm. In the course of integrated tests in a gravity concentrate, gold particles up to 3 mm in size were found, which predetermined the need to include the operation of gravity before flotation. A new approach to subsoil research is protected by a patent (RU 2620823).The technological problems that arise before the researcher associated with the processing of resistant ores require the exploration and development of new means and ways of thinking. New problematic situations on complex mineral and raw materials objects are practically not amenable to resolution by existing methods. Integration of industrial and information technologies is necessary. At present, computer graphics (CG) is one of the most rapidly developing areas of new information technologies. For example, in scientific research, including in fundamental research, the accent from the illustrative function of CG (the visualization of what is already known) is increasingly shifting towards the use of computer cognitive graphics (CCG) tools (Bashlykov, 2016). The function of the CCG is to obtain a new knowledge with the help of a graphic representation - a cognitive image or at least to promote the intellectual process of the logical acquisition of this knowledge. In this study, cognitive images are used to graphically represent the distribution of valuable components in the bowels of the deposit, characterizing the state of mineral-raw materials."

Jan 1, 2018

By Lutz Rolf, Halit Z. Kuyumcu, Salas Cazón. Milton A.

Aim of experimental investigations was the mathematical description of the abrasion process running with a single particle stress. This is on the one hand the basis for the physical interpretation of the process, on the other hand the base for the simulation of abrasion processes carried out in technical scale. With this investigation for the first time the influence of the particle shape changing with increasing abrasion progress was quantitatively described. This influence affects itself particularly strongly on break-fresh particles up to an abrasion degree of approximately 10 to 20%. This is for the description of technical processes the most interesting area.

Jan 1, 2003

By Vladimir Vigdergauz, Elena Belogub, Dmitriy Makarov

The influence of supergene oxidation on physicochemical and technological properties of polysulfide ores was studied. Modeling and analysis of oxidation pyrite copper-zinc ore samples from the Valentorskoye deposit show that sulfide floatability is decreased by the longer-term oxidation. The treatment of oxidized samples by sulfuric acid in oxidative conditions and its impact on the elemental sulfur composition on the surface of sulfides was discussed. It is shown that an enhancement of the floatability of sulfides of oxidized polysulfide ores after leaching by sulfuric acid could be perspective for the developing of combining floatation-hydrometallurgical technology of the nonferrous metals recovery.

Jan 1, 2014

By M. H. Moys, M. M. Bwalya

"INTRODUCTIONThe grinding rate prediction scheme makes use of the energy spectra output from the DEM simulations and the statistical quantification of material strength, which can be done using the drop-weight tester or some other similar equipment. The prediction scheme is evaluated using milling experiments performed under well-defined conditions.MATERIAL STRENGTH QUANTIFICATIONUsing the drop weight test machine, particles of a wide size range were broken singly using different energy inputs. A characteristic equation key to milling rate prediction that relates the probability of fracture with energy input and number of impact attempts was obtained and is stated as follows:"

Jan 1, 2003

By Y. Q. He

The methodology of active pulsing air separation is a new method for dry material classification. Especially, it is suitable to electronic scraps disposal and re-utilization. By studying the difference of drag coefficients of the particles moving through areas of varying Reynolds numbers, and considering the extra-mass forces acting on the particles in the active pulsing air field, models of the dynamic motion which particles follow were developed. A computer simulation was prepared that showed the traces of particles with different densities and/or diameters, but similar aerodynamic characteristics, as they moved through the turbulent flow, to modify and define the parameters of the models. The simulation was found to predict the observed results with artificial tracing spheres being separated by the laboratory equipment. The separation performance, as being affected by the particles, nature, the air velocity, the pulsing frequency and the air pattern, is discussed. In general, lower density particles are more responsive to variations in airflow velocity. In addition, an industrial scale active pulsing air separator was designed, and it provides a new and efficient method for resource re-utilization in China.

Jan 1, 2014

By Wolfgang Öfner

Many technical processes also yield dusty residues which usually contain appreciable amounts of valuable matter. Often they also accumulate substances detrimental to the process. Dumping them entirely in landfills wastes raw material and causes high disposal costs, but recycling them without prior treatment is often not feasible. Physical separation processes are preferable because of their rather low energy demand. In order to develop such treatment systematically, the residues must be characterized properly. The technique for such a characterization is taken from mineral processing: perfect fractionation according to continuous properties of the particles supplemented with chemical analysis are used for plotting the Henry-Reinhardt chart. This represents the benchmark for assessing actual separation processes and tests. Their results are compared in terms of ?selectivity? and plotted in the kappa chart. In this paper, Henry-Reinhardt chart and kappa chart are applied to several different types of residues from iron and steel production and show their potential for being upgraded before reutilization in the production process. This approach is suitable for virtually all dusty residues from other industrial processes as well. Keywords: residue, dust,iron and steel, process development, Henry-Reinhardt chart, kappa chart

Sep 1, 2012

By Thomas Mütze, Petya Atanasova, Kai Bachmann, Urs A. Peuker, Thomas Leißner

"A method is presented for the evaluation of mineral processing by liberation and upgrading. The method bases on the plot of recovery of valuables versus the recovery of gangue (Fuerstenau upgrading curve). The locking curve of a feed material was plotted together with the upgrading curve in a Fuerstenau diagram. The assessment of liberation and upgrading is done by a comparison of surfaces formed by the curves and some characteristic lines of the diagram. This plot allows the calculation of two new quantitative measures for liberation and upgrading. Both parameters can be combined to a third parameter describing the quality of the whole technical setup for mineral processing by subtracting the upgrading parameter from the liberation parameter. The third parameter shows a positive value in cases of upgrading determined processes, a negative value in cases of liberation affected processes and about zero for processes affected equally by liberation and upgrading. Thus it is easily possible to distinguish between poor results in the mineral processing caused by insufficient liberation or poor results caused by insufficient upgrading. Preliminary results from two case studies, performed on two different ore types, are very promising illustrating the practical use of such an approach."

Jan 1, 2014

By J. D. Miller, C. L. Lin

In general, x-ray computed tomographic (CT) techniques are able to provide 3D images of the internal structure of opaque materials in a nondestructive manner. The unique cone beam geometry allows acquisition of all 2D projections with only one rotation of the sample thus providing for fast data acquisition and better x-ray utilization, as a complete 2-D detector array receives the cone-shaped flux of rays. Thus, an isotropic 3D volume can be reconstructed without the mechanical translation and the stacking of sequential slices as is the case for more conventional CT scanners. In this regard, a state-of-theart, custom designed x-ray microtomography facility to provide very detailed 3D spatial analysis of multiphase particles has been installed and is in operation at the University of Utah. The reconstructed 3D tomographic volume allows for an adjustable spatial resolution from 5 to 20 microns for sample dimensions from 10 to 40 mm in diameter, respectively. For example, a packed bed of coal particles is shown below in which different crystalline froms of pyrite are distinguished in 3D.

Jan 1, 2003

By H. Gallardo, J. Yianatos

Flotation is a separation process in which mineral recovery depends on the particle surface properties. The selective collection of particles by air bubbles requires hydrophobic mineral surfaces. Hydrophobicity can be selectively induced on a valuable mineral surface by means of reagents. For this purpose, it is required that mineral grains in the ore become physically liberated or exposed in the particle surface after grinding. The grinding process generates three types of particles according their exposed surface in the floatable mineral: locked particles (0-10%), associated particles (10-90%) and liberated particles (90-100%). Locked particles have low floatability, and they typically show low recovery (<20%), while liberated particles have a high floatability and can be easily recovered (98-100%) at different particle sizes (10-150 µm). The main challenge in the flotation process is the recovery of associated particles. These particles typically have recoveries of 20-80%, but strongly depend on the particle size, particle surface liberation and collector dosage. Recent studies on particle floatability by size-liberation have significantly contributed to improving the characterization of flotation processes. In this work, a study of flotation recovery of associated particles of 10-90% liberation is presented for particle sizes (10-150 µm) and collector dosages (5-40 g/ton). In this work historical data on galena recovery based on particle cross-section composition of galena was used, assuming they represent an acceptable estimate of particle surface composition, as shown by some previous researchers. The results showed that galena recovery can be well represented by a model consisting of the interaction of a linear function and a Gamma distribution function to account for the liberation and the particle size effects. Consequently, an alternative approach for modelling the recovery of associated mineral (10-90% liberation), with a reduced number of parameters, was developed and validated.

Jan 1, 2018

By B. Rath

An effective process plan is an important part of maintaining consistent recoveries in mineral processing operations. Traditionally, Mineralogical studies are completed using chemical and metallurgical methods to monitor recovery and elemental distribution. The development of mineralogy and more efficient processes in mineral analysis techniques means that mineralogy is now more accessible as an efficient and comprehensive study tool. As operating costs increase and feed grades decrease it is important to maintain tight control of process and ensured maximum recovery is maintained at all times. Just a few days of losses in recovery caused by changes in ore type or processing conditions can have a large effect on total metal recovery and profit. Mineralogical audits can be used to minimize these losses by monitoring the fundamental behavior of feed ore on a regular basis. Smart use of mineralogical studies can develop mineralogical and ore type benchmarks in a detailed, which can be used in process control and monitoring. Geological ore types can be used to identify key mineralogical parameters that may be used in routine and cost effective analysis. Mineralogical systems ideally suited to this because of the depth of information on everything from modal mineralogy to locking/liberation characteristics and mineral associations. Mineralogical studies can equally be applied to specific unit operations within the process, which can allow more detailed information to be gathered on areas of the process that have been identified as critical. This will be especially effective for flotation or oxidation processes where process parameters can be very sensitive to small changes in mineralogy. This paper deals with the Ore Morphology, Ore Mineralogy, Gangue mineralogy, Photo micrographs under reflected, transmitted light and XRD studies Ore, Mineral studies of Sub grade Iron ore of Bacheli Complex, Bailadila Sector, India. Keywords: mineralogy, liberation, liberation studies, ore mineral, gangue mineral, morphology, jasper, ferruginous clay

Sep 1, 2012

By Yong Liu, Peng Qian, Shu-Feng Ye, Shao-Jun Chu, Pei-Wei Han

"Chromite with a low mass ratio of Cr to Fe (Cr/Fe ratio) was treated by the carbochlorination method using solid chlorinating agent (MgCl2 and CaCl2) and carbon in the present paper. The results showed that iron could be selective removed mainly in the form of FeCl2. The removal of iron was indirectly, which consisted of the decomposition of solid chlorinating agent to release Cl2/HCl and the carbochlorination of FeO•Cr2O3 by Cl2/HCl and C. The Cr/Fe ratio increased as increasing temperature from 700 ? to 900 ? in air atmosphere, while the tendency was opposite in N2 atmosphere. The removal efficiency of iron by CaCl2 was better than that by MgCl2. At last, a new pelletizing process was proposed to treat fine chromite with a low Cr/Fe ratio based on carbochlorination method, which could produce the high quality roasted chromite pellets with higher Cr/Fe ratio and compressive strength. INTRODUCTION Chromite is mainly used for the production of ferrochromium. A high Cr/Fe ratio (>2) of chromite is usually required to meet the technical specification of ferrochromium.(Gasik, 2013) Attentions have been attracted to the economic and efficient methods for the recovery of chromium from lower-grade ores as the higher-grade ores become depleted. However, the Cr/Fe ratio is difficult to improve through the conventional beneficiation methods (such as gravity concentration, flotation) due to the spinel composition, although beneficiation methods could increase the metal content of chromite ores by removing gangues.(Nafziger, 1982) The main industrial mineral of chromite is (Fe,Mg)O•(Cr,Al,Fe)2O3, which belongs to spinel magnetite.(Liu, 2013) Iron should be selectively removed through the structural dissociation of spinel to increase Cr/Fe ratio.(Nafziger, 1982)"

Jan 1, 2018

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 David I. Verrelli, Boris Albijanic

"Froth flotation is an exceedingly complex physicochemical process. The convenience of distilling much of the complexity of the bubble-particle interactions into a single parameter has led to the continuing popularity of the classical ‘induction time’ to quantify the threshold for bubble-particle attachment to occur. Despite this popularity and the simplicity of the concept, there is no single universal method of evaluating the induction period. In this paper, we begin with a critical review of the available techniques for estimating the induction period. These are: back-calculation from experimental (micro) flotation tests; pushing a particle toward a stationary bubble (or vice versa) using an atomic force microscope (AFM); pushing a bubble toward a stationary bed of particles in the ‘Induction Timer’; pushing a bubble toward a stationary solid surface using the ‘integrated thin film drainage apparatus’ (ITFDA); and dropping particles onto a submerged stationary bubble using the ‘Milli-Timer’ device. Each one of these methods has advantages and disadvantages, and the best choice depends on the application. In the experimental section, we present quantitative comparison of the induction periods estimated using two different techniques, namely the Induction Timer and the Milli-Timer. The same particles were tested in each device, under the same conditions. It was found that by tuning the operation of the particle pick-up device, similar estimates of induction period could be obtained to the estimates made by direct observation with the Milli-Timer. In the former device a bubble is driven toward a particle bed at a controlled rate, whereas in the latter a particle’s motion is governed by the hydrodynamics. The potential to match these presents an intriguing prospect for better understanding the bubble-particle interaction, and the possibility to ‘calibrate’ the simpler Induction Timer against direct observations."

Jan 1, 2014

By Kazimierz Trybalski

"Simulation methods have a big potential in the studies and analyses of complex technological processes and schemes. The simulation method used jointly with flow diagrams and related transmittance models allows describing and analysing dynamic characteristics.The paper presents results of simulation analysis of dynamic characteristics of ore dressing system, called closed circuit mill-classifier-mill. Such systems are widely used in ore processing plants. The system was analysed as a typical system with material feedback, to establish its dynamic characteristics.Flow diagram conforming to the technological scheme is presented in a figure. Transmittances shown in the scheme are defined as follows:GMP - transmittance of rod mill,GP, KZ, GW, KZ - transmittances of overflow and underflow streams of spiral classifier, respectively,GMK - transmittance of ball mill,GT - transmittance of underflow stream from classifier to ball mill,GU, MP, GU, MK - fraction transmittance of outflow streams of rod and ball mill, respectively, summed up at classifier input.Taking into account, in base of carried out analysis the transmittance forms of individual system elements. The calculations are based on numeral forms of transmittances of individual blocks, defined through industrial experimentation.Step input function to rod mill was assumed to be a step of mass ore flow rate to the mill. Responses are defined as product densities.This figure demonstrates the way of input signal transmission by consecutive elements of the system and shape of these elements' responses. It can be noticed that step signal undergoes gradual change from the stream of the first order to those of higher and higher orders as a distance from process leading edge increases. Simultaneously, the impulse signal is subject to systematic smoothing and decay. From the technological point of view, the most important is response stream in point 5 (on the above figure) that characterises classifier overflow, which is a final product of this system."

Jan 1, 2003