Ore Grinding Research Articles

Grinding Kinetics Adjustment of Copper Ore Grinding in an Innovative Electromagnetic Mill

The paper presents a study on the effectiveness of the grinding process in an electromagnetic mill devoted to ultrafine grinding, and the influence of processing parameters on the mill’s performance. The research was focused on the optimization of the duration of the grinding process and selection of the grinding media type in order to obtain the highest relative increase of the selected particle size fraction. Copper ore with a particle size between 0–1 mm was used in the experiments. A model was created that determines the relationship between the processing time and efficiency of the grinding, and can be used for the optimization of the process. A comparison of the relative growth of particle size fractions in milling products was performed. The obtained milling efficiency results measured by the growth of the analyzed particle size fraction in the milling product confirmed that the best grinding media set includes a grinding medium with a diameter of 1 mm and a length of 10 mm.

Theoretical study of the system stabilization of the amplifier properties of the radio channel for units with rotating parts

Automation of ore grinding control is restrain due to the lack of sufficiently accurate systems for transferring information from rotating parts of aggregates to stationary ones. The aim of the work is a theoretical study of the system stabilization of the radio channel reinforcement properties. The work solves the problems of theoretical investigation of the stabilization of the radio channel reinforcement properties, the rationale for the radio transmitter, the radio receiving system and the automatic regulator of the amplification mode. Methods of analysis, studies of radio transmitting and radio receiving devices, discrete control systems, theory of automatic control, digital systems were used. As a result of theoretical studies it was established that the frequency stability of the radio channel is high, and the amplitude stability is low. In this radio channel, the amplitude stability takes the first problem place, which has not been solved in radio engineering yet. It is proved that the amplitude stability can be increased to the required values by setting the preset value of the radio channel gain. The gain is set by applying the reference signal and automatically adjusting in the low-frequency amplifier of the receiver by a digital controller with a relatively low error of ± 1 %. The functional nodes of the radio channel are controlled by a cyclic system. For the first time, a radio channel was created for transmitting signals from rotating parts of aggregates to fixed ones, in which high amplitude stability is achieved. An experimental verification established almost complete coincidence of the parameters of the random process at the input and output of the radio channel. The dispersion of the signals at the modulator input and the output of the radio channel, respectively, amounted to 1.8585 and 1.8489 units, the number of positive emissions for the zero level is 4, and spectral densities occupy the range from 50 to 250 Hz.

Prediction model to estimate the specific energy and product particle size distribution of semi-autogenous mill

The optimal use of energy for grinding of ores in mills is one of the key objectives of this study. An attempt has been made to present an experimental model for the specific energy and product particle size distribution of semi-autogenous mills for the simulating of real conditions of the particles collision. A novel semi-autogenous mill test has been suggested in order to measure the required energy for grinding. The effect of the mill’s operation time and various energy levels on the particle size distribution and feed ore hardness has been investigated with samples collected from the Sarcheshmeh Copper Complex, Kerman, Iran. The obtained results demonstrated that there is a high congruence between the experimental product particle size distribution and energy, which are predicted by the proposed novel method and ball-drop test. Using the proposed analytic relationships, the required comminution energy and semi-autogenous mill operating time to achieve the specific product particle size distribution can be estimated with high accuracy ( R2 = 0.96). Finally, the accuracy of the results was evaluated by a ball drop-weight test.

Comparative Analysis of Autogenous and Media Assisted Grindability of a Copper and Manganese Ores

This paper presents a comparative analysis of autogenous and media assisted grinding of a manganese ore and copper ore both obtained from Otjihase in Namibia. The objective was to understand the relationship between ore properties and Grindability and thus effectively select comminution circuit and equipment based on this relationship. Laboratory studies were carried out to determine the ease of grinding the ore samples relative to one another. The sample of known weight was crushed and the particles thoroughly homogenized for sieve size analysis and Grindability tests. The Grindability test on each ore was both autogenous and media assisted for dry grinding at -250 microns with constant mill charge of 200 g per run, media charge of 40% by weight and mill operations of 100 to 500 revolutions corresponding to mill speeds of 5 to 25 rpm. The Grindability index of each ore was calculated and compared based on the tests results and used to calculate work indexes for the ores based on the Bond’s model. The autogenous tests produced average Grindability values of 0.55 kg/ton/rev and 0.65 kg/ton/rev for the copper and manganese ores respectively; and media assisted tests gave average values of 0.8 kg/ton/rev and 1.45 kg/ton/rev respectively for the copper and manganese ores. The results show that although media charge grinding produced higher Grindability values, both ores are economically amenable to autogenous grinding which suggests that with proper circuit design, the use of autogenous grinding for these ores (especially the manganese) can save significant cost. The results also show that Grindability increases with mill speed up to an optimum value beyond which grindability decreases with increasing speed and may even drop to zero while mill is running. It is also observed that grindability has close relationship with ore properties especially hardness and compressive strength. It should be noted that the inefficiency factors for the grinding are not considered in these results.

Hybrid non-linear model predictive control of a run-of-mine ore grinding mill circuit

A hybrid non-linear model predictive controller (HNMPC) is developed for a run-of-mine ore grinding mill circuit. A continuous-time grinding mill circuit model is presented with a hydrocyclone cluster as the primary classifier. The discrete-time component is the switching of hydrocyclones in the hydrocyclone cluster. The resulting model is a hybrid non-linear model with both continuous and discrete dynamics. A simulation of the HNMPC shows the advantages of using the hydrocyclone cluster as an additional manipulated variable. The advantages of the HNMPC is illustrated by comparing its performance to a non-linear MPC where no switching of hydrocyclones is possible. The genetic algorithm based HNMPC showed increased controller stability in its ability to incorporate discrete dynamics into the controller directly. The methods discussed in this paper can be used to incorporate different types of discrete dynamics into advanced grinding mill circuit controllers due to the modular presentation of the model and HNMPC controller design.

Comparison of Wet and Dry Grinding in Electromagnetic Mill

Comparison of dry and wet grinding process in an electromagnetic mill is presented in this paper. The research was conducted in a batch copper ore grinding. Batch mode allows for precise parametrization and constant repetitive conditions of the experiments. The following key aspects were tested: processing time, feed size, size of the grinding media, mass of the material and graining media, and density of the pulp. The particles size distribution of the product samples was analyzed in the laboratory after each experiment. The paper discusses the experimental results as well as the concept of dry and wet grinding and classification circuits for the electromagnetic mill. The main points of the discussion are the size reduction effectiveness and power consumption of the entire system.

Selective Desintegration and Concentration: Theory and Practice

Investigations on the possibility of selective grinding and benefication of quartz-pecoraite ores of the Ufaleiskoye deposit have been carried out. Methods of computer X-ray microtomography have been used to study the morphometric features and pore volume parameters of samples, and these data was compared with results of quantitative microstructural analysis. The performed research shows the powerful capabilities of X-ray computer microtomography method for solving scientific and practical problems related to the study of physical and mechanical properties of rocks, the determination of ore minerals liberation, the evaluation of their content, the analysis of the granulometric composition and the spatial distribution of their grains. Analysis of mineralogical and geochemical composition of ores showed that these ores meet the criteria for selective disintegration. An analysis of flotation experiments results showed that when material is grinded in a roll mill, the consumption of reagents is 25% lower than when grinding in a ball mill if the same degree of nickel extraction is achieved.

Reengineering of the ore preparation production process in the context of “Almalyk MMC” JSC

The review of ore crushing and grinding processes at the mining-and-processing enterprise is presented. An alternative to the standard technology of crushing ore in cone crushers is proposed after a comparative analysis of ore grinding processes.

Experimental Study on the Effect of Pretreatment with High-Voltage Electrical Pulses on Mineral Liberation and Separation of Magnetite Ore

High-voltage electrical pulses (HVEP) technology was applied in grinding of a magnetite ore as a comminution pretreatment. The effect of HVEP pretreatment on grindability, liberation and separation performance of a magnetite ore was investigated by a systematic experimental study. The results showed that the pretreatment of high-voltage electrical pulses created some intergranular microcracks inside the ore, reduced the mechanical strength and improved liberation. This gave the additional advantage of further breakage,thereby reducing the energy consumption and grinding time. In addition, the HVEP pretreatment before grinding was potentially beneficial in the recovery of the liberated minerals in the subsequent magnetic separation.

Influence of grinding media and water quality on flotation performance of gold bearing pyrite

Flotation performance is strongly dependent on the surface properties of the constituent mineral particles, and may therefore serve as a diagnostic tool to evaluate grinding chemistry interactions. The surface properties can be altered by numerous factors such as the type of grinding media used in the preparation of the flotation feed, the presence of chemical species in the process water, and the characteristics of flotation reagents added. This paper investigates the influence of grinding media (forged steel, 18% chromium and ceramic) and water quality (tap water and synthetic process water) on floatability of gold bearing pyrite using XPS and EDTA extraction technique. The grinding of pyrite ore was performed in a Magotteaux Mill® which allowed better simulation of plant chemical conditions by controlling pH and pulp potential during the grinding. Cupric ions were added as an activator prior to the grinding. This work demonstrated that there is no significant effect of water quality on flotation performance of pyrite. The results also showed that the pyrite recovery was slightly higher when the grinding was performed with the forged steel media rather than with the chromium media or the ceramic media. XPS and EDTA extraction technique demonstrated that the forged steel media produced more iron hydroxide species than the 18% chromium or the ceramic media, indicating the high corrosion rate of the forged media. XPS technique failed to explain the influence of different grinding media on the floatability of pyrite from its ore probably due to the insensitivity of XPS technique to detect the presence of a low amount of copper species on the surface of the particles collected by flotation. The results obtained from this study confirmed that the selection of grinding media may be important to maximize pyrite recovery by flotation. The conclusions should be limited to ores low (<2%) in pyrite content, and where there are no reactive sulfides present other than pyrite. From an economic perspective, the marginal impacts on flotation should be balanced against grinding media wear.

Characterization of the Gold Ore to Acquire an Optimum Degree of Liberation

Gold ore processing is often ineffective in obtaining gold metal. Various methods have been successfully developed on an industrial scale, but small-scale gold mines are often problematic. The problem of inefficiency of processing is caused by gold ore characterization and evaluation of gold ore preparation process is not implemented. In this study, the conditions of gold ore deposits have a thin thickness (vein). These gold ore deposits have an economic value if they are developed by traditional gold mining. The objective of the research is to identify and characterize gold ore as well as to analyze the optimum condition to obtain the perfect gold mineral liberation degree. Research methods include characterization of gold ore geology, sampling for test preparation using rod mill (amalgamation), gold mineral liberation using time variables and number of rods. After the grinding process, grain size analysis is performed with various mesh sizes, and the analysis of each fraction uses a polarization microscope. The results show that goldore minerals are associated with pyrite, chalcopyrite, galena and gangue minerals. Gold minerals are fully liberated at a certain size. The results of this research are very useful for the gold ore grinding process to obtain an efficient gold processing

Effect of design and operational parameters on particle morphology in ball mills

Different factors involving in grinding of ore cause various breakage mechanisms. These different mechanisms differ the morphology of ground particles. In this study, the effect of ball mill types, feed sizes, and ball surface area have been investigated on the morphology of ground quartz particles using MBL cruise optical microscope and Olympus E-510 camera. Measured two-dimensional particle projection was expressed mathematically such as circularity, roundness and aspect ratio by ImageJ software. >20,000 particles were morphologically measured for image analysis. Results show that circularity and roundness of ground particles are enhanced in an ordinary ball mill equipped with smooth liner (OBM). While higher aspect ratio of ground particles are achieved in cylindrical ball mill equipped with wavy liner (CBM). Consequently, the dominant breakage mechanism for OBM and CBM are abrasion and impact, respectively. Circularity and roundness values of coarse-grained ground particles are more than fine-grained particles. The increase of ball surface area causes the increase of circularity as well as roundness values and the decrease of aspect ratio value.

Improvement of Gold Leaching from a Refractory Gold Concentrate Calcine by Separate Pretreatment of Coarse and Fine Size Fractions

A total gold extraction of 70.2% could only be reached via direct cyanidation from a refractory As-, S- and C-bearing gold concentrate calcine, and the gold extraction varied noticeably with different size fractions. The reasons for unsatisfactory gold extraction from the calcine were studied through analyses of chemical composition, chemical phase and SEM-EDS of different sizes of particles. It was found that a significant segregation of compositions occurred during the grinding of gold ore before flotation. As a result, for the calcine obtained after oxidative roasting, the encapsulation of gold by iron oxides was easily engendered in finer particles, whilst in coarser particles the gold encapsulation by silicates was inclined to occur likely due to melted silicates blocking the porosity of particles. The improvement of gold leaching from different size fractions was further investigated through pretreatments with alkali washing, acid pickling or sulfuric acid curing-water leaching. Finally, a novel process was recommended and the total gold extraction from the calcine could be increased substantially to 93.6% by the purposeful pretreatment with alkali washing for the relatively coarse size fraction (+37 μm) and sulfuric acid curing–water leaching for the fine size fraction (−37 μm).

Study on New Desilication Technology of High Silica Bauxite

There are abundant diasporic bauxite resource in China. The gravity separation and flotation process are utilized for treating this kind of ore. When the ore grinding fineness is -200 mesh 80%, the qualified bauxite concentrate can be obtained, and it contains Al2O3 71.62%, SiO2 8.94%, and its Al2O3 recovery rate is 75.43%, A/S is 8.02.Compared with single flotation process, it can be reduced for the dosage flotation reagent and the cost of mineral processing.

TECHNIQUE AND TECHOLOGY OF RARE-METAL ORES DESINTEGRATION AND GRAVITY-BASED BENEFICATION

On the base of the analysis of centrifugal concentrators designs there has been justified the selection of apparatus for the rare-metal ores benefication. Process of pyrochlore ore grinding in mills of different types has been investigated and the expediency of use of impact-centrifugal action mills to ensure selectivity of minirals disclosure has been founded. Efficient technical and technological parameters of the centrifugal action mills have been justified on the base of active experimental method. The influence of disintegration metheds on technologival indication of rare-metal ore benefication of Mazurovske deposits in centrifugal Nelson concentrator has been analyzed.

Effect of Microwave Pretreatment on Grinding of Iron Ore

Effect of Microwave Pretreatment on Grinding of Iron Ore

Analysis of a grinding efficiency in the electromagnetic mill for variable process and feed parameters

Article describes issues related to the assessment of raw materials grinding efficiency in an electromagnetic mill. Application of such type of mill in grinding processes can result in measurable benefits of more efficient raw material grinding by reducing time needed to produce a product of a suitable particle size compared to conventional mills. The expected effect of application of a system based on an electromagnetic mill is to achieve a lower energy consumption of grinding process for raw material processing compared to the existing equipment used for the fine grinding. A key element of correct design of comminution circuits in processing of particular feed mineral is to identify the impact of key factors affecting the efficiency of the grinding process. The most important factors determining the efficiency of the grinding process are the time, the construction parameters of the machine, the type of grinding media used in grinding process, as well as the parameters of the feed, among others the crushing resistance or particle size. The paper presents the results of kinetic study of copper ore grinding in electromagnetic mill for variable feed particle size distribution of and different sizes of grinding media.

Analysis of a grinding efficiency in the electromagnetic mill for variable process and feed parameters

Article describes issues related to the assessment of raw materials grinding efficiency in an electromagnetic mill. Application of such type of mill in grinding processes can result in measurable benefits of more efficient raw material grinding by reducing time needed to produce a product of a suitable particle size compared to conventional mills. The expected effect of application of a system based on an electromagnetic mill is to achieve a lower energy consumption of grinding process for raw material processing compared to the existing equipment used for the fine grinding. A key element of correct design of comminution circuits in processing of particular feed mineral is to identify the impact of key factors affecting the efficiency of the grinding process. The most important factors determining the efficiency of the grinding process are the time, the construction parameters of the machine, the type of grinding media used in grinding process, as well as the parameters of the feed, among others the crushing resistance or particle size. The paper presents the results of kinetic study of copper ore grinding in electromagnetic mill for variable feed particle size distribution of and different sizes of grinding media.

Galena and sphalerite liberation in lead-zinc ore grinding

Galena and sphalerite liberation in lead-zinc ore grinding

Operational parameters affecting the vertical roller mill performance

Vertical roller mills (VRM) have found applications mostly in cement grinding operations where they were used in raw meal and finish grinding stages and in power plants for coal grinding. The mill combines crushing, grinding, classification and if necessary drying operations in one unit and enables to decrease number of equipment in grinding circuits. Sustainable operations and proven benefits of the technology in cement grinding applications attracted interests of the mineral industry. Within the scope of the study, ore grinding performance of the VRM was investigated via a mobile grinding plant and relationships between operational parameters were identified. In this context, gold ore was ground under different process conditions. The samples collected after the test works and size distributions were determined. As a result of the study, effects of operational parameters such as working pressure, and classifier rotor speed on product mass flow and product size were investigated. In addition, correlations of specific energy consumption of the grinding-classifying circuit with product rate and product size are presented. The aim was to develop a VRM performance prediction model that is based on input data from characterization combined with the knowledge of the interaction of the single grinding parameters.