Ore Grinding Research Articles

Improvement of concentrate quality by using fine screening in iron ore grinding stages

Improvement of concentrate quality by using fine screening in iron ore grinding stages

Machine learning in chemical engineering: Hands-on activities

A set of hands-on activities, that were proposed in an introduction course to machine learning in a Chemical Engineering undergraduate course, are presented. The activities aimed to introduce basic concepts of unsupervised learning (e.g., clustering) and supervised learning (e.g., classification and regression). Google Colaboratory, a cloud service provided by Google for free to promote research in Artificial Intelligence and Machine Learning, was used to develop these activities, but the proposed activities can be run similarly in a local Python environment. The datasets used in the activities are publicly available on websites such as Kaggle and University of California (UCI), and a specific example in chemical engineering for the ore grinding process was also used. The student's response to the ML topic within the course was very positive.

Parameters evaluation in the process of solid phase pulp sedimentation in technological units of beneficiation plants

The aim of the research is the analysis and modeling of the process of sedimentation of the solid phase of the pulp in the technological units of processing plants to assess the density of particles of crushed ore. The paper analyzes domestic and foreign experience; methods of mathematical modeling were used, as well as methods of mathematical statistics and probability theory for processing the results of experiments. Scientific novelty consists in developing and substantiating a method for estimating the density of crushed ore particles in the process of their sedimentation directly in the process units of beneficiation plants. Practical value consists in developing a methodology for determining the characteristics of the enriched raw materials, which make it possible to form the degree of grinding necessary for the full disclosure of mineral formations. It was proposed to use the density of ore particles as an indicator of changes in the quality characteristics of the ore received for beneficiation, which is determined on the basis of measurements of the attenuation of volumetric ultrasonic waves and Lamb waves propagating in the pulp and the wall of the technological sump that is in contact with it. These measurements must be synchronized with the results of measurements of the pulp level in the sump during its working operation. The proposed method makes it possible to dynamically correct the parameters of the model of a closed ore grinding cycle, depending on the quality characteristics of the feedstock, and thereby form the conditions for the full disclosure of inclusions of the useful component in the product entering the magnetic separation or flotation.

EFFICIENT USE OF ELECTRIC ENERGY WHEN OPERATING A BALL MILL WITH A CONSTANT ROTATION SPEED

Link for citation: Zakamaldin A.A., Perevoshchikov F.V., Shilin A.A. Efficient use of electric energy when operating a ball mill with a constant rotation speed. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 115-127. In Rus. The relevance. Ball mills are widely used in industry for grinding bulk materials, as well as in the last stages of ore crushing, where the required optimal particle sizes are achieved for enrichment. Although ball mills have a relatively simple design and cover extensive research, the industry is still struggling with the very low energy efficiency of the grinding process. As the retrofitting heavy equipment is the costliest approach, process optimization through control system is the most suitable for energy consumption reduction. As a rule, the feed rate is the main control variable for a mill with a constant rotation speed. Due to insufficient information content, outdated methods of analysis and control of the internal dynamics of the mill, control systems keep the target value of feed rate at a deliberately low level in order not to overload the mill. This article provides an explanation of how, in such a case, an increase in mill feed rate could affect the energy efficiency of grinding. The main aim: study of energy efficient modes of operation of stations; verification of models and confirmation of experimental data: the relationship between door loading and power consumption indicators; construction of buildings for energy efficient control of ball towers. Objects: the process of grinding in a ball tower with a constant rotation speed. Methods: mathematical description of the behavior of the electromechanical part of a machine that consumes current and works on a load in the form of spherical furniture; simulation modeling of the operation of the door electric drive; statistical analysis of production indicators. Results. The paper demonstrate the tendency to increase electricity consumption with a decrease in feed rate and vice versa, respectively for ball mills with a synchronous drive of 2500 kW based on modeling and experimental data. Increase in feed rate in the range of 10–40 t/h, there is a drop in active power by 0,48–1,57 %. The values of the specific power consumption of ~5–8 kWh/t during the grinding of apatite ore were obtained. An increase in productivity by 5 t/h on average leads to a decrease in the specific power consumption by 0,12 kWh/t. It is necessary to increase productivity in the operation of ball mills only after integrating measuring instruments into the control system of the mill, which allow an accurate assessment of the state of loading of the mill drum.

Technological studies of gold ore using centrifugal concentration methods

Relevance. Te use of gravitational enrichment methods, in particular centrifugal concentration, is based upon the presence in gold-bearing ore, along with fnely disseminated free coarse gold, which is not fully recovered in the process of cyanidation and fotation. Te purpose of the work is to conduct technological research on the centrifugal concentration of gold-bearing raw materials in order to assess its applicability in the production process. Te main objectives of the study were: studying the material composition of the sample, conducting tests to determine the gravity recoverable gold (GRG test), as well as tests using a centrifugal concentrator with continuous concentrate discharge (CVD test). Object of study. Te paper presents the results of studies of the enrichability of gold-bearing ore using centrifugal concentration methods. For research, a sample weighing 160 kg, with a size of –100 mm was taken. According to the phase analysis data, when the ore was ground to a fneness of 94,8% of the –0,071 mm class, the amount of free gold was 66%. Te rest of the gold in the amount of 33.9% is found in intergrowths and flms, including closed intergrowths with sulfdes (4,06%) and quartz (3,7%). Based on the results of the research, conclusions were made about the properties of the ore of the deposit and the optimal conditions for its processing (grinding size, concentrate yield) were determined by gravity methods. It has been established that the studied ore is efectively enriched by gravity methods. Centrifugal separation at an intermediate size of 64,6% class –0,071 mm with a low concentrate yield works efciently. A concentrate with a gold content of 432,0 ppm was obtained with a yield of 0,07% and a recovery of 32,04%. Te level of gold recovery by gravity with staged ore grinding (GRG test) is quite high – 53,97%. Te optimal yield of gravity concentrate during enrichment at the KC-CVD concentrator was 10,55%. With this yield, gold recovery was 82,28% at a grade of 7,77 ppm.

A research of the effect of an underwater electric explosion on the selectivity of destruction of quartz raw materials

The work is devoted to the study of the effect of an electric explosion on the selectivity of the destruction of quartz raw materials. The object of the study is quartz ore of the Nadyrbay deposit of the Republic of Kazakhstan. An electrohydroimpulse plant for crushing and grinding quartz raw materials has been developed and assembled. Using the electrohydroimpulse method, the granulometric composition of quartz can be adjusted. This makes it possible to adjust the magnitude of the voltage in the discharge channel and time. In this technology, quartz ore processing was carried out with an increase in the discharge voltage of the storage from 14 kV to 25 kV, the length of the interelectrode distance from 8 to 12, the capacitance of the capacitor 0.5 µF, 0.75 µF and the processing time of 5 min. Using the electrohydroimpulse method, quartz ore particles with an initial fraction of 5 mm, 10 mm and 1 mm were crushed to 0.8. The results of the grinding of quartz raw materials with the influence of an underwater electric explosion in a liquid medium allowed us to determine the degree of grinding of the material. The obtained results can be used in the course of studying the characteristics of crushing and grinding of ores. In the food industry, quartz sand within 0.25–0.5 millimeters can be used as a filler to create filters for water purification, as well as products from oil, industrial effluents, etc. Particles ranging in size from 0.5 to 1 millimeter can be used for rough processing of metal, stone and glass. The structural and quantitative analysis of powdered quartzite samples was made using a scanning electron microscope and the stoichiometry of the elements was calculated

Effect of ore heterogeneity on the ball mill wear rate during a grinding process at gold mines of Saudi Arabia (KSA)

Purpose. The current research aims to study the effect of gold ore grinding on the wear rate of grinding balls. Methods. Six boulder rock samples were selected from some KSA mines; five core samples were taken from each of them to identify the mechanical properties (compressive strength, Young’s modulus, and Poisson’s ratio). These mechanical properties were applied to identify the hardness class of all 30 core samples. Five samples with different mechanical properties from the same boulder sample were milled to study the effect of the compressive strength difference and grinding time on wear rate. Then, six samples were taken from different regions with similar mechanical properties but different petrographic characteristics. They were also milled under the same grinding conditions to study the effect of the microscopic mineral composition on the wear rate. Findings. The results showed that the wear rate increased with the improving mechanical properties and with the increa-sing grinding time. On the other hand, the results based on different microscopic descriptions of the six samples showed that despite similar mechanical properties, the wear rates differed. Petrographic characteristics confirmed the presence of quartz in most of the samples as an associated mineral; it is likely that it has the greatest effect on the grinding ball wear. Originality. The paper proposes a method for investigating ore heterogeneity, which has a major impact on the wear rate during a grinding process, as well as on the reducing costs and improving efficiency of grinding media. Practical implications. The research emphasizes the importance of investigating variables (e.g. ore heterogeneity) other than ball size, grinding medium composition, and wet or dry grinding that have a substantial impact on grinding efficiency. The findings could be applied in feasibility studies to calculate and evaluate grinding costs versus grinding efficiency.

Influence of ore size on the production of micro-sized ore particles by high-pressure gas rapid unloading

Comminution of ore is a critical and energy-intensive process in mineral resource utilization. High-pressure gas rapid unloading (GRU) has emerged as a promising ore grinding technique, wherein high-pressure gas is injected into the ore and is unloaded at high speed to induce tensile failure inside the ore. Although the GRU is capable to achieve more efficient ore comminution with lower energy consumption compared to conventional methods, it is still in the early stages of development. The pulverization effect of different size ores is a crucial question needing to be revealed before the GRU industrial application. This study explores the impact of ore size on ore pulverization by GRU, using kaolin as an experimental material. Specifically, we discuss the following: 1. the impact of ore size on high-pressure gas infiltration, 2. the effect of infiltration time on ore pulverization, and 3. the effect of ore size on GRU-pulverized ore. The results indicate that the GRU pulverization method is highly applicable to kaolin, and different ore sizes have minimal effects on ore pulverization. Finally, we explain the insignificant size effect of GRU-pulverized ore by discussing the ore material length scale, deformation scale, and ore size. The conclusion may provide a basis for extending the GRU method from the experimental lab scale to a larger one. It may also provide a reference for applying GRU in kaolin comminution.

Optimization of Ball Mill Grinding of a Limestone-Type Brecciated Uranium Ore

Optimization of Ball Mill Grinding of a Limestone-Type Brecciated Uranium Ore

Combined microflotation effects in polymetallic ores beneficiation

Producing of heterogeneous concentrates with good recovery in the processing of polymetallic ores is a challenge. Many factors must be taken into account including ore grinding, reagent mode, water composition, pulp density and the volume of supplied bubbles when producing high-quality selective concentrates. Microbubbles smaller than 50 μm in size were produced based on the frother oxal T-92 at different concentrations using a generator. The most optimal number of microbubbles smaller than 50 µm was produced at a T-92 concentration of 0.5 g/dm3. Polymetallic ore of Kazakhstan deposit was used for flotation studies. The studies were conducted in the copper-lead rough concentrate producing cycle. Flotation active minerals chalcopyrite and galena pass into the foam product, while sphalerite and pyrite remain in the chamber product in this cycle. In this paper, the density of pulp (20, 30 and 50%) as one of the main factors that effects the selectivity of flotation is studied. The kinetics of ore flotation in the base mode and with the use of a microbubble generator has been studied at these densities. Test experiments have been performed at the optimum density. The use of a water–air microemulsion generator makes it possible to maintain the quality of the copper-lead concentrate and increase the extraction of copper into the rough concentrate by 7.41%, lead by 5.98%.

Statistical distributions for modeling mineral liberation

Using the algorithm and the results of laboratory studies on grinding of loparite ores from the Lovozero deposit in a ball and rod mill, simulation grinding models were designed based on the transformation of a discrete function of the density distribution of outputs of mineral particle size classes. The model’s adequacy was quantitatively analysed carried out by calculating the determination coefficient without taking into account the constant component of the distribution; for a qualitative assessment of the result the authors used the Cheddock scale. The authors studied the minerals disintegration at ball and rod grinding with the following verification of the proposed algorithm. To identify the distribution of loparite by size classes in the initial ore samples and in the samples obtained in the disintegration taking place at different productivity, the X-ray diffraction analysis and the combined (weight, optical and geometric) methods were used.

Studi pengaruh penggilingan kondisi kering dan basah terhadap kinetika dan karakteristik distribusi ukuran butir bijih sulfida kompleks galena sfalerit – Uji pendahuluan

Grinding is generally carried out in wet conditions, but issues regarding water conservation and high-water treatment costs encourage the application of grinding in dry conditions. Both produce products with certain characteristics that affect the success of the next process. Grinding of P100 6 mesh (3.36 mm) ore was performed using steel ball media with dry and wet grinding with 33.33% solids for 5, 10, 15, 20, 25, and 30 minutes. Particle size distribution of the grinding product was obtained from the wet sieving process and the -200 mesh (-75µm) ore particles were analyzed using a laser diffraction particle size analyzer. The Alyavdin grinding kinetics equation model was used to study the kinetics of ore grinding behavior and the particle size distribution and its characteristics consisting of uniformity index, size modulus and fractal dimension were studied using the logistic, Rosin-Rammler (RR) and Gates-Gaudin-Schuhmann (GGS) equation model. Equivalent particle size (EPS) and specific surface area (SSA) observations were carried out on the -200 mesh (-75µm) grinding product. Grinding in dry condition is more effective in reducing the size of complex galena-sphalerite sulphide ore, indicated by high grinding rate with the highest K value of 0,135/minute, high cummulative % undersize, low size modulus, high uniformity index, high fine particle and high SSA compared to wet grinding. Alyavdin's kinetics model can describe the grinding kinetics of galena sphalerite complex sulfide ore, while the particle size distribution follows the logistic equation model.

Assessment of effect of lining material on energy efficiency of starting up ball mills

The article presents the possibility of increasing the service life of mill lining. Special attention is paid to the use of rubber linings for mills. A mathematical model of the asynchronous motor of ore grinding mills has been developed, i.e., the moment of resistance is shock. A system of equations for a synchronous motor of a mill plant for the d and q axes is described. Based on mathematical modeling of mill plant operating modes, it was determined that the corrosion coating prolongs the mill's service life, and the transition time is reduced to 10%.

Control of ball mill operation depending on ball load and ore properties

Ball mills are used for the second stage of ore grinding in mining operations by proportioning ore piles. Controlling the operating conditions of ball mills is one of the key factors for optimal mill perform and high mill load turnover. One of the factors affecting the efficiency of the ball mill is the loading of the balls. Optimum distribution of ores according to the size of the mill, increasing the efficiency of the grinding process and reducing energy consumption are achieved. In addition, the ore properties are one of the important parameters for the optimal utilizing of the ball mill. Ore can have various properties, such as hardness, density, moisture content, etc., which can affect the ore’s productivity and grinding efficiency

The use of ethoxylated surfactants in flotation concentration of potash ores

This paper studies the use of ethoxylated surfactants (alkylphenols and alkylamines) as flotation collectors for water-insoluble silicatecarbonate impurities contained in potash ores, which form fine slime particles during ore grinding. The highest collector efficiency in flotation desliming of potash ores is achieved with 35 to 45 hydroxyethyl groups in the hydrocarbon radical of the collector. The paper studies the performance of cardanol polyethylene glycol ether, regarded as an alternative slime collector to oxyethylated alkylphenols and alkylamines (currently used at potash flotation plants). It has been shown that in the case of slime flotation in saturated solutions of potassium and sodium chlorides, both when using oxyethylated alkylamines and alkylphenols, as well as alkylcardanol, the best desliming performance is achieved when the hydrocarbon radical of the collector contains 40 ethylene oxide groups. Oxyethylated cardanol is a 100 % undissolved substance, non-flammable and highly soluble in water, with the melting point at around 45 °C. Studies using standard test objects of phyto- and zooplankton have established that the KE-40 flotation agent is not hazardous to the environment. This paper provides industrial use results for this new slime collector obtained in flotation concentration of sylvinite ores of the Verkhnekamskoe deposit. KE-40 enables efficient and selective flotation desliming of potash ores with different contents of water-insoluble silicate-carbonate and anhydrite impurities. It has been adopted for industrial use as an alternative slime collector by Uralkali PJSC.

Reduction of iron ore grinding stages through the use of fine screening in a closed cycle

The possibility of application of a two-stage grinding scheme with the use of fine screening in a closed cycle of the second stage instead of a three-stage scheme with hydrocyclones was studied. Under laboratory conditions, an assessment of the effect of the sieve openings size of the screens used in the second grinding stage on the performance of the production of titanomagnetite concentrate for agglomeration was made. The sizes of sieves are considered: 0.63; 0.315; 0.16 and 0.1 mm. Reduction of the sieve opening size from 0.63 to 0.1 mm leads to an increase in the iron content in the concentrate from 56.32 to 62.71 %. At the same time, the yield of the concentrate decreases from 19.75 to 16.65 % and the extraction of iron into the concentrate from 71.07 to 66.72 %. It is shown that the concentrate for agglomeration with iron content of 61% can be obtained using two stages of grinding. The size of the sieve openings of the screens of the second stage should not exceed 0.2 mm. The results obtained in laboratory and industrial conditions, when using 0.15 and 0.1 mm sieves, do not fundamentally differ. Before industrial testing of the new enrichment scheme, it is necessary to perform experimental simulation of the schemes in the laboratory. The two-stage grinding scheme using fine screening in the second stage can be used in the enrichment of titanomagnetite ore. This will reduce the cost of grinding ore. Reduction of the grinding stages leads to an increase in the size of the concentrate, so the scheme is applicable for the production of concentrate for agglomeration.

Occurrence Characteristics of Fine-Grained Pyrite in Coal and Its Scaling Effect on Flotation Desulfurization.

To explore the occurrence and distribution characteristics of fine-grained pyrites in coal and the effect of pyrite particle size on flotation efficiency, coal samples from Guizhou province and Shanxi province, China, were selected for pyrite morphology observation and sulfur content test before and after flotation desulfurization experiments with different coal particle sizes. Experimental results showed that the fine-grained fine pyrites in coal have various occurrence forms and complex connections with the coal matrix. The fragmentation process can change the distribution of pyrite content in coal. Flotation desulfurization experiments showed that the sum of pyrite content in the cleaned coal and middlings gradually became significantly higher in coal particles with size 15-37 μm compared with particle sizes 37-44 and 44-75 μm. The complex occurrence morphology and crystal structure of fine-grained pyrite make it difficult to be removed from the coal matrix by ore grinding during flotation. Fine-grained pyrite mainly occurs in the form of framboïdal pyrite, disseminated pyrite, and monomer pyrite with a size of 0.69-33.94 μm in the middlings and cleaned coal. Therefore, 37 μm is considered as the critical dimension for ore grinding to improve the effective flotation desulphurization efficiency in this study, and some more effective methods should be used to increase the desulfurization efficiency of fine-grained pyrite.

Monitoring of grinding condition in drum mills based on resulting shaft torque

Grinding is the most energy-intensive process among all stages of raw material preparation and determines the course of subsequent ore beneficiation stages. Level of electricity consumption is determined in accordance with load characteristics forming as a result of ore destruction in the mill. Mill drum speed is one of process variables due to which it is possible to control ore destruction mechanisms when choosing speed operation mode of adjustable electric mill drive. This study on increasing energy efficiency due to using mill electric drive is based on integrated modelling of process equipment – grinding process and electromechanic equipment – electric drive of grinding process. Evaluating load torque by means of its decomposition into a spectrum, mill condition is identified by changing signs of frequency components of torque spectrum; and when studying electromagnetic torque of electric drive, grinding process is monitored. Evaluation and selection of efficient operation mode of electric drive is based on the obtained spectrum of electromagnetic torque. Research results showed that with increasing mill drum speed – increasing impact energy, load torque values are comparable for the assigned simulation parameters. From the spectra obtained, it is possible to identify mill load condition – speed and fill level. This approach allows evaluating the impact of changes in process variables of grinding process on parameters of electromechanical system. Changing speed operation mode will increase grinding productivity by reducing the time of ore grinding and will not lead to growth of energy consumption. Integration of digital models of the technological process and automated electric drive system allows forming the basis for developing integrated methods of monitoring and evaluation of energy efficiency of the entire technological chain of ore beneficiation.

Role of reduced diameter disks in the performance of an IsaMill™

IsaMill™ is utilized mainly for ultrafine grinding of low-grade ores. Although highly efficient, it has certain operational challenges, such as frequent replacement of liners of disks and inner shells. To circumvent this challenge, a design modification of the disks, by introducing a reduced diameter disk (RDD), is commonly implemented. A discrete element method (DEM) based model is developed to investigate the effects of RDD and mill loading on media dynamics, force distribution, power draw, and collision energy. It is demonstrated that implementation of RDD results in a reduction of normal and shear stress on mill parts indicating a reduction in wear. Analysis of media dynamics shows that media mobility decreases hence decreasing total collision energy when RDDs are applied. This reduced mobility can potentially affect the grinding performance of the mill. A single-objective optimization approach based on collision energy data is employed to determine an optimal design configuration of the mill.

TECHNOLOGY FOR PROCESSING LOW-SULFIDE GOLD-QUARTZ ORE

Link for citation: Fedotov P.K., Senchenko A.E., Fedotov K.V., Burdonov A.E., Vlasova V.V. Technology for processing low-sulfide gold-quartz ore. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2022, vol. 333, no. 6, рр.178-189. In Rus.
 The relevance of the research is caused by the necessity to acquire new knowledge about the enrichment of gold-bearing ores and the need to develop the resource base of the Russian Federation, namely involve subsoil use objects in economic circulation. The purpose of the study is to study the processing of low-sulfide gold-quartz ore using an integrated technology for the enrichment of mineral raw materials. Object: gold ore raw materials with an average gold grade of 11,88 g/t. The silver content is negligible – 2,43 g/t. The main ore minerals in the sample are pyrite and pyrrhotite. The average content of these minerals in the ore, according to mineralogical and X-ray diffraction analysis, was about 6 % (in total). The main rock-forming minerals of the original ore are: quartz – 60,1 %; quartz-chlorite-mica aggregates – 3,8 %; carbonates – 7,1 %. Methods. The research methodology was based on the theoretical foundations of mineral processing. The study of the material composition of the ore, and enrichment products, was carried out using chemical, assay, thermal, spectrometric methods, as well as atomic emission spectrometry and other methods. The study of washability was carried out by the methods of gravity and flotation enrichment, namely: GRG test, stage test of the Institute TOMS (Russia) (determination of the optimal size of ore grinding and the number of enrichment stages), modeling of gold extraction in the grinding cycle, determination of the optimal degree of grinding, study of the choice of flotation reagents, study of the kinetics of the process and the implementation of a complex of technological studies. Results. It was found that the gold recovery when performing the GRG test was 72,75 % with a total concentrate yield of 1,34 % and a content of Au 664,78 g/t. At the same time, the gold content in the tailings was 3,29 g/t. A stage test showed that for ore processing only by gravity technology, it is advisable to use a two-stage scheme. The first stage is in the grinding cycle with the ore size of 60–70 % and the second stage – with the final size of the discharge of the classification 90 % size of –0,071 mm. Centrifugal separation, as a free gold recovery operation in a grinding cycle, works efficiently. A concentrate with a gold content of 2426 g/t was obtained with an output of 0,31 % and an extraction of 63,74 %. The enrichment of the first stage tailings crushed to 90 % size of –0,071 mm at the KC-CVD concentrator (modeling) made it possible to extract gold into a total gravity concentrate (KC-MD+KC-CVD) of 87,25 % with a concentrate yield of 22,63 %. The gold content in the tailings was 1,97 g/t. The results of gravity and flotation concentration of the original ore indicate the feasibility of using a combined gravity-flotation technological scheme. In a closed experiment of the initial ore beneficiation according to the gravity-flotation scheme at a natural pH of the pulp (without adding acid), the following products were obtained: gravity concentrate with a gold content of 2426 g/t at a yield of 0,31 % and an extraction of 64,06 %; flotation concentrate (after the II cleaning) with a gold content of 122 g/t with a yield of 2,90 % and recovery of 33,01 %; the total gold recovery in the gravity-flotation concentrate was 94,07 % with a yield of 3,21 % and Au content of 345,87 g/t, the gold content in the flotation tailings was 0,72 g/t.