Ultrafine Grinding Research Articles

Research into thickening processes of concentrates of gold-bearing ores

The aim was to improve the thickening of an ultra-fine flotation concentrate by efficient flocculants when processing refractory sulphide gold-bearing ores from South Urals deposits. The chemical ore composition was studied using gravimetric, atomic absorption, chemical, X-ray fluorescent, assay test and electron microprobe analytical methods. Particle size analysis of the ultra-fine flotation concentrate under study was performed using a Malvern Hydro Mastersizer 2000MU analyser (Malvern Panalytical Ltd, UK). In thickening experiments, samples with the same composition after the ultra-fine grinding process were used. The gold content in the ore was determined (22.8 g/t) based on analytical studies on the material composition of samples. At least 92% of the final grain size class is -20 microns. Laboratory tests performed on eight samples containing polyacrylamide-based flocculants revealed an optimal A44 flocculant (produced in China). The flocculant meets the requirements for minimum flow rate, deposition rate and L:S ratio. The specific performance of the JX20 radial thickener (JPMFex Corp. Ltd., China) was calculated. The optimal flocculant flow rate is 200 g/t per 1 t of thickened material, leading to thickening 50 t of pulp per 1 m2 of thickener per day. The A44 flocculant is recommended for pilot testing. Thus, developing, testing and implementing fundamentally new reagents and improving existing technologies of processing gold-containing ores and concentrates are necessary to intensify the ore dewatering processes after ultra-fine grinding.

ФЛОТАЦИОННЫЕ РЕАГЕНТЫ ДЛЯ ИЗВЛЕЧЕНИЯ ТОНКОВКРАПЛЕННОГО ЗОЛОТА ИЗ ТРУДНООБОГАТИМЫХ РУД И ТЕХНОГЕННЫХ ПРОДУКТОВ

At the present stage of development of the mineral resource base of precious metals, the wider involvement of refractory ores and technogenic products in the mineral processing is playing a very important role. It is due to these types of mineral resources the main Russian and foreign companies plan to get the increase in the production of gold and other precious metals. Refractory ores are characterized by low content and uneven distribution of valuable components, emulsion dissemination of gold, complex material composition, flotation active silicate and carbonaceous rock components. The main technologies for their processing include combined schemes that provide intensive preliminary preparation of ore, fine and ultrafine grinding. Creation of effective reagents for flotation of fine classes of noble metals, selective depression of gold-free sulfides, like pyrite, pyrrhotite, arsenopyrite, and rock minerals is one of the recognized innovative solutions for intensifying the enrichment process of this type of raw material. The studies performed at IPKON RAS in the framework of the scientific school of Academician V.A. Chanturiya helped to develop and substantiate the novel selective reagents-collectors of dithiocarbamate type (DEDTCm, OPDTC, DBDTC, MDTC) and herbal modifiers that possess complexing properties in relation to noble metals and provide an increase in the recovery of valuable components of gold by 5-7%. A set of analytical methods - scanning electron (LEO 1420VP, Carl Zeiss) and laser microscopy (KEYNCE VK-9700, Shimadzu), X-ray fluorescence spectroscopy (ARL ADVANT’X), ICP –MS (Agilent 725 ICP-OES, Agilent Technologies), X-ray diffractometry (DRON-2.0, XRD 7000, Shimadzu), potentiometry, titrimetric analysis, methods of mathematical statistics helped to study the adsorption layer of the reagents on natural minerals and model sulfides with micro- and nanosized gold. Using an original technique for quantitative assessment of the reagent coating by image analysis (SLM), the surface area of the mineral occupied by the reagent was calculated. A method for selective flotation of gold-containing sulfides using OPDTC and oak bark extract has been developed and tested in the separation of the collective gold-arsenic concentrate of the Olympiada deposit. It showed the possibility of obtaining a gold-pyrite concentrate with an arsenic content of less than 2%. The prospect of using plant modifiers for gold recovery during flotation of complex ores has been substantiated.

РАЗВИТИЕ ОБОРУДОВАНИЯ ДЛЯ ТОНКОДИСПЕРСНОГО ИЗМЕЛЬЧЕНИЯ МИНЕРАЛЬНОГО СЫРЬЯ

Introduction. The huge energy costs of fine and ultrafine grinding operations have led to numerous studies aimed at developing new devices and methods for producing powdered materials. The first way leads to an increase in specific productivity while maintaining energy consumption at approximately the same level. The second way allows not only to increase the specific productivity, but also to reduce the specific energy consumption, since with a decrease in the exposure time, the body is more easily deformed and destroyed. The grinders in which the intensification of the destruction process is carried out in the first way can include planetary and vibrating mills. The second method of intensification is used in jet and various types of centrifugal mills. It is determined that vertical centrifugal mills are the equipment of a new type that can effectively perform grinding operations at high technological indicators and low energy consumption. The purpose of the research. Development of measures for obtaining a finely dispersed product by destroying mineral raw materials in vertical centrifugal mills by mechanical means. Research methodology. The paper uses a comprehensive research method: analysis of the state of grinding equipment according to literary and patent sources; development of mathematical models of the movement of bulk material in the working space of a vertical centrifugal mill based on the Navie-Stokes equations; computer modeling of the movement of the crushed material using the OpenFOAM package for solving hydrodynamic equations; a solver program was created to perform calculations, implementing the SIMPLER algorithm and using the MRF model; laboratory experiments; granulometric method for the analysis of grinding products; fractional analysis of crushed material with a grain size of 0.08 mm using an X-ray analytical centrifuge ВrооkhаvеnBI-ХDС. The development of measures for the effective evacuation of the crushed product from the working space of a centrifugal mill was evaluated by comparative tests of mills using various design solutions. Research results and discussion 1. It is established that vertical centrifugal mills are the devices of a new type capable of effectively performing grinding operations at high technological indicators and low energy consumption. 2. A mathematical model of the movement of bulk material in the working space of a vertical centrifugal mill has been developed based on the Navier-Stokes equations, which allows determining the speed and direction of movement of material layers at any point in the working space, the energy costs for their movement, the influence of the height of the material column on the nature of its movement in the space above the rotor. 3. The directions of increasing the efficiency of grinding mineral raw materials in a vertical centrifugal mill are determined by reducing the number of radial ribs installed in the cavity of the mill rotor; making cutouts in the radial ribs of the rotor, in the area near the rotor hub; installing coaxial rings in the working space of the mill above the rotor. 4. A method of effective evacuation of the crushed product from the mill body by installing additional screening surfaces in the peripheral part of the working space of the mill has been developed. 5. For the first time, the distribution of the granulometric composition of fine and medium - dispersed crushed product obtained as a result of processing lump dolomite in a centrifugal mill was obtained. It was found that particles with a size class of -0.08 + 0.03 mm are absent in the output of the crushed product from the mill. Conclusions. A mass-produced vertical centrifugal mill will find its effective application at enterprises of the Russian Federation for the preparation of powdered materials and will allow to obtain a significant effect by reducing the price of the final product, simplicity of design and maintenance of equipment, as well as small occupied production areas.

Two-Stage Grinding as the Most Cost-Effective Option for Organizing the Process of Ultrafine Grinding of Solid Materials

Two-Stage Grinding as the Most Cost-Effective Option for Organizing the Process of Ultrafine Grinding of Solid Materials

Reinforcing effects in elastomeric composites, filled with particles of mineral fillers, based on silicon dioxide and carbon

When creating elastomeric composites, structures and products made from such materials, considerable attention is paid to environmental issues, as well as to improving economic efficiency and energy efficiency in its production. In this regard, the development of new types of strengthening highly dispersed fillers for elastomeric and polymer composite materials, including those of natural origin, providing an optimal balance of mechanical properties of composites and having advantages over existing solutions, is an actual task. In the course of the work, a technology was developed for producing highly dispersed fillers by ultrafine grinding of raw materials. The obtained experimental data shows a significant reinforcement effect (up to five times) with a decrease in the average particle size of the filler. It is established, that he most effective filler, in terms of reinforcement, are particles based on amorphous silicon dioxide, obtained from rice husk processing products and shungite rock. The significant influence of the surface functionality and the carbon/silicon dioxide ratio of submicron filler particles on the mechanical properties of elastomeric composites is shown. It is established that new classes of reinforcing fillers can be recommended for practical use in the future.

An environmentally friendly method for efficient atmospheric oxidation of pyrrhotite in arsenopyrite/pyrite calcine

Pyrite and arsenopyrite are the most common hosts for invisible gold, but pyrite and arsenic are refractory during conventional sulfide oxidation, which significantly challenges subsequent gold extraction. One option is high-temperature pretreatment of arsenical materials to sequester > 90% of the arsenic as a gas, then convert it to a stable form. This process produces a calcine similar in composition to pyrrhotite (Fe1-xS) but with higher porosity. In this study, the calcine product is oxidized with an efficient, cost-effective atmospheric process using acidic and near-neutral solutions. A sulfur mass balance analysis method based on iron sulfide thermal transformation in nitrogen atmosphere was developed to quantify the oxidation efficiency of pyrrhotite leaching. The optimization confirmed that > 90% of the calcine was oxidized by Fe3+ (5 and 10 g/L) and O2 (0.5 L/min) at pH 1 after 48 h and at 95 °C even without ultrafine grinding. Elemental sulfur was the main oxidation product when the oxidation pH was 1,2. This study provides the foundation for the development of a low-cost and environmentally friendly process option for pretreatment of arsenical sulfide refractory gold materials.

Challenges Related to the Processing of Fines in the Recovery of Platinum Group Minerals (PGMs)

In order to increase the recovery of PGMs by flotation, it is necessary to optimise the liberation of the key minerals in which the platinum group elements (PGEs) are contained which include sulphides, arsenides, tellurides, and ferroalloys among others, while at the same time ensuring the optimal depression of gangue minerals. In order to achieve this, comminution circuits usually consist of two or three stages of milling, in which the first stage is autogeneous, followed by ball milling. Further liberation is achieved in subsequent stages using ultra-fine grinding. Each comminution stage is followed by flotation in the so-called MF2 or MF3 circuits. While this staged process increases overall recoveries, overgrinding may occur, hence creating problems associated with fine particle flotation. This paper presents an overview of the mineralogy of most of the more significant PGM ores processed in South Africa and the various technologies used in comminution circuits. The paper then summarises the methodology used in flotation circuits to optimise recovery of fine particles in terms of the collectors, depressants, and frothers used. The effect of entrainment, slimes coating, changes in rheology caused by the presence of a significant amount of fines and of chromite recovery is addressed.

Release property of red ginger essential oil in silica-nanocellulose composite based sachet

Red ginger is an herbal plant that contains active components and can be used to control microorganisms. In this study, active packaging in the form of an antimicrobial sachet was developed. The red ginger essential oil was incorporated into silica-cellulose nanocomposite in powder form in a closed sachet. The silica-nanocellulose composite was fabricated through a sol-gel permeation process in nanocellulose hydrogel. Nanocellulose was isolated from oil palm empty fruit bunches by mechanical treatment, a combination of ultrafine grinding and ultrasonication. Nanocellulose hydrogel was immersed in a sodium silicate solution at three different times. The obtained gel was soaked in 2 M sulfuric acid for 4 hours to produce a silica-nanocellulose composite. Release property of red ginger essential oil from the closed sachet was observed. The effectiveness of the produced antimicrobial sachets depends on the release of the antimicrobial agent from the sachets.

Preparation of Rice Husk Based Carbon–Silicon Reinforcing Agent and Its Enhancement Capability for Styrene Butadiene Rubber Composites

In this paper, a preparing method of rice husk based carbon–silica compound filler was proposed basing on anaerobic roasting of rice husk, ultrafine grinding, chemical precipitation and surface modification. The resultant filler was used to improve the mechanical properties and thermal stability of styrene butadiene rubber. Effect of surfactant types on the particle size and dispersion of filler and on the mechanical properties and thermostability of rubber composites was investigated. The addition of modifier effectively improves the dispersion of filler in rubber composites. The filler modified by titanate coupling agent shows the best enhancement effect. The thermostability of modified rubber is close to that of carbon black filled rubber.

Application of concurrent grinding in direct aqueous carbonation of magnesium silicates

Formation of silica-rich passivation layers formed on the periphery of reacting feed particles is one of the primary obstacles in obtaining high magnesite yields during direct aqueous mineral carbonation of peridotites and serpentinites. The disruption of the silica-rich layer around partially reacted grains as a result of concurrent grinding on the degree of carbonation (magnesite yield) was investigated in this work. Three types of naturally-occurring magnesium silicate feedstocks, dunite, olivine and lizardite, as well as three types of grinding media, were examined.Discrete size fractions of feed samples, with and without grinding media, were carbonated. SEM readily disclosed the formation of a silica-rich shell around a magnesium rich core during carbonation. EDS analysis was employed to study the elemental composition of reacted particles’ shell and core. The method confirmed that during concurrent grinding these silica-rich layers were removed and continuously produced a fresh surface available for further reaction. The removal of the silica-rich layer was shown to significantly improve magnesite yields up to a 600 % increase in yield. Among the three different grinding media used in this work, zirconia and stainless steel media resulted in similar and highest magnesite yields, which is believed to be due to a combination of their high densities and hardness. The findings of this research showed that enhanced magnesite yields could be achieved for all feedstock without the need for energy intensive pre-treatment steps (e.g. ultrafine grinding and heat-activation). Moreover, concurrent grinding resulted in a magnesite yield when raw lizardite was carbonated.

Modification of pea dietary fiber by ultrafine grinding and hypoglycemic effect in diabetes mellitus mice.

This study was designed to investigate the effects of ultrafine grinding on the physicochemical properties of pea dietary fiber (PDF) and the hypoglycemic effect of ultrafine grinding dietary fiber on diabetes mellitus (DM). So, the PDF was treated by ultrafine grinding technology, and its microstructure and physicochemical properties were determined. Then, the DM model was established, and the 4-week ultrafine grinded pea dietary fiber (UGPDF) diet intervention was conducted by using gavage and feeding. During this period, the blood glucose and body weight of the mice were measured, and an oral glucose tolerance test was measured on the last day. The biochemical blood indexes of the mice were determined, and the pancreas was stained with HE after dissecting. The results showed that after ultrafine grinding, the structure fragmentation, specific surface area increased, and UGPDF showed higher swelling ability as well as water and oil holding capacities. Simultaneously, UGPDF had a significant effect on reducing blood glucose and glycosylated hemoglobin in DM mice, improving the wasting state of mice and increasing the tolerance to glucose. Further, the results of the HE section showed that the pancreatic islet cells gradually returned to normal regular morphology. In biochemical blood indicators, UGPDF reduced TC and TG levels in the blood. This study provided a specific data basis for the following research on the hypoglycemic mechanism, and broadens the application field of PDF. PRACTICAL APPLICATION: The physicochemical properties of pea dietary fiber were improved by ultrafine grinding technology. Because of this, the application of pea dietary fiber in the field of hypoglycemic had a better effect, laying a foundation for the next research on hypoglycemic mechanism.

Effects of grinding and dehydration on kaolin in a steam jet mill

AbstractSteam jet milling was applied for the first time to ultra-fine grind the filter cake (moisture content 23.80%) produced by a kaolin concentrator. The material was dehydrated and dried simultaneously during grinding, and the final ground sample met the moisture content requirement for powder products of <2%. The particle size of the ground kaolin samples decreased and the particle-size distribution was more concentrated, indicating that the steam jet milling was more effective for kaolin processing than the conventional dry grinding process. In addition, steam jet milling can improve the whiteness and decrease the crystal order of the samples, thus improving the kaolin properties in follow-up applications.

Investigation of the Influence of Ultrafine Grinding and Ultrasonic Field on the Intensification of the Processes of Extraction of Iron Oxides from Ash and Slag Waste of Energy

The possibility of extracting iron oxides from ash and slag wastes of the Primorskaya GRES power plant - (Luchegorsk, Primorsky Kray) was investigated. The positive influence of the energy of ultrasonic vibrations with frequency of 22 kHz and power at1 kW, on the increase in the percentage of extraction of iron from ash and slag waste from thermal power is presented. The optimal time of exposure to ultrasound radiation on ash and slag pulp is determined. A comparison of the magnetic separation of ash and slag waste (ASW) without additional grinding with magnetic separation with preliminary grinding of sample materials down to 90 and 40 microns is carried out. The positive effect of preliminary grinding of the ASW sample on the efficiency of the subsequent magnetic separation is presented. With double magnetic separation of the ASW sample in a magnetic field of 300 T and preliminary crushing of the sample to a particle size class of less than 40 microns, a concentrate was obtained with an iron oxide content of 52.9; the extraction rate of iron oxides equaled 84.2%.

Isolation and characterization of Cellulose Nanofiber from Subang Pineapple Leaf Fiber waste produced using Ultrafine Grinding method

Pineapple leaf fiber (PALF) is one of natural fibres that has high cellulose content. However, pineapple plants must be replaced with new plants once it is harvested, leaving the leaves as waste. In this research, the isolation and characterization of Subang based PALF were conducted. Chemical pre-treatments including alkaline treatment with Sodium Hydroxide and bleaching to remove nanocellulosic constituents such as lignin and hemicellulose were conducted. This process was followed by mechanical treatment using ultrafine grinder to produce cellulose nanofiber (CNF). Transmission Electron Microscopy (TEM) images showed that the CNF had 45-75 nm in diameters. The percentage crystallinity was determined by X-ray diffraction (XRD). The crystallinity values of raw PALF, treated PALF, and CNF were 74.97%, 76,29%, and 69.52% respectively. Fourier Transform Infrared (FTIR) spectroscopy analysis was carried out to investigate the chemical structure changes after both chemical and mechanical treatments. The presence of a peak that related to cellulose confirmed that the process was well conducted. These results indicated that PALF waste could become added value to agricultural waste and expected to become reinforcement agent in nanocomposite for structural application since PALF had low aspect ratio and had high percentage crystallinity values.

Study on the pozzolanic activity of ultrafine circulating fluidized-bed fly ash prepared by jet mill

The pozzolanic activity of ultrafine circulating fluidized-bed (CFB) fly ash prepared by jet mill has been investigated in this research. The ultrafine powder properties and the hydration heat release process of the cement blended with ultrafine CFB fly ash have been obtained. Furthermore, the dissolution characteristics of SiO2 and Al2O3, the Ca2+ absorption capacity in saturated Ca(OH)2 solution, and the polymerization degree of Si-O and Al-O polyhedrons have been studied to further clarify the mechanism of ultrafine grinding on pozzolanic activity. Compared to raw CFB fly ash (RCFA), the particle morphology, the pore structure of ultrafine CFB fly ash (UCFA, D50 ≤ 5 μm), and the pozzolanic activity of UCFA are significantly improved. The hydration rate of cement blended with UCFA is accelerated, and the total heat release is close to that of pure cement within 72 h. Ultrafine grinding increases the SiO2 and Al2O3 dissolution rate of CFB fly ash and Ca2+ absorption capacity in saturated Ca(OH)2 solution, mainly due to the decrease of polymerization degree of Si-O and Al-O polyhedrons and particle size of CFB fly ash.

Technologies for the production and application of food supplements based on fruits cryopowders

The article presents material on the production of a new class of bio-correctors in the form of cryopowders from fruit raw materials grown in the Adler district of the Krasnodar Territory. Fruits of shadberry, feijoa and persimmon are chosen as research objects. Fruits have high characteristics of quality, but low shelf-life. The chemical composition of fruits contains a significant amount of easily digested carbohydrates, vitamins, macro and micronutrients. The dependence of the moisture content of fruit raw materials on the duration and speed of low-temperature drying is investigated. Mathematical substantiation of the freezing process and the contribution of dry substance heat capacity, ice and water to the heat generated during the water crystallization are given. The technological apparatus scheme for the production of cryopowders from fruit raw materials has been improved. It is based on raw material dehydration in a gaseous nitrogen environment, shock low-temperature freezing of research objects and ultrafine grinding of pre-prepared and dried raw materials in a liquid nitrogen environment.

Sustainability of coal mines: Separation of clean coal from the fine-coal rejects by ultra-fine grinding and density-gradient-centrifugation

Due to the availability of high ash feedstocks and drift origin, Indian coal washeries face tremendous pressure in maintaining the clean coal yield and handling huge quantities of rejects. Since flotation rejects (tailings) discharged in the form of fine-sized (−500 μ) coal-water-slurry, handling and disposal is an environmental concern and it impacts mine sustainability. As conventional methods for extracting clean coal from tailings reported poor yields, a two-stage process i.e. wet-grinding followed by density-gradient-centrifugal separation was explored and optimized for recovering >80% of the carbon values. Clean coal of 19.2%–21.4% ash with >40% yield was obtained by density-gradient-centrifugation of different ultrafine size (−75 μ) coal-water-slurries at 50% pulp density. However, further reduction in clean coal ash by maintaining the yield was limited due to the hindrance in the movement of the high-ash coal particle caused by particle-particle interactions in a thick slurry. Hence, the pulp density of coal-water-slurry was optimized with the addition of extra water, which resulted in 15.1%–17.3% ash clean coal at an average yield of 54–58% from coal tailings having 34.9%–39.3% ash content. Optimization and kinetics of grinding and density-gradient-centrifugation were studied to check the effect of pulp density and other operating conditions. Ash reduction was mainly due to the removal of silica-based materials, where alumina to silica ratio was increased from 0.394 to 0.475. The petrographic analysis showed that the product coal was rich in macerals with ~60% of vitrinites and ~ 30% of inertinites.

Effect of grinding media properties and stirrer tip speed on the grinding efficiency of a stirred mill

Owing to their high energy efficiency, stirred mills are commonly used in the fine or ultrafine grinding of low-grade and fine disseminated ores to enhance liberation. In this study, batch wet grinding studies were conducted in a stirred mill to evaluate the effect of the grinding media density, grinding media diameter, and stirrer tip speed on the ground products and specific energy input. The population balance model was used to simulate the particle size distribution of the ground products. The results obtained indicated that the breakage rates S1 and S2 were highly dependent on the operating parameters, while the breakage distribution value b21 was independent of the grinding media density and stirrer tip speed. Additionally, it was observed that the yield of the desired size (−45 + 10 μm) of ground products increased with grinding media diameter. With the increase of grinding media density and stirrer tip speed, the time efficiency of the grinding process was improved. Moreover, the attainable region method via a contour plot was used to produce the maximum amount of the desired size with lower energy. Furthermore, the results revealed that the grinding process became energy inefficient when the grinding time was close to the turning point.

Электромеханический дезинтегратор многофакторного действия: моделирование и оценка

Одним из способов, позволяющих осуществлять различные технологические процессы тонкого и сверхтонкого измельчения, является применение электромеханических дезинтеграторов многофакторного действия. Дезинтегратор состоит из двух плоских индукторов с трехфазными обмотками, которые образуют бегущие магнитные поля с противоположным порядком чередования фаз, и рабочей камеры с ферромагнитными рабочими телами, расположенной в межиндукторном зазоре.Множество факторов, позволяющих воздействовать на обрабатываемое вещество с необходимой интенсивностью и в нужном направлении, требует знания физической сущности происходящих в вихревом слое явлений.Для определения силы, действующей на ферромагнитное тело, необходимо рассчитать магнитное поле в рабочей зоне электромеханического дезинтегратора. Интересующая величина определяется путем численного решения полевой задачи с использованием метода конечных элементов. Данный метод позволяет точно описать конфигурацию активной части, а также учесть нелинейность свойств материалов. В работе получены картины распределения векторного магнитного потенциала в активной зоне электромеханического дезинтегратора. Представлены результаты моделирования распределения усилий, действующих на ферромагнитные тела и рабочую электропроводящую камеру. Следствием взаимодействия бегущих магнитных полей индукторов и вихревых токов, протекающих в стенках рабочей камеры, является появление характерных прогибов стенок рабочей камеры в пределах каждого полюсного деления. Расчет подтверждает наличие локализации действующих электромагнитных усилий на стенки электропроводящей камеры в пределах полюсного деления индукторов. Деформацию рабочей камеры вызывают, прежде всего, усилия которые направлены нормально к поверхности стенки камеры. Результаты численного расчета могут быть использованы при выборе геометрических размеров активной части с целью получения заданных рабочих свойств и характеристик.

Experimental results from face and lateral fine grinding of fused silica and BK7 using metal and resin bonded tools

The experimental setup shall compare face grinding with lateral grinding in a single processing step using fused silica and BK7 as materials. Resin and metal bonded tools are used in face and lateral grinding strategies. The paper presents the results in order to deepen the knowledge about those grinding technologies and to further improve the properties of fabricated components. Furthermore, the results confirm, that ultra-fine grinding is a technology, which can be used to process inorganic non-metallic materials with high quality surfaces with a low roughness and high flatness in a low processing time.