Selective Crushing Research Articles

Selective crushing, enrichment by friction properties and hydrophobization for obtaining the sustainable blast furnace slag aggregate for road subbase

Air-cooled blast furnace slag is a metallurgical waste that can be used to produce the slag aggregate for pavement subbase. Slag aggregate is much cheaper than natural stone aggregate, but differs in heterogeneity in strength (from 2 to 40 MPa), tendency to absorb water, and low resistance to freezing-thawing. The paper suggests the use of methods of enrichment by friction properties, selective crushing, and hydrophobization to increase slag aggregate resistance to freezing-thawing cycles, crushing, and water penetration. Selection of the most strength (low porous) 75 % slag aggregate grains due to enrichment by friction properties decreases the total water absorption of the sample from 4.45 % to 3.64 %, decreases the sample mass loss after tests for resistance to freezing-thawing cycles from 5.05 % to 2.82 %, reduces the aggregate crushing value (ACV) from 30.71 % up to 23.80 %. Hydrophobization of the pre-enriched slag aggregate additionally reduces its water absorption to 1.08–––1.3 %.

Identification of the impact of electric pulse action on the disintegration of a natural mineral

The work is devoted to the study of the electric pulse disintegration of a natural mineral. The object of the study is the natural mineral quartzite of the Aktas deposit of the Republic of Kazakhstan. For the destruction and grinding of quartzite, a working cell of an electric pulse unit was developed. Electric pulse crushing is a modern technique for grinding a variety of materials, which provides the desired degree of grinding with a certain granulometric composition of the product and has a high ability of selective crushing. With the help of this technology, quartzite grinding was carried out with an increase in the capacity of capacitor banks from 0.25 mF to 1 mF, the pulse discharge voltage changed from 20 kV to 30 kV, the number of pulse discharges from 500 to 1,000, the inner diameter of the working cell from 60 mm to 80 mm. The results of the disintegration of a natural mineral by the electric pulse method allowed us to determine the degree of grinding of the finished product. The obtained results can be used in the study and optimization of the extraction of natural minerals, which is important for ensuring the sustainable use of natural resources and balanced economic development. Crushed quartzite is used in various industries, including the production of optical fibers, electronics and photovoltaic devices. A material with a particle diameter of 0.1 to 0.4 millimeters is used to create glass, ceramic and porcelain products, as well as insulation materials. Due to its homogeneous composition containing up to 98 % silicon oxide (SiO2) and excellent absorbent properties, quartz sand is also used as a filter material for water purification

Laboratory evaluation of a complex treatment technology for reducing water absorption of the pavement subbase aggregate from the blast-furnace slag

When smelting each ton of pig iron, approximately 500 kg of blast-furnace slag is formed and requires recycling. Air-cooled blast-furnace slag can be used for the manufacture of slag aggregate for the pavement subbase layers, as an alternative to natural stone aggregate. The wide use of slag in this area is limited by its high water absorption. This paper proposes a complex technology to reduce water absorption of slag aggregate. This technology includes selective crushing, which allows separating low-porosity aggregate grains from high-porosity ones, and impregnation of selected low-porosity grains with hydrophobic agent (surface hydrophobization). The results of a laboratory evaluation of this technology effectiveness are presented. Article also contains optimal parameters of this complex technological process which allowed to reduce the water absorption of the slag aggregate from 4.54% to 1.05%.

Eco-friendly strategy for advanced recycling waste copper from spent lithium-ion batteries: Preparation of micro-nano copper powder

Massive spent lithium-ion batteries (LIBs) were emerged worldwide as a consequence of the extensive use in energy storage applications. The recovery of cathode electrode materials from spent LIBs has received great attention due to economic benefits, which has led to the neglect of the deep utilization of low-value copper current. The present study focuses on the selective crushing of copper foil and the preparation of micro-nano copper powders through eco-friendly leaching and reduction processes. The occurrence characteristics of copper in the anode material obtained by disassembling the battery after discharge pretreatment were first analyzed, SEM + EDS detection shows that graphite with thickness of tens of microns is attached to the surface of copper foil. Subsequently, the application of mechanical force promoted the graphite to detach from the collector, and the results indicate that significant selective crushing leads to the enrichment of copper foil in coarse-grained particles. Further, an ammonia leaching method was used to leach copper gently. The leaching kinetic behavior of copper foil particles with different particle sizes was analyzed. The diffusion controlled shrinking core model can accurately describe the leaching behavior of copper foil particles in leaching process. The activation energies of +2 mm, 2–1 mm, and 1–0.5 mm are 15.04 kJ/mol, 11.61 kJ/mol, and 8.21 kJ/mol, respectively. Undissociated graphite has negative impact on the leaching behavior, and reduction in the particle size of the copper foil can enhance the leaching behavior. Finally, the glucose and ascorbic acid system reducing reaction promotes the transformation of the copper ions in the leaching solution into regular shaped copper nanoparticles. SEM and XRD results show that high purity copper nanoparticles with hundreds of nanometers was successfully prepared. This study provides an eco-strategy and value-added recovery approach to address the challenges of full component utilization of spent LIBs.

Impact Crushing Characteristics and Relationship between Multicomponent Complex Ore and Its Component Minerals

Based on the JK Drop Weight test and principle of selective crushing, a multicomponent complex ore with its component minerals, i.e., pyrrhotite, sphalerite, and quartz, was used to explore the impact crushing characteristics and relationship between the complex ore and its component minerals. Results show that the order of impact crushing resistance is quartz > pyrrhotite > ore > sphalerite. The particle-size-distribution characteristic curve of ore crushing products is always “sandwiched” between the curves of pyrrhotite, sphalerite, and quartz within the same feed-size range. When the particle size is −63 + 53, −45 + 37.5, −31.5 + 26.5, and −22.4 + 19 mm, the component mineral pyrrhotite has a negative effect on the impact crushing of ore, while the component mineral sphalerite has a positive effect. When the particle size is −16 + 13.2 mm, the component mineral pyrrhotite has a positive effect on the crushing effect of the ore, while the component mineral sphalerite has a negative effect. The component mineral quartz always has a negative effect on the impact crushing effect of ore in all the studied particle sizes.

Study on particle characteristics and metal distribution of waste printed circuit boards based on a shear crusher

The crushing process plays an important role in the separation and purification process of waste printed circuit boards (PCBs). In this work, the fine crushing of waste PCBs was conducted to investigate particle characteristics and metal distribution using a shear crusher. The results demonstrated that a better crushing was obtained with the feed concentration of 183 g/L and crushing time of 60 s. Meanwhile, the coarse and fine particles presented the characteristics of higher circularity and smaller aspect ratio than medium-size particles for waste PCBs. Main metal elements such as Cu, Al, Zn and Fe were distributed in waste PCBs with various particle sizes, and these total metal content in the coarse crushed products was obviously higher than that in the fine crushed products. Overall, waste PCBs can be effectively crushed to a desirable product for subsequent separation and purification process using a shear crusher. • The fine crushing of waste PCBs was conducted using a shear crusher. • Particle shape characteristics and metal distribution were observed. • Coarse and fine PCB particles had the higher circularity and smaller aspect ratio. • Selective crushing of waste PCBs was confirmed under a higher shear crushing.

A study on the possibility of processing quartz-feldspar ore of the Quang Nam deposit in Vietnam

The article presents the results of a study on the possibility of processing quartz-feldspar ore from the Quang Nam deposit in Vietnam using a combined process, including selective crushing, processing by particle shape, and selective flotation of mica and feldspars using Armac T cationic collector to obtain high-grade feldspar, mica, and quartz concentrates. A material composition analysis for the ore has confirmed its fundamental applicability for pre-processing by particle shape through 2 mm class screening after two-stage selective crushing. The resulting muscovite concentrate is monomineral. Subsequent grinding to 62 % –74 μm and 20 μm classification allow isolating into the slurry product a suitable feldspar concentrate that may be used to manufacture ceramics. The main fine muscovite mass is recovered by direct selective flotation of material of over 20 μm using a mix of a fatty acid collector (sodium oleate) and Armac T collector in a medium created by sulfuric acid. A high-grade feldspar concentrate is obtained from mica flotation tailings by feldspar flotation with Armac T collector in a hydrofluoric acid medium. The resulting muscovite and feldspar concentrates meet the requirements of the Vietnamese standard governing raw materials for ceramic glaze. In terms of their grade, these concentrates are comparable to those available in the global market. The quartz flotation tailings meet the raw materials standard for dark glass production and mold making. The process developed is virtually waste-free, which is confirmed by the results of respective larger-scale tests.

Experimental Investigation of Particle Size Alteration and the Selective Crushing Phenomenon of Gangue during the Jaw Crushing Process

This study examines the particle size and distribution of the main chemical components of gangue during the crushing process. Coal mine gangue was chosen as the research object, and its particle size and chemical components at various crusher discharge settings were examined through screening, grinding, chemical composition testing, and other methods. The findings demonstrate that the characteristic particle size in the gangue particle size distribution model has a logarithmic upward trend as the width of the discharge port increases. In contrast, the uniformity index has shown an exponential downward trend. The analysis of the distribution rate and enrichment ratio of the main chemical components of the gangue at different widths of the discharge port shows that the gangue exhibits obvious selective crushing during the crushing process. The distribution rate of each component is affected by the size of the screen aperture to various extents. As the discharge port width increases, the elements of CaO and MgO are enriched in the coarse-grained products, while those containing Fe2O3 are enriched from fine-grained to coarse-grained. Gangue particles containing Al2O3, SiO2, and C are enriched in the fine-grained product. In addition, by analyzing the alterations in the main chemical components of gangue at different particle size intervals, it was found that the amount of each component first rises and then falls, and the trend of enrichment ratio to particle size follows an exponential pattern. The research results have significance for guiding the selection of resource utilization methods of gangue with different particle sizes after crushing.

Analysis and optimization of the selective crushing process based on high voltage pulse energy

With the development of photovoltaic (PV) energy, the recycling technology of end-of-life PV panels has received much attention; the existing recycling methods have various limitations. In this study, high-voltage pulse energy was used to crush PV panels, and the microscopic morphology, particle size structure, and elemental composition of the crushed products were analyzed. The liberation process and element enrichment during the high-voltage pulse crushing of PV panels were studied, the effect of each parameter on the selective crushing degree of high-voltage pulse crushing PV panels was obtained. Furthermore, a collaborative optimization study was carried out on the degree of selective crushing of various operating parameters. The significance order of the effect of various factors and the mathematical correlation between them were obtained. The best combination of operating parameters was obtained. The test results indicate that the source of high-efficiency liberation and element enrichment during the high-voltage pulse crushing of PV panels is the interface crushing and sequential selective crushing characteristics of high-voltage pulses. With the increase in electrode gap, the degree of selective crushing shows a increasing trend. As the voltage and pulses number increases, the degree of selective crushing first increases and then decreases. The significance of influence of each factor decreases in the following order: voltage > electrode gap > pulse number. When the operating conditions are 170 kV, 50 pulses, and 25 mm, the degree of selective crushing of product reached the maximum.

Choosing special methods of selective disintegration and schemes for complex refractory ore

Introduction. The article highlights a new procedure of choosing special methods of disintegration and schemes for complex refractory ore and develops an integrated approach and criteria to comparing different types of crushers and screens, namely, reduction ratio, grinding degree, slime formation degree, and a new selectivity criterion. Research aims to study a new method and derive an equation to determine the crushing in the layer force and a new selectivity criterion. Research methods. The new methods were tested by comparing Otboynoye deposit tantalum ore, Vishnevogorsky deposit niobium ore, and Zashihinsky deposit tantalum-niobium ore crushing in cone inertial and centrifugal impact crushers and a roller press. The process of crushing in machines was studied in the laboratory and semi-industrial conditions. Different operation modes of crushers and screens were also checked. Object of research is tantalum and niobium ore of different deposits. Research results. The crushing selectivity criterion and reduction ratio comparison demonstrated that centrifugal impact crusher and roller press indexes are lower than the cone inertial crusher (KID) indexes. The reduction ratio for different crushing machines is 10.1 for the centrifugal impact crusher, 10.8 for the roller press, and 14.2 for the cone inertial crusher. The selectivity criterion for the crushing machines is 0.632 units for the centrifugal impact crusher, 0.730 units for the roller press, and 0.848 units for the KID. The KID-300А crusher performed the best for Otboynoye deposit tantalum ore and Vishnevogorsky deposit niobium ore. The KID-300А crusher also has the best slime formation degree criterion. The new method has been tested and approved. Summary. The paper analyses different methods and criteria of selective crushing. A new crushing selectivity criterion was proposed based on optical and electron microscopy data. It describes the ratio of liberation in the crushed product and feed.

Selective Crushing of Run-of-Mine as an Important Part of the Hard Coal Beneficiation Process

To obtain commercial product of required quantitative and qualitative parameters, hard coal must be subjected to a number of processing operations. Preliminary stone removal from run-of-mine is one of them. Methods of such removal, including the method of selective crushing are described. Design solutions for a KOMAG-type device for dry stone removal of run-of-mine are presented. The results of laboratory tests for selective crushing susceptibility of steam coal and coke are presented, and a comparative analysis of the tested types of coal is made. Possibilities of increasing the production of commercial products by using a Bradford drum crusher is analyzed from the economical point of view.

Combination of Pyrolysis and Physical Separation to Recover Copper and Tin from Waste Printed Circuit Boards

Waste printed circuit boards (WPCBs) are an essential component in electronic waste (e-waste), and contain a number of valuable metals (e.g., Cu, Sn) as well as non-metal resources (e.g., brominated epoxy resin). Currently, most of the non-metals are disposed of in landfills, causing environmental problems. In this study, a combination of pyrolysis and physical separation is proposed to recover valuable resources, including both metals and non-metals, from WPCBs. The WPCBs were pyrolyzed at 700°C under a nitrogen atmosphere. Pyrolysis oil and gas can be reused as fuel for the pyrolysis of WPCBs. Metals like copper, tin, and iron in the pyrolysis residues were separated by selective crushing, sieving, gravity separation, and magnetic separation. Finally, rich copper (Cu 82.21%, Sn 1.47%), rich tin (Cu 53.20%, Sn 13.43%), rich iron (Fe > 63%), and non-metal products were obtained, and the total recoveries of copper, tin, and iron were 95%, 86%, and 76%, respectively.

Recent Patents on Roll Crushing Mills for Selective Crushing of Coal and Gangue

Background: Gangue is the concomitant product of coal mining. The traditional approach for gangue treatment is to transport it from underground to ground level to accumulate and form gangue hills. Objective: On the basis of summarizing previous research results, this paper introduces the hydraulic roller crusher and the electric machine built-in coal gangue roller crusher, which avoids the complex transmission problems caused by the movement of the central axis when the roller crusher is allowed to roll. Methods: The hydraulic counter-roll crusher directly separates large pieces of coal and underground gangue such that large pieces of coal gangue do not escape from the well. The electric machine built-in roller crusher is an explosion-proof electric machine used in the crushing roller. Results: Both of these crushers can be used in the selective crushing technology of coal gangue in a coal mine and can meet the requirements of crushing different material sizes and generally avoid the centre of the roller crusher. Conclusion: Both of these crushers reduce transportation costs, minimise land occupation, prevent surface subsidence, decrease environmental treatment costs, reduce environmental pollution, and decrease the transport volume of gangue underground. Various patents have been discussed in this article.

Testing the possibility of using a selective crushing process for selected types of hard coal

The article describes the design solutions of KOMAG drum crushers. In the case of significant differences in hardness of coal and gangue, these devices are the most appropriate and the cheapest means of preliminary beneficiation of run-of-mine. The results of laboratory tests of susceptibility to selective crushing of selected hard coal types by the drop method are presented. The possibilities of using a drum crusher for deshaling the analyzed materials are determined.

Compositional modelling and crushing behaviour of MSWI bottom ash material classes

At present, in Europe, 18 million tonnes of MSWI Bottom Ash (BA) is annually stockpiled or used in low-grade applications (e.g. in road bases). Therefore, alternative applications, such as aggregate or as a cement component in concrete, are stimulated. Physical and chemical characteristics remaining after treatment, however, prevent its extensive application in building materials. Hence, knowledge is needed on the distinct properties of the material classes making up a heterogeneous BA, enabling the assessment of its characteristics and the resulting applicability. Furthermore, a user-friendly composition assessment procedure is necessary to evaluate the output of physical treatment processes. Crushing is a commonly applied treatment and its effect on the material classes comprising BA is still unknown. In this paper, the latter are identified and classified into slag, magnetic slag, glass, refractory, metals, and unburned material classes. The individual characteristics of each material class are identified and a suitable tracer for tracking these classes in heterogeneous samples is defined. Furthermore, a fast method to quantify the distribution of material classes based just on the oxide composition is developed and applied to approximate the changes in the configuration of BA through crushing. It is concluded that, although the jaw crushing of BA results in a more homogeneous distribution, beneficiation of material classes occurs and selective crushing is possible in order to improve the quality of the BA and therefore its subsequent application.

Finding Deep Concentration Techniques for Rich Iron Ore of the Kursk Magnetic Anomaly

—The research results on deep concentration of basic mineralogical variety of natural rich ore to obtain high-quality iron ore product for metallization are presented. The main methods of mineral dressing (selective crushing, magnetic separation in weak and strong fields, gravity separation and flotation) are tested in the technological experiments. It is shown that high-quality iron ore product can be obtained from natural rich ore using a simple technology. The simple technology should be applied at the first stage of processing for maximum possible extraction of high-quality product. Wet separation processes should be used at the later stage as they unavoidably result in high loss of marketable product, as well as bring difficulties connected with dewatering and drying.

Qualitative improvement of xylite by mechanical preparation

The experiments were performed to obtain high purity raw material for activated carbon making, by mechanical preparation of xylite recovered from the Oltenia lignite Basin. The study analyzes the most important parameters that involves the selective grinding of a representative amount of 15.7t xylite (moisture, mineral content, botanic origin), using a production equipment (a hammer-crusher of 50t/h) and the yields and characteristics of the fractions obtained for the activated carbon manufacturing, with high usage value. The key objectives of this study are: (1) to establish yields and quality of the fractions obtained by processing a representative amount of xylite; (2) to reveal the decisive role of the preparation stages on the characteristics of the final product; and (3) to reveal the occurrence, selection methods and preliminary assessment of the xylite reserves necessary for designing a capacity for activated carbon commercial-scale processing unit. This paper presents the results obtained at semi-industrial level of xylite preparation (by crushing and volumetric classifying), for obtaining structural unchanged variety sizes suitable for experiments to obtain activated carbon. It was proved that selective crushing and sieving is a very effective technique taking into account also obtaining the convenient output (yields of over 80%) of useful fraction of xylite (greater than 10mm with an ash between 2.0 and 2.5%). The results point out that the higher the selection and preparation go, the more lower the ash in the upper grain size fractions. The xylite fractions represent an appropriate raw material used for activated carbon making, characterized by a pore volume of 0.32cm3/g, developed mainly in the range of very narrow pores (over 70% under 10Å) which give high surface area BET up to 800m2/g for granular type, the average radius of open pores being 6–9Å.

Резервы повышения эффективности санитарной очистки российских городов как подотрасли жилищно-коммунального хозяйства

The article identifies the beneficial use of municipal solid waste is a major contributor to the waste problem solution and to the enhancement of the public utility sector operations efficiency. 
 The articles dwells on the existing methods of extracting food and plant waste out of the municipal solid waste stock, and claims that food and plant waste, with its valuable element proportion of 99% (including the admixture of timber particles), is high-quality raw material for biocompost. 
 With the purpose of integrated food and plant waste treatment for mechanical admixtures, the process of MSW separation is designed to separate MSW components in accordance with their texture, size and capacity for selective crushing in different conditions. Thus the principle of controlling the physical properties of separated components manifests itself.

New Technology for Disaggregation and Slurrying of Florida Phosphate Matrix

Phosphate mining represents a significant industry in the State of Florida. In view of the great demand for resources, the industry is in a strong public focus. In mining and processing, the phosphate ore mining process alone is responsible for about 45% of the total energy consumption. Slurry pumping to the processing plant accounts for one third of the energy consumption during mining. Various studies have shown that the optimum solid-water ratio for slurry pumping is approximately 60 wt%. It is difficult to achieve this value with the technology of hydraulic monitor operations applied at the present time. For operational reasons, more precise control of the solids content is almost impossible. The Florida Industrial and Phosphate Research Institute therefore funded this research project.Disaggregation and slurrying of phosphate matrix represents the principle problem in pumping slurry. It is still state of the art to use draglines in phosphate ore mining. The dragline dumps the phosphate matrix in the pit, where it is slurried with the help of hydraulic monitors and conveyed to a static grizzly. The grizzly is used to scalp larger rocks and roots. It requires cleaning at regular intervals. A suction pump situated behind the grizzly, pumps the slurry to the processing plant. The average solids content of the slurry is only about 25-35wt%, and varies widely depending on the material properties.Under this investigation, four different types of phosphate ore were examined. In the first step the phosphate ores were analyzed and characterized. Then two different methods were evaluated to improve the slurrying process. First, tests were performed using high pressure water jets of up to 200 bars in order to disaggregate the phosphate matrix. In principle, it is possible to achieve disaggregation and slurrying using this technology, but the necessary throughput cannot be acquired due to the long retention time required. Second, selective crushing tests were carried out using a wet hammer mill. This technology was able to achieve a solids content of 60 wt%, while still producing a high degree of disaggregation of the clay agglomerates, without destroying the valuable material. A preliminary design for a mobile disaggregation and slurrying unit was developed on the basis of these test results. The new technology could reduce water demand from 2.16 m3/t to only 0.58 m3/t and energy consumption from 1.32 kWh/t to 0.36 kWh/t.

Technologies for Decreasing Mining Losses

AbstractIn case of stratified deposits like oil shale deposit in Estonia, mining losses depend on mining technologies. Current research focuses on extraction and separation possibilities of mineral resources. Selective mining, selective crushing and separation tests have been performed, showing possibilities of decreasing mining losses. Rock crushing and screening process simulations were used for optimizing rock fractions. In addition mine backfilling, fine separation, and optimized drilling and blasting have been analyzed. All tested methods show potential and depend on mineral usage. Usage in addition depends on the utilization technology. The questions like stability of the material flow and influences of the quality fluctuations to the final yield are raised.