Dry Separation Research Articles

Selective recovery of metals from spent mobile phone lithium-ion batteries through froth flotation followed by magnetic separation procedure

The recycling of valuable metals from spent lithium-ion batteries (S-LIBs) has become more significant in our society, so the focus of most academic studies has been on the recovery of active battery materials. On the contrary, research on the separation of anode-cathode foils and casing metals, which are essential parts of LIBs, remained limited. To reduce costs and maximize the recovery valuable metals need to be pre-treated before chemical treatment. Therefore, the main objective of this study is the recycling of plastics and the selective production of valuable metals using a combination of physical and physicochemical methods. The results showed that most of the plastics with natural hydrophobicity could be removed with the help of a frother. After plastic flotation, the particle size, the dosages of collectors, frother, and activator were investigated and a copper concentrate assaying 53.5% Cu was obtained at the end of the copper flotation circuit. Dry magnetic separation was subjected to copper flotation tailings to separate ferromagnetic metals (Fe and Ni) from diamagnetic Al particles and the process achieved a recovery of around 99%. The proposed flowchart for the LIBs recycling industry is simple and highly efficient for the recycling of metals and plastics.

Efficiency of air classifiers in dry separation of nometallic mineral fines

The article analyzes dry separation of nometallic mineral fines with a view to enhance the process efficiency owing to optimized choice of equipment design variables and operating conditions. The earlier studies neglected the separation process capacity and energy intake, which weakened representativity of the research findings. It is possible to improve the quality and quantity characteristics of air separation using the specific effect criteria which define the perfection rate of the test machines and determine their optimal design variables. The main specific effect criterion is assumed to be a criterion which provides such choice of design variables that the operational factors with respect to the other criteria are the best. In the air classifier efficiency evaluation, the main criterion is a criterion which takes into account both the mechanical energy intake and the processing time. The analysis of the criteria used to assess the classification machines finds out that the main optimization criterion for air classifiers is a criterion that takes into account the quantity of pollutants in separation products, while the main optimization criterion for vibratory air classifiers is a criterion that takes into account the mechanical energy intake of separation. This study also adjusts parameters of air classification machines using their earlier recommended ranges: the grid incline angle αgrid = 8–9 deg, the vibration amplitude Ас = 2.5 mm and the vibration frequency ωc = 100 s–1 of the vibratory air classifier body. The obtained results enable recommending choosing design variables and operating conditions in air classification and vibratory air classification in dry separation of granite by the size of 10 mm and in dry separation of carbonate minerals by the size of 1 mm.

Differences in Early Rejection of Gangue for Low-Grade Iron Ores with Different Textures from HPGR

ABSTRACT The ore texture determines the proportion of the early rejection of gangue of the low-grade iron ores. However, a detailed study of the early rejection of gangue for low-grade iron ores with different textures is still highly desirable. In this study, three types of low-grade iron ores with different grain sizes were crushed to −3 mm by a high-pressure grinding roller (HPGR). Mineral Liberation Analyzer (MLA) and dry magnetic separation tests were performed on the resulting products. The MLA test results showed that the gangue in fine-grained iron ores was more difficult to liberate than in coarse-grained iron ores. The dry magnetic separation tests indicated that only 15.23% of gangue could be rejected for fine-grained iron ores, which was much lower than that of coarse-grained iron ores. Liberation analysis revealed that a large proportion of the gangue contained only a small amount of valuable iron oxide minerals. By returning the middling from dry magnetic separation to HPGR for crushing again, the gangue rejection percentage for fine-grained iron ore increased to 33.56%. These results demonstrate that liberation studies can help improve the efficiency of early rejection of gangue.

The spatial distribution characteristics of autogenous medium and its effect on low rank lignite beneficiation in differential-motion dry cascade beneficiation bed

In the mining process, a large amount of inorganic mineral impurities are produced, leading to the grade reduction of lignite. Promoting the efficient separation and utilization of low rank lignite is the key measure to stabilize energy structure. In this paper, differential-motion dry cascade separation bed was used for separation, ash reduction and upgrading for low rank lignite. The spatial distribution characteristics of 1.5–0 mm pulverized coal particles in the differential-motion dry cascade separation bed was emphatically investigated. The influence of selecting 1.5–0 mm pulverized coal particles as autogenous medium on the uniformity and stability of bed density was systematically analyzed. The interlayer distribution law of low rank lignite in differential-motion dry cascade separation bed was dissected. The results shows that the leading particle size fraction and the leading density fraction of autogenous medium particles are d = 0.25–0.125 mm, ρ = 1.8–2.0 g/cm3, respectively and the autogenous medium particles could be diffused uniformly and stably along XOY and XOZ cross section and could form autogenous medium fluidized bed with uniform and stable density. When the pulverized coal particle size d = 0.25–0.125 mm, the average bed density reaches the maximum value of 1.815 g/cm3 and the standard deviation of bed density reaches the minimum value of 0.029, at this time, the stability of bed space density reaches the optimum. When the leading density fraction of pulverized coal is 1.8–2.0 g/cm3, the distribution range of bed density is 1.81–1.82 g/cm3 and the fluctuation amplitude is 0.01 g/cm3, at this time, the density of autogenous medium bed is uniform and stable. The interlayer distribution law of low rank lignite in the separation bed was determined. The ash content of upper layer materials is distributed relatively uniform and the distribution range is 9.44–9.76 % with small fluctuation amplitude. The ash content distribution fluctuation of middle layer materials is large and the distribution range is 18.69–31.02 %. The ash content of lower layer materials is distributed relatively uniformly and the distribution range is 41.22–42.06 %. The low rank lignite was separated and upgraded. The ash content of clean coal is 9.58 % and the yield is 63.14 %. The ash content of gangue is 42.09 % and the yield is 36.86 %. The probable error is 0.11 g/cm3. The separated products are relatively pure and the efficient ash reduction and upgrading for low rank lignite are realized.

Mineral and Chemical Characterization of Magnetic and Non - Magnetic Products Obtained from Dry Magnetic Enrichment of Lignite Coals

The mineral and chemical composition of magnetic (tailing fraction) and non – magnetic (clean coal fraction) products from the dry magnetic separation of coal samples with high ash and sulfur contents obtained from Çanakkale Çan lignite (S1) and Manisa Kula Pabuçlu lignite (S2) were investigated in this study. The feasibility of the dry magnetic separation technique for the separation of the minerals from the coal matrix was identified as the function of coal types and particle sizes. The separation technique depends on coal fragments being weakly diamagnetic, while most of the minerals present in the coal are weakly to moderately paramagnetic. Three particle sizes (coarse-, medium-, and fine-sized) of feed lignite and their magnetic and non-magnetic fractions were separated and characterized. The influence of coal type on the magnetic separation efficiency was determined by the recovery of tailing fractions obtained from S1 and S2 lignites. The particle sizes of S1 lignite were quite lower than S2 lignite. When the fine-sized lignite samples from S1 and S2 were used, the recovery of tailing fractions was the highest compared to other sizes. The mineral compositions of S2 lignite include typically mica, smectite (clay mineral), gypsum, kaolinite (clay mineral), pyrite, quartz, and plagioclase. The results showed that the Permroll High-Intensity Magnetic Separation method for high calorific value and low ash content at the medium-sized particle was more efficient for the S2 lignite sample than the S1 lignite sample.

On the need to classify rock mass fed to dry magnetic separation

The hypothesis of a possible use of dry magnetic separation is substantiated on the example of ores from ferruginous quartzite deposits operated by plants of PAO “Severstal” Holding. Size class of ore after medium crushing is –80+0 mm when the vibrating feeder is used for feeding ore mass to the separation zone. The rationale is based on the analysis of video recording of physical simulation on a laboratory drum magnetic separator of SMBS-L series, in the VSDC Video Editor, and simulation modelling of dry magnetic separation on its virtual prototype in Rocky DEM software package. It has been proved that the use of a vibrating feeder for feeding the material to the working area of a magnetic separator makes it possible to: form a monolayer on the surface of the vibrating feeder chute with a thickness close to the maximum size of a lump of separated ore; implement batch feed of material to the separation zone; increase the spacing between lumps in the separation zone when passing through the free fall area, thereby allowing dry magnetic separation of ferruginous quartzites of size class –80+0 mm without pre-preparation.

Iron ore beneficiation technologies in Russia and ways to improve their efficiency

Increasing the efficiency of crushing circuits is associated with a decrease in the particle size of finely crushed ore and the use of dry magnetic separation of crushed ore. Reducing grinding costs is achieved by using drum mills jointly with mills of other designs. The use of automation systems, slurry demagnetization, technologies with staged concentrate separation, and beneficiation and fine screening in a closed grinding cycle lead to a reduction in grinding costs. The main industrial technology for improving the quality of concentrate is its additional beneficiation using regrinding, fine screening, flotation, and magnetic-gravity separators. Increasing the integrated use of iron ore raw materials is associated with an increase in the yield of iron concentrate and the production of hematite concentrate during the beneficiation of hematite-magnetite ores and ilmenite concentrate during the beneficiation of titanomagnetite ores. Incremented concentrate yield is possible by using magnetic separators with an increased magnetic induction up to 0.25-0.5 T in the first stages of beneficiation. To obtain hematite and ilmenite concentrates, combined technologies can be used, including fine screening, high-gradient magnetic, gravity, flotation, and electrical separation.

Separation characteristics of dry high-intensity drum magnetic separator

Dry high-intensity drum magnetic separator (DHIDMS) has been effectively used for the utilization of low-grade iron ores, thus an in-depth investigation on the separation characteristics of the DHIDMS separator would contribute to its design and practical operation. A numerical model was established to describe the particles motion in the DHIDMS process, on which the motion trajectories of siderite and quartz particles were simulated in the high and low magnetic field areas above the magnet surface, to reveal their dynamic behaviors; and the effects of two dominant operating parameters affecting the trajectory of particles, i.e., particle size and drum rotation speed, on the separation performance of a pilot-scale DHIDMS separator were investigated for a siderite ore. Simulation analysis indicates that the motion trajectories of the siderite and quartz particles are obviously different from each other in the high magnetic field area, but they generate negligible diversities in the low magnetic field area. In addition, in the high magnetic field area, the particle size and drum rotation speed significantly affect the distance between the motion trajectories of siderite and quartz particles, thereby affecting the separation selectivity of the DHIDMS separator. Experimental investigations indicate that, the feed particle size and drum rotation speed have definitely significant effects on the separation selectivity of the separator in the high magnetic field area; meanwhile, there is no separation selectivity for iron minerals in the low magnetic field area, thus deteriorating the recovery rate of iron concentrate. These results are basically consistent with the simulation analysis. This investigation has provided a general reference for the optimum design and operation of DHIDMS separator.

Dynamics Analysis and Experiment of Novel Compound Dry Separator

China is the world’s largest producer and consumer of coal. The method of dry coal beneficiation is a key method of separation technology in the field of coal mining. In this paper, the structure of a novel compound dry separator (NCDS) was revealed. The dynamic characteristics and vibration behavior of the NCDS were studied through theoretical modeling, simulation research, and experimental test methods. The mathematical model and simulation model based on ADAMS of the NCDS were established. The experiment for the NCDS was carried out using the dynamics characteristic testing system. The dynamic curve and spatial trajectory of the NCDS were obtained. The Lissajous figure of displacement indicated that the space motion trajectory of the NCDS was an oblique line. The dynamic characteristics of the NCDS with different rotational speeds were revealed. The effect of eccentricity on the dynamic characteristics of the NCDS was discussed, and the vibration amplitudes increased with the increase of eccentricity. The results showed that the deviation of the simulation data and theoretical data was within 3.75%, and the result of the experiment data and theoretical data was within 6.98%. Through comparison and verification, the theoretical model with high accuracy can accurately calculate the dynamic characteristics of the NCDS before processing and manufacturing. This paper provides a reference for the design and efficient operation of the new compound dry separation machine.

Improving mechanical properties of manufactured sand concrete with high biotite content: Application of magnetic separation process and equipment optimization

• Degradation mechanism of biotite in manufactured sand on concrete performance was presented. • An empirical formula of compressive strength for different biotite content was presented. • FEM-DEM coupling program was developed to optimize biotite separation process. Harmful components such as biotite in fine aggregates formed by natural rock crushing need to be rigorously assessed and effectively separated to reduce their potential damage to concrete structures. In this study, magnetic separation was used to remove excess biotite from manufactured sand and to realize the upgrade of manufactured sand, and a series of laboratory tests were carried out to study the influences of biotite content on the compressive strength and splitting strength of concrete. Experimental results show that the magnetic separation method can effectively reduce the biotite content in concrete from 10 % to 2 %, thus improving the mechanical properties of concrete. Through microscopic characterization, we found that the surface layer of biotite had a strong bonding effect with the early hydration product. This bonding effect contributes to the early strength of concrete, leading to a small difference in the strength values of manufactured sand concrete with different biotite contents. With increasing curing age, the strength contribution caused by this bonding effect gradually decreases. In addition, FEM-DEM coupling simulation was used to optimize the operation parameters and magnetic system structure of the magnetic separator to further achieve efficient separation of biotite from manufactured sand. Numerical prediction indicates that the dry magnetic separator has an extrusion magnetic system structure, which makes the magnetic induction and magnetic induction gradient at the guide disk higher and provides a much greater magnetic force than other competitive forces for biotite particles. To efficiently recover low-grade manufactured sand (low biotite content) from manufactured sand, the feed rate t , conveyor belt speed V and magnet-to-steel disk thickness ratio μ should be kept at 0.8 kg/s, 0.85 m/s and 3, respectively. This study can provide potential solutions and broad application value for the problem of manufactured sand with high biotite content in practical engineering.

Dry Permanent Magnetic Separator: Present Status and Future Prospects

Dry permanent magnetic separators have been widely used in the mineral and coal processing industries due to their simple operation and high separation efficiency. These tools not only discard some amount of bulk gangue from the raw ore, thereby reducing the volume of the grinding operation and cutting energy consumption, but also do not require water in the sorting process, thereby expanding their applicability to arid and cold areas. With the depletion of global iron ore resources, a dry, low-cost processing or pre-sorting prior to the wet separation has received the attention of industrial practitioners as a potential alternative. The performance of dry magnetic separators plays a critical role in dry processing This paper reviews the dry magnetic separators available in the literature and describes their operating principles, separation performance, and applications. A detailed comparison of different separators is also conducted to evaluate the differences in their sorting performance and mechanisms and to provide a reference for the optimization of dry magnetic separators.

Influence of Separation Angle on the Dry Pneumatic Magnetic Separation

To enhance dry magnetic separation of fine-grained materials, our research team developed the pneumatic drum magnetic separator (PDMS), an airflow-aided magnetic separator. Different positions at the separation surface of PDMS have varied separation angles, so particles at different positions may be subjected to varying composite forces, resulting in a mismatch between airflow velocity and magnetic field intensity. However, because the separation process of PDMS is continuous and the separation of particles at a certain position is instantaneous, the separation performance of PDMS at a specific separation angle cannot be investigated. To evaluate optimal operating features at different separation angles, a laboratory dry pneumatic flat magnetic separator (DPFMS) was manufactured, which also makes the airflow pass through the separation plane in the opposite direction to the magnetic force. The separation performance of PDMS was revealed by separation tests for −0.15 + 0.074 mm artificial mixed ore with 0–0.6 m/s airflow on DPFMS at various separation angles. At separation angles of 70° and 90°, the separation efficiency increases with an increase in airflow velocity from 16.68% and 33.09% to 77.72% and 76.54%, respectively; at separation angles of 110°, the separation efficiency increases initially from 89.53% to 90.69%, then decreases to 88.22% and keeps decreasing. The synergistic relationship between airflow drag, magnetic force and gravity were investigated by analyzing the composite force and the motion trajectory of a single particle. The results show that the proper airflow velocity aids in enhancing the distinctions between magnetite and quartz particles in resultant force and movement. However, throughout a wide range of air velocity, while the airflow can improve magnetite and quartz separation efficiency of at small separation angles, it may diminish the separation efficiency at large separation angles.

Capture effect of dry magnetic separator on biotite in fine aggregates: Experimental results and numerical simulations

In this paper, a series of magnetic separation experiments and FEM-DEM simulations were carried to study the dynamic capture behavior of a dry magnetic separator (DMS) for biotite in fine aggregates. Experimental results show that the capture effect of a DMS on biotite in fine aggregates is greatly affected by the particle size. Coarse particles (2 mm–4.75 mm) and ultrafine particles (0–0.075 mm) are difficult to be captured by the DMS, while fine particles (0.075 mm–2 mm) are easy to be captured. Numerical simulations show that the effect of a DMS on the captured morphology of biotite in fine aggregates comes from the arrangement of magnetic system structure. Compared with magnetic induction, the magnetic induction gradient produced by the extruded magnetic system has a more profound effect on the capture process of biotite. Based on the comprehensive analysis results of experiment and simulation, we conclude that the capture mechanism of DMS on biotite can be divided into four processes: magnetization, extrusion, entraining and separation. This study provides a theoretical basis for evaluating the effectiveness of DMS in sorting biotite from fine aggregates and designing high-performance DMS. • Capture mechanism of biotite by DMS was revealed through experiments and simulations. • A coupled FEM-DEM simulation program is developed. • Captured morphology of DMS on biotite in fine aggregates was demonstrated.

The influence of the synergistic effect of airflow and vibration in compound dry separation bed on upgrading of 6–0 mm fine-grained low-grade high-sulfur lignite

Coal is the important support to guarantee the national energy security system. China is the largest coal producer and consumer country and the lignite reserves are abundant. In recent years, as the high-quality coal resources decrease and the difficulty in mining increases, low-grade lignite resource has been the important component of China’s energy production and supply. Promoting the clean and efficient utilization of low-grade lignite is an important approach to realize the goal of carbon peak and carbon neutrality. In this paper, compound dry separation bed was used for the desulfurization and ash reduction of fine-grained low-grade high-sulfur lignite. The synergistic effect of airflow and vibration on particle force characteristics was emphatically investigated and the leading action stage under different airflow and vibration conditions was determined. The spatial migration acceleration variation rule and spatial migration trajectory of particles in different areas under the synergistic effect of airflow and vibration were systematically analyzed. Meanwhile, the spatial distribution characteristics of sulfur content of fine-grained low-grade high-sulfur lignite on the compound dry separation bed and the segregation rule of particles on the different areas along the bed transverse direction were explored, and the spatial distribution layer of the materials on the bed area was determined. The experimental results demonstrate that under condition of Γ = 10.14, when the gas velocity U = 0.125 m/s, vibration plays a leading role in the particle migration on the bed surface; when the gas velocity U = 0.148 m/s, vibration plays a leading role and the airflow plays a surrounding role; when the gas velocity U = 0.229 m/s, the synergistic effect of airflow and vibration dominates in the particle migration. The motion trajectories of particles in each cross section are all oval shape. The variation of acceleration amplitude along OX-axis determines the transverse migration trajectory of particles; the variation of acceleration amplitude along OY-axis determines the peak force characteristics of particles; the variation of acceleration amplitude along OZ-axis determines the stratification law of particles. Meanwhile, it is determined that the top layer of area Ⅰ is the low density particle distribution layer; the top layer of area II is the medium–low density particle distribution layer; all of the top, middle and bottom layer in area III are the high density particle distribution layer. The separation and upgrading for fine-grained low-grade high-sulfur lignite were conducted and the results were as follows. The yield of clean coal is 66.56 % and its sulfur content is 0.97 %; the yield of gangue is 33.44 % and its sulfur content is 22.41 %; the probable error Ep is 0.105 g/cm3, which means that the efficient and clean desulfurization and ash reduction for fine-grained low-grade high-sulfur lignite have been realized.

PROCESSING OF TECHNOGENIC WASTE OF MINING PRODUCTION

The article considers technologies for the processing of technogenic formations by additional extraction of target components, reduction of waste at the stages of enrichment and after chemical and metallurgical processing. This approach is fundamentally different from the existing basic outlines of the use of technogenic waste as secondary resources in the production of building materials. It is noted that in the tailings of dry magnetic separation of magnetite ores there are fine particles with iron concentration, which are of commercial interest. At the first stage, it is necessary to mechanically separate small classes from the total number of waste rocks. The solution to this problem is based on the use of high-performance air classification methods. The use of apparatuses with an inclined louvered grating is considered, for which the parameters of the degree of fractional extraction of magnetic separation tailings into a fine product are determined. The second stage of tailings enrichment consists in dry magnetic extraction of iron-containing particles from small classes. For these purposes, the use of new magnetic separators, specially developed earlier for working with magnetite particles of small sizes, is discussed. Taken together, this approach makes it possible to increase the overall degree of iron extraction from ore without additional grinding operations and significant financial costs. Another direction of the industrial application of the proposed technologies for the processing of technogenic waste relates to the production of phosphorus. The phosphorus industry is a promising sector of the chemical industry. But its development also bears negative features in the form of largetonnage waste generated after chemical and metallurgical processing. Among them, phosphorus sludge is the most aggressive - it is a drop of phosphorus in an aqueous medium, absorption by a "fur coat" from a mixture of dust and other products associated with phosphorus by absorption bonds in micelles. Applications are being considered for two developed phosphorus mining targets. To achieve this goal, it is necessary to destroy the mineralogical shell of micelles. Then the released phosphorus settles to the bottom due to the higher density and separation occurs. In the first approach, the destruction of the micelle shell is carried out chemically. In the second proposed technology, the destruction process occurs due to the physical cavitation effect, which is created by elastic acoustic vibrations of sound and ultrasonic frequencies. Experimental studies of the application of these technologies to sludge with a phosphorus content of 10-90% have shown the degree of phosphorus recovery of more than 95%.

СПОСОБИ ПІСЛЯЗБИРАЛЬНОЇ ОБРОБКИ ГІБРИДІВ КУКУРУДЗИ ТА ЇХ ВПЛИВ НА ЯКІСТЬ НАСІННЯ ПРИ ТРИВАЛОМУ ЗБЕРІГАННІ

Topicality. The seed stock creation and storage is a prerequisite in seed production of maize hybrids in order to provide sowing material in case of various adverse conditions (crop failure, natural disaster, etc.). Depending on the usage and the storage term, there are the insurance, reserve and breeding seed stocks. During storage, the seed germination may reduce; therefore, seed stock should be refreshed with seeds prepared for long-term storage. Issues. In order to prepare seeds for long-term storage, post-harvest processing aimed at forming longevity of hybrid corn seeds should be carried out. Thus, scientific and practical problem is the definition and optimization of technical and technological processes of the preparation of seeds for storage. Aim. To study the features of the formation of maize hybrid seed longevity, to establish methods and factors of post-harvest processing that ensure long-term storage and high seed quality. Materials and methods. In the experiments, we used maize hybrid seeds developed at the State Enterprise Institute of Grain Crops of NAAS. The moisture levels of the harvested seeds were different, and the seeds were processed for further long-term storage. When harvesting moisture is high, post-harvest processing includes different methods of drying, separation by fractional sieve and gravity methods, chemical treatment (seed dressing). Seeds were stored at different moisture content (7–8, 9–11, 12–14 %), in the different packages (paper, fabric, polyethylene), in the dressing and undressing state for 3–4 years. During storage, we have determined the laboratory germination by various methods, field germination, and the unity of sprout emergence. Results. We have established that the formation of longevity and seed quality of maize hybrids depend on features of harvesting and postharvest processing, such as harvest moisture, methods and temperature regimes of drying, sieve and gravity separation with the selection of various seed fractions, terms of chemical seed dressing. It was found that the laboratory seed germination indicator determined by cold test characterizes the economic suitability of maize hybrids for long-term storage. Conclusions. It was established that to obtain the high-quality seeds capable of long-term storage the following is recommended: to dry the cobs at humidity to temperature ratio of 31–36 % to 36–40 °C or 19–30 % to 40–44 °C; to grade seeds by sieving and gravity separator that to obtain two seed fractions, namely conditionally large and medium; to store undressed seed and carry out the dressing stocks immediately before sowing. Under long-term storage of untreated seeds, it is proposed to protect the seed against harmful objects with a combination of abiotic factors as low seed moisture content, cooling, limiting the oxygen access. When the maize hybrid seed with a moisture content of 9–11 % is hermetically packaged, it is guaranteed the storage period of the seed up to 3–5 years, so this method is most practical and cost-effective. It is recommended to determine the suitability of seeds for long-term storage by the germination indicators determined by the cold test. Keywords: maize seeds, germination, factors and processes of postharvest processing, long-term storage.

Separation behavior of sieved endosperm-enriched oat fractions via tribo-electrostatic approach

Endosperm-enriched oat fraction passed through 106-μm aperture size sieving of oat groats was further processed by dry and chemical-free tribo-electrostatic separation approach for protein enrichment. The sieved oat flour consisting of both bran and endosperm particles was fluidized in dry air to be tribo-charged in a polytetrafluoroethylene (PTFE) tube before being separated under an external electric field into protein-rich and protein-depleted fractions. The effects of airflow rate and electric field strength were assessed by conducting fifteen tribo-electrostatic separations at five different plate voltages of ±1, ±3, ±7, ±12, and ± 15 kV, as well as three different airflow rates of 7, 10, and 14 l per minute (LPM), providing laminar, transient, and turbulent conditions in the tribo-charger tube, respectively. All fractions attracted to the negatively charged plate (i.e., NCP fraction) were enriched in protein. However, the fractions absorbed on the positively charged plate (PCP fraction) or collected by gravity at the bottom of the separation chamber (i.e., CB fraction) were all depleted of proteins. Higher protein enrichments were observed for NCP fractions at laminar airflow rate, where the lowest yields and protein separation efficiencies were obtained. Increasing plate voltages slightly reduced the NCP fractions' protein content but significantly improved their yields and protein separation efficiencies. Therefore, a laminar airflow rate of 7 LPM and a high plate voltage of ±12 kV was selected as the best separation conditions for sieved oat flour. The SEM images of the NCP fraction obtained at 7 LPM and ± 12 kV showed the presence of bran and endosperm particles, while the PCP and CB fractions were depleted of bran particles. The full compositional analysis of the fractions produced at 7 LPM and ± 12 kV conditions showed the highest percentage of dietary fiber content in the PCP fraction. A negative correlation was observed between the protein content and mean particle size (D50) of the electrostatically separated fractions at the laminar and transient airflow rates. However, the protein-rich NCP fractions had the largest particle sizes at the turbulent airflow rate due to particle agglomeration and intense particle-particle interactions. An indirect offline approach was adapted to assess the charging behavior of all electrostatically separated fractions as functions of their protein content and particle sizes. All NCP fractions acquired higher charge density values than other fractions, which could be attributed to their higher protein contents. An online tribo-charge analysis method should be developed to assess the particle-particle interactions in the tribo-charger tube during electrostatic separation.

Zero valent iron or Fe3O4-loaded biochar for remediation of Pb contaminated sandy soil: Sequential extraction, magnetic separation, XAFS and ryegrass growth

In this study, the feasibility of using zero-valent iron (ZVI) and Fe3O4-loaded biochar for Pb immobilization in contaminated sandy soil was investigated. A 180-day incubation study, combined with dry magnetic separation, chemical extraction, mineralogical characterization, and model plant (ryegrass, namely the Lilium perenne L.) growth experiment was conducted to verify the performance of these two materials. The results showed that both amendments significantly transferred the available Pb (the exchangeable and carbonates fraction) into more stable fractions (mainly Fe/Mn oxides-bound Pb), and ZVI alone showed a better performance than the magnetic biochar alone. The magnetic separation and extended X-ray absorption fine structure (EXAFS) analysis proved that Fe (oxyhydr)oxides on aged ZVI particles were the major scavengers of Pb in ZVI-amended soils. In comparison, the reduced Pb availability in magnetic biochar-amended soil could be explained by the association of Pb with Fe/Mn (oxyhydr)oxides in aged magnetic biochar, also the possible precipitation of soil Pb with soluble anions (e.g. OH−, PO43−, and SO42−) released from magnetic biochar. ZVI increased ryegrass production while Fe3O4-loaded biochar had a negative effect on the ryegrass growth. Moreover, both markedly decreased the Pb accumulation in aboveground and root tissues. The simple dry magnetic separation presents opportunities for the removal of Pb from soils, even though the efficiencies were not high (17.5% and 12.9% of total Pb from ZVI and biochar-treated soils, respectively). However, it should be noted that the ageing process easily result in the loss of magnetism of ZVI while the magnetic biochar tends to be more stable and has high retrievability during the dry magnetic separation application.

Material composition and processing technology for quartz-kaolin rocks of the Khodzhakul deposit

This paper describes the material composition and processing technology for quartz sand isolated from the quartz-kaolin rock of the Khodzhakul deposit group located in the Republic of Uzbekistan. The chemical, mineral, and grain-size compositions have been studied for the quartz-kaolin rocks and a processing technology has been developed for the resulting sand. Material composition of the sand was established by X-ray phase analysis after calcination at 900–1350 °C, as well as using chemical and IR spectroscopic analysis methods. The effect of dilution of the kaolin suspension isolated by decantation has been studied. According to the research results, the best processing values are observed when using Uniflok flocculant and sodium phosphate solution as the dispersant at a ratio of 1.0 : 1.0. An 8-EVSV-16/100 electromagnetic separator was used to study the additional processing of quartz sand in an electromagnetic field. Electromagnetic treatment of the quartz product allows removing up to 78.6 % of iron impurities. Based on the results obtained, a process flow was proposed for the extraction and separation of quartz sand from the original rocks and its additional processing. This process includes hydraulic extraction of the raw materials, primary classification in hydrocyclones, quartz flocculation and washing of kaolin slimes, drying of the quartz product, and dry electromagnetic separation using a roller separator. The process includes process water circulation. The quartz sand obtained using this technology contains 97.8 wt% of SiO2, less than 0.05 wt% of Fe2O3, and 1.20 wt% of Al2O3. The quartz product with the specified composition may be used for the manufacture of colorless transparent glass.

Upgrading of low-grade high-sulfur lignite using differential dynamic field dry cascade cleaning apparatus

Coal is an important cornerstone to ensure national energy security under the new situation. China is rich in lignite reserves. In recent years, with the increasing consumption of high-quality coal resources, the development and utilization of low-grade lignite resources has become extremely urgent. Promoting the clean and efficient utilization of low-grade lignite resources is an important way to achieve the goal of carbon emission peak and carbon neutrality. In this paper, the low-grade high-sulfur lignite is desulfurized and ash-reduced by using the differential dynamic field dry cascade separation bed. The temporal and spatial migration and distribution law of material sulfur content in the cascade separation bed are mainly studied, and the dominant period of particle migration is determined. The effects of vibration intensity and airflow velocity on the density uniformity and stability of differential dynamic field cascade separation bed are systematically analyzed. At the same time, the cascade distribution characteristics of low-grade high-sulfur lignite in different transverse areas of the separation bed are explored, and the transverse separation functional area is determined. The experimental results show that when the separation time T = 0–6 s, the particle system is dominated by mixed migration; when T = 0–12 s, the particle system is dominated by mixed-regional layering migration; when T = 0–18 s, the particle system is dominated by stratified migration; when T = 0–24 s, the particle system is dominated by inspective stratification. It is determined that the area of 0–700 mm along the X axis is the transverse separation domain of the materials; the area of 700–1400 mm along the X axis is the transverse transition domain of the materials, and the area of 1400–2000 mm along the X axis is the transverse diffusion domain of the materials. When the operating parameters are in the range of A = 3.1 mm, f = 29 Hz, and v = 0.212–0.314 m/s, the uniformity and stability of the bed density are the best. The low-grade high-sulfur lignite was separated and upgraded by cascade separation bed and the separation result are shown as follows. The sulfur content of clean coal was 0.98%, the ash content was 8.96%; the yield was 67.32%. The sulfur content of gangue was 16.77%, the ash content was 69.59% and the yield was 32.68%. The probable error Ep is 0.1 g/cm3, which means that the high-efficiency desulfurization and ash reduction of low-grade and high-sulfur lignite are realized.