Dry Beneficiation Research Articles

A novel pneumatic dry high-intensity magnetic separator for the beneficiation of fine-grained hematite

This study focuses on the development of a novel pneumatic dry high-intensity magnetic separator (PDHIMS) (maximum magnetic induction of 2 T) to enhance the efficiency of separating hematite ore fines. Force analysis of the novel separator demonstrated that it can potentially reduce the lower size limit of hematite dry beneficiation from 58 μm to 10 μm. A series of experiments of mixed samples, such as hematite–quartz/feldspar/chlorite/augite indicated that PDHIMS is successful in achieving highly selective separation of hematite particles fine to 13 μm, overcoming the slime coating of −13 μm quartz particles on the surface of −150 + 38 μm hematite particles, and improving the separation efficiency between hematite and poorly intergrown particles (or magnetic gangues). Energy dispersive spectrometer (EDS) and microscopic imaging of the concentrate confirmed that −13 μm particles form stable aggregates and cannot be disrupted by the employed aerodynamic field in PDHIMS, resulting in a notable entrapment of quartz particles within the concentrate. Lastly, the induced roll magnetic separators (IRMS) with gravity feed and airflow feed were selected as the objects compared with the PDHIMS. The comparison revealed that PGHIMS exhibits a marked superiority in eliminating slime coatings from coarser magnetic products.

A novel separation density model based on force analysis of coal-based oil shale in pulsed fluidized beds

ABSTRACT It is important to study the theory and technology of coal-based oil shale dry beneficiation in China. Traditional separation density models are obtained through particle force analysis, but most studies tend to ignore the influence of medium resistance and bubble disturbance, which seriously limit the predicted accuracy of the separation density model. Therefore, the force on simulated mineral particles (steel balls) in pulsed fluidized bed (PFB) under different operating conditions was tested. It was found that the force decreases with the increase of gas velocity and distance from the distributor. The change of pulsation frequency has less influence on force. The force equilibrium equation was established and verified to be within 10% error; Finally, we obtain a new separation density model of PFB. This is of great importance for the industrialization and scale-up of dry beneficiation.

Dry beneficiation of bentonite using dynamic separator

Beneficiated bentonites, which contain predominantly smectite minerals, have many uses, such as pharmaceuticals, cosmetics, and advanced composite materials. The beneficiation of bentonites using dry processes is essential to being economical, fast, and accessible. This study developed a new method for the dry beneficiation of bentonites, and for this, a laboratory-scale dynamic separator was used as beneficiation equipment. A stirred media mill was used for grinding raw bentonite before beneficiation studies. The effects of the airflow rate and rotor rotation speed, which are the operating parameters of the separator, on the separation and beneficiation efficiency according to the particle size were investigated in detail. Quartz, opal, muscovite, and feldspars were removed from the raw bentonite sample, while small amounts of calcite and clinoptilolite minerals remained. It was determined that the amount of concentrated product obtained in this way, which had the d90 value of 23.6 μm, was 19.4% compared to the amount of product fed.

Experimental study of oil shale separation using binary medium by pulsed fluidized bed

ABSTRACT A large amount of the<6 mm fine particle oil shale created during mining and processing is frequently discarded, creating waste and an environmental hazard. A suitable fluidized dry separation technology would allow that fine particle to be de-ashed and improve the oil shale quality for effective utilization. This paper studies pulsed fluidized beds to determine the effectiveness of pulsation frequency, fines content and operating gas velocity on fluidization and separation of the fine oil shale. It was found that the introduction of fine particles could significantly improve the fluidization quality. When the content of fine particles is 5%, the average density of the bed is~2.3 g/cm3. The effective separation of the 6–3 mm oil shale was achieved using a mixed medium, with optimal separation conditions of 5% fine particle content, 4 Hz pulsation frequency, and 1.5U mf gas velocity. Finally, high efficiency dry beneficiation of 6-3 mm oil shale in pulsed fluidized bed was achieved, which is of great significance for future industrial applications.

Study on integration of drying and separation for lignite by hot airflow gas–solid fluidized bed

With the continuous consumption of high-quality coal, the efficient development of lignite resources is an important guarantee for the stable and sustainable development of coal industry. Due to the characteristics of lignite with high moisture content, its efficient separation is still a great challenge faced by the current industry. In this study, to improve the dry beneficiation efficiency of lignite, hot airflow and impeller were introduced into the gas–solid fluidized bed to achieve the integration of drying and separation for lignite. Effects of the impeller diameter, airflow velocity, airflow temperature and impeller speed on the drying features and the fluidization characteristics of hot airflow gas–solid fluidized bed were investigated. Drying and fluidization tests indicated that the appropriate operational factors of impeller diameter of 61 mm, airflow velocity of 1.2Umf (that is, Umf is the minimum fluidizing airflow velocity), airflow temperature of 110 °C and impeller speed of 60 r/min should be adjusted to obtain the optimum fluidization environment for the drying and separation of lignite. Under the optimal operating conditions, a high-quality clean coal with ash content of 9.72 %, moisture content of 13.13 %, and calorific value of 4318.33 cal/g was obtained for 25–13 mm lignite, while that with ash content of 13.41 %, moisture content of 12.70 %, and calorific value of 4120.22 cal/g was obtained for 13–6 mm lignite. Efficient drying and separation of lignite could be realized by using the hot airflow gas–solid fluidized bed. This study provides theoretical guidance for efficient beneficiation of lignite resources with high moisture content by hot airflow gas–solid fluidized bed.

Study of enrichment of vermiculite ores of the «Tebinbulak»deposit of the Republic of Uzbekistan

The mineralogical and technological properties of vermiculite raw materials are analyzed in the article, the main properties of natural vermiculite are studied. As a result of the tests, a technological scheme for dry beneficiation of vermiculite ores was developed. The output of vermiculite concentrate by fractions is 10.57%, its amount in enrichment is 85%, the separation of vermiculite in enrichment is 95.95%.

New technologies for diamond ores beneficiation

The main objective of the work is the development and implementation of technology and apparatuses for dry beneficiation of diamond-bearing ores and the creation of a fundamentally new class of modular mobile ore dressing units (MMODU). The article deals with the current state of crushing plants and pneumatic apparatuses. The results of the research of disintegration of lump ore in the DKD-300 crusher and comparison with foreign-made centrifugal impact crushers NP 1007 of the firm "Metso Minerals" by crushing degree are given. The comparative results of the extraction of minerals of different density are given in two types of pneumatic separator with straight and screw-shaped working chambers. The article considers the prospects of introducing dry technologies of mineral processing and beneficiation, which will significantly reduce the cost of diamond production.

Scientific experimental bases for dry beneficiation of mineral ores

The article presents the results of research on the development of processes and equipment for ore preparation and pneumatic dry beneficiation of mineral ores. The methods of crushing and grinding before enrichment of minerals have been considered, dry enrichment of geomaterials is investigated. Highly efficient prototypes of beneficiation equipment are developed and tested: crushers of multiple dynamic impact RD-MDV-900, DKD-300, centrifugal grinders CMVU-800 and VCI-12, pneumatic separator POS-2000. Fundamental designs are created, and a number of new ore preparation and pneumatic beneficiation instruments are being designed. The efficiency of approbation of an autonomous dry beneficiation complex with new safe environmental standards for the processing of gold-bearing ores, which makes it possible to fully release and extract free gold with a particle size from 10,000 to 100 µm, is shown. The introduction of the dry beneficiation method is very promising for the mining industry. It will allow to reduce capital costs for the construction of stationary beneficiation plants, completely or partially withdraw from the use of process water, the construction of a water supply system, a traditional tailing dam, etc.

Beneficiation of Magnetically Separated Iron-Containing Ore Waste

Rough processing of iron ore employs dry methods which means that equipment is tuned to process large particles, but fine magnetic material less than a few tenths of a millimeter in size is not separated as efficiently. The relevance of this study is determined by the fact that dry beneficiation waste contains recoverable iron-bearing magnetite of commercial value. Commercial justification of waste beneficiation is associated with mining and grinding costs that are already included in the prime cost of the commercial concentrate. The future of tailings retreatment prospects depends on technology and efficiency of the employed equipment, the development of which is the subject of this paper. At first stage, fine iron is recovered by air sizing, with pitched curtain air classifiers embedding simple design and high performance. Powder materials were magnetically separated by a manufactured drum-type separator in which, to increase the separation efficiency, the process was performed at increased drum rotation speeds using Nd-Fe-B magnets and a drum made of electrically non-conductive materials. The separator performance was determined for various rotation speeds of the drum. Research has proven that a multi-stage magnetic separation with a consequent increase in drum rpm is reasonable. A new cascade separator was manufactured and tested for this purpose. It is shown that iron-containing ore tailings beneficiation is optimal without any additional grinding.

Dry Beneficiation of Coking Coal Fines using an Advanced Air Cyclone

An attempt is made on coking coal fines dry beneficiation of below 2 mm size, with VSK separator consisting of advanced air cyclone. The results of these investigations reveal that simple size with 250 micron can give a product with 18% ash at 17.4% yield, whereas by using VSK separator the product obtained contains 17.8% ash with 48.1% yield from a feed sample containing 23.3% ash. Since the preliminary investigations has shown encouraging results on reduction of ash, large scale continuous tests can provide better yield for various samples.

Computer-Aided Design and Fabrication of a Dry Wind-Sifter Separator.

In this study, the simulation of a newly designed wind-sifter separator for dry beneficiation was deployed to upgrade −6.7 + 3.36, −3.36 + 1, and −1 mm coal. The wind-sifter principle is very effective for particle separation as it is based on the separation of lighter particles from heavier ones. First, the study entails computer simulations by utilizing the Lagrangian particle tracking method to observe the effectiveness of the wind sifting principle in separating particles based on their density in an air stream. From the three particle size fractions used, the simulation test results show that at a cut-point of 1.5 RD, yields of 29.1, 54.3, and 99.4% were attained at different optimum velocities for −6.7 + 3.36, −3.36 + 1, and −1 mm, respectively. The effect of operating parameters such as the mass flowrate and air velocity on yield, ash content, and calorific value were determined using the fabricated separator. A preliminary experimental study showed that the separator was effective in upgrading the feed coal with 30.28% ash content and 21 MJ/kg calorific value to clean coal with 18.94% ash content and 26.8 MJ/kg calorific value. A laboratory-scale wind-sifter separator was fabricated based on the results from the simulation test, which served as the first applied prototype in the field of dry coal beneficiation.

Dynamics of partially collapsing pulsed fluidized bed

AbstractThe use of flow pulsation as an effective assisted fluidization technique has been suggested in a number of applications, such as drying of food and pharmaceutical products, dry beneficiation of coal, and deagglomeration of nanopowders, owing mainly to its cost‐effectiveness and ease of implementation. The efficacy of this technique is, however, greatly affected by the frequency of pulsation since it controls the collapse dynamics of the fluidized bed. In this study, using ultrafine hydrophilic nanosilica with strong agglomeration tendencies, the pulsation frequency was controlled to allow only partial collapse of the bed between two successive pulsations while the global and local dynamics in different bed regions were carefully monitored. Besides the usual advantages associated with assisted fluidization techniques, such as lower minimum fluidization velocity, higher bed expansion, and elimination of bed non‐homogeneities, the continuous and intense solid motion imparted by the partial bed collapse caused a more substantial increase in the overall pressure drop than the one obtained with the conventional unassisted fluidization. The results of the frequency domain analysis highlighted the fact that the effect of pulsation event was felt differently in different regions of the bed depending upon the amplitude of the pulsation. These results were further corroborated by the similarity analysis.

A novel dry gravity separation method for cleaner production of fine sized iron ore concentrate

ABSTRACT Though wet beneficiation technologies for iron ore are well established, owing to issue like disposal of reject as slurry, the development of dry beneficiation technology is being felt by the concerned Industries. A bench-scale dry gravity separator is fabricated, and detailed experimental studies were carried out to evaluate its performance. This study considered three experimental parameters: superficial air velocity, feed rate, deck inclination. Mathematical formulation results corroborated with experimental response indicate that moderate superficial air velocity, low feed rate, and high inclination angle are favourable conditions for enhancing product Fe content. Further experiments were carried out in multiple stages. It is noted that the fabricated unit can produce the sinter grade concentrate (63.5% Fe) with a mass recovery of 22.7% from iron ore 1 and 24.9% from iron ore 2. The performance of the fabricated dry processing unit is compared with the wet processing unit.

Enhancement of Dry Beneficiation of Coal by Air Distributor Design Modification in an Air-Pulsated Stratifier

Enhancement of Dry Beneficiation of Coal by Air Distributor Design Modification in an Air-Pulsated Stratifier

Quadratic Mathematical Modeling of Sustainable Dry Beneficiation of Kaolin

Clay minerals are one of the most utilized minerals among non-metals. These are hydrous aluminum silicates with a layer (sheet-like) structure. Kaolin is a hydrous aluminosilicate mineral with a thin platelet structure. Kaolin is extensively used in paper, paint, and many other industries. Wet processing of kaolin will not be sustainable over the long term because global freshwater resources are becoming scarce. Hence, a process is necessary that does not consume water during the beneficiation of kaolin. This study developed a dry beneficiation process for low-grade kaolin of 59.6%, with 12% quartz and about 6% titaniferous impurities from Nagar Parkar, Sindh province, Pakistan. To develop a size difference between kaolinite and impurities, steel balls clad with rubber were used as the grinding media in a selective grinding unit. Screens of 60 and 400 mesh were employed to classify the feed of air classifier. Oversize +60 mesh was reground, 400 to 60 mesh fractions were sent to an air classifier, and −400 mesh was considered to be a product with the grade and recovery of 90.6% and 20.5%, respectively. Air classifier experiments were designed using central composite design. An experiment using a fan speed of 1200 revolutions per minute (rpm) and a shutter opening of 4.0 showed optimum results, with maximum kaolinite grade and recovery of 91.5% and 35.9%, respectively. The statistical models developed for grade and recovery predicted the optimum results at a fan speed of 1251 rpm and shutter opening of 3.3 with the maximum kaolinite grade and recovery of 91.1% and 24.7%, respectively. The differences between experimental and predicted grade and recovery were 0.1% and 2.4%, respectively. The characterization results showed the total upgrade of kaolin from 59.6% to 91.2%, with 27.1% recovery during the process. The designed methodology has the potential to improve the yield of the product by focusing on its recovery. Furthermore, the designed process can be improved by using different sized balls in the selective grinding unit. This beneficiation process can utilize more than one air classifier in series to achieve the targeted results.

Economic and Socio-Environmental Benefits of Dry Beneficiation of Magnetite Ores

In our previous studies, we demonstrated the performance of novel superfine crusher and pneumatic planar magnetic separator as energy-efficient technologies for dry processing of magnetite ores. The present study investigates the economic and socio-environmental benefits of applying these technologies in conceptual dry magnetite ore processing flowsheet. The outcome of the study is compared with that of a conceptual wet processing flowsheet for the same ore. The cost estimations used are based on the Brook Hunt C1 methodology whilst revenue estimations are based on the Platts Iron Ore Index specification. The demonstrated economic and socio-environmental benefits show that dry processing flowsheet offers significant energy and cost savings and improved revenue generation compared with the wet process flowsheet. These findings are vital to the magnetite industry, particularly in water- and energy-scarce regions as a benchmark for future studies aimed at deepening and expanding the knowledge base of dry beneficiation of magnetite ores.

Dry beneficiation of coal on KAT air table

ABSTRACT Dry gravity-based separation processes such as pneumatic jigs and tables generally use density stratification of feed material with light and dense particles to achieve separation. Therefore, it is necessary to enhance the stratification of the particles in the separation bed. The main purpose of this work was to evaluate the use of an intrinsic autogenous separation medium of feed coal for the dry separation process by increasing the separation bed height in a pneumatic table separator. Tests were conducted and the results showed that increased bed height and an autogenous separation bed resulted in a significant benefit for the separation efficiency. Bituminous coal samples with high-density impurities containing 48.9% feed ash were reduced to 7.7% ash content with a combustible recovery of 89.7%. In the case of higher density anthracite coal, the experimental separator was able to reduce feed ash 50–60% to 26–28% in the product.

A Novel Pneumatic Planar Magnetic Separator for Magnetite Beneficiation: A Focus on Flowsheet Configuration

In our previous studies, we investigated the performance of a novel pneumatic planar magnetic separator (PMS) for the dry beneficiation of a selected magnetite ore. In the present study, we have extended the studies on the PMS with the focus on investigating how various PMS processing flowsheet configurations influence its performance. The outcomes were subsequently compared with those of a Davis tube recovery (DTR) tester. The study demonstrated that the use of PMS in the dry beneficiation of magnetite ores is feasible, and operating the PMS in different flowsheet configurations positively influences the magnetite concentrate grade and purity. Finally, the study showed that the PMS performance compares well with that of DTR and can potentially replace DTR in operations that are carried out in arid regions.

A comparative study on the effect of chemical additives on dry grinding of magnetite ore

Dry grinding as an alternative to wet grinding is one of Sweden's strategic research areas to promote dry beneficiation. However, dry grinding has remained unpopular due to its higher specific energy consumption (Ec), wider particle size distribution (PSD), difficult material handling, and purported effects on downstream processes. In this work, the effects of the new additives (Zalta™ GR20–587, Zalta™ VM1122, and Sodium hydroxide) employed as grinding aids (GA) on dry grinding and product characteristics of a magnetite ore were studied in light of possible downstream effects. The grinding efficiency of Magnetite increased after using GAs in comparison without the GAs; however, an optimal dosage exists for each of the chemical additives investigated. Comparing to grinding without GA, Zalta™ VM1122, a viscosity modifier was selected as the most effective GA where by using this GA; the Ec decreased by 31.1% from 18.0 to 12.4 kWh/t, the PSD became narrower and finer (the P80 decreasing from 181 to 142 µm), and the proportion of the particles (38–150 µm) increased from 52.5 to 58.3%. Zalta™ VM1122 resulted in increased surface roughness and minimum microstructural defects. Further, it was found that Zalta™ VM1122 resulted in similar zeta potentials and pH values for the product compared to grinding without GA. These comparable product properties are advantageous as they minimize any potential negative effects on all possible downstream processes such as flotation.

Effects of sound fields on hydrodynamic and dry beneficiation of fine coal in a fluidized bed

The difficulty of forming a stable fluidized bed for fine coal (<1 mm) reduces the effectiveness of the density-segregation process and subsequent dry beneficiation of fine coal. Sound fields provide a new method of improving the bed stability of fine coal. In this study, the hydrodynamic and dry beneficiation of fine coal under a sound field was investigated by a numerical simulation and an experiment. The results indicate that when the sound frequency f (or sound pressure level SPL) is increased, the fluidization characteristics of the bed significantly improve, although the increased sound absorption coefficient weakens the positive effects of the sound field on the fluidization characteristics under high frequencies (f > 120 Hz). Moreover, the simulation results indicate that the introduction of the sound field eliminates large bubbles at a high gas velocity, resulting in an expansion of the gas velocity range for the efficient density segregation process of fine coal. Finally, under appropriate operating conditions (f = 120 Hz, SPL = 120 dB, u = Umf), fine coal was separated in a sound-assisted fluidized bed, with probable error E values as low as 0.11 g/cm3, where the clean coal yield was 52.20% with an ash content of 23.28%; the yield of gangue products was 47.80% with an ash content of 47.80%, demonstrating the efficient beneficiation of fine coal in a sound-assisted fluidized bed.