Pneumatic Separation Research Articles

Underground pneumatic separation of coal and gangue with large size (≥ 50 mm) in green mining based on the machine vision system

Coal gangue separation is of key important for green mining. Underground pneumatic separation of coal and gangue based on the machine vision system is proposed in this study. This method has the potential to be used in coal mining due to the real time control and simple work principle. Here, the theoretical pneumatic separation distance formula of coal and gangue is derived based on energy conservation principle. Then hard-sphere model is applied to simulate the particle motion pattern in a three-dimensional model with a pressure–velocity boundary, and key factors affecting coal gangue pneumatic separation for large diameter (≥50mm) are analyzed. An air–solid multiphase flow simulation was conducted to clarify all the three factors (airflow velocity u, the conveyor velocity v0 height difference hp between conveyor belt and air nozzle) have great influence on separation distance. Especially, the optimal parameters for best separation distance are presented at u=320m/s,v0=0.5m/s,hp=0.4m. Besides, the theoretical pneumatic separation distance formula is corrected based on experiment data, the error between experiment value and calculate value of the separation distance is less than 15%. The corrected formula has important guiding significance and practical value for coal gangue pneumatic separation.

Effect of Distance between Orifices in Column Type Pneumatic Separator for Waste Electronic Devices

Effect of Distance between Orifices in Column Type Pneumatic Separator for Waste Electronic Devices

Recycling of printed circuit boards (PCBs) to generate enriched rare metal concentrate

An eco-friendly process for recycling obsolete PCBs to get enriched rare-metal concentrate using physical separation technique is discussed. Metal concentration in digital video disc (DVD) PCBs is ∼43wt.% whereas in vacuum cleaner (VC) PCBs ∼30wt.% with rare metal of ∼ 2.8%. Concentrate grade of ∼88% total metals including ∼5.85% rare metals in-case of DVD-PCBs while ∼90% of total metals including ∼2.81% rare metals in-case of VC-PCBs was achieved by froth flotation. While ∼75% total metals including ∼9.41% rare metals for DVD-PCBs and ∼65% total metals including ∼5.10% rare metals for VC-PCBs was obtained by pneumatic separation.

Upgrading Low-Rank Coal Using a Dry, Density-Based Separator Technology

Low-rank coal such as the coal in the Powder River Basin (PRB) is typically direct shipped without any need for upgrading. Due to the lack of on-site processing capabilities, coal that is mixed with out-of-seam dilution during the mining process is typically left in the mine pit. In some cases, the loss could amount to 5% of the total reserve. Research conducted on laboratory and pilot-scale pneumatic air table separators indicates that sufficient upgrading can be achieved on the +1 mm fraction of the reject material to meet typical end-user specifications. Low-rank coals are especially susceptible to upgrading by density-based processes due its naturally lower density relative to higher rank coals. For example, a PRB coal containing 26% feed ash was reduced to 7% ash content with a combustible recovery of 83% on a dry basis from a coal source that was reject from the mining process. Partition curve data revealed the achievement of relatively low Ep values in the range of 0.12 to 0.22 with separation densities between 1.58 and 1.88 gm/cm3, respectively. Effective separations were achieved using air table separators for particle sizes larger than 1 mm.

Effect of Orifice Introduction on Floating Characteristics of Cuboid Particles Simulating Tantalum Capacitors in Pneumatic Separation Column

To recycle important rare metals (such as tantalum) from the printed circuit boards of waste electronic equipment, devices must first be delaminated from the boards. The devices are then separated into individual device types. For the practical use of the separation process, the authors previously developed a double-tube pneumatic separator. One of the features of this equipment is the introduction of orifices in a pneumatic separation column; an air­solid multiphase flow simulation was conducted to clarify its effect. The effects of the orifices on the floating characteristics and floating rates of cuboid particles and spherical particles with the same solid volume and mass as the cuboid particles were investigated for cases in which the number of orifices and the volumetric airflow rate in the separation column were varied. The results showed that the floating characteristics of cuboid particles were much different from those of spherical particles. It was estimated that the volumetric airflow rate could be decreased by 14% with the cuboid particles and the same particle recovery could still be achieved. When the volumetric airflow rate was identical, the treatment throughput for the cuboid particles was expected to increase by 20­30%. These results were caused by the difference in the cross-sectional areas of the particles, which indicates that taking the particle shape into account is extremely important for the numerical simulation of pneumatic separation. To thoroughly recover the cuboid particles, it is ideal to use a volumetric airflow rate greater than 0.129m3·s11 or less than 0.0615m3·s11, regardless of the orifice introduction. The number of orifices had no effect on either the separation efficiency or floating rate in the range of 0.118­0.129m3·s11. On the other hand, it was shown that the floating rate clearly changed depending on whether the orifices were introduced or not for the 0.103m3·s11 case. [doi:10.2320/matertrans.M-M2014818]

Effect of Orifice Introduction on the Pneumatic Separation of Spherical Particles

In order to recycle important rare metals (such as tantalum) in the print circuit boards of waste electronic equipment, the devices must first be delaminated from the board. The devices are then separated into each device type such as capacitors, resistors, thermistors and so on. In this study, the effect of orifices on spherical particles was clarified through numerical simulations of airflow and air­solid multiphase flow in a vertical single-column pneumatic separator. Airflow velocity profiles and particle trajectories were investigated for different numbers of orifices using spherical particles of identical size and different densities. By introducing multiple orifices, the eccentricity of the velocity profile in the vertical direction could be corrected. This eccentricity is caused by the presence of a mesh, which recovers heavy particles after they pass through the second orifice. When the distance between orifices ranged from 400 to 625mm, it was expected that high-speed and high-efficiency separation between orifices would be possible. It implies that step-by-step separation could be conducted in a single separation column. However, under the calculation conditions of our study, the orifices did not affect the separation efficiency because this factor depends on the velocity profile around the feeding position. The separation rate was maximized when the orifices were separated by 625mm.

The impact of size and shape of particles of undergrowth and herbs mixtures on aerodynamic properties

The impact of the size and shape of a selected group of herbs (dried juniper berries – Juniperus communis, dry blueberries – Vaccinium myrtillus, petals of cornflower – Centaurea cyanus) on the value of the volatility coefficient, the coefficient of sphericity and the critical speed was analysed in the presented research. A laboratory anemometer to measure the speed of air was used. The determination of the volatility coefficient of particular size fractions was conducted on the basis of critical speed values, calculated as an average established after five measurements. The established aerodynamic properties of particular mixtures allow the determination and the assessment of differences among fractions of valuable resources and different impurities. The presented data might constitute a basis to determine the scope of differences among them and establish interrelations which allow the application of proper parameters for the pneumatic separation process in practice.

Development of a Pneumatic Separator Based on a New Conception of Strategic Urban Mining

Development of a Pneumatic Separator Based on a New Conception of Strategic Urban Mining

Wpływ wielkości i kształtu cząsteczek mieszanin runa leśnego i ziół na właściwości aerodynamiczne

The impact of the size and shape of a selected group of herbs (dried juniper berries – Juniperus communis, dry blueberries – Vaccinium myrtillus, petals of cornflower – Centaurea cyanus) on the value of the volatility coefficient, the coefficient of sphericity and the critical speed was analysed in the presented research. A laboratory anemometer to measure the speed of air was used. The determination of the volatility coefficient of particular size fractions was conducted on the basis of critical speed values, calculated as an average established after five measurements. The established aerodynamic properties of particular mixtures allow the determination and the assessment of differences among fractions of valuable resources and different impurities. The presented data might constitute a basis to determine the scope of differences among them and establish interrelations which allow the application of proper parameters for the pneumatic separation process in practice.

Polyphenolic and basic chemical composition of black chokeberry industrial by-products

The aim of the work was to examine basic and polyphenolic composition of chokeberry pomace fractions achieved as a result of industrial-scale processing of fruit into juice. As the result of sieving and pneumatic separation use two kinds of fractions were obtained: containing seeds and seedless ones. The content of dry substance, total dietary fibre (TDF), protein, fat, ash, macro- and micro-elements, saccharides, organic acids, polyphenols and amygdalin were determined in the fractions. The examined fractions differed in the size of particles which resulted from the presence of various morphologic parts of fruits, e.g. flesh, skins, seeds, leaf, stalks as well as their agglomerates. The carried out research indicates that pomaces constituting a waste material should be perviewed as non-homogeneous raw material. The processing of chokeberry pomace should include separation of seeds as valuable raw material rich in fat (13.9%), proteins (24%) and mineral compounds. Seedless fractions, in turn, characterised by particularly high content of TDF (∼75%), proanthocyanidins (12,000mg/100g) and anthocyanins (1200mg/100g) may be applied in production of polyphenolic extracts and/or dietary fibre preparations. Subsequent usage of pomace must take into account the presence of amygdalin, which is present in considerable quantities (120–180mg/100g of dry matter) in seed fractions. These quantities are a few times higher in comparison with seedless fractions. The obtained results were subjected to statistical analysis in which a cluster analysis method was applied in order to present differences between examined fractions.

수직(垂直)컬럼형(形) 풍력선별기(風力選別機)의 분리효율향상(分離效率向上)을 위한 bypass유로(流路)의 적용(適用)

A vertical column pneumatic separator was modified to improve its separation performance. A branch column was installed at the center of the main column, which created a bypass flow and changed the flow rate of the main column before and after the branch column. To separate a mixture comprising light and heavy materials, the airflow in main column after the branch column was set to lift the only light materials and the airflow in main column before the branch column was set to prevent the flow of the light materials from flowing downwards. Materials directed into the branch column were separated from the flow and returned to the feeder through the cyclone linked to the branch column. The performances of the straight-type separator and the modified separator were compared using glass and zirconia beads with a narrow size distribution.

Computer Simulation of the Pneumatic Separator in the Pneumatic–Electrostatic Separation System for Recycling Waste Printed Circuit Boards with Electronic Components

Technologies could be integrated in different ways into automatic recycling lines for a certain kind of electronic waste according to practical requirements. In this study, a new kind of pneumatic separator with openings at the dust hooper was applied combing with electrostatic separation for recycling waste printed circuit boards. However, the flow pattern and the particles' movement behavior could not be obtained by experimental methods. To better control the separation quantity and the material size distribution, computational fluid dynamics was used to model the new pneumatic separator giving a detailed understanding of the mechanisms. Simulated results showed that the tangential velocity direction reversed with a relatively small value. Axial velocity exhibited two sharp decreases at the x axis. It is indicated that the bottom openings at the dust hopper resulted in an enormous change in the velocity profile. A new phenomenon that was named dusting was observed, which would mitigate the effect of particles with small diameter on the following electrostatic separation and avoid materials plugging caused by the waste printed circuit boards special properties effectively. The trapped materials were divided into seven grades. Experimental results showed that the mass fraction of grade 5, grade 6, and grade 7 materials were 27.54%, 15.23%, and 17.38%, respectively. Grade 1 particles' mass fraction was reduced by 80.30% compared with a traditional separator. Furthermore, the monocrystalline silicon content in silicon element in particles with a diameter of -0.091 mm was 18.9%, higher than that in the mixed materials. This study could serve as guidance for the future material flow control, automation control, waste recycling, and semiconductor storage medium destruction.

Novel physical separation process for eco-friendly recycling of rare and valuable metals from end-of-life DVD-PCBs

Present paper reports a simple and eco-friendly physical separation process for the recycling of metallic values from PCBs. The separation of material is based on distribution of metallic and non-metallic constituents in different size fractions depending on their liberation size due to their malleable or ductile nature. The studies showed the enrichment of metals in coarser particles (−1000+150μm) and non-metals in the finer particles −150μm following pneumatic separation and froth flotation process. A grade of 88% with 75% recovery was achieved by froth flotation, but lower grade of ∼75% with ∼65% recovery were obtained by pneumatic separation with −1500μm powder. Overall grade of metals was achieved up to 88% by controlling the feed and air flow rates during pneumatic separation. Using this beneficiation technique, the concentration of rare metals in the different fractions varying from 1.88% to 4.18% was enriched up to 9%.

Constructional and technological characteristic of a shutter air cleaner with curvilinear diversion canal

Researches allowing to determine the design and technological characteristics of shutter air cleaner with curvilinear diversion canal of a small-sized pneumatic separator were carried out. The findings can improve the device’s performance.

A closed small-sized pneumatic separator for seed cleaning

A pneumatic separator equipped by closed small-sized pneumatic system was developed. It ensures cleaning of seed of cereal and grain-legume crops from hard-separable impurities of different aerodynamic features after the air-sieve and trieur machines.

Division of grain heap into fractions by a pneumatic screen separator

Division of grain heap into fractions by a pneumatic screen separator

Sorting Mechanism and Airflow Simulation of Garbage Pneumatic Separator

In order to obtain flow rule and separation mechanism of garbage mixture particle in pneumatic separator, under the conditions of certain parameters and boundary, gas-solid two-phase flow mathematic model of garbage mixture particle was set up, FLUENT software was used to simulation and analyze the flow field of improved pneumatic separator, the separate track of particle in improved pneumatic separator was gained and performance of improved pneumatic separator was forecasted. Numerical simulation results show that the improved pneumatic separator has stable variation of pressure and velocity field. There not exist internal turbulence and back-mixing phenomenon and three particles with different qualities can be separated effectively. The numerical methods can be further optimized pneumatic separator and important theoretical foundation and technology method are provided for improving the structure and performance of pneumatic separator.

The technique and analysis of the process of separation and cleaning grain materials

In the process of pneumatic separation, the aerodynamic properties of particles such as their critical velocity, are used.A pneumatic separator was designed that allowed a wide range of control parameters to be used.The essential factors affecting the course of the separation process were identified and a theoretical correlation between these factors and the separation efficiency were determined.The main aim of the study was to analyse the separation process in an air stream of broken lupine seeds, chiefly involving theoretical considerations of movement and behaviour of mixture particles in a pneumatic canal. Investigations and observations gave ground for an attempt at deriving a movement equation of particles in an unrestrained, uniform air stream.The equations obtained can be used for calculating the parameters of particle movement in pneumatic canals. The velocities of air stream, then, can be a few times higher than the critical velocity/convection/of individual particles. While working out the above problems the following points were considered: on the one hand, possibilities of obtaining the greatest outcome from the separation process and on the other, reducing the losses of valuable material in the discarded lot to a maximum.

Production of ferrosilicomanganese concentrate from tailings slag

The viscosity and electrical conductivity of MnO-SiO2-CaO-Al2O3 slag melts for the largescale smelting of ferrosilicomanganese in RPZ-63 furnaces at PAO Nikol’skii Zavod Ferrosplavov are investigated. Factors responsible for alloy loss are noted, and extraction of the alloy from tailings slag is considered. Instead of pneumatic separation and hydraulic jigging, a new technology is proposed for sorting of the slag and the extraction of metal concentrate, on the basis of electronic sensors and data-processing software.

PHYSICAL AND AERODYNAMIC PROPERTIES OF FLAXSEEDS FOR PROPER SEPARATION BY USING AIRSTREAM

ABSTRACT This study aimed to develop simple empirical equations to predict flaxseeds properties. The first part of the present study deals with the physical, aerodynamic and solid flow properties of flaxseeds which were evaluated as a function of change in moisture content from 8.60 to 23.90% dry basis (d.b.); the dimensions of the length, width and thickness varied from 4.14 to 4.32 mm, 2.03 to 2.13 mm and 0.88 to 0.93 mm, respectively. As the moisture content increased from 8.60 to 23.90% d.b., the bulk density, true density and porosity were found to decrease from 46.65 to 44.89 kg/m3, 1,244 to 1,176 kg/m3 and 46.65 to 44.89%, whereas angle of repose and terminal velocity were found to increase from 27.6 to 35.80 and 2.46 to 3.56 m/s, respectively. The static coefficient of friction on various surfaces, namely plywood, stainless steel, galvanized iron, iron and internal also increased linearly with the increase in moisture content. The results of the experimental investigation may help to optimize some engineering parameters of separation equipment. The present work was carried out to separate flaxseed from light impurities (chaff, other debris from threshed flaxseed since the introduction of harvesting machine). It is difficult to separate seeds from straw and other foreign materials by using primary separation equipment. The difficulty comes from the narrow size and shape, angle for both of natural slope and friction between foreign materials and seeds. The second part was carried out on a series of experiments to specify the optimum conditions of separating operations which insure the highest grade of separation efficiency with minimum losses. Pneumatic separation equipment was manufactured and tested under different combinations of the following factors: airstream velocity, feed rateand sample moisture content. The performance of the equipment was evaluated by using the indices separation efficiency and percentage of seed losses. The results of the equipment performances showed that the combinations of airstream velocity, feed rate and sample moisture content affected significantly the separation efficiency and grain losses. Airstream velocity of 2–6 m/s combined with 8.5 kg/h feed rate and 8.6% moisture content can be considered the most favorable combination values of these variables. They gave the highest grades of separation efficiency and the minimum grain losses. PRACTICAL APPLICATIONSThere are several applications of the physical properties data. Physical attributes and aerodynamic properties are required in the design of combines as well as cleaning and grading equipment. Information about solid flow properties is needed to design handling equipment. Physical properties data are needed for the development of sensors to control machines and processes, as well as detect quality. Physical properties of crops are requisite for better design of storage and ventilation system. The physical properties that we are investigating include: (1) physical attributes such as dimensions and densities; (2) aerodynamic properties such as terminal velocity and drag coefficient; and (3) solid flow properties like angles of repose and internal friction.