Collection Of Fine Particles Research Articles

Selective aggregation of fine copper minerals using charged polyacrylamides

Selective aggregation can be used to improve the collection of fine valuable mineral particles often lost in industrial separation processes. This approach might be applicable to flocculate fine copper mineral particles such as chalcopyrite. It is hypothesised that the polymeric flocculant charge type will influence selectivity between chalcopyrite and waste minerals. This work investigates the use of charged anionic (APAM) and cationic (CPAM) polyacrylamides to selectively aggregate negatively charged chalcopyrite from its common waste (quartz). The interaction of the polymers with the mineral's surfaces as well as its flocculation capability were investigated through adsorption isotherms, turbidity tests, and in-situ aggregate size measurement. Furthermore, the ability to selectively aggregate and recover the valuable chalcopyrite from a quartz mixture by sedimentation was assessed. The results indicated that both charged polymers can be used to aggregate fine chalcopyrite particles, however, CPAM is non-selective towards the valuable mineral, as it also aggregates quartz. CPAM has a stronger affinity for both minerals, probably due to charge-charge interaction adsorption mechanisms, whereas APAM adsorption was lower, and more likely to be driven by hydrogen bonding. The interaction of APAM with quartz was limited probably because its highly negatively charged surface tends to repel the anionic polymer. Finally, the recovery of the chalcopyrite by sedimentation separation improved when using both polymers, but higher recoveries were obtained when using APAM.

Numerical Investigation of Performance of Two-Stage Cyclone Separator for Fine Particle Collection of Medical Waste

Numerical Investigation of Performance of Two-Stage Cyclone Separator for Fine Particle Collection of Medical Waste

Effect of arc element diameter on fine particle collection efficiency of the separator

Clean gas without suspended particles is an essential factor for many industries. The paper is concerned with the design of a separation device with rows of the arc elements, in which a wave-like flow pattern is observed. The separation of solid particles from the gas occurs due to inertial and centrifugal forces. A three-dimensional model of the device and its operating principles are presented. The aim of the work is to numerically study the effect of the size of the arc elements of the separation device on the efficiency of particle collection. In the course of the simulation, the diameter of the arc elements varied from 25 to 50 mm. The exit to the stationary solution was estimated by the pressure drop of the separation device. It was found that about 870 iterations were needed. Results have shown that the diameter of the arc elements, at which the maximum efficiency of collecting particles from gas-solid flow occurs, is 40 mm. The separation efficiency of the device with a diameter of the arc elements of 25, 40, and 50 mm averages 81.1, 90.1, and 86.5%, respectively, at an inlet gas velocity of 0.5 to 5.0 m/s. The pressure loss in the separation device ranged from 12.6 to 1924.1 Pa at a gas velocity of 0.5 to 5.0 m/s. It is concluded that it is important to use a separation device to collect fine particles at a dusty gas velocity of less than 3 m/s because its pressure drop is significantly lower compared with other air separators.

Evaluation of the efficiency of a Venturi scrubber in particulate matter collection smaller than 2.5µm emitted by biomass burning.

Energy demand has increased worldwide, and biomass burning is one of the solutions most used by industries, especially in countries that have a great potential in agriculture, such as Brazil. However, these energy sources generate pollutants, consisting of particulate matter (PM) with a complex chemical composition, such as sugarcane bagasse (SB) burning. Controlling these emissions is necessary; therefore, the aim was to evaluate PM collection using a rectangular Venturi scrubber (RVS), and its effects on the composition of the PM emitted. Considering the appropriate use of biomass as an industrial fuel and the emerging need for a technique capable of efficiently removing pollutants from biomass burning, this study shows the control of emissions as an innovation in a situation such as the industrial one with the use of a Venturi scrubber in fine particle collection, in addition to using portable and representative isokinetic sampling equipment of these particles. The pilot-scale simulation of the biomass burning process, the representative sampling of fine particles and obtaining parameters to control pollutant emissions for a Venturi scrubber, meets the current situation of concern about air quality. The average collection efficiency values were 96.6% for PM> 2.5, 85.5% for PM1.0–2.5, and 66.9% for PM< 1.0. The ionic analysis for PM< 1.0 filters showed potassium, chloride, nitrate, and nitrite at concentrations ranging from 20.12 to 36.5 μg/m3. As the ethanol and sugar plants will continue to generate electricity with sugarcane bagasse burning, emission control technologies and cost-effective and efficient portable samplers are needed to monitor particulate materials and improve current gas cleaning equipment projects.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-22786-3.

Effects of Various Physical and Chemical Disinfection Methods on the Fine Particle Collection Efficiency of N95 Respirators and Surgical Masks.

Several studies have reported on the effectiveness of various disinfection methods for severe acute respiratory syndrome coronavirus 2 and their applicability to the disinfection of N95 respirators and surgical masks. To date, there have been no reports on the decontamination of deep in the intermediate layers of the multilayered structure. In this study, the conditions required for decontamination of such layers were simulated by considering the thickness and shape of N95 respirators or surgical masks (samples). After applying heat (steam, dry heat, or hot water) at 75°C for 60 min or chemical (benzalkonium chloride or laundry detergent) treatment, the collection efficiency of the samples was evaluated. Following the dry heat treatment, the time between the treatment and heat reaching the intermediate layer of the filter fiber was extended by 10 min. A dry heat disinfection method that combines hot water and a closed container was also evaluated, and satisfactory conditions were extended by 60 min. For each heat treatment, there was almost no effect on the collection efficiency, although there were cases where deformation was caused by mechanical stress. In contrast, chemical treatment resulted in a reduction in the collection efficiency of smaller particles.

Effect of Dust Types on the Eco-Physiological Response of Three Tree Species Seedlings: Eucalyptus camaldulensis, Conocarpus erectus and Bombax ceiba

Dust is the collection of fine particles of solid matter, and it is a major issue of atmospheric pollution. Dust particles are becoming the major pollutants of the urban environment due to hyperbolic manufacturing and automobile pollution. These atmospheric pollutants are not only hazardous for human beings, but they also affect tree growth, particularly in urban environments. This study was designed to examine the changes in morphological and physiological traits of three tree species seedlings (Eucalyptus camaldulensis, Conocarpus erectus, and Bombax ceiba) in response to different dust types. In a pot experiment under controlled conditions, three-month-old seedlings of selected trees species were subjected to four treatments of dust: T1 = controlled; T2 = wood dust; T3 = soil dust; and T4 = carbon dust. During the whole experiment, 10 g/plant/dose was applied in 8 doses with a one-week interval. The results depicted that the growth was the maximum in T1 (control) and the minimum in T4 (carbon dust). In our findings, B. ceiba performed better under the same levels of dust pollution as compared with the other two tree species. The B. ceiba tree species proved to be the most tolerant to dust pollution by efficiently demolishing oxidative bursts by triggering SOD, POD, and CAT under different dust types compared to controlled conditions. Stomatal conductance, photosynthetic rate, and transpiration rate were negatively influenced in all three tree species in response to different dust applications. Based on the findings, among these three tree species, B. ceiba is recommended for dust polluted areas followed by E. camaldulensis and Conocarpus erectus due to their better performance and efficient dust-foraging potential.

Performance of reduction on particle emission by combining the charged water drop atomization and electric field in wet electrostatic precipitator

In this study, a wet electrostatic precipitator (WESP) with combination of electric field and charged water drop atomization was designed for fine particle collection, which replaced the traditional water film and mechanically spray. The removal performance was evaluated considering applied voltage, water flow rate, gas residence time, dust concentration, and continuous operation time. Results indicated that supplying charged droplets could acquire higher discharge current and better agglomeration effect than the dry type. The maximum penetration ratio was reduced from 3.8%−11.56% in the dry ESP to 3.58%−8.6% with charged droplets, as the applied voltage increased from 30 kV to 60 kV. Meanwhile, increase of water flow rate improved the total removal efficiency. The advantage of the WESP was more obvious under short gas residence time. The route of synergistically increasing gas residence time and applied voltage could largely reduce the penetration ratio, which decreased from 6.99%−19.81% to 1.03%−2.43% as they were enhanced from 1.50 s and 30 kV to 3.33 s and 60 kV. Increasing the dust concentration led to the trend that the total removal efficiency first increasing and then decreasing gradually, resulted from combined mechanisms of particle agglomeration and suppression of corona current. Moreover, the atomization of charged water drop maintained the advantage on particle removal under continuous operation, and the efficiency drop after long-term operation could be avoided. In particular, the WESP achieved significant reduction on water consumption compared to conventional large-scale and on-site WESPs in application with equivalent levels of removal efficiency.

Experimental investigation on highly efficient collection and cleaning for fine coal dust particles by dry-wet mixed chemical method

The dust removal efficiency of dry dust collectors is low, especially with the decrease of coal dust particle size. To improve the collection and removal efficiency of fine coal dust particles, a dry-wet mixed chemical method was designed. The chemical polymer solution was transformed into fine droplets by an ultrasonic atomizer and added into the dust removal process. A new type of chemical polymer (AM/AA-CMCS) was prepared by modifying carboxymethyl chitosan. The atomizing effect, chemical structure, and surface morphologies of AM/AA-CMCS were investigated in detail. The adsorption process between AM/AA-CMCS and coal dust was simulated from a molecular level. Through the experimental platform, the variation of filtration resistance, filtration cycle, residual pressure, and dust emission concentration were measured under different dust particle size conditions. The results show that the AM/AA-CMCS could better wet, bind, and agglomerate coal dust particles. Compared to dry-type dedusting, the capture and removal of coal dust particles of less than 500 mesh in dry-wet chemical dedusting conditions are improved more significantly. The research results are not limited to the fine coal dust particles produced in mine systems, but could also provide a reference for the application of dust collectors in other energy and industrial fields.

A low-cost solution for the collection of fine particles in square cyclone: A numerical analysis

Generally, the square cyclone separator suffers from low separation efficiency. Therefore, a deeper investigation for developing an effective method to enhance this type of cyclone's overall performance is of interest. Although different methods are available, optimizing the vortex finder's shape for enhancing separation efficiency is a low-cost solution. The present study assesses the effect of vortex finder on the performance of a square cyclone, thus guiding the design for improving the square cyclone separation efficiency. Three different vortex finders namely, cylindrical, convergent, and divergent, are studied. A series of 3D numerical simulations are carried out by solving the Reynolds-Averaged Navier-Stokes equations with the Reynolds Stress Model (RSM) and performing the Eulerian-Lagrangian particle tracking analysis. The results demonstrate that using a convergent vortex finder improves the square cyclone's separation efficiency while producing an increase in pressure drop. Using a convergent vortex finder is beneficial for reducing the 50% cut-size. Among all vortex finders, the convergent one with vortex finder diameter ratio (D2/D1 = 0.75) allows the square cyclone to collect finer particles. As a result, the 50% cut size decreases by approximately 33% at an inlet velocity of 28 m/s.

Experimental study of a string-based counterflow wet electrostatic precipitator for collection of fine and ultrafine particles

ABSTRACT Wet electrostatic precipitators (WESP) have been widely studied for collecting fine and ultrafine particles, such as diesel particulate matter (DPM), which have deleterious effects on human health. Here, we report an experimental and numerical simulation study on a novel string-based two-stage WESP. Our new design incorporates grounded vertically aligned polymer strings, along which thin films of water flow down. The water beads, generated by intrinsic flow instability, travel down the strings and collect charged particles in the counterflowing gas stream. We performed experiments using two different geometric configurations of WESP: rectangular and cylindrical. We examined the effects of the WESP electrode bias voltage, air stream velocity, and water flow rate on the number-based fractional collection efficiency for particles of diameters ranging from 10 nm to 2.5 μm. The collection efficiency improves with increasing bias voltages or decreasing airflow rates. At liquid-to-gas (L/G) as low as approximately 0.0066, our design delivers a collection efficiency over 70% even for fine and ultrafine particles. The rectangular and cylindrical configurations exhibit similar collection efficiencies under nominally identical experimental conditions. We also compare the water-to-air mass flow rate ratio, air flow rate per unit collector volume, and collection efficiency of our string-based design with those of previously reported WESPs. The present work demonstrates a promising design for a highly efficient, compact, and scalable two-stage WESPs with minimal water consumption. Implications: Wet Electrostatic Precipitators (WESPs) are highly effective for collecting fine particles in exhaust air streams from various sources such as diesel engines, power plants, and oil refineries. However, their large-scale adoption has been limited by high water usage and reduced collection efficiencies for ultrafine particles. We perform experimental and numerical investigation to characterize the collection efficiency and water flow rate-dependence of a new design of WESP. The string-based counterflow WESP reported in this study offers number-based collection efficiencies >70% at air flow rates per collector volume as high as 4.36 (m3/s)/m3 for particles of diameters ranging from 10 nm – 2.5 μm, while significantly reducing water usage. Our work provides a basis for the design of more compact and water-efficient WESPs.

Bipolar Precharger for Hybrid Electrostatic Filtration Systems

ABSTRACT Both hybrid electrostatic filtration and agglomeration technologies can effectively improve the efficiency of fine particle collection. A hybrid electrostatic filtration system with a wire-tube bipolar precharger was developed on the basis of bipolar transverse plate electrostatic precipitation technology. Theoretical analyses of electric field and flow field distribution showed that a uniform electric field and high turbulence intensity improve ion migration and particle agglomeration in the novel wire-tube bipolar precharger. The influence of unipolar and bipolar prechargers on dust removal was investigated. In the hybrid electrostatic filtration system with the bipolar precharger, the corona current was 30% higher, the particles deposited on the surface of the filter bag were 19% larger, and the pressure drop was 30% smaller than a filtration system with a unipolar precharger. When silicon powder with a median diameter of 1.7 µm was used, the mean penetration of the experimental device with the bipolar precharger was 45% lower than that of the experimental device with the unipolar precharger.

3D-PIV Measurement for EHD Flow of Spiked Tubular Electrode Corona Discharge in Wide Electrostatic Precipitator

Abstract The electrohydrodynamic (EHD) flow induced by a corona discharge has an important influence on the movement and collection of fine particles in an electrostatic precipitator. In this paper, three-dimensional particle image velocimetry (3D-PIV) is used to investigate the impact of different primary flow velocities and applied voltage on diffusion and transport of the spiked tubular electrode corona discharge EHD flow in a wide type electrostatic precipitator. In order to measure the flow characteristics of different positions of a spiked tubular electrode, the PIV measurements are carried out in several cross-sectional planes along the ESP duct. From 2D flow streamlines, in plane 1 (where the tip of the spike is oriented in the direction of primary flow), the velocity of the counter-clockwise vortex caused by the EHD flow near the plate decreases as the primary flow velocity increases. However, in plane 3 (where the tip direction is opposite to the primary flow), two vortices rotate adversely, and the flow velocity of the clockwise vortex near the plate increases as the primary flow velocity increases. Flow velocity increasing near the plate makes the particles deposited on the plate more easily to be re-entrained. It can be found in the three-dimensional analysis of the flow field that there are mainly “ascending vortex” and downward tip jet in the three observation planes. There is a discrepancy (in terms of distribution region and the magnitude of velocity) between the three-dimensional characteristics of these vortices and tip jets in the different cross-sectional planes.

Cake formation and filtration characteristics of a cyclone-granular bed filter

The dust cake is critical to improve the fine particle collection efficiency in the gas-solid separation process of the granular bed filter (GBF). In this work, the dust cake formation and the corresponding filtration characteristics in a cyclone-granular bed filter (C-GBF) were investigated by experiments under a constant-velocity filtering condition. It was found that cake filtration, deep-bed filtration and the corresponding transitional phenomena could be observed in the C-GBF. A critical porosity was defined to identify the transition from cake filtration to deep-bed filtration. A following parametric study showed that a higher filtration gas velocity could increase the critical porosity and made it more difficult to form a dust cake. It was also demonstrated that the critical porosity was little affected by the dust concentration. However, the time point of the transition of different filtration modes was earlier with a higher dust concentration. The inlet gas velocity ultimately resulted in the different dust concentrations into the GBF. The similar dynamic processes of cake formation were obtained for different granular sizes. These results provided a deeper understanding of the dynamic behaviors of cake formation and filtration mode transition, which played an important role in the design and the scaling-up of the C-GBF filtration systems.

Enhanced collection of fine particles in a cyclone using ultrasonic vapor with surfactants

Using water vapor to improve the efficiency of dust removal in gas cyclones was recently proposed. However, some dust particles are not hydrophilic which can reduce the effectiveness of the vapor. This paper investigates using surfactants to overcome such a difficulty. In particular, surfactants are added to the water solution which is atomized into vapor and added in a cyclone dust collector. The effects of surfactant type and quantity on the removal efficiency of the cyclone are studied by a series of experiments. Three surfactants are used to change the wettability of the two types of fine particles to be collected: molecular sieve dust and white carbon black. The particles in the cyclone are found to form agglomerates, which are measured by using a laser particle size analyzer and scanning electron microscopy. The results show that the addition of surfactants can greatly enhance the agglomeration and thus improve the collection efficiency, especially for particles approximately two microns in size. This indicates that using the atomized vapor with containing surfactants is an effective way to enhance the collection of fine particles in a cyclone separator.

The role of bulk micro-nanobubbles in reagent desorption and potential implication in flotation separation of highly hydrophobized minerals.

Micro-nanobubbles (MNBs) generated during hydrodynamic cavitation (HC) have been extensively studied in mineral processing field in the past two decades. Many researchers have claimed that MNBs can effectively promote the collection of fine particles in flotation, while studies on MNBs assisted mineral separation are rare. In this study, the role of bulk MNBs in desorbing flotation reagent was investigated, with the aim of illustrating the potential effects of MNBs on minerals separation. The results showed that bulk MNBs could efficiently remove the sodium oleate (NaOl) from diaspore surfaces, reducing the residual concentration of NaOl on solids, which was more significant when the amount of NaOl pre-adsorbed was relatively small. Furthermore, lower residual concentration of NaOl on solids caused by MNBs cleaning made the particles less hydrophobic and flocs more friable. Given that gangue entrapment in flocs was one of the main limits for high-selective flotation, the roles of MNBs in enhancing reagent desorption and associated flocs breakup and reorganization probably contribute to higher separation efficiency of different minerals, which was confirmed by the flotation results of diaspore/kaolinite mixture.

Experimental verification of fine particle emission reduction based on acoustic agglomeration for steel sintering flue gas

The sintering flue gas in steel production has the characteristics of large discharge capacity, fine size, high temperature, corrosion and fluctuation of working conditions, and is the primary control object of PM2.5 emission source. Traditional dust removal technologies and equipment are difficult to achieve efficient collection of fine particles. In order to quantitatively study the effect and regularity of high intensity sound waves on fine particles, the online acoustic agglomeration test system was built by using high-power pneumatic source and wave tube with abrupt section. The high intensity standing wave field of 140 to 150 dB was generated in the wide frequency range between 50 Hz and 2 kHz by the acoustic resonance synthesis, and interference from compressed airflow was avoided by the acoustic-flow separation module. Variation of the sintered flue gas PSD was obtained under different sound intensities and frequencies. Data analysis shows that the high concentration condition can greatly reduce the operation time and energy consumption. Under the action of high intensity acoustic waves with a fundamental sound pressure level of 87.3-161.8dB and duration of 3s, the measured PM2.5 removal efficiency is 16%-92%, and the optimal frequency is near 800Hz. This paper verifies the feasibility of acoustic agglomeration (AA) in the treatment of sintering flue gas, and provides a theoretical reference and technical basis for the development of PM2.5 real-time emission control device for steel production.

Numerical study on combined cyclone-filter aerosol collector performance

A cyclone was modified by inserting a stainless steel filter to enhance efficiency in collecting fine particles. Velocity and pressure distributions in the combined cyclone-filter were computed by computational fluid dynamics to explain experimental results from a previous study. Two different filter quantities (0.94 g and 1.83 g) were used. The pressure drop was reduced because the filter increased the turbulence intensity, thus reducing of tangential velocity. Insertion of the filter into the annular space of the original cyclone radically hindered the development of a swirl flow. Most of the gas flows axially through the filter. Good agreement between simulation and experimental results was found for the 1.83 g filter (maximum deviation of 5.1%), while for the 0.94 g filter, agreement was acceptable with the maximum deviations - 39.6%. Single-fiber collection efficiencies were calculated. Larger particles (1 µm) were mainly collected by inertial impaction with 65-70% efficiency at 13.3 m/s and 75–79% at 19.9 m/s, whereas, smaller particles (0.3 µm) are mainly removed by diffusion with 92–94% efficiency at the lower and 89–91% at the higher velocity. Therefore, the added filter enhances the fine particle collection efficiency by changing the centrifugal force to diffusion and inertial impaction mechanisms.

Numerical study on electrohydrodynamic flow and fine-particle collection efficiency in a spike electrode-plate electrostatic precipitator

In this work, a numerical study on the electrohydrodynamic secondary flow and transport of fine particles has been carried out based on spike electrode-plate electrostatic precipitator (ESP). The effect of the inlet flow velocity, negatively applied voltage, and position of spike tip on airflow streamlines distribution are analysed in detail. The electrohydrodynamic (EHD) secondary flow patterns and particle collection efficiencies are examined for three different corona discharge electrode configurations, the spike tip locates at i) upstream, ii) downstream and iii) at both sides of the channel. The results show a complex and turbulent flow structure in the ESP with the spiked electrode. A pair of vortices is formed in the vicinity of the spiked electrode with the tip of the upstream-directed spikes, driving the main airflow toward the collecting plates and improving the collection efficiency of particles. Compared to the EHD secondary flow streamlines in the spike-plate type ESP one can deduce that the stronger vortices occur at higher Ehd/Re2 ratios. Furthermore, the distribution of deposited particles with the aforementioned spike tip locations reflected the real condition of particle deposition. The results help to improve the structural optimization of the spike-type ESP.

Correlation between inorganic pollutants in the suspended particulate matter (SPM) and fine particulate matter (PM2.5) collected from industrial and residential areas in Greater Cairo, Egypt

Simultaneous sampling collection of suspended particulate matter (SPM) and fine aerosol particles with an aerodynamic diameter equal or less than 2.5 μm (PM2.5) from industrial and residential areas of Greater Cairo, Egypt, has been carried out during two different seasons namely autumn 2014 and winter 2014/2015. The average mass concentrations of both SPM and PM2.5 samples are higher than the annual mean levels, especially for the samples collected from the industrial area. In addition, the mass concentrations of SPM are much higher than the PM2.5 mass concentrations during the whole sampling period. The ratios of the mass concentration between the SPM and PM2.5 were determined to be equal to 20 ± 6 and 17 ± 4 for the residential and industrial areas, respectively, and these ratios seem to be constant during the two mentioned seasons. Based on our previous elemental analysis results using multiple secondary target energy dispersive X-ray fluorescence (EDXRF), 18 elements in both SPM and PM2.5 samples have been quantified. Remarkable variations in the elemental concentrations between the SPM and PM2.5 samples were obtained. Comparison and statistical analysis of the elemental composition of both SPM and PM2.5 have been investigated. The PMF model EPA 5.0 was utilized for source identification on both PM fractions. Seven sources were identified and their relative contributions in the two areas of the study were investigated.

Corona discharging and particle collection of bipolar transverse plate ESP

To improve the fine particle collection efficiency, a bipolar transverse plate electrostatic precipitation (ESP) technology was developed. In this ESP, there are not only the negative wire electrodes and ground plate electrodes, but also the ground wire electrodes and the negative plate electrodes. It has aroused a special interest about the corona discharging effect of the ground wire electrodes. Therefore, the corona currents of the negative wire-ground plate, the ground wire-negative plate, as well as the bipolar wire-plate electrodes have been investigated experimentally. In the experiments, the RS barbed wire and the C-plate are used as the electrodes for the purpose of the industrial application. The experimental results have shown that, when the wire-plate spacing is 200 mm, the corona current of the wire in the smooth side of the ground C-plate is 15% higher than that of curved side, however the corona current of the ground wire is about 30% less than that of the negative wires regardless of the wire is located at different sides of the industrial plate electrode. Moreover, the corona current of bipolar wire-plate electrodes is 30% less than that of the traditional wire-plate electrodes, and an important phenomenon had been discovered from this experimental work that, for the bipolar wire-plate electrodes, whenever the front side of the C-plate faces to the gas flow or not, the VI characteristics curve keeps almost no change at given wire-plate spacing. Last, an experimental setup was established for comparison of collection efficiency. When the negative polarity is applied to the bipolar transverse plate ESP, the collection efficiency increases sharply from 69.1% to 99.1%. Since both electrical forces and inertial forces play important roles in the bipolar transverse plate ESP, the penetration of the bipolar transverse plate ESP is 0.9%, which is substantially less than the penetration of 4.2% of the conventional ESP. The advantage of bipolar transverse plate ESP unit has been proved by successful operation in sintering flue control in China.