Capture Of Fine Particles Research Articles

Synergistic capture of fine particles in wet flue gas through cooling and condensation

Coal-fired boilers tend to be equipped with considerable pollutant control equipment given the increase in environmental protection standard, thereby continuously increasing operating cost and decreasing the output rate of coal resources. Synergistic capture of pollutants may be a potential solution. In this work, a method for installing a cooling heat exchanger at the outlet of wet flue gas desulfurization scrubber is proposed to recover waste heat and capture fine particles. The cooling process of this method uses wet atmosphere, thereby indicating that this work differs from previous relevant works that are mainly based on dry deposition. Accordingly, the activity of particle reduction in the exchanger is also considered different. Thus, relevant mechanisms are recently explored on the basis of wet deposition through experiments. In addition to diffusiophoretic and thermophoretic depositions, particle growth or agglomeration is considered a dominant factor. Moreover, condensed water is crucial for cleaning, which may resolve the risk of fouling. Variable analysis of the influences of flue gas temperature drop, trapping surface area, initial particle concentration, and flue gas flow rate are also addressed in this work to provide references for engineering applications. Technical feasibility and economic evaluation of this method are discussed, through which possible measures for improvement are proposed. Furthermore, an applicable mode for heat recovery and a synergistic particle capture are presented, and an acceptable economic performance is estimated.

Agglomeration and capture of fine particles in the coupling effect of pulsed corona discharge and acoustic wave enhanced by spray droplets

Fine particles from industrial processes are considered to be potentially harmful to humans and environment, and massive amounts of fine particles are continuously emitted into the air due to the low removal efficiency of current conventional dust capture devices. A novel pretreatment process using the coupling effect of pulsed corona discharge and acoustic waves enhanced by spray droplets for fine particle agglomeration and capture was investigated in this study. The application of pulsed corona discharge in an acoustic field led to an increase in the efficiency of fine particle agglomeration to 74.7%, and the improvement was much more obvious for low frequency acoustic waves. The spray flow rate delivered by the spray nozzles with a size of 0.30mm or 0.40mm was incrementally increased. Furthermore, the penetration efficiency initially decreased, then increased, and finally decreased when droplets were sprayed in either a pulsed corona discharge field or an acoustic wave field. The penetration efficiency of fine particles substantially decreased to 10% with the enhancement of spray droplets coupled with both a pulsed corona discharge and an acoustic wave, both at their most efficient settings. The penetration efficiency further decreased with the addition of sodium dodecyl sulfonic salt surfactant to the spray droplets, in particular, at a concentration of 0.3%.

Study on the removal of fine particles by using water in a rotating packed bed

AbstractThis study presented an experimental investigation on the capture of fine particles from gas stream by water in a rotating packed bed (RPB). Experiments were carried out to investigate the effects of different operating conditions including packing types, rotation speed, gas‐liquid volumetric ratio, inlet particle concentration, and gas temperature on the removal efficiency of fine particles. The overall removal efficiency of fine particles can reach 98 % under the optimal operating conditions, which are a rotation speed of 1200 rpm, a gas‐liquid volumetric ratio of 600, a gas temperature of 100 °C, and the use of fine metal gauze packing. In addition, the correlation of removal efficiency of fine particles was deduced. It is observed that the predicted removal efficiency and outlet concentration of fine particles are in good agreement with the experimental values, with deviations within 10 % and 20 % respectively. This process exhibits the potential application of RPBs in simultaneous removal of fine particles and SO2 by liquid solution.

Titanium dioxide (TiO2) fine particle capture and BVOC emissions of Betula pendula and Betula pubescens at different wind speeds

Trees are known to affect air quality by capturing a remarkable amount of particles from the atmosphere. However, the significance of trees in removing very fine particles (diameter less than 0.5 μm) is not well understood. We determined particle capture efficiency (Cp) of two birch species: Betula pendula and Betula pubescens by using inert titanium dioxide fine particles (TiO2, geometric mean diameter 0.270 μm) at three wind speeds (1, 3 and 6 ms−1) in a wind tunnel. Capture efficiencies were determined by measuring densities of TiO2 particles on leaf surfaces by scanning electron microscopy. In addition, the particle intake into an inner structure of leaves was studied by transmission electron microscopy. The effects of fine particle exposure and wind speed on emission rates of biogenic volatile organic compounds (BVOCs) were measured. Particles were captured (Cp) equally efficiently on foliage of B. pendula (0.0026 ± 0.0005) % and B. pubescens (0.0025 ± 0.0006) %. Increasing wind speed significantly decreased Cp. Increasing wind speed increased deposition velocity (Vg) on B. pendula but not on B. pubescens. Particles were deposited more efficiently on the underside of B. pendula leaves, whereas deposition was similar on the upper and under sides of B. pubescens leaves. TiO2 particles were found inside three of five B. pendula leaves exposed to particles at a wind speed of 1 ms−1 indicating that particles can penetrate into the plant structure. Emission rates of several mono-, homo- and sesquiterpenes were highest at a wind speed of 3 ms−1 in B. pendula. In B. pubescens, emission rates of a few monoterpenes and nonanal decreased linearly with wind speed, but emission rates of sesquiterpenes were lowest at 3 ms−1 and increased at 6 ms−1. Emission rates of a few green leaf volatile compounds increased with increasing wind speed in both species. The results of this study suggest that the surface structure of trees is less important for capturing particles with a diameter of ca 0.3 μm than for larger particles. Airborne fine particles penetrated into the intercellular space of the leaf via stomata, and this mechanism should be studied further for a better understanding of nanomaterial accumulation in nature. Wind can affect BVOC emissions and composition.

Influence of suspended kelp culture on seabed sediment composition in Heini Bay, China

Kelp aquaculture activities occupy large nearshore areas with significant effects on sediment properties, primarily caused by the influence of the suspended kelp on local hydrodynamics. Changes in sediment composition and grain-size distributions were investigated prior to and following the commencement of kelp aquaculture activities in Heini Bay in eastern China. Seabed sediment types and the particulate matter in suspension during the kelp seeding and harvesting periods, and in sediment cores, were analyzed. While suspended sediment in the kelp aquaculture area was up to 20% organic material, sediment organic content on the seabed remained at similar levels as areas lacking aquaculture. The composition of the seabed sediment in the kelp aquaculture area became finer-grained by the capture of fine particles. Within the kelp aquaculture area, the sediments are poorly sorted and positively skewed, whereas at the shoreward and seaward of the aquaculture area the sediments are relatively coarse-grained, well-sorted and nearly symmetrically distributed. Therefore, the kelp aquaculture activities not only increase the fine particulate fraction in the sediments within the aquaculture area, but also result in similar deposits seaward of it, indicating that seabed erosion and accretion is also controlled by the sediment source and the hydrodynamic conditions. The analysis of sediment cores showed that kelp culturing refines the sediment by preferentially capturing particles in the 38–40 μm size class, while having no effect on the <32 μm fractions, as evidenced by the positive skew of the surficial sediments. The captured particle size class became well mixed into the sediment, thereby changing the composition of the sediment in the uppermost layer of the core, indicating the existence of continuous and stable hydrodynamic conditions within the kelp aquaculture area. The same effect was observed in the seabed sediments seaward of the aquaculture area.

Fine particle sorting and classification in the cyclonic centrifugal field

Abstract Fine particle sorting and classification are not only important processes during the powder preparation, but also vital to the sequential separation of discrete fine particles with different sizes. The moving fine particles with different sizes have different trajectories in the cyclonic centrifugal field under the actions of radial and axial forces, which inspire us to develop a novel cyclonic multi-product sorting classifier. Both particle size and mass distribution gradually increase axially from the inlet side to the outlet side and radially from the inside to the outside at the rectangular outlet of the sorting classifier. When the mean particle size of the inlet is 15.7 μm and the coefficient of variance is 90.1%, 12 different particle sizes (the minimum and maximum particle sizes are 8.41 and 26.16 μm, respectively) with better monodispersion are obtained, all products achieve a particle coefficient of variance below 40%. An effective calculation method was used to represent the overall sorting and classification performance of sorting classifiers with different height. The results show that the best height is 5 times as high as the rectangular inlet, and the optimum gas flow is 30–60 m 3 /h with the pressure drop not exceed of 80 Pa. The present study could also serve as a useful guide in the industrial sequential separation and capture of fine particles of different sizes. Notably, it may exhibit a high potential for the control of PM 2.5 throughout studies in future.

The influence of the fabric filter layout of in a flow mass filtrate

Nowadays, more and more companies are forced to control particulate emissions to the atmosphere, due to economic reasons, legal aspects or simply the change in policy that favors ecological commitment. This new trend induces the necessity for better particle capture equipment and has made the environmental control equipment market increase by 20% in the last few years (Rocha et al., 2012). The dry capture of fine particles is carried out by filtration, and the fabric filter has become a very popular equipment because of its high efficiency and low operational cost. In the other hand, this efficiency is dependent upon proper design and layout, and the particle–filter interactions greatly influence the filtration results and the overall efficiency.In this context, this article presents the computational fluid dynamic (CFD) simulation of the airflow inside an industrial fabric filter with a set of 49 bags and a total surface area of 75 m2. The simulations were performed using the ANSYS FLUENT v13.0. This package applies the Finite Volumes Method, using the URANS approach, as well as the realizable k–ε model for the turbulence and the SIMPLE algorithm for the pressure–velocity coupling (Miltner et al., 2015). Four inlet positions were analyzed in order to determine how the internal flow profile and the equipment filtering performance depends on the inlet position. The simulations allowed concluding that the simple and double inverted feed positions led to a more satisfactory flow, considering not only the overall efficiency but also the bag's useful lifespan.

Flotation of quartz particles assisted by nanobubbles

Experimental studies of flotation of quartz particles, under various conditions and cells (setups), are presented. Pure and well-characterized quartz samples were treated with a commercial alkyl ether monoamine as flotation collector with bubbles in various sizes: coarse bubbles (400–800μm); nanobubbles (200–720nm); and their mixtures. The nanobubbles were generated by selective separation from microbubbles, which are formed together after depressurizing-cavitation of the saturated water in air (as in pressure flotation or dissolved air flotation), at 66.1psi saturation pressure. Flotation with single nanobubbles was not effective due to their very low lifting power or practically nil buoyancy. Yet, size-by-size flotation recoveries with coarse plus nanobubbles, compared with coarse bubbles, enhanced by 20–30 % the very fine quartz fractions by 20–30% (8–74μm; Sauter diameter—D32) and slightly lowered the recoveries of coarse particles (67–118μm; D32 diameter). Flotation of quartz samples (composites) having wide particle size distribution and results in a mechanical cell validated the overall recovery enhancement of the fines. Fine particle capture (nanobubbles enhanced the contact angle of quartz) and aggregation of the quartz ultrafines (proved with micrographs) by the nanobubbles are the main mechanisms responsible for the higher recoveries. The effect on flotation of the coarser quartz fractions, at bench scale, may be explained in terms of a reduced rising velocity of the coarse bubbles, in the presence of nanobubbles, decreasing the degree of bubble carryover. It is expected that the use of collector-coated nanobubbles (tailor-made “bubble-collectors” and flocculants) will broaden options in fine mineral flotation. The future sustainable forms (cheaply produced) of nanobubble generation on a large scale and their injection in cells are envisaged.

Theoretical Study on Magnetic Field Application for Fine Particle Capture

Theoretical Study on Magnetic Field Application for Fine Particle Capture

Study of experimental-industrial design of rotary vortex machine

Comparative assessment of machines by the amount of energy consumed is presented in the paper. For comparison, machines for air purification from dust with the particle size of ~ 3-5 microns were selected. All considered scrubbing machines achieve maximum purification efficiency, but with a different amount of energy spent. A machine with guiding elements reaches maximum purification efficiency with energy consumption by 40% less than a machine with a smooth setting. Testing of industrial design was carried out during purification of gas emissions from cement production ingredients, and purification of flue gases of boiler houses. In both cases using machines not only provided a reduction in dust emissions, but also harmful gas impurities. Dust-gas-air mixture, which has been purified in the rotary vortex machine meets the requirements of state sanitary rules and norms, and may be released into the atmosphere. Testing of the machine has shown that rotary vortex machine with guiding elements, installed on the torus surface provides the purification efficiency of up to 98%, which indicates the usefulness of guiding elements in the rotary vortex machine design. Experiments have shown the appropriateness of using the machine in the technological scheme of gas purification since it provides an effective capture of fine particles.

Influence of Applied Magnetic Field on a Wire-Plate Electrostatic Precipitators Under Multi-Field Coupling

The aim of this work is to find an effective method to improve the collection efficiency of electrostatic precipitators (ESPs). A mathematic model of an ESP subjected to the external magnetic field was proposed. The model considered the coupled effects between the gas flow field, particle dynamic field and electromagnetic field. Particles following a Rosin-Rammler distribution were simulated under various conditions and the influence of the magnetic field density on the capture of fine particles was investigated. The collection efficiency and the escaped particle size distribution under different applied magnetic field intensities were discussed. Particle trajectories inside the ESP under aerodynamic and electromagnetic forces were also analyzed. Numerical results indicate that the collection efficiency increases with the increase of applied magnetic field. It was also found that a stronger applied magnetic field results in a larger particle deflection towards the dust collection plates. Furthermore, the average diameter of escaping particles decreases and the dispersion of dust particles with different sizes increases with the increasingly applied magnetic field. Finally, the average diameter decreases almost linearly with the magnetic field until it drops to a certain value. The model proposed in this work is able to obtain important information on the particle collection phenomena inside an industrial ESP under the applied magnetic field.

Effects of species-specific leaf characteristics and reduced water availability on fine particle capture efficiency of trees

Trees can improve air quality by capturing particles in their foliage. We determined the particle capture efficiencies of coniferous Pinus sylvestris and three broadleaved species: Betula pendula, Betula pubescens and Tilia vulgaris in a wind tunnel using NaCl particles. The importance of leaf surface structure, physiology and moderate soil drought on the particle capture efficiencies of the trees were determined. The results confirm earlier findings of more efficient particle capture by conifers compared to broadleaved plants. The particle capture efficiency of P. sylvestris (0.21%) was significantly higher than those of B. pubescens, T. vulgaris and B. pendula (0.083%, 0.047%, 0.043%, respectively). The small leaf size of P. sylvestris was the major characteristic that increased particle capture. Among the broadleaved species, low leaf wettability, low stomatal density and leaf hairiness increased particle capture. Moderate soil drought tended to increase particle capture efficiency of P. sylvestris.

Pharmaceuticals: Efficient cyclone systems for fine particle collection

Numerically optimised cyclones and recirculation systems have been shown to be highly efficient for the capture of fine particles, such as those occurring in the production of active pharmaceutical and food ingredients. Romualdo Salcedo and Júlio Paiva describe some of the recent developments in this area.

Selective separation of very fine particles at a planar air–water interface

Selective fine particle separation is a key unit operation in the mineral and related industries. In flotation, the capture of fine particles by bubbles is inefficient due to their low mass and momentum, which result in low particle–bubble collision efficiency. We demonstrate that it is possible to selectively separate a mixture of very fine hydrophobic graphite and hydrophilic quartz particles by direct contact with an air–water interface without a particle–bubble collision step involved. We demonstrate that it is possible to scale-up the process from a simple batch to a continuous process. Good selective separation of graphite from quartz gangue could be obtained under continuous conditions.

Fine particle capture in biomass boilers with recirculating gas cyclones: Theory and practice

This paper addresses the theoretical development and experimental validation of optimized recirculating reverse-flow gas cyclones. The simulation of these systems is based on the predictive properties of a finite diffusivity model, modified to include partial recirculation of the cyclones' emissions. Experimental validation was obtained at laboratory and pilot scales at low temperatures (up to 350 K) and for cork waste biomass boilers at higher temperatures (up to 600 K). Under certain circumstances, with recirculation, the proposed system showed a better performance than an online pulse jet bag filter, and substantially better than with multicyclone systems. The generally observed unexpected high collection of submicron particles, which occurs with inlet concentrations as low as 100 μg/m 3, is attributed to turbulent dispersion, either by promoting fine particle capture by larger ones, much like what occurs in recirculating fluidized beds, or by bringing fine particles near the cyclone wall. The extremely fine particle size distributions exiting from the recirculation system, as measured off-line at laboratory, pilot and industrial scales, were confirmed at pilot scale using online measurements through a laser monitor.

Role of gas phase in the deposition dynamics of fine particles in trickle-bed reactors

Experiments were conducted to study the role of gas velocity in the capture of fine particles from non-aqueous suspensions circulated in co-current down-flow trickle flow reactors. The rate of filtration and pressure drop in the trickle bed were investigated using surfactant-stabilized kaolin-containing kerosene suspensions. It was determined that the filter coefficient was sensitive to liquid holdup and specific deposit. The initial collection efficiencies were compared with predictions based on existing theories. Agreement was generally not good with the exception for the limit of low superficial gas velocity. A general correlation establishing the relationship between the filtration rate and the liquid holdup in trickle beds was proposed to reconcile the experimental data with existing filtration theories.

Enhanced sludge dewatering by dual polyelectrolytes conditioning

Sludge dewatering by dual polyelectrolytes conditioning was investigated in this study. Single polyelectrolyte is utilized in sludge conditioning conventionally, in which charge neutralization and bridging are involved in the reactions. In the current study, both cationic and non-ionic polyelectrolytes were utilized simultaneously in the conditioning. Waste activated sludge was sampled from a synthetic fiber plant, and used in the experiment. Capillary suction time (CST), specific resistance to filtration (SRF), and settling rate were used to evaluate the sludge dewatering behaviors. Zeta potentials were also measured. Sludge dewatering behaviors resulting from single and dual polyelectrolytes conditioning were compared. It was found that sludge conditioned with dual polyelectrolytes performed better in fine particle capture and in the formation of larger flocs that resulted in a better dewaterability and less chance of overdosing. The dosing sequence in dual polyelectrolytes also affected the sludge dewaterability. Reaction mechanisms in dual polyelectrolyte conditioning were proposed based on enhanced flocculation of sludge particles.

Particle Capture and Plugging in Packed-Bed Reactors

Fine particles in the liquid feed to packed-bed reactors can be trapped in the catalyst bed, which eventually leads to excessive pressure drop. The fine particles can include coke, corrosion products, clays, and other minerals. The catalyst bed functions as a granular filter to remove particles much smaller than the size of the pores between the catalyst pellets. The efficiency for trapping the particles in the packed bed depends on the flow fields and the attractive forces between the packing and the fine particles. In order to understand the capture of fine particles from nonaqueous media, we studied a model system of carbon black in kerosene. Columns packed with glass beads and a catalyst were operated over a range of flow velocities to Reynolds numbers from 0.1 to 2.3, on the basis of the diameter of the packing in the bed. Flow was in the upward and in the downward direction. The filter coefficient and efficiency were sensitive to liquid velocity. Trapping was slightly more efficient with downward fl...

Capture of fine particles on charged moving spheres: a new electrostatic precipitator

A study of a novel electrostatic approach to fine-particle collection was carried out on a specially designed test apparatus. Copper spheres were first electrostatically and then dynamically suspended between two horizontal parallel plates using an applied DC electric field. The sizes studied were 74-88, 102-25, and 125-47 mu m. The charged spheres, which were larger by a factor of 10 to 100 than the dust captured (mean diameter 2.4 mu m), were then electrostatically propelled into an adjacent duct where they scrubbed a crossflowing dust-laden gas by the processes of impaction and electrostatic attraction. The total collection efficiency of the device and the target collection efficiency of the charged copper spheres were studied. Both were found to increase with the charging electric field strength, the target particle diameter, and the duct air velocity. This research suggests that electrostatic precipitation based on the scrubbing action of charged solid particles is possible, and that total collection efficiencies of up to 99% cleanup (or greater) should be attainable. Fly-ash collection performance exceeding that based on theory with regard to the particle target efficiency was observed. >

Vortex feeding from pits in the sand: A unique method of suspension feeding used by a stream invertebrate

Larvae of the mayfly Ametropus neavei have a unique method of suspension feeding that uses hydrodynamic properties of vortices and pits in the sediment to facilitate capture of fine particles from flowing water. Modified setae on the forelegs function both as “aerosol” filters and in initiating formation of a vortex that spirals within a specially constructed pit. The vortex concentrates seston and transports it to filtering devices below the surface of the sediments. We suggest that vortex feeding allows Ametropus larvae to occupy noncohesive sands of rivers—areas that offer no solid substrate for attachment and are devoid of other suspension feeders.