Characteristics of electrostatic cyclone/bag filter with inlet types (lab and pilot scale)

The main purpose of this study was to investigate experimentally the characteristics of an electrostatic cyclone/bag filter with inlet types (upper and bottom inlet) in order to overcome the low collection efficiency for submicron particles and high pressure drop, which were the main problems of general fabric bag filters. The experiment was performed to analyze the collection efficiency and pressure drop of the electrostatic cyclone/bag filter compared with that of conventional fabric bag filters with various experimental parameters such as the inlet type (upper and bottom), inlet velocity (filtration velocity) and applied voltages. From the results, the upper inlet type showed a slightly higher pressure drop reduction ratio as 40–90% than that of bottom inlet. In addition, the electrostatic cyclone/bag filter represented an increment of over 5% for the collection efficiency of submicron particles (around 1 Μm) in comparison with the general fabric filter. Presented at the Int’/Sym. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

煤气站用旋风收尘器改造

分析了煤气站用旋风收尘器的结构特点,介绍了针对其结构设计中的不足所作的一些有益改进。     

Development of a symmetrical spiral inlet to improve cyclone separator performance

Three cyclone separators with different inlet geometry were designed, which include a conventional tangential single inlet (CTSI), a direct symmetrical spiral inlet (DSSI), and a converging symmetrical spiral inlet (CSSI). The effects of inlet type on cyclone performance characteristics, including the collection efficiency and pressure drop, were investigated and compared as a function of particle size and flow rate in this paper. Experimental result indicated that the symmetrical spiral inlet (SSI), especially CSSI inlet geometry, has effect on significantly increasing collection efficiency with insignificantly increasing pressure drop. In addition, the results of collection efficiency and pressure drop comparison between the experimental data and the theoretical model were also involved.     

Design and performance evaluation of hydrocyclones for removing micron particles suspended in water

A hydrocyclone for collecting micron-sized hydrosols efficiently has been studied through experimentation. Hydrocyclones separate particles of the dispersed phase from the liquid on the basis of the density difference between the phases. The purpose of this study was to design and evaluate the performance of a high-capacity hydrocyclone for the removal of submicron-sized particles suspended in liquid. Furthermore, the performance of three types of hydrocyclone was evaluated with regard to solid particle density using fly ash and coagulation sludge. The particle cut-size decreases with reducing inlet area and increasing inlet velocity in the hydrocyclone. The hydrocyclones have good performance, which is demonstrated by the optimal cut-size of 20 μm in mass median diameter at the inlet diameter per body diameter ratio of 0.21 and the pressure drop of 72.5 kPa with a particle density of 2,500 kg/m³.     

新型高效PSC-250型导叶式旋风管组合多管的试验研究

对新开发的高效PSC 2 5 0型旋风管进行了组合多管试验研究。通过对大量试验结果的分析对比可知 ,由PSC 2 5 0型旋风管组合多管后 ,性能与单管一样。多套工业装置应用标定结果表明 ,在高温下PSC 2 5 0型第三级多管旋风分离器 (简称为三旋 )可将大于 7μm以上的颗粒基本除净 ,含尘浓度大都在5 0mg/m3 以下。给出的性能计算公式可供工程设计参考     

A study on the characteristics of improvement in filtration performance by dust precharging

A hybrid dust-collector combining electrostatic charging with fabric filtration was developed and its performance characteristics were evaluated. Charged particles build porous dendritic structure on the filter surface by electrostatic attraction, increasing the collection efficiency of dust particles and reducing the pressure drop through the deposited dust layer and filter media. The cleaning performance of the dust layer is improved because the dendritic structured dust layer may be removed more easily by pulse jet cleaning flow. The results of the experiment showed a reduction of fine particle emission by 37% and 13% energy saving by precharging dust particles before filtration.     

Performance evaluation of a cyclone with granular packed beds

This paper presents the performance evaluation results of a cyclone packed with granules in the gas outlet and cone. The results showed that a cyclone packed with granules in the gas outlet enhances significantly the particle collection of all sizes at 10 lpm. However, at 30 and 50 lpm, the granules increase only the collection efficiency of small particles, but decrease the collection of large particles to a small extent. In addition, the collection efficiency is higher with 2 mm granules than with 4 mm granules. The enhancement of collection efficiency, with granules in the gas outlet, was much more significant than with granules in the cone. Subsequently, this study showed that the granular cyclone could be used as a particle collector especially for small particles with low flow rate.     

Development and evaluation of multilayer air filter media

Three types of multilayer air filter media were developed and evaluated. Two other existing filters were also used for comparison of filter performance. The pressure drop, the collection efficiency, and the dust-holding capacity of the tested filters were measured, and the internal structure of the filter media was analyzed by using a scanning electron microscope. The multilayer filters tested in this study are composed of pre-surface layer, surface layer, and substrate layer. Among those layers, the surface layer is mainly responsible for particle collection. As a test result, it was found that the thickness of a surface layer has the greatest effect on filtration performance of a multilayer air filter. Additionally, filtration velocity and electrostatic forces should be considered together as important parameters for multilayer air filter design.     

Multi-cyclonic vacuum cleaners as a pedagogic case study of process intensification

Process intensification has emerged as a strategy to satisfy the objectives of process efficiency, sustainable development and economic competitiveness. Unfortunately, intensified technologies are too numerous to fit in a time-constrained academic syllabus. For high pedagogic impact, appropriate case studies should be favored to cover a wide range of strategies while demonstrating these opportunities, using accessible tools and concepts.The developed case study demonstrates the gain of sustainability offered by applying multi-scale design to a cyclonic separation, enabling miniaturization at constant efficiency. The analysis leads to well-known multi-cyclonic systems. This example is particularly striking for students since multi-cyclonic vacuum cleaners are a domestic illustration of this strategy.The analysis aims to miniaturize the separator, at constant efficiency and dissipated mechanical power. By applying a scale factor to cyclone dimensions, while maintaining the efficiency, a first strategy demonstrates that miniaturization alone cannot be sustainable. The best strategy considers parallel miniature cyclones, which enables to satisfy all objectives: the volume and dissipated mechanical power can be reduced simultaneously, requiring a multi-objective optimization.Scenarios for integration of the case study in various curricula are proposed, by differentiating the learning outcomes as a function of student level and course objectives.     

导叶式旋风管整流罩减阻的实验研究

研究开发了一种新型减阻结构——整流罩,安装在排气管的入口处。此减阻元件可以减弱旋风管内旋流的旋转强度,而对外旋流基本没有影响,从而可以在保证总效率基本不变的情况下,较大程度地降低旋风管的压降,达到减阻的目的。     

旋风分离器芯管结构改进的试验研究

在PV型旋风分离器的基础上对其芯管结构进行了改进,并通过正交试验得到了一种新的斜切芯管结构。性能对比试验结果表明,当入口气速为20m/s时,相对于基准模型,改进结构的压降平均降低10%,跑损率降低15%。     

大浓度范围内PV型旋风分离器粒级效率的计算方法

探讨了旋风分离器入口含尘浓度对其分离性能及粒级效率的影响机理。对旋风分离器内部气固两相运动进行了相似分析,得到了包括入口含尘浓度在内的一系列影响分离性能的相似准数。通过相似试验及试验数据的多元回归分析,建立了各相似准数与粒级效率的关系,得出了能精确估计大浓度范围内PV型旋风分离器粒级效率的计算公式。     

高温旋风分离分级效率的理论计算及其分析

旋风分离器是高温除尘技术中优先考虑的预除尘设备。以平衡尘粒模型以及相似理论原理分析为基础,给出了该分离器高温旋风分离的分级效率的计算方法,对反映其在高温状态下分离特性的参数分割粒径dc50和分布指数m进行了分析。以Stairmand高效旋风分离器为例,分级效率的理论计算结果与高温旋风分离的试验值进行了比较对照。     

Filtration properties of electrospun ultrafine fiber webs

Electrospun fiber webs were prepared at various spinning conditions. The effect of electrospinning parameters on fiber morphology and filtration performance of electrospun webs was investigated. The processing variables considered were only the applied voltage and rotation speed of a drum type collector. The fiber diameter and mean pore size of the electrospun webs decreased with increasing applied voltage and collector speed. Pressure drop and aerosol collection efficiency of the electrospun fiber webs were increased with decreasing fiber and pore size. Additionally, it was found that the filtration performance of the electrospun web was much greater than that of a commercial high efficiency air filter media made of glass fibers.     

Experimental investigations on a cyclone separator performance at an extremely low particle concentration

In order to evaluate the influence of extremely low particle concentration on separation performance of cyclone separator, the overall collection efficiencies and grade efficiencies of a cyclone separator with particle concentrations of 5-2000 mg/m³ and inlet velocities of 6-30 m/s have been investigated under ambient temperature and atmospheric pressure conditions. Aerosol spectrometer based on measuring particle number is used to measure the particle concentrations and particle size distributions of the inlet and outlet of the cyclone separator. The overall efficiency is equal to the ratio of the particle concentration difference between the inlet and outlet of the cyclone separator to the inlet particle concentration. The grade efficiency is obtained by comparing the particle size distributions of the inlet and outlet of the cyclone separator. The effects of particle concentration on separation performance are predicted by Smolik empirical model. Particle agglomeration, which has been found in the inlet and outlet of the cyclone separator, has a very important influence on the collection efficiencies and grade efficiencies of the cyclone separator at the particle concentration of 5-2000 mg/m³. The cut sizes for different inlet gas velocity with extremely low particle concentration can be quantitatively calculated by Barth model, Mothes and Loffer model and Muschelknautz model, respectively. Experimental results show that the overall collection efficiencies and grade efficiencies increased with the increasing particle concentrations and inlet velocities, and most of the particles with the diameter bigger than 10 μm can be removed by cyclone separator.     

溢流分率对去油型旋流器性能的影响

溢流分率是去油型放流器的一个重要操作参数。通过一系列试验找到了溢流分率对分离效率和压力降的影响规律,并且分析了产生这些影响规律的原因。     

Optimal design of multi-stage porous plate collection system

The main objective of this study was to investigate the optimal design parameters of a multi-stage porous plate system, numerically and experimentally. Characteristics of pressure drop and collection efficiency are analyzed with the operation parameters such as the stage number, plate interval, hole diameter and system inlet velocity, etc. In the results, pressure drops of a 5 stage system [2, 2, 3, 2, 2mm] at v_s,in=1.0, 1.2 m/s are shown as 296, 428 mmH₂O by the numerical simulation and 259, 399 mmH₂O in the experiment. For 5 stage [2, 2, 3, 2, 2 mm] and v_s,in=1.0 m/s, the overall collection efficiencies with the plate interval 4, 10, 15 mm are estimated as 99.5, 96.0, 92.8% computationally and 97.9, 89.2, 85.3%, showing slightly lower efficiency compared to the numerical results due to the particle rescattering effect, experimentally.     

除油型旋流器压降比特性试验研究

在室内试验装置上对单锥除油型水力旋流器的压降比特性进行了试验研究。研究结果表明 ,除油型旋流器压降比的主要影响因素有分流比、入口流量和溢流背压等操作参数 ;溢流背压对压降比的影响存在一“门槛值”。根据试验结果 ,建立了除油型水力旋流器压降比的半经验计算模型     

除油旋流器入口流量与基本性能的关系研究

对除油旋流器边壁的油滴粒径变化、旋流器的分离效率以及压力降与入口流量之间的关系进行了研究。结果表明 ,当入口流量达到一定程度时 ,旋流器边壁的平均粒径随入口流量的增加而降低 ,分离效率随入口流量的增加而增加。整个旋流器以及旋流器各段的压力降均与入口流量成指数关系 ,都随入口流量的增加而增加。在旋流器的压力损失中 ,进口、旋流腔及大锥段所占比例最大 ,且基本不随入口流量的变化而变化 ;小锥段次之 ,并随入口流量的增大而增大 ;直管段的压力损失所占的比例最小 ,它随入口流量的增大而不断降低。     

高温除尘技术综述

介绍了高温除尘技术的特点,综述了国内外高温除尘设备的现状、水平以及发展趋势,并对该技术在各行业中的应用前景进行了展望。