雾化电晕净化烹调油烟技术

对雾化电晕放电极雾化过程、荷电液滴的捕集原理、自清洗作用进行探讨,在相同电压下雾化负电晕放电电流高于干式负电晕放电电流,极间大量荷电液滴具有很高的荷质比,并高速向极板驱进,对烟尘具有静电凝并和动力凝并除尘作用,具有高效净化油烟、自清洗极板的功能,此项净化烹调油烟的新技术,优于传统油烟净化技术,具有很好的应用价值和前景.     

双极电袋复合除尘器的增效减阻效应

为提高现有电袋复合除尘器的除尘效率,降低压力损失,改进清灰效果,设计出一种线管式双极电袋复合除尘器,并对其增效减阻作用和单极电袋复合除尘器进行了对比研究。在硅微粉中位径1.74μm、过滤风速3 m·min~(-1)、入口粉尘浓度2 500 mg·m~(-3)的实验条件下,双极电袋复合除尘器比单极电袋复合除尘器的粉尘透过率、压力损失分别降低25%、27%以上。为分析双极荷电粉尘的静电凝并增效作用,测定了滤料表面沉积粉尘层的粒度分布,发现单极荷电和双极荷电沉积尘的中位径分别为1.83μm和1.92μm,表明双极荷电粉尘具有较好的静电凝并作用,所形成的较粗团聚颗粒物不易透过滤料,使除尘效率提高。为阐明双极荷电粉尘的减阻作用,采用自然堆积法测出双极荷电粉尘的堆积密度小于单极荷电粉尘,证明粉尘双极荷电后会在滤料表面形成较蓬松的粉尘层,这将有助于降低压力损失、提高清灰效果。     

雾化电晕净化烹调油烟技术

对雾化电晕放电极雾化过程、荷电液滴的捕集原理、自清洗作用进行探讨,在相同电压下雾化负电晕放电电流高于干式负电晕放电电流,极间大量荷电液滴具有很高的荷质比,并高速向极板驱进,对烟尘具有静电凝并和动力凝并除尘作用,具有高效净化油烟、自清洗极板的功能,此项净化烹调油烟的新技术,优于传统油烟净化技术,具有很好的应用价值和前景。     

双区静电除尘器的除尘效率影响因素和理论公式研究

研究了预荷电压、烟气流速、极板间距和电极型式对双区静电除尘器除尘效率的影响,推导了双区静电除尘器的除尘效率理论公式,并与实验值和多依奇公式计算值进行了对比验证。结果表明,双区静电除尘器的除尘效果好于单区静电除尘器,其最佳工况是预荷电压25kV,烟气流速0.50m/s,极板间距400mm,采用芒刺电极。推导得到的双区静电除尘器的除尘效率理论公式不仅收尘电压较低时与实际情况相符,而且收尘电压较高时也与实际情况基本吻合,比多依奇公式更能反映双区静电除尘器的除尘效率。     

电除尘器电源交流分量对PM_(2.5)等细微颗粒物除尘效率的影响

除尘器对颗粒物的除尘效率与颗粒物的荷电量密切相关,PM2.5等细小颗粒物由于其荷电量不足而导致其吸收效率较低,对环境造成危害。为了增加粒子的荷电量,以粒子荷电原理为理论依据,从离子电流密度和通过电凝并扩大尘粒中位径2个方面研究了电除尘电源中交流电压分量对PM2.5等细小颗粒物荷电特性的影响,得出了电除尘器电源中交流电压分量可从以上2个方面提高装置对PM2.5等微小颗粒物的荷电量,且频率越高,幅值越大,荷电效果越好,从而可以提高装置对细小颗粒物的除尘效率。     

电除尘器电源交流分量对PM_（2.5）等细微颗粒物除尘效率的影响

除尘器对颗粒物的除尘效率与颗粒物的荷电量密切相关,PM2.5等细小颗粒物由于其荷电量不足而导致其吸收效率较低,对环境造成危害。为了增加粒子的荷电量,以粒子荷电原理为理论依据,从离子电流密度和通过电凝并扩大尘粒中位径2个方面研究了电除尘电源中交流电压分量对PM2.5等细小颗粒物荷电特性的影响,得出了电除尘器电源中交流电压分量可从以上2个方面提高装置对PM2.5等微小颗粒物的荷电量,且频率越高,幅值越大,荷电效果越好,从而可以提高装置对细小颗粒物的除尘效率。     

双区式电凝并技术对提高细微粉尘凝并效率的影响

为了进一步提高电凝并装置对细微粉尘的凝并效率,降低细微粉尘对人体的危害,设计一种由双极芒刺预荷电区和平行板收尘区组成的双区芒刺式电凝并装置,通过实验探究了安装双区芒刺预荷电装置、极配间距、外加电压3个凝并参数对细微粉尘凝并效率的影响。结果表明:当外加电压≤13 kV时,细微粉尘的凝并效率随外加电压的升高而增大,而当外加电压13 kV时,电凝并效率无明显提高;安装双极芒刺预荷电装置和缩短极配间距都可以有效提高细微粉尘凝并效率,当外加电压为13 kV时,极配间距由0.03 m缩短至0.02 m,各粒径粉尘的凝并效率均有10%以上的提高。根据实验结果可以得出,细微粉尘电凝并最优实验参数为安装双极芒刺预荷电装置、极配间距0.02 m、外加电压13 kV。以上研究结果可为电凝并技术的推广及工业应用提供参考。     

燃煤电厂烟气中颗粒物粒径分布特征研究

采用冲击式尘粒分级仪对某燃煤电厂1、3机组静电除尘器进、出口烟气进行监测,分析了烟气中颗粒物排放规律和静电除尘器对不同粒径颗粒物的去除率.结果表明,除尘前烟气中以大粒径颗粒物为主,小粒径颗粒物含量相对较低.静电除尘器对不同粒径颗粒物的去除率差别较大,1、3机组的静电除尘器对平均粒径(d50)≥3.56 μm的颗粒物的去除率均达到99.99%,对d50为1.01 μm的颗粒物的去除率则分别为92.75%、95.69%.除尘后烟气中PM2.5和PM10所占比例迅速增加,燃煤电厂排放的烟气中颗粒物以PM2.5为主.     

扩散荷电作用下线板式ESP中PM2.5捕集效率的数值模拟

为考察线板式静电除尘器中PM2.5颗粒的除尘性能,建立电场、颗粒动力场和流场多场耦合下的数学理论模型.采用GAMBIT软件构造ESP实体结构,将用户自定义程序UDF导入到FLUENT软件中进行数值仿真,并应用DeutsehAnderson公式计算粉尘在不同荷电机理和2种不同除尘操作参数下的除尘效率.数值结果表明,扩散荷电效应对PM2.5分级除尘效率贡献率随粒径增大非线性减小;外加工作电压越低或烟道气流速越高,扩散荷电效应对PM2.5粉尘颗粒的影响越大;在较高外加电压工况下,扩散荷电对综合效率的影响与降低一定量的烟道气流速相当.     

基于Monte-Carlo方法的静电除尘器除尘效率

针对经典除尘效率未考虑诸多随机因素影响的问题,提出了基于Monte-Carlo方法的效率分析模型,并通过实验数据验证其可靠性。通过该模型分析了粒径大小、电场气流速度、电晕电压、两极间距、粒子浓度等因素对收尘效率的影响规律,结果表明:基于Monte-Carlo方法的仿真结果精度更高,能有效预测静电除尘器的收尘效率,对于改进静电除尘器设计具有一定的理论意义和实用价值。     

Purification characteristics of fine particulate matter treated by a self-flushing wet electrostatic precipitator equipped with a flexible electrode

A self-flushing wet electrostatic precipitator was developed to investigate the removal performance for fine particles. Flexible material (polypropylene, 840A) and carbon steel in the form of a spiked band were adopted as the collection plate and discharge electrode, respectively. The particle concentration, morphology, and trace-element content were measured by electric low-pressure impactor, scanning electron microscope, and energy-dispersive x-ray spectroscopy, respectively, before and after the electrostatic precipitator. With increasing gas velocity, the collection efficiency of fine particles (up to 0.8 μm in diameter) increased, while it decreased for particles with diameters larger than 0.8 μm. Increasing the dust inlet concentration increased the collection efficiency up to a point, from which it then declined gradually with further increases in the inlet concentration. The particulate matter after the wet electrostatic precipitator showed different degrees of agglomeration. The collection efficiency of trace elements within PM₁₀ was less than that of the PM₁₀ itself. Notably, the water consumption in the current setup was significantly lower than for other treatment processes of comparable collection efficiencies.

Implications: Wet electrostatic precipitators, as fine filtration equipment, were generally applicable to coal-fired plants to reduce PM_2.5 emissions in China. However, high energy consumption and unstable operation, such as water usage and spray washing directly in the electric field, seriously restricted the further development. The utilization of self-flushing wet electrostatic precipitator can solve these problems to some extent.     

旋风除尘器流场及浓度场实验与模拟

在研究旋风除尘器内气固两相的运动状况及分离机理方面,计算机模拟替代部分实验的方法能够优化设计旋风除尘器结构参数,提高其对微细颗粒的捕集效率,减少运行压力损失。本研究采用RSM模型和随机轨道模型对旋风除尘器内流场及浓度场进行模拟及实验。研究表明,旋风除尘器压力损失模拟结果与实验结果吻合较好,对于大于5μm的颗粒其捕集效率模拟结果与实验结果基本吻合;旋风除尘器外壁的颗粒浓度呈螺旋带状分布;如将排气管管径减少至原直径0.8倍,可使其对2μm颗粒捕集效率提高6.6%,但压力损失提高36.5%;颗粒的凝并作用有利于提高旋风除尘器微细颗粒的捕集效率。     

Radiation Charging: A Novel Way to Charge Fine Particles Electrically

The purpose of this paper is to describe a scheme to electrically charge fine particles using electric and magnetic fields in conjunction with ionizing radiation. Once charged, particulate matter can be removed from the air stream by directly applying a transverse electric field. In addition, since electrostatic forces can assist filtration and wet collection systems, it may be possible to design new and improved filtration and wet scrubber systems using radiation charging. The objectives of this paper are: (1) to present expressions that predict the charge acquired by particles and (2) to present the results of preliminary experiments.     

Collection of Fly Ash with High Electrical Resistivity in a Pilot Plant Electrostatic Precipitator Preceded by the EPA/SoRI Precharger

It is well known that dust with high electrical resistivity is difficult to collect in electrostatic precipitators (ESP). The difficulty is primarily due to poor particle charging. This poor particle charging is not because particles having high electrical resistivity are intrinsically difficult to charge, but because back corona (which results from deposition of material on the collection electrode) produces a bipolar ion field. When ions of both positive and negative polarity are present in the charging region, the competing effects of the two, plus low values of electric field, produce low electrical charge on particles.     

电除尘技术研究现状及趋势

详细介绍了电除尘技术研究现状、现存问题及其发展趋势.论述了烟尘荷电凝聚机制及其输运特性等,以便解决除尘电场中的电离占空比、输运项甚低等问题;又着重研究了烟尘的荷电、凝聚的物理过程,将有助于解决电除尘器存在的捕集微细烟尘效率低的问题.     

Collection of Aerosol Particles by Electrostatic Droplet Spray Scrubbers

Theoretical calculations and experimental measurements show that the collection of small aerosol particles (0.05 to 5 micron diameter range) by water droplets in spray scrubbers can be substantially increased by electrostatically charging the droplets and particles to opposite polarity. Measurements with a 140 acfm two chamber spray scrubber (7 seconds gas residence time) showed an increase in the overall particle collection efficiency from 68.8% tit uncharged conditions to 93.6% at charged conditions, with a dioctyl phthalate aerosol (1.05 μm particle mass mean diameter and 2.59 geometric standard deviation). The collection efficiency for 0.3 μm particles increased from 35 to 87% when charged. During 1973–1974 a 1000 acfm pilot plant electrostatic scrubber was constructed inside a 40 ft trailer for evaluation on controlling particu-late emissions from pulp mill operations (funded by Northwest Pulp and Paper Association). Field tests performed on the particle emissions exhausting from SO₂ absorption towers treating the gases from a magnesium based sulfite recovery boiler have shown particle collection efficiencies ranging from about 60 to 99% by weight, depending on the electrostatic scrubber operating conditions. Energy requirements for the University of Washington electrostatic scrubber are about 0.5 hp/1000 acfm (350 Watts/1000 acfm) including gas pressure drop, water pressure drop, and electrostatic charging of the water spray droplets and the particles.     

Electrostatic Precipitation of Ultrafine Particles Enhanced by Simultaneous Diffusional Deposition on Wire Screens

Abstract

A laboratory-scale electrostatic precipitator has been designed and constructed in which the grounded collector plate has been substituted by a set of wire screens placed perpendicularly to the gas flow. Particles are deposited onto the screens by two mechanisms—electrostatic deposition and diffusional deposition—which act simultaneously. On the one hand, electrostatic deposition is effective for relatively large particles, but it is quite ineffective for the smallest ones because their charging probability in the corona field is too low. On the other hand, the diffusional collection efficiency of particles on fibers is high for small particles but low for the larger ones. Therefore, the simultaneous diffusional-electrostatic precipitation may become a useful technique for efficient filtration of particles below 0.1 μm. A preliminary experimental evaluation of this filtering device has shown that submicrometer particles with diameters down to a few nanometers can be collected with number efficiencies greater than 99%.     

Electrostatic precipitation of ultrafine particles enhanced by simultaneous diffusional deposition on wire screens

A laboratory-scale electrostatic precipitator has been designed and constructed in which the grounded collector plate has been substituted by a set of wire screens placed perpendicularly to the gas flow. Particles are deposited onto the screens by two mechanisms--electrostatic deposition and diffusional deposition--which act simultaneously. On the one hand, electrostatic deposition is effective for relatively large particles, but it is quite ineffective for the smallest ones because their charging probability in the corona field is too low. On the other hand, the diffusional collection efficiency of particles on fibers is high for small particles but low for the larger ones. Therefore, the simultaneous diffusional-electrostatic precipitation may become a useful technique for efficient filtration of particles below 0.1 microm. A preliminary experimental evaluation of this filtering device has shown that submicrometer particles with diameters down to a few nanometers can be collected with number efficiencies greater than 99%.     

ESP粉尘收集性能的影响因素

为了进一步提高电除尘器的收尘效率,尤其是对高比电阻粉尘的收尘效率,依据非稳态静电收集理论,对影响电除尘器粉尘收集性能各项因素的作用程度及机理进行了进一步研究。实验研究了粉尘收尘效率与不同比电阻粉尘的最优极间距、最优工作电压、粉尘层厚度和比电阻之间的相互关系。研究结果表明,随着极间距的增加,对应比收尘极面积,对于不同比电阻粉尘的收尘效率的增加幅度是不同的,其中高比电阻粉尘的收尘效率增加的趋势更加显著;粉尘比电阻越高,所对应的最优极间距越大,宽间距电除尘器对捕集高比电阻粉尘具有一定优越性;在最优极间距条件下,粉尘比电阻越高,其所对应的最优工作电压越小;相对于正常比电阻粉尘,随极板沉积粉尘层厚度的增加,高比电阻粉尘的最佳收尘效率所对应的最优工作电压升高幅度较大,而且最优工作电压所对应的收尘效率下降显著。随粉尘比电阻的增大,电除尘器收尘效率逐渐降低,特别是当粉尘比电阻大于1011Ω.cm后,粉尘收尘效率显著下降。研究结果与非稳态静电收尘理论提出的观点相吻合,有助于透彻理解电场结构和运行参数与粉尘收集性能的关系,特别是对于今后研发提高高比电阻粉尘收集性能的针对性技术措施具有指导作用。     

The Efficiency of Electrostatic Precipitators Under Conditions of Corona Quenching

The suppression of corona by particle space-charge is of considerable importance in electrostatic precipitators dealing with medium to high concentrations of particulates. However, the effect of the dust concentration on collection efficiency has found no direct answer in the literature. In addition to the expected reduction in corona current due to low mobility dust particles, the presence of these charged particles has two other main effects: 1. The electric field in the vicinity of the discharge electrode is weakened and hence the concentration of ions originating in the ionization zone and forming the charging current is decreased. 2. The resulting space-charge build-up causes an increase in the field strength adjacent to the collecting surface of the precipitator. The importance of each of these effects on the collection efficiency will be dependent on the relative decrease in particle charge as compared to the increase in the collection field. Experiments were carried out under both positive and negative corona with aerosol concentrations having specific surfaces in the range 0 to 44 m²/m³. These results showed: 1. For low values of corona current densities, as the specific surface area increases, the efficiency decreases. In this cqse, the charge per particle decreases as the particle concentration increases and becomes far below the normal charge attainable. Here the increase in the collection field is more than counteracted by the jarge reduction in particle charge. 2. For higher values of initial corona current densities, as the particle specific surface area increases, the efficiency either increases slightly or stays constant, in spite of major reductions in the measured corona current. In this case there should also be a reduction in the charge per particle with the increase in particle concentration, however, this is apparently offset by the increase in the collection field strength. Analysis of the results, coupled with an interpretation of existing theories, indicates that a major parameter that must be considered is the ratio of the initial corona current density and the specific surface of the particles.