关于除尘设备的毕业论文

Experimental study of electrostatic precipitatorperformance and comparison with existingtheoretical prediction . Kim, . Lee*Kwangju Institute of Science and Technology, Department of Environmental Science and Engineering,1 Oryong-dong, Puk-gu, Kwangju 500-712, South KoreaReceived 1 February 1999; received in revised form 21 May 1999; accepted 2 June 1999AbstractA laboratory-scale single-stage electrostatic precipitator (ESP) was designed, built andoperated in a wind tunnel. As a "rst step, a series of experiments were conducted to seek theoperating conditions for increasing the particle collection e$ciency by varying basic operatingparameters including the wire-to-plate spacing, the wire radius, the air velocity, the turbulenceintensity and the applied voltage. As the diameter of the discharging wires and the wire-toplatespacing are set smaller, the higher collection e$ciency has been obtained. In thesingle-stage multiwire ESP, there exists an optimum wire-to-wire spacing which providesmaximum particle collection e$ciency. As the air velocity increases, the particle collectione$ciency decreases. The turbulent #ow is found to play an important role in the relatively lowelectric "eld region. In the high electric "eld region, however, particles can be deposited on thecollection plates readily regardless of the turbulence intensity. The experimental results werecompared with existing theories and Zhibin and Guoquan (Aerosol Sci. Technol. 20 (1994)169}176) was identi"ed to be the best model for predicting the ESP performance. As the secondstep, the in#uence of particle contamination at the discharging electrode and at the collectionplates were experimentally measured. The methods were sought for keeping the high collectione$ciency of ESP over elapsed time by varying the magnitude of rapping acceleration, the timeinterval between raps, the types of rapping system (hammer/vibrator) and the particle rapping e$ciency and the particle re-entrainment were increased withincreasing magnitude of rapping acceleration and time interval between raps. However, whenthe thickness of deposited #y ash layer is su$ciently high, the concentration of re-entrainedparticles starts decreasing abruptly due to the agglomeration force which can interact among0304-3886/99/$ - see front matter ( 1999 Elsevier Science . All rights : S 0 3 0 4 - 3 8 8 6 ( 9 9 ) 0 0 0 4 4 - 3deposited particles. The combined rapping system is found more e!ective for removingdeposited particles than the hammer rapping system only. ( 1999 Elsevier Science . Allrights : Electrostatic precipitation; Turbulent #ow; Rapping; Particle re-entrainment; Collection e$-ciency; Negative corona1. IntroductionElectrostatic precipitators (ESPs) are one of the most commonly employedparticulate control devices for collecting #y ash emissions from boilers, incineratorsand from many other industrial processes. They can operate in a wide range ofgas temperatures achieving high particle collection e$ciency compared with mechanicaldevices such as cyclones and bag "lters. The electrostatic precipitation processinvolves several complicated and interrelated physical mechanisms: creationof a non-uniform electric "eld and ionic current in a corona discharge, ionicand electronic charging of particles moving in combined electro- and hydrodynamic"elds, and turbulent transport of charged particles to a , the collection e$ciency of ESP decreases as the discharging electrodeand collection plates are contaminated with particulates. Thus, a rapping system isneeded for removing the collected particulates periodically. While there have beennumerous theoretical and experimental studies on particle collection characteristics ofelectrostatic precipitators, a relatively small number of the studies addressed thee!ects of particle accumulation both at the discharging electrodes and at the collectionplates. Both phenomena are known to in#uence adversely the performance ofelectrostatic precipitators. Many researchers, such as Deutsch [1], Cooperman [2],Leonard et al. [3], Khim et al. [4], Zhibin and Guoquan [5], and Kallio and Stock[6], conducted particle collection measurements of ESP. However, they concentratedmostly on the e!ects of both turbulent mixing and secondary wind in multiwiresingle-stage electrostatic precipitators. Speci"cally, Cooperman [2] considered reentrainmentand longitudinal turbulent mixing e!ects, Leonard et al. [3] the "nitedi!usivity, and Zhibin and Guoquan [7] the non-uniform air velocity pro"le. Amongthem, only Zhibin and Guoquan [7] measured the collection e$ciency of a singlestageESP covering a wide particle size range. Even though their experimental dataare considered to be practical and useful, their experimental conditions were notidenti"ed the present study, well-de"ned collection e$ciency data for an ESP are presentedcovering the particle size range of }100 lm. The particles used in the present studycame from the Bo-Ryung power plant in Korea. In addition, the ESP performancewas evaluated in terms of optimum operating conditions. Finally, the optimumrapping conditions were sought under which the rapping e$ciency increases and theparticle re-entrainment . Kim, . Lee / Journal of Electrostatics 48 (1999) 3}25Fig. 1. Schematic diagram of the wind tunnel for the eight wired single-stage ESP performance . Review of theoretical . Particle chargingFig. 1 shows the laboratory-scale electrostatic precipitator. The particle chargingsystem consists of discharge wires with diameter (D8) and two grounded parallelplates of length (¸). A high negative voltage (<8) is applied to the corona dischargewires, and suspended particles of diameter (d1) #ow with air between the plates ata velocity (;) in the y-direction. In the whole range of particle sizes, both "eldcharging and di!usion charging mechanisms contribute to signi"cant charges [8,9].In these theoretical analyses, it is nearly correct to sum the rates of charging from thetwo mechanisms and then solve for the particle charging as follows:dq1dt"q4q A1!qq4B2#d21eN04 S8k¹pmexpA! 2qed1k¹B (1)where q1 is the particle charge, q4 is the saturation charge,N0 is the average number ofmolecules per unit volume, e is the electronic charge ("]10~19 C), b is the ionmobility ("]10~4 m2/V s), e0 is the permittivity of free space ("]10~12 F/m), d1 is the diameter of particle, k is the Boltzmann constant ("]10~23 J/K), ¹ is the absolute temperature ("293 K), m is the mass of a particle("(p/6)d31o1), and o1 is the particle density ("]103 kg/m3).. Theoretical models of particle collection ezciencyTheoretical models of ESPs were provided by Deutsch [1], Cooperman [2],Leonard et al. [3], Zhibin and Guoquan [7] and others. The Deutsch model . Kim, . Lee / Journal of Electrostatics 48 (1999) 3}25 5calculating the particle collection in an ESP assumes complete mixing by turbulent#ow and thereby uniform concentration pro"les. In order to improve the drasticassumption of in"nite di!usivity in the Deutsch model, many researchers tried todevelop "nite di!usivity models by dealing with the convective-di!usion equationwith various boundary [2] developed a theory which modi"es the Deutsch model to accountfor the e!ects of turbulence and particle turbulent di!usion. The major limitations ofthe Cooperman model lie absence of a general method to estimate the re-entrainmentfactor and the particle di!usivity. Leonard et al. [3] developed a more complicatedtwo-dimensional model using the method of the separation of variables from theconvective-di!usion equation. He assumed uniformity of velocity components ofcharged particles and particle di!usivity. This assumption fails to adequately describethe particle di!usivity near the collection plates, where it is governed mainly by themolecular transport and, therefore, the di!usivity near the wall is signi"cantly lowerthan the di!usivity in the turbulent core. Zhibin and Guoquan [7] suggested a newmodel for the single-stage ESP which takes into account the e!ect of turbulencemixing by electric wind. Predicted collection e$ciencies of the above theoreticalmodels are summarized as follows:gDe"1!exp(!De), (2)gCoo"1!expC;¸2D!SG A;¸2DB2#(1!R)PeA¸=B2HD, (3)gLeo"1!P10PA m!DeJ2De/PeBdm, (4)gZhi"1!S Pe4pDeP10expC!Pe4De(m!De)2Ddm, (5)where

你是什么专业的？跟我题目一样有材料了给我转发一下啊

电除尘是利用高压电源产生的强电场发生电晕放电，使悬浮尘粒在电场力的作用下，将悬浮尘粒从气体中分离出来的技术。下面是我精心推荐的电除尘技术论文，希望你能有所感触!

减排节能电除尘新技术应用研究

【摘要】本文从电除尘器技术发展现状、减排节能电除尘新技术，以及其他技术这三个方面对减排节能电除尘新技术应用研究进行阐述。

【关键词】减排节能;电除尘技术;应用;研究

中图分类号： TE08 文献标识码： A

一、前言

随着科学技术的不断发展，为了更好的进行节能减排，并且减少污染物的排放，节能减排电除尘新技术得到了广泛的应用。

二、电除尘器技术发展现状

我国全面系统地对电除尘器技术进行研究和开发始于上个世纪60年代。在1980以前，我国在国际电除尘器领域还处于非常落后的地位。改革开放以来，我国国民经济持续不断地高速增长，环境保护对国民经济的可持续发展显得愈来愈重要。受市场经济下的利益驱动，国内许多大、中型环保产业对电除尘器进行技术研究和开发方面的投入不断加大，电除尘器的应用得到了长足的发展。国家更是将高效电除尘器技术列入“七五”国家攻关项目。通过对引进技术的消化、吸收和合理借鉴，到上世纪90年代末，我国电除尘器技术水平基本上赶上国际同期先进水平。

进入21世纪以后，我国把“大力推进科学技术进步，加强环境科学研究，积极发展环保产业”作为经济发展的重要相关政策，环保产业进一步得到重视。随着国家对污染控制要求的不断提高，对粉尘排放的要求也大幅提高。电除尘器作为控制大气污染、解决环保与经济发展之间的矛盾的主要设备之一，其应用技术进一步得到飞速发展。

目前，电除尘器已广泛应用于火力发电、钢铁、有色冶金、化工、建材、机械、电子等众多行业。我国作为世界电除尘器大国立足于国际舞台，不仅在数量上，而且在技术水平上都已进入国际先进行列。电除尘器技术从设备本体到计算机控制的高低压电源，以及绝缘配件、振打装置、极板极线等已全部实现国产化，并且已有部分产品出口到30多个国家和地区。

在1980年以前，我国电除尘器的规模绝大多数都在100m2以下，而其行业占有量为有色冶金行业32% ，钢铁行业30% ，建材行业18% ，电力行业8% ，化工行业5% ，轻工行业4% ，其他行业0% 。

随着我国经济的飞速发展，尤其是电力、建材水泥行业的发展达到空前水平，到上世纪90年代中期，电除尘器行业占有量的格局已改变为：电力行业72% ，建材水泥行业17% ，钢铁行业5% ，有色冶金行业3% ，其他行业3% 。目前火力发电行业的电除尘器用量已占全国总量的75% 以上，648m2的电除尘器已在100MW的火电厂中成功运行。在化工行业，由于受国际硫磺价格的影响，从上世纪90年代中期采用硫磺制酸工艺取代硫铁矿制酸工艺的企业急剧上升，使得电除尘器的行业占有量也随之大幅下降，直到近两年才有触底反弹的迹象。

三、减排节能电除尘新技术

1、余热利用提效技术

在火力发电中，由于煤粉变粗、煤的含水量过多等因素很容易造成锅炉排放的烟雾温度过高，很大程度地降低了电除尘器的工作效率。煤烟温度的过高对电除尘器的影响主要表现在：

1)高温烟雾会增加烟气量，同时使得电场的风速增加，造成烟尘经过电除尘器的处理时间变短，降低除尘效率。

2)高温烟雾也会降低电场的击穿电压，增加了气体分子间的间隙，不利于电子与之碰撞，从而造成电离效应增加，降低除尘效率。

3)容易形成反电晕(除尘器极板上高比电阻尘产生的局部放电)，早晨尘粉二次飞扬，降低除尘效率。

2、高频供电技术

火电厂使用的电源主要为工频段在50Hz 的常规电源，而高频电源对电子和微电子等技术的应用，利用波形转换可以满足电除尘电力要求的同时，有很多优点：

1)提高效率。如果给电除尘器使用高频电源，利用高频电源的电气特性以及放电的性能，可以将电除尘的效率提高很多倍，同时还能降低烟气的排放量。

2)节能。同样利用高频电源的一些特性，可以将电除尘的效率因数提高至，更加的节省能源消耗。

3)体积小，使用便捷。普通的电源在制作中由于工艺的局限性，很难在现有的基础上将体积进一步缩小。而高频电源则因使用的变压器与控制系统集成的技术，体积很小，在安装中可以考虑安装在电除尘器的顶部。集成化的特点也决定了其可以使用更少的电缆，也更加节省空间。

4)绿色环保。高频电源采用了三相电源供电的方法，使用起来对整个电网的影响小，其最大的特点还是无缺相的损耗以及无污染，同时在电路的设计中增加了短路、开路、超温保护等功能，完全可以在十分恶劣的条件下使用。

3、三氧化硫调质技术

三氧化硫是火电厂烟气的主要污染物之一，所以在电除尘技术中如果能减少三氧化硫的排放量，或者能进一步减小排放的三氧化硫对环境的污染，才能达到国家减排的要求。三氧化硫烟气调质技术可以将一定量的三氧化硫与烟气中的少量水分通过一定手段结合成酸气溶胶，这种溶胶在通过除尘器的时候能够轻易地吸附于粉尘表面，从而达到电除尘的效率。

4、低二次扬尘技术

低二次扬尘技术主要是为了解决在电除尘过程中烟气在电风作用下产生的二次扬尘带来的除尘效率低的问题。低二次烟尘技术主要有以下几种措施：

1)对电除尘器内部的振打机构进行一定的改进，优化振打工作的程序，通过合理配置振打的强度以及去除不必要的振打来降低二次扬尘的浓度，让聚集在极板上的粉尘聚成块状而脱落。

2)对电场进行改进来克服高流速下的二次扬尘。目前使用的对电场的改进主要有使用高频电源来减少电晕闭塞，增加电场的工作效率;在电场中增加变阻流格栅，减少扬尘量;增加电场的面积来扩大对烟气流通的阻断作用范围，进一步降低风速。

5、气流分布技术

在对火电厂电除尘技术进行改进的时候，出了对于烟尘成分的研究，还出现了一种气流分布的新技术。这种技术是考虑了在大型的电除尘器中气流分布和浓度分布对于排放量的影响。

为了解决这种气流分布不均带来的影响，气流分布技术从最原始的检测分析入手，通过对电除尘器内部的结构以及气道中气流分布装置的安装情况进行研究，经过一系列的实验来找到影响气流分布的原因，从而对症下药。这种技术主要是通过复杂的运算来找出修正的方案，可以有效保证气流室内的气流分配均匀，最大限度地提高电除尘的效率。

四、其他技术

1、机电多复式双区电收尘技术

常规的电除尘器粉尘荷电与收尘功能是在同一个电场内完成，电场场强往往受荷电电压限制，使电除尘效果不能得到最佳发挥。这里提供一种阴阳极分小区布置、复式组合的机电多复式双区收尘电场新型产品技术，根据设计要求，可沿电场长度方向设置2~3 组荷电与收尘小区并呈复式交错布置。

2、节能电控提效技术

主要是通过对不同煤种、不同工况、不同负荷条件下的各种运行数据的分析、归纳和总结，对电场动态伏安曲线族与工况特性变化的关系规律进行对比和分析，建立不同的工况特性分析诊断的数学模型，基于该模型可以可靠地计算出电除尘器的反电晕指数和常电晕指数，正确地反映整台电除尘器的工况状态和变化趋势。结合锅炉负荷、烟气量、烟气温度、吹灰信号等多种信号;自动分析、诊断电场工况;实时自动选择高压供电的供电占空比和运行参数;实现综合节能，使电除尘器始终运行在功耗最小、效率最高状态。

3、湿法电收尘技术

湿法电除尘器采用洗涤电极的方法，可确保电极清洁，并可有效捕集细微粉尘、去除 SO3及一些重金属等，主要应用在冶金环境除尘等常温型工况场合。用在燃煤锅炉湿法脱硫后，可捕集逃逸的 细微粉尘等，有效解决石膏雨等问题，实现近似零排放。但要注意解决好设备防腐以及废水循环处理。

4、全布袋技术和电加袋技术

全布袋除尘工艺不仅在技术上可行，且具有投资省、占地少、运行费用低等优势，是符合我国特点的新技术，是典型的节能环保工程。电加袋除尘器由电除尘器改造而成，改善了电除尘器的除尘效率收粉尘“比电阻”的影响很大，除尘效率低的缺点。

五、结语

总的来说，各种新技术的不断被研发和应用，极大地促进了节能减排技术的发展，在一定程度上减少了颗粒污染物的排放，促进了生活环境的改善。

参考文献

[1]胡� 减排节能电除尘新技术应用研究 [J] 《城市建设理论研究(电子版)》 -2013年9期-

[2]罗如生，廖增安，陈丽艳 满足新标准采用电除尘新技术改造的应用与分析 [J] 《电力科技与环保》 -2012年4期-

[3]顾范华 燃煤电厂电除尘技术的评估研究和应用 [J] 《电源技术应用》 -2013年3期-

[4]文杰 减排节能电除尘新技术的应用分析 [J] 《建筑遗产》 -2013年17期-

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