【作者】 依成武；

【导师】 吴春笃；

【作者基本信息】 江苏大学 ， 环境工程， 2010， 博士

【摘要】 目前,我国工业已进入高速发展的阶段,大气污染造成的环境问题越来越严重,治理大气污染物已成为十分紧迫的任务。电除尘器由于效率高、能耗低、能处理大烟气量的高温烟气,是颗粒物污染控制设备中应用最广泛的一种,在大气环境污染控制方面起到了十分重要的作用。但由于其存在体积庞大、一次性投资高、钢材用量多、对于PM10以下微细粉尘捕集效率低等问题,严重制约了其更进一步的应用。从高气压(-0.1MPa)非平衡等离子体物理、气体电离放电物理学来分析,目前电除尘器存在的关键问题是电除尘器放电区域离子输运率低,使电除尘器电场中离子浓度仅为106-107/cm3左右,进而使烟尘颗粒荷电量和驱进速度低,是造成电收尘器目前存在问题的主要原因。从带电粒子的运动规律可知,离子在输运过程中需要克服电场对带电粒子的束缚力,因此提高带电粒子的动量是解决离子源输出浓度及输运项低下问题的有效方法。论文设计的新型横向极板电除尘器采用一种新的放电除尘结构形式,选用ω型集尘极板,并将放电极设置在迎气流的集尘极间隙出口端。由于流过放电电场的气体流速高达5m/s～20m/s,大大增加了带电粒子动能,使离子有效摆脱了电场的束缚,提高了离子输运率和离子浓度,进而有利于粉尘荷电和除尘效率的提高。针对电除尘器存在的问题,论文分别进行了新型横向极板电除尘器理论分析、CFD数值模拟与设计、除尘试验系统设计及试验研究四部分工作。分析了新型横向极板电除尘的相关理论,采用CFD数值技术并结合电除尘器设计方法,设计了一套1000m3/h新型横向极板电除尘试验系统,进行了电除尘器离子输运特性和除尘性能试验研究工作。同时根据数值模拟设计并结合离子输运特性和除尘性能试验的结果,改进和优化了除尘器的设计工艺和参数,设计了一套3000m3/h新型横向极板电除尘试验系统,并进行模拟烟气净化试验,研究新型横向极板电除尘器的技术性能,为该项除尘技术的应用和推广提供依据,为解决电除尘技术现存的问题提供一种有效方法。文中在电除尘器结构设计过程中采用计算流体力学(CFD)技术,对课题设计的新型横向极板电除尘器除尘区域内流场进行数值模拟。计算采用SIMPLE算法,用前处理软件ICEM对几何模型进行网格划分,用FLUENT流体仿真软件借助离散相模型考查烟气风速v、粉尘粒径dp、外加电压U三种因素与除尘效率之间的关系,并根据数值分析结果对新型横向极板电除尘器的设计和运行进行优化。模拟设计结果表明,电除尘器内部整体气流分布较好,集尘板间隙处风速较高,可有效减少离子复合,从而提高除尘区域中离子浓度；模拟结果发现,除尘效率随外加电压、粉尘粒径的提高而增大,烟气风速在一定范围内成为了提高除尘效率的有利因素。同时流场分布的模拟结果表明,集尘极板背面风速较小,有利于捕集灰尘。数值模拟结果表明,新型横向极板电除尘器的除尘性能较好,技术经济性较佳。此外,模拟设计结果表明,新型横向极板电除尘系统设计时应在灰斗中设置挡板,防止部分烟气从除尘器下部灰斗中流过,并造成二次扬尘,降低除尘器的粉尘除尘效率。当除尘器入口烟气风速v为1.2-4.4m/s时,压力损失不高,v为4.4m/s时,压力损失也只有几百帕,低于中阻力除尘设备的压力损失。为了获得较高的除尘效率,相邻平行集尘极板间距d应选定为90mm左右,除尘器入口烟气风速v为2.5-3.5m/s,外加直流电场电压U为18-20kV。在试验研究中,首先建立了1000m3/h试验室规模的新型横向极板电除尘系统,并进行了离子输运特性试验,考察了距放电极距离L、外加电场电压U、烟气速度v、集尘板间距d等因素对自制新型横向极板电除尘装置的离子浓度n。的影响。试验结果表明,在横向极板电除尘系统中,随着风速v的提高,增加了放电电场中离子的动量,产生的离子浓度最高可达9.12x109/cm3,与传统除尘器比较,离子浓度可提高2个数量级以上。由于除尘装置有效的提高了离子输运率,可大大增加尘粒荷电的几率,提高粉尘粒子的荷电量和驱进速度。此外,结合离子输运特性试验的结果,进行了模拟烟气净化试验,并考查了外加电压U、有效收尘面积A、烟气流速v、粉尘比电阻p、粉尘浓度C0和粉尘粒度dp等因素对模拟烟气除尘效率η的影响。试验结果表明,当集尘极板间距d=100mm,外加电压U=18.2kV,烟气速度v=2.85m/s,烟尘浓度Co=10.2g/m3,有效除尘面积A=1.12m2时,横向极板电除尘系统除尘效率η可达到99.21%。在保证除尘效率的同时,有效提高了电场内气流速度,对粒径在0-10μm范围内的微细尘粒去除效果良好,捕集效率在90%以上。依据数值模拟设计和试验研究结果,对1000m3/h新型横向极板电除尘试验系统进行了改进和优化,设计了一套3000m3/h新型横向极板电除尘试验系统,并依据该套除尘系统进行了除尘性能试验。实验结果表明：与传统结构的电除尘器相比,新型横向极板电除尘器具有较大技术优势。通过理论分析和试验结果可以看出,新型横向极板电除尘器的横截面积和有效收尘面积与传统结构电除尘器相比,缩小了将近2倍,横向极板电除尘器的体积明显减小。同时,横向极板电除尘器的烟气流速高达3.0m/s,除尘区域内气流速度是传统电除尘器的近3倍；同时荷电尘粒在除尘电场中的驱进速度比普通结构的电除尘器提高了近7倍之多,高达188.6cm/s。因此,与传统结构的电除尘器相比,本课题研究设计的新型横向极板电除尘器具有明显的技术经济优势,可有效降低耗费钢材量和一次性投资,有望解决电除尘器存在的技术问题。更多还原

【Abstract】 Currently, while the industry of our country steped in a highly development stage, the environmental problem caused by the atomosphere pollution had became an urgent task than ever before. How to govern the atomosphere pollution turn to a urgent mission. Because the electrostatic precipitator (ESP) can remove the dust with the high temperature and high humidity, and the ESP has the enormous smoke treating capacity with less pressure loAs, so the ESP is universally accepted as a highly effective equipment. The ESP also play a important role in air pollution control field. However, due to the existence of large volume, a high investment, the amount of steel and more, low efficiency for the fine dust PM10 of the following problems, which seriously restrict its further application.From the high pressure (-0.1MPa) non-equilibrium plasma physics, discharge physics to analyze the gas ionization, the current key problems of ESP, is low ion transport in ESP discharge area, so that the ion concentration is only about 106-107/cm3 in the electric field of ESP, thereby enabling the dust particles charge and drift velocity is low, that is the main reason for causing the ESP current problems.From the motion equation of charged particles, ions in the transport process is to overcome the shackles of charged particles in the electric field strength, thereby increasing the momentum of charged particles is effective way to solving the problem of ion source output lower for ion concentration and transport items.New type ESP with transverse-plate using a new discharge structure, selection of co-type dust collector plates and discharge electrode set in a space welcoming gasflow output, the dust particles velocity through the discharge electric field is up to 5-20m/s, greatly increasing the momentum of charged particles, ions is out of the shackles of the electric field and the effective to improve the rate of ion transport and ion concentration, and thus to dust charged and collecting efficiency.In this paper, the reaarcher conduct the study on theroy analysis, numerical simulation and design by computational fluid dynamic (CFD), device design and experimental study respectively. In order to solve the ESP problem, the project designed a new type transverse plate ESP through mending and optimizing the structure of the traditional ESP.And Combined with experimental methods, the ion transport properties of the electrostatic precipitator and dust Experimental research.In the design process of the transverse plate ESP, the numerical simulation process was conducted by the Fluent software. The SIMPLE algorithm was uAd to calculate and the geometry model was divided by ICEM, which is one kind of pre-processing software. The relationship of gas velocity, dust particle size and voltage was examined by FLUENT software.Then according to the numerical simulation results, the reAarcher optimize the design and structure of the transverA plate ESP. Meanwhile, the simulation results indicated that the gas fluid inside the ESP distribute perferably, and the ion recombination was effective reduced through the high gas velocity between the dust collection plate. The results suggested that with the improvement of applied voltage and dust particle size, collection efficiency was increaAd and gas velocity became a favorable factor to improve collection efficiency in a certain range. So the ion concentration was greatly improved; the results showed that the gas velocity in the reverA of the plate is small to the benefit for collecting dust. According to the simulation results, the transverse-plate ESP has great performent in purify the dust. The experimental study was conducted by the Alf-designed transverA plate ESP, the ion transport properties experimental study investigated the effect of the applied voltage U, gas velocity v and the plate interval d on the ion concentration in the ESP. The experimental results indicited that the momentum of the ion increasing with the gas velocity increasing in the transverse plate ESP. The ion concentration in the system could reach 9.12×109/cm3. All of this showed that the device improved the ion generation obviously.Combine with the results of the ion transport properties experiment, the study carried the simulate gas purification experiment on the Alf-designed transverse-plate ESP. From the experiment results, the dust collecting efficiency can increaA to above 99.21%, when the distance ofωtype collecting plates is 40mm, initial dust density is 10.2g/m3, working voltage is 18.2kV, the area of effective dust collecting plates is 1.12m2, the gas velocity is 2.85m/s; meanwhile, the collection efficiency of fine particles (particle size distribution is 0 to 10μm) in transverse plate electrostatics precipitator system is above 90% when the other conditions remain certain. Therefore, the length, Action area and volume of ESP are reduced by Averal times compared with the conventional construction ESP and its miniaturization is realized.With the traditional structure of the ESP compared to the high speed transverse-plate ESP has a greater advantage.Through theoretical analysis and experimental results can be shown, high velocity transverse-plate ESP dust in the effective area of ESP compare with the traditional structure, nearly twice reduced, lateral plate significantly reduced the volume of ESP. At the same time, gas velocity can reach 3.0m/s or more in high velocity transverse-plate ESP, dust in the region is the traditional ESP up to 3 times; And the drift velocity of charged particals in the electric field is more than the raditional structure ESP of the nearly 7 times, up to 188.6cm/s. Therefore, the research design of high speed horizontal plate electrostatic precipitator technology has obvious economic advantages, the amount of steel consuming less electricity dust removal equipment to achieve the miniaturization.更多还原