A Cost-Effective Electrostatic Precipitator for Aerosol Nanoparticle Segregation

Copyright 2015 American Association for Aerosol Research     

A Wet Electrostatic Precipitator (WESP) for Soft Nanoparticle Collection

Many nanoparticle collection devices have limitations related to retention of particle integrity from bounce, shattering, or aggregation. Suspensions of soft nanoparticles (e.g., proteins, lipids) are required for drug delivery and therapy. To enable direct collection of soft nanoparticles into liquid media, a wet electrostatic precipitator (WESP) was designed and evaluated in this work. Different sections were used for ion generation and particle charging, for minimal contact between the corona wire and particles, which were charged using positive nitrogen ions. WESP dimensions and operating parameters were optimized using charge distribution modeling. The prototype WESP was designed for operation with a continuous flow of liquid over the collection plate, to allow continuous particle collection from the exit stream of an aerosol reactor. The collection efficiency of the WESP, in dry and wet modes, was measured using aerosols of monodisperse polystyrene latex (PSL), polydisperse sucrose, and stearic acid (soft lipid) particles, through SMPS measurements, corrected for diffusional losses, at the entry and exit of the device. Measured collection efficiency was 70%–90% for particles of sizes 80–600 nm diameter in reasonable agreement with theoretical estimates. However, for small particles (20–80 nm diameter) measured collection efficiency ranged 40%–70%, significantly lower than theoretical estimates, possibly from incomplete neutralization of negative charges attained during air-jet atomization. Transmission electron microscopy (TEM) images and dynamic light scattering (DLS) measurements confirm that wet collection produces a suspension of free, unaggregated nanoparticles with sizes similar to their measured mean mobility diameter.

Copyright 2012 American Association for Aerosol Research     

Technical Note: Performance of a Personal Electrostatic Precipitator Particle Sampler

Currently, photocatalytic oxidation (PCO) is considered to be an effective process for removing and destroying low-level pollutants, which makes it a strong candidate for indoor air quality applications. Our study evaluated the titanium dioxide (TiO 2 ) filter media in controlling bioaerosols in a laboratory test chamber. The influences of microorganism species, relative humidity, and face velocity on the germicidal effectiveness of a TiO 2 -coated filter with 365 nm 8 W and 36 W blacklight irradiation were investigated. A Collison nebulizer generated Escherichia coli ( E. coli ), Bacillus subtilis ( B. subtilis ) endospores, yeast cells of Candida famata ( C . famata ) var. flareri , and spores of Penicillium citrinum ( P. citrinum ). The PCO control effectiveness was determined as the ratio, N S / N 0 , where N S and N 0 were the culturable concentrations collected by an Andersen one-stage sampler downstream of TiO 2 -coated filters with and without blacklight irradiation, respectively. Our results demonstrated that there were no significant differences in microorganism penetrations for TiO 2 -coated filters with and without blacklight irradiation. It was recommended that TiO 2 filter media used in this study did not perform as a good germicidal capability for airborne microorganisms.     

Filtration Characteristics of a Miniature Electrostatic Precipitator

This study investigates the filtration characteristics of a miniature dual saw-like electrodes electrostatic precipitator (ESP). Parameters such as particle size, rate of airflow through the ESP, voltage of charge electrode, and discharge polarity were considered to study their influence on aerosol penetration through the ESP. Polydisperse and monodisperse particles with sizes ranging from 30 nm to 10 w m were used as the challenge aerosols. Experimental results indicated that the aerosol penetration through the ESP decreased (from 96% to 15% for 0.3 w m) as the voltage of the discharge electrode increased (from + 4 kV to +8 kV) at a flow rate of 30 L/min. At a fixed electrode voltage (+8 kV), aerosol penetration increased from 15% to 69% for 0.3 w m particles as the flow rate increased from 30 to 120 L/min. The most penetrating particle size was in the range of 0.25 w m to 0.5 w m depending on the discharge voltage and the flow rate. In general, the most penetrating particle size of the ESP decreased with decreasing discharge voltage or with increasing flow rate. At the same voltage level but opposite polarity, the aerosol penetration through the ESP with negative corona was lower than that with positive corona. The difference in aerosol penetration was a factor of about 2 between the negative and positive coronas for 0.3 w m particles, and this difference was found to be independent of discharge voltage. Regarding energy conservation, use of a negative-polarity ESP was more economical if the same efficiency was required. However, the ozone generated by the ESP with negative polarity was about five times greater than that generated with positive polarity. Therefore when using an ESP as an indoor air cleaner, the search for an optimum balance between ozone production and aerosol collection efficiency should be considered.     

湿式电除尘器用导电玻璃钢的性能研究

参照美国标准ASTM C581,采用加速试验的方法对拉挤、手糊、缠绕工艺生产的导电玻璃钢管样块,在质量浓度为50%、温度为80℃的硫酸水溶液中进行28 d的浸泡试验,并周期性地测试其弯曲强度和弯曲模量,基于弯曲强度保留率指标对不同工艺生产的阳极管的耐腐蚀性能进行研究。     

HFCDS系统电除尘器专业设计软件的开发

1前言 电除尘器发展到今天,主要还是一门经验学科,其设计还没有一个理论公式可套用,实际应用的电除尘器主要还是根据实践经验设计确定。为了提高电除尘器选型与设计的准确性,提高电除尘器的性能,同时也为了适应电除尘器开发向大型化、标准化方向发展的要求，合肥水泥工业研究设计院在多年研究与应用电除尘器积累的丰富经验和大量数据的基础上，并结合消化引进国外先进电除尘技术，开发出了专门针对水泥行业窑系统烟气处理的电除尘器设计软件——HFCDS系统电除尘器专业设计软件（简称HFCDS系统软件）。     

窑尾电收尘器操作体会

我公司1000t／d熟料生产线窑尾废气处理系统采用的BS系列鲁奇电收尘（其规格及技术性能见表1）．在投运的四年多时间里，不仪排放浓度远优于国家规定的排放浓度，而且其同步运转率达99．8％以上（见表2）．本文将从工艺，设备两方面谈谈操作体会，供同行参考。     

Design Optimization of a Portable Thermophoretic Precipitator Nanoparticle Sampler

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are developing methods for characterizing diesel particulate matter in mines. Introduction of novel engine and exhaust aftertreatment technologies in underground mines is changing the nature of diesel emissions, and metrics alternative to the traditional mass-based measurements are being investigated with respect to their ability to capture changes in the properties of diesel aerosols. The emphasis is given to metrics based on measurement of number and surface area concentrations, but analysis of collected particles using electron microscopy (EM) is also employed for detailed particle characterization. To collect samples for EM analysis at remote workplaces, including mining and manufacturing facilities, NIOSH is developing portable particle samplers capable of collecting airborne nano-scale particles. This paper describes the design, construction, and testing of a prototype thermophoretic precipitator (TP) particle sampler optimized for collection of particles in the size range of 1–300 nm. The device comprises heated and cooled metal plates separated by a 0.8 mm channel through which aerosol is drawn by a pump. It weighs about 2 kg, has a total footprint of 27 × 22 cm, and the collection plate size is approximately 4 × 8 cm. Low power consumption and enhanced portability were achieved by using moderate flow rates (50–150 cm³/min) and temperature gradients (10–50 K/mm with ΔT between 8 K and 40 K). The collection efficiency of the prototype, measured with a condensation particle counter using laboratory-generated polydisperse submicrometer NaCl aerosols, ranged from 14–99%, depending on temperature gradient and flow rate. Analysis of transmission electron microscopy images of samples collected with the TP confirmed that the size distributions of collected particles determined using EM are in good agreement with those determined using a Fast Mobility Particle Sizer.

Copyright 2012 American Association for Aerosol Research     

德国鲁奇(Lurgi)公司新型电收尘技术的进步

1 前言 我国在上世纪80年代从德国鲁奇公司引进了电收尘器的设计、制造、安装和调试的成套技术,技术合同有效期为10年。经过10多年的技术转化,已制造出几百台鲁奇BS780型电收尘器,但由于种种原因,至今其技术仍停留在鲁奇公司80年代的水平。与此相反,鲁奇公司在这10年间不断地进行研究,其电收尘技术有     

Design and Collection Efficiency of a New Electrostatic Precipitator for Bioaerosol Collection

We have developed and tested a new bioaerosol sampler in which airborne microorganisms are collected by electrostatic means. In this sampler, 2 ionizers charge the incoming particles if they carry insufficient electric charge for efficient collection. The organisms are then subjected to a precipitating electric field and are collected onto 2 square agar plates positioned along the flow axis. Tests with nonbiological NaCl particles versus B. subtilis var. niger (BG) spores and vegetative cells have shown that airborne microorganisms are collected more efficiently than nonbiological particles, even when the microorganisms have first passed through an electric charge neutralizer with no additional charging applied. The difference was attributed to the natural charges contained in cell membranes or spore coats of the microorganisms. Charge-neutralized BG spores and vegetative cells were collected at 4 L/min with efficiencies close to 80%, depending on the precipitation voltage, versus 50-60% for NaCl test particles. When incoming BG spores were charged with positive ions and then collected by a precipitating voltage of + 1,300 V, about 80% of the incoming spores were collected and more than 70% of incoming spores formed colonies. These experiments with BG spores have also indicated that there were no significant particle losses inside the sampler. The collection efficiency of biological and nonbiological particles increased to 90-100% when the particles were externally charged and the precipitating voltage was increased to more than - 4,000 V. It has also been shown that the aerosolized BG spores (used as anthrax simulants for bioaerosol sensors) carry a net negative electric charge. Thus the collection efficiency depends on the polarity of the electric field applied across the agar plates. These findings indicate that the collection of airborne microorganisms is possible by electrostatic precipitation without prior electric charging if the microorganisms already carry electric charges. These are usually high immediately after their release into the air.     

Development of an Electrostatic Precipitator for Off-Line Particle Analysis

Due to the lake of in-situ aerosol particle analysis systems, aerosol samples are taken and analyzed off-line. For detailed analysis of particle properties such as shape, morphology, and composition, off-line operating analytical tools like light microscopes, scanning electron microscopes (SEM), total reflection x-ray fluorescence (TXRF), and so on are used. The analysis must be performed on a representative sample of particles homogeneously deposited on a flat sample plate. This avoids sample preparation steps which may change the sample. In this paper we describe the design, construction, and evaluation of a continuous sampling device that deposits gasborne particles on an analytically suitable sample plate. The collection efficiency and the deposition pattern were optimized using a numerical model and experiments. It turned out that representative samples appropriate for further analysis can be taken in the particle size range from 0.03 mu m < Dp < 10 mu m. Additionally, the sampling efficiency was investigated for particles smaller than 0.03 mu m using electrical and non-electrical deposition mechanisms like diffusion and thermophoresis. The investigations performed demonstrate that the designed electrostatic precipitator (ESP) is a very useful tool for homogeneous particle deposition on analytically suitable flat sample plates and can be used as a back-up filter. Further, the ESP especially can be used in combination with a differential mobility analyzer (DMA) if detailed investigations of a narrow particle size range of a polydisperse aerosol are required.     

电捕焦油器中焦油雾滴预团聚过程的研究

为了提高电捕焦油器对超细焦油雾滴的捕集效率,提出声波法和荷电法两种焦油雾滴的预团聚方法,并对采用这两种方法的雾滴预团聚过程进行了数值模拟,研究了声波频率和电场强度对雾滴预团聚效率的影响.     

电袋复合除尘器开发与应用研究

为了降低大气污染,寻求更加合理的烟气粉尘处理方式,提高除尘效率,降低建设成本和运行成本,结合目前企业除尘方式,提出电袋复合除尘器的应用途径。产生良好的社会公共效益同时,为企业创造更多的经济效益。     

Comparison and Combination of Aerosol Size Distributions Measured with a Low Pressure Impactor,Differential Mobility Particle Sizer,Electrical Aerosol Analyzer,and Aerodynamic Particle Sizer

Data from a different mobility particle sizer (DMPS) or an electrical aerosol analyzer (EAA) has been combined with data from an aerodynamic particle sizer (APS) and converted to obtain aerosol mass distribution parameters on a near real-time basis. A low pressure impactor (LPI), a direct and independent measure of this mass distribution, provided information for comparison.

The number distribution of particles within the electrical measurement range was obtained with the DMPS and EAA. Data from the APS for particles greater than that size were used to complete the number distribution. Two methods of obtaining mass distribution parameters from this number data were attempted. The first was to convert the number data, channel by channel, to mass data and then fit a log-normal function to this new mass distribution. The second method was to fit a log-normal function to the combined number distribution and then use the Hatch-Choate equations to obtain mass parameters.

Both the DMPS / APS and the EAA / APS systems were shown to successfully measure aerosol mass distribution as a function of aerodynamic diameter. Careful operation of the measurement equipment and proper data manipulation are necessary to achieve reliable results. A channel-by-channel conversion from number to mass distribution provided the best comparison to the LPI measurement. The DMPS / APS combination furnishes higher-size resolution and accuracy than the EAA / APS system. A small gap was observed in the EAA / APS combined data; however, this did not seem to adversely affect the determination of mass distribution parameters.     

浅谈电除尘阳极管的加工

我公司石灰车间电除尘器进行大修时,要对内部的数十根阳极管进行更换,不仅采购周期较长,而且费用较为昂贵.针对此问题,将公司现有机加工设备进行改造,自行制作加工阳极管,降低检修成本.     

铅H120型电除雾器的应用

介绍了硫酸装置改用的新型电除雾器其设计概况和运行情况，并提出该电除雾器在操作使用过程中的注意事项和对不足之处的改进意见。     

A New Thermophoretic Precipitator for Collection of Nanometer-Sized Aerosol Particles

A new thermophoretic precipitator (TP) has been designed and used for the collection of nanosized aerosol particles. NaCl and Fe particles, with mean diameters of 55 nm and 3.6 nm, respectively, were used to determine the thermophoretic deposition efficiency as well as the uniformity of the deposition. When the average temperature gradients applied were 2200 K/cm and 2400 K/cm, a high thermophoretic deposition efficiency, close to 100%, was attained at aerosol flow rates below 15 sccm. A gradual decay in the efficiency was observed as the flow rate was increased. Theoretical calculations of particle deposition efficiency were in good agreement with experimental data. The deposition along the TP was shown to be homogenous on a millimeter scale for both NaCl and Fe particles collected on thin foil substrates and microscope grids, respectively. Finally, the thermophoretic precipitator was used to efficiently deposit Fe nanoparticles on a substrate for the subsequent growth of carbon nanotubes.     

电除尘输灰系统自动控制改造

分析了解化化工分公司热动力厂电除尘输灰控制系统存在的问题,并重点介绍了FX2-48MR可编程控制器在输灰控制系统中的组态方法和应用情况。利用闲置设备(FX2-48MR)代替QS系列气力输送系统,对电除尘输灰自动控制系统进行改造,简化了控制程序,提高了控制可靠性,降低了维修成本。     

静电除尘器常见故障原因分析及对策

简单介绍了静电除尘器工作原理及基本结构。对静电除尘器的常见故障,即负载短路、保温箱电加热器损坏、除尘效率降低及二次电压高、二次电流低进行原因分析,提出了处理对策及预防措施。