Performance evaluation of the portable MiniVOL particulate matter sampler

The MiniVOL sampler is a popular choice for use in air quality assessments because it is portable and inexpensive relative to fixed site monitors. However, little data exist on the performance characteristics of the sampler. The reliability, precision, and comparability of the portable MiniVOL PM₁₀ and PM_2.5 sampler under typical ambient conditions are described in this paper. Results indicate that the MiniVOL (a) operated reliably and (b) yielded statistically similar concentration measurements when co-located with another MiniVOL (r²=0.96 for PM₁₀ measurements and r²=0.95 for PM_2.5 measurements). Thus, the characterization of spatial distributions of PM₁₀ and PM_2.5 mass concentrations with the MiniVOL can be accomplished with a high level of confidence. The MiniVOL also produced statistically comparable results when co-located with a Dichotomous Sampler (r²=0.83 for PM₁₀ measurements and r²=0.85 for PM_2.5 measurements) and a continuous mass sampling system (r²=0.90 for PM₁₀ measurements). Environmental factors such as ambient concentration, wind speed, temperature, and humidity may influence the relative measurement comparability between these sampling systems.     

随身自动空气净化处理器的研究

随身自动空气净化器，采用了活性炭、光催化技术相结合的空气过滤装置。空气污染传感器与单片机组成空气质量监测电路，当空气污染超标时，产生语音提示，液晶屏显示空气质量的等级，自动（或手动）控制引风机工作，供给个人清新无污染的空气。     

随身自动空气净化处理器的研究

随身自动空气净化器,采用了活性炭、光催化技术相结合的空气过滤装置.空气污染传感器与单片机组成空气质量监测电路,当空气污染超标时,产生语音提示,液晶屏显示空气质量的等级,自动(或手动)控制引风机工作,供给个人清新无污染的空气.     

脉冲供电在锌沸腾炉电除尘器上的应用

介绍了一种电除尘器脉冲供电的基本原理及其在锌沸腾炉电除尘器上的应用试验情况。结果表明，在基本保持同一工况条件下，脉冲供电比直流供电降低出口烟气含尘浓度50.4%～79.6%；脉冲供电能改善电除尘器运行性能，提高电除尘器改善系数达1.32；脉冲供电运行安全可靠。     

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.     

Validation of a flow-through sampler for pesticides and polybrominated diphenyl ethers in air

At locations without access to the electrical grid, a flow-through sampler (FTS) collects large volumes of air for the analysis of semi-volatile organic compounds (SVOCs). To test its performance under field conditions, an FTS and a traditional pumped high volume air sampler, both using polyurethane foam (PUF) as sampling medium, were co-deployed at the campus of the University of Toronto Scarborough from August 2006 to June 2007. Polybrominated diphenyl ethers (PBDEs) and various pesticides were quantified in the samples taken by both samplers to test the FTS's applicability to relatively non-volatile and slightly polar SVOCs. Air concentrations in samples taken with the FTS over five 2-week periods compare favourably with the average of the concentrations in several 24-h active high volume samples taken during the same period. In particular, time trends, temperature dependence relationships, and isomer ratios show a reasonable agreement between the two sampling techniques. An empirical linear solvation energy relationship for predicting the apparent theoretical plate number of the PUF assembly used in the FTS illustrates the effect of chemical properties, as well as temperature and wind speed, on sampling efficiency. In the absence of electrical power, the FTS can collect SVOCs from large air volumes as reliably and quantitatively as traditional HiVol samplers, although without separating gas and particle phase.     

Performance of a thermally desorbable type-tube diffusive sampler for very low air concentrations monitoring

Perkin-Elmer tubes packed with Tenax TA have been tested for the monitoring of low concentrations of aromatic compounds and linear alkanes using diffusive sampling. The uptake rates have been investigated for different exposure doses. A particular hexane and benzene behaviour has been observed: their uptake rates decrease rapidly in the lower exposure doses and so follow an exponential curve. The uptake rates of heavier compounds adopt another tendency: a slow decrease with time following a linear profile. The relative humidity influence has been studied too, and no water perturbation has been recorded.     

基于非稳态静电收尘理论的电除尘器运行参数的研究

为了进一步提高电除尘器的收尘效率,满足国家新的烟尘排放标准,依据研究建立的非稳态静电收集理论,提出了电除尘器供电电压及振打周期的优化措施.非稳态静电收尘理论研究与实验研究表明,收尘效率对供电电压存在一最大值,且此最佳供电电压是随极板沉积粉尘层比电阻、粉尘层厚度等动态变化的;振打周期的长短与粉尘层比电阻有关.据此提出的运行参数优化结果表明,对于比电阻不同的粉尘,电除尘器收尘效率最高时对应的供电电压随粉尘层比电阻的增大而降低,对于同一粉尘,最佳供电电压随粉尘层厚度的增长而提高;粉尘层比电阻低于1011Ω·cm时,一般保持极板粉尘层厚度在3～5 mm以内为佳,对于高比电阻粉尘应寻求适宜的清灰方式保障极板处于清洁状态.     

Plume analysis from field evaluations of a portable air quality monitoring system

ABSTRACT

Near-road measurements in Rochester, NY with a Portable Air Quality Monitoring System indicate a significant plume control of PM_2.5 black carbon (BC) concentrations. This study evaluates the performance of two portable air quality enclosures deployed at collocated research sites to determine their accuracy and usefulness in field deployments, and specifically in pollution plume analysis. One system deployed collocated sensors for measurement of particulate matter mass concentration (Thermo pDR 1500 against Tapered Element Oscillating Microbalance (TEOM) measurement) and the second system deployed sensors for measurement of black carbon (Magee AE33 aethalometer and Brechtel Tricolor Absorption Photometer) in ambient and near-road locations in Rochester, New York, respectively. While the optical PM_2.5 sensors tended to be biased in their determination of concentration by ~15%, they followed changes and trends in concentration very well. The black carbon sensors in the portable systems agreed very well with each other and with the collocated sensor. As a case study to determine the contribution from statistically significant short-lived excursions of pollutant concentration, Morlet wavelet analysis was performed on data from the portable system sensors. Black carbon was found to be strongly influenced by plume behavior with significant plume excursions representing just over 12% of all data points and contributing on average 1 µg/m³ of black carbon above ambient concentrations.

Implications: This paper first evaluates two air pollutant monitoring enclosures with wide applicability including near-road detection of pollutants. Then, we present a novel method to designate isolate statistically significant excursions in air pollution concentration which can be used to determine the impact of pollutant plumes as observed in PM and black carbon behavior near road.     

新型电袋复合除尘器性能研究

为了提高布袋除尘器对细微粒子的捕集效率,同时降低压力损失,提出了一种新型的电袋复合除尘器,并利用这种新型的除尘器对2 500目的超细滑石粉进行了实验研究。通过普通布袋过滤、电袋复合过滤的对比实验研究,得到了电场强度、气布比、压损、清灰周期和除尘效率等参数的变化规律。实验结果表明,使用新型的复合除尘器过滤粉尘时,粉尘在进入袋室之前就被荷电,通过在滤料表面施加较强的静电场,使得被处理粉尘在滤料的表面有序堆积和排列,能有效地降低压力损失,提高过滤风速,除尘效率均达到97%以上。Vf=3.5 m/min,U=12.3 kV时,新型复合除尘器与普通布袋过滤相比压力损失降低了90 Pa;PM2.5的捕集效率提高了5.9%;清灰周期从10 min延长至36 min。     

湿法电除尘系统处理焦化厂拦焦烟尘

针对焦化厂烟尘高浓度、高温、高湿和高黏度的特征,采用湍流预洗涤塔和湿法电除尘器处理拦焦烟尘。通过中试实验采样分析,利用全因子设计考察烟气流量、湍流预洗涤塔填料高度和喷淋流量对系统除尘效果的影响。实验表明,填料高度和喷淋流量是影响除尘效果的显著项,拦焦烟尘经过湿法电除尘系统的处理,烟尘浓度为8.3 mg·m-3,系统除尘率达到99.9%。     

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。     

侧流电除尘增效机理与检验

针对现有许多电除尘器难以满足日益严苛的颗粒物排放要求而面临提效改造的现状,根据经典电除尘理论,降低电场风速是电除尘器提效的一个有效途径,进而提出一种通过改变烟气流向成倍降低电场风速的侧流电除尘器。首先,为阐明侧流电除尘器的增效机理,基于已有的关于紊流情况下流速对颗粒悬浮作用的研究结果,通过受力分析给出了在有悬浮升力影响下带电颗粒的电除尘效率理论表达式,证明了降低电场风速的增效作用比增加电场长度更有效。然后,在极配结构和处理流量相同、平均入口含尘浓度约1 400 mg·m-3和场强在2.5~4.5 kV·cm-1的情况下,采用中位径为3.5 μm的硅微粉进行了侧流电除尘器和常规电除尘器的减排效果对比实验研究。结果表明,侧流电除尘器的平均排放浓度比常规电除尘器降低45％,减排作用突出。     

Passive air sampler as a tool for long-term air pollution monitoring: Part 2. Air genotoxic potency screening assessment

The capability of passive air sampling to be employed in the evaluation of direct genotoxicity of ambient air samples was assessed. Genotoxic effects of the total extracts from the polyurethane foam filters exposed for 28 days during a regional passive air sampling campaign were investigated. Twenty sampling sites were selected in Brno city on the area of approximately 20x20 km in October and November 2004. Brno is the second largest city of the Czech Republic, highly industrialized with approximately 370,000 of permanent inhabitants. The levels of PAHs, PCBs, and chlorinated pesticides were determined in all samples. Fraction of each extract was also assayed in the bacterial genotoxicity test using Escherichia coli sulA::lacZ. Complete dose-response relationships of the air extracts were determined. The statistical analysis showed significant correlation between observed biological effects and PAHs concentrations in samples.     

Wastewater treatment plants and landfills emit volatile methyl siloxanes (VMSs) to the atmosphere: investigations using a new passive air sampler

Volatile methyl siloxanes (VMSs) are a class of chemicals with an increasing range of applications and widespread distribution in the environment. Passive air samplers (PAS) comprising sorbent-impregnated polyurethane-foam (SIP) disks were first calibrated and then deployed around two wastewater treatment plants (WWTPs) and at two landfill sites to investigate inputs of VMSs to air. SIP-derived air concentrations for ΣVMSs (ng/m³) at background sites on the perimeter of the WWTP were 479 ± 82.3 and comparable to results for the upwind samples at the landfills (333 ± 194). Order of magnitude higher concentrations of ΣVMSs (ng/m³) were found for on-site samples at the WWTPs (3980 ± 2620) and landfills (4670 ± 3360). Yearly emissions (kg/yr) to air were estimated and ranged from 60-2100 and 80-250, respectively, for the cyclic VMSs. These findings demonstrate and quantify for the first time, waste sector emissions of VMSs to the atmosphere.     

粉尘对电除尘器气流分布影响仿真研究

为了更加精确地研究电除尘器入口气流分布特征, 论文采用欧拉-拉格朗日多相流模型,对电除尘器内部气流分布进行了数值仿真。由于在进入除尘器的气流中引入了粉尘粒子,不仅可获得粉尘及粉尘颗粒粒径大小对气流分布均匀性的影响,而且这种模拟更加接近除尘器的气流实际情况。提出的模拟方法为电除尘器的气流分析提供了一条新的途径。     

Development and evaluation of an impactor for a PM2.5 speciation sampler

A conventional impactor for a particle speciation sampler was developed and validated through laboratory and field tests. The speciation sampler consists of the following components: a PM2.5 conventional impactor that removes particles larger than 2.5 microns, an all-glass, coated honeycomb diffusion denuder, and a 47-mm filter pack. The speciation sampler can operate at two different sampling rates: 10 and 16.7 L/min. An experimental characterization of the impactor's performance was conducted. The impactor's collection efficiency was examined as a function of critical design parameters such as Reynolds number, the distance from the nozzle exit to the impaction plate, and the impaction substrate coating method. The bounce of particles larger than the cut point was successfully minimized by using a greased surface as the impaction substrate. Additionally, a series of field intercomparison experiments were conducted at both 10 and 16.7 L/min airflow. PM2.5 mass and SO4(2-) concentrations were measured and compared with the Federal Reference Method (FRM) and found to be in good agreement. Results of the laboratory chamber tests also indicated that the impactor's performance was in good agreement with the FRM.     

电除尘器气流分布与粉尘沉降规律试验研究

简要介绍了斜气流技术机理,进行了均匀气流和斜气流状态下的粉尘沉降试验.通过试验数据分析,总结出了电除尘器内部两种气流分布状态下的粉尘沉降规律,指出斜气流技术的应用在提高除尘效率方面具有重大意义,并为斜气流技术的应用提出了一些建议.     

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。     

烟气和粉尘性质对除尘效率影响的仿真研究

应用欧拉-拉格朗日多相流模型对影响电除尘器内部气流分布的烟气含尘浓度、烟气湿度、粉尘粒径及真密度等因素进行了数值仿真。分析了烟气和粉尘性质对除尘效率的影响。由于在仿真过程中考虑了烟气特性和粉尘性质等因素,不仅可获得各因素对气流分布均匀性的影响,而且仿真结果更能反映电除尘器气流分布的实际情况。提出的烟气和粉尘性质仿真方法可以为电除尘器除尘效率分析提供新的途径。