Comparative Study of Spray Booth Filter System Efficiency

ABSTRACT

During recent years, greater emphasis has been placed on the control of particulate emissions from painting operations. This has gained more importance as more is learned about the potential release of toxic metals to the atmosphere from painting operations. This has led to queries about the efficiency of various painting arrestor systems to reduce particulate discharges to the atmosphere. Even more important is the capability of the arrestor systems to control PM₁₀ emissions.

In 1995, the U.S. Environmental Protection Agency initiated a study to evaluate various dry paint overspray arrestor systems. This study was designed to evaluate not only the total emissions control capability of the arrestor but also the PM₁₀ control capability of the various system designs. Paint overspray arrestor systems using five different filtration concepts or materials were selected. They include systems constructed of fiberglass, paper, Styrofoam, and cardboard materials. These systems used filtration techniques incorporating the following filtration phenomena and designs: cyclone, baffle, bag systems, and mesh systems.

The testing used an optical particle counting procedure to determine the concentration of particles of a given size fraction to penetrate a test arrestor system. The results of the testing indicated that there are significant differences in the efficiency of the tested system designs to capture and retain PM₁₀.

This paper summarizes the results of the research conducted to determine the capability of the arrestor systems to capture particulate of sizes down to approximately 1 μm in surface diameter.     

Comparative study of spray booth filter system efficiency

During recent years, greater emphasis has been placed on the control of particulate emissions from painting operations. This has gained more importance as more is learned about the potential release of toxic metals to the atmosphere from painting operations. This has led to queries about the efficiency of various painting arrestor systems to reduce particulate discharges to the atmosphere. Even more important is the capability of the arrestor systems to control PM10 emissions. In 1995, the U.S. Environmental Protection Agency initiated a study to evaluate various dry paint overspray arrestor systems. This study was designed to evaluate not only the total emissions control capability of the arrestor but also the PM10 control capability of the various system designs. Paint overspray arrestor systems using five different filtration concepts or materials were selected. They include systems constructed of fiberglass, paper, Styrofoam, and cardboard materials. These systems used filtration techniques incorporating the following filtration phenomena and designs: cyclone, baffle, bag systems, and mesh systems. The testing used an optical particle counting procedure to determine the concentration of particles of a given size fraction to penetrate a test arrestor system. The results of the testing indicated that there are significant differences in the efficiency of the tested system designs to capture and retain PM10. This paper summarizes the results of the research conducted to determine the capability of the arrestor systems to capture particulate of sizes down to approximately 1 micron in surface diameter.     

Fabric Filtration for Fly Ash Control

Economic projections and the growing experience with more diverse baghouse applications indicate that fabric filtration will become an even more popular type of control technology. While the fabric filter market shows signs of great promise now, an especially significant upturn is predicted within the next half dozen years when dry scrubbing becomes the primary process for combined S0₂ and par-ticulate control. In the interim, with more and more utility and industrial boilers gaining experience with baghouses, this control method can be expected to develop as an even more acceptable technique, especially on low S coal burning units. Nevertheless, the users stress the need for conservative planning and designing, giving extra care to start-up and maintenance procedures.     

Mixed-model statistical analysis of fuel, equipment, mileage, and driving schedule effects on particulate matter emissions from heavy diesel-powered vehicles

An extensive experimental program has been conducted to evaluate the comparative effects of California Air Resources Board diesel fuel and an ultra-low-sulfur (S) diesel (with and without aftermarket passive filtering devices) on mass emissions of particulate matter (PM) in heavy vehicles. Tests have been performed on 20 Class 8 trucks at two high-mileage levels using two different driving schedules. The design of the test program facilitates the use of mixed-model statistical analysis, which allows more appropriate treatment of the explanatory variables than normally achieved. The analysis suggests that the ultra-low-S diesel fuel yields extremely low mean PM emissions when used in conjunction with a particulate filter, even at high mileage, but that the estimates are highly variable. The high degree of uncertainty, caused at least in part by large vehicle-to-vehicle variation, may obscure the true PM response and adversely impact attainment of increasingly more stringent diesel PM emissions standards in the United States.     

The evolution and impact of testing baghouse filter performance

In 1995, the US. Environmental Protection Agency (EPA) initiated the Environmental Technology Verification (ETV) program for the purpose of generating both independent and credible performance verification of innovative technologies and helping to accelerate acceptance of these products into the marketplace to further benefit the environment and protect public health. The EPA has approved a testing protocol under this program to verify the performance of commercially available filtration products for pulse-jet baghouses in removingfine particulate matter (aerodynamic diameter<2.5 microm; PM2.5). This verification testing protocol was later used as a basis for the development of the American Society for Testing and Materials (ASTM) Method D6830-02 and the International Organization for Standardization (ISO) Method 11057. The South Coast Air Quality Management District (SCAQMD) in California and the EPA s Office of Air Quality Planning and Standards (OAQPS) highly encourage the use of ETV/ASTM-verified filtration media. This paper highlights the evolution of the standard test methods, the EPA's and SCAQMD's regulatory activities, the benefits of using verified filtration media, and the importance of including the filter performance testing in future consideration of baghouse permitting, baghouse operation and maintenance (O&M) plans, quality assurance/quality control (QA/QC), and bag monitoring plans.     

Closing Comments

“Industrial fabric filtration, the sleeping giant, is stirring. It appears that we are about to experience a new period of innovation and development similar to the one that occurred during the 1950’s.” The above remarks by Professor First, as presented in the Symposium, unerscore the renewed interest in filtration as a means for controlling submicron particulate emissions. Bur-chard and others pointed out the significance of fine particulate emissions, especially with regard to health effects and visibility degradation, and Walsh discussed the data required to employ fabric filters appropriately for particulate emission control.     

环境相对湿度对颗粒物过滤性能的影响

以吸湿性氯化钠 (NaCl) 颗粒和非吸湿性氧化铝 (Al₂O₃) 颗粒为实验对象,使用纤维材料过滤介质,引入纳米和微米两类颗粒物尺度,考察不同相对湿度 (RH) 环境下颗粒物过滤性能的变化规律及内在机理。结果表明：低湿度下 (RH20%和50%) 过滤吸湿性颗粒时,压降呈线性增长趋势,高湿度下 (≥RH80%) 会出现压降的急剧升高;非吸湿性颗粒受湿度变化的影响较小,但在饱和湿度下 (RH100%) 压降增长较为显著;滤料初始过滤效率对环境中相对湿度的变化不敏感,也不会受到颗粒吸湿性能差别的影响;在颗粒加载过程中,受滤料纤维表面颗粒物沉积的影响,过滤效率持续缓慢增长,但湿度超过颗粒潮解点后,对吸湿性颗粒的过滤效率出现一定程度下降,类似液体过滤机制;此外,环境湿度的变化对于纳米颗粒物过滤性能的影响远比微米颗粒更为显著。研究结果可为空气污染防治中颗粒物过滤技术的应用与改进提供参考。     

家居环境PM2.5控制用空气滤料

针对目前家居环境净化PM2.5的要求,在现有空气过滤材料的基础上,探讨一种适合于家居环境移动式空气净化装置用低阻、高效和长寿命的过滤材料。采用实验研究的方法对常用玻纤滤纸以及驻极体空气过滤材料进行了过滤特性、电镜、孔径测试的对比实验研究。结果表明,当过滤风速为5 cm/s时,3种驻极体滤料对粒径≤4.5 μm的颗粒物的分级过滤效率要高于玻纤滤纸且都在90%以上,其过滤阻力在4.9~6.4 Pa之间,而高效滤纸的过滤阻力在57.8~78.6 Pa之间;在实验风速条件下,驻极体滤料对PM2.5的过滤效率和过滤阻力分别高于和低于高效玻纤滤纸;对驻极体滤料进行蒸馏水洗涤后,其对颗粒物的过滤效率下降,驻极体滤料静电效应具有不稳定特性;电镜测试发现,玻纤滤纸纤维层排布致密,纤维存在断裂现象,而驻极体滤料较为蓬松,无纤维断裂现象;孔径实验表明,驻极体滤料的平均孔径为玻纤滤纸的11.9~14.7倍,驻极体滤料具有良好的透气和容尘特性。     

Facilities and Techniques for Maintaining a Controlled Fluoride Environment in Vegetation Studies

The principle of fabric filtration has only recently been accepted for fossil fuel fired boiler particulate emissions control. Information on design criteria is, therefore, limited. The paper provides data on the few installations where baghouses have been installed and successfully operated. The general conclusion is that a strong relationship exists between air to cloth ratio and bag life.     

驻极体空气过滤器对办公环境PM2.5的净化效果

针对办公环境PM2.5的净化问题,现场测试了以3种不同过滤面积的驻极体空气过滤器为核心过滤元件的空气净化器的过滤性能,并与普通高效微粒空气过滤器(high-efficiency particulate air,HEPA)、初效碳纤维滤层和活性炭滤网等进行了对比.测试点为上海某三楼办公室座位区离地面1.1 m处人体坐姿呼吸平面.采用蜡烛烟雾作为室内微细颗粒污染物的来源.分别测试了40 min内PM2.5的质量浓度衰减值和相应运行功率,并计算了净化器处理风量和洁净空气量.结果表明,过滤面积在0.20~0.54 m2范围内驻极体过滤器的过滤效率随面积增加而提高;过滤面积为0.29 m2的驻极体处理风量最大;以洁净空气量与功率的比值作为指标,可以直观判断出净化效果最好的是初效滤网叠加过滤面积为0.54 m2的驻极体过滤器;该工况下40 min内PM2.5浓度衰减率与HEPA几乎相同且均接近70%,但是洁净空气量大于HEPA.     

不同过滤介质对PM2.5过滤性能与效果

测定了不同孔径结构的无纺布和聚偏氟乙烯(PVDF)微滤膜电晕前后对Particulate Matter 2.5(PM2.5)的过滤性能,研究了材料的孔径与结构、过滤气流量、电晕放电对PM2.5过滤效率的影响。结果表明,聚酯无纺布和PVDF微滤膜对PM2.5的过滤性能差别较大,电晕放电处理技术能有效提高过滤介质对PM2.5的过滤效率。过滤介质有效过滤面积为10.2 cm2、过滤气流量为4 L/min时,克重数为50 g/m2的聚酯无纺布电晕处理后对PM2.5的过滤效率为77%,过滤压降为2.3 kPa;而孔径分布为0.7~1.0 μm的PVDF微滤膜电晕处理后对PM2.5的过滤效率达到99.79%,过滤压降为2.2 kPa,具备了高效低阻的性能。     

Novel Concepts,Methods and Advanced Technology in Particulate/Gas Separation

Particulate/gas separation techniques have been the subject of much research in recent years. From this research have come new concepts and methods, such as the use of acoustics, high gradient magnetic fields, and electrostatic filtration in particulate/gas separation. Some of the results of the work in the field were discussed by scientists in a workshop held at the University of Notre Dame in April 1977. The highlights of the discussions at that workshop are presented here.     

Toxicologic Appraisal of Particulate Matter,Oxides of Sulfur,and Sulfuric Acid

An examination of the available toxicological literature indicates that sulfur dioxide itself would be properly classified as a mild respiratory irritant, the main portion of which is absorbed in the upper respiratory tract. The reported industrial experience of symptoms of mild chronic respiratory irritation from exposures at or above 5 ppm is compatible with what would have been predicted on the basis of available toxicological data. The basic physiological response to inhalation of pure SO₂ appears to be a mild degree of bronchoconstriction reflected in a measurable increase in flow resistance. Although the response is highly variable, most individuals tested have responded to 5 ppm and levels of 5 to 10 ppm have upon occasion produced severe bronchospasm in sensitive individuals. This serves to point up the fact that experience with the industrial Threshold Limit Value (5 ppm) is not applicable as a guide for the general population. Although the majority of individuals tested have shown no detectable response to levels of 1 ppm, there are again sensitive individuals who have responded. It is not known whether these individuals would have responded to concentrations lower than this. The response of these more sensitive individuals to 1 ppm would be classified as detectable response, not as severe bronchospasm. An examination of the available toxicological literature also indicates that sulfuric acid and irritant sulfates, to the extent that the latter have been examined, are more potent irritants than sulfur dioxide. This has been demonstrated in studies using morality and lung pathology as criteria as well as in studies using alterations in pulmonary function in experimental animals and human subjects. The irritant potency of these substances is affected by particle size and by relative humidity, which factors are probably interrelated. It is unfortunate that these substances have not been as yet studied in as great detail as has the less irritant sulfur dioxide. There is evidence which cannot be ignored, even though it is based entirely on animal experiments of one investigator, indicating that the presence of particulate material capable of oxidizing sulfur dioxide to sulfuric acid caused a three to fourfold potentiation of the irritant response. The aerosols causing this potentiation were soluble salts of ferrous iron, manganese and vanadium all of which would become droplets upon inhalation. Insoluble aerosols such as carbon, iron oxide fume, triphenylphosphate or fly ash did not cause a potentiation of the irritant action of SO₂ even when used at higher concentrations. The concentrations of SO₂ used in these various experiments were in some cases as low as 0.16 ppm. The catalytic aerosols were used at concentrations of 0.7 to 1 mg/m³ which is above any reported levels of these metals in urban air. If the SO₂ present as an air pollutant remained unaltered until removed by dilution, there would be no evidence in the toxicological literature suggesting that it would be likely to have any effects on man at prevailing levels. Studies of atmospheric chemistry have shown that SO₂ does not remain unaltered in the atmosphere, especially under onditions of high humidity and in the presence of particulate material, but is converted to H₂SO₄. Such a conversion increases its irritant potency. On this basis the toxicological literature combined with the literature of atmospheric chemistry suggest that sulfur dioxide levels be controlled in terms of the potential formation of irritant particles. This means that control measures as far as feasible should be aimed at both SO₂ and particulate material and not against either alone.     

Continuous Measurement of Diesel Particulate Emissions

Evaluation of emerging diesel particulate emissions control technology will require analytical procedures capable of continuous or “real-time” measurement of transient organic and elemental carbon emissions. Procedures based on the flame ionlzation properties of organic carbon and the opacity or light extinction properties of elemental carbon are described, and applied for measurement of particulate emissions from diesel engines. The Instrumentation provided adequate sensitivity and time resolution for observation of the transient emissions associated with typical automobile urban driving conditions. Analytical accuracy is evaluated by comparing Integrated average results to measurements using classical gravimetric filtration and solvent extraction procedures. Mass specifc extinction coefficients are evaluated using the Beer-Lambert law. A simplified linear model relating elemental carbon concentration to opacity is also evaluated.     

Effect of chimneys on indoor air concentrations of PM10 and benzo[a]pyrene in Xuan Wei,China

This paper reports the effect of chimneys in reducing indoor air pollution in a lung cancer epidemic area of rural China. Household indoor air pollution concentrations were measured during unvented burning (chimneys blocked) and vented burning (chimneys open) of bituminous coal in Xuan Wei, China. Concentrations of particulate matter with an aerodynamic diameter of 10 μm or less (PM₁₀) and of benzo[a]pyrene (BaP) were measured in 43 homes during normal activities. The use of chimneys led to significant decreases in indoor air concentrations of particulate matter with an aerodynamic diameter of 10 μm or less (PM₁₀) by 66% and of benzo[a]pyrene (BaP) by 84%. The average BaP content of PM₁₀ also decreased by 55% with the installation of a chimney. The reduction of indoor pollution levels by the installation of a chimney supports the epidemiology findings on the health benefits of stove improvement. However, even in the presence of a chimney, the indoor air concentrations for both PM₁₀ and BaP still exceeded the indoor air quality standards of China. Movement up the energy ladder to cleaner liquid or gaseous fuels is probably the only sustainable indoor air pollution control measure.     

An Extended Self-Organizing Map Network for Modeling and Control of Pulse Jet Fabric Filters

ABSTRACT

Pulse jet fabric filters (PJFFs) have become an attractive option of particulate collection utilities, because they can meet stringent particulate emission limits regardless of variation in operating conditions. Despite their wide applications, the present control algorithm for PJFFs can best be described as rudimentary. In this paper, a modeling and control strategy based on the local model network (LMN) is proposed. An extended self-organizing map (ESOM) network is developed to construct the LMN model of the filtration process using the filter's input-output data. Subsequently, these ESOM local models are incorporated into the design of local generalized predictive controllers (GPC), and the proposed controller design is obtained as the weighted sum of these local controllers. Simulation results show that the proposed controller design yields a better performance than both conventional GPC and proportional plus integral (PI) controllers yield.     

Two-Stage,Dry FGD and Particulate Removal System

The results of the Kansas City-Wyandotte County Department of Health study of operation and maintenance ( O &; M) practices at a fiberglass manufacturing facility and a secondary metals smelter demonstrate the substantial impact of O &; M practices on particulate emissions. Both facilities have a history of O &; M problems leading to excessive particulate emissions.

Over a period of time, detailed O &; M information was obtained from facility management and operating personnel. Extended periods of in plant observation of O &; M procedures were correlated with simultaneous outside observations of visible emissions. O &; M related excessive emission problems at the secondary metals smelter were found usually to be caused by operator errors, compounded by marginally effective control equipment. In contrast, the excessive emissions problems at the fiberglass plant were almost always caused by actual process or control equipment malfunctions. These malfunctions appear to be almost inherent in the types of control equipment used, e.g. water washed high voltage electrostatic precipitators, and occurred despite a comprehensive O &; M program at the fiberglass plant.     

Relating Summer Ambient Particulate Sulfur,Sulfur Dioxide,and Light Scattering to Gaseous Tracer Emissions from the MOHAVE Power Project

ABSTRACT

Project MOHAVE was initiated in 1992 to examine the role of emissions from the 1580 MW coal-fired MOHAVE Power Project (MPP) on haze at the Grand Canyon National Park (GCNP), located about 130 km north-northeast of the power plant. Statistical relationships were analyzed between summertime ambient concentrations of a gaseous perfluorocarbon tracer released from MPP and ambient SO₂, particulate sulfur, and light scattering to evaluate whether MPP's emissions could be transported to the GCNP and then impact haze levels there. Spatial analyses indicated that particulate sulfur levels were strongly correlated across the monitoring network, regardless of whether the monitoring stations were upwind or downwind of MPP. This indicates that particulate sulfur levels in this region were influenced by distant regional emission sources. A significant particulate sulfur contribution from a point source such as MPP would result in a non-uniform pattern downwind. There was no suggestion of this in the data.

Furthermore, correlations between the MPP tracer and ambient particulate sulfur and light scattering at locations in the park were virtually zero for averaging times ranging from 24 hr to 1 hr. Hour-by-hour MPP tracer levels and light scattering were individually examined, and still no positive correlations were detected. Finally, agreement between tracer and particulate sulfur did not improve as a function of meteorological regime, implying that, even during cloudy monsoon days when more rapid conversion of SO₂ to par-ticulate sulfur would be expected, there was no evidence for downwind particulate sulfur impacts. Despite the fact that MPP was a large source of SO₂ and tracer, neither time series nor correlation analyses were able to detect any meaningful relationship between MPP's SO₂ and tracer emission “signals” to particulate sulfur or light scattering.     

Options for Controlling Condensation Aerosols to Meet Opacity Standards

The opacity of "detached plumes" formed by condensation of vapors depends upon both the concentration of condensible vapors and the in-stack concentration of fine, submicron, particulate matter. This paper provides an analysis of the condensing aerosol problem and an evaluation of possible control approaches to reduce the downwind detached plume opacity. The opacity of such plumes may be reduced by reducing the concentration of condensible vapors or the in-stack concentration of fine particles or both. The results of the analysis indicate that for low concentrations of condensible vapors the detached plume opacity may be adequately controlled by reducing the in-stack fine particulate concentration alone. For high concentrations of condensible vapors, however, reduction of in-stack fine particulate concentration alone may not be effective, and reduction of vapor concentration may be necessary along with particulate removal for adequate reduction of plume opacity. Different combinations of levels of reduction of vapor concentration and particulate phase concentration are possible to achieve a desired result; and thus may be optimized to obtain a cost-effective combination.