袋式除尘器内部流场的数值模拟

袋式除尘器内部气流分布不均会加剧滤袋磨损,降低除尘效率。采用计算流体动力学(CFD)数值模拟方法对除尘器内部流场进行研究,分析了气流的轨迹及其在各气室中的速度分布。发现原设计中气流分布不均匀的现象比较明显,提出了在进气通道内添加气流均布板的改进措施。结果表明:改进后,除尘器箱体内部气流分布较均匀,各滤袋气流分配系数的波动幅度减小,各气室综合流量不均幅值降低。研究结果为袋式除尘器的结构优化设计提供了理论依据。     

射流加压溶气系统浮上法研究及其在水处理中的应用(续)

三、内循环式射流加压溶气系统的特点 JDF_Ⅱ加压溶气系统与JDF_Ⅰ系统或其它加压溶气系统相比较,它具有下述特点: 1.由于采用水——气射流技术,它依靠水泵所提供的高速喷射水流在射流器的气室部分形成的负压,从大气中直接吸入供加压溶气水所必需的空气,因此该系统不需要其它外加气     

活性焦联合脱硫脱硝脱汞塔入口气流均布与喷氨优化

某新建活性焦联合脱硫脱硝脱汞反应塔在试运行过程中运行阻力大,且脱硫脱硝效率较低。为提升反应塔的性能,以原设备为几何模型,采用CFD方法进行模拟优化。针对影响设备压降和脱硫性能的入口气流均匀性问题,模拟对比了4种导流板方案,考察板间距和圆弧板半径对气流均布的影响。同时为提高喷氨均匀性,结合烟气在过渡气室的流动情况提出了2种喷氨格栅加密方案。模拟结果表明:板间距和圆弧板半径都相同的导流板方案均布气流的效果最好,烟气在活性焦脱硫层的气流均匀性提升了11.48%,同时设备的压降降低了451 Pa。合理的喷氨格栅加密方案使氨气分布均匀性提升了34.88%。反应塔的压降模拟结果与现场实测数据吻合较好,模拟结果对设备的优化设计和实际运行有指导作用。     

徐州市电磁辐射环境的污染现状调查及评价

调查了徐州市电磁辐射污染源的状况,分析了其电磁辐射环境质量的现状,并对全市电磁辐射环境质量进行了评价,指出了分析工作中存在的问题,提出了防治对策。     

小城镇餐饮业污染现状及管理对策

介绍了餐饮业污染状况，对造成的原因进行了分析．提出了解决问题的措施。     

石化废水污染控制技术研究进展

石化废水水量大、成分复杂。探讨了石化企业利用新技术、降低循环冷却水用量、充分回收废料的清洁生产措施。总结了国内外石化废水预处理、生化处理、深度处理的实践经验。介绍了石化废水水质现代检测方法。提出了石化废水处理的研究方向     

臭氧降解乐果机理研究

研究了臭氧对乐果的降解效果，并探讨了降解机理。考查了不同浓度的臭氧及不同的接触时间对乐果的降解情况。试验发现，当初始臭氧浓度为10mg／L时，乐果的降解在5min内就达到80％左右，延长反应时间，降解率无明显增加。通过添加重碳酸盐和叔丁醇，初步探讨了降解机理，实验表明，臭氧降解乐果是个分子臭氧反应。对处理后的水样进行GC-MS检测，发现了氧化乐果的存在，证实了臭氧处理不足的情况下会产生毒副产物。     

基于超临界技术的印刷线路板资源化方法研究

印刷线路板的回收由于其结构和组成材料的复杂性，被认为是电子电器产品回收中的重点和难点之一。提出了将超临界流体技术应用于废弃印刷线路板的回收工艺，研究出了一种环境友好的废弃印刷线路板回收方法。建立了回收模型及回收实验平台，并使用正交实验设计方法对实验进行设计，利用SPSS分析软件对实验数据进行了分析研究并结合实际实验结果得出了最佳工艺参数。通过对反应生成物进行质谱分析，推测出了生成物的主要组分，并据此对反应机理进行了研究。     

中小型工业窑炉NO_x废气的净化技术与应用

介绍了中小型工业窑炉生产过程中排放NOx的现状,并针对NOx的治理问题,从工程应用角度,简述了湿法和干法净化NOx的原理和化学反应过程。讨论了NOx排放特性和NOx废气中NO2/NOx比例的问题。提出了影响NOx治理的主要因素,包括吸收剂、吸附剂、催化剂和设备的部分应用参数,并结合工程实例指出工程需要注意的问题。介绍了多项采用湿法和干法净化NOx的工程应用项目,丰富了中小工业窑炉NOx废气的治理的实践经验,为中小工业窑炉排放NOx治理奠定了基础。     

中小型工业窑炉NOx废气的净化技术与应用

介绍了中小型工业窑炉生产过程中排放NOx的现状,并针对NOx的治理问题,从工程应用角度,简述了湿法和干法净化NOx的原理和化学反应过程。讨论了NOx排放特性和NOx废气中NO2/NOx比例的问题。提出了影响NOx治理的主要因素,包括吸收剂、吸附剂、催化剂和设备的部分应用参数,并结合工程实例指出工程需要注意的问题。介绍了多项采用湿法和干法净化NOx的工程应用项目,丰富了中小工业窑炉NOx废气的治理的实践经验,为中小工业窑炉排放NOx治理奠定了基础。     

Calibration and testing of a dynamic flow-through chamber for field determination of methyl bromide volatilization flux

Accurate emission measurement of highly volatile chemicals such as methyl bromide (MeBr) is a crucial step in assessing their potential for environmental contamination. Use of flux chambers is a simple method for measuring emission rate under field conditions. To validate the applicability of a dynamic flow-through chamber for measuring MeBr emission, we provide a complete presentation of calibration and testing of the chamber. The calibration was made under a controlled system subject to ambient temperature changes. Two field experiments were conducted to test the chamber for measuring MeBr flux under conditions similar to commercial soil fumigation practices. In both the calibration and the two field experiments, the chamber provided accurate emission estimates. The maximum mass balance error was < 10% which is comparable to the micrometerological method. Because of its simplicity, we believe this dynamic flux chamber can be used reliably in quantifying the emission dynamics of highly volatile chemicals such as MeBr.     

有害物质环境测试组合舱的研制及性能评价

研制了一种新型有害物质环境测试组合舱,该测试舱由舱体系（内舱和外舱）、恒温恒湿空气处理系统、空气循环装置和信号控制与处理软件组成。该测试舱具有可分别使用内舱和外舱对样品进行测试的特点,并采用美国FLUNT公司开发的air pack软件包对内舱和外舱的气流进行模拟与计算,并划分出内舱的层流区域,同时也对舱体系的性能进行了测试与评价。结果表明,有害物质环境测试组合舱的温湿度的相对标准偏差分别为0.04℃和0.7%,混合性达到90.7%。因此,该有害物质环境测试组合舱对温湿度控制精准,气流稳定,混合性能良好,能为室内空气污染研究提供条件稳定的室内仿真环境。     

The SITE Demonstration of the Shirco Electric Infrared Incinerator

A test program for the Shirco infrared destruction process is described in this article. This incineration process is transportable and can be an effective method for cleanup of soils from Superfund sites. A pilot-scale unit and a 100-ton per day transportable unit were tested as part of the Superfund Technology Evaluation (SITE) program.

The process consists of a thermal destruction chamber where electricity is used for infrared rods that heat the waste, and a second chamber where propane is used to destroy any remaining hydrocarbons in the exhaust from the first chamber. A venturi scrubber and horizontal packed tower were used for particulate removal before exhausting the gas to the atmosphere. The feed material was reduced to less than one inch in diameter before it was processed by the unit.

The testing indicated that the Shirco system would remove and destroy organics from a waste, but would not remove heavy metals. The scrubber on the full scale system was of marginal capacity for that particular application and did not meet the RCRA specifications of 180 mg/dscm during two of the four tests made for the full scale unit.

Both units achieved Destruction and Removal Efficiencies (DRE) in excess of the 99.99 percent required for RCRA applications. Performance with respect to the TSCA requirement of 99.9999 percent for PCBs could not be ascertained due to the concentration of PCB in the feed.     

Reducing Interference Effects in the Chemiluminescent Measurement of Nitric Oxides from Combustion Systems

Experiments were carried out to determine the relative chemiluminescence quenching efficiencies as a function of third body concentration for each of the common combustion products, H₂O, CO₂, CO, H₂, O₂ and Ar. These results are compared with those of other investigators. The effect of reaction chamber pressure on analyzer response and the development of an analyzer design which incorporates an adjustable sample capillary inlet capable of maintaining a constant molar flow rate of sample gas to the reaction chamber are discussed. The effect of carbon monoxide interference on chemiluminescent NO_x measurement has been isolated and found to be significant. A means of correcting NO, measurements for these CO interference effects is described. Quantification of NO and NO₂ absorption in liquid water in NO_x sampling systems has been made. Recommendations for sample system designs to handle the presence of water in the sample gas are made.     

Design and Operating Parameters for a Large Ambient Aerosol Chamber

Recent investigations of ambient aerosol behavior over urban areas have pointed out the need for controlled experimental data to link together field investigation results and computer simulation studies. This paper describes the design considerations, construction details and operating parameters of a large (8000 ft³) outside reaction chamber constructed in rural North Carolina. The chamber is triangular in cross-section, 20 ft wide, 20 ft high and 40 ft long, and is covered with clear 5 ml Teflon film. The outdoor location of the chamber permits the reaction volume to be exposed to the natural conditions of temperature and solar radiation. A recirculating air system allows the air in the chamber to be passed through an “absolute” fiberglas filter for adjustment of condensation nuclei concentration and also through driers for humidity adjustment. Internal fans are provided for mixing of the chamber contents without use of the recirculating system so that various degrees of turbulence can be approximated. A sampling line from the chamber passes directly to an instrument room, located directly under the chamber, where direct analyses for particle composition, concentration, and size, and gas composition and concentration are carried out. Parameters which can be varied in this system include number, size, distribution, and chemical composition of pre-existing nuclei, as well as humidity, solar radiation, temperature, and trace gas concentration and composition.     

Theory and laboratory study of a tall passive chamber for measuring gas fluxes at soil surface

A tall passive flux chamber with a height significantly greater than its horizontal dimensions is proposed for measuring fluxes of volatile organic compounds (VOCs) at the soil surface. The main feature of this tall chamber is the presence of a vertical concentration gradient of the target gas in the chamber. The emission and transport behavior of the target gas in the soil-chamber system are analyzed using the diffusion theory. A mathematical model is developed to estimate the flux from the soil into the tall chamber, providing the target gas establishes a detectable vertical concentration gradient in the chamber. To obtain the data required for calculating flux, only two gas concentrations (C1 and C2) at two heights (h1 and h2) within the chamber need to be measured at the end of a short chamber placement time (tp). To evaluate the applicability of the tall chamber for measuring flux, several laboratory tests have been conducted, using CH2Cl2 and CH3Br as the target gases. The results indicate that the proposed tall chamber has promising potential as a method for measuring fluxes of VOCs at the soil surface.     

A large-scale fumigation system for investigating interactions between air pollution and cold stress on plants

A new large-scale closed chamber fumigation system with cooling facilities is described for studying effects of low concentrations of SO(2), NO(2) and O(3) and low temperatures on woody species and herbaceous plants. The system is based on modified hemispherical greenhouses with a forced air ventilation system. This provides a chamber environment with low spatial variability of pollutant gas concentrations and rapid air circulation which allows exposure of plants at near ambient temperatures and relative humidity. Large capacity cooling units come into operation when ambient temperatures fall below 0 degrees C, and these allow chamber temperatures to be lowered by an additional 4 to 8 degrees C in experiments designed to test whether exposure to pollutants enhances the frost sensitivity of plants.     

3-D Flow Modeling of a Hazardous Waste Incinerator

A three-dimensional flow model of a hazardous waste incinerator kiln and vertical secondary combustion chamber arrangement was constructed to evaluate critical system parameters. The chamber wall configuration, location and arrangement of burners, and the positioning of the outlet duct were examined to determine the critical secondary combustion chamber gas residence time and mixing of the combustion flows. The scale model consisted of the rotary kiln as a primary combustion chamber, the secondary combustion chamber, two burners, and the exhaust ducting. Flue gas velocities in the model inlets and outlet were maintained to provide a Reynolds numbers equal to the full size unit. Patterns of smoke which were injected into the model inlets were viewed to evaluate flow mixing. Slow motion playback of video tape was used to determine the minimum residence time of flow in the high temperature combustion zone. The results of the model study were used to complete the engineering of a waste incineration system.     

A Comparative Study of Environmental Tobacco Smoke Particulate Mass Measurements in an Environmental Chamber

Particulate mass concentration measurements have been made on environmental tobacco smoke (ETS) for the purpose of assessing the relative accuracy of several measurement procedures. ETS over a range of concentrations was generated in an environmental chamber by three methods. Mass concentration was measured by a gravimetric/spectrophotometric collection procedure, piezoelectric particle mass monitors, two nephelometry-based mass monitors, and a particle counting and sizing system. Two-hour average mass concentrations were determined by each method for concentrations ranging from very low levels up to those achieved by smoking one entire cigarette in the chamber. Statistical comparisons were made among procedures employing the gravimetric filter measurement as the basis for comparison. One nephelometry-based procedure gave significantly higher and the other significantly lower values than the filter determination. In one case, a correction for the difference between the particle mass density of the calibrating aerosol and that of ETS brought the nephelometry-based procedure into reasonable agreement with the filter measurement, while for the other, the correction did not resolve the discrepancy between methods. Statistically significant differences between the responses of two supposedly identical piezoelectric mass monitors were found, as was some slight dependence of the nephelometry- based procedures on method of ETS generation. In summary, the results indicate that significant errors can be expected if the instruments studied are used “off the shelf,” even for ETS generated under controlled laboratory conditions. Caution should be employed in field measurements where numerous sources and types of particulate matter can be encountered.     

A pilot study of methyl chloride emissions from tropical woodrot fungi

Flux chamber measurements made in a rainforest provide evidence that methyl chloride is emitted from rotting wood. However, its net flux was found to be into the soil, probably due to competing production and consumption processes within the soil. Evidence was found for a regional source, possibly vegetation, since its concentration above the canopy was substantially greater than reported average equatorial values.