Flow analysis of major and trace elements in residues from large-scale sewage sludge incineration

Increase of sewage sludge (SS) has led to the construction of more incineration plants, exacerbating to the production of SS incineration residues. However, few studies have considered the mass balance of elements in large-scale SS incineration plants, affecting the residues treatment and utilization. In this study, flow analysis was conducted for major and trace elements in the SS, the fly ash (sewage sludge ash, SSA) and bottom ash from two large-scale SS incineration plants. The elemental characteristics were compared with those of coal fly ash (CFA), and air pollution control residues from municipal solid waste incineration (MSWIA), as well as related criteria. The results showed that the most abundant major element in SSA was Si, ranging from 120 to 240 g/kg, followed by Al (76–348 g/kg), Ca (26–113 g/kg), Fe (35–80 g/kg), and P (26–104 g/kg), and the trace elements were mainly Zn, Ba, Cu, and Mn. Not all the major elements were derived from SS. Most trace elements in the SS incineration residues accounted for 82.4%–127% of those from SS, indicating that SS was the main source of trace elements. The partitioning of heavy metals in the SS incineration residues showed that electrostatic precipitator ash or cyclone ash with high production rates were the major pollutant sinks. The differences in some major and trace elements could be indicators to differentiate SSA from CFA and MSWIA. Compared with related land criteria, the pollutants in SSA should not be ignored during disposal and utilization.     

Characteristics of the vibrating-mesh minimum ignition energy testing apparatus for dust clouds

A novel apparatus for testing the minimum ignition energies of flammable dusts is introduced. Unlike the conventional apparatus (the Hartmann tube), this new apparatus employs a vibrating mesh to produce a dust cloud. Using three kinds of powders, namely lycopodium, anthraquinone and polyacrylonitrile, which are designated as the samples for calibration by the International Electrotechnical Commission (IEC, 1994) standards, fundamental characteristics were experimentally investigated. Concerning the minimum ignition energies (MIEs), the new testing apparatus worked well for two samples, lycopodium and polyacrylonitrile. The MIE for anthraquinone, however, was by far larger than the expected value. We concluded that the aggregation of anthraquinone particles is the main cause of the difference and is attributable to both the tribo-charges acquired by the particles when passing through the mesh and the filamentary shape of the crystal. Other essential factors for characterizing the testing apparatus, such as the concentration of dust, the shape and spacing of the sparking electrode system, and the impedance of the sparking circuit are discussed.     

双极不对称预荷电静电增强过滤除尘技术的应用

双极不对称预荷电静电增强过滤除尘技术 ,是国家“九五”科技攻关课题所取得的成果之一 ,该技术采用双极不对称荷电增强方式 ,将普通静电增强效果与粉尘凝并机能有机地结合在一起 ,既提高了过滤除尘器的收尘效率 ,尤其是呼吸性粉尘的效率 ,同时又极大地改善了滤料粉尘层的结构 ,可显著地降低过滤阻力增值 ,节约运行能耗。笔者研究的该技术应用于焊接车间的焊接烟尘的治理上 ,取得了良好的效果。现场测试表明 ,该技术对焊接烟尘的滤除效率提高了 3% ,尤其对微细粉尘效果显著 ,2 μm粉尘穿透率相对下降了 4 7%。采用超细滑石粉高粉尘负荷测试结果表明 ,过滤阻力增值降低达 30 % ,清灰效果明显改善     

Charging behavior of glass beads using a spiral air type tribocharging apparatus that utilizes a Faraday cup

This paper introduces a novel tribocharging apparatus that utilizes a Faraday cup and experimentally investigates the charging behavior of glass beads. The novel apparatus mainly consists of four parts: an air supply part to control air duration and pressure, a powder supply part for setting the desired amount of powder (1 g in this experiment), a metal pipeline for generating a tribocharge, and a cyclone for collecting the powder that has passed through the pipeline. Four different sizes of spherical glass beads were used in this experiment. As for the results, the charge clearly increased as the glass bead particles passed through the pipeline for all four types of glass beads. The charge amount of the glass beads and the charge amount obtained from the pipeline had a very similar trend and absolute values. This confirmed the reliability of the test and showed that there was no disturbance due to external noise. In all of the tests, the net charge was observed to be negative for all glass beads. This agrees with the triboelectric series relating to the work functions of metals and glass particles. Smaller particles had larger charge amounts than did larger ones with good reproducibility. The charge amount of all glass beads increased as the supplied spiral air pressure increased.     

电捕焦油器在沥青熔化中对沥青烟净化的应用

沥青烟是一种较强的致癌物质,对人的健康会造成极大的伤害。电捕焦油器对消除沥青烟起到了至关重要的作用,是捕集沥青烟气较为理想的净化设备。     

整体环境静电防治

美国ＡＣＬ公司在一般静电防治基础上，突破传统观念，树立新观念，攻克了全方位、整体环境的现代静电防治技术，研制开发出性能优良的ＳＴＡＴＩＣＩＤＥ系列防静电产品，得到广泛应用．     

MKJ型静电空气消毒洁净器的研制

应用工业电除尘的原理,采用正离子浸润来菌和镜象力荷电吸附除菌,只考虑细菌尘粒的粒径,不考虑其生物性的技术路线,设计了一种小型组合式静电场装置,配以高频高压恒流电源室内空气洁净器,面面积２０ｍ＾２,高３ｍ的室内使用可达到１万级洁净度（０．５μｍ粒子浓度〈３５０个／Ｌ）。医院手术室和重症监护病房的应用实例结果表明,具有在有人场合下连续消毒除菌和去除异味的优点。     

Dioxin removal in “energy from waste plants” - comparison of air pollution control methods

The graph below shows the emitted dioxin - equivalents (Eadon) in grams per year in flue gas from municipal solid waste incinerators with various air pollution control methods for plants of capacity of 200 000 ton municipal solid waste (MSW) per year.

Full-size image (15K)

With optimized combustion and an effective air pollution control system the emissions of dioxins can be kept very low (concentrations below 0.1 ng/m³n).

With a very effective air pollution control system the total emission from all Swedish MSW-incinerators burning approximately 1.5 Mton/year will by 1990 be below 2 g/year - a drastic reduction from approximately 15 g today. As the total dioxin - equivalent emission to the environment in Sweden in the year 1987 was almost 500 g we see that municipal waste incineration really is on the way to solve their dioxin problem.     

废印刷电路板的静电分选实验研究

金属与非金属材料的分离是回收利用废印刷电路板的关键环节。对废印刷电路板物料的静电分选进行了实验研究。实验以电压、辊筒转速、电晕电极与辊筒之间的距离、静电极位置、电晕电极位置、电晕电极数量等为考察因素,研究各因素对电选效果的影响规律。结果表明,影响金属与非金属材料分离的主要因素是电压、辊筒转速和电晕电极与辊筒之间的距离,对于-0.9 0.45mm的破碎物料,当电压为24kV,辊筒转速为15Hz(54.6r/min),电晕电极与辊筒之间的距离为5.2cm时,得到最大静电分选综合效率67.37%。     

Charge-separating processes by spraying water under high pressure

Spraying water under high pressure generates charge-separating processes. While cleaning tanks and vessels in which an explosive atmosphere is present, an explosion may occur in the event of a resulting discharge. Water forms electrical double layers at the phase boundaries. Mechanical separation processes dissolve the water into many drops. This leads to charge separation and the charging of the sprayed water. The mechanical separation processes include water exiting from the nozzle, hydrodynamic instability in the jet and impact with an obstacle. Given that water has many charge carriers, the charge is stronger than with solvents. Whether the charges and the resulting discharges are potentially capable of igniting an explosive atmosphere must be investigated. The aim of this research is to define the quantity and polarity of the electrostatic charges of sprayed water under high pressure. Different measurement techniques and methods are used to enable mutual validation and to generate verified measurement results of the electric field and the potential. Water of different electrical conductivity is sprayed in free space and into a grounded conductive 1 m³ vessel. Design changes to the vessel allow centric or oblique spraying. The result is intended to extend the scope of application of the German regulation TRGS 727 and the international IEC TS 60079-32-1, which refer to ignition hazards due to electrostatic charging. This project is funded by the DGUV (German Social Accident Insurance) and partners from industry.