Rapping systems for collecting surfaces in an electrostatic precipitator

Dust build-up on adjacent surfaces is often an unwanted effect in industrial processes handling pulverized materials. In the case of electrostatic precipitation, build-up of dust on the collecting surface is the purpose of the process. Removal of this build-up is sometimes difficult, but necessary to maintain the continuity of the process. Dry-process methods for dust removal include rapping by impact.It is the intent of this paper to provide information on the general subject of dust removal from plates, on rapping systems used in electrostatic precipitators, and on measurements and order of magnitude of rapping forces.Rapping acceleration test results obtained in the laboratory are expanded to cover full-scale collecting surface plates.Effects of plate design, plate height and length, method of support, rapping, hammer weight, and lift are analyzed.     

Evaluation of the George Neal electrostatic precipitator

The Electric Power Research Institute (EPRI) is currently supporting a major research program characterizing the performance of high efficiency electrostatic precipitators (ESP). One such effort evaluating the George Neal ESP of Iowa Public Service Company is described in this paper.Results show that under well tuned conditions the ESP overall collection efficiency was 99.7% at a specific collecting area of 745 ft²/kacfm (147 m²/m³/s) (520 MW) with associated mass concentrations of 0.025 lb/10⁶ Btu and stack opacity of 4.6%. The boiler outlet size distribution was found to be bimodal with submicron and large particle peaks at 0.2 and 5 microns diameter, respectively. Consequently, an apparent bimodal fractional efficiency curve results with efficiencies of 99.6%, 98%, and 90% measured for 20, 2 and 0.2 micron diameter particles, respectively. Rapping reentrainment losses were found to be insignificant except during episodes of high ash hopper levels resulting from a malfunctioning ash removal system, when large rapping puffs were observed. In addition, outlet emissions increased dramatically to 0.08 lb/10⁶ Btu (34 ng/J) during these periods, suggesting that an emission level more representative of daily operation lies somewhere between 0.025–0.08 lb/10⁶ Btu (10.8–34 ng/J).     

Ion current densities produced by energetic electrons in electrostatic precipitator geometries

A new laboratory test system for electron beam ionization in electrostatic precipitator geometries has been constructed to measure ion current density as a function of voltage difference for clean plate (no dust contamination) conditions. The new system incorporates improved electrodes which withstand an applied voltage of ± 55 kV, a factor of 5 increase over the previous test system. A 3 MeV Van de Graaff accelerator produced ionizing electron beams of 1.2 and 2 MeV energy with beam currents of 10.5 and 21 μA in place of corona wire ionization. Ion current densities of up to 130 mA/m² were measured before breakdown between the plates, and no ion current saturation was observed. A comparison of I-V curves and sparkover voltages for various beam energies, currents, and types of collimation is discussed and the need for measurements with good beam geometry is addressed.     

Design of high intensity ionizer—electrostatic precipitator systems

This paper presents the results of a comprehensive set of analytical and experimental studies concerning the application of high intensity ionization technology to retrofit a flyash electrostatic prepitator.Described in detail are the computer-aided methods of performing functional design for ionizer-precipitator systems, selected results of ionizer-precipitator flow model tests, and the chosen physical retrofit. Also presented is the projected performance of an ionizer-precipitator system, derived from two independent design procedures which take into account the effect of space charge and gas velocity distribution on system performance.Results of these studies confirm that high intensity ionizer technology can be applied to significantly improve the collection efficiency of conventional wire-plate electrostatic precipitators.     

Collection efficiency of electrostatic precipitators by numerical simulation

A numerical simulation code has been developed to analyze the coupled electro-aerodynamic phenomena within an electrostatic precipitator operated in both the positive and negative corona modes. The space charge and current densities, as well as the static and space charge components of the electric field, are first obtained using the known cross-sections for ionization and negative ion formation. Data includes the effects of fluid flow. The above quantities (except the static field) are then corrected in a subsequent iteration for the presence of dust particles of known size distribution, charges predominantly by the field charging mechanism. The precipitator collection efficiency is calculated from the trajectories of the charged dust particles. For theory comparison, the collection efficiencies of model precipitators were measured by light-scattering techniques using oil drops as test particles. The variation of efficiency with wire-to-wire spacing will be discussed as a case study.     

Industrial energy efficiency potentials: an assessment of three different robot concepts

The rise in energy consumption and the associated costs instigate financial concerns among industrial energy consumers. For industrial processes addressing heating and cooling as well as material transformation, a wide range of energy efficiency measures have been developed and successfully implemented. In contrast to that, most robot-based operations such as pick-and-place motions or assembly tasks still use inefficient standard concepts causing high-energy consumption and high-energy costs. Thanks to a rather low payload-to-weight ratio of new robot designs, such as parallel kinematic or hybrid robot manipulators, a high potential for energy savings is expected. This article identifies potentials for energy saving concerning industrial consumers by assessing three different robot concepts. Based on a literature review, two existing designs for robots – the conventional serial robot and the parallel kinematic robot are analysed and compared with respect to the energy utilised during a typical item placement task. Afterwards, the concept of PARAGRIP, a hybrid of the two presented robot designs is introduced and examined based on simulation regarding its energy consumption. The final results demonstrate significantly different energy consumptions between the robot concepts, identifying potential savings of about 40% in a selected industrial application scenario.     

Eco-friendly aspects associated with friction welding of tube-to-tube plate using an external tool process

The competitiveness among the manufacturers has been forcing the manufacturing processes to be eco-friendly so as to deliver products with lesser impact on the environment, energy demand and other resources consumption. In this regard, this article presents the unique environmentally friendlier aspects associated with an innovative welding process namely friction welding of tube-to-tube plate using an external tool (FWTPET). This process is capable of generating robust weld joints with lesser energy consumption. A comparative analysis of FWTPET with conventional tungsten inert gas welding process has been narrated.     

Copper uptake by four Elsholtzia ecotypes supplied with varying levels of copper in solution culture

The effects of copper (Cu) on the yield and Cu uptake of three ecotypes of Elsholtzia splendens and one of Elsholtzia argyi were studied using solution culture. Three Cu concentrations were compared: 0.31 (control), 50 and 100 micromol L(-1). Although E. argyi took up more Cu in the aboveground parts, typical visual symptoms of Cu toxicity appeared when the plants grew in 50 and 100 micromol Cu L(-1). In contrast, plants from all three populations of E. splendens showed high Cu tolerance and substantial shoot Cu accumulation of 58-144 mg kg(-1). Shoot Cu concentrations were about 16-27 times higher than root Cu concentrations. Root-to-shoot ratio of the E. argyi ecotype was halved when Cu was supplied at a level of 100 mg L(-1) compared to the control (0.31 mg L(-1)) but the ratio increased by 6-47% in the three E. splendens ecotypes. The increase in root-to-shoot ratio in E. splendens may be a mechanism by which the plants can tolerate high Cu concentrations. There were few differences in morphology among the three E. splendens ecotypes in response to added Cu. The results are discussed in relation to the possible use of E. splendens as a pioneer species in the phytostabilization of Cu-contaminated soils.     

Speciations of trace metals in the Danube alluvial sediments within an oil refinery

A sequential extraction procedure was applied to identify forms of Ni, Zn, Pb and Cu with Fe- and Mn-oxides associated in alluvial sediments of the River Danube within Pancevo Oil Refinery (Serbia). The five steps of the sequential extraction procedure partitioned metals into: CH(3)COONH(4) extractable (S1); NH(2)OH.HCl carbonate extractable and easily reducible (S2); (NH(4))(2)C(2)O(2)/H(2)C(2)O(2) moderately reducible (S3); H(2)O(2)-HNO(3) organic extractable (S4); and HCl acid soluble residue (S5). Extracted concentrations of trace metals, analyzed after all five steps, were found to be (mg kg(-1)) for Mn: 656, Fe: 26734, Ni: 32.3, Zn: 72.8, Pb: 13.4 and Cu: 27.0. Most of the elements were found in acid soluble residue, characterizing stable compounds in sediments. Non-residual fractions of trace metals (sum of the first four fractions) were analyzed because they are more bioavailable than the residual amount. Correlation analysis and two multivariate analysis methods (principal component and cluster analysis) were used to understand and visualize the associations between the non-residual fractions of trace metals and certain forms, more or less crystalline of Fe- and Mn-oxides within the analyzed sediments, since Fe- and Mn-oxides play an important role in trace metal sorption within aquatic systems, especially within the Danube alluvium where the fluctuations of groundwater are very frequent and the level of groundwater could come close to surface.     

移民型城市生态人居环境评价与优化研究

三峡工程建设以来,在大规模移民迁建的拉动下,形成了大量库区移民城市.良好的人居环境是保障移民型城市稳步发展的关键,也是建设生态城市的核心问题.本文基于生态人居清洁、舒适、低环境负荷的特点,以三峡移民第一城--重庆市万州区为例,对其1999-2005年居住适宜性水平进行了评价和分析,并基于评价结果提出了相应的优化调整建议.针对库区移民城市强调社会结构重建的特点,本文分别从基础设施、居住系统、生态环境、社会人文四个方面筛选指标,建立三级评价指标体系,综合运用层次分析法和熵权法确定指标权重,有效避免了主、客观定权方式各自的弱点.评价结果表明:7年来万州城区宜居水平虽呈上升趋势,但综合指数集中在0.45～0.6之间,距离生态人居的标准还存在明显差距.其中,基础设施滞后问题尤为突出,社会人文、生态环境指数自2000年后一直呈下降的趋势.     

Separate waste collection in Italy: the role of socio-cultural factors and targets set by law

The aim of this paper was twofold: on the one hand, we analyse the results achieved in terms of percentages of separate collection in Italy by testing the effectiveness of Legislative Decree 152/2006 in improving the separate collection process; and on the other hand, we investigate on some of the factors, related to the sociocultural local context, that could explain the different impacts of the law in the three macro-areas considered (North, Central and South Italy). To this purpose, an econometric analysis on the Italian regions for the 1996–2013 period is performed, comparing the period before (1996–2006) and after (2006–2013) the date of entry into force of the new law. The results show the effectiveness of Legislative Decree 152/2006 in promoting separate collection, although a regional difference in terms of separate collection rate is observed. Northern regions proved to be more dynamic and reactive to the above-mentioned legislation, while Central and especially Southern regions achieved poorer results in moving to higher separate waste collection rates. Finally, our work provides evidence on some local factors that may have hampered an effective policy implementation in Southern regions, among them, the presence of criminal activities and the lack of citizen participation in politics.     

Technologies,challenges and perspectives of biogas production within an agricultural context. The case of China and Africa

Environment, Development and Sustainability - The use of fossil fuels in modern economies has been a success because of the low cost of fossil resources. However, the depletion of fossil reserves,...     

Using radon-222 as indicator for the evaluation of the efficiency of groundwater remediation by in situ air sparging

A common approach for remediation of groundwater contamination with volatile organic compounds (VOCs) is contaminant stripping by means of in situ air sparging (IAS). For VOC stripping, pressurized air is injected into the contaminated groundwater volume, followed by the extraction of the contaminant-loaded exhaust gas from the vadose soil zone and its immediate on-site treatment. Progress assessment of such remediation measure necessitates information (i) on the spatial range of the IAS influence and (ii) on temporal variations of the IAS efficiency. In the present study it was shown that the naturally occurring noble gas radon can be used as suitable environmental tracer for achieving the related spatial and temporal information. Due to the distinct water/air partitioning behaviour of radon and due to its straightforward on-site detectability, the radon distribution pattern in the groundwater can be used as appropriate measure for assessing the progression of an IAS measure as a function of space and time. The presented paper discusses both the theoretical background of the approach and the results of an IAS treatment accomplished at a VOC contaminated site lasting six months, during which radon was applied as efficiency indicator.     

Presence and behavior of organic pollutants in an aqueous environment surrounded by an industrialized area

Water and sediment samples in a bay surrounded by heavily industrialized areas were analyzed by a combined gas chromatography/mass spectrometry/computer system, and a number of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAH), and polar oxygenated compounds were found. Behavior of PAH in the bay and its surroundings was traced by gas chromatographic fingerprint by using a glass capillary column. Water and sediment, dust fall, and airborne particulate samples were used as environmental samples. It was emphatically suggested that the major origin of sedimentary PAH was airborne dust.     

Measuring water resource use efficiency of the Dong Nai River Basin (Vietnam): an application of the two-stage data envelopment analysis (DEA)

Environment, Development and Sustainability - The recent growth of agriculture, industry and urban areas in Vietnam requires a large amount of water consumption as a production factor. This paper...     

Conservation of Sarawak peat swamp in an urban landscape by fuzzy inference system

Freshwater habitats are one of the planet’s most important, yet most manipulated, environments. This is what happens in Sarawak that the environment has been radically changed due to urban developments. This paper is promoting the idea that we do not need a complicated but a simple tool like fuzzy inference system to strike a balance between the existence of peat swamp and the humans who live nearer and nearer to it. Conditions vital to the survival and continuity of a natural wetland system can be adapted as fuzzy rules. These rules are capable of providing indicators of how much wetland can be exploited and at the same time still allow the system to properly functioning as a wetland.     

Developing an integrated approach to enhance the delivering of environmental goods and services by agro-ecosystems

It is widely acknowledged that the implementation of the majority of agri-environmental measures (AEMs) does not allow for the quantification of expected environmental benefits, thereby undermining the possibilities to assess both their effectiveness and efficiency. The objective of this paper is to show how an approach to develop agri-environmental measures based on the multifunctional character of agro-ecosystem is useful to overcome the difficulties in assessing expected environmental benefits. In the following sections, the main theoretical concepts underlying the actual European model of multifunctional agriculture are introduced. Following a critique of some aspects of the current analysis of the joint production of environmental non-commodities, the rationale to operate a shift of focus from multifunctionality of agriculture to that of agro-ecosystems is proposed. Finally the methodology developed by the AEMBAC project, based on the assessment of impacts exerted by agriculture on the capacity of local agro-ecosystem to perform environmental functions, is presented to explain how this shift of focus facilitates the assessment of the delivering of multiple environmental goods and services.     

Sequential extraction of 226Ra in sediments from an estuary affected historically by anthropogenic inputs of natural radionuclides

Riverbed sediments from an estuary historically affected by wastes discharged by several phosphate fertiliser plants and enriched in uranium-series radionuclides were operationally speciated using a Tessier-based method. In each selective fraction the (226)Ra content was determined by alpha-particle spectrometry after radiochemical isolation and electrodeposition onto stainless steel planchets. These studies were performed in (226)Ra-polluted estuarine sediments collected one year after anthropogenic discharges had ceased in order to obtain useful information about the operational forms in which this radionuclide remains associated with the sediments at this time. The results obtained revealed that one year after (226)Ra inputs had stopped, the radionuclide was associated mostly with the more refractory forms. Consequently, it is possible to foresee little potential remobilisation of (226)Ra contamination from sediments to the aqueous phase in the future under normal environmental conditions.     

Forest fires caused by lightning as an indicator of connections between atmosphere,lithosphere, and biosphere

A significant positive correlation between the density of lightning fires and the horizontal gradient of anomalous geomagnetic field is demonstrated on the basis of studies on lichen pine forests in the Konda River basin (Khanty-Mansi Autonomous Area, Western Siberia) and analysis of published data. Schematic hypotheses of global connections in the atmosphere-lithosphere-forest-lightning fire are proposed.