Using an improved electrostatic precipitator for poultry dust removal

Pubic concerns related to particulate matter emissions from animal housing operations are increasing. The goal of this study was to custom develop a simple and low cost electrostatic precipitator (ESP) for poultry dust control. The performance of the improved electrostatic precipitator (iESP) to remove a test aerosol was evaluated under a series of operating voltages between ?60 kV and 60 kV. The mass and size distributions of the particles were measured by a cascade impactor. The overall dust removal efficiency ranged from 37% to 79% with the maximum efficiency obtained at ?30 kV. The iESP shows high removal efficiencies for particles less than 2.1 μm.     

Electrostatic precipitation in a small scale wood combustion furnace

Wood combustion generates a high concentration of particulate matter emission, but most of the particulates in the exhaust gas can be filtered through an electrostatic precipitator. The objective of this paper is to model the trajectory of particulates in the exhaust chimney of a small scale wood combustion furnace with an electrostatic precipitator. The precipitator consists of a central electrode subjected to a maximum high voltage of 50 kV and an outer electrode of 180 mm diameter, ground potential. The parameters including particle size, ambient temperature, pressure, gas flow rate and the applied voltage have been varied while computing the trajectories of the particles in the chimney. The trajectories of particulates have been analyzed for different sizes of a typical wood combusting stove by taking different forces into account on particulates. The critical conditions give the trajectory of particles as a function of particulate size and applied voltage together with the function of efficiency.     

Photochemical Characterization of Up-Converting Inorganic Lanthanide Phosphors as Potential Labels

We have characterized commercially available up-converting inorganic lanthanide phosphors for their rare earth composition and photoluminescence properties under infrared laser diode excitation. These up-converting phosphors, in contrast to proprietary materials reported earlier, are readily available to be utilized as particulate reporters in various ligand binding assays after grinding to submicron particle size. The laser power density required at 980 nm to generate anti-Stokes photoluminescence from these particulate reporters is significantly lower than required for two-photon excitation. The narrow photoluminescence emission bands at 520–550 nm and at 650–670 nm are at shorter wavelengths and thus totally discriminated from autofluorescence and scattered excitation light even without temporal resolution. Transparent solution of colloidal bead-milled up-converting phosphor nanoparticles provides intense green emission visible to the human eye under illumination by an infrared laser pointer. In this article, we show that the unique photoluminescence properties of the up-converting phosphors and the inexpensive measurement configuration, which is adequate for their sensitive detection, render the up-conversion an attractive alternative to the ultraviolet-excited time-resolved fluorescence of down-converting lanthanide compounds widely employed in biomedical research and diagnostics.     

Charged spray generation for gas cleaning applications

The paper presents results of experimental investigation of properties of charged sprays generated by two types of pressure atomizers with charging by induction. Among other possible methods of charged spray generation, the induction charging has been considered due to its most practical importance. The goal of this research is to optimise the charging process with respect to obtain droplets of required size and charge for their application for exhaust gas cleaning from submicron particles in electrostatic scrubber used for the removal of PM from Diesel engine exhausts. Electrostatic scrubbers use electrostatic forces in order to deposit fine charged particles onto oppositely charged droplets.     

Treatment of submicron particles using an electrostatic agglomerator in DC-negative voltage: Re-entrainment experimental study and modeling

The aim of this study is to highlight the re-entrainment phenomenon encountered with an electrostatic agglomerator having a fibrous collecting electrode and treating submicron particles. The idea is to propose a process to control the particle number emitted by automotive diesel engines. Rather than trying to directly measure agglomerates of diesel particles exiting the agglomerator, we propose working with a synthetic submicron aerosol dispersed in ambient filtered air as a representative exhaust gas. The study will contribute to build a numerical modeling of the behavior of particles in such a process. The particular point that will be treated here is the collected particle re-entrainment as micron-sized agglomerates. We propose a joint experimentation/modeling approach to approximate the re-entrained aerosol size distribution in controlled conditions. From the modeling point of view, a local approach which uses the method of the balance of moments on agglomerates provides the re-entrained particle size in the agglomerator, according to the filtration conditions. The experimental approach confirms the clearly micron-sized character of the re-entrained agglomerates. This is unambiguously shown by measuring a greater micron particle numerical concentration downstream from the agglomerator than upstream. We show that the fluorescein submicron particles use can greatly simplify the characterization of an electrostatic agglomerator by allowing the use of a commercial laser granulometer to measure the size and the number of the generated agglomerates.     

鄱阳湖高浑浊水体悬浮颗粒物粒径分布及其对遥感反演的影响

悬浮颗粒物粒径分布特征为水环境结构与功能研究提供了重要信息,但目前针对内陆湖泊的研究还很少。依据2008年—2011年鄱阳湖丰枯水期实测数据,对悬浮颗粒物粒径分布的时空特征及光学特性进行了研究。鄱阳湖悬浮颗粒物粒径具有季节性变化特点：枯水期南部湖区颗粒物粒径大于北部湖区,而丰水期南北部湖区差异不大。同时,悬浮颗粒物粒径分布对水体吸收系数、衰减系数和散射系数都有影响。鄱阳湖水体总颗粒物吸收系数北部观测值高于南部;颗粒物中值粒径与总颗粒物比吸收系数呈负相关关系,这可能是由浑浊水体中存在的矿物颗粒物打包效应引起。鄱阳湖水体总颗粒物衰减系数和散射系数的时空分布规律相似：枯水期具有明显的区域性差异而丰水期区域性差异不大。遥感反射率、总颗粒物散射系数光谱斜率以及颗粒物粒径分布斜率之间的函数关系为遥感反射率表征粒径分布情况以及定量分析悬浮颗粒物粒径分布特征对遥感反射率的影响提供了依据。悬浮颗粒物粒径分布、颗粒物后向散射概率与颗粒物复折射率密切相关,可以反映鄱阳湖水体悬浮颗粒物组分信息。     

Electrostatic abatement of airborne respirable dust emission from mechanized tree-nut harvesting: Theoretical basis

The mechanized harvesting of tree nuts relies upon mechanically collecting and aerodynamically separating the nuts from extraneous vegetative and soil matter within the orchard using mobile power equipment. Typically the associated high-volume, high-velocity exhaust air disperses into the ambient atmosphere excessive concentrations of respirable-size particulate matter in the PM10 and PM2.5 micrometer realm creating a significant community air-quality problem. Our work developed a cyclonic-separation process for removing the PM10 dust and several candidate electrostatic-abatement processes for the smaller PM2.5 dust. We present the theoretical basis, including relevant mass- and charge-balances, for electrostatically abating the PM2.5 airborne dust via: (a) Ionized-field charging of the dust plume and its space-charge deposition within adjacent grounded tree-leaf canopies as air velocity subsides; (b) Injection of induction-charged spray of like polarity into the ion-charged-dust plume for space-charge-field enhancement; (c) Injection of charged spray alone into the dust plume; and (d) Injection of (+) polarity charged spray into the (?) polarity ionized-field-charged plume for electrostatic wet scrubbing of the dust. In addition to the theoretical basis, we report the technical development of a full-scale prototype to implement these electrostatic-abatement approaches on a mechanical harvester having ～10 g/s PM2.5 dust emission at ～27 m/s in an ～7 m³/s exhaust plume.     

煤燃烧亚微米颗粒数浓度特性实验研究和理论分析

煤粉燃烧过程中亚微米颗粒数浓度的准确采样和测量是一个颇具挑战性的问题,本文基于清华大学高温-维炉实验系统产生的亚微米颗粒物,发展了适用于气溶胶扫描电迁移率颗粒粒径谱仪(SMPS)的两级氮气稀释水冷等速取样技术.为得到炉膛内亚微米颗粒的真实数浓度粒径分布,本文探索了不同稀释比对测量结果的影响,最后发展了基于成核、团聚和表...     

Approximation of transformation media-based reshaping action by genetic optimization

The aim of this paper is to study the laser-induced backside wet cleaning techniques for glass substrates. Two kinds of laser cleaning techniques are proposed in this study. The first involves applying an Nd:YAG laser to the backside of the substrate which is submerged in water. A metal plate is placed below the glass substrate. Most of the laser energy will be absorbed by the metal plate. The metal then vaporizes the water and generates a turbulent bubble flow. The bubble flow removes the alumina particles from the surface of the glass substrate. The second involves using a CO₂ laser to generate turbulent bubble flow to remove the particles. Both methods were successfully demonstrated for the removal of submicron particles of 0.5 μm in size. The phenomena of bubble generation and diffusion are presented in the paper. Because the laser is applied to the backside of the substrate, the damage due to the laser heat can be significantly reduced. The quality and efficient of the backside processing is better than those of the front side processing. The proposed techniques have great potential to provide an improved solution for glass cleaning.     

生物柴油/柴油颗粒的拉曼光谱分析

为了进一步降低柴油机燃用生物柴油的颗粒排放,利用激光拉曼光谱技术,研究了柴油机应用废气再循环(EGR)前后,燃烧柴油(B0)、生物柴油(B100)及其调和油(B50)的颗粒微观结构,采用五带拟合法对一阶拉曼光谱进行拟合,并计算了颗粒石墨微晶尺寸和石墨晶格C—C键长。结果表明：随着生物柴油掺混比的增加,颗粒D1带的半高宽增加,颗粒化学异相性增强;I_D1/I_G逐渐减小,颗粒中有序石墨结构含量增加,石墨化程度提高。引入EGR会使得颗粒D1带的半高宽增加,颗粒化学异相性增强;I_D1/I_G升高,颗粒有序石墨结构含量减少,石墨化程度降低,B0,B50和B100颗粒的I_D1/I_G在应用EGR前后分别降低了约8.5%,10.6%和11.8%。六种颗粒的缺陷类型主要属于石墨烯层边缘缺陷,掺混生物柴油和引入EGR均会使得颗粒碳层边缘缺陷浓度增加,颗粒中挥发性有机物的官能团含量增加,增强了颗粒氧化活性。掺混生物柴油使得颗粒石墨微晶尺寸增加,EGR使得颗粒石墨微晶尺寸减小,生物柴油和EGR对柴油机颗粒石墨晶格C—C键长影响不大,C—C键长约为0.142 nm。     

亚微米颗粒湍流团聚特性的实验研究

燃煤电厂亚微米颗粒物排放是造成大气环境污染和影响人体健康的重要因素。本文搭建亚微米颗粒湍流团聚实验平台,通过场发射扫描电镜(FESEM)对亚微米颗粒的团聚形貌进行微观表征以及扫描电迁移率粒径谱仪(SMPS)对亚微米颗粒团聚前后的粒径分布特性进行宏观测量。结果表明:亚微米颗粒湍流团聚形成多分叉颗粒树聚团结构,进口流速为0.8?5.3m/s条件下,PM1和PM0.1的脱除效率分别为5.6%?18.6%和7.0%?21.4%,且PM1和PM0.1的脱除效率曲线随速度变化呈现二次函数规律。     

Particles detection and analysis of hard disk substrate after cleaning of post chemical mechanical polishing

Scrub, ultrasonic and megasonic are widely used in industry as post-CMP (chemical mechanical polishing/planarization) cleaning procedure. In this paper experiments and results are described to analyze the particle contaminations of hard disk substrate after each process of post-CMP cleaning. A scatter spot method has been exploited to detect the location and characteristics of the particles. SEM with EDX is used to observe and analyze the particles’ shape and size as well as the elements. The results indicate that brush scrub process can remove 99% contaminations after CMP but not that efficient for submicron particle. Megasonic is a refined method for cleaning nano-particles. However, contaminations like metallic particles and bacteria from the equipment may cause pollution. The abrasive particles embedded in the plating pits cannot be removed by mechanical force. Pollution in the dryer is also discussed.     

Modeling of the submicron particles formation and initial layer ash deposition during high temperature oxy-coal combustion

The future use of coal as a fuel for power generation in the US depends on the availability of financially viable technologies for capture and storage of CO₂ emissions from power plants. Key second-generation candidates for CO₂ capture include high temperature and pressurized oxy-firing of coal, which has the potential to increase efficiency, lower capital costs, avoid air ingress and reduce oxygen requirements. However, unquantified challenges, such as flame behavior, heat transfer, ash transformation, ash deposition and char oxidation, still exist for those technologies. This study specifically focuses on the formation of submicron particles and initial layer ash deposition during high temperature oxy-coal combustion. Previous work has shown that the initial layer deposits are mainly formed of submicron size ash aerosols transported by thermophoresis. Unfortunately, the importance of submicron particle deposition has not received much attention, probably due to the insignificant deposit mass and difficulty in prediction of the submicron particles formation. In this work, models including mineral matter vaporization model, scavenging model and deposition model are developed and applied into a three-dimensional CFD framework to predict the submicron particles formation and subsequent initial layer deposits formation. The model results are comparable to experimental data. The merits of this work are that it has led to the development of a novel approach to predict both submicron particle formation and initial layer ash deposition during oxy-coal combustion.     

高效液相色谱测定卷烟及其主流烟气中的维生素E

样品用饱和抗坏血酸乙醇溶液萃取,ZORBAX Extend-C18（5μm,4.6×150mm）色谱柱及FLD检测器在激发波长为298nm,发射波长为325nm下检测,流动相为100%甲醇。采用外标法定量,线性相关系数为0.99996,检出限为0.12μg/mL,卷烟及其主流烟气中维生素E平均回收率分别为97.0%和97.4%,RSD分别为0.70%和4.70%。研究表明：烤烟型卷烟烟丝比混合型卷烟烟丝中维生素E含量高,烤烟型卷烟主流烟气比混合型卷烟主流烟气中维生素E含量高,维生素E从卷烟烟丝到主流烟气的迁移率为7%—16%。     

Laser-induced emission spectrum from high-temperature silica-generating flames

High-temperature silica-generating flames were probed with 266 nm plane, linearly polarized light to produce laser-induced emission spectra with prominent peaks at the blue- and red-shifted sides from the probe wavelength. The radiation induced is ascribed to silicon monoxide (SiO) present in the flame, and appears to be caused by a combination of fluorescence and near-resonance-enhanced Raman scattering. The signal contribution due to strongly depolarized radiation near the probe wavelength complicates extraction of size information based on Rayleigh- and Mie-scattering in investigations of silica nanoparticle formation and growth in flames where temperatures are above 2000 K, oxygen partial pressures are moderate and the particulate matter is in its early stages of evolution. However, the observed radiative process may have utility as the basis for temporally and spatially resolved species and temperature diagnostics.     

Multi-element focused ion beams using compact microwave plasma ion source

Focused ion beams (FIB) are widely used for research and applications in nanoscience and technology. We have developed a compact microwave plasma based multi element FIB (MEFIB) system in order to widen the applications and overcome the limitations faced by conventional Liquid Metal Ion Source (LMIS) based FIB systems, that provide primarily Ga ions. The MEFIB source provides high density plasmas (∼1.5 × 10¹¹ cm⁻³) in a compact cross section. Recently the ion energy spread in the plasma meniscus from where the beams are extracted is found to be small (∼5 eV) [1–3]. The beam extraction and focusing are carried out using electrostatic multi electrode assembly. AXCEL INP and SIMION simulation codes are employed for the design of electrostatic Einzel lenses for beam focusing. The beam focal point is measured using a specially designed three slit Faraday cup and the spot size is measured by the micrography of craters formed by the focused ion beams impinging on copper and aluminium substrates. The initial experimental results show a focused beam spot size of ∼ 25 micron which is in good agreement with the simulations. By further reduction of electrode apertures and operating the second Einzel lens at higher potentials, submicron focused ion beams can be expected.     

Recyclable aligned carbon nanotube-sheet-based particulate air filter with high filtration efficiency and low pressure drop

There is an increasing demand for particulate matter filters to primarily block viruses and fine particulate matter floating in the air from entering the human body. The most commonly used microfiber-based filter has a technical flaw in which the filtration efficiency cannot be maximized as there is a trade-off in terms of performance; the pressure drop increases when the filtration efficiency increases. Here, we report the development of a recyclable macroscopic carbon nanotube (CNT)-based filter consisting of unidirectionally arranged multi-walled carbon nanotube sheets. Owing to the uniform arrangement of the 10–20 nm carbon nanotubes, uniform nanopores are formed. As a result, the CNT-sheet-based particulate matter filter exhibited low pressure drop characteristics, even at a high filtration efficiency. In addition, it was confirmed that the collected particulate matter could rapidly be removed through heat generated by applying a voltage to the conductive CNT sheet.     

Aerosol Generation Method for Measuring Particles Suspended in Water – Detection of Particulate Impurities in Ultrapure Water and Sizing of Fine Powders –

The method described is based on the fact that the measurement of particles in the gaseous phase is generally easier than that in the liquid phase for fine particles smaller than 1 μm in diameter. The system consists of a liquid nebulizing unit, evaporator, condenser, mixing diluter and two different aerosol sizing instruments. It has been found that this method can continuously detect particulate impurities in ultrapure water in situ and can measure the size distribution of fine powders in the submicron particle size range down to about 0.05 μm.     

大气颗粒物重金属元素分析技术研究进展

大气颗粒物已经成为当前大气环境首要污染物,而其中重金属由于具有非降解性和滞后性,严重威胁人类生命和自然环境,已成为当前研究热点。对分析大气颗粒物中重金属元素所用原子吸收光谱法、电感耦合等离子体原子发射光谱法、电感耦合等离子体质谱法、荧光光谱法、中子活化法、辉光放电原子发射光谱法、微波等离子体原子发射光谱法和激光诱导击穿光谱法进行了综述,并尝试对这些技术的不足之处提出一些改进建议：连续光源原子吸收光谱法同时测定多种元素,原子发射光谱法直接测定颗粒物,高分辨率激光剥蚀电感耦合等离子质谱法测定固体样品,低散射同步加速荧光法测定大气颗粒物和k₀中子活化法测定对流层发射性元素。大气颗粒物重金属元素的时空分布差异和人类对环境空气质量要求的提高以及现代仪器科学技术的高速发展促使大气颗粒物重金属元素分析技术朝着实时、快速、检出限低、直接测定和操作简便的方向发展。     

常规净水工艺去除有机物效果的三维荧光光谱分析法

有机物的荧光特性被广泛用来解析其在水体中的来源与分布。荧光光谱技术具有灵敏度高、选择性好、且不破坏样品结构的优点,非常适合用来研究有机物的化学和物理性质。运用三维荧光光谱分析技术对常规净水工艺中有机物的去除效果进行了研究。实验结果表明,三维荧光光谱技术能有效地揭示净水工艺中有机物的变化过程。在整个净水过程中,没有完全消除类富里酸荧光物质,也没有产生新的荧光物质。就类富里酸荧光物质的去除效果而言,混凝沉淀基本没有去除作用,过滤作用的去除率在5%～15%之间。