Fractional Penetrations for Electrostatically Charged Fibrous Filters in the Submicron Particle Size Range

Particle penetrations through commercially available, electrically charged fibrous filters have been measured. The particles were monodisperse and in charge equilibrium. Tests were conducted for several particle sizes in the range 0.02 μm ≤ x ≤ 1 μm. The face velocity was varied in the range of 2 cm/s to 30 cm/s. The penetration has a bimodal dependence on particle size. This behaviour is not found for uncharged filters. The reduction in penetration and bimodal dependence is attributed to electrical collection effects. As the face velocity is increased, the electrostatic collection effects are significantly reduced. The results agree quantitatively with a model for particle penetration through charged fibrous filters recently presented in the literature by the authors.     

Ultrasonic Spectrometry for Particle Size Analysis in Dense Submicron Suspensions

Ultrasonic spectrometry was applied to the particle size analysis of disperse systems. The investigations were made for acoustic conditions called the long-wavelength regime (LWR). In the LWR the acoustic behaviour is governed by dissipative effects rather than by scattering. Two principal theoretical approaches to ultrasonic spectrometry — scattering theory and coupled phase models — are introduced. A model based on a newly developed coupled phase model and the scattering theory (ECAH theory) is implemented in the ultrasonic spectrometer Acousto Phor. Experiments were carried out for several suspensions with a high density contrast. It could be demonstrated that the model successfully describes acoustic attenuation and that the inversion algorithm finds particle size distributions comparable to those given by other measurement techniques. With regard to the particle size, a lower and an upper limit for the applicability were determined, which include three decades. As a further result, the model was validated at concentrations up to 10 vol.%. The model is considered to be open to development to cover even higher concentrations.     

Analysis of Particle Size Distribution by Particle Tracking

Particle tracking is performed using a combination of dark field or fluorescence video microscopy with automatic image analysis. The optical detection together with the image analysis software allows for the time resolved localization of individual particles with diameters between 100 and 1000 nm. Observation of their Brownian motion over a set of time intervals leads to the determination of their mean square displacements under the given room temperature and viscosity. Hereby, the radii of a set of particles visible within a given optical frame are derived simultaneously. Rapid data analysis leads to reliable particle size histograms. The applicability of this method is demonstrated on polystyrene latices and PMMA nanospheres with radii between 51 nm and 202 nm.     

Determination of Particle Size Distribution and Electrokinetic Properties with the AcoustoSizer in Comparison with Other Methods

The characterization of suspensions in process concentration is an important task for the optimization of handling and product properties. Only very few instruments are available. The AcoustoSizer (ACS) (Colloidal Dynamics PTY Ltd.) uses the so-called electrokinetic sonic amplitude (ESA) for particle size and zeta potential determination. In this work, the results obtained at moderate concentrations were compared with results of other instruments mostly working with dilute suspensions. For the electrokinetic investigations three methods (beside the ACS) were used: electroacoustics (ESA8000, Matec Applied Sciences), microelectrophoresis (Zetamaster, Malvern Instruments) and streaming current measurements (Particle Charge Detector PCD 03-pH, Miitek). For particle size determination different measuring techniques were applied: laser diffraction spectroscopy (Mastersizer S, Malvern Instruments), dynamic light scattering (Ultra Fine Particle Analyser, Leeds and Northrup), sedimentation analysis (Sedigraph 5000 D, Micromeritics) and scanning electron microscopy. Mainly three powders were used in the investigations: Monospher M1200 silica (Merck), Selectipur titania (Merck) and Aluminiumoxid C alumina (Degussa). The agreement between the different methods for both particle size and zeta potential measurements was excellent. Especially for the electrokinetic investigations, careful sample preparation is needed. The procedure must not change the equilibria determining the physical and chemical state of the suspension.     

Use of the Maximum Entropy Formalism to Determine Drop Size Distribution Characteristics

The work reported in this paper is an extension of a previous study on the prediction of volume-based drop size distribution from the application of the maximum entropy formalism (M.E.F.). The procedure developed in that study led to the derivation of a two-parameter distribution. The present work investigated the problem of the determination of the two parameters (q and D_q0), i.e. the determination of the information required in the procedure. It was found that the relative span factor Δ_v and the mean drop diameter D₄₃ of the measured distribution constitute reliable information from which q and D_q0 can be calculated. It is shown that the distributions calculated in this way generally show a better fit than distributions obtained from different information or from an extended set of constraints. This work therefore illustrates the importance of the nature of the information to be introduced in the application of the M.E.F. Furthermore, it shows how the M.E.F. can be used to determine relevant spray drop size characteristics and the extent to which this formalism could provide relevant information to study and characterize atomization processes.     

光全散射法颗粒测量中的一种自适应非独立模式算法

光全散射颗粒测量法中需求解第一类Ｆｒｅｄｈｏｌｍ积分方程。在不知道被测颗粒的尺寸范围的情况下如何确定积分方程的上下限、即测量范围，迄今仍是个问题。本文针对此问题提出了一种自适应非独立模式算法。该算法可根据双参数颗粒分布函数的分布参数Ｋ自动确定积分的上下限．数值模拟和实验都证实了此算法。     

In-Process Particle Size Distribution Measurements and Control

In-process measurement of particle size and concentration distributions provides continuous analysis and quality control of a product stream. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream. The EPCS (Ensemble Particle Concentration & Size) described in the following has been used to obtain detailed size distribution measurements in powder production facilities at two second intervals, and has been successfully used for automatic feedback control.     

In-Process Particle Size Distribution Measurements and Control

In-process measurement of particle size and concentration distributions provides continuous analysis, quality control, and optimization of product yield. As process production rates continue to improve, the delay between laboratory analysis and process correction of the product stream becomes more significant and costly in many commercial applications. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream. Insitec has developed such an instrument based on ensemble laser-diffraction that has been successfully applied to a wide range of research and industrial process applications. As part of the adaptation of instrumentation to the specific needs of different process applications, we have developed several different interface arrangements, including a direct inline system and an eductor bypass instrument. A specific window purge design has been developed and shown to operate for extended time periods (exceeding one month and more) without maintenance. To address the wide range of operating concentrations that occur in practice, a variable pathlength interface has been developed along with a deconvolution algorithm that corrects multiple scattering effects for light transmissions down to 20%. Distribution update rates are computed and displayed in less than 5 seconds. This methodology is described along with measurements in a non-steady pharmaceutical powder processing application. Results show uniform size measurement for ten-fold concentration variations. Real time measurements allowed diagnosis and correction of non-steady feed rates to a classifier-mill.     

不同粒径街道灰尘中Zn的分布特征

在宿州市城区采集23个街尘样品,利用X射线荧光光谱法(XRF)测定了4个粒径区间(250-500、150-250、75-150μm和＜75μm)街尘中的Zn含量,并利用单因子指数法评价了宿州市街尘Zn污染状况.结果发现:宿州市街尘Zn含量在各粒径区间存在明显差异,其中以＜75μm和75-150μm粒径段的含量最高,说明...     

Particle Size Distribution and Aspect Ratio of Organic Pigments

Particle size and aspect ratio are amongst the most important parameters which determine the application properties of pigments, fillers and powders for ceramics. A statistical characterization of the samples is therefore needed. In this paper we discuss the measurement of bivariate size distributions of organic pigments and describe a correction procedure for particles with interchanged crystallographic axes. During the crystallization of a pigment, the larger aspect ratios usually result from faster growth rates.     

A Comparative Study of Various Size Distribution

One of the major product specifications of a crystalline material is the crystal size distribution (CSD). In order to monitor and control the CSD in an industrial crystallization process, on‐line sensors are required. Over the years, a number of techniques to measure the CSD have been established. In this paper, three instruments operated in an on‐line fashion and an off‐line method are compared. The instruments were the OPUS, a HELOS/VARIO (both manufactured by Sympatec) and a Malvern 2600c (manufactured by Malvern). They were implemented on an 1100‐l evaporative draft tube baffle (DTB) crystallizer producing ammonium sulfate crystals from aqueous solution. Samples from this crystallizer were also analyzed offline by wet sieving. The results show reasonably good agreement between the different on‐line techniques and the wet sieving technique concerning the shape of the distribution. However, there is a discrepancy regarding the absolute values, which can be explained by the fact that the techniques used are based on different measuring principles.     

激光散射法对尿液中纳米微晶粒径及其分布的研究

泌尿系结石已经成为威胁人类健康的一种常见病、多发病,目前对其形成的机制尚不清楚。文章采用激光散射法测定了正常人尿液和尿石症患者尿液中纳米粒子的粒径和粒径分布,该方法快速准确、经济、容易操作。正常人尿液比尿石症患者尿液的稳定性好,归因于正常人尿液中纳米微晶尺寸分布均匀,不容易聚集,而尿石症患者尿液的纳米微晶尺寸分布不均匀,粒子间容易聚集而沉降。通过分析尿样稀释、离心或者用微孔滤膜过滤后体系的光强-自相关函数曲线,得到了制备稳定的尿样悬浮液的方法：尿样先稀释20%,然后离心或用1.2 μm微孔滤膜过滤,可得到稳定的尿液悬浮液。激光散射法结果与TEM检测结果一致。从尿液中存在的范德华力、尿液粘度、酸碱性、离子强度、尿液中纳米微晶的表面电荷和Zeta电位等方面解释了尿液稳定的原因。     

Determination of Particle Size Distribution in Fluids using photon correlation spectroscopy

Photon correlation spectroscopy (PCS) has been applied to various systems of particles suspended in a fluid. Computer simulations were used to analyse CONTIN, a program for the numerical inversion of the experimental data. Measurements were performed on a spectrometer equipped with a digital correlator. Various suspensions of polysterene latex spheres differing both in size and size distribution were prepared in double distilled water. Further some samples provided by an external institution without prior specification were analysed. Diffusivity measurements on submicron DES (di-2-ethylhexyl sebacate) particles in nitrogen were also performed. The results obtained demonstrate the strengths and the limitations of PCS as a method of determining particle size distributions in particle fluid systems.     

可见-红外波段光全散射法颗粒粒径测量范围的研究

在光全散射法颗粒粒径测量中,采用独立模式算法在可见-红外波段对粒径测量范围进行了深入的研究。通过对多种R-R分布函数反演结果进行分析,比较,以确定光全散射法颗粒粒径测量范围。同时在消光系数计算中,采用修正的消光系数代替原始的消光系数,以便得到更准确的粒径测量范围。仿真计算结果表明,在可见-红外光谱区,相对折射率m=1.235时的粒径测量范围为0.05～18 μm。在此区域内测量粒径分布,反演结果与真值基本吻合。随着颗粒相对折射率、波长范围的变化,粒径测量范围也随之发生改变。采用限制最小二乘算法能够最大限度地克服随机噪声对测量结果的影响,使测量的精度和可靠性明显提高。对测量的消光值加入±1%随机噪声时,颗粒粒径分布的反演均能得到满意的结果。     

On-line Determination of Particle Size Distribution during the manufacture of compound feed

Experimental investigations were carried out with mainly a Mogensen-Sizer, compared with test screening and additionally laser diffraction and light extinction, in order to check the qualification for on-line determination of particle size distribution under the specific conditions of feed milling. The different components of compound feed, the degree of milling, the difference in measured particle characteristics and the possibility of sample dispersion affect the comparability of the results. The results show that laser diffraction is a manysided method with accurate recording of the distribution. The modified Mogensen-Sizer can be a robust low-price alternative if the control of selected distribution parameters is sufficient.     

炸药爆炸作用下液体破碎后颗粒尺寸分布的研究

 对液体抛撒的液滴尺寸进行研究在军事和民用上是很重要的,国内刚开始使用激光散射仪开展此项研究工作。利用R. A. Dobbins等人的液体颗粒测量技术,研制了一套既简单又实用的测量液体抛撒过程中液滴尺寸的实验装置——激光散射仪。对于激光与液体微粒的相互作用,当微粒的反射与折射和吸收效应可被忽略时,可导出液体微粒对激光散射的光强公式。只要测量激光被微粒散射的光强,就可推算出微粒的Sauter平均直径。在使用激光散射仪测量液体抛撒液滴尺寸的实验中,用水代替爆炸抛撒液体,测量结果表明：液体抛撒二次破碎中,在固定位置测量到的云雾区液滴Sauter平均直径随测量时间的增加呈现出减小的趋势;而云雾区的宽度则随着与抛撒中心距离的增大而呈现出增加的趋势;云雾区前沿的液滴Sauter平均直径随着与抛撒中心距离的增加而呈现出先逐渐增大然后迅速减小的趋势。为便于比较,对燃料抛撒二次破碎进行了回收法测量和数值模拟计算,其测量与计算结果与用激光散射仪测量的结果有较好的一致性。     

基于MIE散射理论的粒度分布测量系统研究

粒度测量广泛应用于粉体工程,测量结果直接影响粉体产品优劣。在深入研究MIE散射理论的基础上,提出一种基于改进反演算法的粒度测量系统设计方案,利用激光器、傅里叶透镜、光电传感器采集含有待测微粒信息的电信号,通过调理电路进行处理,应用改进反演算法分析得出粒度值及分布。通过实验验证,效的本文提出的设计方案能实现准确高粒度测量。     

A Theoretical and Experimental Study to Measure the Concentration and Particle Size Distribution in Two‐Phase Flows

Based on light scattering theory, an optical method is presented for measuring the concentration and particle size distribution of the dispersed phase in two‐phase flows. A prototype was also constructed. Comprehensive computer simulation and numerical calculations were carried out to calibrate the correctness of this method. An experimental study was also performed in gas–solid and gas–liquid two‐phase flows. The results of the measurements are given and discussed in detail.     

Determination of Particle Size Distribution Parameters using a Laser-Scattered Light Spectrometer

A method based on the measurement of scattered light intensity distributions is demonstrated to be able to determine directly the particle size of monodisperse supermicron-size particles. In all other cases of a particle cloud, information about the size distribution can be acquired from comparison of measured and calculated intensities as a function of scattering angle. This indirect method is only applicable if the assumptions made in the theory used for comparison are fulfilled. Therefore, the method is limited to spherical particles with known refractive index. The type of size distribution also has to be known. In the cases considered a log-normal size distribution was assumed. The uncertainty of the result increases with increase in the number of parameters that have to be determined. The method seems to be limited to unimodal distributions described with two parameters.     

Particle Size Distribution Analysis of Industrial Colloidal Slurries using ultrasonic spectroscopy

Several solid-liquid suspensions containing submicron particles at moderate to high concentrations (5 to 50 volume percent) are encountered in industrial slurry processing. Measurements of ultrasonic attenuation spectra are used in a newly developed AcoustoPhor particle analysis system to get particle size distributions of such colloidal suspensions. This paper deals with the performance evaluation of the AcoustoPhor system. The automated ultrasonic spectrometer component of the AcoustoPhor system was tested using a reference silicone liquid for its accuracy and precision. The particle size distribution (PSD) estimation capabilities were evaluated using a set of well-dispersed slurries covering a wide range of particle concentrations. Sensitivity to process variations was evaluated in field tests at a pigment manufacturing plant. The AcoustoPhor system appears to be capable of providing reliable PSD data for inorganic pigment slurries with particle diameters ranging from 0.01 to 100 micrometers at particle concentrations as high as 50 volume percent.