摘要:

AbstractThere are three basic philosophies which may be taken towards the problem of calibrating particle size measuring techniques. The first is to assume a model of the process and that the technique is thus absolute. The second is to calibrate an instrument using the particles which are to be measured themselves. In this paper, these three approaches are compared and contrasted. As an example, the programme of certification of the BCR samples is cited and discussed. The paper then advocates the use of the equivalent volume diameter as the basic particle size characterization and its combination with other measurements as shape determinations. The representation of both size and shape in this way is conveniently presented in the form of orthogonal diagrams.

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020101

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractFor several years the size distributions of particulate matter have increasingly been determined by using diffraction pattern analysis.In order to evaluate particle size distributions from the far field intensity distribution of light diffracted by a distribution of particles, a linear set of equations must be solved. Since, in many cases of application, conventional methods for solving linear sets of equations become unstable, the calculated particle size distribution may also be grossly in error. By applying special, known mathematical methods we succeeded in obtaining a parameterfree solution of the above problem.After a brief description of the mathematical method used, a diffraction pattern analyser will be presented as well as some experimental results obtained with it. The results obtained with aerosols and suspensions come from experiments performed with narrow‐sized latexes and mono‐ and bi‐modal particle size distributions of limestone and q

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020102

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractNumerous methods have been reported in the literature for the measurement of (submicron) particle size distribution by turbidimetry. Attempts to apply some of these to coupler dispersions (oil‐in‐water emulsions of importance in the photographic industry) have not in general proved satisfactory, however, because small experimental errors lead to relatively large errors in the calculated distribution. In order to reduce this problem a turbidimetric technique involving measurements at two widely separated wavelengths, 400 nm and 2.22 μm, has been developed. Its accuracy has been demonstrated using polydisperse polystyrene latexes of known size distribution. With the aid of simple, purpose‐built equipment, linked to a desktop computer, the technique has been largely automated so that it is suitable for use by an unskilled operator working in a factory envir

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020103

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractIn order to characterize flow separation and classification processes, particle size distributions must be measured in the airborne state without affecting the state of dispersion or disturbing the flow. Light scattering devices with an optically defined measuring volume are specially designed for this purpose. However the light scattering device must be calibrated using non‐ideal particles which are present within the multiphase flow, preferably on an equivalent diameter based on settling rate. Such a calibration can be achieved by measuring with an optical particle counter before and after an impactor in droplet systems and a sampling cyclone in systems of solid particles. By measuring the calibration curves the size distribution of the investigated particles are also determined. This measuring technique allows the best use of the optical particle counter in industrially relevant cases which may have high particle concentrations, wide distributions, non‐ideal particles and an undefined state of dispers

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020104

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractA modified drop‐shatter test apparatus was used to study the primary breakage of particles of two solid fuels. In this apparatus many particles could be subjected to just one impact under known conditions.About 100000 particles of each fuel, sorted by size and shape into eight separate groups, were dropped from four different heights and the fragments thus formed were sifted to determine their size distributions, that is the experimental breakage functions.The interior of particles, of regular or irregular shape, fails under tension and the resulting fragmentation is due to stress‐activated volume flaws which give rise to coarse fragments whose distribution can be represented by a theoretical breakage function of the form\documentclass{article}\pagestyle{empty}\begin{document}$$ B(z) = \mathop \Sigma \limits_{{\rm \gamma = 1}}^\infty \left[ {\frac{{\lambda \cdot e^{ - \lambda } }}{{{\rm \gamma !(1 - }e^{ - \lambda } )}} \cdot \left\{ {1 - (1 + {\rm \gamma }z^3 )(1 - z^3 )^{\rm \gamma } } \right\}} \right] $$\end{document}wherezis the relative size of the fragments and γ is the number of stress‐activated volume flaws per particle.The average values of γ, given by μγ= λ/(1 – e−λ), ranged from about one to five, corresponding to the formation of two to six coarse fragments per broken particle.The probability of breakage was log‐norma

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020105

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractPractical procedures are described for a stereological method which determines the spatial distribution of particle orientation from the distribution observed on cross sections. First, the two dimensional distribution of needle‐like particles is determined by counting the number of intersections with parallel probe lines. Next, the three dimensional distribution of needle‐like particles is determined by counting the number of intersections with a cutting plane. Then, the three dimensional distribution of disklike particles is determined by counting the number of intersections with a probe line. Finally, the distribution of disklike particles is determined by measuring the total length of the cross sections on a cutting pl

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020106

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractProduct quality is influenced by the properties of feedstocks and by production parameters. In contrast to gases and liquids, the quality of solids is also affected by the particle properties, such as size, specific surface area, structure and shape. These are the properties which are primarily changed in solids process engineering.The accuracy and cost of possible methods for the measurement of the particle properties of feedstocks, intermediates and end products are discussed. Examples of the methods discussed are laser diffraction spectrometry, quantitative image analysis and photon correlation spectroscopy.The measuring techniques required for monitoring production processes in solids process engineering are illustrated by simple examples. In the field of process control in particular, there is still room for improvement, since there is a lack of suitable sensors and models. Process monitoring is necessary in order to ensure that product quality meets requirements which are constantly increasing.

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020107

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractDisperse materials are often characterized by their particle‐size distributions which can be determined by different measuring methods. Frequently the quantitative portions of the particle size classes obtained by way of experiment are considered insufficient and one strives for approximating the measured values by an analytic function. This can be reached, more or less satisfactorily, by power, exponential, or normal distribution functions which may include two, three, or four parameters.Publications as well as common practice have proved again and again that due to very rough or incorrect approximations wrong conclusions are derived from test and operating results, so that it appears expedient to investigate – when such an approximation would actually be advisable and – which function would be expedient in the specific case.Application of distriction functions will always be justified then when there is an actual need for utilizing the advantages connected with an approximation. Evaluation of a great number of measuring results revealed that the two‐parameter functions in most cases only permit an utmost rough approximation which might give rise to wrong conclusions. Carefully classified products, however, mostly require three‐ or four‐parameter functions for making an appropriate approximation.The functions, which appear appropriate for certain types of products, are set out in Table 1.In order to make the tabulated individual results accessible to a practical utilization a systematization was attempted. The outcome is a graph which is meant as an assistance for the practician and which presents the possibility of a quick selection of fu

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020108

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractFractal dimensions are numbers between the classical whole number dimensions which can be used to describe the ruggedness of a fineparticle boundary. This communication explores the utility of fractal dimensions between 1 and 2 for characterizing the ruggedness of fineparticle profiles. This type of fractal boundary is evaluated by estimating the perimeter of a profile of a fineparticle at various levels of scrutiny and then plotting a graph of the logarithm of the perimeter estimates against the logarithm of a unit representing the scale of scrutiny. Such a graph is known as a Richardson plot. Boundaries describable by fractal dimensions exhibit characteristic datalines on this type of graph.Aluminum shot fineparticles produced by the break up of turbulent jet of molten metal have irregular shapes because of the fluid turbulence in the regions where they solidify, but a smooth texture because of the effect of surface tension forces as the fineparticle solidifies. It is shown in this communication that the dataline on a Richardson plot of the estimated perimeter of an aluminum shot fineparticle consists of two regions. The first portion, at coarse levels of scrutiny, permits the calculation of a fractal dimension descriptor of the ruggedness of the profile. A second dataline at high resolution is parallel to the scrutiny axis indicating that at such levels of inspection the profile is effectively smooth and euclidean. Studies are reported of the changes in the ruggedness of an eroding aluminum shot fineparticle suspended in acid. It is shown that fractals can be used to describe the progress of corrosion and that, as corrosion proceeds, the euclidean portion of the Richardson plot of perimeter estimate recedes and disappears within the levels of scrutiny employed in these experiments.

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020109

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe need for particle shape characterization has been internationally recognised and has resulted in a number of publications proposing a variety of methods for particle shape analysis and shape description. Though very important in chemical engineering, correlations between shape parameters and bulk properties are still rare.This paper describes theoretical and experimental investigations of dynamic shape factors for use when calculating the settling velocity of a particle. For this purpose a study of the settling velocities of particles of various shapes has been made. A correlation is developed from the data with which to quantify the effect of shape on settling velocity for particles falling freely in a fluid in the laminar flow range.

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020110

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY