Measurement of Particle Size Distributions

Determine the particle size distributions of feed and product for the compared methods, preferably by light scattering, following principles and procedures described in Chapter 2. 

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FIGURE 5.28 Estimated overall airway deposition as a function of initial particle size and particle hygroscopicity for particles with mass median aerodynamic diameters (MMAD) between 0.1 and 10 p.m. ° Geometric dispersion, a measure of particle size distribution, principally affects only smaller MMAD,... 

Heuer, M. and Lesclioiiski, K., 1985. Results obtained with a new instrument for the measurement of particle size distributions from diffraction patterns. Particle Characterisation, 2, 7-15. 

ALL METHODS FOR PRESENTING DATA FROM THE MEASUREMENT OF PARTICLE SIZE DISTRIBUTIONS, WHETHER INSTRUMENTAL, SEIVING, SEDIMENTATION, OR PHOTOMETRIC METHODS, MEASURE FRACTIONS OF THE TOTAL PARTICLE DISTRIBUTION. IF THE METHOD IS SENSITIVE, THE FRACTION-SEGMENTS CAN BE SMALL, AND THE MEASURED PARTICLE DISTRIBUTION WILL BE CLOSE TO THE ACTUAL ONE. IF THE MEASUREMENT IS LESS SENSITIVE, THERE MAY BE SIGNIFICANT DEVIATIONS FROM THE CORRECT PSD. 

Not all reference materials producers currently employ the various techniques that would characterize materials for microanalytical use. Such techniques include measurement of particle size distribution, particle composition, and the determination of component homogeneity with microanalytical techniques. Nevertheless, some... 

Real Time Measurement of Particle Size Distribution of Airborne Cotton Dust by Light Scattering... 

Characterization of the Bulk Properties of Catalysts Measurements of Particle-size Distribution Functions of Supported Catalysts -... 

For the measurement of particle size distribution with time, samples were collected at set time intervals. 

Moon, M. H., and Giddings, J. C. (1993). Rapid separation and measurement of particle size distribution of starch granules by sedimentation/steric field-flow fractionation./. Food Sci. 58 1166-1171. 

Measurement of particle-size distribution by optical methods. Effect of different wave lengths. Ind. Eng. Chem., Anal. Ed., 9 211-212. 

Strawbridge, K.B., Ray, E, Hallett, F.R., Tosh, S.M., Dalgleish, D.G. 1995. Measurement of particle size distributions in milk homogenized by a microfluidizer estimation of populations of particles with radii less than 100 nm.. /. Coll. Interface Sci. 171, 392-398. 

When evaluating the results of these measurements one has to remember that a property of the particles (light scattering or the velocity of sedimentation) is determined. With models relying on a number of assumptions (for example that all particles are spherical) and further input (for example the complex index of refraction or the density) the particle size distribution is calculated in the final step. Applying the results of the measurement this and other deviations from the model have to be taken into account. Different measurement techniques usually result in different results for the measurements of particle size distributions. 

In-line measurements of particle size distributions are essential in order to maximize production capacity and product quality. Ultrasonic attenuation is emerging as a technique, with capabilities beyond those of light scattering. In addition to the needs of industry for compact, robust instrumentation, this method is capable of operating at high concentrations, thus eliminating the need for an expensive dilution step, which may alter the very properties one wishes to measure [225,226]. 

A method for on-line monitoring of particle size distribution and volume fraction in real time using frequency domain photon migration measurements (FDPM) has been described. In FDPM the time dependence of the propagation of multiply scattered light provides measurement of particle size distribution and volume fraction. The technique has been applied to a polystyrene latex and a titanium dioxide sluny at volume concentrations in the range 0.3 to 1% [341]. 

One of the major uses of transmission electron microscopy in the area of catalysts is the measurement of particle size distributions for supported metals. Chemical techniques can only effectively be used to obtain a global value for the dispersion. By observing the particles directly in transmission electron microscopy, it is possible to check the heterogeneity, and detect the existence of bimodal size distributions. Figure 9.8 shows an example of metallic particles distributed in a zeolite. 

Hukkanen, E.J. Braatz, R.D. Measurement of particle size distribution in suspension polymerization using in situ laser backscattering. Sensors Actuators B 2003, 96 (1-2), 451-459. 

Bernhard, R. (1981) Rapid Measurement of Particle Size Distributions by use of Light Scattering Methods, Paper presented at PARTEC Nuremberg May 6-9 (POLYTEC). 

Simultaneous diffraction on more than one particle results in a superposition of the diffraction patterns of the individual particles, provided that particles are moving and diffraction between the particles is averaged out. This simplifies the evaluation, providing a parameter-free and model-independent mathematical algorithm for the inversion process (M. Heuer and K. Leschonski, Results Obtained with a New Instrument for the Measurement of Particle Size Distributions from Diffraction Patterns, Part. Part. Syst. Charact. 2, 7-13, 1985). 

The measurement of particle size distributions is a distinguishing feature of aerosol in strumentation. The particle size range of interest is so wide—from a few nanometers to tens of micrometers— thai no single instrument is available that can cover the entire range. As a re.su It, in characterizing polydisperse aerosols, it is usually necessary to use several instruments simultaneously. These instruments are based on different physieal principles, and il is found that the match of the experimental results in the region ofinsimmenl overlap i.s often imperfect. 

Two main procedures can be applied for the characterisation of suspensions and assessment of their stability (such as flocculation). The first method depends on the measurement of particle size distribution and the rate of flocculation and/or Ostwald ripening after dilution of the suspension with the dispersion medium, while the second procedure depends on measurement of the state of suspension without dilution, using rheological techniques. As both methods are described in detail in Chapters 19 and 20, only a summary will be provided here. 

The above experiments are carried out at various storage times (perhaps every two weeks) and temperatures. From the change in rj o) and ct with storage time and temperature, information may be obtained on the degree and the rate of flocculation of the system. Clearly, the interpretation of these rheological results requires an expert knowledge of rheology, as well as measurements of particle size distribution as a function of time. 

ALL METHODS FOR PRESENTING DATA FROM THE MEASUREMENT OF PARTICLE SIZE DISTRIBUTIONS, WHETHER INSTRUMENTAL, SIEVING. SEDIMENTATION, OR PHOTOMETRIC METHODS. MEASURE... 

Within the last 30 years, the technical means to measure nucl-eation in operating equipment have been developed that have given a new insight into the design of crystallization equipment, with the result that modern crystallization designs are far more flexible in terms of their ability to control crystal product size and size distribution than earlier equipment. Within the last few years, electronic instruments have been developed that make possible the continuous on-line measurement of particle size distribution and other operating variables required for the control of industrial crystallizers. 

Lloyd, P. J. (ed.). Particle Size-Analysis, Wiley-Interscience, New York, (1988). Allen, T., Particle Size Measurement, 4th ed.. Chapman and Hall, London, 1991. Malghan, S. G., et al.. Statistical analysis of parameters affecting measurement of particle size-distribution of silicon nitride by sedigraph. Powder Technol., 73, 275-284, (1992). 

Present routine methods of measuring particulates in water are based on their mass (suspended solids) or their light scattering properties (turbidity). Neither method provides enough useful information to characterize the transport of the particles in solid-liquid separation, nor the removal of the pollutants they carry. Measurements of particle size distributions, while more diflBcult, should be more rewarding. For example, if a particle size distribution exhibits a slope of 4 in the power-law function (Equation 9), then the area and number concentrations of the solid particles and the pollutants they carry can predominate in the submicron size range (Figure 3C). While these particles escape most routine measurements, those size distribution measurements that are available (for example, Lerman et al (2)) indicate that a value of = 4 is a common occurrence. 

AFS-number measure of particle size distribution of foundry sand... 

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