Particle size, measurement automatic

Particle size measurements are usually made from micrographs. The method is extremely tedious if it is done manually. Automatic image analysis of micrographs or an electronic display can reduce the amount of work considerably. Normally a large number of particles (a few hundred) need to be measured. As would be apparent, microscopy produces a particle size distribution based on the numbCT of particles within an appropriate size range. 

In conclusion, droplet size measurements in the range 10 to 100 m can be performed, also in hostile environments, from the visibility of individual scattered signal. Advantages of this method are simultaneous measurement of particle size, concentration and velocity no calibration is necessary good spatial resolution up to less than 1 mm-3 the visibility is independent on particle trajectory. Limitations are individual scattered signal can be obtained only with moderate particle concentration it is difficult to automatically process scattered signals to extract the visibility value and to check validation conditions it seems very difficult to extend the technique to cover the entire spray distribution the lower limit in the small particle end of the distribution curve depends upon experimental sensitivities and V(d) curve flatness... 

Beside of the progress in the theory of a particle movement in the zetameter measurement cell, there was progress in particle measurement techniques. New models of zetameters enable automatic measurement of electrophoretic mobility on the basis of the shift of light wave scattered on the particle that moves in the electric field [82]. This technique is called photon correlation spectroscopy (PCS). To increase the sensitivity of the measurement, it is supported by multiangle electrophoretic light scattering (ELS). This combination, allows one also to measure the particle size distribution of the dispersed phase [83]. 

Earlier versions comprise the Series 2600 and 3600 and Mastersizer R/IP on-line particle size analyzer. The Malvern 2200 was a droplet and spray particle analyzer and the Fibersizer 600 was designed for fast automatic measurement of fibers in the 4 to 64 pm size range with a resolution of 0.25 pm. 

Brookhaven BI-90 is designed for routine sub-micron particle sizing in quality control. Operation of the instrument is fully automatic and a series of repeat measurements including data processing can be set up easily. 

A particle sampling and measuring system was set up to characterize the suspended particles in the biomass combustion Fig. ). The system was capable of on-line measuring of the concentration number and particle size distribution in the micron and submicron range. In addition, mass concentration, particle morphology and chemical composition were obtained. The aerosol is first extracted from the duct and then led to the sampling station through an isokinetic probe equipped with an automatic control unit. 

These tertiary crushers employ smooth or toothed heavy-duty impact and abrasion-resistant steel-rimmed rolls. The rolls are mounted inline in a horizontal manner and turn toward each other at equal speeds to create a nip into which a friable feed material is introduced (Fig. 4). Heavy-duty compression springs with automatic reset are used to dampen crushing shock and to protect the crusher from tramp iron and oversize material. An adjustable screw that adjusts spring tension changes the crusher opening. A flywheel is used to even out pulses and economize on power consumption. These crushers have a theoretical maximum reduction ratio of 4 1 and will only crush materials to about 10 mesh. Roll crushers produce a controlled product size distribution without a lot of fines. The narrow particle size distribution is achieved by controlling a combination of variables including roll speed, gap measure, differential speed, feed rate, and roll surface. 

As already indicated in Chapter 7, the introduction of laser technology has already had a major impact on light-scattering methods. These have found particular application in the development of new methods of particle sizing, and several instruments are now available commercially which arc designed for the automatic determination of particle size distributions. These methods are being developed steadily, especially in terms of the associated computer software needed for the rapid analysis of experimental data. In particular, while the measurement of the particle size in monodisperse systems is well established, the mathematical analysis for polydisperse systems and for non-spherical particles presents problems which are not yet fully solved. 

Although particulate methods are potentially more informative than bulk methods because of the extra information obtained on particle size, their application in coal mineralogy has been relatively limited The main reason for this has been the lack of automation, as such microscopic measurements are time-consuming and tedious if sufficient data have to be generated manually Recently, however, the application of microcomputers and image-analysis systems to microscopy has progressed to the extent that most of the operation, data collection, and analysis can now be done automatically A number of reports of such automated microscope techniques used in coal research have appeared recently in the literature (3-8) ... 

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