Size analysis, particulate material

Crystallite Size. From the width of the peaks the computer can determine the size of the crystaUites in the sample. The smaller the crystaUite size, the broader are the diffraction peaks. This kind of analysis is important for determining particulate size of certain materials (eg, sUica) where a range of crystaUite size may be a health hazard if inhaled into the lungs. 

Several separating systems are used for particulate sampling. All rely on some principle of separating the aerosol from the gas stream. Many of the actual systems use more than one type of particulate collection device in series. If a size analysis is to be made on the collected material, it must be remembered that multiple collection devices in series will collect different size fractions. Therefore, size analyses must be made at each device and mathematically combined to obtain the size of the actual particulate in the effluent stream. In any system the probe itself removes some particulate before the carrying gas reaches the first separating device, so the probe must be cleaned and the weight of material added to that collected in the remainder of the train. 

A very important analytical tool that is overlooked by many sourcetesting personnel is the microscope. Microscopic analysis of a particulate sample can tell a great deal about the type of material collected as well as its size distribution. This analysis is necessary if the sample was collected to aid in the selechon of a piece of control equipment. All of the efficiency curves for particulate control devices are based on fractional sizes. One would not try to remove a submicron-size aerosol with a cyclone collector, but unless a size analysis is made on the sampled material, one is merely guessing at the actual size range. Figure 32-8 is a photomicrograph of material collected during a source test. 

The choice of method from available resources depends largely upon the properties of the material to be analyzed, the basic significance or physical wearing of the measurement, and the purpose for which the information is required. For example, failure to disperse the particles as discrete entities is the biggest single problem in all size analysis methods that depend on individual particulate behavior. With microscopic techniques particles must be dispersed on the slide to permit observation of individual particles, and in sedimentation techniques the material must be suspended in the fluid so that the particles behave as individuals and not as floes. 

For basic filter material development wall scale models especially the MicroFlowS approach can be applied. During early development of particulate emission control systems single channel models provide a fast and sufficient means for basic DPF design and sizing analysis. In addition, when applicable... 

Pye, K. and Blott, S. J. (2004b). Particle size analysis of sediments, soils and related particulate materials for forensic purposes using laser granulometry. Forensic Sci. Int. 144, 19-27. 

This paper is a brief review of original basic engineering research in morphological analysis applied to particle characterization which has been conducted during the last 20 years at the University of Iowa, Center for Particulate Material Processing Sciences. The topics discussed include definitions, theory, instrumental and experimental aspects of size, shape and texture measurements of particulate material. 

Morphological analysis is concerned with particle characterization in the case of particle size, particle shape and particle texture. Particle texture may deal with the particle surface characteristics and also with the particle microstructure. Particle size and shape influence physical and chemical properties of particulate materials. Morphological analysis is being developed in order to facilitate a more accurate description of the properties and behavior of particulate systems from a fundamental knowledge of the characteristics of the particles of the system [1,2]. 

Submicron particle size analysis employs a scatter theory not completely described by Fraunhofer diffraction. The small particle range down to about 0.1 micrometer in diameter utilizes a combination of Fraunhofer diffraction and Mie theory for the forward scattered light and 90-degree Mie scatter at three (3) wavelengths and two (2) polarizations of each wavelength. Because of its need for a technology more involved than diffraction theory, submicron measurements are influenced by the index of refraction of the material making up the particulates to be sized. 

The variation in total available sediment phosphorus concentration among the three sediment types shown in Table II is clear. A statistical analysis of this data shows that both the suspended sediment and particulate total phosphorus concentrations are greater than the bottom sediment value at the 99% confidence level. Phosphorus content increases in the sequence bottom sediment, suspended sediment, and particulate material in accordance with the increase in surface area (M. M. Reddy, New York State Dept, of Health, unpublished data, 1977). High surface area sediment components may adsorb phosphorus-containing substances,from the water column, increasing their phosphorus concentration. Another possible explanation includes dilution of bottom sediment by relatively inert primary minerals in the sand and silt size fractions. 

As most of the sizing methods are hmited to small sample sizes, an important prerequisite to accurate particle-size analysis is proper powder sampling and sample splitting (upcoming ISO 14488, Particulate Materi —Sampling and Sample Splitting fir the Determination of Particulate Properties). 

This basic classification is complemented by transportation methods because materials must be fed to or discharged from process steps and storage may be necessary before, between, and/or after processing. Particle size analysis quantitatively determines the distribution of particle sizes in the disperse system, a task of utmost importance since particle size, distribution, particle shape, and particle concentration decisively influence the behavior of a particulate system. 

The technique of thermoparticulate analysis (TPA) consists of the detection of evolved particulate material in the evolved gases as a function of temperature. In the presence of supersaturated water vapor, these particles provide condensation sites for water, and hence can be detected by light-scattering techniques. Water droplets grow very rapidly on the particulate matter (condensation nuclei) until they are of a sufficient size to scatter light. The scattered light, as detected by a phototube in a dark-field optical system, is proportional to the number of condensation nuclei initially present. It is an extremely sensitive measurement, with the capability of detecting one part of material in 1015 parts of air. The technique was first employed by Doyle (90) and has been reviewed by Murphy (91. 92). 

Voorhees et al. ° reported a study of the insoluble carbonaceous material in airborne particulates from vehicular traffic using Py-MS and Py-GC/MS (in addition to TGA, elemental analysis, and radiocarbon analysis). The solvent-soluble organic compounds separated from atmospheric particulate matter (which encompasses a broad spectrum of solid and liquid particles generally ranging in size from several hundred angstroms to several hundred micrometers) had been extensively studied by numerous investigators. Due to its complexity, the insoluble carbonaceous material (ICM) in urban and rural particulate material had not been studied in depth. 

Particle size analysis and measurement is an important operation in many industries. The stability, chemical reactivity, opacity, flowability, material strength, and some other properties of many materials are affected by the size distribution and characteristics of the particles within them. There are numerous techniques and instrumentation for all types of particle size analysis and characterization available. Some primary properties of particulate materials, mainly shape, will determine the way the particles are detected or... 

It has since been intensively developed for the particle counting, and the particle size distribution analysis, of almost all forms of finely divided particulate materials. The review which follows concentrates on this aspect of the principle as applied to non-biological particles. 

Particle size analysis of plastic pellets is important in molding and extrusion of materials with special reference to dust particulates. Standard test methods were found insufficient for this purpose and a special method was developed employing wet sieve analysis. This method gives superior data compared with the usually used dry sieve process. ... 

---