Size analysis, particulate

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. 

Table 13.1 covers general information for different particulates, liquids in gas, typical particles and gas dispersoids, behavior of particles in the human body, charging mechanisms, principles of particle size analysis, methods for particle size analysis, and an estimation of the general collection efficiency of available commercial particle removal equipment. 

The first method used for wear particle analysis is routine monitoring and trending of the solids content of machine lubricant. In simple terms the quantity, composition and size of particulate matter in the lubricating oil is indicative of the mechanical condition of the machine. A normal machine will contain low levels of solids with a size less than 10 microns. As the machine s condition degrades, the number and size of particulate matter will increase. 

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... 

Particulates from the sample matrix that are carried over during the sample preparation should be removed prior to analysis by either high-performance liquid chromatography (HPLC) or gas chromatography (GC). This is especially true for particles less than 2 /un in size. These particulates will pass through the frits on a liquid chromatographic column and settle on top of the sorbent which will eventually cause an increase in the back pressure of the chromatographic system and susequently decrease the column performance. 

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. 

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. 

In many cases, plants simply live with these problems. However, use of modern model-based control schemes in conjunction with improved methods for on-line moisture and particle size analysis can help overcome these effects [Ennis (ed.). Powder Tech., 82 (1995) Zhang et al.. Control of Particulate Processes IV (1995)]. 

ASTM E20 Practice for particle size analysis of particulate substances in the range 0.5 pm to 75 pm, 144... 

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. 

McHugh JA, Stevens JF. 1972. Elemental analysis of single micrometer-size airborne particulates by... 

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... 

Automation of process control has created a need for continuous monitoring of the particle size of particulate matter in process streams. Some on-line particle size analysis instrumentation has been developed recently to meet this need it can initiate regulatory or shut-down signals in control systems. The basic requirements for such instrumentation are that it must operate automatically and continuously under preset instructions, and the response time from observation to readout must be so short as to be nearly instantaneous. 

The ability of these cationic polyrotaxanes to condense pDNA into particulate structures was evaluated by agarose gel electrophoresis, particle size analysis, and zeta-potential measurements. All the cationic polyrotaxanes could completely complex the pDNA at N/P ratios of 2 and above, which displayed a similar or slightly better DNA condensation ability than PEI (25K). The particle size of the polyrotaxane/DNA complex decreased with the increase of N/P ratio, and when the N/P ratio reached 6, the particle size remained in the 150-250-nm range. Similarly, the surface net charge of the complexes increased from negative to positive as the N/P ratio increased from 0 to 4 and reached a plateau at N/P ratio of 4 and above. The transfection efficiency of the cationic polyrotaxane was also... 

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. ... 

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