Three types of fly ash of different Australian brown coal collected by bag filters and combusted in an industrial test furnace with a same furnace condition, were fractionated in particle size (149-75, 75-45, 45-25, 25-20, 20-10, 10-5, <5 μm) and density (<1.6, 1.6-2.0, 2.0-2.4, 2.4-2.8 2.8-3.2, >3.2 g/cm3) by means of Nylon sieves ultrasonically. Nine morphological types were classified and film-like particles rich with sulfur were found specifically only in that of Saxonvale coal. Fraction distribution, elemental distribution and morphological distribution give rich informations on their ash softening property, combustibility of coals and their combustion conditions.
In this paper an equation of the deposition velocity in a bent pipe is derived by using some assumptions related to the particle free flight model which was used to derive the equation of deposition velocity in a horizontal pipe. In the equation for bent pipe a correction factor for the secondary flow induced by the centrifugal force is introduced and determined for the equation to agree well with the previous experimental data. The validity of the equation is discussed by comparison with the available experimental data. A rebound function for solid particles in the bend is empirically derived by modifying the rebound function obtained for a vertical pipe and the applicability of the function is also discussed.
The calculated deposition fractions of aerosol particles by existing models for a rough wall pipe are compared with available experimental data, where the deposition fractions are calculated using the author's equation for deposition velocity. The results show that the deposition fractions in a rough wall pipe can be estimated by the equation for deposition velocity into which only a friction factor for the rough wall is incorporated, without incorporation of other additional terms as proposed so for.
Monodisperse prolate spheroidal particles of barium sulfate were produced by the decomposition of the complex of barium and ethylenediaminetetraacetic acid with hydrogen peroxide in the presence of sulfate ions. The size and size distributions of the particles were measured by electron microscopy, and relations between particle size and various operational parameters, such as concentration of reagents, reaction time, reaction temperature and pH, were determined. The mean length of long axis of the particles could be varied in the range from 0.7 to 2.5 μm and the geometric standard deviation was below 1.2. The ratio of the long to short axis of particles was nearly constant under various experimental conditions. Monodisperse spherical BaSO4 particles could be produced by direct mixing of reagents at room temperature. Monodisperse prolate spheroidal and spherical aerosol particles were easily generated by nebulizing the BaSO4 colloidal solutions. Aerosol particles produced by the present method are useful for calibra tion of some aerosol measurement instruments as standard particles.
It is difficult to generate high concentration PSL (polystyrene latex) aerosol particles by existing regular nebulizers or atomizers because the probability that a droplet contains two or more PSL particles increases. To overcome this problem an alternative technique where a high pressure N2 gas operating (up to 12 MPa) ejector is used, has been attempted. High concentration PSL particle suspensions (10 wt%) are fed into the ejector throat and they are accelerated in the N2 gas stream having the critical (sonic) velocity to disintegrate the fragments of the suspension and at the same time to dry them up. The results showed that fairly monodisperse PSL aerosol particles with the concentration as high as 1012-1013 particles/m3 for 0.5-1.7 μm particles could be generated. It is expected that the present technique can be applied to performance tests of high efficiency air filters, to dry particle deposition processes in liquid crystal display production and so forth.