Concentration and particle size

Some concerns directly related to a tomizer operation include inadequate mixing of Hquid and gas, incomplete droplet evaporation, hydrodynamic instabiHty, formation of nonuniform sprays, uneven deposition of Hquid particles on soHd surfaces, and drifting of small droplets. Other possible problems include difficulty in achieving ignition, poor combustion efficiency, and incorrect rates of evaporation, chemical reaction, solidification, or deposition. Atomizers must also provide the desired spray angle and pattern, penetration, concentration, and particle size distribution. In certain appHcations, they must handle high viscosity or non-Newtonian fluids, or provide extremely fine sprays for rapid cooling. 

The need to separate solid and liquid phases is probably the most common phase separation requirement in the process industries, and a variety of techniques is used (Figure 10.9). Separation is effected by either the difference in density between the liquid and solids, using either gravity or centrifugal force, or, for filtration, depends on the particle size and shape. The most suitable technique to use will depend on the solids concentration and feed rate, as well as the size and nature of the solid particles. The range of application of various techniques and equipment, as a function of slurry concentration and particle size, is shown in Figure 10.10. 

Intramuscularly administered products typically form a depot in the muscle mass from which the drug is slowly absorbed. The peak drug concentration is usually seen within 1-2 hours. Factors affecting the drug-release rate from an IM depot include the compactness of the depot (the less compact and more diffuse, the faster the release), the rheology of the product, concentration and particle size of drug in the vehicle, nature of the solvent or vehicle, volume of the injection, tonicity of the product, and physical form of the product. 

Langer, G. and M. A. Fisher, Concentration and particle size of cigarette-smoke particles, A. M. A. Arch. Ind. Hlth., 13 373-378 (1956). 

Although blue dyes usually appear to be blue-black in bulk, a blue colour is seen when they are viewed at the edge of a smoke cloud. This is related to the spectral characteristics, concentration and particle size of the dye. 

Wadge, A., Hutton, M. Peterson, P. J. 1986. The concentration and particle size relationships of selected trace elements in fly ashes from U.K coal-fired power plants and a refuse incinerator. Science of the Total Environment, 54, 13-27. 

CA 52, 20986( 1958)(Some effect of oxidizer concentration and particle size on resonance combustion of composite solid proplnts) 5)E.W. Price J.W. Sofferis, Jet Propulsion 28, 190-92(March 1958) CA 52,... 

The above relationships (Figure 1.10) show that the optical pigment properties depend on the particle size D and the complex refractive index n = n (1 - i/c), which incorporates the real refractive index n and the absorption index k. As a result, the reflectance spectrum, and hence the color properties, of a pigment can be calculated if its complex refractive index, concentration, and particle size distribution are known [1.40]. Unfortunately, reliable values for the necessary optical constants (refractive index n and absorption index k) are often lacking. These two parameters generally... 

Since the early days of industrial ammonia synthesis only minor improvements have been achieved for the magnetite system optimization of manufacturing procedures, promoter concentrations, and particle size to give somewhat higher activity and longer service life. 

While entrained in the air, particulate uranium represents an inhalation source for humans, the extent of which is dependent upon concentration and particle size. For particulate uranium to be an inhalation hazard to humans, the particulates must be in the size range of 1-10 pm (Bigu and Duport 1992 ICRP 1979). In some cases, the solid tailings have been removed from the site for use as fill or construction material, which can lead to external radiation exposures primarily from the uranium progeny. 

Hinde and Lloyd [27] are more interested in extracting samples for continuous on-line analysis. They state that the process streams from industrial wet classifiers can vary in volume flow rate, solids concentration and particle size distribution. Any sampling technique should be able of coping with these variations without affecting the representativeness of the extracted sample. 

Due to their simplicity side-wall samplers are superficially attractive (Figure 1.37) but serious errors in concentration and particle size distribution can arise unless the particles are fine, the concentration is high and a very high sampling velocity is used. A projection extending from the pipe wall only marginally improves sampling efficiency [29]. 

Riebel and Ldffler [240] obtained an acoustic attenuation spectrum with one transducer pair to infer the particle size distribution. Solids concentrations and particle size distribution were obtained using both the Phillips-Twomey algorithm (PTA) and the relaxation method. The PTA gives a least squares solution by simple linear matrix operations to yield a numerical inversion from the attenuation spectra to the size distribution... 

Stone et al. (S29) developed by a mathematical analysis the functional relationship between the rate of extraction of silica from pure quartz in sodium hydroxide solution and time, temperature, sodium hydroxide concentration, and particle size. With the use of response surface methodology, a comprehensive picture of this dissolution process was obtained from a few well-chosen experiments. The fractional extraction of silica can be expressed by a second-order equation. The effect of quartz particle size and temperature are predicted to be about equal and greater than the influence of sodium hydroxide concentration and reaction time. The reaction rate is controlled by the surface area of the quartz. An increase in sodium hydroxide concentration increases the activation energy for the reactions and is found to be independent of quartz size. 

Hoffman E. J. and Duce R. A. (1977) Organic carbon in marine atmospheric particulate matter concentration and particle size distribution. Geophys. Res. Lett. 4, 449—452. 

Figure 12. Relative viscosity as a function of solids concentration and particle size distribution. (Reproduced with...

In practice, testing an emulsion for purposes of pipeline design requires a sample to be removed from a container or a pipeline. Although the testing is often straightforward, sampling is not, especially when an emulsion contains sand. Because the concentration and particle size distribution of the dispersed phase are so important, the rest of this review will deal with this aspect. 

Felton, L.A. McGinity, J.W. Influence of pigment concentration and particle size on adhesion of an acrylic resin copolymer to tablet compacts. Drug Dev. Ind. Pharm. 1999, 25 (5), 599-606. 

The main variables influencing this sampling mode are slurry stability and concentration, and particle size. 

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