Dispersed systems classifications

A classification of dispersed systems on this basis has been worked out by Pawlow (30) (1910), who introduces a new variable called the concentration of the dispersed phase, i.e., the ratio of the masses of the two constituents of an emulsion, etc. When the dispersed phase is finely divided the thermodynamic potential is a homogeneous function of zero degree in respect of this concentration. 

Disperse systems can be classified in various ways. Classification based on the physical state of the two constituent phases is presented in Table 1. The dispersed phase and the dispersion medium can be either solids, liquids, or gases. Pharmaceutically most important are suspensions, emulsions, and aerosols. (Suspensions and emulsions are described in detail in Secs. IV and V pharmaceutical aerosols are treated in Chapter 14.) A suspension is a solid/liquid dispersion, e.g., a solid drug that is dispersed within a liquid that is a poor solvent for the drug. An emulsion is a li-quid/liquid dispersion in which the two phases are either completely immiscible or saturated with each other. In the case of aerosols, either a liquid (e.g., drug solution) or a solid (e.g., fine drug particles) is dispersed within a gaseous phase. There is no disperse system in which both phases are gases. 

Table 1 Classification Scheme of Disperse Systems on the Basis of the Physical State of the Dispersed Phase and the Dispersion Medium... 

Table D3.5.1 The Classification of Dispersed Systems is Based on the Nature of the Involved Phases...

The explosion classification test is usually conducted in a modified Hartmann tube apparatus. The apparatus consists of a 1.2 L vertical tube mounted onto a dust dispersion system. Dust samples of various quantities are dispersed in the tube and attempts are made to ignite the resulting dust cloud by a 10 J electrical arc ignition source. If the material fails to ignite in the modified Hartmann tube apparatus, the testing is continued in the 20 L sphere apparatus. Dust samples of various quantities are dispersed inside the sphere and are exposed to a 10,0001 ignition source. 

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. 

Along with the classification of disperse systems based on the phase state of the dispersed phase and the dispersion medium, and their classification as coarse dispersed or colloidal, structured or unstructured, dilute or concentrated, one can also subdivide disperse systems into lyophilic or lyophobic types. Systems belonging to these principally different classes differ in the nature of colloid stability and in the intensity of interfacial intermolecular interactions. High degree of similarity between the dispersed phase and the dispersion medium, and, consequently, compensation of the... 

Some among them are denoted in literature as eonstrained liquids, others as dispersed systems. This classification is not universaL and it does not take in account other eases. 

Spasic, A.M., Babic, M.D., Marinko, M.M., Djokovic, N.N., Mitrovic, M., and Krstic, D.N., A new classification of finely dispersed systems. Abstract of Papers, Part 5, in Proceedings of the Fourth European Congress of Chemical Engineering, Granada, Spain, September 21-25, 2003, p.5.2.39. 

Demonstrates the classification of finely dispersed systems by identifying fundamental, indivisible elements related to particular transfer phenomena... 

Part I, Introduction, written by Spasic, Mitrovic, and Krstic, gives a brief overview of the finely dispersed systems through their classification considering surface and line continua and point discontinua, states of aggregation, homo and hetero, and their shape, rigid or deformable. 

To a considerable extent, rheological properties of various disperse systems are determined by their random particle fluctuations. In the dispersed phase, these fluctuations play a leading role in the formation of a system of effective stresses that determine, in turn, the observable macroscopic flow characteristics of the dispersions. For this reason, any classification of the dispersions with respect to their hydrodynamic behavior must be based on careful consideration of the main physical mechanisms that induce particulate fluctuations, and that consequently determine fluctuation properties. 

The different ways of classif)dng powders is closely related to the applications in which bulk properties play an important role. Since most applications in powder technology are relevant when considering powders as dispersion systems, they can be classified into different categories according to their particular... 

Fractionating sizing techniques combine a size-related classification process with the measurement of particle quantities. The classification may yield a physical separation of difl erently sized particles (e.g. by sieving, cf. Fig. 2.1) or it may successively deplete the disperse system of the coarsest or finest particles (e.g. in a sedimentation column). Accordingly, the measured quantities, which can be absolute amounts or concentration values, represent either a density or a cumulative function of the size distribution. Anyhow, the type of quantification (e.g. weighing) determines the type of quantity of the measured size distribution (e.g. mass), whereas the classification defines the probed particle property. The classification process should be ideal (i.e. with maximum selectivity) and well-defined by a monotone correlation between the particle property (e.g. settling velocity) and the... 

A universal criterion is that petroleum systems are mostly multiphase and heterogeneous with highly developed interfaces. The degree of dispersity is inversely proportional to a characteristic linear scale of inclusions. The degree of dispersity is a kernel of classification of disperse systems and should be accoimted for as an additional variable in all equations describing the thermodynamic state of a system At nano-scale ranges, this fact becomes especially important (Anisimov, 2004). 

CFD can provide a complete range of tools for modeling of phase separation, solids settling, and particle dispersion and classification. Inertial separation using chevrons or cyclonic separators and filtration systems using filter media can also be modeled. 

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