Example 4-1 Basic Separator Type Selection

Draw a line through the initial point with a slope parallel to the lines marked industrial dust/ Where deviation is not known, the average of this group of lines will normally be sufficiently accurate to predict the mean par- 

OF PAH TICKS N MICRONS U.S, ST 0 MESH SCALE OF ATMOSPHERIC IMPURITIES RATE OF SETTLING IN F PJII. FOR SPHERES SfEC.GRAVI AT Jfff 

IT IS ASSUMED THAT THE PARTICLES ARE OF UNIFORM SPHERICAL SHAPE HAVING SPECIFIC GRAVITY ONE AND THAT THE DUST CONCENTRATION IS 0.6 GRAINS PER 1000 CU. FT. OF AIR. THE AVERAGE OF METROPOLITAN DISTRICTS. 

A projection of this point of collector effluent vertically downward shows that a second high efficiency centrifugal will be less than 50% efficient. A wet collector, fabric arrester and electro-stafic precipitator will be not less than 

Applied Process Design for Chemical and Petrochemical Plants 

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Gas-Liquid Chromatography. In gas-liquid chromatography (GLC) the stationary phase is a liquid. GLC capillary columns are coated internally with a liquid (WCOT columns) stationary phase. As discussed above, in GC the interaction of the sample molecules with the mobile phase is very weak. Therefore, the primary means of creating differential adsorption is through the choice of the particular liquid stationary phase to be used. The basic principle is that analytes selectively interact with stationary phases of similar chemical nature. For example, a mixture of nonpolar components of the same chemical type, such as hydrocarbons in most petroleum fractions, often separates well on a column with a nonpolar stationary phase, while samples with polar or polarizable compounds often resolve well on the more polar and/or polarizable stationary phases. Reference 7 is a metabolomics example of capillary GC-MS. 

In searching for new separation processes, the chromato-grapher develops new types of stationary phase materials in order to gain improvements in selectivity. The development of zirconia-silica composites is an example which—although, at present, applications on these surfaces are limited to their development—typifies the ongoing search. Whether the separations achieved on the zirconia-silica composites are better or worse than those achieved on either zirconia or silica is immaterial to the fundamental process of discovery. The important factor is that the separation is different and, therefore, an alternative separation strategy may be employed. In addition to the differences in selectivity that may be found when new surfaces are developed, beneficial surface properties may also be realized. These may be related to aspects such as the pore stmcture, the acidic or basic properties, or the solubility of the support. 

The analyst usually has some information regarding the nature of the ion to be analyzed (inorganic or organic), its surface activity, its valency, and its acidity or basicity, respectively. With this information and on the basis of the selection criteria outlined schematically in Table 1-1, it should not be difficult for the analytical chemist to select a suitable stationary phase and detection mode. In many cases, several procedures are feasible for solving a specific separation problem. In these cases, the choice of the analytical procedure is determined by the type of matrix, the simplicity of the procedure, and, increasingly, by financial aspects. Two examples illustrate this ... 

If required, relatively pure carbon monoxide can be recovered by cryogenic separation (i.e. condensation at very low temperatures), use of selective scrubbing solutions (for example CUAICI4 in toluene, the COSORB process) or solid adsorbents, and by other methods. Some CO recovery techniques are also applicable to the CO-rich (c. 70% molar) off-gases from basic oxygen furnaces and the leaner off-gases from air blast furnaces produced in steel manufacture, though operations of this type are still limited. 

In most cases, separation and purification via crystallization are highly selective due to the fact that molecular recognition process at the crystal-solution interface acts in such a way as to select the host molecules and reject impurities. However, sometimes the solute and impurity molecules are not discriminated at certain crystal faces, especially when the impurity has many of the structural and chemical characteristics of the primary solute but differs only in some specific way. A systematic approach toward understanding the effects of such impurities on crystal growth has been developed using the concept of tailor-made additives (Weissbuch et al. 2003). These additives are structurally similar to the solute molecules and are basically composed of two moieties. The first, known as the binder, has a similar structure (and stereochemistry) to that of the substrate molecule on the crystal surface where it adsorbs. The second, referred to as the perturber, is modified when compared with the substrate molecule and thus hinders the attachment of the oncoming solute molecules to the crystal surface. Several classic examples in the literature highlight this type of interaction mechanism in molecular crystals. 

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