Exchange zone

When the resin is incompletely ionised, its effective capacity will be less than the maximum. If equilibrium between resin and liquid is not achieved, a dynamic capacity may be quoted which will depend on the contact time. When equipment is designed to contain the resin, it is convenient to use unit volume of water-swollen resin as the basis for expressing the capacity. For fixed-bed equipment, the capacity at breakpoint is sometimes quoted. This is the capacity per unit mass of bed, averaged over the whole bed, including the ion exchange zone, when the breakpoint is reached. 

Comparison of the computerized results obtained for the kinetic curves (Fig. 2a) reveals a very interesting feature of the IE process under discussion. Kinetic curves F (Fo) for variants I and III, resolved when a favorable isotherm of the B ion and the relation D >Dg apply, are described by the kinetic equation of diffusion into a spherical bead with constant diffiisivity D. In other words the kinetic curves F(Fo) coincide with the isotope exchange kinetic curves if a sharp profile appears in the bead and do not coincide if the exchange zone is greatly spread. The remaining kinetic curves in Fig. 2 formally correspond to the exchange process where varies in value. This is especially evident when comparing kinetic curves II and I.e (Fig. 2a). 

Figure 6.7 Solution concentration profiles within an ion exchange column depicting the lon Exchange Zone ...

Favourable Equilibrium If the ion exchange equilibrium is very favourable (. [ 1, >> 1) the exchange zone maintains a... 

An enclosure surrounded by three isothermal surfaces (zones), like that shown schematically in Fig. 5.59, serves as a good approximation for complicated cases of radiative exchange. Zone 1 at temperature 7 and with emissivity is the (net-) radiation source, it is supplied with a heat flow Q1 from outside. Zone 2 with temperature T2 < Tx and emissivity e2 is the radiation receiver, whilst the third zone at temperature TR, assumed to be spatially constant, is a reradiating wall, (Qr = 0). The heat flow Qi = — Q2 transferred by radiative exchange in the enclosure is to be determined. 

Different column design parameters like depth of exchange zone, adsorption rate, adsorption capacity, and so on were calculated. It was found that the adsorption capacity and adsorption rate constant were increased and the minimum column bed depth required was reduced when the rice husk is treated with phosphate, when compared with that of RRH. 

The parallel-flow regenerative kiln consists of two interconnected vertical cylindrical shafts. Burden is charged alternatively to each shaft and drawn downward through a preheating heat exchange zone and into the calcining zone. 

Speed of plane kinematic wave Speed of kinematic shock moving up from container bottom True electrophoretic velocity in electrophoresis cell Speed with which a point with ionic fraction Xg in solution moves Electroosmotic velocity in electrophoresis cell Speed of ion exchange zone front Liquid velocity in electrophoresis cell Maximum fluid velocity at center of circular or straight channel with fully developed velocity profile, Eq. (4.2.14) Velocity at free surface of... 

The degree of column utilization before breakthrough requires a knowledge of the shape of the exchange zone boundary or exchange zone front at the time of breakthrough. Approximately,... 

In the particular case of an infinitely fast exchange rate with diffusional effects neglected, the exchange zone front is discontinuous that is, it is a kinematic shock in the sense of Section 5.4 with, for example, the ionic fraction Xg changing discontinuously across the front, which moves downward with speed (Fig. 6.3.3). 

Figure 6.3.4 Effect of equilibrium isotherm shape on shape of exchange zone front.

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