Adsorption counter-current

Ching C. B., Ruthven D. M. (1985) An Experimental Study of a Simulated Counter-Current Adsorption System - I. Isothermal Steady State Operation, Chem. Eng. Sci. 40 877-885. 

Both batch and continuous adsorption processes are used. In a batch process, the adsorbent bed is allowed to become saturated with adsorbed material and is subsequently regenerated in a cyclic manner. In a continuous process, usually the counter-current mode is adopted for adsorption and desorption, either in time form or in simulated mode. Continuous operation offers many advantages with respect to the efficiency of adsorbent utilization. Thus, for... 

In a partition system the stationary phase is a liquid coated onto a solid support (p. 97). Silica gel, kieselguhr (diatomaceous earth) or cellulose powder are the most frequently used. Conditions closely resemble those of counter-current distribution so that in the absence of adsorption by the solid support, solutes move through the system at rates determined by their... 

Continuous counter current operation of fluidized bed adsorption is used on a very large scale for small molecules, e.g. uranium or residues from mining. Theoretical and practical aspects of this technology have been summarized by... 

Crystallization and adsorption are both widely used to perform the separation distillation is not used (except for orthoxylene separation) because of too small differences between the boiling points (Table 10.1). Despite the still high importance of crystallization, adsorption becomes the most widely used technique because of its high efficiency. The adsorbents which are used for selective adsorption of paraxylene are X or Y zeolites exchanged with adequate cations. Liquid phase Simulated Counter Current adsorption, which is the most efficient process, is generally used (1). In addition to the complexity of this process, the choice of an adsorbent selective for paraxylene is the critical point. 

Simulated counter current adsorption for paraxylene separation... 

Description The separation takes place in an adsorption chamber (2) that is divided into a number of beds. Each bed contains proprietary shape-selective adsorbent. Also, each bed in the chamber is connected to a rotary valve (1). The rotary valve is used along with the shape-selective adsorbent to simulate a counter-current moving bed adsorptive separation. Four streams are distributed by the rotary valve to and from the adsorbent chamber. The streams are as follows ... 

Ruthven D.M. and Ching C.B., Counter-current and simulated counter-current adsorption separation processes, Chem. Eng. Sci. 44 (1989) pp. 1011-1038. 

Figure 1 Flowsheet of hybrid membrane-PSA process. Steps pressurization (PR = PRi + PR2). high-pressure adsorption (HPA), co- and counter-current blowdown (CD, BD), Purge (PG) A stream enriched in less adsorbed component, B-. stream enriched in strongly adsorbed component. Pressure histories of the integrated cycle at CSS.

Storti G., Mazzotti M., Morbidelli M. and Carra S., Robust design of binary counter-current adsorption separation processes, A.l.Ch.E.J. 39 (1993) pp. 471. 

However, Dijkstra states that current industrial bleaching processes are scaled up laboratory experiments. Accordingly, spent bleaching earth has been in adsorption equilibrium with bleached oil and thus has a much lower adsorbate loading than if this spent earth had been in equilibrium with nonbleached oil. He then raises the question of how much bleaching earth could possibly be saved if spent earth were to be in equilibrium with nonbleached earth as in a truly counter-current process with respect to the present, cocurrent processes. 

Here Vsoiid is the apparent solid flow rate, HA and ffB describe the slopes of the adsorption isotherm, which are calculated in the nonlinear case by linearization of the adsorption isotherm for the feed concentration Cfeed, . The transformation reflects the fact that, in a counter-current process, it is not the net flow rates that are important but rather their values relative to the apparent solid movement. For this reason, Morbidelli et al. introduced the m factors in their graphical design (known as the triangle theory) (Biressi et al., 2000 and Mazzotti et al., 1997c). 

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