Continuous adsorption process

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... 

Figure 15.19. The Toray simulated continuous adsorption process, (a) Showing the main valving for a seven-chamber adsorption system [Otani et al., U.S. Pat. 3,761,533, (25 Sep. 1973)]. (b) Flowsketch for recovery of paraxylene by continuous adsorption [Otard et al., Chem. Economy Eng. Rev. 3(6), 56-59 (1971)].

Our objective is to develop the continuous adsorption process for citrus oil processing. In this work, the adsorption breakthrough curves and desorption curves were analyzed to understand the adsorption-desorption behavior of citrus oil on a silica gel adsorbent inSC-C02. Acyclic adsorption-desorption process was developed and demonstrated for the removal of terpenes from orange oil. 

It is reported that this behavior, called channeling, is eliminated in a recently developed process—the Continuous Adsorption Process (CAP).1,S The operation of this process is in some respects similar to the Moving Bed System previously described, but with this important difference the upward-flowing stream of liquid moves at a velocity sufficient to provide an expanded state. In this expanded state, the individual carbon particles are separated very slightly from one another by a moving liquid film. Each carbon particle, however, maintains its position relative to all adjoining particles, and the expanded bed moves downward like a regiment on parade. 

The continuous adsorption process in a packed bed has to be characterized in terms of the flow of an incompressible single fluid through a bed packed with adsorbent, which may be approached using different concepts (velocity, residence time distribution and pressure drops) ... 

The idea of separating a product stream in a continuous adsorption process was developed and patented by United Oil Products (UOP, des Plaines, USA) in the 1950s [8]. At first, the SMB process was realized on the production scale for the purification of petroleum products (patented under the name Sorbex process ). 

Many attempts have been made to develop continuous adsorption processes, but until recently they have met with only limited success. One of the earliest versions, developed by the Union Oil Co, (now Unocal), u.sed a moving bed of activated carbon panicles to recover ethylene and other hydrocarbons from gas streams. Six large plants were built between 1947 and 1949 however, commercial utilization of the process was discontinued shortly thereafter, apparently due to excessive attrition and other solids handling problems (Berg, 1951). 

Bone char and granular carbon are generally used in fixed beds or in cylindrical columns 20 to 25 feet high and about 10 feet in diameter. Some recent systems percolate liquor upward or downward through a stationary bed of adsorbent or by counter-current flow of liquor and adsorbent (CAP or continuous adsorption process). (See below. Fig. 9.17.)... 

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