Adsorption equipment moving beds

In order to design moving-bed equipment, the velocity of the adsorption zone relative to the solid has to be calculated. This gives the velocity at which the solids must move in... 

Because the ion-exchange process is very similar to the adsorption process, the equipment is also similar. Ion exchange occurs in batch tanks, stirred tanks, fixed-bed columns, fluidized-bed columns, and moving-bed processes. The most common process is a fixed-bed column (Figure 8.6), which can be operated in a cocurrent or countercurrent fashion. 

Sometimes reaction rates can be enhanced by using multifunctional reactors, i.e., reactors in which more than one function (or operation) can be performed. Examples of reactors with such multifunctional capability, or combo reactors, are distillation column reactors in which one of the products of a reversible reaction is continuously removed by distillation thus driving the reaction forward extractive reaction biphasing membrane reactors in which separation is accomplished by using a reactor with membrane walls and simulated moving-bed (SMB) reactors in which reaction is combined with adsorption. Typical industrial applications of multifunctional reactors are esterification of acetic acid to methyl acetate in a distillation column reactor, synthesis of methyl-fer-butyl ether (MTBE) in a similar reactor, vitamin K synthesis in a membrane reactor, oxidative coupling of methane to produce ethane and ethylene in a similar reactor, and esterification of acetic acid to ethyl acetate in an SMB reactor. These specialized reactors are increasingly used in industry, mainly because of the obvious reduction in the number of equipment. These reactors are considered by Eair in Chapter 12. 

Washing and adsorption The belt filters are used for washing and dewatering of fine solids in the manufacture of catalysts, zeolites, alumina and other crystalline substances, and so on. The belt filter requires the associated equipment — several vacuum pumps and separation drums. Through-circulation tray driers and through-circulation rotary driers are used to dry solids. All these are continuous crosscurrent processes. These could be replaced with a moving-bed, Hildebrand (screw) conveyer or Kennedy extractor [18], each of which is a countercurrent process. Their potential for PI has not been explored. 

The URPSA equipment (Figure 6) consists of a piston, a cylinder, valves and an adsorption bed. The piston is moved by an arm connected to a rotating disc driven by an electric motor. The basic operational steps are suction, adsorption and production, desorption, and exhaust step, as shown in Figure 7. The operation in each step is as follows. 

The vapor removed, which is mostly air ripe with solvent, is a moving stream of air pollution. Traditionally, the stream was directed to an exhaust vent from the work area. As with many aspects of solvent cleaning, the 1994 NESHAP for halogenated solvents mandated that, under the equipment control options, the exhaust from lip vents be directed to a bed of activated carbon for removal of solvent from the moving stream by adsorption. 

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