Continuous contactors

The second type of mass-exchange units is the differential (or continuous) contactor. In this category, the two phases flow through the exchanger in continuous contact throughout without intermediate phase separation and recontacting. Examples of differential contactors include packed columns (Fig. 2.6), spray towers (Fig. 2.7), and mechanically agitated units (Fig. 2.8). 

T0016 Advanced Separation Technologies, Inc., ISEP Continuous Contactor... 

T0016 Advanced Separation Technologies, Inc., ISEP Continuous Contactor T0132 Brookhaven National Laboratory, Biochemical Recovery of Radionuclides and Heavy Metals... 

Continuous Contactor with Partly Overlapping Channels Solute transfer can occur between immiscible phases each flowing in separate adjacent but displaced microchannels, having only a small conduit in which the fluid interface is stable (partial overlap) [267,268]. 

Figure 4.31 Cut through a continuous contactor with partly overlapping channels revealing rectangular and semicircular channels at adjacent but displaced positions (by courtesy of J. Shaw, CRL) [267],...

The transfer of mass from one phase to another is involved in the operations of distillation, absorption, extraction, humidification, adsorption, drying, and crystallization. The principal function of the equipment used for these operations is to permit efficient contact between the phases. Many special types of equipment have been developed that are particularly applicable for use with a given operation, but finite-stage contactors and continuous contactors are the types most commonly encountered. A major part of this chapter, therefore, is devoted to the design aspects and costs of stagewise plate contactors and continuous packed contactors. 

Continuous Column Operations. When the ionic load of the feed solution is such that the regeneration/elution portion of the operating cycle is nearly as great or greater than the working portion, continuous contactors are recommended instead of column contactors. 

Continuous contactors operate as intermittently moving packed beds, as illustrated by the Higgins contactor " (Fig. 31), or as fluidized staged (compartmented) columns, as shown in Fig. 32, by the Himsley... 

The Higgins type of contactor is able to handle a certain amount of slurry due to the continued introduction of fresh resin material to act as a filter media during the operation. A lower resin inventory should result with continuous contactors than with column reactors handling the same ionic load feedstream. 

In continuous contactors, interphase mass transfer occurs by diffusion—a... 

Analogy to tray columns. In concept, the NTU is analogous to the number of theoretical stages in a tray column, It only depends on the equilibrium and component balance curves (F. 9.16) and is unaffected by the mode of contact. The main difference between NTU and number of theoretical steiges is that NTU is a measure of the separation difficulty best related to a continuous contactor, while the number of theoretical stages is a measure of separation difficulty more useful for a stage-by-sta contactor. In a similar manner, the HTU is analogous to the inverse of trs r efficiency. 

Gas-flowing solids-fixed bed contactors can be used either as two-phase continuous contactors between flowing solids and gas where the fixed bed structure can be specially designed for distribution of both flowing phases or as three-phase contactors where the fixed bed has an active role (e.g., catalyst bed). 

Continuous Contactor with Partly Overlapping Channels... 

The principal function of equipment used for mass transfer operations is to allow for efficient contact between the phases. Finite-stage contactors (plate columns) and continuous contactors (packed columns) are typically used. Different types of distillation methods are as shown next ... 

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