Two-phase contactor

TABLE 5-28 Mass Transfer Correlations for Packed Two-Phase Contactors—Absorption, Distillation, Cooling Towers, and Extractors (Packing Is Inert)... 

Reactor 2 [R 2] Continuous Two-phase Contactor with Partly Overlapping Channeis... 

Reactor type Conhnuous two-phase contactor with partly overlapping channels Silicon micro channel width depth Both typically 50-80 pm... 

As a further disadvantage, it is known concerning operation in many parallel micro channels that mixed flow patterns and even drying of the channels can occur [9, 10]. This comes from phase maldistribution to the channels. To overcome this problem, first solutions for phase equipartition have been proposed recently, but so far have not been applied for the mixers described here, but instead for mini-packed reactors, having feed sections similar to the mixers [11,12]. Nevertheless, numbering-up of dispersive-acting micro devices generally seems to be more complicated than for two-phase contactors (see Section 5.1.1). 

A systematic, rational analysis of both isothermal and nonisothermal tubular systems in which two fluids are flowing must be carried out, if optimal design and economic operation of these pipeline devices is to be achieved. The design of all two-phase contactors must be based on a firm knowledge of two-phase hydrodynamics. In addition, a mathematical description is needed of the heat and mass transfer and of the chemical reaction occurring within a particular system. 

The design of two-phase contactors with heat transfer requires a firm understanding of two-phase hydrodynamics in order to model effectively the heat- and mass-transfer processes. In this chapter we have pointed out areas where further theoretical and experimental research is critically needed. It is hoped that design engineers will be motivated to test the procedures presented, in combination with their use of the details from the original references, in the solution of pragmatic problems. 

H F contactors with planar elements with flowing head of fibers and crossflow of one phase in three and more phases contactor have been suggested in a patent [35] and their scheme is shown in ref. [8]. A two-phase H F contactor with planar elements was developed at TNO and tested in pilot plants [36, 37]. Reviews on two-phase HF contactors are presented in refs. [27, 38-40]. Mass-transfer characteristics of two-phase contactors are presented in ref. [30]. Three-phase HF contactors for pertraction are described in refs. [6-9, 41]. They are not produced commercially. 

As was pointed out in Chapter 1, countercurrent flow is usually the most desirable flow scheme in a two-phase contactor because it results in the largest... 

The design of gas absorbers when only physical absorption is involved, is relatively a simple matter (provided that the necessary data are available) and need not be described here. Apart from the hydrodynamical data such as flooding, only values of kQa and kLa under the prescribed conditions and the parameters of a proper two-phase contactor model are required. The latter will be discussed in some detail in Section 3 in many cases even the simple generalised design procedures, such as those reviewed by Pavlica and Olson (7) are not necessary and ideal flow patterns -for instance, plug flow - may be adequately used. 

MACROSCOPIC SCALE MODELING (TWO-PHASE CONTACTOR MODELS)... 

The first one may be called a "point" model (67,69). Here only the absorption-reaction interaction (that is, microscopic scale phenomena) is simulated so that gas absorption rate per unit interface (R) may be measured for a variety of combinations of bulk gas and bulk liquid compositions. Then, these results are inserted into an appropriate two-phase contactor model (for example, those listed in Tables 3-6), to yield the required capacity. It is clear that the method eliminates theoretical modeling at the microscopic level and none of the quantitative process specific data (i.e. Stage 1 of Figure 1) is needed. However, some qualitative data are required as the model is applicable only to reactions which are fast enough to take place in the diffusion film near the interface so that there is no unreacted dissolved gas, and no reaction in the bulk of the liquid (inappropriate considerations of bulk reactions may result in vast design errors (70)). It is also confined to the case where a single gas is being absorbed. The reason for these limitations is mainly that, in these cases, there is a simple stoichiometric relationship... 

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