Tubular contactors

Fialova, M., Redlich, K. H., and Winkler, K., Axial dispersion of the liquid phase in vertical tubular contactors with static mixers, Collect. Czech. Chem. Commun., 51, 1925-1932 (1986). 

The analysis of two-phase tubular contactors and pipelines is complicated because of the variety of configurations that the two-phase mixture may assume in these systems. The design engineer must have knowledge of the flow pattern that results from a given set of operating conditions if the in situ quantities such as pressure drop, holdup of each phase, phase Reynolds numbers, and interfacial area are to be determined. These in situ quantities must be known if the rate of heat transfer is to be predicted. 

If the vapor-phase temperature is to be evaluated from the Clausius-Clapeyron equation, the pressure in the two-phase tubular contactor must be known at each axial position. This need once again illustrates the necessity of obtaining an understanding of the hydrodynamics of two-phase systems in order to carry out the design of heat-transfer contactors. 

The analysis of tubular contactors for heat transfer with phase changes in fluid-fluid systems was shown to be heavily dependent on a proper understanding of two-phase hydrodynamics. It was shown that three basic flow patterns exist within a tube, each with a different heat-transfer mechanism. The formulation of the proper mass and energy models pinpointed three key... 

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. 

Figure 17.11. Types of contactors for reacting gases with liquids many of these also are suitable for reacting immiscible liquids. Tanks (a) with a gas entraining impeller (b) with baffled impellers (c) with a draft tube (d) with gas input through a rotating hollow shaft, (e) Venturi mixer for rapid reactions, (f) Self-priming turbine pump as a mixer-reactor, (g) Multispray chamber. Towers (h) parallel flow falling film (i) spray tower with gas as continuous phase (j) parallel flow packed tower (k) counter flow tray tower. (1) A doublepipe heat exchanger used as a tubular reactor.

For C02 capture mostly PTFE membranes are used [5] as extractants aqueous solutions of different amines are used [6]. In the past, the use of membrane contactors to capture C02 has been studied by TNO in the Netherlands and by Kvaerner/Gore in Norway and Germany [7]. They have worked with tubular systems. They claim that working with flue gas from a power generation plant can recover 85% of C02. 

Fig. 30. Contacting patterns and contactor types for gas-liquid-solid reactors, (a) Co-current downflow trickle bed. (b) Countercurrent flow trickle bed. (c) Co-current downflow of gas, liquid, and catalyst, (d) Downflow of catalyst and co-current upflow of gas and liquid, (e) Multi-tubular trickle bed with co-current flow of gas and liquid down tubes with catalyst packed inside them coolant on shell side, (f) Multi-tubular trickle bed with downflow of gas and liquid coolant inside the tubes, (g) Three-phase fluidized bed of solids with solids-free freeboard, (h) Three-phase slurry reactor with no solids-free freeboard, (i) Three-phase fluidized beds with horizontally disposed internals to achieve staging, (j) Three-phase slurry reactor with horizontally disposed internals to achieve staging, (k) Three-phase fluidized bed in which cooling tubes have been inserted coolant inside the tubes. (1) Three-phase slurry... 

FIG. A.l. Different types of continuous extraction equipment, (a) Mixer-settler, (b) Spray column, (c) Pulsed column, (d) Tubular centrifugal contactor. 

One advantage of the second method is that the design need not be limited to the same type of reactor. Data taken in a stirred reactor and manipulated to get intrinsic kinetic parameters could be used to estimate the performance of a tubular reactor, a packed bed, or perhaps a new type of contactor for the same reaction. Fundamental kinetic parameters obtained from a small fixed-bed reactor might lead to consideration of a fluidized-bed reactor for the large unit. Of course, pilot-plant tests of the alternate reactor type would be advised. 

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