Annular falling-film reactors

Figure 18. Annular falling film photochemical reactor [2, 3, 71].

There are some case-specific applications where annular flow is used. Falling film reactor is one of the examples. In this case, the liquid flows downward because of gravity in the form of film and gas flows through the open space, which lies in the top cover of the housing. 

Microstructured falling film and micro bubble column reactor Single micro channel operating in annular flow regime Microstructured falling film reactor Microstructured falling film reactor... 

The reactor is of the thin annular falling-film type, similar to the Chemithon reactor. It has a short length of about 2 m and a diameter of typically 0.3 to 1.0 m, depending on the capacity of the reactor. The width of the annulus through which the liquid film flows is about 5.5 to 30 mm. At the base of the film reactor, the reaction mixture is immediately quenched with an excess of... 

Both batch reactors and continuous-flow reactors have been used. Because Ti02 photocatalysis is generally considered of interest in purifying air or water with low concentrations of pollutants, the absorption of the incident photons by the pollutants is most often insignificant. If it is not the case, a falling film annular reactor (49) can be used as in photochemistry. 

Two classes of gas-liquid microchannel reactors were developed in the past years -continuous-phase contacting falling film, overlapping charmel, mesh, and annular flow approaches, and dispersed-phase contacting by Taylor flow reactors, micromixers for bubble and foam formation, and miniaturized packed bed microreactors, which follow classical trickle-bed operation at smaller scale. Recently integration of operations inside a microdevice has been studied and led to the development of membrane microreactors. 

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