Study of a photocatalytic process for removal of antibiotics from wastewater in a falling film photoreactor: Scavenger study and process intensification feasibility

Microstructured reactors with their benefits especially concerning enhanced mass and heat transfer represent a means for process intensification. A broadly used microstructured lab tool in the area of gas/liquid contacting is the Falling Film Microreactor (FFMR) developed by IMM in which liquid films of a few tens of micrometer thickness and interfacial areas of up to 20,000 m2/m3 combined with an effective heat exchange can be obtained. Now the concept of the Falling Film Microreactor has been developed further with regard to increasing throughput in order to reach pilot production level and as a basis for future production scale throughput. Therefore, two different prototypes with a tenfold larger structured surface area have been developed and realized. The feasibility of a corresponding increase of throughput has been demonstrated for the oxidation of an organic compound using oxygen which is closely linked to an industrial relevant reaction and additionally by the absorption of CO2 in an aqueous sodium hydroxide solution. Naturally, process optimisation itself also contributes to the efforts to increase throughput. Therefore, the oxidation reaction has been optimised in both varying process parameters (temperature, flow rates, pressure) and reactor parameters (microchannel width and depth) in the original, standard Falling Film Microreactor. Conducting experiments at 10 bar instead of ambient pressure and using a reaction plate with 1200 µm x 400 µm channels instead of 600 µm x 200 µm channels lead to an increase in conversion. These investigations also encourage exploring more challenging process conditions and thereby following the concept of "novel chemistry."

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Mass transfer in falling film microreactors: measurement techniques and effect of operational parameters

Reviews in Chemical Engineering ◽

10.1515/revce-2018-0065 ◽

2019 ◽

Vol 0 (0) ◽

Author(s):

Ali Alhafiz Mohammed ◽

David Lokhat

Keyword(s):

Mass Transfer ◽

Measurement Techniques ◽

Process Intensification ◽

Liquid Films ◽

Falling Film ◽

Operational Parameters ◽

Transfer Enhancement ◽

Mass Transfer Enhancement ◽

The Relationship ◽

Common Target

Abstract Falling film microreactors have contributed to the pursuit of process intensification strategies and have, over the years, been recognized for their potential in performing demanding reactions. In the last few decades, modifications in the measurement techniques and operational parameters of these microstructured devices have been the focus of many research studies with a common target on process improvement. In this work, we present a review dedicated to falling film microreactors, focusing on the recent advances in their design and operation, with particular emphasis on mass transfer enhancement. Analysis of the recent techniques for the measurement of mass transfer as well as the operational parameters used and their effect on the target objective, particularly in the liquid phase (being the limiting phase reactant), are included in the review. The relationship between the hydrodynamics of falling thin liquid films and the microreactor design, the discrepancies between measured and model results, the major challenges, and the future outlook for these promising microreactors are also presented.

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