Use of 'smart interfaces' to improve the liquid-sided mass transport in a falling film microreactor

It has been shown in the past, that the use of a falling film microreactor is advantageous for operation conditions, during which conventional processing equipment reaches its limits. The reactor design facilitates the development of well controlled, stable menisci. The very large specific gas/liquid interface (up to 20 000 m²/m³) provides excellent mass transfer capabilities between the phases. Nevertheless, despite the excellent gas/liquid mass transfer that occurs the chemical reactions are limited by the mass transfer within the phases. Commonly, the rate limiting step is the diffusive mass transport within the liquid side. This study investigates the potential of falling film microreactors equipped with structured channels to enhance the mass transfer within the liquid phase. To do this, four different reaction plates have been fabricated and are experimentally examined. Besides two reaction plates with straight, unstructured channels (channel width: 600 or 1200 μ m), one plate with fins and one plate with additional grooves in straight 1200 μ m wide channels forming a so-called staggered herringbone mixer are used. Taking carbon dioxide absorption as benchmark reaction it is shown that structured channel walls can significantly enhance the mass transfer within the liquid phase. This leads to an increase of the overall performance of the benchmark reaction. Properly chosen channel geometry can increase the conversion by up to 42%. Hence, by using an optimal reaction plate it is possible to more than double the flow rate, without any loss in conversion.