Axial dispersion modelling of the residence time distribution in a millistructured plate reactor

Abstract

Micro- and millistructured reactors offer significant advantages compared to conventional batch reactors in terms of heat and mass transfer as well as process safety. Especially in case of fast and exothermic reactions, the space-time-yield of batch reactors is often limited by poor heat transfer and slow mixing. The use of millistructured reactors, such as the ART plate reactor PR37 of Ehrfeld Mikrotechnik, can overcome heat and mass transfer limitations and significantly extend applicable process windows, while providing sufficient capacity for industrial applications. Previous investigations showed that the reactor offers high heat transfer coefficients as well as short micromixing times at moderates Reynolds numbers. In order to further characterize the performance of the reactor and the possible operating window, the current work provides a thorough study of the residence time distribution on the basis of pulse experiments and a model-based evaluation of the deviation from ideal plug flow on the basis of the axial dispersion model. The results demonstrate that the reactor closely resembles the ideal plug flow even for Reynolds numbers of just about Re $\approx$ 100. Due to its meandering, periodically diverging/converging process channels, the formation of secondary flow is promoted resulting in an increased cross-mixing and thus a considerably reduced axial dispersion compared straight channels. For further analysis, as well as model-based assessment and design of the reactor, a correlation for the axial dispersion coefficient is derived which is applicable for a wide process window.