Gobby, Darren; (2002) Design of catalytic microengineered reactors. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The demand for safer and more efficient chemical plants has lead the reaction engineer to consider new technologies. Process intensification steers partially towards this goal by the reduction of large inventories. Microreaction technology can be seen to be a limit of process intensification, by performing unit operations in sub mm sized domains. High specific interfacial areas and well a defined hydrodynamic environment allow precise control of an intrinsically safe operation. Microreaction technology is still an emerging discipline and a thorough understanding of the important design and operating parameters are needed to gain industrial acceptance. The aim of this work is to understand the transport characteristics of energy and mass at this scale, in a theoretical manner, to provide the reaction engineer with some modelling tools that allow conceptual insight into the microreactor design. In addition the understanding of transport phenomena at this scale is applied to some unit operations allowing the dominant design and operating parameters to be identified. Analytical and numerical simulations have been used and it is shown that the microreactor is insensitive to the ID velocity profile if R > Pe > 1 for linear and non-linear kinetics in any duct shape. Highly non-isothermal systems were shown to become near isothermal as the conductivity in the reactor wall increased, i.e. acting as a thermal shunt. Multiphase systems were also investigated where it is shown analytically that the effect of interface curvature on reactor performance is negligible and transverse distance to the catalyst is the dominating design parameter. Two multiphase reactors were considered with different flow profiles and under some operating conditions they are shown to have equivalent performance. In all microreactor systems studied it was shown that a high degree of conversion and isothermality could be obtained with design expressions provided to allow rapid prototyping of future microreactors.

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