Reaction-Diffusion Dynamics in a Microreactor - Theoretical Study

In the last decade, Microreactor Technology (MRT) as a new concept in chemical engineering has demonstrated the advantages of microstructured devices for chemical reactions impressively. Microscale reactors are devices whose operations depend on precisely controlled design features with characteristic dimensions from submillimeter to submicrometer. Due to the small amount of chemicals needed and high rate of heat and mass transfer, the systems are especially suited for reactions with highly toxic, flammable, and explosive reactants. The theoretical description of the reaction-diffusion process in a microreactor was investigated in this work. A two-dimensional mathematical model, containing convection, diffusion, and a second-order reaction terms, was developed to analyze and to forecast the reactor performance. Despite the small dimensions of microchannels, it is usually assumed that for liquid systems the transport of momentum is governed by the incompressible Navier-Stokes equations. A fully developed parabolic velocity profile in a microchannel was assumed and considered in proposed mathematical model. Using a wide range of theoretical operating conditions, expressed as different (ReSc) numbers (0.01<ReSc<10), a dimensionless concentration was calculated for the plug-flow reactor (PFR) model, the continuous stirred-tank reactor (CSTR) model, and microreactor 2D model. For the numerical solution of the model equations, an implicite finitedifference method improved by introduction of non-equidistant differences was used. All models were solved by Mathematica 5.2.