Catalytic Reverse-Flow Oxidation Process in Reactors of Various Designs: Axial, Side and Tangential Gas Inlet

The study was dedicated to the mathematical modeling of the catalytic reverse-flow process in reactors of different design, e.g. in reactors with axial, side or tangential arrangement of reaction gas inlet/outlet streams. The oxidation of volatile organic compounds in the fixed adiabatic catalyst beds was considered, using toluene as an example contaminant. Three-dimensional fluid dynamics modelling performed by means of Comsol Multiphysics software showed the existence of the significant gradients of temperature, concentrations of reactants and fluid velocities along the bed radius; such gradients are neglected in the conventional one-dimensional models, usually used for simulation of reverse-flow processes. The spatial distribution of these parameters may be asymmetric in the reactors with asymmetric design. It was shown that efficiency of both toluene conversion and heat regeneration significantly decrease in reactor with side feeding of inlet mixture, finally resulting in lower thermal stability of the process with the significant (∼20%) decline of the maximum possible duration of the cycles between flow reversals compared to reactor with axial gas feeding. Vice versa, the tangential arrangement of gas inlet provides the visible (∼10%) increase of maximum cycle duration. Application of 3D modelling approach to development and optimization of catalytic processes becomes especially important in case of reverse-flow reactors where negative influence of various spatial non-uniformities may impose more significant influence on process parameters.