Zoneflow Structured Catalytic Reactors for Steam Methane Reforming: Experimental Studies of the Reaction Kinetics and Fluid Dynamics and Multi-Scale Modelling

The multi-scale modelling of ZoneFlow structured catalytic reactors for steam methane reforming (zoneflowtech.com) is addressed. Advantages offered by ZoneFlow reactors compared to conventional packed beds include reduced pressure drop, improved heat transfer and increased catalyst effectiveness. Aspects of the catalyst, kinetic modelling, reactor modelling and required scale-bridging strategies are discussed.

The ASC (Alloy Surfaces, Co. Inc.) deformable Ni catalyst that was used is a thin, nanostructured and adherent Ni coating inter-diffused into a metal foil substrate that undergoes an alloying heat treatment followed by a chemical treatment. The kinetic modelling experiments were carried out in a micro-packed bed reactor set-up. The reactor design and operating conditions ensure plug flow, isothermal operation, small pressure drop and absence of interfacial and intra-catalyst transport limitations. Regression followed by physico-chemical and statistical testing were applied for the kinetic modelling and parameter estimation. The rate determining step-based Hougen-Watson Langmuir-Hinschelwood approach was applied to derive rate expressions that account for the details of the reaction mechanism and facilitate use in and integration of the reactor model. Based on possible reaction mechanisms and rate determining steps, 30 different sets of rate expressions were tested.

To account for the complex fluid dynamics, a CFD reactor model was developed. The RANS approach and standard k-epsilon model with wall functions were applied, introducing the turbulent viscosity, conductivity and diffusivity to account for the influence of turbulence. The turbulence model parameters were independently determined from cold flow pressure drop tests in a wide range of flow rates. Radiative heat transfer and thermal conduction in the reactor tube and in the reactor internals coated with catalyst were taken into account. The Rosseland-WSGGM was used to describe radiative heat transfer. The catalyst effectiveness factors were calculated from the intra-catalyst diffusion-reaction equations and the independently determined reaction kinetics was coupled with the CFD code.