(467c) Multi-Scale Modeling of an Annular Structured Catalytic Reactor for Steam Methane Reforming

Structured catalytic reactors have shown potential to intensify catalytic processes. An optimized flow pattern allows increased heat transfer and reduced pressure drop compared to conventional packed bed reactors. A thin layer of catalyst is coated on the internals of the reactor, allowing high catalyst effectiveness factors. Reactor design, optimization and scale-up requires the development of a detailed reactor model accounting for intrinsic reaction kinetics and transport phenomena. A multi-scale approach is presented for the case of an annular structured reactor for methane steam reforming (ZoneFlow^TM Reactor Technologies).

The intrinsic kinetics of steam methane reforming and water-gas shift reactions on a new Ni-based, intrinsically bound thin-layered catalyst adhered on a metal substrate were experimentally studied. The experiments were performed in a tubular packed bed micro-reactor, designed to avoid transport phenomena limitations. Estimation of the parameters and discrimination between the competing models followed from non-linear regression and statistical and physicochemical testing. Intra-catalyst diffusion limitations were accounted for using a pseudo-continuum model.

The commercial reactor performance is also determined by the complex flow pattern. A Computational Fluid Dynamics (CFD) model was developed. The Reynolds-Averaged Navier-Stokes (RANS) approach was adopted and turbulence was accounted for through the k-ε model. Thermal conduction in the walls and the internals of the reactor was accounted for and radiation was described by means of the Rosseland-Weighted Sum of Gray Gases Model. The CFD code was coupled with the intrinsic kinetic model and effectiveness factors independently calculated were imposed. The model parameters were determined from a combination of cold flow pressure drop tests and hot inert and reactive flow tests in different pilot plant units. The complete model was finally used to perform simulations of a commercial steam reformer. Comparison with a conventional packed bed reactor is made to demonstrate the process intensification potential of the annular structured reactor.