A generic Euler-Euler multi-phase chemistry framework for OpenFOAM®

Multi‑phase reactive flows are an immanent aspect of chemical engineering applications, e.g. solid fuel conversion, thermo‑chemical energy storage, or heterogeneous catalysis. In recent years, applying computational methods for process optimization or intensification has become more popular. Computational Fluid Dynamics (CFD) provides a spatially resolved, steady‑state or transient method to investigate complex processes. Flow, temperature, species profiles, and homogeneous chemistry are readily available in common CFD codes. Contrary, heterogeneous chemistry is typically only available in the Eulerian-Lagrangian (EL) modeling approach, while Euler-Euler (EE) implementations of heterogeneous chemistry are hardly available. Despite ever-increasing computational resources, modeling large- or industry‑scale aggregates in the EL framework by e.g. CFD-DEM is still prohibitive. As a consequence, EE two-phase or multi-phase models are often employed to reduce the computational effort of granular phases by modeling their rheology with the Kinetic Theory of Granular Flows (KTGF). Providing a generic framework to include heterogeneous chemistry in the EE framework seems crucial to improve the application of CFD in industry‑scale process development, optimization, or intensification. In this work, we present our implementation of such a multi‑phase chemistry framework in the open‑source CFD toolbox OpenFOAM®. The novel framework integrates seamlessly into the stock OpenFOAM® multiphaseEulerFoam solver and provides heterogeneous chemistry models of different complexity. The currently implemented heterogeneous chemistry models focus on gas‑solid reactivity and range from detailed chemistry based on the SurfaceCHEMKIN formalism to effective rate approximations. A thorough introduction and discussion of the generic EE multi‑phase chemistry framework are followed by an overview of the currently available gas-solid chemistry models. In the last part, we highlight the capabilities of the novel framework by presenting selected reactive multi‑phase processes.