Detailed simulations of heterogeneous reactions in porous media using the Lattice Boltzmann Method

Abstract

Flows though porous media are commonly found in many systems, both naturaland manmade. A few examples from nature include petroleum reservoirs, soil andsolid biomass where industrial applications include fuel cells, foams and packed beds.Most of these areas are still subject to both scientific and engineering challengesranging from basic understanding to detailed optimization. A non-trivial part ofthe remaining challenges includes the interaction between macro-scale performanceand micro-scale characteristics. For some systems, it is possible to control and tunemicro-scale properties to optimize the overall performance of the application. Thisscenario typically manifests in the design of packed beds, especially when reactionsoccur within the bed. In such situations, particle shape and size distribution willaffect not only the pressure drop (and hence the preferential flow paths), but alsolocal reaction rates and thereby efficiency and selectivity.This work aims to understand and identify key design parameters that influencesreactions within a packed bed, and ultimately, the overall performance of the pack-ing. Representative microstructures of packed beds are generated with a DiscreteElement Method. Flow, temperature and concentration fields (cf. Figure 1) are thenfully resolved using the Lattice Boltzmann Method with a first order reaction schemeat the boundaries. Residence time, flow structures and permeability of the systemsare correlated to conversion and selectivity of the chemical reactions in the system.Comparisons between packings of different particle shapes and spacing serve to eluci-date phenomena involved in the process and implies design directions for macro-scaleoptimization