Multi-scale modeling of dense gas-particle flows

Dense gas-particle flows are encountered in a variety of industrially important processes for large scale production of fuels, fertilizers and base chemicals. The scale-up of these processes is often problematic, which can be related to the intrinsic complexities of these flows which are unfortunately not yet fully understood despite significant efforts made in both academic and industrial research laboratories. In dense gas-particle flows both (effective) fluid-particle and (dissipative) particle-particle interactions need to be accounted for, because these phenomena to a large extend govern the prevailing flow phenomena, i.e. the formation and evolution of heterogeneous structures. These structures have significant impact on the queality of the gas-solid contact and as a direct consequense thereof strongly affect the performance of the process. Due to the inherent complexity of dense gas-particles flows the authors have adopted a multi-scale modelling approach in which both fluid-particle and particle-particle interactions ca be properly accounted for. The idea is essentially that fundamental models, taking into account the relevant details of fluid-particle (lattice Boltzmann model) and particle-particle (discrete particle model) interactions, are used to develop closure laws to feed continuum models which can be used to compute the flow structures on a much larger (industrial) scale. Our multi-scale approach (figure) involves the lattice Boltzmann model, the discrete particle model and the continuum model based on the kinetic theory of granular flow. In this presentation the multi-scale modeling strategy for dense gas-partticle flows will be presented together with illustrative computational results. In addition, areas which need substantial further attention will be hightlighted