Boundary Conditions and Algorithms for 2D and 3D Lattice Boltzmann Simulations of Heterogeneous Reactions

In this paper, the formulation and method of implementation of boundary conditions for heterogeneous reactions in porous media are elaborated. These are implemented into a previously validated lattice Boltzmann model for the simulation of heterogeneous reactions in porous media, extending it on multiple fronts. The formulation of the boundary conditions is validated thoroughly. The conversion of solid carbon to CO and CO2 is chosen as a specific case of application. An extensive parametric study is conducted with a specific geometry consisting of spherical substrate particles, coated with a reactive soot layer, to highlight the capability of the code. The code was able to capture the expected evolution of a combustion front and the influence of process parameters onto its propagation velocity. The propagation speed linearly increased with an increase in the reactant mass fraction and exponentially increased with Péclet number. Also, the CO/CO2 ratio obtained from experimental data could be reproduced with good accuracy. Furthermore, an algorithm for the correct evaluation of the specific surface is presented, which is necessary for evolving solid domains based on realistic geometries containing enclosed cavities. The method of implementation, computational overhead and acceleration technique are discussed. Finally, the model and all boundary conditions are extended to 3D and validated.