Pore-scale study of diffusion-reaction processes involving dissolution and precipitation using the lattice Boltzmann method

A pore-scale model combining the lattice Boltzmann method (LBM) and a fluid-solid interface tracking method is employed to simulate the diffusion-reaction processes involving dissolution and precipitation. Coupled sub-processes including mass transport, chemical reactions, and solid structure evolution are considered. Effects of the precipitation of the secondary solid phase on the dissolution of the primary solid phase are investigated under different dissolution-precipitation reaction kinetics, molar volumes of the primary and secondary solid phases, powder size, surface roughness, and nucleation and crystal growth mechanisms. Different morphologies of the precipitates are predicted by the pore-scale simulations. It is found that the precipitation has opposite effects on the underlying dissolution processes. The favorable effect is that the precipitation reaction consumes the product of the dissolution reaction, thus facilitating the dissolution; while the adverse effect is that the generated precipitates cover the surface of the primary solid phase, thus separating the reactive surface from the reactive components. Based on the extent to which the precipitates affect the dissolution, four types of coupled dissolution-precipitation processes are identified and discussed.