Drug dissolution has been investigated experimentally and theoretically at both apparatus and single particle levels. Existing models are usually based on highly idealised shapes such as spheres. The influence of complex microscale structures is, by comparison, less extensively studied. This paper describes in detail a hybrid model for dissolution of granular structures at microscopic scales, using real/realistic particle shapes, with the help of emerging enabling characterization and simulation techniques. The dissolution model is implemented as a finite difference solver of the convection-diffusion equation. A digital particle packing algorithm (DigiPac) together with characterization using X-ray microtomography (XMT) is employed to provide the structural input. Lattice Boltzmann method (LBM) is used to generate flow input for convection. Some benchmark tests are presented. A few hypothetical but illustrative examples are used to demonstrate theoretical capabilities of the model. The ultimate goal is to develop a computer software design aide to help with formulation development.