We propose detailed microscale modelling of flotation processes by means of Density Functional Hydrodynamics (DFH), which is the direct 3D numerical modelling method for compositional flow with gas, liquid and solid phases taking into account viscosity, compressibility, interfacial tension, gravity, diffusion, and a range of rheological models. The DFH governing equations are conservation laws for chemical components, momentum and energy. The constitutive relations involve Helmholtz energy or entropy of the multicomponent multiphase mixture. In this work, we outline the necessary background of the DFH equations. Then we demonstrate a set of relevant numerical simulations for three-phase mixtures comprising contact angles, wettability, rheological properties, and gravitational segregation. The proposed modelling is expected to help in screening and optimization in mineral processing and waste-water treatment.