In this article, multiphase convective and solidification transport phenomena of ice slurry is investigated by developing a one-domain macroscopic model to simulate its formation in a rectangular ice forming unit. Convection, sedimentation, interfacial drag, permeability, remelting and viscosity variations are incorporated into this model through the appropriate governing multiphase transport equations. Validation studies with literature data are performed to determine the most suitable drag law by comparing the position of the interface between the coherent and non-coherent zones. After establishing modified Stokes' Law as the best-suited drag model, solidification study of an aqueous ammonium chloride solution is performed. The results for the evolution of ice fraction, species distribution, temperature profile and multiphase velocity field are presented. Solid fraction gradient, due to the generation of ice particles, has a major influence on the density gradient leading to a counter-clockwise flow current resulting in the homogenization of temperature and species in the generated ice slurry.