Multi-size equations of Iddir and Arastoopour [2005] incorporated in the MFIX code were used to predict particle segregation and annular flow of particles in a riser section of a PSRI CFB. However, the multi-size approach requires a considerable amount of computational time when several particulate phases are considered. On the other hand, population balance equations account for the particle poly-dispersity, particularly in size, and the solution of the population balance equations (PBE) can be obtained by the method of moments requiring lower computational time. Recently, the FCMOM (Finite size domain Complete set of trial functions Method of Moments) was proposed (Strumendo and Arastoopour [2006]), a technique which provides efficiently (in terms of computational time) the solution of the PBE both in terms of the moments and in terms of the particle size distribution; the FCMOM was extensively validated for homogeneous systems. FCMOM was extended to non-homogeneous systems in which two dimensional flow equations are coupled with the population balance equations.