The kernel of a one-dimensional pure aggregation population balance equation is modeled based on the results of simplified micro-scale constant number Monte-Carlo (MC) simulations of spray fluidized bed agglomeration. The effects of micro-processes such as particle collision, droplet deposition and droplet drying are incorporated in the aggregation kernel by taking into account the probabilities of wet collision and adhesion. The aggregation kernel is found to be directly correlated with the total collision frequency per particle, the total number of particles, the number of wet particles, the fraction of wet surface on such particles, and a success factor concerning the dissipation of kinetic energy. The derived expression of the aggregation kernel is computed using information provided by the MC and compared with the aggregation efficiency extracted directly from the MC for validation. Furthermore, a population balance model involving the derived expression for the aggregation kernel is also presented to compute the total number of particles and the number of wet particles independently from the MC. The results of this model concerning particle numbers and particle size distribution are found to be close to the results of corresponding MC simulations. (C) 2013 Elsevier Ltd. All rights reserved.