A multistage spray drying model for zeolite 4A-water suspensions in a counter-current spray dryer

The paper deals with multi stage spray drying model of zeolite 4A suspension. The model builds on upgrading the single stage spray drying model, as used in majority of CFD codes, to a multistage drying model, suitable for the implementation in a multiphase Lagrange-Euler CFD code. In the model, the first stage describes drying of surface moisture, followed by the second stage, in which the moisture in the porous interior of the drying particle is removed. The second stage is governed by the semi open Stefan diffusion model. The removal of the remaining adsorbed moisture in the zeolite crystals is modeled in the third stage by a kinetic model, implementing the temperature vs. moisture gradient data, obtained from the thermogravimetry data for zeolite 4A-water system. The multistage drying model is validated by comparing computational results for the particle, immersed in the drying air under varying process conditions alongside typical particle trajectories, obtained from the CFD analysis of a pilot scale dryer. The results obtained from the numerical model are compared with experimental results, obtained from performing several tests on the pilot scale spray dryer, and confirm the applicability and physical correctness of the proposed model. (C) 2016 Elsevier Ltd. All rights reserved.