Point-by-Point Solution Procedure for the Computational Fluid Dynamics Modeling of Long-Time Batch Drying

Further results of simulations of the drying kinetics in a spouted bed dryer with a draft tube (ICFB) will be presented in this paper. As noted earlier [Ind. Eng. Chem. Res. 2004, 43, 1113-1124], the Eulerian-Eulerian multifluid modeling approach was applied to predict gas-solid flow behavior. The heat- and mass-transfer model was coupled with computational fluid dynamics (CFD) code FLUENT 6.1, through application of user-defined functions (UDF). The falling rate period of drying was described by the linear and nonlinear lumped-parameter models. The new, robust "point-by-point" solution procedure was proposed to predict the kinetics of long-time batch processes and to overcome a lack of sufficient computational performance. The results of the simulations were compared with experimental data and with values obtained from various correlations. The drying kinetics during the constant and falling rate periods of drying of inorganic particles was predicted with sufficient accuracy and efficiency for engineering calculations. The mean relative errors were 3.24% and 19.8% for drying periods I and II, respectively. The biological texture of rapeseed caused higher discrepancies; however, for both types of grain, the results from the CFD simulations were more similar to the experimental data than to the values obtained from correlations. A CFD modeling technique, coupled with classical drying kinetics models, provided useful results for engineering purposes and allows use of the model throughout all phases of research and development.