Supercritical-CO2 drying of foodstuffs in packed beds: Experimental validation of a mathematical model and sensitive analysis

In this contribution, a mathematical model is built to predict the changes in water concentration in both a solid food matrix and a fluid carrier during supercritical carbon dioxide (SC–CO2) drying. The mass balance equations of the model involve five dimensionless parameters: Peclet number modified Sherwood number, Fourier number, mass ratio and equilibrium constant. The differential equations were discretized using the finite explicit difference method. The resulting model was implemented and solved in Matlab/Simulink using an explicit Runge–Kutta solver. A very good agreement (ARD = 7.2%) between experimental data, obtained by an independent group, and the present model was observed. The axial dispersion diffusion coefficient seems not to play a significant role during the drying process. A sensitivity analysis revealed that the predictions are relatively more sensitive to the equilibrium constant and the mass ratio than to Peclet and modified Sherwood numbers. Furthermore, in the case of Peclet and modified Sherwood numbers, the sensitivity and the uncertainty of the output are function of the final moisture content. The present model could be used as an optimization tool for kinetic studies to investigate the effects of different operation conditions on the performance and design of the supercritical drying technology.