Modelling the Superheated-steam Drying of a Fixed Bed of Brewers’ Spent Grain

A set of partial differential equations describing the steam drying of a fixed bed of brewers’ spent grain was developed based on energy and mass balances in a similar manner to the derivation of equations for air drying models. Instead of air humidity as an independent quantity in air drying models, the mass flow rate of steam was used as one of the independent variables in the steam drying model. The simplified model was solved using a finite-difference method, which was accomplished by the computer program written in FORTRAN language. The simulation program was developed based on the finite-difference equations formed from the model, the known initial and boundary conditions, and the division of three possible zones in the fixed bed. The validation of the drying model was made by comparing the predicated results with the experimental data. There existed a good agreement between the calculated and measured average moisture contents in the spent grain samples during the drying process.