Secagem de resíduos cítricos em secador rotativo

Abstract

In this present work, an experimental study about simultaneous heat and mass transfer phenomena was carried out during the drying process of citric solid waste in a direct-heat contact semi-pilot rotary dryer, operating with continuous feed of solids. The drying experiments consisted of obtaining humidity and temperature data as function of time for the solid and gaseous phases, evaluating the influence of the operational variables of the process. The material characterization was studied in relation to the apparent and real specific masses, porosity, specific heat and hygroscopicity. The last one was determined by thermodynamic equilibrium conditions and by the thin-layer drying kinetics of the solid waste in a fixed bed dryer. In parallel, a two-phase mathematical model of lumped parameters was developed based on macroscopic balances of mass and energy for the solid and for the drying air. The differential algebraic system was solved numerically using a computer routine developed in MatLab®, where the drying process was simulated taking into consideration the particle residence time distribution inside the dryer. The comparison between the predicted and observed results showed that the model needs some improvement, but permits a preliminary qualitative analysis of the drying process.