Experimental and Simulation Study of Convective Drying Process of Spent Coffee Grounds Including an Exergoeconomic Analysis

Abstract

A low-cost and highly exergetic efficient drying process assures a sustainable conversion of spent coffee grounds (SCGs) into value-added products. This work aims to conduct an exergoeconomic analysis at a component level of the convective simulated drying process of SCGs. To perform and validate the simulated process, the biomass characterization and the drying kinetic study were carried out using SCGs from a factory in Guayaquil, Ecuador. The values of moisture diffusivity, heat and mass transfer coefficients increased when increasing drying temperature. The simulated drying process was validated, reaching a maximum relative error of 4.0%. The exergy destruction rate varied from 11.9 to 7.0 MJ/kg when the air inlet temperature increased from 60 to 120 °C. Results suggest that working at 120 °C instead of 60 °C will reduce the specific cost of the dried SCGs by up to 79.9% and increase the exergetic efficiency by 13.9%.