The Drying of Spent Coffee Grounds in a Tray Drier

Abstract

Biodiesel has become an important sustainable alternative to petroleum-based diesel. Spent coffee grounds as a starting material to produce biodiesel can be cost effective especially if the grounds are dried before extracting the coffee oil. This work is part of a comprehensive research project to develop a sustainable biodiesel production process and focuses on the drying of spent coffee grounds using a laboratory tray drier. The drying kinetics were studied using two and four samples with controlled geometries at three different air flow rates and temperatures of 28, 30 and 32°C. The experimental data were used to determine the critical transport parameters in the drying process. Effective diffusivities varied from 1.03x10-11 to 8.11x10-10m2/s. The convective mass transfer coefficient was found to vary from 1.25x10-7 to 3.78x10-6m/s, while the heat transfer coefficient varied from eight to 31.2W/m2°C.