(667f) Drying of Spent Coffee Grounds

The objective of this work is to delve into the intricacies of drying spent coffee grounds for purposes such as the facilitation of transport and yield increase for biodiesel production, using a tray dryer as a preliminary study. The research first considers and develops a consistent approach to account for periodic variance in the utilized testing apparatus. This allows for the subsequent analysis of pertinent drying parameters for spent coffee grounds: the convective heat and mass transfer coefficients, the effective diffusivity, and the possible presence of constant rate drying periods to facilitate large-scale drying operations. In order to do this, inlet and outlet airstream qualities were periodically measured in a tray dryer operation concerning spent coffee grounds for over three hours per test. The environmental variance was measured by analyzing two minutes of second-by-second data. Ultimately, temperature and humidity was predictably periodic, and air flow speed proved to be mostly erratic. The results for the convective transfer coefficients seemed reasonable but no studies were not found in pertinent literature to compare against, while the diffusivity was mostly consistent with prior studies. The consistent appearance of two constant rate drying periods, with similar qualities across tests, directly contradicts with prior claims that no such period exists and therefore warrants further investigation.