ABSTRACT
Factors like preprocessing and drying affect directly the final quality of coffee. It is well known that coffee grains without pulp/hull generally result in a final product that gives a smoother taste and reach high market prices. On the other hand, during the drying process, these grains are more susceptible to the injuries caused by factors such as temperature, exposure time and air-drying quality. This research was carried out in the Department of Agricultural Engineering of the Federal University of Viçosa, MG, Brazil. Three tests with three replicates were conducted using different openings in the upper part of furnace. The charcoal from eucalyptus wood was used as fuel. The drying air was kept at 51°C temperature. The environmental air temperature, the drying-air pressure, and the fuel consumption were determined, at regular intervals, for each test. The energy efficiency was determined by the ratio between the energy received by the drying air and that delivered from fuel. Based on the results, it was verified that the highest energy efficiency average occurred with the highest average of the air-drying flow rate and with the lowest charcoal consumption average. After projecting, building and testing the furnace, its redesign was possible by determination of the parameters such as the energy delivery rate (K) and combustion rate (NC), which are more adequate. Thus, viability of this system for drying of coffee grains without pulp/hull was shown particularly because it generates pollution free energy with significant efficiency.
Key words:
furnace; drying; charcoal