Theoretical study of fluidization and heat transfer on fluidized bed coffee roaster

Abstract

The roasting coffee is one of the processing coffee beans which determines the quality of the coffee flavor. In general, the process of roasting coffee uses a rotating cylinder, a fixed drum with agitator and a fluidized bed. Theoretical study of fluidization and heat transfer has been carried out on a fluidized bed coffee roaster 1000 gram capacity with a tubular roasting chamber. Green beans (Robusta coffee) used in the roaster at two different operating temperature settings, 250°C and 220°C for high-temperature short time (HTST) and low-temperature long time (LTLT) roasting processes. At this operating temperature, minimum fluidizing velocity was 2.19 m/s and 2.16 m/s respectively, and the thermal energy for roasting coffee was 8773.25 W and 7639.56 W respectively. The thermal energy was defined based on the heat transfer from hot air to coffee beans which was 3399.63 W for HTST process and 3091.49 W for LTLT process that calculates at hot air velocities 2.5 m/s.