This analysis investigates the fluid dynamics behaviour of the pneumatic system for a coffee roasting plant and particular attention is devoted to the roasting process of the coffee beans. A numerical model is constructed to simulate the complete thermo-pneumatic system that is employed in a reference plant. The numerical tool includes a predictive model for the simulation of the heat and mass transfer between the hot air flow and the coffee beans in order to estimate the coffee roasting process. Thus, submodels for the evaporation of the coffee moisture content and the coffee reactions due to the roasting process are developed and integrated in the simulation tool. The numerical model of the entire roasting plant is based on a lumped and distributed parameter approach and accounts for the physical properties of the different coffee blends as well as for the real operating strategies adopted in the real plant.
The roasting drum is analyzed in more detail by using a multi-phase multi-component flow. Discrete Element Method in STAR-CCM+ is used for simulating the beans within the rotating drum and the heat transfer between the coffee and the hot air flow is modeled. Different configurations of the rotating drum and different roasting operations are simulated and the effects on the quality of the coffee are addressed.