Energy and airflow optimization in an industrial roasting system: A case study

Technical University of Sofia, Faculty of Power Engineering and Power Machines, Department of Heating and Refrigeration, 8 Kliment Ohridski Blvd., Sofia, Bulgaria

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Abstract

This study presents an energy and airflow optimization of industrial drum coffee roasting system, focusing on the influence of airflow on heat transfer, particulate transport, and operational safety. Measurements revealed significant deviations from design conditions, with airflow velocities of 12.3 m/s leading to insufficient transport of coffee chaff and accumulation of deposits within the ductwork, increasing pressure losses and fire risk. In contrast, stable operation was achieved at approximately 19.3 m/s (5583 m³/h), which ensured effective particulate transport and prevented deposition. Based on these findings, a phase-dependent airflow control strategy was developed and implemented using a variable speed drive (VSD), maintaining maximum airflow during the first crack phase and reduced airflow during other stages. This approach improved process stability and thermal performance while reducing energy consumption. The transition from damper-based control to fan speed regulation resulted in energy savings of approximately 51% (3713 kWh/year). In addition, reduced airflow during non-critical phases minimized underpressure in the roasting area and improved overall ventilation balance. The results provide a quantitative basis for airflow design and control in industrial coffee roasting systems.