Application of zonal and segmented temperature control technology in rotary drum dryers: Platform design and experimental analysis for tobacco drying

Abstract Drying is a critical stage in tobacco shred processing. The study focuses on the design of a rotary drum drying system with four independent temperature control zones in order to solve the problems of traditional rotary drum dryers: coarse temperature control, excessive energy consumption, and inconsistent product quality. By establishing a segmented dynamic temperature control strategy, precise adaptation to the multi-stage characteristics of the drying process was achieved. Taking tobacco shred drying as the research object, an orthogonal experimental approach was employed to systematically analyze the effects of seven factors—such as drum zonal wall temperature and hot air parameters—on the drying performance. The findings indicate that convective heat transfer from hot air is the dominant drying mechanism, with a-contribution rate exceeding 80%. Heat conduction from the drum wall shows notable spatial heterogeneity. The wall temperatures in Zones 2 and Zone 3 account for 6.59% and 4.88% of the influence on moisture content variation, respectively, which are substantially higher than that of Zone 4 (0.45%). By increasing the wall temperatures of the middle and front zones (Zones 2 and Zones 3) to 115–130 °C and applying low-temperature control (95–105 °C) to the tail zone (Zone 4), drying efficiency can be improved; and the risk of over-drying at the tail end is reduced, thus achieving both energy optimization and quality assurance. These findings provide new perspectives for improving drying equipment to enhance energy utilization and achieve precise control of the final moisture content.