Airflow regulation in feed machinery dryers is one of the core operating parameters affecting drying uniformity, and its mechanism permeates the entire heat and mass exchange process between hot air and materials. The airflow directly affects the distribution of airflow velocity within the drying chamber, thereby altering the surface moisture evaporation rate and internal moisture migration efficiency, ultimately determining drying uniformity. Proper airflow adjustment requires comprehensive consideration of material characteristics, equipment structure, and process requirements, achieving uniform heat and moisture transfer through dynamic balancing of airflow velocity and material movement.
Insufficient airflow leads to poor airflow circulation within the drying chamber, creating localized stagnant zones. In this case, materials near the heat source rapidly dehydrate due to contact with high-temperature hot air, hardening their surface to form a crust that hinders internal moisture diffusion; while materials farther from the heat source experience slow moisture evaporation due to insufficient hot air supply, resulting in significant differences in drying levels. This coexistence of "localized overheating" and "under-drying" is particularly pronounced in granular or flake feeds, easily causing excessive fluctuations in product moisture content and even the risk of clumping or mold growth.
Excessive airflow, on the other hand, can cause an imbalance in material movement. High-speed airflow can excessively agitate lightweight materials (such as powdered feed or small particles), leading to uneven distribution within the drying chamber. Some materials are carried rapidly through the drying zone by the airflow and are discharged without fully absorbing heat, creating "under-dried zones." Other materials, due to frequent collisions with the equipment's inner walls or mutual compression, experience particle breakage or morphological changes, forming "over-dried zones." Furthermore, excessive airflow increases energy consumption and may cause dust to fly, affecting the production environment.
Airflow adjustment must be closely matched to the material characteristics. For materials with high initial moisture content and high density (such as wet-based feed pellets), a larger airflow is required to enhance hot air penetration and ensure rapid migration of internal moisture to the surface. For fragile or heat-sensitive materials (such as certain vitamin premixes), a reduced airflow is necessary to minimize mechanical impact and thermal damage. For example, when processing oily feed, excessive airflow may accelerate oil oxidation; therefore, airflow control is needed to maintain a suitable combination of drying temperature and time.
The equipment structure has a decisive influence on the effectiveness of airflow adjustment. Vertical feed machinery dryers, due to the top-to-bottom flow of materials, require multi-stage airflow regulation devices (such as adjustable guide vanes) to achieve stratified airflow, preventing over-drying of the upper layer and under-drying of the lower layer. Horizontal feed machinery dryers, on the other hand, require optimized duct design to ensure uniform distribution of hot air along the material conveying direction, preventing rapid moisture loss from the front layer due to contact with high-temperature hot air, and delayed drying of the rear layer due to the decay of hot air temperature. Furthermore, the shape of the drying chamber (e.g., circular or rectangular) also affects the formation of airflow vortices, requiring airflow regulation to eliminate dead zones.
Airflow regulation needs to be coordinated with parameters such as temperature and humidity. In the initial drying stage, when the material moisture content is high, the airflow can be appropriately increased to rapidly increase the evaporation rate; as the drying process progresses and the material moisture content decreases, the airflow needs to be gradually reduced to avoid over-drying. Simultaneously, the airflow needs to be dynamically adjusted according to the ambient humidity: in a humid environment, increasing the airflow accelerates moisture removal; in a dry environment, the airflow needs to be reduced to minimize heat loss. This multi-parameter linkage control mode is key to achieving uniform drying. Modern feed machinery dryers mostly employ variable frequency fans (VFDs) for precise airflow regulation. By changing the motor speed through a frequency converter, the airflow output can be steplessly adjusted, forming a closed-loop control system in conjunction with temperature and humidity sensors. For example, when high humidity is detected in a certain area of the drying chamber, the system automatically increases the airflow in that area; when the material temperature approaches a critical value, the airflow is reduced to prevent thermal damage. This intelligent airflow regulation technology significantly improves the control accuracy of drying uniformity.
Airflow regulation is one of the core means for feed machinery dryers to achieve drying uniformity. Its mechanism involves multiple levels, including airflow distribution, material movement, and heat and mass exchange. It requires the optimization of equipment structure, coordinated parameter control, and the application of intelligent technologies to create a dynamically balanced drying environment. In the future, with the deepening integration of IoT and AI technologies, airflow regulation will develop towards greater precision and adaptability, providing more efficient drying solutions for the feed industry.
