The important role of the airflow distribution plate in a high-efficiency fluidized bed dryer

High-efficiency fluidized bed dryers achieve drying by creating a high-speed airflow through small holes in the material bed, causing the material to boil. During this large-area contact between the gas and solid components, the moisture in the material evaporates rapidly. Therefore, the airflow distribution plate is a crucial component of a high-efficiency fluidized bed dryer. The airflow distribution plate in a high-efficiency fluidized bed dryer serves two purposes: supporting the material layer and ensuring uniform gas distribution.

 

The size, shape, distribution pattern, and orifice ratio of the distribution plate openings all have a significant impact on fluid distribution. Uneven gas distribution can cause "circulation" in the bed, which, in extreme cases, can lead to "channeling" in some areas while other areas remain stagnant. In this case, most of the gas short-circuits through certain channels in the bed, significantly worsening the gas-solid contact – a situation that should be avoided. A well-designed distribution plate should suppress unevenness in the bed; that is, when pressure drop decreases and airflow velocity increases in some areas of the bed, the resistance generated by the distribution plate should be able to suppress the increase in airflow, thereby preventing the deterioration of fluidization.

 

Currently, most fluidized bed dryers use a single type of airflow distribution plate, often a vertical perforated plate or a woven mesh plate. This easily leads to uneven fluidization or dead zones during material fluidization, failing to ensure the uniformity of the drug within the particles. Furthermore, the single perforation type cannot meet the production process requirements of different drugs.

 

On the other hand, to reduce drug leakage, multi-layer mesh structures are commonly used, with the airflow distribution plate and fluidized bed often fixed with numerous bolts. This makes disassembly inconvenient, difficult to clean, and can result in residues causing cross-contamination. Recommendation: Utilize computer fluid dynamics models and heat and mass transfer models to perform aerodynamic and thermodynamic simulations and verification of parameters such as hole spacing, hole diameter, and opening ratio during the design of the airflow distribution plate to meet the production process requirements of different materials. Regarding installation, the connection method should be detachable to ensure quick installation and thorough cleaning.