The working principle of the fluidized bed dryer is to use convection-heated air to be in direct contact with the wet feed, so that the material is suspended in the fluidized bed for drying. During operation, air heated by a natural gas fuel air heater enters the dryer through a perforated air distribution plate (or perforated conveyor plate) upwards to fluidize the wet feed. In order to obtain a dry product with uniform moisture content, the design of the air distribution plate needs to provide a vertical airflow through the material and avoid the air bypassing the material bed. As heated air passes through wet material, the air carries moisture away and cools it before being discharged through a downstream cyclone, baghouse, or other air-material separation equipment. Depending on the type of dryer, the dried finished product is conveyed to the discharge port of the dryer in various ways.
Fluidized bed dryers are usually divided into two categories: single-layer fluidized bed dryers and multi-layer fluidized bed dryers. In a single-layer fluidized bed dryer, the wet material enters the dryer from the top and comes into contact with the hot air through the air distribution plate, which passes through the material layer to carry away the moisture and discharge it. Multi-layer fluidized bed dryers have multiple beds, each with its own air distribution plate and hot air inlet. The material flows between each bed, with air at different temperatures and humidity to achieve the best drying results.
Fluidized bed dryers have many advantages, such as high heat transfer coefficient, low energy consumption, high material throughput, etc. At the same time, it is also suitable for various different types of materials, such as granular, powdery, fibrous, etc. In some cases, fluid bed dryers can also be integrated with other equipment, such as coolers, pulverizers, packaging machines, etc., to form a complete production line.