Fluidized Bed Dryers & Coolers
Materials processed in a Fluidized Bed Dryer or Cooler float on a cushion of air or gas. The process air is supplied to the bed through a perforated distributor plate and flows through the bed of solids at a sufficient velocity to support the weight of particles in a fluidized state. Bubbles form and collapse within the fluid bed of material promoting intense particle movement. In this state the solids behave like a fee-flowing boiling liquid. Very high heat and mass transfer rates are obtained as a result of the intimate contact between individual particles and the fluidizing gas.
Design
Hi-Temp Fluid Bed
The design of the distributor plate ensures that the fluidizing gas is evenly distributed across the area of the bed. The gas velocity is such that only the very fine material fraction is carried over to the dust collection equipment. A high turndown ratio of production capacity is possible and fluctuations of the feed rate are easily absorbed. In most cases, there are no moving parts in contact with the product.
Design variations include:
- Stirred Fluid Beds
- Deep Fluid Beds
- High Temperature Fluid Beds
- Contact Tubes and Plates
- Multiple Zones and Stages
- Integral Drying/Cooling
Features
- Provides extended residence times
- Provides intimate contact between drying/cooling gases and products
- Multi zones, velocities, temperatures, drying & cooling
- Option for easily removable bed plates
- Can be designed for open circuit partial gas recycle and SSD
- Plug flow or well mixed
- Can be designed with straight sides or with an expanded canopy
- Flexibility of residence time and temperatures
- Option for brick, castable and metallic lined washable refractory
- Up to 90% of the thermal duty can be supplied/removed by installing contact heat exchange tubes within a deep fluidized bed
Benefits
- Ideal for removal of surface and bound moisture in powder, crystalline or granular materials
- Good thermal efficiency
- Can handle a wide range of materials, particle size distributions and material cohesiveness
- Enables quick replacements, minimizing shutdown times and maintenance requirements, especially useful for hygienic applications
- Enables energy savings and system integration
- Plug flow is especially suited to products that require longer residence time and a relatively tight moisture specification
- For use as an elutriator or avoid excessive carry-over
- Good when turndown is required
- Enables high inlet temperatures for non-heat sensitive products which reduces the capital and running costs
- Reduces airflow and plant size and improves cost, emissions and power consumption
Process Flow Diagram
Static Fluid Bed
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