FLUID BED DRYERS
With their smaller footprint and greater heat transfer efficiency, fluid bed dryers offer an optimal industrial drying system for operations with less available floor space. As a leader in bulk solids drying equipment, FEECO offers efficient drying methods designed to meet your production goals.
How Does a Fluid Bed Dryer Work
As a pneumatic drying technology, fluid bed drying relies on forced hot air to achieve fluidization of materials ranging from powders to granules to reduce the moisture content according to material specifications and desired throughput. Each material has a unique minimum fluidization velocity, or airflow required to fluidize the heaviest particles and reach a fluidized state. As such, particle size and shape, as well as the weight of the particles influence the fluidizing process.
A hot air stream is forced through a perforated plate at the velocity required based on the specific particle characteristics. This perforated distributor plate ensures uniform air distribution across the bed of material. Air velocity also determines the “regime,” or material flow pattern. Careful temperature control is essential to avoid overheating and degradation of heat-sensitive materials.
In contrast to a static system, the use of fluidization greatly increases the available material surface area exposed to direct contact with the air. Further, as material behaves like a fluid, it experiences complete mixing, resulting in uniform drying (for this reason a fluid bed dryer should not be considered a plug flow system).
While many equate these systems with vibratory fluid bed technology, this type of fluidized bed is distinctly different from a vibrating fluid bed dryer, which employs vibration to assist in moving material through the unit.
The exhaust air system is located above the discharge and uses a filtration system to capture and filter out small particulates. Buildup is prevented along the sides of the unit through turbulent mixing of the solids.
Air temperature and air flow are constantly regulated to yield a superior drying technology, whether employed as part of a granulation system, or as a pretreatment for raw materials.
Retention time is largely determined according to the size distribution of particles.
FEATURES
- Size: 4’ – 20’ Diameter (1.2 – 6m)
- Capacity: 1 – 50 TPH | 1 – 15mmBtu/hr | 3,000 – 50,000 ACFM
- Temperature Range: 300 – 1,500°F
- Smaller footprint
- Simple, cost-effective construction
- Improved heat transfer efficiency
- Minimal structural support requirements
- Minimal maintenance requirements
- Option to reuse recovered waste heat
- Reduced capital cost and lower installation costs
- Non-plug-flow design (continuously stirred tank reactor)
- Variable Frequency Drive (VFD) for precise flow control
- Gentle handling and minimal degradation of most particulates, ideal for fragile materials (application dependent)
- Simple integration of additional components
Optional Components
- Fire Protection
- Tapered Expansion Chamber
Accommodates Various Fuel Types
- Natural Gas
- Propane or Fuel Oil
Material Options
- Carbon Steel
- Stainless Steel
Please note that all FEECO Fluid Bed Dryers are built according to each project’s unique feed material and product requirements.
Fluid Bed Dryer Components
Mechanical Construction of a Fluid Bed Dryer
A – Air Outlet
B – Feed Inlet
C – Air Inlet
D – Air Distributor Plate
FEECO is capable of meeting the requirements necessary for CE marking equipment.
All FEECO equipment and process systems can be outfitted with the latest in automation controls from Rockwell Automation. The unique combination of proprietary Rockwell Automation controls and software, combined with our extensive experience in process design and enhancements with hundreds of materials provides an unparalleled experience for customers seeking innovative process solutions and equipment. Learn more >>
APPLICATIONS & MATERIALS
Fluid bed dryers are used across various industries with a wide range of materials. They are ideal for processing pellets and free-flowing, uniform solids such as:
- Fertilizers
- Specialty Chemicals
- Biomass
- Biosolids
Note: Materials that exhibit poor flowability or have an especially high moisture content may require some pretreatment prior to drying in a fluid bed unit.
Advantages & Disadvantages to Fluid Bed Drying
As with any industrial equipment, fluid bed dryers come with their own inherent advantages and disadvantages:
Fluid Bed Dryer Advantages
Key advantages of the fluid bed dryer include:
- Small footprint
- Thermally efficient
- Gentle handling
- Low cost
- Solids mixing
- Flexible application
- Simple fabrication
- Easily automated
Fluid Bed Dryer Disadvantages
- Requires feedstock uniformity
- Reduced energy savings at lower capacities
- Some dust and attrition
Fluid Bed Dryer Testing & Design (R&D)
The FEECO Innovation Center is a unique testing facility where we can test the material to be dried in our industrial dryers to determine the feasibility of your fluidized bed drying process, establish drying parameters, fine-tune product quality, and gather valuable data points necessary for scale-up.
The FEECO Innovation Center is well-equipped to suit a wide range of testing needs, from agglomeration to high temperature thermal processing, as well as continuous process loops integrating multiple testing methods.
We offer comprehensive testing services in four categories:
Feasibility/Proof of Concept: An initial, non-witnessed batch testing phase in which the possibility of creating a product is explored.
Proof of Product: A more in-depth batch testing phase in which more time is spent determining whether a product can be made to desired specifications.
Proof of Process: A continuous testing phase that aims to establish the equipment setup and parameters required for continuous production of your specific material.
Process/Product Optimization: An in-depth study to optimize your specific material’s characteristics and/or production parameters in an industrial setting.
RESOURCES
Fluid Bed Dryer ARTICLES
Fluid Bed Dryer Design: A Beginner’s Guide
Fluid bed dryers are one of the most popular types of industrial dryers, and for good reason: their high rate of …
Identifying and Resolving Common Fluid Bed Dryer Issues
Fluid bed dryers offer an effective approach to reducing moisture in bulk solids, leveraging fluidization to achieve uniform drying and high …
BROCHURES
Fluid Bed Dryer Brochure
FEECO Complete Offerings Brochure
Fluid Bed Dryer Frequently Asked Questions (FAQs)
A fluid bed dryer works by pneumatically suspending solid particles in a gas stream. This design promotes maximum gas-to-solids contact.
The dryer consists of a stationary vessel, at the bottom of which is a perforated plate through which air is passed at the velocity needed to achieve minimum fluidization of the solids (not exceeding terminal velocity).
It’s important to note that variations on traditional fluid bed dryers, such as vibratory fluid beds, while based in fluid bed technology, are not true fluid beds, due to their employment of mechanical assistance to move particles through the unit.
The advantages of the fluid bed dryer design include high thermal efficiency, a small footprint, and minimal maintenance requirements. Fluid bed dryers are also generally more cost-effective compared to other industrial drying systems.
The disadvantages of the fluid bed dryer design include the requirement for a highly uniform feedstock, an inability to garner energy savings when running at reduced capacities, and the need for a more robust exhaust gas system.
Fluid bed dryers can work with a wide variety of materials. They are commonly used in drying minerals, chemicals, metals, and biomass-derived feeds.
Materials with a large particle size, typically larger than ½ – 1”, are typically better suited to a rotary dryer. This is also the case with materials that exhibit variation in feed characteristics.
A retention time of five to 15 minutes is common for fluid bed dryers, though retention time can vary significantly depending on the application and functional design.
Fluid bed dryers work best for materials that are consistent in particle size and density. Determining whether a fluid bed dryer is a good fit for a given application is often dependent on testing in a process development facility such as the FEECO Innovation Center, where producers can evaluate how the specific qualities of their feedstock respond to fluid bed drying.
Fluid bed dryers can handle capacities ranging from modest pilot-scale to massive systems processing in excess of 100 TPH.
Fluid bed dryers have minimal maintenance requirements due to their lack of moving parts; the primary maintenance associated with fluid beds is related to the ancillary equipment such as fans and combustion systems.
Fluid bed dryers processing abrasive materials such as sand may also require additional maintenance of the unit itself to manage abrasive wear.
A fluid bed dryer manufacturer will require several data points around the raw material and process objectives, including:
- Starting feed moisture content
- Desired outlet moisture content
- Maximum material temperature
- Chemical composition
- Particle size distribution
- Rheological properties (i.e., particle shape, is the material sticky, etc.)
- Desired throughput
- Bulk density
- Specific heat
Yes. Fluid bed dryers can be equipped with automation capabilities, including the ability to incorporate features such as incremental starts and stops, making the need for operator intervention minimal.
Fluid bed dryers use several design parameters to meet process and product objectives. Among them:
- Additional modifications to the dryer configuration
- Air flow velocity (and subsequent fluidization regime)
- Bed distributor plate configuration
- Percent fill
- Feed & product flow rates
- System pressure
- Residence (retention) time
- Temperature profile
The difference between a stationary and vibratory fluid bed dryer lies in how material moves through the unit.
A true fluid bed dryer relies on pneumatic suspension to move material through the dryer. In contrast, a vibratory fluid bed incorporates mechanical action (in this case, an oscillating thrust) to transport the solids.
Vibratory fluid beds can be a good choice when working with less flowable materials. However, this approach translates to a lower internal drying air flow and inherently larger machine; while the vibration helps to move material through the unit more quickly, it does not allow for true suspension (and therefore maximum gas-to-solids contact). The added vibration can also contribute to increased attrition.
A fluid bed dryer requires several pieces of ancillary equipment to function properly and within regulatory requirements:
- A furnace or hot air generator
- A fluidization blower
- An induced draft fan
- An exhaust air cleaning device such as a baghouse, cyclone or wet scrubber
- Feed and product takeaway conveyors
However, this equipment can typically be sourced as a complete system when working with an experienced and reputable manufacturer.
Most fluid bed dryers are continuous, though some specialty applications, such as in the pharmaceutical sector, may utilize batch equipment.
Fluid bed dryers typically operate with inlet gas temperatures between 300°F to 1500°F and exhaust gas temperatures around 170°F – 250°F.
Yes, fluid bed dryers are considered a type of continuously stirred tank reactor (CSTR), because solids are well mixed. In cases where additional mixing is required, an agitator can be incorporated.
The choice between a rotary dryer and fluid bed dryer depends on the material to be dried.
While there is some overlap in their capabilities, each type of industrial dryer offers distinct advantages and disadvantages that can make them preferable in one setting over another.
Rotary dryers are typically best for high-capacity, heavy-duty settings, while fluid bed dryers offer a smaller, more cost-effective approach where solids are highly uniform.