A Side-by-Side Look at Flash Drying Vs. Fluid Bed Drying

Justin Klinger, Sep 4, 2020 6:30:00 AM

flash dry vs fluid bed dry

If you’re new to the subject, or if you’re working with a new material, you may be unsure whether flash drying or fluid bed drying (also called fluidized bed drying, or FBD) is the best process for your material.

Each of these drying processes presents its own distinct advantages (and its own set of potential disadvantages in terms of efficiency, capabilities, and costs), making it more suitable for certain materials.

Your trusted toll processor should be able to not only advise you on the best process for your material and your end goal, but also to consult with you in the case of new materials, R&D, or other special challenges. 

Together with your toll processor, you can investigate, troubleshoot, and develop a customized process solution that achieves your specifications. We’ve put together this list of considerations to help you evaluate contract dryers. Before you jump into that process, let’s take a look at these two essential drying methods, what they have in common, how they differ, and what that means for you and your choices.

Fluid Bed Drying

Fluidized bed drying subjects a wet material to a rising stream of hot gas that flows through a perforated distributor plate or membrane so that the heated gas lifts and surrounds each individual particle, causing the solid material to flow freely and behave like a fluid.

This fluidizing effect enables efficient, continuous, consistent heat transfer via both conduction and convection on all surfaces of each particle. That prevents hot and cold spots in the drying process, which in turn helps maintain product quality and uniformity.

As particles dry, they rise to the top of the drying chamber, where they can be classified as they are collected.

Flash Drying

In a flash drying system, powder, granular material, filter or centrifuge cakes, or slurry is exposed to a high-temperature stream of gas moved by fans within a recirculating loop. This causes rapid evaporation, which enables quick drying of heat-sensitive materials without product degradation.

Specifically, the process of flashing surface moisture off each particle cools the drying gas, preventing the product itself from heating and degrading. The flashing process also prevents materials from agglomerating, or clumping.

Flash drying can also serve as a pre-drying process step, if needed.

Fluid Bed Drying and Flash Drying, Side by Side

These two drying methods have much in common, but there are points of divergence that make each process better for some materials and less suited for others. This table offers a starting point for evaluating a material’s suitability.

Consideration

Fluidized
Bed Drying

Flash
Drying

Typical material examples

Chemicals, pharmaceutical ingredients, dairy products, dyes and pigments, food ingredients, metallurgical materials

High-moisture food ingredients, ceramics, chemicals, starches, effluents, organic salts, sugar, dyes and pigments

Large range of capacities/batch sizing

Yes

Yes

Prevents hot/cold spots

Yes

No

Suitable for heat-sensitive products

Yes

Yes

Good for particle sizes above 50 microns

Yes

Yes

Suited for particle sizes below 50 microns

No

Yes

Suited for varied particle shapes

No

Yes

Potential product loss

Higher

Lower

Potential agglomeration

Higher

Lower

Possible particle size reduction due to attrition or impact

No

Yes

Good for sticky or very wet materials

No

Yes

Suited for removing and recovering organic solvents

No

Yes

Suited for clumped (agglomerated) materials

No

Yes

 

Special Consideration: Combustibles

Combustible materials present a risk of fire or explosion in both flash drying and fluid bed drying processes. It’s therefore essential to provide safety data sheet (SDS) information and any other experiential knowledge you have about your materials with your toll processor, so they can take appropriate preventive steps to reduce risks toward people, equipment, and materials.

After all, you rely on a toll processor for expertise — and a dedication to your bottom line — that you can trust. Their depth of knowledge and experience can make the difference between a successful product and failure, and their expertise can help you control costs to improve your own profitability. This glossary of particle technology terms is a great place to get started. Just click the link below to download, and then reach out to our experts if you have questions.

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