Materials Testing
    Fluid Bed Dryer ensures vigorous mixing

Fluid Bed Dryer

  • 5 kg of wet "ideal" sample can be dried in 15-20 minutes
  • Non-agglomerating
  • Homogeneity of sample

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What is fluid bed drying?

By forcing enough air through a bed of particles, the particle bed may assume a fluid-like state (resembling a boiling liquid). Heating the incoming air and managing air flow rate through the sample, the Model 501 Fluid Bed Dryer provides thorough mixing and maximum contact of solid with moving air. 

The result: more even and quicker drying than conventional methods.


Delivering up to 2.5m3 per minute of air, the Model 501 Fluid Bed Dryer can break up wet samples and ensure vigorous mixing and rapid moisture removal. 

5 kg of wet "ideal" sample (80% moisture) can be dried in 15-20 minutes (5 Litre tub).


Air-separated particles prevent lumps and caking, both of which make other drying processes much slower.


The high airflow rate gives:

  • high moisture removal rates at relatively low temperatures
  • thorough mixing, so no wet spots requiring extra thermal energy to penetrate
  • an air cushion between particles to reduce abrasion and particle size alteration

Homogeneity of sample

Static drying methods leave evaporation residues at the sample surface giving a heterogeneous sample. Fluid Bed Drying achieves the opposite. Mixing during Fluid Bed Drying gives homogeneous samples, making an ideal method of representative sample preparation for subsequent material analyses.


Microprocessor control of airflow, inlet air temperature and drying period coupled with fluid bed action gives highly reproducible experiments and finished samples. After preliminary experiments, a known moisture content in the final sample (ideal for tablet forming) or removal of external (surface) moisture only, may be achieved. Drying times to required moisture content may be optimised and drying patterns studied to aid scale-up and plant design. 

Without a PC connected the Model 501 Fluid Bed Dryer can run one stored program of up to 16 steps (previously downloaded from a PC),or may be used as a conventional (manually controlled) Fluid Bed Dryer. Additional features of this advanced in-lab dryer technology include: 

  • Precise airflow feedback control
  • Membrane-sealed controls to prevent the ingress of particles into the instrument
  • Reduced operating noise


The Model 501 Fluid Bed Dryer offers significant advantages over conventional drying techniques:

  • The high rates of heat and mass transfer ensure much faster and more homogeneous drying than other methods such as oven and vacuum drying
  • Drying times range from a few seconds to minutes. Complete drying is usually achieved in under 15 minutes, the exact time for a given sample, airflow rate and temperature setting are very repeatable. A uniform, reproducible, moisture content can also be achieved with the appropriate settings
  • Materials with moisture contents from a few per cent to over 80 per cent may be dried
  • The inlet air temperature range from ambient to 200°C covers the majority of drying and solvent removal operations. Due to good mixing, the sample temperature is uniform and under close control during drying. This proves advantageous when drying heat-sensitive materials or coating particles
  • Among the wide range of materials that can be processed are pharmaceuticals, chemicals, minerals, foods, coals, wood chips, plastics, resins, etc.

The high-performance characteristics of this instrument allow it to be used for many applications in addition to drying, such as:

  • Quick determination of moisture content (e.g. coal, tobacco, food products) by correlation with weight loss over 5 mins, using specified drying conditions
  • Mixing and blending of solids
  • Granulation and agglomeration
  • A rough classification of particle size (i.e. Stokes Law)

Why choose the Sherwood Scientific Model 501 Fluid Bed Dryer?

Three Dryers in one

Standalone Fluid Bed Dryer

The base unit and specified tub assembly for standalone operation.

Microprocessor control of airflow, inlet air temperature and drying period coupled with fluid bed action gives highly reproducible experiments and finished material samples. The Model 501 Fluid Bed Dryer is the latest model from Sherwood Scientific Ltd and features membrane-sealed controls to prevent particle ingress and reduced operating noise.

Programmable Fluid Bed Dryer

The base unit and specified tub assembly are connected to a PC hosting Sherwood Scientific Ltd's Fluid Bed Dryer Software programme.

The software allows control of all variable functions, data monitoring, feedback and creation of multistep drying protocols designed to dry samples in the most efficient manner. The Model 501 Fluid Bed Dryer can be programmed (via the computer interface) to step through up to 16 drying steps with the following parameters defined and controlled: Timer, Blower motor speed, and inlet air temperature. An optional pulse flow module can also be controlled using the software package. These variable parameters may be monitored and recorded throughout the drying programme. Each programme step may be terminated manually or when a preset time or condition (outlet temperature or relative humidity) has been achieved; whichever condition occurs first.

Analytical Fluid Bed Dryer

The base unit and specified analytical tub assembly (fitted with auxiliary combined temperature and relative humidity probe) are connected to a PC hosting Sherwood Scientific Ltd's Fluid Bed Dryer Software programme.

The ability to monitor in the tub (above sample) "outlet" temperature and relative humidity allows for the capture of additional data which may be used to understand better the drying behaviour of a particular material. The ability to transfer that data for post-run processing expands the scope for material drying behaviour studies, for example, material drying curve generation is possible.

How to specify your dryer and accessories

  • The user has to specify the tub together with the Inlet and Outlet Filters required for their application as follows: 
  • Material of construction: Glass or Stainless Steel 
  • Tub Volume: 5 Litre, 2 Litre or Mini-Tub (for use with Multi-Tub Base Adapter) 
  • Tub Type: Ordinary (Bags),Sealed, Analytical (GL32 side port) Dynamic Moisture Analysis, Classifier, Mini, Custom 
  • Inlet Filter: Material type, pore size Outlet Filter: Bag, Top Cap, Material type, pore size 
  • Bag Material Selection:
  • (Nylon or Terylene are normally chosen) 
  • Nylon is resistant to alkali vapours 
  • Terylene shows greater resistance to acids 
  • Polypropylene is resistant to most chemicals but degrades more rapidly (than the other two) over 100°C 
  • Nomex is an alkali tolerant material suited to sustained high-temperature drying, e.g. ~200°C

Accessories also to be specified include:

With a Pulse Flow Module (50186001) you are able to pulse air into the sample and adjust the frequency of pulsing as well as the duration of alternating between the pulsed and normal continuous flow. Pulsing the flow has been found analogous to providing external shaking and mixing. Samples which are difficult to fluidise, like long wet strands of irregularly shaped leaves of tobacco or tea, are 'blown apart' and mixed by pulsing the flow. 

The addition of a Humidity/Temperature Probe (50186500) to the Programmable Fluid Bed Dryer upgrades the instrument to an Analytical Dryer. 

RS232 Cable (92609052) for downloading program steps to the Fluid Bed Dryer and for collection of data for real-time feedback of temperature and relative humidity. 

Software (50186700) for control of variable functions, data monitoring and feedback and creation of multistep drying programs designed to dry samples in the most efficient manner and taking into account the changes in the behaviour of the material as its moisture content changes. 

The table below lists the available options for Tubs, Inlet and Outlet Filters for the M501 Programmable Fluid Bed Dryer.






2 Litre Tub and Base UnitGlass 50035006
Stainless Steel 50035005
SS 60 Mesh Support Filter (50035113) with 45 Micron Nylon Inlet Filter (50035110) as standard;

Also Available
SS 250 Mesh 50035114 

SS 500 Mesh 50035115
Large Filter Bags

Nomex 50035407
Nylon 50035400
Polypropylene 50035404
Terylene 50035402
5 Litre Tub and Base UnitGlass 50035009
Stainless Steel 50035008
Tub Assembly 5 Litre with GL32 port supplied with screw fitted blank plate
To fit Humidity Probe 50186500
Glass 50035010 (Must use Model 501 Fluid Bed Dryer to use Humidity Probe)
Multi Tub Unit
Stainless Steel Tubs
4 x 50035012
SS 60 Mesh Support Filter as standardSmall Filter Bags

Nomex 50035408
Nylon 50035401
Polypropylene 50035405
Terylene 50035403
Glass Tubs
4 x 50035013
SS 60 Mesh Support Filter (50035309) with 45 Micron Nylon Inlet Filter (50035305) as standard;
Also available 
SS 250 Mesh 50035307
SS 500 Mesh 50035308
3 Micron Polyester 50035306


5 Litre Sealed Glass Tub and Base with Clamp 
SS 60 Mesh Support Filter (50035113) with 45 Micron Nylon Inlet Filter (50035110) as standard;
Also available 
SS 250 Mesh 50035114
SS 500 Mesh 50035115
3 Micron Polyester Filter for smallest particle size 50035120
Top Cap with 45 Nylon Filter 50035020

Top Cap with SS 250 Mesh Filter 50035021

Top Cap with SS 500 Mesh Filter 50035022

Top Cap with Nylon Filter Bag 50035023

Top Cap + 3 Micron Polyester Filter 50035024
Tub Assembly 5 Litre Glass Moisture Analysis (Includes ports for sample and Humidity Probe. Both ports supplied with screw-fitted blank plates)Glass 50135020
(Must use Model 501 Fluid Bed Dryer to use Humidity Probe 50186500)
Low-Density Classifier AssemblyGlass Tub 5003504950035020 fitted as standard to Low Density Classifier
Multi Tub Unit 50035011Glass Tub 
4 x 50035033
Mini Tub, Sealed Tub, Inlet and Outlet Sets
Mini 45 Micron Nylon Filter Set 50035310
Mini 3 Micron Polyester Filter Set 50035311
Mini SS 250 Mesh Filter Set 50035312 
Mini SS 500 Mesh Filter Set 50035313 (SS 60 Mesh Support Filter (50035309) and 45 Micron Nylon Inlet Filter (50035305) as standard)

* (Includes Silicon "O" Ring and Ground Glass Flange with Clamp)

Specifying Process

The Sherwood Scientific Model 501 Fluid Bed Dryer is a Lab Scale (Bench Top) dryer with a maximum sample capacity of 5Kg. There is a wide variety of drying tubs (volume and material of construction),inlet & outlet filters, and other accessories available; both to handle as a wide range of sample types as possible and enhance the capability of the drying system. Therefore each system requires specifying in some detail to reflect individual customer requirements and sample characteristics in order to prepare an appropriate quotation.

Outlined below are prompts about the sample type and required process and hence implications for component selection: 



Sample quantity (weight and/or volume)A wet sample should occupy about 1/3 of the tub assembly volume.  As a sample dries and its density drops, its apparent volume will increase to about ½ the tub volume.  Tubs should be purchased that is 3 x the volume of the sample size.  The mini tubs are 250ml in capacity and can be used effectively on samples weighing from 5 to 50 grams per tub.  Four tubs can be dried simultaneously.
Moisture content at start of the drying processThe Model 501 Fluid Bed Dryer is designed for damp materials not slurries with free water.
Flammable Solvents presentThe Model 501 Fluid Bed Dryer is not sparked or explosion-proof.  It is not suitable for the removal of flammable solvents with low flash points.
Particle size minimum to maximum (not just average)You need to know the minimum particle size in the sample in order to choose a suitable mesh/pore size for inlet and outlet filters to prevent the sample from falling out the bottom of the tub or being blown out the top.
Tub made from glass or metalGlass is ideal for developing drying processes; you can observe the material's behaviour as it dries.  The optimum flow rate is easy to select judging by the appearance of the fluidised sample.  The operator may estimate the state of dryness, shape and particle size distribution by the appearance of the sample flowing in the tub.  Stainless Steel could be useful in the food industry where regulations may not permit the use of glass items within food production or preparation areas.
The sealed tub or filter bagSamples with a wide or bi-modal particle distribution are difficult to fluidise without sample overflow into the bag. A sealed top cap is advisable for such samples and any sample with a particle size less than 40 microns. 3-micron polyester filters can be used for mini tubs, 2 and 5-litre tubs.  These filters are effective for 5 to 25-micron particles
but greatly reduce the airflow rate through the sample. Drying times normally occurring between 10 to 30 minutes can take up to several hours. Many of the main advantages of fluid bed drying may be lost.
Simple dryerStandalone Base Unit
Multistep drying processAdd software and RS232 cable
In-time drying progress feedbackAdd Moisture/Humidity Probe which means you have to select a tub with a GL32 side port. Only the 5-litre glass tub assemblies, 500 35 010 and 501 35 020 can have an inlet for the outlet humidity and temperature probe. Only these tubs can fully utilise all the features on the M501.
Data collectionAdd software and RS232 cable
Data manipulation with drying curve generationAdd software and RS232 cable
Add sample to the dryer without removing outlet filterSpecify Dynamic Moisture Analysis tub (501 35 020)