Fluid Bed Dryer

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.

Fast

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).

Non-agglomerating

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

Mild

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.

Reproducible

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

Advantages

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.

* (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: