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Dryer fluidized bed Biotechnology

Dryer fluidized bed

Product Code:Tornado


Need more Info? (514) 354-2511 - 1-800-463-4363

What is fluid bed drying?

A Fluid Bed is formed when a bed of particulates is transformed into a fluidlike state (resembling a boiling liquid) by forcing a gas through the bed. Perfect fluidisation occurs when the particulates are small, round, and have a uniform size, in which case the solid bed is observed to increase in volume and decrease in density as the gas is introduced showing a uniform rippled top surface.

Irregular shaped particles having a wide particle size range more commonly achieve an effect referred to as a "fountain head" with Boolean flow (the particles rise to the top in the centre of the bed and descend to the bottom on the outside of the bed). The fluid bed principle is used to advantage in heating, cooling, carrying out chemical reactions, homogenising, and drying, but the success of these applications can only be realised when the solid sample is thoroughly mixed during the process.

Thorough mixing during drying makes fluid bed drying reproducible which is not true of drying processes where the sample lies dormant. The same principles apply for our Laboratory Fluid Bed Dryer as for industrial scale units of both batch and continuous design, The Tornado can therefore be used to assess the feasibility, cost and timescale, of different materials which are considered for large scale drying.

 

The basic design

The Tornado incorporates an air pump, heating coil, temperature measurement and control, and timer. Air is drawn in through the Air Inlet filter and is passed over a 2 Kilowatt heating element and then through a support filter (which holds the weight of the sample) and the Tub Inlet Filter (which is selected to be smaller than the particle size) into the sample contained within a tub (glass or stainless), and finally through an Outlet Filter, The Outlet Filter can be a Filter Bag, the material of which is selected to be chemically inert to the emitted sample vapours, or alternately, a "sealed" Tub Assembly is available, where a filter plate seals on a silicon "0" ring (for particles less than 40 microns in size).

At the core of the instrument design lies a powerful air pump able to generate a high volume of air flow at a high back pressure, in order to initiate sample mixing when it is at its wettest, and therefore, most dense and sticky, The maximum achievable back pressure directly relates to the maximum size of wet sample which the dryer can take. Once drying commences, the density reduces and mixing becomes easier as the back pressure reduces. The powerful air pump also allows us to use finer inlet and sealed tub filters (able to accommodate particles down to 5 microns in size),

The Tornado is available in Analogue form with simple timing and temperature analogue controls and a Digital version for the most precise oftying requirements, which has a digital timer and a PID temperature controller displaying both set and actual temperatures simultaneously and able to achieve control within VC.

 

Application area where the tornado has been used
The Tornado has been used on hundreds of different sample drying applications, drying from 10 gms to 5 kilogram sample sizes. In addition, it has been used to mix solids, form a uniform coating, determine drying parameters, analyse for moisture by weight loss, form fine granular particles from agglomerates, act as a chemical reactor, and classify (separate) particulates by density, size, and surface texture.
Food Products & Technology
  • Germinated barley
  • Brewer's yeast
  • Cereals
  • Coffee
  • Grains
  • Animal food
  • Rice
  • Tea
  • Sodium Alginate
Minerals & Mining
  • Coal, Coke
  • Copper Sulphate
  • Feldspar
  • Ferrous Sulphate Hydrous
  • Limestone
  • Magnesium Sulphate hydrate
  • Peat
  • Potassium Fluoride
  • Sand
Chemical & Biochemical
  • Chenodeoxycholic Acid
  • General chemicals
  • Drying Agents
  • Ion exchange Resins
  • Sephadex Mol. Sieve
  • Dyes & Pigments
  • Phosphors & fine silica
Plastics & Resins
  • Diakon acrylic polymer
  • Granular polymer (Nibs)
  • Hydrophobic polymers
  • Hydrophilic polymers
  • Propylene-ethylene copolymers
  • Spherical polymers
Pharmaceuticals
  • Lithium carbonate
  • Cystein chloralose
  • Salicylic Acid
  • Pancreatic Bile acid and salts
  • 5 sulphosalicylic acid
  • Plant extracts

 

Drying technology

FIGURE 1

If water is added to a dry particulate sample, it is preferentially absorbed within each particle until saturation is reached, following which the moisture that is held is external to the particles Drying essentially reverses this process and similarly occurs in two stages, initially removing external moisture before reducing the moisture content within the particle.

The Stage 1 external moisture content removal occurs at a constant rate, depending on Dryer parameters of air temperature and flow rate. (The rate of external moisture removal is very similar, in fact, to the rate of water loss from a tub of water having the same air temperature and flow rate bubbling through it, in other words, the particles have very little influence on this moisture removal).

The point at which Stage 1 drying goes to Stage 2, the loss of moisture within the particle, is known as "the Critical Moisture Content" and is characteristic of each solid sample type, Unlike Stage 1, Stage 2 drying is usually diffusion dependent and is not directly influenced by flow rate or temperature of air, i.e. Dr/er parameters, To change the speed of stage 2 drying one must reduce the particle size, add alcohol (to form an azeotrope), or chemically modify the particle to effect its affinity to water. See Figure 1.

 

The drying curve

FIGURE 2

A drying curve is generated by measuring the sample weight loss (in the tub assembly) over a period of time while drying. Moisture content is determined only after the weight loss stops. This is shown in Figure 2, At the outset of drying, the sample and tub assembly come to thermal equilibrium with the air in the "Settling Down Period" after which the slope (rate of drying) is constant until the Critical Moisture Content is reached.

The Falling rate of drying corresponds to Stage 2 drying where moisture is diffusing out of the particle. The final moisture content in the solid depends on the equilibrium established between the humidity in the incoming air and that within the solid, and is usually low relative to the starting moisture content.

The actual drying curves obtained from a variety of solid samples is shown in Figure 3.
FIGURE 3

It is possible to differentiate, by inspection, the various samples based on how the moisture is held. Curves F and C are primarily all external moisture loss and very little evidence of internal moisture, Curves E and A have the moisture held within the particles, where diffusion out is relatively unhindered with E and much more difficult with A.

The determination and control of moisture levels in solids is one of the most common industrial and laboratory procedures, yet the mechanism of drying and the distinction between rate of drying of external and internal moisture is not generally appreciated since most drying methods are not sufficiently reproducible to construct a reproducible drying curve.

The Tornado Fluid Bed Dryer with its fully controllable flow, temperature and drying time and thorough sample mixing ensures highly reproducible drying which in turn allows the full characterisation of the drying process for solid samples.

 

Why choose tornado?
All laboratories carry out drying processes and there are many options to choose from, It your drying requirements are not critical, then a static oven is probably a more cost effective option for you to consider, but if you do have a critical drying requirement Fluid Bed Drying may very well be the preferred methodology, The Tornado FBD has the most powerful air pump, the most precise temperature controller, and the most optional accessories of any laboratory fluid bed dryer currently available.

 

Advantages
Fast Fluid Bed Drying normally dries up to 5 kilograms of wet solid (up to 80% Moisture Content) in 15 to 20 minutes. This is due to the large volume of air (2.5 m 3 / minute) and vigorous mixing. Conventional drying is normal done overnight to eliminate wet spots trapped within the sample.
Mild The high air flow rates ensure high rates of moisture removal even at relatively low temperatures and the thorough mixing assures no wet spots remains within the sample, The air cushion between particles reduces abrasion so that particle size is not altered during the mixing.
Non-Agglomerating The particles are separated while being dried, preventing lumps from being formed and "caking" by particles being stuck together by residues of evaporation.
Reproducible Drying Since the sample mixes while drying, drying is reproducible. Instead of having to make a sample completely dry, the operator can achieve a known moisture content in the final sample (ideal for forming tablets) or remove only the external moisture content of a sample, Drying can be achieved in the minimal time and the drying process can be studied to aid plant design, etc.
Homogeneity of Sample Static drying methods leave residues of evaporation on the surface of the sample, making the sample heterogeneous, Fluid Bed Drying is quite the opposite since it homogenises the sample during drying, making it ideal for drying a sample prior to an analysis.

When external moisture is present, it is very difficult to make a sample homogeneous in moisture content, Small samples are not representative as an indication of moisture content of the entire sample. Moisture content can be determined by weight loss using up to 5 kilograms of samples using a 5 litre tub assembly.

 

Drying performance
Materials
Initial Water Content
Solvent
Weight Dried
Drying Temp.
Time
Sawdust
21
Water
100 g
25°C
21 min.
Asbestos
58.5
Water
500 g
120°C
30 min.
Tea
33.3
Water
100 g
60°C
18 min.
Sephadex (Mole Sieve)
75
Water
500 g
55°C
15 min.
Dyestuff (5 micron)
95
Water
1000 g
100°C
40 min.
CuS04.5H20
to Monohydrate
Water
210 g
110°C
18 min.
Germinated Barley
38
Water
280 g
80°C
20 min.
Sand
22
Water
1000 g
100°C
7 min.
Diakon Acrylic polymer
10
Water
500 g
90°C
10 min.
Hydrophilic polymer
86
IPA
310 g
34°C
13 min.
Granular Polymer
75
IMS/Water
540 g
40°C
3 min.
Coal
25
Water
220 g
110°C
15 min.

 

Sealed tub assembly
Sealed Tub Assemblies are available as 5 Ltr and 250 millilitre Glass-Tubs. Samples having a wide (or bi-modal) distribution of particles are difficult to fluidise without getting some overflow of sample into the filter bag. Using a Sealed Tub Assembly, the top filter plate seals on a silicon "0" ring, retaining the sample in the tub. By selecting 3 micron inlet and outlet filters, we are now able to fluidise and dry down to 5 micron size particles. The filter size must be specified to ensure maximum drying capacity without sample loss according the requirements of the application.

 

Classifier assembly
The Classifier Assembly allows you to remove fines and classify your product by the Stokes' parameters of size, shape, and density (moisture). With vigorous mixing by air flow, opening the valve on the sampler takes a representative sample in seconds without interrupting the drying process. By gradually increasing the air flow rate, the operator can selectively remove fines or the sample which is the first to dry out, since it is less dense. The Classifier serves as an effective separator with samples having a broad range of parLicle size or bi-modal distribution. Classification is normally achieved after thoroughly drying the sample.

 

Cat. No. Description
A Working system requires a dryer, tub assembly and a filter from the table below
Instrument Options
50100200 Fluid Bed Dryer, PROGRAMMABLE, 110V, 50/60HZ
50100201 Fluid Bed Dryer, PROGRAMMABLE, 230V, 50/60HZ
Sealed Tub Assembly
50035014 5 Litre Sealed Glass Tub Assembly
50035020 Filter top cap ( Specify particle size)
50035013 300 ml Sealed Glass Tub for Multitub Assembly
The Classifier Assembly
50035049 Low Density Particle Classifier Assembly

 

Tub assembly standard options
Tub Unit
Inlet Filters
Filter Bag Materials
Sizes
Materials
 
Material Options
2 Litre
Glass (6MAS1006)
SS 60 Mesh Support filter with 45 Micron Nylon Inlet Filter as standard

Also available
SS 250 Mesh (MPS FIL 04
SS 500 Mesh (MPS FIL 05)
and 3 micron Polyester filter for
smallest particle size
Nylon
Nomex
Polypropylene
Terylene
Stainless (6MAS1005)
5 Liter
Glass (6MAS1009)
Stainless (6MAS1008)
Multi tub unit 4 x 300 ml (6MAS1011)
Glass tubs 4 x (MAS61013)
Stainless tubs 4 x (6MAS1012)

 

 

Convertisseur d'unités