Set-Up; General Description - Techne IFB-201 Operator's Manual

Set-Up

Poor fluidisation causes hot spots, heater failure, and damage to other parts. Follow the manual
carefully. For correct fluidisation, pay attention to;
INSTALLATION
Ensure bath is level and air supply is adequate.
OPERATION
Adjust air valve for even fluidisation.
Do not insert objects larger than recommended.
Ensure objects do not lie in contact with container wall or porous plate.
MAINTENANCE
Regularly inspect and maintain air filter to eliminate oil vapour in air supply.
ALUMINA
Should the fluidised bath be stirred for a long period of time under damp or humid conditions,
moisture may be absorbed by the alumina which is hydroscopic. To avoid violent fluidisation
which occurs when damp alumina is heated above 100°C, operate the bath for a period of
approximately 8 hours at 90°C prior to operation at elevated temperatures.
NEVER ADD COLD OR DAMP ALUMINA TO A HOT BATH AS THIS WILL ALSO CAUSE
VIOLENT FLUIDISATION WHICH CAN BE DANGEROUS. Allow the bath to cool then add the
fresh alumina. If this fresh alumina is a large portion of the charge then dry the whole charge as
above.
FUME EXTRACTION
When used for processing items which may emit toxic or inflammable fumes, it is essential that
an adequate fume extraction system be installed. The extraction system must be correctly sized
to ensure that any toxic fumes are removed from the working environment.
To eliminate the risk of spontaneous ignition, the concentration of inflammable fumes above the
bath and within the exhaust duct work must be kept below the lower explosive limit.

General Description

The fluidised bath employs the principle of fluidisation of a mass of finely divided inert particles by
means of an upward flow of gas. A state of fluidisation is achieved when the individual particles
become microscopically separated from each other by the moving gas. This "fluidisation bed" of
particles has unusual properties which differ markedly from either those of the gas or those of the
solid particles. Instead, the fluidised bed behaves remarkably like liquid, exhibiting characteristics
which generally attribute to a liquid state. For example, the fluidised bed can become agitated
and bubbled; it always seeks a common level; materials of less density will float while those with
densities greater than the equivalent fluidised bed density will sink; and, most important, the heat
transfer characteristics between the fluidised bed and a solid interface can have an efficiency
approaching that of an agitated liquid.
In addition, the fluidised solid phase has a most unusual physical behaviour, in that its basic
characteristics change only slightly over very large temperature ranges; it has no melting point
and no boiling point. The lowest temperature available is the liquefaction point of the gas used for
fluidisation, while the high temperature level is the usable temperature of the inert solids. Various
metal oxides with allowable temperatures of over 1700°C are readily available. The metal oxide
beds commonly used, (eg. aluminium oxide) are non-flammable, non-explosive and non toxic.
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