Fume Cleaning - Techne IFB-121 Operator's Manual

Fume Cleaning

When used for processing items which may emit toxic or inflammable fumes, it is essential that an
adequate fume extraction system be installed. A typical schematic diagram of such a system is shown in
the appendix; the system consists of the following components:-
Ductwork to connect the fluidised bath extract duct via the various fume treatment equipment to the
input of the fume extraction fan. The ductwork should include an air dilution tee, positioned as close as
possible to the fluidised bath. The dilution tee enables the fumes within the system to be diluted with
air. The ductwork should also include a damper valve which is normally positioned adjacent to the
extraction fan. This valve allows the extraction velocity to be reduced. In general the ductwork may be
manufactured out of galvanised mild steel; however, in installations where PVC or other halogenated
polymers are being processed, it is recommended that stainless steel ducting is used.
The ductwork should be as short as possible and contain the minimum number of bends and horizontal
runs so as to reduce the possibility of a blockage.
A cyclone separator should be mounted directly after the dilution tee. The cyclone removes any fluidised
medium that may be present in the extracted fumes. The fluidised medium is collected in the cyclone
collection bin from where it may be returned to the fluidised bath.
In applications where the components being cleaned are contaminated by polymers which contain
inorganic pigments or fillers such as titanium oxide, of a particle size less than 0.005mm diameter which
will not be retained by the cyclone, it is recommended that a filtration system be fitted after the cyclone.
In applications where the materials being treated produce acidic vapours during thermal decomposition,
it is recommended that a fume scrubber be utilised to ensure that the final fume emission from the plant
conforms with local regulations. A caustic dosing system may also be required to ensure that the
scrubbing liquid is maintained at an acceptable pH level.
An extraction fan is required in all applications to provide the motive force for the exhaust. In applications
where it is not permissible to emit visible smoke from the plant or where local regulations specify the
maximum fume concentrations that may be emitted from an exhaust stack, an afterburner may be
required. The afterburner heats the fumes to a point where thermal incineration eliminates the visible
content of the fumes while reducing the fume concentration.Finally, an exhaust stack is required to direct
the treated fumes away from the working environment. The exhaust stack will generally be
manufactured out of the same materials as the ductwork system. However, in installations where an
afterburner is fitted, the exhaust stack should be manufactured out of insulated stainless steel.
The exact combination of fume treatment components required depends upon the application and local
conditions. Technical staff are available to discuss particular applications and offer advice as to which
combination is required.
Techne are able to offer the following fume treatment equipment:
Cyclone
Scrubber
Caustic Doser
Extraction Fan
Afterburner
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