5.5.6. Active carbon adsorbers


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Fig. 5.31: Op. plan of a
BOGE active carbon adsorber Type DC
After passing through high-performance filters and dryers, the technically oil-free compressed air still contains hydrocarbons and diverse odorous and taste substances. There are many applications of pneumatics where these residues would lead to disruptions of production, adverse quality and unpleasant smells.

An active carbon adsorber removes the hydrocarbon vapours from the compressed air. The residual oil-content can be reduced to 0.003 mg/m³. The quality of the compressed air is better than that required for breathing air by DIN 3188. The condensated droplets of oil are already removed by the series-connected filter (BOGE-Microfilter Series F).


Operating principle

The filtration of compressed air by adsorption is a purely physical process. The hydrocarbons are bound to the active carbons by powers of adhesion (uneven molecular attraction ). Chemical compounding does not take place in this process.

The dried and filtered compressed air is directed through a diffusor into the loosely piled active carbon bed. The diffusor distributes the compressed air evenly over the entire bed. This allows long contact times and ideal use of the adsorption material. After the adsorber bed the compressed air passes through emission collector and leaves the active carbon adsorber.


Features
    • Pre-filtration.
      An active carbon filter must always be connected upstream from a high-performance filter and a dryer. Unfiltered compressed air destroys the adsorbant and reduces the filtration effect.
    • After-filtration.
      For safety reasons a high performance filter should be connected downstream from the adsorber. The compressed air take very fine particles of carbon dust (smaller than 1 µm) from the active carbon bed with it.
    • No Regeneration.
      The active carbon filling can not be regenerated. It must be replaced, depending on the degree of saturation.
    • Long working life.
      The active carbon filling must only be replaced after 8000 - 10000 hours of operation.

Areas of application
    • As for active carbon filters.