VOC abatement in Activated Carbon

[AlexEss]

Good Morning All

Is there a simple 'Rule of Thumb' for estimating the volume of an activated carbon bed, based upon the VOC loading of the airstream ?
The VOC in my case is Ethanol in gaseous form, resulting from a spray coating system, which is exhausted to atmosphere via an exhaust fan and stack, after passing through a dust filter.
To give some numbers:
- Flow = 1200 scfm, VOC loading = 160 ppmv, Working Temp = 90 deg F
or in S.I. = ( c. 750 Nm3/hr & 300mg / Nm3 VOC @ 30 deg C )
Ethanol is 46 g/mol
What area or mass of Activated Carbon should I be considering for VOC removal ? I would like to assume a minimum of 500 working hours before replacement or regeneration.

All advice gratefully received.

Thanks

AlexEss

 

[pierreick]

Hi,
Consider the resource attached.
note :
1:AC bed is subject to self-ignition when the amount of organic is reaching is critical mass . A temperature monitoring is needed 24/7 .
2:In some countries disposal of activated carbon is not possible , make sure you or your supplier can treat or dispose the material after use .
3: Why not considering a wet scrubber ? here again you need to be able to eliminate the spent solution .

Hope this is helping you .
Pierre

 

[AlexEss]

Thanks Pierre for your reply, and for the interesting attachment.

Regards

AlexEss

 

[ChemE2014]

Alcohols (like ethanol) are generally not considered a good application for activated carbon. This is due to a low molecular weight, low boiling point and high vapor pressure. The adsorption of alcohols is highly dependent on relative humidity (moisture content) of the vapor stream. The higher the humidity, the worse it gets.
The carbon manufacturers have special software for modeling GAC usage for adsorbing different components, they would be able to confirm how quickly you'll be using and replacing carbon canisters.
Unfortunately I haven't found a good simple answer for this sort of application.