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Reactivating Carbon


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#1 mnbob

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Posted 25 May 2007 - 09:28 AM

I'm not sure that this is a proper topic, but here goes.
There are claims being made that activated carbon that is glued between two layers of fabric can simply be reactivated by being placed in a dryer on the high setting for 30-45 minutes.
What I'm trying to determine if that is even possible and where I could go to get some factual information. It seems highly unlikely that this can take place but I need to find resources that would support that conclusion.
The resource people I have talked with have not really provided the factual information I am trying to locate.
This request may be way off base for these forums but any information would be greatly appreciated and I can go into further detail if necessary

#2 djack77494

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Posted 25 May 2007 - 09:38 AM

mnbob,
I do not consider the "process" you describe as being highly unlikely. Rather, I think it is quite possible that some absorption/desorption could be induced.

The typical reversable absorption process is encouraged by a combination of higher pressure and lower temperature. In the reverse step, the application of reduced pressure and/or increased temperature encourage the sorbent to surrender the absorbed contaminant. The very simple process you suggest do use the application of elevated temperature in the desorption or regeneration step, so, at least in theory it should be possible. Note, however, that it may be a big jump from possible to practical.
Doug

#3 Art Montemayor

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Posted 25 May 2007 - 12:15 PM


I think you have to sit back and reflect on just exactly what "Activated" carbon is, and what it does or is supposed to do - and how it does it.

Activated carbon is an adsorbent and, as such, adsorbs selective impurities on its physical, external surface. It does this by a type of Van de Waals attraction that requires a certain degree of energy to liberate and dispel the captured contaminant molecules and return the parent activated carbon back to its state of “activation”. However – and this is a BIG however – the regeneration of the adsorbent is only effective to the degree that enough energy is supplied to dispel most – never “all” of the captured contaminants. In other words, the effective level of “activation” decreases with succeeding regenerations, until a relatively stable, operational activation level is reached. The effective adsorption level of the carbon depends on the heat energy level (temperature) supplied and its duration (total energy supplied). The higher the temperature, the better the degree of regeneration – as long as the energy duration is sufficient to dispel most of the captured impurities.

With regards to activated carbon, the usual regeneration temperatures recommended are in the range above 300 – 350 oF. Anything less than these temperatures has to be labeled as “token” regeneration and not really taken seriously. But that depends on the quantity and the type of impurities captured on the carbon. Some molecules are easier to dispel than others. If you are talking about microscopic quantities of odor molecules, then you might succeed in regenerating a percentage of the spent activated carbon by using a clothes dryer at a temperature of 250 oF. However, the resultant regenerated product will not have the expected full adsorption capacity. You are going to have to accept a reduction in its future effectiveness if its regeneration is not going to follow the regeneration temperature specifications.

What I have described is essentially what happens in an industrial adsorption unit – such as a Molecular Sieve dryer. If you do not regenerate the Mol Sieve with a temperature of around 500 – 600 oF, you should not expect to obtain an ultra-low dew point product (like 0.5 PPM vol. water content). The higher the regeneration temperature, the more thorough the regeneration and the more efficient the adsorption action of the adsorbent in the next subsequent operation.


#4 jetul

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Posted 25 June 2007 - 10:40 AM

Dear Art.,,

Pls. send me ejector vacuum calculation and KO drum sizing on below email:

jetul@rediffmail.com

thanks in advance

bye




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