[Gasification] Active charcoal

[Alex English]

Darius,
TLUD char is said to have good surface area and sorption properties. 
Using the TLUD camp stove you may be able to enhance this by simply 
increasing underfire air briefly at the end of the burn cycle. You will 
loose a bit of yield but you will also spike the temperature and flush 
the newly formed hot char with CO and CO2 which can have an activating 
effect.

Page 34 of 
http://www.biochar-international.org/sites/default/files/All-Biochars--Version2--Oct2009.pdf
describes a simple test that we have used to test our char. It seems to 
have some value but more public data points would be useful. Although 
our char had only one fifth the weight gain of a high quality AC they 
performed more equally in a  field trial to adsorb a toxin. Although our 
char is not made in a TLUD it does experience a brief CO-CO2 flush at 
approximately 800C .

Thanks to all for contributions to this thread.
Alex English


On 20/02/2012 11:06 PM, Bruno M. wrote:
> Hi Anand,
>
> i think you made a bunch of good ( & cheap) suggestions to Darius,
> Calcium Chloride is probably one of the cheapest ( cheaper and easier 
> to get the K2CO3),
> since it is common used as a deicing salt on roads ( up to -20°C) and also
> in household humidity absorbers ( & odor eliminator) like eg: 
> http://www.damprid.com/faq#  )
> but its very hygroscopic, need to be stored dry and in closed containers,
> so i guess you can't soak your biomass in a 25% solution and then 
> hoping it to dry in the sun
> ( in an humid climate ), but 5% may do fine.
>
> http://en.wikipedia.org/wiki/Calcium_chloride
> Safety: Calcium chloride can get very hot when mixed ( concentrated) 
> in water, and the dust is an irritant.
>
> But there are many sources of material to make charcoal from and
> even so many ways to active those carbons.
>
> My guess is too, that for good activated carbon you need to start from 
> good char,
> that means char made at higher temperatures ( higher temp then 
> normally needed for bio-char )
> 800-900 °C. & you like to have low ash content.
>
> Maybe Darius this may also be of interest to you:
> www.vcharkarn.com/uploads/78/79040.pdf
>
> http://revroum.getion.ro/wp-content/uploads/2010/RRCh_6_2010/Art%2002.pdf
>
> Ones you've done the activation step on your AC,
> you will not know HOW active your char is, compared to
> commercial AC, & that also depends on your purpose for this AC,
> so you'll need some testing of the AC.
> Here an example of a big lab specific known for his AC testing service,
> with price indication, just you know which kind of test could be done 
> on it.
> http://pacslabs.com/activatedcarbon/actesting.php
>
> An example of analyzing different AC made from bagasse:
> www.waset.org/journals/waset/v34/v34-36.pdf
>
> A rather simple but much used test, is the 'iodine number' or 'iodine 
> capacity number',
> if you do this on a before and after the activation sample you get a 
> good impression
> of how much more active area has become available.
> I guess this can be done on a small budget, and without complex apparatus.
> Here is the ASTM Designation: D4607-94
> www.czsochem.com.cn/download/ASTM%20Iodine%20test.doc
>
> you may need more tests.
>
> When we know more of the purpose of your AC, and the scale
> of your operation we may be able to give more precise advice & tips, i 
> guess.
>
> Grts
> Bruno M.
> ( chemist)

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