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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