[Gasification] Active charcoal

[GFWHELL at aol.com]

Regarding the activation of charcoal, I read somewhere that charcoal could  
be reactivated in a micro wave oven, If this is the case any water trapped  
within it would turn to superheated steam and push out impurities after 
which it  would simply evaporate. leaving the charcoal extremely hot??
 
GF
 
 
In a message dated 2/21/2012 7:00:10 A.M. Eastern Standard Time,  
english at kingston.net writes:

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_ 
(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#_ (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_ 
(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://www.vcharkarn.com/uploads/78/79040.pdf) 

_http://revroum.getion.ro/wp-content/uploads/2010/RRCh_6_2010/Art%2002.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_ 
(http://pacslabs.com/activatedcarbon/actesting.php) 

An  example of analyzing different AC made from bagasse:
_www.waset.org/journals/waset/v34/v34-36.pdf_ 
(http://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_ 
(http://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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