Re: "Formula for Biomass" and Charcoaling....

["Das" <das@eagle-access.net>]

Tom

Welcome back.

You always bring a refreshing clarity.
I would propose that we will be able to do a lot to clear the air by
measuring four characteristics of a fuel; moisture, ash, shape, and bulk
density.  
These can be measured with the most inexpensive of tools, as little as an
inexpensive postal scale, a bathroom scale, a household oven, and a 5
gallon bucket. 

Moisture can be simply measured by pre weighing the largest sample of fuel
that can be weighed  on your small scale. Dry in  an oven at 110 C
overnight. Weight loss is moisture.  

Ash can be measured by weighing the ash remaining after a complete burn of
the fuel to white ash.  Pre clean the test stove before the test. Pre weigh
the total weight of fuel burned.   Carefully collect all the ash after the
burn for weighing. 

All biomass fuels have amazingly similar fuel content on a moisture and ash
free basis 20 - 21 MJ/kg (8,000-9,000 Btu/lb) for the reasons Tom presents
below..

Shape of fuel can be characterized by measurement of length width and
thickness reporting the mean, as well as maxiimum, minimum and standard
deviation.  Also characterize fuel as chips, pellets, brush, twig, branch,
round or split.  

Bulk density can be measured as the weight that fits in a five gallon
bucket or the likes.  Since cordwood is sold by volume, it is uncanny how
much air a skilled woodsman can stack into a cord. The true measure of
energy in solid fuels is by weight.  All of those firewood tables are
really just about relative bulk density.
 
What is it about your email format Tom It just comes up blank as email.  I
can only read your message when I reply.

A. Das
Original Sources/Biomass Energy Foundation
Box 7137, Boulder, CO 80306
das@eagle-access.net

----------
> From: Reedtb2@cs.com
> To: pverhaart@optusnet.com.au
> Cc: stoves@crest.org; gasification@crest.org
> Subject: "Formula for Biomass" and Charcoaling....
> Date: Saturday, January 05, 2002 5:51 PM
> 
Dear Piet and all:

Your formula 

C3 H4O2

suggests that we have a single molecule like cellulose, C6H10O5.  We don't.
 
Therefore I suggest you use a "ratio formula" giving the ratio of hydrogens

and oxygens to one carbon, or

C H1.33 O0.66

However, Prof. Ray Desrosiers in 1979 made an extensive study of lots of 
biomass species and came up with 

C H1.4 O0.6          (quite different from the one you gave)

I have used this for 20+ years and found it is very close for all species
of 
wood and most species of other biomass on a dry, ash free basis.  

For instance, you can write the biomass combustion equation

C H1.4 O0.6 + 1.05 (O2 + 3.76 N2) ==> CO2 + 0.7 H2O + 3.95 N2

>From this you can calculate that the air/fuel ratio for stoiciometric
biomass 
combustion is 6.3.    (Perfect adiabatic gasification is then 1/4 of that).
 
etc. etc.    
                                            ~~~~~~~~~~~~~~~
Incidentally, I am soon going to re-issue the 400 page book published at
that 
time which still exceeds most of what I find written today.

Incidentally your friend was correct that charcoal making is approximately 
driving off the water...   Using the above formula I get

C H1.4 O0.6 = C 0.6(H2O) H0.2 ==> All the degrees of charcoal in the order

Torrefied wood; Sea Sweep (oil absorbent); Cooking charcoal; mettalurgical 
charcoal; activated charcoal

corresponding to driving off 0.1, 0.2 etc. waters.... at temperatures of 
275; 360; 425; 600 and 800 C.  

Yours truly,              TOM REED



In a message dated 1/3/02 11:22:40 PM Mountain Standard Time, 
pverhaart@optusnet.com.au writes:


> 
> Stove dried wood contains about 50% carbon (at least I think that was the

> rule of thumb we adopted). Next we assumed the rest was H and O in the 
> proportion of water. This gives .
> Nobody suggests this is accurate but works in the world of stovers.
> There was a staff member at Eindhoven (not in our faculty, I am happy to 
> say), who explained the charcoal making process as driving off the water.
> If things were only that simple.
> 
> Piet
> 




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