Air fuel ratios in gasification and combustion devices

[Reedtb2@cs.com]

Dear Eric and all:

Good question on top down gasification and charcoal making.  

We aren't publishing a final tubro stove design yet because I make
"improvements" daily, some positive, some negative.  I'm attaching our latest
paper on the Turbo Stove, presented at the PITBC conference last Fall.  

Definitely a negative feature of inverted downdraft gasifiers is that once
lit, it is best to burn off all the volatiles. At that point you can

a)  Cut off all air and keep the charcoal

b)  Increase the gasification air and decrease combustion air to have a
BEAUTIFUL CO flame. The Air/FUel ratios in wood and charcoal downdraft
gasifiers (weight basis) are

Generating Volatiles                               <1.5/1
Burning Volatile Gas                                 ~5/1

Generating CO from charcoal                    6/1
Burning the CO from charcoal                    1/1   

so the air requirement in the charcoal combustion stage is the inverse of
that in the volatile combustion stage.  If nothing else, this is a big
problem in valving the air, and also for relighting the top of the pile
(charcoal) which then becomes wood.  

These are VERY important numbers.  Tattoo them on your tutu.

Forward...          TOM REED



In a message dated 2/25/01 9:00:46 AM Mountain Standard Time,
ericbj@club-internet.fr writes:

In our "inverted downdraft" (top burning) TURBO STOVE we find that we can
pack 6 inch long X 1/2 inch sticks in, light on top, and have the whole
mass
burn down to the bottom ... like your 6 inch logs in gasifier...

Most interesting.  Do you publish a design? ... N.B. 3-foot to 6-foot logs
in gasifier ...  But to re-load fuel, must one let it go out, then re-light
at the top?  If so, not so good for long periods of use.   

Dr. Thomas B. Reed, President, The Biomass Energy Foundation, 1810 Smith Rd.,
Golden, CO 80401
Email reedtb2@cs.com; www.woodgas.com; 303 278 0558 home; 303 278 0560 Fax

Turbo Stove MS-PITBC FINAL.doc