Dear Julien and others,
First, Crispin is so quick that I did not have a chance to say what
would have been precisely what he wrote. Spot on.
Second, the experiment has provided the "bookend" experience for slowing
the pyrolysis. The "bookend" of experience for doing the pyrolysis
much faster has also been done and reported here recently. Now Julien
and the collective "we" have a better understanding of control of the
process.
So, repeat with the same fuel packed the same way but with controllable
primary air. Also good to be able to do a coarse adjustment of the
secondary air to prevent the gases from being too diluted. Do not
expect an hour of gas making. But if the grass/straw (or small reeds
as seen in the Wendelbo videos) are properly "managed" in the gasifier,
you will gradually close in on a solution. (I did not say THE
solution, because there could be others, but you (we) only need one that
works.)
You are in new territory, and at the frontier. Reed, Wendelbo,
Anderson, English, Larson, Mukunda, Belonio, Pemberton-Pigott, and
certainly others have also been at that frontier. BUT, with the
possible exception of Wendelbo who used reedy grasses and not your
straw, the others did their work with different fuels. Many of us
"experimented" with grasses and were not successful, and we accepted
success with different fuels. But dedication can have its pay-back.
The classic example is Belonio who was shown an early TLUD and told that
it could not work with rice husks. (The presenter should have said
"has not yet been shown to work with rice husks.) But Alexis LOVES rice
husks, and took up the challenge, and succeeded. And we hope that will
be your story also.
So, Julien (and others), lead on!!!!!!! We need you and more people
like you to push the frontiers of micro-gasification.
I have said before: "I believe that perhaps 20% of what is to be
learned about TLUD and other micro-gasification is currently known."
Maybe it is now 25%??? Certainly not 40% or more. So much to do!
And be sure to keep us all well informed. When appropriate, there are
websites (mine for drtlud.com and the one for Stoves) what are available
to place more substantial documents. But for the time being, keep the
discussion going on the Stoves Listserv.
Best wishes,
Paul
Paul S. Anderson, PhD aka "Dr TLUD"
Email: [email protected] Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 4/4/2013 9:40 PM, Crispin Pemberton-Pigott wrote:
Dear Julien
Crispin offered me the following advice for burning wheat straw in a
gasifier cookstove:
"It sounds like you could afford to reduce the primary air supply. If you
have things right you should be able to turn it off completely. If you are
able to generate a condition that is primary-air-starved, you can then
regulate it."
Following that advice, I packed the paint can with as much straw as I
could. I put the can on top a paint-can lid which blocked off all primary
air.
That is a good example of total control.
Now you can make a controllable hole that allows you to admit a lot of air
(whatever that means) to get it lighted and then restrict it to an
appropriate level. The result will be continuous gas production.
How much air later? At that size I would guess 1 or 6 holes 6mm diameter but
Paul Anderson should comment here. He built these 10 years ago and have
little tubes coming out the side with several small holes which he could
close individually with tape.
The point is to explore the relationship between primary air supply and the
production of burnable gases.
Because the weather is still cold it is hard to know if what you were trying
to ignite was steam (or how much was steam) and how much was smoke. If it
was not pyrolysing at a high enough rate the secondary air may have diluted
it below the concentration needed for ignition.
The news is that you went from a 5 minute burn to more than an hour. Next
you need to get the burn you want which will be in between. The primary air
supply is all the difference. The secondary air needed depends on the gas
production rate.
It is not all that complicated. The vast majority of stoves have far too
much excess air at the primary and secondary level so the first thing to get
a grip on is the air/fuel ratio (just like a car engine which is why
combustion analysers report the air/fuel ratio).
Regards
Crispin
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