[Stoves] Tar in P-Gas

Dean Still deankstill at gmail.com
Sat Dec 10 13:51:06 CST 2011


Hi Tom!

Miss you. Your experiment with tar brings up a question.

So far I've been trying to get as clean as possible and as efficient heat
transfer as possible in TLUDs tuned under the emission hood. So we add just
enough secondary air for clean but not too much that cools gases contacting
the pot. We add a lot of primary air to have the made charcoal burn hot
enough to keep the pot simmering above 93C so all fuel is useful in the
cooking task. That means we can see 50% heat transfer and clean combustion
with a variety of fuels.

I remember your experiments with taking made gas and burning in a separate
burner. A team at Stove Camp got a continual flame for about an hour but we
have a long way to go to get this kind of stove to really work. Lots of tar!

Do you think we should we continue or concentrate on a TLUD approach? Larry
has found the made gas to burner to be too persnickety for home cooking.

Best,

Dean

On Sat, Dec 10, 2011 at 9:00 AM, Thomas Reed <tombreed2010 at gmail.com> wrote:

> Dear Pyrolysers (P-Guys)
>
> Having defined the difference between Woodgas and pyrolysis gas this
> morning, I was inspired to measure the tar content of the gas.
>
> In a 3 1/4 D X 5 1/2 High can, I drilled only four 3/32" primary air holes
> 1/2" above the bottom.  I half filled it with dry wood chips which I then
> lit, giving a modest generation of P-gas, burning about 2.0 g/ min.
>
> I then held a weighed 200 ml Pyrex Becker filled with 150 ml of water down
> in the smoke for one minute.  It collected 63 mg of yellow, sticky, smelly
> tar.  This is 3.1% of the wood that burned during the minute.  The tar
> level may be higher, since probably not all of the tar condensed.
>
> The P-Gasifier was operated at a low superficial velocity to avoid
> asphyxiation.  It may well be that levels are lower in % at higher
> operating levels, though the magnitude will only increase.
>
>
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> Not much speculation here.
>
> Tom Reed
>
> Aka
>
>
> Dr Thomas B Reed
> The Biomass Energy Foundation
> www.Woodgas.co
>
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