[Stoves] Tar in P-Gas

[Otto Formo]

Dear Dean and all,

What type of fuel did you use?

I guess, most likely pellets or woodchips from pine, which contain a lot of tar.
Paal`s experience with the Oorja (forced draft) at full trottle, was a lot of ash and soot in the air as well.
Because of the forced added primary air by the fan, all of the charcoal was burned completely and ash was forced out of the combustion chamber into the room.

In the Peko Pe, which is not "just a TLUD", but a natural draft gasifier, the biomass is turned into excellent biochar, or if you like, can be used for simmering in an ordinary and traditional Mbawula (brazier)

We are just back from Zambia and have started to burn corncobs in the Peko Pe, which contain little or hardly any tar, as far as I know.
The cobs was burning nice and cleanly in the Peko Pe and to our surprise for quite a long time giving a suitable biochar at the end of the process, very promising.
The moistre in the cobs was less than 10% and was burning with a clear flame for more than 1/2 hour.
We also tested the chared cobs in a traditional Mbawula and they were glowing for another hour, boiling the water continously, also very promising as housholdenergy for the peri- and urban settings.

We are now going to test the Jatroha cake in the Peko Pe, as well.

We feel corncobs, is very much the answer to both rural and urban fuel to be used in a proper gasifier, like the Peko Pe.
Any type of biomass with low content of tar, will not give you problems in that sense you are mentioning here, unless you used forced draft or open up for more primary air.

As long as you do not burn the charcoal in the combustion chamber, I belive you should experience the same in your TLUD, Dean, which is not a Peko Pe.

Paal has spend more than twenty years, testing and experimenting with his Peko Pe, and you people think you can copy such an effort within just weeks?

Stay tuned................

Otto
Still a Peko Pe fan, without a fan........


> From: Dean Still [deankstill at gmail.com]
> Sent: 2011-12-10 20:51:06 CET
> To: Thomas Reed [tombreed2010 at gmail.com], Discussion of biomass cooking stoves [stoves at lists.bioenergylists.org]
> Subject: Re: [Stoves] Tar in P-Gas
> 
> 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
> >