[Stoves] TLUD-ND transition from hydrocarbon flame to charcoal flame

Mon Aug 13 17:48:58 CDT 2018

Dear Paul

I have seen the problem for a long time. I can suggest that if the char is a little damp, it will add a tiny bit of cleaning to the burning of very dry materials, and ‎do an even better job.

You may have noticed that Kirk and I offer very different explanations as to the cause of the effect, but there are actually two effects. I am intrigued about his solution‎ and will try it.

The two effects are: the ending of a pyrolysing burn that is not intended to continue as a char burn, and a transition from pyrolysis to a char burn.

If you have an intact memory you will recall I described the solution for the transition in the Vesto from char making to char burning. I suggest that the best solution was to increase the air supply at least a couple of minutes before the end of the pyrolysis of the bottom fuel, thus promoting the ignition of the char while there is still enough heat to go to char burning.

The reason for having a char making them burning phase in the first place was to be able to load the chamber with fuel but still burn for an extended at low power, and not to have to feed fuel in slowly. In 2003-2004 that was the motivation to have a bimodal fuel chamber with the downdrafting primary air - it permits that sequence while burning cleanly.

You may also recall the suggestion that‎ the way to have this transition to a higher air flow automatically was to make additional holes in 'the right place' and cover them with a strip of newspaper. When the fire arrives at the paper, it burns away and opens the hole at exactly the right time.

Kirk might also try that by making additional holes commensurate with the air demand of char burning, and cover them with paper placed on the bottom plate. That too will automatically open the holes at the end of pyrolysis.

If you want the firepower to remain the same, you calculate the air needed for the two very different fuels. ‎Size accordingly.

And even further, you can have the air shut off automatically if you are making char: place a perforated loose plate. Above a perforated bottom plate, elevating it with three balls of wax, such as small pieces of broken crayon. The holes must obscure each other. When the fire arrives, the wax melts and drops the plate. If it is well made, it drops theair flow to zero. You can try it with paper but sometimes that chars and leaves a small gap.

Regards
Crispin

Crispin,

That is an outstanding suggestion.   Not suggested nor tried before, as far as I know.   It will help lengthen the life of the fuel chamber in the TLUD gasifiers.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>       Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434

From: Stoves <stoves-bounces at lists.bioenergylists.org> On Behalf Of Crispin Pemberton-Pigott
Sent: Monday, August 13, 2018 4:12 PM
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] TLUD-ND transition from hydrocarbon flame to charcoal flame

Dear Kirk

Have you tried putting a layer (about 15-20mm) of char from a previous burn before putting in the fuel?  This will absorb the heat that was heating the bottom plate as the pyrolysis front arrives. The effect is to prevent the over-rapid pyrolysation of the last of the fuel, thus avoiding the excess production of gases.

Regards
Crispin
++++++

Hello Kirk,
I don't have a problem with smoky transitions, but would like to offer another solution.  In my 9" TLUD with a 24" high fuel container I use an Aluminum plate that can be loaded with pieces of charcoal or wood.  The pieces nearest the flame ignite and can be shoved into the container where they insure ignition of the smoke that rises up through the char bed.  The plate gets extremely hot and also ignites the raw wood pieces (see photo) and these can be pushed into the fuel container to extend the cooking time.  This stove usually burns at high power for about 90 minutes and if additional simmering time is needed, the charcoal or wood on the plate does the trick.  In the photo, the white material under the bricks is cast into a steel oil drain pan, and consists of Plaster, Perlite, and crushed glass.  This is an insulator, and is heavy enough to hold a steel lid on top of the body of the stove as well as provide mass so the cook has a sturdy cooking surface.  The grate is a cast iron frying pan perforated with many small drilled holes.  This grate will tolerate the use of a small fan (if required) to provide additional air if one chooses to burn some of the charcoal, but I usually dump the charcoal into a tub of water

as soon as the flames die down.

On Mon, Aug 13, 2018 at 2:05 PM Kirk H. <gkharris316 at comcast.net<mailto:gkharris316 at comcast.net>> wrote:
If there are any TLUD-ND people out there who are having problems with smoky and smelly transition from wood flame to charcoal flame, attached is a solution that works for me.

Kirk H.

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