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

[Kirk H.]

Crispin,
Thank you for your response.  I have not tried this, but as I think through it, it seems like a good solution.  I like that it also prevents the over-rapid pyrolysation of the last of the fuel.  I have noted that the perforated plate also reduces this over-rapid pyrolysation.  At first it confused me because it was bringing waste heat into the coals, so wouldn’t it increase this problem.  Thinking through it, it seems to me that the increase of heat in the coals would also increase the draft.  The excess heat would then exit the char upward rather than radiating downward, where it can come back to cause problems.  That is where the excess heat is going so as to reduce the over-rapid pyrolysation.  Also the plate is being cooled by the primary air, whereas without the plate the bottom of the chamber is heated and not cooled by the primary air.  The heated chamber bottom will radiate and reflect heat to the bottom of the char, over heating the very bottom layer of char.  The plate seems to keep the heating even over the entire final period of the wood flame and transition.  It is not as perfect a function as the char solution, but it is built into the stove and so works automatically and does not require any actions on the part of the cook.  One less task.
Thank you for your response, 
Kirk H.

Sent from Mail for Windows 10

From: Crispin Pemberton-Pigott
Sent: Monday, August 13, 2018 2:12 PM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] TLUD-ND transition from hydrocarbon flame to charcoalflame

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> 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.
 
Sent from Mail for Windows 10
 
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