<html><head></head><body bgcolor="#FFFFFF" text="#000000" lang="en-GB" style="background-color: rgb(255, 255, 255); line-height: initial;"> <div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Dear Paul</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">There is another way to operate the TLUD which is what the aforementioned Hirendra Chakbarti's company makes. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Start the stove in the regular manner. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">When the pyrolytic front is well established start loading fuel on top but not a thin layer - lots. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The MPF burns to the bottom and the ignited bottom of the net fuel burns upwards. For a short time it has two fronts. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The bottom burns out and the char and turns all to ash. The upper MPF moves upwards without flaming. New fuel is added on top to keep the front buried in the pile. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">After some time the bottom is opened on the side and ash withdrawn, dropping the pile with the MPF somewhere above the ash and under the raw fuel. More fuel is dumped in top. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">This produces gas which is very wet. The gas is drawn off by a pipe and cooled to remove the water. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">The process is continuous. It can be controlled by means of the primary air flow. There is no secondary air as the combustion is elsewhere. In a stable operating condition it is a BLUD gasifier that can be operated continuously. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">It is the inversion of the Cambodian rice hull gasifiers I described a couple of years ago. Those feed the fuel in from the bottom and take the rice hull char off the top with the gas going up, and the MPF going down. It also runs continuously. Both can be fueled episodically. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Regards </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Crispin thinking this BLUD approach has not been tried within this group of experimenters. </div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div id="_originalContent" style="background-color: rgb(255, 255, 255);">
<div class="moz-cite-prefix">On 11/27/2015 12:10 PM, Ronal W. Larson
wrote:<br>
</div>
<blockquote cite="mid:234A8C82-CD92-46AA-85E6-4CC99B59AD83@comcast.net" type="cite">
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charset=windows-1252">
<div class="">4. Here is an idea that I wonder if you (anyone)
has tried. (I haven’t) </div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>a.
Start a TLUD in the normal way - maximum primary air may be
best (since mostly we want high power only at the beginning).</div>
<span class="Apple-tab-span" style="white-space:pre"> </span>b.
As soon as the pyrolysis front is clearly well established - then
add a “thin” layer of the same (?) combustibles on the top.
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>c.
There should be no ignition at the bottom of the new layer, as
there is no oxygen there. But new pyrolysis should occur - so
increased power. The top of the new added layer could ignite,
if there is plenty of secondary air there. </div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>The
down side of this is that you probably need to control the
secondary air so that you don’t have too much latterm Most os
us never do this. But there could be some inherent control of
the secondary (that secondary follows primary naturally)..</div>
<br>
</blockquote>
This has been done many many times. It is a way to extend the
duration of the TLUD operation. You are correct that causes an
increase in the pyrolytic gas creation but does not increase
secondary air (except through increase of draft from more burning
gases). It is a good way to put soot on the bottom of the pot.
Note that this is anoxic pyrolysis via the heat, with no small
flames (glowing pyrolysis) present as is found in the MPF (migratory
pyrolytic front).<br>
<br>
Actually two conditions are possible.<br>
1. As you describe, while the MPF is also functional and
descending.<br>
2. After the MPF reaches the bottom (and stops because it
transitions into char-burning at the bottom). This is how people
make their unit become "continuous" (at least until it chokes up
with too much char or ash). But it requires the very frequent
attention to the feeding of the fuel, thereby losing one of the
desired aspects of TLUD batch operation (consistent flame without
needing to add more fuel during the batch time of the MPF).<br>
<br>
Therefore, what you describe certainly has been and is frequently
done. Actually, I did that in the testing in 2005 that won the Cat
Pee award at Aprovecho. Then I did not understand it fully.
Trickle feeding of fuel into TLUD stoves does work, has pros and
cons, and is likely to be done by some individuals with or without
their understanding of why or how it works and its limitations.<br>
<br>
Paul<br>
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