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<div class="moz-cite-prefix">Dear Crispin and Kirk, (and I hope it
reaches Tom Reed).<br>
<br>
There are SOOOOOOO many different configurations of DD and UD that
almost anything can probably be shown. For example, a forced
high volume of air into a TLUD can provide sufficient oxygen to
consume the char that is being created. Not the normal case, but
it can be done.<br>
<br>
What is "normal" in down draft (DD) gasifiers? I am not going to
define it. But many of the important DD units have tuyeres (a
nozzle through which an air blast is delivered to a forge or blast
furnace) that are rather near the bottom of the device. This is
in contrast to having air enter at the very top of a fuel chamber
and drawn or push downward through the full stack of fuel before
reaching the hot zone that is ignited at the bottom. What the
tuyeres can do is make enough heat by putting air into the bed of
created char so that the char becomes a significant zone of
glowing hot char. And there is some heat that goes upward and
causes pyrolysis of the nearby biomass. The chamber is closed,
so there is no gas movement upward. The hot pyrolytic gases are
forced downward to the hot char where they are change / cracked /
modified to become the desirable CO and methane and H2 and "good"
gases that exit the gasifier at the bottom. Those gases can be
burned immediately or eventually be used in internal combustion
engines (usually after cooling and filtering). And as the char
is consumed, the created char from above moves into the hot
zone. And new raw fuel can be added at the top, but carefully
and when there is minimal pressure inside the gasifier.)<br>
<br>
THAT type of DD bears little resemblance to TLUD processes. <br>
<br>
But COULD a container of fuel as described by Crispin have an
ignition at the bottom and eventually convert it to charcoal with
the gases exiting the bottom, etc.? I do not doubt it. Was that
ever done in the days of making coal gas for city lighting, etc?
I have not studied that history, so I do not refute Crispin nor
ask for documentation. Many things have been done, some are
important and some are not. <br>
<br>
It is interesting that we are basically discussing what if the
basic TLUD configuration was turned upside down. Could we be
using that method to make more char? And could that become
important as a way to make biochar? That topic is wide open for
anyone who wants to look into it. <br>
<br>
I never asked Tom Reed what type of DD gasifier he was
considering when he had his inspiration for the IDD method.
Maybe he will send us a comment.<br>
<br>
And yes, Crispin and I are friends since about 2002 when I visited
him a couple of times at his home and business is Swaziland. In
case you are wondering, he is almost always argumentative,
presenting different points of view, and with supporting evidence,
often from obscure sources. Not always correct, but none of us
are. Refreshing, challenging, and generally very good-natured.
Under-estimated by many people.<br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
On 12/15/2014 6:14 PM, Crispin Pemberton-Pigott wrote:<br>
</div>
<blockquote
cite="mid:COL401-EAS29028BEC44235BFE5A6F422B16C0@phx.gbl"
type="cite">
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);">Dear Kirk</div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', 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; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);">Within the small
spaces between lumps of fuel there is normal buoyancy for the
hot air or hot gases so it circulates and convects heat
upwards, no matter what the direction of the burn. Generally for
very dry biomass this is a problem with a DD stove if an attempt
is made at the same time to make char. Either it 'cooks' a lot
of fuel at once making wet gas or it races through it and is not
able to properly pyrolyse the fuel. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', 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; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);">Consider this:
in a TLUD with a very low flow of primary air, or with damp
fuel, or a combination of the two, there is a real possibility
it just stops pyrolyzing. It is a limit. The problem is the heat
radiated (and a small amount conducted) downwards is not enough
to sustain a continuous reaction. Taking those identical
conditions and flipping it upside down one finds the pyrolysis
continues because more heat, under the same conditions, rises
into the fuel bed. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', 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; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);">At the other
extreme is the high gasification rate. If the fuel is really dry
and full of oxygen it can burn quite well with no air at all.
This was reported in the news a couple of months ago in Colorado
whereby the roots underground kept burning long after the forest
fire was 'out'. It makes charcoal doing this. It does it with a
combination of water gas shift reaction and combusting the O2 in
the carbohydrates. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', 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; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);">Well, in a DD
burner this situation arises pretty easily if the gap size is
right. When the condition arises and the fuel is setting itself
alight upward and uncontrollably, turn it upside down. It turns
into a TLUD with the heat rising away from the new fuel. That is
a second limit. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', 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; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);">So depending on
whether you want to make char, make gas and not, burn all the <span
style="font-size: initial; line-height: initial; text-align:
initial;">fuel in one go, use low or high density fuel, high
or low moisture, and importantly, high or low Oxygen content,
you choose the burner that is best suited to the range of
conditions anticipated. </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">Consider: suppose you want to run a higher air flow
rate in the physical space available and the fuel is
relatively dry and you want to make char. A DD stove would
give a good yield and work well in those conditions. An UD
would in the same conditions burn much more of the char. I
hope that is explanation enough. </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">On another note don't worry about Paul and me
yelling ultimatums at each other. We know each other very well
and have cooperated for years. He is enthusiastic which I
appreciate but sometimes gets things askew. People think we
are overly hostile but it is OK - he will tell you the same
thing. We communicate frequently and he is a guy I can count
on to want things done right. </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">As things stand, Paul put a decade into TLUD
investigation and I put it into BLDD work. I am going to post
a few small pictures showing the movement of the MPF
vertically in a DD stove fuel hopper. A significant advantage
of a DD combustor is that the secondary combustion can be
maintained directly next to the pyrolysed fuel because the
fuel is always falling against the grate. It means the
combustion is very stable once it is running. It doesn't
change for hours on end. This is very well suited to process
heating and home heating. Cooking is more difficult. </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">With a TLUD cooking is easier and and space heating
for a long time is difficult because of the refuelling. </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">I have seen drawings for a Russian combustor the fed
fuel into a conical TLUD fire that was continuous, burning on
a round steel plate that rotated slowly. It could do what a DD
burner does in terms of long term burns. </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">Regards </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;">Crispin </span></div>
<div style="width: 100%; font-size: initial; font-family: Calibri,
'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align:
initial; background-color: rgb(255, 255, 255);"><span
style="font-size: initial; line-height: initial; text-align:
initial;"><br>
</span></div>
<br>
</blockquote>
<br>
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