<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);"><span style="line-height: initial;">Dear Paul</span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">Are you saying the system described by Hirendra can't be made to work? It doesn't make a gas that can be burned without getting the water out, agreed. The gas has a high energy content. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">From the link:</span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">"TYPES OF GASIFIERS: Generally, gasifiers are of four types. i) Updraft- in which the biomass is fed from the top & air at particular BST is pushed from the bottom. The gaseous products are drawn from the top of the gasifier for cooling & cleaning. Air & biomass move in counter current direction as shown in fig-1."</span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">The sketch shows the position of the pyrolysis layer and it is not at the top, and it is covered by fuel, and you can buy one. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">The fuel is indeed placed on top in large quantities, it does not need to be added frequently (we can quibble about the meaning of 'frequent') and the MPF moves upward. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">So, what to say? I described it, Hirendra makes them, and it is described in the paper, though he was not describing his own product in detail. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">I find it interesting that you were not able to get the system to work except as you describe below. Do you think it is because of the small size? He gives as a lower limit 20 kW though when discussing the system with me he did not indicate why. As indicated in my message the gas is very wet and requires drying. You note that it was too wet to burn directly which confirms this need when operated with the MPF in the middle of the fuel pile and you changed the fueling behaviour to maintaining a thin layer on top. That is a different approach, in my view. If it is maintained continuously, how is the moisture level different? Hirendra's paper mentions that the BLUD method can deal with a 'higher fuel moisture level'. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">On reflection I don't see why it should not be bottom lit in which case it is correctly described as a bottom-lit up-draft device. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">For those with an interest, Anton Soedjarno in Yogyakarta makes a fluidised bed gasifier which is also fed from the top through a trapdoor with quite large fuel particles: 1/2 to 1/4 of an oil palm 'empty fruit bunch' (OPEFB). This approach greatly reduces the need for dealing with the tars contained in the UD gas. Anton says it doesn't make tars, actually, and it is burned directly in an engine. The pyrolysis zone heat is used to create steam in a parallel chamber to drive the process which is a pretty cool idea. The reactor is quite tall. </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">Regards </span></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);"><span style="line-height: initial;">Crispin </span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;"><br></span></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);"><span style="line-height: initial;">Dear Crispin,</span></div><div id="_originalContent" style="background-color: rgb(255, 255, 255);">
<br>
Please check my publication in <i>Boiling Point</i>, 2007 (eight
years ago), available at my website in Quick Picks or directly at<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.drtlud.com/wp-content/uploads/2012/08/BP53-Anderson-14.pdf">http://www.drtlud.com/wp-content/uploads/2012/08/BP53-Anderson-14.pdf</a><br>
<br>
It discusses both TLUD and AVUD methods. The AVUD method is the
basis of the Chip Energy Biomass Furnace (in the range of 200,000
BTU or 50 kW thermal). And I have made AVUD functional in as small
as a gallon container (4 liters). And several hundred of the Chip
Energy Biomass Grill were made and sold (with a plancha top). <br>
<br>
Contrary to what you wrote about the system that you mention:<br>
1. The new fuel on top cannot be piled on in large quantities.
Reason: The heat that rises up to the new fuel will first dry the
fuel, and then torrify and eventually pyrolyze. too much fuel to
be dried at one time results in high moisture in the gases, capable
of making them non-combustible until getting to torrification
temperatures.<br>
<br>
2. Therefore, some degree of frequent fuel feeding is needed.
Works great while the user is happy sitting there feeding
occasionally. OR if the user has the money to pay for automatic
feeding. <br>
<br>
[Now that pellets are obtained so easily in so many places, I should
probably return my attention to this type of unit plus some small
automatic fuel feeder. Related to the Chip Energy Biomass Grill.
Anyone interested in this should write to me directly off-line at
<a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a> ] <br>
<br>
3. In the AVUD processes, there is not any upward MPF (migratory
pyrolytic front) because the pyrolyzed fuel keeps collapsing onto
the lower char bed and air-inlet/grate. Also, any primary air
entering is into a bed of hot char where the O2 will be consumed,
leaving nothing of O2 to go up to the pyrolytic front, therefore no
flaming (glowing) pyrolysis as is found in TLUD stoves. Instead,
AVUD has retort style pyrolysis unless the char is being removed and
the fuel is getting low enough to receive some of the O2, which is
the case in the Chip Energy Biomass Furnace, which is a wonderful
char maker and can run 24/7 for days and days.<br>
<br>
4. This is BB gasification, which is Bottom Burning. It is not
related to being LIT at the top or at the bottom. It is Bottom
BURNING. [Anything that is Bottom LIT is by definition also Bottom
Burning, so that is why I dislike the insinuation that BLUD (which
is BBUD with static location of burning) is anything like a TLUD
technology.] <br>
<br>
Bottom BURNING is the case of virtually all gasifiers until Tom Reed
and Paal Wendelbo built TLUDs that are LIT a the top. But the
pyrolysis does NOT STAY at the top. It eventually gets to the
bottom and becomes BB (and without any further MPF activity). And
the combustion processes transition over from MPF to BB Bottom
Burning.<br>
<br>
5. You put Chakrabarti's paper at your website. <br>
<a class="moz-txt-link-freetext" href="http://www.newdawnengineering.com/website/library/Papers+Articles/Chakrabarti,%20H/BIOMASS%20GASIFICATION%20Hirendra%202013.pdf">http://www.newdawnengineering.com/website/library/Papers+Articles/Chakrabarti,%20H/BIOMASS%20GASIFICATION%20Hirendra%202013.pdf</a><br>
You are welcome to put mine from Boiling Point 2007 there also.
People correctly listen to and read what you provide, and we all
want what you write and say to be as accurate as possible.<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>
<div class="moz-cite-prefix">On 11/27/2015 3:41 PM, Crispin
Pemberton-Pigott wrote:<br>
</div>
<blockquote cite="mid:COL401-EAS48708C4C14BC7934278F938B1030@phx.gbl" type="cite">
<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">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<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>
<br>
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