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Crispin,<br>
<br>
The pyrolytic gases that are created at 550 C will include thase at
450 and 500 C, so the 550 C temperature does not produce only or
even mainl clean gases. Even at 700 C is will still be mainly
tarry gases.<br>
<br>
Let's see what the book say.<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 12/26/2017 11:25 AM, Crispin
Pemberton-Pigott wrote:<br>
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Dear Paul</div>
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<br>
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I am preparing a long message dealing with the earlier question
about what happens when biomass is heated in the absence of
oxygen. The 550 C comes from that investigation. </div>
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<br>
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<span style="line-height:initial">"I do not know of any studies
specifically analyzing the TLUD gases while passing through
the char layer or in the area between the char and the
secondary combustion zone. Probably has been looked at
somewhere."</span></div>
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<span style="line-height:initial"><br>
</span></div>
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<span style="line-height:initial">Riaz Ahmad a rare contributor
to this list, is looking into this. He is ýa PhD candidate in
the Biomass Key Laboratory at CAU. He has built a gasifier
that can operate as a TLUD with an ascending or descending
oxidation zone, at any oxygen level of choice. He is going to
apply the decombustion theory to reverse engineer the gases
produced to determine what fraction of the available solid
fuel just got consumed. This entails analysing the gases
before they are burned instead of after. </span></div>
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<span style="line-height:initial"><br>
</span></div>
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<span style="line-height:initial">I have a book recommended by
'my gasification expert' which I will pass along in that
message. </span></div>
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<span style="line-height:initial"><br>
</span></div>
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<span style="line-height:initial">The mix of gases produced
under different conditions is well know, actually, and forms
the basis of the distillation of biomass and coal industry. </span></div>
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<span style="line-height:initial"><br>
</span></div>
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<span style="line-height:initial">A precondition for getting a
smokeless end to a TLUD burn is that the temperature must be
above 550 so no tarry gases are formed. We must carefully
define 'smoke'. There will be CO, possibly a lot, but no
<b>visible</b><span> condensed smoke. It is obviously a
subjective assessment, but I was pleasantly surprised to see
at least some of the fires burn out very nicely. </span></span></div>
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<span style="line-height:initial"><span><br>
</span></span></div>
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<span style="line-height:initial"><span>Regards </span></span></div>
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<span style="line-height:initial"><span>Crispin </span></span></div>
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<span style="line-height:initial"><span><br>
</span></span></div>
<br>
<div>Chrispin's message below is very useful and confirms that
there are TLUDs that can end without smoke (and some are
smokey).
<br>
<br>
1. It would be useful if we could get more info from the
Indonesian testing. Which of the tested TLUDs were ending with
smoke? Not so important to know the brand names, but to study
the stove characteristics so that the causes of the smoke can be
determined and then corrected. <br>
<br>
At this point I will disagree with Crispin's explanation. This
difference of thought can be settled by science, and I am happy
if he is correct. But I offer a different PART of the
explanation.<br>
<br>
It is easy for all of us to agree that smoke from TLUDs at the
end (or at other times) is mainly because of loss of the
secondary flame. Issues are 1) insufficient gases, 2) loss of
the "pilot" or sustaining flame/spark, and factors (gust of
wind, some difference in the fuel for a moment) that cause those
situations.<br>
<br>
My scientific disagreement relates to this comment (empahsis
added):<br>
<blockquote type="cite"><span style="">they [TLUD stoves] have
produced all the tarry gases they will, and
<b><u>it has been cracked in the hot char</u></b>. </span></blockquote>
That cracking situation occurs in downdraft gasifiers that have
a hot bed of char through which the pyrlolytic gases must
past. Check those resultant (post -charcoal) gases and see
that they are quite clean and (with some filter, cooking and
maybe scrubbing) they can go to internal combustion (IC)
engines. These are clear gases, even when cooled for use in IC
engines.<br>
<br>
But the hot TLUD gases are never that clean. They are
transparent while still hot in the TLUD chamber above the
created char, but if allowed to cool, they will become visible
and will be called "smoke". Without the fire of the secondary
combustion, smoke will be emitted.<br>
<br>
The cracking of the pyrolytic gases ("smoke") requires passing
throught a much hotter bed of charcoal than is found in TLUD
stoves. (Tom Miles and probably some others can comment on the
temperatures in the char-bed of downdraft gasifiers where some
air for O2 is entering to burn (oxidize or char-gasifiy) the
char.)<br>
<br>
I do not know of any studies specifically analyzing the TLUD
gases while passing through the char layer or in the area
between the char and the secondary combustion zone. Probably
has been looked at somewhere.
<br>
<br>
Quick proof of the smokey gases in a WELL-FUNCTIONING TLUD
(which will end without any released smoke) is to extinquish the
secondary flame and see the billowing smoke. Be ready to
relight it quickly !!!!<br>
<br>
So, I am delighted with Crispin's observation about some TLUD
stove models being consistently functional without smoky
incidents at the end. Those are the vast majority of the TLUD
stoves in use. (Poorly functioning stoves do not get used or
accepted.) We are expecting TLUD stoves to have a great year in
2018 as more and more Stovers join these efforts.<br>
<br>
Season's Greetings to all !!!<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" moz-do-not-send="true">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.drtlud.com&data=02%7C01%7C%7Cfd33f7a3b92744d257e008d54c82e3a5%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636499047400175182&sdata=oKlJ1nNKoWMOt6zff%2Fi6CTYObi2hv7YNpODFZThqvEk%3D&reserved=0" moz-do-not-send="true">www.drtlud.com</a></pre>
<div class="moz-cite-prefix">On 12/25/2017 6:21 PM, Crispin
Pemberton-Pigott wrote:<br>
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<p class="MsoNormal"><span style="">Dear IH</span></p>
<p class="MsoNormal"><span style=""> </span></p>
<p class="MsoNormal"><span style="">Some TLUD’s have a
smokeless conclusion to their combustion cycle. I found
it interesting to see the difference. We were testing a
lot of stoves (30?) for the Central Java Pilot and there
are definitely two groups of TLUD’s: those that end in a
cloud of smoke that require one to jump and run, and the
others which have no smoke surge at the end at all.</span></p>
<p class="MsoNormal"><span style=""> </span></p>
<p class="MsoNormal"><span style="">It is the latter
category that are processing the biomass at a
temperature above 500C. That is the secret. When that is
done, they have produced all the tarry gases they will,
and it has been cracked in the hot char. The
distillation gases are produced immediately below the
red hot char so the processing can be above 550 at all
times once it is lit well.</span></p>
<p class="MsoNormal"><span style=""> </span></p>
<p class="MsoNormal"><span style="">This clean ending
permits the TLUD to be used indoors with ease. Many
thousands are being used following the success of the
pilot project.</span></p>
<p class="MsoNormal"><span style=""> </span></p>
<p class="MsoNormal"><span style="">Regards</span></p>
<p class="MsoNormal"><span style="">Crispin</span></p>
<p class="MsoNormal"><span style=""> </span></p>
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