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Crispin, (Friends are not required to agree.)<br>
<br>
Some of what you wrote is correct, but you go too far or leave out
some important distinctions, thereby implying that some things are
equal, that is, some are not really as worthy and distinctive as
others (Ron and Paul) have stated. I give you four cases:<br>
<br>
1. Pyrolysis progresses (migrates) through a piece or pile of
biomass as heat is able to penetrate. True. The Adam retort (and
other retorts) heat the biomass from many sides, but there is no
flame (actual combustion) inside. It is a stretch of language to
say that the pyrolysis in the retort
<blockquote type="cite"><span style="font-size:initial;
text-align:initial; line-height:initial">has an MPF [migrating
pyrolytic front] proceeding in a roughly horizontal direction.</span></blockquote>
Sorry, that should say "has external heating proceeding inward from
several directions from the sides toward the center." It is no
more of a "front" than having the heat in a home reach to the center
of the house from all of the furnace duct registers in each room.
Furthermore, the processes in a retort are in sequential order
during numerous minutes to 1) heat virtually all of the biomass to
drive off the moisture, then 2) add more heat to virtually all of
the biomass to drive off the low-temperature volatiles to create
torrified material, and than 3) to finally get the temperature hot
enough to have actual pryrolysis, first in the 400 deg C range and
then at higher temperatures if the external heating is continued.<br>
<br>
In sharp contrast, in a TLUD there is a distinctive zone of a few cm
depth with actual small amounts of combustion (of some of the
initial offgases). That zone migrates through the pile of biomass,
heating mainly by radiation a small layer of biomass below the MPF,
then with pyrolysis at a rather uniform temperature (generally from
450 to 700 C, depending on USER CONTROLED flow of primary air) to
create the char as the gases move upward.<br>
<br>
You may choose to try to equate the two descriptions above, but that
would diminish your credibility as a precision-seeking scientist.
And to equate a smouldering tree stump to MPF is a stretch beyond a
stretch. Yes, there is fire there, and yes there is pyrolysis
occuring. But such comparison is akin to saying that a ladybug and
a moose are the same because both are living creatures; and in fact
both are animals. Even a petunia and a whale are both living
organisms. Scientific comparisons need precision and detail.<br>
<br>
2. Ron correctly pointed out that in normal operation of TLUD
stoves, there is zero O2 that gets past the MPF. That is vastly
different from having so much primary air enter (as in Rocket stoves
and other burners) that there is O2 moving upward above the fuel
(where the gases were created). You are saying that is good as
preheated secondary O2. Maybe, but not really. It is simply
inadequate combustion, with the results of undesirable emissions.
The excessive primary air (which you state should be secondary air)
has had a cooling effect on the raw fuel that the combustion is
trying to get hot enough to give off the pyrolytic gases. In other
words, that secondary air that has passed over the fuel is part of
the problem, not part of a solution because it has taken heat away
from the fuel.<br>
<br>
Your statements therefore are misleading, and a dis-service to any
novice trying to understand the important differences about where
and how primary and secondary air enters and performs. <br>
<br>
3. Tertiary air: Defined as either 1) the needed secondary air
that did not get into the combustion zone soon enough (meaning that
there was poor stove design) or 2) excess air that will lower the
temperature of the hot gases (meaning that this "tertiary air" was
NOT needed nor part of the combustion process). <br>
<br>
Either way, the concept of "tertiary air" is bogus in the context of
cookstove combustion. The objective is to get the combustion to be
complete with the proper amounts of primary and secondary air at the
correct times and places.<br>
<br>
4. You wrote:
<blockquote type="cite"><span style="font-size:initial;
text-align:initial; line-height:initial">This [MPF} process is
... how the Terra Preta soils in the Amazon were created over
20,000 years of slash and burn agriculture. </span></blockquote>
The origins of Terra Preta are still being debated by the experts in
that field, which is certainly not your claimed field of expertise.<br>
<blockquote type="cite"><span style="font-size:initial;
text-align:initial; line-height:initial">The Amerindians
cultivated land that was already productive, they did not create
it <i>de novo</i>. Cecil confirms they farm patches of land
that are already productive, not random areas. He observed this
when he was doing PhD field research while
</span><span style="font-size:initial; line-height:initial;
text-align:initial">at Harvard. <br>
</span></blockquote>
I have great respect for Cecil Cook. But somehow what you have
attributed to him and his work has not reach my attention
previously. And I do not accept your statements. What happened
thousands of years ago was not witnessed by Cecil. He could only
observe the current day activities on lands that somehow became
fertile. You can take that topic to the Biochar Listserv, if you
want to discuss it further. <br>
<br>
Sorry, I reject much of what you wrote. I would not want you to be
instructing people about TLUD stoves and char making and Terra
Preta. IMHO, your comments about pyrolysis in different devices
reflect poorly on your credibikity regarding your other strongly
expressed positions, but that is a topic for others to discuss.<br>
<br>
Paul<br>
<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 12/9/2017 9:03 PM, Crispin
Pemberton-Pigott wrote:<br>
</div>
<blockquote type="cite"
cite="mid:MWHPR22MB0784AF161D2089DEBF3E3D99B1360@MWHPR22MB0784.namprd22.prod.outlook.com">
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Dear Ron</div>
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I see no systematic differences between the uses of the terms.
You are trying to create some special meaning for quite ordinary
processes of combustion. </div>
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<br>
</div>
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It is unfortunate you mix baseless assertions, projections of
motive onto others and micro-aggressions into your erroneous
analyses and combustion theory. It is wearying trying to
separate your mistakes from your agendas. </div>
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<br>
</div>
<div style="width:100%; font-size:initial;
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For the rest of our readers, these definitions may be useful:</div>
<div style="width:100%; font-size:initial;
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color:rgb(31,73,125); text-align:initial;
background-color:rgb(255,255,255)">
<span style="font-size:initial; text-align:initial;
line-height:initial"><br>
</span></div>
<div style="width:100%; font-size:initial;
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color:rgb(31,73,125); text-align:initial;
background-color:rgb(255,255,255)">
<span style="font-size:initial; text-align:initial;
line-height:initial">Primary air refers to that atmospheric
oxygen used to convert a combustible fuel into a gaseous state
through thermal decomposition. It is needed to combust gaseous
fuels if the gas is not composed of molecules that can be
oxidised directly (evaporated kerosene, for example).</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;
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<span style="font-size:initial; text-align:initial;
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="font-size:initial; text-align:initial;
line-height:initial">Secondary air is that atmospheric oxygen
which is used to combust those gases at some location
generally distinct from the solid fuel. </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="font-size:initial; text-align:initial;
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="font-size:initial; text-align:initial;
line-height:initial">Tertiary air is that atmospheric oxygen
separately added to the gas combustion phase in order to
complete the combustion and or to moderate the gas
temperature to fall within some desired range (for example a
low-NOx burner or a fish dryer).</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="font-size:initial; text-align:initial;
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="font-size:initial; text-align:initial;
line-height:initial">While a TLUD's migrating pyrolytic front
(MPF) can produce char from biomass, there are other methods
of doing so. Two that have a higher theoretical char yield
are the charcoal kilns designed by Chris Adams (the Adam
Retort) and the World Stove. Their working principles are not
the same as the TLUD. Both produce a combustible gas that is
applied to a process outside the charring of biomass. </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="font-size:initial; text-align:initial;
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="font-size:initial; text-align:initial;
line-height:initial">In the char producing section of the
Adam Retort there is no primary air supplied at all but it
still has an MPF proceeding in a roughly horizontal direction.
The World Stove supplies some primary air in the beginning but
only secondary air later. Still later, primary air is again
supplied if the operator wishes to burn the char produced. </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="font-size:initial; text-align:initial;
line-height:initial"><br>
</span></div>
<div style="width:100%; font-size:initial;
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color:rgb(31,73,125); text-align:initial;
background-color:rgb(255,255,255)">
<span style="font-size:initial; text-align:initial;
line-height:initial">All three of these approaches have proven
effective. Of the three, the Adam Retort has the highest char
production fraction per kg of input material, the widest range
of usable materials and the least possible preparation
required. The seven drum kiln designed by Dr AD Karve operates
on the same principles and is specialised to char leaves. A
small percentage of the fuel ends up in the ground as
biochar. </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="font-size:initial; text-align:initial;
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="font-size:initial; text-align:initial;
line-height:initial">A higher fraction of the char ends up in
the ground when it is produced using the earth pit charcoal
production process. I have not seen this discussed on the
Stoves list. An investigation by Cecil Cook in Mozambique into
the ultimate destination of char conducted while working for
ProBEC/GTZ showed that a considerable fraction of char
produced ended up under the pot and the rest ended up on or in
the ground, which you have termed variously as 'sequestration'
and some form of fertilization. </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="font-size:initial; text-align:initial;
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="font-size:initial; text-align:initial;
line-height:initial">There is nothing magical or new about an
MPF and it does not need a special vocabulary to describe it.
In Southern California the devastating forest fires are
leaving behind millions of smouldering tree stumps each of
which has an MPF moving along its stump and major underground
roots. This process is as old as fire. It is how the Terra
Preta soils in the Amazon were created over 20,000 years of
slash and burn agriculture. The Amerindians cultivated land
that was already productive, they did not create it <i>de
novo</i>. Cecil confirms they farm patches of land that are
already productive, not random areas. He observed this when he
was doing PhD field research while
</span><span style="font-size:initial; line-height:initial;
text-align:initial">at Harvard. </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="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,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 hope others can get contribute to
especially the technical aspects of the discussion. I will
close with a reminder that the highest char production
fraction I have encountered (45%) is the Hawaiian pressurised
kiln which uses a controlled primary air supply and an MPF to
char a five foot long log one foot in diameter in 45 minutes.
"45 in 45". </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="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,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">Amazing. </span></div>
<div style="width:100%; font-size:initial;
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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;
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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;
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color:rgb(31,73,125); text-align:initial;
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<span style="font-size:initial; line-height:initial;
text-align:initial">Crispin </span>
</div>
<br>
</blockquote>
Ron Larson wrote: <br>
<blockquote type="cite"
cite="mid:MWHPR22MB0784AF161D2089DEBF3E3D99B1360@MWHPR22MB0784.namprd22.prod.outlook.com">
<div>
<div class="">Todd:</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>Thanks
for the comment. I urge readers to visit <a
href="https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.silverfire.us%2F&data=02%7C01%7C%7C2f4e87e571974e97b4cf08d53f3a03ae%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636484440759723211&sdata=2uvPfW50fAZhf81ZYqCzad40wiN2th9I1xzu7%2BCy7wM%3D&reserved=0"
class="" moz-do-not-send="true">https://www.silverfire.us/</a>.
Some nice looking designs.</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>I
can’t quite accept your message below (and one from Crispin
that we received 1:23 hours later). You are both using the
terms primary and secondary in a different (not wrong - just
different) sense from those of us interested in char-making.
We char-makers (or at least the TLUD design - Nat Mulcahy and
World Stove have a still different meaning to this
nomenclature) use primary air (meaning oxygen) as something
that is totally depleted at/near the pyrolysis front. No
oxygen in the exiting pyrolysis gases, where they are met by
secondary air (oxygen). </div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>I
am pretty sure you and Crispin (who is also discussing
char-using stoves) do not mean the above. Rather “primary”
means plenty of air (controllable to a minimum degree) to both
create and consume char. Your and most Rockets (regardless of
pre-heating) find char to be a defect; you would have
preferred to consume it, I believe. (I’d love to hear that you
welcome the char.) So your “secondary” is to be sure that the
“small” amount of uncombusted gases leaving the fuel bed are
combusted. I am NOT disputing your phrase below (“Secondary
combustion
<i class="">is possible </i>with a rocket stove”). I am only
saying that secondary air is mandatory with TLUDs, and has a
totally different function than “primary” air. Most of your
primary air consumes char.</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>The
dialog between Paul and myself below on secondary air is
different than your own explanation below on its preheating.</div>
<div class=""><br class="">
</div>
<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>Do
we agree that the terms “primary” and “secondary” have very
different meanings in these two different parts of the stove
world?</div>
<div class=""><br class="">
</div>
<div class="">Ron</div>
<div class=""><br class="">
</div>
<br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Dec 9, 2017, at 12:32 AM, Todd Albi <<a
href="mailto:todd.r.albi@gmail.com" class=""
moz-do-not-send="true">todd.r.albi@gmail.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div dir="ltr" class="">Ron:
<div class=""><br class="">
</div>
<div class="">Not quite correct. Secondary combustion<i
class=""> is possible</i> with a rocket stove. Our
Survivor Rocket stove launched 5 years ago introduced
preheated ventilation ductwork at launch. In fact we
only offer a primary & secondary combustion design
rocket stove. Thats why our stove incorporates 360
degree ventilation through base of stove, tied to
ventilation ductwork behind combustion chamber walls.
The double insulated walls allow preheated air to
travel behind firebox and mix at chimney base, before
exiting cooktop. Others have also now added preheated
channels and secondary gasification to rocket stoves.
It is not an inclusive to TLUD designs and can be
adapted to any stove firebox. </div>
<div class=""><br class="">
</div>
<br>
</div>
</div>
</blockquote>
</div>
</div>
</blockquote>
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