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Dean,<br>
<br>
Any solid biomass that is burning is undergoing the same various
chemical and physical processes. But in gasifiers the processes
are somewhat separated (make gases and burn them later in a
different location, even if the later is only a few milli-seconds
and the location is only a few centimeters away). In contrast, the
fires in Rocket stove and bonfires, etc, have the processes
occurring virtually simultaneously and intermingled, some at
essentially the same location (or with mixing). <br>
<br>
In a standard fire (Rocket, etc.) that the relatively cool secondary
air (needed to burn the gases) is entering at or close to the fuel,
resulting in some cooling of fuel that needs to be hot to create the
gases. This is a fundamental difference that allows gasifiers to
be burning gases separately from where the gases are being created,
with benefits of cleaner combustion (if done properly).<br>
<br>
In somewhat simplistic terms, carbonization and pyrolysis are two
sides of the same coin (or process). Carbonization creates char
(focus is on the resultant char) and Pyrolysis creates gases (focus
is on the gases). Both relate to "burning". <br>
<br>
Remember also that the char (once it is created) is hot and IF
exposed to oxygen will itself "char-oxidize" or "char-gasify" (into
CO or CO2) and therefore will "disappear" in a regular fire. But
in a TLUD the char just sits there, being hot but without any O2
(unless fans, etc bring in sufficient air with O2 to reach the
surface of the char.)<br>
<br>
Terminology: Pyrolysis is by HEAT. The heat can be with FIRE
present or not (retort). There is oxic pyrolysis (oxygen present /
coming in) and anoxic pyrolysis (no oxygen from outside the
biomass).<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 5/16/2015 10:34 PM, kgharris wrote:<br>
</div>
<blockquote cite="mid:0100A6B705FF403295FD6BA64D7369AB@phyllisPC"
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<div><font face="Arial" size="2">Dean,</font></div>
<div> </div>
<div><font face="Arial" size="2">Thank you for bringing this up.
I have never really thought about there being a difference
between pyrolysis and gasification. The definition of
gasification in Wikipedia, "<font face="Times New Roman"
size="3">This is achieved by reacting the material at high
temperatures (>700 °C), without combustion, with a
controlled amount of </font><font face="Times New Roman"
size="3">oxygen</font><font face="Times New Roman" size="3">
and/or </font><font face="Times New Roman" size="3">steam",</font> is
different from the definition of pyrolysis which is without
additional oxygen. Your statement seems correct according to
this. </font></div>
<div> </div>
<div><font face="Arial" size="2">As I read further in Wikipedia,
there is a section on chemical reactions. Here there are 5
different processes which the fuel undergoes, pyrolysis being
one of those. This would lead me to believe that pyrolysis is
part of the more general process of gasification. Rather than
it being one or the other, a TLUD would include both. The
small amount of added air supports the combustion of a small
amount of the gas to produce heat, but that air is soon used
up and most of the fuel pyrolyzes without added air. The
combination, including pyrolysis, would be gasification.</font></div>
<div> </div>
<div><font face="Arial" size="2">I will look further to see if
Christa Roth adresses this question in her Micro-gasification
manual. </font></div>
<div> </div>
<div><font face="Arial" size="2">Kirk</font></div>
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<div style="FONT: 10pt arial">----- Original Message ----- </div>
<div style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color:
black"><b>From:</b> <a moz-do-not-send="true"
title="deankstill@gmail.com"
href="mailto:deankstill@gmail.com">Dean Still</a> </div>
<div style="FONT: 10pt arial"><b>To:</b> <a
moz-do-not-send="true"
title="stoves@lists.bioenergylists.org"
href="mailto:stoves@lists.bioenergylists.org">Discussion of
biomass cooking stoves</a> </div>
<div style="FONT: 10pt arial"><b>Sent:</b> Saturday, May 16,
2015 3:50 PM</div>
<div style="FONT: 10pt arial"><b>Subject:</b> [Stoves]
Pyrolysis: No Air?</div>
<div><br>
</div>
<div dir="ltr">
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<div style="PADDING-BOTTOM: 20px; OVERFLOW: hidden">Hi
All,</div>
</li>
</ol>
<div><span style="LINE-HEIGHT: 16px">When I look up the word
pyrolysis I find the following:</span></div>
<ol style="BORDER-BOTTOM: 0px; BORDER-LEFT: 0px;
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<li style="BORDER-BOTTOM: 0px; BORDER-LEFT: 0px;
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none; MARGIN: 0px; PADDING-LEFT: 20px; PADDING-RIGHT:
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PADDING-TOP: 20px">
<div style="PADDING-BOTTOM: 20px; OVERFLOW: hidden"><b
style="LINE-HEIGHT: 1.24; FONT-SIZE: 16px">Pyrolysis</b><span
style="LINE-HEIGHT: 1.24; FONT-SIZE: 16px"> </span><span
style="LINE-HEIGHT: 1.24; FONT-SIZE: 16px">is a
thermochemical decomposition of organic material at
elevated temperatures in the absence of oxygen (or any
halogen). It involves the simultaneous change of
chemical composition and physical phase, and is
irreversible. The word is coined from the
Greek-derived elements pyro "fire" and lysis
"separating".</span></div>
</li>
<li style="BORDER-BOTTOM: 0px; BORDER-LEFT: 0px;
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none; MARGIN: 0px; PADDING-LEFT: 20px; PADDING-RIGHT:
20px; CLEAR: none; BORDER-TOP: 0px; BORDER-RIGHT: 0px;
PADDING-TOP: 20px">
<div style="PADDING-BOTTOM: 20px; OVERFLOW: hidden"><span
style="LINE-HEIGHT: 1.24; FONT-SIZE: 16px">However, I
think that folks use it to describe what happens in a
TLUD, etc? Isn't that gasification not pyrolysis
because of the presence of some air?</span></div>
</li>
</ol>
<div><span style="LINE-HEIGHT: 19px; FONT-SIZE: 16px">Best,</span></div>
<div><span style="LINE-HEIGHT: 19px; FONT-SIZE: 16px"><br>
</span></div>
<div><span style="LINE-HEIGHT: 19px; FONT-SIZE: 16px">Dean</span></div>
</div>
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