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<div class="moz-cite-prefix">Dear Ron,<br>
<br>
Paul O.'s comment brought to mind a major difference between ND
and FA (Natural Draft and Forced Air) TLUD stoves. <br>
<br>
I think that when the flow of air (?? and the resultant
superficial velocity Sv???) is low, the small combustion at the
MPF (migrating pyrolytic front) is mainly or perhaps nearly 100%
of pyrolytic gases close to where they exit from the biomass that
is being heated.<br>
<br>
But when the flow of air is higher (as in the FA in the Oorja), it
is possible for the incoming O2 to reach the surface of the newly
created char layer on the outside of each piece of biomass. This
would result in consumption of char DURING the MPF period (which
is the foundation of the TLUD stove operation),<br>
<br>
I have not yet read the thesis (I am working in Uganda right now).<br>
<br>
Can you or someone try to get the thesis author into this
discussion? And perhaps Dr. Prof. Mukunda also at
IISc-Bangalore? And Dr. Tom Reed? <br>
<br>
And CONGRATULATIONS to the new Doctor from all of us on the Stoves
Listserv.<br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Paul S. Anderson, PhD aka "Dr TLUD"
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 6/27/2013 7:03 PM, Paul Olivier wrote:<br>
</div>
<blockquote
cite="mid:CAOreFva8fpHSaNXK3K5R9Fd-ge_w3xiV2m4os6NuzA=GG-=VNA@mail.gmail.com"
type="cite">
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<div>Ron,<br>
<br>
</div>
</div>
When char is consumed in a fan-powered TLUD, several
negative factors come into play. At the point where char
is consumed, hot zones are created, giving rise to
temperatures that are truly brutal on all types of metal.
As a consequence of such high heat, the walls of the
reactor can be degraded in a matter of months, often
times, in just a few weeks. <br>
<br>
When char is consumed, the descent of the pyrolitic front
is not uniform. The syngas generally contains a lot of
CO2. An inefficiency in heat transfer is created as energy
gets released within the reactor at a considerable
distance from the pot. To compensate for this loss in heat
transfer, the operator might increase the speed of the
fan, and in so doing, make matters worse.<br>
<br>
</div>
<div>If syngas contains a lot of CO2, I wonder how this
affects the combustion CO and H2 within the syngas. If CO
and H2 are diluted with CO2, do they fully combust when
exposed to secondary air? Is there a link between the
presence of CO2 prior to the combustion of the syngas and
the presence of CO after the combustion of the syngas?<br>
</div>
<div><br>
</div>
When char gets consumed, pockets of ash are created, and
they might easily contain high levels of cristobalite. This
is especially true in the case of rice hulls, which contain
high levels of amorphous silica. When char gets consumed,
the quality of the biochar produced is compromised. Ash is
not biochar, and biochar is not ash.<br>
<br>
</div>
Thanks.<br>
</div>
Paul Olivier<br>
<div>
<div>
<div>
<div><br>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Fri, Jun 28, 2013 at 2:43
AM, <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:rongretlarson@comcast.net"
target="_blank">rongretlarson@comcast.net</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div style="font-size:12pt;font-family:Arial">Julien
and list<br>
<br>
1. Thanks very much for providing this cite.
I have read most and find it to be a well done
thesis. I wish we had more like it.<br>
<br>
2. The concepts of char and TLUDs are in here
thoroughly. But nothing on the idea of a stove
designed to make char. All char is presumed and
desired to be consumed. <br>
<br>
3. My conclusion (would like to hear more) is
that a good case is made (not intentionally) for
NOT consuming the produced char in a TLUD (this
one fan-powered and widely sold in India as the
"Oorja" (started by BP)). Very little gain in
overall efficiency as the char is consumed.<br>
<br>
4. A major advance was his study of the
importance of ash in this "char" period as a
poor radiator - thereby responsible for
(undesired) high char temperatures.<br>
<br>
5. Most everything shown as a function of
superficial velocity (Vs) - with 16-17 cm/sec
shown as key dividing point in stove behavior..
Above which velocity one swtches from char
production to char consumption. I have not
seen this before.<br>
<br>
For his highly automated fan system,
measuring Vs was apparently not so difficult.
Anyone able to give a way to get an easy
estimate of Vs, when there is only natural
draft?<br>
<br>
6. Quite a bit on the importance of low
emissions of CO.<br>
<br>
7. Good information on both the experimental
and computational side of top-lit (packed bed)
stoves. Not much here for rocket stoves.<br>
<br>
Have I got #3 right?<span class="HOEnZb"><font
color="#888888"><br>
<br>
Ron<br>
</font></span></div>
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</blockquote>
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<br>
<br clear="all">
<br>
-- <br>
Paul A. Olivier PhD<br>
26/5 Phu Dong Thien Vuong<br>
Dalat<br>
Vietnam<br>
<br>
Louisiana telephone: 1-337-447-4124 (rings Vietnam)<br>
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