Sorry - realized I didn't answer the original question:<div><br></div><div>We measure temperature in the fuel bed.</div><div><br></div><div>JK</div><div><br><br><div class="gmail_quote">On Mon, Jun 17, 2013 at 12:44 PM, Josh Kearns <span dir="ltr"><<a href="mailto:yeah.yeah.right.on@gmail.com" target="_blank">yeah.yeah.right.on@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Using a 1-gal TLUD "Toucan" model in natural and forced air modes, we have seen, pretty consistently, ND peak temps. 600-650 C, and FD peak temps 900-950 C. This has been across feedstocks - wood pellets, sugarcane bagasse pellets, bamboo chips, jatropha presscake pellets, pecan shells, cherry pits. <div>
<br></div><div>Temperature is controlled by draft, and we were lucky to achieve high draft conditions in our 55-gal drum TLUD without applying a fan. Feedstock granularity, density, and bed density had to be within an optimal range however. High draft 55-gal TLUD chars from dense, uniform feedstocks (e.g. eucalyptus branches 1-2-" dia cut into 4-6" segments) seem to offer equivalent sorption performance as 1-gal FD chars made from wood pellets.<br>
<div><br></div><div>Interestingly, temperatures have been more or less independent of feedstock, but burn duration is longer with denser feedstocks. If feedstocks are insufficiently dense, e.g. the bagasse pellets I made with our crappy benchtop pelletizer, then they tend to burn up and the char yield is very low if draft is high.</div>
<div><br></div><div>Also, interestingly, feedstock did not seem to matter much for sorption of our probe compounds (e.g herbicide), where peak temperatures were consistent. This agrees with other work that finds peak temperature, and to a lesser extent heating duration, to be controlling factors in product char properties, with feedstock identity exerting less of an influence (except insofar as feedstock identity exerts intrinsic effects on the pyrolysis regime).</div>
<div><br></div><div>JK</div><div><br></div><div><div><div class="h5"> <br><br><div class="gmail_quote">On Mon, Jun 17, 2013 at 8:56 AM, Alex English <span dir="ltr"><<a href="mailto:english@kingston.net" target="_blank">english@kingston.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
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<br>
Julien,<br>
Josh Kearns has posted graphs of bed temperatures.<br>
<br>
I data logged a T-LUD on wood pellets <br>
<a href="http://www.bioenergylists.org/stovesdoc/English/bigtop2.htm" target="_blank">http://www.bioenergylists.org/stovesdoc/English/bigtop2.htm</a><br>
<br>
Switching units I have choked primary air as low as possible while
maintaining a flame. That corresponded to a peak fuel bed
temperature of 480 C.<br>
My impression, though unmeasured, that the gas composition was
different than at high temperatures. I hav also pushed the TLUD
with a high pressure blower and at no time did it fail to produce
combustible gasses.<span><font color="#888888"><br>
<br>
Alex</font></span><div><div><br>
<br>
<br>
On 16/06/2013 10:57 PM, Julien Winter wrote:<br>
</div></div></div>
<blockquote type="cite"><div><div>
<pre>Dear stovers;
What do we know about the temperature in the fuel bed of top-lit
updraft gasifier stoves (TLUDs)?
Almost all features of TLUD function are affected by the temperature
of the fuel bed. This includes the combustion quality of the effluent
gases, the stability and momentum of the reaction, water boiling rate,
the quality of biochar, the yield of biochar, the nature of effluent
particles, production of crystobalites, production of polynuclear
aromatic hydrocarbons, etc.
In the last 30 years, temperature data has been published for
laboratory bench-top reactors that were, ostensibly, forced-air TLUDs.
Most of this work was done to understand the function of moving grate
gasifiers for urban waste and biomass fuels (and even earlier research
on coal). Along with other measurements, temperature observations
were used to calibrate computer simulations.
An example of bench-top TLUD data is attached as a pdf.
These bench-top TLUDs do not cover the range of conditions experienced
in the real world of feral TLUD cookstoves.
What observations are there on fuel bed temperatures in TLUD cookstoves?
What range of temperatures are possible for a functional stove? If
the reaction is too cool, we just get incombustible shouldering smoke.
Will the stove function poorly if the temperature is too high and
most of the gases oxidized to CO2 within the bed? Is there a sweet
spot temperature range, and does it vary between fuels (e.g., grass,
chips, pellets, briquettes)?
Just as an aside, someone should make virtual TLUD stove for testing
theories and teaching. That shouldn't be too hard for pellets.
Cheers,
Julien-the-eyebrowless
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<br></blockquote></div><br><br clear="all"><div><br></div></div></div><span class="HOEnZb"><font color="#888888">-- <br>Josh Kearns<br>PhD Candidate, Environmental Engineering<br>University of Colorado-Boulder<div>Visiting Researcher, North Carolina State University</div>
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<br><div>Director of Science</div><div>Aqueous Solutions </div><div><a href="http://www.aqsolutions.org" target="_blank">www.aqsolutions.org</a></div><div><br></div><div>Mobile: <a href="tel:720%20989%203959" value="+17209893959" target="_blank">720 989 3959</a><br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br>Josh Kearns<br>PhD Candidate, Environmental Engineering<br>University of Colorado-Boulder<div>Visiting Researcher, North Carolina State University</div><div><br>
<div>Director of Science</div><div>Aqueous Solutions </div><div><a href="http://www.aqsolutions.org" target="_blank">www.aqsolutions.org</a></div><div><br></div><div>Mobile: 720 989 3959<br>Skype: joshkearns<br><br><br><br>
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