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<p class="MsoNormal">Dear Julien, Stovers, </p>
<p class="MsoNormal">Some nice work with well defined curves. Not easy to get with so many variables. I think we can get a lot of info from this
work and I am trying to understand what we can take away from it. This is how I am looking at it:<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Box 1; (of 6-Box system)<o:p class=""></o:p></p>
<p class="MsoNormal">You have controlled the variables of biomass by picking two
very different types and working exclusively with them. <o:p class=""></o:p></p>
<p class="MsoNormal">Box 2; (of 6-Box system)<o:p class=""></o:p></p>
<p class="MsoNormal">You are adding the biomass in a consistent manor for each
run. The sticks are placed vertical and
the pellets uniformly placed by pouring in and falling into place(?). <o:p class=""></o:p></p>
<p class="MsoNormal">Box 3; (of 6-Box system)<o:p class=""></o:p></p>
<p class="MsoNormal">The combustion chamber is the same for each run aside from
the noted variable being tested. (ie of Grate Aperture).<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Comment: Based on Tom Reeds work it appears from his graphs
of charring different biomasses in N2 that there is little weight loss with
increasing temperatures once the weight has stabilized at temperatures above
450c. And the ash value for each of the
two biomasses chosen should be the same. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Suggest: You fill some 1.5”dia. X 6” long iron pipe with
oven dry (105c) biomass chosen. Tighten
one end cap and tighten the other but back turn a turn to let gases escape. Then heat to > 450c until all gases have
escaped. Let cool and calculate the percent char+ash remaining. Then ash (>550c with air) and calculate
the percent maximum good quality char that can be produced. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">So, I’m thinking, you have the total time of combustion and
the total dry-ash free (DAF) weight of fuel in the stove. You can calculate the expected rate of weight
loss during the run (with even heating) of volatiles released just due to heat
and internal oxygen. Anything less means
incomplete pyrolysis occurs and greater means loss of biomass due to combustion
with added outside air during that snap-shot in time. Of course you could end up with a mix of both
torrefied biomass and overly combusted char should the flame front not being
even during the run. So some char
quality of material left may be necessary.
Just pack it tight into the pipe, Heat > 450c and see what weight
loss you get from any torrefied wood left. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Suggestion: Years ago I did some experiments in the
shrinkage of Tongue Depressors (TD) at increasing temperatures in a nitrogen
atmosphere. That work is not available to me anymore but it could easily be
reproduced. I think having a TD placed vertical in the center of the fuel or
cutting the TDs into inch sections and distributing in with the fuel. Then measuring the change in width after a run
could provide info regarding the combination of: 1) temperature reached 2) time of duration of
combustion and 3) oxidation from primary air –combination. I’m thinking these are the three variables
that control the outcome from a known fuel. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">And you are nicely seeing all this; change in weight loss
and temperature based on a constant (pick any) aperture setting in your
experiment. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Looking at Figure 2: Again some very nice data to work with.<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">I would like to see the X axis as Residual DAF percentages
and have an added vertical line showing the maximum good quality char that can
be produced. That way you can a) rule
out points showing incomplete combustion (you have done this but I think can be
better) and show loss of weight from char that had been combusted using primary
air. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">In this Figure 2 you have ventured off from controlling the
Fuel (Box 1) by only using two types for the entire experiment to trying
different fuels. Your list of variables
you found to be necessary for controlling Box 1 is as follows:<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Moisture<o:p class=""></o:p></p>
<p class="MsoNormal">Particle Shape<o:p class=""></o:p></p>
<p class="MsoNormal">Particle Size<o:p class=""></o:p></p>
<p class="MsoNormal">Bulk carbon density<o:p class=""></o:p></p>
<p class="MsoNormal">Particle carbon density<o:p class=""></o:p></p>
<p class="MsoNormal">Void space<o:p class=""></o:p></p>
<p class="MsoNormal">Air resistance (not
sure how to measure)<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p> </p>
<p class="MsoNormal">I would add a few more like a) water soluble Sugars, b)
solvent soluble oils and c) weight loss at 450c (no air-pipe). The sugars and oils are only needed for fuels
that have a lot like dried bananas, pine cones or food waste, sugar cane
etc. Not the fuels you have used, I’m
thinking. I would also add E450c for
others monitoring energy. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">These are all easy tests and would complete the Box 1 fuels
characterization. <o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p> </p>
<p class="MsoNormal">I would like to see a picture of your combustion chamber you
are using.<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Great report<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Regards<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
<p class="MsoNormal">Frank<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p></p>
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Frank Shields<br class=""><a href="mailto:franke@cruzio.com" class="">franke@cruzio.com</a><br class=""><br class="">
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<div><br class=""><blockquote type="cite" class=""><div class=""><br class=""></div><div class="">---------------------------- Original Message ----------------------------<br class="">Subject: [Stoves] Some Basic Properties of ND-TLUD Gasification -- pdf<br class="">From: "Julien Winter" <<a href="mailto:winter.julien@gmail.com" class="">winter.julien@gmail.com</a>><br class="">Date: Sun, 12 July, 2015 8:34 pm<br class="">To: "Discussion of biomass cooking stoves"<br class=""><<a href="mailto:stoves@lists.bioenergylists.org" class="">stoves@lists.bioenergylists.org</a>><br class="">--------------------------------------------------------------------------<br class=""><br class="">Hello all;<br class=""><br class="">I have attached a handout that I prepared for a recent demonstration of<br class="">natural-draft, top-lit updraft gasifiers. I think you may find it<br class="">interesting. The content of Figure 1. I have shared with this list before<br class="">in some form or another.<br class=""><br class="">Figure 2., however is new. It shows the linear relationship between the<br class="">yield of char as a % of dry fuel, and the maximum temperature measured in<br class="">the TLUD reactor. The purpose of the regression is to estimate what the<br class="">maximum temperature could have been, if you don't have a thermocouple, but<br class="">you do have an inexpensive banance.<br class=""><br class="">The explanation for the linear relation is based on the how more biomass is<br class="">pyrolyzed to volatiles rather than char, as the rate of heating and maximum<br class="">pyrolysis temperature increases. While this phenomenon has been know for a<br class="">long time (e.g. the Broido-Shafizadeh model), the chemical mechanism for<br class="">partitioning between volatiles and char still remains obscure.<br class=""><br class="">However, I have two linear relations for the fuels that I used. The fuels<br class="">are distinguished by their size, or the size of the pore space between<br class="">particles. I think we have to remember that when thermocouples are<br class="">inserted into a fuel bed, they measure the radiant, convective, and<br class="">conducted heat in the pore space and not the actual temperature within the<br class="">particles, where pyrolysis occurs. With large particles of cm in<br class="">thickness, the center of the particle can be at ambient 25°C, until heat<br class="">from the outside arrives. A pyrolytic front enters the particle from the<br class="">outside as it heats up, so the major loss of volatiles will occur at a<br class="">lower temperature than outside the particle in the pore space. When the<br class="">pores are large, as between sticks, pore space is more concentrated in the<br class="">fuel bed. With larger pores, there is more space for flaming, and the<br class="">thickness of the pyrolytic front increases with particle thickness (because<br class="">it takes longer for pyrolysis to reach the interior of larger particles<br class="">than smaller ones). So, if flaming is less evenly distributed in fuel beds<br class="">of large particles, the pore space temperature should be higher. Following<br class="">from the above, the reason why there are two regression lines could be<br class="">largely due to differences in pore space temperatures, and not so much<br class="">pyrolysis temperatures inside the particles.<br class=""><br class="">Fuel moisture content didn't have a substantive effect on the Tmax vs.<br class="">%Char relationship. I did not see a large effect of moisture on the<br class="">maximum temperature of flaming pyrolysis, and read a paper where there were<br class="">similar finding. ... but I other studies to read.<br class=""><br class="">Cheers,<br class="">Julien.<br class=""><br class="">-- <br class="">Julien Winter<br class="">Cobourg, ON, CANADA<br class="">_______________________________________________<br class="">Stoves mailing list<br class=""><br class="">to Send a Message to the list, use the email address<br class=""><a href="mailto:stoves@lists.bioenergylists.org" class="">stoves@lists.bioenergylists.org</a><br class=""><br class="">to UNSUBSCRIBE or Change your List Settings use the web page<br class="">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<br class=""><br class="">for more Biomass Cooking Stoves, News and Information see our web site:<br class="">http://stoves.bioenergylists.org/<br class=""><br class=""><br class=""><br class=""></div></blockquote></div></body></html>