<div dir="ltr">Hi All,<div><br></div><div>Measuring the PM out of the stack is very important as well (as well as CO/CO2) and it has been noted by researchers like Kirk Smith, in his textbook, that added air can assist in lowering PM. Getting almost no CO and almost no PM, in my limited experience, does require quite a lot of excess air in open fire type combustion chamber stoves, Rocket stoves and TLUDs.</div>
<div><br></div><div>Best,</div><div><br></div><div>Dean</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Aug 21, 2013 at 1:04 PM, Philip Lloyd <span dir="ltr"><<a href="mailto:plloyd@mweb.co.za" target="_blank">plloyd@mweb.co.za</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div lang="EN-US" link="blue" vlink="purple" style="word-wrap:break-word">
<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Thanks, Ron<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">In essence I think it comes down to what you are trying to
do. Do you want a crude measure of stove performance or an accurate one?
In running a really big stove (and I’m thinking of one that burns around
90kg of fuel per second) it is critically important to get the combustion
optimal, with a balance between CO going up the stack, C leaving in the ash and
minimal N<sub>2</sub>/Ar needing unnecessary heating. You have to get the
excess air just right. You play around, altering it about 0.1% each time,
until you get it right for the stove and the fuel. Near the optimum, 0.1%
shift in the excess air can cost you 100g of carbon per second, or 0.3% in
efficiency as you get excess nitrogen – that’s how closely you have
to monitor the excess air. So if the big stovers can use such a measure,
why can’t we?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Kind regards<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Philip<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<div>
<div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Ronal W. Larson
[mailto:<a href="mailto:rongretlarson@comcast.net" target="_blank">rongretlarson@comcast.net</a>] <br>
<b>Sent:</b> 21 August 2013 06:16<br>
<b>To:</b> Discussion of biomass cooking stoves; Philip Lloyd<br>
<b>Subject:</b> Re: [Stoves] Excess air<u></u><u></u></span></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Prof.Lloyd:<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"> I agree that combustion efficiency is hugely
important. I would love to see it reported separately (and could be
theoretically, I think as CO is already measured and reported). <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> I would love to see excess air reported (and I
think that possible also). <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> I would love to see more on the oxygen content
of various woods (air to fuel ratios for combustion are given as 4-7. If you
are making char, the range is probably wider, as lignin, cellulose and
hemicellulose all have rather different O2 content, and contribute differently
to char. <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> Why not separately also report on the H2
content of all the fuels, and it also has a small content in chars. Then
we can move to sulfur.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> Why not report the lost radiant energy?<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"> If you had all this in an expanded WBT
procedure (with all Crispin and you want about each and every fuel), what
would the average user of Jim Jetter's test do differently than they are now
doing? I just continue to see these as useful academic exercises that
don't advance stove development.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"> I nit pick below a bit more.<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">On Aug 21, 2013, at 12:06 AM, "Philip Lloyd" <<a href="mailto:plloyd@mweb.co.za" target="_blank">plloyd@mweb.co.za</a>> wrote:<u></u><u></u></p>
</div>
<p class="MsoNormal"><br>
<br>
<u></u><u></u></p>
<p class="MsoNormal">Dear List<br>
<br>
In one of his responses to Crispin, Ron said "RWL: In summary, I
think you<br>
are raising issues that are hopelessly complicated for the world of stove<br>
testing and comparisons. I see insufficient reason so far to explore your<br>
metric words "possible" and "to check" and
"Obviously". I hope you will<br>
try again to convince this list (with citations), if you disagree."<br>
<br>
I think stove testing needs to be comparable between both stoves and fuels.<u></u><u></u></p>
<p class="MsoNormal"> <b>[RWL: I think this is now being
done. Each fuel seems to have enough known about it and it is reported.
The unused CO is reported. I don't know this for sure, but
think that the same stove with different fuels gives very comparable results -
and especially in a tier-ranking sense. (Anyone have data on this
last point?)</b><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><b><br>
<br>
</b><u></u><u></u></p>
<p class="MsoNormal">What Crispin has done is bring standard combustion theory to
bear on the<br>
question so as to allow this. <u></u><u></u></p>
<div>
<p class="MsoNormal"> <b>[RWL: Jetter's work is about
improving the performance via measurement. Details about each fuel
doesn't seem as important as reporting the fuel combustion efficiency - which
is (sort of) in the data. (meaning high CO means low combustion
efficiency).</b><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><b> I am not sure that any important aspect of
combustion theory is missing. If so - exactly what?</b><u></u><u></u></p>
</div>
<p class="MsoNormal"><br>
<br>
<u></u><u></u></p>
<p class="MsoNormal">I need, for instance, to be able to compare a<br>
single stove burning either wood or charcoal. <u></u><u></u></p>
<div>
<p class="MsoNormal"> <b>[RWL: I hope not too often. Rarely
will the same stove be the right thing to use for both fuels.</b><u></u><u></u></p>
</div>
<p class="MsoNormal"><br>
<br>
<u></u><u></u></p>
<p class="MsoNormal">I have to be able to take the<br>
oxygen present in the cellulose and other constituents of the wood into<br>
account in calculating the excess air, because it contributes to the<br>
combustion, whereas with charcoal there is essentially no oxygen present in<br>
the fuel. <u></u><u></u></p>
<div>
<p class="MsoNormal"> <b>[RWL: Maybe this is important for
something you are doing, but why impose this on all stove testing? I
think we should concentrate first on getting excess air measured accurately,
not on the percentage coming from the fuel (which can mostly be
determined from the literature - no need I see to encumber each test with
that level of detail). The operation and performance of charcoal-making
and charcoal-using stoves is so different (even ignoring how the char in a
char-using stove was produced), that I think the O2 content of the fuel is in
the noise. Can you give a counter example?</b><u></u><u></u></p>
</div>
<p class="MsoNormal"><br>
<br>
<u></u><u></u></p>
<p class="MsoNormal">The difference is real, measurable, and has an impact on the<br>
efficiency of combustion.<u></u><u></u></p>
<p class="MsoNormal"> <b>[RWL: Yes to all - but I don't think
it needed as a new adjunct to the WBT. On the best stoves (tiny CO
emitted) , the information will change the second or third significant
efficiency digit, and I am still worried about the first digit.</b><br>
<br>
<u></u><u></u></p>
<p class="MsoNormal"><br>
I, for one, am convinced.<u></u><u></u></p>
<p class="MsoNormal"> <b>[RWL: I will be when I see a written
justification for holding up progress on getting an agreed ISO standard.
How about helping me get char production ( a first digit issue)
as an accepted part of the standard?</b><u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><b> Need to repeat, some of the above might
have been covered in yesterday's webinar which had to be cancelled
due to an equipment glitch. Ron</b><u></u><u></u></p>
</div>
<div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
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