<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Arial; font-size: 12pt; color: #000000'>Lists (adding biochar-policy also), Kevin, Alex, Tom (who I add, because he speaks Portuguese and might have caught an answer when we were in Manaus a few years ago)<br><br> See below<br><hr id="zwchr"><b>From: </b>"Kevin" <kchisholm@ca.inter.net><br><b>To: </b>"Discussion of biomass cooking stoves" <stoves@lists.bioenergylists.org>, "Alex English" <english@kingston.net><br><b>Cc: </b>"Discussion of biomass cooking stoves" <stoves@lists.bioenergylists.org><br><b>Sent: </b>Monday, December 10, 2012 8:24:34 PM<br><b>Subject: </b>Re: [Stoves] Equipment required for testing stoves<br><br>
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<div><font face="Arial">Dear Ron</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Would you agree that the Amazonians made Terra Preta with
low temperature char? <br> <b>[RWL1: I think others may have an answer - maybe based on spectroscopy. I will start looking but don't know that field well enough to know what others may have concluded about these ancient soils. I fear that 500 years (minimum) in soil may hide the initial character that we can readily see in a University setting. I know from being in several Amazonian biochar "pits" that it is pretty hard to find a piece big enough to test. I think it entirely possible that char left over from simple three-stone fires could have been made at 500-600 C (or higher). Would you call those temperatures high or low?]</b><br><br><br>If so, are there any test results to show that
an "intermediate temperature char" would give better results than the "low
temperature char?"<br> <b>[RWL2: I think that people like Dr. Johannes Lehmann and Evelyn Krull may be getting to an answer for some specific soil and species. I keep looking for it.<br> My note below to Alex was to make it easier for users to know what is being used Some of my favorite biochar scientists like Drs. Julie Major and Christoph Steiner were forced to use char bought off the side of a remote Amazonian road. <br> I haven't seen any data emphasizing tests with a range of temperatures. Drs. Stephen Joseph (low) and Hugh McLaughlin (high) recommend different temperature regimes.] </b><br><br></font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">I seem to recall that "high temperature char" and/or
"activated char" gives inferior results in a biochar application. <br> <b>[RWL3: How about giving a cite for that?]</b><br><br>Does this
impression make sense to you? <br> <b>[RWL4: No - certainly not as a universal truth/]</b><br> <br><br>If so, is there a "preferred char making
temperature range"? <br> <b>[RWL5: I am sure that it depends a lot on the intended recipient soil - and probably on the plant species. My focus in this exchange below with Alex is to give soil researchers and stove users a better idea of even getting close to knowing what char-T they are using. There is a good bit of information out there relating pH to production temperature - but pH also depends on fuel size and ash content and pH changes over time. Who knows what else leads to a "preference"? <br> And we also hear from Dr. Spokas that what happens after char production is maybe as much or more important. I think it is absolutely amazing that we hear so many good reports (and few bad repors) when we know so little even about the char-production temperature - and even the wood species, etc, etc, etc. Ron]</b><br></font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Best wishes,</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Kevin</font></div>
<blockquote style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<div style="FONT: 10pt arial">----- Original Message ----- </div>
<div style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><b>From:</b>
<a title="rongretlarson@comcast.net" href="mailto:rongretlarson@comcast.net" target="_blank">rongretlarson@comcast.net</a> </div>
<div style="FONT: 10pt arial"><b>To:</b> <a title="english@kingston.net" href="mailto:english@kingston.net" target="_blank">Alex English</a> </div>
<div style="FONT: 10pt arial"><b>Cc:</b> <a title="stoves@lists.bioenergylists.org" href="mailto:stoves@lists.bioenergylists.org" target="_blank">Discussion of biomass cooking
stoves</a> </div>
<div style="FONT: 10pt arial"><b>Sent:</b> Monday, December 10, 2012 9:46
PM</div>
<div style="FONT: 10pt arial"><b>Subject:</b> Re: [Stoves] Equipment required
for testing stoves</div>
<div><br></div>
<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 12pt">Alex:<br><br>
Thanks:<br><br> I see only a few remaining questions related to the
thermocouples. My interest is only in being able to report to the soil
scientists the temperature at which the char was
produced.<br><br> Q1. I think we should be able to say
that a time average of a central thermocouple measurement showing a slight
drop over time of the highest numbers is a pretty good estimate - that could
be reproduced for "any" similar "flaming pyrolysis" approacd. The
properties (pH, surface areas, labile component, etc) of such char should be
compared (a Master's thesis?) with char produced via other means.
I think Nat Mulcahy's non-flaming pyrolysis approach can produce varying
temperature char. An all-electric heating approach in any oxygen-free
environment , operated at different temperature should also be used to compare
the char properties with those from stoves. Maybe that data is already
out there?? <br><br> Q2. I think there could be some
influence of the initial fuel moisture content. Do you (anyone) have an
opinion on that? I am trying to avoid having to always measure
temperatures, but still be able to give an indication of the "likely" char
temperature, by knowing how long a specific volume or weight of fuel
lasted.<br><br> Q3. I wonder if the char temperature
as measured by a thermocouple system like yours would also be a function of
the fuel itself (species, characteristic size, shape,
etc.)<br><br> Q4. I am pretty sure that the top and bottom
char will be significantly different in a typical cooking cycle, where a very
high flame temperature is desired at first (affecting only the top part of the
fuel load), and then a much lower temperature desired later (affecting only
the lowest portion of the fuel load). My question, for anyone, is
whether an average temperature is at all valuable, if the average (obtained
from the total duration of the pyrolysis) covered a wide range of production
temperatures. Actually I have heard so many different opinions on the
best production temperature - maybe a mixture of char temperatures might be an
advantage. Thoughts?<br><br><br>Ron<br><br><br>
<hr id="zwchr">
<b>From: </b>"Alex English" <english@kingston.net><br><b>To:
</b>rongretlarson@comcast.net, "Discussion of biomass cooking stoves"
<stoves@lists.bioenergylists.org><br><b>Sent: </b>Monday, December 10,
2012 4:38:56 AM<br><b>Subject: </b>Re: [Stoves] Equipment required for testing
stoves<br><br>
<div class="moz-cite-prefix">Ron,<br><br>On 09/12/2012 8:33 PM, <a class="moz-txt-link-abbreviated" href="mailto:rongretlarson@comcast.net" target="_blank">rongretlarson@comcast.net</a> wrote:<br></div>
<blockquote cite="mid:491634252.590547.1355103219464.JavaMail.root@sz0133a.emeryville.ca.mail.comcast.net">
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<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 12pt">Alex
etal<br><br> Thanks for the cite. I think I understand most of
the plot - which was of amazing duration!. I am especially
amazed at how uniform (and high) the flame temperature was in the late time
plot, even as the other plots were dropping.<br><br></div></blockquote>It is a
very steady gas producer. Conditions are constant except for the distance and
path composition between the pyrolysis front and the burner. If it can be done
over 100cm then why not 200 or 300.<br>
<blockquote cite="mid:491634252.590547.1355103219464.JavaMail.root@sz0133a.emeryville.ca.mail.comcast.net">
<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 12pt">
a. Since you have this one from 2000, you probably have quite a
few more - from which I/we might extract a good bit more information/
Any other similar plots around that you can post?<br></div></blockquote>No I
don't.<br>
<blockquote cite="mid:491634252.590547.1355103219464.JavaMail.root@sz0133a.emeryville.ca.mail.comcast.net">
<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 12pt"><br>
b. I am surprised that the "pyrolysis gas temperature" was so
much lower than the temperature of the char. Where was the probe for this
measurement - and had there been some mixing of secondary air at this
point?<br></div></blockquote>No mixing of secondary air at that point. That
occurs in and above in a 5cm burner mixing pipe. The tmperature
difference is largely due to the nature of unshielded thermocouples in gas.For
the most part thermocouples radiate away heat according to the temperatures of
the surfaces that make up the sphere around them. A thermocouple buried in the
pellets that are all carbonizing at 700C will give a fairly accurate
measurement. A thermocouple in the gas above the top of the pellet bed will
radiate to the pellet bed and, in this case the uninsulated container walls.
The more that pellet bed shrinks the larger the portion of the radiant sphere
that is the cool container walls. The larger the thermocouple, the greater the
radiant cooling , the lower the measurement. The higher the temperature the
greater the radiant loss, to the forth power. All the gas is also radiating
and convecting heat to the container walls. So there are two reasons for a
slow drop in gas temperature, and one reason for not trusting either. The same
holds true for the absolute value of post combustion measurement.
<br><br>There are <span style="TEXT-ALIGN: left; WIDOWS: 2; TEXT-TRANSFORM: none; BACKGROUND-COLOR: rgb(255,255,255); TEXT-INDENT: 0px; DISPLAY: inline !important; FONT: small/16px arial,
sans-serif; WHITE-SPACE: normal; ORPHANS: 2; FLOAT: none; LETTER-SPACING: normal; COLOR: rgb(34,34,34); WORD-SPACING: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">gas-</span><em style="TEXT-ALIGN: left; LINE-HEIGHT: 16px; WIDOWS: 2; TEXT-TRANSFORM: none; BACKGROUND-COLOR: rgb(255,255,255); FONT-VARIANT: normal; FONT-STYLE: normal; TEXT-INDENT: 0px; FONT-FAMILY: arial,sans-serif; WHITE-SPACE: normal; ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); FONT-SIZE: small; WORD-SPACING: 0px">aspirated
pyrometers which shield a thermocouple with ceramic layers that approach gas
temperatures and give better numbers. We will soon be using an 10 footer to
probe the chain grate stoker gasses in carbonizer- pyrolysis-gasifier
mode.<br><br>Grate fun.<br></em>
<blockquote cite="mid:491634252.590547.1355103219464.JavaMail.root@sz0133a.emeryville.ca.mail.comcast.net">
<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 12pt"><br>
c. What is the present disposition of this
equipment?<br></div></blockquote>Its in the recoverable bone yard. I should
have shown it to Crispin when he was here.....or perhaps not:)
<br><br>Alex<br>
<blockquote cite="mid:491634252.590547.1355103219464.JavaMail.root@sz0133a.emeryville.ca.mail.comcast.net">
<div style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 12pt"><br>Nice
work<br><br>Ron<br><br><br></div></blockquote><br></div>
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