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<div class="moz-cite-prefix">Art,<br>
<br>
It is an interesting problem. One only has to be wrong once.<br>
<br>
Your experience may be the only real advise.<br>
<br>
If coal is a corollary then particle size is an issue. Yes
powdered char, or fines would be less able to convect away heat
than lump or chip char with the voids to aid gas flow. It could
hinder gas movement inward as well. However liquid water could
move in and create a damp zone. The coal fire paper mentioned
previously suggested that it was at the margins between wet and
dry where fire might get started. The logic that works for me is
that a puddle won't catch fire (tough sell) but it provides
humidity to react in neighboring dry regions of char which begin
to heat up. That paper graphed lab tests and in each case the
temperature rise was over hours not days. <br>
<br>
With coal the risk was higher for low rank coal with higher
volatile content. This could suggest that relatively high
temperature TLUD chars are at lower than average risk.<br>
<br>
The spontaneous combustion page which has a short piece on
Charcoal<br>
"<span style="color: rgb(0, 0, 0); font-family: sans-serif;
font-size: 13px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
19.1875px; orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); display: inline !important; float: none;">Charcoal, that
has been exposed to air for a period of eight days, is not
considered to be hazardous."</span><br>
<br>
<a class="moz-txt-link-freetext" href="http://en.wikipedia.org/wiki/Spontaneous_combustion">http://en.wikipedia.org/wiki/Spontaneous_combustion</a><br>
lists the following reference.<br>
<span style="color: rgb(0, 0, 0); font-family: sans-serif;
font-size: 13px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
19.1875px; orphans: auto; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255); display: inline !important; float: none;">Bowes, P. C.
(1984)<span class="Apple-converted-space"> </span></span><i
style="color: rgb(0, 0, 0); font-family: sans-serif; font-size:
13px; font-variant: normal; font-weight: normal; letter-spacing:
normal; line-height: 19.1875px; orphans: auto; text-align: left;
text-indent: 0px; text-transform: none; white-space: normal;
widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; background-color: rgb(255, 255,
255);">Self-heating: Evaluating and Controlling the Hazards</i><span
style="color: rgb(0, 0, 0); font-family: sans-serif; font-size:
13px; font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: 19.1875px; orphans:
auto; text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); display: inline
!important; float: none;">, London: Department of the
Environment, Building Research Establishment. ISBN 011671364</span><br>
<br>
I have been unable to obtain it. Perhaps some one out there in
stoveland can help.<br>
<br>
<br>
We have been making char and dry quenching in leaky, or unsealed,
drums. After a few days I decant into 200 liter plastic bags and
leave them outside. Later, before use, we add water 1 to 1 by
mass. No trouble yet but the ambient temperatures are low.<br>
<br>
I am starting to ponder data logged tests to explore this further.
I don't like the worst case scenarios. <br>
We need to establish what a critical mass or time or miss
treatment is, and then avoid it with a wide margin.<br>
<br>
Alex<br>
PS. Crispin, I know, I know ......no problem........... just make
ash:)<br>
<br>
<br>
<br>
<br>
<br>
On 23/02/2013 9:28 PM, Art Donnelly wrote:<br>
</div>
<blockquote
cite="mid:CALyHvqomOQ-NLY+V4oHj043rvDfT5kEM_MZ6_KqM-bt8mwQabg@mail.gmail.com"
type="cite">Frank,<br>
Glad to hear it was a near miss and not a disaster, but thanks for
using this as an opportunity to flag this important safety issue.
I want to make sure we take away a clear message in terms of best
practices for handling our inventories of biochar.<br>
<br>
<ul>
<li>Is auto-ignition only likely to occur in char that has been
wetted? <br>
</li>
<li>Is there a low risk of auto-ignition in char that has been
dry quenched?</li>
<li>Is particle size a risk factor: IE is powdered char more
likely to ignite?</li>
<li>When you say: "So before storage better give it time to take
up<br>
oxygen." What is the safest way to do this?</li>
</ul>
<p>We (the Estufa Finca project) have picked over 3-tons of
cook-stove biochar from just 32 households over the past 7
months. I currently have an inventory of approx. a ton. It's
piled in woven-plastic feed sacks, under a shed roof. It was all
quenched dry in the steel pails we provide all participants and
we only buy dry biochar. However this is a tropical humid
environment. So we assume the char is taking on moisture. As we
are now starting to develop demand, I expect to see the volume
of material on hand go up substantially in the coming year. We
are trying to figure out how to avoid the problem you just had.
As someone pointed out it's not a matter of whether it is a
matter of when.</p>
<p>chao</p>
<p>Art<br>
</p>
<br>
</blockquote>
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