<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
Charcoal making was not an important objective of the Eindhoven
Woodburning Stove Group; even clean burning was not initially
considered important by the Steering Committee. The objective was
saving fuel in the preparation of food.<br>
The Downdraft stove was the first clean burning stove we developed.
It could be fed continuously but utilising the heat was not
straightforward.<br>
There was no deliberate partitioning of primary and secondary air;
the layer of burning char was not thick enough to deplete the air
completely of oxygen; whatever oxygen was left after passing through
the char bed was used to burn the volatiles. If the fuelbed was not
too thick, enough oxygen passed through to burn the volatiles
downstream.<br>
If the fuelbed thickness was increased the stove worked for a short
period as a gasifier but only while the chimney was very hot from
the proper burning period. After that there was smoke everywhere.<br>
We did have a shot at producing charcoal in a stove that would burn
only the volatiles. Wood sat in a vertical cylinder, closed at the
top with an opening at the bottom. Air was drawn into that opening
to burn the wood in that vicinity. Around the wood filled cylinder
an insulated chimney surrounded it. The idea was that burning part
of the wood would produce hot gas which could be burned at the top
under a pan. The hot gas heated the cylinder, charring the wood
inside.<br>
It didn't work and we had no time to look into proper dimensioning
which might have resulted in something that did work.<br>
<br>
Peter (smoke) Verhaart<br>
<br>
On 13/01/2012 14:25, <a class="moz-txt-link-abbreviated" href="mailto:rongretlarson@comcast.net">rongretlarson@comcast.net</a> wrote:
<blockquote
cite="mid:1896648598.341420.1326428738150.JavaMail.root@sz0133a.emeryville.ca.mail.comcast.net"
type="cite">
<style type="text/css">p { margin: 0; }</style>
<div style="font-family: Arial; font-size: 12pt; color: #000000">Tom
(cc Andrew and list):<br>
<br>
Thanks. Professor Prasad is certainly one of my heroes
in stove work. It was fun to read (I need to re-read) this
report on a helpful down draft design. But char production was
not a part of his analysis. I will look more closely to see if
there is something there to allow for a char-making design. I
think the main issue is predicting something on needed chimney
heights - which seems to be in there. But it appears to me
that both primary and secondary air were traveling through the
fuel - whereas I presume a need to separate the air supplies -
as in the TLUD.<br>
<br>
The message (below) by Andrew to the stoves list was at
least in part generated by some off-list conversation that we
have been having on BLDD and char-making. The issue is why are
almost all gasifiers (which can be operated to give sizeable
char output) based on BLDD, but (apparently) all (?) char-making
stoves are TLUD?<br>
<br>
I hope anyone knowing of a BLDD char-maker will let us know.<br>
<br>
Few items below also on Andrew's e-mail..<br>
<br>
<br>
<hr id="zwchr"><b>From: </b>"Tom Miles"
<a class="moz-txt-link-rfc2396E" href="mailto:tmiles@trmiles.com"><tmiles@trmiles.com></a><br>
<b>To: </b>"Discussion of biomass cooking stoves"
<a class="moz-txt-link-rfc2396E" href="mailto:stoves@lists.bioenergylists.org"><stoves@lists.bioenergylists.org></a><br>
<b>Sent: </b>Thursday, January 12, 2012 5:23:21 PM<br>
<b>Subject: </b>Re: [Stoves] Inverted top lit updraught<br>
<br>
Krishna Prasad described the downdraft stove in a presentation
to ETHOS in<br>
2004 <br>
<a class="moz-txt-link-freetext" href="http://www.vrac.iastate.edu/ethos/ethos05/proceedings2004/presentations/pras">http://www.vrac.iastate.edu/ethos/ethos05/proceedings2004/presentations/pras</a><br>
adbiomasscookstoves.pdf<br>
<br>
<br>
A picture and WBT for Peter Verhaart's down draft barbeque can
be found at:<br>
<a class="moz-txt-link-freetext" href="http://www.stoves.bioenergylists.org/verhaartbarbeque">http://www.stoves.bioenergylists.org/verhaartbarbeque</a><br>
<br>
Tom Miles<br>
<br>
-----Original Message-----<br>
From: <a class="moz-txt-link-abbreviated" href="mailto:stoves-bounces@lists.bioenergylists.org">stoves-bounces@lists.bioenergylists.org</a><br>
[<a class="moz-txt-link-freetext" href="mailto:stoves-bounces@lists.bioenergylists.org">mailto:stoves-bounces@lists.bioenergylists.org</a>] On Behalf Of<br>
<a class="moz-txt-link-abbreviated" href="mailto:ajheggie@gmail.com">ajheggie@gmail.com</a><br>
Sent: Thursday, January 12, 2012 2:48 PM<br>
To: Discussion of biomass cooking stoves<br>
Subject: [Stoves] Inverted top lit updraught<br>
<br>
One for Peter Verhaart to comment on perhaps: we probably all
know by now<br>
the genesis of the inverted down draught stoves which Ronal and
Tom Reed<br>
expounded early on this list and concurrently Paal was
developing with his<br>
early Peko Pe and we understand how burning the pyrolysis offgas
can offer<br>
very low particulates compared with burning whole wood in a
conventional<br>
updraught stove but is the same true of a down draught stove if
the primary<br>
air is similarly controlled?<br>
<strong>[RWL: I think Piet Verhaart's thoughts would be
excellent (for others: Piet's doctoral work was on a BLDD
stove). But for this purpose, I am interested right now in
whether any BLDD is providing (lots of) char.</strong><br>
<br>
The advantage of stratified down draught ( i.e. where the air
moves down<br>
through the charge of wood as that also descends through the
grate) would<br>
seem to be that the fire can be continually stoked. The
disadvantage is all<br>
the extra pipe work and either needing a hot plate or sunken
pots to<br>
maintain the chimney depression required to suck the primary air
down.<br style="font-weight: bold;">
<span style="font-weight: bold;"> [RWL: I think Professor
Prasad's paper shows a BLDD design that doesn't suffer from
these two drawbacks. But also it doesn't seem to produce
char.</span><br>
<br>
Down draught devices are normally intended to gasify all the
fuel, often<br>
with extra air supplied in the "throat" but what if one was not
particularly<br>
concerned if a high char ash were left?<br>
<span style="font-weight: bold;">[RWL: I have recently been
talking with Agua Das [cc'd] about his "Dasifier" - which is
incredibly efficient (very high temperatures) with an
"ejector" supplying this <span style="font-weight: bold;">extra
air</span>. He says he can produce lots of char as well.
This is not what I have had in mind - but could be attractive
if that intermediate secondary air can be introduced and
controlled economically.</span><br>
<br>
For the sake of staying on topic can we avoid the "b" word and
just discuss the concept?<br>
<span style="font-weight: bold;">[RWL: Hmm. "b" word ?
I trust it is OK to talk of saved char (intended for a "b"
purpose).</span><br>
<br style="font-weight: bold;">
<span style="font-weight: bold;"> Andrew - thanks for these
thoughts.<br>
<br>
Ron<br style="font-weight: bold;">
</span><br>
AJH <br>
<br>
_______________________________________________<br>
Stoves mailing list<br>
<br>
to Send a Message to the list, use the email address<br>
<a class="moz-txt-link-abbreviated" href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a class="moz-txt-link-freetext" href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists</a><br>
.org<br>
<br>
for more Biomass Cooking Stoves, News and Information see our
web site:<br>
<a class="moz-txt-link-freetext" href="http://www.bioenergylists.org/">http://www.bioenergylists.org/</a><br>
<br>
<br>
<br>
_______________________________________________<br>
Stoves mailing list<br>
<br>
to Send a Message to the list, use the email address<br>
<a class="moz-txt-link-abbreviated" href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a class="moz-txt-link-freetext" href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br>
<br>
for more Biomass Cooking Stoves, News and Information see our
web site:<br>
<a class="moz-txt-link-freetext" href="http://www.bioenergylists.org/">http://www.bioenergylists.org/</a><br>
<br>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Stoves mailing list
to Send a Message to the list, use the email address
<a class="moz-txt-link-abbreviated" href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a>
to UNSUBSCRIBE or Change your List Settings use the web page
<a class="moz-txt-link-freetext" href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a>
for more Biomass Cooking Stoves, News and Information see our web site:
<a class="moz-txt-link-freetext" href="http://www.bioenergylists.org/">http://www.bioenergylists.org/</a>
</pre>
</blockquote>
</body>
</html>