<div dir="ltr">Ron:<div><br></div><div>Not quite correct. Secondary combustion<i> is possible</i> with a rocket stove. Our Survivor Rocket stove launched 5 years ago introduced preheated ventilation ductwork at launch. In fact we only offer a primary & secondary combustion design rocket stove. Thats why our stove incorporates 360 degree ventilation through base of stove, tied to ventilation ductwork behind combustion chamber walls. The double insulated walls allow preheated air to travel behind firebox and mix at chimney base, before exiting cooktop. Others have also now added preheated channels and secondary gasification to rocket stoves. It is not an inclusive to TLUD designs and can be adapted to any stove firebox. </div><div><br></div><div><br><img src="cid:ii_jaz0kpo72_1603a288c2889d3f" width="472" height="359"><br>SilverFire Rocket stove on left & Hunter Chimney TLUD stove on right.<br> </div><div>Todd Albi, SilverFire</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Dec 8, 2017 at 8:52 PM, Ronal W. Larson <span dir="ltr"><<a href="mailto:rongretlarson@comcast.net" target="_blank">rongretlarson@comcast.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div>Paul:</div><div><br></div><div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>Yes on your item #1. My first response forgot about preheating secondary air - which is why I quickly added this point; heating secondary air is a big fuel conservation advantage. Generally not possible with rocket stoves - or even charcoal cookers. If not used for heating secondary air, that energy would have been just another loss mechanism.</div><div><br></div><div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>Yes also on your #2. I suspected their problem with a concrete inner cylinder was related to the secondary holes.</div><div><br></div><div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>But I think (not mentioned earlier) that there may be satisfactory ways to use only a single concrete cylinder and still get preheating of the secondary air. I’m thinking of some vertical piping or tubing - maybe in the concrete. It is not obvious that two cylinders must be used. Which is I guess your point.</div><div><br></div><div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>Re #3, if meant for me - I can probably find a way to get coconut husks/shells from some local restaurants - but better to ask others than myself. I am trying these days to defend biochar against other CDR approaches on 3 or 4 other internet lists . So not much time left for stoves - or experimenting with char in ground or elsewhere. </div><div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span></div><div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>Tremendous ignorance remains about biochar; the very positive Bangladesh soil experience will be very helpful in defending biochar, however produced. And, of course, in advancing TLUD technology. I’m writing about this elsewhere right now.</div><div><br></div><div>Ron</div><div><br></div><br><div><blockquote type="cite"><div>On Dec 7, 2017, at 6:51 AM, Paul Anderson <<a href="mailto:psanders@ilstu.edu" target="_blank">psanders@ilstu.edu</a>> wrote:</div><br class="m_-3565158579685143792Apple-interchange-newline"><div>
<div text="#000000" bgcolor="#FFFFFF">
Ron,<br>
<br>
About the concrete inner (fuel) cylinder. Hard to be sure without
actually observing it, but I suspect that:<br>
1. The thermal mass is estracting heat, meaning cooler gases inside
the chamber, with risk of insufficient temperature for ignition at
the top, especially when nearing the end of pyrolysis.<br>
<br>
2. Julien and Mahbubul can confirm about this: The concrete (or
ceramic) inner cylinder does not have any of the side holes (24 in
the metal version). Such holes allow for some "pilot light" effect
after the char level is below a hole. I imagine that small holes
would be very difficult to put into a concrete cylinder. However,
maybe 3 or 6 holes could be created at strategic locations (to be
discussed). They could be created in the following way:<br>
When the concrete is being poured (or soon after), place
something like round toothpicks (about 2 mm size??) across the
concrete, sticking out both sides. (might be at a place in the
mould with holes that would leak concrete/water except that they
would soon be "plugged" with the toothpicks. When the piece is
dried, and used for the first time (or two or three times) the wood
would burn out (or be drilled out or poked out), leaving the desired
hole.<br>
Alternatively, do the same with larger diameter pieces like
chopsticks. If the holes are too large (to be determined by
experimentation), then they might be plugges slightly (in a variety
of ways.).<br>
<br>
First, let's get more understanding of the 24 "pilot light" holes in
the metal version.<br>
<br>
3. How much supply of coconut shells (hard part) is there in your
zone?<br>
<br>
Paul<br>
<br>
<pre class="m_-3565158579685143792moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="m_-3565158579685143792moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu" target="_blank">psanders@ilstu.edu</a>
Skype: paultlud Phone: <a href="tel:(309)%20452-7072" value="+13094527072" target="_blank">+1-309-452-7072</a>
Website: <a class="m_-3565158579685143792moz-txt-link-abbreviated" href="http://www.drtlud.com/" target="_blank">www.drtlud.com</a></pre>
<div class="m_-3565158579685143792moz-cite-prefix">On 12/6/2017 11:55 PM, Ronal W. Larson
wrote:<br>
</div>
<blockquote type="cite">
<div>Julien cc List</div>
<div><br>
</div>
<div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>Thanks
for the answers below. Good to hear that both users with and
without land see value in making char. No new questions, two
comments</div>
<div><br>
</div>
<div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>1.
Re a concrete inner cylinder, you said below “..<i>but
their smoke-free combustion was less reliable, and there were
some gas burner issues to solve. “</i></div>
<div>It is not obvious to me why either concern should
occur, so I hope stovers everywhere could try this out. Seems
likely to be cheaper (can even maybe cast in place) and
hopefully longer lived. We know usual cheap steel has a limited
life and the best steels are likely both not readily available
and expensive.</div>
<div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>I
forgot to congratulate on the two metal swinging “doors” at the
bottom. Nice solution.</div>
<div><br>
</div>
<div><span class="m_-3565158579685143792Apple-tab-span" style="white-space:pre-wrap"> </span>2.
Re fuels, the biochar list has had quite a lot of recent
discussion of “blue biochar” - where the source material is kelp
or other seaweeds. Bangladesh is possibly already in that
business, because of its ocean proximity. This could be a
source of employment and a way to save forests while having a
feedstock that should bring back needed minerals and fertilizer
value. Beating the price of wooden blocks seems possible.</div>
<div><br>
</div>
<div>Ron</div>
<br>
<div>
<blockquote type="cite">
<div>On Dec 6, 2017, at 10:05 PM, Julien Winter <<a href="mailto:winter.julien@gmail.com" target="_blank">winter.julien@gmail.com</a>>
wrote:</div>
<br class="m_-3565158579685143792Apple-interchange-newline">
<div>
<div dir="ltr">
<div>Hello all;</div>
<div><br>
</div>
<div>Thanks for you comments on the Akha-Biochar
Project in Bangladesh.</div>
<div><br>
</div>
<div>The cost and payback is not fully worked
out, because it will take about a year for TLUD-biochar
ecosystem to become established in community, and it
will continue to evolve. The stove costs about $20 to
make, this could be brought down as numbers of stoves
increase. Also, we are still at the stove-prototype
stage, so we can expect some modifications and fine
tuning. Payback is developing, as farmers and
gardeners discover the value of biochar for food
production. We have "Farmer Biochar User Groups" that
are conducting field trials, so they can learn from
first-hand experience what biochar can do for them.
There are also graduate students involved in gathering
evidence to make recommendations on optimum application
rates. It could take a couple of years at any one
location for the local population to be able to place
their own value on biochar, and what they are willing to
pay for it. </div>
<div><br>
</div>
<div>Whether people use the char themselves or
sell it depends on their personal opportunities. There
are many families that are landless. Presently, they see
char sales as a way to earn cash or barter. They think
that is a great idea; save fuel, cook faster, AND make
biochar! People with land, especially farmers, see
biochar as a way of making permanent improvements to the
quality of their land, so expect that using biochar
could have very substantial impact on their family's
economic well being.</div>
<div><br>
</div>
<div>
<div>I have been advocating using biochar in
composting, or mixing it with manure before it goes
onto the field. We need work on using it in human
waste management.<br>
</div>
<div><br>
</div>
<div>There is no shortage of good soil
scientists and agronomists in Bangladesh to work on
biochar technology. </div>
</div>
<div><br>
</div>
<div>The outer concrete cylinder of the Akha
stove is cast. We have made stoves with concrete
reactors (lined with clay slip), but their smoke-free
combustion was less reliable, and there were some gas
burner issues to solve. That is not to say that
concrete reactors will not work, but they need quite a
bit of research and development, and a laboratory.
Metal TLUD reactors, on the other hand, are well
understood. About 24 small holes in the side wall of
the metal reactor make the gasification of chunks of
wood more reliable, and less prone loosing the gas
flame. We use cast concrete (rather than clay) because
it is easy to get concrete rings with flat surfaces at
the top and bottom. The concrete components are made
specifically for the Akha. There are many small
business around who can cast concrete. </div>
<div><br>
</div>
<div>Mahbubul has been working with different
ratios of Portand cement, sawdust and biochar dust in
the concrete. The more organics, the lower the heat
capacity and heat conductivity of the stove body. Micro
porosity is supposed to make concrete more resistant
heat by providing spaces for minerals to expand into.
Obviously there is a trade-off between adding organics
and strength of the concrete. Different recipes are
being tested in the field. It is all trial and error.</div>
<div><br>
</div>
<div>Mahbubul has also worked with local ceramic
artisans to make the massive stove components from
clay. There very skilled people to work with, and
kaolinitic clay, so ceramic components are possible.
The more metal components on the stove that we can
replace with ceramics the better, because all metal in
Bangladesh is imported.</div>
<div><br>
</div>
<div>The Akha is about 25% more efficient than a
traditional stove. The Akha has gone through a
water-boiling test at a laboratory in Dhaka, and was
about 30% efficient at getting energy from wood into the
water. The main view that the Akha saves 25% of the
wood comes from household feedback. That is what the
women tell us.</div>
<div><br>
</div>
<div>The Akha-Biocahr Project has funding for its
current intervention until 2019. It is enough to see if
the TLUD-biochar technology will take root. If it does,
then the technology may spread all by itself as local
entrepreneurs see an opportunity. In fact, I think that
if these technologies viable, then they will out of our
control and unstoppable. The 'market' is 25 million
homes. All the same, I am trying to raise money so that
Mahbubul and crew remain as proponents and stakeholders
in what they started. There is work to be done in
developing compressed fuels, because there is not enough
wood in the country. We need to monitor the impact on
forest cover, and make sure that poorest households
don't become energy-starved if the price of wood goes
up.</div>
<div><br>
</div>
<div>One other thing that will push TLUD-biochar
technology forward is that sea-level rise could flood a
third of the country, so soil productivity needs to
increase.</div>
<div><br>
</div>
<div>Cheers,</div>
<div>Julien.</div>
<div><br>
</div>
-- <br>
<div class="m_-3565158579685143792gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">Julien Winter<br>
Cobourg, ON, CANADA<br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
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