My experience installing poly film digesters taught me to keep it as simple as possible to limit the abandonment of the systems afterwards. So in this idea of keeping it simple. What if you evacuated the gas using the exhaust from a car, many of the how to manuals I read when I was carrying out my Biogas project recommended this for inflation of digesters made of poly film. After initial testing I decided not to use it as it adds a step and I didn't see much advantage when I did and didn't use it. But that way you would be mixing a low oxygen gas into the digester to make sure that the Methane was evacuated. I imagine when you stopped getting a flame you would be safe to allow air to enter. But I might be wrong. <br>
<br><div class="gmail_quote">On Thu, Oct 28, 2010 at 10:37 AM, Alexander Eaton <span dir="ltr"><<a href="mailto:alex@sistemabiobolsa.com">alex@sistemabiobolsa.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
In a developing world context, it would also make sense to utilize the as much of the gas production as possible, meaning that maybe a two-chamber system would make the most sense so that you could allow the HRT to be 100+ days in each chamber. Then, if there was a flexible portion of each chamber that could be compressed while venting you would be able to essentially eliminate any risk of an explosive mixture inside the system. My point it that it would make sense to push the gas through to the end-use, then open the chamber while it was empty. Under that scenario I see very little risk. I may also be talking at a small scale, as I am imagining chamber of maybe 50 m3 and smaller. Dry digestion for us would be a huge step, as we have a water limitation that keeps us from installing digesters in many areas of Mexico and Latin America.<br>
<br>I am returning from the UN Genus waste to energy meeting in Costa Rica, where I did have a really interesting discussion about a multi-chambered dry digester system for food waste and solid waste collected at a larger level and installed at landfills. In that scenario, I also envision some sort of flexible cover that could be vacuum pumped empty before the cover was opened. We were also talking about cells with 2+ year HRTs. <br>
<br>Does anyone have some good info on dry digestion, appropriate substrates, HRTs and gas production rates? <br><br>A <br><br><div class="gmail_quote"><div><div></div><div class="h5">On Thu, Oct 28, 2010 at 10:22 AM, David <span dir="ltr"><<a href="mailto:david@h4c.org" target="_blank">david@h4c.org</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex"><div><div></div><div class="h5">
<div bgcolor="#ffffff" text="#000000">
<font face="Georgia"><br>
Yvonne,<br>
</font><div><br>
On 10/28/2010 1:53 AM, Voegeli, Yvonne wrote:
</div><blockquote type="cite">
<div><div><font face="Arial" size="2"><span style="font-size:10pt;font-family:Arial"></span></font><font face="Arial" size="2"><span style="font-size:10pt;font-family:Arial">After visiting a Bekon biogas plant in
Switzerland, I’m
especially concerned regarding the opening of the digester
for emptying and
refilling. Before opening the door, the digester has to be
vented in order to
avoid a gas-air-mixture which is explosive. This
installation seems to me
rather complicated....</span></font>
</div><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10pt;font-family:Arial"> ...Is
it possible to install a simpler venting system?</span></font></p>
</div>
</blockquote>
<br>
I would venture a guess that where the inlet air is being forced in
by bubbling through water, and the outlet air likewise is allowed to
escape by bubbling through water, then the only place in the system
where there would be both a potentially explosive gas mixture and
the potential of a spark would be at the evacuation point of the
exiting gas mixture. Where sufficient air is blown over the water
through which the evacuating air is exiting, then the risk of any
explosion would, I would think, be very close to zero.<br>
<br>
<br>
<br>
d.<br>
<div>-- <br>
<div><span style="font-size:110%">David William
House<br>
</span>
<div style="padding-left:3em;font-size:80%">"The Complete
Biogas Handbook" <code><a href="http://www.completebiogas.com" target="_blank">www.completebiogas.com</a></code><br>
<i>Vahid Biogas</i>, an alternative energy consultancy <code><a href="http://www.vahidbiogas.com" target="_blank">www.vahidbiogas.com</a><br>
<br>
</code></div>
<div style="padding-left:2em">"Make no search for water.
But find thirst,<br>
And water from the very ground will burst."
<div style="padding-left:2em;font-size:80%">(Rumi, a
Persian mystic poet, quoted in <i>Delight of Hearts</i>,
p. 77) <br>
<br>
<a href="http://bahai.us/" target="_blank">http://bahai.us/</a></div>
</div>
</div>
</div>
</div>
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for more information about digestion, see<br>
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<br>
<br></blockquote></div><br><br clear="all"><br>-- <br>Alexander Eaton<br>Sistema Biobolsa<br>IRRI-Mexico<br><br>Mex cel: (55) 11522786<br>US cel: 970 275 4505<br><br><a href="mailto:alex@sistemabiobolsa.com" target="_blank">alex@sistemabiobolsa.com</a><br>
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<br>
for more information about digestion, see<br>
Beginner's Guide to Biogas<br>
<a href="http://www.adelaide.edu.au/biogas/" target="_blank">http://www.adelaide.edu.au/biogas/</a><br>
and the Biogas Wiki <a href="http://biogas.wikispaces.com/" target="_blank">http://biogas.wikispaces.com/</a><br>
<br>
<br></blockquote></div><br><br clear="all"><br>-- <br>Joshua D Bogart<br>Program Coordinator<br>Trees for the Future<br>Siguatapaque HN<br>Barrio Macaruya, Calle, 21 de Agosto <br>cellular (504) 9696-3700<br>home/casa 740-1060<br>