[Digestion] flame trap/ flame arrester

[Paul Harris]

G'day Matt,

 

I don't often check the wiki but I do sort of recall seeing the questions
you left, which I will answer below (and put back on the wiki!).

 

I also distrust steel mesh as a flame trap, but it works by removing the
heat and you could use stainless steel pot scourers for a small unit.

 

I hope this is some help and am happy to answer further questions,

All the best,

HOOROO

 

In flametrap 1, it seems that the pressure relief container should have a
greater water depth than the container through which the gas is bubbling.
Wouldn't the greater water pressure of deeper water stop the gas from
bubbling? If not, then why doesn't it bubble out of the pressure relief? I'm
sure there's something I don't understand.

 

If you start from the burner and work back it may help a little. Let's say
the burner needs 2 cm water, which means the water in the pressure relief
will be 2 cm different in height and you may have another 2 cm of pipe depth
to make sure gas doesn't leak out un-necessarily. Now if the flame trap pipe
is 6 cm into the water the digester pressure will have to be 2 cm burner
pressure plus 6 cm flame trap pressure or a total of 8 cm of water.

In flametrap 2, I'm assuming that there is supposed to be water inside. If
that's the case, I'm having trouble understanding the pipe on the right side
of the diagram (near the words "normal (burner) pressure"). Is this a
pressure relief that works like a manometer? 

 

You are right on both counts, water is used again and it collects in the
first U bend that acts as a flame trap then excess water is pushed out the
second U bend that also functions as a pressure relief. I thought of this
one as it is easier to screw pipes fittings together than weld containers.
The only disadvantage I can see is the limited water storage in the first
bend that may not hold back a large pressure surge caused by a backfire, but
if the digester tube is smallish the inertia of water may mean the job is
done. All parts need to be metal!

I understand that I can make a flame arrester using wire mesh, but I don't
know where to get stainless or brass mesh here in the Philippines. I like
the simple idea of bubbling through water but I'm getting confused looking
at the diagrams. 

Thanks in advance for your help.

 

Mr. Paul Harris, Room S116b, Waite Main Building Faculty of Sciences, The
University of Adelaide, Waite Campus, PMB 1, Glen Osmond SA 5064 Ph    : +61
8 8303 7880      Fax   : +61 8 8303 4386 mailto:paul.harris at adelaide.edu.au
http://www.adelaide.edu.au/directory/paul.harris

 

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From: digestion-bounces at lists.bioenergylists.org
[mailto:digestion-bounces at lists.bioenergylists.org] On Behalf Of Matt Lorig
Sent: Tuesday, 14 December 2010 12:30 PM
To: Digestion at bioenergylists.org
Subject: [Digestion] flame trap/ flame arrester

 


Hello, 

I have a Chinese style AD unit for my pig farm here in the Philippines.  I
would like to improve the safety of my system by installing some kind of
flame trap or flame arrester to make it impossibe for the flame to travel up
the gas pipe to the tank.  I know that I can use a mesh screen but I'm not
sure if I can get suitable materials here that won't corrode.  I like the
simple idea of bubbling the gas through water. I've looked the the flametrap
designs on the safety page of the Beginners Guide to Biogas, but I'm having
trouble understanding the diagrams.

http://www.adelaide.edu.au/biogas/safety/flametrap.jpg and 
http://www.adelaide.edu.au/biogas/safety/flametrap1.jpg

I posted specific questions about the diagrams on the biogas wiki, but so
far no response.

http://biogas.wikispaces.com/message/view/Questions/30782495

Any help or ideas would be greatly appreciated.

Thanks.
Matt Lorig
mattlorig at yahoo.com

 

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