G'day Alexander,
Thanks for your comments and suggestions! I agree that a "diffusion"
flame (with no primary air) may work better at low pressure and possibly
lower gas quality so I will add a comment to the spreadsheet.
All the best,
HOOROO
Mr Paul Harris BEng (Ag) (Melbourne)
Visitor at The University of Adelaide
On 22/05/2012 5:24 AM, Alexander Eaton wrote:
We have had many cases of poor air mixes generating biogas flames that
are not blue. I agree the "blue" does not necessarily mean the most
efficient combustion, but it is a good starting point. In fact, I
would add more value to the "observed" characteristics of the flame as
a good indicator of burner efficiency: If you can see that the flame
is blue (no yellow tips), stable, compact, does not "float" above the
ports, and you can smell that there is not excessive odor, only very
serious tests will give you much better information. We realized this
when we could basically "guess" the results of our burning testing
before the measured results were calculated.
Also, just a comment on the biogas burner information on the wiki site:
First is it very well done and complete, however the equations and
relationships seem to fall apart under the low to "no" pressure that
we have in digesters in Latin America (eg, non-dome-type). After a
lot of trial and error, our "newest" burner does not have any primary
air mixing, our injector jet is a bit larger than the calculations
would suggest, and the burner ports are about equal to that of LP Gas.
This burner performs much better than over ten iterations of other
burners that have better air mixing, and follow the normal
calculations presented in the literature. We believe this has
everything to do with nearly orders of magnitude difference in
pressure between tubular and fixed or floating dome systems. We are
hoping to publish these results shortly. In short, I would add an *
to any guides that allows for differences in burner designs for
systems that normally function at just a few mm of water column pressure.
Best,
A
On Mon, May 21, 2012 at 12:11 PM, Hoysall Chanakya
<[email protected] <mailto:[email protected]>>
wrote:
Dear Dr Tumwesige,
Done well and is self contained.
Would you like to supplement that the primary gas:air mixing
should be at
stoichiometric ratio (calculated based on CH4 content) and
secondary air
is at the burner ports (top openings). Further, methane /biogas
always
burns with a blue flame and so a blue flame cannot be used as an
indicator
for correct air-fuel ratio. At ideal conditions, the flame burns
with a
hissing sound and the flame does not touch the burner tops but
burns 2-3mm
above.
best wishes
Chanakya
> Dear All,
>
> I am writing a paper on biogas appliances, below is an extract
from the
> paper.
>
> All gas burners follow the same principle; the force which
drives the gas
> and air into the burner is the pressure of gas in the pipeline.
A biogas
> stove can have single or double burner with varying gas
consumption rates
> ranging from 220 dm3 hr-1 to 450 dm3 hr-1 at standard
temperature and
> pressure. This consumption rate results from the pressure
provided by the
> biogas plant and the diameter of the inlet pipe. The jet at the
inlet of
> the burner increases the gas speed, so producing a draft that sucks
> primary
> air into the pipe. The primary air must be completely mixed with the
> biogas, and this is achieved by widening the pipe to a minimum
diameter,
> which is in constant relation [JUS1] <#_msocom_1> to the
diameter of the
> jet. The widening of the pipe again reduces the speed of the
gas. This
> diffuse gas goes into the burner head. The burner head is formed
in such a
> way as to allow equal gas pressure everywhere before the gas/air
mixture
> leaves the burner through the orifices at a speed only slightly
above 0.25
> ms-1, the specific flame speed of biogas. More oxygen (secondary
air) is
> supplied by the surrounding air to enable final combustion.
> ------------------------------
>
> [JUS1] <#_msoanchor_1>Specify what this constant relationship
is plus
> reference
> Please, is some one in position to provide more information on the
> highlighted section of the extract?
>
> Thank you in advance,
>
> Regards
> --
> Vianney Tumwesige
> Director - Green Heat (U) Ltd [image: Picture]
> P.O. Box 10235
> Kampala-Uganda
> 256 (0) 71 237 9889
>
> "The more people are self sufficient in cooking fuel, the more
personal
> and
> financial freedom they have." - Emma Casson
>
>
> <http://trustvianney.wordpress.com/>
>
> --
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>
> _______________________________________________
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>
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>
> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
--
Dr. Hoysall Chanakya
Centre for Sustainable Technologies
(Assoc. Faculty at Centre for Infrastructure, Sustainable
Transport and
Urban Planning (CiSTUP) and Centre for Contemporary Studies)
Indian Institute of Science, Bangalore 560 012
ph 91-80-2293 3046; fax-91 80 2360 0683 <tel:80%202360%200683>
--
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_______________________________________________
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to Send a Message to the list, use the email address
[email protected] <mailto:[email protected]>
to UNSUBSCRIBE or Change your List Settings use the web page
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for more information about digestion, see
Beginner's Guide to Biogas
http://www.adelaide.edu.au/biogas/
and the Biogas Wiki http://biogas.wikispaces.com/
--
Alexander Eaton
Sistema Biobolsa
IRRI-Mexico
RedBioLAC
Mex cel: (55) 11522786
US cel: 970 275 4505
[email protected] <mailto:[email protected]>
[email protected] <mailto:[email protected]>
sistemabiobolsa.com <http://sistemabiobolsa.com>
www.irrimexico.org <http://www.irrimexico.org>
www.redbiolac.org <http://www.redbiolac.org>
_______________________________________________
Digestion mailing list
to Send a Message to the list, use the email address
[email protected]
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org
for more information about digestion, see
Beginner's Guide to Biogas
http://www.adelaide.edu.au/biogas/
and the Biogas Wiki http://biogas.wikispaces.com/
_______________________________________________
Digestion mailing list
to Send a Message to the list, use the email address
[email protected]
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org
for more information about digestion, see
Beginner's Guide to Biogas
http://www.adelaide.edu.au/biogas/
and the Biogas Wiki http://biogas.wikispaces.com/
