[Digestion] Response _ Biogas appliances

Mon May 21 19:31:47 CDT 2012

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 
> <chanakya at astra.iisc.ernet.in <mailto:chanakya at astra.iisc.ernet.in>> 
> 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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>     >
>     > 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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>
>     _______________________________________________
>     Digestion mailing list
>
>     to Send a Message to the list, use the email address
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>
>     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
>
> alex at irrimexico.org <mailto:alex at irrimexico.org>
> alex at sistemabiobolsa.com <mailto:alex at sistemabiobolsa.com>
>
> sistemabiobolsa.com <http://sistemabiobolsa.com>
> www.irrimexico.org <http://www.irrimexico.org>
> www.redbiolac.org <http://www.redbiolac.org>
>
>
>
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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/
>
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