[Digestion] Response _ Biogas appliances

Mon May 21 15:17:51 CDT 2012

Hello Alexander,

Do yellow tips indicate incomplete combustion, or too much oxygen (lean mixture)? I'm curious if there is a quick indication of incomplete combustion, which could emit carbon monoxide.

Thanks
Doug Renk

________________________________
From: Alexander Eaton <alex at sistemabiobolsa.com>
To: For Discussion of Anaerobic Digestion <digestion at lists.bioenergylists.org> 
Sent: Monday, May 21, 2012 2:54 PM
Subject: Re: [Digestion] Response _ Biogas appliances

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> 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/>
>>
>> --
>> This message has been scanned for viruses and
>> dangerous content by MailScanner, and is
>> believed to be clean.
>>
>> _______________________________________________
>> Digestion mailing list
>>
>> to Send a Message to the list, use the email address
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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
>
>
>--
>This message has been scanned for viruses and
>dangerous content by MailScanner, and is
>believed to be clean.
>
>
>_______________________________________________
>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
>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/
>
>

-- 
Alexander Eaton
Sistema Biobolsa
IRRI-Mexico
RedBioLAC

Mex cel: (55) 11522786
US cel: 970 275 4505

alex at irrimexico.org
alex at sistemabiobolsa.com

sistemabiobolsa.com
www.irrimexico.org
www.redbiolac.org

_______________________________________________
Digestion mailing list

to Send a Message to the list, use the email address
Digestion at bioenergylists.org

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/
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