[Digestion] flame lifting

[David Fulford]

Dear Deepak and listers,

The issue of burner design and pressure control is one which needs some 
careful planning. Biogas has a very low flame velocity, so if the flame 
lifts from the burner, it means the flow rate of the biogas/air mixture 
is too high, so the velocity from the flame port is faster than the 
flame can burn.

If you are using burners from a reliable source, then the gas pressure 
is too high. If you are using a floating drum, the weight of the drum is 
too much. However, studies by SNV of burners made in different projects 
suggests that the quality of burners from different places in Asia is 
not consistent. (I say this as someone who helped design the one now 
used by BSP Nepal, which was criticised by the SNV study). The biogas 
wiki <http://biogas.wikispaces.com/Biogas+burners> has a section on 
biogas burners, with a link to that SNV report. Our Nepal design used 
too few flame ports. A larger flame port area would have reduced the gas 
mixture velocity through the holes. You may need to look for a better 
burner.

The simplest way to reduce gas pressure is to use a gas valve to control 
the flow. Partly closing the valve will increase the pressure losses, 
reducing the flow rate and the flow velocity. A longer lasting solution 
is to use a pressure control valve.

Regards,

David F

On 31/03/2011 16:31, Deepak D. G. wrote:
> Dear listeners,
>
> I would like to consult on a issue of flame lifting.
>
> I have installed 8 floating digesters and all are working well and the 
> gas production is also very good.
>
> The only issue I have right now is the flame lifting issue, specially 
> with the latest installation. The latest installation, in a village in 
> Bali,   has a capacity of 1000 liter gas tank and the distance between 
> the structure and the stove is about 20 meters. I used a combination 
> of a plastic tube and pvc of equal size and that is 1/2".
>
> I can not get the flame burned immediately above the surface of the 
> burner but it is lifting. I have tried the same stove at home in which 
> the distance between the  biogas and the  stove is about 8 meters and 
> the flame is stable  and not lifting.
>
> Can anybody suggest solutions to this issue? thanks
>
> Rgds,
> Deepak
>
>
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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 David Fulford CEnv MEI, 15, Brandon Ave, Woodley, Reading RG5 4PU
d.j.fulford at btinternet.com <mailto:d.j.fulford at btinternet.com>, Tel: 
+44(0)118 326 9779 Mob: +44(0)7746 806401
Kingdom Bioenergy Ltd, www.kingdombio.com <http://www.kingdombio.com>, 
davidf at kindombio.com <mailto:davidf at kindombio.com>

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