[Digestion] Biogas burner and light Design...

[Hoysall Chanakya]

Dear All,
After sending the mail I have second thoughts about the exact air:fuel
mixture required in the primary mixing tube - I wonder if my memory is
failing me will confirm the same in a few hours (8-10.5, air : 1, gas). 
Anyway the burner opening area to the mixing tube dia should obviously be
in the ratio of 1:1.5 - 1:2.5 depending upon the pressure drop expected. 
I will give these numbers shortly
best wishes
chanakya

Dear Mike Barnet
The critical needs seem to be very simple and these we were taught early
and they are I suppose this much

Whatever be your pressure or flow, the primary air to gas stoichiometric
ratio is 8-10.5:1 (air + biogas for pirmary air mixing), mixing tube
length about 10-15cm at 100-150mm water pressure.  At the top, the gas-air
mixtures need to be brought to the burning surface - the openings are
usually 4-6mm wide for stable high temperature colorless flame.  At the
right air to fuel mix and achieving highest combustion temperatures (1050
celcius) - the flame will be barely stable and will emerge about 5mm above
the burner surface and will usually emit a short hissing sound.  At a
higher air to fuel ratio the flame head becomes unstable.  Gas consumption
at this stage would be about 400L/h giving an equivalence of about 2kW of
thermal efficiency around 55% (heat transfer efficiency) for a flat vessel
or receiving body

For mantle lamps a small deviation is suggested when working under normal
gas pressure 100-150mm water pressure).  First, reduce the mantle's
combustion surface to one third of what is usually available for a
kerosene usage.  That is tie the mantle such that only a third of the area
hangs down the rest is on the ceramic support above.  You should now be
able to support a flow of about 125L/h and yet have the mantle glowing
uniformly round.  If you do not reduce the combustion area (tie the mantle
to allow only a third of it to glow) the glowing area will not be uniform
and will keep moving around.  A burner will consume a third of the gas
used in conventional biogas burners - 4cft/hr (the original rating) about
125L/hr.

I guess you can now succeed without much of a problem

best wishes
chanakya



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