[Digestion] Methane measurement

[Paul Harris]

G'day All,

Invention? I did get the idea from a paper about using a syringe for obtaining
the CO2 content of beer and I remember some high school chemistry.

To make the reading easy I use a flexible tube on the syringe body and use a 10
ml gas sample (including the tube volume - my tube holds 4 ml so I draw up to
the 6 ml mark). I take in extra gas and expel down to the mark. Now leave the
tube end submerged in sodium hydroxide solution (after drawing up 20-30 mls of
solution) while you shake the syringe to get good absorption. Then, with the
syringe vertical so liquid is expelled via the tube, push the plunger down to
the 10 ml mark - now the volume of liquid indicates the volume of CO2 absorbed
(a small amount will still be in the sample - a nice little student project!)
and since you started with 10 ml of gas 3 ml of liquid remaining indicates 30%
CO2 (plus a little bit), but that's OK for field checking. The sodium hydroxide
only needs to be dilute.

Have fun,
HOOROO
-- 
Mr Paul Harris,
Faculty of Sciences
The University of Adelaide
Roseworthy Campus ph 08 8303 7880 fx 8303 7979


Quoting "Zietsman, Rex" <Rex at Process.co.za>:

> What a wonderful low tech idea! Well done to Paul if he is the inventor.
>
>
> Rex
>
>
> Frank, Hi
>
> I tried Paul Harris's very simple idea recently. Fill a disposable
> plastic
> syringe with gas, up to about 80% i.e. a 50 ml syringe should be filled
> to
> 40 ml. Then draw in a solution of a hydroxide so the plunger comes to
> the
> maximum reading (50 ml means drawing in 10 ml of solution). Sodium
> hydroxide is probably the best, but lime water, calcium hydroxide, will
> do.
> Close the end of the syringe. There are rubber caps that are available
> for
> this. Using a finger tip means that you get corrosive hydroxide on it.
> Shake the syringe, so the carbon dioxide dissolves in the solution and
> the
> syringe plunger is pulled in. You can press gently on the plunger to
> overcome friction, but not so hard as to push the solution out. The new
> volume reading is the volume of biogas less that of carbon dioxide
> (probably mainly methane).
>
> The group in India to whom I showed this idea were very pleased. They
> now
> have a low tech method of measuring methane content of the gas.
>
> I normally use a methane analyser that I bought second hand when British
>
> Gas were replacing their old ones. It has a thermal conductivity cell.
> Methane will transfer heat more easily than air or carbon dioxide. It
> was
> calibrated on methane/air mixes, but it should be OK for methane/carbon
> dioxide mixes, if not completely accurate.
>
> Cheers,
>
> David
>
>
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