Help - My gas won't burn.

[JMALW]

I have found the soda lime formula for removing co2 in closed circuit diving apparatus:94% Ca(OH)2  2-4% NaOH  1-3% KOH @ 14-19% water content....I am not a chemist,its from a 1952ish navy manual!

That could be really useful

Thanks
PS I also found that trying to remove CO2 by bubbling the mixture through water actually removes the CH4 since Methane is soluable in water at 17 C.
 

[mespilus]

The soda lime will absorb some CO2, along the lines of

Ca(OH)2 +2CO2 = Ca (HCO3)2

the calcium hydroxide becomes calcium hydrogen carbonate.

You all saw this in school chemistry lessons,
when you blew down a pipe through a test tube
containing a clear liquid that went milky
the calcium hydroxide is (very) soluble in water,
while the calcium hydrogen carbonate is
not so soluble in calcium hydroxide solution.

Enough chemistry.
Practicalities.
J Clarkson, village idiot of this parish, demonstrated
this recently on Top Dull, by attaching 'a box of rocks'
to a diesel Jaguar. The 'box of rocks' should have been
calcium hydroxide.
The box would only have 'solved' the jaguars' emissions
for only a few miles before all the hydroxide became hydrogen carbonate.

How do you regenerate the hydrogen carbonate?
By heating it to drive off the CO2,
(the reaction is pretty much the same as makes chalk,
calcium carbonate, (CaCO3) become calcium oxide, (CaO),
which becomes calcium hydroxide when it gets wet,
CaO + H2O = Ca(OH)2.

So unless you've got some free heat a bit of a dead-end.

Sorry to dampen any enthusiasm.

[JMALW]

hi
Crikey I only got to dropping an Alkazelzer in a glass of water and watched it fizz when I was at school.

I'm impressed and also deflated.

Thanks
PS Should that not be H2S blight zone?

[mespilus]

PS Should that not be H2S blight zone?

Unfortunately not.

It may turn out to be Lord Adonis' final pipedream, but we live close to the
route of the Chiltern line, which is the chosen route for HS2,
or High Speed 2 which will initially connect London to Birmingham.

[JMALW]

Hi folks
From my discovery that water absorbs methane at 17deg c it is obvious that my ingenious water gas pump needs some mods since some of the gas is in contact with the water surface in the IBCs used to pump the gas to storage. I have a solution planned to over come this and will let you know if it works.  This is vital if I get the gases separated otherwise storing the gas will be problematic.

[mespilus]

There is soluble like
sugar in water
(table) salt in water

and there is solubility like methane in water

http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

second graph down.

Unless your water storage vessel holds gazillions of gallons
you will soon reach the saturated solubility of methane in water,
and 'lose' no more.

[northern installer]

re:co2 absorbtion,further discussions with people more chemically minded than myself indicate that caustic soda pellets in dry form will absorb co2;this might be cheaper and simpler for a test rig,to ascertain both burning capacity and co2/other gas ratio,though I admit,not really practical for long term usage .

[JMALW]

Thanks Guys
Do you think the gas would be absorbed into the water if it just sat atop the surface and not bubbled through?  Also would time in contact with the gas and water be significant?
Hang on  - they used to have gasometers sealed with water so I guess it was not a problem.

Still a long way to go

[daftlad]

http://www.fastonline.org/CD3WD_40/CD3WD/INDEX.HTM

This website has lots of articles in biogas, I haven't read them so I don't know if they will help. (they are about a third of the way down (there may be more))
ta ta

[Ivan]

not sure NaOH (caustic soda) would be a good option here - it's very hygroscopic, so if the gas is damp (it will be), the NaOK will rapidly absorb enough water to dissolve itself. You'd need to dry the gas first (conc. H2SO4 in chemistry labs, but not viable or economic on a large scale)

There's a big fuss at the moment on injecting 'scrubbed' biogas into the national grid network in the UK. It would be worth reading up on how they clean up the gas commercially as a starting point.

[northern installer]

I was suggesting caustic soda pellets as a cheap experimental scrubber(ooer!)to see if it removes sufficient co2 then leaves a flammmable gas;Ivan,I agree with you on the hygroscopic side(just leave an open bag of caustic outside and you end up with a mushy mess)but surely the point of experiment is to come up with a  test rig,then move on to better systems if it proves the principle with a flame?