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?

[JMALW]

Hello ALL,
I have been preoccupied on another project for a while. I see the topic gathered quite a lot of interest so I thought I'd let you know the score.
I never got the gas to burn and the reason was because the digester needs to be kept at some 30 degrees and even then the CO2 is to high to allow any combustion.  If I had a farm with plenty of Cow or Pig Poo it would be possible to get a higher percent of Methane in the mix but it would require a lot of fermenting and heat. Frankly it is nor worth the hassle - it would be much better to use the heat source material in a pot belly stove and heat the garage/workshop with it directly.  Last night I watched a program called "Bang goes the Myth" or something like that and they were trying to find a suitable fuel.  They used a gas source to warm the digester ( makes no sense) then used oven cleaner to absorb the CO2.  Now I tried this and it did not work for me. They used a bag to collect the gas but I have a much more efficient way of storing the gas under pressure if it had worked.  In conclusion I believe there is a way to get biogas on a large scale but I suspect it is mainly for waste disposal and a small amount of gas is produced as a by product but I would think if anyone is simply trying to produce gas as the prime reason it is not worth it.  If anyone as found an answer to my problem let me know before I scrap the digester.

[knighty]

JMALW

have a quick look at them on youtube


there's a lot of biodigesters being used in the 3rd world (africa, india, china)

they look to be very easy to use and reliable.... tho I guess there climate is a bit better suited to them than our own

[dhaslam]

Are membranes out of the question for small systems?

http://www.newpointgas.com/naturalgas_carbondioxide.php

[JMALW]

Hi guys,
If you take a look back on some earlier posts here I was told some people were working on membranes to diffuse CO2 but I could not find who it was or where to get hold of some. It has obviously moved on since then and this may be worth reviewing if it can work within low pressure band widths. Knighty - I have seen those on YouTube and it is so unfair that they get the climate and we don't.  However, I have a source of free energy now with PV and small grid ties that gives me a useful surplus of  energy - 1kw per hour during most days currently so I may be able to use some to warm up the barrel more. There maybe some more work to do on it yet.