# New idea for CO2 source?



## megamax42 (Jun 28, 2011)

So I just got an idea tonight and I'd like to know what you think.










The combustion of propane ( C3H8 ) yields CO2 and H2O.
A 16.4 oz can of Propane is about $3-4 depending where you live.
16.4 oz of propane is 464.9 grams of Propane or 10.54 moles of C3H8.
The combustion equation is:
C3H8 + 5 O2 :laser: 3 CO2 + 4 H2O 
Which means that for every one mole of Propane we use, we get as a product 3 moles of CO2.
Therefore a 16.4 oz tank of propane is capable of yielding 31.63 moles of CO2 or 1,391.6 g CO2 
OR 3.07 lbs of CO2.

In order to get the right amount of CO2 production however I imagine one would need quite a tiny flame, so a bunsen burner of sorts capable of producing a very tiny flame would be required. I have no idea how much flame you would ideally want and therefore I'm not sure how possible this is without some serious condensing equipment to cool down the gas in order to prevent the tank from overheating.

This however brought on a new idea, what if you could partially heat the tank via propane and then you could use a smaller heater, saving space and money? This is of course assuming the heat caused by the combustion process wasn't hot enough to overheat the tank, instead only raise it partially so that the small heater gets it the rest of the way to your ideal temperature.

Besides the special bunsen burner you would need, it would also require the entire apparatus to be custom built, and for peace of mind I wouldn't install it without a few safety measures, such as perhaps a propane detector (http://www.google.com/products/catalog?q=propane+detector&hl=en&safe=off&client=firefox-a&rls=org.mozilla:en-USfficial&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1283&bih=575&um=1&ie=UTF-8&tbm=shop&cid=3852326500383702083&sa=X&ei=EJOOTqf9F8SnsAKp1My0AQ&ved=0CHwQ8wIwADgU).

This of course meaning it would be one hell of a DIY project, but I think possibly do-able. 
What do you think?

*Pros:*
- $3-4 for ~3 lbs of CO2
- Easy change out when you go empty (assuming you designed it that way)
- H2O 'top-up' could possibly counteract effects of evaporation somewhat. (Equation yields 4 moles of H2O for every 1 mole of C3H8, for a total of ~0.76 Liters of H2O, not much but couldn't hurt)
- Reliable CO2 production, as well as adjustable (depending on your burner)
- Co-generation; besides the CO2 and H2O being produced perhaps the heat could also be harnessed.
- Easy to turn off CO2 at night by turning off valve to propane.

*Cons:*
- Incomplete combustion could create Carbon Monoxide.
- Possible problem with burning of chemicals used to odorize? However upon checking the AmeriGas msds for odorized propane it says there are no harmful combustion products (which would make sense since you wouldn't wanna go camping with something that produces hazardous fumes). 
- Possibly difficult apparatus to make.
- Heat:CO2 ratio too high and setup requires a condensation or cooling column before gas can enter aquarium.
- Since the burner would need to be in an airtight container, in order to generate pressure, re-lighting the burner after turning the valve off for night-time could be a pain. A solution could be perhaps an electronic sparking system?


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## doubleott05 (Jul 20, 2005)

wow... the idea of seperting that seems more expensive than just going and gettign a bottle and filling it...

oh and where would you put all this stuff ... wiht an open flame

oh and you might kill yourself and not know it


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## megamax42 (Jun 28, 2011)

doubleott05 said:


> wow... the idea of seperting that seems more expensive than just going and gettign a bottle and filling it...
> 
> oh and where would you put all this stuff ... wiht an open flame
> 
> oh and you might kill yourself and not know it


That was the idea for the propane detector. Additionally the setup would be in a metal container.
This would be quite a challenge however one could probably install a thermocouple controlled valve for the propane and have the tiny flame heating the thermocouple. Then if the heat stops the voltage output varies and you could have the propane shut off.

And the flame would be VERY tiny, because you wouldn't wanna use up the propane too fast and have too much CO2.

Like I said it would take some serious design, but I think if designed well it could have a very low operating cost. (Compared to $20-30 for a refill of a 5 lb CO2 tank)


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## jcgd (Apr 8, 2011)

How do you harvest the co2 and get it into the aquarium? The idea works great for greenhouses and stuff where you let the products of combustion go straight into the atmosphere, but how would you capture the co2?


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## Elrodg (Sep 17, 2011)

Regardless of how it is separated you still have a plan that will not work as propane can kill both fish and plants. Even in small amounts.


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## James0816 (Oct 9, 2008)

Sounds interesting I must say....But I'll have to pass on that.


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## Tikulila (Feb 18, 2011)

nice idea, but dangerous, id rather work for making the DIY yeast, than risk my life. 

if you do it, watch out.:flame:


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## megamax42 (Jun 28, 2011)

This has been my big issue with it. Safety.

My plan on capturing the combustion products was a fairly large metal container (chosen specifically to be non reactive with both CO2 and Propane) with a hose leading to the aquarium (possibly through a condenser of sorts if necessary to cool the gas). This container being tall enough and wide enough to keep the flame's heat from concentrating on one spot. Additionally the container might have some sort of fins to help facilitate the dissipation of heat.

Remember that for the kind of CO2 output you would need it would require a* very tiny flame*.

Then in regards to you _Elrodg_, I was thinking, besides the already present propane detectors (both inline with the CO2 system, as well as outside), I would add an igniter of sorts above the burner that continuously sparked, eliminating any possibility of unreacted propane entering the aquarium.

I fully agree that this sounds like a very dangerous idea, I almost didn't post this thread due to it, however I think with very careful designing, with a lot of safety features, it could be accomplished.

And though the initial setup might be costly (depending on how you designed it), replacing materials would be as simple as buying a $3-4 can of propane every month or so.


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## Jeffww (May 25, 2010)

We could also build a bridge from key west to mogadishu but we would never do it... 

Doesn't sound like a good idea too me...

Also how would you pressurize the co2 gas and send it into the tank?


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## megamax42 (Jun 28, 2011)

Jeffww said:


> We could also build a bridge from key west to mogadishu but we would never do it...
> 
> Doesn't sound like a good idea too me...
> 
> Also how would you pressurize the co2 gas and send it into the tank?


The pressure would come from the pressurized propane tank (the $3-4 dollar one).
Since the propane is pressurized this is what will be the driving force behind the output pressure.

The only difference being that the propane has combusted, and will be yielding pressurized CO2 and H20 instead of pressurized propane.

Again I'm not saying 'come on guys, lets build one tonight and see what happens', I'm simply exploring the possibility of a different CO2 source, and there is no harm in conjecture.

Especially regarding something so expensive.


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## ecotanker (Jun 12, 2009)

Some one had the idea of using a solid carbon source like graphite and electricity to slow dissolve the carbon into the water. The last I heard Sicce sold a product along this line.

http://sicceus.com/co2.html

Don't know how effective this is, but would be interesting if we can come up with a DIY version.


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## Tikulila (Feb 18, 2011)

well, try to make a small computer model ,then we can see it at alto more easely, its a nice idea, but you still have to poish it, so a bit of advice.

Two boxes, one inside the other, 1st one in WELDED togather, exept one side, which will be air tight otherwise, to the box will be welded some heat dissapators. 

the second willl have fans, to take more heat out of there. i would put the set up on a heat proof table... (expansive).

a remote swich to open the flame. and some way to close it.

biggest prob:

OXIGEN, PRESSURE. you need to get oxygen in there, but also maintain pressure.


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## megamax42 (Jun 28, 2011)

Tikulila said:


> well, try to make a small computer model ,then we can see it at alto more easely, its a nice idea, but you still have to poish it, so a bit of advice.
> 
> Two boxes, one inside the other, 1st one in WELDED togather, exept one side, which will be air tight otherwise, to the box will be welded some heat dissapators.
> 
> ...


Very good point! This is the kind of discussion I was looking for.

I wonder if the convective forces would be enough to generate the pressure? Perhaps place an oxygen inlet at the bottom of the apparatus, just small enough to let in only the oxygen needed, and have the output tube coming out of the top.

Of course then I imagine heat in the tank from the convection could be a possible problem or benefit.

Or maybe you could have a bunsen burner that has an option to place a hose over the oxygen inlet, then you could re-seal the mostly sealed metal apparatus with the hose coming out. This way hopefully the only oxygen entering the system is gonna burn in the reaction.

When you turned on the propane a venturi effect would happen and oxygen would be sucked in. Now the big problem with this is the pressure differentials and when the pressure required to push the gas under water overcomes the pressure of the venturi system. However I have no idea what pressure that would be so it looks like I need to do some experimenting.


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## James0816 (Oct 9, 2008)

ecotanker said:


> Some one had the idea of using a solid carbon source like graphite and electricity to slow dissolve the carbon into the water.


Are you referring to something like this:

CARBO-PLUS Dial Control CO2 System

They generally have received negative reviews. Just a fancy expensive gadget with sub par results.


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## megamax42 (Jun 28, 2011)

James0816 said:


> Are you referring to something like this:
> 
> CARBO-PLUS Dial Control CO2 System
> 
> They generally have received negative reviews. Just a fancy expensive gadget with sub par results.


Interesting idea, I wanna know what the electrolysis reaction is.

I know simply the combustion of graphite yields CO2.

*Edit:* 
Found it:

(quoted from http://www.thekrib.com/Plants/CO2/electrolysis.html)
"The CO2-producing reaction at the anode:

2H2O + C -> CO2 + 4H+ + 4e-

is actually two reactions.

The first reaction is the oxidation of water:

2H2O -> O2 + 4H+ + 4e-

and the second step is the combination of the oxygen with the carbon
anode:

O2 + C -> CO2"

Although that would create Hydrogen gas as well. I wouldn't be too worried about it combusting, however I would be wary of it possibly reacting with components of the set up.


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## Tikulila (Feb 18, 2011)

that is dangerous, DONT even try that you are letting pure hydrogen and pure oxyget to the air... 


Hydrogen+Oxygen= NASA's starter fuel for rocket...=suicidal
DANGEROUS;

if you try, try the other idea,


you could make CO2 in other ways.

EDIT:

H + O2 VERY explosive

H by itself id dangerous (tried it...)


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## megamax42 (Jun 28, 2011)

Tikulila said:


> that is dangerous, DONT even try that you are letting pure hydrogen and pure oxyget to the air...
> 
> Hydrogen+Oxygen= NASA's starter fuel for rocket...=suicidal
> DANGEROUS;
> ...


I have quite a bit of experience with electrolysis to produce hydrogen gas for hydrogen fuel cells and I too thought there was something wrong with the reaction he posted.

For one being that for efficient electrolysis you need either a strong acid or strong base which means it would be it would be an external unit and from what I could tell the "CARBO-PLUS Dial Control CO2 System" was inside the aquarium.

Secondly although the hydrogen gas produced is insoluble, if you had a glass top I could see it possibly building up until disaster struck, so there's no way anyone sells that.


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## SlyDer (Jul 11, 2007)

i hope this is all just theory 0__O


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## megamax42 (Jun 28, 2011)

SlyDer said:


> i hope this is all just theory 0__O


Theory with possible ultra-precautious testing 

We'll never make CO2 addition cheaper unless someone is willing to test new ideas.

Safely of course.

:deadhorse
Idiom aside, does anyone else find this 'smiley face' slightly disturbing? lol


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## SlyDer (Jul 11, 2007)

Fair enough, there is only one way to innovate, but this is one time I'm glad I'm not the innovator!


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## megamax42 (Jun 28, 2011)

SlyDer said:


> Fair enough, there is only one way to innovate, but this is one time I'm glad I'm not the innovator!


Haha yeah I don't blame you, I'm a little nervous myself, however with proper precautions I should be fine, thankfully it is a very minimal amount of propane being used. I will of course be doing this experiment on a tank with no fish and only plants.

I'll post updates when I get around to testing it.


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