CALLING ALL BRAINS - CO2 PROJECT

[BlindDate]

So this is what I am trying to do. I want to design and build a machine that will produce CO2 gas by heating a chemical using electrical heat or heat produced by a electric heating element.

An example might be some kind of mechanism that feeds a dry carbonate through a heating coil. The mechanics are something I can easily do. My problem is that I know nothing about chemistry. What to heat? Sodium Carbonate? Calcium Carbonate? Sodium BiCarbonate? Something else? What are the by products? What temps are required and for how long? How much gas is produced? etc.

I would like to make this an IC project that will finish with a comprehensive design we all can use.

Let's begin!

 

[Mr Celsius]

Not attempting to troll...

I think the method of burning NG or Propane is most efficient because the resource is readily available. I can't imagine having to order some more Sodium Carbonate, or whatever, when you run out... especially when you can run to the home improvement store and pickup a Propane tank...

Mind you, if it was more energy and cost efficient... I'm fully open to buying materials and experimenting. I'll ask a chemist buddy of mine tonight.

 

[BlindDate]

Lets suppose you are shipwrecked on an island and you only have an undersea cable that washed up in a storm that you can tap electric power from and natural mineral deposits on the island.

Thank you for asking your friend the chemist.

 

[kaljukajakas]

I'm a chemist and I'd like to see this work but it will be difficult...

Calcium or sodium (bi)carbonate are, AFAIK, pretty much the only choices we have since they're cheap and easily available. I guess you could also find magnesium and potassium (bi)carbonate but not as easily. Of course there are a lot of materials that could be oxidized to make CO2 but then you might as well use propane.

How hot would you have to get them? Both sodium and calcium carbonate decompose at about 850 deg. C/1600 deg. F. That's almost yellow heat. Aluminium, for example, melts at a much lower temperature.

Sodium bicarbonate (baking soda) decomposes rapidly at about 200 deg. C/400 deg. F, yielding sodium carbonate, water and CO2. IMHO that would make baking soda the only practical choice in this application. It will start decomposing slowly at 60 deg. C/140 deg. F.

Do you intent to make this CO2 generator operate on continuously or in batches? How will you move powder into and out of the heating chamber?

168 g of baking soda will release up to 44g of CO2 when heated to sane temperatures.

 

[BlindDate]

Thank you Kal

So it looks like Baking Soda is the way to go. I would like to make it continuous.
Double check me, but I think that your 168 grams of Baking Soda will produce 44 liters of gas or 1.58 cu/ft.

I'm thinking that the powder will move through a cylindrical heating chamber via some kind of ceramic screw that scoups it up at one end and dumps the waste at the other.

How fast does baking soda completely decompose once it reaches 400F? What if I took the temp higher?

 

[BlindDate]

I just found a decomposition chart that shows 100% decomposition at 320F (that was the hottest) in about 30 minutes.

That is way too slow for me. Need much higher temps

 

[kaljukajakas]

2NaHCO3 -> Na2CO3 + H2O + CO2

168 grams of baking soda (2 moles) will yield 44g (1 mole) of CO2, at room temperature that is only 25 liters. Or double that if you heat it to extreme temperatures and the carbonate decomposes. For comparison, you can get 25 liters of CO2 from only 16 grams of natural gas.

I don't know exactly how fast it decomposes at a given temperature, you'd have to dial your machine in anyway as there are more issues than simple chemistry: in a continuous system you'll get temperature gradients and uneven heating, incomplete decomposition etc. A lot of factors that govern how hot your oven actually needs to be. Quite different from "ideal" laboratory measurements. It should start decomposing more rapidly the hotter you get in a more or less exponential manner though, so you probably don't need all that high a temperature.


Where are you going to get a big ceramic screw, BTW? Stainless or even aluminium should be fine if you're not going to build a red hot oven. As baking soda is not granulated I'd expect things to clog easily so you'd probably need to do something like vibrating the hopper and screw+oven assembly to deal with it. Try to moving a few pounds of baking soda through one of those hand-cranked meat grinders to get a feel for it. Plenty of friction... Placing the screw vertically might be a really good idea.

 

[flux]

Why not drip an acid solution into a slurry of stirring sodium bicarb, its a much cheaper, ie exothermic method of releasing co2.

 

[Quazi]

Champagne yeast and sugar water will produce CO2 for far longer than baking soda and vinegar. Champagne yeast in particular because it has a high tolerance to alcohol so it will be able to sit in the solution for much longer. Once you have the yeast dialed in, you won't have to add more ingredients or change the ingredients but once every 3 - 5 days.

Just another idea.

-Q

 

[ooga booga]

Lets suppose you are shipwrecked on an island and you only have an undersea cable that washed up in a storm that you can tap electric power from and natural mineral deposits on the island.

Man, I'd be growing outdoors!