Refilling CO2 Tanks with Dry Ice?

However or wherever they do it the fact remains that the delta labor cost for filling a larger bottle is small (or 0) relative to that for the smaller ones so that the labor cost per pound is less for the larger bottles/tanks.

By happenstance, i stumbled upon this thread just by browsing the net. I've spent the past half hour reading this thread and it's various 'theories' and 'speculation' with the occasional 'fact' mixed in. I registered on these forums just to add my two cents.

I am a "chemical" engineer, with a minor in chemistry, so I may be able to add a bit of credible information.

First off, in regards to the 'carbonic acid' argument:
Carbonic acid has negligible effect on aluminum. Basically NR. This is why you see soft drinks safely canned in aluminum.
Carbonic acid *Does* indeed corrode iron. It corrodes [stainless]steels as well. It depends on the grade of steel as to how much corrosion will take place given an amount of carbonic acid and other factors. I cannot comment on the grade of any of your tanks as I do not own one, but lets just say better safe than sorry.

In regards to the 'water in co2' vs 'co2 in water' - This all involves thermodynamics and some fairly complicated mathematics for those not familiar with it, along with phase diagrams and critical temps and pressures of co2 and h2o. For the sake of simplicity, lets just say that the link illustrated in a previous post have to do with the amount and concentration of each species in question relative to pressure and temperature. It's of importance because the pressure inside of your tank will be changing as you are venting the gas. Given that with varying pressures you will have varying concentrations of carbonic acid, the question to ask is 'could there be a point at which the right conditions exist for the inside of my tank to corrode?'
The answer to such a question is yes. To what degree depends on far too many factors to calculate, including the amount of h2o present in the tank, the pressures, the grade of steel, etc. Short answer is that water inside of a steel tank pressurized with co2 is not an ideal situation. This of course is of little importance if you are using an aluminum tank.

In regards to the 'cold dry ice stress', I'm sorry but I cannot give you any answers on this. Yes, it is a fact that metals will have different properties at different temperatures, but whether or not aluminum/steel would be degraded enough by the given temperatures I do not know. It's something chemE's and as AJ is an EE, we were never taught. MechE's on the other hand deal a lot in this area, and now I am interested enough that I'll need to ask a buddy of mine to see if he knows anything about it. If i ever get a definitive answer, I'll make sure to post back

I saw the video on YouTube and did what he said. A few hours later I had a full bottle of CO2 for under $5.00.

This may not be for everyone but if you understand what you are doing and do it the right way, you can save lots of money!

Try it but remember not to over fill it. That's when you'll have problems! This is where you need to know how much dry ice to put in an empty CO2 tank no matter how small or how big the tank is.

Bit late for my input on this. I did recharge a CO2 extinguisher using dry ice and will not do it again. I have since read that steel becomes brittle and can shatter even without pressure at temperatures below -30°C. Dry ice has a temperature of about -79°C.
Filling from one container to another using liquid CO2 under pressure is done at close to room temperature, this is the way it is done commercially and is the safe option.

Seconded (tenthed?) that this is a terrible idea.

Even if you could do the whole thing safely, it seems unlikely you could reach the levels of O2 that you really need to be able to carbonate and serve your beer without severe staling.

acidrain said:

To answer your question, it is possible, but I think you would need to remove the valve to do it, and that can be dangerous itself depending on your skill and knowledge of compressed gas cylinders. You would need to measure (in weight) the dry ice, and not exceed the bottle rating.

That said, you should be able to find a used 5 or 10 lb bottle on craigslist for around $50... more if it includes a regulator.
Take that puppy to your nearest welding shop and exchange it for a new, filled tank (doesn't matter if it's out of date as long as it's NOT a rented tank) for exchange.
I pay $11 for each 5 lb exchange, and the tanks I get look brand new. I understand it's only $20 or so to upgrade from a 5 to 10 lb., and the fills are only a couple dollars more.

Click to expand...

You don't need to remove the valve – there is a hose and a converter fitting that fits on the sodastream.