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-   -   Refilling CO2 Tanks with Dry Ice? (http://www.homebrewtalk.com/f128/refilling-co2-tanks-dry-ice-355502/)

Derick_Z 09-20-2012 02:23 AM

Refilling CO2 Tanks with Dry Ice?
I made this post on another forum, but didn't generate much interest so I'm trying again here.

I'm looking to make the jump to kegging soon (when I get enough cash saved up). I've done a lot of planning and reading/research, so I think I'm pretty much ready for anything that can come at me. In researching prices for C02 refills, however, I've been disappointed and unable to find anything that doesn't seem exorbitantly expensive. What are the average prices nowadays? I'm only finding things from several years back in my searches. On to the point of this post, however..

I saw a YouTube video of a man refilling a soda-making tank by taking the top off the tank, crushing and weighing dry ice, then putting it in the tank and screwing the top back on. Obviously the lid has to be pretty darn tight to prevent leaks, but I was intrigued by the concept. I can buy dry ice here for a buck a pound at the grocery store, which would dramatically cheapen my refills. I know a bit about chemistry, and it does make sense that the ice will sublimate until enough gas pressure has been reached, at which point the remaining ice will melt into the liquid C02 that you get when you refill the tank professionally.

I'd likely start with a pound or two just to see how it works, but I honestly can't see any flaw. There's a safety valve on the tank, but I'll never need it because I'm carefully weighing the amount of CO2 I put in, along with the weight of the tank after filling. I know people will likely talk about how I'll introduce air to the tank when I open it, but I've done some research, and oxygen doesn't liquidate at room temperature, regardless of pressure. That means that the CO2 will liquidate (I believe along with the nitrogen), while the oxygen remains in the headspace under high pressure. If I vent the tank slightly, *most* of that oxygen should be cleared, and the liquid CO2 will boil to refill the headspace. Continuing that process should yield a result identical to purging a keg.

Does anybody have thoughts on this? I've scoured the web and haven't been able to find a single thing about it - either suggesting it or condemning it. I'm not sure if I've stumbled onto some amazing new concept or if I'm just being exceedingly dumb!


GilSwillBasementBrews 09-20-2012 03:09 AM

I don't see why it wouldn't work but I think you'd have a hell of a time getting dry ice in a cylinder.

I have 0 practical advice or experience with this venture however.

I'm sure someone more knowledgable can give you pros or cons with it.

Derick_Z 09-20-2012 04:37 AM

In the video he covered it and beat it with a meat tenderizer until it was basically powder from the looks of it. Then just poured it in with a funnel.

He said he's done it several times I think, but I really can't find a thing on it.

willness33 09-20-2012 05:30 AM

Um, either I'm not getting it or it's total BS. The amount of time and effort it would take to "pour" dry ice powder into a cylinder, why not spend the $17 for a real liquid refill? Is this guy taking the valve off of the tank to pour in the powder? That pesky valve and the 90 degree turn the powder would have to make might make the whole idea nothing more than a nifty way to get cold hands.

alchemedes 09-20-2012 05:54 AM

It only costs $15 where I live. Don't know where you did your research, but your reading the wrong info, imho. Co2 is cheep and over-pressurized exploding tanks do not sound fun...

However, I know people that carb beer in kegs with dry ice and that works out ok.

slider67 09-20-2012 02:21 PM

we bought pelletized dry ice to use in coolers to cool transmission fluid for derby cars. those would have no problem going into the cylinder. but a 5lb co2 refill for me is $8.50

BTW: the dry ice to cool transmission fluid was a bust it gelled the fluid

Derick_Z 09-20-2012 05:06 PM

I really need to find a better supplier I guess.. maybe bite the bullet and buy the 20# tank. I was really trying to get 5# to go low budget on this, but I guess the 20 wouldn't hurt in the long run. I really want to avoid buying a brand new tank only to have to swap it out for some crummy one from my LHBS though! I'll be converting my old dorm fridge into a 2 keg kegerator with just enough room on the hump for a 5# tank, and I really liked the idea of having it all self-contained within the fridge instead of drilling an extra hole for the air and having a CO2 tank sitting beside it.

Misplaced_Canuck 09-20-2012 05:14 PM

Airgas National Welders
2526 East Market Street, Greensboro, NC 2.3 mi E

They'll swap you any 20# CO2 tank for about $25-30, so no need to buy a pretty one, just find one on craigslist or other. You can even ask them for a clean aluminum one with a handle.


acidrain 09-20-2012 05:26 PM

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.

FTG-05 09-20-2012 05:29 PM

While I've never bought CO2, I do buy C25, which is a welding gas. It didn't matter whether I brought a leased tank or my personally owned tank - they just got traded out, an empty for a full one. The cost for a very large C25 is about $45 or so; this is probably a 35-40 lb CO2 equivalent. I fail to see how you can buy dry ice for less.

There is also the matter of taking off and putting back on the high pressure valve. Unless you have the specialized wrenches to precisely fit the valve, I used to do this for living, you're going to have some trouble even taking the valve off. And then there is the matter of correctly installing the valve plus the wear and tear of constantly taking it off and on. They're supposed to be taken off once every 5 years or so at a minimum. You're planning to do that for every "refill". Not smart.

Fooling with high pressure cylinders like this falls into the same category as +120 VAC electricity: Not something to be forked with.

Buy the gas, not the dry ice.

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