Dry ice to purge keg?

[charliethebum]

I hate to waste co2 and feel like a full starsan keg purge does just that. What if instead I threw a chunk of dry ice, say 10g or so, in the empty sanitized keg and let it sublimate before transferring through the dip tube? I also thought it could be done before it was fully sublimated and the resultant co2 bubbles coming off during transfer would purge the headspace at the same time. I know that dry ice isn't necessarily the cleanest thing but I have a hard time believing anything harmful could survive the extreme temperatures.

 

[Jayjay1976]

Have you checked the price of dry ice lately? Are you using a 5# CO2 bottle?

I'd think it would take quite a bit more than 10g to thoroughly purge a keg.

 

[RPh_Guy]

Purge the keg with CO2 from fermentation and then spund. Then all you need is CO2 for serving.
Dry ice is not a good idea.

I have a hard time believing anything harmful could survive the extreme temperatures.

The yeast at a lab is stored at something like -80°C.

 

[charliethebum]

Have you checked the price of dry ice lately? Are you using a 5# CO2 bottle?

I'd think it would take quite a bit more than 10g to thoroughly purge a keg.

I haven't actually. Last time I got dry ice at the grocery store they just gave me a chunk. I have a 5# and a 10#. It's been a while since I've been able to keg but I remember keg purging just blowing through my gas supply.

 

[charliethebum]

Purge the keg with CO2 from fermentation and then spund. Then all you need is CO2 for serving.
Dry ice is not a good idea.


The yeast at a lab is stored at something like -80°C.

I had no idea they survived thst low! I've thought about using fermentation co2 but my conical doesn't leave near enough room in my fermentation chamber for a keg or two.

 

[Jayjay1976]

I use gas to push starsan out of the receiving keg into another clean one, then purge it 3x for an extra measure. I keep the same batch of starsan and use it over and over, it has become carbonated too which in my mind makes it even more effective. Don't fear the foam!! I do worry about sediment forming so I made it with RO water, and when the keg is getting down to ~1 gallon I disconnect it and shake it like it owes me money before completing the transfer. Sometimes I put the starsan keg on tap and enjoy using the cold, carbonated starsan for routine sanitizing tasks.

 

[RPh_Guy]

I've thought about using fermentation co2 but my conical doesn't leave near enough room in my fermentation chamber for a keg or two.

Drill a hole for the tubing.

 

[Nate R]

I hate to waste co2 and feel like a full starsan keg purge does just that. What if instead I threw a chunk of dry ice, say 10g or so, in the empty sanitized keg and let it sublimate before transferring through the dip tube? I also thought it could be done before it was fully sublimated and the resultant co2 bubbles coming off during transfer would purge the headspace at the same time. I know that dry ice isn't necessarily the cleanest thing but I have a hard time believing anything harmful could survive the extreme temperatures.

If you can snag a 20# tank for co2, i think you will get maximum savings. For me, a swap is about $25. I could get cheaper, but i use airgas with has "foodgrade" (note- this is a whole nother topic, and plenty of threads about it.)
I can probably purge 20 or more 5 gallon cornies with it. It is a little heavy, and takes up a bit of space, but i look at it as a cost of maybe $0.50 or so to ensure my keg is fully purged of as much oxygen as i can get it out. Like an insurance policy for my beer!
Even with a 10# i would think your costs are minimal.

Using dry ice scares me onlt as it is an un-regulated amount of expanding gas. Sure the keg has a prv, but it seems like poking a sleeping bear to me....

 

[Brewbuzzard]

I hate to waste co2 and feel like a full starsan keg purge does just that. What if instead I threw a chunk of dry ice, say 10g or so, in the empty sanitized keg and let it sublimate before transferring through the dip tube? I also thought it could be done before it was fully sublimated and the resultant co2 bubbles coming off during transfer would purge the headspace at the same time. I know that dry ice isn't necessarily the cleanest thing but I have a hard time believing anything harmful could survive the extreme temperatures.

STOP!! I had the bright idea years ago to bottle carbonate beer this way. Lucky for me I had the forsight to put the bottle in a strong box. I no sooner closed the lid when the bottle bomb from hell went off. I only used a piece the size a pepper corn. Later I learned that dry ice expands about 1000 times it volume when dropped in a liquid. You might get away with it if the lid is ajar and the relief valve is open. Otherwise you could have a keg bomb.

 

[Jayjay1976]

Hey @charliethebum if you end up trying this, be sure to film it for the Darwin awards.

 

[charliethebum]

Hey @charliethebum if you end up trying this, be sure to film it for the Darwin awards.

Haha I'm pretty dumb but not dumb enough to seal off a keg with dry ice sublimating in it. Either would let it finish up before transferring or at least make sure it's done before I seal it. You guys have convinced me it's worth it to just spend the co2 to get a good full purge anyhow so yeah, no chance of seeing me blow myself up (this time)

 

[Nate R]

Haha I'm pretty dumb but not dumb enough to seal off a keg with dry ice sublimating in it. Either would let it finish up before transferring or at least make sure it's done before I seal it. You guys have convinced me it's worth it to just spend the co2 to get a good full purge anyhow so yeah, no chance of seeing me blow myself up (this time)

This thread had been fun... and i appreciate your out of the box thinking.

I am still failing to see this plan working- you say above:
"not dumb enough to seal off a keg with dry ice sublimating in it. Either would let it finish up before transferring or at least make sure it's done before I seal it."

Yet that is the point of a purge. You have to leave a certain amount of pressure in the keg to ensure no oxygen suck back. With a c02 regulator, you know the set psi. With dry ice, you are guessing that you have barely any left. Eithee you run out and poof- Wasted purge. Start over. Or, you have just a minscule little too much dry ice left, and boom- disaster.
The exact amount of dry ice and the precise time to seal up would be very difficult to pedict.

However, being a die hard Simpsons fan (seasons 2.5 through maybe 12 or 13-- the true classics years), i must commend you on your avatar sir!!