View Full Version : Purge with CO2 from fermentation?

08-21-2010, 04:01 PM
Idea occurred to me as a short-term fix before we have N2 on site : connect CIP line from fermenter (FV) to CIP line on receiving conditioning tank (CT), then we can transfer from FV to an O2-free CT (bottom fill) after primary fermentation. Receiving CT will of course be cleaned & sanitised first, pressure relief by leaving CT top manway cracked during fermentation in FV. Seems too good to be true - what am I missing?

08-21-2010, 04:32 PM
I wasn't quite sure from your post, but are you trying to use excess CO2 from fermentation to purge your brite tanks? Or are you just talking about linking the gas connections on the 2 tanks during beer transfer?

08-22-2010, 01:59 AM
Hi Gregg,
Like Kugeman, I'm not entirely sure if I read you clearly, but I think I'm answering your question. The last brewery I worked in did exactly what you're suggesting; however I would suggest co2 purging from the bottom with your blowoff/CIP arm open. That brewery I worked in was a 25,000 bbl per year brewery in Texas; I'll let you figure out which one.
The only issues I could ever foresee with such a process were possible cross contamination and aromatic/flavor issues.
In other breweries I worked in, we sterile filtered beer into brite and between turns we kept the tanks under pressure and acid cleaned and sanitized. Cross contamination wasn't an issue, but on more than a few occasions, I recall there being residual aromas in the CO2 in the tank and I remember one time for sure a marked flavor impact upon the subsequent beer in the tank.
In my most recent brewery we had no such issues. Between beers, we acid cleaned and sanitized under pressure. We generally only had one strain of house yeast and we did not filter our beer, so again cross contamination wasn't really an issue.
As a side note, my most recent brewery spunded all of its primary fermentations at 48 hours; the yeast was not a sulfur or diacetyl (or anything else) producer, so we were able to capture a ton of CO2 prior to brite. When we would break down the brites, we'd purge it with the co2 from an active fermentation. The flavor/aromatic concerns were assuaged by the fact that the yeast didn't produce a ton of aberrant aromas or flavors and by the fact that we had a balance line between the FV and the BBT. As the beer moved from the Fv to the BBT, the fermentation gas moved from the BBT to the FV. And the polishing CO2 was relied upon to scrub the remaining odd flavors. Your mileage may vary.
Anyone else have thoughts on this? I always liked the re-purposing of our 'waste' co2 for something useful.

08-22-2010, 02:40 AM
Greetings Hutch - thanks for the reply. ABG 2004 seems half a lifetime away, and it is good to be discussing real production questions at last.

Terminology : We make cask ale, and conditioning tanks (CTs) are used to hold beer after primary fermentation - not quite bright beer tanks, as there is still yeast in suspension and there is some secondary fermentation with the beer held at about 9 deg C.

For example : Fermenting in FV2, preparing to transfer to CT2 after primary fermentation and cooling in FV2. During primary fermentation, connect CIP arm of FV2 to bottom port of CT2 (thanks Adam) to purge CT2 with CO2 - everything at atmospheric pressure. After primary fermentation, beer in FV2 is cooled and CT2 also cooled to matching temp. At transfer, connect balancing hose between FV2 and CT2, transfer from racking pipe in FV2 to bottom port in CT2.

As the beer is going into the same CO2 atmosphere that it produced during primary fermentation, there should be no problem with aberrant aromas.

Hope this clarifies; Adam's very helpful response does support my idea, notwithstanding the difference between BBT and CT.


08-22-2010, 07:38 AM
Hey Gregg! I thought that was you...

I think you're idea is worth a try. I've used excess CO2 from a fermenter to add some head pressure to a brite tank (or in your case a conditioning tank) but I was never able to get all of the head pressure I needed. For instance if the FV is at 15 psi and my BT is a 0 psi, I could connect the 2 tanks and they would reach equilibrium at 7-8 psi each.

I've only tried this a few times, so I'd be curious to find out how your experiment turns out...

Good luck!

08-22-2010, 10:10 AM
I often wondered if one of these would be an effective way of cleaning up CO2 from fermentation and make it suitable for long conditioning: http://www.grainger.com/Grainger/general-purpose-filter/compressed-air-treatment/pneumatics/ecatalog/N-c9aZ1z0n9y8?op=search&sst=All
It seems like a pretty inexpensive way to have a little piece of mind, plus the activated carbon element should help scrub any strange aromas. A couple of threaded T/C adaptors could be used and it could be easily connected to the CIP arm on one side and a hose on the other.

08-23-2010, 08:40 AM
Coupla' 'tings.

In our fermentations, we sometimes have 'burping' tanks. In other words, there is some blowoff through the top vent/cip arm. Wouldn't want that transferred into my CV or brite. If I was going to attempt this, I would do it through the CIP arm, not the bottom valve (for just this reason - less chance of crap/barm transfer into destination vessel)

Also, be aware of rapid depressurization of FV's. Can detrimentally affect your head retention, stability etc.

Otherwise, sounds like a great plan.



01-22-2011, 07:51 AM
Update : As described in my second post, we have been connecting a hose from the CIP down arm of the FV to the bottom fill port of the CT, leaving the CIP arm of the CT open to atmosphere. This is done at the start of fermentation, and allows the CO2 from the FV to fill the CT from the bottom. We then have an O2-free (and cost-free) atmosphere to transfer the beer into at the end of fermentation and cooling in the FV.

A quick sniff of the CIP exit of the CT is an imprecise indicator of when the CT is full of CO2 - in practice, this is usually evident within 24 hours of pitching, and I am fairly confident that practice is matching theory.

This has worked satisfactorily so far; of course, we still need to use N2 to add volume to the CT as we draw beer off.

Liam's admonition is helpful :

In our fermentations, we sometimes have 'burping' tanks. In other words, there is some blowoff through the top vent/cip arm. Wouldn't want that transferred into my CV or brite. If I was going to attempt this, I would do it through the CIP arm, not the bottom valve (for just this reason - less chance of crap/barm transfer into destination vessel)

but we have plenty of head space in our fermenters at the moment, so we have not seen this problem arise.

Any questions?

(Edited to respond to Liam)