can't keep CO2 in

[fullmoonwinery]

hi all,

i have my cider (i'm brewing cider but i don't know of any reason it would be different to beer, just a bit more acidic) and its under pressure (0.04Mpa which is 0.4 bar or 5.8psi) from the fermentation. its about 6 weeks old now and clear. temp is 7 degC.

when i open the sample port and pour a glass it gasses out a lot, lots of foam, so i know there is still a lot of CO2 in there left over from fermentation.

however when i taste the cider, it tastes flat like all the CO2 has bubbled out.

i don't have my filling machine yet so i tried to simulate the way that works. i put a rubber bung in the top of a bottle with a pipe and a little shut off valve. i pre-pressurize the bottle with CO2 and then fill from the sample port into the bottle under pressure. that really helps stop foaming. then i take the rubber bung off when full and it looks ok, a little bit of foam comes up, not much, then i cap it.

then i shake it around a bit to simulate deliver and bar handing and open it and pour it, and it its pretty flat.

i really need it fizzy when served and having a hard time understanding why it isn't keeping the gas in suspension?

any ideas? perhaps there is not enough gas left in there naturally from fermentation and it needs more carbonation? it looks very gassy when it comes out of the tank but i have no way to test the actual amount.

thanks for any ideas.

[Guestimate]

Steve,

The excessive foaming from your sample port is due to the rapid pressure change exacerbated by the turbulence created in the sample valve. 0.4 bar at 7 C would have your cider at about 3.5 g/l, which is about twice that of your typical white wine.

Kevin

[fullmoonwinery]

Steve,

The excessive foaming from your sample port is due to the rapid pressure change exacerbated by the turbulence created in the sample valve. 0.4 bar at 7 C would have your cider at about 3.5 g/l, which is about twice that of your typical white wine.

Kevin

i was trying to fix the rapid pressure change by pre-presurizing the bottle and i was able to fill it under pressure without a lot of foam.

however, when i subsequently poured the cider into a glass from the bottle, it didn't look or taste very gassy

i just read this
http://www.probrewer.com/vbulletin/a...hp/t-1599.html and this

http://www.meheen-mfg.com/tankcarb.html

it sounds like the trick is to get it as close to 0degC as possible. and if possible get 15psi pressure in there.
i think my real problem isn't the lack of CO2 in the cider now in the tank, it's full of gas. its just finding a way to keep it in there as it goes into the bottle. i guess low temp is the key.

so i have a question for people who use an isobaric beer filling machine.
what temp is the beer entering the machine?
what temp is the room housing the filling machine?
do you need to chill the beer in the filling machines header tank?
do you chill the bottles prior to filling? what temp?

after the isobaric beer filling head is removed, the beer will be exposed to open atmosphere for a second or two before capping. is there not a problem here with loss of CO2 in solution? i guess it all depends on temperature right?

[schlosser]

CO2 just isnt there

At the temp and pressure you are at you have ~ 1.8 Volumes of CO2 in solution. This is a little more than your average Real Ale. First thing you need to do is to determine how much CO2 you want in your Cider. Beer can range from about 2.5 to 2.8 Volumes of CO2. Malternatives are a bit higher, generally in the 2.8 to 3.2 Volumes. Next you need a CO2 chart that shows CO2 solubility given a Temp and Pressure. The rest is as simple as setting temp and CO2 level for desired carbonation.

And BTW, @ 32 F and 15 psi you will hit ~ 3.25 Volumes at equilibrium. Probably more than you would want.

Cheers,

Dave

[dick murton]

For what it is worth, a typical bottled cider in the UK has a CO2 content of about 5 g / litre, or 2.5 vol / vol. As stated elsewhere, 1.8 vol / vol is about what you get ex tall fermenters, and is perhaps on the high side for a cask beer - so no surprises it tastes a little flat.

This is bottled at a nominal zero deg C, though in practice the temperature in the filler bowl is probably more like 2 or 3 deg C just after start up. Allowing for temperature pick up due to the bottle, this means it is probably closer to 4 deg C as it comes off the filler.

Let's say you want 5 g / litre in the bottle. Allowing for variation in pressures in the filler bowl / cider CO2 content, then you need to run the filler bowl at about 1 bar counter pressure, and snift off the excess pressure in each bottle carfully to prevent the CO2 suddenly coming out of solution like a volcano between the filler head and the capper.

For carbonation, see the Meheen chart for equilibrium pressures

Good luck

Cheers

[fullmoonwinery]

thanks for the help. i attempted to measure the gas content in my cider coming out of the sample port. i fitted a condom (don't laugh!!) over the end of the sample valve and sealed it as tight as i could with rubber bands to get an airtight seal.

then let about about 20ml of cider, enough to fill about 1/3 of the volume of the condom. then i shook it around until i got as much foam out as possible (i told you not to laugh). i took a photo of the mostly inflated condom and on my computer using a 3D cad program, i made solid shapes to closely match the size and shape of the cider part and the gas part.

anyhow, the bottom line is, i am getting about 1.5 vols CO2 out of the cider as far as i can tell with this method.

so this all leads me to my next question. how does carbonation really work? i know about the temperature and pressure from the meheen tables but what about the details. lets see:

TANK CARB

i understand there is usually a carb stone in the bottom of the tank. the beer is brought to about 0C and CO2 is injected at the required pressure through the carb stone. the bit i don't understand is, if the tank is a few thousand liters, its probably a meter or so diameter. the carb stone is only a small thing, a few inches long. all that is happening is a narrow column of bubbles are streaming though the beer. most of the beer will not come into contact with the bubble stream will it? so how does the beer not in the bubble stream get carbonated? how long does carbonation take like this?

once you have bubbled CO2 into the tank for a while, the pressure will rise if the tank is sealed closed right? do you stop at that point or do you keep feeding in more gas? to do this, i assume you would have to vent of excess gas or the tank will explode. how much CO2 gas is required to carbonate, say a 3000 liter (800 gals) tank? does all this CO2 not get a bit expensive?

IN_LINE CARB

i would prefer to do in-line carb since my chillers cannot get down to 0C, the best i can do is 7C (44F). but i can pass the cider though a freezer on the way to the filler and try inject CO2 inline.

i think in-line carbonators use a carb stone just like tank carbonation, but the beer passes over the stone as it bubbles CO2. but i assume not all of that CO2 gets absorbed into the beer? do you not end up with a lot of gas in you lines? does all the gas have to be vented out somewhere? i guess i'm just confused about the whole bright tank -> filter -> inline carb -> filling machine setup. i would really like to know how it works in practice.

BTW, it looks like i need to buy one of these: http://breweryparts.com/index.php/eq...ygenation.html
maybe it will solve all my carbonation problems

thanks again for everyone's help

by the way, my cider tastes pretty good now its cleared and aged a bit but everyone who has tried it agrees, it needs some gas in it, flat cider is just not that interesting.

[dick murton]

OK so lets go back to basics for the in-line carbonation

44 F = 6.7 C, so lets call it 7 C

CO2 in equilibrium at 7 C, at 1 bar (your filler bowl pressure) = 5.1 g / litre - which is pretty much what I would expect you would be aiming for.

However, this does mean you are on a knife edge with temperature, so it really mustn't be allowed to creep up, nor the filler bowl pressure drop.

The CO2 will dissolve faster if the bubbles are extremely fine, and the pressure is high, and the turbulence is high. I guess since you are carbonating in-line to the filler, the flow rate is going to be pretty slow and having just commissioned blender / carbonators running at up to 500 hl / hr ( hardly micro brewery scale stuff), and having had problems dissolving the CO2within 10 metres of the injection point, I feel you are probably better off running into another tank. One thing that will help you dissolve the CO2 is to pass the carbonated cider through a trap filter - which breaks the bubbles up extremely finely, giving high surface to volume ratios, and rapid solution.

Other large scale systems inject the CO2 just before the transfer pump, again to break the bubbles up extremely finely, but with risk of cavitation

So in summary, I suggest if you in line carbonate, you pass it through a fine (less than 100 micron) filter into another tank with a minimum top pressure of 1 bar, and as cold as possible. I believe you will struggle to in tank carbonate successfully.

If you have a recirc loop on the tank you could carbonate this way as well

In tank carbonation does mean you have to vent off as well, simply because not all the CO2 goes into solution before it rises to the top of the tank, so you have to vent off the wasted CO2. The rising gas causes recircualtion currents in the tank so will normally mix it pretty thoroughly.

Cheers

[TL Services]

Definitely go with inline carbonation. Like DM I have seen so many issues with getting CO2 to dissolve (typically up to 100ft of 4" main before it's anywhere near...).

If you're running into a tank then do make sure you have good top pressure - my old software calculator comes out a 1.3bar (gauge) of CO2 top pressure to keep you at 3vol (~6g/l).

Remember you will need the top pressure to be CO2 - if you use N2 then you'll just lose your hard-won carbonation

[gitchegumee]

Don't waste gas!!!

Dick, sorry, but for all the great stuff you post, I disagree with your venting suggestion--and I'm surprised at all Probrewer folks here who support this view. I'm not one of them.

CO2 never has to be vented while carbonating. Ever. All the CO2 will become saturated with a big enough stone & small enough bubbles, good internal (thermodynamic) circulation, and enough time. Those who blow off CO2 are doing something wrong--at least in my book. CO2 will not rise to the top of the tank if it's broken into fine enough bubbles and given an appropriate head pressure in a cold environment. If it did (maybe due to a small stone with large bubbles in a static tank with low pressure/high temperature), it would reabsorb through the now out-of-equilibrium gas/liquid interface. It's fairly basic gas dynamics. Bung up your tank tight as hell, cool it down, inject small bubbles through a large enough stone at the right pressure for enough time and you're done. Simple as that. There are convection currents that will mix the tank contents to a uniform CO2 content.

In-line carbonators are not my favorite due to CO2 stratification, temperature stratification (which exacerbate each other), BBT head pressure changes, beer and CO2 flow rates, and other variables that have to be carefully monitored constantly during the entire run. My preference with an in-line carbonator is to use it on the way to another BBT to rest in bulk before sending to the bottling line. Get it right before you bottle; not on the way. In-line carbonators without a buffer tank and directly into a filler almost require another body to run correctly. Stop your bottling run for a minute and you have to run over and turn off the carbonator, right? Who wants to jerk around with that when the reason you shut down the bottling line is usually another immediate problem.

I use nitrogen every day to push my beer in my canning/kegging line. As long as it is in a reasonable 6 hour run, there is absolutely no loss in carbonation. There's a decent link here somewhere about nitrogen use.

Sorry for being contrarian--just stating my experience. And I'm coming after some of that cider soon...

[dick murton]

Phillip

Fair enough, but it's just that my experience of in tank carbonation using a static sinter has always required the excess to be vented off simply because the gas goes in slightly faster than it will dissolve, and the surface area on th etop is too small to allow rapid gas solution. Leave it long enough at high enough pressure and low enough temperature and I agree the top pressure gas will dissolve.

I guess as usual I am passing on wisdom from larger production sites, and that with smaller volumes of beer the ratio of volume to surface area is more amenable to rapid solution.

[TL Services]

I use nitrogen every day to push my beer in my canning/kegging line. As long as it is in a reasonable 6 hour run, there is absolutely no loss in carbonation.

6 hours is about as far as I'd go; much longer and you will risk losing CO2 in the upper level, given a quiet, non-turbulent empty.

Not so long ago I worked at a brewery where using N2 head pressure in BBT caused major quality issues when the tanks were left like that over the weekend. Eventually mixed gas was used, in the correct blend proportions to match the beer in the vessel.

[gitchegumee]

Dick, I get where you're coming from. I'm biased toward conservation. CO2 here is over $200 per 100 pound tank. So I do everything I can to save it for refilling small tanks for use in draft dispensers. But I can imagine that over 100 bbl, tanks would be difficult to carbonate evenly, quickly, and efficiently. Even with multiple stones. Maybe a circulation loop with a pinpoint carbonator in a large tank? Or, have a tank that will take a few bars or pressure so you can increase the dissolution rate while carbonating to the desired level before venting a small amount to get you into equilibrium. I cringe at blowing off expensive and potentially fragrant gas.

KWLSD, our BBT is only 10 bbl and I think you're about right with your timeline. I won't leave beer sit over night on N2. That said, our last can is carbonated to the same level as the first. I think the difference in density of N2 @ 28 CO2 at 44 seems to create a blanket effect when put in slowly and quietly on top. But over time, diffusion will take place and create a mixed gas environment, lowering the carbonation level at a given pressure.

[schlosser]

Since nobody has mentioned it I'll throw in my 'Nitrogen Disclaimer.' I know Phil uses it safely and I would guess the others are as well, but great care needs to be taken with Nitrogen from a safety standpoint. CO2 can definitely kill you in high concentrations, but at least you know when you are in a High CO2 environment from the smell. Nitrogen has no smell and thus it is easier to have a dangerous environment without knowing it. If you are using it then you need to be sure you have good ventilation and / or O2 sensors to alert you of low O2 environments.

Dave

[TL Services]

Dave,

I must take issue with you here

CO2 does not smell - it is colorless and odorless. The 'smell' you notice is the result of CO2 reacting with other things, eg. the moisture in your nose, throat and lungs.

CO2 is also heavier than air, so will displace O2 and lead to problems; it needs a comparatively low percentage of CO2 to be dangerous.

N2 is lighter than air and in any case, makes up 80% of it; thus you need serious oxygen-depletion for problems to occur.

One of the first results of lack of oxygen is to faint; falling down in a CO2-rich atmosphere is far more likely to be fatal than in an N2-rich one, for the above reasons.

I quite agree that good ventilation is paramount when using any gas and detection should always be used in confined spaces, etc.

[schlosser]

You can take issue all you want, but it is your uninformed view of N2 that causes more people to die each year in the US from Nitrogen Asphyxiation than any other gas (US Department of Labor Statistic averaging 8 people per year and 5 injuries).

Lets look at your post piece by piece:

1. CO2 is colorless and odorless. My MSDS I have for CO2 states it is odorless at low concentrations and has a "sharp acidic odor" at higher concentrations. Whether it is technically a smell or is a body's reaction to the gas is pure semantics in this discussion. The reality is that the human body can detect CO2 at a level BEFORE it is fatal. Doesn't mean that someone will always make it out of an environment that is dangerous, but with proper training people can recognize problems before they occur.

2. CO2 does pose a risk at much lower concentrations than N2. That is because it is a cerebral dilator and Nitrogen is a simple asphyxiant. CO2 will interfere with the body's ability to take up O2 in the lungs. Thus you can die from CO2 when there is still plenty of O2 in the atmosphere. Nitrogen kills by displacing the good air and thus depletes the the amount of O2.

3.

N2 is lighter than air and in any case, makes up 80% of it; thus you need serious oxygen-depletion for problems to occur.

Where do I begin? Yes N2 is lighter than air, but as you state it makes up 80%. You seem to be implying that it would stratify in the top of the cellar. Sorry, given the fact that 80% of air is nitrogen there will not be any stratification in a cellar setting. And yes, you need serious O2 depletion for a problem to occur, but that is not all that difficult to occur. Lets take an example.

A brewery uses N2 for pushing tanks to the filter. The tank is as large as the cellar it occupies (usually not the case at small breweries, but my last brewery I had tanks in some cases that were 5-9 times the volume of the work area). After the tank is empty it has 1 bar of tank pressure, the operator mistakely empties the tank into the cellar. If 50% of the cellar atmosphere and 50% of the tank atmosphere are displaced out of the cellar, then you have the following atmosphere left in the cellar:

50% Cellar Atmosphere + 50% Tank Atmosphere = New atmosphere in cellar
50%( 78% N2 + 21% O2 + 1% other) + 50%(100%N2) = 89% N2 + 10.5% O2 + 0.5% other

You have quite easily gone to 10.5% O2, which is a very dangerous level. And the worst part about this is that the human body will not recognize a lack of O2 until you are in serious trouble.

4. Yes, fainting into a CO2 atmosphere can mean you drop to a higher concentration of CO2. Fainting because of lack of O2 because of N2 will not put you in a worse environment (but it also won't put you in a better environment either). Fact is that since you have gone done in the cellar for either of these reasons means your probably going to die. Will it matter to your family that you lived an extra 2 minutes in the N2 atmosphere.....probably not.



I am not trying to say that CO2 isn't dangerous, in fact as KWLSD states it can get you into trouble at much lower concentrations. But the fact of the matter is that N2, although needed in comparatively much greater volumes than CO2, is more deadly in the fact that the human body cannot perceive a lack of O2 in the environment.

David Schlosser
Brewmaster
Naked Dove Brewing Company
Canandaigua, NY