NaOH + CO2 during CIP

[killroy]

I have noticed a vaccuum is created while doing CIP's on fermenters with NaOH. I was told it was because the CO2 is neutralizing the NaOH, but the exact chemistry could not be described.

The vaccuum shortly subsides. Is this information correct? All I can find is that 2NaOH + CO2 ------> NaCO3 + H2O.

We can't completely vent all the CO2 out of the tanks prior to CIP so a reaction seems reasonable. Does this reaction cause the vaccuum or is it some other mechanism,

Thanks.

[adebower]

venting CO2 from tanks

I can't describe the chemistry, but co2 + caustic = vacuum. Which is no bueno at all. Additionally, it diminishes the efficacy of your caustic solution.

One fairly novel way the brewery I work at has dealt with the removal of co2 from our fermentors or brite tanks is to blow the tank down to no pressure, and then give it a nice cold rinse with the manway open. Then we hook up a shop vac to the bottom of the cone, button up the rest of the tank, open the blow off arm, and turn on the shop vac. The shop vac sucks the heavier than air co2 out of the tank, replaces it with air from the cellar through the cip arm, and makes the environment inside the tank co2-free and friendlier to the cleaning chemicals. We run our CIP with the manway doors closed. In fact, the whole tank cleaning is done in a closed loop (we don't get much temp drop during the cycle) and the tanks come clean easier than I've seen before.
Hope this helps.

Adam

[Guestimate]

NaOH + CO2 => NaHCO3

This reaction would create a vacuum as CO2 in it's gaseous state occupies more space than the precipitate NaHCO3 (baking soda). Also, as your caustic solution cools it will create a vacuum as gas occupies less space at cooler temperatures.

You should be able to adequately vent a tank by opening all of the valves and the manway, then letting it sit open for a couple of hours. If you are in a hurry you can send compressed air through the CIP arm to attempt to push the CO2 out.

Accepting these potential problems, it would probably be wise to make sure that a valve is open to the atmosphere when cleaning the tank.

Kevin

[TL Services]

You must make sure you have adequate anti-vacuum venting during caustic CIP as this can easily suck-in a tank if you haven't!

I have seen a 2500brl (UK) cylindro-conical collapsed like a crushed coke can as a result

[Sulfur]

Trimeta

Note. Ecolab promotes CIPing with an acid product called Trimeta XS.This negates the need for CO2 venting...so they claim. I have no need of this at my scale, but it may be of interest to bigger breweries.

[gabewilson50]

Depending on the size of your fermenters (I've only done this on fermenters as large as 65 bbl), you can do a hot water rinse CIP for about 10 minutes with the manway gasket removed and racking and sample port valves open. This will kill a few birds with one stone: preheat the tank, remove loose trub, and blow out the majority of the CO2 (don't stand in front of the tank when you turn on the pump or you'll get a hot trub bath). I've never had a problem with vacuum formation doing this.

[gitchegumee]

Hey adebower; nice solution! Never heard of that before. Simple, effective, and cheap! I've seen pictures and heard stories of large tanks collapsing because someone didn't know what they were doing in the cellar. Ouch!

[Ted Briggs]

It could also be from the hot caustic cooling and creating a vacume. I think its always good practice to have a vent during cip, an open port or take off the prv...

[dick murton]

Both equations quoted are correct, and active. As are the comments about hot cleaning, and using acid. However, the problem with acid detergents is that they are not very good at removing protein and hop debris, so are normally preceded bya sacrificial caustic rinse - which is an inpractical solution for many large breweries, particularly those built more than a few years ago - Germany and other parts of Europe excepted.

So my best advice is, if you haven't got massive anti vac valves, to open the manyway door, remove the door rubber and manually clean, put a shield around ithe open door to prevent getting splashed, use a cold water rinse until the water is largely debris free - hot (50 to 65 C typically) will require less volume then circulate caustic, and rinse off thoroughly before any sterilisation.

Beware also the hot to cold temperature change vacuum effect - I have very recent knowledge of just such an incident with a week old vessel. Ouch