Purge with Nitrogen

[DowneastCider]

A gas supplier suggested purging with Nitrogen to save money (cheaper than CO2). I had never thought about this before. Anyone else do it? He suggested using Nitrogen for purging tanks, kegs, and canning line. CO2 would be used for force carbonating (obviously) as well as head pressure when packaging.

Any reason not to switch to Nitrogen for purging?

[TL Services]

Most of the UK brewing industry uses N2 for these purposes rather than CO2, because there is a significant cost-saving and also it's positive environmentally due to reduced CO2 usage.

There are some basic handling differerences:

Tanks - as CO2 is heavier than air it is relatively straightforward to purge air/O2 by gentle fillling, as the CO2 will sit (for the most part) at the bottom of the tank. Nitrogen doesn't have this benefit, but by back-filling with N2 when a tanks is being emptied you can minimise air ingress. It's all a matter of managing to a minimum the opportunity for air to get it (which most people do anyway to assist DO2 control);

Mains - pack with water then push this out with N2 to eliminate air/O2

Packaging - direct swap for CO2 as cover gas, etc.

The only thing to keep track of is that, if you're carbonating inline during a transfer, there will be some initial loss of dissolved CO2 as the product initially enter an N2-filled tank, due to partial pressures. This can be managed by having a slightly higher set-point to offset the issue. Obviously as the amount of CO2 in the headspace increases, the dissolved loss reduces to even things out.

You shouldn't find any major issues with nitrogen dissolving into the product to any great extent, maybe 1-2ppm at a rough guess.

Hope that helps!

[DowneastCider]

Tim, thanks for the info. One question about tanks, specifically brite tanks that are kept at 15psi as product is pushed out to the packaging line. Would switching from CO2 to Nitrogen cause carbonation issues? The gas supplier recommended against using Nitrogen in this process and sticking with CO2.

[TL Services]

Hi - that depends on the time it takes for emptying...you may find some loss of dissolved CO2 towards the end of a tank as this will have been exposed to N2 for the longest time and with the greatest headspace volume, so more opportunity/need for CO2 to come out of solution due to partial pressures.

If you're emptying fairly quickly, then the equilibrium shouldn't be disturbed too much; if it's longer then you might want to consider an N2:CO2 mix.

[DowneastCider]

What is your definition of quick? With out current tanks and equipment, it takes 5-10 hours to empty a brite.

[gitchegumee]

Some other posts on this topic...

I've found with beer in a 10Hl BBT that we see no appreciable carbonation difference between beginning and end of pushing our beer through a canning line for 6 hours with N2. Your results may vary... Be sure to have carbonation level perfect at beginning and keep N2 pressure at least as high as your saturation pressure of CO2. Think you'll be fine with less CO2 use. Good luck!

[TL Services]

Good empirical data there!

Quiet, steady emptying shouldn't disturb things too much. Most of my recent experience has been with big cylindro-conicals, taking 12+ hours to empty.