Low cost, accurate means of measuring dissolved CO2

[lhall]

OK, I'll admit I can't figure it out - what is a bottle lifter? How does it work?

[TL Services]

Hmmm...every time I lift a bottle, I find I drink the contents! It seems to work as an automatic process involving my arm and a desire for beer

[Rob Creighton]

OK, I'll admit I can't figure it out - what is a bottle lifter? How does it work?

I'll start a new thread for in Packaging.

[liammckenna]

Zahm, Gehaltemeter and others that use pressure and temperature are fine instruments...so long as there is only CO2 present.

Any other gas - eg. N2 is very commonly used in the UK and elsewhere for improvements in head stability, foam tightness, etc. - and these methods will not give the correct result.

If anyone does use N2 then an Orbisphere 3654/3658 or Anton Paar CarboQC are the way to go.

Is not the N2 in nitrogenated beer very low? I thought its was somewhere around 40 ppm?

Will this level create significant interference with your CO2 estimation using a Zahm?

Pax.

Liam

[TL Services]

Liam,

At 0 deg C, 5g/l of CO2 will have a partial pressure of 1.5 bar.

At 0 deg C, 44ppm of N2 will have a partial pressure of 1.5 bar.

Now at equilibrium the total pressure equals the sum of the partial pressures, so using a method that assumes all the pressure is CO2, then the error would be in the order of 100%, ie. you would appear to have twice as much CO2 as you had in reality.

[liammckenna]

I see. 100% is certainly a significant error.

So, if you could neutralize the CO2, you would be left with the pressure of just the nitrogen (and oxygen and everything else, I guess)?

We are a small brewpub. We nitrogenate only our stout to saturation via a contactor membrane. We measure the CO2 before processing with N2 (after filtration in the bright tank).

It is our experience that if we begin at about 1.5 vol CO2 prior to this process, we can consistently achieve the desired result (I know it sounds primitive, but it is repeatable, consistent, safe and easy to do given good temperature and pressure control).

My question is: Assuming minimal CO2 losses during nitrogenation, using my Zahm shaker, is it possible to estimate the N2 content as the process progresses (given I know my CO2 starting point) merely from the pressure/temp of my Zahm?

Pax.

Liam

[TL Services]

Liam,

My gut feeling is 'yes'

If your temperature control is good during nitrogenation, ie. it stays pretty much the same during the process, then the differences you see between the start (known 1.5 vol. CO2) and your next measuring stage will be a direct result of the increase in N2.

My only concern is that the CO2 level will drop as you increase the nitrogen level, so the relationship won't - in fact - be absolutely perfect.

If your CO2 drops from 1.5 vol to 1.0vol, then around 9ppm of N2 will result in an unchanged total pressure.

On the other hand if your process works; gives good, consistent beer that your customers like (and drink in splendid quantities ) then I'd be inclined to say 'if it ain't broke, don't fix it'!

In other words don't worry about the numbers if the result works