Oxygen

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vacant
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Re: Oxygen

Post by vacant »

Which way does the oxygen travel?

You haven't mentioned bubbles appearing back in the boiler, so I assume the wort flow rate is greater than the upward velocity of oxygen though it. If that is so, you have hardly any time for the two to come in contact and mix - in which case I'd try introducing the oxygen at the top end of the hose.

Introducing oxygen in the middle of the hose means it wouldn't matter which flow rate is greater.
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steve crawshaw
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Re: Oxygen

Post by steve crawshaw »

vacant wrote:Which way does the oxygen travel?

You haven't mentioned bubbles appearing back in the boiler, so I assume the wort flow rate is greater than the upward velocity of oxygen though it. If that is so, you have hardly any time for the two to come in contact and mix - in which case I'd try introducing the oxygen at the top end of the hose.

Introducing oxygen in the middle of the hose means it wouldn't matter which flow rate is greater.
The oxygen stream impinges on the wort stream as it leaves the hose, so there are no back pressure issues. I didn't want to introduce the O2 any further upstream as I was worried that it might act as resistance to the flow of wort. The lance deflects the flow of wort and doesn't seem to restrict the flow.
While I agree that the contact time is limited in my approach, the fact that the gas stream breaks up the flow of wort into droplets as it leaves the hose, spraying the inside of the FV (which is full of pure O2) means that the surface area for O2 absorption is large, even if contact time is limited. I guess it takes 10 minutes or so to fill the FV.

I do have a dissolved oxygen meter, so I might try some measurements with water.

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darrenw
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Re: Oxygen

Post by darrenw »

This is an old thread but having some thoughts.

The first is how much oxygen the wort can actually absorb, chemically from reading water can carry a maximum of 7.6 mg/l so interested to know if this is diminished as the density of the wort increases.

Also if this is the case and after the yeast has been having ago at the yummy stuff for 24hrs would it be beneficial to re-oxygenate after this time.

I personally use the splashing method, and then skim then stir for the first two days with so far no adverse effect.
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steve crawshaw
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Re: Oxygen

Post by steve crawshaw »

darrenw wrote:This is an old thread but having some thoughts.

The first is how much oxygen the wort can actually absorb, chemically from reading water can carry a maximum of 7.6 mg/l so interested to know if this is diminished as the density of the wort increases.

Also if this is the case and after the yeast has been having ago at the yummy stuff for 24hrs would it be beneficial to re-oxygenate after this time.

I personally use the splashing method, and then skim then stir for the first two days with so far no adverse effect.
I have read that the optimum time to oxygenate is 24 - 48 hours after start of ferment. However I do it at the beginning, as the wort enters the FV - see above. I am reluctant to mess with the wort after fermentation starts as i fear infection. If i was to do this, e.g. for a big beer like barley wine i would use a stainless airstone and stainless wand with O2. Optimum levels of O2 are around 8ppm i think which equates to the figure you quote in mg/L

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steve
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PMowdes
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Re: Oxygen

Post by PMowdes »

There's a bit about Dissolved oxygen in water here

http://water.epa.gov/type/rsl/monitoring/vms52.cfm

The maximum dissolve oxygen content will vary with temperature.

I seem to remember that the yeast book suggests that brewers can oxygenate up to 20ppm (mg/L) but i'm not sure if my memory is correct.
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