What's the best way to dissolve CO2 in water in a continuous process at low pressure?

[seagal3232]

Hi all,

I'm trying to dissolve a reasonable amount of CO2 into water to form carbonic acid (so no gas trapped in the liquid at high pressure),

I was thinking of using some sort of absorption column to have a continuous process where CO2 is dissolved into the water, but I don't know if that's the best option, or if there're other possibilities (maybe blowing directly into a water tank with CO2 recirculation?),

Thanks for the help!

 

[georgeverghese]

Must it be plain water at pH=7?
The more alkaline the water (pH > 7), the easier for CO2 to dissolve.

 

[seagal3232]

It doesn't have to be plain water no, we can add a base.

Maybe a stirred tank with base dosage and a bubbling mechanism at the bottom would be a good method then.

 

[pierreick]

Hi,
You may want to consider brine instead of water for your application.
edit:

https://www.sciencedirect.com/science/article/abs/pii/S0011916419316042

Pierre

 

[LittleInch]

A sparger?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[seagal3232]

I've been reading a bit regarding the solubility of CO2 in brine, and it seems that it decreases as you increase the salt concentration due to the salting-out effect,

So on the one hand, solubility should increase by increasing the pH, due to equilibrium, but the salting out effect cancels that? I'm a bit confused.

 

[LittleInch]

But is this a continuous process or are you taking a set amount of water in a tank and adding CO2 until you get to equilibrium?

How is excess Co2 being controlled?

Injection into a pipe would work just as well? Use a quill or a set of tubes with micro holes in?
Or have a pipe in pipe and lots of little holes and fill the annulus with CO2.

what's a "reasonable amount"?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[seagal3232]

It is continuous, it comes from venting at a certain section of the process,

I don't have confirmation of the exact flowrate, a ballpark figure might be 50-100kg/h,

A quill might work, it could be an option. Can't I use a sparger in a tank as long as I have enough residence time?

 

[LittleInch]

Yes - just wasn't sure what tie you had and space for a tank as opposed to a pipe.

A quick google says solubility at STP is about 1.5g/l so 50 kg will need about 35m3 of water?

This looks like an interesting read.

https://www.ncbi.nlm.nih.gov/pmc/ar...standard ambient temperature and,S ≈ 1.5 g/l.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Its not clear what you intend to do with the CO2 dissolved in water. What happens downstream ? - all you say is that you've got high pressure downstream. Does it matter if dissolved CO2 is not sprung out of solution at high pressure ? What other solutes are in this (sea?) water - adding a base such as caustic may precipitate insoluble hydroxides ( Ca, Mg, Ba) which will most certainly bung up everything in sight.
There are specialty solvents that can reversibly dissolve CO2 at low pressure at low concentrations of this solvent, but these are not used in saline solutions.

 

[pierreick]

Hi,
Check the link in my initial reply.
Pierre

 

[bimr]

There are several companies that do this. I beieve that TOMCO does this with in 2 steps to increase the efficiency.

TOMCO