Removing disolved gas from water 1

[sjh]

I am looking for a way to remove disolved gas (H & O) that is produced at an electrode in water while the water is under pressure 20-125 psi range and is flowing 0.5 to 10 gpm range. When pressure on the water is relieved the gas forms bubbles and can be removed, however, I need to remove the gas before pressure is relieved. I would appreciate anyones thoughts or theories.

 

[jay165]

You could use some form of gas stripping with or without a catalyst. One technology is Minox , although the usual size is way bigger than what you need:

http://www.minox.com

 

[TBP]

You could try an air separator, like those used on hot water heating systems. They're cheap, and readily available. You'll need to ensure that they're rated for the pressures & temperatures of your system though.

 

[Montemayor]

sjh:

There is no practical way that I know of to separate dissolved gas within a liquid while the system is pressurized. There are some possibilities that you may investigate such as membrane technology and adsorption, but if the quantity of water is far greater than the dissolved air, I believe you'll find these alternative to be impractical and uneconomical. This only leaves you with what is conventionally done in industrial applications: flashing down to 2-phase conditions and using mechanical means to effect the separation (which is what you say you are doing now).

Gas stripping is not possible without a pressure difference. You state that you can't accept a de-pressurization, so that is out of consideration. As I stated above, this is the mechanical conventional method of choice - but it requires a de-pressurization of the system.

A mechanical air separator will not work because the dissolved air will remain in solution. The pressure in the system is what keeps the air in solution, not a physical change in the piping configuration. The pressurized water will retain its dissolved air no matter what the piping or equipment configuration is.

A theoretical method would be to have the air react with an ingredient in the water - but you will find that 80% of the air (Nitrogen) is essentially inert and this theory has holes because of that. Adsorption would require the addition of solids and this could become a mess. You inherit the batch operation characteristic and the regeneration requirements as well. Without any more basic data and specific scope of work from you, I believe you are stuck with flashing down to atmospheric and mechanically separating the included air with a vacuum. The same technique that is used in Power Plants to "de-aereate" boiler feed water.

I hope this explanation helps out.


Art Montemayor
Spring, TX

 

[Montemayor]

All:

Allow me to correct myself on an oversight error. The dissolved gas in question is not air, but Hydrogen and Oxygen (de-associated water) - so the application of a possible reactant with the two gases (both of which are reactive) might be a fit. However, the problem of separating out the excess reactant and the solid products would be the trade off and this means more elaborate equipment and instrumentation. The solids involved might not be tolerable in the process - but then we don't have any basic data or scope to indicate that.

Sorry for the oversight. Speed reading is not for the aged.


Art Montemayor
Spring, TX

 

[sbush]

Dissolved gases, such as hydrogen and oxygen, can be removed from water without venting to atmosphere.

Our systems use hydrophobic, hollow-fiber membranes (microporous polypropylene) potted inside a pressure vessel that we call a Contactor. The configuration is similar to a tube & shell heat exchanger. Water flows through the pressure vessel (i.e., the shell) while nitrogen (sweep gas) is passed through the lumens of the membrane fiber(i. e., the tubes). In some applications, a nitrogen sweep may not be necessary, relying solely on the vacuum pump to acheive the desired level of gas removal. A closer look at your application will determine which method will work the best.

Your 10 gpm flow rate is not too small for us, and we can go much much higher too.

Please feel free to contact me through our Web site link.

S. Bush

http://www.water-eg.com