Designing a gas sparger

[pdavis3]

Hi,
I'm designing a gas sparger for an acetogenesis/methanogenesis reactor. I am taking 10% of the gas created and recycling back into my reactor at high pressure to mix the contents.
I want to use a ring gas sparger, although I am not too sure how to work out the dimensions of its location (ie. how far from tank walls should ring be, how far from bottom of the reactor base (note it is conical))?
My reactor has a diameter of ~8.5m, and a height of ~26m. I need efficient mixing of these contents! My influent is majority water with glucose, cellulose, amino acids, and proteins, and gases are created in exothermic reactions.
Any help is greatly appreciated!!
PD

 

[MikeHalloran]

My limited experience says the gas pressure needs only to exceed the sum of the gas pressure at the top of the reactor and the hydrostatic head at the bottom. The velocity of the gas leaving the sparger has to be of little consequence, as long as it leaves.

It should leave through a multitude of small orifices. E.g., sintered plastic (polyolefin) air mufflers work very well in open acid tanks. I have no idea if they'd survive in your soup.





Mike Halloran
Pembroke Pines, FL, USA

 

[sshep]

pdavis,

Recycling gas to mix a liquid seems a pretty inefficient way to supply mixing horsepower. Mike's comment about exit velocity does not account for the velocity needed to move liquid for mixing. Without knowing the mass and available pressure of the recycle gas there is no way to advise if your scheme has the available energy to practical with any design. A cone bottom also suggests that the tank may have a solids settling and removal function that has competing objectives with the mixing goal- your sparge ring seems like it should be at or above the transition seam to maximize the mixing area above the ring and allow settling in the cone below.

At this time it appears that a mechanical mixer would serve better in terms of horsepower and ability to meet the well mixed design objective, but this is just my opinion based on the little data provided.

best wishes,
sshep

 

[m777182]

You can achieve some degree of mixing or circulation of the liquid by spargling gas into it but the movement of the liquid will be very slow. The driving force is the difference in density between areas of the cross section of the vessel where gas is distributed in the liquid (lower density, upward movement)and those where it is not(higher density, downward movement). If your vessel stays outside you could perhaps combine synergetic effect of small temperature differences between surrounding air and liquid which cause a slight circulation in the vessel due to the same reason: differences in density.But do not expect a homogeniously mixed suspension!
m777182

 

[NPSH10]

I am working on the detailing of 25' dia X 24'ht Raw water
tank. due to high percent of H2S and CO2 the process recommends for sprinkling of inlet raw water through sparge ring with spray nozzle for removalof the H2S and CO2.
Can any one guide me about the design and detailing of this sparge ringthat what will b ethe size , the no of zozzles and its dia, spacing between the nozzles and the material to be used for both sparge ring and nozzle. The inlet flow is around 509 GPM.
As i am a new comer in this field a detailed answer will be highly appreciated
thanks
NPSH