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# Bubble Rise Velocity In Waterlock Tank?

bubble sparger hydrogen

4 replies to this topic
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### #1 panagiotis_e

panagiotis_e

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Posted 23 September 2022 - 05:08 PM

Good afternoon everyone,

I would like to ask for your assistance on the following problem:

As part of an emergency vent system, hydrogen is sparged in a waterlock vessel, so that the gas is subsequently vented via a stack at the top. The level inside the water tank remains constant, as the water is constantly recirculating.

I am currently investigating the possible consequences for the waterlock vessel in a new emergency scenario, where much more hydrogen is expected to be sparged through the vessel, compared to the current operating case. Essentially I want to investigate whether the displaced liqyuid will reach the High Level setting of the tank.

Available data:

Tank Diameter: 1500 mm

NLL: 1850 mm

HHL: 2300 mm

Mass Flow of H2: 1200 kg/h

P atmospheric, T, 30 oC

Sparger: 2000 holes, 10 mm each, perforated plate, funnel shaped, with a diameter of 1200 mm at the bottom opening of the cone. The sparger is submerged at 1500 mm height, slightly below the NLL. Essentially imagine a pipe entering from the TOP of the tank, then at the submerged end, there is a funnel, like a shower head.

My approach would be the following: calculate the superficial gas velocity, then use empirical correlations to derive the expected gas holdup; then calculate the expected total volume in the tank.

However, where I hesitate is in the fact that I expect the bubble rise velocity to be quite high, which would imply that the gas will escape the water too quickly before causing the level to reach the HHL. As such, I am not sure what to expect in steady state.

Could you please give me feedback on my approach, and provide any suggestions? Thank you very much.

Kind regards,

Panos

### #2 breizh

breizh

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Posted 23 September 2022 - 09:31 PM

Hi,

You will find references in the doc attached(link):

https://www.icheme.o...ix-paper-63.pdf

You need to get enough residence time.

Good luck

Breizh

### #3 Bobby Strain

Bobby Strain

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Posted 23 September 2022 - 10:48 PM

This seems not to be an unfamiliar problem. You should find what you need if you search diligently. From your description, this appears to be similar to the distributor in a flare system water seal. And, why must the hydrogen be sparged through water? I recall having used a similar seal in a flare venting hydrogen to prevent explosions due to flame entry from the tip. I am not sure that such a device is effective. If the rate increase is significant, you will no longer get bubbles of the intended size. So you must perform the necessary calculations and analysis.

Bobby

### #4 panagiotis_e

panagiotis_e

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Posted 24 September 2022 - 05:10 AM

This seems not to be an unfamiliar problem. You should find what you need if you search diligently. From your description, this appears to be similar to the distributor in a flare system water seal. And, why must the hydrogen be sparged through water? I recall having used a similar seal in a flare venting hydrogen to prevent explosions due to flame entry from the tip. I am not sure that such a device is effective. If the rate increase is significant, you will no longer get bubbles of the intended size. So you must perform the necessary calculations and analysis.

Bobby

Good afternoon Mr. Strain,

Thank you for your time and input; indeed the intention of the vessel is as you mention (in your case) to prevent explosion and fire.

Edited by panagiotis_e, 24 September 2022 - 05:15 AM.

### #5 panagiotis_e

panagiotis_e

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Posted 24 September 2022 - 05:11 AM

Hi,

You will find references in the doc attached(link):

https://www.icheme.o...ix-paper-63.pdf

You need to get enough residence time.

Good luck

Breizh

Will have a look, Mr. Breizh; thank you very much.