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# Flash Vessel - Flash Gas

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### #1 BaneAUS

BaneAUS

Junior Member

• Members
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Posted 25 October 2010 - 03:09 AM

Dear Forum,

I'm trying to estimate the amount of flash gas that will evolve from a produced water system when the upstream pressure is 9 barg and the flash vessel operates at 2 barg (40 degC). I've tried using Henry's law and obtained some very useful information from.

http://www.mpch-main.../res/henry.html

If you see the attached Excel, I've used Henry's law to estimate the amount of absorbed gas at the two conditions and the difference should be the flash gas. Now this is all theoretical and I've been told that I should do the following by a colleague.

If you are looking at how much dissolved hydrocarbon will flash out of produced water, the rule of thumb is that at atmospheric pressure the amount of hydrocarbon flashed off equates to approximately 50% by volume vapour and 50% by volume liquid water. If you use this as a guide you can back calculate the amount of flashed hydrocarbon that will break out at a higher pressure.

Now this is fine for getting concentrations, but it's useless in estimating the actual flow rate. I have a feeling that the outlet PCV will be a 2inch regulator, but I'd like to be able to correctly estimate the flow. Also, please note that this system in level controlled and any variation in the level will trip the system. Therefore the flash gas is the sizing factor.

Any advise would be appreciated.

#### Attached Files

Edited by BaneAUS, 25 October 2010 - 03:11 AM.

### #2 breizh

breizh

Gold Member

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• 4,065 posts

Posted 25 October 2010 - 07:41 AM

Hi ,
Let you try this resource or the search button (right hand side) where you can find a excelsheet developped by Ankur ( one of the Jedis).

Hope this helps
Breizh

### #3 ankur2061

ankur2061

Gold Member

• Forum Moderator
• 2,484 posts

Posted 25 October 2010 - 09:49 AM

BaneAUS,

In upstream oil and gas applications the amount of flash gas evolved fom a oil / water/ associated gas mixture (gas is dissolved) is often calculated using the Vasquez and Beggs correlation. To know more about Vasquez and Begs correlation refer the following links:

http://membernet.cap...dt=PDF&dn=38234

http://www.deq.state...VBE_Aug2008.xls

Hope this helps.

Regards,
Ankur.