5 replies to this topic

[CheAmine]

Hello,

 

Currently we are having two sour water storage tanks as per which the overhead vapors are routed to H2S adsorbents and eventually to atmosphere. Since commissioning, the H2S adsorbents are getting saturated very fast leading to H2S and HC release to the atmosphere. For that, we would like to re-route the tanks overhead vapors to the acid gas flare header. However, this is not possible as the sour water tanks design pressure (350 mbarg) is less than the acid gas flare system (3.5 barg).

 

I would like to know if there is any mechanical modification that can be done to the low pressure tanks so that it can be considered as pressure vessels and then we can connect the tanks to the sour water tanks.

 

Thank you.

 

Regards,

[spchauhan12]

Can you send some sketch to elaborate your problem.

 

However, Seems to check for troubleshooting your H2S problem as below:

 

1) Is sour water feed to tank - Compositions is varying ? Check if any change in H2S & HC Content in inlet.

 

2) Check adsorbent Quality ? Any change in quality of adosrbent?

 

3) You may install a Ejector to suck the overhead gas &  small amine scrubber downstream of the ejector with precise tank pressure-control system.

 

Regards,

SP

[fallah]

 

I would like to know if there is any mechanical modification that can be done to the low pressure tanks so that it can be considered as pressure vessels and then we can connect the tanks to the sour water tanks.

 

 

CheAmine,

 

Although an atmospheric storage tank can be mechanically modified by reinforcement to upgrade a little bit in design pressure standpoint, it cannot be converted to a pressure vessel at all. Hence forget about such modification and go to find a low pressure destination to release the overhead vapors or modify/repair the existing H2S adsorbents....
 

[CheAmine]

spchauhan12

 

we have been observing severe emulsion in the upstream sources, and hence ineffective separation of sour water & HC leading to HC carryover with sour water to the sour water treatment unit. we have tried different demulsifier, but with no success. we have analyzed the overhead vapors and found that HC content can range from 10 mol % to 20 mol % and H2S content range from 0.4 mol % to 1.2 mol %. Activated carbon was being used since commissioning.

 

Attached is the drawing

 

Fallah,

 

Thanks for your feedback, what about providing an emergency shutdown valve (maybe HIPPS ?!) so that to close on high pressure in case of back pressure from flare.

 

 

Attached Files

•  Sour water treatment drawing.pptx   36.34KB   16 downloads

[fallah]

 

Fallah,

 

Thanks for your feedback, what about providing an emergency shutdown valve (maybe HIPPS ?!) so that to close on high pressure in case of back pressure from flare.

 

CheAmine,

 

An ESDV might be used to close on high back pressure from flare, but coming line(s) to the tank should also be interrupted at the same time by another ESDV to avoid tank overpressure from incoming side will lead to contaminated gas emission to the atmosphere through the safety protection devices on the tank roof such as emergency vent...

[spchauhan12]

CheAmine,

I think What Fallah sir has advised is OK :

 

Find low pressure destination for this stream or modify adsorbent.

 

Regards,

 

SPC