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Caustic Wash


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#1 Alejandro Guerrero

Alejandro Guerrero

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Posted 17 May 2007 - 09:28 AM

Hi, i am working in the design of a LPG Caustic Wash

Can any help me with some questions:

1.- Any know a rule of thumb to select the orientation of a vessel.
2.- What's the typical % volume of soda for wash LPG.
3.- What's a recommendated concentration of Soda for wash LPG.
4.- Can i wash LPG with a 1%wt of H2S ?
5.- Any know literature about the design of this equipment ??

Regards. blink.gif

#2 Zauberberg

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Posted 18 May 2007 - 02:00 PM

Hello Alejandro,

Caustic washing of refinery LPG streams is usually done after amine scrubbing, where most of H2S is removed. Caustic treatment is second step in LPG purification process, with purpose to remove mercaptans and residual hydrogen sulfide.

Some brief answers on your questions:
1. Vessel orientation is vertical (prewash and extraction units)
2. Recommended caustic concentration is 15 and/or 20Be, for most of the LPG treatment units I have seen.
3. It strongly depends on your LPG spec and caustic treater unit configuration. Most of the units employ caustic regeneration section, where mercaptides are oxidized into disulfide oils and caustic is recycled back to the process - which significantly reduces fresh caustic consumption.
4. I cannot see the reason why you couldn't do it.
5. See the links below. Companies with biggest design and operational experience with caustic treating units are UOP and Merichem.

http://www.merichem....ature/index.php
http://www.bre.com/p.....th Amines.pdf
http://www.bre.com/P...83/Default.aspx

Regards

#3 M S Miglani

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Posted 11 June 2007 - 10:59 PM

Just to add to the reply of Zauberberg,
The allowable concentration of caustic soda depends on the type of process you employ. In case of low capacity systems, you may go for batch process. In case of batch process, caustic is not regenerated and instead it is sent to ETP.

In this scenario, the caustic strength should be less than 15 wt%, as there is a possibility of salt separation.

Other than UOP and Merichem, Engineers India Limited is another company which designs both batch and continous caustic wash systems.

#4 Nurudeen Musah

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Posted 14 March 2012 - 12:25 PM

Just to add to the reply of Zauberberg,
The allowable concentration of caustic soda depends on the type of process you employ. In case of low capacity systems, you may go for batch process. In case of batch process, caustic is not regenerated and instead it is sent to ETP.

In this scenario, the caustic strength should be less than 15 wt%, as there is a possibility of salt separation.

Other than UOP and Merichem, Engineers India Limited is another company which designs both batch and continous caustic wash systems.




initially i was thinking the caustic washing may be like preparing the caustic solution in a plastic drum and pouring the condensate to the solution and stirring
after that allowing the solution to settle and latter draining the spent caustic solution containing the contaminants and pouring out clear oil floating on top
is this the case if you are to do this in the local way?

#5 Nurudeen Musah

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Posted 14 March 2012 - 12:26 PM

Hello Alejandro,

Caustic washing of refinery LPG streams is usually done after amine scrubbing, where most of H2S is removed. Caustic treatment is second step in LPG purification process, with purpose to remove mercaptans and residual hydrogen sulfide.

Some brief answers on your questions:
1. Vessel orientation is vertical (prewash and extraction units)
2. Recommended caustic concentration is 15 and/or 20Be, for most of the LPG treatment units I have seen.
3. It strongly depends on your LPG spec and caustic treater unit configuration. Most of the units employ caustic regeneration section, where mercaptides are oxidized into disulfide oils and caustic is recycled back to the process - which significantly reduces fresh caustic consumption.
4. I cannot see the reason why you couldn't do it.
5. See the links below. Companies with biggest design and operational experience with caustic treating units are UOP and Merichem.

http://www.merichem....ature/index.php
http://www.bre.com/p.....th Amines.pdf
http://www.bre.com/P...83/Default.aspx

Regards



initially i was thinking the caustic washing may be like preparing the caustic solution in a plastic drum and pouring the condensate to the solution and stirring
after that allowing the solution to settle and latter draining the spent caustic solution containing the contaminants and pouring out clear oil floating on top
is this the case if you are to do this in the local way?

#6 Nurudeen Musah

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Posted 26 April 2012 - 12:27 PM

hello every one
some one help me with these questions
how can hexane be used to deasphalt used lube oil for fresh lube oils
what may be additional safer to handle solvent to improve the color quality and viscosity and can be recovered by distillation under low temperatures




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