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Liquid Ring Vacuum Pump Seal Liquor

liquid ring seal liquor

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#1 AndyChemEng


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Posted 16 January 2019 - 02:11 PM

Hi all,


I'm in charge of a continuous filter unit that uses two liquid ring vacuum pumps (3000m3/h @ -200mbarg) to produce the vacuum underneath the cloth.


The unit is operated under a nitrogen blanket with a continuous nitrogen purge (60m3/h) and a fan & control valve for venting.


We currently use water as the seal liquor but the higher humidity this causes in the unit means water is being entrained in the liquor being filtered which is bad for solvent recovery/recycle in a later stage. 


My question is, can anyone recommend a liquid that can meet the following requirements:

  • High boiling point (to minimize the quantity of seal liquor removed/lost);
  • compatible with Viton is a must, as both the pumps and a recirculation pump used for cooling the sealing liquor through a heat exchanger have Viton seals.
  • Low viscosity is a must to ensure an adequate flow around the pumps is maintain at there relatively low operating vacuums.  An oil was tried in the past but water contamination caused it to emulsify and go thick.
  • Ideally low toxicity but this isn't a must
  • A flash point more than 80 oC is desirable
  • high heat capacity would be desirable to minimize the temperature rise across the pump.


Any suggestions/comments/recommendations are welcome.

#2 AndyChemEng


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Posted 16 January 2019 - 02:13 PM

For info, NMP was picked but it turned out it was incompatible with the viton seals.

#3 Bobby Strain

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Posted 16 January 2019 - 03:15 PM

Why not use the liquid you are recovering?

#4 AndyChemEng


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Posted 17 January 2019 - 07:38 AM

The slurry fed to the filter consists of our product dissolved in DMSO and inorganic salts.


DMSO was considered, both fresh and recovered, but DMSO isn't compatible with Viton sadly and the freezing point of fresh DMSO would be problematic and the toxicity of recovered DMSO we have is an issue.


The most likely option is to replace the elastomers in the seals and use NMP but I was hoping to avoid the expense that this would occur. 



#5 breizh


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Posted 17 January 2019 - 07:59 AM


It seems that EPDM is a good candidate for DMSO , definitely Viton is a bad one .


From your favorite engine  "compatibility study of Viton, NBR 70 and EPDM O-rings with selected solvents"


Good luck



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Edited by breizh, 17 January 2019 - 09:55 PM.

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