6 replies to this topic

[anandcpcl]

dear friends, IN OUR PLANT ATF TREATMENT COLOUR IS ON AND OFF GOING OFF SPEC, WHERE THE ACTUAL TROUBLESHOOTING TO BE DONE, WASH WATER COLUMN OR  COALESCER OR AIR FLOW TO REACTOR TO BE ADJUSTED AND WHAT IS THE CHEMISTRY BEHIND THAT, PLEASE.

[RockDock]

Sorry, I really do not understand your question.

 

Please clearly explain your process and the question you have. I've worked on a few Merox units and may be able to help.

[anandcpcl]

dear friend, 

                  I am working in Kero-MEROX treatment based on fixed -bed sweetening process, where air is reacted with mercaptans to remove as mercaptide, and also colour treatment done using clay and sand filter, sometimes colour has gone offspec , but air is adjusted for colour improvement, is it correct.

[P.K.Rao]

Air treatment is not done for removing mercatans as mercaptides. Air treatment oxidizes mercaptans to disulfides which are soluble in ATF..

Air treatment also oxidizes mercaptides to disulfides in another step of air treating caustic soda used in the gasoline merox process. These disulfides are not soluble in caustic and are separated in the disulfide oil separator (of gasoline Merox). But still this caustic contains some entrapped disulfide oils and should not be used for ATF Merox. If used, the disulfides (which are carried over) re-dissolve in ATF giving it yellow color. This could be one reason why ATF is failing in color sometimes because the more the disulfide oil dissolve in ATF, the deeper will be the color. Perhaps gasoline merox caustic is getting mixed with ATF Merox  caustic.

( You may verify this by checking ATF before treatment and after treatment for total sulfur. If disulfide oil is coming from caustic, then ATF after Merox treatment will have higher total sulfur than ATF before Merox treatment).

Hope this answers your question.

 

P.K.Rao

[anandcpcl]

ok sir, we are not using gasoline merox for atf treatment, and sometimes engineer tells to reduce air to reactor when atf colour off, is it correct, then how colour is to be maintained

[P.K.Rao]

I do not know what is the mercaptan content of ATF. In ATF Merox, mercaptans are oxidized to disulfides which impart yellow  color to ATF depending upon their concentration. By reducing the air, it could be insufficient to oxidize all mercaptans. You may try by reducing air if mercaptan content is not a problem. I once gain advocate checking total sulfur before and after merox by ASTM D 4045. You dilute with sulfur free n-decane if sulfur is beyond the scope.

Basic nitrogen and organic acidity is another angle you can look into. If they are high, there is a possibility of color deepening. Color of 10% cuts of ASTM D 86 distillation will thow some light on the nature.

 

P.K.Rao

pkrao2012@yahoo.com

[P.K.Rao]

What is the crude mix going to CDU?