water hydrocarbon separation in reflux drum

[petrochimistul]

Hello!I work in Crude distillation unit.We have a small problem regardind the separation betwen water and hydrocarbons in reflux drum.The water is sent to sour water stripping unit with a high content of hydrocarbons.The reflux drum is a simple vessel as attached.We have a pH analyser that is coted with hydrocarbon and something that looks like soot.When is clean gives a reliable indication,but when coated the pH value rises.Do you have any suggestionfor a better separation?From where does this "soot" come?
Thanks for the help!

 

[dcasto]

The soot sounds like Iron sulfide. The H2S is the system is combining with your steel to make it. I strongly suggest you UT your equipment.