Crude Unit Operation

Dr. Lieberman – Here is Nehi. Should we add NaOH to desalt effluent?

--Best Greetings – Nehi, India

            Nehi – Add caustic to crude effluent from desalter is normal. You should minimize caustic addition. I use two methods. One way is to add NaOH based on ⅓ MgCl₂ content of raw crude. That is, about 65% of MgCl₂ is extracted with brine and the remainder hydrolyzes to HCl. Second method is to reduce chloride content of crude tower overhead drum boot to 10 to 15 ppm. Too much caustic is bad. Regardless never use more than 3-5 ppm of NaOH of crude. Spent caustic from a mercaptan extraction unit can be used as well as fresh 10-15 Be NaHOH.

--I’m not a Doctor – just Norm