Hi Norm – For a crude desalter, what is optimum mix valve delta P? Our crude is 25°API, we use 6 wt% water and desalter temperature is 250-270°F.
--Carl , California
Carl – I used to think 15-25 psi. But, now I know better. Let’s say you have NaOH in the wash water and your brine pH is nine, rather than an optimum 6½. Thus, you have the desalter interface between H2O and crude filled with several feet of emulsion so that you’re getting water carrying over into your crude heater. You then need to back way off on your mix valve delta P to reduce emulsion carry-over. It’s senseless to have a 20 psi mix valve delta P if it promotes excessive emulsion carry-over. In my experience, the most important controllable variable in desalter operation is pH control of the brine. Temperature is also critical but not often controllable. You can call me at 1-504-887-7714 for an in-depth discussion.
--Norm
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