Desalter electrical load problem

[msnsystem]

Hi there all
We ve got 2 series desalter each one has 3 rectifier AC 12000V
After first's one overhaul all three amper meter went from 5-10 to 20-50
Demulsifier, crude oil, temprature didnt change at all
We even checked our water salinity and didnt change too
Electrical guys insist that there is a process thing
With bad dimulsifier our desalter easily over load with 180A

Thx for any tips

 

[EmmanuelTop]

The magnitude of electrical current is directly proportional to conductivity of liquid phase between the electrodes. Having said that, the measured current can be anywhere between zero and the desalter trip point. The fact that you are observing higher currents than usual, means that the interface level has shifted a bit upper inside the vessel, or that the emulsion layer is thicker than usual. There is no real concern here, as long as you are getting the crude oil dewatered properly and there is no crude oil carry-under with the effluent water.

Some crude oils require relatively high mixing pressure drop, whereas the others tend to create stabilized emulsions at increased pressure drop across the mixing valve. Maybe you should try adjusting the mixed valve dP and observe the effects in the desalter.

Dejan IVANOVIC
Process Engineer, MSChE

 

[georgeverghese]

Obviously, with overdose of chemicals into crude, the grids on this desalter will short circuit, with all the strong emulsions. You may have to talk to the people who are responsible for this chemical injection.

Have come across more than one electrostatic desalter / dehydrator where the Operator has given up on this unit and operated it without the grids. Preheating the feed maybe the only way the break these emulsions if your CI injection happy colleagues do not reduce chemical dosing.