Desalter operation

Abstract

Improved separation of oil and water as well as suspended solids from the emulsion layer formed in a petroleum desalter is achieved by injection of demulsifier into the desalter vessel to achieve a higher localized concentration of demulsifier in the emulsion layer so as to promote improved oil/water separation from the emulsion layer. The demulsifier may be injected into the water layer or the oil layer in the region of the emulsion layer or directly into the stabilized emulsion layer.

What is claimed is: 
     
         1 . A petroleum desalter unit having a desalter vessel having:
 an inlet for an oil/water mixture,   electrical grids within the vessel for imposing an electric field on the oil/water mixture in the vessel to cause separation of the mixture into a denser water layer containing dissolved salts and a supernatant oil layer with the formation of a stabilized emulsion layer between the oil layer and the separated water layer,   a water outlet for removing water from the denser water layer,   an oil outlet for removing oil from the supernatant oil layer   demulsifier injectors for injecting demulsifier into the vessel in the region of the emulsion layer.   
     
     
         2 . A petroleum desalter unit according to  claim 1  which comprises demulsifier injectors for injecting demulsifier directly into the emulsion layer. 
     
     
         3 . A petroleum desalter unit according to  claim 1  which comprises demulsifier injectors for injecting demulsifier directly into the denser water layer. 
     
     
         4 . A petroleum desalter unit according to  claim 1  which comprises demulsifier injectors for injecting demulsifier directly into the denser water layer towards the emulsion layer at a distance of not more than 20 cm from the interface between the oil and water layers. 
     
     
         5 . A petroleum desalter unit according to  claim 1  which comprises demulsifier injectors for injecting demulsifier directly into the supernatant oil layer. 
     
     
         6 . A petroleum desalter unit according to  claim 1  which comprises demulsifier injectors for injecting demulsifier directly into the supernatant oil layer towards the emulsion layer at a distance of not more than 20 cm from the interface between the oil and water layers. 
     
     
         7 . A petroleum desalter unit according to  claim 1  in which the oil and water layers flow from the region of the inlet to the respective oil and water outlets in a general flow direction and the vessel comprises demulsifier injectors for angularly injecting demulsifier towards the general flow direction. 
     
     
         8 . A petroleum desalter unit according to  claim 3  which comprises demulsifier injectors for injecting demulsifier directed towards the bottom of the vessel. 
     
     
         9 . A petroleum desalter unit according to  claim 8  in which the injectors for injecting demulsifier directed towards the bottom of the vessel are located not more than 46 cm from the bottom of the vessel.