Processes for desalting crude oil under dynamic flow conditions

Abstract

Presented is a process for desalting crude oil. The process includes mixing a partially dehydrated crude oil, comprising less than 10 vol. % water and at least one water-extractable contaminant, with an aqueous wash fluid. A water-in-oil emulsion is formed. The water-in-oil emulsion is introduced into a first coalescence zone defined by a first vessel. The first vessel is configured to apply an electric field to the emulsion. The water-in-oil emulsion is broken within the first coalescence zone in the presence of the electric field under dynamic flow conditions to form a partially desalted crude oil and a non-emulsified aqueous salt solution. The partially desalted crude oil and the non-emulsified aqueous salt solution are then separated from one another under the dynamic flow conditions to yield a separated, partially desalted crude oil comprising less than 1 vol. % water.

1 . A process, comprising:
 providing a partially dehydrated crude oil that comprises less than 10 vol. % water and a water-extractable contaminant;   mixing an aqueous wash fluid with the partially dehydrated crude oil and forming a water-in-oil emulsion;   introducing the water-in-oil emulsion into a first coalescence zone defined by a first vessel, wherein the first vessel is configured to apply a first electric field to the water-in-oil emulsion and to break the water-in-oil emulsion within the first coalescence zone in the presence of the first electric field and under a dynamic flow condition; and   yielding from the first coalescence zone a partially desalted crude oil, comprising residual emulsified water of less than 1 vol. % water, and a non-emulsified aqueous salt solution.   
     
     
         2 . The process of  claim 1 , wherein the process further comprises:
 introducing the partially desalted crude oil into a second coalescence zone defined by a second vessel configured to simultaneously apply a second centrifugal force and a second electric field to the partially desalted crude oil to convert the residual emulsified water into a further portion of non-emulsified aqueous salt solution; and   removing from the second coalescence zone a desalted crude oil and the further portion of non-emulsified aqueous salt solution.   
     
     
         3 . The process of  claim 2 , wherein the second vessel is a second hydrocyclone having a second longitudinal axis and including a second electrode placed within the second coalescence zone in a non-parallel orientation with respect to the longitudinal axis. 
     
     
         4 . The process of  claim 3 , wherein the second hydrocyclone is inclined with respect to the earth's surface at a second incident angle in the range of from 20 degrees to 60 degrees. 
     
     
         5 . The process of  claim 4 , wherein the non-emulsified aqueous salt solution comprises the water-extractable contaminant. 
     
     
         6 . The process of  claim 5 , wherein the aqueous wash fluid comprises water or an aqueous acid solution. 
     
     
         7 . The process of  claim 6 , wherein the step of providing the partially dehydrated crude oil comprises:
 passing a crude oil, comprising emulsified water, through an inlet element into a separation zone defined by an inclined tubular element housing an electrode and having an upper outlet and a lower outlet, wherein the inclined tubular element provides for converting the emulsified water into bulk water and for forming the partially dehydrated crude oil; and   removing from the separation zone the partially dehydrated crude oil through the upper outlet and the bulk water through the lower outlet.   
     
     
         8 . The process of  claim 7 , wherein the first vessel is further configured to simultaneously apply a first centrifugal force to the water-in-oil emulsion while applying the first electric field. 
     
     
         9 . The process of  claim 8 , wherein the first vessel is a first hydrocyclone having a first longitudinal axis and includes a first electrode placed within the first coalescence zone in a non-parallel orientation with respect to the first longitudinal axis. 
     
     
         10 . The process of  claim 9 , wherein the first hydrocyclone is inclined with respect to the earth's surface at an first incident angle in the range of from 20 degrees to 60 degrees. 
     
     
         11 . The process of  claim 10 , further comprising:
 adding a chemical to the partially dehydrated crude oil or the water-in-oil emulsion, or both, to further promote coalescence of emulsified water into the non-emulsified aqueous salt solution.   
     
     
         12 . The process of  claim 11 , further comprising: refining the desalted crude oil.