Desalting process

Abstract

A compact desalting system for use in a process of desalting crude oil comprises a plurality of separation stages. Each separation stage includes a compact electrostatic coalescer ( 42, 62 ) for coalescing water droplets carried with the crude oil and settling means ( 91, 92; 95, 96 ) for settling separated oil and coalesced water droplets. The system includes a vessel ( 46 ) comprising a plurality of compartments containing the settling means and the compact electrostatic coalescers are each mounted in a housing on top of the vessel.

1 - 20 . (canceled) 
     
     
         21 . A compact desalting system for use in a process of desalting crude oil, comprising:
 a settling vessel comprising a plurality of compartments and a plurality of inlets disposed on a top surface of the settling vessel and corresponding to the plurality of compartments; and   a plurality of separation stages, each separation stage corresponding to a compartment of the settling vessel and comprising:   a compact electrostatic coalescer for coalescing water droplets carried with the crude oil; and   settling means for settling separated oil and coalesced water droplets, wherein the system includes a vessel comprising a plurality of compartments containing said settling means and said compact electrostatic coalescers are each mounted in a housing on top of said vessel.   
     
     
         22 . The compact desalting system of  claim 21 , wherein dilution water is added before each separation stage and water is extracted after each separation stage. 
     
     
         23 . A compact desalting system according to  claim 21  wherein the compact electrostatic coalescers include insulated electrodes tolerating high water cuts and water slugs without short circuiting the electrodes. 
     
     
         24 . A compact desalting system according to  claim 21  wherein the compact electrostatic coalescers are configured to include a turbulent flow pattern for improved coalescence of water droplets. 
     
     
         25 . A compact desalting system according to  claim 21  wherein means are provided for mixing dilution water into the crude oil prior to a second separation stage, and wherein the compact electrostatic coalescer at the second separation stage is configured to operate at very low water cut. 
     
     
         26 . A compact desalting system according to  claim 25  wherein the mixing means includes a static mixer. 
     
     
         27 . A compact desalting system according to  claim 26  wherein the static mixer is used in combination with a valve. 
     
     
         28 . A compact desalting system according to  claim 27  wherein the dilution water is added to the crude oil before it enters the first separation stage. 
     
     
         29 . A compact desalting system according to  claim 21  wherein water from an outlet of a second separator stage is recycled to be mixed with the crude oil before the inlet to the first separator stage. 
     
     
         30 . A method of desalting a crude oil stream in a plurality of separation stages, comprising:
 directing the crude oil stream into a first separation stage;   electrostatically coalescing water droplets carried in the crude oil stream in a first compact electrostatic coalescer associated with the first separation stage;   separating the coalesced water droplets from the oil in a first compartment of a vessel;   mixing dilution water into the flow of oil from the first compartment;   directing the flow of oil to a second separation stage;   electrostatically coalescing water droplets carried in the crude oil stream in a second compact electrostatic coalescer and then separating the coalesced water droplets from the oil in a in a second compartment of said vessel.   
     
     
         31 . A method according to  claim 30 , including mixing dilution water into the crude oil. 
     
     
         32 . A method according to  claim 30  wherein the mixing of dilution water is performed in a static mixer used in combination with a valve. 
     
     
         33 . A method according to  claim 30  wherein the dilution water is added to the crude oil after the first separation stage and before the second separation stage. 
     
     
         34 . A method according to  claim 30  wherein the dilution water is added to the crude oil before it enters the first separation stage. 
     
     
         35 . A method according to  claim 30  wherein water from an outlet of the second separation stage is recycled to be mixed with the crude oil before the inlet to the first separation stage. 
     
     
         36 . A settling vessel for a compact crude oil desalting process having a plurality of separation stages, the settling vessel comprising:
 a first compartment containing at least part of a first separation stage; and   a second compartment containing at least part of a second separation stage, the first and second compartments each having separate outlets for oil and water, and wherein the first compartment has a first inlet and the second compartment has a second inlet, the first and second inlets being arranged such that compact electrostatic coalescers are mountable directly on top of the vessel.   
     
     
         37 . A vessel according to  claim 36  wherein the vessel is of a generally cylindrical form and has a dividing plate dividing the vessel into said first and second compartments. 
     
     
         38 . A vessel according to  claim 37  wherein the dividing plate is a vertical plate extending the entire length of the vessel. 
     
     
         39 . A vessel according to  claim 37  wherein the dividing plate is a horizontal plate, the first and second compartments being an upper compartment and a lower compartment. 
     
     
         40 . A compact desalting system for use in a process of desalting crude oil comprising a plurality of separation stages, each separation stage including a compact electrostatic coalescer for coalescing water droplets carried with the crude oil and settling means for settling separated oil and coalesced water droplets, wherein the system includes a vessel comprising a plurality of compartments containing said settling means and said compact electrostatic coalescers are each mounted in a housing separate from said vessel. 
     
     
         41 . A compact desalting system according to  claim 40 , wherein at least one of said separation stages includes bypass means for isolating said compact electrostatic coalescer to permit maintenance of the coalescer without stopping operation of the desalting process. 
     
     
         42 . A compact desalting system according to  claim 40  wherein the compact electrostatic coalescers include insulated electrodes tolerating high water cuts and water slugs without short circuiting the electrodes. 
     
     
         43 . A compact desalting system according to  claim 40  wherein the compact electrostatic coalescers are configured to include a turbulent flow pattern for improved coalescence of water droplets. 
     
     
         44 . A compact desalting system according to  claim 40  wherein means are provided for mixing dilution water into the crude oil prior to a second separation stage, and wherein the compact electrostatic coalescer at the second separation stage is configured to operate at very low water cut. 
     
     
         45 . A compact desalting system according to  claim 44  wherein the mixing means includes a static mixer. 
     
     
         46 . A compact desalting system according to  claim 45  wherein the static mixer is used in combination with a valve. 
     
     
         47 . A compact desalting system according to  claim 44  wherein the dilution water is added to the crude oil before it enters the first separation stage. 
     
     
         48 . A compact desalting system according to  claim 40  wherein water from an outlet of a second separator stage is recycled to be mixed with the crude oil before the inlet to the first separator stage.