Petroleum Desalting Utilizing Voltage Modulation

Abstract

A method of removing entrained salt containing water from an inlet crude oil stream includes the steps of applying an electrical energy to at least one electrode of a plurality of horizontally oriented, spaced-apart electrodes (12, 14, 16) housed within an elongated desalting vessel (10) and distributing an inlet crude oil stream between the electrodes. Each electrode in the plurality of electrodes is housed in an upper portion of the desalting vessel and may be in communication with a first, second and third transformer (42, 44, 46), respectively. The electrical energy may be at a single frequency and voltage or at a modulated voltage. Or, the electrical energy may be a modulated frequency at a single or modulated voltage. Fresh water may be mixed with the inlet crude oil stream either exteriorly or interiorly of the vessel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional application which claims priority to U.S. patent application Ser. No. 13 / 812,979 filed on Jan. 29, 2013, which claims priority to United States National Phase of PCT Patent Application No. US2011 / 046713 filed on Aug. 5, 2011, which claims priority to U.S. Provisional Patent Application No. 61 / 371,046 filed Aug. 5, 2010, all of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]This invention relates generally to crude oil desalter / dehydrator vessels and, more specifically, to desalter / dehydrator vessels which utilize a set of electrodes.[0003]A common crude oil desalter / dehydrator used by many of the world's refiners was invented by Petreco in 1980 and is illustrated and described in U.S. Pat. Nos. 4,149,958; 4,182,672; 4,188,277 and 4,209,374 (“the Petreco patents.”) Desalters / dehydrators marketed under the Petreco patents have been referred to as BILECTRIC® desalters (hereinafter...

AI Technical Summary

Benefits of technology

The patent describes a system and method for removing salt and water from heavy crude oil using a high frequency AC field. This method can prevent the formation of a filter layer and improve the performance of a desalting and dehydration process. The use of modulating fields allows for optimal coalescence with crude oil and effective removal of entrained salt. This system can provide an improved method for treating heavy crude oils and stabilizing the formation of filters.

Problems solved by technology

If the applied voltage is not an effective one, the interface rag can accumulate which, in turn, places a greater power demand on the power unit.

This effectively reduces the applied voltage and results in a less effective process to control the rag.

When an interface rag consisting of an unresolved oil / water emulsion accumulates on the oil / water interface, the interface rage hinders the strength of the electrostatic field which, in turn, leads to water chaining and shorting of the electrodes.

This reduction in voltage further compromises the bilectric desalter's ability to promote decay of the rag layer.

These “rag-producing” oils compromise the overall dehydration and desalting performance of the bilectric desalter.

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