SYSTEM AND METHOD FOR SEPARATING A TRACE ELEMENT FROM A LIQUID HYDROCARBON FEED

Abstract

The present invention is generally directed to removing a trace element from a liquid hydrocarbon feed. The liquid hydrocarbon feed, containing the trace element, is mixed with the water along with a hydrocarbon-soluble additive. While being mixed, a compound, which in some cases is preferably insoluble, is formed by the hydrocarbon-soluble additive chemically reacting with the trace element. A phase separation device, such as a desalter or an oil-water separator, receives the oil-water emulsion containing the compound and resolves the mixture to produce the compound, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. In some embodiments, the present invention is directed to removing elemental mercury from a liquid hydrocarbon feed. A hydrocarbon-soluble sulfur-containing additive, typically an organic polysulfide, is mixed with the liquid hydrocarbon feed and water. The hydrocarbon-soluble, sulfur-containing additive reacts with the mercury, rapidly forming an agglomeration of mercuric sulfide which is then dispensed with the effluent brine or the effluent liquid hydrocarbon.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 12/132,475 filed Jun. 3, 2008, which is hereby incorporated herein in its entirety by reference.

TECHNICAL FIELD

This invention relates generally to separating a trace element from a liquid hydrocarbon feed within a phase separation device, such as a desalting unit or oil-water separator.

BACKGROUND OF THE INVENTION

Liquid hydrocarbon feeds generally contain an assortment of trace elements in amounts generally ranging from several parts per billion (ppb) to several thousand ppb depending on the feed source. These elements often cause corrosion within equipment and may deteriorate or poison a catalyst of a subsequent treatment process. For example, mercury may amalgamate with a surface metal, such as copper or aluminum, collecting with time in piping, valves and even in larger structures such as fractional distillation columns. Equipment replacement or abstraction of this deleterious metal from the equipment can be very expensive and potentially hazardous. Therefore, it may be preferable to remove the trace elements as early as possible during processing, such as removal prior to distillation of the feed or even while still at the hydrocarbon recovery site. However, due to the liquid hydrocarbon state of the feed prior to distillation being more chemically complex, current technologies for removing the trace elements prior to hydrocarbon distillation tend to be less developed.

Various successful methods for removal of trace metal contaminates within liquid hydrocarbon feed prior to fractional distillation have nonetheless been developed. For example, U.S. Pat. No. 6,350,372 B1 discloses utilizing a solubilized sulfur compound in combination with an absorbent carrier. In particular, a liquid hydrocarbon feed is mixed with a miscible sulfur compound and then placed in contact with a fixed bed absorbent, thus removing at least 85% of the mercury on an elemental basis. U.S. Pat. No. 4,474,896 claims the use of absorbent compositions, mainly polysulfide based, for removal of elemental mercury from gaseous and liquid hydrocarbon streams. Specifically, the absorbent compositions comprise a polysulfide, a support material and metal cation capable of forming an insoluble metal polysulfide. While the approach of using fixed bed absorbents to extract trace elements, including mercury, from a hydrocarbon feed have shown to be successful, they also include a number of less than desirable attributes. Absorbent beds tend to get clogged by solid particulates in the crude, thus impeding the flow of the feed. Absorbents can also be very costly due to the large quantity needed, especially if there is a high concentration of the trace element or elements being extracted. In addition, stripping the absorbent is generally necessary prior to disposal or recycling of the absorbent.

Another method to remove mercury from liquid hydrocarbon condensate is disclosed in U.S. Pat. No. 4,915,818. In this method, the use of absorbent carriers is eliminated by treating the liquid hydrocarbons with a dilute aqueous solution of alkali metal sulfide salt. Due to the high partition coefficient of the sulfur compounds in the aqueous phase, the risk of contaminating the liquid hydrocarbons with sulfur is limited. However, while this process minimizes the risk of sulfur contamination, mercury present in the organic phase may also be less likely to react to the alkali metal sulfide salt as its chemical dependency may be governed by the phase it resides in. In particular, the organic mercury compounds are soluble in the liquid hydrocarbon feed and typically are far less reactive than elemental mercury or inorganic mercury compounds.

In view of the foregoing, previous methods of trace element removal are considered less than desirable and new methods of overcoming the problems associated with trace element extraction from hydrocarbon feed would be extremely useful.

SUMMARY OF THE INVENTION

The present invention comprises removing a trace element from a liquid hydrocarbon, such as crude oil, natural gas, and other petroleum products. The liquid hydrocarbon is mixed or emulsified with water and a hydrocarbon-soluble additive. During mixing, the additive chemically reacts with the trace element forming a compound. This compound is typically an aqueous insoluble compound, such that the compound may easily be separated and removed in subsequent treatment processes. A phase separation device, such as a desalter or an oil-water separator, resolves, i.e., separates, the oil-water emulsion containing the compound. The resolved mixture produces the compound formed by mixing the additive with the trace element, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. The compound may be dispensed from the phase separation device with the effluent brine or the effluent liquid hydrocarbon and may later be filtered out.

In some embodiments, the present invention is directed to removing elemental mercury from a liquid hydrocarbon feed. A sulfur-containing hydrocarbon-soluble additive is mixed with the liquid hydrocarbon feed and water to produce an emulsified solution. In some instances, the liquid hydrocarbon is already emulsified with the water prior to injection of the additive and in other scenarios the additive may be added directly to either the liquid hydrocarbon or water and then can all be mixed together. For instance, an organic polysulfide can be injected directly into the liquid hydrocarbon stream prior to being emulsified with water or it can be injected into an emulsified oil-water mixture. Regardless of the mixing strategy, the sulfur-containing additive reacts with the mercury, concentrated within the liquid hydrocarbon, rapidly forming an agglomeration of mercuric sulfide which is then dispensed with the effluent brine or the effluent liquid hydrocarbon for subsequent filtering.

According to one embodiment of the present invention, a system is employed to remove a trace element from a liquid hydrocarbon. The system includes first and second fluid lines fluidly communicating with a phase separation device. In a refinery setting, where the phase separation device may comprise a desalting unit, the first fluid line can contain a liquid hydrocarbon feed and the second fluid line can contain wash water. A hydrocarbon-soluble additive can be mixed with either the liquid hydrocarbon feed or the wash water, such that it chemically reacts with the trace element as the fluids are emulsified. The fluid mixture is then resolved within the phase separation device producing effluent liquid hydrocarbons with a reduced concentration of the trace element that can be dispensed through a first output line, effluent brine that can be dispensed through a second output line, and the compound formed by mixing the additive with the trace element, which can be dispensed from the phase separation device with either of the effluent brine or the effluent liquid hydrocarbon. If the trace element is removed at the hydrocarbon recovery site, such as an offshore platform, the phase separation device may comprise an oil-water separator. Here, the first fluid line can contain a contaminated oil-in-water mixture and the second fluid line can contain a hydrocarbon-soluble additive that can be directly injected into the first fluid line to treat the mixture. As the additive is mixed with the contaminated oil-in-water mixture, the additive chemically reacts with the contaminant or trace element forming a compound. As the mixture is separated, the liquid hydrocarbon is recovered such that it has a reduced concentration of the trace element.

The above mentioned and other features of this invention will become more apparent and better understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart depicting steps for removing trace elements from liquid hydrocarbon feed, according to one embodiment of the present invention.

FIG. 2 is a schematic diagram depicting a system for removing trace elements from liquid hydrocarbon feed, according to one embodiment of the present invention.

FIG. 3 is a schematic diagram depicting a system for removing trace elements from liquid hydrocarbon feed, according to one embodiment of the present invention.

The figures are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. Similarly, the figures have been simplified from a processing standpoint to exclude certain types of equipment, such as mixing devices, not essential for understanding the invention by one skilled in the art.

DETAILED DESCRIPTION OF THE INVENTION

Hydrocarbon feeds, generally a conglomeration of hydrocarbon chains with approximate lengths ranging between C₅H₁₂ and C₄₂H₈₆, typically contain a variety of trace elements. The trace elements range from alkaline earth metals, transition metals, post-transition metals, and nonmetals and generally consist of calcium (Ca), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), molybdenum (Mo), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), tellurium (Te), barium (Ba), mercury (Hg), thallium (Tl), lead (Pb), and/or bismuth (Bi). For various reasons, including corrosion prevention and ensuring environmental sustainability, it is often desirable to extract one or more of these trace elements during initial treatment of the feed.

FIG. 1 depicts steps, according to one method of the present invention, for removal of a trace element from a liquid hydrocarbon. First, as shown in step 10, a hydrocarbon-soluble additive is mixed with a liquid hydrocarbon having a concentration of a trace element and with water. As these fluids are mixed, the hydrocarbon-soluble additive chemically reacts with the trace element forming a compound. Typically, this compound will be insoluble in both the hydrocarbon and aqueous phase so that it may easily be removed during future processing. Once the oil-water emulsion containing the compound is formed, it is resolved into phases in a phase separation device, as shown in step 20. The effluent phases are then dispensed separately from the phase separation device, as depicted in step 30. The compound formed by the hydrocarbon-soluble additive chemically reacting with the trace element is dispensed along with the effluent phases. The compound then can easily be extracted out of the effluent, as shown in step 40. Therefore, once this process has been completed, the effluent liquid hydrocarbon that is dispensed from the phase separation device has a reduced concentration of the trace element. Note that the “concentration of the trace element” as used herein, is meant to describe the concentration of the trace element within the liquid hydrocarbon when it is in an elemental state; that is, disregarding the content of the trace element once it has chemically reacted with the additive or when it is in a compound state.

In certain embodiments, mercury is the trace element targeted for extraction and a hydrocarbon-soluble additive, such as an organic polysulfide such as Di-Tertiary-Nonyl Polysulfide (TNPS), is utilized to form a compound with the mercury. The hydrocarbon-soluble sulfur-based additive reacts with the mercury rapidly forming an agglomeration of mercuric sulfide through the following reaction:

R—S—S_x—S—R+XHg→R—S—S—R+XHgS

where R is any hydrocarbon or hydrogen, S is Sulfur, and X and x are the same whole number, typically between 3 and 8. As an inorganic salt, mercuric sulfide has essentially no vapor pressure and with the conversion to an ionic salt, makes the mercury more readily available for removal by various techniques already known in the art. In some instances, mercurous sulfide may also be formed from the reaction of the sulfur-based additive with the mercury in the liquid hydrocarbon feed.

FIG. 2 depicts a schematic flow process, according to one embodiment of the present invention, for removing trace elements from liquid hydrocarbon feed, such as in an oil refinery setting. Treatment system 100 includes liquid hydrocarbon feed, commonly referred to as petroleum or crude oil, which is routed via piping 104 from storage container 102. The feed is then heated in a furnace 106 to a temperature above its boiling point, typically ranging from about 500 to 600 degrees Celsius. The heated liquid hydrocarbon feed continues within piping 104 and a hydrocarbon-soluble additive is introduced to the liquid hydrocarbon feed through line 108. The liquid hydrocarbon feed and hydrocarbon-soluble additive are then inputted into a phase separation device 110, such as a desalting unit or desalter, and blended with wash water introduced through line 112 to form an emulsion within the phase separation device 110. To obtain an adequate emulsion the mixture may be passed through a pressure reducing valve (not shown) or stirred by a mixing device (not shown). Alternatively, line 112, containing the wash water, may be injected directly into piping 104 upstream of the phase separation device 110. Similarly, the hydrocarbon-soluble additive can be injected through the same line as the wash water and only one of lines 108 and 112 will be present. While the mixture is emulsifying, the hydrocarbon-soluble additive reacts with one or more trace elements forming compounds, typically insoluble inorganic compounds. Resolving the emulsified solution produces the compound that is formed by a reaction between the hydrocarbon-soluble additive with the trace element, effluent brine, and effluent liquid hydrocarbons with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. As discussed later in more detail, the phase separation device 110 may utilize a plurality of baffles 118, a plurality of electrodes (not shown) that create an electric field, and/or a demulsifying agent to assist in separating the mixture into phases. Additionally, a settling agent may similarly be utilized to accelerate the settling of the compound within the hydrocarbon and/or aqueous phase.

Once separated, the effluent brine flows out of the desalter though a first output 114 and typically is filtered and recycled back through line 112 as wash water. The effluent liquid hydrocarbon is dispensed from the phase separation device 110 into piping 116 and is transported to fractional distillation column 120. Fractional distillation column 120 is comprised of a plurality of spaced plates 122 filled with multiple apertures 124. As the heated effluent hydrocarbon enters the fractional distillation column 120, it separates such that the hydrocarbon vapors continually ascend passing through the apertures 124 within the spaced plates 122. As the hydrocarbon vapors climb in the fractional distillation column 120, they cool down and begin to condense forming liquid fractions that are caught in the plurality of spaced plates 122. Vapors that pass all the way to the top of the fractional distillation column 120 exit through output 126. These vapors are typically very light hydrocarbons and are commonly called naphtha. Heavier hydrocarbons fractions such as gasoline, kerosene, diesel, lubricating oil and heavy gas oil are dispensed through outputs 128 each corresponding to the spaced plates 122 within the fractional distillation column 120. The heaviest hydrocarbon chains collect in the bottom of the fractional distillation column 120 and are dispensed through output 130. These hydrocarbons are commonly referred to as the residual. Depending on the respective output 126, 128, 130, the fractions may pass to subsequent condensers, which cool them further, and then go to storage tanks or be routed to other areas for further chemical processing. For instance, the naphtha dispensed from the top of the fractional distillation column may further be separated into light ends, such as liquefied natural gases, and heavier or denser ends. The compound formed by a reaction between the hydrocarbon-soluble additive with the trace element is dispensed along with the effluent brine or effluent liquid hydrocarbon. Conversion of the trace element to a compound makes it more available for subsequent removal through techniques such as filtration, coagulation, flotation, co-precipitation, ion exchange, reverse osmosis, ultra filtration and other typical treatment processes known in the art.

As previously mentioned, the phase separation device 110 may utilize various separation items, already known in the art, to assist in separating the mixture into phases. For example and as shown in FIG. 2, a plurality of baffles 118 are contained within the phase separation device 110 to assist in separating the emulsified solution into phases. As illustrated in FIG. 2, a series of horizontally spaced baffles are utilized, however, any directional and spatial arrangement of the baffles may be utilized. Similarly, the phase separation device 110 can include a series of charged plates or electrodes (not shown) that operate at relatively high voltages to create an electric field and assist in demulsifying the wash water and the liquid hydrocarbon. The charged plates or electrodes comprise any arrangement of anodes and cathodes disposed to create a sufficient electric field for breaking the emulsified mixture into an aqueous phase and an oil phase. A chemical demulsifying agent may be additionally added to the phase separation device 110 to aid with phase separation. The separated aqueous phase typically consists of effluent brine that flows out of the desalter though first output 114 and can be filtered and recycled back through line 112 as wash water. The oil phase typically consists of effluent liquid hydrocarbons that are dispensed into piping 116 and are transported to fractional distillation column 120. Additionally the compound formed from the reaction of the hydrocarbon-soluble additive with the trace element is produced and dispensed along with either of the effluent brine or effluent liquid hydrocarbon. Again, conversion of the trace element to a compound form provides increased opportunity for subsequent removal, as the compound is larger in size than that trace element, has an increased mass, and is typically more stabile. A chemical settling agent may be utilized to accelerate the settling of the compound mixed with the hydrocarbon and/or aqueous phase. Depending on the type of settling agent, the settling agent can be added to the liquid hydrocarbon directly with the hydrocarbon-soluble additive, along with the wash water, or through a separate injection port upstream or directly into the phase separation device. Additionally, it could be added downstream of the phase separation device directly to either the effluent brine or hydrocarbon. Types of settling agents that may be utilized, are known in that art, and are similar to those characterized in U.S. Pat. Nos. 7,204,927, 7,048,847, 5,681,451, 5,593572, 5,481,059 and 5,476988.

FIG. 3 depicts a schematic flow process, according to another embodiment of the present invention, for removing trace elements from liquid hydrocarbon feed, such as at a hydrocarbon recovery site. Treatment system 200 includes recovered contaminated hydrocarbons from reservoir 202 and routed via piping 204. The recovered hydrocarbons from the reservoir 202 are normally extracted in an emulsion form and comprise an admixture of hydrocarbons with water. The recovered hydrocarbons pass through piping 204 and a hydrocarbon-soluble additive is injected into piping 204 through line 206. To obtain adequate mixing with the additive, a pressure reducing valve (not shown) or mixing device (not shown) may be employed. As the additive is sufficiently mixed with the emulsion, the additive chemically reacts with the trace element, which contaminates the recovered hydrocarbons, to form compounds. Again, these compounds can be insoluble such that they can easily be separated in subsequent processes. The mixture is then passed through phase separation device 210, also known as an oil-water separator, to resolve the emulsion. Similar to the phase separation device 110, phase separation device 210 may also utilize baffles 216, charged plates (not shown), electrodes (not shown), a demulsifying agent, and/or a settling agent to assist in separation of the phases and/or the compound. It can be appreciated by one skilled in the art that neither phase separation device 110 nor phase separation device 210 require such items, and that they are only utilized to expedite the settling time of the emulsified mixture and the compound. Once the mixture has been resolved, the treated liquid hydrocarbon, with reduced contamination of the trace element, passes through line 214 to storage tank 220 where it can be transferred to another operation facility, such as the system shown in FIG. 2. The separated aqueous phase is dispensed through outlet line 212. This produced water may still contain an oily residue and/or other contaminates, and therefore, may pass through another phase separation device (not shown) before being recycled or disposed of. In this case, a similar process may be repeated such that the produced water is injected with an additive prior to passing through the separation device such that additional contaminates are removed.

1. EXAMPLES

The following example shows how mercury content is reduced from a liquid hydrocarbon feed to minimal levels, according to the present invention. Test results were taken at a plurality of locations, each corresponding to a different stage within a liquid hydrocarbon treatment facility, over four hour intervals to measure the variation in the concentration of mercury within a contaminated liquid hydrocarbon feed. As shown in FIG. 2, Point A is located upstream of phase separation device 110 and in this example upstream of where the hydrocarbon-soluble additive is injected through line 108, Point B is located downstream of the phase separation device on first output 114, Point C is located downstream of the phase separation device on second output 116, Point D is located on output 130 of fractional distillation column 120, and Point E is located on output 126 of fractional distillation column 120.

Time	Point A	Point B	Point C	Point D	Point E
(Hours)	(ppb)	(ppb)	(ppb)	(ppb)	(ppb)
0	109.4	13.2	376.2	0	452.4
4	60.7	8.6	201.9	1	748.2
8	82.5	13.2	140.4	2.2	127.3
12	103	14.2	281.8	1.8	2.6
16	17.7	6.8	102	2	7.6
20	170.6	11.5	259.9	2.8	13.2
24	187.3	8.8	246.6	0.2	7.1

The results above indicate that after the hydrocarbon-soluble additive was injected into the liquid hydrocarbon feed, the mercury concentration began to taper off significantly and stabilize by the twelfth hour of testing to a level of less than 15 ppb at point E, which is located downstream of the phase separation device 110 on output 126 of fractional distillation column 120. A more immediate drop at Point E may be realized through proper flushing of the equipment prior to commencing the injection of the additive. While no significant change may be seen at Point B in this example, a settling agent can be used, e.g., by injecting the settling agent at either Points 108 or 112, to promote an increase of mercury concentration in the effluent brine. Considering that a concentration of mercury is continually detected at Point C, it appears that the compound is carried by the effluent liquid hydrocarbon to the distillation chamber. Note that in this example, detection does not speciate and therefore, the readings include the total mercury concentration present in both an elemental and compound state. It is contemplated that the compound may have collected at the bottom of the distillation chamber, as an increased concentration was not detected at Point D, while a significant drop did occur at point E.

2. DEFINITIONS

Certain terms are defined throughout this description as they are first used, while certain other terms used in this description are defined below:

The term “sulfur-based” as used herein means any compound containing one or more sulfur atoms.

The term “mercury salt” as used herein means any chemical compound formed by replacing all or part of the hydrogen ions of an acid with one or more mercury ions.

The term “mercury sulfide” as used herein means mercuric sulfide, mercurous sulfide, or a mixture thereof. Normally the mercury sulfide is present as mercuric sulfide and thus the stoichiometric equivalent would be one mole of sulfide ion per mole of mercury ion.

The term “organic polysulfide” as used herein means any chemical compound containing two or more sulfur atoms bonded to any hydrocarbon or hydrogen atom.

The unit “ppb” as used herein means parts per billion.

The term “oil-water” as used herein means any mixture comprising a liquid hydrocarbon with water. Therefore, it is to be understood that the term “oil-water” is inclusive of both oil-in-water emulsions and water-in-oil emulsions.

While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Those skilled in the art will appreciate that the above described embodiments are merely illustrative of the present invention and that many variations of the above described embodiments can be devised without departing from the scope of the invention. For instance, it is contemplated that the hydrocarbon-soluble additive can be introduced into the liquid hydrocarbon or oil-water mixture through multiple injection points as compared to a single injection line. It is therefore intended that such departures from the present disclosure, that come within the known customary practice in the art to which this invention pertains, be included within the scope of the following appended claims and their equivalents.

Claims

1. A method for removing a trace element from a liquid hydrocarbon comprising:

(a) mixing a liquid hydrocarbon having a first concentration of a trace element, water, and a hydrocarbon-soluble additive to produce an oil-water emulsion containing a compound, the compound formed by the hydrocarbon-soluble additive chemically reacting with the trace element; and

(b) resolving the oil-water emulsion in a phase separation device to produce an effluent brine and an effluent liquid hydrocarbon having a second concentration of the trace element, the second concentration being less than the first concentration.

2. The method of claim 1, wherein the compound is dispensed from the phase separation device with at least one of the effluent brine and the effluent liquid hydrocarbon.

3. The method of claim 1, wherein the trace element is selected from a group consisting of mercury, vanadium, chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, thallium, and lead.

4. The method of claim 1, wherein the phase separation device is selected from a group consisting of a desalting unit and an oil-water separator.

5. The method of claim 1, wherein the step of mixing comprises mixing the hydrocarbon-soluble additive with at least one of the liquid hydrocarbon and the water before the liquid hydrocarbon and the water are mixed to produce the oil-water emulsion.

6. The method of claim 1, wherein the mixing step comprises adding the hydrocarbon-soluble additive to the oil-water emulsion after the liquid hydrocarbon and the water are mixed.

7. A method for processing a liquid hydrocarbon comprising:

(a) providing a liquid hydrocarbon feed with a first concentration of a trace element;

(b) providing a hydrocarbon-soluble additive that is configured to chemically react with the trace element to form a compound;

(c) providing a wash water;

(d) mixing the liquid hydrocarbon feed, the hydrocarbon-soluble additive, and the wash water to form an emulsion containing the compound formed by mixing and reacting the trace element with the hydrocarbon-soluble additive; and

(e) resolving the emulsion in a phase separation device to obtain an effluent brine and an effluent liquid hydrocarbon with a second concentration of the trace element, the second concentration being less than the first concentration.

8. The method of claim 7, further comprising dispensing the compound from the phase separation device in a mixture with at least one of the effluent brine and the effluent liquid hydrocarbon.

9. The method of claim 7, wherein the phase separation device is selected from a group consisting of a desalting unit and an oil-water separator.

10. The method of claim 7, wherein the trace element is selected from a group consisting of mercury, vanadium, chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, thallium, and lead.

11. A method for removing mercury from a liquid hydrocarbon comprising:

(a) mixing a liquid hydrocarbon having a first concentration of mercury, water, and a hydrocarbon-soluble additive to produce an oil-water emulsion containing a mercury salt, the mercury salt formed by the additive chemically reacting with the mercury; and

(b) resolving the oil-water emulsion in a phase separation device to produce an effluent brine and an effluent liquid hydrocarbon having a second concentration of mercury, the second concentration being less than the first concentration.

12. The method of claim 11, wherein the hydrocarbon-soluble additive is sulfur-based and the mercury salt is mercury sulfide.

13. The method of claim 11, wherein the hydrocarbon-soluble additive is an organic polysulfide.

14. The method of claim 11, wherein the phase separation device is selected from a group consisting of a desalting unit and an oil-water separator.

15. A system for treatment of a fluid comprising:

a first feed line containing a first fluid having a first concentration of a trace element;

a second feed line containing a second fluid;

a phase separation device in fluid communication with the first feed line and the second feed line, the phase separation device configured to separate at least portion of a mixture comprised of the first fluid and the second fluid; and

a first output line connected to the phase separation device configured to dispense a third fluid from the phase separation device with a second concentration of the trace element, the second concentration being less than the first concentration.

16. The system of claim 15, wherein:

the phase separation device is a desalting unit;

the first fluid is a liquid hydrocarbon feed;

the second fluid is a wash water;

the third fluid is an effluent liquid hydrocarbon feed; and

further comprising a second output line that is directly connected to the desalting unit configured to dispense an effluent brine.

17. The system of claim 16, wherein:

at least one of the first and second feed lines is configured to receive a hydrocarbon-soluble additive with at least one of the liquid hydrocarbon feed and the wash water, such that the hydrocarbon-soluble additive is configured to chemically react with the trace element to produce a compound; and

the desalting unit is configured to dispense the compound with at least one of the effluent brine and the effluent liquid hydrocarbon.

18. The system of claim 15, wherein:

the phase separation device comprises an oil-water separator;

the first fluid is an oil-water mixture;

the second fluid is a hydrocarbon-soluble additive configured to chemically react with the trace element to produce a compound; and

the third fluid is an effluent liquid hydrocarbon.

19. The system of claim 15, wherein the phase separation device further includes at least one separation item, the separation item being selected from a group consisting of a plurality of baffles, a plurality of electrodes configured to create an electric field, a demulsifying agent, and a settling agent.

20. The system of claim 15, wherein the trace element is selected from a group consisting of mercury, vanadium, chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony, thallium, and lead.