Method of Injecting Solid Organic Acids Into Crude Oil

CATEGORY: DESALTING
PATENT
Method of Injecting Solid Organic Acids Into Crude Oil
United States Patent Application 20120043256
Inventors:
Kremer, Lawrence N. (The Woodlands, TX, US)
Weers, Jerry J. (Richmond, TX, US)
Sandu, Corina L. (Pearland, TX, US)
Application Number:
13/228973
Publication Date:
02/23/2012
Assignee:
Baker Hughes Incorporated (Houston, TX, US)
Abstract:
Solid organic acids may be introduced into hydrocarbon solvents to form dispersions; the dispersions in turn may be introduced into crude oil. A wash water may be added to the crude oil to create an emulsion. The organic acids may transfer metals and/or amines from a hydrocarbon phase into an aqueous phase in an electrostatic desalter which resolves the emulsion into the two phases. Suitable solid organic acids include, but are not necessarily limited to, C2-C4 alpha hydroxyacids, such as, but not necessarily limited to, glycolic acid, malic acid, maleic acid, malonic acid, succinic acid and even sulfamic acid, chloroacetic acid, thiomalic acid, including esters of, polymers of, amine salts of, alkali metal salts of, and/or ammonium salts of all of these acids.
TECHNICAL FIELD

The present invention relates to methods and compositions for introducing solid acids into a hydrocarbon, and more particularly relates, in one non-limiting embodiment, to methods and compositions for introducing solid acids, such as C2-C4 hydroxyacids, into a hydrocarbon, such as crude oil, where subsequently metals and/or amines are transferred to an aqueous phase in an emulsion breaking process.

BACKGROUND

In an oil refinery, the desalting of crude oil has been practiced for many years. The crude is usually contaminated from several sources, including, but not necessarily limited to:
Brine contamination in the crude oil as a result of the brine associated with the oil in the ground;
Minerals, clay, silt, and sand from the formation around the oil well bore;
Metals including calcium, zinc, silicon, nickel, sodium, potassium, etc.;
Nitrogen-containing compounds such as amines used to scrub H2S from refinery gas streams in amine units, or from amines used as neutralizers in crude unit overhead systems, and also from H2S scavengers used in the oilfield; and
Iron sulfides and iron oxides resulting from pipeline and vessel corrosion during production, transport, and storage.

Desalting is necessary prior to further processing to remove these salts and other inorganic materials that would otherwise cause fouling and deposits in downstream heat exchanger equipment and/or form corrosive salts detrimental to crude oil processing equipment. Further, these metals can act as poisons for the catalysts used in downstream refinery units. Effective crude oil desalting can help minimize the effects of these contaminants on the crude unit and downstream operations. Proper desalter operations provide the following benefits to the refiner:

Reduced crude unit corrosion.
Reduced crude preheat system fouling.
Reduced potential for distillation column damage.
Reduced energy costs.
Reduced downstream process and product contamination.

Desalting is the resolution of the natural emulsion of water that accompanies the crude oil by creating another emulsion in which about 2 to about 10 wt % percent relative wash water is dispersed into the oil using a mix valve. For relatively lighter crudes, the wash water proportion may range from about 3 to about 5 wt %; for relatively heavier (lower gravity) crudes, the wash water proportion may range from about 5 to about 8 wt %. The emulsion mix is directed into a desalter vessel containing a parallel series of electrically charged plates. Under this arrangement, the oil and water emulsion is exposed to the applied electrical field. An induced dipole is formed on each water droplet within the emulsion that causes electrostatic attraction and coalescence of the water droplets into larger and larger droplets. Eventually, the emulsion resolves into two separate phases—the oil phase (top layer) and the water phase (bottom layer). The streams of desalted crude oil and effluent water are separately discharged from the desalter.

The entire desalting process is a continuous flow procedure as opposed to a batch process. Normally, chemical additives are injected before the mix valve to help resolve the oil/water emulsion in addition to the use of electrostatic coalescence, although some additives or portions of additives may be injected elsewhere. These additives effectively allow small water droplets to more easily coalesce by lowering the oil/water interfacial tension.

Crude oil that contains a high percent of particulate solids can complicate the desalting process. The particulate solids, by nature, would prefer to transfer to the water phase. However, much of the solids in a crude oil from a field exist in tight water-in-oil emulsions. That is, oil-wetted solids in high concentration in the crude may help form tight oil and water emulsions that are difficult to resolve. These tight emulsions are often referred to as “rag” and may exist as a layer between the separated oil and water phases. The rag layer inside the desalter vessel may grow to such an extent that some of it will be inadvertently discharged with the water phase. This is a problem for the waste water treatment plant since the rag layer still contains a high percentage of unresolved emulsified oil.

As mentioned, much of the solids encountered during crude oil desalting consists of iron, most commonly as particulate iron such as iron oxide, iron sulfide, etc. Other metals that are desirably removed include, but are not necessarily limited to, calcium, zinc, silicon, nickel, sodium, potassium, and the like, and typically a number of these metals are present. Some of the metals may be present in a soluble form. The metals may be present in inorganic or organic forms. In addition to complicating the desalter operation, iron and other metals are of particular concern to further downstream processing. This includes the coking operation since iron and other metals remaining in the processed hydrocarbon yields a lower grade of coke. Removing the metals from the crude oil early in the hydrocarbon processing stages is desired to eventually yield high quality coke as well as to limit corrosion and fouling processing problems.

Several treatment approaches have been made to reduce total metal levels and these all center on the removal of metals at the desalter unit. Normally, the desalter only removes water soluble inorganic salts such as sodium or potassium chlorides. Some crude oils contain water insoluble metal organic acid salts such as calcium naphthenante and iron naphthenate, which are soluble or dispersed as fine particulate matter in the oil but not in water.

U.S. Pat. No. 7,497,943 concerns the discovery that metals and/or amines may be removed or transferred from a hydrocarbon phase to a water phase in an emulsion breaking process by using a composition that contains water-soluble hydroxyacids. Suitable water-soluble hydroxyacids include, but are not necessarily limited to glycolic acid, gluconic acid, C2-C4 alpha-hydroxy acids, poly-hydroxy carboxylic acids, thioglycolic acid, chloroacetic acid, polymeric forms of the above hydroxyacids, poly-glycolic esters, glycolate ethers, and ammonium salt and alkali metal salts of these hydroxyacids, and mixtures thereof. The composition may also optionally include at least one mineral acid to reduce the pH of the desalter wash water. The method permits transfer of metals and/or amines into the aqueous phase with little or no hydrocarbon phase undercarry into the aqueous phase. The composition is particularly useful in treating crude oil emulsions, and in removing calcium and other metals therefrom.

However, typically in the '943 method the water-soluble hydroxyacids are dissolved in water and injected into the desalter wash water. These water-based products are subject to freezing in cold weather environments. In addition, sometimes these water-based products are unstable, that is the hydroxyacids may settle out over time.

It would thus be desirable to develop compositions and methods for introducing solid acids, such as solid organic acids or solid alpha-hydroxyacids into a hydrocarbon to be treated, such as crude oil, by using a composition that is stable and not as susceptible to freezing in cold environments.

SUMMARY

In one non-restrictive version, there is provided a method for introducing a solid acid into a hydrocarbon to be treated, where the method includes dispersing a solid acid into a hydrocarbon solvent to form a dispersion. The solid acid may include, but is not necessarily limited to, C2-C4 alpha-hydroxy acids, sulfamic acid, chloroacetic acid, thiomalic acid, and esters of, polymers of, amine salts of, alkali metal salts of, and ammonia salts of these acids, and mixtures thereof. The hydrocarbon solvent is different from the hydrocarbon to be treated. The method further involves introducing the dispersion into the hydrocarbon to be subsequently treated, e.g. a crude oil, for instance to transfer metals and/or amines from a hydrocarbon phase to an aqueous phase in a desalter.

Further in another non-limiting version there is provided a method of transferring metals and/or amines from a hydrocarbon phase to a water phase in a process. The method involves, in any order, adding a solid acid dispersion to a crude oil and adding wash water to a crude oil to create an emulsion, where the crude oil comprises metals and/or amines. The solid acid dispersion comprises a solid acid dispersed in a hydrocarbon solvent to form a dispersion, where the solid acid includes, but is not necessarily limited to, C2-C4 alpha-hydroxy acids, sulfamic acid, chloroacetic acid, thiomalic acid, and esters of, polymers of, amine salts of, alkali metal salts of, and ammonia salts of these acids, and mixtures thereof. The hydrocarbon solvent is different from the crude oil. The solid acid is present in the emulsion in an amount effective to transfer metals and/or amines from a hydrocarbon phase to a water phase. The method further involves resolving the emulsion into a hydrocarbon phase and an aqueous phase using electrostatic coalescence, where at least a portion of the metals and/or amines are transferred to the aqueous phase.

In another non-limiting embodiment there is provided a stable dispersion that includes a hydrocarbon solvent and a solid acid. Again, the solid acid includes, but is not necessarily limited to, C2-C4 alpha-hydroxy acids, sulfamic acid, chloroacetic acid, thiomalic acid, and esters of, polymers of, amine salts of, alkali metal salts of, and ammonia salts of these acids, and mixtures thereof.

There is provided in different non-restrictive embodiment a treated crude oil emulsion that includes crude oil, wash water and a dispersion. The dispersion involves a hydrocarbon solvent and a solid acid that includes, but is not necessarily limited to, C2-C4 alpha-hydroxy acids, sulfamic acid, chloroacetic acid, thiomalic acid, and esters of, polymers of, amine salts of, alkali metal salts of, and ammonia salts of these acids, and mixtures thereof. The hydrocarbon solvent is different from the crude oil.
Free Full Text Source: http://www.freepatentsonline.com/y2012/0043256.html