Coalescer element with two layers of electrical insulation

Abstract

A coalescer element for an electrostatic coalescer device comprises electrodes encapsulated in an electrical insulator, the electrical insulator comprising i) an inner layer of epoxy material and ii) an outer layer of hydrophobic material.

Description

[Technical Field]

[0001] The present invention relates to a coalescer element for an electrostatic coalescer device, an electrostatic coalescer device equipped with such a coalescer element, and a method for protecting the coalescer element of an electrostatic coalescer device from electrically induced erosion and / or partial discharges during operation of the electrostatic coalescer device. [Background technology]

[0002] Separation of water / oil or gas / water / oil mixtures is necessary in several technical fields, including oil and gas production facilities, oil refineries, chemical plants, gas plants, and supply / distribution facilities. For example, crude oil deposits are often mixed with water and / or must be accessed through water, so the recovered raw material is actually an emulsion of small water droplets in a continuous crude oil phase, which may also contain some gas. To maximize oil yield and ensure that the crude oil meets product quality specifications, the water-containing droplets must be separated from the oil phase. In principle, this separation could be carried out in a settling tank, which allows the oil and water phases to separate by gravity based on the difference in specific gravity between the two phases. However, this separation technique is very slow and does not result in efficient separation, especially when the water droplets dispersed in the oil phase are fine and small. Therefore, phase separation is typically achieved using a coalescer, which promotes coalescence of the dispersed droplet phase of the emulsion, i.e., an increase in dispersed droplet size caused by the coalescence of individual dispersed droplets, thus facilitating gravity-driven phase separation.

[0003] One type of coalescer is a mechanical coalescer, which uses a physical barrier to the emulsion flow to cause coalescence of the dispersed droplet phase of the emulsion. For example, the coalescer may be provided with plates angled relative to the horizontal, such that the water / oil mixture is directed along the horizontal plane, causing the dispersed aqueous phase, which is denser than the continuous oil phase, to coalesce on the plate and then drip down the slope of the plate towards the outlet.

[0004] Another effective type of coalescer is the electrostatic coalescer, which generates a high-voltage electric field within the emulsion. Because water, especially brine, is more electrically polarizable and conductive than oil, brine droplets dispersed in a continuous oil phase form attractive dipoles, causing the brine droplets to coalesce and accelerate gravity-driven phase separation. The electric field is generated using multiple high-voltage electrodes located within the electrostatic coalescer's vessel, with the electrodes immersed in the emulsion during operation. Particularly when separating water / oil mixtures containing a large amount of water relative to the gas and / or oil content, it is necessary to electrically insulate one of the high-voltage electrodes, which is typically achieved by encasing each electrode in an electrically insulating material, such as an electrically insulating organic compound such as a fluorinated polymer. The enclosed electrodes are also called coalescer elements. Without such electrical insulation, the local formation of a water continuous emulsion in a water / oil mixture would cause a short circuit between adjacent coalescer elements, especially when separating water / oil mixtures containing large amounts of water, such as 30% water by weight, up to the amount of water that would cause phase inversion of the water / oil mixture, i.e., an oil-in-water emulsion, resulting in the coalescer elements failing for a period of time and significantly reducing the efficiency of the electrostatic coalescer device.

[0005] However, even though electrical insulators protect the coalescer elements of an electrostatic coalescer from short circuits between adjacent coalescer elements, such electrostatic coalescer devices are not completely satisfactory. That is, in such electrostatic coalescer devices, water droplets or large contaminants, such as sand or crude oil sediments, can create conductive bridges in the direction normal to the electrode surfaces, connecting the electrically insulated surface of one electrode with the electrically insulated surface of the opposing electrode. The electrical insulators would prevent a large resistive current from flowing from one metal electrode to the other. However, in environments such as crude oil emulsions, saltwater droplets can aggregate on the electrically insulated surface, forming large water patches on the surface that contain many ions. In a high-voltage electric field, these saltwater droplets can be understood as reservoirs of charge, which can generate corona discharges that typically travel from one sealed electrode surface through the crude oil, emulsion, or gas and terminate at the water droplets on the opposing sealed electrode or at ground. The destructive effect of such corona discharges on the material sealing the electrodes depends on the energy released (i.e., ion content, voltage level, area of ​​the water droplets, etc.) and the amount of stored energy. When there is a potential difference between the electrodes, the smaller the area of ​​the water droplets, the less energy is released with each discharge. The current peak in a corona discharge, and therefore the energy release, is related to the conductivity of the saltwater droplets. As the voltage difference increases and the surface tension of the saltwater decreases, the likelihood of a corona discharge increases. This is because the lower the surface tension, the more likely the saltwater droplets are to generate sharp tips under the influence of the electric field, which in turn causes a large field amplification near the tips. The sensitivity of corona discharges due to surface tension mentioned above can be related to the electrodes of the coalescer element as follows: If the electrically insulating material on the sealed electrode is hydrophilic, the sealed electrode will be easily wetted by water, which means that when the electrode is exposed to water in emulsion, crude oil, or gas, large water-wetted areas (droplets) will form on the surface of the electrode.The larger the area of ​​such a water film / droplet, the smaller the surface energy stored in the water film / droplet, thus allowing the creation of a tip along the direction of the electric field normal to the surface.

[0006] Another problem with high-voltage electrical isolators is surface deposits. The electric field distribution between the end points of electrically isolated electrodes is not critical as long as the surface resistance remains high. This becomes a problem, however, when conductive contaminants are allowed to deposit on the surface of the electrical isolator. Water from a humid environment interacts with the accumulated deposits and forms conductive paths along the surface of the insulating material between the end points of the electrically isolated electrodes. This generates surface currents on the electrical isolator, which can cause short circuits along the surface (i.e., in a plane), including the sealed surface. Summary of the Invention [Problem to be solved by the invention]

[0007] In view of this, the object underlying the present invention is to provide a coalescer element for an electrostatic coalescer device comprising electrodes, the electrodes being enclosed with electrical insulators that protect against electrically induced erosion and partial discharges, in particular corona discharges, during operation of the electrostatic coalescer device, even when used for separating water / oil mixtures or gas / water / oil mixtures, and which coalescer element can nevertheless be produced easily and cost-effectively even with complex shapes, and which has a long service life for the coalescer element, in particular its electrical insulators, thereby extending the length of time before the coalescer element needs to be replaced with a new one, without reducing the efficiency of the electrostatic coalescer device. [Means for solving the problem]

[0008] According to the present invention, this object is achieved by providing a coalescer element for an electrostatic coalescer apparatus, comprising an electrode encapsulated in an electrical insulator, wherein the electrical insulator comprises i) an inner layer of an epoxy material and ii) an outer layer of a hydrophobic material.

[0009] Because the electrical insulators of the electrodes of the coalescer element comprise an inner layer of epoxy material and an outer layer of hydrophobic material, not only can the electrical insulator be easily and cost-effectively produced, even with complex shapes, but at the same time, the coalescer element obtained is completely and well protected from electrically induced erosion, partial discharges, and especially corona discharges in electrostatic coalescer devices during operation, even when used to separate water / oil or gas / water / oil mixtures. More specifically, the inner layer made of epoxy material is characterized, on the one hand, by very good formability, but also, on the other hand, by very high hardness and resistance to electrical discharges, while the outer layer made of hydrophobic material improves the wetting properties (i.e., non-wetting by water) of the underlying inner layer of epoxy material, thereby reliably avoiding the aforementioned problems, i.e., electrical discharges and surface arcing due to the condensation of saltwater droplets and surface contamination by conductive contaminants such as dust under a given electric field. Reducing the electrically induced erosion for a given electric field increases the useful life of the coalescer elements, particularly the electrical insulators of the coalescer elements, thereby extending the length of time before the coalescer elements need to be replaced with new ones without reducing the efficiency of the electrostatic coalescer device.

[0010] According to the present invention, the electrical insulator of the coalescer element comprises i) an inner layer of an epoxy material and ii) an outer layer of a hydrophobic material. According to the present invention, an epoxy material means one or more epoxy resins, i.e., any material containing one or more crosslinked or non-crosslinked polyepoxides. The polyepoxides or epoxy resins may be homopolymers or copolymers. In addition to the polyepoxides or epoxy resins, the epoxy material may also contain other compounds, such as one or more hardeners or one or more fillers.

[0011] The epoxy material forming the inner layer of the electrical insulator of the coalescer element may, for example, comprise one or more self-crosslinking epoxy resins, i.e., one or more epoxy resins that are each self-crosslinked as a result of, for example, the opening of epoxy groups in the epoxy resin molecules and the covalent bonding of the cleaved epoxy groups in different epoxy resin molecules. Such epoxy group cleavage or oxirane ring opening may be carried out in the presence of a very strong acid, such as hexafluorophosphoric acid. In this example, the epoxy material forming the inner layer of the electrical insulator of the coalescer element may be composed of one or more self-crosslinking epoxy resins, or may additionally include other compounds, such as one or more fillers.

[0012] According to an alternative embodiment of the present invention, the epoxy material of the inner layer of the electrical insulator of the coalescer element comprises one or more epoxy resins that are cured by a curing agent. In this embodiment, the epoxy material of the inner layer of the electrical insulator of the coalescer element may be comprised of one or more epoxy resins that are cured by a curing agent, or may additionally include other compounds, such as one or more fillers.

[0013] According to a particularly preferred alternative embodiment of the present invention, the epoxy material of the inner layer of the electrical insulator of the coalescer element is a composite material comprising one or more epoxy resins and fillers dispersed therein. Such composite materials are characterized, on the one hand, by very good moldability, but also, on the other hand, by very high hardness and resistance to electrical discharge. According to the present invention, a composite material refers to any kind of mixture of one or more epoxy resins and fillers, regardless of whether or not at least some physical or chemical bonding exists between the one or more epoxy resins and the fillers. Furthermore, fillers reduce shrinkage and allow the thermal expansion of the epoxy material to match that of the electrode material, thereby enabling high dielectric strength to be achieved. A composite material may, for example, be a physical mixture of one or more epoxy resins in which one or more fillers are dispersed without chemical bonding between the molecules of the one or more epoxy resins and the fillers. However, non-covalent bonds, such as ionic and hydrogen bonds, or even covalent bonds, may exist between single epoxy resin molecules and filler molecules, atoms, ions, etc.

[0014] The epoxy resin(s) included in the composite materials of the foregoing embodiments may be non-crosslinked, self-crosslinked, or cured with a curing agent.

[0015] The present invention is not particularly limited with respect to the chemical nature of the filler, but particularly good results are obtained when the filler contained in the composite material of the inner layer of the electrical insulator of the coalescer element is a mineral filler and / or a ceramic filler.

[0016] A further development of the concept of the present invention suggests that the filler is made of a material containing one or more compounds selected from the group consisting of zirconium dioxide, zinc oxide, titanium carbide, silicon carbide, silicon nitride, silicon dioxide, barium titanate, and any combination of two or more of the aforementioned compounds. The filler may in particular consist of any of the aforementioned compounds, i.e., it must not contain any other compounds in addition to the aforementioned compounds.

[0017] Particularly good results are obtained when the filler is silicon dioxide, surface-modified silicon dioxide, coated silicon dioxide, or silicon dioxide that is both surface-modified and coated.

[0018] In principle, the present invention is not particularly limited with respect to the shape and size of the filler contained in the composite material of the inner layer of the electrical insulator of the electrostatic coalescer device. The filler is preferably present in the form of powder, granules, small particles, etc. The filler has a diameter of 1 to 1,000 μm. 50 Particularly good results are obtained when the particle size of the filler in the inner layer of the electrical insulator of the coalescer element is 50 The particle size is more preferably 10 to 50 μm, and the d of the filler 50 The particle size is most preferably 15 to 35 μm.

[0019] A further development of the concept of the present invention suggests that the composite material of the inner layer of the electrical insulator of the coalescer element contains 30-60% by weight of epoxy material and 70-40% by weight of filler.

[0020] The present invention is not particularly limited with respect to the chemical nature of the one or more epoxy resins contained in the inner layer of the electrical insulator of the electrostatic coalescer device, regardless of whether the epoxy material forming the inner layer of the electrical insulator of the coalescer element comprises or consists of one or more self-crosslinking epoxy resins, one or more epoxy resins cured with a curing agent, or a composite material comprising one or more epoxy resins and a filler dispersed therein. The one or more epoxy resins contained in the inner layer of the electrical insulator of the coalescer element are preferably selected from the group consisting of glycidylamine-type epoxy resins, glycidyl ether-type epoxy resins, diglycidyl ether-type epoxy resins, epoxy resins having a naphthalene skeleton, biphenyl-type epoxy resins, dicyclopentadiene-type epoxy resins, phenol aralkyl-type epoxy resins, diphenylfluorene-type epoxy resins, and any combination of two or more of the foregoing compounds.

[0021] Particularly good results are obtained when the epoxy resin contained in the inner layer of the electrical insulator of the coalescer element is selected from the group consisting of tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidylaminocresol, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, resorcinol type epoxy resin, and any combination of two or more of the foregoing compounds.

[0022] As noted above, the one or more epoxy resins contained in or forming the inner layer of the electrical insulator of the coalescer element may be non-crosslinked, self-crosslinked, or cured with a curing agent. Preferably, the inner layer of the electrical insulator of the coalescer element comprises one or more epoxy resins cured with a curing agent. The curing agent is preferably a compound having one or more amino groups, one or more acid anhydride groups, one or more azide groups, one or more phenol groups, one or more alcohol groups, one or more thiol groups, or any combination of two or more of the foregoing groups.

[0023] More specifically, the curing agent is preferably selected from the group consisting of diamines, aminobenzoic acid esters, acid anhydrides, imidazole derivatives, aliphatic amines, tetramethylguanidine, thiourea-added amines, carboxylic acid amides, polymercaptans, and any combination of two or more of the aforementioned compounds.

[0024] Particularly good results are obtained when the curing agent is selected from the group consisting of dialkyltoluenediamine, dicyandiamide, diaminodiphenylmethane, diaminodiphenylsulfone, and any combination of two or more of the foregoing compounds.

[0025] According to a particularly highly preferred embodiment of the present invention, the inner layer of the electrical insulator sealing the electrodes of the coalescer element for an electrostatic coalescer device according to the present invention comprises, or preferably consists of, a composite material containing 30 to 60% by weight of an epoxy material and 70 to 40% by weight of a filler, wherein the epoxy material is a diglycidyl ether type epoxy resin cured with a curing agent, and wherein the filler is silicon dioxide, surface-modified silicon dioxide, coated silicon dioxide, or surface-modified or coated silicon dioxide.

[0026] A further development of the concept of the present invention suggests that the inner layer of the electrical insulator of the coalescer element of the present invention has a thickness of 1 to 40 mm.

[0027] According to the invention, the electrical insulator of the coalescer element comprises i) an inner layer of an epoxy material and ii) an outer layer of a hydrophobic material. Particularly good results are obtained if the outer layer, i.e., the hydrophobic material forming the outer layer, has a contact angle between air and salt water, measured according to ASTM D5946(2017) at 23°C, of ​​at least 90°, preferably at least 110°.

[0028] Suitable examples of hydrophobic materials that form the outer layer of the electrical insulator of the coalescer element of the present invention are those selected from the group consisting of polysilanes, fluoropolymers, acrylic resins, polyepoxides, polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polydimethylsiloxane, polysiloxane, polyesters, polyurethanes, hybrid polymers, and any combination of two or more of the foregoing compounds. Preferred examples of hydrophobic materials are fluoropolymers such as polytetrafluoroethylene, and hybrid polymers such as inorganic-organic hybrid polymers.

[0029] According to a particularly preferred embodiment of the present invention, the outer layer of the electrical insulator of the coalescer element is made of an inorganic-organic hybrid polymer. The inorganic-organic hybrid polymer preferably comprises i) glass units and / or ceramic units and ii) organic units. The term "organic units" in the context of an inorganic-organic hybrid polymer refers to a segment of a polymer chain having a substituted or unsubstituted hydrocarbon backbone. Of course, the hydrocarbon backbone may contain heteroatoms such as -O- in the case of polyether segments, -N- in the case of polyamine segments, and -S- in the case of polythiol segments. Furthermore, the term "hydrocarbon backbone" includes polymer segments of aromatic units bonded to one another and polymer segments of alicyclic units bonded to one another. The inorganic-organic hybrid polymer may be composed of multiple glass units and / or ceramic units connected to one another via organic units, with the organic units being chemically bonded to the glass units and / or ceramic units. By "chemically bonded," we mean covalently, ionicly, by hydrogen, or by van der Waals bonds. A covalent bond is preferred.

[0030] Furthermore, the inorganic-organic hybrid polymer preferably contains silicon dioxide units as glass units and / or ceramic units, and siloxane units and / or substituted or unsubstituted hydrocarbon-based polymer units as organic units. The inorganic-organic hybrid polymer preferably contains, for example, an organic portion other than polysiloxane, a polysiloxane portion, and optionally an inorganic portion, where the organic portion preferably contains multifunctional i) urethane groups and ii) ether (meth)acrylate groups or thioether (meth)acrylate groups, and the polysiloxane portion may be, for example, a compound represented by the chemical formula R n Si(OR) (4-n) where R is C 1-It is preferably formed of an alkoxysilane, which is an alkyl group such as a C4-alkyl group. The optional inorganic portion may include silicon dioxide units.

[0031] A further development of the concept of the present invention suggests that the outer layer of the electrical insulator of the coalescer element has a thickness of 10 to 1,000 μm.

[0032] The inner layer of electrical insulation of the coalescer element for the electrostatic coalescer device of the present invention is preferably directly connected to the outer layer of hydrophobic material, i.e., there is preferably no intermediate layer between the inner and outer layers. The inner and outer layers may or may not be connected by physical and / or chemical bonds. Although not preferred, it is possible to provide an intermediate layer between the inner and outer layers, for example, an intermediate layer that functions as an adhesion promoter between the inner and outer layers.

[0033] The electrostatic coalescer device, more particularly the coalescer element, may further comprise a transformer, the electrodes and the transformer being completely enclosed with electrical insulators. The transformer is preferably a high-voltage transformer that converts a low voltage from a power source into a high voltage. The transformer therefore comprises a primary low-voltage winding and a secondary high-voltage winding, the secondary high-voltage winding preferably being connected to the electrodes, while the low-voltage winding is preferably connected to a power source or to a frequency converter which is further connected to a power source.

[0034] The coalescer element according to the invention may be easily and economically produced using a molding step. The coalescer element may more particularly be produced by a method comprising the following steps: i) placing a metal electrode in a mold; ii) filling the mold with one or more epoxy resins, preferably comprising the aforementioned fillers dispersed in the one or more epoxy resins; iii) heating the mold, for example in an oven, to a temperature of 120-190°C, preferably 150-160°C, in order to cure the epoxy resin(s); iv) after the curing of the epoxy resin(s) is complete, removing the part from the mold and optionally trimming off excess epoxy resin so that the coalescer element has the desired shape; v) coating the coalescer element obtained in step iv) with a layer of hydrophobic material; and vi) curing the hydrophobic material, for example in an oven, at a temperature of 120-180°C, preferably 140-160°C, thereby bonding the hydrophobic material to the epoxy.

[0035] In a preferred embodiment in which the coalescer element comprises a transformer, the method of producing the coalescer element preferably comprises the following steps. i) preparing and connecting a transformer comprising a primary low-voltage winding and a secondary high-voltage winding and connecting the transformer to metal electrodes, after which the assembly so obtained is placed in a mold preferably containing wire guides, with the primary wires of the transformer preferably positioned to exit the mold; ii) filling the mold with one or more epoxy resins, preferably comprising the aforementioned fillers dispersed in the one or more epoxy resins; iii) heating the mold, for example in an oven, to a temperature of 120-190°C, preferably 150-160°C, in order to cure the epoxy resin(s); iv) after the curing of the epoxy resin(s) is complete, removing the part from the mold and optionally trimming off excess epoxy resin so that the coalescer element has the desired shape; v) coating the coalescer element obtained in step iv) with a layer of hydrophobic material; and vi) curing the hydrophobic material, for example in an oven, at a temperature of 120-180°C, preferably 140-160°C, thereby bonding the hydrophobic material to the epoxy.

[0036] A further aspect of the present invention is an electrostatic coalescer apparatus comprising: i) a vessel containing at least two of the aforementioned coalescer elements; and ii) an AC power supply that supplies AC voltage to the electrodes of at least two coalescer elements;

[0037] Preferably, the electrostatic coalescer apparatus further comprises one or more power sources and one or more frequency converters arranged outside the vessel, each of the coalescer elements being connected to a frequency converter, each frequency converter being connected to a power source, each coalescer element comprising an electrode and a transformer, the transformer being electrically connected to the frequency converter, the transformer being electrically connected to the electrodes of the coalescer element. Again, the transformer is preferably a high-voltage transformer that converts a low voltage from the power source to a high voltage, and comprising a primary low-voltage winding and a secondary high-voltage winding.

[0038] According to another aspect, the present invention relates to a method for protecting a coalescer element of an electrostatic coalescer device from electrically induced erosion and / or partial discharges, in particular corona discharges, during operation of the electrostatic coalescer device, the method comprising the following steps: a) providing an electrostatic coalescer device as described above; b) feeding a water / oil mixture or a gas / water / oil mixture into the vessel; and c) applying an AC voltage to the electrodes of at least two of the coalescer elements, thereby separating a water / oil mixture into an oil phase and a water phase, or separating a gas / water / oil mixture into a gas phase, an oil phase, and a water phase.

[0039] In step b), the water / oil or gas / water / oil mixture is preferably fed into the vessel so that all coalescer elements are immersed in the water / oil or gas / water / oil mixture.

[0040] The invention will now be described by way of example and not limitation with reference to the figures. [Brief explanation of the drawings]

[0041] [Figure 1] 1 is a schematic diagram of an electrostatic coalescer device including a coalescer element according to one embodiment of the present invention; [Figure 2] FIG. 2 is an electrical diagram of the electrostatic coalescer apparatus shown in FIG. 1, illustrating by example, viewed from the low voltage side. DETAILED DESCRIPTION OF THE INVENTION

[0042] The electrostatic coalescer apparatus 10 shown in Figure 1 comprises a container 12 containing a plurality of coalescer elements 14, each of which comprises an electrode sealed with an electrical insulator. The electrostatic coalescer apparatus 10 further comprises an AC power supply 16 and a frequency converter 18 external to the container 10, with each of the coalescer elements 14 connected to a frequency converter 18, which in turn is connected to the power supply 16. Low-voltage lines 20 run from each of the frequency converters 18 to the electrodes, connecting the electrodes to their respective frequency converters 18. The electrostatic coalescer apparatus 10 additionally comprises a controller (not shown), for example embodied in time-resolved measurement of the electrical impedance of each of the electrodes of the coalescer elements 14 during operation of the electrostatic coalescer apparatus 10. This allows the voltage of each electrode of each of the coalescer elements 14 to be individually controlled in a time-resolved manner.

[0043] FIG. 2 shows the electrical circuit diagram of the electrostatic coalescer apparatus shown in FIG. 1, viewed from the low-voltage side. The electrostatic coalescer apparatus includes a voltage source on the left and a high-voltage coalescer element in the center and right, which includes a transformer and electrodes, both of which are enclosed in electrical insulation. The transformer has an inductance L, and the electrodes have variable resistance R and variable capacitance C. The capacitor and resistor change over time, while the inductor is constant. The inductor represents the inductance of the transformer and is therefore constant over time. The capacitor and resistor will change during operation of the electrostatic coalescer apparatus. The capacitor and resistor will depend, among other things, on the amount of water in the water-in-oil emulsion, the temperature of the emulsion, and the rate of water dropout from the emulsion. All of this time variation will have a time scale of several seconds to several minutes.

[0044] The invention will now be described by way of illustrative, but non-limiting, examples.

[0045] Examples A transformer with a primary low-voltage winding and a secondary high-voltage winding was connected at its high-voltage side to a stainless steel electrode 1 meter long, 4 mm wide, and 50 cm high. The resulting assembly was then placed in a mold containing wire guides. The primary wire of the transformer was positioned to exit the mold, after which the mold was filled with a mixture of 50% by weight of glycidyl ether-type epoxy resin and 50% by weight of zinc oxide filler. The mold was then placed in a heating furnace and heated to approximately 160°C to cure the epoxy resin. The mold was then removed from the furnace, and the coalescer element was removed from the mold. Excess epoxy resin was trimmed off to give the coalescer element the desired shape. The coalescer element was then coated with a layer of FEP (perfluoro(ethylene-propylene)).

[0046] A number of the coalescer elements were arranged in rows within a container and connected to a frequency converter and AC power source to form an electrostatic coalescer apparatus as shown schematically in FIG.

[0047] Thereafter, the electrostatic coalescer was operated by supplying a water / oil mixture into the electrostatic coalescer and operating it at a temperature of 90°C and a voltage of 10 kV for 365 days.

[0048] The coalescer elements were then inspected. No cracks or other damage were found in the coalescer elements. There was also no sign of electrical breakdown in any of the coalescer elements.

[0049] Additionally, five of the coalescer elements were subjected to a methane decompression test. More specifically, the coalescer elements were immersed in methane in a tank at a temperature of 120°C and a pressure of 7.5 MPa (75 bar) for 60 days. After that, heating was stopped and the tank pressure was reduced. The plates were visually inspected weekly for 15 weeks. No signs of damage were found.

[0050] Comparative Example Prior art coalescer elements were fabricated using 3 mm thick Teflon® as the sole insulating and coating material. More specifically, two separate high-voltage transformers and Teflon-insulated electrodes were fabricated for each coalescer element. The electrodes were connected to the high-voltage side of the transformer through high-voltage bushings. Due to the required Teflon thickness and high coating temperatures, the only viable option was to use an oil-filled transformer housing. The transformer was secured within a stainless steel housing, and the housing, under vacuum, was filled with oil to prevent voids and short circuits in the transformer. The electrodes were made of the same stainless steel and had the same dimensions as the electrodes used in the previous examples. However, unlike the examples, the electrodes in the comparative example were coated with a single layer of Teflon®. The transformer connector and the Teflon-coated metal electrodes were then connected to form a single coalescer element.

[0051] Thereafter, a number of these coalescer elements were arranged in rows in a container, and the container was connected to a frequency converter and an AC power source in the same manner as in the previous example. The water / oil mixture was supplied to the device, and the device was operated at a temperature of 90°C and a voltage of 6 kV.

[0052] The combination of high temperature and high voltage accelerated the rate at which water treeing in the insulators progressed. The water treeing eventually caused a short circuit from the internal electrode to a grounded component inside the vessel. The insulators failed after two months.

[0053] Additionally, the coalescer element was subjected to a similar evacuation test as in the previous example, and during the subsequent evacuation of the vessel, some spalling of the insulation was observed. [Explanation of symbols]

[0054] 10 Electrostatic coalescer device 12 containers 14 Coalescer element 16 AC power supply 18 Frequency Converter 20 Low voltage lines

Claims

1. 1. A coalescer element (14) for an electrostatic coalescer device (10) comprising an electrode encapsulated in an electrical insulator, the electrical insulator comprising: i) an inner layer of an epoxy material; and ii) an outer layer of a hydrophobic material.

2. 2. The coalescer element (14) of claim 1, wherein the epoxy material comprises or consists of one or more self-crosslinking epoxy resins.

3. 3. The coalescer element (14) of claim 1 or 2, wherein the epoxy material comprises a composite material comprising one or more epoxy resins and a filler dispersed in the one or more epoxy resins, or consists of a composite material comprising one or more epoxy resins and a filler dispersed in the one or more epoxy resins, and preferably the filler is made of a material comprising or consisting of a compound selected from the group consisting of zirconium dioxide, zinc oxide, titanium carbide, silicon carbide, silicon nitride, silicon dioxide, barium titanate, and any combination of two or more of the foregoing compounds.

4. The coalescer element (14) of claim 3, wherein the composite material comprises 30 to 60 weight percent epoxy material and 70 to 40 weight percent filler.

5. 5. The coalescer element (14) according to claim 1, wherein the one or more epoxy resins comprise an epoxy resin selected from the group consisting of a glycidylamine-type epoxy resin, a glycidyl ether-type epoxy resin, a diglycidyl ether-type epoxy resin, an epoxy resin having a naphthalene skeleton, a biphenyl-type epoxy resin, a dicyclopentadiene-type epoxy resin, a phenol aralkyl-type epoxy resin, a diphenylfluorene-type epoxy resin, and any combination of two or more of the compounds.

6. 6. The coalescer element (14) of any one of claims 1 to 5, wherein the epoxy material comprises an epoxy resin cured by a curing agent which is preferably a compound having one or more amino groups, one or more acid anhydride groups, one or more azide groups, one or more phenolic groups, one or more alcohol groups, one or more thiol groups, or any combination of one or more of two or more of said groups, and wherein the curing agent is preferably selected from the group consisting of diamines, aminobenzoic acid esters, acid anhydrides, imidazole derivatives, aliphatic amines, tetramethylguanidine, thiourea-added amines, carboxylic acid amides, polymercaptans, and any combination of two or more of said compounds.

7. The coalescer element (14) of any one of claims 1 to 6, wherein the inner layer has a thickness of 1 to 40 mm.

8. 8. The coalescer element (14) of any one of claims 1 to 7, wherein the outer layer has a contact angle, measured between air and salt water at 23°C, of ​​at least 90°, preferably at least 120°, more preferably at least 150°.

9. 9. The coalescer element (14) of any one of claims 1 to 8, wherein the outer layer is made of a hydrophobic material selected from the group consisting of polysilanes, fluoropolymers, acrylics, polyepoxides, polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polydimethylsiloxanes, polysiloxanes, polyesters, polyurethanes, hybrid polymers, and any combination of two or more of the foregoing compounds.

10. The coalescer element (14) according to claim 9, wherein said outer layer is made of an inorganic-organic hybrid polymer, preferably comprising glass and / or ceramic units and organic units.

11. The inorganic-organic hybrid polymer comprises an organic portion separate from the polysiloxane portion, a polysiloxane portion, and optionally also an inorganic portion, the organic portion preferably comprising i) urethane groups, and ii) ether (meth)acrylate groups or thioether (meth)acrylate groups, which are preferably polyfunctional, and the polysiloxane portion preferably has a structure such as that of the formula R ｎ Si(OR) （４－ｎ） where R is C １－ C ４ The coalescer element (14) of claim 10, which is formed from an alkoxysilane, the alkyl group being an alkyl group.

12. The coalescer element (14) according to any one of claims 1 to 11, wherein the outer layer has a thickness of 10 to 1,000 µm.

13. 13. The coalescer element (14) of any one of claims 1 to 12, further comprising a transformer, the electrodes and the transformer being completely enclosed by the electrical insulator.

14. A method for producing a coalescer element (14) according to any one of claims 1 to 13, said method comprising: i) placing a metal electrode in a mold; ii) filling the mold with one or more epoxy resins, preferably including a filler dispersed therein; iii) heating the mold to a temperature of 120-190°C, preferably 150-160°C, to cure the one or more epoxy resins; iv) after said curing of said one or more epoxy resins is complete, removing the part from the mold and optionally trimming excess epoxy resin so that the coalescer element has a desired shape; v) coating the coalescer element obtained in step iv) with a layer of hydrophobic material; vi) curing the hydrophobic material at a temperature of 120-180°C, preferably 140-160°C, thereby bonding the hydrophobic material to the epoxy; A method comprising:

15. 15. The method according to claim 14, wherein step i) comprises providing a transformer with a primary low-voltage winding and a secondary high-voltage winding and connecting said transformer to metal electrodes, after which the assembly so obtained is placed in a mold preferably including wire guides, and the primary wire of said transformer is preferably arranged to exit said mold.

16. i) a container (12) containing at least two coalescer elements (14) according to any one of claims 1 to 13; ii) an AC power source (16) for supplying an AC voltage to the electrodes of the at least two coalescer elements (14); Electrostatic coalescer device (10) comprising:

17. 17. The electrostatic coalescer apparatus (10) of claim 16, further comprising one or more power sources (16) and one or more frequency converters (18) disposed outside the vessel (12), each of the coalescer elements (14) being connected to a frequency converter (18), each frequency converter (18) being connected to a power source (16), each coalescer element (14) comprising an electrode and a transformer, the transformer being electrically connected to the frequency converter (18), and the transformer being electrically connected to the electrode of the coalescer element (14).

18. 1. A method for protecting a coalescer element (14) of an electrostatic coalescer device (10) from electrically induced erosion and / or partial discharge during operation of said electrostatic coalescer device (10), said method comprising: a) providing an electrostatic coalescer device (10) according to claim 16 or 17; b) feeding a water / oil mixture or a gas / water / oil mixture into said vessel (12); c) applying an AC voltage to the electrodes of the at least two coalescer elements (14), thereby separating the water / oil mixture into an oil phase and a water phase, or separating the gas / water / oil mixture into a gas phase, an oil phase, and a water phase; A method comprising:

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