Method for reducing coke formation in heavy oil upgrading by using supercritical water

Abstract

A method for reducing coke and coke precursor formation in supercritical water may include generating a supercritical water stream by heating and pressurizing feed water, mixing the supercritical water stream with the heated and pressurized feed oil in a mixing device to produce a combined feed stream, feeding the combined feed stream to a supercritical water reactor to produce an upgraded product, and separating the upgraded product from the supercritical water reactor. In one embodiment, the method comprises the steps of providing a supercritical reactor, producing a cooled, reduced-pressure upgraded product, separating the cooled, reduced-pressure product in a fractionator into a liquid hydrocarbon stream and a hydrocarbon vapor stream, condensing the hydrocarbon vapor stream with a cooling device to produce a light hydrocarbon-water mixture and a separate gaseous product, recycling the light hydrocarbon mixture to mix it with feed water upstream of the supercritical reactor.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application Serial No. 18 / 194,974, filed April 3, 2023, the entire disclosure of which is hereby incorporated by reference. Technical Field

[0003] The embodiments of this disclosure generally relate to supercritical water methods for upgrading heavy oil, and particularly to preventing the formation of coke and coke precursors during the upgrading process. Background Technology

[0004] Traditionally, the upgrading of heavy oils has been carried out through hydrogen addition and carbon rejection. In hydrogenation, heavy oil is fed into one or more catalytic reactors in the presence of an external hydrogen supply for cracking, isomerization, alkylation, hydrogenation, desulfurization, denitrification, deoxygenation, and demetallization. Typically, products from the hydrogenation pathway can be sold as fuel or other suitable petroleum products for customer use. However, the hydrogenation pathway requires significant capital and operating costs. In most refineries, the large consumption of hydrogen necessitates additional hydrogen production units in addition to catalytic reforming units (where paraffinic naphtha undergoes aromatization to produce aromatics and hydrogen). Furthermore, processes operating under the hydrogenation pathway have stricter feedstock limitations. For example, some fixed-bed hydrodesulfurization processes cannot accept high-asphaltite feedstocks due to short catalyst lifetimes and rapid pressure increases in the reactor.

[0005] In contrast, decarbonization processes (such as conventional coking) ideally do not require catalyst and hydrogen supplies, although the products from these processes often fall short of market specifications. Supercritical water is a decarbonization pathway that combines the advantages of external hydrogen supply, including reduced complexity and operating costs, while minimizing the drawbacks of traditional decarbonization methods. Using supercritical water allows for the uniform transfer of heat to hydrocarbons in crude oil during thermal cracking. Supercritical water also reduces coke formation and increases liquid product yields by diluting hydrocarbons in crude oil and forming supercritical water molecular cages around them to inhibit free radical reactions. The surrounding of radical species by supercritical water, also known as the cage effect, results in superior product yields compared to conventional coking processes.

[0006] Despite the numerous advantages of supercritical water, the process still faces unresolved technical challenges, such as high energy requirements and high equipment costs. Furthermore, due to the limited availability of hydrogen and the demanding reaction conditions, supercritical water upgrading methods may adversely form reactor clogging materials, such as solid coke.

[0007] In crude oil, light hydrocarbons and asphaltenes have high solubility in supercritical water (ScW) and therefore dissolve rapidly upon contact. Meanwhile, heavy hydrocarbons and asphaltenes are less soluble and remain in the oil phase. Polycyclic aromatic hydrocarbons, such as asphaltenes (precursors to solid coke), can be converted into solid coke upon exposure to high temperatures (e.g., supercritical water temperatures or temperatures above 400°C). This coke formation adversely increases clogging, thus impairing supercritical water upgrading processes. Therefore, improved supercritical water processes and systems are needed to reduce coke formation. Summary of the Invention

[0008] This disclosure addresses the need to reduce coke formation by enhancing the solubility and dispersion of polycyclic aromatic hydrocarbons (PAHs) in supercritical water, thereby reducing coke formation. Specifically, this embodiment produces light hydrocarbon products to enhance the solubility of PAHs (such as asphaltene), thereby suppressing coke formation without sacrificing process performance. Furthermore, this disclosure recycles the light products composed of light hydrocarbons and water. See also... Figure 1 Asphalt solubles and asphaltenes exhibit different coking properties. Asphalt solubles have high solubility in supercritical water, and the time required for them to form coke is longer than that of asphaltenes. This time required for coke formation is called the induction period. When asphaltenes are mixed with asphalt solubles, the induction period of the asphaltenes is prolonged. Therefore, maximizing the time for asphaltenes and asphalt solubles to separate into separate phases limits the time asphaltenes are exposed to high temperatures, thus limiting coke formation. Unbound from theoretical constraints, by reusing a mixture of recycled light hydrocarbons and water in the ScW reactor, it was unexpectedly found that these recycled liquid hydrocarbons delayed the phase separation of asphaltenes and asphalt solubles, thereby prolonging the induction period for coke formation. This increases the residence time in the ScW, thereby improving upgrading performance, i.e., increasing conversion and desulfurization rates.

[0009] According to one or more aspects of this disclosure, a method for reducing coke or coke precursors in supercritical water is provided. The method may include generating a supercritical water stream by heating and pressurizing feed water. The method may further include mixing the supercritical water stream with pressurized and heated feed oil in a mixing unit to generate a combined feed stream. The method may further include feeding the combined stream into a supercritical water (ScW) reactor to generate an upgraded product, wherein the supercritical water reactor operates at a temperature above the critical temperature of water and a pressure above the critical pressure of water. The method may further include generating a cooled and depressurized upgraded product by cooling and depressurizing the upgraded product, separating the cooled and depressurized upgraded product into a liquid hydrocarbon stream and a hydrocarbon vapor stream in a fractionator, condensing the hydrocarbon vapor stream with a cooling unit to generate a light hydrocarbon-water mixture and a separate gaseous product, and recycling the light hydrocarbon-water mixture to mix it with feed water upstream of the supercritical water reactor. Attached Figure Description

[0010] The following detailed description of specific embodiments of this disclosure can be best understood when read in conjunction with the accompanying drawings, in which:

[0011] Figure 1 This diagram illustrates the formation of coke from asphaltene at high temperatures, and compares it with the coexistence of asphaltene and asphalt-soluble substances (heptane-soluble fraction).

[0012] Figure 2 This is a schematic diagram of a method for reducing coke formation in heavy oil upgrading using supercritical water, according to one or more embodiments of this disclosure.

[0013] Figure 3 is a schematic diagram of the traditional supercritical water upgrading method. Detailed Implementation

[0014] definition

[0015] As used throughout this disclosure, "crude oil" means full-range crude oil, distilled crude oil, residue oil, top-extracted crude oil, product streams from refineries, product streams from steam cracking processes, liquefied coal, liquid products recovered from oil or tar sands, bitumen, oil shale, asphaltenes, biomass hydrocarbons, liquid products from gas-to-liquid (GTL) processes, liquid products from chemical recycling of waste plastics / municipal waste, and other similar petroleum-based oils.

[0016] As used in this disclosure, "effluent" refers to a stream delivered from a reactor, reaction zone, or separation unit after a specific reaction or separation. Typically, the composition of the effluent differs from the stream entering the separation unit, reactor, or reaction zone. It should be understood that when effluent is delivered to another system unit, only a portion of that system stream may be fed in. For example, a wake may carry away a portion of the effluent, meaning that only a portion of the effluent may enter the downstream system unit.

[0017] As used throughout this disclosure, "heavy fraction" refers to the portion of a compound in crude oil that has a boiling point equal to or higher than 650°F when measured in true boiling point (TBP). As a non-limiting example, crude oil contains 10% (by weight) of a heavy fraction when 10% (by weight) of the compound has a boiling point equal to or higher than 650°F (measured in true boiling point).

[0018] As used throughout this disclosure, “supercritical water” or “SCW” refers to water at a temperature above the critical temperature and a pressure above the critical pressure of water.

[0019] As used in this article, "asphalt solubles" refers to the asphalt soluble fraction, which is soluble in alkanes such as n-heptane and n-pentane.

[0020] As used in this article, "asphaltite" refers to asphalt fractions that are insoluble in alkanes, such as n-heptane and n-pentane.

[0021] As used herein, a "reactor" refers to a vessel in which one or more chemical reactions can occur between one or more reactants, optionally in the presence of one or more catalysts. For example, a reactor may include a batch reactor or a tubular reactor configured to operate as a batch reactor, a continuous stirred tank reactor (CSTR), or a plug flow reactor. Exemplary reactors include packed bed reactors (such as fixed bed reactors) and fluidized bed reactors. One or more "reaction zones" may be provided within the reactor. As used herein, a "reaction zone" refers to the volume in the reactor where a particular reaction occurs. For example, a packed bed reactor having multiple catalyst beds may have multiple reaction zones, where each reaction zone is defined by the volume of each catalyst bed.

[0022] As used herein, “residence time” refers to the length of time required for the feed stream to enter and subsequently leave the processing unit, reactor, and separator described herein.

[0023] As used herein, a “separation unit” or “separator” means any separation device that at least partially separates one or more chemical substances mixed in a process stream from each other. For example, a separation unit may selectively separate materials of different chemical types, phases, or sizes to form one or more chemical fractions. Examples of separation units include, but are not limited to, distillation columns, distillation towers, flash tanks, separation tanks, knock-out pots, centrifuges, cyclone separators, filters, traps, scrubbers, expansion devices, membranes, solvent extraction devices, etc. It should be understood that the separation processes described in this disclosure may not completely separate all of one chemical component from all of another chemical component. It should be understood that the separation processes described in this disclosure “at least partially” separate different chemical components from each other, and even if not explicitly stated, separation may include only partial separation. As used herein, one or more chemical components may be “separated” from a process stream to form a new process stream. Typically, a process stream may enter a separation unit and be divided or separated into two or more process streams of desired composition. Furthermore, in some separation processes, "low-boiling fractions" (sometimes called "light fractions" or "light fraction streams") and "high-boiling fractions" (sometimes called "heavy fractions," "heavy hydrocarbon fractions," or "heavy hydrocarbon fraction streams") may exit the separation unit. On average, the lower-boiling fraction stream contains contents with a lower boiling point than the higher-boiling fraction stream. Other streams may fall between the lower and higher boiling points, such as "intermediate-boiling fractions."

[0024] refer to Figure 2 This paper demonstrates a system and method for suppressing coke formation during heavy oil upgrading using supercritical water. The method involves generating a supercritical water flow 50 by heating and pressurizing feed water 7. As shown, feed water 7 is fed to a mixer 5, such as a mixer tee, which combines feed water 7 and recirculated feed 280 (see below) into a combined feed water 40.

[0025] Feed water 7 may include demineralized water with a conductivity of less than 1 microsiemens (μS) / cm, preferably less than 0.5 μS / cm, more preferably 0.1 μS / cm. The sodium content in the feed water may be less than 5 μg / L, preferably 1 μg / L; the chlorine content may be less than 5 μg / L, preferably 1 μg / L; and the silica content may be less than 3 μg / L. Recycled feed 280 and combined feed 40 may have the same or similar composition.

[0026] Various temperatures are considered suitable for feed water 7. For example, it could be ambient temperature or a higher temperature. Furthermore, various pressures are considered for feed water 7. In one or more embodiments, the pressure of feed water 7 can be from 1 psig to 100 psig or from 1 psig to 20 psig. Recirculated feed 280 and combined feed 40 can have the same or similar processing conditions.

[0027] Then, a pressurizing device 10 (such as a compressor) can be used to pressurize the combined feed water 40 to produce pressurized feed water 45. The pressure of the pressurized feed water 45 can be at least 3200 psig, 3200 psig to 5200 psig, 3200 psig to 4200 psig, or 3500 psig to 4500 psig.

[0028] Next, the pressurized feed water 45 is heated in a heating device 22 (e.g., heat exchanger 22) to obtain supercritical water 50. The pressure of the supercritical water 50 may be at least 3200 psig, 3200 psig to 5200 psig, 3200 psig to 4200 psig, or 3500 psig to 4500 psig. The temperature of the supercritical water 50 may be at least 374°C, 374°C to 600°C, or 400°C to 500°C.

[0029] Refer again Figure 2 The supercritical water flow 50 is mixed with pressurized and heated feed oil 70 in the mixing device 25 to generate a combined feed flow 80.

[0030] Feed oil 3 may contain any hydrocarbons derived from: petroleum, coal, coal slurry, biomass, plastics, full-range crude oil, distilled crude oil, residue oil, top-extracted crude oil, product streams from refineries, product streams from steam cracking processes, liquefied coal, liquid products recovered from oil or tar sands, bitumen, oil shale, asphaltenes, biomass hydrocarbons, and liquid hydrocarbons from plastic pyrolysis. The feed oil may have a boiling point above 200°C or above 316°C. In a particular embodiment, the feed oil may contain more than 4% by weight (wt%) of sulfur, at least 2500 ppm of nitrogen, and at least 15% by weight of Conradson carbon content.

[0031] Various temperatures are considered suitable for feed oil 3. For example, it can be at ambient temperature or higher. In certain embodiments, the temperature of feed oil 3 can be 25°C to 300°C, 50°C to 250°C, or 100°C to 200°C. Furthermore, various pressures are considered for feed oil 3. In one or more embodiments, the pressure of feed oil 3 can be 1 psig to 100 psig or 1 psig to 20 psig.

[0032] Subsequently, a booster device 15 (such as a compressor) can be used to pressurize the feed oil 3 to generate pressurized feed oil 65. The pressure of the pressurized feed oil 65 can be at least 3200 psig, 3200 psig to 5200 psig, 3200 psig to 4200 psig, or 3500 psig to 4500 psig.

[0033] Next, the pressurized feed oil 65 can be heated in the heating device 20 to obtain pressurized heated feed oil 70. The heating device 22 can be selected from an electric heater, a gas heater, a fuel oil heater, a heat exchanger, or a combination thereof. The pressure of the pressurized heated feed oil 70 can be at least 3200 psig, 3200 psig to 5200 psig, 3200 psig to 4200 psig, or 3500 psig to 4500 psig. The temperature of the pressurized heated feed oil 70 can be at least 100°C, 100°C to 300°C, 100°C to 250°C, or 150°C to 200°C.

[0034] Refer again Figure 2 Supercritical water flow 50 and pressurized heated feed oil 70 are mixed in mixing device 25 to generate combined feed flow 80. Mixing device 25 can be selected from: static mixer, online mixer, impeller-embedded mixer, CSTR mixer, and combinations thereof. Although this embodiment describes the mixing of supercritical water flow 50 and pressurized heated feed oil 70 in mixing device 25 upstream of supercritical water reactor 30, other options are also considered, such as mixing supercritical water flow 50 and pressurized heated feed oil 70 in supercritical water reactor 30.

[0035] The pressure of the combined feed stream 80 can be at least 3200 psig, 3200 psig to 5200 psig, 3200 psig to 4200 psig, or 3500 psig to 4500 psig. The temperature of the combined feed stream 80 can be at least 374°C, 374°C to 500°C, or 374°C to 425°C.

[0036] like Figure 2 As shown, the combined feed stream 80 is fed into a supercritical water (ScW) reactor 30 to produce upgraded product 100. In some embodiments, the mixed stream may be preheated by a heater (not shown) before passing through the ScW reactor. The ScW reactor is selected from tubular, batch, CSTR, or combinations thereof. A tubular reactor is preferred. The ScW reactor may have external or internal heaters to control the fluid temperature at a preset level. The heaters may be selected from electric heaters, flame heaters, and heat exchangers.

[0037] The residence time in the reactor can range from 0.1 minutes to 120 minutes, or from 1 minute to 60 minutes. The residence time is calculated by assuming the internal fluid is 100% water (for density calculations).

[0038] The upgraded product 100 can then be cooled using a cooling device 110 (such as a heat exchanger) to produce a cooled upgraded product 120. The cooled upgraded product 120 may have a temperature below 374°C, between 100°C and 350°C, between 200°C and 300°C, or between 225°C and 275°C.

[0039] The cooled upgraded product 120 can then be depressurized using a pressure-reducing device 130 (e.g., a valve) to obtain a cooled and depressurized upgraded product 150. The cooled and depressurized upgraded product 150 may have a temperature below 374°C, between 100°C and 350°C, between 150°C and 300°C, or between 150°C and 200°C. The cooled and depressurized upgraded product 150 may have a pressure below 3200 psig, between 10 psig and 650 psig, or between 150 psig and 300 psig.

[0040] Refer again Figure 2 The upgraded product 150, after cooling and depressurization, can then be separated in fractionator 160 into a liquid hydrocarbon stream 400 and a hydrocarbon vapor stream 200. Fractionator 160 may include various suitable devices, such as a flash tank. The flash tank may have internal structures such as mesh pads, diffusers, valves, or other components well known to those skilled in the art. The flash tank may have external or internal heaters or coolers to control the temperature of the internal fluids, thereby achieving superheating or subcooling.

[0041] The liquid hydrocarbon stream 400 and the hydrocarbon vapor stream 200 may each have a pressure of less than 3200 psig, 10 psig to 650 psig, or 150 psig to 300 psig. Furthermore, the liquid hydrocarbon stream 400 and the hydrocarbon vapor stream 200 may each have a temperature of less than 374°C, 100°C to 350°C, or 150°C to 300°C.

[0042] In one or more embodiments, the hydrocarbon vapor stream from fractionator 160 may be fed to cooling device 210 (e.g., a condenser) to produce a light hydrocarbon-water mixture 280 and a separate gaseous product 260. The light hydrocarbon-water mixture 280 may then be recycled to mix with feed water 7 upstream of supercritical water reactor 30. The gaseous product 260 may contain one or more of H2, CO, CO2, H2S, NH3, H2O, and Cl-C5 compounds.

[0043] The light hydrocarbon-water mixture 280 may be primarily water, or 95% to 99.5% by weight of water. Furthermore, the light hydrocarbon-water mixture 280 may contain 0.5% to 5% by weight of hydrocarbons. The hydrocarbons in the light hydrocarbon-water mixture 280 include paraffins, alkenes, cycloalkanes, and aromatics. In embodiments, based on the weight of the hydrocarbons, the hydrocarbons may include 30% to 60% by weight, 30% to 45% by weight, or 30% to 40% by weight of paraffins. In embodiments, based on the weight of the hydrocarbons, the hydrocarbons may contain 10% to 70% by weight, 20% to 60% by weight, or 40% to 50% by weight of olefins. Furthermore, based on the weight of the hydrocarbons, the hydrocarbons may contain 0% to 10% by weight, 2% to 8% by weight, or 4% to 6% by weight of cycloalkanes. Furthermore, based on the weight of the hydrocarbon, the hydrocarbon may contain 5% to 60% by weight, 5% to 40% by weight, 10% to 30% by weight, or 15% to 25% by weight of aromatics. Without being theoretically limited, aromatics contribute to the dispersion and dissolution of heavy hydrocarbons and asphaltenes in supercritical water.

[0044] In this embodiment, most of the hydrocarbons can be C2-C8 hydrocarbons. Without being theoretically limited, the 90% distillation temperature (T90) of the hydrocarbons in the light hydrocarbon-water mixture 280 is below 450°C or below 380°C to ensure immediate dissolution of the hydrocarbons in supercritical water. Furthermore, the light hydrocarbon-water mixture 280 is substantially free of inorganic impurities and is suitable for use as feed water. As used herein, substantially free of impurities means less than 0.1% by weight, less than 0.01% by weight, or less than 0.001% by weight.

[0045] In this embodiment, under standard ambient temperature and pressure (SATP), the volume ratio of feed water 7 to feed oil 3 in the ScW reactor can range from 1 / 0.1 to 1 / 10, or 1 / 0.1 to 1 / 2. Furthermore, under SATP, the ratio of light hydrocarbon-water mixture 280 (i.e., recirculated) to feed water 7 can range from 1 / 0.5 to 1 / 20, or 1 / 2 to 1 / 5. Without theoretical limitations, the mixture of feed water 7 and light hydrocarbon-water mixture 280 should contain more fresh feed water than recirculated water; however, the recirculated water should be in sufficient quantity to have a “solvent” effect on the hydrocarbons in the recirculated water.

[0046] Refer again Figure 2 The liquid flow 400 can undergo gas-water-oil 410 to obtain gas phase product 420, oil phase product 430 and water product 440.

[0047] In such Figure 2In the alternative embodiment shown, the hydrocarbon vapor stream 200 may be cooled by the cooling device 210 before being fed into the splitter 225, and then split into two streams 230 and 240 by the splitter 225. One of the split streams 240 may also be sent to the gas-water-oil separator 410 for further processing.

[0048] Example

[0049] The following examples will further illustrate various implementations of the methods and systems for reducing coke formation. These examples are illustrative in nature and should not be construed as limiting the subject matter of this disclosure.

[0050] Illustrative Examples

[0051] Figure 2 The illustrative embodiments shown were simulated using Aspen HYSYS software. The ScW reactor 30 is a tubular reactor with an inner diameter of 25.84 inches and a length of 180.428 ft. The reactor is vertical (30 ft. upward flow, then 30 ft. downward flow). The residence time of the fluid in the reactor is 1.5 minutes. The flow process conditions for the illustrative embodiment are shown in Table 1, and the feed and oil product hydrocarbon properties are shown in Table 2. Table 3 provides the composition of the recirculated flow (liquid hydrocarbon-water mixture 280).

[0052] Table 1: Flow characteristics of illustrative examples

[0053]

[0054] Table 2: Hydrocarbon properties of feed oil and product in illustrative examples

[0055]

[0056] Table 3: Components of Liquid Hydrocarbon-Water Mixtures

[0057]

[0058] Comparative Example

[0059] The same feedstock was introduced into the comparative method shown in Figure 3; however, as indicated, this method did not include a recirculation stream. The operating conditions for this comparative method are provided in Table 4, and the properties of the feed oil and product hydrocarbons are shown in Table 5. The ScW reactors were of identical dimensions.

[0060] Table 4: Operating conditions for the comparative example

[0061]

[0062]

[0063] Table 5: Hydrocarbon properties of feed oil and product in comparative examples

[0064]

[0065] In the comparative example, the residence time was approximately 2.7 minutes, less than half the 5.7-minute residence time of the illustrative example. By recycling hydrocarbons, the illustrative example was able to operate at longer residence times without facing blockages due to coke formation. Due to the risk of coking, the comparative example needed to minimize its residence time. In contrast, the longer residence time of the illustrative example resulted in a significantly higher desulfurization effect, specifically achieving a final yield of 1.2 wt%, compared to 3.9 wt% in the comparative example. Furthermore, the illustrative example also showed a much greater reduction in nitrogen content and Comstock carbon residue compared to the comparative example.

[0066] This application discloses several technical aspects. A first aspect relates to a method for reducing the formation of coke and coke precursors in supercritical water. The method may include generating a supercritical water stream by pressurizing and heating feed water, and mixing the supercritical water stream with pressurized and heated feed oil in a mixing unit to generate a combined feed stream. The method may also include feeding the combined feed stream into a supercritical (ScW) reactor to produce upgraded products, wherein the supercritical water reactor operates at a temperature above the critical temperature of water and a pressure above the critical pressure of water. The method may further include producing cooled and depressurized upgraded products by cooling and depressurizing the upgraded products, separating the cooled and depressurized upgraded products into a liquid hydrocarbon stream and a hydrocarbon vapor stream in a fractionator, condensing the hydrocarbon vapor stream with a cooling unit to produce a light hydrocarbon-water mixture and separate gaseous products, and recirculating the light hydrocarbon-water mixture to mix it with feed water upstream of the supercritical water reactor.

[0067] The second aspect of this disclosure may include the first aspect, wherein a liquid hydrocarbon stream from a fractionator is fed to a gas-water-oil separator.

[0068] A third aspect of this disclosure may include any of the foregoing aspects, wherein the fractionator includes a flash tank.

[0069] The fourth aspect of this disclosure may include any of the foregoing aspects, wherein the light hydrocarbon-water mixture comprises 95% to 99.5% by weight of water and 0.5% to 5% by weight of hydrocarbons.

[0070] The fifth aspect of this disclosure may include any of the foregoing aspects, wherein, based on the weight of the hydrocarbons, the light hydrocarbon-water mixture comprises 30% to 60% by weight of alkanes, 10% to 70% by weight of olefins, 0% to 10% by weight of cycloalkanes, and 5% to 60% by weight of aromatics.

[0071] The sixth aspect of this disclosure may include any of the foregoing aspects, wherein the feed oil further includes full-range crude oil, distilled crude oil, residue oil, top-extracted crude oil, product streams from refineries, product streams from cracking processes, liquefied coal, liquid products recovered from oil or tar sands, bitumen, oil shale, asphaltenes, biomass hydrocarbons, liquid hydrocarbons from plastic pyrolysis, or combinations thereof.

[0072] The seventh aspect of this disclosure may include any of the foregoing aspects, wherein the feed water includes demineralized water having a conductivity of less than 1 μS / cm, a sodium content of less than 5 μg / L, a chlorine content of less than 5 μg / L, and a silica content of less than 3 μg / L.

[0073] It should be noted that, in this disclosure, descriptions of the components of this disclosure as being "operable" or "sufficient" in a particular manner to embody a particular property or function in a particular way are structural descriptions, not descriptions of their intended use. More specifically, references to the manner in which a component is "operable" or "sufficient" refer to the component's existing physical state and should therefore be considered as explicit descriptions of the component's structural characteristics.

[0074] It should also be noted that terms such as “preferredly,” “usually,” and “generally” as used herein are not intended to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are used only to identify specific aspects of embodiments of this disclosure or to highlight alternative or additional features that may or may not be used in specific embodiments of this disclosure.

[0075] It should be noted that one or more of the following claims use the term "wherein" as a transitional phrase. In defining the invention, it should be noted that this term is introduced in the claims as an open-ended transitional phrase used to introduce a description of a series of features of the structure, and should be understood in a similar manner to the more commonly used open-ended prepositional term "comprising."

[0076] Having referred to specific embodiments and described the subject matter of this disclosure in detail, it should be noted that the various details disclosed herein should not be construed as implying any relation to the essential components of the various embodiments described herein. Furthermore, it will be apparent that modifications and variations may be made without departing from the scope of this disclosure, including but not limited to the embodiments defined in the appended claims.

[0077] Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” all contain plural referents.

[0078] Various ranges are provided throughout this disclosure. It is foreseeable that each discrete value covered by these ranges is also included. Furthermore, it is equally foreseeable that ranges can be formed by each discrete value covered by the explicitly disclosed ranges.

[0079] As used herein and in the appended claims, the words “comprising,” “having,” and “including,” and all their grammatical variations, are intended to have an open, non-restrictive meaning, that is, not excluding other elements or steps.

[0080] As used herein, terms such as “first” and “second” are arbitrarily designated and are used only to distinguish between two or more instances or components. It should be understood that the words “first” and “second” have no other purpose and are neither part of a component name or component description, nor do they necessarily define the relative position, orientation, or order of components. Furthermore, it should be understood that the mere use of the terms “first” and “second” does not require the existence of any “third” component, although such a possibility is considered within the scope of this disclosure.

Claims

1. A method for reducing the formation of coke or coke precursors in supercritical water, comprising: Supercritical water flow is generated by heating and pressurizing the feed water; The supercritical water stream is mixed with pressurized and heated feed oil in a mixing device to generate a combined feed stream; The combined feed stream is fed into a supercritical water (ScW) reactor to produce an upgraded product, wherein the supercritical water reactor operates at a temperature above the critical temperature of water and a pressure above the critical pressure of water. By cooling and depressurizing the improved product, a cooled and depressurized improved product is generated. The cooled and depressurized upgraded product is separated into a liquid hydrocarbon stream and a hydrocarbon vapor stream in a fractionator; The hydrocarbon vapor stream is condensed using a cooling device to produce a light hydrocarbon-water mixture and separate gaseous products; as well as The light hydrocarbon-water mixture is recycled to mix it with the feed water upstream of the supercritical water reactor.

2. The method according to claim 1, wherein, The liquid hydrocarbon stream from the fractionator is delivered to the gas-water-oil separator.

3. The method according to claim 1 or claim 2, wherein, The fractionator includes a flash tank.

4. The method according to any one of claims 1 to 3, wherein, The light hydrocarbon-water mixture comprises 95% to 99.5% by weight of water and 0.5% to 5% by weight of hydrocarbons.

5. The method according to any one of claims 1 to 4, wherein, Based on the weight of the hydrocarbons, the hydrocarbons in the light hydrocarbon-water mixture comprise 30% to 60% by weight of alkanes, 10% to 70% by weight of olefins, 0% to 10% by weight of cycloalkanes, and 5% to 60% by weight of aromatics.

6. The method according to any one of claims 1 to 5, wherein, The feed oil further includes full-range crude oil, distilled crude oil, residue oil, top-extracted crude oil, product streams from refineries, product streams from cracking processes, liquefied coal, liquid products recovered from oil or tar sands, bitumen, oil shale, asphaltenes, biomass hydrocarbons, liquid hydrocarbons from plastic pyrolysis, or combinations thereof.

7. The method according to any one of claims 1 to 8, wherein, The feed water includes demineralized water, which has a conductivity of less than 1 microsiemens / cm, a sodium content of less than 5 micrograms / liter, a chlorine content of less than 5 micrograms / liter, and a silica content of less than 3 micrograms / liter.

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