A method for processing hydrothermal liquefaction of hydrocarbon effluent from plastic waste

Abstract

This disclosure provides a method for treating the effluent from hydrothermal liquefaction of a feedstock into a final liquid hydrocarbon fuel by removing impurities such as silicon, chlorides, metals, heteroatoms, etc., in a pretreatment zone. The feedstock contains plastic oil, pyrolysis oil, synthetic oil, or hydrocarbon distillates from a plastic recycling process using supercritical water as the reaction medium, and the effluent can be fed into a feed tank or a continuous mixing settler vessel. The feed is introduced into a hydrogen atmosphere reactor. The reactor effluent is fed to a separator for extracting a product mixture by adding supplemental or recycled hydrogen to the separator. The overhead product mixture is washed with water to remove acidic water or salts. The separator effluent is fed to a distillation section for extracting a liquid fuel product stream. A portion of the hydrotreated product stream can be recycled back to the feed tank or the continuous mixing settler vessel, which reduces the concentration of dienes.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 588,111, filed on October 5, 2023, which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to a method for treating hydrocarbon effluents from the hydrothermal liquefaction of plastic waste. In examples, the methods and systems described herein relate to treating hydrocarbon effluent streams generated during the hydrothermal liquefaction of plastic waste. Background Technology

[0004] Plastic pyrolysis oil obtained from various plastic recycling processes contains a significant amount of impurities. Some of these impurities may include silicon, chlorides, metals, heteroatoms, etc. These impurities are typically present at elevated levels and can be detrimental to downstream units such as steam cracking units. Therefore, impurities are usually removed. Common methods for impurity removal include adsorption or hydrogen addition to produce a cleaner product.

[0005] Hydrothermal liquefaction (HTL) is a thermochemical process that converts biomass or organic waste into liquid bio-oil under high temperature and pressure. This method is similar to geological methods for producing fossil fuels, but occurs in a much shorter time. During the HTL process, plastic waste (which can be biomass) is mixed with water and then heated in a pressurized reactor to temperatures ranging from 150°C to 600°C. The high pressure and high temperature conditions break down the complex organic molecules in the biomass into smaller molecules, forming bio-oil that can be separated from the remaining solids and water. The resulting bio-oil can be used as a renewable fuel source for transportation or further processed into other products.

[0006] HTL offers several advantages over other biofuel production methods. For example, HTL can process a wide range of feedstocks, including agricultural waste, forestry residues, and even algae. HTL can also be used to convert plastic waste into plastic oil, and then into liquid fuel. This method is similar to that used in pyrolysis, but there are some differences in operating conditions and the use of supercritical water.

[0007] Most refineries use separate diene saturation reactors to saturate dienes in waste plastic oil. Waste plastic oil is associated with a high diene content in the feed, and therefore it polymerizes at elevated temperatures. Dedicated diene saturation reactors are required for operation at temperatures not exceeding 210°C to ensure that these highly reactive substances are removed from the feed before polymerization can occur.

[0008] However, using HTL for plastic waste also presents some challenges. For example, some types of plastics may generate toxic byproducts during HTL, and the method may require additional energy to remove contaminants from the liquid products. Furthermore, the method may be economically infeasible for small-scale operations due to the high capital and operating costs of the reactor. Summary of the Invention

[0009] In the examples, the HTL method disclosed herein can be used to convert plastic waste into plastic oil and other valuable products.

[0010] In this example, the method can be used to convert a wide range of recycled plastic oils into refined hydrocarbons via hydrothermal liquefaction through hydrotreating. In this example, the conversion can result in 100% or nearly 100% of the plastic waste being converted into hydrocarbons.

[0011] In the examples, the methods described can produce steam cracker feedstock or clean fuel products. In the examples, the method can involve a hydrothermal upgrading process configured to utilize supercritical water to produce stable hydrocarbon products from a wide range of mixed plastic waste in a hydrotreating unit.

[0012] In the example, the method can reduce diene formation or eliminate separate diene-saturated reactors used to process hydrocarbon effluents from hydrothermal liquefaction into liquid fuels.

[0013] In this example, a method is provided for processing hydrocarbon effluents from hydrothermal liquefaction into liquid fuels. This method removes impurities from a feed slurry containing plastic oil, pyrolysis oil, synthetic oil, or distillates from plastic recycling processes using a heated medium in a pretreatment section. Impurities, such as silicon, chlorides, metals, heteroatoms, etc., are removed in the pretreatment zone, and the purified slurry can be allowed to enter a feed tank or a continuous mixing settling tank. In the continuous mixing settling tank, an internally inclined blade type or any agitator with blade mixing can be used to establish a stable suspension. Product recirculation streams from the bottom of stripping columns or fractionators can be fed into the continuous mixing settling tank, which helps to generate strong mixing at the bottom of the tank to disperse any fine solid particles present in the feed. The continuously stirred mixing tank helps to eliminate any agglomeration of colloids that may form over time due to the nature of the feed. Due to the varying properties of the feedstocks, the feed may occasionally exhibit peaks of high diene content (albeit for a very short time), which tend to form more gelling material, and therefore the continuous mixing settling vessel helps to eliminate any agglomeration of the gel. An additional advantage of recycling the product back to the mixing settling vessel is the ability to achieve significant dilution of the feedstock.

[0014] In some examples, the continuous mixing settling container can be a vertical container with a conical bottom, which allows for the easy removal of any fine solid particles over time.

[0015] In some examples, if a high level of diene in the feed is expected, a separate diene saturator can be installed downstream of the continuous mixing settling vessel. The feed is introduced into at least one hydrotreating reactor (any reactor with hydrogen present for the reaction—this can be olefin saturation with hydrogen at temperatures between 180°C and 500°C and hydrogen partial pressures between 20.0 barg and 180.0 barg—whether linear, diene, or cyclic olefins, treating heteroatoms such as sulfur, nitrogen, oxygen, or any halides such as chlorides, fluorides, bromides, or any shift in the feed's boiling point due to molecular cracking—more specifically, hydrocracking) to obtain a hydrotreated effluent. The reactor effluent is conveyed to a separator consisting of a hot high-pressure separator and a cold high-pressure separator. The reactor effluent, along with supplemental or recycled hydrogen, is subjected to hydrotreating in the hot high-pressure separator at temperatures between 180°C and 380°C and hydrogen partial pressures between 15.0 barg and 170.0 barg. The hydrogen partial pressure is mixed between barg. The overhead stream from the hot high-pressure separator is mixed with water to dissolve chlorides / salts, which are then removed as acid water. Finally, the separator effluent is fed to the distillation section for extraction of the liquid fuel product stream. A portion of the hydrotreated product stream can be recycled to a continuous mixing settling tank, which reduces the concentration of dienes. Attached Figure Description

[0016] To gain a detailed understanding of the features described herein, the invention can be described in more specific terms with reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of the invention and should not be construed as limiting the scope of the invention, as other equally effective embodiments are permissible.

[0017] Figure 1 Methods and systems for converting hydrocarbon effluents from hydrothermal liquefaction of plastic waste into clean liquid fuel products, according to embodiments described herein, are described.

[0018] Figure 2 A hydrogenation treatment reactor system according to embodiments described herein is shown;

[0019] Figure 3 A high-pressure separator for vapor-liquid separation according to an embodiment as described herein is shown;

[0020] Figure 4A flowchart is shown according to an embodiment as described herein, wherein vapor from a cold high-pressure separator is fed to a recirculating gas compressor separator tank for use as recirculated gas;

[0021] Figure 5 A fractionation column designed to remove light fractions according to embodiments described herein is shown; and

[0022] Figure 6 A system for converting hydrocarbon effluent from the hydrothermal liquefaction of plastic waste into clean liquid fuel products, according to embodiments described herein, is shown. Detailed Implementation

[0023] Hydrothermal liquefaction (HTL) is a method of converting plastic waste into plastic oil in the presence of supercritical water. Cold plastic oil feed at 0–12 barg and 20–100°C is received at the boundary. Figure 1 A method and system for converting hydrocarbon effluent from the hydrothermal liquefaction of plastic waste into clean liquid fuel products, according to embodiments described herein, are described. A cold feed (100) is fed to a feed coalescer (VO2) to remove free water and water-soluble impurities and is then conveyed to a feed contaminant removal system to remove contaminants such as mercury, arsenic, sodium, potassium, etc., at lower severities. This system uses filters or adsorption beds to remove impurities. The impurity-removed plastic oil feed (102) is filtered in a feed filter (F01) to avoid carrying over catalyst fines, thereby preventing clogging and pressure buildup in the downstream high-pressure (HP) reactor.

[0024] It should be noted that processing these feedstocks typically involves high-severity operating conditions (e.g., more demanding conditions such as higher temperatures and pressures) to produce products with higher value than the feedstock itself. These high-severity operating conditions promote methane cracking and aromatic ring cracking, which do not occur at significantly higher rates under typical low-severity conditions (e.g., conventional steam cracking conditions). High-severity and low-severity conversion methods are typically based on different pyrolysis reactors, which may include pyrolysis alone or in combination with combustion chemistry. That is, the reactor may include either standalone pyrolysis chemistry (e.g., thermochemical decomposition of the feedstock at elevated temperatures in the absence of oxygen) or a combination with combustion chemistry (i.e., an exothermic chemical reaction between the feedstock and an oxidant). These pyrolysis reactors can be categorized into different types: partial combustion of the pyrolysis feedstock, indirect combustion involving contact between the pyrolysis feedstock and combustion products, processes that generate an electric arc or plasma to crack the pyrolysis feedstock, and thermal pyrolysis. Each of these pyrolysis types differs in the means of generating and transferring the heat used for pyrolysis, but can be broadly characterized as low or high pyrolysis.

[0025] The term "high severity" refers to pyrolysis conditions that result in the conversion of a pyrolysis feed containing hydrocarbons to produce products based on the weight of hydrocarbons in the pyrolysis feed. Operating conditions for a pyrolysis reactor can be characterized by a severity threshold temperature, which distinguishes between low and high severity operating conditions in a pyrolysis reactor. High severity operating conditions for a pyrolysis reactor can be characterized by a peak pyrolysis gas temperature above the severity threshold temperature. A low severity pyrolysis reactor can be characterized by pyrolysis gas temperatures below the severity threshold temperature and no pyrolysis gas temperature exceeding the severity threshold temperature.

[0026] The HP feed pump draws in feed from the feed buffer tank (V01) and delivers the feed to the required reactor pressure. Oil flow is controlled by a flow control valve located immediately downstream of the feed pump (P01). The pumped feed is then mixed with hydrogen-rich process gas and preheated for the reactor effluent, where the pumped feed is heated to the required reactor inlet temperature by resetting the load via a temperature controller. Because the feed contains cracking feedstock that tends to polymerize, the process gas is injected upstream of the feed / effluent exchanger. The presence of H2 inhibits polymerization, thus reducing the tendency for fouling in the feed / effluent exchanger.

[0027] Figure 2 A hydrogenation treatment reactor system according to an embodiment as described herein is illustrated. Figure 2 The depicted hydrotreatment reactor system comprises a guard bed reactor (processing contaminants such as silicon, arsenic, lead, phosphorus, nickel, vanadium, calcium, iron, tin, lead, antimony, and other metals, and halogens such as chlorides, fluorides, and bromides), a hydrotreatment reactor (processing heteroatoms such as sulfur, nitrogen, and oxygen), and a hydrocracking reactor (processing aromatic saturation and boiling point shifts). These are the main components used to achieve the desired process objectives. The reactions involved are exothermic, resulting in temperature increases across each catalyst bed.

[0028] The protected reactor system consists of one or more reactors with one or more fixed beds to process plastic oils and stripped or fractionated bottom product recycle streams. Primary conversion gas products from the reactor are conveyed downwards through the trickle bed reactor. The pressure level of the reaction is approximately 20-180 barg, with a temperature range of 180°C to 500°C.

[0029] First, contaminants from the plastic oil are removed, and then it is hydrotreated or cracked to achieve product specifications. The optimal inlet temperature of the reactor depends on the space velocity and catalyst activity; therefore, it depends on the reactor catalyst lifetime (start of operation, SOR / end of operation, EOR).

[0030] The reactor operating pressure depends primarily on whether it is HDN (hydrodenitrification) or HDO (hydrodeoxygenation). Typically, feedstocks containing nitrogen in the form of carbazole or acridine are more difficult to crack than nitriles. Similarly, phenols are stable and resistant to hydrotreatment, so higher pressures are recommended if most of the oxygen is present in the form of phenols. Chlorides in the form of PCBs (polychlorinated biphenyls) are highly reactive and readily convert to HCl. The conversion of these substances begins at approximately 250°C.

[0031] Figure 3 A high-pressure separator for vapor-liquid separation according to an embodiment as described herein is illustrated. Cooled reactor effluent flows to a hot high-pressure separator (CO1) for vapor-liquid separation. A feed bypass control valve across the feed / effluent exchanger ensures that the desired HHPS temperature of approximately 180–380 °C is met. The pressure of the hot high-pressure separator can range from 15 barg to 170 barg, depending on the severity of the system. This design ensures that the hot high-pressure separator temperature is maintained sufficiently above the calculated deposition temperature (180–380 °C) based on the chloride level specified in the design basis. The HHPS liquid (140) from the hot high-pressure separator is depressurized and fed to a stripping tower under level control.

[0032] A small purge stream of supplemental or fresh hydrogen (190) is used to strip chlorides or HCl entrained in the HHPS liquid. Most of the HCl will remain in the gas phase and be washed with water in the overhead loop. Some residual saturated HCl will remain in the HHPS liquid.

[0033] Wash water (203) is continuously injected upstream of the reactor effluent air cooler (AC01) to dissolve NH3 and H2S in the reactor effluent, thereby preventing blockage of the exchange tubes due to ammonium salt deposition. The reactor effluent is cooled to <70°C in the reactor effluent air cooler. This air cooler improves the purity of the gas leaving the cold high-pressure system CHPS (VO3) and ensures sufficient quench gas temperature at the outlet of the recirculating gas compressor.

[0034] The cooled reactor effluent is then fed to a cold high-pressure separator (VO3), where vapor, liquid, and aqueous phases are separated. Acidic water (206) from the cold high-pressure separator is discharged to the boundary area under interface level control. Hydrocarbon liquid from the cold high-pressure separator is discharged under level control and directly fed to the top tank of the product stripper. CHPS liquid (137) is mixed with the stripper top condenser outlet stream before entering the top tank (142).

[0035] Figure 4A flowchart illustrating an embodiment as described herein is shown, wherein vapor from a cold high-pressure separator is fed to a recirculating gas compressor separator tank for use as recirculated gas. Figure 4 As depicted, vapor from the cold high-pressure separator (VO3) is sent to the recirculating gas compressor separator (VO4) as recirculated gas. Due to the low sulfur content in the feed, amine scrubbing is not required. The recirculated gas consists of the process gas sent to (E02) and the quenched gas sent to (R01 / R02). The bottom product from the separator (VO4) is sent to the flare.

[0036] Figure 5 A fractionation column designed for removing light fractions according to an embodiment as described herein is shown. Figure 5 As depicted, the fractionator (CO2) is a steam stripping column designed to remove light fractions (including H2S and NH3) from the HHPS liquid effluent stream (142) fed into the column. Stripping of the butane and lighter components from the overhead distillate is accomplished using LP-HP stripping steam. Liquid from the thermal high-pressure separator is fed into the product stripping column (CO2). This column may or may not require any external heat source; the heat required for the column can be provided by preheated feed or an external heater, depending on the product specifications.

[0037] The product (162) is recycled from the bottom of the stripper or fractionator (169) to the buffer / continuous mixing settling vessel (V01), which eliminates the need for a diene reactor, reduces the diene concentration, controls the temperature difference (dT), which helps control the temperature rise due to olefin saturation in the first bed, and significantly reduces the quenching of the recirculated gas to save on compression costs.

[0038] Figure 6 A system for converting hydrocarbon effluent from the hydrothermal liquefaction of plastic waste into clean liquid fuel products, according to embodiments described herein, is shown.

[0039] The hydrothermal liquefaction (HTL) method is a process of converting plastic waste into plastic oil in the presence of supercritical water. A cold plastic oil feed at 0–12 barg and 20–100°C is received at the boundary. This cold feed (100) is sent to a feed coalescer (VO2) to remove free water and water-soluble impurities, and then to a feed contaminant removal system (VO2) to remove contaminants such as mercury, arsenic, sodium, potassium, etc., at lower severities. This system (VO2) uses filters or adsorption beds to remove impurities. The impurity-removed plastic oil feed (102) is filtered in a feed filter (F01) to avoid carrying over catalyst fines, thereby preventing clogging and pressure buildup in the downstream high-pressure (HP) reactor.

[0040] Optionally, the feed (102) can be heated and can be fed into a continuous mixing settling vessel (V01). An internally inclined blade type or any agitator may be required in the continuous mixing settling vessel (V01) to establish a stable suspension. Product recirculation streams from the bottom of a stripping column or fractionator can be fed into the continuous mixing settling vessel (V01), contributing to strong mixing at the bottom of the vessel to aid in the settling of any fine solid particles present in the feed (102). The continuous stirring mixing vessel (V01) helps eliminate any agglomeration of colloids that may form over time due to the nature of the feed. Due to the varying properties of the feed, the feed (102) may occasionally have peaks of higher diene content (albeit for short periods), which tend to form more gelling material, and thus the continuous mixing settling vessel helps address this issue. An additional advantage of introducing product recirculation into this vessel is the ability to achieve significant dilution of the feed.

[0041] The continuous mixing settling container (V01) can be a vertical container or it can have a conical bottom to allow for easy removal of any fine solid particles over time.

[0042] In some examples, if the expected feed diene is high, a separate diene saturator can also be set downstream of the continuous mixing settling vessel (V01).

[0043] The HP feed pump (P01) draws from the continuous mixing settling vessel (V01) and pumps the feed (102) to the required reactor pressure. The oil flow rate is controlled by a flow control valve located immediately downstream of the feed pump (P01). The pumped feed is then mixed with hydrogen-rich process gas and preheated for the reactor effluent, wherein the pumped feed is heated to the required reactor inlet temperature by resetting the load via a temperature controller. Because the feed contains cracking feedstock that tends to polymerize, the process gas is injected upstream of the feed / effluent exchanger. The presence of H2 inhibits polymerization, thereby reducing the tendency for fouling in the feed / effluent exchanger.

[0044] The hydrotreatment reactor consists of a guard bed reactor (processing contaminants such as silicon, arsenic, lead, phosphorus, nickel, vanadium, calcium, iron, tin, lead, antimony, and other metals, and halogens such as chlorides, fluorides, and bromides), a hydrotreatment reactor (processing heteroatoms such as sulfur, nitrogen, and oxygen), and a hydrocracking reactor (processing aromatic saturation and boiling point shifts). These are the main components used to achieve the desired process objectives. The reactions involved are exothermic, resulting in temperature increases across each catalyst bed.

[0045] The protected reactor system consists of one or more reactors with one or more fixed beds to process plastic oils and stripped or fractionated bottom product recycle streams. Primary conversion gas products from the reactor are conveyed downwards through the trickle bed reactor. The pressure level of the reaction is approximately 20-180 barg, with a temperature range of 180°C to 500°C.

[0046] First, contaminants from the plastic oil are removed, and then it is hydrotreated or cracked to achieve product specifications. The optimal inlet temperature of the reactor depends on the space velocity and catalyst activity; therefore, it depends on the reactor catalyst lifetime (start of operation, SOR / end of operation, EOR).

[0047] The reactor operating pressure depends primarily on whether it is HDN (hydrodenitrification) or HDO (hydrodeoxygenation). Typically, feedstocks containing nitrogen in the form of carbazole or acridine are more difficult to crack than nitriles. Similarly, phenols are stable and resistant to hydrotreatment, so higher pressures are recommended if most of the oxygen is present in the form of phenols. Chlorides in the form of PCBs (polychlorinated biphenyls) are highly reactive and readily convert to HCl. The conversion of these substances begins at approximately 250°C.

[0048] The cooled reactor effluent flows to a hot high-pressure separator for vapor-liquid separation. A feed bypass control valve across the feed / effluent exchanger ensures the desired HHPS temperature of approximately 180–380 °C is met. The pressure in the hot high-pressure separator can range from 15 barg to 170 barg, depending on the system's severity. The design ensures that the hot high-pressure separator temperature is maintained sufficiently above the calculated deposition temperature (180–380 °C) based on the chloride levels specified in the design. The HHPS liquid from the hot high-pressure separator is depressurized and fed to a stripping tower under level control.

[0049] A small purge stream of makeup hydrogen or fresh hydrogen is used to strip chlorides or HCl entrained in the HHPS liquid. Most of the HCl will remain in the gas phase and be washed with water in the overhead loop. Some residual saturated HCl will remain in the HHPS liquid.

[0050] Wash water is continuously injected upstream of the reactor effluent air cooler to dissolve NH3 and H2S in the reactor effluent, thereby preventing exchanger tube blockage due to ammonium salt deposition. The reactor effluent is cooled to <70°C in the reactor effluent air cooler. This air cooler improves the purity of the gas leaving CHPS and ensures sufficient quench gas temperature at the outlet of the recirculating gas compressor.

[0051] The cooled reactor effluent is then fed to a cold high-pressure separator, where vapor, liquid, and aqueous phases are separated. Acidic water from the cold high-pressure separator is discharged to the boundary zone under interface level control. Hydrocarbon liquid from the cold high-pressure separator is discharged under level control and directly fed to the top tank of the product stripper. CHPS liquid is mixed with the stripper top condenser effluent before entering the top tank. Vapor from the cold high-pressure separator is sent to the recirculating gas compressor separator for use as recirculated gas. Due to the low sulfur content in the feed, amine washing is not required.

[0052] The product stripping column, or fractionation column, is a steam stripping column designed to remove light fractions (including H2S and NH3) from the HHPS liquid effluent fed into the column. Stripping of butane and lighter components from the overhead distillate is accomplished using LP-HP stripping steam. Liquid from the thermal high-pressure separator is fed into the product stripping column. The column may or may not require any external heat source; the heat required for the column can be provided by preheating the feed or by an external heater, depending on the product specifications.

[0053] The product is recycled from the bottom of the stripper or fractionator to a continuous mixing settling vessel, which eliminates the need for a diene reactor in some examples when the feed diene content is low, but is generally more advantageous due to the significant dilution, which reduces the diene concentration, controls the temperature difference (dT), helps control the temperature rise due to olefin saturation in the first bed, and significantly reduces the quenching of the recirculated gas to save on compression costs.

[0054] In some examples, the reactor diameter can be increased at the minimum mass flux, which helps maintain the minimum reactor mass flux and allows for a more reasonable reactor L / D ratio.

[0055] In some examples, hydrothermal liquefaction methods and systems are described. In these examples, the hydrothermal liquefaction method can be used to convert waste plastic feedstocks. In these examples, the hydrothermal liquefaction method as described may include the presence of supercritical water as a heating medium. In these examples, the products derived from the described methods and systems can be more stable and / or provide high-quality plastic oils with low solids, water, and impurity content. In these examples, the methods and systems as described may allow for much simpler hydrotreating of plastic oils into steam cracker feedstocks or clean liquid fuel products.

[0056] In some examples, the hydrothermal liquefaction methods and systems described can employ supercritical water as the heating medium. In these examples, the supercritical water can be mixed with plastic waste in the reactor. In these examples, this can provide more efficient and more uniform (i.e., no temperature gradient) heat transfer compared to other advanced recycling methods, such as pyrolysis, in which the plastic waste is heated by the reactor itself.

[0057] In the example, the plastic oil derived from the described HTL method may include a negligible amount of carbon. In the example, the produced plastic oil can be fed into a hydrotreating process unit suitable for producing marketable products.

[0058] In the example, the hydrogenation process described may include selectively removing impurities with low severity.

[0059] Cold feed at 0-12 barg and 20-100°C is received at the boundary zone. This cold feed is sent to the feed coalescer to remove free water and water-soluble impurities, and is then conveyed to the feed contaminant removal system to remove contaminants such as mercury, arsenic, sodium, potassium, etc. at lower severity.

[0060] Mercury is most likely to exist as elemental mercury. It can also exist as organometallic mercury and ionic mercury. Organomercury compounds readily decompose into elemental mercury upon heating in a reducing atmosphere, therefore, the majority of the C3 to C6 product stream is expected to be elemental mercury. The main problems are corrosion, catalyst poisoning, and safety concerns. Therefore, removing elemental mercury from the product to below 1 ppbw is crucial. Arsenic in the form of arsine (AsH3) can be readily removed at lower temperatures. This can be coupled with a mercury removal system. Organoarsenic compounds, however, will require higher temperatures for removal. Similarly, this low-severity system can be used to remove sodium and potassium salts from the feed. This solution is capable of removing metals such as arsine, mercury, sodium, and potassium from the system, which will enable an optimal balance between cold and hot system protection bed catalysts. The system can use filters or adsorption bed systems to remove impurities. The feed is filtered in a feed filter to avoid carrying fine catalyst particles, thus preventing clogging and pressure buildup in the downstream high-pressure (HP) reactor.

[0061] In the example, the hydrotreating method may include diluting the feed with the product to reduce the feed diene content, which may lead to the elimination of a separate low-criticality hydrotreating reactor.

[0062] Most refineries use separate diene saturation reactors to saturate dienes in waste plastic oil. Waste plastic oil is associated with a high diene content in the feed, and therefore it polymerizes at elevated temperatures. Dedicated diene saturation reactors are required for operation at temperatures not exceeding 210°C to ensure that these highly reactive substances are removed from the feed before polymerization can occur.

[0063] Plastic oils derived from hydrothermal liquefaction methods are typically associated with low diene values. In this method, the bottom product from the stripping column or fractionator can be recycled back to the continuous mixing settling tank to be mixed with the fresh feed. Therefore, the final concentration of the most reactive dienes will be low, and no pressure drop (dP) issues will arise.

[0064] The requirements for a standalone DIOS reactor are more of a risk assessment, where the risk of pressure drop issues within the unit increases with increasing feed diene concentrations over the target cycle length. Feed diene specifications of <1.2 will be even lower due to product dilution during recycling. Therefore, the final concentration of the most reactive diene will be low enough not to cause dP issues during the short cycle length where the unit might operate due to contaminants. However, occasional feed diene deviations or levels as high as 3.0 in the feed could increase the risk of dP issues. In such cases (if higher levels are expected), adding a DIOS reactor can improve reliability.

[0065] If the diene concentration is expected to be <1.2% most of the time and the catalyst turnaround time for the protection reactor is 1 year, it is generally recommended not to use a standalone DIOS reactor. However, if there are credible concerns, a DIOS reactor can be added.

[0066] DIOS reactors are typically operated at temperatures below 200°C. The reactor temperature is regulated to allow for very little reactor exotherm (up to 5°C). This is to remove the most reactive dienes from the feed. Olefin saturation begins at around 250°C and results in very high exothermic activity. Therefore, for safe operation of DIOS reactors, a very narrow temperature window exists between 200 and 250°C.

[0067] Recycling the bottom product from a stripping or fractionating column to a buffer or continuous mixing settler serves three purposes: eliminating the need for a DIOS reactor – which helps dilute the feed dienes; controlling the temperature difference (dT) – which helps control the temperature rise due to olefin saturation in the first bed; significantly reducing the need for quenching the recycle gas to save on compression costs; and increasing the reactor diameter at minimum mass flux – which helps maintain a minimum reactor mass flux, allowing for a more reasonable reactor L / D ratio.

[0068] In the example, a hydrotreatment method may include processing a reactor using hydrotreatment in the presence of hydrogen to obtain an effluent.

[0069] The HP feed pump draws from the continuous mixing settling tank and delivers the feed to the required reactor pressure. The oil flow rate is controlled by a flow control valve located immediately downstream of the feed pump. The pumped feed is then mixed with hydrogen-rich process gas and preheated for the reactor effluent in the feed / effluent exchanger. Because the feed contains cracked feedstock that tends to polymerize, the process gas is injected upstream of the feed / effluent exchanger. The presence of H2 inhibits polymerization, thus reducing the tendency for fouling in the feed / effluent exchanger. The gas-to-oil ratio is a critical factor in ensuring complete reaction in the reactor. Therefore, the gas-to-oil ratio is closely monitored. If the gas-to-oil ratio falls below a minimum, the oil feed to the unit needs to be reduced to maintain the gas-to-oil ratio.

[0070] The combined feed is heated in a feed / effluent exchanger and then conveyed to the reactor feed heater, where the load is reset by a temperature controller to heat the combined feed to the desired reactor inlet temperature.

[0071] Immediately upstream of the reactor, final temperature control is used to make any fine adjustments to the reactor inlet feed temperature. If a cooler reactor inlet temperature is required, quench hydrogen is added via a temperature controller that resets the quench flow control.

[0072] Hydrotreatment reactors can consist of a guard bed reactor (processing contaminants such as silicon, arsenic, lead, phosphorus, nickel, vanadium, calcium, iron, tin, lead, antimony, and other metals, and halogens such as chlorides, fluorides, and bromides), a hydrotreatment reactor (processing heteroatoms such as sulfur, nitrogen, and oxygen), and a hydrocracking reactor (processing aromatic saturation and boiling point shifts). These are the main components used to achieve the desired process objectives. The reactions involved are exothermic, resulting in temperature increases across each catalyst bed.

[0073] The protection reactor system can consist of a single or multiple reactors with one or more fixed beds to process plastic oils and the bottom product recycle stream from stripping or fractionation. Primary conversion gas products from the reactor are conveyed downwards through the trickle bed reactor. The pressure level of the reaction is approximately 20-180 barg, with a temperature range of 180°C to 500°C.

[0074] First, contaminants from the plastic oil are removed, and then it is hydrotreated or cracked to achieve product specifications. The optimal inlet temperature of the reactor depends on the space velocity and catalyst activity; therefore, it depends on the reactor catalyst lifetime (start of operation, SOR / end of operation, EOR).

[0075] The first bed will have a guard bed, which is used to capture particles and solids and particulates (and / or metals) in the plastic oil during fouling services. The reaction involved is exothermic, resulting in a temperature rise across each catalyst bed. Recycled product from the bottom of the stripping or fractionation column acts as quenching to control the thermal rise due to olefin saturation. Cold recycle gas from the recycle gas compressor can also be injected as quenching between catalyst beds under temperature control to control the average catalyst temperature and limit the bed outlet temperature. The weighted average bed temperature determines the extent of hydrotreatment and hydrocracking reactions. The catalyst beds are separated by an interbed quenching and distribution system, which provides feed distribution and temperature control in the prior art. For highly exothermic reaction systems, a uniform temperature distribution across the reactor is extremely important to avoid hot spots that could lead to unsafe conditions. The benefits of the interbed quenching and distribution system include reactor temperature control, maximum catalyst utilization, and the highest level of safety and reliability. Catalyst performance is determined by a combination of operating conditions (temperature, hydrogen partial pressure and charge rate and gas-to-oil ratio) applied to the GPH reactor system.

[0076] The operating pressure of this unit depends primarily on whether it is HDN (hydrodenitrogenation) or HDO (hydrodeoxygenation). Typically, feedstocks containing nitrogen in the form of carbazole or acridine are more difficult to crack than nitriles. Similarly, phenols are stable and resistant to hydrotreatment, so higher pressures are recommended if most of the oxygen is present in the form of phenols. Chlorides in the form of PCBs (polychlorinated biphenyls) are highly reactive and readily convert to HCl. The conversion of these substances begins at approximately 250°C.

[0077] In the example, the hydrogenation process may include separating the effluent into product fractions.

[0078] The heat content of the reactor effluent is recovered in the feed / effluent exchanger. The cooled reactor effluent flows to a thermal high-pressure separator for vapor-liquid separation. A feed bypass control valve across the feed / effluent exchanger ensures that the desired HHPS temperature of approximately 180–380 °C is met. The pressure in the thermal high-pressure separator can range from 15 barg to 170 barg, depending on the system's severity. The design ensures that the thermal high-pressure separator temperature is maintained sufficiently above the calculated deposition temperature (180–380 °C) based on the chloride levels specified in the design basis. The HHPS liquid from the thermal high-pressure separator is depressurized and fed to a stripping tower under level control.

[0079] A small amount of purge feed, supplemented with hydrogen, is used to strip any HCl entrained in the HHPS liquid. Most of the HCl will remain in the gas phase and be washed with water in the overhead loop. Some residual saturated HCl will remain in the HHPS liquid. Since we are dealing with a high concentration of HCl in the reactor effluent, it is necessary to ensure that the HCl concentration is as low as possible.

[0080] The goal is to achieve a very low HCl concentration in the HHPS liquid to ensure that the operating temperature at the top of the downstream product stripping tower is always higher than the deposition temperature under these conditions.

[0081] Wash water is continuously injected upstream of the reactor effluent air cooler to dissolve NH3 and H2S in the reactor effluent, thereby preventing exchanger tube blockage due to ammonium salt deposition. The reactor effluent is cooled to <70°C in the reactor effluent air cooler. This air cooler improves the purity of the gas leaving CHPS and ensures sufficient quench gas temperature at the outlet of the recirculating gas compressor.

[0082] The cooled reactor effluent is then fed to a cold high-pressure separator, where vapor, liquid, and aqueous phases are separated. Acidic water from the cold high-pressure separator is discharged to the boundary zone under interface level control. Hydrocarbon liquid from the cold high-pressure separator is discharged under level control and directly fed to the top tank of the product stripper. CHPS liquid is mixed with the stripper top condenser effluent before entering the top tank. Vapor from the cold high-pressure separator is sent to the recirculating gas compressor separator for use as recirculated gas. Due to the low sulfur content in the feed, amine washing is not required.

[0083] The product stripping tower or fractionation tower is a steam stripping tower, which is designed to remove light fractions (including H2S and NH3) from the HHPS liquid effluent stream fed into the tower.

[0084] Stripping of the butane and lighter components from the overhead distillate is accomplished using LP-MP stripping steam. Liquid from the thermal high-pressure separator is fed into the product stripping column. This column may or may not require any external heat source; the heat required for the column can be supplied by preheated feed or an external heater, depending on the product specifications.

[0085] A method for processing hydrocarbon effluent from hydrothermal liquefaction into liquid fuels involves removing impurities from a feed slurry containing plastic oil, pyrolysis oil, synthetic oil, or distillates from plastic recycling processes using a heating medium in a pretreatment section. Impurities, such as silicon, chlorides, metals, heteroatoms, etc., are removed in the pretreatment zone, and the purified slurry can be conveyed to a continuous mixing settling tank. The feed, along with hydrogen, is introduced into at least one hydrotreating reactor at a temperature between 180°C and 500°C and a hydrogen partial pressure between 20.0 barg and 180.0 barg to obtain a hydrotreated effluent. The reactor effluent is conveyed to a separator consisting of a hot high-pressure separator and a cold high-pressure separator. The reactor effluent is mixed with supplemental or recycled hydrogen in the hot high-pressure separator at a temperature between 180°C and 380°C and a hydrogen partial pressure between 15.0 barg and 170.0 barg. The overhead stream from the hot high-pressure separator is mixed with water to dissolve chlorides / salts, which are then removed as acid water. Finally, the separator effluent is conveyed to the distillation section for the extraction of a clean liquid fuel product stream.

[0086] In this example, the preheated feed is mixed with a portion of the hydrotreated product, which is recycled back through the reactor system to dilute the diene in the feed. Therefore, the final concentration of the most reactive diene will be low enough not to cause pressure drop (dP) issues over short cycle lengths.

[0087] A method for treating hydrocarbon effluent from the hydrothermal liquefaction of plastic waste into a liquid transport fuel involves removing impurities from a feed slurry containing plastic oil, pyrolysis oil, synthetic oil, or distillates from plastic recycling processes using a heating medium in a pretreatment section. Impurities, such as silicon, chlorides, metals, and heteroatoms, are removed in the pretreatment zone, and the purified slurry can be conveyed to a feed tank or a continuous mixing settling tank. The feed, along with hydrogen, is introduced into a hydrotreating reactor at a temperature between 180°C and 500°C and a hydrogen partial pressure between 20.0 barg and 180.0 barg to obtain a hydrotreated effluent. The reactor effluent is then conveyed to a separator consisting of a hot high-pressure separator and a cold high-pressure separator. The reactor effluent is mixed with supplemental or recycled hydrogen in the hot high-pressure separator at a temperature between 180°C and 380°C and a hydrogen partial pressure between 15.0 barg and 170.0 barg. The overhead stream from the hot high-pressure separator is mixed with water to dissolve chlorides / salts, which are then removed as acid water. Finally, the separator effluent is fed to the distillation section for extraction of liquid fuel product streams. A portion of the hydrotreated product stream can be recycled to a continuous mixing settling tank, which reduces the concentration of dienes.

[0088] In the example, the described hydrotreating method can produce higher quality liquid fuel products than other plastic oil-to-fuel methods (such as pyrolysis) because the method can operate at higher pressures and temperatures.

[0089] Table 1 below presents typical product specifications achieved in this method based on the level of hydrogen saturation. Lower saturation systems will target contaminant removal (metals such as silicon, arsenic, mercury; halogens such as chlorides, fluorides, bromides, etc.), olefin saturation (olefins saturated to alkanes), and heteroatom removal (sulfur, nitrogen, oxygen). Higher saturation systems will additionally target aromatic saturation (aromatics, such as mono-, di-, and tri-(poly)aromatics saturated to alkanes) and boiling point shift (higher boiling point fractions converted to lower boiling point fractions), as depicted in Table 2.

[0090]

[0091] Table 1

[0092]

[0093] Table 2

[0094] The advantages of the hydrotreating method described herein include the ability to reduce the diene content in the feed and eliminate the need for a separate diene reactor through the recycling of the hydrotreating products. In the example, this could lead to capital investment savings in the design of a waste plastic oil upgrading unit.

[0095] Another advantage of the hydrotreating method described in this article is that the upgrading of plastic oils may be limited by the catalyst cycle length to capture very high conversion-elevated contaminant levels.

[0096] Typical plastic oils derived from methods other than hydrothermal liquefaction will have very high levels of contaminants. See Table 3 below.

[0097]

[0098] Table 3

[0099] The catalyst volume required to remove these contaminant levels would be very high, necessitating a large reactor diameter. The reactor diameter is determined by the mass flux (mass per unit area) to maintain the optimized design performance of the method. This, in turn, limits the catalyst volume, and consequently, the catalyst lifetime.

[0100] In this example, plastic oil refined from the HTL method described above may require a smaller catalyst volume to capture impurities. This could result in longer cycle lengths, lower capital costs, and lower operating costs.

[0101] For example, a typical pyrolysis oil with a silicon content of 200 ppm will only have a catalyst life of 2.5 months, while a catalyst with a silicon content of 20 ppm will have a life of more than 2 years.

[0102] Frequent catalyst replacements will be associated with unit downtime, production losses, and increased costs of catalyst unloading (due to high metal loading, spent catalysts are typically non-renewable) / loading (new catalyst loading, catalyst activation).

[0103] These factors directly lead to higher capital and operating costs for typical pyrolysis oil systems.

[0104] Certain embodiments and features have been described using a set of upper and lower numerical limits. It should be understood that, unless otherwise stated, ranges from any lower limit to any upper limit are considered. Some of the lower, upper, and ranges appear in one or more of the following claims. All numerical values ​​are indicated by “about” or “approximately” and take into account experimental errors and variations that would be expected by one of ordinary skill in the art.

[0105] Various terms have been defined above. Where a term used in the claims is not defined above, it shall be given the broadest definition that has been given to a person skilled in the art, as reflected in at least one printed publication or authorized patent. Furthermore, all patents, test procedures, and other documents referenced in this application are fully incorporated by reference, provided that such disclosure does not contradict this application and is permissible in all jurisdictions where such incorporation is permitted.

[0106] While the foregoing describes embodiments of the present invention, other and further embodiments of the present invention may be designed without departing from the basic scope of the present invention, and the scope of the present invention is defined by the appended claims. Claims (as amended under Article 19 of the Treaty) 1. A method for treating hydrocarbon effluent from the hydrothermal liquefaction of plastic waste into a clean hydrotreated product, the method comprising: a) Remove impurities from the hydrocarbon effluent stream through a pretreatment section to produce a pretreated hydrocarbon effluent; b) Transfer the pretreated hydrocarbon effluent to the feed tank; c) In the presence of hydrogen, at a temperature between 180 and 500°C and a hydrogen partial pressure between 20.0 and 180.0 barg, the pretreated hydrocarbon effluent from the feed tank is fed into at least one reactor to obtain a hydrogenated reactor effluent. d) The reactor effluent from the hydrogenation process is transferred to a separator unit comprising a hot high-pressure separator and a cold high-pressure separator; e) At a temperature of 180 to 380°C and a hydrogen partial pressure of 15.0 to 170.0 barg, supplemental or recycled hydrogen is introduced into the thermal high-pressure separator along with the reactor effluent from the hydrogenation process. f) The water-containing top feed from the hot high-pressure separator is transferred to the cold high-pressure separator; g) Remove acidic water containing dissolved salts from the top stream of the tower using the cold high-pressure separator; h) Combine the liquid bottom products from the upstream hot high-pressure separator and the cold high-pressure separator in the distillation section; and i) A portion of the hydrotreated product from the distillation section is recycled back to the feed tank to reduce the concentration of dienes. 2. The method according to claim 1, wherein the hydrocarbon effluent is plastic oil, pyrolysis oil, synthetic oil, or distillate from a plastic recycling process. 3. The method according to claim 1, wherein the reactor in the at least one reactor comprises a hydrogen atmosphere reactor, a protective bed reactor, or a trickle bed reactor. 4. The method according to claim 1, wherein the hydrotreating product is a transport fuel or a steam cracker feedstock. 5. The method according to claim 1, wherein the method further comprises: j) Transferring the pretreated hydrocarbon effluent to a continuous mixing settling tank; and k) A portion of the hydrogenation product is recycled back to the continuous mixing settling vessel to reduce the concentration of dienes. 6. The method of claim 5, wherein the continuous mixing settling tank is a vertical tank with a conical bottom to remove fine solid particles. 7. A system for treating the effluent from the hydrothermal liquefaction of plastic waste into a clean hydrotreated product, the system comprising: a) A contaminant removal unit that reduces impurities from hydrothermal liquefaction effluent; b) A feed tank that receives low-impurity raw materials from the contaminant removal unit; c) A reactor that receives a low-impurity feedstock from the feed tank, treated with fresh, replenished, or recycled hydrogen; d) A separator unit comprising a hot high-pressure separator and a cold high-pressure separator, the hot high-pressure separator being operable to receive a reactor effluent containing water and fresh, replenished, or recycled hydrogen and produce a first liquid stream, the cold high-pressure separator being operable to receive the overhead stream from the hot high-pressure separator and produce a second liquid stream and acidic water, the first liquid stream and the second liquid stream being combined to form the separator effluent; and e) A stripping unit that receives the separator effluent for the extraction of clean hydrotreating products, acid water, and tail gas. 8. The system of claim 7, further comprising recycling a portion of the clean hydrotreating product from the stripping unit back to the feed tank, thereby reducing the concentration of diene. 9. The system according to claim 7, further comprising: A continuous mixing settling vessel receives a portion of the low-impurity feedstock from the contaminant removal unit and a portion of the clean hydrotreated product from the stripping unit to reduce the concentration of dienes. 10. The method of claim 1, further comprising: j) The top feed stream of the cold high-pressure separator is used as the recirculated hydrogen for recirculation. 11. The method of claim 10, wherein the recirculated hydrogen is further configured to quench the at least one reactor. 12. The method of claim 1, further comprising: j) The acid water is treated to produce wash water, which is supplied to the overhead stream of the thermal high-pressure separator or the overhead stream of the distillation section. 13. The method of claim 1, wherein the feed tank is a vertical and continuous mixing settling container with a conical bottom to remove fine solid particles.

Claims

1. A method for treating hydrocarbon effluent from the hydrothermal liquefaction of plastic waste into clean liquid fuel products, the method comprising: a) Remove impurities from the hydrocarbon effluent stream through a pretreatment section to produce a pretreated hydrocarbon effluent; b) Transfer the pretreated hydrocarbon effluent to the feed tank; c) In the presence of hydrogen, at a temperature between 180 and 500 °C and a hydrogen partial pressure between 20.0 and 180.0 barg, the pretreated hydrocarbon effluent is fed into at least one reactor to obtain a hydrogenated effluent. d) The reactor effluent is conveyed to a separator consisting of a hot high-pressure separator and a cold high-pressure separator; e) At a temperature of 180 to 380°C and a hydrogen partial pressure of 15.0 to 170.0 barg, supplemental or recycled hydrogen is introduced into the thermal high-pressure separator along with the reactor effluent; f) The top feed stream from the hot high-pressure separator is transferred together with water to the cold high-pressure separator; g) Remove the acidic water containing dissolved salts from the cold high-pressure separator; h) Transfer the effluent to the distillation section; i) A portion of the hydrogenated product is recycled back to the feed tank to reduce the concentration of diene.

2. The method of claim 1 for processing effluent from hydrothermal liquefaction into clean liquid fuel, wherein the feed is plastic oil, pyrolysis oil, synthetic oil, or distillate from a plastic recycling process.

3. The method for processing effluent from hydrothermal liquefaction into clean liquid fuel according to claim 1, wherein the reactor is a hydrogen atmosphere reactor, a protective bed, or a trickle bed.

4. The method of claim 1 for processing effluent from hydrothermal liquefaction into clean liquid fuel, wherein the product is suitable for use as transport fuel or feedstock for flow crackers.

5. The method for treating effluent from hydrothermal liquefaction into clean liquid fuel according to claim 1, wherein the method further comprises: The pretreated hydrocarbon effluent is transferred to a continuous mixing settling tank. as well as A portion of the hydrogenated product is recycled back to the continuous mixing settling tank to reduce the concentration of dienes.

6. The method of claim 6 for processing effluent from hydrothermal liquefaction into clean liquid fuel, wherein the continuous mixing settling tank is a vertical tank with a conical bottom to remove fine solid particles.

7. A system for processing effluent from hydrothermal liquefaction into clean liquid fuel products, the system comprising: a) A contaminant removal unit that reduces impurities from hydrothermal liquefaction effluent; b) A feed tank that receives low-weight impurity feed from the contaminant removal unit; c) A reactor that receives a low-impurity feed from the feed tank, treated with fresh or supplemental hydrogen; d) A separator unit consisting of a hot high-pressure separator and a cold high-pressure separator, which receives reactor effluent with fresh or replenished hydrogen and water for conversion into liquid fuel products and acid water. e) A stripping unit that receives the separator effluent for the extraction of a clean liquid fuel product stream, the acid water, and the tail gas.

8. The system for processing effluent from hydrothermal liquefaction into clean liquid fuel according to claim 8, further comprising recycling a portion of the liquid fuel product from the separator back to the feed tank, thereby reducing the concentration of dienes.

9. The system for treating effluent from hydrothermal liquefaction into clean liquid fuel according to claim 8, further comprising: A continuous mixing settling vessel receives low-heavy-impurity feedstock from the contaminant removal unit and recycles a portion of the liquid fuel products from the separator unit, thereby reducing the concentration of diolefins.

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