Ethylene-based polymers and methods for producing ethylene-based polymers

Abstract

Embodiments of the present disclosure are directed to a method of producing an ethylene-based polymer, the method including separating a reactor effluent from a reactor into a gas stream containing unreacted monomer and a polymer stream in a high-pressure separator; separating off-gas from the polymer stream in an intermediate-pressure separator, the intermediate-pressure separator being disposed between the high-pressure separator and the low-pressure separator; sending the off-gas from the intermediate-pressure separator to a primary compressor; separating a residual polymer stream from the intermediate-pressure separator into off-gas and an ethylene-based polymer in a low-pressure separator; sending the off-gas from the low-pressure separator to a booster compressor, the booster compressor being disposed between the low-pressure separator and the primary compressor; compressing the off-gas from the low-pressure separator in the booster compressor; and sending the compressed off-gas from the booster compressor to the primary compressor.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of and priority to U.S. Patent Application No. 63 / 485,371, filed February 16, 2023, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to ethylene-based polymers and methods of making ethylene-based polymers. [Background technology]

[0003] High-pressure polymer resins are produced at high pressures, such as 1000 bar or more (bar refers to bar gauge unless otherwise specified), in autoclave reactors, tubular reactors, or both. In high-pressure polymerization processes, the reactor effluent from the reactor may be separated in a high-pressure separator followed by a low-pressure separator. It has been found that increasing production rates (faster reactor feed rates and / or reactor debottlenecking for higher conversion) increase gas entrainment in the polymer flow from the high-pressure separator to the low-pressure separator. This can result in more polymer carryover into the low-pressure separator. The carryover polymer may accumulate on the top and walls of the low-pressure separator and crosslink or mix with high and low melt index contaminants. This can lead to increased gel levels in the final product, thus increasing off-grades.

[0004] Gel performance and production rate can be improved by redesigning or replacing the low-pressure separator. However, in some cases, the building structure cannot support a new or redesigned low-pressure separator. Furthermore, capacity limitations of the booster compressor, which increases the pressure for the off-gas from the low-pressure separator, exist even with a redesigned low-pressure separator.

[0005] Thus, there is a continuing need for improved methods of producing ethylene-based polymers that enhance the production process by reducing gel formation in the low-pressure separator and compensating for capacity limitations in the booster compressor. Summary of the Invention

[0006] Embodiments of the present disclosure address this need by providing an intermediate-pressure separator between the high-pressure separator and the low-pressure separator. The off-gas separated from the intermediate-pressure separator is sent to the primary compressor. The off-gas separated from the low-pressure separator is sent to a booster compressor located between the low-pressure separator and the primary compressor. The off-gas from the low-pressure separator is compressed in the booster compressor before being sent to the primary compressor. This treatment of the off-gas from the intermediate-pressure separator and the low-pressure separator can reduce gel formation in the low-pressure separator, compensate for the limitations of the booster compressor, and increase the production rate of ethylene-based polymers. By separating the off-gas from the polymer stream in the intermediate-pressure separator, the intermediate-pressure separator can reduce gas entrainment in the low-pressure separator and eliminate the capacity limitations of the booster compressor, while improving energy consumption.

[0007] According to one or more embodiments of the present disclosure, a method for producing an ethylene-based polymer may include separating a reactor effluent from a reactor at a pressure of 100 bar or greater into a gas stream containing unreacted monomer and a polymer stream in a high-pressure separator; separating off-gas from the polymer stream in an intermediate-pressure separator at a pressure of 11 bar to 150 bar, the intermediate-pressure separator being disposed between the high-pressure separator and the low-pressure separator; sending the off-gas from the intermediate-pressure separator to a primary compressor; separating a residual polymer stream from the intermediate-pressure separator at a pressure of 0.1 bar to 10 bar into the off-gas and the ethylene-based polymer in a low-pressure separator at a pressure of 0.1 bar to 10 bar; sending the off-gas from the low-pressure separator to a booster compressor, the booster compressor being disposed between the low-pressure separator and the primary compressor; compressing the off-gas from the low-pressure separator in the booster compressor; and sending the compressed off-gas from the booster compressor to the primary compressor.

[0008] Additional features and advantages of the embodiments described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description, or may be learned by practice of the embodiments described herein, including the following detailed description and claims. [Brief explanation of the drawings]

[0009] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the drawings included herewith. [Figure 1] 1 depicts a flow chart for producing an ethylene-based polymer according to one or more embodiments described herein. [Figure 2] 1 illustrates a schematic of a system for producing an ethylene-based polymer according to one or more embodiments described herein. [Figure 3] 1 shows a schematic diagram of a system for producing an ethylene-based polymer according to Comparative Example 3 and Comparative Example 4.

[0010] It should be understood that the drawings are schematic in nature and do not include some components of systems for producing ethylene-based polymers commonly used in the art, such as, without limitation, temperature transmitters, pressure transmitters, level transmitters, flow meters, pumps, valves, etc. It will be appreciated that these components are within the spirit and scope of the disclosed embodiments. However, operating components such as those described in this disclosure may be added to the embodiments described in this disclosure.

[0011] Reference will now be made in more detail to various embodiments, some of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. DETAILED DESCRIPTION OF THE INVENTION

[0012] definition As used in this disclosure, a "reactor" may refer to a vessel in which one or more chemical reactions may occur between one or more reactants, optionally in the presence of one or more catalysts. For example, a reactor may include an autoclave or a tubular reactor. One or more "reaction zones" may be disposed within the reactor. As used in this disclosure, a "reaction zone" refers to the region within the reactor where a particular reaction occurs.

[0013] As used in this disclosure, "separator" refers to any separation device or system of separation devices that at least partially separates one or more chemicals mixed in a process stream from one another. For example, a separator may selectively separate different chemical species, phases, or sized materials from one another to form one or more chemical fractions. Examples of separators include, but are not limited to, distillation columns, flash drums, knockout drums, knockout pots, centrifuges, cyclones, filters, traps, scrubbers, expansion devices, membranes, solvent extractors, and the like. 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 one another. It should also be understood that separation may include only partial separation, even if not explicitly stated. As used in this disclosure, one or more chemical components may be "separated" from a process stream to form a new process stream. Generally, a process stream enters a separator and can be split or separated into two or more process streams of desired compositions.

[0014] As used herein, the term "polymer" can refer to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Thus, the generic term polymer encompasses the term "homopolymer," which is commonly used to refer to a polymer prepared from only one type of monomer, and "copolymer," which refers to a polymer prepared from two or more different monomers. As used herein, the term "interpolymer" refers to a polymer prepared by polymerization of at least two different types of monomers. Thus, the generic term interpolymer includes copolymers and polymers prepared from three or more different monomers, such as terpolymers.

[0015] As used herein, the terms "polyethylene" or "ethylene-based polymer" can refer to a polymer containing greater than 50 mole percent of units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of ethylene-based polymers known in the art include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), single-site catalyzed linear low-density polyethylene (m-LLDPE), which includes both linear and substantially linear low-density resins, medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0016] As used herein, a "high-pressure polymer resin" refers to a polymer produced at pressures greater than 1000 bar and may include high-pressure copolymers or homopolymers. This may include ethylene homopolymers, such as LDPE, or high-pressure ethylene copolymers. The term "LDPE," sometimes referred to as "high-pressure ethylene polymer" or "highly branched polyethylene," is defined to mean that the polymer is partially or fully homopolymerized or copolymerized in an autoclave or tubular reactor at pressures greater than 14,500 psi (100 MPa) using a free-radical initiator such as peroxide (see, for example, U.S. Pat. No. 4,599,392, incorporated herein by reference). LDPE resins typically have densities ranging from 0.916 grams per cubic centimeter (g / cc) to 0.935 g / cc. Furthermore, high-pressure ethylene copolymers may include "ethylene acid copolymers," which are the high-pressure polymerization reaction products of ethylene and one or more unsaturated carboxylic acid-containing monomers. In embodiments, the unsaturated carboxylic acid-containing comonomer may include an unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid, or a combination thereof. High-pressure ethylene copolymers may include ethylene / vinyl acetate (EVA), ethylene ethyl acrylate (EEA), ethylene butyl acrylate (EBA), ethylene methyl acrylate (EMA), ethylene vinyl silane (EVS), ethylene vinyl trimethyl silane (EVTMS), and other copolymers made with "silane-containing" comonomers, copolymers made with dienes (e.g., ENB) or polyenes, and ethylene carbon monoxide (ECO), other vinyl monomers (other acrylates), or other terpolymers.

[0017] Similarly, as used in this disclosure, the term "high pressure polymerization process" may refer to a free radical polymerization process carried out at a pressure of at least 1000 bar and optionally including an initiator or mixture of initiators.

[0018] As used in this disclosure, the term "free radical initiator" can refer to free radicals generated by chemical and / or radiation means. The free radical initiator may be added at the beginning of the reaction or may be added continuously or in stages during the reaction, particularly when monomers are so added. Examples of suitable free radical initiators include peroxyesters, peroxides, persulfates, perborates, percarbonates, azo compounds, and the like. Specific examples of suitable free radical initiators include hydrogen peroxide, tert-butyl peroctoate, tert-butyl peracetate, di(t-butyl)peroxide, lauroyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, 2,2'-azobis[2,4-dimethyl]pentanenitrile, 2-(t-butylazo)-2-methylbutanenitrile, 2-(t-butylazo)-2-4,dimethylpentanenitrile, azobis(isobutyronitrile), azobis(methylbutyronitrile) (AMBN), tert-amylperoxy 2-ethylhexanoate, and mixtures of any two or more thereof.

[0019] As used in this disclosure, the term "recycle" may refer to unreacted reactants that are separated from the polymer in the high-pressure separator, the medium-pressure separator, and / or the low-pressure separator and returned / compressed to the reactor.

[0020] As used in this disclosure, the terms "feed" or "feed flow" or "feed stream" may refer to make-up and / or recycled components, such as ethylene, initiator, or solvent, that are added to a reaction zone.

[0021] Method for producing ethylene-based polymers An embodiment of the present disclosure relates to a method for producing an ethylene-based polymer, which may include separating a reactor effluent from a reactor into a gas stream containing unreacted monomer and a polymer stream in a high-pressure separator, separating off-gas from the polymer stream in an intermediate-pressure separator, the intermediate-pressure separator being disposed between the high-pressure separator and the low-pressure separator, sending the off-gas from the intermediate-pressure separator to a primary compressor, separating the residual polymer stream from the intermediate-pressure separator into off-gas and the ethylene-based polymer in a low-pressure separator, sending the off-gas from the low-pressure separator to a booster compressor, the booster compressor being disposed between the low-pressure separator and the primary compressor, compressing the off-gas from the low-pressure separator in the booster compressor, and sending the compressed off-gas from the booster compressor to the primary compressor.

[0022] Figure 1 shows a flowchart 100 for producing an ethylene-based polymer according to one or more embodiments described herein. Figure 1 includes steps S110, S120, S130, S140, S150, S160, and S170, which may be performed in the order listed (i.e., S110 before S120, S120 before S130, S130 before S140, S140 before S150, S150 before S160, and S160 before S170). Other steps may additionally be included in the methods described herein, and the processes described herein should not be construed as limited to only the steps in Figure 1. Figure 2 schematically illustrates a system for producing an ethylene-based polymer according to one or more embodiments described herein.

[0023] Referring to FIG. 2 , reactor effluent 211 may be produced in high-pressure reactor 210. In embodiments, reactor 210 may include an autoclave reactor, a tubular reactor, or both. The polymerization pressure may be at least 1000 bar, in the range of 1000 to 5000 bar, 1200 to 4000 bar, or 1500 to 3500 bar. The polymerization temperature may be in the range of about 140° C. to about 330° C. All individual values ​​and subranges within the range of about 140° C. to about 330° C. are included herein and disclosed herein, for example, the polymerization temperature ranges from 150° C. to 320° C. The reactor effluent 211 may be cooled by a cooler or ejector(s) from the low-pressure portion of the process.

[0024] 2, recycle stream 261 can be provided from primary compressor 260 to reactor 210 for further polymerization. Reactor 210 can be located downstream of primary compressor 260. Recycle stream 261 can include ethylene. Recycle stream 261 can further include a free radical initiator.

[0025] In some embodiments, a secondary compressor (not shown) may be disposed between the primary compressor 260 and the reactor 210. The secondary compressor may compress the recycle stream 261 from the primary compressor 260. In some embodiments, a preheater (not shown) may be disposed upstream of the reactor 210. The preheater may be disposed between the secondary compressor and the reactor 210. The preheater may heat the recycle stream 261 from the primary compressor 260 to a desired temperature, such as in the range of 60°C to 180°C, particularly 120°C to 180°C, or 140°C to 160°C. Examples of preheaters include, but are not limited to, heat exchangers.

[0026] In some embodiments, a cooler (not shown) can be located upstream of reactor 210. The cooler may be located between the secondary compressor and reactor 210. The cooler can cool the recycle stream 261 from primary compressor 260 to a desired temperature, such as in the range of 20°C to 80°C, particularly 20°C to 60°C. Examples of coolers include, but are not limited to, heat exchangers. After completion of the reaction, reactor effluent 211 can be depressurized, cooled, or both, and then sent to high-pressure separator 220.

[0027] Reactor effluent 211 from reactor 210 may include unreacted ethylene monomer, ethylene-based polymer, and optionally additional unreacted comonomer, chain transfer agent, or both. In one or more embodiments, the concentration of ethylene-based polymer in reactor effluent 211 can be from 10 weight percent (wt%) to 50 wt%, 15 wt% to 50 wt%, 20 wt% to 50 wt%, 10 wt% to 45 wt%, 15 wt% to 45 wt%, 20 wt% to 45 wt%, 10 wt% to 40 wt%, 15 wt% to 40 wt%, 20 wt% to 40 wt%, 10 wt% to 35 wt%, 15 wt% to 35 wt%, 20 wt% to 35 wt%, 10 wt% to 30 wt%, 15 wt% to 30 wt%, 20 wt% to 30 wt%, 10 wt% to 25 wt%, 15 wt% to 25 wt%, or 10 wt% to 20 wt%, based on the total weight of reactor effluent 211.

[0028] 2 (see also step S110 of FIG. 1), reactor effluent 211 from reactor 210 is separated in high-pressure separator 220 into gas stream 221 containing unreacted monomer and polymer stream 222. A system for producing an ethylene-based polymer may include multiple high-pressure separators 220. Gas stream 221 containing unreacted monomer is discharged from high-pressure separator 220 as off-gas.

[0029] Gas stream 221 containing unreacted monomer may contain ethylene, chain transfer agent and solvent, optionally comonomer, and small amounts of additional components, such as 5% by weight or less, 1% by weight or less, 0.5% by weight or less, or 0.1% by weight or less of wax, contaminating polymer, or both. In one or more embodiments, gas stream 221 containing unreacted monomer may consist essentially of ethylene monomer. In one or more embodiments, gas stream 221 containing unreacted monomer may contain 0.1% by weight to 50% by weight of comonomer, such as vinyl acetate. In some embodiments, gas stream 221 containing unreacted monomer may contain 1 mol % to 10 mol % of chain transfer agent, including an alkane, alkene, aldehyde, ketone, alcohol, ether, ester, mercaptan, or phosphine.

[0030] Polymer stream 222 can include an ethylene-based polymer, such as LDPE. Polymer stream 222 can further include an ethylene monomer. In one or more embodiments, the concentration of the ethylene-based polymer in polymer stream 222 can be between 50% and 99% by weight, between 60% and 99% by weight, between 70% and 99% by weight, between 50% and 95% by weight, between 60% and 95% by weight, between 70% and 95% by weight, between 50% and 90% by weight, between 60% and 90% by weight, or between 70% and 90% by weight, based on the total amount of polymer stream 222.

[0031] High pressure separator 220 operates at a pressure of 100 bar or more, 150 bar or more, 200 bar or more, or 250 bar or more. In embodiments, high pressure separator 200 operates at a pressure of 650 bar or less, 600 bar or less, 550 bar or less, or 500 bar or less. In embodiments, reactor effluent 211 from reactor 210 is separated in high pressure separator 200 at a pressure of 100 bar to 650 bar, 150 bar to 650 bar, 200 bar to 650 bar, 250 bar to 650 bar, 100 bar to 600 bar, 150 bar to 600 bar, 200 bar to 600 bar, 250 bar to 600 bar, 100 bar to 550 bar, 150 bar to 550 bar, 200 bar to 550 bar, 250 bar to 550 bar, 100 bar to 500 bar, 150 bar to 500 bar, 200 bar to 500 bar, 250 bar to 500 bar, or any and all subranges of pressure formed from any of these endpoints.

[0032] Additionally, the high-pressure separator 220 may operate at temperatures between 140°C and 310°C, 145°C and 310°C, 150°C and 310°C, 140°C and 305°C, 145°C and 305°C, 150°C and 305°C, 140°C and 300°C, 145°C and 300°C, 150°C and 300°C, 140°C and 295°C, 145°C and 295°C, 150°C and 295°C, 140°C and 290°C, 145°C and 290°C, 150°C and 290°C, or any and all subranges formed from any of these endpoints.

[0033] 2 (see also step S120 of FIG. 1), off-gas 231 is separated from polymer stream 222 in intermediate-pressure separator 230. Intermediate-pressure separator 230 may be located between high-pressure separator 220 and low-pressure separator 240. Intermediate-pressure separator 230 may be directly connected to both high-pressure separator 220 and low-pressure separator 240. A system for producing an ethylene-based polymer may include multiple intermediate-pressure separators 230.

[0034] By separating off-gas 231 from polymer stream 222, intermediate pressure separator 230 can reduce gas entrainment in low pressure separator 240 and eliminate capacity limitations of booster compressor 250 while improving energy consumption.

[0035] Off-gas 231 may include ethylene monomer, optionally comonomer, as well as small amounts of additional components, such as 5% by weight or less, 1% by weight or less, 0.5% by weight or less, or 0.1% by weight or less of wax, contaminating polymer, or both. In one or more embodiments, off-gas 231 may consist essentially of ethylene monomer.

[0036] Polymer stream 232 can include an ethylene-based polymer, such as LDPE. Polymer stream 232 can further include ethylene. In one or more embodiments, the concentration of the ethylene-based polymer in polymer stream 232 can be between 50% and 95% by weight, between 55% and 95% by weight, between 60% and 95% by weight, between 50% and 85% by weight, between 55% and 85% by weight, between 60% and 85% by weight, between 50% and 75% by weight, between 55% and 75% by weight, between 60% and 75% by weight, or between 60% and 70% by weight, based on the total amount of polymer stream 232.

[0037] In one or more embodiments, between 0.1 wt% and 35 wt%, between 0.5 wt% and 35 wt%, between 1 wt% and 35 wt%, between 2 wt% and 35 wt%, between 5 wt% and 35 wt%, between 0.1 wt% and 30 wt%, between 0.5 wt% and 30 wt%, between 1 wt% and 30 wt%, between 2 wt% and 30 wt%, between 5 wt% and 30 wt%, between 0.1 wt% and 25 wt%, between 0.5 wt% and 25 wt%, between 1 wt% and 25 wt%, between 2 wt% and 25 wt%, between 5 wt% and 25 wt%, between 0.1 wt% and 20 wt%, between 0.5 wt% and 20 wt%, between 1 wt% and 20 wt%, between 2 wt% and 20 wt%, between 5 wt% and 20 wt% of the reactor effluent 211 is diverted to the off-gas 231 in the intermediate pressure separator 230.

[0038] 2, in one or more embodiments, off-gas 231 is separated from polymer stream 222 in intermediate pressure separator 230 at a pressure of 11 bar or more, 13 bar or more, 15 bar or more, or 20 bar or more. In embodiments, off-gas 231 is separated from polymer stream 222 in intermediate pressure separator 230 at a pressure of 150 bar or less, 130 bar or less, or 110 bar or less. In embodiments, the intermediate pressure separator 230 operates at a pressure between 11 bar and 150 bar, between 13 bar and 150 bar, between 15 bar and 150 bar, between 20 bar and 150 bar, between 11 bar and 130 bar, between 13 bar and 130 bar, between 15 bar and 130 bar, between 20 bar and 130 bar, between 11 bar and 110 bar, between 13 bar and 110 bar, between 15 bar and 110 bar, between 20 bar and 110 bar, or any and all subranges of pressure formed from any of these endpoints.

[0039] In one or more embodiments, the intermediate pressure separator 140 operates at a temperature between 140°C and 310°C, 145°C and 310°C, 150°C and 310°C, 140°C and 305°C, 145°C and 305°C, 150°C and 305°C, 140°C and 300°C, 145°C and 300°C, 150°C and 300°C, 140°C and 295°C, 145°C and 295°C, 150°C and 295°C, 140°C and 290°C, 145°C and 290°C, 150°C and 290°C, or any and all subranges formed from any of these endpoints.

[0040] 2 (see also step S130 in FIG. 1), the off-gas 231 from the intermediate-pressure separator 230 is sent to a primary compressor 260. The primary compressor 260 may be located downstream of the intermediate-pressure separator 230. The primary compressor 260 may be directly connected to the intermediate-pressure separator.

[0041] The primary compressor 260 may comprise a single or multiple compressor frames. In some embodiments, the primary compressor 260 may be combined with a booster compressor frame.

[0042] The primary compressor 260 may compress the off-gas 231 from the intermediate pressure separator 230. As described below, the primary compressor 260 may further compress the pressurized off-gas 251 from the booster compressor 250.

[0043] 2 (see also step S140 in FIG. 1), residual polymer stream 232 is separated into off-gas 241 and ethylene-based polymer stream 242 in low-pressure separator 240. Low-pressure separator 240 may be located downstream of intermediate-pressure separator 230. Low-pressure separator 240 may be directly connected to intermediate-pressure separator 230. A system for producing an ethylene-based polymer may include multiple low-pressure separators 240.

[0044] Off-gas 241 can include ethylene monomer, chain transfer agent and solvent, optionally comonomer, e.g., 5% by weight or less, 1% by weight or less, 0.5% by weight or less, or 0.1% by weight or less wax, contaminating polymer, or both. In one or more embodiments, off-gas 241 can consist essentially of ethylene monomer. In one or more embodiments, ethylene-based polymer stream 242 can consist essentially of ethylene-based polymer.

[0045] In one or more embodiments, between 0.1 wt% and 35 wt%, between 0.5 wt% and 35 wt%, between 1 wt% and 35 wt%, between 2 wt% and 35 wt%, between 5 wt% and 35 wt%, between 0.1 wt% and 30 wt%, between 0.5 wt% and 30 wt%, between 1 wt% and 30 wt%, between 2 wt% and 30 wt%, between 5 wt% and 30 wt%, between 0.1 wt% and 25 wt%, between 0.5 wt% and 25 wt%, between 1 wt% and 25 wt%, between 2 wt% and 25 wt%, between 5 wt% and 25 wt%, between 0.1 wt% and 20 wt%, between 0.5 wt% and 20 wt%, between 1 wt% and 20 wt%, between 2 wt% and 20 wt%, between 5 wt% and 20 wt% of the reactor effluent 211 is diverted to the off-gas 241 in the intermediate pressure separator 240.

[0046] In one or more embodiments, the residual polymer stream 232 discharged from the intermediate pressure separator 230 is separated in the low pressure separator 240 at a pressure of 0.01 bar or more, 0.05 bar or more, 0.1 bar or more, or 1 bar or more. In embodiments, the residual polymer stream 232 is separated in the low pressure separator 240 at a pressure of 10 bar or less, 9 bar or less, or 8 bar or less. In embodiments, low pressure separator 240 operates at pressures of 0.01 bar to 10 bar, 0.05 bar to 10 bar, 0.1 bar to 10 bar, 1 bar to 10 bar, 0.01 bar to 9 bar, 0.05 bar to 9 bar, 0.1 bar to 9 bar, 1 bar to 9 bar, 0.01 bar to 8 bar, 0.05 bar to 8 bar, 0.1 bar to 8 bar, 1 bar to 8 bar, or any and all subranges of pressure formed from any of these endpoints.

[0047] In one or more embodiments, residual polymer stream 232 is separated in low-pressure separator 240 at a temperature between 130°C and 300°C, between 135°C and 300°C, between 140°C and 300°C, between 130°C and 295°C, between 135°C and 295°C, between 140°C and 295°C, between 130°C and 290°C, between 135°C and 290°C, between 140°C and 290°C, between 130°C and 285°C, between 135°C and 285°C, between 140°C and 285°C, between 130°C and 280°C, between 135°C and 280°C, between 140°C and 280°C, or any and all subranges formed from any of these endpoints.

[0048] 2 (see also step S150 in FIG. 1), the off-gas 241 from the low-pressure separator 240 is sent to a booster compressor 250. The booster compressor 250 may be disposed between the low-pressure separator 240 and the primary compressor 260. The booster compressor 250 may be directly connected to both the low-pressure separator 240 and the primary compressor 260.

[0049] The booster compressor 250 may include a single or multiple compressor frames, and in some embodiments, the booster compressor 250 may be combined with the primary compressor frame.

[0050] In one or more embodiments, the capacity of booster compressor 250 may be 20% by weight or less of reactor effluent 211, 15% by weight or less of reactor effluent 211, or 10% by weight or less of reactor effluent 211. In one or more embodiments, the capacity of booster compressor 220 may be 0.1% by weight or more of reactor effluent 211, or 1% by weight or more of reactor effluent 211. In one or more embodiments, the capacity of booster compressor 250 may be between 0.1% by weight and 20% by weight of reactor effluent 211, between 1% by weight and 20% by weight of reactor effluent 211, between 0.1% by weight and 15% by weight of reactor effluent 211, between 1% by weight and 15% by weight of reactor effluent 211, between 0.1% by weight and 10% by weight of reactor effluent 211, between 1% by weight and 10% by weight of reactor effluent 211, or any and all subranges formed from any of these endpoints.

[0051] Still referring to FIG. 2 (see also step S160 of FIG. 1), off-gas 241 from low-pressure separator 240 is compressed in booster compressor 250.

[0052] The booster compressor 250 may compress the off-gas 241 from the low-pressure separator 240. In one or more embodiments, the booster compressor 250 may increase the pressure of the off-gas 241 from the low-pressure separator 240 to the suction pressure of the primary compressor 260.

[0053] In one or more embodiments, the booster compressor 250 can increase the pressure of the off-gas 241 from the low-pressure separator 240 to at least 10 bar, at least 11 bar, at least 12 bar, at least 13 bar, at least 14 bar, or at least 15 bar, such as 60 bar.

[0054] 2 (see also step S170 of FIG. 1), the compressed off-gas 251 from the booster compressor 250 is sent to a primary compressor 260. The primary compressor 260 may be located downstream of the booster compressor 250. The primary compressor 260 may be directly connected to the booster compressor 250.

[0055] As described above, the primary compressor 260 compresses the off-gas 231 from the intermediate pressure separator 230. The primary compressor 260 may further compress the pressurized off-gas 251 from the booster compressor 250.

[0056] Primary compressor 260 may send recycle stream 261 to reactor 210. Recycle stream 261 may include off-gas 231 from intermediate-pressure separator 230, off-gas 241 from low-pressure separator 240, pressurized off-gas 251 from booster compressor 250, or a combination thereof. Recycle stream 261 may further include additional comonomers, chain transfer agents, and free-radical initiators. [Example]

[0057] The following examples illustrate one or more additional features of the present disclosure. It should be understood that these examples are not intended to limit in any way the scope of the disclosure or the appended claims.

[0058] Examples 1 and 2 of the present invention FIG. 2 shows a schematic diagram of a system 200 for producing an ethylene-based polymer according to Examples 1 and 2 of the present invention. In Examples 1 and 2 of the present invention, high-pressure polymerization was simulated for ethylene using an Aspen Plus V10 manufactured by Aspen Technology. As shown in FIG. 2, reactor effluent 211 from reactor 210 was sent to high-pressure separator 220. Reactor effluent 211 was separated in high-pressure separator 310 into gas stream 221 containing unreacted monomer and polymer stream 222. Polymer stream 222 was sent to intermediate-pressure separator 230. Polymer stream 222 was separated in intermediate-pressure separator 230 into off-gas 231 and polymer stream 232. In Example 1 of the present invention, the pressure of intermediate-pressure separator 230 was set to 30 bar. 1500 kg / h of polymer stream 222 was diverted to off-gas 231 from intermediate-pressure separator 230. In Inventive Example 2, the pressure of the intermediate pressure separator 230 was set at 100 bar. 500 kg / hr of polymer stream 222 was diverted to off-gas 231 from the intermediate pressure separator 230. Polymer stream 232 was sent to low pressure separator 240. Polymer stream 232 was separated into off-gas 241 and ethylene-based polymer (polyethylene) 242. The capacity of booster compressor 250 was designed for 1850 kg / hr. Tables 1 and 2 list the temperature, pressure, flow rate, and composition of each stream.

[0059] [Table 1]

[0060] [Table 2]

[0061] Comparative Examples 3 and 4 FIG. 3 schematically illustrates a system 300 for producing an ethylene-based polymer according to Comparative Examples 3 and 4. In Comparative Examples 3 and 4, high-pressure polymerization was simulated. Reactor effluent 311 from the reactor was sent to high-pressure separator 310. In high-pressure separator 310, reactor effluent 311 was separated into gas stream 312 containing unreacted monomer and polymer stream 313. Polymer stream 313 was sent to low-pressure separator 320. Polymer stream 313 was separated into gas stream 321 containing unreacted monomer and ethylene-based polymer (polyethylene) 322. The capacity of the booster compressor installed downstream of low-pressure separator 320 was designed to be 1850 kg / hr. Tables 3 and 4 list the temperature, pressure, flow rate, and composition of each stream.

[0062] [Table 3]

[0063] [Table 4]

[0064] As shown in Tables 1 to 4, the flow rates of the off-gas from the low-pressure separator in Examples 1 and 2 of the present invention (1038 kg / hour and 1538 kg / hour) were lower than those (1837 kg / hour and 2038 kg / hour) in Comparative Examples 3 and 4. This indicates that the intermediate-pressure separators in Examples 1 and 2 of the present invention reduce the flow rate of the off-gas from the low-pressure separator by separating the off-gas from the intermediate-pressure separator.

[0065] When the booster compressor capacity was designed to be 1850 kg / hr, it was not possible to process the off-gas from the low-pressure separator in Comparative Example 4. Furthermore, it was not possible to design the low-pressure separator with a higher vapor velocity, which would increase the possibility of polymer carryover due to the increased flow of off-gas from the low-pressure separator.

[0066] Furthermore, as shown in Tables 1 to 4, the production rates of ethylene-based polymers in Examples 1 and 2 of the present invention (9007 kg / h and 9007 kg / h) were faster than the production rate of Comparative Example 3 (8106 kg / h). This indicates that separation of off-gas from the intermediate-pressure separator improves the production rate while reducing the possibility of gelation in the low-pressure separator. As described above, the production rate of ethylene-based polymers in Comparative Example 4 was the same as that of Examples 1 and 2 of the present invention. However, when the capacity of the booster compressor in Comparative Example 4 was designed to be 1850 kg / h, it was not possible to process the off-gas from the low-pressure separator.

[0067] A first aspect of the present disclosure may be directed to a method of producing an ethylene-based polymer, the method including: separating a reactor effluent from a reactor at a pressure of 100 bar or greater into a gas stream containing unreacted monomer and a polymer stream in a high-pressure separator; separating off-gas from the polymer stream in an intermediate-pressure separator at a pressure of 11 bar to 150 bar, the intermediate-pressure separator being disposed between the high-pressure separator and the low-pressure separator; sending the off-gas from the intermediate-pressure separator to a primary compressor; separating a residual polymer stream from the intermediate-pressure separator at a pressure of 0.1 bar to 10 bar into the off-gas and the ethylene-based polymer in a low-pressure separator at a pressure of 0.1 bar to 10 bar; sending the off-gas from the low-pressure separator to a booster compressor, the booster compressor being disposed between the low-pressure separator and the primary compressor;

[0068] A second embodiment of the present disclosure may include the first embodiment, wherein 0.1% to 35% by weight of the reactor effluent is diverted to the off-gas in the medium-pressure separator.

[0069] A third aspect of the present disclosure may include either the first or second aspect, wherein 0.1% to 20% by weight of the reactor effluent is diverted to the off-gas in the medium pressure separator.

[0070] A fourth aspect of the present disclosure may include any of the first to third aspects, wherein 0.1 wt % to 35 wt % of the reactor effluent from the reactor is diverted to the off-gas in the low-pressure separator.

[0071] A fifth aspect of the present disclosure may include any of the first to fourth aspects, wherein 0.1% to 20% by weight of the reactor effluent from the reactor is diverted to the off-gas in the low-pressure separator.

[0072] A sixth aspect of the present disclosure may include any of the first to fifth aspects, wherein the high-pressure separator operates at a temperature of 140°C to 290°C.

[0073] A seventh aspect of the present disclosure may include any of the first to sixth aspects, wherein the intermediate pressure separator operates at a temperature of 130°C to 290°C.

[0074] An eighth aspect of the present disclosure may include any of the first to seventh aspects, wherein the low-pressure separator operates at a temperature of 130°C to 280°C.

[0075] A ninth aspect of the present disclosure may include any of the first to eighth aspects, wherein the booster compressor capacity is 20% by weight or less of the reactor effluent.

[0076] A tenth aspect of the present disclosure may include any of the first to ninth aspects, wherein the booster compressor capacity is 10% by weight or less of the reactor effluent.

[0077] An eleventh aspect of the present disclosure may include any of the first to tenth aspects, wherein the booster compressor increases the pressure of the off-gas from the low-pressure separator to the suction pressure of the primary compressor.

[0078] A twelfth aspect of the present disclosure may include any of the first to eleventh aspects, wherein the booster compressor increases the pressure of the off-gas from the low-pressure separator by at least 10 bar.

[0079] A thirteenth aspect of the present disclosure may include any of the first to twelfth aspects, in which the ethylene-based polymer includes low-density polyethylene (LDPE).

[0080] A fourteenth aspect of the present disclosure may include any of the first through thirteenth aspects, in which the ethylene-based polymer comprises a high-pressure ethylene copolymer.

[0081] A fifteenth aspect of the present disclosure may be directed to an ethylene-based polymer produced from the process of any of the first through fourteenth aspects.

[0082] It should be noted that one or more of the claims below utilize the terms "wherein," "where," or "in which" as transitional phrases. For purposes of defining the present technology, this term is introduced in a claim as an open-ended transitional phrase used to introduce a recitation of a series of structural features and should be interpreted similarly to the more commonly used open-ended preamble term "comprising." For purposes of defining the present technology, the transitional phrase "consisting of" may be introduced in a claim as a closed preamble term limiting the claim to the recited components or steps and any naturally occurring impurities. For purposes of defining the present technology, the transitional phrase "consisting essentially of" may be introduced in a claim to limit one or more claims to the recited elements, components, materials, or method steps, as well as any unrecited elements, components, materials, or method steps that do not materially affect the novel characteristics of the claimed subject matter. The transitional phrases "consisting of" and "consisting essentially of" can be interpreted as subsets of open-ended transitional phrases such as "comprising" and "including," such that any use of an open-ended phrase to introduce a recitation of a series of elements, components, materials, or steps should be interpreted as also disclosing the recitation of that series of elements, components, materials, or steps using the closed terms "consisting of" and "consisting essentially of." For example, a description of a composition "comprising" components A, B, and C should be interpreted as also disclosing compositions "consisting of" components A, B, and C, as well as compositions "consisting essentially of" components A, B, and C.Any quantitative values ​​expressed in this application may be considered to include open-ended embodiments consistent with the transitional phrases "comprising" or "including," as well as closed or partially closed embodiments consistent with the transitional phrases "consisting of" and "consisting essentially of."

[0083] As used in this application and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. The verb "comprises" and its conjugations should be construed as a non-exclusive reference to elements, components, or steps. A referenced element, component, or step may be present in, utilized with, or combined with other elements, components, or steps not expressly referenced.

[0084] When an amount, concentration, or other value or parameter is given as either a range, a preferred range, or a list of lower and higher preferred values, this should be understood to specifically disclose all ranges formed from any pairing of any lower range limit or preferred value with any higher range limit or preferred value, regardless of whether the ranges are separately disclosed. When a range of numerical values ​​is recited herein, unless otherwise specified, the range is intended to include its endpoints, and all integers and fractions within the range. The scope of the invention is not intended to be limited to the specific values ​​recited when defining a range. When an element is indicated as being present in a range starting from 0, such element is an optional element (i.e., it may or may not be present). If present, the optional element may be at least 0.1 wt. % of the composition or copolymer.

[0085] When materials, methods, or machines are described herein with the terms "known to those skilled in the art," "conventional," or equivalent words or phrases, this term means that materials, methods, and machines that are conventional at the time of the filing of this application are encompassed by this description.

[0086] It should be understood that any two quantitative values ​​assigned to a characteristic may constitute a range for that characteristic, and that all combinations of ranges formed from all stated quantitative values ​​for a given characteristic are contemplated in the present application. The subject matter of the present disclosure has been described in detail with reference to specific embodiments. It should be understood that any detailed description of an element or feature of one or more embodiments does not necessarily imply that the element or feature is essential to that particular embodiment or any other embodiment. Furthermore, it will be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter.

Claims

1. 1. A method for producing an ethylene-based polymer, comprising: separating the reactor effluent from the reactor in a high pressure separator at a pressure of at least 100 bar into a gas stream containing unreacted monomer and a polymer stream; separating off-gas from the polymer stream in an intermediate pressure separator, the intermediate pressure separator being located between the high pressure separator and the low pressure separator, at a pressure between 11 bar and 150 bar; sending the off-gas from the intermediate pressure separator to a primary compressor; separating the residual polymer stream from the intermediate pressure separator into off-gas and the ethylene-based polymer in the low pressure separator at a pressure between 0.1 bar and 10 bar; routing the off-gas from the low-pressure separator to a booster compressor, the booster compressor being disposed between the low-pressure separator and the primary compressor; compressing the off-gas from the low pressure separator in the booster compressor; and delivering the compressed off-gas from the booster compressor to the primary compressor.

2. 10. The method of claim 1, wherein 0.1 weight percent (wt %) to 35 wt % of the reactor effluent from the reactor is diverted to the off-gas in the intermediate pressure separator.

3. 3. The method of claim 1 or claim 2, wherein 0.1 wt % to 20 wt % of the reactor effluent from the reactor is diverted to the off-gas in the intermediate pressure separator.

4. The method of any one of claims 1 to 3, wherein 0.1 wt% to 35 wt% of the reactor effluent from the reactor is diverted to the off-gas in the low pressure separator.

5. 5. The method of any one of claims 1 to 4, wherein 0.1 wt% to 20 wt% of the reactor effluent from the reactor is diverted to the off-gas in the low pressure separator.

6. The method of any one of claims 1 to 5, wherein the high pressure separator operates at a temperature between 140 degrees Celsius (°C) and 290°C.

7. The method of any one of claims 1 to 6, wherein the intermediate pressure separator is operating at a temperature of from 130°C to 290°C.

8. The method of any one of claims 1 to 7, wherein the low pressure separator is operated at a temperature of from 130°C to 280°C.

9. 9. The method of any one of claims 1 to 8, wherein the capacity of the booster compressor is no more than 20% by weight of the reactor effluent.

10. 10. The method of any one of claims 1 to 9, wherein the capacity of the booster compressor is no more than 10% by weight of the reactor effluent.

11. A method according to any preceding claim, wherein the booster compressor increases the pressure of the off-gas from the low pressure separator to the suction pressure of the primary compressor.

12. A method according to any preceding claim, wherein the booster compressor increases the pressure of the off-gas from the low pressure separator by at least 10 bar.

13. The method of any one of claims 1 to 12, wherein the ethylene-based polymer comprises low density polyethylene (LDPE).

14. The method of any one of claims 1 to 13, wherein the ethylene-based polymer comprises a high-pressure ethylene copolymer.

15. An ethylene-based polymer produced from the method of any one of claims 1-14.

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