A system and method for producing polyethylene

Abstract

The present application relates to the technical field of olefin continuous polymerization reaction, and discloses a high-speed polymerization system and method for industrial preparation of hyperbranched polyethylene. The system comprises the following steps: after gaseous ethylene raw material, solvent and auxiliary catalyst are treated in at least one micro-interface generator, the gaseous ethylene raw material, the solvent and the auxiliary catalyst are introduced into at least one reaction kettle to react with a catalyst; at least part of liquid phase from the reaction kettle is returned to the reaction kettle after cooling; gas phase from the reaction kettle is condensed; gaseous product obtained is returned to the reaction kettle; and liquid product obtained is returned to the reaction kettle after condensation. The system uses the micro-interface generator to strengthen mass transfer, uses comprehensive heat removal means including a cooling feed heat exchanger, a gas phase condensation heat exchanger and / or a liquid phase external circulation heat exchanger and / or a jacket / inner cooling tube heat exchanger to strengthen heat removal, so that the purpose of high-speed polymerization of a large device is achieved.

Description

Technical Field

[0001] This invention relates to the field of continuous olefin polymerization technology, and more specifically to a system and method for preparing polyethylene. Background Technology

[0002] In polyolefin processes, stirred tank slurry polymerization is mainly used to produce high-density polyethylene, while solution polymerization is mainly used to produce ethylene propylene rubber and POE elastomers. Compared with other polymerization processes, this process has relatively mild reaction conditions: the reaction operating pressure is typically <3.0 MPa, and the reaction operating temperature is 60–95℃; the catalyst has lower requirements for raw material impurities; and it can produce high-quality polyolefin products with special properties. Therefore, stirred tank polymerization currently has a very wide range of applications both domestically and internationally.

[0003] Highly branched polyethylene is typically prepared by solution copolymerization of ethylene and α-olefins or by solution polymerization of a single ethylene monomer catalyzed by a transition metal catalyst of α-diimide. Given the significant influence of heat transfer, mass transfer, and micromixing during the polymerization of highly branched polyethylene, enhancing these processes is crucial for the polymerization reaction.

[0004] Ethylene polymerization is an exothermic reaction with a heat of polymerization of approximately 3400 kJ / kg, which is substantial. Existing stirred tank polymerization processes suffer from poor micro-mixing, affecting product quality. Furthermore, heat removal from large polymerization reactors is difficult, and heat removal is a key aspect of reactor design and a bottleneck that must be overcome during scale-up.

[0005] CN201910867780.2 and CN202010554105.7 disclose a system and method for enhancing ethylene polymerization through micro-interfaces. Although these methods can enhance mass transfer, the gas carrying capacity is limited due to the gas / liquid volume ratio limitation of the micro-interface generator, which is far from meeting the total amount of monomer required for polymerization. In addition, the problem of enhancing heat transfer is not considered simultaneously. In large-scale industrial plants, enhancing mass transfer will lead to greater heat removal problems after the reaction.

[0006] Regarding heat removal during the reaction, in the CX polyethylene process technology of Mitsui Chemicals Co., Ltd. in Japan, the heat of polymerization is mainly removed through the evaporation of hexane material at the top of the polymerization reactor and heat exchange in the reactor jacket. CN200710121286.9 discloses a method for producing ultra-high molecular weight polyethylene resin, specifically disclosing a gas external circulation heat removal method during the polymerization process of ultra-high molecular weight polyethylene (UHMW-PE) resin. The escaping gaseous ethylene, hydrogen, and hexane vapors from the polymerization reactor are introduced into a condenser, where the hexane undergoes heat exchange and condensation. After gas-liquid separation in a condensate tank, the liquid hexane is pumped back to the polymerization reactor, achieving the purpose of hexane evaporation and circulation heat removal, thereby avoiding the possibility of local overheating and powder agglomeration. However, when the production scale of polyethylene plants increases, if the majority of the heat of polymerization still relies on hexane evaporation for removal, the diameter of the polymerization reactor must be set very large to prevent gas-phase mist entrainment. This has extremely adverse effects on the manufacturing of the polymerization reactor, the design of the agitator, and the polymerization reaction process.

[0007] In the Basel polyethylene process, the heat of polymerization is removed through external slurry circulation and heat exchange in the polymerization reactor jacket. However, the external circulation system has poor stability and is prone to affecting cooling efficiency due to oligomer solidification on the heat exchange tube walls. Moreover, the temperature difference between the slurry at the inlet and outlet of the cooler needs to be controlled within 6°C to reduce the solidification and adhesion process of oligomers. Therefore, the above factors will affect the heat removal effect of large polymerization reactors.

[0008] In summary, external circulation heat removal from slurry / solution has poor stability and is prone to affecting cooling efficiency due to the solidification and adhesion of oligomers / polymers to the heat exchanger tube walls. Heat removal from the reactor jacket is limited by the reactor's external surface area; the larger the reactor, the smaller the proportion of heat removal. Solvent evaporation heat removal suffers from material backmixing due to entrainment of gaseous solvent mist, affecting the polymerization reaction. Therefore, when the production scale of the batch reactor process reaches a certain level, heat removal remains a bottleneck, thus limiting the further expansion of polyethylene production facilities.

[0009] Therefore, there is an urgent need for a comprehensive reaction enhancement method that can both strengthen mass transfer and further improve reaction rate, and balance problems such as oligomer / polymer adhesion and entrainment of gaseous solvent mist. Summary of the Invention

[0010] The purpose of this invention is to overcome the problems of poor micro-mixing and mass transfer rate lagging behind the intrinsic polymerization reaction rate in the preparation of olefin polymers in existing technologies, which affect product quality and heat removal in large-scale equipment. This invention provides a system and method for preparing polyethylene. The system described in this invention can enhance heat and mass transfer and improve production efficiency in the industrial continuous production process of olefin polymerization.

[0011] To achieve the above objectives, the present invention provides a system for preparing polyethylene, comprising at least one micro-interface generator and at least one reaction vessel. Ethylene-containing gaseous feedstock, solvent, and auxiliary catalyst are processed by at least one micro-interface generator and then enter at least one of the reaction vessels to react with the catalyst. At least a portion of the liquid phase from the reaction vessel is cooled by a cooler and returned to the reaction vessel for reuse. The gaseous phase from the reaction vessel is condensed by a condenser at the top of the vessel, and the resulting gaseous product is returned to the reaction vessel for reuse. The resulting liquid product is condensed and returned to the reaction vessel for reuse.

[0012] Preferably, the system includes a first reaction vessel, a first micro-interface generator group, a second micro-interface generator group, and a third micro-interface generator group.

[0013] After being processed in the first micro-interface generator group, the first ethylene-containing gaseous raw material, solvent and auxiliary catalyst are cooled by the first cooler and then enter the first reactor to be mixed with the catalyst to carry out the first polymerization reaction.

[0014] After being cooled by the second cooler, a portion of the first liquid phase from the first reactor is processed together with the first ethylene-containing gaseous feedstock in the second micro-interface generator group and then returned to the first reactor for reuse.

[0015] The first gaseous phase from the first reactor is condensed by the first reactor top condenser, and the resulting first gaseous product is returned to the first reactor for reuse. The resulting first liquid product is condensed by the first condensate subcooler and then processed with the first ethylene-containing gaseous raw material in the third micro-interface generator group. After being combined with the first product from the first micro-interface generator group, the product is cooled by the first cooler and then enters the first reactor for reuse.

[0016] Preferably, the polyethylene preparation system further includes a first material pipeline, a second material pipeline, and a third material pipeline, wherein the first material pipeline is used to provide a first ethylene-containing gaseous feedstock, the second material pipeline is used to provide a solvent and an auxiliary catalyst, and the third material pipeline is used to provide a catalyst.

[0017] Preferably, the polyethylene preparation system further includes a third cooler, through which the solvent and auxiliary catalyst from the second material pipeline are cooled before entering the first micro-interface generator group.

[0018] Preferably, the polyethylene preparation system further includes a first collection tank for collecting the first gaseous product and the first liquid product obtained after condensation by the first reactor top condenser.

[0019] Preferably, the polyethylene preparation system further includes a second reaction vessel, a fourth micro-interface generator group, a fifth micro-interface generator group, and a sixth micro-interface generator group.

[0020] The second ethylene-containing gaseous feedstock and another portion of the first liquid phase from the first reactor are processed in the fourth micro-interface generator group and then enter the second reactor to carry out the second polymerization reaction.

[0021] After being cooled by the fourth cooler, a portion of the second liquid phase from the second reactor is treated with the second ethylene-containing gaseous raw material in the fifth micro-interface generator group and then combined with the second product obtained from the fourth micro-interface generator group before entering the second reactor for reuse. Another portion of the second liquid phase undergoes post-processing to obtain polyethylene.

[0022] The second gaseous phase from the second reactor is condensed by the second reactor top condenser, and the resulting second gaseous product is returned to the second reactor for reuse. The resulting second liquid product is condensed by the second condensate subcooler and then processed with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group before entering the second reactor for reuse.

[0023] Preferably, the polyethylene preparation system further includes a fourth material pipeline for providing the second ethylene-containing gaseous feedstock.

[0024] Preferably, the polyethylene preparation system further includes a fifth cooler, through which another portion of the first liquid phase from the first reactor is cooled before entering the fourth micro-interface generator group.

[0025] Preferably, the polyethylene preparation system further includes a second collection tank for collecting the second gaseous product and the second liquid product obtained after condensation by the second reactor top condenser.

[0026] Preferably, the upper part of the gas phase space inside the first and second reaction vessels is equipped with a demister, and the liquid phase part is equipped with a gamma ray control device for liquid level control.

[0027] Preferably, the demister is selected from one or more of wire mesh demisters, spherical demisters, baffle plate demisters, and centrifugal demisters, preferably a wire mesh demister and / or a spherical demister, more preferably a combination of a baffle plate demister and a wire mesh demister or a combination of a baffle plate demister and a spherical demister.

[0028] Preferably, the gamma-ray level control device includes a gamma-ray source placed near the level of the reaction bath to be contained in the reactor and a gamma-ray detector that is opposite in diameter to the gamma-ray source and extends vertically along the entire height of the reaction bath.

[0029] A second aspect of the present invention provides a method for preparing polyethylene, said method being carried out in a polyethylene preparation system comprising at least one micro-interface generator and at least one reaction vessel.

[0030] After being processed in at least one micro-interface generator, the ethylene-containing gaseous feedstock, solvent, and auxiliary catalyst are introduced into at least one of the reactors to react with the catalyst. At least a portion of the liquid phase from the reactor is cooled by a cooler and returned to the reactor for reuse. The gaseous phase from the reactor is condensed by a condenser at the top of the reactor, and the resulting gaseous product is returned to the reactor for reuse. The resulting liquid product is condensed and returned to the reactor for reuse.

[0031] Preferably, the method is implemented in a system for preparing polyethylene comprising a first reaction vessel, a first micro-interface generator group, a second micro-interface generator group, and a third micro-interface generator group.

[0032] The method includes the following steps:

[0033] The first ethylene-containing gaseous raw material, solvent, and auxiliary catalyst are sequentially passed into the first micro-interface generator group and the first cooler for treatment, and then enter the first reaction vessel to be mixed with the catalyst to carry out the first polymerization reaction.

[0034] After a portion of the first liquid phase from the first reactor is cooled in the second cooler and processed with the first ethylene-containing gaseous feedstock in the second micro-interface generator group, it is returned to the first reactor for reuse.

[0035] The first gaseous phase from the first reactor is condensed in the first reactor top condenser to obtain a first gaseous product and a first liquid product. The first gaseous product is returned to the first reactor for reuse. The first liquid product is condensed in the first condensate subcooler and then processed with the first ethylene-containing gaseous raw material in the third micro-interface generator group. After being combined with the first product from the first micro-interface generator group, it is cooled by the first cooler and then enters the first reactor for reuse.

[0036] Preferably, the solvent and auxiliary catalyst are cooled in a third cooler before entering the first micro-interface generator assembly.

[0037] Preferably, the method further includes:

[0038] The second ethylene-containing gaseous raw material and another portion of the first liquid phase from the first reactor are treated in the fourth micro-interface generator group and then introduced into the second reactor to carry out the second polymerization reaction.

[0039] A portion of the second liquid phase from the second reactor is cooled in the fourth cooler and then treated with the second ethylene-containing gaseous feedstock in the fifth micro-interface generator group. After being combined with the second product obtained from the fourth micro-interface generator group, it is returned to the second reactor for reuse. Another portion of the second liquid phase undergoes post-processing to obtain polyethylene.

[0040] The second gaseous phase from the second reactor is condensed in the condenser at the top of the second reactor to obtain a second gaseous product and a second liquid product. The second gaseous product is returned to the second reactor for reuse. The second liquid product is condensed in the second condensate subcooler and then processed with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group before entering the second reactor for reuse.

[0041] Preferably, the first ethylene-containing gaseous feedstock and the second ethylene-containing gaseous feedstock contain ethylene and optional gaseous reaction aids.

[0042] Preferably, the gaseous reaction aid includes gaseous comonomers and / or gaseous molecular weight regulators.

[0043] Preferably, the gaseous comonomer is propylene.

[0044] Preferably, the gaseous molecular weight regulator is hydrogen.

[0045] Preferably, the solvent is C3-C. 30 Aliphatic alkanes and / or aromatic compounds.

[0046] Preferably, the solvent is C3-C. 30 Aliphatic alkanes are selected from one or more of propane, butane, pentane, hexane, heptane, octane, and cyclohexane.

[0047] Preferably, the aromatic compound is toluene.

[0048] More preferably, the solvent is selected from combinations of pentane and cyclopentane, propane and hexane, propane and heptane, propane and cyclohexane, propane and heptane and cyclohexane, propane and hexane and cyclohexane, butane and hexane, butane and heptane, butane and cyclohexane, butane and heptane and cyclohexane, butane and heptane and cyclohexane, pentane or cyclopentane.

[0049] Preferably, the catalyst is a complex of a post-transition metal.

[0050] Preferably, the later transition metal is nickel and / or palladium.

[0051] Preferably, the catalyst is a diimine complex of nickel and / or palladium.

[0052] Preferably, the auxiliary catalyst is selected from one or more of aluminoxane, alkylaluminum, and alkylaluminum chloride.

[0053] Preferably, the aluminum oxane is selected from one or more of methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane.

[0054] Preferably, the alkylaluminum is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum.

[0055] Preferably, the alkylaluminum chloride is selected from one or more of dimethylaluminum chloride, diethylaluminum chloride, ethylaluminum dichloride, and trichlorotriethylaluminum.

[0056] Preferably, based on the metal elements contained in the catalyst and the auxiliary catalyst, the molar ratio of the auxiliary catalyst to the catalyst is 100-4000:1, more preferably 400-1000:1.

[0057] Preferably, the conditions for the first polymerization reaction include: a temperature of 0℃-250℃, more preferably 50-80℃; and a pressure of 0.1-5MPa, more preferably 0.5-1.5MPa.

[0058] Preferably, the conditions for the second polymerization reaction include: a temperature of 0°C-250°C, more preferably 50-80°C; and a pressure of 0.1-5 MPa, more preferably 0.5-1.5 MPa.

[0059] Preferably, the difference between the inlet temperature and the outlet temperature of the first liquid phase when it passes through the second cooler, the fifth cooler, and the second liquid phase when it passes through the fourth cooler is less than 10°C, more preferably less than 5°C, and even more preferably less than 2°C.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) Before the reaction, the present invention uses a micro-interface generator to mix the liquid and gaseous materials. On the one hand, this increases the mass transfer area between the gaseous and liquid materials, improves the reaction efficiency, and reduces energy consumption. On the other hand, the gas-liquid mixture is more uniform and the product has higher uniformity, thus improving the product quality.

[0062] (2) Preferably, the present invention adopts 3 to 4 combinations of heat removal measures, such as cold feeding of raw materials for heat removal, gas phase (external circulation) condensation heat removal, jacket / internal cooling pipe heat removal, liquid phase external circulation heat removal, and preferably adopts solvent (system) to enhance gas phase condensation heat removal, so as to well balance the contradiction between reaction rate and heat removal rate, reduce the proportion of jacket / external circulation heat removal, reduce the heat transfer deterioration caused by oligomer / polymer adhesion and solidification, and reduce the difficulties brought by gas phase solvent mist entrainment to the design and manufacture of polymerization reactor;

[0063] (3) The present invention increases heat removal by using a large flow external circulation, and continuously introduces gaseous monomers through the micro-interface generator, which meets the monomer quantity requirements of the polymerization reaction.

[0064] In summary, this invention realizes a high-speed polymerization process for large-scale equipment. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the system for preparing polyethylene according to the present invention.

[0066] Explanation of reference numerals in the attached figures

[0067] 100 First Reactor; 101 First Micro-interface Generator Group; 102 Second Micro-interface Generator Group; 103 Third Micro-interface Generator Group; 104 First Cooler; 105 Second Cooler; 106 First Reactor Top Condenser; 107 First Condensate Subcooler; 108 First Material Pipeline; 109 Second Material Pipeline; 110 Third Material Pipeline; 111 Third Cooler; 112 First Collection Tank; 113 First Circulating Air Blower; 114 First Condensate Circulating Pump; 200 Second Reactor; 201 Fourth Micro-interface Generator Group; 202 Fifth Micro-interface Generator Group; 203 Sixth Micro-interface Generator Group; 204 Fourth Cooler; 205 Second Reactor Top Condenser; 206 Second Condensate Subcooler; 207 Fourth Material Pipeline; 208 Fifth Cooler; 209 Second Collection Tank; 210 Second Circulating Air Blower;

[0068] 211 Second condensate circulation pump. Detailed Implementation

[0069] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0070] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0071] The first aspect of the present invention provides a system for preparing polyethylene, such as... Figure 1As shown, the system includes at least one micro-interface generator and at least one reaction vessel. Ethylene-containing gaseous feedstock, solvent, and auxiliary catalyst are processed by at least one micro-interface generator and then enter at least one of the reaction vessels to react with the catalyst. At least a portion of the liquid phase from the reaction vessel is cooled by a cooler and returned to the reaction vessel for reuse. The gaseous phase from the reaction vessel is condensed by a condenser at the top of the vessel, and the resulting gaseous product is returned to the reaction vessel for reuse. The resulting liquid product is condensed and returned to the reaction vessel for reuse.

[0072] Specifically, such as Figure 1 As shown, the system includes a first reaction vessel 100, a first micro-interface generator group 101, a second micro-interface generator group 102, and a third micro-interface generator group 103.

[0073] like Figure 1 As shown, at the start of the reaction, the first ethylene-containing gaseous raw material (continuously fed gaseous material), solvent, and auxiliary catalyst (continuously fed liquid material) are processed in the first micro-interface generator group 101, cooled by the first cooler 104, and then enter the first reactor 100 to mix with the catalyst for the first polymerization reaction; the mixture obtained after processing in the first micro-interface generator group 101 is cooled by the first cooler 104 and then enters the first reactor 100 for reaction, which is the cooling process through cold feeding.

[0074] Depending on the size of the device and the actual flow rate, micro-interface generator groups 101, 102, and 103 can each contain one or more micro-interface generators. Micro-interface generator groups 101 and 103 can also be combined into one micro-interface generator (group).

[0075] like Figure 1 As shown, after the reaction occurs in the first reactor 100, a portion of the first liquid phase from the first reactor 100 is cooled by the second cooler 105 and then processed with the first ethylene-containing gaseous raw material in the second micro-interface generator group 102 before being returned to the first reactor 100 for reuse. By exporting a portion of the first liquid phase obtained from the first reactor 100, cooling it through the second cooler 105, and then returning it to the first reactor 100 for reuse, external circulation of the liquid phase for heat removal is achieved.

[0076] In this invention, if there is only one reactor, a portion of the first liquid phase from the first reactor 100 is reused, while the other portion is post-processed to obtain polyethylene. If multiple reactors are connected in parallel or series, the other portion of the first liquid phase from the first reactor 100 is used as the liquid phase material for the next reactor.

[0077] like Figure 1As shown, after the reaction occurs in the first reactor 100, the first gaseous phase from the first reactor 100 is condensed by the first reactor top condenser 106, and the resulting first gaseous product is returned to the first reactor 100 for reuse. The resulting first liquid product is condensed by the first condensate subcooler 107 and then treated with the first ethylene-containing gaseous raw material in the third micro-interface generator group 103. After being combined with the first product from the first micro-interface generator group 101, the product is cooled by the first cooler 104 and then enters the first reactor 100 for reuse. By condensing the first gaseous phase of the first reactor 100 and returning the resulting first gaseous product to the first reactor 100 for reuse, and by condensing the first liquid product again and returning it to the first reactor 100 for reuse, the external circulation condensation and heat removal of the gaseous phase is achieved.

[0078] In a preferred embodiment, the system further includes a first circulating gas blower 113, and the first gaseous product obtained after the first gas phase is condensed by the first reactor top condenser 106 is blown into the first reactor 100 for reuse by the first circulating gas blower 113.

[0079] In specific embodiments, all reaction vessels used in this invention have jackets and internal cooling pipes, which can be used to remove heat during the reaction process.

[0080] In the system described in this invention, the reactor is equipped with multiple micro-interface generator groups. Before entering the reactor, the gaseous raw materials are dispersed and broken into microbubbles to form a gas-liquid emulsion with a high specific surface area. This can increase the mass transfer area between the gaseous raw materials and the liquid materials, improve the reaction efficiency, and reduce energy consumption. At the same time, the gas-liquid phase is mixed more uniformly, resulting in a product with higher uniformity and improved product quality.

[0081] In this invention, the first micro-interface generator group 101, the second micro-interface generator group 102, and the third micro-interface generator group 103 can be conventional choices in the art. In specific embodiments, the first micro-interface generator group 101, the second micro-interface generator group 102, and the third micro-interface generator group 103 can each be independently selected from a pneumatic bubble breaker type, a hydraulic bubble breaker type, or a pneumatic-hydraulic linkage bubble breaker type.

[0082] In this invention, at the start of the reaction, the liquid material comes from a continuous feed (a mixture of solvent and auxiliary catalyst). After the reaction occurs, the liquid material comes from the continuous feed and the external circulation of the solution in the reactor and the solution obtained by gas-phase condensation in the reactor.

[0083] In this invention, the gaseous material originates from a continuously fed first ethylene-containing gaseous feedstock and a liquid product that has not liquefied after gas-phase condensation in the reactor. In addition to ethylene monomer, the first ethylene-containing gaseous feedstock may also contain gaseous reaction aids as needed for the actual reaction.

[0084] The feeding unit of the first reactor 100 includes three feeding lines, specifically a first material line 108, a second material line 109, and a third material line 110. The first material line 108 is used to provide a first ethylene-containing gaseous feedstock, the second material line 109 is used to provide a solvent and an auxiliary catalyst, and the third material line 110 is used to provide a catalyst.

[0085] In a preferred embodiment, the polyethylene preparation system further includes a third cooler 111, through which the solvent and auxiliary catalyst from the second material pipeline 109 are cooled before entering the first micro-interface generator group 101. In this invention, by cooling the solvent and auxiliary catalyst and enhancing the cold feed method, the purpose of heat removal from the reaction is further achieved.

[0086] In a specific embodiment, the system of the present invention further includes a first collection tank 112 for collecting the first gaseous product and the first liquid product obtained after condensation by the first reactor top condenser 106; the first gaseous product may still contain gaseous materials that have not been completely reacted, and the first gaseous product is returned to the first reactor 100 for reuse; the first liquid product is condensed by the first condensate subcooler 107 and dispersed and mixed with the continuously fed first ethylene-containing gaseous raw material in the third micro-interface generator group 103.

[0087] In a more specific embodiment, the system further includes a first condensate circulation pump 114, through which the condensate obtained after the first liquid product is condensed by the first condensate subcooler 107 is pumped into the third micro-interface generator group 103.

[0088] In a preferred embodiment, the polyethylene preparation system includes two reactors for continuous industrial production.

[0089] In specific implementations, such as Figure 1 As shown, the polyethylene preparation system also includes a second reaction vessel 200, a fourth micro-interface generator group 201, a fifth micro-interface generator group 202, and a sixth micro-interface generator group 203.

[0090] like Figure 1As shown, the second ethylene-containing gaseous feedstock (continuously fed gaseous material) and another portion of the first liquid phase (the first liquid phase is the liquid phase obtained after the reaction in the first reactor 100, including the catalyst) are processed in the fourth micro-interface generator group 201 and then enter the second reactor 200 to carry out the second polymerization reaction.

[0091] like Figure 1 As shown, a portion of the second liquid phase from the second reactor 200 is cooled by the fourth cooler 204 and then treated with the second ethylene-containing gaseous raw material in the fifth micro-interface generator group 202. After being combined with the second product obtained from the treatment of the fourth micro-interface generator group 201, it enters the second reactor 200 for reuse, realizing external circulation and heat removal of the liquid phase. Another portion of the second liquid phase undergoes post-processing to obtain polyethylene.

[0092] Depending on the size of the device and the actual flow rate, micro-interface generator groups 201, 202, and 203 can each contain one or more micro-interface generators. Micro-interface generator groups 201 and 202 can also be combined into one micro-interface generator (group).

[0093] like Figure 1 As shown, the second gaseous phase from the second reactor 200 is condensed by the second reactor top condenser 205, and the resulting second gaseous product is returned to the second reactor 200 for reuse. The resulting second liquid product is condensed by the second condensate subcooler 206 and then processed with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group 203 before entering the second reactor 200 for reuse, thus realizing external circulation condensation and heat removal of the gas phase.

[0094] In a more specific embodiment, the system further includes a second condensate circulation pump 211, through which the condensate obtained after the second liquid product is condensed by the second condensate subcooler 206 is pumped into the sixth micro-interface generator group 203.

[0095] In the system described in this invention, the liquid phase material and catalyst used in the second reaction vessel 200 are both derived from the first liquid phase obtained from the reaction in the first reaction vessel 100. When another part of the first liquid phase from the first reaction vessel 100 enters the second reaction vessel 200 for reaction, it brings in the solvent, auxiliary catalyst and catalyst required for the reaction.

[0096] In a specific embodiment, the second reactor 200 requires a continuous feed of gaseous material for the reaction. In a preferred embodiment, the polyethylene preparation system further includes a fourth material pipeline 207, which is used to provide the second ethylene-containing gaseous feedstock, continuously supplying gaseous material for the reaction in the second reactor 200.

[0097] The system of this invention also includes a fifth cooler 208, through which another portion of the first liquid phase from the first reactor 100 is cooled before entering the fourth micro-interface generator group 201. By cooling another portion of the first liquid phase, the cold feeding method is enhanced, further achieving the purpose of heat removal from the reaction.

[0098] In a specific embodiment, the polyethylene preparation system further includes a second collection tank 209 for collecting the second gaseous product and the second liquid product obtained after condensation by the second reactor top condenser 205. The second collection tank 209 has the same function as the first collection tank 112, and will not be described again here.

[0099] In a preferred embodiment, the system further includes a second circulating gas blower 210, and the second gaseous product obtained after the second gas phase is condensed by the second reactor top condenser 205 is blown into the second reactor 200 for reuse by the second circulating gas blower 210.

[0100] In a specific embodiment, the upper part of the gas phase space inside the first reactor 100 and the second reactor 200 is equipped with a demister, and the liquid phase part is equipped with a gamma ray control device for liquid level control.

[0101] In a preferred embodiment, the demister is selected from one or more of wire mesh demisters, spherical demisters, baffle plate demisters, and centrifugal demisters, preferably a wire mesh demister and / or a spherical demister, more preferably a combination of a baffle plate demister and a wire mesh demister or a combination of a baffle plate demister and a spherical demister.

[0102] In a preferred embodiment, the gamma-ray level control device includes a gamma-ray source positioned near the level of the reaction bath to be contained in the reactor and a gamma-ray detector that is opposite in diameter to the gamma-ray source and extends vertically along the entire height of the reaction bath.

[0103] A second aspect of the present invention provides a method for preparing polyethylene, said method being carried out in a polyethylene preparation system comprising at least one micro-interface generator and at least one reaction vessel.

[0104] After being processed in at least one micro-interface generator, the ethylene-containing gaseous feedstock, solvent, and auxiliary catalyst are introduced into at least one of the reactors to react with the catalyst. At least a portion of the liquid phase from the reactor is cooled by a cooler and returned to the reactor for reuse. The gaseous phase from the reactor is condensed by a condenser at the top of the reactor, and the resulting gaseous product is returned to the reactor for reuse. The resulting liquid product is condensed and returned to the reactor for reuse.

[0105] In a specific embodiment, the method is implemented in a polyethylene preparation system comprising a first reaction vessel 100, a first micro-interface generator group 101, a second micro-interface generator group 102, and a third micro-interface generator group 103.

[0106] The method includes the following steps:

[0107] At the start of the reaction, the first ethylene-containing gaseous raw material, solvent and auxiliary catalyst are sequentially passed into the first micro-interface generator group 101 and the first cooler 104 for treatment, and then enter the first reaction vessel 100 to be mixed with the catalyst to carry out the first polymerization reaction.

[0108] After the reaction occurs in the first reactor 100, a portion of the first liquid phase from the first reactor 100 is cooled in the second cooler 105 and then processed with the first ethylene-containing gaseous raw material in the second micro-interface generator group 102 before being returned to the first reactor 100 for reuse.

[0109] After the reaction occurs in the first reactor 100, the first gaseous phase from the first reactor 100 is condensed in the first reactor top condenser 106 to obtain a first gaseous product and a first liquid product. The first gaseous product is returned to the first reactor 100 for reuse. The first liquid product is condensed in the first condensate subcooler 107 and then processed with the first ethylene-containing gaseous raw material in the third micro-interface generator group 103. After being combined with the first product from the first micro-interface generator group 101, it is cooled by the first cooler 104 and then enters the first reactor 100 for reuse.

[0110] In the method described herein, heat removal is achieved through various methods such as cold feeding, liquid-phase external circulation heat removal, and gas-phase external circulation condensation heat removal.

[0111] In a specific implementation, the method further includes:

[0112] The second ethylene-containing gaseous feedstock (continuously fed gaseous material) and another part of the first liquid phase (the first liquid phase is the liquid phase obtained after the reaction in the first reactor 100, including the catalyst) are processed in the fourth micro-interface generator group 201 and then introduced into the second reactor 200 to carry out the second polymerization reaction.

[0113] A portion of the second liquid phase from the second reactor 200 is cooled in the fourth cooler 204 and then treated with the second ethylene-containing gaseous feedstock in the fifth micro-interface generator group 202. After being combined with the second product obtained from the treatment of the fourth micro-interface generator group 201, it is recycled back into the second reactor 200 to achieve external circulation and heat removal of the liquid phase. Another portion of the second liquid phase is post-treated to obtain polyethylene.

[0114] The second gaseous phase from the second reactor 200 is condensed in the second reactor top condenser 205 to obtain a second gaseous product and a second liquid product. The second gaseous product is returned to the second reactor 200 for reuse. The second liquid product is condensed in the second condensate subcooler 206 and then treated with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group 203 before entering the second reactor 200 for reuse, thus realizing external circulation condensation and heat removal of the gas phase.

[0115] In the method described in this invention, the first ethylene-containing gaseous feedstock and the second ethylene-containing gaseous feedstock each independently contain ethylene and an optional gaseous reaction aid. The gaseous reaction aid may be a gaseous comonomer or a gaseous chain transfer agent, etc.; preferably, the gaseous comonomer is propylene and / or butene; preferably, the gaseous molecular weight regulator is hydrogen.

[0116] In this invention, the solvent can be C3-C. 30 Aliphatic alkanes and / or aromatic compounds.

[0117] In a specific implementation, the C3-C 30 Aliphatic alkanes may be selected from one or more of propane, butane, pentane, hexane, heptane, octane, and cyclohexane.

[0118] In a specific implementation, the aromatic compound may be toluene.

[0119] To further improve the heat removal effect, reduce heat transfer deterioration, and enhance the polymerization effect, under optimal conditions, a solvent that can enhance gas-phase condensation heat removal is used.

[0120] In a preferred embodiment, the solvent is selected from combinations of pentane and cyclopentane, propane and hexane, propane and heptane, propane and cyclohexane, propane and heptane and cyclohexane, propane and hexane and cyclohexane, butane and hexane, butane and heptane, butane and cyclohexane, butane and heptane and cyclohexane, butane and hexane and cyclohexane, pentane, or cyclopentane. In a preferred embodiment, except for pentane and cyclopentane used alone as solvents, the others are combinations of two or three solvents.

[0121] When the solvent is a combination of propane and hexane, a combination of propane and heptane, or a combination of propane and cyclohexane, the content of propane is 5-40 wt%, preferably 20-30 wt%.

[0122] When the solvent is a combination of propane, heptane, and cyclohexane, or a combination of propane, hexane, and cyclohexane, the content of propane is 5-40 wt%, preferably 20-30 wt%; and the content of cyclohexane is 5-80 wt%, preferably 20-50 wt%.

[0123] When the solvent is a combination of butane and hexane, a combination of butane and heptane, or a combination of butane and cyclohexane, the content of butane is 5-40 wt%, preferably 20-30 wt%.

[0124] When the solvent is a combination of butane, heptane, and cyclohexane or a combination of butane, hexane, and cyclohexane, the content of butane is 5-40 wt%, preferably 20-30 wt%; and the content of cyclohexane is 5-80 wt%, preferably 20-50 wt%.

[0125] In this invention, the catalyst can be a complex of a later transition metal. In a preferred embodiment, the later transition metal is nickel and / or palladium. In a more preferred embodiment, the catalyst is a diimine complex of nickel and / or palladium.

[0126] In the method described in this invention, the auxiliary catalyst is selected from one or more of aluminoxane, alkylaluminum, and alkylaluminum chloride.

[0127] In a preferred embodiment, the aluminum oxane is selected from one or more of methylaluminoxane, triisobutylaluminum-modified methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane.

[0128] In a preferred embodiment, the alkylaluminum is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum.

[0129] In a preferred embodiment, the alkylaluminum chloride is selected from one or more of dimethylaluminum chloride, diethylaluminum chloride, ethylaluminum dichloride, and trichlorotriethylaluminum.

[0130] In the method described in this invention, the ratio of the auxiliary catalyst to the catalyst can be a conventional choice in the art.

[0131] In a specific embodiment, based on the metal elements contained in the catalyst and the auxiliary catalyst, the molar ratio of the auxiliary catalyst to the catalyst is 100-4000:1, preferably 400-1000:1.

[0132] In the method described in this invention, the temperature of the first polymerization reaction can be 0℃-250℃, preferably 50-80℃; the pressure of the first polymerization reaction can be 0.1-5MPa, preferably 0.5-1.5MPa.

[0133] In the method described in this invention, the temperature of the second polymerization reaction can be 0℃-250℃, preferably 50-80℃; the pressure of the second polymerization reaction can be 0.1-5MPa, preferably 0.5-1.5MPa.

[0134] In the method described in this invention, the temperature difference between the inlet and outlet of the first liquid phase passing through the second cooler 105 and the fifth cooler 208, and the temperature difference between the second liquid phase passing through the fourth cooler 204, is less than 10°C, preferably less than 5°C, and more preferably less than 2°C. That is, the temperature differences between the inlet and outlet of the first liquid phase passing through the second cooler 105, the first liquid phase passing through the fifth cooler 208, and the second liquid phase passing through the fourth cooler 204 are all less than 10°C, preferably less than 5°C, and more preferably less than 2°C. The small temperature differences between the inlet and outlet of the second cooler 105, the fifth cooler 208, and the fourth cooler 204 can make the reactions in the two reactors more stable.

[0135] In this invention, the process of post-processing the liquid phase obtained from the reaction in the reactor to obtain polyethylene includes, but is not limited to, common processes in the art such as monomer removal, washing, separation, drying, granulation, and briquetting. The separation process can be selected from commonly known wet coagulation, dry devolatilization, or precipitation separation processes. The monomers or solvents obtained from the post-processing can be recycled and reused.

[0136] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0137] Test method:

[0138] (1) Branching degree and branch distribution:

[0139] The degree of branching of the polymer was determined using 13C NMR: polyethylene was dissolved in 1,2-o-dichlorobenzene, and TMS was used as an internal standard. The sample was measured on a Bruker AVANCE III 500MHz spectrometer. The temperature was set at 100°C, and the number of scans was approximately 3000 (the operating conditions used were a spectral width of 18.8324kHz, a data acquisition time of 0.87s, and a delay of 2s).

[0140] (2) Melting point:

[0141] DSC testing was used, with a temperature range of -50 to 150℃. The temperature change process was as follows:

[0142] First stage: From room temperature to 150℃, heating rate is 10℃ / min, and then hold at 150℃ for 2min;

[0143] Second stage: Temperature drop from 150℃ to -50℃ at a rate of 10℃ / min, and hold at -50℃ for 2 minutes.

[0144] The third stage: from -50℃ to 150℃, the heating rate is 10℃ / min, then the temperature is reduced to 40℃, and the test ends. The melting point is obtained from the melting peak of the third stage heating curve.

[0145] (3) Polymer molecular weight (Mw) and molecular weight distribution (PDI) were determined by high-temperature gel permeation chromatography (PL-GPC220) with 1,2,4-trichlorobenzene as the mobile phase and polystyrene as the standard at 150℃.

[0146] (4) Melt flow rate (melt index): Tested according to standard ASTM D1238 at 190°C and 2.16 kg.

[0147] The following embodiments are all based on the example provided. Figure 1 The system for preparing polyethylene shown is implemented in a manner comprising a first reactor 100, a first micro-interface generator group 101, a second micro-interface generator group 102, a third micro-interface generator group 103, a second reactor 200, a fourth micro-interface generator group 201, a fifth micro-interface generator group 202, and a sixth micro-interface generator group 203.

[0148] The first material pipeline 108 is used to provide a first ethylene-containing gaseous feedstock, the second material pipeline 109 is used to provide a solvent and an auxiliary catalyst, and the third material pipeline 110 is used to provide a catalyst. The solvent and auxiliary catalyst from the second material pipeline 109 are cooled by the third cooler 111 and then enter the first micro-interface generator group 101. The first ethylene-containing gaseous feedstock, solvent and auxiliary catalyst are processed in the first micro-interface generator group 101 and then cooled by the first cooler 104 before entering the first reactor 100 to be mixed with the catalyst to carry out the first polymerization reaction.

[0149] A portion of the first liquid phase from the first reactor 100 is cooled by the second cooler 105 and then processed with the first ethylene-containing gaseous raw material in the second micro-interface generator group 102 before being returned to the first reactor 100 for reuse.

[0150] The first gaseous phase from the first reactor 100 is condensed by the first reactor top condenser 106. The first collection tank 112 is used to collect the first gaseous product and the first liquid product obtained after condensation by the first reactor top condenser 106. The first gaseous product is returned to the first reactor 100 for reuse by the first circulating air blower 113. The condensate obtained after the first liquid product is condensed by the first condensate subcooler 107 is pumped into the third micro-interface generator group 103 by the first condensate circulation pump 114. It is processed in the third micro-interface generator group 103 with the first ethylene-containing gaseous raw material. Then, it is combined with the first product from the first micro-interface generator group 101 and cooled by the first cooler 104 before entering the first reactor 100 for reuse.

[0151] The fourth material line 207 is used to provide the second ethylene-containing gaseous feedstock. Another part of the first liquid phase from the first reactor 100 is cooled by the fifth cooler 208 and then treated with the second ethylene-containing gaseous feedstock in the fourth micro-interface generator group 201 before entering the second reactor 200 to carry out the second polymerization reaction.

[0152] After being cooled by the fourth cooler 204, a portion of the second liquid phase from the second reactor 200 is treated with the second ethylene-containing gaseous raw material in the fifth micro-interface generator group 202 and then combined with the second product obtained from the fourth micro-interface generator group 201 before entering the second reactor 200 for reuse. Another portion of the second liquid phase undergoes post-processing to obtain polyethylene.

[0153] The second gas phase from the second reactor 200 is condensed by the second reactor top condenser 205. The second collection tank 209 is used to collect the second gaseous product and the second liquid product obtained after condensation by the second reactor top condenser 205. The second gaseous product is returned to the second reactor 200 for reuse by the second circulating air blower 210. The condensate obtained after the second liquid product is condensed by the second condensate subcooler 206 is pumped into the sixth micro-interface generator group 203 by the second condensate circulation pump 211. After being processed in the sixth micro-interface generator group 203 with the second ethylene-containing gaseous raw material, it is then returned to the second reactor 200 for reuse.

[0154] The first reactor 100 and the second reactor 200 are equipped with demisters in the upper part of the gas phase space and gamma ray control devices for liquid level control in the liquid phase section. The demisters are selected from one or more of wire mesh demisters, spherical demisters, baffle plate demisters and centrifugal demisters, preferably wire mesh demisters and / or spherical demisters, more preferably a combination of baffle plate demisters and wire mesh demisters or a combination of baffle plate demisters and spherical demisters. The gamma ray liquid level control device includes a gamma ray source placed near the liquid level of the reaction bath to be contained in the reactor and a gamma ray detector opposite to the diameter of the gamma ray source and extending vertically along the entire height of the reaction bath.

[0155] The following embodiments are all implemented according to the following methods:

[0156] The monomer, solvent and auxiliary catalyst are sequentially passed into the first micro-interface generator group 101 and the first cooler 104 for treatment, and then enter the first reaction vessel 100 to be mixed with the catalyst to carry out the first polymerization reaction.

[0157] After a portion of the first liquid phase from the first reactor 100 is cooled in the second cooler 105 and processed with the first ethylene-containing gaseous feedstock in the second micro-interface generator group 102, it is returned to the first reactor 100 for reuse.

[0158] The first gaseous phase from the first reactor 100 is condensed in the first reactor top condenser 106 to obtain a first gaseous product and a first liquid product. The first gaseous product is returned to the first reactor 100 for reuse. The first liquid product is condensed in the first condensate subcooler 107 and then processed with the first ethylene-containing gaseous feedstock in the third micro-interface generator group 103. After being combined with the first product from the first micro-interface generator group 101, it is cooled by the first cooler 104 and then enters the first reactor 100 for reuse.

[0159] After the polymerizable monomer and another portion of the first liquid phase from the first reactor 100 are treated in the fourth micro-interface generator group 201, they are introduced into the second reactor 200 to carry out a second polymerization reaction.

[0160] A portion of the second liquid phase from the second reactor 200 is cooled in the fourth cooler 204 and then treated with the second ethylene-containing gaseous feedstock in the fifth micro-interface generator group 202. After being combined with the second product obtained from the treatment of the fourth micro-interface generator group 201, it is recycled into the second reactor 200. Another portion of the second liquid phase is post-treated to obtain polyethylene.

[0161] The second gaseous phase from the second reactor 200 is condensed in the second reactor top condenser 205 to obtain a second gaseous product and a second liquid product. The second gaseous product is returned to the second reactor 200 for reuse. The second liquid product is condensed in the second condensate subcooler 206 and then treated with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group 203 before entering the second reactor 200 for reuse.

[0162] Example 1

[0163] In this embodiment, the production scale of the polyethylene preparation system is 0.10 million tons / year; the first reactor 100 and the second reactor 200 are 1m³. 3 The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.0 MPa, and the reaction temperature is 70 °C; the solvent is hexane with a flow rate of 1.44 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A, with a feed flow rate of 10 g / h; the auxiliary catalyst is 1 M trichlorotriethylaluminum with a feed flow rate of 2 L / h; the polymerization monomer is ethylene, and the polymerization rate is 0.125 t / h.

[0164] Calculations show that the total heat release of the polymerization reaction system reaches 118.1 kW, of which 87.2 kW is from the first reactor 100 and 30.8 kW from the second reactor 200. The heat removed by the cold 10°C feedstock in the first reactor 100 is 55.1 kW, accounting for 63.2% of the total heat removal required in the first reactor 100. Based on the entrainment gas velocity, the heat removed by solvent evaporation in both the first reactor 100 and the second reactor 200 is 27.6 kW, accounting for 31.7% and 89.8% of the total heat removal required in the first reactor 100 and second reactor 200, respectively. The jacket area of ​​the polymerization reactor is 5.8 m². 2 The heat removal capacity of the jackets of the first reactor 100 and the second reactor 200 is 4.5 kW and 3.2 kW, respectively, accounting for 5.1% and 10.2% of the total heat removal capacity of the first reactor 100 and the second reactor 200. The jackets only need a heat transfer temperature difference of 1.6℃ and 1.1℃, which is almost constant temperature; the liquid phase external circulation heat exchanger is not working.

[0165] The polyethylene elastomer P1 obtained after post-processing of the polymer solution has a melting point of 63℃ and a branching degree of 102 branches / 1000℃ (including 72 C1 side chains, 22 C2-C5 side chains, and 8 long side chains above C6); the melt index at 190℃ and 2.16kg is 11g / 10min, the weight-average molecular weight (Mw) is 72,000, and the molecular weight distribution index (PDI) is 2.0.

[0166] Comparative Example 1

[0167] The system and method of Example 1 are implemented, except that the system for preparing polyethylene does not have the individual micro-interface generator groups, the individual reactor top condensers, the second cooler 105, and the fourth cooler 204.

[0168] In this comparative example, the production scale of the polyethylene preparation system is 0.08 million tons / year; the first reactor 100 and the second reactor 200 are 1m³. 3 The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.0 MPa, and the reaction temperature is 70 °C; the solvent is hexane with a flow rate of 1.44 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A, with a feed flow rate of 10 g / h; the auxiliary catalyst is 1 M trichlorotriethylaluminum with a feed flow rate of 2 L / h; the polymerization monomer is ethylene, and the polymerization rate is 0.1 t / h.

[0169] Calculations show that the total heat release of the polymerization reaction system reaches 94.5 kW, of which 69.6 kW is from the first reactor 100 and 24.6 kW from the second reactor 200. The heat removed by the raw material fed into the first reactor 100 at room temperature (25°C) is 41.3 kW, accounting for 59.3% of the total heat removal required in the first reactor 100; the jacket area of ​​the polymerization reactor is 5.8 m². 2 The heat removal capacity of the jackets of the first reactor 100 and the second reactor 200 is 28.3 kW and 24.6 kW, respectively, accounting for 40.7% and 100% of the total heat removal capacity required by the first reactor 100 and the second reactor 200, respectively, and the heat transfer temperature difference is 9.8℃ and 8.5℃, respectively.

[0170] The polyethylene elastomer P2 obtained by the post-processing of the obtained polymerization solution has a melting point of 58℃, a branching degree of 120 branches / 1000℃ (of which there are 84 C1 side chains, 27 C2-C5 side chains, and 9 long side chains above C6); a melt index of 16 g / 10 min at 190℃ and 2.16 kg, a weight-average molecular weight (Mw) of 65,000, and a molecular weight distribution index (PDI) of 2.4.

[0171] Comparing Example 1 with Comparative Example 1, it can be seen that the micro-interface enhanced reaction technology was adopted. Under the same conditions, the reaction rate was improved, the catalyst utilization rate was improved, the molecular weight of the obtained polyethylene elastomer was improved, and the melting point was improved.

[0172] Example 2

[0173] In this embodiment, the production scale of the polyethylene preparation system is 10,000 tons / year, and the first reactor 100 and the second reactor 200 are 10m³.3 The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.2 MPa, and the reaction temperature is 70 °C; the solvent is pentane with a flow rate of 14.4 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A with a feed flow rate of 100 g / h; the auxiliary catalyst is 1 M trichlorotriethylaluminum with a feed flow rate of 20 L / h; the polymerization monomer is ethylene, and the polymerization rate is 1.25 t / h.

[0174] Calculations show that the total heat release of the polymerization reaction system reaches 1181 kW, of which 872 kW is from the first reactor 100 and 309 kW from the second reactor 200. The heat removed by the cold 10°C feedstock in the first reactor 100 is 551 kW, accounting for 63.2% of the total heat removal required in the first reactor 100. Based on the entrainment gas velocity, the heat removed by solvent evaporation in both the first reactor 100 and the second reactor 200 is 300.3 kW, accounting for 34.4% and 97.5% of the total heat removal required in the first reactor 100 and second reactor 200, respectively. The jacket area of ​​the polymerization reactor is 26.9 m². 2 The heat removal capacity of the jackets of the first reactor 100 and the second reactor 200 is 21.1 kW and 7.8 kW, respectively, accounting for 2.4% and 10.2% of the total heat removal capacity of the first reactor 100 and the second reactor 200. The jackets only need a heat transfer temperature difference of 1.6℃ and 0.6℃, which is almost constant temperature; the liquid phase external circulation heat exchanger is not working.

[0175] The obtained polymerization solution was post-processed to obtain polyethylene elastomer P3 with a melting point of 62℃, a branching degree of 105 branches / 1000℃ (of which there are 74 C1 side chains, 23 C2-C5 side chains, and 8 long side chains above C6); a melt index of 12g / 10min (190℃, 2.16kg), a weight-average molecular weight (Mw) of 71,000, and a molecular weight distribution index (PDI) of 2.1.

[0176] Comparative Example 2

[0177] The system and method of Example 2 are implemented, except that the system for preparing polyethylene does not have individual top condensers, nor does it have a second cooler 105 or a fourth cooler 204.

[0178] In this comparative example, the production scale of the system for preparing polyethylene is 10,000 tons / year; the first reactor 100 and the second reactor 200 are 10m³. 3The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.0 MPa, and the reaction temperature is 70 °C; the solvent is hexane with a flow rate of 14.4 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A, with a feed flow rate of 100 g / h; the auxiliary catalyst is 1 M trichlorotriethylaluminum with a feed flow rate of 20 L / h; the polymerization monomer is ethylene, and the polymerization rate is 1.25 t / h.

[0179] Calculations show that the total heat release of the polymerization reaction system reaches 1181 kW, of which 872 kW is from the first reactor 100 and 308 kW from the second reactor 200. The heat removed by the raw material fed into the first reactor 100 at room temperature (25°C) is 413 kW, accounting for 47.4% of the total heat removal required in the first reactor 100; the jacket area of ​​the polymerization reactor is 26.9 m². 2 The heat removal capacity of the jackets of the first reactor 100 and the second reactor 200 is 459 kW and 308 kW, respectively, accounting for 52.6% and 100% of the total heat removal capacity required by the first reactor 100 and the second reactor 200, respectively, and the heat transfer temperature difference is 34℃ and 22.9℃, respectively.

[0180] The obtained polymerization solution was post-processed to obtain polyethylene elastomer P4 with a melting point of 61℃, a branching degree of 104 branches / 1000℃ (of which 74 are C1 side chains, 22 are C2-C5 side chains, and 8 are long side chains above C6); a melt index of 13g / 10min (190℃, 2.16kg); a weight-average molecular weight (Mw) of 70,000; and a molecular weight distribution index (PDI) of 2.2.

[0181] Example 3

[0182] In this embodiment, the production scale of the polyethylene preparation system is 100,000 tons / year; the first reactor 100 and the second reactor 200 are 100m³. 3 The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.2 MPa, and the reaction temperature is 70 °C; the solvent is pentane with a flow rate of 144 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A, with a feed flow rate of 1000 g / h; the auxiliary catalyst is 1M trichlorotriethylaluminum with a feed flow rate of 200 L / h; the polymerization monomer is ethylene, and the polymerization rate is 12.5 t / h.

[0183] Calculations show that the total heat release of the polymerization reaction system reaches 11806 kW, of which 8724 kW is from the first reactor 100 and 3081 kW from the second reactor 200. The heat removed by the raw material fed into the first reactor 100 at a cold temperature of 10°C is 5510 kW, accounting for 63.2% of the total heat removal required in the first reactor 100. Based on the entrainment gas velocity, the heat removed by solvent evaporation in both the first reactor 100 and the second reactor 200 is 1360 kW, accounting for 15.6% and 45.3% of the total heat removal required in the first reactor 100 and the second reactor 200, respectively. The jacket area of ​​the polymerization reactor is 125 m². 2 The heat removal capacity of the jackets and external circulation of the first reactor 100 and the second reactor 200 is 724 kW and 593 kW, respectively, accounting for 8.3% and 19.2% of the total heat removal capacity required by the first reactor 100 and the second reactor 200. The jackets only require a heat transfer temperature difference of 29.2℃ and 27.0℃. If the heat transfer temperature difference is limited to within 20℃, then an additional heat transfer area of ​​57 m² is required, respectively. 2 and 44m 2 Liquid phase external circulation heat exchanger.

[0184] The resulting polymerization solution, after post-processing, yielded polyethylene elastomer P5 with a melting point of 62℃ and a branching degree of 105 branches / 1000℃ (74 C1 side chains, 23 C2-C5 side chains, and 8 long side chains above C6); a melt index of 12 g / 10 min (190℃, 2.16 kg); a weight-average molecular weight (Mw) of 71,000; and a molecular weight distribution index (PDI) of 2.2.

[0185] Example 4

[0186] In this embodiment, the production scale of the polyethylene preparation system is 100,000 tons / year; the first reactor 100 and the second reactor 200 are 100m³. 3 The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.2 MPa, and the reaction temperature is 70 °C; the solvent is hexane with a flow rate of 144 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A, with a feed flow rate of 1000 g / h; the auxiliary catalyst is 1M trichlorotriethylaluminum with a feed flow rate of 200 L / h; the polymerization monomer is ethylene, and the polymerization rate is 12.5 t / h.

[0187] Calculations show that the total heat release of the polymerization reaction system reaches 11806 kW, with 8724 kW in the first reactor and 3081 kW in the second reactor. The heat removed by the first reactor's feed at room temperature (25°C) is 4133 kW, accounting for 47.4% of the total heat removal required for the first reactor. Based on the entrainment gas velocity, the heat removed by solvent evaporation in both the first and second reactors is 598 kW, accounting for 6.8% and 19.4% of the total heat removal required for the first and second reactors, respectively. The jacket area of ​​the polymerization reactor is 125 m². 2 The heat removal capacity of the first and second reactor jackets is 3996 kW and 2485 kW, respectively, accounting for 45.8% and 80.6% of the total heat removal capacity required for the first and second reactors. The heat transfer temperature differences are 63.9℃ and 39.8℃, respectively. If the heat transfer temperature difference is limited to within 20℃, an additional heat transfer area of ​​275 m² is required for each jacket. 2 and 124m 2 Liquid phase external circulation heat exchanger.

[0188] The obtained polymerization solution was post-processed to obtain polyethylene elastomer P6 with a melting point of 60℃, a branching degree of 110 branches / 1000℃ (of which 78 are C1 side chains, 24 are C2-C5 side chains, and 8 are long side chains above C6); a melt index of 15g / 10min (190℃, 2.16kg); a weight-average molecular weight (Mw) of 69,000; and a molecular weight distribution index (PDI) of 2.2.

[0189] Example 5

[0190] In this embodiment, the production scale of the polyethylene preparation system is 100,000 tons / year, and the first reactor 100 and the second reactor 200 are 100m³. 3 The polymerization reactor has a height-to-diameter ratio (H / D) of 1.50; the reaction pressure of the first reactor 100 and the second reactor 200 is 1.2 MPa, and the reaction temperature is 70 °C; the solvent is a combination of propane (25 wt%) and hexane (75 wt%), with a flow rate of 144 t / h; the catalyst is the post-transition metal diimide nickel complex Ni2 from patent application CN116239494A, with a feed flow rate of 1000 g / h; the auxiliary catalyst is 1 M trichlorotriethylaluminum, with a feed flow rate of 200 L / h; the polymerization monomer is ethylene, and the polymerization rate is 12.5 t / h.

[0191] Calculations show that the total heat release of the polymerization reaction system reaches 11806 kW, of which 8724 kW is from the first reactor 100 and 3081 kW is from the second reactor 200. The heat removed by the raw material fed into the first reactor 100 at a cold temperature of 10°C is 5510 kW, accounting for 63.2% of the total heat removal required in the first reactor 100. Based on the entrainment gas velocity, the heat removed by solvent evaporation in both the first reactor 100 and the second reactor 200 is 1804 kW, accounting for 20.76% and 58.5% of the total heat removal required in the first reactor 100 and second reactor 200, respectively. The jacket area of ​​the polymerization reactor is 125 m². 2 The heat removal capacity of the jackets and external circulation of the first reactor 100 and the second reactor 200 is 1410 kW and 1278 kW, respectively, accounting for 16.2% and 41.5% of the total heat removal capacity required by the first reactor 100 and the second reactor 200. The jackets only require a heat transfer temperature difference of 22.6℃ and 20.5℃. If the heat transfer temperature difference is limited to within 20℃, then the heat transfer area needs to be increased by 57 m², respectively. 2 and 44m 2 Liquid phase external circulation heat exchanger.

[0192] The obtained polymerization solution was post-processed to obtain polyethylene elastomer P7 with a melting point of 61.5℃, a branching degree of 108 branches / 1000℃ (of which 76 are C1 side chains, 24 are C2-C5 side chains, and 8 are long side chains above C6); a melt index of 12.5 g / 10 min (190℃, 2.16 kg); a weight-average molecular weight (Mw) of 70,000; and a molecular weight distribution index (PDI) of 2.2.

[0193] The process parameters of Examples 1-5 and Comparative Examples 1-2 are summarized in Table 1.

[0194] Table 1

[0195]

[0196]

[0197]

[0198] Therefore, as can be seen from the comparison of the above embodiments and comparative examples, the proportion of heat removal through jacket and external circulation in the embodiments is reduced, and the heat removal effect is good. In large-scale polyethylene industrial production equipment, the combination of the measures of the present invention can effectively remove the heat released by the polymerization reaction, further control the temperature of the polymerization reactor, and enable the polymerization reactor to operate stably for a long period of time.

[0199] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A system for preparing polyethylene, characterized in that, The system includes at least one micro-interface generator and at least one reaction vessel. Ethylene-containing gaseous feedstock, solvent, and auxiliary catalyst are processed by at least one micro-interface generator and then enter at least one of the reaction vessels to react with the catalyst. At least a portion of the liquid phase from the reaction vessel is cooled by a cooler and returned to the reaction vessel for reuse. The gaseous phase from the reaction vessel is condensed by a condenser at the top of the vessel, and the resulting gaseous product is returned to the reaction vessel for reuse. The resulting liquid product is condensed and returned to the reaction vessel for reuse. The system includes a first reaction vessel (100), a first micro-interface generator group (101), a second micro-interface generator group (102), and a third micro-interface generator group (103). The first ethylene-containing gaseous raw material, solvent and auxiliary catalyst are processed in the first micro-interface generator group (101), cooled by the first cooler (104) and then enter the first reactor (100) to be mixed with the catalyst to carry out the first polymerization reaction; A portion of the first liquid phase from the first reactor (100) is cooled by the second cooler (105) and then processed with the first ethylene-containing gaseous raw material in the second micro-interface generator group (102) before being returned to the first reactor (100) for reuse. The first gaseous phase from the first reactor (100) is condensed by the first reactor top condenser (106), and the resulting first gaseous product is returned to the first reactor (100) for reuse. The resulting first liquid product is condensed by the first condensate subcooler (107) and then processed with the first ethylene-containing gaseous raw material in the third micro-interface generator group (103). After being combined with the first product from the first micro-interface generator group (101), the product is cooled by the first cooler (104) and then enters the first reactor (100) for reuse.

2. The system according to claim 1, characterized in that, The system also includes a first material line (108), a second material line (109) and a third material line (110), wherein the first material line (108) is used to provide a first ethylene-containing gaseous feedstock, the second material line (109) is used to provide a solvent and an auxiliary catalyst, and the third material line (110) is used to provide a catalyst.

3. The system according to claim 2, characterized in that, The system also includes a third cooler (111), through which the solvent and auxiliary catalyst from the second material line (109) are cooled before entering the first micro-interface generator group (101).

4. The system according to claim 1, characterized in that, The system also includes a first collection tank (112) for collecting the first gaseous product and the first liquid product obtained after condensation by the first reactor top condenser (106).

5. The system according to claim 1, characterized in that, The system also includes a second reactor (200), a fourth micro-interface generator group (201), a fifth micro-interface generator group (202), and a sixth micro-interface generator group (203). The second ethylene-containing gaseous feedstock and another portion of the first liquid phase from the first reactor (100) are processed in the fourth micro-interface generator group (201) and then enter the second reactor (200) to carry out the second polymerization reaction; A portion of the second liquid phase from the second reactor (200) is cooled by the fourth cooler (204) and then treated with the second ethylene-containing gaseous raw material in the fifth micro-interface generator group (202). After being combined with the second product obtained from the treatment of the fourth micro-interface generator group (201), it is returned to the second reactor (200) for reuse. Another portion of the second liquid phase undergoes post-treatment to obtain polyethylene. The second gaseous phase from the second reactor (200) is condensed by the second reactor top condenser (205), and the resulting second gaseous product is returned to the second reactor (200) for reuse. The resulting second liquid product is condensed by the second condensate subcooler (206) and then processed with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group (203) before entering the second reactor (200) for reuse.

6. The system according to claim 5, characterized in that, The system also includes a fourth material line (207) for providing the second ethylene-containing gaseous feedstock.

7. The system according to any one of claims 5 or 6, characterized in that, The system also includes a fifth cooler (208), through which another portion of the first liquid phase from the first reactor (100) is cooled before entering the fourth micro-interface generator group (201).

8. The system according to claim 5, characterized in that, The system also includes a second collection tank (209) for collecting the second gaseous product and the second liquid product obtained after condensation by the second top condenser (205).

9. The system according to claim 5, characterized in that, The upper part of the gas phase space inside the first reactor (100) and the second reactor (200) is equipped with a demister, and the liquid phase part is equipped with a gamma ray control device for liquid level control.

10. The system according to claim 9, characterized in that, The demister is selected from one or more of the following: wire mesh demister, spherical demister, baffle plate demister, and centrifugal demister.

11. The system according to claim 10, characterized in that, The demister is a wire mesh demister and / or a spherical demister.

12. The system according to claim 10, characterized in that, The demister is a combination of a baffle demister and a wire mesh demister, or a combination of a baffle demister and a spherical demister.

13. The system according to claim 9, characterized in that, The gamma ray control device includes a gamma ray source placed near the liquid level of the reaction bath to be contained in the first reaction vessel (100) and the second reaction vessel (200), and a gamma ray detector opposite in diameter to the gamma ray source and extending vertically along the entire height of the reaction bath.

14. A method for preparing polyethylene, characterized in that, The method is implemented in the system described in any one of claims 1-13; The method includes the following steps: The first ethylene-containing gaseous raw material, solvent and auxiliary catalyst are sequentially passed into the first micro-interface generator group (101) and the first cooler (104) for treatment, and then enter the first reaction vessel (100) to be mixed with the catalyst for the first polymerization reaction; A portion of the first liquid phase from the first reactor (100) is cooled in the second cooler (105) and then processed with the first ethylene-containing gaseous feedstock in the second micro-interface generator group (102) before being returned to the first reactor (100) for reuse. The first gaseous phase from the first reactor (100) is condensed in the first reactor top condenser (106) to obtain a first gaseous product and a first liquid product. The first gaseous product is returned to the first reactor (100) for reuse. The first liquid product is condensed in the first condensate subcooler (107) and then processed with the first ethylene-containing gaseous raw material in the third micro-interface generator group (103). After being combined with the first product from the first micro-interface generator group (101), it is cooled by the first cooler (104) and then enters the first reactor (100) for reuse.

15. The method according to claim 14, characterized in that, The solvent and auxiliary catalyst are cooled in the third cooler (111) and then enter the first micro-interface generator group (101).

16. The method according to claim 14 or 15, characterized in that, The method further includes: The second ethylene-containing gaseous feedstock and another portion of the first liquid phase from the first reactor (100) are treated in the fourth micro-interface generator group (201) and then introduced into the second reactor (200) to carry out the second polymerization reaction; A portion of the second liquid phase from the second reactor (200) is cooled in the fourth cooler (204) and then processed with the second ethylene-containing gaseous feedstock in the fifth micro-interface generator group (202). After being combined with the second product obtained from the processing of the fourth micro-interface generator group (201), it is recycled back into the second reactor (200). Another portion of the second liquid phase is post-processed to obtain polyethylene. The second gaseous phase from the second reactor (200) is condensed in the second reactor top condenser (205) to obtain a second gaseous product and a second liquid product. The second gaseous product is returned to the second reactor (200) for reuse. The second liquid product is condensed in the second condensate subcooler (206) and then processed with the second ethylene-containing gaseous raw material in the sixth micro-interface generator group (203) before entering the second reactor (200) for reuse.

17. The method according to claim 16, characterized in that, The first ethylene-containing gaseous feedstock and the second ethylene-containing gaseous feedstock contain ethylene and gaseous reaction aids.

18. The method according to claim 17, characterized in that, The gaseous reaction aids include gaseous comonomers and / or gaseous molecular weight regulators.

19. The method according to claim 18, characterized in that, The gaseous comonomer is propylene and / or butene.

20. The method according to claim 18, characterized in that, The gaseous molecular weight regulator is hydrogen.

21. The method according to claim 14, characterized in that, The solvent is C3-C. 30 Aliphatic alkanes and / or aromatic compounds.

22. The method according to claim 21, characterized in that, C3-C 30 Aliphatic alkanes are selected from one or more of propane, butane, pentane, hexane, heptane, octane, and cyclohexane.

23. The method according to claim 21, characterized in that, The aromatic compound is toluene.

24. The method according to claim 21, characterized in that, The solvent is selected from combinations of pentane and cyclopentane, propane and hexane, propane and heptane, propane and cyclohexane, propane and heptane and cyclohexane, propane and hexane and cyclohexane, butane and hexane, butane and heptane, butane and cyclohexane, butane and heptane and cyclohexane, butane and heptane and cyclohexane, pentane or cyclopentane.

25. The method according to claim 14, characterized in that, The catalyst is a complex of a post-transition metal.

26. The method according to claim 25, characterized in that, The subsequent transition metals are nickel and / or palladium.

27. The method according to claim 25, characterized in that, The catalyst is a diimine complex of nickel and / or palladium.

28. The method according to claim 14, characterized in that, The auxiliary catalyst is selected from one or more of aluminoxane, alkylaluminum, and alkylaluminum chloride.

29. The method according to claim 28, characterized in that, The aluminum oxane is selected from one or more of methylaluminoxane, triisobutylaluminum-modified methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane.

30. The method according to claim 29, characterized in that, The alkylaluminum is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum.

31. The method according to claim 29, characterized in that, The alkylaluminum chloride is selected from one or more of dimethylaluminum chloride, diethylaluminum chloride, ethylaluminum dichloride, and trichlorotriethylaluminum.

32. The method according to claim 14, characterized in that, The molar ratio of the auxiliary catalyst to the catalyst is 100-4000:1, based on the metal elements contained in the catalyst and the auxiliary catalyst.

33. The method according to claim 32, characterized in that, Based on the metal elements contained in the catalyst and the auxiliary catalyst, the molar ratio of the auxiliary catalyst to the catalyst is 400-1000:

1.

34. The method according to claim 14, characterized in that, The conditions for the first polymerization reaction include: a temperature of 0℃-250℃ and a pressure of 0.1-5MPa.

35. The method according to claim 34, characterized in that, The temperature of the first polymerization reaction is 50-80℃.

36. The method according to claim 34, characterized in that, The pressure of the first polymerization reaction is 0.5-1.5 MPa.

37. The method according to claim 16, characterized in that, The conditions for the second polymerization reaction include: a temperature of 0℃-250℃ and a pressure of 0.1-5MPa.

38. The method according to claim 37, characterized in that, The temperature of the second polymerization reaction is 50-80℃.

39. The method according to claim 37, characterized in that, The pressure of the second polymerization reaction is 0.5-1.5 MPa.

40. The method according to claim 16, characterized in that, The difference between the inlet and outlet temperatures of the first liquid phase when it passes through the second cooler (105) and the fifth cooler (208) and the second liquid phase when it passes through the fourth cooler (204) is less than 10°C.

41. The method according to claim 40, characterized in that, The difference between the inlet and outlet temperatures of the first liquid phase when it passes through the second cooler (105) and the fifth cooler (208) and the second liquid phase when it passes through the fourth cooler (204) is less than 5°C.

42. The method according to claim 40, characterized in that, The difference between the inlet and outlet temperatures of the first liquid phase when it passes through the second cooler (105) and the fifth cooler (208) and the second liquid phase when it passes through the fourth cooler (204) is less than 2°C.

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