Process and system for cooling of polymerization reaction effluent and polymerization process and system

Abstract

The present application relates to the technical field of high pressure polymerization of olefins, and in particular to a method and system for cooling polymerization reaction effluent and a method and system for polymerization reaction. The system comprises: a high pressure pressure-reducing valve for reducing the pressure of effluent from a high pressure radical polymerization reactor to obtain a first stream; a first mixing device for mixing the first stream with a cooling monomer raw material stream to obtain a second stream; and a static mixer in communication with the first mixing device for mixing and cooling the second stream again. The method of mixing and cooling the cooling monomer raw material stream with the stream after the high pressure pressure-reducing valve and then mixing and cooling in the static mixer avoids the generation of temperature hot spots, reduces the risk of ethylene decomposition by inhibiting the generation of temperature hot spots, reduces the content of crystal points in the polymer product, improves the product quality, and has good economic benefits.

Description

Technical Field

[0001] This invention relates to the field of high-pressure polymerization technology of olefins, specifically to a method and system for cooling polymerization effluents and a polymerization reaction method and system. Background Technology

[0002] High-pressure free radical polymerization is widely used to produce low-density polyethylene (LDPE) or ethylene-polar monomer copolymers. When producing LLDPE, the reaction pressure typically exceeds 1000 bar, and the reaction temperature exceeds 150°C. For example, when producing LLDPE using a batch reactor, the typical reaction pressure is approximately 1500 to 2500 bar, and the reaction temperature is approximately 200 to 250°C. The production conditions in a tubular reactor are even more demanding, with typical reaction pressures ranging from approximately 1700 to 3000 bar.

[0003] The mass ratio of unreacted ethylene and polar monomers to polymer at the outlet of a high-pressure free radical polymerization reactor is typically 65 wt% to 85 wt%. This unreacted material is depressurized by a high-pressure pressure reducing valve and then sent to a high-pressure separator for polymer separation. Due to the anti-Joule-Thomson effect of ethylene, the material temperature rises significantly after passing through the pressure reducing valve. Excessive temperature poses a risk of ethylene decomposition and can also cause residual initiator to decompose, generating free radicals that continue the reaction and produce high-molecular-weight polymers, leading to crystal point issues in the polymer product.

[0004] To cool the mixture of polymer and unreacted monomers downstream of the high-pressure reducing valve, CN102791369B and CN101472950B employ a quenching system and method. This method involves installing a pump downstream of the reactor, with the pump inlet connected to a first compressor. However, the jet pump in this method has a complex structure and is difficult to maintain. CN10794958A and CN113087830A employ a cooling method and system for high-pressure polyethylene products, which combines a product cooler upstream of the reducing valve and a cold ethylene quenching system downstream of the reducing valve. However, the product cooler upstream of the reducing valve increases the investment cost of ultra-high-pressure pipelines and may result in excessively low material temperatures in the product cooler, posing a risk of phase separation and increasing the probability of scaling in the product cooler. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in existing high-pressure olefin polymerization processes, such as material temperature rise after pressure reduction in the high-pressure reactor, high crystal point level of polymer products, and potential monomer and polymer decomposition. This invention provides a method and system for cooling polymerization effluent, as well as a polymerization reaction method and system. This method for cooling polymerization effluent can reduce the risk of ethylene decomposition and the crystal point content in polymer products.

[0006] To achieve the above objectives, a first aspect of the present invention provides a cooling system for polymerization reaction effluents, the system comprising:

[0007] A high-pressure pressure reducing valve reduces the pressure of the effluent from a high-pressure free radical polymerization reactor to obtain the first stream.

[0008] The first material stream and the cooling unit raw material stream are used to perform a first mixing and cooling process to obtain a second material stream;

[0009] A static mixer connected to the first mixing device further mixes and cools the second stream.

[0010] A second aspect of the present invention provides a method for cooling polymerization effluent, the method comprising:

[0011] The effluent after the high-pressure free radical polymerization reaction is depressurized by a high-pressure reducing valve to obtain the first stream. The first stream is mixed and cooled with the cooled monomer stream to obtain the second stream. The second stream is then fed into a static mixer for further mixing and cooling.

[0012] The pressure of the first logistics component is 15-40 MPa;

[0013] The temperature of the cooled unit stream is 20-80℃.

[0014] A third aspect of the present invention provides a polymerization reaction system, the reaction system comprising:

[0015] A first compressor and a first cooler located at the outlet of the first compressor, the first compressor and the cooler are respectively used to pressurize and cool the monomer raw material to obtain a cooled monomer raw material stream;

[0016] The second compressor and the high-pressure free radical polymerization reactor are connected in series with the first cooler. The second compressor pressurizes the reaction cooling monomer raw material stream and sends it into the high-pressure free radical polymerization reactor for high-pressure free radical polymerization reaction.

[0017] A high-pressure pressure reducing valve reduces the pressure of the effluent from a high-pressure free radical polymerization reactor to obtain the first stream.

[0018] The first stream and the cooling monomer raw material stream are mixed and cooled in the first mixing device to obtain the second stream through a static mixer connected to the first mixing device and the high pressure reducing valve. The second stream is then mixed and cooled again in the static mixer.

[0019] A fourth aspect of the present invention provides a polymerization reaction method, wherein the reaction method is carried out in the reaction system described in the present invention, the method comprising:

[0020] S1. The monomer raw material is pressurized and cooled by the first compressor and the first cooler to obtain a cooled monomer raw material stream, and the cooled monomer raw material stream is divided into two streams;

[0021] S2. A stream of cooled monomer raw material is pressurized again by the second compressor and sent into the high-pressure free radical polymerization reactor to carry out the high-pressure free radical polymerization reaction. The effluent after the high-pressure free radical polymerization reaction is depressurized by the high-pressure pressure reducing valve to obtain the first stream.

[0022] S3. The first stream and another stream of cooled monomer raw material are mixed and cooled in the first mixing device to obtain the second stream; the second stream is mixed and cooled again in a static mixer;

[0023] The pressure of the first logistics component is 15-40 MPa;

[0024] The temperature of the cooled monomer raw material stream is 20-80℃.

[0025] The above technical solution involves mixing and cooling the cooled monomer raw material stream with the stream after the high-pressure reducing valve, followed by further mixing and cooling in a static mixer. This avoids the formation of hot spots. In the static mixer, the radial mixing rate of the second stream is enhanced, increasing the heat transfer rate between the material and the pipe wall, further preventing hot spots. Suppressing hot spots reduces the risk of ethylene decomposition, lowers the crystal point content of polymer products, improves product quality, and offers significant economic benefits. Attached Figure Description

[0026] Figure 1 This is a polymerization reaction system with single-stage cooling at the outlet of the first compressor, provided in one embodiment of the present invention;

[0027] Figure 2 This is a polymerization reaction system with two-stage cooling at the outlet of the first compressor, provided by one embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures

[0029] 1—First compressor; 2 / 2a / 2b—First compressor outlet cooler; 3—Control valve; 4—Second compressor; 5—High-pressure reactor; 6—High-pressure pressure reducing valve; 7—Static mixer; 8—Jacket; 9—Single raw material flow; 10—Cooled single raw material flow to control valve 3; 11—Cooled single raw material flow to downstream of high-pressure pressure reducing valve; 12—First flow; 13—Second flow; 14—Flow to downstream high-pressure separator; 15—Cooled single raw material flow conveying pipeline. Detailed Implementation

[0030] 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.

[0031] The first aspect of the present invention provides a cooling system for polymerization effluent, the system comprising:

[0032] A high-pressure pressure reducing valve reduces the pressure of the effluent from a high-pressure free radical polymerization reactor to obtain the first stream.

[0033] A first mixing device is used to mix and cool the first material stream with the cooling monomer raw material stream to obtain a second material stream;

[0034] A static mixer connected to the first mixing device further mixes and cools the second stream.

[0035] In this invention, the composition of the cooled monomer raw material stream is the same as that of the reactants entering the high-pressure free radical polymerization reactor.

[0036] According to a preferred embodiment of the present invention, the system further includes: a first compressor and a cooler disposed at the outlet of the first compressor, wherein the first compressor and the cooler are respectively used to pressurize and cool the monomer raw material to obtain the cooled monomer raw material stream.

[0037] In this invention, there are no special requirements for the first mixing device, as long as it can mix the two materials. It can be a conventional mixing device in the art. Preferably, the first mixing device is at least one of a constant diameter pipe and a variable diameter pipe; preferably, it is a constant diameter pipe, and more preferably, it is a constant diameter straight pipe.

[0038] This invention does not particularly limit the type of static mixer, and it can be any static reactor conventional in the art. The type of static mixer can be found in the description in JB / T7660-2016.

[0039] According to a preferred embodiment of the present invention, the static mixer includes a pipe and a jacket disposed on the outer surface of the pipe, the second stream is mixed inside the pipe, and a cooling medium flows through the jacket to cool the second stream inside the pipe.

[0040] According to a preferred embodiment of the present invention, the static mixer further includes mixing plates disposed perpendicular to the length direction of the pipe within the pipe, wherein N mixing plates are sequentially connected along the length direction of the pipe, where N is a positive integer greater than or equal to 1; preferably, N is greater than or equal to 3.

[0041] According to a preferred embodiment of the present invention, the static mixer is a KS-type static mixer.

[0042] A second aspect of the present invention provides a method for cooling polymerization effluent, the method comprising:

[0043] The effluent after the high-pressure free radical polymerization reaction is depressurized by a high-pressure reducing valve to obtain the first stream. The first stream is mixed and cooled with the cooled monomer stream to obtain the second stream. The second stream is then fed into a static mixer for further mixing and cooling.

[0044] The pressure of the first stream is 15-40 MPa; the temperature of the cooling monomer stream is 20-80°C. The method of mixing the cooling monomer stream with the stream after the high-pressure reducing valve in a static mixer avoids the generation of temperature hotspots. By suppressing the generation of temperature hotspots, the risk of ethylene decomposition can be reduced, the crystal point content of the polymer product can be decreased, and product quality can be improved, resulting in good economic benefits.

[0045] According to a preferred embodiment of the present invention, the pressure of the first material stream is 20-30 MPa; this is beneficial for reducing the crystal point content of the polymer product and improving product quality.

[0046] According to a preferred embodiment of the present invention, the temperature of the cooled monomer stream is 30-60°C; this is beneficial for reducing the crystal point content of the polymer product and improving product quality.

[0047] According to a preferred embodiment of the present invention, the pressure of the effluent after the high-pressure free radical polymerization reaction is 160-250 MPa and the temperature is 180-280 °C.

[0048] In this invention, there is no particular limitation on the pressure of the cooling unit stream and the first stream. Preferably, the pressure of the cooling unit stream is greater than or equal to the pressure of the first stream, and preferably the pressure difference is 0.1-3 MPa.

[0049] According to a preferred embodiment of the present invention, the average temperature of the second stream is below 320°C, preferably below 300°C.

[0050] In this invention, there is no particular limitation on the average temperature of the second material and the average temperature of the first material. Preferably, the average temperature of the second material is less than the average temperature of the first material. More preferably, the temperature difference is greater than 1°C, and more preferably, the temperature difference is 5-30°C.

[0051] In this invention, as long as the average temperature of the second material is lower than the average temperature of the first material, there is no particular limitation on the flow ratio of the first and second materials. The flow ratio of the first and second materials can be adjusted according to actual needs.

[0052] According to a preferred embodiment of the present invention, in the static mixer, the temperature of the cooling medium is lower than the temperature of the second material, and the temperature difference is greater than 5°C, preferably 10-200°C; more preferably, in the jacket of the static mixer, the temperature of the cooling medium is 30-200°C.

[0053] In this invention, the cooling method described herein can be used for all conventional high-pressure free radical polymerization effluents in the art. This invention does not have any particular limitation on the source of the cooled monomer stream. For example, the cooled monomer stream may include fresh monomer material and unreacted monomer material returned from the low-pressure circulation loop.

[0054] According to a preferred embodiment of the present invention, the cooled monomer feed stream includes polymeric monomers used in the polymerization reaction; preferably, the cooled monomer feed stream further includes at least one of polar monomers and nonpolar monomers; more preferably, the polar monomer is selected from one or more of vinyl acetate, methyl acrylate and ethyl acrylate; the nonpolar monomer is selected from one or more of C3-C12 α-olefins and C4-C12 β-olefins.

[0055] A third aspect of the present invention provides a polymerization reaction system, the reaction system comprising:

[0056] A first compressor and a first cooler located at the outlet of the first compressor, the first compressor and the first cooler are respectively used to pressurize and cool the monomer raw material to obtain a cooled monomer raw material stream.

[0057] The second compressor and the high-pressure free radical polymerization reactor are connected in series with the first cooler. The second compressor pressurizes the cooled monomer raw material stream and sends it into the high-pressure free radical polymerization reactor for high-pressure free radical polymerization reaction.

[0058] A high-pressure pressure reducing valve reduces the pressure of the effluent from a high-pressure free radical polymerization reactor to obtain the first stream.

[0059] The first stream and the cooling monomer raw material stream are mixed and cooled in the first mixing device to obtain the second stream through a static mixer connected to the first mixing device and the high pressure reducing valve. The second stream is then mixed and cooled again in the static mixer.

[0060] Downstream of the first cooler, there is also a cooling unit raw material logistics conveying pipeline connected to the first mixing device, used to convey the cooling unit raw material logistics to the first mixing device.

[0061] According to a preferred embodiment of the present invention, the cooling unit raw material logistics conveying pipeline is located upstream of the second compressor.

[0062] According to a preferred embodiment of the present invention, the first mixing device is a connecting pipe between a high-pressure reducing valve and a static mixer.

[0063] According to a preferred embodiment of the present invention, the polymerization reaction system further includes a control valve disposed between the first cooler and the second compressor for controlling the flow rate of the cooled monomer raw material stream entering the second compressor.

[0064] According to a preferred embodiment of the present invention, the polymerization reaction system further includes a second cooler disposed between the first cooler and the second compressor, for controlling the temperature of the cooled monomer raw material stream entering the second compressor.

[0065] According to a preferred embodiment of the present invention, the present invention provides a polymerization reaction system with single-stage cooling at the outlet of a first compressor, such as... Figure 1 As shown, the polymerization reaction system includes:

[0066] The first compressor 1 and the first cooler 2 located at the outlet of the first compressor 1 pressurize and cool the monomer raw material to obtain a cooled monomer raw material stream.

[0067] The second compressor 4 and the high-pressure free radical polymerization reactor 5 are connected in series with the first cooler 2. The second compressor 4 pressurizes the cooled monomer raw material stream and sends it into the high-pressure free radical polymerization reactor 5 for high-pressure free radical polymerization reaction.

[0068] High pressure reducing valve 6 reduces the pressure of the effluent from high pressure free radical polymerization reactor 5 to obtain the first stream;

[0069] The first stream and the cooling monomer raw material stream are mixed and cooled in the pipeline through a static mixer 7 connected to a mixing pipe and a high-pressure reducing valve 6 to obtain a second stream. The second stream is then mixed and cooled again in the static mixer 7.

[0070] Downstream of the first cooler 2, there is also a cooling unit raw material logistics conveying pipeline connected to the mixing pipeline, used to convey the cooling unit raw material logistics to the mixing pipeline.

[0071] The control valve 3, located between the first cooler 2 and the second compressor 4, is used to control the flow rate of the cooling unit raw material entering the second compressor 4.

[0072] According to a preferred embodiment of the present invention, the present invention provides a polymerization reaction system with two-stage cooling at the outlet of a first compressor, such as... Figure 2 As shown, the polymerization reaction system includes:

[0073] The first compressor 1 and the first cooler 2a disposed at the outlet of the first compressor 1 are each used to pressurize and cool the monomer raw material to obtain a cooled monomer raw material stream.

[0074] The second compressor 4 and the high-pressure free radical polymerization reactor 5 are connected in series with the first cooler 2a. The second compressor 4 pressurizes the cooled monomer raw material stream and sends it into the high-pressure free radical polymerization reactor 5 for high-pressure free radical polymerization reaction.

[0075] High pressure reducing valve 6 reduces the pressure of the effluent from high pressure free radical polymerization reactor 5 to obtain the first stream;

[0076] The first stream 12 and the cooling monomer raw material stream are mixed and cooled in the mixing pipe through the static mixer 7 connected to the mixing pipe to obtain the second stream. The second stream is then mixed and cooled again in the static mixer 7.

[0077] Downstream of the first cooler 2a, there is also a cooling unit raw material logistics conveying pipeline connected to the mixing pipeline, used to convey the cooling unit raw material logistics to the mixing pipeline.

[0078] The control valve 3, located between the first cooler 2a and the second compressor 4, is used to control the flow rate of the cooling unit raw material entering the second compressor 4.

[0079] The second cooler 2b, located between the first cooler 2a and the second compressor 4, is used to control the temperature of the cooling unit raw material stream entering the second compressor.

[0080] A fourth aspect of the present invention provides a polymerization reaction method, wherein the reaction method is carried out in the reaction system described in the present invention, the method comprising:

[0081] S1. The monomer raw material is pressurized and cooled by the first compressor and the first cooler to obtain a cooled monomer raw material stream, and the cooled monomer raw material stream is divided into two streams;

[0082] S2. A stream of cooled monomer raw material is pressurized again by the second compressor and sent into the high-pressure free radical polymerization reactor to carry out the high-pressure free radical polymerization reaction. The effluent after the high-pressure free radical polymerization reaction is depressurized by the high-pressure pressure reducing valve to obtain the first stream.

[0083] S3. The first stream and another stream of cooled monomer raw material are mixed and cooled in the first mixing device to obtain the second stream; the second stream is mixed and cooled again in a static mixer;

[0084] The pressure of the first logistics component is 15-40 MPa;

[0085] The temperature of the cooled monomer raw material stream is 20-80℃.

[0086] In a high-pressure reactor, ethylene, one or more polar and nonpolar monomers, are contacted with a free radical initiator to generate a polymer, which is an ethylene homopolymer, an ethylene-polar monomer copolymer, or an ethylene-nonpolar monomer copolymer, etc. Typically, the polymer content in the mixture 12 at the outlet of the high-pressure reactor is 15 wt%-35 wt%. In some low-load embodiments, the polymer content in the effluent at the outlet of the high-pressure reactor is less than 10 wt%. In some high-load embodiments, the polymer content in the effluent at the outlet of the high-pressure reactor is greater than 35 wt%. When the high-pressure reactor is a batch reactor, the polymer content in the effluent is approximately 10 wt%-25 wt%. When the high-pressure reactor is a tubular reactor, the polymer content in the effluent is approximately 15 wt%-35 wt%.

[0087] The following combination Figure 1 The polymerization reaction method described in this invention will be explained in detail below.

[0088] The monomer feedstock stream 9 includes fresh monomer material and unreacted monomer material returned from the low-pressure circulation loop.

[0089] Monomer raw material stream 9 is compressed by the first compressor 1 and then enters the first cooler 2. The material exiting the first cooler 2 is cooled monomer raw material stream at a temperature of 30-60℃, which splits into two streams. One stream, cooled monomer raw material stream 10, passes through control valve 3 and enters the second compressor 4, where it is pressurized to over 1000 bar and sent to the high-pressure reactor 5. The other stream, cooled monomer raw material stream 11, is sent downstream of the high-pressure reducing valve 6, where it mixes and cools with the first stream 12 from the outlet of the high-pressure reactor 5 to obtain the second stream 13. The second stream 13 enters a pipe with a jacket 8 and is mixed and cooled by a static mixer 7 to obtain stream 14, which goes to the downstream high-pressure separator. Stream 14 is sent to the downstream separation system to separate polyolefins. Unreacted materials are returned to the upstream pipes of the first compressor 1 and the second compressor 4, respectively.

[0090] The first stream 12 obtained after the effluent from the high-pressure reactor 5 passes through the high-pressure pressure reducing valve has a pressure of 15-40 MPa, preferably 20-30 MPa.

[0091] The second stream 13 is thoroughly mixed again in the pipes of the static mixer 7. The static mixer enhances the mixing rate of the cooling monomer raw material stream 10 and the first stream 12, and at the same time enhances the turbulence intensity of the second stream 13 and the inner wall of the static mixer pipe, thereby improving the heat exchange rate between the second stream 13 and the jacket cooling medium. A cooling medium of 30-200°C is introduced into the jacket.

[0092] Figure 2Another embodiment of the invention is illustrated schematically, and... Figure 1 In contrast, the material exiting the first compressor 1 is cooled by two coolers, 2a and 2b, so the temperature of the cooled raw material stream 10 going to the second compressor 4 and the temperature of the cooled raw material stream 11 going to the high-pressure reducing valve 6 can be controlled separately.

[0093] Example 1

[0094] use Figure 1 The polymerization system shown undergoes high-pressure free radical polymerization.

[0095] High-pressure reactor 5 is a tubular reactor. The initiator, which generates free radicals, is fed at four points. The free radicals generated by the initiator contact the reactant monomer ethylene to form polyethylene. The final effluent from high-pressure reactor 5 contains 31 wt% polyethylene at a temperature of 260°C and a pressure of 220 MPa. After passing through high-pressure reducing valve 6, the pressure of the effluent is reduced to 26 MPa, resulting in the first stream 12. The temperature of the first stream 12 is 290°C, and the flow rate is 89 t / h. The cooling monomer feed stream 11 has a flow rate of 3 t / h, a pressure of 27 MPa, and a temperature of 40°C. The second stream 13 has a temperature of 276°C and a flow velocity of 25 m / s within the pipe. Static mixer 7 consists of 10 mixing plates connected together and arranged perpendicular to the length of the pipe. The cooling medium in the jacket has a temperature of 90°C. The material 14, cooled by the pipe jacket cooler of static mixer 7, has a temperature of 240°C.

[0096] The properties of polyethylene products are shown in Table 1.

[0097] Example 2

[0098] use Figure 1 The polymerization system shown undergoes high-pressure free radical polymerization.

[0099] High-pressure reactor 5 is a tubular reactor. The initiator, which generates free radicals, is fed at four points. The free radicals generated by the initiator contact the reactant monomer ethylene to form polyethylene. The final effluent from high-pressure reactor 5 contains 31 wt% polyethylene at a temperature of 260°C and a pressure of 220 MPa. After passing through high-pressure reducing valve 6, the pressure is reduced to 26 MPa to obtain the first stream 12. The temperature of the first stream 12 is 290°C, and the flow rate is 89 t / h. The cooling monomer feed stream 11 has a flow rate of 3 t / h, a pressure of 27 MPa, and a temperature of 40°C. The second stream 13 has a temperature of 276°C and a flow velocity of 25 m / s within the pipe. The static mixer consists of six mixing plates connected vertically in sequence, and the cooling medium temperature within the jacket is 90°C. The material 14, cooled by the pipe jacket of the static mixer 7, has a temperature of 242°C.

[0100] The properties of polyethylene products are shown in Table 1.

[0101] Example 3

[0102] use Figure 2 The polymerization system shown undergoes high-pressure free radical polymerization.

[0103] High-pressure reactor 5 is a tubular reactor. The temperature of the cooled monomer feed stream 10 entering the second compressor is 40℃. The initiator that generates free radicals is fed at four points. The free radicals generated by the initiator contact the reactant monomer ethylene to generate polyethylene. Finally, the effluent from the outlet of high-pressure reactor 5 has a polyethylene mass fraction of 31wt%, a temperature of 260℃, and a pressure of 220MPa. After passing through pressure reducing valve 6, the pressure of the effluent is reduced to 26MPa to obtain the first stream 12. The temperature of the first stream is 290℃, and the flow rate is 89t / h. The flow rate of the cooled monomer feed stream 11 is 4t / h, the pressure is 27MPa, and the temperature is 60℃. The temperature of the second stream 13 is 272℃, and the flow velocity of the second stream 13 in the pipe is 25m / s. The static mixer 7 consists of six mixing plates connected together and arranged perpendicular to the length of the pipe. The temperature of the cooling medium in the jacket is 90℃. The temperature of the stream 14 after being cooled by the pipe jacket cooler of the static mixer 7 is 240℃.

[0104] The properties of polyethylene products are shown in Table 1.

[0105] Example 4

[0106] The method is the same as in Example 2, except that the pressure of the first stream is 36 MPa and the temperature is 294°C; the temperature of the second stream 13 obtained after contacting and mixing with the cooled monomer raw material stream 11 is 282°C.

[0107] The properties of polyethylene products are shown in Table 1.

[0108] Example 5

[0109] The method is the same as in Example 2, except that the temperature of the cooled monomer raw material stream is 80°C, and the temperature of the second stream 13 obtained after contacting and mixing with the first stream 12 is 278°C.

[0110] The properties of polyethylene products are shown in Table 1.

[0111] Comparative Example 1

[0112] The polyethylene product was prepared using the same method as in Example 1, except that a static mixer was not installed in the pipeline after the high-pressure reducing valve. The properties of the polyethylene product are shown in Table 1.

[0113] Comparative Example 2

[0114] The polyethylene product was prepared using the same method as in Example 1, except that no cooling monomer raw material stream was introduced after the high-pressure reducing valve, and no static mixer was installed. The properties of the polyethylene product are shown in Table 1.

[0115] Comparative Example 3

[0116] The polyethylene product was prepared using the same method as in Example 1, except that no cooling monomer raw material stream was introduced after the high-pressure reducing valve, no static mixer was installed, and the flow velocity in the pipe was 10 m / s. The properties of the polyethylene product are shown in Table 1.

[0117] Table 1

[0118]

[0119] As can be seen from the results in Table 1, compared with Comparative Examples 1-3, the method of Examples 1-5, which involves mixing and cooling the cooled monomer raw material stream with the stream after the high-pressure reducing valve and then mixing and cooling them in a static mixer, can reduce the crystal point content of the polymer product and improve the product quality.

[0120] 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 polymerization reaction system, characterized in that, The reaction system includes: A first compressor and a first cooler located at the outlet of the first compressor, the first compressor and the first cooler are respectively used to pressurize and cool the monomer raw material to obtain a cooled monomer raw material stream. A second compressor and a high-pressure free radical polymerization reactor are connected in series with the first cooler. The second compressor pressurizes the cooled monomer raw material stream and sends it into the high-pressure free radical polymerization reactor for high-pressure free radical polymerization reaction. A high-pressure pressure reducing valve reduces the pressure of the effluent from a high-pressure free radical polymerization reactor to obtain the first stream. The first stream and the cooling monomer raw material stream are mixed and cooled in the first mixing device to obtain the second stream through a static mixer connected to the first mixing device and the high pressure reducing valve. The second stream is then mixed and cooled again in the static mixer. Downstream of the first cooler, there is also a cooling unit raw material logistics conveying pipeline connected to the first mixing device, used to convey the cooling unit raw material logistics to the first mixing device.

2. The polymerization reaction system according to claim 1, wherein, The first mixing device is a connecting pipe between the high-pressure reducing valve and the static mixer; The polymerization reaction system further includes a flow control valve disposed between the first cooler and the second compressor; and / or The second cooler, located between the first cooler and the second compressor, is used to control the temperature of the cooling unit raw material stream entering the second compressor.

3. The polymerization reaction system according to claim 1 or 2, wherein, The first mixing device is a constant-diameter pipe and / or a variable-diameter pipe; and / or The static mixer includes a pipe and a jacket disposed on the outer surface of the pipe. The second material is mixed inside the pipe, and a cooling medium flows through the jacket to cool the second material inside the pipe.

4. The polymerization reaction system according to claim 1 or 2, wherein, The static mixer also includes mixing plates arranged perpendicular to the length of the pipe inside the pipe, with N mixing plates connected sequentially along the length of the pipe, where N is a positive integer greater than or equal to 1.

5. The polymerization reaction system according to claim 1 or 2, wherein, The static mixer is a KS type static mixer.

6. A polymerization reaction method, characterized in that, The reaction method is carried out in the reaction system described in any one of claims 1-5, and the method includes: S1. The monomer raw material is pressurized and cooled by the first compressor and the first cooler to obtain a cooled monomer raw material stream, and the cooled monomer raw material stream is divided into two streams; S2. A stream of cooled monomer raw material is pressurized again by the second compressor and sent into the high-pressure free radical polymerization reactor to carry out the high-pressure free radical polymerization reaction. The effluent after the high-pressure free radical polymerization reaction is depressurized by the high-pressure pressure reducing valve to obtain the first stream. S3. The first stream and another stream of cooled monomer raw material are mixed and cooled in the first mixing device to obtain the second stream; the second stream is mixed and cooled again in a static mixer; The pressure of the first logistics component is 15-40 MPa; The temperature of the cooled monomer raw material stream is 20-80℃.

7. The polymerization reaction method according to claim 6, wherein, The pressure of the effluent after the high-pressure free radical polymerization reaction is 160-250 MPa, and the temperature is 180-280℃.

8. The polymerization reaction method according to claim 6, wherein, The pressure of the cooling monomer raw material stream is greater than or equal to the pressure of the first stream; and / or The average temperature of the second logistics link is below 320℃.

9. The polymerization reaction method according to claim 6, wherein, The average temperature of the second logistics item is lower than the average temperature of the first logistics item; and / or In the static mixer, the temperature of the cooling medium is lower than the temperature of the second stream, and the temperature difference is greater than 5°C.

10. The polymerization reaction method according to claim 9, wherein, The average temperature difference between the second and first logistics flows is 10-200℃; and / or In the static mixer, the temperature of the cooling medium is lower than the temperature of the second stream, and the temperature difference is 10-200°C; and / or In the jacket of the static mixer, the temperature of the cooling medium is 30-200℃.

11. The polymerization reaction method according to claim 6, wherein, The cooling monomer feedstock stream includes the monomers used in the polymerization reaction.

12. The polymerization reaction method according to claim 11, wherein, The cooled monomer feedstock stream also includes at least one of polar monomers and non-polar monomers, wherein the polar monomer is selected from one or more of vinyl acetate, methyl acrylate and ethyl acrylate; and the non-polar monomer is selected from one or more of C3-C12 α-olefins and C4-C12 β-olefins.

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