High pressure polymerization process with controlled gas velocity

Abstract

A process for the polymerization or copolymerization of one or more ethylenically unsaturated monomers, the process having a controlled gas velocity for gaseous reaction, and a high pressure polymerization apparatus for performing the process of the present disclosure.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a process for the polymerization or copolymerization of one or more ethylenically unsaturated monomers having a controlled gas velocity for the gaseous reaction, and to a high-pressure polymerization apparatus for carrying out the process of the present disclosure. BACKGROUND ART

[0002] Polymers play an important and ubiquitous role in daily life. One way to obtain polymers is through high-pressure polymerization, which converts relatively low-cost olefin monomers such as ethylene (optionally in combination with one or more comonomers) into valuable polyolefin products. Polyethylene, as the most widely used commercial polymer, can be prepared by different methods, among which polymerization under elevated pressure in the presence of a free-radical initiator is the first method and continues to be a valuable method with high commercial relevance for the preparation of polyethylene.

[0003] General setups for the preparation of polyethylene include a polymerization reactor and additional equipment. The polymerization reactor can be an autoclave or a tubular reactor or a combination of such reactors. To pressurize the reaction components, a set of two compressors is typically used, namely a main compressor and a secondary or super-compressor. At the end of the polymerization sequence, the setup for high-pressure polymerization typically also includes equipment for granulating the resulting polymer, such as an extruder and a granulator. In addition, such a setup typically also includes means for feeding monomers and comonomers, free-radical initiators, modifiers or other substances into the polymerization reaction at one or more locations.

[0004] WO 2017 / 003566 describes a high-pressure polyethylene polymerization system comprising a reactor, a main compressor and a secondary compressor, the secondary compressor comprising: a) a first stage, wherein the first stage comprises at least two cylinders and the discharge pipes of the at least two cylinders are fluidly connected by a first-stage discharge cross-connection pipe; b) a second stage; c) and an intermediate stage; and d) a first cooler, the first cooler being applied to the inter-stage pipe at a location within 10 meters downstream of the first-stage discharge cross-connection pipe.

[0005] WO 2017 / 194491 relates to a process for the polymerization or copolymerization of one or more ethylenically unsaturated monomers in a continuously operated polymerization reactor, wherein the polymerization is carried out in a production line, wherein the monomers are brought to the polymerization pressure by one or more compressors in a series of compression stages, wherein the compressed gas mixture is cooled by a compression stage cooler after each compression stage, the compressed monomers are optionally passed through a preheater or a precooler and transferred to the polymerization reactor, which is optionally cooled by a cooling jacket, the reaction mixture obtained by polymerization leaves the reactor through a pressure control valve and is optionally cooled by a post-reactor cooler, the reaction mixture is separated into a polymeric component and a gaseous component in two or more stages, wherein the gaseous component separated off in the first stage at an absolute pressure of 15 MPa to 50 MPa is recycled via a high-pressure gas recycle line to one or more compressors, and the gaseous component separated off in the second stage at an absolute pressure in the range from 0.1 to 0.5 MPa is recycled via a low-pressure gas recycle line to the first stage of the compression stage sequence, and the polymeric component obtained by polymerization is converted into pellets. In the process described, the occurrence of leaks of monomers or reaction mixture in the surroundings of the production line is monitored by an IR point detector arrangement of at least three groups of IR point detectors capable of detecting hydrocarbons, and the groups of IR point detectors operate according to a voting logic, and when a group of IR point detectors of the IR point detector arrangement detects the presence of hydrocarbons, an emergency pressure relief program is automatically initiated.

[0006] US 7,582,709 provides a process for the manufacture of ethylene polymers and copolymers, which process comprises the steps of compressing ethylene in a main compressor at a throughput of at least 55 tons per hour, then mixing the ethylene with recycled ethylene and further compressing the ethylene in a secondary compressor at a throughput of at least 120 tons per hour to a pressure of at least 2300 bar, heating at least a portion of the compressed ethylene to a temperature of at least 95 °C and introducing the heated ethylene into the front end of a tubular reactor having a maximum inner diameter of at least 65 mm and a length of at least 1500 m, introducing initiator into the tubular reactor at at least three separate locations, thereby defining at least three reaction zones, polymerizing the ethylene and cooling the reaction mixture in at least the first two reaction zones such that at least 28% of the monomer is converted into polymer, maintaining a pressure drop over the length of the tubular reactor such that a flow rate of at least 6 m / s is maintained in the tubular reactor, releasing the reaction mixture through a high-pressure bleed valve, cooling the reaction mixture, and separating the reaction mixture into polymer and unreacted ethylene in a product separator, and recycling the unreacted ethylene.

[0007] EP 3 109 262 A1 discloses a high-pressure polymerization process for forming ethylene-based polymers. The process at least comprises the following steps: polymerizing a reaction mixture comprising ethylene using a reactor system comprising at least three ethylene-based feed streams and a reactor configuration comprising at least four reaction zones.

[0008] WO 2017 / 223467 A1 and WO 2017 / 003566 A1 disclose further high-pressure polymerization processes for forming ethylene-based polymers.

[0009] A disadvantage of conventional processes is that the secondary compressor, also known as the supercompressor, causes pulsations of the gaseous reaction mixture on the suction and discharge sides of the supercompressor cylinders, which in turn causes the connected pipe system containing the gaseous reaction mixture to vibrate. However, any pulsations and vibrations have a negative impact on plant performance. Increased gas pulsations reduce the life of the compressor cylinders, and strong vibrations require expensive measures to avoid damage to the pipe layout and support structures.

[0010] Accordingly, there is a need for a high-pressure polymerization process that overcomes the disadvantages of the prior art and allows compensation for pulsations of the gaseous reaction mixture caused by the compressor. SUMMARY OF THE INVENTION

[0011] The present disclosure provides a process for polymerizing or copolymerizing one or more ethylenically unsaturated monomers at a temperature of from 100 °C to 350 °C and a pressure of from 110 MPa to 500 MPa, wherein the gaseous reaction mixture is compressed in a supercompressor comprising

[0012] · a first compression stage comprising at least two cylinders, the at least two cylinders being connected via a first-stage discharge pipe system to a first-stage discharge collection and distribution system;

[0013] · a second compression stage comprising at least two cylinders, the at least two cylinders being connected via a second-stage suction pipe system to a second-stage suction collection and distribution system and via a second-stage discharge pipe system to a second-stage discharge collection and distribution system;

[0014] · a heat exchanger arranged between the first and second compression stages;

[0015] wherein the reaction mixture is provided to each compression stage via a suction pipe system, and the compressed reaction mixture is discharged from the compression stage via a discharge pipe system;

[0016] wherein

[0017] · the velocity of the gaseous reaction mixture in the first-stage discharge pipe system is from 0.8 m / s to 2.5 m / s; and / or

[0018] · The velocity of the gaseous reaction mixture in the first-stage emission collection and distribution system is 2 m / s to 4 m / s; and / or

[0019] · The velocity of the gaseous reaction mixture in the second-stage emission pipe system is 0.8 m / s to 3.5 m / s; and / or

[0020] · The velocity of the gaseous reaction mixture in the second-stage emission collection and distribution system is 4 m / s to 9 m / s.

[0021] In some embodiments, the gaseous reaction mixture is conveyed from the heat exchanger to the mixing block before entering the second-stage suction collection and distribution system.

[0022] In some embodiments, the velocity of the gaseous reaction mixture in the first-stage emission pipe system is less than 1.7 m / s.

[0023] In some embodiments, the velocity of the gas reaction mixture in the first-stage emission collection and distribution system is less than 3.5 m / s.

[0024] In some embodiments, the velocity of the gaseous reaction mixture in the second-stage emission pipe system is less than 2.5 m / s.

[0025] In some embodiments, the velocity of the gaseous reaction mixture in the second-stage emission collection and distribution system is less than 7 m / s.

[0026] In some embodiments, the inner diameter of the pipes in the second-stage emission pipe system is less than the inner diameter of the pipes in the first-stage emission pipe system. The inner diameter of the pipes in the first-stage emission pipe system can be 100 to 200 mm, preferably 120 to 160 mm. The inner diameter of the second-stage emission pipe system can be about 30 to 100 mm, preferably 50 to 89 mm.

[0027] Preferably, the velocity of the gaseous mixture in the second-stage emission pipe system can be higher than the velocity of the gaseous mixture in the first-stage emission pipe system. In some embodiments, the velocity of the gaseous mixture in the second-stage emission pipe system can be 0.9 to 3.5 m / s, preferably 1 to 3.2 m / s.

[0028] In some embodiments, the second compression stage includes more cylinders than the first compression stage.

[0029] In some embodiments, the first compression stage is connected to the first-stage suction collection and distribution system via the first-stage suction pipe system, and wherein the velocity of the gaseous reaction mixture in the first-stage suction pipe system is preferably between 0.5 m / s and 3 m / s, particularly less than 1.5, and / or the velocity of the gaseous reaction mixture in the first-stage suction collection and distribution system is between 3 m / s and 7 m / s, particularly less than 6 m / s.

[0030] In some embodiments, the velocity of the gaseous reaction mixture in the second-stage suction pipe system is preferably from 0.5 m / s to 2.5 m / s, particularly less than 1.5 m / s and / or the velocity of the gaseous reaction mixture in the second-stage suction collection and distribution system is from 2 m / s to 3.5 m / s, particularly less than 3 m / s.

[0031] In some embodiments, the gaseous reaction mixture is conveyed through one or more mixing blocks from the first-stage discharge collection and distribution system before entering the heat exchanger.

[0032] In some embodiments, the gaseous reaction mixture is conveyed through one or more mixing blocks from the second-stage discharge collection and distribution system before being conveyed to the polymerization reactor.

[0033] In some embodiments, the compressor system further includes a pipe for supplying the reaction mixture to the first-stage suction collection and distribution system, wherein the gas velocity in the pipe is preferably from 3 to 7 m / s, preferably less than 6 m / s.

[0034] In some embodiments, the compressor system further includes a pipe for discharging the reaction mixture from the second-stage collection and distribution system, wherein the gas velocity in the pipe is preferably from 10 to 16 m / s.

[0035] In some embodiments, the reaction is compressed in the main compressor before entering the supercompressor.

[0036] The present disclosure also provides a high-pressure polymerization apparatus for polymerizing or copolymerizing one or more ethylenically unsaturated monomers, the apparatus comprising a supercompressor for compressing a gaseous reaction mixture, the supercompressor comprising

[0037] · a first compression stage comprising at least two cylinders, the at least two cylinders being connected via a first-stage discharge pipe system to a first-stage discharge gas collection and distribution system;

[0038] · a second compression stage comprising at least two cylinders, the at least two cylinders being connected via a second-stage suction pipe system to a second-stage suction gas collection and distribution system and via a second-stage discharge pipe system to a second-stage discharge gas collection and distribution system);

[0039] · a heat exchanger disposed between the first and second compression stages. Description of the Drawings

[0040] Figure 1 The preferred embodiments of the present disclosure are schematically illustrated. Detailed Description

[0041] The present disclosure relates to a process for the high-pressure polymerization or copolymerization of one or more ethylenically unsaturated monomers. The high-pressure polymerization is carried out at a pressure of from 110 MPa to 500 MPa, more preferably from 160 MPa to 350 MPa, particularly preferably from 200 MPa to 330 MPa for polymerization in a tubular reactor, and from 110 MPa to 300 MPa, more preferably from 120 MPa to 280 MPa for polymerization in an autoclave reactor. For polymerization in a tubular reactor, the polymerization temperature is in the range of from 100 °C to 350 °C, preferably in the range of from 180 °C to 350 °C, particularly preferably in the range of from 200 °C to 330 °C, and for polymerization in an autoclave reactor, more preferably in the range of from 110 °C to 320 °C.

[0042] The polymerization is preferably homopolymerization of ethylene or copolymerization of ethylene with one or more other monomers, provided that these monomers can be free-radically copolymerized with ethylene under high pressure. Examples of copolymerizable monomers for use in the present technology are α,β-unsaturated C 3 -C 8 -carboxylic acids, derivatives of α,β-unsaturated C 3 -C 8 -carboxylic acids, such as unsaturated C 3 -C 15 -carboxylic acid esters or acid anhydrides, and 1-olefins. In addition, vinyl carboxylates, such as vinyl acetate, can be used as comonomers. Propylene, 1-butene, 1-hexene, acrylic acid, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, vinyl acetate or vinyl propionate are particularly preferred comonomers.

[0043] In the case of copolymerization, based on the amount of monomers, i.e., the sum of ethylene and other monomers, the proportion of comonomer in the reaction mixture is from 1 to 50% by weight, preferably from 3 to 40% by weight.

[0044] For the purposes of the present disclosure, a polymer or polymeric material is a substance composed of at least two monomer units. The polymer or polymeric material is preferably low-density polyethylene having an average molecular weight M n greater than 20,000 g / mol. The term "low-density polyethylene" (LDPE) includes ethylene homopolymers and ethylene copolymers. The process can also be for the preparation of oligomers, waxes and polymers having a molecular weight M n less than 20,000 g / mol. The polymerization is preferably radical polymerization carried out in the presence of a radical polymerization initiator. Possible initiators for starting the polymerization in the respective reaction zone are generally any substances that can generate free-radical species under the conditions in the polymerization reactor, such as oxygen, air, azo compounds or peroxide polymerization initiators. In an exemplary embodiment of the present disclosure, by using pure O 2Polymerization is carried out in the form of oxygen fed as air. In the case of polymerization initiated by oxygen, the initiator is usually first mixed with the ethylene feed and then fed into the reactor. In this case, not only can the stream containing the monomer and oxygen be fed to the beginning of the polymerization reactor, but also to one or more points along the reactor, thus generating two or more reaction zones. Initiation using an organic peroxide or an azo compound also represents a preferred embodiment of the present disclosure. A single initiator or preferably a mixture of various initiators can be used.

[0045] In high-pressure polymerization, the molecular weight of the polymer to be prepared can be varied, for example, by adding a modifier that acts as a chain transfer agent. Examples of modifiers for use in the present technology are hydrogen, aliphatic and olefinic hydrocarbons such as propane, butane, pentane, hexane, cyclohexane, propylene, 1-butene, 1-pentene or 1-hexene, ketones (such as acetone, methyl ethyl ketone (2-butanone), methyl isobutyl ketone, methyl isopentyl ketone, diethyl ketone or dipentyl ketone), aldehydes (such as formaldehyde, acetaldehyde or propionaldehyde) and saturated aliphatic alcohols (such as methanol, ethanol, propanol, isopropanol or butanol). Particular preference is given to using saturated aliphatic aldehydes, especially propionaldehyde or 1-olefins (such as propylene, 1-butene or 1-hexene), or aliphatic hydrocarbons (such as propane).

[0046] Within the method of the present disclosure, the gaseous reaction mixture comprising the monomer feed is compressed in a supercompressor comprising a first compression stage comprising at least two cylinders, the at least two cylinders being connected via a first-stage discharge piping system to a first-stage discharge collection and distribution system; a second compression stage comprising at least two cylinders, the at least two cylinders being connected via a second-stage suction piping system to a second-stage suction collection and distribution system and via a second-stage discharge piping system to a second-stage discharge collection and distribution system; and at least one heat exchanger arranged between the first and second compression stages. The gaseous reaction is supplied to each compression stage via the suction piping system, and the compressed reaction mixture is discharged from the compression stage via the discharge piping system.

[0047] In a preferred embodiment, the collection and distribution system is selected from the group consisting of cross-connecting pipes, cross-connecting blocks and high-pressure manifolds.

[0048] According to the method of the present disclosure, the gaseous gas mixture is introduced into the first compression stage via the first-stage suction piping system and discharged from the first compression stage via the first-stage discharge system to the first-stage discharge collection and distribution system. The gaseous reaction mixture is conveyed to at least one heat exchanger before entering the second-stage compression system via the second-stage suction collection and distribution system and is introduced into the second compression stage via the second-stage suction piping system. The gaseous reaction mixture leaves the second compression stage through the second-stage discharge pipe to the second-stage discharge collection and distribution system.

[0049] During the process of the present disclosure, it has surprisingly been found that by carefully controlling the velocity of the gaseous reaction mixture and collecting the gaseous reaction mixture discharged from the cylinder in the collection and distribution system, a reduction in gas pulsation is achieved, which in turn results in a reduction in the vibration of the entire system. The method of the present disclosure provides a stable flow of the gaseous reaction mixture with reduced pulsation while maintaining sufficient heat transfer in one or more heat exchangers.

[0050] According to the present disclosure, the gas velocity of the gaseous reaction mixture is thus controlled within the following ranges:

[0051] The velocity of the gaseous reaction mixture in the first-stage discharge pipe system is from 0.8 m / s to 2.5 m / s; and / or

[0052] The velocity of the gaseous reaction mixture in the first-stage discharge collection and distribution system is from 2 m / s to 4 m / s; and / or

[0053] The velocity of the gaseous reaction mixture in the second-stage discharge pipe system is from 0.8 m / s to 3.5 m / s; and / or

[0054] The velocity of the gaseous reaction mixture in the second-stage discharge collection and distribution system is from 4 m / s to 9 m / s.

[0055] It has been found that gas velocities within the claimed ranges provide an optimal damping effect without adversely affecting process performance.

[0056] In one embodiment of the present disclosure, the velocity of the gaseous reaction mixture in the first-stage discharge pipe system is less than 1.7 m / s.

[0057] In one embodiment, the velocity of the gaseous reaction mixture in the first discharge collection and distribution system is less than 3.5 m / s.

[0058] The velocity of the gaseous reaction mixture in the second-stage discharge pipe system is less than 2.5 m / s.

[0059] In one exemplary embodiment, the velocity of the gaseous reaction mixture in the second-stage discharge collection and distribution system is less than 7 m / s.

[0060] In one exemplary embodiment, the gaseous reaction mixture is compressed to a pressure of about 30 MPa to about 120 MPa in the first compression stage, and in the second stage, the gaseous reaction mixture is further compressed to about 120 MPa to the final polymerization pressure.

[0061] To further improve the damping effect of the method of the present disclosure, the gaseous reaction mixture can be passed through an additional collection and distribution system. In an exemplary embodiment, the first compression stage is thus connected to the first-stage suction collection and distribution system of the first-stage suction pipe system. In this case, the velocity of the gaseous reaction in the first-stage suction pipe system is preferably between 0.5 and 3 m / s, particularly less than 1.5. Further or alternatively, a preferred embodiment is one in which the velocity of the gaseous reaction mixture in the first-stage suction collection and distribution system is between 3 m / s and 7 m / s, particularly less than 6 m / s.

[0062] In an exemplary embodiment of the present disclosure, the second compression stage is connected to the second-stage suction collection and distribution system via the second-stage suction pipe system. Here, the velocity of the gaseous reaction mixture in the second-stage suction pipe system can be in the range of 0.5 m / s to 2.5 m / s, which can particularly be less than 1.5. Further preferably or alternatively, the velocity of the gaseous reaction mixture in the second-stage suction collection and distribution system is 2 m / s to 3.5 m / s, particularly less than 3 m / s.

[0063] During the process of the method of the present disclosure, the gaseous reaction mixture can be passed through a plurality of mixing blocks. It has surprisingly been found that this further suppresses any pulsation of the gaseous reaction mixture. In addition, any gaseous reaction mixture discharged from the respective cylinders of the first and / or second compression stages can be combined. Thus, an embodiment is preferred in which the gaseous reaction mixture is conveyed through at least one mixing block from the first-stage discharge collection and distribution system before entering at least one heat exchanger. The gaseous reaction mixture can be conveyed, for example, at a gas velocity of 2 to 4 m / s, particularly less than 3.5 m / s, from the first compression stage to at least one heat exchanger, particularly preferably via one or more mixing blocks.

[0064] Furthermore, when leaving the second compression stage, a preferred embodiment is one in which the gaseous reaction mixture is conveyed through at least one mixing block from the second-stage discharge collection and distribution system before being conveyed to the polymerization reactor. The gaseous reaction mixture is preferably conveyed from the second-stage discharge collection and distribution system to the polymerization reactor at a gas velocity of 2 to 3.5 m / s, particularly less than 3 m / s, particularly through one or more mixing blocks.

[0065] In an exemplary embodiment, the gaseous reaction mixture is conveyed from the heat exchanger to one or more mixing blocks before entering the second-stage suction collection and distribution system. In an exemplary embodiment, the compressor system further includes a pipe for supplying the reaction mixture to the first-stage suction collection and distribution system, and the gas velocity in the pipe is preferably 3 to 7 m / s.

[0066] In some embodiments, the compressor system further includes a pipe for discharging the reaction mixture from the second-stage collection and distribution system, and the gas velocity in the pipe is preferably 10 to 16 m / s.

[0067] According to established techniques, in some embodiments, the gaseous reaction mixture is compressed in a main compressor before entering the supercompressor. The gaseous reaction mixture can be compressed in the main compressor to a pressure of 10 MPa to 50 MPa. The main compressor can include five or six compression stages. In some embodiments, a fresh feed of an ethylenically unsaturated monomer (such as ethylene) can be introduced and the combined gas compressed. In such a case, one embodiment is preferred, wherein the main compressor includes two or three compression stages before the addition of the fresh gas and two or three compression stages after the addition of the fresh gas.

[0068] In some embodiments, a fresh monomer feed is introduced into the gaseous reaction mixture before the gaseous reaction mixture enters the supercompressor.

[0069] In some embodiments of the present disclosure, the entire reaction gas composition provided by the supercompressor is fed via a preheater to the inlet of the polymerization reactor. In another embodiment of the present disclosure, only a portion of the reaction gas composition compressed by the supercompressor is fed via a preheater to the inlet of the polymerization reactor, and the remaining portion of the reaction gas composition compressed by the supercompressor is fed as one or more side streams to the polymerization reactor downstream of the inlet of the polymerization reactor. In such an arrangement, it is preferred to feed 30 to 90 wt%, more preferably 40 to 70 wt% of the reaction gas composition provided by the supercompressor to the inlet of the polymerization reactor, and 10 to 70 wt%, more preferably 30 to 60 wt% of the reaction gas composition provided by the supercompressor as one or more side streams to the polymerization reactor downstream of the inlet of the tubular reactor.

[0070] In another aspect, the present disclosure provides a high-pressure polymerization apparatus for polymerizing or copolymerizing one or more ethylenically unsaturated monomers. The apparatus includes a supercompressor for compressing a gaseous reaction mixture, the supercompressor including

[0071] a first compression stage including at least two cylinders, the at least two cylinders being connected via a first-stage discharge pipe system to a first-stage discharge gas collection and distribution system;

[0072] a second compression stage including at least two cylinders, the at least two cylinders being connected via a second-stage suction pipe system to a second-stage suction gas collection and distribution system and via a second-stage discharge pipe system to a second-stage discharge gas collection and distribution system);

[0073] at least one heat exchanger arranged between the first and second compression stages.

[0074] At least one heat exchanger used in the device of the present disclosure may be a double-pipe heat exchanger.

[0075] After leaving the supercompressor, the compressed gaseous reaction mixture enters a high-pressure polymerization reactor where the actual polymerization takes place. The polymerization can be carried out in all types of high-pressure reactors suitable for high-pressure polymerization. High-pressure reactors used in the present technology are, for example, tubular reactors or autoclave reactors. The polymerization can be carried out in one or more tubular reactors or one or more autoclave reactors or a combination of these reactors.

[0076] A common autoclave reactor is a stirred reactor and has a length-to-diameter ratio in the range of 2 to 30, preferably 2 to 20. Such an autoclave reactor has one or more reaction zones, preferably 1 to 6 reaction zones, more preferably 1 to 4 reaction zones. The number of reaction zones depends on the number of agitator baffles that separate the individual mixing zones within the autoclave reactor. In the case where the polymerization or the first polymerization is carried out in an autoclave reactor, where the only polymerization reactor is an autoclave reactor or where the first reactor in a reactor cascade is an autoclave reactor, the reaction mixture from the compressor can first pass through a pre-cooler before entering the autoclave reactor.

[0077] A suitable tubular reactor is essentially a long thick-walled tube that is about 0.5 km to 4 km, preferably 1 km to 3 km, especially 5 km to 2.5 km long. The inner diameter of the tube is typically in the range from about 30 mm to 120 mm and preferably from 60 mm to 100 mm. Such a tubular reactor preferably has a length-to-diameter ratio greater than 1000, preferably 10000 to 40000 and especially 25000 to 35000. Preferably, the tubular reactor consists of tubes with a length of 5 m to 25 m, more preferably a length of 10 m to 22 m, especially a length of 15 m to 20 m.

[0078] A preferred tubular reactor has at least two reaction zones, preferably 2 - 6 reaction zones, more preferably 2 - 5 reaction zones. The number of reaction zones is given by the number of feed points for the initiator. Preferably, the tubular reactor is equipped with a cooling jacket for removing the heat of reaction. More preferably, all reaction zones of the tubular reactor are cooled by the cooling jacket.

[0079] In a preferred embodiment, the device includes a pre-heater upstream of the polymerization reactor for heating the reaction gas composition to a temperature capable of initiating the polymerization. The pre-heater preferably consists of tubes with a length of 5 m to 25 m, more preferably a length of 10 m to 22 m, especially a length of 15 m to 20 m. Preferably, the individual tubes of the pre-heater are connected together by flanges. These tubes can also be connected to bends, preferably to 180° bends, by flanges.

[0080] In a preferred embodiment, the apparatus for carrying out polymerization according to the present disclosure further includes two or more gas recycle lines for recycling unreacted monomers into the polymerization process in addition to the polymerization reactor. Preferably, the reaction mixture obtained in the polymerization reactor is transferred to a first separation vessel (also referred to as a high-pressure product separator) and separated into a gaseous fraction and a liquid fraction at an absolute pressure of 15 MPa to 50 MPa. The gaseous fraction taken out from the first separation vessel is fed to the suction side of a supercompressor via a high-pressure gas recycle line. In the high-pressure gas recycle line, the gas can be purified through several purification steps to remove unwanted components, such as entrained polymers or oligomers. The liquid fraction taken out from the first separation vessel may also contain dissolved monomers, such as ethylene and comonomers, in an amount of 20 to 40% by weight. It can be transferred to a second separation vessel, also referred to as a low-pressure product separator, and further separated into a polymer component and a gaseous component under reduced pressure, typically at an absolute pressure in the range of 0.1 to 0.5 MPa. The gaseous fraction taken out from the second separation vessel is fed to a main compressor via a so-called low-pressure gas recycle line, preferably to the foremost stage. In addition, the low-pressure gas recycle line may include several purification steps for purifying the gas from unwanted components.

[0081] In one embodiment, the pressure inside the polymerization reactor can be controlled by a pressure control valve, which is arranged at the outlet of the polymerization reactor, and the reaction mixture leaves the reactor through the pressure control valve. The pressure control valve can be any valve arrangement configured to reduce the pressure of the reaction mixture leaving the reactor to the pressure inside the first separation vessel.

[0082] In some embodiments, the apparatus includes a post-reactor cooler for cooling the reaction mixture downstream of the polymerization reactor. The post-reactor cooler can be arranged upstream of the pressure control valve or the post-reactor cooler can be arranged downstream of the pressure control valve. The post-reactor cooler can be arranged downstream of the pressure control valve. The post-reactor cooler can consist of tubes with a length of 5 m to 25 m, more preferably a length of 10 m to 22 m, and especially a length of 15 m to 20 m. The individual tubes of the tubular reactor are preferably connected together by flanges.

[0083] Reference will be made to Figure 1 describe the present disclosure in more detail. However, this specification should in no way be construed as limiting the scope and spirit of the present disclosure.

[0084] A gaseous reaction mixture comprising one or more ethylenically unsaturated monomers is introduced into a main compressor 10, which is connected via a pipe 13 to a supercompressor 100 including a first-stage suction collection and distribution system 11. The gaseous reaction mixture is conveyed from the first-stage suction collection and distribution system 11 via a first-stage suction pipe system 12 to a first compression stage 1. The gaseous reaction mixture leaves the first compression stage 1 via a first-stage discharge pipe system 3 and enters a first discharge collection and distribution system 2 before entering a heat exchanger 4 via one or more mixing blocks 16. After leaving the heat exchanger 4, the gaseous reaction mixture is conveyed to a second-stage suction collection and distribution system 6, which is connected to a second compression stage 2 via a second-stage suction pipe system 7. During its operation, the gaseous mixture passes through one or more mixing blocks 16. The compressed gaseous reaction mixture leaves the second compression stage 2 via a second-stage discharge pipe 9, enters a second-stage discharge collection and distribution system 8, and is then conveyed to a polymerization reactor 15 via a second-stage discharge pipe system 14, passing through one or more mixing blocks 16 arranged between the second-stage discharge collection and distribution system 8 and the polymerization reactor 15. A preheater 18 may be arranged between the mixing block 16 and the polymerization reactor 15.

[0085] The reactor 15 may include an initiator injection point for feeding an initiator mixture into the reactor 15. In Figure 1 this, the initiator feed is schematically shown by an arrow 20. However, the tubular reactor 15 may include a plurality of spatially separated initiator injection points.

[0086] The reaction mixture may leave the tubular reactor 15 through a pressure control valve 22 and pass through a post-reactor cooler 24. Thereafter, the resulting polymer is separated from unreacted ethylene and other low molecular weight compounds (monomers, oligomers, polymers, additives, solvents, etc.) through a first separation vessel 26 and a second separation vessel 28, and is discharged and pelletized via an extruder and a pelletizer 30.

[0087] The ethylene and comonomer that have been separated in the first separation vessel 26 are returned to the inlet end of the tubular reactor 15 in a high-pressure circuit 32. In the high-pressure circuit 32, the gaseous substances separated from the reaction mixture are first removed from other components in at least one purification stage and then added to the monomer stream between the main compressor 10 and the supercompressor 100. The high-pressure circuit 32 may separate the solvent from the wax.

[0088] The ethylene that has been separated in the second separation vessel 28 is post-treated in a low-pressure circuit 34, and the second separation vessel particularly further includes a major portion of polymerized very low molecular weight products (oligomers) and solvents. The low-pressure circuit 34 includes a plurality of separators, and heat exchangers are arranged between each separator. Figure 1Shows two purification stages consisting of heat exchangers 35 and 37 and separators 36 and 38. However, only one purification stage or preferably more than two purification stages can also be used. The low-pressure circuit 34 generally separates oil, solvents and waxes. The treated ethylene is first compressed in a booster compressor 40 and returned to the main compressor 10 via line 42. A chain transfer agent (CTA) can be added to the main compressor together with fresh ethylene via line 44. The comonomer can be added upstream of the supercompressor 100 via line 46.

Claims

1. A process for polymerizing or copolymerizing one or more ethylenically unsaturated monomers at a temperature of 100 to 350 °C and a pressure of 110 to 500 MPa, wherein the gaseous reaction mixture is compressed in a supercompressor (100), said supercompressor (100) comprises: - a first compression stage (1) comprising at least two cylinders, said at least two cylinders being connected via a first stage discharge pipe system (3) to a first stage discharge collection and distribution system (2); - a second compression stage (5) comprising at least two cylinders, said at least two cylinders being connected via a second stage suction pipe system (7) to a second stage suction collection and distribution system (6) and via a second stage discharge pipe system (9) to a second stage discharge collection and distribution system (8); - a heat exchanger (4) arranged between said first and second compression stages (1, 2); wherein the reaction mixture is supplied to each compression stage via a suction pipe system and the compressed reaction mixture is discharged from the compression stage via a discharge pipe system; wherein - the velocity of the gaseous reaction mixture in the first stage discharge pipe system (3) is from 0.8 m / s to 2.5 m / s; and / or - the velocity of the gaseous reaction mixture in the first stage discharge collection and distribution system (2) is from 2 m / s to 4 m / s; and / or - the velocity of the gaseous reaction mixture in the second stage discharge pipe system (9) is from 0.8 m / s to 3.5 m / s; and / or - the velocity of the gaseous reaction mixture in the second stage discharge collection and distribution system (8) is from 4 m / s to 9 m / s.

2. The process according to claim 1, wherein the collection and distribution system is selected from cross-connected pipes, cross-connected blocks and high-pressure manifolds.

3. The process according to any one of the preceding claims, wherein the velocity of the gaseous reaction mixture in the first stage discharge pipe system (3) is less than 1.7 m / s.

4. The process according to any one of the preceding claims, wherein the velocity of the gaseous reaction mixture in the first stage discharge collection and distribution system (2) is less than 3.5 m / s.

5. The process according to any one of the preceding claims, wherein the velocity of the gaseous reaction mixture in the second stage discharge pipe system (9) is less than 2.5 m / s.

6. The process according to any one of the preceding claims, wherein the velocity of the gaseous reaction mixture in the second stage discharge collection and distribution system (8) is less than 7 m / s.

7. The process according to any one of the preceding claims, wherein the first compression stage (1) is connected via a first stage suction pipe system (12) to a first stage suction collection and distribution system (11), and wherein the velocity of the gaseous reaction mixture in the first stage suction pipe system (12) is preferably between 0.5 m / s and 3 m / s, in particular less than 1.5, and / or the velocity of the gaseous reaction mixture in the first stage suction collection and distribution system (11) is between 3 m / s and 7 m / s, in particular less than 6 m / s.

8. The method according to any one of the preceding claims, wherein the velocity of the gaseous reaction mixture in the second-stage suction pipe system (7) is preferably from 0.5 m / s to 2.5 m / s, particularly less than 1.5, and / or the velocity of the gaseous reaction mixture in the second-stage suction collection and distribution system (6) is from 2 m / s to 3.5 m / s, particularly less than 3 m / s.

9. The method according to any one of the preceding claims, wherein the gaseous reaction mixture is conveyed through one or more mixing blocks (16) from the first-stage discharge collection and distribution system (2) before entering the heat exchanger (4).

10. The method according to any one of the preceding claims, wherein the gaseous reaction mixture is conveyed through a mixing block from the second-stage discharge collection and distribution system (8) before being conveyed to the polymerization reactor (15).

11. The method according to any one of the preceding claims, wherein the gaseous reaction mixture is conveyed from the heat exchanger (4) to one or more mixing blocks (16) before entering the second-stage suction collection and distribution system (6).

12. The method according to any one of the preceding claims, wherein the compressor system further comprises a pipe (13) for supplying the reaction mixture to the first-stage suction collection and distribution system (11), wherein the gas velocity in the pipe is preferably from 3 m / s to 7 m / s, preferably less than 6 m / s.

13. The method according to any one of the preceding claims, wherein the compressor system further comprises a pipe (14) for discharging the reaction mixture from the second-stage collection and distribution system (8), wherein the gas velocity in the pipe is preferably from 10 m / s to 16 m / s.

14. The method according to any one of the preceding claims, wherein the reaction is compressed in a main compressor (10) before entering the super-compressor.

15. The method according to any one of the preceding claims, wherein the velocity of the gaseous reaction mixture in the second-stage discharge pipe system is higher than the velocity of the gaseous reaction mixture in the first-stage discharge pipe system.

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