Apparatus for the gas-phase polymerization of olefins, and a process for preparing an olefin polymer

Abstract

This is an apparatus for the gas-phase polymerization of olefins, and a process for preparing an olefin polymer. It is an apparatus for the gas-phase polymerization of olefins, wherein the apparatus comprises a reactor comprising at least one polymerization zone, a recycling line to remove the reaction gas from the reactor and supply the reaction gas back to the reactor, a compressor to transport the reaction gas along the recycling line, and a heat exchanger to cool the reaction gas, wherein at least part of the inner surface of the recycling line that is in contact with the reaction gas has a surface roughness ra of less than 5 µm.

Description

/ 27 APPARATUS FOR THE GAS-PHASE POLYMERIZATION OF OLEFINS, AND A PROCESS FOR PREPARING AN OLEFIN POLYMER Field of invention

[001] The present disclosure provides an apparatus for gas-phase polymerization of olefins. In particular, the present disclosure provides an apparatus for gas-phase polymerization of olefins comprising a recycling line having an inner surface in contact with the reaction gas having a surface roughness Ra less than 5 μm. The present disclosure further provides a process for preparing an olefin polymer that is carried out in the apparatus. Background of the invention

[002] Polyolefins are a family of polymers derived primarily from simple olefins, such as ethylene and propylene. Despite more than eighty years of development, the need for efficient and resource-saving processes for the production of polyolefins is higher than ever.

[003] Gas-phase polymerization processes are economical processes for the production of polyolefins. Suitable reactors for carrying out such gas-phase polymerizations are, for example, fluidized bed reactors, stirred gas-phase reactors, or multi-zone circulation reactors with two distinct interconnected gas-phase polymerization zones. These processes are generally carried out in a gas phase comprising monomers and comonomers and often, additionally, also other gaseous components such as polymerization diluents, for example nitrogen or alkanes, or hydrogen as a molecular weight modifier or low molecular weight reaction products. The products obtained are generally solid polyolefin particles that are formed by polymerization catalyst systems that Petition 870230104989, dated 11 / 29 / 2023, page 13 / 45 / 27 generally comprise particulate solid catalysts.

[004] Gas-phase polymerization processes of olefins are characterized by large quantities of gas being removed from the reaction zone, passed through a heat exchanger to remove the heat of polymerization, and then returned to the polymerization zone. In fluidized bed reactors, the returned reaction gas also serves to maintain the polyolefin particles in a fluidized state. In multi-zone circulation reactors, circulation between the reactor zones is carried out by the returned reaction gas. To conduct all these processes, the reaction gas recycling lines are usually equipped with a centrifugal compressor.

[005] One approach to increasing the efficiency of production processes is to improve the equipment used in production.

[006] Document WO 2018 / 210780 A1 discloses a fluidized bed reactor for gas-phase polymerization of olefins comprising a gas distribution network installed in a lower part of the fluidized bed reactor and a gas recycling line, which is equipped with a compressor and a heat exchanger and which is connected at the upper end to the top of the fluidized bed reactor, wherein the gas recycling line splits at the lower end into at least two substantially horizontal branches that are tangentially connected to the fluidized bed reactor below the gas distribution network. According to the teaching of document WO 2018 / 210780 A1, the described network allows fine polymer particles that are possibly carried by the recycling gas to be easily transported back to the fluidized bed of polymer particles.

[007] Document no. WO 2008 / 074632 A1 refers to a gas distribution network suitable for distributing an upward flow of gas to a vessel containing a fluidized polymer. The disclosed gas distribution comprises a plurality of trays. Petition 870230104989, dated 11 / 29 / 2023, p. 14 / 45 / 27 arranged to form the side walls of an inverted cone, with said plurality of trays fixed to each other to form gaps in the overlapping area of ​​adjacent trays.

[008] Document WO 2007 / 071527 A1 describes a gas-phase process for polymerizing one or more α-olefins in a fluidized bed reactor in the presence of a polymerization catalyst. The fluidized bed reactor is equipped with a fluidization network disposed at its base and external means for recycling and cooling the unreacted gas from the top of said reactor to said fluidization network, and the process is characterized by (i) continuous pneumatic recycling of the polymer by means of a circulation circuit connecting said fluidization network to the upper region of the fluidized bed reactor; and (ii) continuous discharge of polymer from a zone of said circulation circuit having a polymer concentration higher than the polymer concentration within the fluidized polymer bed.

[009] Document no. WO 2019 / 154756 A1 refers to a gas-phase polymerization reactor for the gas-phase polymerization of olefins comprising at least one polymerization zone fitted with a recycle line to extract reaction gas from the reactor, conducting the reaction gas through a heat exchanger to cool and supply the reaction gas back to the reactor, wherein the recycle line is fitted with a heat exchanger, a centrifugal compressor comprising variable guide vanes and a butterfly valve, the variable guide vanes being arranged upstream of the centrifugal compressor and the butterfly valve being arranged downstream of the centrifugal compressor.

[0010] Document No. US 10,781,273 B2 discloses an apparatus and process for the production of multimodal polyolefins, in particular polyethylene resins. Production is carried out using two reactors in series, wherein one of the reactors is a multi-zone circulation reactor that can circulate polyolefin particles through two polymerization zones in Petition 870230104989, dated 11 / 29 / 2023, page 15 / 45 / 27, stating that a reactor is configured to produce a first polyolefin and a second reactor is configured to produce a second polyolefin, wherein the second reactor is configured to receive the first polyolefin from the first reactor or the first reactor is configured to receive the second polyolefin from the second reactor, and wherein the second reactor has an internal surface that is polished to a root mean square of less than about 3.8 μm (150 microinches).

[0011] Document No. US 2015 / 0367319 A1 deals with a process comprising the polymerization of an olefin monomer in a closed-circuit reactor in the presence of a catalyst and a diluent and the production of a fluid paste comprising solid particulate olefin polymer and diluent. The Biot number is maintained at or below about 3.0 within the closed-circuit reactor during the polymerization process. The fluid paste in the closed-circuit reactor forms a paste film that has a film coefficient along an inner surface of the reactor wall.

[0012] Document No. EP 2 602 269 A1 discloses a multi-stage process for the polymerization of olefins. Polyolefin particles are transferred from a first gas-phase polymerization reactor to a second gas-phase polymerization reactor. The first gas-phase reactor is a fluidized bed reactor comprising a gas distribution network and a settling tube, which is integrated with its upper opening into the distribution network and contains a bed of polyolefin particles that moves from top to bottom of the settling tube.

[0013] Document WO 2012 / 031986 A1 describes a gas-phase polymerization reactor having interconnected polymerization zones comprising a riser through which polymer particles flow upwards under fast fluidization or transport conditions. In addition, the reactor comprises a descending tube through which the polymer particles flow downwards in a densified manner under the action of gravity. Petition 870230104989, dated 11 / 29 / 2023, page 16 / 45 / 27, in which the bottom of the downpipe is connected to the lower region of the riser by means of a transport section. The transport section is designed as a curve that descends from the downpipe to the riser.

[0014] A polymer stream transfer process is disclosed in document no. EP 2 110 173 A1. The process concerns heating a stream containing polymer from a polymerization reactor to a separation zone or device. The stream is passed through a heater comprising at least one transfer line for the stream and means for heating the transfer line, wherein the average particle size of the solid polymer is less than 3 mm.

[0015] Document no. WO 2006 / 050919 A1 refers to an apparatus for the gas-phase polymerization of olefins. The apparatus comprises a gas-phase fluidized bed reactor, a recycled gas stream connected to the reactor to discharge and recirculate the recycled gas. In addition, the apparatus comprises a cyclone located in the recycling gas line for the reduction and precipitation of solid particles entrained in the reactor's recycling gas.

[0016] One of the challenges encountered in the gas-phase polymerization of polyolefins is the presence of polymer particles in the circulating reaction gas, which presents the danger of fouling the equipment due to the accumulation of polymer particles that, in extreme cases, can lead to clogging of the equipment, especially the recycling line. Therefore, there is a need to provide equipment for the production of polyolefins that allows the reaction gas to circulate in the recycling line without fouling, even if polymer particles are present in the circulating reaction gas, and that minimizes the effects of entrained dust in the recycling gas and reduces the risk of dust deposition on the internal surfaces of the equipment. Summary of the invention Petition 870230104989, dated 11 / 29 / 2023, page 17 / 45 / 27

[0017] The present disclosure provides an apparatus for gas-phase polymerization of olefins comprising - a reactor comprising at least one polymerization zone, - a recycling line to extract the reaction gas from the reactor and supply the reaction gas back to the reactor, - a compressor to transport the reaction gas along the recycling line and - a heat exchanger for cooling the reaction gas, wherein at least part of the inner surface of the recycle line that is in contact with the reaction gas has a surface roughness Ra of less than 5 μm, preferably less than 3 μm, determined in accordance with ASME B46.1.

[0018] In some embodiments, at least part of the inner surface of the recycling line is produced from stainless steel with a surface roughness Ra of less than 2.5 μm, preferably less than 2 μm, determined in accordance with ASME B46.1.

[0019] In some embodiments, at least part of the inner surface of the recycling line is produced from low-temperature carbon steel (LTCS) that has a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1.

[0020] In some embodiments, the apparatus has no protrusions on the surfaces that come into contact with the reaction gas that exceed a height of 1.5 mm.

[0021] In some embodiments, any curvature of the recycling line satisfies the condition that the radius r of the curvature is greater than 5 times the diameter of the recycling line.

[0022] In some embodiments, the compressor is located upstream of the heat exchanger. Petition 870230104989, dated 11 / 29 / 2023, p. 18 / 45 / 27

[0023] In some embodiments, the compressor is an open-type centrifugal compressor comprising an impeller to increase the pressure of the reaction gas, the impeller having a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1.

[0024] In some embodiments, the apparatus comprises variable guide vanes arranged upstream of the compressor, wherein the surface of the variable guide vanes comes into contact with the reaction gas which has a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1.

[0025] In some embodiments, the apparatus further comprises a butterfly valve disposed downstream of the heat exchanger, the surface of the butterfly valve coming into contact with the reaction gas which has a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1.

[0026] In some embodiments, the butterfly valve comprises a rotating disc that has an area smaller than the cross-section of the recycling line at the butterfly valve location.

[0027] In some embodiments, the heat exchanger is a multitubular heat exchanger comprising an inlet chamber, a bundle of tubes encapsulated in a housing structure and an outlet chamber, wherein each tube comprises an inlet, a longitudinal center and an outlet and the diameter d1 of the inlet of each tube is greater than the diameter d2 of the corresponding longitudinal center of said tube.

[0028] In some embodiments, the reactor is a fluidized bed reactor comprising a fluidized bed of polyolefin particles and a fluidization network at the bottom of the reactor.

[0029] In some embodiments, the fluidization network comprises a plurality of trays arranged to form the side walls of an inverted cone, wherein said plurality of trays are arranged to form slits in the area of ​​overlap of adjacent trays, wherein the Petition 870230104989, dated 11 / 29 / 2023, p. 19 / 45 / 27 trays have a surface roughness Ra of less than or greater than 3 μm, determined in accordance with ASME B46.1.

[0030] In some embodiments, the overlapping area of ​​a first tray forms the upper part of said slots and the successive tray forms the lower part of said slots.

[0031] In some embodiments, the apparatus is a multi-zone circulation reactor, in which in a first polymerization zone, growing polyolefin particles flow upwards under fluidization or rapid transport conditions and in which in a second polymerization zone, growing polyolefin particles flow downwards in a densified form, wherein the first polymerization zone and the second polymerization zone are interconnected and the polyolefin particles exiting the first polymerization zone enter the second polymerization zone and polyolefin particles exiting the second polymerization zone enter the first polymerization zone, thus establishing a circulation of polyolefin particles through the first and second polymerization zones.

[0032] In some modalities, the device is part of a series of devices.

[0033] In another embodiment, the present invention provides a process for preparing an olefin polymer comprising homopolymerizing an olefin or copolymerizing an olefin and one or more other olefins at temperatures of 20 °C to 200 °C and pressures of 0.5 MPa to 10 MPa in the presence of a polymerization catalyst, characterized in that the polymerization is carried out in an apparatus, of the present disclosure.

[0034] In some embodiments, the polymerization is a homopolymerization of ethylene or a copolymerization of ethylene and one or more other olefins selected from the group consisting of 1-butene, 1-hexene and 1-octene, or the polymerization is a homopolymerization of Petition 870230104989, dated 11 / 29 / 2023, p. 20 / 45 / 27 propene or a copolymerization of propene and one or more other olefins selected from the group consisting of ethylene, 1-butene and 1-hexene.

[0035] In some embodiments, the process is carried out at a reaction gas flow rate of 5 m / s 25 m / s, preferably 15 m / s 20 m / s.

[0036] In some embodiments, the fluidization velocity in the reactor is 0.3 to 1.5 m / s, preferably 0.5 to 1.2 m / s. Brief description of the drawings

[0037] Figure 1 schematically shows an apparatus of the present disclosure comprising a fluidized bed reactor for carrying out the process of the present disclosure.

[0038] Figure 2 schematically shows an apparatus of the present disclosure comprising a multi-zone circulation reactor for carrying out the process of the present disclosure. Detailed description of the invention

[0039] The present disclosure provides an apparatus for the gas-phase polymerization of olefins comprising a reactor comprising at least one polymerization zone, a recirculation line for removing reaction gas from the reactor and supplying the reaction gas back to the reactor, a compressor for transporting the reaction gas along the recirculation line, and a heat exchanger for cooling the reaction gas. Such reactors may be fluidized bed reactors, stirred gas-phase reactors, or multi-zone circulation reactors with two distinct interconnected gas-phase polymerization zones. Reactors of these types are generally known to those skilled in the art. Stirred gas-phase reactors may, for example, be stirred horizontally or vertically. Preferred gas-phase polymerization reactors according to the present invention are fluidized bed reactors and multi-zone circulation reactors. Petition 870230104989, dated 11 / 29 / 2023, p. 21 / 45 / 27

[0040] The olefins that can be polymerized in the apparatus of the present disclosure are especially 1-olefins, that is, hydrocarbons having terminal double bonds, without being restricted to this. Non-polar olefinic compounds are preferred. Particularly preferred 1-olefins are linear or branched C2-C12-1-alkenes, in particular, linear C2-C10-1-alkenes such as ethylene, propylene, 1-butene, 1-pentane, 1-hexene, 1-heptane, 1-octene, 1-decene or branched C2-C10-1-alkenes such as 4-methyl-1-pentene, conjugated and non-conjugated dienes such as 1,3-butadiene, 1,4-hexadiene or 1,7-octadiene. It is also possible to polymerize mixtures of various 1-olefins. Suitable olefins also include those in which the double bond is part of a cyclic structure that may have one or more ring systems. Examples are cyclopentene, norbornene, tetracyclododecene or methylnorbornene, or dienes such as 5-ethylidene-2-norbornene, norbornadiene or ethylnorbornadiene.It is also possible to polymerize mixtures of two or more olefins.

[0041] The apparatus are particularly suitable for the homopolymerization or copolymerization of ethylene or propylene and especially preferred for the homopolymerization or copolymerization of ethylene. Preferred comonomers in propylene polymerization have up to 40% by weight of ethylene, 1-butene and / or 1-hexene, preferably from 0.5% by weight to 35% by weight of ethylene, 1-butene and / or 1-hexene. As comonomers in ethylene polymerization, preference is given to the use of up to 20% by weight, more preferably from 0.01% by weight to 15% by weight and especially from 0.05% by weight to 12% by weight of Cs-C8-1-alkenes, in particular 1-butene, 1-pentene, 1-hexene and / or 1-octene. Particular preference is given to polymerizations in which ethylene is copolymerized with 0.1% by weight to 12% by weight of 1-hexene and / or 1-butene.

[0042] The apparatus of the present disclosure is characterized in that at least part, preferably the whole, of the inner surface of the line of Petition 870230104989, dated 11 / 29 / 2023, page 22 / 45 / 27. The recycling line in contact with the reaction gas has a surface roughness Ra of less than 5 μm, preferably less than 3 μm, determined in accordance with ASME B46.1. In the apparatus of the present disclosure, the compressor transports the reaction gas along the recycling line and thus causes the reaction gas to be drawn from the reactor, passed through the heat exchanger and again supplied to the reactor, thus ensuring the circulation of the reaction gas. In this configuration, the entrainment of polymer particles in the circulating reaction gas cannot be completely avoided. Designing the recycling line with an internal surface that has a surface roughness Ra of less than 5 μm minimizes the accumulation of any polymer particles present in the recycling line, thus reducing the risk of clogging of the recycling line and interruption of the manufacturing process.

[0043] With a surface roughness of less than 5 mm, it is possible to operate the apparatus with continuous circulation of fines. Thus, the apparatus makes it possible to operate a gas-phase polymerization of olefins with high reliability, even without the installation of a gas / solid separation device, such as a cyclone. A gas / solid separation device can lead to material loss, since solid particles, such as the catalyst, will be removed from the apparatus. Furthermore, such apparatus comprising a gas / solid separation device are not suitable for polymerizing polymer particles that have a small size, since they can be carried away from the reactor and removed from the apparatus by the gas / solid separation device. Thus, by providing the recycling line with an internal surface that has a surface roughness Ra of less than 5 μm, the operational flexibility of the apparatus is increased.The reactor head typically has an enlarged internal diameter compared to the bottom, to reduce gas flow velocity and prevent small particles from being carried into the recycle line. Although such reactors can still be applied to a... Petition 870230104989, dated 11 / 29 / 2023, p. 23 / 45 / 27. Regarding the apparatus of the present disclosure, it is no longer necessary to have a reactor with an enlarged head. As the recycling line of the above apparatus has low surface roughness, small particles flow through the recycling line back to the reactor without adhering to the inner surface of the recycling line. Thus, the circulation of small particles through the recycling line is permitted, which alleviates the need to mitigate the entrainment of small particles into the recycling line. In some embodiments, the recycling line is not equipped with a cyclone. In particular, the recycling line may not be equipped with a cyclone upstream of the compressor and / or heat exchanger.

[0044] The surface roughness Ra, as defined in this disclosure, can, for example, be obtained by polishing, such as mechanical polishing or electropolishing.

[0045] Preferably, the different components of the apparatus for the gas-phase polymerization of olefins, and in particular the recycling line, are produced from a durable material that does not interfere with the polymerization reaction and is capable of withstanding the high temperature and pressure reaction conditions. In preferred embodiments, at least part of the recycling line and the equipment installed in the recycling line, preferably the entire recycling line and the equipment installed in the recycling line, are produced from steel, preferably stainless steel or low-temperature carbon steel. In the case of stainless steel, the inner surface in contact with the reaction gas preferably has a surface roughness Ra of less than 2.5 μm, preferably less than 2 μm, determined in accordance with ASME B46.1.In preferred alternative embodiments, the recycling line and at least part of the equipment installed in the recycling line are produced from low-temperature carbon steel (LTCS), and the inner surface of the low-temperature carbon steel in contact with the reaction gas has a... Petition 870230104989, dated 11 / 29 / 2023, p. 24 / 45 / 27 surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1.

[0046] In addition to employing an internal surface of the recycling line that has a particularly low surface roughness, further flow improvement was observed in the present disclosure cases where protrusions on any of the surfaces that come into contact with the reaction gas, for example, originating from welding elements of the polymerization apparatus, were kept as small as possible. In preferred embodiments, the apparatus of the present disclosure is therefore characterized in that the apparatus has no protrusions on the surfaces that come into contact with the reaction gas that exceed a height of 1.5 mm.

[0047] In particular, the recycling line of the apparatus according to the present disclosure is designed with the aim of preventing polymer fines from adhering to the internal surfaces and initiating unwanted polymerization, generating sheets or plugs that over time can block the fluidization process. In this respect, it has also been shown to be advantageous to avoid sharp bends or angles in the recycling line. Any bends in the recycling line should therefore have a long diameter to reduce friction from the recirculating polymer fines and limit centrifugal forces on the walls. It has been surprisingly found that this objective can be achieved if the radius r of curvature in the recycling line is greater than its diameter. In some preferred embodiments, any curvature of the recycling line thus fulfills the condition that the radius r of curvature is greater than 5 times the diameter d of the recycling line. The ratio can thus be expressed as r>5d.

[0048] The apparatus of the present disclosure further comprises a compressor, preferably a centrifugal compressor, for transporting the reaction gas along the recycling line. To achieve maximum efficiency of the reaction gas flow, the compressor is preferably Petition 870230104989, dated 11 / 29 / 2023, page 25 / 45 / 27, located upstream of the heat exchanger. In preferred embodiments of the present disclosure, the compressor is designed such that any parts of the surface within the compressor that come into contact with the reaction gas have a surface roughness Ra of less than 3 μm, determined in accordance with ASME B46.1. The compressor employed in the apparatus of the present disclosure is preferably equipped with an impeller. In other preferred embodiments of the apparatus of the present disclosure, the compressor is an open-type centrifugal compressor comprising an impeller. Preferably, the impeller has a surface roughness Ra of less than 3 μm, determined in accordance with ASME B46.1. By ensuring that the surface roughness of the impeller is within the claimed limit, the circulation velocity of the reaction gas could be optimized and the interference of any polymer fines with the flow could be reduced.

[0049] In preferred embodiments, the apparatus further comprises variable guide vanes arranged upstream of the compressor. The surface of the variable guide vanes that comes into contact with the reaction gas preferably has a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1.

[0050] The apparatus of the present disclosure further comprises a heat exchanger for cooling the reaction gas. In preferred embodiments of the present disclosure, the heat exchanger is designed such that any parts of the surface within the heat exchanger that come into contact with the reaction gas have a surface roughness Ra of less than 7 μm, more preferably less than 3 μm and in particular less than 2 μm, determined in accordance with ASME B46.1. In particularly preferred embodiments, the heat exchanger is a tube-shell heat exchanger. In these embodiments, the internal surfaces of the inlet chamber, the tubes and the outlet chamber of the tube-shell heat exchanger preferably have a surface roughness Ra of less than 7 μm, more preferably Petition 870230104989, dated 11 / 29 / 2023, p. 26 / 45 / 27 less than 3 μm and in particular less than 2 μm, determined in accordance with ASME B46.1.

[0051] In particularly preferred embodiments, the heat exchanger is a multitubular heat exchanger comprising an inlet chamber, a tube bundle enclosed in an enclosure structure, and an outlet chamber, wherein each tube comprises an inlet, a longitudinal center, and an outlet, and the diameter d1 of the inlet of each tube is greater than the diameter d2 of the corresponding longitudinal center of said tube. Due to the special design of the tubes, any polymer particles present in the gas flow are smoothly guided through the heat exchanger tubes, and the risk of accumulation and therefore fouling is significantly reduced. In these embodiments, the ratio between diameter d1 and diameter d2 is preferably in the ratio of 1.75:1 to 1.5:1, more preferably from 1.4:1 to 1.3:1.The inlet of each tube preferably has a conical shape, wherein the angle between the cone area and the central geometric axis of the tube is preferably in the range of 20° to 60°, more preferably from 30° to 50°, and in particular 45°. The inlet of each tube preferably has a diameter d1 of 25 mm to 45 mm, preferably from 30 mm to 40 mm. The diameter within the scope of the present disclosure is the internal diameter and is defined for the tube inlets as any straight line segment passing through the center of the circle defined by the periphery of the tube inlet at its widest expansion and whose endpoints were on said circle. Preferably, the diameter d2 of the longitudinal central part of each tube, that is, the internal diameter of the longitudinal central part of each tube, is from 10 mm to 30 mm, more preferably from 15 to 25 mm. Preferably, the longitudinal central part of the tubes has a constant diameter.

[0052] In some preferred embodiments, the apparatus of the present disclosure further comprises a butterfly valve disposed downstream of the Petition 870230104989, dated 11 / 29 / 2023, page 27 / 45 / 27 heat exchanger. The use of a butterfly valve as an instrument to control the flow rate of the reaction gas in the recycling line allows for a variable pressure drop in the recycling line, while presenting a low risk of fouling. Preferably, the butterfly valve is constructed in such a way that sharp edges and corners are avoided within the butterfly valve to minimize the risk of small particles carried in the reaction gas adhering to the parts of the butterfly valve. To further minimize said risk, the surface of the butterfly valve that comes into contact with the reaction gas preferably has a surface roughness Ra of less than 3 μm, determined in accordance with ASME B46.1. Preferably, the butterfly valve comprises a rotating disc that has an area smaller than the cross-section of the recycling line at the location of the butterfly valve.This means that when the butterfly valve is in the fully closed position, i.e., the rotating disc is positioned perpendicular to the gas flow, the gas flow is not completely blocked. Preferably, the area of ​​the rotating disc is 90% to 99% of the cross-section of the recycling line at the butterfly valve location, more preferably the area of ​​the rotating disc is 94% to 98% of the cross-section of the recycling line at the butterfly valve location. In preferred embodiments, the rotating disc is circular and the unblocked area of ​​the recycling line at the butterfly valve location in the closed position forms an annular gap around the rotating disc. In preferred embodiments, the rotating disc is centrally fixed and rotates around a geometric axis passing through the center of the rotating disc. Preferably, the rotating disc has a surface roughness Ra less than 3 μm, determined according to ASME B46.1.

[0053] In preferred embodiments, the apparatus of the present disclosure comprises a reactor which is a fluidized bed reactor comprising a fluidized bed of polyolefin particles, a network of Petition 870230104989, dated 11 / 29 / 2023, page 28 / 45 / 27 fluidization at the bottom of the reactor and optionally a velocity reduction zone at the top of the reactor. This reactor design allows for a constant flow of reaction gas and a stable fluidized bed of polyolefin particles.

[0054] Fluidized bed reactors are reactors in which polymerization occurs in a bed of polymer particles that is maintained in a fluidized state by supplying a reaction gas mixture to a reactor at the lower end of the reactor, typically below a gas distribution network that serves to distribute the gas flow and then return the gas to the top of the fluidized bed reactor. The reaction gas mixture is then returned to the lower end of the reactor via a recirculation line equipped with a compressor and a heat exchanger to remove the heat of polymerization. The velocity of the reaction gas mixture must first be high enough to fluidize the mixed bed of finely divided polymer particles present in the tube that serves as the polymerization zone and, second, to effectively remove the heat of polymerization.

[0055] The fluidization grid of the fluidized bed reactor preferably comprises a plurality of trays arranged to form the side walls of an inverted cone, said plurality of trays being arranged to form slits in the overlapping area of ​​adjacent trays, wherein the trays have a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.1. In preferred embodiments, the overlapping area of ​​a first tray forms the upper part of said slits and the successive tray forms the lower part of said slits. Such grids are particularly suitable for distributing an upward gas flow in a homogeneous manner to a vessel containing a polymer under fluidized conditions. Suitable arrangements of the trays are described, for example, in document no. WO 2008 / 074632 A1. Petition 870230104989, dated 11 / 29 / 2023, p. 29 / 45 / 27

[0056] In other preferred embodiments, the fluidized bed reactor is equipped with a settling tube. The settling tube is preferably integrated with its upper opening into the gas distribution network. Preferably, the gas distribution network and the settling tube are arranged so that the gas distribution network has a conical shape whose downward slope towards the settling tube favors the entry of polyolefin particles into the settling tube due to gravity.

[0057] In preferred embodiments, the fluidization velocity in the fluidized bed reactor is 0.3 to 1.5 m / s, more preferably 0.5 to 1.2 m / s to provide a homogeneous and stable bed of fluidized polymer particles.

[0058] Figure 1 shows schematically an apparatus of the present disclosure comprising a fluidized bed reactor.

[0059] The fluidized bed reactor (1) comprises a fluidized bed (11) of polyolefin particles, a gas distribution network (12) and a velocity reduction zone (13) which has an increased diameter compared to the diameter of the fluidized bed portion of the reactor. The polyolefin bed is maintained in a fluidized state by an upward flow of gas supplied through the gas distribution network (12) located at the bottom of the reactor (1). The reaction gas stream leaving the top of the velocity reduction zone (13) via the recycle line (3) is compressed by the compressor (4) comprising variable guide vanes (5), transferred to a heat exchanger (6) where it is cooled and then recycled at the bottom of the fluidized bed reactor (1) at a point below the gas distribution network (12). The recycle line (3) further comprises, downstream of the heat exchanger (6), a butterfly valve (7).The compensating monomer, molecular weight regulators and optional inert gases and / or process additives can be supplied in the reactor (1) in various positions, for example,. Petition 870230104989, dated 11 / 29 / 2023, page 30 / 45 / 27 through line (8) upstream of compressor (4).

[0060] The fluidized bed reactor (1) is equipped with continuous pneumatic recycling of polyolefin particles by means of a circulation loop (14) connecting the gas distribution network (12) to the upper region of the fluidized bed reactor (1). The circulation circuit (14) comprises a settling tube (15) and a pneumatic conveying pipe (16). The settling tube (15) is integrated with its upper opening into the gas distribution network (12) and is preferably arranged substantially vertically. The gas distribution network (12) has a cone shape, so that its downward slope towards the settling tube (15) promotes the entry of polyolefin particles into the settling tube (15) due to gravity. The upper opening of the settling tube (15) is preferably located in a central position relative to the gas distribution network (12).The carrier gas supplied through line (17) to transport the polyolefin particles through the pneumatic conveyor pipe (16) is taken from the gas recycling line at a point downstream of the compressor (4) and upstream of the heat exchanger (6). The discharge of the polyolefin particles from the fluidized bed reactor (1) occurs from the settling pipe (15) through the discharge conduit (9).

[0061] In other preferred embodiments, the apparatus of the present disclosure comprises a reactor that is a multi-zone circulation reactor, wherein in a first polymerization zone, growing polyolefin particles flow upwards under fluidization or rapid transport conditions and, in a second polymerization zone, growing polyolefin particles flow downwards in a densified form, wherein the first polymerization zone and the second polymerization zone are interconnected and the polyolefin particles exiting the first polymerization zone enter the second polymerization zone and polyolefin particles exiting the second polymerization zone enter the first Petition 870230104989, dated 11 / 29 / 2023, page 31 / 45 / 27 polymerization zone, thus establishing a circulation of polyolefin particles through the first and second polymerization zones. It was found that carrying out the polymerization in a reactor as described allows good control of the polymer properties, in particular the molecular weight distribution.

[0062] Multi-zone circulation reactors are, for example, described in document no. WO 97 / 04015 A1 and document no. WO 00 / 02929 A1 and have two interconnected polymerization zones, a riser, in which the growing polyolefin particles flow upwards under conditions of rapid fluidization or transport, and a downpipe, in which the growing polyolefin particles flow downwards in a densified form under the action of gravity. Polyolefin particles leaving the riser enter the downpipe, and polyolefin particles leaving the downpipe are reintroduced into the riser, thus establishing a polymer circulation between the two polymerization zones, and the polymer is passed alternately several times through these two zones. In such polymerization reactors, a solid / gas separator is arranged above the downpipe to separate the polyolefin and reaction gas mixture coming from the riser.The growing polyolefin particles enter the downpipe, and the reaction gas mixture separated from the uppipe is continuously recycled through a gas recycle line to one or more reintroduction points in the polymerization reactor. Preferably, the main portion of the recycle gas is recycled at the bottom of the uppipe. The recycle line is equipped with a centrifugal compressor and a heat exchanger to remove the heat of polymerization. Preferably, a line to supply the catalyst or a line to supply polyolefin particles from an upstream reactor is arranged in the riser, and a polymer discharge system is located at the bottom of the downpipe. The introduction of... Petition 870230104989, dated 11 / 29 / 2023, page 32 / 45 / 27 monomers, comonomers, hydrogen components and / or inert components may occur at various points along the riser tube and the faller tube.

[0063] Figure 2 shows schematically an apparatus of the present disclosure comprising a multi-zone circulation reactor.

[0064] The multi-zone circulation reactor (2) comprises a riser (21) as the first reaction zone and a downpipe (22) as the second reaction zone. The riser (21) and the downpipe (22) are repeatedly passed through the polyolefin particles. Inside the riser (21), the polyolefin particles flow upwards under conditions of rapid fluidization and inside the downpipe (22), the polyolefin particles flow downwards under the action of gravity. The riser pipe (21) and the downpipe (22) are appropriately interconnected by the interconnecting bends (23) and (24).

[0065] After flowing through the riser (21), the polyolefin particles and the reaction gas mixture leave the riser (21) and are transported to a solid / gas separation zone (25). This solid / gas separation can be effected using conventional separation means, such as, for example, a centrifugal separator like a cyclone. From the separation zone (25), the polyolefin particles move downwards into the downpipe (22). A barrier fluid to prevent the reaction gas mixture from the riser (21) from entering the downpipe (22) can be supplied at an upper part of the downpipe (22) through the line (26).

[0066] The reaction gas mixture exiting the separation zone (25) is recycled to the bottom of the riser (21) by means of a recycling line (3), equipped with a compressor (4) comprising variable guide vanes (5) to establish rapid fluidization conditioning the riser (21). The recycling line (3) further comprises a heat exchanger (6) and a Petition 870230104989, dated 11 / 29 / 2023, page 33 / 45 / 27 butterfly valve (7) downstream of the heat exchanger (6). Replacement monomers, replacement comonomers and, optionally, inert gases and / or process additives may be supplied to the reactor (2) in various positions, for example, through line (8) in the recycling line (3). Between the compressor (4) and the heat exchanger (6), a line (27) branches and carries a portion of the recycled gas to the interconnecting bend (24) to transport the polyolefin particle from the downpipe (22) to the riser (21).

[0067] The bottom of the downpipe (22) is fitted with a butterfly valve (28) which has an adjustable opening to adjust the flow of polyolefin particles from the downpipe (22) through the interconnecting strip (24) to the riser (21). Above the butterfly valve (28), quantities of a recycling gas mixture from the recycling line (3) through lines (26) and (29) are introduced as metering gas into the downpipe (22) to facilitate the flow of polyolefin particles through the butterfly valve (28). The discharge of polyolefin particles from the multi-zone circulation reactor (2) occurs from the downpipe (22) through the discharge conduit (9).

[0068] In other preferred embodiments of the present disclosure, the apparatus is part of a series of apparatuses. Preferably, the series comprises a first gas-phase apparatus and a second subsequent gas-phase apparatus.

[0069] Another object of the present disclosure is a process for preparing an olefin polymer comprising homopolymerizing an olefin or copolymerizing an olefin and one or more other olefins at temperatures from 20 to 200 °C and pressures from 0.5 to 10 MPa in the presence of a polymerization catalyst, wherein the process is carried out in an apparatus of the present disclosure.

[0070] Preferably, the polymerization is a homopolymerization Petition 870230104989, dated 11 / 29 / 2023, p. 34 / 45 / 27 of ethylene or a copolymerization of ethylene and one or more other olefins selected from the group consisting of 1-butene, 1-hexene and 1-octene or the polymerization is a homopolymerization of propylene or a copolymerization of propylene and one or more other olefins selected from the group consisting of ethylene, 1-butene and 1-hexene. In preferred embodiments, the resulting polyolefin is a high-density polyethylene with a density determined according to ISO 1183 at 23 °C from 0.945 to 965 g / cm3.

[0071] The process of the present invention can be carried out at pressures from 0.5 MPa to 10 MPa, preferably from 1.0 MPa to 8 MPa and, in particular, from 1.5 MPa to 4 MPa, wherein these pressures, like all pressures given in the present invention, should be understood as absolute pressures, i.e., pressure with the dimension MPa (abs). Polymerization is preferably carried out at temperatures from 30 °C to 160 °C, particularly preferably from 65 °C to 125 °C, with temperatures in the upper part of this range being preferred for preparing high-density ethylene copolymers and temperatures in the lower part of this range for preparing lower-density ethylene copolymers.

[0072] The process can also be carried out in a condensed or supercondensed mode, in which part of the circulating reaction gas mixture is cooled below the dew point and returned to the reactor separately as either a liquid or gas phase, or together as a two-phase mixture to make additional use of the enthalpy of vaporization to cool the reaction gas. When operating in a condensation or supercondensation mode, the process of the present disclosure is preferably carried out in a fluidized bed reactor.

[0073] In preferred embodiments of the present disclosure, the polymerization is carried out in the presence of an inert gas such as nitrogen or an alkane having from 1 to 10 carbon atoms such as methane, ethane, Petition 870230104989, dated 11 / 29 / 2023, page 35 / 45 / 27 propane, n-butane, isobutane, n-pentane, isopentane or n-hexane or mixtures thereof. The use of nitrogen or propane as an inert gas, if appropriate, in combination with additional alkanes, is preferred. In particularly preferred embodiments of the present disclosure, the polymerization is carried out in the presence of a C3-C5 alkane as a polymerization diluent and, most preferably, in the presence of propane, especially in the case of homopolymerization or copolymerization of ethylene. The reaction gas mixtures within the reactor then further comprise the olefins to be polymerized, i.e., a main monomer and one or more optional comonomers. In preferred embodiments of the present disclosure, the reaction gas mixture has an inert component content of 30 to 99% by volume, more preferably 40 to 95% by volume, and especially 45 to 85% by volume.In other preferred embodiments of the present disclosure, especially if the main monomer is propylene, no inert diluent or only minor amounts of inert diluent are added. The reaction gas mixture may further comprise additional components, such as antistatic agents or molecular weight regulators like hydrogen. The components of the reaction gas mixture may be supplied to the gas-phase polymerization reactor or recycling line in gaseous form or as a liquid that then vaporizes within the reactor or recycling line.

[0074] The polymerization of olefins can be carried out using all the usual olefin polymerization catalysts. This means that polymerization can be performed using chromium oxide-based Phillips catalysts, using Ziegler-Natta or Ziegler catalysts, or using single-site catalysts. For the purposes of the present disclosure, single-site catalysts are catalysts based on chemically uniform transition metal coordination compounds. In addition, it is also possible to use mixtures of two or more of these. Petition 870230104989, dated 11 / 29 / 2023, page 36 / 45 / 27 catalysts for the polymerization of olefins. Such mixed catalysts are often referred to as hybrid catalysts. The preparation and use of these catalysts for olefin polymerization are generally known.

[0075] Preferred catalysts are of the Ziegler type, preferably comprising a titanium or vanadium compound, a magnesium compound and optionally an electron donor compound and / or a particulate inorganic oxide as a support.

[0076] Ziegler-type catalysts are normally polymerized in the presence of a cocatalyst. Preferred cocatalysts are organometallic compounds of metals from Groups 1, 2, 12, 13 or 14 of the Periodic Table of Elements, in particular, organometallic compounds of metals from Group 13 and, especially, organoaluminum compounds. Preferred cocatalysts are, for example, organometallic alkyls, organometallic alkoxides or organometallic halides.

[0077] Preferred organometallic compounds comprise lithium alkyls, magnesium or zinc alkyls, magnesium alkyl halides, aluminum alkyls, silicon alkyls, silicon alkoxides and silicon alkyl halides. More preferably, organometallic compounds comprise aluminum alkyls and magnesium alkyls. Even more preferably, organometallic compounds comprise aluminum alkyls, most preferably trialkylaluminum compounds or compounds of this type in which an alkyl group is replaced by a halogen atom, for example, by chlorine or bromine. Examples of such aluminum alkyls are trimethylaluminum, triethylaluminum, triisobutylaluminum, trinhexylaluminum or diethylaluminum chloride, or mixtures thereof.

[0078] The preferred catalysts are also Phillips-type chromium catalysts, which are preferably prepared by applying a chromium compound to an inorganic support and subsequent activation of the Petition 870230104989, dated 11 / 29 / 2023, page 37 / 45 / 27 catalyst precursor obtained at temperatures in the range of 350 to 1000 °C, resulting in chromium present in valences less than six which are converted to the hexavalent state. In addition to chromium, other elements such as magnesium, calcium, boron, aluminum, phosphorus, titanium, vanadium, zirconium or zinc can also be used. Particular preference is given to the use of titanium, zirconium or zinc. Combinations of the aforementioned elements are also possible. The catalyst precursor can be doped with fluoride before or during activation. As supports for Phillips-type catalysts, which are also known to those skilled in the art, mention can be made of aluminum oxide, silicon dioxide (silica gel), titanium dioxide, zirconium dioxide or their oxides or mixed cogels or aluminum phosphate.Other suitable support materials can be obtained by modifying the surface area of ​​the pores, for example, using compounds of boron, aluminum, silicon, or phosphorus. Silica gel is preferred. Spherical or granular silica gels are preferred, the former also being spray-dried. The activated chromium catalysts can subsequently be prepolymerized or pre-reduced. Pre-reduction is normally carried out using cobalt or hydrogen at 250 °C to 500 °C, preferably 300 °C to 400 °C, in an activator.

[0079] In another preferred embodiment of the present invention, the polymerization is a polymerization in a gas-phase reactor that is part of a cascade of polymerization reactors, wherein one or more polymerizations in other gas-phase reactors of the cascade of polymerization reactors may also be polymerizations according to the present invention. Suitable combinations of such polymerization reactors include a fluidized bed reactor followed by a multi-zone circulating reactor, a multi-zone circulating reactor followed by a fluidized bed reactor, a cascade of two or three fluidized bed reactors and one or Petition 870230104989, dated 11 / 29 / 2023, page 38 / 45 / 27 two loop reactors followed by one or two fluidized bed reactors.

[0080] The apparatus design of the present disclosure allows for rapid circulation of the reaction gas through the recycling line. In preferred embodiments, the process of the present disclosure is therefore carried out at a reaction gas flow rate in the recycling line of 5 m / s ± 25 m / s, more preferably 15 m / s ± 20 m / s. A reaction gas flow rate of this magnitude ensures good exchange and transport of the fine polymer and also helps to avoid any deposit or accumulation of polymer particles.

[0081] The apparatus of the present disclosure allows for gas-phase polymerization of olefins without fouling in the recycling line or in equipment installed in the recycling line and without polymer dust deposits on the internal surfaces of the apparatus, even if polymer particles are present in the circulating reaction gas. The apparatus makes it possible to operate gas-phase polymerization of olefins with high reliability, even without the installation of a gas / solid separation device, such as a cyclone. In preferred embodiments of the present disclosure, the recycling line is not equipped with a cyclone, for example, upstream of the compressor and heat exchanger. The apparatus allows for gas-phase polymerization of olefins with polymer particles that have a small size, thus increasing the operational flexibility of the apparatus.This device also allows the polymerization process to begin with an empty reactor, i.e., without the need to introduce a seed bed of polymer particles before initiating polymerization. The device's insensitivity to circulating polymer particles further increases the reliability of the entire polymerization system. Petition 870230104989, dated 11 / 29 / 2023, pp. 39 / 45

Claims

1 / 3 CLAIMS 1. Apparatus for the gas-phase polymerization of olefins, wherein the apparatus is characterized in that it comprises - a reactor (1,2) comprising at least one polymerization zone; - a recycling line (3) for extracting the reaction gas from the reactor (1,2) and supplying the reaction gas back to the reactor (1,2); - a compressor (4) for transporting the reaction gas along the recycling line (3); and - a heat exchanger (6) for cooling the reaction gas, wherein the whole inner surface of the recycling line (3) that is in contact with the reaction gas has a surface roughness Ra less than 5 μm, preferably less than 3 μm, determined in accordance with ASME B46.

1.

2. Apparatus according to claim 1, characterized in that at least part of the inner surface of the recycling line (3) is produced from stainless steel with a surface roughness Ra less than 2.5 μm, preferably less than 2 μm, determined in accordance with ASME B46.

1.

3. Apparatus according to claim 1, characterized in that at least part of the inner surface of the recycling line (3) is produced from low-temperature carbon steel (LTCS) having a surface roughness Ra less than 3 μm, determined in accordance with ASME B46.

1.

4. Apparatus according to any of the preceding claims, characterized in that the apparatus has no protrusions on the surfaces that come into contact with the reaction gas that exceed a height of 1.5 mm.

5. Apparatus according to any of the claims Petition 870250014562, dated 2 / 21 / 2025, p. 13 / 18 2 / 3 above, characterized in that any curvature of the recycling line (3) meets the condition that the radius r of the curvature is greater than 5 times the diameter of the recycling line (3).

6. Apparatus according to any of the preceding claims, characterized in that the compressor (4) is an open-type centrifugal compressor comprising an impeller for increasing the pressure of the reaction gas, wherein the impeller has a surface roughness Ra less than 3 µm, determined in accordance with ASME B46.

1.

7. Apparatus according to claim 6, characterized in that the apparatus comprises variable guide vanes (5) arranged upstream of the compressor (4), wherein the surface of the variable guide vanes (5) comes into contact with the reaction gas having a surface roughness Ra less than 3 µm, determined in accordance with ASME B46.

1.

8. Apparatus according to any of the preceding claims, wherein the apparatus is characterized in that it further comprises a butterfly valve (7) disposed downstream of the heat exchanger (6), wherein the surface of the butterfly valve (7) comes into contact with the reaction gas having a surface roughness Ra less than 3 µm, determined in accordance with ASME B46.

1.

9. Apparatus according to claim 8, characterized in that the butterfly valve (7) comprises a rotating disc having an area smaller than the cross-section of the recycling line (3) at the location of the butterfly valve (7).

10. Apparatus according to any of the preceding claims, characterized in that the heat exchanger (6) is a multitubular heat exchanger comprising an inlet chamber, a tube bundle enclosed in an enclosure structure and an outlet chamber, wherein each tube comprises an inlet, a longitudinal center and an outlet and the diameter d1 of the inlet of each tube is greater than the diameter d2 of the corresponding longitudinal center of said tube.

11. Apparatus according to any of the preceding claims, characterized in that the reactor (1) is a fluidized bed reactor comprising a fluidized bed (11) of polyolefin particles and a fluidization network (12) at the bottom of the reactor (1).

12. Apparatus according to any one of claims 1 to 10, characterized in that the reactor is a multi-zone circulation reactor (2), wherein in a first polymerization zone (21), growing polyolefin particles flow upwards under fluidization or rapid transport conditions and wherein in a second polymerization zone (22), growing polyolefin particles flow downwards in a densified form, wherein the first polymerization zone (21) and the second polymerization zone (22) are interconnected and the polyolefin particles exiting the first polymerization zone (21) enter the second polymerization zone (22) and polyolefin particles exiting the second polymerization zone (22) enter the first polymerization zone (21), thus establishing a circulation of polyolefin particles through the first and second polymerization zones (21, 22).

13. Apparatus according to any of the preceding claims, characterized in that the recycling line (3) is not equipped with a cyclone for gas / solid separation.

14. Process for preparing an olefin polymer, characterized in that it comprises the homopolymerization of an olefin or the copolymerization of an olefin and one or more other olefins at temperatures of 20 to 200 °C and pressures of 0.5 to 10 MPa in the presence of a polymerization catalyst, wherein the process is carried out in an apparatus as defined in any one of claims 1 to 13.

15. Process according to claim 14, characterized in that the process is carried out at a reaction gas flow rate of 5 m / s to 25 m / s, preferably 15 m / s to 20 m / s. Petition 870250014562, dated 21 / 02 / 2025, p. 15 / 18

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