Fluidized bed reactor for olefin gas phase polymerization

Abstract

A fluidized bed reactor for the gas phase polymerization of olefins, having an inner chamber (2) which in turn has at least one lower part (3) and at least one upper part (4); the fluidized bed reactor (1) comprises: a gas distribution grid (7) located within the inner chamber (2) and at least partially separating the lower part (3) from the upper part (4); a recirculation line (8) configured to feed fluidizing gas to the lower portion (3) and having a first end (9) connected to the inner chamber (2) at the upper portion (4); a polymer discharge channel (17) configured to discharge the polymer obtained inside the upper part (4) downward in a discharge direction (D); and a partition wall (DW) located around at least a section of the polymer discharge channel (17) to define a first region (A) of the inner chamber (2) and to prevent the fluidizing gas from reaching the first region (A), and having a first portion (DW ') intersecting the discharge direction (D).

Description

Technical Field

[0001] The present invention relates to a fluidized bed reactor for olefin gas phase polymerization and a method for preparing olefin polymer. Background Art

[0002] Gas phase polymerization is an economical method for preparing polyolefins (such as homopolymers of ethylene or propylene or copolymers of ethylene and / or propylene with other olefins). Fluidized bed reactors for implementing this method have been around for a long time. These reactors include a bed of polymer particles, which is kept in a fluidized state by an upwardly flowing fluidizing gas. Conventional reactors mainly include a reactor space in the form of an inner chamber of a vertical cylinder provided. These reactors have a recycle gas line, in which a cooler for removing the heat of polymerization, a recycle gas compressor, and, if necessary, other elements such as a cyclone separator for removing fine polymer dust can also be installed. The monomers consumed by the polymerization reaction are usually replaced by adding supplementary gas to the recycle gas stream.

[0003] In order to achieve uniform distribution of the fluidizing gas in the growing bed of polymer particles, some reactors are equipped with a gas distribution grid, sometimes also called a gas fluidizing grid or a distributor plate. Such a gas distribution grid is a device provided with openings that distribute the gas flow introduced below the grid itself into the bed. The grid can also serve as a support for the bed when the gas supply is cut off.

[0004] The gas distribution grid can be configured as a perforated plate or a porous plate, sometimes in combination with an upstream flow divider. For example, as disclosed in EP 0 697 421 A1, a roof-shaped guide plate can be arranged above the opening of the distributor plate, or the opening can be covered with a top cover as described in EP 0 600 414 A1. The geometry of the gas distribution grid can also deviate from the plate. EP0 088 638 A2 discloses a gas distributor with a double cone for a fluidized bed reactor. WO 2008 / 074632A1 describes a gas distribution grid with an inverted cone form. Due to the large amount of recycled fluidizing gas, the size of the gas inlet nozzle also becomes larger, so a relatively large volume is required below the gas distribution grid.

[0005] Over time, fines present in the fluidizing gas accumulate in the space below the reactor grid. These reactive fines can then form polymer agglomerates under stagnant conditions, eventually becoming too large and thus jeopardizing the operability and reliability of the reactor system.

[0006] It would therefore be desirable to provide a fluidized bed reactor which allows fine polymer particles carried by the fluidizing gas to be easily transported back into the fluidized bed of polymer particles.

[0007] The object of the present invention is to provide a fluidized bed reactor and a process for preparing olefin polymers which at least partially overcome the disadvantages of the prior art and which at the same time are simple and inexpensive to implement. Summary of the invention

[0008] According to the present invention, according to the attached independent claim and preferably according to any claim directly or indirectly dependent on the independent claim, there is provided a fluidized bed reactor and a process for preparing olefin polymers.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will be described below with reference to the accompanying drawings, which show some non-limiting embodiments of the invention, in which:

[0011] - Figure 1 is a schematic side view of a fluidized bed reactor according to the present invention;

[0012] - Figure 2 yes Figure 1 A side cross-sectional view of a portion of a fluidized bed reactor;

[0013] - Figure 3 yes Figure 2 A plan view of a portion of the , with some details removed for clarity;

[0014] - Figure 4 yes Figure 3 A front cross-sectional view of a detail;

[0015] - Figure 5 yes Figure 4 A lateral cross-sectional view of a detail of;

[0016] - Figure 6 yes Figure 2 side cross-sectional views of various embodiments of a portion of; and

[0017] - Figure 7 yes Figure 2 A side cross-sectional view of yet another different embodiment of a portion of. DETAILED DESCRIPTION

[0018] exist Figure 1, numeral 1 as a whole denotes a fluidized bed reactor for gas phase polymerization of olefins. The fluidized bed reactor 1 has an inner chamber 2, which in turn has at least one lower portion 3 and at least one upper portion 4. The fluidized bed reactor 1 comprises: at least one side wall 5, which has an inner surface 6, which laterally (at least partially) delimits the inner chamber 2; a gas distribution grid 7, which is located in the inner chamber and separates the lower portion 3 from the upper portion 4 (at least partially); and a gas recirculation line 8, which has a first end 9 connected to the inner chamber 2 at the upper portion 4 and a second end 10 connected to the inner chamber 2 at the lower portion 3.

[0019] More precisely, but not necessarily, the gas recirculation line 8 is configured to convey the recirculated portion of the fluidizing gas from the upper part 4 of the inner chamber 2 through the upper wall 15 and to convey the fluidizing gas through the side wall 5 to the lower part 4 .

[0020] In particular, the olefins that can be polymerized in the fluidized bed reactor 1 of the present disclosure are especially 1-olefins, i.e. hydrocarbons having a terminal double bond, but are not limited thereto. Non-polar olefin compounds are preferred. Particularly preferred 1-olefins are linear or branched C2 to C 12 -1-olefins, especially linear C2 to C 10 -1-olefins, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, or branched C2 to C 10 -1-olefins, 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 a mixture of various 1-olefins. Suitable olefins also include olefins 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 methyl norbornene or dienes, such as 5-ethylidene-2-norbornene, norbornadiene or ethylnorbornadiene. It is also possible to polymerize a mixture of two or more olefins.

[0021] This fluidized bed reactor 1 is particularly suitable for the homopolymerization or copolymerization of ethylene or propylene, and is particularly preferably used for the homopolymerization or copolymerization of ethylene. Preferred comonomers in propylene polymerization are ethylene, 1-butene and / or 1-hexene at most 40 wt %, preferably ethylene, 1-butene and / or 1-hexene from 0.5 wt % to 35 wt %. As comonomers in ethylene polymerization, preferably use C3 to C8-1-olefins at most 20 wt %, more preferably from 0.01 wt % to 15 wt %, and especially from 0.05 wt % to 12 wt %, particularly 1-butene, 1-pentene, 1-hexene and / or 1-octene. Particularly preferably is the polymerization of ethylene copolymerized with 1-hexene and / or 1-butene from 0.1 wt % to 12 wt %.

[0022] In a favorable but non-limiting embodiment of the present disclosure, polymerization is carried out in the presence of an inert gas (such as nitrogen) or an alkane (such as methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane or n-hexane or a mixture thereof) having from 1 to 10 carbon atoms. It is preferred to use nitrogen or propane as an inert gas (if appropriate, used in combination with other alkanes). In a particularly favorable embodiment of the present disclosure, polymerization is carried out in the presence of C3 to C5 alkanes as a polymerization diluent and most preferably in the presence of propane, particularly in the case of homopolymerization or copolymerization of ethylene. The reaction gas mixture in the reactor additionally includes olefin to be polymerized, i.e., main monomer and one or more optional comonomers. In a favorable embodiment of the present disclosure, the reaction gas mixture has an inert component content of from 30% by volume to 99% by volume, more preferably from 40% by volume to 95% by volume, and particularly from 45% by volume to 85% by volume. In another advantageous embodiment of the present disclosure, in particular if the main monomer is propylene, no or only a small amount of inert diluent is added. The reaction gas mixture may also include additional components, such as antistatic agents or molecular weight regulators, such as hydrogen. The components of the reaction gas mixture may be fed into the gas phase polymerization reactor or the recycle gas line in gaseous form or as liquids and then evaporated in the reactor or the recycle gas line.

[0023] According to some non-limiting embodiments, all conventional olefin polymerization catalysts are used to carry out the polymerization of olefins. This means, for example, that a Phillips catalyst based on chromium oxide can be used, a Ziegler catalyst or a Ziegler-Natta catalyst can be used, or a single-site catalyst can be used for polymerization. For the purposes of this disclosure, a single-site catalyst is a catalyst based on a chemically uniform transition metal coordination compound. In addition, a mixture of two or more of these catalysts can also be used for the polymerization of olefins. This mixed catalyst is generally referred to as a composite catalyst. The preparation and use of these catalysts for olefin polymerization are generally known.

[0024] Advantageous examples of Ziegler-type catalysts comprise a compound of titanium or vanadium, a compound of magnesium and optionally an electron donor compound and / or a particulate inorganic oxide as support material.

[0025] Ziegler-type catalysts are usually used in the presence of a cocatalyst. Examples of cocatalysts are organometallic compounds of metals of Groups 1, 2, 12, 13 or 14 of the Periodic Table, in particular organometallic compounds of metals of Group 13, and in particular organoaluminium compounds. Preferred cocatalysts are, for example, organometallic alkyls, organometallic alkoxides or organometallic halides.

[0026] Advantageous examples of organometallic compounds include alkyl lithium, alkyl magnesium or alkyl zinc, alkyl magnesium halides, alkyl aluminum, alkyl silicon, silicon alkoxides and alkyl silicon halides. More advantageously, the organometallic compound includes alkyl aluminum and alkyl magnesium. Even more advantageously, the organometallic compound includes alkyl aluminum, most advantageously trialkyl aluminum compounds or compounds of this type in which the alkyl group is replaced by a halogen atom such as chlorine or bromine. Examples of such alkyl aluminums are trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-hexyl aluminum or diethyl aluminum chloride or mixtures thereof.

[0027] According to some non-limiting embodiments, the fluidized bed reactor of the present disclosure is operated at a pressure of 0.5 MPa to 10 MPa, advantageously from 1.0 MPa to 8 MPa, and particularly at a pressure of 1.5 MPa to 4 MPa. The polymerization is advantageously, but not necessarily, carried out at a temperature of 30° C. to 60° C., particularly advantageously at a temperature of 65° C. to 125° C., and temperatures in the upper half of this range are preferably used to prepare ethylene copolymers with relatively high density, and temperatures in the lower half of this range are preferably used to prepare ethylene copolymers with lower density.

[0028] According to some non-limiting embodiments, the polymerization in the fluidized bed reactor can also be carried out in a condensing or supercondensing mode, wherein a portion of the recycled reaction gas mixture is cooled below the dew point and returned to the reactor as a liquid phase and a gas phase, respectively, or together as a two-phase mixture, in order to additionally utilize the evaporation enthalpy for cooling the reaction gas.

[0029] The gas recycle line 8 is configured to feed the lower part 3 of the inner chamber 2 with a fluidizing gas comprising fresh olefin monomer (added along the gas recycle line 8) and a recycle portion (taken from the inner chamber 2) comprising recycled unreacted and / or partially reacted olefins.

[0030] Specific reference Figure 2 The gas distribution grid 7 (in particular, comprising a plurality of openings 11 ) is configured to allow the passage of the fluidizing gas from the lower portion 3 to the upper portion 4 of the inner chamber 2 .

[0031] The fluidized bed reactor 1 further comprises a polymer discharge channel 17 configured to discharge the polymer obtained inside the upper part 4 from the upper part 4 itself (in particular downwards) in a discharge direction D (in particular through the lower part 3). More precisely, but not necessarily, the discharge direction D is substantially vertical (and in particular parallel to the longitudinal extension of the fluidized bed reactor).

[0032] The fluidized bed reactor 1 further includes a partition wall DW, which is located around at least a section of the polymer discharge channel 17 to define a first region A of the inner chamber 2 and prevents the olefin monomer and the recycled unreacted and / or partially reacted olefin from entering the lower portion 3 through the second end 10 and thus reaching the first region A. The partition wall DW has at least a first portion DW' that intersects (particularly perpendicularly) the discharge direction D.

[0033] The second end 10 is configured to feed the fluidizing gas to the lower part 3 in a direction intersecting the discharge direction D. In other words, the second end 10 is configured to move the fluidizing gas flowing out of the second end 10 in a direction intersecting the discharge direction D. In particular, the second end 10 (the second end of the recirculation line 8) is configured so that the recirculation line 8 feeds the fluidizing gas flowing out of the second end 10 itself in a direction intersecting (particularly substantially perpendicular to) the discharge direction D to the lower part 3.

[0034] By this means, it was experimentally found that the formation of polymer agglomerates was reduced inside the lower portion 3, especially around the discharge channel 17. Note that the experimental results show that the formation of polymer agglomerates was also reduced in the region of the partition wall DW.

[0035] Presumably, these effects are obtained because the shape of the dividing wall DW results in smaller (narrower) spaces for turbulent eddies and / or stagnation, so that fine particles can accumulate. The direction of the fluidizing gas flowing out of the second end 10 also plays a role in this respect, since presumably the movement of the fluid is particularly adapted to the shape of the surface (particularly the shape of the dividing wall DW) in this way.

[0036] In some specific and non-limiting cases, the recirculation line 8 comprises a pipeline, which extends crosswise (particularly, at an angle between 20° and 160°; more particularly, at an angle between 60° and 120°; even more particularly, substantially vertically) relative to the discharge direction D (particularly the polymer discharge channel 17) at the extension portion of the second end 10. In particular, this section of the recirculation line 8 is substantially horizontal.

[0037] According to some embodiments not depicted, the second end 10 is configured such that fluidizing gas is fed to the lower part 4 through the side wall 5 .

[0038] In particular, the dividing wall DW is located (at least partially) in the lower part 3 .

[0039] According to some non-limiting embodiments, the dividing wall DW is a non-pressure-resistant divider. This means that the volume above the dividing wall DW and the volume below the dividing wall DW are preferably maintained at the same pressure by a pressure balance line, and the dividing wall DW does not need to withstand the polymerization pressure in the fluidized bed reactor. In this regard, in some specific cases, the first region A is fed with monomers and / or clean gas (i.e., without polymer fines) so that there is no pressure difference between the two sides of the dividing wall (between the first region A and the second region B - described in more detail below).

[0040] According to some non-limiting embodiments, the opening 11 comprises an opening 11 ′ at least less than 40 mm (particularly less than 20 mm; more particularly less than 5 mm) from the inner surface 6 of the side wall 5 .

[0041] Advantageously, but not necessarily, the fluidized bed reactor 1 comprises lateral supports 12 extending in an annular manner along the inner surface 6 and in contact with the inner surface 6 (and at least partially supporting the gas distribution grid 7). The gas distribution grid 7 has a peripheral edge 13, which is (at least) partially arranged on (in particular resting on) the lateral supports 12 and in contact with the lateral supports. The lateral supports 12 have holes 14, each of which is located below the corresponding opening 11' and is configured to allow the fluidizing gas to flow from the lower part 3 to the upper part 4 of the inner chamber 2 through the corresponding opening 11'. This ensures that the grid 7 has sufficient mechanical stability while not hindering the passage through the opening 11'.

[0042] Please note that Figure 3 In FIG. 1 , only a portion (approximately half) of the grille 7 is depicted in order to better show the structure of the lateral support 12 .

[0043] According to some non-limiting embodiments, the openings 11 are formed in such a way that the flow of the fluidizing gas through the openings 11 is substantially parallel to the plane of the gas distribution grid 7 (particularly substantially tangential to the gas distribution grid 7; more particularly substantially horizontal).

[0044] Advantageously, but not necessarily, the opening 11 is a slot. According to some non-limiting embodiments, the width of the slot (opening 11) is greater than its height (in particular greater than twice its height).

[0045] More precisely, but without limitation, the opening 11 is made in the manner disclosed in patent application WO2008074632 of the same applicant.

[0046] Advantageously, but not necessarily, the partition wall DW has at least one second portion DW″ which is connected to the first portion DW′ at an obtuse angle β facing the lower portion 3 outside the first area A.

[0047] Likewise, by this method, it was surprisingly observed that the formation of polymer agglomerates inside the lower portion 3 was further reduced.

[0048] In some non-limiting embodiments, the fluidized bed reactor 1 includes: an upper wall 15 that defines the top of the inner chamber 2 and is connected to the side wall 5; and a lower wall 16 that defines the bottom of the inner chamber 2 and is connected to the side wall 5.

[0049] The lower wall 16 is also connected to the partition wall DW (particularly, to the first portion DW′ of the partition wall DW) at an obtuse angle α facing the lower portion 3 outside the first area A. Particularly, the second portion DW″ of the partition wall DW is also connected to the lower wall 16 .

[0050] Surprisingly, it has been found experimentally that the implementation of these solutions further reduces the formation of polymer agglomerates inside the lower part 3, in particular at the connection between the lower wall 16 and the dividing wall DW.

[0051] In particular, the first area A is at least partially delimited by the lower wall 16 and the partition wall DW.

[0052] Advantageously, but not necessarily, the first portion DW' is substantially horizontal.

[0053] According to some non-limiting embodiments, the obtuse angle α is at least 100°, in particular, at least 120° (in particular, at most 170°; more in particular, at most 150°).

[0054] Additionally or alternatively, the obtuse angle β is at least 100° (and, in particular, less than 150°).

[0055] Specific reference Figure 6 According to some non-limiting embodiments, the partition wall DW is curved. In this case, it can be said that the partition wall DW has an infinite number of parts DW', DW" ... DW arranged one after another along the curve. n .

[0056] on the contrary, Figure 7 A non-limiting embodiment is shown in which the partition wall DW has only one section DW'.

[0057] exist Figure 2 In the embodiment of the present invention, the partition wall DW has two parts DW' and DW".

[0058] According to some non-limiting embodiments, the fluidized bed reactor 1 comprises a polymer discharge pipe 17' which laterally delimits the polymer discharge channel 17 and extends (particularly from the upper part 4) through the lower wall 16. Particularly, the partition wall DW intersects the longitudinal extension of (the outer surface of) the polymer discharge pipe 17'.

[0059] Additionally or alternatively, the partition wall DW (more precisely but not necessarily, the first portion DW′ of the partition wall DW) is connected to the outer surface of the polymer discharge tube 17 ′ so that the first area A is defined by the polymer discharge tube 17 ′, the partition wall DW and the lower wall 16 .

[0060] According to some non-limiting embodiments, the side wall 5 extends substantially straight along the axial direction of the fluidized bed reactor 1 (particularly the inner chamber 2). More precisely, but not necessarily, the side wall 5 extends substantially straight in the discharge direction D.

[0061] Additionally or alternatively, the lower wall 16 extends substantially crosswise along the axial direction of the fluidized bed reactor 1 (particularly the inner chamber 2). More precisely, but not necessarily, the lower wall 16 extends substantially crosswise to the discharge direction D.

[0062] In some specific and non-limiting cases, the lower wall 16 is circular. In particular, the lower wall 16 has a portion (in the region of the discharge duct 17') substantially perpendicular to the direction D, and a portion (connected to the side wall 5) having a very small angle relative to the direction D (less than 1°).

[0063] According to some non-limiting embodiments, the lower part 3 comprises (particularly consists of) a first region A and a second region B, and the recirculation line 8 is configured to feed the fluidizing gas therein. A dividing wall DW separates the first region A from the second region B (and vice versa).

[0064] In particular, the second zone B is delimited (at least in part) by the dividing wall DW, the lower wall 16 and the grid 7 (and possibly the side walls 5 ), and is designed to receive fluidizing gas coming from the recirculation line 8 .

[0065] In particular, the obtuse angles α and β are within the second region B (they face the second region B).

[0066] In some non-limiting cases, the partition wall DW has no sharp corners on the surface of the lower portion 3 thereof facing the outside of the first area A.

[0067] Particularly, the partition wall DW is connected to the outer surface of the polymer discharge pipe 17' facing the first area A at an acute angle γ of at least 10° (particularly, at least 20°; particularly, at most 50°; more particularly, at most 40°).

[0068] According to some non-limiting embodiments, the polymeric discharge tube 17' is substantially parallel to the side wall 5. Additionally or alternatively, the polymeric discharge tube 17' is substantially parallel to the discharge direction D.

[0069] Advantageously but not necessarily, the polymer discharge pipe 17' comprises an upper opening 18 integrated into the gas distribution grid 7. In particular, the upper opening 18 of the polymer discharge pipe 17' is arranged in the center of the gas distribution grid 7. More particularly, the polymer discharge pipe 17' is configured to discharge polymer produced inside the upper part 4.

[0070] According to some non-limiting (and not shown) embodiments, the gas recirculation line 8 is configured to convey a recirculated portion of the fluidizing gas from the upper portion 4 of the inner chamber 2 through the upper wall 15 and to convey the fluidizing gas through the side wall 5 to the lower portion 4 .

[0071] According to some non-limiting embodiments, the discharge pipe 17' comprises a regulating device 21, such as a discharge valve, which is configured to regulate the mass flow rate of the polymer discharged from the reactor 1. The opening of the regulating device 21 can be continuously adjusted to keep the height of the fluidized polymer bed inside the reactor 1 constant.

[0072] The discharge pipe 17 may be made of uniform diameter, but advantageously comprises more sections with decreasing diameter in the downward direction. Figure 1 As shown, the adjustment device 21 is advantageously placed at the limit between the section of larger diameter and the section of smaller diameter.

[0073] As an alternative, an exhaust system is disclosed in patent application WO2007071527A1 of the same applicant.

[0074] In a specific and non-limiting case, the gas recycle line 8 is provided with (a compressor 19 and) a heat exchanger 20 configured to reduce the heat of the recycle portion. Advantageously, but not necessarily, the recycle line 8 is provided with a supplementary line 22 for feeding fresh olefin monomer, molecular weight regulator and optional inert gas (particularly to the main pipe 23 of the recycle line 8). More precisely, but not necessarily, the supplementary line 22 is configured to feed fresh olefin monomer, molecular weight regulator and optional inert gas (as well as antistatic agent, mileage enhancer, etc.) from upstream of the compressor 19 (particularly between the upper part 4 and the compressor 19; more particularly upstream of the heat exchanger 20).

[0075] Advantageously, but not necessarily, the second end 10 of the recirculation line 8 and the dividing wall DW are configured such that (the flow of) the fluidizing gas flowing out from the second end 10 (and in particular entering the lower part 3; more particularly, entering the second zone B) is (at least partially) substantially tangential to the dividing wall DW (in particular, tangential to the first portion DW′ and / or the second portion DW″).

[0076] It was found experimentally that, surprisingly, the formation of agglomerates in the dividing wall DW is even permanently reduced by this method.

[0077] These effects are presumably achieved because the movement of the fluidizing gas continuously sweeps the surface of the dividing wall DW.

[0078] According to some non-limiting embodiments, the gas distribution grid 7 has a side surface substantially in the form of a truncated cone (and an inverted cone).

[0079] According to another aspect of the present invention, there is also provided a method for preparing olefin polymers, which comprises homopolymerizing olefins or copolymerizing olefins with one or more other olefins in the presence of a polymerization catalyst (in particular, at a temperature of 20°C to 200°C; in particular, at a pressure of 0.5MPa to 10MPa), wherein the polymerization is carried out in a fluidized bed reactor 1 as described above.

[0080] According to some non-limiting embodiments, the fluidized bed reactor 1 includes a polymer discharge pipe 17' through which polymer is continuously discharged.

[0081] According to some non-limiting embodiments, polymerization conditions are the conditions conventionally adopted in the gas phase reactor for olefin polymerization, i.e., temperature is in the range of 60°C to 120°C, and pressure is in the range of 5 bar to 40 bar. Gas phase polymerization process can be combined with conventional techniques operated in slurry, bulk or gas phase to carry out continuous multi-stage polymerization process. Therefore, in the upstream or downstream of the polymerization device of the present invention, one or more polymerization stages operated in a loop reactor, or a conventional fluidized bed reactor, or a stirred bed reactor can be provided. In particular, the gas phase polymerization reactor with interconnected polymerization zones as described in EP 782 587 and EP 1012195 can be advantageously arranged in the upstream or downstream of the device of the present invention.

[0082] The gas phase polymerization process allows the preparation of large quantities of olefin powders with an optimal particle size distribution and a low fines content. The [α]-olefins advantageously polymerized by the process of the invention have the formula CH2=CHR, wherein R is hydrogen or a hydrocarbon radical having 1 to 12 carbon atoms. Examples of polymers that can be obtained are:

[0083] High-density polyethylene (HDPE with a relative density above 0.940), including ethylene homopolymers and ethylene copolymers with [α]-olefins having 3 to 12 carbon atoms;

[0084] Low-density linear polyethylene (LLDPE with a relative density below 0.940) and very-low-density and ultra-low-density linear polyethylene (VLDPE and ULDPE with a relative density between 0.920 and 0.880) consisting of copolymers of ethylene with one or more [α]-olefins having from 3 to 12 carbon atoms; elastomeric terpolymers of ethylene and propylene with minor amounts of dienes, or elastomeric copolymers of ethylene and propylene, wherein the content of ethylene-derived units is from about 30% to 70% by weight; isotactic polypropylene and crystalline copolymers of propylene with ethylene and / or other [α]-olefins, wherein the content of propylene-derived units exceeds 85% by weight;

[0085] Isotactic copolymers of propylene and [α]-olefins, such as 1-butene, wherein the [α]-olefin content is up to 30% by weight; impact propylene polymers obtained by the sequential polymerization of propylene and a mixture of propylene and ethylene, wherein the ethylene content is up to 30% by weight;

[0086] Random polypropylene and amorphous copolymers of propylene with ethylene and / or other [α]-olefins, wherein the content of propylene-derived units exceeds 70% by weight. The gas phase polymerization process disclosed herein is not limited to the use of any particular series of polymerization catalysts. The process can be carried out in any exothermic polymerization reaction using any catalyst, whether it is supported or unsupported, and whether it is in prepolymerized form or not.

[0087] The polymerization reaction can be carried out in the presence of a highly active catalytic system (eg Ziegler-Natta catalyst, single-site catalyst, chromium-based catalyst, vanadium-based catalyst).

[0088] Unless otherwise expressly stated, the contents of the references (articles, books, patent applications, etc.) cited herein are all cited in their entirety herein. In particular, the above references are incorporated herein by reference.

Claims

1. A fluidized bed reactor for gas phase polymerization of olefins; the fluidized bed reactor (1) having an inner chamber (2), the inner chamber having at least one lower part (3) and at least one upper part (4); The fluidized bed reactor (1) comprises: at least one side wall (5) having an inner surface (6) which at least partially laterally delimits the inner chamber (2); a gas distribution grid (7) which is located in the inner chamber (2) and at least partially separates the lower part (3) from the upper part (4); a recirculation line (8) having a first end (9) connected to the inner chamber (2) at the upper part (4) of the inner chamber (2) and a second end (10) connected to the inner chamber (2) at the lower part (3) of the inner chamber (2); a polymer discharge channel (17) which is configured to discharge polymer obtained inside the upper part (4) from the upper part (4) itself in a discharge direction (D); and a lower wall (16) which delimits the bottom of the inner chamber (2) and is connected to the side wall (5); the recycle line (8) being configured to feed a fluidizing gas into the lower portion (3) of the inner chamber (2), the fluidizing gas comprising fresh olefin monomer and a recycle portion comprising recycled unreacted and / or partially reacted olefin monomer; The gas distribution grid (7) is configured to allow passage of the fluidizing gas from the lower portion (3) to the upper portion (4) of the inner chamber (2); The fluidized bed reactor (1) further comprises a partition wall (DW) which is located around at least one section of the polymer discharge channel (17) so as to at least partially define the first region (A) of the inner chamber (2) together with the lower wall (16) and prevent the fresh olefin monomer and the recycled unreacted and / or partially reacted olefin monomer from entering the lower portion (3) through the second end (10) and thereby reaching the first region (A); The partition wall (DW) has at least a first portion (DW') intersecting the discharge direction (D) and connected to the lower wall (16) at a first obtuse angle (α) of the lower portion (3) facing the outside of the first area (A); The second end (10) is configured to feed the fluidizing gas to the lower portion (3) in a direction crossing the discharge direction (D).

2. A fluidized bed reactor according to claim 1, wherein the dividing wall (DW) has at least one second portion (DW"), which is connected to the first portion (DW') at a second obtuse angle (β) of the lower portion (3) facing the outside of the first area (A).

3. A fluidized bed reactor according to claim 2, wherein the first portion (DW') is substantially horizontal and the second obtuse angle (β) is at least 100°.

4. The fluidized bed reactor according to any one of the preceding claims, wherein the first obtuse angle (α) is at least 100° (in particular at least 120°).

5. A fluidized bed reactor according to any one of the preceding claims, and the fluidized bed reactor comprises a polymer discharge pipe (17'), which laterally defines the polymer discharge channel (17) and extends from the upper part (4) through the lower wall (16); the partition wall (DW) is connected to the outer surface of the polymer discharge pipe (17'), so that the first area (A) is defined by the polymer discharge pipe (17'), the partition wall (DW) and the lower wall (16).

6. The fluidized bed reactor according to claim 5, wherein the lower portion (3) comprises the first region (A) and the second region (B), and the partition wall (DW) separates the first region (A) from the second region (B).

7. The fluidized bed reactor according to claim 5 or 6, wherein the dividing wall (DW) is connected to the outer surface of the polymer discharge pipe (17') at an acute angle (γ) of at least 10° facing the first area (A).

8. A fluidized bed reactor according to any one of claims 5 to 7, wherein the polymer discharge pipe (17') comprises an upper opening (18) integrated into the gas distribution grid (7) and is substantially parallel to the side wall (5).

9. A fluidized bed reactor according to any one of the preceding claims, wherein the second end (10) of the recirculation line (8) and the dividing wall (DW) are configured so that the fluidizing gas flowing out from the second end (10) is substantially tangential to at least a portion of the dividing wall (DW).

10. Fluidized bed reactor according to any of the preceding claims, wherein the recirculation line (8) is provided with a heat exchanger (20) configured to reduce the heat of the recirculation portion.

11. A fluidized bed reactor according to any one of the preceding claims, wherein the recycle line (8) is provided with a make-up line (22) for feeding the fresh olefin monomer, molecular weight regulator and optionally inert gas, antistatic agent, mileage enhancer, etc.

12. A fluidized bed reactor according to any one of the preceding claims, wherein the gas distribution grid (7) has a substantially truncated cone lateral surface in the form of a side surface.

13. A process for the preparation of olefin polymers, the process comprising homopolymerizing an olefin or copolymerizing an olefin with one or more other olefins in the presence of a polymerization catalyst, wherein the polymerization is carried out in a fluidized bed reactor (1) according to any one of the preceding claims.

14. The method according to claim 13, wherein the fluidized bed reactor (1) comprises a polymer discharge pipe (17') through which the polymer is continuously discharged.

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