Ethylene polymerization process and reactor system for producing multimodal polymers using a combination of loop reactors and fluidized bed reactors

Abstract

Disclosed are polymerization processes and reactor systems for producing multimodal ethylene polymers using at least one loop reactor and at least one fluidized bed reactor. Configurations include a loop reactor in series with a fluidized bed reactor and two loop reactors in series with a fluidized bed reactor.

Description

Technical Field

[0001] This disclosure relates to methods and reactor systems for producing multimodal ethylene polymers, and more specifically, to methods and systems in which loop reactors and fluidized bed reactors configured in series or in parallel are used to produce multimodal ethylene polymers. Background Technology

[0002] Ethylene-based polymers (such as high-density polyethylene (HDPE) homopolymers and copolymers, and linear low-density polyethylene (LLDPE) copolymers) can be produced using various combinations of catalyst systems and polymerization reactors. There is a persistent need for polymerization processes and reactor systems capable of producing polymers with multimodal molecular weight distributions suitable for membrane, pipe, blow molding, and other end-use applications. Therefore, this invention is generally aimed at these objectives. Summary of the Invention

[0003] The present invention is provided to introduce, in a simplified form, a series of concepts that will be further described in the detailed description below. The present invention is not intended to identify essential or necessary features of the claimed subject matter. Nor is the present invention intended to limit the scope of the claimed subject matter.

[0004] This document describes a process and reactor system for producing a multimodal ethylene polymer. A first process for producing a multimodal ethylene polymer may include: (i) contacting a catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen in an inert hydrocarbon diluent in a loop reactor under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (ii) discharging a first reactor effluent containing the first ethylene polymer from the loop reactor; (iii) separating a light fraction containing hydrogen from the first reactor effluent to form an intermediate material; and (iv) contacting the intermediate material with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon in a fluidized bed reactor under gas-phase polymerization conditions to produce a multimodal ethylene polymer.

[0005] A second process for producing a multimodal ethylene polymer may include: (i) in a first loop reactor, under slurry or supercritical polymerization conditions, contacting a catalyst composition with ethylene, optionally a first olefin comonomer, and optionally hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer; (ii) discharging a first reactor effluent containing the first ethylene polymer from the first loop reactor and introducing the first reactor effluent into a second loop reactor; and (iii) in the second loop reactor, under slurry or supercritical polymerization conditions, reacting the first reactor effluent with ethylene... (iv) contacting an optional second olefin comonomer and optional hydrogen to produce a second ethylene polymer; (v) discharging a second reactor effluent containing the second ethylene polymer from a second loop reactor; (vi) separating a light fraction containing hydrogen from the second reactor effluent to form an intermediate material, wherein hydrogen is present in step (i) or step (iii) or both; and (vi) contacting the intermediate material with ethylene and an optional third olefin comonomer in an inert gas and / or hydrocarbon in a fluidized bed reactor under gas-phase polymerization conditions to produce a multimodal ethylene polymer.

[0006] A third process for producing a multimodal ethylene polymer may include: (i) in a fluidized bed reactor, under gas-phase polymerization conditions, contacting a catalyst composition with ethylene and optionally a first olefin comonomer in an inert gas and / or hydrocarbon to produce a first ethylene polymer; (ii) discharging a first reactor effluent containing the first ethylene polymer from the fluidized bed reactor; (iii) combining an inert hydrocarbon diluent with the first reactor effluent and increasing the pressure to form an intermediate material; and (iv) in a loop reactor, under slurry or supercritical polymerization conditions, contacting the intermediate material with ethylene and optionally a second olefin comonomer to produce a multimodal ethylene polymer.

[0007] A fourth process for producing a multimodal ethylene polymer may include: (i) contacting a first catalyst composition with ethylene and optionally a first olefin comonomer in an inert hydrocarbon diluent in a loop reactor under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (ii) contacting a second catalyst composition with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon in a fluidized bed reactor under gas-phase polymerization conditions to produce a second ethylene polymer; and (iii) combining the first ethylene polymer and the second ethylene polymer to produce a multimodal ethylene polymer.

[0008] Referring now to reactor systems conforming to the present invention, a first polymerization reactor system for producing a multimodal ethylene polymer may include: (a) a loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (b) an effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the loop reactor; (c) a separator configured to remove a light fraction containing hydrogen from the first reactor effluent to form an intermediate material; and (d) a fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a multimodal ethylene polymer.

[0009] A second polymerization reactor system for producing multimodal ethylene polymers may include: (a) a first loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer, and optionally hydrogen in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (b) a second loop reactor configured to contact a first reactor effluent containing the first ethylene polymer with ethylene, optionally a second olefin comonomer, and optionally hydrogen under slurry or supercritical polymerization conditions to produce a second ethylene polymer; and (c) a transfer line configured to draw from the first loop reactor a flow line containing the first ethylene polymer. The first reactor effluent of the polymer is introduced into a second loop reactor, (d) a second discharge line configured to extract the second reactor effluent containing the second ethylene polymer from the second loop reactor, (e) a separator configured to remove light fractions containing hydrogen from the second reactor effluent to form an intermediate material, wherein hydrogen is present in the first loop reactor, the second loop reactor, or both, and (f) a fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a third olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a multimodal ethylene polymer.

[0010] A third polymerization reactor system for producing multimodal ethylene polymers may include: (a) a fluidized bed reactor configured to contact a catalyst composition with ethylene and optionally a first olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a first ethylene polymer; (b) an effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the fluidized bed reactor; (c) a transfer line configured to combine an inert hydrocarbon diluent with the first reactor effluent and increase pressure to form an intermediate material; and (d) a loop reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer under slurry or supercritical polymerization conditions to produce a multimodal ethylene polymer.

[0011] A fourth polymerization reactor system for producing multimodal ethylene polymers may include: (a) a loop reactor configured to contact a catalyst composition with ethylene and optionally a first olefin comonomer in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (b) a fluidized bed reactor configured to contact a second catalyst composition with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a second ethylene polymer; and (c) a mixing device configured to combine the first and second ethylene polymers to produce a multimodal ethylene polymer.

[0012] The foregoing summary and the following detailed description are provided as examples and are merely illustrative. Therefore, the foregoing summary and the following detailed description should not be considered limiting. Furthermore, features or variations may be provided in addition to those set forth herein. For example, certain aspects may be addressed to various combinations and sub-combinations of features described in the detailed description. Attached Figure Description

[0013] The following drawings form part of this specification and are included to further illustrate certain aspects of the invention. The invention can be better understood by referring to one or more of these drawings in combination with specific embodiments and examples.

[0014] Figure 1 The figure illustrates a polymerization reactor system conforming to one aspect of the present invention.

[0015] Figure 2 The illustration shows a polymerization reactor system conforming to another aspect of the present invention.

[0016] Figure 3 The diagram shows the possible connections. Figures 1 to 2 The polymerization reactor system is combined with a polymer recovery system.

[0017] Figure 4 This is a schematic flow chart of a polymerization process having a pressure distribution that conforms to one aspect of the present invention.

[0018] Figure 5 The diagram illustrates what can be integrated into Figures 1 to 2 The double-loop reactor structure in the polymerization reactor system.

[0019] Figure 6 The illustration shows a cyclone separator that can be used in any polymerization reactor system and polymer recovery system described herein.

[0020] Figure 7 The diagram illustrates a bend in the tubular section that can be integrated into any loop reactor and polymerization reactor system described herein.

[0021] While the invention disclosed herein is susceptible to various modifications and alternatives, only a few specific aspects are illustrated by way of example in the accompanying drawings, which are described in detail below. The drawings and the detailed description of these specific aspects are not intended to limit the breadth or scope of the inventive concept or the appended claims in any way. Rather, the drawings and detailed description are provided to illustrate the concept of the invention to those skilled in the art and to enable such persons to acquire and use the concept of the invention.

[0022] definition

[0023] To more clearly define the terms used herein, the following definitions are provided. Unless otherwise specified, the following definitions apply to this disclosure. If a term is used in this disclosure but is not specifically defined herein, the definition in IUPAC Compendium of Chemical Terminology, 2nd Edition (1997) may be applied, provided that the definition does not conflict with any other disclosure or definition applied herein, or render any claim to which the definition applies uncertain or invalid. If any definition or usage provided in any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided herein shall prevail.

[0024] In this document, the features of the subject matter are described such that combinations of different features can be conceived within a particular aspect. For each aspect and feature disclosed herein, all combinations are considered, whether explicitly described or not, that will not adversely affect the systems, compositions, processes, or methods described herein. Furthermore, unless expressly stated otherwise, any aspect or feature disclosed herein may be combined to describe inventive systems, compositions, processes, or methods consistent with this disclosure.

[0025] Generally, element groups are indicated using the numbering scheme indicated in the version of the periodic table published in Chemical and Engineering News, 63(5), 27, 1985. In some cases, a group of elements may be indicated using the common name assigned to that group; for example, alkali metals are indicated by Group 1 elements, alkaline earth metals by Group 2 elements, transition metals by Groups 3–12 elements, and halogens or halides by Group 17 elements.

[0026] Whenever used in this specification and claims, the term "hydrocarbon" refers to a compound containing only carbon and hydrogen, whether saturated or unsaturated. Other identifiers may be used to indicate the presence of a specific group in a hydrocarbon (e.g., halohydrocarbons indicate the presence of one or more halogen atoms that replace the same number of hydrogen atoms in the hydrocarbon).

[0027] For any particular compound or group disclosed herein, unless otherwise stated, any name or structure presented (generally or specifically) is intended to cover all conformational isomers, regio isomers, stereoisomers, and mixtures thereof that can be produced by a particular set of substituents. Unless otherwise stated, the name or structure (generally or specifically) also covers all enantiomers, diastereomers, and other optical isomers (if any), whether enantiomers or racemic forms, and mixtures of stereoisomers, as known to those skilled in the art. For example, general references to pentane include n-pentane, 2-methylbutane, and 2,2-dimethylpropane; and general references to butyl include n-butyl, sec-butyl, isobutyl, and tert-butyl.

[0028] Unless otherwise specified, when used to describe a group, such as when referring to a substituted analogue of a particular group, the term "substituted" is intended to describe any non-hydrogen portion that formally replaces hydrogen in the group and is intended to be non-limiting. Furthermore, unless otherwise stated, a group or groups may also be referred to herein as "unsubstituted," or equivalent terms such as "non-substituted," which refers to the original group in which the non-hydrogen portion does not replace hydrogen in the group. Moreover, unless otherwise indicated, "substituted" is intended to be non-limiting and includes inorganic or organic substituents as understood by one of ordinary skill in the art.

[0029] Unless otherwise stated, the terms “contact,” “combination,” etc., are used herein to describe systems and methods in which materials are contacted or combined together in any order, in any manner, and for any duration. For example, materials can be contacted or combined by using any suitable technique such as blending, mixing, slurrying, fluidizing, etc.

[0030] The term "polymer" is generally used herein to include olefin homopolymers, copolymers, terpolymers, etc., as well as alloys and blends thereof. The term "polymer" also includes impact, block, graft, random, and alternating copolymers. Copolymers can be derived from an olefin monomer and an olefin comonomer, while terpolymers can be derived from an olefin monomer and two olefin comonomers. Therefore, "polymer" encompasses copolymers and terpolymers. Similarly, the scope of the term "polymerization" includes homopolymers, copolymers, and trimers. Thus, ethylene polymers include ethylene homopolymers, ethylene copolymers (e.g., ethylene / α-olefin copolymers), ethylene terpolymers, etc., as well as blends or mixtures thereof, and having any suitable density. Therefore, ethylene polymers encompass polymers commonly referred to in the art as plasmons, elastomers, LLDPE (linear low-density polyethylene), MDPE (medium-density polyethylene), HDPE (high-density polyethylene), and ULDPE, VLDPE, LDLPE, etc. For example, ethylene copolymers can be derived from ethylene and comonomers such as propylene, 1-butene, 1-hexene, or 1-octene. If the monomer and comonomer are ethylene and 1-hexene, respectively, the resulting polymer can be classified as an ethylene / 1-hexene copolymer. The term "polymer" also includes all possible geometries, including isotactic, syndiotactic, and random symmetries, if present and unless otherwise stated. The term "polymer" is also intended to include polymers of all molecular weights, including lower molecular weight polymers.

[0031] Because it involves molecular weight distribution (MWD), multimodal includes bimodal and trimodal molecular weight distributions. A multimodal MWD can include peaks and tails in the molecular weight distribution. A multimodal MWD can contain high (or higher) molecular weight and low (or lower) molecular weight components with different absolute molecular weights (Mn, Mw, Mz), the same or different molecular weight distributions (Mw / Mn, Mz / Mw), the same or different rheological parameters (Carreau-Yasuda "a" parameter, HLMI / MI, MI5 / MI2), etc. For example, a bimodal ethylene polymer can contain a high or higher molecular weight (HMW) component (or the first component) and a low or lower molecular weight (LMW) component (or the second component). These component terms are relative, used with reference to each other, and are not limited to the actual molecular weight of each component. The molecular weight characteristics of these HMW and LMW components can be determined by deconvolving the molecular weight distribution of the complex (the overall polymer) as typically determined using gel permeation chromatography. The relative amounts (weight percentages) of HMW and LMW components in the polymer can be determined using commercial software programs (Systat Software, Inc., PEAK FIT v.4.05). Other molecular weight parameters of the HMW and LMW components (e.g., Mn, Mw, Mz, etc. for each component) can be determined using deconvolution data from the PEAK FIT program, and by applying the PEAK FIT chromatographic / log-normal 4-parameter (area) function and two peaks without any restrictions in the deconvolution according to the following (where a0 = area; a1 = center; a2 = width (>0); and a3 = shape (>0, ≠1)):

[0032]

[0033] In this disclosure, although systems and methods are described in a manner that "comprises" various components or steps, unless otherwise specified, systems and methods may also be described as "substantially composed of various components or steps" or "consisting of various components or steps." The terms "a / an" and "described" are intended to include plural alternatives, such as at least one / an. For example, unless otherwise specified, the disclosure of "reactor" is intended to cover a single reactor or a combination of more than one reactor.

[0034] This invention discloses several types of ranges. When any type of range is disclosed or claimed, it is intended to individually disclose or claim every possible number that such range can reasonably cover, including the endpoints of the range and any sub-ranges and combinations thereof covered therein. For example, in aspects of this invention, polymerization temperatures in a loop reactor can fall within different ranges. By disclosing a polymerization temperature range of 40°C to 130°C, it is intended to state that the polymerization temperature can be any temperature within that range, and may include, for example, any range or combination of 40°C to 130°C (such as 60°C to 120°C or 75°C to 115°C, etc.). Similarly, all other ranges disclosed herein should be interpreted in a manner similar to this example.

[0035] Typically, quantities, sizes, formulations, parameters, ranges, or other quantities or characteristics are expressed as “about” or “approximately,” whether or not explicitly stated otherwise. Claims include equivalents of quantities or characteristics, regardless of whether they are modified by the terms “about” or “approximately.”

[0036] Although any methods, systems, steps, and components similar to or equivalent to those described herein may be used in the practice or testing of this invention, typical methods, systems, steps, and components are described herein.

[0037] All publications and patents mentioned herein are incorporated herein by reference in their entirety for the purpose of describing and disclosing, for example, the constructs and methods described in the publications and patents, which may be used in conjunction with the inventions described herein. Detailed Implementation

[0038] This article discloses a polymerization process and polymerization reactor system for producing multimodal ethylene polymers, which uses at least one loop reactor and at least one fluidized bed reactor.

[0039] Processes for producing multimodal ethylene polymers

[0040] Aspects of the present invention relate to a process for producing a multimodal ethylene polymer. For example, a first process for producing a multimodal ethylene polymer may include (or substantially consist of, or consist of): (i) in a loop reactor, under slurry or supercritical polymerization conditions, contacting a catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer; (ii) discharging a first reactor effluent containing the first ethylene polymer from the loop reactor; (iii) separating a light fraction containing hydrogen from the first reactor effluent to form an intermediate material; and (iv) in a fluidized bed reactor, under gas-phase polymerization conditions, contacting the intermediate material with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce a multimodal ethylene polymer. Optionally, in the first process, hydrogen may be present in step (iv), so that gas-phase polymerization in the fluidized bed reactor can be carried out in the presence of added hydrogen. Hydrogen can be used to control the molecular weight of the polymer produced in each reactor, and the amount of hydrogen present in the loop reactor may be the same as or different from the amount of hydrogen present in the fluidized bed reactor. Depending on the type of multimodal ethylene polymer produced, a first olefin comonomer may be present in step (i), or a second olefin comonomer may be present in step (iv), or both may be present in step (i) and in step (iv). In the latter case, the first olefin comonomer (and its relative amount) in step (i) may be the same as or different from the second olefin comonomer (and its relative amount) in step (iv).

[0041] In another aspect, a second process for producing a multimodal ethylene polymer may include (or substantially consist of, or consist of): (i) in a first loop reactor, under slurry or supercritical polymerization conditions, contacting a catalyst composition with ethylene, optionally a first olefin comonomer, and optionally hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer; (ii) discharging a first reactor effluent containing the first ethylene polymer from the first loop reactor and introducing the first reactor effluent into a second loop reactor; and (iii) in the second loop reactor, under slurry or supercritical polymerization conditions... The process involves (iv) contacting the effluent from the first reactor with ethylene, an optional second olefin comonomer, and optional hydrogen to produce a second ethylene polymer; (v) discharging the second reactor effluent containing the second ethylene polymer from the second loop reactor; (v) separating a light fraction containing hydrogen from the second reactor effluent to form an intermediate material, wherein hydrogen is present in step (i) or step (iii) or both; and (vi) in a fluidized bed reactor, under gas-phase polymerization conditions, contacting the intermediate material with ethylene and an optional third olefin comonomer in an inert gas and / or hydrocarbon to produce a multimodal ethylene polymer. In the second process, optionally, hydrogen may be present in step (i) or step (iii), or in both steps (i) and (iii), and the amount of hydrogen present in the first loop reactor may be the same as or different from the amount of hydrogen present in the second loop reactor. Depending on the type of multimodal ethylene polymer produced, the first olefin comonomer may be present in step (i), or the second olefin comonomer may be present in step (iii), or the third olefin comonomer may be present in step (vi), or any combination thereof. In the latter case, any one of the first olefin comonomer (and its relative amount) in step (i), the second olefin comonomer (and its relative amount) in step (iii), and the third olefin comonomer (and its relative amount) in step (vi) may be the same or different.

[0042] In another aspect, a third process for producing a multimodal ethylene polymer may include (or substantially consist of, or consist of) the following: (i) in a fluidized bed reactor, under gas-phase polymerization conditions, contacting a catalyst composition with ethylene and optionally a first olefin comonomer in an inert gas and / or hydrocarbon to produce a first ethylene polymer; (ii) discharging a first reactor effluent containing the first ethylene polymer from the fluidized bed reactor; (iii) combining an inert hydrocarbon diluent with the first reactor effluent and increasing the pressure to form an intermediate material; and (iv) in a loop reactor, under slurry or supercritical polymerization conditions, contacting the intermediate material with ethylene and optionally a second olefin comonomer to produce a multimodal ethylene polymer. In the third process, optionally, hydrogen may be present in step (i) or step (iv), or in both steps (i) and (iv), and the amount of hydrogen present in the fluidized bed reactor may be the same as or different from the amount of hydrogen present in the loop reactor. Depending on the type of multimodal ethylene polymer produced, the first olefin comonomer may be present in step (i), or the second olefin comonomer may be present in step (iv), or both the first olefin comonomer and the second olefin comonomer may be present in step (iv). In the latter case, the first olefin comonomer (and its relative amount) in step (i) may be the same as or different from the second olefin comonomer (and its relative amount) in step (iv).

[0043] In another aspect, a fourth process for producing a multimodal ethylene polymer may include (or substantially consist of, or consist of): (i) in a loop reactor, under slurry or supercritical polymerization conditions, contacting a first catalyst composition with ethylene and optionally a first olefin comonomer in an inert hydrocarbon diluent to produce a first ethylene polymer; (ii) in a fluidized bed reactor, under gas-phase polymerization conditions, contacting a second catalyst composition with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce a second ethylene polymer; and (iii) combining the first and second ethylene polymers to produce a multimodal ethylene polymer. In the fourth process, optionally, hydrogen may be present in step (i) or step (ii), or in both steps (i) and (ii), and the amount of hydrogen present in the fluidized bed reactor may be the same as or different from the amount of hydrogen present in the loop reactor. Depending on the type of multimodal ethylene polymer produced, a first olefin comonomer may be present in step (i), or a second olefin comonomer may be present in step (ii), or both the first olefin comonomer and the second olefin comonomer may be present in step (ii). In the latter case, the first olefin comonomer (and its relative amount) in step (i) may be the same as or different from the second olefin comonomer (and its relative amount) in step (ii).

[0044] Typically, the features of the first, second, third, and fourth processes (e.g., one or more loop reactors, one or more fluidized bed reactors, polymerization conditions in each reactor, one or more catalyst compositions, and multimodal ethylene polymers, etc.) are described independently herein, and these features may be combined in any combination to further describe the disclosed processes for producing multimodal ethylene polymers. Furthermore, additional process steps may be performed before, during, and / or after these process steps, and, unless otherwise stated, may be used without limitation and in any combination to further describe the first, second, third, and fourth processes for producing multimodal ethylene polymers.

[0045] Each catalyst composition used in the first, second, third, and fourth processes can independently be any suitable transition metal-based catalyst system. The catalyst composition may contain, for example, transition metals (one or more) from Groups 3-10 of the periodic table (e.g., nickel). In one aspect, the catalyst composition may contain transition metals from Groups 4, 5, or 6, or combinations of two or more transition metals. In another aspect, the catalyst composition may contain chromium, titanium, zirconium, hafnium, vanadium, or combinations thereof, or in yet another aspect, chromium, titanium, zirconium, hafnium, or combinations thereof. For example, each catalyst composition can independently be a supported catalyst system comprising a transition metal (e.g., chromium, vanadium, titanium, zirconium, hafnium, or combinations thereof) supported on a suitable support (e.g., a solid oxide or chemically treated solid oxide), wherein the loading indicates that the transition metal is impregnated onto and / or mixed with or co-gelled with the porous solid support. Typical solid supports include solid oxides, activator-supports (chemically treated solid oxides), molecular sieves and zeolites, clays and pillared clays, etc. For example, the catalyst composition may contain chromium impregnated on silica, chromium impregnated on silica-titanium dioxide, chromium impregnated on aluminum phosphate, chromium co-gelled with silica, chromium co-gelled with silica-titanium dioxide, or chromium co-gelled with aluminum phosphate, and this includes any combination of these materials.

[0046] Various catalyst compositions known to those skilled in the art can be used for the polymerization of olefins. These include, but are not limited to, Ziegler-Natta-based catalyst systems, chromium-based catalyst systems, metallocene-based catalyst systems, nickel-based catalyst systems, and combinations thereof. The polymerization processes and reactor systems disclosed herein are not limited to the aforementioned catalyst systems; however, specific aspects involving these catalyst systems are considered. Thus, the catalyst composition can be a Ziegler-Natta-based catalyst system, a chromium-based catalyst system, and / or a metallocene-based catalyst system; alternatively, a Ziegler-Natta-based catalyst system; alternatively, a chromium-based catalyst system; alternatively, a metallocene-based catalyst system; or alternatively, a nickel-based catalyst system. In one aspect, the catalyst composition can be a dual catalyst system comprising at least one metallocene compound, while in another aspect, the catalyst composition can be a dual catalyst system comprising two different metallocene compounds.

[0047] Examples of representative and non-limiting catalyst compositions include U.S. Patent Nos. 3,887,494, 3,119,569, 4,053,436, 4,981,831, 4,364,842, 4,444,965, 4,364,855, 4,504,638, 4,364,854, 4,444,964, 4,444,962, 3,976,632, 4,248,735, 4,297,460, 4,397,766, 2,825,721, 3,225,023, 3,226,205, 3,622,521, 3,625,864, 3,900,457, 4,3 01,034、4,547,557、4,339,559、4,806,513、5,037,911、5,219,817、5,221,654、4,081,407、4,296,001、4,392,990、4,405,501、4,151,122、4,247,421、4,397,769、4,460,756、4,182,815、4,735,931、4,820,785、4,988,657、5,436,305、5,610,247、5,627,247、3,242,099、4,808,561、5 275,992、5,237,025、5,244,990、5,179,178、4,855,271、4,939,217、5,210,352、5,401,817、5,631,335、5,571,880、5,191,132、5,480,848、5,399,636、5,565,592、5,347,026、5,594,078、5,498,581、5,496,781、5,563,284、5,554,795、5,420,320、5,451,649、5,541,272、5,705,478 Those disclosed in 5,631,203, 5,654,454, 5,705,579, 5,668,230, 6,300,271, 6,831,141, 6,653,416, 6,613,712, 7,294,599, 6,355,594, 6,395,666, 6,833,338, 7,417,097, 6,548,442, 7,312,283, 7,026,494, 7,041,617, 7,199,073, 7,226,886, 7,517,939, 7,619,047, 7,919,639 and 8,080,681.

[0048] In some aspects, in addition to transition metals, the catalyst composition may also contain activators and optional co-catalysts. Exemplary activators may include, but are not limited to, aluminoxane compounds (e.g., methylaluminoxane, MAO), organoboron or organoborate compounds, ionized ionic compounds, activator-supports (e.g., solid oxides treated with electron-withdrawing anions), or combinations thereof. Commonly used polymerization co-catalysts may include, but are not limited to, alkyl metal or organometallic co-catalysts, wherein the metal covers boron, aluminum, zinc, etc. For example, alkylboron and / or alkylaluminum compounds are commonly used as co-catalysts in transition metal-based catalyst systems. Representative compounds may include, but are not limited to, tri-n-butylborane, tripropylborane, triethylborane, trimethylaluminum (TMA), triethylaluminum (TEA), tri-n-propylaluminum (TNPA), tri-n-butylaluminum (TNBA), triisobutylaluminum (TIBA), tri-n-hexylaluminum, tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminum ethoxylate, diethylaluminum chloride, etc., including combinations thereof. Exemplary organozinc compounds that can be used as cocatalysts may include, but are not limited to, dimethyl zinc, diethyl zinc (DEZ), dipropyl zinc, dibutyl zinc, dinepentyl zinc, di(trimethylsilyl) zinc, di(triethylsilyl) zinc, di(triisopropylsilyl) zinc, di(triphenylsilyl) zinc, di(allyldimethylsilyl) zinc, di(trimethylsilylmethyl) zinc, etc., or combinations thereof.

[0049] Solid supports or supported catalysts used in any catalyst compositions disclosed herein may have any suitable surface area, pore volume, particle size, particle size distribution, and sphericity, as will be recognized by those skilled in the art.

[0050] In the polymerization process and reactor system disclosed herein, each catalyst composition may be independently contacted with ethylene (to form an ethylene homopolymer) or with ethylene and olefin comonomers (to form an ethylene copolymer, ethylene terpolymer, etc.). Suitable olefin comonomers may include, but are not limited to, propylene, 1-butene, 2-butene, 3-methyl-1-butene, isobutene, 1-pentene, 2-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 2-hexene, 3-ethyl-1-hexene, 1-heptene, 2-heptene, 3-heptene, 1-octene, 1-decene, styrene, etc., or combinations thereof. According to one aspect, the olefin comonomer may include α-olefins (e.g., C3-C4). 10(α-olefin), and in another aspect, the comonomer may include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, styrene or any combination thereof; alternatively, the olefin comonomer may include 1-butene, 1-hexene, 1-octene or a combination thereof; alternatively, the olefin comonomer may include 1-butene; alternatively, the olefin comonomer may include 1-hexene; or alternatively, the olefin comonomer may include 1-octene.

[0051] As disclosed above, each catalyst composition used in the first, second, third, and fourth processes may be independently contacted with ethylene and optionally, an olefin comonomer. When present, the comonomer concentration in each reactor used in the process may be the same or different, and similarly, the ethylene concentration in each reactor used in the process may be the same or different. In one aspect, the comonomer may be used in at least one loop reactor, or in at least one fluidized bed reactor, or in at least one loop reactor and at least one fluidized bed reactor. The comonomer used in the loop reactor may be the same as or different from the comonomer used in the fluidized bed reactor. Additionally, more than one comonomer may be used (e.g., mixed and injected together) in any reactor (e.g., no comonomer in the loop reactor, but two comonomers in the fluidized bed reactor). Alternatively or additionally, multiple fluidized bed reactors with different comonomers may be used for terpolymers and trimodal resins.

[0052] Typically, each ethylene polymer produced in each reactor of the first, second, third, and fourth processes may independently comprise, in one respect, an ethylene homopolymer and / or an ethylene / α-olefin copolymer (e.g., C3-C...). 10 (α-olefin), and in another aspect, may include ethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer and / or ethylene / 1-octene copolymer, and in yet another aspect, may include ethylene / α-olefin copolymer and / or ethylene terpolymer (e.g., ethylene with 1-butene and 1-hexene), and in yet another aspect, may include ethylene / 1-butene copolymer.

[0053] Articles may be formed from, and / or may contain, the multimodal ethylene polymers of the present invention, and are therefore covered herein. For example, articles that may contain the polymers of the present invention may include, but are not limited to, agricultural films, automotive parts, bottles, chemical containers, drums, fibers or fabrics, food packaging films or containers, food service products, fuel tanks, geomembranes, household utensils, linings, molded products, medical devices or materials, outdoor storage products (e.g., panels for outdoor shed walls), outdoor recreational equipment (e.g., kayaks, basketball goal bases), pipes, sheets or tapes, toys or traffic barriers, etc. Various processes can be used to form these articles. Non-limiting examples of these processes include injection molding, blow molding, rotational molding, film extrusion, sheet extrusion, profile extrusion, thermoforming, etc. Furthermore, additives and modifiers are typically added to these polymers to provide beneficial polymer processing or end-use product properties. Such processes and materials are described in Modern Plastics Encyclopedia, mid-November 1995, Vol. 72, No. 12; and Film Extrusion Manual-Process, Materials, Properties, Tappi Press, 1992.

[0054] In some aspects of the invention, the article may comprise any of the multimodal ethylene polymers described herein, and the article may be or may comprise a film, such as a blown film; alternatively, a tubular product; or alternatively, a blown product, such as a blown bottle.

[0055] Referring now to each loop reactor in the first, second, third, and fourth processes, ethylene, an inert hydrocarbon diluent, a catalyst composition, hydrogen (if used), and an olefin comonomer (if used) are typically fed continuously into the loop reactor, where polymerization occurs under slurry or supercritical polymerization conditions. A suspension containing polymer particles and diluent, as well as reactor effluent containing unreacted ethylene, can be continuously removed from the loop reactor. In some aspects, the percentage of solids by weight (based on reactor contents) in each loop reactor can independently range from 30% to 55% by weight, or from 40% to 70% by weight. In other aspects, polymerization conditions include less than 50% by weight, less than 40% by weight, or less than 30% by weight, such as from 25% to 45% by weight, or from 30% to 40% by weight of solids content.

[0056] Suitable inert hydrocarbon diluents used in one or more loop reactors include, but are not limited to, propane, isobutane, n-butane, n-pentane, isopentane, neopentane, cyclohexane, n-hexane, heptane, cycloheptane, octane, and any combination thereof. If more than one loop reactor is used to produce multimodal ethylene polymers, the inert hydrocarbon diluent in one loop reactor may be the same as or different from that in another loop reactor. The selection of the inert hydrocarbon diluent can be based on many factors, including polymerization temperature and pressure, whether supercritical conditions are used, and polymer solubility. In one respect, for example, the inert hydrocarbon diluent contains propane (or is essentially composed of propane, or is composed of propane), while in another respect, the inert hydrocarbon diluent contains isobutane (or is essentially composed of isobutane, or is composed of isobutane).

[0057] General information regarding loop slurry reactors and suitable polymerization conditions can be found, for example, in U.S. Patent Nos. 3,248,179, 4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191, 6,833,415, and 8,822,608. However, typical slurry or supercritical polymerization conditions include polymerization temperatures ranging from 40°C to 130°C, 60°C to 120°C, or 75°C to 115°C, and polymerization pressures ranging from 200 psig to 1500 psig, 400 psig to 1200 psig, 450 psig to 850 psig, or 900 psig to 1100 psig, but polymerization temperatures and pressures are not limited to these representative ranges. In one aspect, loop reactors (or each loop reactor independently) can be configured for the maximum permissible operating pressure (MAWP) of the respective reactor, which is greater than the operating pressure or polymerization pressure by at least 5% and / or at most 30%. Therefore, suitable pressure relief valves can be configured to release pressures at MAWP and / or 5% greater than MAWP, etc.

[0058] In the second process, the first polymerization pressure in the first loop reactor and the second polymerization pressure in the second loop reactor are typically within 25% of each other, and in some cases, within 20%, 10% or 5% of each other.

[0059] Additional slurry or supercritical polymerization conditions in the first, second, third, and fourth processes include an average residence time of 10 to 90 minutes independently in each loop reactor, with other suitable ranges for the average residence time being 15 to 75 minutes or 20 to 60 minutes. Linear velocities within each loop reactor are independently typically as low as 10 feet per second and as high as 60 feet per second, with typical ranges including, but not limited to, 15 to 55 feet per second and 20 to 50 feet per second.

[0060] In one aspect, slurry polymerization conditions in a loop reactor encompass polymerization conditions in which the inert hydrocarbon diluent is liquid within the loop reactor. For example, the polymerization temperature and pressure in the loop reactor may be below the critical point, or the polymerization temperature may be below the critical point and the pressure may be above the critical point. An exemplary inert hydrocarbon diluent used under such conditions is isobutane.

[0061] In another aspect, supercritical conditions in a loop reactor encompass polymerization conditions in which both the polymerization temperature and pressure in the loop reactor are above their critical points. An exemplary inert hydrocarbon diluent used under such conditions is propane—commonly referred to as supercritical propane. Hereinafter, supercritical conditions include temperature and pressure conditions in which the diluent, such as propane, is supercritical (referred to as supercritical propane, where propane exists above its temperature and pressure critical points), and temperature and pressure conditions in which all reactor contents are supercritical (above the respective temperature and pressure critical points of the respective materials). Supercritical conditions (e.g., temperature and pressure) can be readily determined by those skilled in the art. For example, conditions for supercritical propane include pressures equal to or higher than about 618 psia and temperatures equal to or higher than 96 °C. Therefore, representative conditions for supercritical propane in a loop reactor include polymerization temperatures in the ranges of 90°C to 130°C, 96°C to 120°C, or 100°C to 115°C, and polymerization pressures in the ranges of 700 psig to 1500 psig, 800 psig to 1200 psig, or 900 psig to 1100 psig. Advantageously, the polymerization temperature can be lower than the melting point of the corresponding ethylene polymer formed in each loop reactor.

[0062] Each of the first, second, third, and fourth processes may further include a prepolymerization step in a prepolymerization reactor prior to step (i). Therefore, the catalyst composition may be prepolymerized prior to step (i). Any suitable design of the prepolymerization reactor, such as a stirred tank or loop reactor design, may be used. Prepolymerization is a polymerization step, but the reaction rate is much lower than the main polymerization operation in one or more loop reactors and one or more fluidized bed reactors in the first, second, third, and fourth processes. The purpose of prepolymerization is to prepare the catalyst composition for use in the main polymerization reactor and reaction. Prepolymerization affects polymer packing characteristics, including packing density, average particle size, particle size distribution, and fine particle concentration. Morphology (particle shape) depends on the specific catalyst composition or prepolymerization conditions, or both. Catalyst surface area depends on the catalyst / support or prepolymerization conditions, or both. A larger surface area / volume ratio increases the contact area between reactant particles. This increases the chance of successful collisions in the reactor. For the same mass fraction of solids, surface area is inversely proportional to particle diameter (diameter = 4PV / SA, 4 * pore volume / surface area). Therefore, the reaction rate increases with increasing surface area. Furthermore, spherical catalyst particles typically exhibit better flow characteristics and tend to exhibit less catalyst attrition compared to irregular or non-spherical particle beds. In this invention, the sphericity of the catalyst and polymer is typically in the range of 0.5 to 1.0, as described in U.S. Patent No. 10,787,526. Suitable Ziegler-Natta catalysts may be supported on magnesium chloride or silica, or both, with an average particle size of 1 micrometer to 50 micrometers, and a titanium loading on the catalyst ranging from 0.1 wt% to 20 wt%.

[0063] The prepolymerization reactor can be a continuous loop slurry reactor design. The reactor contents can circulate at rates from 5 ft / s to 100 ft / s, with average residence times ranging from 1 minute to 120 minutes. Reactor diameters from 6 feet to 36 inches can be used. Response variables, or reaction rates, can be adjusted by controlling reactor temperature, ethylene concentration, catalyst concentration, and activator and / or co-catalyst concentrations. Typical reactor temperatures range from 20°F to 120°F, ethylene concentrations from 0.1 to 10 lb / lb catalyst, catalyst concentrations from 1 to 50 lb / lb propane, and alkyl concentrations from 1 to 50 mol / mol aluminum / mol titanium.

[0064] The discharge from the prepolymer reactor can be routed to the first reactor in the process, or optionally to a buffer tank and a pump that may be routed to the first reactor in the process (loop slurry reactor or fluidized bed reactor).

[0065] Prepolymerizing the catalyst can also improve polymer stacking characteristics, and this can be done in the presence of ethylene monomer with or without solvent. There are three alternative methods: the first involves adding the ethylene monomer to the catalyst in a mixing tank and then contacting it with a co-catalyst; the second involves adding the ethylene monomer to the catalyst in a mixing tank and then contacting it with a co-catalyst upstream of a static mixer; and the third involves combining the catalyst with a propane solvent and then contacting it with both the co-catalyst and the ethylene monomer upstream of a static mixer.

[0066] In one aspect, the catalyst can be suspended in propane in a mixing tank, where polymerization will not begin without a co-catalyst. The catalyst slurry from the mixing tank can then be transferred (e.g., continuously) to a prepolymerization reactor, where a co-catalyst is added and a controlled prepolymerization reaction occurs.

[0067] Alternatively, in another aspect, the prepolymerization reaction can be carried out in a static mixer. In this aspect, the co-catalyst can be added online to the catalyst slurry before entering the static mixer.

[0068] In another aspect, propane can be used in catalyst slurries and for catalyst transport. In this regard, the prepolymerization reaction takes place in a static mixer or stirred tank. Using propane eliminates polymerization problems prior to static mixing and the need for refrigeration containers and piping.

[0069] Regardless of whether prepolymerization is used, each of the first, second, third, and fourth processes may further include the step of introducing a slurry of the catalyst composition in a solids content of 1% to 15% by weight, 2% to 14% by weight, or 3% to 12% by weight into a loop reactor (or a first loop reactor). Alternatively or additionally, each of the first, second, third, and fourth processes may further include a step of polymerization under gas-phase polymerization conditions in a second fluidized bed reactor. For example, in the first process, low molecular weight HDPE may be formed in the loop reactor, medium molecular weight LLDPE may be formed in the first gas-phase reactor, and high molecular weight LLDPE may be formed in the second gas-phase reactor.

[0070] In one aspect of the first, second, third, and fourth processes, each loop reactor can independently produce an ethylene polymer with lower Mw, higher MI, and higher density than the ethylene polymer produced by a fluidized bed reactor (which produces a higher Mw, lower MI, and lower density ethylene polymer). In another aspect of the first, second, third, and fourth processes, each loop reactor can independently produce an ethylene polymer with higher Mw, lower MI, and lower density than the ethylene polymer produced by a fluidized bed reactor (which produces a lower Mw, higher MI, and higher density ethylene polymer).

[0071] There is no particular limitation on the amount of multimodal ethylene polymer produced in each reactor, but for the first, third and fourth processes, multimodal ethylene polymer is typically produced in loop reactors from 20% to 90% (or from 25% to 85% or from 30% to 70%) and in fluidized bed reactors from 10% to 80% (or from 15% to 75% or from 30% to 70%). For the second process, typically, a multimodal ethylene polymer of 5 wt% to 30 wt% (or 5 wt% to 25 wt%, or 10 wt% to 25 wt%) is produced in a first loop reactor, a multimodal ethylene polymer of 30 wt% to 60 wt% (or 30 wt% to 55 wt%, or 35 wt% to 60 wt%) is produced in a second loop reactor, and a multimodal ethylene polymer of 30 wt% to 60 wt% (or 30 wt% to 55 wt%, or 35 wt% to 60 wt%) is produced in a fluidized bed reactor. In the second process, the first loop reactor can produce low to high molecular weight homopolymers, the second loop reactor can produce low molecular weight ethylene copolymers, and the fluidized bed reactor can produce medium to high molecular weight ethylene copolymers.

[0072] Optionally, at least one contact step (or each contact step) in the first, second, third, and fourth processes may further include contact in the presence of an antistatic compound (e.g., Stadis 450, etc.). Thus, the antistatic compound may be added to one or more fluidized bed reactors and / or to one or more loop reactors at one or more suitable locations.

[0073] Now, specifically referring to one or more loop reactors in the first, second, third, and fourth processes, each loop reactor may independently have any suitable design or construction, but advantageously has a length-to-diameter (L / D) ratio from 500 to 3,000 (e.g., from 700 to 1,500), an internal diameter from 12 inches to 48 inches (e.g., from 18 inches to 40 inches or from 20 inches to 32 inches), a length from 50 feet to 300 feet (e.g., from 100 feet to 250 feet), and from 2 to 16 legs (e.g., from 4 to 14 legs). The loop reactor may be supported or freestanding.

[0074] Furthermore, each loop reactor may independently have an inner surface roughness of less than or equal to 150 microinches, such as less than or equal to 100 microinches, or less than or equal to 50 microinches, or from 10 microinches to 50 microinches. Alternatively or alternatively, each loop reactor may be independently constructed from any suitable material, including carbon steel, stainless steel, cryogenic carbon steel, and combinations thereof.

[0075] In one aspect, the loop reactor (or each loop reactor) may be constructed from a rolled plate having two edges joined along a seam. These edges of the rolled plate may be joined along the seam by welding. The material used in the rolled plate typically has a minimum tensile strength of 50,000 psi. This type of construction allows for the use of thinner walls, typically, but not limited to, 1 / 2” to 3 / 4” thick. Optionally, the loop reactor (or each loop reactor) may include a rust-preventive coating on the reactor surface and flanges.

[0076] For temperature monitoring and control, the loop reactor (or each loop reactor) may have multiple thermocouple sheath locations, each containing a suitable thermocouple or temperature sensing device. Additionally, each loop reactor includes a reactor circulation pump, i.e., one or more reactor circulation pumps, which may be axial, radial, or mixed-flow designs. The pump diameter may be equal to or greater than the inner diameter of the loop reactor. In one aspect, the pump diameter minus the reactor ID may be from 1 inch to 8 inches, such as from 1 inch to 3 inches, from 2 inches to 4 inches, from 4 inches to 6 inches, or from 6 inches to 8 inches, etc. While not limited to this, the pump capacity may be from 25,000 gallons / minute (gpm) to 200,000 gpm; alternatively, from 30,000 gpm to 120,000 gpm; or alternatively, from 40,000 gpm to 100,000 gpm. Total head can range from 50 feet to 400 feet, more typically from 100 feet to 350 feet or from 200 feet to 300 feet. Pump efficiency can typically be 80% or lower, 70% or lower, or 60% or lower, but at least 40%. Therefore, this document covers any pump efficiency from 40% to 80%. Net positive suction head (NPSH) can typically range from 100 feet to 1,000 feet, more typically from 100 feet to 500 feet, or from 100 feet to 300 feet. Pump braking horsepower can range from 1,000 HP to 10,000 HP, such as from 1,000 HP to 4,000 HP, 1,000 HP to 3,000 HP, or 1,000 HP to 2,000 HP. If desired, the pump may also include guide or straightening vanes to improve efficiency.

[0077] Each loop reactor may independently include a bend section (or two or more bend sections) configured to accommodate the Dean number (D) of the reaction mixture flowing within it. n The DA number is maintained at at least 3,000,000. Therefore, polymerization conditions may include a DA number of at least 3,000,000 in the bend section of the loop reactor. n Dean's number (D) n D is a dimensionless number defined as follows: n =(ρVd / μ)*(d / 2R) c ) 1 / 2 Where ρ is the density of the reaction mixture in the loop reactor, V is the circulation rate of the reaction mixture in the loop reactor, d is the inner diameter of the bend section of the loop reactor, μ is the dynamic viscosity of the reaction mixture in the loop reactor, and R c It is the inner bending radius of the bend section in the loop reactor. In one aspect, the Dean number (D...) n The amount can be at least 4,000,000, at least 5,000,000, or at least 6,000,000, and typically includes up to and including 10,000,000 to 15,000,000, or more.

[0078] Advantageously, the loop reactor (or each loop reactor) may include a bend flow meter. The bend flow meter can be used to measure the circulation velocity in the loop reactor. The bend flow meter may be a differential pressure flow meter including a diaphragm located at a high-pressure and low-pressure tap. As fluid flows through the bend section of the loop reactor, centrifugal force generates a pressure differential between the outside and inside of the bend, which can be used to calculate the flow / circulation velocity and mass or volumetric flow rate. Advantageously, the bend flow meter eliminates the need for sensing devices located in the flow path that could obstruct the circulating reaction mixture with the reactor.

[0079] In the first, second, third, and fourth processes, the slurry or supercritical polymerization conditions in each loop reactor can be independently characterized by a Froude number of 10 to 100 (e.g., 15 to 50, 20 to 90, or 40 to 80). The Froude number is a dimensionless parameter that indicates the balance between the tendency of polymer particles in the reactor effluent to suspend and settle, and this applies to both discharge and transfer lines (with or without flash line heaters). The Froude number provides a relative measure of the momentum transfer process from particle to wall compared to the fluid; a lower Froude number indicates a stronger particle-wall (relative to fluid-wall) interaction. The Froude number (Fr) is defined by the following equation: Fr = V / (D*g) 0.5 Where V is the average linear velocity of the reactor effluent (in ft / s), and g is the gravitational constant (32.2 ft / s²). 2), and D is the inner diameter of the discharge or transfer line (or pipe) (in feet). Therefore, in each discharge or transfer line in the first, second, third, and fourth processes, the reactor effluent can be characterized by a Froude number of 10 to 100, such as 15 to 50, 20 to 90, or 40 to 80.

[0080] Alternatively or optionally, the slurry or supercritical polymerization conditions in each loop reactor may be independently characterized by a Biot number less than or equal to 3 (e.g., less than or equal to 2, less than or equal to 1.5, or less than or equal to 1.1). The Biot number is a dimensionless parameter representing the balance between the resistance to heat transfer through the loop reactor wall and the resistance to heat transfer through the fluid in contact with the reactor wall; in other words, the Biot number represents the relative resistance to conductive heat transfer through the reactor wall relative to convective heat transfer from the reactor contents to the reactor wall. The Biot number (B) is defined by the following general formula: B = (h 淤浆 *L R ) / k R , where h 淤浆 It is the slurry film coefficient (BTU / hr-ft) 2 -°F), L R It is the thickness of the reactor wall (ft), and k R This refers to the thermal conductivity of the reactor wall (BTU / hr-ft-°F). Typically, a large Biot number indicates that the conduction resistance to heat transfer through the reactor wall controls the heat transfer from the loop reactor, while a small Biot number indicates that the convective resistance to heat transfer from the reactor contents to the inner surface of the reactor wall controls the heat transfer from the loop reactor. Typically, conditions in each loop reactor during polymerization can be characterized by a Biot number less than or equal to 3, less than or equal to 2, less than or equal to 1.5, or less than or equal to 1.1.

[0081] Alternatively or alternatively, slurry or supercritical polymerization conditions may be characterized by a cavitation number (Ca) of 6 to 60 (e.g., 12 to 50, 18 to 40, or 24 to 36). The cavitation number is a dimensionless number defined as: Ca = (Pr - Pv) / 0.5ρV 2 , where ρ is the density of the reaction mixture in the loop reactor, Pr is the polymerization pressure, Pv is the vapor pressure of the reaction mixture, and V is the circulation rate of the reaction mixture in the loop reactor. Polymerization conditions in the loop reactor minimize or completely avoid cavitation. In one aspect, slurry or supercritical polymerization conditions include cavitation numbers (Ca) of 6 to 60, while in another aspect, Ca is 12 to 50, and in yet another aspect, Ca is 18 to 40, and in yet another aspect, Ca is 24 to 36.

[0082] Alternatively or alternatively, slurry or supercritical polymerization conditions may be characterized by an Euler number greater than or equal to 5 (e.g., greater than or equal to 6 or greater than or equal to 7). The Euler number (Eu) is a dimensionless number defined as follows: Eu = AP / ρV 2 ρ is the density of the reaction mixture in the loop reactor, V is the circulation rate of the reaction mixture in the loop reactor, and AP is the pressure difference between the upstream and downstream pressures of one or more circulation pumps in the loop reactor. This pressure difference can be at least 20 psig, at least 25 psig, or at least 30 psig, and is typically as high as 50 psig to 100 psig, or higher. Advantageously, higher solids content can be achieved in the loop reactor as the Euler number increases.

[0083] In the first, second, third, and fourth processes, the corresponding reactor effluents discharged from the respective loop reactors can be continuously discharged. There may be one or more discharge locations along one or more loop reactors. The continuous take-off (CTO) assembly may extend from a bend in the respective loop reactor, from a horizontal section of the respective loop reactor, or a combination of these options. In one aspect, each loop reactor has a CTO assembly and does not have one or more settling legs. Furthermore, a primary discharge location may exist, with a backup discharge line located elsewhere along one or more loop reactors. Any suitable discharge angle from horizontal to 90° can be used for the discharge assembly.

[0084] There are no particular restrictions on the specific design of the effluent discharge from each loop reactor, but typically the reactor effluent is continuously discharged from the respective loop reactor via a continuous feed assembly, which may include valves, ball valves, V-ball valves, valveless valves, any other type of flow restrictor, or any other device that allows for pressure reduction (decrease). When using V-ball valves, the internal diameter is in the range of 0.5 inches to 6 inches, such as 0.5 inches to 3 inches, or 2 inches to 5 inches. Continuous feed can be achieved by adjusting the size of the conduit (discharge line) without valves or any other flow restrictions. The discharge port from the loop reactor can be located downstream or upstream of the circulation pump to take advantage of pressure differentials. Multiple feeds can be used in online or standby modes. The feed location can be positioned at a solids concentration higher than the average solids content in the loop reactor.

[0085] For a second process in which a first loop reactor and a second loop reactor are present, it is generally convenient for one or more discharge points of the first loop reactor to be located at a higher pressure (e.g., downstream of the circulation pump) than one or more feed points of the second loop reactor (e.g., upstream of the circulation pump), but this is not required.

[0086] In the first, second, third, and fourth processes, reactor effluents discharged from the loop reactor and / or the fluidized bed reactor may be discharged from the respective reactor into an effluent line, and this effluent line may include a flash line heater. Steam heating is typically used in the flash line heater, and after the flash line heater, the temperature of the reactor effluent may be in the range of 55°C to 105°C, such as 75°C to 105°C or 60°C to 100°C, but is not limited thereto.

[0087] As disclosed herein, the discharge port from the loop reactor may include at least one valve. The feed valve may be configured to receive the effluent from the product discharge conduit and control the flow rate of the effluent. The feed valve may be any type of control valve known in the art for controlling the effluent flow rate. Such valves include ball valves, V-ball valves, plug valves, globe valves, and angle valves. In one aspect, the feed valve may have a diameter ranging from 1.27 cm (0.5 inches) to 7.62 cm (3 inches) when 100% open. In another aspect, even when the feed valve is required to open only slightly (e.g., 20% to 25% open), the valve may have a flow channel diameter greater than the maximum expected polymer particle size, providing a wide control range for the feed valve's opening range (e.g., 20% to 100% open). The feed valve may be actuated by a signal from a controller configured to operate the feed valve in a continuous or discontinuous (e.g., intermittent opening) manner. The controller can be configured to completely close and then fully open the feed valve at set time intervals and for a certain duration, and actuate the feed valve to a certain percentage of opening, such as 20% to 100%.

[0088] Continuous Take-Out (CTO) valves can be any valve suitable for slurry, but V-ball valves are generally preferred. Rotary control valves are available from Fishers Controls International, Inc. in Marshall, Iowa.

[0089] The V-ball valve essentially controls the pressure within the reactor. In some embodiments, opening the V-ball valve can reduce the pressure within the loop reactor by allowing a larger flow rate of slurry to exit the reactor. In this implementation, reversing the operation can increase the pressure within the reactor. Pressure and flow sensors, positioned along the length of the transfer line, monitor the pressure and flow rate of the slurry passing through the transfer line, respectively. These sensors relay the flow and pressure information to a control system that automatically adjusts the V-ball valve to keep the pressure and flow rate within the desired operating range.

[0090] The pressure transmitter can be located downstream of the CTO valve. The pressure transmitter can be used to detect blockage in the CTO valve (by detecting a drop in pressure or flow rate or abnormal opening of the valve at a given flow rate) and signal potential blockage to the pressure indicator. Preferably, the pressure indicator is a diaphragm type pressure indicator, but it is not limited thereto.

[0091] The feed direction can be varied. The first option is an attachment angle (the angle between the reactor surface and the feed cylinder outlet) of, for example, 30 to 90 degrees (vertical). This attachment angle can be tangential or vertical, or any angle between 0 and 90 degrees, alternatively 20 to 80 degrees, or alternatively 30 to 60 degrees. The second option is a curve angle (relative to how far the attachment is on the bend of the tube, often referred to as angle α). This curve angle can be 0 to 90 degrees, but preferably 20 to 70 degrees, alternatively 40 to 60 degrees, or alternatively 45 to 70 degrees. Different angles can be selected based on many factors, including the flow direction (upward or downward). For example, the curve angle can be approximately 45 degrees or approximately 70 degrees. The third option is an angle (β) relative to the center plane of the longitudinal section. This center plane angle can be 0 to 60 degrees, and more typically 0 to 45 degrees, such as 0 to 20 degrees, or approximately 0 degrees.

[0092] It may be beneficial to keep at least one CTO mechanism inactive by closing the shut-off valve (or another downstream valve) instead of the plunger valve. The CTO is inactive if it is not used to extract effluent slurry (which is part of normal commercial production of multimodal polymers). If the downstream valve or shut-off valve is closed or blocked, the flush line and flush valve can also be operated to automatically feed diluent to the slurry discharge line. The CTO mechanism can be kept "hot standby" or "hot ready" by closing the shut-off valve or other downstream valve but keeping the plunger valve open; it can be quickly, substantially instantaneously, remotely, and / or automatically put into use when needed. The CTO can be discharged at any angle, including downward, upward, or horizontal flow.

[0093] The discharge line may include a heater and may have any suitable configuration. The heater may be an electric heater wound around a portion of the conduit / line, a heat exchanger such as a shell-and-tube heat exchanger (e.g., where the heating medium is separated by structural elements that transfer heat to the effluent flowing through the heater), a flash line heater (e.g., by injecting steam into the jacket, by an electric heater, or by both, adding heat along alternating sections along the heater), or a combination thereof. The heater may be configured as an open flow channel flash line heater, which is a jacketed tube of constant diameter heated at one end by steam injected into the jacket and at the other end by condensate collected from the jacket. In this open flow channel configuration, the jacket may include a common collection system for steam that condenses into water in the jacket after transferring heat to the product mixture moving through the heater. This collection system may include flow sections configured to collect the condensate at a downward opening angle.

[0094] Optionally, in the first, second, third, and fourth processes, a catalyst deactivator may be introduced into the discharge line. Non-limiting examples of catalyst deactivators include water, oxygen, or alcohols, and combinations thereof. Also optionally, a reaction regulator may be introduced into the discharge line, for example, to slow the reaction (without killing the catalyst / reaction), and may be combined with the effluent from the first reactor (or the second reactor). The reaction regulator may be the same material as the catalyst deactivator or a different material, but in a much smaller amount. In some aspects, alcohols are used as reaction regulators, while in others, CO is used.

[0095] For processes in which a fluidized bed reactor is connected in series after a loop reactor, the reactor effluent from the loop reactor (whether or not heated via a flash line heater) undergoes a separation step, in which a light fraction containing hydrogen is separated from the reactor effluent to form an intermediate material. Typically, but not required, the separation step includes flash evaporation.

[0096] The separator can be specifically defined as a flash tank, flash vessel, flash chamber, cyclone separator, high-efficiency cyclone separator, or centrifuge. The separator can be in fluid communication with the fluidized bed reactor. The separator can have feed streams from the top of the fluidized bed reactor and the discharge port of the loop reactor.

[0097] Cyclone separators use centrifugal force to separate particles from a stream containing gas. Optionally, the stream may contain one or more liquids. Centrifugal force is the g-force generated by rotational motion. Separator design, inlet conditions, and inlet location all contribute to the centrifugal force. One type of cyclone separator covered herein is a hydrocyclone separator, which separates particles from a stream containing liquid. Cyclone separators may also include other separation methods, including flash evaporation by reducing pressure, sedimentation of particles by gravity, or other methods known in the art.

[0098] The cyclone separator downstream of the loop reactor can be a hollow container with a conical shape. The diameter of the top of the cyclone separator is typically larger than the diameter of the bottom. In one aspect, the cone angle of the cyclone separator can be 45° to 90°; alternatively, 50° to 85°; alternatively, 60° to 90°; alternatively, 60° to 85°; alternatively, 60° to 80°; alternatively, 60° to 70°; or alternatively, 70° to 80°. The cyclone separator can be particularly high-efficiency cyclone separators, designed to separate solid particles with a size of 2 to 10 micrometers or larger than 10 micrometers from a gas mixture with an efficiency greater than 95% (or greater than 98%, or greater than 99%).

[0099] The angle of the end of the upper duct connected to the cyclone separator relative to the horizontal plane can be from 0° to 15°. In another aspect, the vertical distance h between the top of the separator and the location where the upper duct connects to the separator can be from 0 m (0 ft) to 6.10 m (20 ft); alternatively, from 0.305 m (1 ft) to 3.048 m (10 ft); alternatively, from 0.305 m (1 ft) to 1.52 m (5 ft). In one aspect, the cyclone separator is a tangential flow cyclone separator, and the inlet is a tangential inlet. The tangential inlet can have an entry angle of 0° to 15° relative to the tangent of the cyclone separator, or alternatively, from 7° to 11°. Constructing a cyclone separator as a tangential flow cyclone separator may require a tangential inlet. The tangential inlet guides the mixture entering the cyclone separator toward the inner wall to facilitate the separation of the solid particles from the gas mixture.

[0100] In one aspect, the tangential entry velocity into the cyclone separator can be from 15.24 m / s (50 ft / s) to 30.48 m / s (100 ft / s); alternatively, from 18.29 m / s (60 ft / s) to 27.43 m / s (90 ft / s); or alternatively, from 21.34 m / s (70 ft / s) to 24.39 m / s (80 ft / s). Level control within the cyclone separator typically provides an average residence time of 5 to 60 minutes.

[0101] The pressure differential between the upstream reactor and the second reactor can be used to transfer intermediate material from the flash cyclone separator to the second reactor. Using the same material for the diluent and inert gas / hydrocarbon in both the loop and fluidized bed reactors simplifies the process. If an alternative diluent is needed in the second reactor, a closed hopper can be used to separate the transferred gas from the intermediate material and / or fluff particles. This gas can be returned to the first reactor via a recirculation purification system. The intermediate material and / or fluff can be driven by circulating gas from the fluidized bed reactor (or other sources, such as a slipstream from a fluidized bed compressor or a compressor using fully separated reactor gases), gravity-flowed through ejectors to the fluidized bed reactor to inject the fluff into the active section of the fluidized bed reactor.

[0102] A line or conduit between the flash cyclone separator and the downstream second reactor can be heated to maintain a target temperature. The heater can be an electric heater wound around a portion of the conduit, a heat exchanger such as a shell-and-tube heat exchanger (e.g., where the heating medium is separated by structural elements that transfer heat to the product mixture flowing through the heater), a flash line heater (e.g., by injecting steam into the jacket, by an electric heater, or by both, adding heat along alternating sections along the heater), or a combination thereof. The heater can be configured as an open-flow-channel flash line heater, which is a jacketed tube of constant diameter heated at one end by steam injected into the jacket and at the other end by condensate collected from the jacket. In this open-flow-channel configuration, the jacket may include a common collection system for steam that condenses into water in the jacket after transferring heat to the product mixture moving through the heater. This collection system may include flow sections configured to collect the condensate at a downward opening angle.

[0103] Now, specifically referring to the fluidized bed reactors (or multiple fluidized bed reactors) in the first, second, third, and fourth processes, these reactors utilize a continuous circulating stream containing ethylene and one or more comonomers, which continuously circulates through the fluidized bed under gas-phase polymerization conditions in the presence of a catalyst. The recirculated stream can be extracted from the fluidized bed reactor and recycled back into it. Simultaneously, the ethylene polymer effluent can be extracted from the reactor, and new or fresh ethylene and optional comonomers can be added to replace the polymerized ethylene and comonomers. General information regarding fluidized bed reactors and suitable gas-phase polymerization conditions can be found, for example, in U.S. Patent Nos. 5,352,749, 4,588,790, 5,436,304, 7,531,606, and 7,598,327. However, typical gas-phase polymerization conditions include polymerization temperatures ranging from 48°C to 95°C, 50°C to 85°C, or 55°C to 82°C, and polymerization pressures ranging from 200 psig to 500 psig, 200 psig to 400 psig, 250 psig to 650 psig, or 250 psig to 350 psig, but polymerization temperatures and pressures are not limited to these representative ranges.

[0104] Gas-phase polymerization conditions in a fluidized bed reactor also include fluidization velocities typically ranging from 1.5 ft / s to 3 ft / s, such as 1.5 ft / s to 2.7 ft / s or 1.7 ft / s to 2.7 ft / s. The inert gas and / or hydrocarbons in the fluidized bed reactor may include any suitable inert gas and / or inert hydrocarbons, but nitrogen, ethane, propane, or combinations thereof are commonly used. In cases where propane is used as an inert hydrocarbon diluent in a loop reactor preceding the fluidized bed reactor, the propane from the loop reactor may be in the liquid phase before entering the fluidized bed reactor. By replacing the inert gas, such as nitrogen, with a non-condensable hydrocarbon, the heat capacity of the gaseous mixture in the fluidized bed reactor increases, which can increase heat removal from the fluidized bed reactor and improve production capacity (e.g., from 5% to 100%, or from 10% to 50%). In a further aspect, some or all of the nitrogen used to deliver any catalyst to the fluidized bed reactor may be replaced with an inert hydrocarbon, such as propane.

[0105] In the fluidized bed reactors (or multiple fluidized bed reactors) of the first, second, third, and fourth processes, gas-phase polymerization conditions may include the presence of any amount of C3-C8 or C4-C8 alkane condensable agents based on up to 30 vol% of the reactor contents during gas-phase polymerization, such as butane (e.g., n-butane and / or isobutane), pentane (e.g., n-pentane and / or isopentane), hexane, etc., or combinations thereof. Typical amounts of this condensable agent range from 5 vol% to 30 vol%, 10 vol% to 30 vol%, or 15 vol% to 25 vol%, but are not limited thereto. It should be noted that propane may act as an inert gas and / or hydrocarbon, or a condensable agent, or both, depending on the operating conditions of the fluidized bed reactor.

[0106] A fluidized bed reactor may have a reaction zone and an expansion zone. The reaction zone comprises a cylindrical portion extending from the bottom to the top of the reactor and has a reaction zone circumference. The expansion zone is located above the reaction zone and has an expansion zone circumference greater than the reaction zone circumference at each vertical distance along the expansion zone. A suitable control system can be used to monitor key aspects of the gas-phase polymerization process. For example, a process for producing multimodal ethylene polymers may further include determining and / or controlling the bed height (or solids level) within the fluidized bed reactor. Once determined, the bed height (or solids level) within the fluidized bed reactor can be adjusted by modifying the solids removal rate, fluidization velocity, catalyst feed rate, reactor gas density, reactor gas composition, polymerization temperature, polymerization pressure, or any combination of these factors.

[0107] Similar to a loop reactor, discharges from the fluidized bed reactor can be intermittent or continuous at one or more locations around the reactor. In one aspect, for example, each ethylene polymer or reactor effluent discharged from the respective fluidized bed reactor may pass through a closed hopper. In another aspect, each ethylene polymer or reactor effluent may be continuously discharged from the respective fluidized bed reactor.

[0108] Any method or apparatus described herein for discharging from a loop slurry reactor (e.g., CTO valve, discharge orientation, etc.) can also be used for discharging from a fluidized bed reactor. In one aspect, an effluent containing a multi-peaked polymer is continuously drawn from the fluidized bed reactor and conveyed to the separation vessel via a pressure differential between the fluidized bed reactor and the separation vessel (although not limited thereto, the fluidized bed reactor can be operated at pressures from 250 psig to 600 psig, and the separation vessel can be operated at pressures from 5 psig to 200 psig).

[0109] For advantageous layout and cost considerations, the separation vessel can be positioned downstream of the loop reactor and upstream of the fluidized bed reactor. In one aspect, the vertical distance between the separation vessel and the loop reactor and the fluidized bed can be approximately at the ground level, with the bottom or outlet end of the separation vessel positioned at a height no higher than approximately the height of the fluidized bed reactor. In another aspect, the bottom or outlet of the separation vessel is positioned at a height above the inlet height of the fluidized bed reactor (thus eliminating the need for a pump to transfer intermediate material from the separator to the fluidized bed reactor). In yet another aspect, the bottom or outlet of the separation vessel is positioned at a height equal to or greater than the top height of the fluidized bed reactor. Still another aspect, the bottom of the separation vessel is positioned at a vertical height relative to the ground that is minimally sufficient (i.e., without unnecessary excess height) to allow valves and transfer lines to be placed below the separation vessel. In another respect, the bottom of the separation container is positioned at a vertical height of approximately 0 feet, or alternatively, approximately 10 feet, or alternatively, approximately 25 feet, or alternatively, approximately 50 feet, or alternatively, approximately 100 feet, or alternatively, approximately 500 feet, relative to the ground.

[0110] The horizontal distance between the separation vessel and the corresponding reactor can also vary based on layout and cost considerations. In one aspect, a first pressure differential transfers the effluent from the first reactor to a separation vessel located 0 to 3,000 horizontal feet from the loop reactor; alternatively, the separation vessel is 0 to 1,500 horizontal feet from the loop reactor; alternatively, the separation vessel is 100 to 1,500 horizontal feet from the loop reactor; alternatively, the separation vessel is 100 to 500 horizontal feet from the loop reactor; alternatively, the separation vessel is 200 to 500 horizontal feet from the loop reactor. In various aspects, the effluent can travel in the x, y, and z coordinates, for example, via a circuitous routing greater than the horizontal distance, vertical spacing / distance, or a linear distance of both.

[0111] In one aspect, a pressure differential between the operating pressure of the separation vessel and the fluidized bed reactor transports intermediate material from the separation vessel to the fluidized bed reactor via a low-pressure line. In another aspect, the pressure differential includes a pressure drop from 275 psig to 800 psig in the separation vessel to 200 psig to 350 psig in the fluidized bed reactor. In one embodiment, using a pressure differential to transport the polymer from the separation vessel to the fluidized bed reactor eliminates the need to position the separation vessel at a height above the fluidized bed reactor. The distance the polymer must be transported from the separation vessel to the fluidized bed reactor can be adjusted to improve polymer fluff transport.

[0112] In one aspect, the same materials are used as diluents and inert gases / hydrocarbons. In another aspect, if the materials are different, a closed hopper can be used to separate the transfer gas from the active fluff particles. This gas can be returned to the loop reactor via a recirculation purification system. The fluff can utilize the circulating gas from the fluidized bed reactor as a driving fluid, with gravity flow reaching the fluidized bed reactor through ejectors to inject the fluff into the active section of the fluidized bed reactor.

[0113] A line between a heatable separation vessel, such as a flash cyclone separator, and a downstream fluidized bed reactor, is used to maintain a target fluff temperature for the intermediate material. The heater can be an electric heater wound around a portion of the conduit, a heat exchanger such as a shell-and-tube heat exchanger (e.g., where the heating medium is separated by structural elements that transfer heat to the material mixture flowing through the heater), a flash line heater (e.g., by injecting steam into the jacket, by an electric heater, or by both, adding heat along alternating sections along the heater), or a combination thereof. The heater can be configured as an open-flow-channel flash line heater, which is a constant-diameter jacketed tube heated at one end by steam injected into the jacket and at the other end by condensate collected from the jacket. In this open-flow-channel configuration, the jacket may include a common collection system for steam that condenses into water in the jacket after transferring heat to the product mixture moving through the heater. This collection system may include flow sections configured to collect the condensate at a downward opening angle.

[0114] Advantageously, the first, second, third, and fourth processes may further include the steps of separating fine polymer particles from unreacted olefins in the gas stream from the fluidized bed reactor, and conveying the fine polymer particles back to the fluidized bed reactor. This can be accomplished by a fine particle separator (e.g., a cyclone separator), from which the fine polymer particles are then conveyed to an ejector (e.g., a vertical ejector), and then the fine polymer particles, together with a motive gas (e.g., unreacted ethylene), are conveyed back to the fluidized bed reactor from the ejector.

[0115] Optionally, low levels of deactivators (such as oxygenated streams) can be injected downstream of the fluidized bed reactor and combined with ethylene polymers to enhance properties (e.g., broaden MWD) and inhibit polymer growth.

[0116] Prior to granulation, the multimodal ethylene polymers produced by the first, second, third, and fourth processes can possess any suitable fluff or powder characteristics, such as bulk density, average particle size, particle size distribution, span, etc. For example, 70% to 90% by weight of the polymer particles can have a size range of 100 micrometers to 500 micrometers, and in a further aspect, a polymer particle size range of 150 micrometers to 400 micrometers.

[0117] To improve the control of multi-reactor processes and ensure consistent production of the desired multi-peak ethylene polymer, each of the first, second, third, and fourth processes may further include steps for determining and / or controlling the polymer properties of the ethylene polymer (e.g., the ethylene polymer produced in each reactor, and / or the final multi-peak ethylene polymer) using any suitable analytical technique. Non-limiting examples include the use of Raman spectroscopy for density determination, melt flow meters for MI and HLMI determination, rheometers for determining rheological parameters, GPCs for determining molecular weight parameters, etc. These can be used intermittently or continuously, and operated offline or online. Suitable feedback control systems can be used in conjunction with these analytical techniques, wherein slurry / supercritical polymerization conditions and gas-phase polymerization conditions are adjusted based on the analytical test results of the corresponding ethylene polymer.

[0118] Consistent with aspects of the first, second, third, and fourth processes, this paper provides favorable pressure distributions for multi-reactor processes and systems, which are described in Figure 4 The schematic flow diagram shows the following components in the polymerization process and reactor system 400: a prepolymerization reactor 410 operating at pressure P1, an optional buffer vessel 420 operating at pressure P2, an optional feed pump 425 operating at pressure P3, a loop reactor 430 operating at pressure P4, an intermediate separation vessel 440 operating at pressure P5, a fluidized bed reactor 450 operating at pressure P6, a final separation vessel 460 operating at pressure P7, and a purge tower 470 operating at pressure P8.

[0119] First, the loop reactor 430 (or each loop reactor independently) can be operated under supercritical conditions at a pressure P4 in the range of 900 psig to 1100 psig, wherein the supercritical conditions are above the critical pressure and temperature of the fluid (diluent such as propane) within the loop reactor. Therefore, the separation step can be carried out in a suitable intermediate separation vessel 440 operating at a pressure P5 in the range of 150 psig to 800 psig, and / or under conditions sufficient to remove at least 80 wt%, at least 90 wt%, or at least 95 wt% hydrogen from the respective reactor effluent. In one aspect of the invention, the pressure ratio of P4 / P5 is in the range of 3 to 6, while in another aspect, the ratio is in the range of 3 to 5.5, and in yet another aspect, the ratio is in the range of 3.5 to 6, and in yet another aspect, the ratio is in the range of 3.5 to 5.5.

[0120] Alternatively or additionally, the fluidized bed reactor 450 can be operated at a pressure P6 within the range of 250 psig to 600 psig, and the effluent stream containing the multimodal ethylene polymer from the fluidized bed reactor can be introduced into a final separation vessel 460 that is operated at a pressure P7 within the range of 5 psig to 200 psig and / or under conditions sufficient to remove at least 60 wt%, at least 70 wt%, at least 80 wt% or at least 90 wt% of propane from the effluent stream. Subsequently, the multimodal ethylene polymer can be discharged from the separation vessel 460 into a purge column 470 that is operated at a pressure P8 within the range of 1 psig to 20 psig. In one aspect, the ratio of P6 / P7 can be greater than the ratio of P4 / P5. Advantageously, in one aspect, the ratio of P5 / P7 can be within the range of 4 to 60, in another aspect within the range of 5 to 55, and in yet another aspect within the range of 10 to 40. Without wishing to be bound by theory, it is believed that the P5 / P7 ratio within these ranges improves hydrocarbon recovery and recycle in the process.

[0121] In one aspect, when a prepolymerization step is present in the first, second, third or fourth process, this can be carried out in a prepolymerization loop reactor 410 (e.g., loop reactor design) at a pressure P1 within the range of 900 psig to 1200 psig and / or at a pressure greater than P4 (i.e., P1 > P4).

[0122] In another aspect, when a prepolymerization step is present in the first, second, third or fourth process, this can be carried out in a prepolymerization loop reactor 410 (e.g., loop reactor design) at a pressure P1 within the range of 400 psig to 800 psig. Generally, when P1 < P4, a feed pump 425 may be required to increase the discharge pressure of the pump (P3). The effluent stream from the prepolymerization reactor can be introduced into a buffer vessel 420 that is operated at a pressure P2 within the range of 400 psig to 800 psig and / or at a pressure less than P1 (P2 < P1). Additionally, the effluent stream from the buffer vessel 420 can be introduced into the feed pump 425 to increase the discharge pressure P3 of the pump to within the range of 925 psig to 1200 psig. Since the loop reactor 430 is operated at supercritical pressure, a higher pressure feed to the reactor will be required and the pump 425 may be beneficial.

[0123] Polymerization Reactor System

[0124] A first polymerization reactor system (or reactor apparatus) conforming to aspects of the present invention for producing a multimodal ethylene polymer may include (or substantially consist of, or consist of) the following: (a) a loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (b) an effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the loop reactor; (c) a separator configured to remove a light fraction containing hydrogen from the first reactor effluent to form an intermediate material; and (d) a fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a multimodal ethylene polymer. In the first polymerization reactor system, the fluidized bed reactor may be further configured to contact hydrogen with the intermediate material, ethylene, and optionally the second olefin comonomer. Alternatively or alternatively, in the first polymerization reactor system, the loop reactor may be configured to contact the catalyst composition with ethylene, the first olefin comonomer, and hydrogen, or the fluidized bed reactor may be configured to contact the intermediate material with ethylene and the second olefin comonomer, or the loop reactor may be configured to contact the catalyst composition with ethylene, the first olefin comonomer, and hydrogen, and the fluidized bed reactor may be configured to contact the intermediate material with ethylene and the second olefin comonomer.

[0125] A second polymerization reactor system (or reactor apparatus) for producing a multimodal ethylene polymer according to an aspect of the invention may comprise (or substantially comprise, or comprise) the following: (a) a first loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer, and optionally hydrogen in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (b) a second loop reactor configured to contact a first reactor effluent containing the first ethylene polymer with ethylene, optionally a second olefin comonomer, and optionally hydrogen under slurry or supercritical polymerization conditions to produce a second ethylene polymer; and (c) a transfer line configured to... The system comprises: (d) a first reactor effluent containing a first ethylene polymer drawn from a first loop reactor and introduced into a second loop reactor; (e) a second discharge line configured to draw from the second loop reactor effluent containing a second ethylene polymer; (f) a separator configured to remove a light fraction containing hydrogen from the second reactor effluent to form an intermediate material, wherein hydrogen is present in the first loop reactor, the second loop reactor, or both; and (c) a fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a third olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a multimodal ethylene polymer. In the second polymerization reactor system, the first loop reactor may be configured to contact the catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen, and / or the second loop reactor may be configured to contact the first reactor effluent with ethylene, optionally a second olefin comonomer, and hydrogen. Furthermore, in the second polymerization reactor system, the first loop reactor may be configured to contact the catalyst composition with ethylene and the first olefin comonomer, or the second loop reactor may be configured to contact the effluent from the first reactor with ethylene and the second olefin comonomer, or the fluidized bed reactor may be configured to contact the intermediate material with ethylene and the third olefin comonomer, or any combination of these variations.

[0126] A third polymerization reactor system (or reactor apparatus) for producing a multimodal ethylene polymer according to an aspect of the invention may include (or substantially consist of, or consist of) the following: (a) a fluidized bed reactor configured to contact a catalyst composition with ethylene and optionally a first olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a first ethylene polymer; (b) an effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the fluidized bed reactor; (c) a transfer line configured to combine an inert hydrocarbon diluent with the first reactor effluent and increase pressure to form an intermediate material (e.g., the transfer line may include a suitable pump); and (d) a loop reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer under slurry or supercritical polymerization conditions to produce a multimodal ethylene polymer. In the third polymerization reactor system, the fluidized bed reactor may be further configured to contact the catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen, and / or the loop reactor may be further configured to contact the intermediate material with ethylene, optionally a second olefin comonomer, and hydrogen. Alternatively or additionally, in the third polymerization reactor system, the fluidized bed reactor may be configured to contact the catalyst composition with ethylene and the first olefin comonomer, and / or the loop reactor may be configured to contact the intermediate material with ethylene and the second olefin comonomer.

[0127] A fourth polymerization reactor system (or reactor apparatus) for producing a multimodal ethylene polymer according to aspects of the present invention may include (or substantially consist of, or consist of) a loop reactor configured to contact a catalyst composition with ethylene and optionally a first olefin comonomer in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer; (b) a fluidized bed reactor configured to contact a second catalyst composition with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a second ethylene polymer; and (c) a mixing device configured to combine the first and second ethylene polymers to produce a multimodal ethylene polymer. In the fourth polymerization reactor system, the loop reactor may be further configured to contact the catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen, and / or the fluidized bed reactor may be further configured to contact the second catalyst composition with ethylene, optionally a second olefin comonomer, and hydrogen. Alternatively or alternatively, in the fourth polymerization reactor system, the loop reactor may be configured to contact the catalyst composition with the ethylene and the first olefin comonomer, and / or the fluidized bed reactor may be configured to contact the second catalyst composition with the ethylene and the second olefin comonomer.

[0128] Typically, the features of the first, second, third, and fourth systems (e.g., one or more loop reactors, one or more fluidized bed reactors, polymerization conditions in each reactor, one or more catalyst compositions, discharge and transfer lines, separators, and multimodal ethylene polymers, etc.) are described independently herein, and these features may be combined in any combination to further describe the disclosed polymerization reactor systems for producing multimodal ethylene polymers. Furthermore, additional components or equipment may be present in these systems and may be used without limitation and in any combination to further describe the first, second, third, and fourth polymerization reactor systems for producing multimodal ethylene polymers, unless otherwise stated. For example, each polymerization reactor system may be further configured to introduce one or more comonomers into any loop reactor or fluidized bed reactor, and if multiple comonomers are used, each comonomer may be introduced separately into any reactor, or mixed and injected together into any reactor.

[0129] As disclosed above, each catalyst composition used in the first, second, third, and fourth processes may be independently contacted with ethylene and optionally, an olefin comonomer. When present, the comonomer concentration in each reactor used in the process may be the same or different, and similarly, the ethylene concentration in each reactor used in the process may be the same or different. In one aspect, the comonomer may be used in at least one loop reactor, or in at least one fluidized bed reactor, or in at least one loop reactor and at least one fluidized bed reactor. The comonomer used in the loop reactor may be the same as or different from the comonomer used in the fluidized bed reactor. Additionally, more than one comonomer may be used (e.g., mixed and injected together) in any reactor (e.g., no comonomer in the loop reactor, but two comonomers in the fluidized bed reactor). Alternatively or additionally, multiple fluidized bed reactors with different comonomers may be used for terpolymers and trimodal resins.

[0130] Each of the first, second, third, and fourth systems may further include a prepolymerization reactor of any suitable design, such as a stirred tank or loop reactor design. This prepolymerization reactor (if present) is configured to prepolymerize the catalyst composition prior to using the catalyst system in the loop reactor or fluidized bed reactor. Regardless of whether the system includes a prepolymerization reactor, the system may further include a catalyst feed port configured to introduce the catalyst composition as a slurry with a solids content of 1% to 15% by weight, 2% to 14% by weight, or 3% to 12% by weight into the loop reactor (or the first loop reactor).

[0131] Alternatively or additionally, each of the first, second, third, and fourth systems may further include a second fluidized bed reactor configured to operate under gas-phase polymerization conditions. For example, in the first polymerization reactor system, the loop reactor may be configured to produce lower molecular weight HDPE, the first gas-phase reactor may be configured to produce medium molecular weight LLDPE, and the second gas-phase reactor may be configured to produce high molecular weight LLDPE.

[0132] Referring now to each loop reactor in the first, second, third, and fourth polymerization reactor systems, each loop reactor may be independently configured to operate under any slurry or supercritical polymerization conditions, polymerization temperature, polymerization pressure, mean residence time, and linear velocity disclosed herein, and using any inert hydrocarbon diluent disclosed herein, such as those described above for the first, second, third, and fourth processes for the production of multimodal ethylene polymers. For example, the loop reactor (or each loop reactor independently) may be configured for a maximum permissible operating pressure (MAWP) greater than the operating pressure or polymerization pressure in the respective reactor, by at least 5% and / or up to 30%. Each loop reactor may independently have one or more pressure relief valves, and these pressure relief valves may be configured to release pressures at MAWP and / or pressures 5% greater than MAWP, as well as other pressure options.

[0133] In the second system, the first loop reactor and the second loop reactor can be configured to polymerize at 25% of each other, and in some cases at 20% of each other, 10% of each other, or 5% of each other.

[0134] In one aspect of the first, second, third, and fourth systems, each loop reactor can be independently configured to produce an ethylene polymer with lower Mw, higher MI, and higher density than the ethylene polymer produced by a fluidized bed reactor (which can be configured to produce a higher Mw, lower MI, and lower density ethylene polymer). In another aspect of the first, second, third, and fourth systems, each loop reactor can be independently configured to produce an ethylene polymer with higher Mw, lower MI, and lower density than the ethylene polymer produced by a fluidized bed reactor (which can be configured to produce a lower Mw, higher MI, and higher density ethylene polymer).

[0135] There is no particular limitation on the amount of multimodal ethylene polymer produced in each reactor, but for the first, third and fourth systems, the system is typically configured to produce 20% to 90% (or 25% to 85% or 30% to 70%) of multimodal ethylene polymer in a loop reactor and to produce 10% to 80% (or 15% to 75% or 30% to 70%) of multimodal ethylene polymer in a fluidized bed reactor.

[0136] For the second polymerization reactor system, the system is typically configured to produce 5 wt% to 30 wt% (or 5 wt% to 25 wt%, or 10 wt% to 25 wt%) of multimodal ethylene polymer in a first loop reactor, 30 wt% to 60 wt% (or 30 wt% to 55 wt%, or 35 wt% to 60 wt%) of multimodal ethylene polymer in a second loop reactor, and 30 wt% to 60 wt% (or 30 wt% to 55 wt%, or 35 wt% to 60 wt%) of multimodal ethylene polymer in a fluidized bed reactor. In the second reactor system, the first loop reactor may be configured to produce low to high molecular weight homopolymers, the second loop reactor may be configured to produce lower molecular weight ethylene copolymers, and the fluidized bed reactor may be configured to produce medium to high molecular weight ethylene copolymers.

[0137] Optionally, the first, second, third, and fourth polymerization reactor systems may be further configured to introduce the antistatic compound into at least one loop reactor or fluidized bed reactor, for example, into a loop reactor, or into a fluidized bed reactor, or into a loop reactor and a fluidized bed reactor.

[0138] Each loop reactor in the first, second, third, and fourth systems may have any suitable design or construction, but advantageously, each loop reactor may independently have a length-to-diameter (L / D) ratio of 500 to 3,000 (e.g., 700 to 1,500), an internal diameter of 12 to 48 inches (e.g., 18 to 40 inches or 20 to 32 inches), a length of 50 to 300 feet (e.g., 100 to 250 feet), and 2 to 16 legs (e.g., 4 to 14 legs). The loop reactor may be supported or freestanding.

[0139] Furthermore, each loop reactor may independently have an inner surface roughness of less than or equal to 150 microinches, such as less than or equal to 100 microinches, or less than or equal to 50 microinches, or from 10 microinches to 50 microinches. Alternatively or alternatively, each loop reactor may be independently constructed from any suitable material, including carbon steel, stainless steel, cryogenic carbon steel, and combinations thereof.

[0140] In one aspect, the loop reactor (or each loop reactor) may be constructed from rolled plate having two edges joined along a seam, which can be joined by welding along the seam. A wall thickness of 1 / 2” to 3 / 4” is typical, and the material used for the rolled plate typically has a minimum tensile strength of 50,000 psi. Optionally, the loop reactor (or each loop reactor) may include a rust-preventive coating on the reactor surface and flanges.

[0141] For temperature monitoring and control, the loop reactor (or each loop reactor) may have multiple thermocouple sheath locations, each containing a suitable thermocouple or temperature sensing device. Additionally, each loop reactor includes a reactor circulation pump, i.e., one or more reactor circulation pumps, which may be axial, radial, or mixed-flow designed.

[0142] Each loop reactor may independently include a bend section (or two or more bend sections) configured to accommodate the Dean number (D) of the reaction mixture flowing within it. n The number should be maintained at at least 3,000,000. (D) n D is a dimensionless number defined as follows: n =(ρVd / μ)*(d / 2R) c ) 1 / 2 Where ρ is the density of the reaction mixture in the loop reactor, V is the circulation rate of the reaction mixture in the loop reactor, d is the inner diameter of the bend section of the loop reactor, μ is the dynamic viscosity of the reaction mixture in the loop reactor, and R c This is the inner bend radius of the bend section in the loop reactor. In one aspect, each loop reactor may independently include a bend section (or two or more bend sections) configured to maintain at least 4,000,000, at least 5,000,000, or at least 6,000,000, and typically up to and including 10,000,000 to 15,000,000, or greater Dean numbers (D). n ).

[0143] Advantageously, the loop reactor (or each loop reactor) may include a bend flow meter. The bend flow meter can be used to measure the circulation velocity in the loop reactor. In one aspect, the bend flow meter can be a differential pressure flow meter, which includes diaphragms located at high-pressure and low-pressure taps. These pressure taps are located on the outside and inside of the bend because centrifugal force causes a pressure difference between the outside and inside of the bend, and this pressure difference can be used to calculate the flow / circulation velocity and mass or volumetric flow rate. Advantageously, the bend flow meter does not have a sensing device located in the flow path that could obstruct the circulating reaction mixture in the loop reactor.

[0144] Each loop reactor in the first, second, third, and fourth polymerization reactor systems can be independently configured to maintain a Froude number of 10 to 100 (e.g., 15 to 50, 20 to 90, or 40 to 80). In one aspect, any discharge and / or transfer lines in the system (with or without flash line heaters) can be configured for reactor effluents contained therein having a Froude number of 10 to 100, such as 15 to 50, 20 to 90, or 40 to 80.

[0145] Alternatively or alternatively, each loop reactor in the first, second, third, and fourth polymerization reactor systems may be independently configured to maintain a Biot number of less than or equal to 3 (e.g., less than or equal to 2, less than or equal to 1.5, or less than or equal to 1.1) during polymerization.

[0146] Alternatively, each loop reactor in the first, second, third, and fourth polymerization reactor systems may be independently configured to maintain a cavitation number (Ca) of 6 to 60 (e.g., 12 to 50, 18 to 40, or 24 to 36).

[0147] Alternatively or alternatively, each loop reactor in the first, second, third, and fourth polymerization reactor systems may be independently configured to maintain an Euler number greater than or equal to 5 (e.g., greater than or equal to 6, or greater than or equal to 7).

[0148] Each corresponding loop reactor in the first, second, third, and fourth polymerization reactor systems can be configured for continuous discharge; therefore, the loop reactor can have a continuous feed assembly. The loop reactor can have one or more discharge assemblies at appropriate locations along the loop reactor. For example, the continuous feed (CTO) assembly can extend from a bend in the corresponding loop reactor, from a horizontal section of the corresponding loop reactor, or a combination of these options. In one aspect, the CTO can replace multiple settling legs in the loop reactor. Furthermore, a main reactor discharge assembly can be present, having backup discharge lines located at other locations along one or more loop reactors. Any suitable discharge angle from horizontal to 90° can be used for the discharge assembly.

[0149] There are no particular restrictions on the specific design of effluent discharge from any loop reactor, but loop reactors are typically constructed to continuously discharge reactor effluent via a continuous feed assembly that includes valves, including V-ball valves, or not. When using V-ball valves, the internal diameter is in the range of 0.5 inches to 6 inches, such as 0.5 inches to 3 inches, or 2 inches to 5 inches.

[0150] Continuous material intake or continuous fluff discharge can be achieved through pipelines, where the pressure drop is determined by the pipeline configuration. Valves can also be used.

[0151] For a second polymerization reactor system containing a first loop reactor and a second loop reactor, it is convenient for one or more discharge points of the first loop reactor to be located at a higher pressure (e.g., downstream of the circulation pump) than one or more feed points of the second loop reactor (e.g., upstream of the circulation pump), but this is not necessary.

[0152] Reactor effluents from the loop reactors and / or fluidized bed reactors in the first, second, third, and fourth polymerization reactor systems may be discharged from the respective reactors into an effluent line (or transfer line), and this effluent line (or transfer line) may include a flash line heater. The flash line heater may be heated using steam and may be configured to maintain an effluent discharge temperature within the range of 55°C to 105°C, such as 75°C to 105°C or 60°C to 100°C, but not limited thereto.

[0153] Optionally, the first, second, third, and fourth polymerization reactor systems may further include catalyst deactivator inlets or reaction modifier inlets leading into the discharge line (or transfer line). Suitable catalyst deactivators or reaction modifiers may be introduced into the discharge line (or transfer line) as needed to kill the catalyst / reaction or slow down the reaction.

[0154] The separator used in the disclosed polymerization reactor system may include a flash chamber, which may be configured to remove light fractions containing hydrogen from the reactor effluent to form intermediate materials. In one aspect, the separator may further include a cyclone separator. Suitable cyclone separators may have cone angles of 45° to 90°, 60° to 90°, 60° to 80°, 60° to 70°, or 70° to 80°, designed for inlet velocities of 50 ft / s to 100 ft / s, and have tangential entry angles of 0° to 15°, such as 7° to 11°. The cyclone separator feed may enter tangentially below the tangent at a distance of 0 to 20 ft / s. The cyclone separator may be designed to have an efficiency of greater than 95% (or greater than 98%, or greater than 99%) for particles larger than 10 micrometers. Cyclone separators can be configured to have a level control located within the cyclone separator, which typically provides an average residence time of 5 to 60 minutes within the cyclone separator.

[0155] Referring now specifically to the fluidized bed reactors (or multiple fluidized bed reactors) in the first, second, third, and fourth polymerization reactor systems, each fluidized bed reactor may (independently) be configured to operate under any gas-phase polymerization conditions, polymerization temperature, polymerization pressure, and fluidization rate disclosed herein, and may be configured to use any inert gas and / or hydrocarbon disclosed herein, such as the inert gases and / or hydrocarbons described above for the first, second, third, and fourth processes for the production of multimodal ethylene polymers.

[0156] The fluidized bed reactors (or multiple fluidized bed reactors) in the first, second, third, and fourth systems may further include a condensable feed port configured to introduce a C3-C8 alkane (or C4-C8 alkane) condensable typically in an amount of up to and including 30% by volume based on the contents of the fluidized bed reactor into each fluidized bed reactor.

[0157] The fluidized bed reactor may have a reaction zone and an expansion zone. The reaction zone includes a cylindrical portion extending from the bottom to the top of the reactor and has a reaction zone circumference. The expansion zone is located above the reaction zone and has an expansion zone circumference greater than the reaction zone circumference at each vertical distance along the expansion zone. The polymerization reactor system may further include a suitable control system for monitoring and controlling key aspects of the gas-phase polymerization process in the fluidized bed reactor. For example, the reactor system may further include a control system configured to control the bed height or solids level in the fluidized bed reactor. This control system may include a plurality of nuclear radiation sources disposed along the outer surface of the fluidized bed reactor between the top and bottom ends, each nuclear radiation source located at a different vertical distance from the bottom end; and a detector array comprising a plurality of radiation detectors disposed along the outer surface of the fluidized bed reactor between the top and bottom ends, each radiation detector located at a different vertical distance from the bottom end. A conduit between each radiation detector and each nuclear radiation source passes through the internal space of the fluidized bed reactor. Although not limited thereto, the plurality of nuclear radiation sources may include at least one radiation source with a radioactivity of 5000 mCi located on the outer surface of the reaction zone and / or expansion zone. The control system may include a computer configured to compare the measured intensities of nuclear radiation at the plurality of radiation detectors and determine the solids level in the fluidized bed reactor based on that information. The solids level in the fluidized bed reactor can be adjusted by adjusting the solids removal rate, fluidization velocity, catalyst feed rate, reactor gas density, reactor gas composition, polymerization temperature, polymerization pressure, or any combination of these factors.

[0158] Similar to a loop reactor, a fluidized bed reactor can be configured to discharge intermittently or continuously at one or more locations around the reactor. In one aspect, for example, each fluidized bed reactor is configured to discharge reactor effluent or ethylene polymer via a feed assembly including a closed hopper. In another aspect, each fluidized bed reactor is configured to continuously discharge reactor effluent or ethylene polymer (the fluidized bed reactor has a continuous feed assembly).

[0159] In some aspects, the first, second, third, and fourth polymerization reactor systems may further include a fine-particle separator (e.g., a cyclone separator) configured to separate fine polymer particles from unreacted olefins in the gas stream from the fluidized bed reactor and to transport the fine polymer particles back to the fluidized bed reactor. For example, the fine polymer particles from the fine-particle separator may be transported to an ejector (e.g., a vertical ejector), from which the fine polymer particles, along with a motive gas (e.g., unreacted ethylene), are transported back to the fluidized bed reactor.

[0160] Optionally, the polymerization reactor system may further include a deactivator inlet configured to inject a low level of deactivator (e.g., an oxygen-containing flow) downstream of the fluidized bed reactor. This addition may be intended to enhance properties (e.g., broaden the molecular weight distribution (MWD)) as well as to inhibit polymer growth. The downstream location is within the loop flow of the fluidized bed reactor. Oxygen will contact the catalyst in the reactor, which can alter the MW of the polymer.

[0161] To improve control over the polymerization reactor systems, various reactors, and various polymerization conditions, each of the first, second, third, and fourth polymerization reactor systems may further include an analytical system configured to determine and / or control the polymer properties of each ethylene polymer produced in the reactors within the system. Any suitable analytical technique can be used, such as Raman spectroscopy for density, melt flow meters for MI and HLMI, rheometers for rheological parameters, and GPCs for MWD. ​​Therefore, the polymerization reactor systems may further include analytical systems incorporating Raman spectrometers, melt flow meters, rheometers, GPCs, and combinations thereof. The analytical system may be configured for batch or continuous operation, and may be operated offline or online. As part of the analytical system, feedback control elements may be integrated to adjust slurry / supercritical polymerization conditions and gas-phase polymerization conditions based on the results of analytical tests on the respective ethylene polymers.

[0162] Now for reference Figure 1 The illustration shows a polymerization reactor system 100 conforming to one aspect of the present invention. System 100 may include a prepolymerization reactor 110, a buffer vessel 120, a feed pump 125, a loop reactor 130, a discharge line 135, a separator 140B, a fluidized bed reactor 150, and a fluidized bed reactor discharge port 155. Figure 1 The catalyst composition feed 105 is prepolymerized in prepolymerization reactor 110 to form a prepolymerized catalyst composition 115, which is then introduced into buffer vessel 120 and feed pump 125, and finally fed into loop reactor 130. Alternatively, the catalyst composition feed 105 is not prepolymerized, but is fed directly into loop reactor 130 (or optionally into buffer vessel 120 and feed pump 125). The catalyst composition feed 105 may contain an inert hydrocarbon diluent, such as isobutane and / or propane. Reactant feed stream 128 is also fed into loop reactor 130, and this feed stream may contain ethylene, comonomer, hydrogen, and an inert hydrocarbon diluent. It should be understood that there are many different methods for introducing the catalyst, diluent, olefin, and hydrogen individually or together, and in any combination, into the loop reactor, and this disclosure is not limited to reference. Figure 1 Those options described herein or otherwise disclosed herein.

[0163] In loop reactor 130, a first ethylene polymer is produced, and a first reactor effluent containing the first ethylene polymer is discharged from loop reactor 130 via discharge line 135. Optionally, the reactor effluent in discharge line 135 may be heated, for example, via flash line heater 138 before separator 140B. In separator 140B, a light fraction containing hydrogen (and optionally some ethylene) is separated at the top of the column, and an intermediate material (containing the first ethylene polymer) exits separator 140B via ejector 142 and enters fluidized bed reactor 150. Feed stream 144 may supply additional ethylene, comonomers, hydrogen, inert gases, and / or hydrocarbons to fluidized bed reactor 150. A second reactor effluent containing a multi-peaked ethylene polymer is discharged from fluidized bed reactor 150 via fluidized bed reactor discharge port 155. The overhead stream 158 can exit the fluidized bed reactor 150 and enter the separator 140B, where it is separated into various components, some of which are directly recycled back to the fluidized bed reactor 150 via the ejector 142. The overhead stream from the separator 140B can pass through the heat exchanger 145 and the compressor 148, and be mixed with the feed stream 144 in any relative proportion before being recycled back to the fluidized bed reactor 150.

[0164] Now for reference Figure 2 The illustration depicts another polymerization reactor system 200 conforming to one aspect of the invention. System 200 may include a prepolymerization reactor 210, a buffer vessel 220, a feed pump 225, a loop reactor 230, a discharge line 235, a separator 240B, a fluidized bed reactor 250, and a fluidized bed reactor discharge port 255, which are typically associated with, for example, [the following is a description of a specific type of reactor]. Figure 1 The components with similar numbering are the same as those described. The catalyst composition feed 205, prepolymerized catalyst composition 215, reactant feed stream 228, ejector 242, heat exchanger 245, compressor 248, and overhead stream 258 leaving the fluidized bed reactor can also be substantially the same as those for... Figure 1 The same applies to components with similar numbers.

[0165] Figure 2 The feed stream 244 (which can supply additional ethylene, comonomers, hydrogen, inert gases and / or hydrocarbons to the fluidized bed reactor 250) is shown as being in Figure 2 Before compressor 248, and in Figure 1 The feed stream is after the compressor. It should be understood that there are many different methods and configurations for feeding components individually or together, and in any combination, into a fluidized bed reactor, and this disclosure is not limited to reference to [the present invention]. Figures 1 to 2 Those options described herein or otherwise disclosed herein. Figure 2Also shown is a first reactor effluent in discharge line 235, which, if desired, can be heated 238 by a flash line heater to enter separation vessel 240A, which continuously discharges intermediate material into fluidized bed reactor 250; and an overhead stream exiting separation vessel 240A, the components of which can be recycled within system 200.

[0166] Figure 3 It shows that it can be integrated into Figures 1 to 2 The reactor system includes a polymer recovery system 300. Fluidized bed reactor effluent 355 containing multimodal ethylene polymers enters a separation vessel 360, and flash gas 362 exits from the top of the column. The polymer is discharged through a continuous fluff outlet 365 into a purge column 370, where it contacts nitrogen or other inert gases entering the purge column 370 through an inert gas inlet 368. The multimodal ethylene polymer 375 with reduced volatile content exits the purge column 370 through a rotary valve 372. Inert gases, hydrocarbons, and other volatiles also exit the purge column through a gas outlet 378 and then enter a gas separator 380. The main stream exiting the gas separator 380 is an inert gas recirculation stream 382 (which is reintroduced into the purge column 370) and a hydrocarbon / volatile stream 384.

[0167] The separation container 360 can be specifically embodied as a flash tank, flash vessel, flash chamber, cyclone separator, high-efficiency cyclone separator, or centrifuge. The cyclone separator can be a hollow container with a conical shape. The diameter of the top of the cyclone separator can be larger than the diameter of the bottom of the separator. In one aspect, the cone angle of the cyclone separator can be 45° to 90°; alternatively, 50° to 85°; alternatively, 60° to 90°; alternatively, 60° to 85°; alternatively, 60° to 80°; alternatively, 60° to 70°; or alternatively, 70° to 80°. The cyclone separator can be particularly a high-efficiency cyclone separator, configured to separate 99% by weight or more of solid particles with a size of 2 to 10 micrometers from a gas mixture.

[0168] The angle of the end of the upper duct connected to the cyclone separator relative to the horizontal plane can be from 0° to 15°. In another aspect, the vertical distance h between the top of the separator and the location where the upper duct connects to the separator can be from 0 m (0 ft) to 6.10 m (20 ft); alternatively, from 0.305 m (1 ft) to 3.048 m (10 ft); or alternatively, from 0.305 m (1 ft) to 1.52 m (5 ft). In one aspect, the cyclone separator is a tangential flow cyclone separator, and the inlet is a tangential inlet. This tangential inlet can have an entry angle of 0° to 15° relative to the tangent of the cyclone separator; alternatively, from 7° to 11°. Constructing a cyclone separator as a tangential flow cyclone separator may require a tangential inlet. The tangential inlet guides the mixture entering the cyclone separator toward the inner wall to facilitate the separation of the solid particles from the gas mixture.

[0169] In another aspect, the tangential entry velocity into the cyclone separator can be from 15.24 m / s (50 ft / s) to 30.48 m / s (100 ft / s); alternatively, from 18.29 m / s (60 ft / s) to 27.43 m / s (90 ft / s); or alternatively, from 21.34 m / s (70 ft / s) to 24.39 m / s (80 ft / s).

[0170] A continuous fluff discharge port 365 may include a 2- to 8-inch ID V-ball valve through which fluff is continuously transferred from the cyclone separator or other separation vessel 360. By maintaining the desired level of solid polymer particles in the cyclone separator zone, the polymer solids residence time, which is the average amount of time polymer particles spend in the medium-pressure zone, can be controlled. An increased polymer solids residence time allows for the flash evaporation and / or separation of more hydrocarbons / hydrogen (including more entrained diluent) from the polymer solids, thereby improving the purity and processability of the polymer leaving the zone. Furthermore, by maintaining the desired level of polymer solids in the cyclone separator, a pressure seal can be formed between this zone and downstream equipment. Additionally, providing a pressure seal between the cyclone separator and the fluidized bed reactor (which eliminates the need for on / off valves) reduces operating and maintenance costs.

[0171] Fluidly connected to or part of a cyclone separator or other separation vessel 360° is a stripping section, where lighter (more volatile) components are removed from the process. The stripping section removes a substance that might be dissolved in another by transferring it from one phase to another. For separators following a loop slurry reactor, the concentration of hydrogen or hydrocarbons can be reduced before transferring to a fluidized bed reactor.

[0172] Hydrocarbon losses can be minimized by modifying the lower section of purge tower 370 to include a zone for ethylene desorption, a zone for nitrogen purging, and a zone for final ethylene removal. The stripping gas entering inert gas inlet 368 typically includes nitrogen and may typically include light hydrocarbons, such as treated or untreated ethylene. Alternatively, the active flakes discharged from the fluidized bed reactor can be used to remove poisons to produce polymerization-grade ethylene without the need for an upstream processor. Optionally, J-purge rings may be used in the purge tower to improve degassing efficiency and / or the mass flow through the purge tower.

[0173] The control scheme can be integrated into Figure 3 In the polymer recovery system, the amount of fresh nitrogen required to degas light hydrocarbons (ethylene) is adjusted and controlled. In one aspect, the hydrocarbon / volatile stream 384 can be recycled to one or more loop reactors, one or more fluidized bed reactors, or any combination thereof.

[0174] Figure 5 It shows that it can be integrated into Figures 1 to 2 The reactor system includes a dual-loop reactor system 500. System 500 comprises a first loop reactor 530A and a second loop reactor 530B, and the catalyst composition feed 505, the first loop reactor feed stream 528A, and the second loop reactor feed stream 528B are substantially compatible with those for... Figure 1 The components with similar numbers are identical as described. The temperature control system for the loop reactor is uniformly designated by the number 532. Each of the loop reactors 530A-B has a circulation pump 533A-B and an associated motor 534A-B for circulating the slurry within the respective reactor. Figure 5 A discharge line 535A (or transfer line) from the first loop reactor 530A to the second loop reactor 530B is shown, along with an optional second discharge / transfer line 535X. Any suitable discharge location along the first loop reactor 530A and any suitable inlet location along the second loop reactor 530B can be used. Reactor effluent from the second loop reactor 530B can be discharged in the second loop reactor discharge line 535B via a continuous feed valve 536 and fed to a separator device 540 (see reference). Figures 1 to 2 (described in more detail), after which the resulting intermediate polymer material enters the fluidized bed reactor.

[0175] Figure 6 Cyclone separator 660 is applicable to any polymerization reactor system and polymer recovery system described herein. For example, cyclone separator 660 can be used as... Figure 1 The separator 140B in Figure 2 The separation container 240A and / or separator 240B in Figure 3Separation container 360 in Figure 4 Intermediate separation container 440 and / or final separation container 460 and Figure 5 The separator device 540 is located in the middle. Figure 6 In this context, the cone angle is represented by α (alpha), and in some respects, a cone angle in the range of 50° to 85°, 60° to 85°, 60° to 80°, 60° to 70°, or 70° to 80° is advantageous. The cyclone separator 660 may have any of the features and characteristics described herein with respect to any cyclone separator, high-efficiency cyclone separator, or similar separator device disclosed herein. Figure 6 It is also described as being directly incorporated into Figure 3 In the polymer recovery system, fluidized bed reactor effluent 655 (containing multi-peak ethylene polymer) enters cyclone separator 660, flash gas 662 exits from the top of the column, and polymer is discharged through continuous fluff outlet 665, generally consistent with the target... Figure 3 The same applies to components with similar numbers.

[0176] Figure 7 This refers to the bend section 731, which can be integrated into any loop reactor and polymerization reactor system described herein. For example, the bend section 731 can be used... Figure 1 The loop reactor 130 in the middle Figure 2 The loop reactor 230 in the middle Figure 4 The loop reactor 430 and Figure 5 The first loop reactor 530A and / or the second loop reactor 530B are described herein. Each loop reactor disclosed herein has multiple bend sections, wherein at least one bend section may have Figure 7 The inner diameter (d) and radius (Rc) of the inner bend 737 are shown. The contents of the loop reactor pass through... Figure 7 The flow in the bend section 731 is indicated by arrows from the horizontal section 757 to the vertical section 759 of the loop reactor. The two inner bends 737 of the bend section 731 can form an arc with a height (H) measured from the midpoint of the arc. The length of each inner bend 737 is half the chord length (W) of the arc (W / 2). Therefore, Figure 7 The length of the inner bend 737 of the bend section 731 is W / 2. Rc is the bending radius of the bend section 731, and is equal to H / 2 + W. 2 / 8H, where W is the chord length of the bend section and H is the height of the bend section.

[0177] The bend section 731 of the loop reactor may include a flow meter 739 (bend flow meter). For example, an internal pressure tap 741 and an external pressure tap 743 may be positioned around the inner and outer walls of the bend section 731 to detect and measure the pressure difference between the inner and outer walls of the bend section 731.

[0178] In a non-limiting example, the inner pressure tap 741 and outer pressure tap 743 are continuously flushed at a relatively high rate with a diluent (e.g., isobutane, or in some cases, recycled isobutane) to prevent polymer slurry from clogging components of the bend flowmeter 739. In another example, the inner pressure tap 741 and outer pressure tap 743 may include an inner diaphragm 751 and an outer diaphragm 753, respectively, located on the inner and outer walls of the bend section 731, thus protecting the inner and outer pressure taps 741 and 743 from clogging or contamination by polymer slurry. In the case of using inner and outer diaphragms 751 and 753, diluent flushing may not be necessary. Eliminating diluent flushing reduces the need for olefin-free diluents. Furthermore, eliminating diluent flushing at the inner pressure tap 741 and outer pressure tap 743 generally improves the consistency of pressure measurements obtained from the bend flowmeter 739.

[0179] The loop reactor maintains a high circulation velocity (V) and high flow rate (e.g., high Diane number (D) of the circulating fluid slurry. n This is particularly true within the bend section 731. The circulation velocity (V) can be measured, for example, by a bend flow meter 739, which can be coupled to an inner pressure tap 741 and an outer pressure tap 743 located on the inner and outer walls of the bend section 731, respectively. In one aspect, the circulation velocity (V) (also referred to as linear velocity) of the slurry in the bend section 731 can be in the range of 10 feet per second to 60 feet per second, and more typically in the range of 15 feet per second to 55 feet per second, 20 feet per second to 50 feet per second, or 30 feet per second to 50 feet per second. Additionally or alternatively, the Dean number of the slurry in the bend section 731 is at least 4,000,000, at least 5,000,000, or at least 6,000,000, and typically at most and including 10,000,000 to 15,000,000, or greater. Since Dean's numbers are dimensionless, the parameters used to calculate them must be converted to consistent units before the calculation, ensuring that these units cancel each other out to produce a dimensionless number. For example, the formula for Dean's numbers is D... n =(ρVd / μ)*(d / 2R) c ) 1 / 2 As shown, increasing the cycle speed (linear velocity) and decreasing the bending radius (e.g., decreasing the chord length) will increase the Dean number.

[0180] For example, a representative slurry with a set density and viscosity can have a Dean number of 4,916,000 in a loop reactor with d = 2 feet, Rc = 6 feet, and V = 32 feet / second, but as V increases to 40 feet / second, the Dean number increases to 6,145,000. As another example, a representative slurry with a set density and viscosity can have a Dean number of 4,609,000 in a loop reactor with d = 2 feet, Rc = 6 feet, and V = 30 feet / second, but as Rc decreases to 1 foot, the Dean number increases to 11,290,000.

[0181] Example

[0182] The present invention is further illustrated by the following embodiments, which should not be construed as limiting the scope of the invention in any way. After reading this description, various other aspects, modifications, and equivalents will arise for those skilled in the art without departing from the spirit of the invention or the scope of the appended claims.

[0183] right Figures 1 to 2 Computer simulations were performed on an ethylene polymerization reactor system to determine the effect of propane content relative to nitrogen content on the performance of the fluidized bed reactor. The loop reactor was operated under supercritical propane polymerization conditions, allowing propane from the loop reactor to be directly introduced into the fluidized bed reactor. The results are summarized in Table I.

[0184] Constructive Example 1 illustrates a basic scenario in which a typical Ziegler catalyst is used in a fluidized bed reactor and nitrogen is used as an inert gas / hydrocarbon to produce 0.918 density LLDPE (ethylene / 1-hexene copolymer). Constructive Examples 2 and 3 are simulations in which the same gas-phase polymerization conditions are used and the same ethylene copolymer is produced, but different amounts of nitrogen are replaced with propane as an inert gas or hydrocarbon. Constructive Example 3 uses propane and nitrogen, while Constructive Example 2 uses propane entirely.

[0185] For Example 2, all nitrogen used in the typical fluidized bed reactor is replaced with propane by supplying the catalyst feed from the upstream loop reactor (using propane as a diluent under supercritical conditions), and advantageously, the heat removal capacity in the fluidized bed reactor is greatly improved. When the propane concentration is sufficiently high, propane appears to act as both an inert gas / hydrocarbon and a condensable agent in the fluidized bed reactor. Unexpectedly, Table I shows a significant increase in the condensation percentage and a 100% improvement in overall productivity—a substantial improvement in heat removal efficiency in the fluidized bed reactor. Furthermore, the reactor inlet temperature can be increased. Other anticipated benefits include lower polymer fluff / powder agglomeration (less caking in the fluidized bed reactor and better flowability during downstream volatile removal) and improved hydrocarbon efficiency during degassing.

[0186] Other computer simulations show that ethane is not as good as propane because ethane cannot provide the same amount of heat sink. Similarly, different types of butane will be worse than propane because they adsorb into the polymer powder / fluff and will therefore adversely affect powder flowability and reactor stability.

[0187] Therefore, in one aspect of the invention, any gaseous composition in a fluidized bed reactor disclosed herein (including reactants such as ethylene, comonomers (if used), and hydrogen (if used)) may contain less than or equal to 20 mol% nitrogen, less than or equal to 15 mol% nitrogen, less than or equal to 10 mol% nitrogen, less than or equal to 5 mol% nitrogen, less than or equal to 2 mol% nitrogen, less than or equal to 1 mol% nitrogen, or less than or equal to 0.5 mol% nitrogen. Additionally or alternatively, the gaseous composition in the fluidized bed reactor may contain at least 20 mol%, at least 30 mol%, at least 40 mol% or at least 50 mol% propane, and typically at most 75 mol%, 70 mol%, 65 mol% or 60 mol% propane. Alternatively or alternatively, the nitrogen:propane molar ratio may be less than or equal to 1:1, less than or equal to 0.75:1, less than or equal to 0.5:1, less than or equal to 0.4:1, less than or equal to 0.3:1, less than or equal to 0.2:1, less than or equal to 0.1:1, less than or equal to 0.05:1, less than or equal to 0.02:1, or less than or equal to 0.01:1. Alternatively or alternatively, the gas-phase polymerization conditions in the fluidized bed reactor may be characterized by a condensation percentage in the range of 7 wt% to 50 wt%, 7 wt% to 30 wt%, 12 wt% to 30 wt%, 15 wt% to 30 wt%, 17 wt% to 30 wt%, 20 wt% to 30 wt%, 12 wt% to 25 wt%, 15 wt% to 25 wt%, 17 wt% to 25 wt%, or 20 wt% to 25 wt%. The condensate percentage (wt%) is the ratio of the flow rate of the liquid entering the fluidized bed reactor (e.g., lb / hr) (under prevailing reactor inlet conditions, such as reactor inlet temperature and reactor pressure) to the total flow rate entering the fluidized bed reactor, and this includes all feed streams, whether fresh or recycled. Typical components that are usually gaseous under gas-phase polymerization conditions include hydrogen, ethylene, ethane, and nitrogen. In contrast, propane and 1-hexene are condensable under gas-phase polymerization conditions. The condensate wt% increases with increasing relative amount of propane compared to nitrogen (under equivalent temperature and pressure conditions).

[0188] Table I

[0189]

[0190]

[0191] The invention has been described above with reference to numerous aspects and specific embodiments. Based on the detailed description above, many variations will occur to those skilled in the art. All such apparent variations are within the full scope of the appended claims. Other aspects of the invention may include, but are not limited to, the following aspects (which are described as “comprising” but may alternatively be “consistent with” or “comprises with”):

[0192] Aspect 1. A process for producing a multimodal ethylene polymer, the process comprising:

[0193] (i) In a loop reactor, under slurry or supercritical polymerization conditions, a catalyst composition is contacted with ethylene, optionally a first olefin comonomer and hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer.

[0194] (ii) Discharging the first reactor effluent containing the first ethylene polymer from the loop reactor;

[0195] (iii) Separating a light fraction containing hydrogen from the effluent of the first reactor to form an intermediate material; and

[0196] (iv) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce a multimodal ethylene polymer.

[0197] Aspect 2. The process as defined in aspect 1, wherein hydrogen is present in step (iv).

[0198] Aspect 3. The process as defined in aspect 1 or 2, wherein the first olefin comonomer is present in step (i), or the second olefin comonomer is present in step (iv), or both.

[0199] Aspect 4. A process for producing a multimodal ethylene polymer, the process comprising:

[0200] (i) In a first loop reactor, under slurry or supercritical polymerization conditions, the catalyst composition is contacted with ethylene, optionally a first olefin comonomer and optionally hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer.

[0201] (ii) Discharge the first reactor effluent containing the first ethylene polymer from the first loop reactor and introduce the first reactor effluent into the second loop reactor;

[0202] (iii) In the second loop reactor, under slurry or supercritical polymerization conditions, the effluent from the first reactor is contacted with ethylene, optionally a second olefin comonomer and optionally hydrogen to produce a second ethylene polymer.

[0203] (iv) Discharge the second reactor effluent containing the second ethylene polymer from the second loop reactor:

[0204] (v) Separating a light fraction containing hydrogen from the effluent of the second reactor to form an intermediate material, wherein hydrogen is present in step (i), or step (iii), or both; and

[0205] (vi) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material is contacted with ethylene and optionally a third olefin comonomer in an inert gas and / or hydrocarbon to produce the multimodal ethylene polymer.

[0206] Aspect 5. The process as defined in aspect 4, wherein hydrogen is present in step (i) or step (iii).

[0207] Aspect 6. The process as defined in Aspect 4 or 5, wherein the first olefin comonomer is present in step (i), or the second olefin comonomer is present in step (iii), or the third olefin comonomer is present in step (vi), or any combination thereof.

[0208] Aspect 7. A process for producing a multimodal ethylene polymer, the process comprising:

[0209] (i) In a fluidized bed reactor, under gas-phase polymerization conditions, a catalyst composition is contacted with ethylene and optionally a first olefin comonomer in an inert gas and / or hydrocarbon to produce a first ethylene polymer.

[0210] (ii) Discharging the first reactor effluent containing the first ethylene polymer from the fluidized bed reactor:

[0211] (iii) Combining an inert hydrocarbon diluent with the effluent from the first reactor and increasing the pressure to form an intermediate material; and

[0212] (iv) In the loop reactor, under slurry or supercritical polymerization conditions, the intermediate material is contacted with ethylene and optionally a second olefin comonomer to produce the multimodal ethylene polymer.

[0213] Aspect 8. The process as defined in aspect 7, wherein hydrogen is present in step (i) or step (iv) or both.

[0214] Aspect 9. The process as defined in Aspect 7 or 8, wherein the first olefin comonomer is present in step (i), or the second olefin comonomer is present in step (iv), or both.

[0215] Aspect 10. A process for producing a multimodal ethylene polymer, the process comprising:

[0216] (i) In a loop reactor, under slurry or supercritical polymerization conditions, a first catalyst composition is contacted with ethylene and optionally a first olefin comonomer in an inert hydrocarbon diluent to produce a first ethylene polymer.

[0217] (ii) In a fluidized bed reactor, under gas-phase polymerization conditions, the second catalyst composition is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce a second ethylene polymer; and

[0218] (iii) Combining the first ethylene polymer and the second ethylene polymer to produce the multimodal ethylene polymer.

[0219] Aspect 11. The process as defined in Aspect 10, wherein hydrogen is present in step (i) or step (ii) or both.

[0220] Aspect 12. The process as defined in Aspect 10 or 11, wherein the first olefin comonomer is present in step (i), or the second olefin comonomer is present in step (ii), or both.

[0221] Aspect 13. The process as defined in any one of Aspects 1 to 12, wherein each catalyst composition is independently a metallocene catalyst system, a Ziegler-Natta catalyst system, a chromium catalyst system, a nickel catalyst system, or any combination thereof.

[0222] Aspect 14. The process as defined in any one of Aspects 1 to 13, wherein each catalyst composition is a Ziegler-Natta catalyst system.

[0223] Aspect 15. The process as defined in any one of Aspects 1 to 14, wherein each catalyst composition is independently a supported catalyst system comprising a transition metal (e.g., chromium, vanadium, titanium, zirconium, hafnium, or a combination thereof) supported on a suitable support (e.g., a solid oxide or a chemically treated solid oxide).

[0224] Aspect 16. A process as defined in any one of Aspects 1 to 15, wherein each catalyst composition independently comprises an activator and / or a co-catalyst, such as an aluminoxane compound, an organoboron or organoborate compound, an organoaluminum compound, an organozinc compound, or any combination thereof.

[0225] Aspect 17. The process as defined in any one of Aspects 1 to 16, wherein each olefin comonomer independently comprises propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, or mixtures thereof.

[0226] Aspect 18. The process as defined in any one of Aspects 1 to 17, wherein each ethylene polymer independently comprises an ethylene homopolymer and / or an ethylene / α-olefin copolymer.

[0227] Aspect 19. The process as defined in any one of Aspects 1 to 18, wherein each ethylene polymer independently comprises an ethylene homopolymer, an ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer and / or an ethylene / 1-octene copolymer.

[0228] Aspect 20. The process as defined in any one of Aspects 1 to 19, wherein each ethylene polymer independently comprises an ethylene / α-olefin copolymer and / or an ethylene terpolymer (e.g., ethylene with 1-butene and 1-hexene).

[0229] Aspect 21. The process as defined in any one of Aspects 1 to 20, wherein the inert hydrocarbon diluent comprises propane, isobutane, n-butane, n-pentane, isopentane, neopentane, cyclohexane, n-hexane, heptane, cycloheptane, octane, or any combination thereof.

[0230] Aspect 22. The process as defined in any one of Aspects 1 to 21, wherein the slurry polymerization conditions include polymerization conditions in which the inert hydrocarbon diluent is a liquid.

[0231] Aspect 23. The process as defined in any of Aspects 1 to 21, wherein supercritical polymerization conditions include polymerization conditions in which the polymerization temperature and pressure are above the critical point.

[0232] Aspect 24. The process as defined in any of Aspects 1 to 23, wherein the slurry or supercritical polymerization conditions include polymerization temperatures in the range of 40°C to 130°C, 60°C to 120°C, or 75°C to 115°C.

[0233] Aspect 25. The process as defined in any one of Aspects 1 to 24, wherein the slurry or supercritical polymerization conditions include polymerization pressures in the range of 200 psig to 1500 psig, 400 psig to 1200 psig, 450 psig to 850 psig, or 900 psig to 1100 psig.

[0234] Aspect 26. The process as defined in any one of Aspects 1 to 25, wherein each loop reactor is independently constructed for a maximum permissible operating pressure (MAWP) of the respective reactor that is at least 5% and / or at most 30% greater than the polymerization pressure.

[0235] Aspect 27. The process as defined in any one of Aspects 4 to 6 or 13 to 26, wherein the first polymerization pressure in the first loop reactor and the second polymerization pressure in the second loop reactor are within 25%, 20%, 10% or 5% of each other.

[0236] Aspect 28. The process as defined in any of Aspects 1 to 27, wherein the slurry or supercritical polymerization conditions include an average residence time of 10 to 90 minutes, 15 to 75 minutes, or 20 to 60 minutes.

[0237] Aspect 29. The process as defined in any one of Aspects 1 to 28, wherein the slurry or supercritical polymerization conditions include linear velocities of 10 ft / s to 60 ft / s, 15 ft / s to 55 ft / s, or 20 ft / s to 50 ft / s.

[0238] Aspect 30. The process as defined in any one of aspects 1 to 29 further includes a prepolymerization step in a prepolymerization reactor (e.g., a loop reactor design) prior to step (i).

[0239] Aspect 31. The process as defined in any one of Aspects 1 to 30, further comprising the step of polymerization in a second fluidized bed reactor under gas-phase polymerization conditions.

[0240] Aspect 32. The process as defined in any one of Aspects 1 to 31, wherein each loop reactor independently produces a polymer with lower Mw, higher MI, and higher density than the polymer (higher Mw, lower MI, and lower density) produced by the fluidized bed reactor.

[0241] Aspect 33. The process as defined in any of Aspects 1 to 31, wherein each loop reactor independently produces a polymer with higher Mw, lower MI, and lower density than the polymer (lower Mw, higher MI, and higher density) produced by the fluidized bed reactor.

[0242] Aspect 34. The process as defined in any one of Aspects 1 to 33, wherein at least one contact step (or each contact step) further includes contact with an antistatic compound.

[0243] Aspect 35. The process as defined in any one of Aspects 1 to 3 or 7 to 34, wherein 20% to 90% by weight of the multimodal ethylene polymer is produced in the loop reactor and 10% to 80% by weight of the multimodal ethylene polymer is produced in the fluidized bed reactor.

[0244] Aspect 36. The process as defined in any one of Aspects 4 to 6 or 13 to 34, wherein 5% to 30% by weight of the multimodal ethylene polymer is produced in the first loop reactor, 30% to 60% by weight of the multimodal ethylene polymer is produced in the second loop reactor, and 30% to 60% by weight of the multimodal ethylene polymer is produced in the fluidized bed reactor.

[0245] Aspect 37. The process as defined in any of Aspects 1 to 36, wherein the multimodal ethylene polymer has any suitable fluff or powder characteristics, such as bulk density, average particle size, particle size distribution, span, etc.

[0246] Aspect 38. The process as defined in any of Aspects 1 to 37, wherein each loop reactor independently has a length / diameter (L / D) ratio of 500 to 3,000, or 700 to 1,500.

[0247] Aspect 39. The process as defined in any of Aspects 1 to 38, wherein each loop reactor independently has an internal diameter of 12 inches to 48 inches, 18 inches to 40 inches, or 20 inches to 32 inches.

[0248] Aspect 40. The process as defined in any one of Aspects 1 to 39, wherein each loop reactor independently has a length of 50 feet to 300 feet, or 100 feet to 250 feet, and has 2 to 16 legs, or 4 to 14 legs.

[0249] Aspect 41. The process as defined in any one of Aspects 1 to 40, wherein each loop reactor independently includes a bend section (or two or more bend sections) configured to allow the reaction mixture flowing therein to pass through a Dean number (D). n The amount is maintained at at least 3,000,000 (e.g., at least 4,000,000, at least 5,000,000, or at least 6,000,000, and less than or equal to 15,000,000 or less than or equal to 10,000,000).

[0250] Aspect 42. The process as defined in any of Aspects 1 to 41, wherein each loop reactor independently has an inner surface with a surface roughness of less than or equal to 150 microinches, less than or equal to 100 microinches, or less than or equal to 50 microinches, for example, from 10 microinches to 50 microinches.

[0251] Aspect 43. The process as defined in any of Aspects 1 to 42, wherein each loop reactor is independently constructed of carbon steel, stainless steel, cryogenic carbon steel, or a combination thereof.

[0252] Aspect 44. The process as defined in any of Aspects 1 to 43, wherein each loop reactor is constructed from a rolled plate having two edges joined along the seam.

[0253] Aspect 45. The process as defined in any one of Aspects 1 to 44, wherein each loop reactor includes a bend flow meter.

[0254] Aspect 46. The process as defined in any one of Aspects 1 to 45, wherein each loop reactor includes a rust inhibitor coating on the reactor surface and flanges.

[0255] Aspect 47. The process as defined in any one of Aspects 1 to 46, wherein the slurry or supercritical polymerization conditions include a Froude number of 10 to 100, 15 to 50, 20 to 90, or 40 to 80.

[0256] Aspect 48. The process as defined in any one of Aspects 1 to 47, wherein the slurry or supercritical polymerization conditions include a Biot number less than or equal to 3, less than or equal to 2, less than or equal to 1.5, or less than or equal to 1.1.

[0257] Aspect 49. The process as defined in any one of Aspects 1 to 48, wherein the slurry or supercritical polymerization conditions include cavitation numbers (Ca) of 6 to 60, 12 to 50, 18 to 40, or 24 to 36.

[0258] Aspect 50. The process as defined in any one of Aspects 1 to 49, wherein the slurry or supercritical polymerization conditions include an Euler number greater than or equal to 5, greater than or equal to 6, or greater than or equal to 7.

[0259] Aspect 51. The process as defined in any of Aspects 1 to 50, wherein the effluent from each reactor is continuously discharged from the respective loop reactor.

[0260] Aspect 52. The process as defined in any of Aspects 1 to 51, wherein the effluent from each reactor is continuously discharged from the respective loop reactor via a continuous feed assembly comprising a valve, a V-ball valve, or a valveless assembly.

[0261] Aspect 53. The process as defined in any one of Aspects 4 to 6 or 13 to 52, wherein one or more discharge points of the first loop reactor are located at a location (downstream of the circulation pump) at a higher pressure than one or more feed points of the second loop reactor (upstream of the circulation pump).

[0262] Aspect 54. The process as defined in any of Aspects 1 to 53, wherein the effluent from each reactor is discharged from the respective loop reactor into an exhaust line comprising a flash line heater.

[0263] Aspect 55. The process as defined in aspect 54 further includes adding a catalyst deactivator (optionally) to the discharge line, such as water, oxygen or alcohol.

[0264] Aspect 56. The process as defined in any one of Aspects 1 to 55, further comprising adding a reaction modifier (optionally) to the effluent from the first reactor (or the effluent from the second reactor).

[0265] Aspect 57. The process as defined in any one of Aspects 1 to 56, wherein the separation step includes flash evaporation.

[0266] Aspect 58. The process as defined in any one of Aspects 1 to 57, wherein the separation step includes the use of a cyclone separator.

[0267] Aspect 59. The process as defined in any of Aspects 1 to 58, wherein each loop reactor includes a reactor circulation pump (one or more).

[0268] Aspect 60. The process as defined in any one of Aspects 1 to 59 further includes the step of introducing the catalyst composition as a slurry with a solid content of 1% to 15% by weight, 2% to 14% by weight, or 3% to 12% by weight into the loop reactor (or the first loop reactor).

[0269] Aspect 61. The process as defined in any one of Aspects 1 to 60, wherein the gas-phase polymerization conditions include polymerization temperatures in the range of 48°C to 95°C, 50°C to 85°C, or 55°C to 82°C.

[0270] Aspect 62. The process as defined in any one of Aspects 1 to 61, wherein the gas-phase polymerization conditions include polymerization pressures in the range of 200 psig to 500 psig, 200 psig to 400 psig, 250 psig to 650 psig, or 250 psig to 350 psig.

[0271] Aspect 63. The process as defined in any one of Aspects 1 to 62, wherein the gas-phase polymerization conditions include fluidization rates of 1.5 ft / s to 3 ft / s, 1.5 ft / s to 2.7 ft / s, or 1.7 ft / s to 2.7 ft / s.

[0272] Aspect 64. The process as defined in any one of Aspects 1 to 63, wherein the inert gas and / or hydrocarbon comprises nitrogen, ethane, propane, or combinations thereof.

[0273] Aspect 65. The process as defined in any one of Aspects 1 to 64, wherein the gas-phase polymerization conditions further include contact in the presence of any amount of C3-C8 alkane or C4-C8 alkane condensable agent, such as butane (e.g., n-butane and / or isobutane), pentane (e.g., n-pentane and / or isopentane), hexane, or combinations thereof, based on up to 30 vol% (e.g., 5 vol% to 30 vol%, 10 vol% to 30 vol% or 15 vol% to 25 vol%) of reactor contents.

[0274] Aspect 66. The process as defined in any of Aspects 1 to 65, wherein each ethylene polymer or reactor effluent is continuously discharged from the respective fluidized bed reactor.

[0275] Aspect 67. The process as defined in any of Aspects 1 to 65, wherein each ethylene polymer or reactor effluent is discharged from the respective fluidized bed reactor through a closed hopper.

[0276] Aspect 68. The process as defined in any one of Aspects 1 to 67, further comprising determining and / or controlling the bed height (solid level) in the fluidized bed reactor.

[0277] Aspect 69. The process as defined in any one of Aspects 1 to 68, further comprising the steps of separating fine polymer particles from unreacted olefins in a gas stream from the fluidized bed reactor, and conveying the fine polymer particles back to the fluidized bed reactor.

[0278] Aspect 70. The process as defined in any one of Aspects 1 to 69 further includes determining and / or controlling the polymer properties of each ethylene polymer using any suitable analytical technique, such as Raman spectroscopy for density, melt flow meters for MI and HLMI, rheometers for rheological parameters, GPC for MWD, etc.

[0279] Aspect 71. The process as defined in any one of Aspects 1 to 70, further comprising injecting a low level of deactivator downstream of the fluidized bed reactor to enhance properties (broaden MWD) and inhibit polymer growth.

[0280] Aspect 72. The process as defined in any one of Aspects 1 to 71, wherein each loop reactor is operated under supercritical conditions at a pressure P4 in the range of 900 psig to 1100 psig.

[0281] Aspect 73. The process as defined in any one of Aspects 1 to 72, wherein the separation step is carried out in a separation vessel operating at a pressure P5 in the range of 150 psig to 800 psig and / or under conditions sufficient to remove at least 80 wt%, at least 90 wt%, or at least 95 wt% of hydrogen from the respective reactor effluent.

[0282] Aspect 74. The process as defined in Aspect 72 or 73, wherein the ratio of P4 to P5 is in the range of 3 to 6, 3 to 5.5, 3.5 to 6, or 3.5 to 5.5.

[0283] Aspect 75. The process as defined in any one of Aspects 1 to 74, wherein the fluidized bed reactor is operated at a pressure P6 in the range of 250 psig to 600 psig.

[0284] Aspect 76. The process as defined in any one of Aspects 1 to 75, wherein an exhaust stream containing the multi-peaked ethylene polymer from the fluidized bed reactor is introduced into a separation vessel, the separation vessel being operated at a pressure P7 in the range of 5 psig to 200 psig and / or under conditions sufficient to remove at least 60 wt%, at least 70 wt%, at least 80 wt%, or at least 90 wt% propane from the exhaust stream.

[0285] Aspect 77. The process as defined in aspect 76, further comprising discharging the multi-peaked ethylene polymer from the separation vessel into a purge tower operating at a pressure P8 in the range of 1 psig to 20 psig.

[0286] Aspect 78. The process as defined in Aspect 76 or 77, wherein the ratio of P6 / P7 is greater than the ratio of P4 / P5.

[0287] Aspect 79. The process as defined in any of Aspects 76 to 78, wherein the ratio of P5 to P7 is in the range of 4 to 60, or 5 to 55, or 10 to 40.

[0288] Aspect 80. A process as defined in any one of Aspects 30 to 79, wherein the prepolymerization step is carried out in a prepolymerization reactor (e.g., a loop reactor design) at a pressure P1 in the range of 900 psig to 1200 psig and / or at a pressure greater than P4 (P1>P4).

[0289] Aspect 81. The process as defined in any one of Aspects 30 to 79, wherein the prepolymerization step is carried out in a prepolymerization reactor (e.g., a loop reactor design) at a pressure P1 in the range of 400 psig to 800 psig.

[0290] Aspect 82. The process as defined in Aspect 81, wherein the effluent stream from the prepolymerization reactor is introduced into a buffer vessel operating at a pressure P2 in the range of 400 psig to 800 psig and / or at a pressure less than P1 (P2 < P1).

[0291] Aspect 83. The process as defined in Aspect 82, wherein the effluent stream from the buffer vessel is introduced into a feed pump to increase the discharge pressure P3 from the pump to a range of 925 psig to 1200 psig.

[0292] Aspect 84. A polymerization reactor system (reactor apparatus) for producing a multimodal ethylene polymer, the system comprising:

[0293] (a) A loop reactor configured to contact a catalyst composition with ethylene, an optional first olefin comonomer, and hydrogen in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer;

[0294] (b) An effluent line configured to withdraw a first reactor effluent containing the first ethylene polymer from the loop reactor;

[0295] (c) A separator configured to remove a light fraction containing hydrogen from the first reactor effluent to form an intermediate material; and

[0296] (d) A fluidized bed reactor configured to contact the intermediate material with ethylene and an optional second olefin comonomer in an inert gas and / or hydrocarbon under gas phase polymerization conditions to produce the multimodal ethylene polymer.

[0297] Aspect 85. The system as defined in Aspect 84, wherein the fluidized bed reactor is further configured to contact hydrogen with the intermediate material, ethylene, and the optional second olefin comonomer.

[0298] Aspect 86. The system as defined in Aspect 84 or 85, wherein:

[0299] The loop reactor is configured to contact the catalyst composition with ethylene, the first olefin comonomer, and hydrogen; or

[0300] The fluidized bed reactor is configured to contact the intermediate material with ethylene and the second olefin comonomer; or

[0301] Both.

[0302] Aspect 87. A polymerization reactor system for producing a multimodal ethylene polymer, the system comprising:

[0303] (a) A first loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer and optionally hydrogen in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer.

[0304] (b) A second loop reactor configured to contact the first reactor effluent containing the first ethylene polymer with ethylene, optional second olefin comonomer and optional hydrogen under slurry or supercritical polymerization conditions to produce a second ethylene polymer.

[0305] (c) A transfer line configured to draw out the first reactor effluent containing the first ethylene polymer from the first loop reactor and introduce the first reactor effluent into the second loop reactor;

[0306] (d) A second discharge line, the second discharge line being configured to extract a second reactor effluent containing the second ethylene polymer from the second loop reactor;

[0307] (e) A separator configured to remove a light fraction containing hydrogen from the effluent of the second reactor to form an intermediate material, wherein hydrogen is present in the first loop reactor, the second loop reactor, or both; and

[0308] (f) A fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a third olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce the multimodal ethylene polymer.

[0309] Aspect 88. The system as defined in Aspect 87, wherein:

[0310] The first loop reactor is configured to contact the catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen; or

[0311] The second loop reactor is configured to contact the effluent from the first reactor with ethylene, an optional second olefin comonomer, and hydrogen.

[0312] Aspect 89. A system as defined in Aspects 84 or 85, wherein:

[0313] The first loop reactor is configured to contact the catalyst composition with ethylene and the first olefin comonomer, or

[0314] The second loop reactor is configured to contact the effluent from the first reactor with ethylene and the second olefin comonomer; or

[0315] The fluidized bed reactor is configured to contact the intermediate material with ethylene and the third olefin comonomer; or

[0316] Any combination of them.

[0317] Aspect 90. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising:

[0318] (a) A fluidized bed reactor configured to contact a catalyst composition with ethylene and optionally a first olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a first ethylene polymer.

[0319] (b) An effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the fluidized bed reactor;

[0320] (c) A transfer line configured to combine an inert hydrocarbon diluent with the effluent from the first reactor and increase pressure to form an intermediate material; and

[0321] (d) A loop reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer under slurry or supercritical polymerization conditions to produce the multimodal ethylene polymer.

[0322] Aspect 91. The system as defined in Aspect 90, wherein:

[0323] The fluidized bed reactor is further configured to contact the catalyst composition with ethylene, the optional first olefin comonomer, and hydrogen; or

[0324] The loop reactor is further configured to contact the intermediate material with ethylene, the optional second olefin comonomer, and hydrogen; or

[0325] Both.

[0326] Aspect 92. A system as defined in Aspects 90 or 91, wherein:

[0327] The fluidized bed reactor is configured to contact the catalyst composition with ethylene and the first olefin comonomer; or

[0328] The loop reactor is configured to contact the intermediate material with ethylene and the second olefin comonomer; or

[0329] Both.

[0330] Aspect 93. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising:

[0331] (a) A loop reactor configured to contact a catalyst composition with ethylene and optionally a first olefin comonomer in an inert hydrocarbon diluent under slurry or supercritical polymerization conditions to produce a first ethylene polymer.

[0332] (b) A fluidized bed reactor configured to contact a second catalyst composition with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce a second ethylene polymer; and

[0333] (c) A mixing apparatus configured to combine the first ethylene polymer and the second ethylene polymer to produce the multimodal ethylene polymer.

[0334] Aspect 94. The system as defined in Aspect 93, wherein:

[0335] The loop reactor is further configured to contact the catalyst composition with ethylene, the optional first olefin comonomer, and hydrogen; or

[0336] The fluidized bed reactor is further configured to contact the second catalyst composition with ethylene, the optional second olefin comonomer, and hydrogen; or

[0337] Both.

[0338] Aspect 95. A system as defined in Aspects 93 or 94, wherein:

[0339] The loop reactor is configured to contact the catalyst composition with ethylene and the first olefin comonomer; or

[0340] The fluidized bed reactor is configured to contact the second catalyst composition with ethylene and the second olefin comonomer; or

[0341] Both.

[0342] Aspect 96. The system of any one of Aspects 84 to 95, wherein the system further comprises a second fluidized bed reactor configured to operate under gas-phase polymerization conditions.

[0343] Aspect 97. A system as defined in any one of aspects 84 to 96, wherein said system further includes a prepolymerization reactor (e.g., a loop reactor design).

[0344] Aspect 98. The system as described in any one of Aspects 84 to 97, wherein each loop reactor is independently configured for any polymerization temperature, polymerization pressure, mean residence time, and linear velocity disclosed herein.

[0345] Aspect 99. The system as defined in any one of Aspects 84 to 98, wherein each loop reactor is independently configured to be at least 5% and / or at most 30% greater than the polymerization pressure of the respective reactor’s maximum permissible operating pressure (MAWP).

[0346] Aspect 100. The system as defined in any one of Aspects 87 to 89 or 96 to 99, wherein the first loop reactor and the second loop reactor are configured for polymerization pressures within 25%, 20%, 10%, or 5% of each other.

[0347] Aspect 101. The system of any one of Aspects 84 to 100, wherein each loop reactor is configured to independently produce a polymer having a lower Mw, higher MI, and higher density than the polymer produced by the fluidized bed reactor (higher Mw, lower MI, and lower density).

[0348] Aspect 102. The system as defined in any of Aspects 84 to 100, wherein each loop reactor is configured to independently produce a polymer with higher Mw, lower MI, and lower density than the polymer (lower Mw, higher MI, and higher density) produced by the fluidized bed reactor.

[0349] Aspect 103. A system as defined in any one of aspects 84 to 102, wherein the system is further configured to introduce an antistatic compound into at least one loop reactor or fluidized bed reactor.

[0350] Aspect 104. A system as defined in any one of Aspects 84 to 86 or 90 to 103, wherein the system is configured to produce 20% to 90% by weight of the multimodal ethylene polymer in the loop reactor and 10% to 80% by weight of the multimodal ethylene polymer in the fluidized bed reactor.

[0351] Aspect 105. A system as defined in any one of Aspects 87 to 89 or 96 to 103, wherein the system is configured to produce 5% to 30% by weight of the multimodal ethylene polymer in a first loop reactor, 30% to 60% by weight of the multimodal ethylene polymer in a second loop reactor, and 30% to 60% by weight of the multimodal ethylene polymer in the fluidized bed reactor.

[0352] Aspect 106. The system as defined in any of Aspects 84 to 105, wherein each loop reactor independently has a length / diameter (L / D) ratio of 500 to 3,000, or 700 to 1,500.

[0353] Aspect 107. The system as defined in any of Aspects 84 to 106, wherein each loop reactor independently has an internal diameter of 12 inches to 48 inches, 18 inches to 40 inches, or 20 inches to 32 inches.

[0354] Aspect 108. A system as defined in any of Aspects 84 to 107, wherein each loop reactor independently has a length of 50 feet to 300 feet, or 100 feet to 250 feet, and has 2 to 16 legs, or 4 to 14 legs.

[0355] Aspect 109. A system as defined in any one of Aspects 84 to 108, wherein each loop reactor independently comprises a bend section (or two or more bend sections) configured to allow the reaction mixture flowing therein to pass through a Dean number (D). n The amount is maintained at at least 3,000,000 (e.g., at least 4,000,000, at least 5,000,000, or at least 6,000,000, and less than or equal to 15,000,000 or less than or equal to 10,000,000).

[0356] Aspect 110. The system as defined in any of Aspects 84 to 109, wherein each loop reactor independently has an inner surface with a surface roughness of less than or equal to 150 microinches, less than or equal to 100 microinches, or less than or equal to 50 microinches, for example, from 10 microinches to 50 microinches.

[0357] Aspect 111. The system as defined in any of Aspects 84 to 110, wherein each loop reactor is independently constructed of carbon steel, stainless steel, cryogenic carbon steel or a combination thereof.

[0358] Aspect 112. The system as defined in any of Aspects 84 to 111, wherein each loop reactor is constructed of a rolled plate having two edges joined along the seam.

[0359] Aspect 113. The system as defined in any of Aspects 84 to 112, wherein each loop reactor includes a bend flow meter.

[0360] Aspect 114. The system as defined in any of Aspects 84 to 113, wherein each loop reactor includes a rust inhibitor coating on the reactor surface and flanges.

[0361] Aspect 115. A system as defined in any of Aspects 84 to 114, wherein each loop reactor is configured to maintain a Froude number of 10 to 100, 15 to 50, 20 to 90, or 40 to 80.

[0362] Aspect 116. A system as defined in any of Aspects 84 to 115, wherein each loop reactor is constructed to maintain a Biot number less than or equal to 3, less than or equal to 2, less than or equal to 1.5, or less than or equal to 1.1.

[0363] Aspect 117. The system as defined in any of Aspects 84 to 116, wherein each loop reactor is configured to maintain a cavitation number (Ca) of 6 to 60, 12 to 50, 18 to 40, or 24 to 36.

[0364] Aspect 118. A system as defined in any of Aspects 84 to 117, wherein each loop slurry reactor is configured to maintain an Euler number greater than or equal to 5, greater than or equal to 6, or greater than or equal to 7.

[0365] Aspect 119. The system as defined in any of Aspects 84 to 118, wherein each loop reactor is configured for continuous discharge (with continuous feed assembly).

[0366] Aspect 120. The system as defined in any of Aspects 84 to 119, wherein each loop reactor is configured to continuously discharge via a continuous feed assembly comprising a valve, a V-ball valve or a valveless component (having a continuous feed assembly comprising a valve, a V-ball valve or a valveless component).

[0367] Aspect 121. The system as defined in any one of Aspects 87 to 89 or 96 to 120, wherein the first loop reactor has one or more discharge points (downstream of the circulation pump) at a higher pressure than one or more feed points (upstream of the circulation pump) of the second loop reactor.

[0368] Aspect 122. The system as defined in any of Aspects 84 to 121, wherein the discharge line (or transfer line) from each loop reactor includes a flash line heater.

[0369] Aspect 123. The system as defined in aspect 122, wherein the system further includes a catalyst deactivator inlet or a reaction modifier inlet into the discharge line (or transfer line).

[0370] Aspect 124. The system as defined in any of Aspects 84 to 123, wherein the separator includes a flash chamber.

[0371] Aspect 125. The system as defined in any of Aspects 84 to 124, wherein the separator comprises a cyclone separator.

[0372] Aspect 126. The system as defined in any of Aspects 84 to 125, wherein each loop reactor includes a reactor circulation pump (one or more).

[0373] Aspect 127. A system as defined in any one of Aspects 84 to 126, wherein the system further comprises a catalyst feed port configured to introduce the catalyst composition as a slurry having a solids content of 1% to 15% by weight, 2% to 14% by weight, or 3% to 12% by weight into the loop reactor (or the first loop reactor).

[0374] Aspect 128. A system as defined in any of Aspects 84 to 127, wherein each fluidized bed reactor is independently configured for any polymerization temperature, polymerization pressure and fluidization rate disclosed herein.

[0375] Aspect 129. A system as defined in any one of Aspects 84 to 128, wherein the system further includes a condensable feed port configured to introduce a C3-C8 alkane or a C4-C8 alkane condensable into each fluidized bed reactor.

[0376] Aspect 130. A system as defined in any of Aspects 84 to 129, wherein each fluidized bed reactor is configured for continuous discharge (with continuous feed assembly).

[0377] Aspect 131. The system as defined in any of Aspects 84 to 129, wherein each fluidized bed reactor is configured to discharge through a feed assembly including a closed hopper.

[0378] Aspect 132. The system as defined in any one of Aspects 84 to 131, wherein the system further includes a control system configured to control the bed height (or solids level) in each fluidized bed reactor.

[0379] Aspect 133. A system as defined in any one of Aspects 84 to 132, wherein the system further comprises a fine particle separator configured to separate fine polymer particles from unreacted olefins in a gas stream from the fluidized bed reactor and to return the fine polymer particles to the fluidized bed reactor.

[0380] Aspect 134. A system as defined in any one of Aspects 84 to 133, wherein the system further comprises an analytical system configured to determine and / or control the polymer properties of each ethylene polymer using any suitable analytical technique, such as Raman spectroscopy for density, melt flow meters for MI and HLMI, rheometers for rheological parameters, and GPC for MWD.

[0381] Aspect 135. A system as defined in any one of Aspects 84 to 134, wherein the system further comprises a deactivator inlet configured to inject a low level of deactivator downstream of the fluidized bed reactor to enhance properties (broaden MWD) and inhibit polymer growth.

Claims

1. A method for producing a multimodal ethylene polymer, the method comprising: (i) In a loop reactor, under supercritical polymerization conditions, a catalyst composition is contacted with ethylene, an optional first olefin comonomer and hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer. (ii) Continuously discharging a first reactor effluent containing the first ethylene polymer from the loop reactor in the continuous feed assembly; (iii) Separating a light fraction containing hydrogen from the effluent of the first reactor in a first cyclone separator to form an intermediate material containing the first ethylene polymer; (iv) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material containing the first ethylene polymer is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce the multimodal ethylene polymer; and (v) The effluent from the second reactor containing the multimodal ethylene polymer is discharged from the fluidized bed reactor into a second cyclone separator to form multimodal ethylene polymer fluff. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

2. The method of claim 1, wherein: The emissions in step (v) are carried out continuously; and The method further includes the step of discharging the multi-peaked ethylene polymer fluff from the second cyclone separator through a continuous fluff discharge port.

3. The method of claim 1, wherein: The loop reactor includes a curved section; and The supercritical polymerization conditions in the bend section include Dean numbers in the range of 4,000,000 to 15,000,000.

4. The method of claim 1, wherein: The first cyclone separator has a cone angle in the range of 60° to 85°; or The second cyclone separator has a cone angle ranging from 60° to 85°; or Both.

5. The method of claim 1, wherein: The molar ratio of nitrogen to propane is less than or equal to 0.05:1; or The gas-phase polymerization conditions are characterized by a condensation percentage in the range of 15% to 30% by weight; or Both.

6. A method for producing a multimodal ethylene polymer, the method comprising: (i) In a loop reactor, under supercritical polymerization conditions, a catalyst composition is contacted with ethylene, optionally a first olefin comonomer and hydrogen in propane to produce a first ethylene polymer. (ii) Discharging the first reactor effluent containing the first ethylene polymer from the loop reactor; (iii) Separating a light fraction containing hydrogen from the effluent of the first reactor in a first cyclone separator to form an intermediate material containing the first ethylene polymer; (iv) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material containing the first ethylene polymer is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce the multimodal ethylene polymer, wherein the gas composition in the fluidized bed reactor contains less than or equal to 20 mol% nitrogen and at least 30 mol% propane.

7. The method of claim 6, wherein: The gas composition contains less than or equal to 5 mol% nitrogen; or The gaseous composition contains 50 mol% to 65 mol% propane; or The molar ratio of nitrogen to propane is less than or equal to 0.2:1; or The gas-phase polymerization conditions are characterized by a condensation percentage in the range of 17% to 25% by weight; or Any combination of them.

8. The method of claim 1 or 6, wherein the first olefin comonomer and the second olefin comonomer independently comprise propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, or mixtures thereof.

9. The method of claim 8, wherein: The first olefin comonomer is present in step (i); or The second olefin comonomer is present in step (iv); or Both.

10. The method of claim 1 or 6, wherein: The catalyst composition is a Ziegler-Natta catalyst system; and The polymerization conditions in step (i) include an average residence time of 15 to 75 minutes and a linear velocity of 15 to 55 feet per second.

11. The method of claim 1 or 6, wherein the method further comprises the step of prepolymerizing the catalyst composition in a prepolymerization reactor prior to step (i).

12. The method of claim 1 or 6, wherein the first ethylene polymer produced in the loop reactor has a lower Mw, a higher MI, and a higher density than the polymer produced in the fluidized bed reactor.

13. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising: (a) A first loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer and optionally hydrogen in an inert hydrocarbon diluent under supercritical polymerization conditions to produce a first ethylene polymer. (b) A second loop reactor configured to contact, under supercritical polymerization conditions, a first reactor effluent containing the first ethylene polymer with ethylene, an optional second olefin comonomer and an optional hydrogen gas to produce a second ethylene polymer. (c) A transfer line configured to draw out the first reactor effluent containing the first ethylene polymer from the first loop reactor and introduce the first reactor effluent into the second loop reactor; (d) A second discharge line, the second discharge line being configured to extract a second reactor effluent containing the second ethylene polymer from the second loop reactor; (e) A separator configured to remove a light fraction containing hydrogen from the effluent of the second reactor to form an intermediate material containing the second ethylene polymer, wherein hydrogen is present in the first loop reactor, the second loop reactor, or both. as well as (f) A fluidized bed reactor configured to contact the intermediate material containing the second ethylene polymer with ethylene and optionally a third olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce the multimodal ethylene polymer. The transfer line is configured to extract the first reactor effluent from the first loop reactor at a discharge position downstream of the first loop reactor circulation pump, and to introduce the first reactor effluent into the second loop reactor at a feed position upstream of the second loop reactor circulation pump. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

14. The system of claim 13, wherein the second discharge line is configured to continuously extract the second reactor effluent containing the second ethylene polymer from the second loop reactor.

15. The system of claim 13, wherein the outlet of the separator is positioned at a height higher than the inlet of the intermediate material into the fluidized bed reactor.

16. The system of claim 15, wherein the separator comprises a cyclone separator.

17. The system of claim 13, wherein the system further comprises a recirculation system configured to separate fine polymer particles from unreacted olefins in the gas stream leaving the fluidized bed reactor and to return the fine polymer particles to the fluidized bed reactor.

18. The system of claim 17, wherein the recirculation system comprises a cyclone separator and an injector.

19. The system of any one of claims 13 to 18, wherein the system further comprises a polymer recovery system configured to receive a third reactor effluent containing the multimodal ethylene polymer from the fluidized bed reactor, remove volatiles from the third reactor effluent, and form multimodal ethylene polymer fluff.

20. The system of claim 19, wherein the polymer recycling system comprises: Cyclone separator; Blow-out tower; as well as The continuous lint discharge port between the cyclone separator and the purging tower.

21. A method for producing a multimodal ethylene polymer, the method comprising: (i) In a loop reactor, under supercritical polymerization conditions, a catalyst composition is contacted with ethylene, an optional first olefin comonomer and hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer. The loop reactor includes a bend section, and the supercritical polymerization conditions in the bend section include a Dean number in the range of 3,000,000 to 15,000,000. (ii) Discharging the first reactor effluent containing the first ethylene polymer from the loop reactor; (iii) Separating a light fraction containing hydrogen from the effluent of the first reactor to form an intermediate material containing the first ethylene polymer; (iv) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material containing the first ethylene polymer is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce the multimodal ethylene polymer; and (v) Discharging the effluent from the second reactor containing the multimodal ethylene polymer from the fluidized bed reactor into a separator to form multimodal ethylene polymer fluff. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

22. The method of claim 21, wherein the bend section includes a flow meter.

23. The method of claim 22, wherein: The molar ratio of nitrogen to propane is less than or equal to 0.05:1; or The gas-phase polymerization conditions are characterized by a condensation percentage in the range of 15% to 30% by weight; or Both.

24. The method of claim 21, wherein the first olefin comonomer and the second olefin comonomer independently comprise propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, or mixtures thereof.

25. The method of claim 24, wherein: The first olefin comonomer is present in step (i); or The second olefin comonomer is present in step (iv); or Both.

26. The method of claim 21, wherein: The catalyst composition is a Ziegler-Natta catalyst system; and The polymerization conditions in step (i) include an average residence time of 15 to 75 minutes and a linear velocity of 15 to 55 feet per second.

27. The method of claim 21, wherein the method further comprises a step of prepolymerizing the catalyst composition in a prepolymerization reactor prior to step (i).

28. The method of claim 21, wherein the first ethylene polymer produced in the loop reactor has a lower Mw, a higher MI, and a higher density than the polymer produced in the fluidized bed reactor.

29. The method of claim 21, wherein step (iii) comprises separating a light fraction containing hydrogen from the effluent of the first reactor in a first cyclone separator to form an intermediate material containing the first ethylene polymer.

30. The method of claim 29, wherein the first cyclone separator has a cone angle in the range of 60° to 85°.

31. The method of claim 21, wherein the separator in step (v) comprises a second cyclone separator.

32. The method of claim 31, wherein the second cyclone separator has a cone angle in the range of 60° to 85°.

33. The method of claim 21, wherein the polymerization conditions in step (i) include a linear velocity of 20 feet per second to 50 feet per second.

34. The method of claim 21, wherein the loop reactor has an inner diameter of 12 inches to 48 inches.

35. The method of claim 21, wherein the loop reactor comprises at least a reactor circulation pump having an axial design.

36. The method of claim 21, wherein: The loop reactor includes at least a reactor circulation pump; and The pump diameter is equal to or greater than the inner diameter of the loop reactor.

37. The method of claim 21, wherein: The loop reactor includes at least a reactor circulation pump; and The diameter of the pump minus the inner diameter of the loop reactor is equal to 1 inch to 8 inches.

38. The method of claim 21, wherein step (ii) comprises continuously discharging the first reactor effluent containing the first ethylene polymer from the loop reactor in the continuous feed assembly.

39. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising: (a) A first loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer and optionally hydrogen in an inert hydrocarbon diluent under supercritical polymerization conditions to produce a first ethylene polymer. The first loop reactor is further configured to maintain the Dean number of the reaction mixture flowing through two or more bends in the first loop reactor at between 3,000,000 and 15,000,000. (b) A second loop reactor configured to contact, under supercritical polymerization conditions, a first reactor effluent containing the first ethylene polymer with ethylene, an optional second olefin comonomer and an optional hydrogen gas to produce a second ethylene polymer. (c) A transfer line configured to draw out the first reactor effluent containing the first ethylene polymer from the first loop reactor and introduce the first reactor effluent into the second loop reactor; (d) A second discharge line, the second discharge line being configured to extract a second reactor effluent containing the second ethylene polymer from the second loop reactor; (e) A separator configured to remove a light fraction containing hydrogen from the effluent of the second reactor to form an intermediate material containing the second ethylene polymer, wherein hydrogen is present in the first loop reactor, the second loop reactor, or both. as well as (f) A fluidized bed reactor configured to contact the intermediate material containing the second ethylene polymer with ethylene and optionally a third olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce the multimodal ethylene polymer. The transfer line is configured to extract the first reactor effluent from the first loop reactor at a discharge position downstream of the first loop reactor circulation pump, and to introduce the first reactor effluent into the second loop reactor at a feed position upstream of the second loop reactor circulation pump. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

40. The system of claim 39, wherein the second discharge line is configured to continuously extract the second reactor effluent containing the second ethylene polymer from the second loop reactor.

41. The system of claim 39, wherein the outlet of the separator is positioned at a height higher than the inlet of the intermediate material into the fluidized bed reactor.

42. The system of claim 41, wherein the separator comprises a cyclone separator.

43. The system of claim 39, wherein the system further comprises a recirculation system configured to separate fine polymer particles from unreacted olefins in the gas stream exiting the fluidized bed reactor and to return the fine polymer particles to the fluidized bed reactor.

44. The system of claim 43, wherein the recirculation system comprises a cyclone separator and an ejector.

45. The system of claim 39, wherein the system further comprises a polymer recovery system configured to receive a third reactor effluent containing the multimodal ethylene polymer from the fluidized bed reactor, remove volatiles from the third reactor effluent, and form multimodal ethylene polymer fluff.

46. ​​The system of claim 45, wherein the polymer recycling system comprises: Cyclone separator; Blow-out tower; as well as The continuous lint discharge port between the cyclone separator and the purging tower.

47. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising: (a) A loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer and hydrogen in an inert hydrocarbon diluent under supercritical polymerization conditions to produce a first ethylene polymer. The loop reactor is further configured to maintain the Dean number of the reaction mixture flowing through two or more bends in the loop reactor at 3,000,000 to 15,000,000. (b) An effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the loop reactor; (c) A separator configured to remove a light fraction containing hydrogen from the effluent from the first reactor to form an intermediate material containing the first ethylene polymer. as well as (d) A fluidized bed reactor configured to contact the intermediate material containing the first ethylene polymer with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce the multimodal ethylene polymer. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

48. The system of claim 47, wherein the separator comprises a cyclone separator.

49. The system of claim 48, wherein the cyclone separator has a cone angle in the range of 60° to 85°.

50. The system of claim 47, wherein the loop reactor is configured such that the linear velocity of the reaction mixture flowing within the loop reactor is in the range of 20 feet per second to 50 feet per second.

51. The system of claim 47, wherein the loop reactor has an inner diameter of 12 inches to 48 inches.

52. The system of claim 47, wherein the loop reactor includes at least a reactor circulation pump having an axial design.

53. The system of claim 47, wherein: The loop reactor includes at least a reactor circulation pump; and The pump diameter is equal to or greater than the inner diameter of the loop reactor.

54. The system of claim 47, wherein: The loop reactor includes at least a reactor circulation pump; and The diameter of the pump minus the inner diameter of the loop reactor is equal to 1 inch to 8 inches.

55. The system of claim 47, wherein the first reactor effluent is continuously extracted from the loop reactor in the continuous feed assembly.

56. The system of claim 47, wherein the discharge line further comprises a flash line heater.

57. The system of claim 47, wherein the system is configured to produce 20% to 90% by weight of the multimodal ethylene polymer in the loop reactor and 10% to 80% by weight of the multimodal ethylene polymer in the fluidized bed reactor.

58. The system of claim 47, wherein the system further comprises a control system configured to control the bed height in the fluidized bed reactor.

59. The system of claim 47, wherein the system further comprises a catalyst feed port configured to introduce the catalyst composition as a slurry having a solids content of 1% to 15% by weight into the loop reactor.

60. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising: (a) A loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen in an inert hydrocarbon diluent under supercritical polymerization conditions to produce a first ethylene polymer. The loop reactor is further configured to maintain the supercritical polymerization conditions at a cavitation number of 6 to 60. (b) An effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the loop reactor; The discharge line includes a flash line heater; (c) A separator configured to remove light fractions containing hydrogen from the effluent of the first reactor to form an intermediate material; (d) A fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce the multimodal ethylene polymer; and (e) A recirculation system configured to separate fine polymer particles from unreacted olefins in the gas stream leaving the fluidized bed reactor and to return the fine polymer particles to the fluidized bed reactor. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

61. The system of claim 60, wherein the recirculation system comprises a cyclone separator and an ejector.

62. The system of claim 60, wherein the separator comprises a cyclone separator with a cone angle in the range of 60° to 85°.

63. The system of claim 60, wherein the cavitation number is 18 to 40.

64. The system of claim 60, wherein the system further comprises a polymer recovery system configured to receive a second reactor effluent containing the multimodal ethylene polymer from the fluidized bed reactor, remove volatiles from the second reactor effluent, and form multimodal ethylene polymer fluff.

65. The system of claim 64, wherein the polymer recycling system comprises: Cyclone separator; Blow-out tower; as well as The continuous lint discharge port between the cyclone separator and the purging tower.

66. A method for producing a multimodal ethylene polymer, the method comprising: (i) In a loop reactor, under supercritical polymerization conditions, the catalyst composition is contacted with ethylene, optionally a first olefin comonomer, and hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer. The catalyst composition is introduced into the loop reactor as a slurry with a solid content of 1% to 15% by weight. The supercritical polymerization conditions mentioned above include cavitation numbers of 6 to 60; (ii) The effluent from the first reactor containing the first ethylene polymer is continuously discharged from the loop reactor into an outlet line including a flash line heater; (iii) Separating a light fraction containing hydrogen from the effluent of the first reactor to form an intermediate material; as well as (iv) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce the multimodal ethylene polymer. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

67. The method of claim 66, wherein the catalyst composition is a Ziegler-Natta catalyst system.

68. The method of claim 67, wherein the Ziegler-Natta catalyst system comprises a supported catalyst with a titanium loading of 0.1% to 20% by weight, and is characterized in that: The sphericity is in the range of 0.5 to 1.0; and The average particle size ranges from 1 micrometer to 50 micrometers.

69. A polymerization reactor system for producing multimodal ethylene polymers, the system comprising: (a) A loop reactor configured to contact a catalyst composition with ethylene, optionally a first olefin comonomer, and hydrogen under supercritical polymerization conditions in an inert hydrocarbon diluent to produce a first ethylene polymer. The loop reactor is further configured to maintain the supercritical polymerization conditions at a Biot number less than or equal to 3; (b) An effluent line configured to extract a first reactor effluent containing the first ethylene polymer from the loop reactor; The discharge line includes a flash line heater; (c) A separator configured to remove light fractions containing hydrogen from the effluent of the first reactor to form an intermediate material; (d) A fluidized bed reactor configured to contact the intermediate material with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon under gas-phase polymerization conditions to produce the multimodal ethylene polymer; and (e) A polymer recovery system configured to receive a second reactor effluent containing the multimodal ethylene polymer from the fluidized bed reactor, remove volatiles from the second reactor effluent, and form multimodal ethylene polymer fluff. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

70. The system of claim 69, wherein the system further comprises a recirculation system configured to separate fine polymer particles from unreacted olefins in the gas stream exiting the fluidized bed reactor and to return the fine polymer particles to the fluidized bed reactor.

71. The system of claim 70, wherein the recirculation system comprises a cyclone separator and an ejector.

72. The system of claim 69, wherein the separator comprises a cyclone separator with a cone angle in the range of 60° to 85°.

73. The system of claim 69, wherein the Biot number is less than or equal to 1.

5.

74. The system of claim 69, wherein the polymer recycling system comprises: Cyclone separator; Blow-out tower; as well as The continuous lint discharge port between the cyclone separator and the purging tower.

75. A method for producing a multimodal ethylene polymer, the method comprising: (i) In a loop reactor, under supercritical polymerization conditions, a catalyst composition is contacted with ethylene, an optional first olefin comonomer and hydrogen in an inert hydrocarbon diluent to produce a first ethylene polymer. The catalyst composition is introduced into the loop reactor as a slurry with a solid content of 1% to 15% by weight. The supercritical polymerization conditions mentioned above include a Biot number less than or equal to 3; (ii) The effluent from the first reactor containing the first ethylene polymer is continuously discharged from the loop reactor into an outlet line including a flash line heater; (iii) Separating a light fraction containing hydrogen from the effluent of the first reactor to form an intermediate material; and (iv) In a fluidized bed reactor, under gas-phase polymerization conditions, the intermediate material is contacted with ethylene and optionally a second olefin comonomer in an inert gas and / or hydrocarbon to produce the multimodal ethylene polymer. The inert hydrocarbon diluent mentioned above includes propane; and The gas composition in the fluidized bed reactor contains less than or equal to 10 mol% nitrogen and at least 50 mol% propane.

76. The method of claim 75, wherein the catalyst composition is a Ziegler-Natta catalyst system.

77. The method of claim 76, wherein the Ziegler-Natta catalyst system comprises a supported catalyst with a titanium loading of 0.1% to 20% by weight.

78. The method of claim 77, wherein the supported catalyst has an average particle size of 1 micrometer to 50 micrometers.

79. The method of claim 75, wherein the supercritical polymerization conditions further comprise a cavitation number of 6 to 60.

80. The method of claim 79, wherein the Biot number is less than or equal to 1.5.

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