Loop flow polymerization reactor

Abstract

The present invention relates to a circulating polymerization reactor (1) comprising an annular reaction section intended to circulate a reaction medium in the loop, the reaction section being provided with one or more feed inlets (11) for at least reagents, optionally for catalysts and / or for solvents, and at least one discharge outlet (12), the reactor comprising at least one means (7) for causing movement of the reaction medium in the loop-shaped reaction section, the loop comprising a plurality of pipe sections fluidly connected to each other, the pipe sections including at least one straight section (5, 3) such that the pipe section or at least one of the pipe sections, particularly the straight section or at least one of the straight sections, accommodates an insert extending over at least 50% of the length of the section and over at least 50% of the cross-section of the section.

Description

Technical Field

[0001] This invention relates to a circulating reactor. Reactors of this type are designed so that the reaction mixture can be circulated / recirculated multiple times within the reaction section forming the loop. The loop can be formed by tubular conduits, particularly a series of straight and curved tubular conduits.

[0002] The present invention relates more particularly to the use of this type of reactor for polymerization reactions, especially for the catalytic polymerization of olefins containing 2 to 4 carbons (referred to as C2-C4 olefins), in order to convert them into higher olefins of the α-olefin type, such as butene, hexene, octene, nonene, and decene, said higher olefins being olefins used as major petrochemical intermediates, said reaction medium being either a two-phase gas / liquid or a single-phase liquid.

[0003] The present invention relates more particularly to the oligomerization of ethylene with the aid of a catalyst to obtain straight-chain olefins, such as 1-butene, 1-hexene, or 1-octene, or mixtures of straight-chain α-olefins from 1-butene to 1-dodecene. It can especially consist of 1-butene and / or 1-hexene obtained by oligomerization of ethylene. Existing technology

[0004] Circulating reactors are known in principle, with examples found in particular in patents EP1842861 concerning ethylene polymerization and EP1316566 concerning propylene polymerization.

[0005] In the case of ethylene oligomerization (examples of the described embodiments will be used illustratively herein), the reaction is exothermic, which requires a cooling device to be provided in at least a portion of the reaction section.

[0006] Regardless of whether the reactor operates in a two-phase or single-phase reaction medium, a common problem in such reactions is the production of polymeric solid fouling byproducts, particularly as explained in the publication “Simulation experiments for maximising the availability of a commercial octene production facility” by RF Rossouw, RLJ Coetzer, and PD Pretorius, Vol. 26(1), pp. 53–77 (2010, published by ORION). Although produced in small quantities, these byproducts tend to deposit on the walls of the reaction section, especially in areas equipped with cooling devices. Their accumulation requires regular cleaning, which is inconvenient.

[0007] Furthermore, efforts are made to homogenize the composition of the reaction medium circulating in the loop as much as possible, and to promote the homogenization of its temperature within the reaction medium, particularly by facilitating heat transfer within the reaction medium in areas equipped with cooling devices. These cooling devices may, for example, take the form of double-walled cooling jackets.

[0008] The object of the present invention is thus to improve the operation of a circulating reactor, particularly to promote heat transfer within the reaction medium circulating in the loop and / or to limit the risk of fouling on the walls of the reactor loop. Summary of the Invention

[0009] The present invention firstly includes a circulating polymerization reactor comprising a reaction section in the form of a loop for circulating the reaction medium through the loop. - The reaction section is equipped with one or more feed inlets for reagents, possibly for catalysts and / or for solvents, and at least one discharge outlet. - The reactor includes at least one device for ensuring the movement of the reaction medium in a loop-type reaction section. - The loop comprises multiple fluid-connected pipe sections, each pipe section including at least one straight section. And such that at least one of the pipe portions accommodates a fixed or movable insert that extends over at least 50% of the length of the portion and over at least 50% of the cross-section of the portion.

[0010] A "movable" insert is an insert that is actively in motion by a dedicated device that moves it, or passively in motion by the circulation of the reaction medium from one end of the loop to the other.

[0011] It has been found that adding this or these inserts improves the operation of the circulating reactor in at least two ways: again, taking the oligomerization of ethylene as an example, the oligomerization reaction produces polyethylene as a byproduct, which, even in small quantities, tends to deposit on the inner walls of the loop, particularly in the areas where the loop is cooled (exothermic reaction), typically the straight sections of the loop, where scaling forms on the walls. However, this scaling has two adverse consequences: on the one hand, it gradually hinders the circulation of the reaction medium, requiring periodic cleaning between production runs; on the other hand, it increasingly hinders the venting of heat released from the loop walls: this disrupts the thermal homogenization of the reaction medium, especially in areas cooled by external cooling devices (double walls surrounding certain sections of the loop, within which cooling fluid circulates); scaling reduces the heat transfer capacity from these cooling devices to the reaction medium and reduces the ability to remove heat through the loop walls.

[0012] Therefore, the insert according to the invention will prevent scaling on the wall and promote heat exchange within the reaction medium by generating turbulence in the flow of the reaction medium and by generating shear near the wall.

[0013] Preferably, the insert extends over at least 70 to 100%, especially 80 to 95%, of the length of the pipe portion that receives it, and over at least 70%, especially at least 80%, and preferably at most 95% or 98% of its cross-section.

[0014] Therefore, if the reaction section loop comprises x straight pipe sections connected to each other by y bends, the insert can be advantageously placed in at least one straight section, especially in all straight sections or at least all those equipped with cooling devices, in other words, those sections with the greatest risk of scaling. The insert can then occupy most of the length of the pipe section and the cross-section of the pipe section in this way to maximize its efficiency (especially its shear effect near the wall).

[0015] According to one embodiment, the insert according to the invention is attached at at least one end or at each end to a conduit portion that receives the insert.

[0016] According to another implementation, its ends are free.

[0017] Preferably, the insert is "passively" movable, meaning that the insert will move / rotate / change position on its own within the pipe section containing it only as the reaction medium circulates in the loop.

[0018] Advantageously, the insert is attached at at least one end by a mechanical device to allow it to rotate freely, particularly about the longitudinal axis of a straight section. In this case, the insert rotates about the axis of the pipe section, thus rotating on its own.

[0019] The mechanical device in question may include, for example, a component forming a bearing, which is attached to the inner wall of a pipe section, and a trunnion that can rotate freely relative to the bearing is mounted on the component, with the insert attached to the trunnion at one end.

[0020] The geometry of the insert can vary widely: the aim is to generate as much turbulence / shear as possible within the reaction medium while limiting the pressure drop caused by its presence in the reaction medium flow.

[0021] According to one variant, the insert according to the invention is in the form of a twisted strip, for example having a spiral shape, and in particular having a constant or variable width.

[0022] According to another variation, the insert according to the invention is in the form of a finned rod, particularly when the pipe portion is straight, a rod oriented along the longitudinal axis of said pipe portion. The fins are preferably regularly distributed along the length of the rod, opposite or staggered to each other, having a flat or curved geometry, or in the form of blades with multiple curvatures. The rod may be fixed and only the fins are movable, or the rod may be rotatable and the fins may be fixed or not fixed relative to the rod.

[0023] According to another variant, the insert according to the invention is in the form of a spiral wire, especially a helix, such as a spring.

[0024] In this variant, the spiral wire can have a pitch (distance from one turn to the next) between 10 mm and 100 mm, particularly between 10 mm and 40 mm. The pitch can be constant or vary along the length of the spiral. The cross-section of the wire is particularly circular or square.

[0025] Preferably, the insert is made of a material with a lower hardness than the inner wall of the pipe portion that houses the insert: this ensures that the inner wall of the pipe where the insert is located will not be damaged in the event of contact between the insert and the wall.

[0026] Preferably, the insert material is selected from metals or metal alloys, such as carbon steel, stainless steel or Inconel alloy.

[0027] Advantageously, the reactor according to the invention is intended to contain a two-phase gas / liquid or a single-phase all-liquid reaction medium.

[0028] Advantageously, the pipe portion of the loop is in the form of a tubular pipe having a cylindrical or substantially cylindrical cross-section.

[0029] Preferably, when cylindrical, the cross-sectional diameter of the pipe portion of the loop is between 5 cm and 100 cm, particularly between 20 cm and 80 cm or between 30 cm and 60 cm. This diameter can be constant or variable. Thus, the circulating reactor can comprise straight pipe portions connected to each other by angled sections, the straight pipe portions being vertically oriented, alternating between straight sections referred to as "descending" (where the reaction medium flows from bottom to top) and straight sections referred to as "ascending" (where the reaction medium flows from top to bottom). In this case, it is advantageous that the cross-sectional diameter of the "ascending" straight section is larger than that of the "descending" straight section.

[0030] Preferably, the length of the straight section of the reaction section is at least 5 m, especially between 10 and 100 m, for example between 20 and 90 m or between 30 and 60 m.

[0031] In general, the length of the loop can be measured as at least 100 meters or several hundred meters, and in particular it can have a length of at least 800 to 900 meters, for example, between 1,000 and 1,500 meters.

[0032] Preferably, at least one pipe section of the loop, especially a straight section or one of the straight sections, is equipped with a cooling device, particularly in the form of a cooling jacket.

[0033] Preferably, the loop-shaped reaction section comprises at least two straight pipe sections, particularly parallel or perpendicular to each other, and connected to each other by a bend in the form of an elbow or a semi-circular shape.

[0034] The present invention also relates to a method for the polymerization, oligomerization, or trimerization of C2-C4 starting olefins to obtain linear olefins. This may be a method for the oligomerization of ethylene to obtain 1-butene and / or 1-hexene, wherein the method uses the reactor described above.

[0035] Advantageously, according to the method of the invention, the reactor is operated under the following conditions: - at least 5×10 5 Pa, especially at 1×10 6 Up to 7×10 6 Under pressure between Pa - At temperatures between 20°C and 150°C - Preferably, the velocity of the circulating reaction medium in the loop reaction section is between 1 and 30 m / s.

[0036] Preferably, the surface velocity of the liquid phase flowing in the reactor is 1 to 30 ms. -1 Between, preferably 1 to 15 ms -1 between.

[0037] Preferably, when the reactor is intended for a reaction between reactants, at least one reactant is in gaseous form, and the surface velocity of the gas phase is 0.1 to 2 ms prior to dissolution. -1 .

[0038] It should be noted that surface velocity is the ratio between the volumetric flow rate of the fluid involved and the cross-section through which the fluid passes.

[0039] Note that in the upstream part of the loop, in the region near the gas injection point, when one of the reactants is injected into the reactor as a gas, there is a gas / liquid mixture, and gradually in the downstream direction, it becomes a completely liquid phase as the injected gas gradually reacts with / dissolves in the liquid phase.

[0040] The terms “upstream” and “downstream” are understood in reference to the direction in which the reaction medium travels through the loop from the injection points of the reactants and catalyst.

[0041] The present invention will now be described in more detail with the aid of embodiments and accompanying drawings. Attached Figure Description

[0042] Figure 1 A first embodiment of a circulating reactor is shown.

[0043] Figure 2 A second embodiment of the circulating reactor is shown.

[0044] Figure 3 The invention is shown as a modified version of the present invention. Figure 2 The second embodiment of the circulating reactor.

[0045] Figure 4 yes Figure 3 A magnified view of a portion of it.

[0046] Figure 5 An insert according to the invention is shown.

[0047] All these figures are highly schematic and do not necessarily depict components to scale, highlighting the components most relevant to illustrating the invention. Components are depicted in space according to possible operating modes.

[0048] The same reference numerals correspond to the same components, the same processes, etc., between the figures. Invention Details To describe the invention in detail, Figure 1 and 2 This demonstrates two different types of circulating reactors to which the present invention can be applied.

[0050] This invention can be applied in a similar manner to any other type of circulating reactor.

[0051] The application of the circulating reactor of the present invention, described as an example, relates to the oligomerization of ethylene in the presence of a solvent and a catalyst: Oligopolymerization corresponds to any reaction involving the addition of a first olefin to a second olefin that is the same as or different from the first olefin. The resulting olefin has the empirical formula C0. n H 2n , where n is equal to or greater than 4, and especially straight-chain olefins (called α-olefins).

[0052] For example, it is the primary reaction of ethylene with itself to produce 1-butene and / or 1-hexene and / or higher oligomers. It includes the case of tetramerization.

[0053] α-olefins (in this case, products obtained after oligomerization) are straight-chain olefins in which the double bonds are located at the end of the alkyl chain.

[0054] Homogeneous oligomerization catalysts are, for example, mixtures of at least one metal precursor and at least one activator (also called catalytic systems), optionally in the presence of at least one additive and optionally a solvent.

[0055] The reaction medium circulating in the circulating reactor is, for example, a gas / liquid mixture, in which the solvent dissolves ethylene and the catalyst.

[0056] This invention can be applied in a similar manner to any other catalytic or non-catalytic oligomerization or polymerization reaction.

[0057] Figure 1 The first example of the circulating reactor 1 is shown, in its simplest construction: the loop comprises four straight tube sections 2, 3, 4, 5 with cylindrical cross-sections, arranged as an example in a vertical plane, perpendicular to each other, and connected to each other by four angular sections 6, 7, 8, 9 with the same cylindrical cross-section to form a loop with a generally rectangular shape with rounded edges (in the front view), wherein two opposing straight tube sections 3, 5 are longer than the other two straight tube sections 2, 4.

[0058] The diameter of the pipe section can be constant or vary along the entire length of the loop, and can be, for example, between 20 and 60 cm.

[0059] These pipes are preferably made of metal or metal alloy.

[0060] In the angled pipe section 9, the loop is provided with an inlet 10 for solvent and catalyst, and in the opposite angled section 8, there is an inlet 11 for reactants (e.g., ethylene in this case) and an outlet 12 for reaction products.

[0061] Turbine 13 ensures that the reaction medium circulates in the loop formed therefrom.

[0062] A heat exchanger (in the form of a double-layer cooling jacket 14 in which cooling fluid circulates) is installed on the straight pipe sections 3 and 5 (the longest) to control the exothermic reaction.

[0063] Once the solvent, catalyst, and ethylene (using a non-limiting example of ethylene polymerization) have been supplied to loop 1, the reaction medium circulates in the loop by means of turbine 13, the desired product is gradually produced, and discharged through outlet 12. The supply and / or discharge can be continuous or intermittent. The turbine is an example and can be replaced by any suitable type of pump, such as a slurry pump, also known as a Lawrence pump.

[0064] Figure 2A second embodiment of the circulating reactor 1' with a slightly different construction is shown. This time, the loop comprises five straight sections 21, 22, 23, 24, and 25, which are arranged, by way of example, in a vertical plane, parallel to each other, and connected by semi-circular pipe sections or sections defining hyperbola to allow fluid connection between two straight sections. This construction allows for a significantly longer loop and a highly compact loop. As mentioned above, it is preferable that the "rising" vertical straight section has a larger cross-section than the "falling" vertical straight section. The length of the vertical straight section is at least 10 meters and at most 100 meters, and the total length of the loop is, for example, 1200 meters.

[0065] like Figure 1 As shown, there is at least one inlet 11 for reagents, an inlet 10 for solvents and catalysts, and an outlet 12 for reaction products, and all straight sections are equipped with heat exchangers 14.

[0066] Figure 1 and 2 This invention is merely an example of a circulating reactor; it can be implemented in any type of circulating reactor, especially those with different overall structures, different numbers of straight pipe sections, different pipe section lengths, and so on. Similarly, the arrangement of the inlet and outlet points may differ, as may the number, arrangement, and type of cooling devices.

[0067] The present invention therefore proposes to add inserts to the circulating reactor to improve the homogenization of the reaction medium, promote heat exchange and prevent or at least reduce fouling on the walls, especially in the most hazardous areas, i.e. the parts of the loop that are usually equipped with cooling devices.

[0068] This shows Figure 3 The document describes a device according to the present invention equipped with the following components. Figure 2 The circulating reactor in the middle: all other aspects are related to Figure 2 The reactor is the same, so the insert 40 is therefore placed in each straight section of the loop.

[0069] In this configuration, the insert has a helical shape, and the diameter of its loop corresponds to at least 80%, preferably at least 90%, and at most 95 or 98%, of the circular cross-section of the pipe section to which it is placed. It extends over the entire length of each straight pipe section, or at least 50, 80, or 90% of that length. The wire has a circular (or square) cross-section with a diameter (or diagonal) between 1 and 3 mm. The pitch between the loops is between 10 and 50 mm, for example, approximately 20-40 mm. It is made of metal. The longitudinal axis of the insert coincides with the longitudinal axis of the pipe section to which it is placed. The insert is attached at its upper end, allowing it to rotate freely under the influence of the circulating reaction medium in the loop; its lower end is free.

[0070] Figure 4 yes Figure 3 An enlarged view of the attachment area at the upper end of the insert 40: The insert includes a bearing 41 attached to the wall of the pipe section by a mechanical device 42 (any known mechanical device, such as a threaded connection, clamp, riveting, etc.), and a trunnion 43, the bearing being integrally connected to the trunnion, but the trunnion being able to rotate freely relative to the bearing. The insert includes a helical wire 44, the upper portion of which is inserted into the trunnion and integrally connected to it, the wire terminating at an end 44a, the end being wider than the hole formed in the trunnion for the wire to enter therein, thereby longitudinally locking the portion of the wire inserted into the trunnion into place.

[0071] Therefore, it should be understood that ( Figure 4 As the reaction medium circulates (as indicated by the circular arrow), wire 44 rotates around the longitudinal axis of the pipe, generating additional motion / turbulence in the reaction medium. Its rotation close to the pipe walls "scrapes" the walls (preferably without contacting them), which has the effect of limiting scaling on the walls and thereby reducing the frequency of wall cleaning, and promoting heat exchange between the reaction mixture and the cooling device.

[0072] This type of insert can be arranged in a similar manner. Figure 1 The reactor shown is in the vertical straight sections 3 and 5.

[0073] Constructing the insert in the form of a spring is particularly advantageous because it ensures good mixing while limiting pressure loss caused by its presence.

[0074] Naturally, the insert according to the invention can take other forms: springs with different pitches, twisted strips, rods with all types of fins (in the form of rosettes or blades, arranged opposite each other or staggered along the rod).

[0075] Therefore Figure 5 The image shows a variant of the insert in the form of a twisted strip 40'.

[0076] It can also be attached to one or both ends, as long as it is suitable for mobility under the action of circulating reaction medium. It can also be constructed to remain fixed, for example by rigid attachment at each of its ends.

[0077] In particular, when it is installed on a straight pipe section that is oriented substantially vertically, it tends to be attached to the upper edge of the "downward" section and to each edge of the "upward" section.

[0078] As mentioned above, the pipe section to which the insert is to be installed can be quite long, ranging from several meters to tens of meters. In this case, the insert can be divided into multiple parts, which are then assembled together to obtain the desired insert length. Such assembly can be performed before the parts are inserted into the pipe, or once each part of the insert has been inserted into the pipe. Therefore, standard length insert sections can be designed, which are subsequently assembled as x parts to achieve the desired insert length.

[0079] Inserts can also be attached in different ways, such as not being attached to the inner wall of the pipe by mechanical attachment, but to the outer wall of the pipe, etc.

[0080] Inserts can also be fitted only to certain pipe sections, not just those with cooling devices.

[0081] The insert may also be configured to operate in curved / angled pipe sections. Example

[0082] To illustrate the advantages of this invention, estimates of the 1-hexene obtained by the method of this invention for obtaining 1-hexene from triethylene, with a capacity of 90 KTY (thousand tons / year), are given below. The operating conditions are summarized below: - Number of rounds: 9 - Length of each course: 100 meters - Operating temperature: 135℃ - Operating pressure: 60 bar (6 x 10) 6 Pa) - Catalyst: Chromium-based, concentration 1.11 ppm by weight - Ethylene flow rate: 5.2 kg / s - Solvent flow rate: 7.75 kg / s - Ethylene conversion rate: 63.2% - 1-Hexene selectivity: 95.1% - Spiral vortex insert: 2 mm wire diameter, 45 mm pitch, stainless steel, rotating. The heat transfer coefficients obtained on the tube side in the straight sections with and without inserts are: - Heat transfer coefficient on the tube side with the insert installed: 879 W / m 2 / K - Heat transfer coefficient on the tube side without inserts: 481 W / m 2 / K.

[0083] This invention thereby improves convective heat transfer by at least +30% and reduces the fouling rate caused by polyethylene deposits on the wall by at least 1 / 2. When the insert is installed, the combined gain thereby increases the heat transfer coefficient by at least 82%.

Claims

1. A circulating polymerization reactor (1) comprising a reaction section in the form of a loop for circulating a reaction medium through the loop, the reaction section being provided with one or more feed inlets (11) for at least a reagent, possibly for a catalyst and / or for a solvent, and at least one discharge outlet (12), the reactor comprising at least one means (7) for ensuring the movement of the reaction medium in the reaction section in the form of a loop, the loop comprising a plurality of fluidly connected pipe sections, the pipe sections including at least one straight section (5, 3, 20, 22, 23, 25), characterized in that The pipe section or at least one of the pipe sections, especially the straight section or at least one of the straight sections, accommodates a fixed or movable insert (40, 40') extending over at least 50% of the length of the section and over at least 50% of the cross-section of the section.

2. The reactor (1) as claimed in the preceding claims, characterized in that... The insert (40, 40') extends over at least 70 to 100%, especially 80 to 95%, of the length of the pipe portion that receives it, and over at least 70%, especially at least 80%, and preferably at most 95% or 98% of its cross-section.

3. The reactor (1) as claimed in any of the preceding claims, characterized in that... The insert (40, 40') is attached at at least one end or at each end to a conduit portion that receives the insert.

4. The reactor (1) as claimed in the preceding claims, characterized in that... The insert (40, 40') is attached at at least one end by a mechanical means to allow the insert to rotate freely, especially about the longitudinal axis of the portion when the portion is a straight portion.

5. The reactor (1) as claimed in the preceding claims, characterized in that... The mechanical device includes a component (41) forming a bearing, the component being attached to the inner wall (23) of the pipe portion, and a trunnion (43) that can rotate freely relative to the bearing is mounted on the component, the insert being attached to the trunnion at one end.

6. The reactor (1) claimed in any of the preceding claims, characterized in that... The insert is in the form of a twisted strip (40'), and in particular has a constant or variable width.

7. The reactor (1) claimed in any one of claims 1 to 5, characterized in that... The insert (40, 40') is in the form of a finned rod, especially when the pipe section is straight, the rod is oriented along the longitudinal axis of the pipe section, the fins are preferably regularly distributed along the length of the rod, opposite or staggered to each other, and have a flat or curved geometry, or in the form of blades with multiple curvatures.

8. The reactor (1) claimed in any of the preceding claims, characterized in that... The insert is in the form of a spiral wire (40), especially a helix, such as a spring.

9. The reactor (1) as claimed in the preceding claims, characterized in that... The insert is a spiral wire (40) having a pitch between 10 mm and 100 mm, particularly between 10 mm and 40 mm, the pitch being constant or varying along the length of the spiral, and the cross-section of the wire being particularly circular or square.

10. The reactor (1) claimed in any of the preceding claims, characterized in that... The inserts (40, 40') are made of a material with a hardness lower than that of the inner wall of the conduit portion that houses the inserts, preferably a material selected from metals or metal alloys such as carbon steel, stainless steel or Inconel alloy.

11. The reactor (1) as claimed in the preceding claims, characterized in that... The reactor (1) is intended to contain a two-phase gas / liquid or a single-phase all-liquid reaction medium.

12. The reactor (1) claimed in any of the preceding claims, characterized in that... The pipe portion of the loop is in the form of a pipe with a cylindrical cross-section, the diameter of which is between 5 cm and 100 cm, particularly between 20 cm and 80 cm or between 30 cm and 60 cm.

13. The reactor (1) claimed in any of the preceding claims, characterized in that... The length of the straight section of the reaction section is at least 5 meters, particularly between 10 and 100 meters, or between 20 and 80 meters.

14. The reactor (1) claimed in any of the preceding claims, characterized in that... At least one pipe section of the loop, especially the straight section or one of the straight sections, is equipped with a cooling device (14), especially in the form of a cooling jacket.

15. The reactor (1) claimed in any of the preceding claims, characterized in that... The loop-shaped reaction section comprises at least two straight pipe sections (20, 25), which are parallel or perpendicular to each other and connected to each other by a bend section (27), which is in particular in the form of an elbow or a semi-circular shape.

16. A method for the polymerization, oligomerization, or trimerization of C2-C4 starting olefins to obtain linear olefins, particularly for the oligomerization of ethylene to obtain 1-butene and / or 1-hexene, characterized in that... The method uses a reactor (1) as claimed in any of the preceding claims.

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