Low-pressure separator, reactor system and application thereof

Abstract

The invention provides a low-pressure separator, a reactor system and application of the low-pressure separator and the reactor system. The low-pressure separator comprises a low-pressure separator body, a feeding inner extending pipe and a grating, the feeding inner extending pipe comprises a cylindrical upper feeding inner extending pipe and a cylindrical lower feeding inner extending pipe which are connected up and down; the axis of the upper feeding inward-extending pipe is perpendicular to the horizontal plane, and the peripheral surface of the upper feeding inward-extending pipe is connected with the top of the low-pressure separator body; the inner diameter of the top of the lower feeding inward-extending pipe is the same as that of the upper feeding inward-extending pipe; the bottom of the lower feeding inward-extending pipe is oval, and the long axis and the short axis of the lower feeding inward-extending pipe are both larger than the inner diameter of the upper feeding inward-extending pipe; and the grating is connected with the bottom of the lower feeding inner extending pipe. The lower feeding inner extension pipe is an elliptical section, and asymmetric velocity gradients in the long-axis direction and the short-axis direction of the lower feeding inner extension pipe cause flowing of a polymer melt in the feeding inner extension pipe to be more disordered, so that the shearing rate of the polymer melt is increased, the viscosity is reduced, feeding diffusion of the polymer melt is facilitated, and flowing separation of a gas-phase polymerization monomer is facilitated; and the two-phase separation precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of separation equipment technology, specifically relating to a low-pressure separator, reactor system and its application. Background Technology

[0002] High-pressure polymer processing can produce various polymers such as low-density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA). After the high-pressure polymerization reaction, unreacted monomers need to be separated from the polymerization product, and the unreacted monomers are then recycled. After the high-pressure polymerization reaction, the crude product generally needs to be separated first by a high-pressure separator and then by a low-pressure separator. In the upstream high-pressure separator, under its operating pressure and temperature, small molecules in the supercritical phase will enter the macromolecules through the gaps between macromolecules. Macroscopically, this manifests as some small-molecule monomers dissolving in the macromolecules (i.e., the bottom liquid phase after preliminary separation contains a large amount of unreacted monomers). When the pressure decreases or the temperature changes, the small-molecule monomers escape from the gaps between the polymer macromolecules, and thus, after entering the low-pressure separator, the monomers precipitate from the molten polymer phase. Therefore, it needs to be transferred to a low-pressure separator for further separation to separate the polymer monomer from the molten polymer. After the two phases are separated by the low-pressure separator, the molten polymer is discharged at the bottom of the low-pressure separator, and the gaseous polymer monomer is discharged at the top, so that the gaseous polymer monomer can be recycled.

[0003] However, the molten polymer phase is a non-Newtonian fluid with flow characteristics different from common fluids. Furthermore, the two-phase flow pattern formed by the non-Newtonian fluid and the gas phase is related to the fluid boundary, making the design of low-pressure separators challenging and hindering the achievement of high two-phase separation accuracy. If the separated gaseous polymer monomers contain a large number of molten polymer droplets, scaling will occur in the downstream low-pressure circulating gas system, potentially leading to excessively rapid scaling in the downstream compressor system and affecting the continuous operation cycle of the unit. Conversely, if the separated polymer melt contains a large number of polymer monomers, excessive combustible gas will enter downstream extrusion and degassing units, affecting the safe and stable operation of the system.

[0004] Therefore, developing a low-pressure separator that can improve the two-phase separation capability has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art and to provide a low-pressure separator, reactor system and its application. It adopts the separation principle of central material falling gravity sedimentation and improves the two-phase separation accuracy of the low-pressure separator by improving the pipe type of the feed inner extension pipe and the low-pressure circulating gas outlet.

[0006] One objective of this invention is to provide a low-pressure separator, comprising a low-pressure separator body, a feed inner tube, and a grid; the feed inner tube includes an upper cylindrical feed inner tube and a lower cylindrical feed inner tube connected vertically; the axis of the upper feed inner tube is perpendicular to the horizontal plane, and its outer circumferential surface is connected to the top of the low-pressure separator body; the inner diameter of the top of the lower feed inner tube is the same as the inner diameter of the upper feed inner tube; the bottom of the lower feed inner tube is elliptical, and both its major and minor axes are larger than the inner diameter of the upper feed inner tube; the grid is connected to the bottom of the lower feed inner tube.

[0007] In a preferred embodiment of the present invention

[0008] The low-pressure separator body, the feed inner pipe, and the grid are coaxially arranged; and / or,

[0009] The grid is connected to the bottom inner wall of the lower feed inner tube; and / or,

[0010] The feed inner tube is a high-pressure internal component; and / or,

[0011] The cross-section of the grid is elliptical, with its major axis equal to the major axis of the bottom of the lower feed inner tube, and its minor axis equal to the minor axis of the bottom of the lower feed inner tube; and / or,

[0012] The surface roughness of the inner wall of the low-pressure separator body is not greater than 0.8 μm, preferably 0.1 to 0.8 μm.

[0013] In a preferred embodiment of the present invention

[0014] At least one intermediate feed inner pipe is provided between the upper feed inner pipe and the lower feed inner pipe. The intermediate feed inner pipe is frustum-shaped, and the inner diameter of its bottom surface is larger than the inner diameter of its top surface.

[0015] In a preferred embodiment of the present invention

[0016] The upper feed inner extension pipe includes a first upper feed inner extension pipe disposed outside the low-pressure separator body and a second upper feed inner extension pipe disposed inside the low-pressure separator body;

[0017] The ratio of the height of the lower feed inner tube to the sum of the heights of the second upper feed inner tube and the lower feed inner tube is 0.3 to 1:1, preferably 0.5 to 0.8:1; and / or,

[0018] The ratio of the inner diameter of the short shaft at the bottom of the lower feed inner tube to the inner diameter of the upper feed inner tube is 2.5 to 5:1, preferably 3 to 4:1; and / or,

[0019] The ratio of the inner diameter of the long axis at the bottom of the lower feed inner tube to the inner diameter of the short axis at the bottom of the lower feed inner tube is 1.2 to 2:1, preferably 1.4 to 1.6:1.

[0020] In a preferred embodiment of the present invention

[0021] The height of the grille is 100–300 mm, preferably 150–250 mm; and / or,

[0022] The thickness of the grating plates in the grating is 5–20 mm, preferably 12–18 mm; and / or,

[0023] The spacing between two adjacent grid plates is 30-100mm, preferably 40-80mm;

[0024] Preferred,

[0025] The top of the grille has two tapered surfaces;

[0026] More preferably,

[0027] The angle between the sharpened surface of the grille and the upper vertical surface is 120° to 170°, and most preferably 150° to 170°.

[0028] In a preferred embodiment of the present invention

[0029] The low-pressure separator body comprises, from top to bottom, an elliptical head, a cylindrical body, and an inverted cone connected in sequence.

[0030] Preferred,

[0031] The elliptical end cap is detachably connected to the cylindrical body;

[0032] More preferably,

[0033] The ratio of the height to the inner diameter of the cylindrical body is 1.2 to 3.0:1, most preferably 2 to 2.4:1; and / or,

[0034] The ratio of the sum of the heights of the second upper feed inner pipe and the lower feed inner pipe to the height of the cylindrical body is 0.2–0.8:1, most preferably 0.4–0.6:1; and / or,

[0035] The vertex angle of the inverted cone is 25° to 90°, and most preferably 30° to 50°.

[0036] In a preferred embodiment of the present invention

[0037] The top of the low-pressure separator body is provided with 1 to 5 low-pressure circulating gas outlets;

[0038] Preferably, the low-pressure circulating gas outlet is inclined;

[0039] More preferably, the angle between the low-pressure circulating gas outlet and the upper vertical plane is 15° to 45°, and most preferably 20° to 40°.

[0040] The second objective of this invention is to provide the application of the low-pressure separator described in the first objective of this invention in polymer separation, comprising the following steps: high-pressure polymer melt enters the interior of the low-pressure separator body through the feed inner pipe, and after two-phase separation through the upper feed inner pipe, the lower feed inner pipe, and the grid, liquid polymer and gaseous monomer are obtained. The liquid polymer is transferred out from the bottom outlet of the low-pressure separator body, and the gaseous polymer monomer is transferred out from the low-pressure circulating gas outlet.

[0041] Preferred,

[0042] The feed pressure of the polymer melt in the low-pressure separator is 20–50 MPa; and / or,

[0043] The feed temperature of the polymer melt to the low-pressure separator is 150–300°C; and / or,

[0044] The feed rate of the polymer melt in the low-pressure separator is 0.3–5 m / s; and / or,

[0045] The operating pressure of the low-pressure separator is 0–2.0 MPaG; and / or,

[0046] The operating temperature of the low-pressure separator is 150–300°C.

[0047] A third objective of this invention is to provide a reactor system comprising a reactor, a high-pressure separator, and a low-pressure separator as described in one objective of this invention, connected in sequence.

[0048] The fourth objective of this invention is to provide the application of the reactor system described in the third objective of this invention in polymer separation, comprising the following steps:

[0049] S1: The reactants react in the reactor to obtain a crude product of high-pressure polymer melt;

[0050] S2: The crude product of the high-pressure polymer melt is separated by a high-pressure separator to obtain the high-pressure polymer melt;

[0051] S3: The high-pressure polymer melt enters the low-pressure separator body through the feed inner pipe in the low-pressure separator. After two-phase separation through the upper feed inner pipe, lower feed inner pipe, and grid, liquid polymer and gaseous monomer are obtained. The liquid polymer is transferred out from the bottom outlet of the low-pressure separator body, and the gaseous polymer monomer is transferred out from the low-pressure circulating gas outlet.

[0052] Preferred,

[0053] The feed pressure of the polymer melt in the low-pressure separator is 20–50 MPa; and / or,

[0054] The feed temperature of the polymer melt to the low-pressure separator is 150–300°C; and / or,

[0055] The feed rate of the polymer melt in the low-pressure separator is 0.3–5 m / s; and / or,

[0056] The operating pressure of the low-pressure separator is 0–2.0 MPaG; and / or,

[0057] The operating temperature of the low-pressure separator is 150–300°C.

[0058] Compared with the prior art, the beneficial effects of the present invention are:

[0059] 1. In the low-pressure separator of the present invention, the bottom of the feed inner tube is elliptical, and the lower feed inner tube is an elliptical segment. When the polymer melt enters the feed inner tube, the asymmetric velocity gradient along the major and minor axes of the feed inner tube causes more chaotic flow of the polymer melt within the feed inner tube, further increasing the shear rate of the polymer melt and reducing its viscosity. This facilitates the diffusion of the polymer melt feed and the flow separation of gas-phase monomers, improving the separation accuracy of the two phases. Simultaneously, the increased diameter of the elliptical segment increases the contact area between the gas and liquid phases, reducing the impact of the polymer melt feed on the liquid surface.

[0060] 2. The low-pressure separator of the present invention, by setting a grid composed of multiple grid plates at the bottom (i.e., the end outlet) of the feed inner tube, forms multiple effective interphase contact surfaces when the material falls into the low-pressure separator, which greatly improves the desorption rate of polymer monomers in the polymer melt, shortens the detachment path of polymer monomers in the polymer melt, and further promotes the separation of the two phases.

[0061] 3. In the low-pressure separator of the present invention, the bottom of the feed inner tube is elliptical and the grid has two sharpened surfaces. This allows the polymer melt to diffuse and the gas-phase polymerizing monomers to flow and separate within the feed inner tube before passing through the grid with two sharpened surfaces. This further increases the contact area between the two phases, improves the desorption rate of the polymerizing monomers, shortens the separation path of the polymerizing monomers in the polymer melt, promotes the separation of the two phases, and ultimately achieves higher two-phase separation efficiency.

[0062] 4. The low-pressure separator of the present invention can improve the two-phase separation capability of the low-pressure separator without increasing equipment costs. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of the low-pressure separator of the present invention;

[0064] Figure 2 This is a schematic diagram of one possible structure of the grid in the low-pressure separator of the present invention;

[0065] Figure 3 This is a schematic diagram of one possible structure of the grid in the low-pressure separator of the present invention;

[0066] Figure 4 This is a schematic diagram of one possible structure of the grid in the low-pressure separator of the present invention;

[0067] Figure 5 This is a schematic diagram of one possible structure of the grid in the low-pressure separator of the present invention;

[0068] Figure 6 This is a schematic diagram of the structure of one of the grating plates;

[0069] In the figure, 1-low-pressure separator body; 21-upper feed inner extension pipe; 22-lower feed inner extension pipe; 3-grid. Detailed Implementation

[0070] In this invention, high-pressure internal components refer to internal components that can withstand high pressure; these components need to be able to withstand extremely high pressure.

[0071] The present invention will now be described in further detail with reference to the accompanying drawings:

[0072] like Figures 1-6As shown, the present invention provides a low-pressure separator, including a low-pressure separator body 1, a feed inner extension pipe, and a grid 3. The feed inner extension pipe includes an upper feed inner extension pipe 21 and a lower feed inner extension pipe 22, which are arranged above and below each other and communicate with each other. The low-pressure separator body 1 and the feed inner extension pipe are coaxially arranged. The circumferential surface of the upper feed inner extension pipe 21 is connected to the top of the low-pressure separator body 1, that is, a part of the upper feed inner extension pipe 21 is located outside the low-pressure separator body 1, and a part of the upper feed inner extension pipe 21 is located inside the low-pressure separator body 1, and the lower feed inner extension pipe 22 is located inside the low-pressure separator body 1. It should be noted that the feed inner extension pipe in this embodiment is a two-section feed structure (unexpanded circular pipe and expanded elliptical pipe), but this does not constitute a limitation of the present invention. For ease of description, the upper feed inner pipe 21 located outside the low-pressure separator body 1 is referred to as the first upper feed inner pipe, and the upper feed inner pipe 21 located inside the low-pressure separator body 1 is referred to as the second upper feed inner pipe. The bottom of the lower feed inner pipe 22 is provided with a grid receiving portion, the inner wall of which is connected to the grid 3. Preferably, the feed inner pipe is a high-pressure internal component to accommodate high-pressure feeding into the low-pressure separator.

[0073] The upper feed inner tube 21 is a hollow cylinder, and the lower feed inner tube 22 is a hollow conical shape. The top of the lower feed inner tube 22 is circular, and its inner diameter is the same as the inner diameter of the bottom of the upper feed inner tube 21; the bottom of the lower feed inner tube 22 is elliptical, and both its major and minor axes are larger than the inner diameter of the bottom of the upper feed inner tube 21. When the feed enters the lower feed inner tube 22 through the upper feed inner tube 21, the asymmetric velocity gradient along the major and minor axes of the lower feed inner tube 22 causes the flow of the polymer melt within the lower feed inner tube 22 to become more chaotic, further increasing the shear rate of the polymer melt. Those skilled in the art know that polymer melts typically exhibit pseudoplastic non-Newtonian fluid behavior, meaning that their viscosity decreases with increasing shear rate; this phenomenon is known as shear thinning. Under the influence of the pseudoplastic non-Newtonian fluid shear-thinning characteristics of the polymer melt, the viscosity of the polymer melt decreases, which is beneficial to the diffusion of the polymer melt feed and the flow and separation of gas-phase monomers. Simultaneously, when the feed enters the lower feed inner tube 22 through the upper feed inner tube 21, it forms an elliptical liquid column. The increased diameter of this elliptical segment increases the contact area between the gas and liquid phases, reducing the impact of the polymer melt feed on the liquid surface. Here, "liquid surface" refers to the operating liquid level within the low-pressure separator.

[0074] In a preferred embodiment of the present invention, at least one intermediate feed inner tube is provided between the upper feed inner tube 21 and the lower feed inner tube 22. The intermediate feed inner tube is frustum-shaped, and the inner diameter of its bottom surface is larger than the inner diameter of its top surface. For example, when a middle feed inner pipe is provided between the upper feed inner pipe 21 and the lower feed inner pipe 22, the feed inner pipe includes, from top to bottom, a non-expanded diameter round pipe, an expanded diameter round pipe, and an expanded diameter elliptical pipe connected in sequence. At this time, the inner diameter of the top surface of the middle feed inner pipe is equal to the inner diameter of the bottom surface of the upper feed inner pipe 21, and the inner diameter of the bottom surface of the middle feed inner pipe is equal to the inner diameter of the top surface of the lower feed inner pipe 22. When two middle feed inner pipes are provided between the upper feed inner pipe 21 and the lower feed inner pipe 22, the feed inner pipe includes, from top to bottom, a non-expanded diameter round pipe, an expanded diameter round pipe, an expanded diameter round pipe, and an expanded diameter elliptical pipe connected in sequence.

[0075] In a preferred embodiment of the present invention, the ratio of the height of the lower feed inner tube 22 to the sum of the heights of the second upper feed inner tube and the lower feed inner tube 22 is 0.3 to 1:1, preferably 0.5 to 0.8:1; and / or, the ratio of the inner diameter of the minor axis of the lower feed inner tube 22 to the inner diameter of the upper feed inner tube 21 is 2.5 to 5:1, preferably 3 to 4:1; and / or, the ratio of the inner diameter of the major axis of the lower feed inner tube 22 to the inner diameter of the minor axis of the lower feed inner tube 22 is 1.2 to 2:1, preferably 1.4 to 1.6:1, to further promote the diffusion of the polymer melt feed and the flow and separation of the gas-phase polymerized monomers.

[0076] Specifically, in this embodiment, the height of the lower feed inner tube 22 is represented by H3, the sum of the heights of the lower feed inner tube 22 and the second upper feed inner tube is represented by H2, the inner diameter of the upper feed inner tube 21 is represented by D4, the inner diameter of the major axis of the lower feed inner tube 22 is represented by D3, and the inner diameter of the minor axis of the lower feed inner tube 22 is represented by D2. Therefore, in this embodiment, H3:H2 is 0.3 to 1:1, D2:D4 is 2.5 to 5:1, and D3:D2 is 1.2 to 2:1.

[0077] In a preferred embodiment of the present invention, the cross-section of the grid 3 is elliptical, with its major axis equal to the major axis of the bottom of the lower feed inner extension pipe 22, and its minor axis equal to the minor axis of the bottom of the lower feed inner extension pipe 22. For example... Figure 2 As shown, the grid 3 can be composed of multiple parallel grid plates. Figure 3 As shown, the grid 3 can be composed of multiple annular grid plates arranged sequentially from the inside out. Figure 4As shown, the grid 3 can be composed of multiple mutually perpendicular grid plates, and these multiple mutually perpendicular grid plates are neither parallel to the major axis nor parallel to the minor axis of the grid 3. Figure 5 As shown, the grid 3 can be composed of multiple mutually perpendicular grid plates, and the multiple mutually perpendicular grid plates are either parallel to the long axis of the grid 3 or parallel to the short axis of the grid 3.

[0078] In existing technologies, when polymer melt flows through a conventional inner tube (such as a circular tube) into a low-pressure separator, only the outer side of the polymer melt serves as an effective interphase contact surface. This small contact surface reduces the desorption rate of monomers in the polymer melt and results in a long escape path for the monomers, hindering phase separation. This invention addresses this by installing a grid 3 composed of multiple grid plates at the bottom (i.e., the end outlet) of the lower feed inner tube 22. This creates multiple effective interphase contact surfaces during flow into the low-pressure separator, significantly improving the desorption rate of monomers in the polymer melt, shortening the escape path, and further promoting phase separation.

[0079] In a preferred embodiment of the present invention, the height of the grid 3 is 100-300 mm, preferably 150-250 mm; and / or, the thickness of the grid plates in the grid 3 is 5-20 mm, preferably 12-18 mm; and / or, the spacing between two adjacent grid plates is 30-100 mm, preferably 40-80 mm. Specifically, in this embodiment, the height of the grid 3 is represented by H4, the thickness of the grid plates in the grid 3 is represented by T1, and the spacing between two adjacent grid plates is represented by L1. Therefore, in this embodiment, H4 is 100-300 mm, T1 is 5-20 mm, and L1 is 30-100 mm.

[0080] In a preferred embodiment of the invention, the top of the grille 3 has two tapered surfaces. Figure 5 A front view of one of the grid plates is shown. The grid plate includes an upper rectangular pyramid and a cuboid arranged upper and lower. The upper rectangular pyramid has a vertex at its top, two sets of opposing triangles on its sides, and a rectangular base (with the same dimensions as the top surface of the cuboid). The total area of ​​the first set of opposing triangles is greater than the total area of ​​the second set of opposing triangles; therefore, the first set of opposing triangles constitutes two tapered surfaces. Preferably, the angle between the tapered surface and the upper vertical plane is 120°–170°, more preferably 150°–170°, to further promote the separation of the two phases. Specifically, in this embodiment, the angle between the tapered surface and the upper vertical plane is denoted by α3; therefore, in this embodiment, α3 is 120°–170°.

[0081] As mentioned above, "the flow of polymer melt within the lower feed inlet pipe 22 becomes more chaotic, further increasing the shear rate of the polymer melt and reducing its viscosity, which is beneficial for the diffusion of the polymer melt feed and the flow and detachment of gas-phase polymerizing monomers." After initial separation, the polymer melt then passes through a grid 3 with two sharpened surfaces. The grid 3 with two sharpened surfaces, combined with the lower feed inlet pipe 22 with an elliptical bottom, can further increase the contact area between the two phases, improve the desorption rate of polymerizing monomers, shorten the detachment path of polymerizing monomers in the polymer melt, promote two-phase separation, and ultimately achieve higher two-phase separation efficiency.

[0082] It should be noted that the specific size ratio of the feed inner tube and the grid 3 not only increases the contact area between the two phases, but more importantly, it optimizes the flow of the polymer melt. Under the action of gravity, the polymer melt is more likely to pass through the gap of the grid 3 with two sharpened surfaces, which achieves the breaking of the polymer melt and is less likely to cause blockage. This improves the separation accuracy of the low-pressure separator and achieves higher separation efficiency.

[0083] In a preferred embodiment of the present invention, the low-pressure separator body 1 comprises three parts, from top to bottom: an elliptical head, a cylindrical body, and an inverted cone. Preferably, the elliptical head and the cylindrical body are detachably connected, and a flange connection can be used as an example, so as to facilitate the removal of the polyethylene shell on the inner wall of the low-pressure separator body 1 during shutdown maintenance, and the elliptical head can be removed entirely during maintenance.

[0084] In a preferred embodiment of the present invention, the ratio of the height of the cylindrical body to its inner diameter is 1.2–3.0:1, preferably 2–2.4:1; and / or, the ratio of the sum of the heights of the second upper feed inner tube and the lower feed inner tube 22 to the height of the cylindrical body is 0.2–0.8:1, preferably 0.4–0.6:1. Specifically, in this embodiment, the height of the cylindrical body is represented by H1, and the inner diameter of the cylindrical body is represented by D1. Therefore, in this embodiment, H1:D1 is 1.5–3, and H2:H1 is 0.2–0.8. In another preferred embodiment of the present invention, the vertex angle of the inverted cone is 25°–90°, preferably 30°–50°. Specifically, in this embodiment, the vertex angle of the inverted cone is represented by α1. Therefore, in this embodiment, α1 is 25°–90°.

[0085] In a preferred embodiment of the present invention, the top of the low-pressure separator body 1 is provided with 1 to 5 low-pressure circulating gas outlets. These outlets are preferably inclined to reduce the impact of the discharge on the outlet pipeline system and further prevent polymer molten droplets from being carried into the downstream outlet pipeline system. Preferably, the angle between the low-pressure circulating gas outlet and the upper vertical plane is 15° to 45°, more preferably 20° to 40°. Specifically, in this embodiment, the angle between the low-pressure circulating gas outlet and the upper vertical plane is denoted by α2; therefore, in this embodiment, α2 is 15° to 45°.

[0086] In a preferred embodiment of the present invention, the surface roughness of the inner wall of the low-pressure separator body 1 is no greater than 0.8 μm, preferably 0.1–0.8 μm, to delay the formation of a polyethylene shell on the inner wall of the low-pressure separator body 1. Those skilled in the art know that when the two phases are separated within the low-pressure separator body 1, some polymer molten droplets adhere to the inner wall of the low-pressure separator body 1, gradually forming a polyethylene shell. All welds on the inner wall of the low-pressure separator body 1 are ground flush, and all welds on internal components and pipe openings are ground smooth with rounded transitions, further delaying the formation of a polyethylene shell on the inner wall of the low-pressure separator body 1. More preferably, both the cylindrical body and the inverted cone are provided with an outer jacket or outer coil to heat the material within the low-pressure separator body 1.

[0087] This invention also provides the application of the aforementioned low-pressure separator in polymer separation, comprising the following steps: the crude reaction product in the reactor body enters a high-pressure separator for high-pressure separation to obtain a high-pressure polymer melt; the high-pressure polymer melt enters vertically into the interior of the low-pressure separator body 1 through the feed inner pipe in the low-pressure separator, and undergoes two-phase separation through the upper feed inner pipe 21, the lower feed inner pipe 22, and the grid 3 to obtain a liquid polymer and a gaseous monomer. The liquid polymer exits from the bottom of the low-pressure separator body 1, and the gaseous polymer monomer exits from the low-pressure circulating gas outlet.

[0088] In a preferred embodiment of the present invention, the feed pressure of the polymer melt in the low-pressure separator is 20-50 MPa; and / or, the feed temperature of the polymer melt in the low-pressure separator is 150-300°C; and / or, the feed velocity of the polymer melt in the low-pressure separator is 0.3-5 m / s; and / or, the operating pressure of the low-pressure separator is 0-2.0 MPaG; and / or, the operating temperature of the low-pressure separator is 150-300°C.

[0089] The present invention also provides a reactor system comprising a reactor body, a high-pressure separator, and the aforementioned low-pressure separator connected in sequence. The present invention also provides the application of the reactor system in polymer separation, comprising the following steps:

[0090] S1: The reactants react in the reactor to obtain a crude product of high-pressure polymer melt;

[0091] S2: The crude product of the high-pressure polymer melt is separated by a high-pressure separator to obtain the high-pressure polymer melt;

[0092] S3: The high-pressure polymer melt enters the low-pressure separator body through the feed inner pipe in the low-pressure separator. After two-phase separation through the upper feed inner pipe, lower feed inner pipe and grid, liquid polymer and gaseous monomer are obtained. The liquid polymer is transferred out from the bottom outlet of the low-pressure separator body, and the gaseous polymer monomer is transferred out from the low-pressure circulating gas outlet.

[0093] In a preferred embodiment of the present invention, the feed pressure of the polymer melt in the low-pressure separator is 20-50 MPa; and / or, the feed temperature of the polymer melt in the low-pressure separator is 150-300°C; and / or, the feed velocity of the polymer melt in the low-pressure separator is 0.3-5 m / s; and / or, the operating pressure of the low-pressure separator is 0-2.0 MPaG; and / or, the operating temperature of the low-pressure separator is 150-300°C.

[0094] Example 1

[0095] This embodiment provides a low-pressure separator and its application, including a low-pressure separator body 1, a feed inner extension pipe, and a grid 3. The feed inner extension pipe includes an upper feed inner extension pipe 21 and a lower feed inner extension pipe 22, which are arranged vertically and interconnected. The low-pressure separator body 1 and the feed inner extension pipe are coaxially arranged. The circumferential surface of the upper feed inner extension pipe 21 is connected to the top of the low-pressure separator body 1; that is, a portion of the upper feed inner extension pipe 21 is located outside the low-pressure separator body 1, and a portion of the upper feed inner extension pipe 21 is located inside the low-pressure separator body 1. The upper feed inner extension pipe 21 located outside the low-pressure separator body 1 is referred to as the first upper feed inner extension pipe, and the upper feed inner extension pipe 21 located inside the low-pressure separator body 1 is referred to as the second upper feed inner extension pipe. The bottom of the lower feed inner tube 22 is provided with a grid receiving part, and the inner wall of the grid receiving part is connected to the grid 3. The feed inner tube is a high-pressure internal component, suitable for high-pressure feeding of the low-pressure separator. The upper feed inner tube 21 is a hollow cylinder, and the lower feed inner tube 22 is a hollow conical shape. The top of the lower feed inner tube 22 is circular, and its inner diameter is the same as the inner diameter of the bottom of the upper feed inner tube 21; the bottom of the lower feed inner tube 22 is elliptical. The height of the lower feed inner tube 22 is 2000mm, the height of the second upper feed inner tube is 500mm, the inner diameter of the minor axis of the lower feed inner tube 22 is 700mm, the inner diameter of the major axis of the lower feed inner tube 22 is 980mm, and the inner diameter of the upper feed inner tube 21 is 160mm.

[0096] The cross-section of the grid 3 is elliptical, with its major axis equal to the major axis of the lower feed inner extension pipe 22, and its minor axis equal to the minor axis of the lower feed inner extension pipe 22. The grid 3 can be composed of multiple mutually perpendicular grid plates (e.g., Figure 5 (As shown). The height of the grid 3 is 200mm, the thickness of the grid plates in the grid 3 is 18mm, and the spacing between two adjacent grid plates is 80mm. The top of the grid 3 has two tapered surfaces. The angle between the tapered surfaces and the upper vertical plane is 150°.

[0097] The low-pressure separator body comprises three parts, from top to bottom: an elliptical head, a cylindrical body, and an inverted cone. The elliptical head is connected to the central cylindrical body via a flange. The cylindrical body has a height of 5000 mm and an inner diameter of 4000 mm. The vertex angle of the inverted cone is 45°. The top of the low-pressure separator body 1 has two low-pressure circulating gas outlets, with an angle of 30° between the outlets and the upper vertical plane. The surface roughness of the inner wall of the low-pressure separator body 1 is 0.6 μm. Both the cylindrical body and the inverted cone are equipped with outer jackets.

[0098] The low-pressure separator of Example 1 is used to separate a mixture of ethylene monomer, vinyl acetate monomer, and EVA polymer. The low-pressure separator has a polymer melt feed pressure of 26 MPa, a feed temperature of 200°C, and a feed velocity of 0.8 m / s. The operating pressure of the low-pressure separator is 0.1 MPaG, and the operating temperature is 200°C. The polymer melt is fed vertically into the low-pressure separator body 1 through the feed inner pipe. After passing through the upper feed inner pipe 21, the lower feed inner pipe 22, and the grid 3, two-phase separation is achieved, yielding a liquid polymer and a gaseous monomer. The liquid polymer exits from the bottom of the low-pressure separator body 1, and the gaseous monomer exits from the low-pressure circulating gas outlet.

[0099] Comparative Example 1

[0100] Comparative Example 1 is basically the same as Example 1, except that the lower feed inner tube 22 is a conical tube with an included angle of 30° on the inner wall of the conical tube.

[0101] The separation accuracy of Example 1 and Comparative Example 1 was calculated. This separation accuracy is indirectly reflected by the content of polymer entrained in the gas phase discharge, as well as the content of ethylene monomer and vinyl acetate monomer entrained in the polymer discharge. The lower the content of polymer entrained in the gas phase discharge, and the lower the content of ethylene monomer and vinyl acetate monomer entrained in the polymer discharge, the higher the separation accuracy of the low-pressure separator. Calculations show that, under the same residence time, compared with Comparative Example 1, in Example 1, the polymer entrained in the gas phase discharge is reduced by 5 wt%, and the content of ethylene monomer and vinyl acetate monomer entrained in the polymer discharge is reduced by 1 wt%. This indicates that the low-pressure separator of Example 1 has greater diffusion efficiency and gas-liquid contact area, resulting in higher gas-liquid separation efficiency.

[0102] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0103] In the description of this invention, unless otherwise stated, the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0104] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the technical solutions described in the specific embodiments of the present invention. Therefore, the foregoing description is only a preferred option and is not restrictive.

Claims

1. A low-pressure separator, characterized in that, The device includes a low-pressure separator body, a feed inner tube, and a grid. The feed inner tube comprises an upper cylindrical feed inner tube and a lower cylindrical feed inner tube connected vertically. The axis of the upper feed inner tube is perpendicular to the horizontal plane, and its outer circumference is connected to the top of the low-pressure separator body. The inner diameter of the top of the lower feed inner tube is the same as the inner diameter of the upper feed inner tube. The bottom of the lower feed inner tube is elliptical, and both its major and minor axes are larger than the inner diameter of the upper feed inner tube. The grid is connected to the bottom of the lower feed inner tube.

2. The low-pressure separator according to claim 1, characterized in that, The low-pressure separator body, the feed inner pipe, and the grid are coaxially arranged; and / or, The grid is connected to the bottom inner wall of the lower feed inner tube; and / or, The feed inner tube is a high-pressure internal component; And / or, The cross-section of the grid is elliptical, with its major axis equal to the major axis of the bottom of the lower feed inner tube, and its minor axis equal to the minor axis of the bottom of the lower feed inner tube; and / or, The surface roughness of the inner wall of the low-pressure separator body is not greater than 0.8 μm, preferably 0.1 to 0.8 μm.

3. The low-pressure separator according to claim 1, characterized in that, At least one intermediate feed inner pipe is provided between the upper feed inner pipe and the lower feed inner pipe. The intermediate feed inner pipe is frustum-shaped, and the inner diameter of its bottom surface is larger than the inner diameter of its top surface.

4. The low-pressure separator according to claim 1, characterized in that, The upper feed inner extension pipe includes a first upper feed inner extension pipe disposed outside the low-pressure separator body and a second upper feed inner extension pipe disposed inside the low-pressure separator body; The ratio of the height of the lower feed inner tube to the sum of the heights of the second upper feed inner tube and the lower feed inner tube is 0.3 to 1:1, preferably 0.5 to 0.8:1; and / or, The ratio of the inner diameter of the short shaft at the bottom of the lower feed inner tube to the inner diameter of the upper feed inner tube is 2.5 to 5:1, preferably 3 to 4:1; and / or, The ratio of the inner diameter of the major axis at the bottom of the lower feed inner tube to the inner diameter of the minor axis at the bottom of the lower feed inner tube is 1.2 to 2:1, preferably 1.4 to 1.6:

1.

5. The low-pressure separator according to claim 1, characterized in that, The height of the grille is 100–300 mm, preferably 150–250 mm; and / or, The thickness of the grating plates in the grating is 5–20 mm, preferably 12–18 mm; and / or, The spacing between two adjacent grid plates is 30-100mm, preferably 40-80mm; Preferred, The top of the grille has two tapered surfaces; More preferably, The angle between the sharpened surface of the grille and the upper vertical surface is 120° to 170°, and most preferably 150° to 170°.

6. The low-pressure separator according to claim 4, characterized in that, The low-pressure separator body comprises, from top to bottom, an elliptical head, a cylindrical body, and an inverted cone connected in sequence. Preferred, The elliptical end cap is detachably connected to the cylindrical body; More preferably, The ratio of the height to the inner diameter of the cylindrical body is 1.2 to 3.0:1, most preferably 2 to 2.4:1; and / or, The ratio of the sum of the heights of the second upper feed inner pipe and the lower feed inner pipe to the height of the cylindrical body is 0.2–0.8:1, most preferably 0.4–0.6:1; and / or, The vertex angle of the inverted cone is 25° to 90°, and most preferably 30° to 50°.

7. The low-pressure separator according to claim 1, characterized in that, The top of the low-pressure separator body is provided with 1 to 5 low-pressure circulating gas outlets; Preferably, the low-pressure circulating gas outlet is inclined; More preferably, the angle between the low-pressure circulating gas outlet and the upper vertical plane is 15° to 45°, and most preferably 20° to 40°.

8. The application of the low-pressure separator according to any one of claims 1 to 7 in polymer separation, characterized in that, The process includes the following steps: High-pressure polymer melt enters the body of the low-pressure separator through the feed inner pipe in the low-pressure separator. After two-phase separation through the upper feed inner pipe, lower feed inner pipe, and grid, liquid polymer and gaseous monomer are obtained. Liquid polymer is discharged from the bottom outlet of the low-pressure separator body, and gaseous polymer monomer is discharged from the low-pressure circulating gas outlet. Preferred, The feed pressure of the polymer melt in the low-pressure separator is 20–50 MPa; and / or, The feed temperature of the polymer melt to the low-pressure separator is 150–300°C; and / or, The feed rate of the polymer melt in the low-pressure separator is 0.3–5 m / s; and / or, The operating pressure of the low-pressure separator is 0–2.0 MPaG; and / or, The operating temperature of the low-pressure separator is 150–300°C.

9. A reactor system, characterized in that, It includes a reactor, a high-pressure separator, and a low-pressure separator as described in any one of claims 1 to 7, connected in sequence.

10. The application of the reactor system of claim 9 in polymer separation, characterized in that, Includes the following steps: S1: The reactants react in the reactor to obtain a crude product of high-pressure polymer melt; S2: The crude product of the high-pressure polymer melt is separated by a high-pressure separator to obtain the high-pressure polymer melt; S3: The high-pressure polymer melt enters the low-pressure separator body through the feed inner pipe in the low-pressure separator. After two-phase separation through the upper feed inner pipe, lower feed inner pipe, and grid, liquid polymer and gaseous monomer are obtained. The liquid polymer is transferred out from the bottom outlet of the low-pressure separator body, and the gaseous polymer monomer is transferred out from the low-pressure circulating gas outlet. Preferred, The feed pressure of the polymer melt in the low-pressure separator is 20–50 MPa; and / or, The feed temperature of the polymer melt to the low-pressure separator is 150–300°C; and / or, The feed rate of the polymer melt in the low-pressure separator is 0.3–5 m / s; and / or, The operating pressure of the low-pressure separator is 0–2.0 MPaG; and / or, The operating temperature of the low-pressure separator is 150–300°C.

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