A solid-liquid separation system for polypropylene

Abstract

The application provides a solid-liquid separation system of polypropylene, characterized in that the solid-liquid separation system comprises a separation chamber, a filtering device and a light component recovery device, the top of the separation chamber is provided with a feeding port and the light component recovery device, a powder outlet is arranged on the side wall of the separation chamber, and a fine powder discharge port is arranged at the bottom of the separation chamber; the filtering device comprises an upper layer filter screen, a lower layer filter screen and porcelain balls filled in a channel between the upper layer filter screen and the lower layer filter screen and arranged in the separation chamber; the surface of the porcelain balls is loaded with a catalyst having a propylene hydrogenation effect, the channel is provided with the powder outlet at the connection with the separation chamber, a material passing hole is arranged at the connection between the upper layer filter screen and the inner wall of the separation chamber, and the upper layer filter screen and the lower layer filter screen are both connected with electromagnetic vibrators. The separation system of the application reduces the hydrogen concentration brought into a gas phase reactor in the powder conveying process and improves the performance of the impact-resistant product.

Description

Technical Field

[0001] This invention relates to the technical field of polyolefin production, and more specifically to a solid-liquid separation system for polypropylene. Background Technology

[0002] Currently, domestic liquid-phase bulk polypropylene production processes all use heating and vaporizing liquid propylene to separate propylene from polypropylene powder. The powder process requires a large amount of steam, resulting in high energy consumption. Without separation, the liquid propylene enters the downstream system, leading to uncontrollable low temperatures or components in the gas phase reactor, resulting in poor product quality. Furthermore, the lack of recovery of large quantities of liquid propylene leads to emissions and significantly increases production costs.

[0003] CN116474561A discloses a liquid-solid separation device, including a frame with a control system, a feed inlet, two rollers, a tensioning device, and other components. A separation membrane is mounted on the two rollers and the tensioning device. A vacuum chamber is located below the separation membrane between the two rollers. A transverse vibration device and a positive pressure device, fixedly connected to the top of the frame, are sequentially arranged between the two rollers. The separation medium in this technology is the separation membrane. By installing multiple flushing nozzles on the desorption block and a cleaning and adjustment device at the bottom of the vacuum chamber, online cleaning of the separation membrane is achieved, reducing the difficulty of cleaning the membrane, preventing clogging, improving separation efficiency, reducing costs, and increasing benefits. This technology integrates wastewater collection, filtration, and clean water collection, achieving timely water treatment, improving the recycling rate of water resources, reducing external water consumption, and constructing a water circulation system. This invention is applicable to water systems; however, because water is a poison to polypropylene catalysts, polypropylene powder cannot be separated using water.

[0004] CN105521642A relates to a self-driven, directional backwashing circulating regeneration jet device and its usage method. The device includes a collection chamber, a first jet inlet, a mixing chamber, an output section, a jet outlet, and a second jet inlet. The collection chamber has a cylindrical structure. Two first jet inlets are located at the top of the collection chamber, with an included angle X between them. The inlet ends of the two first jet inlets are connected to a backwashing pipeline, and the outlet ends of the two first jet inlets are located above the mixing chamber within the collection chamber. The bottom outlet of the mixing chamber is connected to the inlet of the output section. The output section extends out of the bottom of the collection chamber and is movably connected to the bottom of the collection chamber, with the outlet end configured as a funnel-shaped jet outlet. A second jet inlet is also located on the upper side wall of the collection chamber, and the second jet inlet is horizontally tangent to the side wall of the collection chamber. This invention enables self-driven directional adjustment, avoiding problems such as localized deformation and erosion damage of the filter screen, and extending the service life of the rotating filter screen. This invention employs a self-driven, directional backwashing and regeneration jet device, aiming to reduce the impact force on rotating filters in existing technologies, overcome problems such as filter deformation and erosion damage caused by stress fatigue, thereby extending the service life of rotating filters and improving the uneven backwashing of different parts of the filter screen in existing technologies, reducing the "bridging" phenomenon of particulate impurities. This invention uses water as the rinsing fluid and is not suitable for polypropylene devices. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a polypropylene liquid-solid separation device, which separates propylene liquid and polypropylene powder by filtering through two layers of electromagnetically vibrating filter screens, and consumes the residual hydrogen in propylene by setting high-strength ceramic balls loaded with propylene hydrogenation catalyst on the lower filter screen, thereby achieving control of the hydrogen concentration in the counter-impact reactor.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a solid-liquid separation system for polypropylene, the solid-liquid separation system including a separation chamber, a filtration device and a light component recovery device, the top of the separation chamber is provided with a feed inlet and the light component recovery device, the side wall of the separation chamber is provided with a powder outlet, and the bottom of the separation chamber is provided with a fine powder discharge outlet.

[0008] The filtration device includes an upper filter screen, a lower filter screen, and ceramic balls filled in the channel between the upper filter screen and the lower filter screen, all mounted in the separation chamber. The surface of the ceramic balls is loaded with a catalyst that has a propylene hydrogenation effect. The powder outlet is provided at the connection between the channel and the separation chamber. A material passage hole is provided at the connection between the upper filter screen and the inner wall of the separation chamber.

[0009] Both the upper and lower filter screens are connected to electromagnetic vibrators.

[0010] In some specific embodiments, both the upper and lower filter screens are inclined at an angle of 30° to the horizontal; preferably, the inclination angle is 45° to 60°, for example, 50°. In some more specific embodiments, the upper and lower filter screens can be parallel or non-parallel, depending on the specific requirements. Since the upper filter screen is inclined within the separation chamber, the material passage is located at the lowest point in the horizontal direction of the upper filter screen, so that the powder screened out by the upper filter screen falls into the channel and is then discharged from the powder outlet outside the system.

[0011] In some specific embodiments, the upper filter screen and the lower filter screen are composed of multiple long strip-shaped screens.

[0012] In a specific embodiment of the solid-liquid separation system of the present invention, the screens of the upper filter screen and the lower filter screen extend in different directions. In some specific embodiments, the elongated screens in the upper filter screen are distributed laterally, realizing the separation of polypropylene powder and propylene liquid; the elongated screens in the lower filter screen are distributed longitudinally and are more compact, further separating the fine powder entrained in the upper dripping propylene liquid.

[0013] In some specific embodiments, the gap between each screen in the upper filter screen is 150-400 μm, preferably 200-300 μm, for example, 250 μm; the gap between each screen in the lower filter screen is 10-150 μm, preferably 35-100 μm, for example, 70 μm.

[0014] In the solid-liquid separation system provided by this invention, the catalyst loaded on the ceramic balls for propylene hydrogenation is a palladium-based catalyst. As is well known to those skilled in the art, the palladium-based catalyst for propylene hydrogenation can be specifically selected from metallic palladium, palladium on carbon, or palladium alumina catalyst. In the specific separation process, the catalyst-loaded ceramic balls can consume the residual hydrogen in the propylene powder. In some more specific embodiments, the ceramic balls are placed on a lower filter screen and can be fixed at intervals by baffles to avoid collisions between multiple sets of ceramic balls.

[0015] In some specific embodiments, the bottom of the separation chamber is a conical bottom surface; a steam jacket is provided on the fine powder discharge port.

[0016] In the solid-liquid separation system provided by the present invention, the light component recovery device is a condenser. After the gas phase component carrying propylene liquid is condensed by the condenser, the condensed propylene liquid flows back to the upper layer of the filter screen in the solid-liquid separation system.

[0017] In the solid-liquid separation system provided by the present invention, the operating pressure of the solid-liquid separation system is controlled at 1.5 to 4.2 MPa, preferably 2.5 to 3.5 MPa, for example, 3 MPa; the operating temperature of the solid-liquid separation system is controlled at 40 to 90°C, preferably 45 to 60°C, for example, 50°C.

[0018] In some specific embodiments, the vibration frequency of the electromagnetic vibrator is 25 to 100 Hz, preferably 50 to 60 Hz, for example, 55 Hz.

[0019] The above technical solution achieves the following technical effects:

[0020] The polypropylene solid-liquid separation system provided by this invention avoids the traditional gas-solid separation method that uses a large amount of steam for heating. The amount of steam used is less than 1 / 20 of that of the traditional flash evaporation method, and the amount of circulating water consumed is less than 1 / 30 of that of the traditional flash evaporation method, which greatly saves energy consumption.

[0021] The solid-liquid separation system provided by this invention reduces the hydrogen concentration introduced into the gas phase reactor during powder transportation by adding ceramic balls with propylene hydrogenation function between two layers of filter screens, thereby improving the performance of impact-resistant products. Attached Figure Description

[0022] Figure 1 This is a specific embodiment of the polypropylene solid-liquid separation system of the present invention;

[0023] Figure 2 This is a specific embodiment of the upper filter screen in the polypropylene solid-liquid separation system of the present invention;

[0024] Figure 3 This is a specific embodiment of the lower filter screen in the polypropylene solid-liquid separation system of the present invention;

[0025] Among them, 1. feed inlet, 2. upper filter screen, 3. lower filter screen, 4. ceramic ball, 5. powder outlet, 6. electromagnetic vibrator, 7. feed hole, 8. fine powder discharge port, 9. screen, 10. light component recovery device, 11. steam jacket, 12. liquid phase propylene recovery pipeline. Detailed Implementation

[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0027] The polypropylene solid-liquid separation system provided by this invention is as follows: Figure 1As shown, the system includes a separation chamber, a filtration device, and a light component recovery device 10. The top of the separation chamber has a feed inlet 1 and the light component recovery device 10. A powder outlet 5 is located on the side wall of the separation chamber, and a fine powder discharge outlet 8 is located at the bottom of the separation chamber. In some specific embodiments, the bottom of the separation chamber is conical, used to collect the propylene liquid while the solid phase mixed in with the propylene liquid accumulates at the bottom of the separation chamber. More specifically, the fine powder discharge outlet 8 is located at the apex of the conical bottom surface, and the accumulated solid phase is discharged through the fine powder discharge outlet.

[0028] The filtration device of the solid-liquid separation system of the present invention includes an upper filter screen 2, a lower filter screen 3, and ceramic balls 4 filled in the channel between the upper filter screen 2 and the lower filter screen 3, all mounted in the separation chamber. A palladium-based catalyst with propylene hydrogenation activity is loaded on the surface of the ceramic balls 4. Electromagnetic vibrators 6 are connected to both the upper filter screen 2 and the lower filter screen 3. Under the action of the electromagnetic vibrators 6, the propylene liquid and polypropylene powder are initially separated by the upper filter screen 2. The propylene liquid and a small amount of fine powder after the initial filtration enter the lower filter screen 3, where the polypropylene fine powder is separated from the propylene liquid.

[0029] In some specific implementations, the vibration frequency of the electromagnetic vibrator 6 is 50-60Hz.

[0030] The solid-liquid separation system of the present invention has a powder outlet 5 at the connection between the channel between the upper filter screen 2 and the lower filter screen 3 and the separation chamber. A material passage hole 7 is opened at the connection between the upper filter screen 2 and the inner wall of the separation chamber. The polypropylene powder obtained by the initial separation of the upper filter screen 2 falls into the channel through the material passage hole 7, and then is discharged from the separation system through the powder outlet 5. It is then transported through pipeline to the gas phase reactor for the production of impact-resistant products or directly enters the powder post-processing unit.

[0031] In some specific embodiments, the inclination angles of the upper filter screen 2 and the lower filter screen 3 with the horizontal direction are both 30-70°, preferably 45-60°, for example, 50° or 55°.

[0032] like Figure 2 , 3 As shown, in the solid-liquid separation system of the present invention, the upper filter screen 2 and the lower filter screen 3 are composed of multiple elongated screens 9. Preferably, the elongated screens 9 in the upper filter screen 2 are distributed laterally, and the elongated screens 9 in the lower filter screen 3 are distributed longitudinally. In some specific embodiments, the gap between each screen 9 in the upper filter screen 2 is 150–400 μm, preferably 200–300 μm; the gap between each screen 9 in the lower filter screen 3 is 10–150 μm, preferably 35–100 μm.

[0033] In the solid-liquid separation system of the present invention, the light component recovery device 10 is a condenser. After the gas phase component carrying propylene liquid is condensed by the condenser, the condensed propylene liquid flows back to the upper filter screen 2, which promotes the separation effect of liquid and solid.

[0034] In some specific embodiments, the operating pressure of the solid-liquid separation system is controlled at 1.5 to 4.2 MPa, preferably 2.5 to 3.5 MPa; the operating temperature of the solid-liquid separation system is controlled at 40 to 90°C, preferably 45 to 60°C.

[0035] The liquid-solid separation device provided by this invention separates polypropylene powder and propylene liquid after passing through a homopolymer reactor. The specific separation process is as follows:

[0036] Polypropylene powder and propylene liquid produced by the homopolymer reactor enter the polypropylene liquid-solid separation system through inlet 1. Under the vibration of electromagnetic vibrator 6, they pass through upper filter screen 2 and are initially separated into propylene liquid and polypropylene powder. At the same time, the gas carried in the powder is condensed by the top condenser, and the non-condensable vapor is discharged into the light component recovery. The condensed propylene liquid is sprayed into the surface of the screen 9 of upper filter screen 2 through the pipeline at the bottom of the condenser to promote the liquid-solid separation effect.

[0037] After initial filtration, the propylene liquid and a small amount of fine polypropylene powder fall onto the lower filter screen 3. Under the vibration of the electromagnetic vibrator 6, further separation occurs, resulting in fine polypropylene powder and propylene liquid. Simultaneously, under the catalytic action of the palladium-based catalyst loaded between the upper filter screen 2 and the lower filter screen 3, a small amount of hydrogen entrained in the propylene liquid reacts with propylene to generate propane. The hydrogen content in the powder entering the subsequent system is extremely low, which is beneficial for improving the performance of impact-resistant products. Most of the fine polypropylene powder obtained above remains on the lower filter screen 3, while a very small portion falls into the lower part of the separation chamber along with the separated propylene liquid. A liquid propylene recovery pipeline 12 is installed on the conical sidewall below the separation chamber. After settling, the fine polypropylene powder reaches the bottom of the cone and is discharged through the bottom pipeline. A steam jacket 11 is installed on the bottom pipeline. The propylene liquid carrying the fine powder is vaporized and enters the powder post-processing system. The discharge of fine polypropylene powder from the bottom of the cone can purify the propylene liquid and prevent pipeline blockage caused by fine powder deposition or polymerization reaction.

[0038] The polypropylene fine powder remaining on the lower filter screen 3, along with the powder falling through the feed hole 7 into the channel between the upper filter screen 2 and the lower filter screen 3, is discharged from the powder outlet 5 and transported via pipeline to the gas phase reactor for the production of impact-resistant products or directly into the powder post-processing unit.

[0039] Example 1

[0040] Polypropylene powder and liquid propylene produced by the liquid phase bulk reactor enter as follows: Figure 1The polypropylene solid-liquid separation system shown operates at a pressure of 3.0 MPa and a temperature of 45°C, separating the solid and liquid components through two layers of filters equipped with electromagnetic vibrators (vibration frequency of 50 Hz). The upper and lower filter layers are inclined at 45° to the horizontal. The upper filter layer contains transversely distributed elongated screens with a spacing of 300 μm between each screen, while the lower filter layer contains longitudinally distributed elongated screens with a spacing of 100 μm between each screen. The channel between the upper and lower filter layers is filled with high-strength ceramic balls containing a palladium catalyst.

[0041] Example 2

[0042] Polypropylene powder and liquid propylene produced by the liquid phase bulk reactor enter as follows: Figure 1 The polypropylene solid-liquid separation system shown operates at a pressure of 3.0 MPa and a temperature of 45°C, separating the solid and liquid components through two layers of filters equipped with electromagnetic vibrators (vibration frequency of 50 Hz). The upper and lower filter layers are inclined at 60° to the horizontal. The upper filter layer contains transversely distributed elongated screens with a spacing of 300 μm between each screen, while the lower filter layer contains longitudinally distributed elongated screens with a spacing of 100 μm between each screen. The channel between the upper and lower filter layers is filled with high-strength ceramic balls containing a palladium catalyst.

[0043] Example 3

[0044] Polypropylene powder and liquid propylene produced by the liquid phase bulk reactor enter as follows: Figure 1 The polypropylene solid-liquid separation system shown operates at a pressure of 3.0 MPa and a temperature of 45°C, separating the solid and liquid components through two layers of filters equipped with electromagnetic vibrators (vibration frequency of 50 Hz). The upper and lower filter layers are inclined at 60° to the horizontal. The upper filter layer has transversely distributed elongated screens with a spacing of 200 μm between each screen, while the lower filter layer has longitudinally distributed elongated screens with a spacing of 100 μm between each screen. The channel between the upper and lower filter layers is filled with high-strength ceramic balls containing palladium-on-carbon catalyst.

[0045] Example 4

[0046] Polypropylene powder and liquid propylene produced by the liquid phase bulk reactor enter as follows: Figure 1The polypropylene solid-liquid separation system shown operates at a pressure of 3.0 MPa and a temperature of 45°C, separating the solid and liquid components through two layers of filters equipped with electromagnetic vibrators (vibration frequency of 50 Hz). The upper and lower filter layers are inclined at 60° to the horizontal. The upper filter layer has transversely distributed elongated screens with a spacing of 200 μm between each screen, while the lower filter layer has longitudinally distributed elongated screens with a spacing of 35 μm between each screen. The channel between the upper and lower filter layers is filled with high-strength ceramic balls containing palladium-alumina catalyst.

[0047] Comparative Example 1

[0048] The difference between this comparative example and the solid-liquid separation system used in Example 4 is that no electromagnetic vibrator is connected to the upper filter screen.

[0049] Comparative Example 2

[0050] The difference between this comparative example and the solid-liquid separation system used in Example 4 is that neither the upper nor the lower filter screen is connected to an electromagnetic vibrator.

[0051] Comparative Example 3

[0052] The difference between this comparative example and the solid-liquid separation system used in Example 4 is that the ceramic balls between the upper and lower filter screens do not have a catalytic function.

[0053] Comparative Example 4

[0054] The difference between this comparative example and the solid-liquid separation system used in Example 4 is that the light component recovery device is not used at the top of the solid-liquid separation system, and there is no rinsing liquid on the material on the upper filter screen.

[0055] The running time of the separation system in the above embodiments and comparative examples is shown in Table 1 below. The fine powder content in the separated propylene liquid, the hydrogen concentration in the obtained powder, and the performance of the impact-resistant products prepared by using the powder are shown in Table 2 below.

[0056] Table 1

[0057]

[0058] Table 2

[0059]

[0060] As can be seen from the data in the table above, the separation system of the present invention significantly improves the operating cycle of the separation system by connecting an electromagnetic vibrator to the filter screen; at the same time, the ceramic balls play a resonant role between the two layers of filter screen, which can significantly improve the operating cycle of the filter screen, and the ceramic balls with catalyst function significantly reduce the concentration of hydrogen entering the downstream.

Claims

1. A solid-liquid separation system for polypropylene, characterized by, The solid-liquid separation system comprises a separation chamber, a filtering device and a light component recovery device, the top of the separation chamber is provided with a feeding port and the light component recovery device, a powder outlet is formed on the sidewall of the separation chamber, and a fine powder discharge port is arranged at the bottom of the separation chamber; wherein the filtering device comprises an upper layer filter screen, a lower layer filter screen and porcelain balls filled in the channel between the upper layer filter screen and the lower layer filter screen; the surface of the porcelain balls is loaded with a propylene hydrogenation catalyst, the channel is connected with the powder outlet of the separation chamber, and a material passing hole is formed at the connection between the upper layer filter screen and the inner wall of the separation chamber; The upper layer filter screen and the lower layer filter screen are both connected with electromagnetic vibrators; The light component recovery device is a condenser, and the gas phase component entraining propylene liquid is condensed through the condenser, and the condensed propylene liquid flows back to the upper side of the upper layer filter screen in the solid-liquid separation system.

2. The solid-liquid separation system of claim 1, wherein, The inclination angle of the upper layer filter screen and the lower layer filter screen with the horizontal direction is 30-70°. The material passing hole is formed at the lowest position of the upper layer filter screen in the horizontal direction.

3. The solid-liquid separation system of claim 2, wherein, The inclination angle of the upper layer filter screen and the lower layer filter screen with the horizontal direction is 45-60°.

4. The solid-liquid separation system of claim 2, wherein, The upper layer filter screen and the lower layer filter screen are composed of a plurality of long strip-shaped screen meshes.

5. The solid-liquid separation system of claim 4, wherein, The long strip-shaped screen meshes in the upper layer filter screen are distributed horizontally. The long strip-shaped screen meshes in the lower layer filter screen are distributed vertically.

6. The solid-liquid separation system of claim 5, wherein, The gap between the screen meshes in the upper layer filter screen is 150-400 μm. The gap between the screen meshes in the lower layer filter screen is 10-150 μm.

7. The solid-liquid separation system of claim 6, wherein The gap between the screen meshes in the upper layer filter screen is 200-300 μm.

8. The solid-liquid separation system of claim 6, wherein, The gap between the screen meshes in the lower layer filter screen is 35-100 μm.

9. The solid-liquid separation system according to any one of claims 1 to 8, characterized in that, The propylene hydrogenation catalyst loaded on the porcelain balls is a palladium catalyst.

10. The solid-liquid separation system of claim 9, wherein, The bottom of the separation chamber is a conical bottom surface. A steam jacket is arranged on the fine powder discharge port.

11. The solid-liquid separation system according to any one of claims 1 to 8, 10, wherein The operating pressure of the solid-liquid separation system is controlled to be 1.5-4.2 MPa. The operating temperature of the solid-liquid separation system is controlled to be 40-90℃.

12. The solid-liquid separation system of claim 11, wherein, The operating pressure of the solid-liquid separation system is controlled to be 2.5-3.5 MPa.

13. The solid-liquid separation system of claim 11, wherein, The operating temperature of the solid-liquid separation system is controlled to be 45-60℃.

14. The solid-liquid separation system of claim 11, wherein, The vibration frequency of the electromagnetic vibrator is 25-100 Hz.

15. The solid-liquid separation system of claim 14, wherein, The vibration frequency of the electromagnetic vibrator is 50-60 Hz.

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