Multi-kettle series continuous polymerization system and production method

Abstract

The invention provides a multi-kettle series continuous polymerization system and a production method, and relates to the technical field of chemical production equipment. The system comprises a plurality of polymerization kettles which are connected in series, the polymerization kettles are sequentially connected in series through overflow pipes, and at least one overflow pipe is arranged in each polymerization kettle; the overflow pipe extends downwards from the inside of the polymerization kettle and is led out from the bottom or the side wall of the lower part of the polymerization kettle, the overflow pipe of the previous-stage polymerization kettle is led to a feeding hole of the next-stage polymerization kettle, and the overflow pipe of the last-stage polymerization kettle is led to a post-treatment system; a potential difference exists between the adjacent polymerization kettles; and the overflow pipe forms an inclined angle between a part or all of the micro-branched pipe sections of the main body section in the polymerization kettle and a plumb line. Stable liquid level control and stable material transmission are achieved through a pure mechanical overflow pipe structure, an interstage pump and a complex detection control instrument are not needed, and equipment investment, maintenance cost and energy consumption are reduced; the material flows downwards naturally, gas-liquid entrainment is reduced, the pressure fluctuation resistance is high, and operation is stable and reliable.

Description

Technical Field

[0001] This disclosure relates to the field of chemical production equipment technology, and in particular to a multi-reactor series continuous polymerization system and production method. Background Technology

[0002] In multi-reactor series continuous polymerization processes, achieving stable material transfer and precise liquid level control between reactors is crucial. Related technologies mainly rely on two methods: one is to use pumps, regulating valves, and complex detection instruments to construct an active control system, which involves large equipment investment, high maintenance costs, and complex control logic; the other is to use reactor top overflow or siphon methods, which are susceptible to system pressure fluctuations, and the upward flow of materials can easily entrain gas, resulting in poor operational stability, especially during start-up or changes in operating conditions. Therefore, there is an urgent need for a simple and stable inter-reactor material transfer and control scheme. Summary of the Invention

[0003] This disclosure aims to at least partially address one of the technical problems in the related art.

[0004] Therefore, the first aspect of this disclosure provides a multi-tandem continuous polymerization system, including multiple polymerization tanks arranged sequentially in series along the material flow direction;

[0005] The multiple polymerization reactors are connected in series via overflow pipes. Each polymerization reactor is equipped with at least one overflow pipe. The overflow pipe extends downward from the inside of the polymerization reactor and is led out from the bottom or lower side wall of the polymerization reactor. The overflow pipe of the previous polymerization reactor leads to the feed port of the next polymerization reactor, and the overflow pipe of the last polymerization reactor leads to the post-processing system. There is a positional difference between adjacent polymerization reactors; The overflow pipe has a tilt angle between some or all of its differential pipe sections in the main section of the polymerization reactor and the vertical line.

[0006] In some embodiments of this disclosure, the angle between some or all of the differential pipe segments of the main body of the overflow pipe and the vertical line ranges from 5 to 30 degrees.

[0007] In some embodiments of this disclosure, the angle between some or all of the differential pipe segments of the main body of the overflow pipe and the vertical line ranges from 10 to 15 degrees.

[0008] In some embodiments of this disclosure, the overflow pipe is a straight overflow pipe or a curved overflow pipe.

[0009] In some embodiments of this disclosure, the curved overflow pipe is a spiral overflow pipe.

[0010] In some embodiments of this disclosure, the inlet height of the overflow pipe in the polymerization reactor is adjustable to set and maintain the liquid level of the corresponding polymerization reactor.

[0011] In some embodiments of this disclosure, the height of the overflow pipe inside the polymerization reactor is adjusted by any of the following methods: replacing pipe sections of different lengths, using a liftable sleeve with a locking mechanism, or using a flexible pipe in conjunction with a positioning component.

[0012] In some embodiments of this disclosure, an anti-vortex device is provided at the inlet end of the overflow pipe and / or inside the pipe.

[0013] In some embodiments of this disclosure, the anti-vortex device is a plurality of axially arranged guide fins along the inner wall of the overflow pipe, and the guide fins are evenly distributed circumferentially.

[0014] In some embodiments of this disclosure, the anti-vortex device is an anti-vortex baffle disposed above the inlet end of the overflow pipe.

[0015] In some embodiments of this disclosure, each polymerization reactor is provided with a discharge port at the bottom, either independently or shared with the feed port. The discharge port is connected to a discharge pump, and the discharge pipe connected to the discharge port leads to the feed port of the next polymerization reactor or directly to the post-processing system.

[0016] In some embodiments of this disclosure, the discharge pump is a gear pump.

[0017] The second aspect of this disclosure provides a method for producing a multi-reactor tandem continuous polymerization system as described in the first aspect above, comprising: Determine the set liquid level for each polymerization reactor according to the process requirements; Adjust the height of the inlet end of the overflow pipe in each polymerization reactor according to the set liquid level of each polymerization reactor; Reactant material is continuously fed into the polymerization reactor at the first end of the series connection; When the liquid level in the polymerization reactor rises to the height of the corresponding overflow pipe inlet, the material automatically flows into the next polymerization reactor under the action of gravity until the system reaches a stable operating state.

[0018] The multi-tank continuous polymerization system disclosed in this disclosure utilizes gravity flow due to elevation difference, eliminating the need for interstage pumps during continuous operation. This eliminates the need for complex level detection instruments and active flow control units, reducing equipment investment, maintenance complexity, and energy consumption. As it is a purely mechanical structure, it avoids the risk of uncontrolled leveling due to control instrument or system failures. Compared to the material transfer method using a siphon-operated overflow pipe at the top of the reactor, which is susceptible to pressure fluctuations, the multi-tank continuous polymerization system proposed in this disclosure allows for natural downward material flow in practical scenarios. Furthermore, the inclined installation of the overflow pipe facilitates the separation and escape of gases in the reaction gas-liquid system before outflow, reducing gas-liquid entrainment. It is less affected by inter-reactor pressure fluctuations, ensuring stability and reliability, and simplifying start-up and operation. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which: Figure 1 This is a schematic diagram of a multi-reactor series continuous polymerization system provided in an embodiment of the present disclosure; Figure 2 This is a schematic flow diagram of a production method for a multi-reactor series continuous polymerization system provided in an embodiment of this disclosure. Detailed Implementation

[0020] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0021] Specifically, the multi-reactor tandem continuous polymerization system and production method of this disclosure are described below with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of a multi-tank series continuous polymerization system provided in an embodiment of this disclosure. It should be noted that... Figure 1 Taking only three polymerization reactors as an example, there is no limit to the number of polymerization reactors in a multi-reactor series continuous polymerization system.

[0023] like Figure 1 As shown, the multi-reactor continuous polymerization system includes multiple polymerization reactors arranged in series along the material flow direction: polymerization reactor 1-1, polymerization reactor 1-2, and polymerization reactor 1-3; overflow pipe 4-1 and overflow pipe 4-2; gas feed line 5; solvent feed line 6; catalyst or auxiliary catalyst feed line 7; and discharge pipe 8.

[0024] In this system, multiple polymerization reactors are connected in series via overflow pipes. Each polymerization reactor has at least one overflow pipe, which extends downwards from the inside of the reactor and exits from the bottom or lower side wall. The overflow pipe of the preceding polymerization reactor connects to the feed inlet of the next polymerization reactor. The overflow pipe of the final polymerization reactor connects to the post-processing system.

[0025] There is a positional difference between adjacent polymerization reactors, which, along with the overflow pipe, enables gravity-driven transport of liquid materials between the reactors. The overflow pipe has an inclination angle between a portion or all of its main body section and the vertical line within the polymerization reactor. Preferably, this inclination angle ranges from 5 to 30 degrees, and more preferably from 10 to 15 degrees.

[0026] In one implementation, the overflow pipe is a straight overflow pipe or a curved overflow pipe. In one embodiment, when the inclination angle of the main body section of the overflow pipe is greater than or equal to a preset angle threshold, the curved overflow pipe can be a spiral overflow pipe to avoid collisions between the overflow pipe and components such as the vessel wall and the agitator when the inclination angle is large.

[0027] In one implementation, if an infusion pump is provided, the polymerization reactors in a multi-reactor series continuous polymerization system can also be set without any positional difference between them.

[0028] Overflow pipe 4-1 is located between polymerization reactors 1-1 and 1-2, and overflow pipe 4-2 is located between polymerization reactors 1-2 and 1-3. Each overflow pipe extends downward from the inlet end inside the polymerization reactor and exits from the bottom or lower side wall of the polymerization reactor. The overflow pipe of the preceding polymerization reactor leads to the feed inlet of the next polymerization reactor. It should be noted that the directional descriptions of "previous stage" and "next stage" are relative to the material flow sequence.

[0029] Alternatively, the overflow pipe can be led out from the bottom discharge port of the vessel in a concentric manner.

[0030] by Figure 1 For example, overflow pipe 4-1 extends downward from the overflow inlet end inside the polymerization reactor (i.e., polymerization reactor 1-1), with the overflow port located in the liquid phase region of polymerization reactor 1-1. The outlet end of overflow pipe 4-1 is connected to the feed port at the bottom or lower side wall of the next-stage polymerization reactor (i.e., polymerization reactor 1-2). The overflow pipe 4-2 is set up in the same way.

[0031] In one embodiment, the inlet end of the overflow pipe in the front polymerization reactor is higher than the set liquid level height of the next polymerization reactor. The static pressure difference generated by this difference is used as a driving force to drive the liquid material from the front reactor to flow smoothly into the rear reactor through the overflow pipe, so as to adapt to the liquid level height required by different processes.

[0032] The overflow pipe's inlet height within the polymerization reactor is adjustable to maintain different reactor liquid levels according to process settings. Liquid level control is reliable, stable, and offers high operational flexibility. Figure 1 For example, the pipe height of overflow pipe 4-1 in polymerization reactor 1-1 and the pipe height of overflow pipe 4-2 in polymerization reactor 1-2 determine the liquid level height in the corresponding polymerization reactor, enabling flexible operation from partially full to full reactor. Optionally, the height of the overflow pipe in the polymerization reactor can be adjusted by any of the following methods: replacing pipe sections of different lengths, using a liftable sleeve with a locking mechanism, or using flexible pipe with positioning components. Compared to related technologies that set a discharge port at a fixed height on the side wall of the polymerization reactor to provide materials for the next stage of polymerization reactor, the multi-reactor series continuous polymerization system with adjustable overflow pipe height proposed in this disclosure is more flexible and can meet the production or experimentation requirements of different process conditions, especially suitable for scenarios that require frequent adjustments to process conditions.

[0033] In some embodiments of this disclosure, an anti-vortex device may be provided at the inlet end of the overflow pipe and / or inside the pipe. Figure 1 (Not shown) to further optimize the flow state, prevent eddies from forming in the overflow pipe and entraining gas, and significantly improve the stability of liquid level control and material transfer.

[0034] Optionally, the anti-vortex device may be a plurality of axially arranged guide fins along the inner wall of the overflow pipe, with the guide fins evenly distributed circumferentially. In one example, the length of the guide fins may extend to a distance of at least 3 to 30 times the pipe diameter below the pipe opening, and the height may be 1 / 2 to 1 / 15 of the inner diameter of the pipe.

[0035] Optionally, the anti-vortex device can be an anti-swirl baffle installed above the inlet end of the overflow pipe. The anti-swirl baffle is fixed to the pipe opening by a support column, and its diameter is approximately 1.5 to 2.0 times the diameter of the pipe opening, in order to break up any vortices that may form and allow the liquid to flow in smoothly.

[0036] Optionally, the position difference between polymerization reactors can be calculated and determined based on the properties of the material (such as viscosity and density) and the expected flow rate to ensure that the flow rate meets the process requirements.

[0037] In addition to the gas-phase interconnection and isobaric operation of each reactor, with liquid level controlled solely by gravity flow based on the height difference between adjacent polymerization reactors, an independent pressure control system can also be installed in each polymerization reactor within the system. Based on process conditions, by setting the total system feed rate, the overflow pipe height in each polymerization reactor, and the gas pressure, precise control of the material level within the polymerization reactors can be achieved even in an operating mode where a positive pressure difference exists between the reactors.

[0038] In some embodiments of this disclosure, each polymerization reactor is provided with an independent or shared discharge port at the bottom. The discharge port is connected to a discharge pump and is connected to a discharge pipe 8. The discharge pipe leads to the inlet of the next polymerization reactor or directly to the post-processing system, which is used to stably or quickly and completely empty the material in the reactor when the polymerization reaction is terminated or when needed.

[0039] Alternatively, the discharge pump can be a gear pump.

[0040] The multi-tank continuous polymerization system of this embodiment utilizes gravity flow due to elevation difference, eliminating the need for interstage pumps during continuous operation. This eliminates the need for complex level detection instruments and active flow control units, reducing equipment investment, maintenance complexity, and energy consumption. The inclined overflow pipe facilitates gas-liquid separation within the pipe, with gas flowing upwards and liquid flowing downwards, reducing the risk of gas blockage and promoting gas escape. As it is a purely mechanical structure, it avoids the risk of uncontrolled level fluctuations due to control instrument or system malfunctions. Compared to the material transfer method of the siphon-operated overflow pipe at the top of the reactor, which is susceptible to pressure fluctuations, the multi-tank continuous polymerization system proposed in this disclosure allows for natural downward material flow in practical scenarios. This facilitates the separation and escape of gas in the reaction gas-liquid system before it flows out, reducing gas-liquid entrainment. It is less affected by inter-reactor pressure fluctuations, ensuring stability and reliability, and simplifying start-up and operation.

[0041] Figure 2 This is a schematic flow diagram of a production method for a multi-reactor series continuous polymerization system provided in an embodiment of this disclosure. Figure 2 As shown, the production method may include the following steps: Step 201: Determine the set liquid level for each polymerization reactor according to the process requirements.

[0042] Step 202: Adjust the height of the inlet end of the overflow pipe in each polymerization reactor according to the set liquid level of each polymerization reactor.

[0043] Step 203: Continuously introduce the reaction material into the polymerization reactor at the first end of the series connection.

[0044] Step 204: When the liquid level in the polymerization reactor rises to the height of the corresponding overflow pipe inlet, the material automatically flows into the next polymerization reactor through the overflow pipe under the action of gravity until the system reaches a stable operating state.

[0045] Regarding the methods in the above embodiments, the specific manner in which each step is performed has been described in detail in the embodiments of the system, and will not be elaborated here.

[0046] The multi-reactor tandem continuous polymerization system proposed in this disclosure can be widely used in continuous polymerization processes of polyolefins (such as polyethylene and polypropylene), ethylene propylene rubber, POE (polyolefin elastomer), polyester, etc., and is particularly suitable for experimental research and industrial production of small and medium-sized products with multiple grades.

[0047] In one embodiment, to Figure 1For example, this multi-tank continuous polymerization system can be used for solution polymerization of ethylene propylene rubber, solution polymerization of POE (polyolefin elastomer), and slurry polymerization of polyethylene (such as HDPE) or polypropylene. The polymerization reactors are arranged sequentially from high to low, with an appropriate height difference H between adjacent reactors (e.g., 0.3 or more, calculated based on flow rate and material properties). Each polymerization reactor is equipped with an overflow pipe (4-1, 4-2, 4-3), installed at a 15-degree angle. Figure 1 (Not shown in the diagram) The overflow pipe extends outside the reactor via a flange, and its height is adjustable (e.g., via a graduated lifting sleeve). The overflow pipe outlet of the first reactor connects to the feed inlet of the second reactor, and the overflow pipe of the last polymerization reactor connects to the discharge pipe 8. The polymerization reactors are equipped with necessary temperature control systems (such as jacketed cooling water). A vapor-phase interconnection feed / balance pipe is installed between the three reactors.

[0048] The operation process is as follows: 1. Liquid level setting: According to the experimental plan, the target liquid level of each vessel is set in advance (e.g., 75%). The pipe opening is fixed at the corresponding height by adjusting the insertion depth of the overflow pipe (4) of each vessel.

[0049] 2. System preparation: Replace the air in the system with nitrogen, and then add purified polymerization solvent (such as n-hexane) into the system.

[0050] 3. Feeding and Reaction Start-up: Start the feed pump to continuously introduce ethylene monomer, catalyst, and solvent into the first polymerization reactor (1-1). When the liquid level in the first reactor rises to the height of the overflow pipe (4-1), the liquid begins to flow automatically into the second polymerization reactor (1-2) through the overflow pipe due to the level difference H. Similarly, after the liquid level in the second reactor reaches the set value, the material overflows into the third polymerization reactor (1-3). By adjusting the total feed flow rate into the first reactor, the material throughput of the entire system can be indirectly controlled.

[0051] 4. Normal reaction: Under stable conditions, the liquid level in each reactor is automatically maintained at the overflow pipe height, achieving stable continuous operation. The reaction temperature of each reactor is controlled by circulating water within the jacket.

[0052] 5. Reaction Termination and Drainage: When it is necessary to terminate the reaction, stop feeding into the first reactor. After the material in each reactor has basically completed the gravity transfer, the material in the three reactors will polymerize independently for a period of time to achieve the same average residence time. Then, open the bottom discharge valves of each reactor in sequence to discharge the remaining polymer material in the reactor into the post-processing system at the same rate as gravity flow.

[0053] In the foregoing descriptions of the embodiments, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0055] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A multi-tank continuous polymerization system, comprising multiple polymerization tanks arranged in series along the material flow direction, characterized in that, The multiple polymerization reactors are connected in series via overflow pipes. Each polymerization reactor is equipped with at least one overflow pipe. The overflow pipe extends downward from the inside of the polymerization reactor and is led out from the bottom or lower side wall of the polymerization reactor. The overflow pipe of the previous polymerization reactor leads to the feed port of the next polymerization reactor, and the overflow pipe of the last polymerization reactor leads to the post-processing system. There is a positional difference between adjacent polymerization reactors; The overflow pipe has a tilt angle between some or all of its differential pipe sections in the main section of the polymerization reactor and the vertical line.

2. The multi-reactor series continuous polymerization system according to claim 1, characterized in that, The angle between some or all of the differential pipe sections of the main body of the overflow pipe and the vertical line ranges from 5 to 30 degrees.

3. The multi-reactor tandem continuous polymerization system according to claim 2, characterized in that, The angle between some or all of the differential pipe sections of the main body of the overflow pipe and the vertical line is in the range of 10-15 degrees.

4. The multi-reactor tandem continuous polymerization system according to claim 1, characterized in that, The overflow pipe is either a straight overflow pipe or a curved overflow pipe.

5. The multi-reactor tandem continuous polymerization system according to claim 4, characterized in that, The curved overflow pipe is a spiral overflow pipe.

6. The multi-reactor tandem continuous polymerization system according to claim 1, characterized in that, The inlet height of the overflow pipe inside the polymerization reactor is adjustable to set and maintain the liquid level in the corresponding polymerization reactor.

7. The multi-reactor tandem continuous polymerization system according to claim 6, characterized in that, The height of the overflow pipe inside the polymerization reactor can be adjusted by any of the following methods: replacing pipe sections of different lengths, using a liftable sleeve with a locking mechanism, or using flexible pipe with positioning components.

8. The multi-tank continuous polymerization system according to claim 1, characterized in that, An anti-vortex device is installed at the inlet end of the overflow pipe and / or inside the pipe.

9. The multi-reactor tandem continuous polymerization system according to claim 8, characterized in that, The anti-vortex device consists of several axially arranged guide fins along the inner wall of the overflow pipe, and the guide fins are evenly distributed circumferentially.

10. The multi-tank continuous polymerization system according to claim 8, characterized in that, The anti-vortex device is an anti-vortex baffle installed above the inlet end of the overflow pipe.

11. The multi-tank continuous polymerization system according to claim 1, characterized in that, Each of the polymerization reactors is provided with a discharge port at the bottom, either independently or shared with the feed port. The discharge port is connected to a discharge pump, and the discharge pipe connected to the discharge port leads to the feed port of the next polymerization reactor or directly to the post-processing system.

12. The multi-tank continuous polymerization system according to claim 11, characterized in that, The discharge pump is a gear pump.

13. A production method for a multi-reactor series continuous polymerization system as described in any one of claims 1-12, characterized in that, Includes the following steps: Determine the set liquid level for each polymerization reactor according to the process requirements; Adjust the height of the inlet end of the overflow pipe in each polymerization reactor according to the set liquid level of each polymerization reactor; Reactant material is continuously fed into the polymerization reactor at the first end of the series connection; When the liquid level in the polymerization reactor rises to the height of the corresponding overflow pipe inlet, the material automatically flows into the next polymerization reactor under the action of gravity until the system reaches a stable operating state.

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