PBT prepolymer heat exchange system
By designing the PBT prepolymer heat exchange system in the PBT process, the viscosity increase and heat dissipation difficulties caused by high reaction temperature in the prepolymerization kettle are solved, and more stable reaction conditions and higher quality products are achieved.
Patent Information
- Application Number
- CN202420856799.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-24
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2034-04-24
AI Technical Summary
In the PBT process, the high reaction temperature in the prepolymer kettle causes the viscosity of the prepolymer to increase after entering the final polymer kettle, making it difficult to dissipate heat, causing the temperature in the final polymer kettle to rise and affect product quality. The prior art strengthens the reaction conditions by increasing the catalyst and vacuum degree, but this can lead to problems such as blockage of the vacuum system, uneven molecular chain distribution and catalyst hydrolysis.
A PBT prepolymer heat exchange system is designed, including the main conveying pipeline and the thermal media circulation system. The main conveying pipeline is connected to the prepolymer conveying pump, filter, heat exchanger and thermometer. The thermal media circulation system automatically adjusts the thermal media temperature through the air-cooled fin heat exchanger and the regulating valve to achieve effective heat exchange of the prepolymer.
Through the prepolymer heat exchange system, the temperature before the prepolymer enters the final polymerization kettle is reduced, the reaction conditions are stabilized, the amount of catalyst is added is reduced, the use cycle of the vacuum system is extended, the molecular weight distribution is uniform, and the product quality is improved.
Smart Images
Figure CN222799699U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of heat exchange systems, in particular to a PBT prepolymer heat exchange system. Background Art
[0002] In the production process of polybutylene terephthalate (PBT), the three-kettle process consists of three reactors: esterification reactor, prepolymerization reactor, and final polymerization reactor. The polycondensation reaction is carried out in the prepolymerization reactor. Compared with the five-kettle process, the reaction residence time of the materials in the three-kettle process is greatly shortened, so it is necessary to strengthen the reaction conditions, speed up the reaction rate, and control the temperature of the reactor relatively high. However, the polycondensation reaction is an exothermic reaction. If the reaction temperature is high in the prepolymerization reactor reaction stage, the viscosity of the material will increase further after the prepolymer enters the final polymerization reactor, the fluidity will deteriorate, and heat dissipation will become more difficult, which will cause the temperature in the final polymerization reactor to continue to rise. The material in the final polymerization reactor has a high degree of polymerization and a long molecular chain. The higher reaction temperature will cause material degradation, molecular chain breakage, and an increase in the end carboxyl content, affecting product quality.
[0003] In the current PBT chemical process, a special prepolymer heat exchange system is generally not set up. In order to ensure the stable progress of the polycondensation reaction, a lower prepolymerization reaction temperature is generally used, and then the reaction conditions of the prepolymerization kettle are strengthened by increasing the amount of catalyst added and improving the vacuum degree of the prepolymerization kettle. However, a higher vacuum degree will increase the load of the vacuum system, and more oligomers will be extracted, which may easily cause the blockage of the prepolymerization vacuum system and affect the long-term operation of the device. A higher vacuum degree will also cause uneven distribution of the prepolymer molecular chain, affecting the viscosity adjustment of the subsequent final polymerization kettle. An increase in the amount of catalyst added will reduce the activation energy required for the reaction and accelerate the reaction rate, but it will also increase the ash and metal content of the slices, affecting the product quality, and the risk of catalyst hydrolysis will also increase, resulting in a shortened service life of the prepolymer filter. Frequent switching of the prepolymer filter not only increases the workload but also easily causes process fluctuations. Therefore, a PBT prepolymer heat exchange system is proposed. Utility Model Content
[0004] In order to solve the above problems, that is, to solve the problems raised by the above background technology, the utility model proposes a PBT prepolymer heat exchange system, which includes a main delivery pipeline, which is installed between a prepolymerization kettle and a final polymerization kettle, and the main delivery pipeline specifically includes a prepolymer delivery pump, a prepolymer filter, a prepolymer heat exchanger and an outlet prepolymer thermometer connected in sequence; the shell side inlet of the prepolymer heat exchanger is connected to a heat medium oil inlet pipeline, and the heat medium oil inlet pipeline specifically includes a regulating valve, a pump inlet valve, a heat medium filter, a heat medium delivery pump, a pump outlet valve and a heat medium temperature controller connected in sequence to the oil inlet, and the outlet end of the heat medium temperature controller is connected to the shell side inlet of the prepolymer heat exchanger;
[0005] The shell side outlet of the prepolymer heat exchanger is connected to a heat medium oil outlet pipeline, and the heat medium oil outlet pipeline specifically includes a heat medium outlet thermometer, a first valve and an air-cooled outlet thermometer connected in sequence. The heat medium outlet thermometer is connected to the shell side outlet of the prepolymer heat exchanger, and one end of an air-cooled cooling branch is also connected between the heat medium outlet thermometer and the first valve, and the other end of the air-cooled cooling branch is connected between the first valve and the air-cooled outlet thermometer. The air-cooled cooling branch specifically includes an air-cooled fin heat exchanger and a second valve. The outlet of the heat medium oil outlet pipeline is connected to the oil outlet through a check valve, and the outlet of the heat medium oil outlet pipeline is also connected between the regulating valve and the pump inlet valve for reflux into the prepolymer heat exchanger.
[0006] The utility model is further configured as follows: there are two air cooling branches.
[0007] The utility model is further configured as follows: the prepolymer heat exchanger is a shell-and-tube heat exchanger, the medium in the tube side is the prepolymer, and the medium in the shell side is the heat medium.
[0008] The utility model is further configured as follows: the regulating valve is regulated and controlled by the control logic of the heat medium temperature controller.
[0009] The beneficial technical effects of the utility model are as follows: the application adds a heat exchange system between the prepolymerization kettle and the final polymerization kettle to reduce the temperature of the prepolymer, ensuring that the material has a lower temperature before entering the final polymerization kettle, creating conditions for a higher reaction temperature in the prepolymerization kettle. A heat medium is selected as the cooling medium of the prepolymer heat exchanger, and the heat medium is circulated through the reflux of the secondary heat medium. An air-cooled fin heat exchanger is installed on the heat medium circulation pipeline to reduce the temperature of the heat medium. The temperature of the circulating heat medium is automatically adjusted by controlling the amount of the primary heat medium entering through the regulating valve, thereby realizing automatic control of the heat medium temperature of the prepolymer heat exchanger for heat exchange. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 Shown is a schematic diagram of the structure of the utility model.
[0011] Figure numerals: 1. prepolymer delivery pump, 2. prepolymer filter, 3. prepolymer heat exchanger, 4. outlet prepolymer thermometer, 5. regulating valve, 6. pump inlet valve, 7. heat medium filter, 8. heat medium delivery pump, 9. pump outlet valve, 10. heat medium temperature controller, 11. heat medium outlet thermometer, 12. first valve, 13. air-cooled outlet thermometer, 14. air-cooled fin heat exchanger, 15. second valve, 16. check valve. DETAILED DESCRIPTION
[0012] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.
[0013] The utility model proposes a PBT prepolymer heat exchange system, comprising a main delivery pipeline, which is installed between a prepolymerization kettle and a final polymerization kettle, and specifically comprises a prepolymer delivery pump 1, a prepolymer filter 2, a prepolymer heat exchanger 3 and an outlet prepolymer thermometer 4 which are connected in sequence; the shell side inlet of the prepolymer heat exchanger 3 is connected to a heat medium oil inlet pipeline, and the heat medium oil inlet pipeline specifically comprises a regulating valve 5, a pump inlet valve 6, a heat medium filter 7, a heat medium delivery pump 8, a pump outlet valve 9 and a heat medium temperature controller 10 which are connected in sequence to the oil inlet, and the outlet end of the heat medium temperature controller 10 is connected to the shell side inlet of the prepolymer heat exchanger 3;
[0014] The shell side outlet of the prepolymer heat exchanger 3 is connected to a heat medium oil outlet pipeline, which specifically includes a heat medium outlet thermometer 11, a first valve 12 and an air-cooled outlet thermometer 13 connected in sequence. The heat medium outlet thermometer 11 is connected to the shell side outlet of the prepolymer heat exchanger 3. One end of an air-cooled cooling branch is also connected between the heat medium outlet thermometer 11 and the first valve 12. The other end of the air-cooled cooling branch is connected between the first valve 12 and the air-cooled outlet thermometer 13. There are two air-cooled cooling branches, which specifically include an air-cooled fin heat exchanger 14 and a second valve 15. The outlet of the heat medium oil outlet pipeline is connected to the oil outlet through a check valve 16. The outlet of the heat medium oil outlet pipeline is also connected between the regulating valve 5 and the pump inlet valve 6 for reflux into the prepolymer heat exchanger 3.
[0015] Working process: Before the prepolymer starts to be transported, the heat medium delivery pump 8 needs to be started to start the circulation of the heat medium in the prepolymer heat exchanger. The prepolymer heat exchanger is a shell-and-tube heat exchanger, the medium in the tube side is prepolymer, and the medium in the shell side is heat medium. The shell side inlet is connected to the heat medium, and the shell side outlet outputs the heat medium after passing through the prepolymer heat exchanger 3. This system can control whether to cool the heat medium by the opening and closing degree of the first valve 12 and the second valve 15. The heat medium flowing out of the prepolymer heat exchanger 3 can flow out through the check valve 16 or flow back through the air-cooled cooling branch for a second time and enter the prepolymer heat exchanger 3 for cooling.
[0016] The regulating valve 5 is regulated and controlled by the control logic of the heat medium temperature controller 10. If the temperature of the outlet prepolymer thermometer 4 is high, the temperature setting value of the heat medium temperature controller 10 can be lowered to reduce the opening of the regulating valve 5 and reduce the amount of heat medium entering the heat medium system. If the small opening of the regulating valve 5 cannot guarantee the temperature drop of the heat medium temperature controller 10, the temperature of the circulating heat medium can be adjusted by adjusting the air-cooled cooling branch, opening the second valve 15 and closing the first valve 12, and using the air-cooled fin heat exchanger 14 to increase the heat medium flow through the air-cooled fin heat exchanger 14, reduce the temperature shown by the air-cooled outlet thermometer 13, and then reduce the temperature of the heat medium temperature controller 10.
[0017] If the opening of the regulating valve 5 is relatively large, the second valve 15 can be closed and the first valve 12 can be opened to reduce the flow of heat medium passing through the air-cooled fin heat exchanger 14 and increase the temperature shown by the air-cooled outlet thermometer 13, thereby reducing the opening of the regulating valve, reducing the amount of heat medium entering once, and reducing heat consumption.
[0018] The material from the prepolymer kettle, i.e., the prepolymer, is first conveyed under pressure by the prepolymer conveying pump 1, then enters the prepolymer filter 2 to filter impurities, and then flows into the prepolymer heat exchanger 3. After heat exchange in the prepolymer heat exchanger 3, the prepolymer enters the final polymerization kettle. An outlet prepolymer thermometer 4 is arranged behind the outlet of the prepolymer heat exchanger. The temperature indicated by the outlet prepolymer thermometer 4 is an important parameter indicator, and the temperature should not be higher than 242°C, so as to facilitate real-time monitoring of the heat exchange effect.
[0019] After using the prepolymer heat exchanger, the reaction temperature in the prepolymer kettle can be increased from the original 242°C to 248°C, and the intrinsic viscosity of the prepolymer remains unchanged at 0.3dl / g. When producing the same brand of products, the amount of catalyst added is reduced from the original 80-90ppm (one millionth) to 70-80ppm (one millionth), and the vacuum pressure of the prepolymer kettle is increased from 1.2Kpa (absolute pressure) to 2.0Kpa (absolute pressure). The oligomers extracted from the prepolymer vacuum system are reduced, and the molecular weight distribution of the material in the final polymerization kettle is more uniform. The viscosity control fluctuation range is reduced from ±0.012dl / g to ±0.003dl / g, and the viscosity control is more stable.
[0020] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
[0021] In the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0022] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.
[0023] The term "comprise" or any other similar term is intended to cover a non-exclusive inclusion, such that a process, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, article, or apparatus / device.
[0024] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.
Claims
1. A PBT prepolymer heat exchange system, comprising a main transport pipeline, wherein the main transport pipeline is installed between a prepolymerization kettle and a final polymerization kettle, and is characterized in that: The main delivery pipeline specifically comprises a prepolymer delivery pump (1), a prepolymer filter (2), a prepolymer heat exchanger (3) and an outlet prepolymer thermometer (4) which are connected in sequence; the shell side inlet of the prepolymer heat exchanger (3) is connected to a heat medium oil inlet pipeline, and the heat medium oil inlet pipeline specifically comprises a regulating valve (5), a pump inlet valve (6), a heat medium filter (7), a heat medium delivery pump (8), a pump outlet valve (9) and a heat medium temperature controller (10) which are connected in sequence to the oil inlet, and the outlet end of the heat medium temperature controller (10) is connected to the shell side inlet of the prepolymer heat exchanger (3); The shell outlet of the prepolymer heat exchanger (3) is connected to a heat medium oil outlet pipeline, and the heat medium oil outlet pipeline specifically comprises a heat medium outlet thermometer (11), a first valve (12) and an air cooling outlet thermometer (13) which are connected in sequence. The heat medium outlet thermometer (11) is connected to the shell outlet of the prepolymer heat exchanger (3). One end of an air cooling branch is also connected between the heat medium outlet thermometer (11) and the first valve (12). The other end of the air cooling branch is connected between the first valve (12) and the air cooling outlet thermometer (13). The air cooling branch specifically comprises an air cooling fin heat exchanger (14) and a second valve (15). The outlet of the heat medium oil outlet pipeline is connected to the oil outlet via a check valve (16). The outlet of the heat medium oil outlet pipeline is also connected between the regulating valve (5) and the pump inlet valve (6) for reflux into the prepolymer heat exchanger (3).
2. A PBT prepolymer heat exchange system according to claim 1, characterized in that: There are two air cooling branches.
3. A PBT prepolymer heat exchange system according to claim 1, characterized in that: The prepolymer heat exchanger (3) is a shell-and-tube heat exchanger, the medium in the tube side is the prepolymer, and the medium in the shell side is the heat medium.
4. A PBT prepolymer heat exchange system according to claim 1, characterized in that: The regulating valve (5) is regulated and controlled by the control logic of the heat medium temperature controller (10).