A cooling system and process for a partial condenser in a nylon 6 polymerization process

Abstract

The present invention relates to a cooling system that uses a high-boiling-point fluid as a cooling medium for a nylon 6 polymerization partial condenser. The condensation amount of materials in the partial condenser is indirectly adjusted by controlling the circulation flow rate of the high-boiling-point cooling medium, thereby adjusting the reflux ratio of the packing tower and the partial condenser and ensuring the separation effect of the packing tower and the partial condenser. Specifically, a high-boiling-point fluid is used as a cooling medium for a nylon 6 polymerization partial condenser in a nylon 6 polymerization device, thereby avoiding the vaporization problem of the cooling medium at low flow rates and achieving effective control of the condensation amount of materials in the partial condenser. A high-boiling-point fluid refers to a liquid fluid whose boiling point is higher than the working temperature of the condensed material in the partial condenser and is greater than 100°C. The system adopted by the present invention can effectively reduce material and energy consumption, improve production stability, and make production enterprises more competitive.

Description

Technical Field

[0001] The present invention belongs to the technical field of the production process of nylon 6 (nylon) chips, and specifically relates to a cooling system and a process thereof which adopts a high boiling point fluid as a cooling medium for a partial condenser in a nylon 6 polymerization process. Background Art

[0002] The cooling medium commonly used in traditional nylon 6 polymerization devices is circulating water, but in some occasions where the temperature of the cooled material is high, such as the partial condenser at the top of the cracker and the reactor, the cooling medium is not suitable for circulating water. In these occasions, it is necessary to control the condensation amount of the material in the partial condenser by adjusting the flow rate of the cooling medium to achieve the adjustment of the reflux ratio of the packed tower and the partial condenser. Since the temperature of the cooled material is high (greater than 100°C, exceeding the normal pressure boiling point of water), when circulating water is used as the cooling medium, there are two methods to ensure that the circulating water does not vaporize. One method is that the circulating water flow rate cannot be lower than the flow rate when the return water temperature is equal to 100°C, which means that the minimum flow rate of the circulating water is limited, and it is impossible to control the condensation amount of the material in the partial condenser by adjusting the circulating water flow rate; the other method is to increase the circulating water pressure so that the boiling point of the circulating water pressure is higher than the temperature of the cooled material, which can ensure that the circulating water does not vaporize, but this will increase the design pressure of the circulating water system, especially when the temperature of the cooled material is above 200°C, the design pressure of the circulating water system is greatly increased, and additional equipment investment is required.

[0003] That is to say, in the traditional nylon 6 polymerization process, circulating hot water at about 70°C is used as the cooling medium for the partial condenser. In the nylon 6 polymerization process, the temperature of the condensed material in the partial condenser is relatively high, usually above 100°C. When the system condensation capacity needs to be reduced, since the heat exchange area of ​​the partial condenser is fixed, it can only be achieved by reducing the flow rate of circulating hot water. However, the return water temperature of the circulating hot water will increase with the decrease of the hot water flow rate. When the condensation capacity is reduced to a certain value, the return water temperature of the hot water will reach the boiling point under the working pressure, and the hot water will vaporize in the partial condenser, affecting the stability of the operating state of the partial condenser. Therefore, the minimum flow rate of the circulating hot water will be limited, and it is impossible to accurately control the condensation amount of the material in the partial condenser by adjusting the flow rate of the circulating hot water. In the case of using circulating hot water at about 70°C as the cooling medium for the partial condenser in the traditional nylon 6 polymerization process, in order to avoid the above-mentioned problem of vaporization of the circulating water at low flow, it is necessary to increase the working pressure of the circulating water so that the boiling point of the circulating water pressure is higher than the temperature of the cooled material, which in turn brings about the problem of increased design pressure of the circulating water system and increased equipment investment.

[0004] In the traditional nylon 6 polymerization process, partial condensers are respectively arranged on the top of the cracking reactor, the pre-polymerization reactor and the post-polymerization reactor. When circulating hot water is used as the cooling medium for the partial condensers, there are two ways to set up the hot water circulation system. One setting method is that all partial condensers share a set of hot water circulation cooling system, and the other setting method is to set up an independent hot water circulation cooling system for the partial condensers at different positions. Both of these setting methods have their own problems. Due to the different working temperatures, working pressures and required condensation volumes of partial condensers at different locations, when a hot water circulation cooling system is shared, the circulating hot water can only control one working temperature and working pressure, and it is impossible to set the working temperature and working pressure of the circulating hot water according to the process requirements of different partial condensers, which further affects the accurate control of the condensation volume (reflux ratio) of the partial condensers, and ultimately increases the energy and material consumption of the polymerization device and affects the process stability; when a set of independent hot water circulation cooling systems are set for different partial condensers, although the matching problem of the working temperature and working pressure of the circulating hot water system with the working temperature and working pressure of the partial condensers can be solved to a certain extent, it still cannot fundamentally solve the problem of the circulating hot water flow being too low and easy to vaporize mentioned above. At the same time, compared with sharing a set of cooling circulation systems, there are still problems of complex system, large equipment investment and relatively large workload of daily operation and maintenance. Therefore, a new technical solution is urgently needed to solve the above technical problems. Summary of the invention

[0005] The present invention discloses a cooling system and a process flow thereof which use a high boiling point fluid as a cooling medium for a partial condenser in a nylon 6 polymerization process, and is used to indirectly control the condensation amount of materials in the partial condenser by adjusting the flow rate of the cooling medium, and to adjust the reflux ratio of the packing tower and the partial condenser. The system is applied to the cooling system of the top partial condensers of the cracking reactor, the pre-polymerization reactor, the post-polymerization reactor and the like of the nylon 6 polymerization device. The top operating temperature of these reactors is relatively high, and the vapor evaporated from the top of these reactors contains a large amount of caprolactam monomer. It is necessary to partially condense and reflux the materials in the partial condenser to separate the caprolactam in the vapor and reduce the content of the caprolactam monomer in the vapor discharged from the partial condenser. In order to achieve the best separation effect and avoid extra energy consumption due to excessive condensation, it is necessary to accurately control the reflux ratio (condensation amount).

[0006] The present invention improves the cooling system of the partial condenser of the traditional nylon 6 polymerization device, adopts a high boiling point fluid as a cooling medium, and reasonably designs the process flow to achieve the purpose of controlling the condensation amount of the material in the partial condenser by adjusting the flow rate of the cooling medium. The invention wherein the high boiling point fluid medium refers to a liquid fluid whose normal pressure boiling point is higher than the working temperature of the cooled medium and greater than 100°C, and the following liquids can usually be selected, including but not limited to heat transfer oil, biphenyl-biphenyl ether mixture, ethylene glycol, etc. Since the boiling point of the high temperature cooling medium is higher than the temperature of the cooled material in the partial condenser, the high temperature cooling medium always works at a temperature below its boiling point, and no vaporization occurs even at a very low flow rate, and the condensation amount of the material in the partial condenser can be accurately controlled by adjusting the flow rate of the cooling medium.

[0007] In the cooling system described above, preferably, a packing tower is further arranged between the top steam outlet of the cracking reactor, the pre-polymerization reactor, and the post-polymerization reactor and the partial condenser; the connection mode is: the top steam outlet of the cracking reactor, the pre-polymerization reactor or the post-polymerization reactor is connected to the bottom steam inlet of the packing tower, and the top steam outlet of the packing tower is connected to the steam inlet of the partial condenser. A packing tower can also be added upstream of the partial condenser, which is conducive to achieving a better separation effect for the steam material output from the top outlet of the cracking reactor, the pre-polymerization reactor, and the post-polymerization reactor.

[0008] In the cooling system described above, preferably, the high-boiling-point cooling medium is used in a closed circulation system, and the closed circulation system includes a partial condenser connected to the top of the cracking reactor, the pre-polymerization reactor or the post-polymerization reactor described above, as well as a circulation pump, a cooler, a condenser and an expansion tank; wherein the partial condenser, the circulation pump and the cooler are connected by pipelines to form a circulation system, and the circulation pump provides power for the circulation of the high-boiling-point cooling medium; a branch pipeline is connected to the proximal end of the high-boiling-point cooling medium outlet and the proximal end of the inlet of the partial condenser respectively by a three-way pipe fitting, and a condenser is arranged on the branch pipeline;

[0009] A flow meter and a flow regulating valve are arranged on the pipeline near the high boiling point cooling medium inlet of the partial condenser to control the flow of the high boiling point cooling medium entering the partial condenser.

[0010] The expansion tank is arranged at the highest point of the system and is connected to the proximal pipeline of the high boiling point cooling medium inlet of the circulation pump through a pipeline;

[0011] A pressure differential regulating valve is provided on the pipeline near the high boiling point cooling medium inlet of the condenser shell side to control the circulation pressure differential of the high boiling point cooling medium;

[0012] The connection method of the circulation pump, partial condenser and cooler is not limited. The circulation pump, cooler and partial condenser can be connected in sequence to form a circulation pipeline; or the circulation pump, partial condenser and cooler can be connected in sequence to form a circulation pipeline.

[0013] In the cooling system described above, preferably, the high boiling point cooling medium is circulated in a closed system, and the circulation flow rate of the high boiling point cooling medium can be controlled. Specifically, a flow meter and a flow regulating valve are arranged at the outlet of the circulation pump, and the circulation flow rate of the high boiling point cooling medium is controlled by adjusting the opening of the flow regulating valve.

[0014] In the cooling system described above, the cooler is a water cooler; specifically, there are two ways to control the circulation temperature of the high boiling point cooling medium:

[0015] (1) The cooler is also provided with a regulating valve, and the cooling capacity of the cooler is controlled by adjusting the opening of the regulating valve, thereby realizing the control of the circulation temperature of the high boiling point cooling medium.

[0016] (2) A tee is provided near the inlet and outlet of the high-boiling-point cooling medium of the cooler to form a branch pipeline, and a regulating valve is provided, so that the flow rate of the high-boiling-point cooling medium entering the cooler is adjusted by controlling the opening of the regulating valve, and the temperature of the high-boiling-point cooling medium is controlled.

[0017] In the cooling system described above, the condenser is also connected to a collecting tank, and the condensed material outlet of the condenser is connected to the inlet of the collecting tank; the condenser is used to provide cooling for the gas output from the top outlet of the partial condenser, and the product after cooling by the condenser is collected by the collecting tank.

[0018] Preferably, the cooling system described above further comprises a discharge pipeline, and the discharge pipeline is connected to the inlet proximal end pipeline of the high boiling point cooling medium of the circulation pump through a three-way pipe fitting.

[0019] In the cooling system described above, preferably, a pressure differential regulating valve is also provided on the high boiling point cooling medium inlet side pipeline of the condenser.

[0020] In the cooling system described above, preferably, a plurality of temperature meters are arranged on the circulation pipeline of the closed system. Usually, the temperature meters are arranged on the pipeline near the outlet end of the high-boiling-point cooling medium of the cooler or condenser; wherein the temperature meter arranged near the outlet end of the high-boiling-point cooling medium of the cooler cooperates with the regulating valve of the cooling water to realize the control of the circulation temperature of the high-boiling-point cooling medium.

[0021] In the cooling system described above, when there are more than two partial condensers in the system, each partial condenser is connected in parallel through a pipeline, and is connected in parallel with the condenser on the branch pipeline, so that a closed circulation system is formed by multiple partial condensers, a circulation pump, a cooler, a condenser and an expansion tank. In a more preferred case, a flow meter and a flow regulating valve are respectively provided on the pipeline near the high boiling point cooling medium inlet of each partial condenser to control the flow of the high boiling point cooling medium entering each partial condenser.

[0022] Another aspect of the present invention discloses a process for the polymerization production of nylon 6, wherein for a partial condenser disposed on the top of a cracking reactor, a pre-polymerization reactor and / or a post-polymerization reactor, the process flow of the cooling system thereof is as follows:

[0023] In the closed-loop pipeline composed of a partial condenser, a circulating pump, a cooler, a condenser and an expansion tank, a high-boiling-point fluid is used as a cooling medium. The high-boiling-point cooling medium is cooled in the cooler, and the circulating pump provides power for the circulation of the high-boiling-point cooling medium in the pipeline. The high-boiling-point cooling medium, driven by the power of the circulating pump, flows through different branch pipelines to distribute the flow and then returns to the circulating pump to complete the circulation; each branch pipeline is a parallel structure formed by one or more partial condensers and condensers;

[0024] When it is necessary to adjust the flow rate of the high boiling point cooling medium entering each partial condenser, this can be achieved by controlling the opening of the flow regulating valve arranged at the front end of each partial condenser.

[0025] When it is necessary to adjust the pressure difference of the supply and return circulation of the high-boiling-point cooling medium in the closed system, the pressure difference adjustment of the high-boiling-point cooling medium circulating in the closed system can be achieved by controlling the opening of the pressure difference adjustment valve.

[0026] When the high-boiling-point cooling medium used in the closed circulation system needs to be replaced or discharged, the high-boiling-point cooling medium circulating in the closed system can be recovered by opening the manual drain valve provided on the discharge pipeline.

[0027] Beneficial Effects

[0028] 1. The present invention adopts a high boiling point fluid as the cooling medium of the nylon 6 polymerization partial condenser to ensure that the cooling medium does not vaporize in the partial condenser. The condensation amount of the material in the partial condenser can be controlled by adjusting the flow rate of the cooling medium to avoid excessive condensation of the material in the partial condenser, which is beneficial to reducing energy consumption.

[0029] 2. By controlling the circulation flow of the high-boiling-point cooling medium, the condensation amount of the material in the partial condenser is indirectly adjusted to adjust the reflux ratio of the packed tower and the partial condenser, thereby ensuring the separation effect of the packed tower and the partial condenser.

[0030] 3. The present invention adopts high boiling point fluid as the cooling medium of the nylon 6 polymerization partial condenser, ensuring that the cooling medium does not vaporize in the partial condenser, which can reduce the design pressure of the partial condenser and is conducive to reducing equipment investment.

[0031] 4. In the nylon 6 polymerization process, when partial condensers are respectively set on the top of the cracking reactor, the pre-polymerization reactor and the post-polymerization reactor, all partial condensers can share a set of high-boiling-point cooling medium closed circulation cooling system, and each partial condenser is controlled by its own flow regulating valve, which can flexibly meet different cooling requirements. Compared with setting up a set of independent circulation cooling systems for different partial condensers, all partial condensers share a set of circulation cooling system, which can reduce the number of equipment and simplify the process, which is conducive to reducing equipment investment, and at the same time, the manpower and cost invested in daily operation and maintenance are relatively reduced.

[0032] 5. The high boiling point cooling medium used in the present invention is circulated in a closed system. The circulation temperature of the high boiling point cooling medium is controlled by setting a cooling water regulating valve on the cooler. The setting method of the cooling water regulating valve is flexible and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : A schematic diagram of a process using a high boiling point fluid as a cooling medium for a partial condenser; used for the top of a single reactor of a nylon 6 polymerization unit (with a packed tower);

[0034] Figure 2 : A schematic diagram of a process using a high boiling point fluid as a cooling medium for a partial condenser; used for the top of a single reactor of a nylon 6 polymerization unit (with a packed tower);

[0035] Figure 3 : A schematic diagram of a process using a high boiling point fluid as a cooling medium for a partial condenser; used for the top of a single reactor in a nylon 6 polymerization unit (without a packed tower);

[0036] Figure 4 : Schematic diagram of a closed circulation cooling system in which multiple sets of partial condensers share one set of high boiling point cooling medium;

[0037] Figure 5 : A schematic diagram of a process using a high boiling point fluid as a cooling medium for a partial condenser; used for the top of a single reactor of a nylon 6 polymerization unit (with a packed tower);

[0038] Figure 6 : A schematic diagram of a process using a high boiling point fluid as a cooling medium for a partial condenser; used for the top of a single reactor of a nylon 6 polymerization unit (with a packed tower);

[0039] Figure 7 : A schematic diagram of a process using a high boiling point fluid as a cooling medium for a partial condenser; used for the top of a single reactor in a nylon 6 polymerization unit (without a packed tower);

[0040] Figure 8 : Schematic diagram of a closed circulation cooling system in which multiple sets of partial condensers share one set of high boiling point cooling medium;

[0041] Among them, 1. Partial condenser; 1-1. Flow meter and flow control valve; 2. Circulation pump; 2-1. Discharge pipeline; 3. Cooler; 3-1. TC control valve; 4. Expansion tank; 5. TI temperature instrument; 6. Reactor; 7. Packing tower; 8. Condenser; 8-1. Collection tank; 8-2. Pressure difference regulating valve. DETAILED DESCRIPTION

[0042] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0043] The high boiling point cooling medium used in the following embodiments of the present invention may be heat transfer oil, a biphenyl-biphenyl ether mixture or ethylene glycol.

[0044] Example 1

[0045] For the top partial condenser of single reactor 6 in nylon 6 polymerization unit ( Figures 1 to 3 , Figures 5 to 7 ).

[0046] The outlet of the circulating pump 2 is connected to the inlet of the high boiling point cooling medium on the shell side of the partial condenser 1 through a pipeline, and the outlet of the high boiling point cooling medium on the shell side of the partial condenser 1 is connected to the cooler 3 through a pipeline. The high boiling point cooling medium is cooled by cooling water in the cooler 3, and the outlet of the cooler 3 is connected to the inlet of the high boiling point cooling medium on the circulating pump 2 through a pipeline, so as to form a closed circulation of the high boiling point cooling medium; a flow meter and a flow regulating valve 1-1 are arranged on the pipeline between the outlet of the high boiling point cooling medium on the shell side of the circulating pump 2 and the inlet of the high boiling point cooling medium on the shell side of the partial condenser 1, and a flow meter and a flow regulating valve 1-1 are arranged between the outlet of the high boiling point cooling medium on the circulating pump 2 and the flow regulating valve A tee pipe fitting is arranged on the pipeline between 1-1 to connect the branch pipeline, and the other end of the branch pipeline is connected to the pipeline between the high boiling point cooling medium outlet of the shell side of the partial condenser 1 and the cooler 3 through the tee pipe fitting; a condenser 8 is arranged on the branch pipeline; the expansion tank 4 is arranged at the highest point of the system and is connected to the high boiling point cooling medium inlet pipeline of the circulating pump 2 through a pipeline at a position near the high boiling point cooling medium inlet of the circulating pump 2, and the volume change of the high boiling point cooling medium in the closed circulation system caused by the temperature change is compensated by the change of the high boiling point cooling medium liquid level in the expansion tank 4.

[0047] The high boiling point cooling medium is circulated in a closed system, and the circulation flow rate of the high boiling point cooling medium can be controlled. Specifically, a flow meter and a flow regulating valve 1-1 are arranged at the outlet of the circulation pump 2, and the circulation flow rate of the high boiling point cooling medium is controlled by adjusting the opening of the flow regulating valve 1-1.

[0048] In the cooling system described above, the installation position of the cooler 3 can be appropriately selected according to the spatial position conditions of the implementation site, for example: (1) the installation position of the cooler 3 can be installed on the inlet side of the circulating pump 2, that is, the high boiling point cooling medium outlet end of the cooler 3 is connected to the high boiling point cooling medium inlet end of the circulating pump 2 through a pipeline ( Figures 1 to 4 ); (2) It can also be installed on the outlet side of the high boiling point cooling medium of the circulating pump 2, and the high boiling point cooling medium inlet end of the cooler 3 is connected to the high boiling point cooling medium outlet end of the circulating pump 2 through a pipeline ( Figures 5 to 8 ).

[0049] In the cooling system described above, the cooler 3 is a water cooler; specifically, there are two control methods for the circulation temperature of the high boiling point cooling medium:

[0050] (1) The cooler 3 is also provided with a TC regulating valve 3-1, and the cooling capacity of the cooler 3 is controlled by the opening of the TC regulating valve 3-1, thereby realizing the control of the circulation temperature of the high boiling point cooling medium ( Figure 1 , Figure 3 , Figure 5 , Figure 7 ).

[0051] (2) A tee is provided near the inlet and outlet of the high boiling point cooling medium of the cooler 3 to form a branch pipeline, and a TC regulating valve 3-1 is provided, so that the flow rate of the high boiling point cooling medium entering the cooler 3 is adjusted by controlling the opening of the TC regulating valve 3-1, and the temperature of the high boiling point cooling medium is controlled ( Figure 2 , Figure 4 , Figure 6 , Figure 8 ).

[0052] It also includes a discharge pipeline 2-1, which is connected to the inlet proximal pipeline of the high-boiling-point cooling medium of the circulation pump through a three-way pipe fitting, and the discharge pipeline 2-1 is provided with a manual drain valve to recover the high-boiling-point cooling medium circulated in the closed system.

[0053] In the cooling system described above, a pressure differential regulating valve 8-2 is also provided on the high boiling point cooling medium inlet side pipeline of the condenser 8, and the stability of the high boiling point cooling medium supply and return circulation pressure differential is controlled by controlling the opening of the pressure differential regulating valve 8-2.

[0054] In the cooling system described above, the condenser 8 is also connected to the collecting tank 8-2, and the condensed material outlet of the condenser 8 is connected to the inlet of the collecting tank 8-2; the condenser 8 is used to provide cooling for the gas output from the top outlet of the partial condenser 1, and the product after cooling by the condenser is collected by the collecting tank 8-2.

[0055] Example 2

[0056] Partial condensers are respectively arranged on the top of the cracking reactor 6, the pre-polymerization reactor 6 and the post-polymerization reactor 6 of the nylon 6 polymerization device ( Figure 4 , Figure 8 ).

[0057] In the nylon 6 polymerization process, when partial condensers 1 are respectively arranged on the top of the cracking reactor 6, the pre-polymerization reactor 6 and the post-polymerization reactor 6, all partial condensers 1 can share a set of high-boiling-point cooling medium closed circulation cooling system. Specifically, the temperature control of the circulating pump 2, the cooler 3, the expansion tank 4 and the cooling medium is the same as that of Example 1, but in order to realize that the condensation amount of each partial condenser 1 can be controlled, it is necessary to set a flow adjustment for each cooling circuit separately, which specifically involves the following:

[0058] A pipeline is provided at the high-boiling-point cooling medium inlet of each partial condenser 1, which is connected to the outlet of the circulation pump 2 in the cooling system described above, and a flow meter and an FC flow regulating valve 1-1 are provided on each pipeline; a pipeline is provided at the high-boiling-point cooling medium outlet on the shell side of each partial condenser 1, which is connected to the cooler 3, and a TI temperature meter 5 is provided on each pipeline; thereby, the partial condensers 1 are connected in parallel, and each partial condenser 1 has its own corresponding flow meter and flow regulating valve 1-1; a branch pipeline is also provided between the outlet pipeline of the circulation pump 2 and the inlet pipeline of the cooler 3, and an expansion tank 4 is provided on the branch pipeline; the high-boiling-point cooling medium is cooled by cooling water in the cooler 3, and the outlet of the cooler 3 is connected to the inlet of the circulation pump 2 via a pipeline; the partial condensers 1, the cooler 3, the circulation pump 2 and the expansion tank 4 form a closed circulation system; the volume change of the high-boiling-point cooling medium in the closed circulation system caused by temperature change is compensated by the change of the liquid level of the high-boiling-point cooling medium in the expansion tank 4.

[0059] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0060] The present invention relates to a cooling system that uses a high-boiling-point fluid as a cooling medium for a nylon 6 polymerization partial condenser. The condensation amount of materials in the partial condenser is indirectly adjusted by controlling the circulation flow rate of the high-boiling-point cooling medium, thereby adjusting the reflux ratio of the packing tower and the partial condenser and ensuring the separation effect of the packing tower and the partial condenser. Specifically, a high-boiling-point fluid is used as a cooling medium for a nylon 6 polymerization partial condenser in a nylon 6 polymerization device, thereby avoiding the vaporization problem of the cooling medium at low flow rates and achieving effective control of the condensation amount of materials in the partial condenser. A high-boiling-point fluid refers to a liquid fluid whose boiling point is higher than the working temperature of the condensed material in the partial condenser and is greater than 100°C. The system adopted by the present invention can effectively reduce material and energy consumption, improve production stability, and make production enterprises more competitive.

Claims

1. A cooling system for a partial condenser in a nylon 6 polymerization process, the system is a cooling system for a partial condenser at the top of a front polymerization reactor and a rear polymerization reactor, characterized in that: The cooling system uses a high boiling point fluid as a cooling medium, and the high boiling point fluid is selected from at least one of heat transfer oil and a biphenyl-biphenyl ether mixture; The high boiling point cooling medium is used in a closed circulation system, which includes a partial condenser, a circulation pump, a cooler, a condenser and an expansion tank; wherein the partial condenser, the circulation pump and the cooler are connected by pipelines to form a circulation system, and the circulation pump provides power for the circulation of the high boiling point cooling medium; a branch pipeline is connected to the proximal end of the high boiling point cooling medium outlet and the proximal end of the inlet of the partial condenser by a three-way pipe fitting, and a condenser is arranged on the branch pipeline; a flow meter and a flow regulating valve are arranged on the pipeline near the inlet of the high boiling point cooling medium of the partial condenser; the flow regulating valve is used to accurately control the flow of the high boiling point cooling medium entering the partial condenser, so as to achieve accurate control of the condensation amount; A pressure differential regulating valve is provided on the pipeline near the inlet of the high boiling point cooling medium in the shell side of the condenser; The expansion tank is arranged at the highest point of the system and is connected to the proximal pipeline of the high boiling point cooling medium inlet of the circulation pump through a pipeline; Install a flow meter and a flow regulating valve at the outlet of the circulation pump; A plurality of temperature instruments are arranged on the circulation pipeline of the closed system; The temperature instrument is arranged on a pipeline near the outlet end of the high boiling point cooling medium of the cooler or condenser; There are more than two partial condensers in the system, and the partial condensers are connected in parallel through pipelines, and are connected in parallel with the condensers on the branch pipelines, so that a closed circulation system is formed by multiple partial condensers, circulating pumps, coolers, condensers and expansion tanks.

2. The cooling system for a partial condenser in a nylon 6 polymerization process according to claim 1, characterized in that: The connection method of the circulation pump, the partial condenser and the cooler includes: (1) the circulation pump, the cooler and the partial condenser are connected in sequence to form a circulation pipeline; (2) the circulation pump, the partial condenser and the cooler are connected in sequence to form a circulation pipeline.

3. The cooling system of a partial condenser in a nylon 6 polymerization process according to claim 1, characterized in that: The cooler is a water cooler.

4. The cooling system of a partial condenser in a nylon 6 polymerization process according to claim 1, characterized in that: The control method of the circulation temperature of the high boiling point cooling medium includes: (1) the cooler is also provided with a flow regulating valve; (2) a tee is respectively provided near the high boiling point cooling medium inlet end and outlet end of the cooler to form a branch pipeline, and a flow regulating valve is provided.

5. The cooling system of a partial condenser in a nylon 6 polymerization process according to claim 1, characterized in that: The condenser is also connected to a collecting tank, and the condensed material outlet of the condenser is communicated with the inlet of the collecting tank.

6. The cooling system for a partial condenser in a nylon 6 polymerization process according to claim 1, characterized in that: The cooling system also includes a discharge pipeline, which is connected to the inlet proximal end pipeline of the high boiling point cooling medium of the circulation pump through a three-way pipe.

7. The cooling system for a partial condenser in a nylon 6 polymerization process according to claim 1, characterized in that: A flow meter and a flow regulating valve are respectively arranged on the pipeline near the high boiling point cooling medium inlet of each partial condenser.

8. The process of the cooling system of the partial condenser in the nylon 6 polymerization process as claimed in claim 1, characterized in that: The process includes: In the closed-loop pipeline composed of a partial condenser, a circulating pump, a cooler, a condenser and an expansion tank, a high-boiling-point fluid is used as a cooling medium. The high-boiling-point cooling medium is cooled in the cooler, and the circulating pump provides power for the circulation of the high-boiling-point cooling medium in the pipeline. The high-boiling-point cooling medium, driven by the power of the circulating pump, flows through different branch pipelines to distribute the flow and then returns to the circulating pump to complete the circulation; each branch pipeline is a parallel structure formed by one or more partial condensers and condensers; When it is necessary to adjust the flow rate of the high boiling point cooling medium entering each part of the condenser, it is achieved by controlling the opening of the flow regulating valve arranged at the front end of each part of the condenser; When it is necessary to adjust the pressure difference of the supply and return cycle of the high boiling point cooling medium in the closed system, the pressure difference of the high boiling point cooling medium circulating in the closed system is adjusted by controlling the opening of the pressure difference regulating valve; When it is necessary to replace or discharge the high-boiling-point cooling medium used in the closed circulation system, it can be achieved by controlling the manual drain valve set on the discharge pipeline.

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