Efficient chinlon 6 polymerization process cooling device and working method thereof

Abstract

The invention provides an efficient chinlon 6 polymerization process cooling device and a working method thereof.The efficient chinlon 6 polymerization process cooling device comprises a polymerization tower and a tubular cooler arranged on the upper portion of the middle of the polymerization tower, and a heating medium outlet of the tubular cooler is connected with a heating medium pipe; the heating medium pipe is sequentially connected with a three-way control valve, a first branch and a second branch; the first branch is connected with a first heat exchanger taking caprolactam as a cooling medium, and the second branch is sequentially connected with an air cooler and a heating medium heat exchanger taking a low-temperature heating medium (the temperature is 80 DEG C + / -5 DEG C) as a cooling medium; an outlet of the first heat exchanger and the second branch are converged in front of an inlet of the air cooler; according to the device, caprolactam is used as a heat absorption medium, and a low-temperature heating medium of 80 + / -5 DEG C and normal-temperature cold air are also used as cooling media, so that the heating medium and the polymerization temperature can be stably circulated at constant temperature, a polymerization reaction system can be effectively maintained, and the quality of slices is guaranteed and improved.

Description

Technical Field

[0001] This invention relates to the field of polymerization production, and particularly to a high-efficiency cooling device for the polymerization process of nylon 6 and its working method. Background Technology

[0002] In the production of nylon 6 polymer chips, the heating and cooling temperatures in the polymerization process directly affect the polymerization reaction, chemical equilibrium, molecular weight distribution, viscosity, and other process quality of caprolactam, thus affecting the quality of the chips. Generally, a mixture of biphenyl and diphenyl ether at around 200 degrees Celsius is used as the heating and cooling medium (265±10℃ is the heating temperature, and 233±5℃ is the cooling temperature; the mixture of biphenyl and diphenyl ether is also called the heat medium, and will be referred to as the heat medium in the following text). Since the condensation polymerization reaction in the polymerization process generates a large amount of heat, this heat will cause the temperature of the 233±5℃ cooling heat medium to rise rapidly. The heat medium will lose its cooling effect, causing the polymerization temperature to be too high or unstable. In this case, the polymerization reaction system will be disrupted, and the quality of the chips will fluctuate.

[0003] Currently, caprolactam at around 80℃ is used as the cooling medium in the polymerization process. However, the flow rate or temperature of caprolactam can fluctuate, which affects the cooling process temperature and the polymerization reaction temperature. In addition, when the workshop equipment is maintained, the supply of caprolactam is sometimes stopped. This prevents the heat exchange between the cooling medium and caprolactam from being completed normally, causing fluctuations in both the cooling medium temperature and the polymerization reaction temperature. Consequently, the polymerization reaction system becomes unstable, resulting in a decrease in the quality of the chips and a reduction in the factory's production efficiency. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the invention is to provide a high-efficiency cooling device for the polymerization process of nylon 6 and its working method. In addition to using caprolactam as the heat-absorbing medium, the device also uses a low-temperature heat medium of 80°C and a room-temperature cold air as the cooling medium, which can stabilize the heat medium and the constant temperature of polymerization, effectively maintain the polymerization reaction system, and ensure and improve the quality of the chips.

[0005] The technical solution of the invention is as follows:

[0006] A high-efficiency cooling device for nylon 6 polymerization process is characterized by comprising a polymerization tower and a tubular cooler located in the upper part of the polymerization tower. The heat medium outlet of the tubular cooler is connected to a heat medium pipe, which is sequentially connected to a three-way control valve, a first branch, and a second branch. The first branch is connected to a first heat exchanger using caprolactam as the cooling medium, and the second branch is sequentially connected to an air cooler and a heat exchanger using a low-temperature heat medium. The outlet of the first heat exchanger and the second branch merge before the inlet of the air cooler. The outlet of the heat exchanger is sequentially connected to a filter, a heat medium pump, and a heater, and the outlet of the heater is connected to the heat medium inlet of the tubular cooler. A first temperature gauge is installed on the caprolactam outlet pipe of the first heat exchanger, and the first temperature gauge is signal-interlocked with the three-way control valve. A second temperature gauge is installed on the outlet pipe of the heater, and the second temperature gauge is signal-interlocked with the fan of the air cooler and the low-temperature heat medium control valve of the heat exchanger.

[0007] Preferably, the heat transfer pipes inside the air cooler and heat transfer heat exchanger adopt a serpentine structure to increase the heat exchange area.

[0008] Preferably, a first bypass manual valve is connected in parallel to both ends of the above-mentioned three-way control valve, and a second bypass manual valve is connected in parallel to both ends of the low-temperature heat medium control valve, for bypassing the corresponding control valve during maintenance.

[0009] Preferably, a cooler is connected to the low-temperature heat medium outlet pipe of the heat exchanger. The cooler is equipped with a cooling water inlet pipe and a cooling water outlet pipe to cool the low-temperature heat medium after heat exchange to the process temperature for recycling.

[0010] Preferably, the temperature of the caprolactam is 80±5℃, the temperature of the low-temperature heat medium is 80±5℃, and the air cooler uses room temperature cold air as the cooling medium.

[0011] Preferably, the second thermometer is set with a process temperature value of 233±5℃, a high temperature alarm value, and an ultra-high temperature alarm value; when the second thermometer reaches the high temperature alarm value, the fan is triggered to start; when the second thermometer reaches the ultra-high temperature alarm value, the low temperature heat transfer medium control valve is triggered to open; when the temperature of the second thermometer drops back to the process temperature value, the fan stops running and the low temperature heat transfer medium control valve closes.

[0012] Preferably, the heat medium inlet pipe of the air cooler is connected to a heat medium replenishment pipe and a valve for replenishing heat medium to the heat medium circulation pipeline.

[0013] Preferably, the heater is connected to a high-temperature heat transfer medium pipe and a heat replenishment control valve. The heat replenishment control valve is interlocked with the signal of the second temperature gauge. When the temperature of the circulating heat transfer medium is lower than the process value, the high-temperature heat transfer medium is heated by the heater.

[0014] Preferably, the first branch and the second branch can operate independently. When the first heat exchanger stops supplying caprolactam, the second branch starts cooling the heat medium. The heat medium is a mixture of biphenyl and diphenyl ether. The tubular cooler is used to transfer the heat of polymerization reaction in the polymerization tower to the heat medium. The temperature of the heat medium in the high-temperature heat medium pipe of the heater is 330±5℃.

[0015] The working method of the efficient nylon 6 polymerization process cooling device of the present invention includes the following steps:

[0016] (1) Start-up of heat medium circulation: Fill the heat medium circulation pipeline with heat medium through the heat medium replenishment pipe, open the manual valves of each branch, and start the heat medium pump to make the heat medium circulate between the tube cooler of the polymerization tower, the first heat exchanger, the air cooler, the heat medium heat exchanger, the filter and the heater;

[0017] (2) Caprolactam cooling control: Caprolactam at 80±5℃ is introduced into the first heat exchanger. The heat medium is distributed to the first heat exchanger through the three-way control valve. The outlet temperature of caprolactam is detected by the first temperature gauge. The opening of the three-way regulating valve is interlocked to allow the heat medium to exchange heat with caprolactam in the first heat exchanger.

[0018] (3) Intelligent triggering of air cooling and heat exchange of heat medium: The heat medium temperature at the heater outlet is detected by the second temperature gauge. When the temperature reaches the high temperature alarm value of 233±5℃, the fan of the air cooler is started to cool the heat medium. When the temperature reaches the ultra-high temperature alarm value, the low temperature heat medium control valve is opened to introduce the low temperature heat medium of 80±5℃ into the heat medium heat exchanger for secondary cooling. After heat exchange, the low temperature heat medium enters the jacket cooler to be cooled to the process temperature and is recycled.

[0019] (4) Emergency switching in case of failure: When the supply of caprolactam is interrupted, the three-way control valve automatically switches to the fully open second branch state, and the air cooler and heat exchanger of the heat medium start automatically according to the detection value of the second temperature gauge to maintain the stable temperature of the circulating heat medium.

[0020] (5) Dynamic compensation of heat medium temperature: When the second temperature gauge detects that the temperature of the circulating heat medium is lower than the process value, the heater’s heat replenishment control valve is automatically opened to introduce a high-temperature heat medium of 330±5℃ for heating, ensuring that the temperature of the circulating heat medium is constant within the process range.

[0021] Significant advantages of this invention:

[0022] 1. Using 80℃ low-temperature heat medium and room-temperature cold air as cooling medium, the low-temperature heat medium is used in a closed loop, which not only produces no waste liquid, waste gas, or waste material, but also automatically maintains a constant circulating heat medium and polymerization temperature, improving production efficiency. In particular, when the supply of caprolactam stops and the first heat exchanger becomes ineffective, the cooling treatment of the circulating heat medium will not be affected, and the polymerization reaction and chemical equilibrium will not fluctuate. The polymerization production can continue to proceed steadily, and the quality of the chips is guaranteed. It is a very efficient and stable polymerization cooling process.

[0023] 2. Similarly, if another heat exchanger malfunctions or needs to be shut down for maintenance, it will not affect the cooling of the circulating heat medium and the polymerization production.

[0024] 3. After absorbing heat, caprolactam is heated from 80°C to about 160°C before entering the polymerization process. This is equivalent to preheating it before it enters the polymerization tower, which not only saves energy consumption of the heat transfer medium, but also greatly improves the polymerization reaction time and efficiency of caprolactam. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the working principle of the present invention. Detailed Implementation

[0026] The invention will now be further described with reference to the accompanying drawings.

[0027] As shown in the figure, the upper part of the polymerization tower 1 is equipped with a shell-and-tube cooler 01 that uses a heat medium as the heat exchange (cooling) medium. The heat medium outlet end of the shell-and-tube cooler 01 is connected to a heat medium pipe 11. The heat medium pipe 11 is connected to a three-way control valve 12. The front and rear ends of the three-way control valve 12 are connected to manual valves 13 and 14, respectively. The front and rear ends of manual valves 13 and 14 are connected in parallel to a first bypass manual valve 15. The first bypass manual valve 15 is also a bypass valve of the three-way control valve 12 (the first bypass manual valve 15 is used when the three-way control valve 12 is under maintenance). The outlet end of the manual valve 14 (i.e., the first branch) is connected to the first heat exchanger 5. The first heat exchanger 5 is connected to a caprolactam pipe 6. A first thermometer 24 is installed on the outlet pipe of the caprolactam pipe 6 (the heat medium pipe and the caprolactam pipe in the first heat exchanger 5 are independent heat conduction pipes). The first thermometer 24 is signal-interlocked with the three-way control valve 12.

[0028] As shown in the figure, the other outlet end (i.e., the second branch) of the three-way control valve 12 is connected to the manual valve 16. The outlet pipe of the manual valve 16 is connected to the outlet pipe of the first heat exchanger 5, and then to the air cooler 7 (i.e., the outlet of the first heat exchanger 5 and the second branch merge before the inlet of the air cooler 7). The inlet pipe of the air cooler 7 is connected to the heat medium replenishment pipe 32 and the valve 31. The air cooler 7 is connected to the fan 8 and the air pipe 26. The heat medium pipe inside the air cooler 7 is designed in a serpentine shape (the air cooler 7 is also a heat exchanger, and the heat medium pipe and the air pipe inside the air cooler 7 are independent heat-conducting pipes) to increase the heat exchange area. The outlet end of the air cooler 7 is connected to the heat medium heat exchanger 9. The internal heat medium pipes are also designed in a serpentine shape to increase the heat exchange area; the outlet end of the heat medium heat exchanger 9 is connected to a manual valve 17, which is connected to a filter 3. The outlet end of the filter 3 is connected to a manual valve 18, which is connected to a heat medium pump 2. A manual valve 19 is installed at the outlet end of the heat medium pump 2. The outlet pipe of the manual valve 19 is connected to a heater 4 (which is also a heat exchanger). The outlet pipe of the heater 4 is connected to the inlet end of the tubular cooler in the upper part of the polymerization tower 1. A high-temperature heat medium pipe 30 and a heat replenishment control valve 29 are installed on the heater 4 to heat the circulating heat medium in the heat medium pipe 11 (the heat medium pipe in the heater 4 and the pipe through which the high-temperature heat medium flows are independent heat-conducting pipes).

[0029] As shown in the figure, a low-temperature heat medium inlet pipe 33 and an outlet pipe 34 are installed on the heat medium heat exchanger 9. A cooler 10 using cooling water as the cooling medium is installed on the low-temperature heat medium outlet pipe 34. A cooling water inlet pipe 27 and a cooling water outlet pipe 28 are installed on the cooler 10. A low-temperature heat medium control valve 20 is installed on the low-temperature heat medium inlet pipe 33. The front and rear ends of the low-temperature heat medium control valve 20 are connected to manual valves 21 and 22, respectively. The front and rear ends of manual valves 21 and 22 are connected in parallel to a second bypass manual valve 23, which serves as a bypass valve for the low-temperature heat medium control valve 20.

[0030] As shown in the figure, a second thermometer 25 is installed on the outlet pipe of heater 4. The second thermometer 25 is interlocked with the low-temperature heat medium control valve 20, the fan 8, and the heat replenishment control valve 29.

[0031] In this application, the signal interlocking refers to a system consisting of three parts: a detection unit (sensor), a control unit (logic controller), and an execution unit (valve / fan, etc.). The detection unit (such as the first temperature gauge 24 and the second temperature gauge 25) collects the temperature data of the heat medium or caprolactam in real time. The control unit compares the detected value with the preset process threshold to determine whether an action needs to be triggered. The execution unit (such as the three-way control valve 12, the fan 8, and the low-temperature heat medium control valve 20) automatically completes switching, adjustment, and other operations according to the control signal.

[0032] The first thermometer 24 and the second thermometer 25 can be resistance temperature detectors (models can be WEST P8100 series or Omron E5CC series, measuring range: -200~600℃, supporting 4-20mA analog signals or Modbus RTU digital signals, which can be directly connected to a PLC to achieve interlocking control). The control unit (PLC) can be a Siemens S7-1200 series, model: CPU1214C + SM 1231 AI module + SM 1223 DI / DO module, supporting 8 analog inputs and 16 digital outputs (controlling three-way control valves, fans, etc.).

[0033] Operating instructions for the above cooling device:

[0034] 1. Fill the circulating heat medium pipe 11 with sufficient heat medium through the heat medium replenishment pipe 32 and valve 31, open manual valves 13, 14, 16, 17 and 18, start the heat medium pump 2, open manual valve 19, and the heat medium in the heat medium pipe 11 will begin to circulate.

[0035] Caprolactam (temperature 80±5℃) is supplied to the tube side of the first heat exchanger 5 through caprolactam tube 6. The heat medium enters the shell side of the first heat exchanger 5, and the process temperature value of the first temperature gauge 24 is set (generally 160±10℃). The first temperature gauge 24 sends a signal to the three-way control valve 12. At this time, the three-way control valve 12 automatically opens according to the process temperature value of the first temperature gauge 24 and supplies equal or different amounts of heat medium to the first heat exchanger 5 and the manual valve 16. At this time, the caprolactam in the tube side of the first heat exchanger 5 will exchange excess heat in the circulating heat medium, causing the temperature of the circulating heat medium to drop below the temperature of the tube cooler at the top of the polymerization tower 1.

[0036] 2. After the heat medium merges at the first heat exchanger 5 and the manual valve 16, it enters the air cooler 7 and the heat medium heat exchanger 9, then returns to the heat medium pump 2 through the filter 3, and then returns to the shell and tube cooler at the top of the polymerization tower 1 through the heat medium pump 2.

[0037] 3. Set the process temperature value (generally 233±5℃) and high (238℃±2℃) and ultra-high (242℃±2℃) temperature alarm values ​​for the second temperature gauge 25. Based on the process temperature value of the second temperature gauge 25, the supplementary heat control valve 29 automatically opens or closes. The temperature of the heat medium in the high-temperature heat medium pipe 30 is generally 330±5℃. If the process temperature of the second temperature gauge 25 is too high and reaches the alarm value, a signal is sent to the fan 8, which automatically starts to cool the heat medium in the serpentine tube of the air cooler 7. When the process temperature of the second temperature gauge 25 is too high and reaches the ultra-high temperature alarm value, a signal is sent to the low-temperature heat medium control valve 20 (temperature 80±5℃), causing it to automatically open and further cool the heat medium in the serpentine tube of the heat medium heat exchanger 9. After heat exchange, the temperature of the low-temperature heat medium will be higher than the process value. After heat exchange with the cooling water of the double-channel cooler 10, it will return to the process value and return to the low-temperature heat medium system. When the high and ultra-high temperature alarm values ​​of the second temperature gauge 25 are cleared, the second temperature gauge 25 sends a signal to the low-temperature heat medium control valve 20 to make it automatically close. When the second temperature gauge 25 reaches the process temperature value, it sends a signal to the fan 8, and the fan 8 automatically stops running.

[0038] 4. If the supply of caprolactam to the tube side of the first heat exchanger 5 is stopped due to workshop maintenance or other reasons, the heat exchange between the circulating heat medium and caprolactam will stop. At this time, the temperature of the circulating heat medium coming out of the shell and tube cooler in the upper part of the polymerization tower 1 will be abnormally high. Then the operation in step 3 above will automatically take effect to make the temperature of the circulating heat medium (second temperature gauge 25) reach the process temperature value.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-efficiency cooling device for nylon 6 polymerization process, characterized in that: The system includes a polymerization tower (1) and a tubular cooler (01) located in the upper part of the polymerization tower (1). The heat medium outlet of the tubular cooler is connected to a heat medium pipe (11). The heat medium pipe (11) is connected in sequence to a three-way control valve (12), a first branch, and a second branch. The first branch is connected to a first heat exchanger (5) using caprolactam as the cooling medium. The second branch is connected in sequence to an air cooler (7) and a heat medium heat exchanger (9) using a low-temperature heat medium. The outlet of the first heat exchanger (5) and the second branch merge before the inlet of the air cooler (7). The heat medium heat exchanger (9) The outlet of the first heat exchanger (5) is connected in sequence to the filter (3), the heat pump (2) and the heater (4). The outlet of the heater (4) is connected to the heat inlet of the shell-and-tube cooler. A first thermometer (24) is installed on the caprolactam outlet pipe of the first heat exchanger (5). The first thermometer (24) is signal-interlocked with the three-way control valve. A second thermometer (25) is installed on the outlet pipe of the heater (4). The second thermometer (25) is signal-interlocked with the fan (8) of the air cooler (7) and the low-temperature heat medium control valve (20) of the heat exchanger (9).

2. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The heat transfer pipes inside the air cooler (7) and the heat transfer heat exchanger (9) are both designed with a serpentine structure to increase the heat exchange area.

3. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The three-way control valve (12) is connected in parallel with a first bypass manual valve (15) at both ends, and the low-temperature heat medium control valve (20) is connected in parallel with a second bypass manual valve (23) at both ends, for bypassing the corresponding control valve during maintenance.

4. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The low-temperature heat medium outlet pipe of the heat exchanger (9) is connected to a channel cooler (10). The channel cooler is equipped with a cooling water inlet pipe (27) and a cooling water outlet pipe (28) to cool the low-temperature heat medium after heat exchange to the process temperature for recycling.

5. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The temperature of the caprolactam is 80±5℃, the temperature of the low-temperature heat medium is 80±5℃, and the air cooler (7) uses room temperature cold air as the cooling medium.

6. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The second temperature gauge (25) is set with a process temperature value of 233±5℃, a high temperature alarm value, and an ultra-high temperature alarm value; when the second temperature gauge (25) reaches the high temperature alarm value, the fan (8) is triggered to start; when the second temperature gauge (25) reaches the ultra-high temperature alarm value, the low temperature heat medium control valve (20) is triggered to open; when the temperature of the second temperature gauge (25) drops back to the process temperature value, the fan stops running and the low temperature heat medium control valve (20) closes.

7. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The air cooler (7) has a heat medium replenishment pipe (32) and a valve (31) connected to its heat medium inlet pipe for replenishing heat medium to the heat medium circulation pipeline.

8. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The heater (4) is connected to a high-temperature heat medium pipe (30) and a heat replenishment control valve (29). The heat replenishment control valve (29) is interlocked with the signal of the second temperature gauge (25). When the temperature of the circulating heat medium is lower than the process value, it is heated to the process value by the high-temperature heat medium.

9. The high-efficiency nylon 6 polymerization process cooling device according to claim 1, characterized in that, The first branch and the second branch can operate independently. When the first heat exchanger stops supplying caprolactam, the second branch starts cooling the heat medium. The heat medium is a mixture of biphenyl and diphenyl ether. The tubular cooler is used to transfer the heat of polymerization reaction in the polymerization tower to the heat medium. The temperature of the heat medium in the high-temperature heat medium pipe of the heater is 330±5℃.

10. A method for operating the efficient nylon 6 polymerization process cooling device according to any one of claims 1-9, characterized in that, Includes the following steps: S1 Heat medium circulation start-up: Fill the heat medium circulation pipeline with heat medium through the heat medium replenishment pipe (32), open the manual valves of each branch, and start the heat medium pump (2) to make the heat medium circulate between the polymerization tower tubular cooler, the first heat exchanger (5), the air cooler (7), the heat medium heat exchanger (9), the filter (3) and the heater (4); S2 Caprolactam Cooling Control: Caprolactam at 80±5℃ is introduced into the first heat exchanger (5). The heat medium is distributed to the first heat exchanger (5) through the three-way control valve (12). The outlet temperature of caprolactam is detected by the first temperature gauge (24). The opening of the three-way regulating valve is interlocked to allow the heat medium to exchange heat with caprolactam in the first heat exchanger. S3 Intelligent Triggering of Air Cooling and Heat Exchange: The heat medium temperature at the outlet of heater (4) is detected by the second temperature gauge (25). When the temperature reaches the high temperature alarm value of 233±5℃, the fan (8) of the air cooler (7) is started to air cool the heat medium. When the temperature reaches the ultra-high temperature alarm value, the low temperature heat medium control valve (20) is opened to introduce low temperature heat medium of 80±5℃ into the heat medium heat exchanger (9) for secondary cooling. After heat exchange, the low temperature heat medium enters the jacket cooler (10) to be cooled to the process temperature and recycled. S4 fault emergency switching: When the caprolactam supply is interrupted, the three-way control valve (12) automatically switches to the fully open second branch state, and the air cooler (7) and the heat exchanger (9) automatically start according to the detection value of the second temperature gauge (25) to maintain the stable temperature of the circulating heat medium. S5 Dynamic compensation of heat medium temperature: When the second temperature gauge (25) detects that the temperature of the circulating heat medium is lower than the process value, the heat replenishment control valve (29) of the heater (4) is automatically opened to introduce a high-temperature heat medium of 330±5℃ to replenish the heat and ensure that the temperature of the circulating heat medium is constant within the process range.

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