Automatic pH value regulating device of polymerization recovery system

Abstract

The utility model discloses a pH value self-control adjusting device of a polymerization recovery system, and relates to the technical field of polyvinyl chloride chemical industry. The device comprises a vinyl chloride gas phase inlet pipe which is connected with the inlet end of a recovery cooler, and further comprises a liquid caustic soda adding system which consists of a liquid caustic soda storage tank and a liquid caustic soda conveying pipeline, and the liquid caustic soda adding system is used for carrying out acid-base neutralization chemical reaction on a vinyl chloride gas phase entering the recovery cooler; the pH value entering the recovery cooler is controlled to be neutral or slightly alkaline, equipment and pipeline corrosion can be effectively prevented, the production cost is reduced, safety accidents are prevented, meanwhile, condensed monomers can be recovered to participate in a polymerization reaction with more stable performance, and the situation that the product quality is affected due to the fact that a polymerization reaction system is damaged is prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of polyvinyl chloride chemical industry, in particular to a pH value automatic control regulating device for a polymerization recovery system. Background Art

[0002] In the polyvinyl chloride (PVC) production process, as the pressure drop in the polymerization reactor increases, resin particle formation stabilizes, signaling the monomer conversion rate has reached process requirements and the reaction is complete. The resulting PVC resin is then transported to the discharge tank, while the unreacted gaseous monomer is compressed, condensed, and recycled through a recovery system. However, during the polymerization reaction, oxygen in the system causes the vinyl chloride macromolecules to release hydrogen chloride, forming an acidic substance with water. As the reaction time increases, the pH of the reaction system gradually decreases. Currently, the original design of a 108m³ reactor production process in China generally uses a neutralizer in the discharge tank to adjust the pH of the slurry. However, this neglects adjusting the pH of the unreacted gaseous monomer in the recovery system. This results in a chronically acidic recovery system, which not only causes corrosion in the dynamic and static equipment, valves, and piping of the subsequent compression, condensation, and recovery separation systems, but also creates an acidic phenotype in the recovered condensed VCM monomer, impacting the reactor reaction system, causing additive performance changes or failure, and in severe cases, resulting in the formation of coarse material, directly impacting the continuous and stable operation of the production system and product quality control. Utility Model Content

[0003] In response to the above technical problems, the utility model provides a pH automatic control device for a polymerization recovery system, which is used to solve the problem in the existing polyvinyl chloride production process that there is a lack of regulation of the pH value of the gas phase monomers that do not participate in the reaction, resulting in the recovery system being acidic for a long time and affecting the operation of the recovery system.

[0004] In order to achieve the above-mentioned purpose, the technical solution of the present utility model is as follows:

[0005] A pH value automatic control device for a polymerization recovery system comprises a vinyl chloride gas inlet pipe connected to the inlet end of a recovery cooler, and a liquid alkali adding system, the liquid alkali adding system consisting of a liquid alkali storage tank and a liquid alkali delivery pipeline, the inlet end of the liquid alkali storage tank being respectively connected to the liquid alkali inlet pipe and the water distribution inlet pipe, a first manual valve being installed on the liquid alkali inlet pipe, a second manual valve being installed on the water distribution inlet pipe, a motor being installed on the top of the liquid alkali storage tank, a main shaft of the motor passing through the top of the liquid alkali storage tank being connected to a stirring paddle, one end of the liquid alkali delivery pipeline being connected to the outlet end of the liquid alkali storage tank, the other end of the liquid alkali delivery pipeline being connected to the vinyl chloride gas inlet pipe and then to the inlet end of the recovery cooler, a liquid alkali delivery pump, a first automatic control valve, a remote flow transmitter and a sixth manual valve being sequentially installed on the liquid alkali delivery pipeline, the first automatic control valve and the remote flow transmitter being interlocked by a PLC controller, the PLC controller being further interlocked with the motor for control, transmitting control signals to a DCS computer in a central control room, thereby realizing remote continuous operation and monitoring.

[0006] Furthermore, a remote liquid level transmitter is installed on the liquid alkali storage tank, a detection end of the remote liquid level transmitter is located in the liquid alkali storage tank, and the remote liquid level transmitter is interlocked with a PLC controller.

[0007] Furthermore, a glass sight glass is installed on the liquid alkali delivery pipeline, and the glass sight glass is located between the remote flow transmitter and the sixth hand valve.

[0008] Furthermore, it also includes a reflux pipe, one end of the reflux pipe is connected to the liquid alkali delivery pipe between the liquid alkali delivery pump and the first automatic regulating valve, and the other end of the reflux pipe is connected to the reflux port on the top of the liquid alkali storage tank. A second automatic regulating valve is installed on the reflux pipe, and a remote pressure transmitter is provided between the reflux pipe and the first automatic regulating valve on the liquid alkali delivery pipe. The second automatic regulating valve and the remote pressure transmitter are interlocked and controlled by a PLC controller.

[0009] Furthermore, a magnetic flap level gauge is installed on the liquid alkali storage tank, and a detection end of the magnetic flap level gauge is arranged in the liquid alkali storage tank.

[0010] Furthermore, a check valve is installed between the remote pressure transmitter and the first automatic regulating valve on the liquid alkali delivery pipeline.

[0011] Compared with the prior art, the beneficial effects of the utility model are as follows: by adding liquid alkali to the system, an acid-base neutralization chemical reaction is performed on the vinyl chloride gas phase entering the recovery cooler, and the pH value entering the recovery cooler is controlled to be neutral or alkaline, which can effectively prevent corrosion of equipment and pipelines, reduce production costs, and prevent safety accidents. At the same time, it helps to recover condensed monomers to participate in the polymerization reaction with more stable performance, and prevent damage to the polymerization reaction system and affect product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural diagram of the utility model;

[0013] In the picture:

[0014] 1. First manual valve; 2. Liquid caustic soda inlet pipe; 3. Second manual valve; 4. Water distribution inlet pipe; 5. Magnetic flap level gauge; 6. Motor; 7. Agitator; 8. Reflux pipe; 9. Remote level transmitter; 10. Liquid caustic soda storage tank; 11. Third manual valve; 12. Eighth manual valve; 13. Second automatic regulating valve; 14. Seventh manual valve; 15. Liquid caustic soda delivery pump; 16. Remote pressure transmitter; 17. Check valve; 18. Fourth manual valve; 19. First automatic regulating valve; 20. Fifth manual valve; 21. Remote flow transmitter; 22. Liquid caustic soda delivery pipe; 23. Glass sight glass; 24. Sixth manual valve; 25. Vinyl chloride gas inlet pipe; 26. Recovery cooler. DETAILED DESCRIPTION

[0015] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. Furthermore, descriptions of known structures and technologies are omitted in the following description to avoid unnecessary confusion regarding the concepts of the present invention.

[0016] like Figure 1As shown, a pH value automatic control regulating device for a polymerization recovery system includes a vinyl chloride gas inlet pipe 25, which is connected to the inlet end of a recovery cooler 26, and also includes a liquid alkali adding system, which consists of a liquid alkali storage tank 10 and a liquid alkali delivery pipe 22. The inlet end of the liquid alkali storage tank 10 is respectively connected to a liquid alkali inlet pipe 2 and a water distribution inlet pipe 4, a first hand valve 1 is installed on the liquid alkali inlet pipe 2, and a second hand valve 3 is installed on the water distribution inlet pipe 4. A motor 6 is installed on the top of the liquid alkali storage tank 10, and the main shaft of the motor 6 passes through the top of the liquid alkali storage tank 10 and is connected to a stirring paddle 7. One end of the liquid alkali delivery pipe 22 is connected to the outlet end of the liquid alkali storage tank 10, and the other end of the liquid alkali delivery pipe 22 is connected to the vinyl chloride gas inlet pipe 25 and then connected to the inlet end of the recovery cooler 26. A liquid alkali delivery pump 15, a first automatic regulating valve 19, a remote flow transmitter 21 and a sixth hand valve 24 are installed on the liquid alkali delivery pipe 22 in sequence. A third manual valve 11 can be installed between the liquid alkali storage tanks 10 to prevent the liquid alkali delivery pump 15 from being damaged when the flow rate at the outlet of the liquid alkali storage tank 10 is too high. A fourth manual valve 18 and a fifth manual valve 20 can be added on both sides of the first automatic regulating valve 19 respectively. When the first automatic regulating valve 19 fails, the delivery of liquid alkali can be controlled by the fourth manual valve 18 and the fifth manual valve 20. The first automatic regulating valve 19 and the remote flow transmitter 21 are interlocked through the PLC controller. When the remote flow meter detects that the flow rate is too large or too small, the PLC controller controls the valve port of the first automatic regulating valve 19 to open larger or smaller. The PLC controller is also interlocked with the motor 6 for control. When the liquid alkali in the liquid alkali storage tank 10 needs to be stirred, the motor 6 is started by the PLC controller, and the main shaft of the motor 6 rotates to drive the stirring paddle 7 to rotate, ensuring that the liquid alkali and water are evenly mixed and the liquid alkali is effectively diluted. The control signal is transmitted to the DCS computer in the central control room to realize remote continuous operation and monitoring.

[0017] The liquid caustic soda storage tank 10 is equipped with a remote level transmitter 9. The detection end of the remote level transmitter 9 is located inside the liquid caustic soda storage tank 10. The remote level transmitter 9 is interlocked with a PLC controller. The remote level transmitter 9 monitors the liquid level in the liquid caustic soda storage tank 10 in real time and transmits the data to the DCS computer in the central control room via the PLC controller, facilitating liquid level monitoring in the liquid caustic soda storage tank 10. Furthermore, when the DCS computer in the central control room detects that stirring is required in the liquid caustic soda storage tank 10, a control signal is sent to the PLC controller, which controls the rotation of the motor 6, thereby achieving remote operation and reducing labor intensity.

[0018] A glass sight glass 23 is installed on the liquid caustic soda delivery pipeline 22, and is located between the remote flow transmitter 21 and the sixth hand valve 24. Through the glass sight glass 23, the delivery progress of the liquid caustic soda in the liquid caustic soda delivery pipeline 22 can be visually observed, and the opening and closing of the sixth hand valve 24 can be selected according to the observation result.

[0019] It also includes a reflux pipe 8, one end of the reflux pipe 8 is connected to the liquid alkali delivery pipe 22 between the liquid alkali delivery pump 15 and the first automatic regulating valve 19, and the other end of the reflux pipe 8 is connected to the reflux port on the top of the liquid alkali storage tank 10. A second automatic regulating valve 13 is installed on the reflux pipe 8. A seventh manual valve 14 and an eighth manual valve 12 can be added on both sides of the second automatic regulating valve 13 respectively. When the second automatic regulating valve 13 fails, the delivery of liquid alkali can be controlled by the seventh manual valve 14 and the eighth manual valve 12. A remote pressure transmitter 16 is provided between the reflux pipe 8 and the first automatic regulating valve 19 on the liquid alkali delivery pipe 22. The second automatic regulating valve 13 and the remote pressure transmitter 16 are interlocked and controlled by a PLC controller. When the remote pressure transmitter 16 detects that the pressure in the liquid caustic soda conveying pipeline 22 is too high, the second automatic regulating valve 13 is controlled to open, and the liquid caustic soda passing through the liquid caustic soda conveying pump 15 is diverted and depressurized, which not only effectively reduces the pressure in the pipeline, but also can further mix the liquid caustic soda.

[0020] The liquid alkali storage tank 10 is also equipped with a magnetic flap level gauge 5, the detection end of which is arranged in the liquid alkali storage tank 10. The magnetic flap level gauge 5 serves as a backup. When the control system fails, the liquid level height in the liquid alkali storage tank 10 can be manually monitored by the magnetic flap level gauge 5.

[0021] A check valve 17 is installed between the remote pressure transmitter 16 and the first automatic regulating valve 19 on the liquid caustic soda delivery pipeline 22 to prevent vinyl chloride gas from flowing into the liquid caustic soda or other systems and causing safety accidents when the liquid caustic soda delivery pump 15 fails and stops in a pressure-losing state or the pressure is lower than the recovery system pressure.

[0022] When using:

[0023] 1. The concentration of liquid alkali is 32%. The first hand valve 1 is opened to transport liquid alkali to the liquid alkali storage tank 10 through the liquid alkali inlet pipe 2. When the remote liquid level transmitter 9 shows the liquid level is 20%, the DCS computer in the central control room starts the motor 6 to drive the stirring paddle 7 to rotate and continue to transport liquid alkali. When the liquid level rises to 60%, the first hand valve 1 is closed and the second hand valve 3 is opened at the same time to transport water to the liquid alkali storage tank 10 through the water distribution inlet pipe 4. When the remote liquid level transmitter 9 shows the liquid level is 80%, the second hand valve 3 is closed and the water distribution is stopped. After stirring for 30 minutes, the laboratory is notified to take samples to test the concentration of the configured alkali. The test result is qualified when it is 20%±3%, which meets the process control requirements.

[0024] 3. Open the third manual valve 11, the seventh manual valve 14 and the eighth manual valve 12, and prime the liquid alkali delivery pump 15 to prevent cavitation and continuous delivery. Then start the liquid alkali delivery pump 15, and slowly open the second automatic regulating valve 13 to start the liquid alkali circulation. At the same time, observe and adjust the pump pressure according to the remote pressure transmitter 16 to meet the process setting requirements.

[0025] 4. Open the fourth manual valve 18 and the fifth manual valve 20, and at the same time slowly open the first automatic regulating valve 19, and deliver liquid alkali at a small flow rate through the liquid alkali delivery pipeline 22. After observing that the liquid alkali fills the pipeline through the remote flow transmitter 21 and the glass sight glass 23, open the sixth manual valve 24 to deliver the configured liquid alkali to the vinyl chloride gas inlet pipe 25 and into the recovery cooler 26 to achieve the purpose of adjusting the pH value of the recovery system.

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pH value automatic control device for a polymerization recovery system, comprising a vinyl chloride gas phase inlet pipe (25), the vinyl chloride gas phase inlet pipe (25) being connected to the inlet end of a recovery cooler (26), characterized in that: The invention also includes a liquid alkali adding system, which is composed of a liquid alkali storage tank (10) and a liquid alkali delivery pipe (22). The inlet end of the liquid alkali storage tank (10) is connected to a liquid alkali inlet pipe (2) and a water distribution inlet pipe (4), respectively. A first hand valve (1) is installed on the liquid alkali inlet pipe (2), and a second hand valve (3) is installed on the water distribution inlet pipe (4). A motor (6) is installed on the top of the liquid alkali storage tank (10). The main shaft of the motor (6) passes through the top of the liquid alkali storage tank (10) and is connected to a stirring paddle (7). One end of the liquid alkali delivery pipe (22) is connected to the outlet end of the liquid alkali storage tank (10). The other end of the liquid alkali delivery pipeline (22) is connected to the vinyl chloride gas phase inlet pipe (25) and then connected to the inlet end of the recovery cooler (26). The liquid alkali delivery pump (15), the first automatic regulating valve (19), the remote flow transmitter (21) and the sixth manual valve (24) are installed on the liquid alkali delivery pipeline (22) in sequence. The first automatic regulating valve (19) and the remote flow transmitter (21) are interlocked through the PLC controller. The PLC controller is also interlocked with the motor (6) for control and transmits the control signal to the DCS computer in the central control room to realize remote continuous operation and monitoring.

2. The pH automatic control device for a polymerization recovery system according to claim 1, characterized in that: A remote liquid level transmitter (9) is installed on the liquid alkali storage tank (10), a detection end of the remote liquid level transmitter (9) is located inside the liquid alkali storage tank (10), and the remote liquid level transmitter (9) is interlocked with a PLC controller.

3. The pH automatic control device for a polymerization recovery system according to claim 2, characterized in that: A glass sight glass (23) is installed on the liquid alkali delivery pipeline (22), and the glass sight glass (23) is located between the remote flow transmitter (21) and the sixth manual valve (24).

4. The pH automatic control device for a polymerization recovery system according to claim 3, characterized in that: The invention also includes a reflux pipe (8), one end of which is connected to the liquid alkali delivery pipe (22) between the liquid alkali delivery pump (15) and the first automatic regulating valve (19), and the other end of which is connected to the reflux port at the top of the liquid alkali storage tank (10). A second automatic regulating valve (13) is installed on the reflux pipe (8), and a remote pressure transmitter (16) is provided between the reflux pipe (8) and the first automatic regulating valve (19) on the liquid alkali delivery pipe (22). The second automatic regulating valve (13) and the remote pressure transmitter (16) are interlocked and controlled by a PLC controller.

5. The pH automatic control device for a polymerization recovery system according to claim 4, characterized in that: A magnetic flap level gauge (5) is also installed on the liquid alkali storage tank (10), and a detection end of the magnetic flap level gauge (5) is arranged in the liquid alkali storage tank (10).

6. The pH automatic control device for a polymerization recovery system according to claim 5, characterized in that: A check valve (17) is installed between the remote pressure transmitter (16) and the first automatic regulating valve (19) on the liquid alkali delivery pipeline (22).

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