A pH adjusting device for a PVC recycling system

Abstract

The application relates to a pH adjusting device for a PVC recycling system. The device comprises an RVCM condenser, an alkali solution preparation tank, an alkali solution conveying pipeline, a desalted water conveying pipeline and a metering pump. The alkali solution conveying pipeline and the desalted water conveying pipeline are connected with the alkali solution preparation tank, the alkali solution preparation tank is connected with the metering pump through a pipeline, the metering pump is connected with a VCM inlet of the RVCM condenser through a pipeline, a valve is arranged on the pipeline between the alkali solution preparation tank and the metering pump, a dripping flow window for observing the titration speed is arranged on the pipeline between the metering pump and the RVCM condenser, and a sampling port is arranged on the pipeline of a VCM outlet of the RVCM condenser. The alkali solution preparation and conveying device is arranged to convey alkali solution to the RVCM condenser, can effectively neutralize acidic substances in the recycling system, prevent equipment corrosion, guarantee safe and stable operation of a production system, has the remarkable advantages of prolonging the service life of the equipment and improving production continuity.

Description

Technical Field

[0001] This application relates to the field of polyvinyl chloride production equipment technology, and more specifically, to a pH adjustment device for a PVC recycling system. Background Technology

[0002] In the production of polyvinyl chloride (PVC), vinyl chloride monomer is converted into PVC particles through suspension polymerization, but this reaction cannot achieve complete conversion. Unreacted vinyl chloride monomer needs to be recovered through two main stages: polymerization discharge and stripping. The recovered vinyl chloride monomer is then processed through compression and condensation to form recovered vinyl chloride monomer (R-VCM), which is then recycled back into the polymerization system. However, during the recovery process, under compressor pressurization and heating conditions, the vinyl chloride monomer, due to its insufficient thermal stability, decomposes to produce hydrogen chloride gas, causing the recovered gaseous vinyl chloride (VCM) to be acidic. This acidic environment, acting on the recovery system equipment over a long period, especially critical equipment such as the RVCM condenser, can cause serious corrosion problems. Equipment corrosion not only leads to unplanned system shutdowns, affecting production efficiency, but may also cause significant safety hazards such as vinyl chloride leaks. Current technologies lack effective pH adjustment methods to neutralize the acidic environment in the recovery system, failing to fundamentally solve the equipment corrosion problem. Utility Model Content

[0003] The purpose of this application is to provide a pH adjustment device and control method for a PVC recycling system, which has the advantages of automatically adjusting the pH value of the recycling system to neutralize the acidic environment, effectively inhibiting equipment corrosion, extending equipment service life, and ensuring production safety and continuity.

[0004] This application provides a pH adjustment device for a PVC recycling system, the technical solution of which is as follows: The device includes an RVCM condenser, an alkali preparation tank, an alkali delivery pipeline, a demineralized water delivery pipeline, and a metering pump. The alkali delivery pipeline and the demineralized water delivery pipeline are connected to the alkali preparation tank. The alkali preparation tank is connected to the metering pump via a pipeline. The metering pump is connected to the VCM inlet of the RVCM condenser via a pipeline. A valve is installed on the pipeline connecting the alkali preparation tank and the metering pump. A drip window for observing the titration rate is installed on the pipeline between the metering pump and the RVCM condenser. A sampling port is provided on the pipeline at the VCM outlet of the RVCM condenser.

[0005] Furthermore, the device of this application also includes a PLC controller; an electromagnetic regulating valve and a flow sensor are respectively installed on the alkali conveying pipeline and the demineralized water conveying pipeline, and a liquid level sensor is installed in the alkali preparation tank; the PLC controller is electrically connected to the electromagnetic regulating valve, the flow sensor, and the liquid level sensor respectively.

[0006] Furthermore, a nitrogen delivery pipe is connected to the bottom of the alkali preparation tank; the nitrogen delivery pipe extends into the tank body of the alkali preparation tank and is tangent to the inner wall of the tank body.

[0007] Furthermore, a valve is installed on the nitrogen delivery pipe.

[0008] As can be seen from the above, the pH adjustment device for a PVC recycling system provided in this application, by setting up an alkali solution preparation and delivery device, delivers alkali solution (such as NaOH solution) to the RVCM condenser, which can effectively neutralize acidic substances in the recycling system, prevent equipment corrosion, and ensure the safe and stable operation of the production system. It has significant advantages in extending equipment service life and improving production continuity.

[0009] The alkali preparation device of this application uses a PLC controller, an electromagnetic regulating valve and a flow sensor. It can accurately and quickly prepare the required concentrated alkali solution according to the pH value sampled from the RVCM condenser. Through the precise delivery of the metering pump, it can accurately adjust the pH value of the RVCM condenser.

[0010] The liquid level sensor in this application can monitor the alkali solution level in the alkali solution preparation tank. When the alkali solution reaches the upper limit, the electromagnetic regulating valve is shut off via the PLC controller to stop the solution preparation and improve the safety of the solution preparation. The nitrogen delivery pipe continuously fills the alkali solution preparation tank with nitrogen, which enables the alkali solution and demineralized water to mix quickly and evenly, and can also remove the high temperature generated during the alkali solution dilution process, preventing damage to the metering pump diaphragm due to excessive temperature. Attached Figure Description

[0011] Figure 1 This is a system connection diagram of the present invention. Detailed Implementation

[0012] like Figure 1 As shown, this application proposes a pH adjustment device including an RVCM condenser 1, an alkali preparation tank 2, an alkali delivery pipeline 3, a demineralized water delivery pipeline 4, and a metering pump 5. The alkali delivery pipeline 3 and the demineralized water delivery pipeline 4 are connected to the alkali preparation tank 2, which is connected to the metering pump 5 via pipelines. The outlet of the metering pump 5 is connected to the VCM inlet of the RVCM condenser 1 via a dosing pipeline. A valve is installed on the pipeline between the alkali preparation tank 2 and the metering pump 5. A drip window 6 is installed on the pipeline between the metering pump 5 and the condenser. A sampling port is installed on the VCM outlet pipeline of the condenser.

[0013] The alkaline solution preparation tank 2 is a container used for storing and mixing alkaline solutions. It connects to both the alkaline solution delivery pipe 3 and the demineralized water delivery pipe 4 to prepare solutions of different concentrations. The alkaline solution delivery pipe 3 is a channel for transporting high-concentration alkaline solutions (e.g., a 32% NaOH solution), and can be made of corrosion-resistant PTFE pipe to ensure the safe transport of strongly alkaline media. The demineralized water delivery pipe 4 can be made of stainless steel pipe to avoid impurities in the water affecting the accuracy of the solution preparation. The metering pump 5 is a device for precisely controlling the liquid delivery volume, and can be made of a plunger-type reciprocating pump, controlling the amount of alkaline solution added by adjusting the stroke frequency. The drip window 6 is a transparent observation component for observing the liquid flow state, and can be made of a borosilicate glass tube section, allowing for visual inspection of the droplet velocity to determine if the dosage is normal. The sampling port is an interface for extracting fluid samples, and can be made of a quick connector with a shut-off valve, facilitating periodic sampling and testing of the pH value of the fluid at the outlet of the RVCM condenser 1. Samples are collected periodically (weekly) from the RVCM condenser 1, and the pH value is tested. If the sample is acidic, the unit is activated for neutralization. Specifically, alkaline solution and demineralized water are mixed in the alkaline solution preparation tank 2 according to the pH value of the sample, and then fed into the metering pump 5 via a valve. The metering pump 5 delivers a measured amount of alkaline solution to the VCM inlet pipe, where it reacts with the acidic vinyl chloride. The operator observes the dosing rate through the drip window 6, and adjusts the pumping parameters immediately if the flow rate is abnormal. The neutralized mixture then enters the RVCM condenser 1 for further neutralization, ensuring that the pH value in the RVCM condenser 1 is neutral or weakly alkaline.

[0014] like Figure 1 As shown, this application further proposes a PLC controller 7, an electromagnetic regulating valve 8 and a flow sensor 9 respectively installed on the alkali conveying pipeline 3 and the demineralized water conveying pipeline 4, a liquid level sensor 10 installed in the alkali preparation tank 2, and the PLC controller 7 being electrically connected to the electromagnetic regulating valve 8, the flow sensor 9, and the liquid level sensor 10 respectively.

[0015] The PLC controller 7 can be implemented using an industrial-grade Siemens S7-1200 series module, used to receive sensor signals and output control commands. The electromagnetic regulating valve 8 is a flow control component with an electromagnetic drive device, specifically implemented as a direct-acting proportional regulating valve, adjusting the pipeline flow by changing the valve core opening. The flow sensor 9 is a measuring device for real-time detection of liquid flow velocity, specifically implemented as a Coriolis mass flow meter, used to feed back the flow data of alkali solution and demineralized water in the pipeline to the PLC. The level sensor 10 is a detection element for monitoring the liquid level in the container, specifically implemented as a magnetostrictive level transmitter, used to feed back the real-time liquid level status of the alkali solution preparation tank 2 to the PLC.

[0016] Specifically, the PLC controller 7 receives the flow data of alkali and demineralized water from the flow sensor 9, calculates the deviation between the actual ratio and the preset value, and sends an opening adjustment command to the solenoid regulating valve 8 to mix the two liquids in proportion. When the level sensor 10 detects that the liquid level in the alkali preparation tank 2 is lower than the safety threshold, the PLC immediately activates the interlock protection program and closes the solenoid regulating valve 8. The flow sensor 9 and the solenoid regulating valve 8 form a closed-loop control circuit, correcting pipeline flow fluctuations in real time to ensure stable mixed solution concentration. The PLC periodically collects data from each sensor through a preset program, dynamically adjusts the opening of the solenoid valve and the output parameters of the metering pump 5, and achieves continuous and stable delivery of the pH adjuster.

[0017] like Figure 1 As shown, this application further proposes that the bottom of the alkali preparation tank 2 is connected to a nitrogen delivery pipe 11, the nitrogen delivery pipe 11 extends into the tank body of the alkali preparation tank 2 and is tangent to the inner wall of the tank body of the alkali preparation tank 2, and a valve is provided on the nitrogen delivery pipe 11.

[0018] The nitrogen delivery pipe 11 extending into the tank means that the end of the delivery pipe extends into the internal space of the tank. This can be achieved using a straight pipe section or an elbow structure, to ensure the gas injection depth and form a stable flow. The nitrogen delivery pipe 11 being tangent to the inner wall of the tank means that the axial direction of the pipe opening forms a tangential angle with the inner wall of the tank, to cause the gas to flow tangentially along the tank wall and generate a swirling effect.

[0019] Specifically, when nitrogen gas enters the alkali preparation tank 2 through the nitrogen delivery pipe 11 connected to the bottom, the gas forms a spiral upward flow path along the inner wall of the alkali preparation tank 2 due to the tangential arrangement of the pipe opening and the tank wall. This swirling effect generated by the tangential airflow causes the liquid inside the tank to form a vortex motion, promoting thorough mixing of the alkali solution and demineralized water within the tank. The structure of the nitrogen delivery pipe 11 extending into the tank body ensures that the gas is injected from the bottom area, avoiding insufficient mixing due to uneven gas distribution in local areas. The swirling action continuously agitates the liquid, quickly removing the heat generated during the alkali dilution process and preventing damage to the diaphragm of the metering pump 5 due to excessive temperature. When not preparing alkali, a valve is installed on the nitrogen delivery pipe 11 to prevent residual liquid in the alkali preparation tank 2 from flowing into the nitrogen delivery pipe 11.

Claims

1. A pH adjustment device for a PVC recycling system, comprising an RVCM condenser (1), characterized in that: It also includes an alkali preparation tank (2), an alkali delivery pipeline (3), a demineralized water delivery pipeline (4), and a metering pump (5); the alkali delivery pipeline (3) and the demineralized water delivery pipeline (4) are connected to the alkali preparation tank (2), the alkali preparation tank (2) is connected to the metering pump (5) through a pipeline, the metering pump (5) is connected to the VCM inlet of the RVCM condenser (1) through a pipeline, and a valve is provided on the pipeline between the alkali preparation tank (2) and the metering pump (5); a drip window (6) for observing the titration rate is provided on the pipeline between the metering pump (5) and the RVCM condenser (1); a sampling port is provided on the pipeline at the VCM outlet of the RVCM condenser (1).

2. The pH adjustment device for a PVC recycling system as described in claim 1, characterized in that: It also includes a PLC controller (7); electromagnetic regulating valves (8) and flow sensors (9) are respectively installed on the alkali conveying pipeline (3) and the demineralized water conveying pipeline (4), and a liquid level sensor (10) is installed in the alkali preparation tank (2); the PLC controller (7) is electrically connected to the electromagnetic regulating valve (8), the flow sensor (9), and the liquid level sensor (10).

3. A pH adjustment device for a PVC recycling system as described in claim 1 or 2, characterized in that: The bottom of the alkali preparation tank (2) is connected to a nitrogen delivery pipe (11); the nitrogen delivery pipe (11) extends into the tank body of the alkali preparation tank (2) and is tangent to the inner wall of the tank body of the alkali preparation tank (2).

4. The pH adjustment device for a PVC recycling system as described in claim 3, characterized in that: A valve is installed on the nitrogen delivery pipe (11).

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