Polymerization reaction end terminator, additive metering system

Abstract

The utility model relates to a kind of polymeric reaction end terminator, additive metering and adding system.The system includes first desalted water tank, weighing tank, polymerization reactor in turn, and respectively with the terminator of first desalted water tank and weighing tank, additive storage tank, there is also the second desalted water tank and nitrogen storage tank connected with weighing tank, self-control valve is equipped on each connecting pipeline, and first desalted water tank is equipped with flowmeter.Weighing tank has screw agitator, remote liquid level meter and remote pressure gauge, and part storage tank is also equipped with screw agitator.The system is optimized by structure design, utilizes gravity conveying, automatic control and mixing and the like, realizes terminator and additive accurate addition, reduces machine pump failure, improves polymerization kettle equipment utilization, guarantees product quality, improves production automation degree and system flexibility, and is applicable to chemical polymerization reaction production.

Description

Technical Field

[0001] This utility model relates to the field of chemical production technology, specifically to a polymerization reaction terminator and an additive metering and addition system. Background Technology

[0002] In the chemical PVC production field, the suspension polymerization process of vinyl chloride has strict reaction conditions and control requirements. When vinyl chloride undergoes suspension polymerization, if the conversion rate exceeds the critical conversion rate at which pressure drop occurs, the porosity of the PVC resin will decrease if polymerization continues. More importantly, once the conversion rate exceeds 80%, the disproportionation termination reaction between macromolecular free radicals increases significantly, easily generating more branched structures. The presence of these branched structures severely affects the thermal stability and processing performance of the product, leading to a decline in product quality and making it difficult to meet market demands for high-quality PVC products.

[0003] To address the aforementioned issues, adding a terminator is essential when PVC polymerization reaches a certain stage. The terminator reacts with free radicals in the reactor, drastically slowing down or even completely stopping the polymerization reaction, thereby effectively controlling the degree of polymerization and significantly improving the resin's thermal stability and other performance indicators. Furthermore, when the reaction in the reactor becomes particularly vigorous, or when the temperature or pressure exceeds normal ranges and becomes difficult to control, or when abnormal conditions occur in the reactor, or when related equipment malfunctions, timely addition of a terminator can quickly slow down or completely terminate the reaction, preventing production accidents and ensuring the safety and stability of the production process.

[0004] Simultaneously, after the polymerization reaction is completed, an alkaline neutralizing agent (also known as an additive) needs to be added to the slurry to adjust its pH value. However, the current process of adding the terminator and neutralizing agent has many problems. Under the existing addition method, after the polymerization reaction reaches the set pressure drop, the terminator feed pump is started, the valve is opened, and the set amount of terminator is added to the polymerization reactor by metering using a flow meter; a neutralizing agent addition pipeline is set on the pipeline from the slurry discharge to the stripping process, and the set amount of neutralizing agent is added to the discharge pipeline by a feed pump.

[0005] However, in practice, the use of centrifugal pumps to deliver the terminator and neutralizer to the polymerization reactor and slurry discharge pipeline leads to frequent pump start-up and shutdown failures. Once a pump malfunctions, the dosage deviates significantly from the formulated amount. Inaccurate dosage has a severely adverse impact on subsequent product quality and processing performance, not only reducing the product yield but also potentially causing various problems during processing, such as increased processing difficulty and unstable product performance. Furthermore, frequent pump failures also affect the utilization rate of the polymerization reactor, increase equipment maintenance costs and production cycles, reduce production efficiency, and result in significant economic losses for the company. Utility Model Content

[0006] The purpose of this invention is to provide a metering and adding system for polymerization terminators and additives; to solve the problems of frequent pump failures and large deviations in the addition of terminators and neutralizers in the existing PVC production process, which affect product quality and the utilization rate of polymerization reactor equipment.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A polymerization reaction terminator and additive metering and addition system is disclosed. The system includes a first demineralized water tank, a weighing tank, and a polymerization reactor connected sequentially by pipelines; a terminator storage tank and an additive storage tank connected to the first demineralized water tank and the weighing tank respectively by pipelines; and a second demineralized water tank and a nitrogen storage tank connected to the weighing tank respectively by pipelines. A first automatic control valve and a second automatic control valve are sequentially installed on the pipeline between the first demineralized water tank and the weighing tank. A third automatic control valve and a fourth automatic control valve are respectively installed on the drain pipelines of the terminator storage tank and the additive storage tank. The pipelines containing the third and fourth automatic control valves are connected to the pipe section between the first and second automatic control valves. The pipelines between the second demineralized water tank, the nitrogen storage tank, the polymerization reactor, and the weighing tank are respectively equipped with a fifth, a sixth, and a seventh automatic control valve. A flow meter is installed on the drain pipeline of the first demineralized water tank. The drain end of the first demineralized water tank is higher than the top of the terminator storage tank and the additive storage tank. The drain ends of the terminator storage tank and the additive storage tank are higher than the top of the weighing tank. The drain end of the second demineralized water tank is higher than the top of the weighing tank.

[0008] Furthermore, the weighing tank includes a spiral agitator disposed within the tank body, a remote level gauge disposed in the upper part of the tank body, and a remote pressure gauge disposed in the upper part of the tank body.

[0009] Furthermore, the first demineralized water tank is also connected to the terminator storage tank and the additive storage tank via pipelines, and the connected pipelines are respectively equipped with an eighth self-control valve and a ninth self-control valve.

[0010] Furthermore, both the terminator storage tank and the additive storage tank are equipped with spiral agitators.

[0011] The beneficial effects of this utility model are: This automated metering and addition system for polymerization terminators and additives utilizes a combination of flow meters, automatic control valves, and the piping and valves of the weighing tank, along with the potential energy generated by the system's strategic placement, to achieve powerless feeding of the weighing tank. It also allows for precise control of the addition amount, avoiding metering errors and ensuring product quality. The gravity-based potential energy transport design reduces reliance on centrifugal pumps, improving the utilization rate and production efficiency of the polymerization reactor. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the system control of this utility model.

[0013] Among them, 1-first demineralized water tank; 2-weighing tank; 3-polymerization reactor; 4-terminant storage tank; 5-additive storage tank; 6-first automatic control valve; 7-second automatic control valve; 8-second demineralized water tank; 9-nitrogen storage tank; 10-third automatic control valve; 11-fourth automatic control valve; 12-fifth automatic control valve; 13-sixth automatic control valve; 14-seventh automatic control valve; 15-flow meter; 16-remote level gauge; 17-remote pressure gauge; 18-eighth automatic control valve; 19-ninth automatic control valve. Detailed Implementation

[0014] The preferred embodiments of this utility model will be described below with reference to the accompanying drawings.

[0015] like Figure 1 As shown, this polymerization reaction terminator and additive metering system achieves a precise and automated addition process through the coordinated work of its components.

[0016] The various tanks in the system are connected by carefully designed pipelines. The first demineralized water tank 1, weighing tank 2, and polymerization reactor 3 are connected sequentially by pipelines. The terminator storage tank 4 and additive storage tank 5 are respectively connected to the pipeline between the first demineralized water tank 1 and the weighing tank 2 via pipelines. The second demineralized water tank 8 and nitrogen storage tank 9 are also connected to the weighing tank 2 via pipelines. The first demineralized water tank 1 is also connected to the terminator storage tank 4 and the additive storage tank 5 via pipelines, and the connecting pipelines are respectively equipped with an eighth automatic control valve 18 and a ninth automatic control valve 19.

[0017] In this system, a first automatic control valve 6 and a second automatic control valve 7 are installed sequentially between the first demineralized water tank 1 and the weighing tank 2 to control the flow rate and timing of demineralized water supplied from the first demineralized water tank 1 to the weighing tank 2. The terminator storage tank 4 and the additive storage tank 5 are connected between the first automatic control valve 6 and the second automatic control valve 7 via pipelines, respectively. A third automatic control valve 10 and a fourth automatic control valve 11 are respectively installed on the drain pipelines of the terminator storage tank 4 and the additive storage tank 5 to control the flow of the terminator and additive into the weighing tank 2. A fifth automatic control valve 12, a sixth automatic control valve 13, and a seventh automatic control valve 14 are respectively installed on the pipelines connecting the second demineralized water tank 8, the nitrogen storage tank 9, and the polymerization reactor 3 to the weighing tank 2 to achieve precise control of the flow of the second demineralized water, nitrogen, and materials from the weighing tank 2 into the polymerization reactor 3. A flow meter 15 is installed on the drain outlet pipeline of the first demineralized water tank 1 for real-time and accurate measurement of the demineralized water flow rate.

[0018] This system utilizes gravity-assisted material transport, hence the different locations of the various tanks. The drain end of the first demineralized water tank 1 is higher than the tops of the terminator storage tank 4 and the additive storage tank 5, allowing the demineralized water in the first demineralized water tank 1 to flow into the terminator storage tank 4 and the additive storage tank 5 by gravity, or directly into the weighing tank 2, after the corresponding valves are opened. The drain ends of the terminator storage tank 4 and the additive storage tank 5 are higher than the top of the weighing tank 2, facilitating the flow of the terminator and additives into the weighing tank 2 by gravity after the third automatic control valve 10 and the fourth automatic control valve 11 are opened. Similarly, the drain end of the second demineralized water tank 8 is higher than the top of the weighing tank 2, facilitating the flow of the second demineralized water into the weighing tank 2 by gravity.

[0019] As a key component of the system, the weighing tank 2 is designed with an internal spiral agitator. After the material enters the weighing tank 2, the spiral agitator is activated to fully mix the terminator, additives, demineralized water, etc., ensuring that the material is uniform and consistent, thus providing a guarantee for accurate addition in the future.

[0020] The remote level gauge 16 and remote pressure gauge 17 installed in the upper part of the weighing tank 2 monitor the liquid level and pressure information inside the tank in real time and transmit this data remotely to the control system. The control system can be a standalone PC or an internal device in a central control room. Based on changes in liquid level and pressure, combined with preset addition amounts and process requirements, the control system precisely adjusts the opening and closing states of the respective control valves to achieve automatic metering and addition. For example, when the remote level gauge 16 detects that the liquid level in the weighing tank 2 is close to the preset upper limit, the control system can instruct the relevant automatic control valves to reduce their opening or close completely.

[0021] Both the terminator storage tank 4 and the additive storage tank 5 are equipped with spiral agitators to ensure that the internal materials are homogeneous.

[0022] The automatic control valves and spiral agitators involved in this system are all connected to the central control room for overall control, or they can be connected to an independently set controller for control.

[0023] When the polymerization reaction is nearing completion and a terminator and additives are needed, the terminator emulsion is discharged into the weighing tank 2 via the third automatic control valve 10. For example, when the remote level gauge 16 reaches 20% of the set total height, the third automatic control valve 10 automatically closes. Simultaneously, the fourth automatic control valve 11 corresponding to the additive storage tank 5 is opened. After the remote level gauge 16 accumulates to 40% of the set value, the fourth automatic control valve 11 is closed, and the weighing is completed. Then, the first automatic control valve 6 and the second automatic control valve 7 between the first demineralized water tank 1 and the weighing tank 2 are opened to meter the demineralized water into the weighing tank 2. After the demineralized water pipeline flow meter 15 meters 10 kg of demineralized water, the valve is closed. Then, the sixth automatic control valve 13 corresponding to the nitrogen storage tank 9 is opened to pressurize the weighing tank 2. When the remote pressure display of the weighing tank 2 shows 0.2 MPa, the seventh automatic control valve 14 at the bottom of the weighing tank 2 is opened to meter the weighed terminator and additives into the polymerization reactor. When the remote level gauge 16 on the weighing tank 2 displays 0%, the addition is complete. Close the seventh automatic control valve 14 at the bottom of the weighing tank 2 and the sixth automatic control valve 13 at the outlet of the nitrogen storage tank 9. Open the fifth automatic control valve 12 corresponding to the second demineralized water tank 8 to flush the additives and terminator in the weighing tank 2. After flushing, open the valves at the bottom of the nitrogen storage tank 9 and the weighing tank 2, and the flushed solution is pressurized to the polymerization reactor 3 by nitrogen gas. The first demineralized water tank 1 can also use the opening of the eighth automatic control valve 18 and the ninth automatic control valve 19 to flush the terminator storage tank 4 and the additive storage tank 5.

[0024] Through the coordinated operation of the above components, this system achieves automatic and precise metering and addition of terminators and additives after the polymerization reaction is completed, effectively reducing the frequency of pump failures, improving the utilization rate of polymerization reactor equipment, and ensuring product quality and processing performance.

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