System and method for preparing low-concentration initiator for polyvinyl chloride production

Abstract

The invention discloses a preparation system and a preparation method of a low-concentration initiator for polyvinyl chloride production, belongs to the technical field of polyvinyl chloride production, and mainly aims at automatic preparation of an initiator aqueous solution with the mass concentration of 1-2%. The preparation system is composed of a cold pure water storage tank, a hydrogen peroxide storage tank, a chlorinated ester storage tank, a sodium hydroxide storage tank, a dispersant (polyvinyl alcohol) storage tank, a polyethylene glycol storage tank, a neutralizer (citric acid) storage tank and an initiator preparation tank. According to the method, sodium hydroxide, hydrogen peroxide and chlorinated ester are used for synthesizing a di (2-ethylhexyl) peroxydicarbonate initiator (EHP), strong base is used in the reaction process, the system is alkaline, after the reaction is finished, a neutralizer (citric acid) needs to be used for adjusting the pH value to be 3-6, and the stability of the EHP is improved; and the EHP is insoluble in water, so that a dispersing agent (polyvinyl alcohol) needs to be added in the preparation process, the surface tension is reduced, the particle size is controlled, an EHP emulsion is formed, and the catalytic effect of the EHP emulsion in polyvinyl chloride production is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyvinyl chloride production, and specifically relates to a configuration system and configuration method of a low-concentration initiator for polyvinyl chloride production, mainly aiming at the automated configuration of an initiator aqueous solution with a mass concentration of 1-2%. Background Art

[0002] The most commonly used production method for polyvinyl chloride (PVC) is the aqueous suspension method. The basic production principle is to gradually add deionized water and vinyl chloride monomer into a polymerization kettle. Under the action of initiators, dispersants, etc., vinyl chloride (VCM) is suspended in the aqueous phase. Under specific temperature and pressure in the polymerization kettle, the vinyl chloride undergoes polymerization reaction to form polyvinyl chloride resin.

[0003] The role of the initiator is: the initiator generates active free radicals through thermal decomposition, which serves as the starting point of the chain initiation reaction and triggers the chain growth reaction of vinyl chloride monomer. Therefore, the initiator is the most important auxiliary agent in PVC production.

[0004] Traditional PVC manufacturers purchase high-quality concentration (50% or 75%) initiators from outside, store them in cold storage or low-temperature storage tanks, and need to ensure that the storage temperature is around -20°C. This has the following disadvantages: (1) Large equipment investment. In addition to the necessary initiator solution storage tanks, investment in equipment such as cold storage or refrigeration units is also required; (2) There are safety risks. Initiators with a concentration of 50% or 75% usually need to be stored at -15~-20°C. When the temperature rises, there is a risk of decomposition and heat release; (3) High cost. The cost of purchasing finished initiators (peroxides) is about 50~60 yuan / tPVC. Summary of the Invention

[0005] The present invention aims to provide a system and method for preparing a low-concentration initiator for polyvinyl chloride (PVC) production. The system utilizes sodium hydroxide, hydrogen peroxide, and a chloroester to synthesize di(2-ethylhexyl) peroxydicarbonate (EHP) as an initiator. Because a strong base is used during the reaction, the system is alkaline. After the reaction, a neutralizer (citric acid) is used to adjust the pH to between 3 and 6, maintaining an acidic environment and improving the stability of the EHP. Because EHP is insoluble in water, a dispersant (polyvinyl alcohol) is added during the preparation process to reduce surface tension, control particle size, and form an EHP emulsion, thereby enhancing its catalytic effect in PVC production. Furthermore, due to the complex preparation process of EHP, the amount and timing of each additive must be strictly controlled. This is typically achieved through a DCS program that automatically adjusts the amount of additives to control the initiator concentration. Each preparation requires the preparation of a low-concentration initiator for PVC production sufficient for a single polymerization reactor.

[0006] The present invention discloses a system for dispensing low-concentration initiators for polyvinyl chloride production, comprising a cold pure water storage tank, a hydrogen peroxide storage tank, a chloroester storage tank, a sodium hydroxide storage tank, a dispersant (polyvinyl alcohol) storage tank, a polyethylene glycol storage tank, a neutralizer (citric acid) storage tank, and an initiator preparation tank. The outlet pipeline of the cold pure water storage tank is sequentially provided with a cold pure water electromagnetic flowmeter, a cold pure water mass flowmeter, and a cold pure water automatic regulating valve. The outlet pipeline of the hydrogen peroxide storage tank is sequentially provided with a hydrogen peroxide electromagnetic flowmeter, a hydrogen peroxide mass flowmeter, and a hydrogen peroxide automatic regulating valve. The outlet pipeline of the chloroester storage tank is sequentially provided with a chloroester electromagnetic flowmeter, a chloroester mass flowmeter, and a chloroester automatic regulating valve. The outlet pipeline of the sodium hydroxide storage tank is sequentially provided with a chloroester electromagnetic flowmeter, a chloroester mass flowmeter, and a chloroester automatic regulating valve. The outlet pipeline is provided with a sodium hydroxide automatic regulating valve, a sodium hydroxide electromagnetic flowmeter and a sodium hydroxide mass flowmeter in sequence; the outlet pipeline of the dispersant storage tank is provided with a dispersant automatic regulating valve, a dispersant electromagnetic flowmeter and a dispersant mass flowmeter in sequence; the outlet pipeline of the polyethylene glycol storage tank is provided with a polyethylene glycol automatic regulating valve, a polyethylene glycol electromagnetic flowmeter and a polyethylene glycol mass flowmeter in sequence; the outlet pipeline of the neutralizer storage tank is provided with a neutralizer automatic regulating valve, a neutralizer electromagnetic flowmeter and a neutralizer mass flowmeter in sequence; the initiator preparation tank is provided with an initiator preparation tank variable frequency agitator; the initiator preparation tank is of a jacketed structure, and is provided with a jacketed chilled water inlet pipeline and a jacketed chilled water return pipeline.

[0007] The outlets of the cold pure water automatic regulating valve, the hydrogen peroxide automatic regulating valve and the chloroester automatic regulating valve are connected in sequence through pipelines, and an automatic switch valve is arranged on the pipeline between the outlets of the cold pure water automatic regulating valve and the hydrogen peroxide automatic regulating valve.

[0008] An initiator mixer is also provided on the outlet pipeline of the cold pure water automatic regulating valve. The initiator mixer is a pipe structure with an inlet, a middle port and an outlet and a neck in the middle (its principle is the Venturi ejector principle. After the pipe is locally necked, the flow rate suddenly becomes faster, and a negative pressure area is formed locally, so that hydrogen peroxide and chloroester can quickly and evenly enter the initiator mixer through the middle port); the outlet of the cold pure water automatic regulating valve is connected to the inlet of the initiator mixer, the outlet of the chloroester automatic regulating valve is connected to the middle port of the initiator mixer, the outlet of the initiator mixer, the outlet of the sodium hydroxide mass flowmeter, the outlet of the dispersant mass flowmeter, the outlet of the polyethylene glycol mass flowmeter and the outlet of the neutralizer mass flowmeter are connected together in sequence through the cold pure water pipeline, and then connected to the initiator preparation tank.

[0009] Due to the corrosive nature of chloroesters, chloroester storage tanks and export pipelines require high-corrosion-resistant linings, typically using PTFE (polytetrafluoroethylene), PE (polyethylene), or propylene oxide. Hydrogen peroxide and peroxide are oxidizing agents, so hydrogen peroxide storage tanks, initiator synthesis tanks, and related pipelines require acid wash and passivation. The addition of each additive during the initiator synthesis process requires strict control, so dual flowmeters—an electromagnetic flowmeter and a mass flowmeter—are installed to minimize addition errors.

[0010] The method for preparing a low-concentration initiator for polyvinyl chloride production according to the present invention comprises the following steps: Step 1: Open the cold pure water automatic regulating valve and control the flow rate to 6~10m³ / h. The cold pure water at 25~35℃ in the cold pure water storage tank is added to the initiator mixer from the inlet through the cold pure water electromagnetic flowmeter, cold pure water mass flowmeter and cold pure water automatic regulating valve. Then, it enters the initiator preparation tank through the cold pure water pipeline from the initiator mixer outlet. Step 2: When the cold pure water flow rate stabilizes, open the polyethylene glycol automatic regulating valve and control the flow rate to 400-600 kg / h. The polyethylene glycol in the polyethylene glycol storage tank is carried to the initiator preparation tank by the cold pure water in the cold pure water pipeline through the polyethylene glycol automatic regulating valve, polyethylene glycol electromagnetic flowmeter, and polyethylene glycol mass flowmeter. When the polyethylene glycol addition amount reaches 10-12 kg, close the polyethylene glycol automatic regulating valve, and the polyethylene glycol addition is completed. Step 3: After the polyethylene glycol is added, the variable frequency agitator in the initiator preparation tank is turned on at a low speed (1400-1600 rpm. The agitator must run during the initiator synthesis. The agitator is designed to provide sufficient mixing in the initiator preparation tank to create the optimal droplet size for initiator synthesis). Step 4: While the variable frequency stirrer of the initiator preparation tank is stirring at a low speed, the chloroester automatic regulating valve is opened to control the flow rate to 1600~1800kg / h. The chloroester in the chloroester storage tank is added to the initiator mixer through the middle port via the chloroester electromagnetic flowmeter, the chloroester mass flowmeter, and the chloroester automatic regulating valve. Subsequently, the chloroester is brought to the initiator preparation tank through the outlet of the initiator mixer by the cold pure water in the cold pure water pipeline. When the amount of chloroester added reaches 32~34kg, the chloroester automatic regulating valve is closed, and the addition of chloroester is completed; then the variable frequency stirrer of the initiator preparation tank is turned on for high-speed stirring (the speed is 2400~2600rpm); Step 5: After the addition of the chloroester is completed, the automatic on-off valve is opened and held for 8 to 15 seconds before being closed; while the automatic on-off valve is open, 25 to 35°C cold pure water from the cold pure water storage tank is used to flush the chloroester in the pipeline and the initiator mixer; after the automatic on-off valve is closed, the hydrogen peroxide automatic regulating valve is opened to control the flow rate to 500 to 700 kg / h, and the hydrogen peroxide in the hydrogen peroxide storage tank is added to the initiator mixer through the middle port through the hydrogen peroxide electromagnetic flowmeter, the hydrogen peroxide mass flowmeter, and the hydrogen peroxide automatic regulating valve, and then is carried to the initiator preparation tank through the outlet of the initiator mixer by the cold pure water in the cold pure water pipeline; when the amount of hydrogen peroxide added reaches 10 to 12 kg, the hydrogen peroxide automatic regulating valve is closed, and the addition of hydrogen peroxide is completed; Step 6: 60 to 90 seconds after the addition of hydrogen peroxide is completed, the sodium hydroxide automatic regulating valve is opened to control the flow rate to 3 to 5 m³ / h. The sodium hydroxide in the sodium hydroxide storage tank passes through the sodium hydroxide automatic regulating valve, the sodium hydroxide electromagnetic flowmeter, and the sodium hydroxide mass flowmeter and is added to the cold pure water pipeline and carried to the initiator preparation tank by the cold pure water. When the amount of sodium hydroxide added reaches 75 to 80 kg, the sodium hydroxide automatic regulating valve is closed, and the addition of sodium hydroxide is completed; Step 7: After the addition of sodium hydroxide is completed, close the cold pure water automatic regulating valve and wait for 7 to 8 minutes. During this period, the chloroester, hydrogen peroxide and sodium hydroxide are fully reacted in the initiator preparation tank to synthesize the initiator EHP (di(2-ethylhexyl) peroxydicarbonate). The reaction formula is as follows: R-COCl+H2O2+NaOH→R-CO-OO-CO-R+NaCl+H2O, R represents a 2-ethylhexyl group; Step 8: After the initiator synthesis is completed, open the cold pure water automatic regulating valve and the dispersant automatic regulating valve, and control the flow rate to 2~4m³ / h. The dispersant in the dispersant storage tank passes through the dispersant automatic regulating valve, the dispersant electromagnetic flowmeter, and the dispersant mass flowmeter, and is added to the cold pure water pipeline and carried to the initiator preparation tank by the cold pure water. At this time, the dispersant is added to control the initiator particle size. When the amount of dispersant added reaches 40~45kg, the dispersant automatic regulating valve is closed, and the dispersant addition is completed. Step 9: After the dispersant is added, open the neutralizer automatic regulating valve and control the flow rate to 1.5~3.0m³ / h. The neutralizer in the neutralizer storage tank passes through the neutralizer automatic regulating valve, the neutralizer electromagnetic flowmeter, and the neutralizer mass flowmeter, and is added to the cold pure water pipeline and carried to the initiator preparation tank by the cold pure water. When the amount of neutralizer added reaches 40~42kg, close the neutralizer automatic regulating valve, and the neutralizer addition is completed; the neutralizer adjusts the pH value of the synthetic initiator system to 3~6; Step 10: After the neutralizer is added, continue to open the cold pure water automatic regulating valve. When the amount of cold pure water added reaches 2200~2400kg, close the cold pure water automatic regulating valve and control the mass concentration of the initiator in the initiator preparation tank to 1~2%. The initiator preparation is completed. Step 11: After the initiator is prepared, maintain high-speed stirring (speed 2400~2600rpm) of the initiator preparation tank with the variable frequency agitator for 4~6 minutes, and then maintain low-speed stirring (speed 1400~1600rpm) of the initiator preparation tank with the variable frequency agitator for 5~10 minutes to ensure the stability of the initiator system; during the initiator preparation process, the chilled water in the jacket of the initiator preparation tank must be kept open throughout the process, and the temperature of the initiator preparation tank must be controlled at 10~25℃.

[0011] The beneficial effects of the present invention are: (1) Improved safety performance: Usually, the mass concentration of the initiator used in polyvinyl chloride is 45-75%, and the storage temperature needs to be around -20°C. If the temperature is too high, there will be a risk of decomposition. However, the present invention synthesizes an initiator aqueous solution with a mass concentration of 1-2%. The low-concentration initiator aqueous solution is safer to store and does not require a low-temperature cold storage. Further freezing the jacket (7°C) can ensure safe storage, which greatly improves safety. (2) Reduce costs: The cost of producing polyvinyl chloride using low-concentration initiators is about 20 yuan / tPVC, while the cost of purchasing finished initiators (peroxides) is about 50 to 60 yuan / tPVC, which greatly reduces costs; (3) The feeding order of various materials for the synthesis of initiators is an important factor. Chloroester, hydrogen peroxide, and sodium hydroxide are added in sequence. During the addition process, it is necessary to avoid premature reaction between chloroester and hydrogen peroxide in the pipeline. Therefore, after the addition of chloroester is completed, the pipeline must be flushed with cold pure water before adding hydrogen peroxide; (4) Temperature affects the yield of the synthetic initiator. The temperature of the synthetic system is usually controlled at 10~25℃ (synthesis in water). Too low a synthetic temperature will cause the initiator to form slowly and the amount generated is relatively small, that is, the yield is relatively low. Too high a synthetic system temperature will cause CatC and CatD to partially decompose, which will accelerate the decomposition rate of the generated initiator and directly reduce the effective yield. Therefore, temperature is very important for the synthetic initiator. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the configuration system structure of the low-concentration initiator for polyvinyl chloride production according to the present invention. DETAILED DESCRIPTION

[0013] Example 1: like Figure 1As shown, the names of the various parts are: cold pure water storage tank 1, cold pure water electromagnetic flowmeter 2, cold pure water mass flowmeter 3, cold pure water automatic regulating valve 4, hydrogen peroxide storage tank 5, hydrogen peroxide electromagnetic flowmeter 6, hydrogen peroxide mass flowmeter 7, hydrogen peroxide automatic regulating valve 8, chloroester storage tank 9, chloroester electromagnetic flowmeter 10, chloroester mass flowmeter 11, chloroester automatic regulating valve 12, automatic switch valve 13, initiator mixer 14, sodium hydroxide storage tank 15, sodium hydroxide electromagnetic flowmeter 16, sodium hydroxide mass flowmeter 17, sodium hydroxide automatic regulating valve 18, dispersant storage tank Tank 19, dispersant electromagnetic flowmeter 20, dispersant mass flowmeter 21, dispersant automatic regulating valve 22, polyethylene glycol storage tank 23, polyethylene glycol electromagnetic flowmeter 24, polyethylene glycol mass flowmeter 25, polyethylene glycol automatic regulating valve 26, neutralizer storage tank 27, neutralizer electromagnetic flowmeter 28, neutralizer mass flowmeter 29, neutralizer automatic regulating valve 30, initiator preparation tank variable frequency agitator 31, initiator preparation tank 32, initiator preparation tank jacketed chilled water inlet pipeline 33, initiator preparation tank jacketed chilled water return pipeline 34, and cold pure water pipeline 35.

[0014] The present invention relates to a configuration system for a low-concentration initiator for polyvinyl chloride production, comprising a cold pure water storage tank 1, a hydrogen peroxide storage tank 5, a chloroester storage tank 9, a sodium hydroxide storage tank 15, a dispersant (polyvinyl alcohol) storage tank 19, a polyethylene glycol storage tank 23, a neutralizer (citric acid) storage tank 27, and an initiator preparation tank 32. A cold pure water electromagnetic flowmeter 2, a cold pure water mass flowmeter 3, and a cold pure water automatic regulating valve 4 are sequentially arranged on the outlet pipeline of the cold pure water storage tank 1; a hydrogen peroxide electromagnetic flowmeter 6, a hydrogen peroxide mass flowmeter 7, and a hydrogen peroxide automatic regulating valve 8 are sequentially arranged on the outlet pipeline of the hydrogen peroxide storage tank 5; a chloroester electromagnetic flowmeter 10, a chloroester mass flowmeter 11, and a chloroester automatic regulating valve 12 are sequentially arranged on the outlet pipeline of the sodium hydroxide storage tank 15; and a chloroester electromagnetic flowmeter 10, a chloroester mass flowmeter 11, and a chloroester automatic regulating valve 12 are sequentially arranged on the outlet pipeline of the sodium hydroxide storage tank 15. A sodium hydroxide automatic regulating valve 16, a sodium hydroxide electromagnetic flowmeter 17 and a sodium hydroxide mass flowmeter 18 are provided in sequence. A dispersant automatic regulating valve 20, a dispersant electromagnetic flowmeter 21 and a dispersant mass flowmeter 22 are provided in sequence on the outlet pipeline of the dispersant storage tank 19. A polyethylene glycol automatic regulating valve 24, a polyethylene glycol electromagnetic flowmeter 25 and a polyethylene glycol mass flowmeter 26 are provided in sequence on the outlet pipeline of the polyethylene glycol storage tank 23. A neutralizer automatic regulating valve 28, a neutralizer electromagnetic flowmeter 29 and a neutralizer mass flowmeter 30 are provided in sequence on the outlet pipeline of the neutralizer storage tank 27. An initiator preparation tank variable frequency stirrer 31 is provided in the initiator preparation tank 32. The initiator preparation tank 32 is a jacketed structure and is provided with a jacketed chilled water inlet pipeline 33 and a jacketed chilled water return pipeline 34.

[0015] The outlets of the cold pure water automatic regulating valve 4, the hydrogen peroxide automatic regulating valve 8, and the chloroester automatic regulating valve 12 are connected in sequence through pipelines, and an automatic switch valve 13 is provided on the pipeline between the outlets of the cold pure water automatic regulating valve 4 and the hydrogen peroxide automatic regulating valve 8.

[0016] On the outlet pipeline of cold pure water automatic regulating valve 4, also be provided with initiator mixer 14, initiator mixer 14 is for having import, middle port and outlet and the pipeline structure of middle necking (its principle is the Venturi ejector principle, after the local necking of pipeline, flow velocity suddenly becomes faster, locally forms negative pressure zone, makes hydrogen peroxide and chloroester can enter in the initiator mixer quickly and evenly by the middle port); The outlet of cold pure water automatic regulating valve 4 is connected with the import of initiator mixer 14, the outlet of chloroester automatic regulating valve 12 is connected with the middle port of initiator mixer 14, the outlet of initiator mixer 14, the outlet of sodium hydroxide mass flowmeter 18, the outlet of dispersant mass flowmeter 22, the outlet of polyethylene glycol mass flowmeter 26 and the outlet of neutralizer mass flowmeter 30 are connected together by cold pure water pipeline 35 in sequence, and then are connected to initiator preparation tank 32.

[0017] Example 2: A method for preparing a low-concentration initiator for polyvinyl chloride production, which utilizes the low-concentration initiator preparation system for polyvinyl chloride production described in Example 1, comprises the following steps: Step 1: Open the cold pure water automatic regulating valve 4 and control the flow rate to 8m³ / h. The 30°C cold pure water in the cold pure water storage tank 1 is added to the initiator mixer 14 through the cold pure water electromagnetic flowmeter 2, the cold pure water mass flowmeter 3 and the cold pure water automatic regulating valve 4, and then enters the initiator preparation tank 32 after passing through the initiator mixer 14; Step 2: When the flow rate of cold pure water stabilizes, open the polyethylene glycol automatic regulating valve 24 and control the flow rate to 500 kg / h. The polyethylene glycol in the polyethylene glycol storage tank 23 is carried to the initiator preparation tank 32 by the cold pure water through the polyethylene glycol automatic regulating valve 24, the polyethylene glycol electromagnetic flowmeter 25, and the polyethylene glycol mass flowmeter 26. When the amount of polyethylene glycol added reaches 11 kg, close the polyethylene glycol automatic regulating valve 24, and the polyethylene glycol addition is completed. Step 3: After the polyethylene glycol is added, the variable frequency agitator 31 in the initiator preparation tank is maintained at a low stirring speed (1500 rpm). The agitator must be running during the initiator synthesis. The agitator is designed to provide sufficient mixing in the initiator preparation tank 32 to create the optimal droplet size for the synthesis of the initiator; Step 4: when initiator preparation tank variable frequency stirrer 31 is started at low speed, open chloroester automatic regulating valve 12, control flow is 1700kg / h, the chloroester in the chloroester storage tank 9 joins in the initiator mixer 14 through the middle port by chloroester electromagnetic flowmeter 10, chloroester mass flowmeter 11, chloroester automatic regulating valve 12, is brought in the initiator preparation tank 32 by cold pure water, when the chloroester add-on reaches 33kg, close chloroester automatic regulating valve 12, chloroester adds and finishes; Then initiator preparation tank variable frequency stirrer 31 is maintained high-speed stirring (rotating speed is 2500rpm); Step 5: after chloroester has added, open automatic switch valve 13, continue after 10 seconds and close; During the period that automatic switch valve 13 is opened, 30 ℃ of cold pure water from the cold pure water storage tank 1 flushes the chloroester in the pipeline and the initiator mixer 14; Open hydrogen peroxide automatic regulating valve 8 after automatic switch valve 13 closes, and control flow is 600kg / h. The hydrogen peroxide in the hydrogen peroxide storage tank 5 enters in the pipeline after passing through hydrogen peroxide electromagnetic flowmeter 6, hydrogen peroxide mass flowmeter 7, and hydrogen peroxide automatic regulating valve 8. Hydrogen peroxide joins in the initiator mixer 14 through the middle port, and is subsequently taken to the initiator preparation tank 32 through the cold pure water in the cold pure water pipeline 35 through the initiator mixer 14 outlet; After the hydrogen peroxide add-on reaches 11kg, close hydrogen peroxide automatic regulating valve 8, and hydrogen peroxide has added; Step 6: 75 seconds after the addition of hydrogen peroxide is completed, the sodium hydroxide automatic regulating valve 16 is opened to control the flow rate to 4m³ / h. The sodium hydroxide in the sodium hydroxide storage tank 15 passes through the sodium hydroxide sodium hydroxide automatic regulating valve 16, the electromagnetic flowmeter 17, and the sodium hydroxide mass flowmeter 18 and is added to the cold pure water pipeline and brought to the initiator preparation tank 32 by the cold pure water. When the amount of sodium hydroxide added reaches 78kg, the sodium hydroxide automatic regulating valve 16 is closed, and the addition of sodium hydroxide is completed. Step 7: After the addition of sodium hydroxide is completed, the cold pure water automatic regulating valve 4 is closed and a waiting time of 7 minutes is maintained. During this period, the chloroester, hydrogen peroxide and sodium hydroxide are fully reacted in the initiator preparation tank 32 to synthesize the initiator EHP (di(2-ethylhexyl) peroxydicarbonate); Step 8: After the initiator synthesis is completed, the cold pure water automatic regulating valve 4 is opened, and the dispersant automatic regulating valve 20 is opened to control the flow rate to 3m³ / h. The dispersant in the dispersant storage tank 19 passes through the dispersant automatic regulating valve 20, the dispersant electromagnetic flowmeter 21, and the dispersant mass flowmeter 22 and is added to the cold pure water pipeline and carried by the cold pure water to the initiator preparation tank 32. The dispersant is added here to control the initiator particle size. When the amount of dispersant added reaches 42kg, the dispersant automatic regulating valve 20 is closed, and the dispersant addition is completed; Step 9: After the dispersant is added, the neutralizer automatic regulating valve 28 is continued to be opened to control the flow rate to 2.0 m³ / h. The neutralizer in the neutralizer storage tank 27 passes through the neutralizer automatic regulating valve 28, the neutralizer electromagnetic flowmeter 29, and the neutralizer mass flowmeter 30 and is added to the cold pure water pipeline and carried by the cold pure water to the initiator preparation tank 32. When the amount of neutralizer added reaches 41 kg, the neutralizer automatic regulating valve 28 is closed, and the neutralizer addition is completed; the pH value of the synthetic initiator system is adjusted to 6.0 by the neutralizer; Step 10: After the neutralizer is added, open the cold pure water automatic regulating valve 4. When the amount of cold pure water added reaches 2300 kg, close the cold pure water automatic regulating valve 4 and control the mass concentration of the initiator in the initiator preparation tank 32 to 1.5%. The initiator preparation is completed. Step 11: After the initiator is prepared, the variable frequency agitator 31 of the initiator preparation tank is maintained at high speed stirring (speed of 2500 rpm) for 5 minutes, and then the variable frequency agitator 31 of the initiator preparation tank is maintained at low speed stirring (speed of 1500 rpm) for a period of time to ensure the stability of the initiator system; during the initiator preparation process, the chilled water in the jacket of the initiator preparation tank 32 must be kept open throughout the process and the temperature must be controlled at 18°C.

[0018] The relevant index parameters of the prepared initiator are described in Table 1.

[0019] Table 1: Related index parameters of EHP initiator synthesized according to the above initiator synthesis method

[0020] Among them, the active oxygen content is an important parameter for measuring the initiation ability of EHP initiator. The higher the active oxygen content, the stronger the initiation effect. The active oxygen content is related to the amount of each auxiliary agent added when preparing the initiator. The hydrolysis rate of EHP initiator is relatively high, and it is easy to hydrolyze to produce acidic substances in practical applications. In order to reduce the hydrolysis of EHP, it needs to be kept in an acidic environment, and the pH value of the system is controlled to be acidic by adding a weak acid. The particle size of the EHP initiator is generally controlled below 10μm, which helps to ensure the uniform dispersion and efficient distribution of EHP in the polymerization reaction, improve product quality and production efficiency, and ensure its effectiveness and stability in polyvinyl chloride production. The chloride ion content is an important indicator for measuring the impurity content in EHP, and should not be higher than 0.05%, that is, 5000mg / L. As can be seen from the data in Table 1, the initiator prepared by the present invention has good performance.

[0021] The low-concentration initiator prepared by the present invention can replace the original high-concentration initiator purchased from outside for normal use in the polyvinyl chloride polymerization reaction, thereby solving the disadvantages of the high-concentration initiator requiring low-temperature storage and high cost, while having the same initiation effect and final polyvinyl chloride product quality.

Claims

1. A system for preparing low-concentration initiators for polyvinyl chloride production, characterized by: The configuration system consists of a cold pure water storage tank (1), a hydrogen peroxide storage tank (5), a chloroester storage tank (9), a sodium hydroxide storage tank (15), a dispersant storage tank (19), a polyethylene glycol storage tank (23), a neutralizer storage tank (27) and an initiator preparation tank (32); a cold pure water electromagnetic flowmeter (2), a cold pure water mass flowmeter (3) and a cold pure water automatic regulating valve (4) are sequentially arranged on the outlet pipeline of the cold pure water storage tank (1); a hydrogen peroxide electromagnetic flowmeter (6), a hydrogen peroxide mass flowmeter (7) and a hydrogen peroxide automatic regulating valve (8) are sequentially arranged on the outlet pipeline of the hydrogen peroxide storage tank (5); a chloroester electromagnetic flowmeter (10) and a hydrogen peroxide mass flowmeter (11) are sequentially arranged on the outlet pipeline of the chloroester storage tank (9). ), a chloroester mass flowmeter (11) and a chloroester automatic regulating valve (12); a sodium hydroxide automatic regulating valve (16), a sodium hydroxide electromagnetic flowmeter (17) and a sodium hydroxide mass flowmeter (18) are sequentially provided on the outlet pipeline of the sodium hydroxide storage tank (15); a dispersant automatic regulating valve (20), a dispersant electromagnetic flowmeter (21) and a dispersant mass flowmeter (22) are sequentially provided on the outlet pipeline of the dispersant storage tank (19); a polyethylene glycol automatic regulating valve (24), a polyethylene glycol electromagnetic flowmeter (25) and a polyethylene glycol mass flowmeter (26) are sequentially provided on the outlet pipeline of the polyethylene glycol storage tank (23); and a polyethylene glycol automatic regulating valve (24), a polyethylene glycol electromagnetic flowmeter (25) and a polyethylene glycol mass flowmeter (26) are sequentially provided on the outlet pipeline of the neutralizer storage tank (27). A neutralizer automatic regulating valve (28), a neutralizer electromagnetic flowmeter (29) and a neutralizer mass flowmeter (30) are sequentially arranged on the initiator preparation tank (32); an initiator preparation tank variable frequency stirrer (31) is arranged in the initiator preparation tank (32); the initiator preparation tank (32) is a jacketed structure, and is provided with a jacketed chilled water inlet pipeline (33) and a jacketed chilled water return pipeline (34); the outlets of the cold pure water automatic regulating valve (4), the hydrogen peroxide automatic regulating valve (8) and the chloroester automatic regulating valve (12) are connected together in sequence through pipelines, and an automatic switch valve (13) is arranged on the pipeline between the outlets of the cold pure water automatic regulating valve (4) and the hydrogen peroxide automatic regulating valve (8); An initiator mixer (14) is provided on the outlet pipeline. The initiator mixer (14) is a pipeline structure with an inlet, a middle port and an outlet and a middle neck; the outlet of the cold pure water automatic regulating valve (4) is connected to the inlet of the initiator mixer (14), the outlet of the chloroester automatic regulating valve (12) is connected to the middle port of the initiator mixer (14), the outlet of the initiator mixer (14), the outlet of the sodium hydroxide mass flow meter (18), the outlet of the dispersant mass flow meter (22), the outlet of the polyethylene glycol mass flow meter (26) and the outlet of the neutralizer mass flow meter (30) are sequentially connected together through the cold pure water pipeline (35), and then connected to the initiator preparation tank (32).

2. The system for preparing a low-concentration initiator for polyvinyl chloride production according to claim 1, wherein: The dispersant is polyvinyl alcohol and the neutralizer is citric acid.

3. A method for preparing a low-concentration initiator for polyvinyl chloride production, comprising preparing the low-concentration initiator using the system for preparing the low-concentration initiator for polyvinyl chloride production according to claim 1 or 2, wherein: The steps of this configuration method are as follows: Step 1: Open the cold pure water automatic regulating valve (4) and control the flow rate to 6-10 m³ / h. The cold pure water in the cold pure water storage tank (1) is added to the initiator mixer (14) from the inlet through the cold pure water electromagnetic flowmeter (2), the cold pure water mass flowmeter (3) and the cold pure water automatic regulating valve (4), and then enters the initiator preparation tank (32) from the outlet of the initiator mixer (14) through the cold pure water pipeline (35); Step 2: When the flow rate of cold pure water is stable, open the polyethylene glycol automatic regulating valve (24) and control the flow rate to 400~600kg / h. The polyethylene glycol in the polyethylene glycol storage tank (23) is brought to the initiator preparation tank (32) by the cold pure water in the cold pure water pipeline (35) through the polyethylene glycol automatic regulating valve (24), the polyethylene glycol electromagnetic flowmeter (25), and the polyethylene glycol mass flowmeter (26). When the amount of polyethylene glycol added reaches 10~12kg, close the polyethylene glycol automatic regulating valve (24), and the addition of polyethylene glycol is completed. Step 3: After the polyethylene glycol is added, the variable frequency stirrer (31) of the initiator preparation tank is turned on to stir at a low speed; Step 4: While the variable frequency stirrer (31) of the initiator preparation tank is stirring at a low speed, the chloroester automatic regulating valve (12) is opened to control the flow rate to 1600~1800kg / h. The chloroester in the chloroester storage tank (9) is added to the initiator mixer (14) through the middle port via the chloroester electromagnetic flowmeter (10), the chloroester mass flowmeter (11), and the chloroester automatic regulating valve (12). Then, the chloroester is brought to the initiator preparation tank (32) through the outlet of the initiator mixer (14) by the cold pure water in the cold pure water pipeline (35). When the amount of chloroester added reaches 32~34kg, the chloroester automatic regulating valve (12) is closed, and the addition of chloroester is completed; then the variable frequency stirrer (31) of the initiator preparation tank is turned on for high-speed stirring; Step 5: After the addition of the chloroester is completed, the automatic switch valve (13) is opened and closed after 8 to 15 seconds; while the automatic switch valve (13) is open, the cold pure water from the cold pure water storage tank (1) flushes the chloroester in the pipeline and the initiator mixer (14); after the automatic switch valve (13) is closed, the hydrogen peroxide automatic regulating valve (8) is opened to control the flow rate to 500 to 700 kg / h, and the hydrogen peroxide in the hydrogen peroxide storage tank (5) is added to the initiator mixer (14) through the middle port through the hydrogen peroxide electromagnetic flowmeter (6), the hydrogen peroxide mass flowmeter (7), and the hydrogen peroxide automatic regulating valve (8), and then brought to the initiator preparation tank (32) through the outlet of the initiator mixer (14) by the cold pure water in the cold pure water pipeline (35); when the amount of hydrogen peroxide added reaches 10 to 12 kg, the hydrogen peroxide automatic regulating valve (8) is closed, and the addition of hydrogen peroxide is completed; Step 6: 60 to 90 seconds after the addition of hydrogen peroxide is completed, the sodium hydroxide automatic regulating valve (16) is opened to control the flow rate to 3 to 5 m³ / h. The sodium hydroxide in the sodium hydroxide storage tank (15) passes through the sodium hydroxide automatic regulating valve (16), the sodium hydroxide electromagnetic flowmeter (17), and the sodium hydroxide mass flowmeter (18) and is added to the cold pure water pipeline (35) and is carried to the initiator preparation tank (32) by the cold pure water. When the amount of sodium hydroxide added reaches 75 to 80 kg, the sodium hydroxide automatic regulating valve (16) is closed, and the addition of sodium hydroxide is completed. Step 7: After the addition of sodium hydroxide is completed, the cold pure water automatic regulating valve (4) is closed and the mixture is left for 7 to 8 minutes. During the period when the cold pure water automatic regulating valve (4) is closed, the chloroester, hydrogen peroxide and sodium hydroxide are fully reacted in the initiator preparation tank (32) to synthesize the initiator di(2-ethylhexyl) peroxydicarbonate. The reaction formula is R-COCl+H2O2+NaOH→R-CO-OO-CO-R+NaCl+H2O, where R represents a 2-ethylhexyl group. Step 8: After the initiator synthesis is completed, the cold pure water automatic regulating valve (4) is opened, and the dispersant automatic regulating valve (20) is opened to control the flow rate to 2~4m³ / h. The dispersant in the dispersant storage tank (19) passes through the dispersant automatic regulating valve (20), the dispersant electromagnetic flowmeter (21), and the dispersant mass flowmeter (22) and is added to the cold pure water pipeline (35) and is carried to the initiator preparation tank (32) by the cold pure water. When the amount of dispersant added reaches 40~45kg, the dispersant automatic regulating valve (20) is closed, and the dispersant addition is completed; Step 9: After the dispersant is added, the neutralizer automatic regulating valve (28) is opened to control the flow rate to 1.5-3.0 m³ / h. The neutralizer in the neutralizer storage tank (27) passes through the neutralizer automatic regulating valve (28), the neutralizer electromagnetic flowmeter (29), and the neutralizer mass flowmeter (30) and is added to the cold pure water pipeline (35) and is carried to the initiator preparation tank (32) by the cold pure water. When the amount of neutralizer added reaches 40-42 kg, the neutralizer automatic regulating valve (28) is closed, and the addition of the neutralizer is completed. The neutralizer adjusts the pH value of the synthetic initiator system to 2-5. Step 10: After the neutralizer is added, continue to open the cold pure water automatic regulating valve (4). When the amount of cold pure water added reaches 2200-2400 kg, close the cold pure water automatic regulating valve (4) and control the mass concentration of the initiator in the initiator preparation tank (32) to be 1-2%. The initiator preparation is completed. Step 11: After the initiator is prepared, the variable frequency stirrer (31) of the initiator preparation tank is maintained at a high speed for 4 to 6 minutes, and then the variable frequency stirrer (31) of the initiator preparation tank is maintained at a low speed for 5 to 10 minutes to ensure that the initiator system is stable; during the initiator preparation process, the chilled water in the jacket of the initiator preparation tank (32) is kept open throughout the process.

4. The method for preparing a low-concentration initiator for polyvinyl chloride production according to claim 3, wherein: The low-speed stirring speed of the variable frequency stirrer (31) of the initiator preparation tank is 1400~1600 rpm, and the high-speed stirring speed is 2400~2600 rpm.

5. The method for preparing a low-concentration initiator for polyvinyl chloride production according to claim 3, wherein: The temperature of the cold pure water in the cold pure water storage tank (1) is 25~35℃.

6. The method for preparing a low-concentration initiator for polyvinyl chloride production according to claim 3, wherein: During the initiator preparation process, the chilled water in the jacket of the initiator preparation tank (32) is kept open throughout the process, and the temperature of the initiator preparation tank (32) is controlled to be 10~25°C.

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