PVC polymer desalted water vacuum thermal depth oxygen removal system and process

Abstract

The present application relates to PVC polymerization auxiliary industrial water treatment equipment technical field, specifically to a kind of PVC polymerization desalted water vacuum thermal depth oxygen removal system and process, including deoxidizing tower, two-stage vacuum air extraction unit, hot water heating buffer unit, public pipeline assembly and condensate collection tank.Two-stage vacuum air extraction unit is provided with series arrangement first stage, secondary evacuation branch, and two-way evacuation branch shares steam supply pipeline and circulating water cooling pipeline;Hot water heating buffer unit is equipped with hot water heater, hot water tank, circulating pipeline and matching valve, and tank top condenser is connected with first stage evacuation branch by incondensable gas return pipeline, and tower bottom water delivery pipeline is connected with circulating heating pipe.Desalted water is first deoxidized in deoxidizing tower, then combined state oxygen is resolved by heating, and secondary extraction of oxygen-containing gas can prevent oxygen back solution, and water dissolved oxygen is stable to reach standard, and PVC production sticking kettle and plugging problem are relieved;The system runs smoothly under negative pressure, pipeline arrangement is simple, and oxygen removal precision and continuous operation stability are better.

Description

Technical Field

[0001] This invention relates to the field of industrial water treatment equipment for PVC polymerization auxiliary processes, specifically a vacuum thermal deep deoxygenation system and process for PVC polymerization desalination. Background Technology

[0002] In the suspension polymerization process of polyvinyl chloride (PVC), dissolved oxygen in the demineralized water can trigger polymerization side reactions, directly affecting the appearance, particle regularity, and product quality of PVC resin. If the demineralized water has poor deoxygenation effect, residual oxygen entering the polymerization reactor will cause the resin particle size to become finer, which can easily lead to material blockage in the stripping and drying sections. In severe cases, it can generate a large amount of self-polymers and even cause the polymerization reaction to run out of control. Therefore, the production process has strict requirements for controlling the dissolved oxygen index of the influent demineralized water. The deoxygenation unit is a key supporting equipment for the PVC production line. The industry goal is to stably control the oxygen content of the demineralized water below 0.02 mg / L to reduce self-polymerization and sticking to the reactor, reduce the consumption of dispersants and other additives, ensure the smooth progress of the polymerization reaction, and increase the added value of the product.

[0003] Traditional deoxygenation processes in the industry often employ two-stage steam injection combined with shell and tube heat exchangers, resulting in complex pipeline layouts, high steam consumption, the need for liquid sealing facilities for steam condensate, and the addition of centrifugal pumps for circulating water transportation, leading to high overall energy consumption. If water ring vacuum pump units are selected, the installed power of the equipment is large, and the problem of high operating energy consumption also exists.

[0004] Chinese invention patent CN215592660U discloses a PVC suspension polymerization pure water deoxygenation device. This device consists of a pure water deoxygenation tower, a buffer tank, a water jet injector, and a water tank connected in sequence. Gas extracted from the deoxygenation tower first undergoes gas-liquid separation in the buffer tank, and then deoxygenates by creating negative pressure through the water jet injector. A venting device is installed at the top of the water tank to discharge the gas. This solution replaces steam jet equipment with a water jet unit, eliminating the need for a large amount of steam and condensate drainage pipelines, and eliminating the need for a separate liquid seal container. The equipment can be integrally manufactured using polypropylene, resulting in lower manufacturing costs. The system primarily uses water circulation, minimizing media loss and reducing energy consumption compared to traditional processes. It can maintain a vacuum level below -80 kPa within the tower, meeting basic deoxygenation production requirements.

[0005] However, there are two prominent problems in the actual application of this device: On the one hand, the deoxygenation depth is limited, and the effluent quality cannot meet the high standards required for PVC polymerization. The device relies solely on negative pressure within the tower to complete a single gas-liquid separation, which can only remove free oxygen from the water. The removal efficiency of bound dissolved oxygen within the water is low, making it difficult to stably control the dissolved oxygen in the effluent below 0.02 mg / L. Production problems such as adhesion to the reactor and blockage during drying cannot be effectively alleviated. Furthermore, the equipment's air extraction process has only a single path, and the oxygen-containing gas released by the water when heated is directly discharged. Some oxygen will be redissolved into the water along with the condensate return water, resulting in continuous fluctuations in the dissolved oxygen level in the effluent.

[0006] On the other hand, after the water body completes deoxygenation, there is no constant temperature buffer process, so it is impossible to continuously improve the deoxygenation effect and it is also difficult to switch the discharge state according to the water temperature change; the vacuum formation relies on a single-stage water jet equipment, and the negative pressure fluctuation range is large during operation. Summary of the Invention

[0007] The purpose of this invention is to provide a PVC polymer demineralized water vacuum thermal deep deoxygenation system to solve the technical problems of insufficient deoxygenation depth, large fluctuations in dissolved oxygen index of effluent, inability to achieve constant temperature buffer circulation deoxygenation of water, and poor stability of vacuum negative pressure operation in existing deoxygenation devices.

[0008] To achieve the above objectives, in a first aspect, the present invention provides the following technical solution: a PVC polymer demineralized water vacuum thermal deep deoxygenation system, comprising a deoxygenation tower, a two-stage vacuum pumping unit, a hot water heating and buffering unit, a common pipeline assembly, and a condensate collection tank; the top and bottom of one side of the deoxygenation tower are respectively provided with an inlet water distribution assembly and a bottom outlet water conveying pipeline; the two-stage vacuum pumping unit is connected to the top of the deoxygenation tower to provide negative pressure; the hot water heating and buffering unit is connected to the bottom outlet water conveying pipeline and is used to heat and buffer the demineralized water for deep deoxygenation; the common pipeline assembly includes a steam supply pipeline and a circulating water cooling pipeline; the two-stage vacuum pumping unit includes a primary evacuation branch and a secondary evacuation branch arranged in series; the primary evacuation branch and the secondary evacuation branch share a steam supply pipeline to supply driving steam, and simultaneously share a circulating water cooling pipeline to provide cooling medium; The hot water heating buffer unit includes a hot water heater, a hot water tank, a demineralized water circulating feed pump, a tank top condenser, a demineralized water circulating feed pipe, a first connecting pipe, a second connecting pipe, a condensate connecting pipe, a non-condensable gas return pipeline, a circulating heating pipe, a circulating heating shut-off valve, a feed shut-off valve, and a fourth pneumatic regulating valve. The inlet port of the demineralized water circulating feed pipe is connected to the bottom of one side of the hot water tank, and the other end is connected to the polymerization reactor. The demineralized water circulating feed pump and the feed shut-off valve are sequentially installed along the medium flow direction on the section of the demineralized water circulating feed pipe. One end of the circulating heating pipe is connected to the section of the demineralized water circulating feed pipe and is located between the demineralized water circulating feed pump and the feed... Between the shut-off valves, the other end of the circulating heating pipe is connected to the bottom water delivery pipeline of the tower, and the circulating heating shut-off valve is installed on the pipe section of the circulating heating pipe; the two ends of the second connecting pipe are respectively connected to the top of the hot water tank and the condenser at the top of the tank, and the fourth pneumatic regulating valve is installed on the pipe section of the second connecting pipe; the two ends of the condensate connecting pipe are respectively connected to the condenser at the top of the tank and the hot water tank; the two ends of the first connecting pipe are respectively connected to the hot water tank and the hot water heater; one end of the non-condensable gas return pipeline is connected to the condenser at the top of the tank, and the other end is connected to the first-stage vacuum branch, which is used to send the oxygen-containing non-condensable gas that is heated and precipitated in the hot water tank to the two-stage vacuum pumping unit for secondary extraction; The bottom water delivery pipeline includes a demineralized water delivery pipe connected to the bottom of the deoxygenation tower, a first shut-off valve, a demineralized water delivery pump, and a second shut-off valve connected in series along the medium flow direction on the demineralized water delivery pipe section. One end of the demineralized water delivery pipe is connected to a hot water heater; the other end of the circulating heating pipe is connected to the demineralized water delivery pipe and is located downstream of the second shut-off valve.

[0009] Furthermore, the primary evacuation branch includes a primary evacuation pipeline connected to the top of the deoxygenation tower, a primary evacuation steam ejector connected to one end of the primary evacuation pipeline, a connecting pipe connected to the primary evacuation steam ejector, a primary evacuation steam condenser connected to one end of the connecting pipe, and a primary condensate discharge pipe connected to the primary evacuation steam condenser; the secondary evacuation branch includes a secondary evacuation pipeline connected to the primary evacuation steam condenser, a secondary evacuation steam ejector connected to one end of the secondary evacuation pipeline, a secondary evacuation steam condenser connected to the secondary evacuation steam ejector via a pipeline, and a secondary condensate discharge pipe connected to the secondary evacuation steam condenser; one end of both the primary condensate discharge pipe and the secondary condensate discharge pipe converges and connects to the condensate collection tank.

[0010] Furthermore, the circulating water cooling pipeline includes a circulating water inlet pipeline connected to the inlet side of the first-stage vacuum steam condenser, a circulating water connecting pipe bridging the outlet side of the first-stage vacuum steam condenser and the inlet side of the second-stage vacuum steam condenser, and a circulating water return pipe connected to the outlet side of the second-stage vacuum steam condenser; the tank top condenser is equipped with a circulating water inlet pipeline and a circulating water outlet pipeline respectively.

[0011] Furthermore, the water inlet distribution assembly includes a demineralized water inlet pipe connected to the top of one side of the deoxygenation tower, a first inlet regulating valve and a flow meter sequentially arranged on the demineralized water inlet pipe section along the medium flow direction, and multiple inlet nozzles connected to the demineralized water inlet pipe extending into the deoxygenation tower; the top of the deoxygenation tower is equipped with a first pressure transmitter for monitoring the gas phase pressure inside the tower, and the side of the deoxygenation tower is equipped with a first liquid level sensor for monitoring the liquid level inside the tower; the first inlet regulating valve is interlocked with the first liquid level sensor; the inner cavity of the deoxygenation tower is provided with a packing layer located below the inlet nozzles.

[0012] Furthermore, the steam supply pipeline includes a steam main pipe, steam branch pipes, a third pneumatic regulating valve, a second pneumatic regulating valve, and a first pneumatic regulating valve; one end of the steam main pipe is connected to a first-stage vacuum steam ejector, and the third and second pneumatic regulating valves are sequentially installed on a section of the steam main pipe along the steam flow direction; one end of the steam branch pipe is connected to a section of the steam main pipe and is located between the third and second pneumatic regulating valves, and the other end of the steam branch pipe is connected to a second-stage vacuum steam ejector, and the first pneumatic regulating valve is installed on a section of the steam branch pipe.

[0013] Furthermore, the hot water heater is connected to a steam pipeline and a condensate outlet pipe, and an inlet shut-off valve is installed on a section of the steam pipeline; a temperature detection element is installed on the side of the hot water tank, and the temperature detection element is interlocked with the inlet shut-off valve; a second pressure transmitter is installed on the top of the hot water tank, and the second pressure transmitter is interlocked with a fourth pneumatic regulating valve; a second liquid level sensor is installed on the side of the hot water tank, and the demineralized water delivery pump is interlocked with the second liquid level sensor for start and stop.

[0014] Furthermore, the second, first, third, and fourth pneumatic regulating valves are all equipped with PLC pressure interlock control modules; the first shut-off valve, second shut-off valve, feeding shut-off valve, and air inlet shut-off valve are equipped with PLC water temperature interlock switching mechanisms.

[0015] Furthermore, a first local pressure gauge is provided on the section of the demineralized water conveying pipe between the demineralized water conveying pump and the second shut-off valve, and a second local pressure gauge is provided on the section of the demineralized water circulating feed pipe between the demineralized water circulating feed pump and the circulating heating pipe.

[0016] Secondly, this invention discloses a process for deep vacuum thermal deoxygenation of PVC polymerized demineralized water, comprising the following steps: S1. Demineralized water is fed into the deoxygenation tower through the water inlet distribution assembly. The two-stage vacuum pumping unit continuously extracts the gas phase in the deoxygenation tower to form a negative pressure environment. The demineralized water and the packing in the deoxygenation tower are in full contact to complete the initial removal of dissolved oxygen. The liquid level in the deoxygenation tower is automatically stabilized by the first liquid level sensor linked to the first water inlet regulating valve. S2. The demineralized water after pre-deoxygenation at the bottom of the deoxygenation tower is transported to the hot water heater via the demineralized water delivery pipe, and steam is introduced into the steam pipeline to heat the demineralized water. The demineralized water heated by the hot water heater is transported to the hot water tank buffer via the first connecting pipe. The liquid level in the hot water tank is interlocked by the second liquid level sensor to control the start and stop of the demineralized water delivery pump. The temperature detection element collects the water temperature in the tank in real time and links the air inlet shut-off valve to adjust the heating steam supply. S3. Oxygen-containing non-condensable gas is released from the high-temperature water in the hot water tank. The oxygen-containing non-condensable gas enters the condenser at the top of the tank through the second connecting pipe and is condensed. The liquid water formed by condensation flows back to the hot water tank through the condensate connecting pipe. The uncondensed oxygen-containing non-condensable gas is sent to the first-stage vacuum branch through the non-condensable gas return pipeline and is removed by the two-stage vacuum pumping unit. The fourth pneumatic regulating valve works with the second pressure transmitter to stabilize the slight positive pressure inside the hot water tank. S4. When the temperature detection element detects that the water temperature is lower than the process set constant temperature value, the feeding shut-off valve is closed and the circulating heating shut-off valve is opened. The demineralized water flows back to the demineralized water conveying pipe for circulating heating through the circulating heating pipe. When the water temperature reaches the process set constant temperature value, the circulating heating shut-off valve is closed and the feeding shut-off valve is opened. The qualified low dissolved oxygen demineralized water is conveyed to the PVC polymerization reactor for production use along the demineralized water circulating feeding pipe. S5. The condensate waste liquid generated by the primary evacuated steam condenser and the secondary evacuated steam condenser flows into the condensate collection tank for centralized treatment via the primary condensate discharge pipe and the secondary condensate discharge pipe, respectively.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This system integrates a deoxygenation tower, a two-stage vacuum extraction unit, and a hot water heating and buffer unit. First, the deoxygenation tower removes free oxygen from the water, then the hot water heater decomposes bound dissolved oxygen. The oxygen-containing non-condensable gas released from the hot water tank is separated from water vapor by a condenser at the top of the tank and then sent to the primary extraction branch for secondary extraction via the non-condensable gas return pipeline, preventing oxygen re-dissolution. This device relies on a dual deoxygenation mechanism combining vacuum deoxygenation and thermal decomposition, reducing the solubility of oxygen in water according to Henry's Law. It can stably control the dissolved oxygen in the effluent to below 0.02 mg / L, solving the problems of kettle sticking and material blockage in the drying section of PVC polymerization production. The primary and secondary extraction branches share steam and circulating water pipelines, resulting in a simple pipeline layout and facilitating unified media distribution.

[0018] 2. This system is equipped with a circulating heating pipeline and matching valves. A demineralized water circulating feed pump can return the water from the hot water tank to the front-end pipeline for reheating and deoxygenation, continuously reducing the oxygen content in the water. By switching the feed shut-off valve and the circulating heating shut-off valve, the system can flexibly switch between water circulation deoxygenation and feeding to the polymerization reactor based on the water temperature. The entire vacuum system is a two-stage series structure, which provides more stable negative pressure operation compared to the original single-stage water jet equipment. The tank top condenser, in conjunction with a regulating valve, adjusts the gas phase flow rate, and the condensed water is directly returned to the hot water tank for reuse, reducing water waste. The system is equipped with pressure, level, and temperature sensors and a PLC interlock module, enabling fully automatic control without frequent manual operation. Vacuum unit condensate waste liquid is centrally collected and treated in a condensate collection tank, facilitating on-site maintenance and promoting environmental friendliness.

[0019] 3. This device stably controls the dissolved oxygen in the influent, which can delay the formation of residues in the polymerization reactor, reduce the frequency of reactor cleaning, and increase the continuous operation time and production capacity of the polymerization reactor; the finished PVC particles have a more uniform particle size distribution and better processing performance. At the same time, it can reduce the consumption of polymerization aids such as dispersants, lower production costs, stabilize polymerization reaction conditions, and facilitate the production of high value-added PVC products. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the process flow structure of the PVC polymerization demineralization vacuum thermal deep deoxygenation system of the present invention; Figure 2 For the present invention Figure 1 A magnified view of a portion of region A in the middle.

[0021] In the diagram: 1. Deoxygenation tower; 2. Demineralized water inlet pipe; 3. First inlet regulating valve; 4. Flow meter; 5. Inlet nozzle; 6. First pressure transmitter; 7. Primary evacuation pipeline; 8. Primary evacuation steam ejector; 9. Connecting pipe; 10. Primary evacuation steam condenser; 11. Primary condensate discharge pipe; 12. Condensate collection tank; 13. Secondary evacuation pipeline; 14. Secondary evacuation steam ejector; 15. Secondary evacuation steam condenser; 16. Secondary condensate discharge pipe; 17. Steam branch pipe; 18. First pneumatic regulating valve; 19. Steam main pipe; 20. Second pneumatic regulating valve; 21. Third pneumatic regulating valve; 22. Circulating water connecting pipe; 23. Circulating water return pipe; 24. Demineralized water delivery pipe; 25. First shut-off valve; 26. Demineralized water transfer pump; 27. Second shut-off valve; 28. First local pressure gauge; 29. ​​Hot water heater; 30. First connecting pipe; 31. Hot water tank; 32. Demineralized water circulation feed pipe; 33. Demineralized water circulation feed pump; 34. Second local pressure gauge; 35. Feed shut-off valve; 36. Second connecting pipe; 37. Fourth pneumatic regulating valve; 38. Tank top condenser; 39. Non-condensable gas return line; 40. Non-condensable gas return line; 41. Second pressure transmitter; 42. Second liquid level sensor; 43. Temperature detection element; 44. Steam line; 45. Inlet shut-off valve; 46. First liquid level sensor; 47. Circulating heating pipe; 48. Circulating heating shut-off valve. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0023] Please see Figure 1-2A vacuum thermal deep deoxygenation system for PVC polymerization demineralized water is disclosed, suitable for preparing low dissolved oxygen demineralized water required for PVC polymerization production. The system comprises five modules: pre-deoxygenation, heating and thermal desorption, non-condensable gas recovery, constant-temperature circulating feed, and condensate collection. The entire system includes a deoxygenation tower 1, a two-stage vacuum pumping unit, a hot water heating and buffering unit, a common piping assembly, and a condensate collection tank 12. A water inlet and distribution assembly is installed on the top side of the deoxygenation tower 1, and its bottom is connected to the bottom outlet water delivery pipeline. The two-stage vacuum pumping unit is connected to the top of the deoxygenation tower 1 to extract the gas phase and create negative pressure. The hot water heating and buffering unit is connected to the bottom outlet water delivery pipeline to heat and buffer the pre-deoxygenated water and deeply desorb dissolved oxygen. The common piping assembly provides the system with the necessary driving steam and cooling circulating water, and consists of two parts: a steam supply pipeline and a circulating water cooling pipeline. The two-stage vacuum pumping unit consists of a primary pumping branch and a secondary pumping branch arranged in series. The primary and secondary pumping branches share a common piping assembly for supplying the jet-driven steam, and simultaneously share a circulating water cooling pipe for supplying the cooling medium to condense and recover the jet steam. The primary pumping branch extracts non-condensable gases from the deaerator 1 and hot water tank 31. The secondary pumping branch is connected in series at the gas phase outlet of the primary pumping steam condenser 10, which can further enhance the vacuum pumping capacity based on the primary negative pressure, reduce the system operating vacuum pressure, and strengthen the removal of dissolved oxygen from the water.

[0024] The hot water heating and buffer unit is responsible for water heating, deep deoxygenation, constant temperature buffering, and circulating feed functions. This unit includes a hot water heater 29, a hot water tank 31, a demineralized water circulating feed pump 33, a tank top condenser 38, a demineralized water circulating feed pipe 32, a first connecting pipe 30, a second connecting pipe 36, a condensate connecting pipe 40, a non-condensable gas return line 39, a circulating heating pipe 47, a circulating heating shut-off valve 48, a feed shut-off valve 35, and a fourth pneumatic regulating valve 37. The feed end of the demineralized water circulating feed pipe 32 is connected to one side of the bottom of the hot water tank 31, and the discharge end leads to the polymerization reactor. The demineralized water circulating feed pump 33 and the feed shut-off valve 35 are installed sequentially on the demineralized water circulating feed pipe 32 along the medium flow direction. One end of the circulating heating pipe 47 is connected to the demineralized water circulating feed pipe 32, located between the demineralized water circulating feed pump 33 and the feed shut-off valve 35. The other end of the circulating heating pipe 47 is connected to the bottom water delivery pipeline. The circulating heating shut-off valve 48 is installed on the circulating heating pipe 47. The two ends of the second connecting pipe 36 are respectively connected to the top of the hot water tank 31 and the air inlet of the tank top condenser 38. The fourth pneumatic regulating valve 37 is installed in the second connecting pipe 36 to regulate the gas phase discharge flow rate and stabilize the pressure inside the tank. The two ends of the condensate connecting pipe 40 are respectively connected to the condensate outlet of the tank top condenser 38 and the cavity of the hot water tank 31. The two ends of the first connecting pipe 30 are respectively connected to the water outlet side of the hot water heater 29 and the water inlet side of the hot water tank 31, so that the heated water is sent into the buffer tank. One end of the non-condensable gas return pipeline 39 is connected to the non-condensable gas outlet of the tank top condenser 38, and the other end is connected to the first-stage evacuation branch to send the oxygen-containing gas precipitated by the heated hot water into the vacuum unit for secondary extraction, so as to prevent oxygen from dissolving in the water again.

[0025] The water delivery pipeline at the bottom of the tower is used to transport the water after pre-deoxygenation of the deoxygenation tower. It includes a demineralized water delivery pipe 24 connected to the bottom of the deoxygenation tower 1. Along the flow direction of the medium, a first shut-off valve 25, a demineralized water delivery pump 26, and a second shut-off valve 27 are sequentially arranged on the demineralized water delivery pipe 24. The end of the demineralized water delivery pipe 24 is connected to the inlet of the hot water heater 29. The connection position between the circulating heating pipe 47 and the demineralized water delivery pipe 24 is downstream of the second shut-off valve 27, ensuring that the circulating return water can re-enter the hot water heater 29 for heating.

[0026] The primary evacuation branch includes a primary evacuation pipeline 7, a primary evacuation steam ejector 8, a connecting pipe 9, a primary evacuation steam condenser 10, and a primary condensate discharge pipe 11. The primary evacuation pipeline 7 is connected to the top of the deoxygenation tower 1. The inlet end of the primary evacuation steam ejector 8 is connected to the primary evacuation pipeline 7, and the outlet end is connected to the primary evacuation steam condenser 10 via the connecting pipe 9. The bottom of the primary evacuation steam condenser 10 is connected to the primary condensate discharge pipe 11. The secondary evacuation branch includes a secondary evacuation pipeline 13, a secondary evacuation steam ejector 14, a secondary evacuation steam condenser 15, and a secondary condensate discharge pipe 16. The secondary evacuation pipeline 13 is led from the gas phase outlet of the primary evacuation steam condenser 10 to the secondary evacuation steam ejector 14. The secondary evacuation steam ejector 14 is connected to the secondary evacuation steam condenser 15 through a pipeline. The secondary condensate discharge pipe 16 is installed at the bottom of the secondary evacuation steam condenser 15. The ends of the primary condensate discharge pipe 11 and the secondary condensate discharge pipe 16 are merged and connected to the condensate collection tank 12 to collect the steam condensate waste liquid.

[0027] Among them, the first-stage evacuation steam ejector 8 and the second-stage evacuation steam ejector 14 operate based on the Venturi effect. High pressure drives the steam flow through the constriction throat to form a high-speed jet, generating negative pressure in the suction chamber to extract the non-condensable gas from the deoxygenation tower 1 and the hot water tank 31. The outlet of the ejector diffuser is connected to the condenser, and the mixed steam is cooled and liquefied, resulting in a significant volume reduction, which further stabilizes and maintains the system vacuum.

[0028] The circulating water cooling pipeline includes a circulating water inlet pipeline, a circulating water connecting pipe 22, and a circulating water return pipe 23. The circulating water inlet pipeline is connected to the inlet side of the primary vacuum steam condenser 10, the circulating water connecting pipe 22 is connected across the outlet side of the primary vacuum steam condenser 10 and the inlet side of the secondary vacuum steam condenser 15, and the circulating water return pipe 23 is connected to the outlet side of the secondary vacuum steam condenser 15. The tank top condenser 38 is equipped with its own independent circulating water inlet pipeline and circulating water outlet pipeline, and is supplied with its own cooling water source.

[0029] The water inlet and distribution assembly includes a demineralized water inlet pipe 2, a first inlet regulating valve 3, a flow meter 4, and multiple sets of inlet nozzles 5. The demineralized water inlet pipe 2 is connected to the top side opening of the deoxygenation tower 1. The first inlet regulating valve 3 and the flow meter 4 are installed sequentially along the water flow direction. The section of the demineralized water inlet pipe 2 extending into the tower branches downward to connect to multiple sets of inlet nozzles 5. A first pressure transmitter 6 is installed at the top of the deoxygenation tower 1 to monitor the negative pressure inside the tower. A first liquid level sensor 46 is installed on the side wall of the tower to monitor the water storage level. The first inlet regulating valve 3 is interlocked with the first liquid level sensor 46, and the water inlet opening is automatically adjusted according to the liquid level. A regular packing layer is laid in the inner cavity of the deoxygenation tower 1 and below the inlet nozzles 5. An upper grid and a lower grid are installed above and below the packing layer, respectively. A metal wire mesh assembly is laid between the upper and lower grids to support the packing and distribute air and water evenly. The packing layer extends the gas-liquid contact time and improves the vacuum pre-deoxygenation effect.

[0030] The steam supply pipeline includes a steam main pipe 19, a steam branch pipe 17, a third pneumatic regulating valve 21, a second pneumatic regulating valve 20, and a first pneumatic regulating valve 18. The end of the steam main pipe 19 is connected to the first-stage vacuum steam ejector 8. Along the steam flow direction, the third pneumatic regulating valve 21 and the second pneumatic regulating valve 20 are sequentially arranged on the steam main pipe 19. The steam branch pipe 17 is led out from the section of the main pipe between the third pneumatic regulating valve 21 and the second pneumatic regulating valve 20. The end of the steam branch pipe 17 is connected to the second-stage vacuum steam ejector 14. The first pneumatic regulating valve 18 is installed on the steam branch pipe 17 to independently regulate the steam volume of the second-stage ejector.

[0031] The hot water heater 29 is connected to an external steam pipeline 44 and a condensate outlet pipe. An air inlet shut-off valve 45 is installed on the steam pipeline 44. A temperature detection element 43 is installed on the side wall of the hot water tank 31. The temperature signal collected by the temperature detection element 43 is interlocked with the air inlet shut-off valve 45. When the water temperature is insufficient, the steam is increased; when the water temperature exceeds the standard, the steam is reduced. A second pressure transmitter 41 is installed on the top of the hot water tank 31. The second pressure transmitter 41 detects the pressure signal and links with the fourth pneumatic regulating valve 37 to adjust the exhaust volume and maintain a slight positive pressure in the tank. A second liquid level sensor 42 is installed on the side wall of the hot water tank 31. The second liquid level sensor 42 is interlocked with the demineralized water transfer pump 26. When the liquid level is low, the water replenishment pump is started; when the liquid level is too high, the pump is stopped to prevent overflow or dry burning due to lack of water.

[0032] The second pneumatic regulating valve 20, the first pneumatic regulating valve 18, the third pneumatic regulating valve 21, and the fourth pneumatic regulating valve 37 are all equipped with PLC pressure interlock control modules to uniformly manage vacuum injection steam and tank exhaust pressure; the first shut-off valve 25, the second shut-off valve 27, the feeding shut-off valve 35, and the air inlet shut-off valve 45 are equipped with PLC water temperature interlock switching mechanisms to automatically switch between cyclic heating and material discharge modes based on temperature signals.

[0033] A first local pressure gauge 28 is installed on the demineralized water delivery pipe 24, between the demineralized water delivery pump 26 and the second shut-off valve 27; a second local pressure gauge 34 is installed on the demineralized water circulation feed pipe 32, between the demineralized water circulation feed pump 33 and the circulation heating pipe 47, so as to read the pipeline operating pressure in real time and intuitively, which is convenient for on-site inspection.

[0034] This embodiment also includes a PVC polymer demineralized water vacuum thermal deep deoxygenation process, comprising the following steps: S1. Vacuum pre-deoxygenation stage: Demineralized water is fed into deoxygenation tower 1 along the inlet water distribution assembly. The two-stage vacuum pumping unit continuously removes the gas phase in the tower to form a negative pressure. The water is sprayed onto the packing layer through the inlet water nozzle 5, and the gas and liquid fully contact each other to complete the initial removal of dissolved oxygen. The first liquid level sensor 46 collects the liquid level in the tower in real time and automatically adjusts the inlet water flow rate in conjunction with the first inlet water regulating valve 3 to stabilize the operating liquid level in the tower and avoid large fluctuations in the liquid level from affecting the deoxygenation effect. The vacuum degree in the tower is controlled to be stabilized to -85KPa by interlocking the first pressure transmitter 6 at the top of the deoxygenation tower 1 with the third pneumatic regulating valve 21.

[0035] S2, Heating and Buffering Stage: The pre-deoxygenated water at the bottom of the deoxygenation tower 1 is transported through the demineralized water conveying pipe 24, and flows sequentially through the first shut-off valve 25, the demineralized water conveying pump 26, and the second shut-off valve 27 before entering the hot water heater 29; external heating steam is introduced into the heater along the steam pipeline 44 for heat exchange and heating, and the heated high-temperature demineralized water is sent to the hot water tank 31 for storage through the first connecting pipe 30; the second liquid level sensor 42 monitors the liquid level of the hot water tank 31 in real time. If the liquid level is lower than the lower limit, the demineralized water conveying pump 26 is started to replenish water, and if the liquid level is higher than the upper limit, the conveying pump is stopped; the temperature detection element 43 continuously collects the water temperature in the tank. When the water temperature is lower than the set value, the air inlet shut-off valve 45 is opened to increase the heating steam, and when the water temperature reaches the standard, the steam supply is reduced.

[0036] S3. Thermal Deoxygenation and Non-condensable Gas Recovery Stage: The high-temperature water in the hot water tank 31 decomposes the residual dissolved oxygen into oxygen-containing non-condensable gas. The oxygen-containing gas enters the tank top condenser 38 along the second connecting pipe 36. After cooling, most of the water vapor condenses into liquid water. The condensate flows back to the hot water tank 31 by its own weight along the condensate connecting pipe 40. The water vapor entrained in the gas is condensed and separated by the tank top condenser 38. The remaining oxygen-containing non-condensable gas is sent to the primary evacuation branch for secondary extraction through the non-condensable gas return pipeline 39, completely removing the oxygen released from the water. The oxygen content of the demineralized water can be stably controlled at 0.02 mg / L. The second pressure transmitter 41 and the fourth pneumatic regulating valve 37 are interlocked to automatically adjust the gas phase discharge flow rate, stabilize the internal pressure of the hot water tank 31 at a slightly positive pressure of 5~10 kPa, and ensure the deoxygenation efficiency.

[0037] S4. Constant Temperature Circulation / Discharge Switching Stage: The PLC water temperature interlock switching mechanism automatically switches operating conditions based on the signal from the temperature detection element 43. When the temperature detection element 43 detects that the water temperature is below 98℃, the feeding shut-off valve 35 closes and the circulating heating shut-off valve 48 opens. The water from the hot water tank 31 flows back to the upstream of the demineralized water conveying pipe 24 through the demineralized water circulation feeding pipe 32 and the circulating heating pipe 47, and is reintroduced into the hot water heater 29 for circulation and heating, continuously desorbing residual oxygen. When the water temperature rises to 98℃, the circulating heating shut-off valve 48 closes and the feeding shut-off valve 35 opens. The low dissolved oxygen qualified demineralized water is transported to the PVC polymerization reactor along the demineralized water circulation feeding pipe 32 for production use.

[0038] S5. Unified collection stage of condensate waste liquid: The waste liquid generated by steam cooling in the primary evacuated steam condenser 10 and the secondary evacuated steam condenser 15 is collected in the condensate collection tank 12 through the primary condensate discharge pipe 11 and the secondary condensate discharge pipe 16 respectively, and then treated in a unified manner to avoid indiscriminate discharge of wastewater.

[0039] System Working Process and Principle: During operation of this PVC polymer demineralized water vacuum thermal deep deoxygenation system, the demineralized water to be treated is evenly fed into the deoxygenation tower 1 through the demineralized water inlet pipe 2, the first inlet regulating valve 3, the flow meter 4, and the inlet nozzle 5. The two-stage vacuum pumping unit, relying on the series structure of the first-stage pumping pipeline 7, the first-stage pumping steam ejector 8, the connecting pipe 9, the first-stage pumping steam condenser 10, and the second-stage pumping pipeline 13, the second-stage pumping steam ejector 14, and the second-stage pumping steam condenser 15, creates a stable negative pressure environment within the deoxygenation tower 1. The demineralized water fully completes gas-liquid mass transfer within the packing layer of the tower, achieving vacuum pre-deoxygenation. The first liquid level sensor 46 monitors the liquid level inside the tower in real time and interlocks with the first inlet regulating valve 3 to automatically adjust the inlet flow rate, ensuring stable operation of the deoxygenation tower 1. The first pressure transmitter 6 at the top of the deoxygenation tower 1 is interlocked with the third pneumatic regulating valve 21 to adjust the steam supply in real time, so as to keep the vacuum inside the deoxygenation tower 1 stable at -85KPa and ensure the stability of the pre-deoxygenation effect.

[0040] The pre-deoxygenated demineralized water flows out from the bottom of the deoxygenation tower 1, and is sequentially transported to the hot water heater 29 via the demineralized water delivery pipe 24 through the first shut-off valve 25, the demineralized water delivery pump 26, and the second shut-off valve 27. Heating steam is introduced through the steam pipeline 44 to heat the water. The heated demineralized water is then transported to the hot water tank 31 for buffering via the first connecting pipe 30. The second liquid level sensor 42 interlocks to control the start and stop of the demineralized water delivery pump 26, and the temperature detection element 43, in conjunction with the air inlet shut-off valve 45, adjusts the steam supply to achieve constant water temperature control in the hot water tank 31.

[0041] The high-temperature demineralized water in the hot water tank 31 further precipitates residual oxygen-containing non-condensable gases. These gases enter the condenser 38 at the top of the tank via the second connecting pipe 36 for condensation and heat exchange. The condensed liquid water flows back to the hot water tank 31 for recycling via the condensate connecting pipe 40. The uncondensed oxygen-containing non-condensable gases are sent to the primary vacuum branch via the non-condensable gas return pipeline 39, where a two-stage vacuum pumping unit performs secondary negative pressure removal, effectively preventing oxygen re-dissolution. The second pressure transmitter 41 is interlocked with the fourth pneumatic regulating valve 37 to stabilize the slightly positive pressure environment inside the hot water tank 31, ensuring a deep thermal deoxygenation effect. The system regulates the operating pressure of the first pneumatic regulating valve 18, the second pneumatic regulating valve 20, the third pneumatic regulating valve 21, and the fourth pneumatic regulating valve 37 through the PLC pressure interlock control module, and achieves fully automatic operation switching through the PLC water temperature interlock switching mechanism. When the water temperature is lower than the set constant temperature value, the feeding shut-off valve 35 closes and the circulating heating shut-off valve 48 opens. The demineralized water flows back to the demineralized water conveying pipe 24 for circulating heating through the demineralized water circulating feeding pipe 32, the demineralized water circulating feeding pump 33, and the circulating heating pipe 47. When the water temperature reaches the standard, the circulating heating shut-off valve 48 closes and the feeding shut-off valve 35 opens, and the qualified ultra-low dissolved oxygen demineralized water is transported to the PVC polymerization reactor for production use. The circulating water inlet pipeline, the circulating water connecting pipe 22, and the circulating water return pipe 23 continuously provide cooling medium for each condenser. The tank top condenser 38 is equipped with an independent circulating water inlet and outlet pipeline to ensure condensation efficiency. The first local pressure gauge 28 and the second local pressure gauge 34 monitor the pipeline pressure conditions in real time. The condensate waste liquid generated by each condenser is collected in the condensate collection tank 12 for treatment after converging through the primary condensate discharge pipe 11 and the secondary condensate discharge pipe 16.

[0042] The entire system combines vacuum pre-deoxygenation, thermal deep analysis, closed-loop secondary extraction of non-condensable gases, and fully automatic constant temperature and pressure interlock control, which greatly improves the deoxygenation accuracy and operational stability, and is suitable for the ultra-low dissolved oxygen inlet water requirements of PVC polymerization.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A PVC polymer demineralized water vacuum thermal deep deoxygenation system, comprising a deoxygenation tower (1), a two-stage vacuum pumping unit, a hot water heating buffer unit, a common pipeline assembly, and a condensate collection tank (12); the deoxygenation tower (1) is provided with an inlet water distribution assembly and a bottom outlet water conveying pipeline on one side of its top and bottom respectively; the two-stage vacuum pumping unit is connected to the top of the deoxygenation tower (1) to provide negative pressure; the hot water heating buffer unit is connected to the bottom outlet water conveying pipeline and is used to heat and buffer the demineralized water for deep deoxygenation; the common pipeline assembly includes a steam supply pipeline and a circulating water cooling pipeline; characterized in that, The two-stage vacuum pumping unit includes a primary pumping branch and a secondary pumping branch arranged in series. The primary pumping branch and the secondary pumping branch share a steam supply pipeline to supply driving steam, and at the same time share a circulating water cooling pipeline to provide cooling medium. The hot water heating buffer unit includes a hot water heater (29), a hot water tank (31), a demineralized water circulating feed pump (33), a tank top condenser (38), a demineralized water circulating feed pipe (32), a first connecting pipe (30), a second connecting pipe (36), a condensate connecting pipe (40), a non-condensable gas return line (39), a circulating heating pipe (47), a circulating heating shut-off valve (48), a feed shut-off valve (35), and a fourth pneumatic regulating valve (37). The feed port of the demineralized water circulating feed pipe (32) is connected to the bottom of one side of the hot water tank (31), and the other end is connected to the polymerization reactor. The demineralized water circulating feed pump (33) and the feed shut-off valve (35) are sequentially arranged on the pipe section of the demineralized water circulating feed pipe (32) along the medium flow direction. One end of the circulating heating pipe (47) is connected to the pipe section of the demineralized water circulating feed pipe (32) and is located at the demineralized water circulating feed pump (39). Between 33) and the feed shut-off valve (35), the other end of the circulating heating pipe (47) is connected to the bottom water delivery pipeline of the tower, and the circulating heating shut-off valve (48) is located on the pipe section of the circulating heating pipe (47); the two ends of the second connecting pipe (36) are respectively connected to the top of the hot water tank (31) and the tank top condenser (38), and the fourth pneumatic regulating valve (37) is located on the pipe section of the second connecting pipe (36); the two ends of the condensate connecting pipe (40) are respectively connected to the tank top condenser (38) and the hot water tank (31); the two ends of the first connecting pipe (30) are respectively connected to the hot water tank (31) and the hot water heater (29); one end of the non-condensable gas return pipeline (39) is connected to the tank top condenser (38), and the other end is connected to the first-stage vacuum branch, which is used to send the oxygen-containing non-condensable gas that is heated and precipitated in the hot water tank (31) into the two-stage vacuum pumping unit for secondary extraction; The bottom water delivery pipeline includes a demineralized water delivery pipe (24) connected to the bottom of the deoxygenation tower (1), a first shut-off valve (25), a demineralized water delivery pump (26), and a second shut-off valve (27) connected in series along the medium flow direction on the demineralized water delivery pipe (24) section. One end of the demineralized water delivery pipe (24) is connected to a hot water heater (29); the other end of the circulating heating pipe (47) is connected to the demineralized water delivery pipe (24) and is located downstream of the second shut-off valve (27).

2. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 1, characterized in that, The primary evacuation branch includes a primary evacuation pipeline (7) connected to the top of the deoxygenation tower (1), a primary evacuation steam ejector (8) connected to one end of the primary evacuation pipeline (7), a connecting pipe (9) connected to the primary evacuation steam ejector (8), a primary evacuation steam condenser (10) connected to one end of the connecting pipe (9), and a primary condensate discharge pipe (11) connected to the primary evacuation steam condenser (10); the secondary evacuation branch includes a secondary evacuation pipeline (13) connected to the primary evacuation steam condenser (10), a secondary evacuation steam ejector (14) connected to one end of the secondary evacuation pipeline (13), a secondary evacuation steam condenser (15) connected to the secondary evacuation steam ejector (14) via a pipe, and a secondary condensate discharge pipe (16) connected to the secondary evacuation steam condenser (15); one end of the primary condensate discharge pipe (11) and the secondary condensate discharge pipe (16) are both connected to the condensate collection tank (12).

3. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 2, characterized in that, The circulating water cooling pipeline includes a circulating water inlet pipeline connected to the inlet side of the first-stage vacuum steam condenser (10), a circulating water connecting pipe (22) bridging the outlet side of the first-stage vacuum steam condenser (10) and the inlet side of the second-stage vacuum steam condenser (15), and a circulating water return pipe (23) connected to the outlet side of the second-stage vacuum steam condenser (15); the tank top condenser (38) is equipped with a circulating water inlet pipeline and a circulating water outlet pipeline respectively.

4. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 3, characterized in that, The water inlet distribution assembly includes a demineralized water inlet pipe (2) connected to the top of one side of the deoxygenation tower (1), a first water inlet regulating valve (3) and a flow meter (4) arranged sequentially along the medium flow direction on the pipe section of the demineralized water inlet pipe (2), and multiple water inlet nozzles (5) connected to the pipe section of the demineralized water inlet pipe (2) extending into the inner pipe section of the deoxygenation tower (1); the top of the deoxygenation tower (1) is provided with a first pressure transmitter (6) for monitoring the gas phase pressure inside the tower, and the side of the deoxygenation tower (1) is provided with a first liquid level sensor (46) for monitoring the liquid level inside the tower; the first water inlet regulating valve (3) and the first liquid level sensor (46) are interlocked; the inner cavity of the deoxygenation tower (1) is provided with a packing layer located below the water inlet nozzles (5).

5. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 4, characterized in that, The steam supply pipeline includes a steam main pipe (19), a steam branch pipe (17), a third pneumatic regulating valve (21), a second pneumatic regulating valve (20), and a first pneumatic regulating valve (18). One end of the steam main pipe (19) is connected to a first-stage vacuum steam ejector (8). The third pneumatic regulating valve (21) and the second pneumatic regulating valve (20) are sequentially installed on the section of the steam main pipe (19) along the steam flow direction. One end of the steam branch pipe (17) is connected to the section of the steam main pipe (19) and is located between the third pneumatic regulating valve (21) and the second pneumatic regulating valve (20). The other end of the steam branch pipe (17) is connected to a second-stage vacuum steam ejector (14). The first pneumatic regulating valve (18) is installed on the section of the steam branch pipe (17).

6. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 5, characterized in that, The hot water heater (29) is connected to a steam pipeline (44) and a condensate outlet pipe. An air inlet shut-off valve (45) is provided on a section of the steam pipeline (44). A temperature detection element (43) is installed on the side of the hot water tank (31). The temperature detection element (43) is interlocked with the air inlet shut-off valve (45). A second pressure transmitter (41) is provided on the top of the hot water tank (31). The second pressure transmitter (41) is interlocked with the fourth pneumatic regulating valve (37). A second liquid level sensor (42) is provided on the side of the hot water tank (31). The demineralized water transfer pump (26) is interlocked with the second liquid level sensor (42) for start and stop.

7. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 6, characterized in that, The second pneumatic regulating valve (20), the first pneumatic regulating valve (18), the third pneumatic regulating valve (21), and the fourth pneumatic regulating valve (37) are all equipped with a PLC pressure interlock control module; the first shut-off valve (25), the second shut-off valve (27), the feeding shut-off valve (35), and the air inlet shut-off valve (45) are equipped with a PLC water temperature interlock switching mechanism.

8. The PVC polymer demineralized water vacuum thermal deep deoxygenation system according to claim 1, characterized in that, The demineralized water conveying pipe (24) is provided with a first local pressure gauge (28) located between the demineralized water conveying pump (26) and the second shut-off valve (27), and the demineralized water circulating feed pipe (32) is provided with a second local pressure gauge (34) located between the demineralized water circulating feed pump (33) and the circulating heating pipe (47).

9. A process for deep vacuum thermal deoxygenation of PVC polymerized demineralized water according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Demineralized water is fed into the deoxygenation tower (1) through the water inlet distribution assembly. The two-stage vacuum pumping unit continuously extracts the gas phase inside the deoxygenation tower (1) to form a negative pressure environment. The demineralized water and the packing inside the deoxygenation tower (1) are in full contact to complete the initial removal of dissolved oxygen. The liquid level of the deoxygenation tower (1) is automatically stabilized by the first liquid level sensor (46) linked to the first water inlet regulating valve (3). S2. The demineralized water from the bottom of the deoxygenation tower (1) is transported to the hot water heater (29) via the demineralized water conveying pipe (24). Steam is introduced through the steam pipeline (44) to heat the demineralized water. The demineralized water heated by the hot water heater (29) is transported to the hot water tank (31) for buffering via the first connecting pipe (30). The liquid level of the hot water tank (31) is controlled by the second liquid level sensor (42) to start and stop the demineralized water conveying pump (26). The temperature detection element (43) collects the water temperature in the tank in real time and links the air inlet shut-off valve (45) to adjust the heating steam supply. S3. Oxygen-containing non-condensable gas is released from the high-temperature water in the hot water tank (31). The oxygen-containing non-condensable gas enters the tank top condenser (38) along the second connecting pipe (36) and is condensed. The condensed liquid water flows back to the hot water tank (31) through the condensate connecting pipe (40). The uncondensed oxygen-containing non-condensable gas is sent to the first-stage vacuum branch through the non-condensable gas return pipeline (39) and is removed by the two-stage vacuum pumping unit. The fourth pneumatic regulating valve (37) works with the second pressure transmitter (41) to stabilize the slight positive pressure inside the hot water tank (31). S4. When the temperature detection element (43) detects that the water temperature is lower than the process set constant temperature value, the feeding shut-off valve (35) is closed and the circulating heating shut-off valve (48) is opened. The demineralized water flows back to the demineralized water conveying pipe (24) through the circulating heating pipe (47) for circulating heating. When the water temperature reaches the process set constant temperature value, the circulating heating shut-off valve (48) is closed and the feeding shut-off valve (35) is opened. The qualified low dissolved oxygen demineralized water is transported to the PVC polymerization reactor for production use along the demineralized water circulating feeding pipe (32). S5. The condensate waste liquid generated by the primary evacuated steam condenser (10) and the secondary evacuated steam condenser (15) flows into the condensate collection tank (12) for centralized treatment via the primary condensate discharge pipe (11) and the secondary condensate discharge pipe (16).

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