Chemical cleaning method for polar polymer production equipment

Abstract

The invention discloses a chemical cleaning method for polar polymer production equipment, and relates to the technical field of high polymer material production equipment maintaining.The chemical cleaning method comprises the steps that residual samples in the production equipment are collected and analyzed to select an adaptive cleaning agent, and a closed-loop circulation system for executing a cleaning task is built; on the basis of a closed-loop circulation system, softened water is used for positively and negatively flushing production equipment to remove floating impurities; pollutants in the closed-loop circulation system are circularly cleaned through a cleaning agent, and cleaning agent residues are removed through softened water after circulation of the cleaning agent is finished; selecting passivation liquid circulation according to equipment materials, and forming a passivation film on the inner wall of the production equipment; and repeatedly flushing the production equipment by using deionized water, purging and drying. Key links such as isolation, leak detection and verification are designed, secondary pollution and wrong installation are avoided, and the device is suitable for industrial batch cleaning operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer production equipment maintenance, and in particular to a chemical cleaning method for polar polymer production equipment. BACKGROUND

[0002] In the production process of polar polymers (such as nylon, polyester, polycarbonate), complex contaminants composed of monomers, oligomers, catalysts and additives are easily attached to the inner walls of core equipment such as reaction kettles, heat exchangers and melt conveying pipelines. The presence of these contaminants can cause the following problems: first, it reduces the heat transfer efficiency of the equipment, such as the heat transfer coefficient of the heat exchanger bundle, which decreases by 30%-50% after fouling, affecting the production temperature control accuracy and leading to reduced reaction efficiency; second, the residual contaminants mixed into the subsequent products cause product purity to decrease, color to be abnormal, and even mechanical properties to deteriorate, such as the decrease of nylon elongation at break; third, long-term accumulation of residues can easily block the pipeline or the feed inlet of the reaction kettle, causing equipment overpressure, local overheating and other safety accidents.

[0003] The existing cleaning technology has many defects: high-pressure water jet cleaning can remove loose impurities, but it has insufficient removal ability for chemically bonded polar oligomers, and there are cleaning dead angles for complex structures; traditional chemical cleaning often uses single acid or alkali cleaning agents, without customizing the formula for the characteristics of polar polymer residues, which can easily lead to incomplete cleaning or equipment corrosion, such as the corrosion rate of stainless steel equipment in acid cleaning without corrosion inhibitor being above 0.1 mm / a; solvent cleaning has strong solubility for polar residues, but common solvents are highly toxic and have high VOC emissions, which do not meet environmental protection requirements; in addition, the existing cleaning process lacks systematic isolation, leak detection and effect verification links, which can easily cause secondary pollution or residual problems in the cleaned equipment.

[0004] Therefore, it is urgent to design a chemical cleaning method that takes into account "targeted removal of residues, protection of equipment materials, compliance with environmental and safety requirements, and standardized and operable process" to solve the bottleneck of existing technology. SUMMARY

[0005] Therefore, it is necessary to provide a chemical cleaning method for polar polymer production equipment to solve the above technical problems.

[0006] The present application provides a chemical cleaning method for polar polymer production equipment, comprising: S1, isolating the production equipment to be cleaned from the production system, collecting residual samples in the production equipment for analysis to select a suitable cleaning agent, and building a closed-loop circulation system for performing the cleaning task; S2, based on the closed-loop circulation system, using softened water to flush the production equipment forward and backward to remove floating impurities, and after the removal of floating impurities is completed, detecting the sealing property of the production equipment by water injection, pressure boosting and pressure maintaining; S3, cleaning the pollutants in the closed loop circulation system by using the cleaning agent, and removing the cleaning agent residues by using the softened water after the cleaning agent circulation is completed; S4, selecting the passivation liquid circulation according to the material of the equipment, and forming the passivation film on the inner wall of the production equipment; S5, repeatedly flushing the production equipment by using the deionized water and blowing and drying, checking the cleaning effect by using the endoscope, and resetting the parts in the reverse order and processing the waste liquid according to the classification after the checking is passed.

[0007] Further, the production equipment to be cleaned is isolated from the production system, residual samples in the production equipment are collected for analysis to select the cleaning agent, and a closed loop circulation system for performing the cleaning task is built, comprising: S11, cutting off the production equipment to be cleaned from the production system by using the stainless steel blind plate, and adding the oil-resistant asbestos sheet on both sides of the stainless steel blind plate; closing the heating and cooling medium valves matched with the production equipment, and disassembling the equipment accessories according to the principle of giving priority to the precision parts; S12, collecting residual samples at multiple points on the inner wall of the production equipment, analyzing the functional groups by using the Fourier transform infrared spectrum, and determining the composition of the residual samples by using the high performance liquid chromatography, and selecting the cleaning agent accordingly; S13, building a closed loop circulation system composed of a corrosion-resistant centrifugal pump, a PPH liquid storage tank and a stainless steel temporary pipe, and configuring acid and alkali resistant protective equipment for the operator, and an emergency flushing and cleaning equipment, and keeping the VOC concentration in the workshop less than 100 ppm after ventilation.

[0008] Further, the cleaning agent comprises a combination of 5-15wt% sodium hydroxide, 0.1-0.5wt% benzotriazole corrosion inhibitor and 1-2wt% fatty alcohol polyoxyethylene ether surfactant; or a combination of 3-8wt% citric acid or 3-5wt% nitric acid and 0.2-0.6wt% thiourea or urotropine corrosion inhibitor.

[0009] Further, based on the closed loop circulation system, the production equipment is flushed forward and backward by using the softened water to remove floating impurities, and after the removal of the floating impurities is completed, the sealing property of the production equipment is detected by water injection, pressure boosting and pressure maintaining, comprising: S21, injecting the industrial grade softened water into the closed loop circulation system, flushing the sealing gap of the heat exchanger tube bundle, the pipeline elbow and the stirring shaft of the polymerization reactor by using the forward and backward flushing combination, and collecting and detecting the water sample according to the preset sampling time until the turbidity of the detected water sample is less than the preset threshold value, and stopping the flushing; S22, inject softened water into the closed loop circulation system, close all outlet valves, start the booster pump to raise the pressure of the closed loop circulation system to 0.4-1.0 MPa and maintain the pressure for 30 minutes, and use soapy water to smear all pipe joints during the pressure maintaining process, and observe whether bubbles are generated; if no bubbles are generated, it is determined that the closed loop circulation system is qualified for sealing, and if bubbles exist, mark the leakage point and immediately release the pressure.

[0010] Further, the pollutants in the closed loop circulation system are cleaned by circulating the cleaning agent, and the cleaning agent residues are removed by using softened water after the cleaning agent circulation is completed, including: S31, preheat the pre-configured cleaning agent, start the centrifugal pump to circulate the cleaning agent in the closed loop circulation system, and collect chemical cleaning samples every preset sampling time during the circulation until the COD value change rate of the chemical cleaning sample meets the preset range, and stop the cleaning agent circulation; S32, inject softened water into the closed loop circulation system, start the centrifugal pump for flushing, collect cleaning samples every preset sampling time until the pH value of the cleaning sample is 7-8 and the conductivity is less than the preset threshold, stop the softened water flushing and drain the accumulated water in the hole.

[0011] Further, the preheating temperature of the cleaning agent is 40-80℃.

[0012] Further, the passivation liquid is circulated according to the material of the production equipment to form a passivation film on the inner wall of the production equipment, including: S41, inject softened water into the closed loop circulation system, start the centrifugal pump to circulate the softened water in the closed loop circulation system, collect the rinsing sample every preset sampling time during the circulation until the iron ion concentration of the rinsing sample is <10ppm, stop the softened water circulation and empty the accumulated water; S42, select a passivation liquid according to the material of the production equipment, start the centrifugal pump to circulate the passivation liquid in the closed loop circulation system, and end the circulation and empty the passivation liquid when the preset passivation time is up.

[0013] Further, when the material of the production equipment is stainless steel, the passivation agent is a polyphosphate solution with a mass fraction of 2-3%, and when the material of the production equipment is carbon steel, the passivation agent is a mixture of sodium nitrite solution with a mass fraction of 1-2% and sodium hydroxide solution with a mass fraction of 0.1-0.2%.

[0014] Further, the production equipment is repeatedly flushed with deionized water and dried by purging, the cleaning effect is checked by endoscopy, and after the check is passed, the parts are reset in the reverse order according to the disassembly sequence and the waste liquid is treated. S51, inject deionized water into the closed loop circulation system, start the centrifugal pump to circulate the deionized water in the closed loop circulation system, collect the fine washing sample every preset sampling time during the circulation, when the conductivity difference between the outlet water and the inlet water is < 2 mu S / cm and TOC < 10 ppb, stop flushing and empty the deionized water; dry the closed loop circulation system by introducing compressed air; S52, check the inner wall of the reaction kettle, the heat exchanger tube bundle and the pipe elbow by endoscopy, wipe the inner wall of the production equipment with white sterile gauze, and take out the metal test piece to calculate the corrosion rate; S53, reset the equipment of the closed loop circulation system according to the reverse order of disassembly, and recycle and store the alkaline cleaning agent waste liquid, the acid cleaning agent waste liquid and the passivation liquid waste liquid according to the classification collection principle.

[0015] Further, the dew point temperature of the compressed air is < 40 DEG C and the pressure is 0.3-0.5 MPa.

[0016] The beneficial effects of the present application are: through FTIR and HPLC analysis of residual properties, custom cleaning agent formula, combined with surfactant to enhance permeability, the removal rate of polar polymer oligomer and catalyst residue is more than 99%; after passivation treatment, the corrosion resistance of the inner wall of the equipment is improved by more than 50%, prolonging the service life of the equipment; using low-toxicity cleaning agent, such as citric acid and polyphosphate, the solvent has no risk of VOC exceeding the standard; after cleaning, waste liquid is classified and collected for treatment, which meets the GB 18597-2001 standard; in addition, the key links such as isolation, leak detection and verification are clear, the logical relationship between steps is close, secondary pollution and misloading are avoided, and it is suitable for industrial batch cleaning operation. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a flow chart of a chemical cleaning method for polar polymer production equipment according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0019] Please refer to Figure 1 , a chemical cleaning method for polar polymer production equipment is provided, comprising: S1, a preparation stage before cleaning: isolating the production equipment to be cleaned from the production system, collecting residual samples in the production equipment for analysis to select a suitable cleaning agent, and building a closed-loop circulation system for performing the cleaning task.

[0020] In the description of the present application, isolating the production equipment to be cleaned from the production system, collecting residual samples in the production equipment for analysis to select a suitable cleaning agent, and building a closed-loop circulation system for performing the cleaning task include: S11, disconnecting the production equipment to be cleaned from the production system by using a stainless steel blind plate, and adding oil-resistant asbestos sheets on both sides of the stainless steel blind plate. Close the heating and cooling medium valves matched with the production equipment, and disassemble the equipment accessories according to the principle of giving priority to precision parts.

[0021] S12, collecting residual samples at multiple points on the inner wall of the production equipment, analyzing the functional groups by Fourier transform infrared spectroscopy (FTIR), determining the composition of the residual samples by high performance liquid chromatography (HPLC), and selecting a cleaning agent accordingly.

[0022] In the description of the present application, the cleaning agent includes a combination of 5-15wt% sodium hydroxide, 0.1-0.5wt% benzotriazole corrosion inhibitor, and 1-2wt% fatty alcohol polyoxyethylene ether surfactant; or a combination of 3-8wt% citric acid or 3-5wt% nitric acid and 0.2-0.6wt% thiourea or urotropine corrosion inhibitor.

[0023] S13, building a closed-loop circulation system composed of a corrosion-resistant centrifugal pump, a PPH liquid storage tank, and a stainless steel temporary pipe, and configuring acid and alkali resistant protective equipment for the operator, as well as an emergency shower cleaning device, and keeping the VOC concentration in the workshop less than 100ppm after ventilation.

[0024] Specifically, the closed-loop circulation system, i.e. the "cyclic cleaning temporary system", is built with a corrosion-resistant centrifugal pump (material 316L, head 15-20m) as the power source, a PPH material liquid storage tank (volume 1.2-1.5 times the total volume of the equipment, equipped with an electric heating device and a temperature sensor, temperature control accuracy ±2℃), and a temporary pipe made of food-grade 304 stainless steel pipe with a diameter matching the inlet and outlet of the equipment to avoid low local flow rate causing cleaning dead angles. The pipe connection is sealed with a clamp joint, and a pressure gauge (range 0-2MPa, accuracy 0.4) and a flow meter (measurement range 0-50m³ / h) are installed in the system to ensure that the cleaning agent can form a closed-loop circulation between the reactor, the heat exchanger, and the pipeline.

[0025] The operator wears acid and alkali resistant protective clothing (material neoprene), chemical resistant gloves (thickness ≥0.5mm, pH 1-14 resistant), goggles (chemical splash resistant type) and self-suction gas mask (filter box is adapted to organic vapor and acid gas); an emergency shower eye washer is arranged within a range of 5m of the cleaning site, the water outlet pressure is 0.2-0.4MPa, the response time is less than 10s, and 20L of emergency neutralizing agent is provided; the forced ventilation system of the workshop is started (the air exchange frequency is greater than or equal to 10 times / h), and the VOC concentration of the site is detected to be less than 100ppm (benzene series is less than 5ppm) before work can be performed.

[0026] S2, water flushing and system leak detection phase: based on a closed loop circulation system, the production equipment is flushed with softened water to remove floating impurities, and after the removal of floating impurities is completed, the sealing property of the production equipment is detected by water injection, pressure boosting and pressure maintaining.

[0027] In the description of the present application, based on a closed loop circulation system, the production equipment is flushed with softened water to remove floating impurities, and after the removal of floating impurities is completed, the sealing property of the production equipment is detected by water injection, pressure boosting and pressure maintaining, which comprises: S21, industrial grade softened water (hardness <0.03mmol / L to avoid subsequent scale formation) is injected into the closed loop circulation system, the sealing gap of the heat exchanger tube bundle, pipe bend and polymerization reactor stirring shaft is flushed by using a forward and reverse flushing combination mode, and water samples are collected and detected according to a preset sampling time until the turbidity of the detected water sample is less than a preset threshold value, and the flushing is stopped.

[0028] S22, softened water is injected into the closed loop circulation system, all outlet valves are closed, the pressure of the closed loop circulation system is raised to 0.4-1.0MPa by starting a pressure boosting pump and maintaining for 30min, and during the pressure maintaining process, all pipe joints are smeared with soap water, and whether bubbles are generated is observed. If no bubbles are generated, it is determined that the sealing property of the closed loop circulation system is qualified, and if bubbles exist, the leakage point is marked and pressure is immediately released.

[0029] S3, chemical cleaning circulation phase: the pollutants in the closed loop circulation system are cleaned by circulating the cleaning agent, and after the cleaning agent circulation is completed, the cleaning agent residues are removed by using softened water.

[0030] In the description of the present application, the pollutants in the closed loop circulation system are cleaned by circulating the cleaning agent, and after the cleaning agent circulation is completed, the cleaning agent residues are removed by using softened water, which comprises: S31, the preconfigured cleaning agent is preheated, the cleaning agent is circulated in the closed loop circulation system by starting a centrifugal pump, and during the circulation process, chemical cleaning samples are collected every preset sampling time until the COD value change rate of the chemical cleaning sample meets a preset range, and the cleaning agent circulation is stopped.

[0031] S32, inject softened water into the closed loop circulation system, start the centrifugal pump to flush, collect the cleaning sample every preset sampling time until the pH value of the cleaning sample is 7-8 and the conductivity is less than the preset threshold, stop the softened water flushing and drain the accumulated water in the hole.

[0032] In the description of the application, the preheating temperature of the cleaning agent is 40-80℃.

[0033] S4, rinsing and passivation stage: according to the material of the equipment, the passivation liquid is circulated, and the passivation film is formed on the inner wall of the production equipment.

[0034] In the description of the application, according to the material of the equipment, the passivation liquid is circulated, and the passivation film is formed on the inner wall of the production equipment, including: S41, inject softened water into the closed loop circulation system, start the centrifugal pump to circulate the softened water in the closed loop circulation system, collect the rinsing sample every preset sampling time during the circulation, until the iron ion concentration of the rinsing sample is <10ppm, stop the softened water circulation and empty the accumulated water.

[0035] S42, select the passivation liquid according to the material of the production equipment, start the centrifugal pump to circulate the passivation liquid in the closed loop circulation system, and when the preset passivation time is over, stop the circulation and empty the passivation liquid.

[0036] In the description of the application, when the material of the production equipment is stainless steel, the passivation agent is a polyphosphate solution with a mass fraction of 2-3%, and when the material of the production equipment is carbon steel, the passivation agent is a mixture of sodium nitrite solution with a mass fraction of 1-2% and sodium hydroxide solution with a mass fraction of 0.1-0.2%.

[0037] S5, final treatment and effect verification stage: use deionized water to repeatedly flush the production equipment and blow dry, check the cleaning effect through endoscopy, after the check is passed, reset the parts in reverse order and classify the waste liquid.

[0038] In the description of the application, use deionized water to repeatedly flush the production equipment and blow dry, check the cleaning effect through endoscopy, after the check is passed, reset the parts in reverse order and classify the waste liquid, including: S51, inject deionized water into the closed loop circulation system, start the centrifugal pump to circulate the deionized water in the closed loop circulation system, collect the fine cleaning sample every preset sampling time during the circulation, when the conductivity difference between the outlet water and the inlet water is <2μS / cm and TOC<10ppb, stop flushing and empty the deionized water. Blow dry with compressed air into the closed loop circulation system.

[0039] In the description of the application, the dew point temperature of the compressed air is <40℃ and the pressure is 0.3-0.5MPa.

[0040] S52, check the inner wall of the reaction kettle, heat exchanger tube bundle and pipe bend with an endoscope, wipe the inner wall of the production equipment with white sterile gauze, and take out the metal test piece to calculate the corrosion rate.

[0041] S53, reset the equipment of the closed loop circulation system in the reverse order of disassembly, and recover and store the alkaline cleaning agent waste liquid, acid cleaning agent waste liquid and passivation liquid waste liquid according to the classification collection principle.

[0042] Specifically, the system is reset in the reverse order of disassembly: first, install the filter screen and valve core of the check valve, ensure that the valve core sealing surface is clean, uniformly tighten the bolts, then install the flow meter (test the sensor after calibration) and the regulating valve (adjust the opening of the valve core to the initial production value); remove the temporary pipeline and liquid storage tank, clean the site; remove the blind plate at the inlet and outlet of the equipment, restore the connection with the main production system, check the opening and closing status of all valves to ensure that they are in the initial production closed state.

[0043] The following will supplement the description of a chemical cleaning method for a polar polymer production equipment designed by the application in combination with specific embodiments.

[0044] S1, preparation before cleaning: S11, system isolation: insert a 5mm thick 316L blind plate into the flange at the inlet and outlet of the reaction kettle, close the steam and cooling water valves; remove the pneumatic regulating valve (record the valve core opening of 25%) on the pipeline, the electromagnetic flow meter (sensor number FT-01), and the filter screen (pore size 30μm) of the check valve, clean them with alcohol cotton and mark them; S12, dirt analysis: collect the residue at the bottom of the reaction kettle, detect the ester bond (1720cm⁻¹) by FTIR, and determine the PET oligomer content of 65% and the antimony catalyst residue of 8% by HPLC, select "10% NaOH + 0.4% benzotriazole + 1.5% fatty alcohol polyoxyethylene ether" as the alkaline cleaning agent, and "6% citric acid + 0.3% thiourea" as the acid cleaning agent; S13, temporary system: use a 316L centrifugal pump (head 18m), a 10m³ PPH liquid storage tank (with electric heating), and DN50 stainless steel temporary pipeline, and on-site prepare a shower eyewash device, 20L 5% citric acid solution, and detect the VOC concentration of 85ppm after ventilation; S2, water flushing and leak detection: S21, water flushing: flush with industrial softened water at a flow rate of 1.8m / s for 40min in the forward direction and 30min in the reverse direction, the outlet water turbidity decreases from 25NTU to 4NTU, and compressed air (0.4MPa) is blown for 15min; S22, leak detection: fill the water to 0.8MPa, maintain the pressure for 30min, there is no bubble at the flange interface, and the pressure drop is 0.015MPa; S3, chemical cleaning: S31, the cleaning agent is heated to 70 DEG C, and is circulated for 7h, and NaOH is supplemented every 1h to maintain pH 11.5, and COD is increased from 5000mg / L to 18000mg / L and then is stabilized; S32, intermediate rinsing: rinsing for 60min, and the outlet water pH is 7.5, and the conductivity is 95 mu S / cm.

[0045] S4, rinsing passivation: S41, iron ion rinsing: rinsing for 45min, and 8% sodium carbonate solution is supplemented, and the outlet water pH is 6.2, and the iron ion concentration is 7ppm; S42, surface passivation: 2.5% sodium hexametaphosphate solution is circulated for 3h at 60 DEG C, and pH is maintained at 9.0; S5, final treatment: S51, rinsing and drying: deionized water rinsing for 90min, and the outlet water conductivity is 4 mu S / cm (water inlet 3 mu S / cm), and TOC is 8ppb, and nitrogen gas (purity 99.99%) is blown for 40min, and the humidity is 3%; S52, verification reset: endoscopy is free of dirt, and non-woven cloth wiping is white, and the corrosion rate of the test piece is 0.008mm / a;Reset the regulating valve, flow meter, and waste liquid is handed over to a qualified unit for treatment.

[0046] After cleaning, the heat transfer efficiency of the PET reactor is increased by 42%, the color of the PET chip produced subsequently is increased from 88 to 92, the antimony content is reduced from 12ppm to 5ppm, and the food contact level standard is met.

[0047] In summary, by means of the above technical scheme of the present application, the removal rate of polar polymer oligomers and catalyst residues is more than 99% by analyzing the residual characteristics by FTIR and HPLC, customizing the acid-base cleaning agent formula, and enhancing the permeability combined with surfactants;The corrosion resistance of the inner wall of the equipment is increased by more than 50% after passivation treatment, prolonging the service life of the equipment;Low-toxicity cleaning agents such as citric acid and polyphosphate are used, and there is no risk of VOC exceeding the standard in solvents;After cleaning, waste liquid is classified and collected for treatment, meeting the GB18597-2001 standard;In addition, the key links such as isolation, leak detection and verification are clear, the logical relationship between steps is close, secondary pollution and misloading are avoided, and it is suitable for industrial batch cleaning operation.

[0048] It should be understood that although the steps in the flowcharts of the drawings are shown in sequential order, such that each step depends on completion of the previous step before execution of the next step, the steps are not necessarily performed in the order indicated by the arrows. Unless specifically stated otherwise, the steps can be performed in other orders. Moreover, at least some of the steps in the flowcharts of the drawings can include multiple sub-steps or stages, which are not necessarily performed at the same time, but can be performed at different times, and which are not necessarily performed sequentially, but can be performed in rotation or alternation with other steps or sub-steps or stages of other steps.

Claims

1. A chemical cleaning method for a polar polymer production apparatus, characterized by, The application relates to a production equipment cleaning method. S1, isolating the production equipment to be cleaned from a production system, collecting residual samples in the production equipment for analysis to select a suitable cleaning agent, and building a closed loop system for performing a cleaning task; S2, based on the closed loop system, using softened water to positively and negatively flush the production equipment to remove floating impurities, and after the removal of the floating impurities is completed, detecting the sealing property of the production equipment by water injection, pressure boosting and pressure maintaining; S3, using a cleaning agent to circulantly clean pollutants in the closed loop system, and after the circulation of the cleaning agent is completed, using softened water to remove residual cleaning agent; S4, selecting a passivation liquid circulation according to the material of the equipment to form a passivation film on the inner wall of the production equipment; S5, repeatedly flushing the production equipment with deionized water and blowing and drying, checking the cleaning effect through an endoscope, and after the checking is passed, resetting parts in a disassembly reverse order and processing waste liquid in a classified manner.

2. The chemical cleaning method for a polar polymer production apparatus according to claim 1, characterized by, The method comprises the following steps: S11, cutting off the production equipment to be cleaned from the production system by using a stainless steel blind plate, and adding oil-resistant asbestos sheets on both sides of the stainless steel blind plate; closing the heating and cooling medium valves matched with the production equipment, and disassembling equipment accessories according to the principle of giving priority to precision parts; S12, collecting residual samples at multiple points on the inner wall of the production equipment, analyzing functional groups by using Fourier transform infrared spectroscopy, and determining the composition of the residual samples by using high performance liquid chromatography, and selecting a cleaning agent in a targeted manner; S13, building a closed loop system composed of a corrosion-resistant centrifugal pump, a PPH liquid storage tank and a stainless steel temporary pipe, and configuring acid and alkali resistant protective equipment for operators, and emergency flushing and cleaning equipment, and keeping the VOC concentration in the workshop to be less than 100ppm after ventilation.

3. A chemical cleaning method for a polar polymer production apparatus according to claim 2, characterized by, The cleaning agent comprises a combination of 5-15wt% sodium hydroxide, 0.1-0.5wt% benzotriazole corrosion inhibitor and 1-2wt% fatty alcohol polyoxyethylene ether surfactant; or a combination of 3-8wt% citric acid or 3-5wt% nitric acid and 0.2-0.6wt% thiourea or urotropine corrosion inhibitor.

4. The chemical cleaning method for a polar polymer production apparatus according to claim 1, characterized by, The method comprises the following steps: S21, injecting industrial-grade softened water into the closed loop system, using a positive and negative flushing combination to flush the sealing gap of the heat exchanger tube bundle, the pipeline elbow and the stirring shaft of the polymerization reactor, and collecting and detecting water samples according to a preset sampling time, until the turbidity of the detected water sample is less than a preset threshold value, and the flushing is stopped; S22, injecting softened water into the closed loop system, closing all outlet valves, starting a pressure boosting pump to raise the pressure of the closed loop system to 0.4-1.0MPa and maintaining the pressure for 30min, and in the pressure maintaining process, using soap water to smear all pipeline joints, and observing whether bubbles are generated; if no bubbles are generated, it is determined that the sealing property of the closed loop system is qualified, and if bubbles exist, the leakage point is marked and pressure is immediately released.

5. The chemical cleaning method for a polar polymer production apparatus according to claim 1, characterized by, The closed loop circulation system is cleaned by circulating the cleaning agent, and after the cleaning agent circulation is completed, softened water is used to remove the cleaning agent residue, comprising: S31, preheat the pre-configured cleaning agent, start the centrifugal pump to circulate the cleaning agent in the closed loop circulation system, and collect chemical cleaning samples every preset sampling time during the circulation until the COD value of the chemical cleaning sample changes by a rate that meets the preset range, and stops the cleaning agent circulation; S32, inject softened water into the closed loop circulation system, start the centrifugal pump to flush, collect cleaning samples every preset sampling time until the pH value of the cleaning sample is 7-8 and the conductivity is less than the preset threshold, stop the softened water flushing and drain the accumulated water.

6. A chemical cleaning method for a polar polymer production apparatus according to claim 5, characterized by, The preheating temperature of the cleaning agent is 40-80℃.

7. The chemical cleaning method for a polar polymer production apparatus according to claim 1, characterized by, The passivation solution is selected according to the material of the production equipment, and the passivation film is formed on the inner wall of the production equipment, comprising: S41, inject softened water into the closed loop circulation system, start the centrifugal pump to circulate the softened water in the closed loop circulation system, collect the rinsing sample every preset sampling time during the circulation until the iron ion concentration of the rinsing sample is <10ppm, stop the softened water circulation and empty the accumulated water; S42, select the passivation solution according to the material of the production equipment, start the centrifugal pump to circulate the passivation solution in the closed loop circulation system, and when the preset passivation time is up, stop the circulation and empty the passivation solution.

8. A chemical cleaning method for a polar polymer production apparatus according to claim 7, characterized by, When the material of the production equipment is stainless steel, the passivation agent is a polyphosphate solution with a mass fraction of 2-3%, and when the material of the production equipment is carbon steel, the passivation agent is a mixture of sodium nitrite solution with a mass fraction of 1-2% and sodium hydroxide solution with a mass fraction of 0.1-0.2%.

9. The chemical cleaning method for a polar polymer production apparatus according to claim 1, characterized by, The production equipment is repeatedly flushed with deionized water and dried by blowing, and the cleaning effect is checked by endoscopy, and after passing the check, the parts are reset in reverse order and the waste liquid is treated according to the classification, comprising: S51, inject deionized water into the closed loop circulation system, start the centrifugal pump to circulate the deionized water in the closed loop circulation system, collect the fine cleaning sample every preset sampling time during the circulation, when the conductivity difference between the outlet water and the inlet water is <2μS / cm and the TOC is <10ppb, stop flushing and empty the deionized water; introduce compressed air into the closed loop circulation system for drying; S52, check the inner wall of the reaction kettle, the heat exchanger tube bundle and the pipe bend by endoscopy, wipe the inner wall of the production equipment with white sterile cloth, and take out the metal test piece to calculate the corrosion rate; S53, reset the equipment of the closed loop circulation system in reverse order, and recover and store the alkaline cleaning agent waste liquid, acid cleaning agent waste liquid and passivation liquid waste liquid according to the classification collection principle.

10. A chemical cleaning method for a polar polymer production apparatus according to claim 9, characterized by, The dew point temperature of the compressed air is <40℃ and the pressure is 0.3-0.5MPa.

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