A method and system for recovering polymerization inhibitor from styrene tar

Abstract

The present invention relates to a method and system for recovering a polymerization inhibitor from styrene tar. First, styrene tar and a depolymerization solvent are mixed in a mixer and then fed into a separator. After standing and stratification, the upper layer liquid is fed into an inhibition filter, a sedimentation agent is added, and after sufficient reaction and filtration, a filtered solid and a filtrate are obtained. The filtered solid is fed into a solvent recovery device to remove the solvent to obtain a solid. The solid is fed into a premixing tank and mixed with water. The mixed liquid enters an impeller-type high-gravity reaction device and is introduced with carbon dioxide for reaction. The obtained solid is dried to obtain the recovered polymerization inhibitor. The present invention can efficiently recover the polymerization inhibitor from styrene tar without affecting the quality of the recovered solvent oil. Moreover, the overall cost is low and there is no problem of secondary pollution.

Description

Technical Field

[0001] The invention relates to a method and a system for recovering a polymerization inhibitor in styrene tar, belonging to the technical field of solid waste pollution control. Background Art

[0002] Styrene tar is a common solid waste in the styrene production process and is also a hazardous waste specified in the "National List of Hazardous Wastes (2021 Edition)". It mainly consists of aromatic hydrocarbons, heterocyclic compounds containing N / O elements such as denitrification inhibitors, etc. Styrene tar has a high carbon-hydrogen ratio, contains a large number of unsaturated bonds, has a low ash content, and contains almost no heavy metals. At room temperature, it is a relatively viscous (>100mm 2 / s, 20°C). Currently, most manufacturers use it as a fuel for blending or outsourcing its disposal, failing to repurpose styrene tar. Furthermore, because styrene tar contains 10-25% nitrogen-containing polymerization inhibitors, the incineration process easily produces large amounts of NOx, causing secondary pollution.

[0003] Currently, most research directions for the polymerization inhibitors contained in styrene tar are on how to remove the polymerization inhibitors and use the recovered oil after de-inhibition to prepare different products or extract certain monomers. There are not many methods for recovering polymerization inhibitors.

[0004] Xu Tao (Xu Tao. Analysis of styrene tar components and study of base sulfonation reaction [D]. Hefei University of Technology, 2018) disclosed a method for separating DNBP from styrene tar. 100 mL of 3% sodium hydroxide solution was added to 200 g of tar and treated in the order of "mixing-standing and separating". The upper layer obtained was an organic phase and the lower layer was an aqueous phase including inhibitor salt. After the aqueous phase was treated twice, it was neutralized with hydrochloric acid to pH = 5. The precipitated solid was extracted with ethylbenzene three times, and then the ethylbenzene was recovered by vacuum distillation. The remaining solid was DNBP.

[0005] CN105330887A discloses a method and device for reducing the polymerization inhibitor in butadiene rubber recycled solvent oil. The first step is to mix recycled solvent oil containing polymerization inhibitor with an alkaline solution with a mass percentage of 7% to 10% to obtain a primary mixed liquid, wherein the volume ratio of recycled solvent oil containing polymerization inhibitor to the alkaline solution with a mass percentage of 7% to 10% is 1:1 to 2, and the mixing time is 2 seconds to 3 seconds; the second step is to statically separate the primary mixed liquid to obtain recycled solvent oil containing alkali solution and an alkaline solution containing polymerization inhibitor; the third step is to mix the recycled solvent oil containing alkali solution with water to obtain a secondary mixed liquid, wherein the volume ratio of recycled solvent oil containing alkali solution to water is 1:1 to 2, and the mixing time is 2 seconds to 3 seconds; the fourth step is to statically separate the secondary mixed liquid to obtain recycled solvent oil and an alkaline solution. The invention can effectively remove polymerization inhibitors from solvent oil, and the polymerization inhibitor removal rate is 95% to 100%.

[0006] It can be seen from the above existing technologies that the current methods for separating polymerization inhibitors have the following shortcomings: (1) the consumption of acid and alkali is large, which not only increases the cost but also produces a large amount of wastewater; (2) the polymerization inhibitor is only removed from the recovered liquid, and the polymerization inhibitor cannot be recycled and used, and the alkaline solution containing the polymerization inhibitor still needs to be treated. Summary of the Invention

[0007] To address the current issues with recovering polymerization inhibitors from styrene tar, the present invention provides a method and system for recovering polymerization inhibitors from styrene tar. This method efficiently recovers polymerization inhibitors from styrene tar without affecting the quality of the recovered solvent oil. It also offers low overall cost and eliminates secondary pollution.

[0008] The present invention provides a method for recovering a polymerization inhibitor from styrene tar, which mainly comprises the following steps:

[0009] (1) Styrene tar and depolymerization solvent are mixed in a mixer and then sent to a separator. After standing and separating the layers, the upper layer is sent to an inhibitor filter;

[0010] (2) Adding a sedimentation agent to the inhibitor filter, fully reacting and filtering to obtain filtered solid and filtrate;

[0011] (3) The filtered solid is sent to a solvent recovery device to remove the solvent to obtain a solid;

[0012] (4) The solid matter is sent to a premixing tank to be mixed with water. The mixed liquid enters an impeller-type supergravity reaction device and is introduced with carbon dioxide for reaction. The solid obtained is dried to be the recovered inhibitor.

[0013] The styrene tar described in step (1) comes from the distillation residue produced in the production process of ethylbenzene dehydrogenation to styrene, and mainly includes aromatic hydrocarbons, heterocyclic compounds containing elements such as N / O, such as polymerization inhibitors, etc., wherein the polymerization inhibitor is at least one of 2,4-dinitro-6-sec-butylphenol (DNBP), 2,6-dinitro-p-cresol (DNPC), 2,4-dinitrophenol (DNP), etc., with a mass content of 5%-25%.

[0014] The depolymerization solvent in step (1) is an alkane and a mixture thereof, preferably one or more of C2-C12 straight-chain alkanes, branched alkanes, cycloalkanes, etc., more preferably one or more of pentane, hexane, heptane, octane, nonane, etc.

[0015] The mass ratio of the styrene tar to the depolymerization solvent in step (1) is 1:1-4, preferably 1:2-3.5.

[0016] The mixing described in step (1) can be achieved by means including but not limited to stirring, forced circulation, etc., that is, it is sufficient to achieve full and uniform mixing of various substances in the system.

[0017] The anti-agglomeration filter described in step (2) has both reaction and filtration functions, and can prevent the deposition of materials in the pipeline during transportation and blockage. Specifically, a reaction tank with a stirring function and an openable / closable bottom is set above the filter. The depolymerization liquid or filtrate and the sedimentation agent enter the reaction tank for stirring reaction. After the reaction is completed, the bottom of the reaction tank is opened, and the mixed liquid enters the filter below under the action of gravity for filtration, thereby obtaining filtered solids and filtrate.

[0018] The precipitant in step (2) is one or more of ammonia solution, sodium bicarbonate solution, sodium carbonate solution, potassium carbonate solution, calcium hydroxide solution, sodium hydroxide solution, potassium hydroxide solution, etc., with a mass concentration of 2.5%-20%, preferably 5%-15%.

[0019] The sedimentation agent described in step (2) is added according to a volume ratio of the sedimentation agent to the upper liquid of 1:15-120, preferably 1:30-90.

[0020] The sedimentation agent in step (2) is preferably added slowly while stirring to prevent the quality of the recovered polymerization inhibitor from being deteriorated due to rapid addition at one time. The stirring rate is 60-200 rpm, preferably 80-120 rpm.

[0021] The solvent recovery device described in step (3) is mainly used to separate the solvent adhering to the filtered solid from the solid matter. The means of achieving this include but are not limited to flash evaporation, steam stripping, etc. The removed solvent can be recycled.

[0022] In the premixing tank described in step (4), the water used for the first time is fresh water, and recycled water can be used thereafter. The mass ratio of the added water to the solid matter is 1-100:1, preferably 15-30:1.

[0023] The impeller-type high-gravity reactor described in step (4) operates in a gas-liquid two-phase system. The impeller-type high-gravity hydrogen mixing equipment employs a structure with air distribution holes disposed on the rear side of the impeller in the direction of rotation, such as the structure described in CN200610134149.4. CO2 enters the impeller-type high-gravity reactor downward from the upper portion of a hollow shaft connected to the outside world. The liquid phase, carrying solid particles, enters the impeller from the bottom of the impeller at the lower end of the hollow shaft, where it enters the impeller, where it comes into contact with the CO2 entering from the outside world.

[0024] The amount of CO2 gas introduced in step (4) is 30-120 m3 / h per cubic meter of liquid phase. 3 , preferably 50-100m³ of CO2 for regulation.

[0025] The polymerization inhibitor recovered in step (4) can be intermittently discharged from the equipment and dried to obtain the recovered polymerization inhibitor. The drying temperature is 20-100°C, preferably 30-60°C, and the drying time is 3-24 hours, preferably 10-18 hours.

[0026] The present invention also provides a recovery system for the above-mentioned method of recovering the polymerization inhibitor in styrene tar, which mainly includes a mixer, a separator, an polymerization inhibitor filter, a solvent recovery device, a premixing tank and a supergravity reaction device, wherein the mixer is used to fully mix the styrene tar with the depolymerization solvent, the mixed liquid is sent to the separator, and after standing and stratification, the upper layer liquid is sent to the polymerization inhibitor filter, the polymerization inhibitor filter is used for the reaction and filtration of the upper layer liquid and the sedimentation agent, the filtered solid is sent to the solvent recovery device for desolvation, the obtained solid enters the premixing tank and is mixed with water, and then enters the impeller-type supergravity reaction device, CO2 is introduced for reaction, and the obtained solid is dried to obtain the recovered polymerization inhibitor.

[0027] In the system of the present invention, the inhibitor filter performs both reaction and filtration functions, preventing material from settling in the pipeline and causing blockage during transportation. Specifically, a reaction tank with a stirring function and an openable / closable bottom is located above the filter. The supernatant and sedimentation agent are transported to the reaction tank. After stirring and reacting, the bottom of the tank is opened, and the mixed liquid enters the filter below under the action of gravity for filtration.

[0028] Compared with the prior art, the method for recovering polymerization inhibitor from styrene tar of the present invention has the following effects:

[0029] (1) The present invention first uses a depolymerization solvent to treat styrene tar, then uses a sedimentation agent to treat it, and finally combines it with CO2 to cooperate with an impeller-type high-gravity reaction equipment for treatment, thereby achieving efficient recovery of the polymerization inhibitor in styrene tar, with the advantages of good recovery effect and low recovery cost.

[0030] (2) The styrene tar treated by the present invention contains oligomers, unsaturated components, etc., and these substances can be removed by using a depolymerization solvent, which helps to improve the subsequent sedimentation and separation of the polymerization inhibitor and the recovery effect of the polymerization inhibitor without affecting the quality of the recovered solvent oil.

[0031] (3) In the inhibitor salt reaction stage, the conventional strong acid is not used. Instead, a CO2-cooperated impeller-type high-gravity reaction device is used. Under high-gravity conditions, the impeller of the device absorbs CO2 and produces a large number of dense CO2 microbubbles in the mixed liquid, forming a "milky" mixture. The contact area between the gas and liquid phases is greatly increased, the mass transfer effect is greatly improved, and the inhibitor salt can react quickly to achieve the regeneration of the inhibitor. While ensuring the reaction effect, it avoids the problems of reagent consumption and equipment corrosion caused by acid consumption, and also ensures the recycling of water.

[0032] (4) The amount of alkali solution used in the present invention is smaller than that in the prior art, the processing temperature is room temperature, the solvent and water used can be recycled, the cost is low and there is no secondary pollution problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a process for recovering polymerization inhibitor from styrene tar according to the present invention;

[0034] Wherein: 1-mixer, 2-separator, 3-inhibitor filter, 4-solvent recovery device, 5-premixing tank, 6-supergravity reaction equipment; 11-styrene tar, 12-depolymerization solvent, 13-sedimentation agent, 14-filtered solid, 15-recovered solvent, 16-fresh water, 17-carbon dioxide, 18-circulating water, 19-recovered inhibitor.

[0035] Figure 2 It is a structural schematic diagram of the hypergravity reaction equipment used in the present invention;

[0036] Among them: 21-CO2 inlet, 22-circulating water inlet, 23-inhibitor discharge port, 24-impeller, 25-hollow shaft. DETAILED DESCRIPTION

[0037] The method of the present invention and its effects are further illustrated below with reference to specific examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples.

[0038] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0039] The embodiment adopts the present invention Figure 1 The recovery system of the polymerization inhibitor in the styrene tar shown in the figure is mainly composed of a mixer 1, a separator 2, an polymerization inhibitor filter 3, a solvent recovery device 4, a premixing tank 5 and a supergravity reaction device 6, wherein the mixer 1 is used to fully mix the styrene tar 11 with the depolymerization solvent 12, and the mixed liquid is sent to the separator 2. After standing and stratification, the upper layer liquid is sent to the polymerization inhibitor filter 3. The polymerization inhibitor filter 3 is used for the reaction and filtration of the upper layer liquid and the sedimentation agent 13. The filtered solid 14 is sent to the solvent recovery device 4, and the recovered solvent 15 is returned to the mixer for recycling. The obtained solid enters the premixing tank 5 and is mixed with water 16. After mixing, it enters the impeller-type supergravity reaction device 6, and CO2 is introduced into the CO2 inlet on the supergravity reaction device 6 for reaction. The solid obtained after drying is the recovered polymerization inhibitor 19.

[0040] In the present invention, the impeller-type high-gravity reaction equipment adopts the structure introduced in CN200610134149.4, which is a gas-liquid two-phase operation, and the hydrogen mixing equipment adopts a structure in which gas distribution holes are arranged on the rear side of the impeller in the direction of rotation.

[0041] The detection of the recovered polymerization inhibitor component of the present invention uses an Agilent gas chromatography-mass spectrometer.

[0042] Example 1

[0043] The styrene tar used in this example comes from the distillation residue produced during the production of styrene from ethylbenzene dehydrogenation at a Sinopec refinery, with a density of 1.02 kg / m 3 (20°C). The polymerization inhibitor is 2,4-dinitro-6-sec-butylphenol (DNBP), with a mass content of 10%.

[0044] 1000 mL of styrene tar was added to the mixer, and 3000 mL of depolymerization solvent was added. The depolymerization solvent was a mixture of n-heptane and n-octane in a mass ratio of 1:1. After thorough mixing, the mixture was put into the separator. After standing and stratification, the upper layer liquid was collected and transported to the inhibition filter. A sedimentation agent was added, i.e., an appropriate amount of 5 wt% sodium hydroxide solution and sodium carbonate solution (the mass ratio of the two was 1:1). The volume ratio of the sedimentation agent to the upper layer liquid was 1:60. The mixture was slowly added while stirring at a stirring rate of 80 rpm. After sufficient reaction and filtration, the mixture was , collect the filtered solids and send them to the solvent recovery device to remove the residual solvent on the surface of the filtered solids; send the solids to the premixing tank to mix with water, the mass ratio of water to solids is 25:1, the mixed liquid enters the impeller-type supergravity reaction equipment, and at the same time, introduces circulating CO2, and the introduction amount is regulated by introducing 60m³ of CO2 per cubic meter of liquid phase per hour. The obtained solids are intermittently discharged from the bottom of the equipment and are dried at 30°C for 12 hours to obtain the recovered inhibitor, totaling 91.96g; the content of inhibitor DNBP is 87.32% after testing.

[0045] Example 2

[0046] The styrene tar treated is the same as that in Example 1.

[0047] 1000 mL of styrene tar was added to the mixer, and 3000 mL of depolymerization solvent was added. The depolymerization solvent was a mixture of n-pentane and n-hexane in a mass ratio of 1:1. After thorough mixing, the mixture was put into the separator. After standing and stratification, the upper layer liquid was collected and transported to the inhibition filter. A sedimentation agent was added, namely, an appropriate amount of 10 wt% sodium bicarbonate solution and sodium carbonate solution (the mass ratio of the two was 1:1). The volume ratio of the sedimentation agent to the upper layer liquid was 1:30. The mixture was slowly added while stirring at a stirring rate of 120 rpm. The mixture was fully reacted and filtered. Finally, the filtered solids were collected and sent to the solvent recovery device to remove the residual solvent on the surface of the filtered solids; the solids were sent to the premixing tank to mix with water, and the mass ratio of water to solids was 15:1. The mixed liquid entered the impeller-type high-gravity reaction equipment, and circulating CO2 was introduced at the same time. The introduction amount was regulated by introducing 50m³ of CO2 per cubic meter of liquid phase per hour. The obtained solids were intermittently discharged from the bottom of the equipment and were dried at 30°C for 12 hours to obtain the recovered polymerization inhibitor, totaling 89.71g; the content of polymerization inhibitor DNBP was found to be 88.61%.

[0048] Example 3

[0049] The styrene tar treated is the same as that in Example 1.

[0050] 1000mL of styrene tar was added to the mixer, and 3000mL of depolymerization solvent was added. The depolymerization solvent was a mixture of n-octane and n-nonane in a mass ratio of 1:4. After thorough mixing, the mixture was put into the separator. After standing and stratification, the upper layer liquid was collected and transported to the inhibition filter. A sedimentation agent, that is, a potassium hydroxide solution with an appropriate concentration of 5wt%, with a volume ratio of sedimentation agent to upper layer liquid of 1:90, was added slowly while stirring at a stirring rate of 80rpm. After sufficient reaction and filtration, the filtered solid was collected and sent to The mixture was sent into the solvent recovery device to remove the residual solvent on the surface of the filtered solid; the solid was sent to the premixing tank to mix with water, the mass ratio of water to solid was 20:1, and the mixed liquid entered the impeller-type high-gravity reaction equipment, and circulating CO2 was introduced at the same time. The introduction amount was regulated by introducing 80m³ of CO2 per hour into each cubic meter of liquid phase. The obtained solid was intermittently discharged from the bottom of the equipment and was dried at 30°C for 12 hours to obtain the recovered polymerization inhibitor, totaling 86.96g. The content of polymerization inhibitor DNBP was found to be 89.07%.

[0051] Example 4

[0052] The styrene tar treated is the same as that in Example 1.

[0053] 1000 mL of styrene tar was added to the mixer, and 3000 mL of depolymerization solvent was added. The depolymerization solvent was a mixture of n-hexane and n-heptane in a mass ratio of 1:1. After thorough mixing, the mixture was passed into a separator. After standing and stratification, the upper layer liquid was collected and transported to an inhibition filter. A sedimentation agent was added, i.e., an appropriate amount of 10 wt% sodium bicarbonate solution and potassium carbonate solution (the mass ratio of the two was 1:1). The volume ratio of the sedimentation agent to the upper layer liquid was 1:85. The mixture was slowly added while stirring at a stirring rate of 70 rpm. The mixture was fully reacted and filtered. Finally, the filtered solids were collected and sent to the solvent recovery device to remove the residual solvent on the surface of the filtered solids; the solids were sent to the premixing tank to mix with water, and the mass ratio of water to solids was 18:1. The mixed liquid entered the impeller-type high-gravity reaction equipment, and circulating CO2 was introduced at the same time. The introduction amount was regulated by introducing 70m³ of CO2 per cubic meter of liquid phase per hour. The obtained solids were intermittently discharged from the bottom of the equipment and were dried at 30°C for 12 hours to obtain the recovered inhibitor, totaling 87.57g. The content of inhibitor DNBP was found to be 90.21%.

[0054] Example 5

[0055] The styrene tar treated is the same as that in Example 1.

[0056] Add 1000mL of styrene tar to the mixer, add 2000mL of depolymerization solvent (n-octane), mix thoroughly and put into the separator, let it stand for stratification, collect the upper liquid and send it to the inhibition filter, add the sedimentation agent, that is, a 5wt% calcium hydroxide solution and an ammonia solution (the mass ratio of the two is 1:1), the volume ratio of the sedimentation agent to the upper liquid is 1:110, add slowly while stirring, the stirring rate is 60rpm, after sufficient reaction and filtration, collect the filtered solid and send it to In the solvent recovery device, the residual solvent on the surface of the filtered solid is removed; the solid is sent to a premixing tank to be mixed with water, with a mass ratio of water to solid being 30:1. The mixed liquid enters an impeller-type high-gravity reaction device, and circulating CO2 is introduced at the same time. The introduction amount is regulated by introducing 40m³ of CO2 per cubic meter of liquid phase per hour. The obtained solid is intermittently discharged from the bottom of the equipment and is recovered as the polymerization inhibitor after drying at 30°C for 12 hours, totaling 80.11g; the content of the polymerization inhibitor DNBP is found to be 81.89% after testing.

[0057] Example 6

[0058] The styrene tar treated is the same as that in Example 1.

[0059] 1000 mL of styrene tar was added to the mixer, and 3500 mL of depolymerization solvent was added, the depolymerization solvent was n-heptane, and after thorough mixing, the mixture was passed into the separator, and after standing and stratification, the upper layer liquid was collected and transported to the inhibition filter, and a sedimentation agent, that is, a sodium hydroxide solution with an appropriate concentration of 5 wt%, and the volume ratio of the sedimentation agent to the upper layer liquid was 1:110, was added slowly while stirring, and the stirring rate was 60 rpm. After sufficient reaction and filtration, the filtered solid was collected and sent to the solvent recovery device, and the filtered solid was filtered. The solvent remaining on the surface of the solid is removed; the solid is sent to a premixing tank to be mixed with water, and the mass ratio of water to solid is 40:1. The mixed liquid enters the impeller-type high-gravity reaction equipment, and circulating CO2 is introduced at the same time. The introduction amount is regulated by introducing 120m³ of CO2 per cubic meter of liquid phase per hour. The obtained solid is intermittently discharged from the bottom of the equipment and is recovered as the inhibitor after drying at 30°C for 12 hours, totaling 82.78g. The content of inhibitor DNBP is 83.21% after testing.

[0060] Example 7

[0061] The density of the styrene tar used in this example is 1.03 kg / m 3 (20°C), the polymerization inhibitor contained was 2,6-dinitro-p-cresol (DNPC), with a mass content of 15%. The recovery process and operating conditions were the same as in Example 1, and a total of 137.93 g of polymerization inhibitor was recovered; the DNPC content was determined to be 91.57%.

[0062] Example 8

[0063] The density of the styrene tar used in this example is 1.02 kg / m 3 (20°C), the polymerization inhibitor contained was 2,4-dinitrophenol (DNP), with a mass content of 15%. The recovery process and operating conditions were the same as in Example 1, and a total of 134.57 g of polymerization inhibitor was recovered. The content of polymerization inhibitor DNPC was determined to be 90.48%.

[0064] Comparative Example 1

[0065] The same as Example 1, except that xylene was used as the depolymerization solvent. A total of 48.11 g of polymerization inhibitor was recovered, and the content of DNBP was 70.34%.

[0066] Comparative Example 2

[0067] The same as Example 1, except that ethyl acetate was used as the depolymerization solvent, and 56.94 g of polymerization inhibitor was recovered, and the content of DNBP in the polymerization inhibitor was 69.55%.

[0068] Comparative Example 3

[0069] The same method as Example 1 was used, except that the depolymerization solvent treatment in step (1) was not used, and the sedimentation agent treatment was used directly. A total of 49.09 g of polymerization inhibitor was recovered, and the content of the polymerization inhibitor DNBP was 72.09%.

[0070] Comparative Example 4

[0071] The same method as Example 1 was used except that the impeller-type high-gravity reactor and CO2 treatment were not used, but the traditional sulfuric acid acidification method was used. A total of 84.91 g of polymerization inhibitor was recovered, and component analysis of the polymerization inhibitor revealed a DNBP content of 82.16%.

Claims

1. A method for recovering a polymerization inhibitor from styrene tar, characterized in that The following steps are involved: (1) Styrene tar and a depolymerization solvent are mixed in a mixer and then sent to a separator. After standing for stratification, the upper layer liquid is sent to an inhibitor filter; the inhibitor in the styrene tar is at least one of 2,4-dinitro-6-sec-butylphenol (DNBP), 2,6-dinitro-p-cresol (DNPC), and 2,4-dinitrophenol (DNP); the depolymerization solvent is one or more of C2-C12 linear alkanes, branched alkanes, and cycloalkanes; (2) adding a sedimentation agent to the inhibition filter, reacting fully and filtering to obtain filtered solid and filtrate; the sedimentation agent is one or more of ammonia solution, sodium bicarbonate solution, sodium carbonate solution, potassium carbonate solution, calcium hydroxide solution, sodium hydroxide solution, and potassium hydroxide solution; The mass concentration is 2.5%-20%; (3) the filtered solid is sent to a solvent recovery device to remove the solvent to obtain a solid; (4) The solid matter is sent to a premixing tank to be mixed with water. The mixed liquid enters an impeller-type supergravity reaction device and is introduced with carbon dioxide for reaction. The solid obtained is dried to be the recovered inhibitor.

2. The method according to claim 1, wherein: The styrene tar described in step (1) comes from the distillation residue produced in the production process of ethylbenzene dehydrogenation to styrene, and includes aromatic hydrocarbons and polymerization inhibitors.

3. The method according to claim 1 or 2, characterized in that: The mass content of the polymerization inhibitor in the styrene tar is 5%-25%.

4. The method according to claim 1, wherein: The depolymerization solvent in step (1) is one or more of pentane, hexane, heptane, octane and nonane.

5. The method according to claim 1 or 4, characterized in that: The mass ratio of the styrene tar and the depolymerization solvent in step (1) is 1:1-4.

6. The method according to claim 5, characterized in that: The mass ratio of the styrene tar to the depolymerization solvent in step (1) is 1:2-3.

5.

7. The method according to claim 1, wherein: The anti-agglomeration filter described in step (2) has both reaction and filtration functions. Specifically, a reaction tank with a stirring function and an openable / closed bottom is set above the filter. The depolymerization liquid and the sedimentation agent enter the reaction tank for stirring reaction. After the reaction is completed, the bottom of the reaction tank is opened, and the mixed liquid enters the filter below under the action of gravity for filtration to obtain filtered solid and filtrate.

8. The method according to claim 1, wherein: The mass concentration of the sedimentation agent is 5%-15%.

9. The method according to claim 1, wherein: In step (2), the sedimentation agent is added at a volume ratio of 1:15-120 to the upper liquid.

10. The method according to claim 9, characterized in that: In step (2), the sedimentation agent is added at a volume ratio of 1:30 to 90 to the upper liquid.

11. The method according to claim 1, wherein: The sedimentation agent described in step (2) is added slowly while stirring at a stirring rate of 60-200 rpm.

12. The method according to claim 11, wherein: The sedimentation agent described in step (2) is added slowly while stirring at a stirring rate of 80-120 rpm.

13. The method according to claim 1, wherein: The solvent recovery device described in step (3) is used to separate the solvent adhering to the filtered solid from the solid matter, including flash evaporation or steam stripping, and the removed solvent is recovered for use.

14. The method according to claim 1, wherein: In the premixing tank described in step (4), the mass ratio of water to solid matter added is 1-100:

1.

15. The method according to claim 14, characterized in that: In the premixing tank described in step (4), the mass ratio of water to solid matter added is 15-30:

1.

16. The method according to claim 14, wherein: The water used for the first time in step (4) is fresh water, and then recycled water is used.

17. The method according to claim 1, wherein: The impeller-type high-gravity reaction equipment described in step (4) is a gas-liquid two-phase operation.

18. The method according to claim 1, wherein: The polymerization inhibitor recovered in step (4) is intermittently discharged from the equipment, the drying temperature is 20-100°C, and the drying time is 3-24h.

19. The method according to claim 18, wherein: The drying temperature is 30-60° C., and the drying time is 10-18 hours.

20. A recovery system for the method for recovering polymerization inhibitor from styrene tar according to any one of claims 1 to 19, characterized in that It includes a mixer, a separator, an inhibitor filter, a solvent recovery device, a premixing tank and a supergravity reaction device, wherein the mixer is used to fully mix styrene tar and a depolymerization solvent, the mixed liquid is sent to the separator, and after standing and stratification, the upper layer liquid is sent to the inhibitor filter, the inhibitor filter is used for the reaction and filtration of the upper layer liquid and the sedimentation agent, the filtered solid is sent to the solvent recovery device for desolvation, the obtained solid enters the premixing tank and is mixed with water, and then enters the impeller-type supergravity reaction device, and CO2 is introduced for reaction, and the obtained solid is dried to be the recovered inhibitor.

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