A method and system for regenerating wind power waste gear oil

Abstract

The application discloses a kind of wind power waste gear oil regeneration processing method and system, belong to waste lubricating oil resource utilization technical field.The method includes: in wind farm field, waste gear oil is coarsely filtered and filtered to remove dangerous physical pretreatment, obtainable transport pre-treatment oil product;After pre-treatment oil product is transported to centralized processing site, first in the presence of ionic liquid and protective agent, it is carried out first stage low-intensity ozone pre-oxidation, then load type transition metal oxide catalyst is added to carry out second stage catalytic deep oxidation;After reaction, it is separated by phase, adsorbed and refined and vacuum dewatering, and the regenerated oil material is obtained, and the ionic liquid phase is regenerated and recycled.The application can effectively reduce waste oil transportation risk, realize the deep removal of pollutants and the protection of base oil components, with the advantages of high regeneration quality, good process safety and strong applicability.

Description

Technical Field

[0001] This invention relates to the field of waste lubricating oil regeneration technology, and in particular to a method and system for regenerating waste gear oil from wind power plants. Background Technology

[0002] As a crucial component of clean energy, wind power has seen continuous expansion in installed capacity in recent years, leading to a corresponding increase in the consumption and replacement of gearbox lubricating oil used in wind turbine operation. Wind turbine gearboxes typically operate under high load, variable load, strong vibration, and wide ambient temperature fluctuations. The gear oil used not only performs lubrication, cooling, and rust prevention functions but also needs to continuously resist various failure factors such as shearing, thermal-oxidative aging, metal abrasive contamination, and moisture intrusion. With prolonged service life, wind turbine gear oil gradually accumulates wear metal particles, oxidation products, colloids, asphaltenes, and residual degradation additives, resulting in darker oil color, higher acid value, and decreased extreme pressure anti-wear performance. It may also be accompanied by the accumulation of phosphorus- and sulfur-containing additive decay products and other harmful impurities. This type of waste gear oil is typically classified as hazardous waste, making its safe collection, transportation, and resource recycling a critical issue in wind power operation and maintenance and waste lubricating oil treatment.

[0003] From the perspective of current technological development, waste lubricating oil regeneration can be broadly categorized into physical methods, physicochemical methods, and deep chemical refining methods. Physical methods typically include sedimentation, filtration, centrifugation, and dehydration, primarily used to remove larger particulate contaminants, free water, and some suspended impurities. These processes are relatively simple and require lower equipment investment. However, for polar contaminants already dissolved in the oil phase, such as oxidation degradation products, gums, resinous substances, and degradation additives, deep removal by filtration or centrifugation alone is difficult. Therefore, the regenerated oil often struggles to restore key indicators such as color, acid value, oxidation stability, and viscosity index to high levels. Meanwhile, traditional methods such as acid washing and clay refining, while possessing some decolorization and purification effects, generally suffer from large amounts of waste acid and residue, significant secondary pollution, and high base oil loss, gradually failing to meet the development demands for green, low-carbon, and high-value utilization.

[0004] To address the on-site treatment needs of wind turbine gear oil, existing technologies have developed solutions centered on on-site regeneration. For example, patent document CN110252024B discloses an on-site regeneration system and method for wind turbine gear lubricating oil. Its main technical approach involves setting up modules such as a vacuum dehydration system, regeneration system, filtration system, heating system, magnetic filtration system, online oil quality monitoring system, and automatic additive replenishment system at the wind power site. This system dehydrates, filters, regenerates, and monitors the waste gear oil online, adding additives as needed, thus ensuring the regenerated oil meets the requirements for continued use. This solution is significant in reducing the frequency of waste oil replacement and improving on-site maintenance efficiency, indicating that the art has recognized the need for on-site treatment and rapid recovery of wind turbine waste gear oil, rather than relying solely on traditional long-distance transportation and centralized processing. However, the above technical approach still largely follows a closed-loop on-site regeneration model, focusing on restoring oil performance through dehydration, filtration, online monitoring, and additive replenishment. This type of solution is more suitable for scenarios where pollution levels are relatively controllable and the base oil has not yet undergone deep chemical degradation. For wind turbine gear oil that has undergone significant thermo-oxidative aging and contains substantial amounts of gum, asphaltene-like deposits, and degradation additive byproducts, on-site dehydration, filtration, and conventional regeneration units are often insufficient to achieve deep removal of dissolved polar contaminants and stable condensates. Further increasing the complexity of the on-site treatment system leads to larger equipment, higher maintenance requirements, and increased on-site safety management pressures, hindering stable implementation in dispersed wind farm environments. In other words, existing on-site regeneration methods can effectively address the rapid recovery of lightly to moderately contaminated oils, but they remain limited in their ability to deeply regenerate waste wind turbine gear oils with strong hazardous properties and complex contaminant compositions.

[0005] On the other hand, in the field of deep regeneration of waste lubricating oil, there are already solutions that utilize oxidation to improve the efficiency of pollutant removal. Patent document US20190119605A1 discloses a waste lubricating oil regeneration method, which employs a three-stage process of distillation-ozone catalytic oxidation-adsorption: first, water, heavy decomposition products, and other impurities are removed by distillation; then, ozone is used to catalytically oxidize the oil in the presence of a supported transition metal catalyst, converting some oil-soluble non-polar impurities into polar substances; finally, the polar oxidation products formed are removed by an adsorbent containing SiO2 and / or Al2O3, thereby obtaining regenerated lubricating base oil with a quality close to that of new base oil. This technology demonstrates that ozone catalytic oxidation can convert heteroatoms or other difficult-to-treat pollutants into easily removable polar substances under relatively mild conditions, thus representing a deep purification pathway for waste lubricating oil with high application potential. However, the technical route shown in US20190119605A1 also has its limitations. First, this scheme is based on front-end distillation separation, requiring the distillation to obtain a lubricating oil fraction relatively suitable for subsequent oxidation treatment. This implies high requirements for equipment sealing, vacuum systems, heating systems, and continuous operation conditions. For wind power waste gear oil with dispersed sources, varied batches, and high on-site hazardous properties, directly configuring distillation and deep oxidation units at the collection source would not only result in high investment but also complex operation, hindering practical deployment in wind farms. Second, the oxidation and product removal processes in this scheme still exhibit significant staged separation characteristics. Specifically, pollutants are first converted into polar substances through ozone catalytic oxidation, and then removed through subsequent adsorption steps. For wind power waste gear oil containing complex gum and asphaltenes-like oxidation condensation products, this method of oxidation followed by unified removal may still be limited by factors such as mass transfer efficiency, localized over-oxidation, and insufficient protection of base oil components. Furthermore, while single-stage ozone catalytic oxidation can increase the polarity of pollutants, without precise control over the ozone utilization pathway and base oil protection mechanism, it can easily lead to problems such as base oil main chain breakage, viscosity reduction, viscosity index damage, and acid value rebound while improving the depth of pollutant removal.

[0006] In summary, the two existing technologies can be categorized as follows: One type, such as CN110252024B, focuses on on-site filtration, dehydration, monitoring, and additive addition. Its advantage lies in rapid on-site treatment and reuse, but its ability to deeply chemically regenerate complex and degraded components is limited. The other type, such as US20190119605A1, focuses on obtaining higher-quality regenerated base oil through ozone catalytic oxidation and subsequent adsorption. Its advantage lies in a higher treatment depth, but its process is more suitable for centralized, highly automated treatment scenarios, requiring stricter conditions for raw materials and process organization. Existing technologies have not yet adequately addressed the practical problem of how to achieve a balance between transportation safety, treatment depth, base oil protection, and economy for wind power waste gear oil, which is characterized by dispersed sources, strong hazardous properties, and complex contaminant composition, by first performing dehazardization and transport adaptation treatment at the collection source in a simple and mobile manner, and then using a more efficient and base oil-friendly deep chemical regeneration process at a centralized location.

[0007] Especially for the wind power industry, waste gear oil is typically generated from wind farms in different regions, and the amount of waste oil from a single wind farm is intermittent. Relying entirely on on-site construction of high-level deep regeneration facilities would result in high equipment utilization, high operation and maintenance costs, and difficulties in safety management. Conversely, directly transporting hazardous waste oil over long distances without proper pretreatment would increase storage and transportation risks and management costs. Therefore, current technologies lack a two-stage solution that balances simplified on-site pretreatment with centralized deep regeneration. Furthermore, from the perspective of deep purification mechanisms, current technologies also lack a synergistic treatment method that can simultaneously achieve efficient ozone utilization, selective oxidation of pollutants, immediate migration and separation of polar products, and protection of the base oil main chain under relatively mild conditions. Due to these shortcomings, the resource utilization of wind power waste gear oil still faces challenges such as limited recycling radius, high processing costs, significant fluctuations in regenerated quality, and insufficient adaptability to various scenarios.

[0008] Therefore, in view of the above-mentioned defects in the existing technology, there is an urgent need to provide a new method for the regeneration and treatment of wind power waste gear oil, so as to achieve rapid on-site de-hazardous pretreatment of wind power waste gear oil and effectively connect it with subsequent centralized deep chemical regeneration. While ensuring transportation safety and process feasibility, this method can improve the depth of pollutant removal, reduce base oil damage, and improve the quality of regenerated oil. Summary of the Invention

[0009] The technical objective of this invention is to address the problems of dispersed sources, highly hazardous properties, difficulty in configuring complete deep regeneration devices on-site, and the inability of traditional regeneration processes to balance transportation safety and regeneration quality in wind power waste gear oil. This invention provides a regeneration method for wind power waste gear oil by constructing a two-stage process: on-site dehazard physical pretreatment followed by centralized deep chemical regeneration. This process, combined with the synergistic effects of ionic liquids, ozone, protective agents, and catalysts, achieves safe transportation of waste gear oil, efficient removal of pollutants, and effective protection of base oil components, thereby obtaining high-quality regenerated oil.

[0010] Firstly, in order to achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0011] A method for regenerating waste gear oil from wind power plants includes the following steps:

[0012] S1. On-site physical pretreatment to remove hazardous substances: A mobile robotic oil change vehicle equipped with a robotic arm and a visual navigation system is used to travel to the wind turbine site. The robotic arm automatically completes the docking of the oil drain port and the suction of waste oil. After suction, the oil is initially treated by filtering with a filter to reduce the acid value, remove metal ions and desulfurize to obtain pretreated oil (non-hazardous chemical product) that meets the conditions for transfer.

[0013] S2. First-stage protective pre-oxidation treatment: The pretreated oil obtained in step S1 is transferred to a centralized treatment facility and placed in a reactor. Ionic liquid and protective agent are added and mixed evenly. The amount of ionic liquid added is 5% to 20% of the volume of the pretreated oil, and the amount of protective agent added is 0.5% to 5% of the weight of the pretreated oil. Subsequently, ozone-containing gas is introduced into the system at 20 to 60°C. The ozone concentration in the ozone-containing gas is 1 to 5 wt%, and the aeration time is 0.5 to 2 hours. In this first stage, no transition metal oxide catalyst is added, so that the protective agent preferentially consumes the initial strong oxidation demand in the system and promotes the mild oxidation modification of easily oxidized active components, as well as some gums and asphaltenes in the waste gear oil, thereby increasing their polarity.

[0014] S3. Second-stage catalytic deep oxidation treatment: After stopping the ozone flow in step S2, a supported transition metal oxide catalyst is added to the system. The amount of catalyst added is 0.01% to 3% of the pretreated oil mass. Then, ozone-containing gas is introduced into the system at 40 to 80°C. The ozone concentration in the ozone-containing gas is 2 to 8 wt%. The reaction is carried out for 1 to 4 hours to allow the remaining difficult-to-oxidize pollutants to undergo further deep oxidation. The ionic liquid is used to enrich ozone and serve as a migrating phase for the polar degradation products generated by ozone oxidation, allowing the polar degradation products to transfer in situ from the oil phase to the ionic liquid phase, thereby achieving simultaneous oxidation of pollutants and removal of oxidation products.

[0015] S4. Post-processing: After step S3, stop the introduction of ozone gas and allow it to stand or be centrifuged to obtain an upper purified oil phase and a lower ionic liquid phase rich in oxidative degradation products; the purified oil phase is subjected to adsorption purification and vacuum dehydration to obtain regenerated oil; the ionic liquid phase is regenerated and recycled.

[0016] Preferably, the filter agent mentioned in step S1 includes, but is not limited to, diatomaceous earth, activated alumina, metal chelating agents, activated carbon, and adsorption resins. By introducing a specialized filter agent during the on-site pretreatment stage, the acid value, color, and metal content of waste oil can be significantly reduced without introducing complex chemical regeneration equipment, allowing the pretreated oil to be directly transported over long distances by road.

[0017] Preferably, the ionic liquid is one or more of imidazole ionic liquids, pyridine ionic liquids, or quaternary ammonium salt ionic liquids, and more preferably 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, or a composite system formed therewith a carboxylate ionic liquid.

[0018] Preferably, the protective agent is an unsaturated fatty acid ester containing carbon-carbon double bonds, selected from one or more of methyl oleate, ethyl oleate, and methyl linoleate; in step S2, the protective agent preferentially competes with the ozone and highly reactive oxide species initially entering the system to reduce the probability of excessive oxidation and breakage of the base oil main chain.

[0019] Preferably, the supported transition metal oxide catalyst comprises a porous support and a transition metal oxide supported on the porous support, wherein the porous support is one or more of γ-Al2O3, activated carbon, molecular sieve, or silica gel, and the transition metal oxide is one or more of MnOx, FeOx, CuO, or CoOx; preferably, the supported transition metal oxide catalyst is one of MnOx / γ-γ-Al2O3 catalyst, MnOx-FeOx / activated carbon bimetallic catalyst, CuO / molecular sieve catalyst, or CoOx / silica gel catalyst.

[0020] Preferably, the adsorption purification in step S4 uses one or more of the following as adsorbents: white clay, silica gel, and activated carbon. The vacuum dehydration temperature is 60-100°C, and the absolute pressure corresponding to the vacuum degree is not higher than 0.01 MPa, so that the moisture content in the regenerated oil is reduced to below 0.05 wt%.

[0021] Preferably, the ionic liquid phase in step S4 is regenerated by one or more of the following methods: vacuum distillation, adsorption purification, or secondary ozone treatment. The regenerated ionic liquid is then returned to step S2 for reuse.

[0022] Preferably, the waste gear oil from wind power is an industrial gear oil with a viscosity grade of ISO VG150, ISO VG220, or ISO VG320.

[0023] Preferably, in steps S2 and S3, the reactor is one of a bubble column reactor, a stirred tank reactor, or a fixed bed-slurry coupled reactor; when the supported transition metal oxide catalyst is placed in a fixed bed, the mixture of pretreated oil and ionic liquid is transported through the fixed bed by a circulating pump and comes into countercurrent or cocurrent contact with the introduced ozone-containing gas to complete the second stage of catalytic deep oxidation treatment.

[0024] Secondly, the present invention also provides a regeneration system for waste gear oil from wind power plants, comprising a field dehazardization pretreatment module, a transfer and storage module, a centralized deep chemical regeneration module, and a post-treatment module connected in sequence; wherein,

[0025] The on-site dehazard pretreatment module and the transfer and storage module use a mobile robotic oil change vehicle equipped with a robotic arm and a visual navigation system; it is used to pump, temporarily store and transfer the pretreated oil to a centralized processing site.

[0026] The centralized deep chemical regeneration module includes a reactor, an ionic liquid addition unit, a protective agent addition unit, a catalyst addition unit, an ozone generation and supply unit, a stirring unit, and a temperature control unit. The ionic liquid addition unit adds ionic liquid to the reactor. The protective agent addition unit adds a protective agent to the reactor before the first-stage ozone treatment. The ozone generation and supply unit introduces ozone-containing gas with an ozone concentration of 1-5 wt% into the reactor at 20-60°C for the first-stage protective pre-oxidation treatment. The catalyst addition unit adds a supported transition metal oxide catalyst to the reactor after the first-stage treatment. The ozone generation and supply unit also introduces ozone-containing gas with an ozone concentration of 2-8 wt% into the reactor at 40-80°C for the second-stage catalytic deep oxidation treatment. The ionic liquid enriches ozone and serves as a migrating phase for the polar degradation products generated by ozone oxidation, allowing the polar degradation products to transfer in situ from the oil phase to the ionic liquid phase.

[0027] The post-processing module includes a settling or centrifugal separation unit, an adsorption purification unit, a vacuum dehydration unit, and an ionic liquid regeneration unit. The settling or centrifugal separation unit is used to separate an upper purified oil phase and a lower ionic liquid phase rich in oxidative degradation products. The adsorption purification unit and the vacuum dehydration unit are used to purify the purified oil phase to obtain regenerated oil. The ionic liquid regeneration unit is used to regenerate the ionic liquid phase and recycle it back to the centralized deep chemical regeneration module.

[0028] This invention divides the treatment process of waste gear oil from wind power plants into two stages: on-site physical pretreatment for hazardous removal and centralized deep chemical regeneration. First, at the wind farm site, a mobile robotic oil-changing vehicle rapidly filters the waste oil for preliminary treatment, reducing acid value, removing metal ions, and desulfurizing. Then, in the centralized treatment stage, the synergistic effect of ionic liquids, ozone, protective agents, and catalysts achieves efficient removal of complex pollutants such as gums, asphaltenes, oxidation products, and degradation additives from the waste oil. The ionic liquids combine ozone enrichment, active species transfer, and polar oxidation product migration, allowing pollutant oxidation and product removal to occur simultaneously, thereby significantly improving ozone utilization efficiency and overall efficiency. The purification process is highly efficient. Simultaneously, the protective agent preferentially consumes initial strong oxidizing species, inhibiting excessive breakage of the base oil main chain. The catalyst further promotes the degradation of recalcitrant residual pollutants in subsequent stages. Therefore, it can improve decolorization, reduce acid value, and decrease the residue of heteroatoms such as sulfur and phosphorus, while better maintaining the kinematic viscosity and viscosity index of the recycled oil, resulting in high quality stability and reuse value. Furthermore, the process requires relatively mild temperatures and pressures, does not rely on high-risk conditions such as high-pressure hydrogenation, has good equipment adaptability, is environmentally friendly, and has low energy consumption. It is suitable for the resource-based regeneration of wind turbine gear oils of different viscosity grades and has promising engineering application prospects. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall process flow of a wind power waste gear oil regeneration treatment method according to the present invention.

[0030] Figure 2 This is a schematic diagram of the on-site dehazard physical pretreatment system of the present invention.

[0031] Figure 3 This is a schematic diagram of the structure of the concentrated deep chemical regeneration system of the present invention.

[0032] Figure 4 This is a schematic diagram of the post-processing and ionic liquid recycling process of the present invention.

[0033] Figure 5 A comparison chart showing the effects of different treatment methods on acid value and viscosity index.

[0034] Figure 6 A comparative chart showing the effects of different treatment methods on sulfur and phosphorus residues.

[0035] Figure 7 This is a comparison chart of total ozone utilization and recycled oil yield for different treatment schemes.

[0036] Figure 8 This is a schematic diagram illustrating the path by which the two-stage processing of this invention achieves its technical effect.

[0037] Figure 9 A comparative diagram showing the synergistic effects of protective agents, catalysts, and ionic liquids.

[0038] Figure 10 The figure shows the effect of recycling ionic liquids on the stability of regeneration efficiency.

[0039] The system includes: 1. Waste oil collection unit; 2. Oil transfer pump; 3. Coarse filtration unit; 4. Fine filtration unit; 5. Pre-treated oil storage tank; 6. Transfer tank; 7. Centralized treatment reactor; 8. Ionic liquid addition unit; 9. Protective agent addition unit; 10. Catalyst addition unit; 11. Ozone generation and gas supply unit; 12. Stirring unit; 13. Temperature control unit; 14. Static / centrifugal separation unit; 15. Adsorption purification unit; 16. Vacuum dehydration unit; 17. Regenerated oil storage tank; 18. Ionic liquid regeneration unit; 19. Tail gas absorption unit; 20. Circulation pump; 21. Online monitoring unit. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0041] This invention addresses the challenges of dispersed sources, highly hazardous properties, unsuitability for on-site deployment of complex deep regeneration devices, and the difficulty of balancing transportation safety and regeneration quality in existing single-stage filtration or oxidation processes for waste gear oil from wind power generation. It proposes a two-stage regeneration method: on-site dehazardization physical pretreatment, centralized two-stage deep chemical regeneration, and post-treatment with ionic liquid circulation. This method does not simply combine on-site filtration and centralized chemical regeneration in parallel. Instead, through process boundary reconstruction and the design of reaction-migration coupling mechanisms, it first weakens the hazardous properties and makes the waste gear oil transportable at the source. Then, in a centralized location, the synergistic effect of ionic liquids, ozone, protective agents, and catalysts achieves efficient deep removal of pollutants and targeted protection of base oil components.

[0042] I. Terminology Explanation

[0043] To facilitate understanding of the technical solution of this invention, the main terms involved in this specification are explained as follows:

[0044] Waste gear oil from wind power: refers to industrial gear lubricating oil that has been replaced after the gearbox of a wind turbine unit fails due to thermal and oxygen aging, mechanical wear, moisture intrusion, and additive degradation during operation. It usually contains abrasive particles, gum, oxidation products, degradation additives, and some sulfur- and phosphorus-containing compounds.

[0045] Dehazard-removal physical pretreatment: refers to the process of removing mechanical particles, suspended impurities, metal shavings, and some colloidal pollutants from waste oil using mobile filtration equipment without relying on high-temperature, high-pressure, and deep chemical reactions, in order to reduce safety risks during transportation and create transferable intermediate materials.

[0046] Pretreated oil: refers to intermediate oil that meets the requirements of subsequent centralized treatment after on-site coarse and fine filtration. Its main characteristics are a significant reduction in the content of solid particles and some colloidal contaminants, but it still retains dissolved or highly dispersed contaminants such as oxidation products, gums and degradation additives that need to be further removed.

[0047] Ionic liquids refer to salt systems composed of organic cations and inorganic or organic anions that are liquid at low temperatures. In this invention, they preferably possess ozone enrichment capacity, interfacial activation capacity, and polar oxidation product carrying capacity.

[0048] Protective agent: refers to a compound that preferentially reacts with the strong oxidizing components in the system during the first-stage ozone treatment to reduce the risk of excessive breakage of the base oil main chain. In this invention, it is preferably an unsaturated fatty acid ester.

[0049] Supported transition metal oxide catalysts: These are catalytic materials in which one or more transition metal oxides are supported on the surface of a porous support. Their role is to promote ozone decomposition and generate highly reactive species, thereby enhancing the second-stage deep oxidation process.

[0050] The first stage is protective pre-oxidation treatment: This refers to the stage in which easily oxidizable components and some high-molecular pollutants in waste oil are slightly oxidized and modified by using a low ozone concentration and a low reaction temperature without the addition of a catalyst, while the protective agent is used to preferentially consume the initial strong oxidation demand.

[0051] The second stage of catalytic deep oxidation treatment refers to the stage after the first stage, in which a supported catalyst is added and the ozone concentration and reaction temperature are increased to further crack, oxidize and polarize the remaining difficult-to-oxidize pollutants.

[0052] Reaction-migration coupling: refers to the process in which, after pollutants undergo oxidation and transformation under the action of ozone and reactive oxides, the polar products generated simultaneously migrate from the oil phase to the ionic liquid phase, thereby enabling the oxidation reaction and the removal of oxidation products to occur continuously within the same system.

[0053] Regenerated oil refers to the purified oil phase obtained after phase separation, adsorption refining and vacuum dehydration. It can be used directly as lubricating oil in some low-requirement applications, or further blended and compounded as a base oil component.

[0054] II. System Structure

[0055] 1. Overall System Structure

[0056] like Figures 1 to 4 As shown, the system of the present invention can be divided into two main modules: an on-site de-hazardous pretreatment section and a centralized deep regeneration section.

[0057] The on-site dehazard pretreatment section mainly includes: waste oil collection unit 1, oil pump 2, coarse filter unit 3, fine filter unit 4, pretreated oil storage tank 5, and transfer tank 6. A mobile robotic oil exchange vehicle equipped with a robotic arm and visual navigation system is used, suitable for deployment at wind farm sites. Its core function is not to complete all regeneration on-site, but to rapidly reduce solid contaminants and some highly dispersed colloidal contaminants through two-stage filtration, thereby reducing the hazardous properties and transportation risks of the oil.

[0058] The centralized deep regeneration section mainly includes: a centralized treatment reactor 7, an ionic liquid addition unit 8, a protective agent addition unit 9, a catalyst addition unit 10, an ozone generation and supply unit 11, a stirring unit 12, a temperature control unit 13, a settling / centrifugal separation unit 14, an adsorption purification unit 15, a vacuum dehydration unit 16, a regenerated oil storage tank 17, an ionic liquid regeneration unit 18, a tail gas absorption unit 19, a circulation pump 20, and an online detection unit 21. This section is used to achieve two-stage deep chemical regeneration and post-treatment using a synergistic combination of ionic liquid and ozone.

[0059] 2. Structure of the on-site de-hazardous pretreatment section

[0060] like Figure 2 As shown, waste oil collection unit 1 is connected to oil pump 2. The output end of oil pump 2 is sequentially connected to coarse filter unit 3 and fine filter unit 4. The outlet of fine filter unit 4 is connected to pre-treated oil storage tank 5, which is connected to transfer tank 6. Coarse filter unit 3 is preferably a plate and frame filter or a metal filter element filter, used to remove larger abrasive particles, mechanical impurities, and agglomerated particles. Fine filter unit 4 uses a filter medium for preliminary filtration to reduce acid value, remove metal ions, and desulfurize. The above units are connected by oil-resistant pipelines and valves for quick on-site assembly, disassembly, and transfer.

[0061] 3. Structure of the concentrated deep regeneration section

[0062] like Figure 3As shown, the centralized treatment reactor 7 is preferably a bubble column reactor, a mechanically stirred tank reactor, or a fixed-bed-slurry coupled reactor. Reactor 7 is connected to the ionic liquid addition unit 8, the protective agent addition unit 9, and the catalyst addition unit 10 to achieve sequential addition of materials at different stages. The ozone generation and gas supply unit 11 is connected to the bottom or side of reactor 7 via an inlet pipe, facilitating the entry of ozone gas into the reaction system in a bubbling or dispersed form. The temperature control unit 13 is connected to the jacket or coil of reactor 7 for precise control of the reaction temperature at different stages. The gas phase outlet of reactor 7 is connected to the tail gas absorption unit 19 for absorbing unreacted ozone; the liquid phase outlet is connected to the settling / centrifugal separation unit 14, where the upper purified oil phase sequentially enters the adsorption refining unit 15 and the vacuum dehydration unit 16, ultimately entering the regenerated oil storage tank 17; the lower ionic liquid phase enters the ionic liquid regeneration unit 18, and after regeneration, returns to the ionic liquid addition unit 8 for recycling.

[0063] III. Specific Technical Route for Implementing the Method of the Invention

[0064] The method of this invention generally comprises four steps: step S1, on-site de-hazardous physical pretreatment; step S2, first-stage protective pre-oxidation treatment; step S3, second-stage catalytic deep oxidation treatment; and step S4, post-treatment. These steps are not designed as parallel stacks, but rather are interconnected and progressively build-up. The most significant contribution to the invention lies in the sequential control logic of steps S2 and S3 and their coupling relationship with the functional design of the ionic liquid phase. Steps S1 and S4 respectively serve to ensure safety at the source and stabilize the final product quality.

[0065] The following provides a detailed explanation of each step.

[0066] (a) Step S1: On-site physical pretreatment to eliminate hazards

[0067] Step S1 is implemented at the wind farm site. Its purpose is not to directly restore the waste oil into a reusable finished oil, but to quickly remove pollutants that can be efficiently removed by physical means at the source, reduce the particulate pollution level in the waste oil, weaken its hazardous properties, and form intermediate materials suitable for centralized transportation.

[0068] In practical implementation, a robot-equipped vehicle first performs oil changes on the wind turbine equipment, collecting the waste gear oil from the wind farm into waste oil collection unit 1. Collection methods can include manual collection, oil collection tank diversion, negative pressure extraction, or pouring into a sealed container—conventional methods. Subsequently, the waste oil is transported to coarse filtration unit 3 via oil pump 2. The filtration accuracy of coarse filtration unit 3 is preferably 1–10 μm, more preferably 3–8 μm, and even more preferably 5 μm. Coarse filtration unit 3 can be a plate and frame filter, or an oil-resistant sintered metal filter element filter, wedge mesh filter, etc., as long as it can effectively trap larger mechanical particles, abrasive metal shavings, fibrous impurities, and agglomerated contaminants.

[0069] The oil after coarse filtration enters the fine filtration unit 4. The filtration accuracy of the fine filtration unit 4 is preferably 0.5–1 μm, more preferably 0.5 μm. The fine filtration unit 4 can be a bag filter, a precision cartridge filter, or a composite membrane filter. When the particle size distribution of pollutants at the wind farm site is wide, a buffer tank or reversing valve can be installed between the coarse and fine filters to ensure stable flow and avoid instantaneous blockage. The filter media for the fine filter consists of silica gel sand and activated carbon in a mass ratio of 10:1, which initially reduces its acid value, color, desulfurization, and metallic pollutants.

[0070] After step S1 is completed, the resulting pretreated oil enters the pretreated oil storage tank 5. At this point, most of the filterable particles, agglomerated colloids, and some metal oxides attached to the particle surface in the oil have been removed. The oil color is usually lighter than the original waste oil, and the particulate contamination level has significantly decreased. It should be noted that step S1 does not aim to remove all oxidation products, degradation additives, and dissolved polar contaminants. This is because these contaminants are mostly in a molecular or highly dispersed state, and it is difficult to completely remove them by filtration alone. If a complex chemical refining unit is configured on-site, it will significantly increase the equipment size, energy consumption, safety management costs, and personnel operation threshold. Therefore, this invention positions step S1 as a dehazardization and transfer adaptation link, that is, only performing the most necessary and effective source safety treatment to create conditions for subsequent centralized deep regeneration.

[0071] In some embodiments, an online detection unit 21 can be added to step S1 to detect the particulate contamination level, moisture content, color, metal content, or other transport suitability indicators of the oil before and after pretreatment to determine whether the transfer requirements are met. For example, a particle counter can be used to determine the contamination level, an online moisture meter can be used to detect the water content, and ferrography or ICP methods can be used to detect the content of wear metal elements. As long as the preset intermediate material transfer threshold is met, the pretreated oil can be transported to the transfer tank 6 and then transported to the centralized processing site.

[0072] Although step S1 contributes relatively little to the chemical conversion, it plays a fundamental role in the overall process system. Firstly, it transforms the raw hazardous waste oil into an intermediate material suitable for storage and transportation, solving the practical problem of directly transporting highly polluting waste oil over long distances in a dispersed wind farm environment. Secondly, it significantly reduces the particulate contamination load on the subsequent ionic liquid phase and catalyst system, which helps reduce the risk of subsequent reactor wear and catalyst surface coverage by mechanical impurities. Thirdly, it clarifies the boundary difference between this invention and existing on-site complete regeneration technology routes; that is, the on-site section of this invention is not terminal regeneration, but rather a front-end safety pretreatment serving centralized deep regeneration.

[0073] (V) Steps S2 and S3: Two-stage deep chemical regeneration

[0074] 1. Overall concept of two-phase design

[0075] This invention does not employ a single-stage direct high-concentration ozone + catalyst treatment mode, but instead divides chemical regeneration into two interconnected stages. The first stage is a protective pre-oxidation treatment, and the second stage is a catalytic deep oxidation treatment. The key to the first stage is that, without adding a catalyst, at a relatively low ozone concentration and a relatively low reaction temperature, the protective agent preferentially consumes the initial strong oxidation demand in the system, and causes mild oxidative modification of the most reactive highly active components, some gums, and asphaltenes in the waste oil. After the first stage, the highly oxidizable and potentially excessively oxidized active pollutants in the system are preferentially treated, while the remaining pollutants are mainly transformed into relatively stable, high-activation-energy, and difficult-to-treat components. In the second stage, a supported transition metal oxide catalyst is introduced, and the temperature and ozone concentration are increased to further oxidize the remaining difficult-to-oxidize pollutants, while simultaneously utilizing an ionic liquid phase to achieve the synchronous migration and enrichment of polar oxidation products.

[0076] This phased design is not a simple breakdown of process steps, but a targeted control strategy addressing the complex composition of wind power waste gear oil contaminants, high requirements for base oil protection, and the potential for over-oxidation due to strong single-stage oxidation. Adding the catalyst to the system from the outset with high ozone concentrations and high temperatures can indeed increase the oxidation rate of contaminants, but it also easily leads to the breakage of the base oil main chain, an increase in small-molecule acid byproducts, and a decrease in viscosity index. In contrast, this invention first reduces the initial strong oxidative impact through a first-stage mild oxidation combined with a competitive reaction of the protective agent, and then achieves deep purification through a second-stage catalytic enhancement and polar product migration, thus balancing the depth of contaminant removal with the protection of the base oil.

[0077] 2. Functional design and addition method of ionic liquids

[0078] In this invention, the ionic liquid is not a single-function extractant, but rather performs at least three functions:

[0079] First, it can serve as an ozone enrichment medium. Because certain ionic liquids have good dissolving and carrying capacity for ozone or ozone-related reactive species, ozone can preferentially accumulate near the ionic liquid phase or oil-ionic liquid interface after entering the system, thereby increasing the local effective oxidant concentration.

[0080] Second, it serves as an interfacial activation medium. In systems where the oil phase and the ionic liquid phase coexist, pollutants, especially intermediates with enhanced polarity, are more easily transported near the interface. The presence of ionic liquids increases the chances of effective contact between ozone and pollutants.

[0081] Third, as a migrating phase of polar oxidation products. After pollutants are oxidized by ozone and subsequent reactive oxides, the molecules usually change from a nonpolar or weakly polar state to a more strongly polar state, such as generating intermediates containing carbonyl, carboxyl, or other oxygen-containing functional groups. These intermediates tend to migrate from the oil phase to the ionic liquid phase, thereby weakening their accumulation in the oil phase and driving the reaction equilibrium to continue towards pollutant removal.

[0082] Therefore, in this invention, an ionic liquid is added to the reactor at the beginning of step S2. The ionic liquid is preferably an imidazole, pyridine, or quaternary ammonium salt ionic liquid, more preferably 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, or a composite system formed therewith a carboxyl ionic liquid. The amount added is preferably 5% to 20% of the volume of the pretreated oil, more preferably 8% to 15%. If the amount added is too low, the interfacial enrichment and migration carrying capacity will be insufficient; if the amount added is too high, it will increase phase separation and recycling costs. Therefore, it is advisable to optimize within the above range.

[0083] 3. Mechanism of action and implementation methods of protective agents

[0084] In step S2, the protective agent is added to the reactor along with the ionic liquid. The protective agent is preferably an unsaturated fatty acid ester containing carbon-carbon double bonds, such as one or more of methyl oleate, ethyl oleate, and methyl linoleate. The amount added is preferably 0.5% to 5% of the pretreated oil mass, more preferably 1% to 3%.

[0085] The selection of the protective agent is not arbitrary, but based on the following considerations: First, unsaturated fatty acid ester molecules contain carbon-carbon double bonds that can preferentially react with ozone or highly reactive oxides, thus they can act as competitive consumers in the first stage and preferentially accept the initial oxidative shock; second, their reaction process is relatively controllable and will not significantly inhibit the subsequent oxidation of the target pollutant like some strong reducing protective agents; third, they have good compatibility with base oils and ionic liquid systems, are easy to disperse, and are not prone to causing local phase separation or system instability.

[0086] In practice, after adding the protective agent, it is uniformly dispersed in the oil phase by the stirring unit 12. At this point, no catalyst has been added to the system. Therefore, after ozone enters the reactor, its reaction pathway is mainly affected by the protective agent, ionic liquid, and highly reactive pollutants in the waste oil. The protective agent preferentially consumes a portion of the initial ozone or active oxide species, thereby reducing the probability of the base oil chain being directly attacked. At the same time, the highly oxidizable active components in the waste oil, as well as some gums and asphaltenes, are mildly modified in a low-intensity oxidation environment, increasing their polarity but without large-scale deep cracking. This creates a more suitable reaction starting point for further catalytic oxidation in the second stage.

[0087] 4. Process conditions for the first stage of protective pre-oxidation treatment

[0088] The preferred reaction temperature for the first stage is 20–60°C, more preferably 30–50°C; the preferred ozone concentration is 1–5 wt%, more preferably 2–4 wt%; and the preferred aeration time is 0.5–2 h, more preferably 0.8–1.5 h. The stirring speed in the reactor can be adjusted according to the viscosity and volume of the system, and is usually controlled at 200–500 rpm to maintain sufficient contact between the oil phase, ionic liquid phase, and protective agent without causing excessive emulsification.

[0089] Ozone gas is generated by the ozone generator and supply unit 11 and can be introduced in the form of an ozone-oxygen mixture. The ozone can be introduced via bottom bubbling, microporous dispersion, or jet mixing. To prevent unreacted ozone from escaping directly, the top of the reactor is connected to the tail gas absorption unit 19. The tail gas absorption unit 19 can use potassium iodide solution, sodium sulfite solution, or other suitable absorption media to absorb residual ozone.

[0090] In some implementations, ozone utilization can be calculated using the following formula to optimize the process parameters for the first and second stages:

[0091] ;

[0092] in, Ozone utilization rate is expressed as % (%). This indicates the mass of ozone entering the reactor per unit time, expressed in grams. This indicates the mass of unreacted ozone measured by the exhaust gas absorption unit within the same time period, expressed in grams.

[0093] After the first stage, the demand for highly reactive oxygen species in the system is significantly reduced, the protective agent has consumed part of the initial oxidative shock, and some of the gums and asphaltenes in the waste oil have been slightly polarized. If the system proceeds directly to post-treatment at this point, the removal of deep-seated and difficult-to-treat pollutants will be insufficient. Therefore, a second stage of catalytic deep oxidation is required.

[0094] 5. Second-stage catalytic deep oxidation treatment

[0095] After the first stage, ozone supply is stopped, and then a supported transition metal oxide catalyst is added to the reactor through catalyst addition unit 10. This catalyst preferably comprises a porous support and a transition metal oxide supported thereon, wherein the porous support is preferably γ-Al₂O₃, activated carbon, molecular sieve, or silica gel; and the transition metal oxide is preferably one or more of MnOx, FeOx, CuO, or CoOx. The catalyst addition amount is preferably 0.01% to 3% of the pretreated oil mass, more preferably 0.1% to 1.5%.

[0096] The catalyst promotes ozone decomposition and generates more reactive oxide species, thereby accelerating the bond breaking, ring opening, and polarization processes of residual recalcitrant pollutants. Compared to the first stage, the second stage no longer targets the system dominated by initially highly reactive pollutants, but rather stable condensates, some deep oxidation intermediates, and other difficult-to-remove impurities remaining after pre-oxidation. These pollutants have higher activation energies, and if the conditions of the first stage are still used, the reaction rate and removal depth will be insufficient. Therefore, the second stage requires increasing the reaction temperature to 40–80°C, more preferably 50–75°C, and increasing the ozone concentration to 2–8 wt%, more preferably 4–6 wt%, with a preferred reaction time of 1–4 h, more preferably 2–3.5 h.

[0097] In the second stage, the role of the ionic liquid phase is further amplified. On the one hand, the catalyst enhances the conversion of ozone into highly reactive species, prompting recalcitrant pollutants to be converted into polar intermediates more quickly. On the other hand, the newly generated polar intermediates have a higher tendency to dissolve or partition in the ionic liquid phase, thus enabling them to migrate out of the oil phase in a timely manner, reducing their repeated condensation or secondary side reactions in the oil phase. Therefore, this invention forms a synergistic chain of catalytically enhanced oxidation—instantaneous migration of polar products—continuously driven reaction equilibrium, rather than the traditional approach of first oxidizing all pollutants and then removing them separately.

[0098] In some implementation methods, the pollutant removal rate can be used to evaluate the reaction effect:

[0099] ;

[0100] in, Indicates the first Removal rate of target pollutants, in percentage (%) This indicates the concentration of the target pollutant before treatment, and the unit can be ppm, mg / L, or wt%; This indicates the concentration of the target pollutant after treatment, in units of... same.

[0101] It should be noted that the key innovation of steps S2 and S3 lies not in the individual use of ozone, ionic liquid, protective agent, or transition metal catalyst, but in their temporal relationship, functional division of labor, and reaction-migration coupling. If the first stage is omitted and the process proceeds directly to the second stage, the base oil is prone to over-oxidation; if the ionic liquid is omitted and only ozone and catalyst are used, the generated polar oxidation products are difficult to migrate and accumulate in a timely manner, resulting in a decrease in overall removal efficiency; if the catalyst is omitted, the treatment depth of the second stage for residual recalcitrant pollutants is significantly insufficient; if the protective agent is omitted, the protective effect of the first stage on the base oil is insufficient. Therefore, the above combination exhibits a clear synergistic relationship.

[0102] (III) Step S4: Post-processing

[0103] Step S4 includes phase separation, adsorption purification, vacuum dehydration, and ionic liquid phase regeneration.

[0104] After the second stage of the reaction is completed, the ozone supply is stopped, and initial cooling is preferably carried out under conditions of gentle stirring or stillness to facilitate phase separation. The reaction mixture then enters the settling / centrifugation separation unit 14. If the system separates phases quickly, settling can be used; if a fine emulsion exists in the system, centrifugation can be used to accelerate separation. After separation, the upper layer is generally a purified oil phase, and the lower layer is generally a polar phase rich in oxidative degradation products, some depleted protective agent derivatives, and ionic liquids.

[0105] Although the upper purified oil phase has removed a large amount of target pollutants, trace amounts of ionic liquids, protective agent oxidation byproducts, and fine solid particles may still remain. Therefore, it needs to enter the adsorption purification unit 15. One or more of the following can be used as the adsorbent: clay, silica gel, and activated carbon. The adsorption method can be fixed-bed adsorption, slurry adsorption, or filtration adsorption. After adsorption purification, the oil phase enters the vacuum dehydration unit 16, where it undergoes vacuum dehydration at 60–100°C, preferably 70–90°C, with an absolute pressure not exceeding 0.01 MPa, to remove residual moisture and low-boiling components. The final recycled oil enters the recycled oil storage tank 17.

[0106] The lower ionic liquid phase enters the ionic liquid regeneration unit 18. The regeneration method can be selected according to the specific system, including vacuum distillation, adsorption purification, secondary ozone treatment, or a combination thereof. Vacuum distillation is suitable for removing some low-boiling oxidation byproducts; adsorption purification is suitable for removing some highly polar impurities; secondary ozone treatment can further decompose residual oxidizable pollutants. After regeneration, the ionic liquid is returned to the ionic liquid addition unit 8 via circulation pump 20 for reuse, thereby reducing operating costs.

[0107] Step S4 itself belongs to the back-end steady-state protection link in this invention. Its inventive contribution is lower than that of steps S2 and S3, but it is very important in industrial implementation. Through phase separation and adsorption purification, polar products that have been transformed and migrated from the reaction system can be effectively stripped; through vacuum dehydration, the storage stability of the regenerated oil can be restored; and through ionic liquid phase recycling, the process can be made greener and more economical.

[0108] IV. Examples and Comparative Examples

[0109] In the following embodiments, such as Figure 1 As shown, the present invention generally adopts a process of on-site de-hazardous physical pretreatment—centralized two-stage deep chemical regeneration—post-treatment; as Figure 2 As shown, the on-site pretreatment adopts a coarse filtration unit and a fine filtration unit connected in series; as Figure 3 As shown, the centralized treatment system employs a regeneration system consisting of a reactor, an ozone supply unit, an ionic liquid addition unit, a protective agent addition unit, a catalyst addition unit, a tail gas absorption unit, a settling / centrifugal separation unit, an adsorption purification unit, and a vacuum dehydration unit; for example... Figure 4 As shown, the deep chemical regeneration stage adopts a two-stage control logic of first protective pre-oxidation and then catalytic deep oxidation.

[0110] (a) Source and initial properties of crude oil

[0111] Waste industrial gear oil from the same batch replaced at an onshore wind farm was selected as the test subject; the grade was ISOVG320. The waste oil was mixed thoroughly before sampling and then placed in a sealed brown container and stored at room temperature. A simple sieve (100 mesh) was used before testing to remove any accidentally introduced large particles and prevent damage to laboratory equipment; however, this operation is not considered a pretreatment step in this invention.

[0112] The main physicochemical properties of the original waste gear oil are shown in Table 1.

[0113] Table 1 Physicochemical properties of raw waste gear oil

[0114]

[0115] As shown in Table 1, the waste gear oil not only contains high levels of metal abrasives and particulate contaminants, but also has a high acid value, dark color, and a large amount of sulfur and phosphorus impurities, making it unsuitable for direct reuse.

[0116] (II) Description of Testing Methods

[0117] To ensure comparability between the various embodiments and comparative examples, unless otherwise specified, all samples were evaluated using the following uniform method:

[0118] Appearance: Use 25mL transparent colorimetric tubes to visually observe color and transparency against a white background;

[0119] Kinematic viscosity: determined according to GB / T265;

[0120] Viscosity index: calculated according to GB / T1995;

[0121] Acid value: determined according to GB / T264;

[0122] Moisture content: determined according to GB / T260;

[0123] Fe and P elements: determined by ICP-OES;

[0124] S element: determined by XRF;

[0125] Ozone utilization rate: calculated by exhaust gas KI absorption combined with iodometric titration;

[0126] Recycled oil yield: Calculated using the following formula:

[0127] ;

[0128] in, The yield of recycled oil is expressed as %; The mass of the regenerated oil obtained after dehydration is expressed in grams. The unit for the mass of the pretreated oil is g.

[0129] The acid value reduction rate is calculated using the following formula:

[0130] ;

[0131] in, The percentage decrease in acid value is expressed as % . The acid value before treatment is expressed in mgKOH·g. -1 ; The acid value after treatment is expressed in mgKOH·g. -1 .

[0132] (III) Examples

[0133] Example 1: The two-stage processing method of the present invention (basic process)

[0134] 1. On-site physical pretreatment to eliminate hazardous substances

[0135] Reference Figure 2 The raw waste gear oil, replaced by a robotic oil changer, is pumped into a mobile filtration system. The coarse filtration unit uses a plate and frame filter with a filter element pore size of 5μm and an operating pressure of 0.20MPa. The fine filtration unit uses a filter medium composed of silica gel sand and activated carbon in a mass ratio of 10:1 to initially reduce its acid value, color, desulfurization, and metallic contaminants. The resulting pretreated oil is a brownish-yellow color.

[0136] The changes in particulate contamination and metal content before and after pretreatment are shown in Table 2.

[0137] Table 2 Comparison of indicators before and after on-site physical pretreatment

[0138]

[0139] As shown in Table 2, on-site two-stage filtration can significantly reduce particulate contamination and metal abrasive content, creating conditions for subsequent chemical regeneration.

[0140] 2. First-stage protective pre-oxidation treatment

[0141] Add 1000mL of pretreated oil to Figure 3 In the bubble column reactor shown, 100 mL of [BMIM][BF4] ionic liquid was added, representing 10% of the pretreated oil volume; 17.9 g of methyl oleate was added, representing 2.0% of the pretreated oil volume. Mechanical stirring was started at 300 rpm, and the system temperature was controlled at 40°C via jacketed circulating water. Then, an ozone-oxygen mixture was introduced from the bottom of the reactor at an ozone concentration of 2 wt%, a flow rate of 1.5 L / min, and a gas introduction time of 1 h.

[0142] 3. Second-stage catalytic deep oxidation treatment

[0143] After stopping the first stage of gas supply, 4.5 g of MnOx / γ-Al2O3 catalyst (0.5% of the pretreated oil mass) was added to the same reactor. The temperature was raised to 70°C, and an ozone-oxygen mixture was introduced again at an ozone concentration of 6 wt%, a flow rate of 2.0 L / min, and a gas flow time of 3 h. The exhaust gas was absorbed by KI absorbent, and the ozone utilization rate was calculated.

[0144] 4. Post-processing

[0145] After the reaction is complete, the gas supply is stopped and the mixture is allowed to stand for 2 hours to separate the upper purified oil phase. 120g of bleaching clay and 10g of activated carbon are added to the purified oil phase for adsorption and purification. After filtration, the oil is vacuum dehydrated at 80℃ and -0.095MPa until the water content is less than 0.03wt% to obtain the regenerated oil.

[0146] The test results showed that the total ozone utilization rate of Example 1 was 81.6%, and the recycled oil recovery rate was 89.4%.

[0147] Example 2: Two-stage processing method of the present invention

[0148] The process is basically the same as in Example 1, except that: 8.9g of MnOx-FeOx / activated carbon bimetallic catalyst was used in the second stage, which is 1.0% of the pretreated oil mass; the amount of protective agent used in the first stage was adjusted to 13.5g, which is 1.5% of the pretreated oil mass; the temperature in the first stage was 40℃, and the temperature in the second stage was 70℃, with the other conditions being the same.

[0149] According to the test results, the ozone utilization rate in the first stage of Example 2 was 77.9%, the ozone utilization rate in the second stage was 83.8%, the total ozone utilization rate was 82.5%, and the recycled oil recovery rate was 88.7%.

[0150] Example 3: Two-stage processing method of the present invention

[0151] The process is basically the same as in Example 1, except that: the amount of ionic liquid [BMIM][BF4] added is 150 mL, which is 15% of the volume of the pretreated oil; the first-stage protective agent is 18.0 g of ethyl oleate; the second-stage catalyst is 6.0 g of CuO / molecular sieve catalyst; the second-stage reaction temperature is 65 °C; the ozone concentration is 5 wt%; and the reaction time is 3 h.

[0152] The test results showed that the total ozone utilization rate of Example 3 was 84.1%, and the recycled oil recovery rate was 87.9%.

[0153] (iv) Comparative Example

[0154] Comparative Example 1: No Protectant

[0155] Except for the absence of a protective agent, the other conditions were the same as in Example 1. That is: 1000 mL of pretreated oil, 100 mL of [BMIM][BF4], and 4.5 g of MnOx / γ-Al2O3 catalyst were directly introduced into the post-treatment system at 50°C for 2 hours.

[0156] This comparative example illustrates that, in the absence of a protective agent, the base oil backbone is more susceptible to excessive oxidation.

[0157] Comparative Example 2: No catalyst

[0158] The first stage is the same as in Example 2; in the second stage, no catalyst is added, and the temperature is raised to 70°C and then 6wt% ozone-oxygen mixed gas is continuously introduced for 3 hours, with the other conditions being the same.

[0159] This comparative example illustrates that, in the absence of a catalyst, the deep removal effect on residual recalcitrant pollutants is insufficient.

[0160] Comparative Example 3: Non-ionic liquid

[0161] No ionic liquid was added in either the first or second stage, and the remaining conditions were the same as in Example 1, except that methyl oleate was added as a protective agent and MnOx / γ-Al2O3 catalyst was added in the second stage.

[0162] This comparative example illustrates that, although some oxidation reactions can still occur in the absence of ionic liquids, both ozone utilization and the efficiency of removing polar oxidation products decrease.

[0163] Comparative Example 4: Single-stage ozone catalytic oxidation

[0164] The pretreatment steps are the same as in Example 1. 1000 mL of pretreated oil, 100 mL of [BMIM][BF4], 17.9 g of methyl oleate and 4.5 g of MnOx / γ-Al2O3 were added to the reactor at one time, and 6 wt% ozone-oxygen mixed gas was directly introduced at 60°C for 3 h. Subsequent treatment was the same as in Example 1.

[0165] This comparative example illustrates that if a two-stage sequential control method is not used, but rather a single-stage treatment is employed, it is difficult to achieve both the protective effect on the base oil and the deep removal effect.

[0166] Comparative Example 5: Traditional Hydrogenation Refining Method

[0167] The pretreatment steps are the same as in Example 1. 1000 mL of the pretreated oil was added to a fixed-bed hydrotreating reactor, along with 13.5 g of Ni-Mo / Al₂O₃ catalyst (1.5% of the pretreated oil mass). The reactor was operated under hydrogen pressure of 15 MPa, temperature of 310 °C, and liquid hourly space velocity of 0.5 h⁻¹. -1 The mixture was treated under specific conditions, and after the reaction, it was purified by adsorption with clay and then dehydrated under vacuum.

[0168] This comparative example is used to illustrate that although traditional high-pressure hydrogenation can achieve a high degree of purification, the equipment and safety thresholds are significantly higher.

[0169] (V) Experimental Results

[0170] Table 3 Comparison of the performance of regenerated oil in each embodiment and the comparative example

[0171]

[0172] Table 4 Comparison of key performance indicators for each embodiment and comparative example

[0173]

[0174] Note: The acid value reduction rate of Comparative Example 1 is negative, indicating that the acid value increased instead of decreased, indicating excessive oxidation.

[0175] (vi) Results Analysis and Technical Effect Description

[0176] Combining Tables 3 and 4, we can draw the following conclusions.

[0177] 1. On-site de-hazardous pretreatment can significantly reduce particulate and metal pollution loads.

[0178] As can be seen from Table 2, after Figure 2 As shown in the two-stage filtration, the Fe content of the waste gear oil decreased from 24.5 ppm to 3.2 ppm, and the particulate contamination level decreased from 24 / 22 / 18 according to ISO 4406 to 18 / 15 / 11. This demonstrates that the on-site pretreatment step of this invention can effectively remove wear particles, metal shavings, and most suspended contaminants, significantly improving the oil's transferability. Although this step does not directly complete deep chemical purification, it provides more stable feed conditions with lower solids load for subsequent regeneration reactions.

[0179] 2. The two-stage process can simultaneously achieve deep decontamination and base oil protection.

[0180] Examples 1-3 all employed the two-stage route of this invention, and the resulting recycled oils showed significantly better performance than the original waste oil in terms of acid value, color, sulfur and phosphorus residue, and viscosity index. Example 2 demonstrated the best results, with the acid value reduced to 0.08 mg KOH / g, the viscosity index increased to 162, the sulfur content reduced to 35.5 ppm, and the phosphorus content below the detection limit. This indicates that the process can maintain good integrity of the base oil skeleton while achieving high removal rates.

[0181] In contrast, although Comparative Example 4 also incorporated ionic liquids, protective agents, and catalysts, it employed single-stage ozone catalytic oxidation. The resulting product had a viscosity index of only 145, significantly lower than Examples 1-3, indicating that single-stage strong oxidation treatment cannot simultaneously achieve deep removal of contaminants and protection of the base oil. Therefore, it is evident that... Figure 5 The sequential control of protective pre-oxidation followed by catalytic deep oxidation, as shown, is of substantial significance.

[0182] 3. Protective agents can significantly inhibit excessive oxidation.

[0183] In Comparative Example 1, no protective agent was added. Although the ozone utilization rate appeared to increase to 92.8%, the kinematic viscosity at 40°C after treatment decreased from 302 mmHg. 2 / s decreased to 295mm 2 / s, kinematic viscosity at 100℃ drops to 26.8mm 2 The viscosity index dropped to 119 and the acid value rose to 2.63 mg KOH / g, indicating that the system underwent significant over-oxidation, the base oil backbone was damaged, and a large number of small-molecule acidic substances were generated. Compared with Example 1, the presence of the protective agent can effectively buffer the initial strong oxidative shock, causing the oxidation to preferentially target the contaminants rather than the base oil.

[0184] 4. Catalysts are key to achieving deep removal of residual recalcitrant pollutants.

[0185] In Comparative Example 2, no catalyst was added in the second stage, resulting in a high S content of 312.1 ppm, a P content of 8.5 ppm, and an acid value that only decreased to 0.65 mg KOH / g, significantly worse than in Example 2. This indicates that the remaining pollutants after the first stage treatment have shifted to more stable and harder-to-oxidize components, requiring a supported transition metal oxide catalyst to achieve sufficient and deep purification.

[0186] 5. Ionic liquids have a significant promoting effect on ozone utilization and the removal of polar products.

[0187] In Comparative Example 3, without the addition of ionic liquid, the total ozone utilization rate was only 58.4%, with residual S and P at 418.4 ppm and 15.6 ppm, respectively, and an acid value of 0.38 mg KOH / g. This indicates that without the ozone enrichment and polar oxidation product migration functions provided by ionic liquid, the ozone utilization efficiency in the system decreases significantly, the migration and stripping of pollutants after oxidation are insufficient, and the subsequent regeneration effect is significantly worse.

[0188] 6. The process of this invention achieves regeneration quality close to that of the traditional hydrogenation method, but the process conditions are significantly milder.

[0189] The conventional hydrorefining method in Comparative Example 5 exhibits excellent performance in terms of acid value and transparency, achieving a viscosity index of 160, close to 162 in Example 2. However, this method requires high pressure and high temperature conditions of 15 MPa and 310°C, placing extremely high demands on equipment investment and safety management. In contrast, Example 2 of this invention achieves comparable or even better viscosity index and lower sulfur content under normal or near-normal pressure and a maximum temperature of 70°C, demonstrating that this invention provides better safety and engineering adaptability while ensuring regeneration quality.

[0190] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A method for regenerating waste gear oil from wind power plants, characterized in that, Includes the following steps: S1. A mobile robotic oil change vehicle is used to automatically complete the oil drain port docking and waste oil suction; after suction, the oil is pre-treated by filtration with at least one filter to reduce acid value, remove metal ions and desulfurize. S2. After the pretreated oil obtained in step S1 is transferred to a centralized treatment site, it is placed in a reactor, and ionic liquid and protective agent are added and mixed evenly. The amount of ionic liquid added is 5% to 20% of the volume of the pretreated oil, and the amount of protective agent added is 0.5% to 5% of the weight of the pretreated oil. Then, ozone-containing gas is introduced into the system at 20 to 60°C. The ozone concentration in the ozone-containing gas is 1 to 5 wt%, and the aeration time is 0.5 to 2 hours. S3. After stopping the ozone flow in step S2, add a supported transition metal oxide catalyst to the system. The amount of catalyst added is 0.01% to 3% of the pretreated oil mass. Then, introduce ozone-containing gas into the system at 40 to 80°C. The ozone concentration in the ozone-containing gas is 2 to 8 wt%. React for 1 to 4 hours to allow the remaining difficult-to-oxidize pollutants to undergo further deep oxidation. S4. After step S3 is completed, stop the introduction of ozone gas and let it stand or centrifuge to obtain an upper purified oil phase and a lower ionic liquid phase rich in oxidative degradation products; the purified oil phase is subjected to adsorption purification and vacuum dehydration to obtain regenerated oil; the ionic liquid phase is regenerated and recycled.

2. The method for regenerating and treating waste gear oil from wind power plants according to claim 1, characterized in that, The filter agent mentioned in step S1 includes one or more of diatomaceous earth, activated alumina, metal chelating agents, activated carbon, and adsorption resin.

3. The method for regenerating and treating waste gear oil from wind power plants according to claim 1, characterized in that, The ionic liquid is one or more of imidazole ionic liquids, pyridine ionic liquids, or quaternary ammonium salt ionic liquids; preferably 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, or a composite system formed therewith a carboxylate ionic liquid.

4. The method for regenerating waste gear oil from wind power plants according to claim 1, characterized in that, The protective agent is an unsaturated fatty acid ester containing carbon-carbon double bonds, selected from one or more of methyl oleate, ethyl oleate, and methyl linoleate. In step S2, the protective agent preferentially competes with ozone and highly reactive oxide species initially entering the system to reduce the probability of excessive oxidation and breakage of the base oil main chain.

5. The method for regenerating waste gear oil from wind power plants according to claim 1, characterized in that, The supported transition metal oxide catalyst comprises a porous support and a transition metal oxide supported on the porous support, wherein the porous support is one or more of γ-Al2O3, activated carbon, molecular sieve, or silica gel, and the transition metal oxide is one or more of MnOx, FeOx, CuO, or CoOx; preferably, the supported transition metal oxide catalyst is one of MnOx / γ-γ-Al2O3 catalyst, MnOx-FeOx / activated carbon bimetallic catalyst, CuO / molecular sieve catalyst, or CoOx / silica gel catalyst.

6. The method for regenerating waste gear oil from wind power plants according to claim 1, characterized in that, In step S4, the adsorption purification uses one or more of the following as adsorbents: white clay, silica gel, and activated carbon. The vacuum dehydration temperature is 60-100℃, and the absolute pressure corresponding to the vacuum degree is not higher than 0.01MPa, so that the moisture content in the regenerated oil is reduced to below 0.05wt%.

7. The method for regenerating waste gear oil from wind power plants according to claim 1, characterized in that, The ionic liquid phase described in step S4 is regenerated by one or more of the following methods: vacuum distillation, adsorption purification, or secondary ozone treatment. The regenerated ionic liquid is then returned to step S2 for reuse.

8. The method for regenerating waste gear oil from wind power plants according to claim 1, characterized in that, The waste gear oil from wind power plants is an industrial gear oil with a viscosity grade of ISO VG150, ISO VG220, or ISO VG320.

9. The method for regenerating waste gear oil from wind power plants according to claim 1, characterized in that, In steps S2 and S3, the reactor is one of a bubble column reactor, a stirred tank reactor, or a fixed bed-slurry coupled reactor; when the supported transition metal oxide catalyst is placed in a fixed bed, the mixture of pretreated oil and ionic liquid is transported through the fixed bed by a circulating pump and comes into countercurrent or cocurrent contact with the introduced ozone-containing gas to complete the second stage of catalytic deep oxidation treatment.

10. A regeneration system for waste gear oil from wind power plants, implementing the method according to any one of claims 1-9, characterized in that, It includes a field dehazard pretreatment module, a transfer and storage module, a centralized deep chemical regeneration module, and a post-treatment module connected in sequence; among which, The on-site dehazard pretreatment module and the transfer and storage module use a mobile robotic oil change vehicle equipped with a robotic arm and a visual navigation system; it is used to pump, temporarily store and transfer the pretreated oil to a centralized processing site. The centralized deep chemical regeneration module includes a reactor, an ionic liquid addition unit, a protective agent addition unit, a catalyst addition unit, an ozone generation and supply unit, a stirring unit, and a temperature control unit. The ionic liquid addition unit adds ionic liquid to the reactor. The protective agent addition unit adds a protective agent to the reactor before the first-stage ozone treatment. The ozone generation and supply unit introduces ozone-containing gas with an ozone concentration of 1-5 wt% into the reactor at 20-60°C for the first-stage protective pre-oxidation treatment. The catalyst addition unit adds a supported transition metal oxide catalyst to the reactor after the first-stage treatment. The ozone generation and supply unit also introduces ozone-containing gas with an ozone concentration of 2-8 wt% into the reactor at 40-80°C for the second-stage catalytic deep oxidation treatment. The ionic liquid enriches ozone and serves as a migrating phase for the polar degradation products generated by ozone oxidation, allowing the polar degradation products to transfer in situ from the oil phase to the ionic liquid phase. The post-processing module includes a settling or centrifugal separation unit, an adsorption purification unit, a vacuum dehydration unit, and an ionic liquid regeneration unit. The settling or centrifugal separation unit is used to separate an upper purified oil phase and a lower ionic liquid phase rich in oxidative degradation products. The adsorption purification unit and the vacuum dehydration unit are used to purify the purified oil phase to obtain regenerated oil. The ionic liquid regeneration unit is used to regenerate the ionic liquid phase and recycle it back to the centralized deep chemical regeneration module.

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