Waste mineral oil regeneration and separation device and process

Abstract

The invention discloses a waste mineral oil regeneration and separation device and technology, and belongs to the technical field of waste oil treatment.The technology comprises the following steps that waste mineral oil is preheated to 70-95 DEG C and then pumped into a multi-stage series gradient micro-channel; steam generated in the technological process is condensed into a liquid working medium, and the liquid working medium passes through a microporous medium to generate a microbubble flow with the average diameter of 10-50 microns; injecting the microbubble flow into the gradient microchannel at a volume gas content of 1-3%; a gradient contraction and expansion micro-channel structure is adopted, the structure can excite inertial secondary flow (namely Dean vortex) under the condition of low Reynolds number laminar flow, and is coupled with a Marangoni interfacial tension effect caused by axial temperature gradient, so that polar impurity molecules such as naphthenic acid dissolved in the waste mineral oil have a dipole moment and surface activity, and the mechanical property of the waste mineral oil is improved. And under the combined action of flow field shearing and temperature gradient.

Description

Technical Field

[0001] This invention relates to the field of waste oil treatment technology, and in particular to a waste mineral oil regeneration and separation device and process. Background Technology

[0002] Waste mineral oil, as a hazardous waste generated during industrial lubrication, insulation, and heat transfer processes, requires efficient and clean regeneration. This regeneration is crucial not only for the economic benefits of resource recycling but also for ecological security and the implementation of sustainable development strategies. With my country's continuously improving quality standards for recycled oils and increasingly stringent environmental regulations, achieving deep removal of dissolved polar impurities such as naphthenic acids and oxidized colloids from high-acid-value waste mineral oil has become a critical technological bottleneck that urgently needs to be overcome in the waste oil regeneration field.

[0003] In existing technologies, the acid bleaching clay refining process is predominantly used due to its simplicity and relatively reliable removal effect, which has long held a dominant position. This process involves sulfonation and polymerization reactions between concentrated sulfuric acid and alkaline nitrogen compounds, unsaturated hydrocarbons, and some polar impurities in waste oil, generating an acid tar phase. Activated clay is then used to adsorb residual acidic substances and colloids, thereby purifying the oil. In a specific historical period, this method effectively solved problems such as the dark color and poor stability of waste oil, providing crucial support for the early development of the recycled oil industry.

[0004] However, with the continuous development of related technologies and the increasingly stringent performance requirements of application scenarios, some inherent characteristics of the aforementioned technical solutions at the principle level have gradually revealed their deep-seated limitations in addressing new challenges. The acid bleaching clay process is essentially a consumable treatment path relying on exogenous chemical reagents and solid adsorption media. Its core contradiction lies in the fact that to achieve effective removal of impurities, a large amount of highly corrosive acid and high specific surface area bleaching clay must be introduced. This process inevitably generates secondary pollutants that are difficult to dispose of, including acidic waste residue with high oil content, saturated and depleted oily bleaching clay sludge, and acid washing wastewater. Such solid waste is not only highly corrosive and leaching toxic, but also has complex composition and low calorific value. Conventional incineration or landfilling both face high costs and environmental risks, severely restricting the compliant operation and green transformation of recycled oil companies. From the perspective of separation mechanism, the removal efficiency of nanoscale polar molecules dissolved in the oil phase by this process is highly dependent on chemical reaction kinetics and adsorption equilibrium. For structurally stable naphthenic acid derivatives or high molecular weight oxidized gums, it is often difficult to completely remove them, resulting in high acid value and insufficient oxidation stability of regenerated oil, which is difficult to meet the application requirements of high-end base oils. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a waste mineral oil regeneration and separation device and process.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a process for the regeneration and separation of waste mineral oil, comprising the following steps:

[0007] S1. After preheating the waste mineral oil to 70-95℃, pump it into a multi-stage series gradient microchannel.

[0008] S2. The steam generated during the process is condensed into a liquid working fluid, which is then passed through a microporous medium to generate a flow of microbubbles with an average diameter of 10-50 μm.

[0009] S3. Inject the microbubble flow into the gradient microchannel at a volumetric gas content of 1-3%.

[0010] S4. In the gradient microchannel, the flow field inducement effect is used to cause polar impurities in the waste mineral oil to migrate into the channel and aggregate.

[0011] S5. The gas-liquid interface of the microbubbles is used to capture and aggregate impurities, so that the microbubbles carrying impurities are separated from the oil phase, and then the purified oil is collected.

[0012] In a preferred embodiment of the present invention, in step S1, a single periodic unit of the gradient microchannel sequentially includes: a contraction segment with a width linearly shrinking from 1.5-2.5 mm to 0.2-0.5 mm, a throat with a length of 1.0-3.0 mm, and an expansion segment with a width linearly expanding from 0.2-0.5 mm to 1.5-2.5 mm; the depth of the microchannel is 0.5-1.5 mm.

[0013] In a preferred embodiment of the present invention, in step S1, the Reynolds number of the waste mineral oil flowing in the gradient microchannel is controlled between 100 and 800.

[0014] In a preferred embodiment of the present invention, in step S2, the steam is saturated water vapor with a temperature of 100-150°C and a pressure of 0.1-0.5 MPa, and the liquid working fluid has a temperature of 40-60°C and a pressure of 0.05-0.2 MPa.

[0015] In a preferred embodiment of the present invention, in step S2, the microporous medium is a sintered metal porous membrane; the material of the sintered metal porous membrane is any one of stainless steel, nickel-based alloy or titanium alloy.

[0016] In a preferred embodiment of the present invention, in step S4, the flow field induced effect is the synergistic effect of the inertial secondary flow effect and the Marangoni effect; wherein, by maintaining the axial temperature gradient in the channel at no less than 10°C and controlling the dimensionless Dean number between 10 and 50, the migration and aggregation of polar impurities are driven.

[0017] In a preferred embodiment of the present invention, in step S5, the separation is carried out in a cavity having an oleophobic and hydrophilic inner surface; the oleophobic and hydrophilic inner surface is formed by coating with any one of a silica-based coating, a fluorocarbon polymer coating, or an organosilicon resin coating.

[0018] Secondly, the present invention provides a waste mineral oil regeneration and separation device, comprising:

[0019] Heating tank, used for preheating waste mineral oil;

[0020] A liquid pump, with its inlet connected to the heating tank, is used to transport waste mineral oil;

[0021] The processing component includes a gradient microchannel and a flow-splitting cavity for realizing flow field-induced coalescence and separation of impurities;

[0022] The microbubble assembly, connected to the gradient microchannel via a pipe, is used to inject a flow of microbubbles into it.

[0023] In a preferred embodiment of the present invention, the microbubble assembly includes: a connecting pipe, a condenser, a pressurizing pump, and a porous element connected in sequence to the connecting pipe; the end of the connecting pipe away from the porous element is used to receive steam generated during the process, and the porous element is a sintered metal porous membrane, the outlet of which is connected to the starting position of the expansion section of the gradient microchannel through a pipe.

[0024] In a preferred embodiment of the present invention, the processing component further includes: a frame, wherein the gradient microchannel and the flow divider are connected to the frame by bolts, the inlet of the gradient microchannel is connected to the outlet of the liquid pump, and its outlet is connected to the inlet of the flow divider.

[0025] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0026] (1) A gradient contraction-expansion microchannel structure is adopted. This structure can excite inertial secondary flow (i.e., Dean vortex) under low Reynolds number laminar flow conditions and couple the Marangoni interfacial tension effect caused by the axial temperature gradient. This allows polar impurity molecules such as naphthenic acids dissolved in waste mineral oil to overcome Brownian motion and achieve directional migration and collision aggregation under the combined action of flow field shear and temperature gradient, forming larger droplets. This realizes the active induction and pre-enrichment of nanoscale dissolved impurities in the microscale flow field. Compared with the traditional acid clay process that passively relies on the random collision and reaction equilibrium between impurities and chemical reagents or adsorbents, the impurity transport path is actively controlled by the flow field design, which greatly improves the impurity aggregation efficiency. This physical induction mechanism creates favorable conditions for the subsequent capture and separation steps, so that the subsequent separation interface can act on more easily captured aggregates rather than highly dispersed molecules, thus improving the feasibility and efficiency of the overall separation process.

[0027] (2) By using the saturated water vapor generated by the dehydration process at the front end of the process as the gas source, after condensation and pressure regulation, a uniform micron-sized bubble flow is generated through the microporous medium and precisely injected into the microchannel expansion section. This results in the generated microbubbles having extremely high specific surface area and surface free energy at the gas-liquid interface. Polar impurity molecules, due to their hydrophobic and hydrophilic structures, tend to adsorb onto the gas-liquid interface to reduce the total energy of the system. They are stably captured by the bubble interface through van der Waals forces and dipole interactions. Furthermore, as a mobile and efficient dynamic collection platform, the microbubbles can adsorb and carry the impurity droplets that have coalesced in the flow field in situ. Compared with the existing acid bleaching process, which requires continuous input and consumption of a large amount of external concentrated sulfuric acid and activated clay, the process utilizes internal process steam to achieve the interface function without introducing any external chemical additives or solid adsorption media. This achieves the internal circulation of materials and energy, transforming the process steam that might otherwise be emitted into a valuable separation medium, and completely eliminating the generation of dangerous secondary pollutants such as acidic waste residue and oily sludge from the source. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a perspective structural diagram of a preferred embodiment of the present invention;

[0030] Figure 2 This is a three-dimensional structural diagram of a microbubble assembly according to a preferred embodiment of the present invention;

[0031] Figure 3 This is a perspective structural diagram of the processing component according to a preferred embodiment of the present invention;

[0032] Figure 4 This is an exploded view of a gradient microchannel according to a preferred embodiment of the present invention;

[0033] Figure 5 This is a flowchart of a preferred embodiment of the present invention.

[0034] In the diagram: 1. Heating tank; 2. Liquid pump; 3. Microbubble assembly; 31. Support frame; 32. Connecting pipe; 33. Condenser; 34. Pressurizing pump; 35. Porous component; 4. Processing assembly; 41. Frame; 42. Gradient microchannel; 43. Diverter chamber. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0037] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0039] Application Overview:

[0040] Waste mineral oil is a hazardous waste generated by industry. It has a complex and harmful composition. Improper handling will pollute the environment and waste resources. Its efficient and clean regeneration is crucial for pollution control and resource recycling. With the improvement of environmental protection standards, how to deeply remove nano-sized polar impurities such as naphthenic acids and oxidized gums from waste oil has become a key technology. These impurities lead to high acid value and poor stability of regenerated oil, affecting its performance.

[0041] Traditional acid bleaching clay process has long been used for waste oil regeneration, purifying oil through sulfuric acid reaction and bleaching clay adsorption. Although the operation is simple, the applicant found that it is essentially a consumable chemical pathway that requires the input of large amounts of strong acid and bleaching clay, generating secondary pollutants such as corrosive waste residue, oily sludge, and wastewater. The treatment cost is high and the environmental burden is heavy. In addition, the process has low efficiency in removing nanoscale dissolved impurities, relies on chemical reaction equilibrium, and is difficult to stably meet the standards of high-end oil products.

[0042] The applicant conducted in-depth research on the mechanisms of traditional processes and recognized their inherent defects due to chemical consumption. Subsequently, analysis of physical methods such as centrifugation and filtration showed that they could not effectively separate nanoscale impurities. In the process of exploration, the applicant turned to microfluidics and found that simple gradient microchannels could induce impurity migration, but the coalesced droplets were easy to redisperse, resulting in insufficient capture efficiency. The applicant found that microbubbles could be introduced into the microchannels as a dynamic interface, but external gas would introduce impurities. Therefore, combined with the characteristics of the waste oil process itself, the applicant found that the water vapor generated in the front-end dehydration process could be used as a source of bubbles. By condensing and refining the steam into microbubbles and injecting them into a specific flow field, the synergy between the internal interface and the flow field effect was achieved.

[0043] To address the aforementioned issues, this invention proposes an integrated gradient microchannel reactor assisted by endogenous microbubbles. This reactor utilizes the inertial eddy currents of the flow field and the interfacial tension effect of the temperature gradient to induce the migration and aggregation of polar impurities. Simultaneously, the process-generated steam is converted into microbubbles, which serve as a high-specific-surface-area dynamic interface to capture impurities, achieving separation through density difference. The entire process requires no external chemical reagents or adsorption media, eliminating secondary pollution at the source. This technology can reduce the acid value of waste oil, improve oxidation stability, and enable recycled oil to meet high-end standards.

[0044] like Figure 5As shown, a process for the regeneration and separation of waste mineral oil includes the following steps:

[0045] S1. After preheating the waste mineral oil to 70-95℃, pump it into a multi-stage series gradient microchannel.

[0046] S2. The steam generated during the process is condensed into a liquid working fluid, which is then passed through a microporous medium to generate a flow of microbubbles with an average diameter of 10-50 μm.

[0047] S3. Inject the microbubble flow into the gradient microchannel at a volumetric gas content of 1-3%.

[0048] S4. In the gradient microchannel, the flow field inducement effect is used to cause polar impurities in the waste mineral oil to migrate into the channel and aggregate.

[0049] S5. The gas-liquid interface of the microbubbles is used to capture and aggregate impurities, so that the microbubbles carrying impurities are separated from the oil phase, and then the purified oil is collected.

[0050] The core of this invention lies in the Dean vortex induced by channel geometric changes and the Marangoni effect caused by temperature gradients, which actively drive the migration and aggregation of nanoscale polar impurities in waste oil; and the steam generated by the recycling process itself, which is converted into micron-sized bubbles and precisely injected into the flow field, so that the bubble interface acts as a dynamic capture platform to achieve in-situ capture and transport of aggregated impurities. The entire process does not rely on any external chemical reagents or adsorption media, fundamentally eliminating secondary pollution and realizing the internal circulation of materials and energy. Ultimately, it can efficiently and cleanly reduce the acid value of high-acid-value waste mineral oil to below 0.1 mgKOH / g, so that the quality of the recycled oil meets the standards of high-end applications.

[0051] Each step will be explained in detail below.

[0052] S1 refers to waste mineral oil, which is high-acid-value industrial waste oil that needs to be regenerated. The process involves heating the waste oil before it enters the microchannel, with a target preheating temperature of 70-95℃.

[0053] The gradient microchannel is the core flow channel structure inside the reactor, consisting of multiple periodic units connected in series. Each unit controls the flow field through periodic changes in its cross-sectional shape. A single periodic unit of the gradient microchannel sequentially includes: a contraction section with a width that linearly shrinks from 1.5-2.5 mm to 0.2-0.5 mm, a throat with a length of 1.0-3.0 mm, and an expansion section with a width that linearly expands from 0.2-0.5 mm to 1.5-2.5 mm. The depth of the microchannel is 0.5-1.5 mm.

[0054] Pumping refers to the process of using a pump to deliver waste oil to a microchannel at a specific flow rate, wherein the Reynolds number (Re) of the waste oil flowing in the channel needs to be controlled between 100 and 800.

[0055] In S2, process steam refers to steam drawn from the front end of the waste oil regeneration process (such as the dehydration / flash evaporation process), which is the working fluid source for microbubbles. The steam used is saturated water vapor, with a temperature range of 100-150℃ and a pressure range of 0.1-0.5MPa.

[0056] Liquid working fluid refers to the liquid formed after steam condensation. It is the raw material for generating microbubbles. The temperature of the liquid working fluid after condensation is controlled at 40-60℃ and the pressure is 0.05-0.2MPa.

[0057] Microporous media refers to porous materials used to disperse liquid working fluids into tiny bubbles. Among them, microporous media are sintered metal porous membranes, and their materials can be any of stainless steel, nickel-based alloys or titanium alloys.

[0058] Microbubble flow refers to the final generation of a group of tiny bubbles of uniform size, with an average diameter of 10-50 μm.

[0059] In S3, the volumetric gas content refers to the percentage of the injected microbubble volume to the total volume of the gas-liquid mixture. It is a key parameter for controlling the number of bubbles, and the injected volumetric gas content is controlled between 1-3%.

[0060] In S4, the flow field induced effect refers to the physical effect that can drive the movement of impurities in a microchannel due to specific flow field conditions. The flow field induced effect is mainly the synergistic effect of the inertial secondary flow effect (Dean vortex) and the Marangoni effect.

[0061] Polar impurities refer to the target pollutants that need to be removed from waste oil, such as naphthenic acids and oxidized gums. The migration and aggregation of impurities are driven by maintaining an axial temperature gradient of not less than 10°C in the channel and controlling the dimensionless Dean number (De) between 10 and 50.

[0062] Agglomeration refers to the process by which tiny impurity particles or droplets collide, merge, and grow larger.

[0063] In S5, the gas-liquid interface of microbubbles refers to the surface of the microbubbles, which has high surface energy and is an active interface for capturing impurities; microbubbles carrying impurities refer to bubbles whose density decreases and floats after the impurities are captured.

[0064] The process of trapping refers to the adsorption and fixation of impurities at the gas-liquid interface, the process of separating impurity-laden bubbles from the purified oil by utilizing density differences, and the process of collecting refers to the harvesting of the final purified oil. The separation process is carried out in a cavity with an oleophobic and hydrophilic inner surface, which is formed by coating with any one of a silica-based coating, a fluorocarbon polymer coating, or an organosilicon resin coating.

[0065] To further simplify and make the present invention achieve its objectives and effects, the present invention will be further illustrated in conjunction with the following specific embodiments and comparative examples, but the present invention is not limited to the scope of the embodiments described herein.

[0066] It should be noted that the raw materials used in the examples and comparative examples are described below:

[0067] Silica-based oleophobic and hydrophilic coating: average particle size 20µm, purity 99.9%, model KN-SiO2-10, purchased from Keneng (Xi'an) Materials Technology Co., Ltd.

[0068] Concentrated sulfuric acid: 98% concentration, purchased from Nanjing Kaiyan Environmental Protection Technology Co., Ltd.

[0069] Activated clay: decolorization rate 99%, free acid ≤0.2%, CAS number 70131-50-9, purchased from Mingguang Xingxin Mining Co., Ltd.

[0070] Example 1:

[0071] S1. Preheated waste oil to 85℃ is pumped into a gradient microchannel. By adjusting the pump speed, the Reynolds number (Re) of the waste oil flow in the channel is controlled to be 500. The gradient microchannel is composed of 50 periodic units connected in series. The specific structure of each unit is as follows: the width of the contraction section is linearly reduced from 2.0mm to 0.3mm, the throat length is 2.0mm, the width of the expansion section is linearly expanded from 0.3mm to 2.0mm, and the channel depth is 1.0mm.

[0072] S2. Saturated water vapor drawn from the waste oil dehydration process, with a temperature of 120℃ and a pressure of 0.2MPa, is condensed to 50℃ by a condenser to form liquid water. This liquid water is pressurized to 0.1MPa and then passed through a porous membrane made of sintered 316L stainless steel. The membrane has an average pore size of 15μm, generating a flow of microbubbles with an average diameter of about 30μm.

[0073] S3. The generated microbubble flow, with a volumetric gas content of 2%, is injected into the flowing waste oil through an injection point set near the starting position of the microchannel expansion section.

[0074] S4. Through an external temperature control system, a temperature gradient of about 15°C is maintained along the microchannel axis. Combined with the Dean vortex induced by the channel structure, whose dimensionless Dean number De is about 30, a flow field induction effect is generated in synergy. That is, the combined effect of inertial secondary flow and Marangoni effect drives polar impurity molecules such as naphthenic acid dissolved in waste oil to migrate to the area near the channel wall and collide and aggregate into larger droplets.

[0075] S5. The aggregated impurity droplets are efficiently captured by the microbubble gas-liquid interface. The microbubbles carrying impurities float in the subsequent separation chamber, which is coated with a silica-based oleophobic and hydrophilic coating. Finally, the purified oil is collected from the bottom outlet of the separation chamber, while the impurity-rich microbubbles aggregate to form scum and are discharged from the top.

[0076] Example 2:

[0077] This embodiment is basically the same as embodiment 1, except that the preheating temperature is different. Specifically, in step S1, the waste mineral oil is preheated to 70°C and then pumped into a multi-stage series gradient microchannel.

[0078] Example 3:

[0079] This embodiment is basically the same as embodiment 1, except that the preheating temperature is different. Specifically, in step S1, the waste mineral oil is preheated to 95°C and then pumped into a multi-stage series gradient microchannel.

[0080] Example 4:

[0081] This embodiment is basically the same as embodiment 1, except that the microbubble size is different. Specifically, in step S2, it is passed through a microporous medium to generate a flow of microbubbles with an average diameter of 10 μm.

[0082] Example 5:

[0083] This embodiment is basically the same as embodiment 1, except that the microbubble size is different. Specifically, in step S2, the microbubble is passed through a microporous medium to generate a flow of microbubbles with an average diameter of 50 μm.

[0084] Example 6:

[0085] This embodiment is basically the same as embodiment 1, except that the amount of microbubble injected is different. Specifically, in step S3, the microbubble flow is injected into the gradient microchannel with a volumetric gas content of 1%.

[0086] Example 7:

[0087] This embodiment is basically the same as embodiment 1, except that the amount of microbubble injected is different. Specifically, in step S3, the microbubble flow is injected into the gradient microchannel with a volumetric gas content of 3%.

[0088] Example 8:

[0089] This embodiment is basically the same as Embodiment 1, except that the gradient microchannel structure is different. Specifically, in step S1, a single periodic unit of the gradient microchannel sequentially includes: a contraction segment whose width linearly shrinks from 2.0 mm to 0.3 mm, a throat with a length of 1.0 mm, and an expansion segment whose width linearly expands from 0.3 mm to 2.0 mm.

[0090] Example 9:

[0091] This embodiment is basically the same as Embodiment 1, except that the gradient microchannel structure is different. Specifically, in step S1, a single periodic unit of the gradient microchannel sequentially includes: a contraction segment whose width linearly shrinks from 2.0 mm to 0.3 mm, a throat with a length of 3.0 mm, and an expansion segment whose width linearly expands from 0.3 mm to 2.0 mm.

[0092] Comparative Example 1:

[0093] The process principle of this comparative example is completely different from that of Example 1. It uses the traditional acid clay process for comparison. The specific steps are as follows:

[0094] S1. Preheat the waste mineral oil to 85°C.

[0095] S2. Add 5% of the mass of concentrated sulfuric acid to the preheated waste oil, react for 1 hour with stirring, and then let stand to separate the lower layer of acid sludge.

[0096] S3. Add 5% of the weight of activated clay to the pickled oil and adsorb and refine it for 0.5 hours under stirring.

[0097] S4. Filtration to separate white clay residue and collect purified oil.

[0098] Comparative Example 2:

[0099] This comparative example is basically the same as Example 1, except that microbubbles are not injected, and the specific steps of S3 and S4 are as follows:

[0100] S4. Within the gradient microchannel, the flow field inducement effect is used to cause polar impurities in the waste mineral oil to migrate and coalesce into the channel.

[0101] S5. The oil phase containing aggregated impurities is introduced into a settling tank, where the impurities are separated by natural settling under gravity, and then the upper purified oil is collected.

[0102] Comparative Example 3:

[0103] This comparative example is basically the same as Example 1, except that: the inner wall of the separation chamber has no oleophobic and hydrophilic coating, and the specific steps of S5 are: using the gas-liquid interface of the microbubbles to capture aggregated impurities, so that the microbubbles carrying impurities are separated from the oil phase. This separation process is carried out in a chamber with an inner surface of ordinary stainless steel, and then the purified oil is collected.

[0104] Comparative Example 4:

[0105] This comparative example is basically the same as Example 1, except that the preheating temperature is different. The specific steps of S3 are: after preheating the waste mineral oil to 60°C, it is pumped into a multi-stage series gradient microchannel.

[0106] Comparative Example 5:

[0107] This comparative example is basically the same as Example 1, except that the preheating temperature is different. The specific steps of S3 are: after preheating the waste mineral oil to 105°C, it is pumped into a multi-stage series gradient microchannel.

[0108] Comparative Example 6:

[0109] This comparative example is basically the same as Example 1, except that the microbubble diameter is different. The specific steps of S2 are: condensing the steam generated in the process into a liquid working fluid, and passing it through a microporous medium to generate a flow of microbubbles with an average diameter of 5 μm.

[0110] Comparative Example 7:

[0111] This comparative example is basically the same as Example 1, except that the microbubble diameter is different. The specific steps of S2 are: condensing the steam generated in the process into a liquid working fluid, and passing it through a microporous medium to generate a flow of microbubbles with an average diameter of 80 μm.

[0112] Comparative Example 8:

[0113] This comparative example is basically the same as Example 1, except that the amount of microbubble injected is different. The specific step of S3 is: the generated microbubble flow is injected into the flowing waste oil through the injection point set near the starting position of the microchannel expansion section with a volume gas content of 0.5%.

[0114] Comparative Example 9:

[0115] This comparative example is basically the same as Example 1, except that the amount of microbubble injected is different. The specific step of S3 is: the generated microbubble flow is injected into the flowing waste oil through the injection point set near the starting position of the microchannel expansion section with a volume gas content of 5%.

[0116] Comparative Example 10:

[0117] This comparative example is basically the same as Example 1, except that the throat of the gradient microchannel is different. The specific steps of S1 are as follows: the width of the contraction section is linearly contracted from 2.0 mm to 0.3 mm, the throat length is 0.5 mm, the width of the expansion section is linearly expanded from 0.3 mm to 2.0 mm, and the channel depth is 1.0 mm.

[0118] Comparative Example 11:

[0119] This comparative example is basically the same as Example 1, except that the throat of the gradient microchannel is different. The specific steps of S1 are as follows: the width of the contraction section is linearly contracted from 2.0 mm to 0.3 mm, the throat length is 4.0 mm, the width of the expansion section is linearly expanded from 0.3 mm to 2.0 mm, and the channel depth is 1.0 mm.

[0120] Performance testing: The regenerated oils obtained in Examples 1-9 and Comparative Examples 1-11 were subjected to performance tests in sequence, including acid value, oxidation stability, removal rate of polar impurities, yield, and viscosity. The results are shown in Table 1.

[0121] Regenerated oleic acid value: Using potentiometric titration, accurately weigh approximately 20.0 g of homogeneous oil sample and place it in a clean 250 mL titration cup. Add 80 mL of titration solvent consisting of a 1:1 volume ratio of toluene and isopropanol. Stir thoroughly on a magnetic stirrer until the oil sample is completely dissolved. Install an automatic burette containing a 0.1 mol / L potassium hydroxide isopropanol standard solution, a composite pH electrode, and a temperature probe onto the automatic potentiometric titrator and perform system calibration. Place the titration cup containing the sample solution on the titration stage, start the titration program, and add the standard solution at a constant rate. The instrument automatically records the potential-volume curve. The endpoint is determined when the curve shows a characteristic abrupt change. Record the volume of standard solution consumed at the endpoint. (mL). The determination was performed in triplicate. Acid value. (mgKOH / g) is calculated using the following formula: ,in The concentration of the standard solution is (mol / L). 56.1 represents the sample mass (g) and the molar mass of potassium hydroxide. The final result is the arithmetic mean of three parallel determinations.

[0122] Oxidation stability: The rotating oxygen bomb method was used. Before use, the cleanliness and airtightness of the oxygen bomb (including the bomb body, cap, pressure gauge, and sealing ring) were checked. 50.0 g ± 0.5 g of oil sample was accurately weighed and poured into a clean, dry glass sample cup. 5.0 mL of distilled water was added to the sample cup. A standard-sized copper catalyst coil (1.22 m in total length, 1.63 mm in diameter) was wound into a specific shape and placed in the sample cup, immersing it in the oil. The sample cup was carefully placed into the oxygen bomb, the cap was closed, and tightened by hand. The oxygen bomb was connected to an oxygen cylinder, and oxygen was slowly added until the pressure reached 620 kPa (90 psi). Then, the pressure was slowly released to atmospheric pressure to displace the air. This process was repeated twice. A third oxygenation was performed until the pressure stabilized at 620 kPa ± 5 kPa. The oxygen-filled bomb was then smoothly placed in a preheated constant-temperature oil bath at 150.0℃ ± 0.1℃. The rotating device was started, rotating at a rate of 100 r / min, and timing was started simultaneously. The instrument automatically and continuously monitors the internal pressure of the oxygen bomb. Timing automatically stops when the pressure drops by 175 kPa (25 psi) from its highest point; this time period (in minutes) is the rotating oxygen bomb life (RBOT value). The oxygen bomb and sample cup are thoroughly cleaned after each test. Each oil sample is tested twice in parallel. If the difference between the two results exceeds 10% of the average, a third test is performed. The final result is the arithmetic mean of the valid tests.

[0123] Polar impurity removal rate: The polar impurity removal rate is assessed by comparing the changes in the content of characteristic polar components in the oil samples before and after treatment, using Fourier transform infrared spectroscopy (FT-IR) for quantitative analysis. First, a potassium bromide window liquid cell or attenuated total reflectance (ATR) attachment is used. Infrared spectra of untreated raw waste mineral oil (feedstock) and treated regenerated oil are collected. The scanning range is 4000-400 cm⁻¹. -1 4cm resolution -1 The scan was performed 32 times. The focus was on the characteristic peak region of the carbonyl stretching vibration, which characterizes carboxylic acid impurities (such as cycloalkanoic acids) (approximately 1700-1750 cm⁻¹). -1 Select a stable oil-based peak in the spectrum (e.g., 1460 cm⁻¹). -1 The CH2 bending vibration peak at 1710 cm⁻¹ was used as an internal standard peak. The instrument software was used to analyze the target characteristic peak (e.g., 1710 cm⁻¹). -1 Integrate the peak areas of the target characteristic peak and the internal standard peak (near the broad peak) to calculate the peak area ratio of the target characteristic peak to the internal standard peak in the feedstock and recycled oil. Removal rate of polar impurities ( ,%) are calculated using the following formula: ,in This represents the peak area ratio of the feedstock oil. This represents the peak area ratio of the recycled oil. To reduce error, each sample needs to be sampled from different locations and its spectrum measured three times. The average peak area ratio is then calculated before the above calculation is performed.

[0124] Recycled oil yield: The recycled oil yield is the mass yield, calculated by accurately weighing the feed and final product masses. Before the experiment, record the tare weight of the containers used to hold the raw waste oil and the final purified oil. The known mass ( Approximately 1000.0g (accurately weighed) of waste mineral oil feedstock is added to the pretreatment system. The entire separation process (including microchannel treatment, bubble injection, separation chamber separation, etc.) is operated according to the parameters of the embodiment or comparative example. After the process is completed, all oil flowing out of the purified oil outlet of the separation unit is collected, and its total weight with the container is weighed. The tare weight of the container is subtracted to obtain the net weight of the purified oil. Carefully inspect and collect any residual oil inside the device (such as microchannels, pipelines, and the bottom of the separation chamber), and record its mass as [data missing]. Recycled oil yield ( ,%) are calculated using the following formula: If the equipment is designed to ensure that the residual oil level is extremely low ( (If negligible), the formula simplifies to: To ensure accuracy, the entire weighing process must be conducted using the same calibrated electronic balance, and losses due to oil evaporation must be avoided. Each process condition test must be independently repeated three times, and the yield results are taken as the arithmetic mean.

[0125] Regenerated oil viscosity: The capillary Ubbelohde viscometer method is used. Based on the estimated oil sample viscosity range (usually at 40℃), select a suitable Ubbelohde viscometer model (e.g., capillary inner diameter 0.8mm or 1.0mm) with a flow time greater than 200s. Thoroughly clean the viscometer with chromic acid cleaning solution, then rinse with distilled water and acetone, and dry before use. Pour the filtered, homogeneous oil sample into the dry calibration bulb of the viscometer, ensuring the sample volume is between the two filling marks at constant temperature. Vertically install the viscometer with the sample in a transparent constant-temperature water bath maintained at 40.0℃ ± 0.1℃, and adjust its verticality using a plumb line. Maintain the constant temperature for at least 15 minutes, ensuring the sample temperature is completely consistent with the bath temperature. Connect the upper capillary tube of the viscometer using a rubber tube, and gently suck the oil sample above the upper timing bulb mark using a suction bulb, then allow it to flow freely under gravity. The time it took for the oil sample to flow across the upper and lower timing lines on the meniscus was recorded using an electronic stopwatch with an accuracy of 0.1 seconds. Repeat the measurement at least four times, and the difference between each flow time and the average value should not exceed 0.5% of the average value. Take the arithmetic mean of the acceptable flow times. Kinematic viscosity () (mm² / s) is calculated using the following formula: ,in The instrument constant of the viscometer used (given by calibration by the metrology department, unit: mm). 2 / s2 Clean the viscometer immediately after testing with an appropriate solvent. The results for each oil sample are the average of two independent measurements.

[0126] Table 1: Performance test results of regenerated oils from Examples 1-9 and Comparative Examples 1-11

[0127] Group Regenerated oleic acid value (mgKOH / g) Oxidative stability RBOT (min) Polar impurity removal rate (%) Recycled oil yield (%) <![CDATA[Recycled oil viscosity (mm 2 / s)]]> Example 1 0.08 420 98.5 97.5 68.2 Example 2 0.12 380 96.0 96.8 68.5 Example 3 0.18 340 93.5 95.5 68.8 Example 4 0.10 410 97.8 97.2 68.3 Example 5 0.15 360 95.2 96.5 68.6 Example 6 0.13 390 96.5 97.0 68.4 Example 7 0.09 400 98.0 96.0 68.3 Example 8 0.20 320 92.0 94.8 69.0 Example 9 0.11 370 96.8 96.2 68.5 Comparative Example 1 1.20 180 75.0 90.0 70.5 Comparative Example 2 2.50 120 60.0 88.0 72.0 Comparative Example 3 0.25 300 90.5 94.0 69.2 Comparative Example 4 0.50 280 85.0 93.5 69.8 Comparative Example 5 0.22 310 91.0 94.5 69.1 Comparative Example 6 0.30 290 88.0 93.0 69.5 Comparative Example 7 0.28 295 89.5 93.8 69.4 Comparative Example 8 0.40 260 82.0 92.5 70.0 Comparative Example 9 0.10 410 97.5 95.0 68.5 Comparative Example 10 0.35 270 86.0 93.2 69.7 Comparative Example 11 0.19 330 93.0 95.0 68.9

[0128] A comparison between Example 1 and Comparative Example 1 reveals that Comparative Example 1, employing a traditional acid-clay process, exhibits an acid value as high as 1.20 mg KOH / g, an oxidation stability of only 180 min, and a yield of only 90%. This is because the process relies on the chemical sulfonation / polymerization reaction of concentrated sulfuric acid with polar impurities and the adsorption of clay. The reaction is limited by kinetic equilibrium, resulting in incomplete removal of nanoscale dissolved impurities. Furthermore, the introduction of strong acid and clay leads to secondary pollution (acid sludge, oily sludge), and some oil products undergo side reactions and degradation during the reaction, resulting in a decrease in yield and an increase in viscosity. From a molecular perspective, while acid treatment can convert some naphthenic acids, it cannot completely remove high-molecular-weight oxidized colloids, and reaction products may remain in the oil phase, affecting oil stability.

[0129] A comparison between Example 1 and Comparative Example 2 reveals that Comparative Example 2, without microbubble injection, relied solely on flow field-induced aggregation followed by gravity sedimentation, resulting in an acid value as high as 2.50 mg KOH / g and a removal rate of only 60%. This indicates that without microbubble interface trapping, aggregated impurity droplets may redisperse after flowing out of the microchannel due to Brownian motion or flow field shear, making effective separation from the oil phase difficult. Microbubbles, as dynamic interfaces, not only provide high-energy adsorption sites but also enable active transport through flotation, preventing impurity redispersibility.

[0130] A comparison between Example 1 and Comparative Example 3 reveals that Comparative Example 3, lacking an oleophobic and hydrophilic coating on its inner wall of the separation chamber, exhibits a higher acid value (0.25 mg KOH / g) than Example 1 (0.08 mg KOH / g). This indicates that ordinary stainless steel surfaces readily adhere to oil films, hindering bubble coalescence and buoyancy. Consequently, some captured impurities may remain with the oil phase, reducing separation efficiency. The oleophobic and hydrophilic coating, by lowering the oil-solid interfacial energy, promotes rapid bubble-oil phase separation, thereby improving the purity of the purified oil.

[0131] A comparison of Examples 1 / 2-3 with Comparative Examples 4-5 reveals that: in Examples 2-3, preheating temperatures of 70℃ and 95℃ respectively maintained good performance; however, in Comparative Examples 4-5, lowering the temperature to 60℃ or raising it to 105℃ resulted in a significant decrease in performance. At excessively low temperatures (60℃), the viscosity of the oil phase increased, the diffusion rate of impurity molecules decreased, the Dean vortex and Marangoni effects weakened, and the migration and coalescence efficiency decreased; at excessively high temperatures (105℃), it may lead to the volatilization of light components or thermal oxidation of the oil, resulting in poor microbubble stability, reduced interfacial adsorption capacity, and potential oil degradation, affecting stability and yield.

[0132] A comparison of Examples 1 / 4-5 with Comparative Examples 6-7 reveals that in Examples 4-5, the microbubble diameters of 10 μm and 50 μm, respectively, still exhibited superior performance. However, in Comparative Examples 6-7, performance decreased when the bubble diameter was reduced to 5 μm or increased to 80 μm. This is because when the bubble size is too small (5 μm), although the specific surface area is large, the rising speed is slow, resulting in excessive residence time in the channel, potentially leading to being carried away by the oil flow and incomplete separation. Conversely, when the bubble size is too large (80 μm), the specific surface area decreases, resulting in insufficient interfacial trapping sites and a higher likelihood of bubble breakage in the flow field, thus reducing trapping efficiency.

[0133] A comparison of Examples 1 / 6-7 with Comparative Examples 8-9 reveals that: in Examples 6-7, the volumetric gas content of 1% and 3% showed good performance; in Comparative Examples 8-9, performance decreased when the gas content was reduced to 0.5% or increased to 5%. When the gas content is too low, the number of bubbles is insufficient, the interface coverage is low, and some coalesced impurities cannot be captured; when the gas content is too high, bubble-bubble collisions and coalescence intensify, forming large bubbles or even gas plugs, disrupting flow field stability, and potentially carrying excessive oil phase to the surface, reducing yield.

[0134] A comparison of Examples 1 / 8-9 with Comparative Examples 10-11 reveals that: in Examples 8-9, throat lengths of 1.0 mm and 3.0 mm respectively indicate acceptable performance; however, in Comparative Examples 10-11, shortening the throat to 0.5 mm or lengthening it to 4.0 mm results in decreased performance. When the throat is too short, the flow field changes too rapidly, Dean vortices do not develop sufficiently, and impurity migration distance is insufficient; when the throat is too long, the flow field tends to stabilize, secondary flow intensity weakens, and the driving force for impurity aggregation is insufficient, affecting the pre-enrichment effect.

[0135] like Figures 1-4 As shown, the present invention provides a waste mineral oil regeneration and separation device. Specifically, the heating tank 1 is a container used to preheat waste mineral oil and has good heat preservation performance. An electric heating tube is installed inside the heating tank 1 so that the heating device can maintain the temperature inside the heating tank 1 within the range of 70-95°C to meet the preheating requirements of waste mineral oil.

[0136] It should be noted that the top of the heating tank 1 is equipped with a waste mineral oil inlet for receiving waste mineral oil to be processed, and the bottom is connected to the inlet of the liquid pump 2 through a pipe. After the waste mineral oil is heated to a specified temperature in the heating tank 1, it begins to be transported to the subsequent processing component 4 under the action of the liquid pump 2.

[0137] Specifically, the liquid pump 2 is the power source for transporting waste mineral oil. Its inlet is connected to the bottom of the heating tank 1 through a pipe, and its outlet is connected to the inlet of the gradient microchannel 42 in the processing component 4 through a pipe. The liquid pump 2 can transport the preheated waste mineral oil in the heating tank 1 to the gradient microchannel 42 at a specific flow rate and pressure.

[0138] Preferably, the type of liquid pump 2 can be selected according to the actual processing volume and pressure requirements. For example, it can be a centrifugal pump or a gear pump. When working, the blades or gears of the liquid pump 2 rotate to generate centrifugal force or mechanical driving force, which draws the waste mineral oil from the inlet and pushes it out through the outlet, thereby realizing the transportation of waste mineral oil.

[0139] Specifically, the main function of the microbubble component 3 is to generate and inject microbubble flow into the gradient microchannel 42. It is connected to the gradient microchannel 42 through a pipe, which transports the microbubble flow generated by the microbubble component 3 to the starting position of the expansion section of the gradient microchannel 42.

[0140] Furthermore, one end of the connecting pipe 32 is used to receive steam generated during the process, specifically saturated steam from the dehydration / flash evaporation step at the front end of the waste oil regeneration process. The connecting pipe 32 transports the steam to the condenser 33, which condenses the high-temperature, high-pressure steam into a liquid working fluid. The temperature of the liquid working fluid is controlled at 40-60℃, and the pressure is 0.05-0.2MPa. The condensed liquid working fluid then enters the pressurization pump 34 through a pipeline. The pressurization pump 34 pressurizes the liquid working fluid to a suitable pressure, typically around 0.1MPa, and then transports it to the porous element 35. The porous element 35 is a sintered metal porous membrane made of stainless steel, with an average pore size of approximately 15μm. This allows it to disperse the pressurized liquid working fluid into a microbubble flow with an average diameter of 10-50μm. The microbubble flow is ultimately injected through a pipeline into the starting position of the expansion section of the gradient microchannel 42, where it mixes with the waste mineral oil, utilizing the gas-... Impurities are captured and aggregated at the liquid interface.

[0141] Specifically, the processing component 4 is the core part for realizing the impurity flow field-induced coalescence and separation. The gradient microchannel 42 is the key channel structure for the flow of waste mineral oil and the realization of impurity migration and coalescence. It is composed of multiple periodic units connected in series. Each periodic unit includes a contraction section with a width that linearly shrinks from 2.0 mm to 0.3 mm, a throat length of 2.0 mm, an expansion section with a width that linearly expands from 0.3 mm to 2.0 mm, and a channel depth of 1.0 mm.

[0142] Furthermore, when the waste mineral oil flows within the gradient microchannel 42, the polar impurities in the waste mineral oil migrate and coalesce into the channel due to the flow field induction effect (mainly the synergistic effect of inertial secondary flow and Marangoni effect).

[0143] Furthermore, the inlet of the gradient microchannel 42 is connected to the outlet of the liquid pump 2 via a pipe to receive preheated waste mineral oil, while the outlet is connected to the inlet of the splitting chamber 43 via a pipe. The function of the splitting chamber 43 is to separate the oil phase after treatment by the gradient microchannel 42 from the microbubbles carrying impurities. In the splitting chamber 43, because the density of microbubbles is less than that of the oil phase, the microbubbles carrying impurities will float upwards, while the purified oil phase will settle downwards or flow out through a specific outlet.

[0144] It should be noted that the inner wall of the splitting cavity 43 is coated with an oleophobic and hydrophilic coating made of silica-based material. This coating can promote the separation of microbubbles from the oil phase and improve the separation efficiency.

[0145] When using this invention, the waste mineral oil is first preheated to a specified temperature in a heating tank 1, and then pumped into a multi-stage series gradient microchannel 42 by a liquid pump 2.

[0146] The gradient microchannel 42 consists of a periodic contraction section, a throat, and an expansion section. Under low Reynolds number laminar flow conditions, the inertial secondary flow excited by the channel structure and the Marangoni effect induced by the axial temperature gradient work together to drive polar impurity molecules such as naphthenic acids dissolved in the oil to migrate to the channel wall region and collide and coalesce into larger droplets.

[0147] Meanwhile, the saturated water vapor generated in the dehydration process at the front end of the process is introduced into the microbubble assembly 3, condensed into a liquid working fluid by the condenser 33, and then transported to the porous component 35 by the pressurized pump 34. The generated microbubble flow is injected into the starting position of the expansion section of the gradient microchannel 42.

[0148] The gas-liquid interface of microbubbles has a high specific surface area and surface energy, which can efficiently capture impurity droplets that have coalesced in the flow field. The microbubbles carrying impurities are then separated from the oil phase in the subsequent diversion chamber 43 by means of the oleophobic and hydrophilic coating on the inner wall of the chamber, relying on the density difference. The impurities float to the surface and are enriched as scum and discharged, while the purified oil is collected from the bottom, thus completing the efficient and clean regeneration of waste mineral oil.

[0149] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A process for the regeneration and separation of waste mineral oil, characterized in that, Includes the following steps: S1. After preheating the waste mineral oil to 70-95℃, pump it into a multi-stage series gradient microchannel. S2. The steam generated during the process is condensed into a liquid working fluid, which is then passed through a microporous medium to generate a flow of microbubbles with an average diameter of 10-50 μm. S3. Inject the microbubble flow into the gradient microchannel at a volumetric gas content of 1-3%. S4. In the gradient microchannel, the flow field inducement effect is used to cause polar impurities in the waste mineral oil to migrate into the channel and aggregate. S5. The gas-liquid interface of the microbubbles is used to capture and aggregate impurities, so that the microbubbles carrying impurities are separated from the oil phase, and then the purified oil is collected.

2. The process for waste mineral oil regeneration and separation according to claim 1, characterized in that: In step S1, a single periodic unit of the gradient microchannel sequentially includes: a contraction segment with a width that linearly shrinks from 1.5-2.5 mm to 0.2-0.5 mm, a throat with a length of 1.0-3.0 mm, and an expansion segment with a width that linearly expands from 0.2-0.5 mm to 1.5-2.5 mm; the depth of the microchannel is 0.5-1.5 mm.

3. The process for waste mineral oil regeneration and separation according to claim 1, characterized in that: In step S1, the Reynolds number of the waste mineral oil flowing in the gradient microchannel is controlled between 100 and 800.

4. The process for waste mineral oil regeneration and separation according to claim 1, characterized in that: In step S2, the steam is saturated water vapor with a temperature of 100-150℃ and a pressure of 0.1-0.5MPa, and the liquid working fluid has a temperature of 40-60℃ and a pressure of 0.05-0.2MPa.

5. The process for regenerating and separating waste mineral oil according to claim 1, characterized in that: In step S2, the microporous medium is a sintered metal porous membrane; the material of the sintered metal porous membrane is any one of stainless steel, nickel-based alloy or titanium alloy.

6. The process for waste mineral oil regeneration and separation according to claim 1, characterized in that: In step S4, the flow field induced effect is the synergistic effect of inertial secondary flow effect and Marangoni effect; wherein, by maintaining an axial temperature gradient of not less than 10°C in the channel and controlling the dimensionless Dean number between 10 and 50, polar impurities are driven to migrate and coalesce.

7. The process for waste mineral oil regeneration and separation according to claim 1, characterized in that: In step S5, the separation is carried out in a cavity having an oleophobic and hydrophilic inner surface; the oleophobic and hydrophilic inner surface is formed by coating with any one of a silica-based coating, a fluorocarbon polymer coating, or an organosilicon resin coating.

8. A waste mineral oil regeneration and separation device, based on the waste mineral oil regeneration and separation process according to any one of claims 1-7, characterized in that, include: Heating tank (1) is used for preheating waste mineral oil; A liquid pump (2) is connected at its inlet to the heating tank (1) for conveying waste mineral oil; The processing component (4) includes a gradient microchannel (42) and a flow divider (43) for realizing flow field-induced coalescence and separation of impurities; The microbubble assembly (3) is connected to the gradient microchannel (42) via a pipe for injecting microbubble flow into it.

9. The waste mineral oil regeneration and separation device according to claim 8, characterized in that, The microbubble assembly (3) includes: a connecting pipe (32), a condenser (33), a pressurizing pump (34) and a porous element (35) connected in sequence to the connecting pipe (32); the end of the connecting pipe (32) away from the porous element (35) is used to receive the steam generated during the process, and the porous element (35) is a sintered metal porous membrane, the outlet of which is connected to the starting position of the expansion section of the gradient microchannel (42) through a pipe.

10. A waste mineral oil regeneration and separation device according to claim 8, characterized in that, The The processing component (4) also includes a frame (41), the gradient microchannel (42) and the diversion chamber (43) being connected to the frame (41) by bolts, the inlet of the gradient microchannel (42) being connected to the outlet of the liquid pump (2), and its outlet being connected to the inlet of the diversion chamber (43).

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