A method for recovering rolling oil from an aluminum rolling oil-containing filter and detoxifying it

Abstract

The present application relates to the field of hazardous waste resource processing, and particularly relates to a method for recycling rolling oil from aluminum rolling oil-containing filter (hazardous waste HW08) and harmless treatment. The present application separates and desorbs by subsection heating under vacuum environment, and then the quality index of the rolling oil phase obtained by desorption is used to flexibly select and combine one or more processes of distillation cutting, alkali washing, filtration refining and vacuum dehydration; the refined oil product is blended according to the performance requirements to obtain qualified circulating rolling oil which can be directly reused. The oil content of the solid residue after deep desorption is stably lower than 3%, and the hazardous waste HW08 is converted into general industrial solid waste. The present application realizes efficient recycling of rolling oil and complete harmless and reduction of hazardous waste, has strong process adaptability, and has remarkable resource and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste resource utilization, specifically to a method for recovering and harmlessly treating rolling oil from oily filter media used in aluminum rolling. Background Technology

[0002] The aluminum rolling industry, especially aluminum foil production, faces increasingly stringent quality requirements. Rolling oil plays a crucial role in the rolling process, including lubrication, cooling, cleaning, and force transmission; its quality directly impacts product surface quality and production efficiency. To maintain the performance of reusable rolling oil, continuous purification using filtration agents such as diatomaceous earth, clay, and filtrate is necessary. This generates large quantities of oily filter media or oily diatomaceous earth, classified as hazardous waste HW08, with an oil content as high as 20-40 wt%. Roughly estimated, the aluminum rolling industry generates over 100,000 tons of oily filter media annually. Currently, the conventional method for treating oily filter media is incineration or landfill by qualified entities (see the "Technical Guidelines for Hazardous Waste Disposal"). However, this not only wastes rolling oil resources but also incurs high disposal costs and environmental pressure, contradicting environmental and economic principles. The invention patent (CN113388515A) discloses an oil-containing diatomite regeneration process based on the extraction process; the utility model patent (CN205549711U) discloses an oil-containing diatomite recovery device, including rolling oil refining and diatomite regeneration processes. However, although the patent mentions the rolling oil vacuum desorption process, it is difficult to meet the diverse rolling needs, and the regeneration operations such as acid washing and drying of the desorbed diatomite are complicated, resulting in high industrial production costs.

[0003] Therefore, inventing a process that can effectively improve the efficiency of oil-containing filter desorption, reduce production costs, improve the quality of recycled rolling oil, and achieve green and environmentally friendly operation has great application prospects and economic value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for recovering and harmlessly treating rolling oil from aluminum rolling oil-containing filter media (hazardous waste HW08). This invention involves staged heating separation and desorption under vacuum conditions. Based on the quality indicators of the desorbed rolling oil phase, one or more processes, including distillation cutting, alkaline washing, filtration purification, and vacuum dehydration, are flexibly selected for combined refining. The refined oil is then blended according to performance requirements to obtain qualified recycled rolling oil that can be directly reused. The oil content of the solid residue after deep desorption is consistently below 3%, converting hazardous waste HW08 into general industrial solid waste. This invention achieves efficient recovery of rolling oil and complete harmlessness and reduction of hazardous waste, with strong process adaptability and significant resource and environmental benefits.

[0005] This invention discloses a method for recovering and rendering harmless the rolling oil from an oil-containing filter in aluminum rolling, comprising the following steps:

[0006] S1 Vacuum Segmented Desorption Separation: The oil-containing filter material generated during the aluminum rolling process is placed in a closed vacuum desorber, and the system pressure is maintained at -70~-96kPa (gauge pressure). The system is heated in segments to desorb and separate the oil-water fraction, light rolling oil fraction, heavy rolling oil fraction, and desorbed filter material. S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment. S3 Rolling Oil Refining: The light rolling oil fraction and heavy rolling oil fraction collected in step S1 and the oil phase separated in step S2 are refined by one or more processes such as distillation cutting, alkaline washing, filtration refining and vacuum dehydration, depending on the different indicators such as acid value, distillation range, color and moisture content. S4 Oil Blending: The light rolling oil fraction, heavy rolling oil fraction and oil phase that have been refined in step S3 are blended to obtain circulating rolling oil.

[0007] The wastewater generated from each step of the desorption process, such as oil-water separation, alkaline washing, and soft water washing, is neutralized to neutral and then sent to the plant's wastewater treatment system to achieve closed-loop treatment of wastewater throughout the entire process.

[0008] Preferably, in step S1, the oil-containing filter agent is mainly composed of diatomaceous earth, supplemented with one or two of kaolin and filtrate, and the combination forms are three combinations: diatomaceous earth and kaolin, diatomaceous earth and filtrate, and diatomaceous earth, kaolin and filtrate.

[0009] Preferably, in step S1, the segmented heating separation is divided into three stages: the temperature of the first stage is 80~150℃, the temperature of the second stage is 150~260℃, and the temperature of the third stage is 185~310℃. The lower lower limit of the third stage (185℃) is suitable for desorption scenarios where the content of filtrate in the filter is high (>35%).

[0010] Preferably, in step S1, the heating rate is 0.5~1.2℃ / min, and the isothermal time for each temperature range is 30~300min.

[0011] Preferably, in step S3, the distillation cutting process involves reusing the rolled oil fraction with a distillation range of 200~280℃ through a distillation column.

[0012] Preferably, in step S3, the alkaline washing process involves using a sodium hydroxide solution with a mass concentration of 5-15% and stirring and washing at 70-90°C for 20-40 minutes.

[0013] Preferably, the molar ratio of sodium hydroxide to acidic substances in the oil in the sodium hydroxide solution is (1.5~2.5):1.

[0014] Preferably, in step S4, the qualified standard for the circulating rolling oil is a kinematic viscosity of 1.7~2.5 mm at 40°C. 2 / s, flash point ≥80℃, acid value ≤2mgKOH / g, distillation range 200~280℃, transmittance ≥85%.

[0015] Preferably, in step S4, the blending involves uniformly mixing and blending the light and heavy oil phases that have undergone refining processes such as distillation, cutting, alkali washing, filtration, and vacuum dehydration in a specific ratio.

[0016] Preferably, in step S1, the oil content of the desorbing filter is <3%.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a method for recovering and rendering harmless the rolling oil from oily filter media during aluminum rolling, which has the following characteristics: (1) The method provided by the present invention recovers more than 97% of the oil in the oil-containing filter (oil content of the desorbed filter is <3%) through an optimized vacuum segmented desorption process, and the effective recovery rate of qualified oil exceeds 90%. The recovered oil can be directly returned to the rolling system for recycling after refining and blending, which greatly reduces the consumption of new oil, reduces the production cost of enterprises, and conforms to the concept of resource conservation and circular economy.

[0018] (2) After deep desorption treatment, the oil content of the oil-containing filter can be stably reduced to below 3%, and in the preferred embodiment, it can be below 1%. Its hazardous characteristics are completely eliminated, and it is transformed from hazardous waste HW08 into general industrial solid waste. At the same time, the weight of solid residue is significantly reduced. Affected by the fluctuation of the initial oil content of the raw materials, the overall reduction range of solid residue is 25% to 40%. In this experiment, a filter with an initial oil content of 32.2 wt% was used, and the measured reduction was stable at 29% to 33%, which greatly alleviated the environmental disposal pressure of enterprises and reduced production costs.

[0019] (3) The method provided by the present invention can flexibly select and combine refining methods according to the specific deterioration indicators such as acid value, distillation range and transmittance of the recycled rolling oil, which solves the industry problem that it is difficult to recycle the raw oil due to large fluctuations in quality, and significantly improves refining efficiency and oil qualification rate.

[0020] (4) The method provided by the present invention adopts a segmented temperature control strategy in the desorption process, selectively separating different fractions at different temperatures in a vacuum environment, effectively avoiding problems such as overheating cracking and polymerization of rolling oil caused by single high temperature, and at the same time greatly suppressing the catalytic side effects of acidic active sites in the filter, ensuring the quality of the final refined oil.

[0021] (5) The method and process provided by the invention realizes clean production throughout the entire process and ensures that environmental risks are controllable. Detailed Implementation

[0022] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0023] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0024] The qualified standard for circulating rolling oil is a kinematic viscosity of 1.7~2.5 mm at 40℃. 2 / s, flash point ≥80℃, acid value ≤2mgKOH / g, distillation range 200~280℃, transmittance ≥85%.

[0025] Example 1: A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system pressure is maintained at -96 kPa, and segmented heating separation is performed. The heating process is divided into three stages, with a heating rate of 0.8℃ / min. The first stage is at a temperature of 140℃ and a holding time of 60 min, separating and collecting the oil-water fraction. The second stage is at a temperature of 210℃ and a holding time of 120 min, separating and collecting the light rolling oil fraction. The third stage is at a temperature of 300℃ and a holding time of 120 min, separating and collecting the heavy rolling oil fraction. During the heating separation, the remaining solid residue of the desorbed filter material is also collected. The oil-containing filter material is composed of diatomaceous earth and clay in a mass ratio of 4:1. The oil content of the desorbed filter material is <3%.

[0026] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0027] S3 Rolling Oil Refining: Heavy rolling oil D is mixed with oil phase B1 and then fed into a distillation column for distillation and separation, yielding a light fraction with a distillation range of 231~268℃ and a heavy fraction with a distillation range >268℃. The light rolling oil is treated with an alkaline washing process: it is mixed and washed with a 10wt% sodium hydroxide solution at 80℃ for 30 minutes, with a molar ratio of sodium hydroxide to acidic substances in the oil of 2:1. After settling and separation, the oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain refined rolling oil. The aqueous phases generated during the washing and separation processes are combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system. S4 Oil Blending: Light fractions are mixed with refined rolling oil to obtain recycled rolling oil.

[0028] Example 2: A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system pressure is maintained at -96 kPa, and segmented heating separation is performed in three stages at a heating rate of 0.8℃ / min. The first stage is held at 80℃ for 80 min to separate and collect the oil-water fraction. The second stage is held at 150℃ for 140 min to separate and collect the light rolling oil fraction. The third stage is held at 280℃ for 120 min to separate and collect the heavy rolling oil fraction. During the heating separation, the remaining solid residue of the desorbed filter material is also collected. The oil-containing filter material is composed of diatomaceous earth and clay in a mass ratio of 4:1. The oil content of the desorbed filter material is <3%.

[0029] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0030] S3 Rolling Oil Refining: Heavy rolling oil is mixed with the oil phase and then fed into a distillation column for distillation and fractionation, separating a light fraction with a distillation range of 231~255℃ and a heavy fraction with a distillation range of 256~313℃. The light rolling oil is treated with an alkaline washing process: it is mixed and washed with a 5wt% sodium hydroxide solution at 70℃ for 40 minutes, with a molar ratio of sodium hydroxide to acidic substances in the oil of 1.5:1. After settling and separation, the oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain refined rolling oil. The aqueous phases generated during the washing and separation processes are combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system. S4 Oil Blending: Light fractions are mixed with refined rolling oil to obtain recycled rolling oil.

[0031] Example 3: A method for recovering and rendering harmless rolling oil from oily filter media in aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system is maintained at an absolute temperature of -80 kPa, and segmented heating separation is performed in three stages at a heating rate of 0.6℃ / min. The first stage is held at 100℃ for 90 min to separate and collect the oil-water fraction. The second stage is held at 240℃ for 80 min to separate and collect the light rolling oil fraction. The third stage is held at 290℃ for 120 min to separate and collect the heavy rolling oil fraction. During the heating separation, the remaining solid residue of the desorbed filter material is also collected. The oil-containing filter material is composed of diatomaceous earth and clay in a mass ratio of 4:1. The oil content of the desorbed filter material is <3%.

[0032] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0033] S3 Rolling Oil Refining: Heavy rolling oil is mixed with the oil phase and then fed into a distillation column for distillation and fractionation, separating a light fraction with a distillation range of 231~255℃ and a heavy fraction with a distillation range of 256~313℃. The light rolling oil is treated with an alkaline washing process: it is mixed and washed with a 7wt% sodium hydroxide solution at 75℃ for 35 minutes, with a molar ratio of sodium hydroxide to acidic substances in the oil of 1.7:1. After settling and separation, the oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain refined rolling oil. The aqueous phases generated during the washing and separation processes are combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system. S4 Oil Blending: Light fractions are mixed with refined rolling oil to obtain recycled rolling oil.

[0034] Example 4: A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system pressure is maintained at -90 kPa, and segmented heating separation is performed in three stages at a heating rate of 1.0℃ / min. The first stage is held at 120℃ for 90 min to separate and collect the oil-water fraction. The second stage is held at 240℃ for 120 min to separate and collect the light rolling oil fraction. The third stage is held at 310℃ for 90 min to separate and collect the heavy rolling oil fraction. During the heating separation, the remaining solid residue of the desorbed filter material is also collected. The oil-containing filter material is composed of diatomaceous earth and clay in a mass ratio of 4:1. The oil content of the desorbed filter material is <3%.

[0035] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0036] S3 Rolling Oil Refining: Heavy rolling oil is mixed with the oil phase and then fed into a distillation column for distillation and fractionation, separating the light fraction with a distillation range of 232~266℃ and the heavy fraction with a distillation range >266℃. The light rolling oil is treated with an alkaline washing process: it is mixed and washed with a 13wt% sodium hydroxide solution at 85℃ for 25 minutes, with a molar ratio of sodium hydroxide to acidic substances in the oil of 2.3:1. After settling and separation, the oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain refined rolling oil. The aqueous phase generated during the washing and separation process is combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system. S4 Oil Blending: Light fractions are mixed with refined rolling oil to obtain recycled rolling oil.

[0037] Example 5: A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system pressure is maintained at -96 kPa (gauge pressure), and segmented heating separation is performed in three stages at a heating rate of 1.2℃ / min. The first stage is held at 150℃ for 100 min to separate and collect the oil-water fraction. The second stage is held at 250℃ for 100 min to separate and collect the light rolling oil fraction. The third stage is held at 310℃ for 300 min to separate and collect the heavy rolling oil fraction. During the heating separation, the remaining solid residue of the desorbed filter material is also collected. The oil-containing filter material is composed of diatomaceous earth and clay in a mass ratio of 4:1. The oil content of the desorbed filter material is <3%.

[0038] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0039] S3 Rolling Oil Refining: Heavy rolling oil is mixed with the oil phase and then fed into a distillation column for distillation and separation, yielding a light fraction with a distillation range of 231~270℃ and a heavy fraction with a distillation range >270℃. The light rolling oil is treated with an alkaline washing process: it is mixed and washed with a 15wt% sodium hydroxide solution at 90℃ for 20 minutes, with a molar ratio of sodium hydroxide to acidic substances in the oil of 2.5:1. After settling and separation, the oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain refined rolling oil. The aqueous phases generated during the washing and separation processes are combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system. S4 Oil Blending: Light fractions are mixed with refined rolling oil to obtain recycled rolling oil.

[0040] Example 6: A method for recovering and rendering harmless rolling oil from oily filter media in aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system pressure is maintained at -96 kPa (gauge pressure), the temperature is maintained at 210℃, and the constant temperature time is 140 min. The oil and water fractions are separated and collected, and the remaining solid residue of the desorbed filter material is collected at the same time. The oil-containing filter material is composed of diatomaceous earth and white clay in a mass ratio of 4:1. The oil content of the desorbed filter material is <3%.

[0041] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0042] S3 Rolling Oil Refining: The oil phase collected in step S2 is treated by alkaline washing: it is mixed and stirred with a 10wt% sodium hydroxide solution at 80℃ for 30 minutes. The molar ratio of sodium hydroxide to acidic substances in the oil is 2:1. After standing and separation, it is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain circulating rolling oil.

[0043] Example 7: A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: An oil-containing filter medium with an initial oil content of 31.96 wt%, generated during the aluminum rolling process, is introduced into a vacuum desorber. Under a vacuum of -96 kPa, the temperature is increased to 170 °C at a rate of 0.5 °C / min, and then held at this temperature for 270 min to complete desorption. When the desorption temperature reaches 125 °C, the collected liquid is discharged for oil-water separation, yielding an oil phase and a water phase. The oil phase is released after desorption; the oil-containing filter medium consists of diatomaceous earth, kaolin, and filtrate in a mass ratio of 7:2:1.

[0044] S2 Direct Reuse: The above oil phases are directly mixed to obtain total circulating rolling oil. The properties of the circulating rolling oil are as follows: kinematic viscosity at 40℃ 1.797 mmHg. 2 The oil has the following properties: / s, flash point 87℃, acid value 0.03mgKOH / g, H2O content <140ppm, and D86 distillation range 216~241℃. These indicators meet the standards for filtered recycle rolling oil, requiring no further processing in the oil refining process, and can be directly recycled and reused.

[0045] Example 8: A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter medium is placed in the vacuum desorber, and the temperature is increased to 110℃ at a rate of 1.2℃ / min under a vacuum of -96Kpa, and held for 60 min, collecting the oil-water mixture. The temperature is then increased to 150℃ and held for 300 min, collecting the rolling oil. Finally, the temperature is increased to 185℃ and held for 90 min to complete the desorption, collecting the rolling oil. The oil-containing filter medium consists of diatomaceous earth and filtrate in a 1:1 mass ratio.

[0046] S2 Oil Refining: The rolling oil collected in step S1 is filtered and purified. The filtration and purification process is as follows: Fresh diatomaceous earth and rolling oil are stirred and mixed at 40°C to prepare a pre-coating solution with a solid content of approximately 7 wt%. This solution is then pumped into a filter using a circulating pump to form a stable pre-coating layer on the filter element surface. Subsequently, fresh filter media is mixed with diatomaceous earth at a mass ratio of 1:1 to filtrate, controlling the total concentration of the filter media after mixing to approximately 4.5 wt%. Stirring is maintained for 30 minutes to ensure thorough dispersion and adsorption of impurities in the oil. The mixture is then pumped into a filter for filtration to achieve solid-liquid separation, yielding recycled rolling oil.

[0047] Example 9: This example is a comparative example, used to illustrate that the desorption process under normal pressure cannot achieve the beneficial effects of the present invention. A method for recovering and rendering harmless rolling oil from an oil-containing filter in aluminum rolling includes the following steps: S1 Atmospheric Pressure Segmented Desorption Separation: The oil-containing filter medium generated during the aluminum rolling process is placed in a sealed desorber, maintaining the system pressure at 101 kPa (atmospheric pressure). Segmented heating separation is performed in three stages at a rate of 0.8℃ / min. The first stage is held at 140℃ for 60 min to separate and collect the oil-water fraction. The second stage is held at 260℃ for 120 min to separate and collect the light rolling oil fraction. The third stage is held at 300℃ for 120 min to separate and collect the heavy rolling oil fraction. Simultaneously, the remaining solid residue of the desorbed filter medium is collected. The oil-containing filter medium is composed of diatomaceous earth and clay in a 4:1 mass ratio; the oil content of the desorbed filter medium is 7.13%.

[0048] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0049] S3 Rolling Oil Refining: Heavy rolling oil is mixed with the oil phase and then fed into a distillation column for distillation and fractionation, separating a light fraction with a distillation range of 231~255℃ and a heavy fraction with a distillation range of 256~313℃. The light rolling oil is mixed and washed with a 10wt% sodium hydroxide solution at 80℃ for 30 minutes with stirring, and the molar ratio of sodium hydroxide to acidic substances in the oil is 2:1. After settling and separation, the oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5kPa (approximately -96~-96kPa gauge pressure) to finally obtain refined rolling oil. The aqueous phases generated during the washing and separation processes are combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system.

[0050] S4 Oil Blending: Light fractions are mixed with refined rolling oil to obtain recycled rolling oil.

[0051] Example 10: A method for recovering and rendering harmless rolling oil from oily filter media in aluminum rolling, comprising the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material with an initial oil content of 32.2 wt% generated during the aluminum rolling process is placed in a sealed vacuum desorber. The system pressure is maintained at -96 kPa, and segmented heating separation is performed in three stages at a heating rate of 0.8℃ / min. The first stage is held at 140℃ for 60 min to separate and collect the oil-water fraction. The second stage is held at 210℃ for 120 min to separate and collect the light rolling oil fraction. The third stage is held at 300℃ for 120 min to separate and collect the heavy rolling oil fraction. During the heating separation, the remaining solid residue of the desorbed filter material is also collected. The oil-containing filter material is composed of diatomaceous earth and clay in a mass ratio of 4:1. The oil content of the desorbed filter material is 0.34%.

[0052] S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment.

[0053] S3 Rolling Oil Refining: Heavy rolling oil is mixed with the oil phase and light rolling oil, and then washed with a 10wt% sodium hydroxide solution at 80℃ for 30 minutes with stirring. The molar ratio of sodium hydroxide to acidic substances in the oil is 2:1. The mixture is then allowed to stand for separation. The oil phase is washed with soft water and then vacuum dehydrated at 70℃ and an absolute pressure of 2~5 kPa (approximately -96~-96 kPa gauge pressure) to obtain refined rolling oil. The aqueous phases generated during washing and separation are combined and neutralized to pH neutral with 20wt% dilute sulfuric acid to obtain a neutral aqueous solution, which is then sent to the plant's wastewater treatment system.

[0054] S4 Oil Blending: The refined rolling oil has been tested and its final boiling point is 313℃.

[0055] The properties of the rolling oil recovered in Examples 1-10 were tested, and the results are shown in Tables 1-2 below: Table 1

[0056] Table 2

[0057] From the data in Tables 1 and 2 above, we can see that: (1) The total recovery rate of Examples 1-5 remained stable at 28.28-29.86%, with an effective recovery rate of 94.35-96.43%. The oil content of the desorbed filter was 0.34-2.42%, lower than 3%, meeting the standards for general industrial solid waste. The kinematic viscosity of the recovered oil at 40℃ was 2.21-2.26 mm² / s, the flash point was 100-103℃, the acid value was 0.01-0.03 mgKOH / g, the distillation range was 231-270℃, and the transmittance was 90%-95%, showing no significant difference from fresh rolling oil. Therefore, the rolling oil recovered in Examples 1-5 can be recycled. The reason why the rolling oil recovered by the method provided by this invention has high quality and recovery rate is that the vacuum environment lowers the boiling point of the rolling oil by 80~120℃, and the three-stage temperature control realizes the selective separation of oil and water, light oil and heavy oil, which not only avoids oil cracking caused by high temperature alone, but also inhibits the catalytic oxidation of residual aluminum powder; alkaline washing neutralizes acidic impurities and distillation cutting precisely controls the distillation range, which together ensure the quality of the recovered oil.

[0058] (2) The oil-containing filter in Example 7 was composed of diatomaceous earth, clay, and filtrate in a mass ratio of 7:2:1. The rolling oil contained in it had a relatively light distillation range and a slight degree of oil deterioration. Therefore, a single desorption temperature was used to desorb and recover the rolling oil: only a constant temperature desorption at 170℃ for 270 minutes was used, without three-stage temperature-controlled desorption. No refining process was required after desorption, and the effective recovery rate reached 99.45%. Although the recovered oil could be directly reused, the reduction rate was 30.48%, and there was still considerable room for optimization in the resource recovery rate. The oil content of the desorption residue was 2.89%, which was very close to 3%. In actual production, the flexibility of the desorption operation was limited to a certain extent. The oil-containing filter in Example 8 was composed of diatomaceous earth and filtrate in a mass ratio of 1:1. Only filtration refining was used to remove colloids and fine impurities. The transmittance increased from 80% to 89%, the total recovery rate was 29.32%, the effective recovery rate was 98.79%, and the oil content of the desorption residue was 0.57%. Although the acid value was 0.51 mg KOH / g due to the lack of alkaline washing, washing with 10 wt% sodium hydroxide solution for 30 minutes reduced the acid value to 0.05 mg KOH / g, meeting the reuse standard. This invention employs a modular, combined refining system, allowing for flexible selection of single or combined processes such as alkaline washing, filtration, and distillation based on the degradation indicators of the recovered oil, including acid value, distillation range, and transmittance. This solves the industry problem of traditional processes being unable to adapt to fluctuations in raw material quality.

[0059] (3) Example 6 is a single-temperature desorption recovery of rolling oil: only 210℃ isothermal desorption was used without three-stage temperature control, resulting in a narrow boiling range of the recovered oil, which is 221~253℃. Compared with the final boiling point of the corresponding circulating rolling oil, the value is low, but it does not affect the recovery and use; the reduction rate is 30.35%, the total recovery rate is 28.64%, and the effective recovery rate is 97.09%. Although the total recovery rate and effective recovery rate are not inferior in the multiple examples in this article, the oil content of the desorption residue is 2.66%, which is still general solid waste, but close to 3%, resulting in low flexibility of desorption operation in actual production. Comparative Example 9 is the rolling oil recovered by atmospheric pressure segmented desorption. Staged heating desorption under normal pressure leads to deep thermal cracking and oxidation of the oil, increasing the acid value to 5.67 mg KOH / g and lowering the flash point to 72℃. The effective recovery rate is only 87.86%, and the recovered rolling oil is of substandard quality, with an oil content of 9.52% in the desorption residue, which is still hazardous waste. Subsequent treatment is not environmentally friendly and is costly. Example 10 shows rolling oil recovered without distillation and cutting. The desorption steps are the same as in Example 1, and the total recovery rate and effective recovery rate in the desorption stage are comparable to those in Example 1. However, the direct mixing of heavy and light oils forms a wide-fraction system with a final boiling point of 313℃, exceeding the acceptable range of 200~280℃, making it unsuitable for aluminum rolling processes. At the same time, the mixing of heavy and light components easily forms a stable emulsion during alkaline washing and water washing, increasing the risk of oil loss due to entrainment in the aqueous phase. This also shows that distillation and cutting can not only control the oil distillation range but also avoid emulsion loss and ensure final recovery efficiency.

[0060] In summary, the method for recovering and harmlessly treating rolling oil from oily filter media in aluminum rolling processes provided by this invention utilizes a synergistic system of vacuum segmented desorption and combined refining to stably recover high-quality rolling oil while simultaneously converting hazardous waste into general solid waste. Furthermore, it is adaptable to different proportions of raw materials such as diatomaceous earth, clay, and filtrate, and the refining process can be flexibly adjusted according to the degree of oil deterioration. This approach achieves both high-quality recovery and meets the demand for low-cost direct reuse, making it suitable for large-scale industrial application in the aluminum rolling industry.

[0061] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for recovering and rendering harmless rolling oil from oily filter media during aluminum rolling, characterized in that, Includes the following steps: S1 Vacuum Segmented Desorption Separation: The oil-containing filter material generated during the aluminum rolling process is placed in a closed vacuum desorber, and the system pressure (gauge pressure) is maintained at -70~-96kPa. Segmented heating separation is carried out to collect oil-water fraction, light rolling oil fraction, heavy rolling oil fraction and desorbed filter material. S2 Oil-water separation: The oil and water fractions collected in step S1 are separated by static stratification or centrifugation to obtain an oil phase and a water phase. The water phase is sent to the plant's wastewater treatment system for treatment. S3 Rolling Oil Refining: The light rolling oil fraction and heavy rolling oil fraction collected in step S1 and the oil phase separated in step S2 are refined by one or more processes such as distillation cutting, alkaline washing, filtration refining and vacuum dehydration, depending on the acid value, distillation range, color and moisture content. S4 Oil Blending: The light rolling oil fraction, heavy rolling oil fraction and oil phase that have been refined in step S3 are blended to obtain rolling oil for recycling.

2. The method for recovering and harmlessly treating rolling oil from oily filter media during aluminum rolling, as described in claim 1, is characterized in that... In step S1, the oil-containing filter agent is mainly composed of diatomaceous earth, supplemented with one or two of kaolin and filtrate, and the combination forms are diatomaceous earth and kaolin, diatomaceous earth and filtrate, and diatomaceous earth, kaolin and filtrate.

3. The method for recovering and harmlessly treating rolling oil from oily filter media during aluminum rolling, as described in claim 1, is characterized in that... In step S1, the segmented heating and separation is divided into three segments: the temperature of the first segment is 80~150℃, the temperature of the second segment is 150~260℃, and the temperature of the third segment is 185~330℃.

4. The method for recovering and harmlessly treating rolling oil from oily filter media during aluminum rolling, as described in claim 1, is characterized in that... In step S1, the heating rate is 0.5~1.2℃ / min, and the isothermal time for each temperature range is 30~300min.

5. A method for recovering and harmlessly treating rolling oil from an oil-containing filter medium during aluminum rolling, as described in claim 1, characterized in that, In step S3, the distillation cutting process reuses the rolling oil fraction with a distillation range of 200~280℃ by retaining it in the distillation column.

6. A method for recovering and harmlessly treating rolling oil from an oil-containing filter medium during aluminum rolling, as described in claim 1, characterized in that... In step S3, the alkaline washing process involves using a sodium hydroxide solution with a mass concentration of 5-15% and stirring and washing at 70-90°C for 20-40 minutes.

7. A method for recovering and harmlessly treating rolling oil from an oil-containing filter medium during aluminum rolling, as described in claim 6, characterized in that, The molar ratio of sodium hydroxide to acidic substances in the oil in the sodium hydroxide solution is (1.5~2.5):

1.

8. A method for recovering and harmlessly treating rolling oil from an oil-containing filter medium during aluminum rolling, as described in claim 1, characterized in that, In step S4, the qualification standard for the circulating rolling oil is a kinematic viscosity of 1.7~2.5 mm at 40°C. 2 / s, flash point ≥80℃, acid value ≤2.0mgKOH / g, distillation range 200~280℃, transmittance ≥85%.

9. A method for recovering and harmlessly treating rolling oil from an oil-containing filter medium during aluminum rolling, as described in claim 1, characterized in that, In step S4, the blending involves mixing and blending the light rolling oil, heavy rolling oil, and oil-water separated oil phase after distillation, cutting, alkali washing, filtration, and vacuum dehydration to obtain recycled rolling oil that meets the reuse standards.

10. A method for recovering and rendering harmless the rolling oil from an oil-containing filter medium during aluminum rolling, as described in claim 1, characterized in that, In step S1, the oil content of the desorbing filter is <3%.

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