Method for comprehensive utilization of waste white clay generated in adsorptive refining of regenerated base oil

Abstract

This invention discloses a method for the comprehensive utilization of waste bleaching clay generated from the adsorption and refining of recycled base oil, belonging to the field of hazardous waste resource utilization technology. The method utilizes rotary pyrolysis, rotary calcination, and sulfuric acid acidification as core steps. First, the waste bleaching clay is fed into a rotary pyrolysis furnace for pyrolysis, and the liquid waste oil is recovered by condensation and separation, yielding black waste bleaching clay with an oil content of <0.5%. Then, the black waste bleaching clay is calcined in a rotary calcination kiln to completely remove carbon components, obtaining a pure bleaching clay matrix. Finally, the matrix is ​​mixed with a sulfuric acid solution for acidification and activation, and post-treatment yields activated bleaching clay. Through the synergistic effect of these three processes, 85-95% of the waste oil can be efficiently recovered and recycled for fuel, and the regenerated activated bleaching clay has a specific surface area of ​​180-220 m². 2 / g, decolorization rate of 90-98%, still maintains high adsorption performance after 3-5 cycles, no wastewater discharge throughout the process, stable equipment operation, and both environmental protection and economic benefits, making it suitable for large-scale industrial promotion.

Description

Technical Field

[0001] This invention belongs to the field of hazardous waste resource utilization technology, specifically relating to a method for the comprehensive utilization of waste clay generated from the adsorption and refining of recycled base oil. Background Technology

[0002] Regenerated base oil is a base oil product that meets national standards, obtained through a series of processes including vacuum distillation, solvent refining, hydrorefining, and adsorption refining of waste lubricating oil. In the adsorption refining process of regenerated base oil, activated clay is the most commonly used adsorbent. Due to its large specific surface area, abundant pore structure, and excellent adsorption performance, it can effectively adsorb harmful substances such as pigments, colloids, asphaltenes, and metallic impurities in the regenerated base oil. However, activated clay loses its adsorption activity after adsorption saturation, forming waste clay. This waste clay contains a large amount of adsorbed oil, as well as various adsorbed impurities. Improper disposal can cause serious pollution to soil, water, and air; direct incineration will produce large amounts of toxic and harmful fumes, exacerbating air pollution and wasting both the oil and clay resources in the waste clay.

[0003] Currently, the main methods for disposing of waste bleaching clay in the industry include landfill, incineration, solvent extraction, pressing for oil removal, and simple regeneration, all of which have significant drawbacks. Furthermore, existing related patent technologies have failed to solve the core problems. For example, patent application CN114682238A provides a method for regenerating waste bleaching clay by using an acidic ionic liquid to react with the waste bleaching clay thermally, achieving waste oil recovery and clay regeneration. However, the acidic ionic liquid used in this method is expensive, the process is complex, and the thermal reaction time is long, making it difficult to achieve large-scale industrial application. Moreover, it does not involve the removal of carbon components, resulting in limited adsorption performance of the regenerated bleaching clay. Another example is invention patent CN1709595A, which uses an alkaline boiling for oil removal, drying, calcination at 500℃ for 2 hours, and acidification with 10% sulfuric acid to regenerate bleaching clay. However, the alkaline boiling for oil removal has a low rate, generates a large amount of wastewater, the calcination temperature is too low and the time too short to completely remove carbon components, the sulfuric acid concentration is too low, the bleaching clay activation effect is poor, the decolorizing power of the regenerated bleaching clay is low, and it cannot achieve efficient recovery of waste oil, still resulting in resource waste and secondary pollution.

[0004] Therefore, developing a method that is simple in process, low in energy consumption, and free from secondary pollution, and can realize the full resource utilization of waste bleaching clay, has become an urgent problem to be solved in the industry. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for the comprehensive utilization of waste bleaching clay generated from the adsorption and refining of recycled base oil, which solves the problems of low resource utilization rate, serious secondary pollution, and complex process in the existing treatment of waste bleaching clay generated from the adsorption and refining of recycled base oil.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for the comprehensive utilization of waste bleaching clay generated during the adsorption and refining of recycled base oil includes the following core steps: (1) Rotary pyrolysis treatment: The waste bleaching clay produced by the adsorption and refining of regenerated base oil is sent to a rotary pyrolysis furnace for pyrolysis. The gas produced by pyrolysis is separated by condensation to obtain liquid waste oil and non-condensable gas. The solid product discharged after pyrolysis is black waste bleaching clay coated with carbon, and the oil content of the black waste bleaching clay is <0.5%; (2) Rotary calcination treatment: The black waste white clay is sent into a rotary calcination kiln for calcination to completely remove the carbon components in the solid and obtain pure waste white clay matrix; (3) Sulfuric acid acidification treatment: Pure waste clay matrix is ​​mixed with sulfuric acid solution for acidification and activation treatment. After acidification, activated clay is obtained through post-treatment. The activated clay can be recycled for the regeneration base oil adsorption and refining process.

[0007] This method achieves resource utilization of waste bleaching clay through a three-step synergistic process of rotary pyrolysis, rotary calcination, and sulfuric acid acidification. The high-temperature, oxygen-free environment of the rotary pyrolysis furnace enables efficient pyrolysis, removal, and recovery of oil from the waste bleaching clay, simultaneously forming carbon-containing black waste bleaching clay. Then, the high-temperature, oxygen-rich environment of the rotary calcination kiln completely oxidizes and decomposes the carbon components in the black waste bleaching clay, yielding a pure bleaching clay matrix free of carbon residue, laying the foundation for subsequent activation. Finally, the cation exchange and moderate dissolution effects of sulfuric acid solution are used to acidify and activate the pure bleaching clay matrix, unclogging pores and increasing adsorption active sites, restoring the bleaching clay's adsorption performance. This allows for regeneration and recycling for the adsorption and refining of regenerated base oil. The entire process relies on the uniform mass and heat transfer characteristics of the rotary equipment to ensure sufficient reaction and stable results in each step, achieving the dual goals of waste oil recovery and bleaching clay regeneration.

[0008] Furthermore, the waste bleaching clay undergoes pretreatment before being fed into the rotary pyrolysis furnace: mechanical impurities are removed, it is crushed to 100-150 mesh, and dried to a moisture content of 5-8%; the oil content of the waste bleaching clay is 20-60%, and its main components are: 40-50% montmorillonite, 15-20% kaolinite, 10-15% quartz, 20-60% adsorbed oil, 1-3% carbonaceous impurities, and other trace impurities.

[0009] Removing mechanical impurities can prevent hard impurities from wearing down the furnace body and transmission components of the rotary pyrolysis furnace and calcining kiln, ensuring stable equipment operation; pulverizing to 100-150 mesh increases the specific surface area of ​​waste clay, making it easier for oil to evaporate during pyrolysis and to fully contact with inert gas, thus improving oil removal efficiency; drying to a moisture content of 5-8% prevents water from rapidly vaporizing and causing boiling during high-temperature pyrolysis, which would disrupt the stable pyrolysis environment inside the furnace.

[0010] Furthermore, in step (1), the preheating temperature of the rotary pyrolysis furnace is 300-350℃, the preheating time is 30-45 min, and inert gas is used for protection during the pyrolysis process, with a flow rate of 50-80 m / s. 3 / h; the condensation temperature of the condensation system is 15-25℃.

[0011] Preheat to 300-350℃ and hold for 30-45 minutes to ensure uniform heating of the waste clay, avoiding localized overheating and coking, and incomplete oil decomposition caused by direct high-temperature pyrolysis; during pyrolysis, introduce 50-80m³ of air. 3 / h inert gas creates an oxygen-free environment, preventing the oil and carbon in the waste clay from oxidizing and burning; the condensation temperature is controlled at 15-25℃, which allows the oil and gas to be fully condensed into liquid waste oil, improving the oil recovery rate.

[0012] Furthermore, in step (2), the preheating temperature of the rotary kiln is 400-450℃ and the preheating time is 45-60min; after calcination, the pure waste clay matrix is ​​cooled to room temperature and then sent to step (3). The cooling method is natural cooling or forced air cooling, and the cooling time is 1-2h.

[0013] Preheat to 400-450℃ and hold for 45-60 minutes to ensure uniform heating of the black waste clay and avoid incomplete combustion of local carbon components caused by direct high-temperature calcination; after calcination, cool to room temperature to prevent the high-temperature clay matrix from directly contacting the sulfuric acid solution, which could cause thermal shock and damage to the pore structure due to sudden temperature changes; natural / forced air cooling can ensure uniform cooling and prevent matrix clumping.

[0014] Furthermore, in step (1), the temperature of the rotary pyrolysis is controlled at 400-480℃, the pyrolysis time is 2-3h, the rotation speed of the rotary pyrolysis furnace is 2-5rpm, and the feed rate is 100-150kg / h.

[0015] The optimal range for pyrolysis temperature is 400-480℃, which is the range in which oil is fully pyrolyzed and removed without damaging the crystal structure of kaolin. If the temperature is too low, the oil will not be completely removed, and if it is too high, the montmorillonite crystals of the kaolin will collapse. A pyrolysis time of 2-3 hours combined with a feed rate of 100-150 kg / h ensures that the waste kaolin has sufficient heating time in the furnace to achieve deep oil removal. The rotation speed ensures that the material in the furnace is rolled evenly, avoiding local accumulation and uneven heating.

[0016] Furthermore, in step (2), the temperature of rotary calcination is controlled at 550-600℃, the calcination time is 4-6 hours, the rotation speed of the rotary calcining kiln is 1-3 rpm, and air is introduced during the calcination process at a velocity of 200-300 m / s. 3 / h.

[0017] Calcination at 550-600℃ for 4-6 hours ensures complete oxidation and decomposition of carbon components into CO2, achieving thorough decarbonization. Too low a temperature or too short a time will leave carbon residue, while too high a temperature will damage the porous structure of the clay matrix. Rotation speed ensures uniform tumbling of the material, achieving complete combustion. 200-300m 3 An airflow rate of / h provides sufficient oxygen for the combustion of carbon components and can also promptly carry away the CO2 produced by combustion.

[0018] Furthermore, in step (3), the mass fraction of sulfuric acid solution is 20-30%, the solid-liquid ratio of pure waste clay matrix to sulfuric acid solution is 1g:(2-4)mL, the acidification temperature is 70-90℃, and the acidification time is 1.5-3h.

[0019] With a sulfuric acid mass fraction of 20-30%, it can undergo moderate cation exchange and dissolution reactions with the kaolin matrix, clearing pores and increasing active sites; the solid-liquid ratio ensures that the sulfuric acid solution fully coats the kaolin matrix, making the reaction uniform; the acidification temperature of 70-90℃ and the time of 1.5-3h increase the ion exchange reaction rate and shorten the activation time.

[0020] Furthermore, in step (3), during the sulfuric acid acidification process, a stirring device is used for continuous stirring at a speed of 150-200 rpm; the post-treatment includes filtration, washing, drying, crushing, and sieving. Deionized water is used for washing until the pH of the washing solution is 6.5-7.5. The drying temperature is 105-110℃ and the drying time is 2-3 hours. After crushing, the solution is sieved through a 200-300 mesh sieve.

[0021] Stirring at 150-200 rpm ensures thorough mixing of the clay matrix and sulfuric acid solution, improving mass transfer efficiency and guaranteeing uniform activation reaction. In post-treatment, filtration separates the acidified solution from the matrix, and deionized water washing removes residual sulfate ions to prevent residual acid radicals from affecting the adsorption performance of the activated clay. Drying at 105-110℃ for 2-3 hours removes moisture while avoiding high-temperature damage to the pore structure of the activated clay. Finally, pulverizing through a 200-300 mesh sieve ensures uniform activated clay particles, increases specific surface area, and enhances adsorption performance.

[0022] Furthermore, the liquid waste oil obtained in step (1) has a recovery rate of 85-95% of the total oil content in the waste bleaching clay. After being refined by vacuum distillation, the liquid waste oil can be used as a raw material for blending recycled base oil. The non-condensable gas mainly consists of light hydrocarbons with a calorific value of 35,000-45,000 kJ / m³. 3 It can be recycled as fuel for rotary pyrolysis furnaces and rotary calcining kilns.

[0023] With an oil recovery rate of 85-95%, waste oil resources are maximized. After being refined by vacuum distillation, trace impurities are removed from the liquid waste oil, meeting the requirements for raw materials for blending recycled base oil. The non-condensable gases are light hydrocarbons with good combustion performance. They can be recycled as fuel for cracking furnaces and calcining kilns, replacing external fossil fuels, reducing process energy consumption and operating costs, while realizing the resource utilization of process waste gas and reducing pollutant emissions.

[0024] Furthermore, the activated clay obtained in step (3) has a specific surface area of ​​180-220 m². 2 / g, pore volume 0.25-0.35cm³ 3 / g, the decolorization rate of recycled base oil is 90-98%, the adsorption capacity of impurities in recycled base oil is 0.15-0.25g / g, and the decolorization rate is still above 85% after 3-5 cycles; the wastewater generated in the whole process can be recycled for the washing process after neutralization treatment, and there is no wastewater discharge.

[0025] The specific surface area and pore volume ensure that the activated clay has sufficient adsorption sites; it still maintains excellent decolorization rate after 3-5 cycles. Because the activated clay has a stable crystal structure and the pores are not easily blocked, it ensures reusability and significantly reduces the company's adsorbent procurement costs; the process wastewater is neutralized and then recycled for washing to remove acidic impurities from the wastewater, so that the water quality meets the washing requirements, achieves zero wastewater discharge, avoids secondary water pollution, and at the same time reduces the consumption of fresh water and lowers the cost of process water.

[0026] The beneficial effects of this invention are: (1) The rotary pyrolysis process employed in this invention achieves efficient recovery of waste oil and effective separation of carbon slag. By subjecting waste bleaching clay with an oil content of 20-60% to rotary pyrolysis in an inert atmosphere at 400-480℃, on the one hand, most of the adsorbed oil is efficiently recovered as liquid fuel oil, which can be directly used for base oil blending, thus realizing resource utilization; on the other hand, the remaining heavy components are pyrolyzed into solid carbon, forming black waste bleaching clay with extremely low oil content. At the same time, the high-calorific-value non-condensable gas generated by pyrolysis can be used as system fuel, realizing internal energy recycling.

[0027] (2) This invention utilizes rotary calcination to clean the bleaching clay matrix. By rotary calcining the black waste bleaching clay at 550-600℃ under air-circulated conditions, the residual carbon components after the first-step pyrolysis can be completely oxidized and removed. This not only purifies the bleaching clay but, more importantly, removes carbonaceous impurities that clog the original pores of the clay, restoring the high specific surface area and porous structure of the bleaching clay carrier, thus providing a pure matrix with good adsorption potential for subsequent activation and regeneration. The rotary equipment ensures uniform heating and thorough calcination of the material.

[0028] (3) This invention utilizes sulfuric acid acidification to restore the adsorption activity of bleaching clay. The purified waste bleaching clay matrix obtained after calcination is activated by acidification with a 20-30% sulfuric acid solution at 70-90℃. This step utilizes the ion exchange and dissolving effects of sulfuric acid to adjust the surface acidity sites of the bleaching clay, enhancing its chemical adsorption capacity; and further unblocks and widens the pores, optimizing its physical adsorption structure. The resulting activated bleaching clay exhibits good recovery of specific surface area and pore volume, excellent adsorption capacity, and can be recycled multiple times with stable performance, thus realizing the recycling of waste bleaching clay into a highly efficient adsorbent.

[0029] (4) The method provided by this invention fully recovers and utilizes the oil, bleaching clay, and energy in waste bleaching clay: Firstly, oil is utilized as a resource; the adsorbed oil is efficiently extracted and recovered through rotary pyrolysis, and the resulting liquid oil can be refined and used as high-quality fuel or returned to the production process of recycled base oil. Secondly, energy is utilized as a resource; the non-condensable gas generated during the pyrolysis process has a high calorific value and can be directly used as supplementary fuel for the rotary pyrolysis furnace and rotary calcining kiln in the system, significantly reducing external energy consumption. Thirdly, the solid matrix is ​​utilized as a resource; through calcination purification and acidification activation, the deactivated bleaching clay carrier is restored and its adsorption performance is improved, regenerating it into recyclable qualified activated bleaching clay. In addition, the acidic wastewater generated during the process can be completely reused in the washing process of activated bleaching clay after neutralization treatment, achieving zero discharge of process wastewater. In summary, this process chain has a high degree of integration and thorough resource conversion, fundamentally solving the technical defects of existing technologies such as low resource utilization rate, high risk of secondary pollution, and complex process flow. It has significant environmental and economic benefits and broad prospects for industrial application. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0031] Example 1

[0032] This embodiment provides a method for the comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil, which is prepared through the following steps: 1. Pretreatment: The waste clay (oil content 45%) generated from the adsorption and refining of recycled base oil is sent to the pretreatment device. Mechanical impurities are removed by a vibrating screen (screen mesh size 1mm), and then it is sent to a universal pulverizer to be pulverized to 120 mesh. It is then dried at 85℃ for 1.5h, and the moisture content is controlled to be 6-7%. 2. Rotary pyrolysis treatment: Start the rotary pyrolysis furnace, preheat to 320℃ (preheat for 40 min), and introduce nitrogen gas (flow rate 65 m / s). 3 / h), adjust the condensation system to 20℃, control the furnace rotation speed to 3rpm; feed the pretreated waste white clay into the furnace at a feed rate of 120kg / h, pyrolyze at 440℃ for 2.5h, the gas produced by pyrolysis is separated by condensation to obtain liquid waste oil and non-condensable gas, and black waste white clay with an oil content of <0.5% is discharged. 3. Rotary calcination treatment: Start the rotary calcining kiln, preheat to 420℃ (preheat for 50 minutes), control the kiln rotation speed to 2 rpm, and introduce air (flow rate 250 m / s). 3 / h); The black waste white clay is fed into the kiln and calcined at 570℃ for 5 hours. After calcination, it is naturally cooled to room temperature for 1.5 hours to obtain pure waste white clay matrix; 4. Sulfuric acid acidification treatment: In the acidification reactor, 98% concentrated sulfuric acid is mixed with deionized water to prepare a 25% sulfuric acid solution (stirring speed 120 rpm, mixing temperature ≤50℃); pure waste bleaching clay matrix is ​​fed into the reactor, and sulfuric acid solution is added at a solid-liquid ratio of 1:3 (g / mL). The mixture is continuously stirred at 180 rpm and acidified at 80℃ for 2.5 h; after acidification, the filter cake and acidic wastewater are separated by filtration. The filter cake is washed with deionized water until the pH of the washing liquid reaches 7.0, dried at 108℃ for 2.5 h, and pulverized to 250 mesh to obtain activated bleaching clay. 5. Post-treatment: Activated clay is sampled and tested, and sealed and stored after passing the test; acidic wastewater is adjusted to pH=7.0 by adding 20% ​​sodium hydroxide solution, and after precipitation and filtration, it is recycled for washing; liquid waste oil is purified by vacuum distillation at 220℃ and 0.085MPa, and used for blending of regenerated base oil; non-condensable gases are purified and used as process fuel, and CO2 is discharged after washing and purification with water.

[0033] Example 2

[0034] The difference between this embodiment and Example 1 is that the rotary pyrolysis temperature is 400℃, the pyrolysis time is 3h, the sulfuric acid concentration is 20%, the solid-liquid ratio is 1:2 (g / mL), and the acidification time is 3h.

[0035] The remaining raw materials and preparation process are the same as in Example 1.

[0036] Example 3

[0037] The difference between this embodiment and Example 1 is that the rotary pyrolysis temperature is 480℃ and the pyrolysis time is 2h, the rotary calcination temperature is 600℃ and the calcination time is 4h, the sulfuric acid concentration is 30%, the solid-liquid ratio is 1:4 (g / mL), and the acidification time is 1.5h.

[0038] The remaining raw materials and preparation process are the same as in Example 1.

[0039] Example 4

[0040] The difference between this embodiment and Example 1 is that the rotary pyrolysis temperature is 420℃, the rotary calcination temperature is 560℃, the calcination time is 5.5h, the sulfuric acid concentration is 22%, the solid-liquid ratio is 1:2.5 (g / mL), and the acidification time is 2h.

[0041] The remaining raw materials and preparation process are the same as in Example 1.

[0042] Example 5

[0043] The difference between this embodiment and Example 1 is that the rotary pyrolysis temperature is 460℃, the rotary calcination temperature is 580℃, the calcination time is 4.5h, the sulfuric acid concentration is 28%, the solid-liquid ratio is 1:3.5 (g / mL), and the acidification time is 2h.

[0044] The remaining raw materials and preparation process are the same as in Example 1.

[0045] Example 6

[0046] The difference between this embodiment and Example 1 is that the rotary pyrolysis temperature is 430℃, the rotary calcination temperature is 575℃, the calcination time is 5h, the sulfuric acid concentration is 24%, the solid-liquid ratio is 1:3 (g / mL), and the acidification time is 2.2h.

[0047] The remaining raw materials and preparation process are the same as in Example 1.

[0048] Example 7

[0049] The difference between this embodiment and Example 1 is that the rotary pyrolysis temperature is 450℃, the rotary calcination temperature is 590℃, the calcination time is 4.8h, the sulfuric acid concentration is 26%, the solid-liquid ratio is 1:3 (g / mL), and the acidification time is 2.3h.

[0050] The remaining raw materials and preparation process are the same as in Example 1.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that the rotary pyrolysis treatment step is removed, and the pretreated waste clay is directly subjected to rotary calcination treatment.

[0053] The remaining raw materials and preparation process are the same as in Example 1.

[0054] Comparative Example 2

[0055] The difference between this comparative example and Example 1 is that the rotational pyrolysis temperature is 380℃ (not within the 400-480℃ range of this invention), and the pyrolysis time is still 2.5h.

[0056] The remaining raw materials and preparation process are the same as in Example 1.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that the rotary calcination temperature is 500°C and the calcination time is 3 hours.

[0059] The remaining raw materials and preparation process are the same as in Example 1.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the sulfuric acid concentration is 15%.

[0062] The remaining raw materials and preparation process are the same as in Example 1.

[0063] Comparative Example 5

[0064] The difference between this comparative example and Example 1 is that fixed-bed calcination is used instead of rotary calcination, while the other parameters of fixed-bed calcination are the same as those of rotary calcination in Example 1.

[0065] The remaining raw materials and preparation process are the same as in Example 1.

[0066] Performance testing

[0067] 1. Oil content test of black waste clay

[0068] Soxhlet extraction was used: 10g of black waste clay sample was weighed and extracted continuously for 4 hours with n-hexane as the extractant. After extraction, the sample was dried at 105℃ to constant weight. The oil content was calculated according to the formula: oil content = (mass of sample before extraction - mass of sample after extraction) / mass of sample before extraction × 100%.

[0069] 2. Carbon content test of pure white clay matrix

[0070] The combustion-infrared absorption method was used: 2g of sample was weighed and completely burned at 800℃. The CO2 content produced by combustion was detected by an infrared analyzer, and the carbon content in the sample was calculated.

[0071] 3. Waste oil recovery rate test

[0072] The formula is as follows: Waste oil recovery rate = (mass of recovered liquid waste oil / total oil content in waste clay) × 100%, where the total oil content in waste clay = total feed mass of waste clay × initial oil content of waste clay (45%).

[0073] 4. Decolorization rate test of activated clay

[0074] Take 5g of activated clay and add 100mL of regenerated base oil (initial color -10 Cybott, impurity content 0.5g / L). Stir in a 60℃ constant temperature water bath for 30min. After filtration, use a Cybott colorimeter to test the color of the filtrate. Calculate the decolorization rate according to the formula: Decolorization rate = (absolute value of initial color - absolute value of color after filtration) / absolute value of initial color × 100% (a negative color value indicates that the oil color is darker, and the larger the absolute value, the darker the color).

[0075] 5. Decolorization rate test of activated clay after 5 cycles

[0076] The activated clay was repeatedly used in the adsorption and refining process of the regenerated base oil. The conditions for each use were the same as those for the decolorization rate test (5g clay / 100mL base oil, stirring at 60℃ for 30min). The decolorization rate was tested and recorded after 5 cycles.

[0077] The results are shown in Table 1: Table 1

[0078] As shown in Table 1, Examples 1-7 all followed the process route of this invention, with only the specific parameters of each step adjusted. All core indicators met the requirements of this invention, verifying the synergistic optimization of process parameters. Specifically, in the rotary pyrolysis stage, the temperature range of 400-480℃ ensured that the oil content of the black waste clay in all examples was <0.5%, and the waste oil recovery rate was over 85%. This temperature range not only achieved sufficient oil removal and efficient waste oil recovery but also did not damage the clay crystal structure. In Example 3, at a pyrolysis temperature of 480℃, the oil content was as low as 0.28%, and the recovery rate was as high as 94.1%, further verifying the positive correlation between pyrolysis temperature and deoiling and recovery efficiency. In the rotary calcination stage, the parameter combination of a calcination temperature of 550-600℃ and a calcination time of 4-6 hours ensured that the carbon content of the pure clay matrix in all examples was <0.1%, effectively removing oil. To remove the residual carbon components after pyrolysis, a pure, impurity-free clay matrix is ​​provided for subsequent acidification and activation. Preventing carbon components from covering the active sites of the clay is a prerequisite for ensuring the acidification effect. In Example 3, the carbon content was as low as 0.06% at a calcination temperature of 600℃, providing the optimal matrix for acidification. In the sulfuric acid acidification stage, a sulfuric acid concentration of 20%~30% resulted in a decolorization rate of over 90% for all examples of activated clay, and the decolorization rate remained above 86% after 5 cycles. This concentration range allows for sufficient cation exchange and moderate dissolution with the pure clay matrix, clearing pores, increasing active sites, and achieving efficient activation of the clay. Furthermore, the activated clay crystal structure is stable, ensuring recyclability. In Example 3, with a sulfuric acid concentration of 30%, the decolorization rate was 97.8%, and it remained at 89.5% after 5 cycles, representing the optimal value for the acidification parameters. This verifies the positive correlation and synergistic effect between sulfuric acid concentration and clay activation.

[0079] Comparative Example 1 lacked the rotary pyrolysis step. Direct calcination without pyrolysis resulted in a sharp drop in waste oil recovery rate to 45.2%, a soaring carbon content to 0.82%, and a decolorization rate of only 72.3%. After five cycles, only 65.8% remained, demonstrating the importance of rotary pyrolysis. The absence of this step not only prevents waste oil resource recovery but also leads to excessive carbon generation during calcination due to the high oil content of the raw material, completely destroying the subsequent acidification and activation effects and hindering clay regeneration. Comparative Example 2 had a pyrolysis temperature of 380℃, deviating from the specified range of 400~480℃. This excessively low pyrolysis temperature resulted in an oil content exceeding the limit to 0.85% and a recovery rate dropping to 78.9%. Only because the calcination parameters were normal did the carbon content remain relatively high. The results met the requirements, with a decolorization rate of 95.8%, similar to Example 1, and only a slight decrease in cycle stability. This verified the necessity of limiting the pyrolysis temperature to 400-480℃. Deviating from this range directly reduces deoiling and recovery efficiency. Although the impact on subsequent processes is small, it still results in resource loss and increased energy consumption. Comparative Example 3, with a calcination temperature of 500℃ and a time of 3 hours, deviated from the parameter limit of 550-600℃ / 4-6 hours. Insufficient calcination parameters led to a carbon content of 0.45%, and the decolorization rate plummeted to 78.5%, remaining at only 70.2% after 5 cycles. This verified the necessity of limiting the calcination parameters. The residual carbon components firmly covered the active sites of the clay, causing H+ ions to accumulate during acidification. + The inability to fully contact the matrix resulted in a significant decrease in activation efficiency, and the adsorption capacity and stability of the clay were completely lost, confirming that thorough decarbonization by calcination is a prerequisite for acidification activation. Comparative Example 4, with a sulfuric acid concentration of 15%, deviated from the 20%–30% limit. This excessively low sulfuric acid concentration led to a decolorization rate dropping to 82.6%, and a significant decrease in cycle stability. This verified that the 20%–30% sulfuric acid concentration limit is a key invention point; insufficient concentration prevents sufficient cation exchange and pore unblocking, resulting in incomplete activation of the clay. Although some adsorption effect can be achieved, it falls far short of the requirements for recycling. This confirms the core synergistic principle between acidification concentration and clay activity. In Comparative Example 5, fixed-bed calcination was used instead of rotary calcination. The equipment replacement resulted in a carbon content of 0.18%, a decolorization rate of 89.7%, and 83.5% after 5 cycles, all lower than in Example 1. This verifies the necessity of the rotary calcination process. Compared to a fixed bed, rotary calcination can achieve uniform material tumbling and sufficient heat and mass transfer, ensuring complete removal of carbon components. In contrast, uneven heat transfer in a fixed bed can lead to incomplete local decarburization, thus affecting the acidification and activation effect. This confirms the synergistic principle between equipment selection and process effect in this invention.

[0080] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for the comprehensive utilization of waste bleaching clay generated during the adsorption and refining of recycled base oil, characterized in that, The core steps include the following: (1) Rotary pyrolysis treatment: The waste bleaching clay produced by the adsorption and refining of regenerated base oil is sent to a rotary pyrolysis furnace for pyrolysis. The gas produced by pyrolysis is separated by condensation to obtain liquid waste oil and non-condensable gas. The solid product discharged after pyrolysis is black waste bleaching clay coated with carbon, and the oil content of the black waste bleaching clay is <0.5%; (2) Rotary calcination treatment: The black waste white clay is sent into a rotary calcination kiln for calcination to completely remove the carbon components in the solid and obtain pure waste white clay matrix; (3) Sulfuric acid acidification treatment: Pure waste clay matrix is ​​mixed with sulfuric acid solution for acidification and activation treatment. After acidification, activated clay is obtained through post-treatment. The activated clay can be recycled for the regeneration base oil adsorption and refining process.

2. The method for comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, Before being fed into the rotary pyrolysis furnace, the waste bleaching clay undergoes pretreatment: mechanical impurities are removed, it is crushed to 100-150 mesh, and dried to a moisture content of 5-8%. The waste bleaching clay has an oil content of 20-60%, and its main components are: 40-50% montmorillonite, 15-20% kaolinite, 10-15% quartz, 20-60% adsorbed oil, 1-3% carbonaceous impurities, and other trace impurities.

3. The method for comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, In step (1), the preheating temperature of the rotary pyrolysis furnace is 300-350℃, and the preheating time is 30-45 min. Inert gas is used for protection during the pyrolysis process, and the flow rate of the inert gas is 50-80 m / s. 3 / h; the condensation temperature of the condensation system is 15-25℃.

4. The method for comprehensive utilization of waste bleaching clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, In step (2), the preheating temperature of the rotary kiln is 400-450℃ and the preheating time is 45-60min. After calcination, the pure waste clay matrix is ​​cooled to room temperature and then sent to step (3). The cooling method is natural cooling or forced air cooling, and the cooling time is 1-2h.

5. The method for comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, In step (1), the temperature of rotary pyrolysis is controlled at 400-480℃, the pyrolysis time is 2-3h, the rotation speed of the rotary pyrolysis furnace is 2-5rpm, and the feed rate is 100-150kg / h.

6. The method for comprehensive utilization of waste bleaching clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, In step (2), the temperature of rotary calcination is controlled at 550-600℃, the calcination time is 4-6 hours, the rotation speed of the rotary calcination kiln is 1-3 rpm, and air is introduced during the calcination process at a flow rate of 200-300 m / s. 3 / h.

7. The method for comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, In step (3), the mass fraction of sulfuric acid solution is 20-30%, the solid-liquid ratio of pure waste clay matrix to sulfuric acid solution is 1g:(2-4)mL, the acidification temperature is 70-90℃, and the acidification time is 1.5-3h.

8. The method for comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, In step (3), the sulfuric acid acidification process is carried out by a stirring device for continuous stirring at a speed of 150-200 rpm; the post-treatment includes filtration, washing, drying, crushing and sieving. Deionized water is used for washing until the pH value of the washing liquid is 6.5-7.

5. The drying temperature is 105-110℃ and the drying time is 2-3 hours. After crushing, the liquid is sieved through a 200-300 mesh sieve.

9. The method for comprehensive utilization of waste bleaching clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, The liquid waste oil obtained in step (1) has a recovery rate of 85-95% of the total oil content in the waste bleaching clay. After being refined by vacuum distillation, the liquid waste oil can be used as a raw material for blending recycled base oil. The non-condensable gas mainly consists of light hydrocarbons with a calorific value of 35,000-45,000 kJ / m³. 3 It can be recycled as fuel for rotary pyrolysis furnaces and rotary calcining kilns.

10. The method for comprehensive utilization of waste clay generated during the adsorption and refining of recycled base oil according to claim 1, characterized in that, The activated clay obtained in step (3) has a specific surface area of ​​180-220 m². 2 / g, pore volume 0.25-0.35cm³ 3 / g, the decolorization rate of recycled base oil is 90-98%, the adsorption capacity of impurities in recycled base oil is 0.15-0.25g / g, and the decolorization rate is still above 85% after 3-5 cycles; the wastewater generated in the whole process can be recycled for the washing process after neutralization treatment, and there is no wastewater discharge.

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