Method for recovering emulsified oil generated in preparation of alumina carrier by oil column forming process

Abstract

The invention belongs to the technical field of emulsified oil recovery, and particularly relates to a method for recovering emulsified oil generated by preparing an alumina carrier through an oil column forming process. The emulsified oil recovery method comprises the following steps: adding ammonia water into emulsified oil, stirring, preserving heat, centrifuging, collecting upper-layer floating oil A, and removing bottom-layer water and impurities to obtain a first-stage emulsion; adding ammonia water into the primary emulsion, heating by using a heat source until the temperature is higher than 100 DEG C, then stopping heating to obtain a demulsified primary emulsion system, carrying out centrifugal treatment, collecting upper-layer floating oil B, removing bottom-layer water and impurities, and remaining a secondary emulsion; combining the collected upper-layer floating oil A and the collected upper-layer floating oil B, distilling and removing water to obtain an oil body A; carrying out vacuum distillation on the secondary emulsion to remove water, and centrifuging to remove impurities at the bottom layer to obtain an oil body B; and finally, combining the oil body A and the oil body B to obtain recovered oil. The method does not need to add organic auxiliaries such as a demulsifier, the recovery process is simple and easy to control, the treatment temperature is low, the recovered oil quality is good, and the recovery rate is high.

Description

Technical Field

[0001] This invention belongs to the field of emulsified oil recovery technology, specifically relating to a method for recovering emulsified oil generated from the preparation of alumina carriers using an oil column forming process. Background Technology

[0002] Currently, oil column forming is the main production method for high-end alumina. It primarily utilizes the gelation properties of sols, causing them to drip into an oil medium and form droplets due to surface tension. These droplets then gel to form small spheres. In the oil column forming process, aluminum sol is first mixed with a gelling agent, then dripped into hot oil using a dispersing dropper to form the sol. After aging, washing, drying, and calcination, spherical alumina particles are obtained.

[0003] The alumina produced by the oil column forming process has high purity, high strength, excellent roundness, uniform overall quality, and is not prone to pulverization. However, the oil column forming process has high requirements and consumes a lot of energy during production, especially oil. Furthermore, the oil-containing wet carrier formed by gelation generates a large amount of washing wastewater after washing. This wastewater contains small amounts of oil and impurities such as aluminum hydroxide powder, which flows into a recovery oil tank. After enrichment and stratification in the recovery oil tank, most of the oil can be directly recycled for reuse. A portion of the oil emulsifies under the mixture of water and colloids, while simultaneously containing a large amount of wet carrier fragments and powder, which are suspended at the interface between the oil and water layers, forming emulsified oil. This emulsified oil contains a large amount of aluminum hydroxide powder, which is a micron-sized precipitate. After being mixed with water and oil, it becomes viscous and has virtually no fluidity. The formation of emulsified oil increases production costs because it cannot be recycled using conventional methods, increasing oil loss. It also increases subsequent wastewater treatment costs because direct discharge of emulsified oil pollutes water bodies, damages ecosystems, and affects water quality safety.

[0004] Existing technologies for processing conventional emulsified oil mostly involve adding organic additives such as demulsifiers and flocculants to separate water and oil and flocculate and precipitate powder impurities. This method can efficiently demulsify emulsified oil, but the recovered oil obtained after separation contains organic additives that are difficult to remove. As a result, the surface tension, viscosity and other properties of the recovered oil are significantly different from those of the new oil, so it can only be treated as waste oil and cannot be recycled, resulting in low economic benefits.

[0005] Chinese invention patent application CN104560122A discloses a waste oil regeneration method using oil column forming, which involves contacting waste oil with an adsorbent, followed by heating and filtration to obtain regenerated oil. However, this method treats waste oil, which does not contain emulsions, and removes trace impurities such as aluminum ions and gases from the oil. It does not treat emulsified oil generated after washing, and the use of an adsorbent increases costs.

[0006] Chinese invention patent application CN109607919A discloses a high-temperature demulsification method for waste emulsion. This method involves demulsifying the emulsified oil at high temperature, allowing it to settle and separate into layers, taking the upper layer of qualified oil, and then adding new emulsified oil to the remaining bottom layer for further high-temperature treatment. This process is repeated until the oil yield is significantly reduced. However, this method is unsuitable for treating oils containing a large amount of fine impurities that are difficult to separate. Repeated settling can also cause sticky oil residue to adhere to the bottom of the treatment equipment, making it difficult to ensure uniform heating and stirring, thus compromising the safe and stable operation of the equipment. Furthermore, the processing cycle is long, resulting in low industrial efficiency.

[0007] Therefore, how to recover the emulsified oil generated during the preparation of alumina carriers by the oil column forming process and enable the recovered oil to be reused in production has become an urgent technical problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering emulsified oil generated during the preparation of alumina carriers using an oil column forming process. This method eliminates the need for adding demulsifiers or other organic additives, ensures that the quality of the recovered oil is essentially the same as that of the new oil, and features a simple and controllable recovery process with a low processing temperature and a high oil recovery rate.

[0009] The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process described in this invention includes the following steps: (1) Heat the emulsified oil to 40-50℃, stir evenly, add ammonia water to adjust the pH value to 8-9, and then continue to heat to 70-90℃, stir and keep warm to obtain the pre-demulsified emulsified oil system; (2) Centrifuge the pre-demulsified emulsified oil system, collect the upper floating oil A, remove the bottom water and impurities, and the remaining substance is the primary emulsion; (3) Heat the primary emulsion obtained in step (2) to 40-50℃, stir evenly, add ammonia water to adjust the pH value of the primary emulsion system to 8-9, and then continuously heat it with a heat source of 105-120℃ while stirring until the temperature is higher than 100℃ and then stop to obtain the primary emulsion system after demulsification. (4) Centrifuge the primary emulsion system after demulsification, collect the upper floating oil B, remove the bottom water and impurities, and the remaining substance is the secondary emulsion; (5) Mix the upper floating oil A and upper floating oil B collected in steps (2) and (4) and distill to remove water to obtain oil body A; (6) After vacuum distillation to remove water from the secondary emulsion obtained in step (4), centrifugation is used to remove the bottom impurities to obtain oil body B; (7) Combine oil body A and oil body B obtained in steps (5) and (6) to obtain recovered oil.

[0010] In this invention, the emulsified oil is the emulsified oil that is located between the oil layer and the water layer after the oily wastewater generated during the preparation of the alumina carrier by the oil column forming process has been allowed to settle and separate into layers.

[0011] In existing oil column forming processes, aluminum sol is mixed with a gelling agent during the preparation of the alumina carrier, and then dripped into hot oil through a dispersing dropper to form aluminum hydroxide. After the aluminum hydroxide is separated from the hot oil, it needs to be washed with water to remove oil. The oily wastewater generated from the washing process enters a recovery oil tank, which also contains waste oil and wastewater from other steps in the oil column forming process. After settling and stratification, the upper layer of clear oil contains no obvious impurities or water and can be directly recycled. The bottom wastewater can be discharged to the wastewater treatment process. However, there is a thick emulsified oil layer between the upper clear oil layer and the bottom wastewater, with an unclear stratification interface. This emulsified oil layer is formed by water and oil mixed with aluminum hydroxide microparticles that have fallen off during the water washing process. It contains oil, water, aluminum hydroxide microparticles, free aluminum ions, and emulsions that are difficult to separate, and has virtually no fluidity. The presence of the emulsified oil layer makes it difficult for the upper clear oil layer and the bottom wastewater to separate, affecting normal recycling and treatment. Therefore, it is necessary to periodically transfer the emulsified oil from the recovery oil tank for treatment. Because the emulsified oil contains a large amount of aluminum hydroxide powder, it is difficult to completely separate it using conventional high-temperature demulsification methods. Adding demulsifiers and flocculants would affect the indicators of the recovered oil, so special treatment is required.

[0012] In steps (1) and (3), the concentration of ammonia added is 0.01-0.05 wt.%.

[0013] The emulsified oil processed by this invention contains aluminum hydroxide powder and free aluminum ions. This invention adds a small amount of ammonia to the emulsified oil or primary emulsion to adjust the pH to 8-9. This process converts the free aluminum ions into aluminum hydroxide and promotes the precipitation and separation of the aluminum hydroxide powder. Furthermore, the ammonia decomposes under heat during stirring and insulation, generating gas that accelerates the separation of oil, water, and insoluble impurities, thus facilitating demulsification. In addition, it maintains the entire processed material in a near-neutral state, which is beneficial for operational safety and equipment maintenance.

[0014] The stirring in steps (1) and (3) is preferably carried out under negative pressure. This can prevent the gas generated during the heating process of the emulsified oil or primary emulsion from escaping and affecting the production environment. At the same time, it is also conducive to the uniform stirring of the emulsified oil or primary emulsion and the separation of oil and water.

[0015] In steps (1) and (3), the stirring rate is preferably 20-50 r / min. The stirring rate should not be too high, otherwise it will cause the large aluminum hydroxide particles to precipitate and break, which is not conducive to separation.

[0016] In step (1), the stirring and heat preservation time is preferably 1-2 hours. During the stirring and heat preservation process, the aluminum hydroxide powder floating in the emulsified oil separates and precipitates from the system, and aluminum ions are also converted into aluminum hydroxide and separated under the action of ammonia water. After most of the aluminum hydroxide powder separates and precipitates, the water and oil that have not formed emulsions in the emulsified oil will separate into layers, and some water-oil emulsions will also break down and separate into layers under high-temperature stirring. Since the emulsified oil has a high viscosity and poor fluidity at room temperature, the present invention first stirs and disperses it at a lower temperature, which is beneficial to the stability and uniformity of the overall properties of the emulsified oil. After adjusting the pH value, it is stirred at a higher temperature and a certain rate, which can promote the demulsification of the emulsion and the separation of oil, water and solid impurities, preparing for subsequent centrifugal separation.

[0017] The main function of step (1) is to separate most of the aluminum hydroxide precipitate and separate the water and oil that have not formed an oil-water emulsion. The oil-water emulsion containing aluminum hydroxide powder is difficult to break down under high temperature stirring conditions. After centrifugation in step (2), it is used as a primary emulsion and processed in step (3).

[0018] In step (3), since the primary emulsion still contains a large amount of aluminum hydroxide powder, its viscosity remains high and its fluidity is poor at room temperature. Therefore, it is still necessary to stir and disperse it at a lower temperature, then add ammonia to adjust the pH value, so that the remaining aluminum hydroxide powder can precipitate and separate. Then, high-temperature heating and stirring are used to promote the evaporation of water from the oil-water emulsion, thereby achieving emulsion demulsification. In this process, water evaporation is beneficial to the demulsification of the emulsion, but if the water evaporates completely, the aluminum hydroxide powder will remain in the oil layer, making it difficult to remove some fine aluminum hydroxide powder by centrifugation. It will remain in the recovered oil and affect its physical properties. Therefore, it is necessary to retain some water so that the precipitated aluminum hydroxide powder remains in the water layer and is then removed by centrifugation. At the same time, this invention uses a heat source of 105-120℃ to continuously heat the primary emulsion system. When the temperature of the primary emulsion system rises to above 100℃, most of the water has been evaporated, and the precipitated aluminum hydroxide powder remains in the remaining small amount of water for subsequent centrifugation.

[0019] In step (2), the temperature of the pre-demulsified emulsion system during centrifugation is not lower than 60℃, the centrifugation speed is 1000-3000 r / min, and the centrifugation time is 1-4 min. The upper floating oil A obtained after centrifugation is an oil layer containing trace amounts of water; the lower layer is the sedimentation of sewage and solid impurities such as aluminum hydroxide, which is directly discharged, filtered to remove impurities, and sent to the sewage treatment process; the middle layer is an incompletely demulsified water-oil emulsion mixed with aluminum hydroxide powder, which is used as a primary emulsion for subsequent processing.

[0020] In step (4), the temperature of the primary emulsion system after demulsification during centrifugation is not lower than 80℃, the centrifugation speed is 1000-3000 r / min, and the centrifugation time is 1-4 min. The upper floating oil B obtained after centrifugation is an oil layer containing trace amounts of water (less than 0.1%), while the lower layer is a sediment of sewage and solid impurities such as aluminum hydroxide, which is directly discharged and sent to the sewage treatment process after filtration to remove impurities; the middle layer is an incompletely demulsified water-oil emulsion mixed with trace amounts of aluminum hydroxide powder, which is used as a secondary emulsion for subsequent processing.

[0021] In step (5), vacuum distillation is used to remove water from the upper floating oil A and upper floating oil B. The vacuum degree is -0.001 to -0.03 MPa, and the temperature is 100-120℃. Through conventional vacuum distillation to remove water, the water content of the upper floating oil A and upper floating oil B is reduced to below 20 ppm, meeting the usage requirements, and can be reused as recycled oil.

[0022] In step (6), the secondary emulsion is stirred during vacuum distillation to remove water. The stirring rate is 40-80 r / min. Vacuum distillation is first carried out at 80-90℃, and then the temperature is raised to 100-120℃ for vacuum distillation until no water is distilled off.

[0023] The secondary emulsion contains only trace amounts of aluminum hydroxide powder. Its viscosity is relatively lower than that of the initial emulsified oil and the primary emulsion, but higher than that of the recovered oil. In this invention, vacuum distillation is first carried out at 80-90°C to avoid bumping and to gradually demulsify the water-oil emulsion. When there is very little water-oil emulsion remaining, the temperature is raised to 100-120°C to continue vacuum distillation, so that the water-oil emulsion is completely demulsified.

[0024] In step (6), the temperature of the secondary emulsion after vacuum distillation to remove water during centrifugation is 80-90℃; the centrifugation speed is 3000-4000 r / min; and the centrifugation time is 2-4 min.

[0025] Since the secondary emulsion leaves only an oil layer after vacuum distillation, and the aluminum hydroxide powder in the oil is difficult to remove completely, centrifugation at a high speed is necessary to separate the aluminum hydroxide powder at the bottom. The oil body B obtained after this centrifugation step contains only trace amounts of aluminum hydroxide powder that cannot be completely removed, and this does not affect the appearance of the recovered oil or its reuse. In actual production, the amount of secondary emulsion is relatively small, and it can be collected and processed centrally to reduce energy consumption.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention recycles the emulsified oil generated during the preparation of alumina carriers using an oil column forming process. No demulsifiers or other organic additives are needed during this process, ensuring that the tension, viscosity, and other properties of the recycled oil remain consistent with those of the new oil, resulting in high-quality recycled oil. Furthermore, the entire recycling process is simple, easy to control, highly efficient, and yields a high recovery rate, thus reducing production costs. Attached Figure Description

[0027] Figure 1 Here is an image showing the appearance of the emulsified oil to be recycled according to this invention; Figure 2 The image shows the appearance of the recovered oil obtained in Example 1 of this invention; Figure 3 This is an image of the recovered oil obtained by vacuum distillation of the upper floating oil B in Comparative Example 3 of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments. Unless otherwise specified, the raw materials used in the embodiments are all commercially available conventional raw materials; unless otherwise specified, the process methods used in the embodiments are all conventional methods in the art.

[0029] The emulsified oil used in this embodiment is an emulsified oil obtained in the oil column forming process after the washing wastewater generated from the gel-formed alumina carrier is washed with water and the oil layer is removed by stratification. This emulsified oil is formed by emulsifying oil in a mixture of water and colloids, and contains a large amount of wet carrier fragments and powder. It is basically non-flowable, and its appearance is as follows. Figure 1 As shown.

[0030] Example 1 The method of the present invention for recovering emulsified oil comprises the following steps: (1) Under the conditions of stirring speed of 50 r / min and negative pressure, 300 g of emulsified oil was heated to 50°C, stirred evenly, and then 0.01 wt.% ammonia water was added to adjust the pH value to 8. The stirring and heating continued to 70°C and kept warm for 2 h to obtain the pre-demulsified emulsified oil system. (2) The pre-demulsified oil system was immediately centrifuged to ensure that its temperature was not lower than 60°C, the centrifugation speed was 2000 r / min, and after centrifugation for 2 min, the upper layer floating oil A105g was collected. After removing the bottom layer water and impurities, the middle layer primary emulsion 160g was collected. (3) Under the conditions of stirring speed of 50 r / min and negative pressure, 160 g of primary emulsion was heated to 50°C and stirred evenly. Then, 0.01 wt.% ammonia water was added to adjust the pH value of primary emulsion to 8. Then, while stirring, the primary emulsion was continuously heated with a heat source of 110°C until the temperature was higher than 100°C and then stopped to obtain the demulsified primary emulsion system. (4) The primary emulsion system after demulsification is immediately centrifuged to ensure that its temperature is not lower than 80℃, the centrifugation speed is 3000r / min, and after centrifugation for 2min, the upper floating oil B103g is collected. After removing the bottom water and impurities, the middle secondary emulsion 21g is collected. (5) Combine the upper floating oil A and upper floating oil B collected in steps (2) and (4), and perform vacuum distillation under the conditions of stirring speed of 70 r / min, vacuum degree of -0.02 MPa and temperature of 105℃ until no water is distilled out, and oil body A is obtained, which is about 208 g. (6) 21g of secondary emulsion was vacuum distilled at a stirring rate of 70r / min, a vacuum degree of -0.02MPa and a temperature of 90℃. After the water-oil emulsion was completely converted into a clear state, the temperature was raised to 105℃ and vacuum distillation was continued until no water was distilled off. Then, centrifugation was performed at a speed of 3000r / min for 4min. 8g of oil was collected and 3.2g of oil impurities were found at the bottom.

[0031] The oil bodies A and B obtained in steps (5) and (6) are combined to obtain recovered oil, which weighs approximately 216g. Figure 2 As shown, the recovered oil is clear and transparent; only 3.2g of oily impurities are lost during the entire recovery process, the recovery rate of the recovered oil reaches more than 98%, and the amount of wastewater generated during the recovery process is small, the wastewater composition is simple, and the treatment difficulty is low.

[0032] Example 2 The method of the present invention for recovering emulsified oil comprises the following steps: (1) Under the conditions of stirring speed of 20r / min and negative pressure, 300g of emulsified oil was heated to 40℃, stirred evenly, and then 0.05wt.% ammonia water was added to adjust the pH value to 9. The stirring and heating continued to 80℃ and kept warm for 1.5h to obtain the pre-demulsified emulsified oil system. (2) The pre-demulsified oil system was immediately centrifuged to ensure that its temperature was not lower than 60°C, the centrifugation speed was 1000 r / min, and after centrifugation for 4 min, the upper layer floating oil A97g was collected. After removing the bottom layer water and impurities, the middle layer primary emulsion 182g was collected. (3) Under the conditions of stirring speed of 20r / min and negative pressure, 182g of primary emulsion was heated to 40℃ and stirred evenly. Then, 0.05wt.% ammonia water was added to adjust the pH value to 9. Then, the primary emulsion was continuously heated with a heat source of 105℃ while stirring until the temperature was higher than 100℃ and then stopped to obtain the primary emulsion system after demulsification. (4) The primary emulsion system after demulsification is immediately centrifuged to ensure that its temperature is not lower than 80℃, the centrifugation speed is 1000r / min, and after centrifugation for 4min, the upper floating oil B103g is collected. After removing the bottom water and impurities, the middle secondary emulsion 27g is collected. (5) Combine the upper floating oil A and upper floating oil B collected in steps (2) and (4), and perform vacuum distillation under the conditions of stirring speed of 70 r / min, vacuum degree of -0.03 MPa and temperature of 100℃ until no water is distilled out, and oil body A is obtained, which is about 200 g. (6) 27g of secondary emulsion was vacuum distilled at a stirring rate of 40r / min, a vacuum degree of -0.03MPa and a temperature of 80℃. After the water-oil emulsion was completely converted into a clear state, the temperature was raised to 100℃ and vacuum distillation was continued until no water was distilled off. Then, centrifugation was performed at a speed of 3500r / min. After centrifugation for 3min, 9g of oil body B was collected and 3.8g of oil impurities were found at the bottom.

[0033] The oil bodies A and B obtained in steps (5) and (6) were combined to obtain recovered oil, which weighed approximately 209g. Only 3.8g of oily impurities were lost during the entire recovery process, achieving a recovery rate of over 98%. Furthermore, the amount of wastewater generated during the recovery process was small, and the wastewater composition was simple, making treatment easy.

[0034] Example 3 The method of the present invention for recovering emulsified oil comprises the following steps: (1) Under the conditions of stirring speed of 40r / min and negative pressure, 300g of emulsified oil was heated to 45℃, stirred evenly, and then 0.03wt.% ammonia water was added to adjust the pH value to 8.5. The stirring and heating continued to 90℃ and kept warm for 1h to obtain the pre-demulsified emulsified oil system. (2) The pre-demulsified oil system was immediately centrifuged to ensure that its temperature was not lower than 60°C, the centrifugation speed was 3000 r / min, and after centrifugation for 1 min, 90 g of the upper floating oil A was collected. After removing the bottom water and impurities, 206 g of the middle layer primary emulsion was collected. (3) Under the conditions of stirring speed of 40r / min and negative pressure, 206g of primary emulsion was heated to 45℃ and stirred evenly. Then, 0.03wt.% ammonia water was added to adjust the pH value to 8.5. Then, the primary emulsion was continuously heated with a heat source of 120℃ while stirring until the temperature was higher than 100℃ and then stopped to obtain the demulsified primary emulsion system. (4) The primary emulsion system after demulsification is immediately centrifuged to ensure that its temperature is not lower than 80℃, the centrifugation speed is 2000r / min, and after centrifugation for 2min, the upper layer floating oil B112g is collected. After removing the bottom layer water and impurities, the middle layer secondary emulsion 32g is collected. (5) Combine the upper floating oil A and upper floating oil B collected in steps (2) and (4), and perform vacuum distillation under the conditions of stirring speed of 70 r / min, vacuum degree of -0.001 MPa and temperature of 120℃ until no water is distilled out, and oil body A is obtained, which is about 202 g. (6) 32g of secondary emulsion was vacuum distilled under the conditions of stirring speed of 80r / min, vacuum degree of -0.001MPa and temperature of 85℃. After the water-oil emulsion was completely converted into a clear state, the temperature was raised to 120℃ and vacuum distillation was continued until no water was distilled off. Then, centrifugation was performed at a speed of 4000r / min. After centrifugation for 2min, 10g of oil body B was collected and 4.0g of oil impurities were found at the bottom.

[0035] After combining the oil A and oil body B obtained in steps (5) and (6), the recovered oil is obtained. The recovered oil is about 212g. Only 4.0g of oily impurities are lost in the entire recovery process. The recovery rate of the recovered oil reaches more than 98%. The amount of wastewater generated in the recovery process is small and the wastewater composition is simple and easy to treat.

[0036] Comparative Example 1 This comparative example is based on Example 1, with the difference being that: in step (1), no ammonia was added to adjust the pH value, and 300g of emulsified oil was directly heated to 70℃ and kept warm for 2h under a stirring rate of 50r / min and negative pressure. Then, it was immediately centrifuged at 2000r / min for 2min. After centrifugation, only 42g of the upper floating oil was separated. After removing the bottom water and impurities, the weight of the middle layer primary emulsion was 247g. The water-oil separation effect was significantly reduced because, under the condition of not adding ammonia, aluminum hydroxide powder was not easy to precipitate, which not only affected the separation effect of free water and oil, but also affected the demulsification of the water-oil emulsion.

[0037] Comparative Example 2 This comparative example is based on Example 1, with the difference being that: in step (3), no ammonia is added to adjust the pH value, and the primary emulsion obtained after step (2) is continuously heated for 2 hours with a heat source at 110°C under a stirring rate of 50 r / min and negative pressure. Then, it is immediately centrifuged at 3000 r / min for 2 minutes. The separation effect after centrifugation is not obvious. Since the primary emulsion is a water-oil emulsion containing aluminum hydroxide micro powder, it is difficult to break the emulsion by simply stirring at high temperature.

[0038] Comparative Example 3 This comparative example is based on Example 1, with steps (1) and (2) being the same, except that the treatment method for the primary emulsion is different. The steps of this comparative example are as follows: (1) Under the conditions of stirring speed of 50 r / min and negative pressure, 300 g of emulsified oil was heated to 50°C and stirred evenly. Then, 0.01 wt.% ammonia water was added to adjust the pH value of the emulsified oil system to 8. Stirring and heating were continued to 70°C and kept warm for 2 h to obtain the pre-demulsified emulsified oil system. (2) The pre-demulsified oil system was immediately centrifuged to ensure that its temperature was not lower than 60°C, the centrifugation speed was 2000 r / min, and after centrifugation for 2 min, the upper layer floating oil A105g was collected. After removing the bottom layer water and impurities, the middle layer primary emulsion 160g was collected. (3) Under the conditions of stirring speed of 50 r / min and negative pressure, 160 g of primary emulsion was heated to 50°C and stirred evenly. Then, 0.01 wt.% ammonia water was added to adjust the pH value to 8. Then, while stirring, the primary emulsion was continuously heated and distilled with a heat source of 110°C until no water was distilled out, and the demulsified primary emulsion system was obtained. (4) The primary emulsion system after demulsification is immediately centrifuged to ensure that its temperature is not lower than 80℃, the centrifugation speed is 3000r / min, and after centrifugation for 5min, 105g of upper floating oil B is collected and 10.5g of oil impurities are collected at the bottom. The upper floating oil B obtained in this step is slightly turbid and its clarity is lower than that of the upper floating oil A collected in step (2). The reason is that the primary emulsion contains more aluminum hydroxide powder, which enters the oil layer after demulsification. The small aluminum hydroxide powder cannot be removed by centrifugation and is dispersed in the oil layer, resulting in its turbid appearance. (5) The upper layer oil A collected in step (2) was vacuum distilled at a stirring rate of 70 r / min, a vacuum degree of -0.02 MPa, and a temperature of 105 °C until no water was distilled out, resulting in 101 g of clear recovered oil; the upper layer oil B collected in step (4) was vacuum distilled at a stirring rate of 70 r / min, a vacuum degree of -0.02 MPa, and a temperature of 105 °C until no water was distilled out, resulting in 102 g of relatively turbid recovered oil, the appearance of which is as follows. Figure 3 As shown.

[0039] In this comparative recovery method, the water in the primary emulsion is almost completely evaporated during treatment, which can reduce the treatment steps for the secondary emulsion. However, the small-particle aluminum hydroxide powder cannot be removed by centrifugation, and the resulting recovered oil is turbid and cannot be reused.

[0040] The recovered oils obtained after processing in Examples 1-3, and the recovered oil obtained after vacuum distillation of the upper floating oil B in Comparative Example 3, were compared with new oils for performance testing. Surface tension was tested using an automated tensiometer; kinematic viscosity (40℃) was tested according to standard GB / T 265; demulsibility (82℃) was tested according to standard GB / T 7305; moisture content was tested according to standard GB / T 11133; and density (25℃) was tested using the specific gravity bottle method. The test results are shown in Table 1.

[0041] Table 1. Test results of recycled oil and new oil.

[0042] As can be seen from Table 1, the quality of the recovered oil obtained after treatment according to this invention is comparable to that of new oil, especially in terms of surface tension, kinematic viscosity, and demulsibility, which are basically consistent with those of new oil, meeting the requirements for use. In Comparative Example 3, the recovered oil obtained after vacuum distillation of the upper floating oil B was turbid in appearance. Figure 3 It contains many impurities, which affects product quality. All indicators are significantly different from those of new oil, so it can only be treated as waste oil and cannot be reused in production.

Claims

1. A method for recovering emulsified oil generated during the preparation of alumina carriers using an oil column forming process, characterized in that: Includes the following steps: (1) Heat the emulsified oil to 40-50℃, stir evenly, add ammonia water to adjust the pH value to 8-9, and then continue to heat to 70-90℃, stir and keep warm to obtain the pre-demulsified emulsified oil system; (2) Centrifuge the pre-demulsified emulsified oil system, collect the upper floating oil A, remove the bottom water and impurities, and the remaining substance is the primary emulsion; (3) Heat the primary emulsion obtained in step (2) to 40-50℃, stir evenly, add ammonia water to adjust the pH value to 8-9, and then continuously heat with a heat source of 105-120℃ while stirring until the temperature is higher than 100℃, and then stop to obtain the primary emulsion system after demulsification. (4) Centrifuge the primary emulsion system after demulsification, collect the upper floating oil B, remove the bottom water and impurities, and the remaining substance is the secondary emulsion; (5) Mix the upper floating oil A and upper floating oil B collected in steps (2) and (4) and distill to remove water to obtain oil body A; (6) After vacuum distillation to remove water from the secondary emulsion obtained in step (4), centrifugation is used to remove the bottom impurities to obtain oil body B; (7) Combine oil body A and oil body B obtained in steps (5) and (6) to obtain recovered oil; The emulsified oil is an emulsified oil located between the oil layer and the water layer in the oil-containing wastewater generated during the preparation of alumina carrier by the oil column forming process, after being allowed to settle and separate into layers.

2. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In steps (1) and (3), the concentration of ammonia added is 0.01-0.05 wt.%.

3. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: The stirring in steps (1) and (3) is carried out under negative pressure and the stirring rate is 20-50 r / min.

4. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In step (1), the stirring and heat preservation time is 1-2 hours.

5. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In step (2), the temperature of the pre-demulsified oil system during centrifugation is not lower than 60°C, the centrifugation speed is 1000-3000 r / min, and the centrifugation time is 1-4 min.

6. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In step (4), the temperature of the primary emulsion system after demulsification during centrifugation is not lower than 80°C, the centrifugation speed is 1000-3000 r / min, and the centrifugation time is 1-4 min.

7. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In step (5), water is removed by vacuum distillation at a vacuum level of -0.001 to -0.03 MPa and a temperature of 100-120℃.

8. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In step (6), the secondary emulsion is stirred during vacuum distillation to remove water. The stirring rate is 40-80 r / min. Vacuum distillation is first carried out at 80-90℃, and then the temperature is raised to 100-120℃ for vacuum distillation until no water is distilled off.

9. The method for recovering emulsified oil generated during the preparation of alumina carriers using the oil column forming process according to claim 1, characterized in that: In step (6), the temperature of the secondary emulsion after vacuum distillation to remove water during centrifugation is 80-90℃; the centrifugation speed is 3000-4000 r / min; and the centrifugation time is 2-4 min.

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