Method for recovering emulsified oil produced by oil column forming process for preparing alumina carrier

Abstract

The present application belongs to the technical field of emulsified oil recovery, and particularly relates to a method for recovering emulsified oil generated in the preparation of an alumina carrier by an oil column forming process. The method comprises the following steps: adding ammonia water to the emulsified oil and stirring and keeping warm, centrifuging, collecting the upper floating oil A, removing the bottom water and impurities, and leaving the primary emulsified material; adding the primary emulsified material to ammonia water and heating with a heat source until the temperature is higher than 100 DEG C and then stopping, obtaining the primary emulsified material system after demulsification and centrifuging, collecting the upper floating oil B, removing the bottom water and impurities, and leaving the secondary emulsified material; combining the collected upper floating oil A and upper floating oil B and distilling to remove water, obtaining oil body A; vacuum distilling the secondary emulsified material to remove water, centrifuging to remove the bottom impurities, and obtaining oil body B; and finally combining the oil body A and oil body B to obtain recovered oil. The present application does not need to add organic aids such as demulsifiers, the recovery process is simple and easy to control, the processing temperature is relatively low, the quality of the recovered oil is good, and the recovery rate is high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of emulsified oil recovery, and particularly relates to a method for recovering emulsified oil generated in the preparation of an alumina carrier by an oil column forming process. BACKGROUND

[0002] At present, the oil column forming process is a main production method for preparing high-end alumina. The process mainly utilizes the gelation characteristics of sol, so that the sol is dropped in an oil medium, and spherical drops are formed by the action of surface tension, and the spherical drops are gelated to form small balls. In the oil column forming process, first, the aluminum sol is mixed with a gelling agent, and then is dropped into hot oil through a dispersion dropping tube for forming, and then is subjected to aging, washing, drying, calcination and other steps to obtain spherical alumina particles.

[0003] The alumina product produced by the oil column forming process has high purity, high strength, excellent roundness, uniform overall quality and is not easy to be pulverized. However, the oil column forming process has high requirements and large energy consumption, especially large oil consumption, and a large amount of washing wastewater is generated after the gel-formed oil-containing wet carrier is washed. The washing wastewater contains a small amount of oil and aluminum hydroxide powder and other impurities, flows into a recovery oil pool through a pipeline, and the recovery oil pool is enriched and stratified, most of the oil can be directly recovered and reused, and part of the oil is emulsified under the mixing of water and colloid, and at the same time, a large amount of wet carrier slag and powder are mixed and suspended between the oil layer and the water layer to become emulsified oil. The emulsified oil contains a large amount of aluminum hydroxide powder, which is micron-level sediment and is relatively viscous after being mixed with water and oil, and basically has no flowability. The formation of emulsified oil increases the production cost on the one hand, because the emulsified oil cannot be recycled and reused by conventional recovery methods, which increases the loss of oil; on the other hand, it also increases the subsequent sewage treatment cost, because the direct discharge of emulsified oil will pollute the water body, destroy the ecological system and affect the water quality safety.

[0004] In the prior art, when treating conventional emulsified oil, an organic additive such as a demulsifier and a flocculant is usually added to separate water and oil and to flocculate and precipitate the powder impurities. This method can efficiently demulsify the emulsified oil, but the recovered oil obtained after separation contains organic additives and is difficult to remove, resulting in a large difference between the recovered oil and new oil in terms of indicators such as tension and viscosity, so that the recovered oil can only be treated as waste oil and cannot be recycled, which has low economic benefits.

[0005] Chinese patent application with publication number CN104560122A discloses a waste oil regeneration method for oil column forming. The method contacts waste oil with an adsorbent, and then heats and filters the waste oil to obtain regenerated oil. However, the method is for treating waste oil, which does not contain emulsified material, and removes trace impurities such as aluminum ions and gases in the oil, and is not for treating emulsified oil generated after washing. In addition, the method uses an adsorbent, which increases the cost.

[0006] Chinese patent application with publication number CN109607919A discloses a waste emulsion high-temperature demulsification method. After high-temperature demulsification, the emulsified oil is allowed to stand and stratify. After taking the qualified oil in the upper layer, the remaining emulsified oil at the bottom is continuously added with new emulsified oil for high-temperature treatment. This process is repeated until the oil yield is significantly reduced. However, this method is not suitable for treating oil containing a large amount of fine impurities which is difficult to stratify. Multiple standing and sedimentation can also cause the sticky oil residue to adhere to the bottom of the treatment equipment, which cannot guarantee uniform heating and stirring, cannot guarantee the safe and stable operation of the treatment equipment, and has a long treatment cycle and low industrialization efficiency.

[0007] Therefore, how to recycle the emulsified oil produced by the oil column forming process for preparing the alumina carrier and make the recycled oil be repeatedly used for production has become a technical problem to be solved. SUMMARY

[0008] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for recycling emulsified oil produced by the oil column forming process for preparing the alumina carrier, which does not need to add demulsifiers and other organic additives, has basically the same quality as new oil, has a simple and easy-to-control recycling process, a relatively low treatment temperature, and a high oil recovery rate.

[0009] The method for recycling emulsified oil produced by the oil column forming process for preparing the alumina carrier according to the present application comprises the following steps:

[0010] (1) The emulsified oil is heated to 40-50℃, and after uniform stirring, ammonia water is added to adjust the pH value to 8-9. Then, the temperature is continuously increased to 70-90℃, and the mixture is stirred and kept warm to obtain a pre-demulsified emulsified oil system;

[0011] (2) The pre-demulsified emulsified oil system is centrifuged, and the upper layer of floating oil A is collected. The bottom layer of water and impurities are removed, and the remaining material is a first emulsified material;

[0012] (3) The first emulsified material obtained in step (2) is heated to 40-50℃, and after uniform stirring, ammonia water is added to adjust the pH value of the first emulsified material system to 8-9. Then, the mixture is continuously heated with a heat source at 105-120℃ while stirring, until the temperature is higher than 100℃, and then the heating is stopped. A demulsified first emulsified material system is obtained;

[0013] (4) The demulsified first emulsified material system is centrifuged, and the upper layer of floating oil B is collected. The bottom layer of water and impurities are removed, and the remaining material is a second emulsified material;

[0014] (5) The upper layer of floating oil A and the upper layer of floating oil B collected in steps (2) and (4) are mixed and distilled to remove water to obtain an oil body A;

[0015] (6) After vacuum distillation to remove water, the second emulsified material obtained in step (4) is centrifuged to remove the bottom layer of impurities to obtain an oil body B;

[0016] (7) Combine the oil body A and the oil body B obtained in step (5) and step (6) to obtain recovered oil.

[0017] In the present application, the emulsified oil is the emulsified oil between the oil layer and the water layer after the oil-containing wastewater generated during the preparation of the alumina carrier by the oil column forming process is allowed to stand and separate into layers.

[0018] In the existing oil column forming process, the aluminum sol is mixed with a gelling agent, and then is dripped into hot oil through a dispersion dropper to form an aluminum hydroxide. After the aluminum hydroxide is separated from the hot oil, water washing is required to remove oil. The oil-containing wastewater generated by the water washing is introduced into a recovered oil pool. The recovered oil pool also contains waste oil and wastewater generated by other processes of the oil column forming process. After standing and separating into layers, the clear oil in the upper layer does not contain obvious impurities and water, and can be directly recycled. The bottom sewage can be discharged to a wastewater treatment process. However, there is a thick emulsified oil layer between the clear oil in the upper layer and the bottom sewage, and the interface of the layers is not clear. The emulsified oil layer is formed by the aluminum hydroxide powder mixed with water during the water washing to remove the oil. The emulsified oil layer contains oil, water, aluminum hydroxide powder, free aluminum ions, emulsified substances and the like, and has basically no flowability. The presence of the emulsified oil layer makes it difficult to separate the clear oil in the upper layer and the bottom sewage, and affects the normal recycling and treatment. Therefore, the emulsified oil needs to be regularly transferred from the recovered oil pool for treatment. Since a large amount of aluminum hydroxide powder is present in the emulsified oil, the conventional high-temperature demulsification method is difficult to completely separate the emulsified oil. The addition of a demulsifier and a flocculating agent will affect the indicators of the recovered oil, and therefore special treatment is required.

[0019] In step (1) and step (3), the concentration of the added ammonia water is 0.01-0.05wt.%.

[0020] The emulsified oil treated in the present application contains aluminum hydroxide powder and free aluminum ions. In the present application, a small amount of ammonia water is added to the emulsified oil or the primary emulsified substance to adjust the pH value to 8-9. On the one hand, the free aluminum ions can be converted into aluminum hydroxide, and the precipitation and separation of the aluminum hydroxide powder are promoted. On the other hand, the ammonia water is heated and decomposed to generate gas during the stirring and heat preservation process, which accelerates the separation of the oil, water and insoluble impurities, and is beneficial to demulsification. In addition, the entire treated material can be kept in a nearly neutral state, which is beneficial to the operation safety and equipment maintenance.

[0021] The stirring in step (1) and step (3) is preferably carried out under negative pressure. The gas generated during the heating process of the emulsified oil or the primary emulsified substance can be avoided to escape, which affects the production environment. At the same time, the stirring of the emulsified oil or the primary emulsified substance is uniform, and the separation of the oil and water is facilitated.

[0022] The stirring rate in step (1) and step (3) is preferably 20-50 r / min. The stirring rate should not be too high, otherwise the large particles of aluminum hydroxide will be broken, which is not conducive to separation.

[0023] In step (1), the stirring and heat preservation time is preferably 1-2 h. During the stirring and heat preservation process, the aluminum hydroxide powder floating in the emulsified oil is separated and precipitated from the system, and the aluminum ions are also converted into aluminum hydroxide and separated out under the action of ammonia; after most of the aluminum hydroxide powder is separated and precipitated, the water and oil that have not formed emulsions in the emulsified oil will be separated, and part of the water and oil emulsions will be broken and separated under high-temperature stirring. Since the emulsified oil has high viscosity and poor flowability at room temperature, the present application first stirs and disperses it at a lower temperature, which is conducive 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 speed, which can promote the breaking of the emulsions and the separation of oil, water and solid impurities, and prepare for subsequent centrifugal separation.

[0024] The main role of step (1) is to separate and precipitate most of the aluminum hydroxide, while the water and oil that have not formed water and oil emulsions are separated, and the water and oil emulsions doped with aluminum hydroxide powder are difficult to break under high-temperature stirring conditions. After centrifugation in step (2), it is treated as a primary emulsion in step (3).

[0025] In step (3), since the primary emulsion still contains a large amount of aluminum hydroxide powder, it still has high viscosity and poor flowability at room temperature, so it still needs to be stirred and dispersed at a lower temperature, and then ammonia is added to adjust the pH value, so that the remaining aluminum hydroxide powder is precipitated and separated, and then the water in the water and oil emulsion is evaporated by high-temperature heating and stirring, so as to realize the breaking of the emulsion. In this process, the evaporation of water is conducive to the breaking of the emulsion, but if the water is completely evaporated, the aluminum hydroxide powder will remain in the oil layer, which will make it difficult to remove some fine aluminum hydroxide powder by centrifugation, and will remain in the recovered oil, affecting its physical indicators, so a part of water needs to be reserved, so that the precipitated and separated aluminum hydroxide powder remains in the water layer, and then removed by centrifugation. At the same time, the primary emulsion system is continuously heated by using a heat source of 105-120℃. When the temperature of the primary emulsion system rises to above 100℃, most of the water has been evaporated, and the precipitated and separated aluminum hydroxide powder remains in the remaining small amount of water, which is subjected to subsequent centrifugal separation.

[0026] In step (2), the temperature of the pre-demulsified emulsified oil system is not less than 60°C during centrifugation, the centrifugal speed is 1000-3000 r / min, and the centrifugation time is 1-4 min. The upper floating oil A obtained after centrifugal separation is an oil layer containing a small amount of water; the lower layer is sewage and solid impurities such as aluminum hydroxide, which is directly discharged and filtered to remove impurities and then sent to a sewage treatment process; and the middle layer is a water-oil emulsion that has not been completely demulsified and is doped with aluminum hydroxide powder, which is treated as a primary emulsion for subsequent processing.

[0027] In step (4), the temperature of the demulsified primary emulsion system is not less than 80°C during centrifugation, the centrifugal speed is 1000-3000 r / min, and the centrifugation time is 1-4 min. The upper floating oil B obtained after centrifugal separation is an oil layer containing a small amount of water (less than 0.1%), and the lower layer is sewage and solid impurities such as aluminum hydroxide, which is directly discharged and filtered to remove impurities and then sent to a sewage treatment process; and the middle layer is a water-oil emulsion that has not been completely demulsified and is doped with a small amount of aluminum hydroxide powder, which is treated as a secondary emulsion for subsequent processing.

[0028] In step (5), vacuum distillation is used to remove water from the upper floating oil A and the upper floating oil B, the vacuum degree is -0.001 to -0.03 MPa, and the temperature is 100-120°C. By conventional vacuum distillation, the water content of the upper floating oil A and the upper floating oil B is reduced to below 20 ppm, meeting the use requirements and being reused as recovered oil.

[0029] In step (6), the secondary emulsion is stirred during vacuum distillation to remove water, the stirring speed is 40-80 r / min, and the vacuum distillation is first carried out at 80-90°C and then at 100-120°C until no water is distilled out.

[0030] The secondary emulsion only contains a small amount of aluminum hydroxide powder, and its viscosity is relatively low compared to the initial emulsified oil and the primary emulsion, but relatively high compared to the recovered oil. In the present application, vacuum distillation is first carried out at 80-90°C to avoid boiling, and the water-oil emulsion is gradually demulsified. When there is little remaining water-oil emulsion, the temperature is increased to 100-120°C for further vacuum distillation to completely demulsify the water-oil emulsion.

[0031] In step (6), the temperature of the secondary emulsion after vacuum distillation to remove water is 80-90°C during centrifugation; the centrifugal separation speed is 3000-4000 r / min, and the centrifugal separation time is 2-4 min.

[0032] Since only oil layer is left after vacuum distillation of the secondary emulsion, and the aluminum hydroxide powder in the oil is difficult to remove completely, centrifugation needs to be carried out at a high rotating speed, and then the aluminum hydroxide powder at the bottom is separated. The oil body B obtained after centrifugation of this step contains only a trace amount of aluminum hydroxide powder which cannot be completely removed and does not affect the appearance and reuse of the recovered oil. In actual production, the amount of the secondary emulsion is small, and a certain amount can be collected for centralized treatment, thereby reducing the energy consumption for treatment.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] The present application recovers the emulsified oil produced in the preparation of the alumina carrier by the oil column forming process, and no organic additives such as demulsifiers need to be added in the process, so that the tension and viscosity of the recovered oil can be ensured to be consistent with those of the new oil, and the recovered oil with good quality is obtained. Meanwhile, the whole recovery process is simple and easy to control, the treatment efficiency is high, the yield of the recovered oil is high, and the production cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The picture of the appearance of the emulsified oil to be recovered in the present application;

[0036] Figure 2 The picture of the appearance of the recovered oil obtained in Example 1 of the present application;

[0037] Figure 3 The picture of the appearance of the recovered oil obtained after vacuum distillation of the upper floating oil B in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0038] The present application will be further described below in conjunction with examples. In the examples, the raw materials used, unless otherwise specified, are all commercially available conventional raw materials; and the process methods used, unless otherwise specified, are all conventional methods in the art.

[0039] The emulsified oil used in the examples is the emulsified oil obtained after removal of the oil layer from the washing wastewater produced after water washing of the gel-formed alumina carrier in the oil column forming process. The emulsified oil is formed by emulsification of the oil in the mixture of water and colloid, and contains a large amount of wet carrier slag and powder, and has substantially no flowability. The appearance thereof is shown in Figure 1 .

[0040] Example 1

[0041] The emulsified oil is recovered and treated according to the method of the present application, and the steps are as follows:

[0042] (1) 300 g of the emulsified oil is heated to 50℃ under the conditions of a stirring rate of 50 r / min and negative pressure, and after uniform stirring, ammonia water with a concentration of 0.01 wt.% is added to adjust the pH value to 8, and then the stirring and heating are continued to 70℃, and the temperature is maintained for 2 h to obtain the emulsified oil system after pre-demulsification;

[0043] (2) immediately centrifugate the emulsified oil system after pre-emulsion breaking, ensure that the temperature is not lower than 60℃, the centrifugal speed is 2000r / min, after centrifugating for 2min, collect the upper floating oil A105g, remove the bottom water and impurities, and collect the intermediate layer first emulsate 160g;

[0044] (3) under the conditions of stirring speed 50r / min and negative pressure, heat the 160g first emulsate to 50℃, after stirring uniformly, add ammonia water with concentration 0.01wt.% to adjust the pH value of the first emulsate to 8, then continuously heat the first emulsate with heat source of 110℃ while stirring, stop until the temperature is higher than 100℃, and obtain the first emulsate system after emulsion breaking;

[0045] (4) immediately centrifugate the first emulsate system after emulsion breaking, ensure that the temperature is not lower than 80℃, the centrifugal speed is 3000r / min, after centrifugating for 2min, collect the upper floating oil B103g, remove the bottom water and impurities, and collect the intermediate layer second emulsate 21g;

[0046] (5) combine the upper floating oil A and the upper floating oil B collected in step (2) and step (4), and perform vacuum distillation under the conditions of stirring speed 70r / min, vacuum degree-0.02MPa, and temperature 105℃, until no water is distilled out, and obtain oil body A, the oil body A is about 208g;

[0047] (6) perform vacuum distillation on the 21g second emulsate under the conditions of stirring speed 70r / min, vacuum degree-0.02MPa, and temperature 90℃, after the water-oil emulsate is completely converted into clear state, continue vacuum distillation by increasing the temperature to 105℃, until no water is distilled out, and then perform centrifugation, after centrifugating for 4min, collect the oil body B8g, and the bottom oil-containing impurities 3.2g.

[0048] Combine the oil body A and the oil body B obtained in step (5) and step (6) to obtain the recovered oil, the recovered oil is about 216g, as shown in the following formula (I), the recovered oil is clear and transparent; only 3.2g oil-containing impurities are lost in the whole recovery process, the recovery rate of the recovered oil reaches more than 98%, and the waste water generated in the recovery process is less, the waste water components are simple, and the treatment difficulty is low. Figure 2

[0049] Example 2

[0050] The emulsified oil is recovered and treated according to the method of the present application, and the steps are as follows:

[0051] ​(1) under the condition of stirring rate 20r / min and negative pressure, 300g emulsified oil is heated to 40℃, after stirring uniformly, ammonia water with concentration of 0.05wt.% is added to adjust pH value to 9, continue to stir and heat to 80℃, keep for 1.5h, to obtain the pre-demulsified emulsified oil system;

[0052] (2) the pre-demulsified emulsified oil system is immediately centrifuged, to ensure that the temperature is not lower than 60℃, the centrifugal speed is 1000r / min, after centrifuging for 4min, the upper layer oil A97g is collected, after removing the bottom layer water and impurities, the intermediate layer first emulsified material 182g is collected;

[0053] (3) under the condition of stirring rate 20r / min and negative pressure, 182g first emulsified material is heated to 40℃, after stirring uniformly, ammonia water with concentration of 0.05wt.% is added to adjust pH value to 9, then the first emulsified material is continuously heated by 105℃ heat source while stirring, until the temperature is higher than 100℃, then stop, to obtain the demulsified first emulsified material system;

[0054] (4) the demulsified first emulsified material system is immediately centrifuged, to ensure that the temperature is not lower than 80℃, the centrifugal speed is 1000r / min, after centrifuging for 4min, the upper layer oil B103g is collected, after removing the bottom layer water and impurities, the intermediate layer second emulsified material 27g is collected;

[0055] (5) the upper layer oil A and the upper layer oil B collected in step (2) and step (4) are combined, vacuum distillation is carried out under the condition of stirring rate 70r / min, vacuum degree-0.03MPa, temperature 100℃, until no water is distilled out, to obtain oil body A, the oil body A is about 200g;

[0056] (6) 27g second emulsified material is vacuum distilled under the condition of stirring rate 40r / min, vacuum degree-0.03MPa, temperature 80℃, after the water-oil emulsified material is completely converted into clear state, the temperature is increased to 100℃ to continue vacuum distillation, until no water is distilled out, then centrifugation is carried out, the centrifugal speed is 3500r / min, after centrifuging for 3min, the oil body B9g is collected, the bottom oil-containing impurities 3.8g.

[0057] The oil body A and the oil body B obtained in step (5) and step (6) are combined to obtain the recovered oil, the recovered oil is about 209g. In the whole recovery process, only 3.8g oil-containing impurities is lost, the recovery rate of the recovered oil reaches more than 98%, and the waste water produced in the recovery process is less, and the composition of the waste water is simple, and the treatment difficulty is low.

[0058] Example 3

[0059] The emulsified oil is recovered and treated according to the method of the present application, and the steps are as follows:

[0060] (1) Under the condition of stirring rate 40 r / min and negative pressure, 300 g of emulsified oil was heated to 45℃, and after uniform stirring, ammonia water with a concentration of 0.03wt.% was added to adjust the pH value to 8.5, and then the stirring and heating were continued to 90℃, and the temperature was kept for 1 h to obtain a pre-demulsified emulsified oil system;

[0061] (2) The pre-demulsified emulsified oil system was immediately centrifuged to ensure that the temperature was not lower than 60℃, the centrifugal speed was 3000 r / min, and after centrifugation for 1 min, 90 g of upper floating oil A was collected, and after removing the bottom water and impurities, 206 g of intermediate layer primary emulsate was collected;

[0062] (3) Under the condition of stirring rate 40 r / min and negative pressure, 206 g of primary emulsate was heated to 45℃, and after uniform stirring, ammonia water with a concentration of 0.03wt.% was added to adjust the pH value to 8.5, and then the primary emulsate was continuously heated with a heat source of 120℃ while stirring, until the temperature was higher than 100℃, then stopped, to obtain a demulsified primary emulsate system;

[0063] (4) The demulsified primary emulsate system was immediately centrifuged to ensure that the temperature was not lower than 80℃, the centrifugal speed was 2000 r / min, and after centrifugation for 2 min, 112 g of upper floating oil B was collected, and after removing the bottom water and impurities, 32 g of intermediate layer secondary emulsate was collected;

[0064] (5) The upper floating oil A and the upper floating oil B collected in steps (2) and (4) were combined, and vacuum distillation was carried out under the condition of stirring rate 70 r / min, vacuum degree-0.001 MPa, temperature 120℃, until no water was distilled out, to obtain oil body A, and the oil body A was about 202 g;

[0065] (6) 32 g of secondary emulsate was vacuum distilled under the condition of stirring rate 80 r / min, vacuum degree-0.001 MPa, and temperature 85℃, and after the water-oil emulsate was completely converted into a clear state, the temperature was raised to 120℃ for further vacuum distillation, until no water was distilled out, and then centrifugation was carried out, the centrifugal speed was 4000 r / min, and after centrifugation for 2 min, 10 g of oil body B was collected, and the bottom oil-containing impurities were 4.0 g.

[0066] The oil A and the oil body B obtained in steps (5) and (6) were combined to obtain recovered oil, and the recovered oil was about 212 g, and only 4.0 g of oil-containing impurities was lost in the whole recovery process, the recovery rate of the recovered oil reached more than 98%, and the wastewater generated in the recovery process was less, and the wastewater components were simple, and the treatment difficulty was low.

[0067] Comparative Example 1

[0068] The comparative example is based on example 1, the difference is that in step (1), no ammonia water is added to adjust the pH value, 300 g of emulsified oil is directly heated to 70℃ under the condition of stirring rate 50 r / min and negative pressure for 2 h, and then immediately centrifuged at a speed of 2000 r / min for 2 min. After centrifugation, only 42 g of upper floating oil is separated out, and after removing the bottom water and impurities, the weight of the intermediate layer primary emulsifier collected is 247 g. The water-oil separation effect is obviously decreased. The reason is that under the condition of no ammonia water, the aluminum hydroxide powder is not easy to precipitate, which not only affects the separation effect of free water and oil, but also affects the demulsification of water-oil emulsion.

[0069] Comparative example 2

[0070] The comparative example is based on example 1, the difference is that in step (3), no ammonia water is added to adjust the pH value, the primary emulsifier obtained after step (2) is continuously heated at 110℃ under the condition of stirring rate 50 r / min and negative pressure for 2 h, and then immediately centrifuged at a speed of 3000 r / min for 2 min. After centrifugation, the layering effect is not obvious. Since the primary emulsion is a water-oil emulsion containing aluminum hydroxide powder, it is difficult to demulsify it by high temperature stirring alone.

[0071] Comparative example 3

[0072] The comparative example is based on example 1, steps (1) and (2) are the same, the difference is that the treatment method of the primary emulsion is different, the steps of the comparative example are as follows:

[0073] (1) Under the condition of stirring rate 50 r / min and negative pressure, 300 g of emulsified oil is heated to 50℃, after uniform stirring, 0.01wt.% ammonia water is added to adjust the pH value of the emulsified oil system to 8, and then heated to 70℃, and kept for 2 h to obtain a pre-demulsified emulsified oil system;

[0074] (2) The pre-demulsified emulsified oil system is immediately centrifuged to ensure that the temperature is not lower than 60℃, the centrifugal speed is 2000 r / min, and after centrifugation for 2 min, 105 g of upper floating oil A is collected, and after removing the bottom water and impurities, 160 g of intermediate layer primary emulsion is collected;

[0075] (3) Under the condition of stirring rate 50 r / min and negative pressure, 160 g of primary emulsion is heated to 50℃, after uniform stirring, 0.01wt.% ammonia water is added to adjust the pH value to 8, and then the primary emulsion is continuously heated and distilled by using 110℃ heat source while stirring, until no water is distilled out, to obtain a demulsified primary emulsion system;

[0076] (4) The primary emulsate system after demulsification is immediately centrifuged to ensure that the temperature is not lower than 80℃, the centrifugal speed is 3000r / min, and after centrifugation for 5min, the upper floating oil B105g and the bottom oil impurities 10.5g are collected. The upper floating oil B obtained in this step is slightly turbid in appearance, and the clarity is lower than that of the upper floating oil A collected in step (2), because the primary emulsate contains more aluminum hydroxide powder, and the aluminum hydroxide powder with small particle size cannot be removed by centrifugal separation after demulsification, but is dispersed in the oil layer to cause the turbidity of the appearance;

[0077] (5) The upper floating oil A collected in step (2) is vacuum distilled at a stirring speed of 70r / min, a vacuum degree of-0.02MPa and a temperature of 105℃, and after no water is distilled out, the recovered oil 101g with clear appearance is obtained; the upper floating oil B collected in step (4) is vacuum distilled at a stirring speed of 70r / min, a vacuum degree of-0.02MPa and a temperature of 105℃, and after no water is distilled out, the recovered oil 102g with relatively turbid appearance is obtained, as shown in Figure 3

[0078] The recycling method of the comparative example can basically completely evaporate the water in the primary emulsate when the primary emulsate is treated, and can reduce the treatment steps of the secondary emulsate, but the aluminum hydroxide powder with small particle size cannot be removed by centrifugal separation, and the recovered oil obtained is turbid in appearance and cannot be reused.

[0079] The recovered oils obtained after treatment of examples 1-3 and the recovered oil obtained after vacuum distillation of the upper floating oil B in comparative example 3 are subjected to index testing with new oil, in which the surface tension is tested by using a full-automatic tension meter, the kinematic viscosity (40℃) is tested in accordance with standard GB / T 265, the emulsion resistance (82℃) is tested in accordance with standard GB / T 7305, the water content is tested in accordance with standard GB / T 11133, and the density (25℃) is tested by using a specific gravity bottle method. The test results are shown in Table 1.

[0080] Table 1 Index test results of recovered oil and new oil

[0081]

[0082] As can be seen from Table 1, the recovered oil obtained after treatment of the present application is equivalent to new oil in quality, especially the surface tension, kinematic viscosity and emulsion resistance are basically the same as those of new oil, and meet the use requirements. The recovered oil obtained after vacuum distillation of the upper floating oil B in comparative example 3 is turbid in appearance (as shown in Figure 3 ), contains more impurities, and affects the product quality, and the various indexes are quite different from those of new oil, so it can only be treated as waste oil and cannot be used for production again.​

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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