A process for separating different grades of lubricating oil base stocks

Abstract

The application discloses a process method for separating different brand lubricating oil base oils, relates to the chemical and pharmaceutical technical fields, and particularly relates to the production and use fields of synthetic oils. The process method sends the oil to be separated into an atmospheric distillation unit to perform preliminary separation, sends the separated product meeting the brand standard of the device into a corresponding brand product storage tank, and sends the oil not separated by the atmospheric distillation into a vacuum distillation unit to further separate lubricating oil products of different brands. The atmospheric distillation unit and the vacuum distillation unit effectively separate the lubricating oil base oils of different brands, so that the device simultaneously produces lubricating oil base oil products of multiple brands, the product types are enriched, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the fields of chemical and pharmaceutical technology, and particularly to the production and use of synthetic oils. Background Technology

[0002] Lubricating oil base oils are indispensable materials in industry, and high-quality base oils can improve the performance of lubricating oils. Currently, the main high-quality lubricating oil base oils used in the market are fully synthetic oils, whose raw materials can be natural gas, coal-based syngas, C2~C40, etc. 15 Olefins, fatty acids, and fatty alcohols, among others, can be synthesized into oils that can be classified into different grades of lubricating oil base oil products based on their viscosity index. When the viscosity index range of the lubricating oil base oil synthesized by the production unit includes the viscosity range of multiple grades of lubricating oil base oil products, the unit can simultaneously produce multiple different grades of lubricating oil base oil products by separating the lubricating oil base oil product mixture.

[0003] Patent CN117264651A discloses a separation system, method and application of crude Fischer-Tropsch PAO base oil. It separates crude Fischer-Tropsch PAO base oil through continuous multi-stage molecular distillation. However, it requires a lot of molecular distillation equipment, which is costly, and does not mention the separation of ETO lubricating oil base oil.

[0004] Patent CN108467744A mentions a method for obtaining lubricating oil base oil by separating feedstock oil using a vacuum distillation column, but this method uses crude oil vacuum distillation to produce traditional lubricating oil base oil, which is not a fully synthetic oil.

[0005] Existing atmospheric and vacuum distillation technology for separating lubricating oil base oils is often used for the direct separation of different grades of lubricating oils from crude oil rather than for the separation of different grades of lubricating oils from fully synthetic oils. The atmospheric and vacuum distillation technology used for separating different grades of lubricating oil base oils in most fully synthetic oils is rarely studied or optimized in patents as a process in the production of fully synthetic lubricating oil base oils. Summary of the Invention

[0006] The purpose of this invention is to provide a process for separating base oils of different grades of lubricating oil, so as to solve the aforementioned problem.

[0007] A first aspect of the present invention provides an apparatus for separating base oils of different grades of lubricating oil, the apparatus comprising: (a) An atmospheric pressure column, wherein the atmospheric pressure column comprises: Atmospheric pressure tower heater (1), wherein the atmospheric pressure tower heater has a liquid inlet and a gas-liquid mixing outlet; Atmospheric distillation column (2), wherein the atmospheric distillation column has a liquid inlet, a reflux inlet, a gas phase outlet, a side stream inlet and outlet, a bottom liquid phase outlet and a bottom vapor inlet, and the liquid inlet of the atmospheric distillation column is connected to the gas-liquid mixing outlet of the atmospheric distillation column heater; The atmospheric distillation tower top heat exchanger (3) has a gas phase inlet and a liquid phase outlet. After condensation, a first-stage gas-liquid mixture is obtained. The gas phase inlet is connected to the gas phase outlet of the atmospheric distillation tower. The atmospheric pressure tower top reflux tank (4) has a liquid phase inlet, a liquid phase outlet, a wastewater outlet, a nitrogen inlet and a waste gas outlet, and the liquid phase inlet of the atmospheric pressure tower top reflux tank is connected to the liquid phase outlet of the atmospheric pressure tower top heat exchanger. Atmospheric stripping tower (5), the atmospheric stripping tower is located on the side line of the atmospheric distillation tower, and has a feed inlet, a gas phase outlet at the top of the tower and a liquid phase outlet at the bottom of the tower, and the feed inlet of the atmospheric stripping tower is connected to the side line liquid phase outlet of the atmospheric distillation tower. The atmospheric tower side-line heat exchanger (6) has a liquid inlet and an outlet, and the liquid inlet of the atmospheric tower side-line heat exchanger is connected to the liquid outlet of the atmospheric stripping tower. (b) A pressure-reducing tower, said pressure-reducing tower comprising: The pressure reducing tower heater (8) has a liquid phase inlet and a gas-liquid mixing outlet, and the liquid phase inlet of the pressure reducing tower heater is connected to the bottom liquid phase outlet of the atmospheric distillation tower (2); The vacuum distillation tower (9) has a feed inlet, a reflux inlet, a gas phase outlet, a side-stream liquid phase outlet and a bottom liquid phase outlet, and the feed inlet of the vacuum distillation tower is connected to the gas-liquid mixing outlet of the vacuum tower heater. The heat exchanger at the top of the pressure reducing tower (10) has a gas phase inlet and a gas-liquid two-phase outlet, and the gas phase inlet of the heat exchanger at the top of the pressure reducing tower is connected to the gas phase outlet of the pressure reducing distillation tower. The pressure reducing tower top reflux tank (11) has a gas-liquid two-phase inlet, a liquid phase outlet and a wastewater outlet, and the liquid phase inlet of the pressure reducing tower top reflux tank is connected to the gas-liquid two-phase outlet of the pressure reducing tower top heat exchanger. The vacuum stripping tower (12) is located on the side of the vacuum distillation tower and has a liquid inlet, a gas phase outlet at the top of the tower and a liquid phase outlet at the bottom of the tower. The liquid inlet of the vacuum stripping tower is connected to the liquid phase outlet on the side of the vacuum distillation tower. The side-line heat exchanger of the pressure reducing tower (13) has a liquid phase inlet and an outlet, and the liquid phase inlet of the side-line heat exchanger is connected to the bottom liquid phase outlet of the pressure reducing stripping tower. Vacuum pump (14), the vacuum pump draws suction from the pressure reducing tower system through a pipe connected to the pressure reducing tower top reflux tank to maintain the system negative pressure; The vacuum distillation tower bottom heat exchanger (15) has a liquid phase inlet and an outlet, and the liquid phase inlet of the vacuum distillation tower bottom heat exchanger is connected to the bottom liquid phase outlet of the vacuum distillation tower.

[0008] In another preferred embodiment, liquid is transported between the atmospheric distillation column and the vacuum distillation column heater via a pressure difference or elevation difference.

[0009] In another preferred embodiment, the vacuum pump is connected to the gas phase outlet of the heat exchanger at the top of the pressure reducing tower; In another preferred embodiment, the vacuum pump is simultaneously connected to the gas phase outlet of the heat exchanger at the top of the pressure reducing tower and the reflux tank at the top of the pressure reducing tower.

[0010] In another preferred embodiment, the liquid phase outlet of the atmospheric distillation column top reflux tank is connected to the reflux inlet of the atmospheric distillation column; and / or The liquid phase outlet of the reflux tank at the top of the vacuum distillation tower is connected to the reflux inlet of the vacuum distillation tower.

[0011] In another preferred embodiment, the atmospheric stripping tower is equipped with a reflux line, through which the gas phase is returned to the atmospheric distillation tower.

[0012] In another preferred embodiment, a pump (7) is further included between the atmospheric distillation column (2) and the vacuum distillation tower heater (8), the pump having a liquid inlet and an outlet; preferably, the pump is located downstream of the atmospheric distillation column, and the inlet is connected to the bottom liquid outlet of the atmospheric distillation column, and the outlet is connected to the inlet of the vacuum distillation tower heater.

[0013] In a second aspect of the invention, a process method for separating base oils of different grades of lubricating oil is provided, the method being carried out using the apparatus described in the first aspect of the invention, and the apparatus comprising the following steps: (1) The lubricating oil base oil product mixture to be separated is fed into the atmospheric pressure tower heater (1) for primary vaporization to obtain a primary gas-liquid mixture, which is then fed into the atmospheric pressure distillation tower (2) for distillation. The first gas phase product is obtained at the top of the tower, the first liquid phase product is obtained from the side stream, and the first bottom liquid is obtained from the bottom of the tower; wherein: (i) The first gaseous product separated in the atmospheric distillation column (2) enters the atmospheric distillation column top heat exchanger (3) at the top of the column and enters the atmospheric distillation column top reflux tank (4). The oil phase in the reflux tank is partially returned to the atmospheric distillation column (2) after water separation, and part of it is collected as product 1. The aqueous phase is sent to the downstream wastewater treatment device. (ii) The first liquid product obtained from the side stream is fed into an atmospheric stripping tower (5) for stripping to separate a second gaseous product and a second liquid product; the second gaseous product is returned to the atmospheric distillation tower, and the second liquid product is fed into the atmospheric tower side stream heat exchanger for heat exchange to obtain product 2; (2) The first bottom liquid is pumped (7) into the vacuum distillation tower heater (8) for secondary vaporization to obtain a second gas-liquid mixed phase product, which is then separated in a vacuum distillation tower (9) to obtain a second gas phase product, a second side-stream liquid phase product, and a second bottom liquid; wherein: (i) The second gas phase product separated in the vacuum distillation tower (9) enters the vacuum distillation tower top reflux tank (11) through the vacuum distillation tower top heat exchanger (10). The oil phase in the reflux tank is partially returned to the vacuum distillation tower (9) after water separation, and the water phase is sent to the downstream wastewater treatment device. (ii) The second side-stream liquid product is fed into a vacuum stripping tower (12) for stripping to obtain a second gaseous product and a second liquid product; the second gaseous product is returned to the atmospheric distillation tower, and the second liquid product is fed into the vacuum tower side-stream heat exchanger (13) for heat exchange to obtain product 3; (iii) The second bottom liquid is heat-exchanged by the vacuum tower bottom heat exchanger (15) to obtain product 4.

[0014] In another preferred embodiment, step (1) further includes: passing the wastewater separated from the atmospheric pressure tower top reflux tank (4) into a wastewater treatment facility; In another preferred embodiment, step (2) further includes: passing the wastewater separated from the pressure reducing tower top reflux tank (11) into a wastewater treatment facility.

[0015] In another preferred embodiment, step (2) further includes: extracting a portion of the oil phase from the top reflux tank of the pressure reducing tower as a product.

[0016] In another preferred embodiment, products 1, 2, 3 and 4 are lubricating oil base oils with different grades.

[0017] In another preferred embodiment, the lubricating oil product is selected from the group consisting of: From C2~C 15 C obtained from olefin synthesis 10 ~C 5000 olefin polymers; Oil synthesized from natural gas; Oil synthesized from syngas (CO + H2); or Oils obtained by dehydration of fatty acids and fatty alcohols through esterification reaction under the action of a catalyst.

[0018] In another preferred embodiment, the synthetic oil product is a fluid product at room temperature and pressure.

[0019] In another preferred embodiment, the lubricating oil mixture has a viscosity of 1-120 mmHg at 100°C. 2 / s of lubricating base oil.

[0020] In another preferred embodiment, the heater is selected from the group consisting of electric heaters, lava heaters, or heating furnaces.

[0021] In another preferred embodiment, the heat exchanger is selected from the group consisting of: shell and tube heat exchangers, jacketed heat exchangers, plate heat exchangers, etc.

[0022] In another preferred embodiment, the vacuum pump is selected from the group consisting of jet vacuum pumps, screw vacuum pumps, liquid ring vacuum pumps, Roots vacuum pumps, or combinations thereof.

[0023] In another preferred embodiment, the stripping gas used in the atmospheric stripping tower in step (3) is nitrogen or other gases that do not react with the lubricating oil base oil products.

[0024] In another preferred embodiment, the atmospheric distillation column can be provided with one, two or more side streams.

[0025] In another preferred embodiment, the vacuum distillation column can be provided with one, two, or more side lines. Attached Figure Description

[0026] Figure 1 This is a flow chart of a process for separating base oils of different grades of lubricating oil, wherein... 1—Atmospheric pressure tower heater; 2—Atmospheric pressure distillation tower; 3—Atmospheric pressure tower top heat exchanger; 4—Atmospheric pressure tower top reflux tank; 5—Atmospheric pressure stripping tower; 6—Atmospheric pressure tower side-stream heat exchanger; 7—Pump; 8—Vacuum pressure tower heater; 9—Vacuum pressure distillation tower; 10—Vacuum pressure tower top heat exchanger; 11—Vacuum pressure tower top reflux tank; 12—Vacuum pressure stripping tower; 13—Vacuum pressure tower side-stream heat exchanger; 14—Vacuum pump; 15—Vacuum pressure tower bottom heat exchanger.

[0027] Figure 2 This is a mass fraction distribution diagram of different grades of ETO obtained from the raw material after atmospheric and vacuum separation in Example 1.

[0028] Figure 3 This is a distribution chart of the mass fraction of different grades of ETO obtained from the raw material after atmospheric and vacuum separation in Example 2.

[0029] Figure 4 This is a mass fraction distribution diagram of different grades of ETO obtained from the raw material after atmospheric and vacuum separation in Example 3. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Other systems, methods, and / or features of this embodiment will become apparent to those skilled in the art after reviewing the following detailed description. All such additional systems, methods, features, and advantages are intended to be included within this specification, within the scope of this invention, and protected by the appended claims. Further features of the disclosed embodiments are described in the following detailed description, and these features will become apparent from the following detailed description.

[0032] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that the positional relationships are based on the orientation shown in the drawings and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0033] The raw material oil used in the embodiments of the present invention is a mixture of different grades of PAO, CTO and ETO lubricating oil base oils, but it does not limit the present invention to the separation of lubricating oil base oil mixtures obtained by the above process.

[0034] According to one aspect of the invention, see Figure 1 In a specific implementation, the process for separating base oils of different grades of lubricating oil includes the following steps: (1) The lubricating oil base oil product mixture to be separated is fed into the atmospheric pressure tower heater for primary vaporization to obtain a primary gas-liquid mixture. After entering the atmospheric pressure distillation tower, the gas phase goes to the top of the tower and the liquid phase falls to the bottom of the tower. Steam is introduced into the bottom of the atmospheric pressure distillation tower to carry out the light components in the liquid phase that has fallen to the bottom of the tower. (2) The vapor phase at the top of the atmospheric distillation tower enters the atmospheric distillation tower reflux tank through the atmospheric distillation tower top heat exchanger. Part of the oil is returned to the atmospheric distillation tower, and part of the oil is extracted as product 1. The wastewater is sent to the wastewater treatment facility. (3) The liquid phase product from the side stream of the atmospheric distillation tower enters the atmospheric stripping tower. The atmospheric stripping tower uses steam stripping or is equipped with a reboiler for stripping, so that the light components in the liquid phase product from the side stream of the atmospheric distillation tower become gas phase and return to the atmospheric distillation tower. The liquid phase is then removed as product 2 after heat exchange in the side stream heat exchanger of the atmospheric distillation tower. (4) The liquid phase at the bottom of the atmospheric distillation column is pumped into the vacuum distillation column heater for secondary vaporization, thereby obtaining a secondary gas-liquid mixture. After entering the vacuum distillation column, the gas phase goes to the top of the column and the liquid phase falls to the bottom of the column. Steam is introduced into the bottom of the vacuum distillation column to carry out the light components in the liquid phase that has fallen to the bottom of the column. (5) The vapor phase at the top of the vacuum distillation tower enters the vacuum distillation tower reflux tank through the vacuum distillation tower top heat exchanger, the vapor phase is discharged to the waste gas treatment facility as waste gas through the vacuum pump, the oil is returned to the vacuum distillation tower, and the wastewater is fed into the wastewater treatment facility. (6) The liquid phase product from the side stream of the vacuum distillation tower enters the vacuum stripping tower. The vacuum stripping tower uses steam stripping or is equipped with a reboiler for stripping, so that the light components in the liquid phase product from the side stream of the atmospheric distillation tower become gas phase and return to the vacuum distillation tower. The liquid phase is taken out as product 3 after heat exchange by the heat exchanger on the side stream of the vacuum distillation tower. (7) The liquid product at the bottom of the vacuum distillation column is collected as product 4 after heat exchange in the heat exchanger at the bottom of the vacuum distillation column.

[0035] Among them, Product 1, Product 2, Product 3 and Product 4 are lubricating oil base oils with different grades.

[0036] In this process, lubricating oil base oil products are vaporized twice under atmospheric and reduced pressure conditions to obtain lubricating oil base oil products with different boiling points. In steps (1), (2), and (3), the lubricating oil products are fed into a distillation column through a heat exchanger. After the wastewater is removed by the reflux tank at the top of the column, different grades of lubricating oil are collected through the side stream of the atmospheric pressure column. The lubricating oil with higher boiling point remaining at the bottom of the atmospheric pressure column is fed into the reduced pressure column and the above operation is repeated to separate the high-boiling-point lubricating oil products of different grades.

[0037] The process described in this invention is a series of atmospheric and vacuum pressure separation processes, which can be used to separate lubricating oil base products with relatively dense molecular weight distribution, such as ethylene polymers. It can achieve better separation for products with a difference of more than 8 carbon atoms between different grades.

[0038] Through the above process, different grades of lubricating oil base oil products can be separated, enabling the equipment to produce multiple grades of lubricating oil base oil products simultaneously.

[0039] Example 1 100t of CTO feedstock oil with a viscosity of 1.50 cst, obtained from direct coal liquefaction and hydrogenation, was heated and fed into an atmospheric distillation column. Product 1 was collected from the top of the atmospheric distillation column, and product 2 was collected from a side stream. The liquid phase from the bottom of the atmospheric distillation column was vaporized in a secondary stage and sent to a vacuum distillation column. The vacuum distillation column has two side streams: product 3 was collected from the first stream, and product 4 was collected from the second stream. The specifications of the produced products are shown in the table below. Table 1. CTO Product Indicators Example 2 20 tons of PAO feedstock, obtained from the hydrogenation of α-olefin polymerization, with a viscosity of 42.3 cSt, were heated and fed into an atmospheric distillation column for distillation. The atmospheric distillation column has two side streams. The first stream is used as a heat source to supply heat to other sections before returning to the column; no product is collected from this stream. Product 1 is collected from the top of the atmospheric distillation column, and product 2 is collected from the second stream. The liquid phase from the bottom of the atmospheric distillation column is vaporized in a secondary stage and sent to a vacuum distillation column. Product 3 is collected from the side stream of the vacuum distillation column, and product 4 is collected from the bottom. The specifications of the produced products are shown in the table below. Table 2. PAO Product Indicators Example 3 5000t of ETO feedstock, with a viscosity of 99.6 cSt, obtained from the direct polymerization and hydrogenation of ethylene, was heated and fed into an atmospheric distillation column for distillation. The atmospheric distillation column has two side streams: the second side stream is used as a heat source to supply heat to other sections and then returns, without collecting any product; the first side stream collects product 1; the top oil phase of the atmospheric distillation column is completely refluxed and no product is collected. The bottom liquid phase of the atmospheric distillation column is vaporized in a secondary stage and sent to a vacuum distillation column. The atmospheric distillation column has three side streams: the first side stream is used as a heat source to supply heat to other sections and then returns, without collecting any product; the second side stream collects product 2; the third side stream collects product 3; and the bottom product 4 is collected from the vacuum distillation column. The specifications of the produced products are shown in the table below. Table 3. ETO Product Indicators As can be seen from the results of the above embodiments, the process of the present invention has a good separation effect on lubricating oil base oils produced by different processes. Through this process, the device can produce multiple grades of lubricating oil base oil products at the same time, which greatly improves production efficiency.

[0040] While the present invention has been described above with reference to embodiments, it should be understood that the above are merely preferred embodiments of the invention and are not intended to limit the invention. Many changes and modifications can be made without departing from the scope of the invention. That is, the methods, systems, and devices discussed above are examples. Various configurations can be appropriately omitted, substituted, or added to various processes or components. For example, in alternative configurations, methods can be performed in a different order than described, and / or various components can be added, omitted, and / or combined. Moreover, features described with respect to certain configurations can be combined in various other configurations, such as different aspects and elements of the configuration can be combined in a similar manner. Furthermore, the elements therein can be updated as the technology develops; that is, many elements are examples and do not limit the scope of this disclosure or the claims.

[0041] In summary, the above detailed description is intended to be illustrative rather than restrictive, and it should be understood that the following claims (including all equivalents) are intended to define the spirit and scope of the invention. These embodiments should be understood as illustrative only and not as limiting the scope of protection of the invention. After reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent changes and modifications also fall within the scope defined by the claims of this invention.

Claims

1. An apparatus for separating base oils of different grades of lubricating oil, characterized in that, The device includes: (a) An atmospheric pressure column, wherein the atmospheric pressure column comprises: Atmospheric pressure tower heater (1), wherein the atmospheric pressure tower heater has a liquid inlet and a gas-liquid mixing outlet; Atmospheric distillation column (2), wherein the atmospheric distillation column has a liquid inlet, a reflux inlet, a gas phase outlet, a side stream inlet and outlet, a bottom liquid phase outlet and a bottom vapor inlet, and the liquid inlet of the atmospheric distillation column is connected to the gas-liquid mixing outlet of the atmospheric distillation column heater; The atmospheric distillation tower top heat exchanger (3) has a gas phase inlet and a liquid phase outlet. After condensation, a first-stage gas-liquid mixture is obtained. The gas phase inlet is connected to the gas phase outlet of the atmospheric distillation tower. The atmospheric pressure tower top reflux tank (4) has a liquid phase inlet, a liquid phase outlet, a wastewater outlet, a nitrogen inlet and a waste gas outlet, and the liquid phase inlet of the atmospheric pressure tower top reflux tank is connected to the liquid phase outlet of the atmospheric pressure tower top heat exchanger. Atmospheric stripping tower (5), the atmospheric stripping tower is located on the side line of the atmospheric distillation tower, and has a feed inlet, a gas phase outlet at the top of the tower and a liquid phase outlet at the bottom of the tower, and the feed inlet of the atmospheric stripping tower is connected to the side line liquid phase outlet of the atmospheric distillation tower. The atmospheric tower side-line heat exchanger (6) has a liquid inlet and an outlet, and the liquid inlet of the atmospheric tower side-line heat exchanger is connected to the liquid outlet of the atmospheric stripping tower. (b) A pressure-reducing tower, said pressure-reducing tower comprising: The pressure reducing tower heater (8) has a liquid phase inlet and a gas-liquid mixing outlet, and the liquid phase inlet of the pressure reducing tower heater is connected to the bottom liquid phase outlet of the atmospheric distillation tower (2); The vacuum distillation tower (9) has a feed inlet, a reflux inlet, a gas phase outlet, a side-stream liquid phase outlet and a bottom liquid phase outlet, and the feed inlet of the vacuum distillation tower is connected to the gas-liquid mixing outlet of the vacuum tower heater. The heat exchanger at the top of the pressure reducing tower (10) has a gas phase inlet and a gas-liquid two-phase outlet, and the gas phase inlet of the heat exchanger at the top of the pressure reducing tower is connected to the gas phase outlet of the pressure reducing distillation tower. The pressure reducing tower top reflux tank (11) has a gas-liquid two-phase inlet, a liquid phase outlet and a wastewater outlet, and the liquid phase inlet of the pressure reducing tower top reflux tank is connected to the gas-liquid two-phase outlet of the pressure reducing tower top heat exchanger. The vacuum stripping tower (12) is located on the side of the vacuum distillation tower and has a liquid inlet, a gas phase outlet at the top of the tower and a liquid phase outlet at the bottom of the tower. The liquid inlet of the vacuum stripping tower is connected to the liquid phase outlet on the side of the vacuum distillation tower. The side-line heat exchanger of the pressure reducing tower (13) has a liquid phase inlet and an outlet, and the liquid phase inlet of the side-line heat exchanger is connected to the bottom liquid phase outlet of the pressure reducing stripping tower. Vacuum pump (14), the vacuum pump draws suction from the pressure reducing tower system through a pipe connected to the pressure reducing tower top reflux tank to maintain the system negative pressure; The vacuum distillation tower bottom heat exchanger (15) has a liquid phase inlet and an outlet, and the liquid phase inlet of the vacuum distillation tower bottom heat exchanger is connected to the bottom liquid phase outlet of the vacuum distillation tower. In another preferred embodiment, liquid is transported between the atmospheric distillation column and the vacuum distillation column heater via a pressure difference or a height difference; In another preferred embodiment, the vacuum pump is connected to the gas phase outlet of the heat exchanger at the top of the pressure reducing tower; In another preferred embodiment, the vacuum pump is simultaneously connected to the gas phase outlet of the heat exchanger at the top of the pressure reducing tower and the reflux tank at the top of the pressure reducing tower.

2. The apparatus as claimed in claim 1, characterized in that, The liquid phase outlet of the atmospheric distillation column top reflux tank is connected to the reflux inlet of the atmospheric distillation column; and / or The liquid phase outlet of the reflux tank at the top of the vacuum distillation tower is connected to the reflux inlet of the vacuum distillation tower.

3. The apparatus as described in claim 1, characterized in that, The atmospheric stripping tower is equipped with a reflux pipeline, through which the gas phase is returned to the atmospheric distillation tower.

4. The apparatus as claimed in claim 1, characterized in that, The atmospheric distillation column (2) and the vacuum distillation tower heater (8) are further provided with a pump (7), which has a liquid phase inlet and an outlet; preferably, the pump is located downstream of the atmospheric distillation column, and its inlet is connected to the liquid phase outlet at the bottom of the atmospheric distillation column, and its outlet is connected to the inlet of the vacuum distillation tower heater.

5. A process for separating base oils of different grades of lubricating oil, wherein the method is carried out using the apparatus as described in claim 1, and the apparatus includes the following steps: (1) The lubricating oil base oil product mixture to be separated is fed into the atmospheric pressure tower heater (1) for primary vaporization to obtain a primary gas-liquid mixture, which is then fed into the atmospheric pressure distillation tower (2) for distillation. The first gas phase product is obtained at the top of the tower, the first liquid phase product is obtained from the side stream, and the first bottom liquid is obtained from the bottom of the tower; wherein: (i) The first gaseous product separated in the atmospheric distillation column (2) enters the atmospheric distillation column top heat exchanger (3) at the top of the column and enters the atmospheric distillation column top reflux tank (4). The oil phase in the reflux tank is partially returned to the atmospheric distillation column (2) after water separation, and part of it is collected as product 1. The aqueous phase is sent to the downstream wastewater treatment device. (ii) The first liquid product obtained from the side stream is fed into an atmospheric stripping tower (5) for stripping to separate a second gaseous product and a second liquid product; the second gaseous product is returned to the atmospheric distillation tower, and the second liquid product is fed into the atmospheric tower side stream heat exchanger for heat exchange to obtain product 2; (2) The first bottom liquid is pumped (7) into the vacuum distillation tower heater (8) for secondary vaporization to obtain a second gas-liquid mixed phase product, which is then separated in a vacuum distillation tower (9) to obtain a second gas phase product, a second side-stream liquid phase product, and a second bottom liquid; wherein: (i) The second gas phase product separated in the vacuum distillation tower (9) enters the vacuum distillation tower top reflux tank (11) through the vacuum distillation tower top heat exchanger (10). The oil phase in the reflux tank is partially returned to the vacuum distillation tower (9) after water separation, and the water phase is sent to the downstream wastewater treatment device. (ii) The second side-stream liquid product is fed into a vacuum stripping tower (12) for stripping to obtain a second gaseous product and a second liquid product; the second gaseous product is returned to the atmospheric distillation tower, and the second liquid product is fed into the vacuum tower side-stream heat exchanger (13) for heat exchange to obtain product 3; (iii) The second bottom liquid is heat-exchanged by the vacuum tower bottom heat exchanger (15) to obtain product 4.

6. The process as described in claim 5, characterized in that, The lubricating oil product is selected from the following group: From C2~C 15 C obtained from olefin synthesis 10 ~C 5000 olefin polymers; Oil synthesized from natural gas; Oil synthesized from syngas (CO + H2); or Oil obtained by dehydration of fatty acids and fatty alcohols through esterification reaction under the action of a catalyst; In another preferred embodiment, the synthetic oil product is a fluid product at room temperature and pressure; In another preferred embodiment, the lubricating oil mixture has a viscosity of 1-120 mmHg at 100°C. 2 / s of lubricating base oil.

7. The process as described in claim 5, characterized in that, The heater is selected from the group consisting of: electric heaters, lava heaters, or heating furnaces.

8. The process as described in claim 5, characterized in that, The heat exchanger is selected from the following group: shell and tube heat exchanger, jacketed heat exchanger, plate heat exchanger, etc.

9. The process as described in claim 5, characterized in that, The vacuum pump is selected from the group consisting of: jet vacuum pump, screw vacuum pump, liquid ring vacuum pump, Roots vacuum pump, or a combination thereof.

10. The process as described in claim 5, characterized in that, The stripping gas used in the atmospheric stripping tower in step (3) is nitrogen or other gases that do not react with lubricating oil base oil products.

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