A method and system for solvent recovery of a solvent extraction extract from a waste oil regeneration solvent extraction

Abstract

The application discloses a waste oil regeneration solvent extraction extract solvent recovery method and belongs to the technical field of waste oil recycling. The method is as follows: the bottom product of a distillate oil after treatment in an extraction tower is pumped into a reduced-pressure stripping tower after treatment in a normal-pressure distillation tower and a reduced-pressure distillation tower or a double-tower treatment of the reduced-pressure distillation tower and the normal-pressure distillation tower, and the extraction oil is obtained at the bottom of the reduced-pressure stripping tower; the top product of the normal-pressure distillation tower is used to sequentially exchange heat with the reboiler of the reduced-pressure distillation tower and the bottom product of the extraction tower, and the top product of the reduced-pressure distillation tower is also used to exchange heat with the bottom product of the extraction tower; the waste heat of the reduced-pressure distillation tower and the normal-pressure distillation tower is reasonably utilized, and thus the energy consumption is effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of waste oil recycling technology, specifically relating to a method and system for recovering solvent from waste oil regeneration solvent extraction liquid. Background Technology

[0002] Waste oil regeneration solvents are costly. Re-extraction and recycling of these solvents can help reduce production costs. Currently, the re-extraction process involves heating and vaporizing the solvent in an atmospheric distillation column, followed by condensation and recovery. However, prolonged high-temperature heating at the bottom of the column can easily degrade the oil, affecting the solvent recovery rate. Furthermore, prolonged high temperatures lead to high energy consumption, and the high temperature of the product at the top of the column results in significant heat loss during condensation and gas-liquid separation, making efficient utilization of the energy. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for recovering solvent from waste oil regeneration solvent extraction liquid, in order to solve the technical problem of high energy consumption in the existing waste oil regeneration solvent re-extraction process.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for recovering solvent from waste oil regeneration solvent extraction liquid includes the following steps: The bottom product of the distillate oil after treatment in an extraction tower is then processed in a dual-tower system (atmospheric and atmospheric distillation) and pumped into a vacuum stripping tower. Extracted oil is produced at the bottom of the vacuum stripping tower. The top product of the vacuum distillation tower exchanges heat with the bottom product of the extraction tower, and then undergoes condensation and gas-liquid separation to produce solvent I. The top product of the atmospheric distillation tower exchanges heat with the reboiler of the vacuum distillation tower and the bottom product of the extraction tower, and then undergoes condensation and gas-liquid separation to form solvent II. A portion of the liquid from solvent I is pumped into the vacuum distillation tower as top reflux after gas-liquid separation, and a portion of the liquid from solvent II is pumped into the atmospheric distillation tower as top reflux. Non-condensable gases generated during the vacuum stripping and gas-liquid separation processes are vacuum-extracted.

[0005] Furthermore, the extraction tower is a rotary disc extraction tower or a packed extraction tower; when using a rotary disc extraction tower, it operates at atmospheric pressure with an operating temperature of 35–90°C and a solvent-to-distillate oil mass ratio of 1.0–4.0:1; when using a packed extraction tower, it operates at atmospheric pressure with an operating temperature of 45–90°C and a solvent-to-distillate oil mass ratio of 1.2–3.5:1.

[0006] Furthermore, the operating pressure of the vacuum distillation column is 10-50 kPa, and the reflux ratio is 0.3-1.5.

[0007] Furthermore, the atmospheric distillation column operates at a pressure of 60–120 kPa and a reflux ratio of 0.3–2.0.

[0008] Furthermore, the operating pressure of the vacuum stripping tower is 10-60 kPa, and the amount of stripping steam is 2-6% of the extracted oil mass.

[0009] Furthermore, the top product of the vacuum distillation column exchanges heat with the bottom product of the extraction column, and then the bottom product is heated once; the top product of the atmospheric distillation column exchanges heat with the bottom product of the extraction column, and then the bottom product is heated a second time.

[0010] Furthermore, the top product of the atmospheric distillation column exchanges heat with the reboiler of the vacuum distillation column, causing the reboiler to produce a gas phase reflux.

[0011] The present invention also provides a solvent recovery system for waste oil regeneration solvent extraction extract, which is applied to the above-mentioned waste oil regeneration solvent extraction extract solvent recovery method; the system includes: a rotary extraction tower, a vacuum distillation tower, an atmospheric distillation tower and a vacuum stripping tower; When the bottom product of the extraction column is first processed by a vacuum distillation column and then by a normal pressure distillation column: The bottom product of the rotary extraction tower is pumped into the vacuum distillation tower via pipeline through the first bottom pump, the first heat exchanger, and the second heat exchanger. The bottom product of the vacuum distillation column is pumped into the atmospheric distillation column via a pipeline through a second bottom pump and a first reboiler. The gas reflux from the first reboiler is introduced into the vacuum distillation column via a pipeline. The top product of the vacuum distillation column is introduced into the first gas-liquid separator via a pipeline through a first heat exchanger and a first condenser. The first gas-liquid separator is connected to a vacuum pumping device or a vacuum system. The liquid product of the first gas-liquid separator is pumped out in two paths by the first top pump: one path is pumped into the vacuum distillation column via a pipeline, and the other path is pumped into a collection device via a pipeline. The bottom product of the atmospheric distillation column is pumped out in two directions by a third bottom pump. One direction is pumped into the atmospheric distillation column via a pipeline through the second reboiler, and the other direction is pumped into the vacuum stripping column via a pipeline. The top product of the atmospheric distillation column is introduced into the second gas-liquid separator via a pipeline through the first reboiler, the second heat exchanger, and the second condenser. The second gas-liquid separator is connected to a vacuum equipment or a vacuum system. The liquid phase product of the second gas-liquid separator is pumped out in two directions by a second top pump. One direction is pumped into the atmospheric distillation column via a pipeline, and the other direction is pumped into a collection device via a pipeline. The product at the bottom of the vacuum stripping tower is pumped out by the fourth bottom pump, and the exhaust gas at the top of the vacuum stripping tower is connected to a vacuum equipment or a vacuum system. When the bottom product of the extraction tower is first processed by an atmospheric distillation tower and then by a vacuum distillation tower: The bottom product of the extraction tower is pumped into the atmospheric distillation tower via pipeline through the first bottom pump, the first heat exchanger, and the second heat exchanger. The bottom product of the atmospheric distillation column is pumped out in two ways by the fifth bottom pump. One way is pumped into the atmospheric distillation column through the third reboiler via a pipeline, and the other way is pumped into the vacuum distillation column through a pipeline. The top product of the atmospheric distillation column is introduced into the third gas-liquid separator through the fourth reboiler, the second heat exchanger, and the third condenser via pipeline. The liquid product of the third gas-liquid separator is pumped out in two ways by the third top pump. One way is pumped into the atmospheric distillation column through a pipeline, and the other way is pumped into the collection device through a pipeline. The bottom product of the vacuum distillation column is pumped out in two directions by the sixth bottom pump. One direction is pumped into the vacuum distillation column via a pipeline through the fourth reboiler, and the other direction is pumped into the vacuum stripping column via a pipeline. The top product of the vacuum distillation column is introduced into the fourth gas-liquid separator via a pipeline through the first heat exchanger and the fourth condenser. The liquid product of the fourth gas-liquid separator is pumped out in two directions by the fourth top pump. One direction is pumped into the vacuum distillation column via a pipeline, and the other direction is pumped into the collection device via a pipeline. The product at the bottom of the vacuum stripping tower is pumped out by the fourth bottom pump. The vacuum stripping tower, the third gas-liquid separator, and the fourth gas-liquid separator are respectively connected to vacuum equipment or vacuum system.

[0012] The beneficial effects of this invention are: 1. This invention separates and recovers the regenerated solvent (top product solvent I) from the impurity oil containing waste oil regeneration solvent through a vacuum distillation tower, then separates and recovers the regenerated solvent again through an atmospheric distillation tower (top product solvent II), and finally further vaporizes and separates the residual solvent through a vacuum stripping tower. The resulting extracted oil can be sold, increasing revenue streams. Multiple separations and collections can improve the recovery rate of the regenerated solvent. 2. By utilizing the heat released from the condensation of the products in the vacuum distillation column and the atmospheric distillation column to heat the bottom product of the extraction column, the efficient use of thermal energy is achieved, enabling the bottom product of the extraction column to heat up and vaporize without the need for an additional heat source. At the same time, the heat released from the condensation of the high-temperature top product of the atmospheric distillation column also provides a heat source for the reboiler of the vacuum distillation column, further realizing the efficient use of thermal energy. Compared with single-column processing, dual-column processing also has the advantage of shortening the heating time of the distillation columns, thus avoiding oil deterioration and reducing the energy consumption of the reboiler in the atmospheric distillation column. 3. By using two-stage distillation, either reducing pressure before atmospheric pressure or vice versa, the total external heat supply is reduced, resulting in a significant decrease in total energy consumption. At the same time, the total high-temperature residence time of the solvent is shortened, thus extending the solvent's service life. Attached Figure Description

[0013] Figure 1This is a system control flowchart of the decompression followed by atmospheric pressure treatment process in this invention; Figure 2 This is a system control flowchart of the atmospheric pressure followed by depressurization process in this invention. Detailed Implementation

[0014] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[0015] A method for solvent recovery from waste oil regeneration solvent extraction liquid is disclosed. The process route is as follows: the bottom product of the distillate oil after treatment in an extraction tower is pumped into a vacuum distillation tower. The negative pressure of the vacuum distillation tower lowers the vaporization heating temperature of the bottom product. The extraction tower can be a rotating disc extraction tower or a packed extraction tower. The bottom product of the vacuum distillation tower is pumped into an atmospheric distillation tower. The combined use of atmospheric and vacuum distillation towers achieves two-stage separation of the regenerated solvent. The bottom product of the atmospheric distillation tower is pumped into a vacuum stripping tower, where the extracted oil is produced at the bottom and can be sold. Both the vacuum distillation tower and the atmospheric distillation tower are plate distillation towers or packed distillation towers. Based on the dual-tower processing concept, in practical applications, the bottom product after treatment in the extraction tower can be first pumped into an atmospheric distillation tower, then treated in a vacuum distillation tower, and finally the extracted oil is produced through a vacuum stripping tower.

[0016] The overhead product of the vacuum distillation column exchanges heat with the bottom product of the extraction column, and then undergoes condensation and gas-liquid separation to produce the overhead product solvent I, which is the recovered regenerated solvent. The temperature of the overhead product in the vacuum distillation column is 130–160°C. After heat exchange with the bottom product of the extraction column, the bottom product of the extraction column can be heated only once, without the need for an additional heat source to preheat the bottom product of the extraction column.

[0017] The overhead product from the atmospheric distillation column exchanges heat with the reboiler of the vacuum distillation column and the bottom product of the extraction column in sequence. After condensation and gas-liquid separation, it forms the overhead product solvent II, which is also the recovered regenerated solvent. The overhead product temperature of the atmospheric distillation column is 170–210°C. Heating the reboiler of the vacuum distillation column creates a gas-phase reflux, and simultaneously reheats the bottom product of the extraction column, raising its temperature and further reducing the heating requirements for the bottom product of the extraction column.

[0018] Solvent I, the top product from the distillation column, undergoes gas-liquid separation, with a portion of the liquid pumped into a vacuum distillation column for use as cold reflux. Solvent II, the top product from the distillation column, undergoes gas-liquid separation, with a portion of the liquid pumped into an atmospheric distillation column for use as cold reflux. The non-condensable gases generated during the vacuum stripping and gas-liquid separation processes are removed under vacuum. This vacuuming process also serves to depressurize the vacuum distillation column.

[0019] Based on the above-mentioned solvent recovery method, this invention also provides a recovery system for the solvent recovery of the solvent extraction liquid from the above-mentioned waste oil regeneration solvent extraction method. The system includes: a rotary extraction tower T1, a vacuum distillation tower T2, an atmospheric distillation tower T3, and a vacuum stripping tower T4.

[0020] like Figure 1 As shown, when the bottom product of the extraction column is processed by a dual-tower system—first a vacuum distillation tower and then an atmospheric distillation tower: The bottom outlet of the rotary extraction tower T1 is connected to the feed inlet of the vacuum distillation tower T2 via pipelines through the first bottom pump P1, the first heat exchanger E1, and the second heat exchanger E2.

[0021] The vacuum distillation column T2 is either a plate distillation column or a packed distillation column. The bottom outlet of the vacuum distillation column T2 is connected to the feed inlet of the atmospheric distillation column T3 via pipelines, passing sequentially through the second bottom pump P2 and the first reboiler E3. The vapor reflux port of the first reboiler E3 is connected to the bottom reflux port of the vacuum distillation column T2 via a pipeline. The top outlet of the vacuum distillation column T2 is connected to the feed inlet of the first gas-liquid separator V1 via pipelines, passing sequentially through the first heat exchanger E1 and the first condenser E5; the first condenser E5 is a water-cooled condenser. The top exhaust port of the first gas-liquid separator V1 is connected to a vacuum pump or other vacuum equipment, or the existing vacuum system in the workshop. The liquid phase outlet of the first gas-liquid separator V1 is connected to the first top pump P5. The first top pump P5 pumps material out in two paths via a connected electric three-way valve: one path is connected to the top reflux port of the vacuum distillation column T2 via a pipeline, and the other path is connected to a storage tank or other collection equipment via a pipeline.

[0022] The atmospheric distillation column T3 is either a plate distillation column or a packed distillation column. The bottom outlet of the atmospheric distillation column T3 is connected to the third bottom pump P3. The third bottom pump P3 pumps out two streams via a connected electric three-way valve: one stream flows through a pipeline to the bottom reflux port of the atmospheric distillation column T3 via the second reboiler E4, and the other stream flows through a pipeline to the feed inlet of the vacuum stripping column T4. The top outlet of the atmospheric distillation column T3 flows through pipelines sequentially through the first reboiler E3, the second heat exchanger E2, and the second condenser E6 to the feed inlet of the second gas-liquid separator V2. The second condenser E6 is a water-cooled condenser. The top exhaust port of the second gas-liquid separator V2 is connected to a vacuum pump or other vacuum equipment, or the existing vacuum system in the workshop. The liquid phase outlet of the second gas-liquid separator V2 is connected to the second top pump P6. The second top pump P6 pumps out two streams through a connected three-way valve. One stream is connected to the top reflux port of the atmospheric distillation column T3 through a pipeline, and the other stream is connected to a storage tank or other collection equipment through a pipeline.

[0023] The bottom outlet of the vacuum stripping tower T4 is connected to the fourth bottom pump P4, which pumps out the extracted oil. The top exhaust port of the vacuum stripping tower T4 is connected to a vacuum pump or other vacuum equipment, or the existing vacuum system in the workshop. The stripping gas used in the vacuum stripping tower is water vapor.

[0024] In this system, the first reboiler E3 uses the top product of the atmospheric distillation column T3 as its heat source, and the second reboiler E4 uses a thermal oil heater as its heat source; the heat from the top product of the atmospheric distillation column T3 is directly utilized, which helps to reduce overall energy consumption.

[0025] like Figure 2 As shown, when the bottom product of the extraction column is processed by a dual-column system—first by an atmospheric distillation column and then by a vacuum distillation column—the system connection relationship changes, as detailed below: The bottom product of the extraction column T is pumped into the atmospheric distillation column T3 via pipelines through the first bottom pump P1, the first heat exchanger E1, and the second heat exchanger E2. The bottom product of atmospheric distillation column T3 is pumped out in two streams via the fifth bottom pump P7: one stream is pumped into atmospheric distillation column T3 via pipeline through the third reboiler E5, and the other stream is pumped into vacuum distillation column T2 via pipeline. The top product of atmospheric distillation column T3 is introduced into the third gas-liquid separator V3 via pipeline through the fourth reboiler E6, the second heat exchanger E2, and the third condenser E7. The liquid product of the third gas-liquid separator V3 is pumped out in two streams via the third top pump P8: one stream is pumped into atmospheric distillation column T3 via pipeline, and the other stream is pumped into a storage tank or other collection equipment via pipeline.

[0026] The bottom product of vacuum distillation column T2 is pumped out in two streams via the sixth bottom pump P9: one stream is pumped into vacuum distillation column T2 via pipeline through the fourth reboiler E6, and the other stream is pumped into vacuum stripping column T4 via pipeline. The top product of vacuum distillation column T2 is introduced into the fourth gas-liquid separator V4 via pipeline through the first heat exchanger E1 and the fourth condenser E8. The liquid product of the fourth gas-liquid separator is pumped out in two streams via the fourth top pump P10: one stream is pumped into vacuum distillation column T2 via pipeline, and the other stream is pumped into a storage tank or other collection equipment via pipeline.

[0027] The product at the bottom of the vacuum stripping tower T4 is pumped out by the fourth bottom pump P4. The vacuum stripping tower T2, the third gas-liquid separator V3, and the fourth gas-liquid separator V4 are respectively connected to a vacuum pump or other vacuum equipment, or to the existing vacuum system in the workshop.

[0028] In a dual-tower processing method, if a process of first vacuum distillation followed by atmospheric distillation is selected, a combination of a rotary disc extraction tower and a plate distillation tower can be used. This combination is more suitable for situations where the material is dirty, the throughput is large, the feed volume fluctuates greatly, and the separation requirements are high. Taking the solvent recovery process of the solvent extraction liquid involved in a 50,000-ton / year waste lubricating oil regeneration unit as an example, the rotary disc extraction tower T1 has a diameter of 0.8–1.2 meters, a tower height of 12–20 meters, 20–50 layers of rotating rings, and a rotation speed of 50–400 r / min; it operates at atmospheric pressure, with an operating temperature of 35–85℃, and a solvent to distillate mass ratio of 1.0–4.0:1. The vacuum distillation tower T2 is equipped with 8–15 perforated plates, an operating pressure of 10–50 kPa, and a reflux ratio (volume ratio) of 0.3–1.5. The atmospheric distillation column T3 is equipped with 15-20 perforated trays, operates at a pressure of 60-100 kPa, and has a reflux ratio (volume ratio) of 0.3-2.0. The vacuum stripping column T4 is equipped with 3-8 layers of herringbone stripping baffles, operates at a pressure of 10-60 kPa, and has a stripping steam volume of 2-6% of the extracted oil mass.

[0029] In dual-tower processing, if the process of first atmospheric distillation followed by vacuum distillation is selected, a combination of packed extraction tower and packed distillation tower can be used. This combination is more advantageous for situations where the material is relatively clean, the throughput is small, the raw material quantity fluctuates little, and the separation difficulty is moderate. Taking the solvent recovery process of the solvent extraction liquid involved in a 30,000-ton / year waste lubricating oil regeneration unit as an example: In application, extraction tower T1 uses a structured packed tower, with one or two stages of packing, a tower diameter of 0.8–1.5 meters, a tower height of 8–15 meters, atmospheric pressure operation, operating temperature of 45–90℃, and a solvent-to-oil ratio of 1.2–3.5:1. Atmospheric packed distillation tower T2 uses structured packing, with two stages of packing, operating pressure of 70–120 kPa, and a reflux ratio (volume ratio) of 0.5–2.0. Vacuum packed distillation tower T3 uses structured packing, with two stages of packing, operating pressure of 10–50 kPa, and a reflux ratio (volume ratio) of 0.5–1.5. The vacuum stripping tower is equipped with 3 to 8 layers of herringbone stripping baffles, operates at a pressure of 10 to 60 kPa, and the amount of stripping steam is 2 to 6% of the extracted oil mass.

[0030] Table 1 compares the external heating of the reboiler under different processes and reflux ratios using the two systems described above for NMP solvent recovery.

[0031] Table 1 Comparison of different processes and reflux ratios for NMP solvent recovery, along with external heating from the reboiler. As shown in Table 1, under the same reflux ratio, the reboiler energy consumption is significantly reduced when using a dual-tower system compared to a single-tower system.

[0032] When using a process of first reducing pressure and then atmospheric pressure distillation, the solvent recovery rate is 30-60% during reduced pressure distillation and 40-70% during atmospheric pressure distillation. The energy consumption of the dual-tower distillation recovery process is approximately 50-60% of that of the traditional single-tower distillation recovery process. The reflux ratio of the towers has a significant impact on the energy consumption of the distillation process; when the average reflux ratio of the distillation tower decreases from 1.2 to 0.6 at the same recovery rate, the energy consumption of this process decreases by 20%-25%. When using a process of first atmospheric pressure and then reducing pressure distillation, the solvent recovery rate is 40-65% during atmospheric pressure distillation and 35-60% during reduced pressure distillation. Compared with the traditional single-tower distillation recovery process, the energy consumption of the dual-tower distillation recovery process decreases by 40-50%. The reflux ratio in the solvent recovery process has a significant impact on the process energy consumption; when the average reflux ratio of the packed distillation tower increases from 0.5 to 1.1 at the same recovery rate, the energy consumption of the distillation process increases by more than 25%.

Claims

1. A method for recovering solvent from waste oil regeneration solvent extraction liquid, characterized in that, The bottom product of the distillate oil after processing in the extraction tower is then processed in a dual-tower system (atmospheric and atmospheric distillation) and pumped into a vacuum stripping tower. The bottom product of the vacuum stripping tower is the extracted oil. The top product of the vacuum distillation tower exchanges heat with the bottom product of the extraction tower and then undergoes condensation and gas-liquid separation to produce solvent I. The top product of the atmospheric distillation tower exchanges heat with the reboiler of the vacuum distillation tower and the bottom product of the extraction tower, and then undergoes condensation and gas-liquid separation to form solvent II. A portion of the liquid from solvent I is pumped into the vacuum distillation tower as top reflux after gas-liquid separation, and a portion of the liquid from solvent II is pumped into the atmospheric distillation tower as top reflux. The non-condensable gases generated in the vacuum stripping tower and gas-liquid separation processes are vacuum-extracted.

2. The recycling method as described in claim 1, characterized in that, The extraction tower is either a rotary disc extraction tower or a packed extraction tower. When using a rotary disc extraction tower, it operates at atmospheric pressure with an operating temperature of 35–90°C and a solvent-to-distillate oil mass ratio of 1.0–4.0:

1. When using a packed extraction tower, it operates at atmospheric pressure with an operating temperature of 45–90°C and a solvent-to-distillate oil mass ratio of 1.2–3.5:

1.

3. The recycling method as described in claim 1, characterized in that, The vacuum distillation column operates at a pressure of 10–50 kPa and a reflux ratio of 0.3–1.

5.

4. The recycling method as described in claim 1, characterized in that, The atmospheric distillation column operates at a pressure of 60–120 kPa and a reflux ratio of 0.3–2.

0.

5. The recycling method as described in claim 1, characterized in that, The operating pressure of the vacuum stripping tower is 10-60 kPa, and the amount of stripping steam is 2-6% of the extracted oil mass.

6. The recycling method as described in claim 1, characterized in that, The top product of the vacuum distillation column exchanges heat with the bottom product of the extraction column, and then the bottom product is heated once. The top product of the atmospheric distillation column exchanges heat with the bottom product of the extraction column, and then the bottom product is heated a second time.

7. The recycling method as described in claim 1, characterized in that, The top product of the atmospheric distillation column exchanges heat with the reboiler of the vacuum distillation column, causing the reboiler to produce a gas phase reflux.

8. A waste oil regeneration solvent extraction solvent recovery system, characterized in that, The method for recovering solvent from waste oil regeneration solvent extraction liquid according to any one of claims 1-7, the system comprising: a rotary extraction tower, a vacuum distillation tower, an atmospheric distillation tower, and a vacuum stripping tower; When the bottom product of the extraction column is first processed by a vacuum distillation column and then by a normal pressure distillation column: The bottom product of the rotary extraction tower is pumped into the vacuum distillation tower via pipeline through the first bottom pump, the first heat exchanger, and the second heat exchanger. The bottom product of the vacuum distillation column is pumped into the atmospheric distillation column via a pipeline through a second bottom pump and a first reboiler. The gas reflux from the first reboiler is introduced into the vacuum distillation column via a pipeline. The top product of the vacuum distillation column is introduced into the first gas-liquid separator via a pipeline through a first heat exchanger and a first condenser. The first gas-liquid separator is connected to a vacuum pumping device or a vacuum system. The liquid product of the first gas-liquid separator is pumped out in two paths by the first top pump: one path is pumped into the vacuum distillation column via a pipeline, and the other path is pumped into a collection device via a pipeline. The bottom product of the atmospheric distillation column is pumped out in two directions by a third bottom pump. One direction is pumped into the atmospheric distillation column via a pipeline through the second reboiler, and the other direction is pumped into the vacuum stripping column via a pipeline. The top product of the atmospheric distillation column is introduced into the second gas-liquid separator via a pipeline through the first reboiler, the second heat exchanger, and the second condenser. The second gas-liquid separator is connected to a vacuum equipment or a vacuum system. The liquid phase product of the second gas-liquid separator is pumped out in two directions by a second top pump. One direction is pumped into the atmospheric distillation column via a pipeline, and the other direction is pumped into a collection device via a pipeline. The product at the bottom of the vacuum stripping tower is pumped out by the fourth bottom pump, and the exhaust gas at the top of the vacuum stripping tower is connected to a vacuum equipment or a vacuum system. When the bottom product of the extraction tower is first processed by an atmospheric distillation tower and then by a vacuum distillation tower: The bottom product of the extraction tower is pumped into the atmospheric distillation tower via pipeline through the first bottom pump, the first heat exchanger, and the second heat exchanger. The bottom product of the atmospheric distillation column is pumped out in two ways by the fifth bottom pump. One way is pumped into the atmospheric distillation column through the third reboiler via a pipeline, and the other way is pumped into the vacuum distillation column through a pipeline. The top product of the atmospheric distillation column is introduced into the third gas-liquid separator through the fourth reboiler, the second heat exchanger, and the third condenser via pipeline. The liquid product of the third gas-liquid separator is pumped out in two ways by the third top pump. One way is pumped into the atmospheric distillation column through a pipeline, and the other way is pumped into the collection device through a pipeline. The bottom product of the vacuum distillation column is pumped out in two directions by the sixth bottom pump. One direction is pumped into the vacuum distillation column via a pipeline through the fourth reboiler, and the other direction is pumped into the vacuum stripping column via a pipeline. The top product of the vacuum distillation column is introduced into the fourth gas-liquid separator via a pipeline through the first heat exchanger and the fourth condenser. The liquid product of the fourth gas-liquid separator is pumped out in two directions by the fourth top pump. One direction is pumped into the vacuum distillation column via a pipeline, and the other direction is pumped into the collection device via a pipeline. The product at the bottom of the vacuum stripping tower is pumped out by the fourth bottom pump. The vacuum stripping tower, the third gas-liquid separator, and the fourth gas-liquid separator are respectively connected to vacuum equipment or vacuum system.

Images