Aromatic hydrocarbon extraction device

Abstract

The utility model provides an aromatic hydrocarbon extraction device. The aromatic hydrocarbon extraction device comprises a de-heavy tower, an extraction tower, a recovery tower, a first rectifying tower and a second rectifying tower which are connected in sequence, a tower top steam outlet of the de-heavy tower is connected with a heat source inlet of an extraction tower reboiler, and a heat source outlet of the extraction tower reboiler is connected with a feed port of the extraction tower through a de-heavy tower return tank. A discharge port of the extraction tower is connected with a feed port of the recovery tower, a tower top steam outlet of the recovery tower is connected with a feed port of the first rectifying tower through a recovery tower return tank, and a discharge port of the first rectifying tower is connected with a feed port of the second rectifying tower. The aromatic hydrocarbon extraction device disclosed by the utility model has the characteristics of high aromatic hydrocarbon extraction rate, high purity, energy conservation and high efficiency.

Description

Technical Field

[0001] The utility model relates to the technical field of aromatics extraction, and particularly to an aromatics extraction device. Background Art

[0002] Aromatics are important organic chemical raw materials, such as benzene, toluene, xylene, ethylbenzene, etc., which are widely used in the production of products such as plastics, rubbers, and chemical fibers. Aromatics extraction is a widely used aromatics production process, and most aromatics extraction devices adopt the solvent liquid-liquid extraction process. NFM (N-formylmorpholine) is a commonly used aromatics extraction agent, whose boiling point is much lower than that of other extraction solvents such as sulfolane and tetraethylene glycol. It has the advantages of simple recovery, non-toxicity, no corrosion to equipment, good chemical stability, and low selling price. However, since this process requires multiple towers to complete the separation, both the operating cost and the equipment cost are relatively high. Therefore, how to save energy on this basis is crucial.

[0003] CN105511264A discloses an optimization method, device, and system for aromatics extraction operation. By using an economic optimization target model, the optimal raw material inlet flow rate, optimal reflux ratio, and solvent ratio are calculated and sent to the controller, so that the aromatics extraction device operates according to the production operation instructions, thereby improving the aromatics yield. However, energy conservation and consumption reduction are not considered. CN214327643U discloses an energy-saving aromatics extraction device, which recovers the heat of the overhead steam of the toluene tower for the reboiler of the benzene tower, saves the consumption of the reboiler heating steam, and at the same time saves the consumption of the overhead circulating cooling water of the toluene tower, achieving energy conservation and environmental protection. However, the steam consumption of this device is still relatively large, and the heat energy utilization is not sufficient. In the literature "Separation Simulation and Design Optimization of Aromatics in Aromatics Extraction Device", the separation of mixed aromatics (benzene, toluene, xylene) is simulated by conventional two-column distillation and two-column differential pressure thermally coupled distillation. On the premise of ensuring the separation efficiency, the number of theoretical plates, feed position, reflux ratio, etc. are optimized, the most suitable separation process is selected, and the low-temperature heat utilization efficiency is improved to achieve the best energy conservation and consumption reduction effect. Summary of the Utility Model

[0004] In order to solve one of the above technical problems existing in the prior art, the utility model provides an aromatics extraction device, which has the characteristics of low energy consumption, short process, stable system, and high product recovery rate.

[0005] The utility model provides an aromatic extraction device, which includes a deweighting tower, an extraction tower, a recovery tower, a first distillation tower and a second distillation tower connected in sequence. It is characterized in that the overhead steam outlet of the deweighting tower is connected to the heat source inlet of the reboiler of the extraction tower, the heat source outlet of the reboiler of the extraction tower is connected to the feed inlet of the extraction tower through a deweighting tower reflux drum, the discharge outlet of the extraction tower is connected to the feed inlet of the recovery tower, the overhead steam outlet of the recovery tower is connected to the feed inlet of the first distillation tower through a recovery tower reflux drum, and the discharge outlet of the first distillation tower is connected to the feed inlet of the second distillation tower.

[0006] Preferably, the overhead steam outlet of the second distillation tower is connected to the heat source inlet of the reboiler of the first distillation tower, the heat source outlet of the reboiler of the first distillation tower is respectively connected to a benzene storage tank and a liquid phase inlet arranged at the top of the second distillation tower through a second distillation tower reflux drum, and the liquid phase inlet at the top of the second distillation tower is used to make part of the liquid in the second distillation tower reflux drum enter the top of the second distillation tower.

[0007] Preferably, the overhead steam outlet of the first distillation tower is connected to the inlet of the first distillation tower reflux drum through a first distillation tower condenser, the outlet of the first distillation tower reflux drum is respectively connected to the benzene storage tank and a liquid phase inlet located at the top of the first distillation tower through a first distillation tower reflux pump, and the liquid phase inlet at the top of the first distillation tower is used to make part of the liquid in the first distillation tower reflux drum return to the top of the first distillation tower.

[0008] In some embodiments, a reboiler of the second distillation tower is connected to the bottom of the second distillation tower; the discharge outlet of the second distillation tower is connected to a toluene storage tank through a second distillation tower cooler.

[0009] In some embodiments, the outlet of the deweighting tower reflux drum is also connected to a liquid phase inlet located at the top of the deweighting tower through a deweighting tower reflux pump, and the liquid phase inlet at the top of the deweighting tower is used to make part of the liquid in the deweighting tower reflux drum return to the top of the deweighting tower.

[0010] In some embodiments, a reboiler of the deweighting tower is connected to the bottom of the deweighting tower; the discharge outlet of the deweighting tower is connected to a first waste liquid storage tank.

[0011] In some embodiments, the extraction tower is provided with an extraction solvent inlet, which is used to make the extraction solvent contact with the aromatic hydrocarbon material entering the extraction tower from the feed inlet of the extraction tower for extraction.

[0012] In some embodiments, the vapor outlet at the top of the extraction column is connected to the inlet of the extraction column reflux drum through an extraction column condenser, and the outlet of the extraction column reflux drum is connected to the second waste liquid storage tank and the liquid phase inlet at the top of the extraction column through an extraction column reflux pump. The liquid phase inlet at the top of the extraction column is used to return part of the liquid in the extraction column reflux drum to the top of the extraction column.

[0013] In some embodiments, the outlet of the recovery column reflux drum is also connected to the liquid phase inlet at the top of the recovery column. The liquid phase inlet at the top of the recovery column is used to return part of the liquid in the recovery column reflux drum to the top of the recovery column.

[0014] In some embodiments, a recovery column condenser is also connected between the vapor outlet at the top of the recovery column and the recovery column reflux drum. A recovery column reboiler is connected to the bottom of the recovery column, and the product outlet of the recovery column is connected to the extraction solvent storage tank through a recovery column cooler.

[0015] In some embodiments, the number of theoretical plates of the heavy component separation column is 10 - 70.

[0016] In some embodiments, the number of theoretical plates of the extraction column is 20 - 90.

[0017] In some embodiments, the number of theoretical plates of the recovery column is 20 - 80.

[0018] In some embodiments, the number of theoretical plates of the first distillation column is 30 - 80.

[0019] In some embodiments, the number of theoretical plates of the second distillation column is 30 - 80.

[0020] Compared with the prior art, the present utility model has the following beneficial effects:

[0021] The device of the present utility model uses the vapor at the top of the heavy component separation column as the heat source for the reboiler at the bottom of the extraction column, and the vapor at the top of the second distillation column (toluene column) as the heat source for the reboiler of the first distillation column (benzene column). On the basis of ensuring that the product benzene is above 99.95% and the product toluene is above 99.9%, the heat utilization rate is high, the product purity is high, the device energy consumption is saved, and the operation cost is reduced. The equipment investment of the present utility model is small, and the energy consumption can be effectively reduced by more than 40% compared with the traditional process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of an aromatic hydrocarbon extraction device according to a specific embodiment of the present utility model.

[0023] Figure 2 Schematic diagram of the aromatic hydrocarbon extraction device in Comparative Example 1 of the present utility model.

[0024] The reference numerals are as follows:

[0025] 1 - heavy component removal tower; 2 - reboiler of heavy component removal tower; 3 - reflux drum of heavy component removal tower; 4 - reboiler of extraction tower; 5 - reflux pump of heavy component removal tower; 6 - extraction tower; 7 - condenser of extraction tower; 8 - reflux drum of extraction tower; 9 - reflux pump of extraction tower; 10 - bottom liquid pump of extraction tower; 11 - recovery tower; 12 - reboiler of recovery tower; 13 - condenser of recovery tower; 14 - reflux drum of recovery tower; 15 - reflux pump of recovery tower; 16 - NFM cooler; 17 - first rectification tower; 18 - condenser of first rectification tower; 19 - reflux drum of first rectification tower; 20 - reboiler of first rectification tower; 21 - bottom liquid pump of first rectification tower; 22 - reflux pump of first rectification tower; 23 - second rectification tower; 24 - reboiler of second rectification tower; 25 - toluene cooler; 26 - reflux drum of second rectification tower; 27 - reflux pump of second rectification tower; 28 - condenser of heavy component removal tower. Detailed implementation manners

[0026] In order to make the purpose, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below in conjunction with embodiments and drawings. The specific embodiments described herein are only used to explain the present utility model and do not constitute any limitation to the present utility model.

[0027] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0028] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "linked" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be an abutting connection, it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0029] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present utility model. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features.

[0030] As used herein, the term "reformate" or "reformate oil" is an intermediate petroleum product. It is mainly composed of C6 - C11 naphtha fractions. Under certain operating conditions and the action of a catalyst in a catalytic reforming unit, the hydrocarbon molecules are rearranged, and naphthenes and alkanes are converted into aromatics or isoparaffins. After extraction and separation, products such as benzene, toluene, and xylene can be obtained from the reformate.

[0031] According to a specific embodiment of the present utility model, as Figure 1 shown, an aromatics extraction device is provided. The aromatics extraction device includes a de - heavy tower 1, an extraction tower 6, a recovery tower 11, a first distillation tower 17, and a second distillation tower 23 connected in sequence. The top steam outlet of the de - heavy tower 1 is connected to the heat source inlet of the extraction tower reboiler 4. The heat source outlet of the extraction tower reboiler 4 is connected to the feed inlet of the extraction tower through a de - heavy tower reflux drum 3. The outlet of the extraction tower is connected to the feed inlet of the recovery tower 11. The top steam outlet of the recovery tower 11 is connected to the feed inlet of the first distillation tower 17 through a recovery tower reflux drum 14. The outlet of the first distillation tower 17 is connected to the feed inlet of the second distillation tower 23.

[0032] In the present utility model, the de - heavy tower is used to remove non - aromatic heavy components in the reformate with boiling points higher than benzene and toluene. The top steam outlet extracts benzene, toluene, and non - aromatic light components with boiling points lower than benzene and toluene.

[0033] In the present utility model, the recovery tower is used to separate aromatics (benzene and toluene) and an extraction solvent (NFM, N - formylmorpholine) in the extract obtained from the outlet of the extraction tower.

[0034] In the present utility model, the first distillation tower is used to obtain benzene products through distillation separation.

[0035] In the present utility model, the second distillation tower is used to obtain toluene products through distillation separation.

[0036] Further, the top steam outlet of the second rectification column 23 is connected to the heat source inlet of the first rectification column reboiler 20. The heat source outlet of the first rectification column reboiler 20 is respectively connected to the benzene storage tank and the liquid phase inlet provided at the top of the second rectification column 23 through the second rectification column reflux drum 26. The liquid phase inlet at the top of the second rectification column 23 is used to allow part of the liquid in the second rectification column reflux drum 26 to enter the top of the second rectification column 23.

[0037] Further, the second rectification column reflux drum 26 is respectively connected to the benzene storage tank and the liquid phase inlet provided at the top of the second rectification column 23 through the second refining column reflux pump 27.

[0038] Further, the top steam outlet of the first rectification column 17 is connected to the inlet of the first rectification column reflux drum 19 through the first rectification column condenser 18. The outlet of the first rectification column reflux drum 19 is respectively connected to the benzene storage tank and the liquid phase inlet located at the top of the first rectification column through the first rectification column reflux pump 22. The liquid phase inlet at the top of the first rectification column is used to allow part of the liquid in the first rectification column reflux drum to return to the top of the first rectification column.

[0039] Further, the discharge port of the first rectification column 17 is connected to the feed port of the second rectification column 23 through the first rectification column bottom liquid pump 21.

[0040] Further, the bottom of the second rectification column is connected to a second rectification column reboiler 24.

[0041] Further, the discharge port of the second rectification column is connected to the toluene storage tank through the toluene cooler 25.

[0042] Further, the outlet of the deweighting column reflux drum 3 is also connected to the liquid phase inlet located at the top of the deweighting column through the deweighting column reflux pump 5. The liquid phase inlet at the top of the deweighting column is used to allow part of the liquid in the deweighting column reflux drum 3 to return to the top of the deweighting column.

[0043] Further, the bottom of the deweighting column 1 is connected to a deweighting column reboiler 2.

[0044] Further, the discharge port of the deweighting column 1 is connected to a first waste liquid storage tank.

[0045] Further, the extraction column 6 is provided with an extraction solvent inlet. The extraction solvent inlet is used to allow the extraction solvent to contact the aromatic hydrocarbon material entering the extraction column from the extraction column feed port for extraction.

[0046] Further, the vapor outlet at the top of the extraction column 6 is connected to the inlet of the extraction column reflux drum 8 through the extraction column condenser 7, and the outlet of the extraction column reflux drum 8 is respectively connected to the second waste liquid storage tank and the liquid phase inlet at the top of the extraction column through the extraction column reflux pump 9. The liquid phase inlet at the top of the extraction column is used to return part of the liquid in the extraction column reflux drum to the top of the extraction column.

[0047] Further, the discharge port of the extraction column 6 is connected to the feed port of the recovery column 11 through the extraction column bottom liquid pump 10.

[0048] Further, the outlet of the recovery column reflux drum 14 is also connected to the liquid phase inlet at the top of the recovery column. The liquid phase inlet at the top of the recovery column is used to return part of the liquid in the recovery column reflux drum to the top of the recovery column.

[0049] Further, the outlet of the recovery column reflux drum 14 is respectively connected to the feed port of the first distillation column 17 and the liquid phase inlet at the top of the recovery column through the recovery column reflux pump 15.

[0050] Further, a recovery column condenser 13 is also connected between the vapor outlet at the top of the recovery column and the recovery column reflux drum 14.

[0051] Further, a recovery column reboiler 12 is connected to the bottom of the recovery column 11.

[0052] Further, the discharge port of the recovery column 11 is connected to the extraction solvent storage tank through the extraction solvent (NFM) cooler 16.

[0053] Further, the number of theoretical plates of the heavy component removal column 1 is 10 - 70.

[0054] Further, the number of theoretical plates of the extraction column 6 is 20 - 90.

[0055] Further, the number of theoretical plates of the recovery column 11 is 20 - 80.

[0056] Further, the number of theoretical plates of the first distillation column 17 is 30 - 80.

[0057] Further, the number of theoretical plates of the second distillation column 23 is 30 - 80.

[0058] According to a specific embodiment of the present invention, the usage method of the aromatic hydrocarbon extraction device includes the following steps:

[0059] (S1) The reformate containing toluene and benzene enters the heavy component removal column 1, and the gas-phase material I is taken out from the top of the column. Among them, the gas-phase material I includes benzene, toluene, and non-aromatic hydrocarbons with boiling points lower than benzene and toluene.

[0060] (S2) The gaseous material I is condensed by heat exchange with the bottom material of the extraction column 6 in the extraction column reboiler 4 and then enters the deweighting column reflux drum 3, and then is transported to the extraction column 6 to be mixed with the extraction solvent for extraction treatment;

[0061] (S3) The bottom product of the extraction column 6, which contains the extraction liquid of benzene and toluene, is taken out and enters the middle part of the recovery column 11 for separation treatment;

[0062] (S4) The material IV containing benzene and toluene is taken out from the top of the recovery column 11, and the material IV enters the first distillation column 17 for distillation treatment;

[0063] (S5) Benzene is taken out from the top of the first distillation column 17; the material V containing toluene and benzene is taken out from the bottom of the first distillation column 17, and the material V enters the second distillation column 23 for distillation treatment;

[0064] (S6) The gaseous benzene is taken out from the top of the second distillation column 23, and the product toluene is taken out from the bottom; among them, the gaseous benzene taken out from the top of the second distillation column 23 is condensed by heat exchange with the bottom of the first distillation column in the first distillation column reboiler 20 and then enters the second distillation column reflux drum 26.

[0065] Further, in step (S1), the bottom product of the deweighting column is material II, and the material II includes non-aromatics with boiling points higher than benzene and toluene.

[0066] Further, in step (S2), the material in the deweighting column reflux drum 3 is divided into two parts: one part is returned to the top of the deweighting column as reflux liquid by the deweighting column reflux pump 5, and the other part is transported to the extraction column 6 to be mixed with the extraction solvent for extraction treatment.

[0067] Further, in step (S3), the gaseous material is taken out from the top of the extraction column 6, and the gaseous material is condensed by the extraction column condenser 7 and then enters the extraction column reflux drum 8. In some embodiments, in step (S3), the logistics of the extraction column reflux drum 8 is divided into two parts: one part is returned to the top of the extraction column as reflux liquid by the extraction column reflux pump 9, and the other part is sent to the waste liquid storage tank 2.

[0068] Further, in step (S4), the NFM solvent is taken out from the bottom of the recovery column 11, and the NFM solvent is cooled by the NFM solvent cooler 16 and then sent to the solvent storage tank for recycling.

[0069] Further, in step (S5), the gaseous material (benzene) is taken out from the top of the first distillation column 17, and the gaseous material (benzene) is condensed by the first distillation column condenser 18 and then enters the first distillation column reflux drum 19, and then is divided into two parts: one part is returned to the top of the first distillation column as reflux liquid by the first distillation column reflux pump 22, and the other part enters the benzene storage tank.

[0070] Further, in step (S6), the gaseous benzene withdrawn from the top of the second rectification column 23 exchanges heat with the bottom of the first rectification column through the first rectification column reboiler 20, is condensed, and then enters the second rectification column reflux drum 26. Then it is divided into two parts: one part is returned to the top of the second rectification column as reflux liquid through the second rectification column reflux pump 27, and the other part enters the benzene temporary storage tank. The bottom of the second rectification column 23 is heated by the second rectification column reboiler 24, and toluene is withdrawn, cooled by the toluene cooler 25, and then sent to the toluene temporary storage tank.

[0071] Example 1

[0072] Using the extraction device as Figure 1 shown, a mixed solution containing benzene and toluene from an olefin plant has the following composition: 73.21% benzene, 14.96% toluene, with some C5-C8 alkane impurities mixed in, and the feed rate is 18750 kg / h.

[0073] The raw material (mixed solution containing benzene and toluene) enters the de-heavy tower 1. The operating pressure of the de-heavy tower 1 is 400 Kpa, the total tower pressure drop is 40.8 Kpa, the top temperature is 136 °C, and the reflux ratio is 1.48.

[0074] The gaseous material at the top of the de-heavy tower 1 (containing benzene, toluene, and light components with boiling points lower than benzene and toluene) exchanges heat with the bottom material of the extraction tower 6 through the extraction tower reboiler 4, is condensed, and then enters the de-heavy tower reflux drum 3. Then it is divided into two parts: one part is returned to the top of the de-heavy tower as reflux liquid through the de-heavy tower reflux pump 5, and the other part is transported to the middle of the extraction tower 6 for extraction treatment. After the bottom of the de-heavy tower is heated by the de-heavy tower reboiler 2, the heavy components with boiling points higher than benzene and toluene are withdrawn and sent to the waste liquid temporary storage tank 1.

[0075] The solvent NFM enters from the middle of the extraction tower 6, with a feed rate of 147994 kg / h. The operating pressure of the extraction tower is 50 Kpa, the top temperature is 58 °C, and the reflux ratio is 1.36. The gaseous material at the top of the extraction tower 6 is condensed by the extraction tower condenser 7 and then enters the extraction tower reflux drum 8. Then it is divided into two parts: one part is returned to the top of the extraction tower as reflux liquid through the extraction tower reflux pump 9, and the other part is sent to the waste liquid temporary storage tank 2. The extraction liquid withdrawn from the bottom of the extraction tower is transported to the middle of the recovery tower 11 by the extraction tower bottom liquid pump 10 for separation of the solvent and aromatics.

[0076] The gaseous material at the top of the recovery tower 11 is condensed by the recovery tower condenser 13 and then enters the recovery tower reflux drum 14. Then it is divided into two parts: one part is returned to the top of the recovery tower as reflux liquid through the recovery tower reflux pump 15, and the other part enters the middle of the first rectification column 17. The NFM solvent withdrawn from the bottom of the recovery tower is cooled by the NFM cooler 16 and then sent to the NFM temporary storage tank. The operating pressure of the recovery tower is 45 Kpa, the total tower pressure drop is 5 Kpa, the top temperature is 57 °C, and the reflux ratio is 0.92.

[0077] The operating pressure of the first distillation column 17 is 102 Kpa, the total pressure drop across the column is 4 Kpa, the top temperature is 80 °C, and the reflux ratio is 1.15. The vapor phase of the overhead material from the first distillation column 17 enters the first distillation column reflux drum 19 after being condensed by the first distillation column condenser 18, and then is divided into two parts: one part is returned to the top of the first distillation column as reflux liquid by the first distillation column reflux pump 22, and the other part enters the benzene temporary storage tank. The bottom of the first distillation column exchanges heat with the vapor from the top of the second distillation column 23 in the first distillation column reboiler 20 and is then transported to the middle of the second distillation column 23 by the refined column bottom liquid pump 21. The operating pressure of the second distillation column 23 is 250 Kpa, the total pressure drop across the column is 5 Kpa, the top temperature is 114 °C, and the reflux ratio is 2.2. The vapor phase of the overhead material from the second distillation column 23 exchanges heat and is condensed with the bottom of the first distillation column 17 and then enters the second distillation column reflux drum 26, and then is divided into two parts: one part is returned to the top of the second distillation column as reflux liquid by the second distillation column reflux pump 27, and the other part enters the benzene temporary storage tank. The bottom is heated by the second distillation column reboiler 24 and the toluene is withdrawn, cooled by the toluene cooler 25 and then sent to the toluene temporary storage tank.

[0078] In the above Example 1, the mass fraction of benzene obtained in the benzene temporary storage tank is 99.95%, and the mass fraction of toluene obtained in the toluene temporary storage tank is 99.9%. The total energy consumption of the aromatics extraction process in Example 1 is 9231 KW.

[0079] Comparative Example 1

[0080] Using the extraction device as Figure 2 shown, a mixed solution containing benzene and toluene from an olefin plant, with a composition of: 73.21% benzene, 14.96% toluene, and some C5-C8 alkane impurities, and the feed rate is 18750 kg / h.

[0081] The raw material (mixed solution containing benzene and toluene) enters the de-heavy tower 1. The operating pressure of the de-heavy tower 1 is 400 Kpa, the total pressure drop across the column is 40.8 Kpa, the top temperature is 136 °C, and the reflux ratio is 1.48.

[0082] The vapor phase of the overhead material from the de-heavy tower 1 (containing benzene, toluene, and light components with boiling points lower than benzene and toluene) enters the de-heavy tower reflux drum 3 after being condensed by the de-heavy tower condenser 28, and then is divided into two parts: one part is returned to the top of the de-heavy tower as reflux liquid by the de-heavy tower reflux pump 5, and the other part is transported to the middle of the extraction tower 6 for extraction treatment. The bottom of the de-heavy tower is heated by the de-heavy tower reboiler 2, and the heavy components with boiling points higher than benzene and toluene are withdrawn and sent to the waste liquid temporary storage tank 1.

[0083] The solvent NFM enters the middle part of the extraction tower 6, with a feed rate of 147,994 kg / h. The operating pressure of the extraction tower is 50 Kpa, the top temperature is 58 °C, and the reflux ratio is 1.36. The gas phase of the top material of the extraction tower 6 enters the extraction tower reflux drum 8 after being condensed by the extraction tower condenser 7, and then is divided into two parts: one part returns to the top of the extraction tower as reflux liquid through the extraction tower reflux pump 9, and the other part is sent to the waste liquid storage tank 2. The extract taken from the bottom of the extraction tower is transported to the middle part of the recovery tower 11 by the extraction tower bottom liquid pump 10 for the separation of the solvent and aromatic hydrocarbons.

[0084] The gas phase of the top material of the recovery tower enters the recovery tower reflux drum 14 after being condensed by the recovery tower condenser 13, and then is divided into two parts: one part returns to the top of the recovery tower as reflux liquid through the recovery tower reflux pump 15, and the other part enters the middle part of the first distillation tower 17. The NFM solvent is taken from the bottom of the recovery tower 11, cooled by the NFM cooler 16, and then sent to the NFM storage tank. The operating pressure of the recovery tower is 45 Kpa, the total pressure drop of the whole tower is 5 Kpa, the top temperature is 57 °C, and the reflux ratio is 0.92.

[0085] The operating pressure of the first distillation tower 17 is 102 Kpa, the total pressure drop of the whole tower is 4 Kpa, the top temperature is 80 °C, and the reflux ratio is 1.15. The gas phase of the top material of the first distillation tower 17 enters the first distillation tower reflux drum 19 after being condensed by the first distillation tower condenser 18, and then is divided into two parts: one part returns to the top of the first distillation tower as reflux liquid through the first distillation tower reflux pump 22, and the other part enters the benzene storage tank. The bottom of the first distillation tower exchanges heat with the top steam of the second distillation tower 23 in the first distillation tower reboiler 20 and is then transported to the middle part of the second distillation tower 23 by the refined tower bottom liquid pump 21. The operating pressure of the second distillation tower 23 is 250 Kpa, the total pressure drop of the whole tower is 5 Kpa, the top temperature is 114 °C, and the reflux ratio is 2.2. The gas phase of the top material of the second distillation tower 23 exchanges heat and condenses with the bottom of the first distillation tower 17 and then enters the second distillation tower reflux drum 26, and then is divided into two parts: one part returns to the top of the second distillation tower as reflux liquid through the second distillation tower reflux pump 27, and the other part enters the benzene storage tank. The bottom of the tower is heated by the second distillation tower reboiler 24, and the toluene is taken out, cooled by the toluene cooler 25, and then sent to the toluene storage tank.

[0086] In the above Comparative Example 1, the mass fraction of benzene obtained in the benzene storage tank is ≥99%, and the mass fraction of toluene obtained in the toluene storage tank is ≥99%. The total energy consumption of the process is 16,155 KW, which is 75% higher than the total energy consumption in Example 1.

[0087] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. An aromatic extraction device, comprising a deweighting tower, an extraction tower, a recovery tower, a first distillation tower and a second distillation tower which are connected in sequence, characterized in that, The top steam outlet of the deweighting tower is connected to the heat source inlet of the extractor reboiler. The heat source outlet of the extractor reboiler is connected to the feed inlet of the extractor through the deweighting tower reflux drum. The outlet of the extractor is connected to the feed inlet of the recovery tower. The top steam outlet of the recovery tower is connected to the feed inlet of the first rectification tower through the recovery tower reflux drum. The outlet of the first rectification tower is connected to the feed inlet of the second rectification tower.

2. The device according to claim 1, characterized in that, The top steam outlet of the second rectification tower is connected to the heat source inlet of the first rectification tower reboiler. The heat source outlet of the first rectification tower reboiler is connected to the benzene storage tank and the liquid phase inlet provided at the top of the second rectification tower through the second rectification tower reflux drum. The liquid phase inlet at the top of the second rectification tower is used to allow part of the liquid in the second rectification tower reflux drum to enter the top of the second rectification tower.

3. The device according to claim 2, characterized in that The top steam outlet of the first rectification tower is connected to the inlet of the first rectification tower reflux drum through the first rectification tower condenser. The outlet of the first rectification tower reflux drum is connected to the benzene storage tank and the liquid phase inlet located at the top of the first rectification tower through the first rectification tower reflux pump. The liquid phase inlet at the top of the first rectification tower is used to allow part of the liquid in the first rectification tower reflux drum to return to the top of the first rectification tower.

4. The device according to any one of claims 1 to 3, characterized in that The bottom of the second rectification tower is connected to a second rectification tower reboiler; the outlet of the second rectification tower is connected to the toluene storage tank through the second rectification tower cooler.

5. The device according to any one of claims 1 to 3, characterized in that The outlet of the deweighting tower reflux drum is also connected to the liquid phase inlet located at the top of the deweighting tower through the deweighting tower reflux pump. The liquid phase inlet at the top of the deweighting tower is used to allow part of the liquid in the deweighting tower reflux drum to return to the top of the deweighting tower.

6. The device according to any one of claims 1 to 3, characterized in that The bottom of the deweighting tower is connected to a deweighting tower reboiler; the outlet of the deweighting tower is connected to a first waste liquid storage tank.

7. The device according to any one of claims 1 to 3, characterized in that The extractor is provided with an extraction solvent inlet for allowing the extraction solvent to contact the aromatic hydrocarbon material entering the extractor from the extractor feed inlet for extraction. The top steam outlet of the extractor is connected to the inlet of the extractor reflux drum through the extractor condenser. And the outlet of the extractor reflux drum is connected to the second waste liquid storage tank and the liquid phase inlet located at the top of the extractor through the extractor reflux pump. The liquid phase inlet at the top of the extractor is used to allow part of the liquid in the extractor reflux drum to return to the top of the extractor.

8. The device according to any one of claims 1 to 3, characterized in that, The outlet of the recovery tower reflux drum is also connected to the liquid phase inlet located at the top of the recovery tower. The liquid phase inlet at the top of the recovery tower is used to allow part of the liquid in the recovery tower reflux drum to return to the top of the recovery tower.

9. The device according to any one of claims 1 to 3, characterized in that, A recovery tower condenser is also connected between the top steam outlet of the recovery tower and the recovery tower reflux drum. The bottom of the recovery tower is connected to a recovery tower reboiler. The outlet of the recovery tower is connected to the extraction solvent storage tank through the recovery tower cooler.

10. The device according to any one of claims 1 to 3, characterized in that The number of theoretical plates of the deweighting tower is 10 - 70. The number of theoretical plates of the extractor is 20 - 90. The number of theoretical plates of the recovery tower is 20 - 80. The number of theoretical plates of the first rectification tower is 30 - 80. The number of theoretical plates of the second rectification tower is 30 - 80.

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