A dividing wall distillation system and method for extract of an adsorptive separation unit of an aromatics complex

Abstract

The present application relates to a kind of for aromatic hydrocarbon combined plant adsorption separation unit extract partition wall rectification system, including partition wall rectification tower, toluene separation flow path, p-xylene separation flow path and p-diethylbenzene separation flow path;Partition wall rectification tower includes the partition wall being arranged in tower interior, one end of partition wall is fixed in tower bottom, the other end of partition wall extends upwards and is kept a certain distance from tower top, and partition wall separates the space in tower interior into first separation chamber and second separation chamber being arranged left and right, and common rectification chamber being located above partition wall, first separation chamber, second separation chamber and common rectification chamber are in fluid communication;Toluene separation flow path is connected with the top of common rectification chamber;P-diethylbenzene separation flow path is connected with the bottom of first separation chamber;P-xylene separation flow path is connected with the bottom of second separation chamber.Compared with double-tower rectification process, investment is greatly reduced, tower top gas cooling load is less, system waste heat is fully recycled, energy consumption and cost are reduced, and economic benefit is generated.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, specifically to a partition wall distillation system and method for the extract liquid from the adsorption separation unit of an aromatic hydrocarbon complex. Background Technology

[0002] The aromatics complex is a core unit in the petrochemical industry for producing C6-C8 low-carbon aromatics (benzene, toluene, and xylene). The unit consists of seven sections: naphtha pretreatment, continuous reforming, isomerization, extraction, disproportionation, adsorption separation, and xylene distillation. The adsorption separation section is responsible for the rectification of the C8 mixed aromatics (C8A) from the continuous reforming, isomerization, and disproportionation processes to obtain para-xylene (PX) with a purity of 99.80%. C8A comprises four isomers—para-xylene, o-xylene, m-xylene, and ethylbenzene—with very similar boiling points. Direct distillation would result in high energy consumption; therefore, adsorption separation is often used before distillation. In the adsorption separation process, barium / potassium ion-exchange zeolite molecular sieves serve as the adsorbent, and para-diethylbenzene as the desorbent. The adsorbent adsorbs PX from C8A, while the desorbent displaces it. After adsorption separation, a distillate rich in PX and para-diethylbenzene is formed and distilled off.

[0003] The distillation of extractives typically employs a two-tower distillation process: an extractive tower and a product tower. The extractives first enter the extractive tower, where a desorbent is obtained from the bottom, and the overhead distillate enters the product tower. The top of the product tower separates toluene (containing benzene and non-aromatics, sent to a toluene disproportionation unit), while the bottom yields high-purity para-xylene. However, the two-tower distillation process involves significant investment, and the overhead gases (approximately 152°C for the extractive tower and approximately 122°C for the product tower) are cooled, leading to increased energy consumption and high operating costs. Existing technologies offer some improvements, such as utilizing the overhead gas from the extractive tower for compression and heating to produce vapor. However, the high xylene content makes compression prone to liquid carryover. Another approach considers the high toluene content in the product tower's overhead gas, which, while less prone to liquid carryover, results in a low heat load and limited recovery value. Therefore, researching a novel extractive distillation process to reduce separation energy consumption is a pressing issue that needs to be addressed. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the first objective of this invention is to provide a partition wall distillation system for the extract liquid in the adsorption separation unit of an aromatic hydrocarbon complex, comprising a partition wall distillation column, a toluene separation flow path, a p-xylene separation flow path, and a p-diethylbenzene separation flow path. Compared with the dual-tower distillation process of extract liquid tower-finished product tower, the overhead gas cooling load is lower, the system waste heat can be fully recovered and utilized, energy consumption and costs are reduced, investment is greatly reduced, and economic benefits are generated.

[0005] The second objective of this invention is to provide a method for distilling the extract from the adsorption separation unit of an aromatic hydrocarbon complex using a partition wall distillation system for the extract from the adsorption separation unit of the aromatic hydrocarbon complex.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A partition wall distillation system for the extractant from the adsorption separation unit of an aromatics complex includes a partition wall distillation column, a toluene separation flow path, a p-xylene separation flow path, and a p-diethylbenzene separation flow path. The partition wall distillation column includes a partition wall disposed inside the column, one end of which is fixed to the bottom of the column, and the other end extending upwards and maintaining a certain distance from the top of the column. The partition wall divides the internal space of the column into a first separation chamber and a second separation chamber arranged to the left and right, and a common distillation chamber located above the partition wall. The first separation chamber, the second separation chamber, and the common distillation chamber are in fluid communication. The side of the first separation chamber has an inlet for receiving the extractant from the adsorption separation unit, the bottom of the first separation chamber has a first outlet, the bottom of the second separation chamber has a second outlet, and the top of the common distillation chamber has a third outlet. The toluene separation flow path is connected to the top of the common distillation chamber for separating toluene; the p-diethylbenzene separation flow path is connected to the bottom of the first separation chamber for separating p-diethylbenzene; and the p-xylene separation flow path is connected to the bottom of the second separation chamber for separating p-xylene.

[0008] Furthermore, the toluene separation flow path includes a first heat exchanger, a heat pump compressor, a steam generator, a pressure reducing valve, an air cooler, a reflux tank, and a reflux pump connected in sequence. The first heat exchanger is connected to the third outlet through a pipeline. The first heat exchanger is used for heat exchange between toluene and p-diethylbenzene. The reflux pump is connected to the common distillation chamber through a pipeline.

[0009] Furthermore, the p-diethylbenzene separation flow path includes a first reboiler and a second heat exchanger. The first reboiler is circulatedly connected to the bottom of the first separation chamber and is used for heat exchange between p-diethylbenzene and steam. The second heat exchanger is connected to the first discharge port through a pipeline and is used for heat exchange between the extracted liquid and p-diethylbenzene.

[0010] Furthermore, the paraxylene separation flow path includes a second reboiler, which is circulatedly connected to the bottom of the second separation chamber. The second reboiler is used for heat exchange between paraxylene and steam.

[0011] Furthermore, a first reflux distribution plate and a second reflux distribution plate are rotatably provided at the other end of the partition wall. The first reflux distribution plate is located at the top of the first separation chamber, and the second reflux distribution plate is located at the top of the second separation chamber.

[0012] Furthermore, the interior of the first separation chamber is provided with multiple first plates spaced apart in the vertical direction, the interior of the second separation chamber is provided with multiple second plates spaced apart in the vertical direction, the first plates and the second plates are arranged horizontally, and the interior of the common distillation chamber is provided with multiple third plates spaced apart in the vertical direction.

[0013] A method for dividing wall distillation of extractant from adsorption separation unit of aromatic hydrocarbon complex is provided, wherein the above-mentioned dividing wall distillation system for extractant from adsorption separation unit of aromatic hydrocarbon complex is used for distillation.

[0014] Further, the process includes the following steps: After heat exchange in the second heat exchanger, the extract enters the first separation chamber through the inlet. Reboiling heat is supplied through the first reboiler to separate the extract. The separated p-diethylbenzene settles at the bottom of the first separation chamber and is discharged through the first outlet, yielding the p-diethylbenzene product. A mixture containing p-xylene and toluene enters the common distillation chamber through the top of the first separation chamber. Toluene in the common distillation chamber is discharged through the third outlet and sequentially undergoes heat exchange in the first heat exchanger, pressure and temperature increase in the heat pump compressor, heat release in the steam generator, cooling in the air cooler, and reflux in the reflux tank. P-xylene undergoes cold reflux, with a portion of the refluxed toluene returning to the common distillation chamber and the other portion being discharged, yielding the toluene product. Under the influence of cold reflux, the p-xylene in the common distillation chamber settles at the bottom of the second separation chamber and is reboiling heat supplied through the second reboiler to obtain the p-xylene product, which is then discharged through the second outlet.

[0015] Furthermore, the diethylbenzene product first undergoes heat exchange with the extract in a second heat exchanger, and then undergoes heat exchange with toluene in a first heat exchanger.

[0016] Furthermore, the pressure in the common distillation chamber is 4-60 kPag, the temperature in the common distillation chamber is 100-130℃, and the temperature in the reflux tank is 70-80℃; the liquid phase distribution ratio in the first separation chamber is 0.4-0.6, and the liquid phase distribution ratio in the second separation chamber is 0.4-0.6.

[0017] The present invention has the following advantages:

[0018] 1. This invention uses a dividing wall column (DWC) to replace the original extract column and product column, which reduces the footprint and investment cost for new projects.

[0019] 2. This invention uses a partitioned wall distillation column to improve separation efficiency, and the number of plates in the partitioned wall distillation column can be reduced accordingly. Compared with the traditional double-tower distillation process, the investment in the column body is reduced by about 20%-40%. At the same time, the partitioned wall distillation column reduces the backmixing of the intermediate component paraxylene in the original extract column, improves separation efficiency, and has a good distillation effect. Compared with the double-tower distillation process, the separation energy consumption is reduced by about 5%-10%.

[0020] 3. This invention cleverly converts the overhead gas into a C7 component, mainly toluene, through a common distillation chamber, greatly improving the compressibility and laying the foundation for integrated heat pumps.

[0021] 4. This invention improves the heat quality of the top gas by using a heat pump compressor and recovers the latent heat of the top gas by generating steam through a steam generator, which greatly reduces the cooling load and realizes the reuse of waste heat.

[0022] 5. This invention only sets up a single partition wall distillation column, which saves a set of overhead gas condensation and cooling system compared with the double column distillation process. Other supporting facilities can be modified based on the original equipment, such as the first reboiler and the second reboiler.

[0023] 6. This invention can guarantee the quality and yield of toluene, p-xylene, and p-diethylbenzene products without changing the product quality control strategy. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of Embodiments 1, 2 and 3 of the present invention for a partition wall distillation system for the extract liquid of an adsorption separation unit in an aromatic hydrocarbon complex.

[0025] Figure 2 This is a process flow diagram of Comparative Example 1 for the existing dual-tower distillation process of extracting liquid tower-finishing product tower.

[0026] Wherein, 1 is the extracting liquid tower, 2 is the air cooler, 3 is the reflux tank, 4 is the reflux pump, 5 is the first reboiler, 6 is the product tower, 7 is the product tower air cooler, 8 is the product tower reflux tank, 9 is the product tower reflux pump, 10 is the second reboiler, 11 is the paraxylene reflux pump, 12 is the first heat exchanger, 13 is the second heat exchanger, 14 is the partition wall distillation tower, 14a is the first separation chamber, 14b is the second separation chamber, 14c is the common distillation chamber, 1401 is the feed inlet, 1402 is the first outlet, 1403 is the second outlet, 1404 is the third outlet, 1405 is the first plate, 1406 is the second plate, 1407 is the third plate, 1408 is the first reflux distribution plate, 1409 is the second reflux distribution plate, 1410 is the partition wall, 15 is the heat pump compressor, 16 is the steam generator, and 17 is the pressure reducing valve. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1As shown, a partition wall distillation system for the extract of an adsorption separation unit in an aromatics complex includes a partition wall distillation column 14, a toluene separation flow path, a p-xylene separation flow path, and a p-diethylbenzene separation flow path. The partition wall distillation column 14 includes a partition wall 1410 disposed inside the column. One end of the partition wall 1410 is fixed to the bottom of the column, and the other end of the partition wall 1410 extends upward and leaves a certain distance from the top of the column, that is, the other end of the partition wall 1410 does not contact the top of the column. The partition wall 1410 divides the internal space of the column into a first separation chamber 14a and a second separation chamber 14b arranged to the left and right, and a common distillation chamber 14c located above the partition wall 1410. 4a. The second separation chamber 14b and the common distillation chamber 14c are in fluid communication. The side of the first separation chamber 14a is provided with an inlet 1401 for receiving the liquid extracted from the adsorption separation unit. The bottom of the first separation chamber 14a is provided with a first outlet 1402. The bottom of the second separation chamber 14b is provided with a second outlet 1403. The top of the common distillation chamber 14c is provided with a third outlet 1404. The toluene separation flow path is connected to the top of the common distillation chamber 14c for separating toluene. The p-diethylbenzene separation flow path is connected to the bottom of the first separation chamber 14a for separating p-diethylbenzene. The p-xylene separation flow path is connected to the bottom of the second separation chamber 14b for separating p-xylene.

[0029] The components of the first separation chamber 14a, the second separation chamber 14b, and the common distillation chamber 14c are located at different positions due to the different boiling points of the substances. The extract mainly consists of p-diethylbenzene, p-xylene, toluene, benzene, and a mixture of non-aromatics. After entering the first separation chamber 14a, due to their different boiling points, p-diethylbenzene is concentrated at the bottom of the first separation chamber 14a, while other components rise to the top of the first separation chamber 14a and enter the common distillation chamber 14c. The p-xylene in the common distillation chamber 14c settles to the bottom of the second separation chamber 14b, while the mixture of toluene, benzene, and non-aromatics is refluxed to obtain toluene.

[0030] like Figure 1As shown, the toluene separation flow path includes a first heat exchanger 12, a heat pump compressor 15, a steam generator 16, a pressure reducing valve 17, an air cooler 2, a reflux tank 3, and a reflux pump 4 connected in sequence. The first heat exchanger 12 is connected to the third outlet 1404 via a pipeline and is used for heat exchange between toluene and p-diethylbenzene. The reflux pump 4 is connected to the common distillation chamber 14c via a pipeline. The mixture of toluene, benzene, and non-aromatics is the overhead gas. The overhead gas first exchanges heat with the p-diethylbenzene product to raise its temperature and decondense it. Then it enters the heat pump compressor 15, where it is compressed by the heat pump compressor motor or steam turbine. The compressed gas first enters the steam generator 16 to generate low-pressure saturated steam and deoxygenated water. Then it is depressurized by the pressure reducing valve 17 and enters the air cooler 2 and the reflux tank 3 in sequence to form cold reflux. Part of it returns to the common distillation chamber 14c, and the other part forms the product toluene (containing benzene, non-aromatics, and other mixed components) and is sent to the disproportionation unit. The first heat exchanger 12 has an outlet temperature of 130-150℃ after heat exchange; the heat pump compressor 15 has a temperature of 155-188℃ and an outlet pressure of 150-400 kPag, preferably 250 kPag; the steam generator 16 produces steam with a quality of 0.35-0.55 MPag, preferably 0.45 MPag, and an outlet temperature of 120-160℃, preferably 155.47℃. Because the steam generator absorbs the phase change heat of the overhead gas, it greatly reduces the air cooling load. Furthermore, the overhead gas is essentially free of p-diethylbenzene and has a low p-xylene content, so the compression process is liquid-free, facilitating stable operation of the heat pump compressor. The common distillation chamber 14c adjusts the overhead reflux flow rate by controlling the overhead air cooling load to ensure the quality of the overhead toluene product meets standards.

[0031] like Figure 1 As shown, the p-diethylbenzene separation flow path includes a first reboiler 5 and a second heat exchanger 13. The first reboiler 5 is circulatedly connected to the bottom of the first separation chamber 14a and is used for heat exchange between p-diethylbenzene and steam. The second heat exchanger 13 is connected to the first outlet 1402 via a pipeline and is used for heat exchange between the extracted liquid and p-diethylbenzene. The second heat exchanger 13 is also connected to the first reboiler 5 via a pipeline. In other words, the second heat exchanger 13 is connected to both the first reboiler 5 and the first outlet 1402 via pipelines. The first reboiler 5 uses 2.2 MPa steam as the reboiling heat source. Its load regulation ensures a suitable temperature at the bottom of the first separation chamber 14a, thereby controlling the quality of the p-diethylbenzene product (mass concentration ≥ 98.16%) so that the p-diethylbenzene can be returned to the adsorption separation unit for recycling.

[0032] like Figure 1As shown, the paraxylene separation flow path includes a second reboiler 10, which is circulatedly connected to the bottom of the second separation chamber 14b. The second reboiler 10 is used for heat exchange between paraxylene and steam. One end of the second reboiler 10 is connected to the second outlet 1403 via a pipeline, and the other end is connected to the bottom of the second separation chamber 14b via a pipeline, achieving fluid circulation. A paraxylene output pipeline is also provided on the pipeline between one end of the second reboiler 10 and the second outlet 1403 for outputting the paraxylene product. The first separation chamber 14a and the second separation chamber 14b are each equipped with independent bottom reboilers, namely the first reboiler 5 and the second reboiler 10, to provide heat for the distillation process. The second reboiler 10 uses 1.0 MPa steam as the reboiling heat source. Its load regulation ensures a suitable temperature at the bottom of the second separation chamber 14b, thereby controlling the mass of paraxylene (mass concentration ≥ 99.8%) for use as the product exiting the system. For the modification scheme, the first reboiler 5 can utilize the reboiler at the bottom of the original extractor column, and the second reboiler 10 can utilize the reboiler at the bottom of the original product column. The reboiling temperature of the first reboiler 5 is 200-230℃, and the reboiling temperature of the second reboiler 10 is 200-230℃.

[0033] The extract from the adsorption separation unit exchanges heat once with the p-diethylbenzene discharged from the bottom of the first separation chamber 14a through the second heat exchanger 13. Then, it enters from the lower middle part of the outer side of the first separation chamber 14a. After fractionation, p-diethylbenzene (desorbent) is obtained from the bottom of the first separation chamber 14a. p-xylene is distilled from the bottom of the second separation chamber 14b, and the light component toluene is distilled from the top of the common rectification chamber 14c, thus completing the separation task.

[0034] like Figure 1 As shown, a first reflux distribution plate 1408 and a second reflux distribution plate 1409 are rotatably disposed at the other end of the partition wall 1410. The first reflux distribution plate 1408 is located at the top of the first separation chamber 14a, and the second reflux distribution plate 1409 is located at the top of the second separation chamber 14b. The first reflux distribution plate 1408 and the second reflux distribution plate 1409 are disposed at the other end of the partition wall 1410, i.e., at the bottom of the common distillation chamber 14c. By changing the angle of inclination, the liquid flow rate from the common distillation chamber 14c to the first separation chamber 14a and the second separation chamber 14b is adjusted to ensure stable operation of the entire column and the distillation effect of the first separation chamber 14a and the second separation chamber 14b. If the purity of the p-diethylbenzene product at the bottom of the first separation chamber 14a is not up to standard, the amount of liquid received by the first separation chamber 14a can be reduced by adjusting the angle of the first reflux distribution plate 1408. The first reflux distribution plate 1408 and the second reflux distribution plate 1409 have a rotatable angle of 1-90°.

[0035] like Figure 1As shown, the interior of the first separation chamber 14a is provided with multiple first plates 1405 spaced apart in the vertical direction, the interior of the second separation chamber 14b is provided with multiple second plates 1406 spaced apart in the vertical direction, the first plates 1405 and the second plates 1406 are arranged horizontally, and the interior of the common distillation chamber 14c is provided with multiple third plates 1407 spaced apart in the vertical direction. The average single-plate pressure of the first plate 1405, the second plate 1406, and the third plate 1407 is 0.1-1.2 kPa. There are 48 first plates 1405, 50 second plates 1406, and 20 third plates 1407. The position of the feed inlet 1401 corresponds to one of the first plates 1405, preferably to the 10th-30th, and more preferably to the 20th. The position of the first discharge outlet 1402 corresponds to one of the first plates 1405, preferably to the 48th. The position of the second discharge outlet 1403 corresponds to one of the second plates 1406, preferably to the 50th. The number of plates is ordered from top to bottom.

[0036] A method for dividing wall distillation of extractant from adsorption separation unit of an aromatic hydrocarbon complex is disclosed, employing the aforementioned dividing wall distillation system for extractant from adsorption separation unit of an aromatic hydrocarbon complex. The main steps include: after heat exchange in a second heat exchanger 13, the extractant enters the first separation chamber 14a through inlet 1401. Reboiling heat is supplied by a first reboiler 5 to separate the extractant. The separated p-diethylbenzene settles at the bottom of the first separation chamber 14a and is discharged through the first outlet 1402, yielding the p-diethylbenzene product. A mixture containing p-xylene and toluene enters a common distillation chamber 14c through the top of the first separation chamber 14a. The toluene in the common distillation chamber 14c is discharged through the third outlet 1404. The toluene is refluxed sequentially through the first heat exchanger 12, the heat pump compressor 15 for pressurization and temperature increase, the steam generator 16 for heat release, the air cooler 2 for cooling, and the reflux tank 3 for recirculation. Part of the refluxed toluene is returned to the common distillation chamber 14c, and the other part is discharged to the outside, resulting in toluene product. The para-xylene in the common distillation chamber 14c settles to the bottom of the second separation chamber 14b under the action of reflux, and is supplied with reboiling heat through the second reboiler 10 to obtain para-xylene product, which is then discharged to the outside through the second outlet 1403.

[0037] Specifically, the extract from the adsorption separation unit, after passing through the second heat exchanger 13, first exchanges heat with the p-diethylbenzene product discharged from the first separation chamber 14a, and then sends it to the lower part of the first separation chamber 14a of the partition wall distillation column 14. Under the action of the reboiling heat generated by the first reboiler 5, the extract completes the separation, and the p-diethylbenzene product is obtained from the bottom of the first separation chamber 14a, which meets the purity requirement of ≥98.16% and can be returned to the adsorption separation unit as a circulating desorbent. Meanwhile, the light components such as p-xylene and toluene are vaporized and enter the common distillation chamber 14c through the top of the first separation chamber 14a. Under the action of the cold reflux at the top of the partition wall distillation column 14, the p-xylene sinks into the first separation chamber 14a. In the second separation chamber 14b, under the action of reboiling heat generated by the second reboiler 10, para-xylene product with a purity of ≥99.8% is obtained from the bottom of the second separation chamber 14b. The cold reflux process is as follows: the mixture of toluene and non-aromatic gases overflows through the third outlet 1404 at the top of the common distillation chamber 14c, and after being slightly superheated and decondensed by the first heat exchanger 12, it enters the heat pump compressor 15. After being pressurized and heated, it enters the steam generator 16, releases latent heat to produce low-pressure saturated steam, and then sends it to the air cooler 2 and the reflux tank 3 in sequence through the pressure reducing valve 17. After being pressurized by the reflux pump 4, part of the toluene is returned to the common distillation chamber 14c, and the other part is discharged from the system as toluene product.

[0038] like Figure 1 As shown, the diethylbenzene product first exchanges heat with the extractant through the second heat exchanger 13, and then exchanges heat with toluene through the first heat exchanger 12. In this way, the waste heat of the diethylbenzene product can be used to transfer heat to the extractant and toluene in the system, respectively, so as to realize the reuse of waste heat.

[0039] like Figure 1 As shown, the pressure in the common distillation chamber 14c is 4-60 kPag, the temperature in the common distillation chamber 14c is 100-130℃, and the temperature in the reflux tank 3 is 70-80℃; the liquid phase distribution ratio in the first separation chamber 14a is 0.4-0.6, and the liquid phase distribution ratio in the second separation chamber 14b is 0.4-0.6. By adjusting the pressure of the partition wall distillation column 14, the liquid phase distribution ratio during the liquid phase fall in the common distillation chamber 14c, the outlet pressure of the heat pump compressor 15, and the operating temperature of the reflux tank 3, the operation of the partition wall distillation column can be improved, further reducing separation energy consumption. Furthermore, the operating pressure of the partition wall distillation column 14 is 8-60 kPag, the top temperature of the partition wall distillation column 14 is 110-130℃, the bottom temperature is 200-230℃, and the reflux ratio of the partition wall distillation column 14 is 220-280.

[0040] The following example uses the adsorption separation unit of an aromatics complex in a petrochemical plant. The effluent flow rate from the adsorption separation unit is 328.7 t / h. The required purity of the separated p-xylene product is ≥99.8% wt, and the purity of the separated p-diethylbenzene product is ≥98.16% wt. The main operating conditions of Examples 1, 2, 3 and Comparative Example 1 are described below.

[0041] Example 1

[0042] The liquid phase distribution ratio in the first separation chamber 14a is 0.508, and the raw material conditions and product quality requirements are the same as those in Comparative Example 1.

[0043] Table 1 shows the product quality of Example 1.

[0044] Table 1

[0045]

[0046] As can be seen, Example 1 meets the product quality requirements, and the quantity of each product remains unchanged. Table 2 shows the main equipment and operating parameters of Example 1.

[0047] Table 2

[0048]

[0049]

[0050] As shown in Table 2, the total reboiling load in Example 1 is 3490.0 × 10⁻⁶. 4 kcal / h, total cooling load is 993.2×10 4 Kcal / h. Compared with Comparative Example 1, the reboiling load was reduced by 211.7 × 10⁻⁶ kcal / h. 4 kcal / h, a decrease of 5.7%; among which, 5.07 t / h of 1.0 MPa steam was saved, while 1.18 t / h of 2.2 MPa steam was consumed more; cooling load was reduced by 2008.8 × 10 4 The energy consumption of the heat pump compressor decreased by 66.9% (kcal / h); the power consumption was 6764.7 kW / h, and the output of 0.45 MPa steam was 53.2 t / h. Based on an electricity price of 0.67 yuan / kWh, a steam price of 209 yuan / ton, and an annual operating rate of 8400 hours, the annual efficiency improvement is 62.15 million yuan. This approach achieves energy savings while meeting product quality requirements, resulting in economic benefits.

[0051] Example 2

[0052] The difference between this embodiment and Embodiment 1 is that the liquid phase distribution ratio of the first separation chamber 14a is 0.47.

[0053] Table 3 shows the product quality of Example 2.

[0054] Table 3

[0055]

[0056]

[0057] As can be seen, Example 2 meets the product quality requirements, and the quantity of each product remains unchanged.

[0058] Table 4 shows the main equipment and operating parameters for Example 2.

[0059] Table 4

[0060]

[0061] As shown in Table 4, the total reboiling load in Example 2 is 3248.5 × 10⁻⁶. 4 kcal / h, total cooling load is 897.4×10 4 kcal / h. Compared with Comparative Example 1, the reboiling load was reduced by 453.2 × 10⁻⁶ kcal / h. 4 kcal / h decreased by 14.0%; cooling load decreased by 2104.6 × 10 4 The energy consumption per kcal / h decreased by 70.1%; the heat pump compressor consumed 6318.9 kW / h of electricity and produced 50.2 t / h of 0.45 MPa steam, resulting in an efficiency increase of 68.825 million yuan / year. This approach saves energy while meeting product quality requirements, generating economic benefits.

[0062] Example 3

[0063] The difference between this embodiment and Embodiment 2 is that the pressure at the top of the common distillation chamber 14c is 40 kPag.

[0064] Table 5 shows the product quality of Example 3.

[0065] Table 5

[0066]

[0067] As can be seen, Example 3 meets the product quality requirements, and the quantity of each product remains unchanged. Table 6 shows the main equipment and operating parameters of Example 3.

[0068] Table 6

[0069]

[0070]

[0071] As can be seen, the total reboiling load in Example 3 is 3495.0 × 10⁻⁶. 4 kcal / h, total cooling load is 1007.5×10 4kcal / h. Compared with Comparative Example 1, the reboiling load was reduced by 206.7 × 10 kcal / h. 4 Kcal / h decreased by 5.6%; cooling load decreased by 1994.5 × 10 4 The energy consumption of the heat pump compressor decreased by 66.4% (kcal / h), with a power consumption of 5092.9 kW / h and a steam output of 50.2 t / h at 0.45 MPa. This resulted in an annual energy saving of 66.491 million yuan. Energy consumption was reduced while meeting product quality requirements, generating economic benefits.

[0072] Comparative Example 1

[0073] like Figure 2 As shown, Comparative Example 1 employs a dual-tower distillation process. The specific process mainly includes an extractant tower 1 and a product tower 6. The extractant from the adsorption separation unit passes through the second heat exchanger 13, where it first exchanges heat with the p-diethylbenzene product discharged from the bottom of the extractant tower 1 to raise its temperature before entering the extractant tower 1. Under the action of the steam heat from the first reboiler 5 (2.2 MPa steam) at the bottom of the extractant tower 1, the p-diethylbenzene product is distilled off from the bottom of the extractant tower 1. The p-diethylbenzene is then returned to the adsorption separation unit as a desorbent for recycling. Paraxylene, toluene, and other light components are distilled from the top of the extraction tower 1. After air-cooled reflux (passing sequentially through air cooler 2, reflux tank 3, and reflux pump 4), they are first heated by heat exchange with the paraxylene product discharged from the bottom of the product tower 6 in the first heat exchanger 12. Then, they enter the product tower 6 for separation. Under the action of steam heat from the second reboiler 10 (1.0 MPa steam) at the bottom of the product tower 6, paraxylene product is obtained from the bottom of the product tower 6. It is then pumped to the first heat exchanger 12 by the paraxylene reflux pump 11. The toluene mixture is obtained at the top of the product tower 6. After air-cooled reflux (passing sequentially through the product tower air cooler 7, product tower reflux tank 8, and product tower reflux pump 9), toluene is obtained. Part of it is refluxed back to the product tower 6, and the other part is sent to the disproportionation unit as toluene product.

[0074] Table 7 shows the raw material composition and product quality.

[0075] Table 7

[0076]

[0077] Table 8 shows the main equipment and operating parameters for the comparison.

[0078] Table 8

[0079]

[0080]

[0081] As can be seen, the total reboiling load of Comparative Example 1 is 3701.7 × 10⁻⁶. 4 kcal / h, total cooling load is 3002.0×104 kcal / h.

[0082] In summary, this invention replaces the original extract and product columns with a divided wall column (DWC), resulting in a smaller footprint and lower investment costs for new projects. The use of a divided wall column improves separation efficiency and allows for a corresponding reduction in the number of plates, reducing column investment by approximately 20%-40% compared to traditional dual-column distillation processes. Simultaneously, the divided wall column reduces backmixing of the intermediate component paraxylene in the original extract column, further improving separation efficiency and distillation performance. Compared to dual-column distillation, separation energy consumption is reduced by approximately 5%-10%. This invention cleverly converts the overhead gas into a C7 component primarily composed of toluene through a common distillation chamber, significantly improving compressibility and laying the foundation for integrated heat pumps. Furthermore, the invention improves the thermal quality of the overhead gas through a heat pump compressor and recovers the latent heat of the overhead gas by generating steam through a steam generator, greatly reducing the cooling load and enabling waste heat reuse. This invention uses only a single-walled distillation column, saving a separate overhead gas condensation and cooling system compared to a dual-column distillation process. Other supporting equipment can be modified from existing equipment, such as a first reboiler and a second reboiler. This invention can guarantee the quality and yield of toluene, p-xylene, and p-diethylbenzene products without changing the product quality control strategy.

[0083] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A partition wall distillation system for the extract liquid from the adsorption separation unit of an aromatic hydrocarbon complex, characterized in that: This includes a partitioned wall distillation column, a toluene separation flow path, a p-xylene separation flow path, and a p-diethylbenzene separation flow path; The partition wall distillation column includes a partition wall disposed inside the column. One end of the partition wall is fixed to the bottom of the column, and the other end of the partition wall extends upward and leaves a certain distance from the top of the column. The partition wall divides the internal space of the column into a first separation chamber and a second separation chamber arranged on the left and right, and a common distillation chamber located above the partition wall. The first separation chamber, the second separation chamber and the common distillation chamber are in fluid communication. The side of the first separation chamber is provided with an inlet for receiving the extract liquid from the adsorption separation unit. The bottom of the first separation chamber is provided with a first outlet. The bottom of the second separation chamber is provided with a second outlet. The top of the common distillation chamber is provided with a third outlet. The toluene separation flow path is connected to the top of the common distillation chamber for the separation of toluene; The p-diethylbenzene separation flow path is connected to the bottom of the first separation chamber and is used to separate p-diethylbenzene; The para-xylene separation flow path is connected to the bottom of the second separation chamber for separating para-xylene; The toluene separation flow path includes a first heat exchanger, a heat pump compressor, a steam generator, a pressure reducing valve, an air cooler, a reflux tank, and a reflux pump connected in sequence. The first heat exchanger is connected to the third outlet through a pipeline. The first heat exchanger is used for heat exchange between toluene and p-diethylbenzene. The reflux pump is connected to the common distillation chamber through a pipeline.

2. The partition wall distillation system for the extract liquid of the adsorption separation unit in an aromatic hydrocarbon complex according to claim 1, characterized in that: The p-diethylbenzene separation flow path includes a first reboiler and a second heat exchanger. The first reboiler is circulatedly connected to the bottom of the first separation chamber and is used for heat exchange between p-diethylbenzene and steam. The second heat exchanger is connected to the first discharge port through a pipeline and is used for heat exchange between the extracted liquid and p-diethylbenzene.

3. The partition wall distillation system for the extract liquid of the adsorption separation unit in an aromatic hydrocarbon complex according to claim 1, characterized in that: The paraxylene separation flow path includes a second reboiler, which is circulatedly connected to the bottom of the second separation chamber. The second reboiler is used for heat exchange between paraxylene and steam.

4. The partition wall distillation system for the extract liquid of the adsorption separation unit in an aromatic hydrocarbon complex according to claim 1, characterized in that: The other end of the partition wall is rotatably equipped with a first reflux distribution plate and a second reflux distribution plate. The first reflux distribution plate is located at the top of the first separation chamber, and the second reflux distribution plate is located at the top of the second separation chamber.

5. A partition wall distillation system for the extract liquid of an adsorption separation unit in an aromatic hydrocarbon complex, as described in claim 1, characterized in that: The first separation chamber has multiple first plates spaced vertically inside, the second separation chamber has multiple second plates spaced vertically inside, the first and second plates are arranged horizontally, and the common distillation chamber has multiple third plates spaced vertically inside.

6. A method for dividing wall distillation of the extract from the adsorption separation unit of an aromatic hydrocarbon complex, characterized in that: Distillation using the partition wall distillation system for the extract of the adsorption separation unit in an aromatic hydrocarbon complex, as described in any one of claims 1-5, includes the following steps: After heat exchange in the second heat exchanger, the extract enters the first separation chamber through the feed inlet. The first reboiler supplies reboiling heat to separate the extract. The separated p-diethylbenzene settles at the bottom of the first separation chamber and is discharged to the outside through the first discharge outlet to obtain the p-diethylbenzene product. The mixture containing p-xylene and toluene enters the common distillation chamber through the top of the first separation chamber. Toluene in the common distillation chamber is discharged through the third outlet and then passes through the first heat exchanger for heat exchange, the heat pump compressor for pressure and temperature increase, the steam generator for heat release, the air cooler for cooling, and the reflux tank for reflux. The toluene is then refluxed, and part of the refluxed toluene is returned to the common distillation chamber, while the other part is discharged to the outside, thus obtaining the toluene product. In the common distillation chamber, paraxylene settles to the bottom of the second separation chamber under the action of cold reflux, and is then supplied with reboiling heat through the second reboiler to obtain paraxylene product, which is then discharged to the outside through the second outlet.

7. The method for dividing wall distillation of the extract from the adsorption separation unit of an aromatic hydrocarbon complex according to claim 6, characterized in that: The diethylbenzene product first undergoes heat exchange with the extract in a second heat exchanger, and then undergoes heat exchange with toluene in a first heat exchanger.

8. A method for dividing wall distillation of extractant from adsorption separation unit of an aromatic hydrocarbon complex according to claim 6, characterized in that: The pressure in the common distillation chamber is 4-60 kPag, the temperature in the common distillation chamber is 100-130℃, and the temperature in the reflux tank is 70-80℃; the liquid phase distribution ratio in the first separation chamber is 0.4-0.6, and the liquid phase distribution ratio in the second separation chamber is 0.4-0.6.

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