Separation process for C8-C10 aromatic hydrocarbons
By optimizing the process flow of the carbon-octa-carbon decay aromatic hydrocarbon separation process and adjusting the treatment methods and heat source use of each tower, the problems of high energy consumption in the existing technology are solved, and energy consumption is reduced and energy efficiency is improved.
Patent Information
- Application Number
- CN202510083173.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-20
- Publication Date
- 2025-05-27
AI Technical Summary
In the prior art, the separation process of carbon octa to carbon delta aromatic hydrocarbons has a problem of high energy consumption, especially in the aromatic hydrocarbon combined device, the reboiler load at the bottom of the separation tower is high, resulting in a large fuel gas consumption.
By optimizing the process flow, the treatment methods of the xylene tower and xylene redistillation tower are adjusted, and the bottom oil from the isomerization unit deheptane tower is treated only in the xylene tower, and the bottom oil of the reforming oil and the bottom oil of the dispersing unit toluene tower are mixed in the xylene redistillation tower, while the pressure and heat source are adjusted in the heavy aromatic separation tower to reduce overall energy consumption.
The energy consumption of the carbon-octadec-to-carbon-decanoarene separation process is achieved, the fuel gas usage is reduced, the bottom reboiler load of the separation tower is reduced, and the energy efficiency of the process is improved.
Smart Images
Figure CN120040261A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of petrochemical industry, and particularly relates to a separation process for C8 - C10 aromatics. Background Art
[0002] In the petroleum processing technology, the aromatics complex unit is a core unit that uses straight - run naphtha, hydrocracked naphtha, etc. as raw materials to produce benzene, p - xylene, and o - xylene, including catalytic reforming, aromatics extraction, xylene separation, disproportionation, adsorption separation, xylene isomerization and other operating units.
[0003] The xylene separation unit mainly includes a reformate separation tower, a xylene redistillation tower, a xylene tower, and an o - xylene tower. The purpose is to separate C 8 aromatics and C 9 aromatics from the mixed aromatics, which are used as raw materials for adsorption separation and disproportionation respectively. Disproportionation is the disproportionation and transalkylation reaction of toluene and C 9 aromatics to produce the target products benzene and xylene. Isomerization uses poor p - xylene as the raw material, generates a xylene equilibrium mixture through isomerization, and is sent to the xylene separation unit after deheptanization.
[0004] In the existing process, the bottom oil of the reformate tower (≥C 8 aromatics) is treated with clay and then enters the xylene redistillation tower. The bottom mixed xylene of the deheptanization tower in the isomerization unit (mainly C 8 aromatics, with o - xylene content of 19 - 23% wt) is first treated with clay, and then divided into two parts. Most of it enters the xylene redistillation tower, and a small part enters the xylene tower. The bottom oil of the toluene tower in the disproportionation unit (≥C 8 aromatics, with o - xylene content of 12 - 14% wt) enters the xylene tower. The top oils of the xylene redistillation tower and the xylene tower are combined as the feed for the adsorption separation unit. The bottom oil of the xylene tower (≥C 8 aromatics) is used as the feed for the o - xylene tower. The top material of the o - xylene tower is used as the o - xylene product (98.9% wt). The bottom oil of the o - xylene tower and the bottom oil of the xylene redistillation tower are combined and enter the heavy aromatics separation tower. The bottom of the heavy aromatics separation tower separates out the heavy aromatics product (≥C 10 aromatics, flow rate about 0.1 t / h), and the top material is used as the feed for the disproportionation reaction (≥C 9 aromatics). Due to the large circulation volume, the components are relatively heavy, the energy consumption of each fractionation tower is high, and a heating furnace is required as the reboiling heat source. For example, in an aromatics complex unit with a p - xylene production of 110 t / h, the total bottom reboiler load of its xylene redistillation tower, xylene tower, and heavy aromatics separation tower is about 15000×10 4kcal / h, corresponding to approximately 14 t / h of fuel gas. In addition, from the perspective of o-xylene, the bottom oil of the toluene column (with an o-xylene content of 12 - 13% wt) and the mixed xylene at the bottom of the deheptanizer column (with an o-xylene content of 19 - 23% wt) enter the xylene column, and there is a backmixing phenomenon of o-xylene, which also leads to an increase in separation energy consumption.
[0005] Therefore, how to develop a new separation process for C8 - C10 aromatics to reduce separation energy consumption is an urgent problem to be solved at present. Summary of the Invention
[0006] Aiming at the technical problems existing in the prior art, the object of the present invention is to provide a separation process for C8 - C10 aromatics, which reduces separation energy consumption by optimizing the process.
[0007] To achieve the above object, the present invention adopts the following technical solutions:
[0008] A separation process for C8 - C10 aromatics includes the following steps: A part of the bottom oil from the deheptanizer column of the isomerization unit enters the middle of the xylene column, and a heat source is set at the bottom of the xylene column for heating. The rectification conditions of the xylene column are controlled for operation. C8 aromatic substances are separated from the top of the xylene column, and a part of the mixed substance containing o-xylene, C9 aromatics, and C10 aromatics separated from the bottom is refluxed, and the rest enters from the middle of the o-xylene column; the o-xylene column fractionates the mixed substance containing o-xylene, C9 aromatics, and C10 aromatics into o-xylene and a mixed substance containing C9 aromatics and C10 aromatics. The o-xylene flows out from the top of the o-xylene column, and the mixed substance containing C9 aromatics and C10 aromatics flows out from the bottom of the o-xylene column; the bottom oil of the reforming column and the bottom oil of the toluene column of the disproportionation unit are mixed and then enter the middle of the xylene re-distillation column. At the same time, another part of the bottom oil from the deheptanizer column of the isomerization unit enters the upper part of the xylene re-distillation column, and a heat source is set at the bottom of the xylene re-distillation column for heating. The rectification conditions of the xylene re-distillation column are controlled for operation. C8 aromatic substances are separated from the top of the xylene re-distillation column, and a mixed substance containing C9 aromatics and C10 aromatics is separated from the bottom; the mixed substance containing C9 aromatics and C10 aromatics flowing out from the bottom of the o-xylene column is merged with the mixed substance containing C9 aromatics and C10 aromatics flowing out from the bottom of the xylene re-distillation column, and the merged mixed substance enters from the middle of the heavy aromatics separation column, and a heat source is set at the bottom of the heavy aromatics separation column for heating. The rectification conditions of the heavy aromatics separation column are controlled for operation. C9 aromatic substances are separated from the top of the heavy aromatics separation column, and a part of the C10 aromatic substances separated from the bottom is refluxed, and the rest is discharged as a heavy aromatic product.
[0009] Further, the mixture containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons flowing out from the bottom of the xylene re-distillation tower exchanges heat with the bottom oil of the reforming oil tower after being treated with clay, and then converges with the mixture containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons flowing out from the bottom of the o-xylene tower.
[0010] A separation process for C8 - C10 aromatic hydrocarbons includes the following steps: A part of the bottom oil from the deheptanizer of the isomerization unit enters the middle of the xylene tower, and a heat source is set at the bottom of the xylene tower for heating. Under the rectification conditions of the xylene tower, the C8 aromatic hydrocarbon substance is separated from the top of the xylene tower, and a part of the mixture containing o-xylene, C9 aromatic hydrocarbons and C10 aromatic hydrocarbons separated from the bottom is refluxed, and the rest enters from the middle of the o-xylene tower; In the o-xylene tower, the mixture containing o-xylene, C9 aromatic hydrocarbons and C10 aromatic hydrocarbons is fractionated. The o-xylene substance is separated from the top of the o-xylene tower, the C9 aromatic hydrocarbon substance is separated from the side of the tower, and a part of the C10 aromatic hydrocarbon substance separated from the bottom is refluxed, and the rest is used as a heavy aromatic hydrocarbon product; The bottom oil of the reforming oil tower and the bottom oil of the toluene tower from the disproportionation unit are mixed and then enter the middle of the xylene re-distillation tower. At the same time, another part of the bottom oil from the deheptanizer of the isomerization unit enters the upper part of the xylene re-distillation tower, and a heat source is set at the bottom of the xylene re-distillation tower for heating. Under the rectification conditions of the xylene re-distillation tower, the C8 aromatic hydrocarbon substance is separated from the top of the xylene re-distillation tower, and the mixture containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons is separated from the bottom.
[0011] Further, the C9 aromatic hydrocarbon substance flows out from the stripping section of the o-xylene tower and converges with the mixture containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons flowing out from the bottom of the xylene re-distillation tower.
[0012] Further, the mixture containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons flowing out from the bottom of the xylene re-distillation tower first exchanges heat with the bottom oil of the reforming oil tower after being treated with clay, then exchanges heat with the bottom oil of the reforming oil tower before clay treatment, and finally converges with the C9 aromatic hydrocarbon substance flowing out from the side of the o-xylene tower.
[0013] Further, the C8 aromatic hydrocarbon substance at the top of the xylene tower is subjected to gas-liquid separation after condensation and cooling. A part of the liquid-phase C8 aromatic hydrocarbon substance returns to the xylene tower after being pressurized, and the rest is discharged.
[0014] Further, the C8 aromatic hydrocarbon substance at the top of the xylene re-distillation tower is subjected to gas-liquid separation after condensation and cooling. A part of the liquid-phase C8 aromatic hydrocarbon substance returns to the xylene re-distillation tower after being pressurized, and the rest is discharged.
[0015] Further, the C8 aromatic hydrocarbons at the top of the xylene column and the C8 aromatic hydrocarbons at the top of the xylene redistillation column are discharged after converging.
[0016] Further, the o-xylene at the top of the o-xylene column is subjected to condensation and cooling, followed by gas-liquid separation. The liquid o-xylene is pressurized and part of it is returned to the o-xylene column, and the rest becomes the o-xylene product.
[0017] Further, the heat source is selected from reboilers, and the reboilers utilize the waste heat of the reflux materials at the bottom of the xylene column, the bottom of the o-xylene column, and the bottom of the xylene redistillation column.
[0018] In the present invention, the bottom oil of the toluene column in the disproportionation unit (with an o-xylene content of 12 - 13% wt) no longer enters the xylene column but instead enters the xylene redistillation column. The xylene column only processes the bottom oil of the deheptanizer in the isomerization unit (with an o-xylene content of 19 - 23% wt), and the processing capacity is increased by 40 - 60%. Since the total processing amount of the xylene column is reduced and backmixing is decreased, the reboiling load at the bottom of the column is reduced by 25 - 35%.
[0019] The bottom temperature and the withdrawal amount of the xylene column are reduced. Since the xylene column only processes the bottom oil of the deheptanizer in the isomerization unit, the content of ≥C 9 aromatic components in the bottom oil of the xylene column decreases significantly. Therefore, the bottom temperature of the xylene column decreases and the withdrawal amount is reduced. It should be noted that the xylene column needs to control the p-xylene and m-xylene contents in the bottom oil of the xylene column to ensure that the o-xylene product of the downstream o-xylene column meets the standards. The processing amount of the o-xylene column is reduced, and the reboiling load decreases by 60 - 80%. In addition, since the heavy aromatics are concentrated at the bottom of the o-xylene column and the bottom temperature increases, a heating furnace needs to be used as the reboiling heat source.
[0020] The top of the heavy aromatics separation column is modified to be able to produce low-pressure steam at 0.5 MPa. In the traditional process, the top pressure of the heavy aromatics separation column is about 0.06 - 0.08 MPa, corresponding to a top temperature of 215 - 220 °C, and it directly enters the air cooler. During the adjustment process, the top operating pressure remains unchanged, and the top gas is introduced into the steam generator, so that low-pressure steam at 0.5 MPa can be produced.
[0021] The heavy aromatics are concentrated at the bottom of the o-xylene column and the withdrawal amount is greatly reduced. Therefore, a side line can be directly added to the o-xylene column, and the side line material and the bottom oil of the xylene redistillation column are used as the disproportionation reaction feed together. The heavy aromatics product is directly withdrawn from the bottom of the o-xylene column, so that the heavy aromatics separation column can be shut down, and the o-xylene column can use the reboiler of the old heavy aromatics separation column as the reboiling heat source.
[0022] Adjust the heat exchange process of the bottom oil of the xylene redistillation tower. In the traditional process, the bottom oil of the reforming oil tower is preheated to 180°C by the circulating material of the reboiler at the bottom of the xylene redistillation tower and then enters the clay tower. The bottom oil of the reforming oil tower after being treated by the clay then enters the xylene redistillation tower after being heated by the bottom oil of the xylene redistillation tower. The bottom oil of the xylene redistillation tower after heat exchange converges with the bottom oil of the o-xylene tower and enters the heavy aromatics separation tower. However, the separation process of the present invention heats the bottom oil of the xylene redistillation tower successively to the bottom oil of the reforming oil tower after being treated by the clay and the bottom oil of the reforming oil tower before the clay tower, then produces low-pressure steam of 0.5 MPa through a steam generator, and finally converges with the side-line material newly opened in the o-xylene tower as the feed for the disproportionation reaction. In this way, the load of the reboiler can be saved and low-pressure steam of 0.5 MPa can be produced more.
[0023] The present invention has the following advantages:
[0024] 1. The process of the present invention changes the treatment of the bottom oil of the toluene tower from the disproportionation unit entering the xylene tower in the traditional process to entering the xylene redistillation tower, that is, the xylene tower only processes the bottom oil from the deheptanizer of the isomerization unit. This not only reduces the backmixing phenomenon of o-xylene in the xylene tower, thereby reducing the separation energy consumption of the xylene tower, but also reduces the processing volume of the o-xylene tower to reduce energy consumption. In addition, due to the significant reduction in the processing volume of the o-xylene tower, the heavy aromatics product is only 0.1 t / h. By adding a side line in the stripping section of the o-xylene tower, the substances containing C9 aromatics flow out from the side line as the feed for the disproportionation reaction, while the heavy aromatics substances of C10 are enriched at the bottom of the o-xylene tower and directly produce the heavy aromatics product, thus canceling the heavy aromatics separation tower, reducing the operation difficulty, further reducing the separation energy consumption, and reducing the use of fuel gas.
[0025] 2. The energy-saving effect of the present invention is very significant. The traditional aromatics combined unit has a large fuel gas consumption in the C8-C10 aromatics separation process. For example, for an aromatics combined unit with a p-xylene output of 110 t / h, the total load of the reboilers at the bottoms of its xylene redistillation tower, xylene tower, and heavy aromatics separation tower is about 15000×104 kcal / h, which is equivalent to about 14 t / h of fuel gas. However, the process of the present invention can reduce the fuel gas consumption by 15-18%.
[0026] 3. The process modification of the present invention is less. It only needs to improve the pipeline direction of the material, without adding new equipment, which is convenient for the transformation of the old device, and has low investment and high return rate. Description of the Drawings
[0027] Figure 1 It is a schematic flow chart of Comparative Example 1 of the existing C8-C10 aromatics separation process.
[0028] Figure 2 It is a schematic flow chart of Example 1 of the C8-C10 aromatics separation process of the present invention.
[0029] Figure 3 It is a schematic flow chart of Embodiment 2 of the separation process of the present invention for C8 - C10 aromatics.
[0030] Among them, 1 is the xylene tower, 2 is the xylene re - distillation tower, 3 is the o - xylene tower, 4 is the heavy aromatics separation tower, 5 is the clay tower, 6 is the xylene tower reboiler, 7 is the xylene re - distillation tower reboiler, 8 is the heavy aromatics separation tower reboiler, 9 is the o - xylene tower reboiler, 10 is the raffinate tower / extract tower / reforming oil tower reboiler, 11 is the raffinate tower / extract tower / reforming oil tower reboiler, 12 is the o - xylene tower top steam generator, 13 is the o - xylene tower top air cooler, 14 is the heavy aromatics separation tower top air cooler, 15 is the o - xylene product air cooler, 16 is the heavy aromatics product air cooler, 17 is the clay tower heater, 18 - the desorbent re - distillation tower reboiler, 19 is the heat exchanger between the bottom oil of the xylene re - distillation tower and the feed, 20 is the xylene tower top reflux drum, 21 is the xylene re - distillation tower top reflux drum, 22 is the o - xylene tower top reflux drum, 23 is the heavy aromatics separation tower top reflux drum, 24 is the xylene tower top pump, 25 is the xylene tower bottom pump, 26 is the xylene re - distillation tower top pump, 27 is the xylene re - distillation tower bottom pump, 28 is the o - xylene tower top pump, 29 is the o - xylene tower bottom pump, 30 is the heavy aromatics separation tower top pump, 31 is the heavy aromatics separation tower bottom pump, 32 is the o - xylene tower reboiler, 33 is the heavy aromatics separation tower top steam generator, 34 is the xylene re - distillation tower bottom oil steam generator, 35 is the o - xylene tower side - line pump. Detailed implementation manners
[0031] The present invention will be further described in detail below in conjunction with the drawings and specific implementation manners.
[0032] Taking an aromatics complex with an annual output of 840,000 tons of p - xylene as an example, the main operating conditions of Comparative Example 1, Embodiment 1 and Embodiment 2 are described under the same separation requirements.
[0033] Comparative Example 1
[0034] As Figure 1As shown in the figure, a part of the bottom oil from the deheptanizer in the isomerization unit is preheated in the convection section of the reboiler 6 and then enters the xylene column 1. At the same time, the bottom oil of the toluene column from the disproportionation unit enters the xylene column 1. After the bottom oil of the xylene column 1 is pressurized by the pump 25, a part of it is heated by the bottom reboiler 6 of the column and returned to the column, and the other part enters the o-xylene column 3. The top gas of the xylene column 1 first passes through two reboilers installed at the top of the column. One of the reboilers is the reboiler 9 at the bottom of the o-xylene column 3, and the other reboiler is the reboiler 10 of the raffinate column, the extract column or the reformate column, which can be used as its heat source. After condensation and cooling, it enters the reflux drum 20 installed at the top of the column for gas-liquid separation. The liquid-phase C8 aromatic hydrocarbon substance is pressurized by the pump 24, part of it is returned to the column as reflux, and the rest is transported to the adsorption separation unit.
[0035] The top gas of the o-xylene column 3 first passes through the steam generator 12 installed at the top of the column, which can generate steam at 0.5 MPa, and then passes through the air cooler 13. After condensation and cooling, it enters the reflux drum 22 installed at the top of the column for gas-liquid separation. The liquid-phase o-xylene substance is pressurized by the pump 28, part of it is returned to the column as reflux, and part of it is used as the o-xylene product (98.9% wt) to leave the unit through the air cooler 15. The bottom oil of the o-xylene column 3 (a mixture containing C9 and C10 aromatic hydrocarbons) is pressurized by the pump 29, part of it is heated by the reboiler 9 installed at the bottom of the column and returned to the column, and the rest is discharged.
[0036] The bottom oil from the reformate column is first passed through the heater 17 upstream of the clay tower 5 and then enters the clay tower 5. The heater 17 upstream of the clay tower 5 is heated by the reflux material flowing out from the bottom of the xylene rectification column 2. The bottom oil of the reformate column after clay treatment then passes through the heat exchanger 19 downstream of the clay tower 5, and heat exchange is carried out with the bottom oil flowing out from the bottom of the xylene rectification column 2 through the heat exchanger 19, and finally enters from the middle of the xylene rectification column 2. At the same time, another part of the bottom oil of the deheptanizer in the isomerization unit is preheated in the convection section of the reboiler 7 installed at the bottom of the column and then enters the upper part of the xylene rectification column 2.
[0037] Among them, the top gas of the xylene rectification column 2 first passes through the reboiler 11 installed at the top of the column. This reboiler is the reboiler 11 of the raffinate column, the extract column or the reformate column, which can be used as its heat source. After condensation and cooling, it enters the reflux drum 21 installed at the top of the column for gas-liquid separation. The liquid-phase C8 aromatic hydrocarbon substance is pressurized by the pump 26, part of it is returned to the column as reflux, and the rest is transported to the adsorption separation unit. Among them, the C8 aromatic hydrocarbon substances at the top of the xylene column 1 and the C8 aromatic hydrocarbon substances at the top of the xylene rectification column 2 are merged and discharged to the adsorption separation unit.
[0038] Among them, the bottom oil of the xylene redistillation tower 2 is pressurized by the pump 27 and then divided into four streams. The first stream returns to the tower after serving as the heat source for the upstream heater 17 of the clay tower 5. The second stream returns to the tower after serving as the heat source for the reboiler 18 of the desorbent redistillation tower. The third stream is heated by the reboiler 7 installed at the tower bottom and then returns to the tower. The fourth stream serves as the heat source for the downstream heat exchanger 19 of the clay tower 5, and then converges with the bottom oil of the o-xylene tower 3 and enters the middle part of the heavy aromatics separation tower 4 together.
[0039] The top gas of the heavy aromatics separation tower 4 first passes through the air cooler 14, and after condensation and cooling, it enters the reflux drum 23 installed at the top of the tower for gas-liquid separation. The liquid-phase C9 aromatic hydrocarbon substances are pressurized by the pump 30, and part of them returns to the tower as reflux, and part of them are sent out of the device as feed for the disproportionation reaction. The bottom oil of the heavy aromatics separation tower 4 is pressurized by the pump 31. Part of it is heated by the reboiler 8 installed at the tower bottom and then returns to the tower, and the other part is cooled by the air cooler 16 and then sent out of the device as a heavy aromatics product (C 10+ aromatic hydrocarbon content 100% wt, flow rate 0.1 t / h).
[0040] Table 1 is a list of the main process and equipment parameters and energy consumption of Comparative Example 1.
[0041]
[0042]
[0043] Example 1
[0044] As Figure 2 shown, a separation process for C8-C10 aromatics includes the following steps: A part of the bottom oil from the deheptanizer of the isomerization unit enters the middle part of the xylene tower 1, and a heat source is set at the bottom of the xylene tower 1 for heating. Under the distillation conditions of the xylene tower 1, the C8 aromatic hydrocarbon substances are separated from the top of the xylene tower 1, and a part of the mixed substances containing o-xylene, C9 aromatic hydrocarbons and C10 aromatic hydrocarbons separated from the bottom of the tower is refluxed, and the rest enters the middle part of the o-xylene tower 3. The C8 aromatic hydrocarbon substances at the top of the xylene tower 1 are subjected to gas-liquid separation after condensation and cooling. The liquid-phase C8 aromatic hydrocarbon substances are pressurized, and part of them returns to the xylene tower 1, and the rest are discharged. Among them, a reboiler 6 is installed at the bottom of the xylene tower 1. A part of the bottom oil of the deheptanizer of the isomerization unit is preheated by the convection section of the reboiler 6 and then enters the xylene tower 1. The bottom oil of the xylene tower 1 is pressurized by the pump 25. Part of it is heated by the reboiler 6 at the tower bottom and then returns to the tower, and the other part enters the o-xylene tower 3. The top gas of the xylene tower 1 first passes through the reboiler 10 installed at the top of the tower. This reboiler is the reboiler 10 of the raffinate tower, the extract tower or the reformate tower and can serve as its heat source. After condensation and cooling, it enters the reflux drum 20 installed at the top of the tower for gas-liquid separation. The liquid-phase C8 aromatic hydrocarbon substances are pressurized by the pump 24, and part of them returns to the tower as reflux, and the rest are transported to the adsorption separation unit.
[0045] The o-xylene column 3 fractionates the mixture containing o-xylene, C9 aromatics and C10 aromatics into o-xylene and the mixture containing C9 aromatics and C10 aromatics. The o-xylene flows out from the top of the o-xylene column 3, and the mixture containing C9 aromatics and C10 aromatics flows out from the bottom of the o-xylene column 3. The o-xylene at the top of the o-xylene column 3 is subjected to condensation and cooling and then gas-liquid separation. After the liquid o-xylene is pressurized, a part of it returns to the o-xylene column 3, and the rest becomes the o-xylene product. Among them, the top gas of the o-xylene column 3 first passes through the steam generator 12 provided at the top of the column, which can generate steam at 0.5 MPa, and then passes through the air cooler 13. After condensation and cooling, it enters the reflux drum 22 provided at the top of the column for gas-liquid separation. After the liquid o-xylene substance is pressurized by the pump 28, part of it returns to the column as reflux, and part of it passes through the air cooler 15 to be discharged as the o-xylene product (98.9% wt). The bottom oil of the o-xylene column 3 (the mixture containing C9 aromatics and C10 aromatics) is pressurized by the pump 29. Part of it is heated by the reboiler 32 provided at the bottom of the column and returns to the column, and the rest is discharged.
[0046] The bottom oil of the reforming column and the bottom oil of the toluene column in the disproportionation unit are mixed and then enter the middle part of the xylene redistillation column 2. At the same time, another part of the bottom oil of the deheptanizer in the isomerization unit enters the upper part of the xylene redistillation column 2. A heat source is set at the bottom of the xylene redistillation column 2 for heating, and the rectification conditions of the xylene redistillation column 2 are controlled for operation. The C8 aromatics are separated from the top of the xylene redistillation column 2, and the mixture containing C9 aromatics and C10 aromatics is separated from the bottom of the column. The C8 aromatics at the top of the xylene redistillation column 2 are subjected to condensation and cooling and then gas-liquid separation. After the liquid C8 aromatics are pressurized, a part of it returns to the xylene redistillation column 2, and the rest is discharged. Among them, the mixture containing C9 aromatics and C10 aromatics flowing out from the bottom of the xylene redistillation column 2 exchanges heat with the bottom oil of the reforming column after being treated with clay. Specifically, the bottom oil of the reforming column is heated by the heater 17 upstream of the clay tower 5 and then enters the clay tower 5. The heater 17 upstream of the clay tower 5 is heated by the reflux material flowing out from the bottom of the xylene redistillation column 2. The bottom oil of the reforming column after clay treatment first passes through the heat exchanger 19 downstream of the clay tower 5, exchanges heat with the bottom oil flowing out from the bottom of the xylene redistillation column 2 through the heat exchanger 19, then is mixed with the bottom oil of the toluene column from the disproportionation unit, and finally enters the middle part of the xylene redistillation column 2 together. At the same time, another part of the bottom oil of the deheptanizer in the isomerization unit is preheated in the convection section of the reboiler 7 provided at the bottom and then enters the upper part of the xylene redistillation column 2.
[0047] Among them, the bottom oil of the xylene redistillation tower 2 is pressurized by the pump 27 and then divided into four streams. The first stream returns to the tower after serving as the heat source for the upstream heater 17 of the clay tower 5. The second stream returns to the tower after serving as the heat source for the reboiler 18 of the desorbent redistillation tower. The third stream is heated by the reboiler 7 installed at the bottom of the tower and then returns to the tower. The fourth stream serves as the heat source for the downstream heat exchanger 19 of the clay tower 5, and then converges with the bottom oil of the ortho-xylene tower 3 and enters the middle part of the heavy aromatics separation tower 4 together.
[0048] Among them, the top gas of the xylene redistillation tower 2 first passes through the reboiler 11 installed at the top of the tower. This reboiler is the reboiler 11 of the raffinate tower, the extract tower or the reformate tower and can serve as its heat source. After condensation and cooling, it enters the reflux drum 21 installed at the top of the tower for gas-liquid separation. The liquid-phase C8 aromatic hydrocarbon substances are pressurized by the pump 26. Part of them returns to the tower as reflux, and the rest are transported to the adsorption separation unit. Among them, the C8 aromatic hydrocarbon substances at the top of the xylene tower 1 and the C8 aromatic hydrocarbon substances at the top of the xylene redistillation tower 2 converge and are discharged to the adsorption separation unit.
[0049] Among them, the mixed substances containing C9 and C10 aromatic hydrocarbons flowing out from the bottom of the ortho-xylene tower 3 are converged with the mixed substances containing C9 and C10 aromatic hydrocarbons flowing out from the bottom of the xylene redistillation tower 2. The converged mixed substances enter the middle part of the heavy aromatics separation tower 4, and a heat source is installed at the bottom of the heavy aromatics separation tower 4 for heating. Under the rectification conditions of the heavy aromatics separation tower 4, the C9 aromatic hydrocarbon substances are separated from the top of the heavy aromatics separation tower 4, and a part of the C10 aromatic hydrocarbon substances separated from the bottom of the tower is refluxed, and the rest are discharged as heavy aromatic products.
[0050] The top gas of the heavy aromatics separation tower 4 first passes through the steam generator 33 installed at the top of the tower, which can generate steam at 0.5 MPa, and then passes through the air cooler 14. After condensation and cooling, it enters the reflux drum 23 installed at the top of the tower for gas-liquid separation. The liquid-phase C9 aromatic hydrocarbon substances are pressurized by the pump 30. Part of them returns to the tower as reflux, and part of them leave the device as feed for the disproportionation reaction. The bottom oil of the heavy aromatics separation tower 4 is pressurized by the pump 31. One part is heated by the reboiler 8 installed at the bottom of the tower and then returns to the tower, and the other part is cooled by the air cooler 16 and then leaves the device as heavy aromatic products (C 10+ Aromatic content 100% wt, flow rate 0.1 t / h).
[0051] Table 2 is a list of the main process, equipment parameters and energy consumption of Example 1.
[0052]
[0053] Example 2
[0054] The difference between this embodiment and Embodiment 1 lies in that the heavy aromatics separation column 4 is cancelled, the heavy aromatics are enriched at the bottom of the o-xylene column 3, and the extraction amount is greatly reduced. A side line is added to the o-xylene column 3. The side line material and the bottom oil of the xylene redistillation column 2 are used as the disproportionation reaction feed together. The heavy aromatics product is directly extracted from the bottom of the o-xylene column 3, and the o-xylene column 3 can use the reboiler 8 of the old heavy aromatics separation column 4 as the reboiling heat source.
[0055] As Figure 3 shown, a separation process for C8-C10 aromatics includes the following steps: A part of the bottom oil from the deheptanizer of the isomerization unit enters the middle of the xylene column 1, and a heat source is set at the bottom of the xylene column 1 for heating. The xylene column 1 is operated under the rectification conditions. The C8 aromatic substances are separated from the top of the xylene column 1, and a part of the mixed substances containing o-xylene, C9 aromatics and C10 aromatics separated from the bottom is refluxed, and the rest enters from the middle of the o-xylene column 3. The C8 aromatic substances at the top of the xylene column 1 are subjected to gas-liquid separation after condensation and cooling. After the liquid-phase C8 aromatic substances are pressurized, a part returns to the xylene column 1, and the rest is discharged. Among them, a reboiler 6 is arranged at the bottom of the xylene column 1. A part of the bottom oil of the isomerization unit deheptanizer is preheated by the convection section of the reboiler 6 and then enters the xylene column 1. After the bottom oil of the xylene column 1 is pressurized by the pump 25, a part is heated by the bottom reboiler 6 and returned to the column, and the other part enters the o-xylene column 3. The top gas of the xylene column 1 first passes through the reboiler 10 arranged at the top of the column. This reboiler is the reboiler 10 of the raffinate column, the extract column or the reformate column, and can be used as its heat source. After condensation and cooling, it enters the reflux drum 20 arranged at the top of the column for gas-liquid separation. After the liquid-phase C8 aromatic substances are pressurized by the pump 24, part of them returns to the column as reflux, and the rest is transported to the adsorption separation unit.
[0056] In the o-xylene column 3, the mixed substances containing o-xylene, C9 aromatics and C10 aromatics are fractionated. The o-xylene substances are separated from the top of the o-xylene column. The o-xylene at the top of the o-xylene column 3 is subjected to gas-liquid separation after condensation and cooling. After the liquid-phase o-xylene is pressurized, a part returns to the o-xylene column 3, and the rest becomes the o-xylene product. Among them, the top gas of the o-xylene column 3 first passes through the steam generator 12 arranged at the top of the column, which can generate steam at 0.5 MPa, and then passes through the air cooler 13. After condensation and cooling, it enters the reflux drum 22 arranged at the top of the column for gas-liquid separation. After the liquid-phase o-xylene substances are pressurized by the pump 28, part of them returns to the column as reflux, and part of them passes through the air cooler 15 to be the o-xylene product (98.9% wt) out of the device.
[0057] The C9 aromatic substances are separated from the side of the o-xylene column 3, and the C10 aromatic substances are separated from the bottom of the column. A part of them is refluxed, and the rest is used as the heavy aromatics product. Among them, a part of the bottom oil of the o-xylene column 3 (containing C10 aromatic substances) is cooled by the air cooler 16 and then taken out of the device as the heavy aromatics product (C10+ The aromatic hydrocarbon content is 100% wt and the flow rate is 0.1 t / h). The remaining part is heated by the reboiler 8 and returned to the tower. A new side line is opened in the stripping section of the o-xylene tower 3, and the side line material (containing C9 aromatic hydrocarbon substances) is discharged after being pressurized by the pump 35.
[0058] The bottom oil of the reforming tower and the bottom oil of the toluene tower in the disproportionation unit are mixed and then enter the middle part of the xylene redistillation tower 2. At the same time, another part of the bottom oil of the deheptanizer in the isomerization unit enters the upper part of the xylene redistillation tower 2. A heat source is set at the bottom of the xylene redistillation tower 2 for heating, and the operation is controlled under the rectification conditions of the xylene redistillation tower 2. The C8 aromatic hydrocarbon substances are separated from the top of the xylene redistillation tower 2, and a mixed substance containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons is separated from its bottom. The C8 aromatic hydrocarbon substances at the top of the xylene redistillation tower 2 are separated into gas and liquid after condensation and cooling. After the liquid-phase C8 aromatic hydrocarbon substances are pressurized, a part of them is returned to the xylene redistillation tower 2, and the rest is discharged. Among them, the mixed substance containing C9 aromatic hydrocarbons and C10 aromatic hydrocarbons flowing out from the bottom of the xylene redistillation tower 2 is first heat-exchanged with the bottom oil of the reforming tower after being treated by the clay, and then heat-exchanged with the bottom oil of the reforming tower before being treated by the clay. Specifically, the bottom oil of the reforming tower is heated by the heater 17 upstream of the clay tower 5 and then enters the clay tower 5. The heater 17 upstream of the clay tower 5 is heated by the reflux material flowing out from the bottom of the xylene redistillation tower 2. The bottom oil of the reforming tower after being treated by the clay first passes through the heat exchanger 19 downstream of the clay tower 5, and heat-exchanges with the bottom oil flowing out from the bottom of the xylene redistillation tower 2 through the heat exchanger 19, and then is mixed with the bottom oil of the toluene tower from the disproportionation unit, and finally enters the middle part of the xylene redistillation tower 2 together. At the same time, another part of the bottom oil of the deheptanizer in the isomerization unit is preheated in the convection section of the reboiler 7 arranged at the bottom and then enters the upper part of the xylene redistillation tower 2.
[0059] Among them, the bottom oil of the xylene redistillation tower 2 is pressurized by the pump 27 and then divided into four streams. The first stream returns to the tower after being used as the heat source of the heater 17 upstream of the clay tower 5, the second stream returns to the tower after being used as the heat source of the reboiler 18 of the desorbent redistillation tower, the third stream is heated by the reboiler 7 arranged at the bottom and returns to the tower, and the fourth stream is used as the heat source of the heat exchanger 19 downstream of the clay tower 5, then used as the heat source of the heater 17 upstream of the clay tower 5, and then used as the heat source to generate 0.5 MPa steam by the steam generator 34. Finally, it converges with the side line material of the o-xylene tower 3 and is discharged from the device together as the feed for the disproportionation reaction.
[0060] Among them, the top gas of the xylene re - distillation tower 2 first passes through the re - boiler 11 installed at the top of the tower. This re - boiler is the re - boiler 11 of the raffinate tower, the extract tower or the reformate tower, and can be used as its heat source. After being condensed and cooled, it enters the reflux drum 21 installed at the top of the tower for gas - liquid separation. The liquid phase of the C8 aromatic hydrocarbon substances is pressurized by the pump 26. Part of it returns to the tower as reflux, and the rest is transported to the adsorption separation unit. Among them, the C8 aromatic hydrocarbon substances at the top of the xylene tower 1 and the C8 aromatic hydrocarbon substances at the top of the xylene re - distillation tower 2 are merged and then discharged to the adsorption separation unit.
[0061] Table 3 is a list of the main process, equipment parameters and energy consumption of Example 2.
[0062]
[0063]
[0064] Table 4 is a list of the product quantities and properties of Comparative Example 1, Example 1 and Example 2.
[0065]
[0066] It can be seen from Table 1 to Table 4 that:
[0067] In Comparative Example 1, the load of the heating furnace 6 of the xylene tower 1 is 4911×10 4 kcal / h, the load of the heating furnace 7 of the xylene re - distillation tower 2 is 8840×10 4 kcal / h, the load of the heating furnace 8 of the heavy - aromatic separation tower 4 is 1398×10 4 kcal / h. The total load of the heating furnaces in Comparative Example 1 is 15149×10 4 kcal / h. In Example 1, the load of the heating furnace 6 of the xylene tower 1 is 3473×10 4 kcal / h, the load of the heating furnace 7 of the xylene re - distillation tower 2 is 9225×10 4 kcal / h, the load of the heating furnace 8 of the heavy - aromatic separation tower 4 is 938×10 4 kcal / h, the load of the heating furnace 32 of the o - xylene tower 3 is 222×10 4 kcal / h. The total load of the heating furnaces in Example 1 is 13858×10 4 kcal / h, which is 1291×10 4 kcal / h less than that in Comparative Example 1, with a decrease of 8.5%. In Example 2, the load of the heating furnace 6 of the xylene tower 1 is 3473×10 4 kcal / h, the load of the heating furnace 7 of the xylene re - distillation tower 2 is 8878×10 4 kcal / h, the load of the heating furnace 8 of the o - xylene tower 3 is 222×10 4kcal / h. The total heating furnace load of Example 2 is 12573×10 4 kcal / h, 2576×10 less than Comparative Example 1 4 kcal / h, with a reduction of 17%.
[0068] In Comparative Example 1, the steam generation load of the steam generator 12 at the top of the o-xylene column 3 is 703×10 4 kcal / h, equivalent to 12.6 t / h of 0.5 MPa steam (calculated based on the heat of 55.8×10 for producing 1 t of 0.5 MPa steam, the same below). In Example 1, the steam generation load of the steam generator 12 at the top of the o-xylene column 3 is 271×10 4 kcal / h, equivalent to 4.9 t / h of 0.5 MPa steam. The steam generation load of the steam generator 33 at the top of the heavy aromatics separation column 4 is 1362×10 4 kcal / h, equivalent to 24.4 t / h of 0.5 MPa steam. The total production of 0.5 MPa steam in Example 1 is 29.3 t / h, 16.7 t / h more than Comparative Example 1, with an increase of 132.5%. In Example 2, the steam generation load of the steam generator 12 at the top of the o-xylene column 3 is 271×10 4 kcal / h, equivalent to 4.9 t / h of 0.5 MPa steam. The steam generation load of the bottom oil steam generator 34 of the xylene re-distillation column 2 is 205×10 4 kcal / h, equivalent to 3.7 t / h of 0.5 MPa steam. The total production of 0.5 MPa steam in Example 2 is 8.6 t / h, 4 t / h less than Comparative Example 1, with a reduction of 31.7%. 4 kcal / h, equivalent to 3.7 t / h of 0.5 MPa steam. The total production of 0.5 MPa steam in Example 2 is 8.6 t / h, 4 t / h less than Comparative Example 1, with a reduction of 31.7%.
[0069] In Comparative Example 1, the external heat integration load at the top of the xylene column 1 is 4640×10 4 kcal / h, the external heat integration load at the top of the xylene re-distillation column 2 is 7511×10 4 kcal / h, the heat integration load required for reboiling at the bottom of the o-xylene column 3 is 985×10 4 kcal / h. In Comparative Example 1, the total external heat integration load is 11166×10 4 kcal / h. In Example 1, the external heat integration load at the top of the xylene column 1 is 3160×10 4 kcal / h, the external heat integration load at the top of the xylene re-distillation column 2 is 7669×10 4 kcal / h. In Example 1, the total external heat integration load is 10829×10 4 kcal / h, 337×10 less than Comparative Example 1 4 kcal / h, equivalent to 6.7 t / h of 3.5 MPa steam (calculated based on the heat of 50×10 for 1 t of 3.5 MPa and 350℃ steam 4kcal calculation, the same below), with a decrease of 3%. In Example 2, the external heat integration load at the top of the xylene column 1 is 3160×10 4 kcal / h, and the external heat integration load at the top of the xylene re-distillation column 2 is 7669×10 4 kcal / h. In Example 2, the total external heat integration load is 10829×10 4 kcal / h, which is 337×10 4 kcal / h less than that in Comparative Example 1, equivalent to 6.7 t / h of 3.5 MPa steam, with a decrease of 3%.
[0070] The product quantity and purity in Example 1 and Example 2 are the same as those in Comparative Example 1.
[0071] In summary, the process energy consumption in Example 1 and Example 2 is lower than that in Comparative Example 1. Based on the energy price, the fuel gas price is 3.8 yuan / kg (the heating furnace efficiency is taken as 92%, and the calorific value of the fuel gas is calculated according to 1.2×10 4 kcal / kg), 250 yuan / t for 3.5 MPa steam, and 150 yuan / t for 0.5 MPa steam.
[0072] In Comparative Example 1, the total heating furnace load is 15149×10 4 kcal / h, and the energy consumption cost is 52143 yuan / h; the total external heat integration load is 11166×10 4 kcal / h, equivalent to 223.3 t / h of 3.5 MPa steam, with a benefit of 55830 yuan / h; 12.6 t / h of 0.5 MPa steam is produced, with a benefit of 1890 yuan / h.
[0073] In Example 1, the total heating furnace load is 13858×10 4 kcal / h, and the energy consumption cost is 47699.6 yuan / h, which is 4443.4 yuan / h less than that in Comparative Example 1, with a decrease of 8.5%; the total external heat integration load is 10829×10 4 kcal / h, equivalent to 216.6 t / h of 3.5 MPa steam, with a benefit of 54150 yuan / h, which is 1680 yuan / h less than that in Comparative Example 1, with a decrease of 3%; 29.3 t / h of 0.5 MPa steam is produced, with a benefit of 4395 yuan / h, which is 2505 yuan / h more than that in Comparative Example 1, with an increase of 132.5%. Compared with Comparative Example 1, Example 1 saves (increases efficiency) 5268.4 yuan / h.
[0074] In Example 2, the total heating furnace load is 12573×10 4 kcal / h, and the energy consumption cost is 43276.6 yuan / h, which is 8866.4 yuan / h less than that in Comparative Example 1, with a decrease of 17%; the total external heat integration load is 10829×10 4kcal / h, equivalent to 216.6 t / h of 3.5 MPa steam, with a benefit of 54,150 yuan / h, which is 1,680 yuan / h less than Comparative Example 1, a decrease of 3%; producing 8.6 t / h of 0.5 MPa steam, with a benefit of 1,290 yuan / h, which is 600 yuan / h less than Comparative Example 1, a decrease of 31.7%. Compared with Comparative Example 1, Example 2 saves (increases efficiency) 6,586.4 yuan / h.
[0075] Calculated based on the annual operation of the device for 8,400 hours, Example 1 increases efficiency by 44.255 million yuan / year, and Example 2 increases efficiency by 55.326 million yuan / year.
[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.
Claims
1. A separation process for C8 to C10 aromatic hydrocarbons, characterized in that: The following steps are involved: A portion of the bottom oil from the deheptane tower of the isomerization unit enters the middle of a xylene tower, and a heat source is set at the bottom of the xylene tower for heating, and the xylene tower is controlled to operate under distillation conditions, and a C8 aromatic substance is separated from the top of the xylene tower, and a portion of a mixed substance containing o-xylene, C9 aromatics and C10 aromatics is separated from the bottom of the tower, and a portion of the mixed substance is refluxed, and the rest enters from the middle of the o-xylene tower; The o-xylene tower fractionates the mixed substance containing the o-xylene, C9 aromatics and C10 aromatics into o-xylene and a mixed substance containing C9 aromatics and C10 aromatics, wherein the o-xylene flows out from the top of the o-xylene tower, and the mixed substance containing C9 aromatics and C10 aromatics flows out from the bottom of the o-xylene tower; The bottom oil from the reforming oil tower and the bottom oil from the toluene tower of the disproportionation unit are mixed and then enter the middle part of the xylene re-distillation tower, and at the same time, another part of the bottom oil from the deheptanizer tower of the isomerization unit enters the upper part of the xylene re-distillation tower, and a heat source is set at the bottom of the xylene re-distillation tower for heating, and the xylene re-distillation tower is controlled to operate under distillation conditions, and C8 aromatic substances are separated from the top of the xylene re-distillation tower, and a mixed substance containing C9 aromatics and C10 aromatics is separated from the bottom of the tower; The mixed substance containing the nine-carbon aromatics and the ten-carbon aromatics flowing out from the bottom of the o-xylene tower is merged with the mixed substance containing the nine-carbon aromatics and the ten-carbon aromatics flowing out from the bottom of the xylene redistillation tower, and the merged mixed substance enters the heavy aromatics separation tower from the middle, and a heat source is set at the bottom of the heavy aromatics separation tower for heating, and the heavy aromatics separation tower is controlled to operate under the distillation conditions, and the nine-carbon aromatics material is separated from the top of the heavy aromatics separation tower, and a part of the ten-carbon aromatics material separated from the bottom is refluxed, and the rest is discharged as a heavy aromatics product.
2. A separation process for C8 to C10 aromatic hydrocarbons according to claim 1, characterized in that: The mixed substance containing nine carbon aromatics and ten carbon aromatics flowing out of the bottom of the xylene redistillation tower is heat exchanged with the bottom oil of the reforming oil tower treated with white clay, and then merged with the mixed substance containing nine carbon aromatics and ten carbon aromatics flowing out of the bottom of the ortho-xylene tower.
3. A separation process for C8 to C10 aromatic hydrocarbons, characterized in that: The following steps are involved: A portion of the bottom oil from the deheptanizer of the isomerization unit enters the middle of the xylene tower, and a heat source is set at the bottom of the xylene tower for heating, and the xylene tower is controlled to operate under distillation conditions, and eight carbon aromatics are separated from the top of the xylene tower, and a portion of the mixed substance containing o-xylene, nine carbon aromatics and ten carbon aromatics is separated from the bottom of the tower and refluxed, and the rest enters from the middle of the o-xylene tower; the mixed substance containing o-xylene, nine carbon aromatics and ten carbon aromatics is fractionated in the o-xylene tower, the o-xylene substance is separated from the top of the o-xylene tower, nine carbon aromatics are separated from the side of the tower, a portion of the ten carbon aromatics is separated from the bottom of the tower and refluxed, and the rest is used as a heavy aromatics product; The bottom oil from the reforming oil tower and the bottom oil from the toluene tower of the isomerization unit are mixed and then enter the middle part of the xylene re-distillation tower. At the same time, another part of the bottom oil from the deheptane tower of the isomerization unit enters the upper part of the xylene re-distillation tower. A heat source is set at the bottom of the xylene re-distillation tower for heating. The xylene re-distillation tower is controlled to operate under distillation conditions, and C8 aromatic substances are separated from the top of the xylene re-distillation tower, and a mixed substance containing C9 aromatics and C10 aromatics is separated from the bottom.
4. A separation process for C8 to C10 aromatic hydrocarbons according to claim 3, characterized in that: The carbon nine aromatic hydrocarbon material flows out from the stripping section of the o-xylene tower and merges with the mixed material containing carbon nine aromatic hydrocarbons and carbon ten aromatic hydrocarbons flowing out from the bottom of the xylene redistillation tower.
5. A separation process for C8 to C10 aromatic hydrocarbons according to claim 3, characterized in that: The mixed substance containing C9 aromatics and C10 aromatics flowing out of the bottom of the xylene redistillation tower is first heat exchanged with the bottom oil of the reforming oil tower after being treated with bleaching clay, then heat exchanged with the bottom oil of the reforming oil tower before being treated with bleaching clay, and finally merged with the C9 aromatics flowing out of the side of the ortho-xylene tower.
6. A separation process for C8 to C10 aromatic hydrocarbons according to claim 1 or 3, characterized in that: The C8 aromatic substances at the top of the xylene tower are condensed and cooled to separate into gas and liquid. After the liquid phase C8 aromatic substances are pressurized, a portion of them returns to the xylene tower, and the rest is discharged.
7. A process for separating C8 to C10 aromatic hydrocarbons according to claim 1 or 3, characterized in that: The C8 aromatic substances at the top of the xylene re-distillation tower are condensed and cooled to separate gas and liquid. After the liquid phase C8 aromatic substances are pressurized, a portion of them returns to the xylene re-distillation tower, and the rest is discharged.
8. A process for separating C8 to C10 aromatic hydrocarbons according to claim 1 or 3, characterized in that: The C8 aromatic substances at the top of the xylene tower and the C8 aromatic substances at the top of the xylene redistillation tower merge and are discharged.
9. A process for separating C8 to C10 aromatic hydrocarbons according to claim 1 or 3, characterized in that: The o-xylene at the top of the o-xylene tower is condensed and cooled to separate gas and liquid. After the liquid o-xylene is pressurized, a portion of it returns to the o-xylene tower, and the rest becomes the o-xylene product.
10. A process for separating C8 to C10 aromatic hydrocarbons according to claim 1 or 3, characterized in that: The heat source is selected from a reboiler, and the reboiler utilizes the waste heat of the reflux material at the bottom of the xylene tower, the bottom of the ortho-xylene tower, and the bottom of the xylene redistillation tower.