C9 Aromatic Hydrocarbon and C8 Aromatic Hydrocarbon Separation Device and Separation Method

Abstract

A C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device, characterized in that it includes a distillation column (1), a reboiling device (2), a reflux drum (3) and a heat exchanger (6). The side-line inlets of the distillation column (1) successively include a first inlet (11) for inputting C8 mixed aromatic hydrocarbons and a second inlet (12) for inputting C9 mixed heavy aromatic hydrocarbons from high to low. The side-line outlets of the distillation column (1) successively include a first outlet (13) for outputting C8-rich liquid aromatic hydrocarbons, a second outlet (14) for outputting C8 gaseous aromatic hydrocarbons, a third outlet (15) for outputting C9 gaseous aromatic hydrocarbons and a fourth outlet (16) for outputting C9 liquid aromatic hydrocarbons. The aforementioned second inlet (12) is located in the middle and lower part of the distillation column (1) and is lower than the fourth outlet (16). The bottom of the distillation column (1) has a bottom liquid extraction outlet (211). The present invention also discloses a separation method. Compared with the prior art, it has the advantages of low energy consumption and less investment.

Description

Technical Field

[0001] The present invention relates to a separation device for aromatic hydrocarbons, and particularly to a separation device for C9 aromatic hydrocarbons and C8 aromatic hydrocarbons. The present invention also relates to a method for separating C9 aromatic hydrocarbons and C8 aromatic hydrocarbons. Background Art

[0002] When separating C8 and C9 aromatic hydrocarbons in the existing C8 and C9 aromatic hydrocarbon separation device processes, the technologies of separately setting up a xylene tower (for C8 aromatic hydrocarbons) and a heavy aromatic hydrocarbon tower (for C9 and heavier aromatic hydrocarbons than C9) are adopted, and respective heating and reboiling facilities, overhead gas treatment and reflux facilities need to be set up separately. The adopted process flow is as follows: The incoming C8 aromatic hydrocarbons containing a small amount of C7 and lighter hydrocarbons than C7 and C9 and heavier hydrocarbons than C9 are first separated by the xylene tower to obtain C8 aromatic hydrocarbons with a purity meeting the requirements. The C9 and heavier aromatic hydrocarbons obtained from the bottom of the xylene tower are sent to the heavy aromatic hydrocarbon tower for separation again to obtain C9 aromatic hydrocarbons with a purity meeting the requirements. Although this design can ensure the separation accuracy and operability of the products and has a certain process flexibility, it is necessary to set up two fractionation towers and their auxiliary overhead condensation, reflux facilities and bottom reboiling facilities at the same time. There is a situation where intermediate materials are repeatedly condensed and heated. On the one hand, it causes secondary waste of energy, and on the other hand, it also increases the number of equipment, having the disadvantages of large investment, high energy consumption, large floor area, complex start-up and shutdown procedures, and high equipment failure risk. During the production operation process, it is easy to have problems of mutual interference between the front and rear two aromatic hydrocarbon fractionation towers and affecting the stable operation. Summary of the Invention

[0003] The first technical problem to be solved by the present invention is to provide a C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device with low energy consumption and less investment in view of the above technical status.

[0004] The second technical problem to be solved by the present invention is to provide a method for separating C9 aromatic hydrocarbons and C8 aromatic hydrocarbons with low energy consumption and less investment.

[0005] The technical solution adopted by the present invention to solve the above first technical problem is as follows: A C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device, characterized in that it includes

[0006] A distillation tower, the side-line inlets include a first inlet for inputting C8 mixed aromatic hydrocarbons and a second inlet for inputting C9 mixed heavy aromatic hydrocarbons in order from high to low; the side-line outlets of the distillation tower include a first outlet for outputting C8-rich liquid-phase aromatic hydrocarbons, a second outlet for outputting C8 gas-phase aromatic hydrocarbons, a third outlet for outputting C9 gas-phase aromatic hydrocarbons, and a fourth outlet for outputting C9 liquid-phase aromatic hydrocarbons in order from high to low. The aforementioned second inlet is located in the middle and lower part of the distillation tower and is lower than the fourth outlet. The bottom of the distillation tower has a bottom liquid-phase extraction outlet;

[0007] A reboiling device, connected to the bottom of the aforementioned distillation column;

[0008] A reflux drum, connected to the top gas outlet of the aforementioned distillation column. A cooler is provided at the inlet end of the reflux drum to cool the gas flow at the top gas outlet. The reflux drum has an outlet for pumping out the top liquid fraction of the column; and

[0009] A heat exchanger, the feed pipeline of the aforementioned second inlet and the discharge pipeline of the third outlet are connected to the heat exchanger to complete heat exchange.

[0010] In order to separately input the C8 mixed aromatic hydrocarbon raw materials according to their respective properties, specifically as follows: The first inlet includes at least two first sub-inlets located at a lower position and a second sub-inlet located at a higher position. The material at the first sub-inlet has a larger molecular weight than the material at the second sub-inlet, or the material at the first sub-inlet has a higher temperature than the material at the second sub-inlet. Here, the molecular weight is given priority, and then the temperature is considered.

[0011] Further, a gas treatment device is connected to the reflux drum to ensure the air pressure inside the reflux drum.

[0012] Preferably, the reboiling device is a reboiler or a reboiling furnace.

[0013] Further, the discharge pipeline of the third outlet is also connected to a condensate tank after passing through the heat exchanger.

[0014] Further, a reflux pipe is provided at the fourth outlet of the distillation column, and the discharge end of the reflux pipe is connected to the bottom of the distillation column and is lower than the fourth outlet.

[0015] Preferably, the number of trays in the distillation column is not less than 85.

[0016] The technical solution adopted by the present invention to solve the above second technical problem is: A separation method for a C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device, characterized by including the following steps:

[0017] The incoming C8 mixed aromatic hydrocarbons enter the distillation column from the first inlet;

[0018] The incoming C9 or heavier mixed heavy aromatic hydrocarbon raw materials enter the distillation column from the second inlet;

[0019] The material coming out of the top of the distillation column forms condensate through the reflux drum. One part of the condensate is returned to the top of the distillation column as reflux liquid, and the other part of the top liquid fraction is sent out as a product from the outlet for pumping out the top liquid fraction of the column;

[0020] One part of the liquid phase at the bottom of the distillation column enters the reboiling device, is heated and then returned to the bottom of the distillation column, and the other part is sent out as a product through the bottom liquid phase extraction outlet;

[0021] The C8 liquid aromatic hydrocarbon product is sent out through the first outlet, the C8 gaseous aromatic hydrocarbon product is sent out through the second outlet, the C9 gaseous aromatic hydrocarbon product is sent out through the third outlet, and the C9 liquid aromatic hydrocarbon product is sent out through the fourth outlet.

[0022] Compared with the prior art, the advantages of the present invention are as follows: The C9 mixed heavy aromatic hydrocarbon raw material first passes through a heat exchanger and then enters the distillation column for treatment. The original two-column systems of the heavy aromatic hydrocarbon column and the xylene column are integrated. At the same time, side lines are arranged according to the material distribution of the rectification column to ensure the product yield and purity. One heavy aromatic hydrocarbon column and one heavy aromatic hydrocarbon heating furnace are cancelled, reducing the construction investment and operation energy consumption of the device. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of the embodiment. Detailed Description of the Invention

[0024] The present invention will be further described in detail below in conjunction with the embodiments of the drawings.

[0025] As Figure 1 shown, the C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device in this embodiment includes a distillation column 1, a reboiling device 2, a reflux tank 3 and a heat exchanger 6.

[0026] The side-line inlets of the distillation column 1 from high to low successively include a first inlet 11 for inputting C8 mixed aromatic hydrocarbons and a second inlet 12 for inputting C9 mixed heavy aromatic hydrocarbons; the first inlet 11 in this embodiment includes a first sub-inlet 111, a second sub-inlet 112 and a third sub-inlet 113. The first sub-inlet 111 is located at a low position, the second sub-inlet 112 is located at a high position, and the third sub-inlet 113 is higher than the second sub-inlet. Materials with high molecular weight or high temperature are located below, and those with small molecular weight or low temperature are located above, with molecular weight being the priority consideration factor.

[0027] The side-line outlets of the distillation column 1 from high to low successively include a first outlet 13 for outputting C8-rich liquid aromatic hydrocarbons, a second outlet 14 for outputting C8 gaseous aromatic hydrocarbons, a third outlet 15 for outputting C9 gaseous aromatic hydrocarbons, and a fourth outlet 16 for outputting C9 liquid aromatic hydrocarbons. The second inlet 12 is located in the middle and lower part of the distillation column 1 and is lower than the fourth outlet 16. The bottom of the distillation column 1 has a bottom liquid extraction outlet 211, which can be sent out through a pump 22; a reflux pipe 19 is provided on the fourth outlet 16 of the distillation column 1, and the discharge end of this reflux pipe 19 is connected to the bottom of the distillation column 1 and is lower than the fourth outlet 16.

[0028] In this embodiment, there are 134 trays in the distillation column 1. The third sub-inlet 113 is located above the 19th tray, and the second sub-inlet 112 is located above the 25th and 30th trays. The first sub-inlet 111 is located at the 61st tray, the second inlet 12 is located at the 106th tray, the first outlet 13 is located above the 30th tray, the second outlet 14 is located above the 33rd tray, the third outlet 15 is located at the 97th tray, and the fourth outlet 16 is located above the 99th tray.

[0029] The reboiling device 2 is connected to the bottom of the distillation column 1 and provides pressure through the pump 21; the reboiling device 2 here is a reboiler or a reboiling furnace.

[0030] The reflux drum 3 is connected to the top gas outlet of the distillation column 1. A cooler 4 is provided at the gas inlet end of the reflux drum 3 to cool the gas flow at the top gas outlet. The reflux drum 3 has an outlet for pumping out the top liquid fraction; a gas treatment device 31 is connected to the reflux drum 3 to ensure the air pressure inside the reflux drum 3. The gas treatment device 31 in this embodiment can use a fuel gas compressor.

[0031] The feed pipeline 121 of the second inlet 12 and the discharge pipeline 151 of the third outlet 15 are connected to the heat exchanger 6 to complete heat exchange.

[0032] The discharge pipeline of the third outlet 15 is also connected to a condensate tank 7 after passing through the heat exchanger 6. The side-line product is sent out through the condensate pump 23.

[0033] The separation method includes the following steps: The incoming C8 mixed aromatics enter the distillation column 1 from the first inlet 11; the incoming C9 or heavier mixed heavy aromatics raw materials enter the distillation column 1 from the second inlet 12; the material coming out from the top of the distillation column 1 forms condensate through the reflux drum 3. One part of the condensate is returned as reflux liquid to the top of the distillation column 1, and the other part of the top liquid fraction is sent out as a product from the outlet for pumping out the top liquid fraction 20; One part of the liquid phase at the bottom of the distillation column 1 enters the reboiling device 2, is heated and then returned to the bottom of the distillation column 1, and the other part is sent out as a product through the bottom liquid phase extraction outlet 211; The C8 liquid aromatic product is sent out from the first outlet 13, the C8 gas aromatic product is sent out from the second outlet 14, the C9 gas aromatic product is sent out from the third outlet 15, and the C9 liquid aromatic product is sent out from the fourth outlet 16.

[0034] The content of toluene in the C8 aromatics obtained by this method is less than 0.98 wt%, and the content of C9 and heavier aromatics is less than 2.51 wt%, meeting the requirements of the subsequent process for further separating high-purity p-xylene products from the C8 aromatics.

[0035] The content of C8 aromatics in the C9 aromatics product obtained by this method is less than 0.21 wt%, and the content of naphthalene and heavier components is less than 0.07 wt%, meeting the requirements of the subsequent process for the further processing of C9 aromatics to produce mixed C8 aromatics and other processes.

[0036] Integrate the original two-column systems of the heavy aromatics column and the xylene column, appropriately increase the height of the distillation column, and at the same time divide and set multiple feed and discharge side lines according to the material distribution of the rectification column to ensure the product yield and purity. Cancel one heavy aromatics column and one heavy aromatics heating furnace, which reduces the construction investment and operating energy consumption of the unit as a whole. According to the application in a p-xylene and disproportionation combined unit with an annual output of 1.6 million tons, the construction cost of the C8 aromatics and C9 aromatics separation unit can be reduced by 15%, and the operating cost can be saved by 3%.

Claims

1. A C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device, characterized in that including a distillation column (1) whose side inlets from high to low successively include a first inlet (11) for input of C8 mixed aromatics and a second inlet (12) for input of C9 mixed heavy aromatics; the side outlets of the distillation column (1) from high to low successively include a first outlet (13) for output of C8-rich liquid aromatics, a second outlet (14) for output of C8 gas-phase aromatics, a third outlet (15) for output of C9 gas-phase aromatics, and a fourth outlet (16) for output of C9 liquid aromatics. The aforesaid second inlet (12) is located in the middle and lower part of the distillation column (1) and is lower than the fourth outlet (16). The bottom of the distillation column (1) has a bottom liquid draw-off port (211); a reboiling device (2) connected to the bottom of the aforesaid distillation column (1); a reflux drum (3) connected to the top gas outlet of the aforesaid distillation column (1). A cooler (4) is provided at the gas inlet end of the reflux drum (3) to cool the gas flow at the top gas outlet. The reflux drum (3) has an external delivery top liquid fraction draw-off port (20); and a heat exchanger (6). The feed pipeline (121) of the aforesaid second inlet (12) and the discharge pipeline (151) of the third outlet (15) are connected to the heat exchanger (6) to complete heat exchange.

2. The C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, characterized in that The first inlet (11) at least includes two first sub-inlets (111) at a lower position and a second sub-inlet (112) at a higher position. The material of the aforesaid first sub-inlet (111) has a larger molecular weight than that of the material of the second sub-inlet (112), or the material of the aforesaid first sub-inlet (111) has a higher temperature than that of the material of the second sub-inlet (112).

3. The C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, characterized in that A gas treatment device (31) is connected to the reflux drum (3) to ensure the air pressure in the reflux drum (3).

4. The C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, wherein The aforesaid reboiling device (2) is a reboiler or a reboiling furnace.

5. The C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, characterized in that The discharge pipeline of the third outlet (15) is further connected to a condensate tank (7) after passing through the heat exchanger (6).

6. The C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, wherein A reflux pipe (19) is provided at the fourth outlet (16) of the distillation column (1). The discharge end of the reflux pipe (19) is connected to the bottom of the distillation column (1) and is lower than the fourth outlet (16).

7. The C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, wherein The number of trays in the distillation column (1) is not less than 85.

8. A separation method using the C9 aromatic hydrocarbon and C8 aromatic hydrocarbon separation device according to claim 1, characterized in that including the following steps: The incoming C8 mixed aromatics enter the distillation column (1) from the first inlet (11); The incoming C9 or heavier mixed heavy aromatic raw materials enter the distillation column (1) from the second inlet (12); The material coming out of the top of the distillation column (1) forms condensate in the reflux drum (3). One part of the condensate is returned to the top of the distillation column (1) as reflux liquid, and the other part of the top liquid fraction is sent out as a product from the top liquid fraction draw-off port (20); One part of the liquid phase at the bottom of the distillation column (1) enters the reboiling device (2) to be heated and then returns to the bottom of the distillation column (1), and the other part is sent out as a product through the bottom liquid draw-off port (211); The C8 liquid aromatic product is sent out from the first outlet (13), the C8 gas-phase aromatic product is sent out from the second outlet (14), the C9 gas-phase aromatic product is sent out from the third outlet (15), and the C9 liquid aromatic product is sent out from the fourth outlet (16).

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