Energy-saving styrene rectification device

Abstract

The utility model discloses an energy-saving styrene rectification device. Upper end outlets of a first crude styrene tower and a second crude styrene tower are respectively connected with inlets of two heat pumps; a hot flow outlet of the first hot water heat exchanger and a hot flow inlet of the first hot water heat exchanger are respectively connected with a hot flow outlet of a pre-separation tower reboiler and an inlet of a first crude styrene return tank, and a hot flow outlet of a first crude styrene tower reboiler is connected with a hot flow inlet of the pre-separation tower reboiler; outlets of the first crude styrene tower heat pump and the second crude styrene tower heat pump are respectively connected with a hot flow inlet of the first crude styrene tower reboiler and a hot flow inlet of the second crude styrene tower reboiler; and a hot flow outlet of the fine styrene tower reboiler is connected with a hot flow inlet of the second hot water heat exchanger. Tower top ethylbenzene gas phase which is heated and pressurized by a heat pump is respectively used as heat sources of the first crude styrene tower, the pre-separation tower, the second crude styrene tower and the refined styrene tower, so that the use amount of steam of the whole device is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of preparing styrene by dehydrogenating ethylbenzene, in particular to an energy-saving styrene distillation device. Background Art

[0002] Styrene is an important chemical raw material for the production of polystyrene and styrene-based thermoplastic elastomers. At present, the most common production method is to produce styrene by dehydrogenation of ethylbenzene. The ethylbenzene dehydrogenation production method involves the separation of ethylbenzene and styrene during distillation. The boiling points of styrene and ethylbenzene are close, and the separation requires a large amount of steam. At present, the industry mostly uses four-tower distillation devices using high-low pressure tower coupling technology, namely the pre-separation tower, the first crude styrene tower, the second crude styrene tower and the refined styrene tower. The pre-separation tower has two steam reboilers, one open and one standby, and the pre-separation tower consumes a large amount of steam as a heat source. The first crude styrene tower has two steam reboilers, one open and one standby, and the first crude styrene tower consumes a large amount of steam as a heat source. The second crude styrene tower has two reboilers, one reboiler uses the gas phase of the first crude styrene tower as a heat source, and the other is a supplementary reboiler that consumes steam as a supplement when the heat is insufficient. The refined styrene tower has two steam reboilers, which consume a large amount of steam as a heat source.

[0003] The crude styrene product first enters the pre-separation tower to remove light components such as benzene and toluene, and then is divided into two streams according to a certain ratio and enters the first crude styrene tower and the second crude styrene tower respectively to separate ethylbenzene, and finally enters the refined styrene tower to remove heavy components to obtain the styrene product.

[0004] The distillation device couples the first crude styrene tower and the second crude styrene tower, and uses the top gas phase of the first crude styrene tower as the heat source for the bottom reboiler of the second crude styrene tower, so as to reduce the steam usage. However, even with the above method, the steam consumption of the entire device is still quite huge. Utility Model Content

[0005] 1. Technical issues to be resolved

[0006] The technical problem to be solved by the utility model is to provide an energy-saving styrene distillation device, which can greatly reduce the usage of steam in the whole device.

[0007] (II) Technical solution

[0008] The solution adopted by the utility model to solve the above technical problems is an energy-saving styrene distillation device, comprising a pre-separation tower, a first crude styrene tower, a second crude styrene tower and a refined styrene tower, a lower end outlet of the pre-separation tower is connected to a pipeline and is divided into two branches, one branch is connected to the feed inlet of the first crude styrene tower, and the other branch is connected to the feed inlet of the second crude styrene tower; a lower end outlet of the first crude styrene tower and a lower end outlet of the second crude styrene tower are both connected to the feed inlet of the refined styrene tower, and the lower end of the pre-separation tower is connected to a pre-separation Tower reboiler; the lower end of the first crude styrene tower is connected to the first crude styrene tower reboiler, the upper end outlet of the first crude styrene tower is connected to the first crude styrene tower heat pump, and the upper end inlet of the first crude styrene tower is connected to the first crude styrene tower reflux tank; the lower end of the second crude styrene tower is connected to the second crude styrene tower reboiler, the upper end outlet of the second crude styrene tower is connected to the second crude styrene tower heat pump, and the upper end inlet of the second crude styrene tower is connected to the second crude styrene tower reflux tank; the lower end of the refined styrene tower is connected to the refined styrene tower reboiler;

[0009] A first hot water heat exchanger is provided between the reflux tank of the first crude styrene tower and the reboiler of the pre-separation tower; a second hot water heat exchanger is provided between the reflux tank of the second crude styrene tower and the reboiler of the refined styrene tower;

[0010] The outlet of the first crude styrene tower heat pump is connected to the hot flow stream inlet of the first crude styrene tower reboiler, the hot flow stream outlet of the first crude styrene tower reboiler is connected to the hot flow stream inlet of the pre-separation tower reboiler, the hot flow stream outlet of the pre-separation tower reboiler is connected to the hot flow stream inlet of the first hot water heat exchanger, and the hot flow stream outlet of the first hot water heat exchanger is connected to the inlet of the first crude styrene tower reflux tank;

[0011] The hot flow outlet of the second crude styrene tower heat pump is connected to the hot flow inlet of the second crude styrene tower reboiler, and the hot flow outlet of the second crude styrene tower reboiler is connected to the hot flow inlet of the refined styrene tower reboiler; the outlet of the refined styrene tower reboiler is connected to the hot flow inlet of the second hot water heat exchanger, and the hot flow outlet of the second hot water heat exchanger is connected to the inlet of the second crude styrene tower reflux tank.

[0012] By adopting the above scheme, by setting up a first crude styrene tower heat pump and a second crude styrene tower heat pump, the top ethylbenzene gas phase of the first crude styrene tower and the second crude styrene tower that is heated and pressurized by the first crude styrene tower heat pump and the second crude styrene tower heat pump is used as the heat source for the first crude styrene tower, the pre-separation tower and the second crude styrene tower, and the refined styrene tower, respectively, the steam usage of the entire device can be greatly reduced.

[0013] Preferably, it also includes a pre-separation tower supplementary reboiler, a pre-separation tower condenser and a pre-separation tower reflux pump, the lower end of the pre-separation tower is connected to the pre-separation tower supplementary reboiler, the hot flow stream inlet and the hot flow stream outlet of the pre-separation tower condenser are respectively connected to the upper end outlet of the pre-separation tower and the inlet of the pre-separation tower reflux tank, the outlet of the pre-separation tower reflux tank is connected to the inlet of the pre-separation tower reflux pump, and the outlet of the pre-separation tower reflux pump is connected to the upper end inlet of the pre-separation tower.

[0014] As a further preference, it also includes a first crude styrene tower supplementary reboiler and a first crude styrene tower reflux pump, the lower end of the first crude styrene tower is connected to the first crude styrene tower supplementary reboiler, and the inlet and outlet of the first crude styrene tower reflux pump are respectively connected to the outlet of the first crude styrene tower reflux tank and the upper end inlet of the first crude styrene tower.

[0015] As a further preference, it also includes a second crude styrene tower supplementary reboiler and a second crude styrene tower reflux pump, the lower end of the second crude styrene tower is connected to the second crude styrene tower supplementary reboiler, and the inlet and outlet of the second crude styrene tower reflux pump are respectively connected to the outlet of the second crude styrene tower reflux tank and the upper end inlet of the second crude styrene tower.

[0016] As a further preference, it also includes a supplementary reboiler for the fine styrene tower, a condenser for the fine styrene tower and a reflux pump for the fine styrene tower. The lower end of the fine styrene tower is connected to the supplementary reboiler for the fine styrene tower, the hot flow stream inlet and the hot flow stream outlet of the condenser of the fine styrene tower are respectively connected to the upper end outlet of the fine styrene tower and the inlet of the reflux tank of the fine styrene tower, the outlet of the reflux tank of the fine styrene tower is connected to the inlet of the reflux pump of the fine styrene tower, and the outlet of the reflux pump of the fine styrene tower is connected to the upper end inlet of the fine styrene tower.

[0017] As a further preference, a crude styrene tower feed pump is also included, the inlet of the crude styrene tower feed pump is connected to a lower end outlet of the pre-separation tower, and the outlet of the crude styrene tower feed pump is connected to the feed ports of the first crude styrene tower and the second crude styrene tower.

[0018] As a further preference, a first refined styrene tower feed pump is further included, wherein the inlet and outlet of the first refined styrene tower feed pump are respectively connected to a lower end outlet of the first crude styrene tower and the feed port of the refined styrene tower.

[0019] As a further preference, a second refined styrene tower feed pump is also included, and the inlet and outlet of the refined styrene tower feed pump are respectively connected to a lower end outlet of the second crude styrene tower and the feed port of the refined styrene tower.

[0020] As a further preference, a recombinant oil separation pump is further included, and an inlet of the recombinant oil separation pump is connected to a lower outlet of the fine styrene tower.

[0021] (III) Beneficial effects

[0022] Compared with the prior art, the utility model designs an energy-saving styrene distillation device.

[0023] (1) By providing a first crude styrene tower heat pump and a second crude styrene tower heat pump, the ethylbenzene gas phase at the top of the first crude styrene tower and the second crude styrene tower is heated and pressurized, and the heated and pressurized ethylbenzene gas phase is used as the heat source of the first crude styrene tower, the pre-separation tower, the second crude styrene tower, and the refined styrene tower, respectively, which can greatly reduce the use of steam in the entire device;

[0024] (2) The basic structure of the four-tower styrene distillation unit was retained, and the number of distillation towers was not increased or decreased. Only two heat pumps and hot water heat exchangers were added, and some distillation towers, heat exchangers and pipelines were modified. For the styrene distillation unit that has adopted the high- and low-pressure tower coupling technology, the feasibility of technical transformation is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the connection structure of the energy-saving styrene distillation device of the utility model;

[0026] Figure 2 It is a schematic diagram of the prior art described in the background technology of the present utility model.

[0027] Explanation of the reference numerals: 1. heat pump for the first crude styrene tower; 2. heat pump for the second crude styrene tower; 3. first hot water heat exchanger; 4. pre-separation tower; 5. supplementary reboiler for the pre-separation tower; 6. reboiler for the pre-separation tower; 7. condenser for the pre-separation tower; 8. reflux tank for the pre-separation tower; 9. reflux pump for the pre-separation tower; 10. first crude styrene tower; 11. supplementary reboiler for the first crude styrene tower; 12. reboiler for the first crude styrene tower; 13. reflux tank for the first crude styrene tower; 14. reflux pump for the first crude styrene tower; 15. second crude styrene tower; 16. Second crude styrene tower supplementary reboiler; 17. Second crude styrene tower reboiler; 18. Second crude styrene tower reflux tank; 19. Second crude styrene tower reflux pump; 20. refined styrene tower; 21. Reboiler of refined styrene tower; 22. Supplementary reboiler of refined styrene tower; 23. Condenser of refined styrene tower; 24. Reflux tank of refined styrene tower; 25. Reflux pump of refined styrene tower; 26. Feed pump of crude styrene tower; 27. Feed pump of first refined styrene tower; 28. Feed pump of second refined styrene tower; 29. ​​Heavy oil pump; 30. Second hot water heat exchanger. DETAILED DESCRIPTION

[0028] The following is a further detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0029] In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] This embodiment:

[0031] like Figure 1 As shown, an energy-saving styrene distillation device of the present embodiment comprises a pre-separation tower 4, a first crude styrene tower 10, a second crude styrene tower 15 and a refined styrene tower 20, a lower end outlet of the pre-separation tower 4 is connected to a pipeline and is divided into two branches, one branch is connected to the feed inlet of the first crude styrene tower 10, and the other branch is connected to the feed inlet of the second crude styrene tower 15; a lower end outlet of the first crude styrene tower 10 and a lower end outlet of the second crude styrene tower 15 are both connected to the feed inlet of the refined styrene tower 20, and the lower end of the pre-separation tower 4 is connected to a pre-separation tower reboiler 6; the first The lower end of the crude styrene tower 10 is connected to a first crude styrene tower reboiler 12, the upper end outlet of the first crude styrene tower 10 is connected to a first crude styrene tower heat pump 1, and the upper end inlet of the first crude styrene tower 10 is connected to a first crude styrene tower reflux tank 13; the lower end of the second crude styrene tower 15 is connected to a second crude styrene tower reboiler 17, the upper end outlet of the second crude styrene tower 15 is connected to a second crude styrene tower heat pump 2, and the upper end inlet of the second crude styrene tower 15 is connected to a second crude styrene tower reflux tank 18; the lower end of the refined styrene tower 20 is connected to a refined styrene tower reboiler 21;

[0032] A first hot water heat exchanger 3 is provided between the first crude styrene tower reflux tank 13 and the pre-separation tower reboiler 6; a second hot water heat exchanger 30 is provided between the second crude styrene tower reflux tank 18 and the refined styrene tower reboiler 21;

[0033] The outlet of the first crude styrene tower heat pump 1 is connected to the hot stream inlet of the first crude styrene tower reboiler 12, the hot stream outlet of the first crude styrene tower reboiler 12 is connected to the hot stream inlet of the pre-separation tower reboiler 6, the hot stream outlet of the pre-separation tower reboiler 6 is connected to the hot stream inlet of the first hot water heat exchanger 3, and the hot stream outlet of the first hot water heat exchanger 3 is connected to the inlet of the first crude styrene tower reflux tank 13;

[0034] The hot flow outlet of the second crude styrene tower heat pump 2 is connected to the hot flow inlet of the second crude styrene tower reboiler 17, and the hot flow outlet of the second crude styrene tower reboiler 17 is connected to the hot flow inlet of the refined styrene tower reboiler 21; the hot flow outlet of the refined styrene tower reboiler 21 is connected to the hot flow inlet of the second hot water heat exchanger 30, and the hot flow outlet of the second hot water heat exchanger 30 is connected to the inlet of the second crude styrene tower reflux tank 18.

[0035] Specifically, in the present embodiment, by setting up the first crude styrene tower heat pump 1 and the second crude styrene tower heat pump 2, the top ethylbenzene gas phase of the first crude styrene tower 10 and the second crude styrene tower 15 which is heated and pressurized by the first crude styrene tower heat pump 1 and the second crude styrene tower heat pump 2 is used as the heat source for the first crude styrene tower 10, the pre-separation tower 4 and the second crude styrene tower 15, and the refined styrene tower 20 respectively, thereby greatly reducing the use of steam in the entire device.

[0036] Furthermore, as a preferred embodiment, it also includes a pre-separation tower supplementary reboiler 5, a pre-separation tower condenser 7 and a pre-separation tower reflux pump 9, the lower end of the pre-separation tower 4 is connected to the pre-separation tower supplementary reboiler 5, the hot flow stream inlet and the hot flow stream outlet of the pre-separation tower condenser 7 are respectively connected to the upper end outlet of the pre-separation tower 4 and the inlet of the pre-separation tower reflux tank 8, the outlet of the pre-separation tower reflux tank 8 is connected to the inlet of the pre-separation tower reflux pump 9, and the outlet of the pre-separation tower reflux pump 9 is connected to the upper end inlet of the pre-separation tower 4.

[0037] Furthermore, as a preferred embodiment, it also includes a first crude styrene tower supplementary reboiler 11 and a first crude styrene tower reflux pump 14, the lower end of the first crude styrene tower 10 is connected to the first crude styrene tower supplementary reboiler 11, and the inlet and outlet of the first crude styrene tower reflux pump 14 are respectively connected to the outlet of the first crude styrene tower reflux tank 13 and the upper end inlet of the first crude styrene tower 10.

[0038] Furthermore, as a preferred embodiment, it also includes a second crude styrene tower supplementary reboiler 16 and a second crude styrene tower reflux pump 19, the lower end of the second crude styrene tower 15 is connected to the second crude styrene tower supplementary reboiler 16, and the inlet and outlet of the second crude styrene tower reflux pump 19 are respectively connected to the outlet of the second crude styrene tower reflux tank 18 and the upper end inlet of the second crude styrene tower 15.

[0039] Further, as a preferred embodiment, it also includes a refined styrene tower supplementary reboiler 22, a refined styrene tower condenser 23 and a refined styrene tower reflux pump 25, the lower end of the refined styrene tower 20 is connected to the refined styrene tower supplementary reboiler 22, the hot flow stream inlet and the hot flow stream outlet of the refined styrene tower condenser 23 are respectively connected to the upper end outlet of the refined styrene tower 20 and the inlet of the refined styrene tower reflux tank 24, the outlet of the refined styrene tower reflux tank 24 is connected to the inlet of the refined styrene tower reflux pump 25, and the outlet of the refined styrene tower reflux pump 25 is connected to the upper end inlet of the refined styrene tower 20.

[0040] Specifically, in this embodiment, the crude styrene product first enters the pre-separation tower 4 to remove the light components, and the light components benzene and toluene leave from the top of the pre-separation tower 4. The crude styrene product after light removal leaves from the bottom of the pre-separation tower 4. The crude styrene product after light removal is divided into two streams according to a certain ratio and enters the first crude styrene tower 10 and the second crude styrene tower 15 respectively. Ethylbenzene leaves from the top of the first crude styrene tower 10 and the second crude styrene tower 15, and styrene and heavy components leave from the bottom of the first crude styrene tower 10 and the second crude styrene tower 15. Part of the ethylbenzene condensate after heat exchange with the hot water in the first hot water heat exchanger 3 is returned to the first crude styrene tower 10 as reflux, and part of it is returned to the reaction unit as circulating ethylbenzene. Similarly, part of the ethylbenzene condensate after heat exchange with the hot water in the second hot water heat exchanger 30 is returned to the second crude styrene tower 15 as reflux, and part of it is returned to the reaction unit as circulating ethylbenzene. The crude styrene product leaving the first crude styrene tower 10 and the second crude styrene tower 15 enters the refined styrene tower 20 for distillation and separation. Product styrene is obtained at the top of the refined styrene tower 20, and the heavy oil leaves from the bottom of the refined styrene tower 20.

[0041] Specifically, in this embodiment, the pre-separation tower reboiler 6 of the pre-separation tower 4 uses the ethylbenzene gas phase condensate from the first crude styrene tower 10 as a heat source, and the pre-separation tower supplementary reboiler 5 uses steam as a heat source to supplement the insufficient heat of the pre-separation tower 4; a first crude styrene tower heat pump 1 is arranged at the top of the first crude styrene tower 10, and a second crude styrene tower heat pump 2 is arranged at the top of the second crude styrene tower 15, and the ethylbenzene at the top of the first crude styrene tower 10 and the second crude styrene tower 15 is compressed and heated by the first crude styrene tower heat pump 1 and the second crude styrene tower heat pump 2, respectively, and then returned to the first crude styrene tower 10 and the second crude styrene tower 15, respectively. The bottoms of the crude styrene tower 10 and the second crude styrene tower 15 serve as heat sources for the first crude styrene tower reboiler 12 and the second crude styrene tower reboiler 17; the first crude styrene tower supplementary reboiler 11 uses steam as a heat source to supplement the insufficient heat of the first crude styrene tower 10; the second crude styrene tower supplementary reboiler 16 uses steam as a heat source to supplement the insufficient heat of the second crude styrene tower 15; the refined styrene tower reboiler 21 uses the ethylbenzene gas condensate from the second crude styrene tower 15 as a heat source, and the refined styrene tower supplementary reboiler 22 uses steam as a heat source to supplement the insufficient heat of the refined styrene tower 20.

[0042] Specifically, in this embodiment, the ethylbenzene gas condensate after heat exchange in the first crude styrene tower reboiler 12 is sent to the pre-separation tower reboiler 6 as a heat source to provide heat, and the ethylbenzene gas condensate after heat exchange is continuously sent to the first hot water heat exchanger 3 for heat exchange with hot water to provide heat for the hot water. The hot water can be used as a heat source waste heat for refrigeration of the lithium bromide unit to provide cooling capacity for the ethylbenzene dehydrogenation reaction unit. The ethylbenzene gas condensate after heat exchange in the second crude styrene tower reboiler 17 is sent to the refined styrene tower reboiler 21 as a heat source to provide heat, and the ethylbenzene gas condensate after heat exchange is continuously sent to the second hot water heat exchanger 30 for heat exchange with hot water. The hot water is used as a heat source waste heat for refrigeration of the lithium bromide unit to provide cooling capacity for the styrene reaction unit.

[0043] Specifically, in the present embodiment, the crude styrene product (composed of 1.06%wt of benzene, 1.52%wt of xylene, 40.99%wt of ethylbenzene, 0.01%wt of p-xylene, 56.17%wt of styrene, 0.02%wt of n-propylbenzene, and 0.23%wt of heavy oil) from the ethylbenzene dehydrogenation reaction unit first enters the pre-separation tower 4, which is operated under negative pressure, with a tower top pressure of 22KPa, a tower top temperature of 52.4°C, a tower bottom pressure of 28KPa, and a tower bottom temperature of 98.9°C. A pre-separation tower reboiler 6 and a pre-separation tower supplementary reboiler 5 are provided, for a total of two reboilers. The gas phase condensate at the top of the first crude styrene tower 10 is introduced into the pre-separation tower reboiler 6 as a heat source, and steam is introduced into the pre-separation tower supplementary reboiler 5 to supplement the insufficient heat of the tower bottom. The light components (composed of 50.80% wt of benzene, 49.18% wt of toluene, and 0.02% wt of ethylbenzene) are extracted from the top of the pre-separation tower 4, and the crude product after light removal from the pre-separation tower 4 (composed of 0.50% wt of toluene, 41.87% wt of ethylbenzene, 0.01% wt of p-xylene, 57.37% wt of styrene, 0.02% wt of n-propylbenzene, and 0.23% wt of heavy oil) is separated. The bottom liquid of the pre-separation tower 4 is divided into two streams in a ratio of 1:1 and respectively sent to the first crude styrene tower 10 and the second crude styrene tower 15.

[0044] Specifically, in this embodiment, the first crude styrene tower 10 is operated at negative pressure, with a tower top pressure of 30KPa, a tower top temperature of 96.4°C, a tower bottom pressure of 36KPa, and a tower bottom temperature of 110.8°C. The tower top gas phase (composed of 1.17%wt of toluene, 98.29%wt of ethylbenzene, 0.03%wt of p-xylene, and 0.51%wt of styrene) of the first crude styrene tower 10 is directly introduced into the first crude styrene tower heat pump 1 for compression, and the temperature and pressure are increased to 120KPa and 142.6°C. The tower top gas phase after temperature increase and pressure increase is introduced into the first crude styrene tower reboiler 12 as a heat source, and condenses into a liquid phase after releasing latent heat, and at the same time, steam is introduced into the first crude styrene tower supplementary reboiler 11 to supplement the insufficient heat of the tower bottom. The gaseous condensate at the top of the tower is then sent to the pre-separation tower reboiler 6 as a heat source for further heat exchange. The gaseous condensate at the top of the tower after heat exchange continues to exchange heat with the first hot water heat exchanger 3, and the hot water at 80°C is heated to 90°C. The heated hot water is sent to the lithium bromide unit for waste heat refrigeration, and the resulting cold can be used for the ethylbenzene dehydrogenation reaction unit. The gaseous condensate at the top of the tower after heat exchange with the hot water is cooled to 96.5°C by itself, part of which is refluxed to the first crude styrene tower 10, and part of which is returned to the ethylbenzene dehydrogenation reaction unit as circulating ethylbenzene. The bottom liquid of the first crude styrene tower 10 (composed of 0.05%wt of ethylbenzene, 99.51%wt of styrene, 0.03%wt of n-propylbenzene, and 0.40%wt of heavy oil) is sent to the refined styrene tower 20 after merging with the bottom liquid of the second crude styrene tower 15.

[0045] Specifically, in this embodiment, the second crude styrene tower 15 is operated at negative pressure, with a tower top pressure of 30KPa, a tower top temperature of 96.4°C, a tower bottom pressure of 36KPa, and a tower bottom temperature of 110.8°C. The tower top gas phase (composed of 1.17%wt of toluene, 98.31%wt of ethylbenzene, 0.03%wt of p-xylene, and 0.49%wt of styrene) of the second crude styrene tower 15 is directly introduced into the second crude styrene tower heat pump 2 for compression, and the temperature and pressure are increased to 120KPa, 142.6°C. The tower top gas phase after temperature increase and pressure increase is introduced into the second crude styrene tower reboiler 17 as a heat source, and condensed into a liquid phase after releasing latent heat, and at the same time, steam is introduced into the second crude styrene tower supplementary reboiler 16 to supplement the insufficient heat of the second crude styrene tower 15. The gaseous condensate at the top of the tower is then sent to the reboiler 21 of the refined styrene tower as a heat source for further heat exchange. The gaseous condensate at the top of the tower after heat exchange continues to exchange heat with the hot water in the second hot water heat exchanger 30, and the hot water at 80°C is heated to 90°C. The heated hot water is sent to the lithium bromide unit for waste heat refrigeration, and the resulting cold capacity can be used for the ethylbenzene dehydrogenation reaction unit. The gaseous condensate at the top of the tower after heat exchange with the hot water is cooled to 96.5°C by itself, part of which is refluxed into the second crude styrene tower 15, and part of which is returned to the ethylbenzene dehydrogenation reaction unit as circulating ethylbenzene. The bottom liquid of the second crude styrene tower 15 (composed of 0.03%wt of ethylbenzene, 99.53%wt of styrene, 0.03%wt of n-propylbenzene, and 0.40%wt of heavy oil) and the bottom liquid of the first crude styrene tower 10 are sent to the refined styrene tower 20.

[0046] Specifically, in this embodiment, the refined styrene tower 20 is operated at negative pressure, the tower top pressure is 6.5KPa, the tower top temperature is 65.9°C, the tower bottom pressure is 9.5KPa, the tower bottom temperature is 130.8°C, and the refined styrene tower 20 is provided with a refined styrene tower reboiler 21 and a refined styrene tower supplementary reboiler 22, a total of two reboilers. The refined styrene tower reboiler 21 is introduced into the tower top gas phase condensate of the second crude styrene tower 15 as a heat source, and steam is introduced into the refined styrene tower supplementary reboiler 22 to supplement the insufficient heat of the refined styrene tower 20. The tower top of the refined styrene tower 20 produces a styrene product (composed of styrene 99.94%wt, ethylbenzene 0.04%wt, and n-propylbenzene 0.02%wt), and the main component of the tower bottom liquid is heavy oil.

[0047] Furthermore, as a preferred embodiment, it also includes a crude styrene tower feed pump 26, the inlet of the crude styrene tower feed pump 26 is connected to a lower end outlet of the pre-separation tower 4, and the outlet of the crude styrene tower feed pump 26 is connected to the feed ports of the first crude styrene tower 10 and the second crude styrene tower 15.

[0048] Furthermore, as a preferred embodiment, it also includes a first fine styrene tower feed pump 27, the inlet and outlet of the first fine styrene tower feed pump 27 are respectively connected to a lower end outlet of the first crude styrene tower 10 and the feed port of the fine styrene tower 20.

[0049] Furthermore, as a preferred embodiment, a second refined styrene tower feed pump 28 is also included, and the inlet and outlet of the feed pump of the refined styrene tower 20 are respectively connected to a lower end outlet of the second crude styrene tower 15 and the feed port of the refined styrene tower 20.

[0050] Furthermore, as a preferred embodiment, it further comprises a heavy oil separation pump 29 , the inlet of the heavy oil separation pump 29 is connected to a lower end outlet of the fine styrene tower 20 .

[0051] The above are only preferred embodiments of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An energy-saving styrene distillation device, comprising a pre-separation tower (4), a first crude styrene tower (10), a second crude styrene tower (15) and a refined styrene tower (20), wherein a lower end outlet of the pre-separation tower (4) is connected to a pipeline and is divided into two branches, one branch is connected to a feed inlet of the first crude styrene tower (10), and the other branch is connected to a feed inlet of the second crude styrene tower (15); a lower end outlet of the first crude styrene tower (10) and a lower end outlet of the second crude styrene tower (15) are both connected to the feed inlet of the refined styrene tower (20), characterized in that: The lower end of the pre-separation tower (4) is connected to a pre-separation tower reboiler (6); the lower end of the first crude styrene tower (10) is connected to a first crude styrene tower reboiler (12), the upper end outlet of the first crude styrene tower (10) is connected to a first crude styrene tower heat pump (1), and the upper end inlet of the first crude styrene tower (10) is connected to a first crude styrene tower reflux tank (13); the lower end of the second crude styrene tower (15) is connected to a second crude styrene tower reboiler (17), the upper end outlet of the second crude styrene tower (15) is connected to a second crude styrene tower heat pump (2), and the upper end inlet of the second crude styrene tower (15) is connected to a second crude styrene tower reflux tank (18); the lower end of the refined styrene tower (20) is connected to a refined styrene tower reboiler (21); A first hot water heat exchanger (3) is arranged between the first crude styrene tower reflux tank (13) and the pre-separation tower reboiler (6); a second hot water heat exchanger (30) is arranged between the second crude styrene tower reflux tank (18) and the refined styrene tower reboiler (21); The outlet of the first crude styrene tower heat pump (1) is connected to the hot flow stream inlet of the first crude styrene tower reboiler (12), the hot flow stream outlet of the first crude styrene tower reboiler (12) is connected to the hot flow stream inlet of the pre-separation tower reboiler (6), the hot flow stream outlet of the pre-separation tower reboiler (6) is connected to the hot flow stream inlet of the first hot water heat exchanger (3), and the hot flow stream outlet of the first hot water heat exchanger (3) is connected to the inlet of the first crude styrene tower reflux tank (13); The hot flow outlet of the second crude styrene tower heat pump (2) is connected to the hot flow inlet of the second crude styrene tower reboiler (17), and the hot flow outlet of the second crude styrene tower reboiler (17) is connected to the hot flow inlet of the refined styrene tower reboiler (21); the outlet of the refined styrene tower reboiler (21) is connected to the hot flow inlet of the second hot water heat exchanger (30), and the hot flow outlet of the second hot water heat exchanger (30) is connected to the inlet of the second crude styrene tower reflux tank (18).

2. The energy-saving styrene distillation device according to claim 1, characterized in that: It also includes a pre-separation tower supplementary reboiler (5), a pre-separation tower condenser (7) and a pre-separation tower reflux pump (9). The pre-separation tower supplementary reboiler (5) is connected to the lower end of the pre-separation tower (4). The hot flow stream inlet and the hot flow stream outlet of the pre-separation tower condenser (7) are respectively connected to the upper end outlet of the pre-separation tower (4) and the inlet of the pre-separation tower reflux tank (8). The outlet of the pre-separation tower reflux tank (8) is connected to the inlet of the pre-separation tower reflux pump (9), and the outlet of the pre-separation tower reflux pump (9) is connected to the upper end inlet of the pre-separation tower (4).

3. The energy-saving styrene distillation device according to claim 2, characterized in that: It also includes a first crude styrene tower supplementary reboiler (11) and a first crude styrene tower reflux pump (14); the lower end of the first crude styrene tower (10) is connected to the first crude styrene tower supplementary reboiler (11); the inlet and outlet of the first crude styrene tower reflux pump (14) are respectively connected to the outlet of the first crude styrene tower reflux tank (13) and the upper inlet of the first crude styrene tower (10).

4. The energy-saving styrene distillation device according to claim 3, characterized in that: It also includes a second crude styrene tower supplementary reboiler (16) and a second crude styrene tower reflux pump (19). The lower end of the second crude styrene tower (15) is connected to the second crude styrene tower supplementary reboiler (16), and the inlet and outlet of the second crude styrene tower reflux pump (19) are respectively connected to the outlet of the second crude styrene tower reflux tank (18) and the upper end inlet of the second crude styrene tower (15).

5. The energy-saving styrene distillation device according to claim 4, characterized in that: It also includes a refined styrene tower supplementary reboiler (22), a refined styrene tower condenser (23) and a refined styrene tower reflux pump (25). The lower end of the refined styrene tower (20) is connected to the refined styrene tower supplementary reboiler (22). The hot flow stream inlet and hot flow stream outlet of the refined styrene tower condenser (23) are respectively connected to the upper end outlet of the refined styrene tower (20) and the inlet of the refined styrene tower reflux tank (24). The outlet of the refined styrene tower reflux tank (24) is connected to the inlet of the refined styrene tower reflux pump (25), and the outlet of the refined styrene tower reflux pump (25) is connected to the upper end inlet of the refined styrene tower (20).

6. The energy-saving styrene distillation device according to claim 4, characterized in that: It also includes a crude styrene tower feed pump (26), the inlet of the crude styrene tower feed pump (26) is connected to a lower end outlet of the pre-separation tower (4), and the outlet of the crude styrene tower feed pump (26) is connected to the feed ports of the first crude styrene tower (10) and the second crude styrene tower (15).

7. The energy-saving styrene distillation device according to claim 5, characterized in that: It also includes a first refined styrene tower feed pump (27), the inlet and outlet of which are respectively connected to a lower end outlet of the first crude styrene tower (10) and a feed port of the refined styrene tower (20).

8. The energy-saving styrene distillation device according to claim 5, characterized in that: It also includes a second refined styrene tower feed pump (28), the inlet and outlet of the refined styrene tower (20) feed pump are respectively connected to a lower end outlet of the second crude styrene tower (15) and the feed port of the refined styrene tower (20).

9. The energy-saving styrene distillation device according to claim 5, characterized in that: It also comprises a recombinant oil pump (29), the inlet of which is connected to a lower outlet of the refined styrene tower (20).

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