Energy-saving oximation production refining system applied to caprolactam device

Abstract

The invention relates to an energy-saving technology of a rectifying tower in chemical production, in particular to an oximation production refining energy-saving system applied to a caprolactam device, which overcomes the problem of consumption of a large amount of steam, electricity and circulating water in the oximation production process, reduces the steam consumption of a reboiler, the electricity consumption of a feeding pump and the consumption of circulating water of a condenser, and improves the production efficiency. The device comprises a second rectifying tower, a toluene oxime removal tower and a toluene ketone removal tower which are communicated in sequence, and a first tower top three-way regulating valve is arranged on a tower top gas phase pipeline of the second rectifying tower; one path of the first tower top three-way regulating valve is sequentially communicated with a second rectifying tower top condenser, a second rectifying tower return tank and a toluene oxime removal tower feeding pump, an outlet of the toluene oxime removal tower feeding pump is divided into two paths, one path is communicated with the tower top of the second rectifying tower, and the other path is communicated with a toluene oxime removal tower; and the other path of the first tower top three-way regulating valve is communicated with the methylbenzene oxime removal tower.

Description

Technical Field

[0001] The present invention relates to the energy-saving technology of rectification columns in chemical production, and particularly to an energy-saving system for the purification of oximation production applied to a caprolactam plant. Background Art

[0002] During the production process of caprolactam, a large number of rectification column operations are involved. Usually, the material enters the rectification column in the middle of the column, and heat is supplemented by a reboiler for gasification. After the material is gasified, the gas phase at the top of the rectification column is condensed by a top condenser. The reboiler must supplement sufficient heat to enable the normal operation of the rectification column.

[0003] As is well known, in the purification and recovery process of cyclohexanone oxime after extraction and water washing in the oximation unit of a caprolactam plant, four series-connected rectification columns are required, namely the first rectification column, the second rectification column, the toluene deoximation column, and the toluene deketone column. The first rectification column is mainly used to recover toluene for extraction, which is recycled after condensation at the top of the column, and the bottom material enters the second rectification column; the second rectification column is mainly used to separate qualified product cyclohexanone oxime at the bottom, and the gas phase at the top of the column enters the toluene deoximation column after condensation by the top condenser; the toluene deoximation column is mainly used to recover cyclohexanone oxime distilled from the top of the second rectification column and recycle it to the first rectification column for refined purification, and the gas phase at the top of the column enters the toluene deketone column after condensation; the toluene deketone column is mainly used to further separate toluene and alcohol ketone, toluene is recycled to the extraction system, and crude alcohol ketone is refined and separated in the front process of caprolactam. Its defect is that the four rectification columns in the oximation unit are respectively equipped with reboilers and condensers matching the load, resulting in a large consumption of steam and circulating water, which does not conform to the current social concept and measures of energy conservation. Summary of the Invention

[0004] The present invention aims to provide an energy-saving system for the purification of oximation production applied to a caprolactam plant, to overcome the problem of large consumption of steam, electric energy, and circulating water during the oximation production process, reduce the steam consumption of the reboiler, the electric energy consumption of the feed pump, and the circulating water consumption of the condenser, thereby reducing the overall operation consumption of the oximation unit.

[0005] The present invention is achieved through the following technical solutions: An energy-saving system for the purification of oximation production applied to a caprolactam plant, comprising a second rectification column, a toluene deoximation column, and a toluene deketone column connected in sequence, and a first top three-way regulating valve is provided on the gas pipeline at the top of the second rectification column; One path of the first top three-way regulating valve is sequentially connected to a second rectification column top condenser, a second rectification column reflux drum, and a toluene deoximation column feed pump. The outlet of the toluene deoximation column feed pump is divided into two paths, one path is connected to the top of the second rectification column, and the other path is connected to the toluene deoximation column; the other path of the first top three-way regulating valve is connected to the toluene deoximation column; The bottom of the second rectification column is connected in a circulating manner with a second rectification column reboiler, the bottom of the toluene deoximation column is connected in a circulating manner with a toluene deoximation column reboiler, and the bottom of the toluene deketonization column is connected in a circulating manner with a toluene deketonization column reboiler.

[0006] Furthermore, a second top three-way regulating valve is arranged on the top gas pipeline of the toluene deoximation column; One path of the second top three-way regulating valve is successively connected with a toluene deoximation column top condenser, a toluene deoximation column reflux drum, and a toluene deketonization column feed pump. The outlet of the toluene deketonization column feed pump is divided into two paths, one path is connected to the top of the toluene deoximation column, and the other path is connected to the toluene deketonization column; the other path of the second top three-way regulating valve is connected to the toluene deketonization column.

[0007] Furthermore, the top gas pipeline of the toluene deketonization column is successively connected with a toluene deketonization column top condenser, a toluene deketonization column reflux drum, and a toluene deketonization column reflux pump.

[0008] Furthermore, both the toluene deoximation column feed pump and the toluene deketonization column feed pump are variable-frequency pumps.

[0009] Furthermore, 1.0 MPa steam is circulated through the second rectification column reboiler, the toluene deoximation column reboiler, and the toluene deketonization column reboiler.

[0010] The beneficial effects obtained by the present invention compared with the prior art are as follows: 1. A first top three-way regulating valve is arranged on the top gas pipeline of the second rectification column. One path enters the second rectification column reflux drum after passing through the second rectification column top condenser. After being boosted by the toluene deoximation column feed pump, a small part returns to the top of the second rectification column for reflux to ensure the quality of the rectification column, and most enters the middle of the toluene deoximation column; the other path directly enters the bottom of the toluene deoximation column. By adjusting the opening of the first top three-way regulating valve, the path of the gas directly entering the toluene deoximation column is opened wider, and the path entering the second rectification column top condenser is gradually closed smaller until the amount entering the second rectification column top condenser maintains the normal reflux of the second rectification column as the best, thereby reducing the consumption of circulating water in the second rectification column top condenser. By gradually closing the liquid feed of the toluene deoximation column through the regulating valve group, and at the same time, the toluene deoximation column feed pump is adjusted by frequency conversion to an appropriate reflux amount, thereby reducing the operating consumption of the toluene deoximation column feed pump; during the process of adjusting the opening of the first top three-way regulating valve, since the normal-temperature liquid feed is adjusted to the top gas of the second rectification column with high heat, the steam feed of the toluene deoximation column reboiler will gradually be closed smaller, reducing steam consumption; 2. Install a second top three-way regulating valve on the gas pipeline at the top of the toluene deoxime tower. One path enters the toluene deoxime tower reflux drum after passing through the toluene deoxime tower top condenser. After being boosted by the toluene deketone tower feed pump, a small part returns to the top of the toluene deoxime tower for reflux to ensure the quality of the distillation column, and most of it enters the middle of the toluene deketone tower; the other path directly enters the bottom of the toluene deketone tower. By adjusting the opening of the second top three-way regulating valve, the path directly entering the gas phase of the toluene deketone tower is opened wider, and the path entering the toluene deoxime tower top condenser is gradually closed. The optimal situation is that the amount entering the toluene deoxime tower top condenser maintains the normal reflux of the toluene deoxime tower, reducing the consumption of circulating water in the toluene deoxime tower top condenser. Gradually close the liquid feed of the toluene deketone tower through the regulating valve group. At the same time, the toluene deketone tower feed pump is adjusted by frequency conversion to an appropriate reflux amount, thereby reducing the pump operation consumption. During the process of adjusting the opening of the second top three-way regulating valve, since the normal-temperature liquid feed is adjusted to the toluene deoxime tower top gas phase with high heat, the steam feed of the toluene deketone tower reboiler will gradually be closed, reducing steam consumption; 3. The toluene deoxime tower feed pump and the toluene deketone tower feed pump use variable-frequency pumps. During the process of adjusting the tower feed, the starting frequency is reduced to lower the operation load of the pump; 4. Through the energy-saving system for the oximation production and refining of caprolactam plants described in the present invention, the steam consumption of the toluene deoxime tower reboiler and the toluene deketone tower reboiler can be effectively reduced. Through calculation, the steam can be reduced by about 2 / 3, the power consumption of the toluene deoxime tower feed pump and the toluene deketone tower feed pump can be reduced by about half, and the circulating water consumption of the second distillation column top condenser and the toluene deoxime tower top condenser can be reduced by more than 1 / 2. Description of the Drawings

[0011] Figure 1 It is a schematic diagram of the energy-saving system for the oximation production and refining of caprolactam plants described in the present invention; In the figure: 1. Second distillation column reboiler; 2. Second distillation column; 3. Second distillation column top condenser; 4. Second distillation column reflux drum; 5. Toluene deoxime tower feed pump; 6. Toluene deoxime tower; 7. Toluene deoxime tower top condenser; 8. Toluene deoxime tower reflux drum; 9. Toluene deoxime tower reboiler; 10. Toluene deketone tower feed pump; 11. Toluene deketone tower; 12. Toluene deketone tower top condenser; 13. Toluene deketone tower reflux drum; 14. Toluene deketone tower reflux pump; 15. Toluene deketone tower reboiler; 16. First top three-way regulating valve; 17. Second top three-way regulating valve. Detailed Embodiments

[0012] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without making creative efforts shall fall within the protection scope of the present application.

[0013] In the description of the invention, it should be understood that the orientation or positional relationship indicated by the terms "front", "rear", "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0014] As Figure 1 shown, the present invention discloses a refined energy-saving system for the oximation production of caprolactam plants, including a second distillation column 2, a toluene deoxime column 6, a toluene deketone column 11, a second distillation column top condenser 3, a second distillation column reflux drum 4, a toluene deoxime column feed pump 5, a second distillation column reboiler 1, a toluene deoxime column reboiler 9, a toluene deketone column reboiler 15, a toluene deoxime column top condenser 7, a toluene deoxime column reflux drum 8, a toluene deketone column feed pump 10, a toluene deketone column top condenser 12, a toluene deketone column reflux drum 13, and a toluene deketone column reflux pump 14 and other structures. The bottom of the second distillation column is connected in a loop to the second distillation column reboiler 1, the bottom of the toluene deoxime column is connected in a loop to the toluene deoxime column reboiler 9, and the bottom of the toluene deketone column is connected in a loop to the toluene deketone column reboiler 15. The second distillation column reboiler 1, the toluene deoxime column reboiler 9, and the toluene deketone column reboiler 15 are used to circulate 1.0 MPa steam. The top gas pipeline of the toluene deketone column is sequentially connected to the toluene deketone column top condenser 12, the toluene deketone column reflux drum 13, and the toluene deketone column reflux pump 14.

[0015] A first top three-way regulating valve 16 is installed on the top gas pipeline of the second distillation column. One path of the first top three-way regulating valve 16 is connected in sequence through a pipeline to the second distillation column top condenser 3, the second distillation column reflux drum 4, and the toluene deoxime column feed pump 5. The outlet of the toluene deoxime column feed pump 5 is divided into two paths, one path is connected to the top of the second distillation column, and the other path is connected to the toluene deoxime column. The other path of the first top three-way regulating valve 16 is directly connected to the toluene deoxime column.

[0016] A second top three-way regulating valve 17 is installed on the top gas pipeline of the toluene deoxime tower. One path of the second top three-way regulating valve 17 is successively connected through pipelines to the top condenser 7 of the toluene deoxime tower, the toluene deoxime tower reflux drum 8, and the toluene deketone tower feed pump 10. The outlet of the toluene deketone tower feed pump 10 is divided into two paths. One path is connected to the top of the toluene deoxime tower, and the other path is connected to the toluene deketone tower; the other path of the second top three-way regulating valve 17 is directly connected to the toluene deketone tower.

[0017] In this application, both the toluene deoxime tower feed pump 5 and the toluene deketone tower feed pump 10 are variable-frequency pumps. During the tower feed adjustment process, the opening frequency is reduced to lower the operating load of the pumps.

[0018] The working principle of the present invention to achieve reducing the steam consumption of the reboiler, lowering the power consumption of the feed pumps, and reducing the consumption of the condenser circulating water, thereby reducing the overall operating consumption of the oximation unit, is as follows: The gas phase in the second rectification tower enters the first top three-way regulating valve 16 through the top gas pipeline. One path enters the second rectification tower reflux drum 4 after passing through the top condenser 3 of the second rectification tower. After being boosted by the toluene deoxime tower feed pump 5, a small part returns to the top of the second rectification tower for reflux to ensure the quality of the rectification tower, and most enters the middle of the toluene deoxime tower; the other path directly enters the bottom of the toluene deoxime tower. By adjusting the opening of the first top three-way regulating valve 16, the path of the gas phase directly entering the toluene deoxime tower is opened wider, and the path entering the top condenser 3 of the second rectification tower is gradually closed smaller until the amount entering the top condenser 3 of the second rectification tower maintains the normal reflux of the second rectification tower as the best, thereby reducing the consumption of the circulating water of the top condenser 3 of the second rectification tower. The liquid feed of the toluene deoxime tower is gradually closed through the regulating valve group, and at the same time, the toluene deoxime tower feed pump 5 is adjusted by frequency conversion to an appropriate reflux amount, thereby reducing the operating consumption of the toluene deoxime tower feed pump 5; during the process of adjusting the opening of the first top three-way regulating valve 16, since the normal-temperature liquid feed is adjusted to the top gas phase of the second rectification tower with high heat, the steam feed of the toluene deoxime tower reboiler 9 will gradually be closed smaller, reducing the steam consumption; The gas phase in the toluene deoximation tower enters the second top three-way regulating valve 17 through the top gas pipeline. One part passes through the top condenser 7 of the toluene deoximation tower and then enters the toluene deoximation tower reflux drum 8. After being boosted by the toluene deketonization tower feed pump 10, a small part returns to the top of the toluene deoximation tower for reflux to ensure the quality of the distillation column, and most of it enters the middle of the toluene deketonization tower; the other part directly enters the bottom of the toluene deketonization tower. By adjusting the opening of the second top three-way regulating valve 17, the part directly entering the gas phase of the toluene deketonization tower is opened wider, and the part entering the top condenser 7 of the toluene deoximation tower is gradually closed. It is optimal that the amount entering the top condenser 7 of the toluene deoximation tower maintains the normal reflux of the toluene deoximation tower, reducing the consumption of circulating water in the top condenser 7 of the toluene deoximation tower. The liquid feed of the toluene deketonization tower is gradually closed through the regulating valve group, and at the same time, the toluene deketonization tower feed pump 10 is adjusted by frequency conversion to an appropriate reflux amount, thereby reducing the pump operation consumption. During the process of adjusting the opening of the second top three-way regulating valve 17, since the normal-temperature liquid feed is adjusted to the top gas phase of the toluene deoximation tower with high heat, the steam feed of the toluene deketonization tower reboiler 15 will gradually be closed, reducing steam consumption.

[0019] When the energy-saving system for refining in the oximation production of caprolactam plant described in the present invention is specifically adjusted, it can be mainly divided into the following four operation modes of embodiments.

[0020] Embodiment 1 When the system is started up, it can be operated in the order of the second distillation column 2, the toluene deoximation tower 6, and the toluene deketonization tower 11 until the system is stable. Only the first top three-way regulating valve 16 of the second distillation column 2 is adjusted to reduce the steam consumption of the toluene deoximation tower and the cooling water consumption of the top condenser of the second distillation column. At the same time, the operation load of the toluene deoximation tower feed pump 5 is adjusted, which can reduce the power consumption of the toluene deoximation tower feed pump.

[0021] Embodiment 2 After the system is started up and operates stably, the second top three-way regulating valve 17 of the toluene deoximation tower 6 is adjusted, which can reduce the steam consumption of the toluene deketonization tower and the cooling water consumption of the top condenser of the toluene deoximation tower. At the same time, the operation load of the toluene deketonization tower feed pump 10 is adjusted, which can reduce the power consumption of the toluene deketonization tower feed pump.

[0022] Embodiment 3 After the system is started up and operates stably, first adjust the first top three-way regulating valve of the second distillation column 2 to reduce the steam consumption of the toluene deoximation tower and the cooling water consumption of the top condenser of the second distillation column. At the same time, adjust the operation load of the toluene deoximation tower feed pump 5 to reduce the power consumption of the toluene deoximation tower feed pump; then adjust the second top three-way regulating valve of the toluene deoximation tower 6, which can reduce the steam consumption of the toluene deketonization tower and the cooling water consumption of the top condenser of the toluene deoximation tower. At the same time, adjust the operation load of the toluene deketonization tower feed pump 10, which can reduce the power consumption of the toluene deketonization tower feed pump.

[0023] Embodiment 4 After the system runs stably during startup, first adjust the second top three-way regulating valve 17 of the toluene deoxime tower 6, which can reduce the steam consumption of the toluene deketone tower and the cooling water consumption of the top condenser of the toluene deoxime tower. At the same time, adjust the operating load of the toluene deketone tower feed pump 10, which can reduce the power consumption of the toluene deketone tower feed pump; then adjust the first top three-way regulating valve of the second distillation tower 2, which can reduce the steam consumption of the toluene deoxime tower and the cooling water consumption of the top condenser of the second distillation tower. At the same time, adjust the operating load of the toluene deoxime tower feed pump 5, which can reduce the power consumption of the toluene deoxime tower feed pump.

Claims

1. A refined energy-saving system for the oximation production of caprolactam plants, comprising a second distillation column, a toluene deoximation column, and a toluene deketone column that are connected in sequence, characterized in that, A first top three-way regulating valve is provided on the top gas pipeline of the second rectification column; One path of the first top three-way regulating valve is sequentially connected to a top condenser of the second rectification column, a reflux drum of the second rectification column, and a feed pump for the toluene deoxime column. The outlet of the feed pump for the toluene deoxime column is divided into two paths, one path is connected to the top of the second rectification column, and the other path is connected to the toluene deoxime column; the other path of the first top three-way regulating valve is connected to the toluene deoxime column; The bottom of the second rectification column is connected in a loop to a reboiler of the second rectification column, the bottom of the toluene deoxime column is connected in a loop to a reboiler of the toluene deoxime column, and the bottom of the toluene deketone column is connected in a loop to a reboiler of the toluene deketone column.

2. The refined energy-saving system applied to the oximation production of caprolactam device according to claim 1, wherein A second top three-way regulating valve is provided on the top gas pipeline of the toluene deoxime column; One path of the second top three-way regulating valve is sequentially connected to a top condenser of the toluene deoxime column, a reflux drum of the toluene deoxime column, and a feed pump for the toluene deketone column. The outlet of the feed pump for the toluene deketone column is divided into two paths, one path is connected to the top of the toluene deoxime column, and the other path is connected to the toluene deketone column; the other path of the second top three-way regulating valve is connected to the toluene deketone column.

3. The refined energy-saving system for the oximation production of caprolactam device according to claim 2, wherein, The top gas pipeline of the toluene deketone column is sequentially connected to a top condenser of the toluene deketone column, a reflux drum of the toluene deketone column, and a reflux pump for the toluene deketone column.

4. The refined energy-saving system applied to the oximation production of caprolactam device according to claim 3, characterized in that, Both the feed pump for the toluene deoxime column and the feed pump for the toluene deketone column are variable-frequency pumps.

5. The refined energy-saving system applied to the oximation production of caprolactam plant according to any one of claims 1-4, characterized in that, The reboiler of the second rectification column, the reboiler of the toluene deoxime column, and the reboiler of the toluene deketone column are used to circulate 1.0 MPa steam.

Images