Liquid ammonia preparation system

Abstract

According to the liquid ammonia preparation system provided by the invention, the first ammonia gas absorption device is arranged to treat tail gas containing ammonia gas discharged from a hydrolysis section in indigo synthesis to generate dilute ammonia water, the dilute ammonia water is stored in the dilute ammonia water storage tank, and meanwhile, the second ammonia gas absorption device is arranged to absorb the ammonia gas in the dilute ammonia water storage tank. Ammonia distillation wastewater discharged by the ammonia distillation device and clear water supplied by the clear water supply device are used as absorption liquid, ammonia gas in tail gas of a sodium ammonia working section is absorbed, and generated dilute ammonia water is merged into the dilute ammonia water storage tank and conveyed to the ammonia distillation device for ammonia distillation so as to produce liquid ammonia. According to the system, the ammonia gas in the tail gas generated in indigo blue production is recycled through cooperative use of the devices, tail gas recycling is achieved while tail gas treatment is achieved, and the beneficial effects that the production cost is saved, and the environment is protected are achieved.

Description

Technical Field

[0001] This application relates to the field of ammonia recovery technology, and more particularly to a liquid ammonia preparation system. Background Technology

[0002] The molecular formula of indigo is C 16 H 10 N₂O₂, a water-soluble non-azo colorant, is widely used in the food, pharmaceutical, and printing and dyeing industries. Its industrial synthesis uses phenylaminoacetate (sodium or potassium salt, or a mixture of both) as a raw material and sodium amide as a condensing agent. The condensation reaction occurs at 120℃~280℃ under certain pressure conditions to produce indophenol salt, which is then oxidized to obtain indigo. In the indigo production process, the sodium amide used is formed by the combination of liquid ammonia and metallic sodium. The exhaust gas produced in this process contains a large amount of ammonia. Phenylenic acid salt is obtained by alkaline hydrolysis of aniline acetonitrile, and the exhaust gas produced in this process also contains a large amount of ammonia. As can be seen from the above production process, ammonia is both a raw material required for the reaction in the factory and a substance in the exhaust gas discharged from some sections. Therefore, it is necessary to recover the ammonia in the exhaust gas generated in these sections, both for treatment and for reuse in the factory's production needs. Utility Model Content

[0003] This application provides a liquid ammonia preparation system for recovering ammonia gas from the tail gas generated during the production of indigo.

[0004] This application provides a liquid ammonia preparation system, including an ammonia stripping device, a first ammonia absorption device, and a second ammonia absorption device;

[0005] The ammonia stripping device is connected to the first ammonia absorption device via a first heat exchanger, and the ammonia stripping device is also connected to the second ammonia absorption device.

[0006] The first ammonia absorption device and the second ammonia absorption device are both connected to the dilute ammonia water storage tank.

[0007] The first ammonia absorption unit is also connected to the hydrolysis section, and the second ammonia absorption unit is also connected to the sodium ammonia section, the clean water supply unit and the alkali treatment section respectively.

[0008] The ammonia stripping unit is also connected to a liquid ammonia storage tank and a wastewater treatment unit.

[0009] Optionally, the ammonia stripping unit includes an ammonia stripping tower;

[0010] The ammonia stripping tower is connected in sequence to the tube side of the second heat exchanger, the tube side of the third heat exchanger, and the dilute ammonia water storage tank.

[0011] The top of the ammonia stripping tower is connected to the reflux tank via a condenser, and the reflux tank is connected to the reflux pump.

[0012] The reflux pump is also connected to the ammonia stripping tower and the liquid ammonia storage tank, respectively;

[0013] The bottom of the ammonia stripping tower is connected in sequence to the first ammonia absorption device, the second ammonia absorption device, and the wastewater treatment device through the shell side of the second heat exchanger, the shell side of the third heat exchanger, and the wastewater cooler, respectively.

[0014] A first transfer pump is installed between the tube side of the third heat exchanger and the dilute ammonia water storage tank.

[0015] The top of the ammonia stripping tower is also connected to the alkali treatment section.

[0016] Optionally, the first ammonia absorption device includes a first ammonia absorption tower;

[0017] The first ammonia absorption tower is connected to the wastewater cooler via the first heat exchanger.

[0018] The first ammonia absorption tower is connected to the hydrolysis section in sequence through the fourth heat exchanger and the fifth heat exchanger.

[0019] The fifth heat exchanger is also connected to a dilute ammonia storage tank;

[0020] The bottom of the first ammonia absorption tower is connected to the concentrated ammonia water storage tank and the shell side of the sixth heat exchanger via the second transfer pump. The shell side output of the sixth heat exchanger is connected to the bottom of the first ammonia absorption tower.

[0021] Optionally, the second ammonia absorption device includes a second ammonia absorption tower;

[0022] The upper part of the second ammonia absorption tower is connected to the wastewater cooler and the clean water supply device, respectively.

[0023] The bottom of the second ammonia absorption tower is connected to the sodium ammonia section and the third transfer pump, respectively. The third transfer pump is connected to the dilute ammonia water storage tank and the shell inlet of the seventh heat exchanger.

[0024] The shell-side outlet of the seventh heat exchanger is connected to the lower section of the second ammonia absorption tower;

[0025] The top of the second ammonia absorption tower is connected to the alkali treatment section.

[0026] Optionally, the middle section of the second ammonia absorption tower is also connected to the eighth heat exchanger to form a loop via a fourth liquid transfer pump.

[0027] Optionally, the bottom of the second ammonia absorption tower is provided with at least one oil inlet, which is connected to the oil collection tank.

[0028] Optionally, the second ammonia absorption tower is a packed tower; the packing used is one of Pall ring packing, Raschig ring packing, stepped ring packing, rectangular saddle packing or arc saddle packing.

[0029] The liquid ammonia preparation system provided in this application treats the ammonia-containing tail gas discharged from the hydrolysis section of indigo synthesis using a first ammonia absorption device to produce dilute ammonia water, which is then stored in a dilute ammonia water storage tank. Simultaneously, a second ammonia absorption device uses ammonia stripping wastewater discharged from the ammonia stripping unit and clean water supplied by a clean water supply unit as absorbents to absorb ammonia from the tail gas of the sodium ammonia section. The resulting dilute ammonia water is combined with the dilute ammonia water storage tank and then supplied to the ammonia stripping unit for ammonia stripping to produce liquid ammonia. Through the coordinated use of the above devices, this system recovers ammonia from the tail gas generated during indigo production, achieving both tail gas treatment and resource utilization, thus saving production costs and protecting the environment. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of a liquid ammonia preparation system provided in an embodiment of this application;

[0032] Figure 2 This is a schematic diagram of a liquid ammonia preparation system provided in another embodiment of this application;

[0033] Figure 3 This is a schematic diagram of a liquid ammonia preparation system provided in another embodiment of this application.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1. Ammonia stripping unit; 2. First ammonia absorption unit; 3. Second ammonia absorption unit; 4. Hydrolysis section; 5. Sodium ammonia section; 6. Clean water supply unit; 7. Wastewater treatment unit; 10. First heat exchanger; 11. Ammonia stripping tower; 12. First liquid transfer pump; 20. Second heat exchanger; 21. First ammonia absorption tower; 22. Second liquid transfer pump; 30. Third heat exchanger; 31. Second ammonia absorption tower; 33. 34. Third transfer pump; 35. Fourth transfer pump; 40. Oil collection tank; 50. Condenser; 60. Wastewater cooler; 70. Fourth heat exchanger; 80. Fifth heat exchanger; 90. Sixth heat exchanger; 100. Seventh heat exchanger; 200. Dilute ammonia storage tank; 300. Liquid ammonia storage tank; 301. Concentrated ammonia storage tank; 310. Oil intake port; 400. Eighth heat exchanger; 400. Reflux tank; 410. Reflux pump. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0037] like Figure 1 As shown, this application provides a liquid ammonia preparation system, including an ammonia stripping device 1, a first ammonia absorption device 2, and a second ammonia absorption device 3;

[0038] The ammonia stripping device 1 is connected to the first ammonia absorption device 2 through the first heat exchanger 10, and the ammonia stripping device 1 is also connected to the second ammonia absorption device 3.

[0039] The first ammonia absorption device 2 and the second ammonia absorption device 3 are both connected to the dilute ammonia water storage tank 100.

[0040] The first ammonia absorption unit 2 is also connected to the hydrolysis section 4, and the second ammonia absorption unit 3 is also connected to the sodium ammonia section 5, the clean water supply unit 6, and the alkali treatment section 8, respectively.

[0041] The ammonia stripping unit 1 is also connected to the liquid ammonia storage tank 200 and the wastewater treatment unit 7, respectively.

[0042] During operation, the tail gas from hydrolysis section 4 (mainly the tail gas generated during the hydrolysis reaction in the hydrolysis reactor, whose components include approximately 74 wt% water vapor, approximately 20 wt% ammonia, approximately 1 wt% potassium / sodium phenylaminoacetate, approximately 4 wt% nitrogen, and approximately 1 wt% oxygen) is fed into the first ammonia absorption device 2 to condense the water. The ammonia stripping wastewater output from the ammonia stripping device 1, which has been cooled by the first heat exchanger 10, is used as the absorbent to absorb the ammonia. The dilute ammonia water generated during the absorption and treatment of the tail gas from hydrolysis section 4 by the first ammonia absorption device 2 is stored in the dilute ammonia water storage tank 100. The treated tail gas is then released into the atmosphere (the ammonia content is less than 20 ppm).

[0043] Meanwhile, the tail gas from the sodium ammonia section 5 (discharged during the sodium ammonia reactor production process, its main components being approximately 11 wt% hydrogen and approximately 89 wt% ammonia) is input into the second ammonia absorption device 3. The ammonia in the tail gas from the sodium ammonia section 5 is absorbed by the clean water supplied by the clean water supply device 6 and the cooling ammonia stripping wastewater supplied by the ammonia stripping device 1. The dilute ammonia water produced in this process is stored in the dilute ammonia water storage tank 100, and the tail gas produced is sent to the alkali treatment section 8 for treatment.

[0044] Dilute ammonia water from dilute ammonia water storage tank 100 is subjected to ammonia stripping in ammonia stripping device 1, and the extracted liquid ammonia is stored in liquid ammonia storage tank 200. The resulting ammonia stripping wastewater is respectively transported to the first ammonia absorption device 2 and the second ammonia absorption device 3 as absorbent liquid for absorbing ammonia in the tail gas, and another part is transported to the wastewater treatment device 7 for harmless treatment.

[0045] The liquid ammonia preparation system provided in this application treats the ammonia-containing tail gas discharged from the hydrolysis section 4 of indigo synthesis using a first ammonia absorption device 2 to produce dilute ammonia water, which is then stored in a dilute ammonia water storage tank 100. Simultaneously, a second ammonia absorption device 3 absorbs the ammonia from the tail gas of the sodium ammonia section 5 using wastewater from the ammonia stripping unit 1 and clean water supplied by the clean water supply unit 6 as absorbents. The resulting dilute ammonia water is combined and stored in the dilute ammonia water storage tank 100, then fed to the ammonia stripping unit 1 for ammonia stripping to produce liquid ammonia. Through the coordinated use of these devices, the system recovers ammonia from the tail gas generated during indigo production, achieving both tail gas treatment and resource utilization, thus saving production costs and protecting the environment.

[0046] like Figure 2 As shown, optionally, the ammonia stripping device 1 includes an ammonia stripping tower 11;

[0047] The ammonia stripping tower 11 is connected in sequence to the tube side of the second heat exchanger 20, the tube side of the third heat exchanger 30, and the dilute ammonia water storage tank 100.

[0048] The top of the ammonia stripping tower 11 is connected to the reflux tank 400 via the condenser 40, and the reflux tank 400 is connected to the reflux pump 410;

[0049] The reflux pump 410 is also connected to the ammonia stripping tower 11 and the liquid ammonia storage tank 200, respectively;

[0050] The bottom of the ammonia stripping tower 11 is connected to the first ammonia absorption device 2, the second ammonia absorption device 3, and the wastewater treatment device 7 in sequence through the shell side of the second heat exchanger 20, the shell side of the third heat exchanger 30, and the wastewater cooler 50, respectively.

[0051] A first transfer pump 12 is installed between the tube side of the third heat exchanger 30 and the dilute ammonia water storage tank 100;

[0052] The top of the ammonia stripping tower 11 is also connected to the alkali treatment section 8.

[0053] In this application, dilute ammonia from the dilute ammonia storage tank 100 is pressurized by the first transfer pump 12, and then passes through the tube side and shell side of the third heat exchanger 30 and the second heat exchanger 20. After heat exchange, it enters the ammonia stripping tower 11 for distillation. The steam collected from the top of the tower is sent to the condenser 40 to be cooled into liquid ammonia and sent to the reflux tank 400. The liquid ammonia in the reflux tank 400 is pressurized by the reflux pump 410, and part of it is returned to the top of the ammonia stripping tower 11, while part of it is sent to the liquid ammonia storage tank 200.

[0054] The ammonia stripping wastewater collected from the bottom of the ammonia stripping tower 11 passes through the shell side of the second heat exchanger 20 and the third heat exchanger 30, where it exchanges heat with the dilute ammonia water in the tube side. Then, it is cooled to 40°C by the wastewater cooler 50. A portion of the wastewater is sent to the first ammonia absorption device 2 and the second ammonia absorption device 3 as absorbent, while the remaining portion is sent to the wastewater treatment device 7 for biochemical treatment.

[0055] like Figure 2 As shown, optionally, the first ammonia absorption device 2 includes a first ammonia absorption tower 21;

[0056] The first ammonia absorption tower 21 is connected to the wastewater cooler 50 through the first heat exchanger 10;

[0057] The first ammonia absorption tower 21 is connected to the hydrolysis section 4 in sequence through the fourth heat exchanger 60 and the fifth heat exchanger 70.

[0058] The fifth heat exchanger 70 is also connected to the dilute ammonia water storage tank 100;

[0059] The bottom of the first ammonia absorption tower 21 is connected to the concentrated ammonia water storage tank 300 and the shell side of the sixth heat exchanger 80 via the second transfer pump 22. The shell side output end of the sixth heat exchanger 80 is connected to the bottom of the first ammonia absorption tower 21.

[0060] In this application, during use, the tail gas from the hydrolysis section 4 (mainly the tail gas generated during the hydrolysis reaction in the hydrolysis reactor, whose components include approximately 74 wt% water vapor, approximately 20 wt% ammonia, approximately 1 wt% potassium / sodium phenylaminoacetate, approximately 4 wt% nitrogen, and approximately 1 wt% oxygen) is partially condensed in the shell side of the fifth heat exchanger 70. The liquid phase is retained in the dilute ammonia water storage tank 100, while the gas phase enters the shell side of the fourth heat exchanger 60 from the shell side of the fifth heat exchanger 70. The gas phase is partially condensed in the shell side of the fourth heat exchanger 60, and the liquid phase flows by gravity to the bottom of the first ammonia absorption tower 21. The gas phase is then sent to the bottom of the first ammonia absorption tower 21 through a pipeline. To reduce the temperature of the exhaust gas, the gaseous water is cooled into liquid water and absorbs the ammonia in the exhaust gas. An external circulation heat exchanger is set up in the bottom of the first ammonia absorption tower 21 for cooling. That is, the concentrated ammonia water in the bottom of the first ammonia absorption tower 21 is pressurized by the second transfer pump 22, and part of it is sent to the concentrated ammonia water storage tank 300 in the plant area, while the other part enters the shell side of the sixth heat exchanger 80. Low-temperature cooling water at a temperature of about 7°C is used as the heat exchange medium to cool it down. The cooled concentrated ammonia water returns to the tower from the bottom of the first ammonia absorption tower 21, serving as both an absorbent and a cold source to mix with the absorbent (i.e., ammonia water) in the bottom of the tower for further cooling. Part of the ammonia stripping wastewater output from the ammonia stripping tower 11 is cooled to about 40°C by the wastewater cooler 50 and then sent to the first heat exchanger 10. After being cooled to about 20°C, it enters the upper section of the first ammonia absorption tower 21 to further cool and absorb the ammonia-containing tail gas input from the hydrolysis section 4 in the tower, so as to ensure that the ammonia content in the exhaust gas output from the top of the first ammonia absorption tower 21 is reduced to below 20 ppm.

[0061] like Figure 3 As shown, optionally, the second ammonia absorption device 3 includes a second ammonia absorption tower 31;

[0062] The upper part of the second ammonia absorption tower 31 is connected to the wastewater cooler 50 and the clean water supply device 6, respectively.

[0063] The bottom of the second ammonia absorption tower 31 is connected to the sodium ammonia section 5 and the third transfer pump 33, respectively. The third transfer pump 33 is connected to the dilute ammonia water storage tank 100 and the shell inlet of the seventh heat exchanger 90, respectively.

[0064] The shell-side outlet of the seventh heat exchanger 90 is connected to the lower section of the second ammonia absorption tower 31.

[0065] The top of the second ammonia absorption tower 31 is connected to the alkali treatment section 8.

[0066] In this application, during use, the tail gas from the sodium ammonia section 5 (discharged during the sodium ammonia reactor production process, its main components being approximately 11 wt% hydrogen and approximately 89 wt% ammonia) continuously releases heat during absorption due to the high ammonia content in the tail gas output from the sodium ammonia section 5. Therefore, two-stage heat exchange and cooling are set up with the seventh heat exchanger 90 and the eighth heat exchanger 310 to promptly remove the heat released by the tail gas discharged from the sodium ammonia section 5 during the absorption process. The dilute ammonia water in the bottom of the second ammonia absorption tower 31 is pressurized by the third transfer pump 33. Part of the dilute ammonia water is sent to the dilute ammonia water storage tank 100, and the other part enters the shell side of the seventh heat exchanger 90. After being cooled by the seventh heat exchanger 90, it is returned to the tower from the lower section of the second ammonia absorption tower 31 to provide absorbent for the lower absorption stage. Fresh water supplied by the clean water supply device 6, as well as some of the ammonia stripping wastewater discharged from the ammonia stripping tower 11, enter the tower from the upper section of the second ammonia absorption tower 31 to absorb ammonia in the tail gas, ensuring that the ammonia content in the tail gas at the top of the tower is reduced to 0.1% (v / v).

[0067] like Figure 3 As shown, optionally, the middle section of the second ammonia absorption tower 31 is also connected to the eighth heat exchanger 310 to form a loop via the fourth liquid transfer pump 34.

[0068] In this application, during use, the dilute ammonia water collected from the middle of the second ammonia absorption tower 31 is pressurized by the fourth transfer pump 34 and sent to the eighth heat exchanger 310 for heat exchange and cooling before returning to the tower to provide absorbent for the lower section of the tower.

[0069] like Figure 3 As shown, optionally, the bottom of the second ammonia absorption tower 31 is provided with at least one oil inlet 301, which is connected to the oil collection tank 35.

[0070] In this application, considering that the tail gas from the sodium ammonia reactor may contain trace amounts of wax oil (from sodium stored in paraffin oil), at least one oil collection port 301 is provided in the bottom of the second ammonia absorption tower 31 to periodically collect the wax oil-containing components in the upper layer of the bottom liquid into the oil collection tank 35.

[0071] Optionally, the second ammonia absorption tower 31 is a packed tower; the packing used is one of Pall ring packing, Raschig ring packing, stepped ring packing, rectangular saddle packing or arc saddle packing.

[0072] In this application, the second ammonia absorption tower 31 is a packed tower, which can effectively absorb ammonia and other gases in the tail gas and improve the absorption and treatment efficiency of the tail gas.

[0073] This application provides a liquid ammonia preparation system, the working process of which is as follows:

[0074] During operation, the tail gas from hydrolysis section 4 (mainly the tail gas generated during the hydrolysis reaction in the hydrolysis reactor, whose components include approximately 74 wt% water vapor, approximately 20 wt% ammonia, approximately 1 wt% potassium / sodium phenylaminoacetate, approximately 4 wt% nitrogen, and approximately 1 wt% oxygen) is partially condensed in the shell side of the fifth heat exchanger 70. The liquid phase is retained in the dilute ammonia water storage tank 100, while the gas phase enters the shell side of the fourth heat exchanger 60 from the shell side of the fifth heat exchanger 70. The gas phase is partially condensed in the shell side of the fourth heat exchanger 60, while the liquid phase flows by gravity to the bottom of the first ammonia absorption tower 21. The gas phase is then sent to the bottom of the first ammonia absorption tower 21 through a pipeline. To reduce the temperature of the exhaust gas, the gaseous water is cooled into liquid water and absorbs the ammonia in the exhaust gas. An external circulation heat exchanger is set up in the bottom of the first ammonia absorption tower 21 for cooling. That is, the concentrated ammonia water in the bottom of the first ammonia absorption tower 21 is pressurized by the second transfer pump 22, and part of it is sent to the concentrated ammonia water storage tank 300 in the plant area, while the other part enters the shell side of the sixth heat exchanger 80. Low-temperature cooling water at a temperature of about 7°C is used as the heat exchange medium to cool it down. The cooled concentrated ammonia water returns to the tower from the bottom of the first ammonia absorption tower 21, serving as both an absorbent and a cold source to mix with the absorbent (i.e., ammonia water) in the bottom of the tower for further cooling. Part of the ammonia stripping wastewater output from the ammonia stripping tower 11 is cooled to about 40°C by the wastewater cooler 50 and then sent to the first heat exchanger 10. After being cooled to about 20°C, it enters the upper section of the first ammonia absorption tower 21 to further cool and absorb the ammonia-containing tail gas input from the hydrolysis section 4 in the tower, so as to ensure that the ammonia content in the exhaust gas output from the top of the first ammonia absorption tower 21 is reduced to below 20 ppm.

[0075] Meanwhile, the tail gas from sodium ammonia section 5 (discharged during the sodium ammonia reactor production process, its main components being approximately 11 wt% hydrogen and 89 wt% ammonia) continuously releases heat during absorption due to the high ammonia content in the tail gas output from sodium ammonia section 5. Therefore, two-stage heat exchange and cooling are set up with the seventh heat exchanger 90 and the eighth heat exchanger 310 to promptly remove the heat released by the tail gas discharged from sodium ammonia section 5 during absorption. The dilute ammonia water in the bottom of the second ammonia absorption tower 31 is pressurized by the third transfer pump 33. Part of the dilute ammonia water is sent to the dilute ammonia water storage tank 100, and the other part enters the shell side of the seventh heat exchanger 90. After being cooled by the seventh heat exchanger 90, it is returned to the tower from the lower section of the second ammonia absorption tower 31 to provide absorbent for the lower absorption stage. Dilute ammonia water collected from the middle of the second ammonia absorption tower 31 is pressurized by the fourth transfer pump 34 and sent to the eighth heat exchanger 310 for heat exchange and cooling. Part of the dilute ammonia water is returned to the tower from below the packing section, and the remainder is returned to the tower from the feed inlet below the oil collection tank 35, providing absorbent for the lower section of the tower. Fresh water supplied by the clean water supply device 6, as well as part of the ammonia stripping wastewater discharged from the ammonia stripping tower 11, enter the tower from the upper section of the second ammonia absorption tower 31 to absorb ammonia in the tail gas, ensuring that the ammonia content in the tail gas at the top of the tower is reduced to 0.1% (v / v). Considering that the tail gas from the sodium ammonia reactor may contain trace amounts of wax oil, at least one oil collection port 301 is provided at the bottom of the second ammonia absorption tower 31 to periodically collect the wax oil-containing components in the upper layer of the bottom liquid into the oil collection tank 35.

[0076] Dilute ammonia from the dilute ammonia storage tank 100 is pressurized by the first transfer pump 12, and then passes through the tube side and shell side of the third heat exchanger 30 and the second heat exchanger 20. After heat exchange, it enters the ammonia stripping tower 11 for rectification. The steam collected at the top of the tower is sent to the condenser 40 to be cooled into liquid ammonia and sent to the reflux tank 400. The liquid ammonia in the reflux tank 400 is pressurized by the reflux pump 410, and part of it is returned to the top of the ammonia stripping tower 11, while part of it is sent to the liquid ammonia storage tank 200.

[0077] The ammonia stripping wastewater collected from the bottom of the ammonia stripping tower 11 passes through the shell side of the second heat exchanger 20 and the third heat exchanger 30, where it exchanges heat with the dilute ammonia water in the tube side. Then, it is cooled to 40°C by the wastewater cooler 50. A portion of the wastewater is sent to the first ammonia absorption device 2 and the second ammonia absorption device 3 as absorbent, while the remaining portion is sent to the wastewater treatment device 7 for biochemical treatment.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A liquid ammonia preparation system, characterized in that, It includes an ammonia stripping device (1), a first ammonia absorption device (2), and a second ammonia absorption device (3); The ammonia stripping device (1) is connected to the first ammonia absorption device (2) through the first heat exchanger (10), and the ammonia stripping device (1) is also connected to the second ammonia absorption device (3); The first ammonia absorption device (2) and the second ammonia absorption device (3) are both connected to the dilute ammonia water storage tank (100); The first ammonia absorption device (2) is also connected to the hydrolysis section (4), and the second ammonia absorption device (3) is also connected to the sodium ammonia section (5), the clean water supply device (6), and the alkali treatment section (8), respectively. The ammonia stripping device (1) is also connected to the liquid ammonia storage tank (200) and the wastewater treatment device (7), respectively.

2. The liquid ammonia preparation system according to claim 1, characterized in that, The ammonia stripping device (1) includes an ammonia stripping tower (11); The ammonia stripping tower (11) is connected in sequence to the tube side of the second heat exchanger (20), the tube side of the third heat exchanger (30), and the dilute ammonia water storage tank (100); The top of the ammonia stripping tower (11) is connected to the reflux tank (400) via a condenser (40), and the reflux tank (400) is connected to the reflux pump (410); The reflux pump (410) is also connected to the ammonia stripping tower (11) and the liquid ammonia storage tank (200), respectively; The bottom of the ammonia stripping tower (11) is connected in sequence to the first ammonia absorption device (2), the second ammonia absorption device (3), and the wastewater treatment device (7) through the shell side of the second heat exchanger (20), the shell side of the third heat exchanger (30), and the wastewater cooler (50), respectively. A first transfer pump (12) is provided between the tube side of the third heat exchanger (30) and the dilute ammonia water storage tank (100).

3. The liquid ammonia preparation system according to claim 2, characterized in that, The first ammonia absorption device (2) includes a first ammonia absorption tower (21); The first ammonia absorption tower (21) is connected to the wastewater cooler (50) through the first heat exchanger (10); The first ammonia absorption tower (21) is connected to the hydrolysis section (4) in sequence through the fourth heat exchanger (60) and the fifth heat exchanger (70); The fifth heat exchanger (70) is also connected to the dilute ammonia water storage tank (100); The bottom of the first ammonia absorption tower (21) is connected to the concentrated ammonia water storage tank (300) and the shell side of the sixth heat exchanger (80) respectively via the second liquid transfer pump (22). The shell side output end of the sixth heat exchanger (80) is connected to the bottom of the first ammonia absorption tower (21).

4. The liquid ammonia preparation system according to claim 2, characterized in that, The second ammonia absorption device (3) includes a second ammonia absorption tower (31); The upper part of the second ammonia absorption tower (31) is connected to the wastewater cooler (50) and the clean water supply device (6), respectively; The bottom of the second ammonia absorption tower (31) is connected to the sodium ammonia section (5) and the third transfer pump (33), respectively. The third transfer pump (33) is connected to the dilute ammonia water storage tank (100) and the shell-side inlet of the seventh heat exchanger (90), respectively. The shell-side outlet of the seventh heat exchanger (90) is connected to the lower section of the second ammonia absorption tower (31); The top of the second ammonia absorption tower (31) is connected to the alkali treatment section (8).

5. The liquid ammonia preparation system according to claim 4, characterized in that, The middle section of the second ammonia absorption tower (31) is also connected to the eighth heat exchanger (310) via the fourth liquid transfer pump (34) to form a loop.

6. The liquid ammonia preparation system according to claim 4, characterized in that, The second ammonia absorption tower (31) has at least one oil inlet (301) in its bottom, which is connected to the oil collection tank (35).

7. The liquid ammonia preparation system according to claim 4, characterized in that, The second ammonia absorption tower (31) is a packed tower; the packing used is one of Pall ring packing, Raschig ring packing, stepped ring packing, rectangular saddle packing or arc saddle packing.

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