Low-temperature rectification device for ammonia synthesis purge gas

Abstract

The utility model relates to a kind of low-temperature rectifying device of synthetic ammonia release gas, including first nitrogen gas delivery main pipe, first nitrogen gas delivery main pipe is provided with first desorption gas delivery pipe, refrigeration gas delivery pipe, nitrogen compressor unit, turbine expander, first machine after heat exchanger, second machine after heat exchanger, first nitrogen gas delivery branch pipe and second nitrogen gas delivery branch pipe, turbine expander and the inlet end of refrigeration gas delivery pipe are communicated, and first nitrogen gas delivery branch pipe, second nitrogen gas delivery branch pipe and refrigeration gas delivery pipe are provided with main heat exchanger, and main heat exchanger is provided with first release gas delivery pipe, and first release gas delivery pipe is communicated with molecular sieve adsorption tank, and first desorption gas delivery pipe and first machine after heat exchanger are communicated, and first machine after heat exchanger is provided with second desorption gas delivery pipe, and second desorption gas delivery pipe is provided with electric heater.Energy consumption of electric heater can be reduced.The utility model is convenient to use, with extensive market prospect.

Description

Technical Field

[0001] This utility model relates to the field of low-temperature distillation equipment for synthetic ammonia purge gas, and specifically to a low-temperature distillation apparatus for synthetic ammonia purge gas. Background Technology

[0002] During the operation of ammonia synthesis plants, limitations imposed by reaction conditions and the production environment prevent methane and inert gases in the synthesis gas from fully participating in the reaction, necessitating their removal from the unit. However, the discharge of this waste gas also results in the proportional release of substances such as hydrogen and nitrogen. Experimental measurements have shown that the ammonia synthesis purge gas contains a large amount of nitrogen, a significant amount of methane, a small amount of hydrogen, and trace amounts of moisture. Pure methane can be separated as a byproduct through cryogenic distillation, while the large amount of finished nitrogen and oxygen-enriched nitrogen is reused as feedstock in the ammonia synthesis tower. Therefore, fully utilizing the purge gas emitted from the ammonia synthesis process is undoubtedly an important means of reducing energy consumption.

[0003] However, since the ammonia synthesis off-gas contains trace amounts of moisture, it needs to be purified to remove the moisture before cryogenic distillation can proceed. Current technology removes moisture from the ammonia synthesis off-gas by passing it through a molecular sieve layer in a molecular sieve adsorption tank. Multiple molecular sieve adsorption tanks are typically installed for interconnection and backup. When the molecular sieve layer in the adsorption tank reaches its preset usage time, the tank needs to be switched. Specifically, a heated inert gas stream continuously passes through the moisture-adsorbed molecular sieve layer, causing desorption and regeneration. Because a heated inert gas stream is required, conventional processes utilize a low-pressure nitrogen stream from the low-pressure nitrogen pipeline in the ammonia synthesis system, heated by an electric heater to obtain the heated inert gas stream. Clearly, there are various ways to obtain the heated inert gas stream, and there is still room for improvement in the cryogenic distillation process of the off-gas, to reduce the energy consumption of the electric heater, thereby achieving energy conservation and cost reduction for the enterprise. Summary of the Invention

[0004] In view of the shortcomings of the prior art, this utility model provides a low-temperature distillation device for synthetic ammonia purge gas that can reduce the energy consumption of the electric heater and obtain an inert gas flow within a preset temperature range, thereby overcoming the defects in the prior art.

[0005] The technical solution adopted in this utility model is as follows: a low-temperature distillation device for synthetic ammonia purge gas, comprising a first nitrogen delivery main pipe, wherein the first nitrogen delivery main pipe is provided with, in sequence, an inlet end of a first desorption gas delivery pipe, an outlet end of a refrigerant gas delivery pipe, a nitrogen compressor unit, a booster end of a turbine expander, a heat source channel for a first downstream heat exchanger, a heat source channel for a second downstream heat exchanger, an inlet end of a first nitrogen delivery branch pipe, and an inlet end of a second nitrogen delivery branch pipe; a liquid nitrogen temporary storage tank is provided at the outlet end of the second nitrogen delivery branch pipe, and the outlet end of the first nitrogen delivery branch pipe and the turbine expander... The expansion end inlet of the expander is connected to the expansion end outlet of the turbine expander and the inlet of the refrigerant gas delivery pipe. The first nitrogen delivery branch pipe, the second nitrogen delivery branch pipe, and the refrigerant gas delivery pipe are equipped with a main heat exchanger. The main heat exchanger is equipped with a first venting gas delivery pipe. The inlet of the first venting gas delivery pipe is connected to a molecular sieve adsorption tank. The outlet of the first desorption gas delivery pipe is connected to the inlet of the cold source channel of the first machine's downstream heat exchanger. The outlet of the cold source channel of the first machine's downstream heat exchanger is equipped with the inlet of the second desorption gas delivery pipe. The second desorption gas delivery pipe is equipped with an electric heater. The outlet of the second desorption gas delivery pipe is connected to the molecular sieve adsorption tank.

[0006] Preferably, the refrigerant delivery pipe between the expansion end of the turbine expander and the main heat exchanger and the top of the liquid nitrogen storage tank are connected by a pressure relief pipe. The pressure relief pipe is provided with a pressure sensor and a first regulating valve in sequence along the direction from near the liquid nitrogen storage tank to away from the liquid nitrogen storage tank.

[0007] Preferably, the number of molecular sieve adsorption tanks is several. Each molecular sieve adsorption tank is provided with a first conveying pipe at its outlet end and the inlet end of the first venting gas conveying pipe. Each molecular sieve adsorption tank is provided with a second conveying pipe at its outlet end and the outlet end of the second desorption gas conveying pipe. Each of the several molecular sieve adsorption tanks is provided with an outlet end of a third conveying pipe and an inlet end of a fourth conveying pipe at its inlet end. The outlet end of the second venting gas conveying pipe is provided at the inlet end of the several third conveying pipes, and the inlet end of the third desorption gas conveying pipe is provided at the outlet end of the several fourth conveying pipes.

[0008] Preferably, the bottom of the liquid nitrogen temporary storage tank is provided with the inlet end of a first liquid nitrogen delivery pipe, a second regulating valve is provided on the first liquid nitrogen delivery pipe, a second liquid nitrogen delivery pipe is provided on the first liquid nitrogen delivery pipe between the second regulating valve and the liquid nitrogen temporary storage tank, the outlet end of the first venting gas delivery pipe is provided with the inlet end of a heat source channel for a bottom heater, a first distillation column is provided on the cold source channel of the bottom heater, a fourth venting gas delivery pipe is provided on the outlet end of the heat source channel of the bottom heater and the main heat exchanger, a second distillation column is provided on the outlet end of the fourth venting gas delivery pipe, the outlet end of the first liquid nitrogen delivery pipe is connected to the top of the second distillation column, the top of the first distillation column is connected to the outlet end of the second liquid nitrogen delivery pipe, the top of the second distillation column is connected to the first distillation column through a liquid phase delivery pipe, and a third regulating valve is provided on both the liquid phase delivery pipe and the second liquid nitrogen delivery pipe.

[0009] Preferably, the first distillation column includes a first column body and a first packing layer and a second packing layer arranged sequentially from top to bottom within the first column body; the outlet end of the first column body and the liquid phase conveying pipe between the first packing layer and the second packing layer are connected, and the outlet end of the second liquid nitrogen conveying pipe is connected to the first column body above the first packing layer; the second distillation column includes a second column body and a third packing layer arranged within the second column body; the outlet end of the first liquid nitrogen conveying pipe is connected to the second column body above the third packing layer, and the outlet end of the fourth venting gas conveying pipe is connected to the second column body below the third packing layer.

[0010] Preferably, a hydrogen-rich nitrogen gas delivery pipe is provided on the top of the second tower and the main heat exchanger, a second nitrogen gas delivery main pipe is provided on the top of the first tower and the main heat exchanger, a liquefied methane delivery pipe is provided at the bottom of the cold source channel of the bottom heater, an undercooler is provided on the second nitrogen gas delivery main pipe and the liquefied methane delivery pipe between the first tower and the main heat exchanger, and a fourth regulating valve is provided on the liquefied methane delivery pipe.

[0011] Preferably, the second tower body below the third packing layer, the liquid nitrogen temporary storage tank, and the cold source channel of the tower bottom heater are all equipped with liquid level sensors.

[0012] The beneficial effects of this utility model are as follows: First, this utility model utilizes a portion of the low-pressure nitrogen gas transported through the first nitrogen gas transport main pipe as desorption gas. The desorption gas undergoes countercurrent heat exchange through the cold source channel of the first machine's heat exchanger and the heat source continuously supplied to the first machine's heat exchanger to complete the first stage of heating of the desorption gas. Then, it is transported to the electric heater to complete the second stage of heating of the desorption gas. This reduces the temperature range of the electric heater heating the desorption gas, thus reducing the energy consumption in the process of heating the desorption gas by the electric heater.

[0013] Secondly, a first temperature sensor is installed on the second desorption gas delivery pipe between the first heat exchanger and the electric heater, and a second temperature sensor is installed on the second desorption gas delivery pipe between the electric heater and the molecular sieve adsorption tank. Both the first and second temperature sensors are for facilitating the feedback of temperature parameters.

[0014] Furthermore, the second tower body below the third packing layer, the liquid nitrogen temporary storage tank, and the cold source channel of the bottom heater of the tower are all equipped with liquid level sensors; installing liquid level sensors facilitates the feedback of liquid level parameters.

[0015] This utility model has a simple structure, is easy to operate, and has a clever design, which greatly improves work efficiency and has good social and economic benefits. It is a product that is easy to promote and use. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0017] like Figure 1 As shown, a cryogenic distillation apparatus for synthetic ammonia purge gas includes a first nitrogen delivery main pipe 1. Along the direction from the inlet to the outlet of the first nitrogen delivery main pipe 1, the apparatus is sequentially provided with the inlet of a first desorption gas delivery pipe 2, the outlet of a refrigerant gas delivery pipe 3, a nitrogen compressor unit 4, the booster end of a turbine expander 5, a heat source channel for a first downstream heat exchanger 6, a heat source channel for a second downstream heat exchanger 7, the inlet of a first nitrogen delivery branch pipe 8, and the inlet of a second nitrogen delivery branch pipe 9. A liquid nitrogen storage tank 10 is installed at the outlet of the second nitrogen delivery branch pipe 9. The outlet of the first nitrogen delivery branch pipe 8 is connected to the inlet of the expansion end of the turbine expander 5. The expansion end outlet of the turbine expander 5 is connected to the inlet end of the refrigerant gas delivery pipe 3. A main heat exchanger 11 is installed on the first nitrogen delivery branch pipe 8, the second nitrogen delivery branch pipe 9, and the refrigerant gas delivery pipe 3. A first venting gas delivery pipe 12 is installed on the main heat exchanger 11. A molecular sieve adsorption tank 13 is connected to the inlet end of the first venting gas delivery pipe 12. The outlet end of the first desorption gas delivery pipe 2 is connected to the inlet end of the cold source channel of the first downstream heat exchanger 6. The inlet end of the second desorption gas delivery pipe 14 is installed on the outlet end of the cold source channel of the first downstream heat exchanger 6. An electric heater 15 is installed on the second desorption gas delivery pipe 14. The outlet end of the second desorption gas delivery pipe 14 is connected to the molecular sieve adsorption tank 13. A fifth regulating valve 47 is installed on each of the first desorption gas delivery pipe 2, the first nitrogen delivery branch pipe 8, and the second nitrogen delivery branch pipe 9.

[0018] The expansion end of the turbine expander 5 is connected to the top of the liquid nitrogen storage tank 10 via a pressure relief pipe 16, which connects the refrigerant gas delivery pipe 3 between the expansion end and the main heat exchanger 11. A pressure sensor 17 and a first regulating valve 18 are sequentially installed along the pressure relief pipe 16 from near to far from the liquid nitrogen storage tank 10. This facilitates maintaining the safe operating pressure of the liquid nitrogen storage tank 10. Furthermore, the nitrogen gas discharged from the top of the liquid nitrogen storage tank 10 via the pressure relief pipe 16 has a relatively low temperature. This portion of nitrogen gas is then combined into the refrigerant gas delivery pipe 3 before being delivered to the main heat exchanger 11, which also facilitates the recovery of cooling capacity.

[0019] The molecular sieve adsorption tank 13 includes a tank body and a molecular sieve layer disposed within the tank body. Several molecular sieve adsorption tanks 13 are used. Each molecular sieve adsorption tank 13 has a first delivery pipe 19 at its outlet end and a first purge gas delivery pipe 12 at its inlet end. Each molecular sieve adsorption tank 13 has a second delivery pipe 20 at its outlet end and a second desorption gas delivery pipe 14 at its outlet end. Each molecular sieve adsorption tank 13 has a third delivery pipe 21 at its outlet end and a fourth delivery pipe 22 at its inlet end. The inlet end of each third delivery pipe 21 is connected to the outlet end of a second purge gas delivery pipe 23, and the outlet end of each fourth delivery pipe 22 is connected to the inlet end of a third desorption gas delivery pipe 24. An online chromatograph 25 is installed on each of the second purge gas delivery pipe 23, the third desorption gas delivery pipe 24, and the first purge gas delivery pipe 12. The installation of the online chromatograph 25 facilitates the feedback of component parameters. Each of the several first conveying pipes 19, several second conveying pipes 20, several third conveying pipes 21, and several fourth conveying pipes 22 is equipped with a shut-off valve 26. A first temperature sensor 27 is installed on the second desorption gas conveying pipe 14 between the first heat exchanger 6 and the electric heater 15, and a second temperature sensor 28 is installed on the second desorption gas conveying pipe 14 between the electric heater 15 and the molecular sieve adsorption tank 13. Both the first temperature sensor 27 and the second temperature sensor 28 are for facilitating the feedback of temperature parameters.

[0020] The liquid nitrogen temporary storage tank 10 has an inlet end of a first liquid nitrogen delivery pipe 29 at its bottom. A second regulating valve 30 is installed on the first liquid nitrogen delivery pipe 29. A second liquid nitrogen delivery pipe 31 is installed on the first liquid nitrogen delivery pipe 29 between the second regulating valve 30 and the liquid nitrogen temporary storage tank 10. The outlet end of the first venting gas delivery pipe 12 has an inlet end of a heat source channel for a bottom heater 32. A first distillation column is installed on the cold source channel of the bottom heater 32. The outlet end of the heat source channel of the bottom heater 32 is connected to the main heat exchanger. The heater 11 is provided with a fourth venting gas delivery pipe 33. A second distillation column is provided at the outlet end of the fourth venting gas delivery pipe 33. The outlet end of the first liquid nitrogen delivery pipe 29 is connected to the top of the second distillation column. The top of the first distillation column is connected to the outlet end of the second liquid nitrogen delivery pipe 31. The top of the second distillation column and the first distillation column are connected through a liquid phase delivery pipe 34. A third regulating valve 35 is provided on both the liquid phase delivery pipe 34 and the second liquid nitrogen delivery pipe 31. The first distillation column includes a first column body 36 and a first packing layer 37 and a second packing layer 38 arranged sequentially from top to bottom within the first column body 36; the outlet end of the first column body 36 between the first packing layer 37 and the second packing layer 38 is connected to the liquid phase delivery pipe 34, and the outlet end of the second liquid nitrogen delivery pipe 31 is connected to the first column body 36 above the first packing layer 37; the second distillation column includes a second column body 39 and a third packing layer 40 arranged within the second column body 39; the outlet end of the first liquid nitrogen delivery pipe 29 is connected to the second column body 39 above the third packing layer 40, and the outlet end of the fourth venting gas delivery pipe 33 is connected to the second column body 39 below the third packing layer 40.

[0021] A hydrogen-rich nitrogen gas delivery pipe 41 is installed at the top of the second tower body 39 and on the main heat exchanger 11. A second nitrogen gas delivery main pipe 42 is installed at the top of the first tower body 36 and on the main heat exchanger 11. A liquefied methane delivery pipe 43 is installed at the bottom end of the cold source channel of the bottom heater 32. An undercooler 44 is installed on the second nitrogen gas delivery main pipe 42 and the liquefied methane delivery pipe 43 between the first tower body 36 and the main heat exchanger 11. A fourth regulating valve 45 is installed on the liquefied methane delivery pipe 43. Liquid level sensors 46 are installed in the second tower body 39 below the third packing layer 40, the liquid nitrogen temporary storage tank 10, and the cold source channel of the bottom heater 32. The installation of liquid level sensors 46 facilitates the feedback of liquid level parameters.

[0022] The usage instructions for this product are as follows: Figure 1 As shown, it includes the following steps: S1. The purge gas emitted from the synthetic ammonia production system is transported to the second purge gas transport pipe 23, and then to the molecular sieve adsorption tank 13 which is in operation. After the molecular sieve layer in the molecular sieve adsorption tank 13 adsorbs moisture, it is transported to the first purge gas transport pipe 12. After heat exchange with the first heat source channel of the main heat exchanger 11 and the cold source continuously supplied to the main heat exchanger 11, it is transported to the heat source channel of the bottom heater 32 and the cold source channel continuously supplied to the bottom heater 32. After heat exchange with the medium, it is transported to the second distillation column as the distillation feed of the second distillation column.

[0023] Meanwhile, the low-pressure nitrogen pipeline continuously supplies low-pressure nitrogen to the first nitrogen supply main pipe 1. The low-pressure nitrogen is pressurized sequentially by the nitrogen compressor unit 4 and the pressurization end of the turbine expander 5. It is first supplied to the heat source channel of the first machine rear heat exchanger 6 and continuously supplied to the cold source of the first machine rear heat exchanger 6 for heat exchange. Then it is supplied to the heat source channel of the second machine rear heat exchanger 7 and continuously supplied to the cold source of the second machine rear heat exchanger 7 for heat exchange. It is then divided into two parts, namely the first part of pressurized nitrogen and the second part of pressurized nitrogen. The first part of pressurized nitrogen is supplied to the expansion end of the turbine expander 5 through the first nitrogen supply branch pipe 8 for expansion and cooling to form refrigerated nitrogen. Then the refrigerated nitrogen is supplied to the refrigeration gas supply pipe 3, which passes through the second cold source channel of the main heat exchanger 11 and continuously supplied to the heat source of the main heat exchanger 11 for heat exchange. After heat exchange, it is sent back to the first nitrogen supply main pipe 1 through the outlet end of the refrigeration gas supply pipe 3 to form a refrigeration cycle. The second portion of pressurized nitrogen is transported via the second nitrogen delivery branch pipe 9 to the second cold source channel of the main heat exchanger 11 and continuously supplied to the main heat exchanger 11 for heat exchange, forming liquid nitrogen, which is then transported to the liquid nitrogen temporary storage tank 10 for temporary storage.

[0024] S2. The liquid nitrogen temporary storage tank 10 delivers liquid nitrogen to the outside through the first liquid nitrogen delivery pipe 29 and divides it into two parts, namely the first part of liquid nitrogen and the second part of liquid nitrogen. The first part of liquid nitrogen is delivered to the second distillation column through the outlet end of the first liquid nitrogen delivery pipe 29 as the first reflux condensate of the second distillation column. The second part of liquid nitrogen is delivered to the first distillation column through the outlet ends of the first liquid nitrogen delivery pipe 29 and the second liquid nitrogen delivery pipe 31 as the second reflux condensate of the first distillation column.

[0025] Simultaneously, the purge gas enters the second distillation column, forming a first upward flow. This first upward flow and the first reflux condensate of the second distillation column undergo a countercurrent heat exchange. The methane component in the first upward flow is liquefied and merges into the first reflux condensate, forming a first downward flow. This downward flow accumulates at the bottom of the second distillation column, forming a methane-rich liquid nitrogen layer. This layer is then transported to the second distillation column via liquid phase delivery pipe 34 as the third reflux condensate of the first distillation column. The first upward flow continues to rise, eventually forming a hydrogen-rich nitrogen enrichment zone at the top of the second distillation column. This enrichment zone continuously supplies hydrogen-rich nitrogen to the hydrogen-rich nitrogen delivery pipe 41. After heat exchange with the third cold source channel of the main heat exchanger 11 and the continuously supplied heat source, the hydrogen-rich nitrogen is then transported via the hydrogen-rich nitrogen delivery pipe 41 to the gas distribution system of the ammonia synthesis tower as one of the feed gases for ammonia synthesis.

[0026] S3. The third reflux condensate continuously flows downwards, forming a descending liquid flow and accumulating in the cold source channel of the bottom heater 32. The methane-rich liquid nitrogen in the cold source channel of the bottom heater 32 exchanges heat with the heat source channel of the bottom heater 32 to form a second upward gas flow. This second upward gas flow ascends along the second distillation column, first exchanging heat counter-currently with the third reflux condensate of the first distillation column, and then with the second reflux condensate of the first distillation column. During the upward flow of the second upward gas flow, the methane component in the second upward gas flow is continuously liquefied and merged into the continuously descending third reflux condensate and the second reflux condensate. The second reflux condensate continues to descend and merges into the third reflux condensate, ultimately forming the second descending liquid flow of the first distillation column, which is then delivered to the cold source channel of the bottom heater 32. Finally, a nitrogen-rich zone is formed at the top of the first distillation column, and a methane-rich zone is formed in the cold source channel of the bottom heater 32.

[0027] The nitrogen enrichment zone continuously supplies nitrogen to the second nitrogen delivery main pipe 42. After passing through the cold source channel of the subcooler 44 and the heat source continuously supplied to the subcooler 44 for heat exchange, the nitrogen is then supplied to the fourth cold source channel of the main heat exchanger 11 and the heat source continuously supplied to the main heat exchanger 11 for heat exchange. Finally, the nitrogen is delivered to the low-pressure nitrogen pipeline network through the second nitrogen delivery main pipe 42.

[0028] The methane in the methane enrichment zone is transported to the liquefied methane transport pipe 43. After heat exchange with the heat source channel of the cooler 44 and the cold source continuously transported to the subcooler 44, it forms subcooled liquid methane. The subcooled liquid methane is transported to the corresponding container through the outlet end of the liquefied methane transport pipe 43 and sold as a liquid methane by-product.

[0029] During steps S1 to S3, when the molecular sieve adsorption tank 13 in working condition reaches the preset time or when the parameters fed back by the online chromatograph 25 on the first venting gas delivery pipe 12 are abnormal, it is necessary to switch the molecular sieve adsorption tank 13. Specifically, the molecular sieve adsorption tank 13 in standby condition is connected between the second venting gas delivery pipe 23 and the first venting gas delivery pipe 12, while the molecular sieve adsorption tank 13 originally in working condition needs to be disconnected from the second venting gas delivery pipe 23 and the first venting gas delivery pipe 12. At this time, the molecular sieve adsorption tank 13 originally in working condition is now in a state of waiting for desorption, and the molecular sieve adsorption tank 13 originally in standby condition is now in working condition. The molecular sieve adsorption tank 13 in the state of waiting for desorption needs to be regenerated before it can be put back into use. The specific molecular sieve regeneration process includes the following steps: Open the fifth regulating valve 47 on the first desorption gas delivery pipe 2. A portion of the nitrogen gas delivered in the first nitrogen delivery pipe 1 is diverted into the first desorption gas delivery pipe 2 as desorption gas. The desorption gas enters the cold source channel of the first machine heat exchanger 6 through the first desorption gas delivery pipe 2 and undergoes countercurrent heat exchange with the heat source continuously supplied to the first machine heat exchanger 6. After passing through the cold source channel of the first machine heat exchanger 6, the desorption gas completes the first stage of heating. After the temperature parameter is fed back by the first temperature sensor 27, it is sent to the electric heater 15 for the second stage of heating. After the temperature parameter is fed back by the second temperature sensor 28, it is sent to the molecular sieve adsorption tank 13 in the desorption state. Finally, it is emptied through the third desorption gas delivery pipe 24. When the parameter fed back by the online chromatograph 25 on the third desorption gas delivery pipe 24 reaches the preset range, close the fifth regulating valve 47 on the first desorption gas delivery pipe 2 and the electric heater 15. At this time, the molecular sieve adsorption tank 13 in the desorption state is converted back to the standby state.

[0030] In this embodiment, a portion of the low-pressure nitrogen supplied by the first nitrogen supply pipe 1 is diverted as desorption gas. The desorption gas undergoes countercurrent heat exchange through the cold source channel of the first machine post-heat exchanger 6 and the heat source continuously supplied to the first machine post-heat exchanger 6 to complete the first stage of heating of the desorption gas. Then it is supplied to the electric heater 15 to complete the second stage of heating of the desorption gas. This reduces the temperature range of the electric heater 15 for heating the desorption gas, thus reducing the energy consumption of the electric heater 15 in the process of heating the desorption gas.

[0031] The embodiments described above are merely preferred embodiments of this utility model and are not intended to limit the scope of implementation of this utility model. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the patent claims of this utility model should be included within the scope of the patent application of this utility model.

Claims

1. A cryogenic distillation apparatus for ammonia synthesis off-gas, characterized in that: The system includes a first nitrogen delivery main pipe (1), which is provided with the following components in sequence along its length from inlet to outlet: the inlet of a first desorption gas delivery pipe (2), the outlet of a refrigerant delivery pipe (3), a nitrogen compressor unit (4), the booster end of a turbine expander (5), the heat source channel of a first downstream heat exchanger (6), the heat source channel of a second downstream heat exchanger (7), the inlet of a first nitrogen delivery branch pipe (8), and the inlet of a second nitrogen delivery branch pipe (9). A liquid nitrogen storage tank (10) is provided at the outlet of the second nitrogen delivery branch pipe (9). The outlet of the first nitrogen delivery branch pipe (8) is connected to the expansion inlet of the turbine expander (5). The expansion end outlet is connected to the inlet end of the refrigerant gas delivery pipe (3). The first nitrogen delivery branch pipe (8), the second nitrogen delivery branch pipe (9) and the refrigerant gas delivery pipe (3) are equipped with a main heat exchanger (11). The main heat exchanger (11) is equipped with a first venting gas delivery pipe (12). The inlet end of the first venting gas delivery pipe (12) is connected to a molecular sieve adsorption tank (13). The outlet end of the first desorption gas delivery pipe (2) is connected to the inlet end of the cold source channel of the first machine rear heat exchanger (6). The outlet end of the cold source channel of the first machine rear heat exchanger (6) is equipped with the inlet end of the second desorption gas delivery pipe (14). The second desorption gas delivery pipe (14) is equipped with an electric heater (15). The outlet end of the second desorption gas delivery pipe (14) is connected to the molecular sieve adsorption tank (13).

2. The cryogenic distillation apparatus for synthetic ammonia off-gas according to claim 1, characterized in that: The expansion end of the turbo expander (5) and the main heat exchanger (11) are connected to the top of the liquid nitrogen storage tank (10) via a pressure relief pipe (16). The pressure relief pipe (16) is provided with a pressure sensor (17) and a first regulating valve (18) in sequence along the direction from near the liquid nitrogen storage tank (10) to away from the liquid nitrogen storage tank (10).

3. The cryogenic distillation apparatus for synthetic ammonia off-gas according to claim 1, characterized in that: The number of molecular sieve adsorption tanks (13) is several. Each molecular sieve adsorption tank (13) is provided with a first conveying pipe (19) at the outlet end and the inlet end of the first purge gas conveying pipe (12). Each molecular sieve adsorption tank (13) is provided with a second conveying pipe (20) at the outlet end and the outlet end of the second desorption gas conveying pipe (14). Each molecular sieve adsorption tank (13) is provided with an outlet end of a third conveying pipe (21) and an inlet end of a fourth conveying pipe (22) at the inlet end. The outlet end of the second purge gas conveying pipe (23) is provided at the inlet end of the third conveying pipe (21), and the inlet end of the third desorption gas conveying pipe (24) is provided at the outlet end of the fourth conveying pipe (22).

4. The cryogenic distillation apparatus for synthetic ammonia off-gas according to claim 1, characterized in that: The bottom of the liquid nitrogen temporary storage tank (10) is provided with the inlet end of the first liquid nitrogen delivery pipe (29). A second regulating valve (30) is provided on the first liquid nitrogen delivery pipe (29). A second liquid nitrogen delivery pipe (31) is provided on the first liquid nitrogen delivery pipe (29) between the second regulating valve (30) and the liquid nitrogen temporary storage tank (10). The outlet end of the first venting gas delivery pipe (12) is provided with the inlet end of the heat source channel of the bottom heater (32). A first distillation column is provided on the cold source channel of the bottom heater (32). The outlet end of the heat source channel of the bottom heater (32) is provided with the first distillation column. A fourth venting pipe (33) is provided on the main heat exchanger (11). A second distillation column is provided at the outlet end of the fourth venting pipe (33). The outlet end of the first liquid nitrogen pipe (29) is connected to the top of the second distillation column. The top of the first distillation column is connected to the outlet end of the second liquid nitrogen pipe (31). The top of the second distillation column is connected to the first distillation column through a liquid phase pipe (34). A third regulating valve (35) is provided on both the liquid phase pipe (34) and the second liquid nitrogen pipe (31).

5. The cryogenic distillation apparatus for ammonia synthesis off-gas according to claim 4, characterized in that: The first distillation column includes a first column body (36) and a first packing layer (37) and a second packing layer (38) arranged sequentially from top to bottom within the first column body (36); the outlet end of the first column body (36) between the first packing layer (37) and the second packing layer (38) is connected to the liquid phase conveying pipe (34), and the outlet end of the second liquid nitrogen conveying pipe (31) is connected to the first column body (36) above the first packing layer (37); the second distillation column includes a second column body (39) and a third packing layer (40) arranged within the second column body (39), the outlet end of the first liquid nitrogen conveying pipe (29) is connected to the second column body (39) above the third packing layer (40), and the outlet end of the fourth venting gas conveying pipe (33) is connected to the second column body (39) below the third packing layer (40).

6. The cryogenic distillation apparatus for synthetic ammonia off-gas according to claim 5, characterized in that: The top of the second tower body (39) and the main heat exchanger (11) are provided with a hydrogen-rich nitrogen gas delivery pipe (41), the top of the first tower body (36) and the main heat exchanger (11) are provided with a second nitrogen gas delivery main pipe (42), the bottom of the cold source channel of the bottom heater (32) is provided with a liquefied methane delivery pipe (43), the second nitrogen gas delivery main pipe (42) and the liquefied methane delivery pipe (43) between the first tower body (36) and the main heat exchanger (11) are provided with a supercooler (44), and the liquefied methane delivery pipe (43) is provided with a fourth regulating valve (45).

7. The cryogenic distillation apparatus for ammonia synthesis off-gas according to claim 5, characterized in that: The second tower body (39), liquid nitrogen temporary storage tank (10), and cold source channel of the bottom heater (32) below the third packing layer (40) are all equipped with liquid level sensors (46).

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