CN116239127B - Synthetic ammonia hot standby process and synthetic tower - Google Patents

Abstract

The present invention relates to the technical field of ammonia synthesis and preparation, and specifically to a synthetic ammonia hot standby process and a synthetic tower. The structure of the synthetic tower is optimized and designed, and the temperature inside the synthetic tower can be independently controlled by an outer hot standby layer and an inner hot standby layer to achieve hot standby of the synthetic tower. The hot standby process provided by the present invention can keep the temperature inside the synthetic tower uniform and above the activation temperature of the catalyst in an ammonia production system that is frequently stopped. When it is necessary to start ammonia production, it can quickly reach the ammonia production condition and enter the ammonia production operation, which greatly improves the efficiency of restarting after stopping, and improves the efficiency and flexibility of starting the synthetic ammonia system; avoids the cyclic heating of the entire synthetic ammonia system, and reduces the energy consumption of hot standby.

Description

A synthetic ammonia hot standby process and synthesis tower

Technical Field

The invention relates to the technical field of synthetic preparation of ammonia, and in particular to a synthetic ammonia hot standby process and a synthetic tower.

Background Art

During the shutdown of the synthetic ammonia unit, the system temperature and pressure will drop. Each restart will take several hours or even days to increase the temperature and pressure, reducing the effective operation time of the unit. In order to shorten the restart time, it is necessary to put the ammonia synthesis tower in hot standby state.

When a traditional ammonia synthesis unit is shut down and then restarted, it is necessary to start the circulating gas compressor and the heating furnace to heat the entire synthesis loop in series. The gas in the loop must be heated to above 350°C by the heating furnace before entering the synthesis tower; after leaving the synthesis tower, the gas must be cooled to about 40°C before entering the circulating gas compressor for pressure increase. With one cold and one hot, the system consumes a lot of energy and lasts for a long time.

It can be seen that the existing hot standby technology of synthetic ammonia equipment still has room for improvement. It needs to be adjusted and optimized to improve the efficiency of hot standby and reduce the time of restarting after stopping, so as to improve the production efficiency of synthetic ammonia. Therefore, it is necessary to propose a more reasonable technical solution to solve the technical problems existing in the existing technology.

Summary of the invention

In order to overcome at least one of the above-mentioned defects, the present invention proposes a synthetic ammonia hot standby process and a synthesis tower. By optimizing the equipment structure, the synthetic ammonia hot standby process is simplified, the temperature in the synthesis tower is maintained higher than the catalyst activation temperature, and the energy consumption is only the heat loss of the synthesis tower, which facilitates the rapid restart of the device to resume production. The process does not require the entire synthesis loop to be connected in series for hot standby, which greatly saves start-up time and energy consumption compared to traditional processes.

In order to achieve the above purpose, the hot standby process disclosed in the present invention can adopt the following technical solutions:

A synthetic ammonia hot standby process, comprising:

Stop introducing hydrogen into the synthesis tower, and continue introducing nitrogen into the synthesis tower, while controlling the amount of vented air to maintain the gas flow and pressure stability inside the synthesis tower;

Determine the activation temperature required for the catalyst of synthetic ammonia, and set a temperature value higher than the activation temperature as the hot standby temperature;

A heating structure is arranged inside the synthesis tower, the heating structure includes an outer heating layer for heating the inner wall surface of the synthesis tower, and an inner heating layer for heating the reaction bed layer inside the synthesis tower, the outer heating layer and the inner heating layer work together to maintain the temperature balance inside the synthesis tower;

Monitor the temperature inside the synthesis tower and issue an alarm when the temperature inside the synthesis tower is lower than the catalyst activation temperature.

The above disclosed hot standby process can be used for heating the synthesis tower under cold start-up conditions, and can also be used for heat preservation of the synthesis tower during shutdown or low-load operation. By continuously introducing nitrogen and venting with a small amount of controlled volume, the air flow and air pressure inside the synthesis tower are kept stable, and the temperature inside the synthesis tower can be kept balanced. When the synthesis tower is hot-standby, the heating structure makes the internal ambient temperature and catalyst bed temperature reach the hot standby temperature value, meeting the temperature required for catalyst activation, facilitating the subsequent rapid start-up operation, improving the startup efficiency of the ammonia synthesis process, and reducing the delay caused by frequent start-up and shutdown on the effective production time.

Furthermore, in the present invention, the function of the external heating layer is to perform heating and heat preservation, and its specific working mode is not limited to a single one. Here, an optimization is made and one feasible option is proposed: the external heating layer envelops the inner wall surface of the synthesis tower, and radiates heat from the inner wall surface to the interior of the synthesis tower to maintain the temperature by heating. When such a scheme is adopted, the external heating layer can be heated by an electric heating belt or other structures to form a surface, and the interior of the synthesis tower is uniformly and synchronously heated by the circumferential heating structure.

Furthermore, the setting mode and position of the inner heating layer are different from those of the outer heating layer, and are not limited to a single one. In the present invention, optimization is performed and one feasible option is proposed: the inner heating layer is arranged inside the reaction bed layer and bends and extends inside the reaction bed layer to envelop the reaction bed layer structure, and the inner heating layer directly radiates heat to the inner space of the synthesis tower to heat and maintain the temperature. When such a solution is adopted, the inner heating layer is heated inside the reaction bed layer, so that the internal temperature of the reaction bed layer can be increased and maintained, achieving the purpose of hot standby, and the start-up can be completed quickly when it is necessary to start up.

Furthermore, in order to improve the effect of hot standby, or improve the efficiency of hot standby, and realize the start-up switch faster, optimization is performed here and one of the feasible options is proposed: a heating structure and a heat exchange structure are set in the middle of the synthesis tower, and when hot standby is required, the heating structure and the heat exchange structure are always kept in the open working state. When such a scheme is adopted, the heating structure and the heat exchange structure can adopt the structure originally used for gas heating and heat exchange in the synthesis tower, which is not only used for preheating and heat exchange during the cold start-up and normal operation of synthetic ammonia, but also can play an auxiliary role in the hot standby process, improving the effect and efficiency of hot standby.

Furthermore, in the present invention, the electric heater structure and the heat exchanger structure used for heating are not limited to a single one. Here, an optimization is performed and one feasible option is proposed: the heating structure includes an electric heater, and the heat exchange structure includes a plurality of heat exchangers. The electric heater and the heat exchanger preheat the nitrogen entering the synthesis tower to raise the temperature so that the nitrogen reaches the hot standby temperature. When such a scheme is adopted, the electric heater can adopt a structure such as an electric heating tube and an electric heating wire, and generate heat after being energized to increase the temperature inside the synthesis tower.

The above content discloses the content of the hot standby process. The present invention also discloses a synthesis tower for hot standby, which is specifically described here.

A synthesis tower for hot standby comprises a closed tower body, an inner shell is arranged in the tower body, and a shell gap is formed between the inner shell and the tower body; a plurality of reaction beds are arranged in sequence in the longitudinal direction in the inner shell, and adjacent reaction beds are connected to form a unidirectional airflow passage; a plurality of reaction gas inlets and cold shock gas inlets are arranged on the tower body, which are used to guide the reaction gas and the cold shock gas to enter the airflow passage after mixing; an outer heating layer is arranged in the shell gap, an inner heating layer is extended inside the reaction bed layer, and a heating structure and a heat exchange structure are arranged in the inner shell to exchange heat for the reaction gas, and the reaction gas passing through the heating structure and the heat exchange structure enters the airflow passage; a reaction gas outlet is also arranged on the tower body, and the reaction gas outlet is connected to the airflow passage and used to discharge the reacted gas.

The above-disclosed synthesis tower can be introduced with reaction gas during the normal production process of synthetic ammonia, and the internal reaction bed layer is used to realize the synthetic preparation of ammonia. Under this working condition, the external heating layer and the internal heating layer are not started; in the hot standby state after parking, the composition of the air flow introduced is adjusted, and at the same time, a certain flow rate is maintained for continuous venting, and only nitrogen is introduced to maintain the internal air flow and air pressure, and the internal heating layer and the external heating layer are turned on for heating, so as to realize the hot standby of the synthesis tower and facilitate the rapid start-up of the ammonia synthesis work.

Furthermore, in the present invention, the heating structure of the synthesis tower is optimized and one feasible option is proposed: the outer heating layer includes a plurality of electric heating cables evenly arranged along the inner wall of the synthesis tower; the inner heating layer includes a plurality of electric furnace wires spirally wound at least in the uppermost reaction bed layer. When such a solution is adopted, the uppermost reaction bed layer is heated, and the temperature can be uniformly changed under the flow of internal nitrogen.

Furthermore, in the present invention, the scheme that the heating structure can adopt is not limited to a single one, and the interior of the synthesis tower can be heated by a variety of structures. Here, optimization is performed and one feasible option is proposed: a preheating tube is provided in the inner shell, the heating structure includes an electric heater extending to the interior of the preheating tube, at least one reaction gas inlet introduces the reaction gas into the preheating tube and preheats it through the heating structure; the heat exchange structure includes a heat exchanger provided at the reaction bed layer, the heat exchanger connects the airflow path and adjusts the temperature of the internal airflow. When such a scheme is adopted, the heat exchanger can preheat the reaction gas entering the synthesis tower for the first time, and heat exchange and heat up the reaction gas passing through the reaction bed layer, so that the reaction gas reaches the temperature required for synthesizing ammonia; when in the hot standby state, the heat exchanger can heat and heat up the nitrogen to increase the temperature of the nitrogen inside the synthesis tower, and promote the hot standby.

Furthermore, in the present invention, the reaction gas can be introduced into the synthesis tower from different positions and used for ammonia synthesis or for hot standby process. The reaction gas inlet provided on the synthesis tower is used for air intake. The specific number and position are not limited to a single one. Here, optimization is made and one feasible option is proposed: the number of the reaction gas inlets is at least two, and one of the reaction gas inlets guides the reaction gas longitudinally from the middle of the synthesis tower into the preheating tube for preheating and mixing with other reaction gases and cold shock gas; the other reaction gas inlet guides the reaction gas into the shell gap and exchanges heat from the heating structure and mixes with other reaction gases and cold shock gas. When such a scheme is adopted, the reaction gas longitudinally entering the preheating tube from the middle is fully preheated, the temperature is quickly increased and reaches the temperature of synthetic ammonia or the hot standby temperature; the reaction gas entering from the shell gap can also absorb a certain amount of heat and heat up, and the reaction gas entering from the two paths is mixed before entering the reaction bed, and after entering the reaction bed, the corresponding ammonia synthesis reaction occurs or it is only circulated as hot standby gas.

Furthermore, the structures of the reaction bed and the heat exchanger are not limited to a single one, and can be set in a variety of forms to meet the circulation and heat exchange requirements of the airflow. Here, the optimization is carried out and a feasible option is proposed as follows: the reaction bed includes an annular catalyst bed, the heat exchanger is arranged in the middle of the catalyst bed, and the heat exchanger is constructed in an annular shape, the preheating tube passes through the middle hole of the heat exchanger, and the gas inside and outside the heat exchange tube of the heat exchanger exchanges heat, the inlet gas in the tube is preheated, and the reaction gas outside the tube is cooled. When such a scheme is adopted, the outer side of the reaction bed is tightly attached to and sealed with the inner side wall of the inner shell, so that the space between two adjacent reaction beds is closed, and the airflow can only flow in a directional manner through the airflow passage.

Compared with the prior art, some beneficial effects of the technical solution disclosed in the present invention include:

The hot standby process provided by the present invention can keep the temperature inside the synthesis tower uniform and above the activation temperature of the catalyst in an ammonia production system that is frequently shut down. When it is necessary to start ammonia production, it can quickly reach the ammonia production condition and enter the ammonia production operation, which greatly improves the efficiency of restarting after shutdown, and improves the efficiency and flexibility of starting ammonia production; it avoids the need for the entire ammonia production system to remain in hot standby, and reduces the energy consumption of hot standby.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only represent some embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

Figure 1 is a schematic diagram of the synthetic ammonia hot standby process.

FIG. 2 is a schematic diagram of the internal structure of a synthesis tower (in this figure, the reaction gas inlet is located at the lower part of the tower body).

FIG. 3 is a schematic diagram of the internal structure of a synthesis tower (in this figure, the reaction gas inlet is located at the lower and upper parts of the tower body).

FIG. 4 is a schematic diagram of the internal structure of a synthesis tower (in this figure, the reaction gas inlet is located at the lower part and the top of the tower body).

In the above drawings, the meanings of the reference numerals are as follows:

1. Tower body; 2. Inner shell; 3. External heating layer; 4. Internal heating layer; 5. Reaction bed; 6. Heat exchanger; 7. Electric heater; 8. Cold shock gas inlet; 9. Thermocouple; 10. Reaction gas inlet; 11. Reaction gas outlet; 12. Preheating tube.

DETAILED DESCRIPTION

The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments.

In the existing ammonia synthesis process, hot standby is required to maintain the temperature environment in the synthesis tower to facilitate the resumption of production when frequent shutdowns occur. The existing technology has the problems of high energy consumption and low efficiency. The following embodiments are optimized to overcome the defects in the existing technology.

Example 1

As shown in FIG1 , this embodiment provides a synthetic ammonia hot standby process, which is used for a synthetic ammonia system that is frequently shut down or a synthetic ammonia system that needs to be shut down for a long time. The specific process includes:

S01: Stop introducing hydrogen into the synthesis tower and continue to introduce nitrogen into the synthesis tower, while controlling the venting volume to maintain the gas flow and gas pressure inside the synthesis tower stable.

Preferably, when nitrogen is introduced, it can be introduced through multiple air intakes so that the nitrogen can circulate in the synthesis tower to maintain a balanced temperature in the synthesis tower; a certain flow rate of gas is released outward to meet the demand for air circulation in the synthesis tower and maintain uniform temperature transfer.

S02: Determine the activation temperature required for the catalyst for synthesizing ammonia, and set a temperature value higher than the activation temperature as a hot standby temperature.

Preferably, the hot standby temperature is generally set to 350° C., and the reaction bed 5 is allowed to reach this temperature. When the reaction bed 5 reaches the hot standby temperature, its temperature can be maintained by intermittent heating.

S03: A heating structure is arranged inside the synthesis tower, and the heating structure comprises an outer heating layer 3 for heating the inner shell wall of the synthesis tower, and an inner heating layer 4 for heating the reaction bed layer 5 inside the synthesis tower. The outer heating layer 3 and the inner heating layer 4 work together to maintain the temperature balance inside the synthesis tower.

Preferably, in this embodiment, the function of the external heating layer 3 is to perform heating and heat preservation, and its specific working mode is not limited to a single one. Here, an optimization is performed and one of the feasible options is adopted: the external heating layer 3 envelops the inner shell wall of the synthesis tower, and radiates heat from the inner shell wall to the reaction bed inside the synthesis tower to maintain the temperature. When such a scheme is adopted, the external heating layer 3 can be heated by an electric heating belt or other structures to form a surface, and the internal reaction bed of the synthesis tower is uniformly and synchronously heated through the entire circumferential surface heating structure to maintain the temperature of the reaction bed.

The setting mode and position of the inner heating layer 4 are different from those of the outer heating layer 3, and are not limited to the only one. In this embodiment, optimization is performed and one feasible option is proposed: the inner heating layer 4 is arranged inside the reaction bed layer 5 and bends and extends inside the reaction bed layer 5 to envelop the structure of the reaction bed layer 5, and the inner heating layer directly radiates heat to the inner space of the synthesis tower to heat and maintain the temperature. When such a scheme is adopted, the inner heating layer 4 is heated inside the reaction bed layer 5, so that the internal temperature of the reaction bed layer 5 can be increased and maintained, achieving the purpose of hot standby, and the start-up can be completed quickly when it is necessary to start up.

Preferably, in order to improve the effect of hot standby, or to improve the efficiency of hot standby, and to realize the start-up switch faster, this embodiment is optimized and adopts one of the feasible options: a heating structure and a heat exchange structure are arranged in the middle of the synthesis tower, and when hot standby is required, the heating structure and the heat tracing structure are always kept in the open working state. When such a scheme is adopted, the heating structure and the heat exchange structure can adopt the structure originally used for gas heating and heat exchange in the synthesis tower, which is not only used for preheating and heat exchange during the cold start-up and normal operation of synthetic ammonia, but also can play an auxiliary role in the hot standby process, thereby improving the effect and efficiency of hot standby.

In this embodiment, the structure of the electric heater 7 and the heat exchanger 6 used for heating are not limited to a single one. This embodiment is optimized and adopts one of the feasible options: the heating structure includes the electric heater 7, and the heat exchange structure includes a plurality of heat exchangers 6. The electric heater 7 and the heat exchanger 6 preheat the nitrogen entering the synthesis tower to make the nitrogen reach the hot standby temperature. When such a scheme is adopted, the electric heater 7 can adopt a structure such as an electric heating tube and an electric heating wire, and heats and generates heat after being powered on, so that the temperature inside the synthesis tower can be increased.

S04: Monitor the temperature inside the synthesis tower and issue an alarm when the temperature inside the synthesis tower is lower than the catalyst activation temperature.

Preferably, a variety of methods can be used to monitor and alarm the internal temperature of the synthesis tower. When the temperature inside the synthesis tower does not reach the hot standby temperature, a prompt is given, and when it is lower than the activation temperature, an alarm is given. At the same time, when the temperature inside the synthesis tower reaches the hot standby temperature, a prompt is given, and when it exceeds the set temperature upper limit, an alarm is given.

The above disclosed hot standby process can be used for heating the synthesis tower under cold start-up conditions, and can also be used for heat preservation of the synthesis tower during shutdown or low-load operation. By continuously introducing nitrogen and venting with a small amount of controlled volume, the air flow and air pressure inside the synthesis tower are kept stable, and the temperature inside the synthesis tower can be kept balanced. When the synthesis tower is hot-standby, the heat tracing structure makes the internal ambient temperature and the temperature of the reaction bed 5 reach the hot standby temperature value, meeting the temperature required for catalyst activation, facilitating the subsequent rapid start-up operation, improving the startup efficiency of the ammonia synthesis process, and reducing the delay effect of frequent start-up and shutdown on the effective production time.

Example 2

The content of the above-mentioned Example 1 discloses the content of the hot standby process. This example discloses a synthesis tower used for hot standby, which is described in detail here.

As shown in FIG. 2 , a synthesis tower for hot standby comprises a closed tower body 1, wherein an inner shell 2 is arranged in the tower body 1, and a shell gap is formed between the inner shell 2 and the tower body 1; a plurality of reaction beds 5 are arranged in sequence in the longitudinal direction in the inner shell 2, and adjacent reaction beds 5 are connected to form a unidirectional airflow passage; a plurality of reaction gas inlets 10 and cold shock gas inlets 8 are arranged on the tower body 1, which are used to guide the reaction gas and the cold shock gas to mix and enter the airflow passage; an outer heating layer 3 is arranged in the shell gap, an inner heating layer 4 is extended inside the reaction bed 5, and a heating structure and a heat exchange structure are arranged in the inner shell 2 to exchange heat with the reaction gas, and the reaction gas passing through the heating structure and the heat exchange structure enters the airflow passage; a reaction gas outlet 11 is also arranged on the tower body 1, and the reaction gas outlet 11 is connected to the airflow passage and used to discharge the reacted gas.

Preferably, the tower body 1 in this embodiment is configured as a cylindrical structure, and the inner shell 2 inside is also a cylindrical structure, and the inner shell 2 and the side wall of the tower body 1 form an annular shell gap.

The above-disclosed synthesis tower can be introduced with reaction gas during the normal production of synthetic ammonia, and the internal reaction bed layer 5 is used to realize the synthetic preparation of ammonia. Under this working condition, the external heating layer 3 and the internal heating layer 4 are not started; in the hot standby state after parking, the composition of the air flow introduced is adjusted, and at the same time, a certain flow rate is maintained for continuous venting, and only nitrogen is introduced to maintain the internal air flow and air pressure, and the internal heating layer and the external heating layer are turned on for heating, so as to realize the hot standby of the synthesis tower and facilitate the rapid start-up of the ammonia synthesis work.

In this embodiment, the heating structure of the synthesis tower is optimized and one feasible option is proposed: the outer heating layer 3 includes a plurality of electric heating cables evenly arranged along the inner wall of the synthesis tower; the inner heating layer 4 includes a plurality of electric furnace wires spirally wound at least in the uppermost reaction bed layer 5. When such a solution is adopted, the uppermost reaction bed layer 5 is heated, and a uniform temperature change can be achieved under the flow of internal nitrogen.

Preferably, the outer heating layer 3 is heated by an electric heating tape, and the inner heating layer 4 is heated by a catalyst heating wire. A controller for controlling the start and stop of the outer heating layer 3 and the inner heating layer 4 is arranged on the surface of the tower body 1 .

In this embodiment, the scheme that the heating structure can adopt is not limited to a single one, and the interior of the synthesis tower can be heated by a variety of structures. Here, optimization is performed and one of the feasible options is adopted: the inner shell 2 is provided with a preheating tube 12, the heating structure includes an electric heater 7 extending into the interior of the preheating tube 12, at least one reaction gas inlet 10 introduces the reaction gas into the preheating tube 12 and preheats it through the heating structure; the heat exchange structure includes a heat exchanger 6 arranged at the reaction bed 5, the heat exchanger 6 is connected to the air flow path and adjusts the temperature of the internal air flow. When such a scheme is adopted, the electric heater 7 can preheat the reaction gas entering the synthesis tower for the first time, and exchange heat with the reaction gas passing through the reaction bed 5 to increase the temperature, so that the reaction gas reaches the temperature required for synthesizing ammonia; when in the hot standby state, the electric heater 7 can heat the gas in the tower to increase the temperature inside the synthesis tower and maintain the hot standby state in the tower.

In this embodiment, the reaction gas can be introduced into the synthesis tower from different positions and used for ammonia synthesis or for hot standby process. The reaction gas inlet 10 provided on the synthesis tower is used for air intake. The specific number and position are not limited to a single one. Here, optimization is performed and one of the feasible options is adopted: the number of the reaction gas inlets 10 is at least two, and one of the reaction gas inlets 10 guides the reaction gas longitudinally from the middle of the synthesis tower into the preheating tube 12 for preheating and mixing with other reaction gas and cold shock gas; the other reaction gas inlet 10 guides the reaction gas into the shell gap and exchanges heat from the heat tracing structure 3 and mixes with other reaction gas and cold shock gas. When such a scheme is adopted, the reaction gas longitudinally entering the preheating tube 12 from the middle is fully preheated, the temperature is quickly increased and reaches the temperature of synthetic ammonia or the hot standby temperature; the reaction gas entering from the shell gap can also absorb a certain amount of heat and heat up, and the reaction gas entering from the two paths is mixed before entering the reaction bed 5, and after entering the reaction bed 5, the corresponding ammonia synthesis reaction occurs or it is only circulated as hot standby gas.

In some other technical solutions, the position of the reaction gas inlet 10 can also be adjusted. For example, the reaction gas inlet 10 can be set on the lower side of the tower body 1, or the reaction gas inlet 10 can be set on the upper side of the tower body 1, or the reaction gas inlet 10 can be set on the top of the tower body 1; when multiple reaction gas inlets 10 are set, a combination of setting the reaction gas inlets 10 at different positions at the same time can be adopted.

The structures of the reaction bed 5 and the heat exchanger 6 are not limited to a single one, and can be set in various forms to meet the circulation and heat exchange requirements of the airflow. Here, the optimization is performed and a feasible option is adopted as follows: the reaction bed 5 includes an annular catalyst bed, the heat exchanger 6 is arranged in the middle of the catalyst bed, and the heat exchanger 6 is constructed in an annular shape, and the preheating tube 12 passes through the middle hole of the heat exchanger 6. When such a scheme is adopted, the outer bottom of the reaction bed 5 is tightly attached to and sealed with the inner wall of the inner shell 2, so that the space between two adjacent reaction beds 5 is closed, and the airflow can only flow in a directional manner through the airflow passage.

Preferably, a thermocouple 9 is also provided in the tower body 1 for monitoring and feeding back the temperature in the tower body 1 .

The synthesis tower disclosed in this embodiment can be used for heating the synthesis tower under cold start-up conditions, and can also be used for heat preservation of the synthesis tower during parking or low-load operation. The electric heater 7 arranged in the central tube of the synthesis tower can gradually heat the reaction bed of the synthesis tower from a cold state to the catalyst activation temperature. The catalyst electric heating wire arranged in the first catalyst reaction bed of the synthesis tower can be used for heat preservation of the catalyst reaction bed during parking or low-load operation, and maintain the temperature of the catalyst reaction bed not lower than the activation temperature. At the same time, an external heating layer and a heat-insulating layer are arranged on the outside of the first catalyst bed, which can effectively slow down the heat dissipation of the catalyst bed during parking, maintain the temperature of the first catalyst reaction bed, and facilitate rapid restart and resumption of production.

The above are the implementation methods listed in this embodiment, but this embodiment is not limited to the above optional implementation methods. Those skilled in the art can arbitrarily combine the above methods to obtain other various implementation methods. Anyone can derive other various implementation methods under the inspiration of this embodiment. The above specific implementation methods should not be understood as limiting the protection scope of this embodiment. The protection scope of this embodiment should be based on the definition in the claims.

Claims (7)

1. A synthetic ammonia hot standby process, characterized by comprising: Stop introducing hydrogen into the synthesis tower, and continue introducing nitrogen into the synthesis tower, while controlling the amount of vented air to maintain the gas flow and pressure stability inside the synthesis tower; Determine the activation temperature required for the catalyst of synthetic ammonia, and set a temperature value higher than the activation temperature as the hot standby temperature; A heating structure is arranged inside the synthesis tower, the heating structure comprising an external heating layer (3) for heating the inner wall surface of the synthesis tower, and an internal heating layer (4) for heating the reaction bed layer (5) inside the synthesis tower, the external heating layer (3) and the internal heating layer (4) working together to maintain a uniform temperature inside the synthesis tower; Monitor the temperature inside the synthesis tower and give an alarm when the temperature inside the synthesis tower is lower than the catalyst activation temperature; The outer heating layer (3) envelops the inner wall surface of the synthesis tower, radiating heat from the inner wall surface to the interior of the synthesis tower to maintain the temperature by heating; The internal heating layer (4) is arranged inside the reaction bed (5) and bends and extends inside the reaction bed (5) to envelop the structure of the reaction bed (5). The internal heating layer directly radiates heat to the internal space of the synthesis tower to perform heating and maintain the temperature. 2. The synthetic ammonia hot standby process according to claim 1 is characterized in that a heating structure and a heat exchange structure are arranged in the middle of the synthesis tower, and when hot standby is required, the heating structure and the heat tracing structure are always kept in an open working state. 3. The synthetic ammonia hot standby process according to claim 2 is characterized in that: the heating structure includes an electric heater (7), the heat exchange structure includes a plurality of heat exchangers (6), and the electric heater (7) and the heat exchanger (6) preheat and raise the temperature of the nitrogen entering the synthesis tower so that the nitrogen reaches the hot standby temperature. 4. A synthesis tower for realizing the synthetic ammonia hot standby process according to any one of claims 1 to 3, characterized in that: it comprises a closed tower body (1), an inner shell (2) is arranged in the tower body (1), and a shell gap is formed between the inner shell (2) and the tower body (1); a plurality of reaction beds (5) are arranged in sequence in the longitudinal direction in the inner shell (2), and adjacent reaction beds (5) are connected to form a unidirectional air flow passage; a plurality of reaction gas inlets (10) and cold shock gas inlets (8) are arranged on the tower body (1) for guiding the reaction gas and the cold shock gas to enter the air flow passage after mixing; an outer heating layer (3) is arranged in the shell gap, an inner heating layer (4) is extended inside the reaction bed (5), and a heating structure and a heat exchange structure are arranged in the inner shell (2) for heat exchange with the reaction gas, and the reaction gas passing through the heating structure and the heat exchange structure enters the air flow passage; the tower body (1) is also provided with a reaction gas outlet (11), and the reaction gas outlet (11) is connected to the air flow passage and used to discharge the reacted gas; The outer heating layer (3) comprises a plurality of electric heating cables evenly arranged along the inner wall surface of the synthesis tower; the inner heating layer (4) comprises a plurality of electric furnace wires spirally wound at least in the uppermost reaction bed layer (5). 5. The synthesis tower according to claim 4 is characterized in that: a preheating tube (12) is arranged in the inner shell (2), the heating structure includes an electric heater (7) extending into the interior of the preheating tube (12), at least one reaction gas inlet (10) introduces the reaction gas into the preheating tube (12) and preheats it through the heating structure; the heat exchange structure includes a heat exchanger (6) arranged at the reaction bed (5), the heat exchanger (6) is connected to the air flow path and adjusts the temperature of the internal air flow. 6. The synthesis tower according to claim 5 is characterized in that: the number of the reaction gas inlets (10) is at least two, and one of the reaction gas inlets (10) guides the reaction gas longitudinally from the middle of the synthesis tower into the preheating tube (12) for preheating and mixing with other reaction gases and cold shock gas; the other reaction gas inlet (10) guides the reaction gas into the shell gap and exchanges heat from the heating structure and mixes with other reaction gases and cold shock gas. 7. The synthesis tower according to claim 5 is characterized in that: the reaction bed (5) includes an annular catalyst bed, the heat exchanger (6) is arranged in the middle of the catalyst bed, and the heat exchanger (6) is constructed in an annular shape, and the preheating tube (12) passes through the middle hole of the heat exchanger (6).