A system and method for synthesizing ammonia using renewable energy

Abstract

The present invention discloses a system and method for synthesizing ammonia by utilizing renewable energy. The system comprises an ammonia synthesis tower, a waste heat recovery device, a heat exchanger, a cooling device and an ammonia separator. An air inlet pipeline and an air outlet pipeline are connected to the ammonia synthesis tower. A hot circulating gas pipeline is arranged on the air outlet pipeline between the heat exchanger and the ammonia separator. The hot circulating gas pipeline is connected to the air inlet pipeline on the heat exchanger via a circulating gas compressor. A secondary reflux pipeline is arranged at the connection between the hot circulating gas pipeline and the air inlet pipeline to connect the air inlet end of the circulating reflux pipeline. Aiming at the instability of energy supply by renewable energy sources such as wind and light, the present invention controls the ammonia reflux amount by the hot circulating gas pipeline when the total flow rate of hydrogen and nitrogen input into the system differs from the total flow rate of hydrogen and nitrogen at full load, and controls the total gas flow rate of the ammonia synthesis tower by the secondary reflux pipeline, thereby finally ensuring the stability of the overall system of the ammonia synthesis tower under different energy supply conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of wind, solar and storage integration of renewable energy, and in particular to a green ammonia synthesis system and method for synthesizing ammonia using renewable energy, thereby storing renewable energy such as wind and solar energy in the form of green ammonia products. Background Art

[0002] Renewable clean energy includes solar energy, wind energy, hydropower, ocean energy, geothermal energy, bioenergy, etc. They can be recycled in nature and are inexhaustible and environmentally friendly energy.

[0003] The extensive use of renewable clean energy is the direction of future development, especially in the northwest of my country, which has abundant wind energy and light energy. However, the electricity converted from wind energy and light energy cannot be applied on a large scale. The main reason is that due to the influence of the natural environment, wind and solar power generation has the characteristics of intermittent, volatility and instability. The principle of photovoltaic power generation is the "photovoltaic effect" of semiconductors, and its power generation is related to the intensity of light; the principle of wind power generation is to convert the kinetic energy of wind into mechanical kinetic energy through windmills, and then convert mechanical energy into electrical energy. Therefore, the amount of wind power generation is related to the size of wind power. The efficiency of wind and solar power generation is affected by factors such as sunlight and wind power. It has the defects of large volatility and weak stability, which can easily lead to mismatch between the power generation side and the power grid side. The large-scale grid connection of wind and solar renewable energy (generally not exceeding 20% ​​of the total capacity of the power grid) will also bring a greater impact to the power grid, threatening the safety and stability of the power system. For this reason, it is urgent to find a safe and reliable method for converting wind and solar renewable energy on site.

[0004] Producing hydrogen from wind and solar renewable clean energy is a common method. The hydrogen product obtained is green hydrogen, which is green and environmentally friendly. However, the volume energy density of the hydrogen product is only 9.89MJ / m 3 The energy density is very low, resulting in high storage and transportation costs, and is not an effective method for converting wind and solar renewable energy on site. The volume energy density of liquid ammonia is 854MJ / m 3 , and is carbon-free, easy to store and transport. The raw materials for synthesis are only hydrogen and nitrogen. Hydrogen and nitrogen can be extracted through wind and solar renewable clean energy, and then green ammonia products can be obtained through ammonia synthesis reaction, thereby converting wind and solar renewable clean energy into ammonia energy, realizing effective energy conversion.

[0005] For traditional industrial ammonia synthesis equipment, "safety, stability, long-term, full and excellent" are the goals to be pursued and the key to the efficiency of the equipment. However, for wind and solar renewable clean energy, the characteristics of large volatility and weak stability inevitably determine that the matching zero-carbon green ammonia synthesis equipment cannot achieve the comprehensive goals of "stability, long-term, full and excellent". Therefore, on the basis of ensuring safety, the synthesis equipment must be linked with wind and solar renewable clean energy to realize a zero-carbon green ammonia synthesis equipment that moves with wind and solar, thereby realizing the safe, effective and economical conversion of the energy of 10-110% load wind and solar renewable energy. Summary of the invention

[0006] In view of the above-mentioned problems, the purpose of the present invention is to provide an ammonia synthesis process suitable for clean energy supply, so as to avoid the problem that insufficient clean energy supply affects the ammonia synthesis reaction and even causes the equipment to enter a fatigue condition.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a system for synthesizing ammonia using renewable energy, the system comprising an ammonia synthesis tower, a waste heat recovery device, a heat exchanger, a cooling device and an ammonia separator; an air inlet pipeline and an air outlet pipeline are connected to the ammonia synthesis tower, and the ammonia synthesis tower is connected to the waste heat recovery device, the heat exchanger, the cooling device and the ammonia separator in sequence through the air outlet pipeline; heat is exchanged between the air inlet pipeline and the air outlet pipeline through a heat exchanger, a hot circulating gas pipeline is provided on the air outlet pipeline between the heat exchanger and the ammonia separator, the hot circulating gas pipeline is connected to the air inlet pipeline on the heat exchanger through a circulating gas compressor, and a secondary reflux pipeline is provided at the connection between the hot circulating gas pipeline and the air inlet pipeline to connect the air inlet end of the circulating reflux pipeline.

[0008] The system of the present invention is provided with an auxiliary control tower ammonia content control system and a tower inlet flow control system; detection instruments are provided on the air inlet pipeline and the air outlet pipeline connected to the heat exchanger, and the tower inlet ammonia content control system and the tower inlet flow control system are connected through the detection instruments;

[0009] The tower inlet ammonia content control system of the present invention is provided with a heat circulation gas reflux regulating valve and a heat circulation gas outlet regulating valve at the connection position of the heat circulation pipeline and the gas outlet pipeline respectively; the tower inlet flow control system is provided with a flow regulating valve on the secondary reflux pipeline.

[0010] The detection instrument of the present invention includes a fresh gas flow meter, an inlet ammonia content analysis meter and an inlet gas flow meter; in order to maintain the stable operation of the reaction inside the ammonia synthesis tower, the system needs to control the total amount of gas entering the tower and the ammonia content in the inlet gas, and the ammonia-containing hot circulating gas refluxed by the system is mixed with the fresh gas and finally input into the ammonia synthesis tower to control the stable progress of the reaction in the ammonia synthesis tower.

[0011] The air intake pipeline of the present invention is provided with a fresh air compressor connected to the input end of the heat exchanger; the fresh air needs to be compressed before it can be input into the ammonia synthesis tower, which corresponds to the circulating air compressor on the hot circulating air pipeline, and is uniformly compressed and mixed before being input into the ammonia synthesis tower.

[0012] A branched heating pipeline is provided on the air inlet pipeline between the ammonia synthesis tower and the heat exchanger of the present invention, and the heating pipeline is connected to the ammonia synthesis tower via a heater; a further preferred heater is a molten salt heater; the mixed gas introduced into the synthesis tower is auxiliary heated by the molten salt heater, and when the system power supply is insufficient, the molten salt heater is used for auxiliary heating; when the system power supply is sufficient, part of the energy is stored by the molten salt heater to ensure the stable operation of the heating part of the overall system.

[0013] A circulating gas pipeline is arranged on the top of the ammonia separator of the present invention, and is connected to a circulating reflux pipeline after heat exchange with the gas outlet pipeline via a cooling device.

[0014] A control method for a system for synthesizing ammonia using renewable energy, wherein the control method is switched according to the input amount of fresh gas, the fresh gas being a mixture of hydrogen and nitrogen, and the input amount of the fresh gas being determined by the power generation of the renewable energy; specifically including the following working conditions: conventional working condition and reflux regulation working condition;

[0015] 1) Conventional working conditions: The energy supply of renewable energy sources such as wind and light is sufficient. After detection by the fresh gas flow meter, the fresh gas input into the air inlet pipeline reaches the load set by the ammonia synthesis tower. All the fresh gas is input into the ammonia synthesis tower to synthesize a high-ammonia mixed gas. The high-ammonia mixed gas is all input into the ammonia separator through the outlet pipeline, and the ammonia product is obtained after separation and collection;

[0016] 2) Reflux regulation conditions: When the energy supply from renewable energy sources such as wind and light decreases, the amount of fresh air input into the air intake pipeline gradually decreases. After detection by the fresh air flow meter, perform the following operations:

[0017] ①Open the hot circulating gas reflux regulating valve on the hot circulating gas pipeline. Through the combination of the hot circulating gas outlet regulating valve and the hot circulating gas reflux regulating valve, part of the high-ammonia mixed gas produced by the ammonia synthesis tower is refluxed through the hot circulating gas pipeline, and part of it is input into the ammonia separator through the outlet pipeline;

[0018] ② Open the flow reflux valve on the secondary reflux pipeline. Part of the high-ammonia mixed gas in the hot circulating gas pipeline will directly reflux in the hot circulating gas pipeline, and part of it will be mixed with the fresh gas in the intake pipeline and then input into the ammonia synthesis tower.

[0019] The conventional working condition and the reflux adjustment working condition of the present invention are switched according to the input amount of fresh gas, and the load rate of the fresh gas input amount x=(F 新 / F 满 ) · 100%, of which F 新is the actual fresh air flow rate, F 满 The fresh air flow rate set for the device to operate at full load;

[0020] 1) When the load rate x of the fresh gas input is ≥80%, close the hot cycle gas return regulating valve; the system operates under normal conditions;

[0021] 2) When the load rate of the fresh gas input is 0≤x<80%, open the flow regulating valve and adjust the flow of the gas entering the tower in the air inlet pipeline through the tower inlet flow control system; open the hot cycle gas reflux regulating valve and adjust the ammonia content in the gas entering the tower in the air inlet pipeline through the tower inlet ammonia content control system; the system operates in reflux regulation mode.

[0022] The reflux regulation condition is to input the mixed gas flow into the ammonia synthesis tower through the tower flow control system, and control the ammonia content in the mixed gas input into the ammonia synthesis tower through the tower ammonia content control system, so as to finally maintain the stability of the operating pressure of the ammonia synthesis system during the working process, so that the operating pressure △P of the ammonia synthesis system is within the following operating range:

[0023] △P=0.2·(1-x)·P 设计

[0024] Where P 设计 It is the set pressure of the ammonia synthesis system, which is determined by the scale of the ammonia synthesis system actually designed.

[0025] The advantages of the present invention are as follows: the present invention is a control process for ammonia synthesis under special energy supply environment, which realizes that when a whole ammonia synthesis system is powered by clean energy, no matter how much the clean energy supply fluctuates, the overall system can still maintain stable operation.

[0026] The main drawback of clean energy is the instability of energy supply, and the energy supply situation may fluctuate at any time. From the perspective of this system, the hydrogen production capacity of the hydrogen supply system or the nitrogen production capacity of the nitrogen supply system is directly proportional to the energy supply situation of the clean energy supply system. Therefore, when the total flow rate of hydrogen and nitrogen input to this system differs from the total flow rate of hydrogen and nitrogen at full load, the ammonia reflux flow is promptly controlled through the heat circulation gas pipeline, and the total gas flow rate of the ammonia synthesis tower is controlled through the secondary reflux pipeline. The pressure entering the ammonia synthesis tower is controlled by combining the two, and the heat supply of the ammonia synthesis tower is controlled by the molten salt heating system. Finally, the overall system is guaranteed to maintain stable operation when the function of the ammonia synthesis tower fluctuates.

[0027] The ultimate goal of the present invention is to store renewable energy sources such as wind and light in the form of green ammonia products, solving the problem of high losses and operating costs during the storage and transportation of electricity converted from traditional renewable energy sources such as wind and light. This is especially true for areas where renewable energy sources such as wind and light are sufficient but the cost of electricity transportation is too high. The present invention has better applicability and ultimately facilitates the conversion and use of renewable energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of system connection of the present invention;

[0029] Among them, 1 ammonia synthesis tower, 2 waste heat recovery device, 3 heat exchanger, 4 cooling equipment, 4-1 water cooler, 4-2 cold exchanger, 4-3 ammonia cooler, 5 ammonia separator, 6 outlet pipeline, 7 inlet pipeline, 8 hot circulating gas pipeline, 9 secondary reflux pipeline, 10 circulating gas compressor, 11 fresh gas compressor, 12 heater, 13 hot circulating gas outlet regulating valve, 14 hot circulating gas reflux regulating valve, 15 flow regulating valve. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Example 1: Figure 1 A system for synthesizing ammonia using renewable energy is shown, the system comprising an ammonia synthesis tower 1, a waste heat recovery device 2, a heat exchanger 3, a cooling device 4 and an ammonia separator 5; an air inlet pipeline 7 and an air outlet pipeline 6 are connected to the ammonia synthesis tower 1, and the ammonia synthesis tower 1 is connected to the waste heat recovery device 2, the heat exchanger 3, the cooling device 4 and the ammonia separator 5 in sequence via the air outlet pipeline 6; heat exchange is performed between the air inlet pipeline 7 and the air outlet pipeline 6 through the heat exchanger 3, and a hot circulating gas pipeline 8 is provided on the air outlet pipeline 6 between the heat exchanger 3 and the ammonia separator 5, and the hot circulating gas pipeline 8 is connected to the air inlet pipeline 7 on the heat exchanger 3 via a circulating gas compressor 10, and a secondary reflux pipeline 9 is provided at the connection between the hot circulating gas pipeline 8 and the air inlet pipeline 6, which is connected to the air inlet end of the circulating reflux pipeline 8; the cooling device 4 in the system comprises a water cooler 4-1, a cold exchanger 4-2, and an ammonia cooler 4-3.

[0032] The system is provided with an auxiliary control tower ammonia content control system and a tower inlet flow control system; detection instruments are provided on the air inlet pipeline 7 and the air outlet pipeline 6 connected to the heat exchanger 3, and the tower inlet ammonia content control system and the tower inlet flow control system are connected through the detection instruments; the tower inlet ammonia content control system is provided with a hot circulation gas reflux regulating valve 14 and a hot circulation gas outlet regulating valve 13 at the connection position of the heat circulation pipeline 8 and the air outlet pipeline 6 respectively; the tower inlet flow control system is provided with a flow regulating valve 15 on the secondary reflux pipeline 9; the detection instruments include a fresh gas flow meter, an inlet ammonia content analysis meter and an inlet gas flow meter.

[0033] Example 2: Figure 1 As shown, a branched heating pipeline is provided on the air inlet pipeline 7 between the ammonia synthesis tower 1 and the heat exchanger 3, and the heating pipeline is connected to the ammonia synthesis tower via a heater 12; the heater 12 is preferably a molten salt heater.

[0034] Example 3: Figure 1 As shown, a circulating gas pipeline is provided on the top of the ammonia separator 5, which is connected to the circulating return pipeline 8 after heat exchange with the outlet pipeline 6 through the cooling device 4. A fresh air compressor 11 is provided on the intake pipeline 7 to connect the input end of the heat exchanger 3.

[0035] Example 4: Figure 1 As shown, a control method for a system for synthesizing ammonia using renewable energy is provided. The control method is switched according to the input amount of fresh gas. The fresh gas is a mixture of hydrogen and nitrogen. The input amount of fresh gas is determined by the power generation of renewable energy. Specifically, the control method includes a conventional operating condition and a reflux regulating operating condition. The conventional operating condition and the reflux regulating operating condition are switched according to the input amount of fresh gas. The load rate x of the fresh gas input is (F 新 / F 满 ) · 100%, of which F 新 is the actual fresh air flow rate, F 满 The fresh air flow rate set for the device to operate at full load;

[0036] 1) Conventional working conditions: The energy supply of renewable energy sources such as wind and light is sufficient. After detection by the fresh gas flow meter, the fresh gas input into the air inlet pipeline 7 reaches the load set by the ammonia synthesis tower, and the load rate x of the fresh gas input is ≥80%. All the fresh gas is input into the ammonia synthesis tower 1 to synthesize a high-ammonia mixed gas, and the high-ammonia mixed gas is all input into the ammonia separator 5 through the outlet pipeline 6, and the ammonia product is obtained after separation and collection;

[0037] 2) Reflux regulation condition: When the energy supply of renewable energy sources such as wind and light decreases, the amount of fresh air input into the air intake pipeline 7 gradually decreases. After detection by the fresh air flow meter, the load rate of the fresh air input is 0≤x<80%. The following operations are performed:

[0038] ① Open the hot circulating gas reflux regulating valve 14 on the hot circulating gas pipeline 8. Through the combination of the hot circulating gas outlet regulating valve 13 and the hot circulating gas reflux regulating valve 14, part of the high-ammonia mixed gas produced by the ammonia synthesis tower 1 is refluxed through the hot circulating gas pipeline 8, and part of it is input into the ammonia separator 5 through the outlet pipeline 6;

[0039] ② Open the flow reflux valve 15 on the secondary reflux pipeline 9. Part of the high-ammonia mixed gas in the hot circulating gas pipeline 8 directly refluxes in the hot circulating gas pipeline 8, and part of it is mixed with the fresh gas in the intake pipeline 7 and then input into the ammonia synthesis tower 1.

[0040] Example 5: Figure 1 As shown, the reflux regulation working condition is to input the mixed gas flow into the ammonia synthesis tower 1 through the tower inlet flow control system, and control the ammonia content in the mixed gas input into the ammonia synthesis tower 1 through the tower inlet ammonia content control system, and finally maintain the stability of the operating pressure of the ammonia synthesis system during the working process, so that the operating pressure △P of the ammonia synthesis system is within the following operating range:

[0041] △P=0.2·(1-x)·P 设计

[0042] Where P 设计 It is the set pressure of the ammonia synthesis system.

[0043] Example 6: Example of specific application

[0044] like Figure 1 As shown in the figure, the process flow of the ammonia synthesis system can be divided into five continuous cycle units according to its function, namely preheating (heat exchanger), reaction (ammonia synthesis tower), waste heat recovery (waste heat recovery device), cooling (cooling equipment), and separation (ammonia separator).

[0045] 1) Preheating unit

[0046] The fresh hydrogen and nitrogen gas (H2 / N2~3.0) generated from renewable energy is compressed by the fresh gas compressor and then merged with the circulating gas at the outlet of the circulating gas compressor into the cold air inlet of the heat exchanger. After heat exchange to 150~170℃, it is divided into two routes: the main line and the secondary line:

[0047] The main line gas at 150-170℃ directly enters the ammonia synthesis tower.

[0048] The by-line gas at 150-170°C is heated to 360-380°C by a molten salt heater and then enters the ammonia synthesis tower to provide external heat for the ammonia synthesis reaction below 50% load of the ammonia synthesis system.

[0049] 2) Reaction unit

[0050] The inlet gas heated by the heat exchanger is about 150-170℃ and is divided into several streams, namely:

[0051] Ammonia synthesis tower zero meter bypass line - used to adjust the inlet temperature of the catalyst bed into the ammonia synthesis tower 1 to 350 ~ 370 ℃ to adapt to the different operating conditions of the ammonia synthesis tower.

[0052] Ammonia synthesis tower catalyst bed cooling gas - used to adjust the catalyst bed inlet temperature of the synthesis tower to 385 ~ 405 ℃ to adapt to the different operating conditions of the synthesis tower.

[0053] Cooling gas from the bottom heat exchanger of the ammonia synthesis tower is used to adjust the outlet temperature of the synthesis tower to adapt to different operating conditions of the synthesis tower.

[0054] The high-temperature gas of 290-370°C after the reaction directly enters the waste heat recovery device through a direct connection structure.

[0055] 3) Waste heat recovery unit

[0056] The synthesis gas after the reaction directly enters the waste heat recovery device for heat exchange through the connector with internal insulation at the bottom of the ammonia synthesis tower, and produces 2.5-4.0MPa and 0.5-0.8MPa medium-pressure steam and low-pressure steam. The temperature of the synthesis gas drops to 160-180℃ and enters the heat exchanger to exchange heat with the gas entering the tower. The temperature drops to 70-80℃ and enters the cooling unit.

[0057] (4) Cooling and separation unit

[0058] The synthesis gas leaving the heat exchanger is cooled by the cooling device 4 (water cooler 4-1, cold exchanger 4-2, ammonia cooler 4-3) to a temperature of -8 to 0°C, and finally enters the ammonia separator 5 to separate liquid ammonia. The gas after ammonia separation enters the shell side of the cold exchanger to recover the cold, and then enters the circulating gas compressor 10 for pressurization to enter the next cycle; the liquid ammonia separated by the ammonia separator 5 is sent to the ammonia storage device after reduced pressure flash evaporation.

[0059] The synthesis gas at the heat exchanger outlet is provided with a hot circulating gas pipeline 8, and the circulating gas compressor outlet is provided with a secondary reflux pipeline 9. Through the regulation of the two pipelines, the operating pressure fluctuation range of the synthesis system is controlled within the range of the following formula to avoid the equipment from operating under fatigue conditions; the ultimate goal of regulating the hot circulating pipeline is to ensure the stability of the operating pressure of the synthesis system; where P 设计 It is the design pressure of the ammonia synthesis system, which is determined by the scale of the actually designed ammonia synthesis system.

[0060] When the system is in the reflux regulation condition, that is, 0≤x<80%, the pressure fluctuation value through the control system is within the following range:

[0061] △P=0.2(1-x)P 设计

[0062] When the system is in normal working condition, that is, x ≥ 80%, the pressure fluctuation value through the control system is within the following range:

[0063] △P=0.1P 设计

[0064] According to the setting of the ammonia synthesis tower 1, the gas flow rate of the ammonia synthesis tower is adjusted as shown in the following formula, where F 满 F is the gas flow rate of the ammonia synthesis system at 100% load, which is determined by the scale of the ammonia synthesis system actually designed; 循环 is the performance curve flow of the circulating gas compressor, which is determined by the scale of the circulating gas compressor in the actual designed ammonia synthesis system. The parameters of the two formulas below are based on the scale of the ammonia synthesis tower design (parameter is 12.5t / h; tons / hour (100kt / a; thousand tons / year)); the scale of the circulating gas compressor (100% load flow: 103500Nm 3 / h; 80% load flow: 87600Nm 3 / h) proposed.

[0065] When the system is in normal working condition, that is, x ≥ 80%, the air intake into the ammonia synthesis tower is controlled by the control system as follows:

[0066] F=F 循环 +xF 满

[0067] When the system is in reflux regulation condition, that is, 0≤x<80%, the air intake into the ammonia synthesis tower is controlled by the control system as follows:

[0068] F=(0.8x+0.2)F 满

[0069] When the actual scale parameter of the ammonia synthesis tower design is set to 12.5t / h (100kt / a), the parameters controlled by this system are shown in the following table:

[0070]

[0071] Table 1 Parameters of 12.5t / h (100kt / a) ammonia synthesis system

[0072] As shown in the above table: when the ammonia synthesis tower is in normal operating conditions, the hot circulation gas pipeline and the secondary reflux pipeline are both in a closed state, and the gas flow rate is 0. Because the overall system has a stable energy supply, although the working pressure in the system decreases with the decrease in load, the system operating pressure fluctuation range is still within the working range of the formula of this embodiment, and the device stability is good.

[0073] When the ammonia synthesis tower is in the reflux adjustment condition, the hot circulation gas pipeline and the secondary reflux pipeline are all opened, and the gas flow in the two pipelines is timely adjusted. The energy supply in the overall system has been decreasing, and the intake amount of fresh gas has also been decreasing. By continuously adjusting the gas flow in the two pipelines, the system operating pressure fluctuation range of the device is within the working range of the formula of this embodiment. Once the operating pressure fluctuation range of the system becomes larger and exceeds a certain number of fluctuations, the system enters a fatigue condition and brings risks to the system.

[0074] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any combination or equivalent transformation made on the basis of the above embodiments shall fall within the protection scope of the present invention.

Claims

1. A control method for a system for synthesizing ammonia using renewable energy, characterized in that: The system comprises an ammonia synthesis tower, a waste heat recovery device, a heat exchanger, a cooling device and an ammonia separator; an air inlet pipeline and an air outlet pipeline are connected to the ammonia synthesis tower, and the ammonia synthesis tower is sequentially connected to the waste heat recovery device, the heat exchanger, the cooling device and the ammonia separator via the air outlet pipeline; the system is characterized in that heat exchange is performed between the air inlet pipeline and the air outlet pipeline via a heat exchanger, a hot circulating gas pipeline is arranged on the air outlet pipeline between the heat exchanger and the ammonia separator, the hot circulating gas pipeline is connected to the air inlet pipeline on the heat exchanger via a circulating gas compressor, and a secondary reflux pipeline is arranged at the connection between the hot circulating gas pipeline and the air inlet pipeline to connect the air inlet end of the circulating reflux pipeline; the ammonia reflux amount is controlled by the hot circulating gas pipeline, and the total gas flow of the ammonia synthesis tower is controlled by the secondary reflux pipeline; The system is equipped with an auxiliary control tower ammonia content control system and a tower inlet flow control system; the inlet and outlet pipes connected to the heat exchanger are equipped with detection instruments, which are connected to the tower ammonia content control system and the tower inlet flow control system through the detection instruments; The inlet ammonia content control system is provided with a hot cycle gas reflux regulating valve and a hot cycle gas outlet regulating valve at the connection position of the hot cycle pipeline and the outlet gas pipeline; The tower inlet flow control system is equipped with a flow regulating valve on the secondary reflux pipeline; The detection instruments include fresh gas flow meter, tower inlet ammonia content analysis meter and tower inlet gas flow meter; The air intake pipeline is provided with an input end of a fresh air compressor connected to a heat exchanger; The control method is switched according to the input amount of fresh gas, which is a mixture of hydrogen and nitrogen. The input amount of fresh gas is determined by the power generation of renewable energy. Specifically, the control method includes the following working conditions: normal working condition and reflux regulation working condition. 1) Normal working conditions: The wind and solar energy supply is sufficient. After detection by the fresh gas flow meter, the fresh gas input into the air inlet pipeline reaches the load set by the ammonia synthesis tower. All the fresh gas is input into the ammonia synthesis tower to synthesize a high-ammonia mixed gas. The high-ammonia mixed gas is all input into the ammonia separator through the outlet pipeline. After separation and collection, the ammonia product is obtained; 2) Reflux regulation condition: As the wind and solar energy supply decreases, the amount of fresh air input into the air intake pipeline gradually decreases. After detection by the fresh air flow meter, perform the following operations: ①Open the hot circulating gas reflux regulating valve on the hot circulating gas pipeline. Through the combination of the hot circulating gas outlet regulating valve and the hot circulating gas reflux regulating valve, part of the high-ammonia mixed gas produced by the ammonia synthesis tower is refluxed through the hot circulating gas pipeline, and part of it is input into the ammonia separator through the outlet pipeline; ②Open the flow reflux valve on the secondary reflux pipeline. Part of the high-ammonia mixed gas in the hot circulating gas pipeline will directly reflux in the hot circulating gas pipeline, and part of it will be mixed with the fresh gas in the intake pipeline and then input into the ammonia synthesis tower; 3) The normal working condition and the reflux regulating working condition are switched according to the input amount of fresh gas. The load rate of the fresh gas input amount x = (F 新 / F 满 ) · 100%, of which F 新 is the actual fresh air flow rate, F 满 The fresh air flow rate set for the device to operate at full load; ① When the load rate x of the fresh gas input is ≥80%, close the hot cycle gas return regulating valve; the system operates under normal conditions; ② When the load rate of the fresh gas input is 0≤x<80%, open the flow regulating valve and adjust the flow of the inlet gas in the air inlet pipeline through the inlet flow control system; open the hot cycle gas reflux regulating valve and adjust the ammonia content in the inlet gas in the air inlet pipeline through the inlet ammonia content control system; the system operates in reflux regulation mode.

2. The control method according to claim 1, characterized in that: A branched heating pipeline is provided on the air inlet pipeline between the ammonia synthesis tower and the heat exchanger, and the heating pipeline is connected to the ammonia synthesis tower via a heater.

3. The control method according to claim 2, characterized in that: The heater is a molten salt heater.

4. The control method according to claim 1, characterized in that: A circulating gas pipeline is provided on the top of the ammonia separator, which is connected to the circulating reflux pipeline after heat exchange with the outlet pipeline through the cooling equipment.

5. The control method according to claim 1, characterized in that: The reflux regulation working condition is to input the mixed gas flow into the ammonia synthesis tower through the tower inlet flow control system, and control the ammonia content in the mixed gas input into the ammonia synthesis tower through the tower inlet ammonia content control system, so as to finally maintain the stability of the operating pressure of the ammonia synthesis system during the working process, so that the operating pressure fluctuation range of the ammonia synthesis system is within the following operating range: △P=0.2·(1-x)·P 设计 (0≤x<80%) Where P 设计 It is the design pressure of the ammonia synthesis system.

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