Low-temperature low-pressure ammonia synthesis tower and coupled fuel cell renewable flexible ammonia synthesis system

Abstract

The invention discloses a low-temperature low-pressure synthesis ammonia tower and a coupling fuel cell renewable energy flexible synthesis ammonia system, the synthesis ammonia tower comprises a reactor outer cylinder, a catalyst frame is sleeved in the reactor outer cylinder, a catalyst bed layer, a heat exchange tube bundle and a spiral baffle plate are arranged in the catalyst frame, the heat exchange tube bundle passes through the spiral baffle plate, and the spiral baffle plate passes through the reactor outer cylinder. The catalyst bed layer is arranged on the spiral baffle plate; raw material gas enters the catalyst frame and is subjected to ammonia synthesis reaction in the axial and radial directions of the catalyst frame under the action of the spiral baffle plates; high-pressure water in the heat exchange tube bundle absorbs reaction heat from the catalyst frame to generate phase change, and after high-pressure steam is generated, the high-pressure steam is discharged from the steam tube. The design of the spiral baffle plate in the synthesis ammonia tower can guide the raw material gas to form a more complex flow path in the catalyst frame, so that the gas can pass through the catalyst bed layer more uniformly, the contact efficiency of the gas and the catalyst is improved, the retention time of the gas in the catalyst bed layer is prolonged, and the service life of the gas is prolonged. Therefore, the conversion rate and the efficiency of the ammonia synthesis reaction can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of clean energy conversion and storage technology, in particular to a low-temperature and low-pressure ammonia synthesis tower and a coupling fuel cell renewable flexible ammonia synthesis system. BACKGROUND

[0002] At present, the renewable energy power generation industry such as wind energy and solar energy in China is developing rapidly, but these renewable energies are greatly affected by seasons and weather conditions and are not completely matched with relatively stable power demand. In order to reduce the negative impact of renewable energy fluctuation on the power grid, the "three abandon" phenomena such as "abandoning wind", "abandoning light" and "abandoning water" often occur, resulting in low utilization rate of renewable energy. Therefore, it has great economic and social benefits to develop new use fields for renewable power energy that is difficult to use in grid-connected.

[0003] Using electrolysis of water to produce hydrogen can realize large-scale and efficient renewable energy consumption, and using hydrogen as an energy carrier can improve the resilience of the energy system and realize the redistribution of energy between different regions. However, due to the small density and difficulty of liquefaction of hydrogen, the current mature high-pressure hydrogen storage requires 35-70MPa, which consumes a large amount of compression power, and the mass hydrogen storage density is only about 5%, resulting in high cost of hydrogen storage and transportation.

[0004] Ammonia is one of the most basic chemical raw materials in modern industry and agricultural production, and has the advantages of easy liquefaction, high volume energy density, no carbon emission, non-flammability, high safety, etc. It is expected to be used as an efficient hydrogen carrier in the field of new energy and solve the bottleneck problem of hydrogen storage and transportation.

[0005] Modern industrial ammonia synthesis usually adopts Haber-Bosch process, in which hydrogen and nitrogen are introduced into a high-temperature and high-pressure reactor to produce ammonia through catalytic reaction. In the traditional process, hydrogen is produced by catalytic gasification / reforming of fossil fuels coupled with water-gas shift reaction, and a large amount of CO2 emitted in this process accounts for about 1.2% of global carbon emissions. Therefore, in view of the problems of high energy consumption and high carbon emission in industrial ammonia synthesis, the combination of carbon-free and clean renewable energy power with ammonia synthesis industry has great strategic significance for China's sustainable development.

[0006] At present, various ammonia synthesis reactors and system processes are only suitable for large-scale ammonia synthesis industry, and have high operating temperature and pressure, large energy consumption, complex synthesis route, many equipment, and large device scale, which limits the distributed, small-scale application and flexible operation of ammonia synthesis technology in the field of renewable energy. SUMMARY

[0007] The present application aims to solve the problems of the existing synthetic ammonia reactor and system process operation flexibility, large energy consumption, complex synthetic route and large device scale, and provides a low-temperature and low-pressure synthetic ammonia tower and a coupling fuel cell renewable flexible synthetic ammonia system.

[0008] The present application adopts the following technical solutions:

[0009] A low-temperature and low-pressure synthetic ammonia tower, comprising a reactor outer cylinder, a raw material gas inlet pipe and a product gas outlet pipe are arranged on the reactor outer cylinder, a catalyst frame is sleeved in the reactor outer cylinder, a catalyst bed layer of synthetic ammonia catalyst is arranged in the catalyst frame, a plurality of heat exchange pipe bundles penetrating through the inside of all the catalyst bed layers are arranged in the catalyst frame, one end of each heat exchange pipe bundle is in communication with a high-pressure water inlet pipe, and the other end is in communication with a steam pipe;

[0010] A spiral baffle is further arranged in the catalyst frame, the heat exchange pipe bundles penetrate through the spiral baffle, and the catalyst bed layers are arranged on the spiral baffle; raw material gas enters the catalyst frame in communication with the raw material gas inlet pipe, and under the action of the spiral baffle, the synthetic ammonia reaction is carried out in the axial radial direction of the catalyst frame, and the reaction product is discharged from the product gas outlet pipe; high-pressure water in the heat exchange pipe bundle absorbs reaction heat from the catalyst frame to change phase, generates high-pressure steam, and is discharged from the steam pipe.

[0011] A heat exchange assembly is arranged below the reactor outer cylinder, the heat exchange assembly comprises a high-pressure water inlet pipe, a water storage tank and a heat exchange pipe bundle, the water storage tank is located below the inside of the reactor outer cylinder, the high-pressure water inlet pipe penetrates through the reactor outer cylinder and is in communication with the water storage tank to provide high-pressure water for the water storage tank, and the heat exchange pipe bundle is in communication with the water storage tank.

[0012] Preferably, one end of the heat exchange pipe bundle away from the water storage tank is in communication with the steam pipe through a steam drum, and the steam in the heat exchange pipe bundle is separated through the steam drum and discharged from the steam pipe.

[0013] The synthetic ammonia catalyst in the catalyst bed layer is one of Fe-based catalyst, Ni-based catalyst and Ru-based catalyst, and the carrier is one or more of activated carbon, alumina, magnesium oxide, cerium dioxide and barium oxide.

[0014] A kind of coupling fuel cell renewable energy flexible synthetic ammonia system, including low temperature low pressure synthetic ammonia tower, electrolytic water device, nitrogen source providing device, mixer, raw material gas preheater, ammonia condenser group, gas-liquid separator and storage tank, the hydrogen outlet of the electrolytic water device and the nitrogen outlet of nitrogen source providing device are communicated with the gas inlet of the mixer respectively, the gas outlet of the mixer is communicated with the raw material gas inlet pipe of the low temperature low pressure synthetic ammonia tower after passing through the raw material gas preheater, raw material hydrogen and nitrogen are mixed after passing through the mixer, heated after passing through raw material gas preheater and enter the raw material gas inlet pipe into the low temperature low pressure synthetic ammonia tower to carry out the synthesis of ammonia, the product gas outlet pipe of the low temperature low pressure synthetic ammonia tower is sequentially communicated with the ammonia condenser group, gas-liquid separator, the outlet of the gas-liquid separator is two, respectively as liquid outlet and exhaust port, the liquid outlet is communicated with the storage tank, the exhaust port is communicated with the raw material gas inlet pipe, ammonia in the ammonia mixed gas synthesized in the low temperature low pressure synthetic ammonia tower is condensed and liquefied after passing through the ammonia condenser group, together with the gas that is not liquefied into the gas-liquid separator, wherein liquid ammonia is stored into the storage tank through the liquid outlet, the gas that is not liquefied as circulating gas enters the low temperature low pressure synthetic ammonia tower through the raw material gas inlet pipe.

[0015] The system further includes SOFC fuel cell, combustion chamber, turbine, fuel preheater, hydrogen preheater, air preheater and air compressor, the hydrogen outlet of the electrolytic water device is also communicated with the anode of SOFC fuel cell, hydrogen from electrolytic water device enters the anode of SOFC fuel cell after passing through hydrogen preheater, external air enters the cathode of SOFC fuel cell after passing through air preheater after being compressed, the SOFC fuel cell generates electricity by reaction and sends to inverter to supply power to the factory area, the mixture from the anode and cathode outlet of the SOFC fuel cell, purge gas discharged from the storage tank and vent gas when the low temperature low pressure synthetic ammonia tower is vented enter the combustion chamber to burn after generating a large amount of flue gas to drive the turbine to generate electricity, the generated power is sent to the inverter to supply power to the factory area, and the combustion tail gas is discharged after heating the vent gas and purge gas through the fuel preheater, then heated through the air preheater for the air entering the cathode of SOFC fuel cell, and finally heated through the hydrogen preheater for the hydrogen entering the anode of SOFC fuel cell before being discharged.

[0016] Preferably, a 1# auxiliary line inlet pipe is further provided on the low temperature low pressure synthetic ammonia tower, which is communicated with the central part of the catalyst bed in the catalyst frame;The exhaust port on the gas-liquid separator is divided into three pipelines, which are respectively communicated with the raw material gas inlet pipe, the 1# auxiliary line inlet pipe and the vent pipe, part of the circulating gas enters the low temperature low pressure synthetic ammonia tower through the raw material gas inlet pipe and the 1# auxiliary line inlet pipe, and the other part enters the combustion chamber through the vent pipe.

[0017] Preferably, the by-product steam of the steam pipe outlet of the low-temperature and low-pressure ammonia synthesis tower is divided into two paths, one of which is connected to the raw material gas preheater for heating, and the other of which is connected to a turbine for generating power by working.

[0018] The system further comprises a power supply mechanism electrically connected with the water electrolysis device to provide electric energy for electrolysis of water by the water electrolysis device; the power supply mechanism is one or several of photovoltaic power generation, wind power generation, hydroelectric power generation and tidal power generation.

[0019] The power supply mechanism can also be electrically connected with an external power grid through an inverter.

[0020] Preferably, the nitrogen source providing device is a membrane separation device or a pressure swing adsorption device using air separation to provide nitrogen.

[0021] Preferably, the ammonia condenser group comprises a water cooler and an ammonia cooler arranged in series, the inlet of the water cooler is communicated with the product gas outlet pipe, and the outlet of the ammonia cooler is communicated with the inlet of the gas-liquid separator; the exhaust port of the gas-liquid separator is sequentially communicated with a circulating machine and a circulating oil separator, and then respectively communicated with the raw material gas inlet pipe and the 1# auxiliary line inlet pipe.

[0022] The system further comprises a circulating machine and a circulating oil separator, which are electrically connected with the inverter, and the circulating machine and the circulating oil separator are provided with electric energy by the power supply mechanism or the external power grid.

[0023] The working pressure of the water electrolysis device is 0.1-10 MPa, and the working temperature is ≤90℃.

[0024] The ratio of the raw material gas to the circulating gas in the raw material gas inlet pipe is 1:1.5-1:4, and the ratio of the circulating gas in the raw material gas inlet pipe and the 1# auxiliary line inlet pipe is 0:10-5:5.

[0025] The technical scheme of the present application has the following advantages:

[0026] A、The design of the helical baffle in the low-pressure ammonia synthesis tower of the present application can guide the raw material gas to form a more complex flow path within the catalyst frame. This design not only enables the gas to pass through the catalyst bed more uniformly, but also helps to improve the contact efficiency of the gas and the catalyst, thereby enhancing the reaction effect. Due to the more complex flow of the gas under the action of the helical baffle, the residence time of the gas in the catalyst bed is increased. Longer residence time means more reaction opportunities, which helps to improve the conversion rate and efficiency of the ammonia synthesis reaction. In addition, the design of the helical baffle also helps to optimize the heat exchange between the heat exchange tube bundle and the reaction gas. By forcing the gas to flow along a spiral path, the contact area and contact time between the gas and the heat exchange tube bundle can be increased, thereby improving the heat exchange efficiency.

[0027] B、In the ammonia synthesis reaction, temperature control is crucial. The helical baffle in the low-pressure ammonia synthesis tower of the present application helps to more uniformly distribute the temperature of the catalyst bed by optimizing gas flow, preventing local overheating or overcooling, and thus keeping the reaction within the optimal temperature range.

[0028] C、The low-pressure ammonia synthesis tower in the present application arranges multiple heat exchange tube bundles with cold water in the radial catalyst bed. By adjusting the pressure in the water pipes and the arrangement of the heat exchange tube bundles, the temperature of the catalyst bed can be controlled. The cold shock sub-line makes the internal temperature control of the bed more reasonable. Arranging heat exchange tube bundles in the radial bed can achieve by-product steam.

[0029] D、The renewable energy sources in the present application include but are not limited to photovoltaic, wind power, hydroelectric power, tidal power generation, etc. Two modes can be selected: grid-connected mode and off-grid mode. In grid-connected mode, renewable energy sources are connected to the grid within the allowable capacity range. Excess power is used to produce hydrogen by electrolyzing water. When the power of renewable energy sources is insufficient, grid power can be used to meet basic production needs, especially to improve economic efficiency by using valley electricity prices. In off-grid mode, renewable energy power is used entirely for hydrogen production by electrolyzing water to synthesize ammonia.

[0030] E、The present application includes SOFC fuel cells and GT systems. In the SOFC fuel cell, hydrogen gas undergoes an electrochemical reaction to generate electricity, and the heat generated and the unreacted hydrogen gas are sent together with the purge gas and vent gas in the ammonia synthesis system to the GT system. The combustion chamber in the GT system burns these gases and sends them into the turbine to generate electricity. The by-product steam is used to cool the turbine blades, and the steam is then used to generate electricity in the turbine, achieving efficient energy utilization.

[0031] F、The water electrolysis operation in the present application is carried out at a pressure of 0.1-10 MPa, which matches the pressure of the ammonia synthesis process. There is no need for additional hydrogen pressure boosting, and compared with the prior art, the present application can eliminate the pressure boosting process between water electrolysis and ammonia synthesis, i.e. without the need for compressors and supporting equipment.

[0032] G,The whole system of the present application can not only efficiently synthesize ammonia under low-temperature and low-pressure conditions, but also can produce high-pressure steam and high-purity oxygen as by-products, and has the characteristics of high energy efficiency and high economic benefit. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present application, the drawings required in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative labor based on the embodiments in the present application also belong to the scope of protection of the present application.

[0034] Figure 1 It is a schematic diagram of the whole structure of the low-temperature and low-pressure ammonia synthesis tower in the present application.

[0035] Figure 2 It is a schematic diagram of the spiral baffle structure in the low-temperature and low-pressure ammonia synthesis tower in the present application.

[0036] Figure 3 It is a schematic diagram of the whole structure of the flexible ammonia synthesis system of the coupled fuel cell renewable energy in the present application.

[0037] The symbols in the drawings are as follows:

[0038] 1-low-temperature and low-pressure ammonia synthesis tower

[0039] 11-raw material gas inlet pipe; 12-reactor outer cylinder; 13-product gas outlet pipe; 14-catalyst frame, 141-catalyst bed, 142-spiral baffle; 15-heat exchange assembly, 151-high-pressure water inlet pipe, 152-water storage tank, 153-heat exchange pipe bundle; 16-steam pipe; 17-steam drum; 18-1# auxiliary line gas inlet pipe;

[0040] 2-water electrolysis device; 3-nitrogen source providing device; 4-mixer; 5-raw material gas preheater; 6-ammonia condenser group, 61-water cooler, 62-ammonia cooler; 7-gas-liquid separator, 71-liquid outlet, 72-gas outlet; 8-storage tank; 9-power supply mechanism, 91-inverter; 10-circulating machine; 20-circulating oil separator; 30-fuel preheater; 40-turbine; 50-combustion chamber; 60-SOFC fuel cell; 70-hydrogen preheater; 80-air preheater; 90-air compressor. DETAILED DESCRIPTION

[0041] The technical solutions of the present application will be described clearly and completely below in combination with the drawings. Obviously, the described embodiments are some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor also belong to the scope of protection of the present application.

[0042] As shown in Figure 1 , Figure 2 The present application provides a low-temperature and low-pressure ammonia synthesis tower, which comprises a reactor outer cylinder 12, a raw material gas inlet pipe 11 and a product gas outlet pipe 13 are arranged on the reactor outer cylinder 12, a catalyst frame 14 is sleeved in the reactor outer cylinder 12, and a catalyst bed layer 141 filled with ammonia synthesis catalyst is arranged in the catalyst frame 14. A plurality of heat exchange tube bundles 153 penetrating through the inside of all the catalyst bed layers 141 are arranged in the catalyst frame 14, one end of each heat exchange tube bundle 153 is communicated with a high-pressure water inlet pipe 151, and the other end is communicated with a steam pipe 16. A spiral baffle 142 is also arranged in the catalyst frame 14, the heat exchange tube bundles 153 penetrate through the spiral baffle 142, and the catalyst bed layers 141 are arranged on the spiral baffle 142. The raw material gas enters the catalyst frame 14 communicated with the raw material gas inlet pipe 11, and the ammonia synthesis reaction is carried out in the axial and radial direction of the catalyst frame 14 under the action of the spiral baffle 142, and the reaction product is discharged from the product gas outlet pipe 13. The high-pressure water in the heat exchange tube bundle 153 absorbs the reaction heat from the catalyst frame 14 to generate high-pressure steam, which is then discharged from the steam pipe 16. The design of the spiral baffle in the low-temperature and low-pressure ammonia synthesis tower of the present application can guide the raw material gas to form a more complex flow path in the catalyst frame. This design not only enables the gas to pass through the catalyst bed layer more uniformly, but also helps to improve the contact efficiency of the gas and the catalyst, thereby enhancing the reaction effect. Due to the more complex flow of the gas under the action of the spiral baffle, the residence time of the gas in the catalyst bed layer is increased. Longer residence time means more reaction opportunities, which helps to improve the conversion rate and efficiency of the ammonia synthesis reaction. In addition, the design of the spiral baffle also helps to optimize the heat exchange between the heat exchange tube bundle and the reaction gas. By forcing the gas to flow along a spiral path, the contact area and contact time of the gas and the heat exchange tube bundle can be increased, thereby improving the heat exchange efficiency.

[0043] Further, a heat exchange assembly 15 is arranged below the reactor outer cylinder 12, which comprises a high-pressure water inlet pipe 151, a water storage tank 152 and a heat exchange tube bundle 153. The water storage tank 152 is located inside the reactor outer cylinder 12, the high-pressure water inlet pipe 151 penetrates through the reactor outer cylinder 12 and is communicated with the water storage tank 152 to provide high-pressure water for the water storage tank 152, and the heat exchange tube bundle 153 is communicated with the water storage tank 152. The end of the heat exchange tube bundle 153 away from the water storage tank 152 is communicated with the steam pipe 16 through a steam drum 17, and the steam in the heat exchange tube bundle 153 is separated by the steam drum 17 and then discharged from the steam pipe 16. The low-temperature and low-pressure ammonia synthesis tower in the present application arranges a plurality of heat exchange tube bundles through which cold water flows in the radial catalyst bed, adjusts the water pipe pressure and the arrangement of the heat exchange tube bundle to control the temperature of the catalyst bed layer, and uses the cold shock auxiliary line to make the internal temperature control of the bed layer more reasonable; and the heat exchange tube bundle is arranged in the radial bed layer, which can realize the by-product steam.

[0044] The synthetic ammonia catalyst in the catalyst bed 141 is one of Fe-based catalyst, Ni-based catalyst and Ru-based catalyst, and the carrier is one or more of activated carbon, alumina, magnesia, ceria and barium oxide.

[0045] As shown in Figure 3 The application also provides a coupled fuel cell renewable energy flexible synthetic ammonia system, which comprises a low-temperature and low-pressure synthetic ammonia tower 1, a water electrolysis device 2, a nitrogen source providing device 3, a mixer 4, a raw material gas preheater 5, an ammonia condenser group 6, a gas-liquid separator 7 and a storage tank 8. The hydrogen outlet of the water electrolysis device 2 and the nitrogen outlet of the nitrogen source providing device 3 are respectively communicated with the gas inlet of the mixer 4. The gas outlet of the mixer 4 is communicated with the raw material gas inlet pipe 11 of the low-temperature and low-pressure synthetic ammonia tower 1 after passing through the raw material gas preheater 5. The raw material hydrogen and nitrogen mixed by the mixer 4 are heated by the raw material gas preheater 5 and then enter the raw material gas inlet pipe 11 to enter the low-temperature and low-pressure synthetic ammonia tower 1 to synthesize ammonia. The product gas outlet pipe 13 of the low-temperature and low-pressure synthetic ammonia tower 1 is sequentially communicated with the ammonia condenser group 6 and the gas-liquid separator 7. The outlet of the gas-liquid separator 7 has two outlets, i.e. a liquid outlet 71 and a gas outlet 72. The liquid outlet 71 is communicated with the storage tank 8, and the gas outlet 72 is communicated with the raw material gas inlet pipe 11. The ammonia in the ammonia mixed gas synthesized in the low-temperature and low-pressure synthetic ammonia tower 1 is condensed and liquefied by the ammonia condenser group 6 and then enters the gas-liquid separator 7 together with the unliquefied gas. The liquid ammonia enters the storage tank 8 through the liquid outlet 71 for storage, and the unliquefied gas is used as a circulating gas and enters the low-temperature and low-pressure synthetic ammonia tower 1 through the raw material gas inlet pipe 11.

[0046] The system further comprises a SOFC fuel cell 60, a combustion chamber 50, a turbine 40, a fuel preheater 30, a hydrogen preheater 70, an air preheater 80 and an air compressor 90. The hydrogen outlet of the water electrolysis device 2 is further communicated with the anode of the SOFC fuel cell 60. The hydrogen from the water electrolysis device 2 enters the anode of the SOFC fuel cell 60 after passing through the hydrogen preheater 70. The external air enters the cathode of the SOFC fuel cell 60 after passing through the air preheater 80 after being compressed by the air compressor 90. The SOFC fuel cell 60 generates electricity by reaction and sends the electricity to the inverter 91 to supply power to the plant area. The mixture from the anode and the cathode of the SOFC fuel cell 60, the purge gas discharged from the storage tank 8 and the vent gas when the low-temperature and low-pressure synthetic ammonia tower 1 is depressurized are burned in the combustion chamber 50 to generate a large amount of flue gas to drive the turbine 40 to generate electricity. The generated electricity is sent to the inverter 91 to supply power to the plant area. The combustion tail gas is discharged and then heated by the fuel preheater 30 to heat the vent gas and the purge gas, then heated by the air preheater 80 to heat the air entering the cathode of the SOFC fuel cell 60, and finally heated by the hydrogen preheater 70 to heat the hydrogen entering the anode of the SOFC fuel cell 60 before being discharged.

[0047] The low-temperature and low-pressure ammonia synthesis tower 1 is further provided with a 1# auxiliary line gas inlet pipe 18, which is connected to the center of the catalyst bed 141 in the catalyst frame 14; the gas outlet 72 of the gas-liquid separator 7 is divided into three pipelines, which are respectively connected to the raw material gas inlet pipe 11, the 1# auxiliary line gas inlet pipe 18 and the vent pipe; part of the circulating gas enters the low-temperature and low-pressure ammonia synthesis tower 1 through the raw material gas inlet pipe 11 and the 1# auxiliary line gas inlet pipe 18, and the other part enters the combustion chamber 50 through the vent pipe.

[0048] The by-product steam at the outlet of the steam pipe 16 of the low-temperature and low-pressure ammonia synthesis tower 1 is divided into two paths, one of which is connected to the raw material gas preheater 5 for heating, and the other of which is connected to the turbine 40 to drive the turbine 40 to generate electricity.

[0049] The system further comprises a power supply mechanism 9, which is electrically connected to the electrolytic water device 2 to provide power for electrolysis of water; the power supply mechanism 9 is one or more of photovoltaic power, wind power, hydroelectric power and tidal power. The power supply mechanism 8 can also be electrically connected to the external power grid through an inverter 81. In the present application, the renewable energy ammonia synthesis system includes but is not limited to photovoltaic power, wind power, hydroelectric power and tidal power. Photovoltaic power passes through a DC-DC converter, wind power and hydroelectric power pass through an AC-DC converter, and are connected to the power grid power through an inverter 91 to form a bus, and then drive the high-pressure electrolytic water device 2 to work through a DC-DC converter. The connection of renewable energy can be divided into two modes: off-grid and on-grid. In off-grid mode, renewable energy power is used for electrolytic water hydrogen production and ammonia synthesis. In on-grid mode, renewable energy is connected to the grid within the allowable capacity range, and excess power is used for electrolytic water hydrogen production. When the renewable energy power is insufficient, the grid power can meet the basic hydrogen production demand. In particular, the use of valley electricity price can improve the economic efficiency of the system process, and can also balance the renewable energy power and the grid load.

[0050] The nitrogen source providing device 3 can be a membrane separation device or a pressure swing adsorption device for air separation to provide nitrogen. The externally purified water is pressurized by a water pump and sent to the high-pressure electrolytic water device 2 to decompose hydrogen, which is mixed with nitrogen generated by the air separation nitrogen supply device in a certain proportion to form a synthesis ammonia raw material gas, which is sent to the rear-end ammonia synthesis section. The electrolytic water in the present application operates at a pressure of 0.1-10 MPa, which matches the pressure of the ammonia synthesis process, and does not need to be additionally pressurized. Compared with the prior art, the present application can eliminate the pressurization process between electrolytic water and ammonia synthesis, i.e. without the need for a compressor and supporting equipment. The electrolytic water and the air separation nitrogen supply device can both produce high-purity oxygen, and the hydrogen in the ammonia synthesis raw material gas can also come from industrial by-product hydrogen.

[0051] In addition, the ammonia condenser set 6 comprises a water cooler 61 and an ammonia cooler 62 arranged in series, the inlet of the water cooler 61 is communicated with the product gas outlet pipe 13, and the outlet of the ammonia cooler 62 is communicated with the inlet of the gas-liquid separator 7. The exhaust port 72 of the gas-liquid separator 7 is communicated with the raw material gas inlet pipe 11 and the 1# auxiliary line inlet pipe 18 through the circulation machine 10 and the circulation oil separator 20 in sequence, respectively. The gas at the outlet of the gas-liquid separator 7 is discharged as purge gas, and a part of the gas is used as circulation gas, and then enters the low-temperature and low-pressure synthetic ammonia tower 1 through the raw material gas inlet pipe 11 and the 1# auxiliary line inlet pipe 18, so as to realize the regulation and control of the temperature distribution in the tower. The proportion of the raw material gas introduced into the raw material gas inlet pipe 11 and the circulation gas is 1:1.5-1:4, and the proportion of the circulation gas introduced into the raw material gas inlet pipe 11 and the 1# auxiliary line inlet pipe 18 is 0:10-5:5. The circulation machine 10 and the circulation oil separator 20 are electrically connected with the inverter 91, respectively, and the circulation machine 10 and the circulation oil separator 20 are provided with electric energy through the power supply mechanism 9 or an external power grid.

[0052] In the present application, the product hydrogen obtained by electrolysis of water does not need to be deoxygenated and dehydrated; nitrogen can be obtained by on-site air separation and directly purchased liquid nitrogen, if on-site air separation is used, membrane separation technology, pressure swing adsorption, cryogenic technology, etc. can be used; the oxygen in the hydrogen-nitrogen raw material gas can be removed in the synthetic ammonia tower, so that the requirement for the oxygen content in the synthetic ammonia raw material gas can be appropriately reduced. The ammonia separation technology that can be used includes but is not limited to one or even multiple of ammonia cooling separation, ammonia adsorption separation and ammonia absorption separation technology.

[0053] The whole system of the present application can not only efficiently synthesize ammonia under low-temperature and low-pressure conditions, but also can by-product high-pressure steam and high-purity oxygen, and has the characteristics of high energy efficiency and high economic benefit.

[0054] The unmentioned parts of the present application are applicable to the prior art.

[0055] Obviously, the above embodiments are only examples for clearly illustrating, but not limitation on the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A low-temperature, low-pressure ammonia synthesis tower, comprising a reactor outer cylinder (12), wherein the reactor outer cylinder (12) is provided with a raw gas inlet pipe (11) and a product gas outlet pipe (13), characterized in that: A catalyst frame (14) is mounted inside the reactor outer cylinder (12), and a catalyst bed (141) of ammonia synthesis catalyst is mounted inside the catalyst frame (14); a plurality of heat exchange tube bundles (153) are arranged inside the catalyst frame (14) and pass through all the catalyst beds (141), and one end of each heat exchange tube bundle (153) is connected to a high-pressure water inlet pipe (151), and the other end thereof is connected to a steam pipe (16); A spiral baffle (142) is further arranged in the catalyst frame (14), the heat exchange tube bundle (153) passes through the spiral baffle (142), and the catalyst bed (141) is arranged on the spiral baffle (142); the raw gas enters the catalyst frame (14) connected thereto through the raw gas inlet pipe (11), and undergoes a synthetic ammonia reaction in the radial direction of the catalyst frame (14) under the action of the spiral baffle (142), and the reaction product is discharged from the product gas outlet pipe (13); the high-pressure water in the heat exchange tube bundle (153) absorbs the reaction heat from the catalyst frame (14) to undergo phase change, generating high-pressure steam, which is then discharged from the steam pipe (16).

2. The low-temperature, low-pressure ammonia synthesis tower according to claim 1, characterized in that: A heat exchange assembly (15) is provided below the reactor outer cylinder (12). The heat exchange assembly (15) comprises a high-pressure water inlet pipe (151), a water storage tank (152) and a heat exchange tube bundle (153). The water storage tank (152) is located below the interior of the reactor outer cylinder (12). The high-pressure water inlet pipe (151) passes through the reactor outer cylinder (12) and is in communication with the water storage tank (152) to provide high-pressure water to the water storage tank (152). The heat exchange tube bundle (153) is in communication with the water storage tank (152).

3. The low-temperature, low-pressure ammonia synthesis tower according to claim 2, characterized in that: One end of the heat exchange tube bundle (153) away from the water storage tank (152) is connected to the steam pipe (16) through a steam drum (17), and the steam in the heat exchange tube bundle (153) is separated by the steam drum (17) and discharged from the steam pipe (16).

4. The low-temperature, low-pressure ammonia synthesis tower according to claim 1, characterized in that: The ammonia synthesis catalyst in the catalyst bed (141) is one of an Fe-based catalyst, a Ni-based catalyst, and a Ru-based catalyst, and the carrier is one or more of activated carbon, alumina, magnesium oxide, ceria, and barium oxide.

5. A flexible ammonia synthesis system coupled with fuel cell renewable energy, characterized in that: The invention comprises the low-temperature, low-pressure ammonia synthesis tower (1) according to any one of claims 1 to 4, an electrolytic water device (2), a nitrogen source providing device (3), a mixer (4), a raw gas preheater (5), an ammonia condenser group (6), a gas-liquid separator (7) and a storage tank (8), wherein the hydrogen outlet of the electrolytic water device (2) and the nitrogen outlet of the nitrogen source providing device (3) are respectively connected to the air inlet of the mixer (4), and the air outlet of the mixer (4) is connected to the raw gas inlet pipe (11) of the low-temperature, low-pressure ammonia synthesis tower (1) after passing through the raw gas preheater (5). The raw hydrogen and nitrogen are mixed in the mixer (4), heated by the raw gas preheater (5), and then enter the raw gas inlet pipe (11) and enter the low-temperature, low-pressure ammonia synthesis tower (1) for ammonia synthesis. The product gas outlet pipe (13) of the low-pressure ammonia synthesis tower (1) is sequentially connected to the ammonia condenser group (6) and the gas-liquid separator (7). The gas-liquid separator (7) has two outlets, namely a liquid outlet (71) and an exhaust port (72). The liquid outlet (71) is connected to the storage tank (8), and the exhaust port (72) is connected to the raw gas inlet pipe (11). After the ammonia in the ammonia mixed gas synthesized in the low-temperature and low-pressure ammonia synthesis tower (1) is condensed and liquefied by the ammonia condenser group (6), the ammonia enters the gas-liquid separator (7) together with the unliquefied gas. The liquid ammonia enters the storage tank (8) through the liquid outlet (71) for storage, and the unliquefied gas enters the low-temperature and low-pressure ammonia synthesis tower (1) through the raw gas inlet pipe (11) as circulating gas.

6. The system according to claim 5, characterized in that The system further comprises a SOFC fuel cell (60), a combustion chamber (50), a turbine (40), a fuel preheater (30), a hydrogen preheater (70), an air preheater (80) and an air compressor (90). The hydrogen outlet of the water electrolysis device (2) is also connected to the anode of the SOFC fuel cell (60). The hydrogen from the water electrolysis device (2) enters the anode of the SOFC fuel cell (60) through the hydrogen preheater (70). The external air passes through the compressor (90) and then passes through the air preheater (80) to enter the cathode of the SOFC fuel cell (60). The SOFC fuel cell (60) generates electricity through reaction and sends it to the inverter (91) for the plant area. Power is supplied, and the mixture from the anode and cathode outlets of the SOFC fuel cell (60) and the vent gas discharged from the storage tank (8) and the vent air when the low-temperature and low-pressure ammonia synthesis tower (1) is decompressed and vented enters the combustion chamber (50) together with combustion to generate a large amount of flue gas to drive the turbine (40) to generate power, and the generated power is sent to the inverter (91) to supply power to the plant area, and after the combustion tail gas is discharged, it passes through the fuel preheater (30) to heat the vent air and the vent gas, and then passes through the air preheater (80) to heat the air entering the cathode of the SOFC fuel cell (60), and finally passes through the hydrogen preheater (70) to heat the hydrogen entering the anode of the SOFC fuel cell (60) and then is discharged.

7. The system according to claim 5, characterized in that The low-temperature, low-pressure ammonia synthesis tower (1) is further provided with a 1# auxiliary line air inlet pipe (18), which is connected to the center of the catalyst bed (141) in the catalyst frame (14); the exhaust port (72) on the gas-liquid separator (7) is divided into three pipelines, which are respectively connected to the raw gas inlet pipe (11), the 1# auxiliary line air inlet pipe (18), and the vent pipe. A part of the circulating gas enters the low-temperature, low-pressure ammonia synthesis tower (1) through the raw gas inlet pipe (11) and the 1# auxiliary line air inlet pipe (18), and the other part enters the combustion chamber (50) through the vent pipe.

8. The system according to claim 5, wherein: The by-product steam at the outlet of the steam pipe (16) of the low-temperature, low-pressure ammonia synthesis tower (1) is divided into two paths, one path is connected to the raw gas preheater (5) for heating, and the other path is connected to the turbine (40) to generate power for the turbine (40).

9. The system according to claim 5, characterized in that The system further comprises a power supply mechanism (9), which is electrically connected to the water electrolysis device (2) and provides electric energy for the water electrolysis device (2) to electrolyze water; the power supply mechanism (9) is one or more of photovoltaic, wind power, hydropower, and tidal power generation.

10. The system according to claim 5, wherein: The ammonia condenser group (6) comprises a water cooler (61) and an ammonia cooler (62) arranged in series, the inlet of the water cooler (61) is connected to the product gas outlet pipe (13), and the outlet of the ammonia cooler (62) is connected to the inlet of the gas-liquid separator (7); the exhaust port of the gas-liquid separator (7) is connected to the circulation machine (10) and the circulating oil separator (11) in sequence, and then respectively connected to the raw gas inlet pipe (11) and the 1# auxiliary line inlet pipe (18).

11. The system according to claim 5, wherein: The system further comprises a circulation machine (10) and a circulation oil separator (20), wherein the circulation machine (10) and the circulation oil separator (20) are electrically connected to the inverter (91) respectively, and electric energy is provided to the circulation machine (10) and the circulation oil separator (20) via the power supply mechanism (9) or an external power grid.

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