System and method for synthesizing ammonia using chemical compressor having a hydrogen storage alloy embedded therein

Abstract

The present invention provides a system for synthesizing ammonia using a chemical compressor having a hydrogen storage alloy embedded therein, and a method for synthesizing ammonia using the ammonia synthesis system. The system for synthesizing ammonia comprises: a water electrolysis stack that generates hydrogen; a chemical compressor that stores and discharges hydrogen supplied from the water electrolysis stack; and an ammonia synthesis unit that receives hydrogen from the chemical compressor and synthesizes ammonia, wherein the chemical compressor includes: a hydrogen storage unit having the hydrogen storage alloy embedded therein; a cooling unit that cools the hydrogen storage unit; a heating unit that heats the hydrogen storage unit; and a control unit that controls operations of the cooling unit and the heating unit, wherein the heating unit includes a plurality of different heating sources independently controllable from one another, and the control unit controls the cooling unit to cool the hydrogen storage alloy of the hydrogen storage unit when hydrogen is stored in the hydrogen storage unit, and controls at least one of the plurality of heating sources of the heating unit to heat the hydrogen storage alloy when hydrogen is discharged from the hydrogen storage unit.

Description

Ammonia synthesis system and method using a chemical compressor with built-in hydrogen storage alloy

[0001] The present invention relates to an ammonia synthesis system and method using a chemical compressor with a built-in hydrogen storage alloy.

[0002] The present invention is derived from research conducted as part of the International Joint Energy Research Project of the Ministry of Trade, Industry and Energy [Project No.: 2410002321, Project No.: RS-2023-00303645, Research Project Title: Development of Green Ammonia-Based Green Hydrogen Storage Technology and Optimal Transport Model].

[0003] Ammonia is a fundamental chemical essential for various industrial sectors, including fertilizers, chemical raw materials, and pharmaceuticals. In particular, its importance has been increasing recently as its potential as a hydrogen carrier and clean fuel has been highlighted.

[0004] Most commercially used ammonia production methods currently are based on the Haber-Bosch process. This method produces ammonia (NH3) by reacting nitrogen (N2) and hydrogen (H2) using an iron-based catalyst under high temperature (400–500°C) and high pressure (150–300 bar) conditions. Conventional ammonia synthesis systems using the Haber-Bosch process utilize mechanical compressors to react hydrogen and nitrogen at high temperatures and pressures.

[0005] Korean Published Patent No. 10-2024-0153591 discloses an ammonia production system utilizing a reciprocating compressor as a mechanical compressor. Reciprocating compressors have the problem of requiring a complex manufacturing process due to the need for multiple compression trains, as well as high costs and compression units. This is because hydrogen (H2) is a gas with a very small molecular weight, so more compression steps are required than for ordinary gases to compress it to high pressure. In addition, there is a disadvantage that external air or various impurities may be mixed into the gas flow during the mechanical operation process, which necessitates a separate Pressure Swing Adsorption (PSA) purification process to remove oxygen-containing species such as O2, CO, CO2, and H2O, as well as other impurities, from the ammonia reactor.

[0006] Korean Published Patent No. 10-2024-0097909 discloses an ammonia production system utilizing a dynamic compressor, such as a centrifugal compressor. Such a system requires a multi-stage compression process for ammonia synthesis and a separate sealing unit to prevent leakage of hydrogen and nitrogen gases during the compression process. This results in high initial construction costs and separate maintenance costs associated with the additional configuration of the sealing unit.

[0007] Against this backdrop, chemical compressors utilizing hydrogen storage alloys can be used as an alternative to conventional mechanical compressors. Hydrogen storage alloys possess the characteristic of undergoing an exothermic reaction when absorbing hydrogen and an endothermic reaction when releasing it; by utilizing these properties, hydrogen storage and high-pressure release are possible solely through temperature control. Hydrogen storage alloys have the advantage of efficiently storing hydrogen even at low pressures and releasing it at high pressures of 200–300 bar upon heating, allowing for the acquisition of high-purity, high-pressure hydrogen required for ammonia synthesis without the need for separate mechanical compression. Furthermore, chemical compressors have fewer moving parts, significantly reducing the possibility of impurity contamination, and their relatively simple design allows for reduced initial construction and maintenance costs compared to mechanical compressors.

[0008] Existing chemical compressor technologies mostly focus on the storage and transportation of hydrogen itself, and development of integrated systems that efficiently link this with ammonia synthesis is insufficient. Furthermore, existing chemical compressor systems primarily adopt a single energy source for heating hydrogen storage alloys, which presents a limitation in that it is difficult to efficiently respond to changes in energy source availability. Therefore, there is a need to develop systems and methods that effectively integrate chemical compressors containing hydrogen storage alloys with ammonia synthesis systems and flexibly utilize various energy sources.

[0009] The present invention was developed based on the background described above, and aims to provide an ammonia synthesis system and method that can safely produce high-pressure hydrogen (200 bar to 300 bar) using a chemical compressor with a built-in hydrogen storage alloy, with a simple single compression method compared to a mechanical compressor, and can reduce initial construction costs and maintenance costs.

[0010] In addition, the invention aims to provide an ammonia synthesis system and method capable of supplying high-purity (99.99% or higher) hydrogen without a separate PSA purification process.

[0011] In addition, the aim is to provide an ammonia synthesis system and method comprising multiple heat sources that can flexibly respond to changes in the availability of energy sources while efficiently utilizing surplus electricity from renewable energy generation and waste heat from the ammonia synthesis process.

[0012] One aspect of the present invention relates to an ammonia synthesis system utilizing a chemical compressor having a hydrogen storage alloy, comprising a water electrolysis stack for producing hydrogen, a chemical compressor for storing and releasing hydrogen supplied from the water electrolysis stack, and an ammonia synthesis unit for synthesizing ammonia by receiving hydrogen from the chemical compressor, wherein the chemical compressor comprises a hydrogen storage unit having a hydrogen storage alloy, a cooling unit for cooling the hydrogen storage unit, a heating unit for heating the hydrogen storage unit, and a control unit for controlling the operation of the cooling unit and the heating unit, wherein the heating unit comprises a plurality of different heating sources capable of mutually independent control, and the control unit controls the cooling unit to cool the hydrogen storage alloy of the hydrogen storage unit when hydrogen is stored in the hydrogen storage unit, and controls at least one of the plurality of heating sources of the heating unit to heat the hydrogen storage alloy when hydrogen is released from the hydrogen storage unit.

[0013] According to one embodiment of the present invention, an ammonia synthesis system may be provided, wherein the hydrogen storage unit comprises a pressure vessel, a hydrogen storage alloy embedded inside the pressure vessel, a hydrogen supply pipe for supplying hydrogen produced from the water electrolysis stack into the pressure vessel, and a hydrogen discharge pipe for discharging hydrogen released from the hydrogen storage alloy to the outside of the pressure vessel.

[0014] According to one embodiment of the present invention, an ammonia synthesis system may be provided in which the hydrogen storage alloy is a Ti-based alloy comprising one or more transition metals selected from Mn, Zr, Cr, V, Nb, Mo, Al, Fe, Co, Ni, Cu, Sn, and Si.

[0015] According to one embodiment of the present invention, an ammonia synthesis system may be provided, wherein the cooling unit is installed in the hydrogen storage unit and includes one or more cooling water supply lines that circulate cooling water at 10°C or lower.

[0016] According to one embodiment of the present invention, an ammonia synthesis system may be provided in which the heating unit comprises a high-pressure water heating unit or a high-frequency induction heating unit as a plurality of different heating sources.

[0017] According to one embodiment of the present invention, an ammonia synthesis system may be provided in which the high-pressure water heating unit includes a high-pressure water circulation line installed in the hydrogen storage unit, is linked to a high-pressure water supply unit that produces high-pressure water using steam waste heat generated in the ammonia synthesis unit, and heats the hydrogen storage alloy by circulating the high-pressure water supplied from the high-pressure water supply unit through the high-pressure water circulation line.

[0018] According to one embodiment of the present invention, an ammonia synthesis system may be provided in which the high-pressure water has a temperature of 200°C to 300°C and a pressure of 16 bar to 90 bar.

[0019] According to one embodiment of the present invention, an ammonia synthesis system may be provided in which the high-frequency induction heating unit includes an induction coil installed outside the chemical formula compressor, the induction coil is connected to a high-frequency generator that receives surplus power from renewable energy generation, and the hydrogen storage alloy is heated by induction heat by a high-frequency induction current supplied from the high-frequency generator.

[0020] According to one embodiment of the present invention, an ammonia synthesis system may be provided, wherein the ammonia synthesis unit comprises a preheater for preheating hydrogen and nitrogen supplied from the chemical compressor, a gas mixer for mixing the preheated hydrogen and nitrogen, an ammonia synthesis reactor for synthesizing ammonia by receiving the mixed gas produced in the gas mixer, and a condenser and a gas-liquid separator for liquefying and separating the ammonia produced in the ammonia synthesis reactor and recovering steam waste heat.

[0021] According to one embodiment of the present invention, an ammonia synthesis system may be provided in which the control unit controls the output of the high-pressure water heating unit and the high-frequency induction heating unit based on the amount of steam waste heat generated by the ammonia synthesis unit and the amount of surplus power from renewable energy generation, and reduces the output of the high-frequency induction heating unit when the amount of steam waste heat generated increases, and increases the output of the high-frequency induction heating unit when the amount of steam waste heat generated decreases.

[0022] Another aspect of the present invention relates to a method for synthesizing ammonia using a chemical compressor containing a hydrogen storage alloy, comprising the steps of producing hydrogen using a water electrolysis stack, storing the hydrogen produced from the water electrolysis stack in a chemical compressor, releasing the hydrogen stored in the chemical compressor, and synthesizing ammonia in an ammonia synthesis unit by receiving hydrogen from the chemical compressor, wherein the step of storing the hydrogen in the chemical compressor comprises the step of supplying the hydrogen to a hydrogen storage unit containing a hydrogen storage alloy, and the step of cooling the hydrogen storage alloy in the hydrogen storage unit by the control unit of the chemical compressor controlling a cooling unit when the hydrogen is stored in the hydrogen storage unit, and the step of releasing the hydrogen stored in the chemical compressor comprises the control unit of the chemical compressor controlling a heating unit to heat the hydrogen storage alloy by at least one of a plurality of different heating sources capable of mutually independent control.

[0023] According to one embodiment of the present invention, a method for synthesizing ammonia may be provided, wherein the water electrolysis stack produces hydrogen using any one of the following water electrolysis methods: AWE (Alkaline Water Electrolysis), PEMWE (Proton Exchange Membrane Water Electrolysis), AEMWE (Anion Exchange Membrane Water Electrolysis), or SOEC (Solid Oxide Electrolysis Cell) using surplus power from renewable energy generation.

[0024] According to one embodiment of the present invention, a method for synthesizing ammonia may be provided in which a plurality of different heating sources of the heating unit are heated by a high-pressure water heating method or a high-frequency induction heating method.

[0025] According to one embodiment of the present invention, an ammonia synthesis method may be provided in which high-pressure water produced using steam waste heat generated in an ammonia synthesis unit is circulated through a high-pressure water circulation line installed in the hydrogen storage unit to heat a hydrogen storage alloy.

[0026] According to one embodiment of the present invention, an ammonia synthesis method may be provided in which the high-pressure water has a temperature of 200°C to 300°C and a pressure of 16 bar to 90 bar.

[0027] According to one embodiment of the present invention, a method for synthesizing ammonia may be provided in which a high-frequency induction heating method supplies a high-frequency induction current generated from a high-frequency generator receiving surplus power from renewable energy generation to an induction coil installed outside the chemical composition compressor to heat a hydrogen storage alloy with induction heat.

[0028] According to one embodiment of the present invention, an ammonia synthesis method may be provided in which the control unit controls the output of the high-pressure water heating method and the high-frequency induction heating method based on the amount of steam waste heat generated by the ammonia synthesis unit and the amount of surplus power from renewable energy generation, and reduces the output of the high-frequency induction heating method when the amount of steam waste heat generated increases, and increases the output of the high-frequency induction heating method when the amount of steam waste heat generated decreases.

[0029] According to one embodiment of the present invention, an ammonia synthesis method may be provided in which, in the step of heating the hydrogen storage alloy, the heating temperature of the hydrogen storage alloy is 200°C to 300°C.

[0030] According to one embodiment of the present invention, an ammonia synthesis method may be provided in which the pressure of hydrogen released from the hydrogen storage alloy is 200 bar to 300 bar.

[0031] According to one embodiment of the present invention, a method for synthesizing ammonia may be provided, comprising the steps of: supplying hydrogen from the chemical compressor and synthesizing ammonia in an ammonia synthesis unit, preheating the hydrogen and nitrogen supplied from the chemical compressor in a preheater; mixing the preheated hydrogen and nitrogen in a gas mixer; supplying the mixed gas produced in the gas mixer to an ammonia synthesis reactor to synthesize ammonia; and liquefying and separating the ammonia produced in the ammonia synthesis reactor in a condenser and a gas-liquid separator, and recovering steam waste heat.

[0032] According to the present invention, an ammonia synthesis system and method can be provided that can safely produce high-pressure hydrogen (200 bar to 300 bar) using a simple single compression method compared to a mechanical compressor by using a chemical compressor with a built-in hydrogen storage alloy, and can reduce initial construction costs and maintenance costs.

[0033] In addition, an ammonia synthesis system and method capable of supplying high-purity (99.99% or higher) hydrogen without a separate PSA purification process can be provided.

[0034] In addition, an ammonia synthesis system and method including multiple heat sources that can flexibly respond to changes in energy source availability while efficiently utilizing surplus electricity from renewable energy generation and waste heat from the ammonia synthesis process can be provided.

[0035] FIG. 1 is a block diagram schematically illustrating an ammonia synthesis system using a chemical formula compressor according to the present invention.

[0036] FIG. 2 is a front cross-sectional view of a chemical formula compressor according to one embodiment of the present invention.

[0037] FIG. 3 is a block diagram illustrating in detail the overall components and control relationships of an ammonia synthesis system according to the present invention.

[0038] FIG. 4 is a schematic diagram illustrating a step-by-step method for synthesizing ammonia using a chemical formula compressor according to the present invention.

[0039] The embodiments of the present invention are illustrative for the purpose of explaining the technical concept of the present invention. The scope of rights according to the present invention is not limited to the embodiments presented below or the specific descriptions thereof. The technical concept of the present invention includes various modifications, equivalents, alternatives, and embodiments selectively combined from all or part of each embodiment of the present invention. Furthermore, the scope of rights of the technical concept of the present invention is not limited to the various embodiments presented below or the specific descriptions thereof.

[0040] Terms used in this specification, including technical or scientific terms, may have the meaning generally understood by those skilled in the art to which this specification pertains, unless otherwise defined.

[0041] Expressions used herein such as “comprising,” “may compose,” “possessing,” “possessing,” “having,” and “possessing” imply the existence of the subject feature (e.g., function, operation, or component, etc.) and do not exclude the existence of other additional features. In other words, such expressions should be understood as open-ended terms implying the possibility of including other embodiments.

[0042] Singular expressions used in this specification may include the meaning of the plural form unless otherwise indicated by the context, and this applies likewise to singular expressions described in the claims.

[0043] The present invention will be described below with reference to the drawings.

[0044] FIG. 1 is a block diagram schematically illustrating an ammonia synthesis system according to the present invention. Referring to FIG. 1, the ammonia synthesis system according to the present invention includes a water electrolysis stack (100) that produces hydrogen by receiving surplus power from renewable energy generation, a chemical compressor (200) that stores and releases hydrogen supplied from the water electrolysis stack (100), and an ammonia synthesis unit (300) that synthesizes ammonia by receiving hydrogen from the chemical compressor (200).

[0045] Renewable energy generation is a method of producing electricity using renewable energy sources such as solar power and wind power. Since such renewable energy generation has the characteristic of fluctuating output depending on weather conditions, surplus electricity may be generated in excess of the demand for electricity. In the present invention, energy efficiency can be improved by supplying this surplus electricity to a water electrolysis stack (100) and utilizing it to produce green hydrogen. Here, green hydrogen refers to hydrogen produced by electrolyzing water (H2O) using electricity generated from renewable energy, and unlike conventional fossil fuel-based hydrogen production methods, it is an eco-friendly energy source that does not emit carbon dioxide during the production process.

[0046] The water electrolysis stack (100) is a device that separates water into hydrogen and oxygen by electrolyzing water, and any one of the following methods can be used as the water electrolysis method: AWE (Alkaline Water Electrolysis), PEMWE (Proton Exchange Membrane Water Electrolysis), AEMWE (Anion Exchange Membrane Water Electrolysis), or SOEC (Solid Oxide Electrolysis Cell). The water electrolysis stack (100) operates by receiving surplus power from renewable energy generation, and the produced hydrogen is directly supplied to the hydrogen storage unit (210) of the chemical compressor (200).

[0047] The chemical compressor (200) includes a hydrogen storage unit (210), a cooling unit (220), a heating unit (230), and a control unit (240). The hydrogen storage unit (210) is a part that stores and releases hydrogen supplied from the water electrolysis stack (100), and has a hydrogen storage alloy (212) built inside. The hydrogen storage alloy (212) has the characteristic of storing hydrogen by combining with hydrogen to form a metal hydride, and when heated, the metal hydride decomposes into metal and hydrogen to release high-pressure hydrogen.

[0048] The cooling unit (220) is a device for removing heat generated during the hydrogen storage process and controls the exothermic reaction that occurs when the hydrogen storage alloy of the hydrogen storage unit (210) combines with hydrogen. The cooling unit (220) according to the present invention efficiently cools the hydrogen storage unit (210) by supplying cooling water at 10°C or lower.

[0049] The heating unit (230) is a device that heats the hydrogen storage alloy of the hydrogen storage unit (210) to release the stored hydrogen, and includes a plurality of different heating sources capable of mutually independent control. As shown in FIG. 1, the heating unit (230) may include a high-pressure water heating unit (231) and a high-frequency induction heating unit (233), which will be described later, as a plurality of different heating sources.

[0050] The control unit (240) is a device that controls the operation of the chemical compressor (200) and regulates the operation of the cooling unit (220) and the heating unit (230) according to the hydrogen storage and release conditions. When hydrogen is stored in the hydrogen storage unit (210), the control unit (240) controls the cooling unit (220) to cool the hydrogen storage alloy (212), and when hydrogen is released from the hydrogen storage unit (210), it controls at least one of the multiple heating sources of the heating unit (230) to heat the hydrogen storage alloy (212). In particular, since the process of the hydrogen storage alloy (212) combining with hydrogen is an exothermic reaction, the control unit (240) operates the cooling unit (220) to maintain an appropriate temperature, and when hydrogen release is required, it supplies heat to the hydrogen storage alloy through the heating unit (230) to promote the hydrogen separation reaction. Through such precise control by the control unit (240), the hydrogen storage and release process is carried out efficiently, and stable operation of the entire system is possible.

[0051] High-pressure hydrogen released from the chemical compressor (200) is supplied to the ammonia synthesis unit (300). The ammonia synthesis unit (300) is a part that synthesizes ammonia by reacting high-pressure hydrogen supplied from the chemical compressor (200) with high-pressure nitrogen supplied separately. The ammonia synthesis unit (300) according to the present invention is based on the Haber-Bosch process and synthesizes nitrogen and hydrogen into ammonia using a catalyst under conditions of a temperature of 400°C to 500°C and a pressure of approximately 200 bar.

[0052] FIG. 2 is a front cross-sectional view of a chemical formula compressor (200) according to one embodiment of the present invention.

[0053] Referring to FIG. 2, the chemical compressor (200) includes a hydrogen storage unit (210) in which a hydrogen storage alloy (212) is built, a cooling unit (220) for cooling the hydrogen storage unit (210), and a heating unit (230) for heating the hydrogen storage unit (210).

[0054] The hydrogen storage unit (210) includes a pressure vessel (211), a hydrogen storage alloy (212) embedded inside the pressure vessel (211), a hydrogen supply pipe (213) that supplies hydrogen produced from a water electrolysis stack (100) into the pressure vessel (211), and a hydrogen discharge pipe (214) that discharges hydrogen released from the hydrogen storage alloy (212) to the outside of the pressure vessel (211).

[0055] The pressure vessel (211) is designed to withstand high pressure generated during the hydrogen storage and release process. As illustrated in FIG. 2, the pressure vessel (211) according to one embodiment of the present invention may have a double-wall structure consisting of an outer wall and an inner wall. In this case, a cooling water supply line (221) and a high-pressure water circulation line (232) may be installed between the outer wall and the inner wall of the pressure vessel (211). The cooling water supply line (221) provides a passage for cooling water to circulate in order to remove heat generated during hydrogen storage, and the high-pressure water circulation line (232) provides a passage for high-temperature high-pressure water to circulate for heating required during hydrogen release. In this double-wall structure, the cooling section and the heating section can perform heat exchange directly at a location close to the hydrogen storage alloy (212), thereby improving the efficiency and safety of heat management. The pressure vessel (211) is made of a material having sufficient mechanical strength for safe hydrogen storage and high-pressure hydrogen release, and a material with excellent corrosion resistance and hydrogen embrittlement resistance such as stainless steel, chrome-molybdenum alloy steel, aluminum alloy, or nickel alloy may be used.

[0056] A hydrogen storage alloy (212) is embedded inside the pressure vessel (211). The hydrogen storage alloy (212) is an alloy that has the characteristic of chemically bonding with hydrogen to form a metal hydride and releasing hydrogen when heat is applied. In the present invention, a Ti-based alloy is used as the hydrogen storage alloy (212). Specifically, the hydrogen storage alloy (212) may be an alloy that has Ti as the main component and includes one or more transition metals among Mn, Zr, Cr, V, Nb, Mo, Al, Fe, Co, Ni, Cu, Sn, and Si. For example, TiFe, TiMn2, Ti 0.5 Zr 0.5 Alloys such as Mn2, TiCr2, or combinations thereof may be used.

[0057] A hydrogen supply pipe (213) is connected to one end of the hydrogen storage unit (210), and a hydrogen discharge pipe (214) is connected to the other end. The hydrogen supply pipe (213) is a conduit that supplies hydrogen produced from the water electrolysis stack (100) into the interior of the pressure vessel (211). The hydrogen supplied through the hydrogen supply pipe (213) reacts with the hydrogen storage alloy (212) inside the pressure vessel (211) to form a metal hydride. The hydrogen discharge pipe (214) is a conduit that discharges hydrogen released from the hydrogen storage alloy (212) to the outside of the pressure vessel (211) and supplies it to the ammonia synthesis unit (300).

[0058] The cooling section (220) of the chemical compressor (200) is installed in the hydrogen storage section (210) and includes one or more cooling water supply lines (221). Since the process in which the hydrogen storage alloy (212) reacts with hydrogen to form a metal hydride is an exothermic reaction, temperature control is absolutely necessary for efficient reaction and safe operation during hydrogen storage. Therefore, cooling water at a temperature of 10°C or lower is supplied through a cooling water supply pipe (not shown) and circulated in the cooling water supply line (221) to control the continuous rise in temperature of the hydrogen storage alloy (212). As shown in FIG. 2, the cooling water supply line (221) according to one embodiment of the present invention may be installed at the upper and lower parts of the pressure vessel (211), and may be configured to circulate cooling water by utilizing the space between the outer wall and the inner wall as a water jacket. A cooling system with such a water jacket structure can improve cooling efficiency by minimizing the heat transfer distance between the cooling water and the hydrogen storage alloy (212) and securing a large heat exchange area. Specifically, the annular space formed between the outer wall and the inner wall of the pressure vessel (211) is utilized as a cooling water supply line (221). Cooling water is introduced through the inlet (not shown) of this line, circulates through the upper and lower sections, absorbs heat from the hydrogen storage alloy (212) through the inner wall, and is discharged through the outlet (not shown). When the cooling water supply line (221) is installed at the upper and lower sections of the pressure vessel (211), the entire hydrogen storage alloy (212) can be uniformly cooled while avoiding physical interference with the high-pressure water circulation line (232), thereby allowing for efficient control of the temperature of the hydrogen storage alloy (212) during hydrogen storage. However, the installation location of the cooling water supply line (221) is not limited to this embodiment and can be varied. For example, the pressure vessel (211) can be divided into several sections, and the cooling water supply line (221) can be installed in a section excluding the section where the high-pressure water circulation line (232) is installed.This section-by-section installation method can completely eliminate direct interference with the heating unit (230) and improve cooling efficiency.

[0059] The heating section (230) of the chemical compressor (200) may include a high-pressure water heating unit (231) and a high-frequency induction heating unit (233) as a plurality of different heating sources. The high-pressure water heating unit (231) includes a high-pressure water circulation line (232), and the high-frequency induction heating unit (233) includes an induction coil (234). The two heating units can each be controlled independently and operate complementarily to efficiently release hydrogen from the hydrogen storage alloy (212).

[0060] The high-pressure water heating unit (231) is a heating system that utilizes steam waste heat generated in the ammonia synthesis unit (300) to be described later. The high-pressure water heating unit (231) includes a high-pressure water circulation line (232) installed in the hydrogen storage unit (210) and is linked to a high-pressure water supply unit (250) that produces high-pressure water using steam waste heat generated in the ammonia synthesis unit (300), and heats the hydrogen storage alloy (212) by circulating the high-pressure water supplied from the high-pressure water supply unit (250) through the high-pressure water circulation line (232). The high-pressure water circulation line (232) is made of an alloy with excellent heat resistance, pressure resistance, and corrosion resistance, such as stainless steel, so as to withstand high temperature and high pressure. For example, as shown in FIG. 2, the high-pressure water circulation line (232) can be installed in the form of a water jacket in the space between the outer wall and the inner wall of the pressure vessel (211). In the case of a water jacket type, high-pressure water circulates in the annular space between the outer wall and the inner wall of the pressure vessel (211), transferring heat to the hydrogen storage alloy (212) through the inner wall. This water jacket structure has the advantage of providing a uniform heat distribution and enabling constant heating throughout the entire vessel. However, the installation method and location of the high-pressure water circulation line (232) are not limited to this embodiment and can be varied. For example, the high-pressure water circulation line (232) can be installed in a pipe form between the outer wall and the inner wall of the pressure vessel (211). The pipe-type high-pressure water circulation line (232) can be arranged in a spiral or straight structure to perform indirect heat exchange with the hydrogen storage alloy (212) through the inner wall. The high-pressure water circulation line (232) heats the hydrogen storage alloy (212) by circulating high-pressure water supplied from the high-pressure water supply unit (250). In the high-pressure water supply unit (250), steam waste heat generated from the condenser and gas-liquid separator (340) of the ammonia synthesis unit (300) is transferred to water through a heat exchanger, and then the heated water is pressurized by a high-pressure pump system to produce high-pressure water.At this time, the high-pressure water can have a temperature of 200°C to 300°C and a pressure of 16 bar to 90 bar. Due to the high heat capacity and thermal conductivity of the high-pressure water, the hydrogen storage alloy (212) can be heated efficiently.

[0061] The high-frequency induction heating unit (233) is a heating system that directly heats a hydrogen storage alloy (212) through electromagnetic induction using surplus power from renewable energy generation. The high-frequency induction heating unit (233) includes an induction coil (234) installed outside the chemical compressor (200), and the induction coil (234) is connected to a high-frequency generator (260) that receives surplus power from renewable energy generation, and heats the hydrogen storage alloy (212) with induction heat by the high-frequency induction current supplied from the high-frequency generator (260). For example, the induction coil (234) may be made of copper and may be installed by being wound spirally outside the chemical compressor (200) to form a uniform magnetic field in the pressure vessel (211). A high-pressure water circulation line (232) is installed between the outer wall and the inner wall of the pressure vessel (211), and the induction coil (234) is installed outside the chemical compressor (200) so as to be physically separated from each other. At this time, the induction coil (234) heats the hydrogen storage alloy (212) through electromagnetic induction outside the chemical compressor (200), and the high-pressure water circulation line (232) heats the hydrogen storage alloy (212) by circulating high-temperature high-pressure water supplied from the high-pressure water supply unit (250). Through the combination of the two heating methods, the hydrogen storage alloy (212) can be heated efficiently and uniformly. The high-frequency generator (260) receives surplus power from renewable energy generation and generates a high-frequency induction current. When the high-frequency induction current flows through the induction coil (234), an alternating magnetic field is formed around the coil. This magnetic field induces eddy currents within the pressure vessel (211) and the hydrogen storage alloy (212), and the eddy currents are converted into heat by the electrical resistance of the material. In the case of magnetic materials, hysteresis loss due to magnetization reversal also generates additional heat. Through this induction heating process, the hydrogen storage alloy (212) and the pressure vessel (211) themselves become heating elements and generate heat, making direct and efficient heating possible.

[0062] FIG. 3 is a block diagram illustrating in detail the overall components and control relationships of an ammonia synthesis system according to the present invention.

[0063] Referring to FIG. 3, an ammonia synthesis system according to the present invention comprises a water electrolysis stack (100) that produces hydrogen by receiving surplus power from renewable energy generation, a chemical compressor (200) that stores and releases hydrogen supplied from the water electrolysis stack (100), and an ammonia synthesis unit (300) that synthesizes ammonia by receiving hydrogen from the chemical compressor (200). The ammonia synthesis unit (300) shown on the right side of FIG. 3 includes a preheater (310), a gas mixer (320), a reactor for ammonia synthesis (330), and a condenser and gas-liquid separator (340). The ammonia synthesis unit (300) plays the role of efficiently synthesizing ammonia using high-purity, high-pressure hydrogen supplied from the chemical compressor (200).

[0064] The preheater (310) is a device that preheats high-pressure hydrogen supplied from the chemical compressor (200) and high-pressure nitrogen supplied separately. Since the ammonia synthesis reaction generally takes place at a temperature of 400 to 500°C, preheating of the gas supplied to the ammonia synthesis reactor (330) is required. The preheater (310) according to the present invention can use a mixed gas of hydrogen and air or a mixed gas of hydrogen, ammonia, and air as a combustion gas. The heat generated by the combustion of such combustion gas within the preheater (310) is used to preheat the hydrogen and nitrogen. In particular, the economic efficiency of the process can be improved by recycling the gaseous ammonia separated in the condenser and gas-liquid separator (340), which will be described later, as a combustion gas. Furthermore, by using hydrogen and ammonia-based combustion gas, carbon-free heating is possible, which does not emit any carbon dioxide, unlike conventional preheating methods that use fossil fuels.

[0065] The gas mixer (320) is a device that mixes preheated hydrogen and nitrogen in a ratio suitable for ammonia synthesis. Generally, since the ammonia synthesis reaction follows the equation N₂ + 3H₂ → 2NH₃, the theoretical molar ratio of hydrogen gas to nitrogen gas is 3, but in the actual process, it is desirable to supply an excess of hydrogen to shift the reaction equilibrium and improve the conversion rate. In addition, energy efficiency can be improved by supplying steam generated by burning combustion gas in the preheater (310) to the gas mixer (320) and using it to indirectly heat the mixed gas.

[0066] The ammonia synthesis reactor (330) is a device that receives a mixed gas stream produced in a gas mixer (320) and synthesizes it into ammonia using a catalyst. The interior of the ammonia synthesis reactor (330) is maintained at a temperature of 400°C to 500°C and a pressure of approximately 200 bar. The temperature and pressure conditions of the ammonia synthesis reactor (330) are optimized by considering the reaction rate of the ammonia synthesis reaction and the heat exchange efficiency inside the reactor. If the internal temperature and pressure are below the lower limit, the reaction rate and yield of ammonia synthesis are significantly reduced, and if they exceed the upper limit, the heat exchange efficiency decreases along with an increase in the internal exothermic temperature, which may deactivate the catalyst. High-pressure hydrogen in the range of 200 bar to 300 bar supplied by the chemical compressor (200) can directly satisfy the pressure conditions required for ammonia synthesis without additional pressurization, which has the advantage of simplifying the system configuration and improving energy efficiency compared to the conventional multi-stage mechanical compression method. In addition, the hydrogen supplied from the chemical compressor (200) has a high purity of 99.99% or higher, so it can be used directly for ammonia synthesis without a separate PSA purification process.

[0067] The condenser and gas-liquid separator (340) is a device that liquefies and separates ammonia produced in the ammonia synthesis reactor (330) and recirculates steam waste heat and unreacted gas. The condenser cools the synthesis gas supplied from the ammonia synthesis reactor (330) to liquefy the ammonia, and the gas-liquid separator separates the liquefied ammonia and unreacted gas and recirculates them to the gas mixer (320). In addition, the gaseous ammonia separated in the gas-liquid separator can be injected into the preheater (310) as combustion gas. This recirculation process has the effect of improving the yield of the entire process through the reuse of unreacted gas. In addition, the steam waste heat generated in the condenser and gas-liquid separator (340) is transferred to the high-pressure water supply unit (250) and recycled as a heating heat source for the chemical compressor (200).

[0068] As shown by the dotted line at the bottom right of FIG. 3, the steam waste heat generated in the condenser and gas-liquid separator (340) is transferred to the high-pressure water supply unit (250). The high-pressure water supply unit (250) transfers the steam waste heat to water through a heat exchanger and then pressurizes the heated water using a high-pressure pump system to produce high-pressure water having a temperature of 200°C to 300°C and a pressure of 16 bar to 90 bar. This high-pressure water is supplied to the high-pressure water heating unit (231) of the chemical compressor (200) and used to heat the hydrogen storage alloy. Additionally, as shown by the dotted line at the bottom left of FIG. 3, surplus power from renewable energy generation can also be supplied to the high-frequency generator (260). The high-frequency generator (260) receives surplus power directly from renewable energy generation to generate a high-frequency induction current, which is supplied to the high-frequency induction heating unit (233) of the chemical formula compressor (200) and used to heat the hydrogen storage alloy (212) with induction heat.

[0069] The control unit (240) independently controls the output of the high-pressure water heating unit (231) and the high-frequency induction heating unit (233) based on the amount of steam waste heat generated by the ammonia synthesis unit (300) and the amount of surplus power from renewable energy generation. Specifically, the control unit (240) monitors the amount of steam waste heat generated by the condenser and gas-liquid separator (340) in real time, and can optimize energy efficiency by reducing the output of the high-frequency induction heating unit (233) when the amount of steam waste heat generated increases, and increasing the output of the high-frequency induction heating unit (233) when the amount of steam waste heat generated decreases. This mutually complementary control method can implement a system that can flexibly respond to changes in the availability of energy sources. The control unit (240) is composed of a microprocessor, memory, input / output device, communication interface, etc., and collects and analyzes process data from various sensors in real time to output optimal control commands. Control algorithms such as PID (Proportional-Integral-Derivative) control, Fuzzy Logic control, or Model Predictive Control can be applied, thereby optimizing the stability and efficiency of the system.

[0070] FIG. 4 is a schematic diagram illustrating a step-by-step method for synthesizing ammonia using a chemical formula compressor (200) according to the present invention.

[0071] Referring to FIG. 4, the ammonia synthesis method according to the present invention includes the steps of: producing hydrogen using a water electrolysis stack (100) (S100); storing the hydrogen produced from the water electrolysis stack (100) in a chemical composition compressor (200) (S200); releasing the hydrogen stored in the chemical composition compressor (200) (S300); and synthesizing ammonia in an ammonia synthesis unit (300) by receiving hydrogen from the chemical composition compressor (200) (S400).

[0072] In the step (S100) of producing hydrogen using a water electrolysis stack (100), hydrogen is produced by electrolyzing water using surplus electricity from renewable energy generation through any one of the water electrolysis methods of AWE, PEMWE, AEMWE, or SOEC. According to one embodiment of the present invention, the hydrogen produced in the water electrolysis stack (100) may have a pressure in the range of 5 bar to 40 bar. If the pressure is less than 5 bar, the hydrogen storage alloy (212) in the chemical compressor (200) cannot sufficiently absorb hydrogen, so the storage capacity is reduced, and the rate of hydrogen absorption may be reduced due to the low differential pressure. If the pressure exceeds 40 bar, the hydrogen storage capacity of the hydrogen storage alloy (212) increases, but there is a limitation that it is difficult for the hydrogen pressure to exceed 40 bar in the case of hydrogen produced in a general AWE, PEMWE, AEMWE, or SOEC stack. Hydrogen produced in the water electrolysis stack (100) is supplied to the chemical compressor (200).

[0073] In the step (S200) of storing hydrogen produced from the water electrolysis stack (100) in the chemical compressor (200), the hydrogen supplied from the water electrolysis stack (100) reacts with the hydrogen storage alloy (212) in the chemical compressor (200) and is stored in the form of a metal hydride. The hydrogen is stored in a Ti-based hydrogen storage alloy (e.g., TiFe, TiMn2, Ti 0.5 Zr 0.5 When reacting with Mn2, TiCr2, etc., hydrogen in the atomic state penetrates into the space inside the metal crystal lattice, particularly the interstitial sites, and a metal hydride is formed. For example, when TiFe is used as the hydrogen storage alloy (212), the hydrogen storage process can be expressed by the following chemical equation.

[0074] TiFe(s) + H₂(g) → TiFeH₂(s) ΔH < 0

[0075] This reaction is an exothermic reaction, and heat is released. Therefore, it is essential to remove the reaction heat by supplying cooling water at 10°C or lower through the cooling unit (220). Through this, the temperature of the TiFe hydrogen storage alloy (212) is maintained at 20°C to 50°C, and the hydrogen storage efficiency is optimized within this temperature range. If the temperature of the hydrogen storage alloy (212) exceeds 50°C, the equilibrium pressure at which the hydrogen storage alloy (212) absorbs hydrogen is high, so the hydrogen storage capacity decreases. On the other hand, if the temperature of the hydrogen storage alloy (212) is below 20°C, the equilibrium pressure at which the hydrogen storage alloy (212) absorbs hydrogen is low, allowing a large amount of hydrogen to be stored; however, there is a disadvantage that a large amount of energy is consumed for cooling because the cooling system must be continuously operated due to the heat generated continuously during the hydrogen absorption process and the temperature difference with the ambient temperature (room temperature of 20°C to 25°C).

[0076] In the step (S300) of releasing hydrogen stored in the chemical compressor (200), hydrogen stored in the chemical compressor (200) is released by heating the hydrogen storage alloy (212). Specifically, when the control unit (240) of the chemical compressor (200) controls the heating unit (230) and heats the hydrogen storage alloy (212) by at least one of a plurality of different heating sources capable of mutually independent control, the metal hydride is decomposed and hydrogen is released. As a heating source, a high-pressure water heating unit (231) or a high-frequency induction heating unit (233) is used. The high-pressure water heating unit (231) uses high-pressure water produced using steam waste heat generated in the ammonia synthesis unit (300) as a heat source, and the high-frequency induction heating unit (233) uses a high-frequency induction heating method using surplus power from renewable energy generation. The hydrogen release process can be expressed by the following chemical reaction equation.

[0077] TiFeH₂(s) → TiFe(s) + H₂(g) ΔH > 0

[0078] This reaction is an endothermic reaction, and sufficient heat must be supplied from the inside and outside to promote the reaction. Accordingly, the TiFe hydrogen storage alloy is heated to a temperature of 200°C to 300°C through the heating unit (230). The pressure of the hydrogen released from the hydrogen storage alloy (212) is in the range of 200 bar to 300 bar, which can satisfy the pressure conditions required for ammonia synthesis. The released high-purity, high-pressure hydrogen is supplied to the ammonia synthesis unit (300) and utilized for ammonia synthesis.

[0079] The step (S400) of synthesizing ammonia in an ammonia synthesis unit (300) by receiving hydrogen from a chemical compressor (200) includes the steps of preheating the hydrogen and nitrogen supplied from the chemical compressor (200) in a preheater (310), mixing the preheated hydrogen and nitrogen in a gas mixer (320), supplying the mixed gas produced in the gas mixer (320) to an ammonia synthesis reactor (330) to synthesize ammonia, and liquefying and separating the ammonia produced in the ammonia synthesis reactor (330) in a condenser and a gas-liquid separator (340) and recovering steam waste heat. The ammonia synthesis method according to the present invention implements a carbon-free heating system that does not emit any carbon dioxide by using a mixture of hydrogen and air or a mixture of hydrogen, ammonia, and air as a combustion gas in a preheater (310), and at the same time, can improve the energy efficiency of the entire system by recycling the steam waste heat recovered from the condenser and gas-liquid separator (340) as a heat source for the chemical compressor (200). In addition, the economic efficiency and environmental friendliness of green ammonia production can be improved by increasing resource utilization and simplifying the process through the direct supply of high-purity hydrogen and the recirculation of unreacted gas.

[0080] The chemical compressor (200) containing the hydrogen storage alloy (212) according to the present invention utilizes a hydrogen storage and release mechanism to safely produce high-pressure hydrogen using a simple single compression method compared to a mechanical compressor. In addition, since there are no mechanical operating parts, the structure is simple, and the initial construction and maintenance costs are low. Furthermore, since no impurities are mixed in, high-purity hydrogen of 99.99% or higher can be obtained without a separate PSA purification process. Moreover, the pressure of the released hydrogen can be precisely controlled by changing the composition of the hydrogen storage alloy (212) and controlling the heating temperature, so it can be used to provide customized high-pressure hydrogen for various industrial applications such as hydrogen charging stations, fuel cells, combined cycle power plants, and hydrogen co-firing gas turbines.

[0081] An ammonia synthesis system and method using a chemical compressor (200) containing a hydrogen storage alloy (212) according to the present invention can improve energy efficiency by using two different heating sources, a high-pressure water heating unit (231) and a high-frequency induction heating unit (233), in a mutually complementary manner. In particular, the energy circulation efficiency of the entire system can be increased by recycling steam waste heat generated in the ammonia synthesis unit (300) in the form of high-pressure water and utilizing surplus power from renewable energy generation for high-frequency induction heating. Furthermore, the economic feasibility of the process can be improved by maximizing resource utilization through the recirculation of unreacted gas and the utilization of combustion gas from gaseous ammonia. In particular, sustainable ammonia production based on green energy is possible through a control system that can flexibly respond to the variability of renewable energy generation.

[0082] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing its technical concept or essential features.

[0083] Therefore, the embodiments described above should be understood as exemplary in all respects and not limiting. The scope of the invention is defined by the claims rather than by the detailed description above, and all modifications or modified forms derived from the meaning and scope of the claims and equivalents thereof should be interpreted as being included within the scope of the invention.

Claims

1. An ammonia synthesis system utilizing a chemical compressor with an integrated hydrogen storage alloy, Hydrogen-producing electrolysis stack; A chemical compressor for storing and releasing hydrogen supplied from the above-mentioned water electrolysis stack; and An ammonia synthesis system comprising an ammonia synthesis unit that synthesizes ammonia by receiving hydrogen from the above chemical formula compressor; The above chemical formula compressor is, Hydrogen storage unit with built-in hydrogen storage alloy; A cooling unit for cooling the above hydrogen storage unit; A heating unit for heating the above hydrogen storage unit; and A control unit that controls the operation of the cooling unit and the heating unit; is included, The heating unit includes a plurality of different heating sources capable of mutually independent control, and The above control unit controls the cooling unit to cool the hydrogen storage alloy of the hydrogen storage unit when hydrogen is stored in the hydrogen storage unit, and controls at least one of a plurality of heating sources of the heating unit to heat the hydrogen storage alloy when hydrogen is released from the hydrogen storage unit. Ammonia synthesis system.

2. In Paragraph 1, The above hydrogen storage unit is, Pressure vessel; A hydrogen storage alloy embedded inside the above-mentioned pressure vessel; A hydrogen supply pipe for supplying hydrogen produced from the above-mentioned water electrolysis stack into the interior of the above-mentioned pressure vessel; and A hydrogen discharge pipe for discharging hydrogen released from the above hydrogen storage alloy to the outside of the above pressure vessel; including, Ammonia synthesis system.

3. In Paragraph 1 or 2, The above hydrogen storage alloy is a Ti-based alloy comprising one or more transition metals selected from Mn, Zr, Cr, V, Nb, Mo, Al, Fe, Co, Ni, Cu, Sn, and Si. Ammonia synthesis system.

4. In Paragraph 1 or 2, The above cooling unit is installed in the hydrogen storage unit and includes one or more cooling water supply lines that circulate cooling water at 10°C or lower, Ammonia synthesis system.

5. In Paragraph 1, The above heating unit includes a high-pressure water heating unit or a high-frequency induction heating unit as a plurality of different heating sources, Ammonia synthesis system.

6. In Paragraph 5, The above-mentioned high-pressure water heating unit is, It includes a high-pressure water circulation line installed in the above hydrogen storage unit, and It is linked to a high-pressure water supply unit that produces high-pressure water using steam waste heat generated in the ammonia synthesis unit, and Heating the hydrogen storage alloy by circulating the high-pressure water supplied from the high-pressure water supply unit through the high-pressure water circulation line, Ammonia synthesis system.

7. In Paragraph 6, The above high-pressure water has a temperature of 200°C to 300°C and a pressure of 16 bar to 90 bar, Ammonia synthesis system.

8. In Paragraph 5, The above-mentioned high-frequency induction heating unit is, It includes an induction coil installed on the outside of the above chemical formula compressor, and The above induction coil is connected to a high-frequency generator that receives surplus power from renewable energy generation, and Heating the hydrogen storage alloy with inductive heat by the high-frequency induction current supplied from the high-frequency generator, Ammonia synthesis system.

9. In Paragraph 1, The above ammonia synthesis unit is, A preheater for preheating hydrogen and nitrogen supplied from the above chemical compressor; A gas mixer for mixing the above-mentioned preheated hydrogen and nitrogen; A reactor for synthesizing ammonia that receives the mixed gas produced in the above gas mixer and synthesizes ammonia; and A condenser and a gas-liquid separator for liquefying and separating ammonia produced in the above-mentioned ammonia synthesis reactor and recovering steam waste heat; including, Ammonia synthesis system.

10. In Paragraph 5, The above control unit is, Based on the amount of steam waste heat generated by the ammonia synthesis unit and the amount of surplus power from renewable energy generation, the output of the high-pressure water heating unit and the high-frequency induction heating unit is controlled, and When the amount of steam waste heat generated increases, the output of the high-frequency induction heating unit is reduced, and when the amount of steam waste heat generated decreases, the output of the high-frequency induction heating unit is increased. Ammonia synthesis system.

11. A method for synthesizing ammonia using a chemical compressor with a built-in hydrogen storage alloy, wherein A step of producing hydrogen using a water electrolysis stack; A step of storing hydrogen produced from the above-mentioned water electrolysis stack in a chemical compressor; A step of releasing hydrogen stored in the above chemical formula compressor; and A step of synthesizing ammonia in an ammonia synthesis unit by supplying hydrogen from the above chemical formula compressor; Includes, The step of storing the above hydrogen in a chemical compressor is, A step of supplying hydrogen to a hydrogen storage unit containing a hydrogen storage alloy; and The method includes the step of, when storing hydrogen in a hydrogen storage unit, the control unit of the chemical compressor controlling the cooling unit to cool the hydrogen storage alloy of the hydrogen storage unit; The step of releasing hydrogen stored in the chemical formula compressor comprises the control unit of the chemical formula compressor controlling the heating unit to heat the hydrogen storage alloy by at least one of a plurality of different heating sources capable of mutually independent control. Ammonia synthesis method.

12. In Paragraph 11, The above-mentioned water electrolysis stack produces hydrogen using surplus electricity from renewable energy generation through any one of the water electrolysis methods of AWE (Alkaline Water Electrolysis), PEMWE (Proton Exchange Membrane Water Electrolysis), AEMWE (Anion Exchange Membrane Water Electrolysis), or SOEC (Solid Oxide Electrolysis Cell). Ammonia synthesis method.

13. In Paragraph 11, A plurality of different heating sources of the above heating unit heat using a high-pressure water heating method or a high-frequency induction heating method, Ammonia synthesis method.

14. In Paragraph 13, The above high-pressure water heating method heats the hydrogen storage alloy by circulating high-pressure water, produced using steam waste heat generated in the ammonia synthesis unit, through a high-pressure water circulation line installed in the hydrogen storage unit. Ammonia synthesis method.

15. In Paragraph 14, The above high-pressure water has a temperature of 200°C to 300°C and a pressure of 16 bar to 90 bar, Ammonia synthesis method.

16. In Paragraph 13, The above high-frequency induction heating method heats a hydrogen storage alloy with induction heat by supplying a high-frequency induction current generated from a high-frequency generator receiving surplus power from renewable energy generation to an induction coil installed outside the chemical formula compressor. Ammonia synthesis method.

17. In Paragraph 13, The above control unit is, Based on the amount of steam waste heat generated by the ammonia synthesis unit and the amount of surplus electricity from renewable energy generation, the output of the high-pressure water heating method and the high-frequency induction heating method is controlled, and If the amount of steam waste heat generated increases, the output of the high-frequency induction heating method is reduced, and if the amount of steam waste heat generated decreases, the output of the high-frequency induction heating method is increased. Ammonia synthesis method.

18. In Paragraph 11, In the step of heating the hydrogen storage alloy, the heating temperature of the hydrogen storage alloy is 200℃ to 300℃, Ammonia synthesis method.

19. In Paragraph 11, The pressure of hydrogen released from the above hydrogen storage alloy is 200 bar to 300 bar, Ammonia synthesis method.

20. In Paragraph 11 or 12, The step of synthesizing ammonia in the ammonia synthesis unit by supplying hydrogen from the above chemical formula compressor is, A step of preheating hydrogen and nitrogen supplied from the above chemical compressor in a preheater; A step of mixing the above-mentioned preheated hydrogen and nitrogen in a gas mixer; A step of synthesizing ammonia by supplying the mixed gas produced in the above gas mixer to a reactor for ammonia synthesis; and A step of liquefying and separating the ammonia produced in the above-mentioned ammonia synthesis reactor in a condenser and a gas-liquid separator, and recovering steam waste heat; A method for synthesizing ammonia including

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