Apparatus and method for producing ammonia

Abstract

An apparatus (1) for producing ammonia, the apparatus comprising an ammonia reactor (44) for generating ammonia (NH3) from a synthesis gas, where the synthesis gas comprises hydrogen (H2) and nitrogen (N2); the device further comprises an electrolyser (2) for generating hydrogen and oxygen from water; wherein the device also has a compressor (6), which is fluidically connected to the electrolyser (2) and is used for compressing hydrogen gas (H2) from the electrolyser (2), and wherein the compressor (6) is used for compressing hydrogen gas (H2) that can be conveyed.

Description

Technical Field

[0001] The present invention relates to an apparatus for producing ammonia, which comprises an ammonia reactor for producing ammonia (NH 3 ) from syngas, wherein the syngas comprises hydrogen (H 2 ) and nitrogen (N 2 ), and the apparatus further comprises an electrolyzer for producing hydrogen (H 2 ) and oxygen (O 2 ) from water.

[0002] The present invention also relates to a method for producing ammonia, wherein ammonia (NH 3 ) is produced from syngas in an ammonia reactor, wherein the syngas comprises hydrogen (H 2 ) and nitrogen (N 2 ), and wherein hydrogen (H 2 ) and oxygen (O 2 ) are produced by using renewable energy in an electrolyzer.

[0003] The present invention provides a solution for an ammonia production apparatus, the ammonia production apparatus comprising an electrolyzer operating with renewable energy, wherein cooling and heating are performed by a refrigerator or a heat pump in the apparatus, and wherein the apparatus is equipped with a gas turbine operating with hydrogen, and the gas turbine provides nitrogen for producing ammonia. Background Art

[0004] Known methods for producing ammonia generally require a large amount of energy. According to initial estimates, producing ammonia requires approximately 1% of the energy generated worldwide today.

[0005] Ammonia produced from green hydrogen is called green ammonia. Green ammonia is considered a rapidly growing energy carrier for hydrogen. In addition, ammonia is used in many industrial processes, especially in fertilizers. It is estimated that since the liquefaction of pure hydrogen is very energy-intensive, approximately 50% of the green hydrogen produced in the coming years will be directly processed into liquid ammonia for long-distance transportation of hydrogen.

[0006] In addition to producing hydrogen by electrolysis and nitrogen by an air separation unit, the largest energy requirements and compression requirements are for syngas compression and cold box Syngas compression compresses the nitrogen-hydrogen mixture to a pressure of 150 - 200 bar required for the synthesis process, and the cold box provides refrigeration energy for liquefying and cooling ammonia to approximately -33°C at atmospheric pressure.

[0007] A preheating unit for heating the syngas to the reaction temperature is usually required.

[0008] Ammonia is an important chemical, mainly used in the fertilizer industry. The ammonia reaction is a catalytic reaction of hydrogen and nitrogen at high temperature and high pressure. However, the largest part of the energy consumption and about 90% of the carbon emissions are attributed to the production of hydrogen. Hydrogen is almost exclusively produced by steam reforming of fossil fuels. Most ammonia production facilities use steam reforming of natural gas to produce hydrogen and carbon dioxide. Coal, heavy fuel oil, and naphtha can also be used, but the carbon dioxide emissions are relatively high. Therefore, the production of ammonia by these methods accounts for almost 1.5% of the world's CO 2 emissions. Nitrogen is obtained from compressed air or air separation equipment.

[0009] Currently, the nitrogen and hydrogen required for ammonia production are usually compressed to the required synthesis pressure in a syngas compressor. The inlet pressure of this compressor is usually determined by the hydrogen pressure, which is limited to the maximum outlet pressure of the electrolysis system (up to 30 - 40 bar) in on-site electrolysis-based green ammonia applications.

[0010] The shaft power of the compressor is provided by a steam turbine, and the required steam is generated from the heat released during the ammonia synthesis process. The preheating of the syngas must be achieved through a fuel-driven or electric-driven heater or by recovering waste heat from the ammonia process, resulting in a reduction in the amount of steam that can be generated for the steam turbine.

[0011] Liquefaction is achieved through a coolant cycle.

[0012] Given the responsibility to achieve net-zero emission goals, new carbon-free fuels such as green ammonia and green hydrogen are needed to decarbonize energy generation, heating, transportation, and industry.

[0013] It is estimated that approximately 50% of the green hydrogen produced in the coming years will be converted into green ammonia.

[0014] Ammonia can be used as a practical hydrogen energy carrier, and existing industries produce, store, and trade millions of tons of ammonia annually, which means that the infrastructure and technologies for launching a hydrogen economy already exist.

[0015] In conventional ammonia production, hydrogen (H 2 ) is obtained from the most widely used method for hydrogen generation, i.e., steam methane reforming (SMR), and nitrogen (N 2 ) is obtained from air or an air separation unit.

[0016] Nitrogen (N 2 ) and hydrogen (H 2)Mix in stoichiometric ratio (1:3), compress it with a syngas compressor, and introduce it into an ammonia synthesis reactor at a pressure of 150 to 220 bar. The ammonia synthesis gas reactor operates at an operating temperature of about 500 °C. This process is exothermic, releasing a large amount of heat of 46 kJ per mol of ammonia, and this heat is used to generate steam. After the reaction, about 25% of the ammonia is obtained as a product, and the remaining ammonia is returned via a recycle compressor. The ammonia produced is then liquefied by cryogenic distillation.

[0017] In the green ammonia production method, hydrogen is generated from water by electrolysis, which is a mature method. Summary of the Invention

[0018] The object of the present invention is to provide an improved apparatus and an improved method for producing ammonia, especially with improvements in the use of energy required for ammonia production.

[0019] This object is achieved by an apparatus for producing ammonia, which includes an ammonia reactor for producing ammonia (NH 3 ) from syngas, wherein the syngas contains hydrogen (H 2 ) and nitrogen (N 2 ), and the apparatus further includes an electrolyzer (2) for producing hydrogen and oxygen from water, and the apparatus has a compressor (6) which is fluidically connected to the electrolyzer (2) and is used to compress the hydrogen (H 2 ) from the electrolyzer (2), and the compressor (6) is used to compress hydrogen (H 2 ), especially the hydrogen (H 2 ) that can be transported.

[0020] In addition, this object is also achieved by a method for producing ammonia, wherein ammonia (NH 3 ) is produced from syngas in an ammonia reactor, wherein the syngas contains hydrogen (H 2 ) and nitrogen (N 2 ), and hydrogen and oxygen are generated in the electrolyzer by using renewable energy, and the hydrogen generated in the electrolyzer is compressed in the compressor.

[0021] Thus, a new solution for producing green ammonia is proposed. This solution proposes to establish an electrolyzer (also called: electrolytic cell) in remote areas and be able to transport hydrogen hundreds of kilometers via pipelines.

[0022] The electrolyzer receives electrical energy from a wind power generation device or a photovoltaic power generation device and generates hydrogen and oxygen. These gases are generated by the electrolyzer at a pressure of 1 to 40 bar.

[0023] Cooling the electrolyzer requires cold water, which is difficult to achieve in remote areas or desert areas.

[0024] According to the present invention, compressed oxygen is directly expanded in an expansion turbine, and the oxygen is used for cooling after expansion.

[0025] According to the present invention, a heat pump cycle circuit is used, and its heat is used to raise the temperature of oxygen before the oxygen expands in an expansion turbine coupled to a generator. In the condenser, all the latent heat of the coolant is used to convert water into steam and at the same time condense the coolant.

[0026] The pressurized steam can also be used for power generation. In addition, the coolant of the heat pump expands in a J-T valve or a thermoexpander, and the enthalpy of the coolant can be converted into mechanical energy or electrical energy here. The two-phase coolant mixture absorbs heat from the hot water leaving the electrolyzer before entering the heat pump compressor, cools the hot water and vaporizes itself.

[0027] At the location of the ammonia production facility, nitrogen (N 2 ) and hydrogen (H 2 ) need to be mixed in a stoichiometric ratio of 1:3 as raw materials. Nitrogen (N 2 ) is usually supplied through an air separation unit or from the air, while hydrogen is mainly provided by steam reforming of methane.

[0028] Advantageously, with the present invention, it is not necessary to use an air separation unit to supply nitrogen (N 2 ).

[0029] According to the present invention, hydrogen (H 2 ) is generated in the electrolyzer, because hydrogen is one of the raw materials of ammonia and is supplied to the location of the ammonia production facility through a pipeline. A gas turbine is used to generate nitrogen, and the gas turbine runs on hydrogen and drives a syngas compressor. The exhaust gas of the gas turbine mainly consists of hot steam and nitrogen, and the exhaust gas is separated in a condenser and then absorbed in an absorber or a PSA unit. Condensed water is obtained in the condenser unit. The condensed water can be pumped and heated using the exhaust heat from the gas turbine, and then expanded in a steam turbine that generates additional electricity.

[0030] The nitrogen generated from the exhaust gas is separated from the steam and absorbed in an absorber or a PSA unit. Subsequently, the nitrogen is compressed and mixed stoichiometrically with the compressed hydrogen to generate a syngas mixture. The syngas mixture is compressed to the required process pressure in a syngas compressor.

[0031] By integrating the electrolyzer with renewable energy, the present invention proposes an innovative solution for an environmentally friendly ammonia production facility.

[0032] Advantageous improvements are given in the dependent claims.

[0033] Advantages of the device according to the invention and the method according to the invention are:

[0034] - A more efficient, more environmentally friendly and more economical process for green hydrogen and green ammonia

[0035] - Integrating the exhaust gas of a gas turbine operating with hydrogen (H 2 ) to realize the generation of nitrogen (N 2 ), green electrical / mechanical drive energy and water for electrolysis

[0036] Utilizing pressurized oxygen (O 2 ) to convert it into electricity, improving the overall efficiency and providing support for the operation of devices using fluctuating renewable energy.

[0037] The above characteristics, features and advantages of the present invention and the ways to achieve them will be more clearly and explicitly elucidated in conjunction with the following description of embodiments, and the embodiments will be more detailedly explained in conjunction with the accompanying drawings.

[0038] Here, the same components or components with the same functions are provided with the same reference numerals.

[0039] Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings are not intended to show the embodiments to scale, but are schematic diagrams and / or slightly deformed figures for illustration purposes. For supplementary teachings obvious from the drawings, reference may be made to the relevant prior art. Description of the Drawings

[0040] Att Figure 1A and 1B show a schematic diagram of a device for generating ammonia. Detailed Description of the Embodiments

[0041] The drawings show a schematic diagram of a device 1 for generating ammonia.

[0042] The device 1 includes an electrolyzer 2, which is also called an electrolytic cell 2. The electrolyzer 2 is used to generate hydrogen (H 2 ) and oxygen (O 2 ). For this purpose, a large amount of electrical energy generated by a wind power generation device 3, a photovoltaic power generation device 4 or other renewable energy sources is used to decompose water (H 2 O) into its constituent elements: hydrogen (H 2 ) and oxygen (O 2 ).

[0043] The hydrogen (H 2)It is guided through pipeline 5 to compressor 6, where the hydrogen is compressed so that it can be transported over a long distance along pipeline 7. Therefore, the compression in compressor 6 is carried out under high pressure. The dashed line 8 symbolically represents the spatial separation between hydrogen generation and ammonia production 8. The separation between hydrogen generation and ammonia production 8 can be several kilometers here.

[0044] In the first alternative 11, pressurized oxygen (O 2 ) is supplied via pipeline 10 to expander 12. In expander 12, the pressure energy of oxygen (O 2 ) is converted into mechanical energy, and this mechanical energy can be used to drive generator 13.

[0045] The operation of electrolyzer 2 requires cooling. For this purpose, a cooling pipeline 14 with cooled water as the coolant is connected to electrolyzer 2, and the water heated in electrolyzer 2 is discharged from electrolyzer 2 via another cooling pipeline 15.

[0046] In the first alternative 11, hot water is supplied to heat exchanger 16, where the thermal energy of the hot water is transferred to the cold oxygen (O 2 ) from the expander. The oxygen (O 2 ) is heated here. On the contrary, the water is cooled and then supplied to electrolyzer 2 via pipeline 14 again.

[0047] The oxygen (O 2 ) discharged from the heat exchanger can then be used for further energy generation 16 or discharged into the atmosphere.

[0048] In the second alternative 9, the heated water from pipeline 15 is supplied as a heat source to heat pump cycle circuit 17. For this purpose, the water heated in electrolyzer 2 reaches heat exchanger 18 through pipeline 15. At the heat exchanger, the thermal energy of the water is used to heat the coolant located in heat pump cycle circuit 17. The water is cooled here and supplied to electrolyzer 2 again as cooled cold water via pipeline 14.

[0049] The coolant reaches compressor 19 or compressor 19 after passing through heat exchanger 18. At the compressor, the temperature and pressure of the coolant increase. The coolant flows through heat exchanger 20 after passing through compressor 19, and the oxygen (O 2 ) generated in electrolyzer 2 flows through this heat exchanger. The oxygen (O 2 ) heated in heat exchanger 20 is supplied to expander 21 and can be used here to generate electrical energy through generator 22. By supplying thermal energy first, more electrical energy can be generated than in the first alternative. The cooled oxygen 23 is discharged from expander 21.

[0050] The coolant reaches another heat exchanger 24 after passing through heat exchanger 20, where the thermal energy of the coolant is transferred to the water 26 arriving via line 25. Here, heat exchanger 24 converts the water into steam and the steam 27 is supplied to steam turbine 28. Steam turbine 28 can then drive the same generator 22 and thus generate electrical energy. The water 29 that is recondensed into water after passing through steam turbine 28 can be supplied to heat exchanger 24 again.

[0051] The coolant flows to expansion device 30 after passing through heat exchanger 24. The expansion device can be a Joule-Thomson valve (J-T valve) or an expander, where the temperature and pressure of the coolant are reduced. The coolant flows back to heat exchanger 18 after passing through expansion device 30, thereby closing the heat pump cycle loop.

[0052] For the ammonia process, nitrogen (N 2 ) and hydrogen (H 2 ) need to be mixed in a stoichiometric ratio of 1:3 as raw materials. In conventional equipment, nitrogen (N 2 ) is supplied by an air separation unit or from the air, while hydrogen (H 2 ) mainly comes from methane steam reforming.

[0053] Hydrogen reaches mixing chamber 31 via pipeline 7, where hydrogen (H 2 ) and nitrogen (N 2 ) are mixed to form syngas.

[0054] A part of the hydrogen (H 2 ) from pipeline 7 is supplied via line 32 to gas turbine 33 that can operate using hydrogen (H 2 ). The hot exhaust gas flowing out of gas turbine 33 contains a mixture 34 composed of nitrogen (N 2 ), water (H 2 O), hydrogen (H 2 ), nitrogen oxides (NOx) and oxygen (O 2 ). The hot exhaust gas is supplied to heat exchanger 35. The exhaust gas flows to condenser 36 after passing through heat exchanger 35, where the water from the exhaust gas condenses. The water 37 is then guided through a heat exchanger via line 38, where the water is converted into steam. Subsequently, the steam is supplied to steam turbine 39, where the thermal energy of the steam is converted into mechanical energy, and electrical energy is generated by generator 40.

[0055] Air 41, especially ambient air, is supplied to gas turbine 33.

[0056] A part of the exhaust gas flows through absorber 42 or pressure swing adsorption (PSA) 42, where nitrogen (N2 ) is separated from the exhaust gas and flows together with the syngas to the mixing chamber 31. The syngas flows through a compressor 43 driven by a gas turbine and reaches an ammonia reactor 44. The hot ammonia generated in the ammonia reactor 44 is cooled via a heat exchanger 45 and supplied to a storage device 47 via a cooling unit 46. The heat generated in the heat exchanger 45 can be used to generate steam and drive a steam turbine 48 and a generator 49.

[0057] The nitrogen (N 2 ) separated from the GT exhaust gas 2 ) is mixed stoichiometrically with the hydrogen (H

[0058] ) from the electrolysis device to produce a syngas mixture required for ammonia synthesis. 2 ) and nitrogen (N 2 ). The hydrogen (H 2 ) and nitrogen (N 2 ) react in the ammonia reactor 2 according to the following chemical reaction formula:

[0059] N 2 + 3H 2 → 2NH 3 + 92 kJ / mol,

[0060] This chemical reaction is a strongly exothermic reaction, that is, the ammonia NH 3 generated in the ammonia reactor has a relatively high temperature. According to the present invention, this high temperature is used to generate steam and expand it in the steam turbine 48, thereby generating electrical energy in the generator 49.

[0061] A detailed illustration of the ammonia reactor 44 is omitted here.

Claims

1. An apparatus (1) for producing ammonia, said apparatus comprising: An ammonia reactor (44) for producing ammonia (NH 3 ) from syngas, wherein the syngas contains hydrogen (H 2 ) and nitrogen (N 2 ); an electrolyzer (2) for generating hydrogen and oxygen from water, characterized in that The device also has a compressor (6), which is fluidically connected to the electrolyzer (2) and is used to compress the hydrogen (H 2 ) coming from the electrolyzer (2). Among them, the compressor (6) is used to compress hydrogen (H 2 ).

2. The apparatus (1) according to claim 1, wherein Compressed hydrogen (H 2 ) is suitable for being transported in a pipeline (7).

3. The apparatus (1) according to claim 1, wherein the electrolyzer (2) operates using renewable energy.

4. The apparatus (1) according to claim 1, wherein The device has a gas turbine (33) operating with hydrogen (H 2 ), wherein the hydrogen (H 2 ) generated by the electrolyzer (2) is mixed with nitrogen (N 2 ) generated from the exhaust gas of the gas turbine (33) to produce the synthesis gas.

5. The apparatus (1) according to claim 4, wherein the apparatus has a heat exchanger (35) for generating steam from the thermal energy of the exhaust gas of the gas turbine (33), and wherein a steam turbine (39) is provided, and steam from the heat exchanger (35) is supplied to the steam turbine.

6. The apparatus (1) according to claim 5, wherein the apparatus further comprises a generator (40) coupled to the steam turbine (39) in a torque-transmitting manner.

7. The apparatus (1) according to claim 3, wherein the apparatus has a separation unit (42) for separating the exhaust gas from the gas turbine (33) into nitrogen and water, wherein the nitrogen is used for the synthesis gas, and wherein the water is supplied to the heat exchanger (35).

8. The apparatus (1) according to any one of the preceding claims, wherein the apparatus has an oxygen pipeline (10) for the oxygen obtained from the electrolyzer (2), and the apparatus further comprises an expander (12), wherein the oxygen from the oxygen pipeline (10) is in fluid communication with the expander (12), and wherein in the expander (12), the pressure energy of the oxygen from the oxygen pipeline (10) is converted into mechanical energy.

9. The apparatus (1) according to claim 8, wherein the apparatus has a heat exchanger for cooling the coolant of the electrolyzer with the oxygen flowing out of the expander (12).

10. The apparatus (1) according to any one of claims 1 to 7, wherein the electrolyzer (2) can be cooled using a coolant, and wherein the apparatus (1) includes a heat pump cycle circuit (17) for cooling the coolant.

11. The apparatus (1) according to claim 10, wherein the apparatus includes a heat exchanger (20) in fluid communication with the oxygen pipeline (10), and wherein the heat exchanger (20) enables the thermal energy of the coolant in the heat pump cycle circuit (17) to be transferred to the oxygen.

12. A method for producing ammonia, wherein Ammonia (NH 3 ) is produced from syngas in an ammonia reactor (44), where the syngas contains hydrogen (H 2 ) and nitrogen (N 2 ). wherein hydrogen and oxygen are generated in an electrolyzer (2) using renewable energy, and wherein the hydrogen generated in the electrolyzer (2) is compressed in a compressor (6).

13. The method according to claim 12, wherein the hydrogen compressed in the compressor (6) is used for transportation.

14. The method according to claim 12 or 13, wherein an expander (21) is used, and the expander operates using the heated oxygen from the heat exchanger (20).

15. The method according to any one of claims 12 to 14, wherein, a generator (22) operated by using the expander (21) is used, and the generator (22) is used for generating electric energy.

16. The method according to any one of claims 12 to 15, wherein, a separation unit (42) is used, and the exhaust gas from the gas turbine (33) is separated into nitrogen and water by using the separation unit.

17. The method according to any one of claims 12 to 16, wherein, a coolant is used to cool the electrolyzer (2), and the coolant is cooled by using a heat pump cycle circuit (17).

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