Equipment and method for producing ammonia

Abstract

The facility (1) for producing ammonia comprises an ammonia reactor (44) configured to produce ammonia (NH) from synthesis gas, the synthesis gas comprising hydrogen (H) and nitrogen (N), and further comprises an electrolyzer (2) configured to produce hydrogen and oxygen from water, a compressor (6) fluidly connected to the electrolyzer (2) and configured to compress the hydrogen (H) coming from the electrolyzer (2), and the compressor (6) configured to compress the transportable hydrogen (H).

Description

[Technical Field]

[0001] The present invention relates to an ammonia production facility comprising an ammonia reactor configured to produce ammonia (NH3) from synthesis gas, the synthesis gas comprising hydrogen (H2) and nitrogen (N2), and further comprising an electrolyzer configured to produce hydrogen (H2) and oxygen (O2) from water.

[0002] The present invention further relates to a method for producing ammonia, wherein ammonia (NH3) is produced from synthesis gas in an ammonia reactor, and the synthesis gas contains hydrogen (H2) and nitrogen (N2) in an electrolyzer, where hydrogen (H2) and oxygen (O2) are produced using renewable energy.

[0003] The present invention proposes a draft ammonia plant with an electrolyzer operated on renewable energy, where cooling and heating are provided by chillers or heat pumps, and the plant uses a hydrogen-driven gas turbine, which provides nitrogen for ammonia production. [Background technology]

[0004] The production of ammonia is based on known processes that are usually very energy intensive: according to current calculations, approximately 1% of the energy currently produced worldwide is required for the production of ammonia.

[0005] Ammonia produced from green hydrogen is called green ammonia. Green ammonia is considered a rapidly growing energy carrier for hydrogen. Furthermore, green ammonia is used in many industrial processes, especially in fertilizers. Because liquefying pure hydrogen requires so much energy, it is estimated that about 50% of the green hydrogen produced in the last few years will be processed directly into liquid ammonia for long-distance transportation of the hydrogen.

[0006] In addition to producing hydrogen through electrolysis and nitrogen through an air separation system, the largest energy and compression expenses are incurred in syngas compression, which compresses the nitrogen-hydrogen mixture to the 150-220 bar pressure required for the synthesis process, and in the cold box, which provides the refrigeration energy to liquefy the ammonia at atmospheric pressure and cool it to approximately -33°C.

[0007] Typically, a preheat unit is required to heat the synthesis gas to the reaction temperature.

[0008] Ammonia is an important chemical used especially in the fertilizer industry. The ammonia reaction is a catalytic reaction of hydrogen and nitrogen at high temperature and pressure. However, hydrogen production accounts for the largest portion of energy consumption and approximately 90% of carbon emissions. Hydrogen is produced almost exclusively by steam reforming of fossil fuels. Most ammonia plants utilize steam reforming of natural gas to produce hydrogen and carbon dioxide. Coal, heavy oil, and naphtha are also used, but produce higher carbon dioxide emissions. As a result, ammonia production by these methods causes approximately 1.5% of global CO2 emissions. Nitrogen is obtained from compressed air or air separation plants.

[0009] Currently, the nitrogen and hydrogen required for ammonia production are typically compressed to the required synthesis pressure in a synthesis gas compressor. The suction pressure of the compressor for this is typically dictated by the hydrogen pressure, but when using green ammonia, which is electrolyzed on-site, this is limited to the maximum start-up pressure of the electrolysis plant (maximum 30-40 bar).

[0010] Shaft power for the compressor is provided by a steam turbine, while the required steam is generated by heat released during ammonia synthesis. Preheating of the synthesis gas must be done either by fuel-fired or electrically fired heaters or by utilizing waste heat from the ammonia process, which reduces the amount of steam available for the steam turbine.

[0011] Liquefaction is achieved by refrigerant circulation.

[0012] To decarbonise energy production, heat supply, transport and industry, along with the mandate to achieve the net-zero emissions targets mentioned above, new zero-carbon fuels such as green ammonia and green hydrogen are needed.

[0013] It is estimated that around 50% of the green hydrogen produced over the next few years will be converted into green ammonia.

[0014] Ammonia can be used as a practical hydrogen energy carrier, and existing industries producing, storing, and trading millions of tonnes of ammonia each year mean that the infrastructure and technology to launch a hydrogen economy already exists.

[0015] In conventional ammonia production, hydrogen gas (H2) is obtained from steam methane reforming (SMR), the most common method for producing hydrogen, and nitrogen gas (N2) is obtained from air or an air cracking facility.

[0016] Nitrogen (N2) and hydrogen (H2) are mixed stoichiometrically (1:3), compressed in a synthesis gas compressor, and introduced into the ammonia synthesis reactor at a pressure of 150-220 bar. The ammonia synthesis gas reactor operates at an operating temperature of approximately 500°C. The process is exothermic, and a large amount of heat, 46 kJ / mol of ammonia, is released and utilized to produce steam. After the reaction, approximately 25% of the ammonia is obtained as a product, and the remainder is returned via the circulation compressor. The ammonia produced is then liquefied by cryogenic distillation.

[0017] The green ammonia method produces hydrogen through the electrolysis of water, a method that is already well established. Summary of the Invention [Problem to be solved by the invention]

[0018] The present invention aims to provide an improved plant and an improved process for producing ammonia, particularly with regard to the use of energy required to produce the ammonia. [Means for solving the problem]

[0019] This problem is solved by an ammonia production facility comprising an ammonia reactor configured to produce ammonia (NH3) from a synthesis gas containing hydrogen (H2) and nitrogen (N2), and an electrolyzer (2) configured to further produce hydrogen and oxygen from water, wherein a compressor (6) is fluidly connected to the electrolyzer (2) and configured to compress the hydrogen (H2) coming from the electrolyzer (2), and the compressor (6) is configured to compress the hydrogen (H2), in particular transportable hydrogen (H2).

[0020] Furthermore, the above-mentioned problems are solved by a method for producing ammonia, in which ammonia (NH3) is produced from a synthesis gas containing hydrogen (H2) and nitrogen (N2) in an ammonia reactor, hydrogen and oxygen are produced in an electrolyzer using renewable energy, and the hydrogen produced in the electrolyzer is compressed in a compressor.

[0021] Therefore, a new concept for the production of green ammonia is proposed: the solution of the present invention is that electrolysers (also known as electrolysers) are installed in remote locations and hydrogen is transported over hundreds of kilometers via pipelines.

[0022] Electrolysers absorb electrical energy from wind or solar power and produce hydrogen and oxygen, which are produced in the electrolyser at pressures between 1 and 40 bar.

[0023] Cooling water is required to cool the electrolyzers, which is difficult to obtain in remote locations or areas such as deserts.

[0024] According to the invention, it is proposed to directly expand compressed oxygen in an expansion turbine and use it for cooling after expansion.

[0025] According to the invention, it is proposed to use a heat pump circuit and use the heat to raise the temperature of the oxygen before it is expanded in a generator-coupled expansion turbine, where all the latent heat of the refrigerant is utilized to convert water to steam and simultaneously condense the refrigerant.

[0026] Pressurized steam can also be used to generate electrical current. Furthermore, the heat pump's refrigerant is expanded in a JT valve or hot expander, where the refrigerant's enthalpy can be converted into mechanical or electrical energy, respectively. The two-phase refrigerant mixture is evaporated, simultaneously cooling the hot water leaving the electrolyzer and extracting heat from the hot water, which then enters the heat pump compressor.

[0027] On-site ammonia plants require nitrogen (N2) and hydrogen (H2) as starting materials, mixed stoichiometrically in a 1:3 ratio. Nitrogen (N2) is typically supplied via an air separation unit or from air, while hydrogen is primarily supplied from methane steam reforming.

[0028] Advantageously, the present invention does not require an air cracking unit for nitrogen (N2).

[0029] According to the invention, hydrogen (H2) is produced in the electrolyzer, since it is one of the starting materials for ammonia and is supplied to the ammonia plant site via a conduit. Nitrogen is produced using a gas turbine operated with hydrogen, driving a synthesis gas compressor. The exhaust gas of this gas turbine consists mainly of high-temperature steam and nitrogen, which are separated in a condenser and subsequently absorbed in an absorber or PSA unit. Condensed water is obtained in the condenser unit. The condensed water is pumped and heated using the exhaust heat from the gas turbine and subsequently expanded in a steam turbine to form an additional stream.

[0030] The nitrogen produced from the exhaust gas is separated from the steam and absorbed in an absorber or PSA unit. It is then compressed and stoichiometrically mixed with compressed hydrogen to produce a synthesis gas mixture. The synthesis gas mixture is compressed to the required process pressure in a synthesis gas compressor.

[0031] The present invention proposes an innovative concept for an environmentally friendly ammonia plant by integrating electrolyzers with renewable energy.

[0032] Advantageous developments are set forth in the dependent claims.

[0033] The advantages of the installation according to the invention and the method according to the invention are as follows: More efficient, greener and more economical processes for green hydrogen and green ammonia, Centralization of hydrogen (H2)-driven gas turbine exhaust gases allows for the production of nitrogen (N2) and green electrical / mechanical drive energy as well as water for electrolyzers; The use of pressurized oxygen (O2) to develop the flow increases overall efficiency and facilitates operation of the facility on fluctuating renewable energy sources. More efficient, greener and more economical processes for green hydrogen and green ammonia. [Brief explanation of the drawings]

[0034] The above-mentioned characteristics, features and advantages of the present invention, as well as the manner in which they are accomplished, will be more clearly and completely understood in connection with the following description of the embodiments which are set forth in more detail in connection with the drawings.

[0035] The same components or components having the same function are given the same reference numerals.

[0036]

[0013] The following description of embodiments of the present invention is given with reference to the drawings, which are not intended to represent the embodiments to scale; rather, where useful for illustration, the drawings are shown diagrammatically and / or slightly exaggerated. With regard to teachings readily apparent from the drawings, reference is made to the relevant prior art.

[0037] [Figure 1] A schematic diagram of an ammonia production facility is shown. DETAILED DESCRIPTION OF THE INVENTION

[0038] The figure shows a schematic diagram of a facility 1 for producing ammonia.

[0039] The facility 1 comprises an electrolyzer 2, also called an electrolyzer 2. The electrolyzer 2 is configured to produce hydrogen (H2) and oxygen (O2). To this end, water (H2O) is split into its elements hydrogen (H2) and oxygen (O2) using a large amount of electrical energy generated from wind power 3, photovoltaic power 4, or any other renewable energy.

[0040] The hydrogen (H2) thus produced is sent via line 5 to compressor 6, where it is compressed so that it can be transported over long distances in pipeline 7. Compression therefore takes place at high pressure in compressor 6. Dashed line 8 symbolically represents the spatial separation between the hydrogen production and the ammonia production unit 8. The separation between the hydrogen production and the ammonia production unit 8 can therefore amount to several kilometers.

[0041] Pressurized oxygen (O2) is supplied via line 10 to an expander 12 in a first selection 11. In the expander 12, the pressure energy of the oxygen (O2) is converted into mechanical energy, which can be used to drive a generator 13.

[0042] The electrolytic cell 2 requires cooling for operation, for which purpose cooled water is supplied as coolant to the electrolytic cell 2 via a cooling line 14, and water heated in the electrolytic cell 2 is removed from the electrolytic cell 2 via another cooling line 15.

[0043] In the first option 11, hot water is fed to a heat exchanger 16, where its thermal energy is transferred to the cold oxygen (O2) coming from the expander, heating the oxygen (O2) in the process. The water is cooled, and then fed back to the electrolyzer 2 via line 14.

[0044] The oxygen (O2) exiting the heat exchanger may then be used for another energy generating device 16 or vented to the atmosphere.

[0045] In the second option 9, heated water from line 15 is supplied as a heat source to the heat pump circuit 17. For this purpose, the water heated in the electrolyzer 2 reaches the heat exchanger 18 via line 15. Here, the thermal energy of the water is used to heat the refrigerant arranged in the heat pump circuit 17. The water is cooled and supplied as cooling water via line 14 to the electrolyzer 2.

[0046] Downstream of the heat exchanger 18, the refrigerant reaches a compressor 19, where the temperature and pressure of the refrigerant are increased. Downstream of the compressor 19, the refrigerant flows through a heat exchanger 20, through which flows the oxygen (O2) produced in the electrolyzer 2. The oxygen (O2) heated in the heat exchanger 20 is fed to an expander 21 and used to generate electrical energy via a generator 22. The advance provision of thermal energy allows the production of more electrical energy than in the first option. Cooled oxygen 23 leaves the expander 21.

[0047] Downstream of the heat exchanger 20, the refrigerant reaches another heat exchanger 24, where the thermal energy of the refrigerant is transferred to water 26 coming via line 25. The heat exchanger 24 is configured so that the water is converted into steam and the steam 27 is fed to a steam turbine 28, which then drives the same generator 22 and can thus produce electrical energy. The water 29, which is condensed back into water downstream of the steam turbine 28, can be fed to the heat exchanger 24 again.

[0048] Downstream of heat exchanger 24, the refrigerant flows to expansion device 30, which may be either a Joule-Thomson valve (JT valve) or an expander, which reduces the temperature and pressure of the refrigerant. Downstream of expansion device 30, the refrigerant flows again to heat exchanger 18, thereby closing the heat pump circuit.

[0049] The ammonia process requires nitrogen (N2) and hydrogen (H2) as starting materials, which are mixed stoichiometrically in a ratio of 1:3. In conventional plants, nitrogen (N2) is supplied from an air separation plant or air, while hydrogen (H2) is primarily derived from methane steam reforming.

[0050] The hydrogen reaches the mixing chamber 31 via the pipeline 7 where it is mixed with hydrogen (H2) and nitrogen (N2) to form synthesis gas.

[0051] A portion of the hydrogen (H2) from pipeline 7 is supplied via line 32 to a gas turbine 33 that can be operated on hydrogen (H2). The hot exhaust gas leaving gas turbine 33 contains a mixture 34 of nitrogen (N2), water (H2O), hydrogen (H2), nitrogen oxides (NOx), and oxygen (O2). The hot exhaust gas is supplied to heat exchanger 35. Downstream of heat exchanger 35, the exhaust gas flows to condenser 36, where water from the exhaust gas is condensed. Water 37 is then conducted via line 38 through the heat exchanger, where it is converted into steam. The steam is then supplied to steam turbine 39, where the thermal energy of the steam is converted into mechanical energy, and electrical energy is generated via generator 40.

[0052] The gas turbine 33 is supplied with air 41, in particular ambient air.

[0053] A portion of the exhaust gas flows through an absorber 42 or pressure swing adsorption (PSA) unit 42, where nitrogen (N2) is separated from the exhaust gas and flows with the synthesis gas into mixing chamber 31. The synthesis gas flows through a compressor 43 driven by a gas turbine to an ammonia reactor 44. The hot ammonia produced in the ammonia reactor 44 is cooled through a heat exchanger 45 and supplied to a storage device 47 via a refrigeration unit 46. The heat produced in the heat exchanger 45 can be used to generate steam, and the steam turbine 48 can be used to power a generator 49.

[0054] Nitrogen (N2) separated from the GT exhaust gas is stoichiometrically mixed with hydrogen (H2) from the electrolyzer to produce the synthesis gas mixture required for ammonia synthesis.

[0055] The synthesis gas is fed into the ammonia reactor 44. The synthesis gas comprises hydrogen (H2) and nitrogen (N2). The hydrogen (H2) and nitrogen (N2) react in the ammonia reactor 2 according to the following chemical reaction:

[0056] N2 + 3H2 → 2NH3 + 92kJ / mol

[0057] This chemical reaction is highly exothermic, i.e. the ammonia NH3 produced in the ammonia reactor has a relatively high temperature which is used in accordance with the present invention to produce steam for expansion in steam turbine 48 to produce electrical energy in generator 49.

[0058] A detailed description of the ammonia reactor 44 will be omitted here. [Explanation of symbols]

[0059] 1. Ammonia production facility 2 Electrolytic cell 6 Compressor 7 Pipeline 10 Oxygen pipe 12 Expander 17 Heat pump circuit 20 Heat exchanger 21 Expander 22 Generator 33 Gas Turbine 35 Heat exchanger 39 Steam turbine 40 Generator 42 Separation Unit 44 Ammonia Reactor

Claims

1. Ammonia (NH 3 ) to hydrogen (H 2 ) and nitrogen (N 2 an ammonia reactor (44) configured to produce ammonia from a synthesis gas comprising: an electrolyzer (2) configured to produce hydrogen and oxygen from water; An installation (1) for producing ammonia, comprising: A hydrogen generator (H ) is fluidly connected to the electrolytic cell (2) and receives hydrogen (H ) from the electrolytic cell (2). 2 a compressor (6) configured to compress the The compressor (6) is a hydrogen (H 2 ) is configured to compress Ammonia production facility (1).

2. The compressed hydrogen (H 2 2. The installation (1) according to claim 1, wherein the molten metal is suitable for transport in a pipeline (7).

3. 2. The installation (1) according to claim 1, wherein the electrolyzer (2) is powered by renewable energy.

4. Hydrogen (H 2 a gas turbine (33) operating on The hydrogen (H 2 ) is nitrogen (N 2 ) to produce synthesis gas, The installation (1) according to claim 1.

5. a heat exchanger (35) configured to generate steam from thermal energy of the exhaust gas of the gas turbine (33); 5. The installation (1) according to claim 4, further comprising a steam turbine (39) charged with steam from the heat exchanger (35).

6. The installation (1) of claim 5, further comprising a generator (40) coupled to the steam turbine (39) in a torque-transmitting manner.

7. a separation unit (42) configured to separate the exhaust gas from the gas turbine (33) into nitrogen and water; the nitrogen is used in the synthesis gas; The water is supplied to the heat exchanger (35).

4. The installation (1) according to claim 3.

8. the oxygen line (10) for the oxygen obtained from the electrolytic cell (2) further comprises an expander (12); Oxygen from the oxygen line (10) is fluidly connected to the expander (12); In the expander (12), the pressure energy of the oxygen from the oxygen line (10) is converted into mechanical energy. The installation (1) according to one of claims 1 to 7.

9. 9. The installation (1) according to claim 8, further comprising a heat exchanger for cooling the coolant of the electrolyzer (15) with oxygen flowing out of the expander (12).

10. The electrolytic cell (2) can be cooled with a coolant, The facility (1) comprises a heat pump circuit (17) for cooling the coolant. The installation (1) according to one of claims 1 to 7.

11. a heat exchanger (20) fluidly connected to the oxygen line (10); The heat exchanger (20) is configured so that thermal energy of the coolant in the heat pump circuit (17) is transferred to oxygen. The installation (1) according to claim 10.

12. In the ammonia reactor (44), hydrogen (H 2 ) and nitrogen (N 2 ) from synthesis gas containing ammonia (NH 3 ) is generated, Hydrogen and oxygen are produced in an electrolyzer (2) using renewable energy, and the hydrogen produced in the electrolyzer (2) is compressed in a compressor (6). Ammonia production method.

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

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

15. A generator (22) is used which operates in conjunction with the expander (21), the generator (22) is configured to generate electrical energy; 15. The method according to any one of claims 12 to 14.

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

17. A coolant is used to cool the electrolytic cell (2), The coolant is cooled by a heat pump circuit (17).

17. The method of any one of claims 12 to 16.

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