Green synthesis of ammonia system and method

Abstract

The present application relates to a kind of green synthesis ammonia system and method, the device includes: renewable energy power generation device, water electrolysis device, air separation device, catalytic deoxidation device and ammonia synthesis device;Water electrolysis device is connected with renewable energy power generation device, catalytic deoxidation device is connected with water electrolysis device and air separation device respectively, ammonia synthesis device is connected with catalytic deoxidation device;Ammonia synthesis device includes synthesis gas compressor, ammonia synthesis tower, heat exchange component and separation component;Synthesis gas compressor is connected ammonia synthesis tower and heat exchange component respectively, ammonia synthesis tower is connected heat exchange component, and heat exchange component is connected separation component.The present application can be when renewable energy load changes, by flexible adjustment ammonia synthesis loop, makes ammonia synthesis device stable operation.Provides new technology for green synthesis ammonia, can effectively promote energy saving and emission reduction.

Description

Technical Field

[0001] This invention relates to a green ammonia synthesis system and method. Background Technology

[0002] Currently, conventional ammonia synthesis industries typically obtain raw materials and energy from fossil fuels, resulting in carbon dioxide emissions. Ammonia is then produced through ammonia synthesis processes. However, with technological advancements, the energy revolution, and increasing pressure to reduce carbon emissions, utilizing green hydrogen to produce ammonia is gradually becoming the future direction of ammonia synthesis development.

[0003] Currently, the mainstream technology for green hydrogen production involves generating electricity from renewable energy sources and then connecting the electricity to an electrolyzer for water electrolysis. Water electrolysis for hydrogen production mainly includes alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and solid oxide (SOE) electrolysis. In PEM technology, the anode and cathode primarily use noble metal catalysts, and protons are reduced to the hydrogen cathode through the membrane in the form of hydrated proton exchange. PEM electrolyzers do not require an electrolyte, only pure water, can operate at high currents, and can be coupled with renewable energy generation, making it the most efficient technology for renewable energy-based hydrogen electrolysis.

[0004] Nitrogen, another raw material for ammonia synthesis, mainly comes from air. Industrial nitrogen production methods primarily include cryogenic separation, PSA (Pressure Separation Aeration) separation, and membrane separation, with cryogenic separation and PSA being the most mature. Cryogenic separation utilizes the difference in boiling points between nitrogen and oxygen to separate the two components. PSA separation leverages the different adsorption rates of different molecules on specific molecular sieves. Within a certain time, oxygen is enriched in the adsorbed phase, while nitrogen is enriched in the gaseous phase, thus achieving nitrogen and oxygen separation. Compared to PSA, cryogenic separation is more suitable for large-scale applications, while PSA units have a simpler structure, require less land, are more flexible in adjustment, allow for significant load adjustments, have a high degree of automation, start up quickly, and can operate continuously or intermittently. The units are more adaptable and generally more suitable for small-scale nitrogen production. Summary of the Invention

[0005] This invention is made to develop a process for ammonia synthesis using renewable energy. This invention provides a green ammonia synthesis system and method. The technical solution proposed by this invention is as follows:

[0006] As one aspect of the present invention, the present invention provides a green ammonia synthesis system, comprising: a renewable energy power generation device, a water electrolysis device, an air separation device, a catalytic deoxygenation device, and an ammonia synthesis device;

[0007] The water electrolysis device is connected to the renewable energy power generation device, the catalytic deoxygenation device is connected to both the water electrolysis device and the air decomposition device, and the ammonia synthesis device is connected to the catalytic deoxygenation device.

[0008] The ammonia synthesis unit includes a synthesis gas compressor, an ammonia synthesis tower, a heat exchange assembly, and a separation assembly;

[0009] The syngas compressor is connected to the ammonia synthesis tower and the heat exchange assembly, respectively. The ammonia synthesis tower is connected to the heat exchange assembly, and the heat exchange assembly is connected to the separation assembly.

[0010] In a specific embodiment, the heat exchange assembly includes a waste heat recovery unit, a boiler feedwater preheater, a heat exchanger, a water cooler, a cold exchanger, and at least one ammonia cooler.

[0011] The syngas compressor is connected to the inlet and outlet of the heat exchanger, the heat exchanger is connected to the inlet and outlet of the ammonia synthesis tower and the water cooler, the ammonia synthesis tower is connected to the waste heat recovery unit, the waste heat recovery unit is connected to the boiler feedwater preheater, and the boiler feedwater preheater is connected to the heat exchanger.

[0012] The water cooler is connected to the inlet of the syngas compressor and the cold exchanger, respectively. The cold exchanger is connected to the inlet of the syngas compressor and the at least one ammonia cooler, respectively.

[0013] In a specific embodiment, the at least one ammonia cooler includes a primary ammonia cooler and a secondary ammonia cooler, wherein the primary ammonia cooler is connected to the secondary ammonia cooler.

[0014] In a specific embodiment, the separation assembly includes an ammonia separation tank, an ammonia flash tank, and a gaseous ammonia separation tank;

[0015] The secondary ammonia cooler is connected to the ammonia separator, the ammonia separator is connected to the cold exchanger and the ammonia flash tank, and the ammonia flash tank is connected to the gaseous ammonia separator.

[0016] In a specific embodiment, the system further includes an ammonia refrigeration unit connected to the at least one-stage ammonia cooler.

[0017] In a specific embodiment, the air separation unit is a PSA nitrogen generator or a refrigerated nitrogen generator.

[0018] As another aspect of the present invention, the present invention provides a green ammonia synthesis method, comprising:

[0019] Hydrogen and nitrogen are mixed and then fed into a catalytic deoxygenation unit. After deoxygenation by the catalytic deoxygenation unit, the raw material gas is obtained.

[0020] The raw material gas is compressed in a synthesis gas compressor and then compressed together with the circulating gas from the heat exchange assembly to obtain the reaction gas.

[0021] The reaction gas is heated by a heat exchanger and then sent to an ammonia synthesis tower to obtain synthesis gas.

[0022] After the synthesis gas is cooled by the heat exchange component, it is sent to the separation component for gas-ammonia separation to obtain liquid ammonia product.

[0023] In a specific embodiment, the process of cooling the synthesis gas through a heat exchange component and then sending it to a separation component for gaseous ammonia separation to obtain liquid ammonia product includes:

[0024] After the synthesis gas is cooled in the waste heat recovery unit and the boiler feed water preheater, it is sent to the water cooler after exchanging heat with the reaction gas in the heat exchanger. After being cooled by the water cooler, it enters the cold exchanger.

[0025] The gas from the cold exchanger is sent to the first-stage ammonia cooler and the second-stage ammonia cooler for cooling to obtain cooled synthesis gas;

[0026] The cooled syngas is separated by a separation unit to obtain the liquid ammonia product.

[0027] In a specific embodiment, the cooled synthesis gas is separated by a separation component to obtain the liquid ammonia product, including:

[0028] The cooled syngas is sent to an ammonia separator for gas-liquid separation. The resulting gas phase is returned to the heat exchanger for heat exchange and then enters the syngas compressor inlet. The liquid phase is sent to the ammonia flash tank after being depressurized by the pressure reducing valve.

[0029] The gas phase from the ammonia flash tank is sent to the ammonia recovery facility, while the liquid phase enters the gas-ammonia separator for gas-liquid separation to obtain liquid ammonia product.

[0030] In a specific embodiment, the step of heating the reaction gas through a heat exchange component and then sending it to an ammonia synthesis tower to obtain synthesis gas includes:

[0031] All the reactant gas from the syngas compressor is sent to a heat exchanger. After being heated by the heat exchanger, the reactant gas enters the ammonia synthesis tower for internal heat exchange and reaction to obtain the syngas.

[0032] or,

[0033] Part of the reaction gas from the syngas compressor is sent to a heat exchanger for heating, and the other part, together with the outlet gas of the heat exchanger, enters a water cooler for cooling. Part of the reaction gas heated by the heat exchanger directly enters the ammonia synthesis tower for internal heat exchange and reaction, while the other part is directly fed into the outlet pipeline of the ammonia synthesis tower to obtain the syngas.

[0034] In a specific embodiment, the process of entering the cold exchanger after being cooled by the water cooler includes:

[0035] All the synthesis gas cooled by the water cooler is sent to the heat exchanger.

[0036] or,

[0037] After being cooled by the water cooler, part of the syngas is sent to the cold exchanger, and the other part is sent to the inlet of the syngas compressor.

[0038] In a specific embodiment, the step of sending the gas from the cold exchanger to a primary ammonia cooler and a secondary ammonia cooler for cooling to obtain cooled synthesis gas includes:

[0039] All the gas coming out of the cold exchanger is sent to the first-stage ammonia cooler. After being cooled by the first-stage and second-stage ammonia coolers, the cooled synthesis gas is obtained.

[0040] or;

[0041] A portion of the gas exiting the cold exchanger is cooled in a primary ammonia cooler and a secondary ammonia cooler to obtain the cooled syngas, while the other portion of the gas enters the inlet of the syngas compressor for circulation.

[0042] In a specific embodiment, the nitrogen gas is obtained through a PSA nitrogen generation process or a cryogenic nitrogen generation process.

[0043] In a specific embodiment, the mixing ratio of hydrogen and nitrogen is 3:1.

[0044] In a specific embodiment, the raw material gas is compressed to 10-20 MPa by the synthesis gas compressor, and then compressed to 10-20 MPa together with the circulating gas from the cold exchanger.

[0045] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0046] The green ammonia synthesis system provided by this invention connects the outlet of the syngas compressor to the heat exchanger, connects the heat exchanger to the outlet pipeline of the ammonia synthesis tower, and connects the water cooler and cold exchanger to the inlet of the syngas compressor, forming a flexible adjustment link and providing a flexible and adjustable load ammonia synthesis process.

[0047] The green ammonia synthesis system provided by this invention comprehensively utilizes green electricity generated from renewable energy sources, green hydrogen produced by a water electrolysis unit, and high-purity nitrogen produced by an air separation unit to produce ammonia using a high-pressure ammonia synthesis process. It can flexibly adjust the ammonia synthesis loop to ensure stable operation of the ammonia synthesis unit when renewable energy loads change. This provides a new process for green ammonia synthesis, effectively promoting energy conservation and emission reduction, and creating economic benefits.

[0048] The green ammonia synthesis system provided by this invention uses renewable energy and air as raw materials and has no carbon emissions.

[0049] The green ammonia synthesis system provided by this invention can make a series of process adjustments to the flexible adjustment link according to the rapid increase and decrease of load requirements, so that the ammonia synthesis unit can be rapidly and flexibly adjusted within the range of 10% to 100%, maintain the pressure of the ammonia synthesis circuit, and ensure the stable operation of the unit.

[0050] The green ammonia synthesis method provided by this invention, in the case of small-scale green ammonia production, uses PSA nitrogen production technology for the raw material nitrogen. Unlike conventional PSA and water electrolysis technologies for deoxygenation, this invention mixes hydrogen and nitrogen and catalytically deoxygenates them together, and then compresses them through a syngas compressor before sending them to the ammonia synthesis unit, thus optimizing the process flow.

[0051] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0052] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0053] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of the process flow for the green ammonia synthesis method provided in this embodiment of the invention. Detailed Implementation

[0055] The embodiments of the present invention are described in detail below: The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0056] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0057] The inventors discovered that the main problem with current methods of producing hydrogen and ammonia using green electricity through water electrolysis is the poor stability of green electricity, while conventional ammonia synthesis processes generally require stable operation and a stable source of raw materials. Solving the stability problem through energy storage technology involves high equipment investment and poor economic efficiency, failing to meet the inventors' expectations. Therefore, developing an ammonia synthesis technology adaptable to green electricity became the research direction.

[0058] The inventors also discovered that the difficulty in rapidly adjusting the load of the ammonia synthesis process lies in two aspects. On the one hand, the pressure of the ammonia synthesis loop will change after the upstream reactant gas load changes. On the other hand, the heat load of the ammonia synthesis loop comes from the ammonia synthesis reaction. If the load is reduced, the temperature of the ammonia synthesis tower and the heat recovery system of the synthesis loop will change.

[0059] Through further research and development, the inventors have proposed a process for ammonia synthesis using renewable energy sources to address the current difficulties in grid connection of wind and solar power, which leads to power curtailment. This invention utilizes the coupling of renewable energy water electrolysis for hydrogen production and air separation technology to develop a green process for ammonia synthesis that can quickly and flexibly adjust the load based on the characteristics of renewable energy sources.

[0060] Example 1

[0061] This invention provides a green ammonia synthesis system, referring to... Figure 1 As shown, it includes: a renewable energy power generation unit, a water electrolysis unit, an air separation unit, a catalytic deoxygenation unit, and an ammonia synthesis unit;

[0062] The water electrolysis device is connected to the renewable energy power generation device, the catalytic deoxygenation device is connected to both the water electrolysis device and the air decomposition device, and the ammonia synthesis device is connected to the catalytic deoxygenation device.

[0063] The ammonia synthesis unit includes a synthesis gas compressor, an ammonia synthesis tower, a heat exchange assembly, and a separation assembly;

[0064] The syngas compressor is connected to the ammonia synthesis tower and the heat exchange assembly, respectively. The ammonia synthesis tower is connected to the heat exchange assembly, and the heat exchange assembly is connected to the separation assembly.

[0065] The aforementioned renewable energy power generation devices mainly refer to wind power generation devices, hydropower generation devices, or solar power generation devices that generate electricity; the water electrolysis device mainly consists of a water electrolysis cell, a gas-liquid separation device, and a hydrogen purification device. Those skilled in the art can refer to the descriptions in the prior art for the specific structure, which will not be repeated here. In one specific embodiment, the heat exchange components include a waste heat recovery unit, a boiler feedwater preheater, a heat exchanger, a water cooler, a cold exchanger, and at least one stage of ammonia cooler;

[0066] The syngas compressor is connected to the inlet and outlet of the heat exchanger, the heat exchanger is connected to the inlet and outlet of the ammonia synthesis tower and the water cooler, the ammonia synthesis tower is connected to the waste heat recovery unit, the waste heat recovery unit is connected to the boiler feedwater preheater, and the boiler feedwater preheater is connected to the heat exchanger.

[0067] The water cooler is connected to the inlet of the syngas compressor and the cold exchanger, respectively. The cold exchanger is connected to the inlet of the syngas compressor and the at least one ammonia cooler, respectively.

[0068] The number of stages of the ammonia cooler can be set according to actual needs, and no specific limit is made here.

[0069] In one specific embodiment, the at least one ammonia cooler includes a primary ammonia cooler and a secondary ammonia cooler, wherein the primary ammonia cooler is connected to the secondary ammonia cooler.

[0070] In one specific embodiment, the separation assembly includes an ammonia separation tank, an ammonia flash tank, and a gaseous ammonia separation tank;

[0071] The secondary ammonia cooler is connected to the ammonia separator, the ammonia separator is connected to the cold exchanger and the ammonia flash tank, and the ammonia flash tank is connected to the gaseous ammonia separator.

[0072] In one specific embodiment, the system further includes an ammonia refrigeration unit connected to the at least one-stage ammonia cooler.

[0073] In one specific embodiment, the air separation unit is a PSA nitrogen generator or a refrigerated nitrogen generator.

[0074] This invention utilizes renewable energy power generation and water electrolysis to produce high-purity hydrogen (above 99% vol). Nitrogen (above 99.9% vol) is then produced using an air separation unit. This nitrogen is then compressed, synthesized, and refrigerated to produce green ammonia. Due to the instability of renewable energy sources, a flexible and adjustable load ammonia synthesis process has been invented to ensure stable and continuous operation of the ammonia synthesis unit. The process flow of this invention is as follows: Figure 1As shown, this invention optimizes the process flow design to enable rapid adjustment of the ammonia synthesis loop, with streams 16-20 primarily involving flexible adjustment. Specifically, a flexible adjustment mechanism is formed by connecting the syngas compressor to the outlet of the heat exchanger, connecting the heat exchanger to the outlet pipeline of the ammonia synthesis tower, and connecting the water cooler and cold exchanger to the inlet of the syngas compressor. By comprehensively utilizing green electricity generated from renewable energy sources, employing green hydrogen produced by a water electrolysis unit, and combining it with high-purity nitrogen from an air separation unit, ammonia is produced using a high-pressure ammonia synthesis process. This allows for flexible adjustment of the ammonia synthesis loop during changes in renewable energy load, ensuring stable operation of the ammonia synthesis unit. This provides a new process for green ammonia synthesis, effectively promoting energy conservation and emission reduction, and creating economic benefits.

[0075] In another aspect, this invention provides a green ammonia synthesis method, referring to... Figure 1 As shown, it includes:

[0076] A. Hydrogen and nitrogen are mixed and then fed into a catalytic deoxygenation device. After deoxygenation by the catalytic deoxygenation device, the raw material gas is obtained.

[0077] B. After the raw material gas is compressed in the synthesis gas compressor, it is then compressed together with the circulating gas from the heat exchange component to obtain the reaction gas;

[0078] C. The reaction gas is heated by a heat exchanger and then sent to an ammonia synthesis tower to obtain synthesis gas;

[0079] D. After the synthesis gas is cooled by the heat exchange component, it is sent to the separation component for gas-ammonia separation to obtain liquid ammonia product.

[0080] In this embodiment of the invention, the raw material nitrogen is produced using PSA nitrogen production technology. Unlike conventional PSA and water electrolysis technologies that deoxygenate separately, this invention mixes hydrogen and nitrogen and catalytically deoxygenates them together, and then compresses them through a syngas compressor before sending them to the ammonia synthesis unit, thus optimizing the process flow.

[0081] In one specific embodiment, the step D above, in which the synthesis gas is cooled by a heat exchange component and then sent to a separation component for gaseous ammonia separation to obtain liquid ammonia product, includes:

[0082] D1. The synthesis gas is cooled in a waste heat recovery unit and a boiler feed water preheater, and then exchanged heat with the reaction gas in a heat exchanger before being sent to a water cooler. After being cooled by the water cooler, it enters a cold exchanger.

[0083] D2. The gas from the cold exchanger is sent to the first-stage ammonia cooler and the second-stage ammonia cooler for cooling to obtain cooled synthesis gas;

[0084] D3. The cooled synthesis gas is separated by a separation component to obtain the liquid ammonia product.

[0085] In one specific embodiment, step D3 above, which involves separating the cooled syngas in a separation component to obtain the liquid ammonia product, includes:

[0086] D31. The cooled syngas is sent to an ammonia separator for gas-liquid separation. The resulting gas phase is returned to the heat exchanger for heat exchange and then enters the syngas compressor inlet. The liquid phase is sent to the ammonia flash tank after being depressurized by the pressure reducing valve.

[0087] D32. The gas phase from the ammonia flash tank is sent to the ammonia recovery facility, and the liquid phase enters the gas-ammonia separator for gas-liquid separation to obtain liquid ammonia product.

[0088] In one specific embodiment, the step C above, in which the reaction gas is heated by a heat exchanger and then sent to an ammonia synthesis tower to obtain synthesis gas, includes:

[0089] All the reactant gas from the syngas compressor is sent to a heat exchanger. After being heated by the heat exchanger, the reactant gas enters the ammonia synthesis tower for internal heat exchange and reaction to obtain the syngas.

[0090] or,

[0091] Part of the reaction gas from the syngas compressor is sent to a heat exchanger for heating, and the other part, together with the outlet gas of the heat exchanger, enters a water cooler for cooling. Part of the reaction gas heated by the heat exchanger directly enters the ammonia synthesis tower for internal heat exchange and reaction, while the other part is directly fed into the outlet pipeline of the ammonia synthesis tower to obtain the syngas.

[0092] In one specific embodiment, the step D1 above, where the water cooler cools the material before it enters the heat exchanger, includes:

[0093] All the synthesis gas cooled by the water cooler is sent to the heat exchanger.

[0094] or,

[0095] After being cooled by the water cooler, part of the syngas is sent to the cold exchanger, and the other part is sent to the inlet of the syngas compressor.

[0096] In one specific embodiment, step D2 above, which involves sending the gas exiting the cold exchanger to a primary ammonia cooler and a secondary ammonia cooler for cooling to obtain cooled synthesis gas, includes:

[0097] All the gas coming out of the cold exchanger is sent to the first-stage ammonia cooler. After being cooled by the first-stage and second-stage ammonia coolers, the cooled synthesis gas is obtained.

[0098] or;

[0099] A portion of the gas exiting the cold exchanger is cooled in a primary ammonia cooler and a secondary ammonia cooler to obtain the cooled syngas, while the other portion of the gas enters the inlet of the syngas compressor for circulation.

[0100] In one specific embodiment, the nitrogen gas is obtained through a PSA nitrogen generation process or a cryogenic nitrogen generation process.

[0101] In one specific embodiment, the mixing ratio of hydrogen and nitrogen is 3:1.

[0102] In one specific embodiment, the raw material gas is compressed to 10-20 MPa by a synthesis gas compressor, and then compressed together with the circulating gas from the cold exchanger to 10-20 MPa.

[0103] This invention belongs to the field of energy and chemical technology, specifically relating to a method for separating air to obtain nitrogen and oxygen using pressure swing adsorption (PSA) technology or cryogenic technology, and for producing ammonia using green hydrogen prepared from renewable energy. This invention can absorb the electricity generated from renewable energy, and through flexible operation, the operating load can be flexibly adjusted to meet the continuous operation of the ammonia synthesis plant.

[0104] To meet the requirements of rapid load increases and decreases, embodiments of the present invention can achieve rapid and flexible load adjustment of the ammonia synthesis unit within a power load range of 10% to 100% through a series of process adjustment methods, maintaining stable pressure in the ammonia synthesis circuit and ensuring stable operation of the unit. To provide a clear and detailed explanation of the green ammonia synthesis system provided in this embodiment, the present invention applies this green ammonia synthesis system to synthesize green ammonia, and the specific process flow is as follows.

[0105] 1. When the renewable energy power generation unit is at 100% normal load, refer to Figure 1 As shown, the method for synthesizing green ammonia using the above system includes the following steps:

[0106] A. The electricity generated by the renewable energy power generation device supplies a water electrolysis device. The water electrolysis device uses water in a storage tank to electrolyze and produce hydrogen. After gas-liquid separation, the hydrogen is purified and then passed into a hydrogen storage tank. The oxygen produced by electrolysis is stored in an oxygen storage tank as a byproduct. The specific structure of the water electrolysis device and the specific process of hydrogen production by electrolysis can be found in the prior art for those skilled in the art, and will not be repeated here.

[0107] B. Air enters the air separation unit and is processed by the PSA nitrogen generation process or the refrigeration nitrogen generation process to obtain 99.9% nitrogen. Oxygen is stored in the oxygen storage tank, and nitrogen is stored in the nitrogen storage tank.

[0108] C. The hydrogen in the hydrogen storage tank and the nitrogen in the nitrogen storage tank are mixed in a hydrogen-to-nitrogen ratio of 3:1 and fed into the catalytic deoxygenation unit. After removing trace amounts of oxygen, the mixture is compressed to 10-20 MPa by the synthesis gas compressor and then compressed together with the circulating gas (stream 13) from the cold exchanger to 10-20 MPa to obtain the reaction gas.

[0109] D. The reaction gas is heated by the heat exchanger (stream 1) and then enters the ammonia synthesis tower (stream 2) for ammonia synthesis. The synthesis gas coming out of the ammonia synthesis tower is cooled down in stages by the waste heat recovery unit (stream 3), the boiler feed water preheater (stream 4), the heat exchanger (stream 5), the water cooler (stream 6), the cold exchanger (stream 7), the primary ammonia cooler (stream 8), and the secondary ammonia cooler (stream 9) before being sent to the ammonia separator (stream 10).

[0110] E. The gas phase generated by the ammonia separator returns to the cold exchanger (stream 12) for heat exchange and then enters the inlet of the synthesis gas compressor circulation section (stream 13). The liquid phase of the ammonia separator enters the ammonia flash tank (stream 11) after pressure reduction.

[0111] F. The gas phase from the ammonia flash tank goes to the ammonia washing tower, and the liquid phase from the ammonia flash tank enters the gas-ammonia separator (stream).

[0112] G. The gas-liquid separation tank separates the gas and liquid to obtain liquid ammonia product, which is then pumped to the tank area (stream 15).

[0113] In the above process flow, the ammonia refrigeration unit provides cooling capacity to the primary ammonia cooler and the secondary ammonia cooler. The ammonia refrigeration unit adopts a conventional process, and the specific process can be referred to the description in the prior art, which will not be repeated here.

[0114] 2. When the load on upstream renewable energy power generation units decreases, resulting in a shortage of feedstock hydrogen, refer to Figure 1 As shown, the method for synthesizing green ammonia using the above system includes the following steps:

[0115] A. The hydrogen production process is the same as the normal operation process (at 100% load). If PSA nitrogen production is used, the operating load is also reduced; if refrigerated nitrogen production is used, the operating load is adjusted by reducing the operating load and using buffer storage tanks, depending on the process. The operating load of the nitrogen generator can be set according to the nitrogen production process, as long as the ratio of nitrogen to hydrogen produced is the preset ratio.

[0116] B. At low load, the feed gas is compressed to 10-20 MPa by the syngas compressor and then compressed together with the circulating gas (stream 13) from the cold exchanger to 10-20 MPa to obtain the reaction gas. Of the reaction gas (stream 1) exiting the syngas compressor, a portion (stream 21) enters the heat exchanger for heating, depending on the unit load; the remaining portion (stream 16) and the heat exchanger outlet gas (stream 22) enter the water cooler (stream 6) for cooling. The unit load (η) and the molar flow rate F of stream 21 are... 21 The following relationship exists between the 1 mole flow rate F1 and the flow rate F1:

[0117] η=α×F 21 / F1;

[0118] α is 1 to 1.5, and is adjusted according to the reaction of materials in the ammonia synthesis tower.

[0119] After being heated by the heat exchanger, part of stream 21 enters the ammonia synthesis tower (stream 2), and the other part (stream 17) enters the hot side of the heat exchanger (stream 17). The molar flow rate F of stream 17 is... 17 The relationship between the molar flow rate F2 of stream 2 and the following relationship holds:

[0120] F 17 =βF2;

[0121] Among them, β is 0 to 0.5. This value is adjusted according to the reaction situation and unit load of the ammonia synthesis tower to keep the inlet and outlet temperatures of the ammonia synthesis tower within a suitable temperature range.

[0122] C. The synthesis gas from the ammonia synthesis tower is divided into two parts according to the load ratio. Part of the synthesis gas enters the heat exchanger directly through stream 18, and the other part enters the heat exchanger (stream 5) after passing through the waste heat recovery unit (stream 3) and the boiler feedwater preheater (stream 4). Stream 3 has a higher temperature. By adjusting the flow rate of stream 18, the temperature of stream 2 is kept in a suitable range (160-250℃).

[0123] D. The syngas exiting the heat exchanger then enters the water cooler and cold exchanger. Depending on the load level, a portion of the syngas enters the syngas compressor circulation section via stream 19 and / or stream 20, while the remaining syngas sequentially enters the primary ammonia cooler, secondary ammonia cooler, and ammonia separator for cooling. The unit load (η) and the molar flow rate F of stream 19 are specified. 19 Or the molar flow rate F of stream 20 20 The molar flow rate F8 of stream 8 exiting the cold exchanger satisfies the following relationship:

[0124] F 20 (F 19 )=γ×(1-η)×F8;

[0125] γ is 0.7 to 2, and is adjusted according to the temperature of the material exiting the water cooler. If the temperature of the material exiting the water cooler is low, the flow rate of F20 is larger according to the cooling capacity distribution of the system. The flow rate distribution of F19 and F20 is based on the temperature of the circulating gas (stream 13) to keep the circulating gas temperature within a suitable temperature range (10 to 30°C).

[0126] E. The gas phase from the ammonia separator returns to the heat exchanger for heat exchange and then enters the inlet of the syngas compressor circulation section. The liquid phase enters the ammonia flash tank after pressure reduction.

[0127] F. The gas phase from the ammonia flash tank goes to the ammonia washing tower, while the liquid phase enters the ammonia gas separator.

[0128] G. The liquid ammonia product obtained from the gas-ammonia separator is pumped to the tank area.

[0129] Example 2

[0130] This embodiment describes a green ammonia synthesis method. A process flow diagram is provided below. Figure 1 As shown.

[0131] A. A photovoltaic device is used to power a water electrolysis unit, which consumes approximately 160,000 kg / h of raw water to produce hydrogen. After purification, the amount of H2 produced is 197,400 Nm³. 3 / h, O2 byproduct 98700Nm 3 / h, stored in hydrogen and oxygen storage tanks respectively, with oxygen being sent out as a product.

[0132] B. Air is converted to 66000 Nm³ / h by an air separation unit. 3 Nitrogen gas at a pressure of 1.6 MPa / h is delivered to the high-pressure nitrogen storage tank, producing 17700 Nm³ of oxygen. 3 / h is sent to the oxygen storage tank.

[0133] C. 66,000 Nm³ of nitrogen from the high-pressure nitrogen storage tank 3 / h and 197,400 Nm from the hydrogen storage tank 3 After being mixed with hydrogen at a rate of / h, the mixture enters the catalytic deoxygenation unit to remove trace amounts of oxygen. Then, it is compressed to 14MPa by the syngas compressor and mixed with 615000Nm³ of circulating gas from the cold exchanger. 3 The gas is compressed together with the pressure of / h to 15MPa to obtain the reaction gas.

[0134] D. The reaction gas is heated to 188°C by a heat exchanger and enters the ammonia synthesis tower to obtain synthesis gas. The synthesis gas temperature is 453°C and the net ammonia value is 17.9%.

[0135] E. The synthesis gas from the ammonia synthesis tower is cooled to 270°C by the waste heat recovery unit and sent to the boiler feedwater preheater to be cooled to 230°C. The synthesis gas and the reaction gas exchange heat in the heat exchanger, and after the temperature drops to 98°C, it enters the water cooler.

[0136] F. The synthesis gas entering the water cooler is cooled to 37°C by cooling water and then enters the cold exchanger to obtain cooled synthesis gas.

[0137] G. The cooled synthesis gas is further cooled to -10°C in the primary ammonia cooler and the secondary ammonia cooler before entering the ammonia separator.

[0138] H. The gas phase generated by the ammonia separator is returned to the heat exchanger for heat exchange before entering the inlet of the synthesis gas compressor. The liquid phase is depressurized to 2.2 MPa by the pressure reducing valve before entering the ammonia flash tank.

[0139] I. The gaseous phase generated by the ammonia flash tank is sent to an ammonia recovery facility, while the liquid phase enters a gaseous ammonia separator.

[0140] J. The liquid ammonia product obtained by gas-liquid separation in the gas-ammonia separator is pumped to the tank area at a rate of 100t / h.

[0141] Example 3

[0142] This embodiment describes a green ammonia synthesis method. A process flow diagram is provided below. Figure 1 As shown.

[0143] A. A photovoltaic device is used to power a water electrolysis unit with solar energy. Due to the reduced solar load, the power output drops to 50% of that in Example 2. Hydrogen production via the water electrolysis unit consumes approximately 80,000 kg / h of raw water, and after purification, the amount of H2 produced is 98,700 Nm³. 3 / h, O2 byproduct 49350Nm 3 / h, stored in hydrogen and oxygen storage tanks respectively, with oxygen being sent out as a product.

[0144] B. Air is separated into nitrogen gas at a pressure of 1.6 MPa (33000 Nm³) by an air separation unit. 3 / h) is sent to the nitrogen high-pressure storage tank, and the generated oxygen (8850Nm) 3 / h) is sent to the oxygen storage tank.

[0145] C. Nitrogen gas (33000 Nm³) from a high-pressure nitrogen storage tank 3 / h) and hydrogen from the hydrogen storage tank (98700Nm 3 After being mixed with the syngas (768957 Nm³ / h), the mixture enters the catalytic deoxygenation unit to remove trace amounts of oxygen. Then, it is compressed to 14 MPa by the syngas compressor before being mixed with the circulating gas (768957 Nm³ / h) from the cold exchanger. 3 The gas is compressed together with the pressure of ...

[0146] D. 50% of the reactant gas (i.e., 450-454 Nm) 3 The gas enters the heat exchanger via stream 21 and is heated to 188°C before directly entering the ammonia synthesis tower to obtain synthesis gas at a temperature of 443°C.

[0147] E. The synthesis gas from the ammonia synthesis tower is cooled to 270°C by a waste heat recovery unit, then to 230°C by a boiler feedwater preheater, and finally to 70°C by a heat exchanger. It then reacts with the remaining 50% of the reaction gas (i.e., 450-454 Nm³). 3 After the combined flow of 16 streams (approximately 7691 kg / h) is cooled to 52°C, it enters a water cooler and is then cooled to 35°C by cooling water before entering a cold exchanger to obtain cooled synthesis gas. At this point, some ammonia has been liquefied, and the liquid ammonia (approximately 7691 kg / h) is separated into an ammonia separator.

[0148] F. The cooled synthesis gas is further cooled to -10°C in a primary ammonia cooler and a secondary ammonia cooler before entering the ammonia separator. The gas phase (768957 Nm) 3 The gas is circulated through the inlet of the syngas compressor after being heated to 17°C via a cold exchanger through stream 12.

[0149] G. The liquid phase in the ammonia separator is depressurized to 2.1 MPa by a pressure reducing valve and then enters the ammonia flash tank.

[0150] H. The gas phase generated by the ammonia flash tank is used for ammonia recovery, and the liquid phase enters the gas-ammonia separator.

[0151] I. The gas-liquid separation tank performs gas-liquid separation to obtain liquid ammonia product at a rate of 50t / h, which is then pumped to the tank area.

[0152] Example 4

[0153] This embodiment describes a green ammonia synthesis method. A process flow diagram is provided below. Figure 1 As shown.

[0154] A. A photovoltaic device is used to power a water electrolysis unit with solar energy. Due to the reduced solar load, the power generation is reduced to 10% of that in Example 2. Hydrogen production via the water electrolysis unit consumes approximately 16,000 kg / h of raw water, and the purified H2 production is 19,740 Nm³. 3 / h, O2 byproduct 9870Nm 3 / h, stored in hydrogen and oxygen storage tanks respectively, with oxygen being sent out as a product.

[0155] B. Air is separated into nitrogen gas at a pressure of 1.6 MPa (6600 Nm³) by an air separation unit. 3 / h) is sent to the nitrogen high-pressure storage tank, and the generated oxygen (1770Nm) 3 / h) is sent to the oxygen storage tank.

[0156] C. Nitrogen gas (6600 Nm³) from a high-pressure nitrogen storage tank 3 / h) and hydrogen from the hydrogen storage tank (19740 Nm 3 After being mixed with the syngas ( / h), the mixture enters the catalytic deoxygenation unit to remove trace amounts of oxygen. Then, it is compressed to 14 MPa by the syngas compressor and mixed with the circulating gas (211050 Nm³) from the cold exchanger. 3 / h) and the syngas from the stream 19 (83044Nm) 3 / h) and the syngas from the stream 20 (523232Nm) 3 The gas is compressed together with the pressure of ...

[0157] D. The reactant gas is split into two streams through stream 1, of which 12% (101240 Nm) 3 The gas enters the heat exchanger and is heated to 210°C before directly entering the ammonia synthesis tower to obtain synthesis gas at a temperature of 430°C.

[0158] E. 10% (8811 Nm³) of the synthesis gas exiting the ammonia synthesis tower. 3 / h) After passing through stream 18, it directly enters the heat exchanger inlet, 90% (79298Nm) 3 After being cooled by the waste heat recovery unit and boiler feedwater preheater, the mixture temperature with stream 18 is 240℃. After passing through the heat exchanger, the temperature drops to 58℃, and it mixes with stream 16, which is 88% (742441 Nm) of stream 1. 3 The mixture ( / h) is then cooled to 38℃ and enters a water cooler, where it is further cooled to 35℃ by cooling water. 10% of the gas (83044Nm) is then removed. 3 / h) enters the synthesis gas compressor via stream 19, 90% of the gas (747498Nm) 3 After passing through a cold exchanger, the syngas is cooled and remains in a gaseous state.

[0159] F. After cooling, 30% of the gas in the syngas is further cooled to -10°C in the first-stage ammonia cooler and the second-stage ammonia cooler before entering the ammonia separator. The remaining 70% of the gas is directly circulated through stream 20 into the inlet of the syngas compressor.

[0160] G. The liquid phase in the ammonia separator is depressurized to 2.1 MPa by a pressure reducing valve and then enters the ammonia flash tank.

[0161] H. The gas phase generated by the ammonia flash tank is used for ammonia recovery, and the liquid phase enters the gas-ammonia separator.

[0162] I. The gas-liquid separation tank performs gas-liquid separation to obtain liquid ammonia product at a rate of 10t / h, which is then pumped to the tank area.

[0163] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. This invention is not limited to any single aspect, nor to any single embodiment, nor to any combination and / or substitution of these aspects and / or embodiments. Each aspect and / or embodiment of this invention can be used alone, or in combination with one or more other aspects and / or other embodiments.

[0164] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A green ammonia synthesis system, characterized in that, include: Renewable energy power generation equipment, water electrolysis equipment, air separation equipment, catalytic deoxygenation equipment, and ammonia synthesis equipment; The water electrolysis device is connected to the renewable energy power generation device, the catalytic deoxygenation device is connected to both the water electrolysis device and the air separation device, and the ammonia synthesis device is connected to the catalytic deoxygenation device; The ammonia synthesis unit includes a synthesis gas compressor, an ammonia synthesis tower, a heat exchange assembly, and a separation assembly; The syngas compressor is connected to the ammonia synthesis tower and the heat exchange assembly, respectively. The ammonia synthesis tower is connected to the heat exchange assembly, and the heat exchange assembly is connected to the separation assembly. The heat exchange components include a waste heat recovery unit, a boiler feedwater preheater, a heat exchanger, a water cooler, a cold exchanger, and at least one stage of ammonia cooler. The syngas compressor is connected to the inlet and outlet of the heat exchanger, the heat exchanger is connected to the inlet and outlet of the ammonia synthesis tower and the water cooler, the ammonia synthesis tower is connected to the waste heat recovery unit, the waste heat recovery unit is connected to the boiler feedwater preheater, and the boiler feedwater preheater is connected to the heat exchanger. The water cooler is connected to the inlet of the syngas compressor and the cold exchanger, respectively; the cold exchanger is connected to the inlet of the syngas compressor and the at least one-stage ammonia cooler, respectively; wherein when the load of the renewable energy power generation unit decreases, resulting in a shortage of feedstock hydrogen: Part of the reaction gas from the syngas compressor is sent to a heat exchanger for heating, while the other part, along with the outlet gas from the heat exchanger, enters a water cooler for cooling; and the molar flow rate F of the reaction gas entering the heat exchanger for heating is... 21 The molar flow rate F1 of the reactant gas from the syngas compressor and the load η of the renewable energy power generation unit satisfy the following relationship: η = α × F 21 / F1; Wherein, α is 1~1.5, and is adjusted according to the reaction of materials in the ammonia synthesis tower; After being heated by the heat exchanger, a portion of the reaction gas directly enters the ammonia synthesis tower for internal heat exchange and further reaction, while the other portion flows directly into the outlet pipeline of the ammonia synthesis tower to obtain the synthesis gas. The molar flow rates F2 of the reaction gas entering the ammonia synthesis tower and the reaction gas directly flowing into the outlet pipeline of the ammonia synthesis tower are... 17 Satisfy the following relationship: F 17 =βF2; Wherein, β is 0~0.5, and is adjusted according to the reaction conditions and unit load of the ammonia synthesis tower to keep the inlet and outlet temperatures of the ammonia synthesis tower within a suitable temperature range; The syngas exiting the heat exchanger then enters a water cooler and a cold exchanger. Depending on the load level, a portion of the syngas enters the syngas compressor circulation section via the water cooler and / or cold exchanger, while the remaining syngas sequentially enters at least one ammonia cooler and ammonia separator for cooling. The unit load η is related to the molar flow rate F of the syngas entering the syngas compressor from the cold exchanger. 20 The molar flow rate F8 of the synthesis gas entering at least one ammonia cooler from the cold exchanger satisfies the following relationship: F 20 =γ×(1-η)× F8; γ is 0.7~2, and is adjusted according to the temperature of the material coming out of the water cooler.

2. The green ammonia synthesis system according to claim 1, characterized in that, The at least one ammonia cooler includes a primary ammonia cooler and a secondary ammonia cooler, wherein the primary ammonia cooler is connected to the secondary ammonia cooler.

3. The green ammonia synthesis system according to claim 2, characterized in that, The separation assembly includes an ammonia separation tank, an ammonia flash tank, and a gaseous ammonia separation tank; The secondary ammonia cooler is connected to the ammonia separator, the ammonia separator is connected to the cold exchanger and the ammonia flash tank, and the ammonia flash tank is connected to the gaseous ammonia separator.

4. The green ammonia synthesis system according to claim 1, characterized in that, The system also includes an ammonia refrigeration unit connected to the at least one ammonia cooler.

5. The green ammonia synthesis system according to claim 1, characterized in that, The air separation unit is a PSA nitrogen generator or a refrigerated nitrogen generator.

6. A green method for synthesizing ammonia, characterized in that, include: Hydrogen and nitrogen are mixed and then fed into a catalytic deoxygenation unit. After deoxygenation by the catalytic deoxygenation unit, the raw material gas is obtained. The raw material gas is compressed in a synthesis gas compressor and then compressed together with the circulating gas from the heat exchange assembly to obtain the reaction gas. The reaction gas is heated by a heat exchanger and then sent to an ammonia synthesis tower to obtain synthesis gas; wherein, when the load of the renewable energy power generation unit decreases, resulting in a shortage of raw material hydrogen: A portion of the reaction gas from the syngas compressor is sent to a heat exchanger for heating, while the other portion, along with the outlet gas from the heat exchanger, enters a water cooler for cooling; and the molar flow rate F of the reaction gas entering the heat exchanger for heating... 21 The molar flow rate F1 of the reactant gas from the syngas compressor and the load η of the renewable energy power generation unit satisfy the following relationship: η = α × F 21 / F1; Wherein, α is 1~1.5, and is adjusted according to the reaction of materials in the ammonia synthesis tower; After being heated by the heat exchanger, a portion of the reaction gas directly enters the ammonia synthesis tower for internal heat exchange and further reaction, while the other portion flows directly into the outlet pipeline of the ammonia synthesis tower to obtain the synthesis gas. The molar flow rates F2 of the reaction gas entering the ammonia synthesis tower and the reaction gas directly flowing into the outlet pipeline of the ammonia synthesis tower are... 17 Satisfy the following relationship: F 17 =βF2; Wherein, β is 0~0.5, and is adjusted according to the reaction conditions and unit load of the ammonia synthesis tower to keep the inlet and outlet temperatures of the ammonia synthesis tower within a suitable temperature range; After the syngas is cooled in the waste heat recovery unit and the boiler feed water preheater, it is sent to the water cooler after exchanging heat with the reaction gas in the heat exchanger. After being cooled by the water cooler, part of the syngas is sent to the cold exchanger and the other part is sent to the inlet of the syngas compressor. A portion of the gas exiting the cold exchanger is cooled in at least one ammonia cooler to obtain the cooled syngas, while the remaining gas enters the inlet of the syngas compressor for recirculation. The unit load η and the molar flow rate F of the syngas entering the syngas compressor from the cold exchanger are related. 20 The molar flow rate F8 of the synthesis gas entering at least one ammonia cooler from the cold exchanger satisfies the following relationship: F 20 =γ×(1-η)× F8; Among them, γ is 0.7~2, which is adjusted according to the temperature of the material coming out of the water cooler; The cooled syngas is separated by a separation component to obtain liquid ammonia.

7. The green ammonia synthesis method according to claim 6, characterized in that, The cooled synthesis gas is separated in a separation unit to obtain the liquid ammonia product, including: The cooled syngas is sent to an ammonia separator for gas-liquid separation. The resulting gas phase is returned to the heat exchanger for heat exchange and then enters the syngas compressor inlet. The liquid phase is sent to the ammonia flash tank after being depressurized by the pressure reducing valve. The gas phase from the ammonia flash tank is sent to the ammonia recovery facility, while the liquid phase enters the gas-ammonia separator for gas-liquid separation to obtain liquid ammonia product.

8. The green ammonia synthesis method according to claim 6, characterized in that, The nitrogen gas is obtained through a PSA nitrogen generation process or a cryogenic nitrogen generation process.

9. The green ammonia synthesis method according to claim 6, characterized in that, The mixing ratio of hydrogen and nitrogen is 3:

1.

10. The green ammonia synthesis method according to claim 6, characterized in that, The raw material gas is compressed to 10-20 MPa by the synthesis gas compressor, and then compressed to 10-20 MPa together with the circulating gas from the cold exchanger.

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