A system and method for utilizing green ammonia synthesis waste heat

Abstract

The application provides a green ammonia synthesis waste heat utilization system and method, relates to the technical field of waste heat utilization of ammonia synthesis, and comprises a gas inlet pipeline, a synthesis tower and a gas outlet pipeline. The synthesis tower is provided with a synthesis gas outlet. The gas inlet pipeline is communicated with the input end of the synthesis tower. The synthesis gas outlet is communicated with the gas outlet pipeline. A gas compressor is arranged on the gas inlet pipeline. The gas compressor is provided with a first energy supply structure and a second energy supply structure. A steam generator is arranged on the gas outlet pipeline. The steam outlet end of the steam generator is communicated with the first energy supply structure through a steam transportation pipeline. The reaction waste heat carried by the high-temperature synthesis gas discharged from the synthesis tower can be used to exchange heat with feed water to generate steam. The generated steam can be discharged through the steam outlet end and transported to the first energy supply structure through the steam transportation pipeline to provide power for the operation of the gas compressor. In this way, the ammonia synthesis reaction waste heat is recycled and utilized, and the energy utilization efficiency of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology in ammonia synthesis, and more specifically, to a system and method for utilizing waste heat from green ammonia synthesis. Background Technology

[0002] Traditional ammonia synthesis uses fossil fuels as raw materials. The plant has a stable load and smooth operation. The ammonia synthesis reaction is exothermic and uniform. The waste heat recovery system can operate stably, and the generated steam temperature fluctuates little, providing a stable heat source and power, ensuring the system's thermal balance, equipment lifespan, and operational efficiency are at their optimal levels. However, the wind-solar green ammonia synthesis system is affected by the intermittent nature of photovoltaic and wind power generation. The front-end electrolysis hydrogen production load fluctuates frequently and rapidly, causing the ammonia synthesis load to change significantly in sync. As a strongly exothermic reaction, the heat of reaction in ammonia synthesis fluctuates drastically with the load, making the steam pressure, temperature, and flow rate generated by waste heat extremely unstable. If traditional waste heat treatment methods for ammonia synthesis are directly adopted, they are only suitable for steady-state conditions and cannot adapt to the large fluctuations in the green ammonia system. This will cause fluctuations in the speed of rotating equipment such as turbines and compressors, increase the risk of surge, and easily trigger interlocking shutdowns. At the same time, it will disrupt the system's thermal balance, leading to fluctuations in reactor temperature, ammonia net value, and conversion rate, reducing synthesis efficiency and product stability. Frequent temperature fluctuations will also cause thermal shock and fatigue damage to equipment and pipelines, shortening their service life and increasing safety hazards. Furthermore, it is difficult to stably achieve self-heating and self-generation cycles, resulting in low waste heat utilization and a significant decrease in system economy and energy self-sufficiency. Therefore, traditional waste heat treatment models cannot adapt to the dynamic operating characteristics of wind and solar green ammonia synthesis. Summary of the Invention

[0003] The present invention aims to solve the problem that traditional waste heat treatment modes cannot be adapted to the dynamic operating characteristics of wind and solar green ammonia synthesis.

[0004] To address the aforementioned problems, in a first aspect, the present invention provides a waste heat utilization system for green ammonia synthesis, comprising an inlet pipeline, a synthesis tower, and an outlet pipeline. The synthesis tower has a synthesis gas outlet, the inlet pipeline is connected to the input end of the synthesis tower, the synthesis gas outlet is connected to the outlet pipeline, a gas compressor is provided on the inlet pipeline, the gas compressor has a first energy supply structure and a second energy supply structure, a steam generator is provided on the outlet pipeline, and the steam outlet end of the steam generator is connected to the first energy supply structure via a steam transport pipeline.

[0005] The present invention provides a waste heat utilization system and method for green ammonia synthesis, which, compared with the prior art, has the following beneficial effects, but is not limited to: The waste heat carried by the high-temperature synthesis gas discharged from the synthesis tower can be used to exchange heat with feedwater to vaporize and generate steam. The generated steam can be discharged through the steam outlet and transported to the first energy supply structure through the steam transport pipeline to provide power for the operation of the gas compressor. This realizes the recovery and utilization of waste heat from the ammonia synthesis reaction and improves the energy utilization efficiency of the system.

[0006] Furthermore, the first energy supply structure is a steam turbine, the steam generator produces steam, and the steam turbine generates first electrical energy through the steam. The second energy supply structure is electrically connected to the power grid, the power grid generates second electrical energy, and the gas compressor can be driven to operate by the first electrical energy / second electrical energy.

[0007] Furthermore, the first power supply structure is used to introduce steam, converting the thermal energy of the steam into mechanical energy to directly drive the gas compressor to operate. The second power supply structure is electrically connected to the power grid, which generates second electrical energy, enabling the gas compressor to operate by the second electrical energy.

[0008] Furthermore, the outlet pipeline is also equipped with a heat storage device, which contains a heat storage medium that can exchange heat with the medium passing through the heat storage device.

[0009] Furthermore, the steam transport pipeline passes through the interior of the thermal storage device.

[0010] Furthermore, the synthesis tower has a first tower wall gas inlet and a tower wall gas outlet, the tower wall gas outlet being connected to the first tower wall gas inlet via an intermediate pipeline assembly, the intermediate pipeline assembly passing through the interior of the heat storage device.

[0011] Furthermore, the intermediate pipeline group includes an intermediate main pipeline, one end of which is connected to the tower wall gas outlet, and the other end of which is connected to the first tower wall gas inlet. The intermediate main pipeline passes through the interior of the thermal storage device. The intermediate pipeline group also includes intermediate secondary pipelines, one end of which is connected to the intermediate main pipeline between the thermal storage device and the tower wall gas outlet, and the other end of which is connected to the intermediate main pipeline between the thermal storage device and the first tower wall gas inlet. A first intermediate valve is provided on the intermediate secondary pipeline, and a second intermediate valve is provided on the intermediate main pipeline between the thermal storage device and the tower wall gas outlet. The second intermediate valve is located on the side of the connection point between the intermediate secondary pipeline and the intermediate main pipeline closer to the thermal storage device.

[0012] Furthermore, it also includes a heat exchange module, which includes a first heat exchange pipeline, a second heat exchange pipeline, and a third heat exchange pipeline. The medium in the first heat exchange pipeline can exchange heat with the medium in the second heat exchange pipeline, and the medium in the first heat exchange pipeline can also exchange heat with the medium in the third heat exchange pipeline. The exhaust pipeline is connected to the first heat exchange pipeline, and the intake pipeline is connected to the second heat exchange pipeline. The steam generator includes a water supply pipeline, which is connected to the third heat exchange pipeline.

[0013] Furthermore, the steam transport pipeline includes a steam heat exchange pipeline and a steam discharge pipeline. The steam heat exchange pipeline passes through a heat storage device. One end of the steam heat exchange pipeline is connected to a steam outlet end, and the other end of the steam heat exchange pipeline is connected to a first power supply structure. One end of the steam discharge pipeline is connected to a steam outlet end, and the other end of the steam discharge pipeline is connected to an external pipeline. A first steam valve is provided on the portion of the steam heat exchange pipeline located at the heat storage device and the steam outlet end, and a second steam valve is provided on the steam discharge pipeline.

[0014] The second invention provides a waste heat utilization method based on the green ammonia synthesis waste heat utilization system described above, including a first mode: a first steam valve is closed, a second steam valve is open, and the gas compressor is driven to operate through a second energy supply structure; The second mode includes a first steam valve open, a second steam valve closed, a first intermediate valve open, and a second intermediate valve closed, wherein the gas compressor is driven by a second power supply structure / first power supply structure. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall system structure in this invention; Figure 2 This is a schematic diagram of the first part of the system structure in this invention; Figure 3 This is a schematic diagram of the second part of the system structure in this invention.

[0016] Explanation of reference numerals in the attached figures: 1. Inlet pipeline; 2. Synthesis tower; 21. Synthesis gas outlet; 22. First tower wall gas inlet; 23. Tower wall gas outlet; 3. Outlet pipeline; 4. Gas compressor; 41. First power supply structure; 42. Second power supply structure; 5. Steam generator; 51. Steam outlet end; 52. Steam transport pipeline; 521. Steam heat exchange pipeline; 522. Steam discharge pipeline; 53. Water supply pipeline; 54. Second steam valve; 55. First steam valve; 6. Heat storage device; 7. Intermediate pipeline group; 71. Intermediate main pipeline; 72. Intermediate secondary pipeline; 73. First intermediate valve; 74. Second intermediate valve; 8. Heat exchange module; 81. First heat exchange pipeline; 82. Second heat exchange pipeline; 83. Third heat exchange pipeline. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0018] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the specification, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, parts, or groups of features, integers, steps, or parts.

[0022] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0023] See Figure 1-3 As shown, an embodiment of the present invention provides a waste heat utilization system for green ammonia synthesis, comprising an inlet pipeline 1, a synthesis tower 2, and an outlet pipeline 3. The synthesis tower 2 has a synthesis gas outlet 21. The inlet pipeline 1 is connected to the input end of the synthesis tower 2, and the synthesis gas outlet 21 is connected to the outlet pipeline 3. A gas compressor 4 is provided on the inlet pipeline 1. The gas compressor 4 has a first energy supply structure 41 and a second energy supply structure 42. A steam generator 5 is provided on the outlet pipeline 3. The steam outlet end 51 of the steam generator 5 is connected to the first energy supply structure 41 through a steam transport pipeline 52.

[0024] In this embodiment, the inlet pipeline 1 can be used to transport the synthesis gas to be involved in the ammonia synthesis reaction to the synthesis tower 2. The synthesis gas can include fresh gas and recycled gas. The fresh gas can be a mixture of hydrogen and nitrogen in the ammonia synthesis reaction ratio. The recycled gas can be a nitrogen-hydrogen mixture that has not been completely reacted after the ammonia separation process, thereby realizing the recycling of raw material gas and improving the overall conversion rate of raw materials.

[0025] Synthesis tower 2 can be a container for ammonia synthesis reaction. It is filled with a catalyst suitable for ammonia synthesis reaction. Ammonia synthesis reaction can occur in the catalyst bed in synthesis tower 2. The ammonia-containing synthesis gas generated by the reaction can be discharged to the gas outlet pipeline 3 through synthesis gas outlet 21.

[0026] The gas compressor 4 installed on the gas inlet pipeline 1 can pressurize the synthesis gas before it enters the synthesis tower 2, so that the synthesis gas reaches the pressure conditions required for the ammonia synthesis reaction. The gas compressor 4 is equipped with a first power supply structure 41 and a second power supply structure 42, which can form a dual power supply system. This allows the gas compressor 4 to flexibly switch the power supply source according to the actual operating conditions of the system, thereby adapting to the frequent load fluctuations of the wind-solar-green ammonia synthesis system.

[0027] The steam generator 5 installed on the gas outlet pipeline 3 can use the waste heat of the high-temperature synthesis gas discharged from the synthesis tower 2 to exchange heat with the feed water to generate steam. The generated steam can be discharged through the steam outlet end 51 and transported to the first energy supply structure 41 through the steam transport pipeline 52 to provide power for the operation of the gas compressor 4, thereby realizing the recovery and utilization of waste heat from the ammonia synthesis reaction and improving the energy utilization efficiency of the system.

[0028] See Figure 1 As shown, optionally, the first power supply structure 41 is a steam turbine, the steam generator 5 generates steam, and the steam turbine generates first electrical energy through steam drive. The second power supply structure 42 is electrically connected to the power grid, and the power grid generates second electrical energy. The gas compressor 4 can be driven to operate by the first electrical energy / second electrical energy.

[0029] In this embodiment, the first power supply structure 41 can be a steam turbine. The steam generated by the steam generator 5 can be transported to the steam turbine through the steam transport pipeline 52. The thermal energy of the steam can be converted into the mechanical energy of the steam turbine first, and then further converted into the first electrical energy to provide power for the gas compressor 4.

[0030] The second power supply structure 42 is electrically connected to the power grid. When the steam generator 5 produces insufficient or unstable steam and cannot provide sufficient driving power through the first power supply structure 41, it can supplement the gas compressor 4 with second power, thus ensuring the continuous and stable operation of the gas compressor 4.

[0031] This setting allows for flexible switching of the power supply mode of the gas compressor 4. Under conditions of high system load and sufficient waste heat from the reaction, the first electric drive can be used first to maximize the utilization of the recovered waste heat resources. Under conditions of low system load and less waste heat, the second electric drive can be switched to avoid compressor instability caused by fluctuations in steam parameters. This effectively adapts to the characteristics of frequent load fluctuations in the wind-solar-green ammonia synthesis system and reduces the risk of compressor surge and interlock shutdown.

[0032] See Figure 1 As shown, optionally, the first power supply structure 41 is used to introduce steam, converting the thermal energy of the steam into mechanical energy to directly drive the gas compressor 4 to operate, and the second power supply structure 42 is electrically connected to the power grid, the power grid generates second electrical energy, and the gas compressor 4 can be driven to operate by the second electrical energy.

[0033] In this embodiment, specifically, the first power supply structure 41 can adopt a direct-drive structure of a steam turbine. In this case, the steam generated by the steam generator 5 can be directly introduced into the steam turbine through the steam transport pipeline 52. The thermal energy of the steam can be directly converted into mechanical energy, which directly drives the rotor of the gas compressor 4 through the transmission mechanism. There is no need to go through the electrical energy conversion process, which can reduce the loss in the energy conversion process and further improve the utilization efficiency of waste heat.

[0034] The second power supply structure 42 is electrically connected to the power grid, and can drive the gas compressor 4 to operate by means of second electrical energy when the steam generator 5 produces insufficient steam and cannot provide sufficient driving force through the steam turbine.

[0035] This setup balances waste heat utilization efficiency with system operational stability. Under high load conditions, it achieves efficient cascade utilization of waste heat through direct steam drive, while under conditions of load fluctuation and unstable steam supply, it ensures stable compressor operation through electric drive, further enhancing the system's adaptability to dynamic changing operating conditions.

[0036] See Figure 1 and Figure 2 As shown, optionally, the outlet pipeline 3 is also provided with a heat storage device 6, which contains a heat storage medium that can exchange heat with the medium passing through the heat storage device 6.

[0037] In this embodiment, specifically, the heat storage device 6 can be installed on the gas outlet pipeline 3 between the synthesis gas outlet 21 of the synthesis tower 2 and the steam generator 5. The high-temperature synthesis gas discharged from the synthesis tower 2 can first enter the heat storage device 6 and fully exchange heat with the heat storage medium in the heat storage device 6. Part of the heat carried by the high-temperature synthesis gas can be absorbed and stored by the heat storage medium. The synthesis gas after heat exchange and cooling is then transported to the subsequent steam generator 5 for waste heat recovery.

[0038] It is understandable that the high-temperature synthesis gas discharged from the synthesis tower 2 can pass through the heat storage device 6 via a pipeline. Inside the heat storage device 6, the high-temperature synthesis gas and the heat storage medium exchange heat through the pipeline body.

[0039] The heat storage medium can be a solid heat storage medium, or a high-temperature resistant medium with high heat storage density, such as molten salt heat storage medium. Alternatively, the appropriate heat storage medium type and heat storage capacity can be selected according to the system's operating condition fluctuation range and operating temperature range.

[0040] This setup allows for the graded recovery of high-temperature waste heat generated during ammonia synthesis. Under conditions of high system load and abundant waste heat, excess heat is stored through a heat storage medium, preventing the waste of waste heat resources.

[0041] When the system is operating at low load and the synthesis tower is unable to maintain its self-heating balance, the heat storage medium can release the stored heat to heat the gas entering the synthesis tower. By increasing the temperature of the gas entering the tower, the self-heating balance of the synthesis tower can be maintained. This realizes the function of using the waste heat of the system at high load to supplement the heat of the synthesis tower at low load, thereby saving energy and ensuring the stability of the system's thermal balance.

[0042] See Figure 1 and Figure 2As shown, optionally, the steam transport pipeline 52 passes through the interior of the heat storage device 6.

[0043] In this embodiment, a section of the steam transport pipeline 52 can be installed inside the heat storage device 6, allowing the steam transported in the steam transport pipeline 52 to fully exchange heat with the heat storage medium inside the heat storage device 6. When the steam generated by the steam generator 5 is transported to the first power supply structure 41 via the steam transport pipeline 52, it can first pass through the interior of the heat storage device 6, where the heat stored in the heat storage medium is used to reheat the steam, realizing the conversion of medium-grade heat energy in the steam into high-grade heat energy. This allows the steam to better meet the power input requirements of the first power supply structure 41, improving the steam's work capacity and waste heat utilization efficiency.

[0044] This setup can work in synergy with the heat storage function of the heat storage device 6. Under high system load conditions, excess reaction heat is stored by the heat storage medium, and the stored heat is used to increase the steam temperature, further enhancing the waste heat recovery and utilization effect. When the steam temperature changes due to system load fluctuations, the heat storage medium can be used to stabilize the steam temperature, reducing the impact of steam temperature fluctuations on the operational stability of the first energy supply structure 41.

[0045] See Figure 1 and Figure 2 As shown, optionally, the synthesis tower 2 has a first tower wall gas inlet 22 and a tower wall gas outlet 23. The tower wall gas outlet 23 is connected to the first tower wall gas inlet 22 through an intermediate pipeline group 7, which passes through the interior of the heat storage device 6.

[0046] In this embodiment, the synthesis tower 2 may include a tower shell and tower internals. An annular channel may be formed between the tower internals and the tower shell. The tower wall gas outlet 23 may be connected to the annular channel. The intake gas delivered by the intake pipeline 1 may enter the annular channel and exchange heat with the tower internals. On the one hand, the intake gas entering the synthesis tower 2 may be preheated, and on the other hand, the tower wall and tower internals may be cooled and protected, thus ensuring the safe operation and service life of the synthesis tower 2.

[0047] The synthesis gas, after heat exchange through the annular channel, can be discharged through the tower wall gas outlet 23, transported through the intermediate pipeline group 7, and then sent back into the synthesis tower 2 through the first tower wall gas inlet 22 to enter the catalyst bed of the tower internals for ammonia synthesis reaction.

[0048] A section of the intermediate pipeline group 7 can be installed inside the heat storage device 6, so that the synthesis gas transported in the intermediate pipeline group 7 can exchange heat with the heat storage medium in the heat storage device 6. Under low load conditions of the system, the heat released by the heat storage medium can be used to supplement the heat of the synthesis gas, increase the temperature of the gas entering the tower, and stabilize the temperature of the catalyst bed in the synthesis tower 2.

[0049] See Figure 1 and Figure 2 As shown, optionally, the intermediate pipeline group 7 includes an intermediate main pipeline 71, one end of which is connected to the tower wall gas outlet 23, and the other end of which is connected to the first tower wall gas inlet 22. The intermediate main pipeline 71 passes through the interior of the heat storage device 6. The intermediate pipeline group 7 also includes an intermediate secondary pipeline 72, one end of which is connected to the intermediate main pipeline 71 between the heat storage device 6 and the tower wall gas outlet 23, and the other end of which is connected to the intermediate main pipeline 71 between the heat storage device 6 and the first tower wall gas inlet 22. A first intermediate valve 73 is provided on the intermediate secondary pipeline 72, and a second intermediate valve 74 is provided on the intermediate main pipeline 71 between the heat storage device 6 and the tower wall gas outlet 23. The second intermediate valve 74 is located on the side of the connection point between the intermediate secondary pipeline 72 and the intermediate main pipeline 71 that is close to the heat storage device 6.

[0050] In this embodiment, the intermediate main pipeline 71 and the intermediate secondary pipeline 72 can form a parallel syngas delivery channel. By coordinating the opening and closing of the first intermediate valve 73 and the second intermediate valve 74, the syngas delivery path can be flexibly switched to adapt to different operating conditions of the system.

[0051] When the system is under high load, the second intermediate valve 74 can be closed and the first intermediate valve 73 can be opened, so that the synthesis gas discharged from the tower wall gas outlet 23 can be transported through the intermediate secondary pipeline 72 and directly enter the synthesis tower 2 through the first tower wall gas inlet 22 without passing through the heat storage device 6 for heat exchange, thus avoiding the problem of excessively high synthesis gas temperature under high load conditions leading to overheating of the catalyst bed.

[0052] When the system is under low load, the second intermediate valve 74 can be opened and the first intermediate valve 73 can be closed, so that the synthesis gas discharged from the tower wall gas outlet 23 can be transported through the intermediate main pipeline 71, pass through the heat storage device 6, exchange heat with the heat storage medium, and then enter the synthesis tower 2 through the first tower wall gas inlet 22. This increases the temperature of the gas entering the tower under low load conditions, replenishes the heat of the synthesis tower, and stabilizes the synthesis reaction conditions.

[0053] This setup allows for simple valve switching to regulate the temperature of the gas entering the tower under different operating conditions, eliminating the need for additional complex heating equipment. The system has a simple structure and flexible and convenient control, which can further enhance the system's adaptability to load fluctuations. At the same time, it maximizes the utilization of the waste heat stored in the heat storage device 6, thereby improving the system's energy efficiency.

[0054] See Figure 1 and Figure 3As shown, optionally, it also includes a heat exchange module 8, which includes a first heat exchange pipeline 81, a second heat exchange pipeline 82, and a third heat exchange pipeline 83. The medium in the first heat exchange pipeline 81 can exchange heat with the medium in the second heat exchange pipeline 82, and the medium in the first heat exchange pipeline 81 can also exchange heat with the medium in the third heat exchange pipeline 83. The exhaust pipeline 3 is connected to the first heat exchange pipeline 81, and the intake pipeline 1 is connected to the second heat exchange pipeline 82. The steam generator 5 includes a water supply pipeline 53, which is connected to the third heat exchange pipeline 83.

[0055] In this embodiment, the first heat exchange pipeline 81 can be the heat source medium channel of the heat exchange equipment, and the second heat exchange pipeline 82 and the third heat exchange pipeline 83 can be the cold medium channels of the heat exchange equipment. The channel form of each pipeline can also be adjusted according to the actual heat exchange requirements to achieve synchronous and efficient heat exchange of multiple media. The synthesis gas after heat exchange in the steam generator 5 can be transported to the first heat exchange pipeline 81 through the outlet pipeline 3 as the heat source medium for heat exchange.

[0056] Synthetic gas to be transported to synthesis tower 2 in inlet pipeline 1 can be introduced into second heat exchange pipeline 82 to exchange heat with high-temperature synthetic gas in first heat exchange pipeline 81, thereby preheating the synthetic gas entering the tower, further recovering the low-temperature waste heat of the synthetic gas, and reducing the additional energy consumption required for heating the gas entering the tower.

[0057] The feedwater in the feedwater pipeline 53 of the steam generator 5 can be introduced into the third heat exchange pipeline 83 to exchange heat with the high-temperature synthesis gas in the first heat exchange pipeline 81, thereby preheating the feedwater and increasing the temperature of the feedwater entering the steam generator 5. This allows the feedwater to vaporize and generate steam more quickly in the steam generator 5, improving the steam generation efficiency and waste heat recovery effect of the steam generator 5.

[0058] This setup enables the graded recovery and utilization of low-temperature waste heat from syngas, while simultaneously preheating the gas entering the tower and the feedwater. It eliminates the need for additional independent preheating equipment, simplifies the system structure, and further improves the system's waste heat utilization rate.

[0059] Specifically, the heat exchange module 8 may include a raw gas heater and an economizer. The medium in the first heat exchange pipeline 81 and the second heat exchange pipeline 82 can exchange heat in the raw gas heater first, and then the medium in the first heat exchange pipeline 81 and the third heat exchange pipeline 83 can exchange heat in the economizer.

[0060] See Figure 1 and Figure 2As shown, optionally, the steam transport pipeline 52 includes a steam heat exchange pipeline 521 and a steam discharge pipeline 522. The steam heat exchange pipeline 521 passes through the heat storage device 6. One end of the steam heat exchange pipeline 521 is connected to the steam outlet end 51, and the other end of the steam heat exchange pipeline 521 is connected to the first power supply structure 41. One end of the steam discharge pipeline 522 is connected to the steam outlet end 51, and the other end of the steam discharge pipeline 522 is connected to an external pipeline. A first steam valve 55 is provided on the portion of the steam heat exchange pipeline 521 located between the heat storage device 6 and the steam outlet end 51, and a second steam valve 54 is provided on the steam discharge pipeline 522.

[0061] In this embodiment, the steam heat exchange pipeline 521 and the steam discharge pipeline 522 can form a parallel steam output channel. By coordinating the opening and closing of the first steam valve 55 and the second steam valve 54, the steam output path can be switched to adapt to different operating conditions of the system.

[0062] When the system is under high load and the steam generator 5 produces sufficient steam, the first steam valve 55 can be opened and the second steam valve 54 can be closed, so that the steam generated by the steam generator 5 can be transported through the steam heat exchange pipeline 521, passed through the heat storage device 6 for secondary heating, and then transported to the first energy supply structure 41 to provide power for the gas compressor 4, thereby maximizing the utilization of waste heat resources.

[0063] When the system is in the start-up phase or under low load conditions, and the steam generator 5 produces less steam than the first power supply structure 41, the first steam valve 55 can be closed and the second steam valve 54 can be opened. This allows a small amount of steam generated by the steam generator 5 to be transported to the external pipeline via the steam discharge pipeline 522, thus preventing low-pressure and low-temperature steam from entering the first power supply structure 41 and causing equipment instability, and ensuring the safety of system operation.

[0064] This setting allows for flexible switching of the steam delivery path based on the actual steam production of the system. It enables efficient utilization of steam when there is sufficient waste heat, while avoiding the impact of steam temperature fluctuations on power equipment when there is less waste heat, thereby further improving the system's operational stability and adaptability to different operating conditions.

[0065] A waste heat utilization method, based on the above-mentioned green ammonia synthesis waste heat utilization system, includes a first mode: the first steam valve 55 is closed, the second steam valve 54 is open, and the gas compressor 4 is driven to operate through the second energy supply structure 42; The second mode includes: the first steam valve 55 is open, the second steam valve 54 is closed, the first intermediate valve 73 is open, the second intermediate valve 74 is closed, and the gas compressor 4 is driven to operate through the second power supply structure 42 / the first power supply structure 41.

[0066] In this embodiment, the method can adapt to different operating conditions of the wind-solar green ammonia synthesis system by switching the system operation mode, suppress system load fluctuations caused by the intermittency of wind and solar power generation, and achieve efficient recovery and utilization of waste heat from ammonia synthesis reaction while ensuring stable system operation.

[0067] The first mode corresponds to the system's start-up and low-load operation phases. In this mode, the first steam valve 55 is closed, the second steam valve 54 is open, and all the steam generated by the steam generator 5 is transported to the external pipeline via the steam discharge pipeline 522. The gas compressor 4 is driven entirely by the electrical energy provided by the second power supply structure 42. Using the first mode during the start-up phase can avoid power equipment malfunctions caused by insufficient heat generation and substandard steam parameters in the initial stage of the system reaction, ensuring a smooth start-up and temperature / pressure rise of the system during the start-up phase.

[0068] Operating in the first mode during the low-load phase can avoid the problem of unstable compressor power supply caused by less waste heat and less steam. At the same time, the stable power supply of the second power supply structure 42 ensures the stable output pressure of the gas compressor 4, thereby stabilizing the reaction conditions of the synthesis tower 2.

[0069] The second mode can correspond to the high-load operation stage of the system. In this mode, the first steam valve 55 is open and the second steam valve 54 is closed. The steam generated by the steam generator 5 is transported through the steam heat exchange pipeline 521, and after passing through the heat storage device 6 for secondary heating, it is transported to the first energy supply structure 41.

[0070] At the same time, the first intermediate valve 73 is opened and the second intermediate valve 74 is closed. The synthesis gas discharged from the gas outlet 23 of the synthesis tower 2 is directly transported to the gas inlet 22 of the first tower wall via the intermediate secondary pipeline 72, without needing to pass through the heat storage device 6 for heat exchange.

[0071] In this mode, the gas compressor 4 can be driven by the first power supply structure 41 first. When the amount of steam is insufficient and the first power supply structure 41 cannot provide sufficient driving force, it can be switched to the second power supply structure 42 for driving, or the second power supply structure 42 can be used to supplement the power supply.

[0072] By adopting the second mode of operation, the waste heat from the ammonia synthesis reaction can be maximized under high system load and high waste heat conditions. The compressor is driven by steam, which reduces the system's power consumption and improves the system's energy self-sufficiency and operational economy.

[0073] Optionally, the method may also include a third operating mode, corresponding to the low-load heat replenishment condition of the system. The third mode may be: the first steam valve 55 is closed, the second steam valve 54 is open, the first intermediate valve 73 is closed, the second intermediate valve 74 is open, and the gas compressor 4 is driven to operate through the second power supply structure 42. In this mode, the synthesis gas discharged from the gas outlet 23 of the synthesis tower 2 passes through the intermediate main pipeline 71 and the heat storage device 6, exchanges heat with the heat storage medium, and then enters the synthesis tower 2. When the system is under low load and the temperature of the gas entering the tower is insufficient, the heat released by the heat storage device 6 can raise the temperature of the gas entering the tower, stabilize the temperature of the catalyst bed in the synthesis tower 2, and ensure the smooth progress of the ammonia synthesis reaction.

[0074] In one specific embodiment, the system may further include: The intake pipeline 1 has a first intake sub-pipeline and a second intake sub-pipeline connected in parallel. The first intake sub-pipeline is equipped with a first intake valve and a heating device, and the second intake sub-pipeline is equipped with a second intake valve. The output end of the first intake secondary pipeline is connected to the start-up gas inlet of the synthesis tower 2, and the output end of the second intake secondary pipeline is connected to the second tower wall gas inlet of the synthesis tower 2. The synthesis tower 2 is composed of a tower shell and tower internals with an internal catalyst bed. An annular channel is formed between the tower shell and the tower internals. The synthesis tower 2 is also provided with an start-up gas inlet that is directly connected to the catalyst bed and a secondary synthesis gas inlet that is connected to the catalyst bed. The second tower wall gas inlet and the tower wall gas outlet 23 are both connected to the aforementioned annular channel.

[0075] An oil-gas separator is installed on the pipeline between the downstream of the gas compressor 4 and the upstream of the intake pipeline 1 for uniform mixing of fresh gas and circulating gas and removal of oil impurities. Along the medium flow direction of the gas outlet pipeline 3, a water cooler, a cold exchanger, an ammonia cooler, an ammonia separator, and a flash evaporator are sequentially installed downstream of the heat exchange module 8 for the staged cooling and condensation of ammonia-containing synthesis gas and the separation and purification of liquid ammonia products. The condenser, which is connected to the turbine exhaust end of the first power supply structure 41, is used for the condensation and recovery of the exhaust steam after the turbine has done its work, and the condensed water can be reused in the feedwater pipeline 53 of the steam generator 5.

[0076] In a specific process, the nitrogen-hydrogen mixture is used as fresh gas. After being pressurized to the pressure required for the ammonia synthesis reaction by the gas compressor 4, it is mixed and purified by the oil-gas separator and then delivered to the inlet pipeline 1. The system can flexibly switch the inlet path, steam delivery path and tower wall gas circulation path according to the actual operating conditions.

[0077] During the start-up phase, the first inlet valve is opened and the second inlet valve is closed. The pressurized syngas is heated to the reaction initiation temperature via the first inlet sub-pipeline of inlet pipeline 1 and the heating device on the pipeline. Then, it directly enters the internal catalyst bed through the start-up gas inlet of synthesis tower 2 to undergo ammonia synthesis. The high-temperature ammonia-containing syngas generated is discharged through the syngas outlet 21 of synthesis tower 2 to the outlet pipeline 3. It first enters the heat storage device 6 to collect the waste heat from the reaction, and then enters the steam generator 5 to exchange heat with the feed water supplied by the feed water pipeline 53 to generate a small amount of steam. Steam is discharged from the steam discharge pipeline 522 through the opened second steam valve 54. The syngas, after heat exchange in the steam generator 5, enters the first heat exchange pipeline 81 of the heat exchange module 8. It exchanges heat with the syngas to be fed into the tower in the second heat exchange pipeline 82 and the feed water in the third heat exchange pipeline 83 to complete the low-temperature waste heat recovery and medium preheating. Finally, it is cooled, condensed and separated in stages by water cooler, cold exchanger, ammonia cooler, ammonia separator and flash evaporator to obtain qualified liquid ammonia product. The remaining unreacted nitrogen-hydrogen mixture after separation is repressurized as circulating gas and sent to the oil-gas separator for reuse. During the high-load stable operation phase, the first inlet valve is closed and the second inlet valve is opened. The pressurized syngas enters the annular channel between the outer shell and the internal components of the synthesis tower 2 through the second inlet sub-pipeline of inlet pipeline 1 and the second tower wall gas inlet of synthesis tower 2. It is then discharged through the tower wall gas outlet 23 and directly enters the catalyst bed through the first tower wall gas inlet 22 of synthesis tower 2 via the opened first intermediate valve 73 and intermediate sub-pipeline 72 to undergo ammonia synthesis reaction. The high-temperature syngas generated by the reaction is discharged from the syngas outlet 21. After that, it first enters the heat storage device 6 to store the excess reaction waste heat in the heat storage medium, and then enters the steam generator. The generator 5 generates a large amount of saturated steam through heat exchange with the feedwater. This steam passes through the first steam valve 55, through the steam heat exchange pipeline 521, and then through the heat storage device 6 to complete the secondary temperature increase. It is then delivered to the first power supply structure 41 to drive the gas compressor 4. If the steam supply is insufficient, it can be switched to the second power supply structure 42 to supplement the drive. The exhaust steam from the turbine of the first power supply structure 41 is condensed into condensate by the condenser and then reused in the feedwater pipeline 53. The synthesis gas after heat exchange with the steam generator 5 enters the heat exchange module 8 to complete the preheating of the tower gas and feedwater. Then it enters the ammonia separation unit to complete the separation of liquid ammonia products. The circulating gas is pressurized and reused. During the low-load fluctuation operation phase, the first inlet valve is closed and the second inlet valve is opened. The syngas is discharged through the tower wall gas outlet 23 after heat exchange in the annular channel of the synthesis tower 2. It passes through the heat storage device 6 through the opened second intermediate valve 74 and the intermediate main pipeline 71. After the heat storage medium stores the heat for supplementary heating and temperature rise, it enters the catalyst bed through the first tower wall gas inlet 22 of the synthesis tower 2 to carry out the ammonia synthesis reaction, so as to stabilize the catalyst bed temperature and reaction conditions under low-load conditions. The syngas generated by the reaction enters the steam generator 5 after the waste heat is supplemented and stored in the heat storage device 6. The small amount of steam generated is discharged from the steam discharge pipeline 522 through the second steam valve 54. After heat exchange, the syngas enters the ammonia separation unit to complete the low-temperature waste heat recovery after heat exchange module 8, and then enters the ammonia separation unit to complete the liquid ammonia separation and recirculation gas reuse. During this phase, the gas compressor 4 is driven by the second power supply structure 42 throughout.

[0078] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A waste heat utilization system for green ammonia synthesis, characterized in that, It includes an inlet pipeline (1), a synthesis tower (2) and an outlet pipeline (3). The synthesis tower (2) has a synthesis gas outlet (21). The inlet pipeline (1) is connected to the input end of the synthesis tower (2). The synthesis gas outlet (21) is connected to the outlet pipeline (3). A gas compressor (4) is provided on the inlet pipeline (1). The gas compressor (4) has a first power supply structure (41) and a second power supply structure (42). A steam generator (5) is provided on the outlet pipeline (3). The steam outlet end (51) of the steam generator (5) is connected to the first power supply structure (41) through a steam transport pipeline (52).

2. The waste heat utilization system for green ammonia synthesis according to claim 1, characterized in that, The first power supply structure (41) is a steam turbine, the steam generator (5) generates steam, the steam turbine generates first electrical energy through the steam, the second power supply structure (42) is electrically connected to the power grid, the power grid generates second electrical energy, and the gas compressor (4) can be driven to operate by the first electrical energy / second electrical energy.

3. The waste heat utilization system for green ammonia synthesis according to claim 1, characterized in that, The first power supply structure (41) is used to introduce steam and convert the thermal energy of the steam into mechanical energy to directly drive the gas compressor (4) to run. The second power supply structure (42) is electrically connected to the power grid, and the power grid generates second electrical energy, which enables the gas compressor (4) to run.

4. The waste heat utilization system for green ammonia synthesis according to claim 1, characterized in that, The outlet pipeline (3) is also equipped with a heat storage device (6), which contains a heat storage medium that can exchange heat with the medium passing through the heat storage device (6).

5. The waste heat utilization system for green ammonia synthesis according to claim 4, characterized in that, The steam transport pipeline (52) passes through the interior of the heat storage device (6).

6. The waste heat utilization system for green ammonia synthesis according to claim 4, characterized in that, The synthesis tower (2) has a first tower wall gas inlet (22) and a tower wall gas outlet (23). The tower wall gas outlet (23) is connected to the first tower wall gas inlet (22) through an intermediate pipeline group (7). The intermediate pipeline group (7) passes through the interior of the heat storage device (6).

7. The waste heat utilization system for green ammonia synthesis according to claim 6, characterized in that, The intermediate pipeline group (7) includes an intermediate main pipeline (71), one end of which is connected to the tower wall gas outlet (23), and the other end of which is connected to the first tower wall gas inlet (22). The intermediate main pipeline (71) passes through the interior of the heat storage device (6). The intermediate pipeline group (7) also includes an intermediate secondary pipeline (72), one end of which is connected to the intermediate main pipeline (71) between the heat storage device (6) and the tower wall gas outlet (23). The other end of the intermediate secondary pipeline (72) is connected to the intermediate main pipeline (71) between the heat storage device (6) and the first tower wall gas inlet (22). The intermediate secondary pipeline (72) is provided with a first intermediate valve (73). The intermediate main pipeline (71) between the heat storage device (6) and the tower wall gas outlet (23) is provided with a second intermediate valve (74). The second intermediate valve (74) is located on the side of the connection point between the intermediate secondary pipeline (72) and the intermediate main pipeline (71) close to the heat storage device (6).

8. The waste heat utilization system for green ammonia synthesis according to claim 1, characterized in that, It also includes a heat exchange module (8), which includes a first heat exchange pipeline (81), a second heat exchange pipeline (82) and a third heat exchange pipeline (83). The medium in the first heat exchange pipeline (81) can exchange heat with the medium in the second heat exchange pipeline (82), and the medium in the first heat exchange pipeline (81) can also exchange heat with the medium in the third heat exchange pipeline (83). The outlet pipeline (3) is connected to the first heat exchange pipeline (81), and the inlet pipeline (1) is connected to the second heat exchange pipeline (82). The steam generator (5) includes a water supply pipeline (53), which is connected to the third heat exchange pipeline (83).

9. The waste heat utilization system for green ammonia synthesis according to claim 7, characterized in that, The steam transport pipeline (52) includes a steam heat exchange pipeline (521) and a steam discharge pipeline (522). The steam heat exchange pipeline (521) passes through the heat storage device (6). One end of the steam heat exchange pipeline (521) is connected to the steam outlet end (51), and the other end of the steam heat exchange pipeline (521) is connected to the first power supply structure (41). One end of the steam discharge pipeline (522) is connected to the steam outlet end (51), and the other end of the steam discharge pipeline (522) is connected to an external pipeline. A first steam valve (55) is provided on the part of the steam heat exchange pipeline (521) located between the heat storage device (6) and the steam outlet end (51), and a second steam valve (54) is provided on the steam discharge pipeline (522).

10. A waste heat utilization method, implemented based on the green ammonia synthesis waste heat utilization system of claim 9, characterized in that, The first mode includes a first steam valve (55) closed and a second steam valve (54) open, in which the gas compressor (4) is driven to operate via a second power supply structure (42). The second mode includes: the first steam valve (55) is open, the second steam valve (54) is closed, the first intermediate valve (73) is open, the second intermediate valve (74) is closed, and the gas compressor (4) is driven by the second power supply structure (42) / the first power supply structure (41).

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