A high-temperature water vapor production system based on nitrogen Brayton cycle

Abstract

The application provides a high-temperature water vapor production system based on a nitrogen Brayton cycle, and relates to the technical field of energy recycling.The system comprises a heat exchanger and a water vapor generator, which are both in communication with a high-temperature heat pump.The heat exchanger is used for heating low-temperature and low-pressure nitrogen medium by using a low-temperature heat source with air as a medium, obtaining medium-temperature and low-pressure nitrogen and generating cold energy below 0 DEG C at the same time.The high-temperature heat pump is used for heating the medium-temperature and low-pressure nitrogen by using the remaining medium-temperature and high-pressure nitrogen of the water vapor generator, and compressing the medium-temperature and low-pressure nitrogen to obtain high-temperature and high-pressure nitrogen.The water vapor generator is used for heating saturated water medium by using the high-temperature and high-pressure nitrogen, obtaining the medium-temperature and high-pressure nitrogen and high-temperature water vapor.The application effectively solves the technical problems of low COP and the inability to directly utilize 90 DEG C low-temperature waste heat to generate 400 DEG C steam in the prior art.

Description

Technical Field

[0001] This invention relates to the field of energy recycling technology, and more specifically, to a high-temperature steam production system based on the nitrogen Brayton cycle. Background Technology

[0002] Industrial parks, as the core clusters of industrial production activities, undertake the important functions of large-scale production and centralized resource allocation for various industries, and are key engines for regional economic development. Currently, low-carbon transformation has become the core direction for the high-quality development of industrial parks. One of the core demands of zero-carbon industrial parks is to achieve efficient and clean energy utilization, especially by tapping into the value of idle energy sources such as low-temperature waste heat. Through technological innovation, low-grade energy can be converted into high-grade industrial energy. Utilizing low-temperature waste heat (around 90℃) to produce high-temperature steam (above 400℃) is a crucial link in meeting the needs of industrial production in the park (such as process heating and power supply), reducing dependence on fossil fuels, and achieving carbon emission reduction targets.

[0003] In related technologies, a low-temperature heat source of 90°C is generally used to drive a heat pump to generate medium-temperature water vapor of around 200°C, which is then compressed and heated to 400°C by a compressor. This method has low energy conversion efficiency, with the COP (coefficient of performance) of the heat pump system generally below 1.6, and the overall COP of the entire process approaching 1. Its economic benefits are far less than those of traditional electric heating. Summary of the Invention

[0004] The problem addressed by this invention is how to improve energy conversion efficiency, thereby increasing economic benefits.

[0005] To address the above problems, this invention provides a high-temperature steam production system based on a nitrogen Brayton cycle, comprising a heat exchanger and a steam generator both connected to a high-temperature heat pump. The heat exchanger is used to heat the low-temperature, low-pressure nitrogen medium with a low-temperature heat source using air as the medium, and convert the low-temperature, low-pressure nitrogen medium into medium-temperature, low-pressure nitrogen. The high-temperature heat pump is used to heat the medium-temperature low-pressure nitrogen gas with the remaining medium-temperature high-pressure nitrogen gas from the steam generator to obtain high-temperature low-pressure nitrogen gas, and to compress the high-temperature low-pressure nitrogen gas to obtain high-temperature high-pressure nitrogen gas. The steam generator is used to heat a saturated water medium with high-temperature, high-pressure nitrogen to obtain medium-temperature, high-pressure nitrogen and high-temperature steam.

[0006] Optionally, the heat exchanger is specifically used for: The low-temperature, low-pressure nitrogen medium is heated by the low-temperature heat source, converting the low-temperature, low-pressure nitrogen medium into medium-temperature, low-pressure nitrogen, and the low-temperature heat source is converted into a low-temperature cold source.

[0007] Optionally, the high-temperature heat pump is specifically used for: The medium-temperature low-pressure nitrogen gas is heated and compressed by the medium-temperature low-pressure nitrogen gas generated by the steam generator, thereby converting the medium-temperature low-pressure nitrogen gas into high-temperature high-pressure nitrogen gas, and then converting the medium-temperature high-pressure nitrogen gas into low-temperature high-pressure nitrogen gas. The low-temperature, high-pressure nitrogen gas is expanded to obtain the low-temperature, low-pressure nitrogen gas medium.

[0008] Optionally, the high-temperature heat pump includes a nitrogen compressor and a nitrogen expander, both of which are connected to the regenerator, and the regenerator is also connected to the heat exchanger and the steam generator respectively; The regenerator is used to heat the medium-temperature low-pressure nitrogen gas through the medium-temperature high-pressure nitrogen gas from the steam generator, converting the medium-temperature low-pressure nitrogen gas into the high-temperature low-pressure nitrogen gas, and converting the medium-temperature high-pressure nitrogen gas into the low-temperature high-pressure nitrogen gas. The nitrogen compressor is used to compress the high-temperature, low-pressure nitrogen gas to obtain the high-temperature, high-pressure nitrogen gas. The nitrogen expander is used to expand the low-temperature, high-pressure nitrogen gas to obtain the low-temperature, low-pressure nitrogen medium.

[0009] Optionally, the process of determining the heat requirement of the low-temperature heat source includes: Obtain initial design parameters; Based on the initial design parameters, iterative calculations are performed according to the pinch temperature difference of the regenerator to determine the node state parameters and the flow parameters based on the Brayton cycle. The heat demand is determined based on the node status parameters and the flow rate parameters.

[0010] Optionally, the initial design parameters include the pinch temperature difference of the regenerator.

[0011] Optionally, the step of determining the node state parameters and the Brayton cycle-based flow parameters by iterative calculation based on the initial design parameters and the pinch temperature difference of the regenerator includes: When the pinch temperature difference is greater than the preset temperature difference threshold, the cold end outlet temperature of the regenerator is adjusted using the first adjustment strategy, and the pinch temperature difference is re-determined based on the adjusted cold end outlet temperature of the regenerator. When the pinch temperature difference is less than the preset temperature difference threshold, the cold end outlet temperature of the regenerator is adjusted using the second adjustment strategy, and the pinch temperature difference is re-determined based on the adjusted cold end outlet temperature of the regenerator. When the pinch temperature difference is greater than the preset temperature difference threshold, and the absolute value of the difference between the pinch temperature difference and the preset temperature difference threshold is less than the preset difference, the node status parameters and the flow parameters are determined based on the initial design parameters and the cold end outlet temperature of the regenerator at the current step size.

[0012] Optionally, the node status parameters include compressor inlet and outlet status parameters, expander inlet and outlet status parameters, steam generator hot end outlet status parameters, regenerator hot end outlet status parameters, and heat exchanger hot end outlet status parameters. The process of determining the node status parameters and the flow rate parameters based on the initial design parameters and the current step size of the regenerator cold end outlet temperature includes: Based on the initial design parameters, and according to the current step size of the regenerator cold end outlet temperature and the compressor calculation model, the compressor outlet state parameters are determined. Based on the compressor outlet state parameters and the steam generator calculation model, the hot end outlet state parameters of the steam generator and the flow parameters are determined. The hot end outlet state parameters of the regenerator are determined by iterative calculation based on the pinch temperature difference of the regenerator. Based on the expander calculation model, the expander outlet state parameters and the heat exchanger hot end outlet state parameters are determined.

[0013] Optionally, the initial design parameters may also include the inlet state parameters of the heat exchanger hot end, the outlet state parameters of the heat exchanger cold end, the inlet and outlet state parameters of the steam generator cold end, the inlet and outlet flow rates of the steam generator cold end, the system compression ratio, and the system expansion ratio.

[0014] Optionally, determining the heat demand based on the node status parameters and the flow parameters includes: The cold end inlet state parameters of the heat exchanger are determined based on the hot end outlet state parameters of the regenerator and the expansion machine calculation model. The heat demand is determined based on the inlet state parameters of the heat exchanger cold end, the flow rate parameters, and the outlet temperature of the heat exchanger cold end.

[0015] The beneficial effects of the high-temperature steam production system based on the nitrogen Brayton cycle of the present invention are: By using a heat exchanger connected to a high-temperature heat pump, a low-temperature, low-pressure nitrogen medium is heated using a 90°C low-temperature heat source and converted into medium-temperature, low-pressure nitrogen. This successfully and efficiently introduces low-temperature waste heat into the system, providing a suitable initial energy carrier for the subsequent generation of high-temperature steam. This solves the prerequisite problem that existing technologies cannot directly rely on 90°C low-temperature waste heat to generate 400°C high-temperature steam. Next, the high-temperature heat pump, based on a nitrogen Brayton cycle, uses the remaining medium-temperature, high-pressure nitrogen from the steam generator to heat the aforementioned medium-temperature, low-pressure nitrogen to obtain high-temperature, low-pressure nitrogen, which is then compressed to obtain high-temperature, high-pressure nitrogen. This not only recovers the waste heat from the steam generator, reduces energy loss, and improves energy utilization efficiency, but also avoids the low COP problem caused by energy waste in existing technologies. The "waste heat preheating + direct compression" method eliminates the cumbersome process of generating water vapor at around 200°C and then compressing it again, as required by existing technologies. This provides a crucial high-temperature heat source for the direct production of high-temperature steam. Subsequently, a steam generator connected to a high-temperature heat pump uses this high-temperature, high-pressure nitrogen to heat a saturated water medium, directly producing high-temperature steam. This precisely solves the core problem of existing technologies that cannot directly generate high-temperature steam above 400°C using low-temperature waste heat at 90°C. Furthermore, the energy conversion efficiency during the heat exchange process is higher, further contributing to the improvement of the system's COP. While ensuring stable system operation, costs are controlled. Through the sequential connection and coordination of each step, the technical difficulties of low COP and the inability to directly utilize low-temperature waste heat to generate high-temperature steam at 400°C in existing technologies are effectively overcome. Attached Figure Description

[0016] Figure 1 One of the structural schematic diagrams of a high-temperature steam production system based on a nitrogen Brayton cycle provided in an embodiment of the present invention; Figure 2 This is the second schematic diagram of a high-temperature steam production system based on the nitrogen Brayton cycle provided in an embodiment of the present invention. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0018] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0019] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0020] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0021] The names of the messages or information exchanged between the multiple devices in the embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0022] like Figure 1 As shown in the figure, an embodiment of the present invention provides a high-temperature steam production system based on nitrogen Brayton cycle, including a heat exchanger and a steam generator both connected to a high-temperature heat pump.

[0023] Specifically, heat exchangers ( Figure 2 (HR) and steam generator ( Figure 2 All components (SG) are connected to the high-temperature heat pump through high-temperature resistant pipes. The connection method can be flange connection or welding fixation to ensure the sealing and pressure resistance of the system during operation. The heat exchanger can be a type that is suitable for heat transfer from a low-temperature heat source of about 90℃, and the steam generator can be a device with high-efficiency heat exchange capacity.

[0024] The heat exchanger is used to heat the low-temperature, low-pressure nitrogen medium with a low-temperature heat source using air as the medium, and convert the low-temperature, low-pressure nitrogen medium into medium-temperature, low-pressure nitrogen.

[0025] Specifically, the heat exchanger is supplied with industrial low-temperature waste heat at 90°C (adaptable to various low-temperature waste heat resources within the 85-95°C range, such as waste heat from industrial production exhaust gases and wastewater) as a low-temperature heat source. The low-temperature heat source can be air, which enters the heat exchanger. Dry, clean, low-temperature, low-pressure nitrogen gas is introduced to the cold end of the heat exchanger. As the low-temperature, low-pressure nitrogen gas flows through the cold end of the heat exchanger, it fully exchanges heat with the low-temperature heat source at the hot end, raising the temperature of the low-temperature, low-pressure nitrogen gas from its initial temperature (e.g., 90°C). Figure 2Node 7 (approximately -20.191℃) is heated to approximately 80℃ (this temperature can be adjusted within the 75-85℃ range, corresponding to...). Figure 2 Node 8) ultimately converts the nitrogen gas into a medium-temperature, low-pressure gas with a stable pressure of 1.5-1.6 MPa and a flow rate suitable for subsequent circulation needs. The heat exchanger in this embodiment can also be replaced with a plate heat exchanger or a spiral plate heat exchanger, depending on the spatial layout and heat exchange efficiency requirements of the actual application scenario. Plate heat exchangers offer higher heat exchange efficiency and smaller size, making them suitable for space-constrained conditions. Spiral plate heat exchangers, on the other hand, have better anti-fouling performance and are suitable for conditions where the low-temperature heat source contains a small amount of impurities. Both can achieve the core function of heating the low-temperature, low-pressure nitrogen medium through a low-temperature heat source and converting it into medium-temperature, low-pressure nitrogen gas. For example, the low-temperature, low-pressure nitrogen medium can be replaced with carbon dioxide.

[0026] The high-temperature heat pump is used to heat the medium-temperature low-pressure nitrogen gas with the remaining medium-temperature high-pressure nitrogen gas from the steam generator to obtain high-temperature low-pressure nitrogen gas, and to compress the high-temperature low-pressure nitrogen gas to obtain high-temperature high-pressure nitrogen gas.

[0027] Specifically, the high-temperature heat pump integrates a regenerator, compressor, and expander. The compressor's compression ratio can be set to 4 (fine-tuned within the range of 3.8-4.2 to adapt to different pressure requirements), and the expander's expansion ratio can be set to 4 to match the compression ratio. During operation, the regenerator first receives medium-temperature, high-pressure nitrogen gas (approximately 195.6℃, 8MPa) discharged from the steam generator. Figure 2 Node 4 parameters), and use this nitrogen gas to treat the medium-temperature, low-pressure nitrogen gas (temperature approximately 80°C, pressure 2MPa, corresponding to) from the heat exchanger. Figure 2 Node 8 parameters) are heated to fully recover the residual heat from the medium-temperature, high-pressure nitrogen gas, resulting in high-temperature, low-pressure nitrogen gas (temperature approximately 190℃, pressure 2MPa, corresponding to...). Figure 2 Node 6 parameters); High-temperature, low-pressure nitrogen enters the compressor, which compresses the nitrogen to approximately 433.997℃ according to the set compression ratio (adjustable within the range of 430-435℃, corresponding to...). Figure 2 The system compresses high-temperature, high-pressure nitrogen gas (node ​​3 parameters) at a pressure of 8 MPa. During the compression process, the compressor's power consumption is precisely controlled based on the compressor's calculation model, combined with the enthalpy change and isentropic efficiency of the nitrogen gas. At the same time, the expander operates according to the set expansion ratio, expanding the circulating nitrogen gas to do work and helping to balance the system's energy. Through the coordinated operation of various components, the entire system realizes the function of using medium-temperature, high-pressure nitrogen gas to preheat medium-temperature, low-pressure nitrogen gas and compress it to obtain high-temperature, high-pressure nitrogen gas.

[0028] The steam generator is used to heat a saturated water medium with high-temperature, high-pressure nitrogen to obtain medium-temperature, high-pressure nitrogen and high-temperature steam.

[0029] Specifically, high-temperature, high-pressure nitrogen gas (approximately 435.997℃ and 8MPa) from a high-temperature heat pump is introduced into the hot-end inlet of the steam generator. Figure 2 Node 3), the cold end inlet is supplied with industrial saturated water medium (temperature around 180℃, pressure 1.56MPa, corresponding to...). Figure 2 Node 2). During operation, high-temperature, high-pressure nitrogen flows at the hot end, while saturated water flows at the cold end, resulting in efficient heat exchange. The heat exchange area and fluid flow rate can be precisely controlled according to the steam generator calculation model, heating the saturated water to 400℃ (adjustable within the range of 400-420℃). Figure 2 Node 1) High-temperature superheated steam with a pressure of 1.56 MPa (adaptable to the 1.5-1.6 MPa range) meets industrial steam requirements; simultaneously, high-temperature, high-pressure nitrogen gas, after heat exchange, cools to approximately 195.6℃ (fluctuating within the 190-200℃ range, corresponding to...). Figure 2 At node 4, the pressure is maintained at around 8 MPa, forming medium-temperature high-pressure nitrogen gas which flows back to the regenerator of the high-temperature heat pump, realizing the recycling and utilization of heat.

[0030] In this embodiment, a heat exchanger connected to a high-temperature heat pump utilizes a 90°C low-temperature heat source to heat the low-temperature, low-pressure nitrogen medium and convert it into medium-temperature, low-pressure nitrogen. This successfully and efficiently introduces low-temperature waste heat into the system, providing a suitable initial energy carrier for the subsequent generation of high-temperature steam. This solves the prerequisite problem of existing technologies being unable to directly generate 400°C high-temperature steam using 90°C low-temperature waste heat. Next, the high-temperature heat pump, based on a nitrogen Brayton cycle, uses the remaining medium-temperature, high-pressure nitrogen from the steam generator to heat the aforementioned medium-temperature, low-pressure nitrogen to obtain high-temperature, low-pressure nitrogen, which is then compressed to obtain high-temperature, high-pressure nitrogen. This recovers the waste heat from the steam generator, reduces energy loss, improves energy utilization efficiency, and avoids the low COP problem caused by energy waste in existing technologies. Furthermore, by employing a "waste heat preheating + direct compression" method, the cumbersome process of generating approximately 200°C steam followed by secondary compression, as required by existing technologies, is eliminated, providing a crucial high-temperature heat source for the direct production of high-temperature steam. Subsequently, a steam generator connected to a high-temperature heat pump utilizes this high-temperature, high-pressure nitrogen gas to heat a saturated water medium, directly producing high-temperature steam. This precisely solves the core problem of existing technologies being unable to directly generate high-temperature steam above 400°C using 90°C low-temperature waste heat, and also achieves higher energy conversion efficiency during heat exchange, further contributing to the improvement of the system's COP. While ensuring stable system operation, costs are controlled. Through the sequential connection and synergy of each step, the technical challenges of low COP and the inability to directly utilize low-temperature waste heat to generate 400°C high-temperature steam in existing technologies are effectively overcome.

[0031] Optionally, the high-temperature heat pump is specifically used for: The medium-temperature low-pressure nitrogen gas is heated and compressed by the medium-temperature low-pressure nitrogen gas generated by the steam generator, thereby converting the medium-temperature low-pressure nitrogen gas into high-temperature high-pressure nitrogen gas, and then converting the medium-temperature high-pressure nitrogen gas into low-temperature high-pressure nitrogen gas. The low-temperature, high-pressure nitrogen gas is expanded to obtain the low-temperature, low-pressure nitrogen gas medium.

[0032] Specifically, the high-temperature heat pump performs the following operations: First, it receives medium-temperature, high-pressure nitrogen gas (approximately 195.563℃, 8MPa, adaptable to the range of 190-200℃ and 7.5-8.5MPa) discharged from the steam generator. This medium-temperature, high-pressure nitrogen gas is then used to heat the medium-temperature, low-pressure nitrogen gas (approximately 80℃, 2MPa, adjustable to the range of 75-85℃ and 1.8-2.2MPa) from the heat exchanger. During the heating process, sufficient heat transfer is ensured. Subsequently, the heated high-temperature, low-pressure nitrogen gas is converted into high-temperature, high-pressure nitrogen gas through compression. The temperature of this high-temperature, high-pressure nitrogen gas can reach 435.997℃. The temperature is maintained at around 80℃ and the pressure is stabilized at 8MPa (which can be finely adjusted within the range of 430-435℃ and 7.8-8.2MPa). At the same time, the medium-temperature high-pressure nitrogen gas, after participating in the heating, releases heat, and its temperature drops to around 89.23℃ while the pressure is maintained at 8MPa, thus transforming into low-temperature high-pressure nitrogen gas (which can be adapted within the range of 85-90℃ and 7.6-8.1MPa). Finally, this low-temperature high-pressure nitrogen gas is expanded to obtain a low-temperature low-pressure nitrogen medium with a temperature of approximately -20.19℃ and a pressure of 2MPa (which can be adjusted within the range of -25 to -18℃ and 1.9-2.1MPa), so that it can be reintroduced into the heat exchanger to participate in the next cycle. By heating medium-temperature low-pressure nitrogen with medium-temperature high-pressure nitrogen before compression, the waste heat from the nitrogen discharged from the steam generator is effectively recovered, reducing the energy consumption of the compression process. At the same time, the medium-temperature high-pressure nitrogen is converted into low-temperature high-pressure nitrogen and expanded to recover energy, forming a recycling of the low-temperature low-pressure nitrogen medium. This avoids the waste of the working fluid, further improves the system's energy utilization rate, and helps the system's COP stabilize at a relatively high level of 1.6867.

[0033] Optionally, such as Figure 2 As shown, the high-temperature heat pump includes a nitrogen compressor and a nitrogen expander, both of which are connected to the regenerator. The regenerator is also connected to the heat exchanger and the steam generator, respectively. The regenerator is used to heat the medium-temperature low-pressure nitrogen gas through the medium-temperature high-pressure nitrogen gas from the steam generator, converting the medium-temperature low-pressure nitrogen gas into the high-temperature low-pressure nitrogen gas, and converting the medium-temperature high-pressure nitrogen gas into the low-temperature high-pressure nitrogen gas. The nitrogen compressor is used to compress the high-temperature, low-pressure nitrogen gas to obtain the high-temperature, high-pressure nitrogen gas. The nitrogen expander is used to expand the low-temperature, high-pressure nitrogen gas to obtain the low-temperature, low-pressure nitrogen medium.

[0034] Specifically, high-temperature heat pumps include regenerators ( Figure 2 RHA), nitrogen compressor ( Figure 2 (CN) and nitrogen expander ( Figure 2 The regenerator (TN) is connected to the heat exchanger, steam generator, nitrogen compressor, and nitrogen expander via pressure-resistant sealed pipes (the connection method can be flange connection or welding fixation to ensure sealing under high-pressure conditions). The regenerator can be a plate regenerator or, depending on the waste heat recovery requirements, a regenerative regenerator. The nitrogen compressor is a screw compressor, which can be replaced by a centrifugal compressor (compression ratio controlled at around 4, adjustable within the range of 3.8-4.2). The nitrogen expander is an axial flow expander, which can be replaced by a centrifugal expander (expansion ratio and compression ratio set to 4). In operation, the regenerator receives medium-temperature, low-pressure nitrogen (approximately 80°C, 2MPa) from the heat exchanger and medium-temperature, high-pressure nitrogen (approximately 195.6397°C, 8MPa) from the steam generator. Through counter-current heat exchange between the two types of nitrogen within the regenerator, the medium-temperature, low-pressure nitrogen is heated to approximately 190.5768°C and 2MPa, converting it into high-temperature, low-pressure nitrogen (adjustable within the range of 185-195°C and 1.9-2.1MPa). Simultaneously, the medium-temperature, high-pressure nitrogen is cooled to approximately 89.3873°C and 8MPa, converting it into low-temperature, high-pressure nitrogen. The system uses compressed nitrogen (adaptable to temperatures ranging from 85-90℃ and pressures from 7.8-8.2MPa). A nitrogen compressor receives high-temperature, low-pressure nitrogen from the regenerator and compresses it according to a set compression ratio, converting it into high-temperature, high-pressure nitrogen at approximately 433.2523℃ and 8MPa. A nitrogen expander receives low-temperature, high-pressure nitrogen from the regenerator and expands it to produce low-temperature, low-pressure nitrogen at approximately -20.264℃ and 2MPa (adjustable to temperatures from -25℃ to -18℃ and pressures from 1.9-2.1MPa), which is then circulated through the heat exchanger. Through the clear division of labor and coordinated operation of the regenerator, nitrogen compressor, and nitrogen expander, the system achieves orderly conversion between different states of the low-temperature, low-pressure nitrogen medium. The regenerator's waste heat recovery function further reduces the compressor's compression load, and the expander's work assists in system energy balance. The compatible connections of each component ensure smooth circulation, significantly improving system stability and energy efficiency.

[0035] Optionally, the heat exchanger is specifically used for: The low-temperature, low-pressure nitrogen medium is heated by the low-temperature heat source, converting the low-temperature, low-pressure nitrogen medium into medium-temperature, low-pressure nitrogen, and the low-temperature heat source is converted into a low-temperature cold source.

[0036] Specifically, the heat exchanger performs the following operations: It receives industrial low-temperature waste heat at approximately 90°C as a low-temperature heat source (suitable for various low-temperature waste heat sources within the 85-95°C range, such as waste heat from industrial wastewater and exhaust gas), while simultaneously introducing low-temperature, low-pressure nitrogen medium (temperature approximately -20.264°C, pressure 2MPa) from a nitrogen expander. The heat exchanger adopts a shell-and-tube structure (which can be replaced by a plate heat exchanger or a spiral plate heat exchanger; plate heat exchangers have higher heat exchange efficiency, while spiral plate heat exchangers have better anti-fouling performance). Heat exchange is conducted through counter-current flow (which can be replaced by co-current flow heat exchange; counter-current flow heat exchange is more efficient). This process improves heat exchange efficiency, enabling efficient heat transfer between the low-temperature heat source and the low-temperature, low-pressure nitrogen medium. The low-temperature, low-pressure nitrogen medium is heated to approximately 80°C and 2MPa, converting into medium-temperature, low-pressure nitrogen (adjustable within the range of 75-85°C and 1.9-2.1MPa). Simultaneously, the low-temperature heat source releases heat, causing its temperature to drop to approximately -15.2636°C and its pressure to 1.56MPa, transforming into a low-temperature cold source (adjustable within the range of -18 to -12°C and 1.5-1.6MPa). This cold source can be directly used for industrial refrigeration or recycled for storage. By simultaneously heating and converting the low-temperature, low-pressure nitrogen medium, the low-temperature heat source is transformed into a usable low-temperature cold source, achieving cascaded utilization of low-temperature waste heat, improving overall energy efficiency, and avoiding waste caused by solely using the low-temperature heat source for energy supply. This further aligns with the energy efficiency requirements of zero-carbon industrial parks.

[0037] Optionally, the process of determining the heat requirement of the low-temperature heat source includes: Obtain initial design parameters; Based on the initial design parameters, iterative calculations are performed according to the pinch temperature difference of the regenerator to determine the node state parameters and the flow parameters based on the Brayton cycle. The heat demand is determined based on the node status parameters and the flow rate parameters.

[0038] Specifically, the initial design parameters of the system are first obtained (such as compression and expansion ratios, pinch point temperature differences, and basic parameters related to the temperature, pressure, and flow rate of the heat exchanger and steam generator). Based on these initial design parameters, iterative calculations are performed using the pinch point temperature difference of the regenerator. By continuously adjusting the relevant parameters, the state parameters of each node in the system (such as the temperature, pressure, and flow rate of each node) and the flow rate parameters based on the Brayton cycle (the flow rate of circulating nitrogen) are gradually determined. After the node state parameters and flow rate parameters are determined, the heat demand required by the low-temperature heat source is further derived using relevant calculation models. The iterative calculations can be performed automatically using computer programming. This logical flow of initial parameter preparation, iterative calculation to determine key parameters, and derivation of heat demand ensures that the heat supply of the low-temperature heat source is precisely matched with the system's operational needs. This avoids insufficient heat supply leading to the system failing to reach its designed capacity, or excessive heat supply causing energy waste, thus improving the system's compatibility with the low-temperature heat source and ensuring the system's efficient and stable operation.

[0039] Optionally, the step of determining the node state parameters and the Brayton cycle-based flow parameters by iterative calculation based on the initial design parameters and the pinch temperature difference of the regenerator includes: When the pinch temperature difference is greater than the preset temperature difference threshold, the cold end outlet temperature of the regenerator is adjusted using the first adjustment strategy, and the pinch temperature difference is re-determined based on the adjusted cold end outlet temperature of the regenerator. When the pinch temperature difference is less than the preset temperature difference threshold, the cold end outlet temperature of the regenerator is adjusted using the second adjustment strategy, and the pinch temperature difference is re-determined based on the adjusted cold end outlet temperature of the regenerator. When the pinch temperature difference is greater than the preset temperature difference threshold, and the absolute value of the difference between the pinch temperature difference and the preset temperature difference threshold is less than the preset difference, the node status parameters and the flow parameters are determined based on the initial design parameters and the cold end outlet temperature of the regenerator at the current step size.

[0040] Specifically, based on the initial design parameters, the process of iteratively calculating the node status parameters and flow parameters according to the pinch temperature difference of the regenerator is as follows: the preset temperature difference threshold is 5K (which can be adjusted in the range of 4-6K according to the heat exchange efficiency requirements), and the preset difference is 0.01K (which can be adjusted in the range of 0.005-0.02K to meet the accuracy requirements). When the pinch temperature difference of the regenerator is detected to be greater than the preset temperature difference threshold, the first adjustment strategy (i.e., increasing the cold end outlet temperature of the regenerator by 1°C per step, which can be replaced by an adjustment of 0.5°C or 2°C per step) is adopted to adjust the cold end outlet temperature of the regenerator. The new pinch temperature difference is then recalculated and determined based on the adjusted cold end outlet temperature. When the pinch temperature difference is detected to be less than the preset temperature difference threshold, the second adjustment strategy (i.e., decreasing the cold end outlet temperature of the regenerator by 1°C per step, which can be replaced by an adjustment of 0.5°C or 2°C per step) is adopted to adjust the cold end outlet temperature of the regenerator. The pinch temperature difference is recalculated again. The above adjustment process is repeated until the pinch temperature difference is greater than the preset temperature difference threshold, and the absolute value of the difference between the pinch temperature difference and the preset temperature difference threshold is less than the preset difference value. At this point, the adjustment stops, and the node state parameters and the flow parameters based on the Brayton cycle are finally determined based on the initial design parameters and the cold end outlet temperature of the regenerator at the current step size. By employing differentiated adjustment strategies for different pinch temperature differences, the iterative calculations are made precise and efficient, ensuring that the pinch temperature difference of the regenerator remains stable within the optimal range. This improves the heat exchange efficiency of the regenerator and lays the foundation for improving the overall energy utilization of the system. At the same time, the iteration accuracy can be flexibly adjusted through preset differences to adapt to the needs of different scenarios.

[0041] Optionally, the node status parameters include compressor inlet and outlet status parameters, expander inlet and outlet status parameters, steam generator hot end outlet status parameters, regenerator hot end outlet status parameters, and heat exchanger hot end outlet status parameters. The process of determining the node status parameters and the flow rate parameters based on the initial design parameters and the current step size of the regenerator cold end outlet temperature includes: Based on the initial design parameters, and according to the current step size of the regenerator cold end outlet temperature and the compressor calculation model, the compressor outlet state parameters are determined. Based on the compressor outlet state parameters and the steam generator calculation model, the hot-end outlet state parameters of the steam generator and the flow rate parameters are determined. The hot end outlet state parameters of the regenerator are determined by iterative calculation based on the pinch temperature difference of the regenerator. Based on the expander calculation model, the expander outlet state parameters and the heat exchanger hot end outlet state parameters are determined.

[0042] Specifically, inlet and outlet state parameters refer to the inlet state parameters and outlet state parameters. State parameters include parameters such as temperature, pressure, flow rate, and enthalpy, which represent the node state. Furthermore, the compressor and expander each have only one set of inlet and outlet. The heat exchanger, regenerator, and steam generator each have hot-end and cold-end inlet and outlet, respectively. The expander outlet is the cold-end inlet of the heat exchanger, the hot-end outlet of the regenerator is the expander inlet, the compressor inlet is the cold-end outlet of the regenerator, and the compressor outlet is the hot-end inlet of the steam generator. Node state parameters include compressor inlet and outlet state parameters, expander inlet and outlet state parameters, steam generator hot-end outlet state parameters, and heat exchanger hot-end outlet state parameters. Based on the initial design parameters, the process of determining the node state parameters and flow parameters according to the current step size of the regenerator cold end outlet temperature is as follows: First, using the initial design parameters and the current step size of the regenerator cold end outlet temperature as input conditions, substitute them into the compressor calculation model (this model uses isentropic efficiency and enthalpy change as the core calculation basis, and can be replaced by a compressor calculation model that includes variable efficiency), and calculate the compressor outlet temperature, pressure, enthalpy, and other state parameters; then, substitute the compressor outlet state parameters into the steam generator calculation model (which uses heat transfer balance and fluid flow characteristics as the core calculation basis, and can be replaced by a model that includes variable efficiency). A calculation model for a steam generator (including heat transfer coefficient correction) is used to calculate the temperature, pressure, enthalpy, and other state parameters of the steam generator's hot-end outlet, as well as the nitrogen flow rate parameters based on the Brayton cycle. Then, iterative calculations are performed based on the regenerator pinch-point temperature difference to derive and determine the regenerator's hot-end outlet state parameters. Next, based on the expander calculation model, the expander outlet state parameters are determined, along with the heat exchanger's hot-end outlet state parameters, namely, the temperature and pressure parameters at the heat exchanger's hot-end outlet. The determination of these state parameters is performed simultaneously with the regenerator's iterative calculations. When the regenerator's pinch-point temperature difference meets a preset value, the state parameters for each node are obtained. This embodiment clarifies the specific types of node state parameters and determines each parameter step-by-step through a targeted calculation model, ensuring the accuracy and logic of the parameter calculations. This provides reliable data support for determining subsequent heat demand. Furthermore, the calculation model can select alternative schemes based on actual operating conditions, improving the adaptability of the parameter calculations.

[0043] For example, the compressor calculation model includes: ; in, The isentropic efficiency of the compressor, expressed as a percentage. h out,is This represents the enthalpy of the outlet under isentropic efficiency, expressed in J / g. h in The enthalpy value at the inlet. h out The enthalpy value for exports. The power consumption of the compressor is expressed in watts (W). The flow rate parameter of the compressor based on the Brayton cycle is expressed in kg / s.

[0044] The calculation model for the steam generator includes: ; in, Heat, measured in W. This refers to the hot-end flow rate parameter, in kg / s. h hot,in The enthalpy value at the hot end inlet. h hot,out The enthalpy value at the hot end outlet. This refers to the cold end flow rate parameter, in kg / s. h cold,out The enthalpy value at the cold end outlet. h cold,in Let be the enthalpy of the cold end inlet, n be the number of differentials in the heat exchanger, and i be each part of the differential. Let be the enthalpy value of the i-th difference portion. Let be the enthalpy of the (i+1)th difference portion. For the pinch point temperature difference, Let be the hot-end temperature of the i-th differential part. Let be the cold end temperature of the i-th differential part. For unknown flow parameters, Given flow parameters.

[0045] Optionally, the initial design parameters include the pinch temperature difference of the regenerator.

[0046] Specifically, the regenerator calculation model includes: ; in, This represents the enthalpy difference.

[0047] For example, Figure 2 Node 1 is the cold end outlet of the steam generator SG, Node 2 is the cold end inlet of the steam generator SG, Node 3 is the hot end inlet of the steam generator SG, which is also the outlet of the nitrogen compressor CN, Node 4 is the hot end outlet of the steam generator SG, which is also the hot end inlet of the regenerator RHA, Node 5 is the hot end outlet of the regenerator RHA, which is also the inlet of the nitrogen expander TN, Node 6 is the cold end outlet of the regenerator RHA, which is also the inlet of the nitrogen compressor CN, Node 7 is the cold end inlet of the heat exchanger HR, which is also the outlet of the nitrogen expander TN, Node 8 is the cold end outlet of the heat exchanger HR, which is also the cold end inlet of the regenerator RHA, Node 9 is the hot end inlet of the heat exchanger HR, and Node 10 is the hot end outlet of the heat exchanger HR.

[0048] For example, Figure 2 The state parameters of each node are shown in the table below:

[0049] Optionally, the initial design parameters may also include the inlet state parameters of the heat exchanger hot end, the outlet state parameters of the heat exchanger cold end, the inlet and outlet state parameters of the steam generator cold end, the inlet and outlet flow rates of the steam generator cold end, the system compression ratio, and the system expansion ratio.

[0050] Specifically, the initial design parameters include: the inlet state parameters of the heat exchanger (e.g., the temperature, pressure, and flow rate of the low-temperature heat source entering the heat exchanger, i.e.) Figure 2 Temperature, pressure, and flow rate at node 9), and cold-end outlet state parameters of the heat exchanger (e.g., temperature, pressure, and flow rate of the low-temperature, low-pressure nitrogen medium leaving the heat exchanger, i.e.) Figure 2 Temperature, pressure, and flow rate at node 8), and cold-end inlet state parameters of the steam generator (i.e., temperature, pressure, and flow rate when saturated water medium enters the steam generator, i.e.) Figure 2 Temperature, pressure, and flow rate at node 2), and cold-end outlet state parameters of the steam generator (i.e., temperature, pressure, and flow rate of the saturated water medium leaving the steam generator, i.e.) Figure 2 The initial design parameters include the temperature, pressure, and flow rate at node 1; the inlet flow rate of the steam generator at the cold end (e.g., the flow rate when saturated water enters, which can be preset based on flow rate and pipe diameter); the outlet flow rate of the steam generator at the cold end (e.g., the flow rate when saturated water leaves, which can be preset based on flow rate and pipe diameter); the system compression ratio; and the system expansion ratio. The initial design parameters can be preset using theoretical calculations or, alternatively, using preset methods based on experimental data under similar operating conditions. The advantages of this claim are: it clarifies the specific composition of the initial design parameters, providing clear and accurate basic inputs for iterative calculations and subsequent parameter calculations, avoiding calculation errors caused by ambiguity in the initial parameters, ensuring the smoothness of the entire parameter determination process and the reliability of the results, and allowing for flexible preset of the initial parameters, thus improving the adaptability of the system design.

[0051] Optionally, determining the heat demand based on the node status parameters and the flow parameters includes: The cold end inlet state parameters of the heat exchanger are determined based on the hot end outlet state parameters of the regenerator and the expansion machine calculation model. The heat demand is determined based on the inlet state parameters of the heat exchanger cold end, the flow rate parameters, and the outlet temperature of the heat exchanger cold end.

[0052] Specifically, firstly, the determined hot-end outlet state parameters of the regenerator (i.e., the inlet state parameters of the expander) are extracted and substituted into the expander calculation model (this model uses the expansion ratio and enthalpy change as the core calculation basis, and can be replaced by an expander calculation model that includes adiabatic efficiency). The cold-end inlet state parameters of the heat exchanger (i.e., the temperature and pressure of the low-temperature, low-pressure nitrogen medium when it enters the heat exchanger, such as -20.264℃ and 2MPa) are calculated. Then, based on the cold-end inlet state parameters of the heat exchanger, the flow parameters, and the determined cold-end outlet temperature of the heat exchanger (e.g., 80℃), the heat demand required by the low-temperature heat source is calculated using methods such as the heat balance formula, to ensure that the heat supply of the low-temperature heat source can meet the heat demand of heating the low-temperature, low-pressure nitrogen medium from the cold-end inlet temperature of the heat exchanger to the outlet temperature. By accurately deriving the inlet state parameters of the heat exchanger cold end using an expander calculation model, and then combining this with the outlet temperature of the heat exchanger cold end to calculate the heat demand, a logical closed-loop calculation process is formed. This ensures the accuracy of the heat demand calculation, avoids the problem of heat supply being out of sync with actual demand, provides a reliable basis for the selection and matching of low-temperature heat sources, and further ensures that the system can stably produce high-temperature steam above 400℃.

[0053] For example, the expander computational model includes: ; in, The isentropic efficiency of the expander, expressed as %. h out,is This represents the enthalpy of the outlet under isentropic efficiency, expressed in J / g. h in The enthalpy value at the inlet. h out The enthalpy value for exports. The power consumption of the expander is expressed in watts (W). The flow parameters for the expander, based on the Brayton cycle, are expressed in kg / s.

[0054] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc. In this application, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention according to actual needs. Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated units can be implemented in hardware or as software functional units.

[0055] 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 high-temperature steam production system based on a nitrogen Brayton cycle, characterized in that, This includes heat exchangers and steam generators, all of which are connected to a high-temperature heat pump. The heat exchanger is used to heat the low-temperature, low-pressure nitrogen medium with a low-temperature heat source using air as the medium, and convert the low-temperature, low-pressure nitrogen medium into medium-temperature, low-pressure nitrogen. The high-temperature heat pump is used to heat the medium-temperature low-pressure nitrogen gas with the remaining medium-temperature high-pressure nitrogen gas from the steam generator to obtain high-temperature low-pressure nitrogen gas, and to compress the high-temperature low-pressure nitrogen gas to obtain high-temperature high-pressure nitrogen gas. The steam generator is used to heat a saturated water medium with high-temperature, high-pressure nitrogen to obtain medium-temperature, high-pressure nitrogen and high-temperature steam.

2. The high-temperature steam production system based on the nitrogen Brayton cycle according to claim 1, characterized in that, The heat exchanger is specifically used for: The low-temperature, low-pressure nitrogen medium is heated by the low-temperature heat source, converting the low-temperature, low-pressure nitrogen medium into medium-temperature, low-pressure nitrogen, and the low-temperature heat source is converted into a low-temperature cold source.

3. The high-temperature steam production system based on the nitrogen Brayton cycle according to claim 1, characterized in that, The high-temperature heat pump is specifically used for: The medium-temperature low-pressure nitrogen gas is heated and compressed by the medium-temperature low-pressure nitrogen gas generated by the steam generator, thereby converting the medium-temperature low-pressure nitrogen gas into high-temperature high-pressure nitrogen gas, and then converting the medium-temperature high-pressure nitrogen gas into low-temperature high-pressure nitrogen gas. The low-temperature, high-pressure nitrogen gas is expanded to obtain the low-temperature, low-pressure nitrogen gas medium.

4. The high-temperature steam production system based on nitrogen Brayton cycle according to claim 3, characterized in that, The high-temperature heat pump includes a nitrogen compressor and a nitrogen expander, both of which are connected to the regenerator. The regenerator is also connected to the heat exchanger and the steam generator, respectively. The regenerator is used to heat the medium-temperature low-pressure nitrogen gas through the medium-temperature high-pressure nitrogen gas from the steam generator, converting the medium-temperature low-pressure nitrogen gas into the high-temperature low-pressure nitrogen gas, and converting the medium-temperature high-pressure nitrogen gas into the low-temperature high-pressure nitrogen gas. The nitrogen compressor is used to compress the high-temperature, low-pressure nitrogen gas to obtain the high-temperature, high-pressure nitrogen gas. The nitrogen expander is used to expand the low-temperature, high-pressure nitrogen gas to obtain the low-temperature, low-pressure nitrogen medium.

5. The high-temperature steam production system based on nitrogen Brayton cycle according to claim 4, characterized in that, The process of determining the heat requirement of the low-temperature heat source includes: Obtain initial design parameters; Based on the initial design parameters, iterative calculations are performed according to the pinch temperature difference of the regenerator to determine the node state parameters and the flow parameters based on the Brayton cycle. The heat demand is determined based on the node status parameters and the flow rate parameters.

6. The high-temperature steam production system based on the nitrogen Brayton cycle according to claim 5, characterized in that, The initial design parameters include the pinch temperature difference of the regenerator.

7. The high-temperature steam production system based on nitrogen Brayton cycle according to claim 5, characterized in that, The process of determining node state parameters and Brayton cycle-based flow parameters through iterative calculations based on the initial design parameters and the pinch temperature difference of the regenerator includes: When the pinch temperature difference is greater than the preset temperature difference threshold, the cold end outlet temperature of the regenerator is adjusted using the first adjustment strategy, and the pinch temperature difference is re-determined based on the adjusted cold end outlet temperature of the regenerator. When the pinch temperature difference is less than the preset temperature difference threshold, the cold end outlet temperature of the regenerator is adjusted using the second adjustment strategy, and the pinch temperature difference is re-determined based on the adjusted cold end outlet temperature of the regenerator. When the pinch temperature difference is greater than the preset temperature difference threshold, and the absolute value of the difference between the pinch temperature difference and the preset temperature difference threshold is less than the preset difference, the node status parameters and the flow parameters are determined based on the initial design parameters and the cold end outlet temperature of the regenerator at the current step size.

8. The high-temperature steam production system based on the nitrogen Brayton cycle according to claim 7, characterized in that, The node status parameters include compressor inlet and outlet status parameters, expander inlet and outlet status parameters, steam generator hot end outlet status parameters, regenerator hot end outlet status parameters, and heat exchanger hot end outlet status parameters. The process of determining the node status parameters and the flow rate parameters based on the initial design parameters and the current step size of the regenerator cold end outlet temperature includes: Based on the initial design parameters, and according to the current step size of the regenerator cold end outlet temperature and the compressor calculation model, the compressor outlet state parameters are determined. Based on the compressor outlet state parameters and the steam generator calculation model, the hot end outlet state parameters of the steam generator and the flow parameters are determined. The hot end outlet state parameters of the regenerator are determined by iterative calculation based on the pinch temperature difference of the regenerator. Based on the expander calculation model, the expander outlet state parameters and the heat exchanger hot end outlet state parameters are determined.

9. The high-temperature steam production system based on the nitrogen Brayton cycle according to claim 8, characterized in that, The initial design parameters also include the inlet state parameters of the heat exchanger hot end, the outlet state parameters of the heat exchanger cold end, the inlet and outlet state parameters of the steam generator cold end, the inlet and outlet flow rates of the steam generator cold end, the system compression ratio, and the system expansion ratio.

10. The high-temperature steam production system based on the nitrogen Brayton cycle according to claim 9, characterized in that, Determining the heat demand based on the node status parameters and the flow parameters includes: The cold end inlet state parameters of the heat exchanger are determined based on the hot end outlet state parameters of the regenerator and the expansion machine calculation model. The heat demand is determined based on the inlet state parameters of the heat exchanger cold end, the flow rate parameters, and the outlet temperature of the heat exchanger cold end.

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