An air separation device including a diffused nitrogen energy storage power generation device

Abstract

The application discloses a kind of air separation device comprising diffusion nitrogen energy storage power generation device, the air separation device includes first nitrogen compressor (12), nitrogen product pipeline and diffusion nitrogen pipeline, the nitrogen product pipeline and the diffusion nitrogen pipeline are connected to the first nitrogen compressor, and medium-pressure nitrogen product and medium-pressure diffusion nitrogen are output after pressurization by the first nitrogen compressor;And the diffusion nitrogen energy storage power generation device includes energy storage loop and energy release power generation loop, the diffusion nitrogen energy storage power generation device uses the medium-pressure diffusion nitrogen as cold-electricity conversion medium, liquefies storage in the energy storage loop, and the energy release power generation loop is expanded to generate electricity by releasing energy part of the stored liquid nitrogen, and the energy release outlet end nitrogen pipeline in the energy release power generation loop is connected to the nitrogen product pipeline, and medium-pressure nitrogen is output as medium-pressure nitrogen product.The application reduces cost, improves energy and material utilization.

Description

Technical Field

[0001] This invention relates to the fields of power grid peak shaving, energy storage power generation technology, and air separation technology, and in particular to an air separation device including a nitrogen venting energy storage power generation device and a material recovery method. Background Technology

[0002] With the continuous improvement of people's living standards, the scale of residential electricity consumption is constantly increasing, leading to a widening peak-valley difference in power supply. Due to the high proportion of coal-fired power generation in my country, this huge peak-valley difference requires a large number of peak-shaving load units, which reduces unit power generation efficiency and increases carbon emissions. Simultaneously, the instability of renewable energy power generation makes it difficult to meet the needs of grid load regulation. Energy storage technology is increasingly becoming an important supporting technology for solving grid load regulation. Cryogenic energy storage technology (LAES) is an energy storage technology that converts electrical energy into cold energy in cryogenic fluids (such as liquid air or liquid nitrogen) for storage, and converts the cold energy back into electrical energy through vaporization and expansion when needed. It possesses properties such as safety, no geographical limitations, and environmental friendliness. However, independent cryogenic energy storage technology faces problems such as large irreversible system losses, low energy recycling efficiency, a large number of initial equipment, high initial investment, and a long cost recovery period. Therefore, efficient matching of cryogenic energy storage technology with existing process systems is an important means to overcome its application limitations.

[0003] As a crucial foundational equipment in industrial production, air separation technology is widely used in three major industries: coal chemical, petroleum refining, and metallurgy. The refrigeration capacity of air separation technology is well-matched with cryogenic energy storage technology. Furthermore, due to supply and demand imbalances in industrial production, air separation equipment has long suffered from low energy and material utilization rates caused by oxygen / nitrogen emissions. This makes the combined application of air separation technology and cryogenic energy storage technology a promising prospect.

[0004] Currently, existing technologies have proposed energy storage technologies utilizing both liquid air and liquid nitrogen in air separation units. However, technologies for energy storage using nitrogen released during air separation units are not mentioned in existing technologies. Furthermore, existing technologies employ various methods for recovering and utilizing liquid nitrogen during the energy release process, such as pressurizing, reheating, and vaporizing liquid nitrogen for expansion and power generation. However, this method still suffers from issues such as indirect utilization of cold energy, resulting in low energy efficiency. To address these shortcomings, this invention proposes an energy storage and power generation device and a material recovery method utilizing released nitrogen in air separation units. This invention redesigns the integration of air separation units with cryogenic energy storage technology, focusing on the reuse of released nitrogen and the recovery of material energy. Summary of the Invention

[0005] A brief overview of this disclosure is provided below to offer a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the disclosure. It is not intended to identify key or essential parts of the disclosure, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] The technical problem to be solved by this invention is to provide an air separation unit including a nitrogen venting energy storage and power generation device and a material recovery method. This energy storage and power generation device and material recovery method use the venting nitrogen from the air separation unit as the energy storage medium, including an energy storage process that shares a nitrogen compressor with a nitrogen expansion refrigeration air separation unit, and an energy release process that uses the outlet nitrogen as the nitrogen product to replace the original nitrogen product. The material recovery method of this invention realizes the reuse of venting nitrogen in the air separation unit and the effective recovery of the material energy from the venting nitrogen during the energy release process.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] This invention provides an air separation unit including a nitrogen gas energy storage and power generation device, characterized in that: the air separation unit includes a first nitrogen compressor (12), a nitrogen product pipeline, and a nitrogen gas venting pipeline, the nitrogen product pipeline and the nitrogen gas venting pipeline are connected in parallel to the first nitrogen compressor, and after being pressurized by the first nitrogen compressor, medium-pressure nitrogen product and medium-pressure nitrogen gas venting are output; and the nitrogen gas energy storage and power generation device includes an energy storage circuit and an energy release power generation circuit, the nitrogen gas venting and power generation device uses the medium-pressure nitrogen gas venting as a cold-to-electric conversion medium, liquefies and stores the medium-pressure nitrogen gas venting in the energy storage circuit, and expands the liquid nitrogen stored in the energy release power generation circuit to generate electricity, the nitrogen gas pipeline at the energy release outlet end of the energy release power generation circuit is connected to the nitrogen product pipeline, and outputs medium-pressure nitrogen gas as a medium-pressure nitrogen product.

[0009] Furthermore, the nitrogen gas energy storage and power generation device includes a third nitrogen compressor (25), a first heat exchanger (26), a second heat exchanger (27), a third heat exchanger (28), a cryogenic expander (29), a liquid nitrogen storage tank (30), a cryogenic oil tank (35), a cryogenic oil pump (36), a first cold storage tank (45), a second cryogenic pump (46), a second cold storage tank (47), and a third cryogenic pump (48). The energy storage circuit utilizes the third nitrogen compressor (25) to pressurize the medium-pressure nitrogen gas, cools it using the first heat exchanger (26), the second heat exchanger (27), and the third heat exchanger (28), and then utilizes the cryogenic expander (29) to... 9) The pressurized vented nitrogen gas is expanded, liquefied, and stored in the liquid nitrogen storage tank (30). The separated nitrogen gas from the top outlet of the liquid nitrogen storage tank (30) is input to the input channel in front of the first nitrogen compressor (12) via the third heat exchanger (28) and the second heat exchanger (27) for energy storage circulation. The energy storage circuit uses the low temperature medium stored in the low temperature oil tank (35), the first cold storage tank (45), and the second cold storage tank (47) to provide cold energy to the pressurized medium-pressure vented nitrogen gas. The cold energy is transferred to the pressurized medium-pressure vented nitrogen gas in sequence through the first heat exchanger (26), the second heat exchanger (27), and the third heat exchanger (28).

[0010] Furthermore, the cryogenic medium in the cryogenic oil tank (35) is pressurized by the cryogenic oil pump (36) and enters the first heat exchanger (26), the cryogenic medium in the first cold storage tank (45) is pressurized by the second cryogenic pump (46) and enters the second heat exchanger (27), and the cryogenic medium in the second cold storage tank (47) is pressurized by the third cryogenic pump (48) and enters the third heat exchanger (28) to provide cold energy.

[0011] Furthermore, the nitrogen gas energy storage and power generation device further includes a first cryogenic pump (31), a fourth heat exchanger (37), a fifth heat exchanger (38), a sixth heat exchanger (39), a third turbine expander generator (40), a seventh heat exchanger (41), a fourth turbine expander generator (42), an eighth heat exchanger (43), a fifth turbine expander generator (44), a radiator (34), a high-temperature oil tank (32), and a high-temperature oil pump (33). The energy release power generation circuit utilizes liquid nitrogen from the liquid nitrogen storage tank (30) via the first cryogenic pump (31). The gas is pressurized and then the cold energy is recovered in the fourth heat exchanger (37), the fifth heat exchanger (38), the sixth heat exchanger (39), expanded and generated in the third turbine expander (40), recovered in the seventh heat exchanger (41), expanded and generated in the fourth turbine expander (42), recovered in the eighth heat exchanger (43), and expanded and generated in the fifth turbine expander (44) before being output as medium-pressure nitrogen product.

[0012] Furthermore, the energy release power generation circuit utilizes the high-temperature medium stored in the high-temperature oil tank (32), pressurizes it using the high-temperature oil pump (33), and recovers liquid nitrogen cold energy sequentially through the eighth heat exchanger (43), the seventh heat exchanger (41), and the sixth heat exchanger (39). After being cooled by the radiator (34), it is stored in the low-temperature oil tank (35).

[0013] Furthermore, the outlet end of the fifth turbine expander (44) is connected to the nitrogen product pipeline.

[0014] Furthermore, the energy storage circuit operates during off-peak electricity periods.

[0015] Furthermore, the energy-generating circuit operates during peak power periods.

[0016] The beneficial effects of the above-mentioned technical solution of the present invention are as follows:

[0017] This invention, considering the enormous electricity consumption of air separation units, organically integrates cryogenic energy storage technology with the air separation process. Using the vented gas from the air separation unit as raw material for energy storage and power generation, it not only reduces irreversible losses in existing cryogenic energy storage processes but also improves the energy and material utilization rate of the air separation process. Furthermore, it enables large-scale energy storage and peak-valley regulation of the power grid. In addition, combining air separation with cryogenic energy storage technology significantly reduces the initial equipment quantity and investment requirements, improving the economic benefits for enterprises. In the above scheme, by adding a storage and release energy device to the nitrogen expansion refrigeration air separation unit, using vented nitrogen as the energy storage medium, sharing a nitrogen compressor with the nitrogen expansion refrigeration air separation unit, and using the nitrogen at the outlet of the release energy device as a nitrogen product to replace the nitrogen product of the air separation unit, the efficient recycling of the material and energy released from the nitrogen product in the air separation unit is achieved. This technology reduces the initial equipment and capital requirements for retrofitting air separation units by directly integrating cryogenic energy storage technology. It also improves the energy and material utilization rate of air separation units, further reduces peak-season electricity demand, and saves on production electricity costs. At the same time, increasing off-season electricity load and reducing peak-season electricity load can effectively balance the power grid, promote the conversion of some peak-shaving units to base-load units or large generator units, thereby improving unit power generation efficiency and achieving energy conservation and emission reduction on the grid side. Attached Figure Description

[0018] The specific details of this disclosure are described below with reference to the accompanying drawings, which will facilitate a more readily understanding of the above and other objects, features, and advantages of this disclosure. The drawings are merely for illustrating the principles of this disclosure. The dimensions and relative positions of the elements are not necessarily drawn to scale in the drawings.

[0019] Figure 1 A schematic diagram of an existing nitrogen expansion refrigeration air separation unit;

[0020] Figure 2 This is a schematic diagram of the air separation unit of the present invention, which includes a nitrogen gas energy storage and power generation device.

[0021] Figure 3 This is a schematic diagram of the energy storage circuit of the nitrogen gas venting energy storage and power generation device of the present invention;

[0022] Figure 4 This is a schematic diagram of the energy release and power generation circuit of the nitrogen gas energy storage and power generation device of the present invention;

[0023] Figure 5 A graph showing the relationship between nitrogen emission rate and electricity cost savings rate;

[0024] Figure 6 A graph showing the relationship between peak-valley electricity price ratio and electricity cost savings rate;

[0025] Wherein: 1-Air filter; 2-Air compressor; 3-Air-cooled tower; 4-Water-cooled tower; 5-Cooling water pump; 6-Chilled water pump; 7-Chiller unit; 8-Molecular sieve adsorber; 9-Silencer; 10-Electric heater; 11-Main heat exchanger; 12-First nitrogen compressor; 13-Second nitrogen compressor; 14-First turbine expander generator; 15-Second turbine expander generator; 16-Low-pressure tower; 17-Main condenser-evaporator; 18-High-pressure tower; 19-Subcooler; 20-Liquid oxygen pump; 21-Raw argon tower; 22-Raw liquid argon pump; 23-Refined argon tower; 24-Refined argon pump; 25-Third nitrogen compressor; 2 6-First heat exchanger; 27-Second heat exchanger; 28-Third heat exchanger; 29-Cryogenic expander; 30-Liquid nitrogen storage tank; 31-First cryogenic pump; 32-High-temperature oil tank; 33-High-temperature oil pump; 34-Radiator; 35-Cryogenic oil tank; 36-Cryogenic oil pump; 37-Fourth heat exchanger; 38-Fifth heat exchanger; 39-Sixth heat exchanger; 40-Third turbine expander generator; 41-Seventh heat exchanger; 42-Fourth turbine expander generator; 43-Eighth heat exchanger; 44-Fifth turbine expander generator; 45-First cold storage tank; 46-Second cryogenic pump; 47-Second cold storage tank; 48-Third cryogenic pump. Detailed Implementation

[0026] Exemplary aspects of this disclosure will be described below with reference to the accompanying drawings. For clarity and brevity, not all features implementing this disclosure are described in the specification. However, it should be understood that many disclosure-specific decisions can be made in developing any such implementation of this disclosure to achieve the developer's specific goals, and these decisions may vary depending on the specific implementation of this disclosure.

[0027] It should also be noted that, in order to avoid obscuring the contents of this disclosure with unnecessary details, only the pipeline structure closely related to the scheme according to this disclosure is shown in the accompanying drawings, while other details that are not closely related to the contents of this disclosure are omitted.

[0028] It should be understood that this disclosure is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, features may be substituted or borrowed between different embodiments where feasible, and one or more features may be omitted in one embodiment.

[0029] To address the problems of low energy utilization rate of nitrogen products released from air separation units in existing technologies, large investment in equipment for directly combining air separation processes with liquid nitrogen energy storage processes, and limited improvement in energy utilization rate during the storage-release process, this invention provides a staged power generation process and material recovery method for air separation units, including a nitrogen energy storage power generation device, to achieve efficient recovery and utilization of the material energy of nitrogen released from air separation units.

[0030] This method adds a liquid nitrogen energy storage device to the conventional nitrogen expansion refrigeration air separation unit and uses the released nitrogen as a cold energy-electric conversion medium. It transforms the direct expansion power generation process of the conventional energy release process into a staged power generation and material recovery process that combines the power generation process that expands to the nitrogen product pressure of the air separation unit with the material recovery process that is integrated into the nitrogen product pipeline of the air separation unit. This achieves the reuse of the released nitrogen of the air separation unit and reduces the peak power consumption.

[0031] See Figure 1 The same reference numerals in the figures denote the same elements. Figure 1A schematic diagram of a conventional nitrogen expansion refrigeration air separation unit disclosed herein is shown. In this unit, the raw air first undergoes dust removal in an air filter 1, then is pressurized in an air compressor 2, cooled and washed in an air-cooled tower 3, then adsorbed and purified by a molecular sieve adsorber 8 before entering the main heat exchanger 11 to be cooled to the dew point temperature, and finally enters the high-pressure tower 18. The raw air entering the high-pressure tower 18 undergoes component separation within the tower, resulting in oxygen-enriched liquid air at the bottom of the high-pressure tower 18. This oxygen-enriched liquid air is cooled in the subcooler 19 and then enters the bottom of the fine argon tower 23 and the top of the crude argon tower 21 for heat exchange before finally entering the top of the low-pressure tower 16. A portion of high-purity nitrogen is extracted from the upper part of the high-pressure tower 18 and sent into the nitrogen pipeline. High-purity nitrogen is obtained at the top of the high-pressure tower 18 and undergoes heat exchange with liquid oxygen from the bottom of the low-pressure tower 16 via the main condenser-evaporator 17. Part of the condensed liquid nitrogen is returned to the high-pressure tower 18, part is subcooled in the subcooler 19 and then sent to the top of the low-pressure tower 16, and the remaining part is output as liquid nitrogen product. High-purity liquid oxygen is obtained at the bottom of the low-pressure tower 16. After being pressurized by the liquid oxygen pump 20, the liquid oxygen enters the main heat exchanger 11 and is output as an oxygen product after vaporization and reheating. Argon-rich distillate gas is extracted from the middle of the low-pressure tower 16 and sent to the bottom of the crude argon tower 21 for rectification. Waste nitrogen is extracted from the upper middle part of the low-pressure tower 16 and sent to the purification system and precooling system after being reheated by the cooler 19 and the main heat exchanger 11. High-purity nitrogen is extracted from the top of the low-pressure tower 16 and the cold energy is recovered by the cooler 19 and the main heat exchanger 11. The nitrogen exceeding the required amount is discharged as vented nitrogen into the waste nitrogen pipeline. Therefore, the energy utilization rate is low when nitrogen is vented. The remainder enters the first nitrogen compressor 12 for compression. Part of the pressurized medium-pressure nitrogen is output as a nitrogen product, and the other part is pressurized by the second nitrogen compressor 13 and enters the main heat exchanger 11 as high-pressure nitrogen. After being cooled in the main heat exchanger 11, the high-pressure nitrogen gas is divided into two parts: one part enters the upper part of the high-pressure tower 18; the other part enters the first turbine expander generator 14 for expansion and power generation, then transfers its cooling capacity back to the main heat exchanger 11 and enters the second turbine expander generator 15 for further expansion and power generation, finally entering the nitrogen pipeline. High-purity liquid oxygen is obtained at the bottom of the crude argon tower 21, and after being pressurized by the crude argon pump 22, it is sent back to the middle of the low-pressure tower 16. Crude argon gas is obtained at the top of the crude argon tower 21. After exchanging heat with subcooled liquid air at the top of the crude argon tower 21, part of the crude argon gas flows back to the upper part of the crude argon tower 21, and part is directly sent to the lower part of the refined argon tower 23. The endothermic liquid air at the top of the crude argon tower 21 returns to the middle of the low-pressure tower 16 to participate in distillation. Pure liquid argon is obtained at the bottom of the refined argon tower 23, and after being pressurized by the refined argon pump 24, it is output as liquid argon product.

[0032] like Figure 2 This is a schematic diagram of an air separation unit including a nitrogen gas venting energy storage and power generation device in an embodiment of the present invention. From... Figure 2 As can be seen from this, the air separation unit is in Figure 1Based on the existing nitrogen expansion refrigeration air separation unit shown, a liquid nitrogen energy storage and power generation unit using vented nitrogen as the energy storage medium has been added. Figure 2 Numbers 25 to 48, see below for specific structure. Figure 3 energy storage circuit and Figure 4 The released nitrogen gas is not discharged into the waste nitrogen pipeline, but instead enters the first nitrogen compressor 12 for compression. Part of the pressurized medium-pressure nitrogen is output as nitrogen product, and the other part enters the released nitrogen energy storage and power generation device. The released nitrogen gas is used for energy storage and power generation. At the same time, the outlet end of the fifth turbine expander 44 in the released nitrogen energy storage and power generation device is connected to the nitrogen product pipeline of the air separation unit, thus completing the energy storage process and recycling process of the released nitrogen gas.

[0033] like Figure 3 This is a schematic diagram of the energy storage circuit of the vented nitrogen energy storage and power generation device in an embodiment of the present invention. The energy storage process takes place during off-peak electricity hours. The vented nitrogen, after being compressed and pressurized by the first nitrogen compressor 12, becomes medium-pressure nitrogen. It is further pressurized in the third nitrogen compressor 25 and cooled by the cryogenic medium in the first heat exchanger 26, the second heat exchanger 27, and the third heat exchanger 28, respectively. Then, it enters the cryogenic expander 29 and expands to atmospheric pressure. Finally, it enters the liquid nitrogen storage tank 30 as the liquid nitrogen product to be stored. Specifically, the cryogenic medium in the first heat exchanger 26 can be cryogenic hot oil, the cryogenic medium in the second heat exchanger 27 can be methanol, and the cryogenic medium in the third heat exchanger 28 can be propane. The gaseous nitrogen in the liquid nitrogen storage tank 30, after recovering its cold energy through the second heat exchanger 27 and the third heat exchanger 28, is sent to the nitrogen pipeline of the air separation unit to continue the energy storage process. In this process, cryogenic hot oil is pumped from cryogenic oil tank 35 to the first heat exchanger 26 via cryogenic oil pump 36 and then stored in high-temperature oil tank 32. Methanol and propane are driven by the second cryogenic pump 46 and the third cryogenic pump 48, respectively, and stored in the first cold storage tank 45 and the second cold storage tank 47, respectively. During this process, the first cryogenic pump 31, radiator 34, third turbine expander generator 40, fourth turbine expander generator 42, and fifth turbine expander generator 44 stop operating, while the remaining devices operate normally. The energy storage process of the vented nitrogen energy storage power generation device of the present invention differs from the setup of existing nitrogen liquefaction energy storage devices. Existing technology involves setting up a separate nitrogen liquefaction energy storage device on top of an air separation unit. The air separation unit does not output medium-pressure nitrogen products, but directly outputs atmospheric pressure nitrogen. The atmospheric pressure nitrogen from the air separation unit is directly compressed from atmospheric pressure to high pressure for liquefaction and energy storage. In contrast, the energy storage process of the present invention utilizes the redundant compression capacity of the low-to-medium pressure nitrogen compressor unit (i.e., the first nitrogen compressor 12) outputting nitrogen products from the air separation unit to initially compress the vented nitrogen and the nitrogen returning from energy storage to medium pressure. See also... Figure 1As shown, in existing air separation units, nitrogen is released under low pressure during the nitrogen venting process, meaning it is bypassed to the waste nitrogen pipeline before entering the first nitrogen compressor 12. Therefore, the compression capacity of the first nitrogen compressor 12 is not fully utilized and it operates at low efficiency. By utilizing the medium- and low-pressure nitrogen compressor units of the air separation unit to compress the vented nitrogen and the nitrogen for energy storage return, this redundant compression capacity is fully utilized. This not only improves the compression efficiency of the first nitrogen compressor 12 and reduces the pressure ratio and energy consumption of the high-pressure nitrogen compressor unit (i.e., the third nitrogen compressor 25) in the energy storage and release process of the vented nitrogen energy storage power generation device, thus improving the energy utilization rate of the vented nitrogen, but also significantly reduces the initial equipment requirements for independently set up energy storage and release processes. This reduces the initial equipment investment required for directly combining the air separation unit with a cryogenic energy storage device, effectively shortening the payback period for projects involving energy storage process modifications to existing air separation units.

[0034] like Figure 4 This is a schematic diagram of the energy release power generation circuit of the nitrogen energy storage and power generation device designed in this embodiment of the invention. The energy release power generation process takes place during peak power periods. Liquid nitrogen in liquid nitrogen storage tank 30 is pressurized by the first cryogenic pump 31, and its cold energy is recovered in the fourth heat exchanger 37, the fifth heat exchanger 38, and the sixth heat exchanger 39. It then enters the third turbine expander generator 40 for expansion power generation. After being heated by the seventh heat exchanger 41, it enters the fourth turbine expander generator 42 for expansion power generation. After being heated by the eighth heat exchanger 43, it enters the fifth turbine expander generator 44 for expansion power generation until it reaches the air separation nitrogen product pressure. Finally, it is output as nitrogen product and incorporated into the nitrogen product pipeline of the air separation unit. At the same time, excess nitrogen is discharged into the waste nitrogen pipeline. Meanwhile, high-temperature hot oil is pumped from high-temperature oil tank 32 by high-temperature oil pump 33 to the sixth heat exchanger 39, the seventh heat exchanger 41, and the eighth heat exchanger 43 for heat exchange. After being cooled by radiator 34, it is stored in cryogenic oil tank 35. During this process, the third nitrogen compressor 25, the cryogenic expander 29, and the cryogenic oil pump 36 stop operating, while the remaining devices operate normally. The energy release power generation process of this invention differs from conventional energy release processes that directly expand to atmospheric pressure. By expanding the nitrogen at the terminal outlet of the energy release power generation circuit to the nitrogen product pressure of the air separation unit, it not only generates electricity but also reuses the released nitrogen. Furthermore, the reuse of released nitrogen in the energy release power generation process reduces the nitrogen production load of the air separation unit during peak power periods, i.e., reduces the intake air volume and power consumption of the nitrogen compressor. This not only improves the energy utilization efficiency of the air separation unit but also reduces electricity production costs.

[0035] The following embodiment further details the specific implementation of this disclosure. This process utilizes an air separation oxygen production capacity of 75000 Nm³. 3 ·h -1Taking the staged power generation and product recovery method of an air separation unit, including a nitrogen venting energy storage power generation device, as an example. Assuming that the peak, flat, and valley electricity durations are all 8 hours, and the electricity price is based on the industrial electricity price in Beijing, China as shown in Table 1, by implementing electricity demand-side management for this process, the design selects to carry out nitrogen venting liquefaction energy storage during valley electricity periods, liquid nitrogen expansion power generation and product recovery during peak electricity periods, and only the conventional production of the air separation unit during flat electricity periods, with the distillation system of the air separation unit operating at 100% design load.

[0036] Table 1. Beijing Industrial Electricity Price Standards

[0037]

[0038] This invention utilizes ASPEN PLUS V11 simulation software to model and perform preliminary simulation calculations on the energy storage and release processes of the above-mentioned examples with nitrogen emission rates ranging from 0% to 50%. During the simulation, the compressor's mechanical efficiency is 0.98, its isentropic efficiency is 0.89, the turboexpander's isentropic efficiency is 0.9, and the cryogenic pump's isentropic efficiency is 0.75. Energy and resistance losses in various pipelines and equipment components are negligible.

[0039] This method requires changing the nitrogen compressor load during the energy storage and release switching process. For the compressor, its safe operating range is usually 60%-120%. In this example, when the nitrogen release rate is 50%, the inlet flow rate of the first nitrogen compressor 12 in the energy storage process is the highest, which is 111.1% of the design amount. The inlet flow rate of the nitrogen compressor in the release process is 70.1% of the design amount, which is within the safe operating range.

[0040] Based on the comprehensive power consumption of the energy storage and release process of this device, this invention systematically analyzes its economic benefits. Figure 5 The nitrogen emission rate corresponds to the oxygen production of 75,000 Nm³ in the air separation embodiment of this invention. 3 ·h -1 The impact of nitrogen emission energy storage power generation device on the staged power generation and product recovery process of the air separation unit on electricity cost savings. The nitrogen emission rate is positively correlated with the electricity cost savings rate. When the nitrogen emission rate is about 50%, the example of this invention saves 2% of electricity costs.

[0041] Figure 6 The peak-valley electricity price ratio is used to compare the oxygen production of air separation in the embodiment of this invention, which is 75,000 Nm³. 3 ·h -1The invention relates to the impact of energy savings on the staged power generation and product recycling processes of the air separation unit, including the nitrogen venting energy storage power generation device. The peak-valley electricity price ratio is positively correlated with the energy cost savings rate; the higher the peak-valley electricity price ratio, the higher the energy cost savings rate for the air separation unit, including the nitrogen venting energy storage power generation device. As the peak-valley electricity price ratio increases, the energy cost savings also increase. In this example, when the peak-valley electricity price ratio is 3.5, the invention saves 3% of the energy cost.

[0042] Furthermore, considering the application scope and power consumption of air separation equipment in the industrial sector, the staged power generation and product recovery process of this air separation unit, which includes a nitrogen venting energy storage power generation device, will significantly improve the current peak-valley power consumption situation of my country's power grid, effectively promoting peak shaving and valley filling. It will also improve the stability and operating efficiency of power grid generating units, while driving the transformation of small and medium-sized peak-shaving units into baseload units or new large-capacity generating units, thereby reducing coal consumption and carbon emissions from power generation.

[0043] The above specific embodiments are only for illustrating the technical concept and structural features of the present invention, and are intended to enable those skilled in the art to implement them. However, the above content does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the technical features of the present invention should fall within the scope of protection of the present invention.

[0044] The foregoing description of this disclosure in conjunction with specific implementation schemes is exemplary and not intended to limit the scope of protection of this disclosure. Those skilled in the art can make various modifications and variations to this disclosure based on its spirit and principles, and such modifications and variations are also within the scope of this disclosure.

Claims

1. An air separation unit including a nitrogen venting energy storage and power generation device, characterized in that: The air separation unit includes a first nitrogen compressor (12), a nitrogen product pipeline, and a venting nitrogen pipeline. The nitrogen product pipeline and the venting nitrogen pipeline are connected in parallel to the first nitrogen compressor. After being pressurized by the first nitrogen compressor, medium-pressure nitrogen product and medium-pressure venting nitrogen are output. The vented nitrogen energy storage and power generation device includes an energy storage circuit and an energy release and power generation circuit. The vented nitrogen energy storage and power generation device uses the medium-pressure vented nitrogen as a cold-to-electric conversion medium. The medium-pressure vented nitrogen is liquefied and stored in the energy storage circuit. The liquid nitrogen stored in the energy release and power generation circuit is expanded to generate electricity. The nitrogen pipeline at the energy release outlet end of the energy release and power generation circuit is connected to the nitrogen product pipeline, and medium-pressure nitrogen is output as a medium-pressure nitrogen product. The nitrogen gas energy storage and power generation device includes a third nitrogen compressor (25), a first heat exchanger (26), a second heat exchanger (27), a third heat exchanger (28), a cryogenic expander (29), a liquid nitrogen storage tank (30), a cryogenic oil tank (35), a cryogenic oil pump (36), a first cold storage tank (45), a second cryogenic pump (46), a second cold storage tank (47), and a third cryogenic pump (48). The energy storage circuit uses the third nitrogen compressor (25) to pressurize the medium-pressure nitrogen gas, cools it using the first heat exchanger (26), the second heat exchanger (27), and the third heat exchanger (28), and then uses the cryogenic expander (29) to... The pressurized vented nitrogen gas expands, liquefies, and is stored in the liquid nitrogen storage tank (30). The separated nitrogen gas from the top outlet of the liquid nitrogen storage tank (30) is input to the input channel in front of the first nitrogen compressor (12) via the third heat exchanger (28) and the second heat exchanger (27) for energy storage circulation. The energy storage loop uses the low-temperature medium stored in the low-temperature oil tank (35), the first cold storage tank (45), and the second cold storage tank (47) to provide cold energy to the pressurized medium-pressure vented nitrogen gas. The cold energy is transferred to the pressurized medium-pressure vented nitrogen gas in sequence through the first heat exchanger (26), the second heat exchanger (27), and the third heat exchanger (28). The nitrogen gas energy storage and power generation device further includes a first cryogenic pump (31), a fourth heat exchanger (37), a fifth heat exchanger (38), a sixth heat exchanger (39), a third turbine expander generator (40), a seventh heat exchanger (41), a fourth turbine expander generator (42), an eighth heat exchanger (43), a fifth turbine expander generator (44), a radiator (34), a high-temperature oil tank (32), and a high-temperature oil pump (33). The energy release power generation circuit utilizes liquid nitrogen in the liquid nitrogen storage tank (30) pressurized by the first cryogenic pump (31). Then, the cold energy is recovered in the fourth heat exchanger (37), the cold energy is recovered in the fifth heat exchanger (38), the cold energy is recovered in the sixth heat exchanger (39), the cold energy is expanded and generated in the third turbine expander (40), the cold energy is recovered in the seventh heat exchanger (41), the cold energy is expanded and generated in the fourth turbine expander (42), the cold energy is recovered in the eighth heat exchanger (43), and the cold energy is expanded and generated in the fifth turbine expander (44) before outputting medium-pressure nitrogen as a medium-pressure nitrogen product.

2. The air separation unit including a nitrogen venting energy storage and power generation device according to claim 1, wherein, The cryogenic medium in the cryogenic oil tank (35) is pressurized by the cryogenic oil pump (36) and enters the first heat exchanger (26). The cryogenic medium in the first cold storage tank (45) is pressurized by the second cryogenic pump (46) and enters the second heat exchanger (27). The cryogenic medium in the second cold storage tank (47) is pressurized by the third cryogenic pump (48) and enters the third heat exchanger (28) to provide cold energy.

3. The air separation unit including a nitrogen venting energy storage and power generation device according to claim 1, wherein, The energy release power generation circuit utilizes the high-temperature medium stored in the high-temperature oil tank (32), pressurizes it with the high-temperature oil pump (33), and recovers liquid nitrogen cold energy in sequence through the eighth heat exchanger (43), the seventh heat exchanger (41) and the sixth heat exchanger (39). After being cooled by the radiator (34), it is stored in the low-temperature oil tank (35).

4. The air separation unit including a nitrogen venting energy storage and power generation device according to claim 1, wherein, The outlet end of the fifth turbine expander (44) is connected to the nitrogen product pipeline.

5. The air separation unit according to claim 1, comprising a nitrogen venting energy storage and power generation device, wherein, The energy storage circuit operates during off-peak electricity periods.

6. The air separation unit including a nitrogen venting energy storage and power generation device according to claim 1, wherein, The energy release power generation circuit operates during peak power periods.

Images