Method and apparatus for liquefying nitrogen gas using liquid air

Abstract

The application relates to a method and device for liquefying nitrogen gas by using liquid air, wherein the device comprises a heat exchanger, a flash evaporator and a supercooler; four groups of inlets and outlets are arranged on the heat exchanger, and the inlets and outlets are respectively a heat exchange first inlet, a heat exchange first outlet, a heat exchange second inlet, a heat exchange second outlet, a heat exchange third inlet, a heat exchange third outlet, a heat exchange fourth inlet and a heat exchange fourth outlet; a flash evaporation inlet, a flash evaporation gas outlet and a flash evaporation liquid outlet are arranged on the flash evaporator; two groups of inlets and outlets are arranged on the supercooler, and the inlets and outlets are respectively a supercooling first inlet, a supercooling first outlet, a supercooling second inlet and a supercooling second outlet; liquid air produced in a peak-valley low electricity price stage is used as a cold source, a gas source is high-pressure nitrogen gas, the cold energy of the liquid air is used to liquefy the high-pressure nitrogen gas, liquid nitrogen is produced, and the pressure of compressed air is simultaneously increased to 0.8 MPa, so that compressed air is produced through an air separation device. The application expands the application scene of liquid air energy storage, and high-pressure nitrogen gas is liquefied through the cold energy of the liquid air to obtain liquid nitrogen products.

Description

Technical Field

[0001] This invention belongs to the field of liquid air energy storage and utilization technology, and relates to a method and apparatus for liquefying nitrogen using liquid air. Background Technology

[0002] Liquid air energy storage technology is an emerging energy storage technology. Its basic principle is to compress air into a liquid form for storage and use. When energy is needed, the liquid air is released into a gaseous state, enabling it to drive a turbine to generate electricity. This technology has broad application prospects and is a novel technology that can help us solve the challenges of energy storage and conversion.

[0003] The advantages of liquid air energy storage technology lie in its higher storage density and efficiency compared to traditional battery energy storage technology, without causing environmental pollution. Liquid air energy storage technology is also significant for the utilization of renewable energy, as it can store unstable energy sources such as wind and solar power and convert them into electricity when needed, achieving energy balance and conversion.

[0004] Liquid air energy storage technology also has broad application prospects. In the energy sector, it can play a role in energy storage and peak shaving, helping us to utilize energy more efficiently. In the industrial sector, liquid air energy storage technology also has application potential; for example, in the petrochemical industry, it can be used as a coolant and oxidant, providing convenience for industrial manufacturing.

[0005] Overall, liquid air energy storage technology is a very promising technology. Its broad application prospects will have a significant impact on future energy applications and environmental protection, and it is expected to provide us with better options for solving energy storage and conversion problems. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to solve the problem of utilizing the cooling capacity of liquid air, and to provide a method and apparatus for liquefying nitrogen using liquid air. Liquid air produced during peak and off-peak electricity price periods is used to produce liquid nitrogen and compressed air. Compared with using liquid air to reheat and generate electricity, this method saves the pressure energy from being converted into electrical energy and then using electrical energy to produce liquid nitrogen and compressed air, resulting in higher utilization efficiency.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] An apparatus for liquefying nitrogen using liquid air includes a heat exchanger, a flash evaporator, and a subcooler;

[0009] The heat exchanger is provided with four sets of inlets and outlets, namely, heat exchange first inlet, heat exchange first outlet, heat exchange second inlet, heat exchange second outlet, heat exchange third inlet, heat exchange third outlet, heat exchange fourth inlet, and heat exchange fourth outlet; the flash evaporator is provided with flash evaporation inlet, flash vapor outlet, and flash liquid outlet; the subcooler is provided with two sets of inlets and outlets, namely, subcooling first inlet, subcooling first outlet, subcooling second inlet, and subcooling second outlet.

[0010] The first heat exchange inlet is connected to the high-pressure nitrogen pipeline network via a pipe, and the first heat exchange outlet is connected to the flash evaporation inlet; the second heat exchange inlet is connected to the flash vapor outlet, the second heat exchange outlet is connected to the medium-pressure nitrogen pipeline network, the third heat exchange inlet is connected to the subcooled second outlet, the third heat exchange outlet is connected to the vent pipe, the fourth heat exchange inlet is connected to the liquid air storage tank, the fourth heat exchange outlet is connected to the air separation unit, the flash liquid outlet is connected to the subcooled first inlet, the subcooled first outlet is connected to the liquid nitrogen storage tank via a distributor, and the subcooled second inlet is connected to the distributor.

[0011] Furthermore, throttling valves are installed between the first heat exchange outlet and the flash inlet, between the second heat exchange inlet and the flash outlet, and between the second subcooling inlet and the distributor.

[0012] Furthermore, the air separation unit includes an air compression cooling system, a molecular sieve purifier, and an air separation main heat exchanger connected in sequence by pipelines; the fourth heat exchange outlet is connected to the pipeline between the molecular sieve purifier and the air separation main heat exchanger by a pipeline.

[0013] Furthermore, the heat exchanger, flash evaporator, and subcooler are all housed within a single enclosure.

[0014] A method for liquefying nitrogen using liquid air employs the aforementioned apparatus for liquefying nitrogen using liquid air. Liquid air produced during periods of low electricity prices (peak and off-peak) is used as a cold source, and high-pressure nitrogen is used as the gas source. The cold energy of the liquid air is used to liquefy the high-pressure nitrogen to produce liquid nitrogen. Simultaneously, the pressure of compressed air is increased to 0.8 MPa, thereby producing compressed air through an air separation unit.

[0015] Furthermore, after the high-pressure nitrogen is liquefied, the medium-pressure nitrogen obtained by gas-liquid separation in a flash evaporator is reheated by a heat exchanger and returned to the medium-pressure nitrogen pipeline network to recover cold energy and reduce energy waste.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. This invention represents another utilization of liquid air in the field of liquid air energy storage, expanding its application scenarios. It utilizes the cooling capacity of liquid air to liquefy high-pressure nitrogen gas to obtain liquid nitrogen products, and recovers the cooling capacity of the liquid air using the high-pressure nitrogen, thus fully utilizing low-temperature energy. Simultaneously, it reduces the power equipment required for the liquefaction unit's cyclic compression refrigeration, thereby reducing equipment investment.

[0018] 2. In this invention, the compressed air produced by liquid air vaporization replaces a portion of the raw material air compressed by the air compressor in the air separation unit, thus reducing the energy consumption of the air compressor. Utilizing the cooling capacity of liquid air to produce liquid nitrogen while simultaneously obtaining compressed air results in higher efficiency compared to liquid air vaporization power generation in the field of liquid air energy storage.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a schematic diagram of the device for liquefying nitrogen using liquid air in this invention.

[0022] Figure reference numerals: B1-Heat exchanger; B2-Flash evaporator; B3-Subcooler; B4-Distributor; 11-First heat exchange inlet; 12-First heat exchange outlet; 13-Second heat exchange inlet; 14-Second heat exchange outlet; 15-Third heat exchange inlet; 16-Third heat exchange outlet; 17-Fourth heat exchange inlet; 18-Fourth heat exchange outlet; 21-Flash evaporator inlet; 22-Flash vapor outlet; 22-Flash liquid outlet; 31-First subcooler inlet; 32-First subcooler outlet; 33-Second subcooler inlet; 34-Second subcooler outlet. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] Please see Figure 1 A device for liquefying nitrogen using liquid air includes a heat exchanger B1, a flash evaporator B2, and a subcooler B3 installed in a liquefaction cold box.

[0027] Heat exchanger B1 is provided with four sets of inlets and outlets: heat exchange first inlet 11, heat exchange first outlet 12, heat exchange second inlet 13, heat exchange second outlet 14, heat exchange third inlet 15, heat exchange third outlet 16, heat exchange fourth inlet 17, and heat exchange fourth outlet 18; flash evaporator B2 is provided with flash inlet 21, flash vapor outlet 22, and flash liquid outlet 22; subcooler B3 is provided with two sets of inlets and outlets: subcooling first inlet 31, subcooling first outlet 32, subcooling second inlet 33, and subcooling second outlet 34.

[0028] The first heat exchange inlet 11 is connected to the high-pressure nitrogen pipeline network via a pipeline; the first heat exchange outlet 12 is connected to the flash inlet 21; the second heat exchange inlet 13 is connected to the flash outlet 22; the second heat exchange outlet 14 is connected to the medium-pressure nitrogen pipeline network; the third heat exchange inlet 15 is connected to the second subcooling outlet 34; the third heat exchange outlet 16 is connected to the vent pipe; the fourth heat exchange inlet 17 is connected to the liquid air storage tank; the fourth heat exchange outlet 18 is connected to the air separation unit; the flash liquid outlet 22 is connected to the first subcooling inlet 31; the first subcooling outlet 32 ​​is connected to the liquid nitrogen storage tank via distributor B4; and the second subcooling inlet 33 is connected to distributor B4.

[0029] The heat exchanger B1 is used to recover the sensible and latent heat of liquid air, the flash evaporator B2 is used to achieve gas-liquid separation after liquid nitrogen decompression, the subcooler B3 is used to subcool the liquid nitrogen, and the distributor B4 is used to distribute the product and the subcooling. Throttling valves are installed between the first heat exchange outlet 12 and the flash inlet 21, between the second heat exchange inlet 13 and the flash outlet 22, and between the second subcooling inlet 33 and the distributor B4.

[0030] The air separation unit includes an air compression and cooling system, a molecular sieve purifier, and an air separation main heat exchanger B1, which are connected in sequence by pipelines; the fourth heat exchange outlet 18 is connected by a pipeline between the molecular sieve purifier and the air separation main heat exchanger B1.

[0031] A method for liquefying nitrogen using liquid air is described in this embodiment. Liquid air produced during periods of low electricity prices (peak and off-peak) is used as a cold source, and high-pressure nitrogen at 1.8 MPa is used as the gas source. The coldness of the liquid air is used to liquefy the high-pressure nitrogen to produce liquid nitrogen. At the same time, the pressure of compressed air is increased to 0.8 MPa, thereby producing compressed air through an air separation unit.

[0032] Nitrogen gas A41 at 1.8 MPa enters heat exchanger B1. After being cooled and liquefied, the high-pressure liquid nitrogen A42 is throttled by throttle valve V3 to obtain a gas-liquid mixture A50. A50 enters flash evaporator B2 to achieve gas-liquid separation, resulting in medium-pressure liquid nitrogen A51 and medium-pressure nitrogen gas A54. A51 is subcooled by cooler B3 to obtain subcooled liquid nitrogen A52. Liquid air LA from the liquid air storage tank, after being pressurized by the liquid air pump, enters heat exchanger B1 in the liquefaction cold box. The medium-pressure air AIR after being vaporized and reheated enters the air separation unit. After flash evaporation, the medium-pressure nitrogen gas A54 is depressurized by throttle valve V4 to medium-pressure nitrogen gas A55. After being reheated to room temperature by heat exchanger B1, the medium-pressure nitrogen gas A56 enters the medium-pressure nitrogen pipeline network.

[0033] After being subcooled, the medium-pressure liquid nitrogen A52 is divided into two directions by distributor B4. One part is throttled by throttling valve V5 to obtain atmospheric pressure gas-liquid mixture A61, which returns to subcooler B3. The vaporized low-temperature and low-pressure nitrogen A62 then enters heat exchanger B1 to be reheated to room temperature nitrogen A63, and then vented. The majority of the remainder is throttled by throttling valve V6 and sent to the liquid nitrogen storage tank as liquid nitrogen product A100.

[0034] The high-pressure nitrogen pipeline operates at a pressure of 1.8 MPa, with a DN200 interface pipe diameter. Liquid air is supplied from the liquid air pump to the liquefaction cold box, with a junction pressure of approximately 0.8 MPa and a DN50 interface pipe diameter. Atmospheric nitrogen is supplied from the liquefaction cold box and discharged into the atmosphere, with a junction pressure of approximately 15 kPa and a DN100 interface pipe diameter. Liquid nitrogen is supplied from the liquefaction cold box to the liquid nitrogen storage tank, with a junction pressure of approximately 0.3 MPa and a DN50 interface pipe diameter. Compressed air (AIR) is supplied from the liquefaction cold box to the air separation unit, with a junction pressure of approximately 0.65 MPa and a DN200 interface pipe diameter.

[0035] The raw material used in this invention: Liquid air: 7740 Nm 3 / h (converted to gaseous state), 0.8MPa; Nitrogen: 9300Nm 3 / h, 1.8MPa. Product obtained: Liquid nitrogen: 7330Nm 3 / h (converted to gaseous state); Medium-pressure nitrogen: 320m 3 / h, 720kPa; Air: 7740Nm 3 / h, 0.65MPa.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for liquefying nitrogen using liquid air, characterized in that: This includes heat exchangers, flash evaporators, and subcoolers; The heat exchanger is provided with four sets of inlets and outlets, namely, heat exchange first inlet, heat exchange first outlet, heat exchange second inlet, heat exchange second outlet, heat exchange third inlet, heat exchange third outlet, heat exchange fourth inlet, and heat exchange fourth outlet; the flash evaporator is provided with flash evaporation inlet, flash vapor outlet, and flash liquid outlet; the subcooler is provided with two sets of inlets and outlets, namely, subcooling first inlet, subcooling first outlet, subcooling second inlet, and subcooling second outlet. The first heat exchange inlet is connected to the high-pressure nitrogen pipeline network via a pipeline, and the first heat exchange outlet is connected to the flash evaporation inlet; the second heat exchange inlet is connected to the flash vapor outlet, the second heat exchange outlet is connected to the medium-pressure nitrogen pipeline network, the third heat exchange inlet is connected to the subcooled second outlet, the third heat exchange outlet is connected to the vent pipe, the fourth heat exchange inlet is connected to the liquid air storage tank, the fourth heat exchange outlet is connected to the air separation unit, the flash liquid outlet is connected to the subcooled first inlet, the subcooled first outlet is connected to the liquid nitrogen storage tank via a distributor, and the subcooled second inlet is connected to the distributor; Throttling valves are provided between the first heat exchange outlet and the flash inlet, between the second heat exchange inlet and the flash outlet, and between the second subcooling inlet and the distributor; the air separation unit includes an air compression cooling system, a molecular sieve purifier, and an air separation main heat exchanger connected in sequence by pipelines; the fourth heat exchange outlet is connected by a pipeline between the molecular sieve purifier and the air separation main heat exchanger.

2. The apparatus for liquefying nitrogen using liquid air according to claim 1, characterized in that: The heat exchanger, flash evaporator, and subcooler are all housed in one enclosure.

3. A method for liquefying nitrogen using liquid air, characterized in that: The apparatus for liquefying nitrogen using liquid air as described in any one of claims 1 to 2 utilizes liquid air produced during peak and off-peak electricity price periods as a cold source, and high-pressure nitrogen as the gas source. The cold energy of the liquid air is used to liquefy the high-pressure nitrogen to produce liquid nitrogen, while simultaneously increasing the pressure of compressed air to 0.8 MPa, thereby producing compressed air through an air separation unit.

4. The method for liquefying nitrogen using liquid air according to claim 3, characterized in that: After high-pressure nitrogen is liquefied, medium-pressure nitrogen is obtained by gas-liquid separation in a flash evaporator, and then reheated by a heat exchanger before returning to the medium-pressure nitrogen pipeline network to recover cold energy and reduce energy waste.

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