Method for preparing pure oxygen, nitrogen and poor krypton-xenon liquid oxygen by using low-temperature air

Abstract

The invention provides a method for preparing pure oxygen, nitrogen and poor krypton-xenon liquid oxygen by using low-temperature air, which belongs to the technical field of air separation, and mainly comprises the following steps: cooling one path of low-temperature purified air by backflow gas and then entering a lower tower of a nitrogen tower T1 to form moisture-containing air; a second path of low-temperature purified air enters a low-pressure expansion machine ET2 to be pressurized and cooled, then enters a high-pressure expansion machine ET1 to be pressurized and cooled again, is cooled by a main heat exchanger E1, then enters the expansion end of the high-pressure expansion machine ET1 to do work on the pressurization end in an expansion manner, and enters the upper layer of filler at the lower part of the nitrogen tower T1 to participate in rectification; and the third path of low-temperature purified air is subjected to heat exchange, enters a condensation side of a condensation evaporator K2 at the bottom of the krypton-poor tower T2, exchanges heat with krypton-poor xenon liquid oxygen at the evaporation side, is condensed into liquid air and is sent back to the upper layer of tower plate at the bottom of the nitrogen tower T1. The method for preparing the pure oxygen, the nitrogen and the poor krypton-xenon liquid oxygen by using the low-temperature air, provided by the invention, has the advantages of various types of produced products, no increase of energy consumption and high economic benefit.

Description

Technical Field

[0001] This invention relates to the field of air separation technology, and in particular to a method for producing pure oxygen, nitrogen and depleted krypton-xenon liquid oxygen using low-temperature air. Background Technology

[0002] Krypton and xenon are rare gases present in low concentrations in the air and have many important industrial and scientific applications, such as lighting and displays, electronics and semiconductors, medical and scientific research, aerospace, and high-energy physics. These properties make krypton and xenon irreplaceable materials in modern technology, especially valuable in high-end manufacturing, aerospace, and cutting-edge science. Therefore, extracting krypton and xenon from the air has significant economic and social value.

[0003] Currently, the main method for extracting krypton and xenon gas from air is cryogenic fractionation. This method involves compressing, cooling, and purifying air, then performing multi-stage fractionation at low temperatures to obtain lean krypton and xenon, which are then further refined using a purification device to obtain pure krypton, pure xenon, and other gaseous components. However, cryogenic fractionation has the following disadvantages: (1) complex equipment, large footprint, and high investment costs; (2) high energy consumption and high operating costs; (3) low production efficiency and low product purity; (4) high operational difficulty and high safety risks; and (5) few byproducts from traditional air separation, low economic added value, and severe product homogenization.

[0004] Therefore, developing a new process that does not affect the normal production of air separation units and produces new products to improve the economic efficiency of air separation units is of great practical significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for producing pure oxygen, nitrogen and depleted krypton-xenon liquid oxygen using low-temperature air, which produces a variety of products without increasing energy consumption and has high economic benefits.

[0006] To address the aforementioned technical problems, this invention provides a method for producing pure oxygen, nitrogen, and krypton-lean liquid oxygen using low-temperature air, comprising the following steps: The raw air is compressed by a compression system, precooled by a precooling system, and purified by a purification system to obtain low-temperature purified air. The first stream of low-temperature purified air is cooled by the reflux gas after passing through the main heat exchanger E1 and liquefaction unit E2 and then enters the lower tower of nitrogen tower T1 to form humid air. After being distilled in nitrogen tower T1, the humid air is obtained as high-purity, low-temperature nitrogen at the top of nitrogen tower T1 and as oxygen-enriched liquid air at the bottom of nitrogen tower T1, which is then sent to the evaporation side of the main condenser-evaporator K1. The high-purity low-temperature nitrogen gas is sent out of the cold box for downstream users after passing through the liquefaction unit E2 and the main heat exchanger E1 to form room temperature nitrogen gas with a pressure of 0.40MPa(G) to 0.38MPa(G). The other path enters the main condenser-evaporator K1 and exchanges heat with the oxygen-rich liquid air on the evaporation side to condense into liquid nitrogen. The liquid nitrogen first enters the top of nitrogen tower T1 as a downward liquid to participate in distillation, the second enters the liquid nitrogen storage tank N2 after heat exchange in heat exchanger E4, and the third enters the condenser-evaporator K3 at the top of the krypton-lean tower T2 and exchanges heat with the liquid oxygen on the condenser side and evaporator side before returning to the top of nitrogen tower T1 as the downward liquid required for distillation. The oxygen-enriched liquid air at the bottom of the nitrogen tower T1 exchanges heat with the waste nitrogen, oxygen and crude argon in the cooler E3 and then enters the main condenser evaporator K1. It exchanges heat with the high-purity low-temperature nitrogen on the evaporation side and the condensation side to produce waste nitrogen and oxygen-enriched liquid air flowing to the top of the lower tower of the krypton-lean tower T2. The waste nitrogen gas passes through cooler E3 and liquefaction unit E2. One path is through main heat exchanger E1 to exchange heat to room temperature and then sent to the purification system for use as regeneration gas. The other path is through low-pressure expander ET2 to expand and do work, and then through liquefaction unit E2 and main heat exchanger E1 to exchange heat to room temperature and then sent to the purification system for use as regeneration gas. The second stream of low-temperature purified air enters the low-pressure expander ET2 for pressurization and cooling, then enters the high-pressure expander ET1 for further pressurization and cooling. After being cooled by the main heat exchanger E1, it enters the expansion end of the high-pressure expander ET1 to expand and do work on the pressurization end, and then enters the upper packing layer at the bottom of the nitrogen tower T1 to participate in distillation. The third stream of low-temperature purified air exchanges heat with the main heat exchanger E1 and the liquefier E2, and then enters the condenser-evaporator K2 at the bottom of the krypton-lean tower T2. The condenser side exchanges heat with the krypton-lean xenon liquid oxygen on the evaporator side and then condenses into liquid air, which is sent back to the top tray of the nitrogen tower T1. The crude argon gas generated by the heat exchange and evaporation of lean krypton xenon liquid oxygen on the evaporation side of the condenser evaporator K2 is distilled with the oxygen-enriched liquid air flowing to the top of the lower column of lean krypton column T2 to obtain lean krypton xenon liquid oxygen at the bottom of lean krypton column T2. The lean krypton xenon liquid oxygen is cooled by heat exchanger E4 and sent to lean krypton xenon liquid oxygen storage tank. The other route is pressurized and sent to the evaporation side of the main condenser evaporator K3 at the top of lean krypton tower T2 to evaporate pure oxygen. Crude argon is obtained at the top of lean krypton tower T2. The crude argon gas is sent out as molecular sieve regeneration gas after heat exchange through cooler E3, liquefier E2 and main heat exchanger E1. The pure oxygen is sent out for downstream users after heat exchange through cooler E3, liquefier E2 and main heat exchanger E1.

[0007] Furthermore, the compression system adopts a multi-stage isothermal centrifugal compressor, the precooling system adopts a combination of air-cooled tower and water-cooled tower, and the purification system is a molecular sieve purifier and a steam heater; The molecular sieve purifier is equipped with two molecular sieve purifiers that work alternately. One is a molecular sieve purifier for adsorption and the other is a molecular sieve purifier for regeneration and desorption. The molecular sieve purifier for regeneration and desorption is heated by a steam heater or an electric heater to desorb and regenerate the molecular sieve purifier. The molecular sieve purifier is filled with alumina and molecular sieves.

[0008] Furthermore, the pressure of the low-temperature purified air obtained after the raw material air is compressed, pre-cooled and purified is 0.43MPa(G) to 0.48MPa(G) and the temperature is 12℃ to 16℃.

[0009] Furthermore, the first low-temperature purified air is cooled to -174℃ to -171℃ by the return gas through the main heat exchanger E1 and liquefaction unit E2. The return gas includes expanded sludge nitrogen, sludge nitrogen, nitrogen, oxygen, and crude argon.

[0010] Furthermore, the high-purity, low-temperature nitrogen obtained at the top of nitrogen tower T1 after the humid air is distilled in nitrogen tower T1 has an oxygen content of less than 10 ppm, a nitrogen content of greater than 99.99% VOL, a pressure of 0.40 MPa(G) to 0.43 MPa(G), and a temperature of -179℃ to -178℃. The oxygen-enriched liquid air obtained at the bottom of nitrogen tower T1 has an oxygen content of 35% to 39% VOL.

[0011] Furthermore, the temperature of the liquid nitrogen is -179℃ to -178℃, and the temperature of the liquid oxygen that exchanges heat with the liquid nitrogen on the condensing side of the condenser-evaporator K3 at the top of the krypton-poor tower T2 is -183℃ to -180℃.

[0012] Furthermore, the second stream of low-temperature purified air enters the low-pressure expander ET2 and is pressurized to 0.6MPa(G)~0.8MPa(G), then cooled to 30℃~35℃ by the cooler E6. It then enters the high-pressure expander ET1 and is pressurized to 1.6MPa(G)~2.0MPa(G), then cooled to 30℃~35℃ by the cooler E5. After being cooled to -130℃ by the main heat exchanger E1, it enters the high-pressure expander ET1 again. The expansion end expands and does work on the pressurization end to form low-temperature purified air with a pressure of 0.4MPa(G) and a temperature of -174℃. This air then enters the upper packing layer at the bottom of the nitrogen tower T1 to participate in distillation.

[0013] Furthermore, the pressure of the third low-temperature purified air entering the condenser side of the condenser-evaporator K2 at the bottom of the krypton-poor tower T2 is 0.42MPa(G)~0.44MPa(G) and the temperature is -174℃~-171℃. The pressure of the krypton-poor xenon liquid oxygen on the evaporator side of the condenser-evaporator K2 is 30kPa(G)~50kPa(G) and the temperature is -185℃~-183℃.

[0014] Furthermore, the pressure of the krypton-xenon liquid oxygen obtained at the bottom of the krypton-deficient tower T2 is 30 kPa(G) to 50 kPa(G), the temperature is -184℃ to -182℃, the oxygen content is 99% VOL, the nitrogen content is 0.5% VOL, the argon content is 0.5% VOL, and the krypton + xenon content is greater than 1500 ppm.

[0015] Furthermore, the pressure of the depleted krypton xenon liquid oxygen after pressurization is 0.2 MPa(G) to 0.3 MPa(G). The pure oxygen obtained after the depleted krypton xenon liquid oxygen evaporates on the evaporation side of the main condenser evaporator K3 has an oxygen content of 99.99% VOL, a nitrogen content of less than 0.01% VOL, an argon content of 0.01% VOL, a pressure of 0.15 MPa(G) to 0.18 MPa(G), and a temperature of -183℃ to -181℃. The crude argon gas obtained at the top of the depleted krypton tower T2 has a nitrogen content of 62% VOL, an oxygen content of 36% VOL, an argon content of 1.5% VOL, a pressure of 30 kPa(G) to 50 kPa(G), and a temperature of -188℃ to -186℃.

[0016] This invention provides a method for producing pure oxygen, nitrogen, and lean krypton xenon liquid oxygen using low-temperature air. This method overcomes the limitations of traditional air separation processes, which can only produce oxygen or nitrogen, or both simultaneously. It can meet the production needs of traditional air separation processes for oxygen, nitrogen, liquid oxygen, and liquid nitrogen, while also producing high-value-added products such as lean krypton xenon liquid oxygen. This extends the industrial chain of the production process, making the products more advanced and refined, and bringing greater economic benefits to enterprises.

[0017] Furthermore, the method for producing pure oxygen, nitrogen, and lean krypton-xenon liquid oxygen using cryogenic air provided by this invention allows for the independent operation of one or two expanders during production, depending on the cooling load of the equipment and the demand for liquid products. This increases the cooling capacity of the equipment and meets various operating conditions in the production process. Moreover, the switching of the nitrogen tower (T1) and the lean krypton tower (T2) can be freely selected according to actual production needs, thus enabling the production of various products such as nitrogen, oxygen, liquid nitrogen, liquid oxygen, and lean krypton-xenon liquid oxygen without increasing energy consumption. This method is not only low-energy, high-efficiency, and environmentally friendly, but also produces products with high purity, resulting in significant economic benefits and making it worthy of widespread application. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a method for producing pure oxygen, nitrogen, and depleted krypton-xenon liquid oxygen using low-temperature air, provided in an embodiment of the present invention. Detailed Implementation

[0019] See Figure 1 The present invention provides a method for producing pure oxygen, nitrogen, and depleted krypton-xenon liquid oxygen using low-temperature air, comprising the following steps: Step 1) The raw air is compressed by the compression system, pre-cooled by the pre-cooling system, and purified by the purification system to obtain low-temperature purified air.

[0020] Since the raw material air is taken from the atmosphere, it often contains impurities such as dust. Therefore, before subsequent compression, precooling and purification, the raw material air passes through the self-cleaning air filter F101 to filter out mechanical impurities such as dust in the raw material air.

[0021] The compression system employs a multi-stage isothermal centrifugal compressor C101. The raw material air is compressed by the multi-stage isothermal centrifugal compressor C101 to a pressure of 0.45MPa(G) to 0.5MPa(G) and a temperature of 80℃ to 100℃ before being sent to the precooling system.

[0022] The precooling system uses a combination of air-cooled tower T101 and water-cooled tower T102. The compressed raw material air is washed with low-temperature circulating water in air-cooled tower T101 and water-cooled tower T102 to remove mechanical impurities and acidic gases such as SO2, SO3, and NH3 from the raw material air. At the same time, the raw material air is cooled to 8℃~12℃ through mass and heat transfer with the low-temperature water.

[0023] The cooled and washed raw air enters the purification system to adsorb harmful substances for subsequent distillation, resulting in purified air. The purification system includes a molecular sieve purifier MS101 and a steam heater.

[0024] The molecular sieve purifier MS101 consists of two units that operate alternately. One unit, MS101A, is an adsorption molecular sieve purifier filled with alumina and molecular sieves, used to adsorb impurities such as H2O, C2H2, N2O, and CO2 from the compressed and cooled raw material air. The other unit, MS101B, is a regeneration and desorption molecular sieve purifier. MS101B uses a heat source provided by a steam heater or electric heater to heat the waste nitrogen gas and air flowing back from the cold chamber, thus regenerating the molecular sieve purifier through desorption.

[0025] After the raw air undergoes the above-mentioned filtration, compression, precooling and purification, low-temperature purified air with a pressure of 0.43MPa(G)~0.48MPa(G) and a temperature of 12℃~16℃ is obtained.

[0026] Step 2) The first stream of low-temperature purified air is cooled by the reflux gas after passing through the main heat exchanger E1 and liquefaction unit E2 and then enters the lower tower of nitrogen tower T1 to form humid air, which is a mixture of gaseous and liquid components.

[0027] The first low-temperature purified air is cooled to -174℃ to -171℃ by the return gas through the main heat exchanger E1 and liquefaction unit E2. The return gas includes expanded sludge nitrogen 12, sludge nitrogen 11, nitrogen 14, oxygen 15, and crude argon 13.

[0028] Step 3) Moist air moves from bottom to top in nitrogen tower T1 and undergoes multiple partial evaporation and partial condensation distillations on the structured packing in the main condenser-evaporator K1 with the liquid flowing downwards. High-purity, low-temperature nitrogen is obtained at the top of nitrogen tower T1, and oxygen-rich liquid air (i.e., liquid air rich in oxygen) is obtained at the bottom of nitrogen tower T1 and sent to the evaporation side of the main condenser-evaporator K1.

[0029] The high-purity, low-temperature nitrogen obtained at the top of nitrogen tower T1 after the humid air is distilled has an oxygen content of less than 10 ppm, a nitrogen content of more than 99.99% VOL, a pressure of 0.40 MPa(G) to 0.43 MPa(G), and a temperature of -179℃ to -178℃. The oxygen-enriched liquid air obtained at the bottom of nitrogen tower T1 has an oxygen content of 35% to 39% VOL.

[0030] Step 4) One stream of high-purity, low-temperature nitrogen gas passes through the liquefier E2 and the main heat exchanger E1, forming ambient temperature nitrogen gas with a pressure of 0.40 MPa(G) to 0.38 MPa(G), which is then sent out of the cold box for downstream users. The other stream of high-purity, low-temperature nitrogen gas enters the condenser side of the main condenser-evaporator K1 and exchanges heat with the oxygen-rich liquid air on the evaporator side, condensing into liquid nitrogen at a temperature of -179℃ to -178℃.

[0031] Step 5) The liquid nitrogen obtained in Step 4) above is divided into three streams. The first stream of liquid nitrogen enters the top of nitrogen tower T1 as a downward liquid to participate in distillation. The second stream of liquid nitrogen enters the N2 liquid nitrogen storage tank after heat exchange in heat exchanger E4. The third stream of liquid nitrogen enters the condenser side (i.e. nitrogen side) of the condenser-evaporator K3 at the top of the krypton-lean tower T2 and exchanges heat with the liquid oxygen on the evaporator side (i.e. liquid oxygen side) of the condenser-evaporator K3 before returning to the top of nitrogen tower T1 as the downward liquid required for distillation.

[0032] The temperature of the liquid nitrogen is -179℃ to -178℃, and the temperature of the liquid oxygen that exchanges heat with the liquid nitrogen on the condensing side of the condenser-evaporator K3 at the top of the krypton-poor tower T2 is -183℃ to -180℃.

[0033] Step 6) The oxygen-enriched liquid air generated at the bottom of nitrogen tower T1 in step 3) passes through cooler E3 and exchanges heat with waste nitrogen, oxygen and crude argon. It then enters the main condenser evaporator K1 and exchanges heat with high-purity low-temperature nitrogen on the evaporation side (i.e. oxygen-enriched liquid air side) and condensation side (i.e. nitrogen side) to generate waste nitrogen and oxygen-enriched liquid air flowing to the top of the lower tower of krypton-poor tower T2.

[0034] The oxygen-enriched liquid air entering the evaporation side of the main condenser-evaporator K1 after heat exchange with waste nitrogen, oxygen, and crude argon has a pressure of 0.15 MPa(G) and a temperature of -183℃ to -180℃. The high-purity low-temperature nitrogen on the condensation side of the main condenser-evaporator K1 has a pressure of -179℃ to -178℃. The waste nitrogen generated after heat exchange between the oxygen-enriched liquid air and the high-purity low-temperature nitrogen has a pressure of 0.15 MPa(G) and a temperature of -186℃ to -183℃, with an oxygen content of about 37% VOL and a nitrogen content of 61% VOL.

[0035] Step 7) The waste nitrogen gas obtained in Step 6) above is divided into two streams after passing through cooler E3 and liquefaction unit E2: one stream of waste nitrogen gas is heated to room temperature and pressure of 15 kPa(G) to 30 kPa(G) by the main heat exchanger E1 and then sent to molecular sieve purifier MS101 for use as regeneration gas; the other stream of waste nitrogen gas is expanded by the expansion end of low-pressure expander ET2 and then enters liquefaction unit E2 and main heat exchanger E1 for heat exchange to room temperature and then sent to molecular sieve purifier MS101 for use as regeneration gas.

[0036] Step 8) The second stream of low-temperature purified air enters the booster end of the low-pressure expander ET2, is boosted and cooled, and then enters the booster end B1 of the high-pressure expander ET1, is boosted and cooled again, and then enters the expansion end of the high-pressure expander ET1 after being cooled by the main heat exchanger E1. After expanding and doing work on the booster end, it enters the upper packing layer at the bottom of the nitrogen tower T1 to participate in distillation.

[0037] The second stream of low-temperature purified air enters the booster end of the low-pressure expander ET2 and is pressurized to 0.6MPa(G)~0.8MPa(G). Then it is cooled to 30℃~35℃ by the cooler E6. After that, it enters the booster end of the high-pressure expander ET1 and is pressurized to 1.6MPa(G)~2.0MPa(G). After that, it is cooled to 30℃~35℃ by the cooler E5. Then it is cooled to -130℃ by the main heat exchanger E1 and enters the expansion end of the high-pressure expander ET1. After expansion, it does work on the booster end to form low-temperature purified air with a pressure of 0.4MPa(G) and a temperature of -174℃. This air then enters the upper packing layer at the bottom of the nitrogen tower T1 to participate in distillation.

[0038] Step 9) The third stream of low-temperature purified air exchanges heat with the main heat exchanger E1 and the liquefier E2 and then enters the condenser-evaporator K2 at the bottom of the krypton-lean tower T2. The condenser side exchanges heat with the krypton-lean xenon liquid oxygen on the evaporator side of the condenser-evaporator K2 and then condenses into liquid air and is sent back to the top tray of the nitrogen tower T1. Meanwhile, the crude argon gas generated by the krypton-lean xenon liquid oxygen on the evaporator side of the condenser-evaporator K2 is produced by heat exchange and evaporation.

[0039] The pressure of the third low-temperature purified air entering the condenser side of the condenser-evaporator K2 at the bottom of the krypton-deficient tower T2 is 0.42MPa(G)~0.44MPa(G) and the temperature is -174℃~-171℃. The pressure of the krypton-deficient xenon liquid oxygen entering the evaporator side of the condenser-evaporator K2 is 30kPa(G)~50kPa(G) and the temperature is -185℃~-183℃.

[0040] Step 10) The crude argon gas generated by the heat exchange and evaporation of lean krypton xenon liquid oxygen on the evaporation side of the condenser K2 is distilled with the oxygen-enriched liquid air flowing to the top of the lower column of lean krypton column T2 to obtain lean krypton xenon liquid oxygen at the bottom of lean krypton column T2.

[0041] Specifically, the rising gas required for the distillation of lean krypton column T2 comes from the crude argon gas evaporated from the lean krypton xenon liquid oxygen on the evaporation side of the condenser-evaporator K2 at the bottom of lean krypton column T2. ​​The descending liquid required for the distillation of lean krypton column T2 is the oxygen-enriched liquid air from the oxygen-enriched liquid air side of the main condenser-evaporator K1 at the top of nitrogen column T1, which is throttled by a valve and enters the lower top of lean krypton column T2 as the descending liquid. The descending oxygen-enriched liquid air and the rising crude argon gas undergo multiple partial evaporation and partial condensation distillation processes in the structured packing of lean krypton column T2, resulting in lean krypton xenon liquid oxygen at the bottom of lean krypton column T2.

[0042] The pressure of the krypton-xenon liquid oxygen obtained at the bottom of the krypton-depleted tower T2 is 30 kPa(G)~50 kPa(G), the temperature is -184℃~-182℃, the oxygen content is 99% VOL, the nitrogen content is 0.5% VOL, the argon content is 0.5% VOL, and the krypton + xenon content is greater than 1500 ppm.

[0043] Step 11) The lean krypton xenon liquid oxygen obtained in Step 10) is divided into two streams. One stream of lean krypton xenon liquid oxygen is cooled by heat exchanger E4 and then pressurized by the lean krypton xenon liquid oxygen product pump and sent to the lean krypton xenon liquid oxygen storage tank. The other stream of lean krypton xenon liquid oxygen is pressurized by a circulation pump and sent to the evaporation side of the main condenser evaporator K3 at the top of the lean krypton tower T2 for evaporation to obtain pure oxygen. Crude argon gas is obtained at the top of the lean krypton tower T2.

[0044] The depleted krypton xenon liquid oxygen is pressurized by a circulating pump to a pressure of 0.2 MPa(G) to 0.3 MPa(G). The pure oxygen obtained after the depleted krypton xenon liquid oxygen evaporates on the evaporation side of the main condenser evaporator K3 has an oxygen content of 99.99% VOL, a nitrogen content of less than 0.01% VOL, an argon content of 0.01% VOL, a pressure of 0.15 MPa(G) to 0.18 MPa(G), and a temperature of -183℃ to -181℃. The crude argon gas obtained at the top of the depleted krypton tower T2 has a nitrogen content of 62% VOL, an oxygen content of 36% VOL, an argon content of 1.5% VOL, a pressure of 30 kPa(G) to 50 kPa(G), and a temperature of -188℃ to -186℃.

[0045] Step 12) The crude argon gas is sent out as molecular sieve regeneration gas after heat exchange through cooler E3, liquefier E2 and main heat exchanger E1. The pure oxygen is sent out for downstream users after heat exchange through cooler E3, liquefier E2 and main heat exchanger E1.

[0046] This invention provides a method for producing pure oxygen, nitrogen, and lean krypton xenon liquid oxygen using low-temperature air. This method overcomes the limitations of traditional air separation processes, which can only produce oxygen or nitrogen, or both simultaneously. It can meet the production needs of traditional air separation processes for oxygen, nitrogen, liquid oxygen, and liquid nitrogen, while also producing high-value-added products such as lean krypton xenon liquid oxygen. This extends the industrial chain of the production process, making the products more advanced and refined, and bringing greater economic benefits to enterprises.

[0047] Furthermore, the method for producing pure oxygen, nitrogen, and lean krypton-xenon liquid oxygen using cryogenic air provided by this invention allows for the independent operation of one or two expanders during production, depending on the cooling load of the equipment and the demand for liquid products. This increases the cooling capacity of the equipment and meets various operating conditions in the production process. Moreover, the switching of the nitrogen tower (T1) and the lean krypton tower (T2) can be freely selected according to actual production needs, thus enabling the production of various products such as nitrogen, oxygen, liquid nitrogen, liquid oxygen, and lean krypton-xenon liquid oxygen without increasing energy consumption. This method is not only low-energy, high-efficiency, and environmentally friendly, but also produces products with high purity, resulting in significant economic benefits and making it worthy of widespread application.

[0048] The following examples illustrate a method for producing pure oxygen, nitrogen, and depleted krypton-xenon liquid oxygen using low-temperature air, as provided by this invention.

[0049] The main components and their contents of the raw material air used in the method for producing pure oxygen, nitrogen and depleted krypton-xenon liquid oxygen using low-temperature air provided by the present invention are shown in Table 1.

[0050] Table 1

[0051] The physical properties of the raw material air used in the method for producing pure oxygen, nitrogen and depleted krypton-xenon liquid oxygen using low-temperature air provided by the present invention are shown in Table 2.

[0052] Table 2

[0053] The principle of cryogenic air separation includes the following: 99.04% VOL of air consists of oxygen and nitrogen, and 0.932% VOL consists of argon, which remain essentially constant. Hydrogen, carbon dioxide, and hydrocarbons vary within a certain range depending on the region and environment. The water vapor content in the air varies considerably with saturation temperature and geographical conditions. Water vapor and carbon dioxide have properties very different from air; under atmospheric pressure, water vapor reaches 0°C and carbon dioxide reaches -79°C, respectively, turning into ice and dry ice, which can clog the channels of plate heat exchangers and the pores in the packing of distillation columns. Therefore, these components must be removed before the air enters the cold box. Dangerous impurities in the air are hydrocarbons, especially acetylene. During distillation, if acetylene is concentrated to a certain extent in liquid air and liquid oxygen, it may explode. Therefore, the acetylene content in liquid oxygen is limited to no more than 0.1 ppm, which must be given full attention. Non-condensable rare gases, such as neon and helium, tend to accumulate in the condenser-evaporator in a gaseous state due to their very low condensation temperature, occupying heat exchange area and thus affecting heat exchange efficiency. Therefore, they must be frequently vented. The separation process can yield a considerable quantity of high-purity products. Air distillation occurs during the heat and mass exchange between the gas and liquid phases of an oxygen-nitrogen mixture. The gas flows from bottom to top, while the liquid flows from top to bottom, and this process is accomplished by packed columns. Because nitrogen evaporates more easily than oxygen and oxygen condenses more easily than nitrogen in the oxygen-nitrogen mixture, the nitrogen concentration increases continuously as the gas passes through the column. With sufficient packing, high-purity nitrogen can be obtained at the top of the column. Conversely, as the liquid passes through the column, the oxygen concentration increases continuously, resulting in oxygen-rich liquid air at the bottom of the lower column and high-purity liquid oxygen at the bottom of the upper column.

[0054] The heat and mass exchange process between rising gas and descending liquid on the packing can be understood as follows: the liquid gradually flows downwards along the packing, while the steam rises upwards along the packing. The unbalanced steam and liquid come into contact, mix, and undergo heat exchange. The liquid evaporates, releasing more nitrogen into the steam, increasing its oxygen content and raising its temperature. Conversely, the steam condenses, releasing more oxygen into the liquid, increasing its nitrogen content and lowering its temperature. When the steam and liquid temperatures are equal, they are in equilibrium. This process continues, with the steam passing through layers of packing, the nitrogen concentration increases as it ascends, and the oxygen concentration increases as it descends, ultimately yielding high-purity nitrogen and liquid oxygen.

[0055] The present invention provides a method for producing pure oxygen, nitrogen, and depleted krypton-xenon liquid oxygen using low-temperature air, which specifically includes the following steps: 1. The raw material air (atmosphere) passes through the self-cleaning air filter F101 to remove dust and other mechanical impurities from the atmosphere with a filtration accuracy of 2μm. The clean air enters the multi-stage isothermal centrifugal compressor C101, where the atmospheric pressure is compressed to 0.45MPa(G)~0.5MPa(G). After the final exhaust temperature reaches 80℃~100℃, the air is sent to the air-cooled tower T101. The heat generated during the intermediate compression process is carried away by the circulating cooling water (circulating water lines are omitted in the figure).

[0056] 2. Air is fed into air-cooled tower T101. The air-cooled tower is filled with two layers of randomly packed Pall rings to increase the contact area between the air and the circulating water. The air is cooled and washed by the circulating water in the air-cooled tower to remove acidic gases such as SO2. The outlet temperature of the air-cooled tower is 8-12℃ (circulating water line omitted in the figure).

[0057] 3. Compressed air at 0.45MPa(G)~0.5MPa(G) and 8~12℃ exiting the air-cooled tower enters the molecular sieve purification system MS101A / B. The molecular sieve purifier consists of two units, one in operation and one undergoing regeneration. Each purifier is filled with 13X-APG type molecular sieves. During operation, air enters from the bottom and exits from the top, absorbing harmful gases such as H2O, C2H2, CO2, and N2O from the air. During regeneration, the sludge from the molecular sieve purifier enters from the top and exits from the bottom, desorbing and releasing the absorbed H2O, C2H2, CO2, and N2O. The heat source for molecular sieve regeneration is provided by a steam heater or electric heater (not shown in the diagram). The molecular sieve regeneration cycle is 4 hours, after which the two molecular sieve units are switched for use.

[0058] 4. The purified air (0.43MPa(G)~0.48MPa(G), 12℃~16℃) is divided into two streams: one stream enters the air separation cold box, and the other stream enters the high-pressure expander B1 booster end and the low-pressure expander B2 booster end.

[0059] 5. The purified forward air 1 enters E1 and E2 after passing through valve V1. E1 and E2 are plate-fin heat exchangers with different material channels inside. The temperature of air 1 is cooled to -174℃ to -171℃ by nitrogen 14, oxygen 15, waste nitrogen 11 and expanded waste nitrogen 12 and crude argon 13 in the counterflow channel before entering the lower part of nitrogen separation tower T1.

[0060] 6. The nitrogen separation tower T1 employs a structured packing design, with its height determined based on product purity and quantity. Moist air 1 (a mixture of gaseous and liquid states) entering the lower tower of T1 moves upwards, undergoing multiple partial evaporations and condensations of the downstream liquid in the main condenser-evaporator K1 within the structured packing of nitrogen tower T1. At the top of nitrogen tower T1, nitrogen gas with an oxygen content less than 10 ppm, a nitrogen content greater than 99.99% VOL, a pressure of 0.40 MPa (G) to 0.43 MPa (G), and a temperature of -179℃ to -178℃ is obtained. At the bottom of nitrogen tower T1, oxygen-enriched liquid air with an oxygen content of 35% to 39% VOL is obtained.

[0061] 7. Oxygen-enriched liquid air with an oxygen content of 35%–39% VOL at the bottom of nitrogen tower T1 is pumped through pipeline 5 (because the pressure in the lower tower is high and the pressure inside the main condenser-evaporator K1 is low, the liquid air can be pumped up by pressure) to the low-pressure side (also called the evaporation side) of the main condenser-evaporator K1. The internal pressure of the low-pressure side of the main condenser-evaporator K1 is 0.15 MPa (G) and the temperature is -183℃ to -180℃. The flow rate of the oxygen-enriched liquid air and the pressure of the low-pressure side of the main condenser-evaporator K1 are adjusted using valve V12. Liquid level (liquid level is specifically designed according to product flow rate). The waste nitrogen gas evaporated in the main condenser evaporator by the oxygen-enriched liquid air is led out through the top pipe 11. The evaporated waste nitrogen pressure is 0.15MPa(G), temperature is -186℃~-183℃, and purity is about 37%VOL oxygen content and 61%VOL nitrogen content. After being led out, it enters E3 (plate fin heat exchanger), E2, and E1 for heat exchange and is then reheated to room temperature before exiting the cold box. The flow rate and pressure of the delivered gas are regulated by valve V12.

[0062] 8. The nitrogen obtained from the top of nitrogen tower T1 is led out through pipeline 14. One stream of nitrogen 14 passes through E2 and E1 and then undergoes heat exchange with the forward-flowing air 1 before exiting the cold box. The flow rate to downstream users is regulated by valve V6. If the downstream user's consumption is small, excess nitrogen can be released into the atmosphere by valve V7. Another stream branches off from nitrogen pipeline 14 into nitrogen pipeline 16, which enters the high-pressure side (also known as the condensing side) of the main condenser-evaporator K1. The main condenser-evaporator uses a plate-fin heat exchanger. At this time, the nitrogen in the condensate vapor exchanges heat with the oxygen-rich liquid air on the low-pressure side (also known as the evaporating side) of the main condenser-evaporator K1. The incoming nitrogen releases heat and is condensed into liquid nitrogen, while the oxygen-rich liquid air absorbs heat and evaporates into waste nitrogen.

[0063] 9. After nitrogen is condensed into liquid nitrogen in the main condenser-evaporator K1, it exits the main condenser-evaporator K1 in two ways. One way goes through pipe 17 to E4 (plate-fin heat exchanger) to exchange heat with the nitrogen in pipe 13. Before the heat exchange, the temperature and pressure of liquid nitrogen are -179℃ to -178℃ and 0.40MPa(G) to 0.43MPa(G). After the heat exchange, the temperature and pressure are -189℃ to 191℃ and 0.15 to 0.2MPa(G). The cold source for cooling liquid nitrogen pipe 17 comes from nitrogen pipe 13. The opening of valve V16 is used to adjust the liquid nitrogen to throttle it into nitrogen gas. After the heat exchange, the liquid nitrogen in pipe 17 enters the N2 liquid nitrogen storage tank for storage through valve V18. The other way, liquid nitrogen flows back to the lower column of T1 through pipe 7 as the downstream liquid required for the lower column distillation. The flow rate of liquid nitrogen is adjusted by valve V21.

[0064] 10. The liquid nitrogen refluxed from the lower column of T1 is split into two streams on pipeline 7. One stream flows back to the lower column, while the other stream enters the high-pressure side (condensation side) of the liquid oxygen condenser-evaporator K3 through pipeline 8, serving as the heat source for heat exchange in the liquid oxygen condenser-evaporator K3 of column T2. ​​The liquid nitrogen flow rate is regulated by valve V20. After releasing heat, it evaporates into nitrogen gas and is then sent back to the upper part of nitrogen column T1 through pipeline 31.

[0065] 11. A pipeline (pipeline 9) is drawn from the bottom of the evaporation side (low-pressure side) of the main condenser evaporator at the top of nitrogen tower T1 to supply oxygen-enriched liquid air to the bottom and top of tower T2 as the downstream liquid for the lean krypton distillation column. Valve V15 controls the flow rate of the oxygen-enriched liquid air, which can adjust the load on the lean krypton column. The oxygen-enriched liquid air is a liquid mixture containing 67% oxygen, 31% nitrogen, 1.8% argon, and 0.1% krypton / xenon, which is further separated by distillation in the lean krypton column.

[0066] 12. Before entering the lower column T1, air 1 is separated into a pipeline called air 3. Air 3 enters the condensing side (high pressure side) of the condenser-evaporator K2 and exchanges heat with the lean krypton xenon liquid oxygen on the evaporating side (low pressure side) of the condenser-evaporator K2. The lean krypton xenon liquid oxygen evaporates and becomes the rising steam required for the distillation of the lean krypton column T2. After heat exchange, the air in air path 3 condenses into liquid air. The condensed liquid air is sent back to the lower part of nitrogen tower T1 through pipeline 6. The flow rate is adjusted by valve V14, which can control the evaporation rate of lean krypton xenon liquid oxygen, the load of the lean krypton xenon tower, and the product purity of lean krypton xenon liquid oxygen. The condenser evaporator K2 is a plate-fin heat exchanger. The temperature and pressure of the air 3 on the condensing side are 0.42MPa(G)~0.44MPa(G) and -174℃~-171℃. The temperature, pressure, and purity of the lean krypton xenon liquid oxygen on the evaporating side of the condenser evaporator K2 are 30kPa(G)~50kPa(G) and -185℃~-183℃. The oxygen content is above 98%VOL, the nitrogen content is below 1%VOL, the argon content is below 0.5%VOL, and the lean krypton xenon content is above 1500ppm.

[0067] 13. The lean krypton xenon solution on the low-pressure side of the condenser evaporator K2 at the bottom of the lean krypton tower T2 is continuously concentrated until it reaches the required product purity. It is then sent out through the lean krypton xenon liquid oxygen pipeline 11. After passing through the cooling absorption pipeline 13 of E4 to reach the supercooled temperature, it enters the lean krypton liquid oxygen transfer pump P102 to be pressurized to 0.2-0.3 MPa (G) and then enters the lean krypton xenon liquid oxygen (Kr+Xe+O2) storage tank for storage and sale.

[0068] 14. Crude argon gas is extracted from the top of the T2 column (lower section) and sent through pipeline 13. After passing through E3, E2, and E1 to recover cold energy, it is sent to the molecular sieve system pipeline 41 as regeneration gas. The flow rate of the crude argon gas is regulated by valve V4. The crude argon gas exiting the cold box is at room temperature, with a nitrogen content of 62% VOL, an oxygen content of 36% VOL, and an argon content of 1.8% VOL.

[0069] 15. Besides being sent to storage, the lean krypton xenon liquid oxygen at the bottom of the lean krypton tower T2 is also pressurized to 0.2 MPa (G) to 0.3 MPa (G) via the lean krypton xenon liquid oxygen circulation pump P101 and sent to the evaporation side (low-pressure side) of the main condenser-evaporator K3 at the top of the lean krypton tower. The evaporation side liquid oxygen has an oxygen content of 99.9% VOL, a nitrogen content of less than 0.01% VOL, an argon content of 0.01% VOL, a pressure of 0.15 MPa (G) to 0.18 MPa (G), and a temperature of -183℃ to -181℃. The pure oxygen evaporated from the evaporation side of the main condenser-evaporator K3 at the top of the lean krypton tower is led out through pipeline 15, reheated to room temperature by the subcooler E3, liquefier E2, and main heat exchanger E1, and then sent to downstream users. The flow rate is regulated by valve V5.

[0070] 16. A pipeline 18 is led out from the bottom of the evaporation side (low-pressure side) of the main condenser evaporator K3. Liquid oxygen passes through pipeline 18 and absorbs the cooling capacity of pipeline 13 through E4 to reach subcooling before entering the liquid oxygen storage tank for storage and sale. The flow rate of liquid oxygen is controlled by valve V19.

[0071] 17. The cooling required for the operation of the entire unit is provided by two turboexpanders. Each expander consists of an expansion end and a boosting end, coaxially connected. The expansion end provides power to the boosting end. The boosting end pressurizes the air, while the expansion end expands and depressurizes the air. The depressurized air has a lower enthalpy and temperature. Air 21, at 0.43MPa(G)~0.45MPa(G) and 12℃~16℃, first enters the boosting end B2 of the low-pressure expander for pressurization. After being pressurized to 0.6MPa(G)~0.8MPa(G), it passes through cooler E6. The heat generated during pressurization is carried away by circulating water in E6 (not shown in the diagram), cooling the air 21 to 30℃~35℃. Air 21 enters the high-pressure expander ET1, pressurized to 1.6 MPa (G) to 2.0 MPa (G), and then passes through cooler E5. The heat generated by the pressurization is carried away by the circulating water in E5 (not shown in the diagram). Air 22 is cooled to 30℃ to 35℃. Air 22 enters the main heat exchanger E1, where it exchanges heat with the counterflow air and is cooled to -130℃. Air 23, with its flow rate regulated by valve V11, enters the high-pressure expander, expands to the expansion end ET1, and its temperature drops to -168 to -172℃. It then enters the lower part of nitrogen tower T1 via pipeline 4.

[0072] 18. The backflowing waste nitrogen gas 11, after being reheated by E2, has a temperature of -120℃ to -130℃. A branch line 24 from pipeline 11 enters the gas, and the flow rate is regulated by valve V10. After expansion at the expansion end ET2 of the low-pressure expander, the temperature drops to -150℃ to -163℃. The expanded waste nitrogen gas is then sent out of the cold box after being reheated by E2 and E1 through pipeline 12. It is then sent to the molecular sieve as a regenerator and the water-cooled tower T102 as a drying gas through pipeline 41, with the flow rate regulated by valve V3.

[0073] 19. In the initial stage of start-up of this air separation unit, when the flow rate of backflow gas and waste nitrogen in pipeline 11 is insufficient, the V13 valve is opened to supplement the waste nitrogen in pipeline 11 with forward flow air, which can enable the expander ET2 to operate at high load and accelerate the provision of cooling capacity to the unit.

[0074] 20. If the downstream unit does not require oxygen and stops selling lean krypton xenon, the operation of P101 can be stopped by closing valves V14, V15, V20, V4, and V5, thus isolating the lean krypton tower, at which point only pure nitrogen is produced.

[0075] 21. The expander refrigeration system can be selected to operate as a single unit or in pairs, depending on the amount of cooling capacity required during operation. The opening and closing of the low-pressure expander return valve V8 and the high-pressure expander return valve V9 can be used to adjust the operating load of the corresponding expander, and can also serve as a temporary passage when one of the expanders is not running.

[0076] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, 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 technical solutions 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 method for producing pure oxygen, nitrogen, and lean krypton-xenon liquid oxygen using low-temperature air, characterized in that, Includes the following steps: The raw air is compressed by a compression system, precooled by a precooling system, and purified by a purification system to obtain low-temperature purified air. The first stream of low-temperature purified air is cooled by the reflux gas after passing through the main heat exchanger E1 and liquefaction unit E2 and then enters the lower tower of nitrogen tower T1 to form humid air. After being distilled in nitrogen tower T1, the humid air is obtained as high-purity, low-temperature nitrogen at the top of nitrogen tower T1 and as oxygen-enriched liquid air at the bottom of nitrogen tower T1, which is then sent to the evaporation side of the main condenser-evaporator K1. The high-purity, low-temperature nitrogen gas is sent out of the cold box for downstream users after passing through the liquefaction unit E2 and the main heat exchanger E1 to form room-temperature nitrogen gas with a pressure of 0.40MPa(G) to 0.38MPa(G). The other path enters the main condenser-evaporator K1 and exchanges heat with the oxygen-rich liquid air on the evaporation side to condense into liquid nitrogen. The liquid nitrogen first enters the top of nitrogen tower T1 as a downward liquid to participate in distillation, the second enters the liquid nitrogen storage tank N2 after heat exchange in heat exchanger E4, and the third enters the condenser-evaporator K3 at the top of the krypton-lean tower T2 and exchanges heat with the liquid oxygen on the condenser side and evaporator side before returning to the top of nitrogen tower T1 as the downward liquid required for distillation. The oxygen-enriched liquid air at the bottom of the nitrogen tower T1 exchanges heat with the waste nitrogen, oxygen and crude argon in the cooler E3 and then enters the main condenser evaporator K1. It exchanges heat with the high-purity low-temperature nitrogen on the evaporation side and the condensation side to produce waste nitrogen and oxygen-enriched liquid air flowing to the top of the lower tower of the krypton-poor tower T2. The waste nitrogen gas passes through cooler E3 and liquefaction unit E2. One path is through main heat exchanger E1 to exchange heat to room temperature and then sent to the purification system for use as regeneration gas. The other path is through low-pressure expander ET2 to expand and do work, and then through liquefaction unit E2 and main heat exchanger E1 to exchange heat to room temperature and then sent to the purification system for use as regeneration gas. The second stream of low-temperature purified air enters the low-pressure expander ET2 for pressurization and cooling, then enters the high-pressure expander ET1 for further pressurization and cooling. After being cooled by the main heat exchanger E1, it enters the expansion end of the high-pressure expander ET1 to expand and do work on the pressurization end, and then enters the upper packing layer at the bottom of the nitrogen tower T1 to participate in distillation. The third stream of low-temperature purified air exchanges heat with the main heat exchanger E1 and the liquefier E2, and then enters the condenser-evaporator K2 at the bottom of the krypton-lean tower T2. The condenser side exchanges heat with the krypton-lean xenon liquid oxygen on the evaporator side and then condenses into liquid air, which is sent back to the top tray of the nitrogen tower T1. The crude argon gas generated by the heat exchange and evaporation of lean krypton xenon liquid oxygen on the evaporation side of the condenser evaporator K2 is distilled with the oxygen-enriched liquid air flowing to the top of the lower column of lean krypton column T2 to obtain lean krypton xenon liquid oxygen at the bottom of lean krypton column T2. The lean krypton xenon liquid oxygen is cooled by heat exchanger E4 and sent to lean krypton xenon liquid oxygen storage tank. The other route is pressurized and sent to the evaporation side of the main condenser evaporator K3 at the top of lean krypton tower T2 to evaporate pure oxygen. Crude argon is obtained at the top of lean krypton tower T2. The crude argon gas is sent out as molecular sieve regeneration gas after heat exchange through cooler E3, liquefier E2 and main heat exchanger E1. The pure oxygen is sent out for downstream users after heat exchange through cooler E3, liquefier E2 and main heat exchanger E1.

2. The method for producing pure oxygen, nitrogen, and lean krypton-xenon liquid oxygen using low-temperature air according to claim 1, characterized in that, The compression system uses a multi-stage isothermal centrifugal compressor, the precooling system uses a combination of an air-cooled tower and a water-cooled tower, and the purification system consists of a molecular sieve purifier and a steam heater. The molecular sieve purifier is equipped with two molecular sieve purifiers that work alternately. One is a molecular sieve purifier for adsorption and the other is a molecular sieve purifier for regeneration and desorption. The molecular sieve purifier for regeneration and desorption is heated by a steam heater or an electric heater to desorb and regenerate the molecular sieve purifier. The molecular sieve purifier is filled with alumina and molecular sieves.

3. The method for producing pure oxygen, nitrogen and liquid oxygen with low content of krypton and xenon from air according to claim 2, characterized in that, The pressure of the low-temperature purified air obtained after the raw material air is compressed, pre-cooled and purified is 0.43MPa(G) to 0.48MPa(G) and the temperature is 12℃ to 16℃.

4. The method for producing pure oxygen, nitrogen and liquid oxygen with low content of krypton and xenon from air according to claim 1, characterized in that, The first low-temperature purified air is cooled to -174℃ to -171℃ by the return gas through the main heat exchanger E1 and liquefaction unit E2. The return gas includes expanded sludge nitrogen, sludge nitrogen, nitrogen, oxygen, and crude argon.

5. The method for producing pure oxygen, nitrogen and liquid oxygen with low content of krypton and xenon from air according to claim 1, characterized in that, The high-purity, low-temperature nitrogen obtained at the top of nitrogen tower T1 after the humid air is distilled has an oxygen content of less than 10 ppm, a nitrogen content of greater than 99.99% VOL, a pressure of 0.40 MPa(G) to 0.43 MPa(G), and a temperature of -179℃ to -178℃. The oxygen-enriched liquid air obtained at the bottom of nitrogen tower T1 has an oxygen content of 35% to 39% VOL.

6. The method for producing pure oxygen, nitrogen and liquid oxygen depleted in krypton and xenon from air at low temperature according to claim 1, characterized in that, The temperature of the liquid nitrogen is -179℃ to -178℃, and the temperature of the liquid oxygen that exchanges heat with the liquid nitrogen at the top of the K3 condenser-evaporator at the top of the K2 lean krypton tower is -183℃ to -180℃.

7. The method for producing pure oxygen, nitrogen, and depleted krypton-xenon liquid oxygen using low-temperature air according to claim 1, characterized in that, The second stream of low-temperature purified air enters the low-pressure expander ET2 and is pressurized to 0.6MPa(G)~0.8MPa(G). After being cooled to 30℃~35℃ by the cooler E6, it enters the high-pressure expander ET1 and is pressurized to 1.6MPa(G)~2.0MPa(G). After being cooled to 30℃~35℃ by the cooler E5, it enters the main heat exchanger E1 and is cooled to -130℃. Then, it enters the expansion end of the high-pressure expander ET1 and expands, doing work on the pressurization end to form low-temperature purified air with a pressure of 0.4MPa(G) and a temperature of -174℃. This air then enters the upper packing layer at the bottom of the nitrogen tower T1 to participate in distillation.

8. The method for producing pure oxygen, nitrogen and liquid oxygen depleted in krypton and xenon from air at low temperature according to claim 1, characterized in that, The pressure of the third low-temperature purified air entering the condenser side of the condenser-evaporator K2 at the bottom of the krypton-poor tower T2 is 0.42MPa(G)~0.44MPa(G) and the temperature is -174℃~-171℃. The pressure of the krypton-poor xenon liquid oxygen on the evaporator side of the condenser-evaporator K2 is 30kPa(G)~50kPa(G) and the temperature is -185℃~-183℃.

9. The method for producing pure oxygen, nitrogen, and depleted krypton-xenon liquid oxygen using low-temperature air according to claim 1, characterized in that, The krypton-xenon liquid oxygen obtained at the bottom of the krypton-deficient tower T2 has a pressure of 30 kPa(G) to 50 kPa(G), a temperature of -184℃ to -182℃, an oxygen content greater than 99% VOL, a nitrogen content of 0.5% VOL, an argon content of 0.5% VOL, and a krypton + xenon content greater than 1500 ppm.

10. The method for producing pure oxygen, nitrogen and liquid oxygen depleted in krypton and xenon from air at low temperature according to claim 1, characterized in that, The pressurized krypton-xenon liquid oxygen has a pressure of 0.2 MPa(G) to 0.3 MPa(G). The pure oxygen obtained after evaporation of the krypton-xenon liquid oxygen on the evaporation side of the main condenser evaporator K3 has an oxygen content of 99.99% VOL, a nitrogen content of less than 0.01% VOL, an argon content of 0.01% VOL, a pressure of 0.15 MPa(G) to 0.18 MPa(G), and a temperature of -183℃ to -181℃. The crude argon gas obtained at the top of the krypton-lean tower T2 has a nitrogen content of 62% VOL, an oxygen content of 36% VOL, an argon content of 1.5% VOL, a pressure of 30 kPa(G) to 50 kPa(G), and a temperature of -188℃ to -186℃.

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