An apparatus and method for producing ultra-high purity nitrogen

Abstract

The present application belongs to the technical field of high-purity gas production, and relates to a production device system and method of ultrahigh-purity nitrogen gas, which takes ambient air as raw material, first enriches nitrogen gas through a membrane separation module, and after heat exchange of the permeation side gas, the gas can be used for a fresh air system of a workshop or plant to keep the air in the plant fresh and circulating; then the nitrogen gas is divided into two streams, and after heat exchange and cooling by the system, the nitrogen gas becomes cold nitrogen gas and liquid nitrogen, which are used as liquid phase and gas phase in a nitrogen deep cryogenic rectification process; the volume flow rate of the cold nitrogen gas and the liquid nitrogen is adjusted by a first stop valve, so as to change the gas-liquid load of the rectification tower, that is, the separation work of the tower can be optimized in real time; meanwhile, two ultrahigh-purity nitrogen gas products with different purities can be produced, and the product compliance rate is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of high-purity gas production technology, and relates to a production device system and method for ultra-high purity nitrogen. Background Technology

[0002] Ultra-high purity nitrogen plays an irreplaceable role in many high-end technology fields. In the manufacturing process of large-scale integrated circuits and semiconductor components, ultra-high purity nitrogen is widely used as a protective gas, purging gas, sealing gas, displacement gas, and evaporation process gas, and is a key medium to ensure a clean, stable, and reliable process environment. In the field of aerospace technology, ultra-high purity nitrogen is also used as a support gas for key processes such as system purging, propellant delivery, and environmental control.

[0003] Currently, cryogenic distillation technology is one of the main methods for producing high-purity nitrogen in industry. Traditional nitrogen purification units typically employ a single distillation column structure, achieving the separation of nitrogen from impurity components by setting fixed operating parameters under steady-state operating conditions. Such systems can only produce high-purity nitrogen products of a fixed purity under steady-state conditions. Once the distillation column reaches equilibrium, its operating conditions are difficult to adjust in real time, and the separation capacity cannot be flexibly adjusted according to product purity requirements or fluctuations in feed composition.

[0004] In the engineering practice of distillation processes, a certain deviation generally exists between theoretical design calculations and actual operating conditions. For nitrogen products with a volumetric purity requirement not exceeding 99.995%, the deviation between theoretical calculations and actual operation is within an acceptable range, and the unit can still operate stably and meet quality requirements. However, when the volumetric purity of the target product is increased to above 99.999995%, the allowable content of residual impurities such as oxygen, water, carbon dioxide, and carbon monoxide in nitrogen is strictly limited to the ppb (parts per billion) level. Under such ultra-high purity requirements, small deviations between theoretical calculations and actual operation will be significantly amplified, and the separation effect of the distillation process becomes extremely sensitive to changes in operating conditions. Consequently, the distillation column struggles to consistently produce qualified ultra-high purity nitrogen during actual operation, resulting in a significant decrease in the unit's product compliance rate.

[0005] Therefore, there is an urgent need to develop an ultra-high purity nitrogen production device with real-time adjustable separation capacity to overcome the limitations of existing single distillation columns in terms of fixed operating conditions and insufficient adjustment capacity, and to achieve dynamic control of the separation capacity of the distillation process. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a system and method for producing ultra-high purity nitrogen, which can adjust the gas-liquid load of the distillation column in real time, thereby optimizing the separation work of the distillation column.

[0007] To achieve this objective, the present invention employs the following technical solution: In a first aspect, the present invention provides a system for producing ultra-high purity nitrogen, comprising a secondary heat exchanger and a membrane separation module connected sequentially along the direction of ambient air flow. The non-permeable side outlet of the membrane separation module is connected to the top liquid inlet of a distillation column through a first hot end passage of the main heat exchanger, and simultaneously connected to the bottom air inlet of the distillation column through a first shut-off valve and a second hot end passage of the main heat exchanger. The permeable side outlet of the membrane separation module is connected to the secondary heat exchanger. The system also includes a liquid nitrogen storage tank for providing raw materials and cooling capacity to the distillation column. The nitrogen discharged from the top of the distillation column is divided into two paths: one path flows through the main heat exchanger and returns to the top of the distillation column as reflux liquid, and the other path flows through the main heat exchanger to produce first ultra-high purity nitrogen. The nitrogen discharged from the top of the distillation column is divided into two paths: one path flows through the main heat exchanger to produce second ultra-high purity nitrogen, and the other path flows through the main heat exchanger and returns to the top of the distillation column as reflux liquid.

[0008] The ultra-high purity nitrogen production system provided by this invention uses ambient air as raw material. First, the nitrogen volume concentration is enriched to greater than 98% through a membrane separation module. After heat exchange on the permeate side, the gas can be used in the fresh air system of the workshop and factory to keep the air in the factory fresh and circulating. Then, the nitrogen is divided into two streams, which are cooled by heat exchange in the system to become cold nitrogen and liquid nitrogen, which serve as the liquid and gas phases in the deep cryogenic nitrogen distillation process. The volume flow rate of cold nitrogen and liquid nitrogen is adjusted by the first shut-off valve, thereby changing the gas-liquid load of the distillation column, that is, optimizing the column separation work in real time. At the same time, two ultra-high purity nitrogen products with different purities can be produced, improving the product compliance rate.

[0009] Preferably, the secondary heat exchanger is provided with a third hot end passage, and a booster and a second shut-off valve are sequentially arranged at the inlet of the third hot end passage along the direction of ambient air flow, and the outlet of the third hot end passage is connected to the membrane separation module.

[0010] The membrane separation module uses a low-temperature nitrogen-generating membrane, which can achieve a nitrogen enrichment volume concentration of greater than 98%.

[0011] The secondary heat exchanger is provided with a fourth hot end passage. The inlet of the fourth hot end passage is connected to the permeate side outlet of the membrane separation module, and the outlet of the fourth hot end passage is connected to a fresh air system.

[0012] Preferably, the main heat exchanger is provided with a first cold end passage, the secondary heat exchanger is provided with a second cold end passage, and the bottom drain port of the distillation column is connected to the first cold end passage and the second cold end passage in sequence through a first throttle valve, and the discharged dry nitrogen is used as the system instrument gas.

[0013] The main heat exchanger is provided with a third cold end passage, and the secondary heat exchanger is provided with a fourth cold end passage. The liquid nitrogen discharged from the liquid nitrogen storage tank flows through the third cold end passage and the fourth cold end passage in sequence through the pressure reducing valve, and then merges with the gas at the non-permeable side outlet of the membrane separation module.

[0014] Preferably, the liquid nitrogen storage device includes a liquid nitrogen tank.

[0015] Preferably, the main heat exchanger is provided with a fifth hot end passage, through which the nitrogen gas discharged from the top of the distillation column flows through the fifth hot end passage via the third shut-off valve, and then returns to the top of the distillation column as reflux liquid via the second throttling valve.

[0016] The main heat exchanger is provided with a fifth cold end passage. The nitrogen gas discharged from the top of the distillation column flows through the fifth cold end passage via the fourth shut-off valve and then produces the first ultra-high purity nitrogen gas.

[0017] Preferably, the main heat exchanger is provided with a sixth cold end passage, and the nitrogen gas discharged from the top of the distillation column flows through the sixth cold end passage via the fifth and sixth shut-off valves, and then produces a second ultra-high purity nitrogen gas.

[0018] The main heat exchanger is provided with a sixth hot end passage. The nitrogen gas discharged from the top of the distillation column flows through the fifth shut-off valve through the sixth hot end passage, and then returns to the top of the distillation column as reflux liquid through the third throttle valve.

[0019] Secondly, the present invention provides a method for producing ultra-high purity nitrogen gas, wherein the method is operated through the ultra-high purity nitrogen gas production apparatus system described in the first aspect, and specifically includes the following steps: After the ambient air undergoes the first heat exchange, it is separated by membrane separation to obtain permeate-side gas and non-permeate-side gas. The permeate-side gas is then used as fresh air for the fresh air system after the second heat exchange, while the non-permeate-side gas is divided into two streams. One stream is converted into liquid nitrogen after the third heat exchange, and the other stream is converted into cold nitrogen after the fourth heat exchange. Liquid nitrogen and cold nitrogen are distilled to obtain nitrogen gas at the top of the column and nitrogen gas at the top of the column. The nitrogen gas at the top of the column is divided into two streams. One stream is returned to the distillation as reflux liquid after the fifth heat exchange, and the other stream is returned to the distillation as ultra-high purity nitrogen gas after the sixth heat exchange. The nitrogen gas at the top of the column is divided into two streams. One stream is returned to the distillation as reflux liquid after the seventh heat exchange, and the other stream is returned to the distillation as reflux liquid after the eighth heat exchange.

[0020] The method for producing ultra-high purity nitrogen provided by this invention is compatible with ultra-high purity nitrogen production equipment systems. By adjusting the volumetric flow rates of cold nitrogen and liquid nitrogen, and thereby changing the gas-liquid load of the distillation column, the column separation work can be optimized in real time, overcoming the limitations of existing single distillation columns in terms of fixed operating conditions and insufficient adjustment capabilities.

[0021] Preferably, after distillation, liquid nitrogen is obtained at the bottom of the column. The liquid nitrogen at the bottom of the column passes through the ninth and tenth heat exchangers in sequence, and the discharged dry nitrogen gas is used as the instrument gas of the system.

[0022] Liquid nitrogen is additionally provided as raw material and cooling in the distillation process. The liquid nitrogen passes through the eleventh and twelfth heat exchangers in sequence and merges with the gas on the non-permeable side.

[0023] Preferably, the ambient air contains particles with a particle size ≤0.005μm, a temperature of 33-37℃, and a pressure of 1atm.

[0024] The ambient air is pressurized before the first heat exchange.

[0025] The particle size in the ambient air is ≤0.005μm, for example, it can be 0.005μm, 0.004μm, 0.003μm, 0.002μm or 0.001μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] The ambient air temperature is 33-37℃, for example, it can be 33℃, 34℃, 35℃, 36℃ or 37℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] It should be noted that the present invention does not specifically limit the temperature before and after each stage of heat exchange, and those skilled in the art can make adaptive temperature selections according to the actual application scenario.

[0028] Preferably, the volumetric flow rate of the liquid nitrogen is 15-20 Nm³. 3 The volumetric flow rate of cold nitrogen is 210-230 Nm³ / h. 3 / h.

[0029] The volumetric flow rate of the liquid nitrogen is 15-20 Nm³. 3 / h, for example, could be 15Nm 3 / h, 16Nm 3 / h、18Nm 3 / h、19Nm 3 / h or 20Nm 3 / h, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0030] The volumetric flow rate of the cold nitrogen gas is 210-230 Nm³. 3 / h, for example, could be 210Nm 3 / h、215Nm 3 / h, 220Nm 3 / h、225Nm 3 / h or 230Nm3 / h, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0031] Preferably, the volume fraction of nitrogen in the first ultra-high purity nitrogen gas is ≥99.9999999%, and the volume fraction of argon gas is ≤0.6ppb.

[0032] The volume fraction of nitrogen in the second ultra-high purity nitrogen gas is ≥99.9999995%, for example, it can be 99.9999995%, 99.9999996%, 99.9999997%, 99.9999998% or 99.9999999%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] The volume fraction of nitrogen in the first ultra-high purity nitrogen gas is ≥99.9999999%, for example, it can be 99.9999999%, 99.99999995% or 99.99999999%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] The volume fraction of argon in the first ultra-high purity nitrogen gas is ≤0.6ppb, for example, it can be 0.6ppb, 0.5ppb, 0.4ppb, 0.3ppb or 0.2ppb, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0036] Compared with the prior art, the present invention has the following beneficial effects: The ultra-high purity nitrogen production system provided by this invention uses ambient air as raw material. First, it enriches nitrogen by a membrane separation module to a volume concentration greater than 98%. After heat exchange on the permeate side, the gas can be used in the fresh air system of workshops and factories to maintain fresh and circulating air. Then, it is divided into two streams of nitrogen, which are cooled by system heat exchange to become cold nitrogen and liquid nitrogen, serving as the liquid and gas phases in the cryogenic nitrogen distillation process. The volumetric flow rates of the cold nitrogen and liquid nitrogen are adjusted by a first shut-off valve, thereby changing the gas-liquid load of the distillation column and optimizing the column separation work in real time. Simultaneously, it can produce two ultra-high purity nitrogen products with different purities: the first ultra-high purity nitrogen has a nitrogen volume fraction of up to 99.9999999% and an argon volume fraction ≤0.6 ppb; the second ultra-high purity nitrogen has a nitrogen volume fraction of up to 99.9999995%, improving the product compliance rate. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the ultra-high purity nitrogen production device system provided in Embodiment 1 of the present invention.

[0038] Wherein: 1, secondary heat exchanger; 2, main heat exchanger; 3, third hot end passage; 4, fourth hot end passage; 5, second cold end passage; 6, fourth cold end passage; 7, first hot end passage; 8, second hot end passage; 9, fifth hot end passage; 10, sixth hot end passage; 11, first cold end passage; 12, third cold end passage; 13, fifth cold end passage; 14, sixth cold end passage; 15, booster compressor; 16, second shut-off valve; 17, membrane separation module; 18, distillation column; 19, first shut-off valve; 20, liquid nitrogen tank; 21, pressure reducing valve; 22, first throttle valve; 23, third shut-off valve; 24, second throttle valve; 25, fourth shut-off valve; 26, fifth shut-off valve; 27, sixth shut-off valve; 28, third throttle valve. Detailed Implementation

[0039] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0040] Example 1 This embodiment provides a production device system for ultra-high purity nitrogen, as shown in the schematic diagram below. Figure 1 As shown, it includes a secondary heat exchanger 1 and a main heat exchanger 2. The secondary heat exchanger 1 is provided with a third hot end passage 3, a fourth hot end passage 4, a second cold end passage 5, and a fourth cold end passage 6. The main heat exchanger 2 is provided with a first hot end passage 7, a second hot end passage 8, a fifth hot end passage 9, a sixth hot end passage 10, a first cold end passage 11, a third cold end passage 12, a fifth cold end passage 13, and a sixth cold end passage 14.

[0041] A booster 15, a second shut-off valve 16, a third hot-end passage 3, and a membrane separation module 17 are sequentially connected along the ambient air flow direction. The non-permeable side outlet of the membrane separation module 17 is connected to the top liquid inlet of the distillation column 18 through the first hot-end passage 7, and at the same time, it is connected to the bottom air inlet of the distillation column 18 through the first shut-off valve 19 and the second hot-end passage 8. The permeable side outlet of the membrane separation module 17 is connected to the inlet of the fourth hot-end passage 4, and the outlet of the fourth hot-end passage 4 is connected to the fresh air system.

[0042] It also includes a liquid nitrogen tank 20, through which liquid nitrogen discharged from the liquid nitrogen tank 20 flows sequentially through the third cold end passage 12 and the fourth cold end passage 6 via the pressure reducing valve 21, and then merges with the gas at the non-permeable side outlet of the membrane separation module 17 to provide raw materials and cooling capacity for the distillation column 18.

[0043] The bottom drain of the distillation column 18 is connected in sequence to the first cold end passage 11 and the second cold end passage 5 through the first throttle valve 22, and the discharged dry nitrogen is used as the instrument gas of the system.

[0044] The nitrogen gas discharged from the top of the distillation column 18 is divided into two paths. One path flows through the third shut-off valve 23 and then through the fifth hot end passage 9, and then returns to the top of the distillation column 18 as reflux liquid through the second throttle valve 24. The other path flows through the fourth shut-off valve 25 and then through the fifth cold end passage 13, and then produces the first ultra-high purity nitrogen gas. The nitrogen gas discharged from the top of the distillation column 18 is divided into two paths after passing through the fifth shut-off valve 26. One path flows through the sixth shut-off valve 27 and then through the sixth cold end passage 14, and then produces the second ultra-high purity nitrogen gas. The other path flows through the sixth hot end passage 10 and then returns to the top of the distillation column 18 as reflux liquid through the third throttle valve 28.

[0045] Example 2 This embodiment provides a method for producing ultra-high purity nitrogen gas. The method is operated using the ultra-high purity nitrogen gas production apparatus system provided in Embodiment 1, and specifically includes the following steps: Ambient air with a particle size of 0.005 μm, a temperature of 35°C, and a pressure of 1 atm is sequentially pressurized and subjected to a first heat exchange, followed by membrane separation to obtain permeate-side gas and non-permeate-side gas. The permeate-side gas is then used as fresh air for the system after a second heat exchange, while the non-permeate-side gas is split into two streams: one stream forms liquid nitrogen after a third heat exchange, and the other stream forms cold nitrogen after a fourth heat exchange. The volumetric flow rate of the liquid nitrogen is 15 Nm³. 3 / h, the volumetric flow rate of cold nitrogen is 230 Nm 3 / h.

[0046] Liquid nitrogen and cold nitrogen are distilled to obtain top nitrogen inside the column, top nitrogen outside the column, and liquid nitrogen at the bottom of the column. The top nitrogen inside the column is divided into two streams. One stream is returned to the distillation as reflux after passing through the fifth heat exchange, and the other stream is returned to the distillation as ultra-high purity nitrogen with a nitrogen gas fraction of 99.9999999% and an argon gas fraction of 0.6 ppb after passing through the sixth heat exchange. The top nitrogen outside the column is divided into two streams. One stream is returned to the distillation as ultra-high purity nitrogen with a nitrogen gas fraction of 99.9999995% after passing through the seventh heat exchange, and the other stream is returned to the distillation as reflux after passing through the eighth heat exchange. The liquid nitrogen at the bottom of the column is then passed through the ninth and tenth heat exchanges to discharge dry nitrogen gas, which is used as instrument gas in the system. Liquid nitrogen is additionally provided as raw material and cooling in the distillation process. The liquid nitrogen is then passed through the eleventh and twelfth heat exchanges and merged with the gas on the non-permeable side.

[0047] When operating the ultra-high purity nitrogen production apparatus system provided in Example 1 using the ultra-high purity nitrogen production method described above, the specific process is as follows: In this embodiment, the feed gas is ambient air with a particle size of 0.005 μm, a temperature of 35°C, and a pressure of 1 atm. It is first pressurized to 5.5 atm by booster 15, with an outlet gas temperature of 176.4°C. After heat exchange through the third hot-end passage 3 of the secondary heat exchanger 1, the temperature drops to 43.1°C, and then it passes through the membrane separation module 17. The membrane separation module 17 is a low-temperature nitrogen-generating membrane. Its permeate-side outlet gas contains 32.7 mol% O2, 2.1 mol% Ar, and 65.2 mol% N2. This portion of the permeate-side outlet gas, after heat exchange through the fourth hot-end passage 4 of the secondary heat exchanger 1, can be used as a fresh air system in equipment workshops and factories to maintain fresh and circulating air within the facility.

[0048] The non-permeable side outlet gas of membrane separation module 17 has a N2 molar fraction of 98.3 mol%, an O2 molar fraction of 1.5 mol%, and an Ar molar fraction of 0.2 mol%. This portion of the non-permeable side outlet gas is divided into two nitrogen streams. After being cooled by the main heat exchanger 2, it becomes cold nitrogen and liquid nitrogen, serving as the liquid and gas phases in the cryogenic nitrogen distillation process. Specifically, the outlet of the first hot end passage 7 of the main heat exchanger 2 is saturated liquid nitrogen at a pressure of 5.1 ata, which enters the top inlet of the distillation column 18; the outlet of the second hot end passage 8 of the main heat exchanger 2 is cold nitrogen, which enters the bottom inlet of the distillation column 18. The volumetric flow rates of the cold nitrogen and liquid nitrogen are adjusted by the first shut-off valve 19, thereby changing the gas-liquid load of the distillation column 18, i.e., optimizing the column separation work in real time.

[0049] The liquid nitrogen discharged from the liquid nitrogen tank 20 flows through the pressure reducing valve 21 through the third cold end passage 12 of the main heat exchanger 2 and the fourth cold end passage 6 of the secondary heat exchanger 1 in sequence. After heat exchange, it merges with the gas at the non-permeable side outlet of the membrane separation module 17 and serves as a cold source to provide raw materials and cooling capacity for the distillation column 18.

[0050] Liquid nitrogen enters the top inlet of the distillation column 18 through the first hot end passage 7 of the main heat exchanger 2 for distillation, while cold nitrogen enters the bottom inlet of the distillation column 18 through the second hot end passage 8 of the main heat exchanger 2 for distillation. Inside the distillation column 18, as the vapor rises and comes into countercurrent contact with the liquid, the concentrations of oxygen and argon, as heavy components, gradually increase at the bottom of the column, while nitrogen, as a light component, is enriched at the top of the column.

[0051] The liquid nitrogen at the bottom of the distillation column 18 passes through the first throttle valve 22 and then exchanges heat sequentially through the first cold end passage 11 of the main heat exchanger 2 and the second cold end passage 5 of the secondary heat exchanger 1, to obtain dry nitrogen gas with a N2 mole fraction of 83.4 mol% and a total O2+Ar mole fraction of 16.6 mol%, which is used as the instrument gas for the system.

[0052] After distillation in distillation column 18, the nitrogen gas discharged from the top of the structured packing is divided into two streams. One stream flows through the fifth hot end passage 9 and then returns to the top of distillation column 18 as reflux liquid through the second throttle valve 24. The other stream flows through the fourth shut-off valve 25 and the fifth cold end passage 13, producing a first ultra-high purity nitrogen gas with a nitrogen gas integral of 99.9999999% and an argon gas integral of 0.6 ppb.

[0053] The nitrogen gas discharged from the top of the distillation column 18 after distillation is divided into two streams after passing through the fifth shut-off valve 26. One stream flows through the sixth cold end passage 14 of the main heat exchanger 2 through the sixth shut-off valve 27 to obtain the second ultra-high purity nitrogen gas with a nitrogen gas integral of 99.9999995%. The other stream of nitrogen gas flows through the sixth hot end passage 10 of the main heat exchanger 2 for heat exchange and liquefaction, and then returns to the top of the distillation column 18 as reflux liquid through the third throttle valve 28.

[0054] Example 3 This embodiment provides a method for producing ultra-high purity nitrogen. The difference from Embodiment 2 is that the volumetric flow rate of the liquid nitrogen is adjusted to 20 Nm³. 3 / h, the volumetric flow rate of cold nitrogen was adjusted to 210 Nm 3 / h, the rest are the same as in Example 2.

[0055] In this embodiment, the nitrogen gas integral of the first ultra-high purity nitrogen gas is 99.99999995%, and the nitrogen gas integral of the second ultra-high purity nitrogen gas is 99.9999995%.

[0056] Example 4 This embodiment provides a method for producing ultra-high purity nitrogen. The difference from Embodiment 2 is that the volumetric flow rate of the liquid nitrogen is adjusted to 10 Nm³. 3 / h, the volumetric flow rate of cold nitrogen was adjusted to 230 Nm 3 / h, the rest are the same as in Example 2.

[0057] In this embodiment, due to the low volumetric flow rate of liquid nitrogen and the high volumetric flow rate of cold nitrogen, the volumetric purity of the product nitrogen will decrease, resulting in a reduction in the nitrogen gas integral of the first ultra-high purity nitrogen gas to 99.9999995% and a reduction in the nitrogen gas integral of the second ultra-high purity nitrogen gas to 99.999999%.

[0058] Example 5 This embodiment provides a method for producing ultra-high purity nitrogen. The difference from Embodiment 2 is that the volumetric flow rate of the liquid nitrogen is adjusted to 30 Nm³. 3 / h, the volumetric flow rate of cold nitrogen was adjusted to 210 Nm 3 / h, the rest are the same as in Example 2.

[0059] In this embodiment, due to the high volumetric flow rate of liquid nitrogen and the low volumetric flow rate of cold nitrogen, the volumetric purity of the second ultra-high purity nitrogen gas is improved, but the yield decreases. The nitrogen gas fraction of the first ultra-high purity nitrogen gas is 99.99999995%, and the nitrogen gas fraction of the second ultra-high purity nitrogen gas increases to 99.9999999%.

[0060] In summary, the ultra-high purity nitrogen production system provided by this invention uses ambient air as raw material. First, it enriches nitrogen by a volume concentration greater than 98% through a membrane separation module. After heat exchange on the permeate side, the nitrogen can be used in the fresh air system of workshops and factories to maintain fresh and circulating air. Then, it is divided into two streams of nitrogen, which are cooled by system heat exchange to become cold nitrogen and liquid nitrogen, serving as the liquid and gas phases in the cryogenic nitrogen distillation process. The volumetric flow rates of the cold nitrogen and liquid nitrogen are adjusted by a first shut-off valve, thereby changing the gas-liquid load of the distillation column and optimizing the column separation work in real time. Simultaneously, it can produce two ultra-high purity nitrogen products with different purities: the first ultra-high purity nitrogen has a nitrogen volume fraction of up to 99.9999999% and an argon volume fraction ≤0.6 ppb; the second ultra-high purity nitrogen has a nitrogen volume fraction of up to 99.9999995%, improving the product compliance rate.

[0061] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A production system for ultra-high purity nitrogen, characterized in that, The system includes a secondary heat exchanger and a membrane separation module connected sequentially along the ambient air flow direction. The non-permeable side outlet of the membrane separation module is connected to the top liquid inlet of the distillation column through the first hot end passage of the main heat exchanger, and simultaneously connected to the bottom air inlet of the distillation column through the second hot end passage of the main heat exchanger via a first shut-off valve. The permeable side outlet of the membrane separation module is connected to the secondary heat exchanger. The system also includes a liquid nitrogen storage tank for providing feedstock and cooling capacity to the distillation column. The nitrogen gas discharged from the top of the distillation column is divided into two streams. One stream flows through the main heat exchanger and returns to the top of the distillation column as reflux liquid. The other stream flows through the main heat exchanger and produces the first ultra-high purity nitrogen gas. The nitrogen gas discharged from the top of the distillation column is also divided into two streams. One stream flows through the main heat exchanger and produces the second ultra-high purity nitrogen gas. The other stream flows through the main heat exchanger and returns to the top of the distillation column as reflux liquid.

2. The production apparatus system according to claim 1, characterized in that, The secondary heat exchanger is provided with a third hot end passage. The inlet of the third hot end passage is provided with a booster and a second shut-off valve in sequence along the direction of ambient air flow. The outlet of the third hot end passage is connected to the membrane separation module. The secondary heat exchanger is provided with a fourth hot end passage. The inlet of the fourth hot end passage is connected to the permeate side outlet of the membrane separation module, and the outlet of the fourth hot end passage is connected to a fresh air system.

3. The production apparatus system according to claim 1, characterized in that, The main heat exchanger is provided with a first cold end passage, and the secondary heat exchanger is provided with a second cold end passage. The bottom drain port of the distillation column is connected to the first cold end passage and the second cold end passage in sequence through a first throttle valve. The discharged dry nitrogen is used as the system instrument gas. The main heat exchanger is provided with a third cold end passage, and the secondary heat exchanger is provided with a fourth cold end passage. The liquid nitrogen discharged from the liquid nitrogen storage tank flows through the third cold end passage and the fourth cold end passage in sequence through the pressure reducing valve, and then merges with the gas at the non-permeable side outlet of the membrane separation module.

4. The production apparatus system according to claim 1, characterized in that, The main heat exchanger is provided with a fifth hot end passage. The nitrogen gas discharged from the top of the distillation column flows through the fifth hot end passage through the third shut-off valve, and then returns to the top of the distillation column as reflux liquid through the second throttle valve. The main heat exchanger is provided with a fifth cold end passage. The nitrogen gas discharged from the top of the distillation column flows through the fifth cold end passage via the fourth shut-off valve and then produces the first ultra-high purity nitrogen gas.

5. The production apparatus system according to claim 1, characterized in that, The main heat exchanger is provided with a sixth cold end passage. The nitrogen gas discharged from the top of the distillation column flows through the sixth cold end passage via the fifth and sixth shut-off valves and then produces the second ultra-high purity nitrogen gas. The main heat exchanger is provided with a sixth hot end passage. The nitrogen gas discharged from the top of the distillation column flows through the fifth shut-off valve through the sixth hot end passage, and then returns to the top of the distillation column as reflux liquid through the third throttle valve.

6. A method for producing ultra-high purity nitrogen, characterized in that, The production method is operated by the ultra-high purity nitrogen production device system according to any one of claims 1-5, and specifically includes the following steps: After the ambient air undergoes the first heat exchange, it is separated by membrane separation to obtain permeate-side gas and non-permeate-side gas. The permeate-side gas is then used as fresh air for the fresh air system after the second heat exchange, while the non-permeate-side gas is divided into two streams. One stream is converted into liquid nitrogen after the third heat exchange, and the other stream is converted into cold nitrogen after the fourth heat exchange. Liquid nitrogen and cold nitrogen are distilled to obtain nitrogen gas at the top of the column and nitrogen gas at the top of the column. The nitrogen gas at the top of the column is divided into two streams. One stream is returned to the distillation as reflux liquid after the fifth heat exchange, and the other stream is returned to the distillation as ultra-high purity nitrogen gas after the sixth heat exchange. The nitrogen gas at the top of the column is divided into two streams. One stream is returned to the distillation as reflux liquid after the seventh heat exchange, and the other stream is returned to the distillation as reflux liquid after the eighth heat exchange.

7. The production method according to claim 6, characterized in that, After distillation, liquid nitrogen is obtained from the bottom of the column. The liquid nitrogen from the bottom of the column passes through the ninth and tenth heat exchangers in sequence, and dry nitrogen gas is discharged as instrument gas for the system. Liquid nitrogen is additionally provided as raw material and cooling in the distillation process. The liquid nitrogen passes through the eleventh and twelfth heat exchangers in sequence and merges with the gas on the non-permeable side.

8. The production method according to claim 6, characterized in that, The ambient air contains particles with a diameter ≤0.005μm, a temperature of 33-37℃, and a pressure of 1atm. The ambient air is pressurized before the first heat exchange.

9. The production method according to claim 6, characterized in that, The volumetric flow rate of the liquid nitrogen is 15-20 Nm³. 3 The volumetric flow rate of cold nitrogen is 210-230 Nm³ / h. 3 / h.

10. The production method according to claim 6, characterized in that, The volume fraction of nitrogen in the first ultra-high purity nitrogen gas is ≥99.9999999%, and the volume fraction of argon gas is ≤0.6ppb; The volume fraction of nitrogen in the second ultra-high purity nitrogen gas is ≥99.9999995%.

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