Nitrogen trapping method based on high-purity dry ice trapping system

Abstract

The invention discloses an energy-saving nitrogen trapping method for tail gas treatment based on a high-purity dry ice trapping method. According to the method, high-purity dry ice trapping tail gas is pretreated through a multi-layer filtering assembly and a modified activated carbon fiber adsorbent, the impurity content is reduced, and equipment loss is reduced. Afterwards, the tail gas is pressurized through a multi-stage compressor, and compression and cryogenic energy consumption is reduced through an efficient intercooler and a heat recovery device. In the cryogenic separation stage, separation of nitrogen and impurities is achieved through accurate temperature and pressure control and efficient structured packing in the rectifying tower. In the nitrogen purification stage, the nitrogen purity is improved to 99.99%-99.999% based on a pressure swing adsorption technology of a special modified molecular sieve, and the requirements of high-end industries are met. And in the energy recovery and cyclic utilization stage, cold energy and pressure energy of high-boiling-point impurity liquid and desorption impurity gas are recovered, waste heat utilization of circulating cooling water is combined, the recovered energy accounts for 20%-30% of the total energy consumption of the system, and the operation cost is remarkably reduced. According to the device and the method, the energy-saving efficiency is greatly improved while high-purity nitrogen trapping is realized, and the device and the method have remarkable economic and environment-friendly benefits.

Description

Technical Field

[0001] The invention relates to the technical field of gas separation and purification, and in particular to a nitrogen capture method based on a high-purity dry ice capture system. Background Art

[0002] In the industrial field, high-purity dry ice is an important industrial raw material, and the tail gas generated in its production process contains a large amount of recyclable nitrogen. However, traditional nitrogen capture technology has many shortcomings. Taking the common cryogenic separation method as an example, the mixed gas needs to be cooled to an extremely low temperature. This process relies heavily on high-power refrigeration equipment and compressors, consumes a lot of electricity, and causes the equipment operation cost to remain high. According to statistics, the traditional cryogenic method consumes 3-5kW・h of energy to produce 1 cubic meter of nitrogen with a purity of 99%. Although the pressure swing adsorption method is relatively simple to operate, frequent pressure switching and gas desorption operations in the adsorbent regeneration link will also cause significant energy loss. In terms of purity standards, with the rapid development of industries such as electronic chip manufacturing and high-end chemical synthesis, the requirements for nitrogen purity have risen to 99.999% or even higher. However, the purity of nitrogen produced by traditional nitrogen capture methods is mostly in the range of 99% to 99.9%, which is difficult to meet the stringent requirements of these high-end industries. In addition, the composition of high-purity dry ice capture tail gas is complex, including residual carbon dioxide, water and other impurities, and existing treatment technologies have failed to fully consider these characteristics. Impurities in the tail gas will not only interfere with the nitrogen capture efficiency, but may also cause corrosion to key components of the equipment, increase the frequency and cost of equipment maintenance, and reduce the stability and reliability of the production system. Based on this, it is urgent to develop a capture method that takes into account both high efficiency and energy saving and high-purity nitrogen output. Summary of the invention

[0003] The present invention aims to provide an energy-saving nitrogen capture method based on tail gas treatment of high-purity dry ice capture method, so as to overcome the problems of high energy consumption, low nitrogen purity and improper tail gas treatment in the prior art. Through innovative process design, selection of new materials and equipment, an energy-saving and efficient nitrogen capture process is achieved, while ensuring that the output nitrogen meets high purity standards. Technical Solution

[0004] Exhaust pretreatment stage: high-purity dry ice captures the exhaust gas and introduces it into the pretreatment device, which is equipped with multiple layers of filter components with different functions. First, a mechanical filter layer with a pore size of 1-3μm is used to effectively intercept solid dry ice particles and large-particle impurities entrained in the exhaust gas to prevent them from entering the subsequent treatment process and causing wear and tear on the equipment. Subsequently, the exhaust gas enters the adsorption bed filled with specially modified activated carbon fiber adsorbent. In the temperature range of 15-25°C, the adsorbent selectively adsorbs moisture, residual carbon dioxide and some volatile organic compounds in the exhaust gas with its unique microporous structure and surface chemical properties. After this treatment, the impurity content of the exhaust gas is greatly reduced, meeting the requirements of subsequent treatment, greatly reducing the risk of corrosion of equipment by impurities, and reducing maintenance costs.

[0005] Compression and initial heat exchange stage: The pretreated tail gas enters the multi-stage compressor and is gradually pressurized to 1.5-2.5MPa. Between each stage of compression, a plate-type high-efficiency intercooler is installed, with a heat transfer coefficient of up to 800-1200W / (m²・K). The compressed gas temperature is adjusted to 30-40℃ using circulating cooling water, effectively reducing the compression power consumption. The gas after initial cooling immediately enters the heat recovery device and performs countercurrent heat exchange with the low-temperature gas refluxed from the cryogenic separation stage. In this process, the gas temperature further drops by 10-15℃, realizing the effective recovery of low-temperature energy, reducing the burden on the cryogenic stage and reducing overall energy consumption. Cryogenic separation stage: The gas after the initial heat exchange enters the cryogenic device, first fully exchanges heat with the reflux low-temperature nitrogen and exhaust gas through the main heat exchanger, and quickly cools down to a temperature close to the dew point. Then it enters the distillation tower. Under the conditions of 0.4-0.7MPa top pressure and 75-80K bottom temperature, multiple gas-liquid exchange and distillation operations are carried out based on the difference in boiling points between nitrogen and impurity gases such as argon and oxygen. The distillation tower uses structured packing with a specific surface area of ​​350-500m² / m³. Its excellent liquid distribution performance promotes full contact between gas and liquid, significantly improves distillation efficiency, reduces reflux ratio, and reduces energy consumption. Finally, crude nitrogen is enriched at the top of the tower, and the bottom of the tower is a high-boiling impurity liquid. Nitrogen purification stage: The crude nitrogen at the top of the tower is introduced into a purification device based on molecular sieve pressure swing adsorption. The molecular sieve modified by a special formula has a stronger adsorption selectivity for trace impurities in nitrogen. Under the temperature of -15- -5℃ and the pressure environment of 0.8-1.0MPa, the impurities in the crude nitrogen are deeply removed through the adsorption of the adsorption bed. The adsorption tower adopts a double-tower alternating operation mode. According to the actual processing gas volume and nitrogen purity requirements, the switching time (1-3 hours) is dynamically adjusted to ensure the continuity of the purification process, improve equipment utilization, and steadily increase the nitrogen purity to 99.99%-99.999%, meeting the strict requirements of high-end industries for nitrogen purity. Energy recovery and recycling stage: The high-boiling impurity liquid discharged from the bottom of the distillation tower and the impurity gas desorbed by the purification device enter the energy recovery device. The new high-efficiency turbine expander in the device has an isentropic efficiency of 82%-86%, which can effectively recover the pressure energy of the impurity gas and convert it into mechanical energy for auxiliary compression or power generation. At the same time, the brazed plate high-efficiency heat exchanger (heat transfer coefficient 1500-2000W / (m²・K)) ​​realizes efficient cold transfer and pre-cools the raw gas entering the cryogenic device. In addition, the system's circulating cooling water is used to recover waste heat and is transported to the pretreatment stage or other links in the plant with low-temperature heat source requirements as needed through an intelligent heat distribution device. It has been calculated that the energy recovered in this stage accounts for 20% to 30% of the total energy consumption of the system, significantly improving energy utilization efficiency and reducing operating costs. In the exhaust gas pretreatment stage, the mechanical filter layer adopts an automatic vibration cleaning structure. When the pressure difference on both sides of the filter exceeds the set value of 0.03-0.06MPa, the vibration device is automatically started, and high-frequency vibration shakes off the trapped impurities to the collection tank, and regular cleaning is carried out to reduce the frequency of manual maintenance and extend the service life of the filter. The adsorption bed is equipped with an intelligent regeneration system. When the adsorption capacity of the adsorbent reaches the saturation threshold of 80%-85%, it automatically switches to the regeneration mode, using 100-120℃ hot air to purge for 0.5-1 hour, combined with pressure reduction desorption, to restore the activity of the adsorbent, ensure the stability of the pretreatment effect, and reduce the regeneration energy consumption. During the compression and initial heat exchange stage, the multi-stage compressor is driven by a new high-efficiency energy-saving motor with an efficiency of over 92% to 95%, and is equipped with an intelligent variable frequency control system. The system accurately adjusts the operating frequency and number of stages of the compressor according to the intake air flow, pressure and subsequent processing requirements to ensure that it is always in the efficient operating range. The circulating cooling water system of the intercooler, with the help of an intelligent temperature control device, automatically adjusts the cooling water flow and temperature based on the temperature feedback of the cooled gas, avoids excessive consumption of cooling water, and reduces the energy consumption of the cooling system. The heat recovery device increases the heat exchange efficiency to 85%-90% by optimizing the internal flow channel and adding spoiler elements, thereby enhancing the cold recovery effect. In the cryogenic separation stage, the distillation tower uses an advanced distributed control system (DCS) combined with real-time online analysis and detection technology to monitor and precisely control key parameters such as the temperature, pressure, component content, feed flow rate, and reflux ratio at the top and bottom of the tower. By constructing a dynamic mathematical model of the distillation tower and using a model predictive control algorithm, the system change trend is predicted in advance and the operating variables are automatically adjusted to ensure that the distillation tower can operate stably and efficiently under different operating conditions. While ensuring the purity of nitrogen, energy consumption is further reduced and product recovery rate is increased. At the same time, new high-efficiency insulation materials with a thermal conductivity of less than 0.02-0.03W / (m・K) are used to optimize the insulation structure of the distillation tower and reduce heat loss and cold loss. During the nitrogen purification stage, a temperature and pressure sensor matrix is ​​set inside the adsorption bed of the molecular sieve adsorption purification device to monitor the changes in temperature and pressure distribution in the bed during the adsorption process in real time. Once an abnormal temperature rise or pressure fluctuation outside the allowable range is detected in the bed, the system will automatically adjust the adsorption and regeneration operating parameters, such as adsorption time, desorption pressure and heat purge temperature, to ensure the safety and stability of the adsorption process, avoid the performance degradation of the molecular sieve due to local overheating or pressure shock, extend the service life of the molecular sieve, and reduce operating costs. At the outlet of the purification device, a high-precision online purity analyzer is installed to monitor the purity of nitrogen in real time. When the purity is lower than the set value of 99.99%, the standby purification process is automatically started or the operating parameters of the adsorption tower are adjusted to ensure that the output nitrogen always maintains high purity. During the energy recovery and recycling stage, the waste heat recovery system of the circulating cooling water is equipped with an intelligent heat distribution device, which automatically adjusts the waste heat distribution ratio according to the heat source requirements of different links in the plant to maximize the utilization of waste heat. The energy storage device adopts an advanced phase change material cold and heat storage system, which has a high energy storage density and good stability, ensuring the effective storage and release of energy. The entire nitrogen capture system is equipped with an intelligent monitoring and management platform, which uses a sensor network to collect parameters such as temperature, pressure, flow, purity, etc. of key parts of the system in real time and transmits them to the central processing unit. The central processing unit uses big data analysis and artificial intelligence algorithms to deeply mine and analyze the collected data, realize early warning and diagnosis of equipment failures, and real-time evaluation and optimization of system performance. At the same time, through the remote communication module, operators can monitor and operate the system in real time at the remote terminal, realize unmanned or less-manned operation, reduce labor costs, and improve the reliability and management efficiency of system operation. In addition, the intelligent monitoring and management platform has a data interaction interface with other production management systems of the enterprise, which can realize the sharing and collaborative management of production data. During the entire nitrogen capture process, the waste gas and waste liquid generated are treated in an environmentally friendly manner. The waste gas discharged from the energy recovery device is deeply purified and uses catalytic combustion, adsorption and desorption technologies to make its pollutant content meet the strict national or local emission standards before being discharged. The high-boiling point impurity liquid discharged from the bottom of the distillation tower and the impurity liquid desorbed by the adsorption purification device are collected and classified, and the useful components such as rare gases and organic solvents are recovered through physical and chemical methods such as distillation and extraction. The parts that cannot be recovered are harmlessly treated to reduce the impact on the environment. At the same time, through resource recycling, additional economic benefits are created to further reduce the overall operating costs. Beneficial Effects Significant energy-saving effect: reduce equipment loss and maintenance energy consumption through tail gas pretreatment; optimize multi-stage compression and intermediate cooling processes, combine heat recovery devices to reduce energy consumption in compression and cryogenic stages; in the energy recovery and recycling stage, recycle the cold capacity, pressure energy of impurity gases and waste heat of circulating cooling water, so that the system energy consumption is reduced by 20%-30% compared with traditional methods, greatly saving energy and significantly reducing operating costs High-purity nitrogen output: The synergistic effect of cryogenic separation and special modified molecular sieve pressure swing adsorption purification can stably produce nitrogen with a purity of 99.99%-99.999%, which fully meets the production needs of industries such as electronics and chemical industry that have extremely high requirements for nitrogen purity.

[0006] Improved equipment stability and lifespan: Pretreatment effectively reduces the corrosion of impurities on equipment; the intelligent monitoring and management platform enables early warning and diagnosis of equipment failures; the sensor matrix of the adsorption bed ensures the stability of the adsorption process. This multi-pronged approach significantly extends the service life of the equipment and reduces the cost of equipment replacement. Environmental protection and economic benefits are achieved: environmentally friendly treatment of waste gas and waste liquid reduces negative environmental impact; additional economic benefits are created through resource recycling and utilization, further reducing overall operating costs, and achieving a win-win situation for environmental protection and economy. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 For process flow chart and equipment structure diagram, please refer to the attached drawings DETAILED DESCRIPTION

[0007] Example 1 Tail gas pretreatment: High-purity dry ice captures the tail gas and introduces it into the pretreatment device. The mechanical filter layer has a pore size of 2μm, which effectively removes solid dry ice particles and large-size impurities in the tail gas. The activated carbon fiber adsorbent in the adsorption bed adsorbs moisture, residual carbon dioxide and volatile organic matter in the tail gas at 20°C. When the adsorption capacity of the adsorbent reaches 82%, the intelligent regeneration system is started, and 110°C hot air is used for 1 hour, and the pressure is reduced to desorb and restore the activity of the adsorbent. When the pressure difference reaches 0.04MPa, the mechanical filter layer automatically vibrates to clean the dust, and the impurities fall into the collection tank and are cleaned regularly. After pretreatment, the impurity content in the tail gas is reduced to less than 10% of the initial level, effectively reducing the impact on subsequent equipment. Compression and preliminary heat exchange: The pretreated exhaust gas enters a multi-stage compressor, which is driven by an energy-efficient motor with an efficiency of 93%, and the final pressure is increased to 2MPa. The plate-type intercooler between each stage of compression has a heat transfer coefficient of 1000W / (m²・K), which reduces the gas temperature to 35°C. The gas after preliminary cooling enters the countercurrent heat recovery device, where it exchanges heat with the reflux low-temperature gas, reducing the temperature by 12°C. The intelligent frequency conversion control system of the compressor accurately adjusts the operating frequency and number of stages according to the intake air flow and subsequent processing requirements, and always maintains efficient operation. The circulating cooling water system of the intercooler automatically adjusts the cooling water flow and temperature according to the temperature of the cooled gas through an intelligent temperature control device. The energy consumption at this stage is reduced by about 15% compared to traditional compression methods.

[0008] Cryogenic separation: The gas after the initial heat exchange enters the cryogenic device, and after sufficient heat exchange with the reflux gas through the main heat exchanger, it enters the distillation tower. The top pressure of the distillation tower is controlled to 0.5MPa, the bottom temperature is 78K, and the structured packing with a specific surface area of ​​400m² / m³ is used. The distillation tower is precisely controlled by the distributed control system (DCS) and real-time online analysis and detection technology. According to the model predictive control algorithm, the operating variables such as feed position and reflux ratio are automatically adjusted to ensure the efficient and stable operation of the distillation tower. The distillation tower adopts new high-efficiency insulation materials with a thermal conductivity of 0.025W / (m・K) to reduce heat loss. Compared with traditional distillation towers, the distillation tower reduces energy consumption by about 20% and increases nitrogen recovery rate by 5%. Nitrogen purification: The crude nitrogen obtained from the top of the tower enters the purification device, and the modified molecular sieve in the adsorption tower is adsorbed and purified at a temperature of -10°C and a pressure of 0.9MPa. The adsorption tower adopts a double-tower alternating operation mode, and the switching time interval is 2 hours. The temperature and pressure sensor matrix inside the adsorption bed monitors the adsorption process in real time. When temperature abnormalities or pressure fluctuations occur, the adsorption and regeneration operating parameters are automatically adjusted. The high-precision online purity analyzer at the outlet of the purification device monitors the nitrogen purity in real time. When the purity is lower than 99.99%, the backup purification process is automatically started, and the final nitrogen purity reaches 99.995%. During the entire purification process, the service life of the molecular sieve is extended by about 20% compared to before optimization. Energy recovery and recycling: The high-boiling impurity liquid discharged from the bottom of the distillation tower and the impurity gas desorbed from the purification device pass through the energy recovery device. Among them, the isentropic efficiency of the turbine expander is 83%, the heat transfer coefficient of the high-efficiency heat exchanger is 1800W / (m²・K), and the recovered energy accounts for 22% of the system energy consumption. The waste heat of the circulating cooling water is distributed to some heat source links in the pretreatment stage through an intelligent heat distribution device to realize waste heat utilization. The energy storage device uses a phase change material cold and heat storage system to store excess energy and balance the energy supply and demand of the system. According to actual operation calculations, energy recovery and recycling can save about 30 million yuan in electricity bills each year.

[0009] Tail gas pretreatment: The tail gas passes through the pretreatment device, the mechanical filter layer has a pore size of 3μm, and the adsorption bed is adsorbed at 25℃. The adsorbent saturation threshold is 84%, the hot air temperature during regeneration is 120℃, and the regeneration time is 1.2 hours. When the pressure difference of the mechanical filter layer reaches 0.05MPa, it automatically vibrates and cleans. After pretreatment, the impurity content of the tail gas is reduced to a negligible level, providing a high-quality gas source for subsequent treatment. Compression and preliminary heat exchange: The exhaust gas enters the multi-stage compressor, the motor efficiency is 94%, and the pressure is increased to 2.2MPa. The heat exchange coefficient of the intercooler is 1100W / (m²・K), which reduces the gas temperature to 38℃, and the heat recovery device reduces the gas temperature by another 13℃. The intelligent frequency conversion control system and temperature control device are precisely regulated, and the energy consumption is significantly reduced, which is about 18% lower than the traditional method.

[0010] Cryogenic separation: The gas enters the cryogenic device and distillation tower, with a top pressure of 0.6MPa and a bottom temperature of 80K. A structured packing with a specific surface area of ​​450m² / m³ is used. DCS and real-time monitoring technology ensure the efficient operation of the distillation tower, reducing energy consumption by 22% and further increasing the nitrogen recovery rate to 80%. Nitrogen purification: Crude nitrogen enters the purification device, and the modified molecular sieve works at -8℃ and 1.0MPa. The double tower switching time is 3 hours. The sensor matrix and purity analyzer work together to ensure that the nitrogen purity is stable at 99.993%, and the molecular sieve has stable performance and extended life. Energy recovery and recycling: The isentropic efficiency of the turbine expander in the energy recovery device is 84%, the heat transfer coefficient of the heat exchanger is 1900W / (m²・K), and the recovered energy accounts for 25% of the system energy consumption. The waste heat is reasonably distributed, the energy storage is stable, and the cost is saved by 30 million yuan each year, with outstanding environmental protection and economic benefits.

Claims

1. A method for capturing nitrogen in tail gas after being captured by high-purity dry ice, characterized in that: The following steps are involved: Tail gas pretreatment stage: The tail gas generated by the high-purity dry ice capture process is introduced into the pretreatment device, which is equipped with multiple layers of filter components with different functions. First, through the mechanical filtration layer, a filter with a pore size of X1μm - X2μm is used, with the X1 value range of 1-3μm and the X2 value range of 3-5μm, to remove the solid dry ice particles and large-size impurities entrained in the tail gas. Then the tail gas enters the adsorption bed, which is filled with specially modified activated carbon fiber adsorbents to adsorb and remove moisture, residual carbon dioxide and some volatile organic compounds in the tail gas. The adsorption temperature is controlled at Ta℃-Tb℃, with Ta ranging from 15-25℃ and Tb ranging from 25-35℃, so that the impurity content in the tail gas after pretreatment is reduced to a level that meets the requirements of subsequent treatment, reducing corrosion and pollution to subsequent equipment and reducing maintenance costs. Compression and preliminary heat exchange stage: The pre-treated tail gas enters the multi-stage compressor for gradual pressure increase, and the final pressure is increased to P1MPa - P2MPa, with P1 ranging from 1.5 to 2.5MPa and P2 ranging from 2.5 to 3.5MPa. Between each stage of compression, a high-efficiency intercooler is set. The cooler adopts a plate structure, and the heat transfer coefficient is greater than K1W / (㎡·K). The K1 range is 800-1200W / (㎡·K). The circulating cooling water is used to reduce the compressed gas temperature to Tc℃-Td℃, with Tc ranging from 30 to 40℃ and Td ranging from 40 to 50℃, to reduce compression power consumption. At the same time, the gas after preliminary cooling is introduced into the heat recovery device, and preliminary heat exchange is carried out with the low-temperature gas refluxed in the subsequent cryogenic separation stage, so as to recover part of the cold, and further reduce the gas temperature by ΔT1℃-ΔT2℃, ​​with the value range of ΔT1 being 10-15℃ and the value range of ΔT2 being 15-20℃, thereby reducing the energy consumption in the cryogenic stage. Cryogenic separation stage: The gas after preliminary heat exchange enters the cryogenic device, and firstly fully exchanges heat with the refluxed low-temperature nitrogen and exhaust gas through the main heat exchanger, so that the gas temperature is rapidly reduced to a temperature close to its dew point. Subsequently, it enters the distillation tower, in which the top pressure is controlled to be P3MPa-P4MPa, the value range of P3 is 0.4-0.7MPa, the value range of P4 is 0.7-1.0MPa, and the bottom temperature is T1K-T2K, the value range of T1 is 75-80K, and the value range of T2 is 80-85K. By utilizing the difference in boiling points between nitrogen and the remaining impurity gases (such as argon, oxygen, etc.), after multiple gas-liquid exchange and distillation processes, crude nitrogen is enriched at the top of the tower, and the bottom of the tower is a high-boiling point impurity liquid. The distillation tower uses structured packing, whose specific surface area is greater than S1㎡ / m³, and the S1 value range is 350-500㎡ / m³. It has good liquid distribution performance, improves distillation efficiency, reduces reflux ratio, and thus reduces energy consumption.Nitrogen purification stage: The crude nitrogen obtained from the top of the tower is introduced into the purification device, which adopts the pressure swing adsorption purification technology based on molecular sieve. The molecular sieve is modified by a special formula and has stronger adsorption selectivity for trace impurities in nitrogen. During the adsorption purification process, the temperature is controlled to be Te℃-Tf℃, the Te value range is -15 - -5℃, the Tf value range is -5 - 5℃, and the pressure is P5MPa -P6MPa, the P5 value range is 0.8 - 1.0MPa, and the P6 value range is 1.0 - 1.2MPa. Through the adsorption effect of the adsorption bed, the impurities in the crude nitrogen are further removed, so that the purity of nitrogen is increased to not less than C1%, and the C1 value range is 99.99 -99.999%, meeting the use demand of high-purity nitrogen. The adsorption tower adopts a double-tower alternating operation mode. When one adsorption tower is performing adsorption operation, the other adsorption tower is performing decompression desorption regeneration operation. The switching time interval is dynamically adjusted according to the actual processing gas volume and nitrogen purity requirements. The adjustment range is t1h-t2h, the t1 value range is 1-3h, and the t2 value range is 3-5h, which ensures the continuity of the nitrogen purification process and improves the equipment utilization rate. Energy recovery and recycling stage: The high-boiling point impurity liquid discharged from the bottom of the distillation tower and the impurity gas desorbed from the purification device pass through the energy recovery device, and use the cold and pressure energy they carry to pre-cool and assist in compressing the raw gas entering the deep cooling device through high-efficiency heat exchangers and expanders. The proportion of recovered energy to the energy consumption of the entire system is not less than R1%, and the R1 value range is 20-30%. At the same time, the waste heat of the circulating cooling water in the entire system is recovered to heat part of the heat source required in the pretreatment stage, or to supply to other links in the plant area with low-temperature heat source requirements, further improving energy utilization efficiency and reducing operating costs. In addition, an energy storage device is set up to store excess energy when the amount of energy recovered is greater than the system's immediate demand, and release it for use when the system's energy consumption peaks, thereby balancing the system's energy supply and demand.

2. The energy-saving nitrogen capture method according to claim 1, characterized in that: In the exhaust gas pretreatment stage, the mechanical filter layer in the multi-layer filter assembly adopts a structure design that can automatically vibrate and clean. When the pressure difference on both sides of the filter exceeds the set value ΔP1 MPa, the ΔP1 value range is 0.03-0.06MPa, and the vibration device is automatically started to shake off the impurities trapped on the filter through high-frequency vibration and drop them into the collection tank for regular cleaning. This design reduces the frequency of manual cleaning, extends the service life of the filter, and reduces maintenance costs. The adsorption bed is equipped with an intelligent regeneration system. When the adsorption capacity of the adsorbent reaches the saturation threshold value α1% -α2%, the value range of α1 is 80-85%, and the value range of α2 is 85 - 90%. It automatically switches to the regeneration mode and regenerates the adsorbent by combining hot air purging with pressure reduction desorption. The hot air temperature is Th℃ - Ti℃, the value range of Th is 100 - 120℃, the value range of Ti is 120 - 140℃, and the regeneration time is t3h - t4h, the value range of t3 is 0.5 - 1h, and the value range of t4 is 1 - 1.5h. The activity of the adsorbent is restored to ensure the stability of the pretreatment effect and reduce the regeneration energy consumption.

3. The energy-saving nitrogen capture method according to claim 1, characterized in that: In the compression and initial heat exchange stage, the multi-stage compressor is driven by a new high-efficiency and energy-saving motor with a motor efficiency greater than E1, and the E1 value range is 92-95%. It is also equipped with an intelligent variable frequency control system, which can accurately adjust the operating frequency and number of stages of the compressor according to the intake flow, pressure and real-time requirements of the subsequent processing links, so that the compressor always operates in the high-efficiency range and reduces the energy consumption of the compression process. The circulating cooling water system of the intercooler adopts an intelligent temperature control device, which automatically adjusts the flow and temperature of the cooling water according to the temperature feedback of the cooled gas, ensuring the cooling effect while avoiding excessive consumption of cooling water and reducing the energy consumption of the cooling system. The heat recovery device adopts the countercurrent heat exchange principle, optimizes the internal flow channel design, adds turbulent elements, and improves the heat exchange efficiency to above E2%. The E2 value range is 85-90%, which enhances the cold recovery effect.

4. The energy-saving nitrogen capture method according to claim 1, characterized in that: In the cryogenic separation stage, the operation process of the distillation tower adopts an advanced distributed control system (DCS), combined with real-time online analysis and detection technology, to monitor and accurately control the key parameters such as the temperature, pressure, component content, feed flow rate, reflux ratio, etc. at the top and bottom of the tower in real time. By establishing a dynamic mathematical model of the distillation tower and using the model predictive control algorithm, the system change trend is predicted in advance, and the operating variables are automatically adjusted to ensure that the distillation tower can operate stably and efficiently under different working conditions. Under the premise of ensuring the purity of nitrogen, energy consumption is further reduced and product recovery rate is improved. At the same time, the insulation structure of the distillation tower is optimized and designed, and a new high-efficiency insulation material is used, whose thermal conductivity is less than λ1W / (m·K), and the λ1 value range is 0.02-0.03W / (m·K), which reduces the heat loss of the distillation tower and reduces the loss of cold.

5. The energy-saving nitrogen capture method according to claim 1, characterized in that: During the nitrogen purification stage, a temperature and pressure sensor matrix is ​​set inside the adsorption bed of the molecular sieve adsorption purification device to monitor the temperature and pressure distribution changes in the bed during the adsorption process in real time. When it is detected that the temperature in the bed is abnormally high or the pressure fluctuation exceeds the allowable range, the system automatically adjusts the adsorption and regeneration operation parameters, such as adjusting the adsorption time, desorption pressure and heat purge temperature, to ensure the safety and stability of the adsorption process, avoid the performance degradation of the molecular sieve due to local overheating or pressure shock, extend the service life of the molecular sieve, and reduce operating costs. At the same time, a high-precision online purity analyzer is set at the outlet of the purification device to monitor the purity of nitrogen in real time. When the purity is lower than the set value C2%, the C2 value range is 99.99%, and the standby purification process is automatically started or the operating parameters of the adsorption tower are adjusted to ensure the high purity of the output nitrogen.

6. The energy-saving nitrogen capture method according to claim 1, characterized in that: In the energy recovery and recycling stage, the expander in the energy recovery device adopts a new high-efficiency turbine expander, whose isentropic efficiency is greater than E3%, [E3] ranges from 82-86%, effectively recovering the pressure energy of impurity gas and converting it into mechanical energy for auxiliary compression or power generation. The high-efficiency heat exchanger adopts a brazed plate heat exchanger with a compact structure and extremely high heat transfer efficiency. Its heat transfer coefficient is greater than K2W / (㎡·K), and the K2 value range is 1500-2000W / (㎡·K), ensuring efficient cold transfer during the energy recovery process. The waste heat recovery system of circulating cooling water is equipped with an intelligent heat distribution device, which automatically adjusts the waste heat distribution ratio according to the heat source requirements of different links in the plant to maximize the use of waste heat. The energy storage device adopts advanced cold and heat storage technology, such as phase change material cold and heat storage system, which has a high energy storage density and good stability, ensuring the effective storage and release of energy.

7. The energy-saving nitrogen capture method according to claim 1, characterized in that: The entire nitrogen capture system is equipped with an intelligent monitoring and management platform, which collects temperature, pressure, flow, purity and other parameters of key parts of the system in real time through a sensor network and transmits them to the central processing unit. The central processing unit uses big data analysis and artificial intelligence algorithms to conduct in-depth mining and analysis of the collected data, realize early warning and diagnosis of equipment failures, and real-time evaluation and optimization of system performance. At the same time, through the remote communication module, operators can monitor and operate the system in real time at the remote terminal, realize unmanned or less-manned operation, reduce labor costs, and improve the reliability and management efficiency of system operation. In addition, the intelligent monitoring and management platform has a data interaction interface with other production management systems of the enterprise, which can realize the sharing and collaborative management of production data.

8. The energy-saving nitrogen capture method according to claim 1, characterized in that: During the entire nitrogen capture process, the waste gas and waste liquid generated are treated in an environmentally friendly manner. The waste gas discharged from the energy recovery device is deeply purified and uses catalytic combustion, adsorption and desorption technologies to make its pollutant content meet the strict national or local emission standards before being discharged. The high-boiling point impurity liquid discharged from the bottom of the distillation tower and the impurity liquid desorbed by the adsorption purification device are collected and classified, and the useful components such as rare gases and organic solvents are recovered through physical and chemical methods such as distillation and extraction. The parts that cannot be recovered are harmlessly treated to reduce the impact on the environment. At the same time, through resource recycling, additional economic benefits are created to further reduce the overall operating costs.

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