Table of Content

12 October 2022, Volume 53 Issue 10

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DEVELOPMENT AND APPLICATION OF CORE TECHNOLOGY AND TECHNICAL ROUTE SUPPORTING CONTINUOUS UPGRADING OF GASOLINE QUALITY IN CHINA 2. Establishment, In-Depth Development and Industrialization of Stepwise Integrated Process for Olefin Reduction and Desulfurization of FCC Gasoline

2022, 53(10):  1-8. 

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It was found that the reduction of olefin and sulfur content in FCC gasoline would lead to a large loss of octane number and a sharp increase of production cost in the treatment of high-sulfur and high-olefin gasoline. The reason is that when the gasoline desulfurization ratio exceeds 97%, the olefin saturation rate will be increased sharply. In addition, it will also lead to an increase in hydrogen consumption and production cost. Therefore, a step-by-step integrated process for olefin reduction and desulfurization of FCC gasoline was established, and the olefin content reduction of FCC gasoline was realized by means of a catalytic cracking process consisting of a directional control of gasoline, which was enhanced by isomerization and selective hydrogen transfer reaction. The volume fraction of olefin and the mass fraction of sulfur in gasoline were reduced to less than 20% and 300 μg/g, respectively. The post-desulfurization process controls the desulfurization ratio of gasoline to be less than 97% and the olefin saturation ratio to be less than 20%, and the final octane number loss is greatly reduced, cleverly resolving the contradiction chain of desulfurization-olefin saturation-octane number loss-low cost production. The commercial application shows that the olefin saturation and octane number loss of the process are significantly reduced under the same desulfurization ratio, the low-cost production of China V and VI vehicle gasoline is realized, and it can provide strong support for the continuous upgrading of gasoline.

TECHNICAL UPGRADING OF SINOALKY SULFURIC ACID ALKYLATION UNIT

2022, 53(10):  9-15. 

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Based on the analysis of the first cycle operation of a SINOALKY sulfuric acid alkylation unit, some problems affecting the smooth operation of the plant were found. The problem of unstable pressure difference in the vaporizing section was eliminated by optimizing the packing for acid-hydrocarbon coalescence separation in the self-vaporizing acid-hydrocarbon separation tank. The acid carrying capacity of circulating hydrocarbon was greatly reduced by raising the position of the hydrocarbon extraction outlet of the self-vaporized acid hydrocarbon separation tank and increasing coarse packing, and the load of acid recovery pump was further reduced. The vibration of the acid circulating pump was effectively alleviated by adding the vortex breaker at the bottom of the self-vaporizing acid-hydrocarbon separation tank. By optimizing the heat exchange process to recover the heat of by-product condensed water, the 1.0 MPa steam consumption of the deisobutanizer was reduced by 1.5 t/h, and the circulating water consumption was reduced by 200 t/h. Through the process modification, the sulfur-containing gas in the fractionation unit was recovered for alkali washing treatment, which effectively eliminated the corrosion risk. By adding 1.0 MPa steam outlet pressure control valve, the steam pressure could be controlled smoothly, and the anti-interference ability of the device could be improved. By optimizing the regeneration process of the pre-hydrogenation catalyst, the online regeneration of the pre-hydrogenation catalyst could be ensured, and the long-term operation capacity of the unit could be improved.

ANALYSIS ON FLUIDIZATION CHARACTERISTICS OF CATALYST WITH POOR TRANSFER IN REGENERATOR STANDPIPE OF MTO UNIT

2022, 53(10):  16-20. 

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The down-flow part of the catalyst circulation loop in methanol to olefin (MTO) unit is the regeneratr standpipe, which is the precondition to ensure the normal operation of the MTO unit. It has become the bottleneck of the high efficient operation of the regenerator standpipe of a 0.60 Mt/a MTO unit that the catalyst transfer is not smooth. So the reasons of the catalyst transfer were analyzed by measuring the axial pressure distribution and process parameters of the regenerator standpipe. The results show that due to the degassing of the catalyst and the large gas bubbles, the flow patterns of transition filling flow, slug flow and dense-phase flow are formed from top to bottom in the fluidized state of catalyst transfer in the regenerator standpipe, leading to the content of catalyst and the amount of catalyst cycle fluctuating greatly. Based on the analysis results, some suggestions were proposed for structural modification of regenerator standpipe.

APPLICATION OF TECHNOLOGIES FOR REMOVING CARBON OXIDES TO PRODUCE FUEL CELL HYDROGEN WITH LOW LOSS RATE

2022, 53(10):  21-26. 

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In order to solve the shortage problem of hydrogen resource for fuel cells, a refining company expanded the application of low-temperature methanation technology to remove carbon oxides in industrial hydrogen to produce fuel cells hydrogen. The process is the first to produce fuel cell hydrogen in China, which solves the "bottleneck" of fuel cell hydrogen resources and achieves good social and economic benefits. Compared with the common pressure swing adsorption (PSA) method for fuel cell hydrogen production, the loss rate of hydrogen by applicating the low-temperature methanation technology can be reduced by about 20%, and the investment can be saved by 70%. The annual cost can be reduced by 4.9 million Yuan according to the scale of hydrogen production of 3 000 m³/h. Under the situation that the by-product hydrogen resource is insufficient and the hydrogen balance of the whole plant needs to be met by hydrogen production, it has great advantages and rationality to produce fuel cell hydrogen by using the industrial hydrogen produced by hydrogen production plant as raw material and using low-temperature methanation technology.

MOLECULAR DYNAMICS SIMULATION ON THE DIFFUSION BEHAVIOR OF FCC DIESEL FRACTIONS IN IONIC LIQUIDS

2022, 53(10):  27-33. 

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In order to study the diffusion behavior of hydrocarbon molecules from FCC diesel fractions in ionic liquid 1-hexyl-3-methylimidazolium tetrafluoroborate ([C6mim][BF4]), a molecular simulation method was used to study the diffusion behavior of hydrocarbon molecules in the blend model system of the hydrocarbons molecules and [C6mim][BF4]. The mean square displacement of different hydrocarbon molecules in the [C6mim][BF4] system were calculated, and the interactions between hydrocarbon molecules and [C6mim][BF4] were analyzed. The results show that saturated hydrocarbon molecules diffuse more easily in the [C6mim][BF4] system than aromatic hydrocarbon molecules, and the interaction between saturated hydrocarbons and [C6mim][BF4] is dominated by van der Waals interaction. As the number of aromatic rings increases, the electrostatic interaction between aromatic molecules and [C6mim][BF4] is gradually enhanced. For tricyclic aromatic hydrocarbons, the electrostatic interaction is the main interaction between [C6mim][BF4] and aromatic hydrocarbons. The smaller the molecular volume is, the stronger the interaction with the ionic liquid is, and the smaller the free volume fraction of the blends is.

EFFECTS OF ANIONS ON THE CRYSTAL GROWTH OF PSEUDO BOEHMITE

2022, 53(10):  34-41. 

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Pseudo boehmite, as the precursor of alumina, was synthesized by co-precipitation with aluminum sulfate solution and ammonia water as raw materials. Under pH 8.5-9 and pH 5-6 conditions, different pseudo boehmite samples were prepared by introducing sulfate ion, chloride ion, oxalate ion and borate ion, respectively. The main physicochemical properties of the prepared pseudo boehmite samples were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and BET specific surface area measurements. The effects of different anions on the growth of pseudo boehmite crystals and their possible mechanisms were discussed. The results show that the adsorption of anions on the crystal faces of pseudo boehmite is anisotropic, and the growth of crystal facet with the highest amount of adsorbed anions will be inhibited to some extent. The adsorption of anions on the surface of pseudo boehmite is determined by the pH of the solution: when pH of the solution is in the range of 5-6, the anions are strongly selectively adsorbed on the crystal surface; on the other hand, when pH of the solution is in the range of 8.5-9, the adsorption of anions on the crystal surface is weak, which shows that the orientation growth of anions on the crystal surface has no obvious effect on the grain morphology.

SYNTHESIS OF SMALL PARTICLE SIZE ZSM-5 ZEOLITE WITH DIFFERENT Si/Al RATIO AND ITS CATALYTIC ACTIVITY FOR BENZENE/METHANOL ALKYLATION

2022, 53(10):  42-49. 

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Five kinds of Si/Al ratio ZSM-5 zeolites with small particle size and hierarchical pore were prepared by simple in-situ hydrothermal methods. XRD, N₂ adsorption-desorption, NH₃-TPD, Py-IR and SEM were used to characterize the prepared ZSM-5. The catalytic performance of ZSM-5 Zeolites with different Si/Al ratio for benzene/methanol alkylation was investigated. The results showed that the ZSM-5 zeolites with different Si/Al ratio had multi-stage pore structure, irregular particle shape, small crystal size and honeycomb shape. Under the conditions of 470 ℃, 0.5 MPa (H₂) and space velocity 2 h-1, n(methanol): n(benzene)=1:1, the alkylation of benzene with methanol catalyzed by ZSM-5 zeolites with different Si/Al ratio was studied. The results showed that the conversation of benzene was 62.92%, the selectivity of xylene was 37.38%, and the selectivity of ethylbenzene 0.81% when n(SiO₂)/n(Al₂O₃) was 150 and the reaction time was 72 h. The ZSM-5 still has good activity after 1 200 h operation and has a good application prospect.

HIGHLY SELECTIVE CATALYTIC PERFORMANCE OF MODIFIED ZSM-5 ZEOLITE FOR PRODUCING p-XYLENE FROM METHANOL

2022, 53(10):  50-57. 

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The modified ZSM-5 with different Zn loadings and the Zn, Mg and P composite modified ZSM-5 catalysts were prepared by ultrasonic impregnation method, the catalyst samples were characterized by XRD, N₂ adsorption-desorption, NH₃-TPD and Py-FTIR techniques, and the effects of different modification processes on the performance of direct synthesis of p-xylene from methanol were investigated in a fixed bed microreactor. The results show that the ZSM-5 zeolite modified by Zn can effectively improve the aromatization performance, providing a high reactivity level for direct production of p-xylene from methanol. At the optimum Zn loading, Mg and P were further introduced into the zeolite to modify the acidic properties and pore structure, covering the acidic site of the pore and narrowing the pore orifice, thus optimizing the catalytic selectivity for the formation of the target product p-xylene. The complex modified zeolite Zn-Mg-P/HZ-5 catalyst has a lifetime of 36 h, a para-selectivity of 96.00% and a p-xylene selectivity of 18.43%.

EFFECT OF PHOSPHORUS MODIFICATION ON THE ZSM-5 ZEOLITE FOR INCREASING PROPYLENE PRODUCTION IN FCC UNIT

2022, 53(10):  58-65. 

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Direct functional modification of fluid catalytic cracking (FCC) catalyst additives is a simple and effective method for increasing propylene production. ZSM-5 modified by alkali and different content of phosphorus named XP/A/ZSM-5 was prepared for increasing propylene production in FCC unit,in which x means the loading amount of phosphorus (calculated by the mass fraction of P₂O₅,%) . The structure, acidity and phosphorus forms of modified samples were characterized by XRD, TEM, ³¹P NMR and XPS. The performance of increasing propylene production in FCC process was studied. The results show that the propylene yield of all phosphorus modified samples is better than that of ZSM-5, which is related to the decrease of pore volume and acidity. Among the tested additives, 8.0 P/A/ZSM-5 sample had the best catalytic performance, and the yield of propylene was 8.62%. The interaction mechanism of phosphorus and ZSM-5 zeolites showed that phosphorus could interact with framework aluminum and non-framework aluminum to form AlPO₄ species which were detected on the surface of phosphorus modified zeolites.

RESEARCH AND APPLICATION OF ENVIRONMENTAL FRIENDLY LOW-PHOSPHORUS TREATMENT TECHNOLOGY FOR CIRCULATING WATER

2022, 53(10):  66-69. 

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According to the characteristics of the fresh water and the reused wastewater as well as the working conditions of circulating water system, an environmental friendly low-phosphorus treatment technology was developed. The technology was applied in the circulating water system of the refinery units for three months as the industrial experiments. The results showed that the average corrosion rate and the average adhesion rate of carbon steel test tube were 0.032 1 mm/a and 4.187 5 mg/(cm².month), respectively. The proportion of the reused wastewater in all make-up water was promoted to 77.23%. The mass concentration of phosphorus introduced by the water treatment agents was decreased by 70%. This treatment technology has shown remarkable economic and social benefits.

OPTIMIZING DESIGN OF LARGE PX COMPLEX FOR ENERGY SAVING

2022, 53(10):  70-75. 

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Taking the design of a 1.50 Mt/a p-xylene (PX) complex in an enterprise as an example, the energy consumption distribution of each unit in the plant and the influence of adopting energy-saving design on the energy consumption of the plant were analyzed, and the importance of improving fuel thermal efficiency and optimizing low-temperature heat utilization scheme to reduce energy consumption of heating furnace was discussed. The results show that the design of heating furnace for the example device based on the “95+” technology is improved, and the waste heat of flue gas to the maximum extent is reclaimed. The thermal efficiency of heating furnace is more than 95%, obviously higher than that of the conventional design(92%), and fuel cost is reduced by 23.4 million Yuan/a. By adopting the low temperature heat generating steam technology, the output of 1.2 MPa and 0.6 MPa steam was 89.2 t/h and 254.2 t/h, respectively. The output of 1.8 MPa steam could be obtained by steam compression and pressurization, which could meet the needs of many steam users. The 110 ℃ hot water quantity was 746.2 t/h by using low temperature heat. The chilled water prepared by advanced hot water refrigeration technology can not only meet the needs of the equipment itself, but also serve many cooling devices. The energy consumption of p-xylene separation unit, xylene isomerization unit and xylene fractionation unit was only 5 190.9 MJ/t by overall optimization design.

MEASURES FOR ENERGY SAVING AND CONSUMPTION REDUCTION IN SULFURIC ACID ALKYLATION UNIT

2022, 53(10):  76-81. 

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The energy consumption of 200 kt/a sulfuric acid alkylation unit in SINOPEC Luoyang Company was analyzed, and the corresponding measures for energy saving and consumption reduction were put forward in view of the large energy consumption of steam, circulating water and desalinated water in the unit. Through optimizing the compressor speed, the flow rate of isobutane and n-butane removal column and feed process of light hydrocarbon removal column, the total saving of 3.5 MPa and 1.0 MPa steam was 11.75 t/h and 5.32 t/h, respectively. The steam energy consumption was reduced by 3 334.09 MJ/t. By shutting down the circulating water supply of some sampler and cooler and adjusting the water consumption of each equipment in time, the circulating water quantity was saved by 119.55 t/h, and the energy consumption was reduced by 16.63 MJ/t. Through the adjustment of the desalinated water used in the washing of air cooler, alkline tank and all pumps, the demineralized water was saved by 1.58 t/h. Through the implementation of the above energy saving measures, the total energy consumption for the unit was reduced by 3 354.38 MJ/t, and the economic benefit was 34.0947 million Yuan/a

OPTIMIZATION AND ENERGY SAVING ANALYSIS ON THERMAL CARRIER SYSTEM OF SEMI-REGENERATIVE CATALYTIC REFORMING UNIT

2022, 53(10):  82-85. 

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In order to fully tap the potential of energy saving and emission reduction in the semi-regenerative catalytic reforming unit, the heat balance of the heat carrier system of the 250 kt/a semi-regenerative catalytic reforming unit of Qingdao Petrochemical Co., Ltd. was analyzed, and the heat transfer flow and operating parameters of the evaporator, fractionator and stabilizer were optimized. The results show that the heat carrier system of the catalytic reforming unit can stop using the heat carrier furnace. It can save 321.14 (MW.h)/a of electricity consumption and 621.96 t/a of fuel gas consumption, reduce 1 750 t/a of CO₂ emission, and increase the economic benefits by about 2 732 200 Yuan/a.

OPTIMIZATION OF ENERGY-SAVING DISTILLATION SYSTEM BASED ON INTERMEDIATE HEAT EXCHANGER-ABSORPTION HEAT PUMP

2022, 53(10):  86-92. 

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In order to improve the energy efficiency of distillation, an energy-saving distillation system with an intermediate heat exchange and an absorption heat pump was proposed. The mathematical model of 180 kt/a gas distillation column in a petrochemical enterprise was established by using Aspen Plus software. The operating parameters of the intermediate reboiler, the intermediate-condenser and the absorption heat pump in the energy-saving system of the intermediate heat exchange-absorption heat pump distillation were optimized, and the energy-saving effect of the “three-column” distillation process was analyzed. The results show that the steam consumption of the depropane column can be decreased by 25% by using the intermediate heat exchange-absorption heat pump distillation energy saving system, the steam consumption can be reduced by 38.8%, and the softened water consumption can be saved by 42.5% for the complete three-column gas fractionation process. The additional profit is about 5 308 000 Yuan/a, and the fixed investment payback period of the project is about 3 years.

APPLICATION OF ON-LINE NEAR INFRARED SPECTROSCOPY IN S Zorb ADSORPTIVE DESULFURIZATION UNIT

Liu Tianbo Chu Xiaoli

2022, 53(10):  93-99. 

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In order to apply the on-line near infrared spectroscopy (NIR) analysis technology to the on-line analysis of gasoline adsorptive desulfurization (S Zorb) unit, based on a large number of representative S Zorb unit feedstock gasoline and product samples, their near-infrared spectra were collected, and a near-infrared spectral analysis model was developed to predicting the material density, RON, vapor pressure, boiling range and hydrocarbon types composition of gasoline of S Zorb adsorptive desulfurization unit using the chemometric method. There is good consistency between the near infrared spectroscopy analysis method and standard method. Based on on-line FT-NIR analysis system and application of material multi-properties NIR analysis model of S Zorb, the on-line NIR technology was applied in S Zorb unit to perform real-time analysis of density, vapor pressure, RON, boiling range and hydrocarbon type composition of gasoline. The on-line analysis of 65 properties, including the density, octane number, vapor pressure, distillation range and hydrocarbon composition of 3 streams of the unit, can be completed within 1 min. The standard deviations of S Zorb desulfurization gasoline density (20 ℃), RON, olefine content, aromatic content, vapor pressure are 1.5 kg/m³, 0.2, 0.46 percentage point, 0.51percentage point, 1.5 kPa, respectively. The predicted standard deviations of initial boiling point, 10% distillation temperature, 50% distillation temperature, 90% distillation temperature and final boiling point are 2.0, 1.7, 2.1, 2.3, 2.8 ℃, respectively. The accuracy and detection speed of the on-line NIR method can meet the needs of rapid analysis in the industrial process.

DETERMINATION OF BASIC NITROGEN IN PETROLEUM DISTILLATES AND PETROLEUM PRODUCTS BY PHOTOMETRIC TITRATION

2022, 53(10):  100-104. 

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The basic nitrogen in petroleum distillates and petroleum products is an important parameter in petroleum processing. A novel method based on photometric titration was established in order to solve the problems found in the application of the current standard method. The results showed that the test results of many samples determined by photometric titration were in good agreement with the current standard methods. The recovery rate by standard addition of aniline was 93.0%-110.0%. On the basis of ensuring the accuracy, the developed method realizes the automation of the analysis process, expands the applicable range of samples, and improves the environmental friendliness. It provides a better analytical method for determination of basic nitrogen in petroleum distillates and petroleum products.

NUMERICAL CALCULATION AND ANALYSIS FOR COKE BURNING OF COUNTER-CURRENT CONTINUOUS CATALYTIC REFORMING PROCESS

2022, 53(10):  105-114. 

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The dynamic mathematical models of coke burning zone were established, and the mathematical model was solved by using Matlab programming numerical calculation method. Three different operation conditions were selected, and the coke mass ratio, oxygen content of regeneration gas, bed temperature and gas phase temperature were calculated. The influence of initial coke deposit amount or catalyst circulation rate on regeneration was studied. The results show that the coke burning rate increases with the increase of coke deposit amount, oxygen content in regenerated gas and reaction temperature, and the location of the highest temperature in the local bed moves to the direction of the outer screen with increase of initial coke deposit amount. With the increase of the catalyst cycle rate, the local highest temperature position of the bed moves downwards. The calculated results of the model were in good agreement with the measured results, which showed that the calculation method of the model had good accuracy.

RESEARCH ON THE CORRELATION OF SAFETY RISK FACTORS OF PROPANE DEHYDROGENATION (PDH) UNIT SYSTEM BASED ON DEMATEL ALGORITHM

2022, 53(10):  115-121. 

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In order to improve the capability of system risk management of propane dehydrogenation (PDH) unit, a risk influencing factor model of PDH unit system was established. Hazardous factors were identified by the Preliminary Hazard Analysis (PHA).Unsafe events and risk management objects of the PDH unit were obtainedby using Failure Mode and Effect Analysis (FMEA) method.The set of risk influencing factorsto identifythe risks of fire, explosion and dehydrogenation reaction out-of-control in the reactor andto analyze the cause of the risk andcontrol measures were put forward. This paper summarizedtheriskfactors of thePDH unit system in five dimensions: plant operator, operation equipment, materialitself, plant safety management situation, plant operation environment. The relationship between the safety risk factors of the PDH unit systemwas analyzed bythe Decision Making Trial andEvaluation Laboratory (DEMATEL) algorithm. The results showed that the relationship between 7 causal factors and 13 result factors should be considered in the system safety risk control of PDH unit;the corrosion of the materials had the greatest influenceon the risk of the PDH unitsystem;the safety risk awareness was easily affected by other factors;and education and training playedthe most important role in the PDH unit system.

PROGRESS AND COST ANALYSIS OF CENTRALIZED HYDROGEN PRODUCTION TECHNOLOGY

2022, 53(10):  122-126. 

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Hydrogen energy has the characteristics of high mass energy density, diverse sources, rich application scenarios and zero terminal emissions at the end, etc. It is of great significance in ensuring national energy security, coping with climate change, promoting industrial upgrading and realizing high-quality development. This paper mainly introduced the main types of centralized hydrogen production, including natural gas reforming, coal gasification, industrial by-product hydrogen and electrolytic water, and analyzed the cost of hydrogen production. For hydrogen production from coal and natural gas, the technologies are relatively mature and widely used all over the world. The price of raw materials has a great impact on the cost. For industrial by-product hydrogen, it possesses the most market competitiveness at present. For hydrogen production from water electrolysis, it has the greatest development potential. If combined with renewable energy, the produced hydrogen belongs to “green hydrogen”, which is more in line with future green energy demand.

PROGRESS OF HELIUM PURIFICATION TECHNOLOGY

2022, 53(10):  127-134. 

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As a non-renewable strategic rare gas, helium mainly comes from helium containing natural gas, which is generally purified by cryogenic technology. However, the cost of helium obtained by cryogenic method is high. In order to reduce the extraction cost of helium, the traditional cryogenic technologies such as pressure swing adsorption, membrane separation, absorption method, hydrate method and multi-technology combination methods were analyzed and compared. The results show that the multi-technology combination extraction and separation of helium can effectively break the "bottleneck" of single separation technology, reduce investment and consumption, and has a better application prospect.