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CN-121972130-A - Superfine molecular sieve for preparing nitrogen from PSA, preparation method and application thereof

CN121972130ACN 121972130 ACN121972130 ACN 121972130ACN-121972130-A

Abstract

The invention discloses a superfine molecular sieve for preparing nitrogen by PSA, and a preparation method and application thereof, and belongs to the technical field of gas separation. The preparation method comprises the steps of mixing molecular sieve raw powder and a pore canal protective agent, pre-dispersing to obtain a mixture, adding a composite grinding medium into the mixture, carrying out gradient grinding, and sieving to obtain the superfine molecular sieve with granularity of 1-2 mu m, wherein the composite grinding medium consists of phi 0.1mm zirconium beads and phi 0.5mm aluminum oxide beads according to a mass ratio of 3:1, and the solid-liquid ratio in gradient grinding is 1:8-10, and the gradient grinding is carried out, wherein the gradient grinding is carried out in the following steps of grinding for 25-40 minutes at a rotating speed of 900-1100r/min, lifting the rotating speed, and grinding for 50-65 minutes at a rotating speed of 1400-1600 r/min. According to the method, the granularity of the molecular sieve is reduced from the traditional 5-10 mu m to 1-2 mu m under the premise of keeping the original crystal structure of the molecular sieve by the synergistic effect of the composite grinding medium, and the uniformity of the particle distribution is improved by more than 40%.

Inventors

  • CHENG JIAN
  • CAO HONGMEI
  • LI WEIHU
  • GONG YUZHU
  • YI XIAOLU
  • WANG YUNJIANG
  • ZHAO YONG
  • WANG ZIHENG
  • FENG PENGHUI
  • SONG XIAOHUI
  • HAN WEI
  • YAO MINGYU
  • ZHANG WANCHEN
  • LI JIE

Assignees

  • 西安热工研究院有限公司
  • 华能山东发电有限公司众泰电厂
  • 华能山东发电有限公司

Dates

Publication Date
20260505
Application Date
20260127

Claims (10)

  1. 1. The preparation method of the superfine molecular sieve for preparing nitrogen from PSA is characterized by comprising the following steps: mixing molecular sieve raw powder and a pore canal protective agent, and pre-dispersing to prepare a mixture; adding a composite grinding medium into the mixture, carrying out gradient grinding, and then sieving to obtain a superfine molecular sieve with granularity of 1-2 mu m; Wherein the composite grinding medium consists of zirconium beads with the diameter of 0.1mm and aluminum oxide balls with the diameter of 0.5mm according to the mass ratio of 3:1, the solid-liquid ratio in gradient grinding is 1:8-10, and the gradient grinding process comprises the following steps of grinding for 25-40 minutes at the rotating speed of 900-1100r/min, lifting the rotating speed, and grinding for 50-65 minutes at the rotating speed of 1400-1600 r/min.
  2. 2. The method for preparing ultrafine molecular sieves for producing nitrogen from PSA according to claim 1, wherein the mass ratio of the molecular sieve raw powder to the pore-protecting agent is 100:0.5-2.
  3. 3. The method for preparing ultrafine molecular sieves for nitrogen production from PSA according to claim 1, wherein the molecular sieve raw powder is 5A molecular sieve, 13X molecular sieve or carbon molecular sieve, and the initial particle size of the molecular sieve raw powder is 5-10 μm.
  4. 4. The method for preparing ultrafine molecular sieves for nitrogen production from PSA according to claim 1, wherein the pore path protecting agent is silane coupling agent KH-550, KH-560 or KH-570, and the number of the sieved mesh is 2000 mesh.
  5. 5. The method for preparing ultrafine molecular sieves for nitrogen production from PSA according to claim 1, wherein the pre-dispersion is performed at a rotation speed of 500r/min for 10 to 15 minutes.
  6. 6. The method for preparing ultrafine molecular sieves for nitrogen production from PSA according to claim 1, wherein the water cooling control temperature during the gradient milling is 20-25 ℃.
  7. 7. The method for preparing ultrafine molecular sieves for nitrogen production from PSA according to claim 1, wherein the rotational speed increase rate of the gradient grinding is 100r/min/10 min.
  8. 8. An ultrafine molecular sieve for PSA nitrogen production, which is produced by the production method of an ultrafine molecular sieve for PSA nitrogen production according to any one of claims 1 to 7, wherein the ultrafine molecular sieve has a particle size D50 of 1 to 2 μm and a particle size distribution coefficient D90/D10 of 2.0 or less.
  9. 9. The ultrafine molecular sieve for producing nitrogen from PSA of claim 8, wherein the nitrogen adsorption capacity retention rate is not less than 95% relative to the molecular sieve raw powder.
  10. 10. Use of an ultrafine molecular sieve for PSA nitrogen production, which is prepared by the method for preparing an ultrafine molecular sieve for PSA nitrogen production according to any one of claims 1 to 7, in a PSA nitrogen production process.

Description

Superfine molecular sieve for preparing nitrogen from PSA, preparation method and application thereof Technical Field The invention belongs to the technical field of gas separation, and particularly relates to an ultrafine molecular sieve for preparing nitrogen from PSA, and a preparation method and application thereof. Background In Pressure Swing Adsorption (PSA) nitrogen production techniques, molecular sieves are used as the core adsorbent material, the particle size of which directly determines the gas mass transfer efficiency and the equipment operating economics. From the aspect of mass transfer kinetics, the smaller the molecular sieve granularity, the shorter the diffusion path of gas inside the particles, and the shorter the time for adsorption to reach equilibrium. Industrial data shows that when the molecular sieve granularity is reduced from 10 mu m to 1 mu m, the diffusion coefficient of oxygen in the pore canal of the molecular sieve can be improved by 3-5 times, which means that the adsorption period of the PSA system can be compressed from traditional 20-30 minutes to 10-15 minutes, and the nitrogen yield per unit time is remarkably improved. However, this ideal state is difficult to achieve in practical production due to manufacturing technology bottlenecks. Conventional mechanical milling is a major means of industrially reducing molecular sieve particle size, but has unavoidable drawbacks. When a single medium (such as alumina balls) is adopted for high-strength grinding, about 20% -30% of molecular sieve crystals collapse in structure due to severe collision, wherein six-membered ring channels (with the diameter of 0.5 nm) of the 5A molecular sieve are most easily damaged, and the nitrogen adsorption capacity is reduced by 15% -25%. A comparison experiment of a certain equipment enterprise shows that the static adsorption capacity of the 5A molecular sieve which is ground to be 2 mu m by the traditional method is reduced from 30mL/g to 22mL/g, and the dynamic adsorption efficiency is reduced by 10 percent after 500 hours of operation due to pore canal blockage in PSA circulation. More seriously, the uncontrolled grinding process can lead to the widening of the granularity distribution (D90/D10 > 3.5), the proportion of excessively coarse particles (> 5 μm) is more than 20%, and the particles form local mass transfer resistance in the adsorption tower, so that the gas flow in the tower is unevenly distributed, the fluctuation range of the nitrogen purity is enlarged to +/-0.05%, and the severe requirements of industries such as electronics, food and the like on high-purity nitrogen (more than or equal to 99.99%) cannot be met. Although the chemical synthesis method can prepare the superfine molecular sieve (1-2 μm) with uniform granularity, the industrial application is limited by high cost and process complexity. In the hydrothermal synthesis process, a template agent (such as tetrapropylammonium hydroxide) is needed, the price of the template agent is more than 50 times that of a traditional grinding medium, and the energy consumption for removing the template agent by subsequent roasting accounts for 40% of the total preparation cost. In addition, the chemical synthesized molecular sieve has poor batch stability, and the granularity deviation of products in different batches can reach +/-0.5 mu m, so that parameters are required to be debugged again after the PSA system is reloaded, and each debugging takes 2-3 days, thereby causing huge production loss. Some electronics companies have tried to use chemically synthesized 13X ultrafine molecular sieves, which have an initial nitrogen purity of 99.995%, but due to batch fluctuations, 3 times of sudden purity drops occur within 3 months, directly resulting in chip wafer rejection. The prior art improvements still present a significantly shorter plate. The pore canal propping agent method proposed by the Chinese patent with publication number of CN103007878A can reduce the grinding breakage rate, but is only applicable to 5A molecular sieves, and has limited effects on other types of materials such as 13X, carbon molecular sieves and the like. The grinding efficiency of the single alumina medium adopted is low, and 180 minutes are required to reduce the molecular sieve of 5 mu m to 2.5 mu m. More importantly, the technology does not solve the problem of grinding heat, when the grinding time exceeds 60 minutes, the temperature of the system is raised to above 60 ℃, hydroxyl (-OH) on the surface of the molecular sieve can be fallen off, and in the environment with the humidity of more than 60%, the adsorption quantity of the hydroxyl-missing molecular sieve on water vapor is increased by 30%, and nitrogen adsorption sites are further occupied, so that the effective adsorption capacity is reduced. With the expansion of the industrial nitrogen production scale, the performance bottleneck of the traditional molecular sieve is more and more pro