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CN-122006409-A - Multi-bed rapid cycle dynamic PSA

CN122006409ACN 122006409 ACN122006409 ACN 122006409ACN-122006409-A

Abstract

Disclosed herein is a multi-bed Rapid Cycle Pressure Swing Adsorption (RCPSA) process for separating O 2 from N 2 and/or Ar, wherein the process uses at least five adsorbent beds, each comprising a kinetic selective adsorbent for O 2 having an O 2 adsorption rate (1/s) of at least 0.20, as determined by a linear driving force model at 1atma and 86 o F.

Inventors

  • Virbhadra S.J.
  • R.D. Whitley
  • T.C. GORDON
  • WU DINGJUN
  • G.P. wana

Assignees

  • 气体产品与化学公司

Dates

Publication Date
20260512
Application Date
20190814
Priority Date
20180814

Claims (20)

  1. 1. A multi-bed Rapid Cycle Pressure Swing Adsorption (RCPSA) process for separating O 2 from N 2 and/or Ar, wherein the process uses at least five adsorbent beds, each comprising a kinetic selective adsorbent for O 2 having an O 2 adsorption rate (1/s) of at least 0.20 as determined by a linear driving force model at 1 atma and 86 o F, and wherein the RCPSA process comprises subjecting each adsorbent bed to a rapid PSA cycle comprising the following steps performed in the following order: i) Feeding material Ii) first equalized pressure reduction Iii) Second equalization depressurization Iv) countercurrent depressurization V) countercurrent purge Vi) first equalization repressurization Vii) second equalization repressurization Viii) product and/or feed repressurization Wherein when the adsorbent bed is subjected to the equalization depressurization step ii), it is connected to and provides a repressurized stream to one of the other adsorbent beds simultaneously subjected to the equalization repressurization step vii), and When the adsorbent bed is subjected to the equalization depressurization step iii), it is connected to and provides a repressurized stream to another of the other adsorbent beds simultaneously subjected to the equalization repressurization step vi); Wherein the O 2 、N 2 or Ar adsorption rate of the adsorbent is determined by the steps of: Exposing a sample of the sorbent initially under vacuum and 86 o F to a measured amount of adsorbate O 2 、N 2 or Ar at 1atma at the same temperature; Recording the pressure change as a function of time; subtracting the pressure versus time data from a similar pressure history using the same weight of quartz beads instead of the adsorbent sample to obtain an absorption curve of the amount of adsorbed gas as a function of time, and Extracting an adsorption rate of the adsorbate in inverse time (1/s) from the adsorption curve using a linear driving force model; wherein the cycle time of the rapid PSA cycle is equal to or less than 100 seconds; Wherein the kinetically selective adsorbent has an O 2 /N 2 kinetic selectivity of at least 5 as determined by a linear driving force model at 1atma and 86 o F and/or an O 2 /Ar kinetic selectivity of at least 5 as determined by a linear driving force model at 1atma and 86 o F.
  2. 2. The RCPSA process of claim 1, wherein step iii) is a double equalization depressurization step and step vi) is a double equalization repressurization step.
  3. 3. The RCPSA process of claim 1, wherein step viii) is a product and feed repressurization step.
  4. 4. The RCPSA process of claim 1, wherein step ii) is a forward flow equalization depressurization step and step vii) is a reverse flow equalization repressurization step.
  5. 5. The RCPSA process of claim 1, wherein the process uses 5 to 18 adsorbent beds.
  6. 6. The RCPSA process of claim 1, wherein the process uses 7 to 9 adsorbent beds.
  7. 7. The RCPSA process of claim 1, wherein the process uses 7 or 9 adsorbent beds.
  8. 8. The RCPSA process of claim 1, wherein the duration of the feeding step is from 3 to 45 seconds.
  9. 9. The RCPSA process of claim 1, wherein the duration of each of the equalization depressurization and equalization repressurization steps is from 1 to 5 seconds.
  10. 10. The RCPSA process of claim 1, wherein the feeding step is performed at a temperature of 0 o F to 125 o F.
  11. 11. The RCPSA process of claim 1, wherein the feeding step is performed at a temperature of 20 o F to 100 o F.
  12. 12. The RCPSA process of claim 1, wherein the feeding step is performed at a temperature of 20 o F to 40 o F.
  13. 13. The RCPSA process of claim 1, wherein during all or part of the feeding step, a recycle gas is introduced downstream into the bed in which the feeding step is performed, the recycle gas comprising gas obtained from the bed undergoing the step during a countercurrent depressurization step and/or a purge step.
  14. 14. The RCPSA process of claim 1, wherein during all or part of the equilibrium depressurization step ii), a recycle gas comprising gas obtained from the bed undergoing said step during the countercurrent depressurization step and/or the purge step is introduced downstream into the bed undergoing said step.
  15. 15. The RCPSA process of claim 1, wherein the kinetic selective adsorbent is a zeolite or a carbon molecular sieve.
  16. 16. The RCPSA process of claim 1, wherein the process is to separate O 2 from Ar and the kinetically selective adsorbent is a RHO zeolite having a Si/Al ratio of 3.2 to 4.5 and containing aprotic extra-framework cations, wherein the zeolite contains up to 1 proton per unit cell, and wherein the extra-framework cations present in the zeolite are of a size, number and charge such that 1 or less aprotic extra-framework cations are required per unit cell to occupy the 8-ring sites.
  17. 17. The RCPSA process of claim 1, wherein the process is to separate O 2 relative to N 2 , and the kinetically selective adsorbent is a Carbon Molecular Sieve (CMS) having an O 2 /N 2 kinetic selectivity of 5 to 30 as determined by a linear driving force model at 1 atma and 86 o F.
  18. 18. The RCPSA process of claim 1, wherein the process is a rotary bed RCPSA process.
  19. 19. The RCPSA process of claim 1, wherein the process is a rotary valve RCPSA process.
  20. 20. The RCPSA process of claim 1, wherein each adsorbent bed has a void volume of 3% to 15% relative to the bed volume.

Description

Multi-bed rapid cycle dynamic PSA Technical Field The present invention relates to a multi-bed rapid cycle Pressure Swing Adsorption (PSA) process for separating O 2 from N 2 and/or Ar. Background PSA processes have long been used to separate air components. Recently, considerable interest has been generated in the enhancement of separation processes. In recycling processes such as PSA and TSA, reducing the cycle time is the primary means of achieving more production from a given amount of material. However, with decreasing cycle time, the cycle process is generally faced with the problems of decreasing the working capacity per cycle of the component of interest, decreasing the product recovery and increasing the pressure drop. Recent developments in PSA processes involve the use of adsorbents with faster adsorption kinetics, such as relatively rapid kinetics selective lamination of adsorbent structures, to increase productivity. However, such productivity increases generally come at the cost of reduced selectivity, resulting in reduced product recovery. Other developments include the use of adsorbents with relatively slow adsorption kinetics to improve overall product recovery of the process. However, the increase in product recovery generally comes at the cost of reduced process productivity. US7,645,324 discloses a rotary PSA process using a laminated adsorbent for aerodynamic separation. US7,645,324 teaches that the use of kinetically selective laminates can increase productivity, but in order to avoid masking the kinetic selectivity by macroporous mass transfer resistance, the macroporous structure within the adsorbent layer should be as open as possible, i.e. the macropore void fraction should be relatively high. However, a problem in this regard is that having a high void volume often compromises product recovery. US9,895,646 discloses a multi-bed PSA process for producing a compound X rich gas stream from a feed gas stream. US9,895,646 notes that introducing a pressure equalization step into the PSA process can increase product recovery, but doing so typically adversely affects the specific productivity of the process. Notably, the equilibrium shift from 1 to 3 makes it possible to obtain an efficiency of 2.5%, but is detrimental to an increase in adsorbent volume of 40% (since more adsorbent is required). Thus, increasing the number of adsorbent beds can increase the product recovery (more pressure equalization steps can be performed), but this can also result in reduced specific productivity of the process (standard volumetric flow of product divided by total amount of adsorbent in the system). WO2015/199227 discloses a multi-bed (3-bed or more) PSA process for separating methane from biogas. The method performs a pressure equalization process of transferring the gas in the adsorption tower, which has been completed and is in a high pressure state, to another adsorption tower, which is in a lower pressure state, so as to bring the inside of the adsorption tower into a medium pressure state, and receiving the pressure equalization process after the decompression process is completed, bringing the gas from the other adsorption tower into a higher pressure state, so as to bring the inside of the adsorption tower into a medium pressure state. This is said to improve the energy efficiency required for the pressure increase and pressure decrease in the adsorption tower, and also to improve the recovery rate of the gas to be purified, while improving the purity of the gas to be purified. However, the addition of a pressure equalization step does not improve the specific productivity of the process. No kinetic information is provided for the adsorbent used, but the requirement of a long pressure transfer step (6 seconds) suggests that a slow kinetic adsorbent is used. In sum, adsorbents with relatively fast adsorption rates are known to increase process productivity, but this is generally at the expense of lower product recovery because of larger void volumes and/or reduced selectivity levels. In theory, introducing more adsorbent beds and pressure equalization steps during use of the adsorbent may increase product recovery, however, this is expected to be done at the expense of eliminating the increase in productivity that is obtained by using the faster adsorbent first. Alternatively, a slower, more selective kinetic adsorbent can be used to obtain a high purity product with good product recovery, however, this is also at the cost of reducing the overall productivity of the process. Thus, it is apparent from the prior art that there is a tradeoff between product recovery and process productivity, and that process improvements that increase product recovery are generally detrimental to process productivity and vice versa. Thus, there remains a need for PSA processes with high process productivity while maintaining high product recovery. Disclosure of Invention The present inventors have found that when O