Gas separation by a novel hybrid membrane/pressure swing adsorption process

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Abstract

Novel gas separation processes, coupling pressure swing adsorption (PSA) and membrane technologies, are presented for both cooperative and opposing regions of selectivity for the two units. The membrane works as a prebulk separation unit and is coupled to the intrinsically dynamic periodic operation of the PSA in a way that enhances the separation performance of the hybrid unit with respect to that of the stand-alone PSA. The operating pressure of the PSA unit is used as the driving force for permeation. Unlike in a conventional PSA process, the adsorption beds for the integrated system are fed with a varying-composition gas stream, initially rich in the less adsorbed component, which is progressively enriched in the other component with the opposite behavior. This gives rise to sharper concentration fronts and increased product purity. The integrated system allows for two schemes that are introduced and described: scheme A, in which the least adsorbed component is the more permeable one; and scheme B, where the least adsorbed component is the less permeable one. In the current work, the hybrid process is applied to H2/CH 4 separation over activated carbon by coupling the membrane to a five-step PSA cycle using scheme A. The membrane permeances are those commonly expected for a polysulfone membrane, with a typical selectivity of 35 for H 2/CH4 separation. The effect of various operating parameters, such as permeation throughput, total feed amount per cycle, purge-to-feed ratio, and adsorption and blowdown pressures, is assessed through detailed process simulation. Depending on the values of the operating parameters and for an equimolar feed mixture at 35 bar, a 7 min integrated cycle produces H2 and CH4 products with purities within the 83-97% and 81-99% ranges, respectively. The product recoveries obtained are in the ranges of 77-99% for H2 and 81-98% for CH4.

Original languageEnglish
Pages (from-to)5723-5733
Number of pages11
JournalIndustrial and Engineering Chemistry Research
Volume46
Issue number17
DOIs
Publication statusPublished - 15 Aug 2007

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Keywords

  • Adsorption
  • Pressure
  • Adsorption PSA

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