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Separation of krypton and xenon by selective permeation
Author(s) -
Stern S. A.,
Leone S. M.
Publication year - 1980
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690260602
Subject(s) - permeation , krypton , silicone rubber , countercurrent exchange , xenon , analytical chemistry (journal) , materials science , permeability (electromagnetism) , butyl rubber , chromatography , chemistry , oxygen , natural rubber , membrane , composite material , thermodynamics , biochemistry , physics , organic chemistry
The objective of this investigation was to study the separation of krypton and xenon from nuclear reactor atmospheres by selective permeation through silicone rubber capillaries. Effective permeability coefficients for pure krypton xenon, nitrogen, and oxygen were determined between 0 and 40°C and at pressure differences across the capillary walls (Δ p ) of up to 3.45 × 10 5 N/m 2 (50 psi). The silicone rubber capillaries had an O.D. of 635 μm (0.025 in.) and an I.D. of 305 μm (0.012 in.), and were pressurized externally. The effective permeability coefficients decreased with increasing Δ p , due to the elastic deformation of the capillaries, in general agreement with a deformation analysis of thick‐walled elastic tubes. Gas separation studies were made with a Kr‐Xe‐N 2 ‐O 2 mixture in a permeator containing a bundle of silicone rubber capillaries. The permeator had an effective permeation area of 0.480 m 2 (5.165 ft 2 ) at a packing density of 4132 m 2 m 3 permeator volume (1260 ft 2 /ft 3 ), and was operated in a countercurrent mode. The separation studies were conducted at −10 and 20°C and at three Δ p values. The separation achieved in the permeator at Δ p 's of 1.38 × 10 5 N/m 2 (20 Ib/in. 2 ) and 2.07 × 10 5 N/m 2 (30 Ib/in. 2 ) was in good agreement with that predicted from a theoretical model of a permeation stage with countercurrent flow. At 3.45 × 10 5 N/m 2 (50 Ib/in. 2 ), the separation approached that predicted from a “perfect mixing” model. This behavior probably was due to local collapses of the capillaries at weak spots in their walls, as was evidenced also by a sharp increase in the axial pressure drop inside the capillaries.