Carbon monoxide isotope enrichment and separation by pressure swing adsorption

• Published in: Adsorption : journal of the International Adsorption Society Vol. 19; no. 1; pp. 11 - 23
• Main Authors: Bhadra, Shubhra J., Ebner, Armin D., Ritter, James A.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.02.2013
• Subjects: Chemistry; Chemistry and Materials Science; Engineering Thermodynamics; Heat and Mass Transfer; Industrial Chemistry/Chemical Engineering; Surfaces and Interfaces; Thin Films; Isotope separation; Carbon isotope separation; Nuclear waste; PSA; Pressure swing adsorption
• ISSN: 0929-5607; 1572-8757
• DOI: 10.1007/s10450-012-9406-2

Simulations of three different 3-bed 3-step pressure swing adsorption (PSA) cycles were carried out to study the enrichment and recovery of 14 CO from an isotopic mixture of 14 CO, 13 CO and 12 CO using NaX zeolite. Each PSA cycle included feed pressurization/feed (FP/P), heavy reflux (HR) and countercurrent depressurization (CnD) steps; they differed only in the way the CnD step was carried out: PSA Cycle I was carried out under total reflux (i.e., with no 14 CO heavy product production); PSA Cycle II was carried out with discontinuous 14 CO heavy product production; and PSA Cycle III was carried out with continuous 14 CO heavy product production. The effects of the CnD step valve coefficient ( c v ), heavy reflux ratio ( R R ), and cycle time ( t cyc ) on the PSA process performance were determined in terms of the 14 CO enrichment, 14 CO recovery and CO feed throughput. The results showed that there was essentially no limit to the extent of the 14 CO enrichment, despite the inherently low 14 CO/ 12 CO (1.05) and 14 CO/ 13 CO (1.12) separation factors for these isotopes on NaX zeolite. Under total reflux an optimum c v was found for the CnD step and 14 CO enrichments as high as 152 were obtained. Using the optimum c v under finite reflux, a 14 CO enrichment approaching 20 and a 14 CO recovery approaching 100 % were easily achieved with discontinuous (PSA Cycle II) or continuous (PSA Cycle III) 14 CO heavy product production. There was essentially no difference in the performance of PSA Cycles II and III, a counterintuitive result. The 14 CO enrichment and the 14 CO recovery both increased with decreasing CO feed throughputs and higher R R , which were always very close to unity.