Selective Separation of Ammonia from a Ammonia-Hydrogen-Nitrogen Mixture by Pressure Swing Adsorption Method

概要

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A NH3-PSA process was successfully developed for selective separation of NH3 from a NH3 (5%) -H2 (45%) -N2 (50%) mixture which would be produced from a novel nitrogen fixation process catalyzed with Ruthenium over 200-250°C at atmospheric pressure. The PSA process with dual columns (33mlx2) was designed to be operable with mild conditions of the maximum adsorption pressure of 880-1000 Torr and the minimum desorption/vacuuming pressure of 20-60 Torr, processing the feed mixture at rate below 10l/h. A commercial 3A (K, Na) type zeolite demonstrated distinguished performances: unreacted H2+N2 mixture was recovered with containing only 0.2% of NH3, and the NH3 of 5% in the feed was condensed up to 64% without any change in ratio of remaining H2 to N2. The key of the PSA process was the selection of adsorbent which could adsorb NH3 component predominantly in uptake or speed. The adsorbents tested in this study were as follows; the two kinds of commercial zeolites and three kinds of carbonaceous porous carbons such as a supersurface activated carbon, a molecular sieving carbon (MSC) for air separation PSA, and a wood based porous carbon prepared by heat treatment of a compressed saw dust at 1000°C. The selective NH3 adsorption character found in the PSA performance and the porous structure and pore shape were discussed for improvement of more favorable adsorbent specified for this NH3-PSA process.
生態工学会の論文