Enriching PSA Cycle for the Production of Nitrogen from Air

Abstract

A novel 2-bed 4-step enriching pressure vacuum swing adsorption (PVSA) cycle was developed for the production of N2 from air, using an X-type zeolite, with the separation being equilibrium-driven. The four steps were low-pressure feed, countercurrent heavy product pressurization, countercurrent high-pressure heavy reflux, and cocurrent depressurization. The enriched heavy and light products (N2 and O2, respectively) were withdrawn from the system during the feed and heavy reflux steps, with both products being produced at the high pressure. In a series of 20 PVSA experiments, which were performed at a constant high-to-low-pressure ratio (π = 4.1), the effects of the feed and heavy product flow rates on the periodic state process performance were studied in terms of the O2 impurity, N2 recovery, N2 productivity, and feed throughput. The observed trends were as expected, with higher N2 recoveries (and corresponding N2 productivities) and O2 impurities generally being obtained at higher feed throughputs and heavy product flow rates. With regard to performance, in terms of N2 purity, one run produced a relatively high-purity N2 product that contained 0.8 vol % O2 at a N2 recovery of 23.7%, N2 productivity of 7.0 L STP h-1 kg-1, and feed throughput of 38.2 L STP h-1 kg-1. In terms of N2 recovery, another run produced a relatively high N2 recovery of 69.4% at a N2 productivity of 38.5 L STP h-1 kg-1 and feed throughput of 60.6 L STP h-1 kg-1, with the N2 product containing 10.6 vol % O2. This run also resulted in the highest N2 productivity. The overall performance of this relatively simple 2-bed 4-step enriching PVSA cycle compared quite favorably with the performances of the more-familiar N2 PSA processes that are either equilibrium-driven or kinetically driven and based exclusively on the stripping PSA cycle concept, especially because π was reasonably small.

Experimental Study of a Dual Reflux Enriching Pressure Swing Adsorption Process for Concentrating Dilute Feed Streams

“…These two approaches are referred to as stripping PSA and enriching PSA, respectively. [6][7][8]11 The stripping PSA approach dominates the literature, whereas only a paucity of information is available on the enriching PSA approach. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The enriching PSA approach first appeared in the literature in a 1982 patent by Wilson.…”

“…Hirose and co-workers [6][7][8] and also Ebner and Ritter 15,16 showed that the HR enriching PSA process is limited to producing a pure heavy component at less than 100% recovery, and that the DR enriching PSA process has no such limitation and, in principle, can perform the perfect separation of a binary gas mixture by producing two pure components each at 100% recovery. Although either variant of enriching PSA can be used to enrich a heavy gas at any concentration in the feed mixture, such as N 2 from air, 11 enriching PSA appears to have an innate ability to concentrate a trace component in a feed stream, such as Xe in air. [17][18][19] For example, Leavitt examined the enrichment of a low concentration of Ar in N 2 ; 13 Hirose and co-workers studied the enrichment of CO 2 in air; 6-8 they, along with Ritter and coworkers, studied the concentration of Xe in air; [17][18][19] finally, Ritter and co-workers studied the enrichment of a low concentration of ethane in N 2 .…”

Hydrogen and carbon dioxide recovery from the petrochemical flare gas to methanol production using adsorption and absorption combined high-efficient method

“…The mass balance of ith component for the gas phase in the adsorption bed is presented through Eq. (17) [51,52]: Fig. 3 The overall mechanism of CO 2 chemical absorption process where q i in the above equations is described through LDF relation as follows:…”

Numerical Study of Argon Effect on Nitrogen Separation From Air by Pressure Swing Adsorption

“…The demand for high nitrogen purity, over 99%, in a low and medium amount in the industrial sector has urged a lot of companies to produce nitrogen from atmospheric air by PSA process [8]. Zeolite X-type and perovskite-type ceramic were used as adsorbents instead of the CMS sieve for nitrogen separation from air at high pressure [9][10][11][12].…”