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초록

For efficient H-2 production from NH3-cracked gas, a series-bed pressure swing adsorption (PSA) process employing external air purge was developed for the simultaneous removal of NH3 and N-2. The PSA process comprised a relatively small-scale activated carbon guard bed (A-BED) for NH3 removal and a zeolite 5A purifier bed (Z-BED) for N-2 removal, designed to achieve fuel cell-grade H-2 (purity >99.97%, NH3 < 0.1 ppm). After a mathematical PSA model was validated against experimental NH3 breakthrough curve on A-BED, the dynamic behavior of series-bed PSAs was analyzed. The results indicated that the A-BED could sufficiently recover its capacity for NH3 removal using external air as a purge gas. The 3-3 series-bed configuration indicated that introducing a providing-purge (PP) step enhanced H-2 recovery by approximately 5% without compromising fuel cell-grade purity. The 4-4 series-bed configuration exhibited further enhanced H-2 recovery owing to the supply of a relatively high-quality purge gas and two pressure equalization steps between Z-BEDs after the PP step. Consequently, 76.91% H-2 recovery was achieved at fuel cell-grade purity (99.9733%), indicating the importance of effective interconnectivity of A-BEDs and Z-BEDs in the series-bed PSA. Since the purge gases for NH3 desorption and remaining air removal in the A-BED were supplied to a furnace as flare gas, possible heat recovery from these tail gases at various H-2 purity levels was also evaluated. The proposed PSA framework thus offers a technically feasible and energy-efficient approach for high-purity H-2 production in NH3 cracking plants.