Patent ID: 6113671
Filing Date: 2000-09-05
Classification: A23B,B01D,Y02C

Abstract:
A process for modifying the composition of a gaseous atmosphere comprising nitrogen, oxygen, carbon dioxide, water vapor and ethylene contained in a chamber, using a series of four single adsorption vessels, adjacent vessels of the series being connected by a single process flow conduit, by a pressure swing adsorption method comprising the successive steps:(a) pressurizing a portion of said atmosphere to form a pressurized atmosphere;(b) adsorbing water vapor from said pressurized atmosphere by passing it cocurrently through the first adsorption vessel in said series, which contains an adsorbent which preferentially adsorbs water vapor, thereby adsorbing water vapor from said pressurized atmosphere and producing a pressurized water vapor-depleted atmosphere;(c) passing said pressurized water vapor-depleted atmosphere cocurrently through the single process flow conduit between the first and second adsorption vessels and then cocurrently through said second adsorption vessel, which contains an adsorbent which preferentially adsorbs ethylene, thereby adsorbing ethylene from said pressurized said water vapor-depleted atmosphere and producing a pressurized water vapor- and ethylene-depleted atmosphere;(d) passing said pressurized water vapor- and ethylene-depleted atmosphere cocurrently through the single process flow conduit between the second and third adsorption vessels and then cocurrently through said third adsorption vessel, which contains an adsorbent which preferentially adsorbs carbon dioxide, thereby adsorbing carbon dioxide from said pressurized water vapor- and ethylene-depleted atmosphere and producing a pressurized water vapor-, ethylene- and carbon dioxide-depleted atmosphere;(e) passing said pressurized water vapor-, ethylene- and carbon dioxide-depleted atmosphere cocurrently through the single process flow conduit between the third and fourth adsorption vessels and then cocurrently through said fourth adsorption vessel, which contains an adsorbent which preferentially adsorbs nitrogen, thereby adsorbing nitrogen from said pressurized water vapor-, ethylene- and carbon dioxide-depleted atmosphere;(f) isolating and depressurizing said second adsorption vessel, thereby desorbing ethylene from the adsorbent therein, and venting desorbed ethylene to the environment;(g) countercurrently depressurizing said fourth adsorption vessel, thereby desorbing nitrogen-rich gas from the adsorbent therein;(h) purging said third adsorption vessel by passing said nitrogen-rich gas countercurrently through the single process flow conduit between the third and fourth adsorption vessels and then countercurrently through said third adsorption vessel;(i) passing nitrogen-rich gas from said third adsorption vessel countercurrently through the single process flow conduit between the second and third adsorption vessels and then countercurrently through said second adsorption vessel;(j) purging said first bed by passing nitrogen-rich gas from said second adsorption vessel countercurrently through the single process flow conduit between the first and second adsorption vessels and then countercurrently through said first adsorption vessel, thereby producing a moistened nitrogen-rich gas; and(k) returning said moistened nitrogen-rich gas to said chamber.