Pressure swing absorption system

Claim 1

A molecular sieve, pressure swing adsorption process employing at least two columns for generating an enriched gas which comprises the sequential steps of: (a) passing a pressurized gas mixture at an adsorption pressure sufficient to support a pressure swing cocurrently through a first adsorption column of molecular sieves thereby generating enriched gas, said gas flowing to a product tank; (b) prior to breakthrough of said first column, partially pressurizing a second adsorption column of molecular sieves by passing a small fraction of enriched gas from said product tank countercurrently to said second column, thereafter stopping said gas mixture flow to said first column; (c) partially venting said first adsorption column countercurrently, flowing the vented gas cocurrently to said second adsorption column (bottoms equalization), thereafter isolating said first column; (d) substantially simultaneously with step (c), passing said gas mixture cocurrently to said partly pressurized second column, thereby fully pressurizing said second column to the adsorption pressure; (e) countercurrently fully venting said isolated first column to atmospheric pressure while passing the gas mixture cocurrently through said pressurized second column thereby generating enriched gas, said enriched gas flowing to said product tank; (f) regenerating said first column by countercurrently purging said first column with enriched gas from the product tank; (g) repeating the sequence of steps (a)-(f) treating said second column as said first column and vice versa.

Claim 12

An apparatus for the fractionation of a gas mixture, said apparatus comprising a pressure swing adsorption unit having: (a) at least two pressure resistant housings for molecular sieve adsorbent, each housing having an inlet and an outlet; (b) a pressure resistant product gas housing having one inlet and at least two outlets; (c) a main gas mixture inlet; (d) a purge gas/waste gas outlet; (e) a first connecting means between said main gas mixture inlet and each of said molecular sieve housings inlets; (f) a second connecting means between said product gas housing inlet and each of said molecular sieve housings outlets; (g) a third connecting means between said purge/waste gas outlet and each of said molecular sieve housings inlets; (h) a fourth connecting means between one of said product gas housing outlets and each of said molecular sieve housings outlets; there being a valve in each connecting means, said valves being arranged such that said molecular sieve housings are connected in a parallel gas flow arrangement, said valves being connected to a valve control means whereby gas flow in said unit is controlled by the opened or closed position of said valves such that said apparatus is capable of a continuous cycle between said two pressure resistant molecular sieve housings comprising the steps of (1) adsorption; (2) countercurrent venting between molecular sieve housing inlets; (3) product gas purge from said product gas housing; (4) partial repressurization with product gas from said product gas housing; (5) partial cocurrent repressurization using gas vented countercurrently from one molecular sieve housing; (6) final repressurization with feed gas and (7) adsorption.

Claim 13

An apparatus for the fractionation of a gas mixture, said apparatus comprising a pressure swing adsorption unit having: (a) at least two pressure resistant housings for molecular sieve adsorbent, each housing having an inlet and an outlet; (b) a pressure resistant product gas housing having one inlet and at least two outlets; (c) a main gas mixture inlet; (d) a purge gas/waste gas outlet; (e) a first connecting means between said main gas mixture inlet and each of said molecular sieve housings inlets; (f) a second connecting means between said product gas housing inlet and each of said molecular sieve housings outlets; (g) a third connecting means between said purge/waste gas outlet and each of said molecular sieve housings inlets; (h) a fourth connecting means between one of said product gas housing outlets and each of said molecular sieve housings outlets; there being a valve in each connecting means, said valves being arranged such that said molecular sieve housings are connected in a parallel gas flow arrangement, said valves being connected to a valve control means whereby gas flow in said unit is controlled by the opened or closed position of said valves such that said apparatus is capable of a continuous cycle between said two pressure resistant molecular sieve housings comprising the steps of (1) adsorption; (2) countercurrent venting between molecular sieve housing inlets; (3) product gas purge from said product gas housing; (4) partial repressurization with product gas from said product gas housing; (5) partial cocurrent repressurization using gas vented countercurrently from one molecular sieve housing; (6) final repressurization with feed gas and (7) adsorption.