US 5,203,888 AGranted

Pressure swing adsorption process with multiple desorption steps

AssigneeUop LLC

InventorRichard T. Maurer

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Abstract

Pressure swing absorption processes are disclosed which employ a standard pressure swing absorption cycle comprising the steps of adsorption, one or more cocurrent depressurization steps for equalization or providing purge gas, a countercurrent depressurization step, a countercurrent purge step, and repressurization steps. The processes of the present invention also include an additional countercurrent desorption step performed in conjunction with the first countercurrent desorption step at above atmospheric pressure and a countercurrent purge step at about the adsorption temperature which can provide increased capacity and recovery as compared to PSA processes that only have one countercurrent depressurization step or otherwise do not have a countercurrent purge step. Preferably the pressure reduction during the second countercurrent depressurization step is accomplished by passing another stream from the process, such as the effluent from the first countercurrent desorption step, as a motive gas through an ejector which is in operative communication with the adsorber bed undergoing the second countercurrent desorption step.

Claims31

Dependent claims

A pressure swing adsorption process for separating a first component from a feedstream comprising said first component and at least one other component, wherein a plurality of adsorber beds are employed and each of said adsorber beds is subjected to a repetitive cycle comprising the steps of;

(a) passing the feedstream to a first adsorber bed containing adsorbent having adsorptive capacity for said other component at effective adsorption conditions including an adsorption pressure and temperature, and withdrawing a product stream enriched in said first component relative to the feedstream from the first adsorber bed;
(b) cocurrently depressurizing the first adsorber bed to an equalization pressure that is lower than the adsorption pressure and passing the effluent therefrom to a second adsorber bed being repressurized;
(c) countercurrently depressurizing the first adsorber bed to a first desorption pressure that is above atmospheric pressure and lower than the equalization pressure and effective to desorb said other component and withdrawing a first desorption effluent comprising said other component;
(d) countercurrently purging the first adsorber bed with a purge feed at about the adsorption temperature and withdrawing a purge effluent comprising said other component;
(e) either simultaneously with or subsequently to said countercurrently purging further countercurrently depressurizing the first adsorber bed to a second desorption pressure that is lower than the first desorption pressure and effective to further desorb said other component and withdrawing a second desorption effluent stream comprising said other component;
and
(f) repressurizing the first adsorber bed to the adsorption pressure.

4 more elements

A pressure swing adsorption process for separating a first component from a feedstream comprising said first component and at least one other component, wherein a plurality of adsorber beds having a feed end and a product end are employed and each of said adsorber beds is subjected to a repetitive cycle comprising the steps of:

(a) passing the feedstream to the feed end of a first adsorber bed containing adsorbent having adsorptive capacity for said other component at effective adsorption conditions including an adsorption pressure and temperature, and withdrawing a product stream enriched in said first component relative to the feedstream from the product end of the first adsorber bed;
(b) cocurrently depressurizing the first adsorber bed to an equalization pressure that is lower than the adsorption pressure and passing the effluent therefrom to the product end of a second adsorber bed being repressurized;
(c) countercurrently depressurizing the first adsorber bed to a first desorption pressure that is above atmospheric pressure and lower than the equalization pressure and effective to desorb said other component and withdrawing a first desorption effluent comprising said other component from the feed end of the first adsorber bed;
(d) countercurrently purging the first adsorber bed with a purge feed comprising the first component at about the adsorption temperature and withdrawing a purge effluent comprising said other component from the feed end of the first adsorber bed;
(e) either simultaneously with or subsequently to said countercurrently purging, further countercurrently depressurizing the first adsorber bed to a second desorption pressure that is lower than the first desorption pressure and effective to further desorb said other component and withdrawing a second desorption effluent stream comprising said other component from the feed end of the first adsorber bed, wherein said further countercurrently depressurizing is conducted by passing at least a portion of the first desorption effluent stream from a third adsorber bed which is simultaneously undergoing said countercurrently depressurizing to the first desorption pressure, through an ejector in operative communication with the first adsorber bed;
and
(f) repressurizing the first adsorber bed to the adsorption pressure.

4 more elements

A pressure swing adsorption process for enriching the hydrogen concentration of a feedstream comprising hydrogen and at least one other component selected from the methane, ethane, carbon monoxide, carbon dioxide, ammonia, nitrogen, hydrogen sulfide and water, wherein a plurality of adsorber beds having a feed end and a product end are employed and each of said adsorber beds is subjected to a repetitive cycle comprising the steps of:

(a) passing the feedstream to the feed end of a first adsorber bed containing adsorbent having adsorptive capacity for said other component at effective adsorption conditions including an elevated adsorption pressure, and withdrawing a product stream enriched in hydrogen relative to the feedstream from the product end of the first adsorber bed;
(b) cocurrently depressurizing the first adsorber bed to an equalization pressure that is lower than the adsorption pressure and passing the effluent therefrom to the product end of a second adsorber bed being repressurized;
(c) countercurrently depressurizing the first adsorber bed to a first desorption pressure that is lower than the equalization pressure and effective to desorb said other component and withdrawing a first desorption effluent comprising said other component from the feed end of the first adsorber bed;
(d) countercurrently purging the first adsorber bed with a purge feed comprising hydrogen and withdrawing a purge effluent comprising said other component from the feed end of the first adsorber bed;
(e) either simultaneously with or subsequently to said countercurrently purging, further countercurrently depressurizing the first adsorber bed to a second desorption pressure that is lower than the first desorption pressure and effective to further desorb said other component and withdrawing a second desorption effluent stream comprising said other component from the feed end of the first adsorber bed, wherein said further countercurrently depressurizing is conducted by passing at least a portion of the first desorption effluent stream from a third adsorber bed which is simultaneously undergoing said countercurrently depressurizing to the first desorption pressure, through an ejector in operative communication with the first adsorber bed;
and
(f) repressurizing the first adsorber bed to the adsorption pressure.

4 more elements

Dependencies are inferred from the claim text.