US 4,398,926 AGranted

Enhanced hydrogen recovery from low purity gas streams

AssigneeUnion Carbide Corporation

InventorKishore J. Doshi

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Abstract

A high pressure as stream having a hydrogen content of up to about 90 mol percent is passed to a separator containing a permeable membrane capable of selectively permeating hydrogen. The separator is used to achieve a bulk separation of the desired hydrogen from impurities contained in the gas stream. The separated hydrogen is recovered at a reduced pressure and is passed to a pressure swing adsorption system adapted for operation at said reduced pressure. The off-gas from the separator is recovered essentially at the higher pressure of the gas stream. A portion of the off-gas is throttled to a lower pressure, with appropriate power recovery, and is passed to the pressure swing adsorption system as a co-feed gas, thereby contributing to the recovery of purified hydrogen product and to a reduction in the operating costs for the desired hydrogen separation and purification. The remaining off-gas is recovered as a relatively high pressure fuel or feed gas for other purposes.

Claims15

Dependent claims

An improved pressure swing adsorption process for the separation and purification of hydrogen contained in a high pressure feed gas stream comprising:

(a) passing said feed gas stream having a hydrogen content of up to about 90 mol % at a feed gas pressure in excess of about 600 psig into a separator containing a gas permeable membrane capable of selectively permeating said hydrogen;
(b) withdrawing the non-permeate portion of said gas stream from the separator essentially at the feed gas pressure, said non-permeate gas containing a substantial portion of said impurities;
(c) withdrawing the hydrogen-rich permeate gas from the separator at a reduced pressure;
(d) passing said hydrogen-rich permeate gas as a feed gas at said reduced pressure to the feed end of an adsorbent bed capable of selectively adsorbing impuritied from said permeate gas, said bed thereby having an advancing impurity adsorption front therein, with unadsorbed, purified hydrogen product gas being withdrawn from the product end of the bed;
(e) releasing void space gas from the product end of the bed, thereby cocurrently depressurizing said bed and moving said adsorption front toward said product end of the bed;
(f) countercurrently depressurizing the bed to a lower desorption pressure to desorb and release said impurities from the feed end of the bed;
(g) repressurizing said bed from the lower desorption pressure to said pressure level at which permeate gas is passed to the bed;
(h) depressurizing said non-permeate gas or a portion thereof from said feed gas pressure;
(i) passing depressurized non-permeate gas to the feed end of the adsorbent bed at said reduced pressure as a co-feed gas, prior to step (e) above;
and
(j) repeating said steps (a)-(i) with additional quantities of said feed gas stream,
whereby product recovery can be enhanced at reduced operating costs.

9 more elements

An improved pressure swing adsorption apparatus for the separation and purification of hydrogen contained in a high pressure gas stream comprising:

(a) a separator containing a gas permeable membrane capable of selectively permeating said hydrogen at a separator feed gas pressure in excess of about 600 psig;
(b) means for passing said gas stream at said feed gas pressure to the feed inlet portion of said separator;
(c) outlet means for withdrawing hydrogen-rich permeate gas from the separator at a reduced pressure;
(d) outlet means for separately withdrawing the non-permeate portion of the gas stream from the separator essentially at said feed gas pressure;
(e) a pressure swing adsorption system having at least one adsorbent bed therein, said adsorbent bed having a feed end and a product end and being capable of selectively adsorbing impurities from a hydrogen-containing gas stream, said adsorption system being adapted for feed gas introduction-adsorption-hydrogen product gas discharge at said reduced pressure, co-feed with non-permeate gas, cocurrent depressurization to an intermediate pressure level, countercurrent depressurization to a lower desorption pressure, purge and repressurization to said adsorption pressure in each bed, on a cyclic basis;
(f) means for passing said hydrogen-rich permeate gas at said reduced pressure to the feed end of each bed as feed gas;
(g) means for reducing the pressure of said non-permeate gas from said separator feed gas pressure to a lower level(s);
and
(h) conduit means for passing said non-permeate gas to the feed end of each said bed at a reduced pressure as a co-feed gas prior to said cocurrent depressurization of each said bed,
whereby the integration of the processing streams from said separator with said pressure swing adsorption system enables overall hydrogen product recovery to be enhanced at reduced operating costs.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/371,285Filed 23 Apr 1982
Granted: 16 Aug 1983
Term ends: Not estimatedThe source records don’t support an estimate.

Classification17 codes

B01D 53/047
With stationary adsorbents: pressure swing adsorption
B01D 53/229
By diffusion: integrated processes
C01B 3/501
Separation of hydrogen or hydrogen-containing gases from gaseous mixtures, e.g. purification: by diffusion
C01B 3/56
Separation of hydrogen or hydrogen-containing gases from gaseous mixtures, e.g. purification: by contacting with solids; Regeneration of used solids

Family

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