The Boc Group, Inc.

Steven L Lerner

Ramachandran Krish Krishnamurthy

Donald L MacLean

Ravi Kumar Jain

Yagya Shukla

Alan G Stokley

Robert A Mostello

Andrew Lloyd-Williams

A process for separation of a gas mixture containing three components, e.g. a mixture comprising hydrogen, carbon monoxide and carbon dioxide produced by steam reforming a hydrocarbon, by pressure swing adsorption is disclosed. In one embodiment of the process, the gas mixture is sequentially passed through first and second adsorptive regions each of which adsorbs a second component more strongly than a first component but less strongly than a third component, a first fraction enriched in the first component is withdrawn from the downstream end of the second region, introduction of gas mixture to the first region is stopped and the second region is closed to the first region, a second fraction enriched in the second component is withdrawn first from the upstream end of the second adsorptive region while passing gas mixture enriched in the third component into the first region from its upstream end and then from the downstream end of the first region, and withdrawing a third fraction enriched in the third component from the upstream end of the first region. The separation process is also applicable to other gas mixtures such as a mixture of hydrogen, argon, methane and nitrogen commonly available as ammonia plant purge gas from which ammonia has been removed.

Separation of gas mixtures including hydrogen

There is disclosed an improved PSA process and apparatus for gas enrichment wherein the pressure levels of the vent gas stream and/or product stream are used to drive gaseous diffusion cells to produce a feed gas stream and/or a purge gas stream to be used in the pressure swing adsorption process to increase on-line production time and to utilize the waste pressure energy thereby decreasing energy requirements per unit of production.

PSA process and apparatus employing gaseous diffusion barriers

This invention relates to an energy efficient method of vacuum regenerating an adsorbent bed. In a typical process, the adsorbent bed undergoes an adsorption step, a vent step, and a vacuum purge step. According to the present invention, the energy of the usually discarded vent gas is used to raise a dense liquid from a lower tank to a higher tank. The potential energy of the raised liquid, upon returning from the higher tank to the lower tank, is used to generate a vacuum for vacuum regeneration of the adsorbent bed.

Hydrostatic method employing PSA vent gas pressure for vacuum

An improved high yield process is disclosed for argon recovery from an ammonia synthesis plant purge gas comprising hydrogen, nitrogen, argon, ammonia, and methane. In one embodiment of the present invention, this purge gas is subjected to the following steps:

Argon recovery from ammonia plant purge gas utilizing a combination of

An improved process is provided for the recovery of argon from a gas mixture comprising hydrogen, nitrogen, methane and argon. An example of such a gas mixture is purge gas from an ammonia synthesis plant which has been subjected to the conventional steps of ammonia absorption and a membrane separation to obtain hydrogen for recycle to the ammonia plant. In a first embodiment, the gas mixture is treated in a pressure swing adsorption (PSA) system to remove the methane, residual moisture and most of the hydrogen, the resulting gas mixture is treated in a membrane separator to remove most of the hydrogen, which may be used as purge gas for the PSA system, and the resulting stream treat by cryogenic distillation to separate the nitrogen and residual hydrogen to obtain an essentially pure argon product. In a second embodient, the second treatment is eliminated and all of the hydrogen is removed by the cryogenic distillation. In a third embodiment, metal hydride adsorption is used in place of the membrane to separate the hydrogen. The process is enhanced by the recycle of vent gas from the PSA unit to the process itself or to the ammonia synthesis plant. Alternatively, a cocurrent depressurization product from the PSA plant can be recycled into the process.

Argon recovery from hydrogen depleted ammonia plant purge gas utilizing

Argon and nitrogen are produced in a basic two step process. In a first step, oxygen is removed from a compressed air feed using low temperature PSA (pressure swing adsorption). In the second step, argon and nitrogen mixture is separated by cryogenic distillation. The process yields crude liquid argon and very high purity gaseous nitrogen.

Argon and nitrogen coproduction process

An improved process is disclosed for argon recovery from an ammonia synthesis plant purge gas comprising hydrogen, nitrogen, argon, ammonia, and methane. In one embodiment of the present invention, this purge gas is subjected to the following steps:

An improved process is disclosed for argon recovery from an ammonia synthesis plant purge gas stream comprising hydrogen, nitrogen, argon, methane, and ammonia. This purge gas is conventionally subjected to ammonia absorption and a first membrane separation of hydrogen for recycle to the ammonia plant. The hydrogen depleted non-permeate gas stream from the first membrane separator, comprising the aforesaid four components, and any residual moisture from the ammonia absorption, is subjected, according to a first embodiment of the present invention, to the following steps: (i) Separation of methane and residual moisture and most of the nitrogen in the gas stream in a pressure swing adsorption system using molecular sieve or activated carbon material. (ii) Separation of most of the hydrogen in a second membrane separator. The separated hydrogen may be used as purge gas for regeneration of the pressure swing adsorption systems of step (i). (iii) Separation of the nitrogen and residual hydrogen by cryogenic distillation to obtain essentially pure liquid argon product. In a second embodiment, step (ii) above is eliminated and separation of hydrogen is accomplished by cryogenic separation in combination with step (iii). In a third embodiment, separation of most of the hydrogen is accomplished by metal hydride adsorption in place of membrane separation. The present process is equally applicable with minor modifications for the recovery of argon from ammonia synthesis plant purge gas streams, wherein PSA or cryogenic units are employed instead of the first membrane separator, in order to recover hydrogen for recycle to the ammonia synthesis plant.

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Berkeley Heights, NJ, United States of America

Steven L Lerner