Air Products and Chemicals, Inc.

Permea, Inc.

Lyndon J Kellogg, Jr

Jung Soo Choe

Steven R Auvil

Robert F Weimer

Jun S Choe

A membrane-assisted process to produce ammonia is set forth wherein the recycle stream from the ammonia process containing primarily unreacted hydrogen and nitrogen but also containing inerts and unrecovered ammonia is separated in a first ammonia-selective membrane separator into a permeate stream enriched in ammonia and a non-permeate stream enriched in hydrogen, nitrogen and the inerts which is recycled to the reactor feed. A key to the present invention is that the permeate stream enriched in ammonia is recycled to the reactor effluent. In one embodiment of the present invention, the purge stream from the ammonia process (which represents that portion of the recycle stream which must removed from the process in order to prevent the build-up of the inerts in the process) is separated in a second ammonia-selective membrane separator into a permeate stream enriched in ammonia which is recycled to the reactor feed and a non-permeate stream enriched in hydrogen, nitrogen and the inerts which can be further processed for hydrogen recovery. A key to this embodiment is that a portion of the reactor feed is used to sweep the permeate side of the second membrane separator.

Membrane-assisted process to produce ammonia

A two stage pressure swing adsorption process is set forth for producing the less strongly adsorbed component of a feed gas mixture wherein the first stage utilizes a first adsorbent for bulk removal of the more strongly adsorbed component and wherein the second stage utilizes a second adsorbent for trace removal of the more strongly adsorbed component. A further feature of the present invention is that the desorbed gas from the second stage's depressurization step (consisting primarily of the desired less strongly adsorbed component) is recycled to the first stage in order to improve its performance. In a preferred embodiment of the present invention, high purity nitrogen (less than 1000 ppm oxygen, preferably less than 100 ppm oxygen) is produced from an air feed using a kinetically controlled carbon molecular sieve adsorbent in the first stage and an equilibrium controlled metal complex-based adsorbent in the second stage.

Two stage pressure swing adsorption process for producing the less

Valuable process gas is dried to a low water content, for example a dew point of less than -20.degree. F., using membrane separation in which compression of the permeate gases and condensation and separation of liquid water from the permeate stream is combined with a total recycle of uncondensable permeate gases so that no process gas is lost as a result of the drying operation. Feed gas is combined with the recycled gas either prior to compressing, cooling and separating the liquid water from the process gas or subsequent to these steps, depending upon the pressure of the available feed stream to be dried. Membrane separation efficiency is improved by sweeping the downstream surfaces of the membrane with dried product gas. All of the sweep gas is recaptured with the permeate gases and returned to the separation unit, thereby enabling 100%, recovery of the fresh feed gas from the drying operation. Only liquid water and dissolved gases are purged from the system.

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Slatington, PA, United States of America

Lyndon J Kellogg, Jr