Ammonia production with enriched air reforming and nitrogen injection into the synthesis loop

A retrofit method for increasing the production capacity of an ammonia plant having (1) a front end including a primary reformer, a secondary reformer, an air compressor, and a CO.sub.2 removal unit for reacting a hydrocarbon feed stream with steam and compressed air to produce a makeup syngas stream having a HN ratio at a pre-existing capacity, and (2) a synthesis loop wherein a recycle syngas stream is combined with the makeup syngas stream to form a syngas feed to ammonia converters for producing ammonia at a pre-existing capacity, comprising the steps of:

• installing an air separation unit to produce oxygen-rich and nitrogen-rich streams;
• injecting the oxygen-rich stream into the compressed air to form an oxygen enriched stream for feed to the secondary reformer containing from 25 to 40 volume percent oxygen and operating the front end at an increased capacity relative to its pre-existing capacity wherein a raw syngas stream from the CO.sub.2 removal unit has an increased HN ratio relative to the ratio at the pre-existing capacity;
• supplying the nitrogen-rich stream to the synthesis loop;
• and
• modifying the synthesis loop to increase the ammonia production capacity of the synthesis loop.

A process for ammonia synthesis, comprising the steps of:

• (a) separating air into oxygen-rich and nitrogen-rich streams;
• (b) mixing air with the oxygen-rich stream from step (a) to form an oxygen-enriched stream containing 25-40 mole percent oxygen;
• (c) injecting the oxygen-enriched stream from step (b) into an autothermal reformer of a syngas unit including a primary reformer upstream from the autothermal reformer and a downstream shift converter, CO.sub.2 removal unit and methanator, to produce a syngas stream;
• (d) supplying the syngas stream from step (c) and the nitrogen-rich stream from step (a) as makeup gas to an ammonia synthesis loop;
• (e) operating the ammonia synthesis loop to (1) convert nitrogen and hydrogen in an ammonia synthesis reactor feed stream to form an ammonia-rich stream, (2) recover ammonia from the ammonia rich stream to form a recycle gas stream, (3) remove a purge stream from the synthesis loop, (4) recover a hydrogen-rich gas from the purge stream, and (5) combine the hydrogen-rich gas with the recycle stream and the makeup gas from step
• (d) to form the ammonia synthesis reactor feed stream.