This patent describes an integrated ammonia – urea process where a high pressure impure ammonia stream from the ammonia synthesis is used as feed for the urea production. The impurities are hydrogen, nitrogen and argon and typically pressure reduction is applied to reduce these impurities. Recompression is then needed again to enable the synthesis reaction to urea.
The invention claims that it is possible to use this impure ammonia stream because the hydrogen in the ammonia will react with the oxygen in the carbon dioxide forming water.
The patent even describes the option that the total impure ammonia stream of the ammonia plant can be purified in the urea plant leading to even more advantages. It is not clear how a minimum oxygen content is assured for passivation purposes and how the reaction between hydrogen and oxygen will be controlled.

1962 Cook 3069234 Integrated NH3-Urea.pdf