To provide a method for forming high-purity carbon monoxide and forming high-purity compressed hydrogen suitable for use in formation of an ammonia synthesizing mixture.

In this method, the carbon monoxide is formed by partial condensation within a heat exchanger 310 from the condensed fraction removed in the bottom of a pot 320 of a separator. Impure hydrogen 321 is formed in the apex of the pot 320 and is refined by scrubbing with nitrogen in a column 350. The ammonia synthesizing mixture is formed from a stream 353 of the hydrogen collected in the apex of the column. Further, the carbon monoxide is formed also from the fraction 351 collected in the bottom of the nitrogen scrubbing column 350. All the columns and heat exchangers exist within one cold box.