NOVELTY - A gas purification process involves supplying a feed gas stream (110), and cryogenically separating the feed gas into a synthesis gas stream and a waste gas stream. The waste gas stream is divided into a hydrogen/nitrogen gas stream, a nitrogen stream, and a methane rich gas stream (114). The feed gas stream, synthesis gas stream, hydrogen/nitrogen gas stream, nitrogen stream, methane rich gas stream and waste gas stream are cooled and passed through a coldbox unit (115). Then, the synthesis gas stream and the hydrogen/nitrogen gas stream are delivered to an ammonia synthesis process.    USE - Process for purifying gas (claimed) for manufacturing ammonia.    ADVANTAGE - The process enables purifying the gas in an efficient manner.    DETAILED DESCRIPTION - A gas purification process involves supplying a feed gas stream containing hydrogen and nitrogen in a mole ratio of 2:1, and methane and argon. The feed gas is cryogenically separated into a synthesis gas stream containing hydrogen and nitrogen in a mole ratio of 3:1 and into a waste gas stream containing nitrogen, and methane supplied to the feed gas stream. The waste gas stream is divided into a hydrogen/nitrogen gas stream, a nitrogen stream (97 mole%) with the remainder of argon, and a methane rich gas stream as a fuel. The feed gas stream, synthesis gas stream, hydrogen/nitrogen gas stream, nitrogen stream, methane rich gas stream and waste gas stream are cooled and passed through a common cold interior(s) of a coldbox unit. The interior(s) is effectively maintained throughout the entirety of the gas purification process and the same temperature at which the streams are passed through interior(s) of the coldbox unit after the cryogenic separation. Then, the synthesis gas stream and the hydrogen/nitrogen gas stream are delivered to an ammonia synthesis process.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic illustration of a gas purification process.    Feed gas stream (110)    Nitrogen rich gas stream (113)    Methane rich gas stream (114)    Coldbox unit (115)    Refluxed condenser (119)