Purification of gases, in synthesis gas production process

A gas purification process, comprising the steps,

• 1) supplying a first stream of feed gas containing hydrogen and nitrogen in a MOL. Ratio of about 2/1, and also containing methane and argon,
• 2) cryogenically separating the feed gas into the following
• a) a second stream of synthesis gas containing hydrogen and nitrogen in a MOL. Ratio of about 3/1,
• b) a waste gas stream containing principally nitrogen, and also containing substantially all of the methane supplied in the first stream,
• 3) and splitting the waste gas stream into:
• c) a third stream of nitrogen rich gas
• d) a fourth stream of methane rich gas useful as a fuel, or as a feed to a subsequent process,
• 4) there being a cold box having a common cold interior, and wherein said first, second, third and fourth streams, and said waste gas stream after cooling thereof are passed through said common cold interior of said cold box, said interior effectively maintaining throughout the entirety of the gas purification process the same temperature at which said first, second, third and fourth streams are passed through the cold box interior after said cryogenically separating, said second stream of synthesis gas passed to the cold box at a temperature below about −284° F.
• 5) and then delivering said second stream of synthesis gas to an ammonia synthesis process.