System and method for cryogenic purification of a feed stream comprising hydrogen, methane, nitrogen and argon

A method for purifying a stream comprising hydrogen, nitrogen, methane and argon to produce a hydrogen and nitrogen containing synthesis gas, a methane rich fuel gas, and at least one nitrogen product, the method comprising the steps of:

• conditioning the pre-purified feed stream to a temperature near saturation at a pressure greater than about 300 psia;
• directing the conditioned feed stream to a synthesis gas rectification column configured to produce an hydrogen and nitrogen enriched overhead vapor stream and a methane-rich condensed phase stream proximate the bottom of the synthesis gas rectification column;
• vaporizing the methane-rich condensed phase stream to produce a vaporized or partially vaporized methane-rich stream;
• directing the vaporized or partially vaporized methane-rich stream and a nitrogen reflux stream to a nitrogen rectification column configured to produce a nitrogen containing overhead vapor stream substantially free of methane, and a methane enriched liquid bottoms stream;
• warming at least a portion of the nitrogen containing overhead vapor stream via indirect heat exchange with the feed stream to produce a warm gaseous nitrogen stream and directing the warm gaseous nitrogen stream to a nitrogen recovery system to produce the at least one nitrogen product;
• warming the hydrogen and nitrogen enriched overhead vapor stream via indirect heat exchange with the feed stream to produce the hydrogen and nitrogen containing synthesis gas;
• and
• warming the methane enriched liquid bottoms stream via indirect heat exchange with the feed stream to produce the methane rich fuel gas.