Integrated nitrogen liquefier for a nitrogen and argon producing cryogenic air separation unit

A nitrogen liquefier configured to be integrated with an argon and nitrogen producing cryogenic air separation unit, the nitrogen liquefier comprising:

• a gaseous nitrogen product stream produced from the cryogenic air separation unit and a gaseous nitrogen feed stream comprising between about 1% and 10% of the gaseous nitrogen product stream by volume;
• a nitrogen feed compressor configured to receive the gaseous nitrogen feed stream via a flow control valve disposed upstream of the nitrogen feed compressor and compress the gaseous nitrogen feed stream;
• a nitrogen recycle compressor configured to receive the compressed gaseous nitrogen feed stream from the nitrogen feed compressor or receive the gaseous nitrogen feed stream via a bypass valve and further compress the received stream to produce a further compressed warm nitrogen stream;
• a warm booster compressor disposed downstream of the nitrogen recycle compressor and configured to still further compress a first portion of the further compressed warm nitrogen stream to produce a further compressed cold nitrogen stream;
• a cold booster compressor configured to further compress the cold nitrogen stream to produce a primary nitrogen liquefaction stream;
• a booster loaded warm turbine operatively coupled to the warm booster compressor and configured to expand a second portion of the further compressed warm nitrogen stream to produce a warm recycle stream;
• a booster loaded cold turbine operatively coupled to the cold booster compressor and configured to expand a recycle portion of the primary nitrogen liquefaction stream and produce a cold recycle stream;
• a heat exchanger configured to cool the primary nitrogen liquefaction stream via indirect heat exchange with the warm recycle stream and cold recycle stream to produce a liquid nitrogen product stream;
• wherein the warm recycle stream and cold recycle stream are recycled back to the recycle compressor after exiting the heat exchanger;
• wherein the nitrogen liquefier is configured to operate in a first nil liquid nitrogen mode wherein the flow control valve and the bypass valve are oriented in a closed position such that no portion of the gaseous nitrogen product stream is diverted to the nitrogen liquefier and no liquid nitrogen product stream is produced in the nitrogen liquefier;
• wherein the nitrogen liquefier is configured to operate in a second low liquid nitrogen mode wherein the flow control valve is oriented in a closed position and the bypass valve is oriented in an open position such that a portion of the gaseous nitrogen product stream is diverted as a gaseous nitrogen feed stream to the nitrogen recycle compressor and bypasses the nitrogen feed compressor;
• and
• wherein the nitrogen liquefier is configured to operate in a third high liquid nitrogen mode wherein the flow control valve is oriented in an open position and the bypass valve is oriented in a closed position such that a portion of the gaseous nitrogen product stream is diverted as a gaseous nitrogen feed stream to the nitrogen feed compressor.