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

An air separation unit comprising:

• a main air compression system configured for receiving a stream of incoming feed air and producing a compressed air stream;
• an adsorption based pre-purifier unit configured for removing water vapor, carbon dioxide, nitrous oxide, and hydrocarbons from the compressed air stream and producing a compressed and purified air stream;
• a main heat exchange system configured to cool the compressed and purified air stream to temperatures suitable for fractional distillation;
• a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser-reboiler, the distillation column system further includes an argon column arrangement operatively coupled with the lower pressure column, the argon column arrangement having at least one argon column and an argon condenser, the distillation column system configured for receiving the cooled, compressed and purified air stream and produce at least two or more oxygen enriched streams from the lower pressure column;
• an argon product stream, and a gaseous nitrogen product stream;
• wherein at least one of the oxygen enriched streams from the lower pressure column is an oxygen enriched condensing medium directed to the argon condenser;
• and
• a nitrogen liquefier comprising a nitrogen feed compressor;
• a nitrogen recycle compressor;
• a warm booster compressor, a booster loaded warm turbine, a cold booster compressor, and a booster loaded cold turbine, a flow control valve disposed upstream of the nitrogen feed compressor and a bypass valve configured for diverting a gaseous nitrogen feed stream to the nitrogen recycle compressor;
• wherein the nitrogen liquefier is integrated with the main heat exchange system and distillation column system and wherein the nitrogen liquefier is arranged or configured to receive a portion of the gaseous nitrogen product stream and produce a liquid nitrogen stream;
• wherein the nitrogen liquefier is configured to operate in three modes, including:
• (i) a first nil liquid nitrogen mode where 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;
• (ii) a second low liquid nitrogen mode wherein a portion of the gaseous nitrogen product stream is diverted as the gaseous nitrogen feed stream to the nitrogen liquefier, the gaseous nitrogen feed stream bypasses the nitrogen feed compressor and is diverted to the nitrogen recycle compressor;
• and (iii) a third high liquid nitrogen mode wherein a portion of the gaseous nitrogen product stream is diverted as the gaseous nitrogen feed stream to the nitrogen feed compressor of the nitrogen liquefier.