heat exchanger 168 is mixed with incoming low pressure gaseous nitrogen stream 92 and recycled for compression and liquefaction as described earlier liquid nitrogen product flows from the system via stream 182 in the flow diagram shown in fig2 liquid nitrogen stream 182 returning to the air separation unit is indirectly derived from the liquid nitrogen recovered from separator 154 for this purpose a portion of high pressure inlet nitrogen stream 184 is condensed against a portion of liquid nitrogen stream 186 in reboiler condenser 188 condensed liquid nitrogen side stream 182 is sent to the distillation column system not seen vaporized nitrogen overhead stream 162 is either sent totally to heat exchanger 110 as shown or a portion of stream 162 can be sent to the heat exchangers not shown of the air separation unit according to the present invention an energy efficient process is provided which is particularly adapted to recover refrigeration from lng being vaporized for pipeline introduction this obviates the known inefficiencies associated with recirculating fluorocarbon and its ancillary equipment by interstage cooling with lng of the successive component compression steps the inlet volume of the air component feed is reduced this keeps the size of.