MANUFACTURE OF HIGH PURITY LIQUEFIED NITROGEN BASED ON TOTAL LOW PRESSURE FRACTIONATING METHOD AND DEVICE

PURPOSE:To provide a simplified high purity liquefied nitrogen manufacturing method and its manufacturing device which can reduce the concentration of low boiling point impurities to 1 ppb or below at a low cost. CONSTITUTION:A number of new processes are added to the processes of a liquefied nitrogen manufacturing method based on a prior art total low pressure fractionating method. The added processes comprise an introduction process which heat-exchanges a low temperature nitrogen fluid cooled near to a liquefaction point with the liquefied nitrogen in a nitrogen liquefied vessel 21 by means of a heat exchanger 23 and then introduces the heat exchanged fluid into a middle part of a simple fractionating device 24 and a process which brings gas into contact with liquid between the gas rising in the simplified fractionating device and the fluid flowing down from a condensation reboiler 20 in the upper part of the nitrogen liquefied vessel and a process which exhausts a condensed low boiling point component 26 from the top of the condensation reboiler 20.