Patent ID: 9453674
Filing Date: 2016-09-27
CPC Classification: F25J

Claim Text:
1. A method of reboiling a lower pressure column of a double column arrangement, said method comprising: partially vaporizing an oxygen-rich liquid within a down-flow heat exchange zone and a thermosiphon heat exchange zone, situated below the down-flow heat exchange zone; the oxygen-rich liquid produced as a result of a distillation of an oxygen and nitrogen containing mixture within the lower pressure column and the partial vaporization of the oxygen-rich liquid initiating the formation of an ascending vapor phase of the oxygen and nitrogen containing mixture to be distilled within the lower pressure column; partially vaporizing a greater proportion of the oxygen-rich liquid within the down-flow heat exchange zone than within the thermosiphon heat exchange zone and at a lower temperature difference than that of the thermosiphon heat exchange zone; the partial vaporization of the oxygen-rich liquid within the down-flow heat exchange zone occurring through indirect heat exchange between the oxygen-rich liquid, as the oxygen-rich liquid moves in a downward direction, with a first nitrogen-rich vapor stream, composed of nitrogen-rich vapor column overhead produced in a higher pressure column of the double column arrangement, thereby condensing the first nitrogen-rich vapor stream; the partial vaporization of the oxygen-rich liquid within the thermosiphon heat exchange zone occurring through indirect heat exchange between residual liquid, produced as a result of the partial vaporization of the oxygen-rich liquid within the down-flow heat exchange zone and drawn in an upward direction through thermosiphon effect, with a second nitrogen-rich vapor stream, thereby condensing the second nitrogen-rich vapor stream; the second nitrogen-rich vapor stream withdrawn from the higher pressure column at a location thereof below the first nitrogen-rich vapor stream and with a greater oxygen concentration than the first nitrogen-rich vapor stream such that the a sufficient temperature difference is able to be maintained within the thermosiphon heat exchange zone at an operational pressure of the lower pressure column at which the partial vaporization of the oxygen-rich liquid is conducted; and the first nitrogen-rich vapor stream, after having been condensed, at least in part, returned to the higher pressure column as a first reflux and the second nitrogen-rich vapor stream, after having been condensed, at least in part, introduced into the higher pressure column at a location below the first reflux.