| 摘要 |
PURPOSE: Provided are a process and an apparatus for low-temperature fractionation of air using the three-column system which is particularly economically favorable. CONSTITUTION: A process for the low-temperature fractionation of air using a three-column system, which has a high-pressure column(11), a low-pressure column(13) and a medium-pressure column(12), in which process (a) a first charge air stream is introduced into the high-pressure column(11), where it is separated into a first oxygen-enriched liquid and a first nitrogen top gas, (b) a first oxygen-enriched fraction(23,24,26) from the high-pressure column(11) is introduced into the medium-pressure column(12) where it is separated into a second oxygen-enriched liquid and a second nitrogen top gas, (c) a second oxygen-enriched fraction(33,35) from the high-pressure column and/or from the medium-pressure column(12) is introduced into the low-pressure column(13), where it is separated into a third oxygen-enriched liquid and a third nitrogen top gas, (d) a nitrogen product stream and/or an oxygen product stream is removed from the low-pressure column(13), (e) at least a portion(36) of the second nitrogen top gas from the medium-pressure column(12) is at least partially condensed by indirect heat exchange(37) with a cooling fluid, characterized in that (f1) a second charge air stream is liquefied and is then used as cooling fluid(78) for the condensation of the second nitrogen top gas(36) from the medium-pressure column(12), and/or (f2) a liquid from an intermediate point of the high-pressure column(11) is used as cooling fluid for the condensation of the second nitrogen top gas(36) from the medium-pressure column(12).
|
