| 摘要 |
The process and the device are used for low-temperature separation of air with a distilling-column system for nitrogen-oxygen separation (20), which has at least one separation column (21, 22). A main air stream (1, 5) is compressed in an air compressor (2) and purified in a purification device (4). A first air stream (7) and a second air stream (8) are diverted from the main air stream (5). The first air stream (7) is further compressed in two secondary compressors (10, 13) that are connected in series. The further compressed first air stream (15) is cooled by indirect heat exchange (16), and at least partially liquefied or pseudo-liquefied, and then introduced into the distilling-column system for nitrogen-oxygen separation (20). The second air stream (8) is cooled by indirect heat exchange (16) and then, divided into two partial streams (24, 27), is actively depressurized in two expanders (25, 28), whereby the two expanders have essentially the same inlet pressure. The actively depressurized partial streams (26, 29) of the second air stream are introduced (30, 129) at least in part into the distilling-column system for nitrogen-oxygen separation (20). The mechanical energy that is produced in the active depressurization (25, 28) of the second air stream is used at least partially in the driving of the two secondary compressors (10, 13) that are connected in series. A liquid product stream (31) is removed from the distilling-column system for nitrogen-oxygen separation (20), brought to an elevated pressure in the liquid state (32), and evaporated or pseudo-evaporated under this elevated pressure by indirect heat exchange (16) with the first air stream (15), and finally removed as a gaseous product stream (34). Both secondary compressors (10, 13) are operated with an inlet temperature that is higher than 250 K, in particular higher than 270 K.
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