| 摘要 |
642,587. Air separating. ELLIOTT CO. March 31, 1947, No. 8613. Convention date, April 18, 1946. [Class 8(ii)] A method of deriming a counter-current heat exchanger in which a rime depositing gaseous mixture in one passage is cooled by indirect contact with a cold gas in another passage comprises stopping the flow of gaseous mixture to the exchanger, warming said cold gas before it reaches the exchanger and directing the warm gas in reverse direction through the cold gas passage and then in reverse direction through the passage requiring deriming. As shown, air to be separated in a column 14 is deliverd by a compressor 9 to a drier 65 before passing a valve 67 and traverseing warm and cold ends 3, 4 of a countercurrent heat exchanger B, having tubes 5 in which water and carbon dioxide ice are condensed. Cold nitrogen gas from the separator head traverses ducts 21, 22, 41 or valve 66 and the exchanger B and is dis-. charged partly to atmosphere through ducts 48, 49 and a valve 72, and partly through a duct 53 to compressors 27, 28 as explained below. To switch to an exchanger A and to derime the exchanger B, the valves 62, 74 are opened and the valve 66 closed for two or three minutes to allow air from a duct 73 to flow reversely through the cold end 4 of the exchanger B to warm the same. Valves 56, 57 are then opened and valves 67, 68, 72 and a valve 69 closed which results in stopping the air flow through the exchanger B and allowing nitrogen from the warm end 1 of the exchanger A, warmed by a heater 26 if necessary, to pass reversely through the exchanger B past the open valve 74 to flow reversely along the normal air ducts 5 to derime the same. This nitrogen is discharged past a valve 58 into the outlet duct 19. Oxygen gas is separated in the column 14 by liquid nitrogen reflux from a duct 16 cooled by nitrogen from the duct 21. This nitrogen serves as cooling agent in an exchanger 24 after which the nitrogen is joined by nitrogen from the duct 49 and is compressed at 27, 28. This compressed nitrogen is in part fed to a reboiler 18 and in part to a duct 38 where it is joined by compressed nitrogen which has traversed an exchanger 33, a turbo-expander 36 and the duct 22. Oxygen gas is discharged through a duct 19.
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