| 摘要 |
A method of operating a lower pressure of column of a double distillation column unit. In accordance with the method an ascending vapor phase is initiated within a lower pressure column by vaporizing a descending liquid phase at a column location situated between mass transfer elements and a sump region of the lower pressure column. The liquid phase is vaporized within two or more down-flow reboilers fed with the liquid phase so that the unboiled liquid from one of the down-flow reboilers is fed to another of the down-flow reboilers, thereby to cause vaporization to be distributed between the down-flow reboilers. The down-flow reboilers are configured such that sufficient vaporization occurs to produce a predetermined liquid-vapor ratio at the column location between the transfer elements and the sump without the requirement of recirculating sump liquid to prevent dry out.
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