Abstract: An improvement in the downcomer portion of a distillation column having the seal pan of the downcomer positioned above the adjacent lower tray and below the apron of the downcomer and having a first perforated plate extending down from the bottom of the downcomer to the lower adjacent tray wherein the improvement comprises an extension of the downcomer apron along a radius centered in said downcomer through an angle of greater than 0 to less than 180.degree. to form an extension extending into the downcomer to prevent vapor from entering the downcomer because of misalignment during installation, reduce the exit gap from the downcomer and to allow additional vapor perforations.

Abstract: An improved distillation column downcomer, in which the seal pan of the downcomer is spaced above the adjacent lower tray and connected to the tray by a perforated plate, whereby the effective active tray area is increased (by placing that portion of the tray normaly occupied by the downcomer seal pan back into use as a portion of the tray through which vapor may pass for contact with the liquid on the tray--the contact being made by the vapor passing through the perforated plate connecting the seal pan and the tray), which thereby increases the throughput capacity of a given distillation tower.

Abstract: An improved distillation column downcomer, in which the seal pan of the downcomer is spaced above the adjacent lower tray and connected to the tray by a perforated plate, whereby the effective active tray area is increased (by placing that portion of the tray normally occupied by the downcomer seal pan back into use as a portion of the tray through which vapor may pass for contact with the liquid on the tray--the contact being made by the vapor passing through the perforated plate connecting the seal pan and the tray), which thereby increases the throughput capacity of a given distillation tower.