Models and Issues in Consistent Biclustering

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 DEG 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.