Distillation schemes for multicomponent separations

A process for the separation of a feed stream containing three or more constituent components into product streams which are enriched in one of the constituent components by distillation in a distillation column system containing at least two distillation columns comprising:

• (a) feeding the feed stream containing three or more constituent components to a first distillation column;
• (b) establishing a two-way flow communication between the first end of the first distillation column, wherein the first end is either the top end or the bottom end of the first distillation column, and a first location of a second distillation column by feeding at least a portion of the vapor or liquid stream exiting from the first end of the first distillation column to the first location of the second distillation column and in return withdrawing a stream of the opposite phase from the first location of the second distillation column and feeding it to the first end of the first distillation column, wherein liquid and vapor phases are considered as opposite phases, and
• (c) establishing a one-way communication between the second end of the first distillation column that is other than the first end used in step (b) and a second location of the second distillation column by feeding at least a portion of the stream exiting from the second end of the first distillation column to the second location of the second distillation column and wherein there is no return stream from the second location of the second distillation column to the second end of the first distillation column.