NOVELTY - An integrated debutanizer and a low pressure depropanizer column is used to separate a feed stream comprising C3s, C4s and C5+s compounds. A single shell houses a refluxed upper portion (102) and a lower portion (104) of the column. A vertical wall partitions the lower portion of the column into a debutanizer section (106) and a depropanizer stripper section (108). The upper column portion is used as the absorption section of the depropanizer. The feed is supplied to an intermediate stage in the debutanizer, and the debutanizer is operated at a lower pressure (and correspondingly lower temperature) matching that of the low pressure depropanizer.    USE - Used in olefin plants.    ADVANTAGE - The design allows the use of one slightly larger column in place of the large columns previously used for separate debutanization and low pressure depropanization.    DETAILED DESCRIPTION - A distribution pan (110) is located at a lower end of the upper portion of the column for facilitating passage of vapors from the debutanizer and depropanizer stripper sections and for dividing liquid for passage from the upper portion of the column into an upper stage of the debutanizer section and into the depropanizer stripping section.    An INDEPENDENT CLAIM is included for a process for separating a feed stream composed of C3s, C4s and C5+s which comprises supplying the feed stream to one or more feed stages of a the debutanizer section of the lower portion of the integrated column. Overhead vapor from the debutanizer is passed through the distribution pan to the upper portion of the column. Refluxing the upper portion of the column with C3s and recovering C3s which are essentially free of C4s overhead from the upper portion of the column.    Liquid is passed from the distributor pan into an upper stage of the debutanizer section and into an upper stage of the depropanizer stripper section.    Reboiling the depropanizer section stripper section and recovering a C4s bottoms product stream which is essentially free of C3s and C4s    Preferred integrated column: The debutanizer and depropanizer stripper sections comprises from 25 to 45 trays and the upper and lower portions of the column have the same cross-sectional diameter.    The reboilers for the debutanizer and depropanizer sections are heated with steam and quench water respectively.    Liquid lines lead from the distribution pan to the top of the debutanizer section and to the top of the depropanizer stripper section, the line from the top of the debutanizer section including a valve for controlling the amount of liquid supplied to the debutanizer section.    Preferred operating conditions: The operating pressure of the column is from 1.5 to 12 bar (20 to 180 psia)    DESCRIPTION OF DRAWING(S) - The drawing shows a simplified process flow diagram of C3s/C4s recovery in a front end depropanizer process.    High pressure depropanization bottoms (38)    Tower (100)    Upper tower portion (102)    Lower tower portion (104)    Left side (low pressure debutanizer) (106)    Right side (stripping section of depropanizer) (108)    Distribution pan (110)    Valve (114)    Reboilers (132, 136)