To provide a tower in which a deethanizer tower is integrated with an ethylene fractionator tower for an olefin plant which processes propane and a heavier feedstock.

This integrated deethanizer/ethylene fractionator tower separates a feed stream containing ethylene, ethane and C3+ fraction into the ethylene, ethane and C3+ streams, has a single shell containing an upper and lower reflux section, each containing a multiple vapor-liquid contacting element; general vertical walls which separate the lower section into the deethanizer tower zone and ethylene stripper zone; a supply line which supplies at least one feed stream to at least one feed stage of the deethanizer tower zone in the lower section of the tower to separate it into the overhead vapor stream essentially composed of ethylene and ethane, discharged from the deethanizer tower zone, and bottom stream essentially composed of C3 and a heavier fraction; and a distribution pan at the lower end of the upper section of the tower, which promotes the vapors from the deethanizer tower and ethylene stripper zones to pass towards the upper section of the tower, and separates the liquid from the upper section of the tower into the two streams, one passing towards the upper stage and the other passing towards the ethylene stripping zone.