Method and apparatus for recovery of ethylene and propylene from gas produced by the pyrolysis of hydrocarbons

A method for recovery of ethylene and propylene from a raw gas produced by a pyrolysis or hydrocarbons and for splitting said gas into first and second depurated current flows, the first containing almost all ethylene and the second containing almost all propylene, comprising the steps of:

• providing a fractional condensation of the raw gas from compression, caustic washing, and drying sections in a separation system with progressive plural cooling stages;
• feeding a first condensate liquid of the first cooling stage and any mixture of liquid hydrocarbons from the compression section at a predetermined temperature to a deethanizer column to obtain as a bottom produce a depurated current containing almost all propylene;
• feeding a second condensate liquid of the following cooling stages at lower temperatures to a demethanator column to obtain as a bottom produce a depurated current containing almost all the ethylene;
• feeding a deethanizer overhead vapor stream to a heat exchanger employed as a demethanator reboiler, wherein said deethanizer overhead vapor stream is partially condensed;
• supplying said partially condensed overhead vapour from the deethanizer to the demethanator.