Process for increasing ethylene and propylene yield from a propylene plant

A process for recovery of C2 and C3 components via an on-purpose propylene production system comprising:

• cooling a combined de-ethanizer overhead light vapor and cracked gas vapor to a temperature at which at least 80 wt % of the vapor is condensed to form a first partial condensate and a first residual vapor;
• passing the first partial condensate to a bottom portion of a rectifier;
• passing the first residual vapor up through packing of the rectifier while contacting the first residual vapor with a countercurrent stream which comprises from 75 to 95 wt % C2 components, from 5 to 25 wt % C1 components and from 0 to 5 wt % C3 components thereby producing a rectifier overhead stream which comprises from 20 to 45 wt % C1 components, from 40 to 60 wt % C2 components and from 0 to 5 wt % C3 components and a rectifier liquid bottom stream;
• passing the rectifier liquid bottom stream to the de-ethanizer;
• partially condensing the rectifier overhead stream in one or more heat exchanger stages to cool the rectifier overhead stream to produce a second partial condensate with a second residual vapor which comprises less than 5 wt % C2 components and a first residual liquid which comprises from 75 to 95% C2 components;
• passing the combined second residual vapor and first residual liquid to a knockout drum to separate the second residual vapor from the first residual liquid;
• optionally, using the second residual vapor as a fuel gas and/or as a cooling medium in the one or more heat exchanger stages;
• passing a first portion of the second residual liquid to a top portion of the packing in the rectifier to serve as the countercurrent stream;
• and
• passing a second portion of the second residual liquid to a product recovery system.