Fractionation for polymerized reactor effluent

A method comprising:

• recovering a polymerization reactor effluent stream from one or more polymerization reactors;
• flashing the polymerization reactor effluent stream to form a flash gas stream;
• separating, in a first column operated at a first column pressure, the flash gas stream into a first column overhead stream, a first column side stream, and a first column bottoms stream;
• separating the first column overhead stream into a gas stream and a liquid stream;
• and
• introducing a feed comprising the gas stream and at least a portion of the liquid stream to a second column operated at a second column pressure, to produce a second column overhead stream, a second column side stream, and a second column bottoms stream,
• wherein the second column bottoms stream has a second column bottoms stream flow rate of isobutane and the second column side stream has a second column side stream flow rate of isobutane, wherein a total flow rate of isobutane comprises the second column bottoms stream flow rate and the second column side stream flow rate, and wherein the method comprises operating such that the second column bottoms stream flow rate comprises less than or equal to about 25 volume percent (vol %) of the total flow rate and the second column side stream flow rate comprises greater than or equal to about 75 vol % of the total flow rate;
• and
• wherein the method does not include compressing the first column overhead stream, the gas stream, or the at least the portion of the liquid stream prior to introducing the gas stream and the at least the portion of the liquid stream as the feed to the second column.