Optimized inert gas partial pressure in a gas phase polymerization process

A gas phase polyethylene polymerization process, comprising:

• contacting an input stream comprising ethylene and an induced condensing agent in the presence of nitrogen with a Ziegler-Natta, metallocene, or chromium catalyst in a reactor to form (i) a polyethylene homopolymer or copolymer, (ii) unreacted ethylene, and (iii) an output gas;
• recycling a recycle stream of the unreacted ethylene from the reactor to the input stream;
• venting at least a portion of the output gas from the reactor;
• and
• maintaining a partial pressure of the nitrogen in the reactor above a reference nitrogen partial pressure to decrease losses of the recycle stream with the vented output gas.

A gas phase polyolefin polymerization process, comprising:

• contacting an input stream comprising an olefin monomer and an induced condensing agent in the presence of nitrogen with a Ziegler-Natta, metallocene, or chromium catalyst in a reactor to form a polyolefin, unreacted olefin, and output gas;
• recycling a recycle stream of the unreacted olefin monomer from the reactor to the input stream;
• venting at least a portion of the output gas from the reactor;
• maintaining a partial pressure of the nitrogen in the reactor above a reference inert gas pressure to decrease losses of the recycle stream with the vented output gas;
• and
• maintaining a total reactor pressure above a reference total reactor pressure, while maintaining a partial pressure of the olefin monomer in the reactor at a reference olefin monomer pressure and maintaining a partial pressure of the induced condensing agent in the reactor at a reference induced condensing agent pressure.