Initiator injection into high pressure LDPE reactors

A polymerization reactor system comprising:

• a high pressure olefin polymerization reactor;
• and
• an injection nozzle integrated into a reactor bore of the reactor and extending through a wall of the reactor, the injection nozzle comprising:
• (i) a feed section comprising:
• an inner flow channel directing a flow of an initiator stream;
• at least two outer flow channels directing flows of an olefin stream;
• and
• a center portion configured to prevent contacting of the initiator stream with the olefin stream, wherein the center portion is further configured to be in contact with the reactor bore of the reactor;
• and
• (ii) a mixing section comprising a diverting port in the center portion configured to divert a fraction of the olefin stream from at least one of the at least two outer flow channels to enter the inner flow channel and mix with the initiator stream.

An injection nozzle comprising:

• (i) a feed section comprising:
• an inner flow channel directing a flow of an initiator stream;
• at least two outer flow channels directing flows of an olefin stream;
• and
• a center portion configured to prevent contacting of the initiator stream with the olefin stream, wherein the center portion is further configured to be in contact with a reactor bore through a wall of a high pressure olefin polymerization reactor;
• and
• (ii) a mixing section comprising a diverting port in the center portion configured to divert a fraction of the olefin stream from at least one of the at least two outer flow channels to enter the inner flow channel and mix with the initiator stream.

A method for operating a high pressure olefin polymerization reactor, the method comprising:

• (a) introducing an initiator stream through an initiator nozzle into the reactor, the initiator stream comprising:
• from 10 to 99 wt. % ethylene;
• and
• an initiator mixture containing a diluent and from 0.5 to 40 wt. % of an initiator compound;
• wherein:
• the diluent comprises a hydrocarbon compound;
• and
• the initiator compound comprises a peroxide compound;
• (b) introducing an olefin stream through an olefin nozzle into the reactor, the olefin stream comprising ethylene and optionally a comonomer;
• and
• (c) polymerizing ethylene and optionally the comonomer in the presence of the initiator stream in the reactor under high pressure polymerization conditions to produce an ethylene polymer;
• wherein an amount of ethylene in the initiator stream based on an amount of ethylene in the olefin stream is from 0.01 to 2 wt. %.