Initiator Injection Line for High Pressure Polymerization

A method of preparing a polymer in a polymerization reactor system, the polymerization reactor system comprising a tubular reactor, a monomer source, a primary compressor, a secondary compressor, a pressure let-down valve, an initiator source, and an initiator injection line;

• wherein the initiator injection line comprises:
• an initiator pump and an outlet located downstream of the pump, wherein the outlet is connected to the tubular reactor at an initiator injection point, and wherein the pump is configured to pump initiator from the initiator source through the outlet and into the tubular reactor at the initiator injection point;
• the initiator injection line further comprising a back-pressure valve located downstream of the initiator pump and upstream of the outlet, wherein the back-pressure valve has a set-pressure and is configured to maintain a pressure within the initiator injection line upstream of the back-pressure valve and downstream of the initiator pump that is equal to the set-pressure;
• wherein the method comprises the steps of:
• (i) pressurizing monomer from the monomer source in the primary and secondary compressors and introducing the monomer into the tubular reactor;
• (ii) operating the initiator pump so that initiator from the initiator source flows through the back-pressure valve and into the tubular reactor at the initiator injection point;
• (iii) polymerizing the monomer in the tubular reactor to form the polymer;
• (iv) discharging a product mixture comprising the polymer from the tubular reactor through the pressure let-down valve;
• and,
• (v) isolating the polymer;
• wherein step (ii) further comprises operating the back-pressure valve at the set-pressure, wherein the set-pressure is in the range of from 50 bar to 400 bar greater than the pressure of the tubular reactor at the initiator injection point.