Bimodal HDPE from Ethylene and 1-Octene (Similar to Spherilene)

The process under analysis comprises two major sections: (1) Polymerization; and (2) Finishing.

Polymerization. Initially, ethylene and 1-octene are passed through fixed-bed adsorption systems, in which potential catalyst poisons are removed before polymerization. After purification, the ethylene is polymerized in combination with 1-octene in two reaction loops connected in series. Each reaction loop comprises a gas-phase reactor, a compressor, a heat exchanger and a degassing vessel. The polymerization occurs in the gas phase at mild conditions of temperature and pressure. Propane is used as inert diluent, and hydrogen is used as molecular weight regulator. The spherical product particles of each gas-phase reactor are fed to degassing vessels, in which unreacted monomers and hydrogen are removed by a counter-current propane stream. The gaseous streams from the degassing vessels are passed through a couple of distillation columns for the recovery of unreacted monomers and diluent.

Finishing. The degassed polymer particles from the second reaction loop are transferred to a vessel where residual hydrocarbons are removed, and the catalyst is deactivated by stripping with a gaseous stream containing nitrogen and steam. The wet polymer is then dried by nitrogen before being fed into an extruder, which is used to incorporate the required additives, as well as to pelletize the polymer. The product is then sent to product blending, packed and finally sent to storage facilities located Outside Battery Limits (OSBL).