LLDPE from Ethylene and 1-Octene (Similar to DOWLEX)

The process under analysis comprises four major sections: (1) Polymerization; (2) Devolatilization; (3) Distillation; and (4) Finishing.

Polymerization. Ethylene and 1-octene are sent to fixed-bed adsorption systems to remove water, oxygen and other polar impurities (potential catalyst poisons). The purified monomers are then mixed with the polymerization solvent (C8-C9 parrafins mixture) and fed to the first of two continuous stirred tank reactors (CSTR) operating in series, where the polymerization itself takes place. The polymerization is carried out adiabatically in the liquid phase, and hydrogen act as molecular weight regulator.

Devolatilization & Pelletizing. The polymer solution exiting the second reactor is fed into an adiabatic flash vessel, where the reduction in pressure allows volatile components, mainly unreacted ethylene, to vaporize. The concentrated polymer solution from the flash vessel is heated and subsequently passed through a devolatilization vessel, in such a way that residual monomers are removed from the polymer. Volatile components separated from the polymer are cooled and directed to distillation section., while the polymer is directed to finishing section. The devolatilized polymer stream is further 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 and storage.

Raw Materials Recovery. The gaseous streams from the devolatilization, containing unreacted monomers and solvent, are passed through a couple of distillation columns for the recovery of such components and removal of heavy impurities.