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

The process under analysis comprises four major sections: (1) Purification and catalyst preparation; (2) Reaction; (3) Distillation; and (4) Finishing.

Purification and catalyst preparation. The cyclohexane solvent, ethylene and 1-octene are sent to fixed-bed adsorption systems to remove water, oxygen and other polar impurities. The catalysts used in the process are based on mixtures of titanium and vanadium compounds in conjunction with aluminum alkyls cocatalysts.

Reaction. Ethylene, 1-octene comonomer and cyclohexane are mixed and pumped to polymerization reactor. The polymerization is carried out in a solution phase, at a temperature above the melting point of the resulting polymer. The reaction system consists of a tubular reactor and a continuous-stirred-tank reactor (CSTR). The low residence time of the reactors enables a high flexibility for grade transitions and versatility for the production of resins across a wide range of densities, melt indexes, and molecular weight distributions. The reactor output stream is fed into separator vessels where unreacted ethylene and comonomers, solvent, and any other volatile matter are separated from the PE. The polymer is sent to the finishing section while the light stream follows to the distillation system.

Distillation. The distillation step comprises five distillation columns in charge of recovering the unreacted ethylene and comonomers; recovering the solvent; purging impurities, such as oligomers (also called grease), catalyst and deactivators residues; and avoiding the buildup of inert components, such as comonomers isomers.

Finishing. The resulting 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.