Bimodal HDPE from Ethylene and 1-Butene (Similar to UNIPOL)

The process under analysis comprises three major sections: (1) Reaction; (2) Purification; and (3) Finishing.

Reaction. The catalysts used in the process are sensitive to specific impurities in the raw materials feed. Therefore, ethylene and 1-butene are treated to remove water, oxygen and other polar impurities. The monomers are fed to the bottom of the reactor, where ethylene is polymerized in combination with 1-butene in a reaction loop consisting of a reactor, a compressor and a heat exchanger. The copolymerization reaction is conducted in gas-phase fluidized beds of granular polyethylene resin. While the compressor circulates the reaction gas and provides the required agitation, the external cooler removes reaction heat from the circulating gas. The reaction is carried out at low temperatures (80 - 110 °C) and somewhat low pressures of (15 - 35) bar.

Purification. The granular PE powder from the reactor is conveyed to a Purge Bin. In the Purge Bin, residual hydrocarbons are stripped with a nitrogen purge, and the catalyst is deactivated with steam. The purged gas is cooled and fed to two separators, in which condensed reactants are recovered and directly pumped back to the reactor, while uncondensed gas taken is purged.

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.