LDPE Production from Ethylene (High-Pressure Autoclave Process)

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

Compression. Fresh polymer-grade ethylene is mixed with a low-pressure gas stream, containing unreacted monomer recovered downstream, and fed to the primary compressor where the ethylene is compressed to 300 bar. The ethylene stream from the Primary Compressor is mixed with chain transfer agents and recycled ethylene monomer recovered and fed to the secondary compressor, where it is compressed to 2.000 bar.

Reaction. Ethylene, boosted to the reaction pressure, is fed to the autoclave reactor, which is a continuous-stirred-tank reactor (CSTR). Mixtures of organic peroxides diluted in hydrocarbon solvent, injected into the reactor, initiate the free-radical polymerization reaction. The reaction is carried out at high temperatures (as high as 280 °C) and high pressures (2,000 bar). While the reaction is exothermic and the autoclave is an adiabatic reactor, the heat of reaction is balanced by the addition of cooler, fresh monomer feeds.

Finishing. The reaction outlet is decompressed and fed to separators operating at high and low pressures, where unreacted monomer is separated, and then purified and recycled to the polymerization. The polymer passes through an extrusion and pelletizing system, is packed and stored.