In ethylene oxide (EO) production, oxygen and ethylene are reacted to form EO. Since the conversion per pass is not 100%, the reactor is operated in loop mode. Argon, which enters with the oxygen feed, builds up in the reactor loop and must be purged. The vinyl acetate monomer (VAM) process is very similar except acetic acid is also fed to the reactor. A portion of the ethylene feedstock is lost with the argon purge gas from the reactor loop. The value of the lost feedstock is substantial — approximately $500,000 per year for a typical EO or VAM plant.
The VaporSep unit consists of a single-stage membrane system that separates ethylene vapors from argon. The ethylene-enriched permeate is sent to an existing compressor, then returned to the reactor; the argon-enriched residue is flared.
VaporSep systems recover more than 90% of vent ethylene that would otherwise be flared. VaporSep units are currently used by major EO producers including Samsung, Total, PEMEX and Formosa Plastics and VAM producers including Samsung BP and Dairen.