COMBINATION OF MEMBRANE METHOD AND ADSORPTION WITH ALTERNATING PRESSURE IN ISOBUTANE AND NITROGEN RECOVERY UNIT Russian patent published in 2021 - IPC B01D53/47 B01D53/22 C07C7/12 C07C7/144 

FIELD: polymers.

SUBSTANCE: invention generally relates to production of polyethylene. The method for separation of components in a polymer production system is comprised of: (a) separating a polymerization product stream into a gas stream and a polymer stream, wherein the polymer stream is comprised of polyethylene, isobutane, ethylene and ethane; (b) contacting at least a part of the polymer stream with a purging gas in a purge container to produce a purged polymer stream and a processed purging gas stream, wherein the purged polymer stream comprises polyethylene and the processed purging gas stream comprises purging gas, isobutane, ethylene, and ethane; (c) introducing at least a part of the processed purging gas stream into a compressor to produce a compressed gas stream; (d) introducing at least a part of the compressed gas stream into a first separation unit to produce a first hydrocarbon stream and a membrane unit feed material stream, wherein the first hydrocarbon stream is comprised of at least 50% isobutane in the compressed gas stream and the membrane unit feed material stream is comprised of no less than 95% of the purging gas in the compressed gas stream; (e) introducing at least a part of the membrane unit feed material stream into the membrane unit to produce a first recoverable purging gas stream and a retentate stream, wherein the retentate stream is comprised of less than 30% of the purging gas in the membrane unit feed material stream; (f) introducing at least a part of the retentate stream into a second separation unit to produce a second hydrocarbon stream and a pressure swing adsorption (PSA) unit feed material stream, wherein the PSA feed material stream is comprised of no less than 97% of the purging gas in the retentate stream; (g) introducing at least a part of the PSA feed material stream into the PSA unit to produce a second recoverable purging gas stream and a tail gas stream, wherein the molar concentration of the purging gas in the second recovered purging gas stream is greater than the molar concentration of the purging gas in the first recovered purging gas stream; and (h) returning at least a part of the tail gas stream to the compressor.

EFFECT: increased separation efficiency.

29 cl, 5 dwg