Ethylene Recovery by Absorption

Patent metadata

Field	Value
Publication number	US-2016297729-A1
Application number	US-201615189453-A
Country	US
Kind code	A1
Filing date	Jun 22, 2016
Priority date	Oct 15, 2010
Publication date	Oct 13, 2016
Grant date	—

Abstract

A process for recovery of ethylene from a polymerization product stream of a polyethylene production system, comprising separating a light gas stream from the polymerization product stream, wherein the light gas stream comprises ethane and unreacted ethylene, contacting the light gas stream with an absorption solvent system, wherein the contacting the light gas stream with the absorption solvent system occurs at a temperature in a range of from about 40° F. to about 110° F., wherein at least a portion of the unreacted ethylene from the light gas stream is absorbed by the absorption solvent system, and recovering unreacted ethylene from the absorption solvent system to yield recovered ethylene.

First claim

We claim:

1 . A process comprising:
contacting ethylene and a polymerization catalyst in a first loop slurry reactor and in a second loop slurry reactor connected in series with the first loop slurry reactor, under suitable reaction conditions to yield a polymerization product stream flowing from the second loop slurry reactor, wherein the polymerization product stream comprises a bimodal polymer; separating a gas stream from the polymerization product stream, wherein the gas stream comprises unreacted ethylene and ethane; separating, using an absorption solvent system at a temperature in a range of from about 40° F. to about 110° F., at least one gaseous component from the gas stream to form a recycle stream comprising unreacted ethylene and a waste stream comprising ethane; and recycling the unreacted ethylene of the recycle stream to the first loop slurry reactor, the second loop slurry reactor, or both the first loop slurry reactor and the second loop slurry reactor.

2 . The process of claim 1 , wherein the bimodal polymer comprises a high molecular weight polymer and a low molecular weight polymer.

3 . The process of claim 2 , wherein the high molecular weight polymer has a low density, and wherein the low molecular weight polymer has a high density.

4 . The process of claim 1 , wherein the polymerization catalyst is selected from a Ziegler Natta catalyst, a Ziegler catalyst, a chromium catalyst, a chromium oxide catalyst, a chromocene catalyst, a metallocene catalysts, a nickel catalyst, or combinations thereof.

5 . The process of claim 1 , wherein the at least one gaseous component comprises the unreacted ethylene, optionally isobutane, and optionally unreacted comonomer.

6 . The process of claim 1 , wherein the absorption solvent system comprises copper chloride, aniline, and N-methylpyrrolidone.

7 . The process of claim 1 , wherein separating, using an absorption solvent system at a temperature in a range of from about 40° F. to about 110° F., at least one gaseous component from the gas stream comprises:
contacting the gas stream with the absorption solvent system, wherein at least a portion of the unreacted ethylene from the gas stream is absorbed by the absorption solvent system, wherein at least a portion of the ethane is unabsorbed by the absorption solvent system;
recovering the unreacted ethylene from the absorption solvent system in the recycle stream; and
recovering the unabsorbed ethane in the waste stream.

8 . The process of claim 7 , wherein contacting the gas stream with the absorption solvent system occurs at a pressure in a range of from about 40 psig to about 60 psig, and wherein recovering the unreacted ethylene from the absorption solvent system in the recycle stream comprises depressurizing the absorption solvent system utilizing pressure swing absorption.

9 . The process of claim 1 , further comprising:
removing at least a portion of elemental oxygen or oxygen-containing compounds from the gas stream prior to separating the at least one gaseous component from the gas stream.

10 . The process of claim 1 , wherein separating, using an absorption solvent system at a temperature in a range of from about 40° F. to about 110° F., at least one gaseous component from the gas stream comprises:
contacting the gas stream with the absorption solvent system at a pressure in a range of from about 40 psig to about 60 psig, wherein at least a portion of the unreacted ethylene from the gas stream is absorbed by the absorption solvent system, wherein at least a portion of the ethane is unabsorbed by the absorption solvent system;
introducing a complexed stream comprising a complex of the absorption solvent system and unreacted ethylene into a solvent regenerator;
depressurizing the solvent regenerator to a pressure in a range of from about 0 psig to about 10 psig; and
recovering the recycle stream from the solvent regenerator.

11 . The process of claim 1 , wherein separating a gas stream from the polymerization product stream comprises:
routing the polymerization product stream to a separator selected from a distillation column, a flash tank, a filter, a membrane, a reactor, an absorbent, an adsorbent, a molecular sieve, or combinations thereof.

12 . The process of claim 1 , further comprising:
combusting ethane of the waste stream.

13 . The process of claim 1 , further comprising:
converting ethane of the waste stream into ethylene; and recycling the ethylene obtained by converting ethane to the first loop slurry reactor, the second loop slurry reactor, or both the first loop slurry reactor and the second loop slurry reactor.

14 . A polyethylene production system, comprising:
a first loop slurry reactor; a second loop slurry reactor connected in series with the first loop slurry reactor, wherein the first loop slurry reactor and the second loop slurry reactor are configured to contact ethylene with a polymerization catalyst under suitable reaction conditions to yield a polymerization product stream flowing from the second loop slurry reactor, wherein the polymerization product stream comprises a bimodal polymer; a first separator configured to receive the polymerization product stream, to recover the bimodal polymer in a polymer stream, and to recover unreacted ethylene and ethane in a gas stream; and one or more absorption reactors configured to receive the gas stream, wherein the one or more absorption reactors contains an absorption solvent system which is at a temperature in a range of from about 40° F. to about 110° F., wherein at least a portion of the unreacted ethylene received from the gas stream is absorbed by the absorption solvent system, wherein at least a portion of the ethane received from the gas stream is unabsorbed by the absorption solvent system.

15 . The system of claim 14 , wherein the absorption solvent system comprises copper chloride, aniline, and N-methylpyrrolidone.

16 . The system of claim 14 , wherein the one or more absorption reactors operate with pressure swing absorption to recover the unreacted ethylene, the system further comprising:
a recycle stream comprising unreacted ethylene recovered from the one or more absorption reactors, wherein the recycle stream flows unreacted ethylene to the first loop slurry reactor, the second loop slurry reactor, or both the first loop slurry reactor and the second loop slurry reactor; and a waste stream comprising the unabsorbed ethane recovered from the one or more absorption reactors.

17 . The system of claim 16 , further comprising:
a processing device configured to combust ethane received from the waste stream or configured to convert ethane received from the waste stream to ethylene.

18 . The system of claim 14 , further comprising:
a complexed stream flowing from the one or more absorption reactors, wherein the complexed stream comprises a complex of the absorption solvent system and unreacted ethylene; a solvent regenerator configured to receive the complexed stream and to recover the unreacted ethylene from the complex; and a recycle stream comprising the unreacted ethylene recovered from the complex, wherein the unreacted ethylene recovered from the complex is recycled to the first loop slurry reactor, the second loop slurry reactor, or both the first loop slurry reactor and the second loop slurry reactor via the recycle stream.

19 . The system of claim 18 , wherein the complexed stream further comprises ethane, the system further comprising:
a waste gas stream comprising th

Assignees

• Chevron Phillips Chemical Co Lp

Inventors

• Hottovy John D
• Chang Ai-Fu

Classifications

• C08F6/001

  Removal of residual monomers by physical means · CPC title

• B01D2252/20405

  Monoamines · CPC title

• B01D2252/20436

  Cyclic amines · CPC title

• B01D2252/10

  Inorganic absorbents · CPC title

• C07C7/11 Primary

  by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids · CPC title