Monomer/diluent recovery

• US 9,096,694 B1
• Filed: 01/20/2014
• Issued: 08/04/2015
• Est. Priority Date: 01/20/2014
• Status: Active Grant

• Current Assignee: Chevron Phillips Chemical Company LP (Chevron Corp.)
• Original Assignee: Chevron Phillips Chemical Company LP (Chevron Corp.)
• Inventors: Gupta, Anurag, Odi, Timothy O., Romig, Ralph W.
• Primary Examiner(s): CHEUNG, WILLIAM K
• Application Number:
  US14/159,261
• Publication Number:
  US 20150203601A1
• Time in Patent Office: 561 Days
• Field of Search: 526/65, 294/011, 422/132, 422/134, 528/501
• US Class Current: 1/1
• CPC Class Codes: B01J 19/18 Stationary reactors having moving elements inside B01J19/08, B01J19/26 take precedence
• CPC Class Codes: B01J 19/245 placed in series
• CPC Class Codes: B01J 2219/24 Stationary reactors without moving elements inside
• CPC Class Codes: C08F 10/00 Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
• CPC Class Codes: C08F 2/01 characterised by special features of the polymerisation apparatus used
• CPC Class Codes: C08F 2/14 Organic medium
• CPC Class Codes: C08F 2/34 Polymerisation in gaseous state
• CPC Class Codes: C08F 210/14 Monomers containing five or more carbon atoms
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2500/05 Bimodal or multimodal molecular weight distribution
• CPC Class Codes: C08F 6/003 from polymer solutions, suspensions, dispersions or emulsions without recovery of the polymer therefrom
• CPC Class Codes: C08F 6/04 Fractionation
• CPC Class Codes: C08L 23/00 Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers

Abstract

The disclosure includes a polymerization process and an olefin polymerization system. A polymerization product is produced, a vapor phase is recovered from the polymerization product, the vapor phase is fractionated in a first column to yield a fraction stream, and the fraction stream is fractionated in a second column. A first stream of the second column, which comprises a diluent, can be recycled to a first polymerization reactor. A second stream of the second column, which comprises olefin monomer, diluent, and hydrogen, can be recycled to a second polymerization reactor. Comonomer may be recycled from the first column to the first polymerization reactor, the second polymerization reactor, or both.

Claims

1. A polymerization process comprising:

producing a polymerization product;

recovering a vapor phase from the polymerization product;

fractionating the vapor phase in a first column to yield a fraction stream;

fractionating the fraction stream in a second column;

emitting a first stream and a second stream from the second column, wherein the first stream comprises a diluent, wherein the second stream comprises an olefin monomer, the diluent, and hydrogen, wherein the first stream is a bottoms stream of the second column, and wherein the second stream is a side-draw stream of the second column;

recycling at least a portion of the diluent of the first stream to a first polymerization reactor; and

recycling at least a portion of the diluent, at least a portion of the olefin monomer, and at least a portion of the hydrogen of the second stream to a second polymerization reactor.

2. The process of claim 1, wherein producing a polymerization product comprises:

polymerizing the olefin monomer, and optionally an olefin comonomer, in the presence of the diluent to yield a first component of a solid polymer of the polymerization product in a first polymerization reactor; and

polymerizing the olefin monomer, and optionally the olefin comonomer, in the presence of the diluent to yield a second component of the solid polymer of the polymerization product in a second polymerization reactor.

3. The process of claim 2, wherein the first component of the solid polymer of the polymerization product has a molecular weight greater than a molecular weight of the second component of the solid polymer of the polymerization product.

4. The process of claim 3, wherein the first component of the solid polymer of the polymerization product has a density less than a density of the second component of the solid polymer of the polymerization product.

5. The process of claim 2, wherein the olefin monomer comprises ethylene, wherein the olefin comonomer comprises 1-hexene, wherein the diluent comprises isobutane, wherein the solid polymer comprises a multimodal polyethylene.

6. The process of claim 1, wherein a concentration of hydrogen in the second stream is at least 1 ppm.

7. The process of claim 6, wherein the concentration of hydrogen in the second stream is less than about 1 wt % by weight of the second stream.

9. The process of claim 1, further comprising:

feeding fresh diluent to the first column.

10. The process of claim 1, wherein the second stream comprises greater than about 5 wt % monomer by weight of the second stream.

11. The process of claim 10, wherein the second stream comprises greater than about 10 wt % monomer by weight of the second stream.

12. The process of claim 1, wherein the first stream is substantially olefin-free.

13. The process of claim 1, wherein the first column operates at a pressure ranging from about 100 psig to about 250 psig, wherein the fraction stream does not comprise a compressor.

8. A polymerization process comprising:

producing a polymerization product;

recovering a vapor phase from the polymerization product;

fractionating the vapor phase in a first column to yield a fraction stream;

feeding fresh olefin comonomer to the first column;

fractionating the fraction stream in a second column;

emitting a first stream and a second stream from the second column, wherein the first stream comprises a diluent, and wherein the second stream comprises an olefin monomer, the diluent, and hydrogen;

recycling at least a portion of the diluent of the first stream to a first polymerization reactor; and

recycling at least a portion of the diluent, at least a portion of the olefin monomer, and at least a portion of the hydrogen of the second stream to a second polymerization reactor.

14. A polymerization process comprising:

producing a polymerization product;

recovering a vapor phase from the polymerization product;

fractionating the vapor phase in a first column to yield a fraction stream and a comonomer stream comprising olefin comonomer, wherein the comonomer stream is a side-draw stream of the first column;

recycling at least a portion of the olefin comonomer of the comonomer stream to a first polymerization reactor, a second polymerization reactor, or both the first polymerization reactor and the second polymerization reactor;

fractionating the fraction stream in a second column;

emitting a first stream and a second stream from the second column, wherein the first stream comprises a diluent, and wherein the second stream comprises an olefin monomer, the diluent, and hydrogen;

recycling at least a portion of the diluent of the first stream to the first of polymerization reactor; and

recycling least a portion of the diluent, at least a portion of the olefin monomer, and at least a portion of the hydrogen of the second stream to the second polymerization reactor.

15. An olefin polymerization system comprising:

a first polymerization reactor yielding a first component of solid polymer of a polymerization product;

a second polymerization reactor yielding a second component of the solid polymer of the polymerization product, wherein the second polymerization reactor is in fluid communication with the first polymerization reactor;

at least one separator receiving the polymerization product from the first polymerization reactor, the second polymerization reactor, or both the first polymerization reactor and the second polymerization reactor, wherein the separator yields a vapor stream;

a first column receiving the vapor stream from the separator, wherein the first column yields a fraction stream; and

a second column receiving the fraction stream from the first column, wherein the second column yields a first stream comprising a diluent and a second stream comprising the diluent, an olefin monomer, and hydrogen;

wherein the first stream is a bottoms stream of the second column, and wherein the second stream is a side-draw stream of the second column,

wherein at least a portion of the diluent of the first stream flows to the first polymerization reactor,

wherein at least a portion of the diluent, at least a portion of the monomer, and at least a portion of the hydrogen of the second stream flows to the second polymerization reactor.

17. The system of claim 15, wherein the first component of the solid polymer of the polymerization product has a molecular weight greater than a molecular weight of the second component of the solid polymer of the polymerization product.

18. The system of claim 17, wherein the first component of the solid polymer of the polymerization product has a density less than a density of the second component of the solid polymer of the polymerization product.

19. The system of claim 15, wherein a concentration of hydrogen in the second stream is at least 1 ppm.

20. The system of claim 19, wherein the concentration of hydrogen in the second stream is less than 1 wt % by weight of the second stream.

21. The system of claim 15, wherein the first stream is substantially olefin-free.

24. The system of claim 15, further comprising:

a fresh diluent stream fed to the first column.

25. The system of claim 24, wherein the fresh diluent stream comprises diluent and at least one light component, wherein the second column separates the diluent of the fresh diluent stream from the at least one light component.

26. The system of claim 15, wherein the second stream comprises greater than about 5 wt % monomer by weight of the second stream.

27. The process of claim 26, wherein the second stream comprises greater than about 10 wt % monomer by weight of the second stream.

28. The system of claim 15, wherein the first polymerization reactor comprises a loop slurry polymerization reactor, wherein the second polymerization reactor comprises a loop slurry polymerization reactor.

29. The system of claim 15, wherein the olefin monomer comprises ethylene, wherein the diluent comprises isobutane, wherein the polymerization product comprises a multimodal polyethylene.

30. The system of claim 15, wherein the first polymerization reactor is upstream of the second polymerization reactor.

31. The system of claim 15, wherein the first polymerization reactor is downstream of the second polymerization reactor.

32. The system of claim 15, wherein the first column operates at a pressure ranging from about 100 psig to about 250 psig, wherein the fraction stream does not comprise a compressor.

16. An olefin polymerization system comprising:

a first polymerization reactor yielding a first component of solid polymer of a polymerization product;

a second polymerization reactor yielding a second component of the solid polymer of the polymerization product, wherein the second polymerization reactor is in fluid communication with the first polymerization reactor;

at least one separator receiving the polymerization product from the first polymerization reactor, the second polymerization reactor, or both the first polymerization reactor and the second polymerization reactor, wherein the separator yields a vapor stream;

a first column receiving the vapor stream from the separator, wherein the first column yields a fraction stream and a comonomer stream comprising olefin comonomer, wherein the comonomer stream is a side-draw stream of the first column, wherein at least a portion of the olefin comonomer of the comonomer stream flows to the first polymerization reactor, the second polymerization reactor, or both the first polymerization reactor and the second polymerization reactor; and

a second column receiving the fraction stream from the first column, wherein the second column yields a first stream comprising a diluent and a second stream comprising the diluent, an olefin monomer, and hydrogen;

wherein at least a portion of the diluent of the first stream flows to the first polymerization reactor,

wherein at least a portion of the diluent, at least a portion of the monomer, and at least a portion of the hydrogen of the second stream flows to the second polymerization reactor.

22. An olefin polymerization system comprising:

a first polymerization reactor yielding a first component of solid polymer of a polymerization product;

a second polymerization reactor yielding a second component of the solid polymer of the polymerization product, wherein the second polymerization reactor is in fluid communication with the first polymerization reactor;

at least one separator receiving the polymerization product from the first polymerization reactor the second polymerization reactor, or both the first polymerization reactor and the second polymerization reactor, wherein the separator yields a vapor stream;

a first column receiving the vapor stream from the separator, wherein the first column yields a fraction stream;

a fresh comonomer stream fed to the first column;

a second column receiving the fraction stream from the first column, wherein the second column yields a first stream comprising a diluent and a second stream co diluent, an olefin monomer, and hydrogen;

wherein at least a portion of the diluent of the first stream flows to the first polymerization reactor,

wherein at least a portion of the diluent, at least a portion of the monomer, and at least a portion of the hydrogen of the second stream flows to the second polymerization reactor.

23. The system of claim 22, wherein the fresh comonomer stream comprises comonomer and at least one light component, wherein the first column separates the comonomer of the fresh comonomer stream from the at least one light component.