Method and apparatus for reducing fouling

Patent metadata

Field	Value
Publication number	US-9637570-B2
Application number	US-48305709-A
Country	US
Kind code	B2
Filing date	Jun 11, 2009
Priority date	Jun 11, 2009
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

Provided herein is a method for operating a slurry polymerization reaction system to reduce, inhibit, and/or prevent fouling in the polymer recovery and separation apparatus, including one or more portions of a high pressure flash tank. The method generally comprises polymerizing a monomer feed in a slurry polymerization reactor in the presence of catalyst and diluent to produce a polymerization effluent; continuously discharging at least a portion of said polymerization effluent from the reactor through a discharge valve; combining a catalyst poison stream with the polymerization effluent downstream of said discharge valve, wherein the catalyst poison stream comprises a catalyst poison that is a gas at standard conditions; and flashing the combination of polymerization effluent and catalyst poison stream in a first flash tank.

First claim

What is claimed is:

1. A process for producing polymer comprising:
a. polymerizing a monomer feed in a slurry polymerization reactor in the presence of a chromium oxide-based catalyst and diluent to produce a polymerization effluent comprising a slurry of polymer solids, unreacted monomer, and diluent;
b. continuously discharging at least a portion of said polymerization effluent from the reactor through a discharge valve;
c. continuously combining a catalyst poison stream selected from the group consisting of O 2 , O 3 , CO, CO 2 , NH 3 , SO, SO 2 , SO 3 , or mixtures thereof with the polymerization effluent downstream of said discharge valve, wherein the catalyst poison stream comprises a catalyst poison that is a gas at standard conditions and has a molar ratio of catalyst poison to chromium that is less than 0.1, and wherein the catalyst poison stream comprises at least 70 mol % of a carrier gas;
d. flashing the combination of polymerization effluent and the catalyst poison stream in a first flash tank at a pressure greater than or equal to 0.17 MPa to produce a concentrated polymer effluent and a first gas stream comprising vaporized diluent, unreacted monomer, and catalyst poison; and
e. condensing the vaporized diluent and unreacted monomer, and removing the catalyst poison from said condensed diluent and monomer as a gas by venting.

2. The process of claim 1 , wherein the combination of polymerization effluent and the catalyst poison stream are flashed in the first flash tank at a pressure greater than or equal to 0.34 MPa.

3. The process of claim 1 , wherein the catalyst poison stream is injected in one or more of a first transfer conduit leading from the discharge valve to the first flash tank, downstream of a heater on the first transfer conduit leading from the discharge valve to the first flash tank, or in the first flash tank.

4. The process of claim 1 , further comprising recycling the condensed diluent to the reactor without the need for further liquid separation.

5. The process of claim 1 , further comprising:
f. discharging the concentrated polymer effluent from said first flash tank through a seal chamber;
g. combining the concentrated polymer effluent with a catalyst poison stream downstream of the seal chamber, wherein the catalyst poison stream comprises a catalyst poison that is a gas at standard conditions; and
h. flashing the combination of concentrated polymer effluent and the catalyst poison stream in a second flash tank at a pressure greater than or equal to 34.47 kPa to produce a second concentrated polymer effluent and a second gas stream comprising diluent and catalyst poison.

6. The process of claim 5 , wherein the combination of concentrated polymer effluent and the catalyst poison stream are flashed in the second flash tank at a pressure greater than or equal to 48.26 kPa.

7. The process of claim 5 , wherein the catalyst poison stream is injected in one or more of a second transfer conduit leading from a second discharge valve to the second flash tank, downstream of a heater on the second transfer conduit leading from the second discharge valve to the second flash tank, or in the second flash tank.

8. The process of claim 1 , wherein the diluent is selected from propane, butane, isobutane, pentane, isopentane, neopentane, hexane, cyclohexane, and combinations thereof.

9. The process of claim 1 , wherein the catalyst poison is O 2 .

10. The process of claim 9 , wherein the carrier gas comprises N 2 .

11. The process of claim 1 wherein the catalyst poison stream consists essentially of O 2 and N 2 .

12. The process of claim 1 , wherein the amount of catalyst poison introduced is in response to an amount of polymer fouling within the first flash tank.

13. The process of claim 1 , wherein the molar ratio of catalyst poison to chromium is less than or equal to 0.05.

14. The process of claim 1 , wherein the molar ratio of catalyst poison to chromium is less than or equal to 0.01.

Assignees

• Towles Thomas W
• Exxonmobil Chemical Patents Inc

Inventors

• Towles Thomas W

Classifications

• B01J19/002

  Avoiding undesirable reactions or side-effects, e.g. avoiding explosions, or improving the yield by suppressing side-reactions · CPC title

• C08F6/02

  Neutralisation of the polymerisation mass, e.g. killing the catalyst (short-stopping C08F2/42 ){also removal of catalyst residues} · CPC title

• B01J19/1837

  Loop-type reactors · CPC title

• C08F110/02

  Ethene · CPC title

• B01J2219/00247

  Fouling of the reactor or the process equipment · CPC title