Compressible liquid diluent in polyolefin polymerization

Patent metadata

Field	Value
Publication number	US-2016346750-A1
Application number	US-201615169190-A
Country	US
Kind code	A1
Filing date	May 31, 2016
Priority date	Feb 3, 2010
Publication date	Dec 1, 2016
Grant date	—

Abstract

Embodiments of the present application provide a method for manufacturing a polyolefin and a system for implementing the method. The method comprises combining a catalyst with a diluent mixture containing a diluent and an olefin monomer in a polymerization reactor. The diluent may comprise propane, butane, or isobutane, or a combination thereof. The polymerization reactor is operated at a pressure above a critical pressure of the diluent, but below the critical temperature of the diluent.

First claim

1 .- 22 . (canceled)

23 . A system for producing polyolefins, comprising:
a feed system configured to supply a diluent mixture comprising a diluent and an olefin monomer; a polymerization reactor configured to receive the diluent mixture from the feed system and to polymerize the olefin monomer in the presence of a catalyst to form a slurry comprising polyolefin particles and the diluent mixture; a reactor cooling system comprising a reactor jacket and a heat exchanger in a heat exchange relationship with the polymerization reactor; and a controller configured to control a flow of coolant through the heat exchanger to maintain a temperature of the polymerization reactor below a critical temperature of the diluent mixture and to operate the polymerization reactor at a pressure above a critical pressure of the diluent mixture such that the diluent mixture remains compressible and two phase flow of the diluent mixture is substantially prevented within the polymerization reactor.

24 . The system of claim 23 , comprising:
a recovery system configured to separate a majority of the diluent mixture as a flash gas from the slurry discharged from the polymerization reactor; a fractionation system configured to process a portion of the diluent mixture separated from the slurry in the recovery system and to provide recovered diluent substantially free of olefin monomer to the feed system; and an extrusion system configured to extrude and pelletize polyolefin particles recovered from the slurry in the recovery system.

25 . The system of claim 24 , wherein the extrusion system is configured to receive the polyolefin particles discharged from a purge column in the recovery system without intermediate holdup of the polyolefin particles.

26 . The system of claim 24 , wherein the recovery system comprises a separation vessel and does not comprise a flash-gas compressor associated with the separation vessel.

27 . The system of claim 24 , wherein the recovery system comprises a cyclonic separator configured to separate the flash gas from the polyolefin particles.

28 . The system of claim 23 , wherein the critical pressure comprises a vapor pressure of the diluent mixture at the critical temperature and the critical temperature comprises a temperature at which inter-molecular forces are substantially close to zero.

29 . The system of claim 23 , wherein the diluent mixture within the polymerization reactor is in a substantially liquid phase.

30 . The system of claim 23 , comprising at least one circulation pump in the polymerization reactor, wherein the at least one circulation pump comprises an in-line axial flow pump.

31 . The system of claim 23 , wherein the polymerization reactor comprises a loop slurry reactor having a plurality of vertical pipe legs, wherein each vertical pipe leg of the plurality of vertical pipe legs has an internal diameter between about 20 inches and 24 inches or greater than about 24 inches.

32 . The system of claim 31 , wherein each vertical pipe leg of the plurality of vertical pipe legs comprises a corresponding reactor jacket of the reactor cooling system.

33 . The system of claim 23 , wherein the controller is configured to maintain a temperature difference between a first temperature of the coolant at an inlet to the reactor jacket and a second temperature of the coolant at an outlet of the reactor jacket to less than 15° Fahrenheit by controlling the flow of the coolant through the reactor jacket using the valve, or the pump, or both.

34 . The system of claim 23 , comprising one or more feed lines coupled to the polymerization reactor and one or more takeoff lines coupled to an elbow of the polymerization reactor, wherein the polymerization reactor, the one or more feed lines, and the one or more takeoff lines are configured to operate at a pressure between 800 psia and 900 psia.

35 . The system of claim 23 , comprising one or more take-off valves disposed on the polymerization reactor and communicatively coupled to the controller, and wherein the controller is configured to maintain the pressure of the polymerization reactor above the critical pressure of the diluent mixture using the one or more take-off valves.

36 . The system of claim 23 , wherein the controller is configured to determine the pressure above the critical pressure of the diluent mixture and the temperature below the critical temperature of the diluent mixture by modeling a phase diagram of the diluent mixture.

37 . A reactor control system comprising processor-executable instructions that cause the reactor control system to:
control a first flow rate of a catalyst stream into a polymerization reactor, wherein the catalyst stream comprises a catalyst; control a second flow rate of a diluent mixture into the polymerization reactor, such that catalyst contacts the diluent mixture in the polymerization reactor, wherein the diluent mixture comprises a diluent and an olefin monomer; receive an input indicative of a composition of the diluent mixture in the polymerization reactor; and maintain a pressure of the polymerization reactor above a critical pressure of the diluent mixture and a temperature of the polymerization reactor below a critical temperature of the diluent mixture based at least on the input, such that the diluent mixture is in a compressible state and two phase flow of the diluent mixture is substantially prevented within the polymerization reactor.

38 . The reactor control system of claim 37 , wherein the processor-executable instructions cause the reactor control system to:
control a concentration of propane, butane, or isobutane, or any combination thereof in the diluent mixture based at least on the input.

39 . The reactor control system of claim 37 , wherein the processor-executable instructions cause the reactor control system to:
control a concentration of a blend of two or more hydrocarbons that each independently comprises six or less carbons in the diluent mixture based at least on the input.

40 . The reactor control system of claim 37 , wherein the processor-executable instructions cause the reactor control system to:
initiate injection of a kill agent into the polymerization reactor, such that a production rate of the slurry is slowed or the temperature of the polymerization reactor is reduced based at least on the input.

41 . The reactor control system of claim 37 , wherein the processor-executable instructions cause the reactor control system to:
control a third flow rate of a slurry stream exiting the polymerization reactor, and wherein the slurry stream comprises polyolefin particles formed in the polymerization reactor.

42 . A reactor system, comprising:
a feed system configured to supply a catalyst and a diluent mixture; a polymerization reactor coupled to the feed system to receive the catalyst and the diluent mixture, wherein the polymerization reactor is configured to contact the catalyst with the diluent mixture to form a slurry comprising polyolefin particles and the diluent mixture; a recovery system configured to separate a majority of the diluent mixture as a flash gas from the slurry discharged from the polymerization reactor; a reactor cooling system comprising a reactor jacket, a heat exchanger in a heat exchange relationship with the polymerization reactor, and a pump configured to produce a flow of coolant through the reactor jacket; and a controller operatively coupled to the feed system, the reactor system, the recovery system, or

Assignees

• Chevron Phillips Chemical Co Lp

Inventors

• Hottovy John D
• Mutchler Joel A

Classifications

• B01J2219/00094

  Jackets · CPC title

• B01J19/1837

  Loop-type reactors · CPC title

• B01J8/005 Primary

  Separating solid material from the gas/liquid stream (separation processes per se B01D) · CPC title

• B01J19/0013

  Controlling the temperature of the process · CPC title

• B01J2219/00162

  controlling the pressure · CPC title