Flashline heater system and method

Patent metadata

Field	Value
Publication number	US-9302244-B2
Application number	US-201314072649-A
Country	US
Kind code	B2
Filing date	Nov 5, 2013
Priority date	Jun 30, 2011
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

The present embodiments provide a system and method for separation within a polymer production process. Specifically, a flashline heater configured according to present embodiments may provide more time than is required for complete vaporization of liquid hydrocarbons that are not entrained within a polymer fluff produced within a polymerization reactor. Such extra time may allow for liquid hydrocarbons that are entrained within the polymer fluff to be vaporized.

First claim

What is claimed is:

1. A system, comprising:
a flashline heater comprising an upstream end coupled to a polymerization reactor via a continuous take off device and a discharge end coupled to a separation vessel;
a discharged stream within the flashline heater and received from the polymerization reactor via the continuous take off device, wherein the discharged stream comprises a vapor part generated from a liquid part and a solid part in thermal equilibrium with the vapor part at the discharge end of the flashline heater, wherein the vapor part in thermal equilibrium with the solid part is formed by a process comprising:
receiving the discharged stream from the polymerization reactor via the continuous take off device in the flashline heater, the discharged stream comprising the liquid part and the solid part upon entry into the flashline heater;
heating the discharged stream in the flashline heater as the discharged stream passes along a length of the flashline heater such that at least a portion of the liquid part vaporizes to generate the vapor part, wherein a transit time of the discharged stream through the flashline heater is at least approximately 8 seconds; and
equilibrating the temperature between the solid part and the vapor part during the at least approximately 8 seconds within the flashline heater; and

a controller operatively coupled to the continuous take off device and a heat source configured to heat the discharged stream in the flashline heater, wherein the controller is configured to control the transit time of the discharged stream in the flashline heater by adjusting at least a flow rate of the discharged stream through the continuous take off device in relation to an amount of the heat source directed to the flashline heater, such that the transit time is at least approximately 8 seconds.

2. The system of claim 1 , wherein the liquid part of the discharged stream, upon entry into the flashline heater, comprises a first portion and a second portion, wherein the first portion is not entrained in the solid part and the second portion is entrained in the solid part, and wherein equilibrating the temperature between the solid part and the vapor part comprises vaporizing substantially all of the first portion at least approximately 2.5 seconds before reaching the separation vessel.

3. The system of claim 1 , wherein the liquid part of the discharged stream, upon entry into the flashline heater, comprises a first portion and a second portion, wherein the first portion is not entrained in the solid part and the second portion is entrained in the solid part, and wherein equilibrating the temperature between the solid part and the vapor part comprises vaporizing substantially all of the first portion at least approximately 5 seconds before reaching the separation vessel.

4. The system of claim 3 , wherein the discharged stream comprises substantially no second portion of the liquid at the discharge end of the flashline heater.

5. The system of claim 1 , wherein heating the discharged stream in the flashline heater as the discharged stream passes along the length of the flashline heater comprises providing varying amounts of heat to the discharged stream.

6. The system of claim 1 , wherein the flashline heater comprises a first plurality of heat-variable sections and a second plurality of heat-variable sections disposed downstream of the first plurality of heat-variable sections, wherein heating the discharged stream in the flashline heater as the discharged stream passes along the length of the flashline heater comprises providing heat to the discharge stream via a heat transfer medium in the first plurality of heat-variable sections, and not providing heat to the discharge stream via the heat transfer medium in the second plurality of heat-variable sections, and wherein a first velocity of the discharge stream at an upstream section of the second plurality of heat-variable sections is lower than a second velocity of the discharged stream at the discharge end of the flashline heater.

7. The system of claim 1 , wherein the discharged stream comprises the vapor part, the liquid part, and the solid part at thermal equilibrium at the discharge end.

8. A polymer production system, comprising:
a flashline heater receiving a discharged stream from a polymerization reactor via a continuous take off device, the discharged stream comprising a liquid part and a solid part upon entry into the flashline heater, the flashline heater volatilizing at least a portion of the liquid part to generate a vapor part; and
a controller operatively coupled to the continuous take off device and configured to adjust a flow rate of the discharged stream through the continuous take off device based at least on monitored or modeled temperatures of the discharged stream, and wherein at least the flow rate of the discharged stream through the continuous take off device affects a transit time of the discharged stream through the flashline heater, and the controller is configured to adjust the flow rate of the discharged stream such that the transit time is at least approximately 8 seconds; and
wherein the liquid part comprises a first portion and a second portion, wherein the first portion is not entrained in the solid part and the second portion is entrained in the solid part, and wherein the flashline heater operates to vaporize substantially all of the first portion at least approximately 2.5 seconds before reaching a separation vessel coupled to a downstream end of the flashline heater.

9. The polymer production system of claim 8 , wherein the flashline heater is configured to controllably heat the discharged stream to vaporize substantially all of the first portion at least approximately 5 seconds before the discharged stream reaches the separation vessel.

10. The polymer production system of claim 8 , wherein the controller is configured to adjust the pressure of the discharged stream such that the transit time is at least approximately 8 seconds, and the flashline heater is configured to controllably heat the discharged stream to cause the solid part and the vapor part to reach thermal equilibrium within the at least approximately 8 seconds and before reaching the separation vessel.

11. The polymer production system of claim 8 , wherein the controller is configured to cause the solid part and the vapor part to reach thermal equilibrium at least by reducing the pressure of the discharged stream such that a temperature difference of less than about 1° F. exists between the solid part and the vapor part, and the solid part and the liquid part have respective temperatures within approximately 5° F. of a volatilization temperature of the liquid.

12. The polymer production system of claim 8 , wherein the flashline heater comprises:
a first section extending from an upstream end of the flashline heater and comprising a first plurality of heat-variable sections; and
a second section extending from a downstream end of the first section and to a downstream end of the second section, wherein the second section comprises a second plurality of heat-variable sections; and
wherein the flashline heater is configured to controllably heat the discharged stream in the first section of the flashline heater using a heat exchange medium, and the flashline heater is configured to transfer the discharged stream in the second section of the flashline heater such that the second section does not heat the discharged stream using any heat exchange medium, and a velocity of the discharged stream continuously increases from the upstream end of the flashline heater to the downstream end of the flashline heater.

Assignees

• Chevron Phillips Chemical Co

Inventors

• Hottovy John D
• Kufeld Scott E

Classifications

• C08F10/00

  Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond · CPC title

• B01J19/06 Primary

  Solidifying liquids (making microcapsules B01J13/02) · CPC title

• B01D1/24

  to obtain dry solids · CPC title

• B01D1/04

  Evaporators with horizontal tubes · CPC title

• B01J19/1837

  Loop-type reactors · CPC title