System and method for rapid dump tank heating

Patent metadata

Field	Value
Publication number	US-11021549-B2
Application number	US-201916404409-A
Country	US
Kind code	B2
Filing date	May 6, 2019
Priority date	May 6, 2019
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

A method of operating a dump tank of a polymer production process by transferring all or a portion of a content of a polymerization reactor into the dump tank, wherein the reactor contents comprise solid polymer, and liquid and gaseous non-product components, and removing at least a portion of the liquid and gaseous non-product components from the dump tank by: reducing a pressure of the dump tank, subjecting the solid polymer to a first cleaning stage comprising heating the solid polymer by introducing a first heated treatment gas into the dump tank, and subjecting the solid polymer to a second cleaning stage comprising purging the solid polymer by introducing a second heated treatment gas into the dump tank.

First claim

What is claimed is:

1. A method of operating a dump tank of a polymer production process, the method comprising:
transferring all or a portion of a content of a polymerization reactor into the dump tank, wherein the reactor contents comprise solid polymer, and liquid and gaseous non-product components; and
removing at least a portion of the liquid and gaseous non-product components from the dump tank by:
reducing a pressure of the dump tank, whereby a flash gas comprising a first portion of the at least a portion of the liquid and gaseous non-product components is recovered from the dump tank;
subjecting the solid polymer to a first cleaning stage comprising heating the solid polymer by introducing a first heated treatment gas comprising primarily one or more hydrocarbons into the dump tank until a first cleaning stage temperature of the solid polymer is attained and recovering a first gas comprising a second portion of the at least a portion of the liquid and gaseous non-product components from the dump tank during the first cleaning stage; and
subjecting the solid polymer to a second cleaning stage comprising purging the solid polymer by introducing a second heated treatment gas comprising primarily nitrogen into the dump tank and recovering a second gas comprising a third portion of the at least a portion of the liquid and gaseous non-product components from the dump tank during the second cleaning stage.

2. The method of claim 1 , wherein the first heated treatment gas introduced into the dump tank during the first cleaning stage comprises one or more hydrocarbons having from one to five carbons (C1-C5 hydrocarbons).

3. The method of claim 1 , wherein the first heated treatment gas introduced into the dump tank during the first cleaning stage has a temperature that is in a range of from about 85 to about 95% of a melting temperature of the solid polymer, wherein the first cleaning stage temperature is in a range of from about 85 to about 95% of a melting temperature of the solid polymer, or both.

4. The method of claim 1 , wherein the first heated treatment gas comprises isobutane, isopentane, fuel gas, propane, propylene, or a combination thereof.

5. The method of claim 1 , wherein the first heated treatment gas is introduced into a bottom portion of the dump tank.

6. The method of claim 5 , wherein the first heated treatment gas is introduced into the dump tank via a gas distribution system operable to distribute the first heated treatment gas substantially uniformly about a cross sectional area of the dump tank.

7. The method of claim 1 further comprising maintaining a dump tank back pressure during the first cleaning stage.

8. The method of claim 1 , wherein, during the first cleaning stage, a rate of heating per cross sectional area of the dump tank of greater than or equal to about 5000 BTU/h-ft 2 is provided by the introduction of the first heated treatment gas.

9. The method of claim 1 , wherein a time required to remove the at least a portion of the liquid and gaseous non-product components from the polymer fluff is less than or equal to about 80% of a time required to remove a same at least a portion of the liquid and gaseous non-product components from a same solid polymer via a same method except utilizing a single cleaning stage employing a heated treatment gas comprising primarily nitrogen rather two cleaning stages wherein the first cleaning stage employs the first heated treatment gas comprising primarily one or more hydrocarbons.

10. The method of claim 1 further comprising flaring the first gas, wherein the method produces an amount of NOx emissions from flaring that is less than or equal to an amount of NOx emissions produced via a same method except utilizing a single cleaning stage employing a heated treatment gas comprising primarily nitrogen rather two cleaning stages wherein the first cleaning stage employs the first heated treatment gas comprising primarily one or more hydrocarbons.

11. A system comprising:
a dump tank into which all or a portion of a content of a polymerization reactor can be transferred during a polymerization reactor dump in a polymer production process, wherein the dump tank comprises:
a gas distribution system configured to distribute a treatment gas introduced thereto via a treatment gas inlet line substantially uniformly across a cross section of the dump tank, wherein the gas distribution system is located in a bottom portion of the dump tank;
a heater operable to increase temperature of the treatment gas to a treatment gas temperature;
an overhead gas line fluidly connecting the dump tank with a flare; and
a vent filter on the overhead gas line, wherein the vent filter is operable to collect entrained polymer particles in a gas passing through the overhead gas line.

12. The system of claim 11 , wherein the dump tank is a cylindrical vessel having a bottom cone section.

13. The system of claim 12 , wherein the dump tank does not comprise a steam jacket in contact with the bottom cone section.

14. The system of claim 11 further comprising:
a polymerization reactor operable to polymerize a monomer in the presence of a polymerization catalyst to produce a polymerization effluent comprising solid polymer and non-solid components;
a polymerization reactor effluent line operable to remove the polymerization effluent from the polymerization reactor;
one or more flashline heaters positioned proximate the polymerization reactor effluent line and configured to indirectly heat the polymerization reactor effluent;
a separation apparatus configured to receive the heated polymerization reactor effluent, separate a majority of the non-solid components from the solid polymer, and yield a solids discharge comprising a majority of the solid polymer and a minor amount of the non-solid components; and
recycle equipment configured to recycle one or more of the separated non-solid components to the polymerization reactor via a recycle line,
wherein the dump tank is fluidly connected with the polymerization reactor such that the inventory of the polymerization reactor can be transferred into the dump tank during the polymerization reactor dump.

15. The system of claim 14 , wherein the dump tank is fluidly connected with the polymerization reactor effluent line, downstream of at least one of the one or more flashline heaters, whereby at least a portion of a fluid circulated from the polymerization reactor through the separation apparatus and recycled to the polymerization reactor via the recycle equipment during a polymerization reactor dump can be diverted to the dump tank as the treatment gas.

16. The system of claim 14 further comprising a bypass line fluidly connecting the recycle line with the polymerization reactor effluent line, whereby at least a portion of the fluid circulated from the recycle equipment to the polymerization reactor during a polymerization reactor dump can be diverted for introduction into at least one of the one or more flashline heaters without passing through the polymerization reactor and the diverted portion can be introduced into the dump tank as treatment gas.

17. A method of producing polyolefins, the method comprising:
(i) during normal operation:
polymerizing a polymerization feed comprising a monomer, a diluent, and optionally a co-monomer in the presence of a polymerization catalyst to produce a polymerization effluent comprising solid polymer, and liquid and gaseous non-product components;
passing the polymerization reactor effluent through one or more flashline heaters configured to indirectly

Assignees

• Chevron Phillips Chemical Co Lp

Inventors

• Curren Joseph A
• Hein James E
• Romig Ralph W
• Chang Ai-Fu

Classifications

• C08F10/00

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

• C08F6/005 Primary

  from solid polymers · CPC title

• B01D3/06

  Flash distillation · CPC title

• B01D3/009

  in combination with chemical reactions · CPC title

• B01J2208/00761

  Discharging · CPC title