Purge to intermediate pressure in cryogenic distillation

Patent metadata

Field	Value
Publication number	US-10274252-B2
Application number	US-201615154413-A
Country	US
Kind code	B2
Filing date	May 13, 2016
Priority date	Jun 22, 2015
Publication date	Apr 30, 2019
Grant date	Apr 30, 2019

Abstract

A system and method for an intermediate pressure vessel to receive a purge in a cryogenic distillation column system. The vessel operates at an intermediate pressure to reduce solidification of the purge. The cryogenic distillation column receives a natural gas having methane and acid gas. The column discharges an overhead stream rich in the methane, and a bottoms stream rich in the acid gas. An overhead system receives the overhead stream, and discharges a vapor methane product, and a cooled liquid for reflux to the cryogenic distillation column.

First claim

What is claimed is:

1. A cryogenic distillation column system comprising:
a cryogenic distillation column configured to receive a natural gas comprising methane and acid gas, and to discharge:
an overhead stream rich in the methane; and
a bottoms stream rich in the acid gas;

an overhead system connected to the overhead stream and configured to receive the overhead stream, the overhead system including a condensation system and a reflux system, the condensation system and the reflux system configured to cool the overhead stream and discharge a cooled liquid, generated from the cooled overhead stream in the overhead system, for reflux to the cryogenic distillation column during a normal operation of the cryogenic distillation system, the overhead system also discharging a vapor methane product, the condensation system including a compressor and a cooler, the reflux system including a reflux accumulator vessel;
a purge, vented from the overhead system; and
an intermediate pressure vessel that receives the purge only during a startup operation of the cryogenic distillation system and operates at an intermediate pressure to reduce solidification of the purge, wherein the intermediate pressure is between 50-200 psig lower than an operating pressure of the cryogenic distillation column;
a Joule-Thompson valve connected to the overhead system and configured to discharge a cooled vapor from the overhead system into the cryogenic distillation column during the startup operation.

2. The system of claim 1 , comprising a purge valve to provide the purge to the intermediate pressure vessel, and wherein the intermediate pressure vessel comprises a heater.

3. The system of claim 1 , wherein the cryogenic distillation column comprises two columns, and wherein the purge comprises a plurality of purges.

4. The system of claim 1 , wherein the cryogenic distillation column has a freezing section, and wherein the intermediate pressure vessel is configured to discharge to a flare system.

5. The system of claim 1 , comprising a pressure control valve to maintain the intermediate pressure vessel at the intermediate pressure.

6. The system of claim 5 , wherein the pressure control valve is configured to maintain the operating pressure of the intermediate pressure vessel to within at least 200 psig of a purge pressure of the purge.

7. The system of claim 5 , wherein the pressure control valve is configured to maintain the operating pressure of the intermediate pressure vessel to a pressure above the triple point pressure of carbon dioxide.

8. The system of claim 5 , wherein the intermediate pressure vessel is configured to discharge a vapor stream to a flare knockout drum, and wherein the pressure control valve is disposed on the vapor stream at or near the flare knockout drum.

Assignees

• Valencia Jaime A
• Kelman Scott D
• Kimble E Lawrence
• Exxonmobil Upstream Res Co

Inventors

• Valencia Jaime A
• Kelman Scott D
• Kimble E Lawrence

Classifications

• F25J2240/40

  Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval · CPC title

• F25J3/0233 Primary

  separation of CnHm with 1 carbon atom or more · CPC title

• F25J3/0295

  Start-up or control of the process; Details of the apparatus used, e.g. sieve plates, packings · CPC title

• F25J2290/62

  Details of storing a fluid in a tank · CPC title

• F25J2220/66

  Separating acid gases, e.g. CO2, SO2, H2S or RSH · CPC title