Configurations and methods for nitrogen rejection, LNG and NGL production from high nitrogen feed gases

Patent metadata

Field	Value
Publication number	US-9487458-B2
Application number	US-201414194238-A
Country	US
Kind code	B2
Filing date	Feb 28, 2014
Priority date	Feb 28, 2014
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

Variable N2 content in feed gas ranging from 3 mole % to 50 mole % can be rejected from the process using a feed exchanger that is fluidly coupled with a cold separator and a single fractionation column to produce a nitrogen vent stream and streams that are suitable to be further processed for NGL recovery and LNG production.

First claim

What is claimed is:

1. A method of removing nitrogen from a hydrocarbonaceous feed gas having a CO2 content of equal or less than 50 ppmv, a water content of equal or less than 0.1 ppmv, and a nitrogen content of at least 3 mol %, comprising:
cooling the hydrocarbonaceous feed gas in a heat exchanger to condense C3 + components in the hydrocarbonaceous feed gas;
separating in a phase separator the condensed C3 + components as a liquid stream from a vapor stream comprising C1, C2, and nitrogen;
feeding the vapor stream into a fractionation column, and using the fractionation column to produce a nitrogen-enriched overhead product and a nitrogen-depleted bottom product;
partially condensing the nitrogen-enriched overhead product using refrigeration generated by pressure reduction of a portion of the nitrogen-depleted bottom product to thereby produce a liquid reflux to the fractionation column and a gaseous nitrogen vent stream; and
feeding the liquid reflux to the fractionation column.

2. The method of claim 1 wherein the hydrocarbonaceous feed gas has a pressure of about 800-1000 psia, and wherein the hydrocarbonaceous feed gas is cooled to a temperature of −40° F.′ to −60° F.

3. The method of claim 1 wherein at least 80% of the C3 + components are condensed in the step of cooling the hydrocarbonaceous feed gas.

4. The method of claim 1 further comprising a step of heating the condensed C3 + components and feeding the heated C3 + components to a natural gas liquids recovery unit that is configured to produce a C3 + NGL product and a vapor product.

5. The method of claim 4 further comprising a step of feeding the vapor product to a natural gas liquefaction unit.

6. The method of claim 1 further comprising a step of at least partially condensing the vapor stream before feeding the vapor stream into the fractionation column.

7. The method of claim 1 further comprising a step of reducing pressure of the gaseous nitrogen vent stream and extracting refrigeration content from the gaseous nitrogen vent stream in at least one of the heat exchanger and a reflux exchanger.

8. The method of claim 1 further comprising a step of compressing the pressure reduced portion of the nitrogen-depleted bottom product and feeding the recompressed portion of the bottom product to a natural gas liquefaction unit.

9. The method of claim 1 further comprising a step of heating another portion of the nitrogen-depleted bottom product in the heat exchanger, and feeding the heated another portion to a natural gas liquefaction unit.

10. A method of removing nitrogen from a hydrocarbonaceous feed gas having a CO2 content of equal or less than 50 ppmv, a water content of equal or less than 0.1 ppmv, and a nitrogen content of at least 3 mol %, comprising:
cooling the hydrocarbonaceous feed gas to form a liquid stream comprising condensed C3 + components and a vapor stream comprising C1, C2, and nitrogen;
separating in a refluxed fractionation column the vapor stream into a nitrogen-enriched overhead product and a nitrogen-depleted bottom product;
reducing pressure of the nitrogen-depleted bottom product to produce refrigeration for the step of cooling the feed gas and refrigeration for a reflux condenser to so form from the nitrogen-enriched overhead product a gaseous nitrogen vent stream and a reflux stream.

11. The method of claim 10 further comprising a step of feeding the pressure-reduced nitrogen-depleted bottom product to a natural gas liquefaction unit.

12. The method of claim 10 further comprising a step of heating the liquid stream and feeding the heated liquid stream to a natural gas liquids recovery unit to form a C3 + NGL product and a vapor product.

13. The method of claim 12 wherein the vapor product is fed to a natural gas liquefaction unit.

14. The method of claim 10 wherein the hydrocarbonaceous feed gas has a pressure of at least 700 psia, and wherein the refluxed fractionation column is operated at a pressure of 300-400 psia.

Assignees

• Fluor Tech Corp
• Fluor Corp

Inventors

• Mak John

Classifications

• C10G5/06

  by cooling or compressing · CPC title

• C07C9/04

  Methane (production by treatment of sewage C02F11/04; natural gas, synthetic natural gas C10L3/06) · CPC title

• C07C7/09 Primary

  by fractional condensation · CPC title

• F25J2270/90

  External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration · CPC title

• F25J2200/72

  Refluxing the column with at least a part of the totally condensed overhead gas · CPC title