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1. WO2021067559 - LEAN GAS LNG HEAVIES REMOVAL PROCESS USING NGL

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[ EN ]

What is claimed is:

1. A process for removing heavies from natural gas, the process comprising:

combining a natural gas feed stream having a plurality of hydrocarbons including a quantity of heavies with an external natural gas liquid (NGL), in a vessel to form a mixture;

cooling the mixture in a first chiller to generate a liquid portion and a gas portion; introducing the liquid portion and the gas portion into a first stripping column, wherein the gas portion is introduced towards a top of the first stripping column and the liquid portion is introduced below the gas;

removing a liquid bottoms from the first stripping column, wherein the liquid bottoms comprises the external NGL and the quantity of heavies dissolved therein;

introducing the liquid bottoms into a second stripping column and separating a recyclable NGL from the heavies dissolved therein; and

recycling the recyclable NGL to the vessel.

2. A process according to claim 1, wherein the plurality of hydrocarbons of the natural gas feed stream further includes methane and nitrogen.

3. A process according to claims 1-2, wherein the natural gas feed stream is a rich natural gas.

4. A process according to claims 1-2, wherein the natural gas feed stream includes a lean natural gas.

5. A process according to claims 1-2, wherein the natural gas feed stream includes a very lean natural gas.

6. A process according to claims 1-5, wherein the external NGL comprises a C4 and/or C5 hydrocarbon.

7. A process according to claims 1-6, wherein the external NGL comprises a C2-C6 alkane.

8. A process according to claims 1-7, further comprising:

determining the composition of the natural gas feed stream including the quantity of heavies;

selecting an amount of external NGL to combine with the natural gas feed stream that is sufficient to dissolve the quantity of heavies of the natural gas feed stream.

9. A process according to claims 1-8, wherein from about 100 m3/h to about 450 m3/h of external NGL is combined with the natural gas feed stream.

10. A process according to claims 1-9, wherein the first chiller cools the mixture to a temperature below about -30°C.

11. A process according to claims 1-10, further comprising:

separating, via a separator, the liquid portion and the gas portion; and

cooling the gas portion in a second chiller to a temperature below about -45°C, to produce a reduced gas portion and a second liquid portion.

12. A process according to claims 1-11, further comprising separating the second liquid portion from the reduced gas portion in a second separator.

13. A process according to claims 1-12, further comprising combining the liquid portion from the separator and the second liquid portion from the second separator prior to entering the first stripping column.

14. A process according to claims 1-12, further comprising introducing the liquid portion from the separator and the second liquid portion from the second separator at different locations within the first stripping column.

15. A process according to claims 1-14, further comprising:

separating a first methane gas stream via the first stripping column;

separating a second methane gas stream from the liquid bottoms via the second stripping column; and

transferring the first methane gas stream and the second methane gas stream to a liquefaction processing system.

16. A heavies removal system with solvent recycle comprising the following components, in combination:

a vessel configured to receive a natural gas feed stream and a solvent, the natural gas feed stream having a heavies content;

a first chiller for cooling the natural gas feed stream and the solvent to a temperature below about -30°C;

a first stripping column for separating out a gas stream from a liquid stream;

a second stripping column for separating out a methane gas stream from a liquid bottoms including a recyclable solvent and a quantity of heavies, the second stripping column including a liquid recycle line connecting the second stripping column to the vessel for transferring the recyclable solvent to the vessel, and a heavies removal line connected to the second stripping column to remove the quantity of heavies.

17. A heavies removal system with solvent recycle according to claim 16, further comprising:

a first separator for separating the gas stream from the liquid stream;

a second chiller positioned between the first separator and the first stripping column, the second chiller for reducing the temperature of the gas stream to below about -45°C, generating a reduced gas stream and a second liquid stream.

18. A heavies removal system with solvent recycle according to claims 16-17, further comprising a second separator positioned between the second chiller and the first stripping column for separating the reduced gas stream from the second liquid stream, wherein liquid stream and the second liquid stream are combined in the first stripping column.

19. A heavies removal system with solvent recycle according to claims 16-18, wherein the liquid recycle line is adapted to receive fresh solvent prior to coupling with the vessel.

20. A heavies removal system with solvent recycle according to claims 16-19, wherein the solvent is an external natural gas liquid (NGL) comprising a C4 and/or C5 hydrocarbon.

21. A heavies removal system with solvent recycle according to claims 16-19, wherein the solvent is an external natural gas liquid (NGL) comprising a C2-C6 alkane.

22. A method of using external Natural Gas Liquid (NGL) to remove heavies from a natural gas feed stream, the method comprising:

evaluating a composition of a natural gas feed stream to determine at least a heavies quantity;

calculating an amount of external NGL required to dissolve the heavies quantity of the natural gas feed stream;

combining the amount of external NGL with the natural gas feed stream in a vessel to generate a mixture having the quantity of heavies dissolved therein; and

cooling the mixture in a first chiller to a temperature sufficient to separate the mixture into a liquid stream and a gas stream, the liquid stream comprising the external NGL and dissolved quantity of heavies.

23. A method according to claim 22, further comprising determining a natural NGL quantity of the natural gas feed stream, wherein the amount of external NGL is determined at least in part on the natural NGL quantity of the natural gas feed stream.

24. A method according to claims 22-23, wherein the liquid stream further comprises the natural NGL quantity.