METHOD AND SYSTEM FOR OBTAINING COMPONENTS FROM NATURAL GAS

Abstract

The invention relates to a method for obtaining natural gas components, wherein, using natural gas, a feed mixture containing methane and helium is provided and subjected to a separating sequence so as to obtain a natural gas product which is enriched with methane and depleted of helium in comparison to the feed mixture and a helium product which is depleted of methane and enriched with helium in comparison to the feed mixture, which method comprises one or more membrane separating steps and one or more pressure change adsorption steps. According to the invention, the feed mixture is provided using natural gas containing methane, higher hydrocarbons, helium and carbon dioxide, and the providing of the feed mixture comprises depleting the natural gas used for provision of the feed mixture of carbon dioxide and of the higher hydrocarbons. The present invention also relates to a corresponding system.

Claims

1-10. (canceled)

11. A method for obtaining natural gas components, wherein, using natural gas, a feed mixture containing methane and helium is provided and subjected to a separating sequence so as to obtain a natural gas product which is enriched in methane and depleted of helium in comparison to the feed mixture and a helium product which is depleted of methane and enriched in helium in comparison to the feed mixture, which separating sequence comprises one or more membrane separating steps and one or more pressure swing adsorption steps, wherein the feed mixture is provided using natural gas that contains methane, higher hydrocarbons, helium and carbon dioxide and that the provision of the feed mixture comprises depleting the natural gas used for provision of the feed mixture of carbon dioxide and of the higher hydrocarbons.

12. The method according to claim 11, wherein the natural gas used for provision of the feed mixture is withdrawn from an external natural gas source at a pressure level of 10 to 150 bar (abs.) and is not further compressed upstream of the one or more membrane separating steps.

13. The method according to claim 11, wherein the natural gas used for provision of the feed mixture comprises more than 0.5 vol % carbon dioxide.

14. The method according to claim 11, wherein the separating sequence comprises a first membrane separating step, a second membrane separating step and a pressure swing adsorption step, wherein a first retentate and a first permeate are formed in the first membrane separating step, a second retentate and a second permeate are formed in the second membrane separating step and a non-adsorbate and an adsorbate are formed in the pressure swing adsorption step.

15. The method according to claim 14, wherein at least some of the adsorbate and at least some of the second permeate together with the feed mixture are supplied to the first membrane separating step, wherein at least some of the first retentate is supplied to the second membrane separating step, wherein at least some of the first permeate is supplied to the pressure swing adsorption step, wherein at least some of the second retentate is used to provide the natural gas product, and wherein at least some of the non-adsorbate is used to provide the helium product.

16. The method according to claim 15, wherein membranes are used in the first and in the second membrane separating step which have a higher permeability to helium than to methane, and wherein in the pressure swing adsorption step has an adsorbent which has a higher affinity for methane than for helium.

17. The method according to claim 15, wherein the pressure swing adsorption step is operated at an adsorption pressure level of 6 to 20 bar (abs.) and a desorption pressure level of less than 0.5 bar (rel.), wherein the non-adsorbate is provided at the adsorption pressure level and the adsorbate is provided at the desorption pressure level.

18. The method according to claim 15, wherein the second permeate is provided at a permeate pressure level and the first membrane separating step is operated at an inlet pressure level which is above the desorption pressure level and the permeate pressure level of the second permeate, wherein the adsorbate or the portion of the adsorbate that is supplied together with the feed mixture to the first membrane separating step, and the second permeate or the portion of the second permeate that is supplied together with the feed mixture to the first membrane separating step, are compressed to the inlet pressure level of the first membrane separating step.

19. The method according to claim 11, wherein the natural gas used for provision of the feed mixture is first depleted of carbon dioxide and then of the higher hydrocarbons or is first depleted of the higher hydrocarbons and then of carbon dioxide.

20. A system for obtaining natural gas components which is configured to provide a feed mixture containing methane and helium using natural gas, and to subject it to a separating sequence to obtain a natural gas product enriched in methane and depleted of helium in comparison to the feed mixture and a helium product depleted of methane and enriched in helium in comparison to the feed mixture, which separating sequence comprises one or more membrane separating steps and one or more pressure swing adsorption steps, wherein means configured to provide the feed mixture using natural gas that contains methane, higher hydrocarbons, helium and carbon dioxide, and to provide the feed mixture such that the natural gas used for provision of the feed mixture is depleted of carbon dioxide and of the higher hydrocarbons.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 illustrates an embodiment of the present invention in a simplified schematic representation.

[0047] FIG. 2 illustrates an embodiment of the present invention in a simplified schematic representation.

[0048] In the figures, components corresponding to one another in terms of their function or structure are indicated by identical reference signs and for the sake of clarity are not explained repeatedly.

DETAILED DESCRIPTION OF THE DRAWINGS

[0049] FIGS. 1 and 2 show methods according to preferred embodiments of the present invention in a simplified, schematic representation in the form of simplified process flow diagrams. The following explanations relate to the methods described and to corresponding devices in the same way.

[0050] The methods 100, 200 are each used to obtain natural gas components. Using natural gas, which can be provided in the form of a feed stream A and withdrawn, for example, at a suitable pressure level of an external source, such as a tank or a pipeline or a borehole, a feed mixture B comprising methane and helium is provided using method steps that are explained in detail below, and is subjected to a separating sequence designated as a whole with 10 to obtain a natural gas product C enriched in methane and depleted of helium in comparison to the feed mixture and a helium product D depleted of methane and enriched in helium in comparison to the feed mixture.

[0051] In the examples illustrated herein, the separating sequence 10 comprises a first membrane separating step 11, a second membrane separating step 12 and a pressure swing adsorption step 13. A first retentate R1 and a first permeate P1 are formed in the first membrane separating step 11, a second retentate R2 and a second permeate P2 are formed in the second membrane separating step 12, and a non-adsorbate N and an adsorbate A are formed in the pressure swing adsorption step 13. Each of them is a gas mixture.

[0052] In the illustrated examples, at least some of the adsorbate A and at least some of the second permeate P2 are supplied together with the feed mixture B to the first membrane separating step 11, at least some of the first retentate R1 is supplied to the second membrane separating step 12, at least some of the first permeate P1 is supplied to the pressure swing adsorption step 13, at least some of the second retentate R2 is used to provide the natural gas product C, and at least some of the non-adsorbate N is used to provide the helium product D.

[0053] Feed mixture B is provided using natural gas that contains methane, higher hydrocarbons, helium and carbon dioxide. The natural gas stream thus contains these components. The provision of feed mixture B comprises depleting the natural gas A, which is used for provision of the feed mixture, of carbon dioxide in a method step 1 and depleting said natural gas A of the higher hydrocarbons in the manner explained above in a method step 2. As apparent from the combination of FIGS. 1 and 2, the difference between the methods 100 and 200 is in particular the sequence of method steps 1 and 2. A carbon dioxide stream E is formed in method step 1, while a stream F with heavier hydrocarbons is formed in method step 2.

[0054] As illustrated here, the feed mixture can be cooled by means of a heat exchanger 3 before it is combined with the recycled second permeate P2 and the adsorbate A. The latter material streams can be compressed together by means of a compressor 4 and cooled by means of a heat exchanger 5. A compressor 6 is provided for compressing the first permeate P1.