CN116601447A

CN116601447A - Cryogenic process for obtaining valuable products from hydrogen-rich feed gas

Info

Publication number: CN116601447A
Application number: CN202180078839.5A
Authority: CN
Inventors: 诺伯特·彼得斯; 汉斯·施密特
Original assignee: Jeno Holdings LLC
Current assignee: Jeno Holdings LLC
Priority date: 2020-11-23
Filing date: 2021-11-22
Publication date: 2023-08-15
Also published as: WO2022106699A3; DE102020130946B4; WO2022106699A4; EP4244559A2; DE102020130946A1; CA3199710A1; WO2022106699A2; AU2021383567A1; US20240019206A1

Abstract

The present invention relates to a cryogenic process for obtaining a valuable product, in particular hydrogen, from a hydrogen-rich feed gas, in particular a hydrogen-rich natural gas, comprising the steps of: in a first separation column (T1) hydrocarbons having more than two carbon atoms are separated, in a second separation column (T2) methane is separated and in a third separation column (T3) nitrogen is separated, wherein according to steps a) to c) hydrogen rich injection gas is supplied to the separation columns T1 to T3 after optional pre-purification R and the separation columns effect separation into a liquid fraction, i.e. a bottom product, and a gas fraction, i.e. an overhead product. In the cryogenic process according to the invention, the provision of refrigeration is preferably at least partly achieved by one or more refrigeration circuits.

Description

Cryogenic process for obtaining valuable products from hydrogen-rich feed gas

Technical Field

The present invention relates to a cryogenic process for recovering valuable components, especially hydrogen, from a hydrogen-rich feed gas, preferably a hydrogen-rich natural gas. Wherein hydrocarbons having more than two carbon atoms, methane and nitrogen are separated in at least 3 separation columns.

Background

Recently, hydrogen is increasingly being considered as a clean energy source for humans because its combustion produces only water. Industrially produced hydrogen is used in large quantities in chemical processes, and its role as an energy carrier is pushing the energy industry to invest in large scale, including the increasing use of hydrogen for energy storage.

Hydrogen is typically obtained from a residual gas stream from a chemical process such as a reforming or cracking process. Hydrogen is enriched and/or separated from these residual gas streams using membranes and/or pressure swing adsorbers. These residual gas streams typically comprise methane, a mixture of hydrocarbons of different chain lengths, preferably light hydrocarbons, carbon monoxide and carbon dioxide.

Recent discoveries of various sources of natural hydrogen have emphasized the economic benefits of developing natural hydrogen in the future in continental areas. For this reason, there is a need for processes that enable the extraction of hydrogen from these natural hydrogen sources to be cheaper than industrial production from fossil fuels or by electrolysis. Because of the scale of hydrogen-containing natural gas sources that have been found to have high potential yields, such as the hydrogen-rich natural gas sources in braker (mary), the pressure swing adsorption and membrane techniques known in the art are not technically capable of handling satisfactory yields in a cost-effective manner. This requires large plants with a capacity of for example 1000 tons/day or a heat output of about 1.5GW, which corresponds to a flow rate of about 500000 standard cubic meters per hour (Nm 3/h).

It is therefore an object of the present invention to provide an integrated process which has the capacity of large plants, efficiently and cost effectively separates a large yield of hydrogen-rich feed gas, in particular hydrogen-rich natural gas, into valuable components contained therein and, if desired, makes these components available for further processing after adjustment of the purity. Since the natural hydrogen-enriched natural gas sources found at present are located in geographical areas of low industrialization (e.g. mary), it is advantageous here to integrate the process, which on an industrial scale is as efficient, economical and comprehensive as possible in separating all valuable components present in the feed gas and making them available for further use or processes or as energy sources. Of course, such a process is also advantageous for large-scale industrial production of hydrogen-rich feed gases, especially in the context of the increasing use of hydrogen as an energy source by the automotive and other industrial sectors.

Details of the Mary hydrogen-containing natural gas source described in the prior art are described by Prinzhofer et al in J.International H.En. (2018), https:// doi.org/10.1016/j.ijhydgene.2018.08.193.

To solve this problem, a cryogenic process is described for recovering valuable components, in particular hydrogen, from a hydrogen-rich feed gas, preferably a hydrogen-rich natural gas, wherein hydrocarbons having more than two carbon atoms are removed in a first separation column, methane is removed in a second separation column, and nitrogen is removed in a third separation column.

Disclosure of Invention

In a first aspect, the present invention relates to a cryogenic process for recovering valuable components, in particular hydrogen, from a hydrogen-rich feed gas, preferably a hydrogen-rich natural gas, said process comprising the steps of:

a) In the first separation column (T1), in particular in the rectification column, hydrocarbons having more than two carbon atoms are removed,

b) Removing methane in a second separation column (T2), in particular a rectification column, and

c) Nitrogen is removed in a third separation column (T3), in particular a rectification column,

wherein according to steps a) to c) the hydrogen-rich feed gas is fed to the separation columns T1 to T3 after the optional pre-purification R and separated in the separation columns into a liquid fraction, i.e. a bottom product, and a gas fraction, i.e. an overhead product.

For the purposes of the present invention, feed gas means a hydrogen-rich gas having a hydrogen content of more than 50% by volume, which originates from an industrial process or from natural gas sources, which contains the valuable components hydrogen, methane, hydrocarbons having more than two carbon atoms and nitrogen, and which is used as starting gas for the cryogenic process according to the invention.

The term feed fraction means the gas that reaches each separation column, which gas is passed through the corresponding separation column to be separated into at least 2 fractions, i.e., an overhead fraction and a bottom fraction.

Natural gas in the sense of the present invention refers to gases formed by processes occurring naturally below the earth's surface or within the earth. The hydrogen-rich natural gas is preferably from a natural gas source.

The hydrogen-rich feed gas, preferably hydrogen-rich natural gas, has a hydrogen content of 50 to 99.9% by volume, preferably 70 to 99.9% by volume, particularly preferably 90 to 99.9% by volume.

In addition, nitrogen, methane and noble gases, in particular helium, neon and argon, and hydrocarbons having more than two carbon atoms, may be included as additional components in the feed gas, in particular natural gas. Carbon dioxide may also be included at lower concentrations, particularly between 0 and 10% by volume, while carbon monoxide and sulfur components may be present at concentrations between 0 and 0.5% by volume.

In another embodiment, the hydrogen-rich feed gas, in particular hydrogen-rich natural gas, has as main component a hydrogen content of 50 to 99.9% by volume, a methane content of 0.02 to 40% by volume and a nitrogen content of 0.02 to 30% by volume, preferably a hydrogen content of at least 70% by volume, a methane content of at most 20% by volume and a nitrogen content of at most 20% by volume, particularly preferably a hydrogen content of at least 90% by volume, a methane content of at most 10% by volume and a nitrogen content of at most 10% by volume.

In the cryogenic process according to the invention, the first, second, third, fourth and fifth separation columns are advantageously rectification columns.

In the cryogenic process according to the invention, the cold supply is preferably provided at least in part by one or more refrigeration cycles.

In the method according to the invention, the hydrogen-rich feed gas, preferably the hydrogen-rich natural gas, is cooled and at least partially liquefied in a separation column, preferably a rectification column, in at least one heat exchanger (E1) with a refrigerant or a refrigerant mixture.

In another aspect of the invention, the feed gas (B0), i.e. the hydrogen-rich feed gas, particularly hydrogen-rich natural gas from a natural gas source, is pre-purified (R) by removing one or more components of the feed gas that would freeze in the cryogenic part of the plant. These components are selected in particular from water, carbon dioxide, hydrogen sulphide, mercaptans and mercury compounds, in particular mercury, or combinations thereof. These components may be removed by adsorption and/or absorption processes as part of the pre-purification process.

Typically, natural gas wells, particularly hydrogen-rich natural gas wells, contain water that must be removed during pre-cleaning, pretreatment, or drying. If the carbon dioxide, hydrogen sulphide, mercaptans and/or mercury compounds of the natural gas source itself, in particular mercury, are already low, at least in part of the fractions produced, or possibly not at all, further pre-purification work may be omitted as appropriate. Hydrogen-rich feed gases from industrial processes containing the same components are also treated accordingly. In one aspect of the invention, the hydrogen-rich feed gas from the natural gas source is pre-purified to remove at least water components, preferably carbon dioxide, hydrogen sulfide, mercaptans and/or mercury compounds, particularly mercury, by pre-purification.

If a hydrogen-rich feed gas from an industrial process is used as the feed gas, which does not contain any of the above components, which are removed during the pre-purification process, pre-treatment and/or drying may be omitted.

In the process according to the invention, the feed gas, in particular the hydrogen-rich natural gas, is preferably precompressed before the prepurification.

According to the invention, valuable components contained in the feed gas, in particular hydrogen, hydrocarbons having more than two carbon atoms, methane, nitrogen, are separated from the feed gas or the prepurified feed gas in the separation columns T1 to T3, preferably in the rectification columns. It is advantageous to compress the feed gas to a pressure of 20-50 bar before liquefying it. Recovery at high pressure is desirable, particularly in the case of relatively valuable component hydrogen, as hydrogen is typically sent to further applications, such as compression.

The hydrogen-rich feed gas (B1), in particular hydrogen-rich natural gas, which may have been pre-dried and/or pre-purified and may be present at a relatively high pressure, is, after cooling in the heat exchanger E1 and possibly partial condensation, fed via a line in which an expansion valve may optionally be provided to a first separation column (T1), preferably a rectification column, and is separated in this column into liquid and gaseous fractions. Typically, in the corresponding separation column, the liquid phase is referred to as the bottom product and the gas phase is referred to as the top product.

According to the process of the present invention, the bottoms from the first separation column T1, preferably the rectification column, in particular the C2, C3 hydrocarbons and higher hydrocarbons, are fractionated into ethane gas (B3) and LPG (B2) in a further fractionation, namely a fourth separation column T4, preferably the rectification column. The bottom product of the separation column T1 can initially be used as refrigerant in E1 and, possibly after throttling, be fed in two phases to the separation column T4.

Optionally, in another aspect of the invention, after optional pre-purification R (B1), a portion of the stream of hydrogen-rich feed gas may be passed directly to the lower portion of separation column T1, bypassing heat exchanger E1. As a result, the reboiler of the separation column T1 is at least partially depressurized.

At the top of the separation column T1, preferably the top of the rectification column, a fraction (top product) containing at least methane, nitrogen and hydrogen is taken off. The fraction is further cooled in a heat exchanger E1 and is then fed via a line in which an expansion valve may optionally be provided to a second separation column T2, preferably a rectification column.

Optionally, in another aspect of the invention, a portion of the overhead stream of separation column T1 may be fed directly to the lower portion of separation column T2, bypassing heat exchanger E1. This has the effect that the reboiler of the separation column T2 is at least partially depressurized (not shown in fig. 1).

According to the invention, the overhead condenser is cooled by the refrigerant or refrigerant mixture or by a split stream of the refrigerant or refrigerant mixture by means of a heat exchanger E1 of the first separation column T1, preferably a rectification column.

The top condenser of all separation columns, preferably rectification columns, may be a plate-fin heat exchanger, preferably a multi-flow plate-fin heat exchanger, a spiral-wound heat exchanger, preferably a multi-flow spiral-wound heat exchanger, a TEMA heat exchanger, a series of spiral-wound heat exchangers connected in series and/or a plate-fin heat exchanger, and is arranged inside or above each separation column T, preferably rectification column T, whereby an arrangement above the rectification columns may avoid reflux pumps.

By varying the column height and cold supply, the impurities in each overhead product can be kept within a narrow range. For example, the ethane content of the fraction extracted overhead in the separation column T1 can be set almost arbitrarily, i.e. between about 10ppmV and a few vol%, preferably less than 2 vol%, particularly preferably less than 1 vol%. The methane content in the bottom product of the separation column T1 can be adjusted almost arbitrarily, i.e. between about 1ppm and a certain volume%, preferably less than 2 volume%, particularly preferably less than 1 volume%.

The valuable components separated off at the top of the first separation column T1, preferably the rectification column, comprising at least one or more valuable components selected from the group consisting of methane, nitrogen and hydrogen, are, after further cooling in the heat exchanger E1, fed via a line in which an expansion valve may optionally be provided to a separation column T2, preferably the rectification column, and separated in T2 into liquid and gaseous fractions.

Optionally, in another aspect of the invention, a portion of the overhead stream of separation column T2 may be fed directly to the lower portion of separation column T3 bypassing heat exchanger E1. This has the effect that the reboiler of the separation column T3 is at least partially depressurized (not shown in fig. 1).

According to the invention, the top condenser E1 of the second separation column T2, preferably the rectification column, is cooled by the refrigerant or the refrigerant mixture or by a split stream of the refrigerant or the refrigerant mixture.

The methane-rich bottom product from the second separation column T2, preferably a rectification column, is heated and compressed in a heat exchanger (E1) and recovered as methane gas (B4) or further cooled by the heat exchanger (E1), expanded and recovered as LNG.

The valuable components separated off at the top of the separation column T2, preferably the rectification column, comprising at least one or more valuable components selected from the group consisting of nitrogen, helium and hydrogen, are, after further cooling, fed via a line in which a pressure reducing valve may optionally be provided to a third separation column T3, preferably the rectification column, and separated therein into liquid and gaseous fractions.

A portion of the nitrogen-rich bottoms product of separation column T3 may be expanded, heated in heat exchanger (E1), and fed to the refrigeration cycle of E1 as a refrigerant or component of a refrigerant. The nitrogen-rich bottom product may also be heated in E1 without expanding it and further used as high pressure nitrogen (B5).

Alternatively, the bottom product of the separation column T3 (high pressure LIN) may be expanded and used as the first refrigerant stage for the liquefaction of hydrogen or helium.

If carbon monoxide is present in the feed gas, this carbon monoxide is enriched in the nitrogen-rich bottom product of the third separation column T3, preferably the rectification column, and may preferably be converted to carbon dioxide at the hot end of the process by means of oxygen added in an additional process unit. Nitrogen containing small amounts of carbon dioxide is recovered as a valuable product, which can be used and/or sent to additional processes.

In the process according to the invention, the helium gas possibly contained in the hydrogen-rich top product of the third separation column T3, preferably of the rectification column, is separated into two components of helium and hydrogen after further cooling in a fifth separation column, in particular in a hydrogen separation column (T5), preferably of the rectification column, and into two components of helium and hydrogen by rectification or at least one stage of depressurization, the residual impurities being removed separately in low-temperature standard liquefaction plants, liquefied and stored if desired, preferably in a vacuum-insulated dedicated tank.

According to the process of the invention, the hydrogen-rich top product of the third separation column T3, preferably the rectification column, is heated (B6) in a heat exchanger (E1), compressed and fed to a pipeline. Alternatively, it may be liquefied by removing residual impurities in standard hydrogen liquefaction equipment and stored, preferably in a vacuum insulated dedicated tank.

In a further process of the process according to the invention, the hydrogen top product from the separation column T3, preferably the rectification column, can first be purified by adsorption in a special unit according to the prior art and then liquefied and stored, preferably in a vacuum-insulated special tank.

Depending on the number of stages of the respective separation columns (particularly, rectification columns) and the cold/heat supply, the purity of the respective products can be adjusted. In the process according to the invention, the methane-rich bottom product of the separation column T2, the hydrogen-rich top product and the nitrogen-rich bottom product of the separation column T3 and the ethane-rich top product of the separation column T4 are recovered as LPG product (B2) or ethane product (B3) or methane product (B4) or nitrogen product (B5) or hydrogen product (B6) in their purity as valuable products according to the cold supply of E1 and are then available for further processes or uses/purposes. The product of the separation column T5, i.e. the hydrogen bottom product or the helium top product, is also subjected to purity adjustment in the separation column T5. The helium top product is first purified by adsorption and then liquefied and stored, preferably in a vacuum insulated dedicated tank. The bottom product hydrogen is purified by adsorption and stored, preferably in a vacuum insulated dedicated tank.

In a preferred aspect of the invention, the condensers of the separation columns (preferably rectification columns) T1 to T4, and the reboilers of T1 to T3 are connected to E1 or integrated in E1.

The at least one heat exchanger unit E1 used in the method according to the invention is designed as a multi-flow plate-fin heat exchanger or spiral wound heat exchanger, in particular a series of spiral wound heat exchangers and/or plate-fin heat exchangers connected in series, preferably multiply subdivided according to the temperature profile of the separation process to ensure an energetically favourable temperature difference throughout the cooling process, and preferably connected in a plurality of parallel connections, depending on the capacity of the apparatus.

According to the method of the invention, the cold supply of the separation process of the separation column, preferably of the rectification column (T1 to T4), is provided by,

a) The cycle is passed through a nitrogen expander with at least one expander compressor (Xi-Ci), where compressor Ci serves as the final stage of the cycle compression. Nitrogen from the nitrogen product (B5), or from the bottom product of T3, may preferably be provided as a refrigerant component, or

b) By performing an expander cycle with nitrogen and methane as components in analogy to a), the expander compressor X2-C2 can also be replaced by a joule-thomson expansion valve. In this case, methane from the methane product (B4), or from the bottom product of T2, may also be provided as a refrigerant component, or

c) By means of a mixed refrigerant cycle consisting of at least two components selected from the group consisting of nitrogen, methane, ethane, propane, isobutane, n-butane, isopentane, n-pentane, hexane and heptane, these components preferably being selected according to process optimisation in order to achieve a minimum effective performance loss in E1, or

d) According to process optimisation, a minimum effective performance loss in E1 is achieved by a series arrangement of selected refrigeration cycles a) to c).

The cryogenic process for recovering hydrogen, hydrocarbons containing more than two hydrocarbons, methane and nitrogen from a hydrogen-rich feed gas, particularly a hydrogen-rich natural gas, and further advantageous embodiments thereof according to the present invention will be explained in more detail below based on the embodiments shown in the drawings.

Examples of the composition of a hydrogen-enriched natural gas source using the cryogenic process according to the invention are shown in tables 1 and 2, as shown in figures 2 and 3.

Fig. 1 schematically illustrates a cryogenic process according to the invention. The dashed lines illustrate optional further processing steps. The following reference numerals and abbreviations are used:

the process comprises the following steps:

1. pipeline into pre-purification unit R

2. Line from the prepurification unit into the heat exchanger E1

3. Line from heat exchanger E1 into separation column T1

4. Pipeline from top of separation column T1 into heat exchanger E1

5. Line from heat exchanger E1 into separation column T2

6. Pipeline from bottom of separation column T1 into heat exchanger E1

7. Pipeline from bottom of separation column T2 into heat exchanger E1

8. From the bottom of the separation column T2 into the heat exchanger E1 and then into the line of the storage tank S

9. Pipeline from top of separation column T2 into heat exchanger E1

10. Line from heat exchanger E1 into separation column T3

11. Pipeline from top of separation column T3 into heat exchanger E1

12. Pipeline from bottom of separation column T3 into heat exchanger E1

13. Line from line 11 into separation column T5

14. Direction of the pipeline 12 through E1

15. Pipeline for converting No. 14 pipeline into CO

16. A pipeline passing through the heat exchanger E1 from the bottom of the separation tower T1 to enter the separation tower T4

Cooling circuit:

21. line from heat exchanger E1 to recycle compressor

22. Pipeline from recycle compressor to heat exchanger E1

23. Pipeline from heat exchanger E1 to expander X1

24. Pipeline from expander X1 to heat exchanger E1

25. Pipeline from heat exchanger E1 to expander X2

26. Pipeline from expander X2 to heat exchanger E1

27. Line for low pressure refrigerant flow from line 12 to heat exchanger E1

Other:

r pre-purification

S storage tank

E1 Heat exchanger

T1 separation column 1

T2 separation tower 2

T3 separation tower 3

T4 separation column 4

T5 separation column 5

Compressor of Xi-Ci expander

a-h pressure reducing valve

B1-equilibrium Point

B8

R pre-purification

S storage tank

LNG liquefied natural gas

LPG liquefied petroleum gas

H ₂ Liquid hydrogen

C1 Methane

C2 Ethane (ethane)

HD high voltage

LIN liquid nitrogen

In the following, the cryogenic process for recovering hydrogen, hydrocarbons containing more than two hydrocarbons, methane and nitrogen from hydrogen-rich natural gas is explained in more detail in fig. 1.

The cryogenic process is carried out by means of a rectifying column. If desired, a feed fraction comprising at least methane, nitrogen and hydrogen is fed to the pre-purification unit R via line 1. At low feed pressure, the feed fraction is precompressed to a pressure of between 20 and 50 bar, if desired. Furthermore, if water, carbon dioxide and mercury compounds, in particular mercury, are present, carbon dioxide and mercury removal and drying are generally carried out. If a sulfur component is present, it can also be removed by means of a pre-purification.

The feed fraction, which may have been pretreated in this way, is then fed via line 2 to heat exchanger E1, where the feed fraction is cooled and partially condensed. The heat exchanger E1 is typically designed as a plate-fin heat exchanger or a spiral wound heat exchanger. In case of a suitably large capacity, several heat exchangers arranged in parallel and/or in series may be provided, if desired. The cooling and liquefaction of the feed fraction is carried out in at least one refrigeration cycle of any design, which is schematically shown in the figures only by means of pipe sections 21 to 27, which will be discussed in more detail below. The refrigeration cycle is preferably designed as an expander or a mixed refrigerant cycle.

The cooled and possibly partially condensed feed fraction is fed via line 3 to a rectification column T1 (ethane separation column) (an expansion valve a may be located in this line 3) and separated in this column into liquid and gaseous fractions.

If the hydrogen-rich feed gas, in particular the hydrogen-rich natural gas (B1), comprises heavy hydrocarbons, these heavy hydrocarbons may be fed to the heat exchanger E1 via line 6 together with the ethane-rich bottom product from the rectification column T1, heated and fed to the rectification column T4 (propane separation column) via line 16 in which a pressure reducing valve may be provided, and separated into ethane product as top product of the rectification column T4 (B3) and LPG (B2) as bottom product of the rectification column T4. Alternatively, line 6 may bypass heat exchanger E1 and be directly connected to line 16.

It is also possible to bypass the heat exchanger E1 and feed part of the feed fraction as stripping gas directly to the rectification column T1 in order to at least partially depressurize the reboiler.

At the top of the rectification column T1 methane and nitrogen and lighter components, in particular a hydrogen-containing fraction, are withdrawn via line 4. This fraction is further cooled in heat exchanger E1 by a refrigerant and is then fed via line 5 to rectifying column T2 (methane separation column) (expansion valve b may be located in line 5) and separated therein into liquid and gaseous fractions.

A methane-rich liquid fraction, typically having a nitrogen content of less than 3% by volume, is withdrawn from the bottom of rectifying column T2 via line 7, heated in heat exchanger E1 and used further as methane product (B4). Alternatively, the methane-rich liquid fraction may be subcooled in E1 by the refrigerant or refrigerant mixture of the refrigeration cycle and sent as LNG product in valve f to storage tank S via line 8.

Tank return gas from storage tank S may be compressed in one or more stages and vented at the factory boundary, if necessary. Alternatively, tank return gas may be fed into the fuel gas system.

At the top of the rectification column T2, nitrogen and lighter components, in particular a hydrogen-containing fraction, are withdrawn via line 9. This fraction is further cooled in heat exchanger E1 by a refrigerant and is then fed via line 10 to a rectification column T3 (nitrogen separation column) (an expansion valve c may be located in this line 10) and separated in this column into liquid and gaseous fractions.

The nitrogen-rich bottoms product of T3 can be heated in E1 via line 12 and then passed to line 14 for reuse as nitrogen product (B5), or at least a portion of the stream from line 12 can be expanded in throttle valve h to the pressure of the refrigeration cycle and used therein as a refrigerant or at least as part of a refrigerant.

The nitrogen-rich bottoms product of T3 may also be fed via line 12 to a hydrogen liquefaction plant and a helium liquefaction plant where it is expanded and used as a refrigerant.

The hydrogen-rich overhead of T3 is fed via line 11 to heat exchanger E1 where it is heated and can be further used as hydrogen product (B6). The hydrogen product may be compressed and fed to a pipeline or may be fed to standard hydrogen liquefaction equipment after compression.

If the hydrogen-rich overhead of T3 contains a rare gas such as helium, the overhead of T3, after further cooling, may be fed via line 13, possibly via expansion valve d, to another separation column T5 (hydrogen separation column), or to one or more separators, to separate the helium and any other inert gases present from the hydrogen. The top product of T5 may then be fed to an inert gas liquefaction plant (B8), preferably a helium liquefaction plant, and the bottom product of T5 may be further processed to liquid hydrogen (B7). These liquid products are then stored in vacuum insulated dedicated tanks.

According to the invention, the process is supplied with cold by means of a refrigerant or refrigerant mixture and by heating the product in E1. An example of a nitrogen expander cycle is shown; alternatively, a nitrogen-methane expander cycle or a mixed refrigerant cycle may also be optimal. Several identical or different refrigeration cycles may also be applied.

At the warm end of E1, the low pressure refrigerant stream is fed through line 21 to single or multi-stage cycle compression, with the final pressure of the expander cycle set by the compressor coupled to the expander. The high pressure recycle stream, cooled with air or water, is then pre-cooled in E1 via line 22. At a certain temperature set by the process optimisation, part of the stream (line 23) is withdrawn and expanded in expander X1 to provide cooling in E1 (24). The high pressure main stream is further cooled in E1 (25), finally expanded in X2 (26), heated in E1, mixed with the stream to X1, further heated in E1 and fed to the loop compressor 21. The refrigerant component nitrogen may preferably be added in the cold portion of cycle 27, but may also be added after heating the HP nitrogen (B5).

Instead of a pure nitrogen expander cycle, a nitrogen-methane expander cycle may be used, whereby the methane portion of the refrigerant is preferably obtained from the bottom product of methane product (B4) or T2. In this cycle, the second expansion compressor X2-C2 is possibly omitted and replaced by a throttle valve g.

The heat exchanger providing the top refrigeration for each rectification column (T1, T2, T3, T4) can be designed as a plate-fin heat exchanger, a coil heat exchanger or a TEMA heat exchanger and is arranged inside or above each rectification column, whereby the arrangement above the rectification column makes the reflux pump unsuitable. By varying the height of the column and the cold supply, the impurities of the respective overhead product can be kept within a relatively narrow range, for example the methane content in the fraction extracted via line 9 can be set almost arbitrarily, i.e. between about 1ppm and a few vol%, preferably less than 2 vol%, particularly preferably less than 1 vol%.

The process according to the invention for recovering valuable components from a hydrogen-rich feed gas, in particular a hydrogen-rich natural gas, can advantageously be used at a hydrogen content of more than 50% by volume. As long as the hydrogen product and methane product are not liquefied, even though the nitrogen and methane content in the feed fraction is relatively high, the total energy requirement of the process of the invention is only a minor effect, since part of the cold is recovered by heating the hydrogen, nitrogen and methane products in E1.

Claim (modification according to treaty 19)

1. A cryogenic process for recovering valuable components, particularly hydrogen, from hydrogen-enriched natural gas, the process comprising the steps of:

a) Separating out hydrocarbons containing more than two carbon atoms in a first rectifying tower (T1),

b) Separating methane in a second rectification column (T2), and

c) Nitrogen is separated in a third rectifying column (T3),

wherein, according to steps a) to c), the hydrogen-rich natural gas is fed to the rectification columns T1 to T3 after the optional pre-purification R and is separated in the rectification columns into a liquid fraction, i.e. a bottom product, and a gas fraction, i.e. an overhead product.

2. The method according to claim 1, characterized in that the hydrogen-rich natural gas in the rectification column is cooled and at least partially liquefied with a refrigerant or a refrigerant mixture in at least one heat exchanger (E1).

3. The method according to any of the preceding claims, characterized in that the natural gas has a hydrogen content of between 50-99.9 vol.%, a methane content of between 0.02-40 vol.% and a nitrogen content of between 0.02-30 vol.%.

4. The method according to any of the preceding claims, characterized in that the methane-rich bottom product of the rectification column T2 is recovered as methane product (B4) or is further cooled by a heat exchanger (E1) and recovered as LNG.

5. A method according to any of the preceding claims, characterized in that the nitrogen-rich bottom product from the rectification column T3 is expanded and fed into the refrigeration cycle as refrigerant or as a component of refrigerant.

6. The process according to any of the preceding claims, characterized in that after optional pre-purification R (B1) part of the hydrogen-rich feed gas stream is fed to the lower part of the rectification column T1 and/or part of the overhead product of the rectification column T1 is fed to the lower part of the rectification column T2 and/or part of the overhead product of the rectification column T2 is fed to the lower part of the rectification column T3.

7. A method according to any of the preceding claims, characterized in that helium possibly contained in the hydrogen-rich top product of the rectification column T3 is separated into two components, helium and hydrogen, by rectification or by at least one stage of depressurization after further cooling in the hydrogen rectification column (T5), the remaining impurities are removed separately in a cryogenic standard liquefaction plant, and at least the helium product is liquefied and then helium and hydrogen are stored separately.

8. The process according to any of the preceding claims, characterized in that the hydrogen-rich overhead product from rectifying column T3 is heated in E1 (B6) and residual impurities are removed in standard hydrogen liquefaction equipment, then liquefied and stored.

9. The process according to any of the preceding claims, characterized in that the top product hydrogen of the rectification column T3,

a) Optionally heated and compressed, is fed to a conduit, the top product hydrogen of the rectification column T3 comprises any inert gas components which may be present, or

b) Purifying by adsorption in a special device, and liquefying and storing; in particular, for this purpose, the stream of the rectification column T3 obtained from the bottom product can be depressurized and used as the first refrigerant stage for the liquefaction of the hydrogen.

10. The method according to any of the preceding claims, characterized in that carbon monoxide enriched in the nitrogen-rich bottom product of rectifying column T3 is removed in a further process unit, preferably at the hot end of the process, or converted into carbon dioxide.

11. The method according to any of the preceding claims, characterized in that the methane-rich bottom product of the rectification column T2, the hydrogen-rich top product and the nitrogen-rich bottom product of the rectification column T3 and the ethane-rich top product of the rectification column T4 can be adjusted in purity as valuable products to LPG product (B2) or ethane product (B3) or methane product (B4) or nitrogen product (B5) or hydrogen product (B6) depending on the cold supply in E1.

12. The method according to any of the preceding claims, characterized in that the condenser of the rectification columns T1 to T4 and the reboiler of the rectification columns T1 to T3 are connected to E1 or integrated in E1.

13. Method according to any of the preceding claims, characterized in that the heat exchanger unit E1 is designed as at least one multi-flow plate-fin heat exchanger and/or at least one spiral wound heat exchanger.

14. A method according to any of the preceding claims, characterized in that the cold supply is provided to the separation process of the rectification columns T1 to T4 by

a) By a nitrogen expander cycle with at least one expander compressor (Xi-Ci) which serves as the final stage of the cycle compression, or

b) By performing an expander refrigeration cycle with components of nitrogen and methane in analogy to a), the expander compressor X2-C2 can also be replaced by a Joule-Thomson expansion valve, or

c) By circulation of a mixed refrigerant composed of at least two components selected from the group consisting of nitrogen, methane, ethane, propane, isobutane, n-butane, isopentane, n-pentane, hexane and heptane, or

d) According to process optimisation, a minimum effective performance loss is achieved by arranging selected refrigeration cycles of the selected refrigeration cycles a) to c) in series.

Claims

1. A cryogenic process for recovering valuable components, in particular hydrogen, from a hydrogen-rich feed gas, in particular from a hydrogen-rich natural gas, comprising the steps of:

a) Separating hydrocarbons containing more than two carbon atoms in a first separation column (T1),

b) Separating methane in a second separation column (T2), and

c) Nitrogen is separated in a third separation column (T3),

wherein, according to steps a) to c), the hydrogen-rich feed gas is fed to the separation columns T1 to T3 after the optional pre-purification R and separated in the separation columns into a liquid fraction, i.e. a bottom product, and a gas fraction, i.e. an overhead product.

2. The method according to claim 1, characterized in that the hydrogen-rich feed gas in the separation column is cooled and at least partially liquefied with a refrigerant or a refrigerant mixture in at least one heat exchanger (E1).

3. The method according to any of the preceding claims, wherein the feed gas has a hydrogen content of between 50-99.9 vol%, a methane content of between 0.02-40 vol% and a nitrogen content of between 0.02-30 vol%.

4. The method according to any of the preceding claims, characterized in that the methane-rich bottom product of the separation column T2 is recovered as methane product (B4) or is further cooled by a heat exchanger (E1) and recovered as LNG.

5. A method according to any of the preceding claims, characterized in that the nitrogen-rich bottom product from the separation column T3 is expanded and fed to the refrigeration cycle as refrigerant or as a component of refrigerant.

6. The process according to any of the preceding claims, characterized in that after optional pre-purification R (B1) part of the hydrogen-rich feed gas stream is fed to the lower part of the separation column T1 and/or part of the overhead product stream of the separation column T1 is fed to the lower part of the column T2 and/or part of the overhead product stream of the separation column T2 is fed to the lower part of the separation column T3.

7. A method according to any of the preceding claims, characterized in that helium possibly contained in the hydrogen-rich top product of the separation column T3 is separated into two components, helium and hydrogen, by rectification or by at least one stage of depressurization after further cooling in the hydrogen separation column (T5), the remaining impurities are removed separately in a cryogenic standard liquefaction plant, and at least the helium product is liquefied, and helium and hydrogen are then stored separately.

8. The process according to any of the preceding claims, characterized in that the hydrogen-rich overhead product from separation column T3 is heated in E1 (B6) and residual impurities are removed in standard hydrogen liquefaction equipment, then liquefied and stored.

9. The process according to any of the preceding claims, characterized in that the top product hydrogen of the separation column T3,

a) Optionally heated and compressed, is fed into a pipeline, the top product hydrogen of the separation column T3 comprises any inert gas components which may be present, or

b) Purifying by adsorption in a special device, and liquefying and storing; in particular, for this purpose, the stream of the separation column T3 obtained from the bottom product can be depressurized and used as the first refrigerant stage for the liquefaction of the hydrogen.

10. A method according to any of the preceding claims, characterized in that carbon monoxide enriched in the nitrogen-rich bottom product of separation column T3 is removed in a further process unit, preferably at the hot end of the process, or converted into carbon dioxide.

11. The method according to any of the preceding claims, characterized in that the methane-rich bottom product of the separation column T2, the hydrogen-rich top product and the nitrogen-rich bottom product of the separation column T3 and the ethane-rich top product of the separation column T4 can be adjusted as valuable products to LPG product (B2) or ethane product (B3) or methane product (B4) or nitrogen product (B5) or hydrogen product (B6) in terms of purity depending on the cold supply in E1.

12. The method according to any of the preceding claims, characterized in that the condenser of the separation columns T1 to T4 and the reboiler of the separation columns T1 to T3 are connected to E1 or integrated in E1.

14. A method according to any of the preceding claims, characterized in that the cold supply is provided to the separation process of the separation columns T1 to T4 by