TW202424409A - Method and an apparatus for liquefying hydrogen - Google Patents

Abstract

The present invention relates to a method for liquefying hydrogen, wherein a gaseous hydrogen stream (A, A') is subjected to precooling in a hydrogen precooling heat exchanger arrangement (20) and thereafter to further cooling and liquefaction in a hydrogen liquefaction heat exchanger arrangement (20) operated with a hydrogen cooling cycle, wherein said precooling is performed using nitrogen streams (N1, N2, N3) heated in a hydrogen precooling heat exchanger (50) of the hydrogen precooling heat exchanger arrangement (20). Said nitrogen streams (N1, N2, N3) include a first nitrogen stream (N1) supplied to the hydrogen precooling heat exchanger (50) at the cold end with a proportion of liquid of at least 80% and at a first nitrogen pressure level of 1 to 1.5 bar absolute pressure, and a second nitrogen stream (N2) supplied to the hydrogen precooling heat exchanger (50) at an intermediate position in a subcooled and liquid state at a second nitrogen pressure level of 30 to 55 bar absolute pressure. A corresponding apparatus (100-500) is also part of the present invention.

Description

Method and apparatus for liquefying hydrogen

The present invention relates to a method and apparatus for liquefying hydrogen including a nitrogen precooling and a hydrogen cooling cycle.

Hydrogen liquefaction processes comprising nitrogen precooling and hydrogen cooling cycles are known. For example, U. Cardella et al., “Economically viable large-scale hydrogen liquefaction”, IOP Conf. Series: Materials Science and Engineering 171 (2017) 012013, shows in FIG1 a hydrogen Claude cycle in which a hydrogen precooling heat exchanger arrangement is provided. This arrangement or any modification thereof may form the basis of the present invention.

In this arrangement, the gaseous hydrogen feed is cooled in a hydrogen pre-cooling heat exchanger arrangement and thereafter further cooled and finally liquefied in a series of further heat exchangers in a hydrogen liquefaction heat exchanger arrangement (typically including iso/para conversion in a catalytic bed).

In a hydrogen cooling cycle, hydrogen is compressed at a non-extremely low temperature level to a certain pressure level (hereinafter "first pressure level") in a hydrogen compressor arrangement ("high pressure hydrogen"). A first portion of the hydrogen at the first pressure level is cooled to a certain temperature level ("first temperature level") in a hydrogen pre-cooling heat exchanger arrangement and then in a hydrogen liquefaction heat exchanger arrangement. This first portion is expanded to a second pressure level ("medium pressure hydrogen") which is lower than the first pressure level. A second portion of the hydrogen at the first pressure level is also cooled in the hydrogen pre-cooling heat exchanger arrangement and thereafter in the hydrogen liquefaction heat exchanger arrangement to a lower temperature level than the first portion ("second temperature level"). This second portion is also expanded to a pressure level below the second pressure level ("low pressure hydrogen"). Both portions are then used as coolants in the hydrogen liquefaction heat exchanger arrangement and the hydrogen pre-cooling heat exchanger arrangement and are thus heated to a non-extremely cold temperature level at which the two portions are recompressed in the hydrogen compressor arrangement to the first pressure level, closing the hydrogen cooling cycle.

The hydrogen precooling heat exchanger arrangement also operates with nitrogen which can be passed through the hydrogen precooling heat exchanger arrangement, in particular in gaseous form. Such nitrogen can also be initially provided in liquid form and then expanded to form a liquid phase and a gaseous phase thereof, the liquid phase being evaporated in a separate heat exchanger. The gaseous phase and the evaporated liquid phase can then be used for cooling. The nitrogen heated in the hydrogen precooling heat exchanger arrangement can be reliquefied in a nitrogen cooling cycle or discharged to the atmosphere.

The object of the invention is to improve the operation of a hydrogen precooling heat exchanger arrangement of the mentioned type.

In view of the above, the present invention provides a method and apparatus for liquefying hydrogen including nitrogen pre-cooling and hydrogen cooling cycles, the method and apparatus respectively comprising the features of the independent claims. Preferred embodiments are the subject matter of the claims and the following description.

In this document, terms such as "pressure level" and "temperature level" are used to express that pressure ranges rather than exact pressures can be used to implement aspects of the invention and its advantageous embodiments. Different pressure and temperature levels can be in distinct ranges or in overlapping ranges. They can also cover expected and unexpected, in particular unintentional, pressure or temperature changes, such as unavoidable pressure or temperature losses. The values of the pressure levels expressed in Palestinian units are absolute pressure values.

As used herein, the term "liquefaction" refers to the transition of a fluid from a gaseous state to a liquid state, but also refers to the transition of a fluid from a supercritical state to a liquid state. The latter is also referred to elsewhere as "pseudo-liquefaction".

According to the present invention, a method for liquefying hydrogen is provided, wherein a gaseous hydrogen stream is subjected to precooling in a hydrogen precooling heat exchanger arrangement and thereafter subjected to further cooling and liquefaction in a hydrogen liquefaction heat exchanger arrangement operated in a hydrogen cooling cycle, wherein the precooling is performed using a nitrogen stream heated in a hydrogen precooling heat exchanger of the hydrogen precooling heat exchanger arrangement. According to the invention, the nitrogen streams comprise a first nitrogen stream having a liquid proportion of at least 80%, in particular completely in the liquid state, and at a first nitrogen pressure level of 1 to 1.5 bar absolute pressure, supplied to the hydrogen pre-cooling heat exchanger at the cold end, and a second nitrogen stream at a very cold temperature and at a second nitrogen pressure level close to, at, or above its critical pressure, in particular at 30 to 55 bar absolute pressure, supplied to the hydrogen pre-cooling heat exchanger at an intermediate position.

"Cryogenic temperatures" are temperatures below 120 K. Pressures "close to" the critical pressure of nitrogen are pressures that differ from the critical pressure of nitrogen by no more than 5 bar absolute.

In an embodiment of the invention, an additional gaseous nitrogen stream of a proportion less than 30%, and in other embodiments less than 20% or 10%, of the total nitrogen mass heated in the hydrogen pre-cooling heat exchanger is heated in the hydrogen pre-cooling heat exchanger.

The specific nitrogen pre-cooling form provided herein allows for a significant improvement in the cooling efficiency in hydrogen pre-cooled heat exchangers (as, for example, demonstrated by the cooling curves). According to embodiments of the present invention, a mean logarithmic temperature difference LMTD of only about 3.5 K can be achieved. Compared to standard designs, the product of the heat exchange area A and the heat transfer coefficient U can be significantly increased, for example, by 50%.

According to an embodiment of the invention, the nitrogen flows are provided using liquefied nitrogen provided at a supercritical third nitrogen pressure level higher than the second nitrogen pressure level, wherein the liquefied nitrogen at the third nitrogen pressure is provided by cooling gaseous nitrogen at the third nitrogen pressure level. Such an embodiment allows a particularly advantageous coupling with a stand-alone nitrogen liquefaction unit (NLU), i.e. a nitrogen liquefaction unit which is not part of an air separation unit.

Such an embodiment may in particular comprise depressurizing a first portion of the liquefied nitrogen at the third nitrogen pressure level from the third pressure level to the second pressure level to form the second nitrogen stream. The nitrogen used can therefore advantageously be withdrawn directly downstream of the nitrogen liquefaction heat exchanger used for cooling gaseous nitrogen at the third nitrogen pressure level in the nitrogen liquefaction unit. Such an embodiment allows coupling the nitrogen liquefaction unit and the nitrogen pre-cooling heat exchanger without substantial modification of the latter.

A second nitrogen stream at a second nitrogen pressure level (e.g. at about 34 bar) is provided from nitrogen at a third nitrogen pressure level (e.g. at about 58 bar) and under good subcooling conditions (e.g. at about 97 K), i.e. by throttling from liquefied nitrogen at the third nitrogen pressure level to about 34 bar (where the thermodynamic losses are quite low) so that it can be fed back to the nitrogen liquefaction unit as indicated below. This embodiment may allow advantages in capital costs, while the operating costs may be similar to those of the non-inventive option as mentioned above, including the use of liquid nitrogen and bulk gaseous nitrogen cooling. This is due to the fact that the liquefied nitrogen at the third pressure level is, as mentioned, well subcooled and, therefore, the mass (and in particular volume) flow of this stream is significantly lower than that of gaseous nitrogen. This results in reduced pipe and valve diameters for both the "cold" and "warm" piping. The nitrogen pre-cooling heat exchanger can be built tighter because a significantly higher portion of the high pressure flow is therein and because the impact of pressure losses on power at high pressures is lower. The corresponding embodiments are universally applicable because the nitrogen liquefaction plant equipment used can be very close to standard operating conditions that result in an optimized Q-T diagram for the liquefaction process. In summary, if no additional liquefied nitrogen is produced or exported, embodiments of the present invention can result in a reduction of more than 20% in the nitrogen liquefaction unit, or a perceptible increase in liquid nitrogen in the commercial market with unchanged power consumption.

In such embodiments, the second portion of the liquefied nitrogen at the third pressure level can be expanded, in particular using one or more throttling valves, from the third nitrogen pressure level to a fourth nitrogen pressure level between the third nitrogen pressure level and the first nitrogen pressure level, forming a so-called throttled flow. Additional nitrogen that can also be cooled at the third pressure level, in particular together with the nitrogen liquefied at the third pressure level, but which may not or at least not be completely liquefied, can be expanded in the expansion turbine, forming a so-called throttled flow. By expanding the throttled flow, a relatively low proportion of gas (e.g. less than 20%) is formed, while by expanding the turbine flow, a large amount of liquid (e.g. about 10%) can be formed.

The second portion of the liquefied nitrogen at the third pressure level is expanded, and optionally additional nitrogen is expanded, to form a gaseous nitrogen portion and a liquid nitrogen portion, wherein the portions may initially be portions of one or more two-phase streams, wherein at least a portion of the liquid nitrogen portion is used to form the first nitrogen stream. That is, according to embodiments of the present invention, the gaseous phase and the liquid phase may be passed through the nitrogen pre-cooling heat exchanger separately or together.

The second portion of the liquefied nitrogen at the third nitrogen pressure level may be subcooled or further subcooled after expansion from the third nitrogen pressure level to the fourth nitrogen pressure level and/or the liquid nitrogen may be subcooled after the expansion. Subcooling reduces flash losses, in particular when reducing the pressure to the first pressure level. This is particularly relevant for liquid nitrogen transferred to the tank, since cold is lost to the flash gas. Subcooling may also be omitted if no larger amount of liquid nitrogen is stored at the first pressure level.

In an embodiment of the present invention, a hydrogen liquefaction section and a nitrogen supply section may be used, wherein the nitrogen supply section may include a nitrogen liquefaction heat exchanger used when providing the liquefied nitrogen at the third nitrogen pressure level, wherein the hydrogen liquefaction section includes the hydrogen pre-cooling heat exchanger, and wherein the subcooling may be performed using a subcooler disposed closer to the nitrogen liquefaction heat exchanger than to the hydrogen pre-cooling heat exchanger, and/or performed using a subcooler disposed closer to the hydrogen pre-cooling heat exchanger than to the nitrogen liquefaction heat exchanger. In the former embodiment, a subcooler already existing in a known nitrogen liquefaction unit may be used. In the latter embodiment, the subcooler can specifically pre-cool the heat exchanger with nitrogen and adapt to the need for pre-cooling.

In an embodiment of the invention, the subcooling can be performed using a subcooler integrated into the hydrogen precooling heat exchanger. This allows, for example, a particularly compact configuration that is particularly easy to accommodate in a cold box due to its advantageous dimensions.

In an embodiment of the invention, a third nitrogen stream is supplied to the hydrogen pre-cooling heat exchanger in gaseous form. This stream may be formed from nitrogen expanded from cooled but not liquefied nitrogen in an expander. Such nitrogen may be at least a portion of the gas phase formed when the second portion of liquefied nitrogen at the third pressure level is expanded as mentioned above, i.e., the throttling stream and optionally the turbine stream. A considerable amount of additional gaseous nitrogen may also be formed when the nitrogen is expanded for use in forming the first nitrogen stream. Such nitrogen may also be supplied to the nitrogen pre-cooling heat exchanger (preferably into the same channel as that used by the first nitrogen stream).

In an embodiment of the present invention, the gaseous nitrogen liquefied at the third nitrogen pressure level can be compressed to the third nitrogen pressure level using a nitrogen compressor unit and then a first compressor/expander unit and a second compressor/expander unit. Since this configuration corresponds in particular to the configuration of known nitrogen liquefaction units, the corresponding embodiments of the present invention are generally applicable to such units.

In such embodiments, the first nitrogen stream may be heated in the hydrogen pre-cooling heat exchanger and then circulated to a location upstream of the nitrogen compressor unit, and the second nitrogen stream may be heated in the hydrogen pre-cooling heat exchanger and then circulated to a location upstream of the first compressor/expander unit or between the first compressor/expander unit and the second compressor/expander unit.

In an embodiment of the present invention, the hydrogen cooling cycle may operate using hydrogen compressed to a first hydrogen pressure level in the hydrogen pre-cooling heat exchanger and then cooled in the hydrogen liquefaction heat exchanger configuration, and expanded in a first portion to a second hydrogen pressure level lower than the first hydrogen pressure level and in a second portion to a third hydrogen pressure level lower than the first hydrogen pressure level, wherein the first portion and the second portion are heated in the hydrogen liquefaction heat exchanger configuration and then in the hydrogen pre-cooling heat exchanger configuration.

An apparatus for liquefying hydrogen is also part of the invention, the apparatus comprising means adapted to subject a gaseous hydrogen stream to precooling in a hydrogen precooling heat exchanger arrangement and thereafter to further cooling and liquefaction in a hydrogen liquefaction heat exchanger arrangement operating in a hydrogen cooling cycle, and comprising means adapted to carry out the precooling using a nitrogen stream heated in a hydrogen precooling heat exchanger of the hydrogen precooling heat exchanger arrangement. The apparatus is adapted to supply a first nitrogen stream of the nitrogen streams having a liquid proportion of at least 80% and at a first nitrogen pressure level of 1 to 1.5 bar absolute pressure to the hydrogen pre-cooling heat exchanger at the cold end, and to supply a second nitrogen stream of the nitrogen streams subcooled and in a liquid state at a second nitrogen pressure level of 30 to 55 bar absolute pressure to the hydrogen pre-cooling heat exchanger at an intermediate position.

For specific further features and embodiments of such an apparatus, reference is made to the above explanations in connection with the method according to the invention and its advantageous embodiments. This applies equally to a corresponding apparatus adapted to carry out the corresponding method or one of its embodiments. Such an apparatus may in particular comprise a control unit programmed or adapted to control the apparatus accordingly.

The present invention will be further described with reference to the accompanying drawings related to preferred embodiments of the present invention.

Elements with the same or corresponding functions and/or technical implementations are indicated below with similar element symbols. Repeated explanations are omitted only for general reasons. In the following, if reference is made to a method step, a corresponding explanation is given to a technical component that is also applied to a device component for or adapted to implement such a method step, and vice versa.

Figure 1 shows a hydrogenation plant as mentioned at the outset in relation to the prior art (e.g. Cardella et al.). The plant comprises a compression arrangement 10 comprising a first compressor or compressor stage 11 (e.g. dry piston type compressor(s)) and a second compressor or compressor stage 12 (e.g. dry piston type compressor(s)) which can be bypassed by a bypass line shown as a dotted line and a valve not specifically indicated.

The apparatus further comprises a hydrogen precooling heat exchanger arrangement 20, which comprises a first hydrogen precooling heat exchanger 21, a second hydrogen precooling heat exchanger 22, and a third hydrogen precooling heat exchanger 23. The second hydrogen precooling heat exchanger 22 and the third hydrogen precooling heat exchanger 23 can also be combined to form a heat exchanger block. A common hydrogen precooling heat exchanger can also be provided which integrates the functions of the first, second, and third hydrogen precooling heat exchangers 21 to 23. Such a heat exchanger is shown in dashed lines and indicated at 50.

Furthermore, in a specific example, a hydrogen liquefaction heat exchanger arrangement 30 is provided, which comprises six hydrogen liquefaction heat exchangers 31 to 36. As indicated by the shaded area, the third hydrogen precooling heat exchanger 23 and the hydrogen liquefaction heat exchangers 31 to 36 have a catalytic bed adapted for the adjacent/counter conversion of the hydrogen feed stream A. All the heat exchangers mentioned can be integrated in a vacuum cold box as shown in dashed lines.

In the hydrogen compressor arrangement 10, hydrogen is compressed at a non-ultra-cold temperature level to a pressure level also referred to herein as "first pressure level", also referred to herein as "high pressure hydrogen", using first and second compressors or compressor stages 11, 12 to form a hydrogen stream B. A water cooler 13 may be used for aftercooling. Hydrogen stream B then passes through a hydrogen precooling heat exchanger 21 and a second hydrogen precooling heat exchanger 22 of a hydrogen precooling heat exchanger arrangement 20, and then passes through an adsorber 24 and a hydrogen liquefaction heat exchanger 31 of a hydrogen liquefaction heat exchanger arrangement 30.

Afterwards, the hydrogen stream B is split to form a partial stream C and a partial stream D. The partial stream C is expanded in the expansion turbine 41, cooled in the hydrogen liquefaction heat exchanger 33, and expanded in two further expansion turbines 42 and 43 to a pressure level lower than the first pressure level, which is referred to herein as the "second pressure level". The partial stream B is also referred to herein as "medium-pressure hydrogen". The hydrogen expanded to the second pressure level is heated in the hydrogen liquefaction heat exchangers 34 to 31 and in the hydrogen precooling heat exchanger 21, and is recompressed in the hydrogen compressor arrangement 10. The partial stream D is further cooled in the hydrogen liquefaction heat exchangers 32 to 35 and then expanded in valves not explicitly indicated to a pressure level, referred to herein as the "second pressure level", below the first pressure level, to form a gas phase and a liquid phase which are separated in the separation vessel 37. The partial stream D as a whole and comprising the gas phase and the liquid phase is also referred to herein as "low-pressure hydrogen". The liquid phase is evaporated in the hydrogen liquefaction heat exchanger 36 before being combined with the gas phase and heated in the hydrogen liquefaction heat exchangers 35 to 31 and in the hydrogen precooling heat exchanger 21. The low-pressure hydrogen D is then recompressed in the hydrogen compressor arrangement 10.

The gaseous nitrogen stream N passes through the hydrogen precooling heat exchanger 21. This gaseous nitrogen stream N is formed in the example shown using the gas phase and the liquid phase of a saturated liquid nitrogen stream L expanded via a valve not explicitly indicated in the container 25 for phase separation. The amount of the liquid portion is about 98.5% of the total amount of the expanded liquid nitrogen. The liquid phase H is withdrawn from the top of the container 25 as saturated liquid nitrogen in the second hydrogen precooling heat exchanger 22 before being combined with the gas phase H withdrawn from the top of the container 25 as saturated gaseous nitrogen to form the nitrogen stream N. As shown below, the gaseous nitrogen stream N can be reliquefied in a configuration not shown here to form the liquid nitrogen stream L.

The feed hydrogen A to be liquefied passes through the hydrogen precooling heat exchanger 21 and the third hydrogen precooling heat exchanger 23 before being purified in the adsorber arrangement 26. The purified hydrogen stream A' thus formed is then cooled in the third hydrogen precooling heat exchanger 23 and is subjected to a quasi/quasi conversion and liquefaction in the hydrogen liquefaction heat exchangers 31 to 36. The quasi/quasi conversion after purification can be carried out in the third hydrogen precooling heat exchanger, but can also be carried out in a dedicated vessel. Any heating and cooling steps required can be carried out. Auxiliary hydrogen stream X may be supplied to ejector 38 where it may flash expand between hydrogen liquefaction heat exchangers 35 and 36 where it undergoes cooling.

Liquid nitrogen N is typically supplied in a subcooled condition (at about 80 to 81 K) from a nitrogen liquefaction unit at about 5 bar absolute and throttled into vessel 25. The nitrogen is then used at a pressure level of about 1.2 bar absolute to provide the lowest possible pre-cooling temperature for the process.

Precooling with liquid nitrogen is inefficient because it provides too much refrigeration at the lowest temperature level by evaporation of the liquid. This leads to considerable temperature differences in the low-temperature areas of the heat exchanger and causes additional thermodynamic losses.

Figures 2a and 2b show details of possible improvements which do not form part of the present invention. In Figure 2a a heat exchanger 50' is shown which may be used as the heat exchanger 50 according to Figure 1. With regard to streams A to C and A', reference is made to Figure 1. An adsorber 26 or components for neighbor/counter conversion may be present but are not shown for the sake of clarity. Instead a heat exchanger 27 is shown which may represent any of these components.

In the non-inventive embodiment shown in FIG. 2 a , liquid nitrogen N evaporates at two pressure levels, namely about 1.2 bar absolute pressure after expansion into the container 25 in the form of a stream N′, and about 5 bar absolute pressure in the form of an additional stream N″. In the non-inventive embodiment shown in FIG. 2 b , nitrogen is provided in the form of a liquid nitrogen stream L1 and a gaseous nitrogen stream L2.

In FIG. 3 , an apparatus 100 for liquefying hydrogen according to an embodiment of the present invention is shown. The apparatus 100 comprises a hydrogen liquefaction section 110 and a nitrogen supply section 120. The former may be provided in a manner generally known to the skilled person, such as that shown in FIG. 1 or any modification thereof, and comprises a hydrogen pre-cooling heat exchanger arrangement of the hydrogen pre-cooling heat exchanger 50 shown therein. Again, with regard to streams A to C and A′, reference is made to FIG. 1 . An adsorber 26 or component for adjacent/opposite conversion may be present, but is not shown for the sake of clarity. Instead, a heat exchanger 27 is shown, which may represent any of these components.

The nitrogen supply section 120 includes a nitrogen liquefaction arrangement 60, which includes a nitrogen liquefaction heat exchanger 61, a nitrogen subcooler 62, a separation vessel 63, a first compressor/expander unit 64, and a second compressor/expander unit 65. The nitrogen supply section 120 further includes a nitrogen compression arrangement 70 having a first compressor or compressor section 71, also referred to as a "feed compressor," and a second compressor or compressor section 72, also referred to as a "recycle compressor." In all compression steps or units, aftercoolers, not specifically shown, may be used.

In the nitrogen supply section 120, feed or make-up nitrogen F may be provided. If applicable, the nitrogen stream N1 (see below) conveyed from the hydrogenation section 110 to the nitrogen supply section 120, the first recycle stream R1 (see below) recycled in the nitrogen supply section 120, and the feed or make-up nitrogen F are compressed in the first compressor or compressor section 71. The compressed nitrogen stream thus formed is combined with the second recycle stream R2 (see below) recycled in the nitrogen supply section 120 and is then compressed in the first and second compressor sections 71, 72 to form the high-pressure nitrogen stream P.

The high-pressure nitrogen stream P is split into partial streams P1 and P2, wherein the partial stream P1 is further compressed in the first compressor/expander unit 64, combined with the nitrogen stream N2 transferred from the hydrogen liquefaction section 110 to the nitrogen supply section 120 (see below), and then further compressed in the second compressor/expander unit 65 and partially liquefied in the nitrogen liquefaction heat exchanger 61 to form a subcooled but high-pressure liquid nitrogen stream P1L at a pressure level of about 58 bar absolute pressure and a temperature level of about 97 K. Another portion is extracted from the nitrogen liquefaction heat exchanger 61 at the intermediate extraction position as stream P1G and forms a two-phase stream, which is expanded in the first compressor/expander unit 64 into the separation vessel 63.

The partial stream N2 already mentioned above is formed from the subcooled but high-pressure liquid nitrogen stream P1L and is conveyed from the nitrogen supply section 120 to the hydrogenation section 110. The partial stream N2 is throttled in the valve 51 to a vaporization pressure level of about 34 bar absolute pressure, supplied to the hydrogenation heat exchanger 51 at an intermediate feed position, and evaporated therein to convert the partial stream N2 into a gaseous nitrogen stream at a pressure level slightly below the vaporization pressure level (e.g., at about 33.5 bar absolute pressure). The partial stream N2 can then be conveyed back to the nitrogen supply section 120, as explained above. The remaining part of the high-pressure liquid nitrogen stream P1L is expanded using a valve not explicitly indicated and forms a two-phase stream into the separation vessel 63.

The partial stream P2 is expanded in the second compressor/expander unit 65 and fed at an intermediate feed point into the nitrogen liquefaction heat exchanger 61 where it is combined with the top gas from the separation vessel 63 to form the second recycle stream R2 which is recirculated and recompressed to form the high-pressure nitrogen stream P as already explained above. In contrast to the portion which is expanded to form the first recycle stream R1, the bottom liquid from the separation vessel 63 is subcooled again in the subcooler 62. This portion is also recirculated and recompressed as explained above.

The subcooled nitrogen stream indicated as L in the previous figures is transferred from the nitrogen supply section 120 to the hydrogen liquefaction section 110 at a pressure level of about 5 bar absolute pressure and a temperature level of about 80.15 K and is expanded in a valve not specifically indicated to a pressure level of about 1.2 bar absolute pressure to form a two-phase stream to the vessel 25. The liquid from the storage tank of the vessel 25 is evaporated in the hydrogen pre-cooling heat exchanger 50 to form a nitrogen stream N1 which is transferred back to the nitrogen supply section 120 and used as explained. The top gas from the vessel 25 can also be fed to the hydrogen pre-cooling heat exchanger 50, as shown by the dotted line. Since the proportion of liquid in the two-phase stream formed by stream L can be about 0.985, the vessel 25 can be omitted and the two-phase stream can be conveyed in its entirety to the hydrogen pre-cooling heat exchanger 50. The subcooled nitrogen not conveyed from the nitrogen supply section 120 to the hydrogen liquefaction section 110 can be withdrawn from the apparatus 100 in the form of stream L2 and, for example, stored in a tank.

In Fig. 3a, a modification of the apparatus 100 as shown in Fig. 3 is shown. This modification lacks the subcooler 63, which, as mentioned above, may be the case when nitrogen as product is not conveyed to the tank. In this case, all liquid from the container 63 may be used as stream L. All embodiments described herein and further embodiments of the invention may be configured accordingly.

In Fig. 4, a device 200 for liquefying hydrogen according to an embodiment of the present invention is shown. For an explanation of the components and functions of the device 200, please refer to the above explanation.

In contrast to the apparatus 100 shown in FIG3 , the liquid nitrogen stream L is not formed from liquid nitrogen subcooled in the subcooler 62 of the nitrogen liquefaction unit 60 of the nitrogen supply section 120, but as part of the pressurized liquid nitrogen stream P1L downstream of the nitrogen liquefaction heat exchanger 61. In this connection, a subcooler 28 can be used in which this liquid nitrogen stream L is subcooled against the top gas of the vessel 25 before expansion into the vessel. As explained above, the top gas and liquid from the tank of the vessel 28 are heated in the hydrogen precooling heat exchanger 50 to form the nitrogen stream N1.

In Fig. 5, a device 300 for liquefying hydrogen according to an embodiment of the present invention is shown. For an explanation of the components and functions of the device 300, please refer to the above explanation.

As in the apparatus 200 shown in FIG4 , the liquid nitrogen stream L is not formed from liquid nitrogen subcooled in the subcooler 62 of the nitrogen liquefaction unit 60 of the nitrogen supply section 120, but as part of the pressurized liquid nitrogen stream P1L downstream of the nitrogen liquefaction heat exchanger 61. Compared to the apparatus 200 shown in FIG4 , a subcooling section 28 ′ as described above for the subcooler 28 is provided. The subcooling section 28 ′ is integrated into the hydrogen precooling heat exchanger 50 in the form of a channel.

In Fig. 6, a device 400 for liquefying hydrogen according to an embodiment of the present invention is shown. For an explanation of the components and functions of the device 400, please refer to the above explanation.

In the apparatus 400, a portion of the top gas from the separation vessel 63 is conveyed as a further nitrogen stream N3 from the nitrogen supply section 120 to the hydrogen liquefaction section 110, fed into the hydrogen pre-cooling heat exchanger 50 at an intermediate position, heated therein, and recycled to a position corresponding to the position of the stream R2.

In Fig. 7, a device 500 for liquefying hydrogen according to an embodiment of the present invention is shown. For an explanation of the components and functions of the device 500, please refer to the above explanation.

In the apparatus 500, the compressor/expander units 64 and 65 are interchanged compared to the apparatus 100 shown in FIG. 3.

It should be noted that all features previously shown for one of the embodiments in the form of apparatus 100, 200, 300, 400, and 500 may be used in any of the other embodiments, and features may be compared when applicable and if technically useful.

10: Compression configuration; Hydrogen compressor configuration 11: First compressor or compressor stage 12: Second compressor or compressor stage 13: Water cooler 20: Hydrogen precooling heat exchanger configuration 21: First hydrogen precooling heat exchanger; Hydrogen precooling heat exchanger 22: Second hydrogen precooling heat exchanger 23: Third hydrogen precooling heat exchanger 24: Adsorber 25: Container 26: Adsorber configuration; Adsorber 27: Heat exchanger 28: Subcooler 28': Subcooling section; Subcooler 30: Hydrogen liquefaction heat exchanger configuration 31: Hydrogen liquefaction heat exchanger 32: Hydrogen liquefaction heat exchanger 33: Hydrogen liquefaction heat exchanger 34: Hydrogen liquefaction heat exchanger 35: Hydrogen liquefaction heat exchanger 36: Hydrogen liquefaction heat exchanger 37: Separation vessel 38: Ejector 41: Expansion turbine 42: Expansion turbine 43: Expansion turbine 50: Heat exchanger; Hydrogen precooling heat exchanger 50': Heat exchanger 51: Valve 60: Nitrogen liquefaction configuration; Nitrogen liquefaction unit 61: Nitrogen liquefaction heat exchanger 62: Nitrogen subcooler; Subcooler 63: Separation vessel; Container 64: first compressor/expander unit; compressor/expander unit 65: second compressor/expander unit; compressor/expander unit 70: nitrogen compressor configuration; nitrogen compressor unit 71: first compressor or compressor section; first compressor section 72: second compressor or compressor section; second compressor section; nitrogen compressor unit 100: equipment 110: hydrogen liquefaction section 120: nitrogen supply section 200: equipment 300: equipment 400: equipment 500: equipment A: hydrogen feed stream; feed hydrogen; gaseous hydrogen stream A': purified hydrogen stream; gaseous hydrogen stream B: hydrogen stream; hydrogen C: partial stream; first part D: partial stream; low-pressure hydrogen; second part F: feed or make-up nitrogen H: liquid phase; gas phase L: saturated liquid nitrogen stream; liquid nitrogen stream; subcooled nitrogen stream; stream L1: liquid nitrogen stream L2: gaseous nitrogen stream; stream N: gaseous nitrogen stream; nitrogen stream; liquid nitrogen N': stream N": additional stream N1: nitrogen stream; first nitrogen stream N2: nitrogen stream; partial stream; second nitrogen stream N3: nitrogen stream; third nitrogen stream P: high-pressure nitrogen stream P1: partial stream P1G: stream P1L: subcooled but high pressure liquid nitrogen flow; high pressure liquid nitrogen flow; pressurized liquid nitrogen flow; liquefied nitrogen P2: partial flow R1: first recirculation flow R2: second recirculation flow; flow X: auxiliary hydrogen flow

[FIG. 1] schematically illustrates a hydrogen liquefaction apparatus that does not form part of the present invention. [FIG. 2a] and [FIG. 2b] schematically illustrate a hydrogen pre-cooling heat exchanger that does not form part of the present invention. [FIG. 3] to [FIG. 7], including FIG. 3a, schematically illustrate a hydrogen liquefaction apparatus and method according to an embodiment of the present invention.

25:Container

27: Heat exchanger

50: Heat exchanger; Hydrogen pre-cooling heat exchanger

51: Valve

60: Nitrogen liquefaction configuration; nitrogen liquefaction unit

61: Nitrogen liquefaction heat exchanger

62: Nitrogen subcooler; subcooler

63: Separation container; container

64: First compressor/expander unit; compressor/expander unit

65: Second compressor/expander unit; compressor/expander unit

70: Nitrogen compression configuration; nitrogen compressor unit

71: first compressor or compressor section; first compressor section

72: Second compressor or compressor section; Second compressor section; Nitrogen compressor unit

100: Equipment

110: Hydrogen liquefaction section

120: Nitrogen supply section

A: Hydrogen feed flow; feed hydrogen; gaseous hydrogen flow

A': Purified hydrogen stream; gaseous hydrogen stream

B: Hydrogen flow; hydrogen

C: Partial flow; first part

D: Partial flow; low pressure hydrogen; second part

F: Feed or replenish nitrogen

L: saturated liquid nitrogen flow; liquid nitrogen flow; subcooled nitrogen flow; flow

L2: Gaseous nitrogen flow; flow

N1: Nitrogen flow; first nitrogen flow

N2: Nitrogen flow; partial flow; second nitrogen flow

P: High pressure nitrogen flow

P1: Partial flow

P1G: Flow

P1L: subcooled but high-pressure liquid nitrogen flow; high-pressure liquid nitrogen flow; pressurized liquid nitrogen flow; liquefied nitrogen

P2: Partial flow

R1: First recirculation flow

R2: Second recirculation flow; flow

Claims (13)

A method for liquefying hydrogen, wherein a gaseous hydrogen stream (A, A') is subjected to precooling in a hydrogen precooling heat exchanger arrangement (20) and thereafter to further cooling and liquefaction in a hydrogen liquefaction heat exchanger arrangement (20) operating in a hydrogen cooling cycle, wherein the precooling is performed using nitrogen streams (N1, N2, N3) heated in a hydrogen precooling heat exchanger (50) of the hydrogen precooling heat exchanger arrangement (20), characterized in that the nitrogen streams (N1, N2, N3) comprises: a first nitrogen flow (N1) supplied to the hydrogen pre-cooling heat exchanger (50) at the cold end with a liquid ratio of at least 80% and a first nitrogen pressure level of 1 to 1.5 bar absolute pressure; and a second nitrogen flow (N2) supplied to the hydrogen pre-cooling heat exchanger (50) at an intermediate position at a second nitrogen pressure level at an extremely cold temperature and close to, at, or above its critical pressure, in particular at 30 to 55 bar absolute pressure. A method as claimed in claim 1, wherein the nitrogen streams (N1, N2) are provided using liquefied nitrogen (P1L) provided at a third nitrogen pressure level by cooling gaseous nitrogen at a supercritical third nitrogen pressure level higher than the second nitrogen pressure level. A method as claimed in claim 2, wherein a first portion of the liquefied nitrogen (P1L) at the third nitrogen pressure level is depressurized from the third pressure level to the second pressure level to form the second nitrogen flow (N2). A method as in any one of claims 2 or 3, wherein a second portion of the liquefied nitrogen (P1L) at the third pressure level is expanded from the third nitrogen pressure level to a fourth nitrogen pressure level between the third nitrogen pressure level and the first nitrogen pressure level, the fourth nitrogen pressure level forming a gaseous nitrogen portion and a liquid nitrogen portion or a two-phase flow, and wherein at least a portion of the liquid nitrogen portion or the two-phase flow is used to form the first nitrogen flow (N1). The method of claim 4, wherein the second portion of the liquefied nitrogen (P1L) at the third nitrogen pressure level is cooled before expanding from the third nitrogen pressure level to the fourth nitrogen pressure level. The method of claim 5, wherein a hydrogen liquefaction section (110) and a nitrogen supply section (120) are used, wherein the nitrogen supply section (120) includes a nitrogen liquefaction heat exchanger (61) used when providing the liquefied nitrogen (P1L) at the third nitrogen pressure level, wherein the hydrogen liquefaction section (110) includes the hydrogen pre-cooling heat exchanger (5 0), and wherein the subcooling is performed using a subcooler (62) configured to be closer to the nitrogen liquefaction heat exchanger (61) than to the hydrogen pre-cooling heat exchanger (50), and/or using a subcooler (28) configured to be closer to the hydrogen pre-cooling heat exchanger (50) than to the nitrogen liquefaction heat exchanger (61). A method as claimed in claim 5 or 6, wherein the subcooling is performed using a subcooler (28') integrated into the hydrogen pre-cooling heat exchanger (50). A method as claimed in any of the preceding claims, wherein a third nitrogen stream (N3) is supplied to the hydrogen pre-cooling heat exchanger (50) in gaseous form. A method as in any one of claims 2 to 8, wherein the gaseous nitrogen liquefied at the third nitrogen pressure level is compressed to the third nitrogen pressure level using a nitrogen compressor unit (72) and then using a first compressor/expander unit (64) and a second compressor/expander unit (65). A method as claimed in claim 9, wherein the first nitrogen flow (N1) is heated in the hydrogen pre-cooling heat exchanger (50) and then circulated to a position upstream of the nitrogen compressor unit (70), and wherein the second nitrogen flow (N2) is heated in the hydrogen pre-cooling heat exchanger (50) and then circulated to a position upstream of the second compressor/expander unit (65) or to a position between the first compressor/expander unit (64) and the second compressor/expander unit (65). A method as claimed in any of the preceding claims, wherein the hydrogen cooling cycle is operated using hydrogen (B) compressed to a first hydrogen pressure level in the hydrogen pre-cooling heat exchanger (50) and then cooled in the hydrogen liquefaction heat exchanger arrangement (20), and which is expanded in a first part (C) to a second hydrogen pressure level lower than the first hydrogen pressure level and in a second part (D) to a third hydrogen pressure level lower than the first hydrogen pressure level, wherein the first part (C) and the second part (D) are heated in the hydrogen liquefaction heat exchanger arrangement (20) and then in the hydrogen pre-cooling heat exchanger (50). A device (100 to 500) for liquefying hydrogen, comprising means adapted to subject a gaseous hydrogen stream (A, A') to precooling in a hydrogen precooling heat exchanger arrangement (20) and thereafter to further cooling and liquefaction in a hydrogen liquefaction heat exchanger arrangement (20) operating in a hydrogen cooling cycle, and comprising means adapted to perform the precooling using a nitrogen stream (N1, N2, N3) heated in a hydrogen precooling heat exchanger (50) of the hydrogen precooling heat exchanger arrangement (20), characterized in that the device (100 to 500) is adapted to subject the nitrogen streams (N1, N2, N3) to a precooling reaction at the cold end. A first nitrogen stream (N1) having a liquid proportion of at least 80% and a first nitrogen pressure level of 1 to 1.5 bar absolute pressure is supplied to the hydrogen pre-cooling heat exchanger (50), and a second nitrogen stream (N2) in a subcooled and liquid state at a second nitrogen pressure level of 30 to 50 bar absolute pressure is supplied to the hydrogen pre-cooling heat exchanger (50) at an intermediate position. An apparatus (100 to 500) as claimed in claim 12, comprising components adapted to perform a method according to any one of claims 1 to 11.