Method and apparatus for cooling hydrogen

Abstract

The present invention relates to a method for cooling hydrogen, in which a liquefied natural gas is heated by indirect heat exchange with an intermediate fluid stream in a first heat exchanger (E1), the intermediate fluid stream is cooled, a hydrogen gas stream (23) is cooled in a second heat exchanger without condensation, a gas stream derived from the cooled intermediate fluid is heated in a second heat exchanger (E2) to a temperature between -150°C and -90°C, which gas stream leaves the second heat exchanger at said temperature and is compressed in a compressor having an inlet temperature between -150°C and -90°C.

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for cooling hydrogen. [Background technology]

[0002] It is known to optimize the process for cooling hydrogen by recovering cold energy from the vaporization of liquefied natural gas (LNG).

[0003] It is known that hydrogen can be liquefied in two steps: A first step of pre-cooling using a nitrogen cycle or a mixed refrigerant cycle, followed by A second step of liquefying the cooled hydrogen by a cycle of a mixed refrigerant containing hydrogen, helium or a noble gas. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention proposes a solution for the first step of pre-cooling the hydrogen using the cold energy of a vaporized liquefied natural gas stream.

[0005] In particular, the method uses a cycle to transfer the heat of vaporization of liquefied natural gas to cooled hydrogen, the cycle comprising a compressor having an inlet temperature preferably below -90°C and, optionally, an expansion turbine.

[0006] Kuendig et al., “Large scale hydrogen liquefaction in combination with LNG re-gasification”, 16th World Hydrogen Energy Conference 2006, describes a method as set forth in the preamble of claim 1. [Means for solving the problem]

[0007] In accordance with one aspect of the present invention, there is provided a method for cooling hydrogen, the method comprising: i) either liquefied natural gas or vaporized natural gas at a temperature below -50°C is heated to a temperature above 0°C by indirect heat exchange in a first heat exchanger with a stream of intermediate fluid at a pressure of 3 to 70 bar absolute (bar abs) if the intermediate fluid is not nitrogen and 3 to 25 bar abs if the intermediate fluid is nitrogen, which has been cooled to a temperature of -145°C or higher; ii) A flow of intermediate fluid having a temperature of at least -145°C; a) by introducing it at this temperature into a second heat exchanger where it is cooled by indirect heat exchange; and / or b) by expansion in a turbine or valve that optionally drives the compressor of the method; Cooled, iii) the gaseous hydrogen stream is cooled in a second heat exchanger without condensation; iv) a gaseous stream derived from the intermediate fluid cooled in steps a) and / or b) is heated in a second heat exchanger to a temperature between −150° C. and −90° C., withdrawn from the second heat exchanger at this temperature and compressed in a compressor having an inlet temperature between −150° C. and −90° C., at least a portion of the compressed intermediate fluid being first cooled in a first heat exchanger and then heated from a temperature of at most −110° C., v) at least a portion of the heated intermediate fluid constitutes the intermediate fluid stream of step i); characterised in that at least a portion of the compressed intermediate fluid, first cooled in the first heat exchanger, is then heated in a second heat exchanger from a temperature of at most -110°C, so as to constitute the intermediate fluid stream of step i).

[0008] According to another optional aspect of the present invention, The maximum temperature difference in the first exchanger between the countercurrent fluids is less than 25°C, preferably less than 20°C or even less than 15°C. The intermediate fluid contains more than 50 mole % nitrogen, preferably at least 90 mole % nitrogen, or even at least 99 mole % nitrogen. The liquefied natural gas is vaporized in a first heat exchanger, where it is preferably heated to a temperature above 0°C. The gaseous hydrogen stream cooled in the second heat exchanger is condensed in another heat exchanger after cooling to its liquefaction temperature. The vaporized liquefied natural gas or the natural gas heated in the first heat exchanger is sent to a conversion unit for conversion to hydrogen. During start-up, the liquefied natural gas is vaporized in a heat exchanger by heat exchange with water, e.g. sea water. A portion of the compressed intermediate fluid is first cooled in the first heat exchanger to an intermediate temperature of the first heat exchanger, for example -40°C to -90°C, preferably -45°C to -70°C, sent to cool the auxiliary heat transformer, then heated in the auxiliary heat transformer and sent to be cooled in the first heat exchanger. The auxiliary heat transformer serves to cool a gas stream containing carbon dioxide and at least one other component in an apparatus for separating and / or liquefying carbon dioxide. A portion of the compressed intermediate fluid is heated by a heating means connected in parallel with the auxiliary heat transformer. A portion of the cold produced by the liquefied or vaporized natural gas serves to cool the cooling water of the compressor of the process and / or to cool a gaseous hydrogen stream upstream of the drying step and / or the second heat exchanger. A hydrogen stream is first cooled according to the method of any one of the preceding claims and then liquefied by heat exchange via a refrigeration cycle. The hydrogen stream is cooled in a second heat exchanger by heat exchange with a stream of intermediate fluid heated upstream of the cold compression and a stream of intermediate fluid heated downstream of the cold compression. Only the liquefied natural gas and the intermediate fluid exchange heat in the first heat exchanger. Only the hydrogen stream and the intermediate fluid exchange heat in the second heat exchanger. · The approach temperature between the LNG and the intermediate fluid is less than 7°C. an intermediate fluid stream at a temperature above -145°C is cooled by introducing it at this temperature into a second heat exchanger where it is cooled by indirect heat exchange; and / or The intermediate fluid stream at a temperature above -145°C is cooled by expansion in a turbine, which optionally drives a compressor of the method, or in a valve. The intermediate fluid stream at a temperature above -145°C is cooled only by expansion in a turbine, optionally driving a compressor of the method, or in a valve.

[0009] According to another subject of the invention, there is provided an apparatus for cooling hydrogen, comprising a first heat exchanger, a second heat exchanger, a compressor, optionally a turbine, means for directing either liquefied natural gas or vaporized natural gas at a temperature below -50°C to be heated by indirect heat exchange in the first heat exchanger to a temperature above 0°C, means for directing a stream of an intermediate fluid at a pressure of between 3 and 70 bar absolute if the intermediate fluid is not nitrogen, and between 3 and 25 bar if the intermediate fluid is nitrogen, to be cooled in the first heat exchanger to a temperature of -145°C or higher, and means for directing the stream of intermediate fluid at a temperature of -145°C or higher to be cooled in the first heat exchanger a) by introducing it at this temperature into a second heat exchanger where it is cooled by indirect heat exchange; and / or b) by expansion in a turbine or valve that optionally drives the compressor of the method; means for passing the gaseous hydrogen stream to be cooled in a second heat exchanger without condensation; means for passing a gaseous stream derived from the intermediate fluid cooled in steps a) and / or b) to be heated in the second heat exchanger to a temperature of between -150°C and -90°C; means for withdrawing a gaseous stream from the second heat exchanger at this temperature; means for passing the withdrawn gaseous stream to a compressor having an inlet temperature of between -150°C and -90°C to be compressed; and means for compressing at least one of the compressed intermediate fluid. the means for directing at least a portion of the cooled intermediate fluid to the first exchanger so as to be initially cooled in the first heat exchanger, and means for directing at least a portion of the cooled intermediate fluid to the first exchanger so as to be heated from a temperature of at most -110°C, wherein at least a portion of the heated intermediate fluid constitutes the intermediate fluid stream of step i), characterized in that the means for directing at least a portion of the intermediate fluid to be heated in the second heat exchanger so as to be at least a portion of the heated intermediate fluid constitutes the intermediate fluid stream of step i).

[0010] The apparatus may comprise a phase separator for separating the fluids coming from the turbine, the gaseous stream being an overhead gas and / or vaporized liquid from the separator.

[0011] According to another subject of the invention, there is provided an apparatus for liquefying hydrogen, comprising an apparatus for cooling hydrogen as described above and means for liquefying the hydrogen cooled in the cooling apparatus.

[0012] The use of intermediate fluids allows for better control of integration by separating hydrogen and LNG networks.

[0013] Thus, the risk of leakage into H2 is reduced.

[0014] It is possible to modify the intermediate fluid cycle parameters (pressure, flow rate) to mitigate LNG fluctuations.

[0015] The vaporized LNG / cooled H2 output conditions can be precisely adjusted in an independent manner.

[0016] Via an intermediate fluid (so as to avoid transporting natural gas in / out of the LNG terminal), it is possible to make beneficial use of cold from an LNG terminal separate from the H2 liquefaction unit.

[0017] The vaporization of LNG takes place in a single exchanger, and an intermediate fluid distributes the cold to various consumers.

[0018] The intermediate cycle makes it possible to produce cryogenic fluids at lower temperatures than LNG. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a liquefaction method according to the present invention. [Diagram 2] FIG. 2 illustrates another liquefaction method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The dedicated heat exchanger E1 serves to recover cold energy from the liquefied natural gas 1 at -150°C using an intermediate fluid cooled by the liquid 1 in the exchanger E1. The exchanger E1 may be a brazed plate and fin exchanger made of stainless steel or steel. In other cases, the exchanger E1 may be a shell and tube exchanger.

[0021] Liquid 1 is heated, for example, to 15° C. and is optionally vaporized to cool fluid 5 to a temperature below −50° C., preferably below −120° C. In this example, it is cooled to −140° C.

[0022] Gas 1 enters the cold end of exchanger E1 and exits as fluid 3 at the hot end.

[0023] In this example, the fluid 5 is nitrogen. It may for example be natural gas or methane. Preferably, the fluid 5 is inert. The fluid 5 is preferably at a pressure between 3 and 70 bar absolute if the intermediate fluid is not nitrogen and between 3 and 25 bar if the intermediate fluid is nitrogen.

[0024] Nitrogen 13 leaves exchanger E2 at a temperature lower than -90°C, for example -120°C, or even -150°C to -110°C, and is compressed to about 20 bar in a compressor C, for example a centrifugal compressor. The 20 bar nitrogen is then optionally divided into two portions 15, 17, portion 17 not necessarily being present. The portion 17 may be partially cooled in exchanger E1 and is then sent to the element to be cooled 31. The heated portion 19 is thus sent to the hot end of exchanger E1. The portions 15, 21 are sent to the hot end of exchanger E1 at 20°C, where they are cooled to -140°C to form gas 5, which is sent to exchanger E2 at a temperature of -140°C, and therefore colder than the temperature at which gas 13 is taken from exchanger E2. Gas 5 is heated to 20°C in exchanger E2 and then cooled against LNG in exchanger E1. The cooling gas at -140°C is sent to be cooled, in this example, first by entering exchanger E2 and then by expansion in turbine T, which has an inlet temperature lower than -100°C, for example -120°C. The fluid 7 expanded in turbine T at 1.5 bar is two-phase and is sent to a phase separator, where it forms liquid 9 and gas 11. The liquid is vaporized in heat exchanger E3 and joins gas 11 to be heated in exchanger E2, constituting stream 13 to be sent to cold compressor C. Stream 13 may be constituted by vaporized liquid 9 and / or gas 11.

[0025] Thus, nitrogen, or another fluid such as helium or a mixed refrigerant, circulates in a closed cycle, extracting cold energy from the LNG.

[0026] Gaseous hydrogen 23 at ambient temperature, e.g. 20° C., enters the hot end of heat exchanger E2 and passes from one end to the other so as to be cooled to −180° C. It is then cooled in heat exchanger E3 against phase separator liquid to form gaseous hydrogen 25 at −190° C.

[0027] The hydrogen 25 is then cooled and liquefied in another heat exchanger in a known manner. A cycle of hydrogen, helium, or a mixed refrigerant, optionally containing a noble gas, provides the required cold energy.

[0028] Thus, the LNG provides at least a portion of the cold energy required to cool the gaseous hydrogen down to −190° C. This portion may be at least 50%, at least 75%, or at least 99% of the cold energy required to cool the gaseous hydrogen down to −190° C. The LNG may even provide all the required cold energy apart from that coming from turbine T.

[0029] During start-up of the installation, the LNG may be vaporized by heat exchange with water, optionally seawater, in a separate vaporizer, for example of the "open rack vaporizer" type. This vaporizer comprises a series of vertical tubes in which the LNG to be vaporized circulates, the water flowing over the outside of the tubes. Obviously, other types of exchangers can be envisaged.

[0030] The method may also provide cold to another element 31 cooled by the cycle. In the figure it can be seen that a part 17 of the gas compressed in compressor C is cooled in a heat exchanger to an intermediate temperature, in this case -50°C, is withdrawn from the exchanger in its central zone and serves to cool element 31 by being itself heated to form a gas 19 which joins the stream 15 compressed in compressor C to form a stream 21 which enters exchanger E1 at 20°C. As the pressure drop for streams 18, 19 is limited, a small expansion of stream 15 in the valve will be sufficient to allow the mixing of streams 15, 19.

[0031] Element 31 may for example be a liquefaction unit for another gas or a unit for separation by distillation and / or partial condensation at temperatures below 0° C., for example a carbon dioxide liquefaction unit.

[0032] When portion 17 is present but element 31 is not operational, a heater, e.g., an electric heater or a heat exchanger heated with hot water, serves to heat portion 17 so as to form stream 19.

[0033] Figure 2 shows a variant of Figure 1, in which the gas 5 is not cooled in the exchanger E2, but only in the turbine E. Thus, the gas 5 enters the turbine E at the temperature it leaves the heat exchanger E1. The gas 13 is compressed in the cold compressor 1 and then in a booster C1 coupled to the turbine E. It is the gas compressed in the booster C1 that is sent to the exchanger E1 to recover cold from the LNG 1.

[0034] The produced natural gas 3 may be sent to a hydrocarbon conversion unit for conversion and / or as fuel. The unit may be a POX, ATR or SMR type unit.

[0035] The hydrogen to be liquefied can obviously come from this unit.

Claims

1. 1. A method for cooling hydrogen, comprising the steps of: i) either liquefied natural gas (1) or vaporized natural gas at a temperature below −50° C. is heated to a temperature above 0° C. by indirect heat exchange in a first heat exchanger (E1) with a stream of intermediate fluid (5) cooled to a temperature above −145° C. and at a pressure of 3 to 70 bar absolute if the intermediate fluid is not nitrogen, or 3 to 25 bar if the intermediate fluid is nitrogen; ii) said intermediate fluid stream having a temperature of −145° C. or higher; a) by introducing it at this temperature into a second heat exchanger (E2) where it is cooled by indirect heat exchange, and / or b) by expansion in a turbine (E) or in a valve, which optionally drives the compressor (C, C1) of the method, Cooled, iii) a stream of gaseous hydrogen (23) is cooled in said second heat exchanger without condensation; iv) a gaseous stream (11, 13) derived from the intermediate fluid cooled in steps a) and / or b) is heated in the second heat exchanger (E2) to a temperature of between −150° C. and −90° C., withdrawn from the second heat exchanger at this temperature and compressed in a compressor (C) having an inlet temperature of between −150° C. and −90° C., at least a portion (15, 17) of the compressed intermediate fluid being first cooled in the first heat exchanger and then heated from a temperature of at most −110° C., v) at least a portion (15) of said heated intermediate fluid constitutes the intermediate fluid stream of step i). In the method, CHARACTERIZED IN THAT said at least a portion (15, 17) of said compressed intermediate fluid, first cooled in said first heat exchanger, is then heated in said second heat exchanger from a temperature of at most -110°C, so as to constitute said intermediate fluid stream of step i).

2. 2. The method according to claim 1, wherein the maximum temperature difference between the countercurrent fluids in the first exchanger (E1) is less than 25°C, preferably less than 20°C, or even less than 15°C.

3. 3. The method according to claim 1 or 2, wherein the intermediate fluid (5) contains more than 50 mol % nitrogen, preferably at least 90 mol % nitrogen, or even at least 99 mol % nitrogen.

4. The method according to any one of claims 1 to 3, wherein the liquefied natural gas (1) is vaporized in the first heat exchanger (E1) and preferably heated there to a temperature above 0°C.

5. 5. The method according to any one of claims 1 to 4, wherein the gaseous hydrogen stream cooled in the second heat exchanger (E2) is condensed in another heat exchanger after cooling to its liquefaction temperature.

6. 6. The method according to any one of claims 1 to 5, wherein the vaporized liquefied natural gas or the natural gas heated in the first heat exchanger (E1) is sent to a conversion unit for being converted into hydrogen.

7. A method according to any one of claims 1 to 6, wherein during start-up the liquefied natural gas (1) is vaporised in a heat exchanger by heat exchange with water, e.g. sea water.

8. The method according to any one of claims 1 to 7, wherein a portion of the compressed intermediate fluid (17) is first cooled in the first heat exchanger to an intermediate temperature of the first heat exchanger, for example to -40°C to -90°C, preferably to 45°C to -70°C, sent to cool an auxiliary heat transformer (31) and then heated in the auxiliary heat transformer before being sent to be cooled in the first heat exchanger.

9. 9. The method according to claim 8, wherein the auxiliary heat transformer (31) serves to cool a gas stream containing carbon dioxide and at least one other component in an apparatus for separating and / or liquefying carbon dioxide.

10. 10. The method according to claim 8 or 9, wherein the portion of the compressed intermediate fluid (18) is heated by heating means connected in parallel with the auxiliary heat transformer (31).

11. 11. The method according to any one of the preceding claims, wherein a part of the cold produced by the liquefied natural gas (1) or vaporized natural gas serves to cool a cooling water of a compressor of the method and / or to cool the gaseous hydrogen (23) stream upstream of a drying step and / or the second heat exchanger.

12. A method for liquefying hydrogen, wherein the hydrogen (23) stream is first cooled according to the method of any one of claims 1 to 11 and then liquefied by heat exchange via a refrigeration cycle.

13. An apparatus for cooling hydrogen, comprising a first heat exchanger (E1), a second heat exchanger (E2), a compressor (C), and optionally a turbine (E), means for directing either a liquefied natural gas (1) or a vaporized natural gas at a temperature below -50°C to a temperature above 0°C by indirect heat exchange in the first heat exchanger (E1), means for directing a stream of the intermediate fluid (5) at a pressure of 3 to 70 bar absolute if the intermediate fluid is not nitrogen, or 3 to 25 bar if the intermediate fluid is nitrogen, to be cooled in the first heat exchanger to a temperature of -145°C or higher, and means for directing the stream of the intermediate fluid at a temperature of -145°C or higher to a a) by introducing it at this temperature into said second heat exchanger (E2) where it is cooled by indirect heat exchange, and / or b) by expansion in a turbine (E) or in a valve, which optionally drives the compressor (C, C1) of the method, means for directing the cooling; means for sending a gaseous hydrogen (23) stream to be cooled in the second heat exchanger without condensation; means for sending a gaseous stream (11, 13) derived from the intermediate fluid cooled in steps a) and / or b) to be heated in the second heat exchanger (E2) to a temperature between −150° C. and −90° C.; means for withdrawing said gaseous stream from the second heat exchanger at this temperature; means for sending said withdrawn gaseous stream to said compressor (C) having an inlet temperature between −150° C. and −90° C. for compression; means for sending at least a portion (15, 17) of the compressed intermediate fluid to be initially cooled in the first heat exchanger; means for sending said at least a portion of the cooled intermediate fluid to the first exchanger for heating from a temperature of at most −110° C., wherein at least a portion (15) of the heated intermediate fluid constitutes the intermediate fluid stream of step i); In an apparatus comprising:

4. The apparatus according to claim 3, wherein the means for directing said at least a portion (15, 17) of said intermediate fluid to be heated are connected such that said at least a portion is heated in said second heat exchanger from a temperature of at most -110°C so as to constitute the flow of said intermediate fluid of step i).

14. 14. Apparatus according to claim 13, comprising a phase separator (S) for separating the fluid (7) coming from the turbine (E), said gaseous stream (13) being the overhead gas (11) from said separator and / or the vaporized liquid.

15. 15. An apparatus for liquefying hydrogen, comprising an apparatus for cooling hydrogen according to claim 13 or 14 and means for liquefying the hydrogen cooled in the cooling apparatus.

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