Method and device for heating cryogenic hydrogen

Abstract

The invention relates to a method for heating cryogenic hydrogen which, in a liquid, supercritical or cold gaseous state, is brought into thermal contact with a heat transfer medium in a first heat exchanger. In said method, the hydrogen, after passing through the first heat exchanger, is used at least in part in a preheater connected upstream of the first heat exchanger to preheat the hydrogen supplied to the first heat exchanger. The mass flow of the hydrogen returned to the second heat exchanger is controlled in such a way that the heat transfer medium leaves the first heat exchanger in the liquid state and preferably with a viscosity below a predetermined limit value. The heat exchanger medium is used in a second heat exchanger to cool a medium, for example to liquefy a gas such as oxygen or nitrogen.

Description

[0001] MG 24331 17.09.2024

[0002] 1

[0003] Method and apparatus for heating cryogenic hydrogen

[0004] The invention relates to a method and a device for heating hydrogen.

[0005] Hydrogen is typically stored in well-insulated thermal storage containers at atmospheric pressure and a temperature of approximately 20 K (-253°C), the standard boiling point measured at 1013 mbar, or it is stored in pressure tanks at somewhat higher pressures and temperatures. Since hydrogen is mostly used in its gaseous state, it must be heated to a desired temperature, often close to ambient temperature (293 K). The coldness of the hydrogen is often wasted in the process.

[0006] To utilize at least some of the coldness of hydrogen, EP 4 343 247 A1 proposes transferring it to a medium to be cooled, such as an air stream, via a heat exchanger. This air stream is then separated into its components using a cryogenic gas separation process. To prevent air components from freezing during thermal contact with the cold hydrogen, heat transfer is achieved using a heat transfer medium, such as neon, circulated in a cooling circuit. However, during operation of this arrangement, there is a risk that the high viscosity of the heat transfer medium at such low temperatures will increase the pressure drop in the cooling circuit, significantly reducing the efficiency of the process. In the worst-case scenario, there is a risk that the heat transfer medium will freeze and block the cooling circuit.

[0007] The object of the present invention is therefore to provide a method for heating hydrogen present at low temperatures, which efficiently utilizes its coldness and reduces the risk of impairment of the cooling circuit by an excessively cooled heat transfer medium.

[0008] This problem is solved by a method with the features of claim 1 and by a device with the features of MG 24331 17.09.2024

[0009] 2

[0010] Claim 9. Advantageous embodiments of the invention are specified in the dependent claims.

[0011] Starting from a method for heating hydrogen, in which hydrogen in a liquid, cold gaseous or supercritical state is supplied from a hydrogen source, for example a storage tank or a pipeline, to a first heat exchanger and is brought into thermal contact at a heat exchanger surface of the first heat exchanger with a heat transfer medium circulating in a cooling circuit, thereby absorbing heat from the heat transfer medium, and the heat transfer medium is supplied to a second heat exchanger in which it is brought into thermal contact with a medium to be cooled and thereby absorbs heat from it, the invention provides that at least a partial flow of the hydrogen is returned after passing through the first heat exchanger, brought into indirect thermal contact with the hydrogen supplied to the first heat exchanger at a preheating exchanger and then supplied again to the first heat exchanger.

[0012] According to the invention, the hydrogen, which is present in the hydrogen source at a temperature of, for example, 20 K, absorbs heat from the heat transfer medium in the first heat exchanger, causing the latter to cool down. To prevent the heat transfer medium from cooling down to such an extent that its viscosity reduces the efficiency of the heat transfer or that it freezes in the cooling circuit, the hydrogen passing through the first heat exchanger is heated before thermal contact with the heat transfer medium. The hydrogen is heated by recirculating at least a portion of the hydrogen downstream of the first heat exchanger and bringing it into indirect thermal contact with the original hydrogen supplied upstream from the hydrogen source. This hydrogen evaporates if it is below its critical pressure (13 bar); above its critical point, it heats up without a phase change.The recycled hydrogen then passes through the first heat exchanger again, parallel to the originally supplied hydrogen. The temperature difference between the heat transfer medium and the hydrogen at the first heat exchanger is therefore significantly lower than without the MG 24331 17.09.2024.

[0013] 3

[0014] The use of the preheating exchanger significantly reduces the risk of the heat transfer medium freezing in the circuit.

[0015] To counteract the risk of excessively increasing viscosity of the heat transfer medium, particularly in the case of irregular heat input at the second heat exchanger, the flow rate of the recirculated partial flow is preferably controlled as a function of a measured parameter, which is preferably recorded continuously or at regular intervals in the cooling circuit. This parameter could be, for example, the viscosity or the temperature of the heat transfer medium.

[0016] The hydrogen heated in the first heat exchanger is used for a further purpose, for example, fed into a gas network or supplied to a reactor, a combustion chamber, or a fuel cell. Particularly high efficiency of the process according to the invention can be achieved if hydrogen from the hydrogen source passes through the preheating exchanger and the first heat exchanger in several successive loops. In this case, at least a partial flow of the hydrogen extracted from the hydrogen source passes through the preheating exchanger and then the first heat exchanger a total of n times in succession, where n is a natural number greater than 1, preferably greater than 2.

[0017] The liquid and / or gaseous heat transfer medium can be conveyed in the cooling circuit either by means of a conveying device, for example a pump (in the case of a liquid) or a blower or compressor (in the case of a gas).

[0018] In a preferred embodiment of the invention, the heat transfer medium is guided within a temperature and pressure range such that it evaporates in the second heat exchanger and condenses in the first. Alternatively, the two heat exchangers can be connected in the manner of a heat pipe, arranged such that the heat exchangers condense in the first heat exchanger and flow into the second heat exchanger. MG 24331 17.09.2024

[0019] 4. Due to the effect of gravity, the fluid flows downwards, while at the same time the heat transfer medium evaporating in the second heat exchanger rises into the first heat exchanger. A conveying device is therefore unnecessary.

[0020] In an alternative configuration, the heat transfer medium is circulated within a temperature and pressure range such that it remains in a liquid state throughout the cooling circuit. In the first heat exchanger, it is cooled to near its freezing point, and in the second heat exchanger, it is heated to near its boiling point.

[0021] The medium to be cooled in the second heat exchanger can be a gas, a liquid, or a solid; in particular, the coldness of the hydrogen can also be used to condense or freeze a medium. In a preferred application of the present invention, the heat transfer medium cooled by the hydrogen is used in the second heat exchanger to liquefy atmospheric gases, especially nitrogen, oxygen, or argon. For this purpose, it is only necessary that the heat transfer medium in the second heat exchanger is at a temperature lower than the condensation temperature of the corresponding gas, but higher than its own freezing point at the corresponding pressure in the cooling circuit.

[0022] Another advantageous embodiment of the invention provides that, after passing through the first heat exchanger (possibly for the last time), the hydrogen is used in a reaction that generates waste heat, and at least some of the waste heat generated in this reaction is used in the second heat exchanger to heat the heat transfer medium. The heated heat transfer medium, in turn, heats the hydrogen in the first heat exchanger, thus preheating it for the reaction that generates the waste heat, thereby improving its energy efficiency.

[0023] Nitrogen or a noble gas, such as neon or argon, is preferably used as the heat transfer medium. Oxygen would also be technically feasible, but requires stricter safety measures. MG 24331 17.09.2024

[0024] 5

[0025] Furthermore, within the scope of the invention it is also possible to divide the function of the first or the second heat exchanger between two or more devices connected in series or parallel.

[0026] The object of the invention is also solved by a device with the features of claim 9.

[0027] A device for heating hydrogen comprises a first and a second heat exchanger. The first heat exchanger is connected via a chilled hydrogen supply line to a hydrogen source of cryogenically liquefied, cold gaseous, or supercritical hydrogen, such as a storage tank or pipeline. It also includes a supply and return line for a heat transfer medium, a hydrogen outlet flowing in conjunction with the chilled hydrogen line, and a heat exchange surface for the indirect thermal contact of the hydrogen supplied via the chilled hydrogen line with the heat transfer medium supplied via the supply line. The second heat exchanger is integrated with the first heat exchanger in a cooling circuit for the heat transfer medium.The second heat exchanger has an inlet and outlet for the heat transfer medium, both connected to the outlet of the first heat exchanger, as well as an outlet for the medium to be cooled, a supply line and an outlet line for the medium to be cooled, and a heat exchange surface for indirect thermal contact between the heat transfer medium and the medium to be cooled. If necessary, the cooling circuit includes means for circulating the heat transfer medium, such as a pump, compressor, or blower.

[0028] Furthermore, in the device according to the invention, downstream of the first heat exchanger (viewed in the direction of hydrogen flow), a return line branches off from the hydrogen outlet of the first heat exchanger for the return of at least a partial flow of the hydrogen that has passed through the first heat exchanger. A preheating exchanger (here also referred to as a "thermocontroller") is located in the return line for transferring thermal energy from the returned hydrogen. MG 24331 17.09.2024

[0029] 6

[0030] A partial flow of hydrogen is provided to the hydrogen supplied via the chilled hydrogen inlet. In the preheating exchanger, the hydrogen from the hydrogen source is heated before being fed to the first heat exchanger, thereby reducing the risk of the heat transfer medium in the first heat exchanger cooling down too much. The hydrogen from the return line, heated in the thermocontroller, is fed back to the first heat exchanger via a second hydrogen inlet line, which is flow-connected to the return line. There, it is brought into indirect thermal contact with the heat transfer medium before being discharged via a second hydrogen outlet of the first heat exchanger.

[0031] Preferably, a control device is provided by means of which the flow rate of the hydrogen partial flow routed via the return line is regulated. The regulation is carried out according to a predefined program and / or depending on a measured parameter, such as the viscosity or temperature of the heat transfer medium in the cooling circuit or the temperature of the heated hydrogen. A further, possibly additional, control option for the heat transfer from the first to the second heat exchanger consists of controlling the flow rate of the heat transfer medium in the cooling circuit.

[0032] A particularly advantageous embodiment of the device according to the invention provides that the preheating exchanger – including the cold hydrogen inlet and the first hydrogen outlet – has a number n hydrogen inlets, hydrogen outlets, and heat exchanger surfaces, and the first heat exchanger has the same number n hydrogen inlets, hydrogen outlets, and heat exchanger surfaces, wherein the (n-1)th hydrogen outlet of the first heat exchanger is connected to the nth hydrogen inlet of the preheating exchanger, and the nth hydrogen outlet of the preheating exchanger is connected to the nth hydrogen inlet of the first heat exchanger. The number n is a natural number greater than 1, preferably greater than 2.In this configuration, the hydrogen is therefore repeatedly passed through the preheating exchanger and the first heat exchanger in at least a partial flow in several, for example two, three or four loops, and contributes to the heating of the MG 24331 17.09.2024 in each loop.

[0033] 7

[0034] The hydrogen source is used to cool the cold hydrogen or to cool the heat transfer medium. After passing through the last loop, the hydrogen is discharged via an nth hydrogen outlet of the first heat exchanger and used for another purpose.

[0035] The second heat exchanger can be used to cool different media. In a first advantageous embodiment of the invention, it is integrated into a gas liquefaction device. In this case, the hydrogen cooling transferred to the second heat exchanger serves to liquefy gases, for example, atmospheric gases such as oxygen or nitrogen. In another advantageous embodiment, the second heat exchanger is integrated into a device for utilizing the heat generated during a hydrogen reaction, which originates in a reaction chamber, for example, during a chemical reaction or in a fuel cell. The hydrogen heated in the first heat exchanger is thus used in a subsequent exothermic reaction, and the heat generated in this process is used in the second heat exchanger to preheat the hydrogen and, if necessary, to improve the efficiency of the reaction.

[0036] An embodiment of the invention will be explained in more detail with reference to the drawing. The single drawing (Fig. 1) schematically shows a flow diagram of a device according to the invention.

[0037] In the device 1 shown in Fig. 1, a chilled hydrogen supply line 3 with an integrated pump 4 leads from a hydrogen source, for example, a thermally well-insulated storage tank 2 for liquid, cryogenic gaseous, or supercritical hydrogen, to a first heat exchanger 5. A first hydrogen outlet 6a leads from this heat exchanger to remove the hydrogen that has been heated and / or vaporized in the heat exchanger 5. The heated hydrogen from the first heat exchanger 5 can then be fed into a gas network or supplied to a consumer, for example, a reaction chamber 8.

[0038] The first heat exchanger 5 is also equipped with inlet and outlet lines 9, 10 for a heat transfer medium. The heat transfer medium is MG 24331 17.09.2024

[0039] 8 is fed via a supply line 9 to the first heat exchanger 5, where it is liquefied with the hydrogen in indirect heat exchange and discharged via the outlet 10. The supply line 9 and the outlet 10 are connected via a return line 11, thus forming a cooling circuit 12 for the heat transfer medium.

[0040] A second heat exchanger 13 for cooling a medium is integrated into the cooling circuit 12. The medium to be cooled can be gaseous, liquid, or solid. The second heat exchanger 13 has a supply line 14 for the medium to be cooled, an outlet line 15 for discharging the medium cooled in the second heat exchanger 13, and a heat exchange surface 16 for indirect heat exchange.

[0041] In the embodiment shown here, a conveying device 17, for example a pump or a compressor, is used to circulate the heat transfer medium in the cooling circuit 12. Heat transfer medium can be drawn from or supplied to the cooling circuit as needed via a line 18. Alternatively, instead of using a cooling circuit 12 with a conveying device 17, the heat exchangers s, 13 can also be thermally connected to each other via a heat pipe or a system of heat pipes, which, however, is not shown here.

[0042] During operation of the device 1, the hydrogen in the storage tank 2 is, for example, in a cryogenically liquefied state at a temperature of 20 K. It is supplied to the first heat exchanger 5 via the chilled hydrogen line 3 by means of the pump 4. In the first heat exchanger 5, indirect contact occurs at a heat exchanger surface 19 with, for example, a gaseous heat transfer medium, such as nitrogen, supplied via the feed line 9. The hydrogen heated in this process is discharged via the first hydrogen outlet 6a.

[0043] The nitrogen, introduced here in gaseous form via the supply line 9, preferentially condenses upon thermal contact with the liquid hydrogen at the heat exchanger surface 19 and leaves the first heat exchanger 5 in liquid form. MG 24331 17.09.2024

[0044] 9 in a supercooled form, i.e., at a temperature below its boiling point at the corresponding pressure. For example, the temperature of the liquefied nitrogen in the nitrogen drain 10 is 65 K. However, the operation of the cooling circuit 12 can also be carried out in such a way that the nitrogen is cooled in the first heat exchanger 5 to near its freezing point (at the respective pressure) and heated in the second heat exchanger 13 to near its boiling point (at the respective pressure), so that it remains in a liquid state throughout the entire cooling circuit 12.

[0045] A control device 20 ensures that the nitrogen in the cooling circuit 12 neither freezes nor becomes excessively viscous. In the embodiment shown here, the control device 20 comprises a sensor arranged in the line 10, for example a temperature sensor 21, which is in data communication via a control unit 22 with a three-way valve 23 arranged in the first hydrogen outlet 6a.

[0046] At the three-way valve 23, at least a partial flow of hydrogen is diverted after passing through the first heat exchanger 5 and fed via a return line 25a to a further heat exchanger 26, referred to here as the "preheating exchanger" or "thermocontroller," which is located upstream of heat exchanger 5 in the chilled hydrogen supply line 3. In the thermocontroller 26, indirect thermal contact occurs between the hydrogen returned via return line 25a and the hydrogen supplied via the chilled hydrogen supply line 3. This heats the hydrogen, and in the section of the chilled hydrogen supply line 3 downstream of the thermocontroller 26, referred to here as hydrogen supply line 27a, the hydrogen is at a temperature at which the nitrogen in the first heat exchanger 5 has a sufficiently low viscosity.The flow rate of the hydrogen partial flow branched off at the three-way valve 23 is regulated depending on the temperature of the nitrogen in the cooling circuit 12 measured at the temperature sensor 21.

[0047] The hydrogen in the return line 25a passes through the thermocontroller 26 and then, via a hydrogen supply line 27b, again through the first heat exchanger 5 to a second hydrogen outlet 6b. It can then be transferred via an MG 24331 17.09.2024

[0048] 10

[0049] The derivative 28 can be used for a further purpose, for example fed into a gas network or fed into the reaction chamber 8, or mixed with the non-recycled partial stream from the hydrogen discharge 6a.

[0050] In an alternative embodiment, indicated here by a dashed line, at least a partial flow of hydrogen in the hydrogen outlet 6b is routed again via a return line 25b through the thermocontroller 26 and then via another hydrogen supply line 27c through the first heat exchanger 5 to a hydrogen outlet 6c. In both loops, the hydrogen routed via the respective return lines 25a, 25b and hydrogen supply lines 27b, 27c contributes to cooling the heat transfer medium in the first heat exchanger 5. It goes without saying that the recirculated partial hydrogen flow can also pass through more than the two loops shown here, for example, four loops. Finally (if only a partial flow has been diverted), the hydrogen from the hydrogen outlet 6c (or...) merges with the hydrogen in the first heat exchanger 5.the hydrogen from the last hydrogen extraction) with the remaining hydrogen in hydrogen extraction 6a or it is used for another purpose.

[0051] The cooling task to be performed by the second heat exchanger 13 can, for example, consist of inducing a phase transition in a medium to be cooled; for instance, it can be used to liquefy a gas, such as oxygen. Alternatively, the waste heat from an exothermic reaction taking place in the reaction chamber 8 can also be used to heat the heat transfer medium in the second heat exchanger 13, for example, by feeding exhaust gas from the reaction chamber 8 into the supply line 14. In this case, the reaction heat transferred to the hydrogen via the cooling circuit 12 in the first heat exchanger 5 serves to preheat the hydrogen used in the reaction chamber 8.

[0052] Upon thermal contact with the medium to be cooled at the heat exchanger surface 16, the liquid nitrogen evaporates and is transported back to the supply line 9 via the return line 11 by means of the conveying device 17. The cooled medium is transferred via MG 24331 17.09.2024

[0053] 11 the outlet pipe 15 is discharged and fed, for example, to a tank or a consumer in a manner not shown here.

[0054] Instead of a single heat exchanger 5, 13, a system consisting of a plurality of heat exchangers connected in series or in parallel can also be used, of which, for example, a first one can be used to condense the respective substance and a second one to pre-cool the substance to be liquefied.

[0055] MG 24331 17.09.2024

[0056] 12

[0057] List of reference signs

[0058] 1 Device

[0059] 2 storage tanks

[0060] 3 Cold hydrogen supply line

[0061] 4 pump

[0062] 5 heat exchangers

[0063] 6a, 6b, 6c Hydrogen detoxification

[0064] 7

[0065] 8 reaction chamber

[0066] 9 Supply line (for heat transfer medium)

[0067] 10. Drain (for heat transfer medium)

[0068] 11 Return line

[0069] 12 Cooling circuit

[0070] 13 heat exchangers

[0071] 14 Supply line

[0072] 15 Exit line

[0073] 16 heat exchanger surface area

[0074] 17 Funding institution

[0075] 18 Management

[0076] 19 heat exchanger surface area

[0077] 20 Control unit

[0078] 21 temperature sensors

[0079] 22 Control unit

[0080] 23 Three-way valve

[0081] 24 -

[0082] 25a, 25b Return line

[0083] 26 Preheating exchangers (thermocontrollers)

[0084] 27a, 27b, 27c Hydrogen supply line

[0085] 28 Derivative

Claims

MG 24331 17.09.2024 13 Patent claims 1. A method for heating hydrogen, in which hydrogen in a liquid, cold gaseous or supercritical state is extracted from a hydrogen source (2), fed to a first heat exchanger (5) and brought into thermal contact at a heat exchanger surface (19) of the first heat exchanger (5) with a heat transfer medium carried in a cooling circuit (12) and thereby absorbs heat from the heat transfer medium, and the heat transfer medium is fed to a second heat exchanger (13) in which it is brought into thermal contact with a medium to be cooled and thereby absorbs heat from it, characterized in that at least a partial flow of the hydrogen from the hydrogen source (2) is returned after passing through the first heat exchanger (5), brought into thermal contact with the hydrogen carried to the first heat exchanger (5) at a preheating exchanger (26) and then fed back to the first heat exchanger.

2. Method according to claim 1, characterized in that the flow rate of the partial flow of hydrogen recirculated after passing through the first heat exchanger (5) and / or the mass flow rate or the temperature of the heat transfer medium is controlled as a function of a temperature of the heat transfer medium or of the heated hydrogen.

3. Method according to claim 1 or 2, characterized in that at least a partial stream of the hydrogen taken from the hydrogen source (2) passes through the preheating exchanger (26) and subsequently the first heat exchanger (5) a total of n times in succession, wherein n > 2.

4. Method according to one of the preceding claims, characterized in that the heat transfer medium in the cooling circuit (12) is guided in a temperature and pressure range such that the heat transfer medium evaporates in the second heat exchanger (13) and condenses in the first heat exchanger (5). MG 24331 17.09.2024 14 5. Method according to one of claims 1 to 3, characterized in that the heat transfer medium in the cooling circuit (12) is guided in a temperature and pressure range such that the heat transfer medium remains in a liquid state throughout the entire cooling circuit (12).

6. Method according to one of the preceding claims, characterized in that a gas, for example gaseous oxygen, is used as the medium to be cooled, which is in the second heat exchanger (13) is brought into thermal contact with a heat transfer medium located at a temperature below the boiling point of the gas and is thereby liquefied.

7. Method according to one of the preceding claims, characterized in that the hydrogen is used in a reaction generating waste heat after the last passage through the first heat exchanger (5), and at least a part of the waste heat generated is used in the second heat exchanger (13) to heat the heat transfer medium.

8. Method according to one of the preceding claims, characterized in that nitrogen is used as the heat transfer medium (12) in the cooling circuit (12).

9. Device for heating hydrogen, comprising a hydrogen source (2) for cryogenically liquefied, cold gaseous or supercritical hydrogen, with a cold hydrogen supply line (3) leading from the hydrogen source (2) into a first heat exchanger (5) which has a supply line (9) and a discharge line (10) for a heat transfer medium, a first hydrogen discharge line (6a) flow-connected to the cold hydrogen supply line (3) and a heat exchanger surface (19) for indirect thermal contact of the hydrogen supplied via the hydrogen supply line (3) with the heat transfer medium supplied via the supply line (9), MG 24331 17.09.2024 15 together with the first heat exchanger (5) in a cooling circuit (12) the heat transfer medium integrated second heat exchanger (13), which has a supply line connected to the outlet (10) of the first heat exchanger (5), a discharge for the heat transfer medium connected to the supply line (9) of the first heat exchanger (5), a supply line (14) and an outlet line (15) for a medium to be cooled, and a heat exchanger surface (16) for indirect thermal contact of the heat transfer medium with the medium to be cooled, characterized in that a return line (25a) branches off from the first hydrogen outlet (6a) of the first heat exchanger (5) for returning at least a partial flow of the hydrogen passed through the first heat exchanger (5),which passes through a preheating exchanger (26) integrated upstream in the cold hydrogen supply line (3) for the indirect thermal contact of the hydrogen supplied via the hydrogen supply line (3) with the hydrogen supplied via the return line (25a) and downstream to the preheating exchanger (26) is connected by flow to a second hydrogen supply line (27b) and a second hydrogen outlet (6b, 6c) of the first heat exchanger (5).

10. Device according to one of claims 9, characterized in that the partial flow of the hydrogen returned via the return line (25a) can be controlled by means of a control device (20) depending on a parameter measured in the cooling circuit (12) of the heat transfer medium.

11. Device according to one of claims 9 or 10, characterized in that the preheating exchanger (26) is a number of n hydrogen supply lines (25a, 25b), hydrogen outlets and heat exchanger surfaces, and the first heat exchanger (5) is a number of n hydrogen supply lines (27a, 27b, 27c), wherein the (n-1)th hydrogen outlet (6a, 6b, 6c) of the first heat exchanger (5) is connected to the nth hydrogen supply line (25a, 25b) of the preheating exchanger (26), and the nth hydrogen outlet of the preheating exchanger (26) is connected to the nth hydrogen supply line (27a, 27b, 27c) of the first heat exchanger (5). MG 24331 17.09.2024 16 first heat exchanger (5) is flow-connected, where n is a natural number greater than 1.

12. Device according to one of claims 9 to 11, characterized in that the second heat exchanger (13) is integrated in a gas liquefaction device.

13. Device according to one of claims 9 to 12, characterized in that the second heat exchanger (13) is integrated into a device for cooling a reaction product formed in a reaction chamber (8) for the utilization of the hydrogen heated in the first heat exchanger (5).

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