METHOD AND DEVICE FOR COOLING HYDROGEN

Description

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

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

[0003] It is known that hydrogen can be liquefied in two steps: A first pre-cooling stage using a nitrogen cycle or a mixed refrigerant cycle followed by a second stage of liquefaction of the cooled hydrogen with a hydrogen, helium or mixed refrigerant cycle including rare gases.

[0004] The present invention proposes a solution for the first stage of pre-cooling hydrogen using the cooling power of a flow of liquefied natural gas that vaporizes.

[0005] In particular, the process uses a cycle to transfer the heat of vaporization from the liquefied natural gas to the hydrogen which cools, this cycle including a compressor with an inlet temperature preferably below -90°C and possibly an expansion turbine.

[0006] "Large scale hydrogen liquefaction in combination with LNG re-gasification" by Kündig et al, 16th World Hydrogen Energy Conference, 2006 describes a process according to the preamble of claim 1.

[0007] According to one object of the invention, a hydrogen cooling process is provided according to claim 1.

[0008] According to other optional aspects of the invention: The maximum temperature difference in the first counter-current fluid heat exchanger is less than 25°C, preferably less than 20°C, or even less than 15°C. The intermediate fluid contains more than 50 mol% nitrogen, preferably at least 90 mol% nitrogen, or even at least 99 mol% nitrogen. The liquefied natural gas (LNG) vaporizes in the first heat exchanger and is preferably heated there to a temperature above 0°C. The flow of hydrogen gas cooled in the second heat exchanger condenses in another heat exchanger after being cooled to its liquefaction temperature. Vaporized LNG or natural gas heated in the first heat exchanger is sent to a conversion unit to be converted into hydrogen. For start-up, the LNG vaporizes in a heat exchanger by exchanging heat with water, for example, seawater.A portion of the compressed intermediate fluid is first cooled in the first heat exchanger to an intermediate temperature, for example, between -40°C and -90°C, preferably between -45°C and -70°C, and is then sent to cool an auxiliary heat exchanger. After being reheated in the auxiliary heat exchanger, the fluid is sent back to the first heat exchanger to be cooled. The auxiliary heat exchanger is used to cool a flow of gas containing carbon dioxide and at least one other component in a carbon dioxide separation and / or liquefaction apparatus. The portion of the compressed intermediate fluid is reheated using heating means connected in parallel with the auxiliary heat exchanger.Part of the cooling generated by liquefied natural gas or vaporized natural gas is used to cool the cooling water of a process compressor and / or to cool the flow of gaseous hydrogen upstream of a drying stage and / or the second heat exchanger. The hydrogen flow is first cooled according to a process according to one of the preceding claims and then liquefied by heat exchange with a refrigeration cycle. The hydrogen flow is cooled in the second heat exchanger by heat exchange with an intermediate fluid flow that is heated upstream of the cold compression and an intermediate fluid flow that is 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 flow and the intermediate fluid exchange heat in the second heat exchanger. The approach temperature between the liquefied natural gas and the intermediate fluid is less than 7°C. The intermediate fluid flow at a temperature equal to or greater than -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 flow at a temperature equal to or greater than -145°C is cooled by expansion in a turbine, possibly driving a process compressor, or a valve. The intermediate fluid flow at a temperature equal to or greater than -145°C is cooled solely by expansion in a turbine, possibly driving a process compressor, or a valve.

[0009] According to another object of the invention, a hydrogen cooling device is provided according to claim 13.

[0010] The apparatus may include a phase separator to separate a fluid from the turbine, the gas flow being the overhead gas and / or the vaporized liquid from the separator.

[0011] According to another object of the invention, a hydrogen liquefaction apparatus is provided, comprising a hydrogen cooling apparatus as described above, as well as means for liquefying the hydrogen cooled in the cooling apparatus.

[0012] The use of an intermediate fluid allows for better control of the integration by differentiating between the hydrogen and LNG networks.

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

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

[0015] Precise regulation of the outlet conditions of vaporized LNG / independently cooled H2 is possible.

[0016] Cold from an LNG terminal located far from the H2 liquefaction unit can be utilized via an intermediate fluid (to avoid importing / exporting natural gas from the LNG terminal).

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

[0018] The intermediate cycle makes it possible to produce a cold fluid at a lower temperature than LNG. [ Fig.1 ] illustrates a liquefaction process according to the invention. Fig.2 ] illustrates another liquefaction process according to the invention.

[0019] A dedicated heat exchanger E1 is used to recover the cooling capacity of liquefied natural gas 1 at -150°C using an intermediate fluid that is cooled by liquid 1 in the exchanger E1. The exchanger E1 can be a brazed plate and fin heat exchanger made of stainless steel or steel. Alternatively, the exchanger E1 can be a shell and tube heat exchanger.

[0020] Liquid 1 is heated, for example to 15°C and possibly vaporized to cool fluid 5 to a temperature below -50°C, preferably below -120°C. In the example, it is cooled to -140°C.

[0021] Gas 1 enters the cold end of the exchanger E1 and exits the hot end as fluid 3.

[0022] In the example, fluid 5 is nitrogen. It could, for example, be natural gas or methane. Preferably, fluid 5 is inert. Fluid 5 is preferably at a pressure between 3 and 70 bar abs if the intermediate fluid is not nitrogen, and between 3 and 25 bar if the intermediate fluid is nitrogen.

[0023] Nitrogen 13 exits heat exchanger E2 at a temperature below -90°C, for example -120°C, or even between -150°C and -110°C, and is compressed in a compressor C, for example a centrifugal compressor, to approximately 20 bar. The nitrogen at 20 bar is then optionally divided into two parts 15 and 17, part 17 not necessarily being present. Part 17 can be partially cooled in heat exchanger E1 and then sent to a cooling element 31. Thus, the heated part 19 is sent to the hot end of heat exchanger E1. The portion 15, 21 is sent at 20°C to the hot end of the exchanger E1 and cools there to -140°C, forming a gas 5 which is sent to the exchanger E2 at a temperature of -140°C, therefore colder than the temperature at which the gas 13 is drawn from the exchanger E2. The gas 5 heats up in the exchanger E2 to 20°C and is then cooled against the LNG in the exchanger E1.The gas, cooled to -140°C, is sent to cool further, in this example first by passing through heat exchanger E2 and then by expansion in a turbine T with an inlet temperature below -100°C, for example -120°C. The expanded fluid, at 7 to 1.5 bar in turbine T, is two-phase and is sent to a phase separator where it forms a liquid 9 and a gas 11. The liquid is vaporized in a heat exchanger E3 and mixes with the gas 11 to be reheated in heat exchanger E2, forming the flow 13 to be sent to the cold compressor C. The flow 13 can consist of the vaporized liquid 9 and / or the gas 11.

[0024] Thus nitrogen, or another fluid for example helium or a mixed refrigerant, circulates in a closed cycle, taking cooling from the LNG.

[0025] Gaseous hydrogen 23 at room temperature, for example 20°C, enters the hot end of the heat exchanger E2, which it travels through from one end to the other to cool down to -180°C. It is then cooled in the heat exchanger E3 against the liquid of the phase separator to form gaseous hydrogen 25 at -190°C.

[0026] The hydrogen-25 is then cooled and liquefied in another heat exchanger using a known method. A cycle of hydrogen, helium, or mixed refrigerants, possibly including noble gases, provides the necessary cooling capacity.

[0027] Thus, LNG provides at least a portion of the cooling required for pre-cooling gaseous hydrogen to -190°C. This fraction can be at least 50%, 75%, or 99% of the cooling required for cooling gaseous hydrogen to -190°C. LNG can even provide all the necessary cooling except for that supplied by the T turbine.

[0028] During the device's startup, the LNG can be vaporized in a separate vaporizer, for example, an "open rack vaporizer," by exchanging heat with water, possibly seawater. This vaporizer consists of a series of vertical tubes through which the LNG circulates and vaporizes, with water flowing over the outside of the tubes. Other types of heat exchangers can obviously be considered.

[0029] The process can also provide cooling to another element 31, cooled by the cycle. In the figure, a portion 17 of the gas compressed in compressor C is cooled in the heat exchanger to an intermediate temperature, here -50°C, drawn from the exchanger into a central zone of the heat exchanger, and used to cool element 31 while being itself heated to form gas 19. This gas then rejoins the compressed flow 15 in compressor C to form flow 21, which enters exchanger E1 at 20°C. Since the pressure losses for flow 18 and 19 are limited, a small expansion of flow 15 through a valve will suffice to allow flow 15 and 19 to mix.

[0030] Element 31 can for example be a liquefier of another gas or a separation apparatus by distillation and / or partial condensation at a temperature below 0°C, for example a carbon dioxide liquefier.

[0031] If fraction 17 is present but element 31 is not working, a heater, for example an electric heater or a heat exchanger heated by hot water, will be used to heat fraction 17 to form flow 19.

[0032] [ Fig.2 ] shows a variant of the [ Fig.1 where gas 5 is not cooled in the exchanger E2 but only in the turbine E. Thus, gas 5 enters the turbine E at the temperature at which it exits the heat exchanger E1. Gas 13 is compressed in the cold compressor 1 and then in a blower C1 coupled to the turbine E. It is the gas compressed in the blower C1 that is sent to the exchanger E1 to recover the cold from LNG 1.

[0033] The natural gas produced can be sent to a hydrocarbon conversion unit for further processing and / or use as fuel. The unit can be of the POX, ATR, or SMR type.

[0034] The hydrogen to be liquefied can obviously come from this unit.

Claims

1. A method for cooling hydrogen wherein i) Either liquefied natural gas (1) or vaporized natural gas, the vaporized natural gas being at a temperature below -50°C, is reheated by indirect heat exchange in a first heat exchanger (E1) with a flow of intermediate fluid (5) at a pressure between 3 and 70 bars abs which is cooled to a temperature equal to or greater than -145°C, ii) The flow of intermediate fluid at a temperature equal to or greater than -145°C is cooled 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) possibly driving a compressor of the process (C, C1), or a valve, iii) a flow of gaseous hydrogen (23) is cooled in the second heat exchanger without condensing, iv) a gaseous flow (11, 13) derived from the intermediate fluid cooled in step a) and / or b) is reheated in the second heat exchanger (E2) to a temperature between -150°C and -90°C, is withdrawn from the second heat exchanger at this temperature and compressed in a compressor (C) with an inlet temperature between -150°C and -90°C and at least a part (15, 17) of the compressed intermediate fluid is first cooled in the first heat exchanger and then reheats from a temperature of at most -110°C and v) at least a part (15) of the reheated intermediate fluid constitutes the flow of intermediate fluid of step i) the at least one part (15, 17) of the compressed intermediate fluid, first cooled in the first heat exchanger, then reheating from the temperature of at most -110°C to constitute the flow of intermediate fluid of step i), characterized in that the liquefied natural gas or, as the case may be, the vaporized gas is reheated to a temperature above 0°C by indirect heat exchange in the first heat exchanger (E1) with the flow of intermediate fluid (5) at a pressure between 3 and 70 bars abs if the intermediate fluid is not nitrogen and between 3 and 25 bars if the intermediate fluid is nitrogen, and in that the compressed and cooled intermediate fluid in the first heat exchanger is reheated in the second heat exchanger.

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

3. The method according to any one of the preceding claims, 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 the preceding claims, wherein the liquefied natural gas (1) vaporizes in the first heat exchanger (E1).

5. The method according to any one of the preceding claims, wherein the flow of gaseous hydrogen cooled in the second heat exchanger (E2) condenses in another heat exchanger following cooling to its liquefaction temperature.

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

7. The method according to any one of the preceding claims, wherein for start-up the liquefied natural gas (1) is vaporized in a heat exchanger by heat exchange with water, for example sea water.

8. The method according to any one of the preceding claims, wherein a part 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 between - 40°C and -90°C, preferably between 45°C and -70°C, and is sent to cool an auxiliary heat exchanger (31) and is then sent after being reheated in the auxiliary heat exchanger to be cooled in the first heat exchanger.

9. The method according to claim 8, wherein the auxiliary heat exchanger (31) is used to cool a flow of gas containing carbon dioxide and at least one other component in a carbon dioxide separation and / or liquefaction apparatus.

10. The method according to claim 8 or 9, wherein the part of the compressed intermediate fluid (18) is reheated with reheating means connected in parallel with the auxiliary heat exchanger (31).

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

12. A method for liquefying hydrogen, wherein the flow of hydrogen (23) is first cooled according to a method according to one of the preceding claims and then liquefied by heat exchange with a refrigeration cycle.

13. An apparatus for cooling hydrogen comprising a first heat exchanger (E1), a second heat exchanger (E2), a compressor (C), optionally a turbine (E) or a valve, means for sending either liquefied natural gas (1) or vaporized natural gas, the vaporized natural gas being at a temperature below -50°C, to be reheated to a temperature above 0°C by indirect heat exchange in the first heat exchanger (E1) with a flow of intermediate fluid (5), means for sending the flow of intermediate fluid (5) at a pressure between 3 and 70 bars abs if the intermediate fluid is not nitrogen and between 3 and 25 bars if the intermediate fluid is nitrogen to be cooled in the first heat exchanger to a temperature equal to or greater than -145°C, means for sending the flow of intermediate fluid at a temperature equal to or greater than -145°C to be cooled a) by introducing it at this temperature into the second heat exchanger (E2) where it is cooled by indirect heat exchange and / or b) by expansion, as the case may be, in the turbine (E) optionally configured to drive a compressor of the apparatus (C, C1), or the valve, means for sending a flow of gaseous hydrogen (23) to be cooled in the second heat exchanger without condensing, means for sending a gaseous flow (11, 13) derived from the intermediate fluid cooled in step a) and / or b) to be reheated in the second heat exchanger (E2) to a temperature between -150°C and -90°C, means for withdrawing the gaseous flow from the second heat exchanger at this temperature, means for sending the withdrawn gaseous flow to the compressor (C) with an inlet temperature between -150°C and -90°C to be compressed, means for sending at least a part (15, 17) of the compressed intermediate fluid to be first cooled in the first heat exchanger, means for sending the at least one part of the intermediate fluid cooled in the first heat exchanger to be reheated from a temperature of at most -110°C, and for sending the at least one part (15) of the reheated intermediate fluid to the first heat exchanger (E1) constituting the flow of intermediate fluid to be cooled, the means for sending the at least one part (15, 17) of the intermediate fluid to be reheated are connected so that the at least one part is reheated in the second heat exchanger from the temperature of at most -110°C to constitute the flow of intermediate fluid to be cooled in the first heat exchanger.

14. The apparatus according to claim 13, comprising the turbine (E) for cooling by expansion the flow of intermediate fluid and a phase separator (S) for separating a fluid (7) coming from the turbine (E), the gaseous flow (13) being the overhead gas (11) and / or the vaporized liquid of the separator.

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