Process and installation for the production of liquid hydrogen

Abstract

Title: Process and Installation for the Production of Liquid Hydrogen. A liquid hydrogen production installation comprises a circuit of gaseous hydrogen to be liquefied (1) including a catalyst for accelerating the conversion of hydrogen in ortho form to hydrogen in para form, an upstream end intended to be connected to a source of gaseous hydrogen and a downstream end intended to be connected to a collection device for the cooled fluid, a hydrogen cooling cycle (H), at least one bypass line (3A) suitable for extracting hydrogen from the refrigeration cycle circuit, connected to a point in the circuit of gaseous hydrogen to be liquefied, and means for recovering gaseous hydrogen from a storage (P,S) directly connected to the refrigeration cycle circuit. Fig. 1

Description

Title of the invention: Process and installation for the production of liquid hydrogen

[0001] The present invention relates to a process and installation for the production of liquid hydrogen.

[0002] A liquid hydrogen production plant produces liquefied hydrogen by cooling gaseous hydrogen to -253 °C or lower. The substances that can be used as refrigerants to cool gaseous hydrogen for this purpose are limited to only certain substances with a very low freezing point. In an industrial liquid hydrogen production plant, hydrogen is generally used as the refrigerant to bring the hydrogen to the lowest possible temperatures.

[0003] When hydrogen is used as a refrigerant, if the refrigerant hydrogen is contaminated with impurities, there is a risk that the impurities will freeze and damage the equipment. Therefore, hydrogen of very high purity (for example, a hydrogen content of 99.9999 vol% or higher) is used as a refrigerant hydrogen in a cooling cycle. Furthermore, refrigerant hydrogen such as this has a higher purity than the feed hydrogen supplied to the liquid hydrogen production plant.

[0004] Rotating machines such as compressors are provided in the recycling line to circulate the refrigerant hydrogen, and the total quantity of refrigerant hydrogen in the recycling line decreases due to leakage of refrigerant hydrogen from the sealing parts of the rotating machines. The recycling line must therefore be recharged with refrigerant hydrogen, but the purity of the refrigerant hydrogen is higher than the purity of the feed hydrogen, as mentioned above.

[0005] There is a need to recover gaseous hydrogen from liquid hydrogen storage tanks or means of transport, for example those arriving to be filled with liquid hydrogen but which already contain gaseous hydrogen remaining from a previous filling. This prevents the loss of the molecules and allows them to be reused in the hydrogen liquefaction unit.

[0006] To recycle the cold, low-pressure evaporation gases, they are injected into the H2 cooling cycle at a relatively cold temperature. Once compressed with the rest of the H2 cooling cycle, the excess H2 flow is sent to the feed stream intended for liquefaction to maintain a stable inventory in the H2 cooling cycle: a bypass duct is required. This bypass flow corresponds to the recycled evaporation gas flow rate, plus the production of gas by rapid vaporization of liquid upon arrival in storage (negligible with a liquid turbine), less the losses of the H2 cooling cycle (regeneration of the adsorber and the rotational losses of the cycle's compressors for example): the main contributor is the recycled evaporation gas flow.

[0007] It is known from JP2020024067 that the hydrogen inventory of the cooling circuit can be reduced by directing the hydrogen flow from the cooling circuit to the gaseous hydrogen to be liquefied circuit at ambient temperatures, after expansion, upstream of the main compressor of the gas to be liquefied. This document also includes a line connecting the gaseous hydrogen to be liquefied circuit and the cooling circuit at an intermediate temperature of the liquefier to allow the passage of hydrogen to supply the cooling circuit with purified hydrogen to be liquefied in the purification cold unit. However, no part of the cycle gas consists of vaporized gas from storage or transport. Therefore, the cooling circuit is more likely to be deficient in hydrogen than in excess of hydrogen due to hydrogen losses from the cycle.

[0008] Ullmann's Encyclopedia of Industrial Chemistry, Hydrogen, 4. Liquefaction of Ohlig et al shows in Figure 5 a hydrogen liquefier with a bypass circuit from the feed flow to the cycle at an intermediate temperature and a bypass circuit from the cycle to the feed flow at a temperature close to 20K.

[0009] Kündig et al., "Large scale hydrogen liquefaction in combination with LNG re-gasification," shows in Figure 5 a hydrogen liquefier having bypass circuits between the refrigeration cycle and the hydrogen circuit to be liquefied. For the 20K bypass circuit, valve CV15, with its inlet on the hydrogen feed side, is downstream of the ejector, and valve CV14 reduces the fluid to 2 bar. The CV15 line is upstream of the cycle's JT valve CV16 and therefore at high pressure.

[0010] Thus the CV15 valve sends gas from the cycle to the supply flow.

[0011] The Ullmann and Kündig et al. documents describe a cycle gas shipment to The hydrogen is liquefied at a very low temperature (close to 20K) with the evaporation gas recovered via an ejector. In the process of Kündig et al., the gas is taken from the high-pressure cycle, whereas in the Ullmann process, the cycle gas is taken from the low-pressure cycle (downstream of the Joule-Thomson valve of the cooling circuit).

[0012] Furthermore, according to these two documents, the recovered evaporation gases are sent not to the cycle but to the gas to be liquefied. This means that the cooling circuit is primarily deficient in hydrogen rather than in excess during steady operation due to hydrogen losses from the cycle gas. The gas supply circuit cycle to hydrogen to liquefy is therefore used occasionally to reduce the cycle gas inventory (and thus control the cycle gas pressure).

[0013] In the present invention, the gas generated by the expansion of liquid hydrogen downstream of the second heat exchanger and upstream of a storage tank, and / or the evaporation gas, and / or the gas produced by rapid liquid vaporization upon arrival at the storage tank or an intermediate storage tank, are returned to the cycle gas instead of being sent to the gas to be liquefied. This has the advantage of supplying the cycle gas with clean, low-pressure hydrogen without requiring the gas to be pressurized before being injected into the liquefier (the pressure increase occurring in the cycle gas compressors). Optionally, a gas-gas ejector can help to slightly increase the pressure of the evaporation gas for injection into the cycle gas. This therefore avoids the need for a separate gas-liquid ejector, which is difficult to size and operate (due to the liquid hydrogen being close to its saturation point).Furthermore, this allows the recovery of cooling energy from the evaporating gas to contribute to the cooling and liquefaction of the gas to be liquefied. Thus, the cycle gas essentially has an excess of hydrogen in its inventory. This excess must therefore be removed from the cycle gas to maintain a constant or controlled cycle gas inventory.

[0014] The present invention consists of utilizing the excess cycle gas reinjected into the gas circuit to be liquefied in two ways: • By expanding the excess cycle gas to a temperature such that, relative to the Joule-Thomson inversion temperature, the gas cools as its pressure decreases. Advantageously, the pressure reduction can be achieved in a turbine rather than a Joule-Thomson valve to increase the amount of cooling created by the gas expansion.

[0015] And / or • By injecting the cycle gas at a point in the gas circuit to be liquefied, thereby reducing the need for ortho / para conversion of the gas to be liquefied. Indeed, because the evaporation gas and the gas produced by rapid vaporization of liquid have a high concentration of para hydrogen, and because the cycle gas is in excess, the cycle gas has a high concentration of para hydrogen after a certain operating time.

[0016] In the present invention, the bypass line from the cycle gas to the gas to be liquefied is therefore different from those of documents JP2020024067, Ullmann and Kündig et al., because in these three documents the bypass line extracts hydrogen from the cycle gas at a temperature (ambient and 20K) that does not allow for the generation of cooling by gas expansion. Furthermore, these lines are only used occasionally when the hydrogen in the cycle gas needs to be purified (JP2020024067) and when The cycle gas inventory must be reduced. The hydrogen circuit does not have a high para concentration (e.g., 98%) because the cycle gas is fed by the gas to be liquefied at an intermediate temperature (e.g., 50% para hydrogen) and the gas to be liquefied is the main feed source for the cycle gas.

[0017] According to one aspect of the invention, a liquid hydrogen production installation is planned, comprising: • A gaseous hydrogen circuit to be liquefied comprising a catalytic element to accelerate the conversion of hydrogen in ortho form to hydrogen in para form, an upstream end intended to be connected to a source of gaseous hydrogen and a downstream end intended to be connected to a collection element for the cooled fluid. • A set of heat exchangers comprising a first heat exchanger and a second heat exchanger arranged in series in heat exchange with the gaseous hydrogen circuit to be liquefied from upstream to downstream, the catalytic element being located in the gaseous hydrogen circuit upstream of the second heat exchanger and preferably downstream of the first heat exchanger and / or being incorporated in the second heat exchanger. • A cooling device in heat exchange with the first and second heat exchangers, the cooling device comprising a refrigerator with a refrigeration cycle circuit of a cycle gas which is hydrogen, the refrigerator comprising, arranged in series in the refrigeration cycle circuit: at least one cycle gas compression element, at least one cycle gas cooling element, at least one cycle gas expansion element and at least one expanded cycle gas heating element, the hydrogen circuit to be liquefied comprising, between the set of heat exchangers and the downstream end of the gaseous hydrogen circuit, a cooled hydrogen expansion element. • At least one bypass line capable of extracting hydrogen from the refrigeration cycle circuit, the bypass line being connected to a point in the gaseous hydrogen circuit to be liquefied downstream of the first heat exchanger and upstream of the cooled hydrogen expansion unit, and • Means to recover gaseous hydrogen generated by expansion of liquid hydrogen downstream of the second exchanger and upstream of a storage and / or coming from a storage and / or means of transport directly connected to the refrigeration cycle circuit.

[0018] According to other optional aspects: • the bypass line is connected to a point in the gaseous hydrogen circuit at liquefy upstream of the second heat exchanger. • the bypass line is connected to a point in the gaseous hydrogen circuit to be liquefied downstream of the catalytic unit located in the gaseous hydrogen circuit upstream of the second heat exchanger and preferably downstream of the first heat exchanger. • The bypass line includes a pressure relief valve preferably capable of reducing the hydrogen pressure of the cycle by at least 5 bar. • The liquid hydrogen production installation includes a cycle pressure detector capable of controlling the opening and / or closing of the bypass line relief valve. • The bypass line includes a non-return valve. • The cycle includes at least two expansion chambers in series, one of which is the last expansion valve and bypass line is connected to take hydrogen from a point downstream of at least one of the cycle expansion valves other than the last expansion valve. • the bypass line is connected to a point in the circuit of gaseous hydrogen to be liquefied at an intermediate temperature of the second heat exchanger.

[0019] According to another object of the invention, a process for producing liquid hydrogen is provided in which gaseous hydrogen circulates in a gaseous hydrogen circuit to be liquefied comprising a catalytic element, an upstream end intended to be connected to a source of gaseous hydrogen and a downstream end intended to be connected to a collection element for the cooled fluid, the gaseous hydrogen being cooled in a set of heat exchangers comprising a first heat exchanger and a second heat exchanger arranged in series such that the gaseous hydrogen is first cooled in the first heat exchanger, passes through the catalytic element located in the gaseous hydrogen circuit upstream of the second heat exchanger and then is cooled in the second heat exchanger,of the refrigeration for the second heat exchanger being supplied by a cooling device in heat exchange with the first and second heat exchangers, the cooling device comprising a refrigerator with a refrigeration cycle circuit of a cycle gas which is hydrogen, in which the cycle gas is compressed in at least one cycle gas compression element, cooled in at least one cycle gas cooling element, expanded in at least one cycle gas expansion element and heated in at least one expanded cycle gas heating element, the hydrogen to be liquefied being expanded, downstream of its heat exchange with the second heat exchanger, in a cooled hydrogen expansion element, a fraction of the hydrogen from the refrigeration cycle circuit being sent at least occasionally from the refrigeration cycle circuit, management towards the gaseous hydrogen circuit to be liquefied characterized in that gaseous hydrogen is sent, at least occasionally, from at least one storage and / or at least one means of transport to the refrigeration cycle circuit and in that a fraction of the hydrogen from the refrigeration cycle circuit is sent at least occasionally to a point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 40 and 100K and where the gaseous hydrogen to be liquefied contains between 30 and 90% of hydrogen in para form.

[0020] According to other optional aspects: • the fraction of hydrogen from the refrigeration cycle circuit is sent at least occasionally to a point in the gaseous hydrogen circuit to be liquefied downstream of the first heat exchanger and upstream of the cooled hydrogen expansion unit. • the hydrogen from the cycle sent to the hydrogen to be liquefied contains at least 90% hydrogen in para form. • the fraction of hydrogen from the refrigeration cycle circuit is sent at least occasionally to a point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 75 and 100K and where the gaseous hydrogen to be liquefied contains between 30 and 52% of hydrogen in para form. • the fraction of hydrogen from the refrigeration cycle circuit is sent at least occasionally to a point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 50 and 75K and where the gaseous hydrogen to be liquefied contains between 52 and 77% of hydrogen in para form. • the fraction of the cycle gas was expanded in at least one expansion device of the cycle before being sent to join the hydrogen gas to be liquefied, the at least one expansion device being at least one turbine. • at least part of the cycle gas is expanded in at least n turbines in series, n being greater than 1, and the fraction sent pointwise to the hydrogen gas to be liquefied is expanded in at most n-1 of the turbines in series. • the maximum pressure of the cycle gas is substantially equal to the pressure of the gaseous hydrogen to be liquefied at the point where the fraction joins the gaseous hydrogen to be liquefied or is greater than this pressure by no more than 20 bars, the difference between the two pressures preferably being between 0 and 10 bars. • cycle gas is sent at least occasionally to a point in the circuit of gaseous hydrogen to be liquefied downstream of the catalytic unit. • the transfer of cycle gas to the hydrogen gas to be liquefied is triggered if a pressure in the cycle becomes greater than a threshold. • the cycle gas flow rate sent to the hydrogen to be liquefied is equal to the sum of the flow rate of gaseous hydrogen sent from at least one storage and / or at least one means of transport to the refrigeration cycle circuit and a flow rate of make-up gaseous hydrogen less the loss flow rate of the refrigeration cycle circuit. • the cycle gas flow is sent to the hydrogen to be liquefied at a point where the cycle gas is at a temperature such that, relative to its Joule-Thomson inversion temperature, the cycle gas cools when expanded to a lower pressure. • the cycle gas flow is sent to the hydrogen to be liquefied at a point where the hydrogen to be liquefied has a hydrogen content para lower than that of the cycle gas sent to the hydrogen to be liquefied.

[0021] It is assumed that the cooling cycle has the same composition as the inlet evaporation gas flow due to the slow kinetics of natural ortho-para conversion, i.e. 98% para-H2. Consequently, this bypass flow is also converted to 95% para.

[0022] The flow rate of the H2 cooling cycle is equivalent to several times the H2 supply flow rate. It is assumed that a maximum flow rate of evaporated gas, constituting part of the supply flow rate, enters the H2 cooling cycle for part of the time. During the remaining period, no evaporated gas enters the H2 cooling cycle: the evaporated gas flow rate thus represents a fraction of the H2 cooling cycle.

[0023] The hydrogen to be liquefied enters a first thermally insulated heat exchanger with a concentration of 25% para hydrogen, the remainder of the hydrogen being in ortho form, corresponding to the equilibrium composition at room temperature. The hydrogen is cooled to approximately 80 K in the first heat exchanger and enters a catalytic unit where some of the ortho hydrogen is converted to para hydrogen, so that the hydrogen contains 40% to 50% para hydrogen, for example, 45% para hydrogen. In the second heat exchanger, the catalyzed hydrogen is cooled to remove the heat produced by the catalytic conversion or to cool the hydrogen below 80 K, using a hydrogen refrigeration cycle. At the outlet of the second heat exchanger, the hydrogen is 98% para hydrogen.

[0024] As mentioned, the hydrogen cycle receives hydrogen from a liquid hydrogen storage and / or a hydrogen transport means (pipeline, tanker truck, ship). The hydrogen cycle is compressed to a pressure of between 50 and 70 bar absolute. However, the flow rate of hydrogen sent from the cycle to the hydrogen at The liquefied hydrogen must be at a pressure above 20 or 30 bar absolute to achieve this flow rate, and the ability to output hydrogen from the cycle compressor at an intermediate pressure significantly increases the price of the cycle compressor. Several possibilities are suggested for the position where the fraction of hydrogen sent from the cycle joins the gaseous hydrogen to be liquefied, as illustrated in [Fig. 4], which is a graph showing the relationship between the temperature of the hydrogen to be liquefied (x-axis) and the percentage of para-formed hydrogen it contains (y-axis).

[0025] Position 1 (PI)

[0026] If the hydrogen flow rate sent from the cycle to the hydrogen to be liquefied at a point PI upstream of the catalytic unit, or even upstream of the first heat exchanger, is mixed with 25% hydrogen in para form and the fraction coming from the cycle at 98% para hydrogen, and a flow rate constituting a portion of the hydrogen flow rate to be liquefied, a flow rate of 35% para hydrogen is produced upon arrival at the catalytic unit. Thus, the catalysis will only need to increase the para hydrogen content from 35% to 45%, rather than from 25% to 45% without the bypass fraction. Therefore, the portion of the liquefier downstream of the catalytic unit will have to compensate for less heat generated by the catalysis, and the catalytic unit will be smaller. However, the pressure of the fraction, released in at least one valve in the line between the cycle and the hydrogen to be liquefied, is not utilized.For this position, the hydrogen content to be liquefied in para form is between 25 and 35% and the temperature is above 100K.

[0027] Position 2 (P2)

[0028] If the hydrogen flow rate sent from the cycle to the hydrogen to be liquefied at a point P2 downstream of the catalytic converter and the first heat exchanger, and upstream of the second heat exchanger, is mixed with 45% hydrogen in para form and the fraction coming from the cycle at 98% para hydrogen, at a flow rate equal to 17% of the hydrogen flow rate to be liquefied, a flow rate of 52% para hydrogen is produced. Thus, the cooling cycle will only have to compensate for a conversion from 52% para hydrogen to 98% para hydrogen (rather than from 45% to 98%). Here again, the pressure difference does not contribute to significant cooling because the expansion is carried out in a Joule-Thomson valve. For this position, the hydrogen content to be liquefied in para form is between 45 and 52% and the temperature is within the range [75; 100]K.

[0029] Position 3 (P3)

[0030] If the hydrogen flow rate sent from the cycle to the hydrogen to be liquefied at a point P3 downstream of the catalyst and the first heat exchanger, and also downstream of at least one expansion stage in a turbine, for example in two turbines in In this series, the expansion process produces cooling through work extraction, thus utilizing the pressure to which the evaporation gases were compressed. The cycle gas is expanded in at least one 62-bar turbine to a pressure above 25 bar, or even just above 25 bar, so that the cycle gas is at almost the same pressure as the hydrogen to be liquefied. Its temperature is -223°C, and the fraction of cycle gas is fed to the hydrogen to be liquefied at this temperature. At this temperature, the hydrogen to be liquefied contains 74% parhydrogen, and mixing it with the fraction of cycle gas increases its parhydrogen content to 77%.

[0031] For this position, the hydrogen content to be liquefied in para form is between 74 and 77% and the temperature is greater than 50K and less than 80K.

[0032] It may also be necessary to provide a bypass line to send a portion of the hydrogen to be liquefied to the refrigeration cycle. Sending such a portion to the cycle could prove necessary if no evaporation gas is supplying the refrigeration cycle. The position of the point where the hydrogen to be liquefied is drawn off modifies the composition of the hydrogen refrigeration cycle. If the hydrogen to be liquefied is drawn off immediately after the compressor of the gas to be liquefied and sent to the inlet of the cycle compressor, hydrogen with 25% parH2 will enter the cycle. If the hydrogen to be liquefied is drawn off at -245°C just before the last heat exchanger E3 where liquefaction takes place and sent to the cold end of the cycle, hydrogen with 90% parH2 will enter the cycle (or even 98% if it is drawn off from the last catalyst bed).

[0033] In the case where the transfer of hydrogen from the cycle to the hydrogen to be liquefied takes hydrogen downstream of at least one turbine, it is advantageous if the cycle operates with hydrogen in the form of 98% para. Therefore, in this case, the transfer in the opposite direction (towards the cycle) of 25% para hydrogen should be avoided, even if this transfer is only occasional, for example during the regeneration of the adsorbers.

[0034] Since a valve capable of operating at cryogenic temperatures is more expensive than an ordinary valve, and since disturbances at low temperatures have greater effects than those at higher temperatures, it may be preferable to use hydrogen injection from the gas circuit to be liquefied to the cycle at ambient or intermediate temperature at the outlet of the El, so as to send the feed flow to the cycle downstream of the cryogenic purification to fill the cycle with clean gas. On the other hand, the PI version valve is less expensive because it is not cryogenic compared to the P2 version valve for bypassing the cycle to the feed flow.

[0035] Regardless of the position of this shipment, the use of a cycle with at least 98% para hydrogen is recommended.

[0036] The invention will be described in more detail with reference to the figures where:

[0037] [Fig.1] is a schematic configuration diagram of a liquid hydrogen production plant according to a comparative example.

[0038] [Fig.2] is a schematic configuration diagram of a liquid hydrogen production plant according to an embodiment of the invention.

[0039] [Fig.3] is a schematic configuration diagram of a liquid hydrogen production plant according to another embodiment of the invention.

[0040] [Fig.4] is a graph illustrating the relationship between the temperature of the hydrogen to be liquefied and the percentage of para and ortho form hydrogen it contains.

[0041] A liquid hydrogen production plant according to a comparative example will first be described. Figure 1 is a schematic configuration diagram of the liquid hydrogen production plant according to the first embodiment. As shown in Figure 1, a liquid hydrogen production plant comprises a circuit for liquefied gaseous hydrogen 1 including a catalyst, an upstream end intended to be connected to a source of gaseous hydrogen, and a downstream end intended to be connected to a collection device for the cooled fluid.

[0042] A set of heat exchangers of the installation includes a first heat exchanger El and a second heat exchanger E2 arranged in series in heat exchange with the gaseous hydrogen circuit to be liquefied from upstream to downstream, the catalytic element being located in the gaseous hydrogen circuit upstream of the second heat exchanger and preferably downstream of the first heat exchanger.

[0043] The installation includes a cooling device N for cooling the first heat exchanger EL

[0044] The installation includes a cooling device in heat exchange with the first and second heat exchangers E1, E2, the cooling device comprising a refrigerator with a refrigeration cycle circuit H of a cycle gas which is hydrogen. The refrigerator comprises, arranged in series in the refrigeration cycle circuit: at least one compression element C1, C2 of the cycle gas, at least one cooling element of the cycle gas, at least one expansion element T2 of the cycle gas and at least one heating element of the expanded cycle gas, the hydrogen circuit to be liquefied comprising, downstream of its heat exchange with the second heat exchanger, i.e. between the set of heat exchangers and the downstream end of the gaseous hydrogen circuit, a cooled hydrogen expansion element T1, here a turbine.

[0045] The refrigeration circuit H can have a number of compressors and a number of expansion devices chosen according to the size of the liquefier, the cost of the liquefier, and the machines available from the manufacturer. The circuit is therefore illustrated in a certain way, but the invention is not limited to the circuit as illustrated.

[0046] In the case of the example, the hydrogen to be liquefied comes from a compressor (not illustrated) and arrives at 25 bara at the inlet of the heat exchanger El where a fraction of the cycle gas is mixed with it via a bypass line 3A suitable for extracting hydrogen from the refrigeration cycle circuit H connected to the gaseous hydrogen circuit to be liquefied 1.

[0047] The hydrogen to be liquefied is cooled in heat exchanger 1 to a temperature of approximately 80 K. In this case, the catalytic element modifies the ortho / para composition of the hydrogen cooled in heat exchanger E1 to an intermediate temperature of heat exchanger E1 and then returns the modified hydrogen to be cooled in heat exchanger E1. Alternatively, the catalytic element can be located between heat exchangers E1 and E2.

[0048] The hydrogen is cooled in the second exchanger E2 and then in the third exchanger E3 before being expanded in a turbine Tl forming liquid hydrogen for at least one storage S.

[0049] From this storage tank, CCI and CC2 transport means, such as a pipeline, a tanker truck, or a ship, are filled. The filling process generates gaseous hydrogen, which is formed when liquid hydrogen evaporates. The transport means arriving at the liquefier may also contain gaseous hydrogen from a previous filling. The installation includes means for recovering gaseous hydrogen from at least one storage tank S and / or at least one CCI and CC2 transport means and / or from the tank P connected to the refrigeration cycle circuit H, at the coldest part of this circuit, via conduits 9 and 21 and optionally via an ejector E. This gaseous hydrogen thus enters the refrigeration cycle H and must be discharged to the gaseous hydrogen circuit to be liquefied.In this example, the PI position described above is used, and the branch line 3A is connected to a point in the gaseous hydrogen circuit to be liquefied upstream of the first heat exchanger and upstream of the cooled hydrogen expansion unit. Unlike the prior art, the cycle hydrogen arrives downstream of the hydrogen compressor 1 after expansion in a valve at a temperature above 0°C, the cycle operating at a pressure above 25 bara, for example 62 bara.

[0050] The hydrogen flow rate sent from cycle H to the hydrogen to be liquefied 1 at a point upstream of the catalytic unit and upstream of the first heat exchanger El, by mixing the hydrogen to be liquefied 1 with 25% hydrogen in para form and the fraction coming from the cycle at 98% para hydrogen, and a flow rate 3A equal to 17% of the hydrogen flow rate, produces a flow rate of 35% para hydrogen upon arrival at the catalytic unit. Thus, the catalysis will only need to increase the para hydrogen content from 35% to 45%, rather than from 25% to 45% without the bypass fraction. Therefore, the part of the liquefier downstream of the catalytic unit will have to compensate less The heat generated by catalysis and the catalytic unit will be smaller. However, the pressure of fraction 3A, reduced in a valve (not shown) from 61 bara to 25 bara, is not taken into account.

[0051] Here, circuit H comprises a compressor C1 in which a flow 11 of the cycle containing 98% pure hydrogen is compressed. The compressed hydrogen 13 is sent to a second compressor C2, which compresses it to 62 bar, forming a flow 3. A fraction of this flow is expanded to 25 bar and sent to the gas to be liquefied 1. The remaining gas at 62 bar is cooled in the heat exchanger E1 by cycle N, passes through the catalyst, and is sent to the second heat exchanger E2. After initial cooling, it is expanded in a turbine T2 to 25 bar or above, then returned to the heat exchanger and subsequently divided into two parts. Part 7 is expanded in a turbine, mixed with evaporation gas 21, and reheated in heat exchangers E2 and E1 before being returned to compressor C2. Part 9 is sent to the thermosiphon after being partially condensed in the second exchanger E2, separated in the separator P forming a gas and a liquid.The liquid is used to cool the heat exchanger E3 to liquefy the hydrogen and is thus vaporized. The vaporized liquid and gas are mixed with an evaporation gas from storage and / or a means of transport CCI, CC2 and the mixture is heated in the heat exchangers E2, El before compression in the compressor CL.

[0052] Figure 2 is a schematic layout diagram of the liquid hydrogen production plant according to an embodiment of the invention. It should be noted that the same reference symbols are used for the components illustrated in Figure 2 that are identical to, or correspond to, those shown in Figure 1. The following description of the liquid hydrogen production plant according to this embodiment will focus on the differences with the liquid hydrogen production plant 100 according to the first embodiment, and duplicate descriptions will not be given.

[0053] Here the cycle hydrogen is sent to the hydrogen circuit to be liquefied at a point between the exchangers El and E2 by the bypass line 3A.

[0054] The hydrogen flow rate sent from the cycle to the hydrogen to be liquefied at a point downstream of the catalytic unit and the first heat exchanger E1 and upstream of the second heat exchanger E2, by mixing the hydrogen to be liquefied with 45% hydrogen in para form and the fraction coming from the cycle at 98% para hydrogen, and a flow rate equal to 17% of the hydrogen flow rate to be liquefied, produces a flow rate of hydrogen at 52% para hydrogen. Thus, the cooling cycle will only have to compensate for a conversion from 52% para hydrogen to 98% para hydrogen (rather than from 45% to 98%). Here, as in [Fig. 1], the pressure difference contributes little to the production of cooling.

[0055] Figure 3 is a schematic layout diagram of the liquid hydrogen production plant according to the third embodiment. It should be noted that the same reference symbols are used for the components illustrated in Figure 3 that are identical to, or correspond to, those shown in Figure 1. The following description of the liquid hydrogen production plant 200 according to this embodiment will focus on the differences with the liquid hydrogen production plant 100 according to the first embodiment, and duplicate descriptions will not be given.

[0056] The hydrogen flow is sent from the cycle to the hydrogen to be liquefied via bypass line 3A to a point downstream of the catalyst and the first heat exchanger, and also downstream of at least one expansion stage in at least one turbine. The expansion produces cooling, thus utilizing the pressure to which the evaporation gases were compressed. The cycle gas is expanded in at least one turbine with a pressure reduction of at most 20 bar, or even at most 10 bar, so that the cycle gas is at almost the same pressure as the hydrogen to be liquefied. Thus, the fraction taken by line 3A is at an initial pressure substantially equal to the pressure of the gaseous hydrogen to be liquefied at the point where the fraction rejoins the gaseous hydrogen to be liquefied. It is therefore the cycle turbine that produces the fraction at the required pressure in order to produce cold with the gas fraction before its bypass.Its temperature is -223°C and the cycle gas fraction is sent to the hydrogen to be liquefied at this temperature. At this temperature, the hydrogen to be liquefied contains 74% parahydrogen and mixing it with the cycle gas fraction brings it to 77% parahydrogen.

[0057] In this example, it may be necessary to provide another bypass line connected to a point upstream of any turbine of the H cycle but downstream of the first heat exchanger, in order to be able to supply the gas to be liquefied 1 with cycle gas during periods of low load.

[0058] It will be understood that the methods in the figures could be adapted to illustrate that a fraction of the hydrogen from the refrigeration cycle circuit is sent at least occasionally to any point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 50 and 100 K and where the gaseous hydrogen to be liquefied contains between 30 and 77% hydrogen in para form. The fraction can in particular be sent to a point where the temperature of the gaseous hydrogen to be liquefied is between 50 and 60 K or between 60 and 70 K or between 70 and 80 K or between 80 and 85 K or between 85 and 90 K or between 90 and 95 K or between 95 and 100 K.

[0059] The sending of the cycle gas to the hydrogen gas to be liquefied is triggered if a cycle pressure becomes greater than a threshold.

[0060] The flow rate of cycle gas sent to the hydrogen to be liquefied is equal to the sum of the flow rate of hydrogen gas sent from at least one storage and / or at least one means of transport and / or the refrigeration cycle circuit and a flow rate of hydrogen gas make-up which is used to replenish the closed circuit less the loss flow rate of the refrigeration cycle circuit.

[0061] In some cases, the make-up hydrogen flow rate perfectly compensates for the losses. In these cases, the cycle gas flow rate sent to the hydrogen to be liquefied is equal to the sum of the gaseous hydrogen flow rate sent from at least one storage and / or at least one means of transport to the refrigeration cycle circuit.

[0062] The sending of the cycle gas to the hydrogen gas to be liquefied can be triggered if a cycle pressure becomes greater than a threshold, indicating the presence of a surplus of gas coming from at least one storage and / or at least one means of transport.

[0063] A pressure detector can be mounted at any point in the cycle and can send a signal to open the sending of the cycle gas to the hydrogen gas to be liquefied if the cycle pressure becomes greater than a first threshold.

[0064] Similarly, the pressure detector can send a signal to close the sending of the cycle gas to the hydrogen gas to be liquefied if the cycle pressure becomes lower than the first threshold or a second threshold lower than the first threshold.

[0065] [Fig. 4] shows the variation of the contents of ortho hydrogen (H2°) and para hydrogen (H2p) on the ordinate with temperature on the abscissa. It can be seen that at ambient temperatures, hydrogen contains approximately 25% para hydrogen and 75% ortho hydrogen, these proportions being reversed upon cooling so that at very low temperatures hydrogen contains virtually no ortho hydrogen.

[0066] Positions PI, P2, P3 for the hydrogen inlet via branch line 3A are illustrated. Position PI corresponds to the point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 100 and 350K and where the gaseous hydrogen to be liquefied contains between 20 and 40% hydrogen in para form.

[0067] Position P2 corresponds to the point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 75 and 100K and where the gaseous hydrogen to be liquefied contains between 40 and 60% of hydrogen in para form.

[0068] Position P3 corresponds to the point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 50 and 75K and where the gaseous hydrogen to be liquefied contains between 70 and 80% of hydrogen in para form.

Claims

1. Claims Liquid hydrogen production facility comprising: • A gaseous hydrogen circuit to be liquefied (1) comprising a catalysis member for accelerating the conversion of hydrogen in ortho form into hydrogen in para form, an upstream end intended to be connected to a source of gaseous hydrogen and a downstream end intended to be connected to a member for collecting the cooled fluid. • A set of heat exchangers comprising a first heat exchanger (El) and a second heat exchanger (E2) arranged in series in heat exchange with the gaseous hydrogen circuit to be liquefied from upstream to downstream, the catalysis member being located in the gaseous hydrogen circuit upstream of the second heat exchanger and preferably downstream of the first heat exchanger and / or being incorporated in the second heat exchanger. • A cooling device in heat exchange with the first and second heat exchangers, the cooling device comprising a refrigerator with a refrigeration cycle circuit (H) of a cycle gas which is hydrogen, the refrigerator comprising, arranged in series in the refrigeration cycle circuit: at least one compression member (Cl, C2) of the cycle gas, at least one cooling member of the cycle gas, at least one expansion member (T2) of the cycle gas and at least one heating member of the expanded cycle gas, the hydrogen circuit to be liquefied comprising, between the set of heat exchangers and the downstream end of the gaseous hydrogen circuit, an expansion member (Tl) of cooled hydrogen. • At least one bypass line (3A) capable of extracting hydrogen from the refrigeration cycle circuit, the bypass line being connected to a point in the gaseous hydrogen circuit to be liquefied downstream of the first heat exchanger and upstream of the cooled hydrogen expansion member, and • Means for recovering gaseous hydrogen generated by expansion of liquid hydrogen downstream of the second exchanger and upstream of storage and / or coming from storage (P,S) and / or a means of transport (CCI, CC2) directly connected to the refrigeration cycle circuit.

2. Liquid hydrogen production plant according to claim 1, in which the bypass line (3A) is connected to a point in the gaseous hydrogen circuit to be liquefied upstream of the second heat exchanger (E2).

3. Liquid hydrogen production plant according to claim 1 or 2, in which the bypass line (3A) is connected to a point in the gaseous hydrogen circuit to be liquefied downstream of the catalysis member located in the gaseous hydrogen circuit upstream of the second heat exchanger (E2) and preferably downstream of the first heat exchanger (El).

4. Liquid hydrogen production plant according to one of the preceding claims in which the bypass line (3A) comprises an expansion valve preferably capable of reducing the pressure of the hydrogen in the cycle by at least 5 bars.

5. Liquid hydrogen production plant according to one of the preceding claims 1 to 4 in which the cycle (H) comprises at least two expansion members in series (T2) including a last expansion member and the bypass line is connected to take the hydrogen at a point downstream of at least one of the expansion members of the cycle other than the last expansion member.

6. Liquid hydrogen production plant according to claim 5 in which the bypass line is connected to a point in the gaseous hydrogen circuit to be liquefied (1) at an intermediate temperature of the second heat exchanger (E2).

7. A method for producing liquid hydrogen in which gaseous hydrogen (1) circulates in a gaseous hydrogen circuit to be liquefied comprising a catalysis member, an upstream end intended to be connected to a source of gaseous hydrogen and a downstream end intended to be connected to a member for collecting the cooled fluid, the gaseous hydrogen cooling in a set of heat exchangers comprising a first heat exchanger (El) and a second heat exchanger (E2) arranged in series so that the gaseous hydrogen cools first in the first heat exchanger, passes into the catalysis member located in the gaseous hydrogen circuit in upstream of the second heat exchanger and then cools in the second heat exchanger, refrigeration for the second heat exchanger being provided by a cooling device in heat exchange with the first and second heat exchangers, the cooling device comprising a cycle circuit refrigerator for refrigerating a cycle gas (H) which is hydrogen, in which the cycle gas is compressed in at least one cycle gas compression member (C1, C2), cooled in at least one cycle gas cooling member, expanded in at least one cycle gas expansion member (T2) and reheated in at least one expanded cycle gas reheating member, the hydrogen to be liquefied being expanded, downstream of its heat exchange with the second heat exchanger, in a cooled hydrogen expansion member (T1),a fraction of the hydrogen from the refrigeration cycle circuit being sent at least punctually from the refrigeration cycle circuit to the gaseous hydrogen circuit to be liquefied, characterized in that gaseous hydrogen is sent, at least punctually, from at least one storage (P, S) and / or at least one means of transport (CCI, CC2) to the refrigeration cycle circuit and in that a fraction of the hydrogen from the refrigeration cycle circuit being sent at least punctually to a point in the gaseous hydrogen circuit to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 40 and 100K and where the gaseous hydrogen to be liquefied contains between 30 and 90% of hydrogen in para form.,

8. Method according to claim 7 in which the fraction of hydrogen from the refrigeration cycle circuit is sent at least punctually to a point in the gaseous hydrogen circuit to be liquefied downstream of the first heat exchanger (El) and upstream of the cooled hydrogen expansion member (Tl).

9. Method according to claim 7 or 8 in which the hydrogen from cycle (3A) sent to the hydrogen to be liquefied contains at least 90% hydrogen in para form.

10. Method according to claim 7 or 8 or 9 in which the fraction of hydrogen from the refrigeration cycle circuit is sent at least punctually to a point in the gaseous hydrogen circuit to be liquefied (1) where the temperature of the gaseous hydrogen to be liquefied is between 75 and 100K and where the gaseous hydrogen to be liquefied contains between 30 and 52% of hydrogen in para form.

11. Method according to claim 7 or 8 or 10 in which the fraction of hydrogen from the refrigeration cycle circuit is sent at least punctually to a point in the circuit of gaseous hydrogen to be liquefied where the temperature of the gaseous hydrogen to be liquefied is between 50 and 75K and where the gaseous hydrogen to be liquefied contains between 52 and 77% of hydrogen in para form.

12. Method according to one of claims 7 to 11 in which the fraction of the cycle gas has been expanded in at least one expansion member of the cycle (T2) before being sent to join the gaseous hydrogen to be liquefied, the at least one expansion member being at least one turbine.

13. Method according to claim 12 in which at least a portion of the cycle gas is expanded in at least n turbines in series (T2), n being greater than 1, and the fraction sent punctually towards the gaseous hydrogen to be liquefied is expanded in at most n-1 of the turbines in series.

14. Method according to one of claims 12 or 13 in which the maximum pressure of the cycle gas (H) is substantially equal to the pressure of the hydrogen gas to be liquefied at the point where the fraction joins the hydrogen gas to be liquefied or is higher than this pressure by at most 20 bars, the difference between the two pressures preferably being between 0 and 10 bars.

15. Method according to one of claims 7 to 14 in which cycle gas (H) is sent at least punctually to a point in the gaseous hydrogen circuit to be liquefied downstream of the catalysis member.

16. Method according to one of claims 7 to 15 in which the sending of the cycle gas (H) towards the gaseous hydrogen to be liquefied is triggered if a pressure of the cycle (H) becomes greater than a threshold.

17. Method according to one of claims 7 to 16 in which the flow rate of cycle gas (H) sent to the hydrogen to be liquefied is equal to the sum of the flow rate of gaseous hydrogen sent from the at least one storage (P,S) and / or the at least one means of transport (CCI, CC2) to the refrigeration cycle circuit and a flow rate of make-up gaseous hydrogen less the flow rate of losses from the refrigeration cycle circuit.

18. A method according to one of claims 7 to 17 wherein the cycle gas flow is sent to the hydrogen to be liquefied at a point where the cycle gas is at a temperature such that, relative to its Joule-Thomson inversion temperature, the cycle gas cools when expanded to a lower pressure.

19. Method according to one of claims 7 to 18 in which the cycle gas flow is sent to the hydrogen to be liquefied at a point where the hydrogen to be liquefied has a para hydrogen content lower than that of the cycle gas sent to the hydrogen to be liquefied.

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