Patent Application
20250075972
The present invention relates to a device for liquefying a gas and a method for liquefying a gas. It applies, in particular, to the field of liquefying a flow of dihydrogen.
The liquefaction of dihydrogen is an energy-intensive process with a theoretical minimum energy consumption of 3.9 kWh per kilogramme of liquid hydrogen produced. The industrial cycles in use today consume between 11 and 13 kWh/kgLH2. When dihydrogen is used as a cooling fluid or refrigerant, more than half of the consumption can be allocated to its compression. Improving the energy consumption of the hydrogen compressors is therefore crucial for reducing the final cost of the liquefaction of hydrogen.
Dihydrogen exists naturally in two forms according to the number of spins of its two protons, orthohydrogen (“o-H2”) and parahydrogen (“p-H2”). The equilibrium composition of dihydrogen changes with the temperature, as shown in
In the case where dihydrogen has the role of refrigerant, the temperature of the refrigerant fluid varies across the refrigeration cycle and the composition changes slowly because of the natural conversion. In addition, although the volumetric properties of orthohydrogen and parahydrogen are similar, the calorimetric properties are substantially different. Therefore the natural exothermic conversion (orthohydrogen to parahydrogen) and the differences in physical properties between the two forms affect the performance levels of the refrigeration cycle and generate increased consumption at the level of the compressors of a closed refrigeration cycle. This effect is even more significant when the compression is performed at low temperature and/or the dihydrogen is stored at low temperature (e.g. in an intermediate storage).
For open hydrogen liquefaction cycles, such as, for example, the one described in U.S. Pat. No. 7,559,213, the composition of the dihydrogen when it is used as a refrigerant is directly dependent on the state of the conversion of the hydrogen flow to be liquefied and this composition does not vary over time. In effect, the hydrogen recycled in the cycle has a composition of 99% parahydrogen and is mixed in a fixed proportion over time with the dihydrogen to be liquefied whose composition is normal.
Some closed liquefaction cycles use dihydrogen as refrigerant. Beyond 184 K (−89° C.) the equilibrium composition varies little, and because of this the changes in the composition and its impact are largely negligible.
Recent developments have highlighted liquefaction cycles where the average temperature of the hydrogen used as a refrigerant is below 184 K (−89° C.). In “Advanced precooling for optimized hydrogen liquefaction”, H2Tech, March 2021, Howe, Skinner and Finn present a closed cycle compressing hydrogen at low temperature, i.e. at around 120 K (−153° C.). Patent application FR2105720 proposes a closed cycle where the hydrogen used as refrigerant does not exceed a temperature of 150 K (−123° C.). As a consequence, the hydrogen is subject to a slow conversion to a state different from normal hydrogen. In “Large scale hydrogen liquefaction in combination with LNG re-gasification”, 2006, Kuendig mentions that the refrigerant will comprise between 30% and 50% parahydrogen after a long period of operation without giving an order of magnitude.
For information, other uses of the conversion have been proposed in the literature, such as patent application FR2006278, which presents a system converting the parahydrogen of the boil-off gas coming from the storage of liquid hydrogen downstream from the liquefier so as to use the frigories generated to cool the throughput of hydrogen to be liquefied, or the publication “Enhanced dormancy due to para-to-ortho hydrogen conversion in insulated cryogenic pressure vessels for automotive applications” in which J. K. Peng uses the conversion of parahydrogen into orthohydrogen to slow the pressure rise of a storage of cryo-compressed hydrogen.
The open hydrogen liquefaction cycles solve the issue of the change in the composition of the hydrogen by means of the conversion step for the hydrogen to be liquefied. However, these cycles have low energy efficiency.
The literature proposes no solution for controlling the composition of the hydrogen refrigerant for a closed refrigeration cycle. As a result, the composition of the refrigerant changes slowly, which has unforeseen and undesirable effects on the heat exchanges and performance of the compression and expansion steps.
In addition, this change is heavily dependent on the methods considered, exterior conditions and load factor of the installation.
The present invention aims to remedy all or part of these drawbacks.
To this end, according to a first aspect, the present invention envisages a device according to claim 1.
Thanks to these provisions, the hydrogen liquefaction cycle controls the composition of the hydrogen used as refrigerant, for example by using at least one catalytic reactor in the refrigeration cycle set to a selected temperature, to optimise the properties of the refrigerant and reduce the energy consumption of the device by having an operating equilibrium composition that is different from the natural equilibrium composition.
These provisions make it possible to convert the normal hydrogen to a target composition during the initialisation of the refrigeration cycle and to counter the natural conversion taking place throughout the lifespan of the installation. Because of this, the physical properties of the refrigerant remain unchanged and the losses are reduced, preventing excessive energy consumption. In some optional embodiments, the closed refrigeration circuit is configured such that the dihydrogen refrigerant has, on input to the catalytic reactor, a temperature essentially equal to the average temperature of the dihydrogen refrigerant in the closed circuit.
These embodiments make it possible to minimise the thermal impact of the conversion from orthohydrogen to parahydrogen. In some optional embodiments, the catalytic reactor is positioned on a hot branch of the closed refrigeration circuit.
These embodiments make it possible to optimise the parahydrogen content by converting most of the hydrogen refrigerant during each passage in the reactor. These embodiments make it possible to minimise the thermal impact of the conversion if the conversion takes place on the hot branch instead of the cold branch that has the role of coolant.
In some optional embodiments, the catalytic reactor is configured to operate at a temperature between 31 K and 184 K. These embodiments enable an optimum energy efficiency of the device.
In some optional embodiments, the maintenance means is configured to maintain the proportion of parahydrogen in the internal composition of the dihydrogen refrigerant flow between 27% and 96%. These embodiments enable an optimum energy efficiency of the device.
In some optional embodiments, the maintenance means comprises a bypass of the catalytic reactor configured to operate a predefined throughput ratio between the flow passing through the reactor and the flow passing through the bypass. These embodiments enable a dynamic adjustment, proportional to the throughputs bypassed and passing through the reactor, of the composition of the dihydrogen.
In some optional embodiments, the closed dihydrogen refrigerant circuit is configured to maintain an average temperature of the dihydrogen refrigerant between 31 K and 184 K. These embodiments enable an optimum energy efficiency of the device.
In some optional embodiments, the device that is the subject of the present invention comprises a circuit for pre-cooling the gas to be liquefied, this pre-cooling circuit comprising a heat exchanger for exchanging heat between a pre-cooling fluid flow and the dihydrogen refrigerant flow. These embodiments enable an optimum energy efficiency of the device.
In some optional embodiments, the gas to be liquefied is a flow comprised essentially of dihydrogen.
In some optional embodiments, at least one catalytic reactor is integrated into a heat exchanger. Integrating the catalyser into a heat exchanger makes it possible to obtain a continuous conversion during the descent in temperature of the hydrogen to be liquefied, which reduces the overall energy consumption of the liquefaction method.
In addition, this catalytic exchanger for the dihydrogen refrigerant flow makes it possible to eliminate one catalytic reactor, which reduces the cost and complexity of the overall method.
In some optional embodiments, the closed refrigeration circuit comprises a stage of intercooling compression and at least one stage of compression at a temperature below −40° C. for the dihydrogen refrigerant. These provisions make it possible to limit the rise in temperature of the dihydrogen refrigerant and therefore to lower the average temperature in the cooling circuit.
In some optional embodiments, the catalytic reactor is positioned on a cold branch of the closed refrigeration circuit. These embodiments make it possible to lower the overall average temperature of the refrigerant flow in the closed conveyance circuit.
In some optional embodiments, the closed refrigeration circuit comprises at least one compressor of the dihydrogen refrigerant at ambient temperature and a storage tank for the liquid dihydrogen refrigerant.
In some optional embodiments, the catalytic reactor utilises a catalyser comprising a member of the iron oxides family, preferably Fe2O3.
According to a second aspect, the present invention envisages a method for liquefying a gas, which comprises:
The advantages of the method that is the subject of the present invention are similar to those of the device that is the subject of the present invention.
Other advantages, aims and particular features of the invention will become apparent from the non-limiting description that follows of at least one particular embodiment of the device and method that are the subjects of the present invention, with reference to drawings included in an appendix, wherein:
The present description is given in a non-limiting way, in which each characteristic of an embodiment can be combined with any other characteristic of any other embodiment in an advantageous way.
As can be seen from reading the present description, different inventive concepts can be implemented by one or more methods or devices described below, several examples of which are given here. The actions or steps carried out in the framework of realising the method or device can be ordered in any appropriate way. As a consequence, it is possible to construct embodiments in which the actions or steps are carried out in a different order from the one shown, which can include executing some acts simultaneously, even if they are presented as sequential acts in the embodiments shown.
The indefinite articles “one” or “a”, as used in the description and in the claims, must be understood as meaning “at least one”, except when the contrary is clearly indicated.
The expression “and/or”, as it is used in the present document and in the claims, must be understood as meaning “one or other, or both” of the elements thus connected, i.e. elements that are present conjunctively in some cases and disjunctively in other cases. The multiple elements listed with “and/or” must be interpreted in the same way, i.e. “one or more” of the elements thus connected. Other elements can possibly be present, other than the elements specifically identified by the clause “and/or”, whether or not they are linked to these specifically identified elements. Therefore, as a non-limiting example, a reference to “A and/or B”, when it is used in conjunction with open-ended language such as “comprising”, can refer, in one embodiment, to A only (possibly including elements other than B); in another embodiment, to B only (possibly including elements other than A); in yet another embodiment, to A and B (possibly including other elements); etc.
As used here in the description and in the claims, “or” must be understood as having the same meaning as “and/or” as defined above. For example, when separating elements in a list, “or” or “and/or” must be interpreted as being inclusive, i.e. the inclusion of at least one, but also of more than one, of a number or a list of elements, and, optionally, of additional elements not listed. Only the terms clearly indicating the contrary, such as “only one of” or “exactly one of”, or, when they are used in the claims, “consisting of”, refer to the inclusion of a single element of a number or a list of elements. In general, the term “or” as it is used here must only be interpreted as indicating exclusive alternatives (i.e. “one or the other, but not both”) when it is preceded by exclusivity terms, such as “either”, “one of”, “only one of”, or “exactly one of”.
As used here in the present description and in the claims, the expression “at least one”, in reference to a list of one or more elements, must be understood as meaning at least one element chosen from among one or more elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements and not excluding any combination of elements in the list of elements. This definition also allows the optional presence of elements other than the elements specifically identified in the list of elements to which the expression “at least one” refers, whether or not they are linked to these specifically identified elements. Therefore, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B” or, equivalently, “at least one of A and/or B”), can refer, in one embodiment, to at least one, possibly including more than one, A, with no B present (and possibly including elements other than B); in another embodiment, to at least one, possibly including more than one, B, with no A present (and possibly including elements other than A); in yet another embodiment, to at least one, possibly including more than one, A and at least one, possibly including more than one, B (and possibly including other elements); etc.
In the claims, and also in the description below, all the transitive expressions such as “comprising”, “including”, “bearing”, “having”, “containing”, “involving”, “made of”, “formed of” and others, must be understood as being open, i.e. meaning including, but not limited to. Only the transitive expressions “consisting of” and “consisting essentially of” must be understood as closed or semi-closed expressions, respectively.
Note that the figures are not to scale.
The gas 51 to be liquefied can be any type generally liquefied. Preferably, this gas 51 is dihydrogen.
The refrigerant flow is defined as comprising at least dihydrogen refrigerant. The proportion of dihydrogen refrigerant depends on the specific use of the present invention. In some variants, the proportion of dihydrogen refrigerant in the refrigerant flow is at least 30%. In some variants, the proportion of dihydrogen refrigerant in the refrigerant flow is at least 50%. In some variants, the proportion of dihydrogen refrigerant in the refrigerant flow is at least 70%. In some variants, the proportion of dihydrogen refrigerant in the refrigerant flow is at least 90%. In some variants, the proportion of dihydrogen refrigerant in the refrigerant flow is at least 99%. In the description that follows, the terms “refrigerant flow” and “dihydrogen refrigerant” are used interchangeably.
The dihydrogen refrigerant 52 can have the liquefied dihydrogen 51 as source or can come from a third source.
The term “hot branch” of a closed circuit refers to at least one portion of this circuit in which the temperature of the fluid conveyed decreases.
The term “cold branch” of a closed circuit refers to at least one portion of this circuit in which the temperature of the fluid conveyed increases.
The conveyance circuit 55 is, for example, formed of a set of pipes configured to convey the gas 51 to be liquefied, the gas 51 coming from a source (not shown) and being conveyed to a fixed or mobile storage 56. This conveyance circuit 55 is configured to convey the gas 51 through at least one heat exchanger, 201, 202, 203, 204, 205, 206, 207, 208 and/or 209. Each exchanger, 201, 202, 203, 204, 205, 206, 207, 208 and/or 209, can belong to a pre-cooling and/or cooling circuit. The number and arrangement of heat exchangers, 201, 202, 203, 204, 205, 206, 207, 208 and/or 209, are dependent upon the desired configuration for the device 200, desired specifications for the gas 51 on output from this device 200 and desired energy performance for the device 200.
In some embodiments, the gas 51 to be liquefied is dihydrogen in gaseous form, having a mass flow rate of 0.116 kg/s, a pressure of 21 bar and a temperature of 298 K.
The embodiments, 200, 300, 400, 500, 600, 700, 1100, shown in
The storage 56 can be a temporary storage for the separation of the boil-off gas and the liquefied gas 51.
As can be understood, for example, the feed flow is comprised of normal hydrogen (25% parahydrogen and 75% orthohydrogen) having a pressure of 21 bar, a temperature of 298 K (25° C.) and a mass flow rate of 0.116 kg/s. The flow 51 is first cooled to 83 K (−190° C.) by the action of two heat exchangers. This flow 51 next enters into a catalytic heat exchanger performing the first step of the ortho-para conversion. The flow 51 exits from the pre-cooling portion at a temperature of 80 K (−193° C.) and a composition formed of 49% parahydrogen.
In the cooling portion, the feed flow 51 reaches a temperature of 22 K (−251° C.) and a composition of 99% parahydrogen through a sequence of six catalytic heat exchanger in series. The final liquefaction step is performed with an expansion valve that lowers the pressure to 2 bars. The liquid portion of the flow (98%) exits from the device and the gaseous portion remaining is conveyed to an exhaust gas management system.
With regard to the embodiments shown in
Therefore, as can be understood, all or part of the heat exchangers are passed through by the closed refrigeration circuit 210. The refrigeration circuit 210 is, for example, formed of a set of pipes configured to convey the dihydrogen refrigerant 52. This conveyance circuit 210 is configured to convey the dihydrogen refrigerant 52 through at least one heat exchanger, 201, 202, 203, 204, 205, 206, 207, 208 and/or 209. The configuration of the refrigeration circuit 210 is dependent upon the desired energy performance for the device 200 and operating conditions specified for this device 200.
In some embodiments, the dihydrogen refrigerant 52 is configured to have a temperature between 171 K and 22 K, this dihydrogen refrigerant 52 being configured to cool the gas 51 to be liquefied.
In the embodiment of the device 200 shown in
In the embodiment of the device 300 shown in
In the embodiment of the device 400 shown in
In the embodiment of the device 500 shown in
In the embodiment of the device 700 shown in
In the embodiment of the device 800 shown in
In some embodiments of the device 800, such as that shown in
In some embodiments of the device 800, such as that shown in
In some preferred embodiments, such as those shown in
As can be understood, the closed circuit 210 comprises a means 215 for maintaining the internal composition of the dihydrogen. Such a maintenance means 215 comprises, for example, at least one catalytic reactor 220 configured to promote a predefined ratio of parahydrogen to orthohydrogen. This ratio is selected so as to be lower or higher than the same ratio in a state of natural equilibrium of a closed circuit 210 not comprising a maintenance means 215. The increase in the relative proportion of parahydrogen in the composition of the dihydrogen improves the performance of the dihydrogen in the heat exchanges taking place within the device 100.
In some particular embodiments 200, as shown in
In some particular embodiments 300, as shown in
In some particular embodiments 400, as shown in
In some particular embodiments 500, as shown in
In some particular embodiments 600, as shown in
The bypass 616 is, for example, a valve mounted on a pipe for which the inlet is located upstream from the reactor 620 and the outlet is located downstream from the reactor 620. This valve can be flow rate regulated to the flow rate passing through the reactor 620.
In some variants, the bypass 616 is associated with a control device, such as an automaton for example, configured to emit activation or de-activation commands to the bypass 616 as a function of activation criteria determined.
In some embodiments, such as that shown in
In some preferred embodiments, such as those shown in
Any heterogeneous catalyser having a paramagnetic activity, chemically compatible with the dihydrogen and physically compatible with cryogenic temperatures, can be utilised. One example of such a catalyser is the IONEX (Registered Trademark), i.e. a formula containing Fe2O3 of the iron oxides family. Another working example is, for example, the OXYSORB (Registered Trademark), i.e. a formula containing CrO4. A non exhaustive list of compatible catalysers known from the literature is given below:
In some preferred embodiments, the maintenance means, 215, 315, 415, 515, 615, 715 and/or 815, is configured to maintain the proportion of parahydrogen in the internal composition of the dihydrogen refrigerant flow between 27% and 96%.
As can be understood, for example, the cooling loop is a double-pressure loop, referred to as a “Claude” loop, and the refrigerant used is hydrogen. The refrigerant fluid 52 is first compressed to 29 bars by a multi-stage compressor 213. The temperature of the fluid 52 on output from the compressor 213 is approximately 171 K (−102° C.). The fluid 52 is cooled to 80 K (−193° C.) with two heat exchangers, 202 and 203, by exchange with a pre-cooling fluid, such as nitrogen for example. The fluid 52 next enters into a cooling section and is cooled to 69 K (−204° C.) in the first cooling heat exchanger 204. The hydrogen flow 52 passes through a catalytic conversion reactor 220 where the hydrogen reaches an equilibrium composition for the operating temperature considered.
In this case, the hydrogen is, for example, composed of 58% parahydrogen and 42% orthohydrogen. The hydrogen is therefore slightly heated between 0.1 K and 0.5 K in steady rate mode. The refrigerant is then separated, 89% of the total throughput is expanded, by an expander 214, to 18.5 bars and reaches 60 K (−213° C.). The flow 52 is then cooled to 51 K (−222° C.) in a heat exchanger 206, then expanded with a two-stage expander 216 to 4.5 bars to reach 31.5 K (−241.5° C.). From this point, the flow 52 is used as refrigerant in the cooling heat exchangers, 207, 206, 205 and 204. The remaining portion (11%) is cooled to 26 K through four heat exchangers, 205, 206, 207 and 208. This portion is then expanded with an expansion valve 211 to 1.5 bar to reach 22 K. The liquid refrigerant cools the feed flow to 22 K in two biphasic heat exchangers, 209 and 208, and four multi-flow heat exchangers, 207, 206, 205 and 204. The two refrigerant flows, at 4.5 and 1.5 bars, exit from the cooling section at 78 K (−195° C.). The low pressure flow is compressed to 4.5 in a first compressor 212. The flow from the first compressor 212 is then mixed with the medium pressure flow before entering the second compressor 213.
In some preferred embodiments, the closed refrigeration circuit, 210, 310, 410, 510, 610, 710 and/or 810, is configured such that the dihydrogen refrigerant flow 52 has, on input to the catalytic reactor, 220, 320, 420, 520, 620, 720 and/or 820, a temperature essentially equal to the average temperature of the dihydrogen refrigerant 52 in the closed circuit, 210, 310, 410, 510, 610, 710 and/or 810.
In some preferred embodiments, such as those shown in
In some embodiments, the pre-cooling circuit 54 is configured to convey nitrogen having a temperature between 298 K and 80 K. The purpose of such a pre-cooling circuit 54 is to cool the gas 51 to be liquefied and the dihydrogen refrigerant from 90 K to 80 K.
In the embodiments of the device 200, 300, 400, 500 and/or 600 shown in
In a particular embodiment of the device 700 shown in
In a particular embodiment of the device 800 shown in
As can be understood, for example, the pre-cooling from 300 K (27° C.) to 80 K (−193° C.) is performed by a closed nitrogen loop. The nitrogen is first compressed from 1 bar to 50 bars by a multi-stage compressor 57. This nitrogen is then cooled to 200 K (−73° C.) in a heat exchanger 201. The nitrogen is then separated, 97% of the total throughput is expanded to 1.1 bar in an expander 59 and reaches 81 K (−192° C.). This nitrogen returns in the form of coolant in the first pre-cooling heat exchanger 201. The remaining portion (3%) is cooled to 83 K (−190° C.). This portion is then partially liquefied by an expansion valve 56, reaching 78 K (−195° C.), and operates in the third heat exchanger 203 as main coolant. The remaining cold power of the nitrogen is used in the pre-cooling heat exchangers, 202 and 201.
Embodiment of the steps of this method 1000 are described with reference to
As can be understood, a particular composition of the dihydrogen refrigerant that is the subject of the present invention comprises 58% parahydrogen and 42% orthohydrogen, this composition not being the natural equilibrium composition. This is a compromise to obtain the best match of the thermal properties of the gas, both during its compression and in its role as coolant.
In fact, the main effect of the increase in the parahydrogen content is to induce an increase in the thermal calorific capacity of the hydrogen. The result of this is to increase the energy to be supplied or dissipated for modifying its temperature. In compression, this has the effect of reducing the temperature increase between the inlet and the outlet, the density of the hydrogen thus declining accordingly. However, the denser a gas, the easier it is to compress it. The compression power of the hydrogen therefore reduces correspondingly as the latter is compressed in a form converted most into parahydrogen.
As can be understood, the present invention provides high operating performance under the following operating conditions, with regard to the device 200 shown in
In the embodiment of the device 300 shown in
In another embodiment of the device 400, as shown in
In another embodiment of the device 500, as shown in
In another embodiment of the device 600, as shown in
In another embodiment of the device 700, as shown in
In another embodiment of the device 800, as shown in
The present invention is particularly suited to the case of liquid hydrogen production greater than five tonnes a day, because the reduced investment requirement and the stability of the method in operation enable savings in the final cost of the liquefaction of hydrogen.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2114197 | Dec 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/087325 | 12/21/2022 | WO |
