Hydrogen centrifugal compressor system with improved pressure ratio through water injection and its operational method.

Abstract

A compressor system to compress a gas, like hydrogen. The compressor system comprises a multistage compressor, having a plurality of compressing stages for increasing the pressure of a gas flow path. The compressor system comprises an injection unit, with a plurality of nozzles for injecting a cooling fluid, such as water, into the gas flow path.

Description

1 / 12 Hydrogen centrifugal compressor system with improved pressure ratio through water injection and its operational method. DESCRIPTION TECHNICAL FIELD

[0001] The present disclosure relates to a hydrogen compressor plant having a multi-stage hydrogen compressor, which is typically used for energy storage and transportation systems. The present disclosure also relates to the method of operation of such a multi-stage hydrogen compressor. FUNDAMENTALS OF THE TECHNIQUE

[0002] Hydrogen compression is a process that consumes a lot of energy and is carried out through several multi-stage compression trains operating at high speed. In the energy or process sector, hydrogen is typically obtained, for example, by electrolysis.

[0003] In the energy or process sector, a fluid is generally compressed by compressors. For example, natural gas is a typical fluid that is compressed. Compressors can be axial or centrifugal, or a combination of both, and can have a compression ratio on the order of 2 or 3.

[0004] Currently, multi-stage hydrogen compressors are increasingly used for energy storage and therefore improvements in the technology aimed at increasing the pressure ratio would be welcome.

[0005] Furthermore, the polytropic load (or energy per unit mass of gas) required to compress a gas to a certain pressure ratio is inversely proportional to the molecular weight. Thus, for hydrogen compression, the energy required for compression is high when compared to any other gas, such as natural gas or similar. In fact, hydrogen at standard temperature and pressure has extremely low density and therefore large volume. Therefore, to process hydrogen for Petition 870250068080, dated 04 / 08 / 2025, page 14 / 128 2 / 12 For transport or storage, several compressor trains are generally required. This demands a large installation area and high capital expenditure, given the low molecular weight. SUMMARY

[0006] In one aspect, the matter disclosed herein relates to a compressor system for compressing a gas, such as hydrogen and the like. The system comprises a multi-stage compressor, which has one or more compression stages capable of increasing the pressure of a gas flow path. The system also comprises an injection unit, having an injection conduit for injecting a fluid and one or more nozzles, in fluid and dynamic connection with the injection conduit, for injecting the fluid into the gas flow path. The fluid has a temperature lower than the temperature of the gas flow, so that when the fluid is injected into the gas flow and comes into contact with the gas flow, the fluid vaporizes causing an increase in the molecular weight of the gas. The fluid has a temperature equal to or lower than ambient temperature. The gas may be hydrogen and the fluid may be water.

[0007] In another aspect, the matter disclosed here relates to a compression stage which may comprise an impeller, a diffuser connected to the impeller, a U-bend connected to the diffuser, a return channel connected to the U-bend. The compression stage also has a fluid inlet obtained from the diffuser or the U-bend. Each nozzle is disposed of a respective fluid inlet. Furthermore, the compressor may comprise a plurality of compression stages arranged in series, a gas inlet through which the gas enters the compressor, a gas outlet through which the gas exits after compression, and a rotating drive shaft to which the impellers are keyed for compressing the gas.

[0008] In another aspect, a cooler is revealed here that may have an inlet conduit connected to the gas outlet, an outlet conduit through which the saturated vaporized fluid is transported, and a second outlet conduit through which the fluid condensate is extracted. Petition 870250068080, dated 04 / 08 / 2025, p. 15 / 128 3 / 12

[0009] In another aspect, a multi-stage compressor is disclosed here, which may comprise an outer casing and an inner casing, which is molded to contain the compression stages. A distribution channel may be obtained in said inner casing, the distribution channel being in dynamic fluid connection with the injection conduit and nozzles. The distribution channel may be formed of a first part and a second part. The first part may have a rectangular cross-section and the second part has a rectangular cross-section, smaller than the first part. A plurality of nozzles may also be installed in each distribution channel.

[0010] In another aspect, the matter revealed here concerns nozzles that can have an increasing flow rate if they are further away from the nozzle, closer to the connection point of the injection conduit with the distribution channel; in other words, the nozzle flow rate increases as the distance between the nozzle and the point where the injection conduit makes fluid connection with the distribution channel increases. The distribution channel may have a variable cavity / cross-section.

[0011] In another aspect, an injection unit is revealed here which may comprise a plurality of electrically controlled valves, each connected to a respective nozzle via a respective tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A fuller understanding of the disclosed embodiments of the invention and of many of the advantages associated therewith will be readily obtained as a better understanding is gained by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein: Figure 1 illustrates a water injection scheme in a hydrogen compressor according to a first embodiment of a compressor system; Figure 2 illustrates a cross-sectional view of a compression stage, according to the first embodiment; Petition 870250068080, dated 04 / 08 / 2025, page 16 / 128 4 / 12 Figure 3 illustrates a longitudinal section of the compression stage of Figure 2; Figure 4 illustrates a perspective view of a longitudinal section of the compression stage of Figure 2; Figure 5 illustrates a graph showing the effect of water injection on the performance curves of a hydrogen compressor; Figure 6 illustrates a graph showing the energy consumption of the compressor system as a function of flow; Figure 7 illustrates a graph showing the compressor system pressure ratio as a function of flow; Figure 8 illustrates a second embodiment of the multi-stage centrifugal hydrogen compressor system with a cavity of variable area to ensure uniform water injection pressure; Figure 9 illustrates a third embodiment of the multi-stage centrifugal hydrogen compressor system with ports with increasing areas to ensure release at a uniform pressure; Figure 10 illustrates a fourth embodiment of the multi-stage centrifugal hydrogen compressor system with equivalent pressure losses in the piping for injecting at uniform pressures; and Figure 11 illustrates a fifth embodiment of the multi-stage centrifugal hydrogen compressor system. DETAILED DESCRIPTION OF THE MODALITIES

[0013] Compressors are well-known machines used to compress gases. In particular, compressors can be used to compress hydrogen gas. In fact, compressed gas is generally used for energy storage and energy transport. For this purpose, several compressor trains are needed, occupying large areas as well as incurring high maintenance and operating costs. From one perspective, the present matter is directed towards improving the compression process and its costs by reducing the number of stages in the compressor itself. This is achieved by spraying and injecting water. Petition 870250068080, dated 04 / 08 / 2025, page 17 / 128 5 / 12 continuously in all phases, until saturation is reached. In this way, the molecular weight of hydrogen is increased through the vaporized water introduced into the flow path, causing a reduction in energy consumption.

[0014] With reference now to the drawings, Figures 1, 2, 3 and 4 show a schematic view of a first embodiment of the multi-stage centrifugal hydrogen compressor system 1.

[0015] Specifically, the multi-stage hydrogen centrifugal compressor system 1 comprises a compressor 2, an injection unit 3 and a cooler 4.

[0016] The compressor 2 comprises a plurality of compression stages 21, arranged in series, or in cascade, a gas inlet 22, through which the gas enters along arrow A, a gas outlet 23, through which the gas exits along arrow B, a rotating drive shaft 24 and a stator or diaphragm 25. The compression stages 21 are contained in a housing 26, which comprises an outer housing 261, to protect the entire compressor 2, and an inner housing 262, which is molded internally to contain the stages 21 and their respective parts.

[0017] Each compression stage 21 comprises an impeller 211, fixed by key to the rotating drive shaft 24, a diffuser 212, provided on the downstream side of the impeller 211, a U-bend 213, provided on the downstream side of the diffuser 212, and a return channel 214, downstream of the U-bend 213. The compression stages 21 have the function of increasing the speed and then the pressure of the injected gas, thanks to the impeller 211, and the specific shapes of the diffuser 212 and the U-bend 213. Each stage 21 increases the pressure of the injected gas introduced through the gas inlet 22, the gas in this embodiment being hydrogen.

[0018] In addition, for each compression stage 21, there is one or more fluid or water inlets 27 connected to a respective water injection conduit 31 of the injection unit 3, as described in more detail below. Associated with each of the water inlets 27, a Petition 870250068080, dated 04 / 08 / 2025, page 18 / 128 6 / 12 respective nozzle 33, which is then arranged in correspondence with the U-bend 213 or the diffuser 212. Specifically, each nozzle 33 is arranged to atomize water in the gas flow path as it passes through the U-bend 213 or the diffuser 212. The water inlets 27 are connected to the U-bend 213 of each compression stage 21.

[0019] The discharge fluid exiting compressor 23 passes through a cooler 4, which assists in the condensation of water into liquid form. This is separated in the separator, which is a filtering centrifuge capable of separating liquids from gases in a gas-liquid mixture.

[0020] The injection unit 3 comprises a control system 32 for controlling the amount of water injected to the required pressure ratio. The control system 32 may be, for example, a computer or programmable logic controller that may operate autonomously or may be controlled by a central logic unit (not shown in the figure) or a remote computer, to control the multi-stage hydrogen centrifugal compressor system 1.

[0021] Also, the injection unit 3 comprises a plurality or a manifold of injection ducts 31, each connected to a respective water inlet 27 of the compressor 2 through a nozzle 33.

[0022] The injection unit 3 has the function of controlling the water supply at each compression stage 21 of the compressor 2. The water supply can be uniform, i.e., the amount of water passing through each injection conduit 31 can be equal, or it can be differentiated, depending on the needs. In this case, the water passing through each injection conduit 31 can be adjusted by the control system 32 using appropriate flow control devices, such as pumps and the like.

[0023] With particular reference now to Figure 4, in the inner housing 262, corresponding to each compression stage 21, a distribution channel 29 is obtained and machined. Specifically, for each compression stage 21, there is a corresponding distribution channel 29, which is circumferential and has a toroidal shape. In the illustrated embodiment, the channel of Petition 870250068080, dated 04 / 08 / 2025, page 19 / 128 7 / 12 distribution 29 is arranged side by side with the U-shaped curve 213 of each compression stage 21.

[0024] Each of the distribution channels 29 is fluid dynamically connected to at least one respective water injection conduit 31. Specifically, in the embodiment shown, each distribution channel 29 is in dynamic fluid connection with a U-bend 213 and with a respective water injection conduit 31, as through the injection unit 3, it is possible to inject or spray water into a distribution channel 29 through the nozzles 33 connected to it.

[0025] Furthermore, in the embodiment shown, each distribution channel 29 has a cross-section ideally formed by two connected parts, a first part 291 and a second part 292. The first part 291 is rectangular, as is the second part 292. In addition, in the present embodiment, the first part 291 is larger than the second part 292, to better fit the available space near the U-shaped curve 28.

[0026] In other embodiments, the distribution channel 29 may have different cross-sectional shapes, for example, a circular or square cross-sectional shape.

[0027] The cooler 4 comprises an inlet conduit 41, connected to the gas outlet 23 of the compressor 2, from where the saturated gas comes, a second outlet conduit 43, to extract the condensate from the cooling operation, and an outlet conduit 42, which carries the saturated water vapor, as explained in more detail below. The cooler 4 cools the compressed gas to below its dew point, to allow the removal of moisture and water vapor. The cooler 4 can generally be of the type normally used in the oil and gas industry, for example.

[0028] The operation of the multi-stage hydrogen centrifugal compressor system 1 is as follows.

[0029] When the multi-stage centrifugal hydrogen compressor system 1 operates, compressing hydrogen gas through each stage by means of impellers 211, water is continuously injected into each Petition 870250068080, dated 04 / 08 / 2025, page 20 / 128 8 / 12 compression stage 21 through water injection conduits 31 and through water inlets 27. The water is then atomized in the U-bend 213 by nozzles 33, in each compression stage 21, until saturation is reached. The water absorbs heat from the process gas (hydrogen), simultaneously vaporizing and cooling the process gas. The water then vaporizes due to the temperature shock caused by coming into contact with the hot gas flow path. At the same time, the water increases the molecular weight of the gas, improving the gas compression process (which is hydrogen in this embodiment).

[0030] This reduces the required head for each stage and improves compression energy consumption compared to pure hydrogen compression. The power absorbed by a centrifugal compressor is a product of the head and efficiency (see general compressor literature). The head varies inversely with molecular weight. Thus, increasing the molecular weight has the impact of lowering the head and thus the power. The amount of water injected in each compression stage 21 is controlled by the control system 32 of the injection unit 3. After the gas compression operation by compressor 2, the excess water is removed by cooler 4.

[0031] Specifically, the fluid is injected into the gas path to increase the molecular weight, since it is immediately vaporized upon injection, as the fluid temperature is typically at or below ambient temperature, therefore lower than the gas temperature. This causes the fluid to vaporize. Vapor has its own density, and so does gas, i.e., hydrogen, so the density of the mixture is higher than that of the gas (hydrogen) alone.

[0032] Typically, the relative humidity of the gas is less than 100%. In addition, the temperature of the gas stream will typically be high enough to vaporize the fluid immediately upon contact.

[0033] Erosion, possibly caused by the fluid, which is usually water, is prevented by a coating. Instead, possible corrosion, still Petition 870250068080, dated 04 / 08 / 2025, page 21 / 128 9 / 12 possibly caused by the fluid, is avoided by proper material selection, such as erosion-resistant stainless steel, or by adapting the impeller shape at the inlet to minimize erosion.

[0034] With reference now to Figure 5, a pressure / flow diagram is plotted to show the performance of the multi-stage hydrogen centrifugal compressor system 1 with and without water injection. In particular, it can be recognized that with water injection, even with high flow rates of approximately 1.8 x 10⁵ m³ / h, the total gas pressure is approximately 4 bar.

[0035] Furthermore, Figures 6 and 7 show two diagrams, illustrating that for the same mass flow rate and pressure, energy consumption is lower when water (H2O) is injected into the gas flow path (which is water, H2).

[0036] Specifically, the graph in Figure 6 shows the flow on the abscissa axis, represented in a dimensionless way, while the energy consumption is represented on the ordinate axis (again in a non-dimensional parameterization). Instead, with reference to the graph in Figure 7, the flow is represented on the abscissa axis (in a non-dimensional parameterization), while the pressure ratio is represented on the ordinate axis (in a non-dimensional parameterization). As can be seen, with an increase in flow, when water is injected into the gas flow, the energy consumption is reduced, as is the pressure ratio, which at a certain limit is lower than in the case of no water being injected.

[0037] The molecular weight of the process gas (hydrogen or H2) is temporarily increased by mixing it with water vapor. A fine atomized spray of water is introduced into the gas compression path, which is vaporized after introduction, thus cooling the gas and increasing the molecular weight of the gas mixture. This effect reduces the polytropic load required for compression and thus requires fewer stages and less energy to compress the same amount of hydrogen gas.

[0038] The molecular weight of the gas is temporarily increased because water can be removed until saturation is reached downstream of the Petition 870250068080, dated 04 / 08 / 2025, page 22 / 128 10 / 12 cooler 4, which is located downstream of compressor 2. As explained earlier, downstream of the compressor, the cooler and separator are present, which helps to achieve the desired effect mentioned above.

[0039] After that, cooler 4 cools the gas, the hydrogen with saturated water vapor is transported through the first outlet duct 42, while the condensate is extracted through a second outlet duct 43.

[0040] With reference to Figures 8, 9, 10 and 11, additional embodiments of the distribution channel 5 are shown. In general, cooling injection is done only at one or two locations or ports along the 360 ​​degrees of the compressor 2. The efficiency of droplet-to-vapor conversion can be improved by injecting at multiple locations (6 to 8) distributed along the 360 ​​degrees of the diaphragm.

[0041] Specifically, with reference to a second embodiment illustrated in Figure 8, the toroidal distribution channel 29 has a variable cavity / cross-section to ensure uniform water injection pressure. This is due to the variable resistance offered by the toroidal cavity to fluid flow at various circumferential positions in the cavity.

[0042] With reference to Figure 9, a third embodiment of the multi-stage centrifugal hydrogen compressor system 1 is shown, where, to ensure the uniform release of water into the distribution channel 29, the nozzles 33 have different flow rates. Specifically, the water to be introduced into the distribution channel 29 is supplied through the water injection conduit 31 and the respective water inlet 27. Therefore, the water pressure for the nozzles 33 closest to the water inlet 27 is higher than that for those further away. This difference would cause a non-uniform distribution of water in different parts of the distribution channel 29 and, therefore, a non-uniform saturation of the gas. The flow rate of each nozzle 33 is then higher if they are further away from the water inlet 27. In this way, the lower water pressure for the nozzles 33 that are further away from the water injection conduit 31 is compensated for. Petition 870250068080, dated 04 / 08 / 2025, page 23 / 128 11 / 12

[0043] Therefore, still referring to Figure 9, the flow rate of the nozzle 33 placed diametrically opposite the one closest to the water inlet 27, which, as mentioned, is connected to the water injection conduit 31 through which the injection unit 3 supplies water.

[0044] With reference to Figure 10, a fourth embodiment of the multi-stage centrifugal hydrogen compressor system 1 is shown, in which equivalent pressure losses are included to allow injection at uniform pressure. The individual tubes are aligned so as to provide varying resistance to flow. The alignment of the tubes varies with respect to the direction of fluid flow. The closer to the upper region, the more inclined the tube is with respect to the direction of flow. The minimum angle is 90 degrees, which is at the bottom, and in the circumferential progression upwards, the angles of the respective tubes increase. In this case, there is no distribution channel 29; instead, an injection tube connects the water injection conduit 31 to a respective nozzle 33.

[0045] Figure 10 shows an external passage functioning in the same way as the distribution channel 29, which is designed to release fluid (in this case, water) at uniform pressure throughout the 360 ​​degrees. At the point closest to the water injection conduit 31, the pipe resistance would be maximum and at the furthest point, the resistance would be minimum, thus ensuring uniform pressure at all injection nozzles.

[0046] Furthermore, with reference to Figure 11, a fifth embodiment of the multi-stage centrifugal hydrogen compressor system 1 is illustrated, wherein the injection unit 3 comprises a plurality of electrically controlled valves 34, each connected to a respective nozzle 33 via a tube 311. In this way, it is possible to adjust the pressure at each nozzle 33. Specifically, each electrical valve 34 can be individually controlled by the control system 32 of the injection unit 3.

[0047] Nozzles 33 can be fixed or retractable. Fixed nozzles are easier to design. However, there is a possibility that the flushing nozzles may become clogged when not in use. Petition 870250068080, dated 04 / 08 / 2025, page 24 / 128 12 / 12

[0048] Retractable nozzles 33 can be inserted / retracted as needed. One advantage of retractable nozzles 33 is that they can be replaced without stopping compressor 2. The operation of retractable nozzles 33 can be manual or automated.

[0049] Although aspects of the invention have been described in terms of several specific embodiments, it will be evident to those of common skill in the art that many modifications, alterations, and omissions are possible without departing from the spirit and scope of the claims. Furthermore, unless otherwise specified in this invention, the order or sequence of any process or method steps may be varied or resequenced in accordance with alternative embodiments.

[0050] Detailed references have been made herein to the modalities of the revelation, in which one or more examples of which are illustrated in the drawings. Each example is given by way of explanation of the revelation, not as a limitation of the revelation. Indeed, it will be evident to those skilled in the art that various modifications and variations may be made to the present revelation without departing from the scope or spirit of the revelation. The reference throughout the descriptive report to a (1) modality or a modality or some modalities means that the particular feature, structure or characteristic described in connection with a modality is included in at least one modality of the revealed matter. Thus, the appearance of the phrase in a modality or in some modalities in several places throughout the descriptive report is not necessarily referring to the same modality(ies).Furthermore, specific resources, structures, or characteristics can be combined in any suitable way in one or more modalities.

[0051] When elements of various modalities are introduced, the articles a, an, the, and the terms the said and the said are intended to signify that there is one or more of the elements. The terms include, include, and have are intended to be inclusive and mean that there may be additional elements besides the elements mentioned. Petition 870250068080, dated 04 / 08 / 2025, p. 25 / 128

Claims

1 / 3 CLAIMS 1. Compressor system (1) for performing the compression of a gas, such as hydrogen and the like, comprising: a multi-stage compressor (2), having one or more compression stages (21) capable of increasing the pressure of a gas flow path, characterized in that the compressor system (1) further comprises an injection unit (3), having: at least one injection conduit (31) for injecting a fluid, and one or more nozzles (33), each nozzle being in dynamic fluid connection with a respective injection conduit (31), for injecting the fluid into the gas flow path.

2. Compressor system (1), according to claim 1, characterized in that the fluid has a temperature lower than the temperature of the gas stream, so that when the fluid is injected into the gas stream, the fluid vaporizes in contact with the gas stream causing an increase in the molecular weight of the gas.

3. Compressor system (1), according to claim 2, characterized in that the fluid has a temperature equal to or lower than ambient temperature.

4. Compressor system (1), according to any of the preceding claims, characterized in that each compression stage (21) comprises: an impeller (211); a diffuser (212) connected to the impeller (211); a U-bend (213) connected to the diffuser (212); and a return channel (214) connected to the U-bend (213); wherein at least one fluid inlet (27) is obtained at the diffuser (212) or at the U-bend (213), and Petition 870250068080, dated 04 / 08 / 2025, page 26 / 128 2 / 3 wherein each nozzle (33) is disposed at a respective fluid inlet (27).

5. Compressor system (1), according to claim 4, characterized in that the multistage compressor (2) comprises: a plurality of compression stages (21), arranged in series, a gas inlet (22), through which the gas enters the multistage compressor (2), a gas outlet (23), through which the gas exits after compression, and a rotating drive shaft (24), to which the impellers (211) are keyed, for compressing the gas.

6. Compressor system (1), according to claim 5, characterized by comprising a cooler (4), having an inlet conduit (41) connected to the gas outlet (23) of the multi-stage compressor (2), an outlet conduit (42), through which the saturated vaporized fluid is transported, and a second outlet conduit (43), through which the fluid condensate is extracted.

7. Compressor system (1), according to any one of claims 5 to 6, characterized in that the multi-stage compressor (2) comprises: an outer casing (261), and an inner casing (262), which is molded to contain the compression stages (21); wherein a distribution channel (29) is obtained in said inner casing (262), wherein the distribution channel (29) is in dynamic fluid connection with the injection conduit (31), at a connection point, and with one or more nozzles (33). Petition 870250068080, dated 04 / 08 / 2025, page 27 / 128 3 / 3 8. Compressor system (1), according to claim 7, characterized in that the distribution channel (29) is formed by a first part (291) and a second part (292).

9. Compressor system (1), according to claim 8, characterized in that the first part (291) has a rectangular cross-section and the second part (292) has a rectangular cross-section, smaller than the first part (291).

10. Compressor system (1), according to any one of claims 7 to 9, characterized in that one or more nozzles (33) are installed in the distribution channel (29).

11. Compressor system (1), according to claim 10, characterized in that the flow rate of one or more nozzles (33) increases as the distance between the one or more nozzles and the connection point where the distribution channel (29) is in dynamic fluid connection with the injection conduit (31) increases.

12. Compressor system (1), according to any one of claims 5 to 9, characterized in that the distribution channel (29) has a variable cavity / cross-section.

13. Compressor system (1), according to any one of claims 1 to 6, characterized in that the injection unit (3) comprises a plurality of electrically controlled valves (34), each connected to a respective nozzle (33) through a respective tube (311).

14. Compressor system (1), according to any of the preceding claims, characterized in that the gas is hydrogen, and the fluid is water. Petition 870250068080, dated 04 / 08 / 2025, page 28 / 128

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