Hydrogen centrifugal compressor system with increased pressure ratio by water injection and method of operation thereof

Abstract

A compressor system for compressing a gas, such as hydrogen. The compressor system includes a multi-stage compressor having a plurality of compression stages for increasing the pressure of the gas flow path. The compressor system includes an injection unit with a plurality of nozzles for injecting a cooling fluid, such as water, into a gas flow path.

Description

[0001] manual Technical Field

[0002] The present disclosure relates to a hydrogen compressor apparatus having a multi-stage hydrogen compressor, which is typically used in energy storage systems and transportation. The present disclosure also relates to a method of operating such a multi-stage hydrogen compressor. Background Art

[0003] Hydrogen compression is an energy-intensive process and is achieved by multiple compressor stages operating at high speeds. In the energy or process industries, hydrogen is often obtained, for example, by electrolysis.

[0004] In the energy and process industries, fluids are typically compressed using a compressor. For example, natural gas is a typical fluid that is compressed. Compressors can be axial or centrifugal, or a combination thereof, and have compression ratios on the order of 2 or 3.

[0005] Multi-stage hydrogen compressors are increasingly used for energy storage, so improvements aimed at increasing the pressure ratio would be welcome in terms of technology.

[0006] Furthermore, the polytropic head (or energy per unit mass of gas) required to compress a gas to a specific pressure ratio is inversely proportional to its molecular weight. Therefore, the energy required to compress hydrogen is significantly higher than for any other gas, such as natural gas. Indeed, hydrogen at standard temperature and pressure has an extremely low density and, therefore, a large volume. Consequently, processing hydrogen for transport or storage typically requires multiple compressor trains. Given its low molecular weight, this requires significant floor space and capital expenditure. Summary of the Invention

[0007] In one aspect, the subject matter disclosed herein relates to a compressor system for compressing a gas such as hydrogen. The system includes a multi-stage compressor having one or more compression stages capable of increasing the pressure of a gas flow path. The system also includes an injection unit having an injection conduit for injecting a fluid, and one or more nozzles fluidically connected to the injection conduit for injecting the fluid into the gas flow path. The temperature of the fluid is lower than the temperature of the gas flow, such that when the fluid is injected into the gas flow and contacts the gas flow, the fluid vaporizes, causing the molecular weight of the gas to increase. The fluid has a temperature equal to or lower than ambient temperature. The gas can be hydrogen and the fluid can be water.

[0008] In another aspect, the subject matter disclosed herein relates to a compression stage that may include an impeller, a diffuser connected to the impeller, a U-bend connected to the diffuser, and a return flow channel connected to the U-bend. The compression stage also has a fluid inlet obtained on the diffuser or on the U-bend. Each nozzle is arranged on a corresponding fluid inlet. In addition, the compressor may include a plurality of compression stages arranged in series, a gas inlet, a gas outlet, and a rotating shaft, wherein gas enters the compressor through the gas inlet, the gas exits through the gas outlet after being compressed, and the impeller is keyed to the rotating shaft to compress the gas.

[0009] In another aspect, disclosed herein is a cooler that can have an inlet conduit connected to a gas outlet, an outlet conduit through which saturated vaporized fluid is conveyed, and a second outlet conduit through which condensate of the fluid is extracted.

[0010] In another aspect, a multi-stage compressor is disclosed herein. The multi-stage compressor may include an outer housing and an inner housing shaped to house the compression stages. A distribution channel may be provided within the inner housing, wherein the distribution channel is fluidically connected to an injection conduit and to a nozzle. The distribution channel may be formed from a first portion and a second portion. The first portion may have a rectangular cross-section, and the second portion may have a smaller rectangular cross-section than the first portion. Multiple nozzles may also be mounted on each distribution channel.

[0011] In another aspect, the subject matter disclosed herein relates to a nozzle that can have an increased flow rate if the nozzle is further away from the nozzle than if it is closer to the connection point of the injection conduit and the distribution channel; in other words, the nozzle flow rate increases as the distance between the nozzle and the point where the injection conduit is fluidly connected to the distribution channel increases. The distribution channel can have a variable cavity / cross-section.

[0012] In another aspect, disclosed herein is an injection unit that may include a plurality of controlled electric valves, each electric valve being connected to a respective nozzle via a respective tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more complete appreciation thereof will be readily obtained as the disclosed embodiments of the present invention and many of its attendant advantages become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0014] Figure 1 A schematic diagram illustrating water injection in a hydrogen compressor according to a first embodiment of the compressor system;

[0015] Figure 2 illustrates a cross-sectional view of a compression stage according to a first embodiment;

[0016] Figure 3Illustrated Figure 2 The longitudinal section of the compression stage;

[0017] Figure 4 Illustrated Figure 2 a perspective view of a longitudinal section of a compression stage;

[0018] Figure 5 illustrates a graph showing the effect of water injection on the performance curve of a hydrogen compressor;

[0019] Figure 6 illustrates a graph showing power consumption of a compressor system as a function of flow rate;

[0020] Figure 7 illustrates a graph showing pressure ratio of a compressor system as a function of flow rate;

[0021] Figure 8 A second embodiment of a multi-stage hydrogen centrifugal compressor system is illustrated with a variable area cavity to ensure uniform pressure of the water injection;

[0022] Figure 9 A third embodiment of a multi-stage hydrogen centrifugal compressor system is illustrated with ports of increased area to ensure delivery at uniform pressure;

[0023] Figure 10 A fourth embodiment of a multi-stage hydrogen centrifugal compressor system is illustrated, wherein the tube losses generated by injection at uniform pressure are the same; and

[0024] Figure 11 A fifth embodiment of a multi-stage hydrogen centrifugal compressor system is illustrated. DETAILED DESCRIPTION

[0025] Compressors are well-known machines for compressing gas. In particular, they can be used to compress hydrogen. Compressed gas is often used for energy storage and transportation. This requires multiple compressor trains, which require significant floor space and are expensive to maintain and operate. According to one aspect, the present invention improves the compression process and reduces costs by reducing the number of compressor stages. This is achieved by continuously injecting water into each stage until saturation is reached. This increases the molecular weight of the hydrogen through the introduction of vaporized water into the flow path, reducing power consumption.

[0026] Referring now to the accompanying drawings, Figure 1 、 Figure 2 、 Figure 3 and Figure 4 A schematic diagram of a first embodiment of a multi-stage hydrogen centrifugal compressor system 1 is shown.

[0027] Specifically, the multi-stage hydrogen centrifugal compressor system 1 includes a compressor 2 , an injection unit 3 and a cooler 4 .

[0028] The compressor 2 includes a plurality of compression stages 21 arranged in series or in cascade, a gas inlet 22 through which gas enters along arrow A, a gas outlet 23 through which gas exits along arrow B, a rotating shaft 24, and a stator or diaphragm 25. The compression stages 21 are housed in a casing 26, which includes an outer casing 261 that protects the entire compressor 2 and an inner casing 262 that is internally shaped to accommodate the stages 21 and corresponding parts.

[0029] Each compression stage 21 includes an impeller 211 keyed to the rotating shaft 24, a diffuser 212 disposed downstream of the impeller 211, a U-bend 213 disposed downstream of the diffuser 212, and a return passage 214 downstream of the U-bend 213. Thanks to the specific shapes of the impeller 211, diffuser 212, and U-bend 213, the compression stages 21 function to increase the velocity of the injected gas and thereby increase its pressure. Each stage 21 increases the pressure of the injected gas introduced through the gas inlet 22, wherein, in this embodiment, the gas is hydrogen.

[0030] Furthermore, for each compression stage 21, there are one or more fluid inlets or water inlets 27 connected to respective water injection conduits 31 of the injection unit 3, as better described below. Associated with each water inlet 27 is a respective nozzle 33, which is then arranged corresponding to the U-bend 213 or the diffuser 212. Specifically, each nozzle 33 is arranged to atomize water into the gas flow path as it passes through the U-bend 213 or the diffuser 212. A water inlet 27 is connected to the U-bend 213 of each compression stage 21.

[0031] The discharge fluid from the compressor 23 passes through a cooler 4 which helps condense the water into a liquid. This is separated at a separator which is a filter centrifuge that is able to separate the liquid from the gas in the gas-liquid mixture.

[0032] The injection unit 3 includes a control system 32 for controlling the amount of water injected at a desired pressure ratio. The control system 32 may be, for example, a computer or programmable logic controller that can operate autonomously, or it may be controlled by a remote computer or central logic unit (not shown in the figure) to control the multi-stage hydrogen centrifugal compressor system 1.

[0033] Furthermore, the injection unit 3 comprises a plurality of injection ducts 31 or a manifold of injection ducts 31 , each of which is connected to a respective water inlet 27 of the compressor 2 via a nozzle 33 .

[0034] Injection unit 3 controls the flow of water into each compression stage 21 of compressor 2. The water can be supplied uniformly, meaning the amount of water flowing through each injection conduit 31 can be the same or different, depending on the requirements. In this case, the flow of water through each injection conduit 31 can be regulated by control system 32 using a suitable flow control device, such as a pump.

[0035] Now special reference Figure 4 In the inner housing 262, a distribution channel 29 is obtained and machined corresponding to each compression stage 21. Specifically, for each compression stage 21, there is a corresponding distribution channel 29, which is a circumferential channel and has an annular shape. In the illustrated embodiment, the distribution channel 29 is arranged in parallel with the U-shaped bend 213 of each compression stage 21.

[0036] Each distribution channel 29 is fluidically connected to at least one corresponding water injection conduit 31. Specifically, in the embodiment shown, each distribution channel 29 is fluidically connected to one U-shaped bend 213 and fluidically connected to one corresponding water injection conduit 31, such as by an injection unit 3, and water can be injected or sprayed into the distribution channel 29 through a nozzle 33 connected thereto.

[0037] Furthermore, in the embodiment shown, each distribution channel 29 has a cross-section that is ideally formed from two connected portions, a first portion 291 and a second portion 292. The first portion 291 is rectangular, as is the second portion 292. Furthermore, in this embodiment, the first portion 291 is larger than the second portion 292 to better accommodate the available space near the U-shaped bend 28.

[0038] In other embodiments, the distribution channel 29 may have a different cross-sectional shape, such as a circular cross-sectional shape or a square cross-sectional shape.

[0039] The cooler 4 comprises an inlet conduit 41 connected to the gas outlet 23 of the compressor 2, from which saturated gas exits, a second outlet conduit 43 for extracting condensate from the cooling operation, and an outlet conduit 42 for conveying saturated water vapor, as will be better explained below. The cooler 4 cools the compressed gas to below its dew point, thereby removing moisture and water vapor. The cooler 4 may be of a type commonly used, for example, in the oil and gas industry.

[0040] The operation of the multi-stage hydrogen centrifugal compressor system 1 is as follows.

[0041] When the multi-stage hydrogen centrifugal compressor system 1 is in operation, the hydrogen passing through each stage is compressed by the impeller 211, and water is continuously injected into each compression stage 21 through the water injection conduit 31 and through the water inlet 27. Then, at each compression stage 21, the water is atomized into the U-shaped bend 213 through the nozzle 33 until saturation is reached. The water absorbs heat from the process gas (hydrogen), thereby being vaporized and simultaneously cooling the process gas. The water then vaporizes due to the temperature shock caused by encountering the hot gas flow path. At the same time, the water increases the molecular weight of the gas, improving the compression process of the gas (in this embodiment, hydrogen).

[0042] This reduces the head pressure required for each stage and increases the compression power required to compress pure hydrogen. The power absorbed by a centrifugal compressor is the product of head pressure and efficiency (see general compressor literature). Head pressure varies inversely with molecular weight. Therefore, increasing molecular weight has the effect of reducing head pressure, thereby reducing power. The amount of water injected into each compression stage 21 is controlled by the control system 32 of the injection unit 3. After the compressor 2 compresses the gas, the excess water is removed by the cooler 4.

[0043] Specifically, when a fluid is injected into a gas path to increase molecular weight, the fluid vaporizes immediately upon injection because the fluid temperature is typically at ambient temperature or lower, and thus lower than the gas temperature. This causes the fluid to evaporate. The vapor has its own density, and the gas (i.e., hydrogen) also has its own density, resulting in a mixture with a density only higher than the density of the gas (hydrogen).

[0044] Typically, the relative humidity of the gas is less than 100%. In addition, the temperature of the gas stream is usually high enough to vaporize the fluid immediately upon contact.

[0045] Corrosion that may be caused by the fluid (usually water) is avoided by coating. Alternatively, corrosion that may still be caused by the fluid is minimized by appropriate choice of materials such as corrosion-resistant stainless steel or by adapting the shape of the impeller at the inlet.

[0046] Now refer to Figure 5 , a pressure / flow diagram is drawn to illustrate the performance of the multi-stage hydrogen centrifugal compressor system 1 with and without water injection. Specifically, it can be understood that when water injection is performed and at about 1.8×10 5 m 3 At high flow rates of h, the total gas pressure is approximately 4 bar.

[0047] and, Figure 6 and Figure 7 Two graphs are shown illustrating that at the same mass flow and pressure ratio, power consumption is lower when water (H2O) is injected into the gas flow path (which is water, H2).

[0048] Specifically, Figure 6 The horizontal axis of the graph in represents the dimensionless parameterized flow rate, while the vertical axis represents the power consumption (also dimensionless parameterized). Figure 7 The horizontal axis represents the flow rate (dimensionless parameterization), while the vertical axis represents the pressure ratio (dimensionless parameterization). It can be seen that as the flow rate increases, when water is injected into the gas flow, the power consumption and the pressure ratio decrease. At a certain threshold, the pressure ratio is lower than that without water injection.

[0049] The molecular weight of the process gas (hydrogen or H2) is temporarily increased by mixing it with water vapor. A finely atomized water spray is introduced into the gas compression path, where it vaporizes upon introduction, cooling the gas and increasing the molecular weight of the gas mixture. This effect reduces the polytropic head required for compression, thus requiring fewer stages and less power to compress the same amount of hydrogen.

[0050] The molecular weight of the gas increases "temporarily" as water is removed until saturation is reached downstream of the cooler 4, which is arranged downstream of the compressor 2. As previously explained, downstream of the compressor there are coolers and separators, which contribute to achieving the desired effect described above.

[0051] After the gas is cooled down in the cooler 4 , the hydrogen saturated with water vapor is delivered through the first outlet conduit 42 , while the condensate is extracted through the second outlet conduit 43 .

[0052] refer to Figure 8 、 Figure 9 、 Figure 10 and Figure 11 , shows an additional embodiment of the distribution channel 5. Typically, cooling injection is performed at only one or two locations or ports along the 360 ​​degrees of the compressor 2. By injecting at multiple locations (6 to 8) across the 360 ​​degrees of the diaphragm, the efficiency of the droplet conversion to vapor can be improved.

[0053] Specifically, refer to Figure 8 In the illustrated second embodiment, the annular distribution channel 29 has a variable cavity / cross-section to ensure uniform pressure of the injected water, since the annular cavity offers varying resistance to fluid flow at various circumferential positions in the cavity.

[0054] refer to Figure 9, shows a third embodiment of a multi-stage hydrogen centrifugal compressor system 1, in which, in order to ensure that water is evenly delivered to 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 corresponding water inlet 27. Therefore, the water pressure of the nozzle 33 closer to the water inlet 27 is higher than the water pressure of the nozzle 33 farther away from the water inlet 27. This difference will cause the water to be unevenly distributed in different parts of the distribution channel 29, thereby causing uneven gas saturation. If each nozzle 33 is farther away from the water inlet 27, the flow rate of each nozzle 33 is higher. In this way, the lower water pressure of the nozzle 33 farther away from the water injection conduit 31 is compensated.

[0055] Therefore, still refer to Figure 9 The flow rate at the nozzle 33 is diametrically opposite to the flow rate closer to the water inlet 27, which, as mentioned above, is connected to the water injection conduit 31 through which the injection unit 3 is supplied with water.

[0056] refer to Figure 10 , shows a fourth embodiment of a multi-stage hydrogen centrifugal compressor system 1, in which the same tube losses resulting from injection at uniform pressure are included. The tubes are aligned so that they produce varying resistance to flow. The alignment of the tubes varies relative to the direction of fluid flow. The closer to the upper region, the greater the angle of the tube relative to the flow direction. The angle is smallest at the bottom, at 90 degrees, and as one moves upwards in the circumferential direction, the angle of the corresponding tube increases. In this case, there is no distribution channel 29, and instead, an injection pipe connects the water injection conduit 31 to the corresponding nozzle 33.

[0057] Figure 10 An external passage is depicted that functions similarly to the distribution channel 29 and is designed to deliver fluid (in this case, water) at uniform pressure over a 360-degree range. The resistance created by the pipe will be greatest at the point closest to the water injection conduit 31, and will be least at the point furthest away, ultimately ensuring uniform pressure across the entire injection nozzle.

[0058] Moreover, reference Figure 11 , illustrates a fifth embodiment of a multi-stage hydrogen centrifugal compressor system 1. In this fifth embodiment, the injection unit 3 includes a plurality of controlled electric valves 34, each of which is connected to a corresponding nozzle 33 via a pipe 311. In this way, the pressure on each nozzle 33 can be adjusted. Specifically, each electric valve 34 can be individually controlled by the control system 32 of the injection unit 3.

[0059] The nozzle 33 can be fixed or retractable. Fixed nozzles are easier to design. However, when not in use, the washing nozzle may become clogged.

[0060] The retractable nozzles 33 can be inserted / retracted when necessary. An advantage of the retractable nozzles 33 is that they can be replaced without stopping the compressor 2. The retractable nozzles 33 can be actuated manually or automatically.

[0061] Although aspects of the present invention have been described in terms of various specific embodiments, it will be apparent to those skilled in the art that various modifications, variations, and omissions are possible without departing from the spirit and scope of the present claims. Furthermore, unless otherwise indicated herein, the order or sequence of any process or method steps may be changed or re-sequenced according to alternative embodiments.

[0062] Reference has been made in detail to embodiments of the present disclosure, one or more examples of which are shown in the accompanying drawings. Each example is provided by way of explanation of the disclosure, not limitation thereof. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the disclosure without departing from the scope or spirit of the disclosure. References throughout this specification to "one embodiment" or "an embodiment" or "some embodiments" mean that the particular features, structures, or characteristics described in conjunction with the embodiment are included in at least one embodiment of the disclosed subject matter. Therefore, the phrases "in one embodiment" or "in an embodiment" or "in some embodiments" appearing in multiple places throughout the specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0063] When introducing elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Claims

1. A compressor system (1) for compressing a gas such as hydrogen, the compressor system comprising: Multi-stage compressor (2), The multi-stage compressor has one or more compression stages (21) capable of increasing the pressure of a gas flow path, Features of the compressor system The compressor system (1) further comprises an injection unit (3) having at least one injection conduit (31) for injecting fluid, and One or more nozzles (33), each fluidically connected to a respective injection conduit (31), for injecting the fluid into the gas flow path.

2. The compressor system (1) according to claim 1, wherein The temperature of the fluid is lower than the temperature of the gas stream, so that when the fluid is injected into the gas stream, the fluid vaporizes upon contact with the gas stream, causing the molecular weight of the gas to increase.

3. The compressor system (1) according to claim 2, wherein The temperature of the fluid is equal to or lower than the ambient temperature.

4. Compressor system (1) according to any one of the preceding claims, in, Each compression stage (21) comprises: impeller (211); a diffuser (212) connected to the impeller (211); a U-shaped bend (213) connected to the diffuser (212); and a return channel (214), the return channel being connected to the U-shaped bend (213); wherein at least one fluid inlet (27) is obtained on the diffuser (212) or on the U-shaped bend (213), and Each nozzle (33) is arranged on a corresponding fluid inlet (27).

5. The compressor system (1) according to claim 4, wherein The multi-stage compressor (2) comprises: a plurality of compression stages (21), the plurality of compression stages being arranged in series, a gas inlet (22), through which the gas enters the multi-stage compressor (2), a gas outlet (23) through which the gas exits after being compressed, and A rotating shaft (24) to which the impeller (211) is keyed for compressing the gas.

6. The compressor system (1) according to claim 5, 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 conveyed, and a second outlet conduit (43) through which a condensate of the fluid is extracted.

7. The compressor system (1) according to any one of claims 5 to 6, in, The multi-stage compressor (2) comprises an outer housing (261), and an inner housing (262) shaped to house the compression stage (21); A distribution channel (29) is obtained in the inner housing (262), wherein the distribution channel (29) is fluidically connected to the injection conduit (31) at a connection point and fluidically connected to the one or more nozzles (33).

8. The compressor system (1) according to claim 7, wherein The distribution channel (29) is formed by a first portion (291) and a second portion (292).

9. The compressor system (1) according to claim 8, wherein The first portion (291) has a rectangular cross-section, and the second portion (292) has a rectangular cross-section smaller than that of the first portion (291).

10. The compressor system (1) according to any one of claims 7 to 9, wherein: The one or more nozzles (33) are mounted in the distribution channel (29).

11. The compressor system (1) according to claim 10, wherein The flow rate of the one or more nozzles (33) increases as the distance between the one or more nozzles and the connection point at which the distribution channel (29) is fluidically connected to the injection conduit (31) increases.

12. The compressor system (1) according to any one of claims 5 to 9, wherein: The distribution channel (29) has a variable cavity / cross section.

13. The compressor system (1) according to any one of claims 1 to 6, wherein: The injection unit (3) includes a plurality of controlled electric valves (34), each of which is connected to a corresponding nozzle (33) through a corresponding pipe (311).

14. Compressor system (1) according to any one of the preceding claims, in, The gas is hydrogen, and Wherein, the fluid is water.

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