Hydrogen compression assembly, hydrogen production plant, and compression method

Abstract

A hydrogen production plant for producing hydrogen having a compression assembly for increasing the pressure of the hydrogen, the compression assembly having at least one barrel compressor and at least one integrally geared centrifugal compressor. A method of compressing hydrogen is also disclosed.

Description

[Technical Field]

[0001] The present disclosure relates to a hydrogen compression assembly and a plant for producing high-pressure hydrogen including the hydrogen compression assembly, which can be used as a fuel source for turbines and engines, such as different types of gas turbines, which can be used in several industrial processes, such as for producing ammonia, or in different technical fields.

[0002] In the following, the description will refer to the compression of hydrogen, but it will be clear that the description should not be considered limited to this particular use, as the compression assembly may also be used to compress any other type of gas. [Background technology]

[0003] Hydrogen is produced for several industrial uses. For example, one of the most important industrial uses of hydrogen (though not the only one) is the production of ammonia, a well-known chemical product commonly used in a wide range of industrial sectors. For example, ammonia is produced to be used as a fertilizer for fields of different types of crops. In addition, ammonia is also used in the crude oil refining sector, especially as a carrier for hydrogen, i.e., mainly for the transportation of hydrogen.

[0004] Currently, hydrogen is mainly produced by the so-called steam reforming process. According to this production process, methane is first compressed. As is well known, methane is a gas that can be easily compressed due to its very high molecular weight (about 18). A step of separating the hydrogen from the carbon (the so-called reforming step) is then carried out to obtain hydrogen (H2) at a pressure of 30-40 bar, which is then mixed with nitrogen to obtain ammonia. At a pressure of 30-40 bar, hydrogen can be easily transported in storage containers and / or via short and long-distance pipelines.

[0005] As is well known, hydrogen is a very small and light molecule. Therefore, transporting it through pipelines is difficult. Generally, to achieve efficient transport of this gas, pressures of the order of 30 bar to 40 bar are required.

[0006] Although the above-mentioned hydrogen production technologies are effective, they have several technical problems. One of the main problems is that they are not environmentally friendly. In fact, methane must be burned, which results in the production of carbon dioxide (CO2), resulting in so-called "gray hydrogen." Recent industrial interest in producing "green hydrogen," i.e., hydrogen obtained by avoiding the combustion of methane and diffusing the carbon dioxide into the atmosphere, has led to rapid growth in the market.

[0007] Additionally, plants for burning and processing methane traditionally have very high footprints and operating costs. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, improved compression assemblies and methods for compressing hydrogen, and generally any other gas, would be welcome in the field. More generally, it would also be desirable to provide new types of plants that can produce green hydrogen without burning methane or any other fuel.

[0009] In one aspect, the subject matter disclosed herein is directed to a novel, industrially useful hydrogen compression assembly and a hydrogen production plant configured to produce hydrogen by electrolysis. The compression assembly is suitable for increasing the pressure of hydrogen or any other gas. The compression assembly includes at least one compression unit having a barrel compressor and at least one compression unit of an integrally geared centrifugal compressor type.

[0010] In another aspect, the subject matter disclosed herein relates to a compression unit having two barrel compressors with associated gearboxes and a drive electric motor connected to the first gearbox and the second gearbox for operating the barrel compressors.

[0011] In another aspect, disclosed herein is a compression unit having a variable speed electric motor or a fixed speed electric motor.

[0012] In another aspect, disclosed herein is a compression unit having a bull gear, a plurality of impellers mechanically driven by the bull gear, and an electrically driven electric motor operably connected to the bull gear for operating the impellers.

[0013] A further aspect of the present disclosure relates to a method of compressing hydrogen gas, including obtaining hydrogen gas, compressing the hydrogen with at least one centrifugal compressor, and then compressing the hydrogen with at least one integral gear centrifugal compressor. [Brief explanation of the drawings]

[0014] A complete understanding of the disclosed embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. [Figure 1] FIG. 1 shows a schematic diagram of a plant for producing hydrogen according to a first embodiment. [Figure 2] FIG. 2 shows the layout of a plant for producing hydrogen according to the second embodiment. [Figure 3] FIG. 3 shows a barrel compressor stage for increasing the pressure of the hydrogen in the plant of FIG. [Figure 4] FIG. 4 shows an integrally geared centrifugal compressor stage for increasing the pressure of the hydrogen in the plant of FIG. [Figure 5] FIG. 5 shows a flow diagram of a method for compressing hydrogen gas according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hydrogen is used in many industrial applications, such as the production of ammonia. Electrolysis is a method for producing hydrogen without burning methane and thus dispersing carbon dioxide into the atmosphere. However, because hydrogen is a very light molecule, the pressure of the hydrogen obtained by electrolysis must be increased for industrial use. In one aspect, the subject matter of the present disclosure is directed to a compression system or plan that combines different layouts of compressors (i.e., centrifugal compressors) and integrally geared centrifugal compressors to achieve high gas compression ratios and a reduced plant footprint.

[0016] Referring now to the drawings, Figure 1 shows a schematic diagram of a hydrogen production plant 1 according to a first embodiment.

[0017] In particular, the hydrogen production plant 1 comprises a hydrogen production stage generally designated by the reference numeral 2 and a compression assembly 3 for increasing the pressure of the hydrogen to a pressure of 30-40 bar, as will be better explained below.

[0018] Hydrogen production stage 2 is based on water electrolysis. This is based on the well-known production of hydrogen by splitting water using electricity (electrolysis). This involves passing an electric current through water, splitting it into hydrogen and oxygen. When the electric current is generated using renewable energy, electrolysis produces virtually no polluting or toxic by-products.

[0019] Since the hydrogen produced by the hydrogen production stage 2 is at ambient pressure, it is difficult to transport the hydrogen in the state in which it is produced. Such hydrogen must be pressurized and stored in special containers suitable for transport, or pressurized for transport through a pipeline to a predetermined destination (storage vessel, hydrogen turbine, refueling station, etc.). Therefore, a compression assembly 3 is connected downstream of the hydrogen production stage 2 to increase the pressure of the produced hydrogen to reach the pressure of 30 bar to 40 bar mentioned above.

[0020] More specifically, what has been invented is a new method for pressurizing hydrogen produced by electrolysis in a hydrogen production stage 2 or supplied by any other hydrogen production system, using a unique compression assembly 3 of a new hydrogen production plant 1. In the embodiment under consideration, the unique compression assembly 3 of the new hydrogen production plant 1 is ideally divided into multiple sub-stages. In one example, three sub-stages are used, including a low-pressure sub-stage 4 for increasing the hydrogen pressure, in the embodiment under consideration, from ambient pressure to about 6 bar, an intermediate-pressure sub-stage 5 for raising the hydrogen pressure to about 24 bar, and a final-pressure sub-stage 6 for raising the hydrogen pressure to about 30 bar or higher, in accordance with the design requirements of the plant.

[0021] More specifically, and still referring to the schematic diagram of Figure 1, low-pressure sub-stage 4 includes (schematically) a compression unit 41, which has two barrel compressors 411 and 412 arranged in series, respectively. The barrel compressor is a centrifugal compressor including a shaft, a set of impellers fixed to the shaft and arranged in series, and a case having the typical shape of a barrel.

[0022] In the schematic embodiment shown in the figure, barrel compressors 411 or 412 each include nine impellers. In other embodiments, a different number of impellers for each barrel compressor 411 or 412 of compression unit 41 may be provided depending on the desired hydrogen boost as well as hydrogen flow rate. Typically, barrel compressors 411 or 412 each have three or more barrel compressors, particularly when high compression ratios are required for hydrogen.

[0023] Also, in some embodiments, barrel compressor 411 or 412 may be driven by a variable speed or fixed speed electric motor (not shown) to better match the gas pressure of the preceding centrifugal compressor, as better explained below. More specifically, a variable speed electric motor is contemplated.

[0024] The intermediate pressure sub-stage 5 is structurally similar to the low pressure sub-stage 4 and includes a compression unit 51 having two barrel compressors 511 and 512 connected in series.

[0025] Again, each barrel compressor 511 or 512 has a maximum of 10 impellers, although barrel compressors 511 or 512 can be installed with different numbers of impellers depending on the pressure compression ratio.

[0026] The barrel compressor 511 or 512 of the intermediate pressure substage 5 may be driven by a variable speed electric motor or a fixed speed electric motor (not shown) to better match the gas pressure of the preceding centrifugal compressor, as will be better explained below.

[0027] The low-pressure sub-stage 4 and the intermediate-pressure sub-stage 5 may each include two or more compression units 41 or 51 depending on the flow rate of hydrogen to be compressed.

[0028] The final pressure sub-stage 6 increases the temperature of the hydrogen to the desired pressure. In the case in question, it naturally comprises a compression unit 61 of the intercooled integrally geared centrifugal compressor type, including four impellers 612 mechanically driven by a central bull gear 611. The implementation of this layout has advantages in terms of high speed three-dimensional impellers, relatively low costs (when compared to conventional compressors) and higher efficiency. It also proves to be particularly small in terms of installation area, whenever compared to conventional compressors.

[0029] The hydrogen output of the final pressure sub-stage 6 has the required pressure without any wetted parts so that the gas can be introduced immediately.

[0030] Referring now to FIG. 2, there is shown a more specific design of the layout of a hydrogen production plant 1 according to a second embodiment, which is structurally and functionally similar to the first embodiment.

[0031] More specifically, the hydrogen production plant 1 of FIG. 1 comprises a hydrogen production stage 2 in which hydrogen at ambient pressure is produced by electrolysis of water, and a compression assembly 3 .

[0032] The hydrogen production stage 2 operates by electrolysis, as in the first embodiment.

[0033] The compression assembly 3 again comprises a low-pressure sub-stage 4, an intermediate-pressure sub-stage 5 and a final-pressure sub-stage 6. The low-pressure sub-stage 4 comprises a first condenser 43 connected to the hydrogen production stage 2 for condensing a portion of the wet components of the hydrogen coming from the electrolyzer of the hydrogen production stage 2.

[0034] The low-pressure sub-stage 4 also includes a first compression unit 41 connected downstream of the first condenser 43. Referring to Figure 3, the layout of the first compression unit 41 of the low-pressure sub-stage 4 is shown. The first compression unit 41 includes a first barrel compressor 411, a first gearbox 413 connected to a drive shaft 414 of the first barrel compressor 411, a second barrel compressor 412, a second gearbox 415 connected to a drive shaft 416 of the second barrel compressor 412, and a drive electric motor 417 operably connected to the first gearbox 413 and the second gearbox 415 to operate the barrel compressors 411 and 412. The gear ratios of the respective gearboxes 413 and 415 are set according to the required compression performance.

[0035] Also, any type of gearbox may be implemented, such as epicyclic or planetary gearboxes, worm gearboxes, helical gearboxes, bevel gearboxes, etc.

[0036] The suitable gearbox ratio may be determined depending on the desired compression ratio, and the overall compression ratio of the compression assembly 3 may be distributed among the various compression stages according to the particular design needs.

[0037] The drive electric motor 417 is a variable speed electric motor to better adapt the compression ratio of the low pressure sub-stage 4 according to the inlet gas flow rate.

[0038] In other embodiments, the drive electric motor 417 may have a fixed speed, thus saving on the overall cost of the system.

[0039] The first barrel compressor 411 may also be equipped with Inlet Guide Vanes (IGVs) (not shown) to regulate the air flow and pressure entering the centrifugal compressor.

[0040] The low-pressure substage 4 also includes a first heat exchanger 44 (which can be of any type) for intercooling the hydrogen to reduce its temperature and possibly condense the wet hydrogen, a second condenser 45 connected downstream of the first heat exchanger 44, and a second compression unit 42 connected to the second condenser 45. The second compression unit 42 in this embodiment is identical to the first compression unit 41.

[0041] Finally, the low-pressure sub-stage 4 includes a second heat exchanger 46 connected to the second compression unit 42. The intermediate-pressure sub-stage 5 includes a third condenser 53 and a fourth condenser 54 connected in series to the second heat exchanger 44 of the low-pressure sub-stage 4 to reduce the moisture content of the hydrogen gas.

[0042] The intermediate pressure sub-stage 5 also includes a first compression unit 51 which is similar to the compression unit 41 of the low pressure sub-stage 4 from a structural and functional point of view.

[0043] The intermediate pressure substage 5 includes a heat exchanger 55 connected to the first compression unit 51, a fifth condenser 56 connected to the heat exchanger 55, a second compression unit 52 connected to the fifth condenser 56, which is similar to the first compression unit 51 from a structural and functional standpoint, and a sixth condenser 57.

[0044] The final pressure sub-stage 6 includes a compression unit 61 connected to the sixth condenser 57 and a heat exchanger 63 for reducing the temperature of the hydrogen and condensing its moisture. As mentioned above, the compression unit 61 is of the integral gear centrifugal compressor type as shown in Figure 4. The compression unit 61 of the final pressure sub-stage 6 includes a bull gear 611, two impellers 612 mechanically connected to the bull gear 611, and an electric drive electric motor 613 operably connected to the bull gear 611 and acting in series to operate the impellers 612 to compress the hydrogen.

[0045] This layout is particularly useful for increasing the pressure of hydrogen because of its small size and because it does not require water condensation to reduce the temperature of the compressed gas.

[0046] In some embodiments, the number of impellers 612 may vary depending on the flow rate and performance required.

[0047] The green hydrogen production plant 1 operates as follows.

[0048] When hydrogen production stage 2 produces hydrogen electrolysis, the gas is at ambient temperature and moist. The hydrogen then enters the first condenser 43 of the low-pressure sub-stage 4 to reduce its moisture content and is then compressed by the first compression unit 41 by means of a first borrow compressor 411 and a second borrow compressor 412 suitably driven by an electrical monitor 417 and gearboxes 413 and 415.

[0049] The compressed gas is then cooled by a first heat exchanger 44 and treated by a condenser 45 before being further compressed by a second compression unit 42. As described above, the second compression unit 42 is structurally and functionally similar to the first compression unit 41. The further compressed gas then passes through a sixth second heat exchanger before reaching the third condenser 53 and the fourth condenser 54 of the intermediate pressure substage 5, where it is further compressed by the first compression unit 51. The gas then passes through a heat exchanger 55 and a fifth condenser 56 before being compressed by the second compression unit 52.

[0050] Finally, the gas leaves the intermediate pressure substage 5 after passing through a condenser 57, which reduces its wettability again.

[0051] The hydrogen enters the final pressure sub-stage 6 and is compressed by a compression unit 61, which is in particular of the integral gear centrifugal compressor type equipped with two impellers 612 driven by a bull gear 611 driven by an electric material 613, as described above. Between each impeller, the integral gear centrifugal compression unit 61 has an intercooler stage capable of reducing the temperature of the gas.

[0052] Before leaving the hydrogen production plant 1, the compressed gas, now having a pressure of about 30-40 bar, passes through a heat exchanger 63 so as to further reduce the final monster of hydrogen.

[0053] At this point, the high pressure hydrogen is ready to be transported and possibly used to produce ammonia or for any other use.

[0054] Referring to Figure 5, there is shown a method 7 for compressing hydrogen gas performed by the hydrogen production plant 1. The method 7 comprises a step 71 of obtaining hydrogen gas, which is performed by electrolysis by the hydrogen production stage 2 to produce high pressure green hydrogen.

[0055] The method 7 then includes a step 72 of compressing the hydrogen with at least one centrifugal compressor, such as compression units 41, 42, 51, 52, including barrel compressors 411, 412, etc.

[0056] Finally, the method 7 for compressing hydrogen gas further comprises the step 73 of compressing the hydrogen with at least one of the integral gear centrifugal compressors 61 .

[0057] An advantage of the disclosed solution is that it makes it possible to increase the availability and reliability of hydrogen production plants.

[0058] Another advantage is that the hydrogen production plant realized with this layout has a reduced footprint when compared to prior art hydrogen production plants.

[0059] An additional advantage of the compression layout according to the present disclosure is that the application of an integrally geared centrifugal compressor in the final pressure sub-stage is well suited to this series due to the low volumetric flow rate at the end of the compression process.

[0060] A further advantage of the present disclosure is that it provides a compact solution for H2 compression over standard solutions with reciprocating compressors. Furthermore, the mean time between maintenance (MTBM) is dramatically reduced, resulting in reduced operating expenditures (OPEX).

[0061] While 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 many modifications, changes, and omissions are possible without departing from the spirit and scope of the claims. Additionally, unless otherwise specified herein, the order or sequence of any process or method steps may be varied or rearranged according to alternative embodiments.

[0062] Reference will now be made in detail to the embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not as a limitation of the disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. References throughout this specification to "an embodiment" or "one embodiment" or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the appearances of the phrases "in one embodiment," "in one embodiment," or "in some embodiments" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0063] When presenting 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 non-exclusive and mean that there may be additional elements other than the listed elements.

[0064] Barzano & Zanardo Roma SpA

Claims

1. 1. A gas compression assembly for compressing hydrogen obtained by electrolysis, comprising: a low pressure sub-stage having at least one compression unit; an intermediate pressure sub-stage having at least one compression unit; a final pressure substage having at least one compression unit of the integral gear centrifugal compressor type, the low-pressure sub-stage a first compression unit and a second compression unit; a first condenser connected to the first compression unit; a first heat exchanger for intercooling to reduce the temperature and ultimately condense the wet portion of said hydrogen; a second condenser connected downstream of the first heat exchanger and interposed between the first heat exchanger and the second compression unit; a second heat exchanger connected downstream of the second compression unit; A gas compression assembly, wherein the second condenser is connected to the second compression unit without a heat exchanger for heating the hydrogen.

2. Any of the first compression unit and the second compression unit of the low-pressure sub-stage and the at least one compression unit of the intermediate-pressure sub-stage, a first barrel compressor; and a first barrel compressor drive shaft connected to the first barrel compressor; a first gearbox connected to the drive shaft of the first barrel compressor; a second barrel compressor; and a second barrel compressor drive shaft connected to the second barrel compressor; a second gearbox connected to the drive shaft of the second barrel compressor; and a drive electric motor operatively connected to the first gearbox and the second gearbox for operating the first barrel compressor and the second barrel compressor.

3. The gas compression assembly of claim 2 , wherein the electric drive motor is a variable speed electric motor or a fixed speed electric motor.

4. the at least one compression unit of the final pressure sub-stage Brugia and two or more impellers mechanically connected to the bull gear; an electric motor operably connected to the bull gear for operating the impeller; The gas compression assembly of claim 3 , wherein the impellers act in series to compress the hydrogen.

5. The intermediate pressure sub-stage a first compression unit and a second compression unit; a third condenser and a fourth condenser connected in series between the second heat exchanger of the low-pressure sub-stage and the first compression unit of the intermediate-pressure sub-stage, the third condenser and the fourth condenser being capable of reducing wetting of the hydrogen; a heat exchanger connected downstream of the first compression unit of the intermediate pressure sub-stage; a fifth condenser interposed and connected between the heat exchanger of the intermediate pressure sub-stage and the second compression unit; a sixth condenser connected downstream of the second compression unit of the intermediate pressure sub-stage.

6. In the final pressure sub-stage, the integrally geared centrifugal compressor type compression unit is connected to the sixth condenser of the second compression unit of the intermediate pressure sub-stage and has at least one intercooler stage; 6. The gas compression assembly of claim 5, wherein the final pressure sub-stage further comprises a heat exchanger for reducing the temperature of the hydrogen and condensing wetness of the hydrogen.

7. 1. A hydrogen production plant, comprising: a hydrogen production stage configured to produce hydrogen based on the electrolysis of water; A hydrogen production plant comprising: a gas compression assembly according to any one of claims 1 to 6 connected to the hydrogen production stage for increasing the pressure of the hydrogen.

8. 1. A method for compressing hydrogen gas, comprising: obtaining hydrogen gas by electrolysis; compressing the hydrogen with a gas compression assembly according to any one of claims 1 to 6.

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