Hydrogen compression assembly, hydrogen production plant, and compression method

Abstract

A gas compression assembly and a hydrogen production plant are disclosed. The gas compression assembly has a pressure stage for increasing the pressure of hydrogen. The compression assembly has at least one barrel compressor and at least one reciprocating 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, and the hydrogen compression assembly can be used as a fuel source for turbines and engines such as different types of gas turbines that can be used in several industrial processes such as for producing ammonia or in different technical fields.

[0002] In the following, the description refers to the compression of hydrogen, but it should be clear that this description should not be considered limited to this specific use, since the compression assembly can also be used for compressing any other type of gas.

Background Art

[0003] Hydrogen is produced for several industrial applications. For example, one (but not the only one) of the most important industrial applications of hydrogen is the production of ammonia, which is a well-known chemical product commonly used in various industrial fields. For example, ammonia is produced for use as a fertilizer in fields of different types of crops. In addition, ammonia is also mainly used in the crude oil refining sector, particularly as a carrier for hydrogen, i.e., for the transportation of hydrogen.

[0004] Currently, hydrogen is mainly produced by the so-called steam reforming method. According to this production method, methane is first compressed. As is well known, methane is a gas that can be easily compressed because its molecular weight is very high (about 18). Subsequently, a step of separating hydrogen from carbon (the so-called reforming step) is performed to obtain hydrogen (H2) at a pressure of 30 bar to 70 bar, and then this hydrogen is mixed with nitrogen to obtain ammonia. At a pressure of 30 bar to 70 bar, hydrogen can be easily transported in a storage container and / or via short-distance and long-distance pipelines.

[0005] As is well known, hydrogen is an extremely small and light molecule. Therefore, transporting hydrogen through pipelines is difficult. Generally, to achieve efficient transport of this gas, a pressure of around 30 to 70 bar, as mentioned above, is necessary.

[0006] While the hydrogen production technologies described above are effective, they have several technical problems. One of the main problems is that they are not environmentally friendly. In practice, methane must be burned, which results in the production of carbon dioxide (CO2) and so-called "gray hydrogen." Recent industrial interest in "green hydrogen," that is, hydrogen obtained by avoiding the combustion of methane and diffusing carbon dioxide into the atmosphere, is rapidly growing in the market.

[0007] In addition, plants for burning and processing methane traditionally have very high installation area and operating costs.

[0008] Compressors are also known for increasing gas pressure. In particular, there is the field of centrifugal compressors, which are suitable for compressing moderate mass flow rates and enable the achievement of moderate pressure ratios. Compared to centrifugal compressors, there are reciprocating compressors, which can compress lower mass flow rates but perform higher pressure ratios. Reciprocating compressors generally have a larger footprint and shorter mean time between maintenance (MTBM) compared to centrifugal compressors. Finally, there are axial flow compressors, which can always compress high mass flow rates but perform lower pressure ratios compared to other solutions. [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, improved compression assemblies and methods, as well as plants for producing hydrogen, would be welcome in the art. More generally, it is desirable to provide plants that can produce green hydrogen without burning methane or any other fuel.

[0010] In one embodiment, the subject matter disclosed herein relates to a novel and industrially useful hydrogen compression assembly for increasing the pressure of manufactured hydrogen, and a manufacturing plant equipped with a compression assembly for producing compressed hydrogen. The compression assembly includes a compression unit equipped with a barrel compressor and a reciprocating compressor connected downstream of the compression unit.

[0011] In another embodiment, the subject matter disclosed herein relates to a compression unit having one or more barrel compressors having associated gearboxes, and a drive electric motor connected to a necessary gearbox associated with operating the barrel compressors.

[0012] In another embodiment, a compression unit having a variable-speed or fixed-speed electric motor is disclosed herein.

[0013] In another embodiment, disclosed herein is a compression unit having a reciprocating compressor comprising a plurality of piston cylinder assemblies operating by reciprocating motion, each piston cylinder assembly being equipped with a suction valve, which draws the gas to be compressed into the piston cylinder assembly at an input pressure, and a discharge valve, which discharges the compressed gas into the piston cylinder assembly at an output pressure higher than the input pressure. The reciprocating compressor is typically driven by an electric motor directly coupled to the compressor crankshaft.

[0014] A further aspect of the present disclosure relates to a method for compressing hydrogen gas, comprising the steps of: obtaining hydrogen gas; compressing the hydrogen with at least one centrifugal compressor; and then compressing the hydrogen with a reciprocating compressor. [Brief explanation of the drawing]

[0015] A complete understanding of the disclosed embodiments of the present invention and many of the associated advantages will be readily available, when considered in relation to the accompanying drawings, by referring to the following embodiments for carrying out the invention, which will be better understood. [Figure 1] Figure 1 shows a schematic diagram of a plant for producing and compressing hydrogen according to the first embodiment. [Figure 2] Figure 2 shows the barrel compressor stage for increasing the hydrogen pressure in the plant shown in Figure 1. [Figure 3] Figure 3 shows a reciprocating compressor for increasing the hydrogen pressure in the plant shown in Figure 1. [Figure 4] Figure 4 shows a flow diagram of the method for compressing hydrogen gas according to this disclosure. [Modes for carrying out the invention]

[0016] Hydrogen is used in many industrial applications, such as the production of ammonia. Electrolysis is a method for producing hydrogen without burning methane and therefore without releasing carbon dioxide into the atmosphere when electricity is supplied by renewable energy systems. However, because hydrogen is a very light molecule, the pressure of the hydrogen obtained by electrolysis must be increased for industrial use. In one embodiment, the subject matter of the present disclosure relates to a compression system or assembly that combines different layouts of compressors, namely centrifugal compressors and reciprocating compressors, to achieve a high compression ratio of gas and a reduced installation area of ​​the plant.

[0017] Referring to the drawings, Figure 1 shows a schematic diagram of a hydrogen production plant 1 according to the first embodiment.

[0018] In particular, the hydrogen production plant 1 comprises a hydrogen production stage, commonly shown in reference no. 2, and a compression assembly 3 for raising the hydrogen pressure to a pressure of 30 to 70 bar, as better described below.

[0019] The hydrogen production stage 2 is based on the electrolysis of water. This is based on the well-known production of hydrogen by decomposing water using electricity (electrolysis). This involves passing an electric current through water to decompose it into hydrogen and oxygen. When the electric current is generated using renewable energy, electrolysis produces substantially no polluting or toxic by-products.

[0020] The hydrogen produced by the hydrogen production stage 2 is at ambient pressure, so it is difficult to transport it in the state in which it is produced. Such hydrogen must be pressurized and stored in special containers suitable for transportation, or pressurized to be transported through a pipeline to a predetermined destination (such as a storage container, a hydrogen turbine, a fueling station, etc.). Therefore, a compression assembly 3 is connected downstream of the hydrogen production stage 2 to increase the pressure of the produced hydrogen and reach the pressure of 30 bar to 70 bar described above.

[0021] More specifically, in the embodiment to be considered, the compression assembly 3 is ideally divided into two sub-stages, namely a low-pressure sub-stage 4 for increasing the hydrogen pressure from ambient pressure to about 5 bar to 7 bar in the embodiment in question, according to the design requirements of the plant, and a final pressure sub-stage 5 for increasing this hydrogen pressure to a maximum of about 30 bar to 70 bar or more.

[0022] More specifically, referring further to the schematic diagram of FIG. 1, the low-pressure sub-stage 4 (schematically) includes a compression unit 41, and the compression unit 41 has two barrel compressors 411 and 412 arranged in series, respectively.

[0023] More specifically, referring further to the schematic diagram of FIG. 1, the low-pressure sub-stage 4 (schematically) includes a first condenser 43 connected to the hydrogen production stage 2 for condensing a part of the wet component of the hydrogen resulting from the electrolysis of the hydrogen production stage 2.

[0024] The low-pressure sub-stage 4 also includes a first compression unit 41 connected downstream of the first condenser 43. Referring to FIG. 2, 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 the drive shaft 414 of the first barrel compressor 411, a second barrel compressor 412, a second gearbox 415 connected to the 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 416 are set according to the required compression performance.

[0025] Also, any type of gearbox, such as an epicyclic or planetary gearbox, a worm gearbox, a helical gearbox, a bevel gearbox, etc., can be implemented.

[0026] A suitable gearbox ratio can be determined according to the desired compression ratio. Also, the overall compression ratio of the compression assembly 3 is distributed through each compression stage according to specific design requirements.

[0027] The drive electric motor 417 is a variable-speed electric motor so as to better match the compression ratio of the low-pressure sub-stage 4 according to the inlet gas flow rate.

[0028] In other embodiments, the drive electric motor 417 may have a fixed speed, thus saving the overall cost of the system.

[0029] Also, the first barrel compressor 411 may be equipped with an Inlet Guide Vane (IGV) (not shown) to adjust the air flow and pressure entering the centrifugal compressor.

[0030] The low-pressure substage 4 also includes a first heat exchanger 44 for lowering the temperature by intercooling of hydrogen and, optionally, condensing hydrogen moisture; a second condenser 45 connected downstream of the first heat exchanger 44; and a second compression unit 42 connected to the second condenser 45. In this embodiment, the second compression unit 42 is equal to the first compression unit 41, except for the possible compression ratio.

[0031] Finally, the low-pressure substage 4 includes a second heat exchanger 46 connected downstream of the second compression unit 42.

[0032] The final pressure substage 5 includes a third condenser 52 and a fourth condenser 53 connected in series with the second heat exchanger 46 of the low-pressure substage 4 to remove condensates from the gas mixture.

[0033] Furthermore, in this embodiment, the final pressure substage 5 includes a reciprocating compressor 51 for increasing the hydrogen pressure to 30-70 bar and for cooling it.

[0034] The reciprocating compressor 51 is shown in Figure 4. The reciprocating compressor 51 includes a frame 511 (circularly shown in the figure) that houses the crankshaft 512, and four crosshead guides 513 in this case. Each crosshead guide 513 houses a piston rod 514, which is connected to the crankshaft 512 to be actuated in a reciprocating motion.

[0035] In other embodiments, a different number of crosshead guides 512 (and piston rods 514) may be envisioned, depending on the need and the performance to be achieved.

[0036] The reciprocating compressor 51 also includes a piston cylinder assembly 515 for each crosshead guide 512, the piston of the piston cylinder assembly 515 being actuated by an associated piston rod 514 to receive reciprocating motion from the crankshaft 512. The reciprocating compressor 51 also includes a suction valve 514, located within each piston cylinder assembly 515, through which the gas to be compressed, i.e., hydrogen in the embodiment in question, is drawn into the associated piston cylinder assembly 515 at an input pressure, and a discharge valve 516 through which the compressed gas within the piston cylinder assembly 515 is discharged at an output pressure higher than the input pressure.

[0037] Finally, the reciprocating compressor 51 includes an electric motor 518 connected to the crankshaft 512 to operate the crankshaft, enabling the operation of the piston cylinder 515 and the compression of hydrogen.

[0038] Green hydrogen production plant 1 operates as follows:

[0039] When hydrogen production stage 2 produces hydrogen electrolysis, the gas is at ambient temperature and humid. The hydrogen then enters the first condenser 43 of the low-pressure substage 4, where it is condensed and then compressed by the first compression unit 41, by means of a first barrel compressor 411 and a second barrel compressor 412, which are appropriately driven by an electric motor 417 and gearboxes 413 and 415.

[0040] Next, the compressed gas is cooled by the first heat exchanger 44, processed by the condenser 45, and then further compressed by the second compression unit 42. The second compression unit 42 is structurally and functionally similar to the first compression unit 41, as described above. The further compressed gas then passes through the second heat exchanger 46 and then reaches the third condenser 52 and fourth condenser 53 of the final pressure substage 5, where it is further compressed by a reciprocating compressor 51 driven by an electric motor 518. The reciprocating compressor 51, as described above, drives the crankshaft 512 to operate the piston cylinder assembly 515, compressing hydrogen through the suction valve 516 and discharge valve 517. The hydrogen pressure is then increased to a maximum of 30 to 70 bar.

[0041] At this point, the high-pressure hydrogen is ready for transport and, if applicable, ready to produce ammonia or for any other use.

[0042] Referring to Figure 4, a method 6 for compressing hydrogen gas or any other gas is shown, which is performed by the hydrogen production plant 1. Method 6 includes a step 61 for obtaining hydrogen gas, which is performed by electrolysis by the hydrogen production stage 2 to produce high-pressure green hydrogen.

[0043] Method 6 then includes step 62 of compressing hydrogen or any other gas by at least one centrifugal compressor, such as compression units 41, 42.

[0044] Finally, the method 6 for producing hydrogen gas further includes step 63 of compressing hydrogen by at least one reciprocating compressor 61.

[0045] The advantage of the disclosed solution is that it can improve the availability and reliability of hydrogen production plants.

[0046] Another advantage is that the hydrogen production plant implemented with this layout requires a smaller footprint compared to conventional hydrogen production plants.

[0047] An additional advantage of the compression layout provided in this disclosure is that the application of an integrated gear-type centrifugal compressor in the final pressure substage is well suited to this series due to the low volumetric flow rate at the end of the compression process.

[0048] A further advantage of this disclosure is that it provides a compact solution for H2 compression compared to standard solutions using reciprocating compressors. Furthermore, the mean time between maintenance (MTBM) is dramatically increased, and operating expenditures (OPEX) are reduced.

[0049] While aspects of the present invention have been described in relation to 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. In addition, unless otherwise specified herein, the order or arrangement of any process or method step may be changed or rearranged according to the reciprocating embodiment.

[0050] Detailed references are made to embodiments of this disclosure, and one or more of these examples are illustrated in the drawings. Each example is provided for illustrative purposes only and does not limit the disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to this disclosure, as long as they do not deviate from the scope or spirit of the disclosure. Throughout this specification, any reference to “a certain embodiment,” “one embodiment,” or “several embodiments” means that a particular feature, structure, or characteristic described in relation to one embodiment is included in at least one embodiment of the subject matter disclosed. Thus, where the phrases “in a certain embodiment,” “one embodiment,” or “several embodiments” appear in various places throughout this specification, they do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics can be combined in any preferred manner in one or more embodiments.

[0051] When presenting elements of various embodiments, the articles "a," "an," "the," and "said" are intended to indicate that there is one or more of the elements. The terms "comprising," "including," and "having" are intended to be non-exclusive, meaning that additional elements other than those listed may exist. Barzano & Zanardo Roma SpA

Claims

1. A gas compression assembly comprising a low-pressure substage and a final-pressure substage for increasing the pressure of a hydrogen-containing gas, The low-pressure substage comprises two or more compression units, each having a first and second barrel compressor configured as a barrel-type centrifugal compressor. The final pressure substage comprises at least one reciprocating compressor connected downstream of any of the two or more compression units, Each of the two or more compression units is: The first barrel compressor and, The drive shaft of the first barrel compressor, which is connected to the first barrel compressor, A first gearbox connected to the drive shaft of the first barrel compressor, The second barrel compressor is arranged in series with the first barrel compressor, The drive shaft of the second barrel compressor, which is connected to the second barrel compressor, A second gearbox connected to the drive shaft of the second barrel compressor, To operate the first barrel compressor and the second barrel compressor, the system includes a first gearbox and a drive electric motor operably connected to the second gearbox, The first gearbox or the second gearbox includes an epicyclic or planetary gearbox, a worm gearbox, a helical gearbox, or a bevel gearbox. The gear ratios of the first gearbox and the second gearbox can be set to be variable. The aforementioned drive electric motor is a single variable-speed electric motor whose speed is set based on the input gas flow rate and the gear ratio. A gas compression assembly in which each compression unit does not have a compressor different from the first barrel compressor and the second barrel compressor.

2. The aforementioned reciprocating compressor is Frame and, A crankshaft housed within the aforementioned frame, Multiple crosshead guides, Multiple piston rods, each piston rod housed within a crosshead guide, and each piston rod connected to the crankshaft to be actuated in a reciprocating motion, A plurality of piston cylinder assemblies, each piston cylinder assembly being connected to a piston rod, and each of the piston cylinder assemblies being actuated by the corresponding piston rod to receive the reciprocating motion from the crankshaft, A suction valve installed within each of the piston cylinder assemblies, wherein the gas to be compressed is drawn into the piston cylinder assembly by the input pressure, A discharge valve installed within each of the piston cylinder assemblies, which discharges the compressed gas within the piston cylinder assembly at an output pressure higher than the input pressure, The gas compression assembly according to claim 1, further comprising an electric motor connected to the crankshaft.

3. The low-pressure substage is A first compression unit and a second compression unit, A first condenser connected to the first compression unit, A first heat exchanger that lowers the temperature through intercooling and ultimately condenses the wet portion of hydrogen, A second condenser is connected downstream of the first heat exchanger and interposed between the first heat exchanger and the second compression unit, The gas compression assembly according to claim 1, further comprising a second heat exchanger connected downstream of the second compression unit.

4. The gas compression assembly according to claim 3, wherein the final pressure substage includes a third condenser and a fourth condenser connected in series between the second heat exchanger and the reciprocating compressor of the low pressure substage, the third condenser and the fourth condenser being able to reduce wetting of the gas passing through.

5. A hydrogen production plant, A hydrogen production stage configured to produce hydrogen, A hydrogen production plant comprising a gas compression assembly according to any one of claims 1 to 4 for increasing the pressure of the hydrogen produced by the hydrogen production stage.

6. The hydrogen production stage is based on the electrolysis of water, as described in claim 5.

7. A method for compressing hydrogen gas, The steps to obtain hydrogen gas, A method comprising the step of compressing the hydrogen gas using a gas compression assembly according to any one of claims 1 to 4.

8. The method according to claim 7, wherein the step of obtaining the hydrogen gas is carried out by electrolysis.

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