Method and installation for compressing gas

Abstract

The invention relates to a method for compressing gas (a), in particular hydrogen, wherein the gas is obtained and divided into several parallel partial streams, and wherein each partial stream is fed to one of several compression cylinders (106.1, 106.1, 106.3), wherein the several compression cylinders are assigned to the same pressure stage, wherein gas is compressed in the compression cylinders (106.1, 106.1, 106.3) using a fluid (c), in particular an ionic fluid, wherein the fluid and / or pistons of the compression cylinders are moved by means of a pump (120), and wherein the compressed gas is combined to form an output stream, and wherein the compressed gas (b) of the output stream is provided for further use. The invention also relates to a corresponding system (100).

Description

[0001] The invention relates to a method and a plant for compressing gas, in particular hydrogen.

[0002] Hydrogen, which is used as a fuel for vehicles, can be provided via so-called hydrogen filling stations. Two types of hydrogen filling stations can be distinguished: The first type uses liquid hydrogen as a source and compresses the hydrogen in liquid form. The second type, however, uses a gaseous hydrogen source and compresses the hydrogen into a gaseous state. This means that the filling station is supplied with gaseous hydrogen, which is then compressed and usually stored in gaseous form.

[0003] It has become apparent that heavy vehicles such as trucks and buses require hydrogen supply, with the required hydrogen pressures no longer being in the range of 350 bar, but increasingly in the range of 700 bar and above. These vehicles have large storage tanks (with more than 10 kg storage capacity, often 60 kg or more) that need to be filled with hydrogen at pressures of up to 840 bar in an acceptable time. Such refueling requires either a large number of storage devices or high mass flows from the compressors used.

[0004] Piston compressors can be used, which have, for example, two to five large serial compression cylinders. However, the compression of hydrogen or gas in general at these pressures requires high compression energy, and the resulting high temperatures place stress on the compressor seals.

[0005] These compressors typically have a high connected load, thus requiring a lot of cooling capacity. They are generally too large for containerized solutions and require complex maintenance work when the entire compressor is out of service. No refueling is possible during maintenance.

[0006] Against this background, the task is to make the compression of gas, especially at particularly high pressures, as energy-efficient and resource-saving as possible. Disclosure of the invention

[0007] This object is achieved by a method and a system for compressing gas having the features of the independent patent claims. Preferred embodiments are the subject of the dependent patent claims and the following description. Advantages of the invention

[0008] The invention relates to the compression and provision, and optionally also the storage, of gas, as well as to corresponding systems therefor and their operation. As mentioned at the beginning, hydrogen is particularly suitable as the gas, whereby corresponding systems can then be used in particular in hydrogen filling stations, preferably those of the second type, i.e. filling stations with gaseous compression. The invention will therefore be described below in particular with reference to hydrogen and hydrogen filling stations or the refueling of vehicles with hydrogen; however, the principle can in principle also be applied to other gases or corresponding systems, e.g. for other purposes. The method and the system will be described comprehensively below.

[0009] Within the scope of the present invention, it is proposed that gas, e.g., hydrogen, is first obtained, ie, supplied to the system. The gas can be obtained, for example, from a storage tank or a tanker truck, or from another compressor or a cryopump, with which the gas has already been pre-compressed, for example.

[0010] The resulting gas can then optionally be collected in a buffer tank within the system. From the buffer tank, or directly if no buffer tank is available, the resulting gas is then divided into several parallel partial streams, with each partial stream being fed to one of several compression cylinders in the system. For this purpose, an inlet line can be branched into a corresponding number of partial lines, which are then fed to the respective compression cylinder, typically via an inlet and / or suction valve of the respective compression cylinder.

[0011] In the compression cylinders, the gas is then compressed using a fluid, particularly an ionic fluid, with the fluid and / or pistons of the compression cylinders being moved by a pump. The compressed gas is then combined into an output stream, which makes it available for further use. The compressed gas is typically expelled through an outlet valve of the respective compression cylinder. This can be used, for example, to directly refuel a vehicle; however, the compressed gas can also be stored elsewhere.

[0012] The system or type of compression using ionic fluid described can also be referred to as an ionic compressor or ionic compression. With this type of compression, instead of mechanical pistons that move back and forth in the compression cylinders, a type of piston made of fluid is moved back and forth. This can also be referred to as a liquid column. This means that there are fewer mechanical parts that generate heat through friction, so that overall less heat is generated during operation of the system that needs to be cooled down. The (ionic) fluid used in this type of compressor is generally almost incompressible. However, mechanical pistons that move back and forth in the compression cylinders can also be provided, with the pistons then being hydraulically connected to the pump, for example. These mechanical pistons can then be connected to the fluid orbe covered or wetted with an ionic fluid, e.g. with a liquid column.

[0013] A radial piston pump is particularly suitable as a pump. Each piston of the radial piston pump can be connected to one of the compression cylinders, for example, via piping, so that the reciprocating movement of the piston of the radial piston pump moves the fluid in the piping, causing the fluid or the liquid column or the relevant mechanical piston in the respective compression cylinder to move up and down or back and forth. In principle, the compression cylinders can also be actuated in other ways, e.g., through the appropriate use of control valves or the like. However, a radial piston pump represents a particularly robust and efficient design.

[0014] A particular advantage of the proposed approach lies in the division of the resulting gas, i.e. a single stream, into several partial streams and the associated parallel compression in the individual compression cylinders. These multiple compression cylinders are assigned to the same pressure stage. This allows the individual compression cylinders to be relatively small, i.e. with a low compression volume, at least compared to typically used compression cylinders, for example those connected in series. Furthermore, compression does not occur in multiple stages. All of this leads to easier cooling, e.g. because compression cylinders with a smaller diameter have a larger (external) surface-to-volume ratio than compressor cylinders with a larger diameter. This allows for better heat dissipation to the environment.

[0015] The number of compression cylinders in the system can be five or ten, for example, but also a different number, such as just three or four, or even more than ten. In the case of a radial piston pump, it is particularly useful if the radial piston pump has a corresponding number of pistons so that each piston of the radial piston pump can be hydraulically connected to a compression cylinder.

[0016] In one embodiment, the plurality of compression cylinders in which gas is compressed are a selected number as a subset of a plurality of compression cylinders. For example, the system may have five compression cylinders (which then correspond to the aforementioned plurality), while only four, or even just two, or any other desired subset thereof are activated for compression. Thus, optionally, all or just a subset of the existing compression cylinders can be activated and used for compression.

[0017] For this purpose, the system can, for example, have a control block for at least one, preferably each, of the plurality of compression cylinders, by means of which the fluid from the pump can be selectively supplied either to the respective compression cylinder for compressing gas or to an idle state. If no liquid column is moving in a compression cylinder, for example, no gas that could be compressed is drawn into the compression cylinder.

[0018] This allows the system to be operated in a highly variable manner. The mass flow of gas to be compressed can be easily varied or adjusted by operating only the desired number of compression cylinders.

[0019] In this case, entire compression cylinders are simply shut down, resulting in improved energy efficiency. For example, if all compression cylinders or the pump were simply operated more slowly, which could be achieved using a frequency converter, for example, this could potentially eliminate the need for a frequency converter, or at least a particularly powerful one.

[0020] In one embodiment, fluid is separated from the compressed gas of the output stream before it is provided. The separated fluid is then fed back into the compression cylinders. For this purpose, the system can, for example, have a separator through which the compressed gas is passed. In this way, the compressed gas is purified, and the separated fluid is reused rather than simply disposed of.

[0021] In one embodiment, the fluid is cooled after separation and before being fed back into the compression cylinders. This allows cooling of the compression cylinders and the gas directly during compression. This again demonstrates the particular advantage of the ionic compressor.

[0022] In one embodiment, the compressed gas is cooled after it has been compressed, and in particular before it is combined into the output stream. This allows for further and efficient cooling of the gas.

[0023] The system may comprise a cooling device and one or more heat exchangers supplied therewith. The system is then configured to cool the gas before it is compressed, and / or the gas after it has been compressed, and / or the fluid, using the one or more heat exchangers.

[0024] In one embodiment, the gas is received at a pressure of at least 300 bar and in particular compressed to a pressure of at least 700 bar or at least 800 bar. In this way, on the one hand, only a lower compression power is required than with compression at a lower pressure, such as 1 to 10 bar, and on the other hand, existing compressors which compress the gas to 300 or 450 bar, for example, can still be used. The proposed system can then be used in addition and receive the gas from the existing compressor at 300 bar, for example, and compress it further, so that vehicles with 700 bar or more, for example, can also be refueled. If vehicles with only 350 bar, for example, are to be refueled, the (additional) system does not have to be used.

[0025] In one embodiment, the system is designed such that at least one, in particular all, of the plurality of compression cylinders can be removed and replaced. For this purpose, the compression cylinders can, for example, be arranged together on a rail, by means of which the compression cylinders can be removed together from the system, e.g. for maintenance purposes. The compression cylinders can then be reinserted. However, spare or replacement compression cylinders can also be used. This enables particularly simple and uncomplicated maintenance without lengthy interruptions to operation. Such a system is typically flushed with nitrogen before each maintenance; in this context, it can also be ensured that, for example, the nearest possible valves are closed.

[0026] It should be mentioned that the system described is in particular also set up to carry out the described method, i.e., for example, it has appropriately set up components.

[0027] The invention is illustrated schematically in the drawing using an embodiment and is described below with reference to the drawing.

[0028] Short description of the drawing Figure 1 shows schematically a system according to the invention in a preferred embodiment. Detailed description of the drawing

[0029] In Figure 1A preferred embodiment of a system 100 according to the invention is shown schematically, by means of which a method according to the invention can also be carried out. This is a simplified process diagram illustrating fluid and gas flows in the system. The system 100 serves to compress gas, in particular hydrogen, which is then provided, e.g., for refueling a vehicle 150. The system 100 can, for example, be part of a hydrogen filling station. Therefore, the compression of hydrogen will be explained below as an example.

[0030] The system 100 comprises, for example, three compression cylinders 106.1, 106.2, 106.3, as well as a pump 120 designed as a radial piston pump, which is hydraulically coupled to each of the compression cylinders or their mechanical pistons 108.1, 108.2, 108.3. In particular, the radial piston pump 120 comprises three pistons 121.1, 121.2, 121.3, corresponding to the number of compression cylinders, by means of which fluid c, in particular ionic fluid, can be moved in each of the compression cylinders.

[0031] As already mentioned, the system can have a large number of compression cylinders, e.g., five or ten. Accordingly, the radial piston pump can then have five or ten pistons, or multiple radial piston pumps can be used. For the sake of clarity, only three compression cylinders, pistons, and one radial piston pump are shown.

[0032] To compress hydrogen a using system 100, the hydrogen a is obtained, for example, from a compressor 101. The compressor may have already compressed the hydrogen a to, for example, 300 or 450 bar. Compressor 101 is not part of system 100, but may already be present, for example, in a hydrogen filling station. System 100 may therefore be additionally provided to further compress the hydrogen already compressed to, for example, 300 or 450 bar, if necessary.

[0033] The hydrogen thus obtained can then be temporarily stored and / or collected, for example, in a buffer storage 102, if necessary. From there, the hydrogen can then optionally be passed through a heat exchanger 103, which cools or pre-cools the hydrogen. The heat exchanger 103 is supplied with cooling medium e, for example, via a cooling device 111, and cooled.

[0034] The hydrogen is now divided into several parallel partial streams; this occurs, for example, via a corresponding branching 104 of pipes, i.e., a division of an inlet line into several partial lines. Each of these partial streams is then fed to a corresponding compression cylinder 106.1, 106.2, or 106.3. This occurs in particular via inlet valves 105.1, 105.2, 105.3, and by suction through actuation of the compression cylinders by means of the radial piston pump 120. For the sake of completeness, it should be mentioned that the compression cylinders do not necessarily have to have an actual cylindrical shape; rather, this merely refers to a chamber with volume in which the hydrogen is compressed. In particular, the ionic compressor technology does not necessarily require a cylindrical shape, although this is often common in practice.

[0035] Due to the way the radial piston pump works, its pistons are actuated in a staggered manner, which also results in a slight offset between the individual compression cylinders. However, since this process is repeated for each compression cylinder, compression still occurs in parallel across the compression cylinders. This means that during the time interval in which the radial piston pump completes a 360° rotation, the system's parallel compression occurs exactly once across all compression cylinders.

[0036] At the same time as the hydrogen, ionic fluid d, which has been separated from already compressed hydrogen by a separator 112, is also injected into the respective compression cylinder. This also occurs, for example, via an injection valve 107.1, 107.2, or 107.3.

[0037] The ionic fluid can be cooled before being introduced into the compression cylinders. This can be done before branching into individual partial streams, e.g., using a heat exchanger 113. Like heat exchanger 103, heat exchanger 113 can be supplied with cooling medium and cooled, e.g., via cooling device 111. It is understood that the ionic fluid can also be cooled with individual heat exchangers after being divided into the partial streams, in which case multiple, but possibly smaller, heat exchangers can be used.

[0038] After the hydrogen has been drawn into a compression cylinder, it is compressed by the ionic fluid via the pump as the compression cylinder is further actuated, and is thus expelled, for example, via a respective outlet valve 109.1, 109.2, or 109.3. A small amount of the ionic fluid may also be expelled.

[0039] Subsequently, the compressed hydrogen is cooled, e.g., individually for each partial stream, by means of a heat exchanger 110.1, 110.2, or 110.3. Like heat exchanger 103, heat exchangers 110.1, 110.2, and 110 can be supplied with cooling medium and cooled, e.g., via cooling device 111. The thus cooled partial streams of compressed hydrogen are then combined and passed through separator 112. There, as already mentioned, any remaining ionic fluid is separated and reused, i.e., fed back into the compression cylinders.

[0040] Instead of cooling the individual streams of compressed hydrogen with individual heat exchangers, it would also be possible to cool the combined, single hydrogen stream. This might require a single, but larger, heat exchanger.

[0041] In this way, the hydrogen can be compressed to, for example, 700 or 800 bar or even higher. The compressed hydrogen b can then be used, for example, to refuel the vehicle 150, which is typically done via a so-called dispenser 130. It is understood that the compressed hydrogen can also be used for other purposes, for example, by initially storing it.

[0042] As already mentioned, the system 100 can be operated variably by not controlling one or more compression cylinders for compressing hydrogen. For this purpose, a valve or control block can be provided, e.g., for each compression cylinder or jointly for several or all compression cylinders.

[0043] As an example, a valve or control block 122.1, 122.2, 122.3 is schematically indicated for each compression cylinder 106.1, 106.2, or 106.3. For example, if compression cylinder 106.3 is regularly controlled via valve or control block 122.3, the ionic fluid can be moved accordingly, so that the free volume in compression cylinder 108.3 is continuously reduced and increased. The same applies to the other compression cylinders.

[0044] If, however, compression cylinder 106.3 is not intended to be controlled or used to compress hydrogen, the fluid flow from piston 121.3 of radial piston pump 120 can be diverted, e.g., into an idle state. Valve or control block 122.3 can be suitably configured for this purpose. Compression cylinder 108.3 is then inactive, and no hydrogen is drawn in and compressed. The same applies to the other compression cylinders, so that any subset of the compression cylinders can be actively used.

[0045] As also mentioned, the compression cylinders can also be designed to be removable and replaceable. For this purpose, the compression cylinders can be arranged together on a rail or the like, for example, so that the compression cylinders can be removed together and replaced with a set of replacement compression cylinders.

Claims

1. A method for compressing gas (a), in particular hydrogen, wherein the gas is obtained and divided into a plurality of parallel partial streams, and wherein each partial stream is fed to one of a plurality of compression cylinders (106.1, 106.1, 106.3), wherein the plurality of compression cylinders are assigned to the same pressure stage, wherein gas is compressed in the compression cylinders (106.1, 106.1, 106.3) in parallel and using a fluid (c), in particular an ionic fluid, wherein the fluid and / or pistons of the compression cylinders are moved by means of a pump (120), and wherein the compressed gas is combined to form an output stream, and wherein the compressed gas (b) of the output stream is provided for further use.

2. The method according to claim 1, wherein a radial piston pump is used as the pump (120).

3. The method of claim 1 or 2, wherein the plurality of compression cylinders (106.1, 106.1, 106.3) in which gas is compressed are a selected number as a subset of a plurality of compression cylinders.

4. Method according to one of the preceding claims, wherein fluid (d) is separated from the compressed gas of the output stream before provision, and wherein the separated fluid is fed back to the compression cylinders (106.1, 106.1, 106.3).

5. The method according to claim 4, wherein the fluid (d) is cooled after separation and before being fed back to the compression cylinders (106.1, 106.1, 106.3).

6. A process according to any one of the preceding claims, wherein the gas (a) is obtained at a pressure of at least 300 bar and then compressed.

7. A method according to any one of the preceding claims, wherein the compressed gas is cooled after it has been compressed, and in particular before it is combined to form the output stream.

8. Method according to one of the preceding claims, wherein the gas is cooled before being supplied to the plurality of compression cylinders (106.1, 106.1, 106.3), and in particular before being divided into the plurality of partial streams.

9. A system (100) for compressing gas, in particular hydrogen, comprising a plurality of compression cylinders (106.1, 106.1, 106.3), and a pump (120) which is hydraulically coupled to each of the plurality of compression cylinders (106.1, 106.1, 106.3), wherein the plurality of compression cylinders are assigned to a same pressure stage, wherein the system is configured to: receive gas and divide it into a plurality of parallel partial flows, and to supply each partial flow to one of the plurality of compression cylinders (106.1, 106.1, 106.3), to compress gas in the compression cylinders (106.1, 106.1, 106.3) in parallel and using a fluid (c), in particular an ionic fluid, by moving the fluid and / or pistons of the compression cylinders by means of the pump (120), and Combine gas from each of the plurality of compression cylinders (106.1, 106.1, 106.3) into an output stream and make it available for further use.

10. System (100) according to claim 9, which is arranged, wherein the pump (120) is designed as a radial piston pump.

11. Plant (100) according to claim 9 or 10, which is arranged to compress gas selectively in all or only in a selected number as a subset of the plurality of compression cylinders (106.1, 106.1, 106.3).

12. System (100) according to claim 11, which further comprises a control block (122) for at least one, preferably each, of the plurality of compression cylinders (106.1, 106.1, 106.3), by means of which control block the fluid from the pump (120) can be selectively supplied either to the respective compression cylinder (106.3) for compressing gas or can be led into an idle state.

13. Plant (100) according to one of claims 9 to 12, which further comprises at least one separator (112) and is arranged to separate fluid (d) from the compressed gas of the output stream by means of the at least one separator, before provision.

14. Plant (100) according to one of claims 9 to 13, further comprising a cooling device (111) and one or more heat exchangers (103, 110.1, 110.2, 110.3, 113) supplied thereby, and wherein the plant is arranged to cool by means of the one or more heat exchangers: - the gas before it is compressed, and / or, - the gas after it has been compressed, and / or - the fluid.

15. System (100) according to one of claims 9 to 14, which is designed such that at least one, in particular all, of the plurality of compression cylinders (106.1, 106.1, 106.3) are removable and replaceable.

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