System for compressing, storing and providing gas and corresponding method

Abstract

The invention relates to a method for compressing and providing gas, in particular hydrogen, wherein obtained gas (a) is compressed by means of a compression device (140) with one or more compressor stages, and the compressed gas (b) is supplied to a storage and / or pressure regulating system (120), and wherein gas provided by the storage and / or pressure regulating system (120) (d) is supplied to a provisioning device (130) for further use, in particular for delivery to a vehicle, wherein, by means of a refrigerating machine (15), by means of a coolant circuit (e, f, g, h), gas is cooled downstream of the one or downstream of at least one of the plurality of compressor stages, and the compression device is cooled, and wherein, by means of the refrigerating machine (15), the provisioning device (130) is further cooled.

Description

[0001] Description

[0002] Plant for compressing, storing and supplying gas and corresponding process

[0003] The invention relates to a method for compressing, possibly storing, and providing or overflowing gas, in particular hydrogen, as well as a system therefor, e.g. a hydrogen filling station.

[0004] 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.

[0005] Furthermore, two basic system areas can be distinguished at a hydrogen filling station. The first system area concerns the compression of the hydrogen, including compressor cooling to dissipate the compression heat via heat exchangers, and the storage of the hydrogen (usually in special hydrogen storage cylinders at a storage pressure of between 450 and 900 bar). The second system area concerns the filling of the hydrogen into vehicle tanks. It includes, for example, a storage bank control system, (further) cooling via heat exchangers to condition the hydrogen for refueling, and a hydrogen dispenser with the associated refueling equipment, such as a breakaway and refueling coupling, and the refueling hose.

[0006] Second-type hydrogen filling stations or similar systems generally require significant amounts of energy to dissipate the heat released during compression, especially since otherwise compressor components wear out sooner, thus reducing downtime. Against this background, the task arises of making the compression of gas, or rather the operation of a corresponding system, as energy-efficient and resource-conserving as possible. Disclosure of the Invention

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

[0008] Advantages of the invention

[0009] The invention relates to the compression, possibly storage, and provision of gas, as well as to corresponding systems and their operation. As mentioned at the beginning, hydrogen filling stations are particularly suitable as such systems, with the invention particularly benefiting hydrogen filling stations of the second type, i.e., filling stations with gaseous compression. The invention will therefore be described below in particular with reference to hydrogen filling stations; however, the principle can also be applied to other systems for compressing gas, e.g., with other types of gases, or for other purposes.

[0010] As mentioned, two basic system areas can be distinguished in hydrogen refueling stations. The first system area concerns compression, including cooling of the compressor waste heat, and hydrogen storage. The second system area comprises the preparation for the specific use, i.e., preconditioning (especially cooling), the hydrogen dispenser(s), and the associated refueling equipment, such as breakaway and refueling couplings and the refueling hose.

[0011] The present invention primarily aims at improvements in the first system area, but combines the two system areas by using a single, powerful chiller instead of separate chillers / coolers for hydrogen cooling, which is necessary in both system areas. This allows for synergies to be utilized.

[0012] The influence of gas temperature during compression In a second type of hydrogen filling station, hydrogen is usually compressed in several stages (typically interstage and cylinder jacket cooled) to up to 1000 bar and stored in medium and / or high pressure banks at, for example, between 300 and 100 bar or between 450 and 1000 bar in order to provide the hydrogen for refueling cars, buses and commercial vehicles at sufficient pressure.

[0013] In addition to rotary compressor systems, multi-stage piston compressors are often used to compress gaseous hydrogen. An efficient compression process and a long service life of the technical components are extremely advantageous, not least for technoeconomic reasons.

[0014] Both lubricated and non-lubricated reciprocating compressors generally require a sufficiently good sealing system between the high- and low-pressure sides of the compressor stages. These sealing systems are typically made of polymers such as PUR or PTFE and are operable within certain temperature limits. If these temperature limits are exceeded, increased wear occurs and service life is significantly reduced. To counteract this effect, the heat generated during compression should be dissipated from the system as efficiently and resource-efficiently as possible.

[0015] The number of compressor stages in piston compressors is not limited per se, although three or four, for example, may be practical. Gas, such as hydrogen, is cooled after at least one or more of the compressor stages by means of a refrigeration machine via a coolant circuit. Cooling is expedient after each compressor stage, and therefore also between two compressor stages. Suitable heat exchangers can be provided for this purpose. In addition, the compression device is also cooled by means of the coolant circuit. In this case, one or more housing components of the compression device, in particular inlets for the gas and / or a drive, can be cooled via the coolant circuit.

[0016] Cooling requirements during refueling When refueling a vehicle at the dispenser of a hydrogen filling station, the hydrogen or gas in general is usually pre-conditioned in terms of pressure and mass flow using a controllable pressure regulator (“pressure ramp regulator”) in order to maintain the pressure increase rate in the vehicle tank required by the protocol. For the common standards (e.g. SAE J2601, JPEC-S0003, PRHYDE protocol or CEP protocol) it is generally necessary to pre-cool the gas (hydrogen) to temperatures of up to 233.15 K (or -40°C) before refueling. In all temperature ranges relevant for refueling, gaseous hydrogen heats up as a result of the negative Joule-Thomson effect during isenthalpic expansion. This also means that the hydrogen heats up when the pressure is reduced downstream of the pressure ramp regulator.

[0017] At a second-type filling station, both compressor cooling and pre-cooling are necessary for conditioning the hydrogen for refueling. The latter must cool to a specified temperature range, while in the first area (compressor cooler), more intensive cooling, even temporary, would be advantageous.

[0018] Within the scope of the present invention, an optimized concept for a system for hydrogen or, more generally, gas compression is proposed, which enables an extended service life of thermally stressed components by lowering the temperature of these components. The service life-extending effects can preferably be verified through temperature measurements, manufacturer specifications, and material testing. In the long term, this can be used to implement a "predictive maintenance" approach, which allows the need for component replacement to be indicated not only based on operating hours, but also on the temperature profile experienced.

[0019] For this purpose, the resulting gas, e.g., hydrogen, is compressed using a compression device with one or more compressor stages, and the compressed gas is then fed to a storage and / or pressure control system. The storage and / or pressure control system can, for example, comprise a so-called storage bank management system and a pressure ramp control system. Subsequently, the gas can then be made available, e.g., via a supply device or a dispenser for further use, e.g., for refueling a vehicle. Both steps require cooling capacity, which, within the scope of the present invention, is provided by the same refrigeration machine.

[0020] Efficient cooling is possible through the simultaneous use of the chiller for both dispenser cooling and cooling the gas between the compressor stages, as well as the compression device (compressor) and its components. For example, a pump or feed pump can be provided for the coolant circuit. This makes it possible to introduce just as much cooling into the compression system as is necessary to enable service life-enhancing operation of the individual components. This is achieved by having the pumped refrigerant (coolant medium) cool the interstage heat exchangers, the cylinder cooling systems, the compression drive, and any other potentially unwanted heat sources.

[0021] In one embodiment, the coolant of the coolant circuit is cooled by a main heat exchanger, and the gas provided by the storage and / or pressure control system is also cooled by the main heat exchanger. The use of such a main heat exchanger (along with heat exchangers between the compressor stages) allows for efficient cooling not only of the coolant of the coolant circuit, but also of the gas.

[0022] In one embodiment, the coolant and / or gas passing through the main heat exchanger are cooled by the aforementioned refrigeration machine, in particular a compression refrigeration machine. A compression refrigeration machine designed for average performance can, for example, introduce a refrigerant such as CO2, propane, or other natural or F-gas-containing refrigerants into the main heat exchanger via one or more expansion valves. This allows for efficient cooling.

[0023] In one embodiment, a coolant in the main heat exchanger is different from the coolant in the coolant circuit. Potentially possible coolants (or cooling media) for the intermediate stages and drive cooling (compressor) can therefore differ from the coolant contained as a coolant in the main heat exchanger. This can be achieved, for example, by integrating an additional pipe string into the main heat exchanger, thus closing the coolant circuit for component cooling.

[0024] In another embodiment, the coolant in the coolant circuit is usually cooled to ambient temperature in the return line upstream of the main heat exchanger using an air heat exchanger. This allows the coolant (refrigerant) not used for dispenser cooling to be cooled to approximately ambient temperature in the return line upstream of the main heat exchanger using an air heat exchanger, at least if possible (this also applies to the sub-option with different cooling media). Additionally, this cooling circuit can be decoupled from the main heat exchanger by appropriate shut-off devices or shut-off elements, provided that the system temperature of the components within the compression unit that are susceptible to thermal wear can be sufficiently cooled by the ambient cooling described above.

[0025] In one embodiment, a gas temperature is measured after each of the compressor stages using a temperature sensor. Alternatively or additionally, temperatures of components of the compression devices, e.g., affected components such as cylinder walls, hydraulic oil, and the like, can be measured using a temperature sensor. Based on the measured or recorded temperatures (of the gas or components) and based on a model, component replacement is then predicted.

[0026] Using temperature sensors (or temperature transmitters), which measure, for example, the gas or hydrogen temperature before and / or after each compressor stage, it is possible to calculate which components in the compressor system were exposed to elevated temperatures and for what duration. Even with the increased cooling of the intermediate stages, these temperatures still vary greatly from stage to stage, depending on the compression ratio. They can also depend on the ambient conditions. Based on experience and studies by component manufacturers, a model can be created which, based on the temperature history of the component, predicts the next necessary replacement. Instead of replacing all seals, for example, it can be shown that only a few seals were actually exposed to higher temperatures for an extended period. The respective pressure when the temperature was measured can also be included in the model. This procedure is similar to a load cycle count using the so-called

[0027] Rainflow algorithm, but places an emphasis on temperature history.

[0028] The proposed process and corresponding system, in particular, achieves thermal relief for system components such as piston seals or the hydraulic system. Sealing systems are typically made of PUR or PTFE and exhibit increased wear under increased thermal stress. By cooling the gas at the respective cylinder inlet and cooling the cylinder jackets, their service life can be significantly extended.

[0029] The same applies to the cooling of the compressor drive, especially in the case of hydraulically driven compressors, since commercially available hydraulic oils have a limited viscosity range, and hydraulic drives such as radial or axial piston compressors rely on a thermally limited viscosity range. High thermal stress on these oils ultimately leads to shortened oil filter and / or oil change intervals. This is due to the fact that moving components are not operated within the recommended viscosity range, and mechanical wear increases.

[0030] A further advantage is that cooling is not limited to the ambient temperature, allowing a common chiller and therefore a common refrigeration circuit for the entire system. This leads to a significant cost advantage through a modular system design and a cost-optimized design of systems such as hydrogen refueling stations.

[0031] The invention is illustrated schematically in the drawing using an embodiment and is described below with reference to the drawing.

[0032] Short description of the drawing

[0033] Figure 1 shows schematically a system according to the invention in a preferred embodiment.

[0034] Detailed Description of the Drawing Figure 1 schematically shows a preferred embodiment of a system 100 according to the invention, by means of which a method according to the invention can also be carried out. This is a simplified process diagram. In particular, a concrete example of a system 100 designed as a hydrogen filling station with a multi-stage piston compressor as the compression device 140 and a storage and / or pressure control system 120 is shown. A drive 23 of the piston compressor 140 can be designed, for example, mechanically, hydraulically, or pneumatically.

[0035] In the case of refueling a vehicle 200 illustrated in Figure 1, the system 100 is supplied with hydrogen, shown here as stream a, from a source 110 such as an electrolysis system, a pipeline, a trailer, or a comparable system. It is understood that, as a rule, various components or installations may be provided or even necessary between the source 110 and the piston compressor 140 (e.g., input buffers, pressure regulators, sensors, etc.), which, however, are not shown here and are not further relevant to the present invention.

[0036] The resulting hydrogen a then enters, for example, the piston compressor 140 or a first piston unit or cylinder stage 2 there via an inlet valve 1. After the hydrogen has been compressed in the first cylinder stage 2, it enters a heat exchanger 15 via the outlet valve 3. This extracts so much heat energy from the compressed hydrogen that no thermal overload of the corresponding components can occur during further compression by the subsequent compressor stages 6 and 10. An inlet valve 5 and an outlet valve 7 are provided for compressor stage 6, and an inlet valve 9 and an outlet valve 11 are provided for compressor stage 10.

[0037] The number of compressor stages is shown in the example as three, although this number is at least one and, in principle, there is no upper limit. Four, five, six, or more compressor stages are also conceivable, or even just one or two. Generally, heat is extracted from the hydrogen after each compression step.

[0038] After the heat exchanger 17 of the last compressor stage 10, the hydrogen, referred to here as stream b, enters, for example, a so-called bank management system (for storage banks), which serves to enable both filling of the storage cascades by the compressor and cascaded refueling of a hydrogen vehicle 200, or a hybrid of the two operating modes. For the sake of simplicity, the storage and / or pressure control system 12 comprises both the bank management system and the storage cascades, which can include, for example, either medium- or high-pressure storage or a combination of both.

[0039] In particular, the storage and / or pressure control system 12 has a pressure ramp control, which enables targeted vehicle refueling in accordance with the applicable regulations and refueling standards (e.g., SAE J2601, CEP, or PRHYDE*). The heat released by the pressure control is recooled via a main heat exchanger 13 (heat exchanger system) and fed to the hydrogen dispenser or a supply device 130, which can be used to refuel a vehicle 200 (see stream d).

[0040] The main heat exchanger 13 can be filled with a refrigerant or coolant (e.g., Antifrogen or Freezium, or a mixture of water and glycol) to absorb the heat generated during refueling over a certain time interval and thus remove it from the heated hydrogen. A compression refrigeration machine 15, designed for average performance, introduces a conventional refrigerant into the main heat exchanger 13 via one or more expansion valves 16, thus cooling the coolant (refrigerant), which is used to cool the hydrogen lines (stream c) contained in the main heat exchanger 13, including the hydrogen conveyed therein.

[0041] By means of a feed pump 18, coolant is introduced into a coolant circuit (e, f, g, h; specifically, supply e and return f for the compressor stages and supply g and return h for the compression device itself) to introduce exactly the amount of cold into the compression device as is necessary to enable a service life-enhancing operation of the individual components. This is achieved by the coolant delivered by pump 18 cooling the interstage heat exchangers 15, 16 and 17, the cylinder cooling systems 19, 20 and 21 and the compressor drive via a cooling system 22 as well as other potentially unwanted heat sources. Possible coolants for the intermediate stages (heat exchangers 15, 16, 17) and drive cooling (heat exchangers 19, 20, 21, 22) can differ from the coolant contained as a coolant in the main heat exchanger 13. This can be achieved, for example, by installing another pipe string (ora suitable line) downstream of the heat exchanger 15 and upstream of the pump 18 is integrated into the main heat exchanger 13, thus closing the refrigeration circuit for component cooling.

[0042] Likewise, the coolant not used for dispenser cooling can be cooled to approximately ambient temperature in the return line upstream of the main heat exchanger 13 using an air heat exchanger 30, if possible (this also applies to the sub-option with different cooling media). Additionally, this cooling circuit can be decoupled from the main heat exchanger 13 by appropriate shut-off devices if the system temperature of the thermally wear-prone components within the compressor system can be sufficiently cooled by the ambient cooling described above.

[0043] Predictive maintenance can also be implemented. Temperature sensors or temperature transmitters that measure the hydrogen temperature before and after each compressor stage, and possibly also of other compressor components, can be used to calculate which components in the overall compressor system were exposed to elevated temperatures and for what duration. As an example, only a temperature sensor 32 after compressor stage 2 is shown here.

[0044] These temperatures still vary considerably from stage to stage, even with the increased cooling of the intermediate stages. They also depend on ambient conditions. Based on empirical values ​​and studies by component manufacturers, a model can be created that predicts the next necessary replacement based on the component's temperature history. Instead of replacing all seals, for example, it may be possible to determine that only a few seals were actually exposed to higher temperatures (pressure-dependent) for an extended period.

Claims

Patent claims 1. A method for compressing and providing gas, in particular hydrogen, wherein the gas obtained (a) is compressed by means of a compression device (140) having one or more compressor stages, and the compressed gas (b) is fed to a storage and / or pressure control system (120), and wherein gas (d) provided by the storage and / or pressure control system (120) is fed to a supply device (130) for further use, in particular for delivery to a vehicle, wherein gas is cooled downstream of one or more of the plurality of compressor stages and the compression device by means of a refrigeration machine (15) by means of a coolant circuit (e, f, g, h), and wherein the supply device (130) is further cooled by means of the refrigeration machine (15).

2. The method according to claim 1, wherein the compression device (140) has a plurality of compressor stages for multi-stage compression of the gas, and wherein gas is cooled via the coolant circuit between each two compressor stages and after a last one of the plurality of compressor stages.

3. The method according to claim 2, wherein after each of the plurality of compressor stages, a temperature of the gas and / or of components of the compression devices is detected by means of a respective temperature sensor (32), and wherein, based on the temperatures detected by means of the temperature sensors and based on a model, a replacement of components is predicted.

4. Method according to one of the preceding claims, wherein coolant of the coolant circuit is cooled by means of a main heat exchanger (13), and wherein the gas (c) provided by the storage and / or pressure control system (120) and supplied to the supply device (130) is cooled by means of the main heat exchanger (13).

5. The method according to claim 4, wherein coolant passed through the main heat exchanger (13) and / or gas passed through the main heat exchanger (13) is cooled by means of the refrigeration machine, in particular a compression refrigeration machine.

6. The method according to claim 4 or 5, wherein a coolant in the main heat exchanger (13) is different from the coolant of the coolant circuit.

7. Method according to one of claims 4 to 6, wherein coolant of the coolant circuit in the return line before the main heat exchanger is cooled by means of an air heat exchanger, in particular to ambient temperature.

8. Method according to one of claims 4 to 7, wherein the coolant circuit is decoupled from the main heat exchanger by means of shut-off means if necessary.

9. Method according to one of the preceding claims, wherein one or more housing components of the compression device (140), in particular inlets for the gas and / or a drive (41), are cooled via the coolant circuit.

10. A system (100) for compressing and providing gas, in particular hydrogen, comprising a compression device (140) with one or more compressor stages, a storage and / or pressure control system (120), a supply device (130), and a refrigeration machine (15), wherein the system (100) is configured to compress the obtained gas (a) by means of the compression device (140) and to supply the compressed gas (b) to the storage and / or pressure control system (120), wherein the system (100) is configured to supply the gas provided by the storage and / or pressure control system (120) to the supply device (130), in particular for delivery to a vehicle (200), wherein the system (100) further comprises a coolant circuit (e, f, g, h) and is configured to cool gas downstream of one or downstream of at least one of the multiple compressor stages by means of the refrigeration machine (15) via the coolant circuit,and to cool the compression device (140) via the coolant circuit, and to cool the supply device (130) z by means of the refrigeration machine (15).

11. Plant (100) according to claim 10, wherein the compression device (140) has a plurality of compressor stages for multi-stage compression of the gas, and wherein the The system (100) is configured to cool gas between each two compressor stages and after a last one of the plurality of compressor stages via the coolant circuit, and wherein the system (100) further comprises one or more temperature sensors (32) and is configured to detect a temperature of the gas and / or of components of the compression devices by means of one of the temperature sensors (32) after each of the plurality of compressor stages, and to predict a replacement of components based on the temperatures detected by means of the temperature sensors and based on a model.

12. System (100) according to claim 10 or 11, further comprising a main heat exchanger (13), wherein the system (100) is configured to cool coolant of the coolant circuit by means of the main heat exchanger, wherein the system is configured to cool the gas provided by the storage and / or pressure control system (120) by means of the main heat exchanger.

13. Plant (100) according to one of claims 10 to 12, which is designed as a hydrogen filling station.

14. Plant (100) according to one of claims 10 to 13, which is arranged to carry out a method according to one of claims 1 to 9.

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