Gas compression system and method for recovering hydrogen

Abstract

The invention relates to a gas compression system (100) having a compressor (1) for compressing hydrogen gas, at least one recovery device (10) for recovering hydrogen gas escaping from the compressor (1) as leakage gas during compression, and a leakage gas return line (30), the invention relates to a gas compression system (100) having a leakage gas return line (4) which is designed to return leakage gas (2) recovered by at least one recovery device (10) into a position (5) upstream of a compressor (1) in the gas compression system (100) and / or into a suction line (3a) of a compressor stage (5a) of the compressor (1), the compressor (1) having a leakage gas discharge line (4) for discharging the leakage gas (2) from the compressor (1), wherein each recovery device (10) can be fluidly connected to a leak gas discharge line (4) and a leak gas return line (30) and each recovery device has at least one metal hydride tank (11a) which is thermally coupled to a respective heat exchanger (12a), and wherein each metal hydride tank (11a) has at least one hydride-forming metal alloy (15a), when heat is supplied or dissipated through the corresponding heat exchanger (12a), the hydride forms a metal alloy (15a) for cyclic release or absorption of the leaked gas (2). Wherein each recovery device (10) is designed to increase the leakage gas pressure (pL) in the leakage gas discharge line (4) at least to the pressure (p) in the location (5) of the gas compression system (100) and / or at least to the suction pressure (ps) in the suction line (3a) of the compressor stage (5a).

Description

Technical Field

[0001] The present invention relates to a gas compression system, a method for recovering hydrogen leaked from a compressor, and a hydrogen refueling station including the gas compression system as described below. Background Art

[0002] Hydrogen refueling stations are used to refuel fuel cell vehicles with hydrogen. Hydrogen refueling stations known from the prior art are constructed in such a way that hydrogen is taken from a tank containing hydrogen, pressurized in a compressor and then fed into the hydrogen-burning vehicle. Due to the low molar mass (also called molar mass or molar mass-related mass) of hydrogen, the compression of hydrogen is technically challenging, especially at high volume flows. Today, high purity and high pressure, in particular more than 400 bar, are required to refuel fuel cell vehicles with hydrogen.

[0003] EP 3121446A1 describes an oil-lubricated piston compressor for compressing hydrogen and a hydrogenation system for delivering high-pressure hydrogen to vehicles powered by fuel cells. However, a disadvantage of using such an oil-lubricated piston compressor is that the oil content in the hydrogen must be reduced as much as possible before the discharged hydrogen is delivered to the consumer in order not to affect the function of the fuel cell or even to avoid damaging the fuel cell. For this purpose, for example, appropriately designed separators and / or filters are used, which are arranged downstream of the last compression stage. The need for separators and / or filters to separate the lubricant from the compressed hydrogen increases the maintenance costs of such a gas compression system and ultimately leads to higher operating costs.

[0004] The piston compressors known in the prior art generally cannot adopt a pressure encapsulation structure, which means that a certain degree of leakage of the compressed medium into the environment must be accepted. For example, JP 2011-132876A discloses a piston compressor for compressing hydrogen, wherein leakage of hydrogen from the compressor into the environment is acceptable. Due to the flammability and the ability to form explosive mixtures, such a system, in addition to the waste of valuable resources and the associated economic disadvantages, also entails considerable safety risks, depending on the location where the compressor is used.

[0005] In order to prevent leakage losses, WO 2015 / 074740A1 proposes a leakage return line that extends from the inside of the piston compressor housing to an inlet on the first cylinder head of the compressor. Therefore, the housing of the reciprocating compressor is designed to be pressure-resistant at least to the suction pressure of the first compressor stage. However, the disadvantage of the pressure-resistant solution is that the design effort and investment cost are higher than for non-pressure-resistant compressor housings. In addition, such a system cannot satisfactorily solve the problem of uncontrolled release of hydrogen into the environment, because the static seals used therein can only seal the excess hydrogen pressure in the housing without leakage to a limited extent.

[0006] Finally, EP 3163081A1 discloses a hydrogen gas compression system in which the leaking hydrogen of the main compressor is delivered to an auxiliary compressor, wherein both compressors are reciprocating compressors. The hydrogen compressed by the auxiliary compressor is delivered to a recovery tank and from there returned to the suction line of the main compressor. However, this prior art gas compression system also has certain disadvantages due to the use of multiple reciprocating compressors with a large number of moving parts and the potentially large maintenance workload, as well as the pressure fluctuations caused by the oscillating operating mode of the reciprocating piston machine and the need to use an auxiliary tank as a pulsation damper. Summary of the invention

[0007] Based on the above-mentioned prior art, the object of the present invention is to eliminate such disadvantages in the prior art, in particular to provide a gas compression system for compressing hydrogen, which is reliable, requires little maintenance, and has low operating costs, including electricity consumption costs.

[0008] This problem is solved by a gas compression system for compressing hydrogen, a method for recovering hydrogen and a hydrogen filling station comprising a gas compression system as stated in the independent claims. Advantageous embodiments and further embodiments are subject matter of the dependent claims.

[0009] The problem is solved in particular by a gas compression system comprising a compressor for compressing hydrogen. The compressor has a leakage gas discharge line for discharging leakage gas hydrogen generated during the compression process from the compressor. The gas compression system also has at least one recovery device for recovering leakage gas hydrogen generated during the compression process, and a leakage gas return line. The leakage gas return line is designed to return the leakage gas recovered by at least one recovery device to a position upstream of the compressor in the gas compression system. In addition or alternatively, the leakage gas return line is designed to return the leakage gas recovered by at least one recovery device to the suction line of the compressor stage of the compressor. Each recovery device can be fluidically connected to the leakage gas discharge line and the leakage gas return line, and each recovery device has at least one metal hydride storage tank. Each metal hydride storage unit is thermally coupled to a heat exchanger and has at least one metal alloy that forms a hydride, which is designed to cyclically release or absorb leakage gas by supplying or removing heat through respective heat exchangers. The recovery device in the gas compression system is designed to reduce the leakage gas pressure (p L ) is pressurized at least to the pressure at the location of the gas compression system (p) and / or the suction pressure in the suction line of the compressor stage (p S ).

[0010] The use of metal hydrides is a promising method for hydrogen compression that does not require any moving parts and requires very little energy. In this method, a reversible heat-driven interaction of a hydride-forming metal, alloy or intermetallic compound with hydrogen is used to form a metal hydride. The hydride-forming material absorbs low-pressure hydrogen at low temperatures, i.e., takes away heat from the hydride-forming material, which is beneficial to the exothermic formation of the metal hydride. On the other hand, the endothermic decomposition of the metal hydride is beneficial to the desorption of high-pressure hydrogen from the metal hydride at higher temperatures, i.e., adding heat to the metal hydride. In this way, periodic low-pressure hydrogen absorption or high-pressure hydrogen desorption can be achieved by periodically cooling and heating the hydride-forming material or metal hydride, similar to the suction and pressurization process in a mechanical compressor. Therefore, the device based on this principle is also referred to as a metal hydride compressor in the following text.

[0011] In the context of the present invention, a "compressor for compressing hydrogen" (hereinafter referred to as "compressor") is understood to be a device for increasing the pressure and density of hydrogen as the working gas of the compressor, such as a reciprocating compressor, an ion compressor, a screw compressor or a diaphragm compressor, but with the proviso that the compressor is not a metal hydride compressor. According to the present invention, at least one recovery device for increasing the leakage gas pressure to the suction pressure is a single-stage or multi-stage metal hydride compressor.

[0012] The gas compression system of the present invention is simple in structure, reliable, and has low maintenance cost, and can regularly recover hydrogen at low operating cost. In addition, the use of metal hydride accumulators can achieve high compression ratios, low power consumption, and high purity of recovered hydrogen.

[0013] In particular, the compressor of the gas compression system according to the present invention may also be a multi-stage compressor having a plurality of compressor stages, which is configured to compress the working gas stage by stage.

[0014] Preferably, the leakage gas return line is designed to return the leakage gas recovered by the at least one recovery device to the suction line of the first compression stage of the compressor. Therefore, the pressure of the leakage gas only needs to be increased to the relatively low pressure existing in the suction line of the first compression stage, for example to a pressure of about 30 bar.

[0015] In a preferred embodiment, the gas compression system according to the present invention comprises a first recovery device and a second recovery device, which are connected in parallel so that the metal hydride storage tanks arranged in the respective recovery devices can be filled and released independently of each other.

[0016] By providing a plurality of recovery devices in parallel, the gas compression system of the present invention can be used in a continuous process or to continuously recover leaked gas that occurs continuously.

[0017] Another problem that arises from operating metal hydride compressors over a wider temperature range is the high thermal stresses that occur in the metal hydride storage tanks at the beginning of the heating and cooling half-cycles. If the additional stresses caused by the increased gas pressure during hydride desorption (heating) and the increased volume of the hydride-forming metal alloy during hydride formation (cooling) are taken into account, the probability of damage to the metal hydride storage tank (e.g. cracking) increases, which significantly reduces the service life and operating safety.

[0018] In order to make the operating temperature range of each metal hydride storage unit as low as possible during operation, in another preferred embodiment of the gas compression system, each recovery device has a plurality of metal hydride storage units. The metal hydride storage tanks are connected in series with each other from the flow direction of the leakage gas flow, and each is thermally coupled to a heat exchanger. The metal hydride storage tanks connected in series each have at least one hydride-forming metal alloy, which is designed to cyclically release or absorb hydrogen by adding or removing heat through the respective heat exchangers. The first metal hydride storage tank arranged in the flow direction in each recovery device is designed to reduce the pressure of the leakage gas from the leakage gas pressure (p L ) increases to a value higher than the leaking gas pressure (p L The last metal hydride storage tank arranged in the flow direction of each recovery device is designed to increase the pressure of the leaked gas to the suction pressure (p1). s Each metal hydride storage tank disposed between the first and last metal hydride storage tanks is designed to gradually increase the pressure of the leaked gas to an intermediate pressure (p2, p3, ... p1) higher than the first intermediate pressure (p2, p3, ... p2). n ).

[0019] Unless otherwise stated, the term "flow direction" always refers to the flow direction of the leakage gas flow in the gas compression system according to the present invention.

[0020] Preferably, the metal hydride storage tanks connected in series each have a different hydride-forming metal alloy. This allows a higher compression ratio to be achieved.

[0021] In a particularly preferred embodiment of the gas compression system according to the invention, the metal hydride tanks connected in series contain hydride-forming metal alloys that are different from one another, wherein the thermal stability of the hydrated metal alloys decreases in the flow direction, ie compared to the previously arranged metal hydride tanks.

[0022] However, an increase in the number of metal hydride storage tanks in a recovery device, or an increase in the number of stages of metal hydride compressors constructed thereby, will result in a decrease in efficiency, and therefore each recovery device preferably has only two metal hydride storage tanks.

[0023] In a preferred embodiment of the gas compression system according to the invention, the compressor of the gas compression system is designed as a piston compressor, wherein the gas compression system according to the invention can also be transferred or retrofitted to existing widely used compressors.

[0024] Preferably, the compressor of the gas compression system is designed as a dry piston compressor. A dry piston compressor is a compressor that can operate without external lubricants (such as lubricating oil) in the compression part. This greatly reduces the risk of compressed hydrogen being contaminated by lubricants.

[0025] In a preferred embodiment of the gas compression system according to the invention, the hydride-forming metal alloy of the metal hydride storage tank has a dissociation pressure of at least 30 bar, preferably at least 35 bar, particularly preferably at least 40 bar at a temperature of 60-100° C. Methods for measuring the dissociation pressure are known to the skilled person in the prior art, for example from the publication “TiCrVMo alloys with high dissociation pressure for high-pressure MH tank” by T. Matsunaga et al., International Journal of Hydrogen Energy, Vol. 34 (2009), 1458-1462, which is cited herein (see Section 2 “Experiments” therein).

[0026] With regard to alloy systems that can be used, there are many hydrogenatable metal alloys, each of which has very specific pressure-temperature characteristics and is therefore particularly suitable for certain applications, where the alloy composition has a significant effect on the location of the pressure plateau at a specific application temperature. An overview of common metal hydrides and their properties can be found in B. Sakintuna et al., "Metal hydride materials for solid hydrogen storage: A review", International Journal of Hydrogen Energy, Vol. 32 (2007), 1121-1140, which publication is cited herein.

[0027] In a preferred embodiment of the gas compression system according to the present invention, the hydride-forming metal alloy is selected from the group consisting of LaNi5, ZrV2, ZrMn2, TiMn2, FeTi, Zr2Co and Ti2Ni. Preferably, the hydride-forming metal alloy is selected from the group consisting of LaNi5, ZrV2, ZrMn2 and TiMn2.

[0028] The advantage of the above metal alloys is that a larger working pressure range can be set by alloy technology, in particular by combining two or more of the above metal alloys, and the working pressure range is determined by the leakage gas pressure (p L ) and suction pressure (p S ) is determined by the difference between them.

[0029] In a preferred embodiment of the gas compression system according to the invention, the compressor has a housing which is substantially pressure-resistant only up to 40 bar. Preferably, the housing of the compressor is pressure-resistant only up to 15 bar, particularly preferably only up to 2 bar. Such a housing is particularly easy to manufacture and cost-effective.

[0030] In a preferred embodiment, the gas compression system according to the invention has no container for storing leaked gas downstream of at least one recovery device and before the leaked gas is returned to the point upstream of the compressor in the gas compression system. In other words, the gas compression system has no container for storing leaked gas downstream of at least one recovery device and before the leaked gas is fed back to the position upstream of the compressor in the gas compression system and / or the suction line of the compressor stage. Alternatively or in addition, it is also conceivable that the gas compression system between the compressor and at least one recovery device has no container for storing leaked gas. In the latter case, the gas compression system therefore has no container for storing leaked gas - except for the hydrogen source of the compressor.

[0031] It should be understood that elements of the present invention comprising the term "pipeline", ie elements of the device for fluidly connecting a gas compression system, should not be regarded as "containers" within the meaning of the present invention.

[0032] This means that gas compression systems can be designed to be more compact, more space-saving and with less equipment.

[0033] The supply of heat to the metal hydride storage tank and the removal of heat from the metal hydride storage tank by the corresponding heat exchanger are achieved by surrounding the metal hydride storage tank with a heat transfer medium that is isolated from the outside world. The heat released when storing hydrogen is transferred to the heat transfer medium and heats the heat transfer medium and the metal hydride storage tank itself. The volume of the heat transfer medium should be so large that the released heat can be completely absorbed by the heat transfer medium when the metal hydride storage tank is fully filled. Alternatively or in addition, it is also conceivable to exchange the heat transfer medium of the corresponding heat exchanger regularly or continuously by a suitable conveying device (such as a pump). The temperature increase obtained when filling the metal hydride storage tank with hydrogen depends on the filling pressure and the choice of the hydride forming metal alloy.

[0034] In a preferred embodiment of the gas compression system according to the invention, each heat exchanger contains as heat transfer medium a liquid having a boiling point temperature between 30° C. and 180° C. at normal pressure. Preferably, the boiling point temperature of the liquid used as heat transfer medium is between 90° C. and 130° C. at normal pressure. Water, a water-glycol mixture or thermal oil have proven to be particularly suitable heat transfer media, since they are generally readily available and safe to handle.

[0035] For the general application of metal hydride storage tanks, it is necessary to have a heating system as described above to heat the metal hydride storage tanks for release. So far, electric energy or fossil fuels are usually used to heat the metal hydride storage tanks.

[0036] In a preferred embodiment of the gas compression system according to the present invention, a gas cooler that can be cooled with cooling water is connected downstream of the compressor to cool the hydrogen compressed by the compressor. The gas cooler and the heat exchangers of each recovery device are interconnected in such a way that the cooling water heated during the cooling of the gas cooler can be at least partially used to provide heat to each metal hydride storage unit.

[0037] The use of cold cooling water or cooling water heated by a gas cooler means that the metal hydride storage tank can be operated without the need for external heating energy or with only a very small amount of heating energy. This also eliminates the need for electrical connections for heating. In addition to the power consumption for control and regulation, the total energy required to increase the pressure of the leaking gas is almost zero. Using cold or heated cooling water instead of electrical energy to cool or heat metal hydride storage tanks not only improves the overall efficiency of industrial processes, but also indirectly helps to reduce greenhouse gases and other harmful emissions that are byproducts of electricity generation in thermal power plants using fossil fuels.

[0038] In a preferred embodiment of the gas compression system according to the present invention, the leaking gas discharge pipeline has a pressure relief valve. Preferably, the pressure relief valve opens when the pressure is greater than 2 bar.

[0039] Providing a pressure relief valve in the leakage gas discharge line helps to improve operational safety, since, for example, hydrogen which cannot be absorbed by the recovery device due to the closed valve will not accumulate in the leakage gas discharge line beyond its load limit.

[0040] In a preferred embodiment of the gas compression system according to the present invention, each metal hydride storage tank has at least one combination valve or a pair of valves consisting of an inlet valve located upstream of the corresponding metal hydride storage tank along the flow direction and an outflow valve located downstream of the corresponding metal hydride storage tank along the flow direction, which are used to fill the leaked gas into the corresponding metal hydride storage tank and / or release the leaked gas.

[0041] The use of a combination valve to fill or release the leaked gas to the corresponding metal hydride tank has the advantage of reducing the number of required components. The use of a pair of valves consisting of an inflow valve and an outflow valve arranged upstream and downstream of the corresponding metal hydride tank has the advantage that the flow direction of the leaked gas in at least one recovery device can be maintained and the pressure in the recovery device can be increased more effectively, as will be described in detail below.

[0042] It can be imagined that, in the case where a plurality of metal hydride storage tanks are connected in series along the flow direction, the outflow valve of the first metal hydride storage tank arranged along the flow direction is also the inflow valve of the metal hydride storage tank adjacent to the metal hydride storage tank and arranged downstream along the flow direction. Therefore, the total number of valves required can be significantly reduced, and the design complexity of the gas compression system can be further reduced.

[0043] In a preferred embodiment of a gas compression system comprising a combination valve and / or a pair of valves as described above, the gas compression system further comprises a control device for controlling the combination valve or the inflow valve and the outflow valve. If there are inflow valves and outflow valves, the control device controls them in such a way that in normal operation, for each pair of valves adjacent in the flow direction, at least one adjacent valve is closed to exclude a continuous fluid-conducting connection between the leakage gas discharge line and the leakage gas return line.

[0044] In a preferred embodiment of the gas compression system according to the present invention, at least one non-return element that is closed in the opposite direction of the flow is arranged between the metal hydride storage tanks of each recovery device. In addition or alternatively, at least one non-return element that is closed in the opposite direction of the flow is arranged in the leakage gas discharge pipeline. In addition or alternatively, at least one non-return element that is closed against the flow direction is arranged in the leakage gas return pipeline.

[0045] By eliminating the fluid-conducting connection between the leakage gas discharge pipeline and the leakage gas return pipeline by utilizing the actuating device and / or the arrangement of the non-return device, the backflow of leakage gas in the opposite direction of flow due to the pressure difference between the individual metal hydride storage tanks can be eliminated, which significantly reduces the risk of overload and component damage.

[0046] A preferred embodiment of the gas compression system according to the present invention also includes a pre-purification device for pre-purifying the hydrogen leakage gas before it is delivered to the metal hydride storage tank. In this pre-purification device, impurities that may have an adverse effect on the service life of the hydride-forming metal alloy have been filtered out, converted and / or absorbed. To this end, the pre-purification device includes a capture material (getter material), in particular a hydride-forming metal or alloy, wherein the hydride formation only begins when the maximum pressure of the downstream recovery device is much higher than that of the downstream recovery device. This means that during the pre-purification period, hydride formation will not occur at the getter material. However, on the contrary, other components of the hydrogen leakage gas are chemically adsorbed by the getter material, and therefore the actual hydride-forming metal alloy of the metal hydride storage tank will no longer be contaminated or even damaged. This ensures the long-term reliable operation of the metal hydride storage tank of the recovery system.

[0047] Preferably, the pre-cleaning device for pre-cleaning the hydrogen leaking gas is arranged in the leaking gas discharge line, upstream of any branch leading to the respective recovery device, so that the gas compression system can contain only a single pre-cleaning device. Since the getter material has to be replaced with fresh material from time to time depending on the quality of the leaking gas and the required purity of the leaking gas cleaned by the pre-cleaning device, the required workload can be reduced by maintaining a single pre-cleaning device. However, alternatively or in addition, it is also conceivable to assign a pre-cleaning device to each recovery device, which increases the flexibility of operation and maintenance of the gas compression system.

[0048] The problem is also solved by a method for recovering hydrogen generated as leakage gas in a compressor. The method according to the invention comprises: introducing leakage gas into a recovery device having at least one metal hydride storage tank, the storage tank having at least one metal alloy forming hydrides (step a); filling the introduced leakage gas into the metal hydride storage layer, absorbing with the metal alloy, forming metal hydrides (step b); removing the heat released during the formation of the metal hydride by a heat exchanger thermally coupled to the metal hydride storage tank (step c); heating the formed metal hydride to a predetermined temperature by the heat exchanger, while desorbing at least a portion of the previously absorbed leakage gas (step d); releasing the metal hydride storage tank and releasing the desorbed leakage gas from the recovery device into the leakage gas return line and into a position in the gas compression system upstream of the compressor and / or into the suction line of the compressor stage of the compressor at the source of the leakage gas (step e). Step e) can optionally be performed by further heating the metal hydride formed by the heat exchanger. In step d) (if the formed metal hydride is further heated, in step e) the pressure of the leaked gas is reduced from the leaked gas pressure (p) in the leaked gas discharge pipeline by at least one metal hydride storage tank of the recovery device. L ) to at least the pressure at the gas compression system point (p) and / or at least the suction pressure in the compressor stage suction line (p S ). The pressure increase in the recovery device is achieved by appropriately controlling the inlet valve and the outlet valve, which are arranged upstream and downstream of the metal hydride storage tank in the flow direction, as will be described in more detail below.

[0049] Preferably, the method for recovering hydrogen according to the present invention as described herein is carried out using the gas compression system according to the present invention as described herein.

[0050] In a preferred embodiment of the method according to the present invention, a plurality of metal hydride storage tanks connected in series are used in the recovery device along the flow direction to reduce the pressure of the leaked gas from the leaked gas pressure (p L ) is increased in stages to the suction pressure (p SIn this case, the first metal hydride storage tank arranged first in the flow direction of the recovery device changes the pressure of the leaked gas from the leaked gas pressure (p L ) increases to a specific leakage gas pressure (p L ) a higher first intermediate pressure (p1). The last metal hydride storage tank arranged last in the flow direction of the recovery device increases the pressure of the leaked gas to the suction pressure (p S If necessary, the metal hydride storage tanks arranged between the first metal hydride storage tank and the last metal hydride storage tank increase the pressure of the leaked gas in stages to an intermediate pressure (p2, p3, ..., p4) higher than the first intermediate pressure (p1). n ).

[0051] In a preferred embodiment of the method according to the present invention, the method is continuously carried out by cyclically filling and releasing two recovery devices arranged in parallel along the flow direction. Each recovery device comprises at least one metal hydride storage tank.

[0052] In another preferred embodiment of the process according to the invention, the heating of the metal hydride formed in step d) is carried out at least partly with water obtained by cooling a gas cooler downstream of the compressor.

[0053] In a preferred embodiment of the method according to the invention, each metal hydride storage tank is filled and released by at least one valve combination or pair of valves, which consists of an inflow valve located upstream of the respective metal hydride storage tank in the flow direction and an outflow valve located downstream of the respective metal hydride storage tank in the flow direction. In the latter case, the respective inflow valve and outflow valve are actuated by the control device, thereby eliminating a continuous fluid-conducting connection between the leakage gas discharge line and the leakage gas return line.

[0054] The advantages resulting from the implementation of the method described herein substantially correspond to the advantages described for the various embodiments of the gas compression system according to the invention.

[0055] The problem is further solved by a hydrogen refueling station comprising a gas compression system as described herein, the hydrogen refueling station preferably being operated by one of the methods described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Various embodiments of the present invention are described below with reference to the accompanying drawings, wherein the same or corresponding elements are generally provided with the same reference numerals. It is shown:

[0057] Figure 1 A flow chart showing a gas compression system according to the present invention is shown;

[0058] Figure 2 A schematic cross-sectional view of a metal hydride storage tank used in a gas compression system according to the present invention;

[0059] Figure 3 A flow chart showing another embodiment of the gas compression system according to the present invention, wherein two recovery devices are connected in parallel;

[0060] Figure 4a A flow chart showing a gas compression system in a filling step according to the present invention;

[0061] Figure 4b Shows Figure 4a Flow chart of the gas compression system in the release step;

[0062] Figure 5a A flow chart showing another embodiment of the gas compression system according to the present invention, wherein a recovery device is connected in parallel in the filling or releasing step;

[0063] Figure 5b Shows Figure 5a Flowchart of a gas compression system in a release or filling step. DETAILED DESCRIPTION

[0064] Figure 1 A flow chart of a gas compression system 100 with a hydrogen compressor 1 according to the present invention is shown. The compressor 1 can be fluidly connected to a hydrogen source Q via a pipeline 3, so that the hydrogen to be compressed can be supplied to the compressor 1 via the pipeline 3. The gas compression system 100 also includes a recovery device 10, which is used to recover hydrogen escaping from the compressor 1 as leakage gas during compression, which will be described in more detail below. In order to discharge the leakage gas from the compressor, a leakage gas discharge pipeline 4 is provided, which can be fluidically connected to the compressor and the leakage gas flow generated during compression. The gas compression system 100 also has a leakage gas return pipeline 2, which is used to return the leakage gas recovered by the recovery device 10 to a position 5 in the gas compression system 100, which is located upstream of the compressor 1 of the source of the leakage gas. Figure 1 In the embodiment shown, the leakage gas recovered by the recovery device 10 is introduced into the pipeline 3 connecting the hydrogen source Q fluid to the compressor 1 at the position marked with reference numeral 5. The leakage gas return pipeline 30 has a non-return element 31 that is closed opposite to the flow direction S. In the embodiment shown, the recovery device includes two metal hydride storage tanks 11a, 11b, each of which contains a metal alloy that forms a hydride and each of which is thermally coupled to a heat exchanger 12a, 12b. Cold cooling water can be taken from the cooling water source W InThe cooling water is supplied to the gas compression system 100 via the cooling water pump 50 and can be used to cool the two metal hydride storage tanks 11a and 11b. The preheated cooling water, i.e., the cooling water obtained in the process of cooling the hydrogen compressed by the compressor 1 through the gas cooler 7, can be used to heat the two metal hydride storage tanks 11a and 11b. The cold or heated cooling water can be supplied to the two metal hydride storage tanks 11a and 11b through the three-way joints 19a and 19b. The unused or used cooling water is supplied to the cooling water drain pipe W. Out The recovery device 10 can be fluidly connected to the leaked gas discharge pipeline 4 through the inflow valve 13a of the first metal hydride storage tank 11a, and fluidly connected to the leaked gas return pipeline 2 through the outflow valve 14b of the second metal hydride storage tank 11b. The two metal hydride storage tanks 11a and 11b can be fluidly connected together through the connecting pipeline 16 and the valve 14a provided in the connecting pipeline 16, and they are connected in series from the flow direction S of the leaked gas flow. The metal hydride storage tank 11a arranged the frontmost in the flow direction S is designed to reduce the leaked gas pressure p in the leaked gas discharge pipeline 4 to 1. L (e.g. 2 bar) to the same pressure as the leaking gas pressure p L The metal hydride storage tank 11b of the recovery device 10 arranged last in the flow direction S is designed to increase the first intermediate pressure p1 provided by the metal hydride storage tank 11a upstream thereof to the pressure p in the pipeline 3 (for example, 30 bar). The leaked gas recovered in this way, i.e., from the leaked gas pressure p L The leakage gas raised to the pressure p is fed back to the compressor 1 and finally delivered to a consumer V, such as a fuel cell vehicle.

[0065] Figure 2 1 shows a schematic cross-sectional view of a metal hydride storage tank 11a for a gas compression system according to the present invention. In the embodiment shown, the metal hydride storage tank 11a includes a total of twenty-five tubular containers 17a (in Figure 2 17a is shown in cross section in the figure), which is filled with a hydride-forming metal alloy 15a. The container 17a is designed to introduce hydrogen leakage gas into and out of the container 17a, wherein in the case of a tubular container 17a, the inlet and the outlet are preferably arranged at opposite ends of the tube. The container 17a containing the hydride-forming metal alloy 15a is surrounded by a heat transfer medium (particularly water or heat-conducting oil) so that when the heat exchanger 12a supplies heat or dissipates heat, the metal alloy 15a can desorb or absorb the leakage gas. In order to improve the heat conduction between the heat transfer medium and the container wall, a rib plate made of a material with good thermal conductivity can be provided on the outer surface of the container 17a to increase its surface area immersed in the heat transfer medium (not shown).

[0066] Figure 3A flow chart of another embodiment of a gas compression system 100 according to the present invention is shown, which includes two recovery devices 10, 20 connected in parallel for recovering hydrogen escaping from a compressor 1 as leaked gas. The first recovery device 10 includes two metal hydride storage tanks 11a and 11b connected in series, and the second recovery device 20 includes two metal hydride storage tanks 21a and 21b connected in series. The metal hydride storage tank 11a of the first recovery device 10, which is first arranged in the flow direction S, can be connected to the metal hydride storage tank 11b arranged downstream in the flow direction S by connecting the pipeline 16 and the valve 14a arranged therein. Similarly, the metal hydride storage tank 21a of the second recovery device 20, which is first arranged in the flow direction S, can be connected to the metal hydride storage tank 21b arranged downstream in the flow direction S by connecting the pipeline 26 and the valve 24a arranged therein. Hydrogen gas generated as leakage gas during the compression process of the compressor 1 of the gas compression system 100 is discharged from the compressor 1 through the leakage gas discharge pipeline 4 and connected to the first recovery device 10 or the second recovery device 20 through the inflow valve 13a or the inflow valve 23a. The inflow valves 13a and 23a connect the first recovery device 10 or the second recovery device 20 to the leakage gas discharge pipeline 4. The second recovery device 20 and the leakage gas discharge pipeline 4 are alternated in time, that is, the recovery devices 10 and 20 arranged in parallel operate in a push-pull mode. In each recovery device 10 and 20, the pressure of the leakage gas is adjusted from the leakage gas pressure p in the leakage gas discharge pipeline to the pressure p in the leakage gas discharge pipeline. L The suction pressure p in the suction line 3b of the first compressor stage 5b of the compressor 1 is pressurized via the first intermediate pressure p1. S , basically as mentioned above about Figure 1 The metal hydride storage tanks 11a, 11b, 21a, 21b are thermally coupled to heat exchangers 12a, 12b, 22a, 22b, respectively, wherein water for cooling or heating the metal hydride storage tanks can be pumped from a cooling water source W by a cooling water pump 50. In The unused or used cooling water is supplied to the cooling water drain pipe W. Out The first recovery device 10 and the second recovery device 20 can be connected to the leakage gas return line 2 via the outflow valves 14b and 24b arranged downstream of the last metal hydride storage tank 11b, 21b in the respective recovery devices 10, 20 in the flow direction S, wherein the non-return elements 31, 32 are arranged downstream of each recovery device 10, 20 in the flow direction S. Through the leakage gas return line 30, the previously recovered and raised to the suction pressure p SThe leakage gas is conveyed into the suction line 3 b of the first compressor stage 5 b of the compressor 1 , which location is denoted by reference numeral 5 .

[0067] Figure 4a The flow chart of a gas compression system 100 including a single recovery device 10 according to the present invention when filling a single metal hydride storage tank 11a contained therein is shown. A part of the hydrogen supplied from the hydrogen source Q to the compressor 1 through the pipeline 3 is generated as a leakage gas flow during the compression process, and the leakage gas flow is discharged from the compressor through the leakage gas discharge pipeline 4 and is charged into the metal hydride storage tank 11a of the recovery device 10 through the inflow valve 13a. In order to fill the leakage gas in the metal hydride storage tank 11a and form metal hydride, the inflow valve 13a located upstream of the metal hydride storage tank 11a in the flow direction S of the leakage gas is opened, and the outflow valve 14a located downstream of the metal hydride storage tank 11a in the flow direction S of the leakage gas is closed, as shown in FIG. Figure 4a The heat released during the formation of metal hydride is dissipated through a heat exchanger 12a thermally coupled to the metal hydride storage tank 11a, wherein the heat from the cooling water source W In For this purpose, the cold cooling water flows through the cooling water pump 50 and the T-joint 19a (see FIG. 1 ) which connects the cooling water source to the heat exchanger 12a. Figure 4a The spent cooling water heated in the heat exchanger 12a during the cooling of the hydride-forming metal alloy is delivered to the cooling water drain pipe W. Out Once the metal hydride storage tank 11 a is filled with the leaked gas, the inflow valve 13 a located upstream of the metal hydride storage tank 11 a in the flow direction S is closed (not shown).

[0068] Figure 4b Shows Figure 4a Flow chart of the gas compression system 100 during the release of the metal hydride storage tank 11a of the recovery device 10. The metal hydride storage tank 11a is preheated to a predetermined temperature by the heat exchanger 12a to desorb at least a portion of the previously absorbed leakage gas, while the inlet valve and the outlet valve 13a, 14a are closed, wherein when a predetermined leakage gas pressure is exceeded, the pressure relief valve in the leakage gas discharge pipeline continuously discharges the leakage gas from the compressor 1 (not shown). After the pressure in the metal hydride storage tank 11a increases to the pressure p in the pipeline 3, the outlet valve 14a of the metal hydride storage tank 11 downstream in the leakage gas flow direction S is opened, and further heat is input through the heat exchanger 12a to release the metal hydride storage tank 11a. In the present embodiment, heat from the cooling water source W is used for this purpose. In The water is supplied to the gas cooler 7 by the cooling water pump 50 and heated by it (see Figure 4bThe dashed arrows in the figure illustrate the flow of hot water). The three-way connector 19a used can connect the heat exchanger 12a to the cooling water source W In The gas cooler 7 is fluidly connected and can also be used to mix the cooling water source W In The cold cooling water and the cooling water heated by the gas cooler 7 are used to adjust the temperature of the metal hydride storage tank 11a. The desorbed leakage gas under pressure p is discharged from the recovery device 10 through the outflow valve 14a to the leakage gas return pipeline 30, which includes a non-return element 31 opened in the flow direction S and is introduced into the pipeline 3 at the position marked with reference numeral 5. Therefore, the recovered leakage gas is fed back to the compressor 1 and finally discharged to the consumer V.

[0069] Figure 5a The flow chart of another embodiment of the gas compression system 100 according to the present invention is shown, the system comprises two recovery devices 10, 20 connected in parallel, each recovery device having a metal hydride storage tank 11a, 21a. Figure 5a In the embodiment, the first recovery device 10 is in a filling cycle, while the second recovery device 20 is operating in a release cycle opposite to the first recovery device 10. In other words, when the metal hydride storage tank 11a of the first recovery device 10 is filling, the metal hydride storage tank 21a of the second recovery device 20 is releasing. Figure 4a and 4b Compared to the method described in Figure 5a and 5b The method described in the foregoing continuously recovers the leakage gas that occurs during the compression of hydrogen in the compressor 1. Therefore, the overpressure valve in the leakage gas discharge pipeline 4 can usually be omitted, and when the leakage gas pressure therein exceeds a certain p L However, for safety reasons it is still advisable to provide such a pressure relief element in order to prevent pressure peaks and damage in the leaking gas discharge line 4. Figure 5a and 5b In the illustrated embodiment of the gas compression system 100 according to the present invention, the leakage gas discharge line 4 branches into two leakage gas discharge lines 4′ and 4″, wherein one leakage gas discharge line 4′ can be fluidically connected to the first recovery device 10, and the other leakage gas discharge line 4″ can be fluidically connected to the second recovery device 20. The filling of the metal hydride storage tank 11a of the first recovery device 10 is carried out with the inflow valve 13a opened and the outflow valve 14a closed, the inflow valve 13a and the outflow valve 14a being arranged upstream and downstream of the metal hydride storage tank 11a along the flow direction S of the leakage gas, and the heat of the hydride forming metal alloy in the metal hydride storage tank is dissipated by the heat exchanger 12a thermally coupled to the metal hydride storage tank 11a. The cold cooling water used for this purpose is supplied by the cooling water source W InIt is provided by a cooling water pump 50 and a tee 19a which fluidly connects the cooling water source to the heat exchanger 12a (see Figure 5a The used cooling water is discharged to the cooling water outlet W. Out When the inflow valve 23a is closed and the outflow valve 24a is opened, and the metal hydride storage tank 21a is heated by the heat exchanger 22a assigned to it, the metal hydride storage tank 21a of the second recovery device 20 is released. The heat exchanger 22a is fluidly connected to the cooling water source W through the three-way joint 29a. In , wherein the heated cooling water is obtained by a gas cooler 7 which cools the hydrogen compressed by the compressor 1 before discharging it to the consumer V (see Figure 5a The cooling water used in the heat exchanger 22a of the second recovery device 20 is also discharged into the cooling water outlet W Out The first recovery device 10 and the second recovery device 20 can be connected to the leakage gas return line 30 through the outflow valves 14a and 24a of the last metal hydride storage tanks 11a and 21a arranged in the flow direction S in each recovery device 10 and 20, wherein the non-return elements 31 and 32 are arranged downstream of each recovery device 10 and 20 in the flow direction S. The leakage gas pressure p L Compressed to suction pressure p S The leakage gas is conveyed via the leakage gas return line 30 at the location of the suction line 3b (indicated by reference numeral 5) to the first compressor stage 5b of the compressor 1. The gas compression system including the above-mentioned valves is monitored and controlled by a freely programmable system control device (not shown).

[0070] Figure 5b Shows Figure 5a , wherein the first recovery device 10 is now in the release cycle, and the second recovery device 20 is in the filling cycle, only for illustrating the reverse cycle operation of the two recovery devices 10 and 20 connected in parallel. The hot water flow in the gas compression system 100 is represented by the dashed arrows, and the cold water flow is represented by the dotted arrows. Figure 5b The assignment of reference numerals and functional descriptions used for all elements shown in the Figure 5a can be found in the description.

Claims

1. A gas compression system (100) having A compressor (1) for compressing hydrogen; at least one recovery device (10) for recovering leakage gas (2) escaping from the compressor (1) during the compression process; and a leakage gas return line (30) designed to return leakage gas (2) recovered by at least one recovery device (10) to a location (5) upstream of the compressor (1) in the gas compression system (100) and / or to a suction line (3a) of a compressor stage (5a), in particular a suction line (3b) of a first compressor stage (5b) of the compressor (1); in, The compressor (1) comprises a leakage gas discharge line (4) for discharging leakage gas (2) from the compressor (1); wherein each recovery device (10) is fluidically connectable to a leakage gas discharge pipeline (4) and a leakage gas return pipeline (30) and has at least one metal hydride storage tank (11a), each of which is thermally coupled to a heat exchanger (12a); Each metal hydride storage tank (11a) comprises at least one metal alloy (15a) capable of forming hydrides, and is designed to release or absorb leaked gas (2) in a cyclic manner by supplying heat or dissipating heat with the help of a corresponding heat exchanger (12a); and Each recovery device (10) is designed to reduce the leaked gas pressure (p L ) is pressurized at least to the pressure (p) of the location (5) of the gas compression system (100) and / or at least to the suction pressure (p) in the suction line (3a) of the compressor stage (5a) S ).

2. The gas compression system (100) according to claim 1 comprises a first recovery device (10) and a second recovery device (20) for filling and releasing the metal hydride storage tanks (11a, 21a) arranged in each recovery device (10, 20) independently of each other in time.

3. The gas compression system (100) according to claim 1 or 2, in, Each recovery device (10) has a plurality of metal hydride storage tanks, in particular two metal hydride storage tanks (11a, 11b), which are connected in series with each other along the flow direction (S) of the leakage gas flow and are each thermally coupled to a heat exchanger (12a, 12b); The metal hydride storage tanks (11a, 11b) connected in series each have at least one metal alloy (15a, 15b) capable of forming hydrides, preferably different from each other, and are designed to release or absorb hydrogen cyclically by supplying heat or dissipating heat with the help of respective heat exchangers (12a, 12b); The first metal hydride storage tank (11a, 21a) arranged at the front along the flow direction (S) in each recovery device (10, 20) is designed to reduce the pressure of the leaked gas (2) from the leaked gas pressure (p L ) is pressurized to a pressure higher than the leaking gas pressure (p L ) of a first intermediate pressure (p1); The last metal hydride storage tank (11b, 21b) arranged last in the flow direction (S) of each recovery device (10, 20) is designed to increase the pressure of the leaked gas (2) to the suction pressure (p S );and The metal hydride storage tank arranged between the first (11a, 21a) and the last metal hydride storage tank (11b, 21b) is designed to gradually increase the pressure of the leaked gas (2) to an intermediate pressure (p2, p3, ... p4) higher than the first intermediate pressure (p1). n ).

4. A gas compression system (100) according to any one of the preceding claims, wherein: The compressor (1) is designed as a piston compressor, preferably as a dry-running piston compressor.

5. The gas compression system (100) according to any one of the preceding claims, wherein: The metal alloy (15a, 15b, 25a, 25b) used has a separation pressure of at least 30 bar, preferably at least 35 bar and particularly preferably at least 40 bar at a temperature of 60 to 100° C.

6. A gas compression system (100) according to any of the preceding claims, wherein the metal alloy (15a, 15b, 25a, 25b) is selected from the group consisting of LaNi5, ZrV2, ZrMn2, TiMn2, FeTi, Zr2Co and Ti2Ni, preferably from the group consisting of LaNi5, ZrV2, ZrMn2 and TiMn2.

7. A gas compression system (100) according to any of the preceding claims, wherein the compressor (1) has a housing (6) which is designed to withstand a pressure of essentially only up to 40 bar, preferably up to 15 bar, and particularly preferably up to 2 bar.

8. A gas compression system (100) according to any of the preceding claims, wherein the gas compression system (100) does not have a container for storing the leakage gas (2) downstream of at least one recovery device (10, 20) and before the leakage gas (2) returns to a position (5) upstream of the compressor (1) in the gas compression system (100) and / or flows into the suction line (3a) of the compressor stage (5a).

9. A gas compression system (100) according to any of the preceding claims, wherein each heat exchanger (12a, 12b, 22a, 22b) contains a liquid, in particular water or a water-glycol mixture, having a boiling temperature between 30°C and 180°C, preferably between 90 and 130°C at normal pressure, as a heat transfer medium.

10. A gas compression system (100) according to any one of the preceding claims, wherein a gas cooler (7) that can be cooled with cooling water is connected downstream of the compressor (1) for cooling the hydrogen compressed by the compressor (1), wherein the gas cooler (7) and the heat exchangers (12a, 12b, 22a, 22b) of the corresponding recovery devices (10, 20) are connected to each other in the following manner, so that the cooling water heated during the cooling of the gas cooler (7) can be at least partially used to supply heat to the corresponding metal hydride storage tanks (11a, 11b, 21a, 21b).

11. The gas compression system (100) according to any of the preceding claims, wherein the leakage gas discharge line (4) has a pressure relief valve (8) which opens in particular when the pressure in the leakage gas discharge line (4) is greater than 2 bar.

12. A gas compression system (100) according to any one of the preceding claims, wherein each metal hydride storage tank (11a, 21a) comprises at least one combined valve (18) or a pair of valves consisting of an inflow valve (13a, 23a) located upstream of the corresponding metal hydride storage tank (11a, 21a) in the flow direction and an outflow valve (14a, 24a) located downstream of the corresponding metal hydride storage tank (11a, 21a) in the flow direction for filling and / or releasing the corresponding metal hydride storage tank (11a, 21a) with the aid of leaking gas (2).

13. The gas compression system (100) according to claim 12 further comprises an actuating device (9) for actuating the inlet valve and the outlet valve (13a, 13b, 14a, 14b, 23a, 23b, 24a, 24b), wherein the inlet valve and the outlet valve (13a, 13b, 14a, 14b, 23a, 23b, 24a, 24b) are actuated in the following manner so that in operational use, at least one of the adjacent valves in the pairs of valves adjacent in the flow direction is closed to eliminate continuous fluid communication between the leakage gas discharge pipeline (4) and the leakage gas return pipeline (30).

14. The gas compression system (100) according to any one of the preceding claims, wherein Between the metal hydride storage tanks (11a, 11b, 21a, 21b) of each recovery device (10, 20); and / or in the leakage gas discharge line (4); and / or In the leak gas return line (30) At least one non-return element (31, 32) is arranged which blocks counter to the flow direction (S).

15. A method for recovering hydrogen as leakage gas (2) from a compressor (1), preferably implemented with a gas compression system (100) according to any one of claims 1 to 14, the method comprising the following steps: a) introducing the leaked gas (2) into a recovery device (10) having at least one metal hydride storage tank (11a) containing at least one metal alloy (15a) capable of forming hydrides; b) filling the metal hydride storage tank (11a) with the aid of the metal alloy (15a) and forming metal hydride to absorb the introduced leaking gas (2); c) transferring heat released during the formation of the metal hydride through a heat exchanger (12a) thermally coupled to the metal hydride storage tank (11a); d) heating the formed metal hydride to a predetermined temperature by means of a heat exchanger (12a) and desorbing at least part of the previously absorbed leakage gas (2); e) releasing the metal hydride storage tank (11a) and discharging the desorbed leakage gas (2) from the recovery device (10) into the leakage gas return pipeline (30) and into a location (5) in the gas compression system (100) upstream of the compressor (1) and / or into the suction pipeline (3a) of the compressor stage (5a) of the compressor serving as the source of the leakage gas, in particular into the suction pipeline (3b) of the first compressor stage (5b); The pressure of the leaked gas (2) is reduced from the leaked gas pressure (p) in the leaked gas discharge pipeline (4) by at least one metal hydride storage tank (11a) of the recovery device (10). L ) is pressurized at least to the pressure (p) of the location (5) of the gas compression system (100) and / or the suction pressure (p) in the suction line (3a) of the compressor stage (5a) S ).

16. The method according to claim 15, in, Using a plurality of metal hydride storage tanks (11a, 11b) connected in series along the flow direction (S) of the leaked gas flow, the pressure of the leaked gas (2) is adjusted in multiple stages from the leaked gas pressure (p L ) increases to the suction pressure (p S ); The first metal hydride storage tank (11a, 21a) arranged at the front along the flow direction (S) in each recovery device (10, 20) reduces the pressure of the leaked gas (2) from the leaked gas pressure (p L ) rises to a value higher than the leaking gas pressure (p L ) of a first intermediate pressure (p1); The last metal hydride storage tank (11b, 21b) arranged last in the flow direction (S) in each recovery device (10, 20) increases the pressure of the leaked gas (2) to the suction pressure (p S );and The metal hydride storage tanks arranged between the first (11a, 21a) and the last metal hydride storage tanks (11b, 21b) increase the pressure of the leaked gas (2) in stages to intermediate pressures (p2, p3, ... p4) higher than the first intermediate pressure (p1). n ).

17. A method according to claim 15 or 16, wherein the method is carried out continuously by cyclically filling and releasing two recovery devices (10, 20), wherein the two recovery devices (10, 20) are arranged in parallel along the flow direction (S) and each recovery device comprises at least one first metal hydride storage tank (11a, 21a).

18. The method according to any one of claims 15 to 17, wherein the metal hydride formed in step d) is heated at least partly with water obtained from cooling a gas cooler (7) downstream of the compressor (1).

19. A method according to any one of claims 15 to 18, wherein the filling and release of each metal hydride storage tank (11a) is carried out by at least one combined valve (18) or a pair of valves, the pair of valves consisting of an inflow valve (13a, 23a) located upstream of the corresponding metal hydride storage tank (11a, 21a) along the flow direction (S) and an outflow valve (14a, 24a) located downstream of the corresponding metal hydride storage tank (11a, 21a) along the flow direction (S), wherein the corresponding inflow valve and outflow valve (13a, 13b, 14a, 14b, 23a, 23b, 24a, 24b) are actuated by an actuating device (9) to eliminate continuous fluid communication between the leakage gas discharge pipeline (4) and the leakage gas return pipeline (30).

20. A hydrogen refueling station (40) comprising a gas compression system (100) according to any one of claims 1 to 14, preferably operated by a method according to any one of claims 15 to 19.

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