Gas compression system and method for recovering hydrogen
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- BURCKHARDT COMPRESSION AG
- Filing Date
- 2023-05-10
- Publication Date
- 2026-05-14
AI Technical Summary
Existing gas compression systems for hydrogen face challenges such as high maintenance costs, safety risks due to hydrogen leakage, and inefficiencies related to pressure containment and energy consumption.
A gas compression system utilizing a compressor with a leakage gas discharge line, recovery devices with metal hydride reservoirs, and a leakage gas return line to recover and recycle hydrogen leakage gas, thereby reducing maintenance needs and improving operational efficiency.
The system achieves reliable, low-maintenance, and cost-effective hydrogen compression with reduced energy consumption and high purity of recovered hydrogen, addressing the drawbacks of prior art systems.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a gas compression system as described below, a method for recovering hydrogen produced as leakage gas in a compressor, and a hydrogen filling station equipped with the gas compression system. [Background technology]
[0002] Hydrogen filling stations are used to refuel fuel cell vehicles with hydrogen fuel. Hydrogen filling stations known in the prior art are configured such that hydrogen is taken from a reservoir containing hydrogen, pressurized in a compressor, and supplied to the hydrogen vehicle. Compression of hydrogen is technically difficult, especially at larger volumetric flow rates, due to the low molar weight (also known as molar mass or molar mass-related mass) of hydrogen. A high level of purity and high pressure, especially higher than 40 MPa, is currently required for the hydrogen gas to be filled into the fuel cell vehicle.
[0003] Patent document 1 describes an oil-lubricated piston compressor for compressing hydrogen and a refueling system for delivering hydrogen at high pressure to a fuel cell vehicle. However, a drawback of using such an oil-lubricated piston compressor is that the oil content in the released hydrogen gas needs to be reduced as much as possible before it is delivered to the consumer, in order not to impair the function of the fuel cell or, in some cases, to avoid damaging the fuel cell. For this purpose, appropriately designed separators and / or filters are used, which are arranged, for example, downstream of the last compression stage. The need for separators and / or filters to separate the lubricant from the compressed hydrogen leads to increased maintenance costs and, ultimately, higher operating costs for such gas compression systems.
[0004] Piston compressors known from the prior art often cannot be built with pressure containment, which means that the medium to be compressed must be allowed to leak to some extent to the environment. For example, US Pat. No. 5,399,433 discloses a piston compressor for compressing hydrogen, in which case hydrogen is allowed to leak from the compressor to the environment. Due to their flammability and ability to form explosive mixtures, such systems, in addition to the waste of valuable resources and the associated economic disadvantages, also pose a considerable safety risk depending on where the compressor is used.
[0005] To prevent losses due to leakage, US Pat. No. 5,399,633 proposes a leakage return line that runs from the inside of the piston compressor housing to the inlet of the first cylinder head of the compressor. The housing of a reciprocating compressor is therefore designed to be pressure-resistant at least up to the suction pressure of the first compressor stage. However, a drawback of a pressure-resistant solution is that the design effort and investment costs are relatively higher than in the case of a non-pressure-resistant compressor housing. In addition, the problem of uncontrolled release of hydrogen into the environment is not adequately solved by such a system, since the static seals used in such a system only allow a limited degree of leak-free sealing of the housing against excess hydrogen pressure.
[0006] Finally, a gas compression system for hydrogen is known from US Pat. No. 5,399,633, in which the hydrogen leakage from the main compressor is fed to an auxiliary compressor, in which both compressors are reciprocating compressors. The hydrogen compressed by the auxiliary compressor is fed to a recovery tank from where it is returned to the suction line of the main compressor. However, this prior art gas compression system also has certain drawbacks due to the use of several reciprocating compressors with many moving parts and a potentially high maintenance effort, as well as pressure fluctuations resulting from the vibration modes of operation of the reciprocating piston machines and the need for the use of an auxiliary tank as a pulsation damper. [Prior art documents] [Patent documents]
[0007] [Patent Document 1] European Patent Application Publication No. 3121446 [Patent Document 2] JP 2011-132876 A [Patent Document 3] International Publication No. 2015 / 074740 [Patent Document 4] European Patent Application Publication No. 3163081 Summary of the Invention [Problem to be solved by the invention]
[0008] Based on the above-mentioned prior art, the present invention is based on the problem of eliminating these and other drawbacks of the prior art, in particular of providing a gas compression system for compressing hydrogen, which is reliable, requires little maintenance and can be operated at low cost, including the cost of electricity consumption. [Means for solving the problem]
[0009] The object is achieved by a gas compression system for compressing hydrogen, a method for recovering hydrogen and a hydrogen filling station comprising the gas compression system according to the invention as defined in the independent claims. Advantageous and further embodiments are the subject of the dependent claims.
[0010] 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 hydrogen produced as leakage gas during compression from the compressor. The gas compression system also has one or more recovery devices for recovering hydrogen produced as leakage gas during compression and a leakage gas return line. The leakage gas return line is designed to return leakage gas recovered by the one or more recovery devices to a location in the gas compression system upstream of the compressor. Alternatively or additionally, the leakage gas return line is designed to return leakage gas recovered by the one or more recovery devices to a suction line of a compressor stage of the compressor. Each recovery device can be fluidly connected to the leakage gas discharge line and the leakage gas return line, and each recovery device has one or more metal hydride reservoirs. Each metal hydride storage unit is thermally coupled to a heat exchanger and includes one or more hydride-forming metal alloys designed to periodically desorb or absorb leak gas by providing or removing heat through the respective heat exchanger. The recovery device present in the gas compression system recovers the leak gas pressure (p L ) at least to a pressure (p) at a location in the gas compression system, or at least to a suction pressure (p S ) or both.
[0011] The use of metal hydrides is a promising method of hydrogen compression that does not require moving parts and requires little energy. In this method, a reversible heat-driven interaction of hydride-forming metals, alloys or intermetallic compounds with hydrogen gas is used to form metal hydrides. The exothermic formation of metal hydrides is promoted by the absorption of low-pressure hydrogen in the hydride-forming material at low temperatures, i.e. by the removal of heat from the hydride-forming material. On the other hand, the endothermic decomposition of metal hydrides is promoted by the desorption of high-pressure hydrogen from the metal hydride at higher temperatures, i.e. by the addition of heat to the metal hydride. In this way, cyclic absorption of low-pressure hydrogen or desorption of high-pressure hydrogen can be achieved by cyclic cooling and heating of the hydride-forming material or metal hydride, similar to the suction and compression process in a mechanical compressor. Devices based on this principle are therefore also referred to below as metal hydride compressors.
[0012] In the context of the present invention, a "compressor for compressing hydrogen" (hereinafter simply referred to as "compressor") is understood to mean a device for increasing the pressure and density of hydrogen serving as the working gas of the compressor, such as a reciprocating compressor, an ionic compressor, a screw compressor or a diaphragm compressor, provided that said compressor is not a metal hydride compressor. According to the present invention, the one or more recovery devices for increasing the leakage gas pressure to the suction pressure are single-stage or multi-stage metal hydride compressors.
[0013] The gas compression system according to the present invention is simple, reliable, requires little maintenance, and allows for cyclically operated hydrogen recovery with low operating costs. In addition, the use of metal hydride accumulators allows for high compression ratios to be achieved with low power consumption and high purity of the recovered hydrogen.
[0014] In particular, the compressor of the gas compression system according to the present invention can also be a multi-stage compressor having multiple compressor stages configured to compress the working gas in stages. Preferably, the leakage gas return line is designed to return the leakage gas recovered by the one or more recovery devices to the suction line of the first compressor stage of the compressor, so that the pressure of the leakage gas only needs to be increased to a relatively low pressure in the suction line of the first compressor stage (e.g., a pressure of about 3.0 MPa).
[0015] In a preferred embodiment, the gas compression system according to the invention comprises a first recovery device and a second recovery device, which are connected in parallel so as to be able to charge and discharge the metal hydride reservoirs arranged in each recovery device independently of each other.
[0016] By providing several recovery devices connected in parallel, the gas compression system according to the invention can be used in a continuous process or for continuous recovery of continuously occurring leakage gas.
[0017] Another problem resulting from operating metal hydride compressors over a wider temperature range is the high thermal stresses that arise in the metal hydride accumulator at the beginning of the heating and cooling half cycles. When the additional stresses caused by the increase in gas pressure during hydride desorption (heating) and the increase in volume of the hydride-forming metal alloy during hydride formation (cooling) are taken into account, the probability of damage to the metal hydride accumulator, e.g. by cracking, increases, thereby significantly reducing its service life and operational safety.
[0018] In order to keep the operating temperature range of each metal hydride storage unit as low as possible during operation, in a further preferred embodiment of the gas compression system, each recovery unit comprises a plurality of metal hydride storage units. Viewed in the flow direction of the leakage gas stream, the metal hydride storage units are connected in series with one another and each thermally coupled to a heat exchanger. The metal hydride storage units connected in series each comprise one or more hydride-forming metal alloys, which are designed such that hydrogen is periodically desorbed or absorbed by the addition or removal of heat by the respective heat exchanger. The first metal hydride storage unit, which is located first in the flow direction in each recovery unit, reduces the pressure of the leakage gas to the leakage gas pressure (p L ) to the leakage gas pressure (p L ) higher than the first intermediate pressure (p 1 The last metal hydride reservoir located at the end of each recovery unit in the flow direction is designed to increase the pressure of the leaking gas to the suction pressure (p S The metal hydride reservoir disposed between the first and last metal hydride reservoirs is designed to increase the pressure of the leaking gas to the first intermediate pressure (p 1 ) compared to the higher intermediate pressure (p 2 ,p 3 ...p n ) each designed to gradually increase
[0019] Unless otherwise stated, the term "flow direction" always refers to the direction of flow of the leakage gas stream in the gas compression system according to the present invention. Preferably, the metal hydride accumulators connected in series each have a different hydride-forming metal alloy, which allows higher compression ratios to be achieved.
[0020] In a particularly preferred embodiment of the gas compression system according to the invention, the metal hydride reservoirs connected in series contain different hydride-forming metal alloys, in which case the thermal stability of the hydrated metal alloy is reduced in the direction of flow, i.e. compared to the metal hydride reservoir arranged in front of it.
[0021] However, increasing the number of metal hydride reservoirs in the recovery unit, or the number of stages of the metal hydride compressor thus formed, reduces efficiency, which is why each recovery unit preferably has only two metal hydride reservoirs.
[0022] 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, in which case the gas compression system according to the invention can also be used to replace or replace existing compressors that are widely used.
[0023] Preferably, the compressor of the gas compression system is designed as a dry piston compressor, which is a compressor that operates without external lubricants (such as lubricating oil) in the compression section, which significantly reduces the risk of contamination of the compressed hydrogen by lubricants.
[0024] In a preferred embodiment of the gas compression system according to the invention, the hydride-forming metal alloy of the metal hydride reservoir has a dissociation pressure of 3.0 MPa or more, preferably 3.5 MPa or more, particularly preferably 4.0 MPa or more at a temperature of 60° C.-100° C. Measurement of dissociation pressure is known to the skilled person in the prior art, for example in the publication by T. Matsunaga et al., “TiCrVMo alloys with high dissociation pressure for high-pressure MH tank,” International Journal of Hydrogen Energy, Vol. 34 (2009), 1458-1462, which is incorporated herein by reference in its entirety (see Section 2, “Experimental” therein).
[0025] With regard to the alloy systems that can be used, there are numerous hydridable metal alloys, each of which has very specific pressure-temperature properties and is therefore particularly suited to certain applications, where the alloy composition has a significant effect on the location of the pressure plateau at the determined 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 is incorporated herein by reference in its entirety.
[0026] In a preferred embodiment of the gas compression system according to the invention, the hydride-forming metal alloy is LaNi 5 , ZrV 2 , ZrMn 2 , TiMn 2 , FeTi, Zr 2 Co and Ti 2 Ni. Preferably, the hydride-forming metal alloy is selected from the group including LaNi5 , ZrV 2 , ZrMn 2 , and TiMn 2 The compound is selected from the group consisting of:
[0027] The above metal alloys have a leakage gas pressure (p L ) and suction pressure (p S ) can be set with respect to alloy technology, in particular by combining two or more of the abovementioned metal alloys.
[0028] 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 4.0 MPa. Preferably, the compressor housing is pressure-resistant only up to 1.5 MPa, particularly preferably up to 0.2 MPa. Such a housing is particularly easy and cheap to manufacture.
[0029] In a preferred embodiment, the gas compression system according to the invention does not have a container for storing the leaking gas from downstream of the one or more recovery devices until the leaking gas is returned to a location upstream of the compressor in the gas compression system. In other words, the gas compression system does not have a container for storing the leaking gas from downstream of the one or more recovery devices until the leaking gas is returned to a location in the gas compression system upstream of the compressor and / or to the suction line of a compressor stage. Alternatively or additionally, it is also conceivable that the gas compression system between the compressor and the one or more recovery devices does not have a container for storing the leaking gas. In the latter case, the gas compression system therefore does not have a container for storing the leaking gas, except for the hydrogen source of the compressor.
[0030] It will be understood that elements of the present invention that include the term "line," i.e., elements that serve to fluidly connect devices of a gas compression system, are not considered "vessels" within the meaning of the present invention.
[0031] This means that gas compression systems can be designed to be more compact and space-saving, using less equipment. The supply of heat to and removal of heat from the metal hydride reservoirs through the respective heat exchangers is achieved by surrounding the metal hydride reservoirs with a heat transfer medium that is very well insulated from the outside. The heat released when hydrogen gas is stored is transferred to the heat transfer medium and heats it and the metal hydride reservoir itself. The volume of the heat transfer medium is dimensioned such that when the metal hydride reservoir is fully filled, the released heat can be completely absorbed by the heat transfer medium. Alternatively or additionally, it is also conceivable that the heat transfer medium of the respective heat exchanger is periodically or continuously exchanged by a suitable conveying device (e.g. a pump). The temperature increase obtained when filling the metal hydride reservoir with hydrogen depends on the filling pressure and the choice of the metal alloy for forming the hydride.
[0032] 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 at normal pressure between 30° C. and 180° C. Preferably, the boiling point of the liquid used as heat transfer medium is between 90° C. and 130° C. at normal pressure. Water, water-glycol mixtures or thermal oils have proven to be particularly suitable heat transfer media, as they are generally readily available and safe to handle.
[0033] A typical application of a metal hydride reservoir requires a heating system to heat the reservoir for evacuation, as described above. To date, electrical energy or fossil fuels have typically been used to heat the metal hydride reservoir.
[0034] In a preferred embodiment of the gas compression system according to the invention, a gas cooler, which can be cooled by means of cooling water, is connected downstream of the compressor for cooling the hydrogen gas compressed by the compressor, the gas cooler and the heat exchanger of the respective recovery device are at least partially connected to each other such that the cooling water heated during cooling of the gas cooler can be used to supply heat to the respective metal hydride storage unit.
[0035] The use of cold cooling water or cooling water heated by a gas cooler means that no or only a very small amount of thermal energy needs to be provided externally to operate the metal hydride reservoir. This also eliminates the need for a power connection for heating. The total energy required to increase the leakage gas pressure is almost zero, apart from the power consumption for control and regulation. The use of cold or heated cooling water instead of electrical energy to cool or heat the metal hydride reservoir not only increases the overall efficiency of the industrial process, but also indirectly contributes to the reduction of greenhouse gases and other harmful emissions that are by-products of electricity generation in fossil fuel-fired power plants.
[0036] In a preferred embodiment of the gas compression system according to the invention, the leakage gas exhaust line has a pressure relief valve, which preferably opens when the pressure is greater than 0.2 MPa.
[0037] Providing a pressure relief valve in the leak gas exhaust line helps to increase operational safety since, with the valve closed, hydrogen that cannot be absorbed by the recovery device cannot accumulate in the leak gas exhaust line, for example beyond its load limit.
[0038] In a preferred embodiment of the gas compression system according to the invention, each metal hydride reservoir comprises one or more combined valves or a pair of valves consisting of an inlet valve upstream of the respective metal hydride reservoir in the direction of flow and an outlet valve downstream of the respective metal hydride reservoir in the direction of flow, for filling the respective metal hydride reservoir with leaking gas and / or for evacuating the respective metal hydride reservoir with leaking gas.
[0039] The use of a combined valve to fill or vent each metal hydride reservoir has the advantage that the number of components required can be reduced. The use of a valve pair consisting of an inlet valve and an outlet valve located upstream and downstream of each metal hydride reservoir has the advantage that the direction of flow of the leaking gas in one or more recovery devices can be maintained and the pressure build-up in the recovery devices can be made more efficient, as will be explained in more detail below.
[0040] In the case of several metal hydride reservoirs connected in series in the flow direction, it is conceivable that the outlet valve of the metal hydride reservoir arranged first in the flow direction is also the inlet valve of the metal hydride reservoir adjacent to said metal hydride reservoir and arranged downstream in the flow direction, so that the total number of valves required can be significantly reduced, further reducing the complexity of the design of the gas compression system.
[0041] In a preferred embodiment of a gas compression system comprising a combined valve and / or valve pair as described above, the gas compression system also has a control device for controlling the combined valve or the inlet and outlet valves, if present, which are controlled by the control device such that in normal operation, for each valve pair adjacent in the direction of flow, one or more of the adjacent valves are closed to prevent continuous fluid communication connection between the leakage gas exhaust line and the leakage gas return line.
[0042] In a preferred embodiment of the gas compression system according to the invention, one or more non-return elements closing against the direction of flow are arranged between the metal hydride reservoirs of the respective recovery devices. Additionally or alternatively, one or more non-return elements closing against the direction of flow are arranged in the leak gas discharge line. Additionally or alternatively, one or more non-return elements closing against the direction of flow are arranged in the leak gas return line.
[0043] By preventing fluid communication between the leakage gas exhaust line and the leakage gas return line by the actuator and / or the configuration of the check device described above, backflow of leakage gas against the flow direction due to pressure differences between the individual metal hydride reservoirs can be eliminated, thereby significantly reducing the risk of overload and damage to components.
[0044] A preferred embodiment of the gas compression system according to the invention further comprises a pre-purification device for pre-purifying the hydrogen leak gas before it is fed to the metal hydride reservoir. In such a pre-purification device, impurities that may adversely affect the service life of the hydride-forming metal alloy are filtered, converted and / or absorbed. For this purpose, the pre-purification device contains a trapping material (getter material), in particular a hydride-forming metal or hydride-forming alloy, in which the formation of hydrides starts only well above the maximum pressure of the downstream recovery device. This means that no hydride formation occurs in the getter material during pre-purification. Instead, however, it is possible that other components of the hydrogen leak gas are chemisorbed on the getter material, and thus no contamination or possibly damage is caused to the actual hydride-forming metal alloy of the metal hydride reservoir. This ensures a long-term reliable operation of the metal hydride reservoir of the recovery system.
[0045] Preferably, a pre-cleaning device for pre-cleaning the hydrogen leak gas is arranged in the leak gas discharge line upstream of any branch leading to the individual recovery device, so that the gas compression system can be equipped with only a single pre-cleaning device. Since the getter material needs to be replaced with new material from time to time depending on the quality of the leak gas and the required purity of the leak gas purified by the pre-cleaning device, the effort required for this can be reduced by a single pre-cleaning device being maintained. Alternatively or additionally, however, 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.
[0046] The object is furthermore achieved by a method for recovering hydrogen produced as leakage gas in a compressor. The method according to the invention comprises the steps of (a) introducing the leakage gas into a recovery device having one or more metal hydride reservoirs with one or more hydride-forming metal alloys, (b) absorbing the introduced leakage gas by the metal alloys to form metal hydrides, thereby filling the metal hydride reservoirs, (c) removing the heat released during the formation of the metal hydrides by a heat exchanger thermally coupled to the metal hydride reservoirs, (d) heating the formed metal hydrides by the heat exchanger to a predetermined temperature to desorb at least a portion of the leakage gas previously absorbed, and (e) discharging the metal hydride reservoirs and discharging the desorbed leakage gas from the recovery device into a leakage gas return line and into a stage in the gas compression system upstream of the compressor or into the suction line of a compressor stage of the compressor from which the leakage gas originates, or both. Step e) can be optionally carried out with further heating of the metal hydride formed by the heat exchanger. The pressure of the leak gas is controlled in step d) and, if necessary, in step e) if the heating of the metal hydride formed is continued, by the one or more metal hydride reservoirs of the recovery device, so that the leak gas pressure (pL ) to at least a pressure (p) at a point in the gas compression system, or at least a suction pressure (p S ) or both. The pressure increase in the recovery device is achieved by appropriate control of inlet and outlet valves located upstream and downstream of the metal hydride reservoir in the direction of flow, as described in more detail below.
[0047] Preferably, the method for recovering hydrogen according to the invention described herein is carried out using a gas compression system according to the invention described herein. In a preferred embodiment of the method according to the invention, the pressure of the leaking gas is increased in several stages in the direction of flow by using a plurality of metal hydride reservoirs connected in series with each other in the recovery device to reduce the leaking gas pressure (p L ) to the suction pressure (p S In this case, the first metal hydride accumulator arranged first in the recovery device in the flow direction increases the pressure of the leak gas to the leak gas pressure (p L ) to the leakage gas pressure (p L ) compared to the first intermediate pressure (p 1 The last metal hydride reservoir located last in the recovery device in the flow direction increases the pressure of the leaking gas to the suction pressure (p S Optionally, a metal hydride reservoir disposed between the first metal hydride reservoir and the last metal hydride reservoir increases the pressure of the leaking gas to the first intermediate pressure (p 1 ) compared to the higher intermediate pressure (p 2 ,p 3 ...p n ) in stages.
[0048] In a preferred embodiment of the method according to the invention, the method is carried out continuously by cyclic charging and discharging of two recovery devices arranged in parallel in the direction of flow, each recovery device comprising one or more metal hydride reservoirs.
[0049] In a further preferred embodiment of the process according to the invention, said heating step in step d) is carried out at least partly with water obtained from the cooling of a gas cooler downstream of said compressor.
[0050] In a preferred embodiment of the method according to the invention, each metal hydride reservoir is filled and drained via one or more combined valves or a pair of valves consisting of an inlet valve upstream of the respective metal hydride reservoir in the direction of flow and an outlet valve downstream of the respective metal hydride reservoir in the direction of flow, in the latter case the respective inlet and outlet valves being actuated by a control device so as to prevent continuous fluid communication between the leakage gas exhaust line and the leakage gas return line.
[0051] The advantages resulting from the implementation of the method described herein essentially correspond to the advantages already described for each embodiment of the gas compression system according to the invention. The object is furthermore solved by a hydrogen refueling station comprising a gas compression system as described herein, preferably operated according to one of the methods described herein.
[0052] Various embodiments of the present invention are described below with reference to the drawings, in which like or corresponding elements are generally provided with the same reference numerals. [Brief description of the drawings]
[0053] [Figure 1] 1 is a flow diagram illustrating a gas compression system according to the present invention. [Diagram 2] 1 is a cross-sectional schematic diagram of a metal hydride reservoir for use in a gas compression system according to the present invention; [Diagram 3]FIG. 4 is a flow diagram showing a further embodiment of a gas compression system according to the invention having two recovery devices connected in parallel. [Figure 4a] FIG. 2 is a flow diagram showing the gas compression system according to the present invention during the filling process. [Figure 4b] FIG. 4b is a flow diagram showing the gas compression system from FIG. 4a in a discharging process. [Figure 5a] FIG. 4 is a flow diagram showing a further embodiment of a gas compression system according to the present invention having a recovery device connected in parallel during the charging or discharging process. [Figure 5b] FIG. 5b is a flow diagram showing the gas compression system from FIG. 5a during the discharging or charging process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] FIG. 1 shows a flow diagram of a gas compression system 100 according to the invention, with a compressor 1 for hydrogen. The compressor 1 can be fluidly connected to a hydrogen source Q via a line 3, so that hydrogen to be compressed can be supplied to the compressor 1 via the line 3. The gas compression system 100 also comprises a recovery device 10, described in more detail below, for recovering hydrogen escaping from the compressor 1 as leakage gas during compression. To discharge the leakage gas from the compressor, a leakage gas discharge line 4 is provided, which can be fluidly connected to the compressor and to the leakage gas stream generated during compression. The gas compression system 100 also comprises a leakage gas return line 2 for returning the leakage gas recovered by the recovery device 10 to a stage 5, which is located upstream of the compressor 1, the source of the leakage gas, in the gas compression system 100. In the embodiment shown in FIG. 1, the leakage gas recovered by the recovery device 10 is introduced into a line 3, which fluidly connects the hydrogen source Q to the compressor 1, at the stage indicated with the reference number 5. The leakage gas return line 30 has a check element 31 that closes against the flow direction S. In the illustrated embodiment, the recovery device comprises two metal hydride reservoirs 11a, 11b, each containing a hydride-forming metal alloy, and each thermally coupled to a heat exchanger 12a, 12b. A cooling water source W In The two metal hydride reservoirs 11a, 11b can be cooled using cold cooling water, which can be supplied to the gas compression system 100 from the gas cooler 7. The two metal hydride reservoirs 11a, 11b can be heated using preheated cooling water, i.e., cooling water obtained in the process of cooling the hydrogen compressed by the compressor 1 by the gas cooler 7. The cold or heated cooling water can be supplied to the two metal hydride reservoirs 11a, 11b via three-way fittings 19a, 19b. Unused or used cooling water can be discharged from the cooling water drain W Out, and is preferably recycled. The recovery device 10 can be fluidly connected to the leak gas exhaust line 4 via the inlet valve 13a of the first metal hydride storage 11a, and to the leak gas return line 2 via the outlet valve 14b of the second metal hydride storage 11b. The two metal hydride storages 11a, 11b can be fluidly connected to each other via a connecting line 16 and a valve 14a arranged in the connecting line 16, and are connected in series when viewed in the flow direction S of the leak gas flow. In the flow direction S, the metal hydride storage 11a arranged first is connected to the leak gas pressure p L (For example, 0.2 MPa) is the leakage gas pressure p L A first intermediate pressure p 1 (for example, 1.5 MPa). The metal hydride reservoir 11b of the recovery device 10, which is located last in the flow direction S, is designed to increase the pressure p 1 to a pressure p (for example, 3.0 MPa) in line 3. The leaked gas thus recovered, i.e., the leaked gas pressure p L The leakage gas, increased to a pressure p, is returned to the compressor 1 and finally delivered to a consumer V (eg a fuel cell vehicle).
[0055] FIG. 2 shows a schematic cross-sectional view of a metal hydride reservoir 11a for use in a gas compression system according to the invention. In the embodiment shown, the metal hydride reservoir 11a comprises a total of 25 tubular vessels 17a (shown in cross-section in FIG. 2), which are filled with a hydride-forming metal alloy 15a. The vessels 17a are designed for the inlet and outlet of hydrogen leakage gas into the vessels 17a, which in the case of the tubular vessels 17a are preferably located at both ends of the tube. The vessels 17a containing the hydride-forming metal alloy 15a are surrounded by a heat transfer medium (in particular water or thermal oil) so that the metal alloy 15a can desorb or adsorb the leakage gas when heat is supplied or dissipated by the heat exchanger 12a. To improve the heat transfer between the heat transfer medium and the vessel wall, ribs made of a material with good thermal conductivity can be placed on the outer surface of the vessels 17a to increase the surface area, and these ribs are immersed in the heat transfer medium (not shown).
[0056] 3 shows a flow diagram of a further embodiment of a gas compression system 100 according to the invention, which comprises two recovery devices 10, 20 connected in parallel to recover hydrogen leaking as leakage gas from the compressor 1. The first recovery device 10 comprises two metal hydride reservoirs 11a, 11b connected in series, whereas the second recovery device 20 comprises two metal hydride reservoirs 21a, 21b connected in series. The metal hydride reservoir 11a of the first recovery device 10, which is arranged first in the flow direction S, can be fluidly connected to the metal hydride reservoir 11b arranged downstream in the flow direction S via a connecting line 16 and a valve 14a arranged therein. Similarly, the metal hydride reservoir 21a of the second recovery device 20, which is arranged first in the flow direction S, can be fluidly connected to the metal hydride reservoir 21b arranged downstream in the flow direction S via a connecting line 26 and a valve 24a arranged therein. Hydrogen leak gas generated during compression by the compressor 1 of the gas compression system 100 is discharged from the compressor 1 through a leak gas discharge line 4 and connected to the first recovery device 10 or the second recovery device 20 via the inlet valve 13a or 23a, which connects the first recovery device 10 or the second recovery device 20 with the leak gas discharge line 4, i.e. the parallel recovery devices 10, 20 work in push-pull mode. In each recovery device 10, 20, the pressure of the leak gas is substantially equal to the leak gas pressure p in the leak gas discharge line as described above with reference to FIG. L From the first intermediate pressure p 1 The suction pressure p S The metal hydride reservoirs 11a, 11b, 21a, and 21b are thermally coupled to heat exchangers 12a, 12b, 22a, and 22b, respectively, for this purpose, in which case the water used to cool or heat the metal hydride reservoirs is pumped from a cooling water source W by means of a cooling water pump 50. InThe cooling water can be supplied to the heat exchangers 12a, 12b, 22a, 22b via three-way joints 19a, 19b, 29a, 29b from the cooling water drain W Out The first recovery device 10 and the second recovery device 20 can be fluidly connected to the leakage gas return line 2 via the outlet valves 14b and 24b of the metal hydride reservoirs 11b, 21b arranged at the end of the respective recovery devices 10, 20 in the flow direction S, with non-return elements 31, 32 arranged downstream of each recovery device 10, 20 in the flow direction S. Via the leakage gas return line 30, the previously recovered gas, which is supplied to the suction pressure p S The increased leakage gas is fed to the suction line 3b of the first compressor stage 5b of the compressor 1, at the stage designated by reference numeral 5.
[0057] Fig. 4a shows a flow diagram of a gas compression system 100 according to the invention with a single recovery device 10 when a single metal hydride reservoir 11a contained therein is being charged. A portion of the hydrogen supplied to the compressor 1 from the hydrogen source Q via line 3 is produced as a leakage gas stream during compression, is discharged from the compressor via the leakage gas discharge line 4 and is introduced into the metal hydride reservoir 11a of the recovery device 10 via the inlet valve 13a. To charge the metal hydride reservoir 11a with the leakage gas to form metal hydrides, the inlet valve 13a upstream of the metal hydride reservoir 11a in the leakage gas flow direction S is opened and the outlet valve 14a downstream of the metal hydride reservoir 11a in the leakage gas flow direction S is closed, as shown in Fig. 4a. The heat released during the formation of the metal hydride is dissipated through a heat exchanger 12a that is thermally coupled to the metal hydride reservoir 11a, and for this purpose a cooling water source W InCold cooling water from the hydride-forming metal alloy is used via a cooling water pump 50 and a three-way fitting 19a that fluidly connects the cooling water source to the heat exchanger 12a (see dashed arrows in FIG. 4a to indicate the flow of cold water). Spent cooling water that has been heated in the heat exchanger 12a during cooling of the hydride-forming metal alloy is returned to the cooling water drain W Out When the metal hydride reservoir 11a is filled with leaking gas, the inlet valve 13a upstream of the metal hydride reservoir 11a in the flow direction S is closed (not shown).
[0058] FIG. 4b shows the flow diagram of the gas compression system 100 from FIG. 4a during the discharge of the metal hydride reservoir 11a of the recovery device 10. The metal hydride reservoir 11a has previously been heated to a predefined temperature by the heat exchanger 12a for desorption of at least a portion of the previously absorbed leak gas, with the inlet valve 13a and the outlet valve 14a closed, in which case a pressure relief valve present in the leak gas discharge line continuously discharges the leak gas from the compressor 1 when a predefined leak gas pressure is exceeded (not shown). After the pressure inside the metal hydride reservoir 11a has increased to the pressure p in the line 3, the outlet valve 14a of the metal hydride reservoir 11 downstream in the leak gas flow direction S is opened and the metal hydride reservoir 11a is discharged by the heat exchanger 12a with further heat input. In this embodiment example, the cooling water source W supplied to the gas cooler 7 by the cooling water pump 50 and heated by the gas cooler 7 is heated by the gas cooler 7. In Water from a cooling water source W is used for this purpose (see dashed arrows in FIG. 4b showing the hot water flow). In and the gas cooler 7. The three-way fitting 19a used also provides a cooling water source W to regulate the temperature of the metal hydride reservoir 11a. InIt can also be used to mix the cold cooling water from the recovery device 10 with the cooling water heated by the gas cooler 7. The leakage gas desorbed under pressure p is discharged from the recovery device 10 via the outlet valve 14a to a leakage gas return line 30 equipped with a non-return element 31 open in the flow direction S and introduced into the line 3 in the stage indicated with the reference number 5. The recovered leakage gas is thus returned to the compressor 1 and is finally discharged to the consumer V.
[0059] FIG. 5a shows a flow diagram of a further embodiment of a gas compression system 100 according to the invention, comprising two parallel-connected recovery devices 10, 20, each with a metal hydride reservoir 11a, 21a. In FIG. 5a, the first recovery device 10 is in a charging cycle, while the second recovery device 20 operates in the opposite cycle, in a discharging cycle. In other words, the metal hydride reservoir 11a of the first recovery device 10 is being charged, while the metal hydride reservoir 21a of the second recovery device 20 is being discharged. In contrast to the method described in FIGS. 4a and 4b, the recovery of leakage gas occurring during the compression of hydrogen in the compressor 1 can thus be carried out continuously with the method described in FIGS. 5a and 5b. For this reason, an overpressure valve in the leakage gas discharge line 4 can generally be omitted, which overpressure valve is only required to detect a specific leakage gas pressure p in the leakage gas discharge line 4. Lfor safety reasons, however, it may still be desirable to provide such a pressure relief element in order to prevent pressure peaks and damage in the leakage gas discharge line 4. In the embodiment of the gas compression system 100 according to the invention shown in Fig. 5a and 5b, the leakage gas discharge line 4 branches into two leakage gas discharge lines 4' and 4'', one of which, the leakage gas discharge line 4', can be fluidly connected to the first recovery device 10 and the other leakage gas discharge line 4'' can be fluidly connected to the second recovery device 20. The filling of the metal hydride reservoir 11a of the first recovery device 10 is carried out with the inlet valves 13a, arranged upstream and downstream of the metal hydride reservoir 11a in the leakage gas flow direction S, open and the outlet valve 14a closed, with heat dissipated from the hydride-forming metal alloy stored in the metal hydride reservoir by the heat exchanger 12a, which is thermally coupled to the metal hydride reservoir 11a. The cold cooling water used for this purpose is supplied to a cooling water source W via a cooling water pump 50 and a three-way fitting 19a, which fluidly connects the cooling water source to the heat exchanger 12a. In (See the dotted arrows in Figure 5a showing the flow of chilled water.) The used chilled water is discharged to the chilled water outlet W Out The metal hydride reservoir 21a of the second recovery device 20 is discharged when the inlet valve 23a is closed and the outlet valve 24a is open, the metal hydride reservoir 21a being heated by the heat exchanger 22a assigned to it. The heat exchanger 22a is connected to a cooling water source W via a three-way joint 29a. In 5a, the cooling water used in the heat exchanger 22a of the second recovery device 20 is also provided via a cooling water outlet W OutThe first recovery device 10 and the second recovery device 20 can be fluidly connected to a leakage gas return line 30 via the outlet valves 14a and 24a of the metal hydride reservoirs 11a, 21a arranged at the end of the respective recovery devices 10, 20 in the flow direction S, with non-return elements 31, 32 arranged downstream of each recovery device 10, 20 in the flow direction S. The leakage gas pressure p L from suction pressure p S The leakage gas compressed to is supplied via a leakage gas return line 30 to the first compressor stage 5b of the compressor 1 at a stage of the suction line 3b, designated by reference numeral 5. The gas compression system, including the valves described above, is monitored and controlled by a freely programmable system controller, not shown.
[0060] Figure 5b shows a flow diagram of the gas compression system 100 from Figure 5a, where the first recovery device 10 is now in a discharge cycle and the second recovery device 20 is in a charge cycle, simply to illustrate the opposite cycle operation of the two recovery devices 10 and 20 connected in parallel. The flow of hot water in the gas compression system 100 is shown using dashed arrows and the flow of cold water is shown using dotted arrows. The assignment of the reference symbols used and the functional description of all elements shown in Figure 5b can be found in the description of Figure 5a.
Claims
1. A gas compression system (100), - A compressor (1) for compressing hydrogen, - One or more recovery devices (10) for recovering hydrogen leaking out as leak gas (2) from the compressor (1) during compression, - A leak gas return line (30) is designed to return the leak gas (2) recovered by one or more recovery devices (10) to a stage (5) upstream of the compressor (1) in the gas compression system (100), or to the suction line (3a) of the compressor stage (5a) of the compressor (1), particularly to the suction line (3b) of the first compressor stage (5b), or both. The compressor (1) is equipped with a leak gas discharge line (4) for discharging the leak gas (2) from the compressor (1), Each recovery device (10) can be fluidly connected to the leak gas discharge line (4) and the leak gas return line (30), and each recovery device (10) has one or more metal hydride storage containers (11a), and each of the one or more metal hydride storage containers (11a) is thermally coupled to a heat exchanger (12a). Each metal hydride storage container (11a) includes one or more hydride-forming metal alloys (15a), and each of the one or more hydride-forming metal alloys (15a) is designed such that leak gas (2) is periodically desorbed or absorbed by the supply or removal of heat through the respective heat exchangers (12a). Each recovery device (10) measures the leak gas pressure (p) in the leak gas discharge line (4). Ｌ ) to increase at least to the pressure (p) in the stage (5) of the gas compression system (100), or at least to the suction pressure (p) in the suction line (3a) of the compressor stage (5a). Ｓ A gas compression system (100) is designed to increase the pressure to or both of the above.
2. The gas compression system (100) according to claim 1, comprising a first recovery device (10) and a second recovery device (20), wherein the first recovery device (10) and the second recovery device (20) independently of each other with respect to time, fill and release the metal hydride storage devices (11a, 21a) located in their respective recovery devices (10, 20).
3. Each recovery device (10) has a plurality of metal hydride storage containers, in particular two metal hydride storage containers (11a, 11b), the plurality of metal hydride storage containers are connected in series with each other when viewed in the direction of the leak gas flow (S), and are each thermally coupled to a heat exchanger (12a, 12b). Each of the metal hydride storage units (11a, 11b) connected in series has one or more hydride-forming metal alloys (15a, 15b), preferably different hydride-forming metal alloys (15a, 15b), and each of the one or more hydride-forming metal alloys (15a, 15b) is designed so that hydrogen is periodically desorbed or absorbed by the supply or removal of heat through the respective heat exchangers (12a, 12b). In the flow direction (S), the first metal hydride storage units (11a, 21a) initially positioned in each recovery device (10, 20) reduce the pressure of the leaked gas (2) to the leaked gas pressure (p Ｌ ) from the leak gas pressure (p Ｌ A first intermediate pressure (p) that is higher than ) １ It is designed to increase up to ) In the flow direction (S), the last metal hydride storage unit (11b, 21b) located last in each recovery device (10, 20) reduces the pressure of the leaked gas (2) to the suction pressure (p Ｓ It is designed to increase up to ) The metal hydride storage vessels disposed between the first metal hydride storage vessels (11a, 21a) and the last metal hydride storage vessels (11b, 21b) are each designed to gradually increase the pressure of the leakage gas (2) to an intermediate pressure (p １ ) that is higher than the first intermediate pressure (p ２ , p ３ ... p ｎ ), the gas compression system (100) according to claim 1.
4. The gas compression system (100) according to claim 1, wherein the compressor (1) is designed as a piston compressor, preferably as a dry piston compressor.
5. The gas compression system (100) according to claim 1, wherein the metal alloy (15a, 15b, 25a, 25b) used has a dissociation pressure of 3.0 MPa or more, preferably 3.5 MPa or more, and particularly preferably 4.0 MPa at a temperature of 60°C to 100°C.
6. The aforementioned metal alloys (15a, 15b, 25a, 25b) are LaNi ５ ZrV ２ , ZrMn ２ ,TiMn ２ FeTi, Zr ２ Co and Ti ２ From the group including Ni, preferably LaNi ５ ZrV ２ , ZrMn ２ and TiMn ２ A gas compression system (100) according to claim 1, selected from the group including the following.
7. The gas compression system (100) according to claim 1, wherein the compressor (1) has a housing (6) designed to be substantially pressure-resistant only at 4.0 MPa or less, preferably 1.5 MPa or less, and particularly preferably 0.2 MPa or less.
8. The gas compression system (100) according to claim 1, wherein there is no container for storing the leaked gas (2) from downstream of one or more recovery devices (10, 20) until the leaked gas (2) is returned to the stage (5) upstream of the compressor (1) in the gas compression system (100), to the suction line (3a) of the compressor stage (5a), or both.
9. The gas compression system (100) according to claim 1, wherein each heat exchanger (12a, 12b, 22a, 22b) contains as a heat transfer medium a liquid having a boiling point between 30°C and 180°C, preferably between 90°C and 130°C, at atmospheric pressure, particularly water or a water-glycol mixture.
10. A gas cooler (7) capable of being cooled with cooling water is connected downstream of the compressor (1) to cool the hydrogen compressed by the compressor (1), and the heat exchangers (12a, 12b, 22a, 22b) of the gas cooler (7) and the respective recovery devices (10, 20) are connected to each other, at least in part, so that the cooling water heated during the cooling of the gas cooler (7) can be used to supply heat to the respective metal hydride storage devices (11a, 11b, 21a, 21b), the gas compression system (100) according to claim 1.
11. The gas compression system (100) according to claim 1, wherein the leak gas discharge line (4) has a pressure relief valve (8), in particular a pressure relief valve (8) that opens when the pressure in the leak gas discharge line (4) is greater than 0.2 MPa.
12. Each metal hydride storage container (11a, 21a) is provided with one or more composite valves (18) for filling each metal hydride storage container (11a, 21a) with the leaked gas (2), discharging the leaked gas (2) from each metal hydride storage container (11a, 21a), or both, or is provided with a valve pair consisting of an inlet valve (13a, 23a) located upstream of each metal hydride storage container (11a, 21a) in the direction of flow (S) and an outlet valve (14a, 24a) located downstream of each metal hydride storage container (11a, 21a) in the direction of flow (S), the gas compression system (100) according to claim 3.
13. The gas compression system (100) according to claim 12, further comprising an actuator (9) for operating the inlet valve and the outlet valves (13a, 13b, 14a, 14b, 23a, 23b, 24a, 24b), wherein the inlet valve and the outlet valves (13a, 13b, 14a, 14b, 23a, 23b, 24a, 24b) are operated such that, during operation, one or more of the adjacent valves in each pair of adjacent valves in the direction of flow (S) are closed in order to prevent continuous fluid communication between the leak gas discharge line (4) and the leak gas return line (30).
14. - Between the metal hydride storage containers (11a, 11b, 21a, 21b) of each recovery device (10, 20), - The leak gas discharge line (4), and - In at least one of the leaked gas return lines (30), The gas compression system (100) according to claim 3, wherein one or more check elements (31, 32) that close against the direction of flow (S) are provided.
15. A method for recovering hydrogen leaking from a compressor (1) as leak gas (2), preferably carried out using the gas compression system (100) described in claim 1, wherein the method is a) A step of introducing the leaked gas (2) into a recovery device (10) having one or more metal hydride storage containers (11a) that store one or more hydride-forming metal alloys (15a), b) A filling step in which the introduced leaked gas (2) is absorbed by the metal alloy (15a) and a metal hydride is formed, thereby filling the metal hydride storage container (11a), c) A step of removing the heat released during the formation of the metal hydride by a heat exchanger (12a) that is thermally coupled to the metal hydride storage container (11a), d) A heating step in which the formed metal hydride is heated to a predetermined temperature by the heat exchanger (12a) to desorb at least a portion of the previously absorbed leaked gas (2), e) A discharge step comprising: releasing the metal hydride storage (11a) and discharging the desorbed leaked gas (2) from the recovery device (10) to the leaked gas return line (30) and to a stage (5) upstream of the compressor (1) in the gas compression system (100), or to the suction line (3a) of the compressor stage (5a) of the compressor where the leaked gas is generated, particularly to the suction line (3b) of the first compressor stage (5b), or both, The pressure of the leaked gas (2) is reduced by the one or more metal hydride storage containers (11a) of the recovery device (10) to the leaked gas pressure (p) in the leaked gas discharge line (4). Ｌ ) is increased to at least the pressure (p) in the stage (5) of the gas compression system (100), or at least the suction pressure (p) in the suction line (3a) of the compressor stage (5a). Ｓ A method that is increased to or both of the above.
16. The pressure of the leaked gas (2) is measured in several stages using a plurality of metal hydride reservoirs (11a, 11b) connected in series with respect to the direction of flow (S) of the leaked gas flow, and the pressure of the leaked gas (p Ｌ ) from the suction pressure (p Ｓ ) was increased to, In the flow direction (S), the first metal hydride storage units (11a, 21a) initially positioned in each recovery device (10, 20) reduce the pressure of the leaked gas (2) to the leaked gas pressure (p Ｌ ) from the leak gas pressure (p Ｌ A first intermediate pressure (p) that is higher than ) １ Increase it to ) In the flow direction (S), the last metal hydride storage unit (11b, 21b) located last in each recovery device (10, 20) reduces the pressure of the leaked gas (2) to the suction pressure (p Ｓ Increase it to ) The metal hydride storage container located between the first metal hydride storage container (11a, 21a) and the last metal hydride storage container (11b, 21b) controls the pressure of the leaked gas (2) to the first intermediate pressure (p １ ) for higher intermediate pressure (p ２ , p ３ ... p ｎ The method according to claim 15, wherein the amount is increased in stages up to ).
17. The method according to claim 16, which is performed continuously by periodic filling and discharging of two recovery devices (10, 20) arranged in parallel in the direction of flow (S) and each comprising one or more first metal hydride storage devices (11a, 21a).
18. The method according to claim 15, wherein the heating step in step d) is performed at least in part using water obtained from the cooling of a gas cooler (7) located downstream of the compressor (1).
19. The method according to claim 16, wherein the filling step and the discharge step are performed via one or more combined valves (18), or via a valve pair consisting of an inlet valve (13a, 23a) located upstream of each metal hydride reservoir (11a, 21a) in the flow direction (S) and an outlet valve (14a, 24a) located downstream of each metal hydride reservoir (11a, 21a) in the flow direction (S), and each inlet valve and outlet valve (13a, 13b, 14a, 14b, 23a, 23b, 24a, 24b) is operated by an actuator (9) to prevent continuous fluid communication between the leak gas discharge line (4) and the leak gas return line (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 the method according to any one of claims 15 to 19.