Method and system for high efficiency hydrogen compression

Abstract

A hydrogen compression system includes a source of gaseous hydrogen at a first pressure and a mixing unit adapted to mix hydrogen and an additional gaseous component at the first pressure, the additional gaseous component having a higher average molecular weight than hydrogen. The compression unit is adapted to compress a gaseous mixture comprising hydrogen and the additional gaseous component to a second pressure. A separation unit is fluidly coupled to the compression unit and is adapted to separate compressed hydrogen from the compressed additional gaseous component. An energy recovery device is further provided to recover energy during expansion of the compressed additional gaseous component from the second pressure to a third pressure. A method for efficient hydrogen compression is also disclosed.

Description

[0001] manual Technical Field

[0002] The present disclosure relates to hydrogen processing. Embodiments disclosed herein relate specifically to systems and methods for improving hydrogen compression efficiency. Background Art

[0003] Hydrogen is used in many industrial applications. In recent years, hydrogen has received increasing attention, especially considering the possibility of using hydrogen as a fuel instead of natural gas in thermodynamic cycles and as a fuel for fuel cells.

[0004] Many applications require hydrogen to be compressed at high pressure values ​​of about 200 bar or more. In fact, handling hydrogen at normal pressure is inconvenient due to the extremely low molecular weight of the gas. Especially for transport purposes, high pressure values ​​must be reached in order to increase the specific gravity of the gas and thus reduce its volume flow.

[0005] However, compressing low molecular weight gases such as hydrogen is technically challenging. Reaching pressure values ​​of up to 200 bar in gases with low molecular weight requires a lot of power and is traditionally achieved by reciprocating compressors. The latter are characterized by relatively low flow rates and are therefore inconvenient to handle large flow rates of gas.

[0006] Large capacity compression requires the use of dynamic compressors, especially centrifugal compressors, which have large diameter impellers and high rotational speeds to achieve tip speeds and a large number of impeller stages arranged in sequence. These requirements make hydrogen-powered compressors expensive and bulky.

[0007] In order to make hydrogen compression easier, it has been suggested to blend hydrogen with an additional gaseous component having a molecular weight higher than that of hydrogen. The resulting gaseous mixture has an average molecular weight higher than that of hydrogen and is therefore easier to compress even with a smaller centrifugal compressor running at a lower rotational speed. The additional gaseous component is then separated from the compressed hydrogen. In EP3789616 a system for enhancing hydrogen compression based on the use of a heavier gaseous component blended in a hydrogen stream is disclosed.

[0008] Compressing the heavier gaseous mixture and subsequently separating the gaseous components requires process complexity which may lead to a less efficient overall result.Therefore, there remains a need to optimize the blended hydrogen compression system to provide better performance than conventional equipment. Summary of the invention

[0009] In order to improve the efficiency of hydrogen compression, a hydrogen compression system is disclosed herein, which includes a mixing unit adapted to mix hydrogen and an additional gaseous component at a first pressure, and the additional gaseous component has an average molecular weight higher than that of hydrogen. The system also includes a compression unit adapted to compress a gaseous mixture containing hydrogen and the additional gaseous component to a second pressure. A separation unit fluidly coupled to the compression unit is adapted to separate compressed hydrogen from the compressed additional gaseous component. An energy recovery device is also provided, which includes an expansion unit fluidly coupled to the separation unit and adapted to reduce the pressure of the compressed additional gaseous component from the second pressure to a third pressure lower than the second pressure. The energy recovery device is adapted to recover energy during the expansion of the compressed additional gaseous component from the second pressure to the third pressure.

[0010] The recovered energy can be in the form of heat or mechanical energy. The mechanical energy can be converted into electrical energy or used directly to drive the compressor unit.

[0011] Thermal energy may be recovered in the form of a cooling fluid or a refrigerated fluid, which may provide cooling capacity for processes external to the compression system and / or processes internal to the compression system. For example, the additional gaseous component may be used to remove heat in an intercooler of the compression unit to improve compression efficiency, the additional gaseous component being recovered by separation from a mixture of hydrogen and the additional gaseous component and refrigerated by expansion. Alternatively or in combination, if, for example, a cryogenic separation process is used, the expanded additional gaseous component at low temperature may be used to support the separation process in the separation unit. Utilizing the refrigeration capacity of the expanded additional gaseous component in a heat exchanger external to the hydrogen compression system may also be foreseen as an alternative or additional way to recover energy from the expansion of the additional gaseous component.

[0012] Further features of the system are summarized below and defined in the appended claims.

[0013] According to another aspect, disclosed herein is a method for compressing hydrogen, the method comprising the steps of:

[0014] mixing gaseous hydrogen and an additional gaseous component at a first pressure to form a gaseous mixture, the additional gaseous component having a higher average molecular weight than hydrogen;

[0015] compressing the gaseous mixture in a compression unit at a second pressure higher than the first pressure; separating the compressed hydrogen and the compressed additional gaseous component from each other;

[0016] expanding the compressed additional gaseous component at a third pressure lower than the second pressure,

[0017] And energy is recovered from the expansion of the compressed additional gaseous component.

[0018] Further embodiments and advantageous features of the method according to the present disclosure are summarized below and are set out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Reference will now be made briefly to the accompanying drawings, in which:

[0020] Figure 1 is a schematic diagram of a hydrogen compression system in one embodiment;

[0021] Figure 2 is another embodiment of a hydrogen compression system;

[0022] Figure 3 is another embodiment of a hydrogen compression system;

[0023] Figure 4 is another embodiment of a hydrogen compression system;

[0024] Figure 5 is another embodiment of a hydrogen compression system;

[0025] Figure 6 is another embodiment of a hydrogen compression system;

[0026] Figure 7 is another embodiment of a hydrogen compression system;

[0027] Figure 8 is another embodiment of a hydrogen compression system;

[0028] Fig. 9 is another embodiment of a hydrogen compression system; and

[0029] Fig.10 It is another embodiment of the hydrogen compression system. DETAILED DESCRIPTION

[0030] exist Figure 1 A schematic diagram of a hydrogen compression system 1 is illustrated in FIG. In this embodiment, the hydrogen compression system 1 includes a gaseous hydrogen source 3. By way of example, Figure 1 The hydrogen source 3 comprises a green hydrogen production unit, in which energy from renewable energy resources is used to produce hydrogen. Figure 1 In the schematic diagram of , the gaseous hydrogen source 3 comprises an electrolyser 5 which produces hydrogen and oxygen by electrolysis using electrical energy from a photovoltaic field 7, a wind farm, a hydro turbine, a combination thereof or any other energy generator using energy from renewable energy resources.

[0031] Indeed, in other embodiments, different gaseous hydrogen sources may be used, such as steam reforming of natural gas or other light hydrocarbons, coal gasification, biomass gasification, or methane pyrolysis, among others.

[0032] The system 1 also includes a mixing unit 9, in which the gaseous hydrogen delivered by the gaseous hydrogen source 3 is mixed with an additional gaseous component. The additional gaseous component may be carbon dioxide (CO2). The additional gaseous component flows into the mixing unit 9 from a delivery line 11, which may be part of a closed loop, as described in more detail below.

[0033] In the following description, although carbon dioxide is often referred to as an additional gaseous component (also referred to as a "hydrogen dopant"), more generally, in several embodiments, the additional gaseous component may be any gas or gas mixture having an average molecular weight much higher than that of hydrogen. In some embodiments, the hydrogen compression system is combined with a carbon dioxide capture system or any other CO2 production process, in which case the additional gaseous component will be (at least primarily) carbon dioxide.

[0034] However, in other embodiments, and particularly when the system includes a closed loop for the additional gaseous component, a gaseous component other than carbon dioxide may be used. For example, the additional gaseous component may include a hydrocarbon or a mixture of hydrocarbons (CxHy) that may be combined with carbon dioxide. In some embodiments, a mixture of carbon dioxide and propane may be used. In some embodiments, a fluid commonly used in a refrigerant circuit may be used as the additional gaseous component to be mixed with hydrogen. For example, a mixed refrigerant may be used as a dopant to be added to the hydrogen stream.

[0035] The average molecular weight (Mw) of the additional gaseous component forming the hydrogen dopant may depend on the chemical nature of these components. For example, an average value between 16 and 20 may be suitable for natural gas containing hydrocarbons (CxHy), while when using a refrigerant fluid that can be combined with carbon dioxide, a molecular weight between 30 and 40 and a molecular weight above 40 may be selected.

[0036] The percentage of the additional gaseous component in the mixture delivered from the mixing unit 9 may vary, for example, between 30% and 70% by weight, depending on the nature and average molecular weight (Mw) of the additional gaseous component. Typically, if the hydrogen doping agent is pure carbon dioxide, a percentage range of 30% to 50% may be appropriate. When the percentage of carbon dioxide reaches 30% by weight, the power required for compressing hydrogen can be significantly reduced.

[0037] The mixing unit 9 is fluidly coupled to a compression unit 13 via a pipeline 12. The gas mixture in the pipeline 12 has a first pressure P1. If the hydrogen source 3 provides hydrogen at ambient pressure, P1 is about 1 bar. However, in some embodiments, the hydrogen source 3 may deliver hydrogen at a higher pressure (e.g., about 20 bar or more). This may be the case, for example, when the electrolyzer is a high pressure electrolyzer.

[0038] exist Figure 1 In the schematic diagram of FIG. 1 , the compression unit 13 is shown as a single compressor 15 and a drive 17 (e.g., an electric motor). In a practical embodiment, the compression unit 13 may include a plurality of compressors arranged in sequence to form one or more compressor groups, which may be driven by a single drive or more than one drive.

[0039] In some embodiments, compression unit 13 comprises a centrifugal compressor. Preferably, compression unit 13 is composed of one or more centrifugal compressors arranged in series. In some embodiments (not shown), if necessary or preferred, a series of centrifugal compressors and reciprocating compressors can be used.

[0040] The gas mixture delivered at the discharge side of the compression unit 13 is at a pressure P2 that is higher than P1. In some embodiments, the pressure P2 may be about 200 bar or higher (eg, 300 bar or higher).

[0041] The delivery side of the compression unit 13 is fluidly coupled to a separation unit 21 via line 19, which is adapted to separate hydrogen from the additional gaseous component. The compressed hydrogen stream separated from the additional gaseous component is a usable product delivered via a compressed hydrogen delivery line 23, while the compressed additional gaseous component stream flows through an additional gaseous component outlet line 25.

[0042] The separation unit 21 may include any separation device adapted to separate hydrogen from the additional gaseous component. The separation technique may be selected from those available in the art based on the chemical properties of the additional gaseous component, the percentage of the additional gaseous component in the gaseous mixture, the pressure of the gaseous mixture delivered by the compression unit 13, the required flow rate, and other technical considerations.

[0043] Exemplary embodiments of possible separation technologies that the separation unit 21 may be based on include, but are not limited to, pressure swing adsorption, membrane separation, electrochemical hydrogen separation, cryogenic separation, or a combination thereof. The power absorbed by operating the separation unit 21 is Figure 1 It is schematically indicated as Psep in the diagram and can be provided by any suitable power source.

[0044] The system 1 also includes an energy recovery device 27. As will become apparent from the following description, the energy recovery device 27 may include components for converting the pressure energy from the compressed additional gaseous component and utilizing it to generate mechanical energy and possibly electrical energy. However, the energy recovery device 27 is understood herein as any device that is adapted to provide an energy contribution to the system 1 that utilizes the compressed additional gaseous component flow delivered by the separation unit 21. For example, the additional gaseous component can be used to provide cooling capacity through its expansion, being adapted to increase the overall energy efficiency of the system 1.

[0045] The energy recovery device 27 includes an expansion device 28. In some embodiments, the expansion device 28 may include a Joule-Thomson valve or any other static expansion device to produce an expanded, cold additional gaseous component stream that can be used to provide cooling capacity. In a preferred embodiment, the expansion device 28 includes one or more expanders 29 (e.g., turboexpanders (such as radial turboexpanders)), which are adapted to convert the pressure energy of the additional gaseous component into mechanical power available on the shaft 31. Figure 1 In the embodiment of the present invention, the shaft 31 is drivingly coupled to a generator 33, which is adapted to convert mechanical power into electricity, which can be Figure 1 The power distribution network not shown in FIG. 1 is distributed to power users (eg the drive 17 including the compression unit 13 ).

[0046] exist Figure 1 In the exemplary embodiment of the invention, the delivery side of the expander 29 is fluidly coupled to the mixing unit 9 via the pipeline 11. The pressure of the additional gaseous component in the pipeline 11 can be P3. Figure 1 In the exemplary embodiment of , P3 = P1 and may be, for example, 1 bar or higher (eg, 1 bar to 30 bar), depending on the pressure at which the hydrogen is obtained from the hydrogen source 3 .

[0047] The mixing unit 9, the compression unit 13, the separation unit 21 and the expander 29 form a closed loop in which the additional gaseous component circulates and is cyclically compressed after being blended with hydrogen, separated from the hydrogen and expanded.

[0048] Continue to refer Figure 1 ,exist Figure 2 Another embodiment of the hydrogen compression system 1 according to the present disclosure is shown in FIG. Figure 2 Use in Figure 1 The same reference numerals are used in the drawings to designate the same or equivalent parts, and these parts will not be described in detail.

[0049] Figure 2 Implementation plan and Figure 1The main difference of the embodiments of the present invention is that, after the additional gaseous component is separated in the separation unit 21, the mechanical power recovered from the expansion of the additional gaseous component is directly used to drive the compression unit 13. This is graphically represented by the mechanical connection through the shaft 31 between the expander 29 and the compressor 15. In some embodiments, a motor 41 electrically connected to the power distribution network 45 is also arranged along the axis to provide additional mechanical power to drive the compressor 15 in the event that the power recovered by expanding the additional gaseous component in the expander 29 is insufficient to drive the compressor 15. Excess power of the expander 29 can be converted into electricity by the motor 41.

[0050] Continue to refer Figure 1 and Figure 2 , Figure 3 Another embodiment of the hydrogen compression system 1 of the present disclosure is illustrated. Figure 1 and Figure 2 The same reference numerals used in Figure 3 For the same or equivalent parts in the drawings, these parts will not be described in detail.

[0051] exist Figure 3 In the diagram of , the compression unit 13 is shown as including a first compressor or compressor stage 15.1 and a second compressor or compressor stage 15.2 arranged in series. For the sake of brevity, in the following description, only the first compressor and the second compressor will be referred to. The delivery side fluid of the first compressor 15.1 is coupled to the suction side of the second compressor 15.2. An intercooler 15.3 is arranged between the delivery side of the first compressor 15.1 and the suction side of the second compressor 15.2. The gaseous mixture containing hydrogen and the additional gaseous component is partially compressed in the first compressor 15.1 and is cooled before being further compressed in the second compressor 15.2. The number of compressors arranged in series may be greater than two, and corresponding intercoolers may be arranged between some or all pairs of compressors in the compressors arranged in sequence.

[0052] In some embodiments, such as Figure 3 As shown, the partially compressed gaseous mixture comprising hydrogen and the additional gaseous component is cooled by heat exchange with a side stream of the expanded additional gaseous component branched off from the discharge side of the expander 29. For this purpose, a branch line 43 connects the discharge side of the expander 29 to the cold side of the intercooler 15.3. After flowing through the intercooler 15.3, the branched stream of the expanded additional gaseous component flows back to the mixing unit 9.

[0053] If desired, the entire expanded additional gaseous component stream delivered by the expander 29 can be used as cooling medium in the intercooler 15.3 or in any additional equipment or process requiring cooling capacity.

[0054] Therefore, in Figure 3 In the embodiment of the present invention, the expanded additional gaseous component separated from the compressed hydrogen in the separation unit 21 is used to improve the energy efficiency of the hydrogen compression system 1 in two ways. On the one hand, the pressure energy of the compressed additional gaseous component can be converted into mechanical power and then converted into electricity through the expander 29 and the generator 33. On the other hand, the cold expanded additional gaseous component provides refrigeration capacity to remove heat from the partially compressed gaseous mixture, thereby improving the efficiency of the compression unit 13 and reducing the power required to compress the gaseous mixture from the pressure P1 to the pressure P2.

[0055] Continue to refer Figure 1 , Figure 2 and Figure 3 ,exist Figure 4 Another embodiment of a hydrogen compression system 1 according to the present disclosure is shown in FIG. Figure 1 , Figure 2 and Figure 3 The same reference numerals used in Figure 4 For the same or equivalent parts in the drawings, these parts will not be described in detail.

[0056] Similar to Figure 3 implementation plan, Figure 4 The hydrogen compression system 1 comprises an intercooling compression unit 13, which comprises, by way of example, a first compressor 15.1, a second compressor 15.2 and an intercooler 15.3. In addition, Figure 4 The expander 29 in the compressor is driven and coupled to the compression unit 13 via a shaft 31, so that the mechanical power generated by expanding the additional gaseous component in the expander 29 is directly used to drive the compression unit 13. A motor 41 electrically connected to the power distribution network can be arranged on the same axis to provide additional power for driving the compression unit or to convert excess mechanical power from the expander 29 into electricity.

[0057] In the embodiments disclosed so far, the additional gaseous component circulates in a closed loop and undergoes a cyclic thermodynamic transformation. In essence, the additional gaseous component is added to the hydrogen at a pressure P1 in the mixing unit 9; the gaseous mixture is compressed at a pressure P2 in the compression unit 13; the compressed additional gaseous component is separated from the compressed hydrogen in the separation unit 21; and the additional gaseous component is expanded back at a pressure P1 in the expansion device 28 and finally returned to the mixing unit 9 in a closed loop.

[0058] However, this is not the only possible layout of the hydrogen compression system 1 .

[0059] In some embodiments, the additional gaseous component can be processed by: an open circuit; or as such a closed circuit but without directly connecting the expansion device 28 to the mixing unit 9 .

[0060] For example, a continuous stream of an additional gaseous component is added to the hydrogen, compressed with the hydrogen and separated from the hydrogen. The separated compressed additional gaseous component is at least partially expanded for energy recovery purposes and subsequently removed from the hydrogen compression system 1 as a by-product thereof.

[0061] exist Figure 5 An embodiment including an open loop for the additional gaseous component is shown in . In this embodiment, the additional gaseous component is carbon dioxide. The carbon dioxide may be delivered by a carbon dioxide capture system that may be provided to process flue gas from an industrial process or a gas turbine and remove carbon dioxide from the flue gas before it is discharged into the atmosphere. More generally, the carbon dioxide may originate from any industrial process that produces carbon dioxide.

[0062] More specifically, refer to Figure 5 In the embodiment of the present invention, the hydrogen compression system 1 comprises a hydrogen source 3 and a mixing unit 9, wherein the gaseous hydrogen delivered by the hydrogen source 3 is mixed with an additional gaseous component. Figure 5 In the embodiment of the present invention, the additional gaseous component is carbon dioxide delivered by a carbon dioxide (CO2) capture system (CCS for short, referenced as 51). The carbon dioxide capture system 51 can be an amine-based carbon dioxide reduction system, a mixed salt process, a chilled ammonia process or any other process adapted to remove carbon dioxide from flue gas produced by any industrial equipment 53.

[0063] As a non-limiting example, in Figure 5 In the embodiment, the device 53 is a power generation device, which includes a gas turbine engine 55 driven by a fossil fuel. The gas turbine engine 55 can be driven and coupled to a generator 57 to convert mechanical power into electricity. The generator 57 is connected to the power distribution network 45. In other embodiments, the gas turbine engine 55 can be used as a driver for another machine (e.g., a compressor unit) or any other load.

[0064] The flue gas from the gas turbine engine 55 is treated in a gas cleaning plant 59 and subsequently in a carbon dioxide capture system 51 , wherein the carbon dioxide contained in the flue gas is captured and the carbon dioxide-lean flue gas is discharged into the atmosphere (stack 61 ).

[0065] The carbon dioxide capture system 51 is fluidly coupled to the mixing unit 9 via pipeline 11, so that the carbon dioxide from the carbon capture system 51 is mixed with hydrogen from the hydrogen source 3. In some embodiments, only a small portion of the carbon dioxide delivered by the carbon dioxide capture system 51 (or other industrial process for producing CO2) will be delivered to the mixing unit 9.

[0066] The mixing unit 9 is then fluidly coupled to a compression unit 13 via a pipeline 12. The gas mixture in the pipeline 12 has a first pressure P1, and the compression unit 13 compresses the gas mixture at a second pressure P2. In some embodiments, the pressure P2 can be about 200 bar or higher (e.g., 300 bar or higher).

[0067] exist Figure 5 In the diagram of FIG. 1 , the compression unit 13 comprises a compressor group, which includes a first compressor 15.1 and a second compressor 15.2, between which an intercooler 15.3 is located. It is foreseeable to have a different number of compressors on the same or different axes of one or more compressor groups. Figure 5 In the exemplary embodiment of , a drive 17 (eg, an electric motor) drives the compressor groups 15 . 1 , 15 . 2 to rotate and is electrically connected to a power distribution network 45 .

[0068] The delivery side of compression unit 13 is fluidly coupled to separation unit 21 adapted to separate hydrogen from the carbon dioxide via line 19 . A stream of compressed hydrogen separated from the carbon dioxide is delivered via compressed hydrogen delivery line 23 , while a stream of compressed carbon dioxide flows through a carbon dioxide outlet line 25 .

[0069] As already mentioned with respect to the previously described embodiments, the separation unit 21 may comprise any separation device adapted to separate hydrogen from the additional gaseous component. The separation technique may be selected among the separation techniques available in the art based on the chemical nature of the additional gaseous component, the percentage of the additional gaseous component in the gaseous mixture, the pressure of the gaseous mixture delivered by the compression unit 13, the required flow rate and other technical considerations.

[0070] The hydrogen compression system 1 also includes an energy recovery device or section 27. Figure 5 In an embodiment of the present invention, the energy recovery device or section 27 includes an expander 29 (such as a radial turboexpander) and a cooling circuit fluidly coupled to the intercooler 15.3. The expander 29 converts the pressure energy of the compressed carbon dioxide into mechanical power. The cooling circuit provides cooling capacity to improve the efficiency of the compression unit 13, as described above.

[0071] The mechanical power generated by the expander 29 is available on the shaft 31. Figure 5 In an embodiment, shaft 31 is drivingly coupled to a generator 33 adapted to convert mechanical power into electricity that can be delivered via a distribution network 45 to one or more electrical loads (eg, including drive 17 of compression unit 13).

[0072] Through similar Figure 3 and Figure 4 The implementation method of Figure 5In the hydrogen compression system 1 of FIG. 1 , a branch line 43 connects the discharge side of the expander 29 to the cold side of the intercooler 15.3 to provide cooling capacity to the intercooler and improve the efficiency of the compression unit 13. After flowing through the intercooler 15.3, the branched expanded additional gaseous component stream flows back to the main carbon dioxide discharge line 44. In other embodiments, the entire expanded carbon dioxide stream from the expander 19 can be used as a cooling medium in one or more intercoolers of the compression unit 13, or as a cooling medium in a different process or device requiring cooling capacity.

[0073] In some embodiments, the carbon dioxide is expanded in the expander 29 of the expansion device 28 at a pressure P3, which is lower than the delivery pressure P2 of the compression unit 13, but higher than the pressure P1 of the carbon dioxide at the inlet of the mixing unit 9. In some embodiments, the expander 29 can be replaced by an expansion valve or a general static expansion device. For example, the pressure P1 can be about atmospheric pressure (1 bar), or more generally lower than 30 bar. The pressure P2 can be at or above 200 bar, and the final expansion pressure P3 of the carbon dioxide can be higher than 50 bar, preferably about 70 bar. The partially expanded carbon dioxide is in conditions suitable for transportation or storage.

[0074] Similar to the previously described embodiment, also in Figure 5 In an embodiment of the present invention, the overall energy efficiency of the hydrogen compression system 1 is improved by recovering at least a portion of the power used to compress the additional gaseous component (carbon dioxide) contained in the gaseous mixture processed by the compression unit 13 by expanding the carbon dioxide from pressure P2 to pressure P3. The overall energy efficiency of the hydrogen compression system 1 is further improved by reducing the power required for the compression unit 13 by utilizing the cold expanded carbon dioxide stream as a refrigerating medium in the intercoolers.

[0075] Continue to refer Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 ,exist Figure 6 Another embodiment of the hydrogen compression system 1 of the present disclosure is shown in FIG. Figure 6 Use in Figure 5 The same parts are designated by the same reference numerals as above and will not be described in detail again. Figure 5 and Figure 6 The main difference between Figure 4In an embodiment of the present invention, the expander 29 is drivingly coupled to the compression unit 13 via a shaft 31, so that the mechanical power generated by expanding the compressed carbon dioxide is used to directly drive the compression unit 13. An auxiliary motor 41 electrically connected to a power distribution network 45 may be provided on the same axis to generate mechanical power when required to drive the compression unit 13, or to convert excess mechanical power from the expander 29 into electricity.

[0076] Continue to refer Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 , Figure 7 Illustrated with Figure 5 Another embodiment of a hydrogen compression system 1 similar to the system of FIG. The same reference numerals designate the same or similar components already described above, and these components will not be described again. Figure 5 The main difference is that the refrigerated expanded carbon dioxide from the expander 29 is used as refrigerating medium to reduce the power required for the separation unit 21. If the latter needs to cool the mixture of gaseous hydrogen and carbon dioxide to separate the hydrogen, at least part of the refrigeration capacity can be provided by the expanded carbon dioxide, which is conveyed to the heat exchanger 71 in the separation unit 21 via the pipeline 73. The valves can be provided to appropriately distribute the flow of expanded refrigerated carbon dioxide through the bypass line 75, the intercooler 15.3 and the separation unit 21 to adjust the flow of expanded carbon dioxide as required.

[0077] This expanded carbon dioxide stream can be used as a refrigeration medium to reduce the power required for separation unit 21, which also uses a similar Figures 1 to 4 The closed loop structure shown in Figure 8 An embodiment is schematically shown in Figure 4 The same reference numerals used in the drawings designate the same or equivalent elements, and these elements will not be described again. Figure 7 The implementation plan is also in Figure 8 In the separation unit 21, the heat exchanger 71 utilizes the refrigerated expanded carbon dioxide, which is delivered from the delivery side of the expander 29 via the pipeline 73. After cooling the gaseous mixture in the separation unit 21, the preheated carbon dioxide stream is returned to the mixing unit 9.

[0078] In general, the cooling capacity provided by the refrigerated, expanded carbon dioxide stream or other additional gaseous component at the delivery side of the expander 29 can be utilized in any process requiring a cooling medium stream. Fig. 9 Schematically represented in FIG. , which illustrates an example similar to Figure 2A system in which like reference numerals are used to designate like elements. A common heat exchanger 77 can be used to utilize the refrigeration capacity of the expanded additional gaseous component to cool the fluid flowing in the common loop 79 of the common process 81. Although in Fig. 9 In the embodiment, the expander is combined with the compressor on a single axis, but in other embodiments, the expander may be mechanically separated from the compressor; and independent motors may be provided for the expander on one side and for the compressor on the other side, as mentioned with respect to some of the embodiments previously described.

[0079] Although in Figure 5 , Figure 6 and Figure 7 In the description, a combination of a carbon dioxide capture system 51 and a mixing unit 9 has been described, wherein the carbon dioxide originates from a gas turbine engine, but as mentioned above, the additional gaseous component can be a different gas or a gas mixture containing carbon dioxide or any other suitable gas that can be mixed with hydrogen for compression purposes and separated from the hydrogen, thereby producing a beneficial effect in terms of saving compression power.

[0080] Fig.10 A schematic diagram of a hydrogen compression system 1 is illustrated in which the additional gaseous component circulates in a separate circuit, which in turn can be an open circuit or a closed circuit (as shown by way of example), in which a fluid circulates and is adapted to be mixed with the hydrogen for the above-mentioned purpose of reducing the compression power. Figures 1 to 9 The same reference numerals already used in the specification designate the same parts or elements as described above, and these parts or elements will not be described in detail again. Fig.10 In the embodiment of the present invention, the expanded additional gaseous component is collected in loop 91, which may include a general process 93. For example, the additional gaseous component may be a refrigerant (e.g., a mixed refrigerant) that is processed in a refrigeration circuit for natural gas liquefaction or other purposes. Therefore, the additional gaseous component circulates in a closed loop including the expansion device 28, and energy is recovered from the expansion device in the form of thermal power or mechanical power / electricity, as described above, so that the hydrogen compression process requires less power and is more efficient.

[0081] The additional gaseous component may be in a gaseous, liquid or biphasic state (i.e. partly vapor and partly liquid) on the delivery side of the expansion device 28. The state of the expanded additional gaseous component may depend, inter alia, on the chemical composition of the components, the separation technology used in the separation unit 21 and / or the pressure conditions.

[0082] In general, if the additional gaseous component is at least partially in the liquid state on the outlet side of the separation unit 21, the expansion device 28 will generally comprise an expansion valve instead of or in addition to a turboexpander arranged downstream of the expansion valve. When the expansion is carried out in the expansion valve instead of in the turboexpander, energy will be recovered mainly or even exclusively in the form of cooling capacity from the expanded additional component or the expanded additional component recovered in the separation unit 21.

[0083] In some embodiments, for example, when providing Figure 5 , Figure 6 , Figure 7 In the open cycle illustrated in FIG. 1 , the additional gaseous component can be recovered in at least partially liquefied form on the delivery side of the expansion device 28 and usefully used as a cooling medium or further condensed in a fully liquid state for, for example, transportation purposes.

[0084] In a closed loop, such as Figure 1 , Figure 2 , Figure 3 , Figure 4 and Fig. 9 As shown, the (partially) liquefied additional gaseous component located at the delivery side of the expansion device 28 can be liquefied in the heat exchanger 71 of the separation unit 21 (see for example Figure 8 ) and / or in the intercooler 15.3 (e.g. Figure 6 , Figure 7 ) and / or in the common cooling heat exchanger 77 ( Fig. 9 ) for evaporation.

[0085] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. Those skilled in the art will appreciate that various changes, omissions and additions may be made to the specific disclosure herein without departing from the scope of the present invention as defined in the following claims.

Claims

1. A hydrogen compression system, comprising: A gaseous hydrogen source; a mixing unit fluidly coupled to the gaseous hydrogen source via a hydrogen inlet and further fluidly coupled to an inlet line adapted to supply an additional gaseous component to the mixing unit, the additional gaseous component having a higher average molecular weight than hydrogen; wherein the mixing unit is adapted to mix hydrogen from the gaseous hydrogen source and the additional gaseous component at a first pressure and form a gaseous mixture comprising hydrogen and the additional gaseous component; a compression unit fluidly coupled to the mixing unit and adapted to compress the gaseous mixture to a second pressure; a separation unit fluidly coupled to the compression unit and adapted to separate the compressed gaseous mixture into a compressed hydrogen stream and a compressed additional gaseous component stream; a compressed hydrogen delivery line through which the compressed hydrogen stream is removed from the system; An energy recovery device, the energy recovery device comprising an expansion unit, the expansion unit being fluidly coupled to the separation unit and being adapted to reduce the pressure of the compressed additional gaseous component flow from the second pressure to a third pressure lower than the second pressure; wherein the energy recovery device is adapted to recover energy during the expansion of the compressed additional gaseous component from the second pressure to the third pressure.

2. The hydrogen compression system of claim 1, wherein the energy recovery device is adapted to recover thermal energy, mechanical energy, or a combination thereof.

3. The hydrogen compression system according to claim 1 or 2, wherein the expansion unit comprises an expander adapted to generate mechanical power by expanding the compressed additional gaseous component.

4. The hydrogen compression unit of claim 3, wherein the expander is drivingly coupled to the compression unit such that mechanical power generated by the expander is used to drive the compression unit.

5. A hydrogen compression unit according to claim 3 or 4, wherein the expander is drivingly coupled to a generator adapted to convert the mechanical power generated by the expander into electricity.

6. The hydrogen compression system according to one or more of the preceding claims, wherein said energy recovery device comprises a heat transfer loop.

7. A hydrogen compression system according to claim 6, wherein the compression unit includes at least a first compressor or compressor stage, a second compressor or compressor stage and an intercooler therebetween; and wherein the heat transfer circuit is adapted to provide cooling capacity to the intercooler and to remove heat from the partially compressed mixture of hydrogen and the additional gaseous component by heat exchange with an expanded additional gaseous component stream discharged from the expansion unit.

8. A hydrogen compression system according to one or more of the preceding claims, wherein the delivery side of the expansion unit is fluidly coupled to the mixing unit; and wherein the mixing unit, the compression unit, the separation unit and the expansion unit form a closed loop for the additional gaseous component.

9. The hydrogen compression system according to any one of claims 1 to 7, wherein the mixing unit is fluidly coupled to an open circuit in which the additional gaseous component flows.

10. The hydrogen compression system of claim 9, wherein the additional gaseous component comprises carbon dioxide recovered from a carbon dioxide generation process.

11. The hydrogen compression system according to claim 9 or 10, wherein the third pressure is higher than the first pressure.

12. The hydrogen compression system according to one or more of the preceding claims, wherein said compression unit comprises at least one dynamic compressor, preferably at least one centrifugal compressor.

13. The hydrogen compression system of claim 12, wherein the compression unit further comprises at least one reciprocating compressor.

14. A method for compressing hydrogen, the method comprising the steps of: delivering a gaseous hydrogen stream from a hydrogen source to a mixing unit; delivering a stream of an additional gaseous component to the mixing unit; the additional gaseous component having an average molecular weight greater than hydrogen; mixing the gaseous hydrogen and the additional gaseous component in the mixing unit and forming a gaseous mixture at a first pressure; compressing the gaseous mixture in a compression unit at a second pressure higher than the first pressure; delivering the compressed gaseous mixture to a separation unit and separating the compressed hydrogen stream and the compressed additional gaseous component stream from each other; supplying the compressed hydrogen stream via a compressed hydrogen delivery line; as well as The compressed additional gaseous component is expanded at a third pressure that is lower than the second pressure, and energy is recovered from the expansion of the compressed additional gaseous component.

15. The method of claim 14, wherein the step of expanding the compressed additional gaseous component comprises: The compressed additional gaseous component is expanded in an expander and utilized to generate mechanical power.

16. The method of claim 15, further comprising the step of using the mechanical power to drive at least one of: the compression unit; and a motor for converting the mechanical power into electricity.

17. The method according to one or more of claims 14 to 16, comprising the steps of: The expanded additional gaseous component is used as a refrigeration fluid in a heat exchanger and heat energy is recovered from said expansion of said additional gaseous component.

18. A method according to claim 17, comprising one or more of the following steps: cooling part of the compressed gaseous mixture by heat exchange with the expanded additional gaseous component during the stage of compressing the gaseous mixture to the second pressure; removing heat from a separation unit in which the compressed hydrogen and the compressed additional gaseous component are separated from each other by heat exchange with the expanded additional gaseous component.

19. The method according to one or more of claims 14 to 18, wherein the step of compressing the gaseous mixture comprises the steps of: compressing the gaseous mixture at an intermediate pressure in a first compressor; cooling the partially compressed gaseous mixture in an intercooler; further compressing the gaseous mixture in a second compressor; Heat is removed from the partially compressed gaseous mixture by heat exchange with an additional gaseous component which is expanded.

20. The method according to one or more of claims 14 to 19, comprising the steps of: circulating the additional gaseous component in a closed loop; and mixing the expanded additional gaseous component with the gaseous hydrogen stream.

21. The method according to one or more of claims 14 to 20, wherein the additional gaseous component comprises carbon dioxide.

22. The method of claim 21, wherein the carbon dioxide stream is provided by a carbon dioxide generating process.

23. The method of claims 21 and 22, wherein the third pressure is higher than the first pressure.

24. Method according to one or more of claims 14 to 23, wherein said step of compressing said gaseous mixture is performed in a compression system comprising at least one centrifugal compressor or a combination of at least one centrifugal compressor and at least one reciprocating compressor.

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