Solid oxide electrolyzer system including a hydrogen pump and method of operating a solid oxide electrolyzer system

Abstract

SOLUTION: A method of operating a solid oxide type electrolytic tank system includes: bringing a water inlet flow to at least one of solid oxide type electrolytic cells (SOEC); generating a wet hydrogen production stream from at least one SOEC; bringing the wet hydrogen production stream to at least one of hydrogen pumps; generating a compressed hydrogen product and unpumped emissions in one of the hydrogen pumps; and recycling at least part of the unpumped emissions to the upper stream of at least one of the hydrogen pumps.EFFECT: It is possible to continuously recycle the output of a production stream from each hot box until all hydrogen is substantially provided from a production stream into a conduit as a compressed hydrogen product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [Priority] This application is a non-provisional patent application that claims the benefit of U.S. Provisional Patent Application No. 63 / 183,275, filed May 3, 2021, the contents of which are incorporated herein by reference in their entirety.

[0002] This disclosure relates generally to electrolyzer systems, and more particularly to solid oxide electrolyzer cell (SOEC) systems with hydrogen pumps. [Background technology]

[0003] A solid oxide fuel cell (SOFC) can operate as an electrolysis cell to produce hydrogen and oxygen from water. Such a cell is called a solid oxide electrolysis cell (SOEC). In SOFC mode, oxygen ions are transported from the cathode side (air) to the anode side (fuel), driven by a chemical gradient of oxygen partial pressure across the electrolyte. In SOEC mode, a positive potential is applied to the air side of the cell, and oxygen ions are transported from the fuel side to the air side. Because the cathode and anode are reversed between SOFCs and SOECs (i.e., the SOFC cathode becomes the SOEC anode, and the SOFC anode becomes the SOEC cathode), the SOFC cathode (SOEC anode) is called the air electrode, and the SOFC anode (SOEC cathode) is called the fuel electrode. SOECs comprise a ceramic (e.g., solid oxide) electrolyte (e.g., yttria, scandia, and / or ceria-stabilized zirconia), an air electrode, and a fuel electrode. During SOEC mode, water in the fuel stream is reduced (H2O + 2e → O -2 +H2), H2 gas and O -2 ions, forming O -2 After transporting through the solid electrolyte, the ions are oxidized (O -2 →O2), producing molecular oxygen. Summary of the Invention

[0004] According to one embodiment, a method of operating a solid oxide electrolyzer system includes providing a water inlet stream to at least one solid oxide electrolysis cell (SOEC), producing a wet hydrogen product stream from the at least one SOEC, providing the wet hydrogen product stream to at least one hydrogen pump, producing a compressed hydrogen product and an unpumped discharge at the at least one hydrogen pump, and recycling at least a portion of the unpumped discharge upstream of the at least one hydrogen pump.

[0005] In one embodiment, the method further includes condensing water before providing the wet hydrogen product stream to the at least one hydrogen pump and draining the water from the wet hydrogen product stream. At least a portion of the unpumped effluent can be recycled to the inlet of the at least one hydrogen pump by a blower and / or recycled by the blower through the at least one condenser into the water inlet stream. The at least one hydrogen pump can include an electrochemical hydrogen pump producing a compressed hydrogen product comprising greater than 99 volume percent hydrogen. Optionally, the method can further include providing the compressed hydrogen product from the at least one hydrogen pump to at least one additional high-side hydrogen pump, producing an additional high-side compressed hydrogen product and an additional unpumped effluent in the at least one additional high-side hydrogen pump, and recycling at least a portion of the additional unpumped effluent into the water inlet stream.

[0006] According to another embodiment, a solid oxide electrolyzer system comprises a water inlet conduit fluidly connected to a hot box housing at least one solid oxide electrolysis cell (SOEC), at least one hydrogen pump, at least one product conduit fluidly connecting a product outlet of the hot box to an inlet of the at least one hydrogen pump, a compressed hydrogen product conduit connected to a compressed hydrogen product outlet of the at least one hydrogen pump, and at least one recirculation conduit connected to an unpressurized exhaust outlet of the at least one hydrogen pump and configured to recirculate at least a portion of the unpressurized exhaust upstream of the at least one hydrogen pump.

[0007] In one embodiment, the system further comprises a condenser fluidly connected to the at least one product conduit. The system may also comprise a blower configured to recirculate at least a portion of the unpressurized effluent to the inlet of the at least one hydrogen pump and / or the water inlet conduit. The system may optionally comprise at least one additional high-side hydrogen pump fluidly connected to the compressed hydrogen product conduit and configured to produce an additional high-side compressed hydrogen product and an additional unpressurized effluent, and at least one hydrogen recirculation conduit fluidly connected between the additional unpressurized effluent outlet of the at least one additional high-side hydrogen pump and the water inlet conduit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of components of an SOEC system according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of components of an SOEC system according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of components of an SOEC system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] As shown in FIG. 1 , the SOEC system 100 includes at least one SOEC hot box 102. For example, there may be n hot boxes 102, where n is an integer between 1 and 100, e.g., between 2 and 10, e.g., between 4 and 8. Each hot box 102 may be located within a hot box enclosure 103 that houses additional balance of plant (BOP) equipment dedicated to that hot box. Each hot box 102 includes multiple SOECs, such as one or more SOEC stacks or columns. Each hot box 102 or hot box enclosure 103 may also include any other suitable balance of plant components, such as heat exchangers, water evaporators, blowers, conduits, valves, etc. Each hot box 102 may also include a power input (e.g., a power bus) to provide electricity and generate electrolysis of water within the SOEC.

[0010] Each hot box 102 includes a water inlet conduit (e.g., a pipe or manifold) 2 that provides a water inlet flow to a fuel inlet of the hot box 102. Water can be provided to each SOEC fuel electrode within the hot box from conduit 2. Each hot box 102 can also include an air inlet conduit 4 that is connected to an air inlet of the hot box 102. An air inlet flow can be provided from conduit 4 to each SOEC air electrode within the hot box. Conduit 4 can be connected to an air blower (not shown).

[0011] After current or voltage is applied to each SOEC in the hot boxes 102, the SOEC produces an oxygen-rich exhaust stream and a wet hydrogen product stream. The oxygen-rich air stream can be exhausted from the air outlet of each hot box 102 through vent 6. The product stream is output from the product outlet of each hot box 102 through product conduit 8. The product stream is a hot, wet mixture of hydrogen and water vapor, and contains approximately 70 to 90 volume percent hydrogen gas and 10 to 30 volume percent water vapor. The product stream can be at a temperature between 100°C and 150°C and can have a pressure between 0.1 psig and 1 psig (689.476 PaG and 6894.76 PaG), depending on the backpressure required to flow through downstream equipment components and conduits.

[0012] If there are multiple hot boxes 102 in the system 100 , the product streams from the hot boxes 102 may combine at a manifold 104 that is connected to the product conduit 8 .

[0013] The hot gas mixture exits manifold 104 via conduit 10 into condenser 106. The condenser may be cooled with a refrigerant, such as cooling water and / or air, to condense the water vapor into liquid water and reduce the temperature of the hydrogen to less than 100°C, for example, between 50°C and 70°C. The liquid water is removed from the condenser via drain conduit 12. A partially dehydrated product stream is provided from condenser 106 via conduit 14 to at least one hydrogen pump 108. The at least one hydrogen pump 108 may include one or more electrochemical pumps.

[0014] The at least one electrochemical hydrogen pump 108 can include a hydrogen pump and separator that electrochemically pumps pure hydrogen through a polymer membrane when a current or voltage is applied across the membrane. The at least one electrochemical hydrogen pump 108 can include a high-pressure hydrogen separation and compression system available from Skyre, Inc. under the trade name "H2RENEW™" and / or described in U.S. Patent Nos. 10,756,361 and / or 10,648,089. The at least one hydrogen pump 108 can include multiple pumps (e.g., multiple separation membrane stacks) connected in series and / or parallel to facilitate increasing the overall hydrogen recovery and / or throughput.

[0015] In one embodiment, pump 108 recovers greater than 80% of the hydrogen in the dehydrated product stream and outputs a greater than 99% pure compressed hydrogen product through compressed hydrogen product conduit 16. For example, the compressed hydrogen product may be at least 99.99% pure (i.e., dry) hydrogen compressed to a pressure of 15 psig to 10,000 psig (103.421 kPaG to 68,947.6 kPaG), e.g., 15 psig to 2,000 psig (103.421 kPaG to 13,789.5 kPaG), e.g., 15 psig to 150 psig (103.421 kPaG to 1034.21 kPaG). The compressed hydrogen product may be stored or used without further mechanical compression or drying.

[0016] The unpressurized effluent from hydrogen pump 108 comprises primarily water (e.g., steam and / or liquid water) and any remaining hydrogen not separated from the dehydrated product stream in conduit 14. For example, the unpressurized effluent may comprise 1 volume percent to 15 volume percent hydrogen, e.g., 1 volume percent to 10 volume percent hydrogen, with the remainder being water and other impurities typically found in water. The unpressurized effluent is provided from hydrogen pump 108 via conduit 18 to recycle blower and / or compressor 110.

[0017] The unpressurized effluent stream may be recycled into recirculation conduit 20 by blower 110. The unpressurized effluent may be compressed by blower and / or compressor 110 to between 2 psig and 15 psig (13.7895 kPaG and 103.421 kPaG). The pressure may be selected to maintain a resulting dew point below the unintended condensation of water. The higher the pressure, the higher the outlet temperature due to the heat of compression. It may be desirable to compress the unpressurized effluent to a higher pressure so that the compressed effluent is hot enough to avoid inadvertent condensation in recirculation conduit 20. As described in more detail below with respect to FIG. 2, one or more optional additional condensers may be disposed in conduits 18 and / or 20.

[0018] The recirculation conduit 20 may be provided with an optional pressure relief element (such as a pressure relief valve or backpressure regulator) and / or a passive liquid water removal element (e.g., a condensation plate and / or a gravity separator) 112 to control the pressure of the unpressurized effluent and / or to passively remove some of the liquid water from the unpressurized effluent. The unpressurized effluent is then recirculated from element 112 upstream of the hydrogen pump 108 via a return conduit 22. The return conduit 22 may include a flow control element, such as a check valve 24. The unpressurized effluent may be recirculated into conduit 14, which is located upstream of the inlet of the hydrogen pump 108 and downstream of the outlet of the condenser 106. Alternatively, the unpressurized effluent may be provided into manifold 104 and / or conduit 10. The unpressurized effluent is mixed with the product stream upstream of the hydrogen pump 108. Thus, any remaining hydrogen in the unpumped exhaust can be recovered by the hydrogen pump 108 rather than being discarded.

[0019] 2 illustrates an alternative embodiment of a system 200 of the present disclosure in which at least a portion of the unpressurized effluent is recirculated into the hot box 102 via a water inlet stream in conduit 2. System 200 may also optionally include at least one second condenser 114 located in conduit 18 between the unpressurized effluent outlet from the hydrogen pump 108 and the blower 110. Portion 18A of conduit 18 connects the hydrogen pump 108 to the second condenser 114, and portion 18B of conduit 18 connects the second condenser 114 to the blower 110. The at least one condenser 114 may include two condensers arranged in series. The upstream condenser may be a water-cooled or air-cooled condenser, and the downstream condenser may be a refrigerated condenser located downstream of the water-cooled or air-cooled condenser. The unpressurized discharge is first cooled as much as possible with a refrigerant (e.g., air or chilled water) based on the ambient temperature. The unpressurized discharge is then cooled to less than 5°C, for example about 3°C, in a cooling condenser to maximize water removal without dealing with complex freezing. The condensed water is removed from the second condenser 114 via a drain conduit 32. The water removal section can be integrated into the design of the second condenser(s) 114 or can be included as a separate component downstream of the second condenser(s) 114. The condensed water from conduits 12 and 32 can be purified and / or reused.

[0020] The dried unpressurized effluent containing hydrogen and residual water is provided from second condenser 114 to blower / compressor 110 through portion 18B of conduit 18. The dried unpressurized effluent is compressed by blower / compressor 110 to 2 psig to 15 psig (13.7895 kPaG to 103.421 kPaG) and provided into recirculation conduit 20. The higher the pressure of the dried unpressurized effluent, the higher the outlet temperature due to the heat of compression. It may be desirable to compress the dried unpressurized effluent to a higher pressure so that the compressed effluent is hot enough to avoid inadvertent condensation in conduit 20. A lower condenser temperature also serves to lower the water content of the stream in conduit 20, thereby reducing the likelihood of unintended water condensation.

[0021] The low-pressure, substantially dry effluent can be recycled from conduit 20 through pressure relief element 112 and back into the SOEC hot box 102 via return conduit 26. The effluent can contain only approximately 500 ppm to 10,000 ppm of water, with the remainder being hydrogen and unavoidable impurities. Return conduit 26 can recirculate the effluent into water inlet conduit 2 outside the hot box 102 and / or inside the hot box 102. In this embodiment, the SOEC in the hot box 102 operates on an inlet flow containing a mixture of water and recycled effluent containing primarily hydrogen. Optionally, a flow controller 28, such as a mass flow controller (MFC) or proportional solenoid valve (PSV), can be positioned between the return conduit 26 and the water inlet conduit 2 to control the amount of hydrogen recycled into the water inlet conduit 2. The flow controller 28 and blower 110 can be controlled by a control unit, such as a computer or dedicated logic chip. Any excess recycled hydrogen can be returned as a feed stream to the hydrogen pump via conduit 22 upstream of the hydrogen pump 108. If the hydrogen pump recycle flow rate is small, the dew point of the hydrogen pump inlet stream is relatively unchanged by the injection of nearly dry recycled hydrogen, and humidification of the recycled exhaust stream is not necessary. If a significant recycle flow is used for the hydrogen pump 108, the exhaust stream in conduit 22 is rehumidified or diverted upstream of the first condenser 106 and / or second condenser 114.

[0022] 3 illustrates another alternative embodiment system 300 of the present disclosure, which includes a low-side hydrogen pump and a high-side hydrogen pump to increase hydrogen recovery. Specifically, at least one hydrogen pump 108 can be configured to pump hydrogen into hydrogen outlet conduit 34 at a relatively low pressure (e.g., 15 psig to 150 psig (103.421 kPaG to 1034.21 kPaG)). The compressed hydrogen product from the relatively low-pressure hydrogen pump (i.e., low-side pump) 108 is supplied via conduit 34 to at least one relatively high-pressure hydrogen pump (i.e., high-side pump) 116, assuming the water content is still suitable. As discussed above with respect to systems 100 and 200, unpumped effluent from the low-side pump can be provided in conduit 18 for recirculation into low-side pump 108 and / or hot box 102.

[0023] High-side pump 116 outputs a pumped compressed hydrogen product in conduit 16. The compressed hydrogen product in conduit 16 is compressed to a relatively high pressure (e.g., 200 psig to 10,000 psig (1,378.95 kPaG to 68,947.6 kPaG)). An unpressurized discharge comprising relatively dry hydrogen and a minimal amount of residual water is provided from high-side pump 116 to hydrogen recycle conduit 36. The unpressurized discharge may be provided from hydrogen recycle conduit 36 ​​through optional pressure relief element 118, via return conduit 38 into water inlet conduit 2 of hot box 102, and / or via conduit 40 into conduit 14 upstream of the inlet of low-side pump 108. In system 300, hydrogen may be recycled to hot box 102 via one of conduits 26 or 38. Thus, conduit 26 can be omitted in system 300 if hydrogen is recycled to hot box 102 via return conduit 38. Alternatively, although less preferred, conduit 26 can be present in system 300, and hydrogen can be recycled to hot box 102 via both conduits 26 and 38. Conduit 40 can include a flow control element, such as check valve 42. Thus, the cooling condenser can be omitted by using two hydrogen pumps 108 and 116 to recirculate a drier hydrogen stream to hot box 102.

[0024] If the product pumped from low-side pump 108 in conduit 34 is not suitable to be fed to high-side pump 116, high-side pump 116 can be located downstream of the unpumped discharge outlet of low-side pump 108 or upstream of the inlet of low-side pump 108. For example, high-side pump 116 can be located in conduit 18 (e.g., in section 18A or section 18B of conduit 18) or in conduit 14. Alternatively, if the product pumped from low-side pump 108 is too dry to be fed to high-side pump 116, low-side pump 108 and high-side pump 116 can be connected in parallel rather than in series in conduit 14.

[0025] Thus, system 100, 200, or 300 may continuously recirculate the product stream output from each hot box 102 until essentially all of the hydrogen from the product stream is provided as compressed hydrogen product in conduit 16. If the water inlet stream in conduit 2 may contain small amounts of dissolved air, inert species, including but not limited to nitrogen and / or argon, may build up in system 100, 200, or 300. Therefore, an optional small (batch or series) inert species purge outlet may be provided anywhere in the recirculation loop, such as in conduit 10 and / or portion 18B of conduit 18.

[0026] During startup of the SOEC in hot box 102, no recycled hydrogen is produced. In one embodiment, if hydrogen is needed during the startup period of SOEC operation, it can be stored in hydrogen storage containers (e.g., hydrogen cylinders / tanks). These storage containers can be provided from an external hydrogen source and / or can be filled with hydrogen during pre-operation of system 100, 200, or 300. Thus, during startup and / or steady-state operation of the SOEC, if the pressure in return conduit 26 or 38 drops below the hydrogen pressure required for SOEC operation, hydrogen is brought into water inlet conduit 2. This drop in pressure is detected by a sensor and determined by the controller.

[0027] Optionally, a buffer tank may be placed in one or more conduits in the system 100, 200, or 300. The buffer tank provides additional flow if the hydrogen flow rate produced from the hot box 102 does not match the throughput of the hydrogen pump 108 and / or other hydrogen recycling elements.

[0028] The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art. Furthermore, the general principles defined herein may be applied to other embodiments without departing from the scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. A solid oxide electrolyzer system comprising: a water inlet conduit fluidly connected to a hot box containing at least one solid oxide electrolysis cell (SOEC); at least one hydrogen pump; at least one product conduit fluidly connecting a product outlet of the hot box to an inlet of the at least one hydrogen pump; a compressed hydrogen product conduit connected to the compressed hydrogen product outlet of the at least one hydrogen pump; at least one recirculation conduit connected to an unpressurized exhaust outlet of the at least one hydrogen pump and configured to recirculate at least a portion of the unpressurized exhaust upstream of the at least one hydrogen pump; at least one additional high-side hydrogen pump fluidly connected to the compressed hydrogen product conduit and configured to produce an additional high-side compressed hydrogen product and an additional unpumped effluent; at least one hydrogen recirculation conduit fluidly connected between a further unpumped discharge outlet of the at least one further high-side hydrogen pump and the water inlet conduit; A solid oxide electrolyzer system comprising:

2. 10. The solid oxide electrolyzer system of claim 1, further comprising a condenser fluidly connected to the at least one product conduit.

3. 10. The solid oxide electrolyzer system of claim 1, further comprising a blower configured to recirculate said at least a portion of said unpressurized effluent to an inlet of said at least one hydrogen pump.

4. 10. The solid oxide electrolyzer system of claim 1, further comprising a blower configured to recirculate said at least a portion of said unpressurized effluent to said water inlet conduit.

5. 10. The solid oxide electrolyzer system of claim 1, wherein the at least one hydrogen pump comprises an electrochemical hydrogen pump that produces a compressed hydrogen product comprising greater than 99 percent hydrogen by volume.

6. A solid oxide electrolyzer system comprising: a water inlet conduit fluidly connected to a hot box housing at least one solid oxide electrolysis cell (SOEC), the water inlet conduit providing a water inlet stream to the SOEC; at least one hydrogen pump; at least one product conduit producing a wet hydrogen product stream from the SOEC fluidly connecting a product outlet of the hot box to an inlet of the at least one hydrogen pump; a compressed hydrogen product conduit connected to the compressed hydrogen product outlet of the at least one hydrogen pump for producing a compressed hydrogen product; at least one recirculation conduit connected to an unpressurized exhaust outlet of the at least one hydrogen pump and configured to recirculate at least a portion of the unpressurized exhaust upstream of the at least one hydrogen pump; at least one additional high-side hydrogen pump fluidly connected to the compressed hydrogen product conduit and configured to produce an additional high-side compressed hydrogen product and an additional unpumped effluent; at least one hydrogen recirculation conduit fluidly connected between a further unpumped discharge outlet of the at least one further high-side hydrogen pump and the water inlet conduit; A solid oxide electrolyzer system comprising:

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