Solid oxide type electrolytic tank system including hydrogen pump, and method of operating solid oxide type electrolytic tank 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 claiming the benefit of U.S. Provisional Patent Application No. 63 / 183,275, filed on May 3, 2021, the contents of which are hereby incorporated by reference in their entirety.

[0002] The present disclosure generally relates to an electrolytic cell system, and more particularly to a solid oxide electrolyzer cell (SOEC) system equipped with a hydrogen pump.

Background Art

[0003] A solid oxide fuel cell (SOFC) can operate as an electrolytic cell to produce hydrogen and oxygen from water. Such a cell is called a solid oxide electrolyzer cell (SOEC). In the SOFC mode, oxygen ions are transferred from the cathode side (air) to the anode side (fuel), and the driving force is the chemical gradient of the oxygen partial pressure across the electrolyte. In the SOEC mode, a positive potential is applied to the air side of the cell, and oxygen ions are transferred from the fuel side to the air side. Since the cathode and anode are reversed between SOFC and SOEC (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. The SOEC includes a ceramic (e.g., solid oxide) electrolyte (e.g., yttria, scandia, and / or ceria-stabilized zirconia), an air electrode, and a fuel electrode. During the SOEC mode, water in the fuel stream is reduced (H2O + 2e → O -2 + H2), forming H2 gas and O -2 ions, and the O -2 ions are transferred through the solid electrolyte and then oxidized on the air side (2O -2 → O2) to produce molecular oxygen.

Summary of the Invention

[0004] According to one embodiment, a method for operating a solid oxide electrolytic cell system includes bringing a water inlet flow to at least one solid oxide electrolytic cell (SOEC), generating a wet hydrogen product flow from at least one SOEC, bringing the wet hydrogen product flow to at least one hydrogen pump, generating compressed hydrogen product and unpressurized waste in at least one hydrogen pump, and recirculating at least a portion of the unpressurized waste upstream of at least one hydrogen pump.

[0005] In one embodiment, the method further includes condensing water and discharging water from the wet hydrogen product stream before bringing the wet hydrogen product stream to at least one hydrogen pump. At least a portion of the unpressurized discharge can be recirculated by a blower to the inlet of at least one hydrogen pump and / or recirculated by a blower through at least one condenser into the water inlet stream. The at least one hydrogen pump may include an electrochemical hydrogen pump that produces compressed hydrogen products containing more than 99 volume percent hydrogen. The method may optionally further include bringing the compressed hydrogen products from at least one hydrogen pump to at least one further high-pressure side hydrogen pump, generating further high-pressure side compressed hydrogen products and further unpressurized discharge in at least one further high-pressure side hydrogen pump, and recirculating at least a portion of the further unpressurized discharge into the water inlet stream.

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

[0007] In one embodiment, the system further comprises a condenser fluidly connected to at least one product conduit. The system may also comprise a blower configured to recirculate at least a portion of the unpressurized waste to the inlet and / or water inlet conduit of at least one hydrogen pump. Optionally, the system may comprise at least one additional high-pressure hydrogen pump fluidly connected to a compressed hydrogen product conduit and configured to generate additional high-pressure compressed hydrogen products and additional unpressurized waste, and at least one hydrogen recirculation conduit fluidly connected between the additional unpressurized waste outlet of the at least one additional high-pressure hydrogen pump and the water inlet conduit. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the components of the SOEC system according to the embodiment of this disclosure. [Figure 2] This is a schematic diagram of the components of the SOEC system according to the embodiment of this disclosure. [Figure 3] This is a schematic diagram of the components of the SOEC system according to the embodiment of this disclosure. [Modes for carrying out the invention]

[0009] As shown in Figure 1, the SOEC system 100 comprises at least one SOEC hot box 102. For example, there may be n hot boxes 102, where n is an integer from 1 to 100, e.g., 2 to 10, e.g., 4 to 8. Each hot box 102 may be located within a hot box housing 103 that houses additional balance of plant (BOP) equipment dedicated to that hot box. Each hot box 102 comprises one or more SOECs, such as an SOEC stack or column. Each hot box 102 or hot box housing 103 may also include any other suitable balance of plant components, such as a heat exchanger, water evaporator, blower, conduit, valve, etc. Each hot box 102 may also include a power input (e.g., a power bus) that supplies electricity and generates electrolysis of the water in the SOEC.

[0010] Each hot box 102 is provided with a water inlet conduit (e.g., a pipe or manifold) 2 that brings a water inlet flow to the fuel inlet of the hot box 102. Water can be supplied from the conduit 2 to each SOEC fuel electrode in the hot box. Each hot box 102 may also include an air inlet conduit 4 connected to the air inlet of the hot box 102. Air inlet flow can be supplied from the conduit 4 to each SOEC air electrode in the hot box. The conduit 4 may be connected to an air blower (not shown).

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

[0012] If there are multiple hot boxes 102 within the system 100, the product flows from the hot boxes 102 can be merged in the manifold 104 connected to the product conduit 8.

[0013] The high-temperature gas mixture exits the manifold 104 through the conduit 10 into the condenser 106. The condenser is cooled with a refrigerant such as cooling water and / or air, which condenses the water vapor into liquid water, lowering the hydrogen temperature to below 100°C, for example, 50°C to 70°C. The liquid water is removed from the condenser through the drain conduit 12. The partially dehydrated product stream is brought from the condenser 106 through the conduit 14 to at least one hydrogen pump 108. The at least one hydrogen pump 108 may include one or more electrochemical pumps.

[0014] At least one electrochemical hydrogen pump 108 may include a hydrogen pump and separator, which electrochemically pumps pure hydrogen through a polymer membrane when an electric current or voltage is applied across the membrane. At least one electrochemical hydrogen pump 108 may include a high-pressure hydrogen separation and compression system, available from Skyre, Inc. under the trade name "H2RENEW®" and / or as described in U.S. Patent No. 10,756,361 and / or U.S. Patent No. 10,648,089. At least one hydrogen pump 108 may include multiple pumps (e.g., multiple separation membrane stacks) connected in series and / or parallel to enable increased overall hydrogen recovery rate and / or throughput.

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

[0016] The effluent from the hydrogen pump 108 mainly consists of water (e.g., water vapor and / or liquid water) and residual hydrogen that was not separated from the dehydrated product stream in the conduit 14. For example, the effluent may contain 1 to 15 volume percent of hydrogen, for example, 1 to 10 volume percent of hydrogen, the remaining water, and other impurities normally present in water. The effluent is delivered from the hydrogen pump 108 to the recirculation blower and / or compressor 110 via the conduit 18.

[0017] Unpressurized discharge material can be recirculated into the recirculation conduit 20 by the blower 110. Unpressurized discharge material can be compressed to 2 psig to 15 psig (13.7895 kPaG to 103.421 kPaG) by the blower and / or compressor 110. The pressure can be selected to keep the resulting dew point lower than unintended water condensation. The higher the pressure, the higher the outlet temperature due to the heat of compression. It may be desirable to compress the unpressurized discharge material to a higher pressure so that the compressed discharge material is hot enough to avoid unintended condensation in the recirculation conduit 20. One or more optional additional condensers can be placed in conduits 18 and / or 20, as will be described in more detail below with respect to Figure 2.

[0018] The recirculation conduit 20 may be provided with optional pressure relief elements (such as a pressure relief valve or back pressure regulator) and / or passive liquid water removal elements (e.g., a condensation plate and / or gravity separator) 112 to control the pressure of the unpressurized discharge and / or to passively remove some of the liquid water from the unpressurized discharge. The unpressurized discharge is then recirculated from the element 112 upstream of the hydrogen pump 108 through the return conduit 22. The return conduit 22 may include flow control elements such as a check valve 24. The unpressurized discharge can also be recirculated into a conduit 14 located upstream of the inlet of the hydrogen pump 108 and downstream of the outlet of the condenser 106. Alternatively, the unpressurized discharge can be brought into the manifold 104 and / or conduit 10. The unpressurized discharge is mixed with the product flow at the upstream position of the hydrogen pump 108. Therefore, the remaining hydrogen in the unpressurized waste can be recovered by the hydrogen pump 108 instead of being discarded.

[0019] Figure 2 shows a system 200 of an alternative embodiment of the present disclosure, which recirculates at least a portion of the unpressurized waste into the hot box 102 via a water inlet flow in conduit 2. Optionally, system 200 may also include at least one second condenser 114 located in conduit 18 between the unpressurized waste outlet from the hydrogen pump 108 and the blower 110. Section 18A of conduit 18 connects the hydrogen pump 108 to the second condenser 114, and section 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. Unpressurized waste is first cooled as much as possible by a refrigerant (e.g., air or cooling water) based on the ambient temperature. Next, the unpressurized waste is cooled in a cooling condenser to below 5°C, e.g., about 3°C, to remove as much water as possible without dealing with complex freezing. The condensed water is removed from the second condenser 114 via the drain conduit 32. The water removal unit can be integrated into the design of the second condenser(s) 114 or 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] Dry, unpressurized waste containing hydrogen and residual water is delivered from the second condenser 114 through section 18B of conduit 18 to the blower / compressor 110. The dry, unpressurized waste is compressed by the blower / compressor 110 to 2 psig to 15 psig (13.7895 kPaG to 103.421 kPaG) and delivered into the recirculation conduit 20. The higher the pressure of the dry, unpressurized waste, the higher the outlet temperature due to the heat of compression. It may be desirable to compress the dry, unpressurized waste to a higher pressure so that the waste being compressed is hot enough to avoid unintended condensation in conduit 20. Lower condenser temperatures also serve to reduce the water content of the flow in conduit 20, thereby reducing the possibility of unintended water condensation.

[0021] Low-pressure, nearly dry waste can be recirculated from conduit 20 through pressure relief element 112 and back into the SOEC hot box 102 via return conduit 26. The waste may contain only about 500 ppm to 10,000 ppm of water, the remaining hydrogen, and unavoidable impurities. The return conduit 26 can recirculate the waste into the water inlet conduit 2 outside 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 the recirculated waste, mainly containing hydrogen. Optionally, a flow controller 28, such as a mass flow controller (MFC) or proportional solenoid valve (PSV), can be placed between the return conduit 26 and the water inlet conduit 2 to control the amount of hydrogen recirculated 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 a dedicated logic chip. If there is a surplus of recirculated hydrogen, it can be returned to the hydrogen pump as a supply flow through the conduit 22 upstream of the hydrogen pump 108. When the recirculation flow rate of the hydrogen pump is small, the dew point of the hydrogen pump inlet flow does not change significantly with the injection of nearly dry recirculated hydrogen, and humidification of the recirculated exhaust flow is not necessary. When a significant recirculation flow is used for the hydrogen pump 108, the exhaust flow in the conduit 22 is either rehumidified or redirected upstream of the first condenser 106 and / or the second condenser 114.

[0022] Figure 3 shows a system 300 of another alternative embodiment of the present disclosure, comprising a low-pressure side hydrogen pump and a high-pressure side hydrogen pump to increase the hydrogen recovery rate. Specifically, at least one hydrogen pump 108 can be configured to pump hydrogen into the 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-pressure side pump) 108 is supplied through the conduit 34 to at least one relatively high-pressure hydrogen pump (i.e., high-pressure side pump) 116, assuming that the water content is still favorable. As described above with respect to systems 100 and 200, the unpumped discharge from the low-pressure side pump can be brought into the conduit 18 to be recirculated into the low-pressure side pump 108 and / or the hot box 102.

[0023] The high-pressure side pump 116 outputs the compressed hydrogen product to be pumped into the conduit 16. The compressed hydrogen product in the conduit 16 is compressed to a relatively high pressure (e.g., 200 psig to 10,000 psig (1378.95 kPaG to 68947.6 kPaG)). The un-pumped exhaust containing relatively dry hydrogen and a very small amount of residual water is brought from the high-pressure side pump 116 to the hydrogen recirculation conduit 36. The un-pumped exhaust can pass from the hydrogen recirculation conduit 36 through an optional pressure relief element 118 and be brought into the water inlet conduit 2 of the hot box 102 via the return conduit 38 and / or into the conduit 14 upstream of the inlet of the low-pressure side pump 108 via the conduit 40. In the system 300, hydrogen can be recycled to the hot box 102 by one of the conduits 26 or 38. Therefore, when recycling hydrogen to the hot box 102 by the return conduit 38, the conduit 26 can be omitted in the system 300. Alternatively, although less preferred, the conduit 26 can be present within the system 300 and hydrogen can be recycled to the hot box 102 by both the conduits 26 and 38. The conduit 40 can include a flow control element such as a check valve 42. Therefore, the cooling condenser can be omitted by using two hydrogen pumps 108 and 116 to recycle a drier hydrogen stream to the hot box 102.

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

[0025] Therefore, systems 100, 200, or 300 can continuously recycle the output of the product stream from each hot box 102 until essentially all of the hydrogen from the product stream is provided into conduit 16 as compressed hydrogen product. If the water inlet stream in conduit 2 can contain a small amount of dissolved air, inert species including, but not limited to, nitrogen and / or argon may accumulate within systems 100, 200, or 300. Therefore, an optional small (batch or continuous) inert species purge outlet can be provided at any location in the recirculation loop such as in portion 18B of conduit 10 and / or conduit 18.

[0026] During startup of the SOEC in hot box 102, recycled hydrogen is not generated. In one embodiment, if hydrogen is required during startup of SOEC operation, hydrogen can be stored in a hydrogen storage container (e.g., hydrogen cylinder / tank). These storage containers can be provided from an external hydrogen source and / or these storage containers can be filled with hydrogen during pre-operation of systems 100, 200, or 300. Therefore, during startup of the SOEC and / or during steady-state operation, if the pressure in return conduit 26 or 38 drops below the hydrogen pressure required for SOEC operation, hydrogen is introduced into water inlet conduit 2. The above pressure drop is detected by a sensor and determined by a controller.

[0027] Optionally, buffer tanks can be arranged in one or more conduits in systems 100, 200, or 300. The buffer tank provides an additional flow rate if the hydrogen flow rate generated from hot box 102 does not match the throughput of hydrogen pump 108 and / or other hydrogen recirculation elements.

[0028] The above-described embodiments of the disclosure are provided to enable those skilled in the art to practice 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 can be applied to other embodiments without departing from the scope of the invention. Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but rather to be given the broadest 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 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 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 discharge; at least one hydrogen recirculation conduit fluidly connected between a further unpumped exhaust 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 the at least a portion of the unpressurized exhaust to an inlet of the 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 containing greater than 99 volume percent hydrogen.

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 a 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 discharge; at least one hydrogen recirculation conduit fluidly connected between a further unpumped exhaust 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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