Patent Description:
Solid oxide fuel cells (SOFC) can be operated as an electrolyzer in order to produce hydrogen and oxygen, referred to as solid oxide electrolyzer cells (SOEC). In SOFC mode, oxide ions are transported from the cathode side (air) to the anode side (fuel) and the driving force is the chemical gradient of partial pressure of oxygen across the electrolyte. In SOEC mode, a positive potential is applied to the air side of the cell and the oxide ions are now transported from the fuel side to the air side. Since the cathode and anode are reversed between SOFC and SOEC (i.e. SOFC cathode is SOEC anode, and SOFC anode is SOEC cathode), going forward, the SOFC cathode (SOEC anode) will be referred to as the air electrode, and the SOFC anode (SOEC cathode) will be referred to as the fuel electrode. During SOEC mode, water in the fuel stream is reduced (H<NUM>O + 2e→O<NUM>- + H<NUM>) to form H<NUM> gas and O<NUM>- ions, O<NUM>- ions are transported through the solid electrolyte, and then oxidized on the air side (O<NUM>- to O<NUM>) to produce molecular oxygen. Since the open circuit voltage for a SOFC operating with air and wet fuel (hydrogen, reformed natural gas) is on the order of. <NUM> to 1V (depending on water content), the positive voltage applied to the air side electrode in SOEC mode raises the cell voltage up to typical operating voltages of <NUM> to <NUM>. <CIT> discloses a heat management method in a high-temperature steam electrolysis to solid oxide fuel cells and/or to a reversible high-temperature fuel cell having the solid oxide electrolyzer cell and solid oxide fuel cell modes of operation. <CIT> discloses a comprehensive utilization system of nuclear power generation and hydrogen production. <CIT> discloses a method of operating a solid oxide electrolyzer system includes providing a water inlet stream to at least one solid oxide electrolyzer cell (SOEC), generating a wet hydrogen product stream from the at least one SOEC, providing the wet hydrogen product stream to at least one hydrogen pump, generating a compressed hydrogen product and an unpumped effluent in the at least one hydrogen pump, and recycling at least a portion of the unpumped effluent upstream of the at least one hydrogen pump. <CIT> discloses fuel cell system includes at least one hot box including a fuel cell stack and producing an anode exhaust product, at least one hydrogen pump, at least one product conduit fluidly connecting an anode exhaust 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 effluent conduit connected to an unpumped effluent outlet of the at least one hydrogen pump. <CIT> discloses systems and methods in which ammonia is used as a fuel source for solid oxide fuel cell systems. <CIT> discloses a system and method in which a high temperature fuel cell stack exhaust stream is recycled back into the fuel inlet stream of the high temperature fuel cell stack. <CIT> discloses a method for removing and recovering CO<NUM> from exhaust gas from a power and/or heat generating plant by chemical absorption and desorption, where the exhaust gas is fed to an absorber using a chemical absorbent where the CO<NUM> is absorbed in said absorbent and a CO<NUM>-depleted exhaust gas stream is formed. <CIT> discloses a solid oxide fuel cell power generation system that generates electricity from a hydrocarbon fuel, while outputting substantially no pollutants into the atmosphere and cleaning the air by removing carbon dioxide from the air exhaust stream.

In various embodiments, provided is an electrolyzer system comprising: a steam generator configured to generate steam; a stack of solid oxide electrolyzer cells configured to generate a hydrogen stream using the steam generated by the steam generator; a hotbox housing the stack, the hotbox comprising a hydrogen outlet configured to output the hydrogen stream; a hydrogen blower configured to pressurize the hydrogen stream generated by the stack; a hydrogen processor configured to compress the pressurized hydrogen stream output from the hydrogen blower; a first output conduit fluidly connecting the hydrogen outlet to the hydrogen blower; and a second output conduit fluidly connecting an outlet of the hydrogen blower to an inlet of the hydrogen processor as defined in the claims.

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate example embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the features of the invention.

When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about" or "substantially" it will be understood that the particular value forms another aspect. In some embodiments, a value of "about X" may include values of +/- <NUM>% X.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure, while the invention is defined in the appended claims.

Herein, a "solid oxide cell" may refer to a solid oxide electrolyzer cell and/or a solid oxide fuel cell.

<FIG> is a perspective view of a solid oxide cell stack <NUM>, and <FIG> is a side cross-sectional view of a portion of the stack <NUM> of <FIG>. Referring to <FIG>, the stack <NUM> includes multiple solid cells <NUM> that may be solid oxide fuel cells or solid oxide electrolyzer cells. The solid oxide cells <NUM> are separated by interconnects <NUM>, which may also be referred to as gas flow separator plates or bipolar plates. Each solid oxide cell <NUM> includes an air electrode <NUM>, a solid oxide electrolyte <NUM>, and a fuel electrode <NUM>. The stack <NUM> also includes internal fuel riser channels <NUM>.

Each interconnect <NUM> electrically connects adjacent solid oxide cells <NUM> in the stack <NUM>. In particular, an interconnect <NUM> may electrically connect the fuel electrode <NUM> of one solid oxide cell <NUM> to the air electrode <NUM> of an adjacent solid oxide cell <NUM>. <FIG> shows that the lower solid oxide cell <NUM> is located between two interconnects <NUM>.

Each interconnect <NUM> includes ribs that at least partially define fuel channels <NUM> (collectively, layer <NUM>). The interconnect <NUM> may operate as a gas-fuel separator that separates a fuel, such as a hydrocarbon fuel, flowing to the fuel electrode <NUM> of one solid oxide cell <NUM> in the stack <NUM> from oxidant, such as air, flowing to the air electrode <NUM> of an adjacent solid oxide cell <NUM> in the stack <NUM>. At either end of the stack <NUM>, there may be an air end plate or fuel end plate (not shown) for providing air or fuel, respectively, to the end electrode.

<FIG> and <FIG> are schematic views showing a process flows in an electrolyzer system <NUM>, according to various embodiments of the present disclosure. Referring to <FIG>, <FIG> and <FIG>, the system <NUM> may include an electrolyzer cell (SOEC) stack <NUM> including multiple solid oxide electrolyzer cells (SOECs), which may be configured as described with respect to <FIG>. The system <NUM> may also include a steam generator <NUM>, a steam recuperator <NUM>, a steam heater <NUM>, an air recuperator <NUM>, and an air heater <NUM>. The system <NUM> may also include an optional water preheater <NUM> and an optional mixer <NUM>.

The system <NUM> includes a hotbox <NUM> to house various components, such as the stack <NUM> as defined in the claims, optionally also the steam recuperator <NUM>, steam heater <NUM>, air recuperator <NUM>, and/or air heater <NUM>. In some embodiments, the hotbox <NUM> may include multiple stacks <NUM>. The water preheater <NUM> and the steam generator <NUM> may be located external to the hotbox <NUM> as shown in <FIG> and <FIG>. Alternatively, the water preheater <NUM> and/or the steam generator <NUM> may be located inside the hotbox <NUM>.

During operation, the stack <NUM> may be provided with steam and electric current or voltage from an external power source. In particular, the steam may be provided to the fuel electrodes <NUM> of the electrolyzer cells <NUM> of the stack <NUM>, and the power source may apply a voltage between the fuel electrodes <NUM> and the air electrodes <NUM>, in order to electrochemically split water molecules and generate hydrogen (e.g., H<NUM>) and oxygen (e.g., O<NUM>). Air may also be provided to the air electrodes <NUM>, in order to sweep the oxygen from the air electrodes <NUM>. As such, the stack <NUM> may output a hydrogen stream and an oxygen-rich exhaust stream, such as an oxygen-rich air stream ("oxygen exhaust stream").

In order to generate the steam, water may be provided to the system <NUM> from a water source <NUM>. The water may be deionized (DI) water that is deionized as much as is practical (e.g., <<NUM>/cm), in order to prevent and/or minimize scaling during vaporization. In some embodiments, the water source <NUM> may include deionization beds. In various embodiments, the system <NUM> may include a water flow control device (not shown) such as a mass flow controller, a positive displacement pump, a control valve/water flow meter, or the like, in order to provide a desired water flow rate to the system <NUM>.

If the system <NUM> includes the water preheater <NUM>, the water may be provided from the water source <NUM> to the water preheater <NUM>. The water preheater <NUM> may be a heat exchanger configured to heat the water using heat recovered from the oxygen exhaust stream. Preheating the water may reduce the total power consumption of the system <NUM> per unit of hydrogen generated. In particular, the water preheater <NUM> may recover heat from the oxygen exhaust stream that may not be recoverable by the air recuperator <NUM>, as discussed below. The oxygen exhaust stream may be output from the water preheater <NUM> at a temperature above <NUM>, such as above <NUM>, such as a temperature of about <NUM> to <NUM>.

The water output from the water preheater <NUM> or the water source <NUM> may be provided to the steam generator <NUM>. A portion of the water may vaporize in the water preheater. The steam generator <NUM> may be configured to heat the water not vaporized in the water preheater to convert the water into steam. For example, the steam generator <NUM> may include a heating element to vaporize the water and generate steam. For example, the steam generator <NUM> may include an AC or DC resistance heating element, or an induction heating element.

The steam generator <NUM> may include multiple zones/elements that may or may not be mechanically separate. For example, the steam generator <NUM> may include a pre-boiler to heat the water up to, or near to the boiling point. The steam generator <NUM> may also include a vaporizer configured to convert the pre-boiled water into steam. The steam generator <NUM> may also include a deaerator to provide a relatively small purge of steam to remove dissolved air from the water prior to bulk vaporization. The steam generator <NUM> may also include an optional superheater configured to further increase the temperature of the steam generated in the vaporizer. The steam generator <NUM> may include a demister pad located downstream of the heating element and/or upstream from the super heater. The demister pad may be configured to minimize entrainment of liquid water in the steam output from the steam generator <NUM> and/or provided to the superheater.

If the steam product is superheated, it will be less likely to condense downstream from the steam generator <NUM> due to heat loss to ambient conditions. Avoidance of condensation is preferable, as condensed water is more likely to form slugs of water that may cause significant variation of the delivered mass flow rate with respect to time. It may also be beneficial to avoid excess superheating, in order to limit the total power consumption of the system <NUM>. For example, the steam may be superheated by an amount ranging from about <NUM> to about <NUM>.

Blowdown from the steam generator <NUM> may be beneficial for long term operation, as the water will likely contain some amount of mineralization after deionization. Typical liquid blowdown may be on the order of <NUM> %. The blowdown may be continuous, or may be intermittent, e.g. 10x the steady state flow for <NUM> seconds out of every minute, 5x the steady state flow for <NUM> minute out of every <NUM> minutes, etc. The need for a water discharge stream can be eliminated by pumping the blowdown into the hot oxygen exhaust.

The steam output from the steam generator <NUM> may be provided to the steam recuperator <NUM>. However, if the system <NUM> includes the optional mixer <NUM>, the steam may be provided to the mixer <NUM> prior to being provided to the steam recuperator <NUM>. In particular, the steam may include small amounts of dissolved air and/or oxygen. As such, the mixer <NUM> may be configured to mix the steam with hydrogen gas, in order to maintain a reducing environment in the stack <NUM>, and in particular, at the fuel electrodes <NUM>.

The mixer <NUM> may be configured to mix the steam with hydrogen received from a hydrogen storage device <NUM> and/or with a portion of the hydrogen stream output from the stack <NUM>. The hydrogen addition rate may be set to provide an amount of hydrogen that exceeds an amount of hydrogen needed to react with an amount of oxygen dissolved in the steam. The hydrogen addition rate may either be fixed or set to a constant water to hydrogen ratio. However, if the steam is formed using water that is fully deaerated, the mixer <NUM> and/or hydrogen addition may optionally be omitted.

In some embodiments, the hydrogen may be provided by the external hydrogen source during system startup and/or during steady-state operations. For example, during startup, the hydrogen may be provided from the hydrogen storage device, and during steady-state, the hydrogen may be provided from the hydrogen storage device <NUM> and/or by diverting a portion of the hydrogen stream (i.e., hydrogen exhaust stream) generated by the stack <NUM> to the mixer <NUM>. In particular, the system <NUM> may include a hydrogen diverter <NUM>, such as a splitter, pump, blower and/or valve, configured to selectively divert a portion of the generated hydrogen stream to the mixer <NUM>, during steady-state operation.

The steam recuperator <NUM> may be a heat exchanger configured to recover heat from the hydrogen stream output from the stack <NUM>. As such, the steam recuperator <NUM> may be configured to increase the efficiency of the system <NUM>. The steam may be heated to at least <NUM>, such as <NUM> to <NUM> in the steam recuperator <NUM>.

The steam output from the steam recuperator <NUM> may be provided to the steam heater <NUM> which is located downstream from the steam recuperator <NUM>, as shown in <FIG>. The steam heater <NUM> may include a heating element, such as a resistive or inductive heating element. The steam heater <NUM> may be configured to heat the steam to a temperature above the operating temperature of the stack <NUM>. For example, depending on the health of the stack <NUM>, the water utilization rate of the stack <NUM>, and the air flow rate to the stack <NUM>, the steam heater <NUM> may heat the steam to a temperature ranging from about <NUM> to about <NUM>, such as <NUM> to <NUM>. Accordingly, the stack <NUM> may be provided with steam or a steam-hydrogen mixture at a temperature that allows for efficient hydrogen generation. Heat may also be transported directly from the steam heater to the stack by radiation (i.e., by radiant heat transfer).

In one alterative embodiment shown in <FIG>, the steam recuperator <NUM> may be located downstream from the steam heater <NUM> such that steam existing the steam heater <NUM> enters the steam recuperator <NUM> instead of vice-versa. In another alternate embodiment, the steam heater <NUM> may include a heat exchanger configured to heat the steam using heat extracted from a high-temperature fluid, such as a fluid heated to about <NUM> or more. This fluid may be provided from a solar concentrator farm or a power plant, such as a nuclear reactor power plant, for example. Alternatively, if the fluid is a high temperature steam, such as steam provided from a nuclear reactor power plant, then such steam may be provided to the fuel electrodes <NUM> of the stack <NUM>. In this case, the water source <NUM> may comprise a source of high temperature steam, and one or more of the water preheater <NUM>, steam generator <NUM>, steam recuperator <NUM> and/or steam heater <NUM> may be omitted.

In some embodiments, the steam heater <NUM> may include multiple steam heater zones with independent power levels (divided vertically or circumferentially or both), in order to enhance thermal uniformity, in some embodiments.

In some embodiments, the operations of the steam recuperator <NUM> and the steam heater <NUM> may be combined into a single component. For example, the steam recuperator <NUM> may include a voltage source configured to apply a voltage to heat exchange fins of the steam recuperator <NUM>, such that the heat exchange fins operate as resistive heating elements and heat the steam to a temperature high enough to be provided to the stack <NUM>, such as a temperature ranging from about <NUM> to about <NUM>. The high temperature steam (or optionally a steam / hydrogen mixture) output from the steam heater <NUM> may be provided to the fuel electrodes <NUM> of the stack <NUM>.

The oxygen exhaust output from the stack <NUM> may be provided to the air recuperator <NUM>. The air recuperator <NUM> may be provided with ambient air by an air blower <NUM>. The air recuperator <NUM> may be configured to heat the air using heat extracted from the oxygen exhaust. In some embodiments, the ambient air may be filtered to remove contaminants, prior to being provided to the air recuperator <NUM> or the air blower <NUM>.

Air output from the air recuperator <NUM> may be provided to the air heater <NUM>. The air heater may include a resistive or inductive heating element configured to heat the air to a temperature exceeding the operating temperature of the stack <NUM>. For example, depending on the health of the stack <NUM>, the water utilization rate of the stack <NUM>, and the air flow rate to the stack <NUM>, the air heater <NUM> may heat the air to a temperature ranging from about <NUM> to about <NUM>, such as <NUM> to <NUM>. Accordingly, the stack <NUM> may be provided with air at a temperature that allows for efficient hydrogen generation. Heat may also be transported directly from the air heater to the stack by radiation.

The higher the temperature output from the air recuperator, the less power is required for the air heater <NUM>. Increased pressure drop on either side of the air recuperator <NUM> may be counteracted with increased air blower <NUM> power. Increased pressure drop may aid the circumferential mass flow uniformity, creating a more uniform heat transfer environment, and higher temperature for the air inlet stream output from the air recuperator <NUM>.

In alternative embodiments, the air heater <NUM> may include a heat exchanger configured to heat the air using heat extracted from a high-temperature fluid, such as a fluid heated to about <NUM>, or more. This fluid may be provided from a solar concentrator farm or a nuclear reactor, for example.

The air heater <NUM> may include multiple air heater zones with independent power levels (divided vertically or circumferentially or both), in order to enhance thermal uniformity, in some embodiments. In some embodiments, the air heater <NUM> may be disposed below the air recuperator <NUM>, or between the stack <NUM> and the steam recuperator <NUM>. The air heater <NUM> may include baffles having slits of different sizes at different heights along the baffles, to allow air to exit the air heater <NUM> approximately evenly in both temperature and height, at all heights along the air heater <NUM>. Air from the air heater <NUM> is provided to the air electrodes <NUM> of the stack <NUM>.

In some embodiments, the air recuperator <NUM> and the air heater <NUM> may be combined into a single component. For example, the air recuperator <NUM> may include a voltage source configured to apply a voltage to heat exchange fins of a heat exchanger included in the air recuperator <NUM> combined component, such that the fins operate as resistive heating elements and heat the air to a temperature high enough to be provided to the stack <NUM>, such as a temperature ranging from about <NUM> to about <NUM>.

According to various embodiments, the system <NUM> may include an optional air preheater <NUM> disposed outside of the hotbox <NUM>. In particular, the air preheater <NUM> may be configured to preheat air provided to the hotbox <NUM> by the air blower <NUM>. In some embodiments, the air preheater <NUM> may operate using electricity. In other embodiments, the air preheater <NUM> may operate using a hydrocarbon fuel, such as natural gas or the like. For example, if the system <NUM> is provided with power from a power source that is intermittent or provides an insufficient amount of power to operate an electric heater, such solar or wind power generation systems, the air preheater <NUM> may utilize a hydrocarbon power source (e.g., a gas heater). Alternatively, the air preheater <NUM> may be omitted.

Because the air preheater <NUM> is located outside of the hotbox <NUM>, the air preheater <NUM> may be advantageously serviced without the need to access the inside of the hotbox <NUM> and/or interrupt the operation of the stack <NUM> and/or other components located inside of the hotbox <NUM>. In some embodiments, the air preheater <NUM> may allow for the air heater <NUM> to be omitted if the air preheater <NUM> heats the air above stack temperature. However, in other embodiments, the system <NUM> may include both the air preheater <NUM> and the air heater <NUM>.

During system startup, the air preheater <NUM> may be configured to heat air provided to the hotbox to a temperature sufficient to increase the internal temperature of the hotbox <NUM> and/or the temperature of the stack <NUM> up to a temperature approaching the operating temperature thereof. Preheated air provided to the air recuperator <NUM> may also operate to preheat stack exhaust provided through the air recuperator <NUM> to the water preheater <NUM> during system startup. Since the stack oxygen exhaust may be initially output at a relatively low temperature, the air preheater <NUM> may be used to indirectly preheat the water provided from the water source <NUM> to the hotbox <NUM>.

During steady-state operation, the air preheater <NUM> may also be configured heat air to a temperature sufficient to maintain the hotbox <NUM> at steady-state operating temperature, such as <NUM> to <NUM>. For example, the heat output of the air preheater <NUM> may be lower during steady-state operation than during system startup.

In some embodiments, the system <NUM> may be operated in a thermal neutral configuration, where each electrolyzer cell <NUM> in the stack <NUM> is provided with a thermal-neutral voltage. In particular, the current provided to each electrolyzer cell <NUM> may be varied such that the heat generated by I<NUM>R heating balances the (endothermic) heat of reaction. As such, use of the steam heater <NUM> and/or the air heater <NUM> may be minimized or eliminated during steady-state thermal neutral operation.

A hydrogen stream (i.e., hydrogen exhaust stream) from the stack <NUM> may be a warm stream containing hydrogen gas and water. The hydrogen stream may be output from the steam recuperator <NUM> at a temperature of <NUM> to <NUM>. The steam recuperator <NUM> may be fluidly connected to a hydrogen processor <NUM> by an output conduit <NUM>. In some embodiments, the hydrogen processor <NUM> may be connected to, a hydrogen storage device or tank <NUM>.

The hydrogen processor <NUM> may include a hydrogen pump, a condenser, or a combination thereof. The hydrogen pump may be an electrochemical hydrogen pump and/or may be configured to operate at a high temperature. For example, the hydrogen pump may be configured to operate at a temperature of from about <NUM> to about <NUM>, in order to remove from about <NUM>% to about <NUM>% of the hydrogen from the hydrogen stream. The compressor may be a liquid ring compressor or a diaphragm compressor, for example. In some embodiments, the condenser may be an air-cooled or water-enhanced, air-cooled condenser and/or heat exchanger configured to cool a hydrogen stream to a temperature sufficient to condense water vapor in the hydrogen stream. For example, the hydrogen processor <NUM> may be configured to compress the hydrogen stream to a desired pressure, such as about <NUM>*<NUM><NUM> to about <NUM>*<NUM><NUM> bar (about <NUM> to about <NUM> psig). Compression may include multiple stages, with inter-stage cooling, and water removal.

In various embodiments, the hydrogen processor <NUM> may include a series of electrochemical hydrogen pumps, which may be disposed in series and/or in parallel with respect to a flow direction of the hydrogen stream, in order to compress the hydrogen stream. The final product from compression may still contain traces of water. As such, the hydrogen processor <NUM> may include a dewatering device, such as a temperature swing adsorption reactor or a pressure swing adsorption reactor, to remove this residual water, if necessary. The final product may be high pressure (e.g., about <NUM>*<NUM><NUM> to about <NUM>*<NUM><NUM> bar (about <NUM> to about <NUM> psig)) purified, hydrogen. The product may also contain some nitrogen gas, which may be dissolved air in the water. The nitrogen may be removed automatically during electrochemical compression.

A remaining un-pumped effluent from the hydrogen processor <NUM> may be a water rich stream that is fully vaporized. This water rich stream may be fed to a blower for recycle into the mixer <NUM> or stream recuperator <NUM>, eliminating the need for water vaporization in the steam generator <NUM>. The system may be configured to repurify (e.g., in DI beds) the residual water and provide the residual water removed from the compressed hydrogen stream to the water preheater. Electrochemical compression may be more electrically efficient than traditional compression.

The hydrogen streams of multiple stacks <NUM> on site may be combined into a single stream. This combined stream may be cooled as much as practical using, for example, air coolers or heat exchangers cooled by a site cooling water tower, which may be part of the hydrogen processor <NUM>. The hydrogen output from the hydrogen processor <NUM> may be provided to the hydrogen tank <NUM> for storage or use, such as to be used as a fuel in a fuel cell power generation system.

Steam loss into the hydrogen stream may be minimized by increasing the hydrogen pump pressure to a pressure ranging from about <NUM>*<NUM>°-<NUM>*<NUM>° bar (<NUM>-<NUM> psig), for example. This separation may be at the electrolyzer module level, system level, stamp level, or site level.

Water condensation and compression of the hydrogen stream may consume a significant amount of power. In some embodiments, air flow to the stack <NUM> may be reduced or stopped, such that the stack <NUM> outputs pure or nearly pure oxygen gas as stack exhaust. In addition, the air and fuel sides of the electrolyzer cells <NUM> may be operated at an equal pressure ranging from about <NUM>*<NUM>° bar to about <NUM>*<NUM>° bar (about <NUM> psig to about <NUM> psig). In some embodiments, air provided to the stack <NUM> may be provided at a pressure of about <NUM> slm or less.

High pressure operation may allow for the elimination of the power and equipment associated with the first stage of the hydrogen stream compression, may reduce the size of the initial condenser stage, due to the higher dew point due to the higher pressure, and/or may reduce the physical space required for flow channels, due to the higher density associated with higher pressure.

As noted above, the system <NUM> may be configured to operate with a variety of different hydrogen processors <NUM>, which may be provided on site by a third party. As such, it may be difficult to match the flow and/or production rate of the hydrogen stream output from the system <NUM> with the throughput of a particular hydrogen processor <NUM>. In particular, such variations may induce positive and/or negative pressure fluctuations within the output conduit <NUM>. For example, if the throughput of the hydrogen processor <NUM> is too high (e.g., the hydrogen processor <NUM> pulls too hard on the hydrogen stream) a negative pressure may be induced within the system <NUM>, or if the throughput is too low, a positive pressure may be induced within the system <NUM>.

Such pressure fluctuations may cause problems within the system <NUM>. For example, excessive negative pressures may result in air leaking into the system <NUM>, or may result in a high pressure variation across the electrolytes of the stack <NUM>, which may increase the risk of electrolyte damage, such as cracking. Excessively high pressures may also result in pressure variations across the electrolytes and increase the risk of electrolyte damage.

Accordingly, the system includes a first output conduit 502A, a second output conduit 502B, and a hydrogen blower <NUM> as further defined in the claims. The first output conduit 502A fluidly connects the fuel cell stack <NUM> and an inlet of the hydrogen blower <NUM> as defined in the claims. The second output conduit 502B fluidly connects an outlet of the hydrogen blower <NUM> to the hydrogen processor <NUM> as defined in the claims. The hydrogen blower <NUM> may be configured to increase the pressure of the hydrogen stream output from the hotbox <NUM>. For example, the hydrogen blower <NUM> may be configured to increase the pressure of a hydrogen stream by from about <NUM> bar to about <NUM> bar (about <NUM> to about <NUM> pounds per square in gauge (psig)), such as from about <NUM> to about <NUM> bar (about <NUM> to about <NUM> psig). The hydrogen blower <NUM> may also operate to isolate the components of the hotbox <NUM>, such as the stack <NUM>, from pressure fluctuations induced by the operation of the hydrogen processor <NUM>.

In some embodiments, the hydrogen blower <NUM> may be configured to receive a hydrogen stream generated by a single electrolyzer system <NUM> or stack <NUM>, as shown in <FIG>. In other embodiments, the hydrogen blower <NUM> may be configured to receive hydrogen streams generated by multiple electrolyzer systems <NUM> and/or by multiple stacks <NUM>.

In various embodiments, the system <NUM> may include an optional water knockout device <NUM> configured to remove condensed water from the hydrogen stream, in order to reduce and/or prevent liquid water accumulation in the hydrogen blower <NUM>.

In some embodiments, the hydrogen diverter <NUM> may be used to divert the hydrogen stream, such that hydrogen may be fed to displace most or all of the steam in the system <NUM>. The hydrogen diverter <NUM> may then closed to maintain a reducing atmosphere in the stack <NUM>, without any additional hydrogen consumption. Air flow to the stack <NUM> may be significantly reduced or eliminated. In some embodiments, there may be a minimum air flow to keep the air heater <NUM> from overheating.

In some embodiments, condensed water may be recycled to the feed of the process (feed to the DI beds) in the water source <NUM>. Hydrogen added to the steam in the mixer <NUM> may be produced during the first stage or any intermediate stage of the compression train, and may be dehumidified if necessary. The hydrogen storage device <NUM> may include a low/intermediate pressure storage tank for the hydrogen provided through the mixer <NUM> to the stack <NUM>.

According to various embodiments, the system <NUM> may include a controller <NUM>, such as a central processing unit, that is configured to control the operation of the system <NUM>. For example, the controller <NUM> may be wired or wirelessly connected to various elements of the system <NUM> to control the same.

In some embodiments, the controller <NUM> may be configured to control the speed of the hydrogen blower <NUM> based on a flow rate of the hydrogen stream and/or an inlet pressure generated by the hydrogen processor <NUM>.

In some embodiments, the controller <NUM> may be configured to control the system <NUM>, such that the system <NUM> may be operated in a standby mode where no hydrogen stream is generated. During the standby mode, electrical heaters associated with (i.e., located in a heat transfer relationship with) the stack <NUM> may be run at the minimum power level needed to keep the electrolyzer cells <NUM> at a desired standby temperature. The desired standby temperature may be different from the desired production operating temperature, and may be impacted by an acceptable time needed to return to a desired operating temperature.

Recovery from standby mode to steady-state operation may allow for hydrogen generation to be initiated at a lower temperature than the standard steady-state operating temperature. At the lower temperature, cell resistance may be higher, which may provide additional heating to increase the stack <NUM> to the steady-state operating temperature. Water/steam feed can be significantly reduced or eliminated. Hydrogen addition to the steam in the mixer <NUM> may also be significantly reduced or eliminated.

According to various embodiments, the controller <NUM> may be configured to control the operation of the system <NUM> based on various site-wide control parameters. For example, the controller <NUM> may be configured to control hydrogen production based on any of: the operational limits of each SOEC stack; power availability; instantaneous average power costs, including the impact of demand charges at all tiers; instantaneous marginal power costs, including the impact of demand charges at all tiers; instantaneous power renewable content; available hydrogen storage capacity; stored energy available for use (e.g., either thermal storage or electrical storage); a hydrogen production plan (e.g., a daily, weekly, or month plan, etc.); hydrogen production revenue implications (e.g., sales price, adjustments for production levels, penalties for nonperformance, etc.); a maintenance plan; the relative health of all hotboxes on site; the compression/condensation train mechanical status; the water/steam/hydrogen feed availability; the weather conditions and/or forecast; any other known external constraints, either instantaneous, or over some production plan period (e.g., only allowed so much water per month, or so many MW-hr per month); and/or the minimum acceptable time to start producing hydrogen from standby mode (if standby is predicted to last multiple hours, it may be desirable to allow the cells to cool below operating temperature).

<FIG> is a schematic view showing a process flow in an alternative electrolyzer system <NUM>, according to various embodiments of the present disclosure. The electrolyzer system <NUM> may be similar to the electrolyzer system <NUM>, so only the differences there between will be discussed in detail.

Referring to <FIG>, the electrolyzer system <NUM> may include an air preheater <NUM> disposed inside of the hotbox <NUM>. The air preheater <NUM> may be a heat exchanger configured to preheat air provided from the air blower <NUM>, using heat extracted from the hydrogen stream output from the steam recuperator <NUM>. The preheated air may then be provided to the air recuperator <NUM>. Thus, the internal air preheater <NUM> located inside the hotbox <NUM> replaces the external air preheater <NUM> (shown in <FIG> and <FIG>) located outside the hotbox <NUM>. In this embodiment, additional electricity or an additional gas heater is not required to provide heat to the air preheater <NUM>. The air preheater is also beneficial in that the hydrogen/steam stream to the hydrogen diverter <NUM> is substantially cooler, allowing the hydrogen separator to be made of cheaper materials.

In some embodiments, a small amount of liquid water (e.g., from about <NUM>% to about <NUM>% of incoming water) may be periodically or continuously discharged from the steam generator <NUM>. In particular, the discharged liquid water may include scale and/or other mineral impurities that may accumulate in the steam generator <NUM> while vaporizing water to generate steam. Therefore, this discharged liquid water is not desirable for being recycled into the water inlet stream from the water source <NUM>. This liquid discharge may be mixed with the hot oxygen exhaust stream output from the water preheater <NUM> into an exhaust conduit. The hot oxygen exhaust stream may have a temperature above <NUM>, such as <NUM> to <NUM>, for example <NUM> °C. As such, the liquid water discharge may be evaporated by the hot oxygen exhaust stream, such that no liquid water is required to be discharged from the system <NUM>. The system <NUM> may optionally include a pump <NUM> configured to pump and regulate the liquid water discharge output from the steam generator <NUM> into the oxygen exhaust output from the water preheater <NUM>. Optionally, a proportional solenoid valve may be added in addition to the pump <NUM> to additionally regulate the flow of the liquid water discharge.

<FIG> is a schematic representation of a solid oxide fuel cell (SOFC) system <NUM>, according to various embodiments of the present disclosure. Referring to <FIG>, the system <NUM> includes a hotbox <NUM> and various components disposed therein or adjacent thereto. The hotbox <NUM> may contain at least one fuel cell stack <NUM>, such as a solid oxide fuel cell stack containing alternating fuel cells and interconnects. One solid oxide fuel cell of the stack contains a ceramic electrolyte, such as yttria stabilized zirconia (YSZ), scandia stabilized zirconia (SSZ), scandia and ceria stabilized zirconia or scandia, yttria and ceria stabilized zirconia, an anode electrode, such as a nickel-YSZ, a nickel-SSZ or nickel-doped ceria cermet, and a cathode electrode, such as lanthanum strontium manganite (LSM). The interconnects may be metal alloy interconnects, such as chromium-iron alloy interconnects. The stacks <NUM> may be arranged over each other in a plurality of columns.

The hotbox <NUM> may also contain an anode recuperator <NUM>, a cathode recuperator <NUM>, an anode tail gas oxidizer (ATO) <NUM>, an anode exhaust cooler <NUM>, a vortex generator <NUM>, and a water injector <NUM>. The system <NUM> may also include a catalytic partial oxidation (CPOx) reactor <NUM>, a mixer <NUM>, a CPOx blower <NUM> (e.g., air blower), a main air blower <NUM> (e.g., system blower), and an anode recycle blower <NUM>, which may be disposed outside of the hotbox <NUM>. However, the present disclosure is not limited to any particular location for each of the components with respect to the hotbox <NUM>.

The CPOx reactor <NUM> receives a fuel inlet stream from a fuel inlet <NUM>, through a fuel conduit 301A. The fuel inlet <NUM> may be a fuel tank or a utility natural gas line including a valve to control an amount of fuel provided to the CPOx reactor <NUM>. The CPOx blower <NUM> may provide air to the CPOx reactor <NUM> during system start-up. The fuel and/or air may be provided to the mixer <NUM> by a fuel conduit 301B. Fuel flows from the mixer <NUM> to the anode recuperator <NUM> through a fuel conduit 301C. The fuel is heated in the anode recuperator <NUM> by a portion of the fuel exhaust and the fuel then flows from the anode recuperator <NUM> to the stack <NUM> through a fuel conduit 301D.

The main air blower <NUM> may be configured to provide an air stream (e.g., air inlet stream) to the anode exhaust cooler <NUM> through air conduit 302A. Air flows from the anode exhaust cooler <NUM> to the cathode recuperator <NUM> through air conduit 302B. The air is heated by the ATO exhaust in the cathode recuperator <NUM>. The air flows from the cathode recuperator <NUM> to the stack <NUM> through air conduit 302C.

Anode exhaust (e.g., fuel exhaust) generated in the stack <NUM> is provided to the anode recuperator <NUM> through anode exhaust conduit 306A. The anode exhaust may contain unreacted fuel and may also be referred to herein as fuel exhaust. The anode exhaust may be provided from the anode recuperator <NUM> to a shift reactor <NUM>, such as a water gas shift (WGS) reactor, by anode exhaust conduit 306B. A water injector <NUM> may be fluidly connected to the anode exhaust conduit 306B. The anode exhaust may be provided from the shift reactor <NUM> to the anode exhaust cooler <NUM> by anode exhaust conduit 306C. The anode exhaust heats the air inlet stream in the anode exhaust cooler <NUM> and may then be provided from the anode exhaust cooler <NUM> to the fuel exhaust processor <NUM>.

In particular, the anode exhaust may be output from the anode exhaust cooler <NUM> to the fuel exhaust processor <NUM> by a first recycling conduit 308A. In some embodiments, anode exhaust may be provided to the fuel exhaust processor <NUM> by an optional second recycling conduit 308B. In particular, the second recycling conduit 308B may be configured to provide hotter anode exhaust to the fuel exhaust processor <NUM> than the first recycling conduit 308A, since anode exhaust is cooled in the anode exhaust cooler <NUM> prior to entering the first recycling conduit 308A.

The shift reactor <NUM> may be any suitable device that converts components of the fuel exhaust into free hydrogen (H<NUM>) and/or water. For example, the shift reactor <NUM> may comprise a tube or conduit containing a catalyst that converts carbon monoxide (CO) and water vapor in the fuel exhaust stream into carbon dioxide and hydrogen, via the water gas shift reaction (CO + H<NUM>O ↔ CO<NUM> + H<NUM>). Thus, the shift reactor <NUM> increases the amount of hydrogen and carbon dioxide in the anode exhaust and decreases the amount of carbon monoxide in the anode exhaust. For example, the shift reactor <NUM> may reduce the amount of carbon monoxide in the anode exhaust to about <NUM>% by volume or less, such as about <NUM>% or less, or about <NUM>% or less. The catalyst may be any suitable catalyst, such as an iron oxide or a chromium-promoted iron oxide catalyst.

Cathode exhaust generated in the stack <NUM> flows to the ATO <NUM> through cathode exhaust conduit 304A. The vortex generator <NUM> may be disposed in the cathode exhaust conduit 304A and may be configured to swirl the cathode exhaust. The swirled cathode exhaust may mix with hydrogen output from the fuel exhaust processor <NUM> before being provided to the ATO <NUM>. The mixture may be oxidized in the ATO <NUM> to generate ATO exhaust. The ATO exhaust flows from the ATO <NUM> to the cathode recuperator <NUM> through the cathode exhaust conduit 304B. Exhaust flows from the cathode recuperator <NUM> and out of the hotbox <NUM> through cathode exhaust conduit 304C.

Water flows from a water source <NUM>, such as a water tank or a water pipe, to the water injector <NUM> through a water conduit. The water injector <NUM> injects water directly into first portion of the anode exhaust provided in the anode exhaust conduit 306C. Heat from the first portion of the anode exhaust (also referred to as a recycled anode exhaust stream) provided in the exhaust conduit 306C vaporizes the water to generate steam. The steam mixes with the anode exhaust, and the resultant mixture is provided to the anode exhaust cooler <NUM>. The mixture is then routed through the fuel exhaust processor <NUM> and provided to the mixer <NUM>. The mixer <NUM> is configured to mix the steam and first portion of the anode exhaust with fresh fuel (i.e., fuel inlet stream). This humidified fuel mixture may then be heated in the anode recuperator <NUM> by the anode exhaust, before being provided to the stack <NUM>. The system <NUM> may also include one or more fuel reforming catalysts located inside and/or downstream of the anode recuperator <NUM>. The reforming catalyst(s) reform the humidified fuel mixture before it is provided to the stack <NUM>.

The system <NUM> may further a system controller <NUM> configured to control various elements of the system <NUM>. The system controller <NUM> may include a central processing unit configured to execute stored instructions. For example, the system controller <NUM> may be configured to control fuel and/or air flow through the system <NUM>, according to fuel composition data.

<FIG> is a schematic view showing components of the fuel exhaust processor <NUM>, according to various embodiments of the present disclosure. Referring to <FIG> and <FIG>, the fuel exhaust processor <NUM> may include a hydrogen separator <NUM>, a system controller <NUM>, a splitter <NUM>, a low temperature shift reactor <NUM>, and a heat exchanger <NUM>. The system controller <NUM> may be a central processing unit configured to execute stored instructions. For example, the system controller <NUM> may be configured to control anode exhaust, hydrogen and/or carbon dioxide flow through the fuel exhaust processor <NUM>. In some embodiments, the system controller <NUM> may be operatively connected to the system controller <NUM> of the SOFC system <NUM>, such that the system controller <NUM> may control the fuel exhaust processor based on operating conditions of the SOFC system <NUM>.

The splitter <NUM> may be configured to receive anode exhaust from the first recycling conduit 308A. The splitter <NUM> may be fluidly connected to the hotbox <NUM> and the hydrogen separator <NUM>. For example, a first return conduit 406A may fluidly connect an outlet of the splitter <NUM> to the hotbox <NUM>, and a first separator conduit 401A and a second separator conduit 401B may fluidly connect an outlet of the splitter <NUM> to the hydrogen separator <NUM>. In particular, a first portion of the anode exhaust may be output from the splitter <NUM> and provided to the shift reactor <NUM> via the first separator conduit 401A, and anode exhaust output form the shift reactor <NUM> may be supplied to the hydrogen separator <NUM> by the second separator conduit 401B. A second portion of the anode exhaust may be output from an outlet of the splitter <NUM> to the first return conduit 406A. Anode exhaust output from the fuel exhaust processor <NUM> may be move through the first return conduit 406A to the mixer <NUM> of the SOFC system <NUM>, by the anode recycle blower <NUM>. However, the anode recycle blower <NUM> may be disposed in any other suitable location.

The shift reactor <NUM> may be a WGS reactor similar to the shift reactor <NUM>, but may configured to operate at a lower temperature than the shift reactor <NUM>. Accordingly, the shift reactor <NUM> may be referred to as a high temperature shift reactor, and the shift <NUM> may be referred to as a low temperature shift reactor. The shift reactor <NUM> may be configured to further reduce the carbon monoxide content of the anode exhaust provided to the fuel exhaust processor <NUM>. For example, the shift reactor <NUM> may be configured to reduce the carbon monoxide content of the anode exhaust to less than about <NUM>% by volume, such as less than about <NUM> %, or less than about <NUM> %.

Purified anode exhaust (e.g., low carbon monoxide content anode exhaust) output from the shift reactor <NUM> may be provided to the hydrogen separator <NUM> by a second separator conduit 401B. The heat exchanger <NUM> may be operatively connected to the second separator conduit 401B and may be configured to cool anode exhaust passing there through. For example, the heat exchanger <NUM> may include fans and/or cooling fins configured to transfer heat to air supplied thereto. Accordingly, the heat exchanger <NUM> may be configured to cool the anode exhaust, in order to prevent overheating and/or damage to the hydrogen separator <NUM>. In some embodiments, the heat exchanger <NUM> may be omitted. For example, if the shift reactor <NUM> includes an internal cooling system, as disclosed below with respect to FIGS. 4A and 4B, the heat exchanger <NUM> may optionally be omitted.

In various embodiments, the fuel exhaust processor <NUM> may be fluidly connected to multiple fuel cell systems <NUM>. For example, the fuel exhaust processor <NUM> may be configured to process anode exhaust output from two or more fuel cell systems, and may be configured to return hydrogen rich fuel streams to both fuel cell systems.

The hydrogen separator <NUM> may include one or more hydrogen pumps, which may each include electrochemical hydrogen pumping cells <NUM>. For example, as shown in <FIG>, the hydrogen separator <NUM> may include a first hydrogen pump 414A, a second hydrogen pump 414B, and a third hydrogen pump 414C, that each comprise stacked hydrogen pumping cells <NUM>. However, the present disclosure is not limited to any particular number of hydrogen pumps. For example, in various embodiments, the first hydrogen pump 414A and the second hydrogen pump 414B may be combined into a single stack of hydrogen pumping cells <NUM>. In other embodiments, the first, second, and third hydrogen pumps 414A, 414B, 414C may be combined into a single stack of hydrogen pumping cells <NUM>.

In some embodiments, the first hydrogen pump 414A may include a larger number of hydrogen pumping cells <NUM> than the second and/or third hydrogen pumps 414B, 414C. For example, the first hydrogen pump 414A may include twice the number of hydrogen pumping cells <NUM> as the second hydrogen pump 414B and/or the third hydrogen pump 414C.

In still other embodiments, the fuel exhaust processor <NUM> may output only a single hydrogen stream. For example, the third hydrogen pump 414C may be omitted. In particular, heat generated by exothermic reactions in the ATO <NUM> may be used to offset heat losses due to endothermic fuel reformation reactions occurring in the anode recuperator <NUM>, by using the ATO exhaust to heat air provided to the fuel cell stack <NUM> in the cathode recuperator <NUM>.

The second separator conduit 401B may provide anode exhaust to an anode inlet of the first hydrogen pump 414A. An anode outlet of the first hydrogen pump 414A may be fluidly connected to an anode inlet of the second hydrogen pump 414B by a first exhaust conduit 402A. An anode outlet of the second hydrogen pump 414B may be fluidly connected to an anode inlet of the third hydrogen pump 414C, by a second exhaust conduit 402B. An anode outlet of the third hydrogen pump 414C may be fluidly connected to a carbon dioxide processor <NUM> by a third output conduit 502C and a fourth output conduit 502D.

The carbon dioxide processor <NUM> may be fluidly connected to a carbon dioxide storage device or tank <NUM>. The carbon dioxide processor <NUM> may operate to compress and/or cool a carbon dioxide stream received from the fuel exhaust processor <NUM>. The processor may be a condenser and/or dryer configured to remove water from the carbon dioxide stream. The carbon dioxide stream may be provided to the carbon dioxide processor <NUM> in the form of a vapor, liquid, solid or supercritical carbon dioxide.

A first hydrogen conduit 404A may be fluidly connected to a cathode outlet of the first stack 410A, a second hydrogen conduit 404B may be fluidly connected to a cathode outlet of the second stack 410B, and a third hydrogen conduit 404C may be fluidly connected to a cathode outlet of the third stack 410C. The first hydrogen conduit may be fluidly connected to a first return conduit 406A, and the second hydrogen conduit 404B may be fluidly connected to the first hydrogen conduit 404A. In particular, the first return conduit 406A may be configured to provide hydrogen extracted from the anode exhaust by the first hydrogen pump 114A, the second hydrogen pump 414B, and or the third hydrogen pump 414C to the mixer <NUM>, such that the hydrogen may be recycled to the stack <NUM>.

The third hydrogen conduit 404C may be fluidly connected to the fuel cell system <NUM> by a second return conduit 406B. In particular, the second return conduit 406B may be configured to provide hydrogen extracted from the anode exhaust by the third stack 114C to the second return conduit 406B, which may provide the hydrogen to the ATO <NUM>.

In some embodiments, an optional fourth hydrogen conduit 404D may fluidly connect the third hydrogen conduit 404C to the first hydrogen conduit 404A. An optional fifth hydrogen conduit 404E may fluidly connect the second hydrogen conduit 404B to the third hydrogen conduit 404C. A first output conduit 502A and a second output conduit 502B may fluidly connect the first hydrogen conduit 404A to a hydrogen processor <NUM>.

The hydrogen processor <NUM> may include, for example, a condenser and/or a compressor and may be fluidly connected to a hydrogen storage tank <NUM>. The condenser may be an air-cooled or water-enhanced, air-cooled condenser and/or heat exchanger configured to cool a hydrogen stream received from the fuel exhaust processor <NUM>, to a temperature sufficient to condense water vapor in the hydrogen stream. The compressor may also be configured to compress the hydrogen, and the hydrogen tank <NUM> may be configured to store the compressed hydrogen.

The first return conduit 406A may fluidly connect the splitter <NUM> to the mixer <NUM> of the fuel cell system <NUM>. The second return conduit 406B may fluidly connect the first separator conduit 401A to the ATO <NUM>, and may also be fluidly connected to the third hydrogen conduit 404C. In other embodiments, the second return conduit 406B may be fluidly connected to an outlet of the splitter <NUM>. A third return conduit 406C may fluidly connect the second separator conduit 401B to the second return conduit 406B.

In various embodiments, the fuel exhaust processor <NUM> may include various valves to control fluid flow. For example, a first separator conduit valve 401V1 and a second separator conduit valve 401V2 may be respectively configured to control anode exhaust flow through the first and second separator conduits 401A, 401B. A first hydrogen conduit valve 404V1, a second hydrogen conduit valve 404V2, a third hydrogen conduit valve 404V3, a fourth hydrogen conduit valve 404V4, and a fifth hydrogen conduit valve 404V5 may be configured to respectively control hydrogen flow through the first, second, third, fourth, and fifth hydrogen conduits 404A, 404B, 404C, 404D, 404E. A hydrogen storage valve <NUM>, such as a two way valve, may be configured to control hydrogen flow from the first hydrogen conduit 404A into the output conduit <NUM>. A second return conduit valve 406V2 and a third return conduit valve 406V3, may be configured to respectively control anode exhaust flow through the second and third return conduits 406B, 406C.

In some embodiments, the fuel exhaust processor <NUM> may be fluidly connected to multiple hotboxes <NUM>. For example, the splitter <NUM> may receive anode exhaust from multiple recycling conduits 308A/308B, and may be fluidly connected to multiple return conduits 406A, 406B. For example, the recycling conduits 308A/308B and the return conduits 406A, 406B may be branched and connected to different hotboxes <NUM>.

The system <NUM> may be configured to operate with a variety of different hydrogen processors <NUM> and/or carbon dioxide processors <NUM>, which may be provided on site by a third party. As such, it may be difficult to match the flow and/or production rate of the hydrogen and/or carbon dioxide streams output from the fuel exhaust processor <NUM> with the throughput of a particular carbon dioxide processor <NUM>. In particular, such variations may induce positive and/or negative pressure fluctuations. For example, if the throughput of the hydrogen processor <NUM> is too high (e.g., the hydrogen processor <NUM> pulls too hard on the hydrogen stream) a negative pressure may be induced within the system <NUM>, or if the throughput is too low, a positive pressure may be induced within the system <NUM>.

Such pressure fluctuations may cause problems within the system <NUM>. For example, excessive negative pressures may result in air leaking into the system <NUM>, or may result in a high pressure variation across the electrolytes of the system <NUM>, which may increase the risk of electrolyte damage, such as cracking. Excessively high pressures may also result in pressure variations across the electrolytes and increase the risk of electrolyte damage.

Accordingly, the system <NUM> may include a hydrogen blower <NUM> fluidly connected to the first and second output conduits 502A, 502B. The first output conduit 502A may fluidly connect a hydrogen outlet of the fuel exhaust processor <NUM> to an inlet of the hydrogen blower <NUM>. The second output conduit 502B may fluidly connect an outlet of the hydrogen blower <NUM> to the hydrogen processor <NUM>. The hydrogen blower <NUM> may be configured to increase the pressure of the hydrogen stream. For example, the hydrogen blower <NUM> may be configured to increase the pressure of a hydrogen stream by from about <NUM> to about <NUM> bar (about <NUM> to about <NUM> pounds per square in gauge (psig)), such as from about <NUM> to about <NUM> bar (about <NUM> to about <NUM> psig). The hydrogen blower <NUM> may also operate to isolate components of the system <NUM>, such as fuel exhaust processor <NUM> and/or the stack <NUM>, from pressure fluctuations induced by the hydrogen processor <NUM>.

The system <NUM> may also include a carbon dioxide blower <NUM> fluidly connected to the third and fourth output conduits 502C, 502D. The third outlet conduit 502C may fluidly connect a carbon dioxide outlet of the fuel exhaust processor <NUM> and an inlet of the carbon dioxide blower <NUM>. The second carbon dioxide conduit 502B may fluidly connect an outlet of the carbon dioxide blower <NUM> to the carbon dioxide processor <NUM>. The carbon dioxide blower <NUM> may be configured to increase the pressure of the carbon dioxide stream. For example, the carbon dioxide blower <NUM> may be configured to increase the pressure of a carbon dioxide stream by from about <NUM> bar to about <NUM> bar (about <NUM> to about <NUM> pounds per square in gauge (psig)), such as from about <NUM> to about <NUM> bar (about <NUM> to about <NUM> psig). The carbon dioxide blower <NUM> may also operate to isolate the components of the isolate components of the system <NUM>, such as fuel exhaust processor <NUM> and/or the stack <NUM>, from pressure fluctuations induced by the carbon dioxide processor <NUM>.

Claim 1:
An electrolyzer system, comprising:
a steam generator configured to generate steam;
a stack of solid oxide electrolyzer cells configured to generate a hydrogen stream using the steam generated by the steam generator;
a hotbox housing the stack, the hotbox comprising a hydrogen outlet configured to output the hydrogen stream;
a hydrogen blower configured to pressurize the hydrogen stream generated by the stack;
a hydrogen processor configured to compress the pressurized hydrogen stream output from the hydrogen blower;
a first output conduit fluidly connecting the hydrogen outlet to the hydrogen blower; and
a second output conduit fluidly connecting an outlet of the hydrogen blower to an inlet of the hydrogen processor.