SOE apparatus and method for performing solid oxide electrolysis

Abstract

The present invention relates to a method for operating a high temperature solid oxide electrolysis system suitable for converting a fuel stream into a product stream and a system for implementing the method. The method includes drying the moist purge gas and using the waste purge gas as a regeneration gas in the drying unit.

Description

Technical Field

[0001] The present invention relates to a method for operating a high temperature solid oxide electrolysis system suitable for converting a fuel stream into a product stream and a system for carrying out the method. Background Art

[0002] Climate change has accelerated the global shift from fossil fuels to renewable energy. Typically, renewable energy comes from wind and solar power generation. The challenge with renewable energy is its intermittent nature.

[0003] Power-to-X (PtX) is a term used for power conversion, energy storage and reconversion pathways that use electricity. Power-to-X conversion technologies allow power to be decoupled from the electricity sector for use in other sectors (such as transport or chemicals) and have the ability to smooth out the problem of fluctuations in renewable energy generation.

[0004] Currently, electrolysis is the core technology for PtX solutions, where X is typically hydrogen, syngas, chemicals or synthetic fuels. When electrolysis is combined with renewable electricity, the production of fuels and chemicals can be decoupled from fossil resources.

[0005] Solid oxide electrolysis (SOE) technology is particularly attractive because it has higher conversion efficiencies than low temperature electrolysis - this stems from the thermodynamic and kinetic benefits of higher operating temperatures.

[0006] SOECs can be used to electrochemically convert steam (H2O), carbon dioxide (CO2), or both directly into hydrogen (H2), carbon monoxide (CO), or syngas (H2+CO), respectively.

[0007] SOECs can be integrated with a range of chemical synthesis heat to enable the captured CO2 and H2O to be recycled into synthetic natural gas, gasoline, methanol or ammonia, further improving efficiency compared to low-temperature electrolysis technology.

[0008] The decomposition of H2O or CO2 occurs at the electrodes of a solid oxide electrolysis cell (SOEC). Multiple cells are combined into a SOEC stack, and multiple stacks are combined into a SOEC device.

[0009] The fuel stream (H2O and / or CO2) enters the process side of the SOEC where it is (partially) converted into products (H2, CO or syngas). The oxygen produced in the conversion on the fuel side is transferred via an electrochemical cell to the oxygen side of the SOEC where it is recombined into gaseous oxygen. It is usually transported away from the SOEC with a flushing liquid.

[0010] A solid oxide cell (SOC) is an electrochemical conversion device with two compartments (anode side and cathode side) separated by an electrolyte material made of solid oxide or ceramic electrolyte. It can be used as a solid oxide electrolyzer (SOEC) or a solid oxide fuel cell (SOFC). Such a cell is fully reversible, for example, for the components H2O<->H2 and CO2<->CO and their mixtures.

[0011] When operating in SOEC mode, the goal is to produce H2, CO or a mixture of H2 and CO (also known as syngas), and the quality of the converted gas (also known as product gas (or product stream)) may be critical for downstream applications. Therefore, it is desirable to minimize the presence of undesirable components (e.g., air) in the product stream to obtain a high purity product stream.

[0012] A SOEC device typically includes multiple stacks connected in parallel and / or series, the number of which meets the required production needs. In SOEC mode, the cathode side may also be called the fuel side, and the anode side may also be called the oxygen side or flushing side.

[0013] Much attention has been paid to optimizing the performance of SOEC technology by improving the efficiency of the electrolysis stack. However, the optimization of the process equipment supporting the SOEC stack is equally important. Optimizing the design of SOEC-based equipment requires a balance between process complexity, energy consumption per unit of product gas, and equipment production cost.

[0014] Various optimizations for operating SOEC devices have been proposed previously.

[0015] For example, when the SOEC process is operated at a high temperature level, the cold feeds (process feed and flush feed) must be heated to the desired SOEC temperature. Primary heating can be performed by exchanging heat with a hot SOEC fluid (fluid leaving the SOEC). Such a heat exchanger can be referred to as a feed / effluent heat exchanger. Balancing heat can be added using, for example, one or more electric heaters.

[0016] However, there is still a need to optimize the performance of SOEC plants to increase their industrial applicability and rentability for the production of hydrogen, carbon monoxide and synthesis gas. Summary of the invention

[0017] The present inventors have found that moisture or humidity in the purge gas air used for solid oxide electrolysis cells has a negative impact on the life of the cells. It has been found that using a dry purge gas improves performance and extends the life of the SOEC stack.

[0018] Systems and processes for removing moisture from various gas streams have been proposed. For example, in WO 2016 / 091636, ultra-high purity carbon monoxide is produced by high temperature electrolysis of pretreated food-grade carbon dioxide in a solid oxide electrolyzer stack. The heated carbon dioxide feed mixture is passed through a drying unit to remove moisture and then fed to the fuel side of the solid oxide electrolyzer stack. The drying unit uses a combination of temperature swing adsorption and pressure swing adsorption. A method for removing moisture from a methanogenic product stream is disclosed in EP 2 364 766, which is based on the adsorption of moisture. A compressed gas dryer is disclosed in WO 2011 / 017782, which is provided with a drying zone and a regeneration zone, and a drum rotatable in a shell, which accommodates a desiccant that is continuously conveyed through the drying zone and the regeneration zone, wherein the regeneration zone includes a first sub-zone, which has a first inlet to supply a first regeneration gas flow; and a second sub-zone, which has a second inlet to supply a second regeneration gas flow, the relative humidity of the second regeneration gas flow is lower than the relative humidity of the first regeneration gas flow; and the outlet of the drying zone is connected to the second inlet of the second sub-zone via a connecting duct.

[0019] The present inventors have now discovered a new method for operating a high temperature solid oxide electrolysis system suitable for converting a fuel gas into a product gas and a system suitable for practicing the present invention.

[0020] Accordingly, there is provided a method of operating a high temperature solid oxide electrolysis system, the method comprising the steps of:

[0021] -

[0022] - providing a solid oxide electrolysis cell unit, said solid oxide electrolysis cell unit comprising at least

[0023] a solid oxide electrolysis cell having a fuel side and an oxygen side;

[0024] - Provides moist flushing airflow;

[0025] - providing an adsorbent having a moisture adsorption temperature range for adsorbing moisture and a moisture desorption temperature range for desorbing moisture;

[0026] - adjusting the temperature of the moist flushing gas stream to a temperature within the moisture adsorption temperature range to produce a temperature-regulated moist flushing gas stream;

[0027] - operating at least one section of the adsorbent in an adsorption mode by passing the temperature conditioned moist purge gas stream through at least one section of the adsorbent to provide a dry purge gas stream;

[0028] - passing a dry purge gas stream through the oxygen side of the SOEC to produce a waste purge gas stream; and then

[0029] - adjusting the temperature of at least a portion of the waste purge gas stream to a temperature within the water desorption temperature range to produce a temperature-adjusted waste purge gas stream;

[0030] - operating at least one section of the adsorbent in a desorption mode by passing at least a portion of the temperature-conditioned spent purge gas stream through at least one section of the adsorbent to desorb moisture bound in the adsorbent, thereby obtaining regenerated adsorbent and spent regeneration gas.

[0031] In addition, a system for implementing the method of the present invention is provided, which is suitable for converting a fuel stream into a product stream, the system comprising:

[0032] o A solid oxide electrolysis cell unit (8), comprising at least one solid oxide electrolysis cell, wherein the solid oxide electrolysis cell comprises:

[0033] oFuel side (9)

[0034] oOxygen side (10)

[0035] oFlushing gas inlet (11)

[0036] oFlushing gas outlet (12)

[0037] oFuel gas inlet (13)

[0038] o a product gas outlet (14), and

[0039] oDrying unit (1), comprising:

[0040] oAdsorbent Beds (2)

[0041] oDrying unit inlet (3)

[0042] oDrying unit outlet (4)

[0043] oRegeneration gas inlet (5)

[0044] o Regeneration gas outlet (6);

[0045] wherein the adsorbent bed (2) is arranged in the drying unit (1); and

[0046] wherein the drying unit (1) is arranged to convey a moist purge gas stream from a drying unit inlet (3) through the adsorbent bed (2) to a drying unit outlet (4), and wherein the drying unit (1) is arranged to convey a waste purge gas stream from a regeneration gas inlet (5) through the adsorbent bed (2) to a regeneration gas outlet (6); and

[0047] wherein the drying unit outlet (4) is in fluid communication with the flushing gas inlet (11) of the solid oxide electrolysis cell unit (8); and

[0048] wherein the solid oxide electrolysis cell unit (8) is arranged to convey a dry purge gas from a purge gas inlet (11) through the oxygen side of at least one solid oxide electrolysis cell and to a purge gas outlet (12) of the solid oxide electrolysis cell unit (8); and

[0049] wherein the flushing gas outlet (12) is in fluid communication with the regeneration gas inlet (5) of the drying unit (1);

[0050] The method and system according to the present invention have several advantages, all of which contribute to the industrial applicability of the method and system. The method can be carried out at a pressure close to ambient pressure in a drying unit during adsorption and desorption. This is advantageous because it is preferred to provide flushing gas to the solid oxide electrolysis unit at a pressure close to ambient pressure to save compression energy. In addition, it allows a low pressure drop, thereby saving energy. In addition, the claimed method reduces flushing gas consumption by recycling the waste gas from the SOEC process as regeneration gas. In addition, the claimed method provides effective heat integration because a large part of the energy used for regeneration is recovered. Therefore, the method and system according to the present invention can achieve significant cost savings by reducing energy losses.

[0051] It should be understood that the flushing gas stream used to flush the oxygen side of the solid oxide electrolysis cell should be inert relative to the reaction occurring. Suitable flushing gases are, for example, air, nitrogen, carbon dioxide or oxygen; or mixtures thereof. If it is necessary to control the flow through these inlets and / or outlets, the inlets and outlets may be equipped with valves. In the context of the present invention, the moisture removed may be steam water and liquid water. Typically, the moist flushing gas stream will be provided in the form of air. The air may be compressed to generate a driving force for the flow of the stream within the flushing system. When adjusting the temperature of the gas stream, this may include compressing, expanding, heating and cooling the gas stream in any order to obtain the desired temperature. In particular, the regeneration of the adsorbent is preferably performed by gradually increasing the temperature of the regeneration gas stream at the beginning of regeneration and gradually reducing the temperature of the regeneration gas during cooling to control the temperature distribution within the adsorbent. The adsorbent may be operated for any period of time in adsorption mode. However, when the adsorbent is saturated, the efficiency will decrease, and it is preferably replaced with another adsorbent containing less adsorbed water. Similarly, the adsorbent may be operated for any period of time in regeneration mode. However, as the adsorbent releases the adsorbed water, the need for regeneration will decrease, and it is then preferred to allow the thus regenerated adsorbent to cool down. The cooling may be carried out by passing a cooling gas through the adsorbent.

[0052] Before drying the moist purge gas stream in the drying unit, a portion of the moisture may be removed by cooling the stream and removing condensed water from the stream. This improves energy efficiency. The moist purge gas stream may be cooled, for example, by heat exchange between a cooler dry purge gas stream and a warmer moist purge gas stream. The dry purge gas stream may be heated, for example, by heat exchange, before passing it through the oxygen side of at least one solid oxide electrolysis cell.

[0053] In one embodiment, the temperature conditioned spent purge gas stream flows through the adsorbent in a countercurrent flow relative to the temperature conditioned moist purge gas stream.

[0054] Adsorbent

[0055] When referring to "at least one section of the adsorbent", this is meant to refer to a portion of the adsorbent that is used to dry the moist flushing gas and which subsequently has to be regenerated. In the context of the present invention, "at least one section of the adsorbent" means that the method can be carried out in a sequential mode in one embodiment, wherein the entire surface of the adsorbent is first operated in an adsorption mode and then, subsequently, the entire surface of the adsorbent is operated in a desorption mode. After desorption, the adsorbent can be operated in an adsorption mode again, or optionally, the entire surface of the adsorbent can be operated in a cooling mode after desorption and before the adsorbent is operated in an adsorption mode again. Alternatively, the adsorbent can be arranged in sections and each section is operated in an adsorption mode, a desorption mode or a cooling mode. An additional operating mode of standby can also be used, in which a dry gas flow can still pass through the bed. In one embodiment, the method of the present invention includes a subsequent step of operating at least one section of the adsorbent in a cooling mode, which step includes cooling at least one section of the adsorbent from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range.

[0056] Cooling may be achieved by passing at least a portion of the spent purge gas stream through at least one section of the adsorbent and gradually reducing the temperature of the spent purge gas stream from a temperature within the water desorption temperature range to a temperature within the water adsorption temperature range, thereby obtaining a regenerated and cooled adsorbent. Alternatively or in addition, cooling may be achieved by passing at least a portion of the dry purge gas stream through at least one section of the adsorbent and gradually reducing the temperature of at least a portion of the spent purge gas stream from a temperature within the water desorption temperature range to a temperature within the water adsorption temperature range, thereby obtaining a regenerated and cooled adsorbent.

[0057] Any adsorbent suitable for drying air may be used. Exemplary adsorbents are silica gel, activated alumina, zeolites, and mixtures thereof. Each specific adsorbent has a moisture adsorption temperature range for adsorbing moisture and a moisture desorption temperature range for desorbing moisture. The ranges may vary from adsorbent to adsorbent. For example, some silica gels require heating to approximately 175°C, while some zeolites require heating to 250°C to ensure proper desorption. In one embodiment, the adsorbent is selected from silica gel, activated alumina, and zeolites; or mixtures thereof.

[0058] As previously described, the adsorbent can first be operated in an adsorption mode (i.e., a drying mode) at an adsorption temperature within the moisture adsorption temperature range, and then in a desorption mode (i.e., a regeneration mode) at a desorption temperature within the moisture desorption temperature range. In addition, the adsorbent can then be operated in a cooling mode and then in an adsorption mode. Preferably, the desorption is performed by gradually increasing (or raising) the temperature of the regeneration stream until the desired desorption temperature is reached and the temperature is maintained until the desired degree of dryness is reached. In one embodiment according to the present invention, the adsorbent is then operated in a cooling mode, which includes cooling the adsorbent from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range. Preferably, cooling is performed by gradually reducing (or ramping down) the temperature of the cooling stream. According to one embodiment, the cooling stream is obtained from a waste flushing gas. According to another embodiment, the cooling stream is obtained from a dry flushing gas.

[0059] The adsorbent may additionally be operated in a standby mode, wherein the adsorbent is neither used for drying the stream, nor is it regenerated or cooled.When in standby mode, a dry gas stream may still be passed through the bed, preferably at a temperature within the adsorption range.

[0060] The adsorbent can be divided into several sections, which can be operated independently of each other. Each section can be arranged, for example, in a rotary drying drum, wherein one section of the drum is in adsorption mode, another section is in desorption mode, and another section is in cooling mode, and each section moves when the drum rotates. In this case, the moist flushing gas is continuously delivered to one inlet, and the waste flushing gas is continuously delivered to another inlet, while a section of the adsorbent gradually moves from one inlet to another. In addition, the third inlet can provide cooling gas for the adsorbent section after regeneration. Alternatively, each section of the adsorbent can be arranged in a separate bed. According to one embodiment of the present invention, the adsorbent is arranged in a plurality of beds, and each bed is intermittently operated in adsorption mode, regeneration mode, cooling mode and standby mode, so that at least one bed is always in adsorption mode. In one embodiment, the adsorbent includes two or more sections, and each section is operated independently of other sections. Therefore, the adsorbent can be divided into two, three or four sections. Each section can be operated intermittently in adsorption mode, regeneration mode, cooling mode and standby mode. For example, each section may first be operated in adsorption mode, then in regeneration mode, then in cooling mode, and finally in standby mode.

[0061] The moist purge gas stream may be provided as a pressurized stream, and the spent purge gas stream may be pressurized prior to adjusting the temperature to the water desorption temperature range.

[0062] The use of heat exchangers to cool and heat gas streams further improves the energy efficiency of the process and system. In particular, the moist purge gas stream can be conveniently cooled by heat exchange between a cooler dry purge gas stream and a warmer moist purge gas stream; and the regeneration gas stream can be conveniently heated by heat exchange with a warmer spent regeneration gas stream. Heat exchange between other streams is also contemplated.

[0063] system

[0064] The system may include features known in the art.

[0065] Therefore, the system may also include a control module for controlling the flow of a temperature-regulated moist rinse gas stream to the drying unit, the flow of a dry rinse gas stream from the drying unit, the flow of a temperature-regulated dry rinse gas stream from the drying unit, the flow of a temperature-regulated waste rinse gas stream to the drying unit, and the flow of waste regeneration gas flowing out of the drying unit.

[0066] The drying unit outlet (4) of the system is in direct fluid communication with the regeneration gas inlet (5) of the drying unit (1) in addition to being in fluid communication with the flushing gas inlet (11) of the solid oxide electrolysis cell unit (8).

[0067] The solid oxide electrolysis cell unit (8) is typically arranged to convey fuel gas from a fuel gas inlet (13) through the fuel side of at least one solid oxide electrolysis cell and to a product gas outlet (14) of the solid oxide electrolysis cell unit (8).

[0068] The system may include a flushing gas discharge port (16) arranged downstream of the flushing gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of the regeneration gas inlet (5) of the drying unit (1). In addition, a compressor (21) may be arranged downstream of the flushing gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of the regeneration gas inlet (5) of the drying unit (1).

[0069] A temperature regulating element in the form of a cooler and / or a heater may be arranged downstream of the flushing gas outlet of the solid oxide electrolysis cell unit and upstream of the regeneration gas inlet of the drying unit, and / or upstream of the drying unit inlet. Furthermore, the cooler may be arranged upstream of the drying unit inlet, and / or the water separator may be arranged downstream of the cooler and upstream of the drying unit inlet. The cooler and / or the heater may be a heat exchanger. One heat exchanger may be arranged to exchange heat between a moist flushing gas stream and a dry flushing gas stream. Another heat exchanger may be arranged to exchange heat between a spent regeneration gas stream and a spent flushing gas stream.

[0070] The drying unit of the system preferably includes a plurality of adsorbent beds arranged in the drying unit, and the plurality of adsorbent beds are preferably arranged to deliver a gas flow from the drying unit inlet through any one of the plurality of adsorbent beds to the drying unit outlet, and deliver a gas flow from the regeneration gas inlet through the adsorbent bed to the regeneration gas outlet. In such an embodiment, the system typically has a control module for controlling the operation of each of the plurality of beds in an adsorption mode, a regeneration mode, a cooling mode, and a standby mode.

[0071] The operation of a solid oxide electrolyzer unit is generally known. Typically, a fuel gas stream is fed into a fuel gas inlet and passed through the fuel side of at least one solid oxide electrolyzer, while an electric field is applied to at least one solid oxide electrolyzer to convert the fuel gas stream into a product gas stream flowing out of the fuel gas outlet. The fuel gas stream may, for example, be selected from any one of water, hydrogen, carbon monoxide, carbon dioxide, and mixtures thereof. A flushing gas stream is used to flush oxygen produced on the oxygen side out of the cell.

[0072] The operation and optimization of a gas dryer unit is generally known to the skilled person.

[0073] According to one aspect of the present invention, a method is provided, wherein the adsorbent comprises at least a first, a second and a third section, and wherein a temperature-regulated moist flushing gas stream is first passed through a first section of the adsorbent operating in an adsorption mode to provide a dry flushing gas stream; then the dry flushing gas stream is passed through a second section of the adsorbent operating in a cooling mode, then the dry flushing gas stream is passed through the oxygen side of the SOEC to produce a waste flushing gas stream; then the waste flushing gas stream is passed through a third section of the adsorbent operating in a desorption mode to produce a waste regeneration gas, wherein the flushing gas passes through all three containers continuously. This arrangement has the advantage that the method can be operated with a low pressure drop. The driving force on the flushing gas can be applied by, for example, a fan placed between the first and second sections of the adsorbent. In addition, a (balancing) fan can be placed between the flushing gas outlet and the third section of the adsorbent to adjust the driving force as required. A manifold system can be included, which can be guided by an automatic valve or can be guided by a rotary valve to enable automatic switching between the first, second and third sections as required. In this way, the flushing gas always passes through all three sections of the adsorbent, and only the flow rate varies between the three sections of the adsorbent. The sorbent may be arranged, for example, as a radial flow bed or as a parallel bed.Since heating requires a large amount of energy, the overall efficiency may also be improved by utilizing heat originating from the process side of the solid oxide electrolysis cell unit.

[0074] The invention has been described for use in SOEC systems. However, it is to be understood that the drying unit according to the invention can also be used in SOFC units. In SOFC mode, the combustion reaction occurs as follows:

[0075] 2CO+O2=>2CO2 and / or

[0076] 2H2+O2=>2H2O

[0077] Thus, the flushing gas is not only used for flushing, it is actually also the reaction gas. However, the feed can be dried in the same way, and air is a suitable flushing gas, optionally oxygen-enriched gas or another oxygen-generating gas can be used.

[0078] Furthermore, the purge gas can be used to cool the SOFC since in SOFC mode the reaction is exothermic.

[0079] BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 One embodiment of a system according to the invention is shown.

[0081] Figure 2 An embodiment of a plurality of containers (2a and 2b) of a drying unit according to the present invention is shown.

[0082] Figure 3An embodiment of a plurality of containers (2a, 2b and 2c) of a drying unit according to the present invention is shown.

[0083] Figure 4 One embodiment of a system according to the invention is shown.

[0084] Figure 5 The arrangement for drying the product gas from a solid oxide electrolysis cell unit is shown.

[0085] Position number

[0086] 1. Drying unit

[0087] 2. Adsorbent bed

[0088] 3. Drying unit entrance

[0089] 4. Drying unit outlet

[0090] 5. Regeneration gas inlet

[0091] 6. Regeneration gas outlet

[0092] 8. A solid oxide electrolysis cell unit comprising at least one solid oxide electrolysis cell (SOEC unit)

[0093] 9. Fuel side

[0094] 10. Oxygen side

[0095] 11. Flushing gas inlet

[0096] 12. Flushing gas outlet

[0097] 13. Fuel gas inlet

[0098] 14. Product gas outlet

[0099] 15. Control module

[0100] 16. Flush gas exhaust port

[0101] 21. Compressor or blower / fan

[0102] 22. Valve DETAILED DESCRIPTION OF THE INVENTION

[0104] exist Figure 1In the embodiment of the present invention, water is removed from the compressed flushing gas entering the dryer unit (1) through the drying unit inlet (3) to produce a dried flushing gas that leaves through the drying unit outlet (4), which gas reaches the oxygen side (10) of the solid oxide electrolyzer unit (8) through the flushing gas inlet (11) for flushing oxygen. A portion of the flushing gas leaving through the flushing gas outlet (12) is used as regeneration gas, which enters the drying unit (1) through the regeneration gas inlet (5) for regeneration of the dryer unit. The gas desorbs water from the dryer and leaves the drying unit (1) through the regeneration gas outlet (6) as spent regeneration gas. The remaining portion (16) of the spent flushing gas can be used for the operation of other units, for example for drying product gas. Equipment for temperature and pressure regulation may be provided, but is not shown. Fuel gas enters the solid oxide electrolyzer unit (8) through the fuel gas inlet (13), the fuel gas is converted on the fuel side (9), and the product gas leaves the unit (8) through the product gas outlet (14).

[0105] exist Figure 2 , two dryer vessels (2a and 2b) including adsorbent beds are shown, which have valves (22) for controlling gas flow into and out of the adsorbent beds. Vessel 2a in adsorption mode and vessel 2b in regeneration mode (white valves represent open valves and black valves represent closed valves): the dryer inlet flow is directed to vessel 2a through valve (22) on the dryer inlet (3), and the dry gas is directed from vessel 2a to the dryer outlet (4) through a valve on the dryer outlet (4).

[0106] The valve (22) on the regeneration gas inlet (5) directs the regeneration gas flow to the vessel 2b, and the valve (22) on the regeneration gas outlet (6) directs the spent regeneration gas from the vessel 2b to the regeneration gas outlet (6).

[0107] In this embodiment, during adsorber mode, the flow direction is from the top of the vessel to the bottom of the vessel, and in regeneration mode, the flow direction is from the bottom of the vessel to the top of the vessel. This reduces the risk of fluidization of the bed material, as gravity will act.

[0108] Figure 3 is a simplified flow diagram according to one embodiment of the present invention, showing the flow of flushing gas in a drying unit (1) connected to a solid oxide electrolysis cell unit (8), wherein the adsorbent bed (2) of the drying unit (1) is divided into three beds (2a, 2b and 2c). The drying principle in this embodiment is comparable to the operating principle of temperature swing adsorption, although the purpose is different.

[0109] In this embodiment, a temperature-regulated moist flushing gas stream passes through the drying unit inlet (3) and through the adsorbent bed (2a) operating in a dry mode. The resulting dry flushing gas stream is passed through the regenerated adsorbent bed (2b) to cool the regenerated adsorbent bed (2b) while heating the dry flushing gas stream. At the beginning of cooling of the adsorbent bed (2b), the adsorbent bed (2b) has a temperature of about 200°C, which is cooled to a temperature close to ambient temperature. The thus heated dry flushing gas stream from the adsorbent bed (2b) passes through the drying unit outlet and enters the flushing gas inlet (11) to the oxygen side (10) of the solid oxide electrolysis cell unit (8). The oxygen formed in the electrolysis cell unit (8) is absorbed by the flushing gas to produce a waste flushing gas that is discharged from the flushing gas outlet (12). The temperature of the waste flushing gas is adjusted to a desorption temperature of about 150 to 250°C and is passed through the regeneration gas inlet (5) and through the adsorbent bed (2c) to regenerate the adsorbent bed (2c). Regeneration results in drying and heating of the adsorbent bed (2c), while the gas passing through the adsorbent bed (2c) is cooled to produce spent regeneration gas at the regeneration gas outlet (6).

[0110] The fan (21) is placed, for example, between the adsorbent bed (2a) and the adsorbent bed (2b) and applies a driving force to the flow on the flushing side of the entire system (from the drying unit inlet (3) to the regeneration gas outlet (6). In addition, a (balancing) fan (21) can be placed between the solid oxide electrolysis cell unit and the adsorbent bed (2c) to adjust the driving force as needed.

[0111] A manifold system (not shown) may be included which may be guided by automatic valves or may be guided by rotary valves to enable automatic switching between the various containers from A to B and to C as required.

[0112] In this embodiment, the flushing gas always passes through all three vessels, only the flow rate varies. An advantage of such an embodiment is that the system can be operated with a low pressure drop. The adsorbent can be arranged, for example, as a radial flow bed or as a parallel bed.

[0113] Since heating requires a lot of energy, the overall efficiency can also be improved by utilizing heat originating from the process side of the solid oxide electrolysis cell unit.

[0114] exist Figure 4In the embodiment of the present invention, the wet flushing gas is cooled in a heat exchanger (not shown) and further cooled to the adsorption temperature in a cooler (not shown), followed by removal of condensate in a separator (not shown). The wet flushing gas then enters through the drying unit inlet (3) and passes through the drying bed 2a, where most of the remaining moisture is removed to produce dry flushing gas, which leaves the drying unit through the drying unit outlet (4). The dry flushing gas is heated in a heat exchanger (not shown) and used as flushing gas entering the flushing gas inlet (11) to pass through the oxygen side (10) of the solid oxide electrolysis cell unit (8). The oxygen formed in the electrolysis cell unit (8) is absorbed by the flushing gas to produce a waste flushing gas discharged from the flushing gas outlet (12). The waste flushing gas is pressurized in a blower (not shown), and the temperature is adjusted in a heat exchanger (not shown), an electric heater (not shown) and a cooler (not shown), and enters the drying unit (1) through the regeneration gas inlet (5) at the bottom. The regeneration gas passes through the adsorbent bed 2b to desorb moisture. The spent regeneration gas leaving the dryer at the top of the regeneration gas outlet (6) is used to adjust the temperature of the spent purge gas in a heat exchanger (not shown). The moisture is desorbed from the adsorbent bed and leaves the system with the spent regeneration gas.

[0115] On the fuel side (9) of the solid oxide electrolyser unit (8), steam can be converted to a product gas comprising hydrogen, carbon dioxide can be converted to a product gas comprising carbon monoxide, or a combination of steam and carbon dioxide can be converted to a product gas comprising hydrogen and carbon monoxide. Drying of the product gas can also be performed. This is best achieved on compressed product gas, but drying at ambient pressure is also possible. Typically, drying is only required intermittently.

[0116] exist Figure 5 In FIG. 1 , a layout for drying product gas from a solid oxide electrolyzer unit is shown. The moist cooled product stream (labeled "from compressor") is delivered to the top of the drying unit and passed through the adsorbent bed. The dry product stream leaving the bottom of the vessel is directed to downstream processes. In normal continuous operation, there is no moisture in the product stream, in which case the entire product stream can bypass the drying unit.

[0117] For regeneration of the adsorbent bed, the drying unit is isolated from the process (e.g. when the product stream does not contain water). It is filled with a dry inert gas and a loop is established from the blower to the heater, where the gas is heated to 150-200°C (e.g. by temperature-regulated waste purge gas from the solid oxide electrolysis reactor unit). The hot gas flows through the adsorbent bed, removing the moisture. The gas containing moisture leaves the adsorbent bed and is directed to a cooler, where the moisture is condensed. The liquid water is separated in a conventional water separator and the dry gas is sent to the blower, completing the loop.

Claims

1. A method of operating a high temperature solid oxide electrolysis system, comprising the following steps: - - providing a solid oxide electrolysis cell unit comprising at least one solid oxide electrolysis cell having a fuel side and an oxygen side; - Provides moist flushing airflow; - providing an adsorbent having a moisture adsorption temperature range for adsorbing moisture and a moisture desorption temperature range for desorbing moisture; - adjusting the temperature of the moist flushing gas stream to a temperature within the moisture adsorption temperature range to produce a temperature-regulated moist flushing gas stream; - operating at least one section of the adsorbent in an adsorption mode by passing the temperature conditioned moist purge gas stream through the at least one section of the adsorbent to provide a dry purge gas stream; - passing the dry purge gas stream through the oxygen side of the SOEC to produce a waste purge gas stream; Then - adjusting the temperature of at least a portion of the waste purge gas stream to a temperature within the water desorption temperature range to produce a temperature-adjusted waste purge gas stream; - operating at least one section of the adsorbent in a desorption mode by passing at least a portion of the temperature-conditioned spent purge gas stream through at least one section of the adsorbent to desorb moisture bound in the adsorbent, thereby obtaining a regenerated adsorbent and a spent regeneration gas.

2. The method of claim 1, wherein the waste purge gas stream is pressurized and then its temperature is adjusted to a temperature within the water desorption temperature range.

3. The method according to any one of claims 1 or 2, wherein the moist flushing gas stream is provided as a pressurized stream.

4. A process according to any one of claims 1 to 3, wherein a portion of the moisture is removed by cooling the moist flushing gas stream and removing condensed water from the stream before passing the moist flushing gas stream through at least one section of the adsorbent.

5. A method according to any one of the preceding claims, wherein the moist flushing gas stream is cooled by heat exchange between a cooler dry flushing gas stream and a warmer moist flushing gas stream.

6. A process according to any one of the preceding claims, wherein the dry purge gas stream is heated prior to passing it through the oxygen side of at least one solid oxide electrolysis cell.

7. A method according to any one of the preceding claims, wherein a fuel gas stream selected from any one of water, hydrogen, carbon monoxide, carbon dioxide and mixtures thereof is passed through the fuel side of at least one solid oxide electrolysis cell while an electric field is applied across the at least one solid oxide electrolysis cell.

8. A method according to any one of the preceding claims, wherein the method comprises a subsequent step of operating at least one section of the adsorbent in a cooling mode, the step comprising cooling at least one section of the adsorbent from a temperature within the water desorption temperature range to a temperature within the water adsorption temperature range.

9. The method of claim 8, wherein the cooling is obtained by passing at least a portion of the spent purge gas stream through at least one section of the adsorbent and gradually reducing the temperature of the spent purge gas stream from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range, thereby obtaining a regenerated and cooled adsorbent.

10. The method of claim 8, wherein the cooling is obtained by passing at least a portion of the dry purge gas stream through at least one section of the adsorbent, then passing the dry purge gas stream through the oxygen side of the SOEC, and gradually reducing the temperature of at least a portion of the spent purge gas stream from a temperature within the water desorption temperature range to a temperature within the water adsorption temperature range, thereby obtaining a regenerated and cooled adsorbent.

11. The method of claim 1 , wherein the adsorbent comprises at least first, second and third sections, and wherein the temperature conditioned moist purge gas stream is first passed through the first section of the adsorbent operating in an adsorption mode to provide a dry purge gas stream; the dry purge gas stream is then passed through the second section of the adsorbent operating in a cooling mode, the dry purge gas stream is then passed through the oxygen side of the SOEC to produce a spent purge gas stream; the spent purge gas stream is then passed through the third section of the adsorbent operating in a desorption mode to produce a spent regeneration gas, wherein the purge gas passes through all three vessels continuously.

12. The method according to any one of the preceding claims, wherein the adsorbent is selected from silica gel, activated alumina and zeolite; or mixtures thereof.

13. The method according to any one of the preceding claims, wherein the adsorbent comprises two or more sections and each section is operated independently of the other sections.

14. The method of claim 13, wherein each section is intermittently operated in an adsorption mode, a regeneration mode, a cooling mode, and a standby mode.

15. The method according to any one of claims 13 or 14, wherein each section is first operated in adsorption mode, then in regeneration mode, then in cooling mode, and finally in standby mode.

16. The method of any one of the preceding claims, wherein the temperature conditioned spent purge gas stream flows through the adsorbent in a countercurrent flow relative to the temperature conditioned moist purge gas stream.

17. A high temperature solid oxide electrolysis system suitable for converting a fuel stream into a product stream, the system comprising: o A solid oxide electrolysis cell unit (8), comprising at least one solid oxide electrolysis cell, wherein the solid oxide electrolysis cell comprises: oFuel side (9) oOxygen side (10) oFlushing gas inlet (11) oFlushing gas outlet (12) oFuel gas inlet (13) o a product gas outlet (14), and oDrying unit (1), comprising: oAdsorbent Beds (2) oDrying unit inlet (3) oDrying unit outlet (4) oRegeneration gas inlet (5) o Regeneration gas outlet (6); o - wherein the adsorbent bed (2) is arranged in the drying unit (1); and - wherein the drying unit (1) is arranged to convey a moist flushing gas stream from a drying unit inlet (3) through the adsorbent bed (2) to a drying unit outlet (4), and wherein the drying unit (1) is arranged to convey a spent flushing gas stream from a regeneration gas inlet (5) through the adsorbent bed (2) to a regeneration gas outlet (6); and - wherein the drying unit outlet (4) is in fluid communication with the flushing gas inlet (11) of the solid oxide electrolysis cell unit (8); and wherein the solid oxide electrolysis cell unit (8) is arranged to convey a dry flushing gas from a flushing gas inlet (11) through the oxygen side of at least one solid oxide electrolysis cell and to a flushing gas outlet (12) of the solid oxide electrolysis cell unit (8); and - wherein the flushing gas outlet (12) is in fluid communication with the regeneration gas inlet (5) of the drying unit (1); 18. The system of claim 17, wherein the system further comprises a control module for controlling the flow of a temperature-regulated moist rinse gas stream to the drying unit, the flow of a dry rinse gas stream from the drying unit, the flow of a temperature-regulated dry rinse gas stream from the drying unit, the flow of a temperature-regulated waste rinse gas stream to the drying unit, and the flow of waste regeneration gas from the drying unit.

19. A system according to any one of claims 17 or 18, wherein in addition to being fluidly connected to the flushing gas inlet (11) of the solid oxide electrolysis cell unit (8), the drying unit outlet (4) is also directly fluidly connected to the regeneration gas inlet (5) of the drying unit (1).

20. A system according to any one of claims 17 to 19, wherein the solid oxide electrolysis cell unit (8) is arranged to transport fuel gas from the fuel gas inlet (13) through the fuel side of at least one solid oxide electrolysis cell to the product gas outlet (14) of the solid oxide electrolysis cell unit (8).

21. The system according to any one of claims 17 to 20, wherein a flushing gas discharge port (16) is arranged downstream of a flushing gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of a regeneration gas inlet (5) of the drying unit (1).

22. The system according to any one of claims 17 to 21, wherein a compressor (21) is arranged downstream of a flushing gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of a regeneration gas inlet (5) of the drying unit (1).

23. A system according to any one of claims 17 to 22, wherein a temperature regulating element in the form of a cooler and / or a heater is arranged downstream of the flushing gas outlet of the solid oxide electrolysis cell unit and upstream of the regeneration gas inlet of the drying unit.

24. A system according to any one of claims 17 to 23, wherein a temperature regulating element in the form of a cooler and / or a heater is arranged upstream of the drying unit inlet.

25. The system of any one of claims 17 to 24, wherein a cooler is arranged upstream of the drying unit inlet, and a water separator is arranged downstream of the cooler and upstream of the drying unit inlet.

26. The system of any one of claims 23 to 25, wherein at least one of the cooler and / or heater is a heat exchanger.

27. The system of claim 26, wherein the cooler and / or heater is a heat exchanger and is arranged to exchange heat between the moist rinse gas stream and the dry rinse gas stream.

28. A system according to claim 26 or 27, wherein the cooler and / or heater is a heat exchanger and is arranged to exchange heat between the spent regeneration gas stream and the spent purge gas stream.

29. The system according to any one of claims 17 to 28, wherein the drying unit comprises a plurality of adsorbent beds arranged within the drying unit, and the plurality of adsorbent beds are arranged to deliver a gas flow from the drying unit inlet through any one of the plurality of adsorbent beds to the drying unit outlet, and to deliver a gas flow from the regeneration gas inlet through the adsorbent beds to the regeneration gas outlet.

30. The system of claim 29, further comprising a control module for controlling operation of each of the plurality of beds in an adsorption mode, a regeneration mode, a cooling mode, and a standby mode.

31. The system of any one of claims 17 to 30, wherein the adsorbent is selected from silica gel, activated alumina, and zeolite; or mixtures thereof.

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