SOE plant and method for performing solid oxide electrolysis

Abstract

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 this method. In this method, a wet flash gas is dried, and the used flash gas is used as a regeneration gas in a drying unit.

Description

Technical Field

[0001] Field 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.

Background Art

[0002] Background Due to climate change, the global shift from fossil fuels to renewable energy is accelerating. Usually, renewable energy is generated by wind power or solar power. The problem with renewable energy is its intermittent nature.

[0003] Power-to-X (PtX) is a term used for the power conversion, energy storage, and reconversion pathways that use electricity. Power-to-X conversion technologies have the ability to decouple electricity from the power sector and enable its use in other sectors (such as transportation and chemicals), thereby solving the problem of variable renewable energy generation.

[0004] Currently, electrolysis is the core technology of the PtX method, and X is typically hydrogen, syngas, chemicals, or synthetic fuels. Combining electrolysis with renewable power can decouple the production of fuels and chemicals from fossil resources.

[0005] Solid oxide electrolysis (SOE) technology is particularly attractive because of its higher conversion efficiency than low-temperature electrolysis - due to the favorable thermodynamics and kinetics at higher operating temperatures.

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

[0007] The SOEC can be thermally integrated with various chemical syntheses and recycle the recovered CO2 and H2O into synthetic natural gas, gasoline, methanol, and ammonia.

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

[0009] The fuel stream (H2O and / or CO2) enters the process side of the SOEC, where it is (partially) converted into the product (H2, CO, or syngas). The oxygen generated by the conversion on the fuel side moves through the electrochemical cell to the oxygen side of the SOEC, where it recombines as gaseous oxygen. Oxygen is typically transported from the SOEC with a flush fluid.

[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 a solid oxide or ceramic electrolyte. It can be used as a solid oxide electrolysis cell (SOEC) or as a solid oxide fuel cell (SOFC). Such cells are completely reversible, for example, with respect to components such as H2O <-> H2 and CO2 <-> CO and mixtures thereof.

[0011] When operating in the SOEC mode, the purpose is to produce H2, CO, or a mixture of H2 and CO (also called syngas), and the quality of the conversion gas, also called the product gas (or product fluid stream), is important for downstream applications. Therefore, in order to obtain a high-purity product fluid stream, it is desirable to minimize the presence of undesirable components (such as air) in the product fluid stream.

[0012] An SOEC plant generally consists of multiple stacks connected in parallel and / or in series in an amount sufficient to meet the required production volume. In the SOEC mode, the cathode side is also called the fuel side, and the anode side is also called the oxygen side or the flush side.

[0013] Much focus has been placed on optimizing the performance of SOEC technology by increasing the efficiency of the electrolysis stack. However, the optimization of the process equipment that supports the SOEC stack is equally important. Optimizing the design of an SOEC-based plant involves balancing the complexity of the process, the energy consumption per unit of product gas, and the equipment manufacturing cost.

[0014] Regarding the operation of SOEC plants, various optimizations have been proposed so far.

[0015] For example, since the SOEC process operates at a high temperature level, the low-temperature supply (process and flash) must be heated to the desired SOEC temperature. The primary heating is carried out by heat exchange with a high-temperature SOEC fluid (the fluid exiting the SOEC). Such a heat exchanger is called a supply / discharge heat exchanger. The balance heat can be added using, for example, one or more electric heaters.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0017] However, in order to improve the industrial applicability and profitability of SOEC plants for producing hydrogen, carbon monoxide, and synthesis gas, the need to optimize the performance of SOEC plants still remains.

Means for Solving the Problems

[0018] Summary of the Invention The inventors have found that moisture and humidity in the flash gas of a solid oxide electrolysis cell in air have an adverse effect on the cell life. By using a dry flash gas, it has been found that the performance can be improved and the life of the SOEC stack can be extended.

[0019] Systems and methods for removing moisture from various gas streams have been proposed. For example, in WO2016 / 091636, ultra-high purity carbon monoxide is prepared by high-temperature electrolysis of food-grade carbon dioxide pretreated in a solid oxide electrolysis cell stack. The heated carbon dioxide feed mixture is passed through a drying unit to remove moisture and then supplied to the fuel side of the solid oxide electrolysis cell stack. The drying unit employs a combination of temperature swing adsorption and pressure swing adsorption. EP2364766 discloses a method for removing moisture from a stream of methanation products, which is based on the adsorption of moisture. WO2011 / 017782 discloses a compressed gas dryer that includes a drying zone and a regeneration zone and a drum rotatable within a housing containing a desiccant that is sequentially transferred through the drying zone and the regeneration zone, whereby the regeneration zone includes a first subzone having a first inlet for supplying a first regeneration gas stream and a second subzone having a second inlet for supplying a second regeneration gas stream having a lower relative humidity than the relative humidity of the first regeneration gas stream; and the outlet of the drying zone is connected to the second inlet of the second subzone via a connecting conduit.

[0020] The inventors have now found a novel method for operating a high-temperature solid oxide electrolysis system suitable for converting fuel gas to product gas, and a system suitable for practicing the present invention.

[0021] Accordingly, there is provided a method for operating a high-temperature solid oxide electrolysis system including the following steps: providing a solid oxide electrolysis cell unit including at least one solid oxide electrolysis cell having a fuel side and an oxygen side; supplying a wet flash gas stream; 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 wet flash gas stream to a temperature within the moisture adsorption temperature range to generate a temperature-adjusted wet flash gas stream; passing the temperature-adjusted wet flash gas stream through at least one section of the adsorbent to operate the said section of the adsorbent in the adsorption mode and supply a dried flash gas stream; passing the dried flash gas stream through the oxygen side of the SOEC to generate a used flash gas stream; adjusting the temperature of at least a part of the used flash gas stream to a temperature within the moisture desorption temperature range to generate a temperature-adjusted used flash gas stream; passing at least a part of the temperature-adjusted used flash gas stream through at least one section of the adsorbent to operate at least the said section of the adsorbent in the desorption mode and desorb the moisture bound to the adsorbent to obtain a regenerated adsorbent and a used regeneration gas;

[0022] Furthermore, a system for implementing the method of the present invention is provided. This system is suitable for converting a fuel stream into a product stream, and the system includes the following: · a solid oxide electrolysis cell unit (8) including at least one solid oxide electrolysis cell having the following: ○ a fuel side (9) ○ an oxygen side (10) ○ a flash gas inlet (11) ○ a flash gas outlet (12) ○ a fuel gas inlet (13) ○ a product gas outlet (14), and · a drying unit (1) having the following: ○ an adsorbent bed (2) ○ a drying unit inlet (3) ○ a drying unit outlet (4) ○ a regeneration gas inlet (5) ○ a regeneration gas outlet (6) Here, the adsorbent bed (2) is arranged inside the drying unit (1); and Here, the drying unit (1) is arranged to convey a wet flash gas stream from the drying unit inlet (3) through the adsorbent bed (2) to the drying unit outlet (4), and the drying unit (1) is arranged to convey a spent flash gas stream from the regeneration gas inlet (5) through the adsorbent bed (2) to the regeneration gas outlet (6); and Here, the drying unit outlet (4) is in fluid communication with the flash gas inlet (11) of the solid oxide electrolysis cell unit (8); and Here, the solid oxide electrolysis cell unit (8) is arranged to convey the dried flash gas from the flash gas inlet (11) through the oxygen side of at least one solid oxide electrolysis cell to the flash gas outlet (12) of the solid oxide electrolysis cell unit (8); and Here, the flash gas outlet (12) is in fluid communication with the regeneration gas inlet (5) of the drying unit (1).

[0023] 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 the ambient pressure inside the drying unit during both adsorption and desorption. This is advantageous because it is preferable to supply the flash gas to the solid oxide electrolysis unit at a pressure close to atmospheric pressure in order to save compression energy. Furthermore, a low pressure drop is enabled, saving energy. Additionally, by recycling the waste gas from the SOEC process as the regeneration gas, the consumption of the flash gas can be reduced in the method according to the claims. Moreover, since most of the energy used for regeneration is recovered, an efficient heat integration is provided in the method according to the claims. Therefore, by reducing energy losses, significant savings can be achieved by the method and system according to the present invention.

[0024] It should be understood that the flash gas stream (cleaning gas stream) for flushing (washing away) the oxygen side of the solid oxide electrolysis cell should be inert to the reactions that occur. Suitable flash gases are, for example, air, nitrogen, carbon dioxide, oxygen, or mixtures thereof. The inlets and outlets can be equipped with valves if it is desired to control the flow passing through such inlets and / or outlets. In this specification, the moisture to be removed is vapor and liquid water. Generally, the wet flash gas stream is supplied as air. The air may be compressed to create a driving force for the flow within the flash system. When adjusting the temperature of the gas stream, it includes 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 carried out by gradually increasing the temperature of the regeneration gas stream when starting the regeneration and gradually decreasing the temperature of the regeneration gas when cooling, so as to control the temperature profile within the adsorbent. The adsorbent can operate in the adsorption mode for any period. However, since the efficiency decreases when the adsorbent becomes saturated, it is preferable to change to another adsorbent with less adsorbed water. Similarly, the adsorbent can operate in the regeneration mode for any period. However, as the adsorbent releases the adsorbed water, the need for regeneration decreases, and then it is preferable to cool the regenerated adsorbent in this way. A cooling gas can also be passed through the adsorbent.

[0025] Before drying the wet flash gas stream in the drying unit, a part of the moisture can be removed by cooling the stream and removing the condensed water from the stream. This improves the energy efficiency. The wet flash gas stream can be cooled, for example, by heat exchange between a cooler dry flash gas stream and a hotter wet flash gas stream. The dried flash gas stream can be heated, for example, by heat exchange before passing it through the oxygen side of at least one solid oxide electrolysis cell.

[0026] In one embodiment, the temperature-adjusted used flash gas stream is passed through the adsorbent in countercurrent to the temperature-adjusted wet flash gas stream.

[0027] Adsorbent "At least one section of the adsorbent" means a part of the adsorbent that is used for drying the wet flash gas and then needs to be regenerated. In this specification, "at least one section of the adsorbent" means that in one embodiment, the method can be implemented in a continuous mode where the entire surface of the adsorbent is first operated in the adsorption mode and then the entire surface of the adsorbent is operated in the desorption mode. After desorption, the adsorbent may be operated again in the adsorption mode, or optionally, after desorption and before operating the adsorbent again in the adsorption mode, the entire surface of the adsorbent may be operated in the cooling mode. Alternatively, the adsorbent can be divided and arranged, and each part can be operated in any one of the adsorption mode, desorption mode, and cooling mode. Also, a standby operation mode of passing a dry gas stream through the bed can be used. In one embodiment, the method of the present invention includes a subsequent step of operating at least one section of the adsorbent in the cooling mode, and this step includes cooling at least the said section of the adsorbent from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range.

[0028] Cooling can be obtained by passing at least a part of the used flash gas stream through at least one section of the adsorbent and gradually lowering the temperature of the used flash gas stream from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range to obtain a regenerated and cooled adsorbent. Cooling can also be alternatively or similarly achieved by passing at least a part of the dried flash gas stream through at least one section of the adsorbent and gradually lowering the temperature of at least a part of the used flash gas stream from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range to obtain a regenerated cooled adsorbent.

[0029] Any adsorbent suitable for air drying can be used. Exemplary adsorbents include silica gel, activated alumina, zeolite, and mixtures thereof. Each adsorbent has a moisture adsorption temperature range for adsorbing moisture and a moisture desorption temperature range for desorbing moisture. This range may vary depending on the adsorbent. For example, certain types of silica gel need to be heated up to about 175°C, and certain types of zeolite need to be heated up to 250°C to ensure proper desorption. In one embodiment, the adsorbent is selected from the group consisting of silica gel, activated alumina, zeolite, or mixtures thereof.

[0030] As described above, the adsorbent can first operate in the adsorption mode (i.e., the drying mode) at an adsorption temperature within the moisture adsorption temperature range, and then operate in the desorption mode (i.e., the regeneration mode) at a desorption temperature within the moisture desorption temperature range. Further, before operating the adsorbent in the adsorption mode again, it can also operate in the cooling mode. Desorption is preferably carried out by gradually increasing (or ramping up) the temperature of the regeneration stream until the desired desorption temperature is reached and maintaining the temperature until the desired dryness is achieved. In one embodiment according to the present invention, the adsorbent is then operated in a cooling mode including cooling the adsorbent from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range. Cooling is preferably carried out by gradually decreasing (or ramping down) the temperature of the cooling stream. In one embodiment, the cooling stream is obtained from the used flash gas. In another embodiment, the cooling stream is obtained from the dry flash gas.

[0031] The adsorbent can also be operated in a standby mode, where the adsorbent is neither used for drying the stream nor regenerated or cooled. Even in the standby mode, the dry gas stream can preferably pass through the bed at a temperature within the adsorption range.

[0032] The adsorbent can be divided into a plurality of sections that operate independently of each other. Each section can be arranged, for example, within a rotating drying drum. One section of the drum can be in the adsorption mode, another section can be in the desorption mode, and yet another section can be in the cooling mode, and each section moves as the drum rotates. In this case, a wet purge gas is continuously supplied to one inlet, and while the used purge gas is continuously supplied to another inlet, a part of the adsorbent gradually moves from one inlet to the next. Furthermore, a cooling gas can also be supplied to the regenerated adsorbent section from a third inlet. Alternatively, instead, each section of the adsorbent can be arranged in a separate bed. In one embodiment of the present invention, the adsorbent is arranged in a plurality of beds, and each bed is intermittently (periodically) operated in an adsorption mode, a regeneration mode, a cooling mode, and a standby mode in which at least one bed is always in the adsorption mode. In one embodiment, the adsorbent includes two or more sections, and each section operates independently of the other sections. Therefore, the adsorbent can be divided into, for example, two, three, or four sections. Each section can be intermittently operated in an adsorption mode, a regeneration mode, a cooling mode, and a standby mode. For example, each section is first operated in the adsorption mode, then in the regeneration mode, then in the cooling mode, and finally in the standby mode.

[0033] The wet purge gas flow may be supplied as a pressurized flow, and the used purge gas flow can be pressurized before adjusting the temperature to the moisture desorption temperature range.

[0034] The use of heat exchangers for cooling and heating the gas flow further improves the energy efficiency of the method and system. In particular, the wet purge gas flow can be conveniently cooled by heat exchange between a cooler dry purge gas flow and a hotter wet purge gas flow, and the regeneration gas flow can be conveniently heated by heat exchange by a hotter used regeneration gas flow. Heat exchange between other flows is also conceivable.

[0035] This system This system can be provided with features known in the art.

[0036] Accordingly, the system can further include a control module for controlling a temperature-adjusted wet flash gas stream to the drying unit, a dried flash gas stream from the drying unit, a temperature-adjusted dried flash gas stream from the drying unit, a temperature-adjusted used flash gas stream to the drying unit, and a used regeneration gas stream from the drying unit.

[0037] In addition to the drying unit outlet (4) of the system being in fluid communication with the flash gas inlet (11) of the solid oxide electrolysis cell unit (8), it may also be in direct fluid communication with the regeneration gas inlet (5) of the drying unit (1).

[0038] The solid oxide electrolysis cell unit (8) is generally arranged to convey 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).

[0039] The system can include a flash gas vent (16) disposed downstream of the flash gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of the regeneration gas inlet (5) of the drying unit (1). Further, a compressor (21) can be disposed downstream of the flash gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of the regeneration gas inlet (5) of the drying unit (1).

[0040] The temperature regulating element in the form of a cooler and / or a heater may be arranged downstream of the flash gas outlet of the solid oxide electrolysis cell unit and upstream of the regeneration gas inlet of the drying unit, and / or may be arranged upstream of the drying unit inlet. Further, the cooler may be arranged upstream of the drying unit inlet, and / or a 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 effect heat exchange between the wet flash gas stream and the dried flash gas stream. Another heat exchanger may be arranged to effect heat exchange between the used regeneration gas stream and the used flash gas stream.

[0041] The drying unit of the system preferably includes a plurality of adsorbent beds arranged within the drying unit, and the plurality of adsorbent beds are preferably arranged to convey a gas stream from the drying unit inlet through any one of the plurality of adsorbent beds to the drying unit outlet and to convey a gas stream from the regeneration gas inlet through the adsorbent bed to the regeneration gas outlet. In a system of such an embodiment, there is generally a control module for controlling the operation of each of the plurality of adsorption beds in the adsorption mode, the regeneration mode, the cooling mode, and the standby mode.

[0042] The operation of the solid oxide electrolysis cell unit is generally known. Generally, a fuel gas stream is supplied to the fuel gas inlet and passed to the fuel side of at least one solid oxide electrolysis cell, while an electric field acts on the at least one solid oxide electrolysis cell and the fuel gas stream is converted into a product gas stream exiting from the fuel gas outlet. The fuel gas stream can be selected from, for example, any one of water, hydrogen, carbon monoxide, carbon dioxide, and mixtures thereof. The flash gas stream serves to flush (wash out) the oxygen generated on the oxygen side from the cell.

[0043] The operation and optimization of gas dryer units are generally known to those skilled in the art. According to one aspect of the present invention, here, the adsorbent includes at least first, second, and third sections, and the temperature-adjusted wet flash gas stream is first passed through the first section of the adsorbent operating in the adsorption mode to provide a dried flash gas stream; then, the dried flash gas stream is passed through the second section of the adsorbent operating in the cooling mode, and then the dried flash gas stream is passed through the oxygen side of the SOEC to generate a used flash gas stream, and then the used flash gas stream is passed through the third section of the adsorbent operating in the desorption mode to generate a used regeneration gas, where the flash gas continuously passes through all three containers. This setup has the advantage that the method can be operated with low pressure loss. The driving force of the flash gas is provided, for example, by an air fan arranged between the first and second sections of the adsorbent. Further, an (balance) air fan can be arranged between the flash gas outlet and the third section of the adsorbent to adjust the driving force as needed. A manifold system may be included, which may be guided by automated valves or may be guided by a rotary valve that enables automatic switching between the first, second, and third sections as needed. In this way, the flash gas always passes through the three sections of the adsorbent, and only the flow changes between the three sections of the adsorbent. The adsorbent can be arranged, for example, as a radial flow bed or an equilibrium bed. Since a considerable amount of energy is required for heating, the heat generated from the process side of the solid oxide electrolysis cell unit can also be utilized to improve the overall efficiency.

[0044] The present invention is described for use in an SOEC system. However, it should be understood that the drying unit according to the present invention can also be used in an SOFC system. In the SOFC mode, the following combustion reactions occur 2CO + O2 => 2CO2 and / or 2H2 + O2 => 2H2O

[0045] Therefore, the flash gas not only serves as a simple cleaning (flashing) agent but is actually also a reaction gas. However, the same drying as the feed may be carried out, air is a suitable flash gas, an oxygen-enriched gas can optionally be used, and another oxygen-generating gas may be used.

[0046] Furthermore, in the SOFC mode, since the reaction is exothermic, the flash gas can also be used for cooling the SOFC.

Brief Description of the Drawings

[0047] Brief Description of the Drawings Figure 1 shows an embodiment of the system according to the present invention. Figure 2 shows an embodiment of a plurality of containers (2a and 2b) of the drying unit according to the present invention. Figure 3 shows an embodiment of a plurality of containers (2a, 2b and 2c) of the drying unit according to the present invention. Figure 4 shows an embodiment of the system according to the present invention. Figure 5 shows a layout for drying the product gas from the solid oxide electrolysis cell unit.

[0048] Position number 1. Drying unit 2. Adsorbent bed 3. Drying unit inlet 4. Drying unit outlet 5. Regeneration gas inlet 6. Regeneration gas outlet 8. Solid oxide electrolysis cell unit (SOEC unit) including at least one solid oxide electrolysis cell 9. Fuel side 10. Oxygen side 11. Flash (cleaning) of gas inlet 12. Flash of gas outlet 13. Fuel gas inlet 14. Product gas outlet 15. Control module 16. Gas outlet vent 21. Compressor or blower / air fan 22. Valve

Best Mode for Carrying Out the Invention

[0049] Detailed description In FIG. 1, moisture is removed from the compressed flash gas entering the dryer unit (1) from the dryer unit inlet (3), and the dried flash gas is generated through the dryer unit outlet (4). This gas is sent from the flash gas inlet (11) to the oxygen side (10) of the solid oxide electrolysis cell unit (8), where oxygen is flashed. A part of the flash gas exiting from the flash gas outlet (12) enters the dryer unit (1) through the regeneration gas inlet (5) and is used as the regeneration gas for the regeneration of the dryer unit. The gas desorbs moisture from the dryer and exits the dryer unit (1) as the used regeneration gas from the regeneration gas outlet (6). The remainder of the used regeneration gas can be used in the operation (16) of other units, such as the drying of product gas. A device for adjusting temperature and pressure may be provided, but is not shown. The fuel gas enters the solid oxide electrolysis cell unit (8) through the fuel gas inlet (13), is converted on the fuel side (9), and the product gas exits the unit (8) through the product gas outlet (14).

[0050] FIG. 2 shows two dryer vessels containing adsorbent beds (2a and 2b), together with valves (22) for controlling the gas flow to and from the beds. Vessel 2a is in the adsorption mode and vessel 2b is in the regeneration mode (the white valves indicate open valves and the black valves indicate closed valves): The valve (22) at the dryer inlet (3) directs the dryer inlet flow to vessel 2a, and the valve at the dryer outlet (4) directs the dried gas from vessel 2a to the dryer outlet (4).

[0051] The valve (22) at the regeneration gas inlet (5) directs the regeneration gas flow to vessel 2b, and the valve (22) at the regeneration gas outlet (6) directs the used regeneration gas from vessel 2b to the regeneration gas outlet (6).

[0052] In this example, the flow direction is from the upper part to the lower part of the container in the adsorption mode and from the lower part to the upper part of the container in the regeneration mode. This way, gravity helps to reduce the risk of fluidizing the bed material.

[0053] Figure 3 is a simplified flow diagram of an embodiment according to the present invention, showing the flow of the purge gas in the drying unit (1) combined with the solid oxide electrolysis cell unit (8), where the adsorbent bed (2) of the drying unit (1) is divided into three beds (2a, 2b, 2c). The drying principle in this embodiment is equivalent to the operating principle of temperature swing adsorption, although the purpose is different.

[0054] In the embodiment, a temperature-adjusted humid purge gas stream passes through the drying unit inlet (3) and through the adsorbent bed (2a) operating in the drying mode. The resulting dried purge gas stream is passed through the regenerating adsorbent bed (2b), cooling the regenerating adsorbent bed (2b) while heating the dried purge gas stream. At the start of the cooling of the bed (2b), the temperature of the adsorbent bed (2b) is about 200 °C and is cooled to near room temperature. From the adsorbent bed (2b), the purge gas stream thus heated and dried passes through the drying unit outlet and is sent from the purge gas inlet (11) to the oxygen side (10) of the solid oxide electrolysis cell unit (8). The oxygen formed within the cell unit (8) is taken up by the purge gas, and the used purge gas is discharged from the purge gas outlet (12). The temperature of the used purge gas is adjusted to the desorption temperature of 150 - 250 °C, passes through the regeneration gas inlet (5), and passes through the adsorbent bed (2c) for the regeneration of the adsorbent bed (2c). While the adsorbent bed (2c) is dried and heated by the regeneration, the gas passing through the adsorbent bed (2c) is cooled, and the used regeneration gas is generated at the regeneration gas outlet (6).

[0055] The air fan (21) is arranged, for example, between the adsorbent bed (2a) and the adsorbent bed (2b), and exerts a driving force on the flow throughout the entire flash side of the system from the dry unit inlet (3) to the regeneration gas outlet (6). Further, in order to adjust the driving force as needed, the (balance) air fan (21) can be arranged between the solid oxide electrolysis cell unit and the adsorbent bed (2c).

[0056] A manifold system (not shown) may be included, which may be guided by an automatic valve or may be guided by a rotary valve that enables automatic switching between individual containers from A to B and then to C as needed.

[0057] In this embodiment, the flash gas always passes through all three containers, and only the flow changes. The advantage of such an embodiment is that the system can be operated with low pressure loss. The adsorbent can be arranged, for example, as a radial flow bed or a parallel bed.

[0058] Since heating requires a considerable amount of energy, the overall efficiency can be improved by also utilizing the heat generated from the process side of the solid oxide electrolysis cell unit.

[0059] In Figure 4, the wet flash gas is cooled by a heat exchanger (not shown), further cooled to the adsorption temperature by a cooler (not shown), and then condensed water is removed in a separator (not shown). The wet flash gas enters through the dry unit inlet (3), passes through the dry bed 2a, and most of the remaining moisture is removed, generating a dry flash gas that exits the dry unit through the dry unit outlet (4). The dried flash gas is heated by a heat exchanger (not shown) and is used as the flash gas that enters from the flash gas inlet (11) and passes through the oxygen side (10) of the solid oxide electrolysis cell unit (8). The oxygen formed within the cell unit (8) is taken into the flash gas, and the used flash gas exits from the flash gas outlet (12). The used flash gas is pressurized by a blower (not shown) and its temperature is adjusted by a heat exchanger (not shown), an electric heater (not shown), and a cooler (not shown), and enters the dry unit (1) from the regeneration gas inlet (5) at the bottom. The regeneration gas passes through the adsorbent bed 2b for desorption of moisture. The used regeneration gas that exits from the regeneration gas outlet (6) of the dryer from the upper part is used to adjust the temperature of the used flash gas by a heat exchanger (not shown). Moisture desorbs from the adsorption bed and exits the system together with the used regeneration gas.

[0060] On the fuel side (9) of the solid oxide electrolysis cell unit (8), it is also possible to convert water vapor into a product gas containing hydrogen, convert carbon dioxide into a product gas containing carbon monoxide, or convert a combination of water vapor and carbon dioxide into a product gas containing hydrogen and carbon monoxide. Drying of the product gas can also be carried out. This is optimally done with the compressed product gas, but it can also be dried at atmospheric pressure. In many cases, drying is only required intermittently.

[0061] FIG. 5 shows a layout for drying the product gas from the solid oxide electrolysis cell unit. The wet-cooled product gas stream (labeled "from compressor") is sent to the top of the drying unit and passes through the adsorbent bed. The dried product stream exiting from the bottom of the vessel is sent to a downstream process. In normal continuous operation, there is no moisture in the product stream, in which case the entire product stream can be passed through a bypass of the drying unit.

[0062] For regeneration of the adsorbent bed, the drying unit is isolated from the process (e.g., when the product stream contains no water). The drying unit is filled with a dry inert gas, a circuit from the blower to the heater is established, and the gas is heated to 150 - 200 °C (e.g., by the temperature-regulated spent flash gas from the solid oxide electrolysis stack unit). The hot gas flows through the adsorbent bed and the moisture is removed. The gas containing moisture exits the adsorbent bed and is sent to a cooler where the moisture is condensed. The liquid moisture is separated by a conventional water separator, and the dried gas is sent to the blower to complete the circuit.

Claims

1. A method for 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; - supplying a wet purge gas stream; - 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 wet purge gas stream to a temperature within the moisture adsorption temperature range to produce a temperature-adjusted wet purge gas stream; - passing the temperature-adjusted wet purge gas stream through at least one section of the adsorbent to operate at least said section of the adsorbent in adsorption mode and supplying a dry purge gas stream; - passing the dry purge gas stream through the oxygen side of the SOEC to produce a used purge gas stream; and then, - adjusting the temperature of at least a portion of the used purge gas stream to a temperature within the moisture desorption temperature range to produce a temperature-adjusted used purge gas stream; - passing at least a portion of the temperature-adjusted used purge gas stream through at least one section of the adsorbent to operate at least said section of the adsorbent in desorption mode and desorb the moisture bound to the adsorbent to obtain a regenerated adsorbent and a used regeneration gas.

2. The method according to claim 1, wherein the used purge gas stream is pressurized before adjusting the temperature to a temperature within the moisture desorption temperature range.

3. The method according to any one of claims 1 or 2, wherein the wet purge gas stream is supplied as a pressurized stream.

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

5. The method according to any one of claims 1 to 4, wherein the wet purge gas stream is cooled by heat exchange between the relatively low-temperature dry purge gas stream and the relatively high-temperature wet purge gas stream.

6. The method according to any one of claims 1 to 5, wherein the dry purge gas stream is heated before being passed to the oxygen side of the at least one solid oxide electrolysis cell.

7. The method according to any one of claims 1 to 6, wherein a fuel gas stream selected from any one of water, hydrogen, carbon monoxide, carbon dioxide, and mixtures thereof is passed to the fuel side of the at least one solid oxide electrolysis cell while applying an electric field to the at least one solid oxide electrolysis cell.

8. The method according to any one of claims 1 to 7, including a subsequent step of operating at least one section of the adsorbent in a cooling mode, the step including cooling at least the section of the adsorbent from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range.

9. The method according to claim 8, wherein the cooling is performed by passing at least a portion of the used purge gas stream through at least one section of the adsorbent, gradually decreasing the temperature of the at least a portion of the used purge gas stream from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range, to obtain a regenerated and cooled adsorbent.

10. The method according to claim 8, wherein the cooling is performed by passing at least a portion of the dry purge gas stream through at least one section of the adsorbent before passing the dry purge gas stream to the oxygen side of the SOEC, gradually decreasing the temperature of the at least a portion of the used purge gas stream from a temperature within the moisture desorption temperature range to a temperature within the moisture adsorption temperature range, to obtain a regenerated and cooled adsorbent.

11. The adsorbent comprises at least first, second, and third sections, wherein the temperature-adjusted humid purge gas stream is first passed through the first section of the adsorbent operating in the adsorption mode to provide a dry purge gas stream; then the dry purge gas stream is passed through the second section of the adsorbent operating in the cooling mode; then the dry purge gas stream is passed to the oxygen side of the SOEC to generate a used purge gas stream; then the used purge gas stream is passed through the third section of the adsorbent operating in the desorption mode to generate a used regeneration gas, wherein the purge gas continuously passes through all three containers. The method according to claim 1.

12. The method according to any one of claims 1 to 11, wherein the adsorbent is selected from the group consisting of silica gel, activated alumina, and zeolite; or a mixture thereof.

13. The method according to any one of claims 1 to 12, wherein the adsorbent comprises two or more sections, and each section is operated independently of the other sections.

14. The method according to 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 claim 13 or 14, wherein each section is first operated in an adsorption mode, then in a regeneration mode, then in a cooling mode, and finally in a standby mode.

16. The method according to any one of claims 1 to 15, wherein the temperature-adjusted used flash gas stream is passed through the adsorbent in countercurrent to the temperature-adjusted wet flash gas stream.

17. A high-temperature solid oxide electrolysis system suitable for converting a fuel stream into a product stream, ・A solid oxide electrolysis cell unit (8) comprising at least one solid oxide electrolysis cell, comprising: ○ A fuel side (9) ○ An oxygen side (10) ○ A flash gas inlet (11) ○ A flash gas outlet (12) ○ A fuel gas inlet (13) ○ A product gas outlet (14), and, ・A drying unit (1) comprising: ○ An adsorbent bed (2) ○ A drying unit inlet (3) ○ A drying unit outlet (4) ○ A regeneration gas inlet (5) ○ A regeneration gas outlet (6) In a high-temperature solid oxide electrolysis system comprising: - The adsorbent bed (2) is disposed within the drying unit (1); and - The drying unit (1) is arranged to convey a wet flash gas stream from the drying unit inlet (3) through the adsorbent bed (2) to the drying unit outlet (4), and the drying unit (1) is arranged to convey a used flash gas stream from the regeneration gas inlet (5) through the adsorbent bed (2) to the regeneration gas outlet (6); and - The drying unit outlet (4) is in fluid communication with the flash gas inlet (11) of the solid oxide electrolysis cell unit (8); and - The solid oxide electrolysis cell unit (8) is arranged to convey a dry flash gas from the flash gas inlet (11), through the oxygen side of the at least one solid oxide electrolysis cell, to the flash gas outlet (12) of the solid oxide electrolysis cell unit (8); and - The flash gas outlet (12) is in fluid communication with the regeneration gas inlet (5) of the drying unit (1). The high-temperature solid oxide electrolysis system.

18. The system according to claim 17, further comprising a control module for controlling the flow rates of the temperature-adjusted wet flash gas stream to the drying unit, the dry flash gas stream from the drying unit, the temperature-adjusted dry flash gas stream from the drying unit, the temperature-adjusted used flash gas stream to the drying unit, and the used regeneration gas stream from the drying unit.

19. The system according to any one of claims 17 or 18, wherein in addition to the dry unit outlet (4) being in fluid communication with the flash gas inlet (11) of the solid oxide electrolysis cell unit (8), the dry unit outlet (4) is also in direct fluid communication with the regeneration gas inlet (5) of the drying unit (1).

20. The system according to any one of claims 17 to 19, wherein the solid oxide electrolysis cell unit (8) is arranged to convey a fuel gas from the fuel gas inlet (13), through the fuel side of the 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 flash gas vent (16) is arranged downstream of the flash gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of the 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 the flash gas outlet (12) of the solid oxide electrolysis cell unit (8) and upstream of the regeneration gas inlet (5) of the drying unit (1).

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

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

25. A cooler is disposed upstream of the drying unit inlet, and a water separator is disposed downstream of the cooler and upstream of the drying unit inlet, for the system according to any one of claims 17 to 24.

26. At least one of the cooler and / or the heater is a heat exchanger, for the system according to any one of claims 23 to 25.

27. The cooler and / or the heater is a heat exchanger and is disposed to effect heat exchange between the wet flash gas stream and the dry flash gas stream, for the system according to claim 26.

28. The cooler and / or the heater is a heat exchanger and is disposed to effect heat exchange between the used regeneration gas stream and the used flash gas stream, for the system according to claim 26 or 27.

29. The drying unit includes a plurality of adsorbent beds disposed therein, and the plurality of adsorbent beds are arranged to convey a gas stream from the drying unit inlet through any one of the plurality of adsorbent beds to the drying unit outlet and to convey a gas stream from the regeneration gas inlet through the adsorbent bed to the regeneration gas outlet, for the system according to any one of claims 17 to 28.

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

31. The adsorbent is selected from the group consisting of silica gel, activated alumina, and zeolite; or a mixture thereof, for the system according to any one of claims 17 to 30.

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