Solid oxide battery systems and therefore protective bed reactors for silicon removal

Abstract

The present invention relates to a protective bed reactor for removing silicon, a solid oxide electrode system for hydrogen production including a protective bed reactor for removing silicon, a method of operating the system to produce hydrogen, and the use of the protective bed reactor for removing silicon in removing volatile silica from a steam stream.

Description

Technical Field

[0001] The present invention relates to a protective bed reactor for silicon removal, a solid oxide electrode system comprising a protective bed reactor for silicon removal, a method of operating the system to produce hydrogen, and the use of the protective bed reactor for silicon removal in removing volatile silica from a steam stream. Background of the Invention

[0003] Solid oxide electrolysis holds promise for converting renewable energy sources such as wind or solar power into hydrogen, which is expected to replace fossil fuels in a variety of applications, including transportation and energy storage. Solid oxide electrolysis utilizes solid oxide batteries (SOCs) to convert water vapor into hydrogen at high temperatures (approximately 600-1000°C).

[0004] SOCs are still in the early stages of commercialization, with ongoing research aimed at improving their efficiency, lifespan, and robustness. Another key area is integrating SOCs into systems suitable for industrial-scale applications. For industrial-scale applications, cost reduction is a crucial aspect. SOCs have shown promising results and are considered a key technology for the transition to low-carbon energy systems.

[0005] SOCs are typically reversible, meaning they can be used in both solid oxide electrolyzer and solid oxide fuel cell modes.

[0006] A solid oxide battery (SOC) is an electrochemical conversion device that typically includes a fuel electrode, an oxygen electrode, and a solid electrolyte. The solid electrolyte separates the fuel and oxygen electrodes and allows oxygen ions to pass through. SOCs usually also include contact layers to improve in-plane conductivity and enhance electrical contact between adjacent SOCs when arranged in a stack. Adjacent SOCs are typically separated by interconnect layers (also called interconnects). SOC stacks can be further assembled into modules.

[0007] Interconnects are typically used as gas barriers to separate the fuel and oxygen sides of adjacent state-of-the-art (SOCs) cells while enabling current conduction between adjacent cells (i.e., between the fuel electrode of one cell and the oxygen electrode of an adjacent cell). Furthermore, interconnects typically have multiple flow channels to allow process gases to flow across both sides of the interconnect.

[0008] Silicon (Si) is known to cause problems in steam handling equipment. In the presence of steam, volatile silica substances form, which can subsequently deposit on the surfaces of downstream equipment, forming (amorphous) silica barriers. The volatile silica present in steam is known to originate from feedwater and silicon-containing auxiliary equipment (balance of plant) components (supporting and auxiliary components that enable equipment operation). The presence of high-concentration steam at high temperatures is known to cause the silica in these components to volatilize according to the following reaction I: (I) Therefore, the vapor pressure of Si(OH)4 from SiO2 increases with increasing temperature and pressure (pH2O). Consequently, Si(OH)4 present in the vapor may deposit (e.g., forming inclusions) and / or react with metal oxides present in downstream units (including solid oxide batteries).

[0009] To address these issues, known methods include removing silica from water via reverse osmosis or ion exchange before it is fed into, for example, a power plant, or by directly avoiding the use of silicon-containing auxiliary equipment components. Furthermore, WO 2017 / 042574 discloses the possibility of placing a chromium getter before the cathode (oxygen side) of an SOFC to purify the oxidant stream heading towards the cathode, and this chromium getter can also capture volatile silica substances in the oxidant (air stream). It concludes that "by placing an adsorbent getter within the inlet duct of the fuel cell stack to remove chromium and silica substances from the air stream, thereby reducing the concentration of chromium and silica contaminants in the air stream, it helps to extend the life of the fuel cell and fuel cell stack by reducing cathode degradation." WO 2017 / 042574 states that the chromium getter contains "at least one of magnesium oxide, calcium oxide, and manganese oxide, because they are particularly adept at extracting volatile chromium and silica substances from the air stream by reacting with volatile Cr-based substances."

[0010] As mentioned earlier, there are still many aspects of industrial-scale SOC equipment operation that need improvement, such as extending SOC lifespan and reducing operating costs. In particular, current research focuses on designing improved SOEC systems suitable for industrial-scale hydrogen production. Summary of the Invention

[0011] In their efforts to improve existing SOEC systems for industrial applications, the inventors discovered that even in low amounts of silica present in the SOEC steam feed, which were not expected to adversely affect the solid oxide battery, they did observe accumulation of silica material on the fuel side surface of the SOEC during long-term use, even at low silica concentrations. This problem is more pronounced in systems that convert steam to hydrogen, as H2O is consumed, shifting the balance between solid and gaseous Si towards gaseous Si (see reaction (I)).

[0012] The inventors unexpectedly discovered that even when silicon has been removed from the steam feed using conventional methods, the lifespan of solid oxide batteries (SOFCs) can still be significantly improved by removing volatile silica materials (such as Si(OH)4) by adding a protective bed (reactor) upstream of the SOFC inlet for silicon removal. The inventors also found that passing a water-containing hydrocarbon feed through a protective bed (reactor) upstream of the fuel side of the SOFC also facilitates the removal of volatile silica materials. Furthermore, the inventors discovered several metal oxides that have proven particularly suitable as active materials in silicon protective bed reactors for removing even low concentrations of silicon hydroxide (Si(OH)4) from steam-containing feed gases. The inventors found that the silicon concentration in the steam feed leading to the SOC typically needs to be below 50 ppb to avoid or at least significantly reduce the adverse effects of amorphous silica material deposition inside and / or on the surfaces downstream of the SOC.

[0013] According to one aspect of the invention, a protective bed reactor for silicon removal is provided, having a protective bed comprising an active metal (Me) oxide as a Si binding material, wherein the active metal (Me) is selected from alkaline earth metals (Group 2 of the periodic table); and transition metals including rare earth metals (Groups 3-12 of the periodic table); or mixtures thereof.

[0014] Therefore, a suitable active metal (Me) may be, for example, one of the alkaline earth metals Ca, Mg, and Sr; one of the transition metals Zr, rare earth metals La, and Ce; or a mixture thereof. In one embodiment, the guard bed reactor for silicon removal has a guard bed in which the active metal Me is selected from Ca, Mg, Sr, Zr, Ce, and La; or a mixture thereof.

[0015] One advantage of the guard bed reactor for silicon removal according to the invention is that, under the operating conditions of a solid oxide cell (SOC), the adverse effects of the formation of amorphous silica on the surface are significantly reduced both inside the fuel side of the SOC and downstream of the SOC. When using the guard bed reactor according to the invention, the silicon (Si) concentration in the steam feed has been observed to be below 50 ppb molar ratio. For example, when cerium oxide (Me=Ce) is used as the Si bonding material, a 100-fold reduction in Si in the steam feed heading to the fuel side of the SOC can be achieved, and Si concentrations as low as 15 ppb molar ratio have been observed. Another advantage of reducing the silicon concentration in the feed is that the SOC system can operate at a higher steam conversion rate (e.g., above 70 wt%).

[0016] According to another aspect of the present invention, a solid oxide battery (SOC) system for hydrogen production is provided, comprising: - A solid oxide battery comprising an electrolyte layer located between the fuel side and the oxygen side; and - A guard bed reactor for removing silicon, having a guard bed containing Si-binding material, the guard bed reactor being arranged upstream of the fuel side of a solid oxide battery.

[0017] One advantage of the SOC system for hydrogen production according to the present invention is that the guard bed reactor can be positioned after the feed to the fuel side has been heated. The inventors have found that after heating the steam-containing feed, most of the Si present in the steam is removed within the guard bed reactor, likely because most of the Si present in the steam is in gaseous form. Integrating the guard bed reactor into the solid oxide battery (SOC) system for hydrogen production can save energy because there is no need to separately heat the feed to the guard bed reactor. Suitable units for heating the feed are heaters and / or heat exchangers.

[0018] According to another aspect of the present invention, a method for producing hydrogen is provided, comprising: - Pass a steam-containing feed through a protective bed reactor for silicon removal at a temperature of 150°C to 1000°C to produce a lean Si stream; - A lean Si stream is fed to the fuel side of a solid oxide battery, which includes an electrolyte layer located between the fuel side and the oxygen side, wherein the solid oxide battery is operated at a temperature of 600 to 1000°C to produce a product stream containing hydrogen.

[0019] The advantages of the method of the present invention are the same as those described above for SOC systems used for hydrogen production.

[0020] Other aspects of the invention will be set forth in the following description, drawings and appended claims.

[0021] Detailed description of the invention

[0022] definition

[0023] Unless otherwise stated, any given percentage of gas content is a volume percentage.

[0024] In the context of this article, it should be understood that a solid oxide battery (SOC) typically includes a fuel electrode on the fuel side, an oxygen electrode on the oxygen side, and a solid electrolyte layer separating the fuel electrode and the oxygen electrode and allowing oxygen ions and electrons to pass through. SOCs typically include a contact layer to improve in-plane conductivity and provide improved electrical contact.

[0025] In the context of this article, it should be understood that SOCs are typically arranged in the form of stacks (SOC stacks), and adjacent SOCs are typically separated by interconnect layers (also known as interconnects). SOC stacks can be further arranged into modules containing multiple stacks.

[0026] In the context of this document, it should be understood that the fuel side always includes a fuel side inlet, fuel electrodes, and a fuel side outlet. When arranged in the form of a fuel cell stack, a System-on-Chip (SOC) may have a single fuel side inlet that supplies fuel to multiple SOCs and / or a single fuel side outlet that allows products to be discharged from multiple SOCs.

[0027] When discussing solid oxide batteries, it should be understood that: Regardless of whether the SOC operates in SOEC or SOFC mode, the term "fuel side" refers to the side of the SOC that includes the fuel electrode, where the feed gas is converted into product gas (in electrolysis mode) or undergoes electrochemical oxidation (in fuel cell mode). The term "oxygen side" refers to the side of the SOC that includes the oxygen electrode, where oxygen is consumed or generated, depending on whether the SOC is in fuel or electrolysis mode. To avoid ambiguity, it should be noted that regardless of whether the SOC operates in SOEC or SOFC mode, the fuel electrode is always the negative electrode, and the oxygen electrode is always the positive electrode. However, when the SOC operates in SOEC mode, the fuel electrode acts as the cathode; while in SOFC mode, the fuel electrode acts as the anode. Correspondingly, when the SOC operates in SOEC mode, the oxygen electrode acts as the anode; while in SOFC mode, the oxygen electrode acts as the cathode.

[0028] Unless otherwise specified, the terms "Si" and "silicon" refer to the chemical element in Group 14 of the periodic table. It can be in its elemental form or in combination as a chemical composition. These two terms are used interchangeably.

[0029] In the context of this paper, the term "Si binding" should be understood as a general term encompassing various interactions between molecules or particles, including adsorption, absorption, and reaction. Although adsorption, absorption, and reaction are distinct processes, they can all be considered as types of binding interactions between molecules or particles that result in the removal of Si from the feed stream. The same applies to "sulfur binding," "nitrogen binding," and "phosphorus binding."

[0030] "Directly upstream of the fuel side of the solid oxide battery" and "directly fed to the fuel side of the solid oxide battery" mean that there is no cell operation between the two.

[0031] Unless otherwise specified, the Si concentration is determined by ICP-OES (inductively coupled plasma optical emission spectrometry).

[0032] system

[0033] The solid oxide battery (SOC) system for hydrogen production according to the present invention comprises: - A solid oxide battery comprising an electrolyte layer located between the fuel side and the oxygen side; and - A guard bed reactor for removing silicon, having a guard bed containing Si-binding material, the guard bed reactor being arranged upstream of the fuel side of a solid oxide battery.

[0034] The SOC system according to the invention can be used in solid oxide electrolyzer mode (SOEC). Alternatively, it can be used in solid oxide fuel cell mode (SOFC), although for simplicity, some of the following description refers only to SOEC mode. In SOEC mode, the objective is to produce H2, CO, or a mixture of H2 and CO (also known as syngas) from vapor, CO2, or a mixture thereof. In SOFC mode, the objective is to generate energy from, for example, hydrogen or low-molecular-weight hydrocarbons. When used in SOFC mode, the feed to the SOC typically contains vapor.

[0035] Systems with a Si guard bed reactor positioned upstream of the fuel side have the advantage that volatile silica material formed in a steam-containing feed (e.g., during cell operation on a feed upstream of a solid oxide cell) can be removed before entering the SOC, thereby avoiding or at least greatly reducing silica deposition within the SOC.

[0036] In a SOC system, the Si guarded bed reactor can be any suitable Si guarded bed reactor for a feed containing steam, preferably with a temperature range of 150 to 1000°C. Within this temperature range, the Si guarded bed reactor is preferably operated at near ambient pressure. If higher pressures are used, a slightly lower temperature range is preferred.

[0037] Common fuel electrode materials include: Ni / YSZ (=Ni on yttrium-stabilized zirconium oxide) and Ni / GDC (=Ni / CGO=Ni on gadolinium-doped cerium dioxide).

[0038] Commonly used oxygen electrode materials include: LSCF (lanthanum-strontium-cobalt ferrite), LSM (strontium-doped lanthanum manganate), LSC (lanthanum and strontium-doped cobalt oxide?), etc., or mixed electrodes (LSCF / CGO, LSM / YSZ, LSC / CGO).

[0039] According to one embodiment of the system of the present invention, the protective bed reactor for silicon removal is arranged directly upstream of the fuel side of the SOC.

[0040] Further advantages can be gained when the guard bed reactor used for silicon removal is positioned directly upstream of the fuel-side inlet of the SOC. If no further unit operations are performed after the removal of volatile Si from the steam, leaching of volatile Si from these units can be avoided, thus maintaining an extremely low volatile Si content in the steam obtained using the guard bed reactor.

[0041] The system may include other operating units, such as those that perform heat exchange, heating, cooling, oxygen depletion, ion exchange, separation, etc.

[0042] According to one embodiment of the invention, a guard bed reactor for silicon removal is defined as in any one of claims 1-8. The advantages of such a guard bed reactor are described in the "Guard Bed Reactor" section.

[0043] According to one embodiment of the system of the present invention, the guard bed further comprises sulfur, nitrogen, and / or phosphorus binding materials. The advantage of providing a guard bed containing sulfur, nitrogen, and / or phosphorus binding materials within the guard bed reactor is that, in addition to silicon, other impurities, such as sulfur-, nitrogen-, and / or phosphorus-containing compounds, can be removed from the feed.

[0044] According to one embodiment of the system of the present invention, the guard bed reactor for silicon removal is configured to provide an airflow flowing from the upper part of the guard bed reactor through the guard bed and to the lower part of the guard bed reactor.

[0045] In a SOC system, multiple cells are typically arranged as a stack and fluidly connected via, for example, a manifold that provides a single fuel-side inlet to all cells in the stack. The stack can be arranged as a module, which may have a single fuel-side inlet or multiple fuel-side inlets. The production and assembly of solid oxide cells, solid oxide stacks, and stack modules are generally known in the art.

[0046] Protective bed reactor for silicon removal

[0047] The inventors discovered that in order to remove silicon from vapor (i.e., reduce the equilibrium vapor pressure of Si(OH)₄(g) above the protective bed), the Gibbs free energy of formation of the mixed silicate composed of SiO₂ and metal oxides must be negative. However, the inventors considered the Gibbs free energy of the following reaction in the temperature range of 150 to 1000 °C: MeO x + zSiO2 MeSi z O y (II) Where x is an integer between 1 and 5, z is an integer between 1 and 4, and y is an integer between 3 and 8.

[0048] The inventors have discovered that metal oxides satisfying reaction (II) with a Gibbs free energy ΔG < 0 are particularly suitable as Si-binding materials in guard-bed reactors for silicon removal. Typically, this includes basic metal oxides.

[0049] Therefore, the protective bed reactor for silicon removal according to the present invention has a protective bed containing an active metal (Me) oxide as a Si binding material, wherein the active metal (Me) is selected from alkaline earth metals (Group 2 of the periodic table); transition metals including rare earth metals (Groups 3-12 of the periodic table); or mixtures thereof.

[0050] Therefore, a suitable active metal (Me) is, for example, one of the alkaline earth metals Ca, Mg, and Sr; one of the transition metals Zr, rare earth metals La, and Ce; or a mixture thereof. In one embodiment, the guard bed reactor for silicon removal has a guard bed in which the active metal Me is selected from Ca, Mg, Sr, Zr, Ce, and La; or a mixture thereof.

[0051] Those skilled in the art will recognize that a guard bed reactor is a vessel configured to contain a fluid flow from an inlet through a guard bed to an outlet. In the context of this invention, the guard bed should be understood as a porous material that ensures a large contact area between the fluid flowing through the pores and the porous material. The guard bed is arranged within the vessel to restrict the flow of fluid from the vessel inlet to the outlet through the porous material. The Si-bonded material can be integrated into the porous material, or it can be distributed on the surface of the porous material. In the latter case, the porous material may be referred to as a carrier. In the context of this invention, "carrier surface" refers both to the outer surface of the carrier and to the inner surface that can be contacted through the pores of the carrier. For example, if the Si-bonded material is more expensive than the carrier material, or if higher strength is required, the use of a carrier may be more preferable.

[0052] The guard bed used for silicon removal is preferably free of any significant amount of Si. Furthermore, the components of the Si guard bed reactor itself should preferably be free of any significant amount of Si. Any Si present in the Si guard bed reactor may react with the steam in the feed, thereby having adverse effects downstream of the Si guard bed reactor. In one embodiment, the guard bed contains less than 50,000 ppb, for example, less than 1,000 ppb, 100 ppb, or 10 ppb molar ratios of Si.

[0053] In Si guard bed reactors used for silicon removal, another undesirable substance is potassium oxide. In one embodiment, the guard bed contains less than 5000 ppm, for example less than 2000 ppm or 1000 ppm molar ratio of potassium oxide.

[0054] The guard bed reactor can be used in combination with a guard bed reactor for removing sulfur, nitrogen, and / or phosphorus from the feed. Alternatively, the guard bed of the guard bed reactor for removing silicon may contain sulfur, nitrogen, and / or phosphorus binding materials in addition to the Si binding material; or the Si binding material may also contain sulfur, nitrogen, and / or phosphorus. Common sulfur, nitrogen, and / or phosphorus binding materials include metal oxides, such as zinc oxide, nickel oxide, copper oxide, or activated carbon. In one embodiment, the guard bed of the guard bed reactor for removing silicon also contains Ni. In another embodiment, the guard bed of the guard bed reactor for removing silicon also contains Al. The guard bed of the guard bed reactor for removing silicon may contain both Ni and Al in addition to the Si binding material.

[0055] In one embodiment, the protective bed comprises La, Ni, and / or Mg. In another embodiment, the protective bed comprises La, Ni, Mg, and Al. In yet another embodiment, the protective layer comprises the spinel phase Mg(AlO2)2. In still another embodiment, the protective layer comprises the spinel phase Mg(AlO2)2 as a support, and La, Ni, and / or Mg located inside or on the surface of the support.

[0056] Using a guard bed containing La, Ni, and Mg in a SOC system including a guard bed reactor for Si removal before the solid oxide cell offers the advantage of suitability for both normal operation (hydrogen production by steam) and transient operation (where no hydrogen production is performed and the system operates at open-circuit voltage (OCV)). When the guard bed contains La, Ni, and Mg, ammonia can be fed as the main feed into the guard bed reactor for silicon removal during transient operation in the temperature range of 400–900 °C. The ammonia is then converted into hydrogen and nitrogen, which are then fed into the solid oxide cell. When transitioning to normal operation, a steam-containing feed is introduced into the system. This transient operation is suitable for, for example, starting up the SOC system and operating under no-load conditions.

[0057] The guard bed of the guard bed reactor used for silicon removal may further include a support. The support can be used to improve the properties of the silicon-binding material, such as surface area, strength, and durability per unit amount of metal oxide. The support may incorporate the active metal oxide into its structure, or the active metal oxide may be adsorbed onto the surface of the support. According to one embodiment of the invention, the support comprises the spinel phase Mg(AlO2)2. According to one embodiment of the invention, the support is Al-based. According to one embodiment of the invention, the support is La, Mg, and Al-based. It should be understood that the La, Mg, and Al-based support is a La, Mg, and Al oxide support. An exemplary support is a MgAl2O4-based support containing a small amount of La.

[0058] According to one embodiment, the protective bed of the protective bed reactor for silicon removal according to the present invention is provided in the form of porous particles, spheres, or a monolithic material. According to one embodiment, as determined by ASTM D3663-20, the protective bed of the protective bed reactor for silicon removal according to the present invention has a density of 0.01 to 100 m³. 2 / g BET surface area.

[0059] When the Si-protected bed reactor becomes saturated with silica or its efficiency decreases, it can be regenerated or replaced.

[0060] How to use

[0061] Solid oxide batteries typically operate at “high temperatures,” which, in the context of this invention, means an operating temperature in the range of 600 to 1000°C, preferably 650 to 850°C.

[0062] According to one aspect of the present invention, a method for producing hydrogen includes: - Pass a steam-containing feed through a protective bed reactor for silicon removal at a temperature of 150°C to 1000°C to produce a lean Si stream; - A lean Si stream is fed to the fuel side of a solid oxide battery, which includes an electrolyte layer located between the fuel side and the oxygen side, wherein the solid oxide battery is operated at a temperature of 600 to 1000°C to produce a product stream containing hydrogen.

[0063] As previously mentioned, the vapor pressure of Si(OH)4(g) from SiO2(s) increases with increasing temperature and water pressure (pH2O). Therefore, removing Si at high temperatures will result in the removal of a higher proportion of silicon present in the vapor. Furthermore, the closer the temperature of the silicon removal step is to the operating temperature of the solid oxide cell, the less Si evaporates from the Si-lean stream before entering the SOC. According to the invention, the temperature difference (ΔT) between the guard bed reactor and the solid oxide cell is below 200°C, for example below 100°C or below 50°C.

[0064] Other unit operations can also be performed, such as heat exchange, heating, cooling, oxygen removal, ion exchange, separation, etc. However, avoiding such unit operations between the Si removal step and SOC reduces the risk of auxiliary equipment components releasing volatile silica into the steam-containing feed. According to one embodiment of the method of the invention, a lean Si stream is fed directly to the fuel-side inlet of the solid oxide fuel cell.

[0065] According to one embodiment of the method of the present invention, the protective bed reactor for silicon removal is as defined herein.

[0066] According to one aspect of the invention, the protective bed reactor disclosed herein for removing silicon is provided for removing volatile silica substances from a steam stream in a temperature range of 150 to 1000°C.

[0067] Brief description of the attached figures

[0068] The invention will be further illustrated with reference to the accompanying drawings, which show examples of embodiments of the invention.

[0069] Figure 1 A solid oxide battery system according to the invention is shown, which has heat exchange and heating before the protective bed reactor.

[0070] Figure 2 A solid oxide battery system according to the invention is shown, which has heating before the protective bed reactor.

[0071] Figure 3 The experimental setup used in the examples is shown.

[0072] Figure 4 The Si content in condensate samples under different pressurization conditions is shown (measured by ICP-OES).

[0073] Location number

[0074] 01. Feeding (Fuel Side)

[0075] 02. Rinse (Oxygen Side)

[0076] 10. Solid oxide electrolytic cell

[0077] 11. Fuel side

[0078] 12. Fuel side inlet

[0079] 13. Fuel Electrode

[0080] 14. Fuel-side outlet

[0081] 15. Oxygen-side inlet

[0082] 16. Oxygen side

[0083] 17. Oxygen-side outlet

[0084] 20. Protective bed reactor for silicon removal

[0085] 21. Flow entry

[0086] 22. Protective bed containing Si bonding material

[0087] 23. Flowing Outlets

[0088] 30. Preheater fuel side

[0089] 35. Fuel side of heat exchanger

[0090] 40. Oxygen side of the preheater

[0091] 45. Oxygen side of heat exchanger

[0092] Embodiments of the present invention

[0093] In the context of this invention, the term "fuel side" of SOC refers to the side of the SOC that includes the fuel electrode. When operating in SOEC mode, the fuel electrode undergoes the H2O reduction reaction (H2O + 2 e-). -→ H2 + O2 - The position of the fuel electrode; when operating in SOFC mode, the fuel electrode is where the H2 oxidation reaction (H2 + O2) occurs. - → H2O + 2 e - The location of the oxygen electrode. The term "oxygen side" in SOC refers to the side of the SOC that contains the oxygen electrode. When operating in SOEC mode, the oxygen electrode is where the O2 generation reaction (2O2) occurs. - → O2 + 4 e - The position of the oxygen electrode; when operating in SOFC mode, the oxygen electrode is the position where the reverse reaction occurs.

[0094] Unless otherwise specified, the amount of silica present in gaseous streams such as “feed containing steam” or “Si-lean stream” is determined using inductively coupled plasma optical emission spectrometry (ICP-OES). This is an analytical technique that uses inductively coupled plasma optical emission spectrometry to determine the elemental composition of a sample. It is recognized for its powerful ability to simultaneously detect multiple elements and provide accurate results.

[0095] Figure 1 A solid oxide battery system according to one embodiment of the invention is shown, equipped with a guard bed reactor for silicon removal. For proper SOEC operation, both the feed stream and the flush stream need to be heated to the correct operating temperature. For this purpose, heat exchangers 35 and 45 are provided on both the fuel and oxygen sides, which utilize the thermal energy in the fluids leaving the stack to preheat the feed streams. To further heat the process fluids and oxygen fluids to the correct operating temperature, heaters 30 and 40 are provided downstream of the heat exchangers for heating the feed stream and flush stream. Downstream of heater 30, the fuel stream flows through the guard bed reactor according to the invention for silicon removal, located directly upstream of the fuel inlet 12.

[0096] Figure 2 A solid oxide battery system according to one embodiment of the present invention is shown, equipped with a guard bed reactor for silicon removal. For SOEC to operate correctly, both the feed stream and the flush stream need to be heated to the correct operating temperature. In this embodiment, the process fluid and oxygen fluid are heated to the correct operating temperature simply by heating the feed stream and the flush stream using heaters 30 and 40 located downstream of the heat exchanger. Downstream of heater 30, the fuel stream flows through the guard bed reactor for silicon removal according to the present invention, located directly upstream of the fuel inlet 12.

[0097] Example

[0098] Experiment Description

[0099] Example 1: Testing the reaction of hydrogen and / or steam streams by passing the feed stream through a guard bed reactor for silicon removal. Experimental apparatus for removing Si hydroxide

[0100] exist Figure 3 In the experimental setup shown, a cylindrical reactor (13.7 mm outer diameter, 2.7 mm internal thermocouple sheath diameter), representing a protective bed reactor for silicon removal, is placed in a zone six electric furnace. The reactor is equipped with two containers: the upper container holds a Si source in the form of pulverized SiO2 supported on an Al2O3 support; the lower container holds a Si binding material in the form of a mixture of pulverized Me oxide / La, Mg, and Al-based supports, where Me represents the metal oxide to be tested.

[0101] The feed stream, consisting of H2 and H2O, flows through the heating element and is then fed to the inlet at the top of the reactor. Steam flows through the reactor from top to bottom: first through the Si source, introducing Si into the gas stream; then through the Si-binding material to absorb the Si already present in the feed stream.

[0102] The feed stream exits from the bottom of the reactor and is guided through cooling elements and a subsequent separator to separate the condensate and gas phases. The exhaust gas is directed to the burner while an aqueous condensate sample is collected and analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the Si concentration in the sample. The amount of silicon present in the condensate indicates the effectiveness of the Si-bonded material.

[0103] For both the Si source and the Si bonding material, the amount of material loaded into the reactor corresponds to a bed height of approximately 3.6 cm.

[0104] Example 2: Measuring Si in the experimental setup without introducing or removing Si hydroxide.

[0105] In this experiment, a feed stream of H₂O / H₂ at a molar ratio of 9:1 (metered by a mass flow controller) was fed into the experimental setup of Example 1, except that the Si source and Si-binding material were removed. Steam was obtained by evaporating externally supplied deionized water and was further directed through a local ion exchanger before being mixed with hydrogen. The Si content in the deionized feed stream was measured at different locations within the experimental setup with an empty reactor using ICP-OES. The results showed that the Si content was 0.051 μg / ml before water evaporation at the reactor inlet and 0.069 μg / ml after condensation at the bottom of the reactor.

[0106] Example 3: Preparation of Si source

[0107] 5 g of silica / alumina material (mass ratio 19:81) was pulverized to a particle size of approximately 1.5 mm and placed in the upper container of the reactor. Silicon mainly exists in the form of SiO2. ，And will react with the steam in the gas feed according to reaction (1): SiO2(s) + 2H2O(g) Si(OH)4(g) (1) In all experiments, the Si source was placed at a temperature of 500-550℃. This was due to the practical limitations of the experimental setup. It is known that the bonding ability of metal oxides with silicon dioxide increases with increasing temperature.

[0108] Example 4: Testing cerium oxide as a Si-binding material in a protective bed reactor for silicon removal

[0109] To test the Si absorption capacity of cerium oxide, a cerium dioxide-based material was prepared by impregnating a MgAl₂O₄ support with a cerium nitrate precursor solution and then calcining it at 500 °C for 2 hours. Scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) showed that 10–15 wt.% Ce was uniformly distributed in the support. Chemical analysis using ICP-OES confirmed that the Ce concentration in the material was 12.6 wt.%.

[0110] Then, 5 g of cerium oxide-based material was placed in the lower part of the reactor of Example 1 at a temperature of 750-800 °C (the temperature for reproducing commercial fuel cell stacks). The experiments were conducted under pressure to obtain measurable Si content in the gas phase. Experiments were performed at three different total pressures of 11, 21, and 31 bar absolute pressures. At each pressure step (including heating to the desired temperature in different reactor areas, pressurization, and stabilization of the gas mixture), the experiment lasted at least 24 hours. The total gas flow rate was 100 Nl / h. For each experiment (at each pressure), two temperature profile measurements were performed, and two condensate samples were collected approximately 5 hours apart.

[0111] Example 5: Testing Strontium oxide and Lanthanum oxide as Si-binding materials in a guard bed reactor for silicon removal

[0112] To test the Si absorption capacity of strontium oxide, a strontium-based material was prepared by impregnating a La, Mg, and Al-based support with a strontium nitrate precursor solution and then calcining it at 500°C for 2 hours. SEM combined with EDS showed a uniform distribution of 5-10 wt.% Sr in the support. Chemical analysis using ICP-OES confirmed that the Sr concentration in the material was 8.5 wt.%.

[0113] Similarly, to test the Si absorption capacity of lanthanum oxide, a lanthanum-based material was prepared by impregnating a La, Mg, and Al-based support with a lanthanum nitrate precursor solution and then calcining it at 500 °C for 2 hours. SEM combined with EDS showed that 15-20 wt.% La was uniformly distributed in the support. Chemical analysis using ICP-OES confirmed that the La concentration in the material was 16.2 wt.%.

[0114] To test strontium oxide, 5 g of strontium-based material was placed at the bottom of the reactor at a temperature of 750-800 °C (reproducing the temperature of commercial fuel cell stacks).

[0115] The experiment was conducted under pressurized conditions (21 bar absolute pressure) to obtain measurable Si content in the gas phase, with a total gas flow rate of 450 Nl / h. The experimental duration (including heating to the desired temperature in different reactor areas, pressurization, and stabilization of the gas mixture) was 10 hours. Two independent temperature measurements taken at different locations in the reactor showed that the temperature remained stable and close to the desired temperature throughout the experiment. Liquid samples were collected for analysis approximately 5 hours after the start of the experiment. To test lanthanum oxide, 5 g of lanthanum-based material was tested under identical conditions.

[0116] Experimental results.

[0117] Figure 4 The experimental results of Example 4 are presented, reporting the concentration of Si in the aqueous condensate samples measured by ICP-OES under the different pressure conditions studied. In the figure, the solid black squares show the Si concentration measured in the condensate samples with only a Si source (i.e., no Si protection). It can be observed that the Si content in the gas feed increases linearly with increasing total pressure, consistent with the linear relationship expected in reaction (1). The hollow squares show the Si content measured under the same conditions when a cerium oxide-based Si protection material is introduced near the reactor outlet: the amount of Si measured in the condensate samples is observed to be reduced by about 10-fold, with Si concentrations of 0.06, 0.09, and 0.21 μg / ml measured at absolute pressures of 11, 21, and 31 bar, respectively.

[0118] Table 1 presents the experimental results of Example 5, reporting the Si concentration in the aqueous condensate sample measured by ICP-OES for both materials studied, as well as the Si concentration measured in the condensate sample with only a Si source (i.e., without any protection). It can be observed that the presence of both protective materials significantly reduced the Si content in the gas, with the Si concentration decreasing from 1650 μg / ml to 970 μg / ml for the La-based protective material and 250 μg / ml for the Sr-based protective material.

[0119] Table 1: Comparison of Si content measured by ICP-OES for different protective materials with Si content without any protection.

[0120]

Claims

1. A guard bed reactor for silicon removal, comprising a guard bed containing an active metal (Me) oxide as a Si binding material, wherein the active metal (Me) is selected from alkaline earth metals, including Ca, Mg, and Sr; transition metals, including Zr; and rare earth metals, including La and Ce; or mixtures thereof.

2. The protective bed reactor for silicon removal according to claim 1, wherein the active metal Me is selected from Ca, Mg, Sr, Zr, Ce and La; or mixtures thereof.

3. The protective bed reactor for silicon removal according to claim 1 or 2, wherein the protective bed further comprises Ni.

4. A guard bed reactor for removing silicon according to any one of the preceding claims, wherein the guard bed further comprises Al.

5. A guard bed reactor for removing silicon according to any one of the preceding claims, wherein the guard bed contains Si at a molar ratio of less than 10 ppb.

6. A protective bed reactor for removing silicon according to any one of the preceding claims, wherein the protective bed further comprises a carrier.

7. A protective bed reactor for silicon removal according to any one of the preceding claims, wherein the protective bed is provided in the form of porous particles, spheres or a monolithic material.

8. A protective bed reactor for silicon removal according to any one of the preceding claims, wherein the protective bed has a density of 0.01 to 100 m³ as determined by ASTM D3663-20. 2 / g BET surface area.

9. A solid oxide battery (SOC) system for hydrogen production, comprising: a. A solid oxide battery, comprising an electrolyte layer located between a fuel side and an oxygen side; as well as b. A guard bed reactor for removing silicon, having a guard bed containing a Si-binding material, the guard bed reactor being arranged upstream of the fuel side of the solid oxide cell.

10. The system of claim 9, wherein the protective bed reactor for silicon removal is as defined in any one of claims 1-8.

11. The system of claim 9 or 10, wherein the guard bed reactor for silicon removal is arranged directly upstream of the fuel side of the solid oxide battery.

12. The system according to any one of claims 9 to 11, wherein the protective bed further comprises a sulfur, nitrogen and / or phosphorus binding material.

13. The system according to any one of claims 9 to 12, wherein the guard bed reactor for silicon removal is configured to provide an airflow flowing from the upper part of the guard bed reactor through the guard bed to the lower part of the guard bed reactor.

14. A method for producing hydrogen, comprising: i. Pass a steam-containing feed through a protective bed reactor for silicon removal at a temperature of 150°C to 1000°C to produce a lean Si stream; ii. The lean Si stream is fed to the fuel side of a solid oxide battery, the solid oxide battery including an electrolyte layer located between the fuel side and the oxygen side, wherein the solid oxide battery is operated at a temperature of 600 to 1000°C to produce a product stream containing hydrogen.

15. The method of claim 14, wherein the protective bed reactor for silicon removal is as defined in any one of claims 1-8.

16. The method according to any one of claims 14 to 15, wherein the lean Si stream is fed directly to the fuel side of the solid oxide battery.

17. Use of the protective bed reactor for removing silicon according to any one of claims 1-8 at a temperature of 150°C to 1000°C for removing volatile silica substances from a steam stream.

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