Method of operating a sofc to co-produce electricity and nitric oxide

Abstract

The present disclosure discloses a method for the co-production of electricity and nitric oxide. The method comprises the steps of: providing a SOFC comprising: an anode side comprising a gas permeable solid anode, a gas inlet and a gas outlet, a cathode side comprising a gas permeable solid cathode, a gas inlet and a gas outlet, and a fully dense solid electrolyte separating the cathode side from the anode side; introducing an oxygen containing gas into the inlet of the cathode side of the SOFC; introducing an ammonia containing gas stream into the inlet of the anode side of the SOFC; collecting nitric oxide at the outlet of the anode side; and collecting an electrical current flowing between the anode side and the cathode side. The cathode comprises a material suitable for reducing oxygen in the oxygen containing gas and the anode comprises A 1‑X A’ X B 1‑Y B’ Y O 3‑δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3. The present disclosure also relates to a SOFC and a stack thereof for performing the method of the present disclosure, a method and a system for the production of nitric acid and the use of an anode in said method and SOFC and stack thereof.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of solid oxide fuel cells for the combined production of electricity and nitric oxide, and to the integration of related applications of nitric acid production, water electrolysis and air separation. BACKGROUND

[0002] A solid oxide fuel cell (SOFC) is a high temperature device that is a device that directly converts chemical energy into electrical energy. A SOFC consists of a fully dense ceramic electrolyte membrane that is capable of transporting ions (most typically, oxygen ions (O 2- )) when a gradient of partial pressure of the transported species is imposed across it. For a membrane that transports oxygen ions, such a gradient is created when the membrane contains air on one side of the membrane and a low oxygen gas on the other side. As Figure 1 Illustratively, in a SOFC, a low oxygen partial pressure is derived from a fuel gas that is oxidized by the oxygen ions transported through the membrane.

[0003] On the high oxygen partial pressure side of the membrane, oxygen molecules are reduced to oxygen ions and incorporated into the electrolyte membrane.

[0004] O2+ 4e - → 2O 2-

[0005] The oxygen partial pressure gradient across the membrane drives the oxygen ions through oxygen ion vacancies in the lattice of the electrolyte membrane to the fuel side. Upon reaching the surface of the fuel side of the membrane, the oxygen ions react with the fuel gas. A variety of fuel gases can be oxidized, such as hydrogen, carbon monoxide, methane and ammonia, and corresponding examples of reactions are shown below:

[0006] H2+ O 2- → H2O + 2e -

[0007] CO + O 2- → CO2+ 2e -

[0008] 2CH4+ 8O 2- → 4H2O + 2CO2+ 16e -

[0009] 2NH3+ 3 / 2O 2- → 3 / 2H2O + N2+ 3e -

[0010] As can be seen from the above reactions, the oxidation of the fuel gas by the transported oxygen ions results in the release of electrons. To obtain a process in which the oxygen and the fuel surface are not polarized to stop the transport of oxygen ions, it is necessary to transport the electrons from the fuel side to the oxygen side. The electrolyte transports the oxygen ions, but it is an electrical insulator, so electrons cannot pass through the electrolyte. However, when using suitable electrodes on each of the oxygen and fuel surfaces, i.e. an anode at the fuel surface and a cathode at the oxygen surface, and an electrical connection between them, an electrical current flows from the anode to the cathode. The driving force is an electrical potential (i.e. voltage) generated by the difference in oxygen concentration across the membrane, according to the following equation, and electrical power is generated according to the following equation:

[0011]

[0012] where E is the SOFC voltage (V), E max is the maximum voltage (V) given by the Nernst equation, i max is the maximum current density (for a given fuel flow), η f is the fuel utilization factor, and r1 and r2 are the ionic and electronic specific resistances of the electrolyte, respectively. This equation is validated and found to be suitable for optimization and sensitivity studies in plant level modeling of various systems with SOFCs.

[0013] To obtain a high oxygen flux through the membrane, and thus a high current, the electrolyte and electrodes are heated to a low temperature in the range of about 400°C to about 500°C, or to a medium temperature in the range of about 500°C to about 750°C, or to a high temperature in the range of about 750°C to about 1000°C.

[0014] The electrodes in SOFCs should exhibit several functions. First, they should exhibit good electronic conductivity under operating conditions, especially at high temperatures, and a high oxygen partial pressure at the cathode and a low oxygen partial pressure at the anode when the SOFC comprises an oxygen ion conducting electrolyte. They should also exhibit good thermal expansion matching with the chosen electrolyte. In addition, they should not form insulating or resistive reaction products with the electrolyte. Furthermore, they should not melt or evaporate excessively under operating conditions, and provide sufficient stability so that they do not have to be replaced too frequently to minimize operating costs. The electrodes should be mixed ionic and electronic conductors (MIEC), i.e. they should simultaneously conduct oxygen ions in an oxygen ion conducting membrane or protons in a proton electrolyte membrane, and electrons.

[0015] With respect to the anode, the anode should be a good oxidation catalyst.

[0016] SOFCs based on both zirconium oxide and cerium oxide electrolytes typically use a nickel-based composite anode, where the second phase is either yttrium-stabilized zirconium oxide (YSZ) or gadolinium-doped cerium oxide (CGO). Metallic nickel provides electronic conductivity, while YSZ or CGO provides some ionic conductivity.

[0017] Two other components of a planar SOFC are the interconnect plate and the current collector. These components are particularly important in mounting the SOFCs together to form an SOFC stack. Figure 2 The schematic diagram of the SOFC is shown. Like the cathode and anode electrodes, the interconnect needs to be well-matched to the thermal expansion of the selected electrolyte.

[0018] The interconnects are hermetically sealed, electronically conductive plates that separate and guide the oxygen and fuel gas flows. For high-temperature operation (>900°C), these are made of electronically conductive ceramics such as La. 1-X Sr X It is composed of CrO3. The driving force behind the development of electrolytes and thin-film electrolytes with high oxygen transport is to enable operation at temperatures where metal interconnects can be used. To ensure particularly good electrical contact between the electrodes and interconnects, current collectors composed of metal meshes or grids are most commonly used.

[0019] SOFCs operating with pure hydrogen as fuel and air as oxidant can achieve yields of approximately 60% and exhibit high efficiency (up to 2 W / cm³). 2 It boasts a peak power density and can operate at 400°C to 500°C (Minh), making it a leading high-temperature solid oxide fuel cell for the 21st century. st Century), 2016.

[0020] like Figure 3 As illustrated, multiple of these basic SOFC units can be assembled together to produce a stack; 50 to 100 is not unusual. Large SOFC systems are modular and consist of multiple individual stacks. Each stack can generate up to several kW of power. The largest SOFC modules currently produce approximately 300 kW.

[0021] The use of ammonia as a fuel in SOFCs is known. As a fuel it has some positive aspects. It requires almost no handling, such as purification, reforming or humidification, compared to hydrocarbon fuels. There is no risk of carbon deposition on the anode as with hydrocarbons. When operated in a typical SOFC with a nickel-based anode, it gives a similar electrical power output as a SOFC operated with a hydrocarbon fuel, because ammonia is cracked into hydrogen and nitrogen on the nickel-based anode before it is oxidized. In fact, a standard ammonia SOFC is a hydrogen SOFC, because ammonia is cracked into nitrogen and hydrogen (Dekker & Rietveld, 6th SOFC Forum, June 28 - July 2, 2004, Lucerne (CH)). This cracking reaction is so efficient that a standard ammonia SOFC is considered to be a power generation system that produces a lower amount of nitrogen oxides.

[0022] If the three possible products from ammonia oxidation, i.e. nitrogen, nitrous oxide and nitric oxide, are considered according to the following reactions:

[0023] 4NH3+ 3O2→ 2N2+ 6H2O -1267 kJ.mol -1

[0024] 4NH3+ 4O2→ 2N2O + 6H2O -1103 J.mol -1

[0025] 4NH3+ 5O2→ 4NO + 6H2O -906 kJ.mol -1

[0026] It can be concluded that nitrogen is the thermodynamically most favorable product, so if the aim of the SOFC is to produce maximum power, nitrogen is the desired product of ammonia oxidation. However, for the production of nitric acid, ammonia needs to be selectively oxidized to nitric oxide. This means that the thermal cracking of ammonia to nitrogen and hydrogen on its way to the SOFC, as well as the catalytic cracking of ammonia on the anode, must be avoided. Basically, a new type of anode must be designed to direct the oxidation of ammonia to nitric oxide, rather than to nitrogen or nitrous oxide.

[0027] BACKGROUND

[0028] US 4,272,336 (Massachusetts Institute of Technology) discloses a method and apparatus for forming nitric oxide (NO) from ammonia (NH3) by an electrolytic cell while recovering electrical energy directly. It teaches that a typical oxygen ion-conducting solid electrolyte is a solid solution formed between an oxide containing divalent and trivalent oxygen ions such as CaO, Sc2O3, Y2O3, La2O3, etc. and an oxide containing tetravalent oxygen ions such as ZrO2, ThO2 and CeO2. A noble metal catalyst such as Pt is suggested as an electrode. No indication is provided in US 4,272,336 about the achieved conversion of ammonia to nitric oxide. In C. E. Teague, The High Ammonia Fuel Cell, Massachusetts Institute of Technology, 1981, page 39, a conversion of ammonia to nitric oxide of about 24% is achieved at a corresponding power density of about 0.2 mW / cm2. 2

[0029] Dekker & Rietveld (6th SOFC Forum, June 28 - July 2, 2004, Lucerne (CH), page 1524) disclose the oxidation of ammonia to N2 by a SOFC, wherein only traces of nitrogen oxides are produced as by-products. Instead of being used as an anode, lanthanum strontium brenstedite (strontium lanthanum manganate, LSM) is used as a cathode: the anode is a Ni / YSZ composite anode containing nickel.

[0030] US 20160079623 (Korea Institute of Industrial Technology) relates to a method for preparing a solid electrolyte material for a SOFC. Hydrogen gas is used as a fuel. It mentions a SOFC comprising a NiO / YSZ anode, a solid electrolyte (YSZ) and a LSM / YSZ cathode. US 20160079623 suggests replacing YSZ with a high ionic conductive solid electrolyte material. Specifically, ytterbium scandium stabilized zirconia (YbScSZ) is suggested as an alternative solid electrolyte material.

[0031] Cao et al. (ChemCatChem 94, 6, pages 1190-1194, 2014) disclose the use of a fully dense mixed-conducting lanthanum strontium cobalt ferrite (strontium lanthanum cobalt ferrite, LSCF) membrane for the oxidation of ammonia to NO. No electricity is generated in the process according to the disclosure of Cao et al. while transporting electrons from the fuel side or membrane interior to the air side.

[0032] ​US 2017 / 062855 (Kceracell Co. Ltd.) discloses a SOFC comprising a ceria electrolyte. The ceria electrolyte comprises gadolinium (Gd) or samarium (Sm) co-doped with ytterbium (Yb) and bismuth (Bi) and exhibits low temperature sinterability. LSCF is disclosed as a commonly used cathode material and is a MIEC. The ceria electrolyte is specifically used as a buffer layer between a zirconia electrolyte and a MIEC electrode. Ceria-based electrolytes are commonly used in combination with MIEC cathode materials such as LSCF because unlike zirconia electrolytes, they do not react with MIEC cathodes. In particular, ceria-based electrolytes comprising Ce02and 5 to 10 mol% of Gd203or Sm203(Gd or Sm doped Ce02) have high oxygen ion conductivity and do not react with MIEC cathodes such as LSCF, and are thus widely used as a material for a buffer layer between a zirconia (Zr02)-based electrolyte membrane and a MIEC cathode layer of a SOFC. A SOFC comprising a samarium-doped ceria electrolyte is specifically disclosed.

[0033] Hartley et al. (Catalysis Today 55 (2000), pp. 197-204) disclose perovskite materials La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3(LSCF-6428) for simultaneous use as anode and cathode were compared for catalytic activity towards methane oxidation and for susceptibility to deactivation by carbon deposition.

[0034] Jamale et al. (Journal of Materials Science. Materials in Electronics, 2016, Vol. 27, Issue 1, pp. 795-799) disclose fabrication and characterization of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF)-Ce 0.9 Gd 0.1 O 1.95 (GDC) composite thick films for anode-supported solid oxide fuel cells.

[0035] Lai et al. (Journal of Power Sources, 2011, Vol. 196, Issue 4, pp. 1826-1832) disclose nanostructured La 0.6 Sr 0.4 Co 0.8 Fe 0.2O3 / Y 0.08 Zr 0.92 O 1.96 / La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O3(LSCF / YSZ / LSCF) symmetry thin film solid oxide fuel cell.

[0036] Xu et al. (Journal of Materials Science & Technology, 2017, vol. 33, no. 11, pp. 1329-1333) disclose La 0.4 Sr 0.6 Co 0.2 Fe 0.7 Nb 0.1 O 3-δ electrode fabrication and optimization.

[0037] Lu et al. (Electrochimica Acta, 2019, vol. 323, p. 134857) disclose a highly efficient and stable symmetric electrode La 0.6 Sr 0.4 Co 0.2 Fe 0.7 Mo 0.1 O 3-δ for direct hydrocarbon solid oxide fuel cells.

[0038] JP 2017 082670 A relates to an internal combustion engine including an engine operated by burning a hydrocarbon fuel, a combustion device for combusting combustibles in exhaust gas flowing through an exhaust gas flow path in which exhaust gas generated by the engine flows, and a nitrogen oxide for removing nitrogen oxides.

[0039] US2019 / 284052 discloses a process for nitric acid production, the process comprising synthesizing ammonia in an ammonia synthesis loop by catalytic conversion of a make-up gas comprising hydrogen and nitrogen, wherein the off-gas is used as a source of nitrogen for obtaining the make-up gas.

[0040] WO2020 / 035521A1 discloses a novel concept providing a high energy and material efficient process and system for nitric acid production, wherein the process and system for nitric acid production, in particular integrated with a process and system for ammonia production, is configured to recover a substantial amount of energy (in particular in the form of electricity) from consumed ammonia, while maintaining a high nitric acid recovery in the conversion of ammonia to nitric acid. It does not disclose a solid oxide fuel cell (SOFC).

[0041] LIST OF DRAWINGS

[0042] Figure 1 a schematic diagram of a SOFC is shown

[0043] Figure 2 a SOFC unit is shown which can be repeated to form a SOFC stack;

[0044] Figure 3 a SOFC stack is shown

[0045] Figure 4 a schematic diagram of an embodiment of the method of the disclosure is shown in which steam is introduced in the cathode side

[0046] Figure 5 a schematic diagram of an embodiment of the method of the disclosure is shown in which the SOFC is alternately operated in an oxygen consuming mode using air (SOFC mode) and as a water electrolyzer using steam (SOEL mode).

[0047] Figure 6 nitric oxide yields as a function of power density for different anode materials are shown SUMMARY

[0048] According to a first aspect of the disclosure, a method for operating a SOFC for the joint production of electricity and a substantial amount of nitric oxide (NO) is disclosed. The method comprises the steps of:

[0049] a) providing a SOFC comprising an anode side comprising a gas permeable solid anode, a gas inlet and a gas outlet, a cathode side comprising a gas permeable solid cathode, a gas inlet and a gas outlet, and a fully dense solid electrolyte separating the cathode side from the anode side;

[0050] b) introducing an oxygen containing gas into the inlet of the cathode side of the SOFC;

[0051] c) introducing a stream of ammonia containing gas into the inlet of the anode side of the SOFC;

[0052] d) collecting nitric oxide at the outlet of the anode side; and

[0053] e) collecting an electric current flowing between the anode side and the cathode side;

[0054] wherein the method is carried out at a temperature in the range of 500 to 800 °C, and

[0055] wherein the anode comprises a composition A 1-X A’ X B 1-Y B’ Y O 3-δwherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3, and wherein the cathode comprises the composition A 1-X A' X B 1-Y B' Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3.

[0056] According to a second aspect of the present disclosure, a SOFC for the combined production of electricity and large amounts of nitric oxide (NO) is disclosed. The SOFC comprises:

[0057] - an anode side comprising a gas permeable solid anode, a gas inlet and a gas outlet;

[0058] - an ammonia source in fluid communication or connected with the gas inlet of the anode side;

[0059] - a cathode side comprising a gas permeable solid cathode, a gas inlet and a gas outlet;

[0060] - a fully dense electrolyte separating the anode side from the cathode side, in particular having a composition selected from the group of:

[0061] (a) Ce 1-X Gd X O 2-δ wherein X is in the range of 0.1 to 0.2 and wherein δ is in the range of 0.05 to 0.1, and

[0062] (b) Zr 1-(X+Y) Sc X M Y O 2-δ wherein M is Al, Yb, Ce, wherein x is in the range of 0.03 to 0,2 and wherein Y is in the range of 0.001 to 0.01 and wherein δ is in the range of 0.01 to 0.06;

[0063] - means for heating the SOFC to a temperature in the range of 550 to 800 °C; and

[0064] - means for collecting the electric current flowing between the anode side and the cathode side;

[0065] the anode comprises a composition A 1-X A' x B 1-Y B' Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3. The cathode comprises a composition A 1-X A' X B 1-Y B' Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3.

[0066] According to a third aspect of the present disclosure, a SOFC stack is disclosed, the SOFC stack comprising at least two or more SOFCs according to the present disclosure.

[0067] According to a fourth aspect of the present disclosure, a system for the production of nitric acid is disclosed. The system comprises:

[0068] - a Haber-Bosch unit comprising an outlet for transporting ammonia produced by the unit;

[0069] - means for heating the ammonia produced by the Haber-Bosch unit to a temperature in the range of 500 to 800 °C, such that gaseous ammonia is collected at the outlet of the means for heating;

[0070] - a SOFC stack according to the present disclosure, wherein the inlet of the anode side of the cell is fluidly connected to the outlet of the means for heating;

[0071] - means for transferring nitric oxide (NO) delivered at the outlet of the anode side of the cells of the stack to an oxidation section of a nitric acid production unit supplied with an oxygen-containing gas or comprising an ammonia oxidation catalyst, wherein the nitric oxide is oxidized to a nitrogen oxide gas, in particular to nitrogen dioxide and dinitrogen tetroxide; and

[0072] - means for transferring the nitrogen oxide gas to a nitric acid absorption column, wherein the nitrogen oxide gas is absorbed into an aqueous solution, thereby producing nitric acid.

[0073] According to a fifth aspect, a method for producing nitric acid is disclosed. The method comprises the following consecutive steps:

[0074] a) producing ammonia in a Haber-Bosch unit;

[0075] b) collecting the produced ammonia at the outlet of the Haber-Bosch unit;

[0076] c) heating the ammonia produced by the Haber-Bosch unit to a temperature in the range of 500 to 800 °C, such that gaseous ammonia is collected at the outlet of the means for heating;

[0077] d) transferring the ammonia to the inlet of the anode side of the SOFC of the present disclosure, in particular to the inlet of the anode side of the cells of the SOFC stack of the present disclosure;

[0078] e) producing nitric oxide (NO) according to the method for the joint production of electricity and nitric oxide of the present disclosure;

[0079] f) collecting the produced nitric oxide at the outlet of the SOFC of the present disclosure, in particular at the outlet of the anode side of the cells of the stack;

[0080] g) transferring the produced nitric oxide to an oxidation section of a nitric acid production unit supplied with an oxygen-containing gas or comprising an ammonia oxidation catalyst;

[0081] h) oxidizing the nitric oxide to a nitrogen oxide gas, in particular to nitrogen dioxide and dinitrogen tetroxide;

[0082] i) transferring the nitrogen oxide gas to an absorption section of the nitric acid production unit; and

[0083] j) absorbing the nitrogen oxide gas into an aqueous solution to produce nitric acid.

[0084] According to a sixth aspect of the present disclosure, the use of a SOFC according to the present disclosure or a SOFC stack according to the present disclosure for the joint production of electricity and a substantial amount of nitric oxide (NO) is disclosed.

[0085] According to a seventh aspect of the present disclosure, the use of an anode comprising a composition A 1- X A’ X B 1-Y B’ Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A’ is selected from the group consisting of Ca, Sr and Ba, B and B’ are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3, in a SOFC according to the present disclosure, in a SOFC stack according to the present disclosure, in a system for producing nitric acid according to the present disclosure, in a method for co-producing electricity and nitric oxide according to the present disclosure or in a method for producing nitric acid according to the present disclosure. DETAILED DESCRIPTION

[0086] Throughout the description and claims of this specification, the words "comprise", "comprising", "consist", "consisting", "include", "including" and "contain", "containing" mean "including but not limited to" and they are not intended to (and they do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context requires otherwise. In particular, where the indefinite article is used, this is to be understood in the manner set out in the preceding Sentence.

[0087] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the disclosure are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All features and / or steps disclosed in the application file, including any accompanying claims, abstract and drawings, can be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The disclosure is not limited to the details of any foregoing embodiments. The disclosure extends to any novel one, or any novel combination, of the features disclosed in the application file, including any accompanying claims, abstract and drawings, or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0088] Numerical values recited in a digital range include all values and fractions of the range, as well as the recited endpoints. The terms "in the range of", or "from... to...", or between, as used when referring to a range of measurable values such as parameters, amounts, time periods, and the like, is meant to include the boundary values.

[0089] As defined herein, the aqueous solution is selected from the group consisting of water, or up to 0.5 wt% nitric acid in water, or up to 1 wt% ammonium nitrate in water, or a combination thereof.

[0090] As defined herein, air is a gas mixture comprising about 78 vol% nitrogen and about 21 vol% oxygen, further comprising about 0.9 vol% argon, about 0.04 vol% carbon dioxide and small amounts of other gases. Air generally also contains some steam.

[0091] According to a first aspect of the present disclosure, a method for operating a solid oxide fuel cell for the co-production of electricity and a quantity of nitric oxide (NO) is disclosed. The method comprises the steps of: a) providing a SOFC comprising: an anode side comprising a gas permeable solid anode, a gas inlet and a gas outlet, a cathode side comprising a gas permeable solid cathode, a gas inlet and a gas outlet, and a fully dense solid electrolyte separating the cathode side from the anode side; b) introducing an oxygen-containing gas into the inlet of the cathode side of the SOFC; c) introducing an ammonia-containing gas stream into the inlet of the anode side of the SOFC; d) removing a gas stream comprising a quantity of nitric oxide at the outlet of the anode side, or collecting nitric oxide, in particular an ammonia-containing gas stream, at the outlet of the anode side; and e) collecting an electric current flowing between the anode side and the cathode side. One advantage of using ammonia as a fuel is that it is a clean fuel: unlike other fuels such as hydrocarbon fuels, no carbon deposition is observed during the oxidation of the fuel, and no carbon dioxide is generated, which limits the greenhouse gas emissions originating from the process. Possible ammonia-containing gases include, but are not limited to, pure ammonia gas, or a mixture of ammonia gas and steam, or a mixture of ammonia gas and an inert gas such as nitrogen or argon, or a mixture of ammonia gas and several inert gases, or a mixture of ammonia gas, steam and one or more inert gases. It should be understood that depending on the composition of the ammonia-containing gas, steam and / or inert gas can be collected at the outlet of the anode side together with the nitric oxide, as well as ammonia gas that has not been converted into nitric oxide.

[0092] The method is carried out at a temperature in the range of 500 to 800 °C. The cathode comprises a material suitable for reducing oxygen. The anode comprises a composition A 1-X A’ X B 1-Y B’ Y O 3-δwherein A is selected from the group consisting of La, Y, Sm, Pr, Nd, and Gd, A' is selected from the group consisting of Ca, Sr, and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr, and V or mixtures thereof, the first variable X is in the range of 0.05 to 0.6 and particularly 0.1 to 0.4, the first variable Y is in the range of 0 to 1, and the first variable delta is in the range of 0.025 to 0.3. Particularly, A is La.

[0093] Surprisingly, the inventors found that at least 80% conversion of ammonia to nitric oxide can be achieved by applying the method of the present disclosure. In addition, the method of the present disclosure allows for running the SOFC with an electrical resistance as low as 1 Ω.cm -2 , which means that oxygen ions are effectively transported from the cathode to the anode and ammonia is effectively converted to nitric oxide. When the electrical resistance is in the range of 10 to 15 Ω.cm -2 , additional power can be supplied to increase the transport of oxygen ions from the cathode to the anode, thereby achieving at least 80% conversion of ammonia to nitric oxide. Accordingly, the skilled person can optionally supply additional power to the cell.

[0094] The anode comprises a perovskite composition having the general formula A 1-X A' X B 1-Y B' Y O 3-δ A and A' are large cations. A is selected from the group consisting of La, Y, Sm, Pr, Nd, and Gd, and A' is selected from the group consisting of La, Ca, Sr, or Ba. Particularly, A is La, and as the reduction potential of the perovskite composition comprised in the anode decreases, the stability of the anode increases, thereby facilitating the transport of oxygen ions through the composition and thus the conversion of ammonia to nitric oxide. B and B' are smaller cations. B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr, and V or mixtures thereof.

[0095] The oxidation state of the A, A', B, and B' cations has an influence on the electronic structure of the perovskite and thus on the ionic and electronic properties of the SOFC used in the method of the present disclosure. In order to maintain a neutral charge, decreasing the oxidation state of A' can for example result in an increase of the oxidation state of B, or result in a decrease of oxygen ion vacancies in the composition, thereby resulting in a decrease of ionic conductivity.

[0096] It has been found that an increase in the value of the first variable X in the above perovskite structure leads to an increase in the oxygen vacancy concentration, which can increase the oxygen ion mobility; this increase in ion conductivity is a positive effect to be taken into account when considering the perovskite composition. However, increasing the value of X also reduces the stability of the perovskite composition against reduction. Therefore, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4 to achieve the best ion and electronic conductivity, but at the same time achieve sufficient stability of the perovskite composition.

[0097] B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof. It has been found that an increase in the amount of Co and Fe leads to an increase in ion conductivity, however also leads to a decrease in the stability of the perovskite composition against reduction. By replacing a part of Co and / or Fe with Cr, Mn, V or combinations thereof, the stability of the perovskite composition is increased. By increasing the content of Co and / or and / or Mn and / or Cr, the electronic conductivity can be increased.

[0098] The ion conductivity is increased by increasing the gradient of the oxygen partial pressure between the anode and the cathode. Therefore, the more oxygen-rich the oxygen-containing gas introduced at the inlet of the cathode is, the higher the electronic conductivity is.

[0099] In particular, the cathode comprises a composition A 1-X A' X B 1-Y B' Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3. In particular, A' is Sr and Ca to reduce the reaction of the cathode with the oxygen-containing gas introduced in the inlet at the cathode side.

[0100] According to one embodiment of the method of the present disclosure, nitric oxide accounts for at least 10 wt% of the product or gas stream collected or removed at the outlet at the anode side, preferably 10% to 80%.

[0101] According to one embodiment of the method of the present disclosure, the method is carried out at a temperature in the range of 700 to 750 °C.

[0102] According to one embodiment of the method for the joint production of electricity and nitric oxide of the present disclosure, the anode and the cathode comprise a composition La 0.60 Sr 0.40 Co 0.20 Fe 0.80O3. It has been found that by using this particular perovskite composition, 76% conversion of ammonia to nitric oxide is achieved, compared to only 5% conversion of ammonia to nitric oxide using state of the art Pt anode and cathode. In addition, at a temperature of 750°C, a power density of 80 mW / cm 2 may be produced. In addition, the same anode and cathode perovskite composition reduces the operating costs by reducing the number of elements in the cell, thereby simplifying the cell.

[0103] According to one embodiment of the method for the co-production of electricity and nitric oxide according to the present disclosure, the oxygen containing gas is air, steam, oxygen, or a mixture of nitrogen and oxygen. By introducing air or a mixture of nitrogen and oxygen, after reduction in the cathode side, a gas with a reduced oxygen content is obtained, which can be fed to an air separation unit, where air is separated into its main components, nitrogen and oxygen; as the oxygen content of the gas fed to the air separation unit is reduced, the air separation unit requires less work to separate oxygen from nitrogen.

[0104] According to one embodiment of the method for the co-production of electricity and nitric oxide according to the present disclosure, the method is carried out at a temperature in the range of 500 to 750°C, and wherein the electrolyte is a ceria-based electrolyte. An advantage of such a medium temperature operation is the increased stability of the perovskite composition, thus reducing the costs associated with maintaining the anode. Operating the cell in the low range of 350 to 500°C or in the medium range of 500 to 750°C has several benefits. A first benefit is that lower cost materials can be used compared to dedicated alloys such as stainless steel. In addition, the stability of the electrodes is increased. Furthermore, at lower temperatures, the thermal expansion of the electrolyte should decrease, and the formation of resistive interfacial layers between the electrolyte and the electrodes and the interconnectors should decrease. Finally, operating in a lower temperature range enables the use of cheap ceria-based electrolytes. In particular, the composition of the electrolyte is Ce 1-X Gd X O 2-δ wherein the second variable X is in the range of 0.1 to 0.2, and wherein the second variable δ is in the range of 0.05 to 0.1. This ceria electrolyte is particularly suitable for cell operating temperatures in the range of 500 to 750°C, as at higher temperatures, some electronic conductivity can exist, reducing the cell efficiency.

[0105] According to one embodiment of the method for the co-production of electricity and nitric oxide according to the present disclosure, the method is carried out at a temperature in the range of 750 to 800°C, and the electrolyte is a zirconia-based electrolyte. The oxygen ion conductivity in the electrolyte increases with increasing temperature, thus the electrode resistance decreases, which leads to the production of additional power.

[0106] In particular, the composition of the electrolyte is Zr1-(X+Y) Sc X M Y O 2-δ wherein M is Al, Yb, Ce, wherein the third variable X is in the range of 0.03 to 0.2, and wherein the second variable Y is in the range of 0.001 to 0.01, and wherein the third variable delta is in the range of 0.01 to 0.06. Such electrolytes provide satisfactory oxygen ion transport and are particularly suitable at higher temperatures in the range of 750 to 800 °C. The co-dopant M is added to suppress the transition from cubic to rhombohedral phase which occurs at temperatures of 750 to 900 °C and causes mechanical instability and a decrease in ionic conductivity. In particular, the electrolyte is a 50 to 200 micrometer self-supporting membrane on the cathode or anode. By having a thinner membrane, the oxygen flux is increased when the oxygen transport through the electrolyte is directly related to the oxygen potential gradient. In particular, the self-supporting electrolyte membrane has a thickness of 100 to 150 pm and is supported on a cathode or anode with a thickness of about 20 to 50 pm. In particular, the thin film electrolyte is supported on the cathode.

[0107] One alternative to the anode or cathode thickness is a thickness higher than 500 pm, such that it can act as a physical support for a thin film electrolyte with a thickness in the range of 5 to 30 pm. The rare element Scandium is more expensive. However, for temperatures above 750 °C, such self-supporting thin film, scandium doped electrolytes provide satisfactory oxygen ion transport at a reasonable cost.

[0108] According to one embodiment of the method for the joint production of electricity and nitric oxide according to the present disclosure, the steam is the oxygen containing gas introduced in step a) in the inlet on the cathode side and the hydrogen is collected at the outlet of the cathode. By producing hydrogen at the cathode, a useful fuel is generated which can for example be further used for ammonia production in a Haber-Bosch unit. In fact, and as shown in Figure 4 by producing hydrogen, additional ammonia can be produced (such as using a Haber-Bosch unit) which can be fed as a fuel to the anode side of the cell. Thus, the method simultaneously produces nitric oxide and hydrogen which are required in the production of nitric acid and ammonia, respectively.

[0109] Furthermore, the use of steam as oxygen-containing gas and the production of hydrogen are both functions achieved in water electrolysis using a water electrolyzer. This means that the method of the present disclosure also allows water electrolysis, and the system used in the method can be used not only as a SOFC, but also as a water electrolyzer when steam is used as the oxygen-containing gas. In addition, the use of steam and ammonia as feedstock gases on the cathode side and the anode side of the SOFC, respectively, enables the production of hydrogen using less power than in a conventional electrolyzer: the oxygen gradient created by the feeding of a gas richer in oxygen at the cathode side inlet than the gas fed at the anode side inlet generates a natural driven flux of oxygen ions from the cathode to the anode, resulting in the production of hydrogen, nitric oxide and electricity.

[0110] In particular, when steam is used as the oxygen-containing gas, it is recommended to supply a voltage in the range of 0.5 to 0.6 V to the cell to promote the flux of oxygen ions from the cathode, thereby promoting the production of nitric oxide on the anode side.

[0111] In particular, steam is the oxygen-containing gas introduced in the inlet on the cathode side in step a), hydrogen is collected at the outlet of the cathode, the oxygen-containing gas introduced in the inlet on the cathode side is alternated between air and steam, and the gas collected at the outlet on the anode side is alternated between oxygen-depleted air and hydrogen.

[0112] With reference to Figure 5As mentioned above, the method of the present disclosure also allows for water electrolysis, and the system used in the method can be used not only as a solid oxide fuel cell, but also as a water electrolyzer when using steam as the oxygen containing gas. As a reversible unit, the same unit is able to switch between fuel cell mode and electrolyzer mode simply by changing the feed at the cathode from air to steam. Such switching is feasible because the cathode used is able to handle both the strong oxidizing conditions when air is supplied and the strong reducing conditions when hydrogen is produced. One major challenge for beyond water electrolysis to produce hydrogen without producing carbon dioxide is the dynamic load and intermittency, referred to as flexibility, which means that the plant has to be started and stopped depending on the energy input, i.e. green energy supplied by, for example, the sun or the wind. Due to the limited flexibility of the plant, energy storage in the form of batteries or hydrogen storage is needed as the most realistic option, both of which are very expensive. In addition, the lower utilization of the electrolyzer makes the conventional concept quite expensive and shortens the lifetime of the electrolyzer, especially when it is operated at 750 to 900 °C. Now, using the method of the present disclosure, only ammonia and steam storage is needed to produce both nitric oxide and hydrogen simultaneously; both ammonia and steam are relatively inexpensive and produce a constant load of nitric oxide, regardless of fluctuations in energy input. In addition, using the method of the present disclosure, the degradation problem associated with the discontinuous operation of high temperature water electrolyzers is overcome due to the continuous production in the presence of ammonia storage: the operating cost is reduced with full utilization of the plant’s equipment.

[0113] In particular, air is the oxygen containing gas introduced in step a) in the inlet at the cathode side, resulting in the production of oxygen depleted air at the outlet of the cathode, and the oxygen depleted air produced at the outlet of the cathode is fed to the air separation unit. In particular, a mixture of nitrogen and oxygen is the oxygen containing gas introduced in step a) in the inlet at the cathode side, resulting in the production of a mixture of nitrogen and oxygen at the outlet of the cathode, which has a reduced oxygen content with respect to the gas mixture introduced at the inlet of the cathode. This mixture of nitrogen and oxygen collected at the outlet of the cathode is fed to the air separation unit.

[0114] As mentioned above, by introducing air, after reduction in the cathode side, a gas with reduced oxygen content is obtained, which can be fed to the air separation unit; because the oxygen content of the gas fed to the air separation unit is reduced, the air separation unit needs less work to separate oxygen from nitrogen. In addition, the treatment of the air with reduced oxygen content in the air separation unit will result in a higher flux of nitrogen to the Haber Bosch unit.

[0115] According to a second aspect of the present disclosure, a SOFC for the joint production of electricity and large amounts of nitric oxide (NO) is disclosed. The SOFC comprises: an anode side comprising a gas permeable solid anode, a gas inlet and a gas outlet; an ammonia source in fluid communication or connection with the gas inlet of the anode side; a cathode side comprising a gas permeable solid cathode, a gas inlet and a gas outlet; a fully dense electrolyte separating the anode side from the cathode side, in particular having a composition selected from the group consisting of: (i) Ce 1-X Gd X O 2-δ wherein X is in the range of 0.1 to 0.2 and wherein δ is in the range of 0.05 to 0.1 and (ii) Zr 1-(X+Y) Sc X M Y O 2-δ wherein M is Al, Yb, Ce, wherein x is in the range of 0.03 to 0.2 and wherein Y is in the range of 0.001 to 0.01 and wherein δ is in the range of 0.01 to 0.06; and means for heating the SOFC to a temperature in the range of 500 to 800 °C; and means for collecting an electrical current flowing between the anode side and the cathode side.

[0116] The cathode comprises a material suitable for reducing oxygen in an oxygen containing gas and the anode comprises a composition A 1-X A’ X B 1-Y B’ Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A’ is selected from the group consisting of Ca, Sr and Ba, B and B’ are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.025 to 0.3.

[0117] In particular, the cathode comprises a composition A 1-X A’ X B 1-Y B’ Y O 3-δ wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A’ is selected from the group consisting of Ca, Sr and Ba, B and B’ are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6 and in particular 0.1 to 0.4, Y is in the range of 0 to 1 and δ is in the range of 0.25 to 0.3.

[0118] According to one embodiment of the SOFC of the present disclosure, the anode and the cathode comprise a composition La 0.60 Sr0.40 Co 0.20 Fe 0.80 O3.

[0119] In particular, the electrolyte is Ce 1-X Gd X O 2-δ wherein X is in the range of 0.1 to 0.2, and wherein δ is in the range of 0.05 to 0.1, and the means for heating the cell allow heating to a temperature in the range of 500 to 750 °C.

[0120] In particular, the electrolyte is Zr 1-(X+Y) Sc X M Y O 2-δ wherein M is Al, Yb, Ce, wherein x is in the range of 0.03 to 0.2, and wherein Y is in the range of 0.001 to 0.01, and wherein δ is in the range of 0.01 to 0.06, and the means for heating the cell allow heating to a temperature in the range of 750 to 800 °C.

[0121] Suitable sources of ammonia are known in the art. For example, any ammonia container or ammonia reservoir

[0122] According to one embodiment of the SOFC of the present disclosure, the SOFC further comprises means for reacting the nitric oxide in fluid communication with the outlet of the anode side.

[0123] According to one embodiment of the SOFC of the present disclosure, the SOFC further comprises means for reacting the nitric oxide in fluid communication or connection with the outlet of the anode side, and the means for reacting the nitric oxide is an oxidation section of a nitric acid production unit supplied with an oxygen-containing gas or comprising an ammonia oxidation catalyst, wherein the nitric oxide is oxidized to a nitrogen oxide gas, in particular to nitrogen dioxide and dinitrogen tetroxide.

[0124] According to one embodiment of the SOFC of the present disclosure, the SOFC further comprises an oxidation section of a nitric acid production unit supplied with an oxygen-containing gas or comprising an ammonia oxidation catalyst, wherein the nitric oxide is oxidized to a nitrogen oxide gas, in particular to nitrogen dioxide and dinitrogen tetroxide, in fluid communication with the outlet of the anode side and a nitric acid absorption column, wherein the nitrogen oxide gas produced in the oxidation section is absorbed into an aqueous solution. Using the SOFC of the present disclosure, nitric acid can thus be produced without using an ammonia oxidation burner as in a conventional nitric acid production unit.

[0125] According to one embodiment of the SOFC of the present disclosure, the outlet of the cathode is in fluid communication or connection with an air separation unit.

[0126] According to a third aspect of the present disclosure, a SOFC stack is disclosed, comprising at least two or more cells of the present disclosure. In particular, in addition to combining SOFCs to obtain a SOFC stack, a person skilled in the art can directly combine SOFC stacks to achieve the necessary amount of production of nitric oxide and electricity.

[0127] The stack can comprise for example 50 cells. The cells can be sealed by melting a glass-ceramic seal or welding a metal support. Once sealed, it cannot be opened or repaired in case of failure of a single cell. In order to avoid problems such as high resistance in the entire stack due to delamination or coking of the electrodes in only a single cell, it is necessary to ensure, as mentioned above, that the components of the unit cells replicated to form the stack, in particular the electrodes, have sufficient resistance.

[0128] According to a fourth aspect of the present disclosure, a system for the production of nitric acid is disclosed. The system comprises: a Haber-Bosch unit having an outlet for collecting the ammonia produced by the unit; means for heating the ammonia produced by Haber-Bosch to a temperature in the range of 500 to 800°C, so that gaseous ammonia is collected at the outlet of the means for heating; a SOFC of the present disclosure, in particular a SOFC stack of the present disclosure, wherein the inlet of the anode side of the cells is in fluid communication or connected to the outlet of the means for heating the ammonia; means for transferring the nitric oxide collected at the outlet of the anode side of the cells of the stack to an oxidation section of a nitric acid production unit supplied with an oxygen-containing gas or comprising an ammonia oxidation catalyst, wherein the nitric oxide (NO) is oxidized to a nitrogen oxide gas, in particular to nitrogen dioxide and dinitrogen tetroxide; and means for transferring the nitrogen oxide gas to a nitric acid absorption column, wherein the nitrogen oxide gas is absorbed into an aqueous solution, thereby producing nitric acid. In particular, the ammonia gas produced by the Haber Bosch unit is heated by a heat exchange system in which the heat is provided by an exothermic reaction in the ammonia production system belonging to the Haber Bosch unit, or by the oxidation section, or by the absorption of the nitrogen oxide gas in the absorption column. Thus, the system is energy efficient and the heat recovered from the production of ammonia or nitric acid is used in the solid oxide fuel cell to heat the ammonia produced by the Haber Bosch unit to the temperature required for its conversion to nitric oxide.

[0129] In particular, a SOFC stack is used in the system for the production of nitric acid of the present disclosure, since this allows the production of nitric acid on an industrial scale, producing from 100 to 2800 tons of nitric acid per day. Nonetheless, it is clear to a person skilled in the art that the use of a single SOFC also leads to the production of nitric acid.

[0130] Thus, by taking advantage of a system producing simultaneously nitric oxide and hydrogen, the system of the disclosure allows the combination of a high temperature water electrolyzer and an ammonia oxidation combustor (i.e. a unit in which ammonia is oxidized to nitric oxide in a nitric acid plant) in a single unit. The oxidation section and the absorption section of the nitric acid plant are then further integrated to produce nitric acid from the nitric oxide produced by this single unit. Moreover, as mentioned above, the air separation unit can also be integrated by recycling the oxygen-depleted air at the outlets on the cathode side to the air separation unit, and as mentioned above, energy will be saved when operating the air separation unit. Alternatively, it is conceivable to use a lower capacity air separation unit.

[0131] In one particular embodiment, the system further comprises an ammonia combustor located downstream of the outlets on the anode side of the cells of the stack, thus in fluid communication with the outlets, and means for transferring the gases collected at those outlets to the ammonia combustor. The ammonia combustor is designed to oxidize the ammonia that has not been oxidized to nitric oxide in the cells of the stack. Indeed, as mentioned above, the ammonia that has not been oxidized in the cells of the stack will be collected at the outlets on the anode side of the cells of the stack, together with the nitric oxide. In order to minimize the loss of ammonia in the process of production of nitric acid and to increase the amount of nitric acid produced, the unconverted ammonia is oxidized to nitric oxide in the ammonia combustor. The ammonia combustor can comprise well-known ammonia oxidation catalysts, such as platinum-based catalysts or perovskite-based catalysts. Alternatively, the ammonia combustor can comprise oxide-based catalysts. In addition, the ammonia combustor can be equipped with means for supplying an oxygen-containing gas, such as oxygen, air or oxygen-enriched air. The gases resulting from the oxidation in the combustor are then transferred to the oxidation section of the nitric acid plant, and thus the system further comprises means for achieving this transfer.

[0132] According to a fifth aspect of the disclosure, a method for producing nitric acid is disclosed. The method comprises the following successive steps: a) producing ammonia in a Haber-Bosch unit; b) collecting the produced ammonia at the outlet of the Haber-Bosch unit; c) heating the ammonia produced by the Haber-Bosch unit to a temperature in the range of 500 to 800°C, so that gaseous ammonia is collected at the outlet of the means for heating the ammonia; d) transferring the ammonia to the inlet on the anode side of the cells of a SOFC stack of the disclosure; e) producing nitric oxide according to the method for the joint production of electricity and nitric oxide of the disclosure; f) collecting the produced nitric oxide (NO) at the outlet on the anode side of the cells of the stack; g) transferring the produced nitric oxide to an oxidation section of a nitric acid production unit supplied with an oxygen-containing gas or comprising an ammonia oxidation catalyst; h) oxidizing the nitric oxide to nitrogen oxide gases, in particular to nitrogen dioxide and dinitrogen tetroxide; i) transferring the nitrogen oxide gases to an absorption section of the nitric acid production unit; and j) absorbing the nitrogen oxide gases into an aqueous solution to produce nitric acid.

[0133] In particular, a SOFC stack is used in the method for producing nitric acid according to the present disclosure, as this enables the production of nitric acid on an industrial scale. Nonetheless, it will be clear to the person skilled in the art that the use of a single SOFC also results in the production of nitric acid.

[0134] In one specific embodiment, the method further comprises the step of transferring the gas collected at the outlet on the anode side of the cells of the stack to an ammonia combustion chamber. The method further comprises the step of oxidizing in the ammonia combustion chamber the ammonia that has not been converted in the cells of the stack to nitric oxide. The gas resulting from the oxidation in the combustion chamber is then transferred to the oxidation section of the nitric acid plant. Optionally, the method further comprises the step of supplying an oxygen-containing gas, such as oxygen, air or oxygen-enriched air, to the ammonia combustion chamber by means for supplying an oxygen-containing gas, such as oxygen, air or oxygen-enriched air, to the ammonia combustion chamber. By supplying this oxygen-containing gas, the oxidation of ammonia in the ammonia combustion chamber is improved.

[0135] According to a sixth aspect of the present disclosure, use of a SOFC according to the present disclosure or a SOFC stack according to the present disclosure for the joint production of electricity and a large amount of nitric oxide is disclosed.

[0136] According to a seventh aspect of the present disclosure, use of an anode comprising a composition A 1-X A’ X B 1-Y B’ Y O 3-δ in a SOFC according to the present disclosure, in a SOFC stack according to the present disclosure, in a system for producing nitric acid according to the present disclosure, in a method for the joint production of electricity and nitric oxide according to the present disclosure or in a method for producing nitric acid according to the present disclosure is disclosed, said anode comprising a composition A

[0137] EMBODIMENTS

[0138] EMBODIMENT 1

[0139] Material

[0140] A 20 mm diameter cell consisting of a self-supporting scandium-doped zirconia electrolyte (SSZ) with a thickness of 150 pm was prepared. The anode consisted of a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δMixed oxides (LSCF) were prepared for both anode and cathode.

[0141] For comparison with the LSCF anode, a platinum anode prepared from conductive platinum paste was also prepared. After drying at 100°C, the anode was sintered at 1150°C for 2h. Initial testing using the pure platinum paste anode showed very high cell resistance due to the pore adhesion of the platinum layer to the smooth electrolyte surface.

[0142] Cell performance was measured in a test cell consisting of an alumina tube with internal gas distribution tubes and gold mesh and leads as current collectors for the anode. A second gold mesh and leads as current collectors for the cathode.

[0143] The alumina fixture allowed for uniform compression of the cell for sealing of the cell and the cell was sealed by heating in a tube furnace at 950°C for 12h. The fixture also contained a quartz tube allowing for the flow of oxygen in argon over the cathode. With the internal alumina tube, the fuel gas (in this case dilute ammonia) was fed over the anode. To improve the electrical contact between the gold mesh current collector and the anode and cathode, a paste layer of gold was applied to the mesh and electrodes.

[0144] Experimental Setup

[0145] Argon, oxygen and helium were supplied to the cathode. Ammonia was supplied to the anode from a gas cylinder containing 10% NH3 in argon. After the cell, the gas from the anode was further diluted to adjust the composition so that NH3, NO, NO2, N2O and H2O were within the calibration range of the FTIR analyzer.

[0146] A Gasmet CR4000 FTIR spectrometer was used to determine the conversion of ammonia and its oxidation selectivity to NO, NO2 and N2O. The gas lines between the cell anode and the FTIR analyzer and the argon dilution gas were trace heated to 180°C to prevent condensation of acids. The FTIR analyzer was calibrated for NH3, NO, NO2 and N2O using calibration gas mixtures. An Agilent Technologies 490 Micro Gas Chromatograph was used to detect O2 and helium in the exhaust from the anode to check that the cell had been successfully sealed.

[0147] A Gamry Reference 3000 potentiostat / impedance analyzer with ZView software developed by Scribner Associates Inc enabled the determination of the cell potential as a function of current through the cell and the power generated as a function of current through the cell.

[0148] Test program

[0149] After sealing and leakage tests, the battery was cooled from a sealing temperature of 950°C to 700°C. After testing at 700°C, the battery temperature was increased to 750°C for further testing. At each test temperature, ammonia concentrations of 1% and 10% were used. The ammonia-argon gas flow rate was varied from 9 ml / min to 150 ml / min; a lower flow rate was maintained for the 10% ammonia-argon gas feed.

[0150] The current flowing through the battery is controlled by a galvanometer. The LSCF-SSZ-LSCF battery has sufficiently low resistance that, given the oxygen potential gradient caused by the flow of oxygen-containing gas at the cathode and ammonia-containing gas at the anode, no applied potential is required to provide oxygen flux or current. Therefore, the battery generates electrical power.

[0151] 1Ω·cm was obtained at 800℃. -2 The battery resistance is low enough for a battery operating as a fuel cell. A current of 200 mA / cm² is applied to the battery before allowing the ammonia-argon feed. 2 This is to prevent excessive reduction of the anode before the test begins. Afterward, a flow of ammonia in argon gas is applied, and the current through the battery is controlled by a galvanometer.

[0152] result

[0153] Reference Figure 6 The LSCF anode can achieve a NO yield of up to 77% at 700°C, and 4 mW·cm⁻¹. -2 The power density was high. Testing of the battery with the platinum composite anode showed high ammonia conversion, but very low selectivity for the desired NO product: this is attributed to the cracking of ammonia on the Pt anode. A voltage was applied to achieve a power density greater than approximately 55 mA.cm⁻¹. -2 At a current density of 15%, only 15% of the converted ammonia is converted into nitric oxide.

[0154] in conclusion

[0155] The performance of this platinum anode is significantly worse than that of the LSCF anode when operating in fuel cell mode.

Claims

1. A method for operating a solid oxide fuel cell (SOFC) to jointly produce electricity and a gas stream containing nitric oxide (NO), the method comprising the steps of: a) Provide an SOFC, the SOFC comprising: an anode side including a permeable solid anode, a gas inlet and a gas outlet, a cathode side including a permeable solid cathode, a gas inlet and a gas outlet, and a fully dense solid electrolyte separating the cathode side from the anode side; b) Introducing oxygen-containing gas into the inlet on the cathode side of the SOFC; c) Introducing an ammonia-containing gas stream into the inlet on the anode side of the SOFC; d) Collecting nitric oxide at the outlet on the anode side, wherein nitric oxide accounts for at least 10% by weight of the NO-containing gas stream collected at the outlet on the anode side; and e) Collect the current flowing between the anode side and the cathode side; The method is performed at a temperature in the range of 500 to 800°C, and the anode comprises component A. 1-X A' X B 1- Y B' Y O 3-δ Wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd, and Gd; A' is selected from the group consisting of Ca, Sr, and Ba; B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr, and V or mixtures thereof; X is in the range of 0.05 to 0.6; Y is in the range of 0 to 1; and δ is in the range of 0.025 to 0.3; and wherein the cathode comprises the composition A. 1-X A' X B 1-Y B' Y O 3-δ A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6, Y is in the range of 0 to 1, and δ is in the range of 0.025 to 0.

3.

2. The method according to claim 1, wherein X in the composition of the anode is in the range of 0.1 to 0.

4.

3. The method according to claim 1, wherein in the composition of the cathode, X is in the range of 0.1 to 0.

4.

4. The method of claim 1, wherein nitric oxide accounts for 10% to 80% by weight of the NO-containing gas stream collected at the outlet on the anode side.

5. The method of claim 1, wherein the temperature is in the range of 700 to 750°C.

6. The method according to any one of claims 1 to 5, wherein the oxygen-containing gas is air, steam, oxygen, or a mixture of nitrogen and oxygen.

7. The method according to any one of claims 1 to 5, wherein the method is carried out at a temperature in the range of 500 to 750°C, and wherein the electrolyte is a cerium-based electrolyte.

8. The method according to claim 7, wherein the cerium-based electrolyte is Ce. 1-X Gd X O 2-δ , where X is in the range of 0.1 to 0.2, and where δ is in the range of 0.05 to 0.

1.

9. The method according to any one of claims 1 to 5, wherein the method is carried out at a temperature in the range of 750 to 800°C, and wherein the electrolyte is a zirconium oxide electrolyte.

10. The method according to claim 9, wherein the zirconium oxide electrolyte is Zr. 1-(X+Y) Sc X M Y O 2-δ , where M is Al, Yb, Ce, where x is in the range of 0.03 to 0.2, where Y is in the range of 0.001 to 0.01, and where δ is in the range of 0.01 to 0.

06.

11. The method of claim 9, wherein the electrolyte is a 50 to 200 micrometer self-supporting film on the cathode or the anode.

12. The method according to any one of claims 1 to 5, wherein the oxygen-containing gas introduced into the inlet on the cathode side in step b) is optionally vapor alternating with air, and hydrogen gas optionally alternating with oxygen-deficient air is collected at the outlet of the cathode.

13. The method of claim 12, wherein the oxygen-deficient air is fed into the air separation unit.

14. A SOFC for the combined production of electricity and a gas stream containing nitric oxide (NO), wherein NO accounts for at least 10% by weight of the NO-containing gas stream, the SOFC comprising: - Anode side, the anode side includes a permeable solid anode, a gas inlet and a gas outlet; - An ammonia source in fluid communication with the gas inlet on the anode side; - Cathode side, the cathode side includes a gas-permeable solid cathode, a gas inlet and a gas outlet; - A fully dense electrolyte that separates the anode side from the cathode side; - A device for heating the SOFC to a temperature in the range of 550 to 800°C; as well as - A device for collecting the current flowing between the anode side and the cathode side; The anode comprises component A 1-X A' X B 1-Y B' Y O 3-δ Wherein A is selected from the group consisting of La, Y, Sm, Pr, Nd, and Gd; A' is selected from the group consisting of Ca, Sr, and Ba; B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr, and V or mixtures thereof; X is in the range of 0.05 to 0.6; Y is in the range of 0 to 1; and δ is in the range of 0.025 to 0.3; and wherein the cathode comprises the composition A. 1-X A' X B 1-Y B' Y O 3-δ A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are each independently selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6, Y is in the range of 0 to 1, and δ is in the range of 0.025 to 0.

3.

15. The SOFC of claim 14, wherein X in the composition of the anode is in the range of 0.1 to 0.

4.

16. The SOFC of claim 14, wherein X in the composition of the cathode is in the range of 0.1 to 0.

4.

17. The SOFC of claim 14, wherein the fully dense electrolyte has a composition selected from the following: (i) Ce 1-X Gd X O 2-δ , where X is in the range of 0.1 to 0.2, and where δ is in the range of 0.05 to 0.1, and (ii) Zr 1-(X+Y) Sc X M Y O 2-δ , where M is Al, Yb, Ce, where X is in the range of 0.03 to 0.2, where Y is in the range of 0.025 to 0.01, and where δ is in the range of 0.01 to 0.

06.

18. The SOFC according to any one of claims 14 to 17, wherein (i) The electrolyte is composed of Ce 1-X Gd X O 2-δ Where X is in the range of 0.1 to 0.2, and where δ is in the range of 0.05 to 0.1, and where the device for heating the battery allows heating to a temperature in the range of 500 to 750°C, or (ii) The electrolyte is Zr 1-(X+Y) Sc X M Y O 2-δ , wherein M is Al, Yb, Ce, and wherein X is in the range of 0.03 to 0.2, and wherein Y is in the range of 0.001 to 0.01, and wherein δ is in the range of 0.01 to 0.06, and wherein the device for heating the battery allows heating to a temperature in the range of 750 to 800°C.

19. The SOFC according to any one of claims 14 to 17, the SOFC further comprising means for reacting nitric oxide in fluid communication with the gas outlet on the anode side.

20. The SOFC of claim 19, wherein the apparatus for reacting nitric oxide is an oxidation section of a nitric acid production unit supplied with oxygen-containing gas or containing an ammonia oxidation catalyst, wherein nitric oxide is oxidized to nitrogen oxide gas.

21. The SOFC according to claim 20, wherein the nitrogen oxide gas is nitrogen dioxide and dinitrogen tetroxide.

22. The SOFC of claim 20, further comprising a nitric acid absorption tower, wherein the nitrogen oxide gas produced in the oxidation section is absorbed into an aqueous solution.

23. The SOFC according to any one of claims 14 to 17, wherein the outlet of the cathode is in fluid communication with the air separation unit.

24. An SOFC stack, the SOFC stack comprising at least two or more SOFCs according to any one of claims 14 to 23.

25. A system for producing nitric acid, the system comprising: - Haber-Bosch unit, the Haber-Bosch unit including an outlet for conveying ammonia produced by the unit; - An apparatus for heating ammonia produced by the Haber-Bosch unit to a temperature in the range of 500 to 800°C, such that gaseous ammonia is collected at the outlet of the apparatus used for heating; - The SOFC stack according to claim 24, wherein the inlet on the anode side of the battery is fluidly connected to the outlet of the heating device; - A device for transferring nitric oxide (NO) discharged from the outlet on the anode side of the battery in the stack to the oxidation section of a nitric acid production unit supplied with oxygen-containing gas or containing an ammonia oxidation catalyst, wherein the nitric oxide is oxidized to nitrogen oxide gas; and - An apparatus for transferring the nitrogen oxide gas to a nitric acid absorption tower, wherein the nitrogen oxide gas is absorbed into an aqueous solution, thereby producing nitric acid.

26. The system according to claim 25, wherein the nitrogen oxide gas is nitrogen dioxide and dinitrogen tetroxide.

27. A method for producing nitric acid, the method comprising the following sequential steps: a) Production of ammonia in the Haber-Bosch unit; b) Collect the produced ammonia at the outlet of the Haber-Bosch unit; c) Heating the ammonia produced by the Haber-Bosch unit to a temperature in the range of 500 to 800°C, so that gaseous ammonia is collected at the outlet of the heating device; d) Transferring ammonia to the inlet on the anode side of the cell of the SOFC stack according to claim 24; e) Producing nitric oxide by the method according to any one of claims 1 to 13; f) Collect the produced nitric oxide (NO) at the outlet on the anode side of the battery in the stack; g) The produced nitric oxide is transferred to the oxidation section of a nitric acid production unit that is supplied with oxygen-containing gas or contains an ammonia oxidation catalyst; h) Oxidize nitric oxide to nitrogen oxide gas; i) Transfer the nitrogen oxide gas to the absorption section of the nitric acid production unit; as well as j) The nitrogen oxide gas is absorbed into an aqueous solution to produce nitric acid.

28. The method according to claim 27, wherein the nitrogen oxide gas is nitrogen dioxide and dinitrogen tetroxide.

29. Use of the SOFC according to any one of claims 14 to 23 or the SOFC stack according to claim 24 for the combined production of electricity and a NO-containing gas stream, wherein NO accounts for at least 10% by weight of the NO-containing gas stream.

30. Use of an anode in the method according to any one of claims 1 to 13, in an SOFC according to any one of claims 14 to 23, in a stack according to claim 24, in a system according to any one of claims 25-26, or in the method according to any one of claims 27-28, wherein the anode comprises composition A 1-X A' X B 1- Y B' Y O 3-δ A is selected from the group consisting of La, Y, Sm, Pr, Nd and Gd, A' is selected from the group consisting of Ca, Sr and Ba, B and B' are selected from the group consisting of Co, Fe, Mn, Cr and V or mixtures thereof, X is in the range of 0.05 to 0.6, Y is in the range of 0 to 1, and δ is in the range of 0.025 to 0.

3.

31. The use according to claim 30, wherein X is in the range of 0.1 to 0.4.

Images