Method and apparatus for combusting mixed fuel

Abstract

A method for combusting a mixed fuel according to one disclosure comprises: a fuel producing step for producing an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed compared to ammonia on the basis of volume; and a combustion step for supplying the mixed fuel and oxygen to a combustion catalyst, in which an active material containing palladium is supported on a metal oxide support containing alumina, and combusting the mixed fuel.

Description

Combustion method and apparatus for mixed fuel

[0001] The present invention relates to a method and apparatus for burning mixed fuel, and more specifically, to a method and apparatus for burning mixed fuel in which ammonia and hydrogen are mixed.

[0002] Thermal equipment, such as boilers and furnaces, generally supplies the necessary heat by generating an exothermic reaction through the combustion of fuel. To overcome intensifying air pollution and global warming, many countries and companies are developing combustion technologies using carbon-free fuels, such as hydrogen and ammonia, moving away from the use of conventional hydrocarbon fuels to achieve carbon neutrality.

[0003] Ammonia is attracting attention as a hydrogen carrier and a carbon-free fuel because it contains a large amount of hydrogen relative to its storage volume and is advantageous for long-distance transportation due to its high boiling point, which facilitates liquefaction. Furthermore, since ammonia can be combusted directly, it can be used as fuel directly in large-scale power sources such as coal-fired and gas turbine power generation.

[0004] However, ammonia has low combustibility compared to other fuels due to its high latent heat and low flame propagation speed (maximum 0.07 m / s). For example, compared to liquefied natural gas (LNG), the flame propagation speed of ammonia is about one-fifth that of LNG; therefore, if ammonia is injected into combustion facilities intended for LNG, it is difficult to generate a flame or achieve stable combustion due to flame scattering. Consequently, improvements in combustibility are necessary to use ammonia as a combustion fuel.

[0005] According to one embodiment of the present invention, a combustion method and apparatus that improve the low combustibility of ammonia may be provided.

[0006] According to another embodiment of the present invention, a method and apparatus for burning ammonia-containing fuel in which NOx generation is suppressed may be provided.

[0007] According to another embodiment of the present invention, a combustion method and apparatus capable of producing high-purity nitrous oxide along with thermal energy may be provided.

[0008] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0009] A method for burning a mixed fuel according to one embodiment of the present invention comprises: a fuel manufacturing step of producing an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed relative to gaseous ammonia based on volume; and a combustion step of supplying the mixed fuel and oxygen to a combustion catalyst in which an active material including palladium is supported on a metal oxide support including alumina to burn.

[0010] In one embodiment, the combustion catalyst may contain 0.1 to 5.0 wt% of an active substance.

[0011] In one embodiment, the specific surface area of ​​the combustion catalyst is 50 to 150 m² 2 It can be / g.

[0012] In one embodiment, the dispersion of the active material in the mixed fuel may be 5 to 90%.

[0013] In one embodiment, the mixed fuel may contain 1.5Va to 3.5Va of hydrogen based on the volume of ammonia Va.

[0014] In one embodiment, in the combustion step, the ratio of oxygen concentration required according to the stoichiometry during the combustion of the mixed fuel is CR Ost As such, 0.80 CR Ost Up to 1.20 CR Ost Oxygen can be supplied to satisfy the concentration ratio.

[0015] In one embodiment, the combustion step may be performed at 150 to 300°C.

[0016] A combustion method according to one embodiment may include the step of collecting combustion gas emitted by the combustion of the mixed fuel as a nitrous oxide source.

[0017] A combustion device for mixed fuel according to one embodiment of the present invention comprises: a fuel control unit that receives ammonia and hydrogen from an ammonia tank and a hydrogen tank and mixes an excess amount of hydrogen based on the volume of gaseous ammonia to produce a mixed fuel of ammonia and hydrogen; and a combustion unit that includes a combustion space equipped with a combustion catalyst in which an active material including palladium is supported on a metal oxide support including alumina, and in which the mixed fuel supplied from the fuel control unit is combusted.

[0018] In one embodiment, the combustion device further includes a mixing section provided upstream of the combustion section, and the mixing section can mix the oxygen-containing gas and the mixed fuel and supply them to the combustion section.

[0019] In one embodiment, the combustion device further includes a control unit, and the control unit determines the oxygen concentration ratio required according to the stoichiometry of the oxygen-containing gas supplied to the combustion unit during the combustion of the mixed fuel CR Ost As such, 0.80 CR Ost Up to 1.20 CR Ost The above mixing unit can be controlled to satisfy the concentration ratio.

[0020] In one embodiment, the combustion device may further include a nitrous oxide tank for collecting and storing combustion gas discharged from a combustion section.

[0021] In one embodiment, the combustion device may further include a moisture removal unit located upstream of the nitrous oxide tank, which receives combustion gas discharged from the combustion unit and removes moisture contained in the combustion gas.

[0022] A combustion catalyst according to one embodiment of the present invention is a combustion catalyst for the combustion of an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed relative to gaseous ammonia based on volume, and comprises an active material comprising palladium and a metal oxide support comprising alumina on which the active material is supported.

[0023] A mixed fuel combustion device and method according to one embodiment can have a significantly high ammonia conversion rate of 90% or more at a low temperature of 300°C or lower.

[0024] A mixed fuel combustion device and method according to one embodiment can suppress the generation of NOx, such as nitric oxide and nitrogen dioxide, during the combustion of fuel.

[0025] A mixed fuel combustion device and method according to one embodiment can produce high-purity nitric oxide, which is in high demand across industries, along with heat from the combustion of fuel.

[0026] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0027] FIG. 1 is a schematic diagram illustrating a mixed fuel combustion device according to one embodiment.

[0028] FIG. 2 is another configuration diagram illustrating a mixed fuel combustion device according to one embodiment.

[0029] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0030] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0031] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0032] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0033] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0034] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0035] In this specification, terms such as 'top', 'upper', 'upper surface', 'lower', 'lower surface', 'lower surface', and 'side surface' are based on the drawings and may actually vary depending on the direction in which the elements or components are arranged.

[0036] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0037] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0038] The inventors conducted research on ammonia direct combustion technology in which ammonia is used directly as fuel to generate heat (energy) through ammonia combustion. As a result of the research, it was confirmed that the unstable and low combustibility of ammonia can be improved by incorporating hydrogen into ammonia and using a mixed fuel of ammonia and hydrogen. Based on this, further in-depth research was conducted to suppress NOx generated during ammonia combustion while simultaneously improving the combustibility of ammonia using hydrogen. Consequently, the inventors discovered a catalyst and mixed fuel conditions that enable low-temperature combustion during the combustion of the ammonia-hydrogen mixed fuel, suppress NOx generation, and improve the ammonia conversion rate, thereby completing the present invention.

[0039] In the present invention, 'ammonia mixed fuel' or 'mixed fuel' refers to a combustible substance (fuel) and may refer to a gas mixture containing gaseous ammonia and hydrogen.

[0040] In the present invention, the term 'combustion catalyst' refers to an ammonia combustion catalyst that promotes the combustion reaction of ammonia in which ammonia reacts with oxygen to produce nitrogen (N2) and water (H2O). Accordingly, the function and role of the ammonia combustion catalyst differ from that of an ammonia decomposition catalyst that promotes the decomposition reaction in which ammonia is broken down into nitrogen (N2) and hydrogen (H2).

[0041] In the present invention, 'ammonia' means gaseous ammonia unless specifically limited to a liquid state.

[0042] In the present invention, 'hydrogen' may include not only hydrogen originating from a hydrogen storage tank that stores hydrogen, but also hydrogen produced as a product of an electrochemical reaction or a chemical reaction. An example of such hydrogen as a reaction product is hydrogen produced by an ammonia decomposition reaction.

[0043] In the present invention, the temperature at which combustion is performed (or the temperature of the combustion stage) may be at least the temperature of the 'ammonia combustion catalyst' where the mixed fuel and oxygen come into contact. As a specific example, the temperature at which combustion is performed (or the temperature of the combustion stage) may be the temperature of the combustion region, which is a region filled with the ammonia combustion catalyst.

[0044] In the present invention, 'nitrogen oxides' may refer to substances selected from one or more of the group of nitrogen-oxygen compounds, namely nitrogen dioxide, nitrous oxide, and nitric oxide. As a practical example, nitrogen oxides may refer to nitrogen dioxide and nitric oxide, excluding nitrous oxide (N2O), which is in high industrial demand in various industries such as medical, aerospace, semiconductor, food, and organic synthesis. In the present invention, nitrogen dioxide and nitric oxide refer to NO x It can also be referred to as such, and nitrous oxide produced by combustion is referred to as 'nitrous oxide' rather than NOx.

[0045] A method for burning a mixed fuel according to the initiation thereof comprises: a fuel manufacturing step of producing an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed relative to gaseous ammonia by volume; and a combustion step of supplying the mixed fuel and oxygen to a combustion catalyst in which an active material containing palladium is supported on a metal oxide support containing alumina to burn.

[0046] According to the work, by combusting a mixed fuel comprising an excess amount of hydrogen relative to ammonia by volume in the presence of a combustion catalyst in which an active material containing palladium is supported on a metal oxide support containing alumina, the combustibility of ammonia is improved and at the same time NO x It can suppress occurrence.

[0047] Specifically, by catalytically combusting a mixed fuel mixed with an excess amount of hydrogen in the presence of a continuous catalyst in which an active material containing Pd is supported on a support containing alumina, significantly superior ammonia combustion catalytic ability at low temperatures can be achieved due to the synergistic effect of Pd and alumina, and NO containing nitrogen dioxide and nitric oxide x It can inhibit the formation. In this case, the alumina may include γ-alumina.

[0048] Specifically, the complete combustion reaction of a mixed fuel of ammonia and hydrogen is as shown in Equation 1 (ammonia) and Equation 2 (hydrogen), respectively. Since the reactions in Equation 1 and Equation 2 are exothermic reactions, heat can be generated, and clean exhaust gas can be emitted as only nitrogen (N2) and water (H2O) are produced as combustion products without carbon dioxide (CO2).

[0049] Reaction Equation 1: 4NH3 + 3O2 → 2N2 + 6H2O

[0050] Reaction Equation 2: 2H2 + O2 → 2H2O

[0051] On the other hand, when ammonia is combusted, NO, an undesirable product, may be produced through reaction equation 3, and NO2 may be formed as reaction equation 4 proceeds further.

[0052] Reaction Equation 3: 4NH3 + 5O2 → 4NO + 6H2O

[0053] Reaction Equation 4: 2NO + O2 → 2NO2

[0054] By burning an ammonia-hydrogen mixed fuel containing an excess amount of hydrogen in the presence of a combustion catalyst (hereinafter collectively referred to as a Pd-alumina combustion catalyst) in which an active material containing palladium is supported on a metal oxide support containing alumina, Equation 1 can be promoted and Equations 3 and 4 can be suppressed.

[0055] Meanwhile, the mixed fuel containing an excess amount of hydrogen not only improves the combustibility of ammonia together with the Pd-alumina combustion catalyst, but also, through Equation 5, NO x It can be removed.

[0056] Reaction Equation 5: 4H2 + 2NO + O2 → N2 + 4H2O

[0057] In order to stably realize the aforementioned effects of improving the combustibility of ammonia and removing NOx, the mixed fuel may contain hydrogen in a volume of 1.5Va to 3.5Va, more advantageously 2.0Va to 3.5Va, more advantageously 2.5Va to 3.5Va, and more advantageously 2.6 to 3.3Va, based on the volume of ammonia Va.

[0058] When a mixed fuel containing hydrogen of 1.5Va to 3.5Va, more advantageously 2.0Va to 3.5Va, more advantageously 2.5Va to 3.5Va, and even more advantageously 2.6Va to 3.3Va is combusted in the presence of a Pd-alumina combustion catalyst, significantly improved ammonia combustibility can be achieved, with an ammonia conversion rate exceeding 90% even at an extremely low combustion temperature of 150°C.

[0059] In an advantageous example, the Pd-alumina combustion catalyst may contain an active material containing Pd, and may contain 0.1 to 5.0 weight% of the active material, specifically 0.3 to 4.5 weight% of the active material, more specifically 0.3 to 4.0 weight% of the active material based on the total weight of the combustion catalyst. In a more advantageous example, the Pd-alumina combustion catalyst may contain 0.1 to 5.0 weight% of palladium, specifically 0.3 to 4.5 weight% of palladium, more specifically 0.3 to 4.0 weight%, and even more specifically 0.3 to 1.0 weight% of palladium based on the total weight of the combustion catalyst.

[0060] When a mixed fuel containing hydrogen with a volume of 1.5 Va to 3.5 Va based on ammonia volume Va is combusted under a Pd-alumina combustion catalyst containing 0.1 to 5.0 wt% of palladium, combustion of the mixed fuel is possible at a low temperature of 300°C or lower with a high ammonia and hydrogen conversion rate, and at the same time, high-purity nitrous oxide, rather than NOx of carbon dioxide and nitric oxide, can be produced as a by-product during combustion.

[0061] As is well known, nitrous oxide is a substance widely used across various industries, serving as an oxidizer for rockets in the aerospace sector, an analgesic / anesthetic in the medical field, a compressed gas or antioxidant in the food industry, an oxidizer in chemical synthesis, a nitrogen oxide former in the semiconductor industry, and a standard gas in analysis.

[0062] As described above, when a synthetic fuel according to an advantageous example is combusted under an oxidation catalyst according to an advantageous example, industrially useful nitrous oxide can be produced in high purity along with thermal energy from the combustion. Since high-purity nitrous oxide is generated as combustion gas during combustion, the combustion method according to one embodiment may further include a step of collecting the combustion gas emitted by the combustion of the mixed fuel as nitrous oxide.

[0063] In this regard, the present invention includes a method and apparatus for burning a fuel containing ammonia, and a method for producing nitrous oxide.

[0064] A method for producing nitrous oxide according to one embodiment may include: a fuel manufacturing step of producing an ammonia-hydrogen mixed fuel mixed with hydrogen at a concentration of 1.5 Va to 3.5 Va based on the volume Va of ammonia; a combustion step of supplying the mixed fuel and oxygen to a combustion catalyst in which an active material containing palladium is supported at a concentration of 0.1 to 5.0 wt% on a metal oxide support containing alumina, and combusting the mixture; and a step of collecting the combustion gas emitted by the combustion of the mixed fuel in the combustion step as nitrous oxide. Additionally, if necessary, the method for producing nitrous oxide may further include a step of removing moisture from the combustion gas emitted by combustion, and the combustion gas from which moisture has been removed may be collected as nitrous oxide. The removal of moisture may be performed through known methods, such as removal by gas / liquid separation based on condensation or removal by adsorption of moisture by an adsorbent.

[0065] In order to produce a combustion gas that does not impair the combustibility of ammonia and contains 90% or more, specifically 95% or more, of nitrous oxide among nitrogen oxides including nitrogen dioxide, nitric oxide and nitrous oxide, the combustion of the mixed fuel can be carried out at 150 to 300°C, advantageously at 150 to 270°C, more advantageously at 150 to 250°C, and the Pd-alumina combustion catalyst can contain 0.3 to 4.0 weight% of palladium.

[0066] In a more advantageous example, the combustion of the mixed fuel can be carried out at 180 to 220°C so that a combustion gas in which the nitrous oxide content among the nitrogen oxides substantially reaches 100% can be produced, and the Pd-alumina combustion catalyst can contain 0.5 to 0.8 weight% of palladium.

[0067] In a combustion catalyst, by supporting an active material containing Pd on a support containing alumina, the thermal stability of the catalyst is increased, and due to the synergistic effect of Pd and alumina, it can have significantly superior ammonia combustion catalytic ability at low temperatures and further enhance the selectivity for nitrous oxide among various nitrogen oxides generated by combustion.

[0068] In a combustion method according to one embodiment, the Pd-alumina combustion catalyst has a specific surface area of ​​50 to 150 m² 2 / g, specifically 70 to 130 m 2 / g, more specifically 70 to 120 m 2 It can be / g. The specific surface area of ​​a combustion catalyst is the surface area that provides a large number of catalytic active sites and allows for smooth mass transfer of reactants and products.

[0069] In a combustion method according to one embodiment, the dispersion of the active material of the Pd-alumina combustion catalyst may be 5 to 90%, specifically 5 to 85%. Such dispersion of the active material is advantageous as it can improve the ammonia-hydrogen conversion rate at a low temperature of 300°C or lower. Furthermore, in order to generate nitrous oxide combustion gas reaching 100% at a low combustion temperature of 300°C or lower, specifically 250°C or lower, the dispersion of the active material may be 50 to 90%, more specifically 60 to 85%.

[0070] Experimentally, a Pd-alumina combustion catalyst can be prepared by a wet impregnation method in which a support containing alumina is immersed in a precursor solution in which a precursor containing a Pd precursor is dissolved, followed by drying and heat treatment. Representative examples of Pd precursors include palladium chloride, palladium nitrate, palladium acetate, and tetraammonium palladium, and polar solvents such as water or ethanol can be used as the solvent for the precursor solution. At this time, it goes without saying that the amount of active material supported on the support can be controlled by controlling the concentration of the precursor solution immersed in the support or the amount of precursor solution used for immersion. Heat treatment can be performed at a temperature of 400 to 800°C for 30 minutes to 5 hours in an inert gas atmosphere or a reducing atmosphere, but is not necessarily limited thereto.

[0071] Experimentally, the specific surface area of ​​the combustion catalyst can be the BET specific surface area, which is the specific surface area calculated using the BET method from the measured nitrogen adsorption isotherm by measuring the nitrogen adsorption-desorption isotherm of the combustion catalyst at a temperature of 77 K using liquid nitrogen.

[0072] Experimentally, the dispersion of the active material in a combustion catalyst may be calculated using the adsorption amount of a gas selectively adsorbed by the active material. Specifically, the dispersion of the active material may be the ratio calculated based on ASTM D3663-03 by dividing the number of elements of the active material located on the surface of the catalyst—calculated from the adsorption amount of the gas selectively adsorbed by the active material (specific gas) and the adsorption ratio between the specific gas and the elements of the active material—by the total number of elements of the active material contained in the catalyst. As is well known, when the active material is Pd, carbon monoxide may be used as the specific gas.

[0073] The mixed fuel can be supplied to a combustion chamber equipped with a combustion catalyst and combusted. For example, the combustion chamber may include a catalyst region (catalyst bed) filled with particulate combustion catalyst. When filled with particulate combustion catalyst, the contact area between the combustion catalyst and the gas phase can be improved as the gas phase flows through the empty spaces between the particles. As another example, the combustion chamber may be provided with a porous structure having one or more flow paths in the direction of gas flow. In this case, the combustion catalyst may be coated on the surface of the porous structure, or the combustion catalyst itself may form the porous structure.

[0074] When a mixed fuel is combusted, oxygen for combustion can be supplied to the combustion chamber. The supplied oxygen may be injected into the combustion chamber independently of the mixed fuel. Alternatively, oxygen may be pre-mixed with the mixed fuel at the front of the combustion chamber and supplied to the combustion chamber in the form of a reaction gas containing the mixed fuel and oxygen.

[0075] In a favorable example, the ratio of oxygen concentrations required according to stoichiometry during the combustion of a mixed fuel is CR Ost As such, 0.80 CR Ost Up to 1.20 CR Ost The concentration ratio of, specifically 0.90 CR Ost Up to 1.10 CR Ost The concentration ratio of, more specifically 0.95 CR Ost Up to 1.05 CR Ost Oxygen can be supplied to satisfy the concentration ratio. Practically, the stoichiometric ratio CR Ost The oxygen supply conditions corresponding to this are NO during the combustion of mixed fuel x It is advantageous because it can suppress production.

[0076] At this time, the 'stoichiometry' during the combustion of the mixed fuel may be the stoichiometric ratio between the mixed fuel and oxygen based on the combustion reaction of ANH3 + 0.75AO2 → 0.5AN2 + 1.5AH2O for A moles of NH3 and the combustion reaction of BH2 + 0.5BO2 → BH2O for B moles of H2, when the molar ratio of ammonia to hydrogen contained in the mixed fuel is A : B. The 'concentration ratio required according to stoichiometry' may refer to the concentration ratio of [0.75A + 0.5B] / [A+B] based on the aforementioned stoichiometry. At this time, the statement that 'oxygen is supplied to satisfy the concentration ratio required according to stoichiometry' can mean that when a mixed fuel is supplied to a space where combustion occurs, oxygen is supplied to the combustion space such that O' / [A'+B'] satisfies [0.75A' + 0.5B'] / [A'+B'], where A' and B' are the total moles of ammonia supplied as mixed fuel per unit time and O' is the total moles of oxygen supplied to the space where combustion occurs per unit time. Accordingly, the statement that oxygen is supplied to satisfy (an arbitrary number k) x (concentration ratio) can mean that oxygen is supplied to the combustion space such that O' / [A'+B'] satisfies (an arbitrary number k) x [0.75A' + 0.5B'] / [A'+B']. At this time, in a space having constant pressure and constant temperature, it goes without saying that the molar ratio can correspond to the volume ratio.

[0077] For combustion, the oxygen supplied to the combustion catalyst together with or independently of the mixed fuel may be oxygen gas or oxygen from the air. When air is used, it goes without saying that the air may be supplied such that the oxygen from the air satisfies the concentration ratio required according to the aforementioned stoichiometry.

[0078] As described above, the combustion method according to one embodiment is a low-temperature combustion method, and the low temperature may be a temperature of 150 to 300°C, specifically 150 to 270°C, more specifically 150 to 250°C.

[0079] The mixed fuel or the reaction gas mixed with oxygen is 50,000 to 100,000 mL·g cat -1 ·h -1 It may be supplied to a combustion catalyst (a combustion space in which the combustion catalyst is located) at a space velocity, but is not necessarily limited thereto. In this case, if necessary, the reaction gas may further contain a non-combustible gas such as nitrogen, argon, neon, helium, or a mixture thereof. When the reaction gas contains a non-combustible gas, the reaction gas may contain 1 to 99 volume% of the mixed raw material.

[0080] The present invention includes a mixed fuel combustion device in which the aforementioned mixed fuel combustion method is implemented. Accordingly, the mixed fuel combustion device includes all the details described above in the mixed fuel combustion method.

[0081] A mixed fuel combustion device according to the one-time introduction includes: a fuel control unit that receives ammonia and hydrogen from an ammonia tank and a hydrogen tank and mixes an excess amount of hydrogen based on the volume of gaseous ammonia to produce a mixed fuel of ammonia and hydrogen; and a combustion unit in which a mixed fuel supplied from the fuel control unit is combusted, the combustion unit having a combustion catalyst in which an active material including palladium is supported on a metal oxide support including alumina.

[0082] FIG. 1 is a configuration diagram illustrating a combustion device according to one embodiment. As illustrated in FIG. 1, the combustion device may include a fuel control unit (100) and a combustion unit (200). The fuel control unit (100) may produce a mixed fuel (F) by receiving ammonia (A) and hydrogen (H) from an ammonia storage tank (20) that stores ammonia and a hydrogen storage tank (10) that stores hydrogen, and mixing the ammonia and hydrogen so that the hydrogen volume Vh satisfies the hydrogen over-rich condition of Vh / Va > 1 based on the ammonia volume Va.

[0083] The mixed fuel (F) and oxygen-containing gas (O) generated in the fuel control unit (100) can be supplied to the combustion unit (200) where the combustion catalyst is located and combusted.

[0084] As illustrated in FIG. 1, based on the gas flow, the combustion device may further include a mixing section (300) located upstream of the combustion section (200). The mixing section (300) receives mixed fuel (F) and oxygen-containing gas (O) to produce a reaction gas (R), and the produced reaction gas (R) can be supplied to the combustion section (200). Representative examples of the mixing section (300) include an in-line mixer, but it goes without saying that the present invention is not limited by the specific type of the mixing section (300).

[0085] However, the present invention is not limited by the presence or absence of a mixing section (300), and it is obvious that the oxygen-containing gas (O) may be supplied to the combustion section (200) independently of the mixed fuel (F) by the oxygen-containing gas supply section.

[0086] The combustion device may further include a control unit (not shown). The control unit controls a supply unit that supplies oxygen-containing gas to a mixing unit (300) or a combustion unit (200) to control the oxygen concentration ratio required according to stoichiometry during the combustion of the mixed fuel CR Ost As such, 0.80 CR Ost Up to 1.20 CR Ost Oxygen satisfying the concentration ratio can be controlled to be supplied to the combustion unit (200). Additionally, the control unit can control the volume ratio of ammonia gas and hydrogen gas in the mixed fuel by controlling the amount of ammonia gas and hydrogen gas supplied from the ammonia tank (20) and the hydrogen tank (10) to the fuel control unit (100). The oxygen-containing gas may be oxygen gas or air, and if the oxygen-containing gas is air, the air may be supplied from the atmosphere to the combustion unit (200) or the mixing unit (300).

[0087] In the combustion section (200), at least a portion of the space where combustion occurs (combustion space) may be filled with a macroscopic porous structure such as a particulate, pellet, or honeycomb containing a combustion catalyst in which an active material containing palladium is supported on a support containing alumina. Additionally, although not shown in the drawing, the combustion section (200) may further include a cooling member that cools the combustion space through a heat source and / or heat exchange, etc., to supply heat to the combustion space to control the combustion temperature.

[0088] In the combustion section (200), the mixed fuel can be combusted with the help of a combustion catalyst, and combustion energy (heat) and combustion gas (exhaust gas, D) (indicated by a dotted arrow) containing combustion reaction products can be generated by combustion. At this time, as is well known, the combustion energy can be converted into mechanical energy through the operation of a turbine or steam generated by heat exchange.

[0089] Additionally, when controlling the concentration of the mixed fuel using a non-combustible gas, the fuel control unit (100) can produce a reaction gas in which the mixed fuel and the non-combustible gas are mixed by mixing ammonia and hydrogen to satisfy a preset Vh / Va and simultaneously receiving non-reactive gas from a non-reactive gas storage tank that stores the non-combustible gas. However, such non-combustible gas may be optionally mixed with the mixed fuel, and the present invention is not limited by whether or not the non-combustible gas is mixed.

[0090] One example of FIG. 2 is another configuration diagram illustrating a combustion device. As shown in the example of FIG. 2, the combustion device may further include a nitrous oxide tank (400) for collecting and storing combustion gas (D) discharged from the combustion section. In a practical example, the content of nitrous oxide among the nitrogen oxides of nitrous oxide, nitrogen dioxide, and nitric oxide in the combustion gas (D) may be 90% or more, specifically 95% or more, more specifically 99% or more, and more specifically 100%. The nitrous oxide tank (400) can receive and store such high-purity nitrous oxide.

[0091] If necessary, based on the gas flow, a moisture removal unit (500) for removing moisture contained in the combustion gas (D) may be further provided between the combustion unit (200) and the nitrous oxide tank (400). The moisture removal unit may include an adsorber filled with a moisture adsorbent or a heat exchanger-type gas-liquid separator that cools the combustion gas (D) to condense and remove moisture, but is not limited thereto.

[0092] As described above, the present invention includes a method and apparatus for burning a mixed fuel containing ammonia, and a method and apparatus for producing nitrous oxide by means of combustion gas generated during the combustion of the mixed fuel. Accordingly, the method and apparatus for producing nitrous oxide includes all the contents described above in the method and apparatus for burning the mixed fuel.

[0093] The present invention includes a combustion catalyst used in the aforementioned method for burning mixed fuel, a combustion device for mixed fuel, a method for producing nitrous oxide, or a nitrous oxide production device.

[0094] The combustion catalyst according to the first invention is a combustion catalyst for the combustion of an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed relative to gaseous ammonia by volume, and comprises an active material containing palladium and a metal oxide support containing alumina on which the active material is supported.

[0095] In one advantageous example, the combustion catalyst may be a combustion catalyst for mixed fuel combustion containing hydrogen of 1.5Va to 3.5Va, advantageously 2.0Va to 3.5Va, more advantageously 2.5Va to 3.5Va, and more advantageously 2.6 to 3.3Va based on the volume of ammonia Va.

[0096] In a more advantageous example, the combustion catalyst satisfies a ratio (Vh / Va) of the volume of hydrogen (Vh) in the ammonia-hydrogen fuel divided by the volume of ammonia (Va) of 1.5 to 3.5, advantageously 2.0 to 3.5, more advantageously 2.5 to 3.5, and even more advantageously 2.6 to 3.3, and the ratio of oxygen concentrations required according to stoichiometry during the combustion of the mixed fuel is CR Ost As such, 0.80 CR Ost Up to 1.20 CR Ost It can be a combustion catalyst for the combustion of a mixed fuel under combustion conditions where oxygen is supplied to satisfy the concentration ratio.

[0097] In one embodiment, the combustion catalyst may contain 0.1 to 5.0 weight% of an active material, specifically 0.3 to 4.5 weight% of an active material, more specifically 0.3 to 4.0 weight% of an active material, based on the total weight of the combustion catalyst. In an advantageous example, the Pd-alumina combustion catalyst may contain 0.1 to 5.0 weight% of palladium, specifically 0.3 to 4.5 weight% of palladium, more specifically 0.3 to 4.0 weight%, and even more specifically 0.3 to 1.0 weight% of palladium.

[0098] In one embodiment, the combustion catalyst has a specific surface area of ​​50 to 150 m² 2 / g, specifically 70 to 130 m 2 / g, more specifically 70 to 120 m 2 It can be / g.

[0099] In one embodiment, the dispersion of the active material of the combustion catalyst may be 5 to 90%, specifically 5 to 85%. Such dispersion of the active material is advantageous as it can improve the ammonia-hydrogen conversion rate at a low temperature of 300°C or lower. Furthermore, when used as a combustion catalyst for the combustion of mixed fuel and the production of nitrous oxide at a low combustion temperature of 300°C or lower, specifically 250°C or lower, it is advantageous for the dispersion of the active material to be 50 to 90%, more specifically 60 to 85%.

[0100] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0101] (Example 1)

[0102] A combustion catalyst supported with 0.4 wt% Pd on a γ-alumina support was used. The specific surface area of ​​the combustion catalyst was 84 m². 2 / g, and the Pd dispersion was 83.3%. The combustion catalyst was packed into the reactor, and 72,000 mL·g of reaction gas containing ammonia, hydrogen, and oxygen was introduced into the reactor at the temperature (°C) according to Table 1. cat -1 ·h -1 The combustion reaction was carried out while flowing at a space velocity (WHSV). At this time, the ammonia gas content in the reaction gas was 1 volume%, the hydrogen gas content was 2.9 volume%, the oxygen was 2.2 volume% satisfying the oxygen concentration ratio required according to stoichiometry, and the remainder was helium.

[0103] (Example 2)

[0104] 0.6 wt% Pd is supported on a γ-alumina support, and the specific surface area is 110 m² 2The mixed fuel was burned in the same manner as in Example 1 at the reactor temperature of Table 1, except that a combustion catalyst with a Pd dispersion of 67.2% and a Pd dispersion of / g was used.

[0105] (Example 3)

[0106] Pd is supported at 3.7 wt% on a γ-alumina support, and the specific surface area is 103 m² 2 The mixed fuel was burned in the same manner as in Example 1 at the reactor temperature of Table 1, except that a combustion catalyst with a Pd dispersion of 7.0% and a Pd dispersion of 7.0% was used.

[0107] (Comparative Example 1)

[0108] A mixed fuel was burned in the same manner as in Example 1 at the reactor temperature of Table 1, except that a commercial catalyst, Co3O4, was filled into the reactor instead of a combustion catalyst in which Pd was supported on a γ-alumina support.

[0109] (Comparative Example 2)

[0110] Using an empty reactor not filled with catalyst, the mixed fuel was burned at the reactor temperature of Table 1 in the same manner as in Example 1.

[0111] In each of the examples to comparative examples, the gas discharged from the combustion reactor was analyzed by FT-IR (Fourier-transform infrared spectroscopy) to calculate the ammonia conversion rate (CRA, %) and hydrogen conversion rate (CRH, %), and these were summarized in Table 1. In addition, in each of the examples to comparative examples, the content of each substance (N2, N2O, NO, NO2, N2O in Table 1, each unit is %) among the total nitrogen-containing compounds (N2, NO, NO2, N2O) discharged from the combustion reactor was analyzed and summarized in Tables 2 and 3.

[0112] (Table 1)

[0113]

[0114] As shown in Table 1, according to one embodiment, when a combustion catalyst with Pd supported on an alumina support is used and a hydrogen-rich mixed fuel is used, it can be seen that the ammonia conversion rate is over 90% at a low temperature of only 150°C, and when the temperature increases to 200°C, the ammonia conversion rate is over 97%. In addition, it can be seen that as the Pd content in the combustion catalyst increases at the same temperature, the conversion rates of both ammonia and hydrogen increase. Furthermore, even at a low temperature of 150°C, hydrogen is also converted by over 65%, indicating that both ammonia and hydrogen are combusted stably at low temperatures. On the other hand, in the case of a commercial catalyst, an ammonia conversion rate of over 90% was observed only when reaching 350°C, but the hydrogen conversion rate was significantly lower at 25.6%. It can be seen that when a catalyst is not provided, no ammonia is burned at all, and only 5.5% of hydrogen is burned even at a temperature of 400°C.

[0115] (Table 2)

[0116]

[0117] (Table 3)

[0118]

[0119] As can be seen from Tables 2 and 3, when a combustion catalyst supported with Pd on an alumina support according to one embodiment is used and a hydrogen-rich mixed fuel is used, it can be seen that the generation of NOx, including nitric oxide and nitrogen dioxide, is significantly suppressed at low temperatures of 150 to 300°C, and that nitrous oxide among nitrogen oxides is generated with a remarkably high selectivity. In addition, when a combustion catalyst supported with Pd on an alumina support according to one embodiment is used, as the temperature increases beyond 300°C, NOx generation increases and the selectivity for nitrous oxide decreases, so it can be seen that low-temperature combustion at 150 to 300°C, advantageously at 150 to 250°C, is advantageous. Furthermore, when a combustion catalyst supported on an alumina catalyst at a level of 0.6 wt% with a high specific surface area and dispersion is subjected to low-temperature combustion, the production of nitric oxide and nitrogen dioxide substantially reaches 0%, and it can be seen that substantially all nitrogen oxides produced during combustion are nitrous oxide. The results in Tables 2 and 3 demonstrate that heat can be produced by burning a mixed fuel containing ammonia, and at the same time, extremely high-purity nitrous oxide containing substantially only nitrous oxide as a nitrogen oxide is obtained as a by-product, thereby showing that the production of heat and nitrous oxide is possible simultaneously. The present invention is not limited to the embodiments described above but can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without altering the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A fuel manufacturing step for producing an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed relative to gaseous ammonia by volume; and A method for burning a mixed fuel comprising: a combustion step of supplying the mixed fuel and oxygen to a combustion catalyst in which an active material containing palladium is supported on a metal oxide support containing alumina, and burning the mixture.

2. In Paragraph 1, A method for burning mixed fuel, wherein the combustion catalyst contains 0.1 to 5.0 wt% of an active substance.

3. In Paragraph 1, The specific surface area of ​​the above combustion catalyst is 50 to 150 m² 2 Combustion method of mixed fuel, in / g.

4. In Paragraph 1, A method of combustion of a mixed fuel, wherein the dispersion degree of the active substance of the mixed fuel is 5 to 90%.

5. In any one of paragraphs 1 through 4, A method of combustion of the above-mentioned mixed fuel, wherein the mixed fuel contains hydrogen in an amount of 1.5 Va to 3.5 Va based on the volume Va of ammonia.

6. In any one of paragraphs 1 through 4, In the above combustion stage, the ratio of oxygen concentration required according to the stoichiometry during the combustion of the above mixed fuel is CR Ost As such, 0.80 CR Ost Up to 1.20 CR Ost A method of combustion of mixed fuel in which oxygen is supplied to satisfy the concentration ratio.

7. In any one of paragraphs 1 through 4, A method for burning mixed fuel, wherein the combustion step is performed at 150 to 300°C.

8. In Paragraph 7, A method for burning a mixed fuel comprising the step of collecting combustion gas emitted by the combustion of the mixed fuel as a nitrous oxide source.

9. A fuel control unit that supplies ammonia and hydrogen from an ammonia tank and a hydrogen tank, mixes an excess amount of hydrogen based on the volume of gaseous ammonia, and produces a mixed fuel of ammonia and hydrogen; and A mixed fuel combustion device comprising: a combustion space equipped with a combustion catalyst in which an active material containing palladium is supported on a metal oxide support containing alumina, and a combustion section in which a mixed fuel supplied from the fuel control section is combusted.

10. In Paragraph 9 The above combustion device further includes a mixing section provided upstream of the combustion section, and the mixing section mixes the oxygen-containing gas and the mixed fuel and supplies it to the combustion section, a mixed fuel combustion device.

11. In Paragraph 10, The above combustion device further includes a control unit, and the control unit determines the oxygen concentration ratio CR required according to the stoichiometry of the oxygen-containing gas supplied to the combustion unit during the combustion of the mixed fuel. Ost As such, 0.80 CR Ost Up to 1.20 CR Ost A mixed fuel combustion device that controls the mixing section to satisfy the concentration ratio.

12. In Paragraph 10, The above combustion device is a mixed fuel combustion device further comprising a nitrous oxide tank for collecting and storing combustion gases discharged from a combustion section.

13. In Paragraph 12, The above combustion device is a mixed fuel combustion device further comprising a moisture removal unit located upstream of the nitrous oxide tank, which receives combustion gas discharged from the combustion unit and removes moisture contained in the combustion gas.

14. A combustion catalyst for the combustion of an ammonia-hydrogen mixed fuel in which an excess amount of hydrogen is mixed relative to gaseous ammonia by volume, and A combustion catalyst comprising an active material containing palladium and a metal oxide support containing alumina on which the active material is supported.

Images