Production method for hydrogen from ammonia and steel production method

Abstract

To provide a production method for hydrogen from ammonia in which hydrogen production amount per unit time and per unit catalyst mass is improved.SOLUTION: A method for producing hydrogen from ammonia comprises introducing ammonia gas into a reactor and decomposing the ammonia gas in the presence of a catalyst to produce hydrogen gas, wherein an outlet gas temperature of a catalyst layer in the reactor is 750°C or more, a ratio F / W of a flow rate F of the ammonia gas to a mass W of the catalyst is 40,000 mL-NH3 / (h gcat) or more, the catalyst is a NiMgO-based catalyst, and a Ni content of the NiMgO-based catalyst is 1 to 40 mass%.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing hydrogen from ammonia and a method for producing steel. [Background technology]

[0002] In recent years, hydrogen has been attracting increasing attention as an alternative fuel to fossil resources such as natural gas, oil, and coal in order to curb global warming. Methods for producing hydrogen include reforming fossil resources, electrolysis of water, and methods utilizing the dehydrogenation reaction of hydrogen-containing compounds. Among these, methods utilizing the dehydrogenation reaction of hydrogen-containing compounds have attracted attention because of the low CO2 emissions that occur during the hydrogen production process. Examples of hydrogen-containing compounds include ammonia, methylcyclohexane, and methane, but ammonia, which has a high hydrogen content per unit volume, is a particularly promising raw material.

[0003] Patent Document 1 describes an ammonia decomposition catalyst containing nickel and an additive substance that is at least one metal oxide and / or composite oxide selected from the group consisting of metal elements of Groups 2 to 5 and 12 to 15 of the long form periodic table, wherein the ratio (S2 / S1) of the calculated specific surface area of ​​the nickel (S2) to the specific surface area of ​​the catalyst (S1) is 0.50 to 0.85.

[0004] Patent Document 2 describes a catalyst that can be used in an ammonia dehydrogenation reaction, and includes a support containing a single-crystalline material with a hexagonal crystal structure; and a catalytic metal supported on the support.

[0005] Patent Document 3 describes a catalyst structure for producing hydrogen from ammonia, characterized by comprising: a metal substrate structure having a flow path for ammonia gas and made of a metal substrate; and an outer surface layer present on the surface of the metal substrate structure and containing a ruthenium-supported catalyst in which ruthenium is supported on one type of support selected from the group consisting of aluminum oxide, cerium oxide, magnesium oxide, silicon oxide, and zirconium oxide. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-224555 [Patent Document 2] Special Publication No. 2023-513483 [Patent Document 3] Japanese Patent Application Publication No. 2018-134628 Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure provides a method for producing hydrogen from ammonia with improved hydrogen production per unit time and per unit catalyst mass. [Means for solving the problem]

[0008] That is, the present disclosure includes the following aspects. <Aspect 1> A method for producing hydrogen from ammonia, comprising: introducing ammonia gas into a reactor and decomposing it in the presence of a catalyst to produce hydrogen gas; the outlet gas temperature of the catalyst layer in the reactor is 750°C or higher, the ratio F / W of the flow rate F of the ammonia gas to the mass W of the catalyst is 40,000 mL-NH3 / (h gcat) or more; the catalyst is a NiMgO-based catalyst, The Ni content of the NiMgO-based catalyst is 1 to 40 mass%. A method for producing hydrogen from ammonia. <Aspect 2> The ratio F / W (mL-NH3 / (h gcat)) satisfies the following conditions: F / W (mL-NH3 / (h·gcat))≦857.14 × catalyst bed outlet gas temperature (℃) − 576,000 fulfill, The method for producing hydrogen from ammonia according to the above aspect 1. <Aspect 3> 1. A method of manufacturing steel, comprising: The method includes introducing the hydrogen gas obtained by the production method according to the first or second aspect into a blast furnace or a shaft furnace, and reducing iron oxide with the hydrogen gas, The temperature T (°C) of the hydrogen gas from the outlet of the catalyst layer to the introduction into the blast furnace or the shaft furnace satisfies the following conditions: T(℃)≧650℃ fulfill, Steel manufacturing methods. <Aspect 4> The temperature T (°C) is determined under the following conditions: T (℃) ≧ catalyst bed outlet gas temperature (℃) - 100 fulfill, The steel production method according to aspect 3. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a method for producing hydrogen from ammonia, which improves the amount of hydrogen produced per unit time and per unit catalyst mass. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram of a catalyst made of a composite oxide of Ni and Mg. [Figure 2] 1 is a schematic diagram of an exemplary hydrogen production facility from ammonia. [Figure 3] 1 is a graph showing the relationship between F / W and ammonia conversion rate for Study Examples 1 to 6. [Figure 4] 1 is a graph showing the relationship between F / W and ammonia conversion rate for Examples 1 to 21 and Comparative Examples 1 to 8. [Figure 5] 1 is a graph showing the relationship between the outlet gas temperature of the catalyst layer and the maximum value of F / W that gives 100% ammonia conversion when 20 wt% NiMgO / Al2O3 is used. [Figure 6]1 is a graph showing the relationship between F / W and ammonia conversion rate for Examples 22 to 55 and Comparative Examples 9 to 11. [Figure 7] 1 is a graph showing the relationship between F / W and ammonia conversion rate for Examples 56 to 82 and Comparative Examples 12 to 13. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. In this specification, unless otherwise specified, the use of "to" to indicate a range of values ​​means that the values ​​before and after the range are included as the lower limit and upper limit.

[0012] From the viewpoint of energy efficiency, hydrogen production from ammonia using a catalyst is preferably carried out at low temperatures. Therefore, no ammonia decomposition catalysts have been developed to date that focus on activity under high-temperature conditions. To produce hydrogen from ammonia in the presence of a catalyst using equipment of the same scale and with a higher yield, it is necessary to increase the ratio F / W (the ratio of the flow rate of ammonia gas F to the mass of the catalyst W) and the ammonia conversion rate. However, if the F / W is too high, the ammonia conversion rate generally tends to decrease. In hydrogen production from ammonia, due to the toxicity and corrosiveness of ammonia, it is desirable to keep the residual ammonia concentration in the product gas low. Therefore, hydrogen production has traditionally been carried out under low F / W conditions.

[0013] The present inventors have found that by using a NiMgO-based catalyst that has high activity for the ammonia decomposition reaction under high temperature conditions and by carrying out the decomposition reaction at a high temperature, the reaction can proceed with a high conversion even under high F / W conditions.

[0014] One embodiment of a method for producing hydrogen from ammonia includes introducing ammonia gas into a reactor and decomposing it in the presence of a catalyst to produce hydrogen gas, wherein the outlet gas temperature of the catalyst layer in the reactor is 750°C or higher, the ratio F / W of the flow rate F of the ammonia gas to the mass W of the catalyst is 40,000 mL-NH3 / (h·gcat) or higher, the catalyst is a NiMgO-based catalyst, and the Ni content of the NiMgO-based catalyst is 1 to 40 mass%. In the method for producing hydrogen from ammonia, ammonia is decomposed to produce nitrogen and hydrogen according to the following formula: 2NH3 → N2 + 3H2

[0015] The method for producing hydrogen from ammonia may further include a step of removing unreacted ammonia from the gas discharged from the reactor. The method for removing ammonia is not particularly limited, and any method known in the art can be used without limitation.

[0016] The outlet gas temperature of the catalyst layer is 750°C or higher, preferably 800°C or higher, and more preferably 850°C or higher. There is no particular upper limit to the outlet gas temperature of the catalyst layer, but it may be 1300°C or 1200°C. At 750°C or higher, sufficient catalytic activity can be obtained. Although hydrogen can be produced from ammonia at temperatures above 1300°C, temperatures above 1300°C result in increased heat loss due to external heat radiation, reducing energy efficiency. In addition, heat resistance measures are required for the device, which increases costs.

[0017] In this specification, the term "gas temperature at the outlet of the catalyst layer" refers to a temperature measured by a thermocouple installed at the most downstream side of the catalyst layer in the reactor.

[0018] The reaction pressure is not particularly limited, but is usually 0.1 MPaA to 10 MPaA, preferably 0.1 MPaA to 1 MPaA. If the pressure is below 0.1 MPaA, the reaction will be carried out at subatmospheric pressure, requiring pressure reduction equipment, which increases equipment costs. The reaction of producing nitrogen and hydrogen by decomposition of ammonia is an equilibrium reaction in which the number of molecules increases, so a lower pressure is advantageous in terms of conversion rate. If the reaction pressure is 10 MPaA or less, a high ammonia conversion rate can be obtained from the perspective of chemical equilibrium. If the reaction pressure exceeds 10 MPaA, the allowable pressure value of the reactor must be set high, which increases equipment costs. In this specification, the reaction pressure is the pressure measured by an in-system pressure gauge installed upstream of the catalyst layer.

[0019] The ratio F / W of the ammonia gas flow rate F to the catalyst mass W is 40,000 mL-NH3 / (h gcat) or more. The ratio F / W of the ammonia gas flow rate F to the catalyst mass W may be 50,000 mL-NH3 / (h gcat) or more, or 60,000 mL-NH3 / (h gcat) or more. A F / W of 40,000 mL-NH3 / (h gcat) or more reduces the amount of catalyst required to process a given amount of ammonia gas, thereby reducing equipment costs. On the other hand, if the F / W is too high, the ammonia conversion rate decreases. Therefore, the upper limit of the F / W can be determined appropriately based on the outlet gas temperature of the catalyst layer and the ammonia conversion rate required for each application. The F / W may be, for example, 600,000 mL-NH3 / (h gcat) or less, or 500,000 mL-NH3 / (h gcat) or less.

[0020] The ratio F / W of the flow rate of ammonia gas F to the mass W of the catalyst satisfies the following condition: F / W (mL-NH3 / (h·gcat))≦857.14 × catalyst bed outlet gas temperature (℃) − 576,000 By operating with a F / W that satisfies the above conditional formula, the ammonia conversion rate can be increased, which reduces the cost of additional equipment for removing residual ammonia and keeps running costs low.

[0021] Depending on the application, the ammonia concentration in the hydrogen gas supplied to each application does not need to be 0%. For example, ammonia functions as a reducing agent for iron oxide, albeit with low efficiency. Therefore, in the production of hydrogen gas for steel manufacturing, even if the ammonia conversion rate is less than 100%, it is not necessary to remove residual ammonia. In the production of hydrogen gas for steel manufacturing, the upper limit of F / W can be determined based on the conversion rate required for deployment at each steelworks.

[0022] The flow rate F of ammonia gas is measured by a mass flow controller installed upstream of the catalyst layer. The mass W of the catalyst is the mass of the catalyst packed in the reactor, measured by an electronic balance.

[0023] The raw material gas introduced into the reactor contains ammonia gas. The raw material gas may contain gases other than ammonia gas. Examples of other gases include helium gas, nitrogen gas, and argon gas. The ammonia content of the raw material gas is preferably 1 mol% or more, more preferably 10 mol% or more, and even more preferably 50 mol% or more. The upper limit of the ammonia content of the raw material gas may be, for example, 100 mol%, 95 mol%, or 90 mol%.

[0024] The type of reactor is not particularly limited, and specific examples thereof include a fluidized bed type, a moving bed type, and a fixed bed type. When the catalyst is a powder, the fluidized bed type and the moving bed type are preferably used, and when the catalyst is a molded body, the fixed bed type and the moving bed type are preferably used.

[0025] [NiMgO-based catalyst] "NiMgO" is a composite oxide of Ni and Mg. "NiMgO-based catalysts" include not only those composed of NiMgO but also those composed of NiMgO and various additives (other catalysts, co-catalysts, supports, etc.). NiMgO and various additives may be a physical mixture, or at least some of them may form a composite oxide. In NiMgO-based catalysts, nickel functions as the main active component in the ammonia decomposition reaction. The properties of NiMgO-based catalysts are explained using a catalyst composed of a composite oxide of Ni and Mg as an example. As shown in Figure 1, the catalyst is prepared in a state where nickel is solid-dissolved in the crystalline phase of MgO. Because Mg has a high affinity for oxygen, Ni is reduced preferentially over Mg. Therefore, when a reaction is carried out using the catalyst in a reducing atmosphere, some of the nickel contained in NiMgO precipitates as metallic nickel on the catalyst surface in the form of fine clusters, enabling the reaction to proceed efficiently. Specific examples of NiMgO-based catalysts include at least one selected from the group consisting of NiMgO catalyst, NiMgO / Al2O3 catalyst, and NiMgO-CeO2 / Al2O3 catalyst, which will be described later. Among these, at least one selected from the group consisting of NiMgO / Al2O3 catalyst and NiMgO-CeO2 / Al2O3 catalyst is preferred, with NiMgO-CeO2 / Al2O3 catalyst being more preferred.

[0026] The NiMgO-based catalyst may contain an additive. In this specification, "additive" refers to a single oxide or composite oxide other than NiMgO. Examples of the additive include at least one selected from the group consisting of Al2O3, lanthanoid metal oxides such as CeO2, CeO2-ZrO2, Y2O3, silica, and yttria-stabilized zirconia. Among these, Al2O3 is preferred.

[0027] The ratio of the mass of Ni to the total mass of Ni and Mg in the NiMgO-based catalyst (Ni / (Ni+Mg) (metal equivalent)) is preferably in the range of 0.01 to 0.95. If the ratio is 0.95 or less, the amount of Mg is greater than or equal to a preferred level, and the ratio of Ni to Mg present in close proximity to Ni is appropriate, thereby improving the reducibility of Ni through interaction with Mg. As a result, the amount of metallic nickel precipitated on the catalyst surface increases, resulting in high catalytic activity. If the ratio is 0.01 or more, the abundance ratio of Ni is greater than or equal to a preferred level, making it easier for metallic nickel to precipitate on the catalyst surface, resulting in high catalytic activity.

[0028] The Ni content of the NiMgO-based catalyst is preferably 1 to 40% by mass. The Ni content of the NiMgO-based catalyst is more preferably 5% by mass or more, and even more preferably 15% by mass or more. The Ni content of the NiMgO-based catalyst may be 35% by mass or less, 30% by mass or less, or 25% by mass or less. If it is 1% by mass or more, the content of Ni, which is the active metal, per catalyst mass is sufficient, so that an increase in the amount of catalyst used can be suppressed. If it is 40% by mass or less, aggregation of metallic nickel particles precipitated on the catalyst surface can be suppressed, and high catalytic activity can be obtained.

[0029] In this specification, the content of each metal species constituting the catalyst is a value measured using X-ray fluorescence analysis. However, when light elements up to the second period of the periodic table (excluding hydrogen, helium, nitrogen, and oxygen) are contained, accurate component analysis using X-ray fluorescence analysis is difficult, so the value is measured using inductively coupled plasma (ICP). The content of each metal species contained in the catalyst is a value of the mass of each metal species relative to the mass of the entire catalyst after preparation. For example, the Ni content is the Ni mass in metal equivalent relative to the mass of the entire catalyst after preparation. The Ce content is the Ce mass in CeO2 equivalent relative to the mass of the entire catalyst after preparation. The Al content is the Al mass in Al2O3 equivalent relative to the mass of the entire catalyst after preparation. Note that the "catalyst after preparation" refers to the catalyst in a state before reduction treatment.

[0030] The NiMgO-based catalyst may be in powder form or a molded body formed by aggregation of the powder. From the perspective of reducing pressure loss, the NiMgO-based catalyst is preferably a molded body. Examples of the method for manufacturing the molded body include granulation, extrusion molding, press molding, and tableting. Examples of the shape of the molded body include spherical, cylindrical, ring-shaped, wheel-shaped, and granular.

[0031] The NiMgO-based catalyst is preferably reduced before use. The reduction can be carried out, for example, in a gas atmosphere containing hydrogen, preferably in a mixed gas atmosphere of hydrogen mixed with an inert gas such as nitrogen. The reduction can also be carried out with ammonia. In this case, the reduction may be carried out in a mixed gas atmosphere of ammonia mixed with hydrogen and nitrogen. The gas containing ammonia used for reduction may be recycled. The reduction temperature can be appropriately determined according to the catalyst species, but is usually 700°C to 1300°C. The reduction time should be sufficient to reduce the entire catalyst used. The reduction time depends on the amount of catalyst to be treated, etc., but is, for example, 30 minutes to 2 hours.

[0032] <NiMgO catalyst> The NiMgO catalyst is a catalyst containing NiMgO. The NiMgO catalyst can be produced, for example, by the following method. A nickel compound and a magnesium compound are mixed in a predetermined ratio to prepare a mixed aqueous solution. Next, the pH of the prepared mixed aqueous solution is adjusted to precipitate each element of nickel and magnesium dissolved in the aqueous solution in the form of hydroxide, oxyhydroxide, etc. Further, it is desirable to heat and age while stirring the solution, for example, with a stirrer, so that the hydroxides of nickel and magnesium are uniformly mixed and react. For example, the temperature of the aqueous solution may be set to about 65°C and held for about 1 hour. The precipitate thus obtained is thoroughly washed with pure water at about 80°C. Then, after separating water from the precipitate by, for example, suction filtration, the precipitate is dried under reduced pressure and further dried at a high temperature of about 120°C. Thereby, a precursor of the NiMgO catalyst can be obtained. Next, the obtained precursor of the NiMgO catalyst is calcined in air to obtain the NiMgO catalyst. The calcination temperature is usually in the range of 700 to 1300°C.

[0033] When preparing a mixed aqueous solution of a nickel compound and a magnesium compound, it is preferable to use a compound with high solubility in water. Specific examples thereof include nitrates, sulfates, and chlorides. Specific examples of the nickel compound include nickel nitrate hexahydrate, nickel sulfate hexahydrate, and nickel chloride hexahydrate. Specific examples of the magnesium compound include magnesium nitrate hexahydrate, magnesium sulfate, and magnesium chloride hexahydrate.

[0034] <NiMgO / Al2O3 catalyst> The NiMgO / Al2O3 catalyst is a catalyst containing NiMgO and alumina. In the catalyst, aluminum exists as Al2O3, a composite oxide, or a combination thereof. It is preferable that at least a portion of NiMgO and alumina form a composite oxide. The NiMgO / Al2O3 catalyst is preferably a sintered body of a mixture containing a nickel compound, a magnesium compound, and alumina. The Al content of the NiMgO / Al2O3 catalyst, calculated as Al2O3, is preferably 5 to 95% by mass. The Al content of the NiMgO / Al2O3 catalyst, calculated as Al2O3, may be 20% by mass or more, or 40% by mass or more. The Al content of the NiMgO / Al2O3 catalyst, calculated as Al2O3, may be 70% by mass or less, or 60% by mass or less. When the Al content is 5% by mass or more, the moldability of the NiMgO powder can be ensured. When the Al content is 95% by mass or less, the Ni and Mg contents can be ensured, resulting in high catalytic activity.

[0035] The NiMgO / Al2O3 catalyst can be produced, for example, by the following method. A nickel compound and a magnesium compound are mixed in a predetermined ratio to prepare a mixed aqueous solution. Next, the pH of the prepared mixed aqueous solution is adjusted to precipitate the nickel and magnesium elements dissolved in the aqueous solution in the form of hydroxides, oxyhydroxides, etc. Furthermore, it is desirable to heat and age the solution while stirring, for example, with a stirrer, so that the nickel and magnesium hydroxides react in a uniformly mixed state. For example, the temperature of the aqueous solution may be raised to approximately 65°C and maintained for approximately one hour. The precipitate thus obtained is thoroughly washed with pure water at approximately 80°C. After that, water is separated from the precipitate, for example, by suction filtration, and then the precipitate is mixed with Al2O3 sol and water and kneaded to obtain a mixture. The resulting mixture is dried under reduced pressure and then further dried at a high temperature of approximately 120°C. This produces a precursor of the NiMgO / Al2O3 catalyst. The resulting NiMgO / Al2O3 catalyst precursor is then calcined in air to obtain the NiMgO / Al2O3 catalyst. The firing temperature is usually in the range of 700 to 1300°C.

[0036] When preparing an aqueous mixed solution of a nickel compound and a magnesium compound, it is preferable to use a compound with high solubility in water. Specific examples thereof include nitrates, sulfates, and chlorides. Specific examples of the nickel compound include nickel nitrate hexahydrate, nickel sulfate hexahydrate, and nickel chloride hexahydrate. Specific examples of the magnesium compound include magnesium nitrate hexahydrate, magnesium sulfate, and magnesium chloride hexahydrate.

[0037] <NiMgO-CeO2 / Al2O3 catalyst> The NiMgO-CeO2 / Al2O3 catalyst is a catalyst containing NiMgO, ceria, and alumina. In the catalyst, cerium exists as CeO2, a composite oxide, or a combination thereof. In the catalyst, aluminum exists as Al2O3, a composite oxide, or a combination thereof. It is preferable that at least a part of NiMgO, ceria, and alumina forms a composite oxide. The NiMgO-CeO2 / Al2O3 catalyst is preferably a sintered body of a mixture containing a nickel compound, a magnesium compound, a cerium compound, and alumina.

[0038] The Ce content in terms of CeO2 of the NiMgO-CeO2 / Al2O3 catalyst is preferably 1 to 40% by mass. The Ce content in terms of CeO2 of the NiMgO-CeO2 / Al2O3 catalyst is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more. The Ce content in terms of CeO2 of the NiMgO-CeO2 / Al2O3 catalyst may be 30% by mass or less, 20% by mass or less, or 10% by mass or less. If it is 1% by mass or more, the precipitation of metallic nickel from NiMgO can be promoted due to the oxygen storage capacity of cerium oxide. If it is 40% by mass or less, the contents of Ni and MgO can be within an appropriate range, so that the ammonia decomposition activity of the catalyst can be fully exerted.

[0039] The Al content of the NiMgO-CeO2 / Al2O3 catalyst, calculated as Al2O3, is preferably 5 to 95% by mass. The Al content of the NiMgO-CeO2 / Al2O3 catalyst, calculated as Al2O3, may be 20% by mass or more, or 40% by mass or more. The Al content of the NiMgO-CeO2 / Al2O3 catalyst, calculated as Al2O3, may be 70% by mass or less, or 60% by mass or less. If the Al content is 5% by mass or more, the moldability of the NiMgO powder can be ensured. If the Al content is 95% by mass or less, the Ni, Mg, and Ce contents can be ensured, resulting in high catalytic activity.

[0040] The NiMgO-CeO2 / Al2O3 catalyst can be produced, for example, by the following method. A nickel compound, a magnesium compound, and a cerium compound are mixed in a predetermined ratio to prepare a mixed aqueous solution. The pH of the prepared mixed aqueous solution is then adjusted to precipitate the nickel, magnesium, and cerium elements dissolved in the aqueous solution in the form of hydroxides, oxyhydroxides, etc. Furthermore, it is desirable to heat and age the solution while stirring it with a stirrer, for example, so that the nickel, magnesium, and cerium hydroxides react in a uniformly mixed state. For example, the aqueous solution may be heated to approximately 65°C and maintained for approximately one hour. The precipitate thus obtained is thoroughly washed with pure water at approximately 80°C. Water is then separated from the precipitate, for example, by suction filtration, and the precipitate is then mixed with Al2O3 sol and water and kneaded to obtain a mixture. The resulting mixture is dried under reduced pressure and then further dried at a high temperature of approximately 120°C. This allows the precursor of the NiMgO-CeO2 / Al2O3 catalyst to be obtained. The resulting precursor of the NiMgO-CeO2 / Al2O3 catalyst is then calcined in air to obtain the NiMgO-CeO2 / Al2O3 catalyst. The calcination temperature is typically in the range of 700 to 1300°C.

[0041] When preparing a mixed aqueous solution of a nickel compound, a magnesium compound, and a cerium compound, it is preferable to use compounds that are highly soluble in water. Specific examples include nitrates, sulfates, and chlorides of nickel or magnesium, and nitrates and chlorides of cerium. Specific examples of nickel compounds include nickel nitrate hexahydrate, nickel sulfate hexahydrate, and nickel chloride hexahydrate. Specific examples of magnesium compounds include magnesium nitrate hexahydrate, magnesium sulfate, and magnesium chloride hexahydrate. Specific examples of cerium compounds include cerium nitrate hexahydrate and cerium chloride heptahydrate.

[0042] [Uses of hydrogen gas] The use of hydrogen gas is not particularly limited. Hydrogen gas can be used in various applications after removing unreacted ammonia as needed. Depending on the application, hydrogen gas may be used after removing unreacted ammonia and nitrogen as needed. Hydrogen gas can be used, for example, as a reducing agent when reducing iron oxide using a blast furnace, a shaft furnace, or a fluidized bed, or as atmospheric gas in an annealing furnace.

[0043] More specifically, hydrogen gas can be used to reduce iron oxide in a blast furnace or a shaft furnace by injecting the hydrogen gas into the furnace from a lower part of the furnace. In one embodiment, a method for producing iron and steel includes introducing hydrogen gas into a blast furnace or a shaft furnace and reducing iron oxide with the hydrogen gas, and the temperature T (°C) of the hydrogen gas from the outlet of the catalyst layer until it is introduced into the blast furnace or the shaft furnace satisfies the following condition: T(℃)≧650℃ The temperature T (℃) satisfies the following conditions: T (℃) ≧ catalyst bed outlet gas temperature (℃) - 100 It is preferable to satisfy the above requirement. By utilizing the thermal energy obtained from the hydrogen gas produced by the decomposition reaction of ammonia at high temperatures to thermally compensate for the heat absorbed during the reduction of iron oxide, energy efficiency can be improved and steelmaking costs can be reduced. In this case, energy loss can be reduced by introducing the hydrogen gas into the blast furnace or shaft furnace while retaining its heat as much as possible. In particular, by maintaining the temperature of the hydrogen gas within a range equal to or higher than the desired minimum temperature from the outlet of the catalyst layer until it is introduced into the blast furnace or shaft furnace, it becomes possible to introduce the hydrogen gas into the blast furnace or shaft furnace without reheating it. As a result, a hydrogen gas heating furnace is no longer necessary, and equipment costs can be reduced.

[0044] At least a portion of the thermal energy supplied to the reactor used in the method for producing hydrogen from ammonia may be derived from excess waste heat from the iron-making process. By utilizing excess waste heat from the iron-making process, the cost of hydrogen production can be reduced. The facility for producing hydrogen from ammonia may be installed in an area adjacent to the facility for the iron-making process.

[0045] [Hydrogen production facility from ammonia] For example, the production facility shown in FIG. 2 can be used to produce hydrogen from ammonia. In one embodiment, the production facility has a reformer, and for improved energy efficiency, a heat exchange boiler and a water supply system including a water supply preheater and a water supply pump are also installed. Ammonia gas is heated by a raw material heater and introduced into the reformer. The reformer can be a heating furnace in which catalyst-filled reaction tubes and burners are alternately installed. Auxiliary fuel is supplied to the reformer to heat the reaction tube. Specifically, in the heating furnace, ammonia gas flows from top to bottom inside the reaction tube, and while being heated from the outside of the reaction tube, it decomposes to produce AXgas. AXgas is a product gas obtained by thermally decomposing ammonia gas, and contains approximately 25% by volume of nitrogen gas, approximately 75% by volume of hydrogen gas, and a trace amount of unreacted ammonia gas. If necessary, hydrogen gas can be extracted from the AXgas by adsorbing and separating the unreacted ammonia contained in the produced AXgas and separating the nitrogen gas using H2-PSA.Specific examples of auxiliary fuels include hydrocarbons such as natural gas and LPG, and ammonia gas.

[0046] The facility for producing hydrogen from ammonia is not limited to the configuration shown in Figure 2. For example, the feed heater that heats the raw ammonia gas may exchange heat with exhaust gas supplied from the reformer to the boiler, and the feed water preheater may heat the boiler feed water by exchanging heat with exhaust gas leaving the boiler. The facility for producing hydrogen from ammonia may also be configured to condense by-product steam using a deaerator and reuse it as boiler feed water. [Example]

[0047] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these examples.

[0048] (Method for measuring ammonia conversion rate) The product gas discharged from the outlet of the reaction tube was injected into a gas chromatograph with TCD (Shimadzu Corporation, GC-2014) for analysis. The activity of the NH3 decomposition reaction was determined based on the NH3 conversion rate. The NH3 conversion rate was calculated using the following formula (1) from the concentrations of each component in the outlet gas. NH3 conversion rate (%) = (1 - volume of NH3 at outlet / volume of NH3 supplied) x 100 ...Formula (1)

[0049] (Preparation of Catalyst A (5 wt% Ru / CeO2 (JRC-CEO-5))) A ruthenium nitrate solution (Tanaka Kikinzoku Kogyo Co., Ltd., Ru concentration 53 mg / mL) was precisely weighed so that the Ru content of the catalyst was 5% by mass (calculated as Ru metal) and dissolved in 3 mL of pure water to obtain an aqueous solution. The resulting aqueous solution was added dropwise to ceria (Catalysis Society of Japan, Reference Catalyst CEO-5, powder) in an alumina crucible, and the ruthenium component was impregnated by evaporation to dryness. The resulting ruthenium-supported ceria catalyst precursor was placed in an electric muffle furnace together with the alumina crucible, dried in an air atmosphere, and calcined to obtain approximately 2 g of catalyst (Ru / CeO2 (JRC-CEO-5) with a Ru content of 5% by mass). Specifically, the temperature was raised from room temperature to 110°C over 30 minutes, dried for 12 hours, heated to 600°C over 100 minutes, calcined at 600°C for 5 hours, and then cooled to room temperature. The obtained catalyst was press-molded into tablets with a diameter of 20 mm using a pressure molding machine, then crushed, and the particle size was adjusted by sieving through a 300 to 500 μm sieve to obtain catalyst A. Furthermore, the composition of the obtained catalyst was confirmed by X-ray fluorescence analysis, and it was confirmed to be the desired composition.

[0050] (Preparation of catalyst B (5 wt% Ru / CeO2 (citric acid method))) A ruthenium nitrate solution (Tanaka Kikinzoku Kogyo Co., Ltd., Ru concentration 53 mg / mL) was precisely weighed so that the Ru content of the catalyst was 5% by mass in terms of Ru metal, and dissolved in 3 mL of pure water to obtain an aqueous solution. The resulting aqueous solution was added dropwise to ceria (powder) prepared by the citric acid method in an alumina crucible, and the ruthenium component was impregnated by evaporation to dryness. The resulting ruthenium-supported ceria catalyst precursor, along with the alumina crucible, was placed in an electric muffle furnace, dried in an air atmosphere, and calcined to obtain approximately 2 g of catalyst (Ru / CeO2 (citric acid method) with a Ru content of 5% by mass). Specifically, the temperature was raised from room temperature to 110°C over 30 minutes, dried for 12 hours, heated to 600°C over 100 minutes, calcined at 600°C for 5 hours, and then cooled to room temperature. The obtained catalyst was press-molded into tablets with a diameter of 20 mm using a pressure molding machine, pulverized, and the particle size was adjusted by sieving through a 300 to 500 μm sieve to obtain catalyst B. Furthermore, the composition of the obtained catalyst was confirmed by fluorescent X-ray analysis, and it was confirmed to be the desired composition.

[0051] (Preparation of catalyst C (20 wt% NiMgO / Al2O3)) Nickel nitrate hexahydrate (Kanto Chemical Co., Inc., purity >98.0%) and magnesium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >99.5%) were precisely weighed so that the Ni content of the catalyst was 20% by mass in terms of Ni metal and the molar ratio of the metal elements (nickel:magnesium) was 0.36:0.64. The mixture was heated to 60°C to prepare a mixed aqueous solution. While thoroughly stirring this mixed aqueous solution with a stirrer, a potassium carbonate aqueous solution heated to 60°C was added. This resulted in the co-precipitation of nickel and magnesium as hydroxides. The temperature of the aqueous solution was measured by inserting an alcohol thermometer into the solution. The mixed aqueous solution was then aged for a certain period of time while maintaining the temperature at 60°C, followed by suction filtration and thorough washing with pure water at 80°C. The precipitate obtained after washing was placed in a beaker, and alumina sol was added. This mixture was thoroughly mixed in a mixer equipped with a stirring blade and transferred to an eggplant-shaped flask. The eggplant-shaped flask was attached to a rotary evaporator, and the water was evaporated by stirring and suction. The nickel, magnesium, and aluminum compounds adhering to the eggplant-shaped flask wall were transferred to an evaporating dish and dried at an air temperature of 120°C. They were then calcined at an air temperature of 600°C. The resulting powder was formed into rings with a diameter of 15 mm, an inner diameter of 5 mm, and a height of 15 mm using a tableting machine to obtain a molded body. The molded body was then fired in an air atmosphere at 950°C to obtain a catalyst molded body (metal element molar ratio: Ni:Mg:Al = 0.18:0.31:0.51, oxide equivalent mass ratio: NiO:MgO:Al2O3 = 26:24:50). The resulting catalyst molded body was pulverized in an agate mortar and sieved through a 250-500 μm sieve to adjust the particle size, yielding catalyst C. Furthermore, the composition of the resulting catalyst was confirmed to be the desired composition by X-ray fluorescence analysis.

[0052] (Preparation of Catalyst D (20 wt% NiMgO)) Nickel nitrate hexahydrate (Kanto Chemical Co., Inc., purity >98.0%) and magnesium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >99.5%) were precisely weighed so that the Ni content of the catalyst was 20% by mass in terms of Ni metal and the molar ratio of the metal elements (nickel:magnesium) was 0.16:0.84. The mixture was heated to 60°C to prepare a mixed aqueous solution. While thoroughly stirring this mixed aqueous solution with a stirrer, an aqueous potassium carbonate solution heated to 60°C was added. This resulted in the co-precipitation of nickel and magnesium as hydroxides. The temperature of the aqueous solution was measured by inserting an alcohol thermometer into the solution. The mixed aqueous solution was then aged for a certain period of time while maintaining the temperature at 60°C. After filtration under suction, the mixture was thoroughly washed with pure water at 80°C. The precipitate obtained after washing was transferred to an eggplant-shaped flask. The eggplant-shaped flask was attached to a rotary evaporator, and the water was evaporated by suction while stirring. The nickel and magnesium compound adhering to the wall of the eggplant-shaped flask was transferred to an evaporating dish, dried at 120°C in an air atmosphere, and then calcined at 600°C in an air atmosphere. The resulting powder was formed into rings with a diameter of 15 mm, an inner diameter of 5 mm, and a height of 15 mm using a tableting machine to obtain a molded body. The molded body was fired at 950°C in an air atmosphere to obtain a catalyst molded body (metal element molar ratio Ni:Mg = 0.16:0.84, oxide equivalent mass ratio NiO:MgO = 26:74). The obtained catalyst molded body was pulverized in an agate mortar and sieved through a 300-500 μm sieve to adjust the particle size, thereby obtaining catalyst D. Furthermore, the composition of the obtained catalyst was confirmed by fluorescent X-ray analysis, and it was confirmed to be the desired composition.

[0053] (Preparation of catalyst E (20 wt% NiMgO-CeO2 / Al2O3)) Nickel nitrate hexahydrate (Kanto Chemical Co., Inc., purity >98.0%), cerium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >98.0%), and magnesium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >99.5%) were precisely weighed so that the Ni content of the catalyst was 20% by mass (calculated as Ni metal) and the molar ratio of the metal elements (nickel:cerium:magnesium) was 0.41:0.05:0.54. The mixture was heated to 60°C to prepare a mixed aqueous solution. While thoroughly stirring this mixed aqueous solution with a stirrer, a potassium carbonate aqueous solution heated to 60°C was added. This resulted in the co-precipitation of nickel, magnesium, and cerium as hydroxides. The temperature of the aqueous solution was measured by inserting an alcohol thermometer into the solution. The mixed aqueous solution was then aged by continuing stirring for a certain period of time while maintaining the temperature at 60°C, followed by suction filtration and thorough washing with pure water at 80°C. The precipitate obtained after washing was placed in a beaker and alumina sol was added. This mixture was thoroughly mixed in a mixer equipped with a stirring blade and transferred to an eggplant-shaped flask. The eggplant-shaped flask was attached to a rotary evaporator, and the water was evaporated by stirring and suction. The nickel, magnesium, cerium, and aluminum compounds adhering to the eggplant-shaped flask wall were transferred to an evaporating dish and dried at an air temperature of 120°C. They were then calcined at an air temperature of 600°C. The resulting powder was formed into rings with a diameter of 15 mm, a height of 15 mm, and an inner diameter of 5 mm using a tableting machine to obtain a molded body. The molded body was calcined at 950°C in an air atmosphere to obtain a catalyst molded body (molar ratio of metal elements: Ni:Ce:Mg:Al = 0.19:0.02:0.25:0.54, oxide-equivalent mass ratio: NiO:CeO2:MgO:Al2O3 = 25:7:18:50). The obtained catalyst molded body was pulverized in an agate mortar and sieved through a 300 to 500 μm sieve to adjust the particle size, thereby obtaining catalyst E. Furthermore, the composition of the obtained catalyst was confirmed by fluorescent X-ray analysis, and it was confirmed to be the desired composition.

[0054] (Preparation of catalyst F (1 wt% NiMgO / Al2O3)) Nickel nitrate hexahydrate (Kanto Chemical Co., Inc., purity >98.0%) and magnesium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >99.5%) were precisely weighed so that the Ni content of the catalyst was 1% by mass in terms of Ni metal and the molar ratio of the metal elements (nickel:magnesium) was 0.01:0.99. The mixture was heated to 60°C to prepare a mixed aqueous solution. While thoroughly stirring this mixed aqueous solution with a stirrer, an aqueous potassium carbonate solution heated to 60°C was added. This resulted in the co-precipitation of nickel and magnesium as hydroxides. The temperature of the aqueous solution was measured by inserting an alcohol thermometer into the solution. The mixed aqueous solution was then aged for a certain period of time while maintaining the temperature at 60°C, followed by suction filtration and thorough washing with pure water at 80°C. The precipitate obtained after washing was placed in a beaker and alumina sol was added. This mixture was thoroughly mixed in a mixer equipped with a stirring blade and transferred to an eggplant-shaped flask. The eggplant-shaped flask was attached to a rotary evaporator, and the water was evaporated by stirring and suction. The nickel, magnesium, and aluminum compounds adhering to the eggplant-shaped flask wall were transferred to an evaporating dish and dried at an air temperature of 120°C. They were then calcined at an air temperature of 600°C. The resulting powder was formed into rings with a diameter of 15 mm, an inner diameter of 5 mm, and a height of 15 mm using a tableting machine to obtain a molded body. The molded body was then fired in an air atmosphere at 950°C to obtain a catalyst molded body (metal element molar ratio: Ni:Mg:Al = 0.01:0.55:0.44, oxide equivalent mass ratio: NiO:MgO:Al2O3 = 1:49:50). The resulting catalyst molded body was pulverized in an agate mortar and sieved through a 300-500 μm sieve to adjust the particle size, yielding catalyst F. Furthermore, the composition of the resulting catalyst was confirmed by X-ray fluorescence analysis, confirming that it was the desired composition.

[0055] (Preparation of catalyst G (5 wt% NiMgO / Al2O3)) Nickel nitrate hexahydrate (Kanto Chemical Co., Inc., purity >98.0%) and magnesium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >99.5%) were precisely weighed so that the Ni content of the catalyst was 5% by mass in terms of Ni metal and the molar ratio of the metal elements (nickel:magnesium) was 0.07:0.93. The mixture was heated to 60°C to prepare a mixed aqueous solution. While thoroughly stirring this mixed aqueous solution with a stirrer, a potassium carbonate aqueous solution heated to 60°C was added. This resulted in the co-precipitation of nickel and magnesium as hydroxides. The temperature of the aqueous solution was measured by inserting an alcohol thermometer into the solution. The mixed aqueous solution was then aged for a certain period of time while maintaining the temperature at 60°C, followed by suction filtration and thorough washing with pure water at 80°C. The precipitate obtained after washing was placed in a beaker, and alumina sol was added. This mixture was thoroughly mixed in a mixer equipped with a stirring blade and transferred to an eggplant-shaped flask. The eggplant-shaped flask was attached to a rotary evaporator, and the water was evaporated by stirring and suction. The nickel, magnesium, and aluminum compounds adhering to the eggplant-shaped flask wall were transferred to an evaporating dish and dried at an air temperature of 120°C. They were then calcined at an air temperature of 600°C. The resulting powder was formed into rings with a diameter of 15 mm, an inner diameter of 5 mm, and a height of 15 mm using a tableting machine to obtain a molded body. The molded body was then fired in an air atmosphere at 950°C to obtain a catalyst molded body (metal element molar ratio: Ni:Mg:Al = 0.01:0.55:0.44, oxide equivalent mass ratio: NiO:MgO:Al2O3 = 1:49:50). The resulting catalyst molded body was pulverized in an agate mortar and sieved through a 300-500 μm sieve to adjust the particle size, yielding catalyst G. Furthermore, the composition of the resulting catalyst was confirmed to be the desired composition by X-ray fluorescence analysis.

[0056] (Preparation of catalyst H (30 wt% NiMgO / Al2O3)) Nickel nitrate hexahydrate (Kanto Chemical Co., Inc., purity >98.0%) and magnesium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity >99.5%) were precisely weighed so that the Ni content of the catalyst was 30% by mass in terms of Ni metal and the molar ratio of the metal elements (nickel:magnesium) was 0.64:0.36. The mixture was heated to 60°C to prepare a mixed aqueous solution. While thoroughly stirring this mixed aqueous solution with a stirrer, a potassium carbonate aqueous solution heated to 60°C was added. This resulted in the co-precipitation of nickel and magnesium as hydroxides. The temperature of the aqueous solution was measured by inserting an alcohol thermometer into the solution. The mixed aqueous solution was then aged for a certain period of time while maintaining the temperature at 60°C, followed by suction filtration and thorough washing with pure water at 80°C. The precipitate obtained after washing was placed in a beaker, and alumina sol was added. This mixture was thoroughly mixed in a mixer equipped with a stirring blade and transferred to an eggplant-shaped flask. The eggplant-shaped flask was attached to a rotary evaporator, and the water was evaporated by stirring and suction. The nickel, magnesium, and aluminum compounds adhering to the eggplant-shaped flask wall were transferred to an evaporating dish and dried at an air temperature of 120°C. They were then calcined at an air temperature of 600°C. The resulting powder was formed into rings with a diameter of 15 mm, an inner diameter of 5 mm, and a height of 15 mm using a tableting machine to obtain a molded body. The molded body was then fired in an air atmosphere at 950°C to obtain a catalyst molded body (metal element molar ratio: Ni:Mg:Al = 0.29:0.16:0.55, oxide equivalent mass ratio: NiO:MgO:Al2O3 = 38:12:50). The resulting catalyst molded body was pulverized in an agate mortar and sieved through a 300-500 μm sieve to adjust the particle size, yielding catalyst H. Furthermore, the composition of the resulting catalyst was confirmed to be the desired composition by X-ray fluorescence analysis.

[0057] The following commercially available catalysts were used: Catalyst I: Ni-based commercial catalyst, Catalyst J: Fe-based commercial catalyst

[0058] (Examples 1 to 6) Catalysts A–C, I, and J were mixed with SiO2 of the same particle size for catalyst dilution in the amounts listed in Table 1. The resulting mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube. A thermocouple for temperature measurement was inserted at the catalyst layer outlet. The catalyst layer was 2.5 mm thick. This fixed-bed reactor tube was set in the designated position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Hydrogen gas was then introduced into the reactor at a flow rate of 50 mL / min using a mass flow controller. After 1 hour of catalytic reduction, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a total flow rate of 90 mL / min with a molar ratio of He / NH3 = 8 / 1 to 1 / 8, and the F / W was varied from 12,000 to 480,000 mL-NH3 / (h·gcat). The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900° C. The relationship between F / W and ammonia conversion is shown in Figure 3.

[0059] [Table 1]

[0060] Figure 3 shows that 20 wt% NiMgO / Al2O3 has high activity in the decomposition reaction of ammonia under high temperature conditions.

[0061] (Comparative Examples 1 to 3 (F / W (mL-NH3 / (h gcat)): 12,000, 24,000, 36,000), and Examples 1 to 5 (F / W (mL-NH3 / (h gcat)): 48,000, 60,000, 72,000, 84,000, 96,000)) A mixture of 0.025 g of catalyst C and 0.017 g of SiO2 of the same particle size for diluting the catalyst was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube. A thermocouple for temperature measurement was inserted at the catalyst layer outlet. The catalyst layer was 2.5 mm thick. This fixed-bed reactor tube was set in a designated position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 750 °C under a nitrogen atmosphere. Then, using a mass flow controller, hydrogen gas was introduced into the reactor tube at a flow rate of 50 mL / min. After 1 hour of catalyst reduction, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at the designated flow rate. The F / W ratios for Comparative Examples 1 to 3 and Examples 1 to 5 were 12,000, 24,000, 36,000, 48,000, 60,000, 72,000, 84,000, and 96,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 750°C. The relationship between the F / W ratio and the ammonia conversion rate at 750°C is shown in Figure 4.

[0062] (Comparative Example 4 (F / W (mL-NH3 / (h gcat)): 24,000), and Examples 6 to 12 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000)) The reaction was carried out in the same manner as in Example 1, except that the temperature of the reaction tube was changed to 800°C and the F / W was set as follows. The F / W in Comparative Example 4 and Examples 6 to 12 was 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, and 192,000 mL-NH3 / (h gcat), respectively. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 800°C. The relationship between the F / W and the ammonia conversion rate at 800°C is shown in Figure 4.

[0063] (Examples 13 to 14 (F / W (mL-NH3 / (h gcat)): 180,000, 240,000)) The reaction was carried out in the same manner as in Example 1, except that the amount of catalyst C was changed to 0.01 g, the amount of SiO2 to 0.034 g, the temperature of the reaction tube was changed to 900°C, and the F / W was set as follows. The F / W in Examples 13 and 14 was 180,000 and 240,000 mL-NH3 / (h gcat), respectively. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W and the ammonia conversion rate at 900°C (high F / W) is shown in Figure 4.

[0064] (Comparative Example 5 (F / W (mL-NH3 / (h gcat)): 240,000), and Examples 15 to 21 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000)) The reaction was carried out in the same manner as in Example 1, except that the temperature of the reaction tube was changed to 900°C and the F / W was set as follows. The F / W in Comparative Example 5 and Examples 15 to 21 was 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, and 192,000 mL-NH3 / (h gcat), respectively. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W and the ammonia conversion rate at 900°C (low F / W) is shown in Figure 4.

[0065] (Comparative Examples 6~8 (F / W(mL-NH3 / (h gcat)): 24,000, 36,000, 48,000)) The reaction was carried out in the same manner as in Example 1, except that the amount of catalyst C was changed to 0.05 g, SiO2 was not used, the temperature of the reaction tube was changed to 700°C, and the F / W was set as follows. The F / W in Comparative Examples 6 to 8 was 24,000, 36,000, and 48,000 mL-NH3 / (h gcat), respectively. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 700°C. The relationship between F / W and ammonia conversion at 700°C is shown in Figure 4.

[0066] Figure 4 shows that a high ammonia conversion rate can be achieved even under high F / W conditions by using 20wt%NiMgO / Al2O3, which has high activity in the ammonia decomposition reaction under high temperature conditions, and conducting the reaction at a high temperature of 750°C or higher. Therefore, when producing hydrogen from ammonia using equipment of the same scale, it is possible to increase the yield of hydrogen gas by using 20wt%NiMgO / Al2O3 and conducting the reaction at a high temperature of 750°C or higher.

[0067] From the results of Examples 1 to 21 and Comparative Examples 1 to 8, the relationship between the outlet gas temperature of the catalyst layer and the maximum F / W value that gives 100% ammonia conversion under each temperature condition is summarized in Figure 5. As shown in Figure 5, when 20 wt% NiMgO / Al2O3 was used, the relationship between the outlet gas temperature of the catalyst layer and the maximum F / W value that gives 100% ammonia conversion under each temperature condition can be expressed by the following formula: F / W (mL-NH3 / (h·gcat)) = 857.14 × catalyst bed outlet gas temperature (℃) - 576,000 Therefore, when using 20 wt% NiMgO / Al2O3, the reaction can proceed with 100% ammonia conversion by setting F / W to a value equal to or less than that calculated by the above formula.

[0068] (Comparative Example 9 (F / W (mL-NH3 / (h gcat)): 24,000), and Examples 22 to 28 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000)) Catalyst F and SiO2 of the same particle size for diluting the catalyst were mixed in the amounts listed in Table 2. The mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube, and a thermocouple for temperature measurement was inserted at the outlet of the catalyst layer. The thickness of the catalyst layer was as listed in Table 2. This fixed-bed reactor tube was set in a predetermined position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Then, using a mass flow controller, hydrogen gas was introduced into the reactor tube at a flow rate of 50 mL / min. After 1 hour of catalyst reduction, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at the specified flow rate. The F / W ratios for Comparative Example 9 and Examples 22 to 28 were 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, and 192,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W ratio and the ammonia conversion rate is shown in Figure 6.

[0069] (Comparative Example 10 (F / W (mL-NH3 / (h gcat)): 24,000), and Examples 29 to 35 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000)) Reactions were carried out in the same manner as in Example 1, except that catalyst G was used instead of catalyst F and the F / W was as follows. The F / W in Comparative Example 10 and Examples 29 to 35 were 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, and 192,000 mL-NH3 / (h gcat), respectively. The relationship between F / W and ammonia conversion is shown in Figure 6.

[0070] (Comparative Example 11 (F / W (mL-NH3 / (h gcat)): 24,000) and Examples 36 to 47 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000, 240,000, 300,000, 360,000, 420,000, 480,000)) Catalyst C and SiO2 of the same particle size for diluting the catalyst were mixed in the amounts listed in Table 2. The mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube. A thermocouple for temperature measurement was inserted at the outlet of the catalyst layer. When the F / W was 24,000 to 192,000, the amount of catalyst was 0.025 g and the amount of SiO2 was 0.017 g. When the F / W was 240,000 to 480,000, the amount of catalyst was 0.01 g and the amount of SiO2 was 0.034 g. The thickness of the catalyst layer was as listed in Table 2. This fixed-bed reactor tube was set in a designated position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Hydrogen gas was then introduced into the reactor at a flow rate of 50 mL / min using a mass flow controller. After catalyst reduction treatment for 1 hour, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at a predetermined flow rate (F / W). The F / Ws for Comparative Example 11 and Examples 36 to 47 were 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000, 240,000, 300,000, 360,000, 420,000, and 480,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the gas temperature at the catalyst bed outlet was maintained at 900°C. The relationship between the F / W and the ammonia conversion is shown in Figure 6.

[0071] (Examples 48 to 55 (F / W (mL-NH3 / (h gcat)): 60,000, 120,000, 180,000, 240,000, 300,000, 360,000, 420,000, 480,000)) Catalyst H and SiO2 of the same particle size for diluting the catalyst were mixed in the amounts listed in Table 2. The mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube, and a thermocouple for temperature measurement was inserted at the catalyst layer outlet. The thickness of the catalyst layer was as listed in Table 2. This fixed-bed reactor tube was set in a predetermined position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Then, using a mass flow controller, hydrogen gas was introduced into the reactor tube at a flow rate of 50 mL / min. After 1 hour of catalyst reduction, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at the specified flow rate. The F / W ratios for Examples 48 to 55 were 60,000, 120,000, 180,000, 240,000, 300,000, 360,000, 420,000, and 480,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W ratio and the ammonia conversion rate is shown in Figure 6.

[0072] [Table 2]

[0073] From FIG. 6, it was found that increasing the Ni content can improve the catalytic activity for the ammonia decomposition reaction.

[0074] (Comparative Example 12 (F / W (mL-NH3 / (h gcat)): 24,000) and Examples 56 to 67 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000, 240,000, 300,000, 360,000, 420,000, 480,000)) Catalyst C and SiO2 of the same particle size for diluting the catalyst were mixed in the amounts listed in Table 3. The mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube. A thermocouple for temperature measurement was inserted at the outlet of the catalyst layer. When the F / W was 24,000 to 192,000, the amount of catalyst was 0.025 g and the amount of SiO2 was 0.017 g. When the F / W was 240,000 to 480,000, the amount of catalyst was 0.01 g and the amount of SiO2 was 0.034 g. The thickness of the catalyst layer was as listed in Table 3. This fixed-bed reactor tube was set in a designated position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Hydrogen gas was then introduced into the reactor at a flow rate of 50 mL / min using a mass flow controller. After catalyst reduction treatment for 1 hour, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at a predetermined flow rate (F / W). The F / Ws for Comparative Example 12 and Examples 56 to 67 were 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000, 240,000, 300,000, 360,000, 420,000, and 480,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W and the ammonia conversion is shown in Figure 7.

[0075] (Comparative Example 13 (F / W (mL-NH3 / (h gcat)): 24,000), and Examples 68 to 74 (F / W (mL-NH3 / (h gcat)): 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, 192,000)) Catalyst D and SiO2 of the same particle size for diluting the catalyst were mixed in the amounts listed in Table 3. The mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube, and a thermocouple for temperature measurement was inserted at the catalyst layer outlet. The thickness of the catalyst layer was as listed in Table 3. This fixed-bed reactor tube was set in a predetermined position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Then, using a mass flow controller, hydrogen gas was introduced into the reactor tube at a flow rate of 50 mL / min. After 1 hour of catalyst reduction, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at the specified flow rate. The F / W ratios for Comparative Example 13 and Examples 68 to 74 were 24,000, 48,000, 72,000, 96,000, 120,000, 144,000, 168,000, and 192,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W ratio and the ammonia conversion rate is shown in Figure 7.

[0076] (Examples 75 to 82 (F / W (mL-NH3 / (h gcat)): 60,000, 120,000, 180,000, 240,000, 300,000, 360,000, 420,000, 480,000)) Catalyst E and SiO2 of the same particle size for diluting the catalyst were mixed in the amounts listed in Table 3. The mixture was fixed with quartz wool so that it was positioned at the center of a SUS316L reactor tube, and a thermocouple for temperature measurement was inserted at the catalyst layer outlet. The thickness of the catalyst layer was as listed in Table 3. This fixed-bed reactor tube was set in a predetermined position in an electric furnace. Before starting the ammonia decomposition reaction, the reactor tube was heated to 900 °C under a nitrogen atmosphere. Then, using a mass flow controller, hydrogen gas was introduced into the reactor tube at a flow rate of 50 mL / min. After 1 hour of catalyst reduction, the reaction gas was switched to the reaction gas. The reaction gas was introduced at a molar ratio of He / NH3 = 8 / 1 to 1 / 8 at a total flow rate of 90 mL / min, and the reaction was carried out at the specified flow rate. The F / W ratios for Examples 75 to 82 were 60,000, 120,000, 180,000, 240,000, 300,000, 360,000, 420,000, and 480,000 mL-NH3 / (h gcat), respectively. The reaction pressure was 0.1 MPaA. During the reaction, the temperature of the electric furnace was adjusted so that the outlet gas temperature of the catalyst layer was maintained at 900°C. The relationship between the F / W ratio and the ammonia conversion rate is shown in Figure 7.

[0077] [Table 3]

Claims

1. A method for producing hydrogen from ammonia, comprising: introducing ammonia gas into a reactor and decomposing it in the presence of a catalyst to produce hydrogen gas; the outlet gas temperature of the catalyst layer in the reactor is 750°C or higher, The ratio F / W of the flow rate F of the ammonia gas to the mass W of the catalyst is 40,000 mL-NH ３ / (h·gcat) or more, the catalyst is a NiMgO-based catalyst, The Ni content of the NiMgO-based catalyst is 1 to 40 mass%. A method for producing hydrogen from ammonia.

2. The ratio F / W (mL-NH ３ / (h·gcat)) satisfies the following conditions: F / W (mL-NH ３ / (h·gcat)≦857.14×catalyst layer outlet gas temperature (°C)−576,000 fulfill, The method for producing hydrogen from ammonia according to claim 1.

3. A method of manufacturing steel, comprising: The method includes introducing the hydrogen gas obtained by the method according to claim 1 or 2 into a blast furnace or a shaft furnace, and reducing iron oxide with the hydrogen gas, The temperature T (°C) of the hydrogen gas from the outlet of the catalytic layer to the introduction into the blast furnace or the shaft furnace satisfies the following conditions: T (°C) ≧ 650°C fulfill, Steel manufacturing methods.

4. The temperature T (°C) is set under the following conditions: T (°C) ≥ outlet gas temperature of catalyst layer (°C) - 100 fulfill, The method for producing iron and steel according to claim 3.

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