Ammonia reforming plant

Abstract

To provide an ammonia reforming apparatus that can suppress nitriding corrosion and increase the concentration of hydrogen gas obtained. [Solution] The ammonia reforming apparatus 1 according to the present invention comprises an ammonia reformer 13 that generates a hydrogen-containing reformed gas from ammonia using a reforming catalyst 130 filled inside, wherein the reforming catalyst 130 is a ruthenium-based catalyst, and the ammonia reformer 13 is filled with one or more types of thermal conductors 131 together with the reforming catalyst 130, wherein the thermal conductors 131 are at least one selected from porous ceramics, ceramic particles, and metal particles.

Description

Technical Field

[0001] The present invention relates to an ammonia reforming device, and more particularly to an ammonia reforming device that can suppress nitriding corrosion and increase the obtained hydrogen gas concentration.

Background Art

[0002] Conventionally, it is known that ammonia causes nitriding corrosion when it comes into contact with metal at high temperatures. In particular, it is also known that the amount of nitriding corrosion increases as the ammonia concentration in the raw material gas is high or the temperature is high.

[0003] In Patent Document 1, in order to eliminate temperature unevenness, the heater part and the catalyst member are arranged concentrically, but there is a problem that high-concentration ammonia is heated in the heater part, and there is a risk of nitriding corrosion.

[0004] Also, in Patent Document 2, an attempt is made to suppress nitriding corrosion by mixing a dilution gas with the raw material ammonia gas to lower the ammonia concentration, but there is a problem that the obtained hydrogen gas concentration decreases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide an ammonia reforming device that can suppress nitriding corrosion and increase the obtained hydrogen gas concentration.

[0007] Another object of the present invention will become apparent from the following description. [Means for solving the problem]

[0008] The above problems are solved by the following inventions.

[0009] 1. It is equipped with an ammonia reformer that generates a hydrogen-containing reformed gas from ammonia using a reforming catalyst filled inside, The aforementioned reforming catalyst is a ruthenium-based catalyst. The ammonia reformer is filled with one or more types of heat conductors along with the reforming catalyst. The ammonia reforming apparatus is characterized in that the heat conductor is at least one selected from porous ceramics, ceramic particles, and metal particles. 2. The ammonia reforming apparatus according to claim 1, characterized in that the porous ceramic is selected from porous alumina (Al2O3) having a thermal conductivity of 3.5 [W / m·K] at 20°C, or porous zirconia (ZrO2) having a thermal conductivity of 0.8 [W / m·K] at 20°C. 3. The aforementioned ceramic particles are Aluminum nitride (AlN) particles with a thermal conductivity of 150 [W / m·K] at 20°C, Silicon carbide (SiC) particles with a thermal conductivity of 60 [W / m·K] at 20°C, Alumina (Al2O3) particles with a thermal conductivity of 32 [W / m·K] at 20℃, Sapphire particles with a thermal conductivity of 42 [W / m·K] at 20℃, Zirconia (ZrO2) particles with a thermal conductivity of 3 [W / m·K] at 20℃, Alternatively, silicon nitride (Si3N4) particles with a thermal conductivity of 20 [W / m·K] at 20°C. The ammonia reforming apparatus according to claim 1, characterized by being selected from among. 4. The ammonia reforming apparatus according to claim 1, wherein the metal particles are selected from nickel metal particles (Ni) having a thermal conductivity of 85 [W / m·K] at 20°C or SUS304 metal particles having a thermal conductivity of 16 [W / m·K] at 20°C. 5. The ammonia reformer is housed in a container, The ammonia reforming apparatus according to any one of claims 1 to 4, characterized in that in the process of introducing and discharging a heat exchange gas into the container, a heat source capable of supplying an endothermic reaction of ammonia to the reforming catalyst in the ammonia reformer is provided. 6. The ammonia reforming apparatus according to any one of claims 1 to 4, characterized in that the filling ratio of the heat conductor filled in the reforming catalyst is changed in the flow direction from the upstream to the downstream of the ammonia gas.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide an ammonia reforming apparatus that suppresses nitriding corrosion and increases the obtained hydrogen gas concentration.

Brief Description of the Drawings

[0011] [Figure 1] Schematic cross-sectional view showing an example of the ammonia reforming apparatus of the present invention [Figure 2] Explanatory drawing showing an example of an ammonia reformer [Figure 3] Explanatory drawing showing another example of an ammonia reformer [Figure 4] Drawing for explaining the embodiment of the ammonia reformer adopted in the examples [Figure 5] Graph showing the experimental results of the reference example [Figure 6] Graph showing the experimental results of Example 1 [Figure 7] Graph showing the experimental results of Example 2 [Figure 8] Graph showing the experimental results of Example 3 [Figure 9] Graph showing the experimental results of Example 4 [Figure 10]Graph showing the experimental results of Example 5 [Figure 11] Graph showing the experimental results comparing Example 6 and Comparative Example 2 [Figure 12] Graph showing the experimental results comparing Example 7, Example 6, and Comparative Example 2

Mode for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present invention will be described.

[0013] FIG. 1 is a schematic cross-sectional view showing an example of an ammonia reforming apparatus of the present invention, FIG. 2 is an explanatory view showing an example of an ammonia reformer, and FIG. 3 is an explanatory view showing another example of an ammonia reformer.

[0014] In FIG. 1, reference numeral 1 denotes an ammonia reforming apparatus. Although not particularly limited, an ammonia gas storage section 10 is provided at one end, and a reformed gas storage section 11 is provided at the other end. A cylindrical container is formed between the ammonia gas storage section 10 and the reformed gas storage section 11.

[0015] An inlet 100 for ammonia gas as a reforming raw material is provided in the ammonia gas storage section 10, and an outlet 110 for the reformed gas is provided in the reformed gas storage section 11.

[0016] The raw material for generating the reformed gas is preferably ammonia gas. The method for obtaining the raw material ammonia gas is not particularly limited, and liquid ammonia can also be gasified using an evaporator (not shown) to generate ammonia gas as the raw material.

[0017] Ammonia gas is decomposed into nitrogen gas and hydrogen gas by the reaction of 2NH3→N2+3H2 to generate reformed gas. The reformed gas may also contain a small amount of unreacted ammonia gas.

[0018] In this invention, the term "reformed gas" refers to, for example, when using ammonia as engine fuel. While its use as fuel falls under the same category, reforming aims to improve the quality of the fuel, and the resulting gas is called reformed gas. If the components of the reformed gas are nitrogen gas, hydrogen gas, and a small amount of unreacted ammonia gas as described above, the small amount of unreacted ammonia gas is not reformed, and nitrogen gas is an inert component and unsuitable as a fuel. Therefore, the qualitative improvement lies in the generation of hydrogen gas.

[0019] Ammonia is one of the hydrogen carriers, and this invention aims to utilize ammonia by reforming it into hydrogen. The reaction of reforming ammonia into hydrogen is an endothermic reaction, and generally proceeds at high temperatures when the ammonia is in contact with a catalyst.

[0020] In this invention, a heat exchange type reforming apparatus, as shown in Figures 1, 2, and 3, can be preferably used to utilize a heat source such as high-temperature exhaust gas for the reforming reaction. For the separation of hydrogen and nitrogen gases, zeolites or hydrogen separation membranes can be used as needed.

[0021] In the embodiment shown in Figure 1, a heat exchange gas inlet 120 is provided in the cylindrical container 12 between the ammonia gas storage section 10 and the reformed gas storage section 11, and an outlet 121 is provided on the opposite side of the inlet 120. In this embodiment, since the heat source necessary for the endothermic reaction is supplied by such a heat exchange gas, it is referred to as a heat exchange type reformer, as described above.

[0022] A cylindrical ammonia reformer 13 is installed inside the cylindrical container 12. The example shown in Figure 1 is a configuration with one ammonia reformer 13, but two or more can be installed depending on the production target of the reformed gas, etc.

[0023] As shown in Figure 2, the ammonia reformer 13 is filled with a reforming catalyst 130, and the reforming catalyst 130 acts to produce a hydrogen-containing reformed gas from ammonia.

[0024] The side portion 13a of the ammonia reformer 13 is preferably formed of a plate-shaped metal with excellent thermal conductivity. If the heat exchange gas contains corrosive gases, it is preferable to use a corrosion-resistant metal.

[0025] As the reforming catalyst 130, a ruthenium-based catalyst is used. The ruthenium-based catalyst may be a Ru (ruthenium) catalyst alone, but other metal catalysts may be mixed in to the extent that the objectives of the present invention can be achieved.

[0026] As shown in Figure 2, the ammonia reformer 13 contains a mixture of a reforming catalyst 130 and a heat conductor 131. In this embodiment, it is preferable that the ammonia reformer 13 is filled with one or more types of heat conductors 131 along with the reforming catalyst 130.

[0027] The ruthenium-based catalyst used in reforming catalyst 130 promotes the reaction at low temperatures below 500°C, but the endothermic reaction lowers the temperature of the ammonia gas, causing the reaction to halt. Therefore, a higher temperature heat exchange gas is required. By filling the device with one or more types of thermal conductors 131 along with the ruthenium-based catalyst 130, the amount of reforming reaction can be limited while operating at low temperatures, reducing the amount of heat absorbed, thereby eliminating the need for high-temperature heat exchange gases.

[0028] When the purpose is to conduct heat, the thermal conductor 131 is preferably at least one selected from porous ceramics, ceramic particles, metal particles, etc.

[0029] Examples of porous ceramics include porous alumina (Al2O3: 3.5) and porous zirconia (ZrO2: 0.8). Examples of ceramic particles include aluminum nitride (AlN: 150), silicon carbide (SiC: 60), alumina (Al2O3: 32), sapphire (42), zirconia (ZrO2: 3), and silicon nitride (Si3N4: 20). Examples of metal particles (metals) include nickel (Ni: 85) and SUS304 (16). The values ​​in parentheses indicate the thermal conductivity at 20°C [W / m·K].

[0030] Furthermore, in the present invention, when both thermal conductivity and reforming catalytic activity are desired, it is preferable to use at least one selected from nickel-based catalysts, cobalt-based catalysts, iron-based catalysts, platinum-based catalysts, magnesium-based catalysts, and palladium-based catalysts as the thermal conductor.

[0031] In this embodiment, it is preferable to vary the filling (mixing) ratio of the heat conductor 131 mixed into the reforming catalyst 130 with respect to the flow direction of the ammonia gas from upstream (left side in the drawing) to downstream (right side in the drawing), as shown in Figure 3. In terms of the mode of change, for example, it is preferable that the mixing ratio of the reforming catalyst 130 is greater downstream of the ammonia gas than upstream, i.e., that is, that the mixing density is greater.

[0032] According to these embodiments, by increasing the mixing ratio or heat exchange surface area of ​​the reforming catalyst 130 in the direction of ammonia gas flow and balancing the amount of heat absorbed and the amount of heat exchanged, it is possible to prevent a decrease in the ammonia gas temperature.

[0033] In Figure 3, 14 is a first ammonia reformer that generates a hydrogen-containing reformed gas from ammonia using a reforming catalyst 130 packed inside.

[0034] Reference numeral 15 denotes a second ammonia reformer located downstream of the first ammonia reformer 14, which generates a hydrogen-containing reformed gas from ammonia using a reforming catalyst (not shown) packed inside. 16 is a heating element that generates heat when electricity is applied, and it is preferable that, for example, an electric heater, a burner, waste heat from a fuel cell, or a combination of these heat sources be used. The reforming catalysts used to fill the first ammonia reformer 14 and the second ammonia reformer 15 are ruthenium-based catalysts, similar to the embodiment shown in Figure 2.

[0035] In this embodiment, the first ammonia reformer 14 has a heat conductor 131 mixed with the reforming catalyst 130, and the heating unit 16 heats the second ammonia reformer 15.

[0036] The reformed gas that has passed through the first ammonia reformer 14 may contain undecomposed ammonia in addition to the decomposition products hydrogen and nitrogen. Because the ammonia contained in the reformed gas is at a low concentration, heating it with the heater in the heating section 16 of the second ammonia reformer 15 has the effect of suppressing the risk of nitriding corrosion.

[0037] In this embodiment as well, it is preferable to vary the mixing ratio of the heat conductor 131 packed and mixed together with the reforming catalyst 130 with respect to the flow direction of the ammonia gas from upstream to downstream.

[0038] Although preferred embodiments of the present invention have been described above, similar effects can be achieved by using low-supported ruthenium catalysts. However, this does not preclude the use of multiple catalysts with different support amounts to create a support amount gradient.

[0039] Furthermore, when diluting with a thermal conductor, using a ruthenium-based catalyst with a high supported amount can be expected to improve the efficiency of precious metal recovery.

[0040] Furthermore, it reduces costs by decreasing the amount of expensive Ru catalyst used while maintaining the same reforming rate.

[0041] Furthermore, ruthenium-based catalysts undergo sintering at high temperatures, which reduces their catalytic activity. However, operating them at low temperatures can reduce the risk of sintering.

[0042] When the device of the present invention is installed on a ship, nitriding corrosion can be suppressed, which extends the lifespan of the container and reduces the frequency of maintenance and replacement, thus providing an effect or benefit.

[0043] Furthermore, because a lower reforming temperature is required, when using the exhaust gas from a ship's main engine (350°C to 450°C) or auxiliary engine (400°C to 550°C) as the heat exchange gas, it is possible to eliminate or minimize the need for a heating device. [Examples]

[0044] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0045] (Reference example) As shown in the reference example in Figure 4(A), an ammonia reformer (300 mm) was used, and only Ru pellets were packed as the ruthenium (Ru) catalyst (hereinafter abbreviated as Ru catalyst as necessary), without using a heat conductor. Ammonia gas was supplied to the above-mentioned ammonia reformer under fixed conditions of a space velocity (SV) of 1500 (1 / h) (relative to Ru catalyst amount) to conduct reforming experiments. The experimental results are shown in Figures 5(A) and 5(B).

[0046] The graph in Figure 5(A) shows the NH3 reforming rate at the reformed gas outlet when the reforming temperature (heat exchange gas temperature) is changed to 450°C, 500°C, 550°C, and 600°C. Figure 5(B) shows the relationship between catalyst length (mm) and gas temperature (°C). The experiment described above shows that the modification rate does not reach 90% at 500°C.

[0047] (Example 1) As shown in Example 1 of Figure 4(B), an ammonia reformer (550 mm) was used, filled with Ru catalyst and heat conductor. The Ru catalyst layer was arranged so as to sandwich the heat conductor layer. Specifically, the ammonia reformer was arranged as follows: Ru catalyst layer / heat conductor layer / Ru catalyst layer / heat conductor layer / Ru catalyst layer / heat conductor layer / Ru catalyst layer / heat conductor layer / Ru catalyst layer / heat conductor layer / Ru catalyst layer. A Ru catalyst was used in the Ru catalyst layer. The thermal conductor layer used porous alumina without a catalyst support. Ammonia gas was supplied to an ammonia reformer under fixed conditions of a space velocity (SV) of 1500 (1 / h) (relative to Ru catalyst amount), and a reforming experiment was conducted. The experimental results are shown in Figure 6.

[0048] The graph in Figure 6(A) shows the NH3 reforming rate at the reformed gas outlet when the reforming temperature is varied to 450°C, 500°C, 550°C, and 600°C. It is shown in comparison with a reference example. Figure 6(B) shows the relationship between catalyst length (mm) and gas temperature (°C).

[0049] According to the above experiment, the reforming rate improved to 90% at 500°C, and the required heat exchange gas temperature could be reduced by about 25°C. Compared to the reference example, it can be seen that the amount of heat absorbed increased and the decrease in gas temperature was mitigated.

[0050] (Example 2) As shown in Example 2 of Figure 4(C), one ammonia reformer was used, and a 50% thermal conductor was mixed with the Ru reforming catalyst and packed into the reformer. The thermal conductor used was porous alumina without a catalyst support. Ammonia gas was supplied to an ammonia reformer under fixed conditions of a space velocity (SV) of 1500 (1 / h) (relative to Ru catalyst amount), and a reforming experiment was conducted.

[0051] The graph in Figure 7(A) shows the NH3 reforming rate at the reformed gas outlet when the reforming temperature is varied to 450°C, 500°C, 550°C, and 600°C. It is shown in comparison with a reference example. Figure 7(B) shows the relationship between catalyst length (mm) and gas temperature (°C). According to the above experiment, it can be seen that, similar to the alternating lamination in Example 1, the modification rate reaches 90% at 500°C.

[0052] (Example 3) As shown in Example 3 of Figure 4(D), the catalyst layer of the ammonia reformer was divided into three layers, and the mixing and packing ratio of the heat conductor to the catalyst in each layer was changed, gradually increasing the mixing and packing ratio. The mixing ratio of the heat conductor was changed so that it was 40% in the first layer, 50% in the second layer, and 60% in the third layer. Ammonia gas was supplied to an ammonia reformer under fixed conditions of a space velocity (SV) of 1500 (1 / h) (relative to Ru catalyst amount), and a reforming experiment was conducted.

[0053] The graph in Figure 8(A) shows the reforming rate of NH3 at each temperature of the reformed gas outlet, as the reforming temperature was varied to 498°C, 500°C, 502°C, and 504°C. The experiment was conducted in comparison with Example 2. Figure 8(B) shows the relationship between catalyst length (mm) and gas temperature (°C). The experiment was conducted in comparison with Example 2. The above experiment shows that it is possible to further reduce the required heat exchange gas temperature from Example 2. Furthermore, it is evident that by adjusting the mixing ratio, the amount of heat absorbed and the temperature distribution can be adjusted, thereby improving the reforming performance.

[0054] (Example 4) As shown in Example 4 of Figure 4(E), one ammonia reformer was filled with a mixture of Ru catalyst and thermal conductor. A nickel-based catalyst (hereinafter abbreviated as Ni catalyst as needed) was used as a thermal conductor, blended at a ratio of 1:1 to 50% of the Ru catalyst. Ammonia gas was supplied to an ammonia reformer under fixed conditions of a space velocity (SV) of 1500 (1 / h) (relative to Ru catalyst amount), and a reforming experiment was conducted.

[0055] The graph in Figure 9(A) shows the NH3 reforming rate at the reformed gas outlet when the reforming temperature is varied to 450°C, 500°C, 550°C, and 600°C. It is shown in comparison with a reference example. Figure 9(B) shows the relationship between catalyst length (mm) and gas temperature (°C). The experiment was conducted in comparison with the reference example. The above experiment shows that the required heat exchange gas temperature can be reduced by about 40°C. Furthermore, compared to the reference example, it can be seen that the amount of heat absorbed increases, and the decrease in gas temperature is mitigated.

[0056] (Example 5) As shown in Example 5 of Figure 4(F), the catalyst layer of the ammonia reformer was divided into three layers, and the mixing ratio of nickel-based catalyst to the catalyst in each layer was varied to increase from 10%, 50%, and 90%. Ammonia gas was supplied to an ammonia reformer under fixed conditions of a space velocity (SV) of 1500 (1 / h) (relative to Ru catalyst amount), and a reforming experiment was conducted.

[0057] The graph in Figure 10(A) shows the reforming rate of NH3 at each temperature of the reformed gas outlet, as the reforming temperature was varied to 478°C, 480°C, 482°C, and 484°C. The experiment was conducted in comparison with Example 4. Figure 10(B) shows the relationship between catalyst length (mm) and gas temperature (°C). The experiment was conducted in comparison with Example 4. The above experiment shows that it is possible to further reduce the required heat exchange gas temperature from Example 4. Furthermore, it is evident that by adjusting the mixing ratio, the amount of heat absorbed and the temperature distribution can be adjusted, thereby improving the reforming performance.

[0058] (Example 6) In Example 2, the reforming experiment was carried out in the same manner as in Example 2, except that the space velocity (SV) when supplying ammonia gas to the ammonia reformer was fixed at 2900 (1 / h) (relative to Ru catalyst amount).

[0059] (Reference example 2) The reforming experiment was conducted in the same manner as in the reference example, except that the space velocity (SV) was fixed at 2900 (1 / h) (relative to the amount of Ru catalyst).

[0060] The graph in Figure 11 shows the NH3 reforming rate at various temperatures of the reformed gas outlet when the reforming temperature is varied in Example 6 and Reference Example 2. Example 6 and Reference Example 2 are shown for comparison. According to the above experiment, Example 6 showed a slight improvement in modification performance compared to Reference Example 2.

[0061] (Example 7) In Example 6, the modification experiment was carried out in the same manner as in Example 6, except that the catalyst-free porous alumina used as the thermal conductor was replaced with nickel metal particles.

[0062] The graph in Figure 12 shows the NH3 reforming rate at each temperature of the reformed gas outlet when the reforming temperature is varied in Example 6, Example 7, and Reference Example 2. Example 6, Example 7, and Reference Example 2 are shown for comparison. According to the above experiment, Example 7 was able to reduce the required heat exchange gas temperature by 25°C compared to Example 6, and furthermore, the higher the thermal conductivity of the heat conductor, the greater the improvement in reforming performance. [Explanation of Symbols]

[0063] 1. Ammonia reforming plant 10 Ammonia gas storage section 100 Ammonia gas inlet 11. Reformed Gas Storage Section 110 Reformed gas outlet 12 Cylindrical containers 120 Heat exchange gas inlet 121 Heat exchange gas outlet 13 Ammonia reformer 13a Side 130 Reforming catalyst 131 Thermal Conductors 14. First Ammonia Reformer 15. Second ammonia reformer 16 Heating section

Claims

1. It is equipped with an ammonia reformer that generates a hydrogen-containing reformed gas from ammonia using a reforming catalyst filled inside, The aforementioned reforming catalyst is a ruthenium-based catalyst. The ammonia reformer is filled with one or more types of heat conductors along with the reforming catalyst. The ammonia reforming apparatus is characterized in that the heat conductor is at least one selected from porous ceramics, ceramic particles, and metal particles.

2. The porous ceramic is porous alumina (Al) with a thermal conductivity of 3.5 [W / m·K] at 20°C. 2 O 3 ), or porous zirconia (ZrO) with a thermal conductivity of 0.8 [W / m·K] at 20℃. 2 The ammonia reforming apparatus according to claim 1, characterized in that it is selected from ).

3. The aforementioned ceramic particles are Aluminum nitride (AlN) particles with a thermal conductivity of 150 [W / m·K] at 20°C, Silicon carbide (SiC) particles with a thermal conductivity of 60 [W / m·K] at 20°C, Alumina (Al) has a thermal conductivity of 32 [W / m·K] at 20℃. 2 O 3 )particle, Sapphire particles with a thermal conductivity of 42 [W / m·K] at 20℃, Zirconia (ZrO) has a thermal conductivity of 3 [W / m·K] at 20℃. 2 )particle, Alternatively, silicon nitride (Si) with a thermal conductivity of 20 [W / m·K] at 20°C. 3 N 4 )particle The ammonia reforming apparatus according to claim 1, characterized by being selected from among.

4. The ammonia reforming apparatus according to claim 1, characterized in that the metal particles are selected from nickel metal particles (Ni) having a thermal conductivity of 85 [W / m·K] at 20°C, or SUS304 metal particles having a thermal conductivity of 16 [W / m·K] at 20°C.

5. The ammonia reformer is housed in a container, The ammonia reforming apparatus according to any one of claims 1 to 4, characterized in that it comprises a configuration to supply a heat source capable of carrying out an endothermic reaction of ammonia to the reforming catalyst in the ammonia reformer during the process of introducing and discharging heat exchange gas into the container.

6. The ammonia reforming apparatus according to any one of claims 1 to 4, characterized in that the filling ratio of the heat conductors filling the reforming catalyst is changed with respect to the flow direction of the ammonia gas from upstream to downstream.

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