JP2019167265A - Ammonia decomposition device - Google Patents

Abstract

To provide an inexpensive ammonia decomposition device suppressing hydrogen poisoning, in the device, without directly combusting ammonia, supplying hydrogen acquired by decomposing ammonia to a combustor and combusting the hydrogen, thereby capable of being applied for a gas turbin system or the like capable of suppressing use of a selection catalytic reduction (SCR) device to NOx to minimum level.SOLUTION: The ammonia decomposition device has a catalyst filling part 2a comprising a low temperature actuation catalyst 11 and a high temperature actuation catalyst 12, and decomposes ammonia until a decomposition rate of ammonia becomes 50% or greater. As the low temperature actuation catalyst, an Ru based catalyst, and as the high temperature actuation catalyst, a non-Ru based catalyst including one kind, two kinds or more kinds out of the Ni based catalyst, Fe based catalyst and Co based catalyst are used.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ammonia decomposition apparatus for producing hydrogen by ammonia decomposition.

  Generally, fossil fuel is used as the fuel sent to the combustor for power generation. As is well known, reducing the amount of fossil fuel used is an important environmental measure, and using clean hydrogen as a fuel is an effective environmental measure.

On the other hand, hydrogen is difficult to become liquid and difficult to transport. On the other hand, not a hydrogen itself but a hydrogen-containing compound may be used as a hydrogen carrier. One of hydrogen carriers for transporting hydrogen as a liquid is ammonia (NH ₃ ).

Here, when ammonia is used as a hydrogen carrier, ammonia may be decomposed and used as hydrogen (H ₂ ) or ammonia may be used as it is.

As the catalyst used for the decomposition of ammonia, a Ru (ruthenium) -based catalyst that is used at the time of ammonia synthesis and is known to have high performance is effective. However, Ru-based catalysts are expensive, and many Ru-based catalysts are susceptible to a phenomenon (hydrogen poisoning) that causes a decrease in activity when the Ru surface is covered with dissociated and adsorbed hydrogen atoms.
This hydrogen poisoning is more susceptible to the higher the hydrogen partial pressure at low temperatures, and in order to avoid it, it was necessary to lower the hydrogen partial pressure (use it at a low pressure) and use it at a high temperature.

  When ammonia is used as a direct fuel, co-firing with natural gas, which is highly available, has been studied. For example, in Patent Document 1, natural gas and ammonia are supplied to a combustor and burned. However, NOx is generated when co-firing in this way. For this reason, measures such as reducing NOx in the reduction region (R2) or providing a reduction catalyst chamber (1h) downstream of the waste heat recovery boiler are necessary.

JP-A-2006-191507

An object of the present invention is to provide an ammonia decomposition apparatus that suppresses hydrogen poisoning at low cost.
Further, for example, in a gas turbine system that employs the ammonia decomposing apparatus according to the present invention, instead of directly burning ammonia, hydrogen obtained by decomposing ammonia is supplied to the combustor and burned. The use of a selective catalytic reduction (SCR) device for NOx can be minimized.

In order to achieve the above object, an ammonia decomposition apparatus according to the present invention is an apparatus for decomposing ammonia until a decomposition rate of 50% or more is obtained to obtain hydrogen, a low temperature operation type catalyst (for example, a Ru-based catalyst) and a high temperature. It is characterized by using a combination of both working catalysts (non-Ru catalysts). The reaction proceeds according to the following formula:
NH ₃ → 1 / 2N ₂ + 3 / 2H ₂ (1)

  The ammonia decomposing apparatus according to the present invention is a preferred embodiment in which an ammonia decomposing catalyst is incorporated, a low temperature operating catalyst is disposed on the ammonia inlet side, and a high temperature operating catalyst is disposed on the ammonia outlet side. The heat required for decomposition is supplied by a non-contact heat medium.

The low temperature operation type catalyst on the inlet side is preferably a Ru-based catalyst capable of decomposing ammonia even in the region of 400 ° C. or lower. As the high-temperature operation type catalyst (non-Ru catalyst) on the outlet side, it is preferable to use one or more of Ni-based catalyst, Fe-based catalyst, and Co-based catalyst that exhibit activity in a temperature range exceeding 400 ° C. It is. By using an expensive Ru-based catalyst only on the inlet side, it is possible to reduce the amount of Ru-based catalyst used. The heat of reaction for ammonia decomposition is supplied by circulating a heating heat medium countercurrently to the ammonia flow through the reaction tube wall.
Therefore, the temperature of the catalyst layer ammonia inlet is lower than that of the catalyst layer ammonia outlet. When a high-temperature operation type catalyst without hydrogen poisoning is used at the catalyst layer ammonia inlet, the temperature must be maintained in order to improve the reaction rate, and a large amount of heat medium has to be circulated. By using a Ru-based catalyst on the ammonia inlet side of the catalyst layer, a sufficient reaction rate can be obtained even at a low temperature, so that the flow rate of the heat medium can be reduced. In addition, the catalyst layer ammonia inlet has a lower hydrogen partial pressure and is less susceptible to hydrogen poisoning even at higher pressures because the reaction does not proceed compared to the catalyst layer ammonia outlet.
Thus, the ammonia decomposition apparatus according to the present invention can employ a plurality of catalysts suitable for the degree of reaction progress.

  On the ammonia inlet side, the decomposed hydrogen is in a relatively thin state, and even with an ordinary Ru-based catalyst, the problem of hydrogen poisoning can be reduced. The decomposition apparatus minimizes the decrease in activity. In addition, it is also possible to make all Ru-based catalysts by filling the ammonia exit side with Ru-based catalysts that have been subjected to poisoning countermeasures.

  According to the present invention, by suppressing hydrogen poisoning, an ammonia decomposing apparatus having high performance can be provided at low cost.

1 is a conceptual cross-sectional view schematically illustrating an embodiment of an ammonia decomposition apparatus according to the present invention. It is a conceptual diagram explaining one Embodiment which applied the ammonia decomposition apparatus which concerns on this invention to the gas turbine system.

  Embodiments of an ammonia decomposition apparatus according to the present invention, a gas turbine system to which the ammonia decomposition apparatus is applied, and an operation method thereof will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an ammonia decomposition apparatus according to the present invention.
The ammonia decomposition apparatus 2 includes a catalyst filling unit 2a and a heat medium flow path 2b. The catalyst filling portion 2a is configured such that an ammonia flow path is formed, and the heat medium flow path 2b is surrounded in a cylindrical shape around the ammonia flow path. The catalyst filling part 2a and the heat medium flow path 2b are configured to be fluidly blocked from each other. That is, the cylindrical catalyst filling portion 2a is surrounded by the cylindrical heat medium flow path 2b, and FIG. 1 shows a longitudinal section thereof. An example of the heat medium is combustion exhaust gas.
L _{1 to} L ₄ indicate inflow or outflow lines. The lines L _{1 to} L ₄ will be described later in connection with the embodiment of the gas turbine system shown in FIG.

The catalyst filling portion 2a is composed of two layers, an inlet side catalyst layer 11 filled with a low temperature operation type catalyst and an outlet side catalyst layer 12 filled with a high temperature operation type catalyst. The inlet side is the ammonia inlet side, and the outlet side is the ammonia outlet side. The filling ratio (length ratio, C1: C2 in the figure) of the inlet side catalyst layer 11 and the outlet side catalyst layer 12 in the ammonia flow direction is C1 / C2 = 1/3 to 3/2 with the same filling density. Is preferred.
As the low temperature operation type catalyst, for example, a Ru-based catalyst capable of decomposing ammonia even in a region of 400 ° C. or lower is suitable. Examples of the high-temperature operation type catalyst include one or more non-Ru-based catalysts among Ni-based catalysts, Fe-based catalysts, and Co-based catalysts that exhibit activity in a temperature range exceeding 400 ° C. However, any metal or metal compound having ammonia decomposition characteristics can be employed as a high-temperature operation type catalyst.

As the Ru-based catalyst, specifically, Ru / Al ₂ O in which Ru is supported on Al ₂ O ₃ at a rate of 0.1 to 10% by mass, preferably 0.1 to 1.0% by mass. _Three catalysts can be exemplified. The support is not limited to Al ₂ O ₃ but may include MgO, activated carbon, BN, and the like.

Specifically, a Ni / Al ₂ O ₃ catalyst in which a Ni compound such as Ni and / or NiO is supported on Al ₂ O ₃ at a rate of 0.1 to 10% by mass or more as a Ni-based catalyst. It can be illustrated. The support is not limited to Al ₂ O ₃ but may include MgO, activated carbon, BN, and the like. In addition, a Ni compound such as NiO (however, a part including reduced metal Ni) may be employed as the Ni-based catalyst without being supported on the carrier.

Specifically, Fe / Al ₂ O in which Fe compounds such as Fe and / or Fe ₂ O ₃ are supported on Al ₂ O ₃ at a rate of 0.1 to 10% by mass or higher as the Fe-based catalyst. _Three catalysts can be exemplified. The support is not limited to Al ₂ O ₃ but may include MgO, activated carbon, BN, and the like. In addition, an Fe compound such as Fe ₂ O ₃ (however, a part including reduced metal Fe) can be used as the Fe-based catalyst without being supported on the carrier.

Specifically, as a Co-based catalyst, a Co / Al ₂ O ₃ catalyst in which a Co compound such as Co and / or CoO is supported on Al ₂ O ₃ at a rate of 0.1 to 10% by mass or higher. It can be illustrated. The support is not limited to Al ₂ O ₃ but may include MgO, activated carbon, BN, and the like. It is also possible to employ a Co compound such as CoO (provided that part thereof is included as reduced metal Co) as the Co-based catalyst without being supported on the carrier.

FIG. 2 shows an embodiment of a gas turbine system employing the ammonia decomposition apparatus according to the present invention.
The gas turbine system according to the present embodiment includes a gas turbine 1 and an ammonia decomposition device 2.
The gas turbine 1 includes a compressor 3, a combustor 4, and a turbine 5. In the gas turbine 1 of FIG. 1, the compressor 3 and the turbine 5 are directly connected coaxially via a turbine shaft 6. That is, the gas turbine 1 is configured in a conventionally known general form. In addition, what was shown by 7 is a generator, for example.

  The ammonia decomposition apparatus 2 has a configuration conceptually shown in FIG. 1 and includes a catalyst filling portion 2a and a combustion exhaust gas passage 2b. The ammonia decomposition apparatus 2 includes a vaporizer 8 in the upstream and a cooler 9 in the downstream. What is indicated by 10 is a pump.

Next, an operation method of the gas turbine system according to the present embodiment will be described with reference to FIGS. 1 and 2.
First, the decomposition of ammonia in the ammonia decomposition apparatus 2 will be described.
Liquefied ammonia as a raw material, by a pump 10, is heated by the vaporizer 8, it is introduced from the line L ₃ to the ammonia decomposition device 2 become ammonia gas. As the gas for heating the liquefied ammonia by the vaporizer 8, the exhaust gas from the turbine 5 can be used.

Ammonia gas is introduced from the line L ₃ to the catalyst packed portion 2a, it flows from the inlet-side catalyst layer 11 to the outlet side catalyst layer 12, and flows out from the line L _4. On the other hand, exhaust gas usually about 650 ° C. from the turbine 5 is introduced from the line L ₁ in the combustion gas passage 2b, and is discharged from the line L _2. As the ammonia gas and the exhaust gas flow in this way, the ammonia gas receives heat from the exhaust gas, and thereby decomposes according to the following equation.
NH ₃ → 1 / 2N ₂ + 3 / 2H ₂ (1)

  Here, for example, the exhaust gas flowing in at 650 ° C. first thermally decomposes ammonia gas flowing in the outlet side catalyst layer 12. The outlet side catalyst layer 12 is filled with a high temperature operation type catalyst and fulfills its function. The heat of the combustion exhaust gas decreases as it approaches the outlet side due to the reaction heat of ammonia decomposition. However, the inlet side catalyst layer 11 is filled with a low temperature operation type catalyst and fulfills its function. In this way, it is possible to share the temperature range that operates according to the degree of progress of the reaction, to suitably decompose the ammonia gas and obtain hydrogen. In addition, the amount of expensive Ru-based catalyst used can be reduced, and the flow rate of the heat medium flowing through the flow path 2b can be reduced.

  The ammonia decomposition in the ammonia decomposition apparatus can be performed until the ammonia decomposition rate becomes 50% or more. In addition, about the point decomposed | disassembled in this way, it is the same also in other embodiment of the gas turbine system which employ | adopts the ammonia decomposition apparatus which concerns on this invention.

  In the inlet side catalyst layer 11, the decomposed hydrogen is in a relatively thin state, and even if a Ru-based catalyst is employed, the problem of catalyst poisoning can be reduced. In addition, it is also possible to employ a Ru-based catalyst that has been subjected to poisoning countermeasures in the inlet-side catalyst filling section 11 and the outlet-side catalyst filling section 12, both of which have been subjected to poisoning countermeasures. When a Ru-based catalyst is employed, the catalyst filling portion 2a is not configured as in the embodiment of FIG. 1, and all Ru-based catalysts can be used.

Decomposition gas containing hydrogen from the ammonia decomposition device 2, after cooling to a cooler 9, for example, room temperature through line L ₄ (35 ℃), until further compressor 13 for example 5MPa through line L ₄ Pressurized and supplied to the combustor 4.

  The entire gas turbine system according to the present embodiment, which supplies hydrogen from the ammonia decomposition apparatus 2 to the combustor 4 as described above, operates as described below.

Referring to FIG. 2, in gas turbine 1, combustion air is compressed by compressor 3 and sent to combustor 4, and natural gas as fuel is blown into combustor 4 for combustion. The high-temperature and high-pressure combustion gas generated at that time rotates the turbine 5. The turbine shaft 6 transmits compression power to the compressor 3, and the generator 7 generates power. The combustion gas is generally sent to a waste heat recovery boiler via L ₅ and recovered.
On the other hand, the combustor 4, in addition to natural gas, hydrogen gas is introduced via line L ₄ from the ammonia decomposition device 2. That is, in the combustor 4, natural gas and hydrogen gas burn.

As mentioned above, according to embodiment described about FIG. 1, FIG. 2, liquefied ammonia can be vaporized using waste gas. In addition, heat for decomposing ammonia can be obtained using the exhaust gas, and the heat efficiency is good.
Further, since natural gas and hydrogen are co-fired in the combustor 4, the amount of NO _x generated is only the amount corresponding to the undecomposed ammonia content, and the generation of NO _x can be reduced.

  The ammonia decomposition apparatus according to the present invention, the gas turbine system to which the ammonia decomposition apparatus is applied, and the operation method thereof have been described in the above embodiments. However, the present invention is not limited to the above-described embodiment, and all changes, modifications, and modifications within the scope of the technical idea of the present invention are included in the present invention. Specific numerical values appearing in each embodiment, such as temperature, are merely examples, and all variations assumed by those skilled in the art are included in the technical scope of the present invention.

  The ammonia decomposition apparatus according to the present invention can be used as a hydrogen production apparatus for decomposing ammonia as a hydrogen carrier to obtain hydrogen. In addition, to supply hydrogen to equipment, devices or systems that use hydrogen as a fuel or part of fuel, such as gas turbine systems, boilers or gas engines, or to be incorporated into any of them It can be employed as an ammonia decomposition apparatus.

1 Gas turbine 2 ammonia decomposition apparatus 2a catalyst packed portion 2b heating medium passage L ₁ ~L ₄ inflow or outflow line 3 compressor 4 combustor 5 turbine 6 turbine shaft 7 generator 8 vaporizer 9 cooler 10 pump 11 inlet side Catalyst layer 12 Outlet side catalyst layer 13 Compressor

Claims (4)

  An ammonia decomposing apparatus comprising a catalyst filling portion comprising a low-temperature operating catalyst and a high-temperature operating catalyst, and decomposing until ammonia has a decomposition rate of 50% or more.   The ammonia decomposition apparatus according to claim 1, wherein a Ru-based catalyst is disposed on the ammonia inlet side as the low-temperature operating catalyst, and a non-Ru-based catalyst is disposed on the ammonia outlet side as the high-temperature operating catalyst.   A Ru-based catalyst is disposed on the ammonia inlet side as the low-temperature operating catalyst, and the high-temperature operating catalyst includes one or more of Ni-based catalyst, Fe-based catalyst, and Co-based catalyst on the ammonia outlet side. 3. An ammonia decomposition apparatus according to claim 1, wherein a Ru-based catalyst is disposed.   The ammonia inlet side is in a state where the decomposed hydrogen is relatively thin, and even a normal Ru-based catalyst can reduce the problem of hydrogen poisoning. Ammonia decomposition equipment.

Images