JP2021110463A - Ammonia combustion device, and ammonia fuel cell system - Google Patents

Abstract

To provide an ammonia combustion device 10 capable of maintaining a stable combustion condition even when the ratio of ammonia varies in ammonia/hydrogen mixed gas being fed to a combustion chamber 11a as fuel gas.SOLUTION: The ammonia combustion device comprises means 12 of adjusting a hydrogen/ammonia mixing ratio, i.e., a mixing ratio of hydrogen relative to ammonia, in a combustion chamber 11a, and first control means 14b of controlling a hydrogen/ammonia mixing ratio in the combustion chamber 11a at a first mixing ratio or higher using the function of the means 12 of adjusting a hydrogen/ammonia mixing ratio.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ammonia combustion apparatus including a combustion chamber, in which a fuel gas containing at least ammonia is supplied to the combustion chamber to burn the combustion chamber, and an ammonia fuel cell system including the combustion chamber.

As the prior art of the ammonia combustion apparatus, the following Patent Document 1, Patent Document 2 and Non-Patent Document 1 can be mentioned.

Patent Document 1 proposes a fuel combustion device and a combustion method that suppresses emissions of nitrogen oxides and ammonia while avoiding complication of the system for burning fuel. The combustion apparatus disclosed in this document has a combustion chamber to which a fuel and an air-fuel mixture containing a first oxidant and a second oxidant are supplied, and the equivalent ratio of the fuel contained in the air-fuel mixture is set to the first. When the equivalent ratio is set and the equivalent ratio of the fuel contained in the air-fuel mixture and the second oxidizing agent is set as the second equivalent ratio, the first equivalent ratio is set to be larger than 1 and the second equivalent ratio is set to be smaller than 1. By doing so, the above purpose is achieved.

One of the purposes of Patent Document 2 is to provide a fuel combustion device that enhances flame stability and suppresses nitrogen oxide emissions.
SOLUTION: The combustor provided in the combustion apparatus has a structure having a combustion chamber in which an oxidant, a first fuel and a second fuel are supplied and the first fuel and the second fuel are diffused and burned, and the combustion is performed. In the vessel, an oxidant supply port that guides the oxidant to the combustion chamber, a first fuel supply port that is arranged inside the oxidant supply port and guides the first fuel to the combustion chamber, and an outside of the oxidant supply port. A second fuel supply port for supplying the second fuel to the combustion chamber is provided.

Both of these technologies are intended to improve the combustion of ammonia, which is basically relatively low in flammability, by improving the structure of the combustion device, and to suppress the amount of harmful substances generated.

Non-Patent Document 1 examines the enhancement of ammonia flame by hydrogenation.
This document assumes that the combustion characteristics of the ammonia flame are significantly different from those of conventional hydrocarbon fuels and that it is expected to be difficult to use as a fuel for existing internal combustion engines. I'm trying. The laminar combustion characteristics of ammonia / hydrogen / air premixed flame including under high pressure have been reported, but the result is that the hydrogen addition ratio is 0.4 (total fuel gas amount) at the initial air-fuel mixture pressure of 0.1 MPa. 40% of the fuel is hydrogen and the remaining gas is ammonia), which provides a laminar combustion rate equivalent to that of ordinary hydrocarbon fuels, that is, without significantly changing the existing internal combustion engine at this hydrogen addition ratio. , It has been reported that ammonia may be used as a fuel.

Patent Document 3 can be mentioned as a prior art related to an ammonia fuel cell system. The technique disclosed in this document relates to a method of operating a solid oxide fuel cell system, which is an exhaust gas emitted from a combustion cell on the downstream side of a solid oxide fuel cell that operates directly using ammonia as fuel. This type of exhaust gas includes a combustion heating unit 2 that burns ammonia, hydrogen, etc.), and an ammonia-containing gas and an oxygen-containing gas are passed through the power generation module M1 to the combustion heating unit 2 to burn the mixed gas. Therefore, a technique for raising the temperature of the ammonia decomposition unit 1 provided on the upstream side of the fuel cell is disclosed.

Japanese Unexamined Patent Publication No. 2018-155412 JP-A-2019-105382 Japanese Unexamined Patent Publication No. 2017-084593

Hideaki Kobayashi and 1 others, "Carbon-free Ammonia Combustion", Journal of Combustion Society of Japan, Vol. 58, No. 183 (2016), 41-48

However, since the techniques disclosed in Patent Documents 1 and 2 are basically techniques for burning ammonia as fuel, the flame combustion behavior of ammonia in co-firing with hydrogen is not clear.
On the other hand, although the technique disclosed in Non-Patent Document 1 indicates that the flame is strengthened by mixing hydrogen with ammonia and performing co-firing, when a combustion device is actually constructed and the combustion is performed. It is not clear what kind of combustion form it will be. In particular, in the structure in which the ammonia combustion device is arranged on the downstream side of the fuel cell as a part of the ammonia fuel cell system according to the present invention, the ammonia concentration, the hydrogen concentration, etc. in the inflowing fuel gas depend on, for example, the power generation load of the fuel cell. Although it fluctuates, it is not clear what kind of equipment configuration is required to stabilize combustion in the combustion chamber against such fluctuations.

An object of the present invention is to obtain an ammonia combustion apparatus capable of maintaining a stable combustion state even when the ratio of ammonia contained in the fuel gas changes with respect to the fuel gas supplied to the combustion chamber.
Furthermore, it is a point to provide an ammonia combustion battery system which effectively adopted this kind of ammonia combustion apparatus.

The first characteristic configuration of the present invention is
An ammonia combustion device provided with a combustion chamber, in which a fuel gas containing at least ammonia is supplied to the combustion chamber to burn the combustion chamber.
The hydrogen / ammonia mixing ratio adjusting means for adjusting the hydrogen / ammonia mixing ratio, which is the mixing ratio of hydrogen to the ammonia in the combustion chamber, is provided, and the hydrogen / ammonia mixing ratio adjusting means is activated in the combustion chamber. The point is that a first control means for controlling the hydrogen / ammonia mixing ratio to be equal to or higher than the first mixing ratio is provided.

The ammonia combustion apparatus having this characteristic configuration is provided with a combustion chamber, and at least ammonia and hydrogen are contained in the fuel gas supplied to the combustion chamber. As a result, the combustion in the combustion chamber is a co-firing of ammonia and hydrogen, and this combustion forms a flame.

The ammonia combustion apparatus includes a hydrogen / ammonia mixing ratio adjusting means and a first controlling means for controlling the hydrogen / ammonia mixing adjusting means. The control mode by the first control means controls the hydrogen / ammonia mixing ratio in the combustion chamber to be equal to or higher than the first mixing ratio.

As will be described later with reference to FIGS. 4 and 5, in flame combustion in which ammonia and hydrogen are contained in the fuel gas, the combustibility deteriorates as the proportion of ammonia increases, and the combustion becomes unstable. Cheap. Misfire in severe cases.

Therefore, in the ammonia combustion apparatus according to the present invention, it is possible to avoid misfire and maintain the combustion state by controlling the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber to a predetermined first mixing ratio or higher. can.

The second characteristic configuration of the present invention is
When the first mixing ratio is lower than the first mixing ratio of the hydrogen / ammonia mixing ratio of the fuel gas for the fuel gas supplied to the combustion chamber, the combustibility is improved with respect to the combustion in the combustion chamber. The point is that the mixing ratio on the low hydrogen ratio side increases the probability of deterioration.

By setting the first mixing ratio to the hydrogen low ratio side mixing ratio in which the probability of deterioration of flammability increases in this way, a mixing ratio higher than this hydrogen low ratio side mixing ratio is maintained, and a stable flame combustion state is maintained. Can be maintained.

The third characteristic configuration of the present invention is
Ammonia, which is a raw material fuel gas, is supplied, and an ammonia decomposition means for decomposing at least a part of the raw material fuel gas is provided. In the configuration supplied to the combustion chamber, the ammonia decomposition means acts as the hydrogen / ammonia mixing ratio adjusting means.

As shown above, in order to satisfactorily burn a fuel gas containing ammonia, it is preferable to mix and burn highly combustible hydrogen with low combustible ammonia, but this mixing ratio Needs to be controlled to an appropriate range.
Furthermore, when ammonia, which is useful as a hydrogen source, is used as the raw fuel gas, it is necessary to decompose this ammonia to obtain hydrogen and appropriately control the decomposition ratio to bring the combustion state of the ammonia combustion device to an appropriate state. There is. Therefore, by adopting the above-mentioned third characteristic configuration, the ammonia decomposition means can be operated at the same time as the hydrogen / ammonia mixed ratio adjusting means, so that the flame combustion of the fuel gas containing ammonia can be appropriately maintained.

The fourth characteristic configuration of the present invention is
The ammonia decomposition means is provided with an ammonia decomposition chamber configured so that the room temperature can be controlled.
The point is that the room temperature of the ammonia decomposition chamber is controlled to control the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber to act as the hydrogen / ammonia mixing ratio adjusting means.

In this feature configuration, by controlling the room temperature of the ammonia decomposition chamber provided in the ammonia decomposition means, the hydrogen / ammonia mixture ratio of the fuel gas released from the ammonia decomposition means and supplied to the combustion chamber is appropriately adjusted. Therefore, a good combustion state can be ensured.

The fifth characteristic configuration of the present invention is
The point is that the ammonia decomposition chamber is provided with an ammonia decomposition catalyst.

In this characteristic configuration, the decomposition of ammonia, which is a raw material fuel gas, can be appropriately realized by the ammonia decomposition catalyst.
Furthermore, in this type of ammonia decomposition catalyst, the ammonia resolution changes depending on the temperature (usually, the decomposition rate increases as the temperature rises), so by adjusting the temperature appropriately, hydrogen and hydrogen, which have been explained so far, The function of adjusting the ammonia mixing ratio can be exerted.

The sixth characteristic configuration of the present invention is
The point is that the ammonia decomposition catalyst is a decomposition catalyst containing ruthenium (Ru) as an active ingredient.

In this feature configuration, by including ruthenium (Ru) in the ammonia decomposition catalyst, it can be satisfactorily used for both the purpose of decomposing ammonia and adjusting the hydrogen / ammonia mixing ratio. As will be described later, alkali metals (Cs, Rb, K, Na) may be added to the catalytically active ingredient main material (ruthenium) (see FIG. 3).

The seventh characteristic configuration of the present invention is
The point is that the hydrogen / ammonia mixing ratio adjusting means is activated to provide a second controlling means for controlling the hydrogen / ammonia mixing ratio in the combustion chamber to a second mixing ratio higher than the first mixing ratio or less. ..

In this feature configuration, a second control means is provided in addition to the hydrogen / ammonia mixed ratio adjusting means and the first control means. Then, in the control mode by the second control means, the hydrogen / ammonia mixing ratio adjusting means is activated to control the hydrogen / ammonia mixing ratio in the combustion chamber to the second mixing ratio or less. Here, this second mixing ratio is higher than the first mixing ratio.

As will be described later with reference to FIGS. 4 and 5, in flame combustion in which the fuel gas contains ammonia and hydrogen, the combustibility becomes relatively stable as the proportion of hydrogen increases, but the combustion temperature Increases and the amount of nitrogen oxides produced increases.

Therefore, in the ammonia combustion apparatus according to the present invention, the amount of nitrogen oxides generated can be appropriately controlled by controlling the hydrogen / ammonia mixing ratio supplied to the combustion chamber to a predetermined second mixing ratio or less. can.

The eighth characteristic configuration of the present invention is
With respect to the fuel gas supplied to the combustion chamber, the amount of knocks generated in the combustion chamber is excessive when the hydrogen / ammonia mixing ratio of the fuel gas is higher than the second mixing ratio. The point is that it is the mixing ratio on the high hydrogen ratio side.

According to this feature configuration, by setting the second mixing ratio to the hydrogen high ratio side mixing ratio in which the amount of knocks is excessive, a mixing ratio lower than this hydrogen high ratio side mixing ratio is maintained. It is possible to prevent excessive knocking.

The ninth characteristic configuration of the present invention is the ammonia combustion apparatus having any of the above-mentioned third to sixth characteristic configurations.
A fuel gas obtained by decomposing at least a part of the raw material fuel gas by the ammonia decomposition means is supplied to the combustion chamber, and a hydrogen / ammonia mixture is separately supplied to the combustion chamber.
A hydrogen / ammonia mixing ratio confirmation means for estimating or detecting and confirming the hydrogen / ammonia mixing ratio of the separately supplied hydrogen / ammonia mixture is provided.
The point is that the ammonia decomposition means works so as to make the hydrogen / ammonia mixing ratio in the combustion chamber a predetermined mixing ratio based on the hydrogen / ammonia mixing ratio confirmed by the hydrogen / ammonia mixing ratio checking means.

According to this feature configuration
When an ammonia decomposition means is provided and a hydrogen / ammonia mixture is separately supplied to the combustion chamber, the hydrogen / ammonia mixture of the hydrogen / ammonia mixture separately supplied by the hydrogen / ammonia mixing ratio checking means is mixed. It is possible to check the ratio and take into account the confirmed hydrogen / ammonia mixing ratio to properly operate the ammonia decomposition means to control the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber to an appropriate state. can.

The first characteristic configuration of the ammonia fuel cell system of the present invention is
A fuel cell that uses ammonia as fuel to generate electricity,
It is configured with the ammonia combustion device described so far.
The point is that the exhaust gas discharged from the fuel cell is received in the combustion chamber, and at least ammonia contained in the exhaust gas is burned.

According to this feature configuration, ammonia can be satisfactorily processed by the ammonia combustion device while generating electricity with the fuel cell using ammonia as fuel.
The ammonia combustion device according to the present invention forms a flame in its combustion chamber and burns. However, in this type of combustion device, the processing amount can be increased as compared with the conventionally well-known catalytic combustion, and the heat generation thereof can be increased. By securing it, for example, it can be effectively used for preheating combustion air, using it as heat required for decomposition of ammonia, and raising the temperature of a fuel cell. Further, the amount of catalyst required for catalyst combustion can be reduced, and the equipment cost can be reduced. In addition, it becomes possible to respond quickly and appropriately to changes in operating conditions on the fuel cell side, and so-called robustness is improved.

The second characteristic configuration of the ammonia fuel cell system according to the present invention is
A fuel cell that uses ammonia as fuel to generate electricity,
It is configured to include an ammonia combustion device having any of the above-mentioned third to sixth characteristic configurations.
A configuration in which a fuel gas obtained by decomposing at least a part of the raw material fuel gas by the ammonia decomposition means is supplied to the fuel cell to work.
The point is that the exhaust gas discharged from the fuel cell is received in the combustion chamber, and at least ammonia contained in the exhaust gas is burned.

According to this feature configuration
Power can be generated by a fuel cell using a gas decomposed by an ammonia decomposition means (containing at least hydrogen) as a fuel gas for power generation, and the exhaust gas can be satisfactorily treated in a combustion chamber.
That is, in the case of this configuration, not only a fuel cell in which ammonia is directly supplied to the fuel cell to work, but also a normal fuel cell in which ammonia is supplied to work can be adopted. In the case of this configuration, the slip of ammonia may occur on the fuel cell side, but it can be treated satisfactorily by combustion.

Further, when the hydrogen / ammonia mixing ratio confirmation means described above is provided, the state of the fuel gas directly supplied from the ammonia decomposition means to the combustion chamber is added to the hydrogen / ammonia mixing ratio confirmed by the confirmation means. By adjusting this, combustion in the combustion chamber can be maintained well.

The figure which shows the structure of the ammonia fuel cell system provided with the ammonia combustion apparatus which concerns on this invention. The figure which shows the detail of the combustor provided in the ammonia combustion apparatus. The figure which shows the resolution of the ammonia decomposition catalyst The figure which shows the result of the combustion test with the change of the ammonia decomposition rate The figure which shows the relationship between the ammonia decomposition rate and the generated knock The figure which shows the change of the combustion form with the change of the ammonia decomposition rate The figure which shows another embodiment of the ammonia combustion apparatus

Hereinafter, the ammonia fuel cell system 100 including the ammonia combustion device 10 according to the present invention and the device 10 will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing the configuration of the entire ammonia fuel cell system 100, and the portion surrounded by the alternate long and short dash line in the figure corresponds to the ammonia combustion device 10.
As can be seen from FIG. 1, the ammonia fuel cell system 100 is mainly composed of the ammonia combustion device 10 and the fuel cell 101, and is composed of a fuel gas containing ammonia and a gas containing oxygen with respect to the fuel gas. It operates by being supplied with a certain oxygen-containing gas (air in the illustrated example).

Here, in the ammonia combustion apparatus 10, the combustion component contained in the supplied fuel gas is burned by the oxygen contained in the oxygen-containing gas. Combustion components are ammonia, hydrogen and nitric oxide.
On the other hand, in the fuel cell 101, the reducing component contained in the supplied fuel gas reacts with the oxidizing component contained in the oxygen-containing gas. The reducing components are ammonia and hydrogen. The oxidizing component is oxygen.

As is clear from the configuration of the ammonia fuel cell system 100 shown in FIG. 1, in the ammonia fuel cell system 100 of the present invention, ammonia (100% ammonia) as a raw material fuel gas is supplied from an ammonia supply device (for example, an ammonia tank) 99. It is supplied and operates. On the other hand, the exhaust gas discharged from the fuel cell 101 is supplied to the ammonia combustion device 10 (specifically, the combustion chamber 11a of the combustor 11 described later). As a result, components such as ammonia, hydrogen, and nitric oxide, which may be contained in the exhaust gas, are also burned, and the exhaust gas can be made harmless.

The heat generated by the combustion in the combustor 11 constituting the ammonia fuel device 10 is the decomposition of ammonia in the ammonia decomposer 12, the heating and temperature maintenance of the fuel cell 101, and the oxygen sent to the combustor 11 and the fuel cell 101. It is also used for preheating the contained gas in the air preheater 13.

The electric power generated by the fuel cell 101 is taken out to the outside via the inverter 102 and used for a predetermined purpose.

The above is the outline of the ammonia combustion device 10 and the ammonia fuel cell system 100.
Hereinafter, the ammonia combustion device 10 and the ammonia fuel cell system 100 will be described in this order, including their characteristic configurations.

Ammonia combustion device 10
The device 10 is configured with the combustor 11 as the core, and the ammonia decomposer 12 and the air preheater 13 are configured as hardware side devices with respect to the combustor 11. A controller 14 is provided to ensure proper operation of the hardware side devices 12 and 13.

Combustor 11
FIG. 2 shows the configuration of the combustor 11 according to the present invention. In the figure, (a) is a perspective view of the combustor 11, and (b) is a front view of the combustor 11. In these drawings, the lid (not shown) of the combustion chamber 11a is removed. (C) is a cross-sectional view of the combustion burner 11b, and (d) is a partial cross-sectional plan view of the swirler s.
As shown in the figure, the combustor 11 is configured to include a combustion chamber 11a having a substantially square cross section extending in the longitudinal direction thereof, and has a combustion burner 11b inside. In the combustion burner 11b, a fuel gas and a combustion oxygen-containing gas (specifically, air) are supplied from the base end side thereof, and a swirling type combustion flame is formed in the combustion chamber 11a for combustion. The combustion exhaust gas generated by combustion is discharged from the combustion exhaust gas passage 11c provided on the side opposite to the combustion burner 11b.

The combustion burner 11b is formed in a substantially cylindrical shape, and is provided with a fuel gas supply unit 11b1 on the central side thereof and an oxygen-containing gas supply unit 11b2 on the peripheral side thereof, and the axial tip of the fuel gas supply unit 11b1 is oxygen. It is configured to protrude from the axial tip of the contained gas supply unit 11b2.

A plurality of ejection holes h1 are provided in the vicinity of the tip of the fuel gas supply portion 11b1 with openings in the radial direction. The axial tip of the oxygen-containing gas supply section 11b2 is set at a position retreated from the tip of the fuel gas supply section 11b1, and a swirler s is provided in the vicinity of the tip thereof. A plurality of spiral holes h2 are formed in the swirler s, and these spiral holes h2 are opened at the axial end of the oxygen-containing gas supply unit 11b2. Therefore, the oxygen-containing gas supplied into the combustion chamber 11a via the oxygen-containing gas supply unit 11b2 is spirally ejected, and the fuel gas is entrained in this gas flow to mix the two gases in the combustion chamber 11a. Will be performed and burned in the premixed form. The ignition heater 11d works for ignition.
The above is the configuration of the combustor 11 which is the core of the ammonia combustion device 10. Below, the controller 14 provided for satisfactorily operating the configuration of the ammonia combustion device 10 and important in the present invention. The configuration of the working ammonia decomposer 12 and the like will be described.

Ammonia decomposer 12
The ammonia cracker 12 decomposes ammonia (100% ammonia) supplied to the device 12 as a raw material fuel gas from the ammonia supply device 99 at a predetermined ratio, and the devices 11 and 101 provided on the downstream side as the fuel gas. Send to. Therefore, the gas delivered from the ammonia decomposer 12 is basically a gas containing ammonia, hydrogen, and nitrogen in a predetermined ratio. However, if ammonia decomposition is not performed, it becomes 100% ammonia, and if the entire amount is decomposed, it becomes a mixed gas of hydrogen and nitrogen.

The ammonia decomposition device 12 in the present embodiment includes an ammonia decomposition chamber 12a containing an ammonia decomposition catalyst, and the temperature of the decomposition chamber can be controlled.
Today, various ammonia decomposition catalysts have been proposed, and one in which ruthenium (Ru) is supported on a carrier can be adopted as an active ingredient. As an example, it will be described below based on the catalyst proposed by Katsutoshi Nagaoka (Associate Professor, Faculty of Science and Technology, Oita University).

FIG. 3 shows the change state of the conversion rate of such an ammonia decomposition catalyst in relation to the temperature. In FIGS. 3A and 3B, the vertical axis represents the ammonia conversion rate (decomposition rate), and the horizontal axis represents temperature.
FIG. 3A shows the conversion rate of ruthenium (Ru) as the active ingredient and different carriers. FIG. 3B shows the result of adding an alkali metal (Cs, Rb, K, Na) to the active ingredient ruthenium (Ru). In this ammonia decomposition catalyst, placeodymium oxide (Pr ₆ O ₁₁ ) is used as a carrier.
In these drawings, the line shown at the highest position on the figure is the equilibrium conversion rate of _{ammonia (NH 3).}

As is clear from these drawings, the decomposition rate (conversion rate) increases as the temperature of the ammonia decomposition catalyst increases. Therefore, by controlling the temperature of the ammonia decomposition chamber 12a, hydrogen / ammonia of the gas sent from the ammonia decomposition device 12 (“fuel gas in which at least a part of the raw material fuel gas is decomposed” in the present invention) The mixing ratio is adjusted.

As the ammonia decomposition catalyst, the above-mentioned catalysts may be used alone or mixed at an arbitrary ratio.

Therefore, this ammonia decomposer works as an ammonia decomposition means.

Returning to FIG. 1, the destination of the gas from the ammonia decomposer 12 is the combustor 11 and the fuel cell 101. Therefore, this delivery gas becomes a combustion fuel gas in the combustor 11 and a power generation fuel gas in the fuel cell 101.

The function of the ammonia cracker 12 is based on the decomposition control information emitted from the controller 14, and the inflowing ammonia is decomposed into an appropriate ratio based on the decomposition control information. That is, by controlling the temperature of the ammonia decomposition chamber 12a, the hydrogen / ammonia mixing ratio of the fuel gas, which is the delivered gas, is adjusted. The supply amount is controlled by a mass flow controller (MFC).

As shown above, in the combustor 11 according to the present invention, the hydrogen / ammonia mixing ratio plays an important role in maintaining the combustion in the combustor 11 in an appropriate state, but the combustion chamber 11a The ammonia combustor 12 is operated so as to keep this mixing ratio within a predetermined range.

Air preheater 13
The air preheater 13 preheats the oxygen-containing gas (specifically, air) supplied to the device 13 and sends it to a device provided on the downstream side. In this system, the heat supplied from the combustor 11 or the combustion battery 101 is used for this air preheating.
The destination of the oxygen-containing gas from the air preheater 13 is the combustor 11 and the fuel cell 101. Therefore, this delivery gas becomes a combustion oxygen-containing gas in the combustor 11 and an oxidizing gas for power generation in the fuel cell 101.

The amount of oxygen-containing gas after preheating sent from the air preheater 13 is appropriately controlled with respect to the combustor 11 so as to ensure good combustion of the combustion fuel gas. On the other hand, the fuel cell 101 is controlled so as to satisfy an appropriate amount corresponding to the fuel gas for power generation in order to generate power corresponding to the power generation load.

Characteristic configuration of the ammonia combustion device 10 Since the combustion control in the controller 14 is largely involved in this characteristic configuration, it will be described below together with the configuration of the controller 14.

The controller 14, which serves as a control means in the present invention, is configured to include a storage means 14a, a first control means 14b, and a second control means 14c.

The storage means 14a is a so-called memory, and stores control information required for controlling the hardware side devices 11, 12, 13 and the mass flow controller MFC provided incidentally to the controller 14.

The first control means 14b activates the hydrogen / ammonia mixing ratio adjusting means according to the present invention to control the hydrogen / ammonia mixing ratio in the combustion chamber 11a to be equal to or higher than the first mixing ratio. Specifically, the temperature of the ammonia decomposition catalyst housed in the ammonia decomposition device 12 is controlled to a temperature suitable for making the target first mixing ratio or higher.

Here, the first mixing ratio refers to the combustibility of the fuel gas supplied to the combustion chamber 11a with respect to combustion in the combustion chamber when the hydrogen / ammonia mixing ratio of the fuel gas is lower than the first mixing ratio. Is set as the low hydrogen ratio side mixing ratio, which increases the probability that This first mixing ratio will be described later with reference to FIGS. 4 to 6.

The second control means 14c activates the hydrogen / ammonia mixing ratio adjusting means according to the present invention to control the hydrogen / ammonia mixing ratio in the combustion chamber 11a to be higher than the first mixing ratio and equal to or lower than the second mixing ratio. Specifically, the temperature of the ammonia decomposition catalyst housed in the ammonia decomposition device 12 is controlled to an appropriate temperature so as to be equal to or less than the target second mixing ratio.

Here, in the second mixing ratio, with respect to the fuel gas supplied to the combustion chamber 11a, when the hydrogen / ammonia mixing ratio of the fuel gas is higher than the second mixing ratio, the amount of knocks generated in the combustion chamber is excessive. This is the mixing ratio on the high hydrogen ratio side. This second mixing ratio will also be described later with reference to FIGS. 4 to 6.

From the above, the ammonia combustion device 10 according to the present invention is provided with an ammonia decomposition device 12, which functions as an ammonia decomposition means and its operating state (specifically, according to the decomposition control information from the control means 14). By adjusting the temperature of the ammonia decomposition catalyst), it acts as a hydrogen / ammonia mixing ratio adjusting means for adjusting the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber 11a.
As described above, when the ammonia decomposition device 12 is operated as the ammonia decomposition means and the hydrogen / ammonia mixing ratio adjusting means, any ammonia decomposition catalyst whose ammonia decomposition rate changes according to the temperature can be adopted. The ruthenium (Ru) -supported catalyst described above is a typical example.

In the ammonia combustion apparatus 10 according to the present invention, the fuel gas decomposed by the ammonia cracker 12 is supplied to the combustion chamber 11a, and the hydrogen / ammonia mixture is separately supplied to the combustion chamber 11a. Here, the hydrogen / ammonia mixture separately supplied becomes the exhaust gas from the fuel cell 101 in the ammonia fuel cell system 100 shown in FIG.

Therefore, a detector 15 for confirming the hydrogen / ammonia mixing ratio for detecting and confirming the hydrogen / ammonia mixing ratio of the separately supplied hydrogen / ammonia mixture is provided, and this detector 15 mixes hydrogen / ammonia. A configuration that works as a ratio confirmation means is adopted. Then, based on the hydrogen / ammonia mixing ratio confirmed by the hydrogen / ammonia mixing ratio checking means 15, the ammonia decomposer 12 is operated so as to make the hydrogen / ammonia mixing ratio in the combustion chamber 11a a predetermined mixing ratio. That is, the first control means 14b and the second control means 14c described above predict the hydrogen / ammonia mixing ratio of the fuel gas supplied into the combustion chamber 11a, taking into account the confirmation information from the detector 15. However, it keeps combustion in an appropriate state and emits decomposition control information.
As a result, in the ammonia combustion device 10, the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber 11a is appropriately controlled.

The above is mainly a description of the configuration of the ammonia combustion apparatus 10. Hereinafter, the tests conducted by the inventors regarding the hydrogen / ammonia mixing ratio supplied to the combustion chamber 11a described so far will be described.
The combustor used for the test is the combustor 11 described in FIG. 2, and on the supply side of the combustor 11, a supply system of ammonia, hydrogen, and nitrogen is independently provided as a fuel gas supply system, and a supply system of ammonia, hydrogen, and nitrogen is provided independently. A mass flow controller MFC was provided to serve as a test device (not shown). Then, as a detection system for the test results, the temperature inside the combustion chamber 11a (the temperature of the flame forming portion) and the temperature at the outlet of the combustion chamber (the inlet of the combustion exhaust gas passage 11c) were detected. Further, regarding the exhaust gas, its composition was detected by the oxygen concentration and the NOx concentration.

Regarding the gas supply from the independent supply systems of ammonia, hydrogen and nitrogen, at least a part (in all cases) of the supplied ammonia is assumed to supply fuel to the system by the raw fuel gas, ammonia alone. Hydrogen, nitrogen and ammonia produced by decomposition of (including) were to be supplied according to their respective quantity ratios.

The "ammonia decomposition rate (%)" in FIGS. 4 and 5 and the "decomposition rate" in FIG. 6 indicate what percentage of the total amount of ammonia is decomposed. .. Therefore, an ammonia decomposition rate of 0% means that the entire amount of ammonia is supplied to the combustor 11, and a decomposition rate of 100% means that hydrogen and nitrogen obtained by decomposing ammonia are supplied to the combustor 11. It means that.
Below these figures, the hydrogen / ammonia mixing ratio is shown, but this value is shown in terms of the value corresponding to the decomposition rate.

Preliminary test Tables 1 and 2 show the results of changing the air ratio as a preliminary experiment for confirming the change in combustion mode due to the change in the hydrogen / ammonia mixing ratio. Here, the air ratio is the air ratio when hydrogen as a fuel gas is burned, assuming that the entire amount of ammonia as a raw material fuel gas is decomposed. As described in both tables, the values were changed to 1.2, 1.4, and 1.6. Table 1 shows the temperature of each part, and Table 2 shows the composition of the exhaust gas.

However, the unit of oxygen concentration is%, and the unit of NOx and converted NOx concentration is ppm.

As a result of the preliminary test, an air ratio of 1.4, which was able to secure a stable combustion state and had a low conversion NOx concentration, was selected. If this intermediate condition (air ratio 1.4) is used as a reference, a stable combustion range can be secured above and below the air ratio, and the operating state of the system fluctuates (for example, the power load fluctuates), and the combustion rate is changed to burn. The inventors think that a stable combustion state in the combustion chamber 11a can be ensured even when it is necessary to maintain the above.

Confirmation of hydrogen / ammonia mixing ratio Figures 4 to 6 show the results of this test.
In FIG. 4, the horizontal axis represents the ammonia decomposition rate (%) and the corresponding hydrogen / ammonia mixing ratio, and the vertical axis represents the combustion part temperature (° C; indicated by white circles), combustor outlet temperature (° C; indicated by black circles), and It shows the oxygen concentration (%; indicated by a white diamond).
In FIG. 5, the horizontal axis represents the ammonia decomposition rate (%) and the corresponding hydrogen / ammonia mixing ratio, and the vertical axis represents the oxygen concentration (%; indicated by a white rhombus), the NOx concentration (ppm; indicated by a white square), and conversion. The NOx concentration (ppm; indicated by a black square) is shown. In terms of Knox, the standard oxygen concentration is 16% of the nitrogen oxide emission standard for gas turbines.

In the test, combustion was started in a state where the ammonia decomposition rate was 100%, and combustion was continued while reducing the ammonia decomposition rate. FIG. 6 shows the state of the combustion flame at different ammonia decomposition rates.

As a result, a sharp flame is formed by substantial hydrogen combustion at an ammonia decomposition rate of 87.5%, and the temperature of the combustion part is also high. Combustion was extremely stable.
A stable flame was formed with an ammonia decomposition rate of about 25%, and stable combustion could be maintained (see FIG. 5, oxygen concentration, etc.). On the other hand, it was found that the Nox concentration increased in the region where the ammonia decomposition rate was higher than 55%.

When the ammonia decomposition rate was lowered below 25%, the flame length became excessively extended and the flame became unstable. Under the conditions at the time of the test, a misfire occurred with a decomposition rate of 9%.
Therefore, if the ammonia decomposition rate is excessively lowered (approaching ammonia-only combustion), the flame cannot be maintained and a misfire will occur.

Ammonia decomposition rate (hydrogen / ammonia) when a part of ammonia with low flammability is decomposed into highly flammable hydrogen and the generated air-fuel mixture is used as fuel gas to form a flame to maintain combustion. The mixing ratio) has a limit (lower limit) from the stability of the flame and a limit (upper limit) related to the generation of NOx.

Therefore, in the ammonia combustor 11 of the present invention, the former limit is set as the "first mixing ratio" and the latter limit is set as the "second mixing ratio".

Although two vertical broken lines are shown in FIGS. 4 and 5, the long broken line shown at the position where the ammonia decomposition rate is 25% is an example of the first mixing ratio in the present invention. On the other hand, the short broken line shown at the position where the ammonia decomposition rate is 55% is an example of the second mixing ratio in the present invention.
The first mixing ratio and the second mixing ratio serve as a reference for combustion control of the ammonia combustion apparatus according to the present invention.

Regarding the fuel gas supplied to the combustion chamber 11a, the first mixing ratio deteriorates the combustibility with respect to the combustion in the combustion chamber 11a when the hydrogen / ammonia mixing ratio of the fuel gas is lower than this first mixing ratio. It is a mixed ratio on the low hydrogen ratio side that increases the probability of

Regarding the fuel gas supplied to the combustion chamber 11a, the second mixing ratio is that the amount of knocks generated in the combustion chamber 11a is excessive when the hydrogen / ammonia mixing ratio of the fuel gas is higher than this second mixing ratio. This is the mixing ratio on the high hydrogen ratio side.

As described above, the controller 14 of the ammonia combustion device 10 of the present invention includes the first control means 14b and the second control means 14c, and the function thereof is the combustor 11 (combustion chamber (combustion chamber (combustion chamber)). The hydrogen / ammonia mixing ratio of the fuel gas supplied to 11a)) is kept within a predetermined range (first mixing ratio or more, second mixing ratio or less).
More specifically, in the ammonia decomposer 12 according to the present invention, the hydrogen / ammonia mixing ratio is substantially controlled according to the temperature of the decomposition chamber 12a, so that the controller 14 substantially determines the decomposition chamber temperature. It works to control within the range of.
Therefore, the controller 14 monitors the operating state of the entire ammonia fuel cell system 100, and adjusts the temperature of the ammonia cracker 12 so that the hydrogen / ammonia mixing ratio of the fuel gas supplied to the decomposition chamber 12a is within an appropriate range. It is determined and controlled, but when there is a possibility that the lower and upper limits such as the first mixing ratio and the second mixing ratio are exceeded at this determination stage, the first control means 14b and the second control means 14c are substantially the same. It will work as a limiting means.

The above is the description of the ammonia combustion apparatus 10 according to the present invention.
Hereinafter, the ammonia fuel cell system 100 will be described.

[Ammonia fuel cell system]
As is clear from FIG. 1, the ammonia fuel cell system 100 includes a fuel cell 101 that generates electricity using ammonia as fuel, and an ammonia combustion device 10 described above.
A typical fuel cell 101 to be used is a solid oxide fuel cell (described as SOFC in FIG. 1), and an anion exchange membrane fuel cell (shown in FIG. 1) as a fuel cell 101 that directly uses ammonia as a fuel. Is described as AEMFC) can also be adopted.

As shown above, in the ammonia fuel cell system 100, the exhaust gas from the fuel cell 101 is discharged. Therefore, a detector 15 for detecting and confirming the hydrogen / ammonia mixing ratio of the exhaust gas is provided and works as a means for confirming the hydrogen / ammonia mixing ratio. Then, based on the hydrogen / ammonia mixing ratio confirmed by the detector 15, the ammonia cracker 12 is operated so as to make the hydrogen / ammonia mixing ratio in the combustion chamber 11a a predetermined mixing ratio. As a result, in the ammonia fuel cell system 100, the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber 11a can be appropriately controlled.

[Another Embodiment]
(1) The ammonia combustion device 10 described so far is provided with an ammonia decomposition device 12, and the decomposition rate in the ammonia decomposition device 12 is changed to change the hydrogen of the fuel gas supplied to the combustion chamber 11a. The ammonia mixing ratio is adjusted to the range of the mixing ratio intended by the present invention. This configuration is because the ammonia combustion device 10 and the ammonia fuel cell system 100 provided with the device 10 work only with ammonia as a raw material fuel gas.
However, the ammonia decomposer 12 is not always necessary in a configuration in which not only ammonia but also hydrogen can be supplied separately.
That is, it suffices if both gases can be supplied to the combustion chamber 11a at the target hydrogen / ammonia mixing ratio. Therefore, the mechanism for adjusting the hydrogen / ammonia mixing ratio supplied to the combustion chamber 11a is collectively referred to as the hydrogen / ammonia mixing ratio adjusting means. In the latter system capable of independently supplying hydrogen and ammonia, the mass flow controller MFC provided in the hydrogen supply system and the ammonia supply system, respectively, plays this role.

Alternatively, if the raw material fuel gas is only ammonia, a system that supplies ammonia as it is and a system that decomposes and supplies ammonia are provided separately, and the amount of supply from both systems can be adjusted appropriately. , Hydrogen / ammonia mixed ratio adjusting means can also be configured (see FIG. 7).
(2) In the above embodiment, an example of controlling both the first mixing ratio and the second mixing ratio is shown as a reference index of the ammonia combustion device 10, but nitrogen is separately placed on the lower side of the ammonia combustion device 10. When an oxide treatment apparatus (not shown) is equipped, a configuration in which only the first mixing ratio is used as a control index may be adopted.

(3) In the above embodiments, an example in which the hydrogen / ammonia mixed ratio is used as a reference index has been described basically from the meaning of co-firing hydrogen and ammonia, but any index that can represent the co-firing state has been described. The combination of the hydrogen concentration and the ammonia concentration in the fuel gas can be used as a reference index, and of course, the ammonia decomposition rate can be used as a reference index.

(4) In the ammonia fuel cell system described so far, an example of using a fuel cell (SOFC, AEMFC) that directly uses ammonia as fuel is shown, but when the ammonia decomposer 12 is provided, hydrogen is used as a fuel gas. Since it can be supplied to a fuel cell, a fuel cell that is supplied with ordinary hydrogen to generate power can also be adopted. However, in this system, since ammonia is used as a hydrogen source, ammonia that is supplied to the fuel cell 10 in an undecomposed state and passes through the fuel cell 10 tends to remain. This tendency is particularly high at low temperatures such as when starting and stopping. Therefore, it is effective to provide the ammonia combustion device 10 according to the present invention together with the fuel cell 101.

(5) In the ammonia fuel cell system 100 described above, a detector 15 for detecting and confirming the hydrogen / ammonia mixing ratio of the exhaust gas discharged from the fuel cell 101 is provided, but the operating conditions of the fuel cell 101 are provided. The composition of the exhaust gas emitted to the fuel cell is controlled, and this composition information is conventionally known. Therefore, instead of providing the detector 15, a hydrogen-ammonia mixing ratio estimating means (not shown) for estimating the hydrogen-ammonia mixing ratio of the exhaust gas according to the operating conditions of the fuel cell 101 from the database is provided in the controller 14. May be good.
Therefore, the detector 15 and the hydrogen-ammonia mixed ratio estimating means are collectively referred to as a hydrogen / ammonia mixed ratio checking means.

10 Ammonia combustion device 11 Combustor 11a Combustion chamber 11b Combustion burner 11c Combustion exhaust gas path 11d Ignition heater 12 Ammonia decomposition device (ammonia decomposition means, hydrogen / ammonia mixture ratio adjusting means)
13 Air preheater 14 Controller (control means)
14a Storage means 14b First control means 14c Second control means 15 Detector (hydrogen / ammonia mixed ratio confirmation means)
100 Ammonia fuel cell system 101 Fuel cell SOFC Solid oxide fuel cell (fuel cell)
AEMFC anion exchange membrane fuel cell (fuel cell)

Claims (11)

An ammonia combustion device provided with a combustion chamber, in which a fuel gas containing at least ammonia is supplied to the combustion chamber to burn the combustion chamber.
A hydrogen / ammonia mixing ratio adjusting means for adjusting the hydrogen / ammonia mixing ratio, which is the mixing ratio of hydrogen to the ammonia in the combustion chamber, is provided, and the hydrogen / ammonia mixing ratio adjusting means is activated in the combustion chamber. An ammonia combustion device provided with a first control means for controlling the hydrogen / ammonia mixing ratio to be equal to or higher than the first mixing ratio. When the first mixing ratio is lower than the first mixing ratio of the hydrogen / ammonia mixing ratio of the fuel gas for the fuel gas supplied to the combustion chamber, the combustibility is improved with respect to the combustion in the combustion chamber. The ammonia combustion apparatus according to claim 1, wherein the hydrogen low ratio side mixing ratio increases the probability of deterioration. Ammonia, which is a raw material fuel gas, is supplied, and an ammonia decomposition means for decomposing at least a part of the raw material fuel gas is provided. The ammonia combustion apparatus according to claim 1 or 2, wherein the ammonia decomposition means acts as the hydrogen / ammonia mixed ratio adjusting means in a configuration supplied to the combustion chamber. The ammonia decomposition means is provided with an ammonia decomposition chamber configured so that the room temperature can be controlled.
The ammonia combustion apparatus according to claim 3, wherein the room temperature of the ammonia decomposition chamber is controlled to control the hydrogen / ammonia mixing ratio of the fuel gas supplied to the combustion chamber to act as the hydrogen / ammonia mixing ratio adjusting means. .. The ammonia combustion apparatus according to claim 4, wherein the ammonia decomposition chamber is provided with an ammonia decomposition catalyst. The ammonia combustion apparatus according to claim 5, wherein the ammonia decomposition catalyst is a decomposition catalyst containing ruthenium (Ru) as an active ingredient. Claim 1 provided with a second control means for controlling the hydrogen / ammonia mixing ratio in the combustion chamber to be higher than the first mixing ratio and equal to or lower than the second mixing ratio by operating the hydrogen / ammonia mixing ratio adjusting means. The ammonia combustion apparatus according to any one of 1 to 6. With respect to the fuel gas supplied to the combustion chamber, the amount of knocks generated in the combustion chamber is excessive when the hydrogen / ammonia mixing ratio of the fuel gas is higher than the second mixing ratio. The ammonia combustion apparatus according to claim 7, which is a mixing ratio on the high hydrogen ratio side. A fuel gas obtained by decomposing at least a part of the raw material fuel gas by the ammonia decomposition means is supplied to the combustion chamber, and a hydrogen / ammonia mixture is separately supplied to the combustion chamber.
A hydrogen / ammonia mixing ratio confirmation means for estimating or detecting and confirming the hydrogen / ammonia mixing ratio of the separately supplied hydrogen / ammonia mixture is provided.
Claims 3 to 3 in which the ammonia decomposition means works to make the hydrogen / ammonia mixing ratio in the combustion chamber a predetermined mixing ratio based on the hydrogen / ammonia mixing ratio confirmed by the hydrogen / ammonia mixing ratio checking means. 5. The ammonia combustion apparatus according to any one of 5. A fuel cell that uses ammonia as fuel to generate electricity,
It is configured to include the ammonia combustion apparatus according to any one of claims 1 to 9.
An ammonia fuel cell system that receives exhaust gas discharged from the fuel cell into the combustion chamber and burns at least ammonia contained in the exhaust gas. A fuel cell that uses ammonia as fuel to generate electricity,
It is configured to include the ammonia combustion apparatus according to any one of claims 3 to 6.
A configuration in which a fuel gas obtained by decomposing at least a part of the raw material fuel gas by the ammonia decomposition means is supplied to the fuel cell to work.
The ammonia fuel cell system according to claim 7, wherein the exhaust gas discharged from the fuel cell is received in the combustion chamber, and at least ammonia contained in the exhaust gas is burned.

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