FUEL PREHEATER

Abstract

The fuel preheater includes a first mixer provided in a fuel supply line connected to a combustion facility that combusts fuel including ammonia, the fuel supply line supplying ammonia to the first mixer, the first mixer being connected to an oxidizer supply line that supplies an oxidizer and mixing the ammonia flowing in the fuel supply line with the oxidizer from the oxidizer supply line to produce a mixed gas, and a reactor provided downstream of the first mixer in the fuel supply line, the reactor including a catalyst that promotes a reaction of the ammonia and that causes an exothermic reaction, the catalyst causing the exothermic reaction with at least a part of the ammonia in the mixed gas that is supplied from the first mixer and heating the mixed gas.

Claims

1. A fuel preheater comprising: a first mixer provided in a fuel supply line connected to a combustion facility that combusts fuel including ammonia, the fuel supply line supplying ammonia to the first mixer, the first mixer being connected to an oxidizer supply line that supplies an oxidizer, the first mixer mixing the ammonia flowing in the fuel supply line with the oxidizer from the oxidizer supply line to produce a mixed gas; and a reactor provided downstream of the first mixer in the fuel supply line, the reactor including a catalyst that promotes a reaction of ammonia and that causes an exothermic reaction, the catalyst causing the exothermic reaction with at least a part of the ammonia in the mixed gas that is supplied from the first mixer and heating the mixed gas.

2. The fuel preheater according to claim 1, comprising: a second mixer provided downstream of the reactor in the fuel supply line, the second mixer being connected to the oxidizer supply line by a first bypass line and mixing the mixed gas supplied from the reactor with the oxidizer supplied from the first bypass line.

3. The fuel preheater according to claim 1, comprising: a first valve provided in the oxidizer supply line and adjusting a flow rate of the oxidizer supplied to the first mixer; a temperature sensor provided downstream of the reactor in the fuel supply line and measuring a temperature of the mixed gas; and a controller communicatively connected to the first valve and the temperature sensor, wherein, the controller stores a predetermined threshold associated with a temperature at which a material forming the fuel supply line begins to be nitrided, and the controller controls the first valve to adjust the flow rate of the oxidizer supplied to the first mixer so that the temperature of the mixed gas measured by the temperature sensor is below the threshold.

4. The fuel preheater according to claim 1, wherein the reactor includes heating means for heating the catalyst, and the heating means includes a heater.

5. The fuel preheater according to claim 1, wherein the reactor includes heating means for heating the catalyst, and the heating means includes a first heat exchanger that heats the catalyst by exhaust gas from the combustion facility.

6. The fuel preheater according to claim 1, wherein the reactor includes heating means for heating the catalyst, and the heating means includes a second heat exchanger that heats the catalyst by steam extracted from the combustion facility.

7. The fuel preheater according to claim 1, comprising: a third mixer provided downstream of the reactor in the fuel supply line, the third mixer being connected to a position upstream of the first mixer in the fuel supply line by a second bypass line and mixing the mixed gas supplied from the reactor with the ammonia supplied from the second bypass line.

8. The fuel preheater according to claim 1, comprising: a second valve provided upstream of the first mixer in the fuel supply line and adjusting a flow rate of the ammonia supplied to the first mixer; a temperature sensor provided downstream of the reactor in the fuel supply line and measuring a temperature of the mixed gas; and a controller communicatively connected to the second valve and the temperature sensor, wherein: the controller stores a predetermined threshold associated with a temperature at which a material forming the fuel supply line begins to be nitrided, and the controller controls the second valve to adjust the flow rate of the ammonia supplied to the first mixer so that the temperature of the mixed gas measured by the temperature sensor is less than the threshold.

9. The fuel preheater according to claim 1, wherein the fuel preheater supplies the mixed gas to a plurality of burners in the combustion facility.

10. The fuel preheater according to claim 1, wherein the exothermic reaction on the catalyst of the reactor is catalytic combustion.

11. A method of installing a fuel preheater in a combustion facility, the method comprising: preparing a first mixer configured to mix ammonia and an oxidizer; preparing a reactor including a catalyst that causes an exothermic reaction with ammonia; installing the first mixer in a fuel supply line connected to a combustion facility that combusts fuel including ammonia, the fuel supply line supplying ammonia to the first mixer; connecting an oxidizer supply line supplying an oxidizer to the first mixer, the first mixer mixing the ammonia flowing in the fuel supply line with the oxidizer from the oxidizer supply line to produce a mixed gas; and installing the reactor downstream of the first mixer in the fuel supply line, the catalyst causing the exothermic reaction with at least a part of the ammonia in the mixed gas that is supplied from the first mixer and heating the mixed gas.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a schematic diagram of a combustion facility including a fuel preheater according to a first embodiment.

[0024] FIG. 2 is a schematic diagram of the combustion facility including a fuel preheater according to a second embodiment.

[0025] FIG. 3 is a schematic diagram of the combustion facility including a fuel preheater according to a third embodiment.

DESCRIPTION OF EMBODIMENTS

[0026] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Specific dimensions, materials, and numerical values described in the embodiments are merely examples for a better understanding, and do not limit the present disclosure unless otherwise specified. In this specification and the drawings, duplicate explanations are omitted for elements having substantially the same functions and configurations by assigning the same sign. Furthermore, elements not directly related to the present disclosure are omitted from the figures.

[0027] FIG. 1 is a schematic diagram of a combustion facility 100 including a fuel preheater 10 according to a first embodiment. The fuel preheater 10 is installed in a fuel supply line L1 that is connected to the combustion facility 100. Gas including ammonia flows in the fuel supply line L1. For example, the combustion facility 100 can be a boiler, an industrial furnace, or a combustion furnace. The combustion facility 100 is not limited thereto, and can be a variety of facilities that use ammonia as fuel. The combustion facility 100 can be an existing facility. In another embodiment, the combustion facility 100 may be a newly constructed facility. For example, the combustion facility 100 includes one or more burners B.

[0028] The burner B combusts fuel including ammonia. For example, the burner B may combust a mixed fuel of ammonia and another fuel such as pulverized coal. Furthermore, the burner B may only combust ammonia. Moreover, the burner B may burn fuel that does not include ammonia, if necessary.

[0029] For example, the fuel preheater 10 includes a first mixer 1, a reactor 2, a second mixer 3, and a controller 90. The fuel preheater 10 may further include other components (not shown).

[0030] The first mixer 1 is provided in the fuel supply line L1. For example, the first mixer 1 may be installed for an existing fuel supply line L1 connected to an existing combustion facility 100. For example, the first mixer 1 is a gas mixer. The fuel supply line L1 supplies ammonia to the first mixer 1. For example, the fuel supply line L1 supplies gaseous ammonia to the first mixer 1.

[0031] An oxidizer supply line L2 is connected to the first mixer 1. The oxidizer supply line L2 supplies an oxidizer (e.g., air) to the first mixer 1.

[0032] A valve (first valve) V1 is provided in the oxidizer supply line L2. The valve V1 is communicatively connected to the controller 90 by wire or wirelessly, and is controlled by the controller 90. The controller 90 adjusts a flow rate of the oxidizer supplied to the first mixer 1 by controlling a degree of opening of the valve V1.

[0033] The first mixer 1 mixes the ammonia flowing in the fuel supply line L1 and the oxidizer supplied from the oxidizer supply line L2, and produces a mixed gas including the ammonia and the oxidizer. The mixed gas flows through the fuel supply line L1, and is supplied to the reactor 2.

[0034] A nitrogen supply line L3 is connected to the first mixer 1. The nitrogen supply line L3 supplies nitrogen to the first mixer 1.

[0035] A valve V2 is provided in the nitrogen supply line L3. The valve V2 is communicatively connected to the controller 90 by wire or wirelessly, and is controlled by the controller 90. The controller 90 adjusts a flow rate of the nitrogen supplied to the first mixer 1 by controlling a degree of opening of the valve V2.

[0036] The reactor 2 is provided downstream of the first mixer 1 in the fuel supply line L1. Similar to the first mixer 1, the reactor 2 may be installed for an existing fuel supply line L1 connected to an existing combustion facility 100. The reactor 2 receives the mixed gas from the first mixer 1. The reactor 2 includes a catalyst that promotes a reaction of ammonia and that causes an exothermic reaction. Specifically, the catalyst promotes the reaction of at least a part of the ammonia in the mixed gas supplied from the first mixer 1, and causes catalytic combustion. The mixed gas is heated by the catalytic combustion. The heated mixed gas flows through the fuel supply line L1, and is provided to the second mixer 3.

[0037] For example, the catalyst may include a transition element (may also be referred to as a transition metal). For example, the catalyst may include a noble metal such as Ru and the like. Furthermore, for example, the catalyst may include a non-noble metal such as Fe, Co, Ni and the like among transition elements. Non-noble metals may be highly active when combined with a certain carrier. For example, an oxide such as Al.sub.2O.sub.3 or SiO.sub.2 may be used as a carrier. Furthermore, a carrier that can curb sintering such as CeO.sub.2 may be used, if necessary.

[0038] A temperature sensor S1 is provided in the reactor 2. The temperature sensor S1 is configured to measure the temperature of the catalyst. The temperature sensor S1 is communicatively connected to the controller 90 by wire or wirelessly, and transmits measured data to the controller 90.

[0039] The reactor 2 is provided with heating means H. The heating means H heats the catalyst. For example, the heating means H may include an electric heater. Alternatively or additionally, the heating means H may include a first heat exchanger that heats the catalyst by exhaust gas from the combustion facility 100. Alternatively or additionally, if the combustion facility 100 includes a boiler, the heating means H may include a second heat exchanger that heats the catalyst by steam extracted from the combustion facility 100. The heating means H is communicatively connected to the controller 90 by wire or wirelessly, and is controlled by the controller 90.

[0040] For example, when the fuel preheater 10 starts operation, the controller 90 starts operation of the heating means H to heat the catalyst until the temperature measured by the temperature sensor S1 reaches a temperature at which the catalyst begins to be active (e.g., 400 C.). When the temperature measured by the temperature sensor S1 reaches the temperature at which the catalyst begins to be active, the controller 90 stops the operation of the heating means H. Thereafter, the catalyst is maintained at a sufficient temperature by the catalytic combustion.

[0041] The second mixer 3 is provided downstream of the reactor 2 in the fuel supply line L1. Similar to the first mixer 1 and the reactor 2, the second mixer 3 may be installed for an existing fuel supply line L1 connected to an existing combustion facility 100. For example, the second mixer 3 is a gas mixer. The second mixer 3 receives the heated mixed gas from the reactor 2.

[0042] The second mixer 3 is connected to the oxidizer supply line L2 by a bypass line (first bypass line) BL1. The bypass line BL1 directly connects the oxidizer supply line L2 to the second mixer 3 without passing through the first mixer 1 and the reactor 2. Accordingly, at least a part of the oxidizer flowing in the oxidizer supply line L2 is supplied to the first mixer 1, and the rest of the oxidizer is supplied to the second mixer 3.

[0043] A valve V3 is provided in the bypass line BL1. The valve V3 is communicatively connected to the controller 90 by wire or wirelessly, and is controlled by the controller 90. The controller 90 adjusts a flow rate of the oxidizer supplied to the second mixer 3 by controlling a degree of opening of the valve V3.

[0044] The second mixer 3 further mixes the mixed gas flowing in the fuel supply line L1 with the oxidizer supplied from the bypass line BL1. The mixed gas flows through the fuel supply line L1, and is supplied to the burners B as fuel (premixed combustion system). In another embodiment, the burner B may be a diffusion combustion system.

[0045] A temperature sensor S2 is provided at a position downstream of the reactor 2 in the fuel supply line L1, specifically, at a position downstream of the second mixer 3 in the present embodiment. The temperature sensor S2 is configured to measure the temperature of the mixed gas flowing in the fuel supply line L1. The temperature sensor S2 is communicatively connected to the controller 90 by wire or wirelessly, and transmits measured data to the controller 90.

[0046] The fuel supply line L1 branches into a plurality of lines at a position downstream of the temperature sensor S2, and is connected to each of the plurality of burners B.

[0047] The controller 90 controls the fuel preheater 10. The controller 90 may also control at least a part of components in the combustion facility 100. Furthermore, for example, the combustion facility 100 may include a main controller (not shown), and the controller 90 may communicate with the main controller. The controller 90 includes components such as a processor 90a, a memory 90b, and a connector 90c, and these components are connected to each other via buses. For example, the processor 90a includes a CPU (Central Processing Unit). For example, the memory 90b includes a hard disk, a ROM in which programs are stored, and a RAM as a work area. The controller 90 is communicatively connected to each component of the fuel preheater 10 by wire or wirelessly via the connector 90c. For example, the controller 90 may further include other components, such as a display such as an LCD or a touch panel, and an input device such as a keyboard, a button and a touch panel. For example, operation of the controller 90 may be realized by executing programs stored in the memory 90b on the processor 90a.

[0048] The catalyst in the reactor 2 promotes the reaction of ammonia, causing the following reactions (1), (2), or a combination thereof.

[00001]$\begin{array}{cc}N{H}_3.fwdarw.1.5H_2+0.5N_{2}H=45.4\left(\mathrm{kJ}/\mathrm{mol}\right)& \left(1\right)\end{array}$$\begin{array}{cc}2N{H}_3+1.5O_2.fwdarw.N_2+3H_{2}OH=-382.6\left(\mathrm{kJ}/\mathrm{mol}\right)& \left(2\right)\end{array}$

[0049] For example, in the present embodiment, the catalyst may cause both the reactions (1) and (2). For example, the controller 90 may control the valve V1 to adjust the amount of oxidizer allocated from the oxidizer supply line L2 to the first mixer 1, i.e., the amount of oxidizer supplied to the reactor 2, so that the majority of the oxidizer in the mixed gas supplied to the reactor 2 is used by the reaction (2) which is an exothermic reaction. The controller 90 may also control the valve V3, if necessary.

[0050] For example, if the reactor 2 requires more oxidizer for the catalytic combustion, the controller 90 increases the flow rate of the oxidizer supplied from the oxidizer supply line L2 to the reactor 2. In contrast, for example, if the amount of oxidizer supplied to the reactor 2 is excessive, the controller 90 reduces the flow rate of the oxidizer supplied from the oxidizer supply line L2 to the reactor 2.

[0051] The oxidizer required for combustion in the burners B is supplied from the oxidizer supply line L2 to the second mixer 3 via the bypass line BL1, and is mixed with the heated mixed gas in the second mixer 3. The controller 90 controls the valve V3 to adjust the amount of oxidizer allocated from the oxidizer supply line L2 to the bypass line BL1, i.e., the amount of oxidizer supplied to the second mixer 3. The controller 90 may also control the valve VI, if necessary.

[0052] For example, if the burners B require more oxidizer for combustion, the controller 90 may increase the flow rate of the oxidizer supplied from the oxidizer supply line L2 to the second mixer 3. In contrast, for example, if the amount of oxidizer supplied to the burners B is excessive, the controller 90 may reduce the flow rate of the oxidizer supplied from the oxidizer supply line L2 to the second mixer 3.

[0053] Furthermore, the controller 90 stores a predetermined threshold in the memory 90b. This threshold is associated with the temperature at which the material forming the fuel supply line L1 begins to be nitrided. For example, the fuel supply line L1 may be formed by steel, such as stainless steel. Many steels are known to be nitrided when exposed to an environment containing ammonia at substantially 400 degrees Celsius to 600 degrees Celsius. Thus, many steels will not be nitrided even when exposed to an environment containing ammonia if the temperature is below the above range. Specifically, for example, the threshold may be 400 degrees Celsius.

[0054] Furthermore, the threshold may be determined by an experiment. For example, a specimen made of the same material that forms the fuel supply line L1 is placed in an environment that simulates an interior of the fuel supply line L1. The environment is maintained for a predetermined period of time (e.g., one month, multiple months, one year, or multiple years). Thereafter, a nitrided case depth of the specimen is measured, and a nitriding rate per year (mm/year) is calculated. The experiment is conducted at multiple temperatures. For example, a temperature at which the nitriding rate is less than a predetermined value may be determined as the threshold (e.g., less than 1 mm/year). For example, the nitrided case depth may be measured by the method of measurement by hardness test or the method of measurement by metallographic test of the method of measuring nitrided case depth for iron and steel defined by JIS G0562.

[0055] The controller 90 may control at least one of the valves V1 and V3 to adjust the flow rate of the oxidizer supplied to the reactor 2 and the flow rate of the oxidizer supplied to the second mixer 3 so that the temperature of the mixed gas measured by the temperature sensor S2 is below the threshold.

[0056] If the temperature of the mixed gas measured by the temperature sensor S2 is excessively high, i.e., if the catalyst is excessively heated by the exothermic reaction, the controller 90 may open the valve V2 to add nitrogen as an emergency coolant to the mixed gas.

[0057] Note that the fuel supply line L1 may be provided with an unshown valve to adjust the flow rate of ammonia supplied to the first mixer 1. Furthermore, each of the lines L1, L2, and L3 may be provided with an unshown pump for pumping fluid. The valve and the pumps may be communicatively connected to the controller 90 by wire or wirelessly, and may be controlled by the controller 90.

[0058] Next, operation of the fuel preheater 10 will be described.

[0059] When the fuel preheater 10 starts operation, the controller 90 starts operation of the heating means H. The catalyst is heated until the temperature measured by the temperature sensor S1 reaches the temperature at which the catalyst begins to be active.

[0060] When the temperature measured by the temperature sensor reaches the temperature at which the catalyst begins to be active, the controller 90 controls the valve V1 and starts to supply the oxidizer to the first mixer 1. The first mixer 1 also receives ammonia from the fuel supply line L1. The first mixer 1 mixes the ammonia with the oxidizer to produce the mixed gas. The mixed gas is supplied to the reactor 2 by the fuel supply line L1.

[0061] The controller 90 stops the operation of the heating means H. Thereafter, the catalyst is maintained at a sufficient temperature by the catalytic combustion.

[0062] At least a part of the oxidizer in the mixed gas, e.g., most of the oxidizer in the mixed gas, reacts with the ammonia on the catalyst in the reactor 2, causing the catalytic combustion. This heats the mixed gas. The heated mixed gas is supplied to the second mixer 3 by the fuel supply line L1.

[0063] The controller 90 controls the valve V3 to start supplying the second mixer 3 with the oxidizer required for the combustion in the burners B. The second mixer 3 also receives the heated mixed gas from the fuel supply line L1. The second mixer 3 further mixes the ammonia with the oxidizer. The heated mixed gas is supplied to the plurality of burners B by the fuel supply line L1 as premixed fuel.

[0064] The fuel preheater 10 as described above includes the first mixer 1 provided in the fuel supply line L1 connected to the combustion facility 100 that combusts fuel including ammonia, and the reactor 2 provided downstream of the first mixer 1 in the fuel supply line L1. The fuel supply line L1 supplies the ammonia to the first mixer 1. The first mixer 1 is connected to the oxidizer supply line L2 supplying the oxidizer, and mixes the ammonia flowing in the fuel supply line L1 and the oxidizer from the oxidizer supply line L2 to produce the mixed gas. The reactor 2 includes the catalyst that promotes the reaction of the ammonia and that causes the exothermic reaction. The catalyst causes the exothermic reaction with at least a part of the ammonia in the mixed gas supplied from the first mixer 1, and heats the mixed gas. According to such a configuration, the mixed gas that includes ammonia and that is heated by the exothermic reaction in the reactor 2 can be supplied to the combustion facility 100. Since the mixed gas is heated by the exothermic reaction, the ammonia in the mixed gas is also heated, thereby the combustion rate of ammonia is increased. As such, the fuel can be supplied to the combustion facility 100 with the increased combustion rate.

[0065] Furthermore, the fuel preheater 10 includes the second mixer 3 provided downstream of the reactor 2 in the fuel supply line L1. The second mixer 3 is connected to the oxidizer supply line L2 by the bypass line BLI, and mixes the mixed gas supplied from the reactor 2 with the oxidizer supplied from the bypass line BL1. According to such a configuration, the amount of oxidizer supplied from oxidizer supply line L2 to the reactor 2 can be adjusted more precisely.

[0066] Furthermore, the fuel preheater 10 includes the valve V1 provided in the oxidizer supply line L2 and adjusting the flow rate of the oxidizer, the temperature sensor S2 provided downstream of the reactor 2 in the fuel supply line L1 and measuring the temperature of the mixed gas, and the controller 90 communicatively connected to the valve V1 and the temperature sensor S2. The controller 90 stores the predetermined threshold associated with the temperature at which the material forming the fuel supply line L1 begins to be nitrided. The controller 90 controls the valve V1 to adjust the flow rate of the oxidizer supplied to the first mixer 1 so that the temperature of the mixed gas measured by the temperature sensor S2 is below the threshold. According to such a configuration, embrittlement of the fuel supply line L1 due to nitriding can be curbed.

[0067] Furthermore, the reactor 2 includes the heating means H that heats the catalyst, and the heating means H may include a heater. According to such a configuration, the catalyst can be quickly heated to the temperature at which the catalyst begins to be active.

[0068] Alternatively or additionally, the heating means H may include the first heat exchanger in which the catalyst is heated by the exhaust gas from the combustion facility 100. According to such a configuration, the catalyst can be quickly heated to the temperature at which the catalyst begins to be active and the exhaust gas can be reused.

[0069] Alternatively or additionally, the heating means H may include the second heat exchanger that heats the catalyst with the steam extracted from the combustion facility 100. According to such a configuration, the catalyst can be quickly heated to the temperature at which the catalyst begins to be active.

[0070] Furthermore, the fuel preheater 10 supplies the mixed gas to the plurality of burners B in the combustion facility 100. According to such a configuration, there is no need to provide a fuel preheater for each burner B.

[0071] Furthermore, the exothermic reaction on the catalyst of the reactor 2 is the catalytic combustion. According to such a configuration, flameless combustion is conducted as a main surface reaction in the reactor 2, thereby the safety is increased. Furthermore, an air ratio in the reactor 2 can be changed by changing the flow rate of the oxidizer, and the temperature of the mixed gas can be controlled. By increasing the temperature of the mixed gas, ignitability and combustion stability of ammonia having flame retardancy can be improved in the burners B.

[0072] Furthermore, the fuel preheater 10 as described above can be installed in an existing combustion facility 100. The method of installing the fuel preheater 10 in the combustion facility 100 includes preparing the first mixer 1 configured to mix ammonia and the oxidizer, preparing the reactor 2 including the catalyst that causes the exothermic reaction with ammonia, and installing the first mixer 1 in the fuel supply line L1 connected to the combustion facility 100 that combusts fuel including ammonia. The fuel supply line L1 supplies the ammonia to the first mixer 1. The method also includes connecting the oxidizer supply line L2 that supplies the oxidizer to the first mixer 1. Thereby, the first mixer 1 mixes the ammonia flowing in the fuel supply line L1 with the oxidizer from the oxidizer supply line L2 to produce the mixed gas. The method also includes installing the reactor 2 in the fuel supply line L1 at the position downstream of the first mixer 1. Thereby, the catalyst causes the exothermic reaction with at least a part of the ammonia in the mixed gas supplied from the first mixer 1, and heats the mixed gas. According to such a configuration, the fuel can be supplied to the existing combustion facility 100 with an increased combustion rate without major construction work.

[0073] Note that in FIG. 1 and FIGS. 2 and 3 below, the fuel preheaters 10, 10A and 10B include components surrounded by dashed lines. Accordingly, the method of installing the fuel preheater 10, 10A or 10B in the combustion facility 100 according to the present disclosure may further include installing components surrounded by the dashed lines other than the first mixer 1 and the reactor 2 in the existing fuel supply line L1.

[0074] Next, other embodiments will be described.

[0075] FIG. 2 is a schematic diagram of the combustion facility 100 including a fuel preheater 10A according to a second embodiment. The fuel preheater 10A differs from the fuel preheater 10 of the first embodiment in that it has a bypass line (second bypass line) BL2 for ammonia and a third mixer 4, instead of the bypass line BL1 for the oxidizer and the second mixer 3. For other configurations, the fuel preheater 10A may be the same as the fuel preheater 10.

[0076] The third mixer 4 is provided downstream of the reactor 2 in the fuel supply line L1. The third mixer 4 may be installed in an existing fuel supply line L1 connected to an existing combustion facility 100. For example, the third mixer 4 is a gas mixer. The third mixer 4 receives the heated mixed gas from the reactor 2.

[0077] The third mixer 4 is connected to the fuel supply line L1 at a position upstream of the first mixer 1 by the bypass line BL2. The bypass line BL2 connects the fuel supply line L1 directly to the third mixer 4 without passing through the first mixer 1 and the reactor 2. Accordingly, at least a part of the ammonia flowing in the fuel supply line L1 is supplied to the first mixer 1, and the rest of the ammonia is supplied to the third mixer 4.

[0078] In the present embodiment, a valve (second valve) V4 is provided in the fuel supply line L1 between a connected part to the bypass line BL2 and the first mixer 1. The valve V4 is communicatively connected to the controller 90 by wire or wirelessly, and controlled by the controller 90. The controller 90 adjusts a flow rate of the ammonia supplied to the first mixer 1 by controlling a degree of opening of the valve V4.

[0079] A valve V5 is provided in the bypass line BL2. The valve V5 is communicatively connected to the controller 90 by wire or wirelessly, and controlled by the controller 90. The controller 90 adjusts a flow rate of the ammonia supplied to the third mixer 4 by controlling a degree of opening of the valve V5.

[0080] The third mixer 4 further mixes the mixed gas flowing in the fuel supply line L1 with the ammonia supplied from the bypass line BL2. The mixed gas flows through the fuel supply line L1, and is supplied to the burners B as fuel.

[0081] For example, the controller 90 may control the valve V4 to adjust the flow rate of the ammonia allocated from the fuel supply line L1 to the first mixer 1, i.e., the flow rate of the ammonia supplied to the reactor 2, so that the majority of the ammonia in the mixed gas supplied to the reactor 2 is used by the reaction (2) which is the exothermic reaction. The controller 90 may also control the valve V5, if necessary.

[0082] For example, if the reactor 2 needs to heat the mixed gas more, the controller 90 may increase the flow rate of the ammonia supplied from the fuel supply line L1 to the reactor 2. In contrast, for example, if the reactor 2 heats the mixed gas excessively, the controller 90 may reduce the flow rate of the oxidizer supplied from the fuel supply line L1 to the reactor 2.

[0083] The ammonia required for the combustion in the burners B is supplied from the fuel supply line L1 to the third mixer 4 via the bypass line BL2, and mixed with the heated mixed gas in the third mixer 4. The controller 90 controls the valve V5 to adjust the amount of ammonia allocated from the fuel supply line L1 to the bypass line BL2, i.e., the amount of ammonia supplied to the third mixer 4. The controller 90 may also control the valve V4, if necessary.

[0084] For example, if the burners B require more ammonia for the combustion, the controller 90 may increase the flow rate of ammonia supplied from the fuel supply line L1 to the third mixer 4. In contrast, for example, if the amount of ammonia supplied to the burners B is excessive, the controller 90 may reduce the flow rate of ammonia supplied from the fuel supply line L1 to the third mixer 4.

[0085] As in the first embodiment, the controller 90 may also control at least one of the valves V4 and V5 to adjust the flow rate of the ammonia supplied to the reactor 2 and the flow rate of the ammonia supplied to the third mixer 4, so that the temperature of the mixed gas measured by the temperature sensor S2 is below the threshold (e.g., 400 C.).

[0086] The fuel preheater 10A as described above has generally the same effects as the fuel preheater 10 of the first embodiment. Furthermore, the fuel preheater 10A includes the third mixer 4 provided downstream of the reactor 2 in the fuel supply line L1. The third mixer 4 is connected to the fuel supply line L1 at the position upstream of the first mixer 1 by the bypass line BL2, and mixes the mixed gas supplied from the reactor 2 with the ammonia supplied from the bypass line BL2. According to such a configuration, the amount of ammonia supplied from the fuel supply line L1 to the reactor 2 can be adjusted more precisely.

[0087] Furthermore, the fuel preheater 10A includes the valve V4 provided upstream of the first mixer 1 in the fuel supply line L1 and adjusting the flow rate of the ammonia supplied to the first mixer 1, the temperature sensor S2 provided downstream of the reactor 2 in the fuel supply line L1 and measuring the temperature of the mixed gas, and the controller 90 communicatively connected to the valve V4 and the temperature sensor S2. The controller 90 stores the predetermined threshold associated with the temperature at which the material forming the fuel supply line L1 begins to be nitrided. The controller 90 controls the valve V4 to adjust the flow rate of the ammonia supplied to the first mixer 1 so that the temperature of the mixed gas measured by the temperature sensor S2 is below the threshold. According to such a configuration, embrittlement of the fuel supply line L1 due to nitriding can be curbed.

[0088] FIG. 3 is a schematic diagram of the combustion facility 100 including a fuel preheater 10B according to a third embodiment. The fuel preheater 10B differs from the fuel preheater 10 of the first embodiment in that it does not include the bypass line BL1 and the second mixer 3. For other configurations, the fuel preheater 10B may be the same as the fuel preheater 10.

[0089] In the present embodiment, each burner B of the combustion facility 100 is a diffusion combustion system. Each burner B is supplied with air necessary for diffusion combustion. The combustion facility 100 may include unshown components such as an air register and a damper to adjust the amount of air to each burner B. Note that in FIG. 3, air is shown only for the topmost burner B.

[0090] For example, the controller 90 controls the valve V1 to adjust the amount of oxidizer supplied from the oxidizer supply line L2 through the first mixer 1 to the reactor 2 so that the majority of the oxidizer in the mixed gas supplied to the reactor 2 is used by the reaction (2) which is the exothermic reaction.

[0091] As in the first embodiment, the controller 90 also controls the valve V1 to adjust the flow rate of the oxidizer supplied to the reactor 2, so that the temperature of the mixed gas measured by the temperature sensor S2 is below the threshold (e.g., 400 C.).

[0092] The fuel preheater 10B as described above has generally the same effects as the fuel preheater 10 of the first embodiment.

[0093] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, the present disclosure is not limited thereto. It is obvious that a person skilled in the art can conceive of various examples of variations or modifications within the scope of the claims, which are also understood to belong to the technical scope of the present disclosure. Furthermore, the processes of the method of the above embodiments do not have to be executed in the above order, and may be executed in a different order as long as there is no technical inconsistency.

[0094] The present disclosure can promote the use of ammonia to reduce CO.sub.2 emissions, thus contributing to

[0095] Sustainable Development Goals (SDGs), Goal 7 Ensure access to affordable, reliable, sustainable and modern energy, and Goal 13 Take urgent action to combat climate change and its impacts, for example.