JP2022152684A - boiler system - Google Patents

Abstract

To provide a boiler system that prevents generation of carbon dioxide by using a metal material as fuel, and performs heat recovery equivalent to that in the case of using coal as fuel.SOLUTION: A boiler system comprises: a boiler 100 comprising a furnace 10, and combustion burners 21-25 for injecting a metal material and combustion air into the furnace 10, and for generating combustion gas containing metal oxide by burning the metal material; and a recirculation fan 600 for supplying inert gas having a temperature lower than that of the combustion gas discharged from the boiler 100, to the combustion burners 21-25.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a method of operating a boiler system having a boiler that burns metallic materials.

In thermal power generation, thermal energy obtained by burning fossil fuels such as coal is used as the source of electric power, but the greenhouse effect caused by carbon dioxide generated by burning fossil fuels is a problem as a factor of global warming. are viewed. Conventionally, it has been proposed to use aluminum as a fuel to replace fossil fuels (see, for example, Patent Document 1).

Japanese Patent No. 6080034

When coal is used as a fuel, it has a burner that injects pulverized coal pulverized together with combustion air, and a furnace that burns the pulverized coal injected by the burner and the combustion air. A boiler that produces steam is used.

However, when burning at a predetermined equivalence ratio, the adiabatic flame temperature of metal materials such as aluminum is higher than the adiabatic flame temperature of coal. Therefore, if a metal material is used as fuel in a boiler that has the same configuration as existing boilers that use coal as fuel, the heat load distribution in the furnace will be different from that of coal, and it may not be possible to generate steam appropriately. have a nature.

In addition, the theoretical amount of air required to completely burn the metallic material is smaller than the theoretical amount of air required to completely burn the coal when the same calorific value is obtained. Therefore, in order to obtain the same calorific value, the total gas amount of the combustion air supplied into the furnace and the combustion gas generated in the furnace is lower than that of using coal as fuel when metal materials are used as fuel. less than the case. As a result, when adopting the same structure as existing boilers that use coal as fuel, the amount of heat recovery when using metal materials as fuel can be less than the amount of heat recovery when using coal as fuel. have a nature.

The present disclosure has been made in view of such circumstances, and it is possible to prevent the generation of carbon dioxide by using a metal material as a fuel, and to perform heat recovery equivalent to the case of using coal as a fuel. The object is to provide a boiler system with a possible boiler.

In order to solve the above problems, a boiler system according to one aspect of the present disclosure employs the following means.
A boiler system according to an aspect of the present disclosure includes a furnace, a boiler that has a burner that injects a metal material and combustion air into the furnace, and burns the metal material to generate a combustion gas containing metal oxides. and an inert gas supply unit for supplying an inert gas having a temperature lower than that of the combustion gas discharged from the boiler to the burner.

According to the present disclosure, it is possible to provide a boiler system having a boiler capable of preventing the generation of carbon dioxide by using a metal material as a fuel and performing heat recovery equivalent to the case of using coal as a fuel. can.

1 is a schematic configuration diagram showing a boiler system according to a first embodiment of the present disclosure; FIG. It is a side view which shows schematic structure of the boiler shown in FIG. FIG. 4 is a diagram showing the relationship between the equivalence ratio and the adiabatic flame temperature when aluminum powder is used as fuel. FIG. 5 is a side view showing a schematic configuration of a boiler according to a second embodiment of the present disclosure; FIG. 5 is a front view showing a furnace portion of the boiler shown in FIG. 4;

[First Embodiment]
A boiler system 1 according to a first embodiment of the present disclosure will be described below with reference to the drawings. The boiler system 1 according to the present embodiment uses metal powder (metal material) as fuel, burns the metal powder with a combustion burner, and generates steam from the heat generated by this combustion, so that heat can be recovered. It is a system with a boiler that is

FIG. 1 is a schematic configuration diagram showing a boiler system 1 of this embodiment. 2 is a side view showing a schematic configuration of the boiler 100 shown in FIG. 1. FIG. As shown in FIG. 1, the boiler system 1 includes a boiler 100, a denitration device 200, an air preheater (cooler) 300, a dust collector 400, a chimney 500, a recirculation fan (inert gas supply unit ) 600 , a fan 700 , and a control device 800 .

The boiler 100 is a device capable of recovering heat by combusting metal powder with a combustion burner and generating steam from the heat generated by this combustion. The boiler 100 burns metal powder to generate combustion gas containing metal oxides. As shown in FIG. 2 , the boiler 100 of this embodiment has a furnace 10 , a combustion device 20 , a flue 30 , a fuel supply device 40 and a heat exchanger 50 .

The furnace 10 has a hollow rectangular tubular shape and is installed along the vertical direction. The furnace 10 is connected to a flue 30 in the vertical direction upper part.

Combustion device 20 has a plurality of combustion burners 21, 22, 23, 24, 25 mounted on the furnace wall. Combustion burners 21 , 22 , 23 , 24 and 25 are devices for injecting metal powder (metal material) and combustion air into furnace 10 , respectively. Combustion burners 21 , 22 , 23 , 24 , 25 are supplied with metal powder from fuel supply device 40 and with combustion air from fuel supply device 40 and blower 700 .

The combustion burners 21 , 22 , 23 , 24 , 25 blow metal powder into the furnace 10 and combustion air into the furnace 10 , and ignite at this time to form flames. In the furnace 10, the metal powder and the combustion air are combusted to generate a flame, and when the flame is generated in the vertically lower region in the furnace 10, the combustion gas (exhaust gas) rises in the furnace 10 and smoke. It is discharged onto road 30 .

In the present embodiment, the combustion burners 21, 22, 23, 24, and 25 are arranged in the circumferential direction with the vertical direction in which the furnace 10 extends as one set at equal intervals. Five sets (five stages) are arranged along the direction. Although five sets are used here, six sets or any other number of sets may be used.

The combustion burners 21, 22, 23, 24, and 25 may be installed only on the front wall of the furnace 10 (the left end in FIG. 2) (front combustion method). In addition, the combustion burners 21, 22, 23, 24, and 25 are installed on both the front wall (the left end in FIG. 2) and the rear wall (the right end in FIG. 2) of the furnace 10 (opposing combustion method). may be

Each combustion burner 21, 22, 23, 24, 25 is connected to fuel supply parts 41, 42, 43, 44, 45 via supply pipes 21a, 22a, 23a, 24a, 25a. The fuel supply units 41, 42, 43, 44, 45 supply powder of metal materials (eg, aluminum, magnesium) to the supply pipes 21a, 22a, 23a, 24a, 25a together with a carrier gas supplied from the outside.

A wind box 26 is provided at the mounting position of each combustion burner 21, 22, 23, 24, 25 of the furnace 10, and one end of an air duct 26a is connected to the wind box 26. As shown in FIG. Combustion air blown from a blower 700 is supplied to the air duct 26a. Further, the furnace 10 is provided with an additional air supply port 29 vertically above the mounting positions of the combustion burners 21, 22, 23, 24 and 25. As shown in FIG.

The additional air supply port 29 is connected to the end of a branch air duct 26b branched from the air duct 26a. Therefore, the combustion air sent from the blower 700 can be supplied from the air duct 26 a to the wind box 26 and from the wind box 26 to the combustion burners 21 , 22 , 23 , 24 and 25 . Further, the combustion air sent by the blower 700 can be supplied to the additional air supply port 29 from the branch air duct 26b.

The fuel supply device 40 has fuel supply units 41 , 42 , 43 , 44 , 45 and an air blower 46 . The blower 46 blows atmospheric air to the fuel supply units 41 , 42 , 43 , 44 and 45 as combustion air. The combustion air blown by the blower 46 is mixed with the inert combustion gas (inert gas) containing little oxygen supplied by the recirculation fan 600 to form a mixed gas. , 44 and 45. The fuel supply units 41, 42, 43, 44, 45 supply the metal powder together with the mixed gas to the supply pipes 21a, 22a, 23a, 24a, 25a.

The flue 30 has an exhaust gas pipe 31 for discharging the combustion gas that has undergone heat exchange with the heat exchanger 50 on the downstream side in the flow direction of the combustion gas. The combustion gas discharged from the exhaust gas pipe 31 is guided to the denitrification device 200 shown in FIG.

The heat exchanger 50 exchanges heat between the water supplied from the feed water pump (not shown) and the combustion gas flowing through the flue 30, and generates superheated steam from the heat of the combustion gas to the turbine (not shown). It is a device that supplies The heat exchanger 50 has superheaters 51 , 52 , reheaters 53 , 54 , and economizers 55 , 56 , 57 .

The water supplied from the feedwater pump is preheated by the economizers 55, 56, 57 and then heated while being supplied to each water pipe (not shown) of the furnace wall to become saturated steam, forming a steam drum (not shown). ). The saturated steam in the steam drum is introduced into superheaters 51, 52 and superheated by the combustion gas.

The superheated steam generated by the superheaters 51 and 52 is supplied to a turbine (not shown) of the power plant. Also, the steam supplied to the turbine is taken out in the middle of the expansion process and introduced into the reheaters 53 and 54 . The steam re-superheated in the reheaters 53, 54 is returned to the turbine, expanded, and rotationally drives the turbine.

The denitration device 200 is a device that removes nitrogen oxides (NOx) contained in the combustion gas discharged from the boiler 100 . The denitrification device 200, for example, mixes ammonia (NH ₃ ) with combustion gas, passes through a catalyst layer, and decomposes nitrogen oxides into nitrogen and water by a dry ammonia selective catalytic reduction method (SCR method) to convert nitrogen oxides into nitrogen oxides. to remove The combustion gas from which nitrogen oxides have been removed by the denitrification device 200 is supplied to the air preheater 300 .

The air preheater (cooling) 300 is a device that exchanges heat between the combustion gas supplied from the denitrification device 200 and air in the atmosphere (outside air). The air preheater 300 is a device that heats the air in the atmosphere and cools the combustion gas discharged from the boiler 100 . The combustion gas cooled by the air preheater 300 is supplied to the dust collector 400 .

Air preheater 300 is supplied with air blown by blower 700, exchanges heat with the supplied air with combustion gas, and supplies the heated air to boiler 100 as combustion air. The temperature of the combustion gas discharged from the boiler 100 and having a temperature of about 360°C is adjusted to about 130°C by heat exchange in the air preheater 300 . Also, the combustion air is heated to about 330° C. by heat exchange with the combustion gas.

The dust collector 400 is a device that removes metal oxides and other dust particles contained in the combustion gas supplied from the air preheater 300 . Combustion gas from which metal oxides and other dust and the like have been removed by the dust collector 400 is released into the atmosphere from a chimney 500 . The metal oxides collected by the dust collector 400 are reduced by a reducing device (not shown) and supplied to the fuel supply device 40 again as fuel.

The recirculation fan 600 is a device for supplying the combustion burners 21 , 22 , 23 , 24 , 25 with combustion gas (inert gas) having a lower temperature than the combustion gas discharged from the boiler 100 . The recirculation fan 600 supplies the combustion gas cooled by the air preheater 300 to the combustion burners 21, 22, 23, 24, 25 as inert gas. As shown in FIG. 1 , the recirculation fan 600 is arranged in a recirculation line L 1 branched from the discharge line L 0 leading the combustion gas from the dust collector 400 to the chimney 500 .

The control device 800 is a device that controls each part of the boiler system 1 . The controller 800 controls the recirculation fan 600 to adjust the amount of combustion gas supplied from the discharge line L0 to the combustion burners 21, 22, 23, 24, 25 via the recirculation line L1. Further, the control device 800 controls the blower 700 to adjust the amount of combustion air supplied to the combustion device 20 of the boiler 100 via the combustion air supply line L2. Further, the control device 800 adjusts the amount of combustion air supplied from the blower 46 to the fuel supply device 40 by controlling the blower 46 .

Next, the amount of combustion gas supplied from the exhaust line L0 to the combustion burners 21, 22, 23, 24, 25 through the recirculation line L1 by the recirculation fan 600 will be described. FIG. 3 is a diagram showing the relationship between the equivalence ratio and the adiabatic flame temperature when aluminum powder is used as fuel. FIG. 3 shows the data obtained to determine the amount of combustion air that is directed from the blower 46 to the fuel supply 40 .

In FIG. 3, α indicates a dilution factor for diluting nitrogen contained in the combustion air supplied to the furnace 10 together with the aluminum powder with an inert gas. α=0 indicates that the nitrogen contained in the combustion air is not diluted with inert gas. α=1.0 indicates that the nitrogen contained in the combustion air supplied to the furnace 10 together with the aluminum powder is diluted with the same amount of inert gas as the nitrogen.

α=1.5 indicates that the nitrogen contained in the combustion air supplied to the furnace 10 together with the aluminum powder is diluted with an inert gas having a volume 1.5 times that of nitrogen. α=2.0 indicates that the nitrogen contained in the combustion air supplied to the furnace 10 together with the aluminum powder is diluted with an inert gas of 2.0 times the volume of nitrogen.

FIG. 3 shows, as a comparative example, an example in which pulverized coal is used as the fuel and nitrogen contained in the combustion air supplied to the furnace 10 together with the pulverized coal is not diluted with an inert gas.

When using aluminum powder as fuel, if α=0, the boiler 100 is supplied with only the theoretical amount of air required for complete combustion of the aluminum powder. For example, when the equivalence ratio is 1.0, the adiabatic flame temperature exceeds 3500K when aluminum powder is used as the fuel. This temperature is 1000 K or more higher than the adiabatic flame temperature when pulverized coal is used as fuel at an equivalence ratio of 1.0.

On the other hand, when the equivalence ratio is 1.0, the adiabatic flame temperature in the case of using aluminum powder as the fuel is sufficiently below 3500 K if α=1.0. Thus, by setting the dilution factor α for diluting the nitrogen contained in the combustion air supplied to the furnace 10 together with the aluminum powder with the inert gas to 1.0 or more, the adiabatic flame temperature becomes excessive compared to the pulverized coal. can be suppressed.

If the dilution ratio α is increased, the adiabatic flame temperature will decrease, but the load on the recirculation fan 600 will increase as the dilution ratio α increases. That is, in order to increase the amount of combustion gas supplied from the discharge line L0 to the combustion burners 21, 22, 23, 24, 25 via the recirculation line L1, the load on the recirculation fan 600 must be increased. Therefore, if the dilution factor α is set too high, the load on the recirculation fan 600 will increase. Therefore, in the present embodiment, the dilution ratio α is set to 2.0 times or less.

As described above, the inventors examined the data shown in FIG. The recirculation fan 600 is controlled so as to supply combustion gas with a flow rate of 2.0 times or less to the combustion burners 21, 22, 23, 24, and 25. Here, the combustion air supplied to the furnace 10 is a combination of both the combustion air supplied from the blower 46 to the fuel supply device 40 and the combustion air supplied from the blower 700 to the additional air supply port 29. It is a thing.

When the dilution ratio α is set to 1.5, the control device 800 transfers 0.6 of the nitrogen contained in the combustion gas discharged from the boiler 100 from the discharge line L0 to the recirculation line L1. The recirculation fan 600 is controlled to direct the In this case, 0.4 of the nitrogen contained in the combustion gas discharged from the boiler 100 is released from the chimney 500 into the atmosphere.

The nitrogen contained in the combustion gas discharged from the boiler 100 is 1, and the nitrogen introduced from the discharge line L0 to the recirculation line L1 is 0.6. Nitrogen contained in the operating air is 0.4. Thus, when the dilution ratio α is 1.5, the recirculation fan 600 has a flow rate of 1.5 times the nitrogen (0.4) contained in the combustion air supplied to the furnace 10 per unit time. of nitrogen (0.6) is supplied to the combustion burners 21, 22, 23, 24, 25.

Further, when the dilution ratio α is 1.0 times, the recirculation fan 600 supplies nitrogen to the combustion burner 21 at a flow rate of 1.0 times the nitrogen contained in the combustion air supplied to the furnace 10 per unit time. , 22, 23, 24, 25. Similarly, when the dilution ratio α is set to 2.0, the recirculation fan 600 supplies nitrogen to the combustion burner 21 at a flow rate of 2.0 times the nitrogen contained in the combustion air supplied to the furnace 10 per unit time. , 22, 23, 24, 25.

The control device 800 controls the blower 46 and the fuel supply units 41, 42, 43, 44, 45 to adjust the equivalence ratio of the mixed gas containing metal powder supplied from the combustion burners 21, 22, 23, 24, 25. can be controlled to a predetermined value.

For example, the control device 800 sets the equivalence ratio of the mixed gas containing metal powder supplied from the combustion burners 21, 22, 23, 24, 25 to a predetermined value of 0.8 or more and less than 1.0, and the combustion burner 21 , 22, 23, 24, and 25 are controlled so that the mixed gas having the same equivalence ratio is supplied to the furnace 10. In this case, the controller 800 controls the amount of combustion air supplied from the additional air supply port 29 so that the metal powder supplied from the combustion burners 21, 22, 23, 24, 25 to the furnace 10 is completely combusted. to adjust.

Further, for example, the control device 800 sets the equivalence ratio of the mixed gas containing metal powder supplied from the combustion burners (first burners) 23, 24, 25 to less than 1.0 (more preferably, 0.7 or less). , and the equivalence ratio of the mixed gas containing the metal powder supplied from the combustion burners (second burners) 21 and 22 may be 1.0 or more (more preferably 1.5 or more). The reason for this is to lower the adiabatic flame temperature when the mixed gas containing the metal powder is burned.

As shown in FIG. 3, when the metal powder is aluminum and the dilution ratio α is 1.0, the equivalence ratio of the mixed gas containing the metal powder is 0.7 or less, so that the adiabatic flame temperature is about 2700 K or less. Become. Similarly, when the metal powder is aluminum and the dilution ratio α is 1.0, the adiabatic flame temperature becomes about 2750 K or less by setting the equivalence ratio of the mixed gas containing the metal powder to 1.5 or more.

Further, as shown in FIG. 3, when the metal powder is aluminum and the dilution ratio α is 1.5, the equivalence ratio of the mixed gas containing the metal powder is 0.8 or less, so that the adiabatic flame temperature is about 2500K. It is as follows. Similarly, when the metal powder is aluminum and the dilution factor α is 1.5, the adiabatic flame temperature becomes about 2500 K or less by setting the equivalence ratio of the mixed gas containing the metal powder to 1.4 or more.

Further, as shown in FIG. 3, when the metal powder is aluminum and the dilution factor α is 2.0, the equivalence ratio of the mixed gas containing the metal powder is less than 1.0, so that the adiabatic flame temperature is about 2500K. It is as follows. Similarly, when the metal powder is aluminum and the dilution ratio α is 2.0, the adiabatic flame temperature becomes about 2500 K or less by setting the equivalence ratio of the mixed gas containing the metal powder to 1.0 or more.

In addition, in the combustion burners 21, 22, 23, 24, and 25, the equivalence ratio of the mixed gas is 1.0 or more (more preferably 1.5 or more), and the equivalence ratio of the mixed gas is less than 1.0 (more preferably, 0.7 or less), the average equivalence ratio of all the combustion burners 21, 22, 23, 24, 25 can be brought closer to 1.

In the above example, the equivalence ratio of the mixed gas containing metal powder supplied from the combustion burners 23, 24, 25 is set to less than 1.0 (more preferably, 0.7 or less), and the combustion burners 21, 22 Although the equivalence ratio of the mixed gas containing the metal powder to be supplied is set to 1.0 or more (more preferably 1.5 or more), other aspects may be adopted. For example, the equivalence ratio of the mixed gas containing the metal powder supplied from the combustion burners 24 and 25 is set to less than 1.0 (more preferably 0.7 or less), and the metal powder supplied from the combustion burners 21, 22 and 23 The equivalence ratio of the mixed gas containing may be less than 1.0 (more preferably 1.5 or more). In addition, a combustion burner with a mixed gas equivalent ratio of less than 1.0 (more preferably 0.7 or less) and a mixed gas equivalent ratio of 1.0 or more (more preferably 1.5 or more) Other combinations may be used as long as they are combined with a combustion burner.

In the boiler 100 shown in FIG. 2, the combustion burners 21, 22, 23, 24, and 25 are arranged in five sets (five stages) along the vertical direction, but other arrangements may be made. For example, any number of stages other than five may be used so as to reduce unevenness in the heat load of the entire furnace 10 .

In addition, in the boiler 100 shown in FIG. 2, the additional air supply port 29 is arranged in one stage. good. Furthermore, a combustion burner may be provided in the additional air supply port 29 and metal powder may be supplied to the furnace 10 from the combustion burner.

The operation and effects of the boiler system 1 of the present embodiment described above will be described.
According to the boiler system 1 of the present embodiment, since the combustion gas containing metal oxides is generated by burning the metal powder in the boiler 100, it is possible to prevent the generation of carbon dioxide when obtaining thermal energy. can. Combustion gas having a lower temperature than the combustion gas discharged from the boiler 100 is supplied to the combustion burners 21, 22, 23, 24 and 25 by the recirculation fan 600 and injected into the furnace 10 together with the combustion air.

Since the gas in the furnace 10 is diluted by the combustion gas, which is an inert gas, the adiabatic flame temperature of the mixed gas in which the gas in the furnace and the inert gas are mixed becomes lower than when the inert gas is not mixed. As a result, in a boiler having the same configuration as an existing boiler using coal as fuel, the heat load distribution in the furnace 10 when using metal materials as fuel is brought closer to the heat load distribution when using coal as fuel. , and steam can be generated properly.

In addition, since the gas in the furnace is diluted with the inert gas, the total amount of gas supplied to the furnace increases compared to the case where the gas in the furnace is not diluted with the inert gas. As a result, in a boiler that uses the same structure as an existing boiler that uses coal as fuel, compared to the case where the gas in the furnace is not diluted with inert gas, the heat recovery amount when using metal materials as fuel is Steam can be appropriately generated in a state close to the amount of heat recovered when coal is used as fuel.

Further, according to the boiler system 1 of the present embodiment, the combustion gas (inert gas) is burned at a flow rate of 1.0 to 2.0 times the nitrogen contained in the combustion air supplied to the furnace 10. By supplying the fuel to the burners 21, 22, 23, 24, and 25, the heat load distribution in the furnace 10 when using metal materials as fuel can be appropriately brought close to the heat load distribution when using coal as fuel. . In addition, the amount of heat recovered when using a metal material as fuel can be brought closer to the amount of heat recovered when using coal as fuel.

Further, according to the boiler system 1 of the present embodiment, by setting the equivalence ratio of the first combustion burner included in the plurality of combustion burners 21, 22, 23, 24, 25 to less than 1.0, the adiabatic flame temperature can be suppressed from rising excessively. Similarly, by setting the equivalence ratio of the second burners included in the plurality of combustion burners 21, 22, 23, 24, 25 to 1.0 or more, it is possible to suppress an excessive rise in the adiabatic flame temperature. can. Further, by setting the equivalence ratio of the first burner to less than 1.0 and the equivalence ratio of the second burner to 1.0 or more, the average equivalence ratio of both the first burner and the second burner can approach 1.

Further, according to the boiler system 1 of the present embodiment, the combustion gas discharged from the boiler 100 is cooled by the air preheater 300 and supplied to the combustion burners 21, 22, 23, 24, 25 as inert gas. , the combustion gas generated in the boiler system 1 can be appropriately reused as the inert gas without supplying another inert gas different from the combustion gas.

[Second embodiment]
A boiler system 1 according to a second embodiment of the present disclosure will be described below with reference to the drawings. The second embodiment is a modified example of the first embodiment, and is assumed to be the same as the first embodiment except for the case where it will be particularly described below, and the description thereof will be omitted. FIG. 4 is a side view showing a schematic configuration of the boiler according to this embodiment. 5 is a front view showing a furnace portion of the boiler shown in FIG. 4. FIG.

As shown in FIG. 4 , the boiler 100A of this embodiment includes a combustion device 60 provided on a furnace bottom portion 11 that is the bottom surface of the furnace 10 . As shown in FIG. 4 , the combustion device 60 includes metal powder supplied from the fuel supply unit 47 of the fuel supply device 40 , combustion air supplied from the blower 46 , and combustion air supplied from the recirculation fan 600 . A mixed gas with gas is supplied. Combustion air blown by a blower 700 is supplied to the combustion device 60 .

As shown in FIG. 5 , the combustion device 60 has bottom burners 61 and bottom burners 62 provided at both ends of the bottom portion 11 . The bottom burners 61 and 62 can change the injection angle at which the mixed gas is injected into the furnace 10 to an arbitrary angle. The operator adjusts the injection angles of the mixed gas from the bottom burners 61 and 62 so that the heat load distribution in each area inside the furnace 10 is less uneven.

By injecting the mixed gas from the furnace bottom 11 from the combustion device 60, even if the combustion period of the metal material is long or the particle size of the metal material is large, the residence time of the metal material in the furnace 10 is long. You can definitely burn it. In addition, by sufficiently charging combustion air from the furnace bottom 11, complete combustion of the metal materials charged from the combustion burners 21, 22, 23, and 34 can be promoted. In addition, a sufficient amount of heat can be absorbed in the furnace bottom portion 11, and the heat load distribution of the entire furnace 10 including the furnace bottom portion 11 can be adjusted more appropriately.

[Other embodiments]
In the above description, the metal powder is used as the fuel to be supplied to the furnace 10, but other modes are possible. For example, liquid metal may be used as the fuel supplied to the furnace 10 . When using liquid metal, the fuel supply device 40 heats a metal material (for example, aluminum or magnesium) to a melting point or higher to make it liquid, and supplies the liquid metal to the combustion burners 21 , 22 , 23 , 24 and 25 . The combustion burners 21 , 22 , 23 , 24 and 25 are supplied with combustion gas supplied from a recirculation fan 600 . The combustion burners 21 , 22 , 23 , 24 , 25 atomize the liquid metal with combustion gas and inject it into the furnace 10 .

In the above description, the combustion gas supplied from the recirculation fan 600 is supplied to the fuel supply device 40 as an inert gas, but other modes may be adopted. For example, instead of using the combustion gas supplied from the recirculation fan 600, inert gas may be supplied to the fuel supply device 40 from an inert gas supply source such as nitrogen gas.

The boiler system (100) described in the embodiment described above is grasped, for example, as follows.
The boiler system of this embodiment has a furnace (10) and burners (21 to 25) for injecting a metal material and combustion air into the furnace, and burns the metal material to produce a combustion gas containing metal oxides. and an inert gas supply unit (600) for supplying inert gas having a temperature lower than that of the combustion gas discharged from the boiler to the burner.

According to the boiler system of the present embodiment, the combustion gas containing the metal oxide is generated by burning the metal material in the boiler, so it is possible to prevent the generation of carbon dioxide when obtaining thermal energy. In addition, an inert gas having a lower temperature than the combustion gas discharged from the boiler is supplied to the burner by the inert gas supply unit and injected into the furnace together with the combustion air.

Since the inert gas dilutes the gas in the furnace, the adiabatic flame temperature of the mixed gas in which the gas in the furnace and the inert gas are mixed is lower than that in the case where the inert gas is not mixed. As a result, in a boiler with the same configuration as existing boilers that use coal as fuel, the heat load distribution in the furnace when using metal materials as fuel is brought closer to the heat load distribution when coal is used as fuel. , can properly generate steam.

In addition, since the gas in the furnace is diluted with the inert gas, the total amount of gas supplied to the furnace increases compared to the case where the gas in the furnace is not diluted with the inert gas. As a result, in a boiler that uses the same structure as an existing boiler that uses coal as fuel, compared to the case where the gas in the furnace is not diluted with inert gas, the heat recovery amount when using metal materials as fuel is Steam can be appropriately generated in a state close to the amount of heat recovered when coal is used as fuel.

In the boiler system of the present embodiment, the inert gas supply unit supplies the inert gas of 1.0 times or more and 2.0 times or less of nitrogen contained in the combustion air supplied to the furnace per unit time. The configuration may be such that an active gas is supplied to the burner.
According to the boiler system of this configuration, by supplying the inert gas to the burner at a flow rate of 1.0 to 2.0 times the nitrogen contained in the combustion air supplied to the furnace, the metal material is The heat load distribution in the furnace when using coal as fuel can be appropriately brought close to the heat load distribution when coal is used as fuel. In addition, the amount of heat recovered when using a metal material as fuel can be brought closer to the amount of heat recovered when using coal as fuel.

In the boiler system having the above configuration, the boiler has a plurality of the burners, and the first burner included in the plurality of burners mixes the metal material and the combustion air at an equivalence ratio of less than 1.0. A second burner that supplies the furnace and is included in the plurality of burners may supply the metal material and the combustion air to the furnace at an equivalence ratio of 1.0 or more.

According to the boiler system of this configuration, by setting the equivalence ratio of the first burner included in the plurality of burners to less than 1.0, it is possible to suppress an excessive rise in the adiabatic flame temperature. Similarly, by setting the equivalence ratio of the second burner included in the plurality of burners to 1.0 or more, it is possible to suppress an excessive rise in the adiabatic flame temperature. Further, by setting the equivalence ratio of the first burner to 1.0 or less and the equivalence ratio of the second burner to 1.0 or more, the equivalence ratio obtained by averaging both the first burner and the second burner can approach 1.

The boiler system of the present embodiment has a cooler (300) for cooling the combustion gas discharged from the boiler, and the inert gas supply unit supplies the inert gas cooled by the cooler to the inert gas. It may be configured to be supplied to the burner as an active gas.
According to the boiler system of this configuration, the combustion gas discharged from the boiler is cooled by the cooler and supplied to the burner as an inert gas. Combustion gas generated in the boiler system can be appropriately reused as inert gas.

In the boiler system of the present embodiment, a combustion device is provided on the bottom surface of the furnace and injects a mixed gas obtained by mixing the metal material and the combustion air, and the combustion device emits the mixed gas into the furnace. It is good also as a structure which can change the injection angle which injects inside to arbitrary angles.
According to the boiler system of this configuration, the injection angle for injecting the mixed gas in which the metal material and the combustion air are mixed into the furnace can be changed to any angle. Therefore, by adjusting the injection angle of the mixed gas by the operator, it is possible to reduce the uneven heat load distribution in each region inside the furnace.

In the boiler system of the present embodiment, the metal material is metal powder, and the burner transports the metal powder with the combustion air and injects the combustion air and the metal powder into the furnace. good too.
According to the boiler system of this configuration, the metal powder carried by the combustion air can be supplied as fuel from the burner to the furnace.

In the boiler system of the present embodiment, the metal material may be liquid metal, and the burner may atomize the liquid metal with the inert gas and inject it into the furnace.
According to the boiler system of this configuration, the liquid metal atomized by the inert gas can be supplied from the burner to the furnace as fuel.

1 Boiler System 10 Furnace 11 Furnace Bottom 20 Combustion Devices 21, 22, 23, 24, 25 Combustion Burners 21a, 22a, 23a, 24a, 25a Supply Pipe 29 Additional Air Supply Port 30 Flue 31 Exhaust Gas Pipe 40 Fuel Supply Device 41, 42, 43, 44, 45, 47 fuel supply part 46 blower 50 heat exchanger 60 combustion device 61, 62 hearth burner 100, 100A boiler 200 denitration device 300 air preheater (cooler)
400 dust collector 500 chimney 600 recirculation fan (inert gas supply unit)
700 Blower 800 Control device L0 Discharge line L1 Recirculation line L2 Combustion air supply line α Dilution ratio

Claims (7)

a boiler having a furnace and a burner for injecting a metallic material and combustion air into the furnace and burning the metallic material to generate a combustion gas containing a metal oxide;
and a boiler system comprising an inert gas supply section that supplies an inert gas having a temperature lower than that of the combustion gas discharged from the boiler to the burner. The inert gas supply unit supplies the inert gas to the burner at a flow rate of 1.0 times or more and 2.0 times or less than nitrogen contained in the combustion air supplied to the furnace per unit time. 2. The boiler system of claim 1, supplying The boiler has a plurality of burners,
a first said burner included in said plurality of said burners supplies said metallic material and said combustion air to said furnace at an equivalence ratio of less than 1.0;
3. The boiler system according to claim 1, wherein the second burner included in the plurality of burners supplies the metal material and the combustion air to the furnace at an equivalence ratio of 1.0 or more. Having a cooler for cooling the combustion gas discharged from the boiler,
The boiler system according to any one of claims 1 to 3, wherein the inert gas supply section supplies the combustion gas cooled by the cooler to the burner as the inert gas. A combustion device is provided on the bottom surface of the furnace and injects a mixed gas obtained by mixing the metal material and the combustion air,
The boiler system according to any one of claims 1 to 4, wherein the combustion device can change an injection angle for injecting the mixed gas into the furnace to an arbitrary angle. The metal material is metal powder,
The boiler system according to any one of claims 1 to 5, wherein the burner transports the metal powder with the combustion air and injects the combustion air and the metal powder into the furnace. the metal material is a liquid metal,
The boiler system according to any one of claims 1 to 5, wherein the burner atomizes the liquid metal with the inert gas and injects the atomized liquid metal into the furnace.

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