JP6926960B2 - boiler - Google Patents

Description

The present invention relates to a boiler.

Patent Document 1 below discloses a complex energy system that burns a fuel containing ammonia. This combined energy system adds ammonia to natural gas, which is the main fuel, and burns it for the purpose of reducing carbon dioxide emissions.

Japanese Unexamined Patent Publication No. 2016-032391

By the way, when ammonia is burned as a part of fuel, there is a concern that nitrogen oxides (NOx) contained in the combustion gas will increase. The background technology is solely aimed at reducing carbon dioxide emissions and does not offer any solution for reducing nitrogen oxides (NOx). When a carbon fuel such as natural gas and a nitrogen-containing fuel such as ammonia are burned together, it is indispensable to suppress an increase in nitrogen oxides (NOx) from the viewpoint of practicality.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress an increase in nitrogen oxides (NOx) in a boiler capable of burning ammonia as a fuel.

The present invention employs the following configuration as a means for solving the above problems.

The first invention is a boiler including a combustion device capable of burning ammonia as fuel, a furnace equipped with the combustion device, and a flue for guiding combustion gas generated by burning the fuel. A configuration is adopted in which a reducing agent supply unit that supplies a part of the ammonia supplied as fuel to the combustion device as a reducing agent to at least one of the furnace and the flue at a position downstream of the combustion device is provided.

In the second invention, in the first invention, the reducing agent supply unit is connected to the furnace so as to be able to individually supply the ammonia as the reducing agent to a plurality of locations in the height direction. Adopt the configuration of being.

In the third invention, in the first or second invention, the reducing agent supply unit is connected so as to be able to individually supply the ammonia as the reducing agent to each of the furnace and the flue. Adopt the configuration that is.

In the fourth invention, in any one of the first to third inventions, the temperature measuring unit for measuring the internal temperature of at least one of the furnace and the flue is provided, and the reducing agent supply unit is the temperature measuring unit. A configuration is adopted in which the flow rate of the ammonia supplied as the reducing agent is set based on the measurement result of.

The fifth invention includes, in any one of the first to fourth inventions, a concentration measuring unit for measuring the concentration of nitrogen oxides contained in the combustion gas discharged from the flue, and the reducing agent supply unit. However, a configuration is adopted in which the flow rate of the ammonia supplied as the reducing agent is set based on the measurement result of the concentration measuring unit.

In the sixth invention, in any one of the first to fifth inventions, a combustion device capable of burning carbon fuel is provided, and the reducing agent supply unit is supplied as the reducing agent based on the characteristics of the carbon fuel. The configuration of setting the flow rate of the above-mentioned ammonia is adopted.

In the seventh invention, in any one of the first to sixth inventions, the reducing agent supply unit is arranged inside at least one of the furnace and the flue and is supplied as the reducing agent. A configuration is adopted in which an injection unit for injecting ammonia is provided.

In the eighth invention, in any one of the first to seventh inventions, the total flow rate of ammonia, which is the sum of the flow rate of the ammonia supplied as the reducing agent and the flow rate of the ammonia supplied as the fuel, is determined. A configuration is adopted in which a control unit that adjusts according to the flow rate of the ammonia supplied as the reducing agent is provided.

According to the present invention, a part of ammonia supplied to the combustion apparatus as fuel is supplied as a reducing agent to at least one of the furnace and the flue. Therefore, the nitrogen oxides generated by burning the ammonia supplied as the fuel are reduced by the ammonia supplied as the reducing agent. Therefore, according to the present invention, it is possible to suppress an increase in nitrogen oxides (NOx) in a boiler that can burn using ammonia as fuel.

It is a schematic diagram which shows the main part structure of the boiler in 1st Embodiment of this invention. It is a schematic diagram which shows the main part structure of the boiler in the 2nd Embodiment of this invention. It is a schematic diagram which shows the main part structure of the boiler in the 3rd Embodiment of this invention. It is a schematic diagram which shows the main part structure of the boiler in 4th Embodiment of this invention. It is a schematic diagram which shows the main part structure of the boiler in 5th Embodiment of this invention. It is a schematic diagram which shows the main part structure of the boiler in 6th Embodiment of this invention. It is a schematic diagram which shows the main part structure of the boiler in 7th Embodiment of this invention. It is a bar graph which shows the simulation result of the boiler in 1st Embodiment of this invention. It is a bar graph which shows the simulation result of the boiler in 1st Embodiment of this invention. It is a bar graph which shows the result of simulating the amount of nitric oxide contained in the exhaust gas in the boiler which uses only pulverized coal as fuel.

Hereinafter, an embodiment of the boiler according to the present invention will be described with reference to the drawings. In the drawings below, the scale of each member is appropriately changed in order to make each member recognizable.

(First Embodiment)
FIG. 1 is a schematic view showing a configuration of a main part of the boiler 1 of the first embodiment. As shown in FIG. 1, the boiler 1 includes a furnace 2, a flue 3, a burner 4 (combustion device), a two-stage combustion air supply unit 5, an ammonia supply unit 6, and a pulverized coal supply unit 7. I have.

The furnace 2 is composed of a furnace wall provided vertically and in a tubular shape, and is a furnace body that burns fuel such as ammonia or pulverized coal to generate combustion heat. In this furnace 2, high-temperature combustion gas is generated by burning fuel. Further, the bottom of the furnace 2 is provided with a discharge port 2a for discharging ash generated by combustion of fuel to the outside.

The flue 3 is connected to the upper part of the furnace 2 and guides the combustion gas generated in the furnace 2 to the outside as exhaust gas. Such a flue 3 includes a horizontal flue 3a extending horizontally from the upper part of the furnace 2 and a rear flue 3b extending downward from the end of the horizontal flue 3a.

Although omitted in FIG. 1, the boiler 1 is provided with a superheater installed in the upper part of the furnace 2 or the like. The superheater generates steam by exchanging heat between the combustion heat generated in the furnace 2 and water. Further, although omitted in FIG. 1, the boiler 1 is provided with a reheater, an economizer, an air preheater and the like, if necessary.

The burner 4 is arranged on the lower wall of the furnace 2. A plurality of the burners 4 are installed in the circumferential direction of the furnace 2. Further, although omitted in FIG. 1, a plurality of burners 4 are also installed in the height direction of the furnace 2. These burners 4 are two-dimensionally and opposed to each other in the lower part of the furnace 2 to inject fuel and burn it. Each of these burners 4 is a composite burner that can be injected into the furnace 2 using ammonia and pulverized coal as fuel. Although omitted in FIG. 1, the furnace 2 is provided with an ignition device for igniting the fuel (ammonia and pulverized coal) injected from the burner 4. Further, although omitted in FIG. 1, the boiler 1 has a combustion air supply unit that supplies combustion air to the burner 4. The fuel (ammonia and pulverized coal) injected from each burner 4 into the furnace 2 together with the combustion air is ignited and burned by the action of the above-mentioned ignition device.

The burners 4 installed in the boiler 1 do not necessarily have to be the composite burners as described above. For example, a configuration including a coal-fired burner or an ammonia-fired burner can be adopted. However, in the boiler 1 of the present embodiment, at least one burner 4 is capable of burning using ammonia as fuel, and it is possible to co-fire ammonia and pulverized coal inside the furnace 2.

Here, ammonia is a compound _{of hydrogen (H) and nitrogen (N) as shown by the molecular formula (NH 3} ), and does not contain carbon (C) as a constituent atom. Although this ammonia (low carbon fuel) is known as a flame-retardant substance, it is a hydrogen carrier substance having three hydrogen atoms like _{methane (CH 3).} On the other hand, pulverized coal is a fossil fuel obtained by crushing coal to a size of about several micrometers, and is generally used as a fuel for boilers. That is, ammonia is a low-carbon fuel having a lower carbon concentration than pulverized coal (carbon fuel).

The two-stage combustion air supply unit 5 is connected to the furnace 2 above the burner 4, and supplies air for two-stage combustion to the inside of the furnace 2. By supplying air for two-stage combustion by such a two-stage combustion air supply unit 5, the unburned portion of the fuel burned by the burner 4 is burned by the two-stage combustion air, and the heat collection performance of the boiler 1 is improved. At the same time, the unburned content of the fuel contained in the exhaust gas can be reduced.

The ammonia supply unit 6 includes an ammonia supply source 6a, a fuel ammonia supply unit 6b, a reducing agent supply unit 6c, and an ammonia supply control device 6d (control unit). The ammonia supply source 6a includes a tank or the like for storing ammonia. The ammonia supply source 6a does not necessarily have to be a component of the ammonia supply unit 6. That is, the ammonia supply unit 6 may take in ammonia from the ammonia supply source 6a installed outside.

The fuel ammonia supply unit 6b includes a fuel ammonia supply pipe 6b1 that connects the ammonia supply source 6a and the burner 4, an overall flow rate control valve 6b2 and a fuel ammonia flow rate control valve 6b3 that are installed in the middle of the fuel ammonia supply pipe 6b1. It has. The fuel ammonia supply pipe 6b1 is a pipe that guides the portion (fuel ammonia) of the ammonia supplied from the ammonia supply source 6a that is supplied as fuel to the burner 4. The overall flow rate control valve 6b2 is a valve that regulates the overall flow rate of ammonia supplied from the ammonia supply source 6a to the fuel ammonia supply pipe 6b1. The total flow rate of ammonia is the flow rate of fuel ammonia plus the flow rate of ammonia (reducing agent ammonia) supplied to the furnace 2 or the like as a reducing agent via the reducing agent supply unit 6c. The fuel ammonia flow rate control valve 6b3 is arranged on the downstream side of the overall flow rate control valve 6b2, and is a valve that regulates the flow rate of fuel ammonia.

The reducing agent supply unit 6c includes a reducing agent supply pipe 6c1 connected to the furnace 2 and a reducing agent flow rate control valve 6c2 installed in the middle of the reducing agent supply pipe 6c1. One end of the reducing agent supply pipe 6c1 is connected to the fuel ammonia supply pipe 6b1 between the overall flow rate control valve 6b2 and the fuel ammonia flow rate control valve 6b3. That is, the reducing agent supply pipe 6c1 connects the fuel ammonia supply unit 6b and the furnace 2, takes in a part of the fuel ammonia from the fuel ammonia supply unit 6b, and guides the fuel ammonia to the furnace 2 as the reducing agent ammonia. Such a reducing agent supply unit 6c supplies the reducing agent ammonia to a position downstream (that is, above) of the combustion gas from the burner 4. The reducing agent flow rate control valve 6c2 is a valve that regulates the flow rate of the reducing agent ammonia.

For example, as shown in FIG. 1, inside the furnace 2 and the flue 3, a burner region R1 where a flame is formed, a staged combustion region R2 where staged combustion is performed, an upper part of the furnace 2 and a horizontal flue It is divided into an upper region R3 including the inside of 3a and a rear region R4 including the inside of the rear flue 3b. Here, in the present embodiment, in the reducing agent supply unit 6c, the reducing agent supply pipe 6c1 is connected to the burner region R1 to supply the reducing agent ammonia to the burner region R1.

The ammonia supply control device 6d controls the overall flow rate control valve 6b2, the fuel ammonia flow rate control valve 6b3, and the reducing agent flow rate control valve 6c2. Adjust the opening. The ammonia supply control device 6d adjusts the total flow rate of ammonia taken in from the ammonia supply source 6a by adjusting the opening degree of the total flow rate control valve 6b2 based on an external command or the like.

Further, the opening degree between the fuel ammonia flow rate control valve 6b3 and the reducing agent flow rate control valve 6c2 determines the distribution of ammonia taken in from the ammonia supply source 6a to the fuel ammonia and the reducing agent ammonia. That is, the fuel ammonia flow rate control valve 6b3 and the reducing agent flow rate control valve 6c2 form a mechanism (distribution adjustment mechanism 6b4) for adjusting the distribution ratio of the fuel ammonia and the reducing agent ammonia. The ammonia supply control device 6d adjusts the distribution ratio of the fuel ammonia and the reducing agent ammonia by controlling the distribution adjusting mechanism 6b4 including the fuel ammonia flow rate control valve 6b3 and the reducing agent flow rate control valve 6c2.

Further, in the present embodiment, the ammonia supply control device 6d controls to adjust the total flow rate of ammonia, which is the sum of the flow rate of the reducing agent ammonia and the flow rate of the fuel ammonia, according to the flow rate of the reducing agent ammonia. For example, in the present embodiment, when the flow rate of the reducing agent ammonia is increased, the ammonia supply control device 6d increases the opening degree of the total flow rate control valve 6b2, and increases the total flow rate of ammonia by the increase in the flow rate of the reducing agent ammonia. Increases by the same amount as. Further, in the present embodiment, when the flow rate of the reducing agent ammonia is reduced, the ammonia supply control device 6d reduces the opening degree of the total flow rate control valve 6b2, and reduces the total flow rate of ammonia by the decrease in the flow rate of the reducing agent ammonia. It decreases by the same amount as. As a result, the flow rate of the fuel ammonia supplied to the burner 4 can be kept constant at all times.

The pulverized coal supply unit 7 is connected to the burner 4, and crushes the coal into pulverized coal and supplies the pulverized coal to the burner 4. The pulverized coal supply unit 7 includes, for example, a mill for crushing coal to a particle size of about several micrometers to obtain pulverized coal, and a coal feeder for supplying the pulverized coal produced by the mill to the burner 4. .. The pulverized coal supply unit 7 may be configured to directly supply the pulverized coal to the burner 4 from the mill without providing a coal feeder.

In such a boiler 1 of the present embodiment, fuel ammonia is supplied from the ammonia supply unit 6 to the burner 4, pulverized coal is supplied from the pulverized coal supply unit 7 to the burner 4, and the burner 4 uses the fuel ammonia and the pulverized coal as fuel. A flame is formed at. Further, the unburned fuel contained in the combustion gas is burned by supplying the air for the two-stage combustion to the inside of the furnace 2 by the two-stage combustion air supply unit 5. The combustion gas generated by burning the fuel moves from the lower part to the upper part of the furnace 2 and is guided to the outside through the flue 3. Further, in the boiler 1 of the present embodiment, a part of the fuel ammonia is supplied to the inside of the furnace 2 as the reducing agent ammonia by the reducing agent supply unit 6c of the ammonia supply unit 6. As a result, nitrogen oxides (NOx) contained in the combustion gas are reduced.

According to the boiler 1 of the present embodiment as described above, a part of the fuel ammonia is supplied to the furnace 2 as a reducing agent. Therefore, the nitrogen oxides generated by the combustion of the fuel ammonia are reduced by the reducing agent ammonia. Therefore, according to the boiler 1 of the present embodiment, the increase of nitrogen oxides (NOx) can be suppressed. Further, according to the boiler 1 of the present embodiment, it is not necessary to separately store the reducing agent, and the boiler 1 can be miniaturized.

Further, in the boiler 1 of the present embodiment, the ammonia supply control device 6d controls to adjust the total flow rate of ammonia, which is the sum of the flow rate of the reducing agent ammonia and the flow rate of the fuel ammonia, according to the flow rate of the reducing agent ammonia. .. Therefore, even if the flow rate of the reducing agent ammonia fluctuates, the flow rate of the fuel ammonia supplied to the burner 4 can be kept constant, and the heat collection performance of the boiler 1 can be prevented from fluctuating. be able to.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the description of the second embodiment, the description of the same parts as those of the first embodiment will be omitted or simplified.

FIG. 2 is a schematic view showing a configuration of a main part of the boiler 1A of the second embodiment. As shown in this figure, in the boiler 1A of the present embodiment, the tip of the reducing agent supply pipe 6c1 is branched, and the reducing agent supply pipe 6c1 is connected to a plurality of locations in the height direction of the furnace 2. Further, an on-off valve 6c3 that is opened and closed by the ammonia supply control device 6d is provided for each of the tip portions of the branched reducing agent supply pipe 6c1.

According to the boiler 1A of the present embodiment as described above, by adjusting the opening and closing of each on-off valve 6c3, it is possible to change the supply position of the reducing agent ammonia with respect to the furnace 2 in the height direction. That is, in the present embodiment, the reducing agent supply unit 6c is connected to the furnace 2 so as to be able to individually supply the reducing agent ammonia to a plurality of locations in the height direction.

The internal temperature of the furnace 2 differs in the height direction. Therefore, by making it possible to change the supply position of the reducing agent ammonia with respect to the furnace 2 in the height direction, it is possible to supply the reducing agent ammonia to regions where the temperatures of the furnace 2 are different. For example, the exhausted combustion gas can be monitored, and the position in the height direction in which the reducing agent ammonia is supplied can be changed according to the result.

A flow valve is installed at each tip of the branched reducing agent supply pipe 6c1 to supply reducing agent ammonia to the inside of the furnace 2 from a plurality of positions different in the height direction of the furnace 2. You can also do it.

(Third Embodiment)
Next, a third embodiment of the present invention will be described. In the description of the third embodiment, the description of the same parts as those of the first embodiment will be omitted or simplified.

FIG. 3 is a schematic view showing a configuration of a main part of the boiler 1B of the third embodiment. As shown in this figure, in the boiler 1B of the present embodiment, the tip portion of the reducing agent supply pipe 6c1 is branched, and each of the branched tip portions is a burner region R1, a staged combustion region R2, and an upper region. It is connected to R3 and the rear region R4. Further, an on-off valve 6c4 opened and closed by the ammonia supply control device 6d is provided for each of the tip portions of the branched reducing agent supply pipe 6c1. According to the boiler 1B of the present embodiment as described above, it is possible to change the supply region of the reducing agent ammonia to the furnace 2 by adjusting the opening and closing of each on-off valve 6c4. That is, in the present embodiment, the reducing agent supply unit 6c is connected so as to be able to individually supply the reducing agent ammonia to the furnace 2 and the flue 3.

It is also possible to adopt a configuration in which a flow valve is installed at each of the tip portions of the branched reducing agent supply pipe 6c1 to supply the reducing agent ammonia to a plurality of different regions of the furnace 2 and the flue 3.

(Fourth Embodiment)
Next, a fourth embodiment of the present invention will be described. In the description of the fourth embodiment, the description of the same parts as those of the first embodiment will be omitted or simplified.

FIG. 4 is a schematic view showing a configuration of a main part of the boiler 1C of the fourth embodiment. As shown in this figure, the boiler 1C of the present embodiment includes a temperature measuring unit 9 for measuring the internal temperature of the upper part of the furnace 2. The temperature measuring unit 9 is electrically connected to the ammonia supply control device 6d, and outputs the measurement result to the ammonia supply control device 6d.

The ammonia supply control device 6d sets the flow rate of the reducing agent ammonia based on the measurement result of the temperature measuring unit 9. The temperature range in which the supplied reducing agent ammonia is highly effective is acquired in advance by experiments and simulations and stored in the ammonia supply control device 6d, and when it is in the above temperature range, the reducing agent is controlled by the ammonia supply control device 6d. Ammonia may be supplied to the furnace 2.

According to the boiler 1C of the present embodiment as described above, the reducing agent ammonia can be effectively acted as a reducing agent, and the nitrogen oxide (NOx) can be reduced with a smaller amount of the reducing agent ammonia. ..

The temperature measuring unit 9 does not need to have a structure in which the measuring terminal is directly inserted into the furnace 2. For example, a non-contact temperature measuring unit may be installed outside the furnace 2 and the internal temperature of the furnace 2 may be measured by the non-contact temperature measuring unit.

(Fifth Embodiment)
Next, a fifth embodiment of the present invention will be described. In the description of the fifth embodiment, the description of the same parts as those of the first embodiment will be omitted or simplified.

FIG. 5 is a schematic view showing a configuration of a main part of the boiler 1D of the fifth embodiment. As shown in this figure, the boiler 1D of the present embodiment includes a concentration measuring unit 10 for measuring the concentration of nitrogen oxides (NOx) contained in the combustion gas discharged from the flue 3. The concentration measuring unit 10 is electrically connected to the ammonia supply control device 6d, and outputs the measurement result to the ammonia supply control device 6d.

The ammonia supply control device 6d sets the flow rate of the reducing agent ammonia based on the measurement result of the concentration measuring unit 10. For example, the ammonia supply control device 6d increases the flow rate of the reducing agent ammonia when the measurement result of the concentration measuring unit 10 exceeds the appropriate range, and when the measurement result of the concentration measuring unit 10 is below the appropriate range. Reduces the flow rate of the reducing agent ammonia.

According to the boiler 1C of the present embodiment as described above, it is possible to reduce nitrogen oxides (NOx) with a small amount of reducing agent ammonia.

The temperature measuring unit 9 of the fourth embodiment may be further installed on the boiler 1D of the present embodiment. This makes it possible to reduce nitrogen oxides (NOx) with a smaller amount of reducing agent ammonia. However, the concentration measurement unit 10 measures when the measurement result of the temperature measurement unit 9 indicates an appropriate temperature range so that the flow rate of the reducing agent ammonia does not increase unnecessarily when the temperature of the furnace 2 is not appropriate. It is preferable to fine-tune the flow rate of the reducing agent ammonia based on the result.

(Sixth Embodiment)
Next, a sixth embodiment of the present invention will be described. In the description of the sixth embodiment, the description of the same parts as those of the first embodiment will be omitted or simplified.

FIG. 6 is a schematic view showing a configuration of a main part of the boiler 1E of the sixth embodiment. As shown in this figure, in the boiler 1E of the present embodiment, a water content measuring instrument 11 for measuring the water content (characteristics of carbon fuel) of the pulverized coal is attached to the pulverized coal supply unit 7. There is. The water content measuring instrument 11 is electrically connected to the ammonia supply control device 6d, and outputs the measurement result to the ammonia supply control device 6d.

For example, the ammonia supply control device 6d has a tail that shows the relationship between the amount of water per unit volume of pulverized coal and the amount of nitrogen oxides (NOx) that are expected to be generated when such pulverized coal is burned. Is memorized in advance. When the measurement result is input from the water content measuring device 11, the ammonia supply control device 6d sets the flow rate of the reducing agent ammonia with reference to the above table.

According to the boiler 1E of the present embodiment as described above, it is possible to supply an appropriate flow rate of reducing agent ammonia to the furnace 2 even when the characteristics of the pulverized coal are changed depending on the production area or the like. Become.

In the present embodiment, the configuration for measuring the characteristics of the pulverized coal with the water content measuring instrument 11 has been described. For example, the composition (characteristics) of pulverized coal differs depending on the production area. Therefore, by storing a table in which the production area and the flow rate of the reducing agent ammonia are related in advance in the ammonia supply control device 6d and inputting the production area of the pulverized coal into the ammonia supply control device 6d, an appropriate reducing agent can be obtained. It is also possible to adopt a configuration that sets the flow rate of ammonia.

(7th Embodiment)
Next, a seventh embodiment of the present invention will be described. In the description of the seventh embodiment, the description of the same parts as those of the first embodiment will be omitted or simplified.

FIG. 7 is a schematic view showing a configuration of a main part of the boiler 1F of the seventh embodiment. As shown in this figure, in the boiler 1F of the present embodiment, the reducing agent supply unit 6c is arranged inside the furnace 2 and the reducing agent ammonia is injected into the inside of the furnace 2 nozzle header 12 (injection unit). It has. Such a nozzle header 12 is a straight pipe whose end is connected to the reducing agent supply pipe 6c1 and in which a plurality of nozzles are formed in the longitudinal direction. Such a nozzle header 12 disperses and injects the reducing agent ammonia supplied from the reducing agent supply pipe 6c1 from a plurality of nozzles.

According to the boiler 1F of the present embodiment as described above, even with a small amount of reducing agent ammonia, the reducing agent ammonia can be reliably reached to the central portion of the furnace 2, and nitrogen oxides (NOx) can be more reliably reached. Can be reduced.

Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above-described embodiment. The various shapes and combinations of the constituent members shown in the above-described embodiment are examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

For example, in the above embodiment, a boiler that co-fires pulverized coal and ammonia as fuel has been described. However, the present invention is not limited to this. For example, it is possible to adopt a configuration in which natural gas and ammonia are co-fired as fuel, a configuration in which heavy oil or light oil and ammonia are co-fired as fuel, a configuration in which only ammonia is burned as fuel, and the like.

Further, for example, a check valve may be provided in both or one of the fuel ammonia supply pipe 6b1 and the reducing agent supply pipe 6c1.

(simulation)
Next, the results of simulating the boiler 1 of the first embodiment will be described with reference to FIGS. 8 to 10.

First, the burner region R1 is divided into a mixed region where fuel and combustion air are mixed, a flame region where a flame exists, a circulation region where combustion gas returns toward the flame, and a flame back region behind the flame. I created a separate model. Using this model, when ammonia is charged into the mixed region together with pulverized coal, when it is charged into the combustion air sent to the flame, when it is directly charged into the flame, and when it is charged into the two-stage combustion region R2. The amount of nitric oxide contained in the exhaust gas was simulated. As a comparative example, the same simulation was performed under the condition that only pulverized coal was used without using ammonia as the fuel.

FIG. 8 is a bar graph showing the results of the simulation. In FIG. 8, (a) shows the result of the comparative example. Further, (b) shows the result when ammonia is charged into the mixed region, (c) shows the result when ammonia is charged into the combustion air, and (d) shows the result when ammonia is directly charged into the flame. (E) shows the result when ammonia is put into the staged combustion region R2. In FIG. 8, the result of the comparative example is used as a reference, and the other results are shown as relative values with the comparative example.

As shown in FIG. 8, the result of the boiler 1 of the above embodiment does not increase significantly as compared with (a). In particular, when ammonia is directly added to the flame, the amount of nitric oxide discharged is suppressed to the same extent as in (a). Therefore, it was found that when ammonia is charged into the burner region R1 or the staged combustion region R2, it is preferable to charge ammonia directly to the flame. In addition to this, in the boiler 1 of the above embodiment, the amount of nitrogen monoxide emission is about the same as that of the boiler that burns only pulverized coal as fuel even though ammonia is burned as fuel. From this, it was found that the conversion rate of nitrogen components to nitrogen oxides was low.

Next, based on the results shown in FIG. 8, the case where ammonia as a fuel is directly added to the flame together with the pulverized coal, and the case where the ammonia as a fuel is added to the flame together with the pulverized coal and the ammonia as a reducing agent is further added to the upper region. Ammonia as a fuel is added to the flame together with pulverized coal and ammonia as a reducing agent is added to the upper region R3 and the rear region R4, and ammonia as a fuel is added to the flame together with the pulverized coal. Furthermore, the amount of nitrogen monoxide contained in the exhaust gas was simulated when ammonia as a reducing agent was added to the rear region R4. Similarly, as a comparative example, the same simulation was performed under the condition that only pulverized coal was used as the fuel and no ammonia was added.

FIG. 9 is a bar graph showing the results of the simulation. In FIG. 9, (a) shows the result of the comparative example. Further, (b) shows the result when ammonia as a fuel is directly added to the flame together with the pulverized coal, and (c) shows the result when ammonia as a fuel is added to the flame together with the pulverized coal and ammonia as a reducing agent is further added. The results when the fuel is charged into the upper region R3 are shown, and (d) shows the results when ammonia as a fuel is charged into the flame together with pulverized coal and ammonia as a reducing agent is charged into the upper region R3 and the rear region R4. , (E) show the results when ammonia as a fuel is charged into the flame together with pulverized coal and ammonia as a reducing agent is further charged into the rear region R4. In FIG. 9, the result of the comparative example is used as a reference, and the other results are shown as relative values with the comparative example.

As shown in FIG. 9, the result of the boiler 1 of the above embodiment does not increase significantly as compared with (a). In particular, when ammonia as a fuel is added to the flame together with pulverized coal and ammonia as a reducing agent is further added to the upper region R3, and when ammonia as a fuel is added to the flame together with pulverized coal and ammonia as a reducing agent is further added. When charged into the upper region R3 and the rear region R4, the amount of nitric oxide discharged is suppressed more than in (a). Therefore, it was found that it is preferable to supply the reducing agent ammonia to the upper region R3 or the upper region R3 and the rear region R4. These results are considered to indicate that the nitric oxide generated by the two-stage combustion was reduced by the reducing agent ammonia, and by supplying the reducing agent ammonia to the downstream side of the two-stage combustion region R2, the reducing agent ammonia was further reduced. It is considered that nitrogen oxides (NOx) can be suppressed.

FIG. 10 is a bar graph showing a simulation result when ammonia is supplied as a reducing agent to a boiler using only pulverized coal as a fuel by changing the distribution condition of the amount of air in the burner portion three times. In FIG. 10, (a2) shows the result of supplying ammonia as a reducing agent to (a1), (b2) shows the result of supplying ammonia as a reducing agent to (b1), and (c2) shows the result. The result of supplying ammonia as a reducing agent to (c1) is shown. From these results, it can be seen that in a boiler that uses only pulverized coal as fuel, the amount of nitric oxide contained in the exhaust gas is reduced to about one-fourth when ammonia is added as a reducing agent. As can be seen from the fact that the results shown in FIGS. 9 (c) and 9 (d) are about one-fourth of the results shown in FIG. 9 (a), ammonia and pulverized coal are co-fired. By adding the reducing agent ammonia, the boiler of the above embodiment can reduce the amount of nitric oxide emissions to the same extent as when ammonia is added as the reducing agent to the boiler using only pulverized coal as fuel. I found out.

1 …… Boiler 1A …… Boiler 1B …… Boiler 1C …… Boiler 1D …… Boiler 1E …… Boiler 1F …… Boiler 2 …… Fire furnace 2a …… Discharge port 3 …… Smoke path 3a …… Horizontal flue 3b… ... Rear flue 4 ... Burner 5 ... Two-stage combustion air supply unit 6 ... Ammonia supply unit 6a ... Ammonia supply source 6b ... Fuel ammonia supply unit 6b1 ... Fuel ammonia supply pipe 6b2 ... Overall flow control valve 6b3 …… Fuel ammonia flow control valve 6b4 …… Distribution adjustment mechanism 6c …… Reducing agent supply unit 6c1 …… Reducing agent supply pipe 6c2 …… Reducing agent flow control valve 6c3 …… On-off valve 6c4 …… On-off valve 6d …… Ammonia Supply control device 7 …… Boiler supply unit 9 …… Temperature measurement unit 10 …… Concentration measurement unit 11 …… Moisture content measuring instrument 12 …… Nozzle header R1 …… Burner region R2 …… Two-stage combustion region R3 …… Upper Area R4 …… Rear area

Claims (7)

A boiler equipped with a combustion device capable of burning ammonia as fuel, a furnace equipped with the combustion device, and a flue for guiding the combustion gas generated by burning the fuel.
A reducing agent supply unit that supplies a part of the ammonia supplied as fuel to the combustion device as a reducing agent to at least one of the furnace and the flue at a position downstream of the combustion device is provided .
A control unit that adjusts the total flow rate of ammonia, which is the sum of the flow rate of the ammonia supplied as the reducing agent and the flow rate of the ammonia supplied as the fuel, according to the flow rate of the ammonia supplied as the reducing agent. With
The boiler is characterized in that the control unit adjusts the total flow rate of ammonia so that the flow rate of the ammonia supplied as the fuel becomes constant. The boiler according to claim 1, wherein the reducing agent supply unit is connected to the furnace so as to be able to supply the ammonia as the reducing agent individually to a plurality of locations in the height direction. The boiler according to claim 1 or 2, wherein the reducing agent supply unit is connected to each of the furnace and the flue so as to be able to supply the ammonia as the reducing agent individually. A temperature measuring unit for measuring the internal temperature of at least one of the furnace and the flue is provided.
The boiler according to any one of claims 1 to 3, wherein the reducing agent supply unit sets the flow rate of the ammonia supplied as the reducing agent based on the measurement result of the temperature measuring unit. A concentration measuring unit for measuring the concentration of nitrogen oxides contained in the combustion gas discharged from the flue is provided.
The boiler according to any one of claims 1 to 4, wherein the reducing agent supply unit sets the flow rate of the ammonia supplied as the reducing agent based on the measurement result of the concentration measuring unit. Equipped with a combustion device capable of burning carbon fuel
The boiler according to any one of claims 1 to 5, wherein the reducing agent supply unit sets a flow rate of the ammonia supplied as the reducing agent based on the characteristics of the carbon fuel. Claims 1 to 6 include the reducing agent supply unit, which is disposed inside at least one of the furnace and the flue and also includes an injection unit for injecting the ammonia supplied as the reducing agent. The boiler described in any one item.

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