JP2008039341A - Coal combustion method and coal combustion apparatus - Google Patents

Abstract

A without requiring significant capital investment, even with existing equipment, it is possible to reduce the NO _X concentration with reducing ash in unburned concentration when burned plural kinds of pulverized coal A coal combustion method and a coal combustion apparatus are provided.
[Solution]
In a coal combustion method for burning pulverized coal using a combustion apparatus (coal combustion apparatus 100) in which a plurality of burners using pulverized coal as fuel in the combustion chamber (boiler furnace 2) are provided in the vertical direction, 1 pulverized coal and second pulverized coal having a combustion ratio lower than that of the first pulverized coal, and the first pulverized coal is supplied to the burners 3a and 3b located below and the second pulverized coal. Is supplied to the burner 3c located above the burners 3a and 3b located below.
[Selection] Figure 1

Description

  The present invention relates to a coal combustion method and a coal combustion apparatus using the method.

  At present, Japan's electricity is mainly made from fossil fuel energy, and one-third of it uses coal. Electricity made from fossil fuels is mainly produced by thermal power plants, and thermal power generation facilities play an important role in our lives.

  In recent years, from the viewpoint of energy security, the introduction of pulverized coal-fired power using coal with abundant reserves has been advancing rapidly, and coal that has been used as fuel and other types with abundant reserves available. A thermal power generation facility using a mixed pulverized coal mixed with a certain amount of coal as a fuel is being actively studied.

  However, the mixed pulverized coal used as fuel for such a thermal power generation facility contains coal having a component different from that of coal conventionally used as the fuel for the thermal power generation facility. When the mixed pulverized coal is burned by the same method as in the past using NO, there is a problem that the NOx concentration and the unburned ash concentration in ash become higher than in the case of burning the conventional pulverized coal. .

To solve such a problem, for example, by extracting the combustion exhaust gas passing through the center part in the furnace width direction of the exhaust gas outlet part and recirculating it to the combustion part, NO _X in the combustion exhaust gas is increased without increasing the amount of recirculation gas. the recirculated efficiently combustion section, a method for reducing the emissions of the NO _X has been proposed (e.g., see Patent Document 1).

JP 2003-56810 A

  However, the above-described method has a problem that equipment such as a boiler has to be remodeled significantly and a large amount of capital investment is required.

In view of the circumstances described above, the present invention does not require a large amount of capital investment and reduces the unburned ash concentration in ash when multiple types of pulverized coal having different fuel ratios are burned even when existing facilities are used. and to provide a coal combustion method and coal combustion apparatus which can reduce the NO _X concentration with is.

  A first aspect of the present invention that solves the above-described problem is a coal combustion method in which pulverized coal is burned using a combustion device in which a plurality of burners using pulverized coal as fuel are provided in a vertical direction in a combustion chamber. The charcoal includes first pulverized coal and second pulverized coal having a combustion ratio lower than that of the first pulverized coal, and supplies the first pulverized coal to a burner located below and the second pulverized coal. The pulverized coal is supplied to a burner located above the burner located below.

In the first aspect, it is possible to fuel ratio reduces the NO _X concentration with reducing ash in unburned concentration upon combustion of different types of pulverized coal. Here, the fuel ratio is a value obtained by dividing the fixed carbon content of coal by the volatile content.

  According to a second aspect of the present invention, in the coal combustion method according to the first aspect, an air ratio of air supplied to each burner together with the first pulverized coal and the second pulverized coal is 0.5 to 0.5. The coal combustion method is characterized by being 0.99.

In the second aspect, it is possible to fuel ratio is reduced more NO _X concentration with further reducing the ash in unburned concentration upon combustion of different types of pulverized coal. Here, the air ratio is a value obtained by dividing the amount of air actually supplied to the burner by the amount of air (theoretical air amount) required to completely burn coal (pulverized coal).

  According to a third aspect of the present invention, in the coal combustion method according to the first or second aspect, a ratio of a fuel ratio of the first pulverized coal to a fuel ratio of the second pulverized coal is 1.5 or more. It is in the coal combustion method characterized by being.

In the third aspect, it is possible to fuel ratio to further reduce the NO _X concentration with further reduce the ash in unburned concentration upon combustion of different types of pulverized coal.

  According to a fourth aspect of the present invention, in the coal combustion method according to any one of the first to third aspects, the latter stage air is introduced into the combustion atmosphere of the pulverized coal.

In the fourth aspect, the NO _X concentration can be further reduced.

  According to a fifth aspect of the present invention, in the coal combustion method according to any one of the first to fourth aspects, the first pulverized coal is bituminous coal and the second pulverized coal is subbituminous coal. There is a characteristic coal combustion method.

  In the fifth aspect, the same effect as described above can be obtained.

  The sixth aspect of the present invention has a combustion chamber in which a plurality of burners using pulverized coal as fuel are provided in the vertical direction, and the burner located below is a first fuel in which the first pulverized coal is stored. And a burner located above the burner located below is connected to a second fuel chamber in which a second pulverized coal having a combustion ratio lower than that of the first pulverized coal is stored. It is in the coal combustion apparatus characterized by this.

In the sixth aspect, it is possible to fuel ratio reduces the NO _X concentration with reducing ash in unburned concentration upon combustion of different types of pulverized coal.

According to the coal combustion method and the coal combustion apparatus according to the present invention, unburned in ash when burning a plurality of pulverized coals having different fuel ratios without using a large amount of capital investment and using existing facilities. it is possible to reduce the NO _X concentration with reducing the partial concentration.

  Hereinafter, the best mode for carrying out the present invention will be described. The description of the present embodiment is an exemplification, and the present invention is not limited to the following description.

(Embodiment 1)
FIG. 1 is a schematic system diagram showing an example of a coal combustion apparatus for carrying out the coal combustion method according to Embodiment 1 of the present invention. As shown in FIG. 1, a plurality of burners 3a, 3b, and 3c, which will be described later, are provided around a boiler furnace 2 included in the coal combustion apparatus 100 according to the present embodiment. The coal pulverizers 8a and 8b are connected to the pulverized coal passages 11a and 11b, respectively. In FIG. 1, burners 3a, 3b, and 3c are shown on the left and right sides of the boiler furnace 2, respectively. The coal crushers 8a and 8b are respectively connected to hoppers 9a and 9b for storing coal, and coal having different fuel ratios is charged into the hoppers 9a and 9b.

  Valves 10a and 10b for adjusting the flow rate of coal are respectively provided at the discharge ports of the hoppers 9a and 9b, and the hoppers 9a and 9b are connected to the coal crushers 8a and 8b via the valves 10a and 10b. .

  The first coal is input to the hopper 9a, and the second coal having a fuel ratio lower than that of the first coal is input to the hopper 9b. When each coal is put into each hopper 9a, 9b, valves 10a, 10b, which are means for adjusting the flow rate of each coal, adjust the flow rate of each coal put into the hoppers 9a, 9b, and a desired amount of coal is coal. It is carried to the pulverizers 8a and 8b. Each coal is adjusted to a desired particle size by the coal crushers 8a and 8b to become pulverized coal. In the present embodiment, the hopper 9a and the coal pulverizer 8a correspond to the first fuel chamber, and the hopper 9b and the coal pulverizer 8b correspond to the second fuel chamber.

  As described above, after the particle diameters of the coals having different fuel ratios are adjusted, the coals pass through the pulverized coal passages 11a and 11b and are introduced into the boiler furnace 2 from the burners 3a, 3b, and 3c provided around the boiler furnace 2. And burn. On the other hand, primary air, secondary air, and tertiary air, which will be described later, are fed into the boiler furnace 2 through, for example, burners 3a, 3b, and 3c. Specifically, these primary to tertiary air passes through the air passage 6 from the air control device 7, and the flow rate is controlled by the air valve 5, and the boilers 3 a, 3 b, 3 c provided around the boiler furnace 2 are boilers. It is sent to the furnace 2. In FIG. 1, the state in which the primary to tertiary air is sent is indicated by three arrows on the left and right in the vicinity of the left and right burners 3 a, 3 b, and 3 c provided around the boiler furnace 2. In FIG. 1, one upper air nozzle 4 connected to the air control device 7 is shown on the left and right around the boiler furnace 2. Here, introducing the latter stage air into the combustion atmosphere of the pulverized coal is referred to as the latter stage combustion, and the ratio of the latter stage air amount to the total air amount introduced into the boiler furnace 2 is referred to as the latter stage combustion rate. The latter stage air refers to the air introduced from the upper stage air nozzle 4 in FIG. 1, and the latter stage air amount refers to the amount of the latter stage air introduced into the boiler furnace 2.

  In this way, the air discharged from the air control device 7 passes through the air passage 6, the flow rate of which is adjusted by each air valve 5, and the boiler furnace from the burners 3 a, 3 b, 3 c and the upper air nozzle 4 provided at the lower stage. 2 is sent. As a result, the pulverized coal is completely burned in the boiler furnace 2. Eventually, the pulverized coal burned in the boiler furnace 2 becomes combustion ash and is discharged from the coal ash discharge ports 12 at the upper right portion and the lower portion of the boiler 1.

  Next, the burners 3a, 3b, and 3c will be described. The burners 3a, 3b, and 3c are not particularly limited as long as they are coal combustion burners, but a CI-α · WR burner will be described as an example. Since the burners 3a, 3b, and 3c all have the same structure, only the left burner 3a shown in FIG. 1 will be described below. FIG. 2 is a schematic cross-sectional view of the burner 3a. As shown in FIG. 2, the burner 3a includes a primary air pipe 30, a secondary air inlet 31, and a tertiary air inlet 32 connected to the pulverized coal passage 11b. The burner 3 is further provided with an oil burner 37 for igniting the burner.

  The primary air pipe 30 has a double pipe structure composed of an outer pipe 34 and an inner pipe 33 provided therein, and passes through the space between the inner pipe 33 and the outer pipe 34 to make fine powder. Primary air containing charcoal can be supplied to the furnace 2. Further, as shown in FIGS. 2 and 3, the secondary air swirling blade 311 and the tertiary air swirling blade 321 are provided at the secondary air introducing port 31 and the tertiary air introducing port 32, respectively. A plurality of secondary air inlets 32 are attached. And by adjusting these secondary air swirl vanes 311 and tertiary air swirl vanes 321, the swirl angles can be controlled in a wide range together with the flow rates of the secondary air and the tertiary air. Yes. Here, as shown in FIG. 4, the swirl angle refers to the inclination angle θ of the swirl vane with respect to the central axis 21 of the boiler furnace 2. It becomes equal to the inclination angle with respect to the axis. Therefore, no swirl flow occurs when the swivel angle is 0 degree (deg). And the pulverized coal is burned in the boiler furnace 2 as shown below using the burners 3a, 3b, 3c configured in this way.

  First, the pulverized coal that has passed through the pulverized coal passage 11b is fed into the furnace 2 through the primary air pipe 30 together with the transfer air (primary air). The pulverized coal sent to the furnace 2 is combusted with the primary air and the secondary air and the tertiary air sent as a swirling flow from the secondary air inlet 31 and the tertiary air inlet 32. The swirling directions of the secondary air and the tertiary air sent into the furnace 2 as swirling flow may be clockwise or counterclockwise, swirling in the same direction, or mutually You may turn in different directions. In the following experiment, both the secondary air and the tertiary air are swung counterclockwise.

Next, the coal combustion method according to the present embodiment will be described using the coal combustion apparatus 100 described above. The coal combustion method according to the present embodiment uses the above-described coal combustion apparatus 100 to supply the first pulverized coal to the burner located below and the second pulverized powder having a fuel ratio lower than that of the first pulverized coal. by supplying the burner located above the burner located charcoal thereunder, reduce NO _X concentration with reducing ash in unburned concentration when fuel ratio to burn out the different types of pulverized coal It can be made to. Specifically, the coal combustion method according to the present embodiment supplies the first pulverized coal to the burners 3a and 3b located below using the coal combustion apparatus 100 described above, and from the first pulverized coal. Also, by supplying the second pulverized coal having a low fuel ratio to the burner 3c located above the burners 3a and 3b, the concentration of unburned ash in the ash when burning a plurality of types of pulverized coal having different fuel ratios is obtained. it is that it is possible to reduce the NO _X concentration with decrease.

  Here, the first pulverized coal and the second pulverized coal used in the present embodiment are not limited as long as the fuel ratio of the second pulverized coal is lower than the fuel ratio of the first pulverized coal. The ratio of the fuel ratio of the first pulverized coal to the fuel ratio of 2 pulverized coal is preferably 1.5 or more, and more preferably 2.4 or more. Examples of the first pulverized coal include bituminous coal, and examples of the second pulverized coal include bituminous coal and sub-bituminous coal having a fuel ratio lower than that of the first pulverized coal.

The air ratio of the air supplied to each burner 3a, 3b, 3c together with the first pulverized coal and the second pulverized coal is not particularly limited as long as it is smaller than 1.0, but is in the range of 0.5 to 0.99. Those in the range of 0.5 to 0.8 are more preferable. When the air ratio of the air supplied to each burner 3a, 3b, 3c is greater than 1.0, the nitrogen content (primary amine [RNH ₂ ], secondary amine [R ₂ NH], 3 amines [R ₃ N] and the like) are easily oxidized, and the NO _X concentration increases. Here, the air ratio is a value obtained by dividing the amount of air actually supplied to the burners 3a, 3b, 3c by the amount of air (theoretical air amount) required to completely burn coal (pulverized coal).

  The air ratio of the air supplied to the upper air nozzle 4 is not particularly limited as long as it is smaller than 1.0, but is preferably in the range of 0.5 to 0.99, preferably 0.5 to 0.8. Those within the range are more preferred.

FIG. 5 shows the unburned ash concentration in the ash when the coal combustion method (low fuel specific coal in-furnace blend) according to this embodiment under the conditions shown in Table 1 and the conventional conditions under the conditions shown in Table 2. Coal combustion method (low fuel specific coal line blend: mixed pulverized coal in which the first pulverized coal and the second pulverized coal are uniformly mixed is introduced into the boiler furnace 2 from each burner 3a, 3b, 3c and burned uniformly. FIG. 6 shows the NO _x concentration when using the coal combustion method according to the present embodiment, and when using the conventional coal combustion method. show the NO _X concentration. Here, Newlands coal (fuel ratio 1.9) as bituminous coal is used as the first pulverized coal, and Tanitoharm coal (fuel ratio 1.0) as bituminous coal is used as the second pulverized coal. Charcoal was burned at a ratio of 2: 1 (coal input heat: 2390 kW). Here, Air / Coal in Table 1 indicates the mass ratio of the incoming air to the pulverized coal.

  Table 3 shows the properties of Newlands coal and Tanitoharum coal used in this experiment.

  First, considering the concentration of unburned ash in ash, as shown in FIG. 5, by using the coal combustion method according to the present embodiment, the concentration of unburned ash in ash is 1% compared to the conventional coal burning method. It was found that the degree decreased.

  This is considered to be due to the influence of the properties of the pulverized coal supplied from each burner and the residence time of the pulverized coal in the boiler furnace. Specifically, the first pulverized coal with a relatively large fuel ratio is supplied to the burners 3a and 3b located below the boiler furnace 2, and the second pulverized coal with a relatively small fuel ratio is When supplied to the burner 3c located above, the first pulverized coal supplied from the burner 3a is first heated by the boiler furnace due to the updraft generated by the combustion of the pulverized coal supplied from each burner 3a, 3b, 3c. It burns while moving above 2. That is, the first pulverized coal supplied from the burner 3a is sufficiently combusted because the residence time in the combustion atmosphere by the burners 3a, 3b, and 3c becomes longer.

  Moreover, the 1st pulverized coal supplied from the burner 3b will burn while moving above the boiler furnace 2 by the updraft generated by combustion of the pulverized coal supplied from the burners 3b and 3c. That is, the first pulverized coal supplied from the burner 3b is not as much as that supplied from the burner 3b, but the residence time in the combustion atmosphere by the burners 3b and 3c becomes longer, so that the first pulverized coal is sufficiently burned. Become.

  And the 2nd pulverized coal supplied from burner 3c is different from the 1st pulverized coal supplied from burners 3a and 3b, by the updraft generated only by combustion of pulverized coal supplied from burner 3c, Combusting while moving above the boiler furnace 2. However, since the second pulverized coal has a fuel ratio lower than that of the first pulverized coal, the second pulverized coal burns in a short time. Therefore, even in the combustion atmosphere by the burner 3c (the residence time in the combustion atmosphere). It will burn well (even if short).

  What has been described above can be understood from the gas residence time in the furnace of the air (gas) supplied from each burner, as shown in Table 4.

  Here, the gas residence time in the furnace shown in Table 4 was obtained when the above-mentioned Newlands coal was supplied from the burner as pulverized coal under the conditions shown in Table 2 (boiler furnace temperature 1200 ° C.). It is. Specifically, the furnace gas residence time is calculated as described below.

  First, as shown in FIG. 7, there are four areas including an area 1 including the burner 3 a, an area 2 including the burner 3 b and an area 3 including the burner 3 c, and an area 4 including the upper air nozzle 4. The boiler furnace 2 is divided and the amount of air passing through each region is calculated. For example, the amount of air passing through the region 1 is equal to the amount of air supplied from the burner 3a, and the amount of air passing through the region 2 is equal to the amount of air supplied from the burner 3a and the burner 3b. The amount of air passing through can be calculated.

  Next, the amount of air passing through each region (0 ° C.) is converted to the amount of air at 1200 ° C. (converted air amount), and the converted air amount is divided by the volume of each region to obtain the local residence time in each region. calculate. Then, the local residence time is integrated along the air flow in each region to calculate the furnace gas residence time. For example, since the air in the region 1 flows through the regions 1 to 4, the gas residence time in the furnace of the region 1 becomes 5.5 seconds by adding the local residence times in the regions 1 to 4. Similarly, the gas residence time in the furnace of the air in the region 2 is 3.7 seconds by adding the local residence times in the regions 2 to 4. The numerical values obtained as described above are shown in Table 5.

  In this way, the furnace gas residence time can be calculated. In addition, even if it changes the kind of coal to burn, the gas residence time in a furnace hardly changes.

  From the above, it is considered that by using the coal combustion method according to the present embodiment, the concentration of unburned ash in ash is reduced as compared with the conventional coal combustion method.

Considering now the NO _X concentration, as shown in FIG. 6, by using the coal combustion method according to the present embodiment, found to be NO _X concentrations compared with conventional coal combustion method is reduced about 10ppm It was.

As described above, since the pulverized coal supplied from the burners 3a and 3b is sufficiently combusted, the nitrogen content (first amine [RNH ₂ ], second amine [R ₂ ] contained in the first pulverized coal is sufficient. NH], tertiary amines [R ₃ N], etc.) are oxidized and a relatively large amount of NO _X is generated. On the other hand, since the 2nd pulverized coal supplied from the burner 3c consists of coal with a low fuel ratio, it has a comparatively large amount of hydrocarbons in the inside. The hydrocarbon fraction is under combustion atmosphere from the burner 3c to the upper air nozzle 4, than is consumed in the oxidation reaction, to be consumed in the reduction reaction of the NO _X generated by the combustion of the first pulverized coal As a result, the NO _X concentration at the coal ash discharge port 12 of the boiler furnace 2 is reduced. That is, the burners 3a, the NO _X generated by the combustion of the first pulverized coal supplied to 3b, by reducing the hydrocarbon content of the reduction reactions involved in the second pulverized coal supplied to the burner 3c, consequently NO _X concentration is decreased.

What has been described above, it can also be understood from the graph showing the relationship between the height and the concentration of NO _X from the middle burner of the present embodiment (3b) shown in FIG. Therefore, the use of coal combustion method according to the present embodiment, the NO _X concentration is believed to decline as compared to conventional coal combustion method.

As described above, by using the coal combustion method and the coal combustion apparatus according to the present embodiment, the concentration of unburned ash in ash when burning a plurality of types of pulverized coal with different fuel ratios and NO _X The concentration can be reduced.

(Embodiment 2)
In Embodiment 1, as the second pulverized coal, Tanitoharum coal that is bituminous coal is used, but in this embodiment, Adaro coal (sub fuel ratio 0.88) that is subbituminous coal is used instead of Tanitoharum coal. The same experiment as 1 was performed.

FIG. 9 shows the unburned ash concentration in the ash when using the coal combustion method (low fuel specific coal blend) according to the present embodiment under the conditions shown in Table 6, and the conventional conditions under the conditions shown in Table 7. The unburned ash concentration in the ash when using the coal combustion method (low fuel specific coal line blend) is shown, and FIG. 10 shows the NO _x concentration when using the coal combustion method according to the present embodiment and the conventional coal. It shows the concentration of NO _X when using the combustion method. In the present embodiment, Newlands coal and Adaro coal are burned at a ratio of 2: 1 (coal input heat: 2390 kW).

  Table 8 shows the properties of Newlands coal and Adaro coal used in this experiment.

First, considering the concentration of unburned ash in ash, as shown in FIG. 9, the concentration of unburned ash in ash is 2. as compared with the conventional coal burning method by using the coal burning method according to this embodiment. It was found to decrease by about 2%. Also, considering the NO _X concentration, as shown in FIG. 10, by using the coal combustion method according to the present embodiment, NO _X concentration was found to decrease about 10ppm compared to conventional coal combustion method . These are also considered to be due to the same reason as in the first embodiment.

  As described above, even when the mixed coal of bituminous coal and sub-bituminous coal is burned, the same effect as in the first embodiment can be obtained by using the coal combustion method and the coal combustion apparatus according to the present embodiment.

(Other embodiments)
In the first embodiment, the first pulverized coal is supplied from the burners 3a and 3b and the second pulverized coal is supplied from the burner 3c. However, the present invention supplies the first pulverized coal to the burner located below. In addition, there is no particular limitation as long as the second pulverized coal is supplied to the burner located above the burner. For example, in the above-described coal combustion apparatus 100, the first pulverized coal may be supplied to the burner 3a and the second pulverized coal may be supplied to the burners 3b and 3c, or the first pulverized coal may be supplied to the burner 3a. Alternatively, the second pulverized coal may be supplied only to the burner 3c. Even if it does in this way, the effect similar to Embodiment 1 will be acquired.

1 is a schematic system diagram of a coal combustion apparatus according to Embodiment 1. FIG. It is a schematic sectional drawing of the burner which concerns on Embodiment 1. FIG. It is the schematic front view which showed only the swirl | wing blade of the burner at the time of seeing from the A direction shown in FIG. FIG. 3 is a schematic diagram illustrating a turning angle in the first embodiment. It is a graph which shows the relationship between the unburned content concentration in ash at the time of using the coal combustion method which concerns on Embodiment 1, and the unburned content concentration in ash at the time of using the conventional coal combustion method. It is a graph showing the relationship between the concentration of NO _X when using the NO _X concentration and conventional coal combustion method when using coal combustion method according to the first embodiment. It is a schematic perspective view which shows the area | region used when calculating the gas residence time in a furnace. Is a graph showing the relationship between the height and the concentration of NO _X from the middle burner embodiment 1 (3b). It is a graph which shows the relationship between the unburned content concentration in ash at the time of using the coal combustion method which concerns on Embodiment 2, and the unburned content concentration in ash at the time of using the conventional coal combustion method. It is a graph showing the relationship between the concentration of NO _X when using the NO _X concentration and conventional coal combustion method when using coal combustion method according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boiler 2 Boiler furnace 3a, 3b, 3c Burner 4 Upper stage air nozzle 5 Air valve 6 Air path 7 Air control device 8a, 8b Coal crusher 9a, 9b Hopper 10a, 10b Valve 11a, 11b Pulverized coal path 12 Coal ash discharge port 21 Central shaft 30 Primary air pipe 31 Secondary air inlet 32 Tertiary air inlet 33 Inner pipe 34 Outer pipe 37 Oil burner 100 Coal combustion device 311 Secondary air swirl vane 321 Tertiary air swirl vane

Claims (6)

In a coal combustion method of burning pulverized coal using a combustion device in which a plurality of burners using pulverized coal as fuel in the combustion chamber are provided in the vertical direction,
The pulverized coal comprises a first pulverized coal and a second pulverized coal having a combustion ratio lower than that of the first pulverized coal,
A coal combustion method characterized by supplying the first pulverized coal to a burner located below and supplying the second pulverized coal to a burner located above the burner located below. In the coal combustion method according to claim 1,
The coal combustion method, wherein an air ratio of air supplied to each burner together with the first pulverized coal and the second pulverized coal is 0.5 to 0.99. In the coal combustion method according to claim 1 or 2,
A ratio of the fuel ratio of the first pulverized coal to the fuel ratio of the second pulverized coal is 1.5 or more. In the coal combustion method in any one of Claims 1-3,
A coal combustion method characterized by introducing latter-stage air into the combustion atmosphere of the pulverized coal. In the coal combustion method in any one of Claims 1-4,
The first pulverized coal is bituminous coal;
The coal combustion method, wherein the second pulverized coal is subbituminous coal. It has a combustion chamber in which a plurality of burners using pulverized coal as fuel are provided in the vertical direction,
The burner located below is connected to the first fuel chamber in which the first pulverized coal is stored,
The burner located above the burner located below is connected to a second fuel chamber in which a second pulverized coal having a combustion ratio lower than that of the first pulverized coal is stored. Combustion device.

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