JP2510568B2 - Combustion method of coal / water mixed fuel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for burning a fuel such as a flame-retardant solid fuel, a liquid fuel, a slurry fuel, and the like, and particularly, to a coal / water mixed fuel having high combustion efficiency and It relates to a method of burning with low NOx.

[Conventional technology]

One of the problems in using coal is that it is not easy to handle such as transportation and storage because the coal is solid. Therefore, various coal-based fluid fuel technologies are being advanced. Among them, coal-water mixed fuel (hereinafter referred to as CWM), which is a mixture of atomized coal and water, has been attracting worldwide attention because it has low manufacturing and transportation costs, is easy to handle, and is economical. There is.

In order to burn CWM, it must be made into fine particles and sprayed into the combustion furnace. A two-fluid atomizer that causes a high-speed atomizing medium to collide with the atomizing medium is generally used for atomizing a relatively viscous fluid such as CWM. In the two-fluid atomizer, the atomization performance is higher as the flow velocity of the spray medium is higher,
Further, the ignitability of CWM improves as it becomes finer. Therefore, the speed of CWM ejected from the atomizer is about 5 times faster than when pulverized coal is conveyed by air. Furthermore, atomized CWM requires evaporation of water prior to its ignition. As a result of the high ejection speed and the need to evaporate water, the ignition position of CWM tends to shift to the wake side of the jet. Such retreat of the ignition position adversely affects combustion efficiency and fire stability.

In CWM combustion as well as other fuels, it is necessary to suppress NOx, and at least low NOx combustion of pulverized coal combustion is required. Coal emits reducing gases such as hydrogen and carbon monoxide under combustion conditions of insufficient air, so-called low air ratio combustion conditions, and NO is reduced by various reducing agents in a fuel excess region where oxygen concentration is low. To reduce NOx emissions,
It is necessary to completely form this reduction region.

Some low-NOx burners for pulverized coal have a structure in which combustion air is largely separated and gradually mixed with pulverized coal to stably form a reduction region.

On the other hand, as described above, CWM takes a long time to ignite by the evaporation time of water, and since it is ejected at high speed when atomized, the fire is easily separated from the burner surface.
That is, since combustion proceeds in the downstream region where CWM and air are rapidly mixed, it is not easy to form a reducing region such as pulverized coal combustion, and it is difficult to suppress NOx emissions. In addition, the low ignitability is of course the direct cause of the lowering of the combustion rate, and when the fire leaves the burner, it becomes an unstable combustion state that easily causes a misfire, which causes a problem in the reliability of the combustion device. .

As described above, in CWM combustion, the retreat of the ignition position adversely affects the combustion characteristics. Therefore, it is a key point in developing the burner for CWM to draw the ignition position as close to the burner as possible.

As a method of drawing the ignition position, a method of introducing combustion air as a swirling flow is known. For example, there is a burner in which the position of the tertiary air nozzle is separated from the fuel nozzle and the tertiary air is injected as a strong swirl flow, such as the pulverized coal burner disclosed in Japanese Patent Laid-Open No. 59-208305. When fuel is ejected at a flow rate of air such as pulverized coal, it is effective to inject the combustion air having a strong swirl flow. However, when fuel is ejected from the fuel nozzle at a high speed that is 3 to 5 times faster than the combustion air flow rate as in CWM, when the flame is held only by the swirling force of the air,
The optimum turning strength range is very narrow, which makes it difficult to operate the burner.

Further, as a burner for oil fuel, there is a burner device disclosed in JP-A-59-145405 for the purpose of shortening a fire.

This device is very effective for burners with good ignitability such as oil fuel, but does not give good flammability for fuel with low ignitability such as CWM. First of all, if the primary air nozzle is installed on the outer circumference of the fuel nozzle and the fuel is burned in the primary burner metal installed around this,
Since the negative pressure region formed by the high-speed jet of fuel is eliminated by the primary air, the secondary air is not entrained in the ignition region formed by the primary burner metal, and the ignitability is improved. Is hindered. That is, ignition and flame holding are required to form a large and stable circulating flow around the fuel flow, and the introduction of the primary air has an adverse effect on the formation of the circulating flow. The device is therefore unsuitable as a burner for CWM combustion.

[Problems to be solved by the invention]

As mentioned above, in the combustion of CWM, CWM ejected at high speed
The ignition quality of NOx is poor and a stable fire cannot be obtained.
Cannot be reduced.

The object of the present invention is to improve the ignitability of fuel, especially coal-water mixed fuel, to obtain a stable fire and at the same time to improve the combustion rate and
It is to provide a combustion method of a coal-water mixed fuel that achieves reduction of NOx.

[Means for solving problems]

The present invention provides a cone-shaped primary pre-combustion chamber in the shape of a divergent cone in front of a fuel nozzle that ejects a coal-water mixed fuel, and an annular primary air nozzle on the outer periphery of the primary pre-combustion chamber as the fuel nozzle. The inner cylinder side tip of the annular primary air nozzle, which is provided concentrically, is located at the same position as the tip of the primary precombustion chamber, and the outer cylinder side tip is located forward of the tip of the primary precombustion chamber. A secondary preliminary combustion chamber is formed in front of the primary preliminary combustion chamber by projecting it, and an annular secondary air nozzle is provided on the outer periphery of the secondary preliminary combustion chamber concentrically with the fuel nozzle, Using a burner in which a gap is provided in the conical wall surface of the primary pre-combustion chamber that spreads toward the end and seal air is ejected along the wall surface, the coal-water mixed fuel is injected from the fuel nozzle, and the primary Coal / water mixed combustion from air nozzle Is swirled with an amount of primary air smaller than the amount of air required for complete combustion of the secondary air nozzle to produce a sufficient amount of secondary air for complete combustion of the coal-water mixed fuel. Injecting into a swirling flow, a negative pressure region is formed on the outer periphery of the jet flow of the coal / water mixed fuel by the jet flow of the primary air, and inside the secondary pre-combustion chamber whose temperature is higher than the atmospheric gas of the primary pre-combustion chamber. Atmosphere gas is drawn back into the primary pre-combustion chamber to remove water in the coal / water mixed fuel jet to ignite coal, and a reducing combustion region is formed by the coal and primary air in the secondary pre-combustion chamber to generate NOx. The secondary air is made to burn the coal completely, and the coal-water mixed fuel is attached to the wall surface by the seal air ejected along the wall surface of the primary pre-combustion chamber having the conical shape that spreads toward the end. Special feature of prevention In the combustion process of the coal-water mixture fuel to.

[Action]

In the combustion method according to the present invention, the ignitability to the CWM is enhanced by forming the negative pressure region outside the CWM jet in the primary precombustion chamber. Ignition of CWM forms the above-mentioned negative pressure region so that the action of blowout by the jet of CWM does not occur. In order to form a negative pressure region in the primary precombustion chamber, the jet flow of CWM injected from the fuel nozzle is obtained by injecting the CWM inward from the inner peripheral surface of the outer wall of the primary precombustion chamber. Furthermore, it is necessary to eject the air from the primary air nozzle so that the air is ejected in the same direction as the CWM. Therefore, the primary air is jetted as a swirling flow along the outer wall of the primary pre-combustion chamber. Further, by ejecting the sealing air along the inner peripheral surface from the gap provided on the inner wall surface of the primary pre-combustion chamber, which has a conical shape that spreads toward the end, CWM is prevented from adhering to the inner wall surface. .

〔Example〕

1 and 2 are provided with two combustion chambers, a primary pre-combustion chamber and a secondary pre-combustion chamber, which are in the shape of a divergent cone.
Figure 3 shows a sectional view of a CWM burner. However, in this example, 1
Seal air is not flowing along the inner wall surface of the secondary pre-combustion chamber. Reference numeral 1 is a fuel nozzle for atomizing and ejecting CWM, and 4 is arranged concentrically with the fuel nozzle 1, and the fuel nozzle 1
The primary pre-combustion chamber 2 and the secondary pre-combustion chamber 2, which are formed in a conical shape that widens from the tip end of the
A ring-shaped primary air nozzle that ejects combustion air as a swirl flow with the axis of the fuel nozzle as its center.
The inner cylinder of the secondary air nozzle 2 also serves as the outer peripheral surface of the primary preliminary combustion chamber 4. The inner cylinder of the primary air nozzle is formed shorter than the outer cylinder in the fuel injection direction. 5
Is a secondary preliminary combustion chamber formed by the outer cylinder of the primary air nozzle 2 in front of the primary preliminary combustion chamber 4. Reference numeral 3 denotes an annular secondary air nozzle that is installed on the outer periphery of the secondary preliminary combustion chamber 5 and ejects combustion air as a swirling flow.
The cylinder of the secondary air nozzle 3 also serves as the outer cylinder of the primary air nozzle 2. Reference numeral 6 denotes a swirl flow generator provided at the inlets of the nozzles 2 and 3, and the air jetted from the nozzles 2 and 3 is jetted as a swirl flow. Reference numeral 7 indicates a block portion of the primary pre-combustion chamber, and reference numeral 9 indicates a combustion furnace.

FIG. 2 shows the structure of the radial flow swirl flow generator 6. The air flowing into the generator from the radial direction flows along the guide vanes 6a, and becomes a swirling flow having a radial flow component at the vane outlet.

In the above configuration, the CWM of the fuel is atomized by the fuel nozzle 1 to an average particle size of about 50 to 100 μm and ejected. The atomized CWM is ignited in the conical primary pre-combustion chamber 4 installed on the outer circumference of the fuel nozzle, and then the cylindrical secondary pre-combustion provided downstream of the primary pre-combustion chamber 4. Room 5
After being combusted with the primary air inside, it is completely combusted with the secondary air inside the combustion furnace. The jetting speed of CWM is usually set to a high speed of 3 to 5 times or more the fuel air flow rate in order to promote atomization. Further, the primary air is ejected as a swirling flow centered on the axis of the fuel nozzle 1. Therefore, the static pressure around the CWM jet becomes negative and a part of the primary air, that is, 1
Atmospheric gas in the secondary pre-combustion chamber having a temperature higher than that of the next pre-combustion chamber is pulled back into the primary pre-combustion chamber 4. This atmosphere gas
Used for water removal and ignition of CWM. The remaining primary air that was not used for ignition, before the CWM mixes with the secondary air,
It is mixed with CWM in the secondary preliminary combustion chamber 5 and burned at a low air ratio. As a result, a reduction region is formed and NOx is reduced. Next, the secondary air from the secondary air nozzle 3 is mixed and completely burned. The air outlet of the primary air nozzle 2 is 2
In order to form the next preliminary combustion chamber 5, it is installed inside the air ejection port of the secondary air nozzle 3. The ratio of the primary air caught in the primary pre-combustion chamber 4 and the ratio of the primary air consumed in the secondary pre-combustion chamber 5 is controlled by the swirling strength of the primary air, which is effective for stable fire formation. , An appropriate turning strength is selected. The primary air is thus used to ignite the CWM and form a low air ratio fire, and is set to a flow rate lower than the air flow rate required for complete combustion of the CWM.

The material of the block 7 constituting the primary pre-combustion chamber 4 may be steel, but heat-resistant ceramics, bricks, etc. are effective in consideration of heat storage and life due to burning. Typically, the CWM combustor is preheated with a gaseous or liquid fuel until the furnace reaches a temperature sufficient to form a CWM fire. Therefore, a block with a high heat storage material is used.
With this configuration, heat is stored in this at the time of preheating, and the ignition of the CWM is facilitated by this heat. When a heating element such as a ceramic heater is used as the material of the block 7, the CWM jet can be heated by the heating element, and ignition can be controlled by the amount of heat generation. If the material of the block 7 is selected from the viewpoint of heat storage or heat generation, the ignitability at the start of CWM injection is improved. Once a stable fire is formed, the block 7 is heated by heat transfer from the fire, so that the problem of ignitability of CWM is reduced.

In addition to this heat supply for ignition, if a primary pre-combustion chamber 4 as shown in FIG. 1 is installed, it is ejected at high speed.
Since the flow velocity of CWM attenuates before mixing with the primary air in the secondary pre-combustion chamber 5, the residence time during air mixing becomes long, and it is effective in bringing the ignition position closer to the burner surface. That is, it becomes easy to form a fire in the secondary preliminary combustion chamber 5. Therefore, it is desirable to make the primary pre-combustion chamber 4 as large as possible also in order to reduce the CWM flow velocity, but if it is made too large, CWM particles will adhere to the inner wall in addition to the deviation of the jet flow as described later. There is a high fear that it will be required to design an appropriate size. Further, the opening angle α of the primary pre-combustion chamber 4 is set to CWM in order to suppress the adhesion of CWM particles.
It is preferable that the spray angle be larger than the spray angle of the fuel nozzle 1.

The secondary pre-combustion chamber 5 is formed by the inner cylinder of the annular secondary air nozzle 3, and is installed downstream of the primary pre-combustion chamber 4. As already mentioned, this secondary pre-combustion chamber 5 has
It is used to burn CWM with secondary air. As described above, the formation of the reduction region obtained by a low air ratio fire is important for low NOx combustion. Secondary preliminary combustion chamber 5
The installation of this makes it easier to form this low air fire,
Clarify the action of secondary air. Since the outlet of the secondary air is the wake of the secondary preliminary combustion chamber 5, the mixing with the secondary air becomes slow. Further, the flow of the primary air is prevented from spreading to the outer periphery by the inner wall of the secondary pre-combustion chamber 5 (that is, the inner cylinder of the secondary air nozzle 3), so that mixing with CWM is promoted and low The formation of an air-ratio fire becomes easier. The material of the secondary air or primary air nozzle is usually steel, but like the block 7, in order to promote low air ratio combustion, the inner wall has a heat-resistant ceramic with high heat storage, or It is also effective to use a heating element such as a ceramic heater.

As described above, according to the burner of FIG. 1, since the ignitability of the CWM is improved, it is easy to obtain a stable fire and the combustibility is improved. Further, the formation of a low air ratio fire is facilitated, and at the same time, the reduction region can be made larger due to the delay in the mixing of the secondary air, and the burner of FIG. 1 is effective in suppressing NOx emissions. If you add more,
Slow mixing of the secondary air has the disadvantage of lengthening the fire, i.e. increasing the size of the combustion device. 2 for this
It is important to eject the secondary air as a swirling flow. When ejected as a swirling flow, the inside of the swirling flow becomes negative pressure,
In the wake of the fire, a reverse flow is formed from the downstream side to the combustion device side. This promotes the mixing of the secondary air and CWM in the wake and prevents the fire from becoming longer.

In the example of FIG. 3, the shape of the primary pre-combustion chamber 4 is different from that of FIG. 1, and in order to increase the size of the combustion chamber, the expansion of the primary pre-combustion chamber around the fuel nozzle 1 for spraying CWM is performed. The cylindrical portion is made long after being enlarged and its cross section is enlarged. When the primary pre-combustion chamber 4 has such a shape, the effect of the primary pre-combustion chamber 4 is increased, but if the central axis of the combustion chamber and the central axis of the fuel nozzle 1 do not match well, the primary air The amount of pullback is uneven, the jet of CWM tends to shift from the center, and caution is required when manufacturing and assembling burner parts.

In the burner shown in FIG. 3, in addition to the shape of the primary pre-combustion chamber 4, a baffle plate 8 is provided at the outlet of the secondary air so that the mixing of the secondary air is further delayed than the burner shown in FIG. Has been done. It is of course possible to install such a baffle plate 8 in the burner shown in FIG.
It is effective in improving the effect of combustion. Such modification of the air injection nozzle is required when changing the burner capacity, that is, the burner combustion amount. The larger the volume, the larger the entire burner diameter, so the mixing of the secondary air will be slower even without using a means such as the baffle plate 8. The mixing of the secondary air becomes faster, and it is necessary to devise to clarify the role of each air.

Fig. 4 shows the result of burning CWM with the burner shown in Fig. 1. In the figure, the low NOx burner for pulverized coal shown in JP-A-59-208305 is used, and instead of the pulverized coal nozzle, CWM is used.
The results when the CWM was burned with the jet nozzle of No. 3 were also shown for comparison. The fuel nozzle used was the same for both burners. The horizontal axis of the figure shows the proportion of the unburned ash contained in the combustion ash collected at the combustion furnace outlet. If this value is small, the combustion rate is high. The vertical axis represents the value obtained by converting the NOx concentration measured at the combustion furnace outlet into a 6% O ₂ concentration standard. Generally, when the amount of ash in the ash becomes high, the amount of N content remaining in the ash increases, so that the NOx concentration becomes low. Therefore, a burner that reduces NOx at the same time as reducing the amount of ash in the ash is the most desirable and has good combustion characteristics. The CWM used consisted of 63 wt% Pacific charcoal and 37 wt% water. In the figure, the symbol □ shows the result when CWM was burned using a low NOx burner for pulverized coal. Pulverized coal is C
Compared to WM, it has better ignitability and even if the combustion air and fuel are mixed for a relatively long time, the burner of JP-A-59-208305
It is possible to obtain high combustibility and reduce NOx at the same time. On the other hand, when CWM is burned using a burner for pulverized coal, it is difficult to achieve NOx reduction and high-efficiency combustion at the same time. Become. The circles show the results of burning CWM with the burner shown in FIG. Compared with the result of burning with a conventional burner for pulverized coal, the burner shown in Fig. 1 can burn CWM in a place where the amount of ash in the ash is small, and this burner is effective in improving the burning rate. . Also, NO
As for x, it can be seen that the emission amount can be reduced while maintaining a high combustion rate. This adjustment of NOx emission is
This is performed by distributing the flow rates of the primary and secondary air and selecting the swirling strength of each air. From the result of FIG. 4,
As shown in FIG. 1, it is understood that the burner in which the inner wall surface of the primary pre-combustion chamber is formed in a conical shape that widens toward the end is effective for CWM combustion.

Next, an embodiment of the present invention will be described with reference to FIGS.

The combustion device shown in FIG. 5 and FIG.
CWM adhesion prevention means is added to the inner wall of the primary pre-combustion chamber of the combustion apparatus shown in the figure. Other structures are first
Since it is almost the same as the embodiment shown in the figure, the description thereof is omitted.

In the embodiment of FIG. 5, the conical primary precombustion chamber 4 is defined by a flame stabilizer 10. The flame stabilizer 10 has a small diameter portion connected to a seal pipe 11 arranged concentrically with the fuel nozzle 1, and a large diameter portion connected to a sleeve pipe 12 arranged concentrically with the seal pipe 11. The sleeve pipe 12 is provided with a damper 15 for adjusting the flow rate of the seal air 14 from the wind box 13. As shown in FIGS. 6 and 7, the flame stabilizer 10 has a plurality of blades 10a extending in the fuel injection direction. Each blade 10a has a trapezoidal shape, and each blade 10a has the same side surface. The inclined surfaces of the adjacent blades 10a are arranged with a predetermined clearance as shown in detail in FIG. Seal air from the wind box 13
14 passes through this gap and flows into the primary preliminary combustion chamber 4. Since the gap is inclined, the seal air 14 flows along the inner wall of the flame stabilizer 10 in a swirling flow centered on the axis of the fuel nozzle 1. This swirling direction is the same as the swirling direction of the primary air injected from the primary air nozzle 2. The swirling flow of the seal air 14 prevents the CWM from adhering to the inner wall of the primary pre-combustion chamber 4. It should be noted that the flow rate of the seal air 14 is an amount that does not prevent the primary air from drawing the atmospheric gas in the secondary preliminary combustion chamber 5 back into the primary preliminary combustion chamber 4. If there is a risk that CWM will adhere to the tip of the fuel nozzle 1, the seal pipe 11 and the fuel nozzle 1
A small amount of air may be jetted from the gap between the and. Needless to say, this amount is an amount that does not hinder the withdrawal of the atmospheric gas in the secondary preliminary combustion chamber.

FIG. 8 is a modified embodiment of the gap formed in the flame stabilizer of the combustion apparatus of FIG. The cone-shaped primary pre-combustion chamber 4 is defined by a flame stabilizer 16. The flame stabilizer 16 is composed of a plurality of frustoconical rings 16a of different sizes, and each frustoconical ring 16a has a predetermined annular gap inside the small diameter side end of the large frustoconical ring adjacent to the large diameter side end. Are arranged so as to be located. As a result, a plurality of annular gaps are formed in the flame stabilizer 16 as shown in FIG. The sleeve pipe 12 is provided with a swirl flow generator 6, the seal air 14 flowing into the sleeve pipe 12 from the wind box 13 flows in as a swirl flow, and as a swirl flow from the annular gap, the primary preliminary combustion is performed. It flows along the inner wall of the room. The seal air 14 prevents the CWM from adhering to the inner wall of the primary preliminary combustion chamber.

 10 and 11 show a modification of the flame stabilizer shown in FIG.

In the flame stabilizer shown in FIG. 10, the flame stabilizer cross section is formed in a concave shape with respect to the line connecting the ejection port of the fuel nozzle 1 and the tip of the flame stabilizer. In this case, the seal air ejected from the annular gap is efficiently ejected on the inner wall surface of the flame stabilizer, and the sealing performance against CWM adhesion is enhanced. Therefore, it is effective in preventing the adhesion of CWM particles.

In the flame stabilizer shown in FIG. 11, the flame stabilizer cross section is formed in a convex shape with respect to a line connecting the ejection port of the fuel nozzle 1 and the tip of the flame stabilizer. In this case, since the distance between the jet and the inner wall surface of the flame stabilizer becomes larger as it goes to the wake side of the CWM jet, the CWM of the atmosphere gas in the secondary pre-combustion chamber is pulled back. Even when the mixed flow becomes large, the contact of CWM with the inner wall of the flame stabilizer is reduced. This is also effective in preventing the adhesion of CWM particles.

〔The invention's effect〕

According to the present invention, it is possible to improve the ignitability of the CWM by installing two pre-combustion chambers in the burner for CWM, and further to eject the seal air along the inner wall surface of the primary pre-combustion chamber to discharge the CWM. Since the adhesion is prevented and the formation of a low air ratio fire is facilitated, the CWM combustion rate is improved and NOx is reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a CWM burner having a primary pre-combustion chamber in the shape of a divergent cone, FIG. 2 is a perspective view of the swirl flow generator shown in FIG. 1, and FIG. FIG. 4 is a vertical cross-sectional view of a burner having an enlarged next pre-combustion chamber, FIG. 4 is a diagram showing the combustion characteristics of the combustion apparatus shown in FIG. 1, and FIG. 5 is an embodiment of a burner for carrying out the combustion method of the present invention. 6 is a vertical sectional view showing the combustion apparatus of FIG. 5, FIG. 7 is a sectional view taken along the line VII-VII of FIG. 6, and FIG. 8 is another sectional view of the combustion method of the present invention. FIG. 9 is a longitudinal sectional view showing an embodiment of a burner, FIG. 9 is a view taken in the direction of arrow B in FIG. 8, and FIGS. 10 and 11 are main parts of another embodiment of the primary precombustion chamber of the combustion apparatus in FIG. Sectional view. 1 ... Fuel nozzle, 2 ... Primary air nozzle, 3 ... Secondary air nozzle, 4 ... Primary preliminary combustion chamber, 5 ... Secondary preliminary combustion chamber, 6 ... Swirling flow generator, 10 ... Flame instrument, 11 …… Seal pipe, 12 …… Sleeve pipe, 13 …… Wind box, 14 ……
Seal air.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keishin Kobayashi 4026 Kujimachi, Hitachi, Ltd. Hitachi Ltd., Hitachi Research Laboratory (72) Kenichi Soma 4026, Kujicho, Hitachi Hitachi Ltd. Hitachi, Ltd. In-house (72) Inventor Toru Inada 4026 Kujimachi, Hitachi City Hitachi Ltd., Hitachi Research Laboratory (72) Inventor Norio Arashi 4026 Kujimachi, Hitachi City Hitachi Ltd. (72) Invention Person Hiroshi Miyadera 4026, Kujimachi, Hitachi City Hitachi, Ltd., within Hitachi Research Laboratory (56) References JP 61-231320 (JP, A) JP 63-87516 (JP, A) Actual development Sho 62- 24233 (JP, U) JP 60-21281 (JP, B2)

Claims (1)

(57) [Claims] 1. A primary precombustion chamber having a conical shape that spreads toward the front is provided in front of a fuel nozzle for ejecting coal-water mixed fuel, and an annular primary air nozzle is provided on the outer periphery of the primary precombustion chamber. And the inner cylinder side tip of the annular primary air nozzle is located at the same position as the tip of the primary pre-combustion chamber, and the outer cylinder side tip is forward of the tip of the primary pre-combustion chamber. A secondary precombustion chamber is formed in front of the primary precombustion chamber by projecting into the secondary precombustion chamber, and an annular secondary air nozzle is provided concentrically with the fuel nozzle on the outer periphery of the secondary precombustion chamber. A coal-water mixed fuel is injected from the fuel nozzle by using a burner configured to eject a seal air along the wall surface of the primary pre-combustion chamber having a conical wall surface that spreads toward the end, and Mixing coal and water from the primary air nozzle The secondary air in an amount smaller than the amount of air required for complete combustion of the fuel to be swirled and injected into the secondary air nozzle to completely burn the coal-water mixed fuel. Injecting air into a swirling flow,
A negative pressure region is formed outside the jet flow of the coal-water mixed fuel by the jet flow of the primary air, and the atmospheric gas in the secondary pre-combustion chamber having a higher temperature than the atmospheric gas in the primary pre-combustion chamber is subjected to the primary pre-combustion. It is pulled back into the room to remove the water content of the coal / water mixed fuel jet, ignite the coal, form a reducing combustion region with the coal and the primary air in the secondary precombustion chamber to reduce NOx, and the secondary air Completely burn the coal by means of the seal air ejected along the conical wall surface of the primary pre-combustion chamber, which expands toward the end of the primary pre-combustion chamber.
A method for burning coal-water mixed fuel, which is characterized in that water-mixed fuel is prevented from adhering.