JP2005265297A - Boiler device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler device provided with a compact system configuration capable of using various pulverized coal having different kinds of coal, sludge, biomass fuel or the like, reducing amount of generated NOx, achieving stable combustion, and realizing excellent energy efficiency. <P>SOLUTION: This boiler device is provided with a furnace for injecting fuel for combustion and generating steam having high temperature by a water pipe arranged in an upper part, a heat exchange means for heating air for combustion up to such temperature that exceeds ignition temperature of fuel using combustion exhaust gas exhausted from the furnace and having high temperature as a heat source after generating steam, a combustion air supply means for injecting air for combustion, and a fuel nozzle means for injecting fuel and forming flame. Reduction atmosphere is formed in the vicinity of flame by air for combustion supplied from the combustion air supply means and fuel supplied from the fuel nozzle means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a boiler device capable of obtaining high-temperature water vapor by burning solid fuel such as pulverized coal, sludge, biomass fuel, etc. In particular, various fuels including low-quality fuel can be burned, and the load is low. The present invention relates to a boiler device capable of reducing NOx in combustion exhaust gas including time and making the device main body compact.

  Conventionally, in thermal power plants, boilers using pulverized coal as fuel have been known. However, as problems of such pulverized coal combustion boilers, (1) so-called fuel NO caused by fuel is mainly used. The amount of NOx generated is large, and (2) the low volatile coal type has poor ignitability and it is difficult to stably burn, and further downsizing of the boiler has been desired from the viewpoint of cost reduction. .

  In the prior art, as means for ensuring ignitability and reducing fuel NO, the pulverized coal concentration in the vicinity of the ignition point is adjusted to ensure ignitability, and the amount of combustion air is adjusted to make the vicinity of the ignition point a reducing atmosphere. It has been practiced to suppress the generation of fuel NO by suppressing the oxidation of the fuel N. For example, the structure of a burner that jets and burns pulverized coal makes the pulverized coal flow dark or dark, or the nozzle for supplying combustion air is coaxial with the nozzle of the burner and controls the direction of jetting, For example, the flow of combustion air in the vicinity of the combustion flame of charcoal is adjusted to keep the vicinity of the ignition point in a reducing atmosphere. Furthermore, in the vicinity of the ignition point, the combustion air to be supplied is limited so that combustion is performed in a reducing atmosphere, and further air is supplied to the subsequent stage of combustion to completely remove unburned fuel remaining in the combustion near the ignition point. Two-stage combustion is also carried out.

However, depending on the conventional technology as described above, there is a limit to the improvement of ignitability, so there is a limit to the suppression of NOx generation by the formation of a reducing atmosphere, and in the end, NOx treatment with a large denitration apparatus must be performed. There was no problem.
In recent years, an invention for improving the ignitability by applying a high-temperature air combustion technique to pulverized coal combustion has been performed (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 2001-2115013

By the way, in order to apply the high-temperature air combustion technique proposed in Patent Document 1 to an actual boiler, there are various problems as follows.
(1) It is desirable that the boiler apparatus to which the high-temperature air combustion technology is applied has a system configuration capable of easily designing various furnaces having different capacities from small to large furnaces by applying a unified technical idea.
(2) Using various coal types including low-volatility coal types as fuel, low NOx and stable combustion must be possible over a wide operating range from low load to high load.
(3) Moreover, it is necessary to improve the efficiency at the time of low load, in particular, to reduce the internal ratio and to improve the steam conditions (ensure the amount of high-temperature steam).
(4) It is necessary to reduce the cost by making the device compact.
(5) It can be applied to low-quality fuels such as sludge and biomass, and it is desirable that stable combustion is possible.

The above will be described in detail below.
It goes without saying that the system configuration of the boiler apparatus should be able to support boilers of all sizes without greatly changing the design individually.
Pulverized coal is heated and gasified in a boiler and combusted, but the ease (volatility) of such gas generation varies depending on the type of coal. For example, anthracite coal with a high degree of carbonization and low smoke has low volatility. Sexually bad. It is almost impossible to stably burn various coal types including anthracite coal in a wide operating range from low load to rated operation.

  As described above, NOx generated in pulverized coal combustion is often caused by so-called fuel NOx, and in the conventional combustion method, fuel NOx from the furnace is also taken by measures such as an exhaust gas recirculation method effective for thermal NOx. Since it is difficult to reduce the generation sufficiently, it is unavoidable to remove it with a large-scale denitration apparatus as compared with the case where heavy oil or the like is used as fuel.

  Furthermore, since the combustion of pulverized coal becomes unstable during operation at a low load, the amount of air required to stably burn the same amount of pulverized coal increases compared to during rated output operation, Due to the increase in the amount of supplied air, the atmosphere in the vicinity of the burner becomes an oxidizing atmosphere, resulting in an increase in the amount of generated NOx. In addition, the increase in the amount of air increases the power of the exhaust fan for blowing the air (increase in the in-house ratio), and is discharged to the atmosphere while being held in the air (combustion air). The amount of heat that is generated also increases, and high-temperature steam cannot be secured efficiently, leading to a decrease in boiler efficiency. For this reason, the total energy efficiency of a boiler apparatus falls at the time of low load driving | operation.

In addition, from the viewpoint of environmental conservation, the use of sludge and biomass fuel that generate combustible gas by heating is also required, but these fuels generally have a high water content and poor ignitability, so existing boilers It is difficult to burn.
This invention is made | formed in view of said situation, The objective can use low quality fuels, such as various pulverized coals from which coal types differ, sludge, and biomass fuel, and includes low load operation. There are few NOx generations over a wide operating range, stable combustion is possible, excellent overall energy efficiency, compactness of the entire system, and various furnaces with different capacities from small to large furnaces Is to provide a boiler apparatus having a system configuration that can be easily designed by applying a unified technical idea.

  In order to achieve the above object, according to the first aspect of the present invention, a fuel is ejected and burned in a lower combustion region, and a furnace that generates high-temperature steam by a water pipe disposed in the upper part and the steam are generated. Thereafter, heat exchange means for heating the combustion air to a temperature equal to or higher than the ignition temperature of the fuel using the high-temperature combustion exhaust gas discharged from the furnace as the heat source, and combustion for injecting the heated combustion air into the combustion region Air supply means, and fuel nozzle means for injecting the fuel into the combustion region to form a flame, combustion air supplied from the combustion air supply means, and fuel supplied from the fuel nozzle means Provides a boiler device characterized in that a reducing atmosphere is formed in the vicinity of the flame.

A dust removing unit that removes dust in the combustion exhaust gas and supplies the dust to the heat exchange unit may be provided.
A plurality of the heat exchange means (Claim 3) or the combustion air supply means (Claim 4) may be provided, and the amount of combustion air may be increased or decreased according to increase or decrease of the load or capacity of the boiler device. A plurality of means (Claim 5) may be provided, and the fuel ejection amount may be increased or decreased according to the increase or decrease of the load or capacity of the boiler device.

  The combustion air supply means may include a first combustion air nozzle that is disposed in the vicinity of the fuel nozzle and ejects combustion air to form a reducing atmosphere in the vicinity of the flame. 6) The combustion air supply means is disposed on the flame downstream side of the first combustion air nozzle, and ejects combustion air to burn unburned fuel. (Claim 7).

  Here, “in the vicinity of the fuel nozzle” can form a reducing atmosphere around the combustion flame generated by the fuel ejected from the fuel nozzle and the combustion air ejected from the first combustion air nozzle. It means that the fuel nozzle and the first combustion air nozzle are disposed in the range, and the centers of the fuel nozzle and the first combustion air nozzle may be installed apart from each other, and are coaxial. Each center may be disposed.

  The fuel nozzle means and the combustion air supply means may be disposed on each wall surface of the furnace facing each other, and the fuel nozzle and the combustion air nozzle on each wall surface may be disposed to face each other. The fuel nozzle means and the combustion air supply means are arranged so that the fuel and the combustion air can be ejected in the tangential direction of a horizontal virtual circle in the furnace to generate a swirl flow in the furnace. The solid fuel may be burned while being allowed to burn (claim 9).

Various fuels can be applied to the present invention, which may be sludge, biomass, etc. When the fuel is pulverized coal, it is desirable to heat the combustion air to 800 ° C. or higher.
The heat exchange means may be a multi-tube heat exchanger (Claim 11) or a heat storage heat exchanger (Claim 12).

  If necessary, combustion exhaust gas from the furnace may be used as a carrier gas, and solid fuel may be conveyed to the fuel nozzle by the carrier gas (Claim 13). In addition, the coal is pulverized into pulverized coal. A pulverized coal may be produced by providing a mill device, using the combustion exhaust gas from the furnace as an atmospheric gas, and supplying the combustion exhaust gas to the mill device (Claim 14). There may be provided dust collecting means for removing the ash ash (claim 15).

  A feature of the invention of claim 1 is that high-temperature combustion air at or above the ignition temperature of fuel (800 ° C. or more for various pulverized coal fuels) is secured over a wide range (preferably the entire region) of the operating range. For this reason, in order to obtain the high-temperature combustion air by the heat exchange means, the exhaust exhaust gas discharge position is provided at a position where the entire amount of the high-temperature combustion exhaust gas can be used as a heat source immediately after water vapor is generated by the water pipe, Unlike the conventional case, the combustion exhaust gas temperature is set to a high level (for example, about 900 ° C.). The combustion air heated to a high temperature is ejected to the combustion region by the combustion air supply means, and a high-temperature reducing atmosphere is formed in the vicinity of the flame generated from part of the ejected air and the fuel. . Thus, the fuel (for example, pulverized coal) ejected from the fuel nozzle is exposed to a high temperature, combustion gas due to thermal decomposition (volatilization) is generated early, and the flame is surrounded by a reducing atmosphere. The decomposed combustion gas burns while suppressing the generation of fuel NO due to the oxidation of the nitrogen component, and the generation of NOx is suppressed.

In addition, since the combustion air supplied to the combustion region is heated above the ignition point, even if the fuel is low-volatile, volatilization is promoted and ignitability is improved, enabling stable combustion. . Furthermore, since the ignitability is stable, the flame is not extinguished even during low-load operation.
In addition, by adjusting the amount of combustion air supplied appropriately, the atmosphere in the vicinity of the flame can always be maintained in a high temperature reducing atmosphere, so the above stable combustion can be achieved in a wide operating range from low load operation to high load operation. Is possible. For this reason, generation | occurrence | production of fuel NOx by the early oxidation of the nitrogen component contained in fuel is suppressed, and the NOx generation amount discharged | emitted from a boiler apparatus can be reduced. Therefore, the energy consumed by the de-extinguishing device and the exhaust fan power can be reduced, and the energy efficiency is improved.

Fuel is burned with combustion air heated above the ignition temperature, so high-temperature combustion gas is generated, and the amount of radiant heat transfer from the flame increases due to the high temperature of the combustion flame, ensuring high-temperature steam efficiently and at the top of the boiler The radiant heat transfer surface can be reduced in size, and the combustion exhaust gas after the generation of water vapor can be maintained at a high temperature.
In addition, since the amount of heat released from the furnace once accompanied by the high-temperature combustion exhaust gas is also returned to the furnace as high-temperature combustion air, energy efficiency is improved. In addition, since the combustion is stable during low-load operation as described above, the supply amount of combustion air for burning the same amount of pulverized coal even during low-load operation is different from the conventional technology. Therefore, there is no need to increase the exhaust air power for blowing the combustion air, and there is no increase in the thermal energy released into the atmosphere accompanying the combustion exhaust gas. Therefore, overall energy efficiency can be improved also from this point.

  Furthermore, since the high-temperature combustion exhaust gas is discharged from the furnace as it is, thorough heat recovery from the combustion exhaust gas in the boiler body including the furnace, which has been done with conventional boiler equipment, is no longer necessary. The entire boiler device can be made compact by eliminating the economizer and other devices. Furthermore, by supplying high-temperature combustion air, the speed of the combustion reaction itself increases, and complete combustion takes place in a short time, so that the residence time of pulverized coal in the furnace can be reduced. For this reason, the furnace can be made more compact.

In addition to these, due to the heating effect of high-temperature combustion air, sludge and biomass fuel containing a large amount of water can be instantly dried, volatilized and burned in the furnace.
According to the invention of claim 2, preferably, by providing a dust removing means for removing dust in the combustion exhaust gas and supplying the dust to the heat exchange means, the heat exchange means is blocked by the dust contained in the combustion exhaust gas. It is possible to prevent the device from becoming unusable and to achieve another purpose of extending the continuous operation time of the apparatus.

  According to the invention of claim 3, claim 4 and claim 5, depending on the rated capacity of the boiler device to be designed, a plurality of heat exchange means, combustion air supply means or fuel nozzle means can be appropriately provided. Since the combustion air amount or the fuel injection amount is increased / decreased according to the load of the apparatus, even if the operation load fluctuates, it is possible to respond by appropriately increasing / decreasing the radix of the operating fuel nozzle means, etc. It is possible to supply high-temperature combustion air to the fuel, thereby realizing stable combustion and low NOx.

Further, according to the present invention, it is possible to more easily construct furnaces of various capacities by increasing or decreasing the number of bases while keeping the design of the combustion capacity of the fuel nozzle means and the like the same, so that the size can be reduced. Various furnaces with different capacities up to large furnaces can be designed more easily by applying a unified technical idea.
According to the sixth aspect of the present invention, the first combustion air nozzle of the combustion air supply means is arranged in the vicinity of the fuel nozzle so as to form a reducing atmosphere in the vicinity of the flame. Can be easily reduced and NOx can be reduced.

  According to the seventh aspect of the invention, since the second combustion air nozzle of the combustion air supply means is disposed on the downstream side of the flame of the first combustion air nozzle, high-temperature combustion is performed on the downstream side of the combustion. By supplying the working air, the remaining unburned fuel can be efficiently burned in a high temperature atmosphere. Note that the nitrogen component contained in the pulverized coal is stabilized in the pre-combustion stage of the reducing atmosphere, and therefore fuel NO is not generated in the post-stage combustion.

  According to the present invention, the fuel nozzle means and the combustion air supply means are arranged on each wall surface of the furnace facing each other, and the fuel nozzle and the combustion air nozzle on each wall face each other, A stable combustion region can be formed in the vicinity of the axis of the furnace (Claim 8), and the fuel nozzle means and the combustion air supply means are provided for fuel and combustion in the tangential direction of a horizontal virtual circle in the furnace. As an arrangement in which fuel is burned while jetting air and generating a swirling flow in the furnace, a stable combustion region can be formed at the center of the boiler to improve combustion stability.

Various fuels can be applied to the device of the present invention, and as described above, sludge, biomass, and the like may be used, but when pulverized coal is used as the fuel as in the invention of claim 10, preferably, Stable combustion can be secured by heating the combustion air to 800 ° C. or higher.
According to the inventions of claims 11 and 12, a multi-tube heat exchanger or a heat storage heat exchanger is used as the heat exchanging means, and the combustion air is heated above the ignition temperature of the fuel by using a high-temperature combustion exhaust gas as a heat source. Can be heated to a high temperature.

  According to the invention of claim 13, preferably, the combustion exhaust gas from the furnace is used as the carrier gas, and the solid fuel is carried to the fuel nozzle by the carrier gas. The oxygen concentration of the air ejected into the inner combustion region decreases, and a reducing atmosphere due to oxygen shortage near the ignition point can be realized more easily. Normally, if the oxygen concentration in the carrier air is lowered and the oxygen concentration in the vicinity of the ignition point is lowered, combustion becomes unstable, but the temperature in the vicinity of the ignition point is high due to the presence of the high-temperature combustion air. Stability can be maintained. As another effect due to a decrease in oxygen concentration in the carrier air, pulverized coal can be prevented from burning in an unexpected place, and conditions such as temperature control for preventing such combustion can be relaxed.

  In addition to the invention of claim 13, the invention of claim 14 is provided with a mill device for pulverizing coal into pulverized coal, the combustion exhaust gas from the furnace is used as the atmospheric gas, and the combustion exhaust gas is supplied to the mill device. Since pulverized coal is produced, pulverized coal is produced not in a normal air atmosphere having a high oxygen concentration but in a combustion exhaust gas atmosphere having a reduced oxygen concentration. For this reason, it can suppress that pulverized coal combusts in an unexpected place, and can ease conditions, such as temperature control for preventing such combustion.

  Furthermore, since the dust collecting means for removing the ashes in the combustion exhaust gas from the furnace is provided, it is possible to prevent the ashes from being blocked in the mill apparatus or the like (claim 15).

Hereinafter, embodiments of the boiler device according to the present invention will be described with reference to various examples.
First, a boiler apparatus 10 according to a first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a boiler apparatus 10 according to the present invention includes a furnace 11 for injecting and burning pulverized coal fuel into a lower combustion region 11c, and generating high-temperature steam by a water pipe 12 disposed at the upper part. After generating water vapor, a multi-tubular heat exchanger (heat exchange means: heat exchange means: heating the combustion air A2 to a temperature of 800 ° C. or higher, for example, using the high temperature combustion exhaust gas EG discharged from the furnace 11 as a heat source. A shell and tube heat exchanger) 21, a combustion air nozzle 31 connected to the combustion air outlet 21 b of the heat exchanger 21 through a pipe, and jetting the heated combustion air A 2 into the furnace 11, and An air supply blower 32 for pumping the combustion air A2 to the combustion air nozzle 31 and a fuel nozzle 41 (fuel nozzle means) for injecting and burning pulverized coal into the furnace 11 are provided.

  In addition, since FIG. 1 aims at explaining the outline of the system configuration | structure of the boiler apparatus of this invention, the structure of a boiler is simplified and shown typically. For example, (1) In practice, a large number of water pipes may be arranged not only on the top of the furnace but also on the side wall of the furnace. (2) Even if a superheater or reheater is provided near the water pipe. Good. However, since these are not essential in the description of the apparatus of the present invention, the description of the water pipes such as the furnace side wall is omitted. In this specification, “water pipe” refers to a superheater, It demonstrates as what also includes a heater.

  However, the “water pipe” of the present invention is disposed at a position facing the combustion region, and heat is transferred from the flame to the water pipe mainly by radiation. In other words, the water pipe of the present invention is disposed in the radiant heat transfer region, and is disposed in the convection heat transfer region in the conventional boiler, and is necessary for sufficiently recovering the thermal energy of the combustion exhaust gas. The economizer is not necessary in the boiler device 10. In the present invention, heat recovery is performed by the heat exchanger 21 without performing heat recovery by an economizer or the like.

  The furnace 11 is a box-type structure that is long in the vertical direction, and the bottom 11b has a quadrangular pyramid shape opened upward, and a pulverized coal incineration ash recovery device (not shown) is provided at the lowest part. The upper portion is provided with the above-described water pipe 12 for generating water vapor and heating the generated water vapor to a higher temperature. Further, a fuel nozzle 41 and a combustion air nozzle 31 are opened near the lower end of the body 11a of the furnace 11, and pulverized coal and combustion air are respectively ejected to the combustion region 11c in the furnace 11 to burn the pulverized coal. It has a structure that can.

One end of the exhaust pipe 13 for exhausting the entire amount of the combustion exhaust gas EG from the furnace 11 is disposed on the upper part of the furnace 11 and on the downstream side of the water pipe along the flow of the combustion exhaust gas. The exhaust pipe of the cyclone 14 is connected to the combustion exhaust gas inlet 21 c of the heat exchanger 21.
The heat exchanger 21 transmits the combustion exhaust gas EG passing through the cyclone 14 and flowing into the heat exchanger 21 and the low-temperature combustion air A2 blown from the supply air blower 32 through the combustion air inlet 21a. Flowing in opposite directions across the hot surface, the combustion air A2 is heated to 800 ° C., for example, using the combustion exhaust gas EG as a heat source. A combustion exhaust gas discharge port 21d of the heat exchanger 21 is connected to an exhaust pipe (not shown) through an exhaust blower 22 and a combustion exhaust gas processing device such as a denitration device (not shown). For the heat exchanger 21, it is necessary to select a material considering that there is a portion in contact with high-temperature combustion exhaust gas at 800 to 900 ° C. For this portion, for example, a heat-resistant alloy can be suitably used.

  The combustion air discharge port 21b of the heat exchanger 21 is connected to one end of the combustion air nozzle 31 via a pipe, and the other end of the combustion air nozzle 31 opens into the furnace 11 as described above, and is heated. The combustion air A <b> 2 thus provided has a function of appropriately swirling in an appropriate direction and ejecting it into the furnace 11. The combustion air nozzle 31 includes a temperature sensor 31a such as a thermocouple for measuring the temperature of the combustion air A2 flowing inside. As the combustion air nozzle 31, various types that can eject the combustion air to a desired position in the combustion region 11 c in the furnace 11 can be used. The combustion air nozzle 31 and the air supply blower 32 constitute combustion air supply means.

  The fuel nozzle 41 has a function of connecting one end to the furnace 11 and ejecting pulverized coal into the furnace 11, and the other end is connected to the mill 42 via a pipe. The mill 42 pulverizes the coal C into pulverized coal and has a function of conveying and supplying the pulverized coal to the fuel nozzle 41 by the conveying air A <b> 1 supplied via the conveying air blower 43. The shape, size, material, ejection direction, swirl strength, fuel density distribution, etc. of the fuel nozzle 41 are not particularly limited, but pulverized coal is ejected without obstruction to a desired position in the combustion region 11c in the furnace 11. Various forms that can be applied are applicable. However, it goes without saying that an ignition mechanism (not shown) for igniting the pulverized coal is provided at the tip of the nozzle, and a necessary device such as a slagging prevention device can be appropriately added.

  In addition, various aspects of the positional relationship between the combustion air nozzle 31 and the fuel nozzle 41 can be applied. In the present embodiment, the center of the combustion air nozzle 31 and the center of the fuel nozzle 41 are installed apart from each other. However, if the combustion air supplied from the combustion air nozzle 31 and the fuel supplied from the fuel nozzle 41 are arranged so that a reducing atmosphere can be formed in the vicinity of the flame F, their centers are coaxial. May be installed (coaxial nozzle) to reduce the installation area.

  The boiler device 10 controls the air temperature so that the combustion air A2 becomes equal to or higher than the necessary air temperature even if the coal type (volatile) of pulverized coal supplied to the furnace 11 and the operating load state change. A device 45 is provided. The control device 45 obtains data such as an air flow rate, an air temperature, and a coal supply amount from at least the air supply blower 32, the exhaust blower 22, the transfer air blower 43, the mill 42, the temperature sensor 31a, etc. It has a function to control. More specifically, the controller 45 calculates the temperature of the combustion air A2 supplied from the combustion air nozzle 31 by calculating and processing the fuel command such as the volatility of pulverized coal and the operation command information related to the operation load. (A temperature equal to or higher than the ignition temperature corresponding to the coal type, for example, 850 ° C.) is set, and a difference between the combustion air temperature data of the temperature sensor 31a and the set temperature is detected and the air supply is performed so that the difference becomes zero A function of setting and controlling the discharge pressure, flow rate, and the like of the blower 32 and the exhaust blower 22 is provided. Further, it also has a function of setting and controlling the discharge pressure, flow rate, etc. of the conveying air blower 43 or the amount of coal to be crushed in the mill 42 based on the operation command information and the operation state information.

Next, the operation of the boiler device 10 will be described.
First, in the mill 42, the coal C is pulverized to a desired average particle size to produce pulverized coal, and a necessary amount of pulverized coal is conveyed by the conveying air A1, and is fed from the fuel nozzle 41 into the high temperature reducing atmosphere of the combustion region 11c. Blow out and ignite to form a flame F and burn. At this time, a predetermined amount of high-temperature combustion air A2 determined by the pulverized coal supply amount is supplied from the combustion air nozzle 31. The amount of combustion air supplied at this time is appropriately adjusted, and the combustion air A2 flows around the flame F so as to wrap the flame F, so that a large amount of air is supplied in the vicinity of the ignition point F1 of the flame F. In the vicinity of the ignition point F1, oxygen is insufficient and a reducing atmosphere is maintained, and the generation of fuel NOx is suppressed. On the other hand, the combustion air temperature is high, and in addition to that, a high-temperature atmosphere near the ignition point F1 is maintained by the heating effect by the radiant heat of the later stage combustion, so that the pulverized coal fuel is a low-volatile coal type, for example. However, the combustible gas is sufficiently volatilized from the pulverized coal, the ignitability is maintained, and stable combustion continues without extinguishing the flame. Further, since the combustion air is filled around the flame F, unburned fuel is burnt completely by causing so-called post-stage combustion.

In addition to these, an optimum reducing atmosphere in the vicinity of the ignition point F1 can be achieved by adjusting the amount of conveying air A1 for conveying pulverized coal as necessary.
Water vapor having a desired property is generated in the water pipe 12 by heat radiation from the combustion flame F of the pulverized coal. At this time, since the temperature of the flame F itself is increased by high-temperature air combustion, the amount of heat transmitted to the water pipe 12 as radiant heat is larger than that of the conventional boiler, and high-temperature steam can be efficiently generated. . In addition, high-temperature air combustion generates, for example, high-temperature combustion exhaust gas EG of 1300 ° C. or higher. The combustion exhaust gas EG rises in the furnace 11 and comes into contact with the water pipe 12 so that water in the water pipe 12 or Gives heat to steam. At that time, the temperature of the combustion exhaust gas EG itself is lowered to about 900 ° C. and is discharged from the upper portion of the furnace 11. Here, the combustion exhaust gas EG temperature discharged from the furnace needs to be discharged while maintaining the combustion air at a temperature higher than the fuel ignition temperature in order to heat the combustion air to a temperature equal to or higher than the fuel ignition temperature. When the ignition temperature of the fuel is ˜800 ° C., the exhaust gas EG temperature to be discharged is made ˜900 ° C. Dust and the like are removed from the discharged combustion exhaust gas EG in the cyclone 14. Further, the combustion exhaust gas EG flows into the heat exchanger 21 and heats the low-temperature combustion air A2 supplied from the supply air blower 32 to, for example, 800 ° C. or higher. The combustion exhaust gas EG cooled by this heat exchange is discharged into the atmosphere through the exhaust blower 22, a combustion exhaust gas processing device such as a denitration device, and an exhaust pipe (not shown).

On the other hand, the heated combustion air A2 is ejected from the combustion air nozzle 31 into the furnace 11, and burns pulverized coal while maintaining the atmosphere in the vicinity of the flame F in a high temperature reducing atmosphere as described above.
Depending on the prior art, it is necessary to increase the combustion air at a maximum by nearly 10 to 20% at the time of low load operation as compared with the case of burning the same amount of pulverized coal at the time of full output operation. According to the boiler apparatus 10 according to the present invention, such an increase in combustion air is almost unnecessary, so that NOx reduction and energy efficiency can be improved.

  Further, as described above, the economizer and other devices and the storage space required for sufficiently recovering the thermal energy of the combustion exhaust gas in the conventional boiler are unnecessary and deleted in the boiler device 10. Has been. In addition, the combustion reaction is completed in a short time due to high-temperature air combustion, so that the required residence time of the pulverized coal in the furnace 11 is reduced, and the distance that the pulverized coal moves along the flow of the combustion exhaust gas during that time Since it decreases, the furnace part 11 volume can be reduced accordingly. Further, since the temperature of the combustion flame F is high, the efficiency of radiant heat transfer is improved, so that the water pipe 12 can be downsized and the upper portion of the furnace 11 that accommodates it can be downsized. Due to these three effects, the furnace 11 is more compact than the conventional boiler apparatus.

Although the description of the embodiment of the boiler device 10 according to the first embodiment of the present invention has been completed, it is needless to say that the first embodiment has various aspects. The example of the aspect concerning this is demonstrated below.
In the present embodiment, a cyclone is used as a dust removing means in the combustion exhaust gas, but as an alternative, a dust removing means for removing dust adhering to the heat exchanger 21 in the heat exchanger 21, for example, A soot blower that blows and removes dust by blowing water vapor or compressed air onto the adhering part, or a device that removes dust by dropping a steel ball and hitting the falling steel ball with a falling steel ball, or Alternatively, a device for removing dust by vibrating the entire heat exchanger may be installed. Alternatively, these dust removing means and dust removing means may be used in combination.

  In this embodiment, the heat exchanger, the cyclone connected to the heat exchanger, the combustion air supply means, and the fuel nozzle are set as one set. However, according to the rated capacity of the boiler device, the heat exchanger, the cyclone, Multiple combustion air supply means and fuel nozzles are installed, and the number of heat exchangers, cyclones, combustion air supply means and fuel nozzles that are actually operated by increasing or decreasing the operating load is increased or decreased, and the amount of combustion air or combustion The amount of fuel may be increased or decreased. It is possible to cope with fluctuations in operating load without changing the driving load of each group. Or, by changing the number of heat exchangers, cyclones, combustion air supply means and fuel nozzles of the same design, various furnaces with different capacities from small to large furnaces can be easily applied by applying a unified technical concept. Can be designed. In this case, the number of sets of heat exchangers, cyclones, combustion air supply means, and fuel nozzles may be increased or decreased, for example, one by one, and each device is not particularly used as a set. It may be increased or decreased individually.

  As shown in FIG. 2, combustion air may be supplied to the furnace 51 in two upper and lower stages. In this case, the lower nozzle (first combustion air nozzle) 52 is disposed in the vicinity of the fuel nozzle 54, and first, the amount of high-temperature combustion air supplied from the nozzle 52 is slightly reduced to perform strong reduction. An atmosphere is formed in the vicinity of the fuel nozzle 54 to achieve stable combustion at low NOx, and unburned fuel is supplied by high-temperature combustion air supplied from the upper stage side nozzle (second combustion air nozzle) 53. It can be efficiently burned under high temperature conditions.

  In this embodiment, one combustion air nozzle 31 and one fuel nozzle 41 are provided, but a plurality of them may be provided. The number of combustion air nozzles and fuel nozzles may be different, and a plurality of these nozzles may be arranged on a horizontal plane or arranged vertically on the furnace body. For example, as shown in the horizontal sectional view of the furnace of FIG. 3, a plurality of fuel nozzles 62 and a plurality of combustion air nozzles 63 (four each in FIG. 3) are installed on the opposite wall surfaces of the body of the furnace 61 so as to face each other. These nozzles may be arranged in a plurality of stages on the furnace body.

  As shown in FIG. 4, a plurality (four in FIG. 4) of fuel nozzles 64 and combustion air nozzles 65 are arranged so that the respective jet directions are horizontal and the tangential direction of the virtual circle 67 on the horizontal cross section of the furnace 66 is set. You may arrange | position so that it may face, and you may arrange | position so that the pulverized coal and the air for combustion may form a swirl flow. A fireball is formed on the virtual circle 67 along the swirl flow, so that more stable combustion can be continued.

  In this embodiment, a multi-tube heat exchanger (shell-and-tube type) is used as the heat exchange means, but a rotary heat storage heat exchanger or an alternating heat storage type exchanger may be used instead. In the case of heat exchange under a high temperature condition of 800 to 900 ° C., it is necessary to select a heat-resistant alloy that can withstand such a high temperature and a material having excellent heat conduction characteristics in a multi-tubular heat exchanger, and an expensive material is used. However, in the case of a heat storage type heat exchanger, an inexpensive heat exchange means can be provided because a heat storage material made of ceramics or the like that is inexpensive for heat exchange is used. Further, when using a rotary heat storage type heat exchanger, the same effect can be obtained by simply substituting the multi-tubular heat exchanger with a rotary heat storage type heat exchanger. On the other hand, when using an alternating heat storage heat exchanger, for example, as shown in FIG. 5, it is composed of two alternating heat storage heat exchangers 71 and 72 and two four-way valves 73 and 74, A heat exchange system in which one end of each of the heat exchangers 71 and 72 is connected to the four-way valve 73 and the other end of each of the heat exchangers 71 and 72 is connected to the four-way valve 74 can be used. Here, the other two ends of the four-way valve 73 are connected to a combustion air nozzle and a cyclone combustion exhaust gas outlet, and the other two ends of the four-way valve 74 are connected to an exhaust blower of combustion exhaust gas and combustion air. It connects to an air supply blower, and each can switch and connect to the heat exchangers 71 and 72. In the state of FIG. 5, the combustion air supply blower heat exchanger 71-combustion air nozzle is connected, and the cyclone outlet-heat exchanger 72-combustion exhaust gas exhaust blower is connected. The four-way valve 73 has a structure that can withstand particularly high temperatures. To explain the operation, combustion air is blown from the combustion air supply blower to the heat exchanger 71, and the air is heated to a predetermined temperature by the heated heat storage material in the heat exchanger 71. The air is blown to the nozzle and ejected into the furnace. On the other hand, the high-temperature combustion exhaust gas exiting the cyclone flows into the heat exchanger 72, heats the heat storage material in the heat exchanger 72, is cooled by itself, and is sent from the exhaust blower to the combustion exhaust gas processing device. When the heat storage material in the heat exchanger 71 loses heat due to the operation for a certain period of time, the four-way valves 73 and 74 are switched when the heat storage material in the heat exchanger 72 is sufficiently heated to supply combustion air. The air blower heat exchanger 72-combustion air nozzle and the cyclone outlet-heat exchanger 71-combustion exhaust gas exhaust blower are connected to perform the same operation. By repeating this, the combustion air using the combustion exhaust gas as a heat source can be heated.

  In this embodiment, the fuel is pulverized coal which is a solid fuel, but biomass fuel such as finely crushed wood chips may be used. In addition, sludge containing a large amount of moisture is ejected into the furnace by a pump instead of being transported by transporting air, the moisture is evaporated by high-temperature combustion air, and the dried sludge is further heated to combustible in the sludge. The components may be volatilized and burned. Depending on the prior art, for example, when burning sludge having a moisture content of about 60% or more, it is necessary to preheat and dry the sludge in advance or to take measures such as oil co-firing. There is no such need, and it is possible to burn (exclusively burn) sludge having a higher moisture content, for example, about 80%.

Next, a boiler apparatus 80 according to a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment, the carrier air A1 is used as the carrier gas for the pulverized coal. However, the boiler device 80 heats the high-temperature combustion air in the heat exchanger 82 and its temperature decreases. The later combustion exhaust gas EG is used as a carrier gas and an atmospheric gas when producing pulverized coal in a mill (mill apparatus) 85.

  More specifically, as shown in FIG. 6, the boiler device 80 is connected to the downstream side of the heat exchanger 82 in addition to or instead of the equipment of the boiler device 10 described in the first embodiment. A dust collector (dust collecting means) 83 and the combustion exhaust gas EG dedusted in the dust collector 83 are extracted and pumped to the mill 85, and the pulverized coal is mixed in the mill 85 to be fed from the fuel nozzle 87 to the furnace 81. And a control device 86 for controlling the transport air blower 84 and the like.

Since the system configuration other than the above, the function, shape, arrangement, and operational effects of each facility are the same as those in the first embodiment, description thereof will be omitted.
The operation of the boiler device 80 will be described below.
That is, a part of the combustion exhaust gas EG is extracted from the outlet of the dust collector 83 and supplied to the mill 85 by the carrier air blower 84 as an atmosphere gas at the time of producing the pulverized coal instead of the carrier air A1. Combustion exhaust gas EG has a low oxygen concentration, so there is little risk of unexpected pulverized coal combustion during pulverized coal production, and conditions such as temperature control to prevent the unexpected pulverized coal combustion should be relaxed And can be suitably used to maintain a reducing atmosphere due to lack of oxygen in the vicinity of the ignition point of the flame. At this time, since the temperature near the ignition point of the flame is maintained at a high temperature due to the presence of the high-temperature combustion air, it goes without saying that stable combustion is maintained even if the oxygen concentration in the carrier gas decreases.

In the present embodiment, since it is desirable that the gas used for conveying the pulverized coal does not contain dust, the combustion exhaust gas is extracted at the outlet of the dust collector 83. Thereafter, for example, the air may be extracted from any point of the combustion exhaust gas processing device such as an exhaust pipe (not shown).
In addition, embodiment described here is an example, Comprising: This invention is not limited only to this, It cannot be overemphasized that a change can be added in the range of the summary of this invention.

1 is a system diagram of a boiler apparatus according to a first embodiment of the present invention. It is a system diagram which shows the example of the combustion air nozzle for the two-stage combustion of another Example concerning this invention. It is a schematic horizontal sectional view of the furnace which shows the example of arrangement | positioning of the combustion air nozzle of another Example concerning this invention, and a fuel nozzle. It is a schematic horizontal sectional view of the furnace which shows the example of arrangement | positioning of the combustion air nozzle of another Example concerning this invention, and a fuel nozzle. It is a system diagram at the time of using a pair of alternating heat storage type heat exchanger as another Example concerning this invention. It is a system diagram of the boiler apparatus of the 2nd Example concerning the present invention.

Explanation of symbols

10, 80 Boiler unit 11, 51, 61, 66 Furnace 11c Combustion region 12 Water pipe 13 Exhaust pipe 14 Cyclone 21, 82 Heat exchanger 22 Exhaust blower 31, 63, 65 Combustion air nozzle 32 Supply air blower 41, 54, 62 , 64, 87 Fuel nozzle 42, 85 mil 43, 84 Air blower for conveyance 52 Lower nozzle 53 Upper nozzle 67 Virtual circle 83 Dust collector

Claims (15)

A furnace that injects fuel into a lower combustion region and burns it, and generates high-temperature water vapor by a water pipe disposed in the upper part;
Heat exchange means for heating the combustion air to a temperature equal to or higher than the ignition temperature of the fuel by using the high-temperature combustion exhaust gas discharged from the furnace as a heat source after generating the water vapor;
Combustion air supply means for ejecting the heated combustion air to the combustion region;
Fuel nozzle means for injecting the fuel into the combustion region to form a flame,
A boiler apparatus characterized in that a reducing atmosphere is formed in the vicinity of the flame by the combustion air supplied from the combustion air supply means and the fuel supplied from the fuel nozzle means.   The boiler apparatus according to claim 1, further comprising dust removing means for removing dust in the combustion exhaust gas and supplying the dust to the heat exchange means.   The boiler according to claim 1, comprising a plurality of the heat exchange means, and increasing or decreasing the amount of combustion air heated to a high temperature by heat exchange according to an increase or decrease in load or capacity of the boiler device. apparatus.   The boiler apparatus according to any one of claims 1 to 3, wherein a plurality of the combustion air supply means are provided, and the amount of combustion air is increased or decreased in accordance with increase or decrease in load or capacity of the boiler apparatus.   The boiler device according to any one of claims 1 to 4, wherein a plurality of the fuel nozzle means are provided, and the fuel ejection amount is increased / decreased in accordance with increase / decrease in load or capacity of the boiler device.   The combustion air supply means includes a first combustion air nozzle that is disposed in the vicinity of the fuel nozzle and ejects combustion air to form a reducing atmosphere in the vicinity of the flame. Item 6. The boiler device according to any one of Items 1 to 5.   The combustion air supply means has a second combustion air nozzle that is disposed on the downstream side of the flame of the first combustion air nozzle and jets combustion air to burn unburned fuel. The boiler device according to claim 6, wherein:   8. The fuel nozzle means and the combustion air supply means are arranged on each wall surface of the furnace facing each other, and the fuel nozzle and the combustion air nozzle on each wall face each other. The boiler apparatus in any one.   The fuel nozzle means and the combustion air supply means eject the fuel and combustion air in the tangential direction of a horizontal virtual circle in the furnace, respectively, and generate the swirl flow in the furnace while generating the solid fuel. The boiler device according to claim 1, wherein the boiler device is burned.   The boiler according to any one of claims 1 to 9, wherein the fuel is pulverized coal, and the combustion air is heated to 800 ° C or higher.   The boiler device according to any one of claims 1 to 10, wherein the heat exchange means is a multi-tube heat exchanger.   The boiler device according to any one of claims 1 to 10, wherein the heat exchange means is a regenerative heat exchanger.   The boiler apparatus according to any one of claims 1 to 12, wherein combustion exhaust gas from the furnace is used as a carrier gas, and the solid fuel is conveyed to the fuel nozzle by the carrier gas.   A mill device for crushing coal into pulverized coal is provided, and combustion exhaust gas from the furnace is used as an atmospheric gas, and the combustion exhaust gas is supplied to the mill device to produce pulverized coal, and the combustion exhaust gas is used as a carrier gas. The boiler apparatus according to any one of claims 1 to 13, wherein pulverized coal is conveyed from a mill apparatus to a fuel nozzle.   The boiler apparatus according to any one of claims 13 and 14, further comprising dust collecting means for removing ash in the combustion exhaust gas from the furnace.

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