JP2005265299A - Boiler device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler device capable of achieving stable low NOx combustion over a wide operation scope including a low load operation condition using various pulverized coal, sludge, biomass fuel or the like as fuel, realizing excellent and general energy efficiency, performing continuous operation easily, and reducing cost. <P>SOLUTION: This boiler device is provided with a furnace for injecting solid fuel into a combustion region in a lower part for combustion, a high temperature combustion oxidized gas generation means for generating high temperature combustion oxidized gas having such temperature that exceeds ignition temperature of solid fuel, a fuel nozzle for injecting solid fuel into the combustion region and forming flame, and a high temperature combustion oxidized gas supply means for injecting high temperature combustion oxidized gas into the combustion region to form reduction atmosphere in the combustion region in the vicinity of flame. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a boiler device capable of obtaining high-temperature steam by burning solid fuel such as pulverized coal, sludge, biomass fuel, etc., and exhaust gas including low-quality fuel and various fuels including low-load fuel The present invention relates to a boiler apparatus that is capable of reducing NOx in the interior and that is less likely to be clogged with dust in exhaust gas and that is excellent in economic efficiency.

Conventionally, in thermal power plants, boilers using pulverized coal as fuel have been known, but as problems of such pulverized coal combustion boilers, (1) a large amount of NOx generated centering on fuel NO is large. (2) The low volatile coal type has poor ignitability and 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. 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) Low NOx and stable combustion are possible over a wide operating range from low loads to high loads using various types of coal including low-volatility coal types as fuel.
(2) Also, improve the efficiency at low loads, especially reduce the internal ratio and improve the steam conditions (ensure the amount of high-temperature steam).
(3) The cost can be reduced by downsizing the apparatus.
(4) Since it is assumed that the conventional pulverized coal combustion boiler is modified to a high temperature combustion technology boiler, the modification work can be made as small as possible.
(5) A continuous operation for a long period of time can be performed without being hindered due to a failure of the movable part or a blockage caused by dust in the combustion exhaust gas.
(6) Applicable to low-quality fuels such as sludge and biomass, and capable of stable combustion.

The above will be described in detail below.
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 so-called fuel NO, and it is possible to reduce the generation of fuel NO from the furnace even by measures such as an exhaust gas recirculation method effective for thermal NOx. Since it is difficult, compared with the case where heavy oil or the like is used as fuel, this must be removed by a large denitration apparatus.
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 that blows the air (internal ratio increases), and the air is released into the atmosphere while being held in the air (a part of the combustion exhaust gas). The amount of heat that is wasted increases, and high-temperature steam cannot be secured efficiently, resulting in 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.

  Further, when the invention of Patent Document 1 is applied to a boiler apparatus as it is, a large apparatus for heating the combustion air to a high temperature is required, which tends to increase the cost. In particular, the conventional boiler apparatus is modified. In order to improve ignitability, a large-scale device for heating the combustion air was installed and a large-scale modification such as piping work around the furnace was necessary.

  When high-temperature air combustion technology is applied to boiler equipment, a heat exchanger is generally used as a means for generating oxidizing gas for high-temperature combustion, and the combustion exhaust gas temperature is as high as ˜900 ° C. Therefore, an alternating or rotary heat storage heat exchanger using a ceramic heat storage material is suitable. However, in the case of an alternating type, there is a movable part called a four-way switching valve, and in the case of a rotary type, a rotary heat accumulator itself that is exposed to high heat. Therefore, there is a possibility that the movable part breaks down and hinders continuous operation. . In addition, a large amount of dust is contained in the combustion exhaust gas, and the dust may block the heat exchanger and hinder continuous operation. As a countermeasure, a cyclone that removes dust in the combustion exhaust gas or In some cases, a dust removing means such as a soot blower that removes dust once adhered by blowing compressed air or steam is added.

In addition, from the viewpoint of environmental conservation, it is desirable to also burn sludge and biomass fuel that generate combustible gas by heating in the boiler device, but these also have high moisture content and poor ignitability, so they are burned in existing boilers. It is difficult to make it.
The present invention has been made in view of the above circumstances, and its purpose is to be able to use various pulverized coals with different coal types, sludge, biomass fuel, and other low-quality fuels, and to achieve a low-load operation state. To provide a boiler apparatus that generates a small amount of NOx over a wide operating range, includes stable combustion, is excellent in overall energy efficiency, can be easily continuously operated, and is low in cost. .

  In order to solve the above problems, according to the invention of claim 1, a furnace for injecting solid fuel into a lower combustion region and burning it, and extracting a part of combustion exhaust gas from the furnace and mixing it with combustion air A high-temperature combustion oxidizing gas generating means for generating a high-temperature combustion oxidizing gas having a temperature equal to or higher than the ignition temperature of the solid fuel, a fuel nozzle for injecting the solid fuel into the combustion region to form a flame, and the flame A boiler device is provided, comprising: a high-temperature combustion oxidizing gas supply means for injecting the high-temperature combustion oxidizing gas into the combustion region so as to form a reducing atmosphere in a nearby combustion region.

Here, the “solid fuel” includes solid fuel such as pulverized coal of various coal types, biomass fuel such as wood chips, and slurry fuel such as sludge.
“Combustion air” refers to air that does not contain combustion exhaust gas and is taken in from the atmosphere, and in that sense, is synonymous with “combustion air”.
The boiler device includes: air preheating means for preheating the combustion air to a temperature lower than that of the high temperature combustion oxidizing gas to generate combustion secondary air; and the second air for injecting the combustion secondary air into the combustion region. It is good also as providing a secondary air supply means (Claim 2).

The high-temperature combustion oxidizing gas generating means may be an air ejector that uses the combustion air as a working fluid (Claim 3), and exhaust gas that pressurizes and discharges high-temperature combustion exhaust gas extracted from the furnace. An air blower may be provided (claim 4). Further, the high-temperature combustion oxidizing gas generating means includes the exhaust fan that pressurizes and discharges the combustion exhaust gas, a flow rate adjustment valve that adjusts the flow rate of combustion air, and the exhaust gas discharged from the exhaust fan. Mixing means for mixing combustion exhaust gas and combustion air whose flow rate is adjusted by the flow rate adjustment valve may be provided (Claim 5), or a flow rate adjustment valve for adjusting the flow rate of combustion air; Combustion air whose flow rate is adjusted by the flow rate control valve and the combustion exhaust gas are mixed to generate high-temperature combustion oxidizing gas, and high-temperature combustion oxidizing gas from the mixing unit is sucked and pressurized and discharged. In addition, the high-temperature oxidizing gas supply means may be provided with an exhaust fan that can be supplied as an oxidizing gas for high-temperature combustion (claim 6).
The high-temperature combustion oxidizing gas generation means is discharged from the exhaust fan that pressurizes and discharges the combustion exhaust gas, a flow rate control valve that can adjust the flow rate of combustion air flowing inside, and the exhaust fan. The combustion exhaust gas may be mixed with combustion air whose flow rate is adjusted by the flow rate control valve, and may be provided with mixing means for supplying the high temperature oxidizing gas supply means as high temperature combustion oxidizing gas. 5) A flow rate adjustment valve capable of adjusting the flow rate of combustion air flowing inside, and the combustion air and the combustion exhaust gas adjusted in flow rate by the flow rate adjustment valve are simultaneously sucked in and pressurized and discharged. The high-temperature oxidant gas supply means may include an exhaust fan that can be supplied as an oxidant gas for high-temperature combustion (claim 6).

The fuel nozzle and the high temperature oxidizing gas supply means may be arranged such that the fuel ejection position of the fuel nozzle and the gas ejection position of the high temperature oxidizing gas supply means are separated from each other (Claim 7). The fuel ejection center and the gas ejection center of the high-temperature oxidizing gas supply means may be arranged coaxially with each other (claim 8).
The air ejection position of the secondary air supply means may be arranged farther away from the fuel ejection position of the fuel nozzle than the gas ejection position of the high-temperature oxidizing gas supply means (Claim 9). The high-temperature oxidizing gas supply means and the secondary air supply means are configured such that the fuel ejection center of the fuel nozzle, the gas ejection center of the high-temperature oxidation gas supply means, and the air ejection center of the secondary air supply means are coaxial with each other. In addition, the high-temperature oxidizing gas supply means and the secondary air supply means may be arranged in an annular shape outside the fuel nozzle (claim 10).

A post-stage high-temperature oxidant gas supply unit that ejects a part of the oxidant gas for high-temperature combustion may be provided in the combustion region downstream from the position where the high-temperature oxidant gas supply unit is disposed. The secondary air for combustion from the secondary air supply means may be jetted into a region (claim 12).
A post-stage fuel in which a part of the solid fuel is ejected to the combustion region downstream from the position where the high-temperature oxidizing gas supply means is disposed, and is mixed with the secondary air for combustion from the secondary air supply means and burned You may provide a nozzle and the air jet outlet of the back | latter stage secondary air supply means to which the said combustion secondary air is jetted in the said combustion area | region downstream from the arrangement position of this back | latter stage fuel nozzle.

  The fuel nozzle, the air jet nozzle of the secondary air supply means, and the gas jet nozzle of the high-temperature oxidizing gas supply means may be arranged to face each other on the wall surfaces of the furnace facing each other. Alternatively, the fuel and combustion air may be ejected in the tangential direction of a horizontal virtual circle in the furnace, and the solid fuel may be burned while generating a swirling flow in the furnace. Good (claim 15).

The air preheating means may preheat combustion air with exhaust gas from the furnace (claim 16).
In the boiler apparatus of the present invention, various solid fuels such as biomass fuel such as sludge and wood chips can be used. However, when pulverized coal is selected as the solid fuel, the oxidizing gas for high-temperature combustion is 800 ° C. or higher. It is desirable to heat to (Claim 17).

  The exhaust gas from the furnace may be used as a carrier gas, and the solid fuel may be transported to the fuel nozzle by the carrier gas (Claim 18). In addition, a mill device that pulverizes coal into pulverized coal is provided. The exhaust gas from the furnace may be an atmospheric gas, and the exhaust gas may be supplied to a mill device to produce pulverized coal (Claim 19). Dust for removing ash in the exhaust gas from the furnace It is preferable to further comprise a removing means (claim 20).

  The invention according to claim 21 is a furnace for injecting and burning solid fuel in a lower combustion region, a fuel nozzle for injecting the solid fuel into the combustion region to form a flame, and ignition of the solid fuel from the furnace High temperature combustion oxidizing gas extraction supply means for extracting a part of combustion exhaust gas having a temperature equal to or higher than the temperature and ejecting the combustion exhaust gas as a high temperature combustion oxidizing gas to the combustion region so as to form a reducing atmosphere in the combustion region near the flame And air preheating means for preheating combustion air to a temperature lower than that of the high temperature combustion oxidizing gas to generate combustion secondary air, and jetting the combustion secondary air to the combustion region in the wake of the flame Secondary air supply means.

The feature of the invention of claim 1 is that the high temperature combustion exhaust gas is directly mixed with the combustion air so that the high temperature combustion oxidizing gas above the ignition temperature of the fuel (800 ° C. or higher considering various pulverized coals) The purpose is to secure a wide operating range (preferably the entire range) from a low load to a high load, and to inject into the combustion region in the furnace to cause high-temperature air combustion.
That is, the pulverized coal ejected from the fuel nozzle is burned in the combustion region in the furnace to form a flame, and the combustion exhaust gas and combustion air partially extracted from the furnace by the high-temperature combustion oxidizing gas generating means Are mixed, and high-temperature combustion oxidizing gas having a temperature equal to or higher than the ignition temperature is generated. The high-temperature combustion oxidizing gas is ejected by the high-temperature oxidizing gas supply means so as to form a reducing atmosphere in the combustion region near the flame, and the combustion in the vicinity of the ignition point is changed to high-temperature and high-temperature air combustion in the reducing atmosphere.

The effects of the present invention having such a configuration include (1) the effect of high-temperature air combustion, and (2) the effect of mixing combustion exhaust gas and combustion air to generate oxidation gas for high-temperature combustion. First, the effect of high-temperature air combustion will be described.
First, in the vicinity of a flame generated by combustion in the boiler apparatus of the present invention, a high-temperature atmosphere is formed, and fuel (for example, pulverized coal) ejected from a fuel nozzle is exposed to high temperature to be thermally decomposed (volatile). Combustible gas is generated early. At this time, since the atmosphere is high temperature, even if the fuel is low volatile, volatilization is promoted and ignitability is improved and stable combustion can be performed. For this reason, it does not extinguish including the time of low load operation.

  In addition, since the ignitability is improved, the supply amount of the oxidizing gas for high-temperature combustion is appropriately adjusted so that the atmosphere in the vicinity of the flame is always kept in a high-temperature reducing atmosphere without extinguishing the flame. The above stable combustion is possible in a wide operating range up to high load operation. As the effect of such reducing atmosphere combustion, the generation of fuel NOx due to the early oxidation of the nitrogen component contained in the fuel is suppressed, so the amount of NOx generated from the boiler device 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.

In addition to these, sludge and biomass fuel containing a large amount of moisture can be instantly dried, volatilized and burned in the furnace due to the heating effect of the oxidizing gas for high-temperature combustion.
Next, the effect obtained by mixing the high-temperature combustion exhaust gas directly with the combustion air will be described below.
First, since a part of the combustion exhaust gas is returned to the furnace and exposed to a high-temperature, reducing atmosphere flame, NOx contained in the combustion exhaust gas is reduced, and the NOx reduction effect is further improved as a whole. Promoted.

Second, since the oxygen concentration in the high-temperature combustion oxidizing gas generated by mixing the combustion exhaust gas with air is lower than the oxygen concentration in the air, it is easier to achieve a reducing atmosphere and further reduce NOx. effective.
As a third effect, since no heat exchanging means is required, a movable part that is likely to cause a failure (for example, a four-way valve of an alternating heat storage type heat exchanger), particularly a high-temperature movable part (for example, There is no rotary heat storage body of the rotary heat storage type heat exchanger), and accordingly, continuous operation can be easily performed with less occurrence of failure.

Furthermore, since high-temperature combustion air is produced by simple mixing rather than heat exchange means, there are few narrow parts that tend to be clogged with dust, such as a large number of thin pipes in a heat exchanger or a heat storage body with a honeycomb structure. In terms of structure, there is little occurrence of blockage due to dust, and continuous operation can be easily performed.
As a result, a device for removing dust from combustion exhaust gas such as a cyclone and equipment for removing dust once attached are not required.

Note that the combustion air may be mixed with the high-temperature combustion exhaust gas in this way to generate the high-temperature combustion oxidizing gas at or above the ignition temperature. However, all or part of the combustion air is preheated before mixing. May be.
The invention according to claim 2 is provided with an air preheating means for preheating a part of the combustion air to not more than the ignition temperature of the fuel, for example, to about 300 to 350 ° C., and the preheated combustion air (two combustion airs). Secondary air) is supplied to the rear of the flame by the secondary air supply means. The feature is to ensure the ignitability in a high temperature and reducing atmosphere with the minimum amount of oxidizing gas for high temperature combustion and high temperature combustion. The purpose is to reduce the size / optimization of equipment and the like related to the oxidizing gas generating means. As a result, the present invention has the following effects.

  As described above, a high temperature reducing atmosphere is formed in the flame combustion region, and stable low NOx combustion is realized. In this high-temperature reducing atmosphere, the combustion is not completed with only the high-temperature combustion oxidizing gas, but the above ignition quality is improved. In other words, a stable fire type (pre-stage combustion) is created, and the secondary combustion air is formed in the rear stage. (Solid fuel ignition temperature or less) is supplied to cause subsequent combustion to complete the combustion. Although the temperature of the secondary combustion air is not high, the combustion reaction has already progressed by the high-temperature combustion oxidizing gas in the pre-combustion stage, partly as unburned fuel, and part of the combustion is not completed As intermediate reaction species including active species, the remainder reaches the subsequent combustion region as burned gas, and can immediately react with the secondary air for combustion. Therefore, a high-temperature atmosphere is achieved over the entire combustion flame including the post-stage combustion region, and stable combustion continues even in the post-combustion stage. That is, the entire combustion can be made stable high-temperature air combustion only with the minimum amount of the oxidizing gas for high-temperature combustion necessary for the pre-stage combustion, so that the NOx generation amount can be reduced over the entire combustion.

  Secondly, when low volatile coal types are used as fuel or during low load operation, combustion air is usually used to compensate for combustion instability due to a decrease in ignitability and a decrease in furnace temperature. An increase in volume is required. However, according to the present invention, when a low-volatile coal type is used as a fuel or during low-load operation, the supply ratio of the combustion secondary air is appropriately reduced and the high-temperature combustion oxidizing gas is reduced accordingly. By appropriately increasing the supply ratio, the atmosphere near the ignition point can be easily maintained above the ignition temperature to maintain stable combustion, and the total of fuel, secondary air for combustion, and oxidizing gas for high-temperature combustion (total The ratio (air ratio) to the combustion air amount) can be kept constant regardless of the type of coal and the operation output. This eliminates the increase in exhaust fan power accompanying the increase in the total amount of combustion air, and the increase in the amount of heat dissipated in the atmosphere accompanying the exhaust gas (including the air not used for combustion). be able to. That is, it is possible to prevent a decrease in the overall energy efficiency even when any fuel is used or during a low load operation.

Thirdly, in the present invention, it is not necessary to set a large amount of combustion air at a high temperature, so that the equipment for that purpose can be miniaturized. This feature is particularly advantageous when the present invention is applied by adding equipment for supplying high temperature combustion oxidizing gas by remodeling a conventional boiler, and the scale of remodeling is reduced by utilizing most of the existing equipment as it is. It is important because it can be done.
According to the invention of claim 3, the high-temperature oxidizing gas generating means preferably includes an air ejector that uses combustion air as a working fluid. Therefore, since the structure is simple and there are no moving parts, there is almost no failure. A part of the high-temperature combustion exhaust gas is easily extracted from the furnace by the air ejector, and mixed with the combustion air that also acts as a working fluid in the air ejector to generate an oxidation gas for high-temperature combustion. be able to.

According to the invention of claim 4, the high-temperature oxidizing gas generating means preferably pressurizes and discharges the high-temperature combustion exhaust gas extracted from the furnace and supplies it to the high-temperature oxidizing gas supply means as high-temperature combustion oxidizing gas. Therefore, a part of the high-temperature combustion exhaust gas can be extracted easily from the furnace and supplied as the oxidizing gas for high-temperature combustion.
Preferably, the high-temperature combustion oxidant gas generating means includes an exhaust fan that pressurizes and discharges combustion exhaust gas, a flow rate control valve that adjusts a flow rate of combustion air, and the combustion exhaust discharged from the exhaust fan. If the mixing means for mixing the gas and the combustion air whose flow rate is adjusted by the flow rate control valve is provided with the combustion air combustion air (Claim 5), the combustion exhaust gas discharged from the exhaust fan, and the combustion The high-temperature combustion oxidizing gas can be generated by mixing the working air with the mixing ratio thereof with the flow rate control valve and supplied to the high-temperature oxidizing gas supply means. Alternatively, a flow rate adjusting valve that adjusts the flow rate of the combustion air, and a mixing means that mixes the combustion air flow-adjusted by the flow rate adjusting valve and the combustion exhaust gas to generate a high-temperature combustion oxidizing gas; The same effect can be obtained even if the high-temperature combustion oxidizing gas from the mixing means is sucked and pressurized and discharged, and the high-temperature oxidizing gas supply means is provided with exhaust air for combustion that can be supplied as high-temperature combustion oxidizing gas. (Claim 6).

  The nozzle positions of the fuel nozzle and the high-temperature oxidizing gas supply means can be arranged apart from each other (Claim 7), or can be arranged coaxially with each other (Claim 8). By supplying high-temperature combustion oxidizing gas that exceeds the ignition temperature of the fuel, the degree of freedom in boiler design is improved, and consideration is given to the positional relationship with the arrangement space and the mechanism for supplying fuel and high-temperature oxidizing gas. Optimal arrangement is possible.

  Moreover, the supply of the secondary air for combustion to the post-stage combustion region as described above can be made closer to the fuel nozzle side as necessary, but in any case, as in the invention of claim 9, The air ejection position of the secondary air supply means is arranged farther away from the gas ejection position of the high temperature oxidizing gas supply means with respect to the fuel ejection position of the fuel nozzle, or the fuel nozzle, The high-temperature oxidizing gas supply means and the secondary air supply means are arranged such that the fuel ejection center of the fuel nozzle, the gas ejection center of the high-temperature oxidation gas supply means, and the air ejection center of the secondary air supply means are coaxial with each other. It is necessary to arrange the high-temperature oxidizing gas supply means and the secondary air supply means in an annular form outside the nozzle in this order. First, the high-temperature combustion oxidizing gas contacts the combustion flame at the tip of the fuel nozzle, and the ignition point Previous to neighborhood Along with forming the high-temperature reducing atmosphere, the combustion secondary air is supplied from the surrounding combustion flame, it is possible to complete the combustion.

  Furthermore, by providing a post-stage high-temperature oxidizing gas supply means for injecting a part of the high-temperature combustion oxidizing gas to the downstream combustion region from the position where the high-temperature oxidizing gas supply means is disposed, if necessary (claim 11). Or, if necessary, the combustion secondary air from the secondary air supply means is jetted into the combustion region (claim 12), and in the pre-stage combustion, it is not burned because it is burned in a reducing atmosphere. Combustion fuel can be burned to complete the entire combustion.

  Further, if necessary, the latter stage fuel in which a part of the solid fuel is ejected from the position where the high temperature oxidizing gas supply means is disposed to the downstream combustion region and is mixed with the secondary air for combustion from the secondary air supply means and burned. A nozzle, and an air outlet of a downstream secondary air supply means for injecting the secondary air for combustion into the combustion region downstream from the position where the downstream fuel nozzle is disposed (Claim 13); Fuel can be supplied to the extension of the high-temperature and powerful reducing atmosphere formed in the vicinity of the flame ignition point of the latter-stage fuel nozzle and burned with the secondary air for combustion. Since it is a reducing atmosphere, NOx generation is suppressed, and the generated NOx is reduced, so that stable low NOx combustion can be realized as a whole. In the combustion in the vicinity of the rear stage fuel nozzle, unburned fuel is combusted by the secondary air for combustion supplied from the outlet of the secondary air supply means installed further downstream of the rear stage fuel nozzle to complete the combustion. .

  Stable combustion near the center of the furnace by disposing the fuel nozzle, the air injection nozzle of the secondary air supply means, and the gas injection nozzle of the high-temperature oxidizing gas supply means opposite to each other on each wall of the furnace facing each other The fuel nozzle means and the combustion air supply means jet the fuel and the combustion air in the tangential direction of a horizontal virtual circle in the furnace, respectively. It is also possible to improve the combustion stability by arranging the solid fuel to burn while generating a swirling flow in the furnace, thereby forming a stable combustion zone at the center of the boiler. (Claim 15).

In the invention of claim 16, preferably, the combustion air is preheated by the exhaust gas from the furnace as the air preheating means. Therefore, the amount of heat dissipated in the atmosphere is reduced by effectively using the heat amount of the exhaust gas. It is possible to improve energy efficiency and prevent generation of costs such as preheating equipment such as a burner and fuel.
The present invention is applicable to various solid fuels, and may be biomass fuel such as wood chips, sludge, etc., but when the solid fuel is pulverized coal as in the invention of claim 17, it is for high temperature combustion. Stable combustion can be ensured by heating the oxidizing gas preferably to 800 ° C. or higher.

  According to the invention of claim 18, preferably, the exhaust gas from the furnace is used as a carrier gas, and the solid fuel is carried to the fuel nozzle by the carrier gas. The oxygen concentration of the air jetted into the combustion region of the gas is reduced, 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. Another effect of lowering the oxygen concentration in the carrier air is to reduce the possibility of unintended ignition of activated pulverized coal, and to ease conditions such as temperature control to prevent such ignition. it can.

  In addition to the invention of claim 18, the invention of claim 19 is provided with a mill device for pulverizing coal into pulverized coal, using the exhaust gas from the furnace as the atmospheric gas, and supplying the exhaust gas to the mill device. Therefore, pulverized coal is produced not in a normal air atmosphere with a high oxygen concentration but in a combustion exhaust gas atmosphere with a low oxygen concentration. For this reason, the possibility of unintended ignition of the activated pulverized coal can be reduced, and conditions such as temperature control for preventing such ignition can be relaxed. In any of the inventions of claims 18 and 19, by providing dust removing means for removing ash in the exhaust gas, it is possible to prevent a large amount of dust or the like from being mixed and clogged during transportation. (Claim 20).

  The invention of claim 21 does not generate high-temperature combustion oxidizing gas by mixing combustion air and combustion exhaust gas, but supplies only the combustion exhaust gas in the vicinity of the fuel nozzle and remains in the combustion exhaust gas. A high temperature reducing atmosphere is formed in the vicinity of the flame with only about 12% oxygen to perform the pre-stage combustion, and new air is exclusively supplied to the post-combustion stage as secondary combustion air. .

  That is, solid fuel is ejected from the fuel nozzle into the combustion region of the furnace to form a flame, and a part of the combustion exhaust gas having a temperature equal to or higher than the ignition temperature of the solid fuel is discharged from the furnace by the oxidizing gas extraction supply means for high temperature combustion. Bleeding is performed so as to form a reducing atmosphere in the combustion region near the flame, and a high-temperature reducing atmosphere is formed in the vicinity of the fuel nozzle to perform pre-stage combustion by high-temperature air combustion. On the other hand, since the secondary air for combustion preheated by the air preheating means is jetted to the downstream of the flame by the secondary air supply means, the unburned fuel is burned as post-stage combustion to complete the combustion. Thereby, the combustion exhaust gas amount as the whole furnace can be reduced, and exhaust fan power can be reduced.

Hereinafter, embodiments of the boiler device according to the present invention will be described with reference to various examples.
First, a first embodiment of the present invention will be described with reference to FIG. The boiler apparatus 1 according to the first embodiment uses a furnace 10 for burning pulverized coal (solid fuel) and a combustion air BA supplied by an air supply blower 28 as working fluid from the furnace 10 through an extraction pipe 25. The air ejector 27 (high-temperature oxidant gas generating means) which sucks and bleeds the high-temperature combustion exhaust gas EG2 and mixes the exhaust gas EG2 and the combustion air BA to form, for example, a high-temperature combustion oxidant gas BG of 800 ° C. or higher. ), A high-temperature oxidizing gas nozzle (high-temperature oxidizing gas supply means) 26 for injecting the gas BG into the combustion region 10a of the furnace 10, a fuel nozzle 31 for injecting pulverized coal fuel into the combustion region 10a to form a flame, and combustion Air preheater 22 (air preheating means) that preheats the combustion air BA to make the combustion secondary air BA1 and a secondary air nozzle (secondary) that ejects the combustion secondary air BA1 to the combustion region 10a It has an air supply means) 21, and the like.

  The furnace 10 is provided with a fuel nozzle 31 and the like at the bottom to form a combustion region 10a, and a furnace body 11 having a radiation heat transfer region 10b formed mainly facing the combustion region 10a at the top, and radiation heat transfer. A box-shaped convection heat transfer section 12 and the like are provided adjacent to the area 10b, and the combustion exhaust gas EG having a lowered temperature passing through the radiant heat transfer area 10b flows downward. A plurality of fuel nozzles 31 and a plurality of high-temperature air nozzles 26 are opened close to the lower end of the side wall of the furnace body 11, and a plurality of secondary air nozzles 21 are opened slightly above the side wall of the furnace body 11. ing. The positional relationship between these nozzles will be described later.

  One end of an extraction pipe 25 for extracting the high-temperature combustion exhaust gas EG2 from the furnace 10 is disposed on the upper side wall in the vicinity of the top of the furnace body 11, and the other end is connected to the suction portion of the air ejector 27. Yes. Although the opening position of the extraction pipe 25 is after steam generation and overheating, the high-temperature combustion oxidizing gas BG is not less than the ignition temperature of pulverized coal (solid fuel) by mixing (ignition of the majority of coal types). In order to reduce the unburned pulverized coal contained in the combustion exhaust gas EG2 at a position where the combustion exhaust gas EG2 can be extracted at a temperature (for example, 900 ° C. or more) considering the temperature. In order to ensure a sufficient residence time, the position is separated from the fuel nozzle 31 to some extent and is upstream of the convection heat transfer section 12 and has no temperature drop due to convection heat transfer.

At the bottom of the convection heat transfer section 12, there is an exhaust port 13 for exhaust gas EG1 that has lost its heat quantity due to the generation and overheating of water vapor, for example, the temperature has dropped to about 400 ° C., and the exhaust port 13 is a denitration device 14, an air preheater. It is connected to an exhaust gas treatment facility (not shown) via 22 or the like.
The air ejector 27 ejects the combustion air BA from the nozzles in the air ejector at high speed to form a negative pressure, and sucks the high-temperature combustion exhaust gas EG2 through the extraction pipe 25 by the negative pressure. Although the air BA and the combustion exhaust gas EG2 are mixed to generate and discharge the high temperature combustion oxidizing gas BG, the air ejector itself is a well-known one, and detailed description thereof is omitted. .

The high-temperature combustion oxidizing gas outlet 27a of the air ejector 27 is connected to the high-temperature oxidizing gas nozzle 26 via a pipe, and the high-temperature oxidizing gas nozzle 26 opens into the furnace body 11 as described above to supply the high-temperature combustion oxidizing gas BG. It has a function of giving a swirl of an appropriate strength in an appropriate direction and ejecting it to the combustion region 10 a of the furnace body 11.
The high-temperature oxidizing gas nozzle 26 can employ various shapes that can eject the high-temperature combustion oxidizing gas BG to the combustion region 10a.

  The fuel nozzle 31 is attached to the furnace body 11 so as to face the combustion region 10a, and has a function of ejecting pulverized coal conveyed from a mill 32 described later to the combustion region 10a. The mill 32 has a function of pulverizing the coal C into pulverized coal, and feeding the pulverized coal to the fuel nozzle 31 by feeding the pulverized coal with the transfer air A <b> 1 supplied via the transfer air blower 33. The shape, size, material, ejection direction, swirl strength, and density distribution of the ejected fuel are not particularly limited, but pulverized coal may be used as a desired position in the combustion region 10a in the furnace body 11. Various types that can be ejected without blocking can be employed. 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 the vicinity of the lower end of the furnace 10 side wall, the fuel nozzle 31 and the high-temperature oxidizing gas nozzle 26 are opened close to each other as described above, but the secondary air nozzle 21 is opened slightly above the furnace side wall. The secondary air nozzle 21 can adopt various types in which the combustion secondary air BA1 is jetted into the combustion region 10a by giving a swirl of strength in an appropriate direction.
The positional relationship among the secondary air nozzle 21, the high temperature oxidizing gas nozzle 26 and the fuel nozzle 31 is set as follows. That is, only the high temperature combustion oxidizing gas EG2 flows in the vicinity of the ignition point near the tip of the fuel nozzle 31 to maintain the vicinity of the ignition point in a high temperature atmosphere, and the combustion secondary air BA1 flows to the downstream side of the combustion flame F. The combustion air necessary for burning the unburned fuel (after combustion) is supplied, and the fuel is set at a position where the combustion is completed. In order to achieve the above state, considering the arrangement of each nozzle including the distance between each nozzle, the amount of fuel, the oxidizing gas for high-temperature combustion, the amount of secondary air for combustion, the speed and direction of injection, etc. Although various modes can be adopted, it is desirable to arrange the high-temperature oxidizing gas nozzle 26 in the vicinity of the fuel nozzle 31 and to arrange the secondary air nozzle 21 on the downstream side of the flame F when viewed from the position of the fuel amount nozzle 31. In the present embodiment, as shown in FIG. 1, the plurality of high-temperature oxidant gas nozzles 26 are slightly upwardly directed close to the lower sides of the plurality of fuel nozzles 31 installed perpendicularly to the wall surface of the furnace body 11, and the ignition point F1 of the flame F is slightly upward. The fuel nozzle 31 and the secondary air nozzle 21 are located on the upper side of the fuel nozzle 31 (that is, on the downstream side of the fuel nozzle 31), and the distance between the fuel nozzle 31 and the secondary air nozzle 21 is larger than the distance between the fuel nozzle 31 and the high-temperature oxidizing gas nozzle 26. A plurality of secondary air nozzles 21 are arranged corresponding to the fuel nozzles 31 respectively. As described above, the fuel nozzle 31, the high-temperature oxidizing gas nozzle 26, and the secondary air nozzle are distributed in the vertical direction of the furnace body 11 (downstream and upstream along the flow of combustion exhaust gas), FIG. 2 which is an AA arrow view of FIG. 1 shows the arrangement on the plane. As shown in FIG. 2, for example, two sets of the high-temperature oxidizing gas nozzle 26, the fuel nozzle 31, and the secondary air nozzle 21 are installed on each wall surface so as to face each other on the wall surfaces facing each other. Is done. However, since the high-temperature oxidizing gas nozzle 26 and the fuel nozzle 31 are located below the secondary air nozzle 21, they are overlapped in FIG.

  The air preheater 22 is the remaining combustion exhaust gas generated by combustion and not extracted from the extraction pipe 25, and generates water vapor through the radiant heat transfer region 10 b and the convection heat transfer unit 12 in the furnace 10. The fuel is recovered by heat, and the temperature is reduced to, for example, about 400 ° C., and the combustion supplied by the supply blower 23 using the exhaust gas EG1 discharged from the exhaust port 13 at the bottom of the convection heat transfer unit 12 as a heat source. It has a function to preheat the working air BA to 300-350 ° C. The air preheater 22 is connected to the exhaust port 13 via the denitration device 14, and the exhaust gas preheated with the combustion air BA in the air preheater 22 is blown to an exhaust gas treatment facility (not shown). ing. Since the air preheater 22 and the air supply blower 23 for supplying air to the air preheater 22 are well known, the description thereof is omitted here.

  In the boiler apparatus 1, even if the volatility of the pulverized coal supplied to the furnace body 11 and the operating load state change, the oxidation gas BG for high-temperature combustion requires the necessary air temperature (above the ignition temperature of the pulverized coal: for example, 800 ° C.). The combustion exhaust gas EG2 bleed flow rate, the high temperature combustion oxidation gas BG, and the combustion secondary air BA1 so that appropriate amounts of the high temperature combustion oxidation gas BG and the combustion secondary air BA1 required for combustion are supplied. The control apparatus 35 which adjusts the flow volume of is provided. The control device 35 has a function of obtaining data such as an air flow rate and a coal supply amount from at least the air supply blowers 23 and 28 and simultaneously controlling these operating states. More specifically, the control device 35 performs arithmetic processing on the fuel command such as volatility of pulverized coal and the operation command information related to the operation load, which are separately input, and the high temperature combustion oxidizing gas BG and the combustion secondary air BA1. A function of setting and controlling the discharge pressure and flow rate of the air supply blowers 23 and 28 by appropriately setting the flow rate is provided.

Here, the control device 35 increases the ratio of the high-temperature combustion oxidizing gas BG amount as the volatility of the pulverized coal is lower or the operation output (load) is lower than the rated output. By reducing the ratio of the amount of secondary air BA1, the ratio of the total amount of combustion air to the amount of fuel burned (air ratio) will be constant regardless of the coal type (volatile) and operating output of pulverized coal To control.
Further, it also has a function of setting and controlling the discharge pressure, flow rate, etc. of the air blower 33 for conveyance or the amount of coal to be crushed in the mill 32 based on the operation state information.

The boiler apparatus 1 includes a water pipe for generating water vapor, a superheater for superheating water vapor, an economizer for removing heat from the exhaust gas, and the like. Since there is no place to replace the device, illustration and description are omitted here.
Next, the operation of the boiler device 1 will be described.
Depending on the boiler apparatus 1, the combustion exhaust gas EG <b> 2 generated and extracted in the furnace 10 and the combustion air BA are mixed in the air ejector 27 to form a high-temperature reducing atmosphere in the vicinity of the ignition point of the flame F. A minimum amount of high-temperature combustion oxidizing gas BG necessary for high-temperature air combustion in the front stage is generated and supplied to the furnace 10 through the high-temperature oxidizing gas nozzle 26, and air required for the rear stage combustion is preheated by the air preheater 22. The secondary air nozzle 21 is supplied as the secondary combustion air BA1.

  Therefore, only a part of the oxidizing gas necessary for combustion is heated to a high temperature (for example, 800 ° C.), and a high-temperature reducing atmosphere is formed in the vicinity of the flame (near the ignition point). First, stable low NOx combustion is achieved in the entire combustion including the subsequent combustion. Moreover, the NOx reduction effect by recirculation that the combustion exhaust gas once extracted outside the furnace 10 is again exposed to a high-temperature reducing atmosphere in the furnace 10 to reduce NOx in the combustion exhaust gas also occurs.

Furthermore, since only a part of the oxidizing gas necessary for combustion needs to be heated, miniaturization / optimization of the air ejector 27 and the like is achieved.
Further, since the high-temperature oxidizing gas generating means is composed only of static equipment having a simple structure such as the air ejector 27 (there is no movable part such as a rotating part that is likely to cause a failure), the operation is stopped due to the failure. Therefore, when the combustion air is heated by the heat effector to generate the high temperature combustion oxidizing gas, a dust removing means such as a cyclone is also unnecessary.

  This will be described in more detail below. High-temperature (for example, 1,300 ° C.) combustion exhaust gas EG is generated by combustion of pulverized coal ejected from the fuel nozzle 31 of the boiler apparatus 1. A part of the combustion exhaust gas EG is extracted through the extraction pipe 25 by the suction action of the air ejector 27 using the combustion air BA supplied from the supply air blower 28 as a working fluid, and is heated at a high temperature (for example, 900 ° C.). The combustion exhaust gas EG2 flows into the air ejector 27, and the combustion exhaust gas EG2 is mixed with the combustion air BA that is also the working fluid to generate the high-temperature combustion oxidation gas BG. The high temperature combustion oxidizing gas BG generated in this way is ejected from the high temperature oxidizing gas nozzle 26 to the vicinity of the flame F formed in the vicinity of the fuel nozzle 31. As a cooperative action by the combustion of the air BG and the pulverized coal ejected from the fuel nozzle 31, a high-temperature reducing atmosphere is formed in the vicinity of the ignition point F1 of the flame F. Further, since the pulverized coal carrier air A1 is also ejected from the fuel nozzle 31, the amount of air is also adjusted as necessary to form an optimum high-temperature reducing atmosphere.

  At this time, in the boiler apparatus 1, the combustion is not performed by the high-temperature combustion oxidizing gas BG, but the combustion secondary air BA <b> 1 is supplied to the subsequent combustion, so the high-temperature combustion supplied from the high-temperature oxidizing gas nozzle 26. The amount of oxygen contained in the oxidizing gas BG for use is smaller than the amount of oxygen required for the entire combustion. For this reason, first, in the pre-stage combustion that occurs in the high-temperature reducing atmosphere formed in the vicinity of the ignition point F1 of the flame F, the generation of NOx is suppressed and the flame is extinguished even when the low-volatile coal type is fuel. And stable combustion continues.

  The upper part (rear stream) of the flame F is filled with the secondary air BA1 which is abundantly burned in the furnace body 11 from the secondary air nozzle 21 but is abundantly low. By supplying the secondary air BA1, unburned fuel is first burnt and burnt completely, and combustion is completed. In this way, stable low NOx combustion is realized over the entire combustion including the subsequent combustion.

  The secondary combustion air BA1 is generated by preheating the combustion air BA supplied from the supply air blower 23 to about 300 to 350 ° C. in the air preheater 22 using the exhaust gas EG1 as a heat source. . Further, the exhaust gas EG1 is the remaining combustion exhaust gas that has not been extracted as the above-described high-temperature combustion exhaust gas EG2 among the high-temperature combustion exhaust gas EG generated by the combustion in the furnace 10, When passing through the radiant heat transfer region 10b and the convection heat transfer unit 12, steam is generated and heated by heat exchange, and the temperature drops to about 400 ° C., for example, and is discharged from the exhaust port 13 to the outside of the furnace 10. Then, it flows into the air preheater 22 through the denitration device 14.

  Note that the amount of high-temperature combustion oxidizing gas produced is appropriately adjusted by adjusting the amount of combustion air BA supplied to the air ejector 27 and adjusting the amount of combustion exhaust gas EG2 sucked. At this time, by changing the amount of combustion air BA, the ratio of the amount of combustion air BA and the amount of combustion exhaust gas EG2 also changes to some extent, so the temperature of the high-temperature combustion oxidizing gas can also be adjusted.

In the boiler apparatus 1, since the fuel nozzle 31, the high-temperature oxidizing gas nozzle 26 and the secondary air nozzle 21 are all opposed to each other as described above, the flames F face each other in the furnace body 11. Therefore, a particularly stable combustion region is secured near the center of the furnace body 11, and stable low NOx combustion continues.
Furthermore, the boiler device 1 according to the present embodiment has the following further effects. That is, when the present technology is applied to an existing pulverized coal fired boiler, only the extraction pipe 25, the air ejector 27, the high-temperature oxidant gas nozzle 26, etc., which are means for generating and supplying the high-temperature combustion oxidant gas into the furnace, are provided. What is necessary is just to add by remodeling work, and high-temperature air combustion can be achieved only by modifying a part of existing fuel supply equipment and secondary air supply equipment.

Moreover, in this boiler apparatus 1, since combustion reaction time is shortened by high temperature of combustion, the residence time of pulverized coal in the furnace 10 can be shortened, and pulverized coal moves with combustion exhaust gas in the meantime. Therefore, the entire boiler apparatus 1 including the furnace 10 can be made compact.
Although the description of the boiler device 1 of the first embodiment according to the present invention is finished as described above, it is needless to say that the boiler device 1 has various modes, and other modes of the first embodiment according to the following. Will be explained.

  In the present embodiment, with respect to the arrangement of the fuel nozzles and the like, for example, only one stage of the fuel nozzle 31 is installed in the vertical direction, but a plurality of stages of fuel nozzles 31 may be arranged in the vertical direction. Further, in the present embodiment, all the nozzles are disposed apart from each other, but the centers of the fuel nozzle 31 and the high temperature oxidizing gas nozzle 26 may be arranged coaxially, and further, the fuel nozzle 31 and the high temperature oxidizing gas nozzle 26 are arranged. The centers of the secondary air nozzles 21 are coaxial with each other, and the high-temperature oxidizing gas nozzle 26 and the secondary air nozzle 21 are arranged annularly in this order around the fuel nozzle 31 (that is, a coaxial nozzle). May be reduced.

  In this embodiment, a high-temperature combustion exhaust gas extraction pipe 25 is installed on the downstream side of the combustion exhaust gas from a superheater, a water pipe, etc., and the combustion exhaust gas for generating high-temperature combustion air also generates water vapor. It was decided to contribute to overheating. However, the opening position of the extraction pipe 25 to the furnace 10 is a position where the high-temperature combustion oxidizing gas BG can be extracted by mixing the combustion exhaust gas EG2 having a temperature that can be made higher than the ignition temperature of pulverized coal (solid fuel). There is no particular limitation as long as it is separated from the fuel nozzle 31 to some extent so that a sufficient residence time can be secured to reduce the unburned pulverized coal contained in the combustion exhaust gas EG2.

  In the present embodiment, the flow rate adjustment of the combustion exhaust gas EG2 is based on the flow rate of the combustion air BA supplied as the working fluid from the supply blower 28 to the air ejector 27. May be installed in the extraction pipe 25. High-temperature combustion is achieved by adjusting the amount of combustion air BA by adjusting the discharge flow rate and pressure of the supply air blower, and adjusting the amount of combustion exhaust gas sucked into the combustion air BA by adjusting the pressure loss of the orifice. It is possible to easily and independently adjust the temperature of the oxidizing gas for high-temperature combustion by changing the ratio between the amount of oxidizing gas produced and the amount of combustion air BA and the amount of combustion exhaust gas EG2.

  In this embodiment, an extraction system using an air ejector is employed as the oxidizing gas generating means for high-temperature combustion. As an alternative technique, as shown in FIG. 3, for example, connection ports 44a and 44b are provided in three directions. , 44c, a surge tank (mixing means) 44 that can uniformly mix the gas flowing in from any of the connection ports, a suction side connected to the extraction pipe 43 of the furnace 41, and a discharge side of the surge tank 44 A blower (exhaust air) 45 connected to the connection port 44a, a flow rate adjusting valve 46 whose outlet side is connected to the connection port 44b, and whose inlet side is connected to a supply blower (not shown) so that the combustion air BA can be supplied in a flow-adjustable manner. The combustion exhaust gas EG2 and the combustion air BA mixed in the surge tank 44 are oxidized at a high temperature for combustion at the bottom of the furnace body 42 and connected to the connection port 44c via a pipe. Scan BG may comprise a high temperature oxidation gas nozzle 47 which may be ejected in a desired position in the combustion region of the furnace body 42 as. The combustion exhaust gas EG2 is sucked by the blower 45 and discharged into the surge tank 44. In the surge tank 44, the combustion exhaust gas EG2 and the combustion air BA pumped from a supply air blower (not shown) are uniformly mixed, The gas is ejected from the high temperature oxidizing gas nozzle 47. At this time, the mixing ratio of the combustion exhaust gas and the combustion air can be appropriately set by adjusting the flow rate adjustment valve 46 to adjust the amount of combustion air BA. Here, both the blower 45 and the blower 55 described later require that a heat-resistant material is used in a necessary part such as a rotor so that high-temperature combustion exhaust gas can be sucked and discharged. Can be used.

  Alternatively, as shown in FIG. 4, for example, there are connection ports 54 a, 54 b, 54 c in three directions, and the gas flowing in from any of the connection ports can be mixed uniformly, and the connection port 54 a is connected to the furnace 51. A surge tank (mixing means) 54 connected to the bleed pipe 53, a flow rate adjusting valve 56 whose outlet side is connected to a connection port 54b, and whose inlet side is connected to a supply blower (not shown) so that the combustion air BA can be supplied in a flow-adjustable manner; , A blower connected to the connection port 54c and capable of simultaneously sucking the combustion exhaust gas EG2 and the combustion air BA mixed in the surge tank 54 and discharging them to the high-temperature oxidizing gas nozzle 57 provided at the lower portion of the furnace body 52. (Exhaust device) 55 may be provided. The combustion exhaust gas EG2 and the combustion air BA are simultaneously sucked by the blower 55 and uniformly mixed in the surge tank 54, and the high temperature combustion oxidizing gas BG generated by the mixing is ejected from the high temperature oxidizing gas nozzle 57 into the furnace body 52. . At this time, the mixing ratio of the combustion exhaust gas and the combustion air can be set as appropriate by adjusting the flow rate adjustment valve 56 to adjust the amount of combustion air BA.

  In this embodiment, the high-temperature oxidizing gas nozzle is arranged in only one stage in the flow direction of the combustion exhaust gas. However, as shown in FIG. 5, the high-temperature combustion oxidizing gas BG is arranged from the upstream to the downstream of the flow of the combustion exhaust gas. Alternatively, it may be supplied to the furnace body 62 in two stages, front and rear. In this case, the front-stage nozzle (high-temperature oxidizing gas supply means) 64 is disposed in the vicinity of the fuel nozzle 63, and first, the high-temperature oxidizing gas is appropriately adjusted and supplied from the front-stage nozzle 64, and the reducing atmosphere is supplied to the fuel nozzle 63. It is formed in the vicinity to achieve stable combustion at low NOx, and unburned fuel can be completely burned by the high-temperature combustion oxidizing gas supplied from the rear-stage nozzle (rear-stage high-temperature oxidizing gas supply means) 65. . In the latter stage combustion, since the nitrogen component in the pulverized coal is already stabilized, fuel NO is not generated in the latter stage combustion.

  In this embodiment, the fuel is pulverized coal, which is a solid fuel. However, for example, 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 conveyed by conveying air, the moisture is evaporated by radiant heat from the high-temperature combustion oxidizing gas and the combustion flame, and the dried sludge is further heated. It is good also as volatilizing the combustible component contained in sludge and burning. Depending on the conventional technology that does not use the high-temperature air combustion technology, 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. However, depending on the present invention, there is no such need, and it is possible to burn sludge having a higher water content, for example, about 80%.

In this embodiment, an air preheater using exhaust gas as a heat source is used as the preheating means. However, for example, a preheating burner and a heater may be separately provided to preheat the combustion secondary air.
In the present embodiment, a dust removing device for removing dust in the combustion exhaust gas is not installed between the extraction pipe and the air ejector, but the amount of dust in the combustion exhaust gas, for example, via a cyclone. May be reduced.

  Furthermore, in this embodiment, the air necessary for combustion was supplied to the furnace as combustion air BA, combustion secondary air BA1, and a small amount of carrier air A1. However, when the ignition temperature of the solid fuel is relatively low, etc., the reduction of the vicinity of the flame F without reducing the ignitability even if the amount of combustion air BA is increased and the temperature of the high-temperature combustion oxidizing gas is decreased. In some cases, stable low NOx combustion may continue in a sexual atmosphere. In such a case, since all the oxygen necessary for the entire combustion can be supplied with only the combustion blank BA and a small amount of carrier air A1, it is not necessary to supply the combustion secondary air. In this case, even if the secondary air nozzle 21, the air preheater 22, and the supply air blower 23 are deleted from the configuration requirements shown in the first embodiment, (1) stable low NOx by high-temperature air combustion Combustion and the improvement of energy efficiency by it, and (2) NOx reduction effect by recirculation of combustion exhaust gas, etc. can be produced.

Next, the boiler apparatus 70 concerning the 2nd Example concerning this invention is demonstrated with reference to FIG.
The boiler device 70 includes a plurality of fuel nozzles 73, secondary air nozzles 74, and high-temperature oxidizing gas nozzles 75 (four in FIG. 6) as shown in FIGS. 6 (a) and 6 (b). In the direction, pulverized coal or the like is ejected so that the jet forms a swirling flow in the furnace main body 72. Accordingly, the overall system configuration, equipment function, shape, arrangement, etc. other than the above three types of nozzle arrangement are the same as those in the first embodiment, and the description will be given here.

  The boiler device 70 includes fuel nozzles 73 in the vicinity of the four corners of the lower portion of the furnace main body 72 as shown in FIG. 6B, which is a view taken along the line AA in FIG. The ejection direction of the fuel nozzle 73 is determined as follows. That is, a horizontal circle 76 having a center at the center of the furnace main body 72 is assumed, and the ejection axis of the fuel nozzle 73 is determined to be tangent to the horizontal circle 76. At this time, the radius of the horizontal circle 76 is appropriately adjusted to prevent the generated swirling flow from colliding with the side wall of the furnace body 72 and causing slagging. Further, as shown in FIG. 6A, the high temperature oxidizing gas nozzles 75 are arranged in close proximity to each of the four fuel nozzles 73, and the ejection direction of the nozzles is the fuel nozzle directly above each of the high temperature oxidizing gas nozzles 75. In FIG. 6 (b), the high-temperature oxidizing gas nozzle 75 overlaps with the fuel nozzle 73 and cannot be described so as to be parallel to 73 (described in parentheses). Further, the secondary air nozzle 74 is located immediately above each of the four fuel nozzles 73 (on the downstream side as the flow of combustion exhaust gas), at least than the separation distance between the fuel nozzle 73 and the high-temperature nozzle 75 immediately below it. The fuel nozzle 73 and the secondary air nozzle 74 are arranged so that the separation distance is large, and the ejection direction is made to coincide with the ejection direction of the fuel nozzle 73.

  The operation of the boiler device 70 will be described. A part of the combustion exhaust gas generated by the combustion in the vicinity of the fuel nozzle is extracted and mixed with the combustion air to generate a high-temperature combustion oxidizing gas, and the vicinity of the flame formed at the tip of the fuel nozzle 73 is reduced to a high temperature. In the second embodiment, low NOx combustion that is stable as an atmosphere is generated, and secondary combustion air preheated by an air preheater is supplied to the downstream side of the flame to burn the unburned fuel to complete the combustion. There is no difference with the example. The feature of the boiler device 70 of the third embodiment is that the jet direction of the fuel nozzle 73, the high temperature oxidizing gas nozzle 75 and the secondary air nozzle 74 described above is aligned with the tangential direction of a horizontal circle 76 imaginary in the furnace body 72. Since a swirl flow along a virtual horizontal circle 76 is generated in the furnace main body 72, and the swirl flow is strengthened by a jet flow from each of the nozzles 73 to 75, the swirl flow is completed and combustion is completed. An extremely stable high-temperature circulation combustion region is generated along the horizontal circle 76, and stable low NOx combustion is realized.

  Next, a boiler device 80 according to a third embodiment will be described with reference to FIG. The feature of the boiler device 80 is that, apart from the fuel nozzle 83 installed in the vicinity of the high-temperature oxidizing gas nozzle 84, a post-stage fuel nozzle 85 is installed on the downstream side (upper side) of the fuel nozzle 83 and secondary in the vicinity thereof. An air nozzle 86 is installed to supply combustion secondary air in the vicinity of the rear fuel nozzle, and a rear secondary air nozzle 87 is installed further downstream of the rear fuel nozzle 85 and the secondary air nozzle 86. The purpose is to reduce the NOx generated by the combustion in the vicinity of the fuel nozzle 83 by the combustion in the vicinity of the rear fuel nozzle 85 in the high temperature reducing atmosphere, and supply the unburned fuel in the combustion from the rear secondary air nozzle 87. Combustion with secondary air for combustion is to complete the combustion. Accordingly, the system configuration other than the nozzle arrangement, the fuel nozzle 83, the fuel supply to the rear stage fuel nozzle 85, and the secondary air supply to the rear stage secondary air nozzle 87, the functions, shapes, arrangements, and operational effects of the respective facilities are the first. Since it is the same as the embodiment, the description is omitted here.

  As shown in FIG. 7, for example, the fuel nozzle 83 and the high temperature oxidizing gas nozzle 84 installed at the lower part of the furnace body 82 are arranged and opened as coaxial nozzles, and the fuel and the oxidizing gas for high temperature combustion are ejected and burned. A structure in which the rear stage fuel nozzle 85 and the secondary air nozzle 86 are arranged and opened as, for example, a coaxial nozzle on the upper side, that is, the downstream side as the flow of combustion exhaust gas, and the fuel and the secondary air for combustion are ejected and combusted. And In addition, a rear secondary air nozzle (rear secondary air supply means) 87 is installed on the upper side of the rear fuel nozzle 85 and the secondary air nozzle 86, that is, on the rear stream side as the flow of combustion exhaust gas, and combustion secondary air. It is made the structure which spouts.

  The operation of the boiler device 80 will be described. In the vicinity of the fuel nozzle 83, a high temperature and highly reducing atmosphere region (enhanced reducing atmosphere region) 88 is formed by the high temperature oxidizing gas, in which stable low NOx combustion is performed, and an enhanced reducing atmosphere region. In the vicinity of 88, the fuel supplied from the post-stage fuel nozzle 85 is burned. At this time, since a high temperature reducing atmosphere region is also formed in the vicinity of the reinforced reducing atmosphere region 88, the generation of NOx is suppressed, and the generated NOx is reduced to promote the reduction of NOx as a whole. Can do. Further, the unburned fuel in the combustion in the reducing region is combusted by the secondary air for combustion supplied from the rear-stage secondary air nozzle 87, and the combustion is completed.

  The boiler device 80 further has the following effects. That is, when remodeling an existing boiler into a high-temperature air combustion boiler, the burner on the uppermost stream side (the lowermost stage) of the boiler is burned with pulverized coal using high-temperature oxidizing gas (for example, the fuel nozzle 83 and the high-temperature oxidation). It is also possible to use an existing burner that supplies secondary air and burns pulverized coal for the other burners. Therefore, the above-described effects such as NOx reduction by the high-temperature air combustion technique can be obtained with a minimum modification.

The fuel nozzle 83 and the high-temperature oxidizing gas nozzle 84, and the rear-stage fuel nozzle 85 and the secondary air nozzle 86 are all coaxial nozzles here, but may be arranged apart from each other.
Next, a boiler apparatus 90 according to a fourth embodiment of the present invention will be described with reference to FIG.
In the first embodiment, normal air is used as the carrier air A1, but the boiler apparatus 90 uses the exhaust gas EG1 after preheating the combustion air in the air preheater 91 as the carrier gas and Used as an atmospheric gas when producing pulverized coal in a mill (mill apparatus) 94.

  More specifically, as shown in FIG. 8, the boiler device 90 is connected to the downstream side of the air preheater 91 in addition to or in place of the equipment of the boiler device 1 described in the first embodiment. In order to extract the dust collector (dust removing means) 92 and the exhaust gas EG1 removed from the dust collector 92, pump it to the mill 94, mix the pulverized coal in the mill 94, and eject it from the fuel nozzle 96. And a control device 95 that also controls the carrier air blower 93.

Since the system configuration other than the above, the function, shape, arrangement, and function and effect of each facility are the same as those in the first embodiment, description thereof will be omitted.
The operation of the boiler device 90 will be described below.
That is, a part of the exhaust gas EG1 is extracted from the outlet of the dust collector 92 by the air supply blower 93, and the extracted exhaust gas EG is used as an atmosphere gas at the time of producing the pulverized coal instead of the carrier air A1. To supply. Since the exhaust gas EG1 has a reduced oxygen concentration, there is little risk of unintended ignition of the pulverized coal activated during the production of pulverized coal, and there are conditions such as temperature control for preventing the unintended pulverized coal ignition. It can be mitigated 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 oxidizing gas for high-temperature combustion, 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 exhaust gas is extracted at the outlet of the dust collector 92. If so, for example, the air may be extracted from any point of the exhaust gas processing system such as an exhaust pipe (not shown).
A boiler apparatus 100 according to a fifth embodiment of the present invention will be described with reference to FIG.

  The boiler apparatus 100 does not mix combustion air with the high-temperature combustion exhaust gas EG2 partially extracted from the furnace 101, but supplies the combustion exhaust gas EG2 as it is as a high-temperature combustion oxidation gas, and mainly the combustion exhaust gas EG2. Combustion is performed in a high-temperature reducing atmosphere near the oxygen ignition point F1 remaining inside. At this time, the transport air A1 used for transporting the pulverized coal also acts as combustion air although the amount thereof is small. Needless to say, secondary combustion air is supplied for the subsequent combustion.

  On the lower side surface of the furnace body 102 of the furnace 101 of the boiler apparatus 100, a fuel nozzle 103 for injecting fuel pulverized coal into the furnace body 102 to form a flame F, and high-temperature combustion exhaust gas EG2 are oxidized for high-temperature combustion. And a high-temperature oxidizing gas nozzle 104 which forms a high-temperature reducing atmosphere in the vicinity of the ignition point F1 of the flame F in cooperation with the combustion of pulverized coal, and is provided on the side of the furnace body 102 above the nozzles 103 and 104. Includes a secondary air nozzle 105 that ejects secondary combustion air around the upper part of the flame F (on the downstream side). Further, an extraction pipe 106 for extracting a part of the high-temperature combustion exhaust gas as the combustion exhaust gas EG2 is provided on the upper side wall near the top of the furnace body 10. The arrangement, shape, etc. of these nozzles and extraction pipes are the same as in the first embodiment.

  The fuel nozzle 103 is connected to a mill 109 that pulverizes the coal C into pulverized coal and pumps the pulverized coal with the transfer air from the transfer blower 108. The extraction pipe 106 and the high-temperature oxidizing gas nozzle 104 are connected via a blower 107 that pressurizes the combustion exhaust gas EG2 and discharges it to the nozzle 104. The blower 107 is capable of pressurizing and discharging combustion exhaust gas at a high temperature (for example, 800 ° C.). Preferably, a necessary part such as a rotor is preferably made of, for example, a ceramic material having excellent heat resistance. .

Since the system configuration other than the above, the shape, function, arrangement, and operational effects of the equipment are the same as those in the first embodiment, the description is omitted here.
The operation of the boiler apparatus 100 will be described. The boiler apparatus 100 recirculates the combustion exhaust gas EG2 in the vicinity of the ignition point F1 of the flame to maintain a high-temperature reducing atmosphere, while a small amount of carrier air is in the vicinity of the ignition point F1, and abundant combustion in the subsequent stage of combustion. By supplying the secondary air for operation, stable low NOx combustion can be continued. Details will be described below.

  The pulverized coal ejected from the fuel nozzle 103 forms a flame F and burns. At this time, only the combustion exhaust gas EG2 ejected from the high-temperature oxidizing gas nozzle 104 and a small amount of carrier air A1 are supplied in the vicinity of the ignition point F1. It is. In the combustion exhaust gas EG2, only oxygen whose concentration has decreased due to combustion remains, so a reducing atmosphere is formed in the vicinity of the ignition point F1. Even under such low oxygen concentration conditions, the ignitability is improved due to the high temperature, and stable low NOx combustion occurs as pre-stage combustion. In the subsequent stage of combustion, the secondary air BA1 for combustion is supplied from the secondary air nozzle 105, so that unburned fuel burns and completes combustion. That is, two-stage combustion occurs in the entire furnace. The high-temperature combustion exhaust gas generated by the combustion is extracted from the extraction pipe 106, pressurized and discharged by the blower 107, and ejected from the high-temperature oxidizing gas nozzle 104, forming a high-temperature reducing atmosphere in the vicinity of the ignition point F1 as described above.

  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 cross-sectional view which shows arrangement | positioning of the fuel nozzle etc. of the boiler apparatus of 1st Example concerning this invention. It is explanatory drawing which shows the example which uses a blower as an oxidation gas production | generation means for high temperature combustion as another aspect of the 1st Example concerning this invention. It is explanatory drawing which shows another example which uses a blower as an oxidizing gas production | generation means for high temperature combustion as another aspect of 1st Example concerning this invention. It is a system diagram which shows the example of arrangement | positioning of the high temperature oxidizing gas nozzle for two-stage combustion as another aspect of the 1st Example concerning this invention. In the boiler apparatus according to the second embodiment of the present invention, the secondary air nozzle, the high-temperature oxidizing gas nozzle, the fuel ejected from the fuel nozzle, and the like are arranged to form a horizontal swirling flow, The arrangement | positioning of the up-down direction of each nozzle is shown. It is explanatory drawing which shows arrangement | positioning of the horizontal direction of the high temperature oxidizing gas nozzle and fuel nozzle of the boiler apparatus shown to Fig.6 (a). It is a system diagram which shows the example which has arrange | positioned the high temperature oxidizing gas nozzle and the fuel nozzle, the secondary air nozzle, and the back | latter stage fuel nozzle as a coaxial nozzle which is 3rd Example concerning this invention, respectively. FIG. 6 is a system diagram in the case of using combustion exhaust gas as the carrier air, which is a fourth embodiment according to the present invention. FIG. 9 is a system diagram showing a case where high-temperature air combustion is caused by recirculating combustion exhaust gas without using combustion air, which is a fifth embodiment according to the present invention.

Explanation of symbols

1, 70, 80, 90, 100 Boiler device 10, 41, 51 Furnace 10a Combustion region 21, 74, 86, 105 Secondary air nozzle 22, 91 Air preheater 23, 28 Supply blower 25, 43, 53, 106 Extraction pipe 26, 47, 57, 75, 84, 104 High temperature oxidizing gas nozzle 27 Air ejector 27a High temperature combustion oxidizing gas outlet 31, 63, 73, 83, 96, 103 Fuel nozzle 32, 94, 109 Mill 33, 93, 108 Transport air blowers 44, 54 Surge tanks 44a, 44b, 44c, 54a, 54b, 54c Connection ports 45, 55, 107 Blowers 46, 56 Flow control valve 64 Pre-stage nozzle 65 Sub-stage nozzle 85 Sub-stage fuel nozzle 87 Sub-stage secondary Air nozzle 92 Dust collector

Claims (21)

A furnace that injects and burns solid fuel into the lower combustion region;
A high-temperature combustion oxidizing gas generating means for extracting a part of the combustion exhaust gas from the furnace and mixing it with combustion air to generate a high-temperature combustion oxidizing gas having a temperature equal to or higher than the ignition temperature of the solid fuel;
A fuel nozzle that ejects the solid fuel into the combustion region to form a flame;
A boiler apparatus comprising: a high-temperature combustion oxidizing gas supply means for injecting the high-temperature combustion oxidizing gas into the combustion region so as to form a reducing atmosphere in the combustion region near the flame. Air preheating means for preheating combustion air to a temperature lower than that of the high temperature combustion oxidizing gas to generate combustion secondary air;
The boiler apparatus according to claim 1, further comprising secondary air supply means for ejecting the combustion secondary air to the combustion region in the wake of the flame.   The boiler apparatus according to claim 1, wherein the high-temperature combustion oxidizing gas generating means includes an air ejector that uses the combustion air as a working fluid.   3. The boiler device according to claim 1, wherein the high-temperature combustion oxidizing gas generating means includes an exhaust fan that pressurizes and discharges high-temperature combustion exhaust gas extracted from the furnace. .   The high-temperature combustion oxidizing gas generating means includes the exhaust fan that pressurizes and discharges the combustion exhaust gas, a flow rate control valve that adjusts the flow rate of combustion air, and the combustion exhaust discharged from the exhaust fan. The boiler apparatus according to claim 4, further comprising a mixing unit that mixes gas and combustion air whose flow rate is adjusted by the flow rate control valve.   The high temperature combustion oxidizing gas generating means mixes a flow rate adjusting valve for adjusting the flow rate of combustion air, combustion air whose flow rate is adjusted by the flow rate adjusting valve, and the combustion exhaust gas, thereby oxidizing high temperature combustion. A mixing means for generating a gas; and a high-temperature combustion oxidizing gas from the mixing means that is sucked and discharged, and is supplied to the high-temperature oxidizing gas supply means as a high-temperature combustion oxidizing gas. The boiler device according to claim 4, wherein the boiler device is provided.   7. The fuel nozzle and the high-temperature oxidizing gas supply means are arranged such that the fuel ejection position of the fuel nozzle and the gas ejection position of the high-temperature oxidizing gas supply means are spaced apart from each other. The boiler apparatus in any one.   7. The fuel nozzle and the high temperature oxidizing gas supply means are arranged such that a fuel ejection center of the fuel nozzle and a gas ejection center of the high temperature oxidizing gas supply means are arranged coaxially with each other. The boiler apparatus according to crab.   9. The air jet position of the secondary air supply means is arranged farther away from the gas jet position of the high-temperature oxidizing gas supply means with respect to the fuel jet position of the fuel nozzle. The boiler apparatus according to crab.   The fuel nozzle, the high temperature oxidizing gas supply means, and the secondary air supply means include a fuel ejection center of the fuel nozzle, a gas ejection center of the high temperature oxidizing gas supply means, and an air ejection center of the secondary air supply means. The boiler apparatus according to any one of claims 1 to 9, wherein the boilers are arranged in an annular shape on the outside of the fuel nozzle in the order of a high-temperature oxidizing gas supply means and a secondary air supply means.   11. A post-stage high-temperature oxidant gas supply unit that ejects a part of the high-temperature combustion oxidant gas to the combustion region downstream from the position where the high-temperature oxidant gas supply unit is disposed. The boiler apparatus in any one of.   12. The combustion secondary air from the secondary air supply means is ejected to the combustion region downstream from the position where the high-temperature oxidizing gas supply means is disposed. The boiler device described in 1. A post-stage fuel in which a part of the solid fuel is ejected to the combustion region downstream from the position where the high-temperature oxidizing gas supply means is disposed, and is mixed with the secondary air for combustion from the secondary air supply means and burned A nozzle,
13. An air outlet of a rear-stage secondary air supply means for jetting the secondary air for combustion into the combustion region downstream from the position where the rear-stage fuel nozzle is disposed. The boiler apparatus in any one.   The fuel nozzle, the air jet nozzle of the secondary air supply means, and the jet nozzle of the high-temperature oxidizing gas supply means are arranged to face each other on each wall surface of the furnace facing each other. The boiler apparatus in any one of 1 thru | or 13.   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 device according to any one of claims 1 to 15, wherein the air preheating means preheats combustion air with exhaust gas from the furnace.   The boiler device according to any one of claims 1 to 16, wherein the solid fuel is pulverized coal, and the oxidizing gas for high-temperature combustion is heated to 800 ° C or higher.   18. The boiler device according to claim 1, wherein the 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 pulverizing coal into pulverized coal is used. The exhaust gas from the furnace is used as an atmospheric gas, and the exhaust gas is supplied to the mill device to produce pulverized coal. The boiler device according to any one of claims 1 to 18, wherein the boiler device is transported from a mill device to a fuel nozzle.   The boiler device according to any one of claims 18 and 19, further comprising dust removing means for removing ashes in the exhaust gas from the furnace. A furnace that injects and burns solid fuel into the lower combustion region;
A fuel nozzle that ejects the solid fuel into the combustion region to form a flame;
A part of the combustion exhaust gas having a temperature equal to or higher than the ignition temperature of the solid fuel is extracted from the furnace and ejected as a high-temperature combustion oxidizing gas to the combustion region so as to form a reducing atmosphere in the combustion region near the flame. High temperature combustion oxidizing gas extraction supply means;
Air preheating means for preheating combustion air to a temperature lower than that of the high temperature combustion oxidizing gas to generate combustion secondary air;
A boiler device comprising: secondary air supply means for ejecting the combustion secondary air to the combustion region in the wake of the flame.

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