JPH10103616A - Boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce the generation of NOX increase efficiency, reduce size, and make selection of kind of fuel unnecessary. SOLUTION: At least two annular heat transmission parts 4 and 5 are arranged in a multiple manner and a combustion device 7 to use liquid fuel and gas fuel through selective switch is arranged at one opening end of a first annular heat transfer part on the innermost peripheral side such that the injection direction of flame approximately parallels the axial direction of a first annular heat transfer part 4. The inside of the first heat transfer part 4 forms a first combustion space 11, and a space between the first annular heat transfer part 11 and a second annular heat transfer part 5 positioned at the outside thereof forms a second combustion space 12. The first annular heat transfer part 4 is arranged in the direction of the center thereof in the vicinity of the combustion device 7. A flow gap to communicate together the inside and the outside of the first annular heat transfer part 4 is formed in the peripheral surface of the first annular heat transfer part 4. Flame in the first combustion space 11 is introduced in the second combustion space 12 through the flow gap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a boiler.

[0002]

2. Description of the Related Art Conventionally, relatively small-capacity water tube boilers have been generally used, such as a plurality of water tubes arranged in a ring or a single or a plurality of water tubes wound in a coil shape. The one having a cylindrical can body structure is generally used. A water pipe boiler of this type has a combustion chamber on the innermost annular water pipe row or the inner circumference of the spiral water pipe, and has a heat transfer fin attached to the water pipe, or a pipe from the combustion chamber to the exhaust pipe. Various improvements, such as devising the combustion gas flow path, have resulted in low NOx
And efficiency has been improved. However, with the recent can body structure, a limit has been seen in reducing NOx and improving efficiency, and there is a need to respond to recent demands for space saving.

In recent years, a water tube boiler having a so-called square-shaped can structure has been developed and put into practical use in order to escape from such a cylindrical water tube boiler and achieve space saving and improvement in thermal efficiency. Has been provided.

The water tube boiler having the cylindrical can structure has an advantage that it can be manufactured relatively inexpensively. On the other hand, the water tube boiler having the square can structure has a premixed gas combustion device. High thermal efficiency and low NO
x has been achieved.

[0005] Further, due to the recent tightening of exhaust gas regulations, the ratio of boilers using gaseous fuel, which has a lower nitrogen content than liquid fuel and is easy to reduce NOx and CO, is increasing. There is a growing demand for boilers that can operate on fuel. This is because if a gas or fuel gas (such as city gas) supply network is cut off due to a disaster or accident, operation will not be possible with a boiler that uses only gas fuel.
This is because if liquid fuel can be used, operation can be performed even in such an emergency.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to achieve a further reduction in NOx, higher efficiency, and smaller size in the above-mentioned boiler having a cylindrical can body structure. And to provide a boiler that does not depend on the type of fuel.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a combustion apparatus in which at least two annular heat transfer sections are arranged in a multiplex manner and a liquid fuel and a gas fuel are selectively switched is used. At one opening end of the first annular heat transfer section, the direction of flame ejection is provided so as to be substantially parallel to the axial direction of the first annular heat transfer section, and the inside of the first annular heat transfer section is subjected to first combustion. Space, and the space between the first annular heat transfer section and the second annular heat transfer section located outside the second annular heat transfer section is defined as a second combustion space. The first annular heat transfer section is provided with a communication gap formed between the inside and outside of the first annular heat transfer section on the peripheral surface of the first annular heat transfer section, and the flame in the first combustion space is subjected to the second combustion through the communication gap. The above-described problem is solved by a boiler configured to be introduced into a space.

Further, the present invention provides a first annular heat transfer portion having a flow gap communicating between the inside and the outside, and a first annular heat transfer portion disposed outside the first annular heat transfer portion at a predetermined interval. Bi-annular heat transfer section, and one opening end in the axial direction of the first annular heat transfer section, was arranged facing the inside of the first annular heat transfer section,
A combustion device for selectively switching between liquid fuel and gaseous fuel for use, wherein the first annular heat transfer portion is located close to the center of the flame so as to be located in a flame ejected from the combustion device. The above-mentioned problem is solved by a boiler configured so as to be arranged.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is embodied as a boiler for obtaining steam or hot water. This invention arranges at least two annular heat transfer sections in a multiplexed manner, and selectively switches between liquid fuel and gaseous fuel for use in a combustion apparatus using one of the innermost peripheral first heat transfer sections. A basic embodiment is a boiler having a configuration in which a flame ejection direction is provided at an open end so as to be substantially parallel to an axial direction of a first annular heat transfer portion. The inside of the first annular heat transfer section is defined as a first combustion space, the space between the first annular heat transfer section and the second annular heat transfer section located outside the second annular heat transfer section is defined as a second combustion space, The heat transfer section is disposed in the center direction close to the combustion device, and a flow gap communicating between the inside and outside of the first annular heat transfer section is formed on the peripheral surface of the first annular heat transfer section. The flame in the first combustion space is introduced into the second combustion space via.

In other words, a first annular heat transfer portion having a flow gap communicating the inside and the outside thereof, and a second annular heat transfer portion disposed outside the first annular heat transfer portion at a predetermined interval. An annular heat transfer section and an axially open end of the first annular heat transfer section, which are disposed so as to face the inside of the first annular heat transfer section, are used by selectively switching between liquid fuel and gaseous fuel. And the first annular heat transfer section is arranged close to the center of the flame so as to be located in the flame ejected from the combustion apparatus.

Therefore, in the boiler according to the present invention, the flame from the combustion device reaches the second combustion space from the first combustion space via the flow gap of the first annular heat transfer portion, and therefore, the combustion temperature Is rapidly cooled by the first annular heat transfer section and is adjusted to a temperature range where the rate of thermal NOx generation is low. After the quenching, the flame that has flowed into the second combustion space hardly conducts heat in the second combustion space, so that the temperature does not decrease much. Therefore, unburned fuel reacts, and CO Is also oxidized to CO ₂ .
Furthermore, the first annular heat transfer section not only controls the combustion temperature of the flame, but also performs heat transfer from the flame, so that the amount of heat recovery increases as compared with a boiler having the same external dimensions.

Further, since the boiler of the present invention is used by selectively switching between liquid fuel and gas fuel, even if supply of any fuel becomes impossible, the boiler is operated by switching to another fuel. It is possible to use low NOx not only when using gaseous fuel but also when using liquid fuel.
To achieve low CO. That is, as described above, even if the gas fuel supply network is cut off due to a disaster or accident, the boiler can be operated by using the liquid fuel.

In the boiler according to the present invention, the inside of the first annular heat transfer section is used as a first combustion space. In the first combustion space, fuel and combustion air are ejected from a combustion device, and the two are mixed. It has been done. This mixed fluid produces a flame by a so-called combustion reaction. In this document, a portion of a gas that is undergoing a combustion reaction and is clearly visible as light is referred to as a flame. In addition, a high-temperature gas region that is invisible is generated on the downstream side of the flame, and a part of the gas region continues the combustion reaction. In this document, a portion containing the high-temperature gas during the combustion reaction is referred to as a combustion gas.

Further, the boiler according to the present invention is configured such that the temperature of the flame ejected from the flow gap of the first annular heat transfer section toward the second annular heat transfer section becomes 800 to 1,300 degrees C. By setting the distance to the annular heat transfer section and the flow gap, the generation of thermal NOx is suppressed and the oxidation of CO is promoted, so that the NOx reduction and CO reduction are achieved. This flame temperature of 1,300 degrees or less is equivalent to thermal NO.
The temperature range in which x is less generated, and the flame temperature of 800 ° C. or more means a temperature range in which the oxidation reaction from CO to CO ₂ is relatively active. That is, in the region where the flame temperature is 1,300 degrees or more, thermal NO due to oxidation of nitrogen in the air
x increases rapidly, and in the region below 800 degrees, C
This is because the reaction rate of O to CO ₂ is reduced.

Further, the distance between the combustion device and the first annular heat transfer portion and the setting of the flow gap are determined according to the amount of heat generated by the combustion device. By appropriately adjusting the number.

Here, the first annular heat transfer portion refers to a component that allows a fluid to be heated to flow therein and performs heat exchange between the fluid to be heated and the flame. It includes a water pipe array in which water pipes are annularly arranged at appropriate intervals, and a water pipe formed by a spiral water pipe wound in a coil shape. When the first annular heat transfer section is constituted by such a water pipe, the temperature of the flame flowing into the second combustion space is set to 800 ° C or higher.
To achieve 1,300 degrees, the spacing between the water pipes must be
This is achieved by setting the distance between the combustion device and the first annular heat transfer portion to be 0.1 to 2 times the diameter of the water pipe.

The flow gaps formed in the first annular heat transfer portion include those having the same dimensions or different dimensions as appropriate, and the intervals at which the flow gaps are formed are equal to those at equal intervals. Including the case of forming at different intervals. Further, when the first annular heat transfer section is formed of water tubes, all the water tubes may be the same, or the size, shape, and material may be different. On the other hand, the second annular heat transfer section includes, in addition to the same configuration as the first annular heat transfer section, a configuration in which a furnace tube such as a furnace tube type boiler is used. That is, the first annular heat transfer section may have a communication gap that communicates the first combustion space and the second combustion space, and the second annular heat transfer section does not necessarily need to provide such a communication gap. Absent. Furthermore, the arrangement of the first annular heat transfer section and the second annular heat transfer section may be such that the second annular heat transfer section is arranged outside the first annular heat transfer section. The axis is not limited to the horizontal direction and the vertical direction.

Further, by widening the flow gap on the combustion device side of the first annular water pipe row, the combustion gas (including the flame) on the downstream side of the combustion device is supplied again to the root portion of the combustion device. (Recirculation), thereby lowering the flame temperature and achieving low NOx. In this configuration,
The recirculation of the combustion gas is performed by devising the circulation gap, but when the combustion device is a so-called self-recirculation type combustion device having a self-recirculation function, the recirculation function of the exhaust gas is ensured. And can further reduce NOx.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a water tube boiler will be described below with reference to FIGS. FIG. 1 is an explanatory view showing a vertical sectional structure of a first embodiment of a boiler according to the present invention, and FIG. 2 is an explanatory view showing a cross section taken along line II-II of FIG.

The boiler shown is a so-called multi-tube water tube boiler provided with a large number of water tubes. In the drawings, a boiler can 1 has an annular upper header 2 and a lower header 3.
In addition, between the upper header 2 and the lower header 3, inner and outer double annular heat transfer portions 4 and 5 spaced apart in the radial direction are arranged. The two annular heat transfer portions 4 and 5 are each configured as an annular water tube row in which a number of vertical water tubes 6 are annularly arranged at predetermined intervals. The upper header 2 and the lower header 3 are hollow containers each having an annular shape with a rectangular cross section, and both headers 2 and 3 are provided with a number of vertical water pipes 6 constituting the annular heat transfer portions 4 and 5. It is connected with. Here, a heated fluid is supplied into each water pipe 6 from the upper header 2 or the lower header 3.

Among the double annular heat transfer sections 4 and 5, the first annular heat transfer section 4 located inside has the vertical water pipes 6 arranged at a predetermined interval. Is set wider than that of the second annular heat transfer section 5 located on the outside. The second annular heat transfer section 5 has water pipes 6 arranged at relatively narrow intervals. On the outer peripheral side of the second annular heat transfer section 5, each water pipe 6 is provided with a flat plate along its axial direction. The heat transfer fin 9 is attached.

At one opening end side of the first annular heat transfer section 4 in the axial direction, that is, inside (central portion) of the upper header 2,
A combustion device 7 for selectively supplying liquid fuel and gaseous fuel is provided. The combustion device 7 is provided so as to protrude below the upper header 2, and blows out a flame substantially along the axial direction of the first annular heat transfer portion 4. Therefore, the inside of the first annular heat transfer section 4 becomes the first combustion space 11 in which the fuel and the combustion air react to form a flame.

The first annular heat transfer section 4 and the second annular heat transfer section 5
The space between the first combustion space 11 and the first combustion space 11 is formed by a gap (hereinafter referred to as a flow gap) 30 between the water tubes 6 constituting the first annular heat transfer section 4. They are communicating. Here, the first annular heat transfer section 4
Are arranged in a direction intersecting with the direction in which the flame is ejected from the combustion device 7 in a state of being close to the combustion device 7. Therefore, the flame from the combustion device 7 flows into the second combustion space 12 through the flow gap 30.

Due to the above-described arrangement of the first annular heat transfer section 4, the second annular heat transfer section 5, and the combustion device 7, an independent boiler is formed downstream of the combustion device 7 in the conventional boiler to fill the flame. The combustion chamber as a wide space is formed beyond the first annular heat transfer section 4 to the second annular heat transfer section 5 outside the combustion chamber. In other words, in the boiler of the present invention, the water pipe 6 of the first annular heat transfer section 4 is arranged so as to be located in the flame ejected from the combustion device 7, and the axis of the water pipe 6 is:
The direction is along the direction in which the flame is ejected.

Next, the detailed structure of the combustion device 7 will be described with reference to FIG. In the drawing, a combustion device 7 is fixed to a wind box 10 mounted on the upper header 2. This wind box 10
Rectifies combustion air from a blower (not shown) and supplies the rectified air to the combustion device 7 as is well known.

The combustion device 7 includes first to fourth coaxially arranged combustion devices.
A third cylindrical member 4 provided on the innermost peripheral side;
Inside the nozzle 3, a liquid fuel nozzle (hereinafter, referred to as an oil nozzle) 44 is disposed substantially coaxially. An end portion on the upstream side (upper side in FIG. 1) of the outermost first cylindrical member 41 is opened in the wind box 10 and the second cylindrical member 4
An annular first air passage 45 is formed between the first air passage 45 and the second air passage 45. The second cylinder member 42 forms an annular gas fuel flow path 46 between the second cylinder member 42 and the third cylinder member 43. The upstream end (upper side in FIG. 1) of the second cylindrical member 42 is connected to the third cylindrical member 43.
, And the upstream end of the gaseous fuel flow passage 46 is opened to the outside of the wind box 10. The upstream end (upper side in FIG. 1) of the third cylindrical member 43 also opens into the wind box 10 to form a second air passage 47.

The downstream side (the lower side in FIG. 1) of the first cylindrical member 41 is open so as to face the first combustion space 11. Further, the downstream end of the third cylindrical member 43 is open at an upper position deeper than the downstream open end of the first cylindrical member 41, and the downstream end of the second cylindrical member 42 is The cylinder member 43 is opened at an upper position slightly deeper than the downstream opening end. In addition, with flame holding,
In order to improve the mixing of fuel (gas fuel or liquid fuel) and combustion air, a downstream opening of the second cylindrical member 42
The first diffuser plate 48 is attached to the downstream opening of the third tubular member 43, and the second diffuser plate 49 is attached to the first diffuser plate 48.

A gaseous fuel supply line (hereinafter, referred to as a gas line) 50 is connected to the gaseous fuel passage 46, and a liquid fuel supply line (hereinafter, referred to as an oil line) is connected to the fuel nozzle 44. 51 are connected. further,
Switching means 52 for selectively switching between the supply of gaseous fuel to the gaseous fuel flow path 46 and the supply of liquid fuel to the oil nozzle 44
It has. The switching means 51 includes, for example, control valves 53 and 54 connected to the gas line 50 and the oil line 51, respectively, as shown in the figure. here,
This switching means 52 may be manually operated,
The gas line 50 and the oil line 51 may be appropriately connected to the combustion device 7 depending on the fuel to be used.

Further, in the boiler according to the present invention, the amount of heat generated by the combustion device 7, the dimensions of each portion of the first annular heat transfer portion, the interval between the combustion device 7 and the first annular heat transfer portion 4, the first annular heat transfer portion 4
The size, the number, the arrangement interval, and the like of the flow gap 30 are set so that the temperature of the flame ejected from the flow gap 30 toward the second annular heat transfer section 5 is 800 to 1,300 degrees. this
A flame temperature of 1,300 degrees or less is a temperature range where the generation of thermal NOx is small, and a flame temperature of 800 degrees or more means a temperature range where the oxidation reaction from CO to CO ₂ is relatively active. That is, in the region where the flame temperature is 1,300 ° C or higher, the amount of thermal NOx generated by the oxidation of nitrogen in the air sharply increases, and in the region where the flame temperature is 800 ° C or lower, the reaction rate of CO to CO ₂ decreases. It is.

In order to set the temperature of the flame flowing into the second combustion space 12 to 800 to 1,300 degrees, the first annular heat transfer section 4 is constituted by a large number of water pipes 6 as in the first embodiment. In this case, the interval between the water pipes 6 (that is, the flow gap 30).
Is set to 0.1 to 2 times the outer diameter of the water pipe 6, and the distance between the combustion device 7 and the first annular heat transfer section 4 is set to 0.1 times the outer diameter of the water pipe 6.
Up to 2 times. Here, the lower limit of the flow gap 30 is an interval at which the flame does not extinguish and can maintain the flame when the flame passes through the flow gap 30, and further, the flame maintains the lower limit of the above-mentioned temperature range. This is a possible interval. On the other hand, the upper limit is an interval for cooling the flame to 1,300 degrees or less and maintaining the heat transfer surface area per outer diameter of the boiler.
(Of course, if the flow gap 30 is set large, the number of water tubes in the first annular heat transfer section will decrease). Furthermore, the lower limit value of the interval between the combustion device 7 and the first annular heat transfer portion 4 is determined based on the convenience of the attachment of the combustion device 7 and the first annular heat transfer portion 4 to the upper header 2, and the upper limit value is The interval is such that the flame can be cooled so as not to generate a temperature region exceeding 1,300 degrees in the first annular heat transfer section 4 and the overheating of the first annular heat transfer section 4 can be prevented.

Further, in the upper header 2,
A refractory material 18 is applied to the joint between the second annular heat transfer sections 4 and 5 and the water pipe 6 so as to cover this section. Also on the lower header 3 side, a refractory material 18 is provided so as to cover a portion where the first and second annular heat transfer portions 4 and 5 are joined to the water pipe 6. Further, in the lower header 3,
The central cavity is closed with a suitable refractory or other material.

Further, a boiler outer wall 8 is provided outside the second annular heat transfer section 5 so as to surround the second annular heat transfer section 5. A gas flow path 17 is formed between the second annular heat transfer section 5 and the outer wall 8 so as to be continuous with the exhaust port 20. The gas flow path 17 communicates with the second combustion space 12 through a gap 32 (hereinafter, referred to as a second circulation gap) between the water tubes 6 constituting the second annular heat transfer section 5.

Now, the operation of the combustion device 7 in the above configuration will be described. When starting the combustion device 7, combustion air is supplied to the wind box 10 from a blower. The combustion air is supplied to the first and second air passages 4.
5 and 47 are injected into the first combustion space 11. here,
First, when using gaseous fuel, the switching means 52 is operated to open the control valve 53 on the gas line 50 side,
The control valve 54 on the oil line 51 side is closed, and gaseous fuel is supplied from the gas line 50 to the combustion device 7. The gaseous fuel flows through the gaseous fuel passage 46 to the second cylindrical member 42.
The fuel is injected into the first combustion space 11 from the gap between the first combustion space 11 and the third cylindrical member 43. Accordingly, a flow of combustion air is formed inside and outside the annular gaseous fuel flow, and when ignited by an ignition means (not shown), they are mixed and burned (so-called diffusion combustion). The flame at this time is held by the first diffuser plate 48.

On the other hand, when the liquid fuel is used, the switching means 52 is operated to open the control valve 54 on the oil line 51 side, and close the control valve 53 on the gas line 50 side. The liquid fuel is supplied to the combustion device 7. The liquid fuel is ejected from the inside of the third cylindrical member 43 into the first combustion space 11 by the oil nozzle 44. Therefore, the liquid fuel is ejected from the inside of the third cylindrical member 43 in a state where the primary air is mixed, and in this state, when the fuel is ignited by the ignition means (not shown), the liquid fuel is further discharged outside the second cylindrical member 42. The secondary air is supplied from the one air passage 45 and burns while mixing (so-called diffusion combustion). The flame at this time is also held by the second diffuser plate 49.

As shown in the drawing, the flame formed as described above blows out from the upper header 2 toward the lower header 3 in the axial direction of the first annular heat transfer section 4, and the flame is discharged. It is formed so as to spread in a direction intersecting the ejection direction. Therefore, the flame is formed so as to lick the surface of each water pipe 6 of the first annular heat transfer section 4, and flows into the second combustion space 12 through the flow gap 30 of the first annular heat transfer section 4.

This flame is generated in a portion close to the combustion device 7.
Since it does not spread so much in the direction intersecting with the jetting direction, high-temperature combustion gas formed on the downstream side of the flame flows into the second combustion space 12 through the flow gap 30.
Therefore, the flame and the combustion gas exchange heat with the fluid to be heated flowing in each of the water tubes 6 of the first annular heat transfer section 4 and are rapidly cooled to lower the temperature.
The generation of thermal NOx is suppressed. The flame that has passed through the flow gap 30 between the first annular heat transfer sections 4 is relatively long in a state where it is maintained at a certain temperature (800 degrees described above) or more in the second combustion space 12 on the downstream side. Owing to the residence time, the oxidation reaction is promoted, and in particular, generation of CO is prevented.

This operation is performed in a direction intersecting the direction in which the flame is ejected from the combustion device 7, that is, in the radial direction of the first and second annular heat transfer portions 4 and 5. Focusing on the axial direction of the flame, the flame
Therefore, as described above, each of the water tubes 6 of the first annular heat transfer section 4 is formed so as to be licked. Therefore, the temperature of the front end of the flame is lower due to the heat transfer to the water pipe 6.
That is, the hot end of the flame or the outer peripheral portion of the flame does not come into contact with the water pipe 6, and the flame temperature is sequentially reduced by the heat transfer with the water pipe 6, so that overheating can be prevented. In addition, since the temperature of the water pipe 6 is made uniform in this way, there is no locally high-temperature portion in the first and second combustion spaces 11 and 12, so that the thermal NO
x can be suppressed.

As described above, the flame whose temperature has been adjusted to 800 to 1,300 degrees and which has flowed into the second combustion space 12 is:
From the second flow gap 32 of the second annular heat transfer section 5 to the boiler outer wall 8
The gas flows into the inner gas passage 17. At this time, more heat can be recovered by the heat transfer fins 9 attached to the water pipes 6 of the second annular heat transfer section 5, and the gas flow path 1
The combustion gas passing through 7 heats the fluid to be heated in the water pipe 6 by performing heat transfer from outside the second annular heat transfer section 5,
The gas is discharged from the exhaust port 20 to the outside of the boiler.

That is, in the boiler according to the present invention, the first annular heat transfer section (in the first embodiment, an annular water pipe array) 4 is arranged in the flame ejected from the combustion device 7, and the first annular heat transfer section is provided. 4
The flame is ejected from the circulation gap 30 to the outside of the first annular heat transfer section 4, and the flame is rapidly cooled to a predetermined temperature or lower by the first annular heat transfer section 4. By maintaining the temperature of the quenched flame in the second combustion space 12 between the second annular heat transfer section 5 and the predetermined temperature at a predetermined temperature or higher, the temperature is adjusted along the flame ejection direction, and the thermal N
Generation of harmful combustion exhaust such as Ox and CO can be suppressed.

Further, as described above, the first annular heat transfer section 4 is provided so as to be located in the flame from the combustion device 7, and a predetermined space extends downstream in the direction in which the flame is ejected. Therefore, even a device requiring a predetermined space downstream of the combustion device 7 can be applied without impairing the flammability. That is, as the combustion device 7 used in the boiler of the present invention, a space or a spray nozzle for mixing fuel (including liquid and gas) and combustion air is provided downstream of the combustion device 7 described above. The flame can be formed immediately from the downstream side of the combustion device in addition to the switching-only combustion device of the premixing type (also referred to as diffusion combustion type) which requires a space for atomizing the fuel (particularly liquid fuel). Various switching-only combustion devices such as a premixed combustion device and a device incorporating a vaporization combustion type combustion device for vaporizing and burning liquid fuel can be applied. Therefore, the boiler according to the present invention can selectively use the liquid fuel and the gas fuel, so that the liquid fuel can be used even if the gas fuel supply network is cut off due to a disaster or an accident. By doing so, the boiler can be operated. Moreover,
Due to the configuration of the boiler can, not only when using gaseous fuel but also when using liquid fuel, low NOx,
Achieve low CO.

Next, a second embodiment of the boiler according to the present invention will be described with reference to FIG. In addition, FIG.
FIG. 4 is an explanatory view showing a vertical cross-sectional structure of a second embodiment of the boiler according to the present invention, and the same reference numerals are given to the same components as those in the first embodiment, and the detailed description is omitted. Further, in the second embodiment, the arrangement of the water pipes is the same as that of the first embodiment, so that the drawing showing the arrangement of the water pipes is omitted.

In the second embodiment, the flow gap 30 of the water pipe 6 on the side of the upper header 2 is set wider than other places. That is, the upper header 2 and the first annular heat transfer section 4
The refractory material 18 as described above is not applied to the joint portion between the first annular heat transfer portion 4 and the water pipe 6 on the combustion device 7 side of the first annular heat transfer section 4 by drawing the water pipe 6 at each location. Is set wider than other locations.

With this configuration, the combustion gas (including the flame) on the downstream side of the combustion device 7 can be supplied again (recirculated) to the root portion of the combustion device 7 via the second combustion space 12.
This lowers the flame temperature and achieves a low NOx. That is, in such a flow of the combustion gas, the main flow of the combustion gas from the combustion device 7 flows through the first annular heat transfer section 4. Due to this main flow, a pressure drop is generated between the second combustion space 12 and the combustion device 7 in the first combustion space 11 from above the second combustion space 12. Circulates nearby. Therefore, an increase in the reaction temperature of the combustion flame is suppressed, and an unnecessary increase in the temperature is prevented, so that the generation of thermal NOx is suppressed. In this case, the time for retaining the combustion gas in the can body by the second combustion space 12 is prolonged, and in particular, the oxidation reaction of the unburned matter is caused. Can be achieved.

Further, in the second embodiment, the combustion device 7 is a so-called self-recirculation type combustion device 7 having a self-recirculation function, so that the above-described exhaust gas recirculation function is reliably exhibited. And a further reduction in NOx can be achieved.

[0045]

As described above, in the boiler according to the present invention, the space between the first combustion space inside the first annular heat transfer section, the first annular heat transfer section, and the second annular heat transfer section is provided. The second combustion space is communicated with the first annular heat transfer unit through the flow gap,
Since the flame formed in the first combustion space is introduced into the second combustion space from the flow gap of the first annular heat transfer section, the flame passes through the flow gap of the first annular heat transfer section and passes through the second combustion space. In this case, the temperature of the flame can be rapidly cooled by the first annular heat transfer portion to a temperature region where thermal NOx is less generated, and the NOx emission can be greatly reduced. further,
In the second combustion space, the temperature of the quenched flame is maintained at a predetermined temperature or higher, so that CO is reduced to CO2.
_Since it can be oxidized to ₂ , the emission of CO can be greatly reduced. Therefore, according to the boiler according to the present invention, NOx or CO
As a result, it is possible to provide a clean exhaust gas boiler that can cope with environmental issues.

Further, according to the boiler according to the present invention,
A first annular heat transfer section is provided close to the combustion device, and the first annular heat transfer section defines a combustion space formed on the downstream side of the combustion device into two sections. Thus, the number of water pipes to be installed can be increased as compared with the case where an independent wide combustion chamber is provided downstream of the combustion device, and in this respect, the amount of heat recovery can be increased. This means that if the heat recovery amount is the same, miniaturization and space saving can be achieved.

Further, since the boiler according to the present invention can be used by selectively switching between liquid fuel and gaseous fuel, any fuel supply becomes impossible due to a change in fuel supply. In addition, operation can be performed by switching to another fuel, and even when using gaseous fuel or liquid fuel, low NOx and low CO can be achieved. That is, as described above, even if the gas fuel supply network is cut off due to a disaster or accident, the boiler can be operated by using the liquid fuel.

Further, in the boiler according to the present invention, since the combustion gas is recirculated in the can body,
Compared with the conventional one having the independent combustion gas recirculation flow path, there is no unnecessary heat radiation from the combustion gas, and a decrease in thermal efficiency can be prevented.

Further, since the combustion gas is recirculated inside the boiler and supplied to the combustion device side, the unburned portion contained in the flame from the combustion device is heated, mixing is promoted and uniformity is obtained. A combustion flame can be obtained, and at this time, since combustion gas is supplied into the combustion flame, a rise in the temperature of the combustion flame can be suppressed, and generation of harmful exhaust gas, particularly, thermal NOx can be suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a vertical sectional structure of a first embodiment of a boiler according to the present invention.

FIG. 2 is an explanatory diagram showing a cross section taken along line II-II of FIG.

FIG. 3 is an explanatory view showing a vertical cross-sectional structure of a second embodiment of the boiler according to the present invention.

[Explanation of symbols]

 Reference Signs List 4 first annular heat transfer wall (first annular heat transfer portion) 5 second annular heat transfer wall (second annular heat transfer portion) 6 vertical water pipe (water pipe) 7 combustion device 11 first combustion space 12 second combustion space 30 Distribution gap

Claims (8)

[Claims] 1. A combustion device 7 in which at least two annular heat transfer sections 4 and 5 are arranged in a multiplex manner, and a liquid fuel and a gas fuel are selectively switched and used, a first annular transfer section on the innermost peripheral side. Hot part 4
At one of the open ends, the direction of flame ejection is the first annular heat transfer section 4.
The first annular heat transfer section 4 and the second annular heat transfer section located outside the first annular heat transfer section 4 are provided so as to be substantially parallel to the axial direction of the first annular heat transfer section 4. A portion between the first annular heat transfer portion 4 and the portion 5 is defined as a second combustion space 12.
It is arranged in the center direction close to the combustion device 7, and a flow gap 30 communicating between the inside and outside of the first annular heat transfer section 4 is formed on the peripheral surface of the first annular heat transfer section 4. A boiler characterized in that the flame in the first combustion space 11 is introduced into the second combustion space 12 through the second combustion space. 2. A first annular heat transfer section 4 having a flow gap 30 communicating between the inside and the outside, and a second annular heat transfer section 4 disposed outside the first annular heat transfer section 4 at a predetermined interval. An annular heat transfer section 5 and a liquid fuel or a gaseous fuel, which is disposed at one opening end in the axial direction of the first annular heat transfer section 4 so as to face the inside of the first annular heat transfer section 4, are provided. The first annular heat transfer section 4 is disposed close to the center of the flame so as to be located in the flame ejected from the combustion apparatus 7. Boiler. 3. The temperature of the flame ejected from the flow gap 30 of the first annular heat transfer section 4 toward the second annular heat transfer section 5 is set to 800.
The space between the combustion device 7 and the first annular heat transfer section 4 and the flow gap 30 of the first annular heat transfer section 4 are set so as to be in the range of 1 to 1,300 degrees. The boiler according to claim 2. 4. The first annular heat transfer section 4 includes a plurality of water tubes 6
4. The boiler according to claim 1, wherein the boiler is a water pipe row which is annularly arranged at appropriate intervals. 5. The first annular heat transfer section 4 is a spiral water pipe wound in a coil shape.
The described boiler. 6. The gap according to claim 4, wherein the gap between the first annular heat transfer section 4 and the combustion device 7 is 0.1 to 2 times the outer diameter of the water pipe. Boiler. 7. A flow gap 30 of the first annular heat transfer section 4.
6. The boiler according to claim 4, wherein the outer diameter of the boiler is 0.1 to 2 times the outer diameter of the water pipe 6. 8. A flow gap 30 of the first annular heat transfer section 4.
The boiler according to any one of claims 1 to 7, wherein a side to which the combustion device 7 is attached is set wider than others.