JPH10246403A - Water tube boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive the reduction of generation of NOx by a simple constitution in a water tube boiler. SOLUTION: A water tube boiler is constituted of a plurality of water tubes 5, arranged annularly in a zone in a combustion chamber 9, in which gas during combustion reaction exists, so that the temperature of the gas during combustion reaction after contacting respective water tubes 5 becomes lower than 1400 deg.C. In this case, the water tube boiler is constituted so as to form a gap 13, permitting the flow of gas during combustion reaction, between neighboring water tubes 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water pipe boiler such as a once-through boiler, a natural circulation water pipe boiler, and a forced circulation water pipe boiler.

[0002]

2. Description of the Related Art A water tube boiler is a boiler in which a can is constituted by water tubes. As a can body structure of such a water pipe boiler, there is a water pipe boiler in which a plurality of water pipes are annularly arranged. In a water pipe boiler of this type, a cylindrical space surrounded by an annular water pipe row is used as a combustion chamber. The water tube boiler as described above,
Heat transfer is mainly performed by radiation in the combustion chamber, and heat transfer is mainly performed by convection downstream of the combustion chamber.

In recent years, there has been a demand for further reduction of NOx in such a water pipe boiler. Therefore, NOx reduction is achieved by attaching a low NOx burner to an existing can body or attaching an exhaust gas recirculation device.

[0004]

The problem to be solved by the present invention is to realize a low NOx with a simple structure.

[0005]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 has a structure in which a plurality of water pipes are provided in a region in a combustion chamber where a gas during combustion reaction exists. It is a water tube boiler arranged in a ring.

According to a second aspect of the present invention, there is provided a water pipe boiler in which the plurality of water pipes are arranged in a combustion chamber such that the temperature of the gas during the combustion reaction after contacting the water pipes is 1400 ° C. or less.

According to a third aspect of the present invention, there is provided a water pipe boiler in which a gap is formed between adjacent water pipes to allow a gas during combustion reaction to flow.

The invention according to claim 4 is a water tube boiler in which a part of the plurality of water tubes is closely arranged.

The invention according to claim 5 is a water pipe boiler in which the plurality of water pipes are arranged at locations where the widths C of the gaps are different.

The invention according to claim 6 is a water pipe boiler in which the plurality of water pipes are arranged in two or more rows in an annular shape.

The invention according to claim 7 is a water pipe boiler in which the plurality of water pipes are inclined pipes or bent pipes.

The invention according to claim 8 is a water tube boiler in which a heat recovery water tube is arranged outside the annularly arranged water tube.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is embodied as a multi-tube water tube boiler. Furthermore, the water tube boiler of the present invention
In addition to a steam boiler and a hot water boiler, it is applied as a heat medium boiler for heating a heat medium.

First, in the first aspect of the present invention, a plurality of water pipes are annularly arranged in a region (hereinafter, referred to as a combustion reaction region) where a gas during a combustion reaction exists in a combustion chamber. The combustion chamber is a space in which a part or all of the inside is subjected to a combustion reaction. The combustion chamber may be divided by a water tube row or by an outer wall formed of a refractory or the like. The combustion reaction gas refers to a high-temperature gas that is undergoing a combustion reaction in the combustion chamber. The combustion reaction region is preferably a region where a flame is generated in the combustion reaction gas or a region where a high temperature of the combustion reaction gas is 900 ° C. or higher. The flame as referred to herein is a phenomenon that occurs in a gas during a combustion reaction in which a combustion reaction is actively performed. This flame may be visible, may be difficult to view, or may not be visible. In the invention described in claim 1,
By arranging a plurality of water pipes in the combustion reaction region as described above, the temperature of the gas during combustion reaction is cooled by the plurality of water pipes to lower the temperature, thereby suppressing the generation of thermal NOx. The reason for this is that, as explained by the Zeldovich mechanism, as the temperature of the combustion reaction increases, the rate of generation of the thermal NOx increases remarkably, and the amount of thermal NOx increases. This is because the generation speed decreases and the generation amount decreases. In particular, when the temperature of the combustion reaction is 1400 ° C. or lower, the generation rate of thermal NOx becomes extremely slow.

In the first aspect of the present invention, since a plurality of water tubes are arranged in a ring, the combustion reaction gas contacts each of the water tubes to perform heat transfer, so that the heat load is substantially uniform. Further, since the gas during the combustion reaction is cooled by each water pipe, the action of reducing NOx is performed almost uniformly over the entire circumference of the annular water pipe row.

Further, according to the first aspect of the present invention, the plurality of water pipes are arranged in a ring. As this annular arrangement,
In addition to arranging a plurality of water pipes in a perfect circle, they can be arranged in an elliptical shape. Further, the plurality of water tubes may be arranged in a triangular shape, a quadrangular shape, or a polygonal shape of more than that. Further, when arranging the plurality of water pipes in a ring,
The lines connecting the centers of the water tubes may be arranged so as to form irregularities.

According to a second aspect of the present invention, the plurality of water tubes are arranged in a combustion chamber such that the temperature of the gas during the combustion reaction after contacting each of the water tubes is 1400 ° C. or less. With this arrangement, the temperature of the gas during the combustion reaction is reduced, so that the generation of thermal NOx is reduced, so that the NOx of the boiler is reduced.

According to a third aspect of the present invention, a gap is provided between adjacent water pipes to allow a gas to flow during the combustion reaction. That is, the gap has a width C at which the gas under combustion reaction passing through the gap can maintain the combustion reaction even when cooled by the water pipes, and the width C needs to be at least 1 mm.

According to a fourth aspect of the present invention, a part of the plurality of water tubes is closely arranged.
According to such an arrangement, the heat transfer amount can be adjusted by adjusting the contact state between the water pipe and the gas under combustion reaction.

According to a fifth aspect of the present invention, the plurality of water pipes are arranged in a ring shape at locations where the gaps C have different widths. That is, the plurality of water pipes are arranged in an annular shape such that a wide gap and a narrow gap are formed. According to this arrangement, the heat transfer amount can be adjusted by adjusting the contact state between the water pipe and the gas under combustion reaction.

According to a sixth aspect of the present invention, these water pipes are arranged in two or more rows in an annular shape. By arranging the plurality of water pipes in such a manner, the amount of heat transferred to the gas during the combustion reaction can be increased, so that the temperature of the gas during the combustion reaction can be further reduced, and the amount of generated thermal NOx is greatly reduced. . In this case, it is preferable to arrange the outer row of water pipes between adjacent water pipes in the inner row.

According to a seventh aspect of the present invention, a plurality of water pipes are provided.
It is an inclined tube or a bent tube. Here, the inclined pipe is a water pipe that is entirely inclined. Further, the bending pipe is a water pipe having a bent portion or a curved portion. As described above, when the plurality of water pipes are inclined pipes or bent pipes, more gas during the combustion reaction can be brought into contact with the water pipes, so that the gas during the combustion reaction can be effectively cooled to reduce NOx. it can.

Further, in the invention according to claim 7, all of the plurality of water pipes do not need to be inclined pipes or bent pipes, and some of the plurality of water pipes are at least one of the inclined pipe and the bent pipe. Should be fine. Further, the bent tube includes a case where only one of the bent portion and the bent portion is provided, and a case where the bent tube includes both of the bent portion and the bent portion. Further, the bent tube is not limited to one bent portion or curved portion.
Furthermore, the bending tube includes a case where the whole is curved.

According to an eighth aspect of the present invention, a heat recovery water pipe is arranged outside the annularly arranged water pipe.
This heat recovery water pipe further recovers heat from the gas during the combustion reaction and the gas after the combustion reaction that has passed through the gaps between the water pipes (hereinafter, referred to as a combustion reaction end gas) to improve the boiler efficiency.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a multi-tube once-through boiler will be described below with reference to FIGS. FIG. 1 is an explanatory view of a longitudinal section of a first embodiment of the present invention, and FIG. 2 is an explanatory view of a section along line II-II in FIG.

In FIGS. 1 and 2, the boiler can 1
Has an upper header 2 and a lower header 3 arranged at a predetermined distance from each other. An outer wall 4 is arranged between the outer circumferences of the upper header 2 and the lower header 3.

Between the upper header 2 and the lower header 3, a plurality (10 in the first embodiment) of water tubes 5 are arranged in a ring. These water pipes 5 constitute an annular first water pipe row 6. Further, a plurality (30 in the first embodiment) of heat recovery water pipes 7 are annularly arranged between the upper header 2 and the lower header 3 and near the inner peripheral side of the outer wall 4. Thus, an annular second water pipe row 8 is formed. The second water pipe row 8 and the first water pipe row 6 form a double annular water pipe row. Further, each end of each of the water pipes 5 and the heat recovery water pipes 7 is connected to each of the upper header 2 and the lower header 3.

The boiler combustion chamber 9 is defined by the upper header 2, the lower header 3, and the second water pipe row 8. A combustion device 10 is mounted above the combustion chamber 9. The combustion device 10 is inserted from the inside (central portion) of the upper header 2 toward the combustion chamber 9. The axis 11 of the combustion device 10 and each water pipe 5 of the first water pipe row 6 are They are almost parallel. This combustion device 10
Is a premixed combustion device.

The combustion device 10 forms a region in the combustion chamber 9 in which a gas under combustion reaction is present, that is, a combustion reaction region. Of the combustion reaction region, a region where a flame is generated. (Hereinafter referred to as the flame presence area)
The first water pipe row 6 is located at the first position. Further, the first water pipe row 6 is arranged in the combustion reaction region so that the temperature of the gas during the combustion reaction after contacting with each of the water pipes 5 becomes 1400 ° C. or less. Further, in the first water tube row 6,
Gap 1 between each water pipe 5 to allow the flow of gas during combustion reaction
2 are formed.

The first water pipe row 6 and the second water pipe row 8
A region (hereinafter referred to as a combustion reaction continuation region) 13 in which the combustion reaction of intermediate products of the combustion reaction such as CO and HC and unburned fuel is continuously performed.
There is no heat absorbing member such as the water pipe 5 in the combustion reaction continuation region 13.

In the second water pipe row 8, a gap (hereinafter referred to as a second gap) 14 between adjacent heat recovery water pipes 7 is narrow, and is usually set to 1 to 4 mm. Further, on the outer peripheral side of the second water pipe row 8, each heat recovery water pipe 7 is provided with a heat transfer fin 15.
Is attached.

Further, an exhaust gas outlet 16 is provided on the outer wall 4.
Is provided. The exhaust gas outlet 16 communicates with an annular exhaust gas passage 17 between the outer wall 4 and the second water pipe row 8.

In the water tube boiler having the above structure, when the combustion device 10 is operated, a gas during combustion reaction is generated in the combustion chamber 9. In the initial stage of the combustion reaction of the gas during the combustion reaction, the fuel is decomposed, and thereafter the decomposed fuel and oxygen react actively. Then, in the next stage, intermediate products such as CO and HC generated in the combustion reaction at this time further react, and the combustion reaction end gas after the combustion reaction is discharged from the can body 1 as exhaust gas. . Usually, a flame is generated in a region where the combustion reaction is actively performed.

The gas during the combustion reaction flows in the central portion of the first water pipe row 6 while spreading substantially in the axial direction toward the lower header 3, and flows into the combustion reaction continuation area 13 from the gap 12. . Therefore, as shown in FIG. 1, the flame is formed to the outside of the first water pipe row 6 with the flow of the gas during the combustion reaction. Therefore, each of the water pipes 5 is located in the flame existing area in the combustion reaction area. Then, when the combustion reaction gas generating the flame passes through the gap 12, heat exchange is performed with the fluid to be heated inside each water pipe 5. The combustion reaction gas generating the flame is rapidly cooled by this heat exchange and its temperature is reduced, so that the generation of thermal NOx is suppressed. Here, since the first water pipe row 6 is a ring-shaped water pipe row, the combustion reaction gas generating the flame comes into contact with each water pipe 5 almost evenly.
The heat load in each water pipe 5 is also substantially uniform. Further, the gas during the combustion reaction is substantially uniformly contacted with each of the water pipes 5 and cooled, so that the action of reducing the NOx by each of the water pipes 5 becomes almost equal. As a result, the formation of a flame is reduced in the combustion reaction gas.

Then, the gas under combustion reaction that has passed through the gap 12 flows through the combustion reaction continuation region 13 through the second water pipe row 8.
Distribute to. At this time, until the gas during combustion reaction reaches the second water pipe row 8, there is no contact with a member that performs heat exchange such as the water pipe 5, and the temperature does not decrease so much. Therefore, the gas during the combustion reaction flows through the combustion reaction continuation region 13 while continuing the combustion reaction, during which the C
The oxidation reaction from O to CO ₂ is promoted. At this time, in the combustion reaction continuation region 13, in addition to the oxidation reaction, a combustion reaction such as the intermediate product and unburned fuel is performed.

Then, the combustion reaction gas becomes a high-temperature gas which has almost completed the combustion reaction before reaching the second water pipe row 8, and flows into the exhaust gas passage 17 through the second gap 14. When the gas during the combustion reaction passes through the second gap 14, more heat is transferred to the fluid to be heated in each of the heat recovery water pipes 7 by the heat transfer fins 15. Then, the combustion reaction end gas that has passed through the second gap 14 and flowed into the exhaust gas passage 17 is supplied from the outside of the second water pipe row 8 to each heat recovery water pipe 7.
After performing heat transfer to the fluid to be heated inside, the exhaust gas is discharged from the exhaust gas outlet 16 to the outside of the boiler as exhaust gas. Here, since the second water pipe row 8 is an annular water pipe row composed of a plurality of heat recovery water pipes 7, the combustion reaction gas and the combustion reaction end gas almost uniformly contact each heat recovery water pipe 7, Second water pipe row 8
As a whole, heat is recovered from the combustion reaction gas and the combustion reaction end gas, so that the heat load on each heat recovery water pipe 7 in the second water pipe row 8 is also substantially uniform.

In the above description, the flow of the gas during the combustion reaction is in the radial direction of the first water pipe row 6.
Next, the axial direction of the first water pipe row 6 will be described with attention. As described above, the gas during the combustion reaction flows in the central portion of the first water pipe row 6 while spreading toward the lower header 3 substantially in the axial direction. The temperature decreases on the side due to heat transfer to each water pipe 5. Therefore, generation of thermal NOx is suppressed.
Further, since the first embodiment is a once-through boiler, the fluid to be heated is supplied from the lower header 3 into each of the water pipes 5 and each of the heat recovery water pipes 7, and each of the water pipes 5 and each of the heat recovery water pipes 7 are heated. While rising, and is taken out as steam from the upper header 2.

Next, the water tube boiler of the first embodiment will be described more specifically. The water tube boiler of the first embodiment was implemented as a once-through boiler having an evaporation amount of 500 to 4000 kg / hour. In the once-through boiler of the first embodiment, the outer diameter B of the water pipe 5 is about 60 mm. Normal,
In a once-through boiler, a water pipe 5 having an outer diameter B of about 25 to 80 mm is used.
A water pipe 5 having an outer diameter B of about the same is used. In the first embodiment, the diameter D of the pitch circle when the plurality of water pipes 5 are arranged in a perfect circle is about 344 mm. The diameter D of the pitch circle must be at least 100 mm. That is,
If the diameter D of the pitch circle is smaller than this, the space on the inner peripheral side of the first water pipe row 6 becomes smaller, and it becomes difficult to continue a stable combustion reaction. On the other hand, if the diameter D of the pitch circle is large, the space on the inner peripheral side of the first water pipe row 6 becomes large, and a high-temperature region which promotes the generation of thermal NOx tends to be generated inside. Therefore, the upper limit value of the diameter D of the pitch circle is determined in consideration of this point. The upper limit of the diameter D of the pitch circle is determined according to the required amount of evaporation of the boiler.
For example, in a water tube boiler with an evaporation of 4000 kg per hour,
The upper limit of the diameter D of the pitch circle is 1000 mm.

Further, in the first embodiment, the distance A between the centers of the adjacent water pipes 5 in the first water pipe row 6 is set to about 106 mm.
The ratio A / B between the center distance A and the outer diameter B of the water pipe 5 is set to 1.8. The width C of the gap 12 is equal to the difference between the center distance A and the outer diameter B, and is about 46 mm. When the gap 12 is provided between the water pipes 5 as in the first embodiment, the width C of the gap 12
Is set to a value such that the combustion reaction gas does not stop the combustion reaction due to cooling by the water pipes 5. In this case, the width C of the gap 12 needs to be at least 1 mm. Therefore, when the gap 12 is provided between the adjacent water pipes 5, the ratio A / B is set to 1 <A / B ≦ 2. This ratio A /
B can be changed according to the degree of the request for NOx reduction.

Further, the combustion apparatus 10 of the first embodiment
Sets the air ratio to 1.3, in which case
The maximum temperature of the gas during the combustion reaction is approximately 1700 ° C.
Here, in a combustion apparatus for a water tube boiler, combustion is generally performed with the air ratio set in a range of 1.1 to 1.3. In this case, the maximum temperature of the gas during combustion reaction is 1. 1 to
It is approximately 1800 ° C. in the range of 1.2, and the air ratio is 1.2
Approximately 1700 ° C. in the range of １1.3.

As described above, by setting the distance A between the centers of the water pipes 5 and the outer diameter B of the water pipes 5, the temperature of the gas during the combustion reaction at the time of passing through the gaps 12 can be reduced by the cooling by the water pipes 5. To about 1100 ° C. This temperature is equal to or lower than the temperature (approximately 1400 ° C.) at which the amount of generated thermal NOx is greatly reduced. Therefore, a water tube boiler that emits a small amount of NOx can be provided. Incidentally, the NOx emission of the water tube boiler of the first embodiment is O ₂
It is about 30 ppm in terms of 0%.

Further, this temperature is higher than the temperature at which the oxidation reaction from CO to CO ₂ is actively performed (about 800 ° C.). Therefore, when the combustion reaction gas flows through the combustion reaction continuation region 13, the oxidation reaction from CO to CO ₂ is actively performed, and a water tube boiler that emits less CO can be obtained. .

As described above, in the boiler of the first embodiment, the temperature of the combustion reaction gas flowing out of the gap 12 of the first water pipe line 6 is controlled to approximately 1100 ° C. 80 depending on the degree of NOx reduction and CO reduction
Control within the range of 0 to 1400 ° C. Here, the temperature of the combustion reaction gas flowing out of the gap 12 is preferably as low as possible from the viewpoint of reducing NOx, and is preferably as high as possible from the viewpoint of reducing CO. From this viewpoint, the temperature is more preferably in the range of 900 to 1300 ° C.

Further, in the first embodiment, the radial interval E between the first water pipe row 6 and the second water pipe row 8 is set as the width of the combustion reaction continuation area 13. The interval E is about 84 mm, which is 1.4 times the outer diameter B of the water pipe 5.
It is twice. By setting the radial interval E between the first water pipe row 6 and the second water pipe row 8 in this manner, the residence time of the combustion reaction gas in the combustion reaction continuation region 13 is reduced to about 47 milliseconds. Has been adjusted to. In this case, the amount of emitted CO is about 15 ppm. That is,
In order to surely cause the oxidation reaction, it is necessary to keep the temperature of the gas during the combustion reaction at a certain temperature (approximately 800 ° C.) or more and at the same time to have a certain or more reaction time. This reaction time is required to be shorter as the temperature of the gas during the combustion reaction is higher, and to be longer as the temperature is lower. Therefore, the set value of the interval E is changed in accordance with the temperature of the combustion reaction gas flowing out from the gap 12 of the first water pipe row 6, and the residence time of the combustion reaction gas in the combustion reaction continuation region 13 is adjusted. I do. The radial distance E between the first water pipe row 6 and the second water pipe row 8 is changed according to the number and width C of the gaps 12 in the first water pipe row 6. The lower limit of the residence time is selected from the range of 1 to 10 milliseconds. Therefore, the lower limit of the interval E between the first water pipe row 6 and the second water pipe row 8 is about 0.5 times the outer diameter B of the water pipe 5. In addition, it is advantageous to set the residence time to be longer, in terms of lowering the CO.
It is determined according to the degree of demand for downsizing and boiler miniaturization. In this case, the upper limit of the interval E is preferably about six times the outer diameter B of the water pipe 5.

In the first embodiment described above, the plurality of water pipes 5 are arranged in a substantially circular shape and at substantially equal intervals in the combustion reaction region in the combustion chamber 9. The arrangement of the water tubes 5 in the embodiment is not limited to such an arrangement, and may be, for example, an annular arrangement as shown in FIGS. Here, in the following description of each embodiment, the same reference numerals are given to the same components as those in the first embodiment, and the detailed description thereof will be omitted. FIG.
In FIG. 5 to FIG. 5, only the first water pipe row 6 is shown, and other components are not shown.

First, in the water pipe boiler of the second embodiment shown in FIG. 3, when a plurality of water pipes 5 are arranged in a ring, the line connecting the centers of adjacent water pipes 5 (dashed line in FIG. 3) has irregularities. It is arranged to form. In the second embodiment, each water pipe 5 is arranged so as to be shifted from the adjacent water pipe 5 in the center direction of the first water pipe row 6 or in the radial direction. According to this arrangement, the number of water tubes 5 can be increased as compared with a case where the water tubes 5 are arranged in a perfect circle. In the second embodiment, the ratio A / B between the center distance A and the outer diameter B is:
1.2. Further, in the second embodiment, the water pipes 5 are alternately shifted inward and outward, but a plurality of water pipes 5 may be alternately shifted according to the embodiment.

Next, the water tube boiler of the third embodiment shown in FIG. 4 has a plurality of water tubes 5 arranged in a perfect circle.
Some of the plurality of water pipes 5 are closely arranged. In the third embodiment, a plurality of water pipes 5 are grouped into groups 18 of a predetermined number (in FIG. 4, every three),
The first water pipe row 6 is configured by arranging a plurality of groups 18 (five groups in FIG. 4). In each of the groups 18, the water pipes 5 are arranged in close contact with no gap. Therefore, within each group 18, the ratio A
/ B is 1. The gaps 12 are formed between the groups 18. The ratio A / B between the center distance A between the water tubes 5 adjacent to each other with the gap 12 therebetween and the outer diameter B of the water tubes 5 is 2.0. That is, in the third embodiment, the ratio A / B is 1 ≦ A / B ≦ 2. When some of the plurality of water pipes 5 are closely arranged in this way, the number of the gaps 12 formed in the first water pipe row 6 can be adjusted, and the gaps between the groups 18 can be adjusted. 12, the width C can also be adjusted. Therefore, the flow of the gas during the combustion reaction from the inside of the first water pipe row 6 to the gap 12 is controlled in accordance with the characteristics of the combustion device 10 to adjust the contact time between the first water pipe row 6 and the gas during the combustion reaction. The amount of heat recovered by the water pipes 5 and the temperature of the gas during the combustion reaction after passing through the gap 12 can be adjusted. In the third embodiment, the number of water pipes 5 in each group 18 is the same, but depending on the implementation,
It is also preferable that the number of water tubes 5 in each group 18 be different.

Next, the water pipe boiler of the fourth embodiment shown in FIG. 5 is an example in which a plurality of water pipes 5 are arranged in a plurality of rows in an annular manner. In the fourth embodiment, two water pipes 5 are arranged in an annular manner in two rows. is there. In the third embodiment, the center distance A of each water pipe 5
Is set as follows. First, for each of the water pipes 5 in the inner row, the ratio A / B between the center distance A between adjacent water pipes 5 in the row and the outer diameter B of the water pipes 5 is set to 1.3. The ratio A / B between the center distance A of the adjacent water pipes 5 and the outer diameter B of the water pipes 5 is set to 1.3 between each water pipe 5 in the outer row and each water pipe 5 in the outer row. It has been set. Further, in the fourth embodiment, the water pipes 5 in the outer row are located between the adjacent water pipes 5 in the inner row. Therefore, the first water pipe row 6 includes a plurality of water pipes 5 in its circumferential direction.
Are arranged in a zigzag pattern. According to such an arrangement of the water pipe 5, since the amount of heat recovered from the gas during the combustion reaction can be increased, the gas during the combustion reaction can be sufficiently cooled.
Further, since the heat recovery amount can be increased in this manner, a large-capacity combustion device 10 can be used. Here, in the fourth embodiment, the plurality of water pipes 5 are arranged in two rows in an annular shape, but it is also preferable to arrange them in three rows or more rows depending on the implementation.

In the first to fourth embodiments described above, the gaps 12 are all of the same width C. However, depending on the implementation, the water pipe 5 is formed so that the gaps 12 have different widths C. They can also be placed.

In the first to fourth embodiments described above, a plurality of vertical water pipes 5 are arranged in a ring to form a first water pipe row 6 having a substantially cylindrical shape. However, in the present invention, each water pipe 5 is not limited to a vertical water pipe, and may be configured as shown in FIGS. Here, in the following description of each embodiment, the same reference numerals are given to the same components as those in the first to fourth embodiments, and the detailed description thereof will be omitted. In the fifth to seventh embodiments, the second water pipe row 8
In the same manner as in the first embodiment, a plurality of vertical heat recovery water pipes 7 are annularly arranged so as to surround the first water pipe row 6 and have a cylindrical shape.

First, in the water tube boiler of the fifth embodiment shown in FIG. 6, the water tube 5 is an inclined tube. The water pipe 5 in the fifth embodiment has its upper end side inclined toward the outside of the can body 1. By arranging the plurality of water pipes 5 in this inclined state in an annular shape, the water pipe 5 has a tapered shape that becomes narrower toward the lower side. Is formed. According to this configuration, each water pipe 5 is inclined so as to cross the direction of the axis 11 of the combustion device 10, that is, the direction in which the fuel is ejected from the combustion device 10, so that the contact with the gas during the combustion reaction is good. Become. Therefore, the cooling effect of the gas during the combustion reaction by each water pipe 5 can be enhanced, which contributes to the reduction of NOx.

Next, in the water tube boiler of the sixth embodiment shown in FIG. 7, the water tube 5 is a bent tube. The water pipe 5 in the sixth embodiment has a bent portion formed in the middle, the upper half is inclined toward the outside of the can body 1, and the lower half is vertical. By arranging the plurality of bent water pipes 5 in an annular shape, a funnel-shaped first water pipe row 6 is formed. In this configuration, the position of the lower half of each water pipe 5 is closer to the axis 11 of the combustion device 10 than the connection position of each water pipe 5 in the upper header 2. Therefore, the contact between each water pipe 5 and the gas during combustion reaction is improved, and the cooling effect of the gas during combustion reaction by each water pipe 5 can be enhanced, which contributes to the reduction of NOx.

Next, in the water pipe boiler of the seventh embodiment shown in FIG. 8, the water pipe 5 is formed as a bent pipe, and bent portions are formed at two upper and lower portions. The water pipe 5 in the seventh embodiment has the upper and lower parts of the water pipe 5 inclined toward the outside of the can 1. The first water pipe row 6 is formed by arranging the plurality of bent water pipes 5 in a ring shape. In this configuration, the position of the middle part of each water pipe 5 is closer to the axis 11 of the combustion device 10 than the connection position of each water pipe 5 in the upper and lower headers 2 and 3. Therefore, the contact between each water pipe 5 and the gas during combustion reaction is improved, and the cooling effect of the gas during combustion reaction by each water pipe 5 can be enhanced, which contributes to the reduction of NOx. Further, in the seventh embodiment, each water pipe 5 is placed in the combustion reaction gas only by changing the shape of each water pipe 5 without changing the connection position between the upper and lower headers 2 and 3 and each water pipe 5. Can be located.

In the sixth and seventh embodiments, the water pipe 5 is a bent pipe having one or two bent portions, but a water tube having a bent portion instead of the bent portion may be used. it can. Further, the bending tube may have only one of a bent portion and a bent portion, or may have both of them. Further, the bending tube is not limited to one having a bent portion or a curved portion. In addition, the bending tube includes a case where the entirety is curved.

In the first to seventh embodiments, the water pipes 5 constituting the first water pipe row 6 are vertical pipes, inclined pipes or bent pipes. In the present invention, all of the water pipes 5 are of the same type. However, two or more types of water pipes 5 can be used in combination. Further, the water pipe 5 may be one in which various grooves and heat transfer fins are added to the outer peripheral surface and the inner peripheral surface to improve the heat transfer performance. The water tubes 5 do not all need to have the same outer diameter, and some of the water tubes 5 may have different outer diameters. Further, in the case where the first water pipe row 6 is arranged in two or more rings, the number of the water pipes 5 may be different between the inner row and the outer row depending on the implementation. As described above, in the water tube boiler according to the present invention, the arrangement of the plurality of water tubes 5 can be variously changed without departing from the technical idea of the present invention. It is desirable to dispose the plurality of water pipes 5 so that the gas during the combustion reaction uniformly contacts each water pipe 5 of the first water pipe row 6 according to the gas formation state. Further, in the first embodiment, no water pipe is arranged in the area between the first water pipe row 6 and the second water pipe row 8, but in the water pipe boiler according to the present invention, a predetermined number of water pipes are provided in this area. A water pipe can also be arranged.

Further, in each of the above embodiments, the ratio A / B of the distance A between the centers of the adjacent water pipes 5 and the outer diameter B of the water pipes 5 is described.
Is set to 1 ≦ A / B ≦ 2, but in the water pipe boiler according to the present invention, depending on the degree of demand for lowering NOx,
The ratio A / B can be set to 1 ≦ A / B ≦ 3.
Further, the ratio A / B can be selected in the range of 1 ≦ A / B ≦ 5.

Further, the water tube boiler according to the present invention is not limited to the one in which the combustion device 10 is attached to the upper header 2, but also includes the one in which the combustion device 10 is attached to the lower header 3. Further, the combustion device 10 is not limited to a specific type of combustion device, and various types of combustion devices can be used. For example, in addition to a premixed combustion device and a premixed combustion device (also referred to as a diffusion combustion type combustion device), various types of combustion devices such as a vaporization combustion type combustion device can be applied. Can be selected regardless of liquid or gas. In particular, the premixed combustion device mixes fuel (including liquid and gas) and combustion air downstream of the combustion device to start a combustion reaction (hereinafter referred to as an initial combustion reaction region). is required. In the water tube boiler according to the present invention, the combustion device 10 is a form in which the axis is aligned and inserted from one opening of the first water tube row 6, and the first water pipe row is provided on the downstream side in the direction of the axis 11 of the combustion device 10. 6, there is a space on the inner peripheral side where the water pipe 5 does not exist.
This space is secured as the initial combustion reaction region.
In particular, most combustion devices that use liquid fuel are of a premix type, and in a water tube boiler using such a combustion device, mixing of fuel and combustion air and effective combustion are not hindered. In addition, it is possible to achieve a low NOx.

[0058]

As described above, according to the present invention, it is possible to provide a water pipe boiler for clean exhaust gas which achieves a further reduction in NOx and is compatible with environmental problems by a simple configuration based on the arrangement of water pipes.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a longitudinal section of a first embodiment of the present invention.

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

FIG. 3 is an explanatory view of a second embodiment of the present invention, schematically illustrating an example of an annular arrangement of water pipes.

FIG. 4 is an explanatory view of a third embodiment of the present invention, schematically illustrating an example of an annular arrangement of water pipes.

FIG. 5 is an explanatory view of a fourth embodiment of the present invention, schematically showing an annular arrangement of water tubes.

FIG. 6 is an explanatory view of a fifth embodiment of the present invention, schematically illustrating an example of the shape of a water pipe.

FIG. 7 is an explanatory view of a sixth embodiment of the present invention, schematically illustrating an example of a shape of a water pipe.

FIG. 8 is an explanatory view of a seventh embodiment of the present invention, schematically illustrating an example of the shape of a water pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Can body 2 Upper header 3 Lower header 4 Outer wall 5 Water pipe 6 First water pipe row 7 Heat recovery water pipe 8 Second water pipe row 9 Combustion chamber 10 Combustion device 11 Axis 12 Gap 13 Combustion reaction continuation area 14 Second gap A Neighbor Distance between centers of fitting water pipes B Outside diameter of water pipes C Width of gap

Continued on the front page (72) Inventor Kanta Kondo 7 Horie-cho, Matsuyama-shi, Ehime Pref.

Claims (8)

[Claims] 1. A water tube boiler, wherein a plurality of water tubes 5 are annularly arranged in a region of a combustion chamber 9 where a gas under combustion reaction exists. 2. The plurality of water tubes 5 are arranged in a combustion chamber 9 such that the temperature of a gas during a combustion reaction after contacting each of the water tubes 5 is 1400 ° C. or less. Water tube boiler. 3. The water pipe boiler according to claim 1, wherein a gap 12 is formed between adjacent water pipes 5 so as to allow a gas during combustion reaction to flow. 4. A part of the plurality of water tubes 5
Are closely arranged.
The water tube boiler according to claim 3. 5. The water pipe boiler according to claim 1, wherein the plurality of water pipes 5 are arranged at locations where the width C of the gap 12 is different. 6. The plurality of water pipes 5 are arranged in an annular shape in two or more rows.
The water tube boiler according to any one of the above. 7. The water pipe boiler according to claim 1, wherein the plurality of water pipes 5 are inclined pipes or bent pipes. 8. The water tube boiler according to claim 1, wherein a heat recovery water tube 7 is arranged outside the annularly arranged water tube 5.