JP2759705B2 - Water tube boiler - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a water tube boiler.

[Problems to be solved by conventional technology and invention]

A conventional water tube boiler includes a can body formed by connecting an upper header and a lower header with two sets of annular water pipe groups of an inner row and an outer row, and is provided on a central axis of the can body. In addition, a burner port is provided at the upper or lower part of the can body, and combustion is performed in a furnace including the inner peripheral surface of the inner row water pipe, the furnace bottom and the furnace top.

However, in the water tube boiler with the above structure, the temperature inside the furnace becomes high, and NOx due to nitrogen bond in the combustion air
(So-called thermal knock). In order to reduce this thermal knock, a special mechanism for NOx countermeasures was required.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a water tube boiler that can suppress combustion temperature and reduce NOx.

[Means for solving the problem]

In order to solve the above problems, the present invention relates to a water tube boiler in which a can body is formed by connecting an upper header and a lower header with two annular water pipe groups of an inner row and an outer row. An opening is provided at a predetermined position in the water tube group and a burner port is provided at the opening to form a small-capacity furnace, and the combustion gas burned in the furnace is passed between the two rows of water tube groups. A combustion gas passage leading to the inside of the water pipe group in the inner row is provided later, and a singing gas outlet is provided above the center of the can body.

Further, in the present invention, a feed water heater is incorporated inside the water pipe group in the inner row.

In the present invention, a gap is provided between two or three water pipes located in the vicinity of the opening in the outer row of water pipe groups, and the gap is configured as air or exhaust gas or an air and exhaust gas inlet.

[Action]

According to the present invention as described above, the furnace formed by providing a burner port at the opening provided in the outer row water pipe group has a small capacity,
Combustion in the furnace continues to take place in the gap between the inner row of water pipes and the outer row of water pipes. Since the combustion in the gap between the inner water pipe group and the outer water pipe group is performed while heat is absorbed by the two water pipe groups, the combustion temperature does not increase. The lower the combustion temperature, the lower the production of thermal knock.

Also, a gap is provided between two or three water pipes located near the opening in the outer row of water pipe groups, and when air or exhaust gas or air and exhaust gas are blown from the gap, this causes
Stage combustion or exhaust gas recirculation is performed, combustion slows down,
Further, the combustion temperature is lowered, and the NOx is further reduced.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing a schematic structure of a water pipe boiler according to the present invention, wherein FIG. 1 (a) is a transverse sectional view and FIG. 1 (b) is a longitudinal sectional view.

As shown in the figure, this water pipe boiler includes an inner row water pipe group 4 in which water pipe groups are arranged in a ring, and an outer row water pipe group 5 in which water pipe groups are also arranged in a ring outside the inner row water pipe group 4. The upper and lower ends of the inner row water pipe group 4 and the outer row water pipe group 5 are respectively connected to an upper pipe 8 and a lower pipe 9 to form a can body, and the outer periphery of the outer water pipe group 5 is covered with a can body. 6 and a structure in which a shielding plate 12 is arranged on the inner periphery of the inner row water pipe group 4.
A bottom plate 14 is attached to a lower part of the inner row water pipe group 4, and a top plate 13 is attached to an upper part of the inner row water pipe group 4.

On the other hand, an opening 5a is provided at a predetermined position of the water tube group constituting the outer row water tube group 5, and a portion of the can body cover 6 at the opening 5a is expanded outward to form the wind box 2. I have. This wind box 2 has a refractory 11 inside.
The wind box 2 has a plurality of multi-burners 1 inserted therein. The opening 5a of the outer row water pipe group 5, the inner row water pipe group 4 and the wind box 2 form a small-volume furnace A.

On the opposite side of the opening 5a of the inner row water pipe group 4, an opening 4a for guiding the combustion gas between the inner row water pipe group 4 and the shielding plate 12 is provided, and near the opening 5a of the shielding plate 12. An opening 12a for guiding the combustion gas to the inside of the shielding plate 12 is provided in the portion.

Further, a combustion gas outlet 7 for discharging the combustion gas in the shielding plate 12 to the outside is provided at the center of the top plate 13.

When the combustion is performed in the furnace A, the furnace A
The combustion is not completed only by the furnace A, but continues to be performed between the inner water pipe group 4 and the outer water pipe group 5 which are the combustion gas passages.

Here, the combustion in the gap between the inner row water pipe group 4 and the outer row water pipe group 5 is combustion while the heat is absorbed by the inner row water pipe group 4 and the outer row water pipe group 5, so that the combustion temperature does not rise. . As a result, the combustion temperature is lowered, and the generation of thermal knock is reduced.

The combustion gas passes through the gap between the inner row pipe group 4 and the outer row pipe group 5, and the combustion gas passes through the opening 4a of the inner row pipe group 4 and passes between the inner row pipe group 4 and the shielding plate 12. And the opening of the shielding plate 12
The fuel gas is guided from the inside 12a to the inside of the shielding plate 12 and discharged from the combustion gas outlet 7 to the outside.

FIG. 2 is a schematic longitudinal sectional view showing another embodiment of the present invention.

The difference between the water tube boiler shown in FIG. 1 and the embodiment shown in FIG. 1 is that a feed water heater 10 is disposed inside a shielding plate 12.

With this configuration, the combustion gas introduced into the inside of the shielding plate 12 further heats the feed water heater 10, and is thereafter discharged to the outside from the combustion gas outlet 7.

By disposing the feed water heater 10 inside the shielding plate 12 in this way, a water pipe boiler with a small installation space can be configured.

FIGS. 3 to 5 are views showing still another embodiment of the present invention, and are schematic views of a main part showing an enlarged portion near the opening 5a.

In the embodiment shown in FIG. 3, gaps 5b are provided at two places in each of the water pipes on both sides of the opening 5a of the outer row water pipe group 5, and a passage 16 provided outside the gap 5b passes through the gap 5b. The secondary air is introduced into the outer water pipe group 5.

With this configuration, the second-stage combustion is performed between the inner row water pipe group 4 and the outer row water pipe group 5 by the secondary air, following the combustion in the small-capacity furnace A.

When the two-stage combustion is performed in this manner, the combustion is delayed, the combustion temperature is further reduced, and the NOx is further reduced.

In the embodiment shown in FIG. 4, gaps 5b are provided at two places in each of the water pipes on both sides of the opening 5a of the outer row water pipe group 5, and a passage 16 provided outside the gap 5b passes through the gap 5b. Exhaust gas is introduced into the outer row water pipe group 5.

With this configuration, the exhaust gas can be sent to the burning gas that has started burning in the furnace A, and the exhaust gas can be recirculated. This also slows down the combustion and lowers the combustion temperature. In addition, the NOx can be further reduced.

Further, in the embodiment shown in FIG.
A gap 5b is provided at each of two places of the water pipes on both sides of the opening 5a, and secondary air and exhaust gas are introduced into the outer row water pipe group 5 through the gap 5b from a passage 16 provided outside the gap 5b. It has a configuration.

With this configuration, the inner row water pipe group 4 and the outer row water pipe group 5
During this time, secondary air and exhaust gas are sent in,
Step combustion and exhaust gas recirculation can be performed at the same time, and the combustion is slowed down, the combustion temperature is lowered, and the NOx is further reduced as in the above embodiment.

〔The invention's effect〕

As described in detail above, according to the water tube boiler according to the present invention, combustion in the furnace is continued to be performed also in the gap between the inner row water pipe group and the outer row water pipe group, so that the combustion temperature does not rise, Knox generation has an excellent effect of being reduced.

Further, in the present invention, the combustion gas outlet is provided above the center of the can body, and the feedwater heater is built in the inner row of water pipe groups, so that the water pipe boiler can be downsized.

When a gap is provided between two or three water pipes located near the opening in the outer row of water pipe groups, and air or exhaust gas or air and exhaust gas are blown from the gap, the combustion temperature is further reduced. And has an excellent effect of further reducing NOx.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic structure of a water tube boiler according to the present invention, FIG. 2 is a schematic longitudinal sectional view showing another embodiment of the present invention,
FIGS. 3, 4, and 5 are views showing still another embodiment of the present invention, and are schematic views of a main portion showing an enlarged portion near the opening 5a. In the figure, 1 ... Multi burner, 2 ... Wind box,
4 ... inner row water pipe group, 5 ... outer row water pipe group, 5a ... opening,
5b: gap, 7: combustion gas outlet, 8: upper pipe, 9
... lower pipe, 10 ... feed water heater, A ... furnace.

Claims (3)

(57) [Claims] 1. A water tube boiler in which a can body is formed by connecting an upper header and a lower header with two groups of annular water pipes of an inner row and an outer row, wherein: An opening is provided at a predetermined position, a burner port is provided at the opening to form a small-capacity furnace, and the combustion gas burned in the furnace is passed between the two rows of water pipe groups, and then the inner row of water pipe groups is formed. A water tube boiler, wherein a combustion gas passage leading to the inside is provided, and a combustion gas outlet is provided above the center of the can body. 2. A water pipe boiler according to claim 1, wherein a feed water heater is incorporated inside the water pipe group in the inner row. 3. A gap is provided between a plurality of water pipes located in the vicinity of an opening in the outer row of water pipe groups, and the gap is an air or exhaust gas or an air and exhaust gas inlet. A water tube boiler according to item (1) or (2).