JP2005188779A - Boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler capable of reducing a heat radiation loss. <P>SOLUTION: In this boiler comprising a boiler body B comprising a burner 1 for burning fuel while applying outside air supplied by a blower means 2 as combustion air, and an exhaust passage 4 for guiding the combustion gas of the burner 1, exhausted from an exhaust port 3 at the upper part of the boiler body B to a chimney 5, the exhaust passage 4 is provided with an outside air introducing port 16 for introducing outside air into the exhaust passage 4, and an outside air introduction damper D for closing the outside air introducing port 16 when pressure in the exhaust passage is same as or higher than the pressure outside of the exhaust passage, and opening the outside air introducing port 16 when pressure in the exhaust passage becomes lower than pressure outside the exhaust passage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention includes a boiler body including a burner that burns fuel using outside air supplied by a blowing means as combustion air,
The present invention relates to a boiler provided with an exhaust passage that guides the combustion gas of the burner discharged from an exhaust port at the top of the boiler body to a chimney.

  In the above-described boilers, conventionally, the exhaust path is configured to allow the combustion gas discharged from the exhaust port to flow upward and then flow horizontally until reaching the chimney to be led to the chimney. It was. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 10-82519

By the way, in such a boiler, in order to allow the combustion gas to flow smoothly to the exhaust port and appropriately discharge, normally, in the boiler body, the internal combustion is performed so that the combustion gas flows horizontally or upward. A gas flow path is configured so that the combustion gas flows smoothly through the internal combustion gas flow path.
In such a boiler, when the steam consumption is reduced and the load is reduced, combustion of the burner may be stopped and the burner may be burnt intermittently according to the load.

When the boiler is operated by intermittently burning the burner in this way, the internal combustion gas flow path is heated by the heating target water stored in the boiler body in a heated state while the burner is stopped. Therefore, as the combustion gas in the internal combustion gas flow path flows toward the exhaust port, outside air (air) is sucked from the suction port of the blower, and the outside air flows into the internal combustion gas flow. It flows into the flow path and is heated by the water to be stored and heated and flows toward the exhaust port, so that the outside air is sucked in from the suction port of the blower, and the outside air flows into the internal combustion gas flow path. In other words, a so-called draft that flows to the outside through the exhaust path and the chimney is generated.
And when a draft occurs, the internal combustion gas flow path, the exhaust path, and the outside air that flows through the chimney form the heat retained by the stored heating water and the internal combustion gas flow path. Since the retained heat of the boiler body such as the retained heat of the member to be radiated is radiated, the heat radiation loss is increased.

  However, conventionally, as described above, the exhaust passage allows the combustion gas discharged from the exhaust port to flow upward, and then flows horizontally to reach the chimney until reaching the chimney. As a result, the combustion gas and the outside air that have flowed into the exhaust passage from the exhaust port easily flow toward the chimney, so that there is a problem that a draft is likely to occur, and the heat dissipation loss is large.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a boiler capable of reducing heat dissipation loss.

The boiler of the present invention includes a boiler main body including a burner that burns fuel using the outside air supplied by the blowing means as combustion air,
An exhaust path for guiding the combustion gas of the burner discharged from the exhaust port at the top of the boiler body to the chimney is provided;
The first characteristic configuration is provided with an outside air inlet for introducing outside air into the exhaust passage,
When the pressure inside the exhaust passage is equal to or higher than the pressure outside the exhaust passage, the outside air inlet is closed, and when the pressure inside the exhaust passage becomes lower than the pressure outside the exhaust passage, the outside air inlet is opened. A feature is that a constructed outside air introduction damper is provided.

That is, when the pressure in the exhaust passage is equal to or higher than the pressure outside the exhaust passage (ie, atmospheric pressure), the outside air introduction port is closed by the outside air introduction damper, and the pressure in the exhaust passage is more than the pressure outside the exhaust passage. When the temperature becomes lower, the outside air introduction opening is opened by the outside air introduction damper, and outside air is introduced into the exhaust passage through the outside air introduction port.
In other words, when exhausting the combustion gas discharged from the exhaust port to the outside through the exhaust channel and the chimney, the exhaust channel and the chimney are set to zero pressure (atmospheric pressure) or substantially zero pressure in the vicinity of the exhaust port in the exhaust channel. In this way, the combustion gas is designed to be discharged into the atmosphere by the draft action of the chimney.
While the burner is being burned, the inside of the exhaust passage is at atmospheric pressure or more due to the flow of combustion gas, the outside air introduction damper is closed by the outside air introduction damper, and the inside of the exhaust passage through the outside air introduction port is closed. Since outside air is prevented from being introduced into the exhaust gas, the combustion gas is appropriately discharged through the exhaust passage and the chimney.
When the combustion of the burner is stopped and the draft begins to occur, the pressure inside the exhaust passage decreases and becomes lower than the pressure outside the exhaust passage, so that the outside air introduction damper opens the outside air introduction port, and the outside air Outside air is introduced into the exhaust passage through the inlet, and the outside air thus introduced flows toward the chimney. Such an external airflow suppresses the combustion gas and the outside air sucked from the suction port of the blower means and flowing through the internal combustion gas flow path from flowing into the exhaust path, and the exhaust path and the chimney are Since it is cooled, it is possible to suppress the occurrence of drafts and reduce heat dissipation loss.
Therefore, it has become possible to provide a boiler that can reduce heat dissipation loss.

The second feature configuration is
The exhaust path is configured to include a downward flow path portion that allows combustion gas to flow downward.

That is, even if the combustion of the burner is stopped and the draft starts to occur, the combustion gas or the outside air sucked from the suction port of the blowing means and flowing through the internal combustion gas flow path can flow into the exhaust path, The combustion gas or the outside air that flows into the exhaust passage in such a manner has a low temperature, and the draft force acting so as to be discharged to the outside by the chimney is small. Is suppressed.
In other words, while the burner is being burned, high-temperature combustion gas with a large draft force flows through the exhaust passage, so that the combustion gas also flows smoothly through the downward flow path portion of the exhaust passage, and appropriately passes through the exhaust passage and chimney. Discharged.
When the combustion of the burner is stopped and the draft begins to occur, the combustion gas whose temperature has decreased or the low temperature outside air sucked from the suction port of the blower means will flow into the exhaust passage. The combustion gas or the outside air having such a low temperature has a small draft force and is difficult to flow through the downward flow path portion of the exhaust path, so that the generation of the draft is suppressed.
Therefore, it has become possible to provide a boiler that can reduce heat dissipation loss.

In addition to the first or second feature configuration, the third feature configuration is
The boiler body is characterized in that it is configured as a furnace flue tube type.

That is, the furnace tube-type boiler main body is provided with a water storage part for storing water to be heated, a combustion chamber is formed in the furnace inside the water storage part, and the combustion gas discharged from the combustion chamber is discharged. A smoke pipe to be flown is provided inside the water storage part, and the combustion target gas stored in the water storage part is generated by causing the combustion gas to flow through the combustion chamber and the smoke pipe to generate steam. is there.
And in the furnace flue-tube type boiler provided with such a furnace flue-tube type boiler main body, it is possible to store a lot of heating object water in the water storage part, and the heating stored in the water storage part Since the temperature fluctuation of the target water is unlikely to occur, it is easy to adopt an operation mode that operates by burning the burner intermittently. By adopting such an operation mode, the control configuration is simplified and the cost is reduced. Is possible. However, since the burner is burned intermittently, there is a drawback that heat dissipation loss due to the draft becomes large.
Therefore, by implementing the present invention in such a flue-tube type boiler, it is possible to suppress the generation of drafts even if an operation mode in which the burner is operated by burning it intermittently is adopted, It is possible to reduce the heat dissipation loss.
In short, it has become possible to provide a furnace tube-type boiler that can suppress heat dissipation while reducing costs.

[First Embodiment]
Hereinafter, based on drawings, a 1st embodiment at the time of applying the present invention to a flue tube type boiler is described.
As shown in FIGS. 1 and 2, a furnace tube-type boiler includes a boiler body B including a burner 1 for burning gas fuel, and a push-type blower 2 that supplies outside air as combustion air to the burner 1 ( An exhaust duct 4 as an exhaust passage for guiding the combustion gas of the burner 1 discharged from the exhaust port 3 at the upper part of the boiler body B, and the combustion gas guided by the exhaust duct 4 in the atmosphere Are provided with a chimney 5 or the like for discharging.

  The boiler body B will be described in detail. The boiler body B is disposed in the horizontal cylindrical can body 6 as a water storage section for storing water to be heated, and burns inside the can body 6. Disposed from the combustion chamber 7 by being disposed between the horizontal cylindrical furnace tube 8 serving as the chamber 7, the burner 1 for burning the gas fuel in the combustion chamber 7, the can 6 and the furnace tube 8. And a plurality of smoke pipes 9 through which the combustion gas is passed, and an upward flue 10 through which the combustion gases discharged from the plurality of smoke pipes 9 are collected and passed.

The furnace tube 8 is provided so as to penetrate the can 6, and the burner 1 is provided at one end of the furnace tube 8 so as to form a flame toward the other end side.
The plurality of smoke tubes 9 are provided between the furnace tube 8 and the can body 6 and at positions above the bottom of the furnace tube 8 so as to penetrate the can body 6.
An opening on the opposite side to the burner installation side of the furnace tube 8 and an opening on the opposite side to the burner installation side of the plurality of smoke pipes 9 are connected in communication by a smoke chamber 11, and the flue 10 is connected to the plurality of smoke pipes 9. In a state of communicating with the opening on the burner installation side, it is erected vertically, and the upper end opening of the flue 10 is configured as the exhaust port 3.

  The blower 2 is provided integrally with the boiler body B so that the suction port 2i is positioned below the bottom of the combustion chamber 7, and is sucked and discharged from the suction port 2i by the blower 2. The blower 2 and the burner 1 are connected by an air supply duct 12 so that the outside air to be supplied is supplied to the burner 1 as combustion air.

In the first embodiment, the air supply duct 12 is configured so that the combustion air discharged from the blower 2 flows upward and then flows downward and is supplied to the burner 1. It is formed in an inverted U shape.
In the first embodiment, the air preheater 13 preheats the combustion air by exchanging heat between the combustion gas flowing through the flue 10 and the combustion air flowing through the air supply duct 12. Is provided.
The air preheater 13 is constituted by a heat pipe type heat exchanger, and since the heat pipe type heat exchanger is well known, description thereof will be omitted.

That is, as shown by the broken-line arrows in FIGS. 1 and 2, the combustion air sucked and discharged from the suction port 2i by the blower 2 flows upward through the air supply duct 12 and then flows downward. The air is preheated by the air preheater 13 in the course of the flow, and then supplied to the burner 1.
Then, the burner 1 burns the gas fuel supplied through the fuel supply passage 14 with the combustion air supplied through the air supply duct 12 in the combustion chamber 7, and the combustion gas is shown by a solid line in FIGS. As indicated by the arrows, the combustion chamber 7, the smoke chamber 11, the plurality of smoke pipes 9, and the flue 10 are sequentially passed through and discharged from the exhaust port 3.
Then, the heating target water stored in the can 6 is heated by the combustion gas flowing through the combustion chamber 7 and the plurality of smoke pipes 9, and the vapor evaporated by the heating is the vapor above the can 6. It is supplied to the steam demand section (not shown) through the delivery port 15.

  Incidentally, the combustion chamber 7, the smoke chamber 11, the plurality of smoke pipes 9 and the flue 10 are provided as described above, and the internal combustion gas flow is made to flow horizontally or upward without flowing the combustion gas downward. A flow path is formed, and the combustion gas is caused to flow through the internal combustion gas flow path, thereby reducing the flow resistance of the combustion gas and smoothly discharging it from the exhaust port 3.

The chimney 5 is erected vertically, and the exhaust duct 4 is formed in a rectangular tube shape, and the exhaust port 3 is arranged in the middle of the longitudinal direction of the rectangular tube-shaped exhaust duct in a horizontal orientation. And one open end thereof is provided in communication with the chimney 5.
A lateral opening at the opening end opposite to the side connected to the chimney 5 in the exhaust duct 4 is configured to function as an outside air introduction port 16 for introducing outside air into the exhaust duct. The outside air inlet 16 is closed when the pressure inside the exhaust duct is equal to or higher than the pressure outside the exhaust duct, and the outside air inlet 16 is opened when the pressure inside the exhaust duct becomes lower than the pressure outside the exhaust duct. The outside air introduction damper D is provided.

The outside air introduction damper D will be described.
As shown in FIGS. 1 and 3, the outside air introduction damper D is capable of swinging a rectangular damper plate 18 with a horizontal swing shaft 17 along the upper edge of the rectangular outside air introduction port 16. The suspension is supported.
Furthermore, a receiving portion 19 is provided at the lower edge portion of the outside air introduction port 16 so as to receive and support the damper plate 18 in a state where the damper plate 18 is lifted to the inside of the exhaust duct with respect to the vertical direction by a set inclination angle θ. The outside air inlet 16 is configured to be closed by the damper plate 18 in a state where the damper plate 18 is received and supported by the receiving portion 19.
When the pressure inside the exhaust duct becomes lower than the pressure outside the exhaust duct by a set pressure P, the damper plate 18 is pushed toward the inside of the exhaust duct 4 by the pressure difference between the inside and outside of the exhaust duct. Thus, the outside air inlet 16 is opened.

Hereinafter, a method for setting the set inclination angle θ will be described. As shown in FIG. 3, the size of the damper plate 18 is set to L × L (m), the weight is set to m (kg), and the rotational moment is balanced. The following formula 1 is obtained.

Then, L = 0.3 (m), m = 0.5 (kg), and P = 9.8 (p) so that the outside air introduction damper D is opened with the pressure difference inside and outside the exhaust duct being as small as possible. When set to Pa), the set inclination angle θ is 10 °.
That is, when the pressure inside the exhaust duct is equal to or higher than the pressure outside the exhaust duct, the damper plate 18 hangs down by its own weight and is received and supported by the receiving portion 19, and the outside air introduction port 16. Is closed, and the pressure in the exhaust duct becomes lower than the set pressure P with respect to the pressure outside the exhaust duct, the damper plate 18 is lifted by the pressure difference inside and outside the exhaust duct, and the outside air inlet 16 is opened.

In other words, the outside air introduction damper D is provided with the damper plate 18 suspended and supported so as to be swingable around a horizontal swing shaft, and when the pressure in the exhaust duct is equal to or higher than the pressure outside the exhaust duct. When the damper plate 18 hangs down by its own weight to close the outside air introduction port 16 and the pressure inside the exhaust duct becomes lower than the pressure outside the exhaust duct, the damper plate 18 is pushed by the pressure difference inside and outside the exhaust duct, and the outside air introduction port. 16 is configured to open.
In addition, the outside air introduction damper D is configured to close the outside air introduction port 16 in a state where the damper plate 18 is supported by the receiving portion 19 while being lifted and set to the inside of the exhaust duct by a set inclination angle θ with respect to the vertical direction. Therefore, when the pressure in the exhaust passage is equal to or higher than the pressure outside the exhaust passage, the damper plate 18 is brought into contact with the receiving portion 19 by its own weight, and the outside air inlet 16 is securely closed. It is configured to be able to.

In such a flue-tube type boiler, when combustion of the burner 1 is stopped, outside air passes through the suction port 2i of the blower 2, the air supply duct 12, and the burner 1 to the internal combustion gas flow path. The draft which flows in and flows through the internal combustion gas flow path, the exhaust duct 4 and the chimney 5 in this order is generated.
In the present invention, when the draft starts to occur as described above and the pressure inside the exhaust duct becomes lower than the pressure outside the exhaust duct by a set pressure P, the outside air introduction damper D is opened and the outside air is introduced through the outside air introduction port 16. Flows into the exhaust duct and flows toward the chimney 5, and the external airflow prevents the air flowing through the internal combustion gas flow path from flowing into the exhaust duct 4 from the exhaust port 3. In addition, since the exhaust duct 4 and the chimney 5 are cooled, the occurrence of the draft as described above is suppressed.
Therefore, heat dissipation loss due to the draft can be suppressed.

  Further, in the flue tube type boiler of the first embodiment, the air supply duct 12 is formed in an inverted U shape as described above, and an air preheater 13 is interposed in the air supply duct 12. Also, since the flow resistance is increased, the generation of drafts can be suppressed, so that the heat dissipation loss due to the drafts can be further suppressed.

[Second Embodiment]
Hereinafter, the second embodiment of the present invention will be described, but the same components as those in the first embodiment and the components having the same action are omitted by giving the same reference numerals in order to avoid duplicate description, A configuration different from the first embodiment will be mainly described.
That is, in the second embodiment, as shown in FIG. 4, the configuration of the air supply duct 12 and the exhaust duct 4 is different from that of the first embodiment, and the air preheater 13 is not provided. Since it is different from the embodiment, the configuration of the air supply duct 12 and the exhaust duct 4 will be mainly described below.

The blower 2 is provided separately from the boiler body B in a state where the suction port 2 i is positioned below the lower end of the combustion chamber 7.
The air supply duct 12 is provided obliquely upward so that the combustion air discharged from the blower 2 flows obliquely upward and is supplied to the burner 1.

The exhaust duct 4 has a rectangular tube-shaped upward channel portion 4u that allows combustion gas to flow vertically upward, and an intermediate portion in the longitudinal direction is connected to the upper end of the upward channel portion 4u so that the combustion gas flows horizontally. A rectangular tube-shaped horizontal channel portion 4h that flows in the direction and a rectangular tube-shaped downward channel portion that is connected to one end side of the horizontal channel portion 4h and allows the combustion gas to flow obliquely downward. 4d, the exhaust duct 4 is connected to the exhaust port 3 in communication with the open end of the upward flow passage portion 4u, and the open end of the downward flow passage portion 4d is connected to the chimney 5. The blower 2 is provided in communication with the suction port 2i at the same height as the suction port 2i.
The horizontal opening at the opening end opposite to the downward flow path portion 4d in the horizontal flow path portion 4h of the exhaust duct 4 is configured to function as the outside air introduction port 16 as in the first embodiment. When the pressure inside the exhaust duct is equal to or higher than the pressure outside the exhaust duct, the outside air introduction port 16 is closed and the pressure inside the exhaust duct is exhausted to the outside air introduction port 16 as in the first embodiment. An outside air introduction damper D configured to open the outside air introduction port 16 when lower than the outside pressure is provided.

In the flue-tube type boiler according to the second embodiment, the draft starts to be generated as described above while the combustion of the burner 1 is stopped, and the outside air flows from the suction port 2i of the blower 2 and enters the internal combustion gas. Even if it flows through the flow path and flows into the exhaust duct 4 from the exhaust port 3, it becomes difficult to flow in the downward flow path portion 4d of the exhaust duct 4, so that the generation of the draft is suppressed and the draft starts to occur. When the pressure inside the exhaust duct becomes lower than the pressure outside the exhaust duct by a set pressure P, the outside air introduction damper D is opened and the outside air flows into the exhaust duct through the outside air introduction port 16. As described in the first embodiment, the draft is suppressed.
That is, in addition to suppressing the occurrence of drafts in the downward flow path portion 4d of the exhaust duct 4, the generation of drafts can be suppressed by the outside air introduction damper D, and thus the generation of drafts is further suppressed. And heat dissipation loss due to the draft can be further suppressed.

[Another embodiment]
Next, another embodiment will be described.
(A) A receiving portion 19 is provided for receiving and supporting the damper plate 18 of the outside air introduction damper D in a state where the damper plate 18 is lifted by a set inclination angle θ with respect to the vertical direction on the inside of the exhaust duct. When the outside air introduction damper D is configured to be closed while the plate 18 is received and supported, the set inclination angle θ can be variously changed and set. However, in order to effectively suppress the draft, the outside air introduction damper D is opened in a state where the pressure difference between the inside and outside of the exhaust passage in the state where the pressure inside the exhaust passage becomes lower than the pressure outside the exhaust passage is as small as possible. Therefore, it is preferable to set the set inclination angle θ as small as possible.

  Further, the receiving portion 19 may be omitted, and the outside air introduction damper D may be closed with the damper plate 18 hanging vertically.

(B) When the outside air introduction damper D is configured to open with the driving force as the pressure difference inside and outside the exhaust passage when the pressure inside the exhaust passage is lower than the pressure outside the exhaust passage, the pressure difference is It is not limited to 9.8 Pa illustrated in the embodiment, and various changes can be set. However, in order to effectively suppress the draft, the pressure difference is preferably set as small as possible.

(C) The specific configuration of the outside air introduction damper D is not limited to the configuration exemplified in each of the above embodiments. For example, when the pressure in the exhaust passage becomes lower than the pressure outside the exhaust passage while the damper plate 18 is urged to return to the closed position by the spring, the opening direction against the biasing force of the spring is caused by the pressure difference. You may provide so that it may move to.
Moreover, you may comprise so that it may open and close by the effect | action of a diaphragm.
Incidentally, when the outside air introduction damper D is configured to be urged to return to a closed state by a spring as described above, or to be opened and closed by the action of a diaphragm, the outside air introduction port 16 is not necessarily provided sideways. It can be provided downward or upward.

(D) In each of the above embodiments, the installation position of the outside air inlet 16 in the exhaust passage 4 can be variously changed.
For example, in the first embodiment, the outside air inlet 16 may be provided on the side wall of the exhaust path 4 by opening the side wall of the exhaust path 4.
In the second embodiment, the outside air introduction port 16 is provided on the side wall of the horizontal channel portion 4h by opening the side wall of the horizontal channel portion 4h of the exhaust channel 4, or the downward channel portion 4d. You may provide in the side wall of the downward flow path part 4d by opening a side wall.

(E) In the second embodiment, the outside air introduction port 16 and the outside air introduction damper D can be omitted.

(F) When the exhaust path 4 is configured to include the downward flow path portion 4d, the form of the downward flow path part 4d and the overall form of the exhaust path 4 are limited to the forms exemplified in the second embodiment. Is not to be done.
For example, the upward channel portion 4u and the horizontal portion 4h may be omitted, and only the downward channel portion 4d obliquely downward may be provided. In this case, the upper opening end of the downward flow path portion 4d is connected to the exhaust port 3, and the lower opening end is connected to the chimney 5.
Alternatively, the downward flow path portion 4d may be vertically downward, and the horizontal flow path portions 4h may be provided at both ends thereof. In this case, the open end of the horizontal flow path portion 4h connected to the upper end of the downward flow path portion 4d is connected to the exhaust port 3, and the horizontal flow connected to the lower end of the vertical downward flow path portion 4d is connected. The open end of the path portion 4h is connected to the chimney 5 in communication.
Alternatively, the upward flow path portion 4u may be omitted. In this case, the exhaust port 3 is connected in communication with an intermediate portion in the longitudinal direction of the horizontal channel portion 4h.

(G) The height for connecting the downward flow path portion 4d of the exhaust passage 4 and the chimney 5 is limited to the same height as the suction port 2i of the blower 2 illustrated in the second embodiment. It may be set to a position higher than the suction port 2i or a position lower than the suction port 2i. However, when setting the position higher than the suction port 2i of the blower 2, it is preferable to set the position as low as possible in order to suppress the draft as much as possible.

(H) In the first embodiment, the exhaust passage 4 is illustrated as being horizontally oriented over its entire length, but the combustion gas is allowed to flow downward as in the second embodiment. You may comprise so that the downward flow path part 4d may be provided.

(L) The burner 1 is not limited to the one using gas fuel as fuel, and may be one using liquid fuel as fuel, for example.

(Nu) The present invention can be applied to various types of boilers other than the furnace tube type exemplified in the above embodiment. For example, burner combustion with a furnace tube type with a furnace tube whose inside is the combustion chamber of the burner, a smoke tube type with a smoke tube that allows the combustion gas of the burner to flow, and a plurality of water tubes that allow water to be heated to flow It is possible to apply to a once-through boiler provided indoors.

Longitudinal front view of a furnace tube type boiler according to the first embodiment Longitudinal side view of the boiler body of the flue-tube type boiler according to the first embodiment Longitudinal front view of the main part of the exhaust duct of the furnace flue tube boiler according to the first embodiment Longitudinal front view of a flue-tube type boiler according to the second embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Burner 2 Air blow means 3 Exhaust port 4 Exhaust path 4d Downward flow path part 5 Chimney 16 Outside air inlet B Boiler body D Outside air introduction damper

Claims (3)

A boiler body equipped with a burner that burns fuel using the outside air supplied by the blowing means as combustion air;
A boiler provided with an exhaust passage for guiding the combustion gas of the burner discharged from the exhaust port at the top of the boiler body to a chimney;
The exhaust path is provided with an outside air inlet for introducing outside air into the exhaust path,
When the pressure inside the exhaust passage is equal to or higher than the pressure outside the exhaust passage, the outside air inlet is closed, and when the pressure inside the exhaust passage becomes lower than the pressure outside the exhaust passage, the outside air inlet is opened. A boiler provided with a configured outside air introduction damper. A boiler body equipped with a burner that burns fuel using the outside air supplied by the blowing means as combustion air;
A boiler provided with an exhaust passage for guiding the combustion gas of the burner discharged from the exhaust port at the top of the boiler body to a chimney;
A boiler configured such that the exhaust path includes a downward flow path portion that allows combustion gas to flow downward.   The boiler according to claim 1 or 2, wherein the boiler body is configured as a furnace tube type.

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