JPH0735301A - Compact-type energy saving boiler - Google Patents

Abstract

PURPOSE:To attempt miniaturization and improvement of the efficiency of a boiler by discharging exhaust gas of high temperature combustion gas to the outside of a combustion furnace through regenerative heat exchangers and exchanging heat with combustion air or combustion gas by means of the regenerative heat exchangers. CONSTITUTION:High temperature combustion gas to be generated by burning fuel in a combustion furnace recovers heat through a heat transfer part. The heat transfer part is composed of a radiant heat transfer surface 4 and a convective heat transfer surface 5, and exhaust gas 30 of high temperature combustion gas subjected to heat recovery by the radiant heat transfer surface 4 and the convective heat transfer surface 5 is discharged to the outside of a combustion furnace through regenerative heat exchangers 6a, 6b. And combustion air to be supplied into the combustion furnace or combustion gas 12 wherein component such as the concentration of oxygen is adjusted in air exchanges heat by the regenerative heat exchangers 6a, 6b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler for recovering heat from a high-temperature combustion gas in a heat transfer section, in order to improve the boiler efficiency in a more compact manner, or combustion gas whose components are adjusted according to the purpose. Relates to a boiler that needs to exchange heat with the exhaust gas after heat recovery in the heat transfer section.

[0002]

2. Description of the Related Art With the increasing awareness of global environmental protection in recent years, there is no doubt that energy-saving technology will become more and more important in the future. Technology is required for. In a boiler that burns fuel and recovers heat from the generated high-temperature combustion gas, install a economizer and / or an air preheater after the convection heat transfer section in order to improve the energy utilization efficiency. Has been trying to exchange heat from exhaust gas.

However, in the downstream side of the convection heat transfer section, the economizer, and the air preheater, heat is exchanged between the exhaust gas and the boiler water or air through the heat transfer surface made of metal or the like, so that the heat transfer coefficient is Since it is low and the temperature difference cannot be large,
The heat transfer area becomes large with respect to the recovered heat amount, and in a relatively small-scale boiler, exhaust gas may be discharged at a temperature of 300 ° C. or higher due to the balance between equipment cost and recovered energy.

Next, an example of a boiler to which a conventional heat recovery technique is applied will be described with reference to FIGS. 8 and 9.

In FIG. 8, a water tube type boiler 1 having a furnace 3, a radiant heat transfer section 4 and a convection heat transfer section 5 has a fuel 11 and combustion air or a component such as oxygen concentration depending on the purpose. The combustion gas 12 having been adjusted is mixed in the burner section 7 and burned in the furnace 3. High-temperature combustion gas 30 after combustion
First, heat is collected and cooled in the radiant heat transfer section 4, and further, heat is collected and cooled in the convection heat transfer section 5. The exhaust gas 30 that has been heat-recovered by the convection heat transfer section 5 is a economizer 15, a gas type air preheater 16
A predetermined amount of heat is further recovered through the exhaust gas, and the low temperature exhaust gas 31 is discharged from the chimney 17.

FIG. 9 shows an example in which the heat storage type air preheaters 6a and 6b are added to the existing water pipe boiler as shown in FIG. 8 to improve the heat recovery rate. Fuel 1
1, and the combustion air or combustion gas 12 preheated by the regenerative air preheater 6a is mixed in the burner section 7a and burned in the furnace 3. The high-temperature combustion gas 30 after combustion first receives heat in the radiant heat transfer section 4, but thereafter the opening degree of the adjustment damper 14 provided in the downstream duct section of the convection heat transfer section 5 adjusts the convection heat transfer section. 5 or controlled to pass through the regenerative air preheater 6b. The control is adjusted so that the temperature of the convection heat transfer section 5 and the outlet gas of the regenerative air preheater 6b after the merging is the lowest. In such a system, the gas type air preheater in the latter stage may be omitted.

[0007]

However, in the conventional boiler shown in FIG. 8, the exhaust gas and can water or combustion air or combustion air in the downstream portion of the convection heat transfer section 5, the economizer 15, and the gas type air preheater 16 are used. Since heat is exchanged with the combustion gas through a heat transfer surface made of metal or the like, the heat transfer coefficient is low, the temperature difference cannot be large, and a large heat transfer area is required for the recovered heat quantity. It was a problem in terms of installation space and equipment cost. In particular, in a relatively small-scale boiler, the economizer 15 and the air preheater 16 may be omitted and the relatively high temperature exhaust gas may be unavoidably discharged.

Also in the improved boiler system shown in FIG. 9, since a part of the exhaust gas that should originally pass through the convection heat transfer section 5 is introduced into the regenerative air preheater, the temperature of the combustion section rises. However, the gas flow velocity in the convection heat transfer section 5 decreases, and the heat transfer coefficient accordingly decreases, so the amount of heat recovered in the convection heat transfer section decreases. Therefore, it is necessary to raise the temperature of the furnace 3 in order to supplement the amount of heat recovered in the convection heat transfer section 5 with the amount of heat collected in the radiant heat transfer section 4, but if the temperature is raised too much, thermal NOx increases. However, in the case of fuel containing ash, there is a possibility that problems such as melting and fusing of ash may occur, and there is a problem that a predetermined amount of evaporation cannot be obtained.

The present invention has been made in view of the above problems, and a heat storage type air preheater is added to an existing water pipe boiler so that a predetermined evaporation amount or more can be reliably obtained, or a fuel amount smaller than that in the conventional case is used. With the boiler that obtains the conventional evaporation amount,
Another object of the present invention is to provide a compact compact energy-saving boiler, which is a basic and provides a compact and highly efficient boiler system at a low price.

[0010]

In order to achieve the above-mentioned object, a compact type energy-saving boiler of the present invention is a boiler for recovering heat from a high temperature combustion gas generated by burning fuel in a combustion furnace through a heat transfer section. In the above, the heat transfer part is composed of a radiant heat transfer surface and a convective heat transfer surface, the exhaust gas of the high temperature combustion gas recovered by the radiant heat transfer surface and recovered by the convective heat transfer surface is a heat storage type. The combustion air discharged to the outside of the combustion furnace through a heat exchanger and the combustion gas supplied to the inside of the combustion furnace or the combustion gas in which components such as oxygen concentration are adjusted in the air are heated by the heat storage heat exchanger. It is characterized by being exchanged.

Further, the heat transfer part is constituted by only the radiant heat transfer surface without the convective heat transfer surface, and the exhaust gas of the high temperature combustion gas whose heat is recovered on the radiant heat transfer surface is directly burned by the heat storage type heat exchanger into the combustion air or It is characterized by exchanging heat with gas.

Further, the exhaust gas of the high-temperature combustion gas and the inlet and outlet passages of the combustion air or gas are fixed, and the passages of two or more series of heat storage type heat exchangers are alternately switched over. It is characterized by arranging units.

[0013]

According to the present invention having the above-described configuration, when the heat storage type air preheater is added to the existing water pipe boiler, the amount of exhaust gas passing through the convection heat transfer section is the same as that of the conventional one, so that heat in the convection heat transfer section is not changed. There is no decrease in the recovery amount, and the exhaust gas temperature further decreases compared to a system without an air preheater, and the combustion air or combustion gas is preheated by that amount of heat, and the temperature in the combustion section rises, The amount of heat collected increases not only in the radiant heat transfer section but also in the convection heat transfer section. The heat storage type air preheater is mostly composed of only a heat storage body, and the volume per heat exchange amount is smaller than that of the economizer and the gas type air preheater.
Boiler efficiency can be improved by adding very compact equipment.

Further, in the boiler according to the present invention, the exhaust gas temperature at the heat storage type air preheater inlet is raised, that is, the area of the convection heat transfer section is reduced, and finally the convection heat transfer section is eliminated and only the radiation heat transfer section is provided. It is possible to configure the heat transfer section. By increasing the temperature of the combustion part to the extent that problems such as increase in thermal NOx and melting and fusing of ash do not occur, radiative heat transfer whose heat transfer coefficient is much higher than convective heat transfer is effectively used, It is possible to design a more compact boiler.

Further, by arranging the heat storage type air preheating unit, it becomes possible to attach the heat storage type heat exchanger to the existing boiler without requiring any modification to the existing boiler. This makes it possible to easily save energy and make the existing boiler compact.

Further, by appropriately arranging the heat transfer surfaces and using the multi-stage combustion method, the ratio of the radiant heat transfer is significantly increased, and finally the convective heat transfer surface is omitted and only the radiant heat transfer surface is used. It is also possible to design a boiler to be constructed. Further, even if the fuel has a small calorific value and cannot be self-combusted by the conventional boiler, it can be self-combusted by auxiliary combustion at the time of startup and raising the temperature of the regenerative air preheater.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a compact type energy saving boiler according to the present invention will be described below with reference to FIGS.

FIG. 1 is a basic configuration diagram of a compact type energy-saving boiler system according to a first embodiment of the present invention. In the figure, reference numeral 1 is a water tube boiler. Combustion air 12 from the blower or fan 2 is designed to be guided to the furnace 3 through the regenerative air preheater 6a or 6b, the switching valve unit 9, the burner 7, and the exhaust gas is a gas switching valve 10, a regenerative system. It is adapted to be guided to the low temperature exhaust gas switching valve 24 through the air preheater 6b or 6a.

The fuel 11 is the air 1 which has been preheated to a high temperature by the regenerative air preheater 6a or 6b through the burner 7.
It is burned together with 2 in the furnace 3 and becomes high temperature combustion gas. After the high temperature combustion gas is collected by the radiant heat transfer section 4, the convection heat transfer section 5
After passing through, the heat is further collected and is guided to the switching valve 10.

The gas switching valve 10, the air / gas switching valve 9, and the air switching valve 8 are interlocked with each other so that the combustion air is allowed to flow through only one of the flow paths of the regenerative air preheater 6a or 6b, and the remaining The exhaust gas can be made to flow through one of the flow paths, and can be switched alternately.

The switching of the gas switching valve 10, the air / gas switching valve 9, and the air switching valve 8 is performed by deciding the switching time and carrying out at regular intervals of ten to several seconds to several minutes.
A method of detecting when the outlet exhaust gas temperature of the heat storage air preheater 6b has reached a predetermined temperature or higher, or detecting that the outlet air temperature of the heat storage air preheater 6a has reached a predetermined temperature or lower Can be adopted.

As a matter of course, the heat exchange medium of the heat storage type air preheater does not have to be of two series as shown in FIG.
It does not matter if you use the series more than once.

With such a system, even if the existing boiler is remodeled, the temperature of the exhaust gas at the outlet of the convection heat transfer section 5 can be kept at the conventional temperature, so that a predetermined evaporation amount can be reliably maintained. .

Further, in the case of newly designing a boiler, in order to obtain a boiler efficiency equivalent to that of the conventional boiler, the average exhaust gas temperature at the outlet of the regenerative air preheater 6a or 6b is the convection transmission of the conventional boiler. Since it may be designed to be equal to the outlet exhaust gas temperature of the heat section, even if the outlet exhaust gas temperature of the convection heat transfer section 5 in this system is high by the amount corresponding to the heat exchange amount in the regenerative air preheater. good. Therefore,
The heat transfer surface of the convection heat transfer unit can be reduced as compared with the conventional boiler.

Ultimately, the heat transfer section may be composed of only the radiation heat transfer surface without the convection heat transfer surface. In the boiler having such a configuration, the high temperature combustion gas is subjected to heat recovery on the radiant heat transfer surface and then directly exchanged with the combustion air or the like in the heat storage type heat exchanger.

The heat storage type air preheater used in the boiler system of this embodiment will be described in detail.

The heat storage type air preheaters 6a and 6b have a high heat transfer coefficient due to the direct contact of the heat storage body with the gas and air. Further, a heat exchange medium such as an integral honeycomb structure having a large area in contact with air and a small resistance to ventilation and gas passage is used. Further, as the material, ceramic or the like is used so as to withstand high temperature.
Therefore, although the heat exchange function is excellent, there is a problem in mechanical strength, and there is a possibility of damage due to thermal stress.

In order to solve the above-mentioned problem, as shown in FIG. 6, in the heat storage type heat exchanger of this embodiment, the heat exchange medium 23 is perpendicular to the flow direction of exhaust gas and combustion air or combustion gas. The edges 32 are cut off. By doing so, not only damage due to thermal stress can be prevented, but also heat diffusion in the heat exchange medium can be suppressed and temperature efficiency is improved, so that heat exchange at high temperature becomes easy. Therefore, the length of the heat exchange medium 23 that has been trimmed is appropriately set depending on the required temperature efficiency, the material of the heat exchange medium, and the like.

Since the heat storage type air preheater unit has a large amount of exchange heat per unit volume, it is extremely compact compared to the conventional economizer and air preheater even if the amount of exchange heat is the same. Therefore, it is possible to achieve the same boiler efficiency as the conventional one with a much smaller equipment than the conventional one.

Furthermore, since the heat exchange medium of the above-mentioned heat storage type air preheater can be made of a material excellent in corrosion resistance such as ceramics, it can be cooled to the dew point temperature of exhaust gas or less, and the boiler efficiency is improved. To do.

Further, since the heat exchange medium of the above-mentioned heat storage type air preheater can also use a material having excellent heat resistance such as ceramics, the exhaust gas from the boiler cannot be practically used in the conventional gas type air preheater. For example, the heat transfer section of the boiler body can be composed of only the radiant heat transfer section, as described above, even if the temperature is as high as 1000 ° C. or higher.

Next, a second embodiment of the present invention, which is a boiler having a heat storage type air preheater unit, will be described with reference to FIG.

In the figure, reference numeral 1 is a water tube boiler.
The high temperature combustion gas 30 passes through the convection heat transfer section 5, is guided to the exhaust gas side inlet passage 27a of the regenerative air preheater unit 27, undergoes heat exchange, and is then discharged from the outlet passage 27b. The combustion air 12 or the combustion gas 12 in which components such as oxygen concentration are adjusted in the air is preheated into the regenerative air preheater unit 27 from the inlet flow passage 27c, and the outlet flow passage 27d.
And is supplied to the combustion furnace.

Next, the regenerative air preheater unit 27 used in the above embodiment will be described with reference to FIG. The heat storage type air preheater unit 27 is a flow path switching damper 25.
It is composed of a duct in which the heat exchange medium 23 is arranged between a and 25b. The ducts including the heat exchange medium 23 from the flow passage switching dampers 25a to 25b are separated into upper and lower flow passages, and the exhaust gas 30 and the combustion air 12 are separated from each other by the heat exchange medium 23.
Although the upper half flow path and the lower half flow path flow in opposite directions, the flow path switching dampers 25a and 25b interlock with each other to cause the flow paths to flow through the flow path switching damper 25a.
It is only possible to switch between the range from 25b to 25b. However, due to the action of the same flow path switching dampers 25a to 25b, the exhaust gas 30 flows from the inlet flow path 27a to the outlet flow path 27 in the inlet / outlet flow path of the heat storage air preheater unit 27.
To b, the combustion air 12 always flows in a constant direction from the inlet passage 27c to the outlet passage 27d.

If the system uses such a unit instead of the economizer, it is possible to make the system more compact and have a high boiler efficiency without modifying the conventional boiler itself.

Further, in the case of newly designing the boiler, the average gas temperature at the inlet of the regenerative air preheater unit 27 can be made as high as 1000 ° C. or higher, so that the radiant heat transfer section without the convection heat transfer section is used. It is possible to make a boiler composed of only one.

A convection heat transfer section is required in order to reduce the thermal NOx as much as possible without increasing the temperature of the flame and to obtain a specified evaporation amount. In this case, the temperature of the exhaust gas entering the heat storage type air preheater unit is as low as about 300 ° C. Therefore, it is not necessary to use ceramics as the heat storage medium. The larger the heat transfer coefficient and the specific heat, and the larger the heat storage capacity, the more compact it becomes. If it is a metal, for example, Cu or Al is preferable. Further, the shape does not need to be a honeycomb shape, and may be, for example, a stack of pipes or a packing of particulate linear materials.

FIG. 3 is a basic block diagram of a boiler having a heat storage type air preheater unit according to a third embodiment of the present invention. In the present embodiment, the heat transfer section is composed of only the radiant heat transfer section 4 and does not have a convection heat transfer section. By installing the heat storage type air preheater unit 27, the temperature of the exhaust gas from the boiler is raised, and the heat transfer part of the boiler is changed to the radiant heat transfer part 4.
Only, the convection heat transfer section is eliminated. Therefore,
Combustion air 12 from a blower or a fan is preheated through a regenerative air preheating unit 27 and then guided to a burner 7, and together with the fuel 11, the burner 7 is heated.
Is charged into the furnace 3 and burned to form high temperature combustion gas 30. After the high temperature combustion gas 30 is collected by the radiant heat transfer section 4,
Immediately after, the exhaust gas side inlet 2 of the heat storage type air preheater unit 27
7a, after undergoing heat exchange, it is discharged.

However, if the heat transfer surface of the convection heat transfer section is reduced as described above, the preheating temperature of the combustion air rises, so that the temperature of the flame rises and the generation of thermal NOx may increase. In particular, when the combustion mode of the fuel is single-stage combustion, since the combustion occurs at one time, the temperature of the flame easily rises, and the heat transfer surface of the convection heat transfer section cannot be greatly reduced.

As a method for solving the above-mentioned problems, there is an appropriate arrangement of heat transfer surfaces and a multi-stage combustion method, and the details thereof will be described with reference to FIG.

FIG. 4 shows a means for suppressing an abnormal rise in flame temperature by appropriately disposing the heat transfer surface in a single-stage combustion boiler. Make the area close to burner 7 dense (many) and the area far away (small)
The heat transfer tubes 13 are arranged so that the flame temperature is averaged over the entire furnace by the heat transfer surface arrangement according to the combustion zone.

However, this method has a drawback that the position of the combustion zone changes when the amount of combustion changes or the preheating temperature of the combustion air changes, and it does not function sufficiently.

Therefore, FIG. 5 shows a flame temperature averaging method by the multi-stage combustion method. Along the length of the furnace 3,
A plurality of burners 19a to 19j are provided, and fuel flow rate adjusting valves 21a to 21b and combustion air adjusting valves 22a to 22b are provided so as to control the fuel input amount and the combustion air supply amount, respectively. The main burner 7 and auxiliary burners 19a-
Properly distributed from 19j and supplied. The inner surface of the furnace is a radiant heat transfer surface 4.

The distribution of the fuel amount and the combustion air to each burner is such that at the maximum load, each thermometer 20a installed in the furnace
It is controlled so that ~ 20j have almost the same temperature. By doing so, the radiant heat transfer surface 4 on the inner surface of the furnace is subjected to almost the same heat load as a whole, so that the effective utilization rate of the heat transfer surface is improved and further downsizing can be achieved.

If all of the fuel is supplied from the main burner 7 and only the combustion air is supplied from the auxiliary burner in an appropriate distribution, the NOx generation amount is also reduced by the effect of multistage combustion.

However, when a strong reducing atmosphere is formed in the furnace by multi-stage combustion, there is a risk that the material forming the heat transfer surface may be corroded depending on the type of fuel. Therefore, if there is such a possibility, the combustion air may be entirely supplied from the main burner 11 and only the fuel may be dispersed and charged.

Which of the above-mentioned methods is selected is determined from the components of the fuel, the material of the heat transfer surface, the strength of low NOx requirement, and the like.

As an alternative to the combustion air,
It is also possible to adjust the combustion zone in the furnace by using the combustion gas whose oxygen concentration and the like have been adjusted. As a matter of course,
The combustion gas can be used as a fluid for oxidizing the fuel of the boiler, in addition to the purpose of adjusting the combustion zone.

By using the method as described above, the boiler in which the convection heat transfer area is drastically reduced without increasing the thermal NOx, and finally, there is no convection heat transfer surface and the heat recovery heat recovery It is possible to design a boiler whose part consists only of radiant heat transfer surfaces.

[0050]

The effects of the present invention are listed below. (1) By exchanging heat between the exhaust gas after passing through the convection heat transfer section and the combustion air or the combustion gas, the exhaust gas temperature can be lowered without reducing the heat collection amount in the convection heat transfer section, and the boiler efficiency can be improved. Is improved. (2) By using a heat storage type heat exchanger as the air preheater, even if heat exchange is performed in a region where the temperature difference is relatively small like the air preheater, compared to a normal gas type air preheater. It becomes a compact heat exchanger. Furthermore, by using the heat storage type air preheating unit, it is possible to make the existing boiler highly efficient and compact without modifying the existing boiler. (3) Similarly, by using a heat storage type heat exchanger as the air preheater, the air preheat is performed to a temperature range that is impossible with the shell and tube gas air preheater due to the material and economical problems. Therefore, the temperature of the flame can be increased. Therefore, the ratio of the heat collected on the radiant heat transfer surface to the total heat collected by the boiler can be increased, and the overall size can be further reduced. (4) By providing a radiant heat transfer surface that is abundant in the vicinity of the burner and decreases with distance from the burner, combustion can be performed without raising the flame temperature even if air preheating is performed, and generation of thermal NOx can be suppressed. (5) By adjusting the combustion of the fuel by multi-stage combustion so as to eliminate the temperature distribution in the furnace, it is possible to further increase the rate of heat collection on the radiant heat transfer surface, and to reduce the radiant heat without convective heat transfer parts. It is possible to use a boiler having only a heat transfer section. (6) By edging the heat exchange medium of the heat storage type heat exchanger by a plane perpendicular to the gas flow direction, the temperature efficiency of the heat exchanger is improved and the heat exchange medium is a brittle material such as ceramic. However, the risk of damage due to thermal stress is reduced, and the reliability of the device is improved.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a compact type energy-saving boiler system according to a first embodiment of the present invention.

FIG. 2 is a basic configuration diagram of a compact type energy-saving boiler system according to a second embodiment of the present invention.

FIG. 3 is a basic configuration diagram of a compact energy-saving boiler system according to a third embodiment of the present invention.

FIG. 4 is a schematic view showing a means for suppressing an abnormal rise in flame temperature by appropriately disposing a heat transfer surface in a single-stage combustion boiler.

FIG. 5 is a schematic diagram showing a multi-stage combustion method for eliminating the temperature distribution in the furnace.

FIG. 6 is a diagram showing an installed state of a heat exchange medium in a heat storage type heat exchanger.

FIG. 7 is a structural diagram showing a heat storage type air preheating unit.

FIG. 8 is a basic configuration diagram showing a conventional standard boiler system.

FIG. 9 is a view showing a boiler in which a heat storage type heat exchanger is slightly improved in a conventional standard boiler.

[Explanation of symbols]

 1 Water Tube Boiler 2 Combustion Air Fan 3 Furnace (Combustion Section) 4 Radiation Heat Transfer Section 5 Convection Heat Transfer Section 6a Heat Storage Air Preheater 6b Heat Storage Air Preheater 7 Burner 8 Combustion Air Changeover Valve 9a Combustion Air / Exhaust Gas Changeover valve 9b Combustion air / exhaust gas changeover valve 10 Exhaust gas changeover valve 11 Fuel 12 Combustion air or tempered gas 13 Heat transfer tube 14 Exhaust gas adjustment damper 15 Carbon economizer 16 Gas air preheater 17 Chimney 19a-19j Burner 20 Thermometer 20a-20j Thermometer 21a-21j Fuel adjustment valve 22a-22j Combustion air adjustment damper 23 Heat exchange medium 24 Low temperature exhaust gas switching valve 27 Heat storage air preheater unit 30 High temperature exhaust gas 31 Low temperature exhaust gas 32 Edged surface

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Seiichiro Toyoda 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside the EBARA Research Institute, Inc. (72) Inventor Yo Ueda 11-1 Haneda-cho, Ota-ku, Tokyo Issue EBARA CORPORATION

Claims (6)

[Claims] 1. A boiler for recovering heat from a high-temperature combustion gas produced by burning fuel in a combustion furnace through a heat transfer section, wherein the heat transfer section comprises a radiant heat transfer surface and a convective heat transfer surface. The exhaust gas of the high-temperature combustion gas, which has been heat-recovered by the heat transfer surface and has been heat-recovered by the convective heat transfer surface, is discharged to the outside of the combustion furnace via a heat storage heat exchanger and is supplied into the combustion furnace. A compact energy-saving boiler characterized in that combustion air or a combustion gas in which components such as oxygen concentration are adjusted in the air is heat-exchanged by the heat storage heat exchanger. 2. A boiler for recovering heat from a high-temperature combustion gas produced by burning fuel in a combustion furnace through a heat transfer section, wherein the heat transfer section comprises only a radiant heat transfer surface, and The recovered exhaust gas of the high-temperature combustion gas is discharged to the outside of the combustion furnace through a heat storage heat exchanger, and the components such as oxygen concentration are adjusted in the combustion air or the air supplied into the combustion furnace. A compact energy-saving boiler characterized in that the combustion gas is heat-exchanged by the heat storage type heat exchanger. 3. An inlet flow path and an outlet flow path of the exhaust gas of the high-temperature combustion gas after heat recovery in the heat transfer section, and an inlet flow path and an outlet flow path of the combustion air or the combustion gas. And at least two connected between the inlet and outlet flow paths
The heat storage type heat exchanger having a flow path of a series or more, and a valve for switching the flow path in the heat storage type heat exchanger provided at both ends of the heat storage type heat exchanger, the exhaust gas, and combustion air or While the combustion gas always flows from a constant inlet flow path to the outlet flow path, in the flow path in the heat storage heat exchanger, the exhaust gas and the combustion air or gas are alternately switched by a valve that switches the flow paths. The compact energy-saving boiler according to claim 1 or 2, wherein a flowing heat storage type air preheater unit is arranged. 4. A large number of the radiant heat transfer surfaces are arranged in the vicinity of a burner that burns fuel in the combustion furnace, and a small number of the radiant heat transfer surfaces are arranged as the distance from the burner increases. Item 1. A compact type energy-saving boiler according to item 1 or 2. 5. The combustion air or combustion gas and / or fuel preheated by using the heat storage type heat exchanger are distributed to a plurality of and injected into the combustion furnace in multiple stages. 2. A compact type energy-saving boiler described in 2 or 3. 6. The heat storage type heat exchanger according to claim 1, wherein the heat exchange medium is bordered by a surface perpendicular to the flow direction of the exhaust gas or the combustion air or the combustion gas. 2. A compact type energy-saving boiler described in 2 or 3.