KR102229911B1 - A Once-through Boiler Equipped with a Porous Medium Burner and its Operation Method - Google Patents

Abstract

The present invention relates to a once-through boiler having a porous combustor, and more particularly, a porous body that reduces nitrogen oxide emissions and enables uniform heating in a small once-through boiler using gaseous fuel or a small combustion-type heating device. It relates to a once-through boiler with a combustor.

Description

A Once-through Boiler Equipped with a Porous Medium Burner and its Operation Method}

The present invention relates to a once-through boiler having a porous combustor, and more particularly, a porous body that reduces nitrogen oxide emissions and enables uniform heating in a small once-through boiler using gaseous fuel or a small combustion-type heating device. It relates to a once-through boiler having a combustor and a method of operating the same.

A boiler is a device that generates steam with high temperature and pressure by transferring combustion heat of fuel to water, etc., and is used to supply steam to steam engines such as thermal power plants and ships, and to devices for work or heating of various factories.

There are several types of boilers depending on their structure, but among them, once-through boilers, which belong to forced circulation boilers, are pipe-only boilers made of single water pipes or bundles of water pipes, they are also referred to as forced once-through boilers. It refers to a boiler in which water is supplied from one end of the water pipe and is pumped by a pump, which is heated, evaporated, and superheated in sequence in the middle, and is transmitted as superheated steam from the other end of the pipe.It is suitable for generating high-pressure steam, especially supercritical pressure boiler. It is a kind of forced circulation boiler which is advantageous in the case of

The once-through boiler has a small quantity, so it is possible to start and stop quickly, and because it is possible to freely arrange the heating surface, it is advantageous for miniaturization and high efficiency of the boiler. In addition, it is easy to automate due to its simple structure and high safety. When a large amount of steam is needed, a number of small boilers are connected in parallel, rather than using a single large boiler, so that individual boilers operate under the design load with the highest efficiency. There is a possible advantage.

_{On the other hand, with regard to the generation of low nitrogen oxides (hereinafter NO x} ) to be achieved in the present invention, the once-through boiler has a high volume heat load (burning heat per unit volume) of the boiler combustion chamber due to its compact structure, thereby forming a high-temperature flame. NO _x is generated, and it is very disadvantageous in reducing _{NO x} generation compared to other boiler types because the combustion chamber volume is not provided as necessary for the _{existing low NO x combustion technology to be effective.}

_{NO x} generated in the process of combustion of gaseous fuel _{is thermal NO x} generated by oxidation of nitrogen in the air in a high temperature (about 1300°C or higher) flame or burned gas, and the high concentration of fuel is high temperature (about 1000°C). ℃ or higher) to generate a hydrocarbon radical (CH radical), which can be divided into _{prompt NO x generated by reacting with nitrogen.}

Since Thermal NO _x is generated in the high temperature region where excess oxygen exists, it is possible to equalize the temperature of the firebox so that local high temperature regions do not occur, and also reduce the amount of excess oxygen in the root region of the flame where a large amount of it is generated. I can.

On the other hand, prompt NO _x is relatively insensitive to temperature as long as it goes above the pyrolysis temperature of the fuel, and it is generated instantaneously (within about 1 ms) in the fuel-rich region. By allowing rapid mixing at the outlet end of the combustor, its formation can be suppressed.

Conventionally, the nitrogen oxide reduction technique of industrial burners is a mixing accelerating type that promotes rapid mixing of fuel and air as in Patent Document 1, and various flames are controlled by controlling the shape of fuel and air nozzles as in Patent Document 2. A flame split type to form, a multistage combustion type that operates under conditions deviating from the theoretical mixing ratio through staged combustion as in Patent Document 3, and recirculates the exhaust gas exhausted after combustion from the outside as in Patent Document 4 or internally through flow control inside the combustion chamber. It can be classified as a recirculating exhaust gas recirculation type, and all of these technologies are technologies that suppress the formation of local high-temperature flames to reduce thermal NOx generation or minimize prompt NOx generation by minimizing the fuel-rich area.

However, since the above techniques form a long flame in the spraying direction, it is difficult to apply when the heat load of the firebox is large and the volume is small, such as a once-through boiler.

Republic of Korea Patent Publication 10-2017-0073104 Korean Patent Registration 10-2003-0052891 Korean Patent Registration 10-1583509 Korean Patent Registration 10-0838163

_{The present invention has been made to solve the above problems, and an object of the present invention is to provide a low NO x} once-through boiler for lowering the NOx emission concentration to a level of 10 ppm in a small once-through boiler or a small combustion device.

In addition, for the purpose of increasing energy utilization efficiency and forming a high-temperature flame, heat recirculation occurs due to conduction and radiant heat transfer of the porous body itself by allowing combustion to occur inside the porous body without using an additional device, and ultimately, excess enthalpy. An object of the present invention is to provide a once-through boiler including a _{low NO x} combustion device capable of easily achieving high-temperature combustion of and a method of operating the same.

A cylindrical once-through boiler according to a first embodiment of the present invention for achieving the above object includes: a cylindrical housing having a water supply port, a steam discharge port, and a combustion gas discharge port; A cylindrical porous body combustor disposed inside the housing and including a first porous body having a cylindrical shape and a second porous body surrounding the outside of the first porous body; A fuel oxidizer supply unit for supplying a premixer to the cylindrical porous combustor; An upper header disposed inside the housing and connected to the water supply port; A lower header disposed inside the housing and connected to the steam outlet; And a plurality of water pipes connected to the upper header and the lower header and arranged in an annular shape spaced apart from each other at predetermined intervals around the outer periphery of the cylindrical porous combustor. It may include.

A flame surface may be formed between the first porous body and the second porous body.

The fuel oxidant supply unit may include a mixer provided on the cylindrical porous combustor; A fuel supply pipe provided on one surface of the mixer; An air supply pipe provided on one surface of the mixer; And a premixer inlet pipe provided below the mixer. It may include.

The cylindrical porous body combustor may further include a porous distribution pipe formed inside the hollow portion of the first porous body.

The plurality of water pipes may be connected by a heat transfer plate to form a water pipe wall.

The water pipe wall may be formed of an inner water pipe wall and an outer water pipe wall.

A first opening may be formed in a portion of the inner water pipe wall, and a second opening may be formed in the outer water pipe wall in a direction opposite to the first opening.

The inner water pipe wall and the outer water pipe wall may be connected to the same upper header and lower header.

The inner water pipe wall may be connected to an inner upper header and an inner lower header, and the outer water pipe wall may be connected to an outer upper header and an outer lower header.

A flat plate type once-through boiler according to a fourth embodiment of the present invention includes a polyhedral housing having a water supply port, a steam discharge port, and a combustion gas discharge port; A flat plate type porous body combustor provided on one side of the housing and including a first porous body and a second porous body stacked in the flow direction of the premixer; A fuel oxidizer supply unit for supplying a premixer to the flat porous combustor; An upper header disposed inside the housing and connected to the steam outlet; A lower header disposed inside the housing and connected to the water supply port; And a plurality of water pipes connecting the upper header and the lower header. It may include.

A flame surface may be formed between the first porous body and the second porous body.

The fuel oxidizer supply unit may include a mixer provided at a front end of the planar porous combustor; A fuel supply pipe provided on one surface of the mixer; An air supply pipe provided on one surface of the mixer; And a premixer inlet pipe provided at a rear end of the mixer. It may include.

The housing may further include a first guide member and a second guide member for forming a flow path of the combustion gas on the inner surface.

The planar porous body combustor may further include a porous distribution plate between the mixer and the first porous body.

In the operating method of the cylindrical once-through boiler or flat-type once-through boiler,

(a) mixing fuel and an oxidizing agent in the mixer, and supplying the mixed gas to the fuel inlet;

(b) performing excess enthalpy combustion by supplying fuel into the first porous body in step a;

(c) heating the boiler water inside the water pipe by the excess enthalpy combustion to discharge steam;

It may include.

The step (d) of first igniting a small combustor for ignition provided in the outer periphery of the cylindrical or flat porous combustor between steps (a) and (b) to generate a flame in the second porous body located outside the combustion tube. It may contain more.

As described above, according to the present invention, by applying the porous body combustion in the combustor of the once-through boiler _{, the high temperature region required for NO x} generation is narrowed due to the rapid temperature drop downstream of the flame, and at the same time, due to the rapidly increased combustion rate. The speed of the gas increases, and consequently, the residence time in the high-temperature region decreases rapidly, and the _{generation of NO x} can be suppressed because a sufficient time is not provided for the nitrogen to be oxidized.

In addition, compared to external heat recirculation through a conventional heat exchanger, a simple and effective heat recirculation effect can be obtained.

In addition, since uniform combustion occurs in the porous body and high-temperature thermal radiation is radiated from the porous body, the water pipe of the boiler can be uniformly heated, which is advantageous for improving the performance and durability of the device.

1 is a perspective view of a cylindrical once-through boiler according to a first embodiment of the present invention.
2 is a vertical cross-sectional view of a cylindrical porous combustor according to the present invention.
3 is a perspective view of a cylindrical once-through boiler according to a second embodiment of the present invention.
4 is a horizontal cross-sectional view of a cylindrical once-through boiler according to a second embodiment of the present invention.
5 is a perspective view of a water pipe wall according to a second embodiment of the present invention.
6 is a perspective view of a cylindrical once-through boiler according to a third embodiment of the present invention.
7 is a horizontal cross-sectional view of a cylindrical once-through boiler according to a third embodiment of the present invention.
8 is a perspective view of a flat plate type once-through boiler according to a fourth embodiment of the present invention.
9 is a vertical cross-sectional view of a flat plate type once-through boiler according to a fourth embodiment of the present invention.

Hereinafter, exemplary embodiments in which the present invention can be easily implemented by those of ordinary skill in the art to which the present invention pertains will be described in detail with reference to the accompanying drawings. However, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention in describing the operating principle of the preferred embodiment of the present invention in detail, the detailed description thereof will be omitted.

The present invention will be described as a detailed embodiment according to the drawings.

1 is a perspective view of a cylindrical once-through boiler 100 according to a first embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a cylindrical porous combustor 120.

Referring to Figure 1, the cylindrical once-through boiler 100 according to the first embodiment of the present invention is a cylindrical housing 110 in which a water inlet 111, a steam outlet 112 and a combustion gas outlet 113 are formed, The housing 110 may include a cylindrical porous combustor 120, an upper header 140, a lower header 150, a plurality of water pipes 161, and a fuel oxidant supply unit 130.

The fuel oxidizer supply unit 130, a mixer 131, a fuel supply pipe 132, an air supply pipe 133, and a premixer inlet pipe 134 may be included. The mixer 131 is disposed above the cylindrical porous combustor 120. A fuel supply pipe 132 and an air supply pipe 133 may be provided in a part of the mixer 131, and a premixer inlet pipe 134 may be formed under the mixer 131.

Accordingly, air and fuel may each be introduced into the mixer 131 to be premixed, and introduced into the cylindrical porous combustor 120 through the premixer inlet pipe 134. In this case, the air supplied to the air supply pipe 133 may be an oxidizing agent.

As shown in FIG. 2, the cylindrical porous body combustor 120 has a cylindrical first porous body 121 having a hollow portion 124 in the center and a second porous body 122 surrounding the outside of the first porous body 121. ) Can be included.

A flame surface 123 may be formed between the first porous body 121 and the second porous body 122.

A porous distribution pipe 125 may be provided inside the hollow portion 124 of the first porous body 121. Accordingly, fuel and air introduced into the cylindrical porous body combustor 120 uniformly pass through the first porous body 121 and continuously pass through the second porous body 122, thereby enabling more stable combustion. .

When there is no heat loss to the outside, the maximum temperature that the fuel and oxidizing agent in a given condition can reach by burning is called the single flame temperature. At this time, heat from the high-temperature combustion gas to cold unburned gas. Given recirculation, it is possible to achieve high temperatures above the single flame temperature, which is called excess enthalpy combustion.

As in the present invention, without using an additional device such as a heat exchanger for heat recirculation, if combustion is performed inside the porous body using the cylindrical porous body combustor 120, heat recirculation is performed by conduction and radiant heat transfer of the porous body itself. Occurs and ultimately, excess enthalpy combustion can be easily achieved.

On the outer periphery of the cylindrical porous combustor 120, a plurality of water pipes 161 are spaced apart and arranged in an annular shape. The water pipe 161 is a passage through which boiler water moves, and may have a long pipe shape. The upper part of the water pipe 161 is connected to the upper header 140, and the lower part of the water pipe 161 is connected to the lower header 150.

The upper header 140 and the lower header 150 have a ring shape having a diameter larger than that of the cylindrical porous combustor 120, and an inner space may be formed.

The lower header 150 is connected to the water supply port 111 to uniformly supply the boiler water supplied from the water supply port 111 to the plurality of water pipes 161.

The boiler water supplied from the lower header 150 moves from the bottom of each of the water pipes 161 to the top, is heated by the combustion heat of the cylindrical porous combustor 120 and is collected in the upper header 140 in a state of saturated steam, and then the upper header ( It is discharged through the steam outlet 112 connected to 140).

The combustion gas discharged from the cylindrical porous combustor 120 moves between the plurality of water pipes 161 and is discharged through the combustion gas discharge port 113.

3 is a perspective view of a cylindrical once-through boiler 100 according to a second embodiment of the present invention, Figure 4 is a horizontal cross-sectional view of a cylindrical once-through boiler 100 according to a second embodiment of the present invention, and Figure 5 is the present invention It is a perspective view of the water pipe wall 160 according to an embodiment of.

3 to 4, the cylindrical once-through boiler 100 according to the second embodiment of the present invention is a cylindrical housing in which a water inlet 111, a steam outlet 112, and a combustion gas outlet 113 are formed ( 110), a cylindrical porous combustor 120 provided in the housing 110, an upper header 140, a lower header 150, a water pipe wall 160, and a fuel oxidant supply unit 130.

Hereinafter, the same reference numerals are assigned to the same components as those of the first embodiment of the present invention, and detailed descriptions thereof will be omitted.

A water pipe wall 160 may be formed around the outer periphery of the cylindrical porous combustor 120. The water pipe wall 160 may have a structure in which a plurality of water pipes 161 are connected by a heat transfer plate 162.

Referring to FIG. 5, the water pipe wall 160 is fixed in a state in which the water pipes 161 are spaced apart from each other by a predetermined interval as both ends of the heat transfer plate 162 are connected to the water pipes 161, respectively.

Since the heat transfer plate 132 may be made of a thermally conductive material, heat transfer may be promoted.

At least one water pipe wall 160 may be provided, and in the present invention, a boiler having two water pipe walls 160 will be described as an example.

The water pipe wall 160 may be formed of an inner water pipe wall 164 and an outer water pipe wall 165.

The outer water pipe wall 165 may have the same structure as the inner water pipe wall 164.

In addition, a first opening 166 may be formed in a portion of the inner water pipe wall 164, and a second opening 167 may be formed in the outer water pipe wall 165.

The second opening 167 may be formed in a direction opposite to the first opening 166.

The first opening 166 and the second opening 167 may be passages for the combustion gas. That is, the combustion gas discharged from the cylindrical porous combustor 120 moves to the second opening 167 through the first opening 166 and is discharged to the combustion gas discharge port 113.

An upper header 140 connected to the water inlet 111 is disposed on the inner water pipe wall 164 and the outer water pipe wall 165, and a lower header 150 connected to the steam outlet 112 is disposed at the lower portion, respectively. Can be connected.

As in Example 1, the upper header 140 and the lower header 150 have a ring shape having a diameter larger than that of the cylindrical porous combustor 120, and the inner water pipe wall 164 and the outer water pipe wall 165 are one It may be connected to the upper header 140 and one lower header 150.

With the structure as described above, boiler water is collectively supplied from the lower header 150 to the water pipes of the inner water pipe wall 164 and the outer water pipe wall 165, and the inner water pipe wall 164 and the outer water pipe wall 165 ), the saturated steam generated in the water pipe 161 is discharged through the upper header 140.

6 is a perspective view of a cylindrical once-through boiler 100 according to a third embodiment of the present invention, and FIG. 7 is a horizontal cross-sectional view of a cylindrical once-through boiler 100 according to a third embodiment of the present invention.

6 and 7, the cylindrical once-through boiler 100 according to the second embodiment of the present invention has a cylindrical housing in which a water inlet 111, a steam outlet 112, and a combustion gas outlet 113 are formed ( 110), a cylindrical porous combustor 120 provided in the housing 110, an upper header 140, a lower header 150, a water pipe wall 160, and a fuel oxidant supply unit 130.

Hereinafter, the same reference numerals are assigned to the same components as those of the first embodiment of the present invention, and detailed descriptions thereof will be omitted.

A water pipe wall 160 may be formed around the outer periphery of the cylindrical porous combustor 120. The water pipe wall 160 may be formed of an inner water pipe wall 164 and an outer water pipe wall 165.

A first opening 134 may be formed in a portion of the inner water pipe wall 130, and a second opening 135 may be formed in the outer water pipe wall 130 in a direction opposite to the first opening 134.

The inner water pipe wall 164 and the outer water pipe wall 165 may be connected to the independent upper header 140 and the lower header 150, respectively. That is, the inner water pipe wall 164 is connected to the inner upper header 141 and the inner lower header 151, and the outer water pipe wall 165 is connected to the outer upper header 142 and the outer lower header 152. .

Accordingly, the boiler water supplied from the inner lower header 151 flows into the inner water pipe wall 164 and is discharged through the inner upper header 141, and the boiler water supplied from the outer lower header 152 is the outer water pipe wall ( 165 and discharged through the outer upper header 142.

8 is a perspective view of a plate type once-through boiler 200 according to a fourth embodiment of the present invention, and FIG. 9 is a vertical cross-sectional view of a plate type once-through boiler 200 according to a fourth exemplary embodiment of the present invention.

8 and 9, the flat-type once-through boiler 200 includes a polyhedral housing 210 in which a water inlet 211, a steam outlet 212, and a combustion gas outlet 213 are formed, and the housing 210 It includes a planar porous combustor 220, an upper header 240, a lower header 250, a plurality of water pipes 261 and a fuel oxidant supply unit 230 provided on an upper side of one side.

The planar porous body combustor 220 includes a first porous body 221 and a second porous body 222 stacked in the flow direction of the premixer, and a flame surface between the first porous body 221 and the second porous body 222 223 is formed.

A porous distribution plate 225 may be provided between the fuel oxidant supply unit 230 and the first porous body 221. With the above configuration, the fuel introduced into the flat porous body combustor 220 uniformly passes through the first porous body 221, and continuously passes through the second porous body 222, thereby enabling more stable combustion.

The fuel oxidizer supply unit 230 may include a mixer 231, a fuel supply pipe 232, an air supply pipe 233, and a premixer inlet pipe 234.

Air and fuel supplied through the fuel supply pipe 232 and the air supply pipe 233 may be premixed by being introduced into the mixer 230, respectively, and the inside of the plate-type porous combustor 220 through the premixer inlet pipe 233 Flows into. In this case, the air supplied to the air supply pipe 233 may be an oxidizing agent.

The housing further includes a first guide member 270 and a second guide member 280 for forming a flow path of the combustion gas therein.

The premixer may be a fuel and/or an oxidizing agent.

The fuel may be a hydrocarbon compound, and the hydrocarbon compound may have 1 to 6 carbon atoms. The fuel may be synthetic gas, by-product gas, hydrogen, LNG, or LPG.

The oxidizing agent is not limited as long as it is a gaseous substance containing oxygen. Preferably it may be air.

Specifically, when defining a side surface on which the planar porous combustor is disposed as an A surface and a side facing A as a B surface, the first guide member 270 may extend horizontally from the A surface toward the B surface. In this case, the first guide member 270 may be spaced apart from the B surface by a predetermined distance.

The second guide member 280 may extend horizontally from the B surface to the A surface. In this case, the second guide member 280 is disposed under the first guide member 270 and may be spaced apart from the A surface by a predetermined distance.

The first guide member 260 and the second guide member 270 have a plate shape, and are positioned between the upper header 240 and the lower header 250 to pass through a plurality of water pipes 261.

With the above structure, a first space 291 is formed between the upper surface of the housing 210 and the first guide member 270, and between the first guide member 270 and the second guide member 280. A second space 292 is formed, and a third space 293 is formed between the second guide member 280 and the bottom surface of the housing.

In the plate type once-through boiler according to the third embodiment of the present invention, the combustion gas from the plate type porous combustor 220 sequentially passes through the first space 291, the second space 292, and the third space 293. It passes through and heats the water pipe 261, and is discharged through the combustion gas outlet 213.

The boiler water introduced into the lower header 250 passes through a plurality of water pipes 261, is heated, and is discharged to the steam outlet 212 through the upper header 240 in a state of saturated steam.

Although the above description has been made with reference to the drawings according to the embodiments of the present invention, a person of ordinary skill in the field to which the present invention belongs will be able to perform various applications and modifications within the scope of the present invention based on the contents.

100: cylindrical once-through boiler
200: flat plate type once-through boiler
110, 210: housing
111, 211: water inlet
112, 212: steam outlet
113, 213: flue gas outlet
120: cylindrical porous body combustor
220: flat plate type porous combustor
121, 221: first porous body
122, 222: second porous body
123, 223: flame side
124: hollow part
125: porous distribution pipe
225: porous distribution plate
130, 230: fuel oxidizer supply unit
131, 231: mixer
132, 232: fuel supply pipe
133, 233: air supply pipe
134, 234: premixer inlet pipe
140, 240: upper header
150, 250: lower header
141: inner upper header
142: outer upper header
151: inner lower header
152: outer lower header
160: water pipe wall
161, 261: water pipe
162, 262: heat transfer plate
164: inner water pipe wall
165: outer water pipe wall
166: first opening
167: second opening
270: first guide member
280: second guide member
291: first space
292: second space
293: third space

Claims (14)

A cylindrical housing having a water supply port, a steam discharge port, and a combustion gas discharge port;
A cylindrical porous body combustor disposed inside the housing and including a first porous body having a cylindrical shape and a second porous body surrounding the outside of the first porous body;
A fuel oxidizer supply unit for supplying a premixer to the cylindrical porous combustor;
A lower header disposed inside the housing and connected to the water supply port;
An upper header disposed inside the housing and connected to the steam outlet; And
And a plurality of water pipes that connect the upper header and the lower header, and are spaced apart from each other at a predetermined interval and arranged in an annular shape around the outer periphery of the cylindrical porous combustor; and
A flame surface is formed between the first porous body and the second porous body,
The cylindrical once-through boiler including excess enthalpy combustion further comprising a porous distribution pipe formed in the hollow portion of the first porous body in the cylindrical porous body combustor. The method of claim 1,
The fuel oxidant supply unit,
A mixer provided above the cylindrical porous combustor;
A fuel supply pipe provided on one surface of the mixer;
An air supply pipe provided on one surface of the mixer; And
A premixer inlet pipe provided below the mixer;
Cylindrical once-through boiler containing wool. delete The method of claim 1,
The plurality of water pipes are connected by a heat transfer plate to form a water pipe wall. The method of claim 4,
The water pipe wall is a cylindrical once-through boiler consisting of an inner water pipe wall and an outer water pipe wall. The method of claim 5,
A first opening is formed in a part of the inner water pipe wall,
The outer water pipe wall is a cylindrical once-through boiler having a second opening formed in a direction opposite to the first opening. The method of claim 4,
The inner water pipe wall and the outer water pipe wall are cylindrical once-through boilers connected to the same upper and lower headers. The method of claim 1,
The inner water pipe wall is connected to the inner upper header and the inner lower header,
The outer water pipe wall is a cylindrical once-through boiler connected to the outer upper header and the outer lower header. A polyhedral housing having a water supply port, a steam discharge port, and a combustion gas discharge port;
A flat plate type porous body combustor provided on one side of the housing and including a first porous body and a second porous body stacked in the flow direction of the premixer;
A fuel oxidizer supply unit for supplying a premixer to the flat porous combustor;
An upper header disposed inside the housing and connected to the steam outlet;
A lower header disposed inside the housing and connected to the water supply port; And
A plurality of water pipes connecting the upper header and the lower header;
Including,
A flame surface is formed between the first porous body and the second porous body,
A flat plate type once-through boiler comprising an excess enthalpy combustion provided with a flat plate type porous body combustor further comprising a porous distribution plate between the mixer and the first porous body. The method of claim 9,
The fuel oxidant supply unit,
A mixer provided at a front end of the flat porous combustor;
A fuel supply pipe provided on one surface of the mixer;
An air supply pipe provided on one surface of the mixer; And
A premixer inlet pipe provided at the rear end of the mixer;
A flat plate type once-through boiler comprising a. The method of claim 10,
The housing is a plate type once-through boiler having a plate type porous combustor further comprising a first guide member and a second guide member for forming a flow path of the combustion gas on the inner surface. delete In the method of operating the cylindrical once-through boiler or the flat once-through boiler according to any one of claims 1, 2 and 4 to 11,
(a) mixing the fuel and the oxidizing agent in a mixer, and supplying the mixed gas to the fuel inlet;
(b) performing excess enthalpy combustion by supplying fuel into the first porous body in step a;
(c) heating the boiler water inside the water pipe by the excess enthalpy combustion to discharge steam;
A method of operating a cylindrical once-through boiler or a flat-type once-through boiler comprising a. The method of claim 13,
The step (d) of first igniting a small combustor for ignition provided in the outer periphery of the cylindrical or flat porous combustor between steps (a) and (b) to generate a flame in the second porous body located outside the combustion tube. A method of operating a cylindrical once-through boiler or a flat-type once-through boiler further comprising.

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