JP5174703B2 - Multi-pipe once-through boiler - Google Patents

Description

  The present invention relates to a multi-tube once-through boiler in which heat absorption fins are provided in an inner water pipe facing a combustion chamber.

  As disclosed in Japanese Patent No. 3413107, a multi-tube once-through boiler having a configuration in which a combustion chamber is provided in the center of the boiler and water tubes extending in the vertical direction are arranged in two rows around the combustion chamber is widely used. Yes. In such a boiler, a water pipe wall is formed by connecting adjacent water pipes with a closing fin, and the side facing the combustion chamber of the inner water pipe row is first heated by performing combustion in the combustion chamber. A combustion gas passage is provided between the inner water tube row and the outer water tube row, and a part of the closing fin is opened, so that the combustion gas flows into the combustion gas passage from the opening of the inner water tube row without the closing fin. In this way, the water pipe is also heated by the combustion gas flow flowing through the combustion gas passage.

  In Japanese Patent No. 3413107, the amount of heat absorbed by the water pipe is increased by installing heat absorption fins on the surface of the water pipe facing the combustion gas passage. When heat absorption fins are installed in the water pipe, turbulent flow is generated in the combustion gas flow, and the efficiency of heat transfer with the water pipe is improved by generating turbulent flow in the combustion gas, so the amount of heat absorbed by the water pipe Will increase. Moreover, the amount of heat absorption also increases when the area for absorbing heat increases. In Japanese Patent Laid-Open No. 58-12910, heat absorption fins are also provided in the inner water pipe to increase the area in contact with combustion gas and increase the amount of heat absorption. In this case, the combustion gas flows in such a manner as to pull out between the heat absorption fins, and the heat absorption amount is increased not by the generation of turbulent flow but by the increase of the heat transfer area.

  Thus, although the device for increasing heat absorption amount has been conventionally performed, further increase in heat absorption efficiency is desired in order to reduce fuel consumption. However, as described in Japanese Patent Application Laid-Open No. 58-12910, the heat absorption amount increases as the heat absorption area increases. When a large heat-absorbing fin connected to the periphery is provided, there is a problem that the heat-absorbing fin is overheated and burnout occurs.

Japanese Patent No. 3413107

  The problem to be solved by the present invention is to provide a multi-tube once-through boiler capable of further increasing the amount of heat absorbed while preventing the occurrence of problems such as burning of the heat absorbing fins. .

The center part is a combustion chamber, and a number of water pipes extending in the vertical direction are arranged around the combustion chamber in a double annular shape, and the inner water pipes arranged inside and the outer water pipes arranged outside are connected to each other. Thus, the inner water tube row and the outer water tube row are respectively formed, and the portion facing the combustion chamber of the inner water tube row is first heated by the combustion gas, and then the combustion gas is formed between the inner water tube row and the outer water tube row. In the boiler that is sent into the gas passage and flows in the gas passage,
The inner water pipe facing the combustion chamber and the outer water pipe facing the gas passage are provided with a plurality of heat absorption fins extending in a direction perpendicular to the longitudinal direction of the water pipe. The heat absorption fin for the combustion chamber provided in the portion facing the combustion chamber of the water pipe is lower in height from the surface of the water pipe and is thicker than the gas passage heat absorption fin provided in the portion facing the gas passage. Is installed only at a position lower than the water level in the boiler when the boiler is started. The combustion chamber heat absorbing fins preferably have a height from the surface of the water tube of 10 mm or less and a thickness of 4.5 mm or more.

  By providing the heat absorption fin for the combustion chamber on the surface of the water tube facing the combustion chamber, turbulent flow can be generated in the combustion gas flow flowing along the surface of the water tube in the combustion chamber, and the amount of heat absorbed by the water tube Can be increased. The heat absorption fin for the combustion chamber is lower in height and thicker than the heat absorption fin for the gas passage, and is installed at a position lower than the water level when the boiler is started, so that the upper part of the water pipe and the heat absorption fin It is possible to prevent the portion of the portion from being overheated and burned out.

  An embodiment of the present invention will be described with reference to the drawings. 1 is a longitudinal sectional view of a boiler embodying the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a partial sectional view of the water pipe portion of FIG. 1, and FIGS. It is the partial sectional view which extracted the water pipe part in other examples.

  The boiler is provided with an annular upper header 1 at the upper part of the can body and an annular lower header 2 at the lower part. Between the upper and lower headers, a large number of vertical water tubes are arranged in two rows, and the upper and lower headers are connected by two inner and outer water tube rows. Each vertical water pipe is arranged with a gap, and the inner water pipe 5 and the outer water pipe 6 form a water pipe wall by closing the adjacent water pipes with the closing fins 4. A combustion chamber 10 is provided at the boiler central portion inside the water tube row, and the combustion device 3 is disposed above the combustion chamber 10. An annular space is formed between the inner water tube row and the outer water tube row, and combustion gas flows through the annular space as a gas passage 9. A number of heat absorption fins 8 for gas passages extending in the horizontal direction from the surface of the water tube are provided in portions of the inner water tube 5 and the outer water tube 6 facing the gas passage 9. The heat absorption fin is also provided on the surface of the inner water pipe 5 facing the combustion chamber, and the heat absorption fin on the combustion chamber side is the heat absorption fin 7 for the combustion chamber.

  The closing fins 4 that connect the inner water pipes are installed halfway through the water pipes, and an opening is provided between the inner water pipes by not providing the closing fins 4 at the lower part of the inner water pipes. The opening at the lower part of the inner water tube row is provided on the entire circumference, and the combustion gas that has reached the lower part of the combustion chamber 10 is dispersed radially and passes through the opening. Further, the closing fin 4 provided in the outer water pipe 6 is also set up to the middle of the water pipe, and an opening is provided between the upper outer water pipes by not providing the closing fin in the upper part of the outer water pipe. Since the opening in the upper part of the outer water pipe row is also provided in the entire circumference, the combustion gas that has reached the upper part of the gas passage 9 also flows in the circumferential direction.

  In the boiler, boiling water of the boiler is generated together with the steam, and since the steam taken out from the upper header 1 contains boiler water, a steam / water separator 12 for separating the liquid component from the steam is provided. The boiler water separated by the steam separator 12 is returned to the lower header 2. The water level in the boiler is detected by a water level detection device 11 connected to the steam separator 12, and water supply is controlled so as to maintain a constant water level in the boiler.

The heat absorption fins 8 for gas passages installed on the gas passage 9 side of the water pipe are installed in multiple stages having a height of 13 mm and a thickness of 4 mm from the water pipe surface. The heat absorption fins 7 for the combustion chamber installed in the inner water pipe 5 are provided at a position lower than the water level when the boiler is started. The combustion chamber heat absorption fins 7 have a lower height from the water tube surface than the gas passage heat absorption fins 8 such that the height from the water tube surface is 10 mm or less and the thickness is 4.5 mm or more. Use a thicker one.

This is because the combustion gas flow flowing through the gas passage 9 portion has a temperature lowered by heat exchange with the inner water pipe 5, and the combustion gas flow flowing through the combustion chamber is burned by the combustion device 3. This is because the combustion gas having a high temperature flows as it is. Since the combustion gas in the gas passage 9 is difficult to burn out the heat absorption fins, the heat absorption fin 8 for the gas passage is used with emphasis on heat transfer efficiency, but the heat absorption fins 7 for the combustion chamber are difficult to burn out. It is necessary to. In addition, when the combustion chamber heat absorption fins 7 extend over the entire circumference of the water tube, the combustion gas flows away from the surface of the water tube and strongly heats only the combustion chamber heat absorption fins. The angle θ in the circumferential direction of the heat absorption fin for the combustion chamber is set to be smaller than 45 ° so that a portion without fin exists between the heat absorption fin 7 for the combustion chamber and the closing fin 4. . The heat absorption fins 7 for the combustion chamber are fan-shaped in FIGS. 2 and 3, but may be other shapes such as a pin shape as shown in FIG. 4, and the heat absorption fins 7 as shown in FIG. The thickness may be larger than the height.

  When combustion is performed by the combustion device 3, high-temperature combustion gas is generated in the combustion chamber 10. The combustion gas first heats the portion of the inner water pipe 5 facing the combustion chamber 10. The combustion gas flows downward along the surface of the inner water pipe 5 and heats the portion of the inner water pipe 5 facing the combustion chamber. Since the inner water pipe 5 has the combustion chamber heat absorbing fins 7 on the surface, the combustion gas flowing downward along the combustion chamber side surface of the inner water pipe 5 flows while generating turbulent flow. When the turbulent flow is generated in the combustion gas flow, the heat transfer efficiency from the combustion gas to the water pipe is increased, so that heat can be efficiently transferred to the inner water pipe 5. Since the surface of the inner water pipe 5 is provided with the heat absorption fins 7 for the combustion chamber, the turbulent flow can be more effectively reduced compared to the case where irregularities are provided by simply processing the surface of the inner water pipe. Can be generated.

  When the combustion gas reaches the lower part of the combustion chamber 10, since the opening is provided in the lower part of the inner water pipe row, the combustion gas passes through the opening in the lower part of the inner water pipe row and enters the gas passage 9. Since the outlet of the gas passage 9 is the upper part of the outer water tube row, the combustion gas that has entered the gas passage 9 flows upward in the gas passage 9. Although the temperature of the combustion gas that has entered the gas passage 9 has decreased due to the heat exchange so far, the portion of the inner water pipe 5 and the outer water pipe 6 facing the gas passage 9 has a number of gas passages. Since the heat absorption fins 8 are provided, a turbulent flow is generated in the gas flow in the gas passage 9 and heat exchange is actively performed between the combustion gas and the water pipe.

  Since the combustion gas in the combustion chamber 10 is a combustion gas having a very high temperature immediately after combustion in the combustion device 3, a portion of the inner water pipe 5 facing the combustion chamber 10 receives a high heat load. . Since the temperature conditions differ between the combustion gas in the combustion chamber and the combustion gas in the gas passage, if the heat absorption fins are installed in the combustion chamber as in the case of the gas passage 9, the heat absorption fins in the combustion chamber are burned out, etc. May cause problems. Therefore, the heat absorbing fin provided in the combustion chamber 10 is 10 mm or less in height and 4.5 mm or more in thickness. And the installation position of the heat absorption fin 7 for combustion chambers provided in the inner side water pipe 5 shall be only a position lower than the water level at the time of boiler starting, and should not be installed in a position higher than the water level at the time of boiler startup.

  In a portion higher than the boiler starting water level of the inner water pipe 5, since there is no boiler water on the inner surface of the water pipe when the boiler is started, heat transfer from the water pipe to the boiler water is delayed. Therefore, when the combustion chamber heat absorption fins 7 are installed up to the top of the inner water pipe 5, the heat absorbed by the combustion chamber heat absorption fins 7 is accumulated in the water pipe portion, and the water pipe is overheated. This means that the combustion chamber heat absorbing fins 7 burn out.

  In the present invention, the heat absorption fins 7 for the combustion chamber are lowered in height and increased in thickness, and the installation position is lower than the water level when the boiler is started. Since the heat thus transmitted is promptly transmitted to the boiler water in the inner water pipe 5, overheating of the inner water pipe portion can be prevented, and burning of the heat absorbing fins for the combustion chamber can be prevented.

The longitudinal cross-sectional view which showed the outline | summary of the boiler which is implementing this invention AA sectional view of FIG. Partial sectional view of the water pipe portion of FIG. 1 extracted and enlarged Partial sectional view of the water pipe portion extracted and enlarged in the second embodiment Partial sectional view of the water pipe portion extracted and enlarged in the third embodiment

1 Upper header
2 Lower header
3 Combustion device
4 Closure fin
5 inner water pipe
6 Outer water pipe
7 Heat absorption fin for combustion chamber
8 Heat absorption fin for gas passage
9 Gas passage
10 Combustion chamber
11 Water level detector
12 Air-water separator

Claims (2)

The center part is a combustion chamber, and a number of water pipes extending in the vertical direction are arranged around the combustion chamber in a double annular shape, and the inner water pipes arranged inside and the outer water pipes arranged outside are connected to each other. Thus, the inner water tube row and the outer water tube row are respectively formed, and the portion facing the combustion chamber of the inner water tube row is first heated by the combustion gas, and then the combustion gas is formed between the inner water tube row and the outer water tube row. In the boiler that is fed into the gas passage and is caused to flow in the gas passage, the portion of the inner water pipe facing the combustion chamber and the portion of the outer water pipe facing the gas passage are arranged in the longitudinal direction of the water pipe. The heat absorbing fins for the combustion chamber provided in a portion facing the combustion chamber of the inner water pipe are provided in the portion facing the gas passage. More water than gas passage heat absorption fins Low height from the surface, and be one is thicker, multi-tube once-through boiler, characterized in that it is installed only at a position lower than the boiler water level at boiler startup. The multi-tube once-through boiler according to claim 1, wherein the heat absorption fin for the combustion chamber has a height from the surface of the water tube of 10 mm or less and a thickness of 4.5 mm or more. .

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