JP2018031502A - Boiler with feed water and preheater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase heat absorption amount of water feed pre-heater device 7 for pre-heating fed water with exhaust gas got from a boiler.SOLUTION: This invention is a boiler including a main body of a boiler 1 for heating boiler water with combustion gas and a fed water pre-heating device having exhaust gas passage 2 for flowing the exhaust gas discharged from the boiler and a fed water pre-heating device 7 installed at the midway part of the exhaust gas passage. A heat transmitting pipe 3 having a connected end part is installed in the fed water pre-heating device, boiler fed water before pre-heating is fed from a fed water inlet heat transmitting pipe with one end of the connected heat transmitting pipe being applied as a fed water inlet heat transmitting pipe 6 and there is provided a fed-water pre-heating device operated to pre-heat the boiler fed water in the heat transmitting pipe with exhaust gas flowed around the heat transmitting pipe, the fed water inlet heat transmitting pipe 6 is installed at an exhaust gas flow most-downstream side of the heat transmitting pipe arranged at the downstream side of exhaust gas in the heat transmitting pipe installed at the most-downstream side of the exhaust gas flow in a group of heat transmitting pipes and there is provided a shutting-off plate 12 for shutting-off a part in the exhaust gas passage at the exhaust gas downstream side of the heat transmitting pipe, the exhaust gas downstream side of the fed water inlet heat transmitting pipe is not shut off, but opened.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boiler having a feed water preheating device that preheats feed water using the heat of combustion exhaust gas.

As described in Japanese Patent Application Laid-Open No. 2013-108643, it is widely performed to provide a feed water preheating device in an exhaust gas passage through which combustion exhaust gas discharged from a boiler passes and to preheat boiler feed water with the combustion exhaust gas. The boiler efficiency can be improved by preheating boiler feedwater using the exhaust gas discharged. In the feed water preheating device, heat exchange is performed between the combustion exhaust gas in the exhaust gas passage and the boiler feed water flowing in the heat transfer pipe provided in the exhaust gas passage, and the amount of heat absorbed by the heat transfer pipe from the combustion exhaust gas increases. The temperature of the boiler can be raised, and the efficiency of the boiler is improved.

In JP 2013-108643 A, the feed water preheating device is installed side by side with the boiler, and the exhaust gas discharged from the boiler enters the feed water preheating device from the side of the feed water preheating device. As shown in FIG. 4, this feed water preheating device is provided with an exhaust gas inlet 8 on the side surface, and a large number of heat transfer tubes are installed in the exhaust gas flow path of the feed water preheating device 7. The heat transfer pipe passes boiler feed water inside and is installed in a direction crossing the exhaust gas flow flowing in the exhaust gas passage, and heat is generated between the exhaust gas flowing around the heat transfer pipe and the boiler feed water flowing in the heat transfer pipe. Exchange.

The heat transfer tube connects the ends of adjacent heat transfer tubes to form a long flow path in which the boiler feed water meanders and flows in the exhaust gas passage, and the boiler feed water is installed at the lowermost stage. It enters from the heat transfer tube, flows to the upper heat transfer tube while meandering, is taken out from the uppermost heat transfer tube, and preheated boiler feed water is sent into the boiler. The water supply path in the water supply preheating device may be a plurality of parallel paths. In this case, the water supply piping branches before entering the water supply preheating device, and merges immediately after exiting the water supply preheating device.

The exhaust gas preheated from the boiler water by the feed water preheating device 7 is finally discharged from the chimney to the outdoors, so the exhaust gas outlet 9 of the feed water preheating device is provided in the upper part of the feed water preheating device. Although the exhaust gas inlet 8 is on the side of the feed water preheating device, it is also provided on the upper portion of the side surface, so both the exhaust gas inlet and the exhaust gas outlet are provided on the upper portion of the feed water preheating device. In this case, if the exhaust gas flows directly from the exhaust gas inlet 8 to the exhaust gas outlet 9, the heat recovery in the feed water preheating device 7 cannot be sufficiently performed. Therefore, a partition plate 4 that separates the exhaust gas inlet side and the exhaust gas outlet side is provided inside the feed water preheating device. The exhaust gas flow passes under the partition plate 4. The interior of the feed water preheating device 7 is divided by the partition plate 4 to provide an exhaust gas flow down flow path 10 on the exhaust gas inlet 8 side and an exhaust gas flow up flow path 11 on the exhaust gas outlet 9 side. The exhaust gas flow flows downward in the exhaust gas flow descending flow path 10, passes below the partition plate 4, flows upward in the exhaust gas flow upward flow path 11, and is discharged from the exhaust gas outlet 9. The heat transfer tube 3 of the feed water preheating device is provided in the exhaust gas flow downward passage 10 where the exhaust gas flow flows downward, and heats the heat transfer tube with the exhaust gas flowing downward.

In the feed water preheating device, by performing heat exchange between the exhaust gas and the boiler feed water, the exhaust gas temperature is lowered and the boiler feed water temperature is raised. The heat transfer from the exhaust gas to the boiler feedwater becomes larger when the exhaust gas temperature is higher than the boiler feedwater temperature and the temperature difference is large. The exhaust gas flow is from top to bottom, and the boiler feed water is swirled from the bottom to the top so that the flow direction of both faces each other. By doing so, more heat can be transferred to the boiler water supply.

Further, the temperature of the exhaust gas flow in the exhaust gas flow down passage 10 is lowered by heating the heat transfer tube 3, and the volume of the exhaust gas is lowered by lowering the temperature. If the cross-sectional area of the exhaust gas flow path is the same, the flow rate of the exhaust gas decreases as the exhaust gas volume decreases, and the heat transfer efficiency from the exhaust gas to the boiler feedwater decreases.

JP 2013-108643 A

  The problem to be solved by the present invention is that in a boiler having a feed water preheating device that preheats boiler feed water by installing a heat transfer tube in an exhaust gas passage for passing exhaust gas from the boiler, the heat absorption amount of the boiler feed water is determined. There is to increase.

The invention according to claim 1 has a boiler body for heating boiler water by the heat of combustion gas, an exhaust gas passage for passing exhaust gas discharged from the boiler, and a feed water preheating device installed in the middle of the exhaust gas passage A boiler with a preheating device, in which a large number of heat transfer tubes are installed in the feed water preheating device, and the heat transfer tubes are connected to the ends of the adjacent heat transfer tubes, and one end of the connected heat transfer tubes is connected to the feed water inlet heat transfer tube In a boiler having a feed water preheating device in which boiler feed water before preheating is introduced from the feed water inlet heat transfer tube and the boiler feed water in the heat transfer tube is preheated by exhaust gas flowing around the heat transfer tube, the feed water inlet heat transfer tube is The heat transfer tube group is provided at the most downstream portion of the exhaust gas flow, and a shielding plate for shielding a part of the exhaust gas passage is provided on the downstream side of the exhaust gas flow of the heat transfer tube provided at the most downstream portion of the exhaust gas flow. Biography Exhaust gas flow downstream of the tube is characterized in that so as to be opened without shielding.

  By implementing this invention, the heat absorption amount of boiler feed water in a feed water preheating apparatus can be increased, and as a result, boiler efficiency can be improved.

Flow chart of feed water preheating device of one embodiment of the present invention The perspective view which extracted the feed water preheating apparatus heat exchanger tube part of one example of the present invention Flow chart of feed water preheating device of another embodiment of the present invention Conventional water supply preheater flow chart

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram of a feed water preheating apparatus embodying the present invention, and FIG. 2 is a perspective view of a heat transfer tube portion extracted from a feed water preheating apparatus according to an embodiment of the present invention. The combustion exhaust gas generated in the boiler 1 is discharged outside through the exhaust gas passage 2, and a feed water preheating device 7 is provided in the middle of the exhaust gas passage 2, and the exhaust gas is discharged outside after passing through the feed water preheating device 7. . The feed water preheating device 7 has a substantially rectangular parallelepiped shape, and has an exhaust gas inlet 8 on the side surface and an exhaust gas outlet 9 on the upper surface. The exhaust gas sent through the exhaust gas passage 2 enters the feed water preheating device 7 from the exhaust gas inlet 8 on the side surface, passes through the inside of the feed water preheating device 7 and then is discharged from the exhaust gas outlet 9 on the upper surface.

A partition plate 4 that divides the interior into an exhaust gas inlet 8 side and an exhaust gas outlet 9 side is installed in the feed water preheating device. The partition plate 4 is connected to the exhaust gas flow passage wall surface of the feed water preheating device at the upper end side and the left and right ends, and has a gap between the bottom surface of the feed water preheating device at the lower end side. It is divided except under 4. Therefore, the exhaust gas that has entered the upper portion of the feed water preheating device 7 from the exhaust gas inlet 8 flows downward in the feed water preheating device 7, turns in the space below the partition plate 4, flows upward from there, and flows into the exhaust gas outlet. 9 is discharged.

The interior of the feed water preheating device is divided into two exhaust gas flow paths by a partition plate, the flow path on the exhaust gas inlet 8 side is the exhaust gas flow down flow path 10, and the flow path on the exhaust gas outlet 9 side is the exhaust gas flow up flow It becomes road 11. The exhaust gas flow descends in the exhaust gas flow descending flow path 10, turns below the partition plate 4, and then rises in the exhaust gas flow ascending flow path 11.

A large number of heat transfer tubes 3 extending in the horizontal direction are provided in the exhaust gas flow down flow path 10. The heat transfer tube 3 is provided with a large number of heat absorbing fins 5. The heat absorption fins 5 are provided in the entire circumference in the circumferential direction from the surface of the heat transfer tube extending in the horizontal direction, and the heat transfer area is increased by arranging the heat absorption fins 5. Can do. In the heat transfer tube 3, the heat of the combustion exhaust gas is absorbed by a large heat transfer surface in which the heat absorption fins 5 are densely provided. The exhaust gas that has entered from the exhaust gas inlet 8 at the top of the feed water preheating device 7 flows from the exhaust gas inlet through the exhaust gas flow down passage 10 toward the turn part below the partition plate. A large number of heat transfer tubes 3 are installed in the exhaust gas flow down flow path 10, and boiler feed water having a low temperature flows in the heat transfer tubes 3, and the temperature is initially high in order to exchange heat between the exhaust gas and the boiler feed water. The exhaust gas decreases in temperature as the boiler feed water in the heat transfer tube 3 is heated.

Each heat transfer pipe in the feed water preheating device 7 forms a long water supply flow path by connecting the ends, introduces boiler feed water before preheating from one end of the connected heat transfer pipe, and from the other end of the connected heat transfer pipe Remove boiler water after preheating. Water is supplied into the feed water preheating device from the feed water inlet heat transfer tube 6 installed at the lowest stage of the heat transfer tube group. In the embodiment, since the two water supply flow paths are formed in the heat transfer tube group, there are two water supply inlet heat transfer tubes 6 connected to the water supply pipe. The water supply pipe is branched immediately before the heat transfer tube group, and feeds water from the two water supply inlet heat transfer tubes 6.

The feed water in the feed water preheating device sequentially passes from the lower heat transfer tube and is heated while meandering to reach the uppermost heat transfer tube. Two feed water outlet heat transfer tubes are installed at the top of the heat transfer tube group, and the boiler feed water that has been preheated is taken out from the feed water preheating device through the two feed water outlet heat transfer tubes, and the two water supplies are merged. To the boiler 1. In the feed water preheating device, the feed water sequentially flows from the lower stage to the upper stage. Therefore, the lower the heat transfer pipe, the lower the temperature of the boiler feed water passing through the interior, and the higher the heat transfer pipe, the higher the boiler feed water temperature.

On the contrary, the exhaust gas temperature decreases as the exhaust gas heats the boiler feed water in the heat transfer tube, so the lower the heat transfer tube, the lower the temperature. The shielding plate 12 is installed immediately below the heat transfer tube installed in the exhaust gas flow down flow path, that is, downstream of the exhaust gas flow. The shielding plate 12 is installed below the heat transfer pipe other than the water supply inlet heat transfer pipe 6 connected to the water supply pipe, and an opening through which the exhaust gas passes is provided below the water supply inlet heat transfer pipe 6. The shielding plate 12 blocks the flow of exhaust gas, and the exhaust gas flows through a portion where the shielding plate 12 is not provided. The exhaust gas that has reached the lowest stage of the heat transfer tube group flows toward the opening below the feed water inlet heat transfer tube 6 where the shielding plate 12 is not provided, and passes through the opening of the shielding plate 12. Therefore, the exhaust gas heats the feed water inlet heat transfer tube 6 last.

Thereafter, the exhaust gas turns under the partition plate 4 and flows upward in the exhaust gas flow rising flow path 11. The exhaust gas outlet 9 is provided in the upper part of the feed water preheating device 7, and the exhaust gas flows toward the upper exhaust gas outlet 9 and exits from the feed water preheating device 7 through the exhaust gas outlet 9.

In the case of the above configuration, since the boiler feed water is not yet preheated in the feed water inlet heat transfer pipe 6 in which the boiler feed water first flows in the feed water preheating device, the boiler feed water in the feed water inlet heat transfer pipe 6 is The temperature becomes the lowest in the feed water preheating device 7. The temperature of the exhaust gas flowing through the heat transfer tube group and reaching the lowermost heat transfer tube has greatly decreased due to the heat exchange so far, and there is little room for heating the boiler feedwater. However, the exhaust gas is finally heat exchanged with the feed water inlet heat transfer tube 6 so that the boiler feed water can be preheated even if the exhaust gas has a lowered temperature. The amount of preheating of boiler feed water can be increased.

Moreover, the volume of the exhaust gas that has reached the most downstream of the heat transfer tube group of the feed water preheating device is also reduced due to a decrease in temperature. Therefore, in the conventional feed water preheating device 7 having a constant cross-sectional area of the exhaust gas passage as shown in FIG. 4, the flow rate of the exhaust gas decreases in the downstream region of the heat transfer tube group.

However, in the present embodiment, the shielding plate 12 is installed as described above, and the flow area of the exhaust gas flow down flow path 10 is reduced. Therefore, in the downstream area of the exhaust gas flow down flow path 10, the temperature of the exhaust gas decreases. The volume is reduced by the reduction of the flow path area through which the exhaust gas flows, and the heat transfer tube can be efficiently heated by the exhaust gas even in the downstream region of the exhaust gas flow down flow path 10.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention. For example, FIG. 3 shows another embodiment of the present invention. In this case, the feed water preheating device 7 is provided with the exhaust gas inlet 8 below the side surface, and the exhaust gas outlet 9 is installed on the upper surface, and the exhaust gas flow in the feed water preheating device flows upward. Since the exhaust gas flow and boiler feed water are countercurrent, the feed water inlet heat transfer pipe 6 is installed at the uppermost stage of the heat transfer pipe group, and the boiler feed water descends to the lower stage while meandering from the uppermost heat transfer pipe of the heat transfer pipe group. Go. Also in this case, the shielding plate 12 is installed on the downstream side of the exhaust gas flow of the heat transfer tube group, that is, above the exhaust gas group. The shielding plate 12 is opened above the water supply inlet heat transfer tube 6 so that the exhaust gas flow finally heats the water supply inlet heat transfer tube 6.

1 boiler
2 Exhaust gas passage
3 Heat transfer tubes
4 Partition plate 5 Heat absorption fin
6 Water supply inlet heat transfer tube
7 Water supply preheating device 8 Exhaust gas inlet 9 Exhaust gas outlet
10 Exhaust gas flow down flow path 11 Exhaust gas flow up flow path 12 Shield plate

Claims (1)

A boiler having a feed water preheating device that has a boiler body that heats boiler water by the heat of combustion gas, and an exhaust gas passage for passing exhaust gas discharged from the boiler, and a feed water preheating device installed in the middle of the exhaust gas passage. In addition, a large number of heat transfer tubes are installed in the feed water preheating device, and the heat transfer tubes are connected to the end portions of adjacent heat transfer tubes. In a boiler having a feed water preheating device that introduces boiler feed water and preheats the boiler feed water in the heat transfer tube with the exhaust gas flowing around the heat transfer tube, the feed water inlet heat transfer tube is the most downstream part of the exhaust gas flow of the heat transfer tube group In addition, a shielding plate that shields a part of the exhaust gas passage is provided on the downstream side of the heat transfer pipe provided in the most downstream portion of the exhaust gas flow. Boiler having a water preheating device, characterized in that so as to be opened without.

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