JP2017020708A - Boiler having supply water preheating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supply water preheating device capable of increasing a heat absorption amount and lowering a pressure loss of an exhaust gas flow in the supply water preheating device.SOLUTION: In a boiler in which a partitioning plate 4 extending in a longitudinal direction, and having a partition with respect to a bottom surface of a supply water preheating device at its lower end side, is disposed in the supply water preheating device 7, so that the inside of the supply water preheating device is divided into an exhaust gas inlet 8 side and an exhaust gas outlet 9 side, an exhaust gas enters an upper portion of the supply water preheating device, flows downward in an exhaust gas flow downward flow channel 10, passes through a partitioning plate lower part, then flows upward in the exhaust gas flow upward flow channel 11, and exits from the upper portion of the supply water preheating device 7 and which has the supply water preheating device 7 in which a number of heat transfer pipes 3 are disposed in the exhaust gas flow downward flow channel in the supply water preheating device, a lower end of the partitioning plate 4 is located at a height position on the way of a group of the heat transfer pipes, and a guide plate 12 projecting from the partitioning plate side toward the heat transfer pipe side, is disposed at the exhaust gas flow downward flow channel side of the partitioning plate lower portion.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. FIG. 3 shows a water supply preheating device having a general configuration conventionally used for comparison. In this feed water preheating device 7, an exhaust gas inlet 8 is provided on the side surface, and a large number of heat transfer tubes are installed in the exhaust gas flow path in 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 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 directly flows from the exhaust gas inlet 8 to the exhaust gas outlet 9, heat recovery cannot be performed by the feed water preheating device 7, and therefore a partition plate 4 is provided inside the feed water preheating device to separate the exhaust gas inlet side and the exhaust gas outlet side. 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.

The exhaust gas flow in the exhaust gas flow descending channel 10 tends to take the shortest path when flowing from the exhaust gas inlet toward the turn part below the partition plate. Further, the temperature of the exhaust gas is decreased by heating the heat transfer tube 3, and the volume of the exhaust gas is decreased by decreasing the temperature. Therefore, when a heat transfer tube is installed in a substantially rectangular parallelepiped region of the exhaust gas flow channel, the exhaust gas flow flowing in the exhaust gas flow descending flow channel 10 is gradually shifted even if it initially flows through the entire flow channel. Occur. In this case, since the exhaust gas flow is reduced on the exhaust gas flow downstream side of the heat transfer tube installation part and away from the turn part at the lower part of the partition plate, the heat absorption amount decreases in this part. It was.

Further, in the turn portion of the flow path in which the exhaust gas flow flowing downward is reversed and flows upward, resistance is generated in the combustion gas flow and pressure loss is generated. When pressure loss occurs in the exhaust passage, the pressure in the furnace in the boiler increases, and the combustion state in the boiler may be deteriorated.

JP 2013-108643 A

  The problem to be solved by the present invention is that in a boiler having a feed water preheating device in which an exhaust gas passage for passing exhaust gas from the boiler is turned inside, the heat absorption amount is increased and the exhaust gas in the feed water preheating device is increased. It is to reduce the pressure loss of the flow.

The invention according to claim 1 recovers the heat of exhaust gas by a boiler that heats 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 having a feed water preheating device for preheating boiler feed water, and by installing a partition plate extending in the vertical direction in the feed water preheating device, the interior of the feed water preheating device is connected to the exhaust gas inlet side and the exhaust gas outlet. The partition plate is connected to the exhaust gas flow passage wall surface of the water supply preheating device at the upper end side and the left and right ends, and has a gap between the bottom surface and the bottom surface of the water supply preheating device. It enters the upper part of the preheating device, passes through the lower part of the partition plate, and then exits from the upper part of the feed water preheating device. In a boiler having a feed water preheating device that preheats boiler feed water by the heat of gas, the lower end of the partition plate is positioned at a height in the middle of the heat transfer tube group, In addition, a guide plate protruding from the partition plate side toward the heat transfer tube side is provided.

According to a second aspect of the present invention, in the boiler having the feed water preheating device, the exhaust gas flow space provided between the lower end of the heat transfer tube group and the bottom plate of the feed water preheating device is eliminated, and the exhaust gas is in the lower part of the heat transfer tube group. It is characterized by flowing in the horizontal direction.

The invention described in claim 3 is characterized in that, in the boiler having the water supply preheating device, the guide plate is provided with an inclination so that the tip side is lowered.

  By carrying out the present invention, the heat absorption amount in the feed water preheating device can be increased, and the pressure loss of the exhaust gas flow in the feed water preheating device can be reduced.

1 is a cross-sectional view of a feed water preheating apparatus according to an embodiment of the present invention. Cross section of conventional water supply preheating device

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a feed water preheating apparatus embodying 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 the feed water preheating device 7 is provided with an exhaust gas inlet 8 on the side surface and an exhaust gas outlet 9 on the upper surface. The exhaust gas inlet 8 is provided on a side surface of the feed water preheating device 7 but close to the upper surface, and the exhaust gas enters the upper part of the feed water preheating device. 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 from the exhaust gas outlet 9. 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. Each heat transfer tube in the feed water preheating device 7 forms a long feed water flow path by connecting the end portions, and the feed water into the feed water preheating device is supplied from the lowermost heat transfer tube of the heat transfer tube group. The feed water in the feed water preheating device sequentially passes from the lower heat transfer tube and reaches the uppermost heat transfer tube while being heated. The pre-heated feed water is taken out from the feed water pre-heating device and supplied into the boiler 1. Therefore, in the feed water preheating device, the temperature of the feed water passing through the inside is lower in the lower heat transfer tube, and the temperature of the feed water is higher in the upper heat transfer tube.

At the lower end of the partition plate 4, the root side end is connected to the partition plate 4, and the guide plate 12 protruding toward the heat transfer tube 3 is installed on the tip side. The guide plate 12 is inclined so that the tip side is lowered, and the cross-sectional area of the exhaust gas flow descending flow path 10 is reduced by providing the guide plate 12. By setting the lower end of the partition plate 4 to a height position in the middle of the heat transfer tube group, the installation height of the guide plate 12 is set to a height position in the middle of the heat transfer tube group. The heat transfer tube 3 is removed from the portion where the guide plate 12 is installed, but the heat transfer tube 3 is installed in a space below the guide plate 12.

  The combustion exhaust gas that has reached the feed water preheating device 7 from the boiler heats the heat transfer tubes 3. When the combustion exhaust gas flows downward between the heat transfer tubes in the feed water preheating device 7, heat exchange with the heat transfer tubes is performed, and when the heat transfer tubes are heated, the temperature of the exhaust gas decreases. When the exhaust gas heats the heat transfer tube, the temperature of the exhaust gas decreases, and when the temperature decreases to the condensation temperature, condensed water is generated. In addition, when soot or the like adheres to the heat transfer tube 3, the heat transfer efficiency is lowered, so that when the heat transfer tube is cleaned, cleaning water for the heat transfer tube is generated. Since condensed water and washing water need to be discharged from the feed water preheating device 7, a drain discharge port 6 is provided at the bottom of the feed water preheating device 7, and drainage from the feed water preheating device 7 is discharged from the drain discharge port 6. .

In the heat transfer tube 3, since the heat absorption fins 5 are densely provided, the heat transfer area is large, and the heat of the combustion exhaust gas is absorbed by a large heat transfer surface. 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. Will decrease.

The volume of the exhaust gas becomes large when the exhaust gas temperature is high. Since the exhaust gas immediately after entering the exhaust gas flow down flow path 10 is hot, it flows through the entire exhaust gas flow path. And in the upstream area in the heat transfer tube group, it flows downward. Then, the guide plate 12 is installed in the middle of the heat transfer tube group, and the flow path on the side close to the partition plate 4 is blocked at the portion where the guide plate 12 is installed. Therefore, in the middle region of the exhaust gas flow descending flow path 10, the exhaust gas flow flows in a direction away from the partition plate 4. When the exhaust gas flow passes through the portion of the guide plate 12, the exhaust gas flows toward the opening below the partition plate 4, so that the exhaust gas flow becomes a meandering flow in the exhaust gas flow down flow path 10. By keeping the guide plate 12 inclined, the exhaust gas flow smoothly meanders.

The exhaust gas flow in the lower part of the heat transfer tube group flows sideways toward the inlet to the exhaust gas flow ascending channel below the partition plate 4. Even if the exhaust gas flow is flowing sideways, the heat transfer tube 3 is heated by being in contact with the heat transfer tube 3, and the boiler feed water is preheated.

In this case, the boiler feed water flowing in the heat transfer tube 3 flows in a direction opposite to the exhaust gas flow. In the heat transfer tube group below the guide plate 12, the combustion gas flow flows from left to right in the drawing. Therefore, in the heat transfer tube group below, the boiler feed water flows from right to left, and the heat transfer tube group above the guide plate 12. Then, since the combustion gas flow flows from the top to the bottom, the boiler feed water flows from the bottom to the top in the upper heat transfer tube group. If the exhaust gas flow and the boiler feed water are made to face each other, the low temperature boiler exhaust gas is used to preheat the low temperature boiler feed water, and the high temperature exhaust gas is used to further preheat the high temperature boiler feed water. For this reason, boiler feed water can be preheated to a higher temperature.

The combustion exhaust gas flows toward the lower part while heating the heat transfer tube, and the temperature gradually decreases by heating the heat transfer tube. As the temperature goes down, the temperature of the feed water flowing in the heat transfer tube is lower, so the exhaust gas temperature further decreases, and the exhaust gas volume decreases as the exhaust gas temperature decreases. For this reason, the flow rate of the exhaust gas decreases in the downstream heat transfer tube group, but the exhaust gas flow meanders in the flow path by the guide plate 12 so that the exhaust gas flow flows through the entire heat transfer tube group. Become. Since heat exchange is performed in the entire heat transfer tube without a shortcut of the exhaust gas flow, the amount of heat recovered from the exhaust gas by the heat transfer tube is increased, and the feed water preheating device 7 can preheat the boiler feed water at a higher temperature.

When the exhaust gas flow passes through an opening opened below the partition plate 4 and enters the exhaust gas flow ascending flow path 11, the exhaust gas flow changes upward by about 90 ° and moves upward. 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.

As the exhaust gas in the feed water preheating device 7 is subjected to heat exchange with the heat transfer tube 3, the exhaust gas temperature decreases and the volume of the exhaust gas decreases, so the flow rate of the exhaust gas decreases in the downstream region of the heat transfer tube group. In the conventional water supply preheating device 7 shown in FIG. 2, a space is provided below the heat transfer tube group so that the exhaust gas flows through the heat transfer tube group so that the exhaust gas flows through the heat transfer tube group. However, as described above, the flow toward the turn part below the partition plate 4 is increased as described above, and the flow rate of the exhaust gas is reduced in the portion away from the partition plate 4 below the heat transfer tube group.

In this case, a lot of exhaust gas is reversed by about 180 ° at the turn part below the partition plate. At that time, a large turbulent flow is generated in the exhaust gas flow, and resistance is generated in the exhaust gas flow. . However, if the guide plate 12 is provided and the opening below the guide plate 12 is opened without providing a partition plate, the exhaust gas flow flows laterally between the lower heat transfer tubes to the opening below the partition plate. It will head, and after entering the exhaust gas flow rising flow path as it is, the direction change of about 90 ° is performed. Therefore, the resistance generated in the exhaust gas flow can be reduced as compared with the case where the reversal of about 180 ° is performed at one place.

Furthermore, since the exhaust gas flows through the entire heat transfer tube group by the guide plate 12, there is no need to narrow the opening between the lower end of the partition plate 4 and the bottom surface of the exhaust gas passage. If it was the conventional water supply preheating apparatus, in order to prevent the shortcut of exhaust gas flow, it was necessary to install the lower end of the partition plate 4 to the lower end of the heat exchanger tube 3 installation position. Since the exhaust gas flows further below the lower end of the partition plate, a space is provided downward from the installation area of the heat transfer tube, and the bottom surface of the feed water preheating device 7 is below that. In this embodiment, the exhaust gas flow passes between the heat transfer tubes provided in the lower part and passes through the opening below the partition plate 4, so there is no need to provide an exhaust gas flow path below the heat transfer tube installation region. The bottom surface of the feed water preheating device 7 can be provided in the immediate vicinity of the heat transfer tube installation area. Therefore, the effect that the feed water preheating apparatus 7 can be reduced in size can also be acquired.

The exhaust gas flow channel cross-sectional area provided below the partition plate 4 is smaller than the exhaust gas flow channel cross-sectional area of the exhaust gas flow descending channel 10 and the exhaust gas provided below the partition plate in the conventional water supply preheating device. It should be larger than the flow path cross-sectional area. Also by this, when exhaust gas is flowed, the pressure loss in the exhaust gas flow turn part can be reduced. Moreover, since it is not necessary to provide an exhaust gas flow path below the heat transfer tube group, there is an effect that the volume of the feed water preheating device 7 can be reduced.

  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.

1 boiler
2 Exhaust gas passage
3 Heat transfer tubes
4 Partition plate 5 Heat absorption fin
6 Drain outlet
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 Guide plate

Claims (3)

A boiler that heats 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 to recover the heat of the exhaust gas and preheat boiler feed water A boiler having a feed water preheating device, and by installing a partition plate extending vertically in the feed water preheating device, the inside of the feed water preheating device is divided into an exhaust gas inlet side and an exhaust gas outlet side, and the partition plate is The upper end side and the left and right ends are connected to the wall surface of the exhaust gas flow path of the feed water preheating device, and the lower end side is separated from the bottom surface of the feed water preheating device. After passing under the plate, it exits from the upper part of the feed water preheating device, and a large number of heat transfer tubes are installed in the exhaust gas flow down passage in the feed water preheating device, so that the boiler feed is generated by the heat of the exhaust gas. In the boiler having a water preheating devices so as to preheat a
The lower end of the partition plate is positioned at a height in the middle of the heat transfer tube group, and a guide plate protruding from the partition plate side toward the heat transfer tube side is installed on the exhaust gas flow down flow path side below the partition plate. Boiler with a feed water preheating device. In the boiler having the feed water preheating device according to claim 1, the exhaust gas flow space provided between the lower end of the heat transfer tube group and the bottom plate of the feed water preheating device is eliminated, and the exhaust gas flows laterally in the lower part of the heat transfer tube group. A boiler having a feed water preheating device characterized by the above. The boiler with the feed water preheating device according to claim 1 or 2, wherein the guide plate is provided with an inclination so that the tip side is lowered.

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