JP2023037664A - Latent heat recovery economizer - Google Patents

Abstract

To provide a latent heat recovery economizer that attains both high-efficiency latent heat recovery from combustion exhaust gas and waste heat recovery using the heat quantity of steam drain or the like to raise a supply water temperature, to enable high system efficiency.SOLUTION: In an economizer 20, a large number of heat transfer tubes 3 extending horizontally are provided in an exhaust gas passage through which combustion exhaust gas from a boiler 1 passes, a continuous water supply flow path is formed by connecting the heat transfer tubes 3, and supply water to the boiler 1 is preheated by heating the heat transfer tubes 3 with the combustion exhaust gas. The economizer 20 is divided into a latent heat recovery area (latent heat recovery unit) 23 and a sensible heat recovery area (sensible heat recovery unit) 24, the latent heat recovery area (latent heat recovery unit) 23 is supplied with low-temperature water, and the sensible heat recovery area (sensible heat recovery unit) 24 is supplied with high-temperature water.SELECTED DRAWING: Figure 2

Description

The present invention relates to an economizer that recovers heat from flue gas discharged from a boiler.

A typical boiler is provided with an economizer for the purpose of further recovering heat from the flue gas discharged from the boiler in order to improve efficiency.
In the economizer, when the temperature of the feed water is low, the water vapor contained in the combustion exhaust gas is drained, so the latent heat can be recovered.
On the other hand, waste heat recovery may be performed by utilizing the heat quantity of steam drain after the process is used to raise the temperature of the feed water. In that case, since the temperature of the feed water supplied to the economizer becomes high, there is a problem that the latent heat in the flue gas cannot be recovered. For example, when the feed water temperature becomes equal to or higher than the exhaust gas dew point temperature, the latent heat cannot be recovered in principle.

In addition, in Patent Document 1 below, as an economizer that increases the amount of heat absorption by absorbing latent heat to the maximum, fins are provided around the entire circumference of the heat transfer tubes in the sensible heat absorption part on the upstream side of the combustion exhaust gas flow of the heat transfer tube group. A heat transfer pipe for absorbing sensible heat is provided, and fins are provided only on the upper surface of the heat transfer pipe in the latent heat absorbing portion downstream of the combustion exhaust gas flow than the sensible heat absorbing portion, and fins are not provided on the lower surface for absorbing latent heat. A configuration in which heat transfer tubes are provided is disclosed.

JP-A-11-248105

As described above, when the temperature of the feed water supplied to the economizer becomes high, for example, when the temperature of the feed water exceeds the exhaust gas dew point temperature, there is a problem that the latent heat in the combustion exhaust gas cannot be recovered.

In the present invention, the economizer is divided into a latent heat recovery section and a sensible heat recovery section, and the water supply to the economizer is divided into low-temperature water supply and high-temperature water supply, so that highly efficient latent heat recovery from combustion exhaust gas and steam drain, etc. It is an object of the present invention to provide a latent heat recovery economizer capable of achieving high system efficiency while simultaneously recovering waste heat by utilizing the heat of the heat to raise the temperature of feed water.

In the latent heat recovery economizer of the present invention, a large number of heat transfer tubes extending in the horizontal direction are provided in an exhaust gas passage through which flue gas from a boiler passes. In an economizer that preheats feed water to a boiler by heating heat transfer tubes, the economizer is divided into a latent heat recovery section (latent heat recovery area) on the exhaust gas outlet side and a sensible heat recovery section (sensible heat recovery area) on the exhaust gas inlet side, Low-temperature water supply is supplied to the latent heat recovery part, and high-temperature water supply is supplied to the sensible heat recovery part.

In addition, the latent heat recovery economizer of the present invention is provided with a large number of heat transfer tubes extending in the horizontal direction in the exhaust gas passage through which the flue gas from the boiler passes, and an inlet header and an intermediate header provided as a feed water inlet connection and a feed water outlet connection. The outlet headers provided are sequentially connected by the heat transfer tubes, the heat transfer tubes are connected to form a continuous water supply flow path, and the heat transfer tubes are heated by the combustion exhaust gas to preheat the water supply to the boiler. The economizer is divided into a latent heat recovery section on the exhaust gas outlet side and a sensible heat recovery section on the exhaust gas inlet side, the latent heat recovery section is provided with the inlet header, the sensible heat recovery section is provided with the intermediate header, and the inlet header is provided. low-temperature feed water is supplied to the intermediate header, and high-temperature feed water is supplied to the intermediate header.

Further, in the latent heat recovery economizer of the present invention, a large number of heat transfer tubes extending in the horizontal direction are provided in the exhaust gas passage through which the combustion exhaust gas from the boiler passes, and an inlet header provided as a feed water inlet connection and a feed water outlet connection are provided. In an economizer in which the outlet headers are connected in order by the heat transfer tubes, the heat transfer tubes are connected to form a continuous water supply flow path, and the heat transfer tubes are heated by the flue gas to preheat the water supply to the boiler, wherein the economizer comprises: is divided into a latent heat recovery economizer on the exhaust gas outlet side and a sensible heat recovery economizer on the exhaust gas inlet side. A recovery outlet header is provided, low temperature water is supplied to the latent heat recovery inlet header, and high temperature water is supplied to the sensible heat recovery inlet header.

In the present invention, a part of the hot water after heat exchange at the outlet of the economizer may not be supplied to the boiler, but may be supplied to a process using high temperature water.

In the present invention, for example, the "low temperature" of the low-temperature water supply can include the case where the temperature of the water supply is lower than the combustion exhaust gas dew point temperature. Further, the "high temperature" of the high-temperature water supply can include the case where the water supply temperature is equal to or higher than the combustion exhaust gas dew point temperature.

The latent heat recovery economizer of the present invention supplies low-temperature feed water to the latent heat recovery unit and high-temperature feed water to the sensible heat recovery unit. It is possible to achieve both exhaust heat recovery and high system efficiency.

If part of the high-temperature feedwater after heat exchange at the economizer outlet is not supplied to the boiler but is supplied to a process that uses high-temperature water, the low-temperature feedwater amount can be increased, increasing the amount of latent heat recovered from the flue gas. can be made

FIG. 1 is an explanatory diagram showing an example of the configuration of the latent heat recovery economizer of the present invention. FIG. 2 is an explanatory diagram showing an example of the schematic configuration of the latent heat recovery economizer of the present invention. FIG. 3 is an explanatory diagram showing another example of the schematic configuration of the latent heat recovery economizer of the present invention. FIG. 4 is an explanatory diagram showing still another example of the schematic configuration of the latent heat recovery economizer of the present invention.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments and can be modified as appropriate.

1 and 2 show a first embodiment of the invention.
As shown in FIG. 1, the economizer 20 has a large number of heat transfer tubes 3 extending horizontally in an exhaust gas passage 2 through which combustion exhaust gas from the boiler 1 passes, and an inlet header 17 and an intermediate header 18 provided as feed water inlet connections. In addition, outlet headers 19 provided as water supply outlet connections are connected in order by the heat transfer tubes 3, and by connecting the heat transfer tubes 3, a continuous water supply flow path is formed, and the heat transfer tubes 3 are heated by the combustion exhaust gas. This preheats the feed water to the boiler 1 . 7 is a boiler body, 8 is a steam separator, 9 is a safety valve, 10 is a main steam stop valve, 11 is a water column pipe, 12 is a low temperature feed water pump, 13 is a feed water check valve, 14 is a feed water stop valve, and 15 is an economizer. A bypass valve, 16, is the hot feedwater pump. Although not shown, the high-temperature water supply pipe is also provided with a water supply check valve and a water supply stop valve.

The economizer 20 is divided into a latent heat recovery area (latent heat recovery section) on the exhaust gas outlet side and a sensible heat recovery area (sensible heat recovery section) on the exhaust gas inlet side. An intermediate header 18 is provided in the region, the inlet header 17 being supplied with cold feed water and the intermediate header 18 being supplied with hot feed water.

A more detailed description will be given based on FIG.
The economizer 20 is provided with the inlet header 17 and the intermediate header 18, as described above, as feedwater inlet connections. The inlet header 17 is supplied with low-temperature water from a low-temperature water supply tank 21 by a low-temperature water supply pump 12 , and the intermediate header 18 is supplied with high-temperature water from a high-temperature water supply tank 22 by a high-temperature water supply pump 16 . In addition, in the high-temperature water supply tank 22, some heat recovery is performed to raise the temperature of the water supply.

In a latent heat recovery area (latent heat recovery section) 23 between the inlet header 17 and the intermediate header 18, latent heat is recovered from the flue gas. In a sensible heat recovery area (sensible heat recovery section) 24 between the intermediate header 18 and the outlet header 19, sensible heat is recovered from the flue gas.
The water supply to the boiler 1 is controlled such that the total amount of high-temperature water supply and low-temperature water supply is equal to the amount of evaporation of the boiler. Although not shown in FIG. 2, the inlet header 17, the intermediate header 18, and the outlet header 19 are connected in order by heat transfer tubes (see FIG. 1). Moreover, each temperature shown in FIG. 2 is an example, and is not limited to these.

FIG. 3 shows a second embodiment of the invention. In the first embodiment shown in FIG. 2, an integrated economizer is used, but as in the second embodiment shown in FIG. 3, separate economizers may be used for the latent heat recovery section and the sensible heat recovery section. Moreover, the second embodiment shown in FIG. 3 shows an example of an embodiment at the time of high-pressure drain recovery.

A detailed description will be given with reference to FIG.
A latent heat recovery economizer 30 on the exhaust gas outlet side is provided with a latent heat recovery inlet header 31 and a latent heat recovery outlet header 32 . A sensible heat recovery inlet header 34 and a sensible heat recovery outlet header 35 are provided in the sensible heat recovery economizer 33 on the exhaust gas inlet side. The latent heat recovery inlet header 31 is supplied with low-temperature water from a water supply tank 36 by a low-temperature water supply pump 12 , and the sensible heat recovery inlet header 34 is supplied with high-temperature water from a steam drain recovery tank 37 by a high-temperature water supply pump 16 . In the steam drain recovery tank 37, some heat recovery is performed to raise the temperature of the feed water.

The latent heat recovery economizer 30 between the latent heat recovery inlet header 31 and the latent heat recovery outlet header 32 recovers latent heat from the flue gas. The sensible heat recovery economizer 33 between the sensible heat recovery inlet header 34 and the sensible heat recovery outlet header 35 recovers sensible heat from the flue gas.
Note that each temperature shown in FIG. 3 is an example, and is not limited to these.
Other configurations and actions are the same as those of the first embodiment.

FIG. 4 shows a third embodiment of the invention. In the third embodiment shown in FIG. 4, in order to increase the amount of latent heat recovered from the flue gas, part of the high-temperature feedwater after heat exchange at the economizer outlet is not supplied to the boiler for the purpose of increasing the amount of low-temperature feedwater. It also feeds processes that use hot water. Moreover, the third embodiment shown in FIG. 4 shows another example of the embodiment at the time of high-pressure drain recovery.

A detailed description will be given with reference to FIG.
The economizer 20 is provided with the inlet header 17 and the intermediate header 18, as described above, as feedwater inlet connections. Low-temperature water is supplied to the inlet header 17 by the low-temperature water supply pump 12 from the water supply tank 36 , and high-temperature water is supplied to the intermediate header 18 by the high-temperature water supply pump 16 from the steam drain recovery tank 37 . In the steam drain recovery tank 37, some heat recovery is performed to raise the temperature of the feed water.

In a latent heat recovery area (latent heat recovery section) 23 between the inlet header 17 and the intermediate header 18, latent heat is recovered from the flue gas. In a sensible heat recovery area (sensible heat recovery section) 24 between the intermediate header 18 and the outlet header 19, sensible heat is recovered from the flue gas.
In order to increase the amount of latent heat recovered from flue gas, part of the hot water after heat exchange at the economizer outlet is not supplied to the boiler, but is supplied to processes that use high-temperature water for the purpose of increasing the amount of low-temperature water. . That is, a portion of the post-heat exchange hot feedwater from outlet header 19 is supplied to hot water utilization process 38 (eg, district heating). 40 is a relief valve.
Note that each temperature shown in FIG. 4 is an example, and is not limited to these.
Other configurations and actions are the same as those of the first and second embodiments.

As described above, in the present invention, the economizer is divided into a latent heat recovery section (latent heat recovery region or latent heat recovery economizer) and a sensible heat recovery section (sensible heat recovery region or sensible heat recovery economizer), and water supply to the economizer is By separately supplying low-temperature water supply and high-temperature water supply, it is possible to realize high system efficiency by achieving both high-efficiency latent heat recovery from combustion exhaust gas and waste heat recovery using the heat of steam drain to raise the water supply temperature. can.

1 boiler 2 flue gas passage 3 heat transfer tube 7 boiler main body 8 steam separator 9 safety valve 10 main steam stop valve 11 water column pipe 12 low temperature feed water pump 13 feed water check valve 14 feed water stop valve 15 economizer bypass valve 16 high temperature feed water pump 17 inlet header 18 intermediate header 19 outlet header 20 economizer 21 low temperature feed water tank 22 high temperature feed water tank 23 latent heat recovery area (latent heat recovery section)
24 sensible heat recovery area (sensible heat recovery part)
30 latent heat recovery economizer 31 latent heat recovery inlet header 32 latent heat recovery outlet header 33 sensible heat recovery economizer 34 sensible heat recovery inlet header 35 sensible heat recovery outlet header 36 feed water tank 37 steam drain recovery tank 38 hot water utilization process 40 relief valve

Claims (4)

A large number of heat transfer tubes extending horizontally are provided in an exhaust gas passage through which flue gas from the boiler passes, and the heat transfer tubes are connected to form a continuous water supply flow path. In the economizer that preheats the feed water, the economizer is divided into a latent heat recovery section on the exhaust gas outlet side and a sensible heat recovery section on the exhaust gas inlet side, low temperature water supply is supplied to the latent heat recovery section, and high temperature water supply is supplied to the sensible heat recovery section. A latent heat recovery economizer characterized by: A large number of heat transfer tubes extending in the horizontal direction are provided in an exhaust gas passage through which combustion exhaust gas from the boiler passes, and an inlet header and an intermediate header provided as a feed water inlet connection and an outlet header provided as a feed water outlet connection are arranged in order with the heat transfer tubes. The heat transfer tubes are connected to form a continuous water supply flow path, and the heat transfer tubes are heated by the flue gas to preheat the water supply to the boiler. The latent heat recovery part is divided into a latent heat recovery part and a sensible heat recovery part on the exhaust gas inlet side, the inlet header is provided in the latent heat recovery part, the intermediate header is provided in the sensible heat recovery part, low-temperature water is supplied to the inlet header, and the intermediate A latent heat recovery economizer characterized in that high-temperature feed water is supplied to a header. A large number of heat transfer tubes extending in the horizontal direction are provided in an exhaust gas passage through which combustion exhaust gas from the boiler passes, and an inlet header provided as a feed water inlet connection and an outlet header provided as a feed water outlet connection are connected in order by the heat transfer tubes. , in the economizer that forms a continuous water supply flow path by connecting the heat transfer tubes and preheats the water supply to the boiler by heating the heat transfer tubes with the combustion exhaust gas, the economizer is a latent heat recovery economizer on the exhaust gas outlet side and the exhaust gas. The sensible heat recovery economizer on the inlet side is divided, the latent heat recovery economizer is provided with a latent heat recovery inlet header and a latent heat recovery outlet header, the sensible heat recovery economizer is provided with a sensible heat recovery inlet header and a sensible heat recovery outlet header, and the latent heat recovery inlet A latent heat recovery economizer, wherein low temperature water is supplied to a header and high temperature water is supplied to the sensible heat recovery inlet header. 4. A latent heat recovery economizer according to claim 1, 2 or 3, wherein a part of the high temperature feed water after heat exchange at the economizer outlet is not supplied to the boiler but is supplied to a process using high temperature water.

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