JP2024054593A - Water recovery system, water recovery system operation method, and gas turbine cogeneration system modification method - Google Patents

Abstract

[Problem] To provide a water recovery system, an operating method for a water recovery system, and a method for modifying a gas turbine cogeneration system that can more reliably suppress the generation of white smoke from exhaust gas discharged into the outside air. [Solution] A water recovery system for recovering moisture from exhaust gas discharged from a boiler includes an exhaust gas reheater for heating the exhaust gas flowing through a water recovery outlet exhaust line using recovered water extracted from a water recovery device or a recovered water discharge line as a heat source, an exhaust gas extraction line for guiding exhaust gas extracted from an exhaust gas supply line, which is a supply line for exhaust gas from the boiler to the water recovery device, to the water recovery outlet exhaust line, and an exhaust gas extraction damper provided in the exhaust gas extraction line. [Selected Figure] Figure 2

Description

This disclosure relates to a water recovery system, a method for operating a water recovery system, and a method for modifying a gas turbine cogeneration system.

Conventionally, water recovery systems for recovering moisture from exhaust gas discharged from a boiler are known. For example, the water recovery system disclosed in Patent Document 1 includes a water recovery device that recovers moisture contained in exhaust gas discharged from a gas turbine system, and an exhaust gas reheater for heating the exhaust gas discharged from the water recovery device. The exhaust gas reheater heats the exhaust gas using recovered water discharged from the water recovery device after heat exchange with the exhaust gas as a heat source. Heating by the exhaust gas reheater is expected to prevent white smoke from being generated from the exhaust gas released into the outside air.

JP 2016-217308 A

However, because there is an upper limit to the temperature of the recovered water discharged from the water recovery device after heat exchange, there is a limit to the amount of heating of the exhaust gas by the exhaust gas reheater. Therefore, when at least one of the following conditions is satisfied: the temperature of the outside air is low, or the humidity of the outside air is high, the exhaust gas reheater cannot heat the exhaust gas sufficiently, and white smoke may be generated from the exhaust gas released into the outside air.

The objective of this disclosure is to provide a water recovery system, an operating method for a water recovery system, and a method for modifying a gas turbine cogeneration system that can more reliably suppress the generation of white smoke from exhaust gas released into the outside air.

A water recovery system according to at least one embodiment of the present disclosure includes:
A water recovery system for recovering moisture from exhaust gas discharged from a boiler, comprising:
a water recovery device for recovering the moisture in the exhaust gas as recovered water by bringing the exhaust gas into gas-liquid contact with refrigerant water;
a recovered water cooling device for cooling the recovered water discharged from the water recovery device;
a recovered water discharge line for guiding the recovered water discharged from the water recovery device to the recovered water cooling device;
a recovered water supply line for guiding the recovered water cooled by the recovered water cooling device to the water recovery device as the refrigerant water;
a water recovery outlet exhaust line for discharging the exhaust gas discharged from the water recovery device to the outside air;
an exhaust gas reheater for heating the exhaust gas flowing through the water recovery outlet exhaust line by using the recovered water extracted from the water recovery device or the recovered water discharge line as a heat source;
an exhaust gas extraction line for guiding the exhaust gas extracted from an exhaust gas supply line, which is a supply line of the exhaust gas from the boiler to the water recovery device, to the water recovery outlet exhaust line;
an exhaust gas extraction damper provided in the exhaust gas extraction line;
Equipped with.

A method of operating a water recovery system according to at least one embodiment of the present disclosure includes:
A method for operating a water recovery system for recovering moisture from exhaust gas discharged from a boiler, comprising the steps of:
The water recovery system comprises:
a water recovery device for recovering the moisture in the exhaust gas as recovered water by bringing the exhaust gas into gas-liquid contact with refrigerant water;
a recovered water cooling device for cooling the recovered water discharged from the water recovery device;
a recovered water discharge line for guiding the recovered water discharged from the water recovery device to the recovered water cooling device;
a recovered water supply line for guiding the recovered water cooled by the recovered water cooling device to the water recovery device as the refrigerant water;
a water recovery outlet exhaust line for discharging the exhaust gas discharged from the water recovery device to the outside air;
an exhaust gas reheater for heating the exhaust gas flowing through the water recovery outlet exhaust line by using the recovered water extracted from the water recovery device or the recovered water discharge line as a heat source;
an exhaust gas extraction line for guiding the exhaust gas extracted from an exhaust gas supply line, which is a supply line of the exhaust gas from the boiler to the water recovery device, to the water recovery outlet exhaust line;
an exhaust gas extraction damper provided in the exhaust gas extraction line;
a branched recovered water supply line for supplying the recovered water extracted from the recovered water discharge line to the exhaust gas reheater;
a branched recovered water flow rate control valve provided in the branched recovered water supply line;
a branched recovered water return line for guiding the recovered water discharged from the exhaust gas reheater to the water recovery device;
An outside air temperature and humidity acquisition unit for measuring the outside air temperature and humidity;
a water recovery outlet exhaust gas temperature sensor for measuring the temperature of the exhaust gas at the outlet of the water recovery device;
an exhaust gas discharge temperature sensor for measuring an exhaust gas discharge temperature, which is the temperature of the exhaust gas discharged to the outside air from the water recovery outlet exhaust line;
Including,
The method for operating the water recovery system includes:
The method further includes an exhaust gas discharge temperature control step for controlling the exhaust gas extraction damper and the branched recovered water flow rate control valve based on the results obtained by the outside air temperature and humidity obtaining unit and the measurement results of the water recovery outlet exhaust gas temperature sensor and the exhaust gas discharge temperature sensor so that the temperature deviation between the exhaust gas discharge temperature and the outside air temperature is equal to or greater than a specified value according to the humidity of the outside air.

A method for retrofitting a gas turbine cogeneration system according to at least one embodiment of the present disclosure includes:
A method for retrofitting a gas turbine cogeneration system, comprising the steps of:
The gas turbine cogeneration system includes:
A gas turbine;
a generator configured to generate electricity by being driven by the gas turbine;
a heat recovery boiler for generating steam from boiler feed water by utilizing heat recovered from exhaust gas discharged from the gas turbine;
a water recovery device for recovering moisture as recovered water from the exhaust gas discharged from the heat recovery boiler;
a water recovery outlet exhaust line for discharging the exhaust gas discharged from the water recovery device to the outside air;
an exhaust gas supply line which is a supply line of the exhaust gas from the exhaust heat recovery boiler to the water recovery device;
a connecting exhaust line connected to the exhaust gas supply line between the exhaust heat recovery boiler and the water recovery device, for discharging the exhaust gas to the outside air;
Equipped with
The method for retrofitting a gas turbine cogeneration system includes the steps of:
an exhaust gas extraction line installation step of connecting the connection exhaust line and the water recovery outlet exhaust line by an exhaust gas extraction line;
an exhaust gas extraction damper installation step of installing an exhaust gas extraction damper in the exhaust gas extraction line;
Equipped with.

The present disclosure provides a water recovery system that can more reliably prevent white smoke from being generated from exhaust gas discharged into the outside air, a method for operating a water recovery system, and a method for modifying a gas turbine cogeneration system.

1 is a schematic diagram illustrating a power plant according to an embodiment. FIG. 1 is a schematic diagram illustrating a water recovery system according to an embodiment. 1 is a graph conceptually illustrating a psychrometric chart according to one embodiment. FIG. 2 is a schematic diagram illustrating a configuration of a controller according to an embodiment. FIG. 2 is a schematic diagram illustrating a water recovery system when a first reheat is performed according to an embodiment. FIG. 2 is a schematic diagram illustrating a water recovery system when first and second reheating are performed according to one embodiment. 4 is a flowchart showing an exhaust gas discharge temperature control process according to an embodiment. 1 is a flowchart illustrating a method for retrofitting a power plant according to an embodiment. FIG. 1 is a schematic diagram illustrating a pre-retrofit power plant according to an embodiment. FIG. 1 is a schematic diagram illustrating a power plant undergoing retrofit according to an embodiment.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.
For example, expressions expressing relative or absolute configuration, such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial," not only express such a configuration strictly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained.
For example, expressions indicating that things are in an equal state, such as "identical,""equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained.
On the other hand, the expressions "comprise", "include", or "have" a certain element are not exclusive expressions excluding the presence of other elements.
In addition, the same components are denoted by the same reference numerals and the description thereof may be omitted.

1. Overview of power plant 100
FIG. 1 is a schematic diagram showing a power plant 100 according to an embodiment of the present disclosure. The power plant 100 as a gas turbine cogeneration system illustrated in the figure includes a compressor 1 for generating compressed air 7 from the atmosphere 6, a combustor 3 configured to mix the compressed air 7 with fuel, a gas turbine 2 for rotating using combustion gas 12 discharged from the combustor 3 as a driving source, a generator 5 connected to the gas turbine 2, and a heat recovery boiler 14. The generator 5 is configured to generate power by driving the gas turbine 2. The heat recovery boiler 14 is a boiler configured to generate steam from boiler feed water by utilizing heat recovered from moisture-containing exhaust gas 13 discharged from the gas turbine 2. The boiler feed water is water to be supplied to the heat recovery boiler 14.

Although not an essential component of the present disclosure, the power plant 100 further includes a desuperheater 22 for lowering the temperature of the steam discharged from the heat recovery steam generator 14. The desuperheater 22 is configured, for example, so that a portion of the boiler feed water supplied to the heat recovery steam generator 14 flows in as cold water (see arrow B), and the cold water is injected inside the desuperheater 22 to cool the steam. The cooled steam is guided to the head end of the combustor 3 and injected into the flame region using compressed air 7 as an oxidizer to suppress thermal NOx generated during fuel combustion in the combustor 3.

The combustor 3 according to one embodiment of the present disclosure can be selectively supplied with fuel gas or oil fuel. As a specific example, the power plant 100 includes a fuel gas supply line 151 and an oil supply line 152. The fuel gas supply line 151 supplies the combustor 3 with fuel gas generated by a liquefied fuel vaporization system 50 for vaporizing the liquefied fuel gas. The liquefied fuel gas is, for example, liquefied natural gas (LNG), but the present disclosure is not limited thereto. The liquefied fuel gas may be liquid ammonia or liquid hydrogen, etc. The oil supply line 152 supplies the oil fuel, which may be, for example, heavy oil or kerosene, from the supply source 8 to the combustor 3. In addition, the fuel gas supply line 151 and the oil supply line 152 are provided with fuel supply valves 151A and 152A, respectively. Fuel supply valves 151A and 152A are selectively controlled to open and close, so that either fuel gas or oil fuel is supplied to the combustor 3.

In the combustor 3, either fuel gas or oil fuel is mixed with the compressed air 7, and combustion occurs. The above-mentioned steam is injected into the flame caused by the combustion. The exhaust gas 13 from the gas turbine 2 contains atmospheric moisture, moisture produced by combustion, and moisture from injected steam. The moisture contained in the exhaust gas 13 discharged from the heat recovery steam generator 14 is recovered by a water recovery system 40, which will be described later. The exhaust gas 13 from which moisture has been recovered by the water recovery system 40 is discharged outside the system (arrow A). Details of the exhaust line of the exhaust gas 13 indicated by arrow A will be described later.

The power plant 100 of this example includes a make-up water line 15, a make-up water tank 17 that stores the make-up water supplied from the make-up water line 15 as boiler feed water, a feed water line 19 connected to the make-up water tank 17 and the heat recovery boiler 14, and a feed water pump 18 provided on the feed water line 19. When the feed water pump 18 is driven, the boiler feed water stored in the make-up water tank 17 flows through the feed water line 19 and is supplied to the heat recovery boiler 14. It is preferable that the temperature of the boiler feed water supplied to the heat recovery boiler 14 is high. This is because the amount of heat required by the heat recovery boiler 14 to generate steam is reduced, improving the efficiency of the power plant 100.

The power plant 100 includes an exhaust gas supply line 57, which is a supply line for exhaust gas 13 from the heat recovery boiler 14 to the water recovery system 40 (more specifically, from the heat recovery boiler 14 to the water recovery device 33 described later), a connection exhaust line 29 connected to the exhaust gas supply line 57 between the heat recovery boiler 14 and the water recovery system 40, and a connection exhaust damper 31 provided on the connection exhaust line 29. In this example, an exhaust gas supply damper 36 is provided on the exhaust gas supply line 57, and the connection exhaust line 29 is connected to the exhaust gas supply line 57 between the exhaust gas supply damper 36 and the heat recovery boiler 14. When the exhaust gas supply damper 36 is closed and the connection exhaust damper 31 is opened, the connection exhaust line 29 can guide all the exhaust gas 13 flowing through the exhaust gas supply line 57 to the exhaust tower 30. The exhaust tower 30 releases the exhaust gas 13 to the outside.

For example, if oil fuel such as heavy oil is supplied to the combustor 3 and the amount of impurities such as sulfur contained in the exhaust gas 13 exceeds the allowable value, it is not preferable to supply the exhaust gas 13 to the water recovery system 40. In such a case, the exhaust gas supply damper 36 is closed and the connection exhaust damper 31 is opened, and the exhaust gas 13 is led to the exhaust tower 30. On the other hand, if the amount of impurities contained in the exhaust gas 13 is equal to or less than the allowable value, the connection exhaust damper 31 is closed and the exhaust gas supply damper 36 is opened. As a result, at least a portion of the exhaust gas 13 discharged from the exhaust heat recovery boiler 14 is supplied to the water recovery system 40 via the exhaust gas supply line 57.

Note that the power plant 100 according to the above embodiment is a gas turbine power plant equipped with a gas turbine 2, but the present disclosure is not limited thereto. For example, the power plant 100 according to another embodiment may be a steam power plant equipped with a steam turbine.

2. Overview of the Water Recovery System 40
2 is a schematic diagram showing a water recovery system 40 according to an embodiment of the present disclosure. The water recovery system 40 is generally as follows.

The water recovery device 33, which is a component of the water recovery system 40, is configured to recover moisture in the exhaust gas 13 as recovered water by bringing the exhaust gas 13 and the refrigerant water into gas-liquid contact. As a more detailed example, the water recovery device 33 includes a heat exchange vessel 130 into which the exhaust gas 13 and the refrigerant water flow, a sprinkler device 34 for sprinkling the refrigerant water inside the heat exchange vessel 130, and a filler 35 located below the sprinkler device 34 inside the heat exchange vessel 130. The exhaust gas 13 flowing through the exhaust gas supply line 57 flows into the heat exchange vessel 130. The refrigerant water sprinkled by the sprinkler device 34 adheres to the filler 35 and exchanges heat with the exhaust gas 13 flowing into the heat exchange vessel 130. This causes the moisture in the exhaust gas 13 to condense. The recovered water, which contains the condensed moisture and the refrigerant water that has completed the heat exchange, falls and is stored in a water tank 136 that constitutes the lower part of the heat exchange vessel 130.

The water recovery system 40 further includes a recovered water cooling device 110 for cooling the recovered water discharged from the water tank 136 of the water recovery device 33, a recovered water discharge line 39 for guiding the recovered water discharged from the water tank 136 of the water recovery device 33 to the recovered water cooling device 110, and a recovered water supply line 42 for guiding the cooled recovered water discharged from the recovered water cooling device 110 to the heat exchange vessel 130 of the water recovery device 33 as refrigerant water. The recovered water supply line 42 and the recovered water discharge line 39 function as a recovered water circulation line for circulating the recovered water between the water recovery device 33 and the recovered water cooling device 110. For convenience of explanation, the recovered water flowing from the recovered water supply line 42 to the inlet of the water recovery device 33 (the inlet of the heat exchange vessel 130) is referred to as refrigerant water below.

The recovered water cooling device 110 of this example is configured to cool the recovered water with cooling water, which may be, for example, seawater. A cooling water supply pump 52 including an inverter is provided in a cooling water supply line 41 for supplying cooling water to the recovered water cooling device 110. The rotation speed of the cooling water supply pump 52 is controlled by a controller 90, which is a component of the water recovery system 40.

In this example, a recovered water pump 38 including an inverter (not shown) is provided in the recovered water discharge line 39, and the rotation speed of the recovered water pump 38 is controlled by the controller 90. This controls the circulation flow rate of the recovered water in the recovered water circulation line. In this example, the circulation flow rate of the recovered water is controlled by controlling the rotation speed of the recovered water pump 38 so that the temperature of the exhaust gas 13 discharged from the water recovery device 33 becomes a specified temperature. Also, in this example, the temperature of the recovered water at the outlet of the recovered water cooling device 110 is controlled so that the temperature of the exhaust gas 13 becomes a specified temperature. Controlling the temperature of the recovered water at the outlet of the recovered water cooling device 110 includes controlling the rotation speed of the cooling water supply pump 52.

Although not an essential component of the present disclosure, the water recovery system 40 illustrated in FIG. 2 further includes a water supply line 4 for guiding the recovered water to the make-up water tank 17, and the water supply line 4 includes a high-temperature water supply line 44 and a low-temperature water supply line 47. The high-temperature water supply line 44 is connected to the recovered water discharge line 39 and is configured to guide the recovered water taken out from the recovered water discharge line 39 to the make-up water tank 17. The recovered water taken out from the recovered water discharge line 39 has a relatively high temperature because it contains heat recovered from the exhaust gas 13 (in this example, the temperature of the recovered water flowing through the recovered water discharge line 39 is about 60 to 70°C). The low-temperature water supply line 47 is connected to the recovered water supply line 42 and is configured to guide the recovered water taken out from the recovered water supply line 42 to the make-up water tank 17. The recovered water taken out of the recovered water supply line 42 has a relatively low temperature because it has been subjected to a cooling process by the recovered water cooling device 110 (in this example, the temperature of the recovered water flowing through the recovered water supply line 42 is about 30 to 40°C).

The low-temperature feed water line 47 is provided with a water treatment device 46, which is a component of the water recovery system 40. The water treatment device 46 is configured to treat the recovered water flowing through the low-temperature feed water line 47 to remove impurities such as sulfur. The impurities are generated during combustion in the combustor 3 (see FIG. 1) and may be mixed into the exhaust gas 13. At least a portion of these impurities dissolve in the recovered water due to heat exchange between the exhaust gas 13 and the refrigerant water in the water recovery device 33. The water treatment device 46 removes impurities contained in the recovered water, thereby suppressing the inclusion of impurities in the boiler feed water stored in the make-up water tank 17. In general, the lower the temperature of the water to be treated, the better the impurity removal processing capacity of the water treatment device 46. If the temperature of the recovered water is high, the ion exchange resin 146 constituting the water treatment device 46 may be damaged, and there is a risk of the impurity removal processing capacity decreasing.

The high-temperature feedwater line 44 is provided with a high-temperature feedwater valve 48, and the low-temperature feedwater line 47 is provided with a low-temperature feedwater valve 45. For example, when fuel gas is supplied from the liquefied fuel vaporization system 50 to the combustor 3, the amount of impurities contained in the exhaust gas 13 is equal to or less than a specified amount (the specified amount is lower than the above-mentioned allowable value). In this case, the high-temperature feedwater valve 48 is opened and the low-temperature feedwater valve 45 is closed. This allows high-temperature recovered water that does not require impurity removal treatment to flow into the make-up water tank 17 via the high-temperature feedwater line 44. The temperature of the boiler feedwater supplied from the make-up water tank 17 to the exhaust heat recovery boiler 14 can be increased, improving the efficiency of the power plant 100.

On the other hand, when oil fuel such as kerosene is supplied to the combustor 3, the amount of impurities contained in the exhaust gas 13 exceeds the specified amount. In this case, the high-temperature feed water valve 48 is closed and the low-temperature feed water valve 45 is opened. As a result, the low-temperature recovered water that requires impurity removal processing flows into the make-up water tank 17 via the water treatment device 46 provided in the low-temperature feed water line 47. This prevents impurities from adhering to the equipment that constitutes the power plant 100, such as the make-up water line 15 and the heat recovery boiler 14, and suppresses deterioration of the power plant 100. In this way, in the water recovery system 40 of this example, it is possible to switch the supply line of the recovered water sent to the make-up water tank 17 depending on the type of fuel supplied to the combustor 3.

The controller 90 is configured by a computer and includes a processor, a memory, and an external communication interface. The processor may be a CPU, a GPU, an MPU, a DSP, or a combination of these. The processor according to other embodiments may be realized by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to store various data temporarily or non-temporarily, and may be realized by at least one of a RAM, a ROM, or a flash memory, for example. The processor executes various control processes according to the instructions of a program loaded into the memory. The controller 90 may also be a DCS panel that constitutes one of multiple control panels that constitute the power plant 100.

3. Overview of the reheating system for the exhaust gas 13 discharged from the water recovery device 33
In the present disclosure, the flue gas 13 cooled by heat exchange with the refrigerant water in the water recovery device 33 is reheated after being discharged from the water recovery device 33. The outline of the reheating system for the flue gas 13 is as follows.

As illustrated in FIG. 2, the water recovery system 40 includes a water recovery outlet exhaust line 59 for discharging the exhaust gas 13 discharged from the heat exchanger 130 of the water recovery device 33 to the outside air, and an exhaust gas reheater 51 for heating the exhaust gas 13 flowing through the water recovery outlet exhaust line 59. The heat source of the exhaust gas reheater 51 is recovered water extracted from the water tank 136 or the recovered water discharge line 39 (the water extraction system will be described later). The extracted recovered water exchanges heat with the lower temperature exhaust gas 13, thereby heating the exhaust gas 13.

The water recovery outlet exhaust line 59 includes an upstream water recovery exhaust line 59A connected to the water recovery device 33 and the exhaust gas reheater 51, and a downstream water recovery exhaust line 59B connected to the exhaust gas reheater 51 and the exhaust tower 32. The upstream water recovery exhaust line 59A is configured to guide the exhaust gas 13 from the water recovery device 33 to the exhaust gas reheater 51, and the downstream water recovery exhaust line 59B is configured to guide the exhaust gas 13 from the exhaust gas reheater 51 to the exhaust tower 32. The exhaust tower 32 in the example of FIG. 2 is separate from the exhaust tower 30, but the exhaust tower 32 in other examples may be a single unit formed integrally with the exhaust tower 30.

The water recovery system 40 includes an exhaust gas extraction line 55. The exhaust gas extraction line 55 is configured to guide the exhaust gas 13 extracted from the exhaust gas supply line 57 to the water recovery outlet exhaust line 59. The exhaust gas extraction line 55 illustrated in the figure is connected to the connection exhaust line 29 upstream of the connection exhaust damper 31, and is connected to the downstream water recovery exhaust line 59B of the water recovery outlet exhaust line 59. The exhaust gas extraction line 55 is also provided with an exhaust gas extraction damper 56. When the connection exhaust damper 31 is closed and the exhaust gas extraction damper 56 is opened, the exhaust gas 13 extracted from the exhaust gas supply line 57 flows into the downstream water recovery exhaust line 59B via the connection exhaust line 29 and the exhaust gas extraction line 55 in this order. The exhaust gas 13 extracted from the exhaust gas supply line 57 does not flow into the water recovery device 33, so the temperature of the exhaust gas 13 is relatively high.

According to the above configuration, when the exhaust gas extraction damper 56 is opened, the relatively high-temperature exhaust gas 13 extracted from the exhaust gas supply line 57 is guided to the water recovery outlet exhaust line 59 and mixed with the exhaust gas 13 discharged from the water recovery device 33. This heats the exhaust gas 13 discharged from the water recovery device 33. The exhaust gas 13 discharged from the water recovery device 33 is heated not only by the exhaust gas reheater 51 but also by mixing with the exhaust gas 13 flowing through the exhaust gas extraction line 55, so that the temperature of the exhaust gas 13 discharged to the outside air can be made sufficiently higher than the dew point temperature of water in the outside air. This realizes a water recovery system 40 that can more reliably suppress the generation of white smoke from the exhaust gas 13 discharged to the outside air.

In other embodiments of the present disclosure, the exhaust gas extraction line 55 may be connected to the upstream water recovery exhaust line 59A instead of the downstream water recovery exhaust line 59B when certain conditions are met, such as a low exhaust gas temperature or a low exhaust gas flow rate. In this case, the exhaust gas 13 discharged from the water recovery device 33 mixes with the exhaust gas 13 flowing through the exhaust gas extraction line 55 and then flows into the exhaust gas reheater 51. The exhaust gas extraction line 55 may also be directly connected to the exhaust gas supply line 57 without passing through the connecting exhaust line 29. In any embodiment, for the reasons already described, a water recovery system 40 is realized that can more reliably suppress the generation of white smoke from the exhaust gas 13 released into the outside air.

<4. Recovery water extraction system for exhaust gas reheater 51>
The water recovery system 40 illustrated in FIG. 2 includes a branched recovered water supply line 54 connected to the recovered water discharge line 39 and the exhaust gas reheater 51, and a branched recovered water return line 37 connected to the exhaust gas reheater 51 and the water tank 136. In the example illustrated in the figure, the branched recovered water supply line 54 is connected to the recovered water discharge line 39 between the recovered water pump 38 and the recovered water cooling device 110. In addition, the branched recovered water supply line 54 is provided with a branched recovered water flow rate adjustment valve 53 controlled by a controller 90. The flow rate of the recovered water supplied to the exhaust gas reheater 51 is controlled through the opening control of the branched recovered water flow rate adjustment valve 53 by the controller 90. In other words, the controller 90 can control the amount of heat exchange between the exhaust gas 13 and the recovered water in the exhaust gas reheater 51. Note that the branched recovered water supply line 54 according to another example may be connected to the recovered water discharge line 39 between the recovered water pump 38 and the water recovery device 33, or may be connected to the water tank 136 of the water recovery device 33. Even in this case, it is possible to supply recovered water to the exhaust gas reheater 51 , but a pump for sending the recovered water to the exhaust gas reheater 51 is required in addition to the recovered water pump 38 .
The branched recovered water return line 37 in this example is configured to guide the recovered water that has been discharged from the exhaust gas reheater 51 and has completed heat exchange to the water tank 136. Note that the branched recovered water return line 37 in other examples may be configured to guide the recovered water that has completed heat exchange to the recovered water discharge line 39.

As described above, the upstream end (inlet) of the branched recovered water supply line 54 may be connected to the water tank 136 of the water recovery device 33 or to the recovered water discharge line 39. In the example of FIG. 2, a configuration is adopted in which the upstream end of the branched recovered water supply line 54 is connected to the recovered water discharge line 39 between the recovered water pump 38 and the recovered water cooling device 110. With this configuration, the recovered water extracted from the recovered water discharge line 39 by driving the recovered water pump 38 can flow through the branched recovered water supply line 54. Since a dedicated pump for supplying recovered water to the exhaust gas reheater 51 is not required, the configuration of the water recovery system 40 can be simplified.

As described above, the downstream end (outlet) of the branched recovered water return line 37 may be connected to the recovered water discharge line 39 or to the water tank 136. In other words, the branched recovered water return line 37 may be configured to guide the recovered water discharged from the exhaust gas reheater 51 to the recovered water discharge line 39 or to the water tank 136. In the example of FIG. 2, the branched recovered water return line 37 is configured to guide the recovered water to the water tank 136. According to this configuration, since the branched recovered water return line 37 guides the recovered water to the water tank 136 of the water recovery device 33, even if the recovered water contains gas such as air, the water recovery device 33 can recover the gas. Therefore, it is possible to suppress the mixture of gas into the recovered water flowing through the recovered water discharge line 39, and to avoid a failure of the recovered water pump 38.

As described above, the exhaust gas extraction line 55 may be connected to either the upstream water recovery exhaust line 59A or the downstream water recovery exhaust line 59B. In the example of FIG. 2, a configuration is adopted in which the exhaust gas extraction line 55 is connected to the downstream water recovery exhaust line 59B. According to this configuration, the exhaust gas 13 discharged from the water recovery device 33 is heated by the exhaust gas reheater 51 before being mixed with the exhaust gas 13 guided by the exhaust gas extraction line 55. The recovered water that serves as the heating source in the exhaust gas reheater 51 heats the exhaust gas 13 whose temperature is not yet sufficiently increased, so that the temperature of the recovered water flowing from the branched recovered water return line 37 into the water tank 136 is reduced. As a result, the temperature of the recovered water flowing from the recovered water discharge line 39 into the recovered water cooling device 110 is reduced, and the heat load of the recovered water cooling device 110 is reduced. Therefore, the power of the cooling system of the recovered water cooling device 110 (the power of the cooling water supply pump 52 in this example) can be reduced, and the water recovery system 40 can improve its operating efficiency.

5. Control of the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53
The water recovery system 40 according to one embodiment of the present disclosure includes an outside air temperature and humidity acquisition unit 81 for acquiring the outside air temperature and humidity, a water recovery outlet exhaust gas temperature sensor 82 for measuring the water recovery outlet exhaust gas temperature, which is the temperature of the exhaust gas 13 at the outlet 27 of the water recovery device 33, and an exhaust gas discharge temperature sensor 83 for measuring the exhaust gas discharge temperature, which is the temperature of the exhaust gas 13 discharged to the outside air from the downstream water recovery exhaust line 59B.

In this example, the outside air temperature and humidity acquisition unit 81 is a thermometer and hygrometer. The measurement results of the thermometer and hygrometer are output to the controller 90. In another example, the outside air temperature and humidity acquisition unit 81 may be a computer device configured to acquire weather data including temperature and humidity, for example, via the Internet. In this case, the temperature and humidity included in the weather data are also output to the controller 90. The water recovery outlet exhaust gas temperature sensor 82 is provided at the outlet 27 of the water recovery device 33. The exhaust gas discharge temperature sensor 83 is provided in the downstream water recovery exhaust line 59B. The exhaust gas discharge temperature sensor 83 illustrated in FIG. 2 is located between the location where the exhaust gas extraction line 55 and the downstream water recovery exhaust line 59B are connected and the exhaust tower 32. The measurement results of the water recovery outlet exhaust gas temperature sensor 82 and the exhaust gas discharge temperature sensor 83 are output to the controller 90.

The controller 90 is configured to control the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53 based on the results of the acquisition by the outside air temperature and humidity acquisition unit 81 and the results of the measurements by the water recovery outlet exhaust gas temperature sensor 82 and the exhaust gas discharge temperature sensor 83 so that the temperature deviation between the exhaust gas discharge temperature and the outside air temperature is equal to or greater than a specified value. The specified value is a value that changes depending on the outside air temperature and humidity. According to this control, the exhaust gas discharge temperature can be sufficiently increased by the control of the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53 by the controller 90, and the generation of white smoke from the exhaust gas 13 discharged into the outside air can be suppressed. The principle by which white smoke can be suppressed is described in detail below.

<6. Principle of suppressing generation of white smoke from exhaust gas 13>
FIG. 3 is a graph conceptually illustrating a psychrometric chart according to an embodiment of the present disclosure. The graph depicts a saturated water vapor line H of 100% relative humidity. The horizontal axis of the graph represents the temperature (dry bulb temperature) of the flue gas 13, and the vertical axis represents absolute humidity. Humid air is a concept that includes the flue gas 13, and points A, B1, B2, C0, C1, and C2 shown in the graph each represent the state of the flue gas 13 in the process of being discharged from the water recovery device 33 to the outside air, that is, the temperature and absolute humidity of the flue gas 13. More specifically, point A represents the temperature and absolute humidity of the flue gas 13 at the outlet 27 of the water recovery device 33. Points B1 and B2 represent the temperature and absolute humidity of the flue gas 13 in the process of being reheated. Points C0, C1, and C2 represent the temperature and absolute humidity of the flue gas 13 after being discharged from the exhaust tower 32 and mixed with the outside air. The temperatures of the exhaust gas 13 at points C0, C1, and C2 are approximately equal to the temperature of the outside air because they are the temperatures after the exhaust gas 13 is mixed with the outside air. At least one of the temperature and absolute humidity of the exhaust gas 13 differs between points C0, C1, and C2 because at least one of the assumed temperature and absolute humidity of the outside air differs at each of points C0, C1, and C2.

Since the relative humidity of the exhaust gas 13 at the outlet 27 of the water recovery device 33 is 100%, point A is located on the saturated water vapor line H. The multiple arrows starting from point A and reaching points C0, C1, and C2 indicate the state transition of the exhaust gas 13 until the exhaust gas 13 at the outlet 27 is mixed with the outside air. If the state of the exhaust gas 13 that changes during this state transition, that is, the exhaust gas state point defined by the temperature and absolute humidity of the exhaust gas 13, is to the right of the saturated water vapor line H, white smoke is not generated from the exhaust gas 13. On the other hand, if the exhaust gas state point of the exhaust gas 13 is to the left of the saturated water vapor line H, white smoke is generated from the exhaust gas 13. The relative humidity of the outside air changes depending on the season, day, time of day, or weather conditions, and is 100% relative humidity when it is raining, and is less than 100% otherwise. In other words, the state of the outside air is indicated by a point to the right of the saturated water vapor line H unless it is raining.

The transition from point A to point C0 (arrow R0) is a comparative example showing the process in which the exhaust gas 13 discharged from the water recovery device 33 is discharged to the outside air without being reheated at all. In this case, the exhaust gas 13 discharged from the outlet 27 of the water recovery device 33 reaches the exhaust tower 32 as is, so the relative humidity of the exhaust gas 13 in the exhaust tower 32 is 100%. In the process in which the temperature of the exhaust gas 13 discharged to the outside air drops to the temperature of the outside air (the temperature indicated by point C0), the moisture contained in the exhaust gas 13 is always in a supersaturated state. Therefore, while the temperature of the exhaust gas 13 drops until it becomes equal to the temperature of the outside air, the exhaust gas 13 mixes with the outside air and the absolute humidity of the exhaust gas 13 drops slightly, but since the exhaust gas state point C0 is to the left of the saturated water vapor line H, white smoke is generated from the exhaust gas 13. In addition, at point C0, which indicates the time when the temperature of the exhaust gas 13 becomes equal to the temperature of the outside air, the moisture contained in the exhaust gas 13 is still in a supersaturated state. Therefore, white smoke is further generated from the exhaust gas 13 until the moisture contained in the exhaust gas 13 is saturated. In this way, if no reheating is performed at all on the exhaust gas 13 discharged from the water recovery device 33, the conditions for generating white smoke tend to be established, which is undesirable. From another perspective, if the controller 90 executes control processing so that at least one of reheating by the exhaust gas reheater 51 (hereinafter referred to as first reheating) and heating by the exhaust gas 13 flowing through the exhaust gas extraction line 55 (hereinafter referred to as second reheating) is performed on the exhaust gas 13 discharged from the water recovery device 33, it is expected that the generation of white smoke will be suppressed. The process of suppressing the generation of white smoke by the first reheating and second reheating will be described in detail below.

The transition from point A through point B1 to point C1 (arrows R1, S1) shows a first embodiment in which only the first reheating is performed on the exhaust gas 13 discharged from the water recovery device 33. In the first embodiment, the exhaust gas extraction damper 56 is closed, and the second reheating is not performed. In the process in which the exhaust gas 13 discharged from the water recovery device 33 is reheated by the exhaust gas reheater 51 (arrow R1), the temperature of the exhaust gas 13 increases and the absolute humidity of the exhaust gas 13 is maintained. Although not visible in the graph, the relative humidity of the exhaust gas 13 decreases during the process of arrow R1.

As the exhaust gas 13 released into the outside air cools down to the temperature of the outside air (the temperature indicated by point C1) (arrow S1), the exhaust gas 13 mixes with the outside air, which has a lower absolute humidity than the exhaust gas 13, and the amount of moisture per unit volume of the exhaust gas 13 decreases. At this time, the amount of moisture contained in the exhaust gas 13 is less than the amount of saturated water vapor at that temperature. Therefore, the generation of white smoke from the exhaust gas 13 released into the outside air is suppressed. Even at point C1, which indicates the time when the temperature of the exhaust gas 13 becomes equal to the temperature of the outside air, the amount of moisture contained in the exhaust gas 13 is less than the amount of saturated water vapor. Therefore, the generation of white smoke from the exhaust gas 13 can be suppressed.
However, the temperature of the outside air changes depending on the season or the surrounding environment. If the temperature of the outside air is not the temperature indicated by point C1 but the temperature indicated by point D, the exhaust gas 13 may change from the state of point B1 to a state in a region (not shown) to the left of the saturated water vapor line H by extending the arrow S1. In this case, the moisture contained in the exhaust gas 13 becomes supersaturated, so that white smoke is generated from the exhaust gas 13. Thus, when the temperature of the outside air is low, the effect of suppressing the generation of white smoke may not be sufficiently exhibited by only performing the first reheating on the exhaust gas 13. Therefore, in the present disclosure, when the temperature of the outside air is low and the humidity is high, the second reheating is performed in addition to the first reheating as shown below.

The transition from point A to point C2 via points B1 and B2 in order (arrows R1, R2, S2) shows a second embodiment in which the first reheating and the second reheating are performed in order on the exhaust gas 13 discharged from the water recovery device 33. In the second embodiment, the exhaust gas extraction damper 56 is open. The process in which the first reheating is performed on the exhaust gas 13 discharged from the water recovery device 33 (arrow R1) is the same as in the first embodiment. The exhaust gas 13 discharged from the exhaust gas reheater 51 mixes with the high-temperature exhaust gas 13 in the downstream water recovery exhaust line 59B. This causes the temperature of the exhaust gas 13 discharged from the water recovery device 33 to further increase (arrow R2). The temperature and absolute humidity of the exhaust gas 13 that has been subjected to the second reheating are indicated by point B2. The absolute humidity increases slightly because the high-temperature exhaust gas 13 that is mixed during the second reheating and has not been subjected to water recovery by the water recovery device 33 contains a large amount of moisture.

In the process (arrow S2) of the exhaust gas 13 released into the outside air decreasing to the temperature of the outside air (the temperature indicated by point C2), the exhaust gas 13 mixes with the outside air, which has a lower absolute humidity than the exhaust gas 13, and the moisture content per unit volume decreases. At this time, the amount of moisture contained in the exhaust gas 13 is less than the amount of saturated water vapor. Therefore, the generation of white smoke from the exhaust gas 13 released into the outside air is suppressed. Even at point C2, which indicates the time when the temperature of the exhaust gas 13 becomes equal to the temperature of the outside air, the moisture contained in the exhaust gas 13 does not become supersaturated. In other words, by increasing the temperature of the exhaust gas 13 by the second reheating, the exhaust gas state point, which is a point on the graph in Figure 3 that defines the state (temperature and absolute humidity) of the exhaust gas 13, can be prevented from passing through the area to the left of the saturated water vapor line H in the process of change (arrow S2). Therefore, the generation of white smoke from the exhaust gas 13 can be suppressed.

The higher the temperature of the exhaust gas 13 at the time of release to the outside air, the further to the right the exhaust gas state point (for example, point B2) at that time can be from the saturated water vapor line H. The absolute humidity of the exhaust gas 13 decreases by mixing with the outside air until the temperature of the exhaust gas 13 released from the exhaust tower 32 becomes equal to the temperature of the outside air. At this time, the exhaust gas state point moves to the lower left, but does not move to the left of the saturated water vapor line H. In other words, by performing both the first reheating and the second reheating, the exhaust gas state point at the time of release to the outside air can be moved to the right from the saturated water vapor line H, so that the exhaust gas state point can be prevented from passing through the area to the left of the saturated water vapor line H, and the generation of white smoke can be avoided. Note that although the relative humidity of the outside air is less than 100%, when the temperature is constant, the lower the absolute humidity, the less likely it is that white smoke will be generated by the same exhaust gas 13. In this way, if the controller 90 executes control processing so that the temperature of the exhaust gas 13 released into the outside air is a value corresponding to the temperature and absolute humidity of the outside air, it is expected that the generation of white smoke will be suppressed regardless of the temperature and humidity of the outside air. The specific configuration of the controller 90 will be described below.

7. Specific configuration example of the controller 90
FIG. 4 is a schematic diagram showing a configuration of a controller 90 according to an embodiment of the present disclosure. The controller 90 includes a target exhaust gas discharge temperature calculation unit 95. The target exhaust gas discharge temperature calculation unit 95 is configured to calculate a target exhaust gas discharge temperature based on the acquisition result of the outside air temperature and humidity acquisition unit 81 and the measurement result of the water recovery outlet exhaust gas temperature sensor 82. The target exhaust gas discharge temperature is an exhaust gas discharge temperature at which the above-mentioned temperature deviation is equal to or greater than a specified value. The specified value may be a value that changes depending on the temperature and humidity of the outside air. For example, the lower the temperature of the outside air or the higher the humidity of the outside air, the higher the specified value used by the target exhaust gas discharge temperature calculation unit 95 may be. In the first embodiment described above with reference to FIG. 3, the specified value corresponds to the dimension L1, and the target exhaust gas discharge temperature corresponds to the temperature indicated by the point B1. In the second embodiment, the specified value corresponds to the dimension L2, and the target exhaust gas discharge temperature corresponds to the temperature indicated by the point B2.

The target exhaust gas discharge temperature is calculated, for example, based on the following concept. Since the relative humidity of the exhaust gas 13 at the outlet 27 of the water recovery device 33 is 100%, the absolute humidity of the exhaust gas 13 can be determined based on the measured value of the water recovery outlet exhaust gas temperature. In other words, the amount of moisture contained in the exhaust gas 13 can be determined. If the temperature and humidity of the outside air are known, the temperature and humidity (close to the temperature and humidity of the outside air) that the exhaust gas 13 discharged from the exhaust tower 32 will ultimately reach when it mixes with the outside air, and the process of state change until it reaches that state (corresponding to the arrows S1 and S2) can also be roughly predicted. In the process of state change until the exhaust gas 13 reaches the final temperature and humidity state, the target exhaust gas discharge temperature calculation unit 95 may set a specified value so that the exhaust gas state point is always located to the right of the saturated water vapor line H. In this way, the target exhaust gas discharge temperature is calculated. As an example, the specified value is obtained by inputting the temperature and humidity of the outside air and the exhaust gas temperature at the water recovery outlet into a function formula stored in the memory of the controller 90. In addition, when calculating the specified value, a data table may be used instead of a function formula, or a learning model based on machine learning may be used. In addition, the exhaust gas 13 extracted from the exhaust gas supply line 57 and passed through the exhaust gas extraction line 55 contains more moisture than the exhaust gas 13 from which moisture has been recovered by the water recovery device 33. Therefore, when calculating the specified value when the second reheating is performed, correction may be made taking into account the humidity of the exhaust gas 13 that has passed through the exhaust gas extraction line 55.

The controller 90 further includes a control unit 93. The control unit 93 is configured to control the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53 based on the measurement results of the water recovery outlet exhaust gas temperature sensor 82 and the exhaust gas discharge temperature sensor 83 so that the exhaust gas discharge temperature measured by the exhaust gas discharge temperature sensor 83 becomes the target exhaust gas discharge temperature.
For example, when the target exhaust gas release temperature is equal to or lower than a threshold value (temperature Ts in FIG. 3) that may vary depending on the temperature and humidity of the outside air, it is possible to set the exhaust gas release temperature to the target exhaust gas release temperature by only the first reheating. On the other hand, when the target exhaust gas release temperature exceeds the threshold value, it is difficult to set the exhaust gas release temperature to the target exhaust gas release temperature unless not only the first reheating but also the second reheating is performed. Therefore, the control unit 93 is configured to change the control of the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53 depending on the magnitude relationship between the target exhaust gas release temperature and the threshold value. The specific configuration is as follows.

The control unit 93 has a first control unit 91 and a second control unit 92. The first control unit 91 is configured to execute control for closing the exhaust gas extraction damper 56 and control the opening degree of the branched recovered water flow rate adjustment valve 53 when the target exhaust gas release temperature is equal to or lower than the threshold value. The opening degree control of the branched recovered water flow rate adjustment valve 53 is executed by the first control unit 91 sending to the branched recovered water flow rate adjustment valve 53 a signal corresponding to the temperature deviation, which is the deviation between the exhaust gas release temperature measured by the exhaust gas release temperature sensor 83 and the target exhaust gas release temperature.

Figure 5 is a schematic diagram showing the water recovery system 40 when the first reheating is performed. The thick lines in this figure indicate the lines through which the exhaust gas 13 flows (similar to Figure 6). As shown in this figure, when the first reheating is performed, the exhaust gas 13 does not flow through the exhaust gas extraction line 55, so the exhaust gas 13 discharged from the water recovery device 33 is reheated only by the exhaust gas reheater 51.

Returning to Fig. 4, when the target exhaust gas release temperature exceeds the threshold value, the second control unit 92 is configured to execute control for opening the exhaust gas extraction damper 56 and control the opening degrees of the exhaust gas extraction damper 56 and the branch recovered water flow rate adjustment valve 53. Specifically, the second control unit 92 generates a signal for setting the opening degree of the branch recovered water flow rate adjustment valve 53 to the upper limit opening degree, and transmits the signal to the branch recovered water flow rate adjustment valve 53. Furthermore, the second control unit 92 transmits to the exhaust gas extraction damper 56 a signal corresponding to a temperature deviation, which is the deviation between the exhaust gas release temperature measured by the exhaust gas release temperature sensor 83 and the target exhaust gas release temperature.
Note that the present disclosure is not limited to the second control unit 92 executing control to maintain the opening degree of the branched recovered water flow rate adjustment valve 53 at the upper limit opening degree. The second control unit 92 according to another example may generate signals for controlling the opening degrees of the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53 based on the temperature deviation, and transmit the signals to the exhaust gas extraction damper 56 and the branched recovered water flow rate adjustment valve 53, respectively.

Figure 6 is a schematic diagram showing the water recovery system 40 when the first reheating and the second reheating are performed. As shown in the figure, in this case, the exhaust gas 13 extracted from the exhaust gas supply line 57 flows into the downstream water recovery exhaust line 59B via the exhaust gas extraction line 55. In other words, the exhaust gas 13 is reheated by the exhaust gas reheater 51 and by mixing with the exhaust gas 13 flowing through the exhaust gas extraction line 55.

According to the above configuration, when the target exhaust gas discharge temperature is equal to or lower than the threshold value, it is expected that the exhaust gas 13 will be sufficiently heated by the exhaust gas reheater 51 without flowing the exhaust gas 13 through the exhaust gas extraction line 55. In this case, the first control unit 91 executes control to close the exhaust gas extraction damper 56. This reduces the amount of exhaust gas 13 discharged to the outside air without passing through the water recovery device 33, so that the water recovery system 40 can recover the moisture contained in the exhaust gas 13 discharged from the exhaust heat recovery boiler 14 without waste. On the other hand, when the target exhaust gas discharge temperature exceeds the threshold value due to a low temperature or high humidity of the outside air, it is difficult to sufficiently heat the exhaust gas 13 by the exhaust gas reheater 51 alone. In this case, the second control unit 92 opens the exhaust gas extraction damper 56, and the relatively high-temperature exhaust gas 13 extracted from the exhaust gas supply line 57 is led to the water recovery outlet exhaust line 59. This ensures that the temperature of the exhaust gas 13 discharged to the outside air reaches the target exhaust gas discharge temperature.

8. Operation method of the water recovery system 40
7 is a flowchart showing an exhaust gas discharge temperature control process according to an embodiment of the present disclosure. The exhaust gas discharge temperature control process is a control process for setting the exhaust gas discharge temperature to a target exhaust gas discharge temperature. The exhaust gas discharge temperature control process is an example of an operation method of the water recovery system 40, and is executed by the processor of the controller 90. In the following description, the "processor of the controller 90" may be abbreviated to "processor" and "step" may be abbreviated to "S".

First, the processor executes a process for acquiring the target exhaust gas discharge temperature (S11). For example, the processor acquires the outside air temperature and humidity from the outside air temperature and humidity acquisition unit 81, and acquires the water recovery outlet exhaust gas temperature from the water recovery outlet exhaust gas temperature sensor 82. Based on the acquisition results, the processor identifies a specified value. The processor acquires the target exhaust gas discharge temperature by adding the set specified value to the outside air temperature acquired by the outside air temperature and humidity acquisition unit 81. The processor executing S11 corresponds to the target exhaust gas discharge temperature calculation unit 95.

Next, the processor determines whether the target exhaust gas discharge temperature acquired in S11 is equal to or lower than a threshold value (S13). The threshold value is set based on the temperature and humidity of the outside air acquired in S11. If the target exhaust gas discharge temperature is equal to or lower than the threshold value (S13: YES), the processor executes the first control process (S15). In S15, the processor transmits a signal to the exhaust gas discharge damper 56 to close the exhaust gas discharge damper 56. Furthermore, the processor acquires a temperature deviation based on the exhaust gas discharge temperature measured by the exhaust gas discharge temperature sensor 83 and the target exhaust gas discharge temperature acquired in S11. The processor transmits a signal to the branched recovered water flow rate adjustment valve 53 so that the opening degree corresponds to the acquired temperature deviation (the opening degree is equal to or lower than the upper limit opening degree described above). This controls the amount of heat of the exhaust gas 13 by the exhaust gas reheater 51, thereby making it possible to reduce the temperature deviation. After that, the processor ends the exhaust gas discharge temperature control process.

On the other hand, if the target exhaust gas discharge temperature acquired in S11 exceeds the threshold value (S13: NO), the processor executes the second control process (S17). In S17, the processor transmits a signal to the exhaust gas discharge damper 56 to open the exhaust gas discharge damper 56. Furthermore, the processor transmits a signal to the branched recovered water flow rate control valve 53 so that the opening degree of the branched recovered water flow rate control valve 53 becomes the upper limit opening degree. The processor also acquires a temperature deviation based on the exhaust gas discharge temperature measured by the exhaust gas discharge temperature sensor 83 and the target exhaust gas discharge temperature acquired in S11. The processor transmits a signal to the exhaust gas discharge damper 56 so that the opening degree becomes the degree according to the acquired temperature deviation. As a result, the amount of heating of the exhaust gas 13 by the exhaust gas reheater 51 reaches the upper limit heating amount, and the flow rate of the exhaust gas 13 flowing from the exhaust gas discharge line 55 into the downstream water recovery exhaust line 59B is controlled, and the temperature deviation becomes small. After that, the processor ends the exhaust gas discharge temperature control process.

According to the above-mentioned method of operating the water recovery system 40, for the reasons already described, a method of operating the water recovery system 40 is realized that can more reliably suppress the generation of white smoke from the exhaust gas 13 released into the outside air.

9. Method for modifying the power plant 100
A method for retrofitting the power plant 100, which is an example of a gas turbine cogeneration system, will be described with reference to Figs. 8 to 10. Fig. 8 is a flowchart showing a method for retrofitting the power plant 100 according to an embodiment of the present disclosure. Fig. 9 is a schematic diagram showing a pre-remodeling power plant 100A, which is the power plant 100 before retrofitting according to an embodiment of the present disclosure. Fig. 10 is a schematic diagram showing a power plant 100B during retrofitting, which is the power plant 100 in the process of being retrofitted according to an embodiment of the present disclosure. The pre-remodeling power plant 100A will be provided with an exhaust gas reheater 51, a water recovery outlet exhaust line 59, a branched recovered water supply line 54, a branched recovered water return line 37, a branched recovered water flow rate control valve 53, an exhaust gas extraction line 55, and an exhaust gas extraction damper 56, which are components of the power plant 100.

As shown in FIG. 8, first, a step of installing an exhaust gas reheater 51 in the pre-modification power plant 100A is performed (S101). Then, a step of installing a water recovery outlet exhaust line 59 is performed (S103). S103 includes a step of connecting the water recovery device 33 and the exhaust gas reheater 51 with an upstream water recovery exhaust line 59A, and a step of connecting the exhaust gas reheater 51 and the exhaust tower 32 with a downstream water recovery exhaust line 59B. This allows the exhaust gas 13 to flow from the water recovery device 33 to the exhaust tower 32 (see FIGS. 9 and 10).

As shown in FIG. 8, a branched recovered water supply line installation step is then performed (S105) in which the water recovery device 33 or the recovered water discharge line 39 is connected to the exhaust gas reheater 51 by the branched recovered water supply line 54. In this example, in S105, the branched recovered water supply line 54 is connected to the recovered water discharge line 39 of the water recovery device 33 or the recovered water discharge line 39 (see FIG. 10). More specifically, the branched recovered water supply line 54 is connected to the recovered water discharge line 39 between the recovered water pump 38 and the recovered water cooling device 110 (see FIG. 10).

Next, a branched recovered water return line installation step is performed to connect the exhaust gas reheater 51 and the water tank 136 with the branched recovered water return line 37 (S107), and a step is performed to install the branched recovered water flow rate adjustment valve 53 in the branched recovered water supply line 54 (S109). After completion of S109, the recovered water extracted from the recovered water discharge line 39 can return to the water tank 136 via the exhaust gas reheater 51 (see FIG. 10).

As shown in FIG. 8, next, an exhaust gas extraction line installation step is performed in which the exhaust line 28 and the water recovery outlet exhaust line 59 are connected by the exhaust gas extraction line 55 (S111). In this example, the exhaust gas extraction line 55 is connected to the exhaust line 28 via the connecting exhaust line 29 (see FIG. 2). Next, an exhaust gas extraction damper installation step is performed in which an exhaust gas extraction damper 56 is installed in the exhaust gas extraction line 55 (S113). This completes the method for modifying the power plant 100 (see FIG. 2).

The above-mentioned modification method is merely one example of the present disclosure. The pre-modification power plant 100A may include the exhaust gas reheater 51, the recovered water supply line 42, the branched recovered water flow rate control valve 53, and the branched recovered water return line 37 as existing components. In this case, S101 to S109 exemplified above are not necessary. S113 may be executed before S111. That is, the exhaust gas extraction line 55 in which the exhaust gas extraction damper 56 is installed may be connected to the connection exhaust line 29 and the downstream water recovery exhaust line 59B.

According to the above-described modification method, for the reasons already described, a method for modifying the power plant 100 is realized that can more reliably suppress the generation of white smoke from the exhaust gas 13 discharged into the outside air.
Furthermore, in the exhaust gas extraction line installation step (S111), the exhaust gas extraction line 55 is connected to the downstream water recovery exhaust line 59B. In this case, for the reasons described above, the operating efficiency of the power plant 100 can be improved.
Furthermore, in the branched recovered water supply line installation step (S105), the branched recovered water supply line 54 is connected to the recovered water discharge line 39 between the recovered water pump 38 and the recovered water cooling device 110. In this case, for the reasons already described, the configuration of the power plant 100 can be simplified.

<10. Summary>
The contents described in the above-mentioned embodiments can be understood, for example, as follows.

1) A water recovery system (40) according to at least one embodiment of the present disclosure comprises:
A water recovery system (40) for recovering moisture from exhaust gas (13) discharged from a boiler (heat recovery boiler 14), comprising:
a water recovery device (33) for recovering the moisture in the exhaust gas (13) as recovered water by bringing the exhaust gas (13) into gas-liquid contact with refrigerant water;
a recovered water cooling device (110) for cooling the recovered water discharged from the water recovery device (33);
a recovered water discharge line (39) for guiding the recovered water discharged from the water recovery device (33) to the recovered water cooling device (110);
a recovered water supply line (42) for guiding the recovered water cooled by the recovered water cooling device (110) to the water recovery device (33) as the refrigerant water;
a water recovery outlet exhaust line (59) for discharging the exhaust gas (13) discharged from the water recovery device (33) to the outside air;
an exhaust gas reheater (51) for heating the exhaust gas (13) flowing through the water recovery outlet exhaust line (59) using the recovered water extracted from the water recovery device (33) or the recovered water discharge line (39) as a heat source;
an exhaust gas extraction line (55) for guiding the exhaust gas (13) extracted from an exhaust gas supply line (57), which is a supply line for the exhaust gas (13) from the boiler (exhaust heat recovery boiler 14) to the water recovery device (33), to the water recovery outlet exhaust line (59);
an exhaust gas extraction damper (56) provided in the exhaust gas extraction line (55);
Equipped with.

According to the configuration of 1) above, when the exhaust gas extraction damper (56) is opened, the relatively high-temperature exhaust gas (13) extracted from the exhaust gas supply line (57) is guided to the water recovery outlet exhaust line (59) and mixed with the exhaust gas (13) discharged from the water recovery device (33). This heats the exhaust gas (13) discharged from the water recovery device (33). The exhaust gas (13) discharged from the water recovery device (33) is heated not only by the exhaust gas reheater (51) but also by mixing with the exhaust gas (13) flowing through the exhaust gas extraction line (55), so that the temperature of the exhaust gas (13) discharged to the outside air can be made sufficiently higher than the dew point temperature of water in the outside air. This realizes a water recovery system (40) that can more reliably suppress the generation of white smoke from the exhaust gas (13) discharged to the outside air.

2) In some embodiments, the water recovery system (40) described in 1) above,
The water recovery outlet exhaust line (59)
an upstream water recovery exhaust line (59A) for supplying the exhaust gas (13) discharged from the water recovery device (33) to the exhaust gas reheater (51);
a downstream water recovery exhaust line (59B) for discharging the exhaust gas (13) discharged from the exhaust gas reheater (51) to the outside air;
Including,
The exhaust gas extraction line (55) is connected to the downstream water recovery exhaust line (59B).

According to the configuration of 2) above, the exhaust gas (13) discharged from the water recovery device (33) is heated by the exhaust gas reheater (51) before being mixed with the exhaust gas (13) led by the exhaust gas extraction line (55). In the exhaust gas reheater (51), the recovered water heats the exhaust gas (13) whose temperature is not yet sufficiently increased, so that the temperature of the recovered water discharged from the exhaust gas reheater (51) is reduced. This reduces the thermal load of the recovered water cooling device (110), and therefore the power of the cooling system of the recovered water cooling device (110) can be reduced. Therefore, the water recovery system (40) can improve its operating efficiency.

3) In some embodiments, the water recovery system (40) described in 1) or 2) above,
a recovered water pump (38) disposed in the recovered water discharge line (39);
a branched recovered water supply line (42) connected to the recovered water discharge line (39) between the recovered water pump (38) and the recovered water cooling device (110), the branched recovered water supply line (42) being for supplying the recovered water extracted from the recovered water discharge line (39) to the exhaust gas reheater (51);
It further comprises:

According to the configuration of 3) above, the recovered water extracted from the recovered water discharge line (39) can flow through the branched recovered water supply line (42) by driving the recovered water pump (38). Since a dedicated pump for supplying recovered water to the exhaust gas reheater (51) is not required, the configuration of the water recovery system (40) can be simplified.

4) In some embodiments, the water recovery system (40) according to any one of 1) to 3) above,
The water recovery device (33) includes a water tank (136) for storing the recovered water,
The water recovery system (40) further includes a branched recovered water return line (37) for conducting the recovered water discharged from the exhaust gas reheater (51) to the water tank (136).

According to the configuration of 4) above, the branched recovered water return line (37) guides the recovered water to the water tank (136) of the water recovery device (33), so even if the recovered water contains gas such as air, the water recovery device (33) can recover the gas. Therefore, it is possible to prevent gas from being mixed into the recovered water flowing through the recovered water discharge line (39).

5) In some embodiments, the water recovery system (40) according to any one of 1) to 4) above,
a branched recovered water supply line (42) for supplying the recovered water extracted from the recovered water discharge line (39) to the exhaust gas reheater (51);
a branched recovered water flow rate control valve (53) provided in the branched recovered water supply line (42);
An outside air temperature and humidity acquisition unit (81) for acquiring the outside air temperature and humidity;
a water recovery outlet exhaust gas temperature sensor (82) for measuring the temperature of the exhaust gas (13) at the outlet of the water recovery device (33);
an exhaust gas discharge temperature sensor (83) for measuring an exhaust gas discharge temperature, which is the temperature of the exhaust gas (13) discharged to the outside air from the water recovery outlet exhaust line (59);
a controller (90) for controlling the exhaust gas extraction damper (56) and the branched recovered water flow rate adjustment valve (53) based on the results of measurement by the outside air temperature and humidity acquisition unit (81) and the results of measurement by the water recovery outlet exhaust gas temperature sensor (82) and the exhaust gas discharge temperature sensor (83) so that a temperature deviation between the exhaust gas discharge temperature and the outside air temperature is equal to or greater than a specified value according to the humidity of the outside air;
It further comprises:

According to the configuration of 5) above, the exhaust gas discharge temperature can be made sufficiently high by controlling the exhaust gas extraction damper (56) and the branched recovered water flow rate control valve (53) by the controller (90). This makes it possible to suppress the generation of white smoke from the exhaust gas (13) discharged into the outside air.

6) In some embodiments, the water recovery system (40) described in 5) above, further comprising:
The controller (90)
a target exhaust gas discharge temperature calculation unit (95) for calculating a target exhaust gas discharge temperature, which is the exhaust gas discharge temperature at which the temperature deviation becomes equal to or greater than the specified value, based on the results of the acquisition by the outside air temperature and humidity acquisition unit (81) and the measurement results of the water recovery outlet exhaust gas temperature sensor (82);
a control unit (93) for controlling the exhaust gas extraction damper (56) and the branched recovered water flow rate control valve (53) based on measurement results of the water recovery outlet exhaust gas temperature sensor (82) and the exhaust gas discharge temperature sensor (83) so that the measured exhaust gas discharge temperature becomes the calculated target exhaust gas discharge temperature;
Further comprising:
The control unit (93)
a first control unit (91) for executing control to close the exhaust gas extraction damper (56) and controlling the branched recovered water flow rate adjustment valve (53) when the calculated target exhaust gas release temperature is equal to or lower than a threshold value;
a second control unit (92) for executing control to open the exhaust gas extraction damper (56) and for controlling the exhaust gas extraction damper (56) and the branched recovered water flow rate adjustment valve (53) when the calculated target exhaust gas release temperature exceeds the threshold value;
has.

According to the configuration of 6) above, when the target exhaust gas discharge temperature is equal to or lower than the threshold value, it is expected that the exhaust gas (13) will be sufficiently heated by the exhaust gas reheater (51) even if the exhaust gas (13) is not flowed through the exhaust gas extraction line (55). In this case, the first control unit (91) executes control to close the exhaust gas extraction damper (56). This reduces the amount of exhaust gas (13) discharged to the outside air without passing through the water recovery device (33), so that the water recovery system (40) can recover moisture contained in the exhaust gas (13) discharged from the boiler (exhaust heat recovery boiler 14) without waste. On the other hand, when the target exhaust gas discharge temperature exceeds the threshold value due to at least one of the temperature and humidity of the outside air being low, it is difficult to sufficiently heat the exhaust gas (13) by the exhaust gas reheater (51) alone. In this case, the second control unit (92) opens the exhaust gas extraction damper (56), and the relatively high-temperature exhaust gas (13) extracted from the exhaust gas supply line (57) is led to the water recovery outlet exhaust line (59). This ensures that the temperature of the exhaust gas (13) released into the outside air reaches the target exhaust gas release temperature.

7) A method of operating a water recovery system (40) according to at least one embodiment of the present disclosure, comprising:
A method for operating a water recovery system (40) for recovering moisture from exhaust gas (13) discharged from a boiler (heat recovery boiler 14), comprising the steps of:
The water recovery system (40) comprises:
a water recovery device (33) for recovering the moisture in the exhaust gas (13) as recovered water by bringing the exhaust gas (13) into gas-liquid contact with refrigerant water;
a recovered water cooling device (110) for cooling the recovered water discharged from the water recovery device (33);
a recovered water discharge line (39) for guiding the recovered water discharged from the water recovery device (33) to the recovered water cooling device (110);
a recovered water supply line (42) for guiding the recovered water cooled by the recovered water cooling device (110) to the water recovery device (33) as the refrigerant water;
a water recovery outlet exhaust line (59) for discharging the exhaust gas (13) discharged from the water recovery device (33) to the outside air;
an exhaust gas reheater (51) for heating the exhaust gas (13) flowing through the water recovery outlet exhaust line (59) using the recovered water extracted from the water recovery device (33) or the recovered water discharge line (39) as a heat source;
an exhaust gas extraction line (55) for guiding the exhaust gas (13) extracted from an exhaust gas supply line (57), which is a supply line for the exhaust gas (13) from the boiler (exhaust heat recovery boiler 14) to the water recovery device (33), to the water recovery outlet exhaust line (59);
an exhaust gas extraction damper (56) provided in the exhaust gas extraction line (55);
a branched recovered water supply line (42) for supplying the recovered water extracted from the recovered water discharge line (39) to the exhaust gas reheater (51);
a branched recovered water flow rate control valve (53) provided in the branched recovered water supply line (42);
a branched recovered water return line (37) for guiding the recovered water discharged from the exhaust gas reheater (51) to the water recovery device (33);
An outside air temperature and humidity acquisition unit (81) for measuring the temperature and humidity of the outside air;
a water recovery outlet exhaust gas temperature sensor (82) for measuring the temperature of the exhaust gas (13) at the outlet of the water recovery device (33);
an exhaust gas discharge temperature sensor (83) for measuring an exhaust gas discharge temperature, which is the temperature of the exhaust gas (13) discharged to the outside air from the water recovery outlet exhaust line (59);
Including,
The method of operating the water recovery system (40) comprises:
The method further includes an exhaust gas discharge temperature control step (S11 to S17) for controlling the exhaust gas extraction damper (56) and the branched recovered water flow rate control valve (53) based on the results of measurement by the outside air temperature and humidity acquisition unit (81) and the results of measurement by the water recovery outlet exhaust gas temperature sensor (82) and the exhaust gas discharge temperature sensor (83) so that the temperature deviation between the exhaust gas discharge temperature and the outside air temperature is equal to or greater than a specified value according to the humidity of the outside air.

The configuration of 7) above realizes an operating method of the water recovery system (40) that can more reliably suppress the generation of white smoke from the exhaust gas (13) released into the outside air, for the same reason as 1) above.

8) A method for modifying a gas turbine cogeneration system (power plant 100) according to at least one embodiment of the present disclosure, comprising:
The gas turbine cogeneration system (power generation plant 100) comprises:
A gas turbine (2);
a generator (5) configured to generate electricity by driving the gas turbine (2);
a heat recovery boiler (14) for generating steam from boiler (heat recovery boiler 14) feed water by utilizing heat recovered from exhaust gas (13) discharged from the gas turbine;
a water recovery device (33) for recovering moisture as recovered water from the exhaust gas (13) discharged from the exhaust heat recovery boiler (exhaust heat recovery boiler 14);
a water recovery outlet exhaust line (59) for discharging the exhaust gas (13) discharged from the water recovery device (33) to the outside air;
an exhaust gas supply line (57) which is a supply line of the exhaust gas (13) from the exhaust heat recovery boiler (exhaust heat recovery boiler 14) to the water recovery device (33);
a connection exhaust line connected to the exhaust gas supply line (57) between the heat recovery boiler (heat recovery boiler 14) and the water recovery device (33), for discharging the exhaust gas (13) to the outside air;
Equipped with
The method for modifying the gas turbine cogeneration system (power plant 100) includes the steps of:
an exhaust gas extraction line installation step (S111) of connecting the connection exhaust line and the water recovery outlet exhaust line (59) by an exhaust gas extraction line (55);
an exhaust gas extraction damper installation step (S113) of installing an exhaust gas extraction damper (56) in the exhaust gas extraction line (55);
Equipped with.

According to the configuration of 8) above, the relatively high-temperature exhaust gas (13) extracted from the exhaust gas supply line (57) is guided to the water recovery outlet exhaust line (59) and mixed with the exhaust gas (13) discharged from the water recovery device (33). This allows the temperature of the exhaust gas (13) discharged to the outside air to be sufficiently higher than the dew point temperature of water in the outside air, thereby realizing a method of modifying a gas turbine cogeneration system (power generation plant 100) that can more reliably suppress the generation of white smoke from the exhaust gas (13) discharged to the outside air.

9) In some embodiments, a method for retrofitting the gas turbine cogeneration system (power plant 100) described in 8) above, comprising the steps of:
The gas turbine cogeneration system (power generation plant 100) comprises:
a recovered water cooling device (110) for cooling the recovered water discharged from the water recovery device (33);
a recovered water discharge line (39) for guiding the recovered water discharged from the water recovery device (33) to the recovered water cooling device (110);
In addition,
The method for modifying the gas turbine cogeneration system (power plant 100) includes the steps of:
an exhaust gas reheater installation step (S101) of installing an exhaust gas reheater (51) for heating the exhaust gas (13) flowing through the water recovery outlet exhaust line (59) using the recovered water extracted from the water recovery device (33) or the recovered water discharge line (39) as a heat source;
a branched recovered water supply line installation step (S105) for connecting the water recovery device (33) or the recovered water discharge line (39) to the exhaust gas reheater (51) by a branched recovered water supply line (42);
a branched recovered water return line installation step (S107) for connecting the exhaust gas reheater (51) and the water recovery device (33) by a branched recovered water return line (37);
It further comprises:

The configuration of 9) above provides a method for modifying a gas turbine cogeneration system (power plant 100) that can more reliably prevent white smoke from being generated from the exhaust gas (13) discharged into the outside air, for the same reason as 1) above.

10) In some embodiments, a method for retrofitting the gas turbine cogeneration system (power plant 100) described in 9) above, comprising the steps of:
The water recovery outlet exhaust line (59)
an upstream water recovery exhaust line (59A) for supplying the exhaust gas (13) discharged from the water recovery device (33) to the exhaust gas reheater (51);
a downstream water recovery exhaust line (59B) for exhausting the exhaust gas (13) discharged from the exhaust gas reheater (51) to the outside air;
having
In the exhaust gas extraction line installation step (S111), the exhaust gas extraction line (55) is connected to the downstream water recovery exhaust line (59B).

The configuration of 10) above can improve the operating efficiency of the gas turbine cogeneration system (power plant 100) for the same reason as 2) above.

11) In some embodiments, a method for retrofitting the gas turbine cogeneration system (power plant 100) described in 9) or 10) above, comprising:
The gas turbine cogeneration system (power plant 100) further includes a recovered water pump (38) disposed in the recovered water discharge line (39),
In the branched recovered water supply line installation step (S105), the branched recovered water supply line (42) is connected to the recovered water discharge line (39) between the recovered water pump (38) and the recovered water cooling device (110).

The configuration of 11) above can simplify the configuration of the gas turbine cogeneration system (power generation plant 100) for the same reason as 3) above.

2: Gas turbine 5: Generator 13: Exhaust gas 14: Exhaust heat recovery boiler 27: Outlet 28: Exhaust line 29: Connection exhaust line 33: Water recovery device 37: Branched recovered water return line 38: Recovered water pump 39: Recovered water discharge line 40: Water recovery system 42: Recovered water supply line 51: Exhaust gas reheater 53: Branched recovered water flow rate control valve 54: Branched recovered water supply line 55: Exhaust gas extraction line 56: Exhaust gas extraction damper 57: Exhaust gas supply line 59: Water recovery outlet exhaust line 59A: Upstream water recovery exhaust line 59B: Downstream water recovery exhaust line 81: Outside air temperature and humidity acquisition unit 82: Water recovery outlet exhaust gas temperature sensor 83: Exhaust gas release temperature sensor 90: Controller 91: First control unit 92: Second control unit 93: Control unit 95: Target exhaust gas release temperature calculation unit 100: Power plant 110 : Recovered water cooling device 136 : Water tank

Claims (11)

A water recovery system for recovering moisture from exhaust gas discharged from a boiler, comprising:
a water recovery device for recovering the moisture in the exhaust gas as recovered water by bringing the exhaust gas into gas-liquid contact with refrigerant water;
a recovered water cooling device for cooling the recovered water discharged from the water recovery device;
a recovered water discharge line for guiding the recovered water discharged from the water recovery device to the recovered water cooling device;
a recovered water supply line for guiding the recovered water cooled by the recovered water cooling device to the water recovery device as the refrigerant water;
a water recovery outlet exhaust line for discharging the exhaust gas discharged from the water recovery device to the outside air;
an exhaust gas reheater for heating the exhaust gas flowing through the water recovery outlet exhaust line by using the recovered water extracted from the water recovery device or the recovered water discharge line as a heat source;
an exhaust gas extraction line for guiding the exhaust gas extracted from an exhaust gas supply line, which is a supply line of the exhaust gas from the boiler to the water recovery device, to the water recovery outlet exhaust line;
an exhaust gas extraction damper provided in the exhaust gas extraction line;
A water recovery system comprising: The water recovery outlet exhaust line is
an upstream water recovery exhaust line for supplying the exhaust gas discharged from the water recovery device to the exhaust gas reheater;
a downstream water recovery exhaust line for discharging the exhaust gas discharged from the exhaust gas reheater to the outside air;
Including,
The exhaust gas extraction line is connected to the downstream water recovery exhaust line.
The water recovery system of claim 1 . A recovered water pump disposed in the recovered water discharge line;
a branched recovered water supply line connected to the recovered water discharge line between the recovered water pump and the recovered water cooling device, the branched recovered water supply line being for supplying the recovered water extracted from the recovered water discharge line to the exhaust gas reheater;
Further comprising:
3. The water recovery system according to claim 1 or 2. The water recovery device includes a water tank that stores the recovered water,
The water recovery system further includes a branched recovered water return line for guiding the recovered water discharged from the exhaust gas reheater to the water tank.
3. The water recovery system according to claim 1 or 2. a branched recovered water supply line for supplying the recovered water extracted from the recovered water discharge line to the exhaust gas reheater;
a branched recovered water flow rate control valve provided in the branched recovered water supply line;
an outside air temperature and humidity acquisition unit for acquiring the outside air temperature and humidity;
a water recovery outlet exhaust gas temperature sensor for measuring the temperature of the exhaust gas at the outlet of the water recovery device;
an exhaust gas discharge temperature sensor for measuring an exhaust gas discharge temperature, which is the temperature of the exhaust gas discharged to the outside air from the water recovery outlet exhaust line;
a controller for controlling the exhaust gas extraction damper and the branched recovered water flow rate adjustment valve based on the results of measurement by the outside air temperature and humidity acquisition unit and the results of measurement by the water recovery outlet exhaust gas temperature sensor and the exhaust gas release temperature sensor so that a temperature deviation between the exhaust gas release temperature and the outside air temperature is equal to or greater than a specified value according to the humidity of the outside air;
Further comprising:
3. The water recovery system according to claim 1 or 2. The controller:
a target exhaust gas discharge temperature calculation unit for calculating a target exhaust gas discharge temperature, which is the exhaust gas discharge temperature at which the temperature deviation is equal to or greater than the specified value, based on the results of the acquisition by the outside air temperature and humidity acquisition unit and the measurement results of the water recovery outlet exhaust gas temperature sensor;
a control unit for controlling the exhaust gas extraction damper and the branched recovered water flow rate control valve based on measurement results of the water recovery outlet exhaust gas temperature sensor and the exhaust gas discharge temperature sensor so that the measured exhaust gas discharge temperature becomes the calculated target exhaust gas discharge temperature;
Further comprising:
The control unit is
a first control unit that executes control to close the exhaust gas extraction damper and controls the branched recovered water flow rate adjustment valve when the calculated target exhaust gas release temperature is equal to or lower than a threshold value;
a second control unit that executes control to open the exhaust gas extraction damper and controls the exhaust gas extraction damper and the branched recovered water flow rate adjustment valve when the calculated target exhaust gas release temperature exceeds the threshold value;
having
6. The water recovery system of claim 5. A method for operating a water recovery system for recovering moisture from exhaust gas discharged from a boiler, comprising the steps of:
The water recovery system comprises:
a water recovery device for recovering the moisture in the exhaust gas as recovered water by bringing the exhaust gas into gas-liquid contact with refrigerant water;
a recovered water cooling device for cooling the recovered water discharged from the water recovery device;
a recovered water discharge line for guiding the recovered water discharged from the water recovery device to the recovered water cooling device;
a recovered water supply line for guiding the recovered water cooled by the recovered water cooling device to the water recovery device as the refrigerant water;
a water recovery outlet exhaust line for discharging the exhaust gas discharged from the water recovery device to the outside air;
an exhaust gas reheater for heating the exhaust gas flowing through the water recovery outlet exhaust line by using the recovered water extracted from the water recovery device or the recovered water discharge line as a heat source;
an exhaust gas extraction line for guiding the exhaust gas extracted from an exhaust gas supply line, which is a supply line of the exhaust gas from the boiler to the water recovery device, to the water recovery outlet exhaust line;
an exhaust gas extraction damper provided in the exhaust gas extraction line;
a branched recovered water supply line for supplying the recovered water extracted from the recovered water discharge line to the exhaust gas reheater;
a branched recovered water flow rate control valve provided in the branched recovered water supply line;
a branched recovered water return line for guiding the recovered water discharged from the exhaust gas reheater to the water recovery device;
An outside air temperature and humidity acquisition unit for measuring the outside air temperature and humidity;
a water recovery outlet exhaust gas temperature sensor for measuring the temperature of the exhaust gas at the outlet of the water recovery device;
an exhaust gas discharge temperature sensor for measuring an exhaust gas discharge temperature, which is the temperature of the exhaust gas discharged to the outside air from the water recovery outlet exhaust line;
Including,
The method for operating the water recovery system includes:
and an exhaust gas discharge temperature control step of controlling the exhaust gas extraction damper and the branched recovered water flow rate control valve based on the results of measurement by the outside air temperature and humidity acquisition unit and the results of measurement by the water recovery outlet exhaust gas temperature sensor and the exhaust gas discharge temperature sensor so that a temperature deviation between the exhaust gas discharge temperature and the outside air temperature is equal to or greater than a specified value according to the humidity of the outside air.
How to operate a water recovery system. A method for retrofitting a gas turbine cogeneration system, comprising the steps of:
The gas turbine cogeneration system includes:
A gas turbine;
a generator configured to generate electricity by being driven by the gas turbine;
a heat recovery boiler for generating steam from boiler feed water by utilizing heat recovered from exhaust gas discharged from the gas turbine;
a water recovery device for recovering moisture as recovered water from the exhaust gas discharged from the heat recovery boiler;
a water recovery outlet exhaust line for discharging the exhaust gas discharged from the water recovery device to the outside air;
an exhaust gas supply line which is a supply line of the exhaust gas from the exhaust heat recovery boiler to the water recovery device;
a connecting exhaust line connected to the exhaust gas supply line between the exhaust heat recovery boiler and the water recovery device, for discharging the exhaust gas to the outside air;
Equipped with
The method for retrofitting a gas turbine cogeneration system includes the steps of:
an exhaust gas extraction line installation step of connecting the connection exhaust line and the water recovery outlet exhaust line by an exhaust gas extraction line;
an exhaust gas extraction damper installation step of installing an exhaust gas extraction damper in the exhaust gas extraction line;
Equipped with
How to retrofit a gas turbine cogeneration system. The gas turbine cogeneration system includes:
a recovered water cooling device for cooling the recovered water discharged from the water recovery device;
a recovered water discharge line for guiding the recovered water discharged from the water recovery device to the recovered water cooling device;
In addition,
The method for retrofitting a gas turbine cogeneration system includes the steps of:
an exhaust gas reheater installation step of installing an exhaust gas reheater for heating the exhaust gas flowing through the water recovery outlet exhaust line by using the recovered water extracted from the water recovery device or the recovered water discharge line as a heat source;
a branched recovered water supply line installation step of connecting the water recovery device or the recovered water discharge line to the exhaust gas reheater by a branched recovered water supply line;
a branched recovered water return line installation step of connecting the exhaust gas reheater and the water recovery device by a branched recovered water return line;
Further comprising:
The method for retrofitting a gas turbine cogeneration system according to claim 8. The water recovery outlet exhaust line is
an upstream water recovery exhaust line for supplying the exhaust gas discharged from the water recovery device to the exhaust gas reheater;
a downstream water recovery exhaust line for exhausting the exhaust gas discharged from the exhaust gas reheater to the outside air;
having
In the exhaust gas extraction line installation step, the exhaust gas extraction line is connected to the downstream water recovery exhaust line.
The method for retrofitting a gas turbine cogeneration system according to claim 9. The gas turbine cogeneration system further includes a recovered water pump disposed in the recovered water discharge line,
In the branched recovered water supply line installation step, the branched recovered water supply line is connected to the recovered water discharge line between the recovered water pump and the recovered water cooling device.
The method for modifying a gas turbine cogeneration system according to claim 9 or 10.

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