Exhaust heat recovery system

Abstract

To provide an exhaust heat recovery system capable of more efficiently recovering exhaust heat as energy.SOLUTION: An exhaust heat recovery system includes: a duct configured to cause an exhaust gas to flow therein; a partitioning section extending in an extending direction of the duct and configured to partition an inner space of the duct into a first space and a second space; an evaporator disposed in the duct to be located on a downstream side in an exhaust gas flowing direction of the partitioning section; a superheater disposed in the first space and on an upstream side in the exhaust gas flowing direction of the evaporator; an economizer disposed in the duct so as to be located on the downstream side in the exhaust gas flowing direction of the evaporator; an auxiliary burner disposed in the first space and on the upstream side in the exhaust gas flowing direction of the superheater; a flow rate adjustment section configured to enable adjustment of a flow rate of the exhaust gas in the first space; and a control section configured to control the adjustment amount of the flow rate of the exhaust gas in the first space by using the flow rate adjustment section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a waste heat recovery system. [Background technology]

[0002] Heat recovery boilers in cogeneration systems, combined power generation systems, and the like are configured to recover steam using waste heat and use the resulting steam to operate a steam turbine to recover electricity. This allows for effective use of thermal energy and achieves high efficiency in energy use. Patent Documents 1 and 2 disclose examples of cogeneration systems including a gas turbine power generation system and a steam turbine power generation system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-110511 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-054808 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure describes a waste heat recovery system that can more efficiently recover waste heat as energy. [Means for solving the problem]

[0005] Example 1. One example of an exhaust heat recovery system is an exhaust heat recovery system that uses the heat of exhaust gas to heat boiler feed water to generate steam, and includes a duct configured to allow the exhaust gas to flow, a partition extending along the extension direction of the duct and configured to divide the internal space of the duct into a first space and a second space, an evaporator arranged in the duct so as to be located downstream of the partition in the flow direction of the exhaust gas and configured to generate steam from the boiler feed water, and an evaporator arranged in the first space and upstream of the evaporator in the flow direction of the exhaust gas, and configured to convert the steam supplied from the evaporator into a first space. the first space and the upstream side of the superheater in the direction of exhaust gas flow, and configured to heat the exhaust gas flowing through the first space; a superheater configured to further heat the exhaust gas by the exhaust gas flowing through the first space to generate superheated steam; a coal economizer arranged in the duct so as to be located downstream of the evaporator in the direction of exhaust gas flow, and configured to preheat boiler feed water and supply it to the evaporator; an auxiliary burner arranged in the first space and upstream of the superheater in the direction of exhaust gas flow, and configured to heat the exhaust gas flowing through the first space; a flow rate adjuster configured to adjust the flow rate of the exhaust gas in the first space; and a control unit configured to control the amount of adjustment by the flow rate adjuster.

[0006] Depending on the conditions for generating superheated steam (e.g., the temperature of the superheated steam, the amount of steam, etc.), the exhaust gas may be preheated by a supporting burner, and the heated exhaust gas may be applied to the superheater. In this case, if the inside of the duct is not divided into first and second spaces by a partition, as in the system of Example 1, the entire amount of exhaust gas introduced into the duct must be heated by the supporting burner, which consumes a large amount of reheating fuel and reduces energy efficiency. However, in the system of Example 1, the inside of the duct is divided into the first and second spaces by a partition, the supporting burner and the superheater are disposed in the first space, and the flow rate of the exhaust gas flowing through the first space is adjusted by a flow rate adjuster. Therefore, a portion of the exhaust gas introduced into the duct flows through the first space and is heated by the supporting burner, and then heats the steam in the superheater. Therefore, an appropriate amount of exhaust gas can be heated to an appropriate temperature by the auxiliary burner depending on the conditions for generating superheated steam. As a result, the consumption of reheating fuel in the auxiliary burner is suppressed, enabling more efficient recovery of exhaust heat as energy. Furthermore, in the system of Example 1, the partition is arranged within the duct so as to extend along the extension direction of the duct. Therefore, compared to a configuration without a partition, a decrease in the flow rate of exhaust gas flowing within the first space is suppressed. Therefore, the exhaust gas is more likely to become turbulent within the first space, and the thermal boundary layer is thinner, thereby improving the heat exchange efficiency between the exhaust gas and the superheater. As a result, it is possible to make the superheater more compact. Note that, for example, the above effects can be achieved by a very simple modification to an existing exhaust heat recovery system, such as adding a partition inside the duct.

[0007] Example 2: The system of Example 1 may further include a heat transfer tube extending through the partition and configured to supply the boiler feedwater after flowing through the partition to an evaporator or an economizer. In this case, heat can be recovered from the exhaust gas in the partition as well and used to heat the boiler feedwater. This makes it possible to more efficiently recover exhaust heat as energy.

[0008] Example 3: In the system of Example 1 or Example 2, the superheater does not have to be disposed in the second space. In this case, the operational effect of Example 1 can be obtained more significantly.

[0009] Example 4: The system of any one of Examples 1 to 3 may further include a rectifying member disposed in the first space and upstream of the auxiliary burner in the flow direction of the exhaust gas, and configured to rectify the flow of the exhaust gas toward the auxiliary burner. In this case, the rectifying member makes it easier for the exhaust gas to flow toward the auxiliary burner. This makes it possible to effectively heat the exhaust gas with the auxiliary burner.

[0010] Example 5: The system of any one of Examples 1 to 4 may further include a gas turbine configured to generate electricity by burning combustion gas and introduce the burned gas as exhaust gas into the inlet of the duct. In this case, the gas used for power generation in the gas turbine can be further used to generate superheated steam in the exhaust heat recovery system. This makes it possible to further improve the energy efficiency of the entire system.

[0011] Example 6: The system of any of Examples 1 to 5 may further include a supply unit configured to supply boiler feedwater to the superheater, and the control unit may be configured to execute a process of calculating a target value for the adjustment amount to be made by the flow rate adjuster based on the amount of boiler feedwater supplied to the superheater by the supply unit. In this case, if the amount of boiler feedwater supplied to the superheater by the supply unit becomes relatively small, there is a concern that the temperature of the generated superheated steam will fluctuate. Therefore, the target value for the adjustment amount to be made by the flow rate adjuster is set in a direction that increases the flow rate of exhaust gas in the first space so as to match the target value for the supply rate of boiler feedwater. On the other hand, if the amount of boiler feedwater supplied to the superheater by the supply unit becomes relatively large, the amount of heat exchange in the evaporator and the economizer decreases and the amount of reheating fuel consumed in the auxiliary burner increases. Therefore, the target value for the adjustment amount to be made by the flow rate adjuster is set in a direction that decreases the flow rate of exhaust gas in the first space. In this way, when the supply rate of boiler feedwater to the superheater by the supply unit fluctuates, the target value of the adjustment rate by the flow rate regulator also fluctuates to match the target value of the boiler feedwater supply rate, thereby suppressing fluctuations in the boiler feedwater supply rate. Therefore, for example, superheated steam can be generated while maintaining a small and approximately constant amount of boiler feedwater supply. Therefore, it is possible to suppress the consumption of reheating fuel in the auxiliary burner.

[0012] Example 7: The system of any of Examples 1 to 6 may further include a measurement unit configured to measure the temperature of the exhaust gas flowing between the auxiliary burner and the superheater in the first space, and the control unit may be configured to execute a process of calculating a target value for the amount of adjustment by the flow rate adjustment unit so as to increase the flow rate of the exhaust gas in the first space when it is determined that the temperature measured by the measurement unit exceeds a predetermined threshold. In this case, when the temperature measured by the measurement unit exceeds the predetermined threshold, most of the exhaust gas introduced into the duct flows through the first space and is heated by the auxiliary burner, making it difficult for the temperature of the exhaust gas flowing through the first space to increase. Therefore, it is possible to automatically prevent, for example, a situation in which the temperature of the exhaust gas exceeds the heat resistance temperature of the duct or the auxiliary burner.

[0013] Example 8. The system of any one of Examples 1 to 7 may further include a gas turbine configured to generate power by burning combustion gas and introduce the burned gas as exhaust gas into the inlet of the duct, and the control unit may be configured to execute a process of calculating a target value for the adjustment amount by the flow rate adjuster based on the load factor of the gas turbine. In this case, the same effects as in Example 5 can be obtained. However, when the load factor of the gas turbine decreases, the flow rate of the exhaust gas introduced into the duct decreases, which can cause the exhaust gas to be excessively heated by the auxiliary burner and become too hot. However, in Example 8, the target value is calculated based on the load factor of the gas turbine. For example, when the load factor of the gas turbine is relatively small, the target value is set to increase the flow rate of the exhaust gas in the first space. On the other hand, when the load factor of the gas turbine is relatively large, the target value is set to decrease the flow rate of the exhaust gas in the first space. Therefore, even if the load factor of the gas turbine fluctuates, fluctuations in the temperature of the exhaust gas flowing through the first space are suppressed. Therefore, superheated steam that meets the conditions for generating superheated steam can be generated. Furthermore, it is possible to automatically prevent situations such as a sudden drop in the load factor of a gas turbine due to a power outage or the like, causing the temperature of exhaust gas to exceed the heat resistance temperature of the duct or auxiliary burner.

[0014] Example 9: In the system of Example 8, the process of calculating the target value based on the load factor of the gas turbine may include setting the target value so that the flow rate of the exhaust gas in the first space becomes an estimated flow rate calculated in advance according to the load factor of the gas turbine. In this case, for example, by calculating in advance an estimated adjustment amount by the flow rate adjustment unit under conditions such as a gas turbine load factor of 25%, 50%, 75%, or 100% using heat transfer calculation, the target value can be set without adding a device such as a sensor. Therefore, it is possible to suppress fluctuations in the temperature of the exhaust gas flowing through the first space through feedforward control while suppressing costs.

[0015] Example 10: In any of the systems of Examples 6 to 9, the control unit may be configured to execute a process of adjusting the adjustment amount by the flow rate adjuster using the minimum value among target values ​​calculated based on a plurality of factors. In this case, for example, the value that maximizes the increase in the flow rate of the exhaust gas in the first space is selected as the target value. Therefore, it becomes possible to automatically prevent a sudden increase in the temperature of the exhaust gas in the first space through control.

[0016] Example 11: In the system of Example 10, the control unit may be configured to execute a process of stopping the integral calculation for the remaining elements among the multiple elements whose target values ​​are not the minimum value. In this case, deviations do not accumulate over time in the target values ​​calculated based on the remaining elements, so the target values ​​do not fluctuate significantly over time. Therefore, when the initial target value selected as the minimum value increases over time, the target value that becomes the minimum value is switched at an appropriate time. This makes it possible to more precisely control the temperature of the exhaust gas in the first space.

[0017] Example 12: In any of the systems of Examples 6 to 11, the control unit may be configured to execute a process of gradually changing the adjustment amount by the flow rate adjustment unit until the calculated target value is reached. In this case, since the target value changes gradually, the temperature of the exhaust gas in the first space also changes gradually. Therefore, it is possible to prevent a situation in which thermal stress occurs in a duct or the like due to a sudden change in the temperature of the exhaust gas in the first space.

[0018] Example 13. The system of any of Examples 1 to 5 may further include a supply unit configured to supply boiler feedwater to the superheater, a measurement unit configured to measure the temperature of exhaust gas flowing between the auxiliary burner and the superheater in the first space, and a gas turbine configured to generate electricity by burning combustion gas and introduce the burned gas as exhaust gas into an inlet of a duct, wherein the control unit may be configured to execute the following processes: a first process of calculating a first target value for the adjustment amount to be made by the flow rate adjustment unit based on the load factor of the gas turbine; a second process of calculating a second target value for the adjustment amount to be made by the flow rate adjustment unit so as to increase the flow rate of the exhaust gas in the first space when it is determined that the temperature measured by the measurement unit exceeds a predetermined threshold; a third process of calculating a third target value for the adjustment amount to be made by the flow rate adjustment unit based on the amount of boiler feedwater supplied to the superheater by the supply unit; and a fourth process of adjusting the adjustment amount to be made by the flow rate adjustment unit using the minimum of the first target value, the second target value, and the third target value. In this case, the same effects as those of Examples 5 to 8 and Example 10 can be obtained.

[0019] Example 14: In the system of Example 13, the third process may include setting a target value for the amount of adjustment by the flow rate adjuster so that the flow rate of the exhaust gas in the first space becomes an estimated flow rate calculated in advance according to the load factor of the gas turbine. In this case, the same effects as those of Example 9 can be obtained.

[0020] Example 15: In the system of Example 13 or Example 14, the control unit may be configured to further execute a fifth process of stopping the integral calculation for a process that calculates a target value that does not indicate a minimum value among the first to third processes. In this case, the same effects as those of Example 11 can be obtained.

[0021] Example 16: In any of the systems of Examples 13 to 15, the control unit may be configured to execute a process of gradually changing the amount of adjustment by the flow rate adjuster until it reaches a minimum value. In this case, the same effects as in Example 12 can be obtained.

[0022] Example 17: In any of the systems of Examples 1 to 16, the flow rate regulator may be a damper disposed in the second space, and the amount of regulation by the flow rate regulator may be the opening degree of the damper. In this case, it is possible to easily adjust the flow rate of the exhaust gas in the first space with a simple configuration. [Effects of the Invention]

[0023] According to the exhaust heat recovery system according to the present disclosure, it is possible to more efficiently recover exhaust heat as energy. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing an example of an exhaust heat recovery system. [Figure 2] FIG. 2 is a schematic diagram mainly showing the hardware configuration of the controller. [Figure 3] FIG. 3 is a block diagram showing an example of an exhaust heat recovery system. [Figure 4] FIG. 4 is a diagram showing an example of the correspondence relationship between the load factor of the gas turbine and the opening degree of the damper. [Figure 5] FIG. 5 is a schematic diagram partially illustrating another example of an exhaust heat recovery system. DETAILED DESCRIPTION OF THE INVENTION

[0025] In the following description, the same elements or elements having the same functions will be designated by the same reference numerals, and redundant explanations will be omitted. Note that in this specification, when referring to the top, bottom, right, and left of a figure, the directions of the reference numerals in the figure will be used as the reference.

[0026] As illustrated in FIG. 1, the exhaust heat recovery system 1 is, for example, a combined power generation system, and includes a gas turbine power generation system 10, a steam turbine power generation system 20, and a controller Ctr (control unit).

[0027] The gas turbine power generation system 10 includes a compressor 11, a combustor 12, a gas turbine 13, a generator 14, and a load factor sensor SE1.

[0028] The compressor 11 is configured to compress the intake air and supply the compressed air to the combustor 12. The compressor 11 is connected to a gas turbine 13 and a generator 14 via a shaft 15. The combustor 12 is configured to inject fuel supplied via a valve 16 into the compressed air, combust it, and supply the resulting high-temperature, high-pressure combustion gas to the gas turbine 13.

[0029] The gas turbine 13 is rotated by the combustion gas supplied from the combustor 12, and rotates the compressor 11 and the generator 14 through the shaft 15. As a result, electricity is generated in the generator 14, and air is continuously drawn in and compressed in the compressor 11. High-temperature exhaust gas discharged from the gas turbine 13 is supplied to an exhaust heat recovery system 100, which will be described later.

[0030] The load factor sensor SE1 is configured to detect the load factor of the gas turbine 13 based on, for example, the output of the generator 14. The load factor sensor SE1 is configured to transmit a measurement value PV1 of the detected load factor to the controller Ctr.

[0031] The steam turbine power generation system 20 includes a steam turbine 21 , a generator 22 , a condenser 23 , a pump 24 , a water supply tank 25 , a pump 26 , a chimney 27 , and a waste heat recovery facility 100 .

[0032] The steam turbine 21 is connected to the generator 22 via a shaft 28. The steam turbine 21 is rotated by steam generated by heat exchange with the exhaust gas in the exhaust heat recovery equipment 100, and rotates the generator 22 via the shaft 28. As a result, electricity is generated in the generator 22.

[0033] Condenser 23 cools the steam discharged from steam turbine 21 and condenses it into water. Pump 24 is configured to send water stored in condenser 23 to feedwater tank 25. Pump 26 is configured to send water stored in feedwater tank 25 toward exhaust heat recovery system 100 as boiler feedwater. Chimney 27 is connected to exhaust heat recovery system 100, and releases the exhaust gas into the atmosphere after heat exchange with the boiler feedwater in exhaust heat recovery system 100. Note that feedwater tank 25 may store make-up water supplied from another water source in addition to the water from condenser 23.

[0034] The exhaust heat recovery equipment 100 includes a duct 110, a partition 120, a damper 130 (flow rate adjustment section), a coal economizer 140, an evaporator 150, a superheater 160, a valve 170 (supply section), a supporting burner 180, a temperature sensor SE2 (measurement section), a flow rate sensor SE3, a temperature sensor SE4, and a flow rate sensor SE5.

[0035] The duct 110 is a body that fluidly connects the gas turbine 13 and the chimney 27. The duct 110 is configured to allow high-temperature exhaust gas discharged from the gas turbine 13 to flow toward the chimney 27. In the example shown in Fig. 1, the duct 110 extends horizontally, but it may also extend vertically or obliquely.

[0036] The partition 120 is disposed in the duct 110 and is located, for example, on the upstream side of the duct 110 in the flow direction of the exhaust gas (hereinafter simply referred to as the "upstream side"). The partition 120 may be, for example, a box-shaped member extending along the extension direction of the duct 110. In the example shown in FIG. 1, the partition 120 divides the internal space V of the duct 110 in the up-down direction. That is, the partition 120 divides the upstream region of the internal space V of the duct 110 into an upper space V1 (first space) and a lower space V2 (second space). The partition 120 may divide the internal space V of the duct 110 in the horizontal direction, or may divide the internal space V of the duct 110 in a direction intersecting the flow direction of the exhaust gas, for example.

[0037] As illustrated in FIG. 1 , the damper 130 is disposed in the space V2. The damper 130 is configured to operate based on instructions from the controller Ctr and fluidly open or close the space V2. The smaller the opening of the damper 130, the smaller the flow rate of the exhaust gas flowing through the space V2, thereby increasing the flow rate of the exhaust gas flowing through the space V1. On the other hand, the larger the opening of the damper 130, the larger the flow rate of the exhaust gas flowing through the space V2, thereby decreasing the flow rate of the exhaust gas flowing through the space V1. In other words, the flow rate of the exhaust gas in the space V1 can be adjusted depending on the opening of the damper 130.

[0038] Economizer 140 includes a heat transfer tube disposed in duct 110, and is located downstream in the flow direction of the exhaust gas (hereinafter simply referred to as the "downstream side") of partition 120. Economizer 140 is configured to heat boiler feedwater supplied from feedwater tank 25 by pump 26 to a temperature below the boiling point by exchanging heat between the boiler feedwater flowing through the heat transfer tube and the exhaust gas flowing through duct 110.

[0039] The evaporator 150 includes a heat transfer tube disposed in the duct 110, and is located between the partition 120 and the economizer 140. The evaporator 150 is configured to heat the boiler feedwater supplied from the economizer 140 and generate steam by exchanging heat between the boiler feedwater flowing through the heat transfer tube and the exhaust gas flowing through the duct 110. Note that the boiler drum of the evaporator 150 is not shown in FIG. 1.

[0040] The superheater 160 includes a heat transfer tube disposed in the space V1 and is located between the partition 120 and the evaporator 150. That is, the economizer 140, the evaporator 150, and the superheater 160 are arranged in this order from upstream to downstream in the duct 110. The superheater 160 is configured to further heat the steam supplied from the evaporator 150 by exchanging heat between the steam of the boiler feedwater flowing through the heat transfer tube and the exhaust gas flowing through the space V1, thereby generating superheated steam. The superheated steam generated by the superheater 160 is supplied to the steam turbine 21. In this way, the boiler feedwater flows and circulates from the feedwater tank 25 through the pump 26, the economizer 140, the evaporator 150, the superheater 160, the steam turbine 21, the condenser 23, and the pump 24 in this order, while changing phases between liquid and gas.

[0041] The valve 170 is disposed in a bypass flow path 171 (supply section) that connects the inlet side of the economizer 140 and the superheater 160. The valve 170 operates based on instructions from the controller Ctr and is configured to be able to adjust the flow rate of the boiler feedwater flowing through the bypass flow path 171. Therefore, the amount of boiler feedwater supplied to the superheater 160 is adjusted depending on whether the valve 170 is opened or closed.

[0042] The auxiliary burner 180 is disposed in the space V1 and is located upstream of the superheater 160. The auxiliary burner 180 is configured to heat the exhaust gas flowing through the space V1 by burning fuel supplied via a valve 181. As illustrated in FIG. 1 , the source of fuel supplied to the auxiliary burner 180 may be the same as the source of fuel supplied to the combustor 12. Alternatively, the same or different fuel as that supplied to the combustor 12 may also be supplied to the auxiliary burner 180 from a separate source.

[0043] The temperature sensor SE2 is configured to measure the temperature of the exhaust gas flowing in the space V1 between the auxiliary burner 180 and the superheater 160. The temperature sensor SE2 is configured to transmit a measurement value PV2 of the detected temperature to the controller Ctr.

[0044] The flow rate sensor SE3 is configured to detect the flow rate of the boiler feedwater flowing through the bypass flow path 171. The flow rate sensor SE3 is configured to transmit a measurement value PV3 of the detected flow rate to the controller Ctr.

[0045] The temperature sensor SE4 is configured to measure the temperature of the superheated steam flowing from the superheater 160 to the steam turbine 21. The temperature sensor SE4 is configured to transmit a measured value PV4 of the detected temperature to the controller Ctr.

[0046] The flow rate sensor SE5 is configured to detect the flow rate of superheated steam flowing from the superheater 160 to the steam turbine 21. The flow rate sensor SE5 is configured to transmit a measurement value PV5 of the detected flow rate to the controller Ctr.

[0047] The controller Ctr is configured to process data received from the load factor sensor SE1, the temperature sensors SE2 and SE4, and the flow rate sensors SE3 and SE5 to control the opening degree of the damper 130 and the opening degree of the valve 170.

[0048] The hardware of the controller Ctr is configured, for example, by one or more control computers. The hardware configuration of the controller Ctr includes, for example, a processor Ctr1 (arithmetic unit), a memory Ctr2 (storage unit), an input port Ctr3 (input unit), and an output port Ctr4 (output unit), as shown in Fig. 2. The controller Ctr may be configured by electric circuit elements.

[0049] The processor Ctr1 executes programs in cooperation with the memory Ctr2 and performs input and output of signals via the input port Ctr3 and the output port Ctr4, thereby configuring each functional module described below. That is, the processor Ctr1 is configured to generate output signals for driving the damper 130 and the valves 170, 181 based on input signals from the sensors SE1 to SE5. The memory Ctr2 is configured to store programs, input signals, output signals, etc. The input port Ctr3 is configured to transmit input signals from the sensors SE1 to SE5 to the processor Ctr1. The output port Ctr4 is configured to transmit output signals generated by the processor Ctr1 to the damper 130 and the valves 170, 181.

[0050] As shown in Fig. 3, the controller Ctr includes, as functional modules, a function unit M1, a calculation unit M2, a PID control unit M3, a calculation unit M4, a PID control unit M5, a minimum value selection unit M6, an integral stop unit M7, a variable operation unit M8, a calculation unit M9, a PID control unit M10, a calculation unit M11, and a PID control unit M12. These functional modules merely divide the functions of the controller Ctr into multiple modules for convenience, and do not mean that the hardware constituting the controller Ctr is divided into such modules. Each functional module is not limited to being realized by executing a program, but may also be realized by a dedicated electric circuit (e.g., a logic circuit) or an integrated circuit (ASIC: Application Specific Integrated Circuit) integrating such circuits.

[0051] The function unit M1 is configured to calculate a manipulated variable MV1 (first target value) for the opening of the damper 130 based on a measured value PV1 of the load factor of the gas turbine 13 detected by the load factor sensor SE1 and a preset function. As illustrated in FIG. 4, this function indicates the correspondence relationship between the load factor of the gas turbine 13 and the opening of the damper 130. That is, when the measured value PV1 is input, the function unit M1 calculates, as a target value, the manipulated variable MV1 for the opening of the damper 130 that corresponds to the measured value PV1. The function unit M1 is configured to output the calculated manipulated variable MV1 to a minimum value selection unit M6.

[0052] Incidentally, when the load factor of the gas turbine 13 decreases, the flow rate of the exhaust gas introduced into the duct 110 decreases. As a result, the exhaust gas is excessively heated by the auxiliary burner 180, and the exhaust gas tends to become relatively hot. In this case, by reducing the aperture of the damper 130 and increasing the flow rate of the exhaust gas flowing through the space V1, the increase in the temperature of the exhaust gas in the space V1 is suppressed. Conversely, when the load factor of the gas turbine 13 increases, the flow rate of the exhaust gas introduced into the duct 110 increases. As a result, the exhaust gas is less likely to be heated by the auxiliary burner 180, and the exhaust gas tends to become relatively cold. In this case, by increasing the aperture of the damper 130 and decreasing the flow rate of the exhaust gas flowing through the space V1, the decrease in the temperature of the exhaust gas in the space V1 is suppressed. In other words, by adjusting the aperture of the damper 130 according to the load factor of the gas turbine 13, the temperature of the exhaust gas in the space V1 can be controlled. In this way, there is a correspondence relationship between the load factor of the gas turbine 13 and the opening degree of the damper 130 (the flow rate of exhaust gas in the space V1), and this correspondence relationship can be estimated in advance by simulation (heat transfer calculation). The function of the function section M1 may be obtained by, for example, calculating in advance by heat transfer calculation the estimated opening degree of the damper 130 (the estimated flow rate of exhaust gas in the space V1) under conditions such as the load factor of the gas turbine 13 being 25%, 50%, 75%, and 100%.

[0053] The estimated opening of the damper 130 according to the load factor of the gas turbine 13 may take on different values ​​depending on external conditions. Therefore, the function unit M1 may hold a plurality of functions according to the external conditions. When calculating the estimated opening of the damper 130, the function unit M1 may select a function that best suits the external conditions at that time. Examples of the external conditions include the type (model) of the gas turbine 13, the intake temperature of the gas turbine 13, the steam conditions of the steam turbine 21, and the arrangement of the heat transfer tubes.

[0054] The calculation unit M2 is configured to calculate a deviation PV2-Tth between a threshold value Tth of the temperature of the exhaust gas flowing through the space V1 and a measured value PV2 of the temperature of the exhaust gas detected by the temperature sensor SE2. The calculation unit M2 is configured to output the calculated value to the PID control unit M3. The threshold value Tth may be any value input in advance by an operator. The threshold value Tth may be, for example, approximately 800°C.

[0055] The calculation unit M2 may be configured to output 0 when the deviation is negative, and to output the deviation to the PID control unit M3 when the deviation is equal to or greater than 0. That is, the calculation unit M2 may be configured to determine whether the measured value PV2 exceeds a predetermined threshold value Tth. The threshold value Tth may be set to a value according to the heat resistance temperature of the exhaust heat recovery equipment 100 (e.g., the duct 110, the auxiliary burner 180, etc.).

[0056] The PID control unit M3 is configured to perform PID calculations on the output from the calculation unit M2 and calculate an operation amount MV2 (second target value) for the opening of the damper 130. The PID control unit M3 is configured to output the calculated operation amount MV2 to the minimum value selection unit M6.

[0057] Incidentally, when the calculation unit M2 outputs 0, the exhaust gas in the space V1 does not affect the exhaust heat recovery equipment 100. In this case, the PID control unit M3 calculates a value that does not change the current opening degree of the damper 130 as the manipulated variable MV2. As a result, the current opening degree of the damper 130 is maintained.

[0058] On the other hand, if a positive deviation is output from the calculation unit M2, there is a possibility that the heat of the exhaust gas in the space V1 will affect the exhaust heat recovery equipment 100, such as by thermal distortion. In this case, the PID control unit M3 calculates an operation value MV2 of a magnitude that reduces the opening of the damper 130 in accordance with the deviation. This increases the flow rate of the exhaust gas in the space V1 and reduces the temperature in the space V1, thereby suppressing the effect of the heat of the exhaust gas in the space V1 on the exhaust heat recovery equipment 100. In other words, the PID control unit M3 may be configured to increase the flow rate of the exhaust gas in the space V1 when it is determined that the measurement value PV2 measured by the temperature sensor SE2 exceeds the threshold value Tth.

[0059] The calculation unit M4 is configured to calculate the deviation SV1-PV3 between a predetermined target value SV1 and a measured value PV3 of the boiler feedwater flow rate detected by the flow sensor SE3. The calculation unit M4 is configured to output the calculated value to the PID control unit M5. The target value SV1 may be any value input in advance by an operator. The target value SV1 may be, for example, approximately 1 ton / h.

[0060] The PID control unit M5 is configured to perform PID calculations on the output from the calculation unit M4 and calculate an operation amount MV3 (third target value) for the opening of the damper 130. The PID control unit M5 is configured to output the calculated operation amount MV3 to a minimum value selection unit M6.

[0061] For example, when the measured value PV3 is equal to or less than the target value SV1 (when the deviation is equal to or greater than 0), the amount of boiler feedwater supplied to the superheater 160 is relatively small, which raises concerns about temperature fluctuations in the steam flowing through the superheater 160. Therefore, a manipulated variable MV3 is calculated to reduce the opening of the damper 130. When the opening of the damper 130 is controlled based on the manipulated variable MV3 calculated in this manner, the flow rate of the exhaust gas in the space V1 increases, which increases the amount of heat exchanged between the exhaust gas in the space V1 and the steam flowing through the superheater 160, thereby increasing the amount of boiler feedwater supplied to the superheater 160. On the other hand, when the measured value PV3 is greater than the target value SV1 (when the deviation is negative), the amount of boiler feedwater supplied to the superheater 160 is relatively large, which reduces the amount of heat exchanged in the evaporator 150 and the economizer 140 and increases the amount of reheating fuel consumed by the auxiliary burner 180. Therefore, a manipulated variable MV3 is calculated to increase the opening of the damper 130. When the opening of the damper 130 is controlled based on the manipulated variable MV3 calculated in this manner, the flow rate of the exhaust gas in the space V1 decreases, and the amount of heat exchanged between the exhaust gas in the space V1 and the steam flowing through the superheater 160 decreases, thereby decreasing the amount of boiler feedwater supplied to the superheater 160. In other words, the PID control unit M5 may be configured to calculate the manipulated variable MV3 based on a target value of the amount of boiler feedwater supplied to the superheater 160.

[0062] The minimum value selection unit M6 is configured to select the smallest manipulated variable as a minimum value MVmin from the manipulated variable MV1 calculated in the function unit M1, the manipulated variable MV2 calculated in the PID control unit M3, and the manipulated variable MV3 calculated in the PID control unit M5. The minimum value selection unit M6 is configured to output the selected minimum value MVmin to the variable manipulation unit M8. The minimum value selection unit M6 is configured to identify elements (hereinafter referred to as "remaining elements") that have calculated manipulated variables that do not indicate the minimum value MVmin among the function unit M1, the PID control unit M3, and the PID control unit M5, and to output the information about them to the integration stop unit M7.

[0063] The integral stop unit M7 is configured to stop the integral calculation of the remaining elements based on the information output from the minimum value selection unit M6. For example, when the minimum value selection unit M6 selects the manipulated variable MV1 as the minimum value MVmin, the integral stop unit M7 may output an integral calculation stop signal to the PID control unit M3,5 that includes the integral calculation. When the minimum value selection unit M6 selects the manipulated variable MV2 as the minimum value MVmin, the integral stop unit M7 may output an integral calculation stop signal to the PID control unit M5 that includes the integral calculation. When the minimum value selection unit M6 selects the manipulated variable MV3 as the minimum value MVmin, the integral stop unit M7 may output an integral calculation stop signal to the PID control unit M3 that includes the integral calculation.

[0064] Here, assume that, in the absence of the integral stop unit M7 (i.e., when the integral calculation is not stopped), the manipulated variable MV1 is calculated as 60%, the manipulated variable MV2 is calculated as 45%, and the manipulated variable MV3 is calculated as 50%, and the minimum value selector M6 selects the manipulated variable MV2 as the minimum value MVmin. In this case, the PID control unit M5 continues the integral calculation while the deviation SV1-PV3 remains. Therefore, the manipulated variable MV3 calculated by the PID control unit M5 increases from 50% over time. Therefore, the minimum value selector M6 continues to select the manipulated variable MV2 as the minimum value MVmin until the manipulated variable MV2 surpasses the magnitude of the increased manipulated variable MV3. On the other hand, if the integral calculation of the PID control unit M5 is stopped by the integral stop unit M7, the manipulated variable MV3 calculated by the PID control unit M5 remains at 50% even over time. Therefore, the minimum value selector M6 selects the manipulated variable MV3 as the minimum value MVmin when the manipulated variable MV2 exceeds 50%.

[0065] The variable operating unit M8 is configured to calculate a corrected manipulated variable MV by correcting the minimum value MVmin selected by the minimum value selection unit M6, and to adjust the opening degree of the damper 130 based on the calculated corrected manipulated variable MV.

[0066] For example, the variable manipulation unit M8 may calculate the corrective manipulation amount MV so that the opening of the damper 130 gradually changes until it reaches a minimum value MVmin. As one example, the variable manipulation unit M8 may calculate the corrective manipulation amount MV so that the opening of the damper 130 is changed continuously or intermittently by a change rate of α% (e.g., 10%) per minute until it reaches the minimum value MVmin. The variable manipulation unit M8 may variably manipulate the opening of the damper 130 only when the current opening of the damper 130 is greater than the minimum value MVmin, that is, only when the opening of the damper 130 is adjusted so that the opening of the damper 130 becomes smaller.

[0067] The calculation unit M9 is configured to calculate the deviation SV2-PV4 between a predetermined target value SV2 and a measured value PV4 of the temperature of the superheated steam detected by the temperature sensor SE4. The calculation unit M9 is configured to output the calculated value to the PID control unit M10. The target value SV2 may be any value set in accordance with the steam conditions of the steam turbine 21. The target value SV2 may be, for example, approximately 540°C to 550°C.

[0068] The PID control unit M10 is configured to perform PID calculations on the output from the calculation unit M9 and calculate a manipulated variable MV4 for the opening of the valve 170. The PID control unit M10 is configured to adjust the opening of the valve 170 based on the calculated manipulated variable MV4.

[0069] For example, when the measured value PV4 is equal to or less than the target value SV2 (when the deviation is 0 or more), the manipulated variable MV4 is calculated to reduce the opening of the valve 170. This reduces the amount of boiler feedwater supplied to the superheater 160, making it more difficult for the superheated steam to be cooled by the boiler feedwater, thereby accelerating the temperature rise of the superheated steam. On the other hand, when the measured value PV4 is greater than the target value SV2 (when the deviation is negative), the manipulated variable MV4 is calculated to increase the opening of the valve 170. This increases the amount of boiler feedwater supplied to the superheater 160, making it more difficult for the superheated steam to be cooled by the boiler feedwater, thereby accelerating the temperature drop of the superheated steam.

[0070] The calculation unit M11 is configured to calculate a deviation SV3-PV5 between a predetermined target value SV3 and a measured value PV5 of the flow rate of superheated steam detected by the flow sensor SE5. The calculation unit M11 is configured to output the calculated value to the PID control unit M12. The target value SV3 may be any value set in accordance with the steam conditions of the steam turbine 21. The target value SV3 may be, for example, approximately 70 tons / h to 100 tons / h.

[0071] The PID control unit M12 is configured to perform PID calculations on the output from the calculation unit M11 and calculate a manipulated variable MV5 for the opening of the valve 181. The PID control unit M12 is configured to adjust the opening of the valve 181 based on the calculated manipulated variable MV5.

[0072] For example, when the measured value PV5 is equal to or less than the target value SV3 (when the deviation is 0 or more), an operation amount MV5 is calculated to increase the opening of the valve 181. This increases the amount of fuel supplied to the auxiliary burner 180, and more superheated steam is generated in the exhaust heat recovery equipment 100. On the other hand, when the measured value PV5 is greater than the target value SV3 (when the deviation is negative), an operation amount MV5 is calculated to decrease the opening of the valve 181. This reduces the amount of fuel supplied to the auxiliary burner 180, and the amount of superheated steam generated in the exhaust heat recovery equipment 100 is suppressed.

[0073] [Effect] According to the above example, the interior of the duct 110 is divided into a space V1 and a space V2 by the partition 120, the auxiliary burner 180 and the superheater 160 are disposed in the space V1, and the flow rate of the exhaust gas flowing through the space V1 is adjusted by the damper 130. Therefore, a portion of the exhaust gas introduced into the duct 110 flows through the space V1 and is heated by the auxiliary burner 180, and then heats the steam in the superheater 160. Therefore, an appropriate amount of exhaust gas can be heated to an appropriate temperature by the auxiliary burner 180 depending on the conditions for generating superheated steam. As a result, consumption of reheating fuel in the auxiliary burner 180 is suppressed, making it possible to more efficiently recover exhaust heat as energy.

[0074] According to the above example, the partition 120 is disposed in the duct 110 so as to extend along the extension direction of the duct 110. Therefore, compared to a configuration in which the partition 120 is not present, a decrease in the flow velocity of the exhaust gas flowing in the space V1 is suppressed. Therefore, the exhaust gas is likely to become turbulent in the space V1, and the thermal boundary layer becomes thinner, thereby improving the efficiency of heat exchange between the exhaust gas and the superheater 160. As a result, it is possible to make the superheater 160 more compact.

[0075] According to the above example, the gas used for power generation in the gas turbine 13 can be further used to generate superheated steam in the exhaust heat recovery equipment 100. This makes it possible to further improve the energy efficiency of the entire exhaust heat recovery system 1.

[0076] According to the above example, when the temperature of the superheated steam generated in the superheater 160 fluctuates, the opening of the valve 170 is adjusted accordingly, and the amount of boiler feedwater supplied to the superheater 160 fluctuates. The PID control unit M5 can be configured to calculate the manipulated variable MV3 based on the amount of boiler feedwater supplied to the superheater 160. In this case, fluctuations in the amount of boiler feedwater supplied to the superheater 160 can be suppressed. Therefore, for example, superheated steam can be generated while maintaining the supply amount at a small and substantially constant amount. Therefore, it is possible to suppress the amount of reheating fuel consumed in the auxiliary burner 180.

[0077] According to the above example, the PID control unit M3 can be configured to increase the flow rate of the exhaust gas in the space V1 when it is determined that the measurement value PV2 measured by the temperature sensor SE2 exceeds the threshold value Tth. In this case, when the measurement value PV2 measured by the temperature sensor SE2 exceeds the threshold value Tth, most of the exhaust gas introduced into the duct 110 flows through the space V1 and is heated by the auxiliary burner 180, making it difficult for the temperature of the exhaust gas flowing through the space V1 to increase. Therefore, it is possible to automatically prevent, by control, a situation in which the temperature of the exhaust gas exceeds the heat resistance temperature of the duct 110 or the auxiliary burner 180.

[0078] According to the above example, the manipulated variable MV1 of the opening of the damper 130 can be set based on the measured value PV1 of the load factor of the gas turbine 13 detected by the load factor sensor SE1. Therefore, even if the load factor of the gas turbine 13 fluctuates, fluctuations in the temperature of the exhaust gas flowing through the space V1 are suppressed. Therefore, superheated steam that meets the steam conditions can be generated. Furthermore, it is possible to automatically prevent, through control, a situation in which the load factor of the gas turbine 13 suddenly drops due to a power outage or the like, causing the temperature of the exhaust gas to exceed the heat resistance temperature of the duct 110 or the auxiliary combustion burner 180.

[0079] According to the above example, the manipulated variable MV1 of the opening of the damper 130 can be calculated based on the measured value PV1 of the load factor of the gas turbine 13 detected by the load factor sensor SE1 and a preset function. In this case, for example, by estimating in advance the correspondence relationship between the load factor of the gas turbine 13 and the opening of the damper 130 (the flow rate of exhaust gas in the space V1) through a simulation (heat transfer calculation), the manipulated variable MV1 of the opening of the damper 130 can be set without adding a device such as a sensor. Therefore, it is possible to suppress fluctuations in the temperature of the exhaust gas flowing through the space V1 through feedforward control while suppressing costs.

[0080] According to the above example, the minimum value selection unit M6 can be configured to select the smallest manipulated variable from among the manipulated variables MV1 to MV3 as the minimum value MVmin. In this case, for example, the value at which the flow rate of the exhaust gas in the space V1 increases the most is selected as the minimum value MVmin. Therefore, it is possible to automatically prevent a sudden rise in the temperature of the exhaust gas in the space V1 through control.

[0081] According to the above example, the integral stop unit M7 can be configured to stop the integral calculation of the remaining elements based on the information output from the minimum value selection unit M6. In this case, deviations do not accumulate over time in the manipulated variable (manipulated variable MV2 or manipulated variable MV3) calculated based on the remaining elements, so the manipulated variable does not fluctuate significantly over time. Therefore, when the manipulated variable initially selected as the minimum value MVmin increases over time, the manipulated variable with the minimum value is switched at an appropriate timing. This makes it possible to more precisely control the temperature of the exhaust gas in space V1.

[0082] According to the above example, the variable manipulation unit M8 can calculate the corrective manipulation amount MV so that the opening of the damper 130 gradually changes until it reaches the minimum value MVmin. In this case, since the corrective manipulation amount MV changes gradually, the temperature of the exhaust gas in the space V1 also changes gradually. This makes it possible to prevent a situation in which thermal stress occurs in the duct 110, etc., due to a sudden change in the temperature of the exhaust gas in the space V1.

[0083] According to the above example, the opening degree of the damper 130 arranged in the space V2 is adjusted to adjust the flow rate of the exhaust gas in the space V1. In this case, it is possible to easily adjust the flow rate of the exhaust gas in the space V1 with a simple configuration.

[0084] [Variations] The disclosure in this specification should be considered to be illustrative in all respects and not restrictive. Various omissions, substitutions, modifications, etc. may be made to the above examples without departing from the scope and spirit of the claims.

[0085] (1) The partition 120 may be installed inside the duct 110 when constructing a new exhaust heat recovery system 100. Alternatively, the exhaust heat recovery system 100 according to the present disclosure may be constructed by adding the partition 120 inside the duct 110 of an existing exhaust heat recovery system that does not have the partition 120. In the latter case, the effects of the exhaust heat recovery system 100 according to the present disclosure can be obtained by the extremely simple modification work of adding the partition 120 inside the duct 110.

[0086] (2) If the flow rate of the exhaust gas in the space V1 can be adjusted, the damper 130 may be disposed in the space V1, may be disposed in the space V2, or may be disposed in both the spaces V1 and V2. Furthermore, if the flow rate of the exhaust gas in the space V1 can be adjusted, other means (for example, a valve) may be employed instead of or together with the damper 130.

[0087] (3) As in the above example, the superheater 160 does not have to be disposed in the space V2. In this case, the effects of the exhaust heat recovery system 100 according to the present disclosure can be more significantly obtained. Alternatively, a portion of the superheater 160 may also be disposed in the space V2.

[0088] (4) The bypass flow path 171 may be connected to the inlet of the superheater 160 instead of the middle of the superheater 160, or may be connected to the outlet of the superheater 160.

[0089] (5) As illustrated in Figures 1 and 5, the upstream end of the duct 110 may be an expanding section in which the flow path expands from the upstream side to the downstream side. In this case, as illustrated in Figure 5, the partition 120 may also be disposed in the expanding section. Alternatively, the duct 110 may not have such an expanding section. In other words, the flow path cross-sectional area of ​​the duct 110 may be approximately constant in the extension direction of the duct 110.

[0090] (6) As illustrated in FIG. 5 , a heat transfer tube 121 extending inside the partition 120 may be disposed inside the partition 120. One end of the heat transfer tube 121 may be fluidly connected to the water supply tank 25, and the other end of the heat transfer tube 121 may be fluidly connected to the economizer 140 or the evaporator 150. In this case, the boiler feedwater supplied from the water supply tank 25 exchanges heat with the exhaust gas from the gas turbine 13 while flowing through the heat transfer tube 121, and is supplied to the economizer 140 or the evaporator 150. Therefore, heat can be recovered from the exhaust gas in the partition 120 as well and used to heat the boiler feedwater. This makes it possible to more efficiently recover exhaust heat as energy.

[0091] (7) As illustrated in Fig. 5, at least one rectifying member 190 may be disposed within the space V1 and upstream of the auxiliary burner 180. The rectifying member 190 is configured to rectify the flow of exhaust gas toward the auxiliary burner 180. In this case, the rectifying member 190 makes it easier for the exhaust gas to flow toward the auxiliary burner 180. Therefore, the exhaust gas can be effectively heated by the auxiliary burner 180.

[0092] When multiple rectifying members 190 are arranged in the space V1, the multiple rectifying members 190 may be lined up along a cross direction that crosses the flow direction of the exhaust gas. The multiple rectifying members 190 may be lined up at approximately equal intervals in the cross direction, or may be lined up at different intervals.

[0093] (8) As illustrated in Fig. 5, when the auxiliary burner 180 has a plurality of nozzles 182, the plurality of nozzles 182 may be aligned along a cross direction that intersects with the flow direction of the exhaust gas. The plurality of nozzles 182 may be aligned at approximately equal intervals in the cross direction, or may be aligned at different intervals. [Explanation of symbols]

[0094] 1...waste heat recovery system, 10...gas turbine power generation system, 13...gas turbine, 20...steam turbine power generation system, 100...waste heat recovery equipment, 110...duct, 120...partition section, 121...heat transfer tube, 130...damper (flow rate adjustment section), 140...coal economizer, 150...evaporator, 160...superheater, 170...valve (supply section), 171...bypass flow path (supply section), 180...support burner, 181...valve, 190...rectifying member , Ctr...controller (control section), M1...function section, M2...calculation section, M4...calculation section, M6...minimum value selection section, M7...integration stop section, M8...variable operation section, MV1...operated variable (first target value), MV2...operated variable (second target value), MV3...operated variable (third target value), SE1...load factor sensor, SE2...temperature sensor (measurement section), SE3...flow rate sensor, V...internal space, V1...space (first space), V2...space (second space).

Claims

1. A waste heat recovery system that uses the heat of exhaust gas to heat boiler feedwater and generate steam, a duct configured to allow the exhaust gas to flow; a partition portion extending along the extension direction of the duct and configured to divide an internal space of the duct into a first space and a second space; an evaporator disposed in the duct so as to be located downstream of the partition portion in a flow direction of the exhaust gas, and configured to generate steam from boiler feedwater; a superheater that is disposed in the first space and upstream of the evaporator in the flow direction of the exhaust gas, and that is configured to further heat steam supplied from the evaporator by the exhaust gas flowing through the first space to generate superheated steam; an economizer disposed in the duct so as to be located downstream of the evaporator in the flow direction of the exhaust gas, and configured to preheat the boiler feedwater and supply the boiler feedwater to the evaporator; an auxiliary burner disposed in the first space and upstream of the superheater in the flow direction of the exhaust gas, and configured to heat the exhaust gas flowing through the first space; a flow rate adjusting unit configured to adjust the flow rate of the exhaust gas in the first space; a control unit configured to control an adjustment amount by the flow rate adjustment unit; a heat transfer pipe provided to extend inside the partition portion and configured to supply boiler feedwater after circulating inside the partition portion to the evaporator or the economizer.

2. A waste heat recovery system that uses the heat of exhaust gas to heat boiler feed water and generate steam, a duct configured to allow the exhaust gas to flow; a partition portion extending along the extension direction of the duct and configured to divide an internal space of the duct into a first space and a second space; an evaporator disposed in the duct so as to be located downstream of the partition portion in a flow direction of the exhaust gas, and configured to generate steam from boiler feedwater; a superheater that is disposed in the first space and upstream of the evaporator in the flow direction of the exhaust gas, and that is configured to further heat steam supplied from the evaporator by the exhaust gas flowing through the first space to generate superheated steam; an economizer disposed in the duct so as to be located downstream of the evaporator in the flow direction of the exhaust gas, and configured to preheat the boiler feedwater and supply the boiler feedwater to the evaporator; an auxiliary burner disposed in the first space and upstream of the superheater in the flow direction of the exhaust gas, and configured to heat the exhaust gas flowing through the first space; a flow rate adjusting unit configured to adjust the flow rate of the exhaust gas in the first space; a control unit configured to control an adjustment amount by the flow rate adjustment unit; a supply unit configured to supply boiler feedwater to the superheater; The control unit is configured to execute a process of calculating a target value for the amount of adjustment by the flow rate adjustment unit based on the amount of boiler feedwater supplied to the superheater by the supply unit.

3. a measuring unit configured to measure a temperature of the exhaust gas flowing between the auxiliary burner and the superheater in the first space, The system described in claim 2, wherein the control unit is configured to, when it determines that the temperature measured by the measurement unit exceeds a predetermined threshold, execute a process of calculating a target value for the adjustment amount by the flow rate adjustment unit so that the flow rate of the exhaust gas in the first space increases.

4. A waste heat recovery system that uses the heat of exhaust gas to heat boiler feed water and generate steam, a duct configured to allow the exhaust gas to flow; a partition portion extending along the extension direction of the duct and configured to divide an internal space of the duct into a first space and a second space; an evaporator disposed in the duct so as to be located downstream of the partition portion in a flow direction of the exhaust gas, and configured to generate steam from boiler feedwater; a superheater that is disposed in the first space and upstream of the evaporator in the flow direction of the exhaust gas, and that is configured to further heat steam supplied from the evaporator by the exhaust gas flowing through the first space to generate superheated steam; an economizer disposed in the duct so as to be located downstream of the evaporator in the flow direction of the exhaust gas, and configured to preheat the boiler feedwater and supply the boiler feedwater to the evaporator; an auxiliary burner disposed in the first space and upstream of the superheater in the flow direction of the exhaust gas, and configured to heat the exhaust gas flowing through the first space; a flow rate adjusting unit configured to adjust the flow rate of the exhaust gas in the first space; a control unit configured to control an adjustment amount by the flow rate adjustment unit; a measurement unit configured to measure the temperature of the exhaust gas flowing between the auxiliary burner and the superheater in the first space, The control unit is configured to execute a process of calculating a target value for the adjustment amount by the flow rate adjustment unit so that the flow rate of the exhaust gas in the first space increases when it determines that the temperature measured by the measurement unit exceeds a predetermined threshold.

5. a gas turbine configured to generate electricity by burning combustion gas and to introduce the gas after combustion into the inlet of the duct as the exhaust gas; The system according to claim 4 , wherein the control unit is configured to execute a process of calculating a target value of an adjustment amount to be performed by the flow rate adjustment unit based on a load factor of the gas turbine.

6. A waste heat recovery system that uses the heat of exhaust gas to heat boiler feed water and generate steam, a duct configured to allow the exhaust gas to flow; a partition portion extending along the extension direction of the duct and configured to divide an internal space of the duct into a first space and a second space; an evaporator disposed in the duct so as to be located downstream of the partition portion in a flow direction of the exhaust gas, and configured to generate steam from boiler feedwater; a superheater that is disposed in the first space and upstream of the evaporator in the flow direction of the exhaust gas, and that is configured to further heat steam supplied from the evaporator by the exhaust gas flowing through the first space to generate superheated steam; an economizer disposed in the duct so as to be located downstream of the evaporator in the flow direction of the exhaust gas, and configured to preheat the boiler feedwater and supply the boiler feedwater to the evaporator; an auxiliary burner disposed in the first space and upstream of the superheater in the flow direction of the exhaust gas, and configured to heat the exhaust gas flowing through the first space; a flow rate adjusting unit configured to adjust the flow rate of the exhaust gas in the first space; a control unit configured to control an adjustment amount by the flow rate adjustment unit; a gas turbine configured to generate power by burning combustion gas and to introduce the gas after combustion into the inlet of the duct as the exhaust gas, The control unit is configured to execute a process of calculating a target value of an adjustment amount to be performed by the flow rate adjustment unit based on a load factor of the gas turbine.

7. 7. The system according to claim 5, wherein the process of calculating the target value based on a load factor of the gas turbine includes setting the target value so that a flow rate of the exhaust gas in the first space becomes an estimated flow rate calculated in advance in accordance with a load factor of the gas turbine.

8. The system according to any one of claims 2 to 7, wherein the control unit is configured to execute a process of adjusting the amount of adjustment by the flow rate adjustment unit using the minimum value of the target values ​​calculated based on multiple factors.

9. The system according to claim 8 , wherein the control unit is configured to execute processing to stop integration operations for remaining elements of the plurality of elements whose target values ​​do not indicate the minimum value.

10. The system according to any one of claims 2 to 9, wherein the control unit is configured to execute a process of gradually changing the amount of adjustment by the flow rate adjustment unit until the calculated target value is reached.

11. A waste heat recovery system that uses heat from exhaust gas to heat boiler feed water and generate steam, a duct configured to allow the exhaust gas to flow; a partition portion extending along the extension direction of the duct and configured to divide an internal space of the duct into a first space and a second space; an evaporator disposed in the duct so as to be located downstream of the partition portion in a flow direction of the exhaust gas, and configured to generate steam from boiler feedwater; a superheater that is disposed in the first space and upstream of the evaporator in the flow direction of the exhaust gas, and that is configured to further heat steam supplied from the evaporator by the exhaust gas flowing through the first space to generate superheated steam; an economizer disposed in the duct so as to be located downstream of the evaporator in the flow direction of the exhaust gas, and configured to preheat the boiler feedwater and supply the boiler feedwater to the evaporator; an auxiliary burner disposed in the first space and upstream of the superheater in the flow direction of the exhaust gas, and configured to heat the exhaust gas flowing through the first space; a flow rate adjusting unit configured to adjust the flow rate of the exhaust gas in the first space; a control unit configured to control an adjustment amount by the flow rate adjustment unit; a supply configured to supply boiler feedwater to the superheater; a measurement unit configured to measure the temperature of the exhaust gas flowing between the auxiliary combustion burner and the superheater in the first space; a gas turbine configured to generate power by burning combustion gas and to introduce the gas after combustion into the inlet of the duct as the exhaust gas, The control unit a first process of calculating a first target value of an adjustment amount to be performed by the flow rate adjustment unit based on a load factor of the gas turbine; a second process of calculating a second target value of an adjustment amount to be performed by the flow rate adjuster so that a flow rate of the exhaust gas in the first space increases when it is determined that the temperature measured by the measurement unit exceeds a predetermined threshold value; a third process of calculating a third target value of an adjustment amount by the flow rate adjuster based on an amount of boiler feedwater supplied to the superheater by the supply unit; and a fourth process of adjusting the amount of adjustment by the flow rate adjuster using the smallest value among the first to third target values.

12. 12. The system according to claim 11, wherein the first processing includes setting a target value of an adjustment amount to be performed by the flow rate adjuster so that a flow rate of the exhaust gas in the first space becomes an estimated flow rate calculated in advance according to a load factor of the gas turbine.

13. The system according to claim 11 or 12, wherein the control unit is further configured to execute a fifth process of stopping integral calculation for a process among the first to third processes that calculates a target value that does not indicate the minimum value.

14. The system according to any one of claims 11 to 13, wherein the control unit is configured to execute a process of gradually changing the amount of adjustment by the flow rate adjustment unit until the amount of adjustment reaches the minimum value.

15. The system according to any one of claims 2 to 14, further comprising a heat transfer tube provided to extend inside the partition and configured to supply boiler feedwater after flowing inside the partition to the evaporator or the economizer.

16. The system according to any one of claims 1 to 15, wherein the superheater is not disposed in the second space.

17. The system described in any one of claims 1 to 16, further comprising a straightening member arranged within the first space and upstream of the auxiliary burner in the flow direction of the exhaust gas, and configured to straighten the flow of the exhaust gas toward the auxiliary burner.

18. 18. The system of any one of claims 1 to 17, further comprising a gas turbine configured to generate electricity by combustion of combustion gases and to introduce post-combustion gases into the inlet of the duct as the exhaust gas.

19. the flow rate adjusting unit is a damper disposed in the second space, The system according to any one of claims 1 to 18, wherein the amount of adjustment by the flow rate adjustment unit is the opening degree of the damper.

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