JP7465641B2 - Once-through boiler control device, power plant, and once-through boiler control method - Google Patents

Description

This disclosure relates to a control device for a once-through boiler, a power generation plant, and a control method for a once-through boiler.

Boiler equipment capable of generating steam is used for a variety of purposes, including power plants such as thermal power plants that use steam energy to generate electricity. One type of boiler equipment of this type is known as a once-through boiler.

Patent Document 1 discloses, as an example of a once-through boiler, a once-through boiler equipped with multiple superheaters arranged in series in a flow path through which steam generated in a furnace flows, and multiple sprayers that can be sprayed on the outlet side of each superheater. The once-through boiler disclosed in Patent Document 1 is configured to be able to adjust the steam temperature by controlling the water-fuel ratio so that the steam temperature at the furnace outlet side and the most downstream superheater outlet side reaches a predetermined set value (target steam temperature).

Patent Document 2 also discloses a once-through boiler in which a final attenuator (spray) is arranged between a group of upstream superheaters arranged in series downstream of a steam generator and a final superheater. The once-through boiler disclosed in Patent Document 2 is configured to control the amount of water spray by the final attenuator so that the steam temperature at the outlet side of the final superheater becomes a predetermined set value (final target steam temperature), and to control the amount of fuel combustion so that the temperature upstream of the final attenuator becomes a predetermined set value.

Japanese Patent No. 5840032 Patent No. 4453858

In a once-through boiler such as those described in Patent Documents 1 and 2 above, it is desirable to adjust the amount of heat increase by each superheater for the steam from the furnace water wall, the amount of heat reduction by each spray, and the amount of fuel supplied so that the final steam temperature becomes the target steam temperature, and to perform various controls and adjustments so that the steam temperature profile, which is the temperature distribution at each point in the steam flow path, becomes the ideal design temperature profile.

However, when a once-through boiler is in operation, the heat balance of the once-through boiler can change due to various factors, causing the steam temperature profile to deviate from the design temperature profile. For example, if scale or other contaminants form on the heat transfer surface of the steam flow path over time, the detected steam temperature in the steam flow path can decrease and the superheating performance of the superheater can decrease. In addition, a change in the type of fuel fed into the furnace water wall can increase heat transfer through the furnace water wall and superheater. When the steam temperature profile deviates from the design profile in this way, it can affect the reliability and quality of the once-through boiler, such as affecting the expected lifespan of each component that makes up the once-through boiler.

Some aspects of the present disclosure have been made in consideration of the above circumstances, and aim to provide a once-through boiler control device, a power plant, and a once-through boiler control method that can prevent the steam temperature profile balance from deviating from the design temperature profile as the heat balance conditions of the once-through boiler change.

In order to solve the above problems, a control device for a once-through boiler according to some aspects of the present disclosure includes:
A control device for a once-through boiler capable of adjusting the temperature of steam generated in a furnace water wall and a plurality of superheaters by a plurality of superheaters arranged in series and a plurality of sprayers configured to spray a portion of the water supplied to the furnace water wall to an outlet side of each of the plurality of superheaters,
A spray control unit configured to be able to control the amount of heat reduction of the steam by at least a part of the plurality of sprays to a target amount of heat reduction;
A steam temperature detection unit configured to detect a steam temperature upstream of a spray position of the spray controlled by the spray control unit in the steam flow path in which the plurality of superheaters are provided;
Equipped with
The target deheating amount is set by adding a bias value, which is set based on the deviation between the detection value of the steam temperature detection unit and the target steam temperature, to a basic target deheating amount.

In order to solve the above problems, a power plant according to some aspects of the present disclosure includes:
The once-through boiler;
A control device according to some aspects of the present disclosure;
A turbine configured to be driven by steam from the once-through boiler;
A generator configured to be driven by the turbine;
Equipped with.

In order to solve the above problems, a method for controlling a once-through boiler according to some aspects of the present disclosure includes:
A method for controlling a once-through boiler capable of adjusting the temperature of steam generated in a furnace water wall and a plurality of superheaters by a plurality of superheaters arranged in series and a plurality of sprayers configured to spray a portion of the water supplied to the furnace water wall to an outlet side of each of the plurality of superheaters, comprising:
A spray control process of controlling a temperature reduction amount of the steam by at least a part of the plurality of sprays to be a target temperature reduction amount;
A steam temperature detection process for detecting a steam temperature upstream of a spray position of the spray controlled by the spray control unit in the steam flow path provided with the plurality of superheaters;
Equipped with
The target deheating amount is set by adding a bias value, which is set based on the deviation between the detection value of the steam temperature detection unit and the target steam temperature, to a basic target deheating amount.

According to some aspects of the present disclosure, it is possible to provide a control device for a once-through boiler, a power plant, and a control method for a once-through boiler that can prevent the steam temperature profile balance from deviating from the design temperature profile as the heat balance conditions of the once-through boiler change.

1 is a schematic diagram showing an overall configuration of a power plant according to one embodiment of the present disclosure. FIG. 2 is a schematic diagram showing the configuration of the once-through boiler of FIG. 1 together with a steam temperature profile. FIG. 2 is a block diagram showing an internal configuration of a control device according to an embodiment of the present disclosure. 4 is a flowchart showing each step of a control method for a once-through boiler performed by the control device of FIG. 3 . 4 is an example showing a transition of a steam temperature profile by the control device of FIG. 3. 4 is an example showing a transition of a steam temperature profile by the control device of FIG. 3. 4 is an example showing a transition of a steam temperature profile by the control device of FIG. 3. 5 is another example showing the transition of the steam temperature profile by the control device of FIG. 3 . 5 is another example showing the transition of the steam temperature profile by the control device of FIG. 3 . 5 is another example showing the transition of the steam temperature profile by the control device of FIG. 3 . FIG. 13 is a block diagram showing an internal configuration of a control device according to another aspect of the present disclosure. 8 is a flowchart showing each step of a control method for a once-through boiler performed by the control device of FIG. 7 . 8 is an example showing a transition of a steam temperature profile by the control device of FIG. 7. 8 is an example showing a transition of a steam temperature profile by the control device of FIG. 7. 8 is an example showing a transition of a steam temperature profile by the control device of FIG. 7. 8 is another example showing a transition of a steam temperature profile by the control device of FIG. 7 . 8 is another example showing a transition of a steam temperature profile by the control device of FIG. 7 . 8 is another example showing a transition of a steam temperature profile by the control device of FIG. 7 .

Below, several embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the following embodiments. The dimensions, materials, shapes, relative positions, etc. of the components described in the following embodiments are merely illustrative examples and are not intended to limit the scope of the present invention thereto.

<Power plant>
1 is a schematic diagram showing an overall configuration of a power plant 100 according to one embodiment of the present disclosure. The power plant 100 includes a once-through boiler 1 capable of generating steam, a turbine 110 configured to be driven by the steam from the once-through boiler 1, and a generator 120 configured to be driven by the turbine 110.

The once-through boiler 1 is an example of a steam generator configured to generate steam by burning fuel. The steam generated in the once-through boiler 1 is supplied to the turbine 110 via a steam supply line 112. The turbine 110 is driven by the steam supplied via the steam supply line 112. A generator 120 is connected to the output shaft of the turbine 110, and the rotational energy of the turbine 110 is converted into electrical energy. The electrical energy generated by the generator 120 is supplied to an electric power system (not shown) via a specified path.

A steam valve 114 (main steam valve) is installed in the steam supply passage 112 to adjust the flow rate of steam supplied from the once-through boiler 1 to the turbine 110. The opening of the steam valve 114 is controlled, for example, so that the flow rate of steam supplied from the once-through boiler 1 to the turbine 110 becomes a predetermined target flow rate value set based on the load command value Ld for the power plant 100.

The power plant 100 has a control device 2 for controlling each component of the power plant 100. The control device 2 has a hardware configuration consisting of an electronic computing device such as a computer, and is configured to function as a control device according to some aspects of the present disclosure by installing a program for implementing a control method according to some aspects of the present disclosure.

The control device 2 is a control unit capable of comprehensively controlling the power plant 100. In this specification, of the various types of control that the control device 2 can perform, the control of the once-through boiler 1 will be specifically described, and for other controls, unless otherwise specified, known controls for the power plant 100 can be appropriately performed.

The steam temperature control by the control device 2 is performed so that the steam temperature (the third steam temperature T3SO described below) supplied to the turbine 110 becomes a preset target steam temperature (the third target steam temperature T3SOtarget described below). This target steam temperature (the third target steam temperature T3SOtarget described below) may be set manually by an operator, or may be set automatically based on a predetermined signal received by the control device 2. In the latter case, the target steam temperature (the third target steam temperature T3SOtarget described below) is set according to a load command value Ld acquired by the power plant 100 according to the supply and demand state of the power system to which the power plant 100 supplies power, for example.

<Configuration of once-through boiler>
Next, a specific configuration of the once-through boiler 1 included in the power plant 100 having the above configuration will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the configuration of the once-through boiler 1 in Fig. 1 together with a steam temperature profile.

The once-through boiler 1 has a furnace water wall 4 capable of generating steam. The furnace water wall 4 has a heat transfer tube into which cooling water can be introduced, and is configured to generate steam by heating the cooling water flowing through the heat transfer tube by burning fuel (e.g., pulverized coal produced by crushing coal). Water and fuel are supplied to the furnace water wall 4 by, for example, a water supply pump unit and a fuel supply unit (not shown). The fuel flow rate to the furnace water wall 4 is basically determined according to, for example, the load command value Ld for the power plant 100, but the water-fuel ratio, which is a correction signal for correcting the fuel flow rate according to the deviation between the actually generated steam temperature and the target steam temperature, is controlled as one of the control parameters of the control device 2, as described later.

Downstream of the furnace water wall 4, a plurality of superheaters 6 are provided for superheating the steam generated by the furnace water wall 4. The plurality of superheaters 6 are provided in series with each other with respect to the steam flow path 8 through which the steam from the furnace water wall 4 flows. In the embodiment shown in FIG. 2, the plurality of superheaters 6 include a first superheater 6a, a second superheater 6b, and a third superheater 6c. The first superheater 6a is arranged downstream of the furnace water wall 4, and is configured to be able to superheat the steam generated by the furnace water wall 4. The second superheater 6b is arranged downstream of the first superheater 6a, and is configured to be able to further superheat the steam superheated by the first superheater 6a. The third superheater 6c is arranged downstream of the second superheater 6b, and is configured to be able to further superheat the steam superheated by the second superheater 6b.

Note that, although FIG. 2 illustrates an example in which the once-through boiler 1 has three superheaters 6, the number of superheaters 6 that the once-through boiler 1 has is not limited to this.

The steam flow path 8 is provided with a plurality of sprays 10 configured to spray cooling water onto the steam flowing through the steam flow path 8. In the embodiment of FIG. 2, the plurality of sprays 10 include a first spray 10a provided on the outlet side of the first superheater 6a (between the first superheater 6a and the second superheater 6b) of the steam flow path 8, and a second spray 10b provided on the outlet side of the second superheater 6b (between the second superheater 6b and the third superheater 6c). The first spray 10a sprays cooling water onto the steam from the first superheater 6a to reduce the temperature of the steam heated by the first superheater 6a and adjust the steam temperature. The second spray 10b sprays cooling water onto the steam from the second superheater 6b to reduce the temperature of the steam heated by the second superheater 6b and adjust the steam temperature.

The multiple sprays 10 are configured to be able to spray a portion of the water supply to the furnace water wall 4 to the steam flow path 8. Specifically, a sub-supply water passage 14 that branches off to the spray 10 side is provided in the main water supply passage 12 for the water supply to the furnace water wall 4. The sub-supply water passage 14 is configured to be able to supply water in parallel to each of the multiple sprays 10. In this way, the multiple sprays 10 spray a portion of the water supply supplied to the furnace water wall 4, so that when the amount of spray at the spray 10 increases, the amount of water supply to the furnace water wall 4 decreases, and conversely, when the amount of spray at the spray 10 decreases, the amount of water supply to the furnace water wall 4 increases.

The first spray 10a and the second spray 10b each have a first spray valve 16a and a second spray valve 16b that can be opened and closed to variably adjust the amount of spray. The opening degree of the first spray valve 16a and the second spray valve 16b are configured to be controllable independently of each other based on a control signal from the control device 2.

Note that, although FIG. 2 illustrates an example in which the once-through boiler 1 is equipped with two sprays 10, the number of sprays 10 equipped in the once-through boiler 1 is not limited to this. The number of sprays 10 may be set, for example, so that they are each disposed on the outlet side of the other superheaters 6 except for the most downstream superheater 6.

The steam generated in the furnace water wall 4 is controlled so that the steam temperature supplied from the once-through boiler 1 to the turbine 110 becomes the target steam temperature by adjusting the temperature of the steam using the multiple superheaters 6 and multiple sprays 10. As shown in FIG. 2, the steam from the furnace water wall 4 is first heated to the first steam temperature T1SO by passing through the first superheater 6a. The steam that has passed through the first superheater 6a is cooled by the first spray 10a at the outlet side of the first superheater 6a by the first de-heating amount 1DSDT. The steam cooled by the first spray 10a is then heated to the second steam temperature T2SO by passing through the second superheater 6b. The steam that has passed through the second superheater 6b is cooled by the second spray 10b at the outlet side of the second superheater 6b by the second de-heating amount 2DSDT. The steam cooled by the second spray 10b passes through the third superheater 6c and is heated to the third steam temperature T3SO, which is the final outlet temperature of the once-through boiler 1.

The steam temperature profile shown in FIG. 2 is basically controlled to be the ideal design temperature profile Pr by the control device 2 controlling each component of the once-through boiler 1 (furnace water-cooled wall 4, multiple superheaters 6, and multiple sprays 10) (FIG. 2 shows a state in which the steam temperature profile matches the design temperature profile Pr). Specifically, the control device 2 controls each component of the once-through boiler 1 so that the detection value of a temperature sensor installed at a specified measurement point of the once-through boiler 1 approaches the design temperature profile Pr, thereby managing the steam temperature profile to be the design temperature profile.

However, in an actual once-through boiler 1, the heat balance in the once-through boiler 1 may change due to various factors, causing the steam temperature profile to deviate from the design temperature profile Pr. For example, if scale or other dirt accumulates on the heat transfer surfaces in the once-through boiler 1 over time, the detection value of the temperature sensor installed at a specific measurement point on the once-through boiler 1 may decrease, or the superheating performance of the first superheater 6a to the third superheater 6c may decrease. In addition, if the type of fuel fed into the furnace water wall 4 is changed, the amount of heat transfer by the furnace water wall 4 and the first superheater 6a to the third superheater 6c may increase or decrease. In some embodiments of the present disclosure, when the steam temperature profile deviates from the design temperature profile Pr in this way, the control device 2 controls the once-through boiler 1 so that the steam temperature profile approaches the design temperature profile Pr, as described below.

The steam flow path 8 is configured to be able to detect the steam temperature at each position. Specifically, as shown in FIG. 2, the steam temperature T1SO at the outlet side of the first superheater 6a, the steam temperature T2SO at the outlet side of the second superheater 6b, the steam temperature T3SO at the outlet side of the third superheater 6c, the steam temperature T2SI after cooling by the first spray 10a, and the steam temperature T3SI after cooling by the second spray 10b are each configured to be able to detect. Each of these temperatures is detected by arranging a detection element such as a temperature sensor.

Figure 3 is a block diagram showing the internal configuration of a control device 2 according to one embodiment of the present disclosure, and Figure 4 is a flowchart showing each step of a control method for a once-through boiler 1 implemented by the control device 2 of Figure 3.

As shown in FIG. 3, the control device 2 according to this embodiment includes a water-fuel ratio control unit 50 for controlling the water-fuel ratio of the furnace water-cooled wall 4, a spray control unit 60 for controlling the sprays 10 (first spray 10a and second spray 10b), and a bias value calculation unit 70 for calculating a bias value for the target deheating amount of the spray 10. The spray control unit 60 includes a first spray control unit 60a for controlling the first spray 10a, and a second spray control unit 60b for controlling the second spray 10b.

The water-fuel ratio control unit 50 controls the water-fuel ratio as a fuel flow rate correction so that the third steam temperature T3SO, which is the final steam temperature of the once-through boiler 1, becomes the third target steam temperature T3SOtarget set in advance. Specifically, the water-fuel ratio control unit 50 receives the third steam temperature T3SO, which is an actual measurement value (e.g., the steam temperature detection value downstream of the third superheater 6c in the steam flow path 8) detected at the corresponding location of the once-through boiler 1, and the third target steam temperature T3SOtarget set in advance. The water-fuel ratio control unit 50 calculates the deviation ΔT3SO between the third steam temperature T3SO and the third target steam temperature T3SOtarget, and outputs a water-fuel ratio control signal as a fuel flow rate correction so that the deviation ΔT3SO becomes zero (i.e., so that the third steam temperature T3SO becomes the third target steam temperature T3SOtarget), thereby feedback controlling the water-fuel ratio.

The third target steam temperature T3SOtarget may be set as a steam temperature value required for the once-through boiler 1 according to the load command value Ld.

The second spray control unit 60b controls the second spray 10b so that the third steam temperature T3SO becomes the third target steam temperature T3SOtarget and the second de-heating amount 2DSDT becomes the second target de-heating amount 2DSDTtarget. Specifically, the second spray control unit 60b receives the third steam temperature T3SO, which is an actual measurement value detected at the corresponding location of the once-through boiler 1 (for example, the steam temperature detection value downstream of the third superheater 6c in the steam flow path 8), the preset third target steam temperature T3SOtarget, the second de-heating amount 2DSDT, which is an actual measurement value detected by a sensor at the corresponding location of the once-through boiler 1 (for example, the difference between the steam temperature detection values detected upstream and downstream of the spray position by the second spray 10b in the steam flow path 8 between the second superheater 6b and the third superheater 6c), and the preset second target de-heating amount 2DSDTtarget. The second spray control unit 60b feedback controls the second spray 10b by outputting an opening command value (second spray valve opening signal) for the second spray valve 16b so that the third steam temperature T3SO becomes the target steam temperature T3SOtarget and the amount of heat reduction 2DSDT by the second spray 10b becomes the target amount of heat reduction 2DSDTtarget.

The second heat reduction target value 2DSDTtarget is set according to the load command value Ld.

The first spray control unit 60a performs feedback control of the first spray 10a by outputting an opening command value (first spray valve opening signal) for the first spray valve 16a based on the temperature detection value T2S0 and the target temperature T2SOtarget. In other words, the first spray control unit 60a determines the opening signal for the first spray valve 16a so that the steam temperature at the outlet side of the second superheater 6b becomes a predetermined target value.

The bias value calculation unit 70 calculates a bias value α for the second target heat reduction amount 2DSDT based on the deviation ΔT0 between the steam temperature T0 upstream of the spray position of the spray 10 (in this embodiment, the second spray 10b, whose heat reduction amount 2DSDT is controlled by the second spray control unit 60b) in the steam flow path 8 in which the first superheater 6a to the third superheater 6c are provided, and a predetermined target steam temperature T0target.
The bias value calculation unit 70 performs, for example, integral control of the deviation ΔT0, and calculates the output as the bias value α.

The steam temperature T0 is detected by a steam temperature detection unit 72 installed upstream of the spray position of the second spray 10b, whose deheating amount 2DSDT is controlled by the second spray control unit 60b. In the embodiment shown in Figures 5A to 5C and 6A to 6C, the steam temperature detection unit 72 is configured to detect the steam temperature T0 in the steam flow path 8 between the furnace water wall 4 and the first superheater 6a, as an example.

The target steam temperature T0target is set as the steam temperature T0 at a position corresponding to the steam temperature detection unit 72 according to the load command value Ld.

The control device 2 having such a configuration performs the control shown in FIG. 4. First, the control device 2 detects the steam temperature at the outlet of the steam flow passage 8, for example, at the furnace water-cooled wall 4 (step S100), and determines whether the steam temperature profile deviates from the design temperature profile Pr (step S101).

If it is determined that the steam temperature profile deviates from the design temperature profile Pr (step S101: YES), the bias value calculation unit 70 calculates the deviation ΔT0 between the steam temperature T0 upstream of the spray position of the second spray 10b in the steam flow path 8 in which the first superheater 6a to the third superheater 6c are provided and a preset target steam temperature T0target (step S102), and calculates the bias value α based on the deviation T0 (step S103).

The sign of the bias value α is set based on the magnitude relationship between the steam temperature T0 and the target steam temperature T0target. Specifically, if the steam temperature T0 is lower than the target steam temperature T0target, the sign of the bias value is set to positive. Conversely, if the steam temperature T0 is higher than the target steam temperature T0target, the sign of the bias value is set to negative. The absolute value of the bias value is set to increase relative to the deviation ΔT0.

The spray control unit 60 then adds the bias value α set in step S103 to the second target de-energization amount 2DSDTtarget (step S104), and controls the second spray 10b so that the second de-energization amount 2DSDT by the second spray 10b becomes the second target de-energization amount 2DSDTtarget to which the bias value α has been added (step S105). By adding the bias value α to the target de-energization amount of the spray valve, which is controlled so that the de-energization amount becomes the target de-energization amount in this manner, the steam temperature profile of the once-through boiler 1 can be brought closer to the design temperature profile Pr.

Now, the transition of the steam temperature profile due to the above control will be explained in more detail. Figures 5A to 5C are an example showing the transition of the steam temperature profile due to the control device 2 of Figure 3. In this example, as shown in Figure 5A, the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr to the lower temperature side due to some factor. Such factors include, for example, the formation of scale or other dirt on the heat transfer surface of the steam flow path 8 over time, which reduces the detected steam temperature in the steam flow path 8, a decrease in the superheating performance of the first to third superheaters 6a to 6c, or a change in the type of fuel fed to the furnace water wall 4.

In this case, since the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr to the lower temperature side, a bias value α having a positive sign is added to the second deheating amount target value 2DSDTtarget, as shown in FIG. 5B. This increases the amount of water supplied to the spray 10 side and decreases the amount of water supplied to the furnace water-cooled wall 4. As a result, as shown in FIG. 5C, the steam temperature profile is shifted overall to the higher temperature side and controlled to approach the design temperature profile Pr.

Figures 6A to 6C are other examples showing the transition of the steam temperature profile by the control device 2 of Figure 3. In this example, as shown in Figure 6A, the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr to the higher temperature side due to some factor. One such factor is, for example, a change in the type of fuel fed into the furnace water wall 4.

In this case, since the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr to the high temperature side, a negative bias value α is added to the second deheating amount target value 2DSDTtarget, as shown in FIG. 6B. This reduces the amount of water supplied to the spray 10 side and increases the amount of water supplied to the furnace water-cooled wall 4. As a result, as shown in FIG. 6C, the steam temperature profile shifts overall to the low temperature side, approaching the design temperature profile Pr.

Figure 7 is a block diagram showing the internal configuration of a control device 2 according to another aspect of the present disclosure. The control device 2 according to this aspect includes a water-fuel ratio control unit 50 for controlling the water-fuel ratio, a spray control unit 60 for controlling the sprays 10 (first spray 10a and second spray 10b), and a bias value calculation unit 70 for calculating a bias value for a target temperature reduction amount. The spray control unit 60 includes a first spray control unit 60a for controlling the first spray 10a, and a second spray control unit 60b for controlling the second spray 10b.

The water-fuel ratio control unit 50 controls the water-fuel ratio so that the second steam temperature T2SO becomes the second target steam temperature T2SOtarget set in advance. Specifically, the water-fuel ratio control unit 50 receives the second steam temperature T2SO, which is an actual measurement value detected at a corresponding location of the once-through boiler 1 (for example, the steam temperature detection value between the second superheater 6b and the third superheater 6c in the steam flow path 8), and the second target steam temperature T2SOtarget set in advance. The water-fuel ratio control unit 50 calculates the deviation ΔT2SO between the second steam temperature T2SO and the second target steam temperature T2SOtarget, and outputs a water-fuel ratio control signal as a fuel flow rate correction so that the deviation ΔT2SO becomes zero (i.e., so that the second steam temperature T2SO becomes the second target steam temperature T2SOtarget), thereby feedback controlling the water-fuel ratio.

The second target steam temperature T2SOtarget is set according to the load command value Ld.

The first spray control unit 60a controls the first spray 10a so that the second steam temperature T2SO becomes the second target steam temperature T2SOtarget and the first deheating amount 1DSDT becomes the first target deheating amount 1DSDTtarget. Specifically, the first spray control unit 60a receives as input the second steam temperature T2SO, which is an actual measurement value detected at a corresponding location of the once-through boiler 1 (for example, the steam temperature detection value between the second superheater 6b and the third superheater 6c in the steam flow path 8), a preset second target steam temperature T2SOtarget, a first heat reduction amount 1DSDT, which is an actual measurement value detected by a sensor at a corresponding location of the once-through boiler 1 (for example, the difference between the steam temperature detection values detected upstream and downstream of the spray position by the first spray 10a in the steam flow path 8 between the first superheater 6a and the second superheater 6b), and a preset first target heat reduction amount 1DSDTtarget. The first spray control unit 60a feedback controls the first spray 10a by outputting an opening command value (first spray valve opening signal) for the first spray valve 16a so that the second steam temperature T2SO becomes the second target steam temperature T2SOtarget and the first deheating amount 1DSDT by the first spray 10a becomes the first target deheating amount 1DSDTtarget.

The first target deheating amount 1DSDTtarget is set according to the load command value Ld.

The second spray control unit 60b performs feedback control of the second spray 10b by outputting an opening command value (second spray valve opening signal) for the second spray valve 16b so that the third steam temperature T3SO becomes the third target steam temperature T3SOtarget.

The bias value calculation unit 70 calculates a bias value α for the first target deheating amount 1DSDT based on the deviation ΔT0 between the steam temperature T0 upstream of the spray position of the spray 10 (in this embodiment, the first spray 10a, whose first deheating amount 1DSDT is controlled by the first spray control unit 60a) in the steam flow path 8 in which the first superheater 6a to the third superheater 6c are provided, and a preset target steam temperature T0target.

The steam temperature T0 is detected by a steam temperature detection unit 72 installed upstream of the spray position of the first spray 10a, whose first deheating amount 1DSDT is controlled by the first spray control unit 60a. In an embodiment described below with reference to Figures 9A to 9C and 10 to 10C, the steam temperature detection unit 72 is configured to be able to detect the steam temperature T0 in the steam flow passage 8 between the furnace water wall 4 and the first superheater 6a.

The control device 2 having such a configuration performs the control shown in FIG. 8. FIG. 8 is a flowchart showing each step of the control method for the once-through boiler 1 performed by the control device 2 of FIG. 7.

First, the control device 2 detects the steam temperature at the outlet of the steam flow path 8, for example, at the furnace water wall 4 (step S200), and determines whether the steam temperature profile deviates from the design temperature profile Pr (step S201). If it is determined that the steam temperature profile deviates from the design temperature profile Pr (step S201: YES), the bias value calculation unit 70 calculates the deviation ΔT0 between the steam temperature T0 upstream of the spray position of the first spray 10a in the steam flow path 8 in which the first superheater 6a to the third superheater 6c are provided and a preset target steam temperature T0target (step S202), and calculates the bias value α based on the deviation T0 (step S203).

The sign of the bias value α is set based on the magnitude relationship between the steam temperature T0 and the target steam temperature T0target. Specifically, if the steam temperature T0 is lower than the target steam temperature T0target, the sign of the bias value is set to positive. Conversely, if the steam temperature T0 is higher than the target steam temperature T0target, the sign of the bias value is set to negative. The absolute value of the bias value is set to increase relative to the deviation ΔT0.

The spray control unit 60 then adds the bias value α set in step S203 to the first target de-energization amount 1DSDTtarget (step S204), and controls the first spray 10a so that the first de-energization amount 1DSDT by the first spray 10a becomes the first target de-energization amount 1DSDTtarget to which the bias value α has been added (step S205). By adding the bias value α to the target de-energization amount of the spray valve, which is controlled so that the de-energization amount becomes the target de-energization amount in this manner, the steam temperature profile of the once-through boiler 1 can be brought closer to the design temperature profile Pr.

Now, the transition of the steam temperature profile due to the above control will be explained in more detail. Figures 9A to 9C are an example showing the transition of the steam temperature profile due to the control device 2 of Figure 7. In this example, as shown in Figure 9A, the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr to the lower temperature side due to some factor. Such factors include, for example, the formation of scale or other dirt on the heat transfer surface of the steam flow path 8 over time, which reduces the detected steam temperature in the steam flow path 8, a decrease in the superheating performance of the first to third superheaters 6a to 6c, or a change in the type of fuel fed to the furnace water wall 4.

In this case, since the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr toward the lower temperature side, the bias value calculation unit 70 calculates a bias value α having an absolute value based on the deviation ΔT0 and a positive sign, as shown in FIG. 9B. As a result, as shown in FIG. 9C, the steam temperature profile is shifted overall toward the higher temperature side, approaching the design temperature profile Pr.

Figures 10A to 10C are other examples showing the transition of the steam temperature profile by the control device 2 of Figure 7. In this example, as shown in Figure 10A, the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr to the higher temperature side due to some factor. One such factor is, for example, a change in the type of fuel fed into the furnace water wall 4.

In this case, since the steam temperature profile of the once-through boiler 1 deviates from the design temperature profile Pr toward the higher temperature side, the bias value calculation unit 70 calculates a bias value α that has an absolute value based on the deviation ΔT0 and has a negative sign, as shown in FIG. 10B. As a result, as shown in FIG. 10C, the steam temperature profile is shifted overall toward the lower temperature side, approaching the design temperature profile Pr.

As described above, according to some aspects of the present disclosure, it is possible to provide a control device 2 for a once-through boiler 1, a power plant 100, and a control method for a once-through boiler 1 that can prevent the steam temperature profile at each position in the steam flow path of the once-through boiler 1 from deviating from the design temperature profile as the heat balance conditions of the once-through boiler 1 change.

In addition, the components in the above-described embodiments may be replaced with well-known components as appropriate without departing from the spirit of this disclosure, and the above-described embodiments may be combined as appropriate.

The contents described in each of the above embodiments can be understood, for example, as follows:

(1) A control device for a once-through boiler according to one aspect of the present disclosure includes:
A control device (e.g., the control device 2 of the above embodiment) for a once-through boiler (e.g., the once-through boiler 1 of the above embodiment) capable of adjusting temperatures of steam generated in a furnace water wall and a plurality of superheaters (e.g., the first superheater 6a, the second superheater 6b, and the third superheater 6c of the above embodiment) arranged in series, and a plurality of sprays (e.g., the first spray 10a and the second spray 10b of the above embodiment) configured to spray a portion of the water supplied to the furnace water wall (e.g., the furnace water wall 4 of the above embodiment) to an outlet side of each of the plurality of superheaters,
A spray control unit (e.g., the spray control unit 60 in the above embodiment) configured to control the steam temperature reduction amount (e.g., the first temperature reduction amount 1DSDT or the second temperature reduction amount 2DSDT in the above embodiment) by at least a part of the plurality of sprays to a target temperature reduction amount (e.g., the first target temperature reduction amount 1DSDTtarget or the second target temperature reduction amount 2DSDTtarget in the above embodiment);
A steam temperature detection unit (e.g., the steam temperature detection unit 72 in the above embodiment) configured to detect the steam temperature upstream of the superheater that is arranged upstream of the spray position of the spray controlled by the spray control unit in the steam flow path (e.g., the steam flow path 8 in the above embodiment) in which the plurality of superheaters are provided;
Equipped with
The target temperature reduction amount is configured to be set by adding a bias value (e.g., the bias value α in the above embodiment) that is set based on the deviation between the detection value of the steam temperature detection unit and the target steam temperature (e.g., the deviation ΔT0 in the above embodiment) to the basic target temperature reduction amount.

According to the above aspect (1), a bias value is added to the target derating amount of the spray. The bias value is set based on the deviation of the steam temperature upstream of the spray position of the spray, which is controlled so that the derating amount becomes the target derating amount, from the target steam temperature. This makes it possible to control the steam temperature so that the steam temperature profile approaches the design temperature profile, even if some factor causes the steam temperature profile in the steam flow path to deviate from the ideal design temperature profile.

(2) In another embodiment, in the above embodiment (1),
When the detected value of the steam temperature detection unit is lower than the target steam temperature, the sign of the bias value is set to be positive.

According to the above aspect (2), when the steam temperature profile in the steam flow path deviates toward the lower temperature side from the ideal design temperature profile, the sign of the bias value is set to positive. This allows the steam temperature profile to be shifted toward the higher temperature side, and brought closer to the design temperature profile.

(3) In another embodiment, in the above embodiment (1) or (2),
When the detected value of the steam temperature detection unit is higher than the target steam temperature, the sign of the bias value is set to negative.

According to the above aspect (3), when the steam temperature profile in the steam flow path deviates toward the high temperature side from the ideal design temperature profile, the sign of the bias value is set to negative. This allows the steam temperature profile to be shifted toward the low temperature side, and closer to the design temperature profile.

(4) In another embodiment, in any one of the above (1) to (3),
The absolute value of the bias value is set to increase with respect to the deviation.

According to the above aspect (4), the bias value is set to increase as the deviation between the steam temperature profile in the steam flow path and the design temperature profile increases. In this way, when the deviation of the steam temperature profile from the design temperature profile is large, a large bias value is added to the target deheating amount, so that the steam temperature profile can be suitably brought close to the design temperature profile.

(5) In another aspect, in any one of the above (1) to (4),
The plurality of superheaters include
A first superheater (for example, the first superheater 6a in the above embodiment) configured to be able to superheat steam from the furnace water-cooled wall;
A second superheater (for example, the second superheater 6b in the above embodiment) configured to be able to superheat steam from the first superheater;
A third superheater (for example, the third superheater 6c in the above embodiment) configured to be able to superheat steam from the second superheater;
Including,
The plurality of sprays include
A first spray (for example, the first spray 10a in the above embodiment) provided on the outlet side of the first superheater;
A second spray (for example, the second spray 10b in the above embodiment) provided at the outlet portion of the second superheater;
including.

According to the above aspect (5), by controlling multiple superheaters and multiple sprays, the steam temperature profile from the furnace water wall can be suitably brought close to the design temperature profile.

(6) In another embodiment, in the above embodiment (5),
The spray control unit is configured to control the second spray based on the deviation between the amount of temperature reduction caused by the second spray (e.g., the second temperature reduction amount 2DSDT in the above embodiment) and the target temperature reduction amount (e.g., the second target temperature reduction amount 2DSDTtarget in the above embodiment).

According to the above aspect (6), in a once-through boiler in which the second spray is controlled so that the amount of heat reduction by the second spray becomes the target amount of heat reduction, the steam temperature profile from the furnace water wall can be suitably brought close to the design temperature profile.

(7) In another embodiment, in the above embodiment (5),
The spray control unit is configured to control the first spray so that the temperature reduction amount by the first spray (e.g., the first temperature reduction amount 1DSDT in the above embodiment) becomes the target temperature reduction amount (e.g., the first target temperature reduction amount 1DSDTtarget in the above embodiment).

According to the above aspect (7), in a once-through boiler in which the first spray is controlled so that the amount of heat reduction by the first spray becomes the target amount of heat reduction, the steam temperature profile from the furnace water wall can be suitably brought close to the design temperature profile.

(8) In another aspect, in any one of the above (1) to (7),
The amount of temperature reduction is calculated based on temperature detection values on the upstream and downstream sides of the spray that is the object of control of the spray control unit.

According to the above aspect (8), the amount of temperature loss due to the spray is suitably calculated based on the temperature detection values upstream and downstream of the spray.

(9) In another aspect, in any one of the above (1) to (8),
The once-through boiler is a coal-fired boiler that uses coal or oil as fuel.

According to the above aspect (9), by using a process in which coal is pulverized using a coal pulverizer, the steam temperature profile from the furnace water wall can be suitably brought close to the design temperature profile even in a power plant that uses a coal-fired boiler with low responsiveness to load command values by operation control or an oil-fired boiler as a steam generator.

(10) A power plant according to one aspect of the present disclosure,
The once-through boiler;
A control device according to any one of the above (1) to (9),
A turbine configured to be driven by steam from the once-through boiler;
A generator configured to be driven by the turbine;
Equipped with.

According to the above aspect (10), even when factors arise that cause the steam temperature profile of the once-through boiler to deviate from the design temperature profile, the steam temperature profile can be brought closer to the design temperature profile, enabling more stable operation of the power plant and achieving good reliability.

(11) A method for controlling a once-through boiler according to one aspect of the present disclosure,
A method for controlling a once-through boiler capable of adjusting the temperature of steam generated in a furnace water wall and a plurality of superheaters by a plurality of superheaters arranged in series and a plurality of sprayers configured to spray a portion of the water supplied to the furnace water wall to an outlet side of each of the plurality of superheaters, comprising:
A spray control process of controlling a temperature reduction amount of the steam by at least a part of the plurality of sprays to be a target temperature reduction amount;
A steam temperature detection process for detecting a steam temperature upstream of the superheater that is arranged upstream of a spray position of the spray controlled by the spray control unit in the steam flow path in which the plurality of superheaters are provided;
Equipped with
The target deheating amount is set by adding a bias value, which is set based on the deviation between the detection value of the steam temperature detection unit and the target steam temperature, to a basic target deheating amount.

According to the above aspect (11), a bias value is added to the target derating amount of the spray. The bias value is set based on the deviation of the steam temperature upstream of the spray position of the spray, which is controlled so that the derating amount becomes the target derating amount, from the target steam temperature. This makes it possible to control the steam temperature so that the steam temperature profile approaches the design temperature profile, even if the steam temperature profile in the steam flow path deviates from the ideal design temperature profile due to some factor.

Reference Signs List 1 Once-through boiler 2 Control device 4 Furnace water-cooled wall 6 Superheater 6a First superheater 6b Second superheater 6c Third superheater 8 Steam flow path 10 Spray 10a First spray 10b Second spray 12 Main water supply path 14 Sub water supply path 16a First spray valve 16b Second spray valve 50 Water-fuel ratio control unit 60 Spray control unit 60a First spray control unit 60b Second spray control unit 70 Bias value calculation unit 72 Steam temperature detection unit 100 Power plant 110 Turbine 112 Steam supply path 114 Steam valve 120 Generator

Claims (8)

A control device for a once-through boiler capable of adjusting the temperature of steam generated in a furnace water wall and a plurality of superheaters by a plurality of superheaters arranged in series and a plurality of sprayers configured to spray a portion of the water supplied to the furnace water wall to an outlet side of each of the plurality of superheaters,
a water-fuel ratio control unit configured to control the water-fuel ratio of the once-through boiler so that the temperature of the steam becomes a target steam temperature;
A spray control unit configured to be able to control the amount of heat reduction of the steam by at least a part of the plurality of sprays to a target amount of heat reduction;
A steam temperature detection unit configured to detect a steam temperature upstream of the superheater that is arranged upstream of a spray position of the spray controlled by the spray control unit in the steam flow path in which the plurality of superheaters are provided;
Equipped with
The plurality of superheaters include
A first superheater configured to be able to superheat steam from the furnace water wall;
a second superheater configured to be able to superheat steam from the first superheater;
a third superheater configured to be able to superheat steam from the second superheater;
Including,
The plurality of sprays include
A first spray provided on the outlet side of the first superheater;
A second spray provided at an outlet portion of the second superheater;
Including,
The spray control unit includes:
Controlling the second spray so that the temperature of the steam becomes the target steam temperature and the amount of heat reduction by the second spray becomes the target amount of heat reduction, and controlling the first spray so that the steam temperature at the outlet side of the second superheater becomes a predetermined target value, or
controlling the first spray so that the steam temperature at the outlet side of the second superheater becomes a predetermined target value and the amount of heat reduction by the first spray becomes the target amount of heat reduction, and controlling the second spray so that the temperature of the steam becomes the target steam temperature;
The control device for a once-through boiler is configured so that the target temperature reduction amount is set by adding a bias value that is set based on a deviation between a detection value of the steam temperature detection unit and a target steam temperature to a basic target temperature reduction amount. The control device for a once-through boiler according to claim 1, configured to set the sign of the bias value to positive when the detected value of the steam temperature detection unit is lower than the target steam temperature. The control device for a once-through boiler according to claim 1 or 2, configured so that the sign of the bias value is set to negative when the detected value of the steam temperature detection unit is higher than the target steam temperature. The control device for a once-through boiler according to any one of claims 1 to 3, wherein the absolute value of the bias value is set to increase relative to the deviation. The control device for a once-through boiler according to any one of claims 1 to 4 , wherein the amount of temperature reduction is calculated based on temperature detection values upstream and downstream of the spray that is the control target of the spray control unit. The control device for a once-through boiler according to any one of claims 1 to 5 , wherein the once-through boiler is a coal-fired boiler that uses coal or oil as fuel. The once-through boiler;
A control device according to any one of claims 1 to 6 ;
A turbine configured to be driven by steam from the once-through boiler;
A generator configured to be driven by the turbine;
A power generation plant comprising: A method for controlling a once-through boiler capable of adjusting the temperature of steam generated in a furnace water wall and a plurality of superheaters by a plurality of superheaters arranged in series and a plurality of sprayers configured to spray a portion of the water supplied to the furnace water wall to an outlet side of each of the plurality of superheaters, comprising:
a water-fuel ratio control step of controlling a water-fuel ratio of the once-through boiler so that a temperature of the steam becomes a target steam temperature;
A spray control process of controlling a temperature reduction amount of the steam by at least a part of the plurality of sprays to be a target temperature reduction amount;
A steam temperature detection process for detecting a steam temperature upstream of the superheater that is arranged upstream of a spray position of the spray controlled in the spray control process in the steam flow path provided with the plurality of superheaters;
Equipped with
The plurality of superheaters include
A first superheater configured to be able to superheat steam from the furnace water wall;
a second superheater configured to be able to superheat steam from the first superheater;
a third superheater configured to be able to superheat steam from the second superheater;
Including,
The plurality of sprays include
A first spray provided on the outlet side of the first superheater;
A second spray provided at an outlet portion of the second superheater;
Including,
In the spray control step,
Controlling the second spray so that the temperature of the steam becomes the target steam temperature and the amount of heat reduction by the second spray becomes the target amount of heat reduction, and controlling the first spray so that the steam temperature at the outlet side of the second superheater becomes a predetermined target value, or
controlling the first spray so that the steam temperature at the outlet side of the second superheater becomes a predetermined target value and the amount of heat reduction by the first spray becomes the target amount of heat reduction, and controlling the second spray so that the temperature of the steam becomes the target steam temperature;
a bias value that is set based on a deviation between a detection value detected in the steam temperature detection step and a target steam temperature, to a basic target steam reduction amount.

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