JP2018091600A - Steam temperature control device and control unit including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam temperature control device which can reduce a variation width of a temperature of main steam which is generated from a boiler.SOLUTION: In a steam temperature control device (3) for controlling a main steam temperature, a temperature of main steam which is generated from a superheater (14) of a boiler including a temperature reducer (13) for lowering the temperature of the steam by using spray water having a water amount based on a water amount control value, and the superheater (14) for heating steam which is discharged from the temperature reducer (13) by an exhaust gas, the steam temperature control device comprises a water amount control value calculation part (311) for calculating a water amount control value on the basis of the main steam temperature so that the main steam temperature reaches a target temperature, and transmitting the water amount control value to a spray water injection valve (24). The water amount control value calculation part (311) transmits a water amount control minimum value which is calculated on the basis of a water supply amount to the temperature reducer (13), or a moving average within a constant period of the water amount control value to the spray water injection valve (24) as a lower limit value of the water amount control value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steam temperature control device for controlling the temperature of main steam generated from a boiler in facilities for processing waste.

  Conventionally, a system for generating main steam by recovering heat generated in an incinerator or the like in a waste treatment facility with a boiler is known. Since the main steam generated in this system is sent to the user, it is desirable that the temperature of the main steam is as stable as possible. Usually, in such a system, the boiler is a superheater that reduces the temperature of steam discharged from the boiler drum with spray water and heats the steam discharged from the temperature reducer with exhaust gas discharged from the incinerator. The amount of spray water supplied to the temperature reducer is adjusted by adjusting the opening of the spray water injection valve.

  For example, Patent Document 1 discloses a steam temperature control device that stabilizes the temperature of main steam generated from a boiler. This steam temperature control device calculates the water amount control value that determines the opening of the spray water injection valve based on the main steam temperature so that the main steam temperature (main steam temperature) discharged from the superheater becomes the target temperature. And it has the water quantity control value calculation part which transmits the opening degree control value to a spray water injection valve. For this reason, the main steam temperature changes in the vicinity of the target temperature. However, in an incinerator or the like of a waste treatment facility, calories due to combustion may vary depending on the properties of the waste, and in this case, the main steam temperature may also vary. In the steam temperature control device described in Patent Document 1, the lower limit value of the water amount control value is set to be variable in order to suppress a rapid increase in the main steam temperature. Specifically, the water amount control value calculation unit calculates a water amount control minimum value that increases / decreases as the exhaust gas temperature increases / decreases as a lower limit value of the water amount control value, and transmits the water amount control minimum value to the spray water injection valve. doing. In other words, since the water control minimum value also increases / decreases as the exhaust gas temperature increases / decreases, the rapid increase in the main steam temperature is suppressed as compared with the case where the minimum value of the water control value is fixed to a specific value. It is suppressed that temperature deviates from target temperature.

Japanese Patent Laid-Open No. 2006-145552

  In the steam temperature control device described in Patent Document 1, there is a concern that the fluctuation range of the main steam temperature may increase when the soot blower operation (operation to remove ash or the like attached to the heat transfer tube of the superheater) is performed in the boiler. is there. Specifically, when the soot blower operation is performed in the boiler, the amount of heat exchanged between the steam and the exhaust gas in the superheater (the amount of heat received from the exhaust gas by the steam passing through the heat transfer pipe) increases. If it does so, while the temperature of the main steam discharged | emitted from a superheater will rise, the temperature of the waste gas discharged | emitted from a boiler will fall. On the other hand, in the steam temperature control device described in Patent Document 1, when the temperature of the exhaust gas decreases, the minimum water amount control value, that is, the amount of water supplied to the temperature reducer decreases, so the temperature of the main steam tends to increase. Thus, in the control by the steam temperature control device described in Patent Document 1, for example, the temperature of the main steam may rise after the soot blower operation of the boiler.

  The objective of this invention is providing the steam temperature control apparatus which can reduce the fluctuation range of the temperature of the main steam generated from a boiler, and a control unit including the same.

  In order to solve the above problems, the present inventors have focused on the relationship between the main steam temperature and the amount of water supplied to the temperature reducer. Specifically, since the water supply amount, that is, the water amount control value of the spray water injection valve is adjusted by feedback control based on the main steam temperature, the tendency of increase and decrease of the water supply amount and the tendency of increase and decrease of the main steam temperature are mutually I found it to be the same. For this reason, the fluctuation range of the main steam temperature after the boiler soot blower operation, etc. can be reduced by adopting the water supply amount (water amount control value) instead of the exhaust gas temperature as an index for obtaining the water amount control minimum value. I thought it was possible. The present invention has been made from such a viewpoint.

  Specifically, the present invention includes a temperature reducer for reducing the temperature of the steam by the amount of water spray water based on a water amount control value for controlling the opening of the spray water injection valve, and discharging from the temperature reducer by the exhaust gas discharged from the furnace. A steam temperature control device for controlling a main steam temperature, which is a temperature of a main steam generated from the superheater of a boiler, including a superheater that heats the generated steam so that the main steam temperature becomes a target temperature The water amount control value is calculated based on the main steam temperature, and includes a water amount control value calculation unit that transmits the water amount control value to the spray water injection valve, and the water amount control value calculation unit is a lower limit of the water amount control value. Provided is a steam temperature control device that transmits, as a value, a water amount control minimum value calculated based on a moving water amount to the temperature reducer or a moving average of the water amount control value over a fixed period to the spray water injection valve.

  In this steam temperature control device, the water supply amount or the water amount control value to the temperature reducer is adopted as an index for calculating the water amount control minimum value (the lower limit value of the water amount control value). The fluctuation range of the main steam temperature is reduced. In addition, since the water amount control value calculation unit of this device calculates the water amount control minimum value based on the moving amount of the water supply amount or the water amount control value for a certain period of time, the fluctuation range of the main steam temperature is more reliable. Reduced to

  In this case, when the main steam temperature is equal to or lower than a set temperature lower than the target temperature, the water amount control value calculation unit sets a predetermined minimum value to the spray water injection valve as the water amount control minimum value. It is preferable to transmit.

  In this way, when the main steam temperature is equal to or lower than the set temperature, the opening (water supply amount) of the spray water injection valve is maintained at the minimum value. Therefore, it is suppressed that the main steam temperature falls excessively.

  Specifically, the water amount control value calculation unit is a coefficient indicating the minimum value when the main steam temperature is equal to or lower than the set temperature, as the water amount control minimum value, based on the moving average or the value based on the moving average. When the main steam temperature is higher than the set value, it is preferable to transmit a value calculated by multiplying a main steam temperature coefficient determined based on the main steam temperature to the spray water injection valve.

  In this way, when the main steam temperature is equal to or lower than the set temperature, the opening (water supply amount) of the spray water injection valve is maintained at the minimum value, and when the main steam temperature is higher than the set temperature, it is based on the main steam temperature. The amount of spray water is supplied to the desuperheater.

  Further, in the steam temperature control device, the water amount control value calculation unit uses the water amount control minimum value as the lower limit value of the water amount control value when the main steam temperature continues to decrease for a predetermined period. It is preferable to transmit to.

  As described above, when the amount of waste supplied from the dust feeder to the incinerator is significantly reduced in the state where the control is performed by the steam temperature control device, the flow rate of the exhaust gas supplied from the incinerator to the superheater In other words, since the main steam temperature decreases, the amount of water supplied to the temperature reducer also decreases significantly. On the other hand, a certain amount of exhaust gas (amount of heat) continues to be supplied to the boiler superheater. Then, the pipe connected to the temperature reducer (pipe through which steam flows) is heated by the exhaust gas, so that the temperature of the pipe rises. Thereafter, when the amount of waste supplied to the incinerator recovers (when the flow rate of exhaust gas supplied to the boiler recovers), the main steam temperature starts to rise. Then, although the amount of water supplied to the desuperheater is increased by the control of the steam temperature control device, a part of the cooling water of this water is cooling the pipe until the temperature of the pipe is lowered to an appropriate temperature. Therefore, there is a concern that the main steam temperature will rise above the target temperature.

  Therefore, the present invention is a control unit comprising the steam temperature control device and a target temperature control device that controls the target temperature of the main steam temperature and transmits the target temperature to the steam temperature control device, When the target temperature control device receives a heat amount decrease signal indicating that the heat amount of the exhaust gas supplied to the superheater has decreased, the target temperature control device receives the target temperature to be transmitted to the steam temperature control device. There is provided a control unit having a target temperature changing unit for changing to a lower target temperature lower than a previous target temperature.

  In this control unit, the target temperature changing unit transmits the low target temperature as the target temperature to the steam temperature control device when receiving the heat amount lowering signal. Increase the amount of water supplied to the temperature reducer to reach the target temperature. Therefore, the rise in the temperature of the pipe connected to the temperature reducer is suppressed. Therefore, after that, even when the main steam temperature rises due to the recovery of the amount of heat supplied to the boiler, an excessive rise in the main steam temperature is suppressed.

  In this case, when the target temperature changing unit receives a heat recovery signal indicating that the amount of heat of the exhaust gas supplied to the superheater has recovered, the target temperature to be transmitted to the steam temperature controller is decreased. It is preferable to return to the target temperature before receiving the signal.

  In this way, when the amount of heat supplied to the boiler is restored, the boiler is restored to a state where heat can be effectively recovered.

  As described above, according to the present invention, it is possible to provide a steam temperature control device capable of reducing the fluctuation range of the temperature of the main steam generated from the boiler and a control unit including the same.

It is a figure which shows the outline of a structure of the steam temperature control apparatus of one Embodiment of this invention. It is a graph which shows the relationship between the moving average in the fixed period of the water supply amount to a temperature reducer, and a water supply amount coefficient. It is a graph which shows the relationship between main steam temperature and a main steam temperature coefficient. It is a figure which shows the relationship between the deviation of target temperature and main steam temperature, and a control gain. It is a figure which shows the structure and content example of a main steam temperature log table. It is a flowchart of a water injection valve control value calculation process. It is a flowchart of a target temperature control process.

  A control unit including a steam temperature control device 3 and a target temperature control device 4 according to an embodiment of the present invention will be described with reference to the drawings.

<Configuration>
FIG. 1 shows a configuration example of a boiler 1 in a waste treatment facility, a configuration example of a steam temperature control device 3, and a configuration example of a target temperature control device 4.

  The boiler 1 generates steam by recovering heat of exhaust gas discharged from the incinerator 5 in the waste treatment facility. Waste is supplied from the dust supply device 6 to the incinerator 5. The dust supply device 6 includes a feed unit (not shown) that sends waste to the incinerator 5 and a motor (not shown) that drives the feed unit.

  As shown in FIG. 1, a boiler 1 includes a boiler drum 11, a primary superheater 12 that heats steam discharged from the boiler drum 11 with the exhaust gas, and steam discharged from the primary superheater 12 using spray water. It has a temperature reducer 13 for reducing the temperature and a secondary superheater 14 for heating the steam discharged from the temperature reducer 13 with the exhaust gas. The steam discharged from the secondary superheater 14, that is, the main steam is sent to the user.

  Each of the superheaters 12 and 14 has a plurality of heat transfer tubes for passing steam sent from the boiler drum 11. That is, in each superheater 12 and 14, the steam which flows through each heat exchanger tube is heated by the exhaust gas which contacts the outer peripheral surface of each heat exchanger tube. Since the ash contained in the exhaust gas adheres to each heat transfer tube, the boiler 1 periodically performs a soot blower operation for removing the ash and the like. When the soot blower operation is performed in the boiler 1, the amount of heat exchanged between the steam and the exhaust gas in each superheater 12, 14 (the amount of heat received by the steam passing through the heat transfer pipe from the exhaust gas) increases. For this reason, after the soot blower operation, the temperature of the steam discharged from each of the superheaters 12 and 14 increases, and the temperature of the exhaust gas discharged from the boiler 1 decreases.

  A water amount of spray water based on the opening of the spray water injection valve 24 is supplied to the temperature reducer 13. That is, the temperature of the main steam generated in the boiler 1 is adjusted by the opening of the spray water injection valve 24 (hereinafter referred to as “water amount control value”). In addition, the spray water injection valve 24 is provided in the water supply flow path 26 for supplying spray water to the temperature reducer 13 from the outside.

  The steam temperature control device 3 is a device that controls the temperature of the main steam generated from the boiler 1 (hereinafter referred to as “main steam temperature”). Specifically, the steam temperature control device 3 controls the opening degree of the spray water injection valve 24 in order to set the main steam temperature to the target temperature SV. The steam temperature control device 3 is a so-called computer and collects data detected by various sensors at a predetermined cycle. The steam temperature control device 3 generates control data (water amount control value MV) for controlling the opening degree of the spray water injection valve 24 based on data such as temperature acquired from each sensor, and the water amount control value MV. Is transmitted to the spray water injection valve 24. That is, the steam temperature control device 3 performs feedback control by so-called PID control (Proportional-Integral-Derivative Controller) so that the main steam temperature becomes the target temperature SV. The sensor includes a main steam temperature detector 21 that detects the temperature of the main steam discharged from the secondary superheater 14 and a main steam flow detector 22 that detects the flow rate of the main steam discharged from the secondary superheater 14. And an outlet temperature detector 23 for detecting the temperature of steam flowing between the temperature reducer 13 and the secondary superheater 14 (steam flowing out from the temperature reducer 13), and the amount of water flowing through the water supply channel (temperature reduction). A feed water flow rate detector 25 for detecting an instantaneous value of the spray water supplied to the vessel 13. The target temperature SV is input from the target temperature control device 4.

  The steam temperature control device 3 includes a main steam temperature controller 31, an outlet temperature controller 32, and a feed water flow rate controller 33.

  The main steam temperature controller 31 acquires data detected by each sensor in a predetermined cycle (for example, 1 second), and the temperature of the steam output from the secondary superheater 14 is set to the target temperature SV based on the acquired data. A water amount control value MV is calculated such that The main steam temperature controller 31 detects the data acquisition timing by an interrupt from a timer (not shown) built in the steam temperature control device 3.

  Moreover, the main steam temperature controller 31 memorize | stores the data acquired from the sensor as a log in memory (not shown) as needed. This memory may be an internal memory of the steam temperature control device 3 or an external memory connected via a network. In the embodiment, the main steam temperature controller 31 stores the main steam temperature acquired from the main steam temperature detector 21 in time series. Note that each data stored in the memory can be referred to from other functional units.

  FIG. 5 shows an example of the configuration and contents of the main steam temperature log table 210. Each time the main steam temperature controller 31 acquires data from the main steam temperature detector 21, one record is added to the main steam temperature log table 210. The main steam temperature log table 210 has a log count 211 and a main steam temperature 212.

  The number of logs 211 indicates the number of the acquired main steam temperature (log data), and the main steam temperature 212 indicates the contents of the data, that is, the acquired main steam temperature. . For example, in the main steam temperature log table 210, a record whose log count 211 is “n” (main steam temperature log data acquired for the nth time) is a record added most recently, and the main steam temperature 212 is “ Therefore, the current main steam temperature is 500 ° C. The main steam temperature controller 31 acquires data from the sensor at a predetermined cycle (for example, 1 second). Accordingly, the record whose log count 211 is “n−1” is log data before a predetermined period, that is, one second before, and the main steam temperature 212 is “505”, so that the main record one second before is recorded. The steam temperature was 505 ° C. Details of the processing of the main steam temperature controller 31 will be described in the section <Operation>.

  The outlet temperature controller 32 corrects (adjusts) the water amount control value MV calculated by the main steam temperature controller 31 using the steam temperature on the outlet side of the temperature reducer 13 detected by the outlet temperature detector 23.

  The water supply flow rate controller 33 transmits the water amount control value MV corrected by the outlet temperature controller 32 to the spray water injection valve 24. As a result, the amount of spray water corresponding to the water amount control value MV is supplied to the temperature reducer 13.

  Here, the configuration of the main steam temperature controller 31 will be described in detail. The main steam temperature controller 31 includes a water amount control value calculation unit 311, a control gain calculation unit 312, and a water amount control minimum value calculation unit 313.

  The water amount control value calculation unit 311 performs so-called PID control, the deviation between the main steam temperature detected by the main steam temperature detector 21 and the target temperature SV, and the main steam flow rate detected by the main steam flow rate detector 22. Based on the above, the water amount control value MV is calculated.

  The control gain calculation unit 312 calculates a so-called control gain (proportional gain) used when the water amount control value calculation unit 311 calculates the water amount control value MV. In the present embodiment, the control gain calculation unit 312 calculates a control gain using a function as shown in FIG. In the graph of FIG. 4, the horizontal axis indicates the deviation between the target temperature SV and the main steam temperature detected by the main steam temperature detector 21, and the vertical axis indicates the control gain. For example, in FIG. 4, when the deviation is 0 or less, the control gain is 5, when the deviation is 5 or more, the control gain is 30, and when the deviation is 0 to 5, the control gain is proportional to the deviation from 5 to 30. Increase.

  The water amount control minimum value calculation unit 313 calculates the water amount control minimum value ML, which is the lower limit value of the water amount control value MV, and sends this water amount control minimum value ML to the water amount control value calculation unit 311. This water amount control minimum value ML is used when the water amount control value calculation unit 311 calculates the water amount control value MV. As will be described in the section of <Operation>, the water amount control value calculation unit 311 controls the water amount control minimum value ML calculated by the water amount control minimum value calculation unit 313 when the main steam temperature shows a downward trend. The value MV is transmitted to the outlet temperature controller 32. When the main steam temperature tends to decrease, even when the main steam temperature is higher than the target temperature SV, the water amount control minimum value ML is set as the water amount control value MV. The steam temperature control device 3 estimates that the main steam temperature will continue to decrease when the main steam temperature tends to decrease, and sets the amount of water supplied to the temperature reducer 13 as the water amount control minimum value ML.

  In the present embodiment, the water amount control minimum value calculation unit 313 calculates the water amount control minimum value ML based on the moving average of the amount of water supplied to the temperature reducer 13 (the detection value of the water supply flow rate detector 25) over a certain period. More specifically, the water amount control minimum value calculating unit 313 calculates a value obtained by multiplying the water supply amount coefficient shown in FIG. 2 by the main steam temperature coefficient shown in FIG. 3 as the water amount control minimum value ML. The water amount control minimum value calculation unit 313 may calculate the water amount control minimum value ML based on a moving average of the water amount control value MV over a certain period.

  In the graph of FIG. 2, the horizontal axis indicates the moving average of the amount of water supplied to the temperature reducer 13 over a certain period (20 minutes in this embodiment), and the vertical axis indicates the water supply amount coefficient. The water supply amount coefficient indicates the opening degree of the spray water injection valve 24 according to the moving average (value on the horizontal axis in FIG. 2). As shown in FIG. 2, the water supply amount coefficient gradually increases as the moving average increases.

  In the graph of FIG. 3, the horizontal axis indicates the main steam temperature, and the vertical axis indicates the main steam temperature coefficient. As shown in FIG. 3, the main steam temperature coefficient shows a minimum value (zero in this embodiment) when the main steam temperature is equal to or lower than a set temperature (450 ° C. in this embodiment), and the main steam temperature is When the temperature is higher than the set temperature, the temperature rises to 1.0 as the main steam temperature rises. In the present embodiment, the main steam temperature coefficient increases from the lowest value to 1.0 as the main steam temperature increases from a set temperature toward a specified temperature (for example, 460 ° C.), and the main steam temperature is a specified temperature. 1.0 is shown at the above time. The minimum value may be a numerical value smaller than 1.0 and larger than zero.

  That is, when the main steam temperature is equal to or lower than the set temperature, the water amount control minimum value calculation unit 313 sends the minimum value as the water amount control minimum value ML to the water amount control value calculation unit 311 so that the main steam temperature is higher than the set temperature. In the range, the product of the water supply amount coefficient and the main steam temperature coefficient is sent to the water amount control value calculation unit 311 as the water amount control minimum value ML. More specifically, the water amount control minimum value calculation unit 313 sends the value of the water supply amount coefficient itself to the water amount control value calculation unit 311 as the water amount control minimum value ML in a range where the main steam temperature is equal to or higher than the specified temperature.

  As described above, in the present embodiment, the amount of water supplied to the temperature reducer 13 is employed as an index for calculating the water amount control minimum value ML. Since this water supply amount is adjusted by feedback control based on the main steam temperature, the tendency of increase or decrease of the water supply amount is the same as the tendency of increase or decrease of the main steam temperature. Therefore, in this embodiment, the fluctuation range of the main steam temperature after the soot blower operation of the boiler 1 is reduced. In addition, since the water amount control minimum value calculation unit 313 calculates the water amount control minimum value ML based on the moving average of the water supply amount over a certain period, the fluctuation range of the main steam temperature is more reliably reduced.

  In addition, when the main steam temperature is equal to or lower than the set temperature, the water amount control minimum value calculation unit 313 sends a minimum value to the water amount control value calculation unit 311 as the water amount control minimum value ML. For this reason, when the main steam temperature is equal to or lower than the set temperature, the amount of water supplied to the temperature reducer 13 (the opening of the spray water injection valve 24) is maintained at the minimum value. Therefore, it is suppressed that the main steam temperature falls excessively.

  As described above, the steam temperature control device 3 of the embodiment can be configured by using a computer such as a personal computer, for example, and a water amount control value calculation method stored in a storage unit (not shown) such as a hard disk. The above-described water amount control value calculation unit 311 and the like are functionally configured in the computer by executing the software programmed.

<Operation>
Next, the water supply amount control process (steam temperature control process) performed by the steam temperature control device 3 will be described with reference to FIG. FIG. 6 is a flowchart of the water supply amount control process.

  When the main steam temperature controller 31 receives an interrupt indicating the timing of data acquisition from the timer (step S10: Yes), the main steam temperature controller 31 acquires data measured by the sensor from each sensor. Specifically, the main steam temperature is acquired from the main steam temperature detector 21, the main steam flow rate (instantaneous value) is acquired from the main steam flow rate detector 22, the outlet temperature is acquired from the outlet temperature detector 23, and the water supply A feed water flow rate (instantaneous value) is acquired from the flow rate detector 25 (step S11). The main steam temperature controller 31 stores the acquired data in a memory. Further, the main steam temperature controller 31 sets the acquired main steam temperature as the main steam temperature 212, and sets the value obtained by adding 1 to the value set as the log count 211 in the last record as the log count 211 1 A record is created and added to the main steam temperature log table 210.

  The main steam temperature controller 31 having the data stored in the memory requests the water amount control value calculation unit 311 to calculate the water amount control value MV.

  The water amount control value calculation unit 311 that has received the request first determines whether or not the main steam temperature detected by the main steam temperature detector 21 has fallen over a predetermined period (step S12). The predetermined period is determined in advance according to the rule of thumb, the type of boiler, and the like. The water amount control value calculation unit 311 first reads a record corresponding to a predetermined period from the main steam temperature log table 210. For example, when the predetermined period is 2 seconds and the predetermined period is 1 second, three records are read from the newest record. Specifically, three records having “n”, “n−1”, and “n-2” set as the log count 211 are read. The water amount control value calculation unit 311 then sets the main steam temperature set as the main steam temperature 212 in the newest record in which “n” is set as the log count 211, and “n−1” as the log count 211. The main steam temperature 212 that is lower than the main steam temperature set as the main steam temperature 212 in the set record and that is set to “n−1” as the log count 211 is set as the main steam temperature 212 When the steam temperature is lower than the main steam temperature set as the main steam temperature 212 in the record in which “n−2” is set as the log count 211, the steam temperature has fallen over a predetermined period (main steam The temperature is declining). Further, in the water amount control value calculation unit 311, the main steam temperature set as the main steam temperature 212 is set in the record in which “n” is set as the log count 211, and “n−1” is set as the log count 211. Is higher than the main steam temperature set as the main steam temperature 212 in the record, or the main steam set as the main steam temperature 212 in the record in which “n−1” is set as the log count 211 When the temperature is higher than the main steam temperature set as the main steam temperature 212 in the record in which “n−2” is set as the log count 211, the temperature has not decreased for a predetermined period (main steam Temperature is not decreasing).

  When the water amount control value calculation unit 311 determines that the main steam temperature detected by the main steam temperature detector 21 has not decreased over a predetermined period (step S12: No), the water amount control value calculation unit 311 causes the control gain calculation unit 312 to Request calculation of control gain.

  Upon receiving the request, the control gain calculation unit 312 reads the main steam temperature acquired from the main steam temperature detector 21 and the target temperature SV from the memory, and obtains the control gain using the function shown in FIG. The control gain calculation unit 312 passes the obtained control gain to the water amount control value calculation unit 311 (step S13).

  Receiving the control gain, the water amount control value calculation unit 311 calculates the water amount control value MV based on the data stored in the memory (step S14). For example, the water amount control value calculation unit 311 obtains the main steam flow rate (instantaneous value) acquired from the main steam flow rate detector 22. Then, the water amount control value calculation unit 311 obtains a correction value by adding an external gain and an external bias to the difference between the value obtained this time and the value obtained last time, and sets the obtained correction value as the previous water amount control value MV. In addition, the current water amount control value MV is calculated.

  On the other hand, when the water amount control value calculation unit 311 determines in step S12 that the main steam temperature detected by the main steam temperature detector 21 has decreased over a predetermined period (step S12: Yes), The water amount control minimum value calculation unit 313 is requested to calculate the water amount control minimum value ML.

  The requested water amount control minimum value calculation unit 313 reads the moving average of the feed water flow rate acquired from the feed water flow rate detector 25 from the memory, and uses the function shown in FIGS. 2 and 3 to set the water amount control minimum value ML. Ask. The water amount control minimum value calculation unit 313 passes the obtained water amount control minimum value ML to the water amount control value calculation unit 311 (step S15).

  The water amount control value calculation unit 311 that has received the water amount control minimum value ML sets the received water amount control value ML as the water amount control value MV (step S16).

  The water amount control value calculation unit 311 that has obtained the water amount control value MV passes the obtained water amount control value MV to the outlet temperature controller 32.

  The outlet temperature controller 32 that has received the water amount control value MV reads the steam outlet temperature acquired from the outlet temperature detector 23 from the memory, and corrects the water amount control value MV based on the read outlet temperature (step S17). For example, when the outlet temperature is higher than a predetermined set value, the outlet temperature controller 32 adds a correction value obtained by multiplying the deviation between the outlet temperature and the set value by a coefficient to the water amount control value MV. A corrected water amount control value MV is calculated. The predetermined set value is, for example, a value obtained by subtracting a predetermined temperature from the target temperature SV.

  The outlet temperature controller 32 that has calculated the water amount control value MV passes the calculated water amount control value MV to the feed water flow rate controller 33.

  The water supply flow rate controller 33 controls the spray water injection valve 24 based on the passed water amount control value MV, and adjusts the amount of water supplied to the temperature reducer 13 (step S18).

  The steam temperature control device 3 repeats the processes in steps S10 to S18 at a predetermined cycle.

  Thus, the steam temperature control device 3 performs the soot blower operation of the boiler 1 by changing the water amount control minimum value ML based on the moving average of the feed water flow rate detected by the feed water flow rate detector 25 in a predetermined cycle. Even in this case, the amount of water supplied to the temperature reducer 13 can be increased or decreased so as to follow the increase or decrease in the main steam temperature. That is, the steam temperature control device 3 can control the main steam temperature so as not to deviate from the target temperature SV as much as possible.

  In the present embodiment, whether or not the main steam temperature is in a downward trend for a predetermined period is determined with reference to the main steam temperature log table 210 that is a history of the main steam temperature. It may be used. For example, each time the main steam temperature is acquired from the main steam temperature detector 21, the water amount control value calculation unit 311 compares the previous main steam temperature and stores the number of times in the memory when the temperature is low. Specifically, when the main steam temperature acquired this time is lower than the main steam temperature acquired last time, 1 is added to the stored number, and when the temperature is high, the number is cleared, that is, 0 (zero) ) Is set. And when the frequency | count memorize | stored becomes a predetermined frequency | count, for example, 3 times, the water quantity control value calculation part 311 judges that it exists in the downward tendency for a predetermined period.

  Here, when the amount of waste supplied from the dust supply device 6 to the incinerator 5 is significantly reduced in the state where the control by the steam temperature control device 3 is performed, each superheater 12, 14 from the incinerator 5. Since the flow rate of the exhaust gas supplied to the refrigerant decreases, that is, the main steam temperature decreases, the amount of water supplied to the temperature reducer 13 also decreases significantly. On the other hand, a certain amount of exhaust gas (amount of heat) continues to be supplied to each of the superheaters 12 and 14. As a result, the pipes (pipes through which steam flows) 13a and 13b connected to the temperature reducer 13 are heated by the exhaust gas, so that the temperatures of the pipes 13a and 13b rise. Thereafter, when the amount of waste supplied to the incinerator 5 is restored (when the flow rate of the exhaust gas supplied to the boiler 1 is restored), the main steam temperature starts to rise. Then, although the amount of water supplied to the desuperheater 13 is increased by the control of the steam temperature control device 3, a part of the cooling heat of this water is until the temperature of the pipes 13a and 13b is lowered to an appropriate temperature. Since it is used for cooling the pipes 13a and 13b, there is a concern that the main steam temperature rises higher than the target temperature SV.

  The control unit of the present embodiment includes a target temperature control device 4 in order to solve such a problem.

  The target temperature control device 4 controls the target temperature SV of the main steam temperature and transmits the target temperature SV to the main steam temperature controller 31 of the steam temperature control device 3. The target temperature control device 4 includes a target temperature setting unit 41 and a target temperature changing unit 42.

  The target temperature setting unit 41 transmits the target temperature SV to the target temperature changing unit 42. The target temperature SV (for example, 490 ° C.) set in the target temperature setting unit 41 is input from the outside of the target temperature control device 4 by, for example, an operator.

  When the target temperature changing unit 42 receives a heat amount decrease signal indicating that the heat amount of the exhaust gas supplied to each of the superheaters 12 and 14 has decreased, the target temperature SV transmitted to the steam temperature control device 3 is decreased. The target temperature SV before receiving the signal (the target temperature SV received from the target temperature setting unit 41) is changed to a lower target temperature. That is, the target temperature changing unit 42 transmits the low target temperature to the steam temperature control device 3 when receiving the heat amount decrease signal.

  This indicates that the detection value of the rotational speed detector 27 that is provided in the dust supply device 6 and detects the rotational speed of the motor of the dust supply device 6 has become a predetermined value (for example, 15%) or less as the heat amount reduction signal. A signal and a signal indicating that the detected value of the main steam temperature detector 21 has become a predetermined value (for example, 470 ° C.) or less can be mentioned.

  Further, the target temperature changing unit 42 receives the heat amount recovery signal indicating that the heat amount of the exhaust gas supplied to each of the superheaters 12 and 14 has been recovered, and sets the target temperature to be transmitted to the steam temperature control device 3 as the heat amount. It returns to the target temperature SV before receiving the decrease signal. That is, the target temperature changing unit 42 transmits the target temperature SV received from the target temperature setting unit 41 to the steam temperature control device 3 when receiving the heat recovery signal.

  As a heat recovery signal, a signal indicating that the state where the detection value of the rotational speed detector 27 is equal to or greater than the predetermined value (for example, 15%) continues for 90 seconds or more, and the detection value of the main steam temperature detector 21 are predetermined. The signal which shows that the state beyond a value (for example, 470 degreeC) has continued for 5 minutes or more is mentioned.

  Next, the target temperature control process will be described with reference to FIG. This control process is performed in parallel with the water supply amount control process shown in FIG.

  In the target temperature control process, first, the target temperature changing unit 42 determines whether or not a heat quantity lowering signal has been received (step S20). As a result, when the heat amount decrease signal is not received, the target temperature changing unit 42 returns to step S20 again. When the heat amount decrease signal is received, the target temperature changing unit 42 sets the target temperature SV to the low target temperature. (Step S21). At this time, the target temperature changing unit 42 decreases the target temperature SV by 10 ° C. at a rate of 2 ° C. per minute, for example. As a result, the steam temperature control device 3 increases the amount of water supplied to the temperature reducer 13 so that the main steam temperature becomes the low target temperature. Therefore, the temperature of the pipes 13a and 13b connected to the temperature reducer 13 is increased. The rise is suppressed. Therefore, after that, even when the main steam temperature rises due to the recovery of the amount of heat supplied to the boiler 1, an excessive rise in the main steam temperature is suppressed.

  Subsequently, the target temperature changing unit 42 determines whether a heat recovery signal has been received (step S22). As a result, when the heat recovery signal is not received, the target temperature changing unit 42 returns to step S22 again. When the heat recovery signal is received, the target temperature changing unit 42 increases the target temperature (step S22). ). Specifically, the target temperature changing unit 42 returns the target temperature transmitted to the steam temperature control device 3 from the low target temperature to the target temperature SV. At this time, the target temperature changing unit 42 increases the target temperature by 10 ° C. at a rate of 1 ° C. per minute, for example. For this reason, when the amount of heat supplied to the boiler 1 is recovered, the boiler 1 is restored to a state where heat can be effectively recovered.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

DESCRIPTION OF SYMBOLS 1 Boiler 3 Steam temperature control apparatus 4 Target temperature control apparatus 11 Boiler drum 12 Primary superheater 13 Temperature reducer 14 Secondary superheater 24 Spray water injection valve 31 Main steam temperature controller 32 Outlet temperature controller 33 Feed water flow rate controller 41 Target temperature setting part 42 target temperature changing unit 311 water amount control value calculating unit 312 control gain calculating unit 313 water amount control minimum value calculating unit

Claims (6)

A temperature reducer that reduces the temperature of the steam by the amount of water spray water based on a water amount control value that controls the opening of the spray water injection valve, and a superheater that heats the steam discharged from the temperature reducer by the exhaust gas discharged from the furnace A steam temperature control device for controlling the main steam temperature, which is the temperature of the main steam generated from the superheater of the boiler,
The water amount control value is calculated based on the main steam temperature so that the main steam temperature becomes the target temperature, and the water amount control value is transmitted to the spray water injection valve.
The water amount control value calculation unit uses, as the lower limit value of the water amount control value, the water amount control minimum value calculated based on the amount of water supplied to the temperature reducer or the moving average of the water amount control value over a certain period. Steam temperature control device that transmits to the valve. The steam temperature control device according to claim 1,
The water quantity control value calculation unit transmits a preset minimum value to the spray water injection valve as the water quantity control minimum value when the main steam temperature is equal to or lower than a set temperature lower than the target temperature. Temperature control device. The steam temperature control device according to claim 2,
The water amount control value calculation unit is a coefficient indicating the minimum value when the main steam temperature is equal to or lower than the set temperature, as the water amount control minimum value, based on the moving average or the value based on the moving average, A steam temperature control device that transmits a value calculated by multiplying a main steam temperature coefficient determined based on the main steam temperature to the spray water injection valve when the main steam temperature is larger than the set value. In the steam temperature control device according to any one of claims 1 to 3,
The water amount control value calculating unit transmits the water amount control minimum value to the spray water injection valve as a lower limit value of the water amount control value when the main steam temperature continues to decrease for a predetermined period. 5. A control unit comprising: the steam temperature control device according to claim 1; and a target temperature control device that controls a target temperature of the main steam temperature and transmits the target temperature to the steam temperature control device. Because
When the target temperature control device receives a heat amount decrease signal indicating that the heat amount of the exhaust gas supplied to the superheater has decreased, the target temperature control device receives the target temperature to be transmitted to the steam temperature control device. A control unit having a target temperature changing unit for changing to a lower target temperature lower than the previous target temperature. The control unit according to claim 5, wherein
When the target temperature changing unit receives a heat recovery signal indicating that the heat of exhaust gas supplied to the superheater has recovered, the target temperature changing unit receives the target temperature to be transmitted to the steam temperature control device. Control unit to return to the previous target temperature.

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