JP4690904B2 - Boiler system and control method thereof - Google Patents

Description

  The present invention relates to a boiler system and a control method thereof.

  There is known a boiler system that generates high-temperature gas in a boiler, heats the steam using the gas, and drives a steam turbine by the steam. In such a boiler system, when the temperature of the steam is lowered, the control for suppressing the drop in the steam temperature is performed by increasing the flow rate of the gas used for heating the steam. There is a need for a boiler system and a control method thereof that can further improve the followability to a load change.

  In Patent Document 1, in view of the problem that, when the load increases, a large amount of heat is consumed due to the combustion of fuel to increase boiler heat storage, and the reheater outlet steam temperature is unavoidably reduced. A reheat steam temperature control device for a boiler in which the opening of the gas damper is widened before the actual load change is described.

Patent Document 2 discloses a reheat boiler that is intended to prevent a transient decrease in the reheater steam temperature during a rapid load drop without impairing stable combustion and without increasing the amount of NOx generated. , And how to operate the reheat boiler. This document describes control using a boiler input acceleration signal (BIR) when the load changes.
Japanese Patent Laid-Open No. 2002-168406 Japanese Patent Laid-Open No. 2003-322332

An object of the present invention is to improve the controllability of a boiler.
Another object of the present invention is to improve the stability of the steam temperature of the boiler when the load fluctuates.
Still another object of the present invention is to provide a boiler system capable of setting a large load fluctuation speed.

  In the following, means for solving the problem will be described using the numbers used in [Best Mode for Carrying Out the Invention] in parentheses. These numbers are added to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers should not be used to interpret the technical scope of the invention described in [Claims].

  The boiler system according to the present invention includes a reheater (10) that heats internal steam by heat exchange with surrounding gas (6), and a part of the introduced steam that is introduced into the reheater (10) as internal steam. An extraction unit (45, 46, 102, 104) that is reduced by extracting as extraction steam, and an extraction control unit that controls the amount of extraction steam based on the temperature of the internal steam detected by the reheater (10) ( 56).

  The boiler system according to the present invention includes a gas flow rate control unit (54) that controls the flow rate of the surrounding gas (6) in response to the opening degree command. The extraction control unit (56) increases the amount of extraction steam when the opening degree command of the gas flow control unit (54) is larger than a predetermined reference.

  In the boiler system according to the present invention, the extraction control unit (56) reduces the amount of extraction steam when the opening degree command of the gas flow rate control unit (54) is smaller than a predetermined second reference smaller than a predetermined reference.

  In the boiler system according to the present invention, the gas flow rate control unit (54) includes a gas damper (12) that controls the flow rate by changing the cross-sectional area of the flow path (6) through which the surrounding gas flows.

  The boiler system according to the present invention comprises a furnace (4) that burns fuel therein and supplies it to the reheater (10) as ambient (6) gas. The gas flow rate control unit (54) includes a recirculation fan (50) that controls the flow rate by circulating the gas in the surrounding (6) downstream of the reheater (10) into the furnace.

  The boiler system according to the present invention drives a furnace (4) that burns fuel therein and supplies the fuel as ambient (6) gas to the reheater (10), and internal steam supplied from the reheater (10). Turbine (32, 34) used as steam and a fuel command value generation unit for generating a fuel command value for controlling the amount of fuel supplied to the furnace (4) in response to the load of the turbine (32, 34) (24) and a fuel command value correction unit (25) that performs feedforward control so that the fuel command value decreases when the load decreases.

  The boiler system according to the present invention includes a furnace (4) that burns fuel therein and supplies it to the reheater (10) as ambient (6) gas, and heats the steam by heat generated by the furnace (4). A superheater (not shown) that generates superheated steam, and a turbine (34) that drives using superheated steam as drive steam and discharges introduced steam. The extraction unit (45, 46) extracts a part of the introduced steam discharged from the turbine (34) as extraction steam.

  The boiler system according to the present invention includes a furnace (4) that burns fuel therein and supplies it to the reheater (10) as ambient (6) gas, and heats the steam by heat generated by the furnace (4). A superheater (not shown) that generates superheated steam, and a turbine (34) that drives using superheated steam as drive steam and discharges introduced steam. The extraction unit (102, 104) extracts a part of superheated steam flowing between the superheater and the turbine (34) as extracted steam.

  The boiler system control method according to the present invention includes the steps of heating the steam flowing through the steam flow path of the reheater (10) by heat exchange with the combustion gas generated by the boiler (2a), and the reheater (10). Detecting the steam outlet temperature on the outlet side of the heater, and increasing the opening of the damper (12, 52) for adjusting the flow rate of the combustion gas around the reheater (10) when the outlet temperature decreases. A step of increasing the flow rate by extracting a part of the introduced steam introduced into the reheater (10) as the extraction steam when the opening degree of the damper (12, 52) is equal to or greater than a predetermined reference opening degree. Reducing steps.

According to the present invention, the controllability of the boiler is improved.
Furthermore, according to this invention, the stability of the steam temperature of the boiler at the time of load fluctuation improves.
Furthermore, according to the present invention, there is provided a boiler system capable of setting a large load fluctuation speed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a boiler system. The boiler system includes a boiler 2a. The boiler 2a includes a furnace 4 having a combustion space inside. A burner (not shown) is installed in the furnace. Fuel is supplied to the burner from the fuel supply unit 18 through the fuel pipe 20, and air is supplied through the air pipe 22.

  The furnace 4 is connected to the rear heat transfer section. The rear heat transfer section includes a reheater channel 6 and a superheater channel 8 that are partitioned by a partition wall. A reheater 10 is installed in the reheater flow path 6. The reheater 10 is provided with a water supply spray 16 for preventing overheating. The reheater 10 includes a steam flow path through which internal steam flows. The internal steam exchanges heat with the gas around the reheater 10, that is, inside the reheater flow path 6. A reheater gas damper 12 is provided in the reheater channel 6 on the downstream side of the reheater 10. The reheater gas damper 12 adjusts the flow rate of the gas flowing through the reheater flow path 6 by reducing the cross-sectional area of the reheater flow path 6. A superheater gas damper 14 for adjusting the flow rate of the gas flowing through the superheater flow path 8 is provided downstream of the superheater flow path 8 from the superheater.

  A plurality of superheaters connected in series are installed in the boiler 2a. These superheaters are provided with a steam channel through which steam flows. The outlet side of the lowermost steam flow path among the plurality of superheaters is connected to the inlet of the high-pressure turbine 34.

  The outlet side of the high pressure turbine 34 is connected to one end of the reheater inlet side pipe 42. The introduced steam introduced into the reheater 6 flows inside the reheater inlet pipe 42. The other end of the reheater inlet pipe 42 is connected to the inlet of the steam flow path of the reheater 10. The outlet side of the steam flow path of the reheater 10 is connected to the inlet of the intermediate / low pressure turbine 32 via a reheater outlet side pipe. The outlet side of the intermediate / low pressure turbine 32 is connected to the inlet of the condenser 40 via a condenser inlet side pipe. The high-pressure turbine 32 and the medium-low pressure turbine 34 are connected by a shaft for synthesizing torque. The combined torque is transmitted to the generator 38.

  An extraction point 44 is set in the reheater inlet side pipe 42. At the extraction point 44, the reheater inlet side pipe 42 is connected to one end of the bypass pipe 45. The other end of the bypass pipe 45 is connected to the condenser inlet side pipe. The bypass pipe 45 is provided with a bleed valve 46.

  The boiler system includes a fuel command value generation unit 24. The fuel command value generation unit 24 receives a load command 26 that is a signal for controlling a load applied to the turbine group including the medium-low pressure turbine 32 and the high-pressure turbine 34. When the load command 26 is input, the fuel command value generation unit 24 generates an opening command 23 indicating the amount of fuel and air supplied to the burner of the furnace 4 using a function stored in advance. To do.

  The boiler system further includes a BIR unit 25. BIR is an abbreviation for “Boiler Input Regulator” or “Boiler Incremental Rate”. The BIR unit 25 receives an opening degree command 23 generated by the fuel command value generation unit 24 and a preceding signal 27 used for correcting the load command 26. When the load command 26 is not input, the BIR unit 25 outputs the opening command 23 as it is to the fuel supply unit 18 as the corrected opening command 28. When the load command 26 is input, the BIR unit 25 generates a corrected opening command 28 in which the opening command 23 is corrected in response to the preceding signal 27 and outputs the corrected opening command 28 to the fuel supply unit 18. The fuel supply unit 18 controls the amount of fuel and air supplied to the furnace 4 using the input correction opening degree command 28.

  The reheater outlet side pipe is provided with a temperature sensor 30 that detects the temperature of the steam flowing through the pipe and generates a reheater outlet steam temperature detection value. The boiler system further includes a control unit 48a. The controller 48a generates the reheater gas damper opening command and the reheater bypass control valve opening command using the temperature information received from the temperature sensor 30. The opening degree of the reheater gas damper 12 changes in response to the reheater gas damper opening degree command. The opening degree of the extraction valve 46 changes in response to the reheater bypass control valve opening degree command.

  FIG. 2 shows the configuration of the control unit 48a. The control unit 48 a includes a gas flow rate control unit 54 and a bypass control unit 56. The bypass control unit 56 is also referred to as an extraction control unit in order to control extraction from the reheater inlet side pipe. The gas flow rate control unit 54 includes a subtractor 58 and a PI calculator 60. The subtractor 58 receives the recombustor outlet steam temperature set value and the reheater outlet steam temperature detection value generated by the temperature sensor 30. The subtractor 58 outputs the difference between the input reheater outlet steam temperature setting value and the reheater outlet steam temperature detection value. The PI calculator 60 performs a proportional integral compensation calculation, and generates and outputs a reheater gas damper opening command so as to reduce the difference output from the subtractor 58.

  The bypass controller 56 includes a first opening command determination unit 62, a second opening command determination unit 64, a switch 66, a signal generator 68, a PI calculator 70, a switch 72, a signal generator 74, and a gate limiter 76. Is provided. A reheater gas damper opening command output from the PI calculator 60 is input to the first opening command determination unit 62. The first opening command determination unit 62 stores a first opening command reference value. The first opening command reference value is preferably set to a value indicating that the reheater gas damper 12 is fully open or close to full open. The first opening command determination unit 62 generates bypass use start information including information indicating a magnitude relationship between the reheater gas damper opening command and the first opening command reference value. In the following description, the bypass use start information when the reheater gas damper opening command is smaller than the first opening command reference value is “not start using bypass”, and the reheater gas damper opening command is the first opening. Bypass use start information when it is larger than the command reference value is expressed as “bypass use start”.

  The second opening command determination unit 64 receives a reheater gas damper opening command output from the PI calculator 60. The second opening command determination unit 64 stores a second opening command reference value. The second opening command reference value is set to the same value as the first opening command reference value or a value smaller than the first opening command reference value. Hereinafter, the case where it is set to a value smaller than the first opening command reference value will be described. The second opening command determination unit 64 generates bypass use stop information including information indicating the magnitude relationship between the reheater gas damper opening command and the second opening command reference value. In the following description, the bypass use stop information when the reheater gas damper opening command is larger than the second opening command reference value is “no bypass use stop”, and the reheater gas damper opening command is the second opening. Bypass use stop information when it is smaller than the command reference value is expressed as “bypass use stop”.

  The signal generator 68 generates numerical information indicating the numerical value 0. The switch 66 receives the bypass use start information generated by the first opening command determination unit 62, the difference output from the subtractor 58, and the numerical information generated by the signal generator 68. When the bypass use start information is “not start using bypass”, the switch 66 outputs the numerical information input from the signal generator 68 to the PI calculator 70 as a PI calculation input deviation. When the bypass use start information is “bypass use start”, the switch 66 outputs the difference input from the subtractor 58 to the PI calculator 70 as a PI calculation input deviation. The PI calculator 70 performs proportional integral compensation calculation, and generates and outputs a reheater gas damper control valve opening command so as to reduce the PI calculation input deviation.

  The signal generator 74 generates numerical information indicating the numerical value 0. The switching unit 72 includes bypass use stop information output from the second opening command determination unit 64, reheater gas damper control valve opening command output from the PI calculator 70, and numerical information generated by the signal generator 74. Are entered. When the bypass use stop information is “no bypass use stop”, the switching unit 72 outputs the reheater gas damper control valve opening command input from the PI calculator 70 as a gate limiter input value. When the bypass use stop information is “bypass use stop”, the switching unit 72 outputs the numerical information input from the signal generator 74 as the gate limiter input value. The gate limiter 76 corrects the gate limiter input value input from the switching unit 72 so that it falls within a predetermined range, and outputs it as a reheater bypass control valve opening command.

  The fuel command value generation unit 24, the BIR unit 25, or the control unit 48 can be realized using a computer system. In that case, each external communication is performed via a communication interface, and each internal information process is executed by software by reading and executing a program stored in a storage medium by the arithmetic and control unit. .

Next, operation | movement of a boiler system provided with the above structure is demonstrated.
(When load is settled)
A control device (not shown) that controls the load transmits a load command 26 used for the control to the fuel command value generation unit 24 at a predetermined time period. When the load is settled, the preceding signal 27 is not input to the BIR unit 25. At this time, the BIR unit outputs the opening degree command 23 as the corrected opening degree command value 28 as it is.

  The fuel supply unit 18 supplies fuel and air in amounts corresponding to the corrected opening command value 28 to the burner of the furnace 4. The burner 4 generates a flame using the fuel and air, and heats the gas inside the furnace 4. The heated gas is introduced into the rear heat transfer section and discharged through the reheater flow path 6 and the superheater flow path 8. The gas flow rate in the reheater channel 6 and the gas flow rate in the heater channel 8 are controlled by the opening degree of the reheater gas damper 12 and the opening degree of the superheater gas damper 14.

  The steam flowing through the steam flow path inside the superheater (not shown) is heated by exchanging heat with the gas of the boiler 2a, and is introduced into the high-pressure turbine 34 through the high-pressure turbine inlet pipe 36 as driving steam. The driving steam discharged from the high-pressure turbine 34 is introduced into the steam flow path inside the reheater 10 via the reheater inlet side pipe 42. Normally, the reheater bypass control valve 46 is fully closed, and the driving steam discharged from the high-pressure turbine 34 does not flow through the bypass pipe 45.

  The driving gas (internal steam) introduced into the steam flow path of the reheater 10 is heated by exchanging heat with the gas flowing through the reheater flow path 6 around the reheater 10, and the reheater outlet side pipe Is introduced as driving steam into the medium-low pressure turbine 32. The driving steam discharged from the intermediate / low pressure turbine 32 is condensed by the condenser 40.

  The temperature sensor 30 detects the temperature of the steam flowing through the inside of the reheater outlet side pipe at a predetermined cycle, generates a reheater outlet steam temperature detection value indicating the detected temperature, and transmits the detected value to the control unit 48a. . The controller 48a further inputs a reheater outlet steam temperature set value. The gas flow rate control unit 54 of the control unit 48a performs proportional integral control of the reheater gas damper opening so that the absolute value of the difference between the reheater outlet steam temperature detection value and the reheater outlet steam temperature setting value becomes small. To output a reheater gas damper opening degree command.

  The bypass control unit 56 inputs the reheater gas damper opening command generated by the PI calculator 60. When the reheater gas damper opening command is smaller than the first opening command reference value, “bypass use is not started”, and the switching unit 66 transmits numerical information indicating 0 input from the signal generator 68 to the subsequent stage. To do. The PI calculator 70 continues to output 0 while 0 is being input. The switching unit 72 selects either 0 input from the PI calculator 70 or 0 output from the signal generator 74 and eventually outputs 0 to the subsequent stage. This output signal passes through the gate limiter 76 and is output as a reheater bypass control valve opening command. By this signal, the reheater bypass control valve 46 is controlled so that the opening degree is zero. The driving steam discharged from the high-pressure turbine 34 is supplied to the reheater 10 through the reheater inlet side pipe 42 without escaping to the bypass pipe 45.

(At load drop)
When the load applied to the turbine section including the low and intermediate pressure turbine 32 and the high pressure turbine 34 drops (decreases), the amount of heat stored in the boiler 2a is large, and thus a response delay of the boiler 2a occurs. That is, since the amount of heat required for the boiler 2a decreases when the load drops, control is performed so that the fuel and air supplied to the burner decrease to weaken the flame, but the amount of heat stored in the boiler 2a is large. Therefore, the pressure and temperature of the combustion gas generated by the furnace 4 do not decrease immediately (boiler response delay).

  In order to avoid a response delay of the boiler, the boiler system includes a BIR unit 25. When the load is lowered, a control device (not shown) that controls the load transmits a preceding signal 27 notifying the lowering of the load to the BIR unit 25 in advance. The BIR unit 25 performs feedforward control of the amount of air and heat supplied to the burner of the furnace 4 using the preceding signal 27. That is, the BIR unit 25 performs correction opening so that the amount of fuel and air supplied to the burner of the furnace 4 is narrowed at a rate (BIR) larger than the opening degree command 23 generated by the fuel command value generation unit 24. A degree command 28 is generated and output. The fuel supply unit 18 reduces the amount of air and fuel supplied to the burner of the furnace 4 in response to the corrected opening degree command 28. The gas flow rate and combustion temperature of the furnace 4 are lowered.

  As a result of the feedforward control by the BIR section, there is a possibility that the amount of heat is reduced more than compensating for the heat storage of the boiler 2a. In that case, on the other hand, when the gas flow rate of the boiler 2a decreases, the temperature of the internal steam heated in the steam flow path inside the reheater 10 temporarily decreases. On the other hand, when the load drops, the flow rate of the steam flowing through the steam flow path of the reheater 10 also decreases, and this decrease in the flow rate acts in the direction of increasing the steam temperature. As a result, the temperature of the steam becomes stable again after a transition period.

  In the transition period, the steam temperature on the outlet side of the reheater 10 tends to decrease. At this time, the gas flow rate control unit 54 generates a reheater gas damper opening command so that the opening of the reheater gas damper 12 increases. As a result, the flow rate of the gas flowing through the reheater flow path 6 increases, and the temperature of the steam on the outlet side of the reheater 10 increases. This control is performed until the opening degree of the reheater gas damper 12 approaches full opening.

  When the reheater gas damper 12 is fully opened and it is desired to further increase the steam temperature on the outlet side of the reheater 10, the reheater bypass control valve 46 is opened. Then, a part of the steam is extracted from the reheater inlet side pipe 42 into the bypass pipe 45. Since the pressure difference between the reheater inlet pipe 42 and the condenser 40 is large, extraction is performed at a high speed. As a result, the flow rate of the steam introduced into the reheater 10 decreases, and the steam temperature on the outlet side of the reheater 10 increases. By such control, even when the reheater gas damper 12 is fully opened, it is possible to further increase the steam temperature. Thereby, the stability of the steam temperature of the boiler at the time of load drop improves. Alternatively, the load fluctuation speed can be set large while maintaining the stability of the steam temperature.

  Control of the reheater bypass control valve 46 will be described below. When the reheater gas damper 12 is fully opened (or an opening close to full open), the reheater gas damper opening command exceeds the first opening command reference value stored in the first opening command determination unit 62. Then, the switcher 66 transmits the difference between the detected value of the reheater outlet steam temperature output from the subtractor 58 and the set value to the PI calculator 70. The PI computing unit 70 generates a reheater bypass control valve opening command based on the difference.

  Since the second opening command reference value stored in the second opening command determination unit 64 is set to be equal to or less than the first opening command reference value, the switch 72 uses the output of the PI compensator 70 as a gate limiter. The input value is selected and output to the gate limiter 76. The gate limiter 76 corrects the gate limiter input value so as to be within a predetermined range, and outputs it as a reheater bypass control valve opening command. As a result, the reheater bypass control valve 46 is proportionally integrated based on the difference between the detected value of the steam temperature on the outlet side of the reheater 10 and the set value.

  When the reheater bypass control valve 46 is opened, the reheater outlet steam temperature detection value increases. As a result, the value of the reheater gas damper opening command becomes small. When the reheater gas damper opening command falls below the second opening command reference value stored in the second opening command determination unit 64, the switching device 72 gates numerical information indicating the numerical value 0 generated by the signal generator 74. This is selected as a limiter input value and output to the gate limiter 76. As a result, the reheater bypass control valve 46 is closed at the fastest speed permitted by the gate limiter 76. Thereby, when an increase in the steam temperature is not required, the steam escaped to the bypass pipe 45 is reduced, and highly efficient operation is possible.

When the second opening command reference value is set smaller than the first opening command reference value, it is preferable that hunting of the opening of the reheater bypass control valve 46 is reliably prevented. This will be described in more detail below. When the steam temperature on the downstream side of the reheater 10 decreases, hunting may occur due to the following four processes being repeated in a self-circulating manner.
(1) The reheater gas damper opening command is increased in response to a decrease in the steam temperature and exceeds the reference value.
(2) The reheater bypass control valve is opened.
(3) The reheater gas damper opening command becomes smaller in response to the increase in the steam temperature and falls below the reference value.
(4) The reheater bypass control valve is closed.
Setting the second opening command reference value to be smaller than the first opening command reference value means that the reference value in (3) is set to be smaller than the reference value in (1). The margin between the reference values avoids the possibility of hunting control of the reheater bypass control valve 46.

  The control unit 48a preferably has a function of performing processing related to the temperature decrease reference value. In this case, the control unit 48a stores the temperature decrease reference value. Then, the reheater bypass control valve 46 is opened only when the temperature drop of the reheater outlet steam temperature detection value falls below the temperature drop reference value compared to the time when the reheater gas damper 12 is fully opened. to approve. Such control prevents the steam from escaping to the bypass pipe 45 and reducing the efficiency when the temperature drop is small and it is not required to recover the temperature.

  FIG. 3 shows another embodiment of a control unit for controlling the boiler system. Instead of the control unit 48a in the boiler system described in FIG. 1, the control unit 48b shown in FIG. 3 can be used. The control unit 48 b includes a gas flow rate control unit 78 and a bypass control unit 80. The gas flow rate controller 78 includes the same subtractor 58 and PI calculator 60 as the gas flow rate controller 54 shown in FIG. The gas flow rate controller 78 does not have a signal line for transmitting the output signal of the subtractor 58 to the switch 66 in the gas flow rate controller 54 shown in FIG. Other configurations of the gas flow rate control unit 78 are the same as those of the gas flow rate control unit 54.

  The bypass control unit 80 includes the same first opening command determination unit 62, second opening command determination unit 64, and gate limiter 76 as the bypass control unit 56 in FIG. The bypass control unit 80 further includes a switch 90, a signal generator 92, a switch 94, and a signal generator 96.

  The switch 90 is input with bypass use start information generated by the first opening degree determination unit 62, numerical information generated by the signal generator 96, and numerical information generated by the signal generator 96. The numerical information generated by the signal generator 92 indicates a predetermined opening, for example, 100% (fully open), which is greater than 0% (fully closed) of the reheater bypass control valve 46. The numerical information of the signal generator 92 is set by input performed by the operator from the input device. The numerical information generated by the signal generator 96 indicates the opening degree 0% of the reheater bypass control valve. The switch 90 transmits numerical information (opening degree 0%) input from the signal generator 96 to the switching unit 94 when the bypass use start information is “not start using bypass”. When the bypass use start information is “bypass use start”, the switch 90 transmits numerical information (a predetermined opening degree greater than 0%) input from the signal generator 92 to the switch unit 94.

  The switching unit 94 receives bypass use stop information generated by the second opening degree determination unit 64, information output by the switching unit 94, and numerical information generated by the signal generator 96. The switching unit 94 outputs the information input from the switching unit 90 to the gate limiter 76 when the input bypass use stop information is “no bypass use stop”. The switching unit 94 outputs the information input from the signal generator 96 to the gate limiter 76 when the input bypass use stop information is “bypass use stop”. The gate limiter 76 corrects the input information so that it falls within a predetermined range, and outputs it as a reheater bypass control valve opening command.

  Control of a boiler system provided with such a control unit 48b will be described below. When the reheater gas damper 12 is fully opened (or an opening close to full open), the reheater gas damper opening command exceeds the first opening command reference value stored in the first opening command determination unit 62. Then, the switch 66 transmits the numerical information generated by the signal generator 92 (indicating a predetermined opening greater than 0%) to the switch 94.

  Since the second opening command reference value stored in the second opening command determination unit 64 is set to be equal to or less than the first opening command reference value, the switch 94 inputs the output of the switch 90 to the gate limiter. The value is selected and output to the gate limiter 76. The gate limiter 76 corrects the gate limiter input value so as to be within a predetermined range, and outputs it as a reheater bypass control valve opening command. As a result, the reheater bypass control valve 46 is controlled using the predetermined opening degree stored in the signal generator 92 as a target value.

  When the reheater bypass control valve 46 is opened, the reheater outlet steam temperature detection value increases. As a result, the value of the reheater gas damper opening command becomes small. When the reheater gas damper opening command falls below the second opening command reference value stored in the second opening command determination unit 64, the switch 94 gates numerical information indicating the numerical value 0 generated by the signal generator 96. This is selected as a limiter input value and output to the gate limiter 76. As a result, the reheater bypass control valve 46 is closed at the fastest speed permitted by the gate limiter 76.

  In such a controller 48b, the reheater bypass control valve 46 is opened with a predetermined opening set by the operator as a target value. This operation is performed when the reheater gas damper 12 is required to be fully opened and the steam temperature further increased. Since this is an exceptional operating condition, control based on the operator's human judgment may be desirable. In that case, the control of this embodiment using the opening degree (stored in the signal generator 68) set by the operator is desirable.

  FIG. 4 shows the configuration of a boiler system according to another embodiment. The boiler system includes a boiler 2b. The boiler 2b includes a furnace 4 having a combustion space inside. A burner (not shown) is installed in the furnace. Fuel is supplied to the burner from the fuel supply unit 18 through the fuel pipe 20, and air is supplied through the air pipe 22.

  The furnace 4 is connected to the rear heat transfer section. The rear heat transfer section includes a reheater channel 6a. A reheater 10a is installed in the reheater channel 6a. The reheater 10a includes a steam channel through which steam flows. The boiler 2b further includes a recirculation flow path 49, a recirculation fan 50, and a recirculation fan inlet vane. On the downstream side of the reheater 10 a, a part of the gas flowing through the reheater flow path 6 a is introduced into the furnace 4 through the recirculation flow path 49 by the flow generated by the recirculation fan 50. Another part of the gas flowing through the reheater channel 6a is discharged to the outside of the boiler 2a. The flow rate of the gas through the recirculation flow path 49 is adjusted by controlling the opening degree of the recirculation fan inlet vane.

  The boiler system includes a control unit 48c. The configuration of the control unit 48c is substantially the same as the configuration of the control unit 48a shown in FIG. 2 or the control unit 48b shown in FIG. The difference is that the recirculation fan inlet vane opening command is set to be output instead of the reheater gas damper opening command output by the gas flow rate control unit 54, and the others are the same. . 2 or 3, the first opening command reference value stored in the first opening command determination unit 62 and the second opening command reference value stored in the second opening command determination unit 64 are reheated. Means the opening of the recirculation fan inlet vane 52, not the value indicating the opening of the gas damper 12.

  In such a boiler system, when it is required to increase the steam temperature on the outlet side of the reheater 10a and the recirculation fan inlet vane 52 is fully open, the control unit 48c performs control to open the reheater bypass control valve 46. A part of the steam introduced into the reheater 10 a escapes to the bypass pipe 45. As a result, the steam flowing through the steam flow path of the reheater 10a decreases, and the steam temperature on the outlet side of the reheater 10a increases.

  FIG. 5 shows the configuration of a boiler system in still another embodiment. The boiler system in the present embodiment is replaced with a bypass pipe 102, a high-pressure turbine bypass control valve 104, and a control instead of the bypass pipe 45, the reheater bypass control valve 46, and the control unit 48 included in the boiler system shown in FIG. 48d. One end of the bypass pipe 102 is connected to an extraction point 100 set in a pipe on the inlet side of the high-pressure turbine 34 that supplies steam to the reheater 10. The other end of the bypass pipe 102 is connected to a pipe on the inlet side of the condenser 40.

  The configuration of the control unit 48d is almost the same as the configuration of the control unit 48a shown in FIG. 2 or the control unit 48b shown in FIG. The difference is that instead of the reheater bypass control valve opening command output by the bypass control unit, a high pressure turbine bypass opening command is set to be output, and the others are the same. 2 or 3, the first opening command reference value stored in the first opening command determination unit 62 and the second opening command reference value stored in the second opening command determination unit 64 are reheated. Means the opening of the high-pressure turbine bypass control valve 104 rather than a value indicating the opening of the gas damper 12.

  In such a boiler system, when it is required to increase the steam temperature on the outlet side of the reheater 10 and the reheater gas damper 12 is fully open, the control unit 48c performs control to open the high pressure turbine bypass control valve 104, and the high pressure A part of the steam introduced into the turbine 34 escapes to the bypass pipe 102, and the amount of steam discharged from the high-pressure turbine 34 also decreases. As a result, the steam flowing through the steam flow path of the reheater 10 decreases, and the steam temperature on the outlet side of the reheater 10 increases.

  FIG. 6 shows the configuration of a boiler system in still another embodiment. The boiler system in the present embodiment is replaced with a bypass pipe 102, a high-pressure turbine bypass control valve 104, and a control instead of the bypass pipe 45, the reheater bypass control valve 46, and the control unit 48c included in the boiler system shown in FIG. A portion 48e is provided. One end of the bypass pipe 102 is connected to an extraction point 100 set in a pipe on the inlet side of the high-pressure turbine 34 that supplies steam to the reheater 10. The other end of the bypass pipe 102 is connected to a pipe on the inlet side of the condenser 40.

  The configuration of the control unit 48e is almost the same as the configuration of the control unit 48c of FIG. The difference is that instead of the reheater bypass control valve opening command output by the bypass control unit, a high pressure turbine bypass opening command is set to be output, and the others are the same.

  In such a boiler system, when it is required to increase the steam temperature on the outlet side of the reheater 10 and the recirculation fan inlet vane 52 is fully open, the control unit 48e performs control to open the high-pressure turbine bypass control valve 104, A part of the steam introduced into the high-pressure turbine 34 escapes to the bypass pipe 102, and the amount of steam discharged from the high-pressure turbine 34 also decreases. As a result, the steam flowing through the steam flow path of the reheater 10 decreases, and the steam temperature on the outlet side of the reheater 10 increases.

FIG. 1 shows the configuration of a boiler system. FIG. 2 shows the configuration of the control unit. FIG. 3 shows the configuration of the control unit. FIG. 4 shows the configuration of the boiler system. FIG. 5 shows the configuration of the boiler system. FIG. 6 shows the configuration of the boiler system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Boiler 4 ... Furnace 6 ... Reheater flow path 8 ... Superheater flow path 10 ... Reheater 12 ... Reheater gas damper 14 ... Superheater gas damper 16 ... Feed water spray pipe 18 ... Fuel supply part 20 ... Fuel pipe 22 ... Air piping 23 ... Opening degree command 24 ... Fuel command value generating unit 25 ... BIR part 26 ... Load command 27 ... Predecessor signal 28 ... Correction opening degree command 30 ... Temperature sensor 32 ... Medium and low pressure turbine 34 ... High pressure turbine 36 ... High pressure turbine Inlet piping 38 ... Generator 40 ... Condenser 42 ... Reheater inlet side piping 44 ... Extraction point 45 ... Bypass piping 46 ... Reheater bypass control valve 48 ... Control unit 50 ... Recirculation fan 52 ... Recirculation fan inlet Vane 54 ... Gas flow rate control unit 56 ... Bypass control unit 58 ... Subtractor 60 ... PI calculator 62 ... First opening degree determination part 64 ... Second opening degree determination part 66 ... Switcher 68 ... Signal generator 70 ... PI calculation Vessel 72 Switch 74 ... Signal generator 76 ... Gate limiter 78 ... Gas flow rate controller 80 ... Bypass controller 90 ... Switch 92 ... Signal generator 94 ... Switch 96 ... Signal generator 100 ... Bleed point 102 ... Bypass piping 104 ... High pressure turbine bypass control valve

Claims (7)

A reheater that heats the internal steam by heat exchange with surrounding gas,
An extraction part that reduces by extracting a part of the introduction steam introduced as the internal steam into the reheater as extraction steam;
An extraction control unit that controls the amount of the extraction steam based on the temperature of the internal steam detected by the reheater;
A gas flow rate control unit for controlling the flow rate of the surrounding gas in response to an opening degree command,
The extraction control unit starts extraction by the extraction unit when the opening degree command is larger than a predetermined reference value .
Furthermore, a furnace for burning fuel inside and supplying the reheater as the surrounding gas;
A superheater that generates superheated steam by heating steam with heat generated by the furnace;
A turbine that drives using the superheated steam as driving steam and discharges the introduced steam;
The extraction unit is a boiler system that extracts a part of the introduced steam that is discharged from the turbine and introduced into the reheater as the extracted steam. A boiler system according to claim 1,
The extraction control unit is a boiler system that reduces the amount of extraction steam when the opening degree command is smaller than a predetermined second reference smaller than the predetermined reference. A boiler system according to claim 1,
The gas flow control unit includes a gas damper that controls the flow rate by changing a cross-sectional area of a flow path through which the surrounding gas flows. A boiler system according to claim 1,
And a furnace for combusting fuel therein and supplying the surrounding gas as the surrounding gas to the reheater,
The gas flow control unit includes a recirculation fan that controls the flow rate by circulating the surrounding gas on the downstream side of the reheater into the furnace. A boiler system according to claim 3,
Furthermore, a furnace for burning fuel inside and supplying the reheater as the surrounding gas;
A turbine that uses the internal steam supplied from the reheater as driving steam;
A fuel command value generator for generating a fuel command value for controlling the amount of the fuel supplied to the furnace in response to the load of the turbine;
A boiler system comprising: a fuel command value correction unit that performs feed-forward control so that the fuel command value decreases when the load decreases. A boiler system according to claim 4, wherein
Furthermore, a turbine that uses the internal steam supplied from the reheater as driving steam;
A fuel command value generator for generating a fuel command value for controlling the amount of the fuel supplied to the furnace in response to the load of the turbine;
A boiler system comprising: a fuel command value correction unit that performs feed-forward control so that the fuel command value decreases when the load decreases. Heating the steam flowing through the steam flow path of the reheater by heat exchange with the combustion gas generated by the boiler;
Detecting the outlet temperature of the steam on the outlet side of the reheater;
Increasing the flow rate by increasing the opening of a damper that adjusts the flow rate of the combustion gas around the reheater when the outlet temperature decreases;
Reducing the amount of introduced steam introduced into the reheater by extracting as extracted steam when the opening of the damper is equal to or greater than a predetermined reference opening;
The reducing step is started when the opening command of the opening of the damper is larger than a predetermined reference value ,
Furthermore, heating the steam with heat generated by a furnace that burns fuel inside and supplies the reheater as the combustion gas in the surroundings to generate superheated steam;
Driving the turbine that discharges the introduced steam by using the superheated steam as driving steam,
A boiler system control method in which a portion of the introduced steam discharged from the turbine and introduced into the reheater is extracted as the extracted steam.

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