JP2019174085A - Exhaust heat recovery boiler, control device, and combined cycle plant - Google Patents

Abstract

To suppress control delay by improving followability of steam temperature control and enable highly-accurate steam temperature control, in an exhaust heat recovery boiler, a control device, and a combined cycle plant.SOLUTION: An exhaust heat recovery boiler is provided with: a temperature reducer 43 that supplies cooling water to generated steam to reduce the temperature; a flow regulating valve 46 that regulates the amount of cooling water supplied to the temperature reducer 43; a valve opening setting part 61 that sets a valve opening At of the flow regulating valve 46 on the basis of a deviation between a preset target steam temperature Thpt and an actual steam temperature Thp supplied to a steam turbine 13; and a valve opening correction part 62 that increases the valve opening At when an exhaust gas temperature Text exceeds a preset exhaust gas upper limit temperature Textu.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust heat recovery boiler that generates steam by exhaust heat of exhaust gas, a control device for the exhaust heat recovery boiler, and a combined cycle plant.

  In combined cycle power generation, first, a gas turbine is driven using natural gas or the like as a fuel to generate power, and then an exhaust heat recovery boiler recovers the exhaust gas from the gas turbine to generate steam, which is used to generate the steam turbine. Drive to generate electricity. The combined cycle plant is a power plant for executing this combined cycle power generation.

  The waste heat recovery boiler of a combined cycle plant has a superheater, an evaporator, and a economizer as a heat exchanger. The exhaust heat recovery boiler generates steam by performing heat recovery in the order of the superheater, the evaporator, and the economizer when the exhaust gas from the gas turbine passes through the inside. At this time, the exhaust heat recovery boiler is provided with an upper limit value for the temperature of the generated steam, and is provided with a temperature reducer for adjusting the steam temperature. The temperature reducer lowers the temperature of the steam by spraying cooling water on the steam supplied from the first superheater to the second superheater.

  An example of such a combined cycle plant is described in Patent Document 1 below.

Japanese Patent No. 4166420

  Steam temperature control in the exhaust heat recovery boiler is performed by adjusting the amount of cooling water sprayed by the temperature reducer onto the steam. That is, the reference spray amount of the cooling water by the temperature reducer is set based on the preset target steam temperature, and the reference spray amount is corrected by feeding back the temperature of the steam after spraying the cooling water. However, in recent years, the exhaust gas temperature tends to increase due to the upsizing of the gas turbine, and the temperature of the steam generated in the exhaust heat recovery boiler may reach the upper limit early due to the increase of the exhaust gas temperature. In the steam temperature control in the conventional exhaust heat recovery boiler, the steam temperature is fed back to correct the spray amount of the cooling water by the temperature reducer. Therefore, a control delay for correcting the spray amount occurs here, and it becomes difficult to follow the correction control of the spray amount of the cooling water accompanying the increase in the steam temperature with respect to the rapid increase in the exhaust gas temperature.

  The present invention solves the above-described problem, and an exhaust heat recovery boiler, a control device, and a highly accurate steam temperature control capable of suppressing a control delay by improving the followability of the steam temperature control, and The purpose is to provide a combined cycle plant.

  In order to achieve the above object, an exhaust heat recovery boiler of the present invention is an exhaust heat recovery boiler that generates steam by exhaust heat of exhaust gas from a gas turbine, and reduces the temperature by supplying cooling water to the generated steam and reducing the temperature. A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer, and the flow rate adjusting valve based on a deviation between a preset target steam temperature and the actual steam temperature of steam supplied to the steam turbine. A valve opening degree setting unit that sets the valve opening degree, and a valve opening degree correction unit that increases the valve opening degree when the exhaust gas temperature exceeds a preset exhaust gas upper limit temperature. Is.

  Therefore, the valve opening degree setting unit sets the valve opening degree of the flow rate adjustment valve based on the deviation between the target steam temperature and the actual steam temperature of the steam supplied to the steam turbine, and the valve opening degree correcting unit sets the exhaust gas temperature. When the exhaust gas exceeds the exhaust gas upper limit temperature, the valve opening is increased. That is, when the exhaust gas temperature rises rapidly, the temperature of the generated steam also rises rapidly, but there is a possibility that the adjustment control of the valve opening degree in the flow rate adjustment valve will not be in time. Therefore, when the exhaust gas temperature suddenly rises, the valve opening degree of the flow rate adjustment valve is increased early to suppress the sudden rise in the exhaust gas temperature. As a result, it is possible to perform highly accurate steam temperature control by suppressing the control delay by improving the followability of steam temperature control.

  In the exhaust heat recovery boiler according to the present invention, the valve opening correction unit increases the valve opening based on a valve opening increasing rate with respect to the preset exhaust gas temperature.

  Therefore, since the valve opening degree correction unit increases the valve opening degree based on the rate of increase in the valve opening degree with respect to the exhaust gas temperature, it is possible to suppress a rapid increase in the exhaust gas temperature.

  In the exhaust heat recovery boiler of the present invention, the exhaust gas upper limit temperature is set by subtracting a margin value from the heat resistance temperature of the steam pipe.

  Therefore, since the exhaust gas upper limit temperature is set by subtracting the margin value from the heat resistance temperature of the steam pipe, damage to the steam pipe due to the rise in steam temperature can be prevented.

  In the exhaust heat recovery boiler according to the present invention, when the load change rate of the gas turbine is higher than a preset lower limit load change rate and the exhaust gas temperature exceeds a preset exhaust gas lower limit temperature, the target steam temperature is lowered. A target steam temperature correction unit is provided.

  Therefore, when the load change rate is higher than the lower limit load change rate and the exhaust gas temperature exceeds the exhaust gas lower limit temperature, the target steam temperature is lowered. Cooling water can be supplied to the steam to suppress a rapid rise in the steam temperature.

  In the exhaust heat recovery boiler according to the present invention, the valve opening degree setting unit holds the opening degree of the flow rate adjusting valve regardless of the deviation when the exhaust gas temperature is equal to or lower than a preset exhaust gas lower limit temperature. .

  Therefore, when the exhaust gas temperature falls below the exhaust gas lower limit temperature, the opening degree of the flow rate adjustment valve is maintained regardless of the deviation, so even if the exhaust gas temperature falls below the lower limit exhaust gas temperature, the valve opening degree of the flow rate adjustment valve becomes a minimum value. Even if the exhaust gas temperature rises rapidly, the temperature reducer can supply an appropriate amount of cooling water at an early stage and suppress the rapid rise in steam temperature.

  In the exhaust heat recovery boiler of the present invention, the valve opening setting unit includes a control amount based on a deviation between the target steam temperature and the actual steam temperature, and a post-temperature-reducing steam temperature reduced by the temperature reducer. The valve opening is set on the basis of the deviation.

  Therefore, the valve opening is set based on the deviation between the controlled variable based on the deviation between the target steam temperature and the actual steam temperature and the post-temperature-reducing steam temperature reduced by the temperature reducer. Can be set with high accuracy.

  Further, the exhaust heat recovery boiler of the present invention is an exhaust heat recovery boiler that generates steam by exhaust heat of exhaust gas from a gas turbine, and supplies a cooling water to the generated steam to reduce the temperature, and A flow rate adjustment valve that adjusts the amount of cooling water supplied to the heater, and the valve opening of the flow rate adjustment valve is set based on a deviation between a preset target steam temperature and the actual steam temperature of the steam supplied to the steam turbine. And a target for lowering the target steam temperature when the load change rate of the gas turbine is higher than a preset lower limit load change rate and the exhaust gas temperature exceeds a preset exhaust gas lower limit temperature. And a steam temperature correction unit.

  Further, the exhaust heat recovery boiler of the present invention is an exhaust heat recovery boiler that generates steam by exhaust heat of exhaust gas from a gas turbine, and supplies a cooling water to the generated steam to reduce the temperature, and A flow rate adjustment valve that adjusts the amount of cooling water supplied to the heater, and the valve opening of the flow rate adjustment valve is set based on a deviation between a preset target steam temperature and the actual steam temperature of the steam supplied to the steam turbine. And a valve opening setting unit that holds the opening of the flow rate adjusting valve regardless of the deviation when the exhaust gas temperature becomes equal to or lower than a preset exhaust gas lower limit temperature.

  Further, the control device of the present invention includes a temperature reducer for reducing the temperature by supplying cooling water to steam generated by exhaust heat of the exhaust gas of the gas turbine, and a flow rate adjustment for adjusting the amount of cooling water supplied to the temperature reducer. And a valve opening degree for setting the valve opening degree of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine. A setting unit and a valve opening correction unit that increases the valve opening when the exhaust gas temperature exceeds a preset exhaust gas upper limit temperature.

  Further, the control device of the present invention includes a temperature reducer for reducing the temperature by supplying cooling water to steam generated by exhaust heat of the exhaust gas of the gas turbine, and a flow rate adjustment for adjusting the amount of cooling water supplied to the temperature reducer. And a valve opening degree for setting the valve opening degree of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine. And a target steam temperature correction unit that lowers the target steam temperature when the load change rate of the gas turbine is higher than a preset lower limit load change rate and the exhaust gas temperature exceeds a preset exhaust gas lower limit temperature. These are provided.

  Further, the control device of the present invention includes a temperature reducer for reducing the temperature by supplying cooling water to steam generated by exhaust heat of the exhaust gas of the gas turbine, and a flow rate adjustment for adjusting the amount of cooling water supplied to the temperature reducer. An exhaust heat recovery boiler comprising a valve, and setting the valve opening of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine, and an exhaust gas temperature Is provided with a valve opening setting unit that holds the opening of the flow rate adjusting valve regardless of the deviation when the temperature becomes equal to or lower than a preset exhaust gas lower limit temperature.

  The combined cycle plant of the present invention is generated by a gas turbine having a compressor, a combustor, and a turbine, an exhaust heat recovery boiler that generates steam by exhaust heat of the exhaust gas from the gas turbine, and the exhaust heat recovery boiler. A high-pressure turbine driven by the generated steam and a steam turbine having a low-pressure turbine.

  Therefore, the gas turbine drives the turbine by the combustion gas generated by supplying fuel to the compressed air and burning it, the exhaust heat recovery boiler generates steam by the exhaust heat of the exhaust gas from the gas turbine, It is driven by the steam generated by the exhaust heat recovery boiler. At this time, in the exhaust heat recovery boiler, the valve opening degree setting unit sets the valve opening degree of the flow rate adjustment valve based on the target steam temperature, and the valve opening degree correcting unit sets the exhaust gas temperature above the exhaust gas upper limit temperature. Sometimes this valve opening is increased. As a result, it is possible to perform highly accurate steam temperature control by suppressing the control delay by improving the followability of steam temperature control.

  According to the exhaust heat recovery boiler, the control device, and the combined cycle plant of the present invention, it is possible to perform highly accurate steam temperature control while suppressing control delay by improving the followability of steam temperature control.

FIG. 1 is a schematic configuration diagram illustrating a combined cycle plant of the present embodiment. FIG. 2 is a schematic diagram illustrating a control block of the exhaust heat recovery boiler. FIG. 3 is a schematic diagram showing steam temperature control of the exhaust heat recovery boiler. FIG. 4 is a graph showing the rate of increase in the valve opening relative to the exhaust gas temperature. FIG. 5 is a flowchart showing correction control of the target steam temperature with respect to the gas turbine load and the exhaust gas temperature. FIG. 6 is a graph showing the exhaust gas temperature with respect to the gas turbine load. FIG. 7 is a flowchart showing valve opening degree control with respect to the exhaust gas temperature.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an exhaust heat recovery boiler, a control device, and a combined cycle plant according to the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment, and when there are two or more embodiments, what comprises combining each embodiment is also included.

  FIG. 1 is a schematic configuration diagram illustrating a combined cycle plant of the present embodiment.

  In the present embodiment, as shown in FIG. 1, the combined cycle plant 10 includes a gas turbine 11, an exhaust heat recovery boiler (HRSG) 12, a steam turbine 13, and generators 14 and 15.

  The gas turbine 11 includes a compressor 21, a combustor 22, and a turbine 23. The compressor 21 and the turbine 23 are connected by a rotating shaft 24 so as to be integrally rotatable, and the generator 14 is connected to the rotating shaft 24. The compressor 21 compresses the air taken in from the air intake line L1. The combustor 22 mixes and combusts the compressed air supplied from the compressor 21 through the compressed air supply line L2 and the fuel gas supplied from the fuel gas supply line L3. The turbine 23 is rotationally driven by the combustion gas supplied from the combustor 22 through the combustion gas supply line L4. The generator 14 generates electric power by the rotational force transmitted as the turbine 23 rotates.

  The exhaust heat recovery boiler 12 generates steam by exhaust heat of the exhaust gas discharged from the gas turbine 11 (turbine 23) through the exhaust gas discharge line L5. Although not shown, the exhaust heat recovery boiler 12 includes a high-pressure, medium-pressure, and low-pressure superheater, an evaporator, and a economizer as a heat exchanger. The exhaust heat recovery boiler 12 generates steam by performing heat recovery in the order of the superheater, the evaporator, and the economizer when the exhaust gas from the gas turbine 11 passes through the inside. The exhaust heat recovery boiler 12 is connected to a chimney (not shown) via an exhaust gas exhaust line L6 that exhausts used exhaust gas that has generated steam.

  The steam turbine 13 is driven by superheated steam generated by the exhaust heat recovery boiler 12 and has a turbine 31. In the turbine 31, a high-pressure turbine 32, an intermediate-pressure turbine 33, and a low-pressure turbine 34 are connected by a rotary shaft 35 so as to be integrally rotatable, and the generator 15 is connected to the rotary shaft 35. A high-pressure steam supply line L11 for supplying high-pressure steam from the high-pressure superheater of the exhaust heat recovery boiler 12 to the high-pressure turbine 32 is provided, and medium-pressure steam that has driven the high-pressure turbine 32 is returned to the reheater of the exhaust heat recovery boiler 12. An intermediate pressure steam recovery line L12 is provided. An intermediate pressure steam supply line L13 for supplying the intermediate pressure steam superheated by the superheater to the intermediate pressure turbine 33 is provided, and a low pressure steam conveyance line L14 for supplying the intermediate pressure steam driving the intermediate pressure turbine 33 to the low pressure turbine 34. Is provided. The generator 15 generates electric power by the rotational force transmitted as the turbine 31 rotates.

  The steam turbine 13 is provided with a condenser 36 that cools the steam that has driven the low-pressure turbine 34. The condenser 36 cools the steam discharged from the low-pressure turbine 34 with cooling water (for example, seawater) to make condensate. The condenser 36 sends the generated condensate to the exhaust heat recovery boiler 12 (carbon-saving device) via the condensate supply line L15. The condensate supply line L15 is provided with a condensate pump 37. The condenser 36 is provided with a cooling water line L16 for cooling the steam with seawater.

  Therefore, when the combined cycle plant 10 is in operation, the compressor 21 compresses air in the gas turbine 11, and the combustor 22 mixes the supplied compressed air and fuel gas and combusts them. The turbine 23 is rotationally driven by the combustion gas supplied from the combustor 22, and the generator 14 generates power. Further, the exhaust gas discharged from the gas turbine 11 (turbine 23) is sent to the exhaust heat recovery boiler 12, the exhaust heat recovery boiler 12 generates steam, and the superheated steam is sent to the steam turbine 13. The high pressure turbine 32, the intermediate pressure turbine 33, and the low pressure turbine 34 are rotationally driven by the superheated steam, and the generator 15 generates power. The steam used in the low-pressure turbine 34 is cooled by the condenser 36 to become condensed water, and is returned to the exhaust heat recovery boiler 12.

  FIG. 2 is a schematic diagram illustrating a control block of the exhaust heat recovery boiler.

  As shown in FIG. 2, the exhaust heat recovery boiler 12 generates steam by exhaust heat of exhaust gas from the gas turbine 11 (see FIG. 1), and includes a first superheater 41 and a second superheater 42. ing. The 1st superheater 41 and the 2nd superheater 42 superheat the vapor | steam produced | generated by the evaporator (not shown), and produce | generate superheated steam. The first superheater 41 and the second superheater 42 are provided with a temperature reducer 43 between them. The temperature reducer 43 reduces the temperature by spraying cooling water on the steam superheated by the first superheater 41. The temperature reducer 43 is connected to a water supply system (not shown) via a cooling water supply line L21. The cooling water supply line L21 is provided with a flow rate adjusting valve 46 that adjusts the amount of cooling water, and the opening degree of the flow rate adjusting valve 46 can be adjusted by a valve driving device 47.

  Therefore, in the exhaust heat recovery boiler 12, the steam is superheated by the first superheater 41 and the second superheater 42 to become superheated steam, and the temperature of the steam is adjusted by the temperature reducer 43. Superheated steam is supplied to the high pressure turbine 32 of the steam turbine 13. At this time, the valve drive device 47 adjusts the supply amount of the cooling water supplied from the water supply system through the cooling water supply line L21 by adjusting the opening degree of the flow rate adjusting valve 46. Then, an appropriate amount of cooling water is sent to the temperature reducer 43, and the temperature reducer 43 adjusts the steam temperature by spraying an appropriate amount of cooling water to the steam.

  The control device 51 can control the valve drive device 47. A steam line between the temperature reducer 43 and the second superheater 42 is provided with a first steam temperature sensor 52 that measures a post-temperature-reducing steam temperature (hereinafter referred to as a first steam temperature) Tdsh after spraying the cooling water. It has been. Further, a second steam temperature sensor 53 that measures an actual steam temperature (hereinafter referred to as a second steam temperature) Thp supplied to the steam turbine 13 is provided in the steam line downstream of the second superheater 42. The controller 51 receives the first steam temperature Tdsh measured by the first steam temperature sensor 52 and the second steam temperature Thp measured by the second steam temperature sensor 53.

  The gas turbine 11 (see FIG. 1) is provided with an exhaust gas temperature sensor 54 that measures the exhaust gas temperature Text in the exhaust gas discharge line L5 (see FIG. 1). The control device 51 receives the exhaust gas temperature Text measured by the exhaust gas temperature sensor 54. The control device 51 receives a load command value Lc of the gas turbine 11 from a gas turbine control unit (not shown).

  The control device 51 adjusts the opening degree of the flow rate adjustment valve 46 based on the first steam temperature Tdsh, the second steam temperature Thp, the exhaust gas temperature Text, and the load command value Lc. That is, the control device 51 corrects the target steam temperature Thpt by PI control based on the deviation Dt1 between the preset target steam temperature Thpt and the second steam temperature Thp of the steam generated by the exhaust heat recovery boiler 12. Based on the deviation Dt2 between the subsequent target steam temperature Thpt and the first steam temperature Tdsh of the steam that has been reduced by the temperature reducer 43, the valve opening degree At of the flow rate adjusting valve 46 is set by PI control.

  Further, the control device 51 includes a valve opening setting unit 61, a valve opening correction unit 62, and a target steam temperature correction unit 63.

  The valve opening setting unit 61 sets the valve opening At of the flow rate adjustment valve 46 based on the deviation between the preset target steam temperature Thpt and the actual steam temperature Thp supplied to the steam turbine 13. The valve opening correction unit 62 sets the correction valve opening Atc by increasing the valve opening At set by the valve opening setting unit 61 when the exhaust gas temperature Text exceeds a preset exhaust gas upper limit temperature Textu. .

  The target steam temperature correction unit 63 sets the target steam when the load change rate Lcr of the gas turbine 11 is higher than a preset lower limit load change rate Lcru and the exhaust gas temperature Text exceeds a preset exhaust gas lower limit temperature Textl. The correction target steam temperature Thptc is set by lowering the temperature Thpt.

  Further, when the exhaust gas temperature Text exceeds a preset exhaust gas lower limit temperature Textd, the valve opening setting unit 61 sets the flow rate adjustment valve 46 regardless of the deviation Dt1 between the target steam temperature Thpt and the second steam temperature Thp. The valve opening degree At is maintained.

  Here, the steam temperature control in the exhaust heat recovery boiler will be described in detail. 3 is a schematic diagram showing steam temperature control of the exhaust heat recovery boiler, FIG. 4 is a graph showing the rate of increase in the valve opening relative to the exhaust gas temperature, and FIG. 5 is a correction control of the target steam temperature with respect to the gas turbine load and exhaust gas temperature. FIG. 6 is a graph showing the exhaust gas temperature with respect to the gas turbine load, and FIG. 7 is a flowchart showing the valve opening degree control with respect to the exhaust gas temperature.

  Hereinafter, the processing content of the control device 51 in the steam temperature control in the exhaust heat recovery boiler of the present embodiment will be described. As shown in FIGS. 2 and 3, the target steam temperature Thpt is set based on the performance of the gas turbine 11, the exhaust heat recovery boiler 12, the steam turbine 13 and the heat resistant temperature of the steam pipe. For example, when the heat resistance temperature of the steam pipe is 650 ° C. and the steam dynamic temperature for operating the interlock for stopping the combined cycle plant 10 is 610 ° C., the gas turbine 11, the exhaust heat recovery boiler 12, the steam turbine Considering the performance of 13, the temperature is set to 590 ° C.

  Further, the valve opening setting unit 61 includes a control input setting unit 61a, a first opening / closing unit 73, a first PI control unit 74, a second subtraction unit 75, a second opening / closing unit 76, and a second PI control unit 77. Yes. The valve opening correction unit 62 includes a valve opening correction value setting unit 62 a and a second correction unit 78. The target steam temperature correction unit 63 includes a target steam temperature correction value setting unit 63a and a first correction unit 71.

  The first correction unit 71 corrects the target steam temperature Thpt by the target steam temperature correction value setting unit 63a. That is, as shown in FIG. 6, when the operation of the gas turbine 11 is started and the load L is increased, the exhaust gas temperature Text is increased. When the predetermined load L1 (for example, 50%) is reached, the exhaust gas temperature Text becomes constant. When the predetermined load L2 is reached, the exhaust gas temperature Text temporarily decreases, and the exhaust gas temperature at the predetermined load L3 (for example, 90%). Text rises again. In this case, when steam temperature control is performed by PI control, if the exhaust gas temperature Text rises rapidly, the second steam temperature Thp, which is the actual steam temperature generated by the exhaust heat recovery boiler 12, also rises rapidly, and the control of the temperature reducer 43 is in time. Interlock will work without it.

  Therefore, as shown in FIG. 5, the target steam temperature correction unit 63 takes in the load command value Lc of the gas turbine 11 in step S11, and takes in the exhaust gas temperature Text of the gas turbine 11 in step S12. In step S13, it is determined whether the exhaust gas temperature Text is higher than the exhaust gas lower limit temperature Textl. Here, if it is determined (No) that the exhaust gas temperature Text is equal to or lower than the exhaust gas lower limit temperature Textl, the routine exits without doing anything. On the other hand, if it determines with the exhaust gas temperature Text having exceeded the exhaust gas minimum temperature Textl (Yes), it will transfer to step S14. Here, the exhaust gas lower limit temperature Textl is a steam temperature at which the temperature of the steam generated by the exhaust gas at this temperature does not need to operate the temperature reducer 43, and is, for example, 560 ° C.

  In step S14, it is determined whether or not the load command value Lc of the gas turbine 11 is changing. Specifically, it is determined whether or not the load change rate Lcr of the load command value Lc of the gas turbine 11 is higher than a lower limit load change rate Lcru (for example, 0%). Here, if it is determined (No) that the load change rate Lcr is equal to or lower than the lower limit load change rate Lcru, this routine is exited without doing anything. On the other hand, when it is determined that the load change rate Lcr is higher than the lower limit load change rate Lcru (Yes), in step S15, the steam temperature decrease value (for example, 10 ° C.) is reduced from the target steam temperature Thpt to correct the target steam. Set the temperature Thptc. That is, in FIG. 6, the target steam temperature Thpt is lowered between the regions P1 and P2 where the load change rate Lcr is changing. Here, the lower limit load change rate Lcru is set to 0%, but may be set in a range of 0% to 5%.

  Returning to FIG. 3, if the target steam temperature correction value setting unit 63a does not change the target steam temperature Thpt, the first correction unit 71 leaves the target steam temperature Thpt as it is, and the target steam temperature correction value setting unit 63a sets the corrected target steam. When the temperature Thptc is set, the first correction unit 71 changes the target steam temperature Thpt to the corrected target steam temperature Thptc.

  The valve opening setting unit 61 sets the valve opening At of the flow rate adjusting valve 46 based on the deviation between the target steam temperature Thpt and the second steam temperature Thp that is the actual steam temperature supplied to the steam turbine 13. That is, the control input setting unit 61 a closes the first opening / closing unit 73 and the second opening / closing unit 76 and controls the first PI control unit 74 and the second PI control unit 77.

  Specifically, the first subtraction unit 72 calculates a deviation Dt1 between the target steam temperature Thpt (or the corrected target steam temperature Thptc) and the second steam temperature Thp of the steam generated by the exhaust heat recovery boiler 12. When the first opening / closing unit 73 is closed, the first PI control unit 74 performs the PI control based on the deviation Dt1, and the second subtraction unit 75 performs the temperature reduction by the output of the first PI control unit 74 and the temperature reducer 43. A deviation Dt2 of the steam after the temperature reduction from the first steam temperature Tdsh is calculated. When the second opening / closing unit 76 is closed, the second PI control unit 77 sets the valve opening degree At (0% to 100%) of the flow rate adjusting valve 46 by PI control based on the deviation Dt2.

  Here, since the second PI control unit 77 sets the valve opening degree At by PI control based on the deviation Dt2, when the exhaust gas temperature Text rises rapidly, the control of the temperature reducer 43 is controlled due to the delay of the integration operation by the PI control. The interlock operates without being in time.

  Therefore, the 2nd correction | amendment part 78 correct | amends the valve opening degree At by the valve opening correction value setting part 62a. That is, the valve opening correction value setting unit 62a sets the correction valve opening Atc by increasing the valve opening At when the exhaust gas temperature Text exceeds the exhaust gas upper limit temperature Textu. As shown in FIG. 4, the rate of increase in the valve opening relative to the exhaust gas temperature is preset. That is, the valve opening correction value setting unit 62a applies the valve opening At as it is when the exhaust gas temperature Text is equal to or lower than the exhaust gas upper limit temperature Textu, and the valve opening when the exhaust gas temperature Text exceeds the exhaust gas upper limit temperature Textu. The valve opening increase rate is added to At to obtain a corrected valve opening Atc.

  Here, the exhaust gas upper limit temperature Textu is set based on the heat resistant temperature of the steam pipe of the exhaust heat recovery boiler 12. For example, when the heat resistance temperature of the steam pipe is 650 ° C. and the steam dynamic temperature for operating the interlock for stopping the combined cycle plant 10 is 610 ° C., a margin value (for example, 20 ° C.) is considered. Set to 590 ° C. In this case, the margin value may be set as appropriate. Therefore, when the exhaust gas temperature Text is the exhaust gas upper limit temperature Textu (590 ° C.), the valve opening increase rate is 0%. When the exhaust gas temperature Text is 600 ° C. and the exhaust gas upper limit temperature Textu (590 ° C.) exceeds 10 ° C., the valve opening increase rate is 30%, the exhaust gas temperature Text is 610 ° C., and the exhaust gas upper limit temperature Textu (590 ° C.). When the temperature exceeds 20 ° C., the rate of increase in valve opening is 40%.

  Further, as described above, the valve opening setting unit 61 sets the valve opening At of the flow rate adjusting valve 46 by PI control based on the deviations Dt1 and Dt2. At this time, PI control is also performed when the exhaust gas temperature Text is low and the second steam temperature Thp is also low, but the PI control calculates the valve opening degree At by proportional control and integral control. That is, the valve opening At becomes a minimum opening. Then, when the exhaust gas temperature Text rises rapidly, the valve opening degree At cannot be increased early by PI control, a control delay of the valve opening degree At occurs, and the second steam temperature Thp becomes high and the temperature decreases. Interlock will be activated without the control of the device 43 in time.

  Therefore, when the exhaust gas temperature Text falls below the preset exhaust gas lower limit temperature Textd, the valve opening setting unit 61 sets the flow rate adjustment valve 46 regardless of the deviation Dt1 between the target steam temperature Thpt and the second steam temperature Thp. The valve opening degree At is maintained. As shown in FIG. 7, in step S21, the valve opening setting unit 61 takes in the exhaust gas temperature Text, and determines in step S22 whether the exhaust gas temperature Text has exceeded the exhaust gas lower limit temperature Textd. If it is determined that the exhaust gas temperature Text exceeds the exhaust gas lower limit temperature Textd (Yes), the first opening / closing part 73 and the second opening / closing part 76 are closed in step S24. On the other hand, when it is determined (No) that the exhaust gas temperature Text is equal to or lower than the exhaust gas lower limit temperature Textd, the first opening / closing part 73 and the second opening / closing part 76 are opened in step S23.

  As shown in FIG. 3, when the first opening / closing part 73 is in an open state, the deviation Dt1 between the target steam temperature Thpt (or the corrected target steam temperature Thptc) calculated by the first subtraction part 72 and the second steam temperature Thp is obtained. Without being sent to the first PI control unit 74, the first PI control unit 74 performs PI control based on the deviation Dt1 before the first opening / closing unit 73 is opened. That is, the output value before the first opening / closing part 73 is opened is maintained. Further, when the second opening / closing unit 76 is in the open state, the deviation Dt2 between the output value of the first PI control unit 74 calculated by the second subtraction unit 75 and the first steam temperature Tdsh is not sent to the second PI control unit 77, The second PI control unit 77 sets the valve opening degree At (0% to 100%) of the flow rate adjustment valve 46 by PI control based on the deviation Dt2 before the second opening / closing unit 76 is opened. That is, the valve opening degree At (0% to 100%) before the second opening / closing part 76 is opened is maintained.

  For example, when the exhaust gas temperature Text is a low temperature equal to or lower than the exhaust gas lower limit temperature Textd (for example, 560 ° C.), the second steam temperature Thp is reasonably low with respect to the target steam temperature Thpt (for example, 590 ° C.). And the second steam temperature Thp become larger in deviation Dt1. For this reason, the integral value in the first PI control unit 74 becomes a large negative value as time elapses. Then, when the exhaust gas temperature Text rises thereafter, feedback control is performed based on the deviation Dt1 between the target steam temperature Thpt (for example, 590 ° C.) and the second steam temperature Thp approaching it. At this time, the first PI control unit 74 returns to a normal feedback control, that is, control with a small deviation Dt1 and a small PI integrated value because the integration with the large deviation Dt1 is a large negative value. take time. In order to prevent this phenomenon, in this embodiment, when the exhaust gas temperature Text is low, the first opening / closing part 73 and the second opening / closing part 76 are opened, and the input to the first PI control part 74 and the second PI control part 77 is zero. Therefore, negative integration is not performed.

  As described above, in the exhaust heat recovery boiler of the present embodiment, the temperature reducing device 43 that supplies the generated steam with cooling water to reduce the temperature, and the flow rate adjustment that adjusts the amount of cooling water supplied to the temperature reducing device 43. A valve 46, a valve opening setting unit 61 for setting the valve opening At of the flow rate adjusting valve 46 based on a deviation between a preset target steam temperature Thpt and the actual steam temperature Thp supplied to the steam turbine 13, and exhaust gas A valve opening correction unit 62 is provided for increasing the valve opening At when the temperature Text exceeds a preset exhaust gas upper limit temperature Textu.

  Therefore, the valve opening setting unit 61 sets the valve opening At of the flow rate adjusting valve 46 based on the deviation between the target steam temperature Thpt and the actual steam temperature Thp supplied to the steam turbine 13, and the valve opening correction unit 62. Increases the valve opening degree At when the exhaust gas temperature Text exceeds the exhaust gas upper limit temperature Textu. That is, when the exhaust gas temperature Text rises rapidly, the temperature of the generated steam (second steam temperature Thp) also rises rapidly, but the adjustment control of the valve opening degree At in the flow rate adjusting valve 46 may not be in time. Therefore, when the exhaust gas temperature Text rapidly increases, the valve opening At of the flow rate adjustment valve 46 is increased early to suppress the rapid increase of the exhaust gas temperature Text. As a result, it is possible to perform highly accurate steam temperature control by suppressing the control delay by improving the followability of steam temperature control.

  In the exhaust heat recovery boiler of the present embodiment, the valve opening correction unit 62 increases the valve opening At based on a valve opening increase rate with respect to a preset exhaust gas temperature Text. Therefore, a rapid increase in the exhaust gas temperature Text can be suppressed.

  In the exhaust heat recovery boiler of the present embodiment, the exhaust gas upper limit temperature Textu is set by subtracting a margin value from the heat resistance temperature of the steam pipe. Therefore, it is possible to prevent damage to the steam piping due to the temperature rise of the steam.

  In the exhaust heat recovery boiler of the present embodiment, the target steam temperature is when the load change rate Lcr of the gas turbine 11 is higher than the preset lower limit load change rate Lcru and the exhaust gas temperature Text is equal to or lower than the preset exhaust gas lower limit temperature Textd. A target steam temperature correction unit 63 that reduces Thpt is provided. Therefore, even if the exhaust gas temperature Text rises rapidly, the temperature reducer 43 operates early to supply cooling water to the steam, and the rapid rise of the steam temperature can be suppressed.

  In the exhaust heat recovery boiler of the present embodiment, the valve opening degree setting unit 61 is concerned with the deviation Dt1 between the target steam temperature Thpt and the second steam temperature Thp when the exhaust gas temperature Text becomes equal to or lower than the preset exhaust gas lower limit temperature Textl. The opening degree of the flow rate adjusting valve 46 is maintained. Therefore, even when the exhaust gas temperature Text becomes equal to or lower than the exhaust gas lower limit temperature Textl, the valve opening At of the flow rate adjusting valve 46 does not become a minimum value. An appropriate amount of cooling water can be supplied to suppress a rapid rise in steam temperature.

  In the exhaust heat recovery boiler of the present embodiment, the valve opening setting unit 61 performs PI control based on the deviation Dt1 between the target steam temperature Thpt and the second steam temperature Thp that is the actual steam temperature, and the first PI control unit 74. The valve opening degree At is set based on the deviation Dt2 between the output value (control amount) and the first steam temperature Tdsh reduced in temperature by the temperature reducer 43. Therefore, the valve opening degree At can be set with high accuracy.

  The control device of the present embodiment is a control device for the exhaust heat recovery boiler 12, and includes any one of the target steam temperature correction unit 63, the valve opening degree setting unit 61, and the valve opening degree correction unit 62. Yes. Therefore, by improving the followability of steam temperature control, control delay can be suppressed and highly accurate steam temperature control can be performed.

  Further, in the combined cycle plant of the present embodiment, the gas turbine 11 having the compressor 21, the combustor 22, and the turbine 23, and the exhaust heat recovery boiler 12 that generates steam by exhaust heat of the exhaust gas from the gas turbine 11. And a steam turbine 13 having a high pressure turbine 32 and a low pressure turbine 33 driven by steam generated by the exhaust heat recovery boiler 12.

  Therefore, the gas turbine 11 drives the turbine 31 with combustion gas generated by supplying fuel to compressed air and burning it, and the exhaust heat recovery boiler 12 generates steam by exhaust heat of the exhaust gas from the gas turbine 11. The steam turbine 13 is driven by the steam generated by the exhaust heat recovery boiler 12. At this time, in the exhaust heat recovery boiler 12, the valve opening setting unit 61 sets the valve opening At of the flow rate adjusting valve 46 based on the deviation between the target steam temperature Thpt and the actual steam temperature Thp supplied to the steam turbine 13. The valve opening degree correcting unit 62 sets the valve opening degree At when the exhaust gas temperature Text exceeds the exhaust gas upper limit temperature Textu. As a result, it is possible to perform highly accurate steam temperature control by suppressing the control delay by improving the followability of steam temperature control.

  In the above-described embodiment, the exhaust heat recovery boiler 12 includes the first superheater 41 and the second superheater 42, and the temperature reducer 43 is provided between the first superheater 41 and the second superheater 42. However, the present invention is not limited to this configuration, and the position of the temperature reducer 43 may be another position.

DESCRIPTION OF SYMBOLS 10 Combined cycle plant 11 Gas turbine 12 Exhaust heat recovery boiler 13 Steam turbine 14,15 Generator 21 Compressor 22 Combustor 23 Turbine 24 Rotating shaft 31 Turbine 32 High pressure turbine 33 Medium pressure turbine 34 Low pressure turbine 35 Rotating shaft 36 Condenser 37 Condensate pump 41 First superheater 42 Second superheater 43 Temperature reducer 46 Flow rate adjusting valve 47 Valve drive device 51 Control device 52 First steam temperature sensor 53 Second steam temperature sensor 54 Exhaust gas temperature sensor 61 Valve opening setting Unit 61a Control input setting unit 62 Valve opening correction unit 62a Valve opening correction value setting unit 63 Target steam temperature correction unit 63a Target steam temperature correction value setting unit 71 First correction unit 72 First subtraction unit 73 First opening / closing unit 74 First PI control unit 75 Second subtraction unit 76 Second opening / closing unit 77 Second PI control unit 78 2 correction unit

Claims (12)

In an exhaust heat recovery boiler that generates steam by exhaust heat of gas turbine exhaust gas,
A temperature reducer that supplies cooling water to the generated steam to reduce the temperature;
A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer;
A valve opening degree setting unit for setting the valve opening degree of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine;
A valve opening correction unit that increases the valve opening when the exhaust gas temperature exceeds a preset exhaust gas upper limit temperature; and
An exhaust heat recovery boiler comprising:   2. The exhaust heat recovery boiler according to claim 1, wherein the valve opening correction unit increases the valve opening based on a valve opening increase rate with respect to the preset exhaust gas temperature.   3. The exhaust heat recovery boiler according to claim 1, wherein the exhaust gas upper limit temperature is set by subtracting a margin value from a heat resistant temperature of the steam pipe.   A target steam temperature correction unit is provided for lowering the target steam temperature when the load change rate of the gas turbine is higher than a preset lower limit load change rate and the exhaust gas temperature exceeds a preset exhaust gas lower limit temperature. The exhaust heat recovery boiler according to any one of claims 1 to 3, wherein:   5. The valve opening degree setting unit holds the opening degree of the flow rate adjusting valve regardless of the deviation when the exhaust gas temperature is equal to or lower than a preset exhaust gas lower limit temperature. An exhaust heat recovery boiler according to claim 1.   The valve opening setting unit is configured to control the valve opening based on a deviation between a control amount based on a deviation between the target steam temperature and the actual steam temperature and a post-temperature-reducing steam temperature reduced by the temperature reducer. The exhaust heat recovery boiler according to any one of claims 1 to 5, wherein: In an exhaust heat recovery boiler that generates steam by exhaust heat of gas turbine exhaust gas,
A temperature reducer that supplies cooling water to the generated steam to reduce the temperature;
A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer;
A valve opening degree setting unit for setting the valve opening degree of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine;
A target steam temperature correction unit that lowers the target steam temperature when the load change rate of the gas turbine is higher than a preset lower limit load change rate and the exhaust gas temperature exceeds a preset exhaust gas lower limit temperature;
An exhaust heat recovery boiler comprising: In an exhaust heat recovery boiler that generates steam by exhaust heat of gas turbine exhaust gas,
A temperature reducer that supplies cooling water to the generated steam to reduce the temperature;
A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer;
When the opening degree of the flow rate adjusting valve is set based on the deviation between the preset target steam temperature and the actual steam temperature of the steam supplied to the steam turbine, and the exhaust gas temperature falls below a preset exhaust gas lower limit temperature A valve opening setting unit for holding the opening of the flow rate adjusting valve regardless of the deviation;
An exhaust heat recovery boiler comprising: A temperature reducer that reduces the temperature by supplying cooling water to the steam generated by the exhaust heat of the exhaust gas of the gas turbine;
A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer;
In a waste heat recovery boiler comprising
A valve opening degree setting unit for setting the valve opening degree of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine;
A valve opening correction unit that increases the valve opening when the exhaust gas temperature exceeds a preset exhaust gas upper limit temperature; and
A control device comprising: A temperature reducer that reduces the temperature by supplying cooling water to the steam generated by the exhaust heat of the exhaust gas of the gas turbine;
A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer;
In a waste heat recovery boiler comprising
A valve opening degree setting unit for setting the valve opening degree of the flow rate adjusting valve based on a deviation between a preset target steam temperature and an actual steam temperature of steam supplied to the steam turbine;
A target steam temperature correction unit that lowers the target steam temperature when the load change rate of the gas turbine is higher than a preset lower limit load change rate and the exhaust gas temperature exceeds a preset exhaust gas lower limit temperature;
A control device comprising: A temperature reducer that reduces the temperature by supplying cooling water to the steam generated by the exhaust heat of the exhaust gas of the gas turbine;
A flow rate adjusting valve for adjusting the amount of cooling water supplied to the temperature reducer;
In a waste heat recovery boiler comprising
When the opening degree of the flow rate adjusting valve is set based on the deviation between the preset target steam temperature and the actual steam temperature of the steam supplied to the steam turbine, and the exhaust gas temperature falls below a preset exhaust gas lower limit temperature A control device comprising a valve opening setting unit for holding the opening of the flow rate adjusting valve regardless of the deviation. A gas turbine having a compressor, a combustor, and a turbine;
The exhaust heat recovery boiler according to any one of claims 1 to 8, wherein steam is generated by exhaust heat of exhaust gas from the gas turbine;
A steam turbine having a high-pressure turbine and a low-pressure turbine driven by steam generated by the exhaust heat recovery boiler;
A combined cycle plant comprising:

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