JP3697310B2 - Method and apparatus for stopping combined cycle plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention suppresses the loss of steam that can be used in a steam turbine in a combined cycle plant in which steam is generated by heat exchange between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and the steam turbine is driven by this steam. However, the present invention relates to a combined cycle plant stopping method and a stopping device for safely stopping the plant.
[0002]
[Prior art]
FIG. 11 is a system diagram showing a configuration of a conventional combined cycle power plant. As shown in FIG. 11, the high-temperature exhaust gas from the gas turbine is led to an exhaust heat recovery boiler (HRB) 1, so that the feed water in the steam drum 2 is converted into steam by the evaporator 3 and then further heated. It becomes superheated steam in the vessel 4. The superheated steam passes through the main steam pipe 5, flows into the steam turbine 7 through the steam control valve (MCV) 6, performs work, and is returned to water by the condenser 8.
[0003]
A turbine bypass pipe 9 is connected to the main steam pipe 5, and the steam bypassing the steam turbine 7 passes through the turbine bypass pipe 9, passes through a turbine bypass valve (TBV) 10, is led to a condenser 8, and is supplied with water. Returned to A main steam pressure sensor 11 is attached to the main steam pipe 5.
[0004]
FIG. 12 is a block diagram showing a circuit configuration according to a conventional combined cycle plant stopping method. FIG. 12 shows a control method of the turbine bypass valve (TBV) 10. The turbine bypass valve 10 is adjusted in opening by an electropneumatic converter 12 that converts an electrical signal into an air output. Is supplied with an electric signal from the PID calculator 13.
[0005]
This PID computing unit 13 performs ΡID control using the input given to the PV (process value) part as a process value and the value inputted to the SV (set value) part as a pressure control set value. The main steam pressure a that is the output of the main steam pressure sensor 11 is input to the PV section of the PID calculator 13, while the pressure control set value b that is the output of the switch 14 is input to the SV section.
[0006]
The switch 14 selects the MCV closing pressure d when the switching command c is established, and selects and outputs the actual pressure tracking pressure e when the switching command c is not established. When the switching command c is established, the storage device 15 stores the value of the main steam pressure a at that time and holds it until the switching command c is not established. The actual pressure tracking pressure e is a pressure obtained by adding the tracking bias f output from the signal generator 16 to the main steam pressure a by the adder 17.
[0007]
The OR circuit 18 takes the logical sum of the switching command c and the MCV (steam control valve) closing command g, and outputs the switching command c only when the MCV closing command g is output. When the disconnection signal h is output, the value of the main steam pressure a held in the storage device 15 is released.
[0008]
FIGS. 13A, 13B, 13C, and 13D show time charts at the time of stopping when controlled by such a circuit. When a stop command is output to the plant, as shown in FIG. 13C, the gas turbine (GT) drops the load and throttles the fuel flow, so that the amount of heat input decreases, as shown in (A). Thus, the main steam pressure a gradually decreases.
[0009]
At this time, the actual pressure tracking pressure e is selected by the switch 14 as the pressure control set value (SV) b of the turbine bypass valve 10 and is higher than the main steam pressure a by the tracking bypass f. Here, when the generator output decreases to a predetermined value as shown in (D), the steam control valve (MCV) 6 shuts off the inflow of steam to the steam turbine 7 and is closed as shown in (B). Start operation.
[0010]
On the other hand, the pressure control set value b of the turbine bypass valve 10 is fixed to the MCV closing pressure d which is a value storing the main steam pressure a at this moment. Here, since the steam control valve (MCV) 6 is closed, the pressure of the steam generated from the steam drum 2 rises and tends to exceed the pressure control set value b as shown in FIG. 10 opens to allow the main steam to escape to the condenser 8 and maintain the main steam pressure at the pressure control set value b.
[0011]
[Problems to be solved by the invention]
However, as described above, the stopping method according to the related art has a problem that it takes time to start next time because it stops while releasing the drum pressure of the steam drum 2. Further, since the turbine bypass valve 10 is opened at the time of stopping and the steam that can be used in the steam turbine 7 is thrown away, there is a problem that heat energy is lost and it is uneconomical.
[0012]
The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a combined cycle plant stopping method and apparatus for safely stopping an exhaust heat recovery boiler while reducing steam loss.
[0013]
[Means for Solving the Problems]
  In order to solve the above-described problem, the stopping method of claim 1 of the present invention generates steam by heat exchange between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and supplies the steam to the steam turbine. In the combined cycle plant in which the steam turbine is bypassed through the turbine bypass pipe and the pressure of the turbine bypass pipe is adjusted by the pressure adjusting means,Select storage means for storing main steam pressure value when predetermined plant condition is established, main steam pressure value read from this storage means, and actual pressure tracking pressure value with bias value added to main steam pressure value And a control means comprising a switching means for outputting to the PID computing unit. The control means uses the pressure signal at the time when either the plant stop command or the gas turbine stop command is established as the pressure control set value as the pressure control set value. Controlling the pressure adjusting means of the turbine bypass pipe when stopping the heat recovery boiler.
[0014]
  The stop device of claim 2 includes an exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam, a main steam pipe that supplies the steam generated in the exhaust heat recovery boiler to the steam turbine, In a combined cycle plant comprising a turbine bypass pipe connected to a steam pipe and bypassing the steam turbine, and a pressure adjusting means provided in the turbine bypass pipe,Selects a storage device that stores the main steam pressure value when a predetermined plant condition is established, a main steam pressure value read from the storage device, and an actual pressure tracking pressure value obtained by adding a bias value to the main steam pressure value And a control unit comprising a switch for outputting to the PID computing unit. The control unit uses the pressure signal at the time when either the plant stop command or the gas turbine stop command is established as the pressure control set value as the pressure control set value. The pressure adjusting means of the turbine bypass pipe when the heat recovery boiler is stopped is configured to be controlled..
[0015]
  The stopping method of claim 3 is:Steam is generated by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and the steam is supplied to the steam turbine for driving, while the steam turbine is bypassed through the turbine bypass pipe and the turbine bypass In a combined cycle plant in which the pressure of the pipe is adjusted by the pressure adjusting means, a storage means for storing a main steam pressure value when a predetermined plant condition is established, a main steam pressure value read from the storage means, and a main steam pressure A first switching means for selectively outputting an actual pressure tracking pressure value obtained by adding a bias value to the value, and two limiting means for setting an upper limit and a lower limit of the pressure value output from the first switching means. In parallel with the downstream side of the first switching means, an upper limit value or a lower limit value is selectively PI on the downstream side. And a second switching means for outputting to the computing unit. The control means outputs a pressure signal on the limiting means side that is switched based on a closing command for a steam control valve provided in the main steam pipe. Controlling pressure adjusting means of the turbine bypass pipe when stopping the exhaust heat recovery boiler as a control set value.
[0016]
  The stop device according to claim 4 comprises:An exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam, a main steam pipe that supplies steam generated in the exhaust heat recovery boiler to the steam turbine, and the steam turbine connected to the main steam pipe In a combined cycle plant comprising a turbine bypass pipe that bypasses the pressure and a pressure adjusting means provided in the turbine bypass pipe, a storage device that stores a main steam pressure value when a predetermined plant condition is satisfied, and the storage device The first switch for selectively outputting the main steam pressure value read from the main steam pressure value and the actual pressure tracking pressure value obtained by adding the bias value to the main steam pressure value, and the pressure value output from the first switch Two limiters for setting the upper and lower limits of the first switch are provided in parallel on the downstream side of the first switch, and an upper limit value or lower limit value is further selected on the downstream side. And a second switching unit that outputs to the PID computing unit, and the control unit includes a pressure signal on the limiter side that is switched based on a closing command for a steam control valve provided in the main steam pipe. The pressure control setting value of the turbine bypass pipe when the exhaust heat recovery boiler is stopped is set as a pressure control set value..
[0017]
  The stopping method of claim 5 is the stopping method of the combined cycle plant of claim 1,Pressure setting calculation means for calculating pressure based on a predetermined external process signal is provided on the upstream side of the switching means, and the pressure control setting value of the pressure adjustment means at the time of stop is set as gas turbine exhaust gas temperature, steam At least one of temperature, steam pressure, steam turbine metal temperature, and drum pressure is used..
[0018]
  The stop device of claim 6 is the stop device of the combined cycle plant according to claim 2,A pressure setting calculator that calculates pressure based on a predetermined external process signal is provided upstream of the switch, and the pressure control setting value of the pressure adjusting means at the time of stop is set as the gas turbine exhaust gas temperature, steam It is configured as a set value using at least one of temperature, steam pressure, steam turbine metal temperature, and drum pressure..
[0019]
  The stopping method of claim 7 is:Steam is generated by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and the steam is supplied to the steam turbine for driving, while the steam turbine is bypassed through the turbine bypass pipe. The pressure adjusting means is controlled by a pressure adjusting means, and when the exhaust heat recovery boiler is stopped, the pressure adjusting means of the turbine bin bypass pipe is controlled using a value obtained by adding a bias value to the main steam pressure. In a combined cycle plant, the control setting value of the pressure adjusting means is temporarily set to the pressure of the turbine bypass pipe using a stop command or plant conditions, and then the rate of change is limited to the value obtained by adding the bias value to this value. Output as a set value.
[0020]
  Claim 8ofStop deviceAn exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam, a main steam pipe that supplies steam generated in the exhaust heat recovery boiler to the steam turbine, and the steam turbine connected to the main steam pipe A value obtained by adding a bias value to the main steam pressure in the turbine bypass pipe, the pressure adjusting means provided in the turbine bypass pipe, and the pressure adjusting means of the turbine bypass pipe when stopping the exhaust heat recovery boiler In a combined cycle plant comprising control means for controlling as a set value, a plurality of change rate limiters having different change rate limits are provided for the pressure adjusting means of the turbine bypass pipe, and these are switched based on a stop command. It is possible to configure.
[0021]
  The stopping method of claim 9 is:9. The combined cycle plant stop device according to claim 8, wherein the control set value of the pressure adjusting means is temporarily set to the pressure of the turbine bypass pipe using the stop command or the plant condition, and then the bias value is added to this value. A set value output means for outputting a set value by limiting the rate of change is provided..
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0028]
FIG. 1 is a block diagram showing a combined cycle plant stopping method and a circuit configuration of the stopping apparatus according to the first embodiment of the present invention. Note that the same or corresponding parts as in the prior art will be described using the same reference numerals as in FIG.
[0029]
In this first embodiment, the opening of the turbine bypass valve 10 as the pressure adjusting means of the turbine bypass pipe 9 is adjusted by an electropneumatic converter 12 that converts an electrical signal into an air output, as in the conventional example. The empty converter 12 receives an electrical signal from the PID calculator 13.
[0030]
The PID computing unit 13 performs ΡID control using the input given to the PV unit as a process value and the value inputted to the SV unit as a pressure control set value. The PV section of the PID calculator 13 receives the main steam pressure a which is the output of the main steam pressure sensor 11, while the SV section receives the pressure control set value b which is the output of the switch 14.
[0031]
The switch 14 selects the stop pressure i when the switching command c is established, and selects and outputs the actual pressure tracking pressure e when the switching command c is not established. When the switching command c is established, the storage device 15 stores the value of the main steam pressure a at that time and holds it until the switching command c is not established. The actual pressure tracking pressure e is a pressure obtained by adding the tracking bias f output from the signal generator 16 to the main steam pressure a by the adder 17.
[0032]
The OR circuit 18 takes a logical sum of the switching command c and the stop command j, and outputs the switching command c only when the stop command j is output. When the disconnection signal h is output, the value of the main steam pressure a held in the storage device 15 is released.
[0033]
That is, in the first embodiment, the stop command j is changed to use the stop command j as a condition for giving the timing of the switching command c for selecting the output from the storage unit 15 with respect to FIG. 12 showing the circuit configuration of the conventional example. is there. Examples of the stop command j include a plant stop command or a gas turbine stop command.
[0034]
Then, the control means 19 is constituted by the PID calculator 13, the switch 14, the memory 15, the signal generator 16, the adder 17, the OR circuit 18, the stop command j and the disconnection signal h, and the control means 19 is stopped. When the command j is established, the opening degree control of the turbine bypass valve 10 of the turbine bypass pipe 9 is started.
[0035]
Therefore, since the main steam pressure at the moment when the stop command j is established becomes the pressure control set value b of the turbine bypass valve 10, the main steam pressure at the start of closing the steam control valve 6 is the pressure control set value of the turbine bypass valve 10. As compared with the conventional stopping method, the control can be continued without opening the turbine bypass valve 10 even if the main steam pressure a rises during the closing operation of the steam control valve 6.
[0036]
Next, the operation of the first embodiment will be described.
[0037]
2A to 2D are time charts at the time of stopping according to the first embodiment. As in the prior art, when the plant stop command j is established, the gas turbine (GT) starts to drop the load and the heat input decreases, so the main steam pressure a begins to decrease.
[0038]
However, at this time, the pressure control set value b of the turbine bypass valve 10 is already fixed to a value obtained by adding the tracking bias f to the main steam pressure a at the time of the stop command. Therefore, even if the steam control valve 6 starts the closing operation and the main steam pressure a rises, the pressure control set value b of the turbine bypass valve 10 is not immediately exceeded, and the turbine bypass valve 10 remains fully closed. The plant stops. Thereby, the amount of the steam that can be used in the steam turbine 7 is discarded, and the plant can be safely stopped.
[0039]
In this embodiment, the establishment of the stop command j is used as a plant condition for starting the control of the turbine bypass valve 10 of the turbine bypass pipe 9 with the pressure of the steam drum 2 or the steam pipe pressure at that time as a set value. However, if it is temporally before the MCV closing command, substantially the same effect can be obtained even with a signal at the time when the determined plant condition is satisfied. The stop command includes a plant stop command and a gas turbine stop command.
[0040]
FIG. 3 is a block diagram illustrating a combined cycle plant stopping method and a circuit configuration of the stopping apparatus according to the second embodiment of the present invention, and FIGS. 4A to 4D are time charts at the time of stopping according to the second embodiment. It is. The same parts as those in the first embodiment will be described with the same reference numerals. The same applies to the following embodiments.
[0041]
In FIG. 3, in this embodiment, the switch 14, the storage device 15, and the OR circuit 18 are not installed as in the first embodiment, and the stop command j, the disconnection signal h, and the switch command c are not used. A change rate limiter 20 is arranged between the PID calculator 13 and the adder 17. The PID calculator 13, the signal generator 16, the adder 17, and the change rate limiter 20 constitute a control means 21, which controls the turbine of the turbine bypass pipe 9 when the exhaust heat recovery boiler 1 is stopped. The bypass valve 10 is controlled using a value obtained by adding the tracking bias f value to the main steam pressure a as a set value.
[0042]
Thus, according to this embodiment, as shown in FIG. 4, the pressure control set value b of the turbine bypass valve 10 is always controlled to the value of the actual pressure tracking pressure e obtained by adding the tracking bias f value to the main steam pressure a. Therefore, even if the steam control valve 6 is closed during stoppage and the main steam pressure a rises, the turbine bypass valve 10 remains fully closed, and the amount of steam that can be used in the steam turbine 7 is discarded. The plant can be safely stopped.
[0043]
However, since the change rate limiter 20 is provided for the actual pressure tracking pressure e against a sudden increase in the main steam pressure a due to plant abnormality or the like, the turbine bypass valve 10 is opened and the steam pressure is increased. Can escape.
[0044]
In the second embodiment, a plurality of change rate limiters having different change rate limit setting values are additionally arranged, and during normal operation in which the main steam pressure value remains relatively constant, the change rate control value The change rate limiter with a small change rate is used, and at the time of stop, the change rate limiter with a large change rate limit value is switched using a stop command to reduce the opening operation of the turbine bypass valve 10 at the time of stop. May be.
[0045]
Further, in order to prevent the wear of equipment such as the exhaust heat recovery boiler 1 and the steam turbine 7, it is necessary to keep the rate of change of the metal temperature below a certain level. As the saturation temperature rises rapidly, the steam temperature changes abruptly, causing the metal temperature of the equipment to change abruptly, resulting in an inconvenience that shortens the life of the equipment. Therefore, a change rate limiter with a different change rate limit setting value is added, and when stopping, the change rate limit set value is switched to a larger one using a stop command to prevent the sudden metal temperature change. May be.
[0046]
Furthermore, in the present embodiment, when the exhaust heat recovery boiler 1 is stopped, the bias value to be added to obtain the control set value of the turbine bypass valve 10 is set to a value different from the value during normal operation at the time of stop. You may make it switch.
[0047]
FIG. 5 is a block diagram showing a combined cycle plant stopping method and a circuit configuration of the stopping apparatus according to the third embodiment of the present invention, and FIGS. 6A to 6D are time charts at the time of stopping according to the third embodiment. It is.
[0048]
As shown in FIG. 5, in this embodiment, in FIG. 12 showing a conventional circuit configuration, a normal limiter 22 and a stop limiter 23 are arranged in parallel between a PID computing unit 13 and a switch 14. These are provided, and these and the switch 24 are connected in series.
[0049]
Therefore, by providing the normal limiter 22 and the stop limiter 23 in parallel, the upper and lower limits of the pressure limit value are set, and the normal limiter 22 is set to the metal temperature of the device as in the second embodiment. On the other hand, the limiter of the rate of change set together, the pressure limit value of the stop limiter 23 is set to a value determined corresponding to the exhaust gas temperature of the gas turbine. Then, when the steam control valve 6 starts to close due to the MCV closing command g, the switch 24 switches the normal limiter 22 to the stop limiter 23.
[0050]
The PID calculator 13, the switch 14, the memory 15, the signal generator 16, the adder 17, the OR circuit 18, the normal limiter 22, the stop limiter 23, the switch 24, the MCV closing command g and the solution The control means 25 is constituted by the column signal h.
[0051]
By the way, if the pressure of the steam drum 2 increases excessively when the plant is stopped, the saturation temperature of the generated steam increases. Here, since the exhaust gas temperature of the gas turbine gradually decreases while the plant is stopped, if the exhaust gas temperature becomes lower than the saturation temperature of the steam in the superheater 4, the cooling phenomenon of the steam in the superheater 4 will occur. In the worst case, problems such as drainage occur. When drain is generated by the superheater 4, in a state where the steam control valve 6 is open, this drain flows into the steam turbine 7 and may damage the steam turbine blades.
[0052]
Further, the generation of drain in the superheater 4 has problems such as damage to the superheater 4 due to a drain attack, and it is necessary to discard the drain generated in the restart after the stop, resulting in an increase in startup time.
[0053]
On the other hand, according to the present embodiment, the normal limiter 20 and the stop limiter 21 are provided in parallel, so that the main steam pressure a is the pressure of the stop limiter 21 at the time of stop as shown in FIG. When the limit value is exceeded, the turbine bypass valve 10 can be opened so that the steam pressure does not increase too much, and the above-described problems can be solved.
[0054]
FIG. 7 is a block diagram showing a combined cycle plant stopping method and a circuit configuration of the stopping apparatus according to the fourth embodiment of the present invention, and FIGS. 8A to 8E are time charts at the time of stopping according to the fourth embodiment. It is. There is a fourth embodiment as another solution to the problem of drain generation described in the description of the third embodiment.
[0055]
In the combined cycle plant, since the steam drum 2 pressure is often transformed, it is difficult to set the pressure at which the cooling phenomenon occurs in the superheater 4 as a constant value. For this reason, in the fourth embodiment, the gas turbine exhaust gas temperature (EXHT) 1 is used as an index for causing the cooling phenomenon in the superheater 4 or the like, and the pressure control at the time of stopping the turbine bypass valve 10 as the pressure adjusting means is performed. Set the set value k. As described above, not only the gas turbine exhaust gas temperature but also at least one of steam temperature, steam pressure, steam turbine metal temperature, and drum pressure may be used.
[0056]
That is, in the fourth embodiment, for example, the pressure control of the turbine bypass valve 10 is performed using the gas turbine exhaust gas temperature 1 and the stop time pressure setting calculator 26 as shown in FIG. The stop-time pressure setting calculator 26 is a calculator that calculates and outputs a pressure at which the gas turbine exhaust gas temperature l is a saturation temperature.
[0057]
The control means is based on the PID calculator 13, the switch 14, the signal generator 16, the adder 17, the OR circuit 18, the stop-time pressure setting calculator 26, the MCV closing command g, the disconnect signal h and the gas turbine exhaust gas temperature l. 27 is configured.
[0058]
Therefore, as shown in FIG. 8A, the pressure control set value b of the turbine bypass valve 10 is fixed to a value obtained by adding the tracking bias f to the main steam pressure a until the MCV closing command g is output. When the MCV closing command g is output, the switch 14 is switched to the stop pressure control set value k. When the disconnection signal h is output, the pressure control set value b is a value obtained by adding the tracking bias f by the switch 14.
[0059]
Further, when the gas turbine (GT) trips, the gas turbine exhaust gas temperature l rapidly decreases, so that the stop time pressure control set value k also decreases rapidly. The set value b is a value obtained by adding the tracking bias f and does not affect the plant operation.
[0060]
As described above, according to the present embodiment, the pressure control set value b of the turbine bypass valve 10 is set by the stop-time pressure setting calculator 26 based on the gas turbine exhaust gas temperature l, whereby the cooling phenomenon in the superheater 4 or the like. The steam pressure is controlled to be higher than the pressure at which the above occurs, and the above-mentioned problems can be solved even if the operation stops from any operating state.
[0061]
FIG. 9 is a block diagram showing a combined cycle plant stopping method and a circuit configuration of the stopping apparatus according to the fifth embodiment of the present invention, and FIGS. 10A to 10D are time charts at the time of stopping according to the fifth embodiment. It is.
[0062]
In order to prevent wear and tear of equipment such as the exhaust heat recovery boiler 1 and the steam turbine 7, it is necessary to keep the rate of change of the metal temperature below a certain level. However, if the steam pressure rises rapidly when the plant is shut down, the saturation temperature of the steam As the temperature rises rapidly, the steam temperature changes abruptly, causing the metal temperature of the equipment to change abruptly, resulting in a problem of shortening the life of the equipment.
[0063]
In order to prevent this problem, in this embodiment, as shown in FIGS. 9 and 10, the pressure control set value b of the turbine bypass valve 10 as the pressure adjusting means is set to the pressure of the turbine bypass pipe 9 using the MCV close command. Step down.
[0064]
That is, in the present embodiment, as shown in FIG. 9, in addition to the configuration of the second embodiment of FIG. 3, a switch 28 is arranged between the adder 17 and the change rate limiter 19, and the switch 28 includes The MCV closing command g is input via the one-shot circuit 29, while the MCV closing command g is input to the change rate limiter 19 via the one-shot circuit 29 and the knot circuit 30.
[0065]
The tracking bias f output from the signal generator 16 is also input to the subtractor 31, and the subtracter 31 subtracts the tracking bias f from the output signal of the change rate limiter 19, and the subtracted signal is Input to the switch 28.
[0066]
The signal generator 16, adder 17, change rate limiter 19, switch 28, one-shot circuit 29, knot circuit 30, subtractor 31, and MCV closing command g constitute a set value output means 32.
[0067]
This set value output means 32 is a value obtained by temporarily setting the pressure control set value b of the turbine bypass valve 10 to the pressure of the turbine bypass pipe 9 using a stop command or plant conditions, and then adding the tracking bias f value to this value. Then, the change rate limiter 19 limits the change rate and outputs it as a set value.
[0068]
Here, the switch 28 selects the actual pressure tracking pressure e when the output of the one-shot circuit 29 is 0, while the tracking bias f value is subtracted by the subtractor 31 when the output of the one-shot circuit 29 is 1. The selected main steam pressure a is selected.
[0069]
Further, when the output of the knot circuit 28 is 0, the change rate limiter 19 outputs a signal that does not limit the change rate to the signal on the input side, while the output of the knot circuit 28 is 1. In this case, a signal that limits the rate of change on the input side signal is output to the output side.
[0070]
Next, the operation of the fifth embodiment will be described.
[0071]
When the plant stop command j is established, the gas turbine (GT) starts to drop the load and the heat input decreases, so the main steam pressure starts to decrease. That is, if the MCV close command g is not input, the switch 26 is not switched, and is set as a pressure control set value in which the rate of change is limited to the actual pressure tracking pressure e obtained by adding the tracking bias f value to the main steam pressure a. Is output.
[0072]
When the MCV close command g is input, the one-shot circuit 27 is activated to switch the switch 28 to the signal from the subtractor 31, and the rate of change is limited to the main steam pressure a from which the tracking bias f value is subtracted. It is output as a pressure control set value that is not applied.
[0073]
Thus, according to the present embodiment, the pressure control set value b of the turbine bypass valve 10 is stepped down to the pressure of the turbine bypass pipe 10 using the MCV closing command g, so that the drum pressure at the start of MCV closing is increased. Compared with the second embodiment, the turbine bypass pipe 10 can be opened in advance, so that the above-described problems can be solved. Thereafter, by controlling a value obtained by adding a bias value to the pressure of the steam drum 2 as a set value, it is possible to perform the same operation as in the second embodiment.
[0074]
【The invention's effect】
  As described above, according to the stopping method of claim 1 of the present invention, steam is generated by heat exchange between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and this steam is supplied to the steam turbine. In the combined cycle plant in which the steam turbine is bypassed through a turbine bypass pipe and the pressure of the turbine bypass pipe is adjusted by pressure adjusting means while being driven,Select storage means for storing main steam pressure value when predetermined plant condition is established, main steam pressure value read from this storage means, and actual pressure tracking pressure value with bias value added to main steam pressure value And a control means comprising a switching means for outputting to the PID computing unit. The control means uses the pressure signal at the time when either the plant stop command or the gas turbine stop command is established as the pressure control set value as the pressure control set value. Since the pressure adjusting means of the turbine bypass pipe when stopping the heat recovery boiler is controlled,By bypassing the steam turbine through the turbine bin bypass pipe to the condenserExhaustedThe plant can be safely stopped while reducing the amount of steam. As a result, the next startup time can be shortened.
[0075]
  According to the stop device of claim 2, an exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam, a main steam pipe that supplies the steam generated in the exhaust heat recovery boiler to the steam turbine, In a combined cycle plant comprising a turbine bypass pipe connected to the main steam pipe and bypassing the steam turbine, and a pressure adjusting means provided in the turbine bypass pipe,Selects a storage device that stores the main steam pressure value when a predetermined plant condition is established, a main steam pressure value read from the storage device, and an actual pressure tracking pressure value obtained by adding a bias value to the main steam pressure value And a control unit comprising a switch for outputting to the PID computing unit. The control unit uses the pressure signal at the time when either the plant stop command or the gas turbine stop command is established as the pressure control set value as the pressure control set value. Since the pressure adjusting means of the turbine bypass pipe when stopping the heat recovery boiler is controlledThe effect similar to that of claim 1 can be obtained.
[0076]
  According to the stopping method of claim 3,Steam is generated by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and the steam is supplied to the steam turbine for driving, while the steam turbine is bypassed through the turbine bypass pipe and the turbine bypass In a combined cycle plant in which the pressure of the pipe is adjusted by the pressure adjusting means, a storage means for storing a main steam pressure value when a predetermined plant condition is established, a main steam pressure value read from the storage means, and a main steam pressure A first switching means for selectively outputting an actual pressure tracking pressure value obtained by adding a bias value to the value, and two limiting means for setting an upper limit and a lower limit of the pressure value output from the first switching means. In parallel with the downstream side of the first switching means, an upper limit value or a lower limit value is selectively PI on the downstream side. And a second switching means for outputting to the computing unit. The control means outputs a pressure signal on the limiting means side that is switched based on a closing command for a steam control valve provided in the main steam pipe. Since the pressure adjusting means of the turbine bypass pipe when stopping the exhaust heat recovery boiler is controlled as a control set value, the combined cycle plant can be made stable operation without waste during the stop process.
[0077]
  According to the stopping device of claim 4,An exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam, a main steam pipe that supplies steam generated in the exhaust heat recovery boiler to the steam turbine, and the steam turbine connected to the main steam pipe In a combined cycle plant comprising a turbine bypass pipe that bypasses the pressure and a pressure adjusting means provided in the turbine bypass pipe, a storage device that stores a main steam pressure value when a predetermined plant condition is satisfied, and the storage device The first switch for selectively outputting the main steam pressure value read from the main steam pressure value and the actual pressure tracking pressure value obtained by adding the bias value to the main steam pressure value, and the pressure value output from the first switch Two limiters for setting the upper and lower limits of the first switch are provided in parallel on the downstream side of the first switch, and an upper limit value or lower limit value is further selected on the downstream side. And a second switching unit that outputs to the PID computing unit, and the control unit includes a pressure signal on the limiter side that is switched based on a closing command for a steam control valve provided in the main steam pipe. Is set to control the pressure adjusting means of the turbine bypass pipe when stopping the exhaust heat recovery boiler with the pressure control set value, so that unnecessary turbine bypass operation is restricted and wasteful energy consumption is suppressed. be able to.
[0080]
  According to the stopping method of claim 7,Steam is generated by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, and the steam is supplied to the steam turbine for driving, while the steam turbine is bypassed through the turbine bypass pipe. The pressure adjusting means is controlled by a pressure adjusting means, and when the exhaust heat recovery boiler is stopped, the pressure adjusting means of the turbine bin bypass pipe is controlled using a value obtained by adding a bias value to the main steam pressure. In a combined cycle plant, once the control setting value of the pressure adjusting means is set to the pressure of the turbine bypass pipe using a stop command or plant conditions, the value of the bias value is added to this value to limit the rate of change. Since it is output as a set value, the combined cycle plant can be operated in a stable and detailed manner without waste. It is possible.
[0081]
  Claim 8ofAccording to the stop deviceAn exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam, a main steam pipe that supplies steam generated in the exhaust heat recovery boiler to the steam turbine, and the steam turbine connected to the main steam pipe A value obtained by adding a bias value to the main steam pressure in the turbine bypass pipe, the pressure adjusting means provided in the turbine bypass pipe, and the pressure adjusting means of the turbine bypass pipe when stopping the exhaust heat recovery boiler In a combined cycle plant comprising a control means for controlling as a set value, a plurality of change rate limiters having different change rate limits are provided for the pressure adjusting means of the turbine bypass pipe, and these are switched based on a stop command. Since it is configured to be possible, claim 7The same effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a combined cycle plant stop method and a circuit configuration of the stop device according to the first embodiment of the present invention.
FIGS. 2A, 2B, 2C, and 2D are time charts at the time of stop according to the first embodiment;
FIG. 3 is a block diagram showing a combined cycle plant stop method and a circuit configuration of the stop device according to the second embodiment of the present invention.
4A, 4B, 4C, and 4D are time charts at the time of stopping according to the second embodiment.
FIG. 5 is a block diagram showing a combined cycle plant stop method and a circuit configuration of the stop device according to the third embodiment of the present invention.
FIGS. 6A, 6B, 6C, and 6D are time charts at the time of stop according to the third embodiment.
FIG. 7 is a block diagram showing a combined cycle plant stopping method and a circuit configuration of the stopping device according to a fourth embodiment of the present invention.
FIGS. 8A, 8B, 8C, 8D and 8E are time charts at the time of stopping according to the fourth embodiment.
FIG. 9 is a block diagram showing a combined cycle plant stop method and a circuit configuration of the stop device according to a fifth embodiment of the present invention.
10 (A), (B), (C), and (D) are time charts when stopped according to the fifth embodiment. FIG.
FIG. 11 is a system diagram showing a configuration of a conventional combined cycle power plant.
FIG. 12 is a block diagram showing a circuit configuration of a conventional combined cycle plant stopping method and apparatus.
13 (A), (B), (C), and (D) are time charts when a conventional combined cycle plant is stopped.
[Explanation of symbols]
1 Waste heat recovery boiler
2 Steam drum
3 Evaporator
4 Superheater
5 Main steam pipe
6 Steam control valve
7 Steam turbine
8 Condenser
9 Turbine bypass pipe
10 Turbine bypass valve
11 Main steam pressure sensor
12 Electro-pneumatic converter
13 PID calculator
14 change over device
15 Memory
16 Signal generator
17 Adder
18 OR circuit
19 Control means
20 Change rate limiter
21 Control means
22 Limiter for normal use
23 Stop limiter
24 selector
25 Control means
26 Stop pressure setting calculator
27 Control means
28 selector
29 One-shot circuit
30 knot circuit
31 Subtractor
32 Set value output means

Claims (9)

While generating steam by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, this steam is supplied to the steam turbine and driven,
Bypassing the steam turbine through a turbine bypass pipe;
In the combined cycle plant for adjusting the pressure of the turbine bypass pipe by the pressure adjusting means,
Storage means for storing a main steam pressure value when a predetermined plant condition is established;
Switching means for selectively outputting a main steam pressure value read from the storage means and an actual pressure tracking pressure value obtained by adding a bias value to the main steam pressure value to a PID calculator;
A control means comprising:
The control means controls the pressure adjusting means of the turbine bypass pipe when the exhaust heat recovery boiler is stopped by using a pressure signal when either the plant stop command or the gas turbine stop command is established as a pressure control set value.
A method for stopping a combined cycle plant. An exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam;
A main steam pipe for supplying steam generated in the exhaust heat recovery boiler to the steam turbine;
A turbine bypass pipe connected to the main steam pipe and bypassing the steam turbine;
In a combined cycle plant having a pressure adjusting means provided in the turbine bypass pipe,
A storage device for storing a main steam pressure value when a predetermined plant condition is established;
A switch for selectively outputting a main steam pressure value read from the storage device and an actual pressure tracking pressure value obtained by adding a bias value to the main steam pressure value to a PID computing unit;
A control means comprising:
The control means controls the pressure adjusting means of the turbine bypass pipe when the exhaust heat recovery boiler is stopped by using a pressure signal when either the plant stop command or the gas turbine stop command is established as a pressure control set value. A combined cycle plant stop device characterized by having a configuration. While generating steam by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, this steam is supplied to the steam turbine and driven,
Bypassing the steam turbine through a turbine bypass pipe;
In the combined cycle plant for adjusting the pressure of the turbine bypass pipe by the pressure adjusting means,
Storage means for storing a main steam pressure value when a predetermined plant condition is established;
First switching means for selectively outputting a main steam pressure value read from the storage means and an actual pressure tracking pressure value obtained by adding a bias value to the main steam pressure value;
Two limiting means for setting the upper limit and the lower limit of the pressure value output from the first switching means are provided in parallel on the downstream side of the first switching means,
Furthermore, a second switching means for selectively outputting an upper limit value or a lower limit value to the PID computing unit on the downstream side;
A control means comprising:
This control means uses the pressure signal of the limiting means switched based on the closing command of the steam control valve provided in the main steam pipe as a pressure control set value, and the pressure of the turbine bypass pipe when stopping the exhaust heat recovery boiler A method for stopping a combined cycle plant, wherein the adjusting means is controlled. An exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam;
A main steam pipe for supplying steam generated in the exhaust heat recovery boiler to the steam turbine;
A turbine bypass pipe connected to the main steam pipe and bypassing the steam turbine;
Combined cycle plan provided with pressure adjusting means provided in the turbine bypass pipe In
A storage device for storing a main steam pressure value when a predetermined plant condition is established;
A first switch for selectively outputting a main steam pressure value read from the storage device and an actual pressure tracking pressure value obtained by adding a bias value to the main steam pressure value;
Two limiters for setting an upper limit and a lower limit of the pressure value output from the first switch are provided in parallel on the downstream side of the first switch,
And a second switch for selectively outputting an upper limit value or a lower limit value to the PID computing unit on the downstream side;
A control means comprising:
The control means uses the pressure signal of the turbine bypass pipe when the exhaust heat recovery boiler is stopped with the pressure signal on the limiter side switched based on the closing command of the steam control valve provided in the main steam pipe as the pressure control set value. A combined cycle plant stop device characterized in that the adjusting means is controlled. In the combined cycle plant stopping method according to claim 1,
A pressure setting calculation means for calculating a pressure based on a predetermined external process signal is provided upstream of the switching means;
In the combined cycle plant, the pressure control setting value of the pressure adjusting means at the time of stop is at least one of gas turbine exhaust gas temperature, steam temperature, steam pressure, steam turbine metal temperature, and drum pressure. How to stop. In the combined cycle plant stop device according to claim 2,
A pressure setting calculator that calculates pressure based on a predetermined external process signal is provided on the upstream side of the switch,
The pressure control set value of the pressure adjusting means at the time of stop is configured as a set value using at least one of gas turbine exhaust gas temperature, steam temperature, steam pressure, steam turbine metal temperature, and drum pressure. Stop device for combined cycle plant. While generating steam by exchanging heat between the exhaust gas of the gas turbine and the feed water of the exhaust heat recovery boiler, this steam is supplied to the steam turbine and driven,
The steam turbine is bypassed through a turbine bypass pipe, and the pressure of the turbine bypass pipe is adjusted by pressure adjusting means;
When the exhaust heat recovery boiler is stopped, in the combined cycle plant that controls the pressure adjusting means of the turbine bin bypass pipe as a set value by adding a bias value to the main steam pressure,
The control set value of the pressure adjusting means is temporarily set to the pressure of the turbine bypass pipe using the stop command or the plant condition, and then the value obtained by adding the bias value to this value is limited by the rate of change and output as the set value. A method for stopping a combined cycle plant. An exhaust heat recovery boiler that exchanges heat with the exhaust gas of the gas turbine to generate steam;
A main steam pipe for supplying steam generated in the exhaust heat recovery boiler to the steam turbine;
A turbine bypass pipe connected to the main steam pipe and bypassing the steam turbine;
Pressure adjusting means provided in the turbine bypass pipe;
Control means for controlling, as a set value, a value obtained by adding a bias value to the main steam pressure for the pressure adjusting means of the turbine bypass pipe when stopping the exhaust heat recovery boiler;
In a combined cycle plant with
A stop device for a combined cycle plant, characterized in that a plurality of change rate limiters having different change rate limits are provided for the pressure adjusting means of the turbine bypass pipe, and these can be switched based on a stop command. In the combined cycle plant stop device according to claim 8,
A setting that temporarily sets the control setting value of the pressure adjustment means to the pressure of the turbine bypass pipe using the stop command or plant condition, and then outputs a setting value by limiting the rate of change to the value obtained by adding the bias value to this value Combined cycle plastic characterized by providing value output means Stop device.

Images