JPS6239655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler switching system when additionally connecting or additionally disconnecting an exhaust gas boiler for a combined plant.

In a combined plant that aims to be a high-efficiency power generation plant and consists of a combination of multiple gas turbines, an exhaust gas boiler that uses their exhaust gas, and one steam turbine that is driven by the steam generated by them, the An automatic switching device that sequentially connects or disconnects the exhaust gas boilers at the time of switching is essential, but such a device has not yet been developed.

Minimize fuel loss, shorten startup, shutdown and switching times, and meet various limiting conditions in starting, stopping and switching the number of combined plants consisting of multiple gas turbines, exhaust gas boilers and one steam turbine. It is necessary to switch between starting and stopping while satisfying the requirements. In particular, since there are multiple exhaust gas boilers, one of the key points for the success or failure of a combined plant is to be able to perform complex operations safely, reliably, and automatically. Therefore, providing an exhaust gas boiler switching system that achieves these objectives is one of the essential conditions for the success of a combined plant.

Among such exhaust gas boiler switching systems for combined plants, the present invention particularly provides a boiler addition/shutdown control system during plant operation that increases or decreases the number of gas turbines in operation in order to improve plant operational efficiency. The purpose is

The present invention controls the pressure at the outlet of the exhaust gas boiler according to the plant condition in order to obtain the required pressure for starting, stopping, and switching a combined plant, and the rate of change in the load of the steam turbine is controlled at a predetermined rate of change. To do this, the opening and closing speed of the exhaust gas boiler outlet stop valve is controlled in order to adjust the amount of air sent from the exhaust gas boiler, and the steam sent from the exhaust gas boiler is allowed to flow into the steam turbine, while at the same time controlling the pressure at the steam control valve inlet to the plant. The basic idea is to control the steam turbine control valve according to the state and to prevent the pre-pressure from falling below a specified pressure, and to connect and disconnect the exhaust gas boiler.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below as illustrated in the accompanying drawings.

FIG. 1 shows a steam system that supplies air from, for example, three steam generating equipment (boilers) to one steam turbine in a combined plant, and control equipment and circuits that control them.

In the steam system, steam generated in No. 2 exhaust gas boiler 1 passes through a boiler stop valve 2 and a steam turbine control valve 3, is sent to a steam turbine 4, and becomes condensed in a condenser 5. Similarly, the steam generated in No. 1 and No. 3 boilers (not shown) passes through boiler stop valves 6 and 7, and then is combined with steam from other boilers and sent to the steam turbine 4.

When the boiler stop valve 2 is closed, the pressure transmitter 8 detects the boiler pressure of No. 2 boiler 1, and the pressure controller 9 compares and controls this boiler pressure with the set pressure, and this output signal is common. After being compared and selected by the control signal from the pressure controller 13 and the high signal selector 10,
The amount of steam released to the condenser 5 is adjusted by controlling the turbine bypass control valve 11. With this No.2
Steam pressure in boiler 1 is maintained at a specified value.

When the boiler stop valve 2 is open, the common pressure after merging with steam from other boilers is transmitted to the pressure transmitter 12.
The steam pressure of the three boilers is commonly controlled by the common pressure controller 13.

The set pressure is determined as follows depending on the plant status.

When the boiler stop valve 2 is closed, if you want to control the boiler pressure individually, set it arbitrarily with the pressure setting device 14 and switch the signal switch 15 to the individual setting signal side. If not, common pressure setting device 1
In step 6, set the pressure common to all three boilers,
Switch the signal switch 15 to the common setting side. Furthermore, when the boiler pressure is made to follow the turbine inlet pressure, the signal from the pressure transmitter 12 is smoothed by the signal smoother 17 and then the bias is added by the bias adder 18, or the signal from the smoother 17 is smoothed by the signal smoother 17. It is directly applied to the common pressure setter 16 via a signal switch to command the set pressure.

When the boiler stop valve 2 is open, the above-mentioned common pressure setting device detects the turbine inlet pressure with the pressure transmitter 37 in addition to the follow-up setting, and based on this signal (i.e. turbine load factor), the program pressure setting device 20
The boiler set pressure can be programmed by the set pressure of . That is, ultimately, the high signal among the program setting value, follow-up or common setting, and minimum pressure setting (set by the minimum pressure setting device 21) is selected by the high signal selector 22, and then the maximum pressure setting is selected by the high signal selector 22. (set by the highest pressure setter 23), a low signal is selected by the low signal selector 24, and the set pressure is applied to the individual pressure controller 9 or the common pressure controller 13.

The boiler stop valves 2, 6, and 7 select one of the control signals from the high-speed opening/closing controller 25 or the low-speed opening/closing controller 26 with the signal switcher 27,
It is opened and closed by this signal.

As a protection at this time, the rate of change of the turbine inlet pressure (ie, the rate of change of the turbine load) is kept within a limit value. For this, the turbine inlet pressure is detected by the pressure transmitter 37, the rate of change is detected by the change rate detector 28, and when the value exceeds the limit value, the signal limiter 29 is activated, and the opening/closing controller 25 is activated. The opening/closing operations of 26 and 26 are temporarily suspended. Similarly, the pressure change rate of the boiler is monitored by a pressure transmitter 8, a change rate detector 30, and a signal limiter 31. In addition, since there is a limit to the minimum pressure of the boiler pressure, the signal limiter 32 monitors the minimum pressure and operates in the same manner.

The turbine inlet steam pressure is adjusted by controlling the steam turbine control valve by the pressure controller 34 so that the pressure detected by the pressure transmitter 12 becomes the pressure set by the pressure setting device 33. The pressure settings of the pressure setting device 33 include direct pressure setting, in which the pressure setting device 33 directly sets the pressure, and signal switching device 35.
The actual inlet pressure of the steam turbine control valve 3 is detected by the pressure transmitter 12, and this is passed through a signal smoother to set the set pressure, thereby making the pressure setting follow the turbine inlet pressure. There are pressure setting and ramp pressure setting in which the target pressure setter 36 is selected by the signal switch 35 to increase or decrease the target set pressure at a predetermined rate of change.

In a combined plant consisting of multiple gas turbines, exhaust gas boilers, and one steam turbine, when the plant is operated at partial load, it is necessary to increase or decrease the number of gas turbines in operation to improve plant operational efficiency. be.

Examples of additional start-up and additional stop curves of the gas turbine are shown in FIGS. 2 and 3, respectively. This shows an example in which the total plant output increases or decreases in accordance with the increase or decrease in the gas turbine output that is additionally started or stopped. The operation of the exhaust gas boiler switching system corresponding to this will be explained below.

In FIG. 1, it is assumed that two gas turbines are already in operation, that is, boiler outlet stop valves 6 and 7 of No. 1 and No. 3 are fully open. The case where the No. 2 gas turbine is additionally activated and the No. 2 boiler 1 is additionally installed will be explained with reference to FIG. 1.

The pressure setter 33 and target pressure setter 36 of the front pressure control system of the steam turbine control valve 3 are activated by the switching command, and the set pressure is gradually increased from the current pressure to the turbine inlet pressure corresponding to the turbine load after the completion of the additional startup. and increase the pressure at the inlet of the steam turbine control valve 3.

Similarly, the switching device 19 is activated by the switching command,
The common pressure setting device 16 is set to follow mode, and the set pressure to the pressure controller 9 is made to follow the inlet pressure of the steam turbine control valve 3. As a result, the differential pressure across the boiler stop valve 2 is maintained at (α) ^K .

When the pressure rise is completed, the switching device 27 is operated and the boiler stop valve 2 is opened by the high-speed opening/closing controller 21.

When the boiler stop valve 2 opens, the bypass control valve 11 opens.
gradually closes and finally closes completely, completing the additional valve of No. 2 boiler.

During this time, the steam turbine control valve 3 is opened so that its front pressure is maintained at the pressure set by the pressure setting device 33, so the amount of steam flowing into the steam turbine increases as the boiler stop valve 2 opens.

When the bypass control valve 11 is fully closed, the steam turbine control valve 3 is fully opened to return to normal operation. In addition, the common pressure setting value is returned to the lowest pressure so that the program setting device 20 virtually sets the pressure.
The bypass control valve 11 returns to the function of the advance safety valve.

Even when additionally starting one gas turbine to two gas turbines, the flow rate air supply control method using the boiler outlet stop valve 2 is performed in the same manner.

Next, the case of disconnecting the boiler illustrated in FIG. 3 will be explained. Boiler outlet stop valves 2, 6 and 7 are 3
A case in which both the machines are open and one of them is closed will be explained with reference to FIG.

The signal switch 19 is activated by the disconnection command, and the common pressure setting device 16 is placed in the follow-up mode. Then, the pressure controller 19 has the current steam turbine control valve 3.
The pressure that is +α to the inlet pressure is set. Subsequently, the signal switch 27 is activated to switch the high-speed opening/closing controller 25
Select and close the boiler stop valve 2 at high speed. When the boiler stop valve 2 closes and a pressure difference occurs before and after the boiler stop valve 2 and exceeds α ^K , the pressure transmitter 8 detects this and the pressure controller 9 operates to adjust the boiler pressure to the turbine inlet. Control by following pressure.

When the boiler stop valve 2 is fully closed, the signal switch 15 is operated to select the individual pressure setting device 14 to perform individual pressure control. This completes boiler disconnection.

As described above, according to the control in which the total plant output is changed according to additional startups and stops, the number of operating units can be reduced by coordinating the turbine bypass control system, boiler stop valve control system, and turbine regulator valve inlet pressure control system. It was possible to increase and decrease the amount more easily and safely than in conventional plants. Furthermore, when adding an additional boiler, by increasing the turbine regulator inlet pressure in advance, the turbine bypass system can be greatly reduced. It is necessary to dump the steam generated from the boiler to the condenser through the turbine bypass system while maintaining the same pressure. In other words, a bypass system is required to bypass the boiler's maximum evaporation amount at the minimum pressure. Further, in the present invention, by appropriately selecting the boost pressure, it is possible to set the capacity according to the plant.

In the examples shown in Figures 2 and 3, we explained how to change the number of gas turbines when the total plant output increases or decreases as the gas turbines start and stop, but the total plant output is assumed to be constant even when the number of gas turbines changes. There are things I want to leave alone.

The present invention operates effectively in this case as well.

Examples of starting/stopping curves in this case are shown in FIGS. 4 and 5.

In Figs. 2 and 3, the boiler stop valve 2 was opened immediately after the completion of pressure increase, but in the example shown in Figs. 4 and 5,
Since the load remains constant, it goes without saying that the pressure increase target value is set to a low pressure that is commensurate with the variation in steam amount due to the variation in the number of gas turbines.

In addition, in order to keep the total plant output constant before increasing the load on the gas turbines to be additionally started, the load control device (not shown) that controls the total output of the power plant is set to automatic, and the gas turbines other than the gas turbines to be started or stopped are be under its control.

After that, increase the load on the gas turbine to be added, and when the steam generated from the exhaust gas boiler to be added can be mixed into the steam turbine, switch the boiler using the same procedure as in the previous section.

During this time, the outputs of other gas turbines are reduced to match the increased load of the added gas turbine, and the outputs of other gas turbines are also adjusted in response to the increase in the output of the steam turbine due to the addition of the boiler. Therefore, boiler switching is possible while keeping the total plant output constant.

Although the present invention has been described above in detail with reference to its preferred embodiments, the present invention is not limited to these specific embodiments and can be modified in many ways without departing from the spirit of the invention.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing the exhaust gas boiler switching system according to the present invention, Figure 2 is a diagram showing an additional startup curve, Figure 3 is a diagram showing an additional shutdown curve, and Figures 4 and 5 are constant plant total output. FIG. 6 is a diagram showing a switching curve when the spoiler is switched as it is. 1... Boiler, 2, 6, 7... Boiler stop valve, 3... Steam turbine control valve, 4... Steam turbine, 5... Condenser, 8, 12, 37... Pressure transmitter, 9, 13, 3
4...Pressure controller, 10,22...High signal selector, 1
1...Turbine bypass control valve, 14, 16, 3
3, 36...Pressure setting device, 15, 19, 27, 35
...Signal switcher, 17...Signal smoother, 18...Bias adder, 20...Program pressure setter, 21...
Minimum pressure setter, 23... Maximum pressure setter, 24...
Low signal selector, 25...High speed switching controller, 26...Low speed switching controller, 28, 30... Rate of change detector, 2
9, 31, 32...Signal limiter.

Claims (1)

[Claims] 1. In a combined plant consisting of multiple gas turbines, multiple exhaust gas boilers that generate steam using exhaust gas from the gas turbines, and one steam turbine, a boiler outlet provided at the outlet of each exhaust gas boiler. Each turbine is equipped with a turbine bypass control valve and a boiler stop valve for pressure control, and a steam turbine control valve that adjusts and controls the steam after merging at the outlet of these boiler stop valves and supplies the steam to the steam turbine. It has an individual pressure controller that individually controls the bypass control valves and a common pressure controller that controls all of these control valves simultaneously, and the individual pressure settings are related to the pressure settings of the individual pressure controllers, and the individual pressure controller and the common pressure controller are connected to each other. The pressure controller includes a turbine bypass control valve control device that is associated with a common pressure setting to be the lowest pressure, a follow-up pressure setting to follow the steam regulator inlet pressure, and a program pressure setting to be set according to the steam turbine inlet pressure; It has a boiler stop valve control device that opens and closes the boiler stop valve at high speed, and a pressure controller that controls the steam turbine control valve. The system is equipped with a steam turbine control valve control device that has a ramp pressure setting, a minimum pressure setting, and a follow-up setting, and when a boiler is added during plant operation, the pressure setting of the steam turbine control valve control device is set to the ramp pressure setting. The pressure setting of the turbine bypass control valve control device is changed from the program pressure setting to the follow-up pressure setting, and when the steam turbine regulator valve inlet pressure reaches the target, the boiler stop valve of the boiler to be followed-up is opened at high speed, and bypass control is performed. When the valve gradually closes and becomes fully closed, the pressure setting is returned to the setting during normal operation, and when the boiler is additionally disconnected, the pressure setting of the turbine bypass control valve control device is changed from the program pressure setting to the follow-up pressure setting, and the pressure setting is changed from the program pressure setting to the follow-up pressure setting. A boiler switching system at the time of addition/disconnection of a combined plant, characterized in that the boiler stop valve of the boiler to be disconnected is closed at high speed, and the pressure setting of the individual pressure controller for the disconnected boiler is set to the individual pressure setting.