JPS607164B2 - Once-through boiler temperature increase control device - Google Patents

Description

[Detailed Description of the Invention] In general, boiler input (e.g., water supply, fuel, etc.) is rapidly reduced by detecting a system failure or turbine no-load, and the turbine governor is reduced to a specified level, allowing for isolated operation within the plant. The function is FshiptCMBack (hereinafter referred to as FC).
It is called B) and enables rapid restart when rejoining, helping to ensure a stable supply of electricity.

The present invention relates to a boiler temperature increase control device during rapid plant restart after FCB.

Temperature control has been carried out by manually raising and lowering the fuel/water ratio setting device, but the boiler water cooling wall outlet temperature drops rapidly after FCB, and the heat retained in the energy saver (residual heat ) will rise again due to high water supply.

On the other hand, if the fuel is throttled too much to suppress this, recovery of the main steam temperature will be delayed. In this way, adjustment operations for conflicting parameters are required, making operations difficult and FC
Since these temperature characteristics also change due to differences in the amount of heat held by the economizer depending on the amount of load before B occurs, the operation becomes increasingly complicated. Therefore, an object of the present invention is to fix the temperature characteristics of the boiler at the rate of change in the temperature at the outlet of the economizer, regardless of the load amount before FCB generation, and to improve the magnitude of the rate of change. It is an object of the present invention to provide a monitoring and control device that can automatically set the set value of a fuel/water supply ratio setting device to obtain desired temperature control. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a once-through boiler to which the present invention is applied will be described with reference to the accompanying drawings.

Figure 1 is a main system diagram of a once-through boiler. The water supplied to the boiler is first heated by the boiler exhaust gas in the economizer 1,
The fluid is turned into superheated steam and guided to the turbine 7 while being sequentially heated through the furnace water wall 2, the primary superheater 3, and the final superheater 4. On the other hand, when FCB occurs due to a system accident, etc., the system switches to the boiler startup system, the startup stop valve 8 is fully closed, the startup bypass valve 9 is opened, and the fluid is separated into steam and water by the steam separator 5, and steam is generated. Only the superheater passes through the primary superheater 3 and the final superheater 4 and is led to the turbine 7. When this startup system is configured, the overflow control raises the temperature of the fluid at the outlet 10 of the water cooling wall of the furnace to the target temperature, but when the target temperature is reached, the boiler startup system is switched to the once-through system.

This switching is performed by gradually opening the starting stop valve bypass valve 11 and gradually closing the starting bypass valve. Once the system becomes a once-through system, the water supply and fuel base will gradually increase.
The start stop valve bypass valve 11 is fully opened, and the start stop valve 8 also begins to open. In this process, as can be understood from FIG. 3, when FCB occurs, the temperature 12 of the feed water at the outlet of the economizer (Eco) rises rapidly.

On the other hand, the water wall outlet steam temperature 10 of the furnace falls extremely, but then the retained heat of the Eco outlet feed water on the upstream side is brought in, causing the water wall outlet steam temperature to rise rapidly by 1 river.
If the fuel is throttled too much in order to suppress this, recovery of the main steam temperature (same as the boiler outlet) 13 and the reheater outlet steam temperature 14, which are the ultimate targets, will be delayed. FIG. 2 shows a detailed block diagram of the temperature increase control device 25 according to the present invention. This device is a cost saving outlet feed water temperature change rate calculator 1 that performs differential calculation on the temperature detected by the saver outlet feed water temperature detection device 16.
a temperature change rate determination section 18 that determines the magnitude of the temperature change rate based on the output signal of 7; and a setting operation section that positions the fuel/water supply ratio setting device 24 and operates the setting device based on the determined signal. It consists of 21. Furthermore, this temperature increase control device 25 detects respective temperature signals from the furnace water cooling wall outlet temperature detection device 19 and the boiler outlet temperature detection device 20, and uses the former temperature signal to control the setting device 24 from the setting operation section 21. a block/correction operation determination unit 22 that causes the set signal to perform a block or correction operation;
A normality determining section 23 is provided which determines recovery of the main steam temperature based on the latter temperature signal and excludes the device of the present invention.
Next, the operation of the temperature increase control device 25 according to the present invention will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows the temperature characteristics of each part of the boiler at the time of restart after rejoining following the occurrence of FCB. The temperature change rate is determined by the temperature change rate determination section 18, and the magnitude of the temperature change rate is determined by the temperature change rate determination section 18. Based on the magnitude of this temperature change rate, the setting operation section 21 determines the fuel/water supply ratio setting value as shown in FIG. 4, and performs a positioning operation of the fuel/water supply ratio setting device 24. A fuel/water supply ratio setting device 24, which is a part of a known overall plant control device set at a predetermined position, adjusts a predetermined base fuel/water ratio based on the boiler input signal at that time to adjust the fuel/water supply ratio. By adjusting the input amount, temperature increase control of the furnace water wall steam temperature of 10 can be obtained.

In addition, the temperature signal detected by the furnace water cooling wall steam temperature detection device 19 is monitored and the setting device 24 is turned on when the fuel/water ratio setting device 24 is raised or the target temperature is exceeded through the setting operation section 21 at the specified temperature. Performs forced lowering correction action. On the other hand, the main steam temperature detection device 20 which is the final target
The temperature signal detected from this is monitored, and after the minimum temperature has passed, the normality determination unit 23 confirms that the main steam temperature has recovered to a specified temperature or higher. Exclude via. In other words, the operation described above is taken over by a known plant general control device, and fuel control becomes automatic and steam control continues. Since the heat retained in the economizer brought into the steam at the outlet of the water-cooled wall of the furnace is fixed at the rate of change of the feed water temperature at the outlet of the economizer, which has the greatest effect on the steam temperature at the outlet of the water-cooled wall of the furnace, The most effective settings can be made.

This also makes it possible to effectively control the early recovery of the main steam temperature by setting the target temperature of the furnace water-cooled wall outlet steam temperature to the full limit value, and at the same time prevent the risk of excessive rise in the furnace water-cooled wall temperature. . As a result, it is possible to quickly and automatically restart a thermal power plant after FCB, contributing to early power transmission.

[Brief explanation of the drawing]

Fig. 1 is a main system diagram of a once-through boiler in which the salt rise control device according to the present invention is adopted, Fig. 2 is a detailed block diagram of the temperature rise control device according to the present invention, and Figs. FIG. 3 is a characteristic diagram for explaining the operation of the temperature increase control device according to the invention. 1...Coal economizer, 2...Furnace water cooling wall, 3
...Primary superheater, 4...Final superheater, 5.
...Steam water separator, 6...Reheater, 7...
...High pressure turbine, 8...Start stop valve, 9
...Start-up bypass valve, 10...Furnace water cooling wall outlet temperature, 11...Start-up stop valve bypass valve, 1
2... Economizer outlet water supply temperature, 13...'
Main steam temperature, 14...Reheater outlet steam temperature, 1
5...Intermediate pressure turbine, 16, 19, 20...Temperature detection device, 17...〇Temperature change rate calculation unit, 18...
...Temperature change rate discrimination unit, 21...Setting operation unit, 22...Flock/correction operation discrimination unit, 23
. . . Normality determination section, 24 . . . Fuel/water supply ratio setting device, 25 . . . Temperature increase control device. Figure l Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a once-through boiler that has the function of rapidly restricting the boiler input upon detection of a system failure, etc., and also restricting the turbine governor to a specified position and operating the plant independently, detecting the temperature of the feed water at the exit of the economizer upon restart after the above function occurs. death,
A setting operation section that positions a fuel/water supply ratio setting device that controls the steam temperature at the outlet of the water-cooled wall of the furnace based on the magnitude of the temperature change rate, and a setting operation section that positions the steam temperature at the outlet of the water-cooled wall of the furnace and monitors its target temperature. A block/correction operation discriminator that instructs the setting operation section to perform a block or correction operation, and a normality discriminator that detects the main steam temperature and stops the control operation by determining recovery of the main steam temperature. A temperature increase control device for a once-through boiler, characterized by the following.