JPH0412329Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a device for controlling steam temperature, and more particularly to a device that can perform good control over the entire load range of a boiler.

In recent years, boilers in thermal power plants have become larger and larger, and have become high-temperature and high-pressure types. In such high-temperature, high-pressure boilers, the permissible fluctuation range of steam temperature is severely limited due to the material of the boiler and the thermal stress of the turbine, and it is necessary to precisely control the steam temperature. Steam temperature can be controlled either by controlling the combustion state in the boiler, such as by changing the burner angle or by recirculating exhaust gas, or by cooling the steam. Among these methods, the method of controlling the temperature by controlling the combustion state has poor responsiveness and cannot perform precise control, and precise control is mainly performed by a method of cooling the steam.

FIG. 1 shows one conventional example of steam temperature control using a steam cooling method. In this steam cooling system, a small-capacity attemperator is installed outside the large-capacity attemperator, and by lowering the steam temperature at the inlet of the large-capacity attemperator to a certain extent, the steam inside the large-capacity attemperator is The flow rate is maintained above a certain value to ensure good mixing of cooling water within the large-capacity desuperheater and to enable large-capacity starts. In the figure, a portion of the steam S flows into the small capacity attemperator 2 via the first steam line 1. In this attemperator 2, the temperature regulator 3 detects the steam temperature at the outlet of the attemperator, and by feeding back this detection result, the valves 5 and 6 provided in the cooling water pipe 4 are adjusted. Adjust the amount of cooling water _W1 sprayed inside. The steam adjusted to a predetermined temperature in the water capacity attemperator 2 in this manner merges with the steam supplied from the second steam pipe line 7 and flows into the large capacity attemperator 8. In this large-capacity attemperator 8 as well, the temperature regulator 9 detects the steam temperature at the outlet of the attemperator, and the detection result is fed back to the valve 1 of the cooling water pipe 10.
Adjust 1 and 12. Thereby, the amount of cooling water W sprayed into the desuperheater 8 is adjusted, and the steam temperature is controlled. If each desuperheater is controlled independently in this way, the temperature in each desuperheater can be accurately controlled, but since there is no interlock between each desuperheater,
There is a problem in that the control as a whole becomes unstable, and this tendency becomes particularly noticeable at low loads, resulting in inaccurate temperature control.

FIG. 2 shows another example of control. In this control example, the temperature controller 3 that controls the small-capacity attemperator 2 generates a function based on the result detected by another temperature regulator 9 placed downstream of the large-capacity attemperator 8. The cascade control is performed by inputting the data through the device 13. This dramatically improves the control accuracy, especially at low loads, compared to the control example described above, but on the other hand, there is a problem that the interlock becomes complicated and the device becomes complicated and expensive.

This invention was constructed in view of the above-mentioned problems, and the object is to provide a steam temperature control device that can accurately control steam temperature over a wide load range without delay in control.

In short, this invention provides a large-capacity attemperator in the main channel of superheated steam, a small-capacity attemperator in a side channel that bypasses the main channel upstream, and a signal indicating the outlet steam temperature of the small-capacity attemperator. and a signal circuit is provided for inputting a signal of the outlet steam temperature of the large capacity attemperator to a ratio setting device and controlling a control valve provided in each water injection pipe by a command signal from the ratio setting device. This is a steam temperature control device with improved controllability.

An embodiment of this invention will be described below with reference to the drawings.

In FIG. 3, a temperature regulator 9 provided on the downstream side of the large-capacity attemperator 8 and a valve 5 provided in the pipe line that supplies cooling water W ₁ and W ₂ to each attemperator 2 and 8 are shown. ，
6, 11, and 12 are connected to each other by a command signal circuit 20. Reference numeral 15 denotes a ratio setting device provided for this command signal circuit, and the circuit is connected to the temperature regulator 3 provided on the downstream side of the small capacity attemperator 2.

In the above configuration, the temperature regulator 9 detects the outlet steam temperature of the large-capacity attemperator 8, and adjusts each valve 5, 6, 11, 12 based on the detection result. In this case, the outlet steam temperature of the small capacity attemperator 2 is detected by the temperature controller 3, and this detection result is inputted to the ratio setting device 15 as a correction value, and the temperature change signal from the temperature controller 9 is generated using this correction value. Each valve 5, 6, 11, 12 is controlled before inputting the input signal to perform feed forward control. This can prevent control delays due to detection of the large-capacity attemperator outlet steam temperature, that is, final steam temperature detection.

By implementing this idea, a small capacity desuperheater outlet steam temperature signal is also input in addition to the final steam temperature.
Since feedback control is performed, there is no control delay, and unlike feedback control, the influence of disturbances applied to the system does not appear on the control amount, making it possible to always perform accurate steam temperature control.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing single control in conventional steam temperature control, Figure 2 is a system diagram of cascade control, which is another conventional control method, and Figure 3 is a system diagram of the control device according to this invention. be. 2...Small capacity desuperheater, 3,9...Temperature controller,
5, 6, 11, 12...Flow rate control valve, 8...Large capacity desuperheater, 20...Command signal circuit, S...Steam,
W ₁ , W ₂ ...cooling water.

Claims (1)

[Scope of utility model registration request] A large-capacity attemperator is provided in the main channel of superheated steam, and a small-capacity attemperator is provided in a side channel that bypasses the main channel upstream thereof, and a signal of the outlet steam temperature of the small-capacity attemperator and the large-capacity attemperator are provided in the main channel of the superheated steam. Improved controllability, characterized by the provision of a signal circuit that inputs the steam temperature signal at the outlet of the desuperheater into a ratio setting device and controls the control valves installed in each water injection pipe using the command signal from the ratio setting device. steam temperature control device.