JPH0412330Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device for controlling steam temperature, and particularly to a device that can precisely control steam temperature.

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 desuperheater is installed in addition to the large-capacity desuperheater, and by lowering the steam temperature at the inlet of the large-capacity desuperheater to a certain extent, The steam flow rate is maintained above a certain value, allowing good mixing of cooling water in the large-capacity desuperheater and enabling large-capacity starts.

In FIG. 1, part of the steam S is in the first steam pipe 1
It flows into the small capacity attemperator 2 through the. This desuperheater 2
In this case, the steam temperature at the outlet of the desuperheater is controlled by temperature controller 3.
The valves 5 and 6 provided in the cooling water pipe 4 are detected by
and adjust the amount of cooling water _W1 sprayed into the desuperheater 2. The steam adjusted to a predetermined temperature in the water capacity desuperheater 2 in this way is transferred to the second steam pipe line 7.
It joins with the steam supplied from 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 valves 11 and 12 of the cooling water pipe 10 are adjusted by feeding back the detection result. Thereby, the amount of cooling water W ₂ sprayed into the attemperator 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, the overall control becomes unstable. There is a problem in that this tendency becomes remarkable especially when the load is low, and temperature control becomes inaccurate.

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.

In view of the above-mentioned problems, the purpose of this invention is to provide a device that can precisely control steam temperature over a wide load range.

In short, this invention provides a steam temperature control device in which a large-capacity attemperator is provided in the main channel of superheated steam, and a small-capacity attemperator is provided in the side channel that bypasses the main channel upstream. The cooling water main pipe 21 with a cooling water flow rate regulator 22 is branched into two water injection pipes with valves downstream of the cooling water flow rate regulator 22, and each of the pipes is connected to the small capacity attemperator 2 and the large capacity attemperator 8. Then, the flow rate signal of the steam flow rate regulator 23 and the temperature signal of the temperature detector 24 downstream of the large-capacity attemperator are sent to the cooling water flow rate regulator 22 via the comparison setting device 25, This is a precision control type steam temperature control device characterized by providing a signal circuit that controls water injection valves 11 and 12 of a large capacity desuperheater with a signal.

An embodiment of this invention will be described below with reference to FIG. In the figure, the pipe line that supplies cooling water to the small-capacity attemperator 2 and the large-capacity attemperator 8 is a single cooling water supply main pipe 21, and from this main pipe 21 to each attemperator 2. Pipes 4 and 10 for supplying cooling water to and 8 are branched. A flow rate regulator 22 that detects the flow rate of the cooling water W and controls the flow rate is attached to the main pipe upstream of each branch pipe. On the other hand, a flow rate regulator 23 for detecting the steam flow rate and a temperature detector 24 for detecting the steam temperature are attached to the steam pipe downstream of the large-capacity attemperator 8. The flow rate regulator 23 is connected to the flow rate regulator 22 via a ratio setter 25, and a temperature sensor 24 is connected to the ratio setter 25. Further, the flow rate regulator 22 and the valves 11 and 12 of the conduit 10 that supplies cooling water to the large-capacity attemperator 8 are connected by a command signal circuit.

In the above device, in the small-capacity desuperheater 2, the amount of cooling water sprayed (injected) is kept constant and the steam supplied from the steam pipe line 1 is cooled, and the steam supplied from the second steam pipe line 7 is and flows into the large-capacity attemperator 8 where it is cooled. Downstream of the large-capacity attemperator 8 , a flow rate regulator 23 measures the flow rate of the cooled steam, and this result is input to the cooling water flow rate regulator 22 . The flow rate regulator 22 adjusts the opening degrees of the valves 11 and 12 in proportion to the steam flow rate, adjusts the amount of cooling water sprayed to the large-capacity attemperator 8, and controls the steam temperature. In this case, the final steam temperature is detected by the temperature detector 24, and the opening degrees of the valves 11 and 12 are adjusted by inputting this detection result as a correction value.

By implementing this idea, the cooling water spray amount is adjusted in proportion to the steam flow rate, so there is no delay in steam temperature control, and the steam temperature itself is also input as a correction value, making the control more accurate.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing independent control among conventional temperature control devices, Fig. 2 is a system diagram of cascade control, which is another conventional control method, and Fig. 3 is a system diagram of the control device according to this invention. be. 2...Small capacity desuperheater, 8...Large capacity desuperheater, 2
1... Cooling water main pipe, 22... Cooling water flow rate regulator,
23...Steam flow rate regulator, 24...Temperature detector,
S...Steam, W...Cooling water.

Claims (1)

[Scope of utility model registration request] In a steam temperature control device in which 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, a cooling water main with a cooling water flow rate regulator 22 is provided. The pipe 21 is branched into two valved water injection pipes downstream of the cooling water flow rate regulator 22 and connected to the small capacity attemperator 2 and the large capacity attemperator 8, respectively. Flow rate signal of steam flow regulator 23 downstream of the attemperator and temperature sensor 2
A signal circuit is provided for sending the temperature signal of No. 4 to the cooling water flow rate regulator 22 via the comparison setting device 25 and controlling the water injection valves 11 and 12 of the large capacity desuperheater with the signal from the cooling water flow rate regulator. A precision control steam temperature control device featuring: