JPS59212606A - Controller for temperature of steam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to a device for controlling steam temperature.

In recent years, boilers in thermal power plants have become increasingly larger, and have become high-temperature, 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 insufficient responsiveness and cannot perform precise control. Precise control is achieved primarily by cooling the steam.

FIG. 1 shows one conventional example of steam humidity control using a steam cooling method. In the figure, the − part of the steam S is the first steam pipe line 1
It flows into the small capacity dehumidifier 2 through the. In this attemperator 2, the temperature controller 3 detects the steam humidity 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, and the water injection nozzle 2
Cooling water W sprayed into the desuperheater 2 from a and 2b! Adjust the amount. The steam thus adjusted to a predetermined temperature in the small-capacity attemperator 2 merges with the steam supplied from the main steam line 7 and flows into the large-capacity attemperator 8. In this large-capacity attemperator 8 as well, the humidity regulator 9 detects the steam humidity at the outlet of the attemperator, and the valves Nl and 12 of the cooling water pipe 10 are adjusted by feeding back the detection result. As a result, the amount of cooling water W2 sprayed into the desuperheater 8 is adjusted, and the steam temperature is controlled.

If each dehumidifier is controlled independently in this way, the temperature in each dehumidifier can be accurately controlled, but since each dehumidifier is controlled independently and there is no relationship, overall control is difficult. This becomes unstable, and since only the steam temperature is used as a control signal, the amount of steam changes rapidly based on changes in the amount of cooling water at the outlet of the large-capacity desuperheater.

FIG. 2 shows another example of control. In this control example, the temperature controller 3 that controls the small-capacity dehumidifier 2 generates a function based on the results detected by another temperature regulator 9 placed downstream of the large-capacity dehumidifier 8. The cascade control is performed manually 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 addition, in recent years, there has been a strong demand for a large variation range between the minimum load and maximum load and for a small error in the rated temperature of the supplied steam.

An object of the present invention is to provide an apparatus which is constructed in view of the above-mentioned problems and is capable of accurately controlling steam temperature over the so-called entire load range.

In short, this invention is a device configured to accurately control the steam temperature in response to all loads by detecting the steam flow rate in addition to measuring the steam temperature downstream of the desuperheater and performing feedforward control. .

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

In FIG. 3, on the downstream side of the large-capacity dehumidifier 8, in addition to a temperature regulator 9 that detects steam temperature and controls valves, a flow rate detector 15 that detects the steam flow rate is installed.

In order to control the steam temperature at a constant level, the small-capacity auxiliary attemperator 2 and the small attenuator 8 are operated in accordance with the steam flow rate. ji nozzle 2
It is necessary to adjust the cooling water spray ports for a, 2b, 8a, and 8b, but simply detecting the steam temperature on the downstream side of the desuperheater will cause a detection delay6, and a delay in tracking the supplied steam temperature, resulting in control. becomes unstable. For this reason, in the present invention, a flow rate detector 15 is provided below the large-capacity attemperator 8 to constantly detect the steam flow rate, and this detection result is input to the ratio setting device 17 provided in the signal circuit of the temperature transmitter 9. Configure the circuit so that

The temperature transmitter 9 detects the temperature of the steam dehumidified in the main attemperator 8, and based on this detection result, the command signal circuit 20 controls the valves of the cooling water supply pipes for each attemperator 2 and 8. 5. Adjust the opening degree of 6.11.12 to control the steam temperature to a predetermined humidity.

In this case, the flow rate detector 15 detects the steam flow rate as a disturbance, and inputs this flow rate detection signal before a change occurs in the cooling steam temperature, and uses it as a correction value for the valve opening adjustment signal. As a result, even if the steam flow rate fluctuates, feedforward control can be performed by adjusting the valve opening degree so as to cancel out this fluctuation.

FIG. 4 is a pipe system diagram of the second embodiment. In this case, two small-capacity attemperators, designated by numerals 2 and 21, are installed in side channels 1 and 10, respectively.
-1, and a flow control valve 31, 33 is provided on each inlet side. Similarly, a flow rate control valve 32 is provided in the pressure line 7. When the steam load is wide, first use the flow rate control valve 31 and the small capacity dehumidifier 2 to handle the small load.
, by slightly opening the control valve 32, or by using the small capacity dehumidifier 21 together with the small capacity desuperheater 2. Next, the amount of steam flowing through the main pipe 7 is set to a certain value. Also, if necessary, a steam flow rate transmitter 150.
151 are provided in the conduits 1 and 101, respectively, and the flow rate signals thereof are input into the control box 17. Although not shown, side road 1,101
A temperature transmitter may be provided at the outlet of the small capacity attemperator, and the signal may be sent to the control box 17.

By implementing this invention, the humidity of the steam sent out from the large-capacity attemperator can be highly accurate, ranging from +4 to 7°C, and can respond to a wide range of changes in e:W and O. . This detects the steam flow rate in addition to the steam temperature and performs feedforward control, so there is no control delay and accurate steam humidity control can be performed at all times.

Further, since the control system can be integrated into one, complicated interlocking systems are not required, which is economical and improves the reliability of the device.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a control device according to the present invention among conventional steam temperature control systems. 2...Small capacity desuperheater 5, 6.11.12...Flow rate control valve 7...
...Steam main line 8...Large capacity desuperheater 9...Temperature regulator'ITj device 15...Flow rate detector 17...Control box

Claims (1)

[Claims] 1. In a device that controls steam temperature by water injection,
One or more side passages are provided in the main pipe upstream of the main desuperheater installed in the main steam pipe line, and a sub-dehumidifier with a smaller capacity than the main desuperheater is provided in each side passage, and the flow rate is controlled on the steam inlet side. A control valve is provided respectively, and a steam temperature transmitter is provided in the outlet pipe of the main attemperator and each sub-attemperator, and the amount of sprayed ice from the water injection nozzle of each attemperator is controlled based on the temperature signal. The water injection nozzle and the control box are connected by a signal circuit, and the flow fit signal of the steam flow meter installed in the outlet pipe of the main desuperheater is manually inputted to the control box as a correction value by the signal circuit to adjust the steam temperature. A steam humidity control device configured to perform feedforward control. 2. The steam temperature control device according to claim 1, characterized in that a steam flow meter is provided downstream of each sub-wetting device, and a signal circuit is provided for inputting each flow rate signal to a control box.