JP2690511B2 - Steam temperature control method and control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method of controlling steam temperature so as not to cause a sudden temperature change when starting a steam turbine driven by supplying steam from a boiler. And a control device suitable for carrying out the above control method.

[Conventional technology]

FIG. 4 shows the latest known example (Japanese Patent Publication No. 61-23441, Japanese Patent Laid-Open No.
1 is a system diagram of steam turbine equipment in No. 1-49301).

The steam generated in the boiler B is the primary superheater 5, the desuperheater 4,
The secondary superheater 6 is sequentially passed into the high-pressure turbine 1 to drive it.

The steam discharged from the high pressure turbine 1 is reheated by the reheater 7 and supplied to the intermediate pressure turbine 2 and the low pressure turbine 3.

In order to increase the efficiency and output of the high-pressure turbine 1, it is desirable that the main steam to be supplied be at high temperature and high pressure, but it is limited by the heat resistance and high temperature strength of the members exposed to high temperatures.

The allowable fluctuation range of the main steam temperature is usually ± 10 ° C,
Very narrow.

However, even if an attempt is made to adjust the main steam temperature to adjust it, the instantaneous response cannot be achieved, and the time constant is generally 3 to 15
Minutes, quite long.

Therefore, for the control of the main steam temperature, the advance control is performed by predicting the temperature fluctuation. 10,11,12 shown in FIG.
Are main steam temperature, main steam flow rate, and desuperheater outlet temperature detection signals, respectively. 13 is the main steam temperature signal 10 and its set value
Reference numeral 15 is a subtractor for obtaining the deviation from 14, and 15 is a proportional integrator for proportionally integrating the output of the subtractor. Reference numeral 16 is a function generator that receives the main steam flow rate signal 11 as an input, converts it into a load leading control signal, and sends it to the adder 21. 17 is also a function generator that receives the main steam flow rate signal 11, 18 is the set temperature at the outlet of the desuperheater,
Reference numeral 19 is a subtractor for obtaining the deviation between the set value 18 and the desuperheater outlet signal 12, and 20 is an amplifier for amplifying the output of the subtractor 19 and sending it to the adder 21. The adder 21 adds the outputs of the proportional integrator 15, the function generator 16, and the amplifier 20 and outputs a spray valve opening command signal 22.

As described above, in the conventional main steam control circuit, the load (= main steam flow rate) advance control and the desuperheater outlet temperature advance control are performed as the advance control of the main steam temperature.

[Problems to be solved by the invention]

The above-mentioned conventional technique cannot capture the rapid rise of the main steam temperature at the time of co-merging, resulting in a response lacking adaptability. Specifically, considering the superheater as one lumped constant system, and considering the change in steam temperature when it is combined, the energy conservation equation is applied to the internal fluid side and gas side of the superheater, and the following equation (I ),
(B). It can be seen that the steam flow rate expressed by this equation flows in at the same time, and the fuel is injected with a slight delay, so that the main steam temperature rises sharply.

(A) Steam flow side (B) Gas side However, W: Weight of steam in the pipe H _So : Steam enthalpy at outlet of secondary superheater H _Si : Steam enthalpy at inlet of secondary superheater F _s : Main steam flow rate Q _ms : Heat transfer amount from tube to steam Q _gm : Gas to tube Heat transfer to TM: Pipe temperature By means of the steam temperature controller shown in Fig. 4, the desuperheater 4
FIG. 5 shows the control characteristics when the opening degree of the spray valve 8 is automatically adjusted.

The horizontal axis is time, the ignition timing t _1, the ventilation time t _2, the incorporation time
t _3, ramping time t _4, are respectively the timing t ₆ to give rated load.

 Curve 10 is the main steam temperature.

Between the incorporation time t ₃ to time t ₆ to the rated load, simply in the prior art of providing spray calculated from the vapor condition, main steam temperature was also not good responsiveness and spray flow rate and hunting like You can see that it is fluctuating.

Since such a temperature change occurs, the following problems occur.

(I) Excessive thermal stress is generated inside the boiler and turbine, shortening the life, and sudden temperature drop due to overinjection of spray as a reaction to the sudden temperature rise causes cracks inside the boiler, It also leads to destruction.

(Ii) Since the temperature rise and the temperature fall due to the reaction of the operation are rapid, the conventional closed-loop control system that incorporates the main steam temperature change as the preceding signal is not possible. It will be damaged.

The present invention has been made in view of the above circumstances, and an object thereof is to change the temperature of the main steam at start-up from the merge time to the rated arrival time without causing a sudden sudden change, (EN) It is an object to provide a steam temperature control method capable of smoothly and surely increasing the temperature, and a control device suitable for carrying out the control method.

[Means for solving the problem]

The basic principle of the present invention created in order to achieve the above-mentioned object is that the spray flow rate is stepwise from the insertion time to the rated arrival time (specifically, according to a predetermined flow rate / time pattern). It is a forced injection.

As a specific configuration for applying the above principle to practical use, the method of the present invention detects the steam condition at the inlet of the steam turbine, and the spray valve is stepwise based on the detected value (according to a predetermined pattern. ) Open and close.

When carrying out the method of the present invention, it is desirable to use at least one of the main steam temperature, the main steam flow rate, and the desuperheater outlet temperature as the physical quantity representing the above steam condition.

Further, the device of the present invention created to carry out the above-mentioned method of the present invention comprises: (a) a step spray valve opening setting device for transmitting a step spray opening command based on the outlet temperature of the desuperheater; A step open signal switching device that switches between the spray valve opening command signal and the step spray opening command is provided, and (c) a timer that gives a step spray opening interlock signal to the step open signal switching device.

When implementing the device according to the invention, said timer is
If the step open time setting device is provided based on the outlet temperature of the desuperheater, it is easier to automatically perform good control.

[Action]

As described above, the response of the steam temperature change is slow even if the spray valve is controlled to open and close.

For this reason, when the spray valve is actuated sharply to open and close violently, there is a hunting state in which the spray becomes momentarily excessive or the spray is momentarily stopped to cancel it (Fig. 5). reference).

The method of the present invention described in the preceding section does not open and close such a sensitive spray valve, but opens and closes in stages according to a preset position. When the stepwise control is performed in this manner, the spray valve is not opened too much, the spray valve is fully closed at the next moment, and the valve is almost opened.

According to the device of the present invention, the above-described stepwise spray valve opening / closing control can be automatically performed.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of the device of the present invention configured to carry out the method of the present invention.

The apparatus of this embodiment (FIG. 1) is obtained by applying the present invention to the apparatus of the prior art (FIG. 4).

A control circuit Cr surrounded by a chain line is a component added to the conventional device by the application of the present invention.

In addition to the spray valve opening command signal 22 output from the adder 21 in the device of the conventional example, a step spray valve opening setting device 41 for generating a step spray opening command 45 at the time of insertion is provided, and the temperature reducer is provided. A signal representing the outlet temperature 12 of No. 4 is input to the step spray valve opening degree setting device 41.

A step open signal switch 44 for switching and giving the two command signals (the spray valve opening command signal 22 similar to the conventional example and the step spray opening command 45 peculiar to the present invention) to the spray valve 8 is provided. Set up.

A step opening time setting device 42 for outputting a step spray opening interlock 48 which is a command signal for causing the step opening signal switching device 44 to perform a switching operation is provided.

In the step opening time setting device 42, the outlet temperature of the desuperheater
A signal representing 12 is provided, and the step opening time signal 46, which is the output of the step opening time setting device 42, operates the timer 43 for the step opening time, and a predetermined time from the time when the signal rises in the merge condition 47, A step open command is issued to the spray valve 8.

In order to explain the operation, FIG. 2 shows the setting functions of the setters 41 and 42, and FIG. 3 (A) shows the spray valve operation and the main steam temperature characteristic at the time of parallel insertion. The step open setting at the time of co-merging is appropriately set by the steam temperature at the outlet of the desuperheater in the preceding stage of the main steam temperature before co-merging in order to eliminate the rise of the parallel hatched portion in FIG. 5 showing the prior art example. Specifically, step opening is performed at c ₁ point or more shown in FIG. ₂ , and step opening time 46 and step spray opening 45 are increased step by step up to c ₂ point and c ₃ point, and more than (c
₃ points or more) is fixed. By setting in this way, when the boiler stop period is long, the steam temperature before merger is low and the temperature rise at the time of merger is relatively small, so the amount of spray is small and the rise control by normal spray is performed. The degree of opening changes, and the equipment can be automatically started at a constant rate of temperature rise. The solid curve in FIG. 3 (A) is the characteristic of this embodiment. For comparison, it can be seen that the characteristics are significantly improved over the characteristics of the prior art shown by the broken line.

FIG. 3 (B) shows the details near the portion B shown in FIG. 3 (A).
Shown in

The broken line curve (a) shows the spray flow rate according to the conventional example.
In this conventional example, since the flow rate control is performed based on the temperature detection value, the response delay suffers and the spray flow rate suddenly increases,
It keeps getting 0 again.

The one-dot chain line curve (b) shows an example, and at the same time as it is combined, a spray of a predetermined flow rate Q is forcibly injected for a predetermined time t _p regardless of the steam temperature, and further predetermined. Increase the spray flow rate according to the pattern (see curve (c)).

As a result, the main steam temperature rises smoothly without pulsation.

The above description is for the control method after the merger time, but better control can be performed by preparing the following before merger.

That is, it is desirable that the flow rate of the steam be set to such an extent as to mitigate the rapid increase in the steam temperature during the merger before the merger.

In order to perform such control, it is convenient to provide means for automatically controlling the turbine bypass circuit.

〔The invention's effect〕

According to the steam temperature control method of the present invention, since the spray is forcibly injected according to a predetermined pattern, it is possible to prevent a rapid change in the steam temperature at the time of startup, to smoothly raise the steam temperature, and to prevent excessive heat. It has an excellent practical effect of preventing the generation of stress.

Further, according to the apparatus of the present invention, it is possible to easily carry out the above-mentioned method of the present invention and sufficiently and surely exhibit its effect.

[Brief description of the drawings]

FIG. 1 is a system diagram of steam turbine equipment including an embodiment of a steam temperature control device according to the present invention. 2 and 3 are charts for explaining the operation and effect of the above embodiment. FIG. 4 is a system diagram of steam turbine equipment including an example of a steam temperature control device according to a conventional example. FIG. 5 is a chart for explaining the problems in the above conventional example. 1 ... High pressure turbine, 2 ... Medium pressure turbine, 4 ... Desuperheater, 8 ... Spray valve, 10 ... Main steam temperature signal, 11 ... Main steam flow signal, 12 ... Decompressor outlet temperature signal , 16,17 ……
Function generator, 41 ... Step spray valve opening setting device, 42 ...
… Step open time setter, 44 …… Step open signal switch, 45 …… Step spray opening command, 49 …… Step opening corrected valve opening command signal.

Claims (3)

(57) [Claims] 1. A start-up operation of a steam turbine plant provided with a boiler for generating steam, a desuperheater equipped with a spray valve, and a steam turbine, comprising: (a) detecting a steam condition at an inlet of the steam turbine; (B) The spray valve is opened / closed based on the steam condition detection value, and after being mixed, a predetermined amount of spray is forcibly injected for a predetermined time, and the temperature at the outlet of the desuperheater is adjusted to A method for controlling steam temperature, which comprises controlling the rise. 2. A device for controlling the steam temperature when starting a steam turbine plant provided with a boiler that generates steam, a desuperheater having a spray valve, and a steam turbine, In a steam temperature control device provided with an arithmetic circuit that detects a condition of steam flowing into a turbine and outputs an opening command signal of the spray valve based on the detected value, (a) based on a temperature of the desuperheater outlet A step spray valve opening setting device for transmitting a step spray opening command, (b) a step opening signal switching device for switching between the spray valve opening command signal and the step spray opening command, and (c) the step A steam temperature control device, comprising: a timer that gives a step spray open interlock signal to an open signal switch. 3. The steam according to claim 2, wherein the timer is provided with a step opening time setting device for transmitting a step opening time signal based on an outlet temperature of the desuperheater. Temperature control device.