JPH0768885B2 - Cooling steam temperature controller for steam turbine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cooling steam temperature control device for a steam turbine having a cooling steam system and performing a medium pressure startup.

[Conventional technology]

Hitherto, high and medium pressure starting has been widely used as a starting method for a steam turbine. As the high-medium pressure starting, there is a starting method in which the high-pressure turbine and the medium-pressure and low-pressure turbines are ventilated almost at the same time. In the case of a steam turbine equipped with a cooling steam system, according to the above-mentioned high-intermediate pressure starting method, high-pressure turbine extracted steam and reheated steam that form cooling steam are obtained almost at the same time. Therefore, if the valve of the cooling steam system is opened at the same time as the startup, after the startup, the cooling steam temperature rises with a smooth change as the load and the steam temperature rise. An example of a conventional cooling steam system is shown in FIG. The cooling steam system includes a line 3 for introducing extracted steam of the high-pressure turbine and a line 4 for introducing reheated steam. A cooling steam valve 6, an orifice 10 ', a drain valve 8, and a manual adjusting valve 19 are provided in the line 3 for introducing the high-pressure extracted steam. Further, the line 4 for introducing the reheated steam is equipped with a medium pressure cooling steam valve 20.

[Problems to be Solved by the Invention]

In contrast to the above high-medium pressure start-up, there is a medium-pressure start-up as a start-up method in which the ventilation of the medium-pressure and low-pressure turbines precedes the ventilation of the high-pressure turbine. The above-mentioned medium-pressure starting method vents the boiler superheater at the time of starting, so it is possible to prevent overheating of the boiler superheater, and since the turbine can be started while the boiler pressure is low, the start-up time can be shortened. It has the advantage.

However, when the steam turbine equipped with the cooling steam system described above is started by the medium pressure start-up method, the valve of the cooling steam system must be closed until ventilation of the high pressure turbine is started. The reheated steam flows back.

Further, since it is desired to obtain extracted steam from the high-pressure turbine after the medium-pressure turbine is aerated and before the high-pressure turbine is aerated, cooling steam cannot be formed. Therefore, in the conventional system, each valve must be controlled to open and close as shown in FIG. At this time, the medium pressure cooling steam valve may be used at initial load (shown by a dotted line), opened at high pressure ventilation (shown by a solid line), or any of them.

However, since the valve conventionally provided in the cooling system is just an on-off valve, when the valve of the cooling system is opened after being started and ventilated to the high-pressure turbine, the cooling with low temperature inside the medium-pressure turbine is performed. Steam may flow into the rotor, causing a rapid temperature change in the rotor, which may cause excessive thermal stress.

An object of the present invention is to provide a cooling steam temperature control device for a steam turbine capable of preventing the occurrence of excessive thermal stress due to a sudden increase in the temperature of a rotor cooling section that occurs when cooling steam flows into a steam turbine by a medium pressure starting method. To do.

[Means for Solving the Problems]

The above object can be achieved by providing a control valve in the cooling steam system, detecting steam temperature and load, controlling the opening of these control valves, and controlling the cooling steam temperature.

[Action]

The conventional cooling steam system has only valves for opening and closing, but these valves are used as control valves to detect cooling steam temperature, high-pressure turbine extraction steam temperature, reheat steam temperature, load, etc. As a result, by making it possible to control the opening degree of the control valve of the cooling steam system, it becomes possible to control the cooling steam temperature when the cooling steam flows into the intermediate pressure turbine at the time of startup,
It is possible to prevent a rapid temperature change of the rotor that occurs when the cooling steam flows in.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cooling steam system diagram that is well represented as having the features of the present invention, and FIG. 2 is a graph showing the opening degree of each control valve at the time of starting at medium pressure.

In FIG. 1, the cooling steam system is composed of a line 3 for introducing extracted steam of the high-pressure turbine 1 and a line 4 for introducing reheated steam. A cooling steam inlet control valve 5, a cooling steam valve 6, an orifice 10 'and a drain valve 8 are provided in the extraction line 3 for the extracted steam of the high-pressure turbine. On the other hand, the line 4 for introducing the reheated steam is provided with a medium pressure cooling steam control valve 11. Further, temperature detectors 9, 12, and 13 are provided at the inlet of the high-pressure extraction pipe, the reheat steam pipe, and the intermediate-pressure turbine of the cooling steam to measure the respective steam temperatures. Further, the generator 15 is provided with a load detector 14. Then, the signals from the temperature detectors 9, 12, 13 and the load detector 14 are processed to process the cooling steam inlet control valve.
5, a calculator 16 for controlling the opening of the intermediate pressure cooling steam control valve 11, a setter 17, and an oscillator 18 are provided.

At the time of starting the medium pressure, the medium pressure turbine 2 is ventilated before the high pressure turbine 1 to be started. And a certain load x
The first time it is vented to the high pressure turbine when it reaches%.
At this time, the opening / closing state of each valve of the cooling steam system is
As shown in FIG. That is, at the time of turbine set, the cooling steam valve 6, the medium pressure cooling steam control valve 1
1, the drain valve 8 (omitted in FIG. 2) is open and the other valves are closed. By controlling the opening and closing in this manner, it is possible to prevent the steam from flowing back into the high pressure turbine at the time of starting the medium pressure.

Then, the drain valve 8 is closed at the time of the initial load. And
When the load reaches x% and the high pressure turbine 1 is ventilated, cooling becomes possible, and the cooling steam inlet control valve 5 starts to open. At this time, the cooling steam inlet control valve 5 controls the opening so as to open for a certain time Δt. As shown in FIG. 5, this time Δt is determined by the function consisting of the high pressure turbine extraction steam T ₂ and the reheat steam temperature T ₁ during the high pressure turbine ventilation and the starting pattern.

Then, after the high-pressure ventilation, the cooling steam temperature T ₃ is detected, and the opening degree of each control valve is controlled so that the temperature T ₃ becomes a set value.

Fig. 5, as a function of T _1, T _2, takes the difference between T ₁ and T _2,
The case where there are four patterns of a, b, c, and d as starting patterns is shown.

The details of the control in this embodiment are shown in FIG.

According to this embodiment, since the cooling steam inlet control valve can control the cooling steam temperature at the start of cooling when the high pressure turbine is ventilated, this occurs in the case of the conventional open / close only control as shown in FIG. It is possible to prevent a sudden change in the temperature of the rotor cooling section.

In the above-mentioned embodiment, the medium pressure cooling steam control valve is opened at the time of reset, but it may be opened at the start of the high pressure turbine ventilation as in the control method shown in FIG.

In the above embodiment, the cooling steam inlet control valve 5 was controlled by detecting the temperatures T ₁ and T ₂ and determining Δt. However, as shown in FIG. 8, if the medium pressure cooling steam control valve is opened during resetting, senses only the temperature T _3, may control the opening degree of Yotsute cooling steam inlet control valve 5 to the temperature T _3.

In the above embodiment, the control valve is provided in the line 4 for introducing the reheated steam and the line 3 for introducing the high pressure extracted steam, but it is not always necessary to provide two control valves.
As shown in FIG. 9, it may be provided only in the line for introducing high-pressure bleed air.

The determination of Δt in the above embodiment is performed by detecting each steam temperature, but a signal from the load detector 14 may be used.
For example, as shown in FIG. 10, it may be determined by the rate of increase in load.

Also, at the time of start-up after a short stop, when the steam temperature does not decrease so much and cooling steam is required at the same time as the medium-pressure turbine ventilation, as shown in FIG. 11, An orifice 10 may be provided in the line for introducing the reheated steam, and the medium pressure cooling steam control valve 11 may be controlled as shown in FIG. That is, the opening of the intermediate-pressure cooling steam control valve is set to a half open state up to x% load of the high pressure turbine ventilation at which cooling steam can be obtained, and is opened after x%. In this way, by controlling the opening of the medium pressure cooling steam control valve according to the load, before x% where cooling steam cannot be obtained, there are two stages of the orifice 10 and the intermediate pressure cooling steam control valve 11 in the half open state. The cooling effect can be obtained by the vapor temperature drop due to the isenthalpic expansion.

In the above embodiment, since the cooling steam inlet control valve 5 is closed until high pressure ventilation, steam does not flow back into the high pressure turbine at startup, but if backflow is prevented, as shown in FIG. Further, the cooling steam system may be provided with the check valve 7.

〔The invention's effect〕

As described above in detail, according to the present invention, since the cooling steam temperature at the time of starting the medium pressure can be controlled, it is possible to prevent the sudden change of the cooling steam temperature at the start of cooling and prevent the occurrence of excessive thermal stress. it can. Therefore, there is an excellent practical effect that the reliability of the steam turbine can be improved.

[Brief description of drawings]

FIG. 1 is a cooling steam system diagram showing an embodiment of the present invention. FIG. 2 is a chart showing the relationship among the load, the opening degree of the valve, and the temperature of the rotor cooling ring in the above embodiment. FIG. 3 is a conventional cooling steam system diagram, and FIG. 4 is a table showing the relationship between load and valve opening in the conventional system. FIG. 5 is a chart showing a method of determining the time Δ required for the valve to open in the above embodiment. FIG. 6 is a flow chart showing the control method of the above embodiment. FIG. 7 and FIG. 8 are flow charts showing examples of control methods other than the above. FIG. 9 is a cooling steam system diagram in an embodiment other than the above. FIG. 10 is an explanatory chart of a method of determining Δt in the above embodiment. FIG. 11 is a cooling steam system diagram in a further different embodiment, and FIG. 12 is a table showing the valve opening / closing. FIG. 13 is a cooling steam system diagram of a further different embodiment. 1 ... High pressure turbine, 2 ... Medium pressure turbine, 5 ... Cooling steam inlet control valve, 6 ... Cooling steam valve, 7 ...
… Check valve, 9 …… Temperature detector, 10,10 ′ …… Olihuis, 11 …… Medium pressure cooling steam control valve, 12,13 …… Temperature detector, 14 …… Load detector, 15 …… Power generation Machine, 16 …… Calculator, 17 …… Setting device, 18 …… Oscillator.

Claims (7)

[Claims] 1. A medium pressure turbine comprising: (a) a high pressure turbine; (b) a medium pressure turbine separate from the high pressure turbine; and (c) a mixed steam of extraction steam and reheated steam from the high pressure turbine. Has a system for cooling steam of the turbine rotor,
And (d) control for performing temperature control of the cooling steam in the cooling steam system in the steam turbine facility in which the intermediate pressure turbine is ventilated to start before the ventilation of the high pressure turbine. A cooling steam temperature control device for a steam turbine, which is provided with a valve. 2. The steam turbine according to claim 1, wherein the control valve is provided in a line for introducing extracted steam from a high pressure turbine in the cooling system. Cooling steam temperature controller. 3. The control valve is provided in both a line for introducing reheat steam and a line for introducing high-pressure turbine extracted steam in the cooling system. 2. A cooling steam temperature control device for a steam turbine according to claim 1. 4. A control valve provided in a high-pressure turbine extraction steam system of the control valves has a structure controlled according to a load of a generator driven by the steam turbine,
The cooling of the steam turbine according to any one of claims 1 to 3, characterized in that the cooling turbine is provided in a line for supplying cooling steam to the intermediate pressure turbine. Steam temperature control device. 5. A control valve provided in a line for introducing reheated steam in the cooling steam system, according to a load of a generator driven by the steam turbine at the time of starting at an intermediate pressure. Cooling steam for a steam turbine according to claim 1 or 3, further comprising means for adjusting and controlling the opening degree of the cooling steam so as to control the temperature of the cooling steam. Temperature control device. 6. A check valve is provided between a cooling steam inlet control valve of a line for introducing extracted steam from a high-pressure turbine and a confluence point of a line for introducing reheated steam in the cooling steam system. The cooling steam temperature control device for a steam turbine according to claim 1, wherein the cooling steam temperature control device is provided. 7. The steam turbine according to claim 1, wherein the control valve provided in the line for introducing the reheated steam in the cooling system is provided with an orifice. Cooling steam temperature controller.