JP2017057837A - Steam turbine appliance and operational method of steam turbine appliance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine capable of increasing the output by increasing the amount of steam flowing through the first stage of a high pressure turbine even when overload operation with rating output or more is performed when the frequency of an electric power system drops while since a steam regulating valve can be fully opened at the rating output and the loss in the steam regulating valve can be reduced, the efficiency at the rating output can be improved.SOLUTION: A steam turbine 100 comprises: a by-pass pipe 31 for branching the steam in the steam chest of the first stage in a plurality of stages of a high pressure turbine 10 into a flow to the downstream stage of the high pressure turbine and a flow to the outside of the high pressure turbine; a flow control valve 32 for controlling the amount of steam flowing through the by-pass pipe; and a control part that controls to fully open a steam regulating valve 8 with the flow control valve fully open at the rating output and to open the flow control valve while the steam regulating valve is being fully opened during the overload operation accompanying the frequency fluctuation at the rating output.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steam turbine facility and an operation method thereof.

In a steam turbine facility of a thermal power plant, steam is generated by heat generated by burning fossil fuel, and the steam is supplied to a steam turbine as a working fluid and driven to generate power.

Generally, steam turbine equipment is operated without fully opening the steam control valve at the rated output so that the system frequency can be returned to the specified value when the power demand of the power system increases and the system frequency drops. Yes. That is, the steam control valve is not fully opened at the rated output, but has a margin so that the steam control valve can be further opened when the power demand increases and the system frequency drops. In other words, if the power demand of the power system increases and the system frequency drops, the steam turbine output in parallel with the power system will behave accordingly, so the steam control valve will be opened further. It means that it is waiting so that the output can be increased.

However, in an operation in which the steam control valve is not fully opened, there is a problem that the pressure loss at the steam control valve is large and the efficiency at the rated output is lowered. As a means for preventing this, there is a method of installing a bypass pipe provided with an overload valve in addition to the main steam pipe. When performing “overload operation” exceeding the rated output, the steam flowing through the main steam pipe is supplied to the first stage of the steam turbine via the steam control valve, and the steam flowing through the main steam pipe bypasses the steam control valve. Then, it flows into the bypass pipe and is supplied to the intermediate stage of the steam turbine through the overload valve. (For example, see Patent Document 1)

JP 2013-194720 A

FIG. 4 is a system schematic diagram of a conventional steam turbine facility that performs “overload operation”.

The steam turbine equipment 1 includes a boiler 2, a high-pressure turbine 10, and an intermediate-pressure turbine 1 as main equipment.
6. It has a low-pressure turbine 20, a condenser 24, and a generator 22. The high-pressure turbine 10, the intermediate-pressure turbine 16, and the low-pressure turbine 20 are connected by a rotor 23, and the rotor 23 is connected to a generator 22.

The main steam generated in the boiler 2 flows down the main steam pipe 4 and is guided to the inlet of the high-pressure turbine 10. The exhaust steam discharged by driving the high-pressure turbine 10 flows down from the high-pressure turbine 10 through the low-temperature reheat pipe 12 and is guided to the reheater 13 of the boiler 2 to be reheated. The steam heated by the reheater 13 flows down the high-temperature reheat pipe 14 and is guided to the intermediate pressure turbine 16. After driving the intermediate pressure turbine 16, the steam flows down the main steam pipe 18 and is guided to the low pressure turbine 20. . The exhaust steam discharged by driving the low-pressure turbine 20 is introduced into the condenser 24, cooled, condensed, and then reintroduced into the boiler 2 as feed water.

A main steam pipe 4 through which main steam flowing from the boiler 2 to the high-pressure turbine 10 passes is provided with a main steam stop valve 6 and a steam control valve 8 from the upstream side to the downstream side in the steam flow direction. Further, a bypass pipe 26 is branched from the main steam pipe 4 between the main steam stop valve 6 and the steam control valve 8. The bypass pipe 26 branched from the main steam pipe 4 is connected to an intermediate stage of the high-pressure turbine 10, and a part of the main steam flowing through the main steam pipe 4 bypasses a part of the upstream stage of the high-pressure turbine 10. It is introduced into the high-pressure turbine 10 from the middle stage. Bypass pipe 26
Is provided with a valve (overload valve) 28 for controlling the amount of bypass steam flowing through the bypass pipe 26. This control is performed by the control unit 50.

In the conventional steam turbine equipment using such a valve (overload valve) 28, since a part of the main steam flows from the middle stage of the high-pressure turbine 10, the pressure in the steam chamber in the first stage of the high-pressure turbine 10 is in the middle stage. As a result, the pressure difference between the inlet of the high-pressure turbine 10 and the intermediate stage is insufficient, and the amount of steam passing through the nozzle and the moving blades in the first stage is reduced. There is a problem that the output decreases.

Therefore, the present invention aims to reduce the output of the first paragraph of the high-pressure turbine 10 from decreasing and to enable “overload operation” exceeding the rated output required when the frequency of the power system at the rated output is lowered. To do.

In order to solve the above problems, the present invention branches the steam in the steam chamber of the first stage of the plurality of stages in the high-pressure turbine into a flow to the downstream stage of the high-pressure turbine and a flow to the outside of the high-pressure turbine. A bypass pipe, a flow control valve for controlling the amount of steam flowing through the bypass pipe, and at the rated output, the steam control valve is fully opened and the flow control valve is fully closed. During the overload operation, the above object is achieved by providing a steam turbine including a control unit that controls to open the flow rate control valve while keeping the steam control valve fully open.

According to the present invention, when the frequency of the power system drops, the steam from the first stage steam chamber of the high-pressure turbine is
By supplying the flow control valve after the first stage, the amount of steam passing through the first stage of the high-pressure turbine is increased, and the output of the first stage of the high-pressure turbine is increased. As a result, the steam control valve can be fully opened at the rated output, and the loss at the steam control valve can be reduced, leading to improved efficiency at the rated output and overload operation exceeding the rated output when the frequency of the power system drops. Even if you do
It is also possible to increase the output by increasing the passing steam amount in the first stage of the high-pressure turbine.

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

(First embodiment)
A first embodiment of the present invention will be described below. FIG. 1 is a system schematic diagram of a steam turbine facility according to a first embodiment of the present invention. The same reference numerals are given to the same devices shown in the system schematic diagram of the conventional steam turbine equipment, and the descriptions of the same devices will be omitted and different portions will be described.

A main steam pipe 4 through which main steam flowing from the boiler 2 to the high-pressure turbine 10 passes is provided with a main steam stop valve 6 and a steam control valve 8 from the upstream side to the downstream side in the steam flow direction. The main steam pipe 4 from the steam control valve 8 is connected to the inlet of the high-pressure turbine 10, that is, the first stage of the high-pressure turbine. After working in the high-pressure turbine 10, the main steam pipe 4 flows down to the low-temperature reheat pipe 12 side.

On the other hand, in order to discharge from the steam chamber in the first stage to the outside inside the high-pressure turbine 10, the extraction port 30 of the high-pressure turbine 10 and the inlet portion 28 of the intermediate-pressure turbine 16 are connected by a bypass pipe 31. A flow control valve 32 is provided in the middle of 31. In the first embodiment of the present invention shown in FIG. 1, there is no bypass pipe 26 or valve 28 branched from the main steam pipe 4 of the conventional system shown in FIG.

The flow control valve 32 in the first embodiment is configured to control the amount of steam supplied from the steam chamber in the first stage of the high-pressure turbine 10 to the intermediate-pressure turbine inlet 28 connected via the bypass pipe 31. Yes. The bypass pipe 31 is connected to the intermediate pressure turbine inlet 28 here, but if it is downstream from the steam chamber of the first stage of the high pressure turbine, it is supplied to any stage of the high pressure turbine, the intermediate pressure turbine, and the low pressure turbine. Also good. The opening degree adjustment of the steam control valve 8 and the flow rate control valve 32 is performed by the control unit 40.

Next, the characteristics of the steam control valve 8 and the flow control valve 32 will be described with reference to FIGS. 2a and 2b. FIG. 2A is a valve opening characteristic diagram of the steam control valve 8 and the flow rate control valve 32, where the vertical axis indicates the valve opening, and the horizontal axis indicates the load (output) and describes the entire stroke from increase to decrease.

When the load of the steam turbine is 0%, the valve openings of the steam control valve 8 and the flow control valve 32 are fully closed. The steam control valve 8 opens as the load increases based on the opening command signal from the control unit 40. During the period from symbol C to symbol E, since the load is 100%, the fully open signal is input as the opening command signal from the control unit 40, and the steam control valve 8 remains fully open.

Here, the conventional steam turbine has a margin so that the steam control valve 8 can be further opened when the power demand of the power system increases and the system frequency decreases (hereinafter referred to as frequency fluctuation) in a state of 100% load. Therefore, even when the load is 100%, the valve opening degree of the steam control valve 8 is halfway open (not fully open). For this reason, there is a problem that the pressure loss in the steam control valve 8 is large. However, in the first embodiment, the operation is performed when the load is 100%, so that the pressure loss is reduced compared to the conventional case, and the efficiency is improved.

The period from symbol C to symbol E in FIG. 2a shows the process of opening the flow rate control valve 32 in order to continuously increase the load in case of frequency fluctuation at the time of 100% load (at the time of rated output). Yes.
That is, when frequency fluctuation occurs at the time of 100% load (at the time of rated output), the control unit 40
Since the flow control valve 32 that was fully closed when the load is 100% can be opened to an arbitrary valve opening (arbitrary fully open) based on the opening command signal from ) Frequency fluctuations. Furthermore, since the load of the steam turbine increases from 100% (rated output) to + α%, an overload operation of 100% (rated output) or more can be performed.

FIG. 2b is a flow rate characteristic diagram of the passing steam of the steam control valve 8. The vertical axis indicates the flow rate flowing through the first stage (first stage) of the high-pressure turbine, that is, the flow rate flowing through the steam control valve 8. The entire process of load (output) is described as well.

The period from the symbol A to the symbol C and the period from the symbol E to the symbol G in FIG. 2b indicate the range of flow rate control by the steam control valve 8 alone. During the period from symbol C to symbol E, when the steam control valve 8 is kept fully open, the steam control valve 8 is opened by opening as shown in the opening characteristic diagram of the flow control valve 32 shown in FIG. Flow rate increases from 100% (rated flow rate) to + α%.

Next, the operation of the steam control valve 8 and the flow control valve 32 will be described with reference to FIGS. 2a and 2b. When the power demand of the power system increases and the system frequency decreases at the symbol C where the load is 100%, the flow control valve 32 is based on the opening command signal from the control unit 40 while the steam control valve 8 is kept fully open. And operate to open.

When the flow control valve 32 opens, the high-pressure turbine 1 having a high steam pressure according to the opening degree of the flow control valve 32.
Since steam is supplied from the steam chamber of the first stage 0 to the inlet portion of the intermediate pressure turbine 16 having a low steam pressure, the amount of steam in the steam chamber of the first stage of the high-pressure turbine 10 is reduced, resulting in a decrease in the pressure of the steam chamber. It will be.

That is, the main steam pressure of the main steam pipe 4 supplied to the high-pressure turbine 10 is constant, and the pressure difference between the inlet of the high-pressure turbine 10 and the steam chamber is reduced by reducing the steam chamber pressure in the first stage of the high-pressure turbine 10. Therefore, the amount of steam passing through the nozzle and rotor blade in the first stage (first stage) of the high-pressure turbine increases and the output in the first stage increases.

Further, the flow control valve 32 is opened and the steam supplied to the inlet of the intermediate pressure turbine 16
Since the amount of steam flowing from the intermediate pressure turbine 16 in the downstream paragraphs increases, the output in these downstream paragraphs increases. Thus, in the first embodiment, by opening the flow control valve 32, the increased outputs of the high-pressure turbine 10, the intermediate-pressure turbine 16, and the low-pressure turbine 20 are added together, which contributes to an increase in output. The effect to do is great.

Note that when the valve 28 in the conventional embodiment is used, the first paragraph of the high-pressure turbine 10 is bypassed, and thus a remarkable effect cannot be obtained. However, in the first embodiment, the high-pressure turbine 1
Since the amount of steam flowing in the first stage 0 is increased, a large adiabatic heat drop can be obtained, so that the effective work of the steam turbine equipment 100 can be increased.

Further, since the amount of steam flowing in the first stage of the high-pressure turbine 10 increases, the flow rate passing through the steam control valve 8 also increases, so the pressure loss naturally increases, but the steam control valve 8 has already been fully opened. Since the steam is not squeezed, the amount of increase is small and does not affect the adiabatic heat drop of the high-pressure turbine 10.

(Second Embodiment)
A second embodiment of the present invention will be described below. FIG. 3 is a system schematic diagram of the steam turbine facility according to the second embodiment of the present invention. The second embodiment is characterized by having a plurality of connection destinations of the bypass system. That is, the bypass pipe 31 connected to the discharge port 30 provided in the steam chamber in the first stage of the high-pressure turbine 10 has a novel structure in which the branch bypass pipes 33 and 34 are branched.

One branch bypass pipe 33 is connected to the inlet of the intermediate pressure turbine 16, and a flow control valve 32 is provided in the middle of the branch bypass pipe 33. The other branch bypass pipe 34 is connected to the low pressure turbine 2.
A flow control valve 35 is provided in the middle of the branch bypass pipe 34.

The flow rate control valve 32 and the flow rate control valve 35 are simultaneously opened during the period from the symbol C to the symbol E in FIG. 2A and flow through the first paragraph (first paragraph) of the high-pressure turbine, that is, through the steam control valve 8. When operated to increase the flow rate, the effect is the same as in the first embodiment.

Note that the method of opening the flow rate control valve 32 and the flow rate control valve 35 may be improved not only to the above-described two-valve simultaneous operation but also to the sequential opening method. Further, only one flow rate control valve 32 is provided in the bypass pipe 31, connected to the inlet portion of the intermediate pressure turbine 16 through the branch bypass pipe 33, and connected to the inlet portion of the low pressure turbine 20 through the branch bypass pipe 34. Even if the configuration is changed so as to be connected, the effect and action are the same.

Although the embodiment of the present invention has been described, it is possible to cope with frequency fluctuations on the condition that the steam control valve is fully opened in the load zone at the rated output and above, and the “overload” exceeding the rated output is possible. If “operation” is possible, the steam outlet of the bypass system is not limited to the steam chamber in the first stage of the high-pressure turbine. Needless to say, it may be a downstream paragraph from the first paragraph of the high-pressure turbine.

The system schematic of the steam turbine equipment in connection with the 1st Embodiment of this invention The valve opening characteristic diagram with respect to the generator load of the steam control valve and the flow control valve according to the first embodiment of the present invention Passing steam flow rate characteristic diagram of the steam control valve according to the first embodiment of the present invention System schematic diagram of steam turbine equipment according to a second embodiment of the present invention System schematic showing conventional steam turbine equipment

2 Boiler 4 Main Steam Pipe 6 Main Steam Stop Valve 8 Steam Control Valve 10 High Pressure Turbine 12 Low Temperature Reheat Pipe 13 Reheater 14 High Temperature Reheat Pipe 16 Medium Pressure Turbine 18 Main Steam Pipe 20 Low Pressure Turbine 22 Generator 24 Condenser 30 Drain Outlet 31 Bypass pipe 32 Flow control valve 33 Branch bypass pipe 34 Branch bypass pipe 35 Flow control valve 100 Steam turbine equipment

Claims (5)

Driven by main steam from a boiler through a steam control valve, a high pressure turbine having a plurality of paragraphs, an intermediate pressure turbine driven based on exhaust steam of the high pressure turbine, and driven by exhaust steam of the intermediate pressure turbine A steam turbine facility comprising a low-pressure turbine,
A bypass pipe for branching the steam in the steam chamber of a predetermined stage including the first stage of the plurality of stages in the high-pressure turbine into a flow to a downstream stage of the high-pressure turbine and a flow to the outside of the high-pressure turbine. When,
A flow control valve for controlling the amount of steam flowing through the bypass pipe;
At the rated output, the steam control valve is fully opened and the flow control valve is fully closed.At the time of overload operation at the time of frequency fluctuation at the rated output, the steam control valve is left fully open. A steam turbine facility comprising: a control unit that controls the valve to open. 2. The steam turbine according to claim 1, wherein the bypass pipe is connected to an arbitrary stage including the intermediate-pressure turbine and the low-pressure turbine downstream from the steam chamber of the predetermined stage of the high-pressure turbine. Facility. The steam turbine equipment according to any one of claims 1 to 3, wherein the bypass pipe has a plurality of connection destinations, and flow control valves are installed in the respective bypass pipes. 5. The flow rate control valve opens and closes based on a valve opening request signal, and the opening and closing operation is performed in an operating region after the steam control valve is fully opened. Steam turbine equipment. The high pressure turbine driven by the main steam from the boiler via the steam control valve;
The intermediate pressure turbine driven based on the exhaust steam of the high pressure turbine, and the low pressure turbine driven by the exhaust steam of the intermediate pressure turbine,
The steam turbine branches steam in a predetermined stage including a first stage of the plurality of stages in the high-pressure turbine into a flow to a downstream stage of the high-pressure turbine and a flow to the outside of the high-pressure turbine. An operation method of a steam turbine facility comprising a bypass pipe for controlling the flow rate and a flow rate control valve for controlling the amount of steam flowing through the bypass pipe,
At the rated output, the steam control valve is fully opened and the flow control valve is fully closed.
An operation method for steam turbine equipment, wherein the flow control valve is opened while the steam control valve is fully opened during an overload operation associated with frequency fluctuation at the rated output.

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