JPH10176503A - Method and device for controlling operation of reheat steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the safe operation of a turbine, and while to increase the quantity of extraction steam in the case where a necessity for increasing the quantity of extraction steam, which is to be extracted from the exhausted steam of a high-pressure turbine and to be supplied to an external plant, to a predetermined value or more. SOLUTION: In this turbine, the exhausted steam of a high-pressure turbine 1 is sent to an intermediate-pressure turbine 2 through a reheater 8, an intercept valve 2b, and while a part of the exhausted steam is extracted from this side of the reheater 7 so as to be supplied to an external plant 9. In this case, as a throttle control means of the intercept valve 2b, a control system, which is provided with a steam flow detecting unit, an exhaust pressure detecting unit and a computer for deciding the open degree of throttle of the intercept valve 2b on the basis of each detected value, is provided, and the intercept valve 2b is throttled in response to the increase of the extraction steam flow to outside so as to control that the exhaust pressure of the high-pressure turbine 1 is not lowered than the preset pressure value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reheat steam turbine in which a part of exhaust steam of a high pressure turbine is extracted and supplied to a plant outside the system. The present invention relates to an operation control method and apparatus for ensuring safe driving of a vehicle.

[0002]

2. Description of the Related Art FIG. 2 shows a steam system of a reheat steam turbine described above. In the figure, 1 is a high-pressure turbine, 1
a is a main steam stop valve, 1b is a steam control valve, 2 is a medium pressure turbine, 2a is a reheat steam stop valve, 2b is an intercept valve,
Reference numeral 3 denotes a low-pressure turbine, 4 denotes a condenser, 5 boilers, 6 denotes a feedwater heater, 7 denotes a reheater, 8 denotes a feedwater heater 6, and an auxiliary steam system for supplying steam to an out-of-system plant 9.

In the reheat steam turbine having such a configuration,
Conventionally, the intercept valve 2b provided on the inlet side of the intermediate pressure turbine 2 is closed when the load is cut off or when the turbine emergency stop device is operated, and a large amount of steam present in the reheater 7 and the reheat steam pipe is closed. Is medium pressure turbine 2 and low pressure turbine 3
The intercept valve 2b is kept in a fully open state during other steady operations.

In the reheat steam turbine, the exhaust pressure of the high-pressure turbine is applied to the thrust bearing under rated operating conditions in consideration of the amount of extracted steam consumed by the feed water heater 6, the external plant 9, and the like. It is designed so that the residual thrust load and the force applied to the turbine cascade do not exceed the allowable range, and maintain the planned value. The planned value is, as shown by the characteristic line A in FIG. The proportional relationship is set such that the exhaust pressure increases with the increase in the steam flow rate.

[0005]

By the way, in the reheated steam turbine having the above-described structure, when the amount of extracted steam supplied to the out-of-system plant 9 through the auxiliary steam system 8 is increased, the following problems occur in terms of safety of turbine operation. Such a problem occurs. That is, if the amount of extracted steam to be sent from the exhaust side of the high-pressure turbine 1 to the out-of-system plant 9 is increased beyond the initially set planned value, the exhaust pressure of the high-pressure turbine 1 in FIG. The exhaust pressure falls below the planned value represented by the characteristic line A as represented by the characteristic line B. As a result, in the high-pressure turbine 1, the pressure difference between the steam inlet and the outlet increases, so that the residual thrust load acting on the rotor increases. If the force exceeds the allowable load value of the thrust bearing and the mechanical strength of the cascade, the worst case will lead to a serious accident such as damage to the thrust bearing and turbine blade. There is a possibility that.

[0006] For this reason, it is the current practice that the turbine output and the amount of extracted steam are limited to relatively low values at present. The range in which the amount can be increased is extremely narrow, and it has not been possible to cope with a large demand for consumption. The present invention has been made in view of the above points, and its object is to solve the above-mentioned problems, and to safely operate the turbine even when it is necessary to increase the amount of extracted steam supplied to the out-of-system plant to a planned value or more. It is an object of the present invention to provide an operation control method and apparatus for a reheat steam turbine that can increase the amount of extracted steam while ensuring the above.

[0007]

The above objects can be attained by employing the following operation control method and operation control device according to the present invention. First, according to the operation control method of the present invention, the exhaust steam of the high-pressure turbine is sent to the intermediate-pressure turbine via the reheater and the intercept valve, and the high-pressure turbine is supplied from the front of the reheater through the auxiliary steam system. In the reheat steam turbine that extracts a part of the exhaust steam and supplies it to the out-of-system plant, the intercept valve is throttled in response to the increase in the amount of extracted steam to the outside of the system, and the exhaust pressure of the high-pressure turbine is set in advance. The pressure value is adjusted so as not to fall below the pressure value, and specifically, it can be implemented in the following form.

1) The degree of opening of the intercept valve is controlled in the pre-pressure control mode, and the set pressure is adjusted so as to follow a proportional relationship with the main steam flow rate of the high-pressure turbine. 2) The throttle valve opening of the intercept valve corresponding to the upper limit of the flow rate of the extracted steam to be supplied to the outside of the system is set in advance, and the intercept valve is narrowed to the valve opening when the flow rate of the extracted air increases.

As described above, by narrowing the intercept valve, the exhaust pressure of the high-pressure turbine increases as indicated by the characteristic line C in the characteristic diagram of FIG. 3, and the extracted steam supplied to the out-of-system plant in the state after the narrowing Even if the amount increases, the decrease in the exhaust pressure remains at the characteristic line D, and the operation in a state where the exhaust pressure does not fall below the planned exhaust pressure value (the characteristic line A) is secured. This ensures safe operation with the residual thrust load of the turbine and the load applied to the cascade within an allowable range within a range that does not exceed the upper limit of the main steam flow rate of the high-pressure turbine. It is possible to increase the amount of extracted steam to be supplied to a value greater than the initially planned value.

In the control method described in 1), the exhaust pressure of the high-pressure turbine is corrected in the direction of increasing the exhaust pressure set value so that the exhaust pressure does not fall below the planned value in advance in accordance with the increase in the flow rate of the extracted steam. The throttle opening of the intercept valve is adjusted in accordance with the corrected pressure set value. In the control method 2), when the amount of extracted air increases, the intercept valve is throttled down to the preset upper limit of the throttle opening. Regardless of the degree, the safe operation of the turbine is ensured without the exhaust pressure of the high-pressure turbine falling below the planned value.

According to the present invention, on the other hand, according to the present invention, a flow detector for measuring the main steam flow rate of the high-pressure turbine and a pressure detector for measuring the exhaust pressure of the high-pressure turbine And a calculator for determining the throttle opening of the intercept valve based on the signal of each detector. When the control method described in 1) above is performed, the arithmetic unit is operated based on the main steam flow rate of the high-pressure turbine detected by the flow rate detector when the flow rate of the extracted steam increases and the exhaust pressure of the high-pressure turbine detected by the pressure detector. Then, the exhaust pressure set value is corrected so that the exhaust pressure does not fall below a predetermined value set in advance, and the throttle opening of the intercept valve is adjusted based on the corrected set value.

When the control method described in the item 2) is carried out, if the detected flow rate increases with an increase in the flow rate of the extracted steam, the intercept valve is operated in accordance with a command from the arithmetic unit to correspond to the upper limit of the extracted steam amount. To a predetermined valve opening that has been set in advance.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention.
It will be described based on. Note that, in FIG. 1, portions corresponding to FIG. 2 are denoted by the same reference numerals. That is, in the embodiment of FIG. 1, a flow detector 10 that measures a main steam flow rate at the inlet side of the high-pressure turbine 1 and an exhaust side of the high-pressure turbine with respect to the intercept valve 2 b provided at the inlet side of the intermediate-pressure turbine 2. And a valve throttle control system combining a pressure detector 11 for measuring the exhaust pressure and a calculator 12 for determining the throttle valve opening of the intercept valve 2b based on the detection values of the detectors 10, 11. .

When the flow rate of extracted steam supplied from the exhaust side of the high-pressure turbine 1 to the out-of-system plant 9 through the auxiliary steam system 8 increases, the intercept valve 2b is throttled by a command from the arithmetic unit 12, and the high-pressure turbine 1 Is controlled so as not to fall below the planned value (characteristic line A) shown in FIG. Here, the following embodiments are specifically described as a method of controlling the narrowing down of the intercept valve 2b.

[Embodiment 1] The opening degree of the intercept valve 2b is controlled in a pre-pressure control mode, and its set pressure is adjusted so as to follow a proportional relationship with the main steam flow rate of the high-pressure turbine 1. In this control method, when the extraction flow rate supplied from the exhaust side of the high-pressure turbine 1 to the out-of-system plant 9 increases,
The computing unit 12 corrects the exhaust pressure set value so as not to fall below a planned value set in advance (characteristic line A in FIG. 3), and adjusts the throttle opening of the intercept valve 2b in accordance with the corrected pressure set value. adjust. As a result, it is possible to increase the amount of extracted steam supplied to the out-of-system plant 9 while ensuring safe operation by preventing the residual thrust load of the turbine and the load applied to the cascade from exceeding an allowable range.

[Embodiment 2] In this embodiment, the throttle valve opening set value of the intercept valve 2b set in advance in accordance with the upper limit value of the flow rate of the extracted steam supplied to the out-of-system plant 9 is stored in the arithmetic unit 12. If the bleed flow rate increases, the intercept valve 2b is narrowed down to the valve opening regardless of the degree of the increase in the flow rate.

According to this control method, when the extraction flow rate supplied to the out-of-system plant 9 increases, the exhaust pressure of the high-pressure turbine does not fall below the planned value regardless of the degree of increase in the extraction flow rate within the allowable range. In addition, safe operation of the turbine is ensured.

[0018]

As described above, according to the operation control method and apparatus of the present invention, the intercept valve of the intermediate pressure turbine is set in accordance with the increase in the amount of bleed air supplied from the exhaust side of the high pressure turbine to the out-of-system plant. Since the narrowing down is performed, even if the amount of extracted steam is increased in response to a request from a non-system plant, the exhaust pressure of the high-pressure turbine does not fall below a planned value corresponding to the main steam flow rate of the high-pressure turbine. As a result, unlike the conventional operation method, the amount of extracted steam supplied to the out-of-system plant is not limited by the relationship between the blade row strength and the residual thrust load, and does not exceed the upper limit of the steam flow rate of the high-pressure turbine. It is possible to greatly increase the amount of extracted steam to the outside of the system within the range, and to meet the consumption demand of the outside system.

[Brief description of the drawings]

FIG. 1 is a diagram showing a steam system of a reheat steam turbine and a control system of an intercept valve according to an embodiment of the present invention.

FIG. 2 is a diagram of a steam system of a conventional reheat steam turbine.

FIG. 3 is a characteristic diagram showing a relationship between a steam flow rate and an exhaust pressure of a high-pressure turbine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure turbine 2 Medium-pressure turbine 2b Intercept valve 5 Boiler 7 Reheater 8 Auxiliary steam system 9 Out-of-system plant 10 Flow detector 11 Pressure detector 12 Computing unit

Claims (4)

[Claims] An exhaust steam of a high-pressure turbine is sent to a medium-pressure turbine through a reheater and an intercept valve, and a part of the exhaust steam of the high-pressure turbine is passed through an auxiliary steam system from before the reheater. In a reheat steam turbine that is bleed and supplied to an out-of-system plant, the intercept valve is throttled in response to an increase in the bleed steam flow out of the system, and the exhaust pressure of the high-pressure turbine falls below a preset pressure value. An operation control method for a reheat steam turbine, wherein the method is adjusted so as not to occur. 2. The operation control method according to claim 1, wherein the valve opening of the intercept valve is controlled in a pre-pressure control mode, and the set pressure is adjusted so as to follow a proportional relationship with the main steam flow rate of the high-pressure turbine. An operation control method for a reheat steam turbine, comprising: 3. The operation control method according to claim 1, wherein the throttle valve opening of the intercept valve corresponding to the upper limit value of the flow rate of the extracted steam supplied to the outside of the system is set in advance.
An operation control method for a reheat steam turbine, characterized in that an intercept valve is narrowed to the valve opening when the bleed air flow rate increases. 4. Exhaust steam of the high-pressure turbine is sent to the intermediate-pressure turbine through a reheater and an intercept valve, and a part of the exhaust steam of the high-pressure turbine is passed through an auxiliary steam system before the reheater. In a reheat steam turbine in which bleed air is supplied to an out-of-system plant, as a control means for narrowing the intercept valve in response to an increase in the bleed air flow out of the system, a flow detector for measuring a main steam flow of a high-pressure turbine A pressure detector for measuring an exhaust pressure of the high-pressure turbine; and a calculator for determining a throttle opening of the intercept valve based on a signal of each detector.
4. An operation control device for a reheated steam turbine used for carrying out the operation control method according to any one of claims 3 to 3.