JP2007046504A - Steam turbine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steam turbine control system maintaining optimum efficiency of a steam turbine by controlling the opening of a main steam governing valve and main steam pressure even when a steam condition (heat balance) in the turbine is varied by change of the steam main pressure, an extraction steam flow rate and exhaust pressure. <P>SOLUTION: The main steam pressure 2 is measured, a pressure loss between before and after the main steam governing valve 3 is calculated, and the main steam pressure 2 and the opening of the main steam governing valve 3 are controlled based on the calculation result so that the pressure loss between before and after the main steam governing valve 3 becomes minimum. When there is extraction steam 8 such as process steam, the extraction steam flow rate 6 is measured, and it is recalculated how the steam condition (heat balance) in the turbine varies according to the extraction steam flow rate. The opening of the main steam governing valve 3 is adjusted and a steam flow rate is controlled based on the recalculation result so that the turbine efficiency in that steam condition becomes maximum. When a measurement result of exhaust pressure 9 is inputted in the recalculation, the steam flow rate and the main steam pressure can be controlled more efficiently. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steam turbine control system, and more particularly, to a means for increasing the efficiency of a steam turbine by controlling the opening degree of main steam control and / or steam pressure from a boiler.

  As an example of a steam turbine plant, a boiler capable of controlling the pressure, four main steam control valves for controlling the steam flow, a bleed control valve for controlling the bleed flow, and main steam pressure, bleed pressure, and exhaust pressure are measured. An example of a steam turbine power plant that includes a sensor and uses part of the extracted air from the steam turbine for purposes other than power generation will be described.

  In general, the main steam control valve is designed to control the flow rate of steam in accordance with the start-up and to operate with three of the four main steam control valves fully open and one fully closed. Has been. The main purpose of the fully-closed control valve is to increase the steam flow rate and ensure the necessary output when the turbine efficiency is low, such as in summer.

  However, in actuality, the steam flow rate is controlled with the first valve and the second valve fully opened, and the third valve and the fourth valve being set as intermediate openings because of the problem of easy control of the steam flow rate. Among these, the fourth valve has a narrow opening degree from its original purpose, and thus has problems such as large pressure loss and hunting.

  Further, the efficiency of the steam turbine is calculated so as to be optimal when operated under certain conditions.

  However, if there is extraction used for applications other than the rotation of the steam turbine as described above, the pressure change before and after extraction, the change in steam flow after the extraction stage, Due to changes in pressure conditions and the like, steam turbines are not always operated with optimal efficiency.

  Furthermore, the steam condition (heat balance) in the steam turbine also changes due to the change in the exhaust pressure. For example, in a turbine having a condenser, the exhaust pressure depends on a change in the temperature of seawater used for steam cooling, a change in the extraction flow rate described above, and the like.

  In addition, the main steam pressure set value is automatically corrected during plant operation, the opening degree of the adjusting valve is automatically corrected, the opening degree of the adjusting valve is adjusted dynamically, and the adjustment test period is shortened. Have been proposed (see, for example, Patent Document 1 and Patent Document 2). Further, a control method has been proposed that minimizes the opening of the main steam control valve and the pressure loss before and after that in all operating ranges (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2004-316998 (pages 5 to 7 and FIGS. 1 to 3) JP 2004-011608 A (Pages 4-7, FIGS. 1-3)

  Thus, when controlling the main steam flow rate, if only the opening degree of the main steam control valve is controlled, some of the multiple main steam control valves are set at intermediate opening degrees because of the relationship between the opening degree and the flow rate characteristics. I have to drive.

  In general, the larger the vapor flow rate, the greater the pressure loss of the fluid flowing in the pipeline. Therefore, if there is no particular limitation, maximizing the flow path of the steam pipe maximizes the pressure loss reduction effect, and ultimately increases the turbine efficiency to the maximum.

  With respect to extraction used for purposes other than the rotation of the steam turbine, depending on the purpose of use, not only a simple switching operation with or without extraction but also an operation may be performed by changing the flow rate of extraction.

  Therefore, in a turbine designed to maximize efficiency in the absence of bleed, if the steam flow after bleed and the bleed stage changes, the turbine will be operated in a state deviating from the optimum steam conditions at the time of design. Thus, the turbine efficiency is not necessarily maximized.

  On the other hand, in a turbine that is designed to maximize efficiency in the state of bleed or bleed at a constant flow rate, the turbine is operated without bleed, or the bleed steam flow rate is the efflux flow rate at the maximum efficiency point. If different, the turbine is not necessarily operated at maximum efficiency as well.

  In addition, changes in the exhaust pressure also have the same effect. If the engine is operated outside the design point where the turbine efficiency is maximized, the optimum steam conditions are different from the optimum steam conditions at the time of turbine design. It was not always driven in the state.

  An object of the present invention is to control the opening of the main steam control valve and the main steam pressure even when the steam conditions (heat balance) in the turbine differ due to changes in the main steam pressure, the bleed flow rate, and the exhaust pressure. It is to provide a steam turbine control system that maintains the optimal efficiency of the system.

  In order to solve the above problems, the present invention controls at least one boiler capable of pressure control, at least one steam turbine driven by steam from the boiler, and a flow rate of steam flowing from the boiler into the steam turbine. A pressure gauge that measures the main steam pressure between the steam control valve, the boiler and the main steam control valve, and a pressure loss calculation that calculates the pressure loss that occurs before and after the main steam control valve based on the pressure from the pressure gauge Main steam control valve opening calculation means for calculating the optimum main steam control valve opening based on the output of the pressure loss calculation means, and the optimum main steam pressure is calculated based on the output of the pressure loss calculation means A steam turbine control system comprising main steam pressure calculating means is proposed.

  As a result, for example, if the first to second valves of the four main steam control valves are fully opened, the fourth valve is fully closed, and only the third valve is set to an intermediate opening, it passes through a flow path with a narrow opening. Pressure loss can be reduced.

  If there is bleed, such as process steam, measure the bleed flow rate, recalculate how the steam conditions (heat balance) in the turbine change according to the bleed flow rate, and based on the recalculation results, The opening degree of the main steam control valve is adjusted so as to maximize the turbine efficiency at, and the steam flow rate is controlled. Alternatively, the main steam pressure is controlled to ensure an optimal steam flow rate.

  If the measurement result of the exhaust pressure is also input at the time of the recalculation, more efficient control of the steam flow rate and the main steam pressure becomes possible.

  According to the present invention, while ensuring ease of control of the steam flow rate of the main steam control valve, it can be operated in a state where pressure loss is minimized, and the turbine efficiency is improved and each state corresponding to the demand for extraction is achieved. Thus, a steam turbine control system that can be operated at an optimum turbine efficiency is obtained.

  Next, with reference to FIG. 1 and FIG. 2, the Example of the steam turbine control system by this invention is described.

  FIG. 1 is a block diagram showing a system configuration of an embodiment of a steam turbine control system according to the present invention. The steam turbine plant of the present embodiment has an extraction system that is used in addition to the rotation of the steam turbine.

  The steam turbine control system of this embodiment is installed between a boiler 1 capable of pressure control, a steam turbine 5 that rotates using steam of the boiler 1, and the boiler 1 and the steam turbine 5 and flows into the steam turbine 5. Four main steam control valves 3 for controlling the flow rate of steam, a main steam pressure gauge 2 installed between the main steam control valve 3 and the boiler 1 for measuring the main steam pressure generated in the boiler 1, and a steam turbine 5 The extraction system 7 for guiding steam mainly used for applications other than turbine rotation, the extraction control valve 8 installed in the extraction system 7 for controlling the extraction steam flow, and the extraction flow meter for measuring the extraction flow 6 and an exhaust pressure gauge 9 for measuring the exhaust pressure from the steam turbine 5 and taking in the main steam pressure, the main steam control valve opening, the extraction flow rate, the exhaust pressure, etc., and the main steam pressure and the main steam control valve are optimally opened. Calculate the degree, main And controlling the opening of pressure force and the main steam control valve, and a control unit 4 for holding the turbine efficiency in the optimal state.

  FIG. 2 is a block diagram illustrating an example of an internal configuration of a control device that configures the steam turbine control system of FIG. 1.

  The control device 4 includes input means 41, calculation means 42, and output means 43.

  The input means 41 includes a main steam pressure input unit 10, an extraction flow rate input unit 11, and an exhaust pressure input unit 12.

  The calculation means 42 is a pressure loss calculation means 13, a heat balance calculation means 14, and a main steam control valve optimum opening calculation means for calculating an optimum main steam control valve opening based on the pressure loss calculation result and the heat balance calculation result. 15, main steam pressure calculating means 16 for calculating the optimum main steam pressure, and control object determining means for finally determining which of the main steam pressure and the main steam control valve opening is used to control the turbine inflow steam amount. 17 and so on.

  The output means 43 includes a main steam control valve optimum opening output section 18 that outputs an opening control signal to the main steam control valve based on the output of the control target determination means 17, and main steam pressure calculation based on the output of the control target determination means 17. And a main steam pressure output unit 19 for sending the result to a control means (not shown) on the boiler side.

  During normal operation, the steam generated in the boiler 1 flows into the steam turbine 5 while the flow rate is adjusted by the main steam control valve 3 to rotate the steam turbine 5.

When process steam is required as a plant, the extraction control valve 8 is opened, and extraction is performed while controlling the amount of extracted steam within the constraints of the steam turbine.
≪Steady operation state≫
In the steady operation state, the four main steam control valves 3 fully open the two main steam control valves, the first valve and the second valve, in order to ensure controllability of the steam flow. The valve is opened as much as possible within an easy-to-control range, and the fourth valve is opened to the extent that it is possible to supply a shortage of steam within an easy-to-control range.

  In this state, the main steam pressure from the boiler 1 is measured by the main steam pressure gauge 2, and the main steam pressure is taken into the control device 4 from the main steam pressure input unit 10.

  The pressure loss calculation means 13 in the control device 4 calculates the pressure loss before and after the main steam control valve based on the taken-in pressure and the opening degree of the main steam control valve.

  Further, the main steam pressure calculation means 16 calculates the main steam pressure such that the pressure on the rear side of the main steam control valve 3 is the same when the third valve is fully opened and the fourth valve is fully closed.

  The main steam pressure calculation means 16 sends the main steam pressure calculation result to the control object determination means 17.

  The control target determining means 17 determines whether or not the main steam pressure can be matched with the main steam pressure calculation result under the condition that the third valve is fully opened and the fourth valve is fully closed. .

  If the control object determining means 17 determines that control is possible, the main steam control valve optimum opening output unit 18 sends a command signal for fully opening the third valve and fully closing the fourth valve to the third valve of the main steam control valve. , Instruct to output to the fourth valve. Further, the main steam pressure output unit 19 is instructed to output steam to the boiler 1 side so as to be the main steam pressure.

  The main steam control valve optimum opening output unit 18 outputs command signals for full opening and closing to the third valve and the fourth valve of the main steam control valve 3 in accordance with an instruction from the control target determining means 17. The main steam pressure output unit 19 outputs a command signal to the boiler 1 in accordance with the main steam pressure calculation result in accordance with the instruction of the control target determining means 17.

  After the output control is completed, measure the main steam pressure again, calculate the pressure loss before and after the main steam control valve 3 using the opening of the main steam control valve 3, and the pressure behind the main steam control valve 3 is the required pressure. Make sure that

  If the required pressure is not reached, the main steam pressure calculation to the pressure loss calculation before and after the main steam control valve 3 is performed again, the main steam pressure is controlled, and the pressure behind the main steam control valve 3 is the required pressure. Feedback control is continued until

  When the third valve is fully open and the fourth valve is fully closed, and the pressure on the rear side of the main steam control valve 3 is controlled to the required pressure, the steam turbine 5 has an optimal and necessary and sufficient steam flow rate, As long as the steam flow rate is controllable, the operation with the minimum pressure loss is maintained.

In this state, for example, when the energy loss at the time of main steam pressure control in the boiler 1 is compared with the pressure loss before and after the main steam control valve 3, this operating state is the operating state of the entire plant. If it is not determined to be optimum, the main steam pressure and the main steam control valve opening are controlled so that the optimum state can be maintained under the required conditions.
≪Bleeding operation state≫
Next, a description will be given of a case where extraction is necessary together with the rotational driving of the steam turbine.

  The state where the main steam generated in the boiler 1 is rotating the turbine 5 will be described as a base point. At this time, the main steam pressure and the main steam control valve opening are controlled in a steady operation state.

  In this state, if there is a demand for steam in addition to the rotational drive of the steam turbine, the extraction control valve 8 is opened and the extraction is performed.

  In this bleed operation state, the steam condition (heat balance) in the turbine is different from the optimum condition during steady operation.

  Therefore, the extraction flow rate is measured by the extraction flow meter 6 and is taken into the control device 4 from the extraction flow rate input unit 11.

  The extracted bleed flow rate is sent to the pressure loss calculation means 13 and the heat balance calculation means 14 together with the main steam pressure already input, and the pressure loss before and after the main steam control valve 3 and the heat balance of the entire turbine are calculated. Is done.

  The calculation results calculated by the pressure loss calculation means 13 and the heat balance calculation means 14 are sent to the main steam control valve opening degree calculation means 15 and the main steam pressure calculation means 16.

  The main steam control valve opening degree calculation means 15 that has received the pressure loss calculation result and the heat balance calculation result calculates the optimum main steam control valve opening degree and feeds it back to the pressure loss calculation means 13.

  The pressure loss calculation means 13 maintains the calculated main steam amount from the received main steam control valve opening, and the third valve of the main steam control valve 3 is fully opened and the fourth valve is fully closed. Is calculated again, and the calculation result is sent to the main steam pressure calculation means 16.

  The main steam pressure calculation means 16 calculates the main steam pressure from the received calculation result so that the pressure behind the main steam control valve becomes the pressure when the third valve is fully open and the fourth valve is fully closed.

The recalculation result is sent to the main steam pressure output unit 19 and sent to the control means of the boiler 1 as a main steam pressure control signal on the boiler 1 side.
≪Exhaust pressure change state≫
Next, a case where the exhaust pressure changes will be described.

  The exhaust pressure is generated due to various factors in addition to the main steam pressure change and the extraction flow rate change. Here, a case where the exhaust pressure changes due to factors other than the main steam pressure change and the extraction flow rate change will be described.

  A description will be given based on a state where the main steam generated in the boiler 1 is rotating while the turbine 5 is rotating and is being extracted.

  The main steam pressure and the main steam control valve opening are controlled in the extraction operation state, and the main steam pressure and the main steam control valve opening control when the extraction flow rate changes are also controlled as before. Suppose you are.

  In this state, when the exhaust pressure changes for some reason, the steam condition (heat balance) in the turbine assumed at the time of turbine design becomes different from the optimum condition.

  Therefore, the exhaust pressure measured by the exhaust pressure gauge 9 is taken into the control device 4 from the exhaust pressure input unit 12.

  At this time, the main steam pressure measured by the main steam pressure gauge 2 and the extraction flow rate measured by the extraction flow meter 6 are taken into the control device 4.

  The main steam pressure and the extracted steam flow rate. The exhaust pressure is sent to the pressure loss calculation means 13 and the heat balance calculation means 14, and the pressure loss before and after the main steam control valve 3 and the heat balance of the entire turbine are calculated.

  Also in this case, the operation is performed by the same control method as in the case where there is extraction.

  Therefore, while ensuring ease of control of the steam flow rate of the main steam control valve, it can be operated with minimum pressure loss, increasing turbine efficiency, and optimal for each condition that meets the demand for extraction. It can be operated with turbine efficiency.

It is a block diagram which shows the system configuration | structure of one Example of the steam turbine control system by this invention. It is a block diagram which shows an example of the internal structure of the control apparatus which comprises the steam turbine control system of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boiler 2 Main steam pressure gauge 3 Main steam control valve 4 Control apparatus 41 Input means 42 Calculation means 43 Output means 5 Steam turbine 6 Extraction flow meter 7 Extraction system 8 Extraction control valve 9 Exhaust pressure gauge 10 Main steam pressure input part 11 Extraction Flow rate input unit 12 Exhaust pressure input unit 13 Pressure loss calculation unit 14 Heat balance calculation unit 15 Main steam control valve optimum opening calculation unit 16 Main steam pressure calculation unit 17 Control target determination unit 18 Main steam control valve optimal opening output unit 19 Main steam pressure output section

Claims (3)

At least one boiler capable of pressure control;
At least one steam turbine driven by steam from the boiler;
A main steam control valve for controlling the flow rate of steam flowing from the boiler into the steam turbine;
A pressure gauge for measuring a main steam pressure between the boiler and the main steam control valve;
Pressure loss calculating means for calculating the pressure loss generated before and after the main steam control valve based on the pressure from the pressure gauge;
Main steam control valve opening calculation means for calculating the optimum opening of the main steam control valve based on the output of the pressure loss calculation means;
A steam turbine control system comprising main steam pressure calculation means for calculating an optimum main steam pressure based on an output of the pressure loss calculation means. At least one boiler capable of pressure control;
At least one steam turbine driven by steam from the boiler;
A main steam control valve for controlling the flow rate of steam flowing from the boiler into the steam turbine;
A pressure gauge for measuring a main steam pressure between the boiler and the main steam control valve;
An extraction system for guiding steam mainly used for applications other than turbine rotation from any paragraph of the steam turbine;
A bleed control valve that is installed in the bleed system and controls the flow rate of the bleed steam;
An extraction flow meter for measuring the extraction flow rate;
Pressure loss calculating means for calculating the pressure loss generated before and after the main steam control valve based on the pressure from the pressure gauge;
A heat balance calculation means for recalculating the steam condition (heat balance) in the steam turbine, which changes according to the measured main steam pressure and the extraction flow rate, to an optimum state;
Main steam control valve opening calculation means for calculating the optimum opening of the main steam control valve based on the output of the pressure loss calculation means;
A steam turbine control system comprising a main steam pressure calculating means for calculating an optimum main steam pressure based on the output of the pressure loss calculating means and the heat balance calculating means. At least one boiler capable of pressure control;
At least one steam turbine driven by steam from the boiler;
A main steam control valve for controlling the flow rate of steam flowing from the boiler into the steam turbine;
A pressure gauge for measuring a main steam pressure between the boiler and the main steam control valve;
An extraction system for guiding steam mainly used for applications other than turbine rotation from any paragraph of the steam turbine;
A bleed control valve that is installed in the bleed system and controls the flow rate of the bleed steam;
An extraction flow meter for measuring the extraction flow rate;
An exhaust pressure gauge for measuring the exhaust pressure from the steam turbine;
Pressure loss calculating means for calculating the pressure loss generated before and after the main steam control valve based on the pressure from the pressure gauge;
A heat balance calculation means for recalculating the steam condition (heat balance) in the steam turbine, which changes according to the measured main steam pressure, extraction flow rate, and exhaust pressure, to an optimum state;
Main steam control valve opening calculation means for calculating the optimum opening of the main steam control valve based on the output of the pressure loss calculation means;
A steam turbine control system comprising a main steam pressure calculating means for calculating an optimum main steam pressure based on the output of the pressure loss calculating means and the heat balance calculating means.

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