JP2023064323A - Turbine bypass device and power generation plant - Google Patents

Abstract

To provide a turbine bypass device capable of continuing safer and efficient operation in a case where a steam control valve executes steam cut-off operation, and a power generation plant.SOLUTION: A turbine bypass device that adjusts the opening of a low-pressure turbine bypass control valve 19 to control steam flowing into a condenser 51, comprises: valve inflow allowable steam volume calculation means of calculating a valve inflow allowable steam volume in an operation state based on the pressure and temperature of steam flowing into the low-pressure turbine bypass control valve 19, and a condenser inflow allowable steam volume as a fixed value; and opening conversion means of obtaining the opening of the low-pressure turbine bypass control valve 19 corresponding to the valve inflow allowable steam volume to set the opening to an upper limit.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to turbine bypass arrangements and power plants.

Conventionally, steam generated from a steam generator and steam piping, a steam turbine driven by steam and a steam control valve, and condensing exhaust steam that has finished work in the steam turbine to condense water for steam generation. It consists of a condenser and steam cooling auxiliary equipment, and a steam pipe and turbine bypass control valve that bypasses the excess steam that is generated when the steam turbine starts and stops or when the steam is suddenly cut off from before the steam turbine to the condenser. power generation cycle systems are known.

FIG. 4 shows an example of a reheat condensate turbine system in a conventional thermal power plant that drives a steam turbine with high-pressure steam and reheat steam. The system comprises a steam generator 101 , a high/medium pressure turbine 102 , a low pressure turbine 103 and a condenser 104 . In FIG. 4, the arrows in the figure indicate the flow of steam during operation of the conventional thermal power plant. 4, 11 is the high-temperature reheat steam pressure, 12 is the high-temperature reheat steam temperature, 18 is the high-pressure turbine bypass control valve, 19 is the low-pressure turbine bypass control valve, and 21 is the high-pressure main steam pressure.

Also, FIG. 5 shows an example of a reheat condensate turbine system in a combined cycle power plant of a gas turbine and a steam turbine, in which the steam turbine is driven by high-pressure steam, intermediate-pressure steam and low-pressure steam. The system comprises a steam generator 101 , a high/medium pressure turbine 102 , a low pressure turbine 103 , a condenser 104 as well as a gas turbine 105 . In FIG. 5, the arrows in the figure indicate the flow of steam during operation of the combined cycle power plant. 5, 21 is the high pressure main steam pressure, 22 is the high pressure main steam temperature, 29 is the high pressure turbine bypass control valve, 31 is the intermediate pressure main steam pressure, 32 is the intermediate pressure main steam temperature, and 39 is the intermediate pressure turbine bypass. Control valves, 41 low-pressure main steam pressure, 42 low-pressure main steam temperature, and 49 low-pressure turbine bypass control valve.

In the system described above, when the steam control valve executes a steam cutoff operation due to a sudden decrease in the turbine load during an emergency shutdown of the steam turbine or during load cutoff, the surplus that has no place to go from the steam generator to the steam turbine inlet pipe Steam is generated. A safety valve is installed as an emergency relief valve when the maximum allowable pressure of the steam pipe exceeds the maximum allowable pressure, but it should be avoided as much as possible considering repair after operation and replenishment of water with quality control that is insufficient due to steam release outside the cycle. Therefore, it is necessary to open the turbine bypass control valve to reduce the rapidly generated surplus steam and suppress the pressure rise in the steam pipe, allowing the surplus steam to escape to the condenser at once (turbine bypass operation). Become.

FIG. 6 shows an operation example of turbine bypass operation in a conventional thermal power plant, and FIG. 7 shows an operation example of turbine bypass operation in a combined cycle power plant. In these figures, arrows indicate the flow of steam during turbine bypass operation. In the conventional thermal power plant of FIG. 6 , the high pressure turbine bypass control valve 18 and the low pressure turbine bypass control valve 19 are opened to guide steam to the condenser 104 . 7, the high pressure turbine bypass control valve 29, the intermediate pressure turbine bypass control valve 39, and the low pressure turbine bypass control valve 49 are opened to guide the steam to the condenser 104.

Here, as a transitional phenomenon of turbine bypass control, the steam accumulated in the steam pipe is released to the condenser at once immediately after the occurrence of steam cutoff, but depending on the steam state at that time, there is a possibility of excessive inflow. . If the excessive inflow of steam exceeds the steam cooling capacity of the condenser, the temperature and pressure inside the condenser will rise abnormally, and in the worst case, the pressure safety device installed at the steam turbine exhaust will fail. it will work.

Furthermore, this pressure safety device often applies a non-regenerative rupture disk, and if it operates (breaks), it will take a long time to replace it, so it is impossible to operate the plant during that time. turn into.

Therefore, in turbine bypass control, it is necessary to consider not only the suppression of the pressure rise in the steam turbine inlet steam pipe, but also the amount of steam that excessively flows into the condenser.

The means for suppressing excessive inflow is to suppress the opening of the turbine bypass control valve. There is also a method of forcibly suppressing the opening to a specified opening as an interlock depending on the state and conditions inside the condenser.

JP-A-54-077803 JP-A-63-277805 JP-A-11-270305 JP-A-2013-064372

As a means to suppress the turbine bypass control valve opening considering the excessive amount of steam flowing into the condenser, for example, if a flow rate detector is installed, the cost and installation for additional flow rate detector There are hardware restrictions such as the need for space for the length of piping. In addition, when forcibly suppressing the opening to the specified opening as an interlock, the opening is set according to the assumed state or it is a time-limited release operation, so depending on the steam that is actually bypassed, there may be excess or deficiency. may occur.

Therefore, it is a problem to variably control and limit the optimum maximum amount of steam that can flow into the condenser by a simple method. In addition, even if the opening limit operation works for the condenser during the inflow of steam, the condition inside the condenser may approach the maximum steam cooling capacity point at the initial time of the inflow. Therefore, the condenser that receives the steam also needs to improve the steam cooling performance.

SUMMARY OF THE INVENTION The present invention was made in response to the above-described conventional circumstances, and its object is to continue operation more safely and efficiently when a steam control valve performs a steam cutoff operation. To provide a turbine bypass device and a power plant capable of

A turbine bypass device according to an embodiment is a turbine bypass device that controls steam flowing into a condenser by adjusting an opening degree of a turbine bypass control valve, wherein the pressure and temperature of the steam flowing into the turbine bypass control valve are controlled. a valve inflow allowable steam volume calculating means for calculating a valve inflow allowable steam volume in an operating state from the condenser inflow allowable steam volume as a fixed value; and the turbine corresponding to the valve inflow allowable steam volume. and opening converting means for obtaining the opening of the bypass control valve and setting the opening to the upper limit.

According to the present invention, it is possible to provide a turbine bypass device and a power plant that can continue to operate more safely and efficiently when a steam control valve performs a steam cutoff operation.

The figure which shows the schematic structure of 1st Embodiment. The figure which shows schematic structure of 2nd Embodiment. The figure which shows schematic structure of 3rd Embodiment. The figure which shows the structural example of a conventional thermal power plant. The figure which shows the structural example of a combined cycle power plant. FIG. 4 is a diagram showing an operation example of turbine bypass operation in a conventional thermal power plant; FIG. 4 is a diagram showing an operation example of turbine bypass operation in a combined cycle power plant;

Hereinafter, a turbine bypass device and a power plant according to embodiments will be described with reference to the drawings.

In this embodiment, the maximum amount of steam that can flow into the condenser is controlled by the amount of steam that actually flows into the condenser through the turbine bypass control valve. The amount of steam is calculated from the amount of steam passing through the turbine bypass control valve (CV value), which varies depending on the steam conditions.

The amount of steam passing through the turbine bypass control valve (CV value) varies depending on the conditions (pressure and temperature) of the inflowing steam even if the amount of steam passing through the valve is constant. If it is varied, it is possible to achieve an optimum restriction that is neither too much nor too little. In order to achieve this, the maximum amount of steam that can flow into the condenser is fixed, the steam conditions are constantly monitored, the CV value is constantly corrected, and the limit opening is varied. As a result, the high-pressure and high-temperature steam conditions at the beginning of the occurrence of transient phenomena are restricted by a low opening, and the relief operation improves the steam conditions and relaxes the restriction, resulting in the optimal condition for the inflow situation. Management becomes possible, and it becomes possible to reduce replenishment of insufficient quality-controlled water due to discharge outside the cycle.

In addition, the improvement of steam cooling performance at the initial stage of steam inflow into the condenser will improve the condenser cooling water volume, condenser cooling water temperature, and condenser internal pressure by improving the steam cooling incidental equipment. can be solved by It is possible to prepare the optimum steam cooling performance that matches the inflow situation by doing this ahead of time when the opening limit operation is approached, instead of doing it by detecting an abnormal state in the condenser. becomes.

(First embodiment)
First, a first embodiment will be described with reference to FIG. The example shown in FIG. 1 shows a case of application to a low-pressure turbine bypass control valve 19 of a conventional thermal power plant, and parts corresponding to those in FIG. 6 described above are denoted by the same reference numerals. As shown in FIG. 1, in the power plant according to the embodiment, in the low-pressure turbine bypass control valve 19, the state values of the steam flowing into the low-pressure turbine bypass control valve 19 (valve inflow steam pressure 1, valve inflow steam temperature 2) Measured value) and condenser inflow allowable steam amount (fixed value) 4, the valve inflow allowable volume amount (CV value) calculator 5 always calculates the valve inflow allowable volume amount, and it is obtained by normal pressure PID control. With respect to the opening command set by the excess steam release control amount 8, the upper limit opening corresponding to the calculated CV value is set by the upper limit opening limiter 9, and the amount of steam flowing into the condenser 104 is Restrict.

In the conventional thermal power plant shown in FIG. 1 , the surplus amount of high-pressure turbine supply steam generated by the steam generator 101 is bypassed by the high-pressure turbine bypass control valve 18 to reduce the temperature and pressure, and returns to the steam generator 101 . This steam, which has been superheated again by the steam generator 101 , performs a cascade operation in which the excess amount is similarly released to the condenser 104 by the low-pressure turbine bypass control valve 19 .

The high-temperature reheat steam pressure 11 and the high-temperature reheat steam temperature 12 are applied as state values to the valve inflow steam pressure 1 and the valve inflow steam temperature 2 . From these, the valve inflow steam superheat degree 3 is obtained, and using this and the condenser inflow allowable steam amount 4 which is a fixed value, the valve inflow allowable volume (CV value) calculator 5 calculates the actual inflow steam volume. . The calculation result is converted from the CV value to the opening degree by the CV value/opening degree converter 6, and the excess steam release control amount that is PID control with the high temperature reheat steam pressure 11 set as the normal control amount as the control amount. 8 is set to the upper limit opening limiter 9. If it is necessary to limit the degree of opening by interlocking, switching is performed by the signal switching device 7 . Also, the lower limit opening limiter 90 sets 0% or interlock forced opening as required.

The state of control at this time is schematically shown in the upper right portion of FIG. 1 as a schematic chart. In this schematic chart, the dotted line indicates the maximum possible opening, which is the output of the CV value/opening converter 6, and the solid line indicates the valve opening, which is the output of the excess steam release control amount 8. As shown here, the permissible volume of steam passing through the control valve changes depending on the properties of the steam, which varies depending on the load of the plant. In addition, the PID control is continued while always monitoring the allowable steam capacity amount that can flow into the condenser 104 as the upper limit opening, and the opening is restricted as the inflow restriction only during the time when the upper limit is exceeded. In other words, limit only the necessary time and continue continuous control as much as possible.

Further, in the present embodiment, the high-pressure turbine in the combined cycle power plant shown in the operation example of FIG. A bypass control valve 29, an intermediate-pressure turbine bypass control valve 39 that bypasses the surplus amount of the intermediate-pressure turbine supply steam generated from the steam generator 101 to the condenser 104 by reducing the temperature and reducing the pressure, and the low pressure generated from the steam generator 101. In the low-pressure turbine bypass control valve 49, which bypasses the excess steam supplied to the turbine and releases it to the condenser 104, the valve inflow steam pressure 1 and the valve inflow steam temperature 2 in FIG. 21, high pressure main steam temperature 22, medium pressure main steam pressure 31, medium pressure main steam temperature 32, low pressure main steam pressure 41, low pressure main steam temperature 42 are applied, and the total amount of steam that can flow into the three turbine bypass control valves It can be applied by giving each turbine bypass control valve a setting where the value is below the amount of steam that can flow into the condenser.

As described above, according to the first embodiment, the CV value can always be corrected and calculated according to the inflow steam condition of the turbine bypass control valve, and the opening limit can be varied. As a result, the high-pressure and high-temperature state at the initial stage of the transient phenomenon is restricted to a low opening, the steam conditions are improved, the restriction is relaxed, and the control can be transferred to the conventional PID calculation result.

(Second embodiment)
Next, a second embodiment will be described with reference to FIG. In order to maintain the cooling performance of the condenser 104, the condenser cooling water cooled by the cooling tower fan 62 in the cooling tower of the incidental equipment is circulated by the condenser circulation pump 63 to perform heat exchange. In the second embodiment, when the possible upper limit opening and the excess steam release control amount in the above-described first embodiment approach, the output of the cooling tower fan 62 and the condenser circulation pump 63 is increased, and the number of standby units is increased. By increasing the temperature, the cooling performance of the condenser 104 is improved in advance.

As shown in FIG. 2, in the second embodiment, a comparator is installed to detect the deviation between the possible upper limit opening 61 and the excess steam release control amount 8, and to manage the approach of the control amount to the possible upper limit opening. That is, the valve opening, which is the output of the excess steam release control amount 8, and the possible upper limit opening 61, which is the output of the CV value/opening converter 6, are input to the deviation setter 10, and the deviation between them is calculated. be. Then, when these deviations exceed the threshold value and decrease, a cooling performance stabilization signal 66 is given to the accessory control device 65, and the accessory control device 65 controls the cooling tower fan 62 and the condenser circulation pump 63. In addition, the cooling performance will be improved by increasing the number of spare units and increasing the output of inverters.

In the second embodiment, when the possible upper limit opening degree 61 and the excess steam release control amount are close, there is a concern that more steam will flow into the condenser 104 and its cooling performance will deteriorate. By increasing the output of the fan 62 or increasing the number of standby units, the temperature of the condenser cooling water can be reduced and the cooling performance can be stabilized. Further, by increasing the output of the condenser circulation pump 63 or increasing the number of standby units, the amount of cooling water in the condenser can be increased and the cooling performance can be stabilized.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. The condenser 104 is evacuated by a condenser vacuum pump 64 in order to maintain cooling performance. In the third embodiment, when the maximum possible opening degree and the excess steam release control amount in the above-described first embodiment are approaching, the output of the condenser vacuum pump 64 is increased and the number of standby units is increased to proactively In addition, the cooling performance of the condenser 104 is improved.

As shown in FIG. 3, in the third embodiment, a comparator is installed to detect the deviation between the possible upper limit opening 61 and the excess steam release control amount 8, and to manage the approach of the control amount to the possible upper limit opening. That is, the valve opening, which is the output of the excess steam release control amount 8, and the possible upper limit opening 61, which is the output of the CV value/opening converter 6, are input to the deviation setter 10, and the deviation between them is calculated. be. Then, when these deviations exceed the threshold value and decrease, the cooling performance stabilization signal 66 is given to the auxiliary equipment control device 65, and the auxiliary equipment control device 65 increases the number of standby equipment of the condenser vacuum pump 64. The cooling performance is improved by increasing the output of the inverter, etc.

In the third embodiment, the fact that the possible upper limit opening degree 61 and the excess steam release control amount are close to each other means that more steam flows into the condenser 104, and there is a concern that the cooling performance thereof will deteriorate. By increasing the output of the condenser vacuum pump 64 or increasing the number of standby machines, the degree of vacuum in the condenser 104 can be maintained, and the cooling performance can be stabilized.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

1...Valve inflow steam pressure, 2...Valve inflow steam temperature, 3...Valve inflow steam superheat, 4...Condenser inflow allowable steam amount (fixed value), 5...Valve inflow allowable volume calculator , 6 CV value/opening converter, 7 signal selector, 8 excess steam release control amount, 9 upper limit opening limiter, 10 deviation setter, 11 high temperature reheat Steam pressure 12 High temperature reheat steam temperature 18 High pressure turbine bypass control valve 19 Low pressure turbine bypass control valve 21 High pressure main steam pressure 22 High pressure main steam temperature 29 High pressure Turbine bypass control valve 31 Intermediate pressure main steam pressure 32 Intermediate pressure main steam temperature 39 Intermediate pressure turbine bypass control valve 41 Low pressure main steam pressure 42 Low pressure main steam temperature 49 ... Low-pressure turbine bypass control valve, 62 ... Cooling tower fan, 63 ... Condenser circulation pump, 64 ... Condenser vacuum pump, 65 ... Auxiliary machine control device, 66 ... Cooling performance stabilization signal, 90...Lower limit opening limiter, 101...Steam generator, 102...High pressure/intermediate pressure turbine, 103...Low pressure turbine, 104...Condenser, 105...Gas turbine.

Claims (8)

A turbine bypass device that controls steam flowing into a condenser by adjusting the opening of a turbine bypass control valve,
a valve inflow allowable steam volume calculation means for calculating an allowable valve inflow steam volume in an operating state from the pressure and temperature of the steam flowing into the turbine bypass control valve and a fixed value of the condenser inflow allowable steam volume; ,
A turbine bypass apparatus, comprising: opening conversion means for obtaining an opening of said turbine bypass control valve corresponding to said valve inflow allowable steam volume and setting it as an upper limit opening. A turbine bypass device according to claim 1, wherein
a control unit that calculates the valve opening degree of the turbine bypass control valve for controlling the excess steam release control amount from the steam pressure so that it becomes a target value;
setting the upper limit opening degree by the opening degree conversion means for the valve opening degree calculated by the control unit, and suppressing excessive inflow of steam into the condenser;
A turbine bypass device characterized by: A turbine bypass device according to claim 2,
Calculate the deviation between the upper limit opening and the valve opening calculated by the control unit, and increase the output of the cooling tower fan or increase the number of standby units when the deviation becomes smaller than the threshold value A turbine bypass device characterized by operating. A turbine bypass device according to claim 2,
Calculate the deviation between the upper limit opening and the valve opening calculated by the control unit, and when the deviation becomes smaller than the threshold value, increase the output of the condenser circulation pump or turn on the standby machine A turbine bypass device characterized by increased operation. A turbine bypass device according to claim 2,
Calculate the deviation between the upper limit opening degree and the valve opening degree calculated by the control unit, and when the deviation becomes smaller than the threshold value, increase the output of the condenser vacuum pump or turn on the standby machine A turbine bypass device characterized by increased operation. The turbine bypass device according to any one of claims 1 to 5,
A turbine bypass system, wherein the turbine bypass control valve is a low-pressure turbine bypass control valve for a conventional thermal power plant. The turbine bypass device according to any one of claims 1 to 5,
A turbine bypass system, wherein said turbine bypass control valves are high pressure, intermediate pressure and low pressure turbine bypass control valves of a combined cycle power plant. A power plant comprising a turbine bypass control valve and a condenser into which steam from the turbine bypass control valve flows,
A power plant comprising the turbine bypass device according to any one of claims 1 to 7.

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