JP7305347B2 - BYPASS CONTROL SYSTEM FOR POWER PLANT AND CONTROL METHOD AND CONTROL PROGRAM THEREOF, POWER PLANT - Google Patents

Description

The present invention relates to a power plant bypass control system, its control method and control program, and a power plant.

In a power plant, for example, there is a configuration in which steam discharged from a high-pressure turbine is reheated and supplied to an intermediate-pressure turbine or a low-pressure turbine. In a power plant that uses such reheated steam, when the load fluctuates, such as during start-up, part of the surplus reheated steam is bypassed to the condenser, etc., without being supplied to the intermediate pressure turbine or the low pressure turbine. sometimes. When the reheat steam is bypassed, spray water or the like is used to reduce the temperature of the bypassed reheat steam so as not to damage the condenser.

Patent Literature 1 discloses a thermal power plant having a configuration in which reheated steam is bypassed to a condenser. Further, Patent Literature 1 discloses setting a maximum allowable degree of opening for a bypass valve that controls the steam flow rate to be bypassed.

Japanese Patent Publication No. 62-17081

If the piping from supplying spray water bypassing reheat steam to introducing it into the condenser is short, the spray water will not be sufficiently mixed with the reheat steam, resulting in sudden load changes. , the temperature reduction of the bypassed reheat steam becomes incomplete, and reheat steam exceeding the allowable temperature in the condenser may be supplied and damage the condenser. Moreover, since the reheat steam bypassed to the condenser does not have a uniform temperature distribution, it is difficult to accurately measure the temperature, which may damage the condenser.

In addition, even if the amount of spray water supplied is controlled based on the enthalpy state of bypassed reheat steam, steam conditions change significantly during load fluctuations such as during start-up, making it difficult to accurately control spray water. Met.

Further, when setting the maximum allowable degree of opening for the bypass valve as in Patent Document 1, for example, if the degree of opening gauge deteriorates over time or malfunctions, the actual degree of opening of the bypass valve becomes larger than the degree of opening command. There is a possibility of becoming a degree state. In such a case, even if the opening command is less than or equal to the maximum allowable opening, the actual opening of the bypass valve will be the maximum allowable opening, possibly causing damage to the condenser.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a bypass control system for a power plant, a control method thereof, a control program, and a power plant that can more reliably prevent damage to a condenser. intended to

A first aspect of the present invention includes a reheater that outputs reheated steam, a turbine to which the reheated steam is supplied, a condenser that condenses the steam discharged from the turbine, and the reheated steam. A bypass line that bypasses the turbine and feeds a part of the steam to the condenser, a bypass valve that adjusts the steam flow rate of the bypass line, a desuperheater that reduces the temperature of the steam in the bypass line, and the A power plant comprising a spray water supply line for supplying part of the condensate generated in the condenser as spray water to the desuperheater, and a spray valve for adjusting the flow rate of the spray water flowing through the spray water supply line. wherein the opening command output unit outputs an opening control command for the bypass valve according to the operating state of the power plant; When the steam flow rate in the bypass line reaches a preset allowable steam flow rate, a valve control unit that maintains the actual opening of the bypass valve, controls the desuperheater, and controls the opening of the spray valve. The temperature reduction control unit controls the flow rate of the steam in the bypass line, the enthalpy of the reheated steam, the enthalpy of the steam in the bypass line supplied to the condenser, and the enthalpy of the spray water. as a parameter , the valve control unit controls the opening of the spray valve based on the flow rate of the spray water calculated using as a parameter, and the valve control unit outputs a single-shot signal is a bypass control system for a power plant that maintains the opening degree command of the bypass valve .

When bypassing part of the reheated steam output from the reheater to the condenser, if the bypass valve is controlled to open according to load fluctuations, etc., a large amount of high-temperature reheated steam will flow into the condenser. , the condenser could be damaged (eg, even with a desuperheater, reheated steam could flow into the condenser without sufficient desuperheating). Therefore, the permissible steam flow rate is set in advance with respect to the steam flow rate of the bypass line. Then, when the steam flow rate of the bypass line reaches a preset allowable steam flow rate while the opening control command is being output, the actual opening degree of the bypass valve is maintained. Since the circulating steam flow rate does not exceed the allowable steam flow rate, damage to the condenser can be more reliably prevented.

In the above-described bypass control system, the valve control unit controls the bypass valve at a point in time when the steam flow rate in the bypass line reaches the allowable steam flow rate in a period in which the steam flow rate in the bypass line reaches the allowable steam flow rate. The actual opening may be maintained.

According to the above configuration, when the steam flow rate in the bypass line reaches the allowable steam flow rate due to the bypass valve opening control, the bypass valve is actually opened at the time when the steam flow rate in the bypass line reaches the allowable steam flow rate. Since the temperature is maintained, it is possible to more reliably prevent the steam flow rate from exceeding the allowable steam flow rate.

In the bypass control system, the opening command output unit may output the opening control command when the power plant is started or when the load fluctuates by a preset threshold or more within a predetermined time. good.

According to the above configuration, since the opening control command is output when the load fluctuates, such as when the power plant is started or when the load is cut off, the opening control command can be output appropriately according to the operating state of the power plant. .

In the above bypass control system , the valve control unit may close the bypass valve when the temperature of the dump tube in the condenser reaches or exceeds a predetermined specified value.

According to the above configuration, even if the temperature of the steam in the bypass line is reduced by the desuperheater, the bypass valve is closed when the temperature of the dump tube in the condenser exceeds a predetermined specified value. It becomes possible to suppress damage to the condenser more reliably.

In the above bypass control system, the allowable steam flow rate may be set based on the specifications of the condenser.

According to the configuration as described above, by setting the allowable steam flow rate based on the specifications of the condenser, it is possible to effectively calculate the allowable steam flow rate for preventing damage to the condenser.

In the above-described bypass control system, the valve control unit may maintain the opening degree command for the bypass valve at the time when the steam flow rate in the bypass line reaches the allowable steam flow rate.

According to the above configuration, by maintaining the bypass valve opening command at the time when the steam flow rate of the bypass line reaches the allowable steam flow rate, fluctuations in the actual opening degree of the bypass valve due to fluctuations in the opening command can be reduced. It is possible to suppress and maintain the actual opening at the time when the allowable steam flow rate is reached.

A second aspect of the present invention includes a reheater that outputs reheated steam, a turbine to which the reheated steam is supplied, a condenser that condenses the steam discharged from the turbine, and the reheated steam. to the condenser, a desuperheater for reducing the temperature of the steam in the bypass line, a bypass valve for adjusting the flow rate of the steam in the bypass line, and the bypass control system of the power plant and a power plant.

A third aspect of the present invention includes a reheater that outputs reheated steam, a turbine to which the reheated steam is supplied, a condenser that condenses the steam discharged from the turbine, and the reheated steam. A bypass line that bypasses the turbine and feeds a part of the steam to the condenser, a bypass valve that adjusts the steam flow rate of the bypass line, a desuperheater that reduces the temperature of the steam in the bypass line, and the A power plant comprising a spray water supply line for supplying part of the condensate generated in the condenser as spray water to the desuperheater, and a spray valve for adjusting the flow rate of the spray water flowing through the spray water supply line. wherein the opening command output step of outputting an opening control command for the bypass valve according to the operating state of the power plant; a valve control step of maintaining the actual opening of the bypass valve when the steam flow in the bypass line reaches a preset allowable steam flow; and controlling the desuperheater and controlling the opening of the spray valve. The temperature reduction control step includes the steam flow rate in the bypass line, the enthalpy of the reheated steam, the enthalpy of the steam in the bypass line supplied to the condenser, and the spray water. The opening degree of the spray valve is controlled based on the flow rate of the spray water calculated using the enthalpy as a parameter, and in the valve control step, when the steam flow rate of the bypass line reaches the allowable steam flow rate, a single shot A bypass control method for a power plant that maintains the bypass valve opening command, which is a signal .

A fourth aspect of the present invention includes a reheater that outputs reheated steam, a turbine to which the reheated steam is supplied, a condenser that condenses the steam discharged from the turbine, and the reheated steam. A bypass line that bypasses the turbine and feeds a part of the steam to the condenser, a bypass valve that adjusts the steam flow rate of the bypass line, a desuperheater that reduces the temperature of the steam in the bypass line, and the A power plant comprising a spray water supply line for supplying part of the condensate generated in the condenser as spray water to the desuperheater, and a spray valve for adjusting the flow rate of the spray water flowing through the spray water supply line. wherein the bypass control program includes: an opening command output process for outputting an opening control command for the bypass valve according to the operating state of the power plant; When the steam flow rate in the bypass line reaches a preset allowable steam flow rate, the valve control process maintains the actual opening of the bypass valve, controls the desuperheater, and controls the opening of the spray valve. The computer executes a temperature reduction control process, and the temperature reduction control process includes the steam flow rate in the bypass line, the enthalpy of the reheated steam, the enthalpy of the steam in the bypass line supplied to the condenser, and the spray The opening degree of the spray valve is controlled based on the flow rate of the spray water calculated using the enthalpy of water as a parameter, and the valve control process is performed when the steam flow rate of the bypass line reaches the allowable steam flow rate. 4 is a power plant bypass control program for maintaining the bypass valve opening command, which is a single-shot signal ;

ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to prevent a condenser from being damaged more reliably.

It is a figure showing a schematic structure of a boiler concerning one embodiment of the present invention. 1 is a schematic diagram showing a power plant according to an embodiment of the invention; FIG. FIG. 3 is a diagram showing in detail the configuration related to circulation of reheat steam in the power plant in FIG. 2 ; FIG. 2 is a functional block diagram showing functions provided by a control device according to one embodiment of the present invention; It is the figure which showed the flowchart of the bypass valve control process which concerns on one Embodiment of this invention. It is the figure which showed the flowchart of the spray valve control process which concerns on one Embodiment of this invention. It is a figure showing operation of bypass valve control concerning one embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bypass control system for a power plant, a control method thereof, a control program, and a power plant according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a boiler 10 provided in a power plant 1 according to this embodiment.

The boiler 10 uses pulverized coal obtained by pulverizing coal as a pulverized fuel (carbon-containing solid fuel), burns the pulverized coal with a combustion burner, recovers the heat generated by this combustion, and exchanges heat with water supply and steam. It is a coal-fired (pulverized coal-fired) boiler capable of generating superheated steam. In the following description, "up" and "up" indicate the upper side in the vertical direction, and "down" and "lower side" indicate the lower side in the vertical direction.

In this embodiment, the boiler 10 has a furnace 11, a combustion device 12, and a flue 13, as shown in FIG. The furnace 11 has a hollow rectangular shape and is installed along the vertical direction. A furnace wall (heat transfer tube) constituting the furnace 11 is composed of a plurality of evaporating tubes and fins connecting them, and suppresses temperature rise of the furnace wall by exchanging heat with feed water and steam.

The combustion device 12 is provided on the lower side of the furnace wall that constitutes the furnace 11 . In this embodiment, the combustion device 12 has a plurality of combustion burners (eg 21, 22, 23, 24, 25) mounted on the furnace wall. For example, the combustion burners 21, 22, 23, 24, and 25 are arranged in a plurality of stages along the vertical direction as one set, which are arranged at equal intervals along the circumferential direction. However, the shape of the furnace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

Each combustion burner 21 , 22 , 23 , 24 , 25 is connected to pulverizers (mills) 31 , 32 , 33 , 34 , 35 via pulverized coal supply pipes 26 , 27 , 28 , 29 , 30 . Although not shown, the crushers 31, 32, 33, 34, and 35 have, for example, a housing in which a rotary table is supported so as to be driven and rotatable. It is configured to be rotatably supported. When coal is fed between a plurality of rollers and a rotary table, it is pulverized to a predetermined size of pulverized coal here, and then transported to a classifier (not shown) by a carrier gas (primary air) to classify the fine powder. Coal can be supplied to the combustion burners 21 , 22 , 23 , 24 , 25 from pulverized coal supply pipes 26 , 27 , 28 , 29 , 30 .

Further, the furnace 11 is provided with a wind box 36 at the mounting position of each combustion burner 21, 22, 23, 24, 25, and one end of an air duct 37 is connected to the wind box 36. As shown in FIG. Air duct 37 is provided with blower 38 at the other end.

Furthermore, the furnace 11 is provided with additional air nozzles 39 above the mounting positions of the combustion burners 21, 22, 23, 24 and 25. As shown in FIG. An end of a branch air duct 40 branched from the air duct 37 is connected to the additional air nozzle 39 . Therefore, the combustion air (fuel gas combustion air/secondary air) sent by the blower 38 is supplied from the air duct 37 to the wind box 36, from which the combustion burners 21, 22, 23, 24, 21, 22, 23, 24, . 25 and additional air for combustion delivered by blower 38 can be supplied to additional air nozzles 39 from branch air duct 40 .

The flue 13 is connected to the upper part of the furnace 11 in the vertical direction. The flue 13 is provided with superheaters 41, 42, 43, reheaters 44, 45, and economizers 46, 47 as heat exchangers for recovering the heat of the combustion gas. Heat is exchanged between combustion gas generated by combustion and water or steam flowing through each heat exchanger.

A gas duct 48 is connected to the downstream side of the flue 13 through which the combustion gas that has undergone heat exchange is discharged. The gas duct 48 is provided with an air heater (air preheater) 49 between the air duct 37 and heat exchange between the air flowing through the air duct 37 and the combustion gas flowing through the gas duct 48 . , 23, 24, 25 can be heated.

A denitration catalyst 50 is provided in the flue 13 upstream of the air heater 49 . The denitrification catalyst 50 supplies a reducing agent such as ammonia or urea water, which has an action of reducing nitrogen oxides, into the flue 13, and causes the reaction between the nitrogen oxides and the reducing agent in the combustion gas to which the reducing agent is supplied. By promoting it, nitrogen oxides in the combustion gas are removed and reduced. A gas duct 48 connected to the flue 13 is provided with a dust processing device (electric dust collector, desulfurization device) 51, an induced draft fan 52, etc. at a position downstream of the air heater 49, and a chimney 53 at the downstream end. ing.

On the other hand, when the pulverizers 31, 32, 33, 34, and 35 are driven, the pulverized coal fuel is fed through the pulverized coal supply pipes 26, 27, 28, 29, and 30 together with the carrier gas to the combustion burners 21, 21, and 29. 22, 23, 24, 25. Also, heated combustion air is supplied from an air duct 37 to each combustion burner 21 , 22 , 23 , 24 , 25 via a wind box 36 . Then, the combustion burners 21, 22, 23, 24, and 25 blow into the furnace 11 a pulverized fuel mixture in which pulverized coal and a carrier gas (primary air) are mixed, and blow combustion air into the furnace 11. At this time, A flame can be formed by igniting the A flame is generated in the lower part of the furnace 11 , combustion gas rises in the furnace 11 and is discharged to the flue 13 .

After that, the combustion gas undergoes heat exchange in the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47 arranged in the flue 13, and then the nitrogen oxides are reduced and removed by the denitration catalyst 50. After the particulate matter is removed and the sulfur content is removed by the dust processing device 51, the dust is discharged from the chimney 53 into the atmosphere.

Next, heat exchange in the boiler 10 of the power plant 1 will be described in detail. FIG. 2 is a schematic diagram showing each heat exchanger provided in the boiler 10 in the power plant 1. As shown in FIG.

As shown in FIG. 2, in this embodiment, the flue 13 is provided with a combustion gas passage 60 through which combustion gas passes. Devices 44, 45 and economizers 46, 47 are arranged. The superheaters 41, 42, 43 may be provided in series via a header, but the header is omitted in FIG.

A steam turbine 61 driven by the steam generated by the boiler 10 includes, for example, a high pressure turbine 62 and an intermediate pressure turbine 63 . The steam turbine 61 may include a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine, and the reheat steam, which will be described later, may flow into the intermediate-pressure turbine and then into the low-pressure turbine. For the sake of convenience, the intermediate pressure turbine and the low pressure turbine will be referred to as intermediate pressure turbines. A condenser 64 is connected to the intermediate pressure turbine 63, and the steam that drives the intermediate pressure turbine 63 is cooled by cooling water (eg, seawater) in the condenser 64 to become condensed water. The condenser 64 is connected to the inlet header 65 of the first economizer 47 via the water supply line L1. The inlet header 65 is provided in the combustion gas passage 60, and the water supply line L1 is provided with a condensate pump 83, a low-pressure water supply heater 84, a water supply pump 66, and a high-pressure water supply heater 85 from the downstream side of the condenser 64. there is The second economizer 46 is arranged above the first economizer 47 , and an intermediate header 67 is provided between the economizers 46 and 47 . The second economizer 46 has an outlet header 68 connected to its upper portion, and the outlet header 68 is arranged outside the combustion gas passage 60 .

The outlet header 68 is connected to a steam drum 69 arranged outside the combustion gas passage 60 via a water supply line L2. The steam drum 69 is connected to each heat transfer tube (not shown) of the furnace wall, and is also connected to superheaters 41, 42, 43. The superheaters 41, 42, 43 are connected to high-pressure steam via a steam line L3. It is connected to turbine 62 . A main steam valve 81 is provided in the steam line L3, and the flow rate of steam supplied to the high-pressure turbine 62 is controlled by controlling the degree of opening of the main steam valve 81 . The high pressure turbine 62 is connected to an inlet header (header) 70 of the first reheater 45 via a steam line L4. An inlet header 70 is provided in the combustion gas passage 60, the first reheater 45 is connected to the second reheater 44 via an intermediate header 71, and the second reheater 44 exits at the top. A header 72 is connected, and the intermediate header 71 and the outlet header 72 are arranged outside the combustion gas passage 60 . The outlet header 72 is connected to the intermediate pressure turbine 63 via the steam line L5 to drive the intermediate pressure turbine 63 to rotate. Thus, in the boiler 10, reheated steam is generated by the first reheater 45 and the second reheater 44. FIG. A turbine steam valve 82 is provided in the steam line L5, and the flow rate of the reheat steam supplied to the intermediate pressure turbine 63 is controlled by the control of the turbine steam valve 82. A discharge valve 86 may be provided in the steam line L5 so that part of the reheated steam generated in the boiler 10 can be discharged outside the system. In addition, a bypass line is provided on the downstream side of the main steam valve 81 (the inlet side of the high pressure turbine 62) in the steam line L3 and the steam line L4 (the outlet side of the high pressure turbine 62), and the bypass line is provided with a control valve 87. good too.

When the combustion gas flows through the combustion gas passage 60 of the flue 13, the combustion gas is heat-recovered through the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47 in this order. On the other hand, the water supplied from the feedwater pump 66 is preheated by the economizers 47 and 46, supplied to the steam drum 69, and heated while being supplied to each heat transfer tube of the furnace wall (not shown) to produce saturated steam. , and returned to the steam drum 69 . The saturated steam in the steam drum 69 is introduced into the superheaters 41, 42, 43 and superheated by the combustion gas. The superheated steam generated by the superheaters 41, 42, 43 is supplied to the high pressure turbine 62 and drives the high pressure turbine 62 to rotate. The steam discharged from the high-pressure turbine 62 is introduced into the reheaters 45 and 44 and reheated, and then supplied as reheated steam to the intermediate-pressure turbine 63 to drive the intermediate-pressure turbine 63 to rotate. A generator is connected to the rotating shaft of the steam turbine 61 to generate power. The steam discharged from the intermediate pressure turbine 63 is cooled by the condenser 64 to become condensed water and sent to the economizers 47 and 46 again.

Further, the flue 13 may have a soot blower (injection device) 80 arranged between the inlet header 70 and the economizer 47 . The soot blower 80 extends in a direction parallel to the longitudinal direction of the inlet header 70 and is arranged at a position facing the inlet header 70 . The soot blower 80 is an injection device that takes the longitudinal direction of the inlet header 70 as its axial direction and injects steam (gas) in a direction perpendicular to the axial direction, and can also change the injection direction. The steam injected from the soot blower 80 toward the economizer 47 removes combustion ash deposited on the surface of the heat transfer tube of the economizer 47 .

Next, a detailed configuration of the power plant 1 related to circulation of reheated steam generated in the boiler 10 will be described.
FIG. 3 is a diagram showing in detail the configuration related to circulation of reheat steam in the power plant 1 in FIG. 3 shows the boiler 10, the high-pressure turbine 62, the intermediate-pressure turbine 63, the condenser 64, and the like, like the configuration in FIG. In addition, FIG. 3 shows a bypass unit BL and a control device 100 that controls the reheat steam as a detailed configuration related to the circulation of the reheat steam.

The bypass section BL has a bypass line L6, a bypass valve 90, a desuperheater 91, a spray water supply line L7, and a spray valve 92. Note that the configuration of the bypass portion BL is not limited to the above configuration as long as the reheat steam can be bypassed.

A bypass line L6 is a pipe that bypasses part of the reheated steam to the condenser 64 . Therefore, one end of the bypass line L6 is connected to the steam line L5 (upstream of the turbine steam valve 82), and the other end is connected to the condenser 64. Part of the reheat steam generated in the boiler 10 flows through the bypass line L6 as bypass steam.

The bypass valve 90 adjusts the flow rate of bypass steam flowing through the bypass line L6. Therefore, the bypass valve 90 is provided on the bypass line L6. The degree of opening of the bypass valve 90 is controlled by a control device 100, which will be described later. The bypass valve 90 also plays a role of controlling the pressure of the reheat steam.

The desuperheater 91 reduces the temperature of the steam in the bypass line L6. The desuperheater 91 is provided downstream of the bypass valve 90 in the bypass line L6. The desuperheater 91 reduces the temperature of the bypass steam using spray water supplied from a spray water supply line L7, which will be described later. Specifically, in the desuperheater 91, the bypass steam is sprayed with spray water, and the bypass steam and the spray water are mixed to reduce the temperature of the bypass steam. The spray water is preferable because it evaporates after being mixed with the bypass steam so that the latent heat of the spray water can also be used for temperature reduction.

The spray water supply line L7 is a pipe that supplies part of the condensed water generated in the condenser 64 to the desuperheater 91 as spray water. For this reason, the spray water supply line L7 has one end connected to the water supply line L1 and the other end connected to the desuperheater 91 . An orifice 93 is provided in the spray water supply line L7. Further, the orifice 93 of the spray water supply line L7 is provided with a flow meter 108 for measuring the flow rate of the circulating spray water.

The spray valve 92 adjusts the flow rate of spray water flowing through the spray water supply line L7. Therefore, the spray valve 92 is provided in the spray water supply line L7. The opening of the spray valve 92 is controlled by a controller 100, which will be described later.

A controller (bypass control system) 100 controls the flow rate of bypass steam. Further, the control device 100 controls the flow rate of the spray water that reduces the temperature of the bypassed reheat steam.

The control device 100 includes, for example, a CPU (Central Processing Unit) (not shown), a memory such as a RAM (Random Access Memory), a computer-readable recording medium, and the like. A series of processes for realizing various functions described later is recorded in the form of a program on a recording medium, etc., and the CPU reads this program into RAM, etc., and executes processing and arithmetic processing of information. Various functions, which will be described later, are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

FIG. 4 is a functional block diagram showing functions provided in the control device 100. As shown in FIG. As shown in FIG. 4 , the control device 100 includes an opening degree command output section 101 , a valve control section 102 and a temperature reduction control section 103 .

The opening degree command output unit 101 outputs an opening degree control command for the bypass valve 90 according to the operating state of the power plant 1 . Specifically, the opening degree command output unit 101 outputs the opening degree control command (open control command ).

In the power plant 1, for example, when the load condition drops, the reheat steam generated in the boiler 10 becomes surplus to the steam supplied to the intermediate pressure turbine 63, and it is necessary to bypass the generated reheat steam. Thus, when the load state of the power plant 1 fluctuates, control of the bypass valve 90 is required. In particular, the bypass valve 90 is controlled to be wide open at a large load change rate where the load fluctuates more than a preset threshold within a predetermined time, such as when the power plant 1 is started or when the load is cut off, or when the load fluctuates suddenly. There is a need. Therefore, the opening degree command output unit 101 outputs an opening degree control command when it is necessary to control the opening of the bypass valve 90 due to load fluctuation. That is, the opening degree control command is, for example, a command to start control in the opening direction of the bypass valve 90 . In particular, a large load change rate at which the load fluctuates more than a preset threshold within a predetermined period of time, such as at startup or load shedding, or an opening degree control command at the time of a sudden change in the load, causes the bypass valve 90 to change at a predetermined rate. It is preferable that the command is a command to control in the opening direction at a rate equal to or higher than the rate (rapid opening control command). The predetermined rate of change is, for example, 25 (%/sec) or more. The opening degree control command is used in the valve control section 102, which will be described later.

The valve control unit 102 controls the degree of opening of the bypass valve 90 . Specifically, the valve control unit 102 acquires the temperature Tr and the pressure Pr of the reheated steam output from the boiler 10 from the measuring instruments 106 and 107 . Then, a part of the reheat steam generated in the boiler 10 is sent to the condenser 64 through the bypass valve 90 and dumped, and control is performed so that the reheat steam pressure is kept constant. Also, from the obtained information and the degree of opening of the bypass valve 90, a bypass steam flow rate Fst, which is a reheat steam flow rate passing through the bypass valve 90 out of the reheat steam flow rate Fr generated in the boiler 10, is calculated.

If the bypass steam flow rate Fst is too high, it may damage the downstream condenser 64 . Therefore, the valve control unit 102 compares the calculated bypass steam flow rate Fst with the allowable steam flow rate of the condenser. do.

Specifically, the valve control unit 102 maintains the actual opening of the bypass valve 90 when the flow rate of the bypass steam reaches a preset allowable steam flow rate while the opening control command is being output. (fixed). The allowable steam flow rate is the allowable bypass steam flow rate in the condenser 64 . Therefore, the allowable steam flow rate is set based on the specifications of the condenser 64 (the design specifications including the capacity of the condenser 64, design temperature, design pressure, etc.). Note that the allowable steam flow rate may be set in consideration of the planned flow rate of the bypass steam in addition to the specifications of the condenser 64 . The planned flow rate of bypass steam is the maximum flow rate of bypass steam assumed in the planned operating state of the power plant 1 . Also, the allowable steam flow rate may be set by increasing the accuracy of the allowable flow rate in consideration of the flow rate of spray water, which will be described later. The actual opening degree of the control valve such as the bypass valve 90 can be detected by using, for example, an LVDT (differential transformer type displacement gauge).

The bypass steam flow rate Fst may be measured using a measuring instrument. In addition, the bypass steam flow rate Fst is set based on the pressure Pr, temperature Tr, enthalpy, and opening of the bypass valve 90 of the reheat steam generated in the boiler 10 (that is, the opening of the bypass valve 90 and the (based on the pressure difference of the bypass steam in ). Note that the method for acquiring the flow rate of bypass steam in the current operating state is not limited to the above, and can be applied. The bypass steam flow rate may be calculated by subtracting the reheat steam flow rate Flp required to be supplied to the intermediate pressure turbine 63 from the reheat steam flow rate Fr generated in the boiler 10 .

The valve control unit 102 compares the set allowable steam flow rate with the calculated bypass steam flow rate Fst, and when the bypass steam flow rate Fst reaches the allowable steam flow rate, a bypass steam flow rate greater than this is allowed to flow. The degree of opening of the bypass valve 90 is fixed to prevent this from happening. That is, the valve control unit 102 maintains the opening degree command for the bypass valve 90 at the time when the steam flow rate of the bypass line L6 reaches the allowable steam flow rate. More specifically, the valve control unit 102 controls the actual opening of the bypass valve 90 when the steam flow rate of the bypass line L6 reaches the allowable steam flow rate during the period when the steam flow rate of the bypass line L6 reaches the allowable steam flow rate. degree (opening command). For example, when the bypass steam flow rate Fst reaches the allowable steam flow rate, the valve control unit 102 tracks the opening command of the valve control unit 102 with the actual opening signal of the bypass valve 90 so that the bypass steam flow rate Fst becomes the allowable steam flow rate. While exceeding the steam flow rate, the actual opening degree of the bypass valve 90 at that time is maintained without being changed. Here, in order to prevent erroneous control of the bypass valve due to a deviation between the actual opening signal of the bypass valve 90 and the opening command from the valve control unit 102, the opening command of the bypass valve 90 should not be a continuous signal. By controlling the opening of the bypass valve 90 with the maintenance command signal, the opening command of the bypass valve 90 is fixed. That is, when the bypass steam flow rate Fst reaches the allowable steam flow rate, the opening command is tracked to the actual opening by the maintenance command signal.

Since the valve control unit 102 prevents bypass steam having a flow rate equal to or higher than the allowable steam flow rate from flowing into the condenser 64 , damage to the condenser 64 can be prevented more reliably.

Also, the valve control unit 102 acquires the dump tube temperature Te in the condenser 64 from the measuring device 105 . The dump tube temperature is the temperature of the steam inside the dump tube provided in the condenser 64 . The dump tube is a pipe for discharging (flashing) the bypass steam supplied through the bypass line L6 in the condenser 64 and condensing it. That is, the dump tube temperature is the temperature of the bypass steam in the condenser 64 and must not reach a predetermined specified value. Then, the valve control unit 102 determines whether the dump tube temperature Te is equal to or higher than a predetermined specified value, and if the dump tube temperature Te is equal to or higher than the specified specified value, the bypass valve 90 is closed. Control to fully close (interlock). The predetermined specified value is the maximum allowable steam temperature in the dump tube of the condenser 64 that is set so as not to damage the inside of the condenser 64. set. Since the valve control unit 102 has an emergency stop function that fully closes the bypass valve 90, damage to the condenser 64 can be prevented more reliably.

The temperature reduction control unit 103 controls the temperature reduction device 91 that reduces the temperature of the bypass steam supplied to the condenser 64 via the bypass line L6. Specifically, the temperature reduction control unit 103 performs enthalpy control on the flow rate of the spray water in the temperature reduction device 91 . That is, the temperature reduction control unit 103 uses the enthalpy of the bypass steam and the like to set the flow rate of the spray water to be applied to the bypass steam.

The spray water flow rate Fwset is given, for example, by the following equation.

In equation (1), Fst is the flow rate of the bypass steam, hr is the enthalpy of the reheated steam generated in the boiler 10, and hd is the bypass steam supplied to the condenser 64 (downstream of the desuperheater 91). is the enthalpy of the bypass steam) and hw is the enthalpy of the spray water. The enthalpy hr of the reheated steam generated in the boiler 10 is set based on the measured temperature Tr and pressure Pr of the reheated steam generated in the boiler 10 . In the steam line L5 (downstream of the boiler 10), a measuring device 106 for measuring the temperature Tr of the reheated steam and a measuring device 107 for measuring the pressure Pr of the reheated steam are provided. Since the enthalpy hd of the bypass steam and the enthalpy hw of the spray water that are supplied to the dump tube of the condenser 64 can be approximated to be substantially constant in the operating state of the power plant 1, they are set in advance as fixed values. good too. The bypass steam flow rate Fst is based on the degree of opening of the bypass valve 90 and the pressure difference of the bypass steam before and after the bypass valve 90 (that is, the pressure Pr of the reheat steam generated in the boiler 10, the temperature Tr, the pressure of the bypass valve 90 , based on the enthalpy difference, the flow coefficient due to the opening of the bypass valve 90). A sum of the bypass steam flow rate Fst and the spray water flow rate Fwset is fed to the dump tube of the condenser 64 .

The dump tube temperature Te in the condenser 64 is obtained from the measuring device 105, and the flow rate Fwset of the spray water is set so as not to reach a predetermined specified value. In this regard, the temperature reduction control unit 103 calculates the flow rate Fwset of the spray water using the equation (1) as enthalpy control, and controls the opening of the spray valve 92 based on the calculated flow rate Fwset of the spray water.

In this manner, the enthalpy control of the spray water is executed in the temperature reduction control unit 103, and in a situation where the bypass steam and the spray water are not sufficiently mixed in the desuperheater 91, Even if it is difficult to measure the steam temperature, it is possible to calculate the required spray water flow rate Fwset corresponding to the bypass steam flow rate Fst. That is, even when the load changes at a large load change rate exceeding a preset threshold value within a predetermined time such as at startup or load cutoff, or when the bypass steam flow rate Fst changes suddenly when the load changes suddenly, the dump tube temperature The spray water flow rate Fwset can be appropriately set so that Te does not exceed a predetermined specified value.

Next, the bypass valve 90 control processing by the valve control unit 102 described above will be described with reference to FIG. The flow shown in FIG. 5 is repeatedly executed at a predetermined control cycle while the power plant 1 is in operation.

First, the temperature Tr and pressure Pr of reheated steam generated in the boiler 10 are obtained (S101). The temperature Tr and the pressure Pr are acquired from the measuring instruments 106 and 107 provided in the power plant 1 .

Next, an opening command for the bypass valve 90 is output so that the target pressure value of the reheat steam is met and the detected pressure Pr is kept constant (S102).

Next, the bypass steam flow rate Fst is determined based on the degree of opening of the bypass valve 90 and the pressure difference of the bypass steam before and after the bypass valve 90 (that is, the reheat steam pressure Pr, the temperature Tr, the enthalpy difference of the bypass valve 90, (S103).

Next, it is determined whether or not the bypass steam flow rate Fst has reached the allowable steam flow rate (S104). If the bypass steam flow rate Fst has not reached the allowable steam flow rate (NO judgment in S104), the process is terminated, and thereafter the above process is repeatedly executed from the beginning (S101) at a predetermined control cycle.

When the bypass steam flow rate Fst reaches the allowable steam flow rate (YES determination in S104), the opening command for the bypass valve 90 at the time the bypass steam flow rate reaches the allowable steam flow rate is By tracking and maintaining the actual opening signal of the bypass valve 90, the actual opening of the bypass valve 90 is maintained (fixed) (S105). The above processing from S101 to S105 is repeatedly executed at a predetermined control cycle.

When the bypass steam flow rate Fst is estimated, the process may be executed from S105 after estimating the bypass steam flow rate Fst.

Next, the spray valve control processing by the temperature reduction control section 103 will be described with reference to FIG. The flow shown in FIG. 6 sets the spray water flow rate Fwset in correspondence with the bypass steam flow rate Fst so that the dump tube temperature Te does not exceed a predetermined specified value. Together with the flow of the control process, it is repeatedly executed at a predetermined control cycle while the power plant 1 is in operation.

First, the dump tube temperature Te is acquired (S201). The dump tube temperature Te is obtained from the measuring instrument 105 .

Next, it is determined whether or not the dump tube temperature Te is equal to or higher than a predetermined specified value (S202). When the dump tube temperature Te is equal to or higher than a predetermined specified value (YES determination in S202), control is performed to fully close the bypass valve 90 (S203). After the process is terminated, the above process is repeatedly executed from the beginning (S201) at a predetermined control cycle.

If the dump tube temperature Te is not equal to or higher than the predetermined specified value (NO judgment in S202), the flow rate of the spray water is appropriately set, and the spray valve 92 is controlled (S204). Enthalpy control is used for spray water flow rate setting. That is, using equation (1), the flow rate Fwset of the spray water is set corresponding to the bypass steam flow rate Fst. Then, the above process is repeatedly executed at a predetermined control cycle. Therefore, the spray water flow rate Fwset can be stably set even when the bypass steam flow rate Fst set in FIG. can be done.

Next, control of the bypass valve 90 by the control device 100 described above will be described with reference to FIG. In FIG. 7, the vertical axis is the load (boiler load) and the horizontal axis is time. In the lower part, a diagram is shown in which the degree of opening of the bypass valve 90 is taken as the vertical axis and time is taken as the horizontal axis. In FIG. 7, each horizontal axis (time axis) has a common scale. FIG. 7 exemplifies the case where the load is suddenly changed and lowered, and shows changes over time in the load, the opening command value of the inlet valve, and the opening of the bypass valve 90 .

At time T1, when the load suddenly changes (decreases), the opening degree of the turbine steam valve 82 is controlled in the closing direction in accordance with the sudden load change. When the opening degree of the turbine steam valve 82 is controlled in the closing direction, the amount of steam supplied to the intermediate pressure turbine 63 decreases, so it is necessary to increase the flow rate of the bypass steam. Therefore, at time T1, opening control (rapid opening control) of the bypass valve 90 is executed.

When the bypass valve 90 is controlled to open and the degree of opening increases, the flow rate of the bypass steam increases. Then, at time T2, the flow rate of the bypass steam reaches the allowable steam flow rate. For this reason, the control device 100 maintains the opening degree α of the bypass valve 90 at the time when the flow rate of the bypass steam reaches the allowable steam flow rate, and prevents the bypass valve 90 from opening any further (the flow rate of the bypass steam is increased). The bypass valve 90 is restricted so as not to increase. When the bypass valve 90 is not restricted, as indicated by the dashed line, the opening of the bypass valve 90 is greater than the opening α, and a larger flow rate of bypass steam is condensed. It will flow into the container 64 .

At time T3, the process of decreasing the amount of steam supplied to the intermediate pressure turbine 63 ends, and at time T4, the process of rapidly changing and decreasing the load ends.

When the load reduction process is completed, the flow rate of the reheat steam generated in the boiler 10 is maintained in a reduced state. Therefore, the flow rate of the bypass steam is controlled in the closing direction to reduce the flow rate of the bypass steam. At time T5, the flow rate of the bypass steam becomes less than the allowable steam flow rate, and the opening degree maintenance process for the bypass valve 90 ends. That is, during the period ΔT, the flow rate of the bypass steam due to the open control that does not exceed the opening degree α of the bypass valve 90 is reliably prevented from exceeding the allowable steam flow rate, and damage to the condenser 64 is prevented. be able to.

As described above, according to the bypass control system of the power plant 1, its control method and control program, and the power plant 1 according to the present embodiment, steam in the bypass line L6 is By maintaining the actual opening degree of the bypass valve 90 when the flow rate reaches the preset allowable steam flow rate, the flow rate of steam flowing through the bypass line L6 does not exceed the allowable steam flow rate. 64 can be prevented from being damaged more reliably.

Further, when the steam flow rate of the bypass line L6 reaches the allowable steam flow rate due to rapid opening control of the bypass valve 90, the actual opening degree of the bypass valve 90 at the time when the steam flow rate of the bypass line L6 reaches the allowable steam flow rate is maintained. Therefore, it is possible to more reliably prevent the steam flow rate from exceeding the allowable steam flow rate.

Further, by maintaining the opening command for the bypass valve 90 at the time when the steam flow rate of the bypass line L6 reaches the allowable steam flow rate, fluctuations in the actual opening degree of the bypass valve 90 due to fluctuations in the opening command are suppressed, and the allowable It is possible to maintain the actual opening when the steam flow rate is reached.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention.

1: Power plant 10: Boiler 11: Furnace 12: Combustion device 13: Flue 21-25: Combustion burner 26-30: Pulverized coal supply pipe 31-35: Crusher 36: Wind box 37: Air duct 38: Blower 39 : Additional air nozzle 40 : Branch air ducts 41-43 : Superheater 44 : Reheater (second reheater)
45: reheater (first reheater)
46: Economizer (second economizer)
47: Economizer (first economizer)
48 : Gas duct 49 : Air heater 50 : Denitration catalyst 51 : Soot and dust treatment device 52 : Induced draft fan 53 : Chimney 60 : Combustion gas passage 61 : Steam turbine 62 : High pressure turbine 63 : Intermediate pressure turbine 64 : Condenser 65 : Inlet header 66 : Feed water pump 67 : Intermediate header 68 : Outlet header 69 : Steam drum 70 : Inlet header 71 : Intermediate header 72 : Outlet header 80 : Soot blower 81 : Main steam valve 82 : Turbine steam valve 83 : Condensate pump 84 : Low pressure feed water Heater 85 : High-pressure water supply heater 86 : Discharge valve 87 : Control valve 90 : Bypass valve 91 : Attemperator 92 : Spray valve 93 : Orifice 100 : Control device 101 : Opening command output unit 102 : Valve control unit 103 : Temperature reduction Control units 105-107: Measuring device 108: Flow meter BL: Bypass units L1, L2: Water supply lines L3, L4, L5: Steam line L6: Bypass line L7: Spray water supply line

Claims (8)

A reheater for outputting reheated steam, a turbine to which the reheated steam is supplied, a condenser for condensing the steam discharged from the turbine, and a part of the reheated steam bypassing the turbine a bypass line that feeds the steam to the condenser, a bypass valve that adjusts the steam flow rate of the bypass line, a desuperheater that reduces the temperature of the steam in the bypass line, and condensate generated in the condenser to the desuperheater as spray water, and a spray valve for adjusting the flow rate of the spray water flowing through the spray water supply line, a bypass control system for a power plant,
an opening command output unit that outputs an opening control command for the bypass valve according to the operating state of the power plant;
a valve control unit that maintains the actual degree of opening of the bypass valve when the flow rate of steam in the bypass line reaches a preset allowable steam flow rate while the degree-of-opening control command is being output;
A detemperature control unit that controls the desuperheater and controls the opening of the spray valve,
The temperature reduction control unit uses the steam flow rate in the bypass line, the enthalpy of the reheated steam, the enthalpy of the steam in the bypass line supplied to the condenser, and the enthalpy of the spray water as parameters. controlling the opening of the spray valve based on the flow rate of water;
A bypass control system for a power plant, wherein the valve control unit maintains an opening degree command for the bypass valve, which is a single-shot signal, at the time when the steam flow rate in the bypass line reaches the allowable steam flow rate. The valve control unit maintains the actual opening degree of the bypass valve at the time when the steam flow rate in the bypass line reaches the allowable steam flow rate during a period in which the steam flow rate in the bypass line reaches the allowable steam flow rate. The power plant bypass control system according to claim 1 . 3. The power generation according to claim 1, wherein the opening command output unit outputs the opening control command when the power plant is started or when the load fluctuates by a preset threshold value or more within a predetermined time. Plant bypass control system. 4. The power plant bypass control according to any one of claims 1 to 3, wherein the valve control unit closes the bypass valve when a dump tube temperature in the condenser reaches or exceeds a predetermined specified value. system. The power plant bypass control system according to any one of claims 1 to 4, wherein the allowable steam flow rate is set based on the specifications of the condenser. a reheater that outputs reheated steam;
a turbine to which the reheat steam is supplied;
a condenser for condensing the steam discharged from the turbine;
a bypass line that bypasses a portion of the reheat steam to the condenser;
a desuperheater for reducing the temperature of steam in the bypass line;
a bypass valve that adjusts the steam flow rate of the bypass line;
A power plant bypass control system according to any one of claims 1 to 5 ;
A power plant with a A reheater for outputting reheated steam, a turbine to which the reheated steam is supplied, a condenser for condensing the steam discharged from the turbine, and a part of the reheated steam bypassing the turbine a bypass line that feeds the steam to the condenser, a bypass valve that adjusts the steam flow rate of the bypass line, a desuperheater that reduces the temperature of the steam in the bypass line, and condensate generated in the condenser to the desuperheater as spray water; and a spray valve for adjusting the flow rate of the spray water flowing through the spray water supply line.
an opening command output step of outputting an opening control command for the bypass valve according to the operating state of the power plant;
a valve control step of maintaining the actual opening of the bypass valve when the steam flow rate of the bypass line reaches a preset allowable steam flow rate while the opening control command is being output;
a temperature reduction control step of controlling the desuperheater and controlling the opening of the spray valve;
In the temperature reduction control step, the spray calculated using the steam flow rate in the bypass line, the enthalpy of the reheated steam, the enthalpy of the steam in the bypass line supplied to the condenser, and the enthalpy of the spray water as parameters. controlling the opening of the spray valve based on the flow rate of water;
A bypass control method for a power plant, wherein, in the valve control step, the opening command of the bypass valve, which is a single-shot signal, is maintained when the steam flow rate of the bypass line reaches the allowable steam flow rate. A reheater for outputting reheated steam, a turbine to which the reheated steam is supplied, a condenser for condensing the steam discharged from the turbine, and a part of the reheated steam bypassing the turbine a bypass line that feeds the steam to the condenser, a bypass valve that adjusts the steam flow rate of the bypass line, a desuperheater that reduces the temperature of the steam in the bypass line, and condensate generated in the condenser to the desuperheater as spray water, and a spray valve for adjusting the flow rate of the spray water flowing through the spray water supply line. A bypass control program for a power plant,
an opening command output process for outputting an opening control command for the bypass valve according to the operating state of the power plant;
valve control processing for maintaining the actual opening of the bypass valve when the steam flow rate of the bypass line reaches a preset allowable steam flow rate while the opening control command is being output;
Controlling the desuperheater and causing a computer to execute a temperature reduction control process for controlling the opening degree of the spray valve,
In the temperature reduction control process, the spray calculated using the steam flow rate in the bypass line, the enthalpy of the reheated steam, the enthalpy of the steam in the bypass line supplied to the condenser, and the enthalpy of the spray water as parameters controlling the opening of the spray valve based on the flow rate of water;
The valve control process is a bypass control program for a power plant that maintains an opening degree command for the bypass valve, which is a single-shot signal, at the time when the steam flow rate in the bypass line reaches the allowable steam flow rate .

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