JP2022124996A - Thermal power generation plant and control method for thermal power generation plant - Google Patents

Abstract

To provide a thermal power generation technology capable of flexibly responding to a change of power generation amount of renewable energy while maintaining high operability.SOLUTION: A thermal power generation plant includes: a boiler; a steam turbine driven by steam from the boiler; a turbine bypass line for sending steam bypassing the steam turbine; a condenser cooling exhaust gas of the steam turbine and generating condensed water; a low-pressure feed water heater heating the condensed water by using extraction steam from the steam turbine; and a deaerator deaerating the condensed water by using extraction steam. The thermal power generation plant also includes: a hot water heater converting condensed water supplied from the condenser into high temperature water by using main steam in the turbine bypass line as a heat source; a high temperature water tank storing the high temperature water; and a high temperature water pump sending the high temperature water stored in the high temperature water tank to a back flow side of the low-pressure feed water heater or the deaerator.SELECTED DRAWING: Figure 1

Description

The present invention relates to a thermal power plant using steam generated by a boiler and a control method for the thermal power plant.

2. Description of the Related Art A thermal power plant that uses steam generated by a boiler (steam generator) to drive a steam turbine is known. As a large-scale power source in conventional electric power systems, this type of thermal power plant mainly bears the base load, and has contributed to the stable supply of domestic power together with the ability to respond to load fluctuations of GTCC (gas turbine combined cycle) plants.

By the way, due to the recent increase in the amount of renewable energy-derived power connected to the power system, the ratio of the power transmission amount of thermal power plants and GTCC plants in the power system during the daytime is decreasing year by year. Although it is necessary to reduce the number of units in operation to the minimum required level for maintaining the frequency of the power grid and adjusting supply and demand, there is still a possibility that the surplus renewable energy-derived power will be refused connection to the power grid. There is

In order to further expand renewable energy-derived power to the power system, it is necessary to reduce the amount of power transmitted at the plant's lowest load among conventional large-scale power sources, and the time required to restart the plant in DSS (daily start-stop) operation. It is essential to improve the operability of thermal power plants with long life spans.

Japanese Utility Model Laid-Open No. 64-54605

In Patent Document 1, part of the feedwater is stored in a hot water tank during low-load operation of the plant, and the hot water is discharged to the high-pressure feedwater heater group at the time of peak load of power demand, and air is extracted to the high-pressure feedwater heater. By cutting or decreasing, the output of the steam turbine is increased.

On the other hand, the plant low-load operation in Patent Document 1 is based on the premise that all the main steam and reheat steam generated in the boiler are introduced into the steam turbine through the governor to generate power, and can be realized in a thermal power plant. The minimum load is the amount obtained by subtracting the extraction air in the turbine from the heat amount of the main steam and reheat steam generated at the boiler minimum load, generally 25% load, even at the minimum, 10% load or more power It was essential to transmit power to the grid.

By making it possible to reduce the power sent from a coal-fired thermal power plant (thermal power plant) to the power system from the conventional minimum 10% load to almost 0% load (parallel non-transmission operation), In addition to expanding the range of renewable energy accepted into the electric power system, by always paralleling the turbine generator of the coal-fired thermal power plant (thermal power plant) in the same time period, renewable energy accompanying changes in weather It is desired to increase the amount of power transmission quickly in response to the decrease in the amount of power generated, and contribute to the maintenance of the frequency of the power supply system and the adjustment of supply and demand.

In addition, in conventional thermal power plants that use light oil for startup fuel and are operated with DSS, by making it possible to operate the plant continuously using inexpensive coal, it is possible to reduce fuel costs and operate DSS. Therefore, it is desired to avoid the wear and tear of equipment associated with this, and thus avoid troubles at the time of start-up.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal power generation technology capable of flexibly coping with changes in the power generation amount of renewable energy while maintaining high operability.

The present invention comprises a boiler, a steam turbine driven by steam from the boiler, a turbine bypass line for sending steam bypassing the steam turbine, and a condenser for cooling the exhaust of the steam turbine to produce condensate. A thermal power plant comprising: a water unit; a low-pressure feed water heater that heats the condensate with the steam extracted from the steam turbine; and a deaerator that deaerates the condensate with the steam extracted from the steam turbine, A hot water heater using the main steam of the turbine bypass line as a heat source and using the condensate supplied from the condenser as high temperature water, a high temperature water tank for storing the high temperature water, and the water stored in the high temperature water tank and a high-temperature water pump for sending high-temperature water to the downstream of the low-pressure feed water heater or to the deaerator.

ADVANTAGE OF THE INVENTION According to this invention, the thermal power generation technology which can respond flexibly to the change of the electric power generation amount of renewable energy can be provided, maintaining high operability.

1 is a schematic configuration diagram of a thermal power plant according to one embodiment; FIG. 1 is a schematic configuration diagram of a thermal power plant similar to one embodiment; FIG. It is an example of operation during heat storage operation of a thermal power plant according to one embodiment. It is an example of operation at the time of heat radiation operation of the thermal power plant according to one embodiment. 1 is a schematic configuration diagram showing the range of a water heat storage system according to one embodiment; FIG. 1 is a schematic configuration diagram for explaining an auxiliary steam line of a thermal power plant according to one embodiment; FIG. 1 is a schematic configuration diagram of a control device for a thermal power plant according to one embodiment; FIG. It is a schematic block diagram of the thermal power plant which concerns on the modification 1 of one embodiment. FIG. 7 is a schematic configuration diagram of related parts of a thermal power plant according to Modification 2 of one embodiment; 9 is a flow chart of confluence switching processing of a thermal power plant according to Modification 2 of one embodiment. FIG. 11 is an explanatory diagram for explaining partial water flow in a thermal power plant according to Modification 3 of one embodiment; FIG. 11 is a schematic configuration diagram of related parts of a thermal power plant according to Modification 4 of one embodiment; FIG. 11 is an explanatory diagram for explaining heat storage operation of a thermal power plant according to Modification 4 of one embodiment; FIG. 11 is an explanatory diagram for explaining heat dissipation operation of a thermal power plant according to Modification 4 of one embodiment; FIG. 11 is a schematic configuration diagram of related parts of a thermal power plant according to Modification 5 of one embodiment;

Several embodiments of the present invention will now be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiment or shown in the drawings are not meant to limit the scope of the present disclosure, but are merely illustrative examples. do not have.
For example, expressions denoting relative or absolute arrangements such as "in a direction", "along a direction", "parallel", "perpendicular", "center", "concentric" or "coaxial" are strictly not only represents such an arrangement, but also represents a state of relative displacement with a tolerance or an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which express that things are in the same state, not only express the state of being strictly equal, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, expressions that express shapes such as squares and cylinders do not only represent shapes such as squares and cylinders in a geometrically strict sense, but also include irregularities and chamfers to the extent that the same effect can be obtained. The shape including the part etc. shall also be represented.
On the other hand, the expressions "comprising", "comprising", "having", "including", or "having" one component are not exclusive expressions excluding the presence of other components.

In the following embodiments, a thermal power plant 1 will be described as an example of a coal-fired thermal power plant that is at least one embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a thermal power plant 1 according to one embodiment.

The thermal power plant 1 includes a boiler 2, a steam turbine 4, a condenser 13, a water heat storage system 70, and a controller 80 (see FIG. 7). In this embodiment, the thermal power plant 1 includes a high-pressure turbine 4A, an intermediate-pressure turbine 4B, and a low-pressure turbine 4C as the steam turbines 4, but the thermal power plant 1 has one or two steam turbines 4. , or four or more steam turbines 4 .

The boiler 2 is a steam generator that can generate superheated steam by exchanging heat generated by burning pulverized fuel with feed water or steam. The boiler 2 is, for example, a coal-fired (pulverized coal-fired) boiler that uses pulverized coal (carbon-containing solid fuel) as pulverized fuel and burns this pulverized fuel with a burner.

In this embodiment, a coal-fired boiler is exemplified as the boiler 2, but the boiler 2 uses solid fuel such as biomass fuel, PC (petroleum coke) fuel generated during petroleum refining, and petroleum residue. You may In addition, the boiler 2 can use not only solid fuel but also petroleum such as heavy oil, light oil, and heavy oil, and liquid fuel such as factory waste liquid as fuel, and gas fuel (natural gas, By-product gases, etc.) can also be used. Furthermore, the boiler 2 may be a mixed firing boiler that uses a combination of these fuels.

Steam (superheated steam) generated by the boiler 2 is supplied to the steam turbine 4 via the main steam line 6 . In this embodiment, the steam from the boiler 2 is first supplied to the high pressure turbine 4A provided upstream, thereby driving the high pressure turbine 4A.

The steam that has finished work in the high-pressure turbine 4A is reheated by the reheater 35 through the reheat steam line 9, and supplied to the intermediate-pressure turbine 4B provided downstream, whereby the steam is supplied to the intermediate-pressure turbine 4B. to drive. A reheat steam line 9 connects between the high pressure turbine 4A and the intermediate pressure turbine 4B. The steam that has finished work in the intermediate pressure turbine 4B is supplied via the intermediate pressure turbine exhaust line 12 to the low pressure turbine 4C provided downstream, thereby driving the low pressure turbine 4C. The intermediate pressure turbine exhaust line 12 connects between the intermediate pressure turbine 4B and the low pressure turbine 4C. The steam that has finished work in the low-pressure turbine 4C is discharged to the condenser 13 to generate condensate.

A turbine bypass line 7 connecting the main steam line 6 and the condenser 13 is also provided. A turbine bypass valve 8 is provided in the turbine bypass line 7, and by adjusting the degree of opening of the turbine bypass valve 8, part of the steam flowing through the main steam line 6 bypasses the steam turbine 4 and is condensed. It can be discharged to the vessel 13.

The output shafts of the high pressure turbine 4A, the intermediate pressure turbine 4B and the low pressure turbine 4C are connected to the rotating shaft of the generator 5. The power generator is driven by power from these steam turbines 4 to generate power. Electric power generated by the generator is supplied to a power system (for example, a commercial system) via a power transmission line (not shown).

The high-pressure turbine 4A, the intermediate-pressure turbine 4B, and the low-pressure turbine 4C may each have a common output shaft, and the output shaft may be connected to a common generator. A first generator to which the output shaft of the intermediate pressure turbine 4B is connected and a second generator to which the output shaft of the low pressure turbine 4C is connected may be provided.

6, the steam extracted from the high-pressure turbine 4A and the intermediate-pressure turbine 4B (extracted steam; hb, ib) is supplied to the second high-pressure feed water heater 21 and the first high-pressure feed water heater, respectively. 20. A portion of the exhaust steam (he) from the high pressure turbine 4A is also supplied to the second high pressure feed water heater 21 . Saturated drain (condensed from extraction steam hb and exhaust steam he) discharged from the second high pressure feed water heater 21 is supplied to the first high pressure feed water heater 20 . Drain discharged from the first high-pressure feed water heater 20 (condensed saturated drain and extracted steam ib discharged from the second high-pressure feed water heater 21 ) is supplied to the deaerator 17 . Also, part of the exhaust steam (ie) from the intermediate pressure turbine 4B is supplied to the deaerator 17 . Also, the steam extracted from the low-pressure turbine 4</b>C (low-pressure extracted steam; lb) is supplied to the low-pressure feed water heater 16 . Saturated drain (condensed low-pressure bleed air lb) discharged from the low-pressure feed water heater 16 is supplied to the condenser 13 . In order to avoid complication, the auxiliary steam lines from each steam turbine 4 to each of the high-pressure feed water heaters 21 and 20 and the low-pressure feed water heater 16 are omitted as appropriate in each drawing.

The condensate generated in the condenser 13 is pressurized by the condensate pump 14, supplied to the low-pressure feed water heater 16 through the condensate line 15, and heated by the extracted steam (lb) from the low-pressure turbine 4C. into the deaerator 17. In the deaerator 17, condensate is deaerated by part of the exhaust steam (ie) of the intermediate pressure turbine 4B. The condensate degassed by the deaerator 17 is pressurized by the feed water pump 18, supplied to the first high pressure feed water heater 20 and the second high pressure feed water heater 21 via the water feed line 19, and extracted from the intermediate pressure turbine 4B. It flows into the boiler 2 after being heated by the steam (ib), the steam extracted from the high-pressure turbine 4A and the exhaust steam (hb, he).

Boiler 2 is operated in subcritical conditions at low load conditions. At that time, the steam mixed water at the furnace outlet of the boiler 2 is separated from steam by the water drain separator 31, the steam is sent to the superheater 36, and the saturated drain is sent to the condenser via the water drain separator drain line 33 and the water drain separator drain control valve 32. Flow into 13.

Next, the water heat storage system 70 provided in the thermal power plant 1 will be described. The thermal power plant 1 of this embodiment performs low-load operation. The low-load operation is an operation in which the boiler 2 and the steam turbine 4 are each under the minimum load. For example, the output of the boiler 2 is lowered to 15% of the minimum output, the output of the steam turbine 4 is lowered to 5%, and all the output of the steam turbine 4 is used for in-house power. As a result, the generator circuit breaker is closed, and the power transmission is set to 0 while maintaining the state of connection to the grid, so-called grid non-transmission operation (parallel non-transmission operation) is realized.

The water heat storage system 70 of this embodiment corresponds to an output of 10%, which is the difference between, for example, 15% of the minimum load of the boiler 2 and 5% of the load of the steam turbine 4, which occurs during low load operation. The above heat is stored as hot water. Specifically, during low-load operation, the main steam in the turbine bypass line 7 is used as a heat source to heat the condensate supplied from the condenser 13 and store it as high-temperature water. Then, the stored high-temperature water is supplied to the deaerator during subsequent heat dissipation operation (during high-load operation).

As a result, the water heat storage system 70 achieves a reduction in the system output power of the thermal power plant 1 over a long period of time. Also, the water heat storage system 70 cuts the low pressure extraction air (lb) from the steam turbine 4 to the low pressure feed water heater 16 during high load operation after low load operation. By cutting the low-pressure extracted air (lb), it is possible to increase the output of the steam turbine 4 corresponding to the amount of heat of the cut low-pressure extracted air (lb). Alternatively, since the boiler steam flow rate corresponding to the increased output of the steam turbine 4 is reduced, the amount of fuel input to the boiler 2 can be reduced. Hereinafter, the details of the water heat storage system 70 of this embodiment, which realizes this, will be described.

The water heat storage system 70 includes a hot water heater 51, a high temperature water pump 52, a high temperature water tank 53, and a low temperature water tank 59, as indicated by thick lines in FIG. The hot water pump 52 comprises a first hot water pump 52A and a second hot water pump 52B. The water heat storage system 70 also includes a heat storage steam line 55 , a heat storage drain line 57 , a low temperature water supply line 49 , a low temperature water storage line 58 and a makeup water line 60 .

The heat storage steam line 55 is a line that supplies steam passing through the turbine bypass line 7 branched from the main steam line 6 to the hot water heater 51 , and includes a heat storage steam flow control valve 54 . The heat storage drain line 57 is a line that supplies saturated drain separated by the water drain separator 31 to the hot water heater 51 , and includes a heat storage drain flow rate control valve 56 .

The low-temperature water supply line 49 is a line branched from the condensate line 15 for supplying condensate supplied from the condensate pump 14 to the hot water heater 51 , and includes a low-temperature water flow control valve 50 .

The hot water heater 51 brings the incoming main steam and saturated drain into contact with the supplied low temperature water to produce high temperature water. The generated hot water is, for example, 140°C. The hot water heater 51 is, for example, a direct contact feedwater heater that mixes and heats incoming condensate (low-temperature water), main steam, and saturated drain.

The water heat storage system 70 shown in FIGS. 1 and 5 includes, as the high-temperature water pumps 52, a first high-temperature water pump 52A and a second high-temperature water pump 52B. The first high-temperature water pump 52A feeds high-temperature water produced by the hot water heater 51 to the high-temperature water tank 53 . The second high-temperature water pump 52B sends the high-temperature water stored inside the high-temperature water tank 53 to the deaerator 17 . The high-temperature water may be supplied to the deaerator 17 alone, or may be supplied together with the low-pressure water supply at the outlet of the low-pressure water supply heater 16 .

In addition, the first high-temperature water pump 52A and the second high-temperature water pump 52B do not necessarily need to be separately installed, and one or more high-temperature water pumps 52 having both roles are installed, and the hot water heater 51 and the high temperature The outlet lines of the water tank 53 may be connected to the inlets of the high-temperature water pumps 52, respectively, and switched appropriately.

The high-temperature water tank 53 is a tank that stores high-temperature water generated by the hot water heater 51 . Since the temperature of the high-temperature water stored inside the high-temperature water tank 53 is approximately 140° C., the high-temperature water tank 53 must have a structure that can withstand the saturated vapor pressure of such high-temperature water. Adequate insulation should be provided to minimize heat dissipation from the water. The capacity of the high-temperature water tank 53 may be arbitrarily determined at the design stage according to the daily low-load operation time required for the thermal power plant 1 .

The low-temperature water storage line 58 is a line for supplying condensate supplied from the condensate pump 14 to the low-temperature water tank 59 . The supplied condensate is stored in the low-temperature water tank 59 .

The makeup water line 60 is a line for supplying the low-temperature water stored in the low-temperature water tank 59 to the condenser 13 .

The low-temperature water tank 59 is a tank that stores surplus water in the condenser 13 as make-up water to the condenser 13 . In this embodiment, it has a water storage amount equal to or greater than the water storage amount of the high-temperature water tank 53 .

As shown in FIG. 7, the control device 80 receives instructions from the outside (such as a control console 81 placed in the power plant) or various sensors installed in the thermal power plant 1, including a temperature sensor and a water level sensor. The opening and closing of each control valve (valve) in the thermal power plant 1 is controlled in accordance with the signal from. The control valve is controlled to open and close according to, for example, heat storage operation (low load operation) and heat dissipation operation (high load operation), which will be described later. The controller 80 also controls the output of each pump. The control device 80 includes, for example, a CPU, a memory, and a storage device, and implements the above-described control by causing the CPU to load a program stored in the storage device in advance into the memory and execute the program.

Note that the thermal power plant 1 may bypass the steam turbine 4 and discharge part of the steam flowing through the reheat steam line 9 to the condenser 13, like the thermal power plant 1 shown in FIG. . In this case, the connection destination of the turbine bypass line 7 is the outlet of the high pressure turbine 4A of the reheat steam line 9, and the low pressure turbine bypass line 10 is branched from the upstream of the inlet of the intermediate pressure turbine 4B of the reheat steam line 9 to branch the low pressure turbine bypass valve. 11 to condenser 13 .

<Heat storage operation>
FIG. 3 shows the heat storage operation of the thermal power plant 1, that is, the storage form of high-temperature water during low-load operation. During low-load operation, the amount of main steam generated in the boiler 2 is greater than the amount of main steam consumed for power generation in the steam turbine 4, resulting in surplus steam. Further, the boiler 2 is operated in a subcritical state, and saturated drain continuously flows into the water drain separator 31 .

Upon receiving an instruction to perform heat storage operation, the control device 80 opens the heat storage steam flow rate control valve 54 , the heat storage drain flow rate control valve 56 and the low temperature water flow rate control valve 50 . As a result, as indicated by the thick line in FIG. 3, all or part of the main steam that is surplus in the main steam line 6 is transferred to the hot water heater 51 via the heat storage steam line 55 and the heat storage steam flow rate control valve 54. supplied. All or part of the saturated drain flowing out of the water drain separator 31 is supplied to the hot water heater 51 via the heat storage drain line 57 and the heat storage drain flow rate control valve 56 . Furthermore, as indicated by the thick line in FIG. 3, all or part of the condensate supplied from the condensate pump 14 is passed through the low-temperature water supply line 49 and the low-temperature water flow control valve 50 as low-temperature water to the hot water heater. 51.

The hot water heater 51 brings the incoming main steam and saturated drain into contact with low-temperature water to generate hot water of about 140°C. The amounts of main steam and saturated drain that flow in are uniquely determined by the operating conditions of the boiler 2 and steam turbine 4 . The controller 80 controls the low-temperature water flow rate by controlling the low-temperature water flow rate control valve 50 so that the temperature of the high-temperature water at the outlet of the hot water heater 51 is about 140°C. Moreover, the control device 80 always controls the water level of the hot water heater 51 by controlling the first high-temperature water pump 52A. If the main steam pressure rises temporarily or the water level of the water drain separator 31 rises due to a change in the operating state of the boiler 2 or the like, the control device 80 closes the turbine bypass valve 8 and the water drain separator drain control valve 32. open to discharge excess steam and saturated drain to the condenser 13 through these control valves. Thereby, the hot water heater 51 can maintain constant operation.

High-temperature water supplied from the first high-temperature water pump 52A is stored in the high-temperature water tank 53 . The heat storage operation is completed when the high-temperature water tank 53 is full or when the low-load operation of the thermal power plant 1 ends. The control device 80 monitors the water level of the high-temperature water tank 53, and when it determines that the tank is full, or when it receives a signal indicating that the low-load operation has ended, the heat-storage steam flow control valve 54 and the heat-storage drain The control valves of the flow rate control valve 56 and the low temperature water flow rate control valve 50 are closed. The water level of the high-temperature water tank 53 is acquired from a water level sensor provided in the high-temperature water tank 53 .

While the high-temperature water is stored in the high-temperature water tank 53, a considerable amount of water is condensed from the low-temperature water tank 59 through the make-up water line 60 by, for example, differential pressure, as indicated by the thick line in FIG. supplied to the vessel 13.

In addition, when the output of the steam turbine 4 is in a low load operation of about 5% of the rated load, the control device 80 controls the high pressure turbine 4A, the intermediate pressure turbine 4B, the low pressure turbine 4C from the second high pressure feed water heater 21, (1) Control to cut the bleeding to the high-pressure feed water heater 20 and the low-pressure feed water heater 16 . This is because, during low-load operation, in each steam turbine 4, sufficient pressure is not obtained to push the saturated drain generated in each feed water heater to the deaerator or condenser.

When the steam turbine 4 is in low-load operation, the main steam temperature at the inlet of the high-pressure turbine 4A and the reheat steam temperature at the inlet of the intermediate-pressure turbine 4B are appropriately adjusted to avoid the exhaust steam from the low-pressure turbine 4C entering a dry region. There is a need. For this purpose, a desuperheater may be installed in each of the main steam line 6 and the reheat steam line 9 at the outlet of the boiler 2 to supply a desuperheating spray.

If the low-load operation of the thermal power plant 1 cannot be terminated even when the high-temperature water tank 53 is full, and the main steam from the boiler 2 and the saturated drain from the water drain separator 31 continue to be in a surplus state, these is supplied to the condenser 13 via the turbine bypass line 7 and the water drain separator drain line 33, the low load operation of the thermal power plant 1 can be continued. However, at that time, the steam that has flowed into the condenser 13 and the heat of the drain are released to a condenser cooling medium such as seawater.

<Heat dissipation operation>
FIG. 4 shows the heat dissipation operation of the thermal power plant 1, that is, the release form of high-temperature water during high-load operation. High-load operation here generally refers to operation at 30% or more of the rated load of the thermal power plant.

The control device 80 operates the second high-temperature water pump 52B upon receiving the instruction for heat dissipation operation. As a result, the high-temperature water stored in the high-temperature water tank 53 is supplied to the condensate line 15 by the second high-temperature water pump 52B and flows into the deaerator 17 . In this case, the condensate from the condenser 13 is heated by the low-pressure feed water heater 16 through the condensate line 15, as indicated by the thick dashed line in FIG. Alternatively, all or part of the condensate may be stored in the cold water tank 59 via the cold water reservoir line 58 .

During heat dissipation operation, the supply of extracted air from the low-pressure turbine 4C under high load operation to the low-pressure feed water heater 16 is stopped (cut), and the output of the generator 5 is increased or the fuel consumption of the boiler 2 is reduced. come true. Specifically, the control device 80 switches all or part of the condensate flowing into the deaerator 17 to high-temperature water when the steam turbine 4 is in a high-load operation state. As a result, the amount of condensate passing through the low-pressure feedwater heater 16 is reduced or cut off, so the extraction air supplied from the low-pressure turbine 4C to the low-pressure feedwater heater 16 is reduced or cut. As a result, the steam turbine 4 can be operated at an increased output corresponding to the decrease in extraction air, and the output of the generator 5 can be increased. At this time, if the increased output operation is not required in this operating state, the main steam flow rate from the boiler 2 is reduced to keep the load on the steam turbine 4 constant, and the fuel consumption of the boiler 2 can also be reduced. good.

When the operating load is low and the internal temperature of the deaerator 17 drops below the high-temperature water temperature, it is necessary to reduce the temperature of the water flowing into the deaerator 17 in accordance with the internal temperature of the deaerator 17. There is In such cases, the condensate is routed through the low pressure feedwater heater 16 and mixed with hot water supplied from the hot water tank 53 .

When the water level in the high-temperature water tank 53 reaches the minimum water level, the heat radiation operation ends. That is, the control device 80 monitors the water level of the high-temperature water tank 53 during heat dissipation operation, and stops the second high-temperature water pump 52B when the water level reaches the predetermined minimum water level. As a result, the thermal power plant 1 transitions to normal plant operation. In normal plant operation, the supply of high-temperature water via the second high-temperature water pump 52B is stopped and the supply of low-temperature water to the low-temperature water tank 59 from the outlet of the condensate pump 14 is also stopped. It is supplied to deaerator 17 via low pressure feed water heater 16 .

<Water heat storage system>
FIG. 5 is an explanatory diagram of the addition range when the water heat storage system 70 is additionally installed in the thermal power plant 1 . The additional installation range of the water heat storage system 70 is the range illustrated by the thick line in the figure. The water heat storage system 70 is mainly composed of the hot water heater 51, the high temperature water tank 53, the low temperature water tank 59, and the high temperature water pump 52, as described above. The construction cost can be reduced by additionally installing the water heat storage system 70 to the existing thermal power plant 1 by utilizing the empty space of the site.

Next, the schematic specifications of the water heat storage system 70 in the 1000 MW class coal-fired unit are illustrated below. The low-temperature water tank 59 has a water storage amount equal to or greater than the water storage amount of the high-temperature water tank 53 . This is so that when the high temperature water stored in the high temperature water tank 53 is supplied to the water supply line, the low temperature water tank 59 can store the condensed water corresponding to the supply amount.
Hot water heater: Direct contact feed water heater High temperature water tank capacity: 5 x 3300 m3 (0.3 MPa) Total 16500 m3
Low temperature water tank capacity: 2 x 8300m3 (atmospheric pressure) Total 16600m3
Heat storage time: about 6.0 hours Heat release time: about 5.0 hours (100% ECR)

According to the above specifications, in the case of a 1000 MW class coal-fired unit, when the boiler is operated at a minimum load of 15%, the heat of the steam/saturated drain equivalent to 10% load (100 MW) excluding 5% (50 MW) of the in-house power is stored. However, parallel non-transmission operation (external power transmission 0% operation) with inertial force remaining is possible.

Since the water heat storage system 70 is of a type in which the stored heat is returned to the deaerator 17 together with the heat medium, substantially all of the heat can be recovered within the cycle. The heat exchange loss between the heat medium and water and/or steam, which must be considered in molten salt heat storage and metal PCM heat storage, does not need to be considered in water heat storage. However, it is necessary to take into consideration heat dissipation during storage in the high-temperature water tank 53 and heat loss (3 to 5% depending on the time until heat dissipation) due to piping warming at the start of heat storage. Due to the limit of the amount of water that can be supplied to the deaerator 17 during heat dissipation (limit on mass balance), the heat storage time is about 6.0 hours, while the heat dissipation time is about 5.0 hours at 100% ECR. becomes.

The operation image of the conventional plant assuming daytime DSS operation and the thermal power plant 1 of the present embodiment in which the water heat storage system 70 is provided in the coal-fired thermal power plant will be compared. It is assumed that three units of plants A, B, and C are connected to the system. Assumed operation during a time period (for example, daytime) when a large amount of renewable energy is generated and surplus power is generated can be exemplified as follows.
<Conventional plant>
Plant A: Minimum load 15% operation (5% in-house power, 10% power transmission)
Plant B: DSS operation (temporary stop and restart of plant)
Plant C: DSS operation (temporary stop and restart of plant)
Total transmission amount: equivalent to 10% load <Thermal power plant of the present embodiment>
Plant A: Parallel non-transmission operation (minimum load 15% operation (5% on-site power, 10% heat storage))
Plant B: Parallel non-transmission operation (minimum load 15% operation (5% on-site power, 10% heat storage))
Plant C: Parallel non-transmission operation (minimum load 15% operation (5% in-house power, 10% heat storage))
Total amount of transmission: No transmission (0% load)

As described above, for conventional plants, one plant (here, plant A) operates at 15% of minimum load and the remaining two plants (B and C) operate in DSS. Even in that case, 10% is transmitted to the grid. On the other hand, the thermal power plant 1 of this embodiment is capable of parallel non-transmission operation in all thermal power plants.

That is, by using the thermal power plant 1 of the present embodiment, the amount of power transmission can be reduced to the point of no power transmission for all three plants. As a result, DSS operation can be avoided while increasing the amount of renewable energy received. Furthermore, in the thermal power plant 1 of the present embodiment, by dissipating the stored heat during peak demand hours (for example, in the evening), fuel consumption can be reduced (approximately 3 to 4%) during peak demand hours. becomes possible.

The advantages of introducing the water heat storage system 70 of this embodiment into the thermal power plant 1 are as follows.
(1) Contribution to expansion of renewable energy introduction Reducing the plant minimum load makes it possible to expand the acceptance of renewable energy while maintaining system inertia.
(2) Reduction of plant start-up costs through low-load continuous operation Continuous low-load operation using inexpensive coal makes it possible to significantly reduce the unavoidable starting light oil cost of DSS operation.
(3) Avoidance of equipment wear and start-up troubles through DSS operation Various risks associated with DSS operation can be avoided by continuously operating the power generation unit.
(4) Respond to sudden load increase requests, etc. Since the generator 5 is continuously operated at an extremely low load while maintaining system parallelism, it is possible to respond to sudden load increase requests due to sudden accidents, etc. .
(5) Heat recovery at plant start-up It is now possible to recover and use the heat that was conventionally discarded as start-up loss.

As described above, the thermal power plant 1 of the present embodiment includes the water heat storage system 70, and main steam corresponding to the difference between the steam generated from the boiler 2 and the steam consumed by the steam turbine 4 during low-load operation. And the heat of the saturated drain is stored in the high-temperature water tank 53 as high-temperature water. Also, during high-load operation, the stored high-temperature water is supplied to the deaerator 17 .

As a result, even if the operating load of the generator 5 (steam turbine 4) is reduced below the minimum load of the boiler 2 during low-load operation, the thermal power plant 1 of the present embodiment dissipates heat corresponding to the difference. , can be stored as hot water. That is, during low-load operation, the operating load of the generator 5 (steam turbine 4) can be reduced below the minimum load of the boiler 2 without waste. This makes it possible to reduce the system output power of the thermal power plant 1 over a long period of time. Also, during low-load operation, it is possible to reduce the power sent from the coal-fired thermal power plant to the power grid to almost 0% load (parallel non-transmission operation).

In addition, the load on the low-pressure feed water heater 16 can be reduced by supplying the high-temperature water stored during low-load operation to the deaerator 17 during high-load operation. As a result, the low-pressure extraction air from the steam turbine 4 can be reduced or cut during high-load operation. Then, the output of the steam turbine 4 corresponding to the reduced or cut heat amount of the low-pressure extracted air can be increased. Alternatively, when maintaining the output of the steam turbine 4, the steam flow rate from the boiler 2 can be reduced by the amount corresponding to the reduced or cut heat quantity of the low-pressure extracted air, and as a result, the amount of fuel input to the boiler 2 can be reduced.

That is, according to the present embodiment, by reducing the plant transmission amount by reducing the operating load of the generator 5 (steam turbine 4) in the thermal power plant from the boiler minimum load, high operability is maintained while regeneration It is possible to provide thermal power generation technology that can flexibly respond to changes in the amount of energy generated.

<Modification 1>
In the above embodiment, the case where the thermal power plant 1 includes one low-pressure feedwater heater 16 and one second high-pressure feedwater heater 21 is described as an example. good too.

FIG. 8 shows a configuration example in which the thermal power plant 1 includes four low-pressure feedwater heaters 16 and two second high-pressure feedwater heaters 21 .

In this case, part of the steam extracted from each steam turbine 4 and part of the exhaust steam exhausted from each steam turbine 4 are supplied to different locations depending on their temperature.

For example, the high pressure extraction steam hb of the high pressure turbine 4A is supplied to the second high pressure feed water heater 21 on the downstream side. Saturated drain (condensed high-pressure steam hb) discharged from the second high-pressure feed water heater 21 on the downstream side is supplied to the second high-pressure feed water heater 21 on the upstream side. A part of the high pressure exhaust steam he of the high pressure turbine 4A is supplied to the second high pressure feed water heater 21 on the upstream side. Saturated drain (condensed high pressure extraction steam hb and high pressure exhaust steam he) discharged from the second high pressure feed water heater 21 on the upstream side is supplied to the first high pressure feed water heater 20 . The intermediate pressure extraction steam ib of the intermediate pressure turbine 4B is supplied to the first high pressure feed water heater 20. Saturated drain (condensed high-pressure extraction steam hb, intermediate-pressure extraction steam ib, and high-pressure exhaust steam he) discharged from the first high-pressure feed water heater 20 is supplied to the deaerator 17 . A part of the intermediate pressure exhaust steam ie from the intermediate pressure turbine 4B is supplied to the deaerator 17 . Bleed steam (lb1, lb2, lb3, lb4) of the low pressure turbine 4C is supplied from the downstream side of each low pressure feed water heater 16 in descending order of temperature. Saturated drain (condensed steam) discharged from each low-pressure feedwater heater 16 is supplied to the upstream low-pressure feedwater heater 16 of each low-pressure feedwater heater 16 . Saturated drain (condensed steam lb 1 , lb 2 , lb 3 , lb 4 ) discharged from the most upstream low-pressure feedwater heater 16 is supplied to the condenser 13 .

As a result, steam can be supplied to the optimum feed water heater according to the steam temperature, and efficient operation can be achieved without waste.

<Modification 2>
Further, in the above-described embodiment and Modification 1, the confluence point of the high-temperature water supplied from the high-temperature water tank 53 is provided on the outlet side of the low-pressure feed water heater 16 on the most downstream side during heat radiation operation. For example, when a plurality of low-pressure feed water heaters 16 are provided, a plurality of confluence points may be provided and switched according to the temperature of the high-temperature water.

In this modified example, a confluence point is provided on the outlet side of each low-pressure feed water heater 16 to join the high-temperature water from the high-temperature water tank 53 to the condensate line 15 . The temperature of the condensate supplied by the condensate pump 14 rises as it passes through the low-pressure feed water heater 16 . In this modified example, the high-temperature water is merged at the confluence point where the temperature of the condensate on the outlet side of the low-pressure feed water heater 16 is not lowered.

In order to achieve this, the control device 80 monitors the temperature of the high-temperature water, and when the temperature of the high-temperature water drops, the confluence is switched to the low temperature side (low-pressure feed water heater 16 one step upstream). The switching of the confluence to the low temperature side is performed, for example, when the temperature of the high-temperature water flowing out of the high-temperature water tank 53 falls below the outlet temperature of each low-pressure feed water heater 16 for a certain period of time.

Hereinafter, as in Modification 1, four low-pressure feed water heaters 16A, 16B, 16C, and 16D are provided in series from the downstream side downstream of the condensate pump 14 on the condensate line 15 as an example. Give and explain in detail. FIG. 9 shows only the relevant parts extracted.

As shown in the figure, in this modification, the thermal power plant 1 includes a high-temperature water confluence line 71 that merges the high-temperature water in the high-temperature water tank 53 into the condensate line 15, and a temperature sensor that measures the temperature of the condensate. 72A, 72B, 72C, 72D, 72E; switching valves 73A, 73B, 73C, 73D, 73E, 73F; Also, the high-temperature water confluence line 71 has three branch points 74A, 74B, and 74C. The high-temperature water merging line 71 merges at merging points 75A, 75B, 75C, and 75D provided on the outlet sides of the low-pressure feed water heaters 16A, 16B, 16C, and 16D, respectively.

In the following description, the low-pressure feed water heater 16, the temperature sensor 72, the switching valve 73, the branch point 74, and the confluence point 75 are representative, respectively, when there is no need to distinguish them.

The branch point 74A is a branch point where the high-temperature water junction line 71 directed to the low-pressure feed water heaters 16B, 16C, and 16D branches from the high-temperature water junction line 71 directed to the outlet of the low-pressure feed water heater 16A. A branch point 74B is a branch point where the high-temperature water merging line 71 toward the low-pressure feed water heaters 16C and 16D branches from the high-temperature water merging line 71 toward the outlet of the low-pressure feed water heater 16B. A branch point 74C is a branch point where the high-temperature water junction line 71 directed to the low-pressure feed water heater 16D branches from the high-temperature water junction line 71 directed to the outlet of the low-pressure feed water heater 16C.

Temperature sensors 72A, 72B, 72C, and 72D are provided near the outlets of the low-pressure feed water heaters 16A, 16B, 16C, and 16D, respectively, and measure the temperature of the condensate near the outlets. The temperature sensor 72E is provided between the outlet of the high-temperature water tank 53 and the branch point 74A, and measures the temperature of the high-temperature water supplied from the high-temperature water tank 53. In this figure, it is provided between the second high-temperature water pump 52B and the branch point 74 .

A switching valve 73A is provided between the branch point 74A and the confluence point 75A, and controls the flow into the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16A. The switching valve 73B is provided between the branch point 74B and the confluence point 75B, and controls the flow into the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16B. The switching valve 73C is provided between the branch point 74C and the confluence point 75C, and controls the flow into the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16C. A switching valve 73D is provided between the branch point 74C and the confluence point 75D, and controls the flow into the high-temperature water confluence line 71 toward the outlet of the low-pressure feed water heater 16D. A flow control valve 76 is provided downstream of the second high-temperature water pump 52B, and controls the flow rate of high-temperature water.

At predetermined time intervals, the controller 80 receives temperature information from each temperature sensor 72, the hot water temperature received from the temperature sensor 72E, the outlet temperature received from each temperature sensor 72A, 72B, 72C, 72D, are compared in order, and the junction is switched according to the result.

Here, the flow of confluence switching processing by the control device 80 will be described. FIG. 10 is a processing flow of the confluence switching processing of this modification.

Here, both the confluence point and the low-pressure feed water heater 16 are numbered consecutively from the downstream side. It is also assumed that N (N is an integer equal to or greater than 1) number of confluence points and low-pressure feed water heaters 16 are provided. Moreover, n is a counter. Then, let T1 be the "predetermined time" for switching determination. Also, the temperature of the high-temperature water and the temperature on the outlet side of the low-pressure feed water heater 16 are measured at predetermined time intervals.

The control device 80 first initializes the counter (n=1) and initializes the elapsed counter Δt (Δt=0) (step S1001).

First, the control device 80 sets the first merging point to a merging point to be used (referred to as a merging point to be used) (step S1002), and switches the switching valves 73 so that the high-temperature water merges at the merging point to be used. to control.

Next, the control device 80 acquires the high-temperature water temperature TH and the outlet side temperature TLn of the n-th low-pressure feed water heater 16 (comparison target heater) (step S1003).

The control device 80 determines whether the acquired high-temperature water temperature TH is less than the outlet-side temperature TLn (step S1004). (step S1009) and returns to step S1003.

On the other hand, if the high-temperature water temperature TH is lower than the outlet-side temperature TLn (Yes), the control device 80 determines whether or not this state has elapsed for a certain period of time T1 (step S1005). If it has not yet passed (No), the process returns to step S1003.

On the other hand, if the predetermined time has elapsed (Yes), the control device 80 switches the use confluence to the confluence provided on the outlet side of the low-pressure feed water heater 16 one stage upstream (step S1006), and after switching Each switching valve 73 is controlled so that the high-temperature water merges at the use confluence point of .

After that, the control device 80 increments the counter n by 1, initializes the elapsed counter Δt (step S1007), and determines whether or not the confluence used is the most upstream confluence (n=N?) (step S1008). If the confluence set as the confluence to be used is not the most upstream confluence, the flow returns to step S1003 to repeat the process. On the other hand, if the most upstream confluence is set as the use confluence, the process ends.

A specific example will be used to explain the above-described confluence switching process. First, the controller 80 compares the hot water temperature with the outlet temperature (TLA) acquired by the temperature sensor 72A. When the hot water temperature is equal to or higher than the outlet temperature TLA, the controller 80 opens the switching valve 73A and closes the switching valves 73B, 73C, and 73D. This causes the hot water to join the condensate line 15 at the junction 75A, ie, on the outlet side of the low pressure feedwater heater 16A.

When the hot water temperature remains below the outlet temperature TLA for a certain period of time, the controller 80 compares the hot water temperature with the outlet temperature (TLB) acquired by the temperature sensor 72B. When the hot water temperature is equal to or higher than the outlet temperature TLB, the control device opens the switching valve 73B and closes the switching valves 73A, 73C, and 73D. This causes the hot water to join the condensate line 15 at the junction 75B, ie between the outlet of the low pressure feedwater heater 16B and the inlet of the low pressure feedwater heater 16A.

If the hot water temperature remains below the outlet temperature TLB for a certain period of time, the controller 80 compares the hot water temperature with the outlet temperature (TLC) obtained by the temperature sensor 72C. When the hot water temperature is equal to or higher than the outlet temperature TLC, the controller 80 opens the switching valve 73C and closes the switching valves 73A, 73B, and 73D. This causes the hot water to join the condensate line 15 at the junction 75C, ie between the outlet of the low pressure feedwater heater 16C and the inlet of the low pressure feedwater heater 16B.

When the high-temperature water temperature remains below the outlet temperature TLC for a certain period of time, the controller 80 opens the switching valve 73D and closes the switching valves 73A, 73B, and 73C. This causes the hot water to join the condensate line 15 at the junction 75D, ie between the outlet of the low pressure feedwater heater 16C and the inlet of the low pressure feedwater heater 16B.

Note that the control device 80 may be configured to start control by the switching valve 73 when the temperature of the high-temperature water supplied from the high-temperature water tank 53 becomes less than a predetermined threshold value. Specifically, when the temperature of the high-temperature water supplied from the high-temperature water tank 53 drops from 140° C. to 100° C., the confluence switching process described above is started.

In addition, in this modification, the high-temperature water temperature and the outlet temperature of each low-pressure feed water heater 16 are sequentially compared from the downstream side of the low-pressure feed water heater 16, and the switching valve 73 is controlled. is not limited to this. For example, the controller 80 may compare the hot water temperature with the outlet temperatures of all low pressure feedwater heaters 16 to determine the use junction. In this case, the switching valves 73 are controlled so that the high temperature water merges at the confluence point 75 on the outlet side of the low pressure feed water heater 16 having an outlet temperature lower than the high temperature water temperature and closest to the high temperature water temperature.

In the example of FIG. 9, when the high-temperature water temperature is less than the outlet temperature of the low-pressure feedwater heater 16C, even if it is less than the outlet temperature of the low-pressure feedwater heater 16D, the water is merged at the confluence point 75D. For example, a confluence point may be further provided on the inlet side of the low-pressure feed water heater 16D, and when the temperature of the high-temperature water is lower than the outlet temperature of the low-pressure feed water heater 16D, control may be performed to merge at the confluence point. In this case, since the number of confluences is N+1, it is determined whether n=N+1 in step S1008 of the processing flow of the confluence switching process shown in FIG.

According to this modification, when the high-temperature water in the high-temperature water tank 53 joins the condensate line 15 during heat dissipation operation, the joining point is changed according to the temperature. That is, the high temperature water is merged at the outlet side of the low pressure feedwater heater 16 having an outlet temperature that is less than the high temperature water temperature and closest to the high temperature water temperature. As a result, the temperature of the condensate heated by the low-pressure feed water heater 16 is not lowered by the high temperature water to be merged, and the low-pressure feed water heater 16 and the high temperature water can be efficiently utilized.

<Modification 3>
In the above embodiment, the high-temperature water generated in the hot water heater 51 is stored in the high-temperature water tank 53 during heat storage operation. In this modified example, a part of the high-temperature water generated in the hot water heater 51 is controlled to be supplied to the deaerator 17 instead of the high-temperature water tank 53 .

During the heat storage operation, the steam turbine 4 is operated at an extremely low load, so the steam for heating the feed water may be cut off and the steam for heating the deaerator 17 may be supplied from the auxiliary steam system. This is because the exhaust gas temperature of the boiler 2 must be maintained above a certain temperature even during low-load operation, and the feed water must be degassed. In this operating state, the temperature of the condensate flowing into the deaerator 17 drops as the low-pressure feed water heater 16 bleeds off, so it is necessary to increase the amount of auxiliary steam to compensate for this. In this modified example, the drop in the temperature of the condensate flowing into the deaerator 17 due to the cut off of the bleeding is compensated by supplying the outlet water of the hot water heater 51 . As a result, an increase in auxiliary steam consumption of the thermal power plant 1 can be suppressed.

FIG. 11 shows parts related to this modification of the thermal power plant 1 . As indicated by the thick dotted line in the figure, in this modified example, part of the high-temperature water generated by the hot water heater 51 is supplied to the deaerator 17 during heat storage operation.

Note that the water supply from the hot water heater 51 to the deaerator 17 during heat storage operation may be performed continuously by a predetermined amount. Moreover, when the temperature of the condensate supplied to the deaerator 17 is lowered, it may be controlled to be supplied.

In the latter case, thermal power plant 1 includes temperature sensor 72 and flow control valve 76 . The temperature sensor 72 measures the temperature of the condensate on the outlet side of the low-pressure feed water heater 16 and is provided on the outlet side of the low-pressure feed water heater 16 . A flow rate control valve 76 controls the supply of high-temperature water from the hot water heater 51 to the deaerator 17, and is provided on the high-temperature water junction line 71 connecting the high-temperature water tank 53 and the condensate line 15. be done.

The control device 80 acquires the temperature data measured by the temperature sensor 72 at predetermined time intervals, and when the temperature data is less than a predetermined threshold value, issues an instruction to open the flow control valve 76 to heat the high-temperature water. It is supplied from the device 51 to the deaerator 17 .

As a result, the high-temperature water from the hot water heater 51 is mixed with the condensate and supplied to the deaerator 17, so that the temperature of the condensate flowing into the deaerator can be increased, and the auxiliary steam consumption can be reduced. can be suppressed.

In addition, the above operation is particularly useful when remodeling an existing unit with restrictions on the size of the auxiliary steam line due to its layout, or when avoiding an unnecessary increase in the diameter of the auxiliary steam line when installing a new unit. be. In addition, instead of supplying condensate to the hot water heater 51 and supplying water to the deaerator 17 independently, a part of the high-temperature water is diverted to supply water to the deaerator 17. At the time of remodeling, it becomes possible to operate within the capacities of the condensate pump 14 and the condensate demineralizer. When the unit is newly installed, it is also possible to design the capacity of the pumps and devices to simultaneously fill the condensate supply to the hot water heater 51 and the water supply to the deaerator 17 . However, in view of the fact that costs are expected to increase due to the increased capacity of pumps and devices, it is desirable to use a portion of the high-temperature water to feed the deaerator 17, as in the case of remodeling the existing unit.

<Modification 4>
In the above embodiment, two tanks, the high-temperature water tank 53 and the low-temperature water tank 59, are provided. stored in However, it is not limited to this configuration. For example, one thermocline tank 61 may be provided to have the functions of the high temperature water tank 53 and the low temperature water tank 59 .

The thermocline tank 61 is a single-tank tank that includes a high-temperature water section, a low-temperature water section, and a thermocline in one tank, and can store high-temperature water and low-temperature water. A hot water section is located at the top of the tank, a cold water section is located at the bottom of the tank, and the hot and cold water sections are separated by a thermocline.

FIG. 12 shows parts of the thermal power plant 1 related to this modification. As shown in the figure, the thermocline tank 61 has a high-temperature water inlet/outlet through which high-temperature water is supplied and discharged, and a low-temperature water inlet/outlet through which low-temperature water is supplied and discharged.

As indicated by the thick line in FIG. 12, the high-temperature water inlet/outlet is connected to a high-temperature water supply line 64 for supplying hot water from the hot water heater 51 and a high-temperature water merging line 71 . On the other hand, a low-temperature water return line 62 connected to the condenser 13 and a second low-temperature water supply line 63 branched from the low-temperature water supply line 49 are connected to the low-temperature water inlet/outlet.

During heat storage operation, in the above embodiment, condensed water is supplied from the condenser 13 to the hot water heater 51 , and high temperature water is generated by the hot water heater 51 and stored in the high temperature water tank 53 . While condensed water is being supplied from the condenser 13 to the hot water heater 51 , an amount of water corresponding to the supplied condensed water is supplied from the low-temperature water tank 59 to the condenser 13 .

In this modification, as in the above embodiment, hot water is supplied from the condenser 13 to the hot water heater 51, high-temperature water is generated in the hot water heater 51, and the high-temperature water in the thermocline tank 61 is passed through the high-temperature water supply line 64. stored in the department. However, in this modification, as indicated by the thick dashed line in FIG. 13, an amount of water corresponding to the supplied condensed water is reconstituted from the low temperature water portion of the thermocline tank 61 via the low temperature water return line 62. It is supplied to the water vessel 13 . Also, as indicated by the dotted line, water is partially passed from the hot water heater 51 to the deaerator 17 .

Further, during heat dissipation operation, in the above embodiment, high-temperature water is supplied from the high-temperature water tank 53 to the deaerator 17, and the amount of condensate in the condenser 13 is transferred to the low-temperature water via the low-temperature water storage line 58. It is stored in tank 59 . On the other hand, in this modified example, as indicated by the thick line in FIG. , is supplied from the condenser 13 to the low-temperature water portion of the thermocline tank 61 via the second low-temperature water supply line 63 branched downstream from the condensate pump 14 of the condensate line 15 .

In this modification, the capacity of the thermocline tank 61 is the required capacity of the high-temperature water tank 53 or the low-temperature water tank 59 plus the capacity corresponding to the thermocline that does not contribute to the tank capacity, and is always operated in a full water state. be.

According to this modification, by using the thermocline tank 61, it is possible to save space for installation of the tank, which is effective especially when there are restrictions on the power generation site. Also, if the thermocline tank 61 is inexpensive, the cost can be reduced compared to installing the tank separately.

The thermocline tank 61 has a structure that can withstand the saturation pressure of the high-temperature water, and avoids mixing of the high-temperature water and the low-temperature water in the tank. The configuration and operation of lines connected to the water supply unit and the low temperature water unit are the same as when the high temperature water tank 53 and the low temperature water tank 59 are separately installed.

<Modification 5>
In the above embodiment, the boiler 2 is a supercritical boiler that is used in a supercritical state except under low-load conditions, but the type of boiler is not limited to this. For example, a subcritical boiler operated at subcritical conditions at all loads may be used.

The subcritical boiler includes a steam drum 34, a continuous blow tank 37, a flash tank 38, and an intermittent blow line 39 instead of the water drain separator 31, as shown by a thick line in FIG.

Steam drum 34 separates steam and saturated water (saturated drain). The separated steam and saturated drain flow into the superheater 36 and the continuous blow tank 37, respectively. The saturated drain passes through steam separation and steam recovery in continuous blow tank 37 and flows into flash tank 38 . An intermittent blow line 39 provided in the steam drum 34 is used for avoiding the drum level from rising due to boiler water swelling at startup and for blowing boiler water when the boiler water quality deteriorates.

Part of the saturated drain that has flowed into the continuous blow tank 37 becomes flash steam, is supplied to the deaerator 17 , and is used as part of the heating steam of the deaerator 17 .

When using a subcritical drum, the heat storage drain line 57 branches off from the intermittent blow line 39 . During heat storage operation, all or part of the saturated drain separated by the steam drum 34 is supplied to the hot water heater 51 via the heat storage drain line 57 branching from the intermittent blow line 39 and the heat storage drain flow control valve 56. be done.

During heat storage operation, in the subcritical boiler, as in the case of using a supercritical boiler, all or part of the excess main steam in the main steam line 6 is transferred to the heat storage steam line 55 and the heat storage steam flow control valve 54. is supplied to the hot water heater 51 via. During heat storage operation, the hot water heater 51 uses this main steam and saturated drain supplied from the steam drum 34 as heat sources, and generates high-temperature water from condensate supplied from the condenser 13 .

In the subcritical boiler, the amount of drain drawn from the steam drum 34 is determined based on the amount of fuel input and the flow rate of the main steam. Level control of the steam drum 34 is provided by a drum level control valve. When the drum level temporarily rises due to fluctuations in the operating conditions, in addition to the control by the drum level control valve, the intermittent blow valve is opened and closed as necessary.

That is, the control device 80 monitors the drum level, and when the drum level exceeds a predetermined threshold value for a certain period of time or more, the opening degree of the drum level control valve is lowered to suppress the inflow water supply amount. Alternatively, an intermittent blow valve may be opened to extract saturated drain as intermittent blow. The drum level is obtained from a water level sensor provided on the steam drum 34 .

<Modification 6>
The heat source of the hot water heater 51 is not limited to turbine bypass steam. For example, it may be reheated steam passing through a reheated steam line, or extracted air or exhaust from each steam turbine 4 .

In addition, you may combine each modification. For example, the thermal power plant 1 of the above-described embodiment includes a plurality of low-pressure feed water heaters 16, a configuration for switching the confluence destination of the high-temperature water merging line 71 according to the temperature of the high-temperature water, a configuration that allows partial water flow, a high-temperature water tank 53, and At least one of a configuration using a thermocline tank 61 instead of the low-temperature water tank 59, a configuration using a subcritical boiler, and a configuration using various types of steam as a heat source for the hot water heater 51 may be provided.

1 Thermal Power Plant 2 Boiler 4 Steam Turbine 4A High Pressure Turbine 4B Intermediate Pressure Turbine 4C Low Pressure Turbine 5 Generator 6 Main Steam Line 7 Turbine Bypass Line 8 Turbine Bypass Valve 9 Reheat Steam Line 10 Low Pressure Turbine Bypass Line 11 Low Pressure Turbine Bypass Valve 12 Medium-pressure turbine exhaust line 13 Condenser 14 Condensate pump 15 Condensate line 16 Low-pressure feedwater heater 16A Low-pressure feedwater heater 16B Low-pressure feedwater heater 16C Low-pressure feedwater heater 16D Low-pressure feedwater heater 17 Deaerator 18 Feedwater pump 19 Water supply line 20 First high-pressure feed water heater 21 Second high-pressure feed water heater 31 Water drain separator 32 Water drain separator drain control valve 33 Water drain separator drain line 34 Steam drum 35 Reheater 36 Superheater 37 Continuous blow tank 38 Flash tank 39 intermittent blow line 49 low temperature water supply line 50 low temperature water flow control valve 51 hot water heater 52 high temperature water pump 52A first high temperature water pump 52B second high temperature water pump 53 high temperature water tank 54 heat storage steam flow control valve 55 heat storage steam line 56 Heat storage drain flow rate control valve 57 Heat storage drain line 58 Low temperature water storage line 59 Low temperature water tank 60 Makeup water line 61 Thermocline tank 62 Low temperature water return line 63 Second low temperature water supply line 64 High temperature water supply line 70 Water heat storage system 71 High temperature water Merging line 72 Temperature sensor 72A Temperature sensor 72B Temperature sensor 72C Temperature sensor 72D Temperature sensor 72E Temperature sensor 73A Switching valve 73B Switching valve 73C Switching valve 73D Switching valve 74 Branch point 74A Branch point 74B Branch point 74C Branch point 75 Junction point 75A Junction point 75B Junction 75C Junction 75D Junction 76 Flow control valve 80 Control device 81 Control console

Claims (11)

a boiler, a steam turbine driven by steam from the boiler, a turbine bypass line for directing the steam to bypass the steam turbine, and a condenser for cooling the exhaust of the steam turbine to produce condensate; A thermal power plant comprising: a low-pressure feedwater heater that heats the condensate with steam extracted from the steam turbine; and a deaerator that deaerates the condensate with the steam extracted,
a hot water heater using the main steam of the turbine bypass line as a heat source and using the condensate supplied from the condenser as high-temperature water;
a high-temperature water tank for storing the high-temperature water;
a high-temperature water pump for sending the high-temperature water stored in the high-temperature water tank to the downstream of the low-pressure feed water heater or the deaerator;
Thermal power plant with. The hot water heater is a direct contact feedwater heater that mixes the condensate and the main steam.
The thermal power plant according to claim 1. The boiler includes a water drain separator that separates brackish mixed water from the furnace outlet,
The hot water heater also uses saturated drain separated from brackish water by the water drain separator as the heat source,
The thermal power plant according to claim 1 or 2. The boiler comprises a steam drum for separating steam and saturated water,
The hot water heater also uses the intermittent blow from the steam drum as the heat source,
The thermal power plant according to claim 1 or 2. A low-temperature water tank for storing surplus water in the condenser as make-up water for the condenser, further comprising a low-temperature water tank having a water storage amount equal to or greater than the water storage amount of the high-temperature water tank,
The thermal power plant according to any one of claims 1 to 4. The high-temperature water tank is a thermocline tank capable of storing the high-temperature water and the low-temperature water across a thermocline, and the low-temperature water is surplus water in the condenser. store for make-up water,
The thermal power plant according to any one of claims 1 to 4. A plurality of the low-pressure feed water heaters are provided in series in a condensate line that conveys the condensate from the condenser to the deaerator,
A high-temperature water merging line for merging the high-temperature water at a confluence point where the temperature of the condensate on the outlet side of the plurality of low-pressure feed water heaters is not lowered the least according to the temperature of the high-temperature water. further comprising
The confluence points are respectively provided in the condensate lines on the outlet side of the plurality of low-pressure feedwater heaters,
The thermal power plant according to any one of claims 1 to 6. A control method for a thermal power plant according to any one of claims 1 to 7,
during low-load operation of the thermal power plant, generating the high-temperature water using the main steam corresponding to the difference between the steam generated by the boiler and the steam consumed by the steam turbine as the heat source, and storing the high-temperature water in the high-temperature water tank;
A method of controlling a thermal power plant, wherein the high-temperature water stored in the high-temperature water tank is supplied to the deaerator during high-load operation of the thermal power plant. 9. The thermal power plant according to claim 8, further supplying part of said high-temperature water produced in said hot water heater to said deaerator according to the temperature of said deaerator during low-load operation of said steam turbine. How to control a power plant. The thermal power plant includes a plurality of the low-pressure feed water heaters in series in a condensate line that feeds the condensate from the condenser to the deaerator, and the high-temperature water is merged. further comprising confluence points for merging the high-temperature water, respectively provided in the condensate lines on the outlet side of the low-pressure feed water heater,
9. During high-load operation of the thermal power plant, according to the temperature of the high-temperature water, the condensate on the outlet side of the plurality of low-pressure feed water heaters is joined at a junction where the temperature of the condensate is not lowered the least. Or the control method of the thermal power plant according to 9. setting the most downstream low-pressure feed water heater among the plurality of low-pressure feed water heaters as a comparison target heater, and setting the confluence point at which the high-temperature water merges to a confluence point on the outlet side of the comparison target heater;
At predetermined time intervals, the temperature of the high-temperature water is compared with the temperature of the condensate on the outlet side of the comparison target heater, and the temperature of the high-temperature water is lower than the temperature of the condensate for a predetermined period. , the confluence point for joining the high-temperature water is switched to the outlet side of the low-pressure feed water heater one step upstream of the comparison target heater, and the low-pressure feed water heater one step upstream is switched to the comparison target heating 11. The method of controlling a thermal power plant according to claim 10, further comprising repeating the process of forming a unit.

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