JP2980384B2 - Steam power plant repowering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repowering system for a steam power plant, and more particularly to a repowering system capable of operating safely even at a partial load operation.

[0003]

2. Description of the Related Art Conventionally, a gas turbine plant has been added to an existing steam power generation facility, and the exhaust of the gas turbine is used as combustion air for a boiler, and the heat of the exhaust gas of the boiler is transferred to a steam turbine cycle system. 2. Description of the Related Art A repowering system in which an exhaust gas reburning combined cycle is configured to be collected is generally known. This type of repowering system has the following features.

[0004] First, the power generation efficiency can be improved by combining an existing power generation plant. Secondly, since a gas turbine is additionally installed, the amount of generated power of the entire power plant can be increased. Third
In addition, the remodeling of existing steam power plants can be reduced,
Repowering can be performed in a relatively short period of time. Considering the recent significant growth in power demand, the resulting decrease in the reserve ratio of each power company, and the difficulty of quickly constructing a new power plant to deal with this,
The repowering system is one of effective means for solving these problems.

FIG. 6 shows an example of a conventional steam power generation facility. Steam generated in a boiler 1 is guided to a high-pressure steam turbine 3 by a main steam pipe 2. The steam that has worked in the high-pressure steam turbine 3 is supplied to the boiler 1 by the low-temperature reheat steam pipe 4.
To the reheater 5. The steam heated by the reheater 5 is guided to a medium-pressure steam turbine 7 by a high-temperature reheat steam pipe 6.
The steam that has worked in the medium-pressure steam turbine 7 is guided to the low-pressure steam turbine 9 by the crossover pipe 8. Furthermore,
The steam that has worked in the low-pressure steam turbine 9 is guided to the condenser 11 and is condensed. The rotating shaft of each of the high-pressure steam turbine 3, the medium-pressure steam turbine 7, and the low-pressure steam turbine 9 is a generator 1
0, and is driven to generate electricity by driving the generator 10. The condensed water condensed in the condenser 11 is pressurized by the condensate pump 12, sent to the low-pressure feed water heaters 14 a, 14 b, and 14 c via the condensate pipe 13 and heated there, and reaches the deaerator 15. . The condensed water degassed by the deaerator 15 is guided to the water supply pipe 16. The feedwater further pressurized by the feedwater pump 17 is supplied to high-pressure feedwater heaters 18a, 18b, 18
The heating is performed by c to reach the boiler 1, and power is generated while repeating the above-described cycle. Reference numeral 19 denotes an air preheater, which is installed to increase the combustion efficiency of the boiler 1 and heats boiler combustion air with high-temperature exhaust gas from the boiler 1.

FIG. 7 shows an example of a conventional repowering system in which a gas turbine plant is added to a steam power generation facility to constitute an exhaust gas reburning combined cycle. In this repowering system, a gas turbine plant including a compressor 20, a combustor 21, a gas turbine 22, a gas turbine generator 23, a gas damper 24, and the like is added to a conventional steam power generation facility. Further, since the exhaust gas of the gas turbine 22 is used as combustion air for the boiler 1, an air preheater is not required. Further, a high-pressure stack gas cooler 25 is additionally installed for the purpose of effectively utilizing the high-temperature exhaust gas of the boiler 1 and for reducing the temperature of the exhaust gas because the high-temperature exhaust gas cannot be discharged from the chimney as it is.

The high-pressure stack gas cooler 25 heats the feed water by exchanging heat between the water branched from the feed water pipe 16 and the exhaust gas of the boiler 1, and returns the heated feed water to the steam turbine cycle system again.

FIG. 8 shows another example of the conventional repowering system. The low-pressure stack gas cooler 2 to which the exhaust gas of the boiler 1 that has undergone heat exchange by the high-pressure stack gas cooler 25 is supplied to the repowering system shown in FIG.
6 has been added. This low pressure stack gas cooler 26
Performs heat exchange between the water branched from the condenser 13 and the exhaust gas of the boiler 1 to heat the condensate, and returns the condensed water whose temperature has been raised to the steam turbine cycle system again.

[0009]

SUMMARY OF THE INVENTION In the conventional repowering system shown in FIGS.
2 always rotates at a constant speed, so that the amount of air compressed by the compressor does not change much even at a partial load. Therefore, the exhaust gas amount at the time of partial load discharged from the boiler 1 to the high-pressure stack gas cooler 25 does not change so much as during the rated operation.

On the other hand, when looking at the steam turbine cycle system, when the load becomes a partial load, in the steam turbine cycle, the amount of water flowing through the condenser pipe 13 and the water supply pipe 16 decreases according to the load. Further, since the extraction pressure of the steam turbine also decreases with the load, each of the low-pressure feed water heaters 14a, 14
b, 14c, deaerator 15, high-pressure water heater 18a, 18
The internal pressures of b and 18c also decrease.

As a result, at a partial load, the outlet feed water temperature of the high-pressure stack gas cooler 25 becomes too high, and steaming may occur in the boiler 1 in the economizer. Further, in the conventional equipment, the high-pressure stack gas cooler 25
If the outlet feedwater temperature is not excessively increased, a part of the exhaust gas of the boiler 1 must be discharged from the chimney as it is, and there is a problem that the plant efficiency is deteriorated.

Further, in the repowering system having the low-pressure stack gas cooler 26 in addition to the high-pressure stack gas cooler 25, the partial condensate causes the inlet condensing temperature of the low-pressure stack gas cooler 26 to drop too much. There is a problem that sulfur in gas turbine exhaust adheres and causes corrosion.

The present invention has been made in view of the above circumstances, and has a steam power capable of preventing occurrence of steaming in a boiler economizer even at a partial load without lowering plant efficiency. An object of the present invention is to provide a repowering system for a power generation facility.

Another object of the present invention is to provide a repowering system for a steam power plant capable of preventing the sulfur content in the exhaust gas of a gas turbine from adhering to the outer wall of a tube of a low-pressure stack gas cooler even at a partial load. It is in.

[Configuration of the Invention]

[0016]

Means for Solving the Problems A first invention of the present invention is:
As a means for achieving the above object, a gas turbine plant is added to a steam power generation facility, and exhaust gas from a gas turbine is used as combustion air for a boiler, and exhaust gas from the boiler is used to heat water supplied to a steam turbine cycle system. In a repowering system configured as an exhaust reburn type combined cycle by supplying to a high-pressure stack gas cooler, an exhaust heat recovery boiler that heats and evaporates feed water with exhaust gas from the boiler is provided in parallel with the high-pressure stack gas cooler with respect to the flow of exhaust gas. And a distribution means for controlling the distribution ratio of exhaust gas to the exhaust heat recovery boiler and the high-pressure stack gas cooler, and a control means for controlling the flow rate of water supply to the exhaust heat recovery boiler and the high-pressure stack gas cooler, respectively. I do.

Further, according to a second aspect of the present invention, there is provided a low-pressure stack gas cooler for heating condensate of the steam turbine cycle system by exhaust gas from the boiler, and an inlet return of the low-pressure stack gas cooler as means for achieving the above object. A heat exchanger for exchanging heat between water and steam from the exhaust heat recovery boiler.

According to a third aspect of the present invention, as a means for achieving the above object, a gas turbine plant is added to a steam power generation facility, and exhaust gas from the gas turbine is used as combustion air for a boiler. In the repowering system, the exhaust gas of the boiler is sequentially supplied to a high-pressure stack gas cooler for heating feed water of the steam turbine cycle system and a low-pressure stack gas cooler for heating condensate of the steam turbine cycle system to constitute an exhaust heat reburning combined cycle, A heat exchanger for exchanging heat between the inlet condensate of the low-pressure stack gas cooler and the inlet water supply of the high-pressure stack gas cooler is provided.

[0019]

In the repowering system of the steam power plant according to the first aspect of the present invention, when the water supply amount decreases due to partial load and the water supply temperature at the boiler inlet starts to rise, the distribution means is activated to operate the high pressure stack. The ratio of exhaust gas distribution to the gas cooler is reduced, and the rise in feedwater temperature at the boiler inlet is suppressed. At the same time, the distribution ratio of exhaust gas to the exhaust heat recovery boiler increases, and the control means controls the feedwater flow rate accordingly, and the steam generated in the exhaust heat recovery boiler
Used in steam turbine cycle systems.

Further, in the repowering system of the steam power plant according to the second invention of the present invention, at a partial load, the temperature of the condensate of the inlet of the low-pressure stack gas cooler tends to decrease. Since heat is exchanged and heated by the heat exchanger by the steam from the boiler, a decrease in temperature is prevented or reduced. Therefore, it is possible to prevent or reduce the adhesion or corrosion of sulfur due to a decrease in the temperature of the low-pressure stack gas cooler through which the inlet condensate flows.

In the repowering system for a steam power plant according to the third aspect of the present invention, when a partial load is applied, heat is exchanged between the inlet condensate of the low-pressure stack gas cooler and the inlet water supply of the high-pressure stack gas cooler by the heat exchanger. Exchange is performed. This suppresses an excessive increase in the feed water temperature at the outlet of the high-pressure stack gas cooler, prevents steaming in the boiler economizer, heats the condensate at the inlet of the low-pressure stack gas cooler, and reduces the sulfur content of the low-pressure stack gas cooler to the tube. Is prevented from adhering.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows an example of a repowering system for a steam power plant according to the present invention. In FIG. 1, reference numeral 1 denotes a boiler, and steam generated from the boiler 1 is a main steam pipe 2.
, And the steam that has worked in the high-pressure steam turbine 3 is guided to a reheater 5 of the boiler 1 through a low-temperature reheat steam pipe 4.

The steam heated by the reheater 5 is guided to a medium-pressure steam turbine 7 through a high-temperature reheat steam pipe 6 as shown in FIG. The steam that has worked in the above is guided to the low-pressure steam turbine 9 through the crossover pipe 8, and the steam that has worked in the low-pressure steam turbine 9 is guided to the condenser 11 to be condensed. .

As shown in FIG. 1, the rotating shafts of the steam turbines 3, 7, and 9 are connected to the rotating shaft of a generator 10, and when the generator 10 is driven, electricity is generated. I have.

On the other hand, the condensate condensed in the condenser 11 is pressurized by a condensate pump 12 as shown in FIG.
a, 14b, and 14c, and are heated. The heated condensate is deaerated by the deaerator 15. The degassed condensed water is pressurized by a water supply pump 17 via a water supply pipe 16, sent to high-pressure water heaters 18 a, 18 b, and 18 c and heated, and then sent to the boiler 1. ing.

As shown in FIG. 1, the steam power generation equipment having the above configuration includes a compressor 20, a combustor 21, a gas turbine 22, a gas turbine generator 23, and a gas damper 2.
A gas turbine plant consisting of 4 etc. has been added,
The exhaust gas of the gas turbine 22 is used as combustion air for the boiler 1. And boiler 1
The high-temperature exhaust gas is supplied to a high-pressure stack gas cooler (HPGC) 25 and an exhaust heat recovery boiler (HR) connected in parallel with each other.
SG) 30 via a damper 31.

The high-pressure stack gas cooler 25 is shown in FIG.
As shown in (1), heat exchange is performed between the water branched from the water supply pipe 16 and the exhaust gas of the boiler 1 to heat the water, and the heated water is returned to the steam turbine cycle system again.

Further, as shown in FIG. 1, the exhaust heat recovery boiler 30 includes a economizer 30a, a drum 30b, and an evaporator 30.
c and a superheater 30d, and performs heat exchange between water branched from the high-pressure stack gas cooler 25 and exhaust gas from the boiler 1 to heat and evaporate feed water. Through the pipe 33, the steam is supplied to a middle stage of the steam turbine such as the medium-pressure steam turbine 7.

As shown in FIG. 1, the damper 31 includes a high-pressure stack gas cooler 25 and an exhaust heat recovery boiler 30.
And functions as distribution means for controlling the distribution ratio of the exhaust gas boiler 1 is supplied to the bets, the damper 31 is adapted to be controlled on the basis of the feedwater temperature T _1. The exhaust gas of the boiler 1 distributed by the damper 31 undergoes heat exchange in the high-pressure stack gas cooler 25 and the exhaust heat recovery boiler 30, and then merges to form a chimney (not shown).
It is to be discharged from.

The outlet position of the water supply pump 17 is shown in FIG.
As shown in FIG.
A regulating valve 34 for controlling the flow rate of the feed water distributed to the 18b, 18c side and the high pressure stack gas cooler 25 side, and a regulating valve 35 for controlling the flow rate of the feed water distributed to the high pressure stack gas cooler 25 side and the exhaust heat recovery boiler 30 side. There are provided respectively, regulating valve 34, while being controlled by the exhaust gas outlet temperature T _2, the adjustment valve 35 is adapted to be controlled by the water level L ₁ of the drum 30b of the exhaust heat recovery boiler 30.

Next, the operation of this embodiment will be described.

At the rated load, the opening of the damper 31 is controlled so that the entire amount of the exhaust gas from the boiler 1 flows into the high-pressure stack gas cooler 25 and the amount of heat exchange in the exhaust heat recovery boiler 30 becomes zero.

In this state, if the regulating valve 35 is fully closed,
The configuration is the same as that of the conventional repowering system without the exhaust heat recovery boiler 30, and the same performance is obtained.

The high-pressure stack gas cooler 25 is designed to obtain the best performance in this state.

On the other hand, the water supply amount is reduced becomes part load, when the boiler 1 inlet of the feed water temperature T ₁ is begins to rise, the damper 3
1 operates, the amount of exhaust gas flowing into the high-pressure stack gas cooler 25 is reduced, the temperature rise of the feedwater temperature T ₁ is suppressed, and the remaining exhaust gas is guided to the exhaust heat recovery boiler 30 for heat exchange. Can be

When the exhaust gas is supplied to the exhaust heat recovery boiler 30, the internal pressure in the drum 30b rises, and when the pressure rises above the pressure in the middle stage of the steam turbine, the check valve 32 opens to generate steam. Is supplied to the turbine. When the supply of the steam water level L ₁ in the drum 30b decreases, control valve 35 is opened, water is supplied to the exhaust heat recovery boiler 30.

The superheater 30d of the exhaust heat recovery boiler 30
Is designed to minimize the mismatch with the temperature of the middle stage of the turbine to which the steam is supplied.
a is designed to lower the exhaust gas outlet temperature as much as possible for heat exchange.

[0039] Thus, it is possible to suppress an increase in the feed water temperature T _1, the boiler 1 to the exhaust heat recovery boiler 30
The steam can be generated by supplying the exhaust gas, and guided to a turbine for power generation.

FIG. 2 shows a high-pressure stack gas cooler (HPG).
FIG. 2 shows the relationship between the exchanged heat quantity Q and the temperature distribution T in the C) 25 and the waste heat recovery boiler (HRSG) 26.
2A shows the case of the high-pressure stack gas cooler 25, and FIG. 2B shows the case of the exhaust heat recovery boiler 26.

[0041] In the rated load, the quantity of heat exchange in the exhaust heat recovery boiler 30 is zero, quantity of heat exchange with high pressure stack gas cooler 25 is assumed to be Q _1. Temperature distribution in the high-pressure stack gas cooler 25 at this time, the gas side 1a, become distributed as the water supply side 1b, the outlet temperature T ₁ of the water is lower than the T _max of steaming limits.

Next, at a partial load, as in the conventional system,
Assuming that the amount of heat exchanged in the exhaust heat recovery boiler 30 is zero, the amount of heat exchanged in the high pressure stack gas cooler 25 is almost Q
_1, and becomes a substantially 1a also the temperature distribution of the gas side, the temperature distribution of the feed water side is as shown in 2b due to a decrease in supply volume, the outlet temperature T ₂ would undergo steaming beyond T _max.

On the other hand, as in this example, reducing the amount of exhaust gas to the high pressure the stack gas cooler 25, lowering the amount of heat exchanged with high pressure stack gas cooler 25 to Q _2, the temperature distribution of the gas side 3a, the feed water side temperature of The distribution becomes 3b, and the feedwater outlet temperature can be made lower than _Tmax .

Here, in the exhaust heat recovery boiler 30 to which the remaining exhaust gas is supplied, the exchange heat quantity is substantially (Q ₁ -Q ₂ ).
And the temperature distribution is 3c on the gas side and 3d on the water supply side. On the water supply side, the amount of heat is shared between Q ₃ for heating the feed water, Q _{4 for} evaporating, and Q ₅ for heating the steam.
0d. Incidentally, the heat transfer area of the superheater 30d, it generates steam temperature T _3, it is designed to be substantially the same as the temperature of the supply destination of the turbine halfway stage.

FIG. 3 shows a second embodiment of the present invention. In addition to the high-pressure stack gas cooler 25 of the first embodiment, a low-pressure stack gas cooler 26 is additionally provided to further improve heat recovery and plant efficiency. It is like that.

That is, the low-pressure feed water heater 1 of the condenser pipe 13
Condensed water branched from the 4a exit side position, as shown in FIG.
The gas is supplied to a low-pressure stack gas cooler (LPGC) 26 via a heat exchanger 40 and a regulating valve 41, and the exhaust gas discharged from the high-pressure stack gas cooler 25 and the exhaust heat recovery boiler 30 in the low-pressure stack gas cooler 26. Heat exchange between the condensing pipe 1
3 is returned to the low pressure feed water heater 14c exit side position.

As shown in FIG. 3, a part of the steam generated in the exhaust heat recovery boiler 30 is supplied to the heat exchanger 40 through a regulating valve 42 to heat the condensate. and it is capable of increasing to a temperature required condensate temperature T ₄ thereby.

[0048] Further, the adjusting valve 41, as shown in FIG. 3, so that the flow control so that the exhaust gas outlet temperature T ₃ of the boiler 1 is a suitable temperature.

The other points are the same as those of the first embodiment.

Next, the operation of the present embodiment will be described.

At the time of rated load, as in the case of the first embodiment, the supply of exhaust gas and feed water to the exhaust heat recovery boiler 30 is zero, and the exhaust gas of the boiler 1 is heat-exchanged with the feed water by the high-pressure stack gas cooler 25. After that, the condensed water and the heat exchange are further performed in the low-pressure stack gas cooler 26, and then discharged from a chimney (not shown). Incidentally, the low pressure stack gas cooler 26 is designed to possible heat recovery by lowering the exhaust gas outlet temperature T ₃ during this.

The reason why the condensate is branched not from the outlet of the condensate pump 12 but from the outlet of the low-pressure feed water heater 14a is that if the condensate temperature is too low, the low-pressure stack gas cooler 26 This is because the sulfur content in the exhaust gas of the boiler 1 adheres to the outer surface of the heat transfer tube and corrosion is likely to occur.

[0053] In the partial load, as in the case of the first embodiment, the control of the damper 31, the boiler 1 to the high-pressure stack gas cooler 25 so that the feed water temperature T ₁ is not too high reduces the quantity of exhaust gas, the remaining The exhaust gas flows into the exhaust heat recovery boiler 30 to generate steam. Waste heat recovery boiler 3
The steam generated at 0 flows into the middle stage of the steam turbine and is used for power generation.

The exhaust gas whose temperature has been lowered by heat exchange in the high-pressure stack gas cooler 25 or the exhaust heat recovery boiler 30 is
It is led to the low pressure stack gas cooler 26. Incidentally, the exhaust gas outlet temperature T ₂ of this time, the high pressure stack gas cooler 2
5 and the low-pressure stack gas cooler 26 are selected so as to have an appropriate load sharing, and are adjusted by controlling the amount of water supplied to the high-pressure stack gas cooler 25 by the adjusting valve 34. Similarly the exhaust gas outlet temperature T ₃ after the heat exchange with low pressure stack gas cooler 26 is adjusted by controlling the recovery amount of water into the low pressure stack gas cooler 26 by adjusting valve 41 so as to be optimum.

At the time of partial load, the condensate temperature at the outlet of the low-pressure feed water heater 14a is lower than at the time of rated load, so that the outer surface of the heat transfer tube of the low-pressure stack gas cooler 26
As sulfur content in the exhaust gas boiler 1 is not attached, it is necessary to adjust the condensate temperature T _4.

Therefore, in this embodiment, the exhaust heat recovery boiler 30
Some of the in generated steam, sent to the heat exchanger 40 to perform heat exchange between the condensate, so that increase to a temperature required condensate temperature T _4. Adjustment of condensate temperature T ₄ is carried out by controlling the heating steam amount control valve 42, also heated steam or drain after the heat exchange is recovered and recycled to the deaerator 15.

Since heat is exchanged also in the low-pressure stack gas cooler 26, the heat recovery efficiency and the plant efficiency can be improved as compared with the first embodiment.

FIG. 4 shows a third embodiment of the present invention, in which a two-drum type exhaust heat recovery boiler 50 is used instead of the exhaust heat recovery boiler 30 in the second embodiment. .

As shown in FIG. 4, the exhaust heat recovery boiler 50 includes a low-pressure economizer 50a, a low-pressure drum 50b, and an evaporator 5.
0c, high-pressure economizer 50d, high-pressure drum 50e, evaporator 5
0f and a superheater 50g, a part of the condensed water from the heat exchanger 40 is supplied to the low-pressure economizer 50a via a regulating valve 51, and the saturated water of the low-pressure drum 50b is It is sent to the high-pressure economizer 50d via the high-pressure pump 52 and the regulating valve 53. The steam separated from the steam by the high-pressure drum 50e is guided to the middle stage of the steam turbine via the steam pipe 33 having the check valve 32. The steam separated from the steam by the low-pressure drum 50b is , Through a steam pipe 55 having a check valve 54, is guided to the middle stage of the steam turbine, and a part of the steam in the steam pipe 55 is supplied to the heat exchanger 40 via the regulating valve 42, The drain after the heat exchange is collected in the condenser 11. The adjusting valve 51, while being controlled by the water level _{L 1} of the low-pressure drum 50b, the adjusting valve 53 is controlled by the water level _{L 1} of the high-pressure drum 50e,
Thus, the amount of water supplied to the exhaust heat recovery boiler 50 is controlled.

The other points are the same as those of the second embodiment.

Next, the operation of the present embodiment will be described.

At the rated load, the exhaust gas to the exhaust heat recovery boiler 50 is zero, and the entire amount of the boiler exhaust gas is heat-exchanged with feed water by the high-pressure stack gas cooler 25, and is further heat-exchanged with condensed water by the low-pressure stack gas cooler 26. From the chimney.

At a partial load, the amount of exhaust gas from the boiler 1 to the high-pressure stack gas cooler 25 is reduced by the damper 31 so that the supply water temperature does not rise too much, and the remaining exhaust gas is supplied to the exhaust heat recovery boiler 50 for steam generation. Is done.

A part of the condensed water heated by the heat exchanger 40 is supplied to the exhaust heat recovery boiler 50 through the regulating valve 51 and heated by the low-pressure economizer 50a.
b and is sent to the evaporator 50c and heated. And
The steam separated from the water by the low-pressure drum 50b is guided to the middle stage of the steam turbine via the steam pipe 55.

On the other hand, the saturated water in the low-pressure drum 50b is supplied to the high-pressure drum 50e via the high-pressure economizer 50d after the pressure thereof is increased by the high-pressure pump 52. And evaporator 50f
Is heated to an appropriate temperature by a superheater 50 g, and then guided to a middle stage of the steam turbine.

[0066] Thus, the heating steam source for the heat exchanger 40 to the condensate temperature T ₄ to a predetermined value or more, the high-pressure drum 50
e from the low pressure drum 50
The steam from b is used. Therefore, high plant efficiency can be maintained.

The regulating valves 51 and 53 and the regulating valve 42
The pressure loss in the control valve 3
5 and 42, it is possible to improve the plant efficiency at a partial load.

FIG. 5 shows a fourth embodiment of the present invention, in which the condensate at the inlet of the low-pressure stack gas cooler 26 is heated by the inlet water supply of the high-pressure stack gas cooler 25 at a partial load.

As shown in FIG. 5, a feed water branch pipe 62 having a feed water flow control valve 60 and a heat exchanger 61 is connected to the high pressure stack gas cooler 25 inlet feed water line.
A condensate branch pipe 64 having a condensate flow control valve 63 is connected to the inlet condensate line of the low-pressure stack gas cooler 26 so that condensate is supplied to the heat exchanger 61.

As shown in FIG. 5, the feed water temperature at point A on the exit side of the high-pressure stack gas cooler 25 is, as shown in FIG.
The condensate temperature at the point B on the inlet side of the low-pressure stack gas cooler 20 is determined by the temperature detector 6.
6 to be detected. The two flow rate adjusting valves 60 and 63 are connected to the two temperature detectors 65 and 66, respectively.
Is controlled by an opening signal from an arithmetic unit 67 which performs an operation by using a detection signal from the computer as an input.

The remaining configuration is the same as that of the first embodiment.

Next, the operation of the present embodiment will be described.

During normal operation, it is not necessary to use the heat exchanger 61, so that the feedwater flow control valve 60 and the condensate flow control valve 63 are fully closed, and the feedwater and condensate flowing into the heat exchanger 61 are set to zero. .

On the other hand, when a partial load is applied, an imbalance occurs in the relationship between the amount of condensed water or the amount of water supplied to the turbine cycle system and the amount of exhaust gas from the boiler 1, so that the outlet water supply temperature of the high-pressure stack gas cooler 25 rises Also, a situation occurs where the inlet condensing temperature of the low-pressure stack gas cooler 26 is too low.

Therefore, in this embodiment, the temperature at point A on the exit side of the high-pressure stack gas cooler 25 and the temperature at point B on the entrance side of the low-pressure stack gas cooler 26 are measured by the temperature detectors 65 and 66.
, And each detection value is calculated by a calculator 67 to control the opening of each of the flow control valves 60 and 63.
Thereby, in the heat exchanger 61, heat exchange is performed between the feed water and the condensate water, and the outlet feed water temperature of the high-pressure stack gas cooler 25 and the inlet condensate temperature of the low-pressure stack gas cooler 26 are prevented from being too low. You.

Thus, even at the time of partial load, it is possible to prevent the occurrence of steaming in the economizer of the boiler 1 and the adhesion of sulfur to the outer wall of the tube of the low-pressure stack gas cooler 26.

[0077]

As described above, according to the first aspect of the present invention, the exhaust heat recovery boiler for heating and evaporating the feed water with the exhaust gas of the boiler is installed in parallel with the high-pressure stack gas cooler, and Since the distribution means for controlling the distribution ratio of the exhaust gas to the high-pressure stack gas cooler and the control means for controlling the flow rate of the water supply to the exhaust heat recovery boiler and the high-pressure stack gas cooler are provided,
By reducing the amount of exhaust gas supplied to the high-pressure stack gas cooler, it is possible to prevent the occurrence of steaming in the boiler economizer. Then, the remaining exhaust gas is supplied to the exhaust heat recovery boiler to generate steam, and the steam is used in the steam turbine cycle system, whereby plant efficiency can be improved.

Further, according to the second aspect of the present invention, at the time of partial load, the temperature of the condensate of the inlet of the low-pressure stack gas cooler tends to decrease, and the condensate of the inlet is supplied to the heat exchanger by steam from the exhaust heat recovery boiler. Since the heat is exchanged and heated, the temperature is prevented or reduced. Therefore, it is possible to prevent or reduce the adhesion or corrosion of sulfur due to a decrease in the temperature of the low-pressure stack gas cooler through which the inlet condensate flows.

In the third aspect of the present invention, a heat exchanger for performing heat exchange between the condensed water of the inlet of the low-pressure stack gas cooler and the water supply of the inlet of the high-pressure stack gas cooler is provided. By performing heat exchange between feed water and condensate in this heat exchanger, it is possible to prevent the outlet feed water temperature of the high pressure stack gas cooler from rising too high and the inlet condensing temperature of the low pressure stack gas cooler from dropping too much. , And the adhesion of sulfur to the outer wall of the tube of the low-pressure stack gas cooler can be prevented.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a repowering system for a steam power plant according to a first embodiment of the present invention.

2A is a QT diagram of a high-pressure stack gas cooler according to the first embodiment, and FIG. 2B is a QT diagram of an exhaust heat recovery boiler according to the first embodiment.

FIG. 3 is a system diagram showing a repowering system for a steam power plant according to a second embodiment of the present invention.

FIG. 4 is a system diagram showing a repowering system for a steam power plant according to a third embodiment of the present invention.

FIG. 5 is a system diagram showing a repowering system for a steam power plant according to a fourth embodiment of the present invention.

FIG. 6 is a system diagram showing an example of a conventional steam power generation facility.

FIG. 7 is a system diagram showing an example of a conventional repowering system in which a gas turbine plant is added to an existing steam power generation facility.

8 is a system diagram showing a conventional repowering system in which a low-pressure stack gas cooler is added to the system of FIG. 7;

[Explanation of symbols]

 1 Boiler 3 High Pressure Turbine 7 Medium Pressure Turbine 9 Low Pressure Turbine 10 Generator 11 Condenser 22 Gas Turbine 23 Gas Turbine Generator 25 High Pressure Stack Gas Cooler 26 Low Pressure Stack Gas Cooler 30,50 Exhaust Heat Recovery Boiler 31 Damper 35,51,53 Adjustment Valve 61 heat exchanger

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) F01K 19/00 F01K 7/02 F01K 23/02 F01K 23/10 F01K 7/40-7/44 F22D 1 / 00 F22D 11/00

Claims (3)

(57) [Claims] 1. A high-pressure stack gas cooler in which a gas turbine plant is added to a steam power generation facility, and exhaust gas of a gas turbine is used as combustion air of a boiler, and exhaust gas of the boiler is heated to feed water of a steam turbine cycle system. In a repowering system configured as an exhaust reburn type combined cycle by supplying an exhaust heat recovery boiler that heats and evaporates feed water with exhaust gas from the boiler, the exhaust heat recovery boiler is installed in parallel with the high-pressure stack gas cooler with respect to the flow of exhaust gas, And a distribution means for controlling an exhaust gas distribution ratio to the exhaust heat recovery boiler and the high-pressure stack gas cooler, and a control means for controlling a flow rate of water supply to the exhaust heat recovery boiler and the high-pressure stack gas cooler. Repowering system. 2. A low-pressure stack gas cooler for heating condensate of the steam turbine cycle system by exhaust gas from the boiler, and heat exchange between a condensate condensate of the low-pressure stack gas cooler and steam from the exhaust heat recovery boiler. The repowering system for a steam power plant according to claim 1, further comprising a heat exchanger. 3. A high-pressure stack gas cooler for adding a gas turbine plant to a steam power generation facility, using exhaust gas from the gas turbine as combustion air for a boiler, and heating exhaust gas from the boiler to feed water for a steam turbine cycle system. In a repowering system in which a condensate of a steam turbine cycle is sequentially supplied to a low-pressure stack gas cooler for heating condensate and constitutes an exhaust heat re-combustion combined cycle, an inlet condensate of the low-pressure stack gas cooler and an inlet water supply of a high-pressure stack gas cooler are provided. A repowering system for steam power generation equipment, which is provided with a heat exchanger that performs heat exchange.