JP3101451B2 - Exhaust-reburn combined cycle power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steam turbine plant, in which a gas turbine is combined, and the exhaust gas of the gas turbine is introduced into a boiler of the steam turbine plant. The present invention relates to an exhaust gas reburning combined cycle power plant in which the operation of a ventilator is omitted and the heat efficiency of a high-temperature exhaust gas from a gas turbine is recovered to improve the thermal efficiency of the plant.

[0002]

2. Description of the Related Art FIG. 10 is a schematic diagram of a general steam turbine plant, in which high-pressure, high-temperature main steam generated in a boiler 1 is introduced into a high-pressure turbine 2a and a low-pressure turbine 2b in order, and works there. By driving the generator 3, power is obtained. The steam that has performed the work in the turbine 2 is condensed by a condenser 4 as exhaust gas, and the condensed water is pressurized by a condensate pump 5 and dewatered through low-pressure feedwater heaters 6a and 6b connected in parallel with each other. It is sent to the porcelain 7.

[0003] The feed water degassed by the deaerator 7 is pressurized by a booster pump 8 and a feed water pump 9 and passes through high pressure feed water heaters 10a and 10b connected in parallel to each other to regenerate the boiler 1 again.
Sent to In the drawings, reference numerals 11a, 11b, and 11c denote bleed tubes for supplying heating steam to the high-pressure feedwater heaters 10a and 10b, the deaerator 7, and the low-pressure feedwater heaters 6a and 6b, respectively.

Meanwhile, in the boiler 1, combustion is carried out by fuel and air sent from the forced air blower 12, and the feed water is heated to generate main steam, while the exhaust gas generated in the boiler 1 is burned by the air preheater 13. After exchanging heat with the air for use to recover the heat of the exhaust gas, the exhaust gas is released from the chimney 14 into the atmosphere.

On the other hand, an exhaust gas reburning combined cycle power plant in which a gas turbine is combined with the steam turbine plant as described above is as shown in FIG.

That is, in the figure, reference numeral 15 denotes a compressor, and air compressed by the compressor 15 is supplied to a combustor 16, where it is burned together with fuel supplied to the combustor 16, and high-temperature gas is removed from the gas turbine. The generator 18 is driven by the gas turbine 17. The exhaust gas from the gas turbine 17 is introduced into the boiler 1 and used for heat recovery, and unburned oxygen is used for boiler combustion.

The exhaust gas from the boiler 1 is supplied to high-pressure feed water heaters 10a and 10b and low-pressure feed water heaters 6a and 6b.
b through a high-pressure stack gas cooler 19 and a low-pressure stack gas cooler 20 provided in parallel with each other.
4 to the atmosphere.

[0008]

As described above, an exhaust gas reburning combined cycle power plant is constructed by combining a steam turbine plant and a gas turbine plant, but the gas turbine is a device using high-temperature combustion gas as a medium. Therefore, the parts are worn out faster than the steam turbine side, and the intervals of the periodic inspection and the maintenance / inspection are short. Also, the regular inspection intervals specified by laws and regulations do not match the steam turbine equipment.

Further, the ratio of the output of the gas turbine to the plant is generally 1/3 or less. Therefore, when it is necessary to stop the gas turbine for a periodical inspection or for some reason, stopping the high-power steam turbine together is disadvantageous in terms of effective utilization of power generation equipment and stable supply of power. Become.

Therefore, when the gas turbine is operable, a combined cycle operation with high thermal efficiency is performed, and during the gas turbine stop period, the steam turbine side is independently operated by a forced draft fan provided as a spare machine. It is preferable that combined cycle operation and single operation of the steam turbine can be realized in the same facility.

[0011] In the case of realizing both the combined cycle operation and the sole operation on the steam turbine side in the exhaust reburning combined cycle power plant, the following can be considered as plant operation.

A) When the gas turbine is healthy and can always be operated, the main operation is a combined cycle operation with high efficiency and high power generation capacity as a power station. In particular, when power demand is tense such as in the summer, it is expected that the operation will continue for a long time in the combined cycle operation.

B) The gas turbine is a device equipped with a compressor, and it is difficult to narrow down the exhaust gas amount even in the partial load operation.
It is assumed that it is relatively high at about 50%. Therefore, operations such as shutting down the plant in the load zone where excess power is generated at night or on weekends, or excluding the gas turbine from combined cycle operation and shifting to single operation of the steam turbine to reduce the minimum load are also anticipated. Is done.

C) At the time of periodic inspection of the gas turbine, the operation shifts to the steam turbine alone operation systematically. If the gas turbine side stops for some reason during the combined cycle operation, the operation immediately shifts to the steam turbine alone operation. Operation is expected.

However, in the combined cycle operation, since the heat of the boiler exhaust gas is recovered by the stack gas cooler installed in parallel with the feed water heater on the steam turbine side, a large amount of feed water and condensate are supplied from the steam turbine side. Therefore, there is a problem that the flow rate of feed water and condensate flowing through the feed water heater side is extremely reduced to about 1/2 to 1/3 in comparison with the rated output operation of the steam turbine alone operation. .

Further, even when the total load of the combined cycle operation is reduced by reducing the load of the gas turbine, the exhaust gas is gently reduced with the decrease in load due to the characteristics of the gas turbine. Therefore, the steaming of the stack gas cooler is prevented. Therefore, it is necessary to positively increase the ratio of water supply and condensate supply, and if the load is less than the load, the entire amount of water supply and condensate is supplied to the stack gas cooler, and the flow rate on the feed water heater side becomes zero.

Therefore, in order to control a small flow rate in the combined cycle operation by a large-capacity bleed valve system or a drain control valve system in consideration of the steam turbine alone operation, a small bypass is required for the bleed valve system and the drain control valve system. Switching systems such as adding a valve system, etc., are required during the combined cycle operation with this small bypass valve system, while the steam turbine alone operation requires a large valve system to perform switching control. It is difficult to secure operability and operability at the same time.

Generally, the shell and water chamber of the feed water heater are made of steel, and a steel tube is used for the tube. Therefore, the quality of the water supply and condensate remaining in the supply water heating chamber on the stop side deteriorates with time, and if it exceeds about 100 hours, it will be unacceptable for plant operation. Therefore, there is a possibility that poor quality water may flow into the clean system on the operation side at the time of start of the stop side. After the operation, it is necessary to perform a cleanup operation such as repeating the out-of-system blow several times again.

Furthermore, air and moisture remaining inside the feedwater heater shell on the steam chamber side generate iron oxide on the outer surface of the tube and the inside of the shell. In order to prevent the inflow of iron, it is necessary to use a shell blow system to discharge a large amount of condensed water extracted from the system over a long period of time.

In order to perform a series of cleanup operations and shell blow operations of the feed water heater on the stop side, it is necessary to perform the operation for about ten and several hours after completely stopping the plant, which impairs operability. Becomes In addition, in a feedwater heater having a thick-walled portion, when it is quickly started from a cold state after a long stoppage, an excessive thermal stress is generated, and cracks are generated due to frequent start-stops. There is a problem that they may be linked.

In view of the above, the present invention can effectively switch between the combined cycle operation and the single operation of the steam turbine plant, and can easily and arbitrarily restart the feed water heater on the stop side. Exhaust refueling that enables switching to the operation side and enables the restart of the feedwater heater on the stop side promptly even in the event of a short-term shift to independent operation of the steam turbine plant due to a gas turbine failure, etc. The purpose is to obtain an integrated combined cycle power plant.

[0022]

SUMMARY OF THE INVENTION The present invention is directed to a stack gas cooler installed in parallel with a steam turbine plant feed water heater while supplying exhaust gas from a gas turbine to a boiler of a steam turbine plant. In an exhaust gas reburning combined cycle power plant in which heat is exchanged with a part of feedwater to recover heat, at least two feedwater heaters are provided in parallel with each other, and a feedwater inlet of a high-pressure feedwater heater of each system. Side and is connected to the discharge side of the booster pump for the water supply pump connected to the upstream side of the water supply pump via a warming valve provided in parallel with the inlet valve, and the water supply outlet side of the high-pressure water heater is reconnected. It is characterized by being connected to a deaerator through a recirculation pipe having a circulation valve.

Further, the second invention is characterized in that a small-diameter low-pressure warming valve is connected in parallel with the outlet valve of the low-pressure feedwater heater of each system.

According to a third aspect of the present invention, the outlet sides of the high-pressure feed water heaters of the respective systems are connected by a feed water communication system having respective stop valves, and the outlet sides of the respective valves are connected via a single flow control valve. It is characterized by being connected to the water supply pipe to the boiler.

[0025]

During the combined cycle operation, a small amount of moderately warm water is constantly supplied from the steam turbine system during operation to the feed water heater on the stopped side, so that the heater enters a warming state.
Therefore, it is possible to suppress the generation of thermal stress at the time of restarting, and to prevent corrosion and water quality deterioration due to stagnant water during a long-term stop, and to always keep a standby state.

In particular, for a high-pressure feed water heater having a thick-walled structure, hot water from a deaerator system is appropriate. Supply water is supplied from a discharge system of a booster pump for a water feed pump, and the return is collected by a deaerator. As a result, the object can be achieved without lowering the thermal efficiency of the plant. Also, for the low-pressure feedwater heater, by providing a small-diameter system that bypasses the outlet valve of the low-pressure feedwater heater, a small flow of condensate can flow to the deaerator side.

In the combined cycle operation, the distribution of the water supply between the high-pressure feedwater heater and the stack gas cooler is controlled by a control valve installed at the outlet or the inlet of the high-pressure feedwater heater, but the flow rate of the feedwater flowing through the high-pressure feedwater heater is small. , And one-system operation. Furthermore, since no control valve is provided for each of the two systems because they are not used at all in the steam turbine plant, two systems of the high-pressure feed water heater are connected to share one control valve. As a result, sizing that is most suitable for system simplification and combined cycle operation can be achieved.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same parts as those in FIGS. 10 and 11 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a view showing one embodiment of the present invention. The high pressure feed water heaters 10a and 10b have high pressure feed water heater inlet valves 21a and 21b and high pressure feed water heaters respectively on the inlet side and the outlet side. Outlet valves 22a, 22b are provided. A high-pressure warming system 23 branches out from the discharge side of the booster pump 8 connected in series to the upstream side of the feedwater pump 9, and the high-pressure warming system 23 is connected in parallel with the high-pressure feedwater heater inlet valves 21a and 21b. It is connected to the outlet side of the high pressure feed water heater inlet valves 21a, 21b via the provided high pressure warming valves 24a, 24b, respectively.

Recirculation pipes 25a and 25b are connected to outlets of the high-pressure feed water heaters 10a and 10b, respectively.
a, 26b are connected to the deaerator 7; In addition,
In the figure, reference numerals 27a and 27b are high-pressure bleed valves, and reference numeral 2
Reference numerals 8 and 29 denote a water supply inlet valve and a water supply outlet valve of the high-pressure stack gas cooler 19.

On the other hand, an inlet valve 30 and a low-pressure feedwater heater inlet valve 30 are provided at the inlet and outlet sides of the low-pressure feedwater heaters 6a and 6b, respectively.
a, 30b and low-pressure feedwater heater outlet valves 31a, 31b are provided, and the low-pressure feedwater heater outlet valves 31a, 3b are provided.
Low-pressure warming valves 32a, 32b in parallel with 1b
Is provided. In the drawings, reference numerals 33a and 33b denote low-pressure bleed valves, respectively, and reference numerals 34 and 35 denote a feedwater inlet valve and a feedwater outlet valve of the low-pressure stack gas cooler 20, respectively.

In the combined cycle operation, when the operation of one system of the feed water heater, that is, the operation of the A system including the low-pressure feed water heater 6a and the high-pressure feed water heater 10a and the parallel operation of the stack gas cooler are performed, The inlet valve 21b and the outlet valve 22b of the B-series high-pressure feedwater heater 10b are closed, and the recirculation valve 26a, the high-pressure bleed valve 27b, and the high-pressure warming valve 24a are closed.

Therefore, the water supplied by the water supply pump 9 is introduced into the high-pressure water heater 10a through the inlet valve 21a, where it is heated by exchanging heat with the bleed air supplied through the high-pressure bleed valve 27a, and is heated. After being supplied to the high-pressure stack gas cooler 19 via the high-pressure stack gas cooler 19, it is supplied to the boiler 1.

On the other hand, a part of the supply water which is moderately warm water discharged from the booster pump 8 is sent to the high pressure feed water heater 10b of the B series via the high pressure warming valve 24b of the high pressure warming system 23, Further, the residual water is collected by the deaerator 7 through the recirculation pipe 25b having the recirculation valve 26b, and ventilation and warming of the residual water in the high-pressure feed water heater 10b on the stop side are performed, and a long-term stop state is achieved. Even in the water chamber and tube of the high pressure feed water heater,
Further, the water quality of the supply water remaining in the connecting pipe is prevented from being lowered, and a provision is made for restart.

The water supply from the high-pressure warming system 23 may be taken out from the deaerator main body or the blow system and the downcomer. In this case, the condenser 4 is appropriate as the recovery destination.

For the low-pressure feed water heater, ventilation and warming of the residual B-series water on the stop side are performed. Therefore, the outlet valve 31b of the stop system is closed and the low-pressure warming valve 32b is opened. In the low-pressure feed water heater 6b, a small amount of condensed water limited by the low-pressure warming valve 32b is combined with the condensate flowing out of the operating low-pressure feed water heater 6a and supplied to the deaerator 7.

The low-pressure warming system may be connected to the condenser 4 to recirculate the condensate water, and the low-pressure warming system and the low-pressure warming valves 32a and 32b may be omitted to provide a low-pressure feed water heater outlet. The valve 31b may be slightly opened.

FIG. 2 shows an example of starting the steam turbine in the single operation mode of the steam turbine plant, and FIG. 3 shows the relationship between the plant load and the boiler feedwater flow rate. According to this figure, the plant load and the feedwater flow rate are almost proportional, and the feedwater passes through the feedwater heater in its entirety. Become.

On the other hand, FIG. 4 shows an example of starting the plant in the combined cycle operation mode. First, the gas turbine is started to increase the load, and the boiler is ignited at the gas turbine load β where the exhaust gas temperature has risen to some extent. Further, the concept shows the case where the main steam pressure and the temperature of the boiler generation are appropriately increased at the gas turbine load γ to start the steam turbine to perform the combined cycle operation. FIG.
The schematic relationship between the load on the steam turbine side and the flow rate of the boiler feedwater, and the load on the steam turbine side and the distribution of feedwater to the stack gas cooler and the feedwater heater in the combined cycle operation are shown. In this figure, at a low load, there is a load region where the feedwater on the feedwater heater side becomes zero, and the flow rate changes from a to b and c as the load increases.

FIG. 6 shows an example of start-up of the plant in the combined cycle operation mode. First, the steam turbine plant is started up in the single operation mode, and the gas turbine is started up with the intermediate load α to perform the combined cycle operation. It shows the concept.

FIG. 7 shows a schematic relationship between the load on the steam turbine side and the flow rate of the boiler feedwater, and the load on the steam turbine side and the distribution of the feedwater of the stack gas cooler and the feedwater heater in the combined cycle operation. The stack gas cooler is activated by a load α in the middle of the steam turbine to flow water. Therefore, after the flow rate of the feed water heater is once decreased from the flow rate A to the flow rate B, the flow rate is changed to the flow rate C as the load increases.

Therefore, in the combined cycle operation of the combined cycle power generation plant of the exhaust gas re-combustion type, the feed water heater is operated in one line, and the control capacity is adapted to the low-flow water supply and the condensate, so that the load change of the plant can be reduced. Also, it is possible to improve the operability in starting and stopping.

Further, in the steam turbine alone operation in which it is necessary to operate the feed water heater under multi-flow water supply and condensate water, operating the feed water heater in two systems enables proper control performance. And the operability at the time of load change and start / stop of the plant is improved.

As described above, by switching the feed water heater series in accordance with the operation of the plant, the feed water heater is switched between the two series in the steam turbine alone operation and the one series in the combined cycle operation, and the feed water heater is switched. And the heater drain and the bleeding control equipment can be optimized and optimized.
In addition, the feed water heater while the operation is stopped always performs warming and ventilation so that the operation series can be switched quickly and easily.

FIG. 8 is a diagram for explaining a method of storing the steam system and the heater drain system of the stop-side feedwater heater in the method of operating the feedwater heater in the combined cycle operation according to the present invention.

In the figure, high pressure feed water heaters 10a, 10a
b is connected to the deaerator 7 via a heater drain system 40 having heater drain valves 40a and 40b, respectively, and connected to the condenser 4 via a vacuum communication system 41 having vacuum communication valves 41a and 41b, respectively. I have. The low-pressure feedwater heaters 6a and 6b are also connected to the condenser 4 by a vacuum communication system 42 having vacuum communication valves 42a and 42b, respectively.

The stop-side feedwater heaters 10a, 10a
b, the high-pressure bleed valve 27b, the low-pressure bleed valve 33b, and the heater drain valve 40b
Is closed, and the inflow of bleed air to the high-pressure feedwater heater 10b and the low-pressure feedwater heater 6b is shut off. At the same time, when the operation is stopped for a long time, the vacuum communication valves 41b and 42b are opened. Therefore, both feed water heaters 10
The insides of b and 6b communicate with the condenser 4 to form a vacuum to prevent oxidation of the inside of the shell and the outer surface of the tube.

The vacuum communication system and the vacuum communication valves 41a, 41
1b, 42a, and 42b may use a shell blow valve system provided in the feed water heater.

In order to control feed water distribution during the operation of the high pressure feed water heater in the combined cycle operation and the parallel operation of the stack gas cooler, the high pressure feed water heaters 10a and 10b are required.
The upstream side of the outlet valves 22a and 22b of the water supply distribution control valve 45
You may contact each other via.

That is, as shown in FIG. 9, the upstream sides of the outlet valves 22a, 22b of the high-pressure feed water heaters 10a, 10b are connected by a feed water communication system 46 having stop valves 46a, 46b. Water supply distribution control valve 45
May be connected to the inlet pipe 47 of the boiler 1 via the. Alternatively, the outlet valve 29 of the high-pressure stack gas cooler 19 may be a water supply distribution control valve.

In the combined cycle operation,
By closing the outlet valve 22a of the operating high-pressure feed water heater 10a, opening the stop valve 46a, and fully closing the stop valve 46b, the feedwater flowing out of the high-pressure feed water heater 10a is
The flow rate of the water is controlled by the water supply distribution control valve 45 through the stop valve 46a, and the water flows out of the high-pressure stack gas cooler 19 to be merged. The same operation can be performed by controlling the outlet valve 29 serving as the water supply distribution control valve.

By connecting the A and B series of high pressure feed water heaters and controlling them with one valve in this manner, sizing suitable for small flow rate control in combined operation and simplification of the system by common use can be achieved. it can. Further, the feedwater distribution control valve may be provided on the inlet valves 21a, 21b side of the high-pressure feedwater heater.

[0053]

Since the present invention is configured as described above, even in a long-term one-system operation of the feedwater heater in the combined cycle operation, a small amount of system water having an appropriate temperature is supplied to the stop-side feedwater heater. By flowing and warming to always be in a standby state, it can be started in a short time without imposing excessive thermal stress on the feedwater heater with thick structure,
Emergency switching between combined cycle operation and steam turbine independent operation is possible, and good combined cycle operation and steam turbine independent operation can be achieved at the same time, and various and flexible plant operability can be achieved.

Further, when restarting the feed water heater on the long-term stop side, a long-term clean-up operation on the water chamber side is unnecessary, and when the steam side is kept in a vacuum storage state, the generation of iron oxide in the inside becomes impossible. And the time required for shell blowing can be reduced, and system water can be saved.

Furthermore, by arbitrarily activating the feed water heater on the stop side during the combined cycle operation and switching to the operation side, the equipment life and scale adhesion of the two feed water heaters can always be made the same level. It is possible to maintain high reliability in maintenance inspection and management plan.

When the warming water of the high pressure feed water heater is supplied from the discharge system of the booster pump for the feed water pump, the differential pressure of the valve and the piping is as small as about 20 to 40 atm.
This has the advantages of high reliability in withstand voltage design and suppression of system erosion.

[Brief description of the drawings]

FIG. 1 is a diagram showing a single-line operation of a feedwater heater and a parallel operation of a stack gas cooler in a combined cycle operation of an exhaust gas reburning combined cycle power plant of the present invention, and an operation state of a feedwater system and a condensate system of a stop-side feedwater heater. FIG.

FIG. 2 is an explanatory view of starting a steam turbine in an isolated operation of the steam turbine plant.

FIG. 3 is a diagram showing a relationship between a plant load and a boiler water supply amount.

FIG. 4 is an explanatory diagram of startup in a combined cycle operation according to the present invention.

FIG. 5 is a diagram showing the load on the steam turbine side and the sharing of water supply or condensate of a feedwater heater and a stack gas cooler when performing a combined operation by starting up the steam turbine side after starting up the gas turbine side.

FIG. 6 is a start explanatory diagram in a case where a combined operation is performed by starting up the gas turbine side after starting up the steam turbine side.

FIG. 7 is a diagram showing the load on the steam turbine side and the sharing of water supply or condensate of a feedwater heater and a stack gas cooler in the case of FIG. 6;

FIG. 8 is a diagram showing a steam system and a heater drain system of a stop-side feedwater heater.

FIG. 9 is a diagram showing another embodiment of the present invention.

FIG. 10 is a schematic system diagram of a general steam turbine plant.

FIG. 11 is a schematic system diagram of an exhaust gas reburning combined power plant in which a gas turbine is combined with a steam turbine plant.

[Explanation of symbols]

 Reference Signs List 1 boiler 2a high-pressure turbine 2b low-pressure turbine 4 condenser 5 condensate pump 6a, 6b low-pressure feedwater heater 7 deaerator 8 booster pump 9 feedwater pump 10a, 10b high-pressure feedwater heater 14 chimney 15 compressor 16 combustor 17 gas turbine 19 High pressure stack gas cooler 20 Low pressure stack gas cooler 21a, 21b High pressure feed water heater inlet valve 22a, 22b Low pressure feed water heater outlet valve 24a, 24b High pressure warming valve 25a, 25b Recirculation pipe 26a, 26b Recirculation valve 30a, 30b Low pressure water Heater inlet valve 31a, 31b Low pressure feed water heater outlet valve 32a, 32b Low pressure warming valve 40a, 40b Heater drain valve 41a, 41b, 42a, 42b Vacuum communication valve 45 Water supply distribution control valve

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01K 23/10 F22D 1/22 F01K 7/40

Claims (4)

(57) [Claims] An exhaust gas from a gas turbine is supplied to a boiler of a steam turbine plant, and the exhaust gas from the boiler is heat-exchanged with a part of feed water in a stack gas cooler installed in parallel with a feed water heater of the steam turbine plant. In the exhaust gas reburning combined cycle power plant configured to perform heat recovery, the feedwater heaters are provided in at least two systems that are provided in parallel with each other, and are branched at the feedwater inlet side of the high-pressure feedwater heaters of each system to form an inlet valve. A recirculation pipe having a recirculation valve connected to the discharge side of the booster pump for the water supply pump connected to the upstream side of the water supply pump through a warming valve provided in parallel, and a water supply outlet side of the high-pressure water heater. A combined regenerative-exhaust-type power plant characterized by being connected to a deaerator through a gas turbine. 2. A combined regenerative exhaust power plant according to claim 1, wherein a small-diameter low-pressure warming valve is connected in parallel with the outlet valve of the low-pressure feedwater heater of each system. 3. A high-pressure feed water heater outlet side of each system is connected by a feed water communication system having a stop valve.
2. The combined cycle power generation plant according to claim 1, wherein the outlet side of each valve is connected to a water supply pipe to a boiler via one flow control valve. 4. The heating steam outlet side of each high-pressure feed water heater is branched into a vacuum communication system having a vacuum communication valve and a heater drain system having a heater drain valve, wherein the vacuum communication system is connected to a condenser and the heater drain system is connected to a condenser. The exhaust-gas re-combustion combined cycle power plant according to claim 1, wherein the combined plant is connected to a deaerator.