JPH1061413A - Exhaust reburning type compound power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently operate an exhaust reburning type compound power plant without changing an existing back pressure extraction type boiler air supply pump driving turbine into a condensation type, by connecting the back air pipe of the back pressure extraction type boiler water supply pump driving turbine to a condenser through a back pressure controlling/adjusting valve. SOLUTION: Exhaust gas finished its work in a gas turbine 20 is introduced to a boiler 1, steam generated in the boiler 1 is introduced to respective high, middle and low pressure turbines 2 to 4, and worked in the turbines 2 to 4, and after that, water is condensed in a condenser 6, and condensate is refluxed to the boiler 1 after being heated and degased. At this time, a boiler supply pump 11 is interposed in the middle of a condensation circuit, steam extracted from a low temperature reheating steam pipe 30 is supplied to a turbine 24 for BFP by which the boiler supply pump 11 is driven, and the heating steam of a water supply heater 12a is extracted from the middle turbine stage of the turbine 24 for BFP. The back air of the turbine 24 for BFP is introduced to a water supply heater 8b through a back air pipe 31, however, a second back air pipe 33 is branched from the back air pipe 31 and connected to the condenser 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas reburning combined cycle power plant in which a gas turbine is added to an existing steam turbine plant.

[0002]

2. Description of the Related Art FIG. 7 is a system diagram showing a schematic configuration of a general steam turbine plant, in which high-pressure and high-temperature main steam generated in a boiler 1 is introduced into a high-pressure turbine 2 and works there. The steam is reheated in the boiler 1 and sequentially introduced as high-temperature reheated steam into the medium-pressure turbine 3 and the low-pressure turbine 4, where the work is performed and the generator 5 is driven to generate power.

[0003] The steam that has worked in the low-pressure turbine 4 is condensed by a condenser 6, and the condensed water is pressurized by a condensate pump 7 and sent to a deaerator 9 through low-pressure feedwater heaters 8 a and 8 b. Sent. Then, the feed water degassed by the deaerator 9 is pressurized by the booster pump 10 and the boiler feed pump 11 and returned to the boiler 1 again through the high pressure feed water heaters 12a, 12b, 12c.

The boiler 1 has a fuel f and a forced ventilation 13
And the air supplied therefrom is supplied, where it is combusted to heat the feed water and generate main steam. The exhaust gas after heating the feed water in the boiler 1 is preheated by exchanging heat with air supplied to the boiler 1 in the air preheater 14, and then the chimney 1
5 to the atmosphere.

On the other hand, the boiler feed pump 11 is driven by a boiler feed pump drive turbine 16. The boiler feedwater pump drive turbine 16 is operated by bleed air extracted from the intermediate pressure turbine 3, and the exhaust gas of the boiler feedwater pump drive turbine 16 is introduced into the condenser 6.
The high-pressure water supply devices 12a, 12b, and 12c are supplied with bleed air from appropriate stages of the medium-pressure turbine 3 and the high-pressure turbine 2 to heat the water supply, and the low-pressure water heaters 8a, 8b.
Is supplied with bleed air from the middle stage of the low-pressure turbine 4,
Condensate heating is performed.

FIG. 8 shows a boiler feed pump 11 driven by a boiler feed pump driving turbine 17 of bleed-back pressure. However, in such a plant, the bleed air and back air from the bleed air back pressure type boiler feed pump drive turbine 17 are supplied to the high pressure feed water heater 12.
a and the deaerator 9 and the low-pressure feed water heater 8b are heat-recovery cycles, so that the operation and control of the plant are relatively difficult, so recently a condensing boiler feed pump as shown in FIG. Those using the drive turbine 16 are the mainstream.

Recently, a gas turbine has been added to an existing steam turbine plant as described above, and the exhaust gas from the gas turbine has been introduced into a boiler to constitute an exhaust gas reburning type combined power generation plant. The output is generally increased.

FIG. 9 is a diagram showing an example in which a gas turbine is added to the existing steam turbine plant.
The air pressurized by the compressor 18 is introduced into the combustor 19, where it is burned with separately supplied fuel, and the combustion gas is supplied to the gas turbine 20. Then, the generator 21 is driven by the gas turbine 20.

On the other hand, the exhaust gas of the gas turbine 20 is introduced into the boiler 1 and used as alternative air required for combustion. The boiler exhaust gas after heating the feed water in the boiler 1 is supplied to the high-pressure stack gas cooler 22 connected in parallel to the high-pressure feed heaters 12a, 12b, and 12c and the low-pressure stack connected in parallel to the low-pressure feed heaters 8a and 8b. The gas is discharged from the chimney 15 to the atmosphere via the gas cooler 23.

[0010]

By the way, in a plant already constructed as a steam turbine plant as described above, a gas turbine is newly installed, and its exhaust gas is introduced into a boiler to perform heat recovery. Furthermore, in a waste heat reburning combined turbine plant that uses unburned oxygen contained in exhaust gas as a substitute for boiler combustion air,
In order to improve the thermal efficiency of the plant, it is necessary to recover the heat retained in the exhaust gas from the boiler by supplying and condensing water on the steam turbine side.

Therefore, the existing high pressure feed water heaters 12a,
A high-pressure stack gas cooler 22 and a low-pressure stack gas cooler 23 are installed in parallel with 12b, 12c and the low-pressure feedwater heaters 8a, 8b, respectively, so that the water supply system becomes complicated, and further, exhaust gas heat recovery and flow distribution of feedwater and condensate water. There is a problem that control is added and control becomes difficult.

In particular, in the case of repowering an existing plant employing a bleed-back pressure boiler feed pump turbine as shown in FIG. 8, in order to simplify the system configuration and improve the operation and controllability, As shown in Fig. 9, the boiler feed pump drive turbine 24 was remodeled into a condensate type, and all the bleeding and back air supply from the boiler feed pump turbine 24 to the feed water heater were abolished, and the heating cycle was greatly improved. I needed to.

Further, in the existing steam turbine plant in which the feedwater pump is driven by the bleed-back pressure type boiler feedwater pump-driven turbine as described above, the bleed air and the back-air of the boiler feedwater pump-driven turbine are converted to the high pressure of the turbine system. In addition, the steam is condensed by recovering heat to the low-pressure feedwater heater and the deaerator, thereby making the steam work inside the turbine driven by the boiler feedwater pump to obtain power. Therefore, when the amount of bleed air and the amount of back air of the boiler feed pump drive turbine are reduced by narrowing the feed water and the return water of the feed water heater, the power generated by the boiler feed pump drive turbine is reduced.

However, in the back-air reburning combined turbine plant, as shown in FIG. 9, the stack gas cooler 2 is arranged in parallel with the high and low pressure feed water heaters of the steam turbine system.
2 and 23, and the stack gas coolers 22 and 23
A large amount of feed water and condensed water is branched from the steam turbine system and supplied. As a result, on the feed water heater side, the extraction capacity of the boiler feed pump driven turbine and the ability to collect back air are reduced, and the generated power is also reduced, so the supply of feed water to the boiler by the feed water pump is also reduced,
There is a problem that good operation and control of the exhaust reheat-type combined turbine plant are not established or extremely difficult, so that repowering cannot be realized.

Further, the ratio of the supply amount of water and condensate to the stack gas cooler varies depending on the plant load during combined operation, and the lower the load operation, the more the ratio of supply amounts of water and condensate to the stack gas cooler side. At low load, the feed water heater side is stopped and the whole amount may be supplied to the stack gas cooler side, so that it becomes more difficult to perform better operation and control.

In view of the above, the present invention has been made in consideration of the economical efficiency of an existing steam turbine plant employing a bleed-back pressure type boiler feedwater pump driven turbine without significantly changing the existing original feedwater heating cycle. It is an object of the present invention to obtain a high-efficiency and high-reliability combined-cycle exhaust gas turbine plant with the accompanying modification.

[0017]

According to a first aspect of the present invention, a gas turbine is newly installed in a steam turbine plant in which a boiler feed pump is driven by a bleed-back pressure type boiler feed pump drive turbine. Is introduced into a boiler and used for combustion in the boiler, and a high-pressure stack gas cooler and a low-pressure stack gas cooler for heat-exchanging exhaust gas from the boiler with feed water or condensate are respectively supplied with a high-pressure feed water heater and a low-pressure feed water heater. And a back-respiratory tube of the bleed-back pressure boiler feed pump driven turbine is connected to a condenser via a back-pressure control valve.

According to a second aspect of the present invention, in the exhaust-gas reheating combined cycle power plant, a deaerator heating bleed is extracted from the main turbine, and the deaerator heating bleed is supplied to the deaerator via a pressure reducing control valve. It is characterized in that it is supplied.

In a third aspect of the present invention, in the exhaust-gas reburning combined cycle power plant, a drain system that receives supply of bleed air from the main turbine and recovers the heater drain to a high-pressure feedwater heater that receives bleed air from the boiler feedwater pump turbine is provided. It is characterized by being connected to a condenser or a low-pressure feedwater heater.

A fourth aspect of the present invention is characterized in that a feedwater spillover pipe for spillover of feedwater from the high-pressure feedwater heater outlet to the condenser is provided.

A fifth aspect of the present invention is characterized in that a motor-driven boiler feed pump is provided in parallel with a boiler feed pump driven by a boiler feed pump turbine.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, the same portions as those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, the flow of air and gas on the gas turbine side is as follows.
9 to generate combustion gas. The combustion gas generated in the combustor 19 is supplied to a gas turbine 20, where power is generated to drive a generator 21. Exhaust gas from the gas turbine 20 is introduced into the boiler 1, and unburned oxygen contained therein is discharged. Is used for combustion of the boiler 1 to burn fuel. On the other hand, in the steam turbine system, the steam generated in the boiler 1 performs work in the high-pressure turbine 2, the medium-pressure turbine 3, and the low-pressure turbine 4, and is condensed in the condenser 6, and the low-pressure feed water heater 8a , 8b, the deaerator 9, and the high-pressure feedwater heaters 12a, 12b, 12c, and are returned to the boiler 1 again.

By the way, to the boiler feed water pump drive turbine 24 for driving the boiler feed pump 11, the extracted air extracted from the low temperature reheat steam pipe 30 for supplying the steam discharged from the high pressure turbine 2 to the reheater is supplied. The steam for heating the high pressure feed water heater 12a is extracted from the middle stage. Further, a stop valve 32 is provided in the back trachea 31 for introducing the back air of the boiler feed pump drive turbine 24 into the low-pressure feed water heater 8b, and a stop valve 32 connected to the condenser 6 from the upstream side of the stop valve 32 is provided. Two back trachea 33 are branched and introduced, and the second back trachea 33 is provided with a back pressure control regulating valve 35 controlled by a boiler feed pump driven turbine back pressure controller 34.

The deaerator 9 is supplied with bleed air extracted from the last stage of the intermediate-pressure turbine 3 as heating steam, and the deaerator bleed system 36 has a pressure-reducing control valve 37. Is controlled so that the kinetic pressure of the deaerator 9 does not exceed the design pressure at the time of the existing construction.

Further, a spillover pipe 38 is provided at the outlet side of the high-pressure feedwater heater 12c closest to the boiler 1 to return the feedwater flowing out of the high-pressure feedwater heater 12c to the condenser 6.

The heater drain, which receives bleed air from the main turbine, supplies the heater drain to the boiler feed pump drive turbine 24.
A drain system 39 that collects the high-pressure feed water heater 12a that receives bleed air from the condenser 6 includes the condenser 6 or the low-pressure feed water heater 8a,
A drain pipe 40 for discharging the drain is connected to 8b.

On the other hand, condensate flow distribution valves 41 and 42 are provided on the inlet side of the low-pressure feed water heater 8a and the inlet side of the low-pressure stack gas cooler 23, respectively. Further, the inlet side of the high-pressure feed water heater 12a and the high-pressure stack gas cooler 22 are provided. On the inlet side, are provided water supply flow rate distribution valves 43 and 44, respectively. Further, a motor-driven boiler feed pump 45 is connected in parallel with the turbine-driven boiler feed pump 11.

When the plant is started up and operated at a low load, the boiler feed pump driven turbine 24
The back pressure is controlled by the back pressure control regulating valve 35 to switch the back air to be supplied to the condenser 6, thereby eliminating the interference between the operation states of the feed water heater and the stack gas cooler system, and driving the boiler feed pump. Flexible and independent operation of the turbine can be achieved. FIG. 2 shows a comparison between back pressure control of a bleed back pressure boiler feed pump driven turbine and exhaust pressure characteristics of a condensate boiler feed pump driven turbine.

FIG. 3 is a diagram conceptually showing the operation state of the water supply and condensate system in the conventional steam turbine plant. The flow rate of the water supply and condensate in the rated output operation is 100% high pressure feed water heater and low pressure. Water is passed through the feedwater heaters, and all of them are passed through the high-pressure feedwater heater and the low-pressure feedwater heater, although they decrease almost proportionally at the partial load.

However, during combined operation in an exhaust-refueling combined cycle power plant, as shown in FIG. 4, the flow rates of feed water and condensate water in rated output operation are the same as those of the feed water heater at a ratio of B: C. It is distributed to the stack gas cooler side. At the time of partial load, the air is distributed proportionally, but actually, more air flows toward the stack gas cooler for suppressing the occurrence of steaming.

As described above, in the combined operation, the high-pressure and low-pressure feedwater heaters distribute the feedwater / combined flow with the stack gas cooler, while the deaerator 9 operates in the combined motion and the single operation of the steam turbine. In either case, since the entire amount of condensate is introduced, the bleeding for the relevant portion does not change significantly. That is, when the bleed air from the boiler feed pump drive turbine is supplied to the deaerator, for example, in the combined operation, the bleed air from the boiler feed pump drive turbine 24 to the high-pressure feed water heater 12a is reduced by half. Since there is almost no change on the degasser side, the pressure distribution inside the deaerator significantly changes, causing problems in operation and design.

On the other hand, in the present invention, since the bleed air from the main turbine, that is, the medium pressure turbine is supplied to the deaerator as described above, the boiler feed pump in the combined operation and the steam turbine alone operation is used. Extreme fluctuations in the bleed pressure of the drive turbine 24 can be suppressed, and stable operation can be ensured.

Further, in a system in which bleed air is supplied from a main turbine such as a high-pressure turbine and the drain of the feed water heater is recovered by a high-pressure feed water heater 12a that receives bleed air downstream from a boiler feed pump drive turbine 24, If the turbine driven by the boiler feedwater pump is not started, it is extremely difficult to start the high-pressure feedwater heater and to operate the service in and out.

However, in the present invention, the drain system 39 for collecting the drain in the high-pressure feed water heater 12a is provided with a drain pipe 40 for discharging the drain to the condenser 6 or the low-pressure feed water heaters 8a and 8b. Therefore, the high-pressure feed water heaters 12b, 12b receiving the bleed air from the main turbine
The drain of c alone is used as a condenser 6 or a low-pressure feed water heater 8
It can be discharged to the sides a and 8b, so that the above inconvenience can be solved.

In addition, when the plant is partially loaded in combined operation, a large amount of water and condensate must be supplied to the stack gas cooler, and the supply and condensate of the feed water heater are extremely restricted. The bleed air / back air of the drive turbine is not recovered by the feed water heater, and the power of the boiler feed pump drive turbine may not be secured.

Therefore, in the present invention, a spillover pipe 38 communicating with the condenser is provided at the outlet side of the high pressure feed water heater. Therefore, as shown in FIG. 5, the feedwater is supplied by forcibly utilizing the high-pressure feedwater heaters 12a, 12b, and 12c, and is forcibly returned to the condenser 6 from the outlet side of the high-pressure feedwater heater. be able to. Therefore, the bleed air and the condensing capacity of the back-air steam of the turbine driven by the boiler feed water pump can be enhanced, and the drive capacity of the feed water pump can be sufficiently ensured.

The drive system of the boiler feed pump is connected in parallel with the turbine drive by the boiler feed pump drive turbine 24 and the motor-driven feed pump 45, so that the main turbine is driven to drive the feed pump during combined operation. The amount of steam extracted from the boiler can be prevented from increasing and exceeding the design steam amount of the existing boiler. FIG. 6 shows the distribution of the water supply amount when the parallel operation is performed.

In the present invention, the steam turbine can be operated independently even when the gas turbine is stopped.

[0040]

Since the present invention is constructed as described above, a gas turbine is added to an existing steam turbine plant employing a bleed-back pressure type boiler feed pump driven turbine to achieve high efficiency and increased output. It is possible to obtain an exhaust gas reburnable combined cycle power plant that can be used. In other words, large-scale remodeling to increase the boiler design evaporation, major remodeling of the main turbine, and the front of the feedwater heater and deaerator, without changing the existing extraction back pressure boiler feed pump driven turbine to the condensing type It is possible to achieve an effect such as being able to operate efficiently as an exhaust gas reburning combined cycle power plant without modification such as replacement with a new product.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a schematic configuration of an exhaust gas reburning combined cycle power plant according to the present invention.

FIG. 2 is a comparative explanatory diagram of back pressure control of a bleed back pressure boiler feed pump driven turbine and back pressure characteristics of a condensate boiler feed pump driven turbine in combined operation.

FIG. 3 is an explanatory diagram of a flow rate of a feedwater heater in a conventional steam turbine plant.

FIG. 4 is a diagram showing the distribution of the feed water heating amount and the flow amount of the stack gas cooler during combined operation.

FIG. 5 is a diagram showing distribution of the flow rate of a feed water heater and a stack gas cooler when a spillover pipe is used during combined operation.

FIG. 6 is an explanatory diagram of water supply distribution when a boiler feed pump is operated in parallel with a motor drive and a turbine drive.

FIG. 7 is a schematic system diagram of a steam turbine plant in which a boiler feedwater pump driven turbine is a condensing type.

FIG. 8 is a schematic system diagram of a steam turbine plant in which a boiler feedwater pump driven turbine is of a bleed back pressure type.

FIG. 9 is a schematic system diagram showing a state in which a boiler feed pump-driven turbine is converted into a condensate type to form an exhaust re-burning combined cycle power plant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler 2 High pressure turbine 3 Medium pressure turbine 4 Low pressure turbine 6 Condenser 7 Condenser pump 8a, 8b Low pressure feed water heater 9 Deaerator 11 Boiler feed pump 12a, 12b, 12c High pressure feed water heater 15 Chimney 16, 24 Boiler Feed water pump drive turbine 18 Compressor 19 Combustor 20 Gas turbine 22 High pressure stack gas cooler 23 Low pressure stack gas cooler 31, 33 Back tracheal pipe 35 Back pressure control control valve 36 Deaerator extraction system 37 Pressure reduction control valve 38 Spillover pipe 39 Drain system 40 Drain pipe 41, 42 Condensate flow distribution valve 43, 44 Feedwater flow distribution valve 45 Motor-driven boiler feedwater pump

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F02C 6/18 F02C 6/18 A

Claims (5)

[Claims] 1. A gas turbine is additionally installed in a steam turbine plant in which a boiler feed pump is driven by a turbine driven by a bleed-back pressure boiler feed pump. Exhaust gas from the gas turbine is introduced into the boiler and burned in the boiler. And a high-pressure stack gas cooler and a low-pressure stack gas cooler that exchange heat between exhaust gas from the boiler and feed water or condensate are connected in parallel to the high-pressure feed water heater and low-pressure feed water heater, respectively. In the combined cycle power plant, an exhaust re-combustion combined cycle power plant characterized in that a back trachea of the bleed back pressure boiler feed pump driven turbine is connected to a condenser via a back pressure control valve. 2. A steam turbine plant in which a boiler feedwater pump is driven by a bleed-back pressure boiler feedwater pump drive turbine, a gas turbine is newly installed, and the exhaust gas of the gas turbine is introduced into the boiler for combustion in the boiler. And a high-pressure stack gas cooler and a low-pressure stack gas cooler that exchange heat between exhaust gas from the boiler and feed water or condensate are connected in parallel to the high-pressure feed water heater and low-pressure feed water heater, respectively. In a combined cycle power plant, a deaerator heating bleed is extracted from a main turbine, and the deaerator heating bleed is supplied to the deaerator through a pressure reducing control valve. Combined power plant. 3. A steam turbine plant, in which a boiler feedwater pump is driven by a bleed-back pressure boiler feedwater pump drive turbine, a gas turbine is newly installed, and the exhaust gas of the gas turbine is introduced into the boiler to burn the boiler. And a high-pressure stack gas cooler and a low-pressure stack gas cooler that exchange heat between exhaust gas from the boiler and feed water or condensate are connected in parallel to the high-pressure feed water heater and low-pressure feed water heater, respectively. In the combined cycle power plant, the drain system that receives the supply of bleed air from the main turbine and recovers the heater drain to the high-pressure feedwater heater that receives bleed air from the boiler feedwater pump turbine is connected to the condenser or the low-pressure feedwater heater. Characteristic, combined-cycle reburning power plant. 4. A steam turbine plant in which a boiler feedwater pump is driven by a turbine driven by a bleed-back pressure boiler feedwater pump, a gas turbine is newly installed, and the exhaust gas of the gas turbine is introduced into the boiler to burn the boiler. And a high-pressure stack gas cooler and a low-pressure stack gas cooler that exchange heat between exhaust gas from the boiler and feed water or condensate are connected in parallel to the high-pressure feed water heater and low-pressure feed water heater, respectively. In the combined cycle power plant, there is provided a feed water spillover pipe for spillover of feedwater from an outlet of the high-pressure feedwater heater to the condenser. 5. A steam turbine plant in which a boiler feedwater pump is driven by a turbine driven by a bleed-back pressure boiler feedwater pump, a gas turbine is newly installed, and the exhaust gas of the gas turbine is introduced into the boiler to burn the boiler. And a high-pressure stack gas cooler and a low-pressure stack gas cooler that exchange heat between exhaust gas from the boiler and feed water or condensate are connected in parallel to the high-pressure feed water heater and low-pressure feed water heater, respectively. A combined cycle power plant, wherein a motor driven boiler feed pump is provided in parallel with the boiler feed pump driven by the boiler feed pump turbine.