JPH08312905A - Combined cycle power generation equipment - Google Patents

Abstract

PURPOSE: To reduce the amount of necessary recirculating water to save a power for a recirculating pump and improve a plant efficiency by a method wherein the recirculating water for increasing a condensed water temperature at the inlet port of a low-pressure stack gas cooler is heated by the drain of a waste heat recovering heat exchanger and a high-pressure feed water heater to increase the temperature thereof. CONSTITUTION: In a combined cycle power generating facility, in which the energy of exhaust gas of a gas turbine is converted into steam by a boiler and a steam turbine is driven by the steam, a part of condensed water from a condenser for condensing the steam discharged out of the steam turbine is conducted into a low-pressure stack gas cooler 26 from a condensed water pipe 13 through a condensed water line 42. In this case, a second waste heat recovering heat exchanger or a second low-pressure stack gas cooler 29 is installed in a recirculation line 28 branched from the condensed water line 42. The recirculated condensed water is heated by exhaust gas, guided from a high-pressure stack gas cooler through an exhaust gas pipeline 143 to increase the temperature thereof, whereby the amount of heat of the recirculating water can be secured sufficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined cycle power generation facility, and more particularly to an exhaust gas re-combustion type combined cycle plant that uses gas turbine exhaust as combustion air for a boiler.

[0002]

2. Description of the Related Art Exhaust gas that combines steam power generation equipment and a gas turbine plant, uses the exhaust gas of a gas turbine as combustion air for a boiler, and recovers the heat of the exhaust gas of the boiler to a steam turbine cycle system The reburn type combined cycle system has the following features.

First, by combining the power generation plant, the power generation efficiency can be improved. Secondly, since the gas turbine is combined, it is possible to increase the amount of electric power generated in the power plant as a whole. Third,
Since remodeling of the existing steam power generation equipment can be reduced in repowering, repowering can be performed in a relatively short period of time.

FIG. 4 shows an example of a conventional system in which an exhaust gas recombustion combined cycle is constructed by combining a steam power generation facility and a gas turbine plant. In this system, a conventional steam power generation facility 40 is combined with a gas turbine plant 41 including a compressor 20, a combustor 21, a gas turbine 22, a gas turbine generator 23, a gas damper 24, and the like.

In FIG. 4, a gas turbine 22 and a compressor 20 are shown.
Are coaxially connected, and the air supplied by the compressor 20 is guided to the combustor 21 and used for combustion of fuel. The high-temperature, high-pressure combustion gas resulting from this combustion is guided to the gas turbine 22, which drives the gas turbine 22 to rotate, and the gas turbine generator 23 coaxially connected to the gas turbine 22 performs work.

The high-temperature, high-pressure combustion gas that drives the gas turbine 22 is guided to the boiler 1 via the gas damper 24. The steam that has undergone heat exchange by the boiler 1 is guided to the high-pressure turbine 3 via the main steam pipe 2. The steam, which has worked at the high-pressure turbine 3 and has decreased in temperature, is heated from the low-temperature reheat pipe 4 through the reheater 5 and guided to the intermediate-pressure turbine 7 by the high-temperature reheat pipe 6. This medium pressure turbine 7
The steam that has worked at is introduced to the low pressure turbine 9 through the crossover pipe 8, and the high, medium and low pressure turbines 3,
The generator 10 connected coaxially with 7, 9 performs work to generate electricity.

The steam that has worked in the low-pressure turbine 9 is condensed in a condenser 11 to become condensed water, which is pressurized by a condensate pump 12 via a condensate pipe 13. The pressure of the condensed water is raised by the low-pressure feed water heaters 14a, 14b, 14c, and is guided to the deaerator 15 to be deaerated. The degassed condensate is boosted by the water supply pump 17, and the high-pressure water heater 18a,
The temperature is further raised at 18b and 18c, and it is introduced again into the boiler 1 via the water supply pipe 16.

In the above structure, since the exhaust gas of the gas turbine 22 is used as the combustion air of the boiler 1, the air preheater is unnecessary. Further, in order to effectively use the high temperature exhaust gas of the boiler 1 and because the high temperature exhaust gas cannot be discharged from the chimney as it is, the high pressure exhaust heat recovery heat exchanger is used for the purpose of lowering the temperature of the exhaust gas. A stack gas cooler 25 is installed.

The high pressure stack gas cooler 25 is a water supply pipe.
The feed water branched from the upstream side of the high pressure feed water heater 18a of 16 and the exhaust gas of the boiler 1 are heat-exchanged to heat the feed water, and the raised feed water is led to the downstream side of the high pressure feed water heater 18c of the feed pipe 16 and again. Returning to the steam turbine cycle system.

Further, the exhaust gas of the boiler 1 which has exchanged heat with the high pressure stack gas cooler 25 is supplied to the low pressure stack gas cooler 26 which is a heat exchanger for recovering low pressure exhaust heat. This low pressure stack gas cooler 26 is a low pressure feed water heater.
The condensate branched from the condensate pipe 13 between the low pressure feed water heater 14a and the low pressure feed water heater 14b is heat-exchanged with the exhaust gas of the boiler 1 to heat the condensate, and the heated condensate is heated by the low pressure feed water heater of the condensate pipe 13. It is led to the downstream side of 14c and returned to the steam turbine cycle system again.

Here, in order to protect the gas cooler 26 from sulfuric acid corrosion in the low pressure stack gas cooler 26, it is necessary to set the gas cooler inlet feed water temperature to some extent higher. For this reason, the feed water temperature is raised by branching from the gas cooler feed water outlet of the condensate line 42, installing the recirculation pump 27, and providing the recirculation line 28 for recovery at the gas cooler feed water inlet.

[0012]

In the conventional example using the recirculation pump, the plant efficiency is lowered due to the pump power, and particularly at the time of partial load operation of the plant, the feed water heater bleed pressure is lowered and the inlet feed water temperature is lowered. However, the amount of recirculation increased and the power of the recirculation pump increased, further lowering the plant efficiency. Therefore, an object of the present invention is to obtain a combined cycle power generation facility that can reduce power of a recirculation pump and improve plant efficiency.

[0013]

In order to achieve the above object, the present invention according to claim 1 converts exhaust energy of a gas turbine into steam by a boiler and guides it to a steam turbine. In a combined cycle power generation facility that condenses the steam that has worked at the condenser into condensate, raises the temperature of the condensate through the feed water heater and then reintroduces it to the boiler, in parallel with the feed water heater. First, using the exhaust gas of the gas turbine introduced from the boiler as the heating source
A heat exchanger for recovering exhaust heat is arranged, the upstream side and the downstream side of this first heat exchanger for recovering exhaust heat are connected by a recirculation line, and a gas turbine guided from the boiler to this recirculation line. The second aspect of the present invention provides a combined cycle power generation facility comprising a second heat recovery heat exchanger for recovering exhaust heat as a heating source. The low-pressure feed water heater is configured by connecting a low-pressure feed water heater and a high-pressure feed water heater in series, and the high-pressure and low-pressure feed water heaters are provided with a first exhaust heat recovery heat exchanger in parallel. A combined cycle power generation facility, characterized in that a first exhaust heat recovery heat exchanger arranged in parallel with a heater is provided with a recirculation line via a second exhaust heat recovery heat exchanger. The present invention according to claim 3 provides the second exhaust heat recovery of the invention according to claim 2. Instead of the heat exchanger, a drain line of the high-pressure feed water heater is provided, which leads to the inlet of the first heat recovery heat exchanger that is arranged in parallel with the low-pressure feed water heater. The present invention according to claim 4 provides a combined cycle power generation facility comprising a low pressure feed water heater and a high pressure feed water heater instead of the recirculation line of the invention according to claim 2. A deaerator recirculation line that leads a part of the condensate of the deaerator arranged between them to the inlet of the first heat recovery heat exchanger, which is arranged in parallel with the low-pressure feed water heater, Provided is a combined cycle power generation facility characterized by being arranged.

[0014]

According to the present invention as set forth in claims 1 and 2, since the second heat exchanger for recovering exhaust heat is arranged in the recirculation line,
The temperature of the recirculated water can be raised, and the amount of recirculated water for securing the amount of heat required for recirculation can be reduced.

In the present invention according to claim 3, since the drain water of the high-pressure feed water heater can be used as recirculation water,
The recirculation condensate flow rate can be reduced by the amount of heat of the available drain water. In the present invention described in claim 4, since the condensate of the deaerator is used as the recirculation water, the recirculation line can be eliminated.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same parts as those in FIG. 4 are designated by the same reference numerals, and the description of the structure of those parts will be omitted.
In FIG. 1, a part of the condensate flows to the low-pressure stack gas cooler 26, so that a condensate line 42 branches from the condensate pipe 13. The branched condensate is sent to the low pressure stack gas cooler 26, but when the temperature is low due to sulfuric acid corrosion of the gas cooler, it becomes necessary to raise the temperature. Therefore, the second low-pressure stack gas cooler 29, which is the second heat recovery heat recovery system, is installed on the recirculation line 28, and the exhaust gas guided from the high-pressure stack gas cooler 25 through the exhaust gas pipe 43 shown by the dotted line in the figure is discharged. First, it is sent to the second low pressure stack gas cooler 29 to raise the temperature of the recirculated condensate. As a result, it is possible to secure a sufficient amount of heat of the recirculated water for sufficiently increasing the temperature of the condensate at the inlet of the low pressure stack gas cooler 26, even if the amount of condensed water is small.
Therefore, the required recirculation condensate flow rate is reduced and the recirculation pump 27
The power of can be reduced. As a result, it is possible to further improve the plant efficiency without adding a new heating source.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same parts as those in FIG. The second embodiment shown in FIG. 2 is a cycle in which the inlet condensate temperature of the low pressure stack gas cooler 26 is raised by the sulfuric acid corrosion of the gas cooler by the drain of the high pressure feed water heater 18a. In the present invention, the high pressure feed water heater drain line
The recovery destination of 30 is the inlet of the low pressure stack gas cooler 26.

With the above structure, by mixing the drain of the high-pressure feed water heater 18a having a temperature sufficiently higher than the condensate branched from the condensate pipe 13 and guided from the condensate line 42 with the condensate guided by the branch. The inlet feed water temperature of the low pressure stack gas cooler 26 is raised. If the temperature is not sufficiently raised, it is recirculated by the recirculation line 28 to raise the temperature sufficiently for sulfuric acid corrosion, but the recirculated condensate flow rate can be reduced by the amount of heat generated by the high-pressure feed water heater drain. It is possible to reduce the power consumption of the recirculation pump and to improve the plant efficiency by reducing the power of the recirculation pump.

Next, a third embodiment of the present invention will be described with reference to FIG. Note that, in FIG. 3, the same parts as those in FIG.

The third embodiment of the present invention shown in FIG. 3 is the first embodiment.
This is a cycle in which the recirculation line 28 shown in the embodiment is deleted, and the degasser recirculation line 32 is used to raise the low pressure stack gas cooler inlet condensate temperature against the sulfuric acid corrosion of the low pressure stack gas cooler 26.

In FIG. 3, a deaerator recirculation line 32 in which a deaerator recirculation pump 31 is arranged is connected to the lower part of the deaerator 15, and the deaerator recirculation line 32 is circulated. The condensate is recovered at the inlet side condensate line 42 of the low pressure stack gas cooler 26. As a result, the condensate for deaerator recirculation, which has a sufficiently higher temperature than the condensate branched from the condensate pipe 13, is mixed, so that the inlet temperature of the low pressure stack gas cooler 26 is sufficiently raised. The rate of this temperature rise can be adjusted by the deaerator recirculation pump 31.

As a result, it is not necessary to newly install a recirculation line and a recirculation pump, and the deaerator 15 has a temperature higher than that of the condensate at the outlet of the low pressure stack gas cooler 26 used for condensate for conventional recirculation. Since the outlet condensate temperature is sufficiently high, the amount of condensate that is recirculated in order to sufficiently raise the inlet condensate of the low pressure stack gas cooler 26 against sulfuric acid corrosion is reduced. Deaerator recirculation pump
31 power is reduced. As a result, plant efficiency can be improved.

[0023]

As described above, according to the present invention as set forth in claims 1 to 3, the recirculated water for raising the condensate temperature at the inlet of the low pressure stack gas cooler is supplied to the second heat recovery heat recovery heat exchanger. Since the required recirculation water can be reduced by raising the temperature by the drain of the feed water heater, the recirculation pump power can be reduced and the plant efficiency can be improved. Further, in the present invention according to claim 4, since the condensate of the deaerator is used as the recirculation water, it is possible to dispose the conventional recirculation line and recirculation pump.

[Brief description of drawings]

FIG. 1 is a system diagram of a combined cycle power generation facility showing a main part of a first embodiment of the present invention.

FIG. 2 is a system diagram of a combined cycle power generation facility showing a main part of a second embodiment of the present invention.

FIG. 3 is a system diagram of a combined cycle power generation facility showing a main part of a third embodiment of the present invention.

FIG. 4 is a system diagram showing a conventional example of a combined cycle power generation facility.

[Explanation of symbols]

1 ... Boiler, 3 ... High-pressure turbine, 7 ... Medium-pressure turbine, 9
... Low-pressure turbine, 11 ... Condenser, 14a, 14b, 14c ... Low-pressure feed water heater, 18a, 18b, 18c ... High-pressure feed water heater, 22 ...
Gas turbine, 25 ... High-pressure stack gas cooler, 26 ... Low-pressure stack gas cooler (first heat recovery heat exchanger), 27 ...
Recirculation pump, 28 ... Recirculation line, 29 ... Second low pressure stack gas cooler (second heat recovery heat exchanger), 30 ... High pressure feed water heater drain line, 31 ... Deaerator recirculation pump, 32 ...
Deaerator recirculation line, 42 ... Condensate line, 43 ... Exhaust gas piping

Claims (4)

[Claims] 1. The exhaust energy of a gas turbine is converted into steam by a boiler and guided to a steam turbine, and the steam that has worked in this steam turbine is condensed in a condenser to form condensate. In a combined cycle power generation facility in which the temperature is raised via a feed water heater and is again introduced into the boiler, the first exhaust heat using exhaust gas of a gas turbine introduced from the boiler in parallel with the feed water heater as a heating source. A heat exchanger for recovery is arranged, and an upstream side and a downstream side of the first heat recovery heat exchanger for exhaust heat are connected by a recirculation line, and a gas turbine guided from the boiler is connected to the recirculation line. A combined cycle power generation facility comprising a second heat recovery unit for recovering exhaust heat using exhaust gas as a heating source. 2. The feed water heater comprises a low-pressure feed water heater and a high-pressure feed water heater connected in series, and the first and second heat recovery heat exchangers are connected in parallel to the high-pressure and low-pressure feed water heaters. The first exhaust heat recovery heat exchanger provided in parallel with the low-pressure feed water heater is provided with a recirculation line via the second exhaust heat recovery heat exchanger. The combined cycle power generation facility according to claim 1. 3. A heat exchanger for recovering the second exhaust heat, in place of the second heat recovery heat exchanger,
A drain line of the high-pressure feed water heater, which leads the drain of the high-pressure feed water heater to the inlet of the first heat recovery heat exchanger, which is arranged in parallel with the low-pressure feed water heater. The combined cycle power generation facility according to claim 2. 4. A part of condensate of a deaerator arranged between the low-pressure feed water heater and the high-pressure feed water heater is arranged in parallel with the low-pressure feed water heater instead of the recirculation line. The combined cycle power generation facility according to claim 2, wherein a deaerator recirculation line that leads to the inlet of the disposed first heat recovery heat recovery system is disposed.