JP4690885B2 - Gas turbine combined cycle plant and power generation method. - Google Patents

Description

  The present invention relates to a gas turbine combined cycle plant and a power generation method, and more particularly to prevention of water vapor condensation on the intake side of a compressor.

  Gas turbine combined cycle power generation is known in which, in addition to the output of a gas turbine by combustion gas, steam is generated from exhaust gas from the gas turbine and the steam turbine is rotated to generate power. In order to improve the efficiency of this gas turbine combined cycle (hereinafter abbreviated as “GTCC”), the combustor outlet temperature needs to be high. However, increasing the outlet temperature of the combustor increases the nitrogen oxide (NOx) emission concentration. As a method for solving this problem, an exhaust gas recirculation gas turbine is known in which exhaust gas from a gas turbine is returned to the inlet of a compressor to reduce the oxygen concentration in the intake air.

  FIG. 19 shows a conventional exhaust gas recirculation type GTCC plant. Combustion air is supplied to the compressor 202 and compressed, and the compressed air is supplied to the combustor 204 and mixed with fuel to burn. The exhaust gas generated in the combustor 204 rotates the gas turbine 207. The generator 206 generates power by the rotation of the gas turbine 207. The exhaust gas that has passed through the gas turbine 207 is supplied to the exhaust heat recovery boiler 208. The exhaust gas is exhausted to the line 222 after generating steam of the high pressure steam turbine 216 and the low pressure steam turbine 218 in the exhaust heat recovery boiler 208. A part of the exhausted exhaust gas is extracted as recirculated exhaust gas into the line 223, mixed with air by the blower 228, and supplied to the compressor 202 again. (For example, Patent Document 1)

JP-A-6-26362 (FIG. 3)

  However, in the existing exhaust gas recirculation gas turbine, a part of the combustion gas returns to the compressor and the humidity becomes high, so that moisture partially condenses or condenses near the compressor inlet, causing damage to the compressor blades. There was a problem. Particularly in a plant having a high combustor outlet temperature, the fuel-air ratio is high, and the water vapor concentration in the exhaust gas is high. For this reason, moisture may condense near the inlet of the compressor, which may cause water droplets and damage the compressor.

Table 3 shows the temperature (° C.), dry air, moisture, and total flow rate at the first, seventh, and eighth measurement points. The dry air, moisture, and total flow rate are shown as a ratio with the total flow rate at the eighth measurement point.

The first, seventh, and eighth measurement points are shown as [1], [7], and [8] in FIG. 19, respectively.
At the first measurement point, the recirculated exhaust gas provided in the line 229 is measured.
At the seventh measurement point, air taken in from the outside is measured.
At the eighth measurement point, a mixed fluid of recirculated exhaust gas and air is measured near the inlet of the compressor 2.

  The temperature at the eighth measurement point is 34 ° C., and the weight absolute humidity calculated from the dry air and moisture is 0.041 / 0.959 = 0.043 kg / kg. On the other hand, the weight absolute humidity of the saturated water vapor amount at a temperature of 34 ° C. is 0.034 kg / kg. The fluid near the inlet of the compressor exceeds the amount of saturated water vapor. For this reason, the water | moisture content of the amount exceeding saturation water vapor | steam will condense, and it will cause the droplet to damage a compressor.

  The present invention has been made in view of such circumstances, and realizes a low nitrogen oxide (NOx) concentration and high efficiency, and also prevents exhaust from being generated near the compressor inlet. An object is to provide a recirculating GTCC.

In order to solve the above problems, the GTCC of the present invention employs the following means.
That is, the first embodiment according to the present invention is a compressor that compresses air introduced from outside air, a combustor that burns fuel using the compressed air to generate combustion gas, and is driven by the combustion gas. Gas turbine, exhaust heat recovery boiler that recovers heat from exhaust gas exhausted from the gas turbine, steam turbine driven by steam of the exhaust heat recovery boiler, and part of exhaust gas exhausted from the exhaust heat recovery boiler Extraction means for extracting the recirculated exhaust gas into the recirculated exhaust gas, the temperature raising means for heating the recirculated exhaust gas, and the mixing means for mixing the recirculated exhaust gas heated by the temperature raising means with the air. The plant is configured.

  By raising the temperature of a part of the exhaust gas, mixing it with air, and sending it to the compressor, it is possible to suppress the exhaust concentration of nitrogen oxide (NOx) while maintaining high efficiency. Further, since the recirculated exhaust gas is heated by the temperature raising means, it is possible to provide an exhaust recirculation type GTCC in which droplet generation due to condensation near the inlet of the compressor is prevented.

  The second mode according to the present invention is the GTCC plant according to the first mode in which the temperature raising means mixes and raises the temperature of the exhaust gas extracted from the middle stage of the exhaust heat recovery boiler.

  By extracting the exhaust gas having two different temperatures and mixing the exhaust gas, the temperature of the recirculated exhaust gas can be adjusted, and the condensation of water vapor near the inlet of the compressor can be prevented.

  A third aspect of the present invention is the GTCC plant according to the first aspect, wherein the temperature raising means is a heat exchange means for heating by exhaust heat of the compressed air of the compressor.

The recirculated exhaust gas is heat-exchanged with the cooling air for cooling the high-temperature parts taken out from the outlet of the compressor, and then mixed with the inlet air of the compressor. Can be cooled to. In addition, the temperature of the recirculated exhaust gas can be increased to prevent water vapor from condensing near the compressor inlet.
Heat generated at a place where cooling is required can be used at a place where heating is required without being transferred far away, and high efficiency can be obtained.

  According to a fourth aspect of the present invention, the GTCC plant according to the first aspect is configured such that the temperature raising unit is a heating unit that heats by exhaust heat of exhaust gas from the exhaust heat recovery boiler.

  By using the exhaust heat of the exhaust gas that is not recirculated to heat the recirculation exhaust gas, the exhaust heat can be effectively used.

  According to a fifth aspect of the present invention, the compressor is a two-stage compressor including a compressor upstream stage and a compressor downstream stage, and the temperature raising means is configured to supply compressed air in the compressor upstream stage. The GTCC plant described in the first embodiment, which is a heat exchange means for heating by exhaust heat, is configured.

  By using the heat exchange means for heating the recirculated exhaust gas by the exhaust heat of the compressed air in the upstream stage of the compressor, the temperature of the recirculated exhaust gas can be increased and condensation of water vapor near the compressor inlet can be prevented. . For example, the exhaust heat of the intermediate cooler can be used as the heat exchange means, and high efficiency can be obtained by using the exhaust heat of the intermediate cooler.

  According to a sixth aspect of the present invention, the GTCC plant according to any one of claims 1 to 5 is provided with a temperature lowering unit that cools the recirculated exhaust gas before the temperature raising unit.

  After cooling the recirculated exhaust gas and removing the water in excess of the saturated water vapor amount, the temperature of the recirculated exhaust gas is increased by the temperature raising means, and this is mixed with air and supplied to the compressor. The humidity in the vicinity of the inlet of the compressor becomes sufficiently low to prevent moisture aggregation.

  The seventh aspect of the present invention is the gas turbine combined cycle plant according to claim 6, wherein the temperature raising means uses the exhaust heat of the temperature lowering means as a heat source.

  After cooling the recirculated exhaust gas to remove moisture, the heat of the recirculated exhaust gas before cooling is used to raise the temperature of the recirculated exhaust gas. It is not necessary to prepare a separate heat source for raising the temperature of the recirculated exhaust gas, and the efficiency of GTCC can be increased.

  According to an eighth aspect of the present invention, in the gas turbine combined cycle plant according to the seventh aspect, the temperature lowering means includes a multi-stage cooling means, and the final-stage cooling means is performed by water cooling or air cooling.

  By using a multistage cooling means, the exhaust heat of cooling can be used sequentially for raising the temperature of the recirculated exhaust gas. By making the last stage cooling means water-cooled or air-cooled, the exhaust heat of the recirculated exhaust gas recovered in the final stage is carried out of the GTCC, and the recirculated exhaust gas is reliably cooled and heated.

  According to a ninth aspect of the present invention, the gas turbine combined cycle plant according to the sixth aspect is configured, wherein the temperature lowering means is a cooling means for cooling with water supplied from the steam turbine.

  The exhaust heat of the temperature lowering means can be used for heating the feed water of the steam turbine, and the efficiency can be improved by effectively using the exhaust heat.

  According to a tenth aspect of the present invention, a compressor that compresses air introduced from outside air, a combustor that generates combustion gas by burning fuel using the compressed air, and a gas that is driven by the combustion gas A turbine, an exhaust heat recovery boiler that recovers heat from exhaust gas exhausted from the gas turbine, a steam turbine that is driven by the steam of the exhaust heat recovery boiler, and a part of the exhaust gas exhausted from the exhaust heat recovery boiler A GTCC plant comprising extraction means for making recirculated exhaust gas, dehumidifying means for dehumidifying the recirculated exhaust gas, and mixing means for mixing the recirculated exhaust gas dehumidified by the dehumidifying means with the air And

Water is removed by spraying a hygroscopic agent on the recirculated exhaust gas. By removing water from the recirculated exhaust gas, it is possible to prevent moisture from condensing in the vicinity of the inlet of the compressor.

According to an eleventh aspect of the present invention, the dehumidifying means regenerates a used hygroscopic agent that has been sprayed by the hygroscopic agent spraying means for spraying the hygroscopic agent on the recirculated exhaust gas and the hygroscopic agent spraying means to absorb moisture. to comprise a moisture absorbent reproduction means, and to constitute a GTCC plant tenth embodiment of transferring again said desiccant spraying means regenerated desiccant in the desiccant regeneration means.

  The used hygroscopic agent is removed by heating to evaporate the water and used again as the hygroscopic agent. It is economical because a small amount of moisture absorbent can be used.

  According to a twelfth aspect of the present invention, in the eleventh aspect, the hygroscopic agent regeneration means heats the hygroscopic agent using the heat of the exhaust gas in the exhaust heat recovery boiler or the air compressed by the compressor. A GTCC plant is configured.

  By using the exhaust heat of the exhaust heat recovery boiler or the exhaust heat of the compressed air, the hygroscopic agent can be heated without preparing another heat source, and the efficiency can be increased.

  A thirteenth mode according to the present invention is the eleventh mode or the twelfth mode, wherein the hygroscopic agent regenerating unit comprises a plurality of stages, and the pre-stage hygroscopic agent is heated by steam generated by the subsequent hygroscopic agent generating unit. The described GTCC plant is configured.

  Efficiency can be improved by utilizing the steam generated when the hygroscopic agent in the subsequent stage of the hygroscopic agent regeneration apparatus is regenerated for heating the hygroscopic agent in the previous stage. Heat from outside the GTCC cycle can be used to heat the hygroscopic agent, simplifying the device and effectively using the heat.

  A fourteenth aspect according to the present invention is the gas turbine according to the eleventh aspect, wherein the moisture absorbent is processed into a disk shape or a sheet shape, and dehumidification of the recirculated exhaust gas and regeneration of the moisture absorbent are performed by rotation. Combining a combined cycle.

  The moisture in the recirculated exhaust gas can be removed by reciprocating the disk or sheet holding the hygroscopic agent between the flow path of the recirculated exhaust gas and the heating means that is the moisture absorbent regenerator. Further, the moisture in the recirculated exhaust gas can be removed with a relatively simple device, and the moisture absorbent can be regenerated.

  A fifteenth aspect according to the present invention is the GTCC plant according to the tenth aspect, wherein the dehumidifying means is a hollow fiber membrane system.

  By using a hollow fiber membrane type dehumidifier as the dehumidifying means, it is excellent in durability, has almost no performance deterioration, and can be operated at a lower cost than the adsorbent method. In addition, it is easy to install because it does not require a power source and has a simple structure, small size and light weight.

  According to a sixteenth aspect of the present invention, the mixing means may be any one of the first to sixteenth aspects that mixes the recirculated exhaust gas with the air when the inlet temperature of the gas turbine is equal to or higher than a predetermined temperature. The described GTCC plant is configured.

  When the amount of recirculated exhaust gas is increased, nitrogen oxides can be reduced, but the efficiency is lowered. Therefore, when the temperature exceeds a predetermined temperature, the amount of recirculated exhaust gas is adjusted at the turbine inlet temperature. The concentration of nitrogen oxides can be reduced, and high partial load efficiency can be achieved.

According to a seventeenth aspect of the present invention, there is provided a compression step in which air taken from outside is compressed air, a combustion step in which fuel is burned using the compressed air to make exhaust gas, and a gas turbine is driven by taking in the exhaust gas A first power generation process, a steam generation process using the exhaust heat of the exhaust gas used in the first power generation process as steam for feed water, and a second power generation process for driving the steam turbine by taking in the steam A condensate step for returning the steam used in the second power generation step to the steam generation step as feed water, and a extraction step for extracting a part of the exhaust gas that has undergone the steam generation step to recirculate exhaust gas, The power generation method includes a recirculation gas heating step for heating the recirculation exhaust gas and a mixing step for mixing the recirculation exhaust gas that has passed through the recirculation exhaust gas heating step with the air .

  According to an eighteenth aspect of the present invention, the recirculated exhaust gas extracted in the extraction process is returned to the recirculation gas heating process after cooling and removing water exceeding the saturated water vapor amount. The power generation method described in the above is configured.

According to a nineteenth aspect of the present invention, a compression process using compressed air as air sucked from the outside, a combustion process using the compressed air to burn fuel and using it as exhaust gas, and driving the gas turbine using the exhaust gas A first power generation process, a steam generation process using the exhaust heat of the exhaust gas used in the first power generation process as steam for feed water, and a second power generation process for driving the steam turbine by taking in the steam A condensate step for returning the steam used in the second power generation step to the steam generation step as feed water, and a extraction step for extracting a part of the exhaust gas that has undergone the steam generation step to recirculate exhaust gas, The power generation method includes a dehumidifying step for dehumidifying the recirculated exhaust gas and a mixing step for mixing the recirculated exhaust gas that has passed through the dehumidifying step with the air .

  By raising the temperature of a part of the exhaust gas as recirculated exhaust gas, mixing it with air and sending it to the compressor, it is possible to reduce the nitrogen oxide (NOx) emission concentration, and to generate electricity while maintaining high efficiency it can. Furthermore, it is possible to prevent the generation of droplets near the inlet of the compressor, and it is possible to generate power with reduced costs for equipment maintenance.

  By cooling the recirculated exhaust gas once and removing the moisture, even when the humidity of the air taken in from the outside air is high, it is possible to generate electricity while preventing the generation of droplets near the inlet of the compressor.

  By supplying a part of the exhaust gas as recirculated exhaust gas and supplying it to the air sucked by the compressor, the exhaust concentration of nitrogen oxides can be suppressed, and the GTCC plant can be operated with high efficiency. In addition, since the humidity of the recirculated exhaust gas is reduced, it is possible to prevent the generation of droplets in the vicinity of the inlet of the compressor. When heating or cooling is performed in order to reduce the humidity of the recirculated exhaust gas, the heat generated in GTCC can be used effectively.

Embodiments according to the present invention will be described below with reference to the drawings.
[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows an exhaust gas recirculation type GTCC plant of the present embodiment.
The GTCC plant is composed of a gas turbine part, an exhaust heat recovery boiler part of the gas turbine, and a steam turbine part.

  In order to drive the gas turbine 7, the compressor 2 compresses air taken from the outside. The compressed air is sent to the combustor 4 and burned with fuel. The exhaust gas discharged from the combustor 4 drives the gas turbine 7. The gas turbine 7 generates electricity by rotating the connected generator 6.

  Next, the exhaust gas that has driven the gas turbine 7 is transferred to an exhaust heat recovery boiler (HRSG) 8. The exhaust heat recovery boiler 8 generates steam for driving with a steam turbine. Part of the exhaust gas exhausted from the exhaust heat recovery boiler 8 is recirculated to the gas turbine as recirculated exhaust gas.

Inside the exhaust heat recovery boiler 8, a low-pressure economizer 9, a low-pressure evaporator 10, a low-pressure superheater 11, a high-pressure economizer 12, a high-pressure evaporator 13, and a high-pressure superheater 14 are housed.
The economizer uses the heat of the boiler exhaust gas to heat the feed water of the steam boiler and improve the boiler efficiency. The evaporator uses the water that has been returned to the liquid as steam again. The superheater is a heating device for converting the steam generated from the evaporator into dry steam.

Low pressure steam is generated by the low pressure economizer 9, the low pressure evaporator 10, and the low pressure superheater 11. The low pressure steam turbine 16 is driven by the generated low pressure steam. The generator 19 converts the rotational energy of the low-pressure steam turbine 18 into electric power.
The line from the low-pressure economizer 9 to the low-pressure evaporator 10 branches from the middle to the high-pressure economizer 12, and the pump 15 supplies boiler feed water to the high-pressure economizer 12 as well.

  High-pressure steam is generated by the high-pressure economizer 12, the high-pressure evaporator 13, and the high-pressure superheater 14. The high-pressure steam turbine 16 is driven by the generated high-pressure steam. The generator 17 converts the rotational energy of the high-pressure steam turbine 16 into electric power. The steam used in the high-pressure steam turbine 16 is mixed with the low-pressure steam supplied from the low-pressure superheater 11 to drive the low-pressure steam turbine 18.

  The steam that has driven the low-pressure steam turbine 18 is returned to the water supply by the condenser 20. This feed water is again supplied to the low-pressure economizer 9 of the exhaust heat recovery boiler 8 by the pump 21.

  The exhaust gas after generating steam in the exhaust heat recovery boiler 8 is exhausted to the line 22. A part of the exhaust gas is drawn from the line 22 by the blower 28 to the line 23 as recirculated exhaust gas. A valve 24 for adjusting the flow rate of the recirculated exhaust gas is provided on the way from the line 23 to the line 27.

  Further, the line 25 is connected to the line 27. The line 25 extracts exhaust gas from the middle stage of the exhaust heat recovery boiler 8 as recirculated exhaust gas. For example, as shown in FIG. 1, the outlet can be provided between the high pressure economizer 12 and the low pressure superheater 11 of the exhaust heat recovery boiler. A valve 26 for adjusting the flow rate of the recirculated exhaust gas is provided in the middle of the line 25.

  The blower 28 supplies the recirculated exhaust gas supplied from the line 23 and the line 25 to the compressor 2 through the line 29.

  The vapor cycle may be any of single pressure, double pressure, and reheat triple pressure type. The exhaust heat recovery boiler 8 may change the arrangement of the high-pressure superheater, high-pressure evaporator, high-pressure economizer, low-pressure superheater, low-pressure evaporator, and low-pressure economizer from the upstream side of the high-temperature gas depending on the temperature conditions. Is possible. Some or all of the compressor, gas turbine, and steam turbine may be the same shaft. The generator may be shared with the gas turbine and the steam turbine as the same shaft.

Table 1 shows the fluid temperature (° C.), dry air, moisture, and total flow rate at the first, sixth, seventh, eighth, and twelfth measurement points. The dry air, moisture, and total flow rate are shown as a ratio to the total mass flow rate at the eighth measurement point.

The first, sixth, seventh, eighth, and twelfth measurement points are displayed as [1], [6], “7”, [8], and [12] in FIG. 1, respectively.
At the first measurement point, the recirculated exhaust gas extracted from the line 22 is measured.
At the sixth measurement point, the recirculated exhaust gas in which the recirculated exhaust gas extracted from the line 26 and the recirculated exhaust gas extracted from the line 23 are mixed is measured.
At the seventh measurement point, air taken in from the outside is measured.
At the eighth measurement point, a mixed fluid of recirculated exhaust gas and air near the inlet of the compressor 2 is measured.

  The mixed fluid at the eighth measurement point has a temperature of 44 ° C., a dry air ratio of 0.959, and a moisture ratio of 0.041. The weight absolute humidity calculated from the dry air ratio and the water ratio is 0.041 / 0.959 = 0.043 kg / kg. On the other hand, since the weight absolute humidity of the saturated water vapor amount at a temperature of 44 ° C. is 0.061 kg / kg, the fluid flowing through the eighth measurement point is below the weight absolute humidity of the saturated water vapor amount, and the water is not saturated.

  In this way, the exhaust gas is drawn out from two locations downstream and in the middle of the exhaust heat recovery boiler 8 and mixed with the air by changing the mixing ratio of the two types of recirculated exhaust gas having different temperatures, thereby supplying the compressor 2. Condensation of water vapor near the inlet of the compressor can be prevented, and damage to the compressor can be prevented.

  Since the exhaust gas extracted from the middle stream of the exhaust heat recovery boiler 8 has a higher temperature than the exhaust gas extracted downstream, the compressor 2 can supply a higher temperature. For this reason, if it is set as this structure, compressor inlet temperature can fully be raised with a simple installation, without using a heating means separately.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 2 shows a schematic diagram of the exhaust gas recirculation type GTCC plant of the present embodiment.
In addition, about each embodiment demonstrated below, the same structure as 1st embodiment attaches | subjects the same code | symbol, and abbreviate | omits the description.

  The exhaust gas is exhausted from the exhaust heat recovery boiler 8 to the line 22, and a part of the exhaust gas is extracted by the blower 28 as recirculated exhaust gas. The extracted recirculated exhaust gas is supplied to the heat exchange means 30a. The heat exchange means 30 a exchanges heat between the air supplied from the compressor 2 and the recirculated exhaust gas from the line 29. The cooled compressed air is supplied to the gas turbine 7 as cooling air. The heated recirculated exhaust gas is mixed with the air supplied to the compressor 2 through the line 31.

  The temperature of the compressed air is lowered by the heat exchanger 30a, and the high-temperature components of the gas turbine 7 can be cooled. The temperature of the recirculated exhaust gas is increased by the heat exchanger 30a, and the temperature in the vicinity of the inlet of the compressor 2 can be increased to prevent condensation of water vapor. Since the heat generated at the place where cooling is required can be recovered and used, the efficiency of GTCC can be increased.

[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 3 shows a schematic diagram of the exhaust gas recirculation type GTCC plant of the present embodiment.
In the third embodiment, the compressor has a two-stage configuration of a compressor upstream stage 2a and a compressor downstream stage 2b. The air is first supplied to the compressor upstream stage 2a and compressed. The compressed air exchanges heat with the intercooler 32a. The air subjected to the heat exchange is supplied to the compressor downstream stage 2b and further compressed. The air compressed by the compressor downstream stage 2 b is carried to the combustor 4. The compressor upstream stage 2a, the compressor downstream stage 2b, the gas turbine 7, and the generator 6 are configured coaxially.

  The intercooler 32a exchanges heat with the recirculated exhaust gas supplied from the line 29 and the air compressed by the compressor upstream stage 2a. The heated recirculated exhaust gas is mixed with air supplied to the compressor upstream stage 2a.

  Since the temperature of the recirculated exhaust gas can be increased by the intermediate cooler 32a, the condensation of water vapor near the inlet of the compressor 2a can be prevented. Since the exhaust heat of the intercooler 32a can be used, the efficiency of GTCC can be increased.

[Fourth embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 4 shows a schematic diagram of the exhaust gas recirculation type GTCC plant of the present embodiment.
The fourth embodiment differs from the third embodiment in the configuration of the heat exchange means 33. The heat exchanging means 33 extracts the air compressed in the line 34 from the compressor upstream stage 2 a to the compressor downstream stage 2 b and exchanges heat with the recirculated exhaust gas supplied from the line 29. The extracted air that has heated the recirculated exhaust gas is discharged to the outside 35.

Since the temperature of the recirculated exhaust gas can be increased by the heat exchange means 33, it is possible to prevent condensation of water vapor near the inlet of the compressor 2a. Since the exhaust heat of the heat exchange means 33 can be utilized, the efficiency of GTCC can be improved.
Moreover, the GTCC plant provided with the existing two-stage compressor can be modified with a simple device to heat the recirculated exhaust gas. Efficiency can be increased with inexpensive capital investment.

[Fifth embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 5 shows a schematic diagram of the exhaust gas recirculation type GTCC plant of the present embodiment.
The exhaust gas is exhausted from the exhaust heat recovery boiler 8 to the line 22, and a part of the exhaust gas is extracted from the line 22 as recirculated exhaust gas and supplied to the cooling unit 36 a. The recirculated exhaust gas cooled by the cooling means 36a is heated by the blower 28 by the heating means 37a. Thereafter, the recirculated exhaust gas is mixed with the air supplied to the compressor 2 via the line 31.

  The cooling means 36a can be, for example, a water cooling type or an air cooling type. In this embodiment, the feed water of the condenser 20 is supplied to the cooling means 36a (A) by the pump 21 to cool the recirculated exhaust gas, and the exhaust heat heats the feed water of the steam turbine. Thereafter, the feed water is returned to the exhaust heat recovery boiler 8 from (B) of the cooling means 36a. The water removed from the recirculated exhaust gas is discharged from the cooling means 36a.

  The blower 28 supplies the recirculated exhaust gas cooled by the cooling means 36a to the heating means 37a. The heating means 37a heats the recirculated exhaust gas. Since the recirculated exhaust gas cooled by the cooling means 36a is saturated with water, if the recirculated exhaust gas is supplied to the compressor 2 as it is, the water vapor easily aggregates, so that the recirculated exhaust gas needs to be heated.

The cooling means 36a can remove the amount exceeding the amount of saturated water vapor after cooling from the water vapor contained in the recirculated exhaust gas before cooling by lowering the temperature of the recirculated exhaust gas. Since the exhaust heat of heat exchange can be used for heating the feed water, the efficiency of GTCC can be increased.
The heating means 37a can prevent condensation of water vapor in the vicinity of the inlet of the compressor 2 by increasing the temperature of the recirculated exhaust gas.

  The cooling means 36a can be the cooling means 36b shown in FIG. That is, this cooling means 36b does not heat the feed water of the steam turbine.

  The heating means 37a can be replaced with the heating means 37b shown in FIG. 6, the heat exchange means 30b shown in FIG. 7, or the intercooler 32b shown in FIG.

  The heating means 37b shown in FIG. 6 exchanges heat between the recirculated exhaust gas cooled by the cooling means 36b and the recirculated exhaust gas exhausted from the exhaust heat recovery boiler 8. Since the heating means 37b can recover the heat of the exhaust gas supplied from the line 22, the efficiency of GTCC can be increased.

  The heat exchange means 30b shown in FIG. 7 exchanges heat between the compressed air supplied from the compressor 2 and the recirculated exhaust gas cooled by the cooling means 36b.

  The temperature of the compressed air is lowered by the heat exchanger 30b, and the high-temperature components of the gas turbine 7 can be cooled as cooling air. Since the temperature of the recirculated exhaust gas is increased by the heat exchanger 30b, the temperature in the vicinity of the inlet of the compressor 2 can be increased and condensation of water vapor can be prevented. Since the heat generated at the place where cooling is required can be recovered and used, the efficiency of GTCC can be increased.

  The intermediate cooler 32b shown in FIG. 8 exchanges heat between the recirculated exhaust gas cooled by the cooling means 36b and the air compressed by the compressor upstream stage 2a. The heat-recirculated recirculated exhaust gas is mixed with air supplied to the compressor upstream stage 2a.

  Since the temperature of the recirculated exhaust gas can be increased by the intermediate cooler 32b, condensation of water vapor in the vicinity of the inlet of the compressor 2a can be prevented. Since the exhaust heat of the intercooler 32b can be used, the efficiency of GTCC can be increased.

[Sixth embodiment]
Next, a sixth embodiment of the present invention will be described with reference to FIG.
FIG. 9 shows a schematic diagram of the exhaust gas recirculation type GTCC plant of the present embodiment.
The line 23 is provided with a cooling means 38a, a cooling means 38b, and a cooling means 38c for removing moisture from the recirculated exhaust gas. In addition, the cooling means should just be arrange | positioned in multiple stages, for example, a cooling means can be made into three steps.

The cooling unit 38a cools the recirculated exhaust gas introduced from the line 23, the cooling unit 38b further cools the recirculated exhaust gas cooled by the cooling unit 38a, and the cooling unit 38c cools the recirculated exhaust gas cooled by the cooling unit 38b. Is further cooled. The cooled recirculated exhaust gas is supplied to the line 29 by the blower 28.
In the present embodiment, the cooling means 38a and the cooling means 38b can be configured to use the recirculated exhaust gas cooled by the cooling means 38c as the refrigerant. The cooling means 38c can use water introduced from the outside as a refrigerant.

  The line 29 has a blower 28 and sends the recirculated exhaust gas cooled by the cooling means 38c to the cooling means 38b. This recirculated exhaust gas is heat-exchanged with the recirculated exhaust gas in the middle of cooling by the cooling means 38b and warmed. Thereafter, the recirculated exhaust gas warmed by the cooling means 38b is introduced into the cooling means 38a, and is heat-exchanged with the recirculated exhaust gas in the middle of cooling to be warmed.

Table 2 shows the fluid temperature (° C.), dry air, moisture, and total flow rate at the first to eighth measurement points. In addition, the moisture temperature and the moisture amount at the ninth to eleventh measurement points are shown. The dry air, moisture, and total flow rate are shown as a ratio with the total flow rate at the eighth measurement point.

The first to eleventh measurement points are respectively displayed as [1] to [11] in FIG.
At the first measurement point, the recirculated exhaust gas extracted from the line 22 is measured.
At the second measurement point, the recirculated exhaust gas cooled by the cooling means 38a is measured.
At the third measurement point, the recirculated exhaust gas cooled by the cooling means 38b is measured.
At the fourth measurement point, the recirculated exhaust gas cooled by the cooling means 38c is measured.
At the fifth measurement point, the recirculated exhaust gas heated by the cooling means 38b is measured.
At the sixth measurement point, the recirculated exhaust gas heated by the cooling means 38a is measured.
At the seventh measurement point, air taken in from the outside is measured.
At the eighth measurement point, a mixed fluid of recirculated exhaust gas and air is measured near the inlet of the compressor 2.
At the ninth measurement point, the water discharged by the cooling means 38a is measured.
At the tenth measurement point, the water discharged by the cooling means 38b is measured.
At the eleventh measurement point, the water discharged by the cooling means 38c is measured.

The recirculated exhaust gas at the first measurement point has a temperature of 90 ° C., a dry air ratio of 0.217, a moisture ratio of 0.033, and a total flow ratio of 0.250.
The recirculated exhaust gas at the second measurement point has a temperature of 70 ° C., a dry air ratio of 0.217, a moisture ratio of 0.033, and a total flow ratio of 0.250.
From the comparison between the first measurement point and the second measurement point, water did not aggregate in the cooling means 38a, but the temperature of the recirculated exhaust gas decreased from 90 ° C to 70 ° C.

The recirculated exhaust gas at the third measurement point has a temperature of 55 ° C., a dry air ratio of 0.217, a moisture ratio of 0.025, and a total flow ratio of 0.242.
From the comparison between the third measurement point and the second measurement point, in the cooling means 38b, water aggregated and was removed from the recirculated exhaust gas by 0.008. This water is equal to the amount of water measured at the tenth measurement point. The temperature of the recirculated exhaust gas decreased from 70 ° C to 55 ° C.

The recirculated exhaust gas at the fourth measurement point has a temperature of 40 ° C., a dry air ratio of 0.217, a moisture ratio of 0.011, and a total flow ratio of 0.228.
From the comparison between the fourth measurement point and the third measurement point, in the cooling means 38c, water aggregated and was removed from the recirculated exhaust gas by 0.014. This water is equal to the amount of water measured at the eleventh measurement point. The temperature of the recirculated exhaust gas decreased from 55 ° C to 40 ° C.

The recirculated exhaust gas at the fifth measurement point has a temperature of 55 ° C., a dry air ratio of 0.217, a moisture ratio of 0.011, and a total flow ratio of 0.228.
From the comparison between the fifth measurement point and the fourth measurement point, the recirculated exhaust gas to be heated again after cooling in the cooling means 38b received heat from the recirculated exhaust gas before cooling, and the temperature rose from 40 ° C to 55 ° C. .

The recirculated exhaust gas at the sixth measurement point has a temperature of 70 ° C., a dry air ratio of 0.217, a moisture ratio of 0.011, and a total flow ratio of 0.228.
From the comparison between the sixth measurement point and the fifth measurement point, the recirculated exhaust gas whose temperature is increased again after cooling in the cooling means 38a takes heat from the recirculated exhaust gas before cooling, and the temperature rises from 55 ° C to 70 ° C. .

  The air taken in from the outside at the seventh measurement point has a temperature of 15 ° C., a dry air ratio of 0.764, a moisture ratio of 0.008, and a total flow rate ratio of 0.772.

The recirculated exhaust gas at the sixth measurement point and the air at the seventh measurement point are mixed and supplied to the compressor 2.
The mixed fluid at the eighth measurement point (near the inlet of the compressor 2) has a temperature of 27 ° C., a dry air ratio of 0.981, a moisture ratio of 0.019, and a total flow ratio of 1.000.
The weight absolute humidity calculated from dry air and moisture is 0.019 / 0.981 = 0.19 kg / kg. On the other hand, since the weight absolute humidity of the saturated water vapor amount at a temperature of 27 ° C. is 0.023 kg / kg, the fluid flowing through the eighth measurement point is not saturated with water.

  In the recirculation type GTCC plant that heats the recirculated exhaust gas after cooling the recirculated exhaust gas to remove moisture, the cooling exhaust heat can be effectively used for reheating. It is not necessary to separately supply the heat necessary for heating, and the efficiency is improved.

[Seventh embodiment]
Next, a seventh embodiment of the present invention will be described with reference to FIG.
FIG. 10 shows an exhaust gas recirculation type GTCC plant in the present embodiment.
The line 23 is provided with a moisture absorbent spraying means 40. Inside the moisture absorbent spraying means 40, the moisture absorbent 39 is sprayed, and the moisture of the recirculated exhaust gas passing through the moisture absorbent spraying means 40 is adsorbed by the moisture absorbent 39. The decirculated exhaust gas that has been dehumidified is extracted from the moisture absorbent spraying means 40 by the blower 28, mixed with air and supplied to the compressor 2.

The used hygroscopic agent 41a that has taken moisture in the hygroscopic agent spraying means 40 is regenerated in the hygroscopic agent regenerating device 42a. The hygroscopic agent 39 regenerated in the hygroscopic agent regenerating device 42 a is supplied again to the hygroscopic agent spraying means 40.
The hygroscopic agent spraying means 40 heats the used hygroscopic agent 41a to release the moisture adsorbed by the hygroscopic agent. Moisture is taken out from the moisture absorbent spraying means 40 as water vapor.

  As the moisture absorbent 39, for example, a lithium chloride aqueous solution, a calcium chloride aqueous solution, a lithium bromide aqueous solution, a calcium bromide aqueous solution, a silica gel powder, or the like can be used.

  By bringing the moisture absorbent 39 and the recirculated exhaust gas into contact with each other, moisture in the recirculated exhaust gas can be removed, and aggregation of moisture near the inlet of the compressor 2 can be prevented. The used moisture absorbent can be reused by heating to remove moisture, and the moisture in the recirculated exhaust gas can be removed using a small amount of moisture absorbent.

  The means for removing moisture from the recirculated exhaust gas using a hygroscopic agent may be configured as shown in FIGS.

  FIG. 11 shows a disk 43 holding a hygroscopic agent and a heating means 42b for removing moisture from the hygroscopic agent.

  The disk 43 holding the hygroscopic agent rotates to adsorb moisture in the recirculated exhaust gas in the line 23. When the disk rotates further, the disk 43 holding the moisture absorbent is heated by the heating means 42b to release moisture.

The disk 43 and the heating means 42b in FIG. 11 can be further configured as shown in FIG.
FIG. 12 shows the sheet 44 holding the moisture absorbent, the sheet driving means 45, and the heating means 42c.

  The sheet 44 holding the hygroscopic agent is formed in a ring shape, and is rotated by providing sheet driving means 45 at both inner ends. A part of the sheet passes through the recirculated exhaust gas in the line 23 and adsorbs moisture of the recirculated exhaust gas. Furthermore, by rotating, moisture is removed from the hygroscopic agent holding moisture in the heating means 42c.

  Thus, moisture can be removed from the recirculated exhaust gas with a simple device, and aggregation of moisture in the vicinity of the inlet of the compressor 2 can be prevented.

[Eighth embodiment]
Next, an eighth embodiment of the present invention will be described with reference to FIG.
FIG. 13 shows an exhaust gas recirculation type GTCC plant in the present embodiment.
In the present embodiment, the heat of the exhaust heat recovery boiler 8 is utilized when regenerating the moisture absorbent that has adsorbed moisture.
The moisture absorbent 39 is sprayed by the moisture absorbent spraying means 40 provided in the line 23. The hygroscopic agent 39 adsorbs moisture in the recirculated exhaust gas. The used hygroscopic agent 41a that has adsorbed moisture is sent to the heating means 42d and heated to release moisture. This hygroscopic agent is sent to the heating means 42e as the used absorbent 41b and further heated. The moisture adsorbed by the two-stage heating process is released and regenerated, and is sprayed again as the moisture absorbent 39 by the moisture absorbent spraying means 40.

Here, the heating means 42e uses the heat of the exhaust heat recovery boiler 8. A heat recovery unit 46 is provided in the middle stage of the exhaust heat recovery boiler 8, and water vapor is sent to (C) of the heating means 42e. The used hygroscopic agent 41b is heated by condensation latent heat of water vapor. The water vapor becomes water and is returned to the heat recovery section 46 from (D) of the heating means 42e.
In the heating of the hygroscopic agent, it is preferable from the viewpoint of effective use of the heat that the heat from another part in the GTCC plant is utilized and the apparatus is simplified.

On the other hand, the water vapor released from the hygroscopic agent generated in the heating means 42e is sent to the heating means 42d to heat the used hygroscopic agent 41a.
By using multiple stages of moisture absorbent heating means and using the heat of condensation when water vapor generated downstream from the moisture absorbent condenses as a heat source for the upstream heating means, moisture in the moisture absorbent is removed with a small amount of heat. It becomes possible.

  In addition to using the heat of the intermediate stage of the exhaust heat recovery boiler 8, exhaust heat when cooling air is cooled as shown in FIG. 14 or exhaust heat of the compressor intermediate cooling as shown in FIG. 15 is used. You may do it.

  The heat exchange means 30 c shown in FIG. 14 supplies the compressed air supplied from the compressor 2 as cooling air to the turbine 7. The exhaust heat in the heat exchange means 30c is utilized for the regeneration of the hygroscopic agent in the heating means 42e.

  By using the air for cooling the gas turbine high-temperature parts to heat the moisture absorbent, the temperature of the cooling air is lowered to effectively cool the gas turbine high-temperature parts and use the exhaust heat effectively. Water can be removed from the used hygroscopic agent.

  In FIG. 15, the compressor has a two-stage configuration of a compressor upstream stage 2a and a compressor downstream stage 2b. The air compressed in the compressor upstream stage 2a is cooled by the intermediate cooler 32c. This exhaust heat is used for the regeneration of the hygroscopic agent by the heating means 42e.

  By cooling the compressor intermediate air, the compressor power can be reduced and a large output can be obtained, and moisture can be removed from the used hygroscopic agent by effectively utilizing the exhaust heat.

[Ninth embodiment]
Next, a ninth embodiment of the present invention will be described with reference to FIGS.
FIG. 16 shows a control flow of the compressor inlet temperature adjusting means 55. This control flow can be applied to any of the first to eighth embodiments.
The compressor inlet humidity detecting means / calculating means 50 obtains the compressor inlet humidity 51 and inputs it to the optimum compressor inlet temperature calculating means 53.

  The optimum compressor inlet temperature calculation means 53 stores compressor inlet humidity, compressor inlet temperature, and a diagram. A certain margin is taken in the relationship between the humidity and the dew point temperature of the optimum compressor inlet temperature calculation means 53. In FIG. 16, the relationship between humidity and dew point temperature having a margin used for control is shown by a solid line, and the theoretical relationship between humidity and dew point temperature is shown by a broken line.

  The optimum compressor inlet temperature calculating means 53 determines the compressor inlet temperature 54 and outputs it to the compressor inlet temperature adjusting means 55. The compressor inlet temperature adjusting means 55 adjusts the flow rate and temperature of the recirculated exhaust gas, the amount of air introduced from the outside, and the like to obtain an optimum compressor inlet temperature.

FIG. 17 shows a control flow of the compressor inlet humidity adjusting means 60. This control flow can be applied to any of the first to eighth embodiments.
The compressor inlet temperature detecting means / calculating means 56 obtains the compressor inlet temperature 57 and inputs it to the optimum compressor inlet humidity calculating means 58.

  The optimum compressor inlet humidity calculating means 58 stores a diagram of the compressor inlet temperature and the compressor inlet humidity. A fixed margin is taken in the relationship between the humidity and the dew point temperature of the optimum compressor inlet humidity calculating means 58. In FIG. 17, the relationship between humidity and dew point temperature having a margin used for control is shown by a solid line, and the theoretical relationship between humidity and dew point temperature is shown by a broken line.

  The optimum compressor inlet humidity calculating means 58 determines the compressor inlet humidity 59 and outputs it to the compressor inlet humidity adjusting means 60. The compressor inlet humidity adjusting means 60 adjusts the flow rate and temperature of the recirculated exhaust gas, the amount of air introduced from the outside, and the like to obtain the optimum compressor inlet humidity.

  In order to prevent damage to the compressor, it is necessary to increase the temperature at the compressor inlet to prevent moisture condensation near the compressor inlet. On the other hand, in order to obtain high efficiency and output, the compressor inlet temperature is preferably low. By performing control according to this embodiment, high efficiency and output can be obtained while preventing damage to the compressor.

[Tenth embodiment]
Next, a tenth embodiment of the present invention will be described with reference to FIG.

  FIG. 18 shows a control means for the optimum flow rate of the recirculated exhaust gas. This control means can be applied to any of the first to ninth embodiments.

  The inlet temperature 47 of the turbine 7 is input to the optimum flow rate ratio calculating means 48. The optimum flow rate ratio calculating means controls the valve 49 provided in the line 31 based on the relational expression of the Gg / Ga ratio between the recirculated exhaust gas flow rate Gg and the air flow rate Ga and the turbine inlet temperature. This relational expression is such that Gg / Ga = 0 until a predetermined temperature, and Gg / Ga> 0 at a predetermined temperature or higher. That is, when the turbine inlet temperature is low, no nitrogen oxide is generated, so the valve 49 is closed. When the turbine inlet temperature is high, nitrogen oxide is generated, and the valve 49 is opened.

  Increasing the amount of recycle can reduce nitrogen oxides, but also reduces efficiency. By adjusting the amount of recirculation at the turbine inlet temperature, both reduction of nitrogen oxide concentration and high partial load efficiency are achieved. Although the flow rate of the recirculated exhaust gas may be adjusted with a valve, the flow rate of the recirculated exhaust gas can be adjusted by changing the rotational speed of the blower 28.

1 is a schematic diagram of an exhaust gas recirculation type GTCC (GTCC plant) according to a first embodiment of the present invention. It is the schematic of the exhaust gas recirculation type | mold GTCC plant of 2nd embodiment of this invention. It is the schematic of the exhaust gas recirculation type | mold GTCC plant of 3rd embodiment of this invention. It is the schematic of the exhaust gas recirculation type | mold GTCC plant of 4th embodiment of this invention. It is the schematic of the exhaust gas recirculation type | mold GTCC plant of 5th embodiment of this invention. It is the schematic which changed the heating means of the recirculation waste gas of the exhaust gas recirculation type | mold GTCC plant of 5th embodiment of this invention. It is the schematic which made the heating means of the recirculation waste gas of the exhaust gas recirculation type | mold GTCC plant of 5th embodiment of this invention the heat exchange means. It is the schematic which made the heating means of the recirculation waste gas of the exhaust gas recirculation type | mold GTCC plant of 5th embodiment of this invention the intercooler. It is the schematic of the exhaust gas recirculation type | mold GTCC plant of 6th embodiment of this invention. An exhaust gas recirculation type GTCC plant according to a seventh embodiment of the present invention is shown. The schematic of the exhaust gas recirculation type | mold GTCC plant which made the moisture absorption means of 7th embodiment of this invention the disk shape is shown. The schematic of the dehumidification means of the recirculation waste gas which made the moisture absorption means of 7th embodiment of this invention into the sheet form is shown. It is the schematic of the exhaust gas recirculation type | mold GTCC plant of 8th embodiment of this invention. It is the schematic of the exhaust gas recirculation type | mold GTCC plant which shows an example of the moisture absorbent regeneration apparatus of 8th embodiment of this invention. It is the schematic of the exhaust gas recirculation type | mold GTCC plant which shows an example of the moisture absorbent regeneration apparatus of 8th embodiment of this invention. The control flowchart of the compressor inlet temperature adjusting means of the ninth embodiment of the present invention is shown. A control flow diagram of the compressor inlet humidity adjusting means of the ninth embodiment of the present invention is shown. It is the schematic of the control means of the optimal flow volume of the recirculation waste gas of 10th embodiment of this invention. This is a conventional exhaust gas recirculation type GTCC plant.

Explanation of symbols

2 Compressor 2a Compressor upstream stage 2b Compressor downstream stage 4 Combustor 6 Generator 7 Gas turbine 8 Waste heat recovery boiler (HRSG)
16 high pressure steam turbine 17 generator 18 low pressure steam turbine 19 generator 20 condenser 30a heat exchange means 30b heat exchange means 32a intermediate cooler 32b intermediate cooler 33 heat exchange means 36a cooling means 36b cooling means 37a heating means 37b heating means 38a Cooling means 38b Cooling means 38c Cooling means 39 Hygroscopic agent 40 Hygroscopic agent spraying means 41a Used hygroscopic agent 41b Used hygroscopic agent 42a Hygroscopic agent regenerating device 42b Heating means 42c Heating means 42d Heating means 42e Heating means 43 Holding the hygroscopic agent Disk 44 Sheet holding moisture absorbent

Claims (19)

A compressor for compressing air introduced from outside air;
A combustor that burns fuel using the compressed air to generate combustion gas;
A gas turbine driven by the combustion gas;
An exhaust heat recovery boiler that recovers heat from exhaust gas exhausted from the gas turbine;
A steam turbine driven by steam of the exhaust heat recovery boiler;
Extraction means for extracting a part of the exhaust gas exhausted from the exhaust heat recovery boiler to recirculate exhaust gas;
Heating means for heating the recirculated exhaust gas;
Mixing means for mixing the recirculated exhaust gas heated by the temperature raising means with the air;
Gas turbine combined cycle plant equipped with.   The gas turbine combined cycle plant according to claim 1, wherein the temperature raising means mixes and raises the temperature of the exhaust gas extracted from the middle stage of the exhaust heat recovery boiler.   The gas turbine combined cycle plant according to claim 1, wherein the temperature raising means is a heat exchange means for heating by exhaust heat of the compressed air of the compressor.   The gas turbine combined cycle plant according to claim 1, wherein the temperature raising means is a heating means for heating by exhaust heat of exhaust gas from the exhaust heat recovery boiler. The compressor is a two-stage compressor including a compressor upstream stage and a compressor downstream stage,
2. The gas turbine combined cycle plant according to claim 1, wherein the temperature raising means is a heat exchange means for heating by exhaust heat of the compressed air in the upstream stage of the compressor.   The gas turbine combined cycle plant according to any one of claims 1 to 5, further comprising a temperature lowering unit that cools the recirculated exhaust gas before the temperature raising unit.   The gas turbine combined cycle plant according to claim 6, wherein the temperature raising means uses the exhaust heat of the temperature lowering means as a heat source.   The gas turbine combined cycle plant according to claim 7, wherein the temperature lowering unit includes a multi-stage cooling unit, and the last-stage cooling unit is performed by water cooling or air cooling.   The gas turbine combined cycle plant according to claim 6, wherein the temperature lowering unit is a cooling unit that cools by supplying water from the steam turbine. A compressor for compressing air introduced from outside air;
A combustor that burns fuel using the compressed air to generate combustion gas;
A gas turbine driven by the combustion gas;
An exhaust heat recovery boiler that recovers heat from exhaust gas exhausted from the gas turbine;
A steam turbine driven by steam of the exhaust heat recovery boiler;
Extraction means for extracting a part of the exhaust gas exhausted from the exhaust heat recovery boiler to recirculate exhaust gas;
Dehumidifying means for dehumidifying the recirculated exhaust gas;
Mixing means for mixing the recirculated exhaust gas dehumidified by the dehumidifying means with the air;
Gas turbine combined cycle plant equipped with. The dehumidifying means is a moisture absorbent spraying means for spraying a moisture absorbent on the recirculated exhaust gas,
A hygroscopic agent regenerating means for regenerating a used hygroscopic agent that has been sprayed by the hygroscopic agent spraying means and absorbed moisture;
With
The gas turbine combined cycle plant according to claim 10, wherein the hygroscopic agent regenerated by the hygroscopic agent regenerating unit is transferred again to the hygroscopic agent spraying unit.   The gas turbine combined cycle plant according to claim 11, wherein the moisture absorbent regeneration means heats the moisture absorbent using heat of exhaust gas in the exhaust heat recovery boiler or air compressed by the compressor.   13. The gas turbine combined cycle plant according to claim 11, wherein the hygroscopic agent regenerating unit includes a plurality of stages and heats the pre-stage hygroscopic agent with steam generated by the subsequent hygroscopic agent generating unit.   The gas turbine combined cycle plant according to claim 11, wherein the hygroscopic agent is processed into a disk shape or a sheet shape, and dehumidification of the recirculated exhaust gas and regeneration of the hygroscopic agent are sequentially performed by rotating.   The gas turbine combined cycle plant according to claim 10, wherein the dehumidifying means is a hollow fiber membrane system.   The gas turbine combined cycle plant according to any one of claims 1 to 15, wherein the mixing means mixes the recirculated exhaust gas with the air when an inlet temperature of the gas turbine is equal to or higher than a predetermined temperature. A compression process using compressed air as the air taken from outside;
A combustion step of combusting fuel using the compressed air to produce exhaust gas;
A first power generation step for driving the gas turbine by taking in the exhaust gas;
A steam generation step using the exhaust heat of the exhaust gas used in the first power generation step as feed water as steam;
A second power generation step of taking in the steam and driving a steam turbine;
A condensate step of returning the steam used in the second power generation step to the steam generation step as feed water;
An extraction process for extracting a part of the exhaust gas that has undergone the steam generation process to obtain a recirculated exhaust gas;
A recirculation exhaust gas heating step for heating the recirculation exhaust gas;
A mixing step of mixing the recirculated exhaust gas that has undergone the recirculated exhaust gas heating step with the air;
Power generation method.   The power generation method according to claim 17, wherein the recirculated exhaust gas extracted in the extraction step is cooled to remove moisture exceeding a saturated water vapor amount and then returned to the recirculation gas heating step. A compression process using compressed air as the air taken from outside;
A combustion step of combusting fuel using the compressed air to produce exhaust gas;
A first power generation step for driving the gas turbine by taking in the exhaust gas;
A steam generation step using the exhaust heat of the exhaust gas used in the first power generation step as feed water as steam;
A second power generation step of taking in the steam and driving a steam turbine;
A condensate step of returning the steam used in the second power generation step to the steam generation step as feed water;
An extraction process for extracting a part of the exhaust gas that has undergone the steam generation process to obtain a recirculated exhaust gas;
A dehumidifying step for dehumidifying the recirculated exhaust gas;
A mixing step of mixing the recirculated exhaust gas having undergone the dehumidification step with the air;
Power generation method.

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