Patent Description:
In a power plant using fossil fuels, for example, a gas turbine plant, exhaust gas is generated as a gas turbine operates. The exhaust gas contains carbon dioxide. From the viewpoint of environmental protection, a technique for removing the carbon dioxide from exhaust gas as much as possible is required. As such a technique, for example, a method described in PTL <NUM> below is known. In the method according to PTL <NUM>, the carbon dioxide is adsorbed and removed by absorption liquid by bringing at least a part of the exhaust gas into contact with the absorption liquid.

Incidentally, depending on an operating state of a plant, the exhaust gas may contain moisture (humidity). When such moisture is condensed, white smoke is generated when the exhaust gas is discharged. In addition to spoiling the surrounding landscape, since the exhaust gas is accompanied by nitrogen oxide remaining in a minute amount in the exhaust gas by direct dropping of the exhaust gas in the vicinity of a discharge port of the exhaust gas, white smoke is required to be suppressed. Therefore, in the technique according to PTL <NUM> below, a method is adopted in which a used absorption liquid is heated and regenerated by heat of the exhaust gas, and the exhaust gas is heated by utilizing the heat of the regenerated absorption liquid. As a result, it is said that the moisture in the exhaust gas evaporates, and generation of white smoke can be suppressed.

PTL <NUM> discloses a method for operating a gas turbine power plant with exhaust gas recirculation. In the method, a setpoint concentration of one component of the inlet gas and/or of the hot working gas and/or of the exhaust gas of the gas turbine is determined in a first step, in accordance with the operating conditions of the gas turbine, from a combination of a setpoint value of a control loop, a feedforward control signal and a correction value. In a second step, the position of a control element is adjusted in accordance with the setpoint/actual deviation in the concentration of the component.

PTL <NUM> discloses a cogeneration plant that includes a gas turbine, a heat recovery steam generator, a steam turbine and a cooler/condenser. A division module is provided at a division point, via which downstream the heat recovery steam generator the combustion gas is cooled and dehumidified in the cooler/condenser and then divided into a first combustion gas flow and a second combustion gas flow. A second condenser is provided for receiving the second combustion gas flow to separate contained carbon dioxide from contained water by condensation of the water. The cogeneration plant further includes a heater and a compressor for receiving the first combustion gas flow, which is heated, compressed and partly extracted to by-pass the combustor for cooling of the gas turbine before it enters the combustor and mix with the flow of oxygen and fuel to be burned in the gas turbine.

PTL <NUM> discloses a method for operating a combined cycle power plant including a CO<NUM> capture system and flue gas recirculation system. The method includes controlling a flue gas recirculation rate and a re-cooling temperature of the recirculated flue gases, depending on load, to optimize the overall plant efficiency including the CO<NUM> capture system.

However, since the heat of the regenerated absorption liquid is limited, there is a possibility that the exhaust gas cannot be sufficiently heated only by using the absorption liquid. In addition, in order to facilitate recovery of CO2 in the exhaust gas, there is a technique for increasing the concentration of CO<NUM> in the exhaust gas by recirculating the exhaust gas to the intake air. In this case, since the concentration of moisture in the exhaust gas also increases at the same time, there is a high possibility that white smoke may be generated when the exhaust gas is not sufficiently heated. Therefore, there is still a possibility that white smoke may occur in a device described in patent document <NUM>.

The present invention has been made to solve the above problems, and an object thereof is to provide a gas turbine plant capable of further suppressing generation of white smoke.

In order to solve the above problems, there is provided a gas turbine plant as set out in independent claim <NUM>. Advantageous developments are defined in the dependent claims.

According to the gas turbine plant of the present invention, generation of white smoke can be further suppressed.

Hereinafter, a gas turbine plant <NUM> according to a first embodiment of the present invention will be described with reference to <FIG>. As illustrated in <FIG>, the gas turbine plant <NUM> is provided with a gas turbine <NUM>, a heat recovery steam generator <NUM>, a steam turbine <NUM>, exhaust gas treatment equipment <NUM>, an EGR line L2, an EGR heater <NUM>, and a control device <NUM>.

The gas turbine <NUM> includes a compressor <NUM>, a combustor <NUM>, and a turbine <NUM>. The compressor <NUM> compresses outside air guided through an intake line La to generate high-pressure air. An outside air temperature measurement part To that measures the temperature of the outside air and an outside air humidity measurement part H that measures the humidity of the outside air are provided on the intake line La. In addition, on the intake side of the compressor <NUM>, an air intake duct 11D and a filter F disposed in the air intake duct 11D are provided.

The combustor <NUM> generates high-temperature and high-pressure combustion gas by mixing fuel with the high-pressure air generated by compressor <NUM> and combusting the fuel. The turbine <NUM> is driven by the combustion gas. Rotational energy of the turbine <NUM> is taken out from a shaft end and utilized for driving, for example, a generator G. The exhaust gas discharged from the turbine <NUM> is recovered by an exhaust line L1 and sent to the heat recovery steam generator <NUM>.

The heat recovery steam generator <NUM> generates superheated steam by exchanging heat between the exhaust gas circulating in the exhaust line L1 and water. The superheated steam is sent to the steam turbine <NUM> through a first line S1 and used to drive the steam turbine <NUM>. The rotational energy of the steam turbine <NUM> is utilized, for example, to drive the generator G. The steam discharged from the steam turbine <NUM> is recovered by a condenser <NUM>. In the condenser <NUM>, the steam is condensed by exchanging heat with a medium introduced from the outside to generate water. The water generated in the condenser <NUM> is supplied to the heat recovery steam generator <NUM> through the fifth line S5.

The exhaust gas treatment equipment <NUM> is provided on the exhaust line L1 and on the downstream side of the heat recovery steam generator <NUM>. The exhaust gas treatment equipment <NUM> is provided to keep the exhaust gas circulating in the exhaust line L1 in a clean state and diffuse the exhaust gas to the outside air. The exhaust gas treatment equipment <NUM> includes a carbon dioxide recovery device <NUM> and an exhaust gas heater <NUM>.

The carbon dioxide recovery device <NUM> is a device for recovering and removing carbon dioxide contained in the exhaust gas. The carbon dioxide recovery device <NUM> includes a quencher <NUM>, an absorber <NUM>, and a regenerator <NUM>.

The quencher <NUM> is a facility for cooling the exhaust gas circulating through the exhaust line L1 prior to the recovery of the carbon dioxide in the absorber <NUM> described later. In a case where the temperature of the exhaust gas circulating through the exhaust line L1 is approximately <NUM>, the quencher <NUM> cools the exhaust gas to approximately <NUM>. The exhaust gas cooled by the quencher <NUM> is sent to the absorber <NUM> through the exhaust line L1.

The absorber <NUM> has a cylindrical shape extending in the vertical direction, and the exhaust line L1 extending from the quencher <NUM> is connected to a lower part thereof. An absorption liquid capable of chemically bonding with the carbon dioxide flows from above to below inside the absorber <NUM>. Specifically, as such an absorption liquid, an aqueous solution of an amine containing monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), and methyldiethanolamine (MDEA), an organic solvent containing no water, a mixture thereof, and an amino acid-based aqueous solution are preferably used. In addition, other than amine may be used as the absorption liquid.

The exhaust gas flowed into the lower part of the inside of the absorber <NUM> rises in the absorber <NUM> while coming into contact with the absorption liquid flowing from above. At this time, the carbon dioxide contained in the exhaust gas is chemically absorbed by the absorption liquid. The residual exhaust gas from which the carbon dioxide is removed flows into the exhaust line L1 again from the upper part of the absorber <NUM>.

The absorption liquid from which the carbon dioxide is absorbed is sent to the regenerator <NUM> through an absorption liquid recovery line L4 connected to the lower part of the absorber <NUM>. The regenerator <NUM> is a device for regenerating the absorption liquid (separating carbon dioxide) in a state where the carbon dioxide is absorbed. A third line S3 through which steam taken out from the heat recovery steam generator <NUM> described above flows is connected to the regenerator <NUM>. A reboiler <NUM> is provided on the third line S3. Steam from the heat recovery steam generator <NUM> is supplied to the reboiler <NUM> through the third line S3. In the reboiler <NUM>, a part of the water contained in the absorption liquid is heated by the heat exchange with the steam to be stripping steam. The stripping steam is sent into the regenerator <NUM> through an absorption liquid extraction line L7. In the regenerator <NUM>, the stripping steam comes into contact with the absorption liquid before regeneration supplied from the absorption liquid recovery line L4. As a result, the carbon dioxide is diffused from the absorption liquid before regeneration, and the absorption liquid is regenerated (state not containing carbon dioxide). Carbon dioxide diffused from the absorption liquid before regeneration is sent from the regenerator <NUM> to a carbon dioxide compressor (not illustrated). In addition, the steam discharged from the reboiler <NUM> is sent to the above-described condenser <NUM> through the third line S3.

A part of the absorption liquid after regeneration (that is, component that is not stripping steam) is sent to an absorption liquid supply line L5 connected to a lower part of the regenerator <NUM>. A heat exchanger, a pump, and a cooler (not illustrated) are provided on the absorption liquid supply line L5. By driving the pump, the absorption liquid after regeneration is supplied from the regenerator <NUM> to the heat exchanger. As a result, heat exchange is performed between the absorption liquid before regeneration and the absorption liquid after regeneration. Furthermore, in a cooler, the absorption liquid after regeneration is appropriately cooled to a temperature suitable for absorbing the carbon dioxide. The absorption liquid after regeneration at a low temperature is supplied to the upper part of the absorber <NUM>.

The exhaust gas heater <NUM> heats the exhaust gas in order to suppress whitening of the exhaust gas discharged from the carbon dioxide recovery device <NUM> through the exhaust line L1. The exhaust gas heater <NUM> is a heat exchanger. Steam (<NUM> to <NUM> as an example) extracted through a second line S2 branching off from the above third line S3 circulates through the exhaust gas heater <NUM> as a heat medium. That is, the exhaust gas heater <NUM> uses the steam extracted from the heat recovery steam generator <NUM> as a heat medium. The fact that "steam extracted from the heat recovery steam generator <NUM>" includes at least one of steam directly extracted from the heat recovery steam generator <NUM> and steam extracted from the heat recovery steam generator <NUM> after being used to drive the steam turbine <NUM>. As a result, heat exchange occurs between the exhaust gas and steam circulating through the exhaust line L1, and the temperature of the exhaust gas rises. At this time, at least a part of the moisture (humidity) contained in the exhaust gas evaporates. The steam as a heat medium passed through the exhaust gas heater <NUM> is sent to an EGR heater <NUM> described later through the second line S2 as a heat medium. The heat medium may be in liquid phase (water) or gas phase (steam).

The EGR line L2 extracts at least a part of the exhaust gas passed through the quencher <NUM> of the carbon dioxide recovery device <NUM> and guides the exhaust gas to the intake side of the gas turbine <NUM> (compressor <NUM>). More specifically, one end of the EGR line L2 is provided on the upstream side (that is, side that contacts the outside air) of the filter F in the air intake duct 11D described above. An EGR heater <NUM> and an exhaust gas temperature measurement part Te are provided in order from the quencher <NUM> side toward the gas turbine <NUM> side on the EGR line L2. The EGR heater <NUM> is a heat exchanger. In the EGR heater <NUM>, heat exchange is performed between the heat medium guided from the exhaust gas heater <NUM> through the above second line S2 and the exhaust gas. As a result, the exhaust gas passed through the EGR heater <NUM> is heated. As an example, in a case where the temperature of the exhaust gas supplied from the quencher <NUM> is approximately <NUM>, the temperature of the exhaust gas after passing through the EGR heater <NUM> is preferably approximately <NUM>.

The heat medium passed through the EGR heater <NUM> is guided to the condenser <NUM> through the second line S2. A valve device V (supplying flow regulating section) is provided between the EGR heater <NUM> and the condenser <NUM> on the second line S2. By changing the opening degree of the valve device V, the flow rate of the heat medium circulating through the second line S2 is changed. That is, the valve device V is a flow regulation valve. The degree of opening of the valve device V is determined and regulated by the control device <NUM> based on the humidity of the exhaust gas measured by the temperature of the exhaust gas measured by the exhaust gas temperature measurement part Te, the temperature of the outside air measured by the outside air temperature measurement part To, and the humidity of the outside air measured by the outside air humidity measurement part H.

According to the above configuration, the exhaust gas passed through the absorber <NUM> is heated by the exhaust gas heater <NUM>. As a result, the humidity contained in the exhaust gas evaporates, so that it is possible to further reduce the possibility of white smoke when the exhaust gas is diffused to the outside. Furthermore, in the above configuration, a part of the exhaust gas discharged from the quencher <NUM> is guided (recirculated) to the intake side of the gas turbine <NUM> through the EGR line L2. At this time, when the exhaust gas contains humidity, the moisture adheres to the filter F provided in the air intake duct 11D of the compressor <NUM>, and there is a possibility that intake resistance increases. In addition, as such moisture becomes water droplets and collides with the rotor blade of the compressor <NUM>, so that there is a possibility that erosion may be generated. Furthermore, the EGR line L2 concentrates not only CO2 but also moisture, which tends to increase the possibility of white smoke being generated. In the above configuration, the EGR heater <NUM> heats the exhaust gas circulating through the EGR line L2. As a result, the humidity of the exhaust gas is reduced, so that adhesion of moisture to the filter F is suppressed. As a result, an increase in intake resistance can be suppressed.

According to the above configuration, the amount of heat medium supplied to the EGR heater <NUM> is regulated based on the temperature of the exhaust gas circulating through the EGR line L2. As a result, the amount of heating of the exhaust gas by the EGR heater <NUM> can be changed. For example, in a case where the temperature of the exhaust gas supplied to the gas turbine <NUM> is too high, by reducing the opening degree of the valve device V as the supplying flow regulating section, the amount of the heat medium can be reduced, and the temperature can be changed in the direction of lowering. As a result, the amount of heat medium used is reduced and the efficiency of the plant can be improved. Conversely, in a case where the temperature of the exhaust gas is too low, the temperature can be changed in the direction of increasing by increasing the amount of the heat medium. As a result, the temperature of the exhaust gas supplied to the gas turbine <NUM> is optimized, and the mixed gas of the outside air and the exhaust gas is not saturated with humidity.

According to the above configuration, the amount of heat medium supplied to the EGR heater <NUM> is regulated based on the temperature of the outside air supplied to the gas turbine <NUM>, in addition to the temperature of the exhaust gas circulating through the EGR line L2. For example, in a case where the temperature of the outside air is low, the amount of the heat medium is increased by increasing the opening degree of the valve device V as the supplying flow regulating section, and the temperature of the exhaust gas is increased. As a result, the temperature of the exhaust gas supplied to the gas turbine <NUM> is optimized so that the temperature of the mixed gas of the outside air and the exhaust gas exceeds the dew point and it cannot be saturated with humidity.

According to the above configuration, the amount of heat medium supplied to the EGR heater <NUM> is regulated based on the humidity of the outside air, in addition to the temperature of the exhaust gas circulating through the EGR line L2 and the temperature of the outside air. For example, in a case where the humidity of the outside air is excessively high, the temperature of the exhaust gas is raised by increasing the amount of heat medium supplied to the EGR heater <NUM>. On the other hand, in a case where the humidity of the outside air is excessively low, the temperature of the exhaust gas is lowered by reducing the amount of heat medium supplied to the EGR heater <NUM>. As a result, the temperature and humidity of the exhaust gas supplied to the gas turbine <NUM> are optimized, and the mixed gas of the outside air and the exhaust gas is not saturated with humidity.

Hereinbefore, the first embodiment of the present invention is described. In the above-described first embodiment, the example in which the exhaust gas temperature measurement part Te and the outside air humidity measurement part H are provided on the EGR line and the outside air temperature measurement part To is provided on the intake line La is described. However, it is also possible to adopt a configuration in which the outside air temperature measurement part To is not provided or a configuration in which the outside air humidity measurement part H is not provided. In other words, it is possible to adopt a configuration that includes only the exhaust gas temperature measurement part Te.

Next, a second embodiment of the present invention will be described with reference to <FIG>. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the configuration of the steam turbine <NUM> is different from that of the first embodiment. In addition, in the present embodiment, in addition to the exhaust gas heater <NUM> described in the first embodiment, an auxiliary exhaust gas heater 5B is further provided.

The steam turbine <NUM> includes a high-pressure steam turbine <NUM> and a low-pressure steam turbine <NUM>. The low-pressure steam turbine <NUM> and the high-pressure steam turbine <NUM> may be coaxially connected to each other or may be independent of each other. The high-pressure steam turbine <NUM> is driven by steam guided from the heat recovery steam generator <NUM> through the first line S1. The steam passed through the high-pressure steam turbine <NUM> is guided to the low-pressure steam turbine <NUM> to drive the low-pressure steam turbine <NUM>. Steam passed through the low-pressure steam turbine <NUM> is sent to the condenser <NUM>.

A sixth line S6 is connected to an intermediate stage of the high-pressure steam turbine <NUM>. High-temperature steam (<NUM> to <NUM> as an example) extracted through the sixth line S6 is sent to the auxiliary exhaust gas heater 5B described later as a heat medium. It is possible to adopt a configuration in which the steam turbine <NUM> has only one turbine. In this case, the sixth line S6 is preferably connected to the high-pressure side stage of the steam turbine <NUM>.

The auxiliary exhaust gas heater 5B is provided downstream of the exhaust gas heater <NUM> in the exhaust line L1. The auxiliary exhaust gas heater 5B is a heat exchanger that exchanges heat between the steam extracted from the high-pressure steam turbine <NUM> and the exhaust gas circulating through the exhaust line L1.

In addition, in the present embodiment, the steam as a heat medium passed through the auxiliary exhaust gas heater 5B can be guided to the second line S2 through an auxiliary line S7.

According to the above configuration, the exhaust gas passed through the exhaust gas heater <NUM> is further heated by the auxiliary exhaust gas heater 5B. As a result, the humidity contained in the exhaust gas is further reduced, and the possibility of white smoke formation can be further reduced.

Hereinbefore, the second embodiment of the present invention is described.

For example, as a modification example common to each embodiment, it is possible to adopt a configuration in which only steam extracted from the steam turbine <NUM> is supplied to the EGR heater <NUM> as a heat medium. In addition, it is also possible to use only the steam extracted from the heat recovery steam generator <NUM> as the heat medium for the EGR heater <NUM>. Furthermore, the steam extracted from the steam turbine <NUM> and the steam extracted from the heat recovery steam generator <NUM> can be used together. In this manner, three types of aspects are considered as the heat medium for the EGR heater <NUM>.

In addition, the exhaust gas heater <NUM> can use only the steam extracted from the steam turbine <NUM> as a heat medium. Furthermore, it is also possible to use only the heat recovery steam generator <NUM> as the heat medium for the exhaust gas heater <NUM> as in the above embodiment. The steam extracted from the heat recovery steam generator <NUM> and the steam extracted from the steam turbine <NUM> can be used together as a heat medium for the exhaust gas heater <NUM>. In this manner, three types of aspects are considered as the heat medium for the exhaust gas heater <NUM>. In other words, a total of nine types of configurations are considered as a combination with the heat medium of the EGR heater <NUM> described above. A suitable configuration can be appropriately selected from these nine types of combinations according to the design and specifications.

Claim 1:
A gas turbine plant (<NUM>) comprising:
a gas turbine (<NUM>);
a heat recovery steam generator (<NUM>) that generates steam by exchanging heat between an exhaust gas of the gas turbine (<NUM>) and water;
a quencher (<NUM>) that cools the exhaust gas discharged from the heat recovery steam generator (<NUM>);
an absorber (<NUM>) that recovers carbon dioxide contained in the exhaust gas cooled by the quencher (<NUM>);
an EGR line (L2) that extracts a part of the exhaust gas and guides the exhaust gas to an intake side of the gas turbine (<NUM>);
an exhaust gas heater (<NUM>) that heats the exhaust gas by exchanging heat between a heat medium and the exhaust gas passed through the absorber (<NUM>) using steam extracted from the heat recovery steam generator (<NUM>) as the heat medium; and
an EGR heater (<NUM>) that is provided on the EGR line (L2) and heats the exhaust gas circulating through the EGR line (L2) by exchanging heat between the exhaust gas circulating through the EGR line (L2) and the heat medium discharged from the exhaust gas heater (<NUM>), wherein
the EGR line (L2) extracts a part of the exhaust gas discharged from the quencher (<NUM>) and guides the exhaust gas to the intake side of the gas turbine (<NUM>).