Thermal power plant, steam turbine and control method for a thermal power plant

1. A thermal power plant comprising: a boiler for burning fossil fuel to generate steam, a steam turbine including a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine which are driven by steam generated in the boiler, an absorber for absorbing and capturing CO2 contained in boiler exhaust gas discharged from the boiler in an absorbing liquid, a desorber for circulating the absorbing liquid between the desorber and the absorber and separating CO2 from the absorbing liquid that has absorbed CO2, a reboiler for feeding a heating source for separating CO2 from the absorbing liquid to the desorber, a steam pipe system for feeding steam taken out from the high-pressure turbine and the intermediate-pressure turbine to the reboiler, and

a steam feed source switching device which is installed in the steam pipe system for switching a steam feed source for feeding steam to the reboiler between the intermediate-pressure turbine and the high-pressure turbine so as to satisfy a steam pressure required by the reboiler while the steam turbine is under a partial load operation.

2. The thermal power plant according to claim 1 , further comprising:

a pressure control device is installed in a pipe for feeding the steam discharged from the intermediate-pressure turbine to the low-pressure turbine for regulating a pressure of the steam flowing down through the steam pipe system from the intermediate-pressure turbine toward the reboiler.

3. The thermal power plant according to claim 2 , wherein: the pressure control device is provided with a pressure control valve to control an opening angle thereof while the steam turbine is under the partial load operation, so that the pressure of the steam flowing down through the steam pipe system from the intermediate-pressure turbine toward the reboiler satisfies a steam pressure required by the reboiler.

4. The thermal power plant according to claim 1 , wherein: the steam feed source switching device is provided with a switching valve for switching the steam feed source for feeding the steam to the reboiler from the intermediate-pressure turbine to the high-pressure turbine, when the pressure of the steam fed from the intermediate-pressure turbine to the reboiler is equal to or lower than the steam pressure required by the reboiler, and

the steam pipe system is provided with a pressure control valve to control an opening angle thereof, so that the pressure of the steam fed from the high-pressure turbine to the reboiler satisfies the steam pressure required by the reboiler is installed.

5. A control method for a thermal power plant comprising: a boiler for burning fossil fuel to generate steam,

a steam turbine including a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine which are driven by the steam generated in the boiler,

a carbon dioxide separation and capture apparatus including an absorber for absorbing and capturing CO2 contained in boiler exhaust gas discharged from the boiler into an absorbing liquid, a desorber for circulating the absorbing liquid between the desorber and the absorber and separating CO2 from the absorbing liquid that has absorbed CO2, and a reboiler for feeding a heating source for separating CO2 from the absorbing liquid to the desorber, and

a steam pipe system for feeding steam taken out from the high-pressure turbine and the intermediate-pressure turbine to the reboiler, wherein:

a steam feed source for feeding steam to the reboiler is controlled to switch from the intermediate-pressure turbine to the high-pressure turbine when the pressure of the steam fed from the intermediate-pressure turbine to the reboiler is equal to or lower than the steam pressure required by the reboiler.

6. The control method for a thermal power plant according to claim 5 , wherein:

the steam turbine is provided with a pressure control valve installed in a pipe for feeding the steam discharged from the intermediate-pressure turbine to the low-pressure turbine, and

the pressure control valve is controlled an opening angle thereof while the steam turbine is under the partial load operation, so that the pressure of the steam flowing down through the steam pipe system from the intermediate-pressure turbine toward the reboiler satisfies a steam pressure required by the reboiler.

7. The control method for a thermal power plant according to claim 5 , wherein:

the pressure control valve provided in the steam pipe system is controlled an opening angle thereof, so that the pressure of the steam flowing down from the high-pressure turbine toward the reboiler satisfies a steam pressure required by the reboiler.

8. A steam turbine comprising: a boiler for burning fossil fuel to generate steam,

a steam turbine including a high-pressure turbine, an intermediate-pressure turbine and a low-pressure turbine which are driven by the steam generated in the boiler,

a carbon dioxide separation and capture apparatus for separating and capturing carbon dioxide from exhaust gas discharged from the boiler, to which the steam is fed from the high-pressure turbine and the intermediate-pressure turbine, and

a steam feed source switching device is installed for switching a steam feed source for feeding steam to the carbon dioxide separation and capture apparatus between the high-pressure turbine and the intermediate-pressure turbine so as to satisfy a steam pressure required by the carbon dioxide separation and capture apparatus while the steam turbine is under a partial load operation.

9. The steam turbine according to claim 8 , further comprising:

a pressure control device is provided in a pipe for feeding the steam discharged from the intermediate-pressure turbine to the low-pressure turbine for regulating a pressure of the steam fed from the intermediate-pressure turbine to the carbon dioxide separation and capture apparatus.

10. The steam turbine according to claim 9 , wherein: the pressure control device is provided with a pressure control valve to control so as to totally open thereof while the steam turbine is at a rated load operation, and

the pressure control valve is controlled in an opening angle thereof so that the pressure of the steam fed from the intermediate-pressure turbine to the carbon dioxide separation and capture apparatus satisfies the steam pressure required by the carbon dioxide separation and capture apparatus while the steam turbine is under a partial load operation.

11. The steam turbine according to claim 9 , further comprising:

a steam pipe system for feeding the steam taken out from the high-pressure turbine and the intermediate-pressure turbine to the carbon dioxide separation and capture apparatus,

the steam feed source switching device is provided with a switching valve installed in the steam pipe system for switching the steam feed source for feeding the steam to the carbon dioxide separation and capture apparatus from the intermediate-pressure turbine to the high-pressure turbine when the pressure of the steam fed from the intermediate-pressure turbine to the carbon dioxide separation and capture apparatus is reduced to a pressure equal to or lower than the steam pressure required by the carbon dioxide separation and capture apparatus, and

the steam pipe system is provided with a pressure control valve to control an opening angle thereof, so that the pressure of the steam fed from the high-pressure turbine to the carbon dioxide separation and capture apparatus satisfies the steam pressure required by the carbon dioxide separation and capture apparatus.

12. The thermal power plant according to claim 3 , wherein: the steam feed source switching device is provided with a switching valve for switching the steam feed source for feeding the steam to the reboiler from the intermediate-pressure turbine to the high-pressure turbine, when the pressure of the steam fed from the intermediate-pressure turbine to the reboiler is equal to or lower than the steam pressure required by the reboiler, and

the steam pipe system is provided with a pressure control valve to control an opening angle thereof, so that the pressure of the steam fed from the high-pressure turbine to the reboiler satisfies the steam pressure required by the reboiler is installed.

13. The control method for a thermal power plant according to claim 6 , wherein:

the pressure control valve provided in the steam pipe system is controlled an opening angle thereof, so that the pressure of the steam flowing down from the high-pressure turbine toward the reboiler satisfies a steam pressure required by the reboiler.

14. The steam turbine according to claim 10 , further comprising:

a steam pipe system for feeding the steam taken out from the high-pressure turbine and the intermediate-pressure turbine to the carbon dioxide separation and capture apparatus,

the steam feed source switching device is provided with a switching valve installed in the steam pipe system for switching the steam feed source for feeding the steam to the carbon dioxide separation and capture apparatus from the intermediate-pressure turbine to the high-pressure turbine when the pressure of the steam fed from the intermediate-pressure turbine to the carbon dioxide separation and capture apparatus is reduced to a pressure equal to or lower than the steam pressure required by the carbon dioxide separation and capture apparatus, and

the steam pipe system is provided with a pressure control valve to control an opening angle thereof, so that the pressure of the steam fed from the high-pressure turbine to the carbon dioxide separation and capture apparatus satisfies the steam pressure required by the carbon dioxide separation and capture apparatus.