Steam turbine plant, control method of same, and control system of same

Abstract

In one embodiment, a steam turbine plant includes a first turbine driven by steam from a boiler, a second turbine driven by steam from a reheater, a third turbine driven by the steam exhausted from the second turbine, and a carbon dioxide capturing system including a reboiler to heat an absorbing liquid with the steam exhausted or extracted from the second turbine. The plant further includes a steam pipe to feed the steam exhausted from the second turbine to the third turbine, and a first steam extraction pipe to send the steam exhausted or extracted from the second turbine to the reboiler. The plant further includes a pressure detector to detect a pressure of the steam flowing through the steam pipe or the first steam extraction pipe, a pressure adjustment valve provided on the steam pipe, and a controller to control the valve based on the detected pressure.

1 . A steam turbine plant comprising:
 a boiler configured to heat water to change the water into steam;   a first turbine configured to be driven by the steam from the boiler;   a reheater configured to heat the steam exhausted from the first turbine;   a second turbine configured to driven by the steam from the reheater;   a third turbine configured to driven by the steam exhausted from the second turbine;   a carbon dioxide capturing system including an absorbing tower configured to cause an absorbing liquid to absorb carbon dioxide, a regeneration tower configured to cause the absorbing liquid to release the carbon dioxide, and a reboiler configured to heat the absorbing liquid with heat of the steam exhausted or extracted from the second turbine;   a steam pipe configured to feed the steam exhausted from the second turbine to the third turbine;   a first steam extraction pipe configured to send the steam exhausted or extracted from the second turbine to the reboiler;   a pressure detector configured to detect a pressure of the steam flowing through the steam pipe or the first steam extraction pipe;   a pressure adjustment valve provided on the steam pipe; and   a controller configured to control the pressure adjustment valve based on the pressure detected by the pressure detector.   
     
     
         2 . The plant of  claim 1 , wherein the controller controls the pressure adjustment valve so that a value of the pressure is maintained to be a constant value or within a constant range. 
     
     
         3 . The plant of  claim 1 , further comprising:
 a second steam extraction pipe configured to send the steam exhausted or extracted from the first turbine to the reboiler;   a first valve provided on the first steam extraction pipe and configured to be controlled by the controller; and   a second valve provided on the second steam extraction pipe and configured to be controlled by the controller.   
     
     
         4 . The plant of  claim 3 , wherein the controller controls the first and second valves based on a generator load and a limit value of the generator load. 
     
     
         5 . The plant of  claim 3 , wherein the controller controls the first and second valves to bring one of the first and second valves into an opened state and the other valve into a closed state. 
     
     
         6 . The plant of  claim 1 , further comprising:
 a second steam extraction pipe configured to send the steam exhausted from the first turbine to the reboiler;   a third steam extraction pipe configured to send the steam extracted from the first turbine to the reboiler; and   a steam ejector arranged between the first and third steam extraction pipes and the reboiler, and configured to mix the steam from the first steam extraction pipe and the steam from the third steam extraction pipe to send the mixed steam to the reboiler.   
     
     
         7 . A control system configured to control a steam turbine plant, the plant comprising:
 a boiler configured to heat water to change the water into steam;   a first turbine configured to be driven by the steam from the boiler;   a reheater configured to heat the steam exhausted from the first turbine;   a second turbine configured to driven by the steam from the reheater;   a third turbine configured to driven by the steam exhausted from the second turbine;   a carbon dioxide capturing system including an absorbing tower configured to cause an absorbing liquid to absorb carbon dioxide, a regeneration tower configured to cause the absorbing liquid to release the carbon dioxide, and a reboiler configured to heat the absorbing liquid with heat of the steam exhausted or extracted from the second turbine;   a steam pipe configured to feed the steam exhausted from the second turbine to the third turbine; and   a first steam extraction pipe configured to send the steam exhausted or extracted from the second turbine to the reboiler, the control system comprising:   a pressure detector configured to detect a pressure of the steam flowing through the steam pipe or the first steam extraction pipe;   a pressure adjustment valve provided on the steam pipe; and   a controller configured to control the pressure adjustment valve based on the pressure detected by the pressure detector.   
     
     
         8 . A control method of controlling a steam turbine plant, the plant comprising:
 a boiler configured to heat water to change the water into steam;   a first turbine configured to be driven by the steam from the boiler;   a reheater configured to heat the steam exhausted from the first turbine;   a second turbine configured to driven by the steam from the reheater;   a third turbine configured to driven by the steam exhausted from the second turbine;   a carbon dioxide capturing system including an absorbing tower configured to cause an absorbing liquid to absorb carbon dioxide, a regeneration tower configured to cause the absorbing liquid to release the carbon dioxide, and a reboiler configured to heat the absorbing liquid with heat of the steam exhausted or extracted from the second turbine;   a steam pipe configured to feed the steam exhausted from the second turbine to the third turbine; and   a first steam extraction pipe configured to send the steam exhausted or extracted from the second turbine to the reboiler, the control method comprising:   detecting a pressure of the steam flowing through the steam pipe or the first steam extraction pipe with a pressure detector;   supplying a detected value of the pressure by the pressure detector to a controller; and   controlling a pressure adjustment valve provided on the steam pipe based on the detected value of the pressure with the controller.