Combined cycle power plant with co2 capture and method to operate it

Abstract

A combined cycle power plant with a gas turbine, steam turbine, and first HRSG comprises a CO2 capture plant for the at least partial capture of CO2 from the exhaust gases from the gas turbine. It comprises in particular a second HRSG or boiler arranged to receive a portion of the exhaust gases and transfer its heat to steam and feedwater. Steam generated in the second HRSG or boiler is used for the operation of the CO2 capture plant and/or to operate a steam turbine that drives a generator and optionally a CO2 compressor. The power plant according to the invention allows for greater flexibility in power plant part load control and power plant efficiency. A method to operate the power plant is also claimed.

1 . A combined cycle power plant for the generation of electrical power comprising at least one gas turbine a first or main heat recovery steam generator HRSG for generating steam by means of gases exhausted by the gas turbine and directed to the HRSG via an exhaust gas line and at least one steam turbine driven by steam generated in the first HRSG, where the power plant is operationally connected with a CO2 capture plant arranged and configured for the removal of CO2 contained in the gas turbine exhaust gas by means of an absorption solution, where the absorption solution may be reheated in order to release pure gaseous CO2, wherein the power plant comprises a second heat recovery steam generator HRSG or a boiler configured and arranged to receive gas turbine exhaust gas and to transfer the heat from the gas turbine exhaust gas to steam and/or feedwater, and the second HRSG or boiler is configured and arranged to generate steam for at least one further steam turbine or the CO2 capture plant or both, and the combined cycle power plant comprises a damper or flow divider in a gas turbine exhaust gas line arranged to divide an exhaust gas flow into a first and second partial exhaust gas flow, where the power plant comprises lines to direct the first partial exhaust gas flow to a stack and the second partial exhaust gas flow to the second HRSG or boiler, wherin the damper or flow divider is arranged to divert 10 to 60% of the exhaust gas flow reaching the flow divider or damper into the second exhaust gas flow and to the second HRSG or boiler. 
     
     
         2 . A combined cycle power plant according to  claim 1  wherein the damper or flow divider is arranged in an exhaust gas line leading from the gas turbine to the first HRSG and a line is arranged to direct the first partial exhaust gas flow from the flow divider to the first HRSG and a further line is arranged to direct the second partial exhaust gas flow from the flow divider to the second HRSG or boiler. 
     
     
         3 . A combined cycle power plant according to  claim 1  wherein the damper or flow divider is arranged in an exhaust gas line leading away from the first HRSG and to the stack and a line is arranged to direct the first partial exhaust gas flow from the flow divider to the stack and a further line is arranged to direct the second partial exhaust gas flow from the flow divider to the second HRSG or boiler. 
     
     
         4 . A combined cycle power plant according to  claim 1  wherein the power plant comprises at least one line to direct steam generated in the second HRSG or boiler to the CO2 capture plant. 
     
     
         5 . A combined cycle power plant according to  claim 1  wherein the power plant comprises a line to direct steam generated in the second HRSG or boiler to a further steam turbine. 
     
     
         6 . A combined cycle power plant according to  claim 1  wherein the power plant comprises a supplementary firing assembly. 
     
     
         7 . A combined cycle power plant according to  claim 1  wherein the power plant further comprises a line for gas exhausted by the second HRSG or boiler leading to the CO2 capture plant. 
     
     
         8 . A combined cycle power plant according to  claim 5  wherein the power plant comprises a high- or intermediate pressure steam turbine driven by steam generated in the second HRSG or boiler and a generator arranged on a single shaft and in that the power plant comprises a CO2 compressor arranged on the single shaft. 
     
     
         9 . A combined cycle power plant according to  claim 5  wherein the power plant comprises a steam turbine arranged to receive steam from the second HRSG or boiler and to drive a generator, and the power plant further comprises lines to direct steam from the second HRSG or boiler or steam extracted from said steam turbine or from both to the CO2 capture plant. 
     
     
         10 . Method to operate combined cycle power plant comprising a gas turbine, a first heat recovery steam generator HRSG, a steam turbine, and a CO2 capture plant comprising directing a first portion of the exhaust gas flow from the gas turbine to a stack, directing a second portion of an exhaust gas flow from the gas turbine to an additional second HRSG or a boiler, operating the second HRSG or boiler to generate steam and directing this steam to the CO2 capture plant or to a further steam turbine or both. 
     
     
         11 . Method according to  claim 10  further comprising diverting the second portion of the exhaust gas flow from the gas turbine to the second HRSG by means of a flow divider arranged in the exhaust gas line after the gas turbine and prior to the first HRSG or by diverting the second portion of the exhaust gas flow from the gas turbine to the second HRSG by means of flow divider arranged in the exhaust gas line after the first HRSG. 
     
     
         12 . Method according to  claim 10  further comprising directing at least a portion of the exhaust gas flow exiting from the second HRSG or boiler to the CO2 capture plant. 
     
     
         13 . Method according to  claim 10  further comprising using the steam generated in the second HRSG or boiler to reheat a CO2 absorption solution in the CO2 capture plant. 
     
     
         14 . Method according to  claim 10  further comprising combusting in the second HRSG or boiler residue oxygen in the exhaust gas by means of supplementary firing. 
     
     
         15 . Method according to  claim 10  further comprising combusting in the second HRSG or boiler residue oxygen to maintain a constant CO2 concentration in the flue gas leaving the second HRSG or boiler, and controlling the power output of the plant by changing the ratio of flue gas mass flow directed to first HR SG or boiler to the flue gas mass flow directed to the second HRSG or boiler. 
     
     
         16 . Method according to  claim 11  further comprising directing at least a portion of the exhaust gas flow exiting from the second HRSG or boiler to the CO2 capture plant. 
     
     
         17 . A combined cycle power plant according to  claim 6  wherein the power plant comprises a high- or intermediate pressure steam turbine driven by steam generated in the second HRSG or boiler and a generator arranged on a single shaft and in that the power plant comprises a CO2 compressor arranged on the single shaft. 
     
     
         18 . A combined cycle power plant according to  claim 7  wherein the power plant comprises a high- or intermediate pressure steam turbine driven by steam generated in the second HRSG or boiler and a generator arranged on a single shaft and in that the power plant comprises a CO2 compressor arranged on the single shaft. 
     
     
         19 . A combined cycle power plant according to  claim 6  wherein the power plant comprises a steam turbine arranged to receive steam from the second HRSG or boiler and to drive a generator, and the power plant further comprises lines to direct steam from the second HRSG or boiler or steam extracted from said steam turbine or from both to the CO2 capture plant. 
     
     
         20 . A combined cycle power plant according to  claim 7  wherein the power plant comprises a steam turbine arranged to receive steam from the second HRSG or boiler and to drive a generator, and the power plant further comprises lines to direct steam from the second HRSG or boiler or steam extracted from said steam turbine or from both to the CO2 capture plant.