Method for removal of entrained gas in a combined cycle power generation system

A method for operating a combined cycle power generation system of the type having (i) a Rankine cycle providing a first source of power via a first turbine, and (ii) a combustion process, having a variable reaction temperature, providing a second source of power via a second turbine, and a HRSG coupled between the first and second turbines to generate saturated steam with thermal energy received from the second turbine, the HRSG including a first stage configured to provide high pressure steam and a second stage configured to provide lower pressure steam, the power generation system including a first condenser coupled to transfer working fluid from a low pressure stage of the steam turbine system to the HRSG, the method comprising the steps of:

• placing components of the system in a start-up mode in which the turbines generate increasing power output relative to maximum values and whereby the steam is generated with thermal energy received from the second turbine by evaporating working fluid from a liquid state with heat recovered from the combustion process;
• providing, during the start-up mode, a portion of the saturated steam generated in the HRSG with thermal energy received from the second turbine to create superheated steam and injecting the superheated steam into a combustion chamber associated with operation of the second turbine;
• and
• prior to creating the superheated steam, processing the saturated steam in a second condenser to increase concentration of carbon dioxide and return condensed steam to the Rankine cycle, where the second condenser is positioned to receive the saturated steam from either the first stage of the HRSG or the second stage of the HRSG before the portion of the saturated steam generated in the HRSG is provided with the thermal energy received from the second turbine to create the superheated steam.

A method for operating a combined cycle power system of the type having a Rankine cycle providing a first power component and a combustion process providing a second power component, comprising:

• providing a source of working fluid, a component of which is in a liquid state during a portion of a Rankine cycle, the liquid state resulting from a first condensation of working fluid during transfer of the working fluid from a low pressure stage of the Rankine cycle;
• generating steam in a HRSG having a first stage configured to provide high pressure steam and a second stage configured to provide lower pressure steam by evaporating a first portion of the working fluid with thermal energy received from the combustion process so that a portion of entrained gas present in the system mixes with the first portion to form a gaseous mixture;
• during the start-up mode, the liquid state also resulting from a second condensation performed along a flow path which receives the saturated steam from either the first stage of the HRSG or the second stage of the HRSG before a remaining portion of the gaseous mixture is superheated along the flow path, the second condensation condensing a portion of the steam present in the gaseous mixture and returning condensed steam to the HRSG;
• and
• after condensing the portion of the steam during the start-up mode, superheating said remaining portion the of the gaseous mixture and injecting said remaining superheated portion the of the gaseous mixture into a combustion chamber which provides the second power component.