Method and apparatus for controlling the final feedwater temperature of a regenerative rankine cycle

A device for a thermal system in which a final feedwater temperature is to be controlled, said thermal system consisting of a steam generator and a regenerative Rankine cycle having an Intermediate Pressure turbine and a feedwater path, the device comprising:

• a heat exchanger installed in the feedwater path of the regenerative Rankine cycle and before the steam generator with a means of feedwater heating, resulting in an installed Exergetic Heater;
• an instrument for measuring a final feedwater temperature between the installed Exergetic Heater and the steam generator, having an output final feedwater temperature signal;
• a control valve having an inlet connection and an outlet connection;
• a pipe carrying fluid from the Intermediate Pressure turbine to the inlet connection of the control valve;
• and
• a pipe carrying fluid from the outlet connection of the control valve to the installed Exergetic Heater;
• and
• a control device for controlling the final feedwater temperature having as an input signal the output final feedwater temperature signal, and having an output signal which actuates the control valve such that the final feedwater temperature is controlled.

A method for quantifying the operation of a thermal system in which a final feedwater temperature is to be controlled, the thermal system consisting of a steam generator and a regenerative Rankine cycle having an Intermediate Pressure turbine and a feedwater path carrying a flow of feedwater, the method comprising the steps of:

• installing a heat exchanger having a shell-side and a tube-side in the feedwater path of the regenerative Rankine cycle and upstream from the steam generator, resulting in an Exergetic Heater;
• obtaining a final feedwater temperature associated with optimum operation of the steam generator, resulting in an optimized final feedwater temperature;
• routing an extraction steam source from the Intermediate Pressure turbine to the shell-side of the Exergetic Heater;
• routing the flow of feedwater to the tube-side of the Exergetic Heater;
• and
• controlling the extraction steam source such that the optimized final feedwater temperature is achieved.