Method and apparatus for controlling the final feedwater temperature of a regenerative Rankine cycle using an exergetic heater system

A method for quantifying the operation of a thermal system in which its thermal efficiency is to be improved, the thermal system consisting of a steam generator and a regenerative Rankine cycle, the regenerative Rankine cycle having a feedwater path carrying a high pressure feedwater flow, and a turbine supplying a high temperature extraction steam flow, the method comprising the steps of:

• installing a reboiler in the thermal system which, by using the high temperature extraction steam flow, causes a portion of the high pressure feedwater flow to vaporize resulting in a reboiler outlet flow;
• installing a thermocompressor in the thermal system wherein its motive flow employs the reboiler output flow, and wherein its supply flow employs the high temperature extraction steam flow resulting in a higher pressure extraction steam flow;
• and
• using the higher pressure extraction steam flow in a condensing feedwater heater thereby increasing the thermal system's final feedwater temperature entering the steam generator and thereby improving the system's thermal efficiency.

A device for a thermal system in which a final feedwater temperature is to be increased, said thermal system consisting of a steam generator and a regenerative Rankine cycle comprising a turbine supplying an extraction steam flow and a feedwater path carrying a high pressure feedwater flow, the device comprising:

• a reboiler installed in the thermal system;
• a pipe carrying a portion of the high pressure feedwater flow from the feedwater path to an inlet of the reboiler;
• a means of heating the reboiler producing a reboiler vaporized feedwater flow;
• a thermocompressor installed in the thermal system having an inlet connection for a supply steam flow, an inlet connection for a motive steam flow, and an outlet connection for a higher pressure extraction steam flow;
• a pipe carrying the extraction steam flow from the turbine to the inlet connection for the supply steam flow;
• a pipe carrying the reboiler vaporized feedwater flow from the reboiler to the inlet connection for the motive steam flow;
• a heat exchanger installed in the feedwater path with a means of feedwater heating, resulting in an installed Exergetic Heater;
• and
• a pipe carrying the higher pressure extraction steam flow from the thermocompressor, to the installed Exergetic Heater, and, by cooling the higher pressure extraction steam flow, thereby increasing the final feedwater temperature.

A control device 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 comprising a turbine, a feedwater path, a thermocompressor, a reboiler employing a reboiler heat source and an Exergetic Heater;

• the turbine supplying an extraction steam flow to the thermocompressor as a compressor supply flow, the feedwater path supplying a feedwater flow to the reboiler whose output is a reboiler vaporized feedwater flow, the thermocompressor using the reboiler vaporized feedwater flow as a compressor motive steam flow, the feedwater path supplying a feedwater flow to the Exergetic Heater, the Exergetic Heater supplying the steam generator with a final feedwater flow, the control device comprising:
• an instrument for measuring a temperature of the final feedwater flow, producing the final feedwater temperature;
• a control valve installed to control the feedwater flow to the reboiler, having as an input a signal to control the feedwater flow to the reboiler if necessitated for controlling the final feedwater temperature;
• a device for controlling the reboiler heat source, having as an input a signal for controlling the reboiler heat source if necessitated for controlling the final feedwater temperature;
• a control valve installed to control the compressor supply flow, having as an input a signal for controlling the compressor supply flow if necessitated for controlling the final feedwater temperature;
• a control valve installed to control the compressor motive steam flow having as an input a signal for controlling the compressor motive steam flow if necessitated for controlling the final feedwater temperature;
• and
• a control device for controlling the final feedwater temperature having as an input signal the final feedwater temperature, and having as an output signal at least one signal selected from the group comprising:
• the signal to control the feedwater flow to the reboiler, the signal for controlling the reboiler heat source, the signal for controlling the compressor supply flow, and the signal for controlling the compressor motive steam flow.

A control device for increasing a boiler efficiency of a thermal system, the thermal system consisting of a steam generator and a regenerative Rankine cycle comprising a turbine a feedwater path, a compressor device, a reboiler employing a reboiler heat source, and an Exergetic Heater;

• the turbine supplying an extraction steam flow to the compressor device as a compressor supply flow, the feedwater path supplying a feedwater flow to the reboiler whose output is a reboiler vaporized feedwater flow, the compressor device using the reboiler vaporized feedwater flow as a compressor motive steam flow, the feedwater path supplying a feedwater flow to the Exergetic Heater, the Exergetic Heater supplying the steam generator with a final feedwater flow, the control device comprising:
• an instrument for measuring a temperature of the final feedwater flow, producing an output of a final feedwater temperature signal;
• a device for computing the boiler efficiency of the thermal system, producing an output of a boiler efficiency signal;
• a control valve installed to control the feedwater flow to the reboiler, having as an input a signal to control the feedwater flow to the reboiler if necessitated for controlling the final feedwater temperature;
• a device for controlling the reboiler heat source, having as an input a signal for controlling the reboiler heat source if necessitated for controlling the final feedwater temperature;
• a control valve installed to control the compressor supply flow, having as an input a signal for controlling the compressor supply flow if necessitated for controlling the final feedwater temperature;
• a control valve installed to control the compressor motive steam flow, having as an input a signal for controlling the compressor motive steam flow if necessitated for controlling the final feedwater temperature;
• and
• a control device for increasing the boiler efficiency of the thermal system by controlling the final feedwater temperature, said device comprising inputs of the final feedwater temperature signal and the boiler efficiency signal, and having as an output signal at least one signal selected from the group comprising:
• the signal to control the feedwater flow to the reboiler, the signal for controlling the reboiler heat source the signal for controlling the compressor supply flow and the signal for controlling the compressor motive steam flow.

A control device for increasing a thermal efficiency of a thermal system, the thermal system consisting of a steam generator and a regenerative Rankine cycle comprising a turbine, a feedwater path, a compressor device, a reboiler employing a reboiler heat source, and an Exergetic Heater;

• the turbine supplying an extraction steam flow to the compressor device as a compressor supply flow, the feedwater path supplying a feedwater flow to the reboiler whose output is a reboiler vaporized feedwater flow, the compressor device using the reboiler vaporized feedwater flow as a compressor motive steam flow, the feedwater path supplying a feedwater flow to the Exergetic Heater, the Exergetic Heater supplying the steam generator with a final feedwater flow, the control device comprising:
• an instrument for measuring a temperature of the final feedwater flow, producing an output of a final feedwater temperature signal;
• a device for computing the thermal efficiency of the thermal system, producing an output of a thermal efficiency signal;
• a control valve installed to control the feedwater flow to the reboiler, having as an input a signal to control the feedwater flow to the reboiler if necessitated for controlling the final feedwater temperature;
• a device for controlling the reboiler heat source, having as an input a signal for controlling the reboiler heat source if necessitated for controlling the final feedwater temperature;
• a control valve installed to control the compressor supply flow, having as an input a signal for controlling the compressor supply flow if necessitated for controlling the final feedwater temperature;
• a control valve installed to control the compressor motive steam flow, having as an input a signal for controlling the compressor motive steam flow if necessitated for controlling the final feedwater temperature;
• and
• a control device for increasing the thermal efficiency of the thermal system by controlling the final feedwater temperature, said device comprising inputs of the final feedwater temperature signal and the thermal efficiency signal, and having as an output signal at least one signal selected from the group comprising:
• the signal to control the feedwater flow to the reboiler, the signal for controlling the reboiler heat source, the signal for controlling the compressor supply flow, and the signal for controlling the compressor motive steam flow.