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A structure, system, and method for controlling a power output and flue gas temperature of a power plant by adjusting final feedwater temperature are disclosed herein. In an embodiment, a turbine having a plurality of valved steam extraction ports is provided. Each steam extraction port is fluidly c

A structure, system, and method for controlling a power output and flue gas temperature of a power plant by adjusting final feedwater temperature are disclosed herein. In an embodiment, a turbine having a plurality of valved steam extraction ports is provided. Each steam extraction port is fluidly connected with a feedwater heater. Each of the plurality of valves in the valved steam extraction ports may be opened and closed to the passage of steam therethrough, in order to vary a final feedwater temperature.

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1. A structure comprising: a variable feedwater heating system including: a turbine having a plurality of steam extraction ports;a plurality of pipes, wherein each pipe has a first end, a valve, and a second end, the first end of each pipe being fluidly connected to a respective plurality of steam e

1. A structure comprising: a variable feedwater heating system including: a turbine having a plurality of steam extraction ports;a plurality of pipes, wherein each pipe has a first end, a valve, and a second end, the first end of each pipe being fluidly connected to a respective plurality of steam extraction ports, wherein the second end of each of the plurality of pipes is connected in parallel to a single line;a steam extraction line having a first end and a second end, the first end of the steam extraction line being fluidly connected to the single line and configured to extract steam therefrom;a feedwater heater to heat feedwater to a final feed water temperature fluidly connected to the second end of the steam extraction line, wherein the feedwater heater is downstream of the connection between the single line and the steam extraction line, the feedwater heater including a feedwater heating line therein, wherein the feedwater heating line is in thermal communication with the steam extracted from the steam extraction line;wherein the steam extraction line delivers an extraction fraction of steam from the turbine to the feedwater heater; anda steam generator in circuitous fluid connection with the feedwater heating line,wherein the final feedwater temperature is a temperature of the feedwater upon exiting the feedwater heater and upon entering the steam generator, and wherein the final feedwater temperature is varied based on the extraction fraction of steam. 2. The structure of claim 1, further comprising a control system for opening and closing each of the plurality of steam extraction ports in response to a change in a load at which the turbine operates to maintain a desired final feedwater temperature, wherein the desired final feedwater temperature is based on at least one of a fuel type and the load at which the turbine operates. 3. The structure of claim 1, wherein the plurality of feedwater extraction ports further comprises between two and seven feedwater extraction ports. 4. The structure of claim 2, wherein the control system prevents more than one of the plurality of steam extraction ports from being open at a time. 5. The structure of claim 2, wherein each of the plurality of pipes has a different extraction pressure. 6. The structure of claim 3, wherein the plurality of feedwater extraction ports further comprises four feedwater extraction ports. 7. A system for controlling a power output of a power plant, the system comprising: a variable feedwater heating system including:a turbine having a plurality of steam extraction ports;a plurality of pipes, wherein each pipe has a first end, a valve, and a second end,the first end of each pipe being fluidly connected to a respective plurality of steam extraction ports, wherein the second end of each of the plurality of pipes is connected in parallel to a single line;a steam extraction line having a first end and a second end, the first end of the steam extraction line being fluidly connected to the single line and configured to extract steam therefrom;a feedwater heater for heating feedwater to fluidly connected to the second end of the steam extraction line, wherein the feedwater heater is downstream of the connection between the single line and the steam extraction line, the feedwater heater including a feedwater heating line therein, wherein the feedwater heating line is in thermally communication with the steam extracted from the steam extraction line;wherein the steam extraction line delivers an extraction fraction of steam from the turbine to the feedwater heater for;a control system including a processor and a memory, the memory having instructions stored thereon which, when executed by the processor, perform the steps of:opening or closing at least one valve of the plurality of valved steam extraction ports in response to a desired final feedwater temperature,wherein executing an instruction to open or close a valve of the plurality of valved steam extraction ports changes the extraction fraction of steam, and a change in the extraction fraction of steam changes the desired final feedwater temperature; and a steam generator in circuitous fluid connection with the feedwater heating line,wherein the desired final feedwater temperature is a temperature of the feedwater upon exiting the feedwater heater upon entering the steam generator, and wherein the final feedwater temperature is varied based on the extraction fraction of steam. 8. The system of claim 7, wherein the desired final feedwater temperature is based on at least one of a fuel type and a load at which the turbine operates. 9. The system of claim 7, wherein the steam generator further comprises one or more of: a multi-fuel boiler, a biomass fueled boiler, a fossil fueled boiler, an oxygen combustion boiler, and an air combustion boiler. 10. The system of claim 7, wherein the steam generator further comprises one of: a nuclear reactor, a geothermal energy source, and a solar energy source. 11. The system of claim 7, wherein the extraction fraction is adjusted in accordance with a fuel type used in the steam generator in order to vary the desired final feedwater temperature in accordance with the fuel type used in the steam generator. 12. The system of claim 7, wherein at most one of the plurality of valves may be open at a time. 13. The system of claim 7, wherein the plurality of feedwater extraction ports further comprises between two and seven feedwater extraction ports. 14. The system of claim 7, wherein the desired final feedwater temperature further comprises a final feedwater temperature at which a flue gas exhausted from the steam generator remains in a gaseous state and does not condense on a pipe. 15. The system of claim 7, wherein the turbine is operating at a partial load, and the desired final feedwater temperature is determined according to an equation: FFWT=Tsat(P)whereFFWT=the desired final feedwater temperature;Tsat=a saturation temperature of steam at an extraction port pressure; andP=the extraction port pressure in the feedwater heater and of the extraction fraction. 16. The system of claim 8, wherein each of the plurality of pipes has a different extraction pressure. 17. The system of claim 13, wherein the plurality of feedwater extraction ports further comprises four feedwater extraction ports. 18. A method for optimizing a final feedwater temperature comprising: providing a variable feedwater heating system including: a turbine having a plurality of valved steam extraction ports;a plurality of pipes, wherein each pipe has a first end, a valve, and a second end, the first end of each pipe being fluidly connected to a plurality of steam extraction ports, wherein the second end of each of the plurality of pipes is connected in parallel to a single line;extracting steam from a steam extraction line having a first end and a second end, the first end of the steam extraction line being fluidly connected to the single line;heating feed water in a feedwater heater fluidly connected to the second end of the steam extraction line, wherein the feedwater heater is downstream of the connection between the single line and the steam extraction line, and the feedwater heater including a feedwater heating line therein, wherein the feed water heating line is in thermal communication with the steam extracted from the steam extraction line;delivering via the steam extraction line an extraction fraction of steam from the turbine to the feedwater heater; andgenerating steam using a steam generator positioned in circuitous fluid connection with the feedwater heating line;actively controlling an extraction fraction of steam from the turbine by opening and closing a valve in the plurality of valved steam extraction ports in response to a desired final feedwater temperature, wherein opening and closing a valve changes the extraction fraction of steam, and a change in the extraction fraction of steam changes the desired final feedwater temperature; anddelivering the extraction fraction of steam from the turbine to the feedwater heater through the steam extraction line,wherein the desired final feedwater temperature is a temperature of the feedwater upon exiting the feedwater heater and upon entering the steam generator, and wherein the desired final feedwater temperature is varied based on the extraction fraction of steam. 19. The method of claim 18, further comprising: operating the turbine at a partial load; and determining the desired final feedwater temperature according to an equation: FFWT=Tsat(P)in which:FFWT=the desired final feedwater temperature;Tsat=a saturation temperature of steam at an extraction port pressure; andP=the extraction port pressure in the feedwater heater and of the extraction fraction.