Combined cycle power plant having reduced parasitic pumping losses

A combined cycle power plant (CCPP) comprising:

• a gas turbine having a compressor section, a combustion section, and a turbine section;
• a heat recovery steam generator (HRSG) that receives a flow of exhaust gas from the turbine section, the HRSG having a high pressure economizer, comprising a forward high pressure economizer and an aft high pressure economizer in series, and a low pressure economizer;
• a fuel heating system comprising a fuel supply line, a high temperature heat exchanger, and a low temperature heat exchanger, the fuel supply line fluidly coupled to the combustion section, the high temperature heat exchanger and the low temperature heat exchanger disposed in thermal communication on the fuel supply line, the high temperature heat exchanger fluidly coupled to the forward high pressure economizer, and the low temperature heat exchanger fluidly coupled to the low pressure economizer;
• and a feedwater pump fluidly coupled to the high temperature heat exchanger, wherein a first pump supply line extends from the low pressure economizer to a first inlet of the feedwater pump, and wherein the high temperature heat exchanger is fluidly coupled to a second inlet of the feedwater pump via a second pump supply line.

A feedwater pump control system comprising:

• a heat recovery steam generator (HRSG) having a low pressure economizer and at least one high pressure economizer;
• a fuel heating system having a fuel supply line fluidly coupled to a combustion section, a high temperature heat exchanger, and a low temperature heat exchanger disposed in thermal communication on the fuel supply line;
• a feedwater pump having a plurality of stages;
• a first pump supply line extending between the one of the low pressure economizer, a low pressure steam drum, or a deaerator, and an initial stage of the plurality of stages;
• a second pump supply line extending between the high temperature heat exchanger and an intermediate stage of the plurality of stages;
• a feedwater supply line extending between a last stage of the plurality of stages and the at least one high pressure economizer;
• one or more sensors disposed on one or more of the first pump supply line, the second pump supply line, and the feedwater supply line, the sensor configured to provide data indicative of at least one of a pressure, a temperature, or a flow rate of water;
• one or more valves disposed on one or more of the second pump supply line and the feedwater supply line;
• and
• a controller communicatively coupled to the sensor and operatively coupled to the valve, the controller comprising memory and one or more processors, the memory storing instructions that when executed by the one or more processors causes the feedwater pump control system to perform operations including:
• monitoring data indicative of a temperature difference between water entering the feedwater pump and water exiting the feedwater pump via the one or more sensors;
• determining when the temperature difference is outside of a predetermined temperature range;
• and
• adjusting a flow of water to the feedwater pump by actuating the one or more valves to restore the temperature difference to be within the predetermined temperature range.