Fuel preheating system for a combustion turbine engine

A combined cycle power plant comprising:

• a gas turbine;
• a heat recovery steam generator (HRSG) operably engaged to a steam turbine via a water steam cycle that includes three pressure levels, wherein the three pressure levels comprise:
• a high pressure level;
• an intermediate pressure level;
• and a low pressure level;
• a fuel line configured to deliver a fuel to a combustion system;
• a fuel preheater for preheating the fuel before delivery to the combustion system;
• a high pressure system comprising a high pressure feedwater branch that operably engages and extends through the fuel preheater, wherein the high pressure feedwater branch comprises upstream and downstream segments defined to each side of the fuel preheater such that:
• the upstream segment carries a higher pressure feedwater to the fuel preheater;
• and
• the downstream segment carries the higher pressure feedwater away from the fuel preheater;
• an intermediate pressure system comprising an intermediate pressure feedwater branch;
• a junction point at which the downstream segment of the high pressure feedwater branch is combined with the intermediate pressure feedwater branch;
• a combined feedwater line extending from the junction point for directing a combined feedwater therefrom, wherein the combined feedwater line operably engages and extends through the fuel preheater;
• a first heat exchanger of the fuel preheater that is configured to exchange heat between the combined feedwater within the combined feedwater line and the fuel within the fuel line;
• a second heat exchanger of the fuel preheater that is configured to exchange heat between the higher pressure feedwater within the high pressure feedwater branch and the fuel within the fuel line;
• a check valve disposed on the intermediate pressure feedwater branch at a position that is upstream relative to the junction point;
• and
• a pressure relief valve disposed on the downstream segment of the high pressure feedwater branch or the combined feedwater line, wherein the check valve and the pressure relief valve are configured to protect the intermediate pressure system from higher pressures originating in the high pressure system.

A system, comprising:

• a fuel heating system, comprising:
• a fuel path configured to supply a fuel flow to a combustion system;
• a first fluid path configured to couple to a first section of a heat recovery steam generator (HRSG) to receive a first flow of a first fluid;
• a second fluid path configured to couple to a second section of the HRSG to receive a second flow of a second fluid, wherein the second section operates at a higher pressure than the first section of the HRSG;
• a combined fluid path coupled to the first and second fluid paths, wherein the combined fluid path is configured to receive a combined flow of the first and second fluids received from the first and second fluid paths;
• a first heat exchanger disposed along the combined fluid path and disposed along the fuel path, wherein the first heat exchanger is configured to transfer heat from the combined flow to the fuel flow;
• a second heat exchanger disposed along the second fluid path and disposed along the fuel path downstream from the first heat exchanger;
• a check valve disposed along the first fluid path;
• and
• a pressure relief valve disposed along the second fluid path downstream of the second heat exchanger or disposed along the combined fluid path, wherein the check valve and the pressure relief valve are configured to protect the first section of the HRSG from higher pressures originating in the second section of the HRSG.