Fuel Preheating System for Combustion Turbine Engine
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Solution Overview
Problem
Conventional fuel preheating systems in combined cycle power plants suffer from significant energy losses and are overly complex and costly to maintain, limiting their efficiency and operational effectiveness.
Innovation Solution
A combined cycle power plant design that incorporates a fuel preheater using a blended stream of high and low pressure feedwater from a multi-pressure level heat recovery steam generator to preheat fuel, with a junction point and heat exchangers to optimize fuel temperature and reduce waste, and protective valves to manage pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional fuel preheating systems are used, then fuel temperature is increased, but significant energy losses occur
Solution Approach 1:
The patent combines multiple feedwater streams (high-pressure and low-pressure) into a single blended stream that passes through the fuel preheater. This merging allows efficient heat transfer from the blended feedwater to the fuel, increasing fuel temperature while minimizing energy losses by utilizing the thermal energy in both high-pressure and low-pressure streams that would otherwise be wasted.
2Temperature
If conventional fuel preheating systems are used, then fuel temperature is increased, but system complexity increases
Solution Approach 1:
The blended feedwater stream serves multiple functions: it preheats the fuel in the fuel preheater, and after passing through the fuel preheater, it continues to provide heat to the evaporator and economizer sections of the HRSG. This multi-functionality reduces system complexity by eliminating the need for separate heating systems for each component.
3Use of energy by moving object
If high pressure feedwater is used alone, then heating efficiency is high, but lower pressure components are exposed to elevated pressures
Solution Approach 1:
The feedwater system is segmented into high-pressure and low-pressure streams that are separately controlled and then blended. The high-pressure stream provides efficient heating when needed, while the low-pressure stream protects downstream components from excessive pressure. The blending occurs at a controlled junction point, allowing precise pressure management.
4Productivity
If fuel preheating is implemented, then overall plant efficiency is improved, but operational costs increase
Solution Approach 1:
The fuel preheater is integrated into the existing feedwater system of the HRSG, utilizing the feedwater that would otherwise pass through the evaporator and economizer sections. The system serves itself by using the thermal energy already present in the feedwater stream, eliminating the need for separate fuel heating equipment and reducing operational costs while improving plant efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances system efficiency by achieving higher fuel temperatures and reducing waste high-pressure feedwater, while protecting lower pressure components from elevated pressures and temperatures.
Implementation Method 1
The first heat exchanger may be configured for exchanging heat between: the combined feedwater delivered to the first heat exchanger by the combined feedwater line; and the fuel within of the fuel line. The second heat exchanger may be configured for exchanging heat between: the higher pressure feedwater that is delivered to the first heat exchanger by the upstream segment of the higher pressure feedwater branch; and the fuel within the fuel line.
Data Source
AI summary
A combined cycle power plant that includes a gas turbine and HRSG engaged with a steam turbine via a water steam cycle having higher and lower pressure levels. The CCPP further includes a fuel line and fuel preheater. A higher pressure feedwater line delivers higher pressure feedwater to a higher pressure feedwater branch that extends through the fuel preheater, the high pressure feedwater branch including upstream and downstream segments defined to each side of the fuel preheater. A lower pressure feedwater line delivers lower pressure feedwater to a lower pressure feedwater branch. The downstream segment of the higher pressure feedwater branch is combined with the lower pressure feedwater branch at a junction point and a combined feedwater line extends therefrom. A first heat exchanger exchanges heat between the combined feedwater line and fuel line. A second heat exchanger exchanges heat between the higher pressure feedwater branch and fuel line.