Turbine Exhaust Heat Recovery for Combustor Fuel
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Solution Overview
Problem
Existing gas turbine systems do not effectively utilize residual heat from combustion gases to enhance fuel heating, which can lead to reduced efficiency and increased NOx emissions.
Innovation Solution
A system comprising a turbine exhaust stack, a mixing plenum, a heat exchanger, a blower, and an exhaust recirculation plenum that recirculates and attemperates exhaust gases to transfer residual heat to combustor fuel, reducing thermal stresses and optimizing fuel temperature for efficient combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If residual heat from combustion gases is not utilized for fuel heating, then system complexity remains low, but fuel heating efficiency decreases and NOx emissions increase
Solution Approach 1:
The patent combines the fuel heating function with the exhaust gas recirculation system by integrating a heat exchanger into the existing exhaust pathway. The heat exchanger is positioned to utilize exhaust gases from the turbine, allowing simultaneous heat recovery for fuel heating and exhaust gas recirculation for combustion control, thereby improving fuel heating efficiency without proportionally increasing system complexity
Solution Approach 2:
The exhaust gas recirculation system serves multiple functions: it provides heat for fuel heating through the heat exchanger, maintains combustion stability by recirculating exhaust gases, and controls NOx emissions. This multi-functionality allows the system to achieve improved fuel heating efficiency while keeping the overall system complexity manageable through shared infrastructure
2Temperature
If high temperature exhaust gases are directly used for fuel heating, then fuel heating efficiency improves, but thermal stresses on system components increase
Solution Approach 1:
The heat exchanger acts as an intermediary device between the high-temperature exhaust gases and the fuel. It enables heat transfer from the exhaust gases to the fuel while physically isolating the two streams, allowing the fuel to be heated to the desired temperature without direct exposure to extreme thermal conditions that would cause thermal stresses
Solution Approach 2:
The system controls the temperature parameters by regulating the flow rate of exhaust gases through the heat exchanger and adjusting the fuel flow rate. By changing these operational parameters, the system optimizes heat transfer efficiency while maintaining thermal stresses within acceptable limits for the heat exchanger and associated components
3Stress or pressure
If exhaust gases are recirculated without attemperation, then system complexity is reduced, but thermal stresses on heat exchanger increase
Solution Approach 1:
The mixing plenum is positioned upstream of the heat exchanger to perform preliminary mixing and temperature equalization of the exhaust gases before they enter the heat exchanger. This preliminary action reduces temperature gradients and thermal stresses on the heat exchanger components, while the relatively simple mixing plenum design minimizes the increase in system complexity
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
The system enhances fuel heating efficiency, reduces NOx emissions, and extends the turndown range of gas turbines by effectively utilizing residual heat from combustion gases, improving overall gas turbine performance.
Implementation Method 1
a heat exchanger downstream from the turbine exhaust plenum that allows turbine exhaust gases to transfer residual heat to the combustor fuel
Implementation Method 2
controlling a recirculated exhaust flow from the heat exchanger to attemperate the turbine exhaust gases prior to entering the heat exchanger
Data Source
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AI summary
A system 40 for heating combustor fuel includes a turbine exhaust plenum 34 and a heat exchanger 42 downstream from the turbine exhaust plenum 34. The heat exchanger 42 has an exhaust inlet 52, an exhaust outlet 54, a fuel inlet 56, and a fuel outlet 58. An exhaust recirculation plenum 64 has a recirculation inlet connection 66 downstream from the exhaust outlet 54 and a recirculation outlet connection 68 upstream from the exhaust inlet 52. The system further includes structure for controlling a recirculated exhaust flow 70 from the exhaust outlet 54 into the exhaust recirculation plenum 64.