Turbine Combustor NOx Reduction via Flue Gas Recirculation
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Solution Overview
Problem
Conventional gas turbines face challenges in effectively reducing nitrogen oxide (NOx) emissions due to difficulties in controlling oxygen concentration within the combustion process, leading to inefficient NOx reduction.
Innovation Solution
A flue gas recirculation combustor system is implemented, featuring an ejector nozzle and bypass path that lower oxygen concentration by recirculating combustion air from the combustor chamber to the premixing space, allowing for efficient NOx reduction regardless of combustion temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional combustion control methods are used, then combustion stability is maintained, but NOx emissions cannot be sufficiently reduced
Solution Approach 1:
The combustion control system is segmented into multiple independent control zones: a premixing zone where fuel and air are mixed before combustion, and a combustion zone where actual burning occurs. This segmentation allows independent control of oxygen concentration in each zone, enabling NOx reduction through controlled premixing while maintaining combustion stability in the combustion zone.
Solution Approach 2:
A recirculation passage acts as an intermediary mechanism, transporting a portion of the combustion products back to the premixing zone. This intermediary pathway enables the introduction of recirculated gases (containing CO2 and H2O) into the premixing zone, effectively lowering the oxygen concentration without requiring direct modification of the combustion process itself.
2Object-generated harmful factors
If oxygen concentration is reduced to lower NOx emissions, then NOx reduction efficiency improves, but combustion stability deteriorates
Solution Approach 1:
Different oxygen concentrations are applied to different spatial zones: the premixing zone operates with reduced oxygen concentration (due to recirculated gases) to suppress NOx formation, while the combustion zone maintains sufficient oxygen for stable combustion. This local differentiation of quality (oxygen concentration) allows simultaneous achievement of NOx reduction and combustion stability.
Solution Approach 2:
The fuel and air are preliminarily mixed in the premixing zone before entering the combustion zone. This preliminary mixing action ensures homogeneous distribution of fuel and oxidizer, which stabilizes combustion. The recirculated gases are also introduced in advance into this premixing zone, allowing the system to prepare a controlled fuel-air mixture with reduced oxygen concentration that still supports stable combustion when properly mixed.
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 effectively reduces NOx emissions in the exhaust gas of gas turbines by optimizing the configuration of nozzles and injection control mechanisms, enhancing the mixing of fuel and air to achieve lower oxygen concentrations and improved combustion efficiency.
Implementation Method 1
an ejector nozzle... to lower the oxygen concentration by recirculating combustion air from the combustor chamber to the premixing space
Implementation Method 2
recirculating combustion air from the combustor chamber to the premixing space
Data Source
Figure 1
Figure 2~3
Figure 3B~4
AI summary
A flue gas recirculation combustor includes a combustor chamber (100) configured such that fuel and combustion gas are injected therein to cause combustion and having a nozzle-side end and a combustor outlet, a nozzle can (200) connected to the nozzle-side end of the combustor chamber (100), a plurality of nozzles (300) disposed in the nozzle can (200) and configured such that an injection direction thereof is directed to a side of the combustor chamber (100), and a sleeve (400) disposed in a premixing space (700) defined between the nozzle can (200) and the nozzle-side end of the combustor chamber (100), the sleeve (400) including a recirculation pathway to recirculate combustion air from the combustor chamber (100) to the premixing space (700).