Flue Gas Recirculation Combustor for Low NOx and Stable Flame
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Solution Overview
Problem
Combined cycle power plants face challenges in reducing NOx and CO emissions while maintaining stable combustion due to the increase in NOx emissions with higher combustion temperatures and the reduction in oxygen content caused by flue gas recirculation, which affects combustion stability and efficiency.
Innovation Solution
The method involves controlling the imposed combustion inhomogeneity ratio as a function of flue gas recirculation rate and combustion pressure to enhance flame stability, using measures such as piloting, staged premixed injection, and staged grouping of burners, while also optimizing the recirculation rate to maintain low NOx and CO emissions and increase CO2 concentration for more efficient CO2 capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If flue gas recirculation is used to reduce NOx emissions, then NOx emissions are reduced, but oxygen content in inlet gases decreases affecting combustion stability
Solution Approach 1:
The combustor is divided into multiple zones with different oxygen concentrations. A first zone receives recirculated flue gas to suppress NOx formation, while a second zone receives fresh oxygen-containing gas to maintain combustion stability. This spatial segmentation allows simultaneous achievement of low NOx emissions and stable combustion.
Solution Approach 2:
Different regions of the combustor are provided with different gas compositions tailored to their specific functions. The first zone has low oxygen content optimized for NOx reduction, while the second zone has high oxygen content optimized for combustion stability. This local optimization resolves the contradiction between NOx reduction and combustion stability.
2Productivity
If higher combustion temperatures are used to increase power plant efficiency, then power plant efficiency is improved, but NOx emissions increase
Solution Approach 1:
The combustion process is segmented into distinct zones: a first zone with controlled lower temperature and low oxygen content for NOx suppression, and a second zone with higher temperature and high oxygen content for efficient power generation. This allows the plant to operate at high efficiency while maintaining low NOx emissions.
Solution Approach 2:
The oxygen concentration and temperature parameters are independently controlled in different zones. By changing the oxygen content parameter in the first zone to be low and in the second zone to be high, the system achieves both high efficiency and low NOx emissions simultaneously.
3Productivity
If flue gas recirculation rate is increased to increase CO2 concentration, then CO2 capture efficiency is improved, but combustion stability deteriorates
Solution Approach 1:
The combustor is segmented to separate the CO2 concentration function from the combustion stability function. The first zone handles CO2 concentration by receiving recirculated flue gas, while the second zone handles combustion stability by receiving fresh oxygen-containing gas. This allows high CO2 concentration in the flue gas without compromising combustion stability.
Solution Approach 2:
Different zones are provided with locally optimized gas compositions. The first zone has high CO2 content from recirculated flue gas optimized for CO2 capture efficiency, while the second zone has high oxygen content optimized for combustion stability. This local differentiation resolves the contradiction between CO2 capture efficiency and combustion stability.
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 allows for stable, low-NOx, and low-CO emissions operation at high flame temperatures, optimizing CO2 capture efficiency and reducing the energy consumption and costs associated with CO2 capture systems.
Implementation Method 1
flue gas recirculation has been suggested
Implementation Method 2
NOx emissions increase with higher combustion temperature
Implementation Method 3
There are several technologies known to remove CO2 from a flue gas such as absorption, adsorption, membrane separation, and cryogenic separation
Implementation Method 4
There are several technologies known to remove CO2 from a flue gas such as absorption, adsorption, membrane separation, and cryogenic separation
Implementation Method 5
There are several technologies known to remove CO2 from a flue gas such as absorption, adsorption, membrane separation, and cryogenic separation
Implementation Method 6
There are several technologies known to remove CO2 from a flue gas such as absorption, adsorption, membrane separation, and cryogenic separation
Data Source
AI summary
An exemplary method for the operation of a CCPP with flue gas recirculation to reduce NOx emissions and/or to increase the CO2 concentration in the flue gases to facilitate CO2 capture from the flue gases as well as a plant designed to operate is disclosed. To allow a high flue gas recirculation ration (rFRG) an imposed combustion inhomogeneity ratio (ri) is used for flame stabilization. The imposed combustion inhomogeneity ratio (ri) is controlled as function of the flue gas recirculation rate (rFRG) and/or combustion pressure. Oxygen or oxygen enriched air to the gas turbine inlet gases or to the combustor is admixed to enhance operatability.