Hydrogen Combustor Segmentation for Low NOx and Reliability
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Solution Overview
Problem
Combustors using hydrogen-containing gases face challenges in reducing NOx emissions while maintaining burner reliability, as hydrogen's high burning velocity can lead to flashback and increased NOx generation, and existing methods like nitrogen injection or steam injection are inefficient or reduce plant efficiency.
Innovation Solution
A combustor design with a diffusive combustion system that includes separate fuel and air injection paths, using a primary combustion zone for fuel-rich conditions and a secondary zone for lean combustion, with nitrogen injection to reduce oxygen concentration and hydrogen injection to react with NOx, creating a reduction zone to minimize NOx emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a premixed combustion burner is used with hydrogen-containing gas, then NOx emission is reduced, but the flame forms too close to the burner causing reliability issues
Solution Approach 1:
The combustion process is divided into two distinct zones: a primary combustion zone using diffusive combustion to ensure burner reliability, and a secondary combustion zone using premixed combustion to reduce NOx emission. This segmentation allows each zone to perform its specific function optimally without compromising the other.
Solution Approach 2:
Different combustion modes are applied to different spatial locations within the combustor. The primary zone near the burner uses diffusive combustion with fuel-rich conditions to protect the burner, while the secondary zone downstream uses premixed combustion with fuel-lean conditions to reduce NOx. This local differentiation resolves the contradiction between reliability and emission control.
2Reliability
If a diffusive combustion burner is used, then burner reliability is ensured, but flame temperature increases causing increased NOx generation
Solution Approach 1:
The combustor is divided into two functional zones that operate in sequence. The primary zone handles the reliability-critical ignition and initial combustion using diffusive mode, while the secondary zone handles the emission-critical complete combustion using premixed mode. This segmentation allows each zone to optimize for its primary function.
Solution Approach 2:
The combustion parameters (fuel-air ratio, mixing intensity, residence time) are changed between the two zones. The primary zone operates with fuel-rich conditions and lower mixing to ensure reliable ignition, while the secondary zone operates with fuel-lean conditions and higher mixing to reduce flame temperature and NOx formation.
3Reliability
If air is supplied to cool the liner wall surface, then burner reliability is improved, but oxygen concentration increases leading to higher flame temperature and NOx emission
Solution Approach 1:
A reducing agent (hydrogen or carbon monoxide) is introduced as an intermediary substance in the secondary combustion zone. This reducing agent reacts with formed NOx to convert it back to nitrogen, thereby counteracting the harmful effect of increased oxygen concentration from cooling air supplies.
Solution Approach 2:
The excess oxygen from cooling air supplies, which would normally increase flame temperature and NOx formation, is converted into a benefit by introducing a reducing agent that utilizes this oxygen to reduce NOx back to nitrogen through chemical reactions.
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 effectively reduces NOx emissions while ensuring burner reliability by controlling flame temperature and oxygen concentration, maintaining high efficiency and compliance with environmental regulations.
Implementation Method 1
a combustion chamber (12) that burns the fuel with air
Implementation Method 2
The NOx that is generated by the combustion of the fuel supplied from the first fuel nozzle can be reduced by the fuel containing hydrogen
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An object of the present invention is to provide a gas turbine combustor that supports hydrogen-containing gas having a high burning velocity and is capable of performing low NOx combustion without reducing reliability of a burner. A first fuel nozzle 301 is provided upstream of a combustion chamber 12 and supplies fuel for activation and hydrogen-containing gas. The combustor 3 has a primary combustion zone, a reduction zone and a secondary combustion zone. In the primary combustion zone, the fuel supplied from the first fuel nozzle 301 is combusted under a fuel rich condition to form a burned gas containing a low concentration of oxygen. In the reduction zone, a hydrogen-containing gas is injected into the combustion chamber 12 through a second fuel injection hole 12a from a second fuel nozzle 302 so that NOx generated in the primary combustion zone is reduced by an oxygen reaction of the hydrogen. In the secondary combustion zone, air for lean combustion is supplied into the combustion chamber 12 so that unburned part of fuel is combusted under a fuel lean condition.