Oxygen-Fired Burner With Eductor-Jet Pump For Low-NOx Combustion
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Solution Overview
Problem
Current NOx reduction techniques in thermal processes, such as staged combustion and flue gas recirculation, face challenges in safety risks and layout issues, particularly in narrow combustion chambers, and there is a need for improved low-NOx oxygen-fuel combustion methods.
Innovation Solution
A burner assembly utilizing an eductor-jet pump to mix primary fuel and ballast gas, injecting a mixed jet into the combustion zone, with staged injection of secondary oxidizer and fuel, and additional ballast gas to dilute the flame and reduce NOx formation, while maintaining compact burner dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If separate injection of recycled flue gas and oxygen is used, then flame length increases, but combustion chamber overheating occurs
Solution Approach 1:
The injection process is divided into two separate stages: first injecting the mixed jet of fuel and ballast gas, then separately injecting oxidizer at a distance. This segmentation allows the flame to develop progressively without excessive lengthening, preventing overheating of combustion chamber elements while still achieving NOx reduction through the ballast gas effect.
Solution Approach 2:
Ballast gas (recycled flue gas or CO2-rich gas) is introduced as an intermediary substance that dilutes the fuel-oxidizer mixture. This intermediary reduces the combustion temperature and slows the flame propagation speed, allowing controlled combustion without excessive flame length, thus preventing overheating while maintaining NOx reduction benefits.
2Length of moving object
If low injection velocity is used, then flame length is controlled, but burner size increases
Solution Approach 1:
The system uses pneumatic injection through specialized nozzles to deliver the mixed jet and oxidizer. By optimizing the nozzle design and injection pressure, the system achieves effective flame control without requiring excessively large burner dimensions, resolving the contradiction between compact size and flame length control.
3Device complexity
If flue gas is mixed with oxygen before injection, then operation is simplified, but safety risk increases
Solution Approach 1:
Ballast gas serves as a safe intermediary that can be pre-mixed with fuel without creating explosive conditions. The ballast gas dilutes the mixture to below explosive limits, enabling simplified pre-mixing operation while maintaining safety. This resolves the contradiction by allowing operational simplicity without compromising safety through the use of the diluting ballast gas.
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 solution effectively reduces NOx emissions without flame lengthening, suitable for narrow combustion chambers, and is robust and low maintenance, allowing for regulation of flame properties and efficient operation in steam generation boilers.
Implementation Method 1
an eductor-jet pump for generating a mixed jet of the primary fuel and the primary ballast gas by entrainment of the primary ballast gas with the primary fuel
Implementation Method 2
a mixed jet of the primary fuel and the primary ballast gas is generated and injected into a combustion zone... where it combusts with oxidizer
Data Source
Figure 1
Figure 2
AI summary
Reduced NOx staged combustion method and corresponding burner assembly, whereby an eductor-jet pump (30) is used for generating a mixed jet of primary fuel and primary ballast gas which is injected into the combustion zone in contact with a jet or primary oxidizer so as to generate a primary flame (110) and whereby secondary oxidizer and/or secondary fuel is injected at a distance (los/lfs) from the mixed jet.