Solid-Fuel Burner Flame Stabilizer for NOx Reduction
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Solution Overview
Problem
Conventional pulverized-coal-combustion burners face challenges in flame stabilization and NOx production due to separation of fuel gas flow and high oxygen concentration at the flame stabilizer, especially when coal contains moisture or volatile content, making it difficult to adjust operation parameters effectively.
Innovation Solution
A solid-fuel-combustion burner design featuring a split member as an inner flame stabilization mechanism, which divides the fuel and air flow to create a recirculation zone and suppresses hot oxygen zones at the flame periphery, reducing NOx production by promoting inner ignition and finely dividing the ignition surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional flame stabilizer is used at the front end portion, then flame stabilization is provided, but flow separation occurs at the rear end portion making it difficult to sufficiently exhibit flame stabilization ability
Solution Approach 1:
The flame stabilizer is divided into a front end portion and a rear end portion with different functions. The front end portion provides flame stabilization while the rear end portion is designed to prevent flow separation, creating a segmented structure where each portion optimizes its specific function rather than requiring a single complex design to handle all requirements
Solution Approach 2:
Instead of trying to prevent flow separation at the rear end portion of a conventional flame stabilizer, the invention inverts the approach by designing the rear end portion to actively promote smooth flow attachment. The rear end portion is shaped to guide the flow back toward the furnace center, converting the problematic flow separation into a beneficial flow control mechanism
2Productivity
If pulverized coal with moisture or volatile content is burned, then combustion is achieved, but operation parameters need to be adjusted based on boiler output making it difficult to directly set parameters from coal characteristics
Solution Approach 1:
The burner introduces secondary air at a specific location (rear end portion of the flame stabilizer) with specific flow control characteristics, creating a localized region where coal particles can ignite and burn efficiently regardless of their moisture or volatile content. This local quality control allows consistent combustion performance across different coal types without requiring extensive parameter adjustments
Solution Approach 2:
The invention changes the flow parameters in the rear end portion by controlling secondary air injection, creating a recirculation zone with specific velocity and temperature characteristics. This parameter change enables the system to accommodate variations in coal properties (moisture, volatile content) while maintaining stable combustion, reducing the need for operator intervention to adjust parameters
3Reliability
If fuel gas flow collides with flame stabilizer, then flame stabilization occurs, but hot oxygen remaining zone forms at outer periphery increasing NOx production
Solution Approach 1:
The rear end portion of the flame stabilizer acts as an intermediary element between the primary combustion zone and the outer periphery. It controls the interaction between fuel gas flow and secondary air, preventing the formation of a hot oxygen remaining zone at the outer periphery while maintaining effective flame stabilization at the front end portion
Solution Approach 2:
By controlling secondary air injection at the rear end portion, the invention creates a less oxygen-rich environment at the outer periphery of the flame stabilizer. This reduces the concentration of hot oxygen that would otherwise remain in that region and contribute to NOx formation, while still maintaining adequate oxygen supply for complete combustion in the core zone
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 design enhances flame stabilization and reduces NOx production by ensuring inner ignition and minimizing unburned combustible content, effectively lowering NOx emissions by suppressing hot oxygen zones at the flame periphery.
Implementation Method 1
the split member forms a recirculation zone at the front side of the split member
Implementation Method 2
the split member that is provided near the center of the outlet opening divides the passage of the pulverized coal and the air so as to disturb the flow therein
Implementation Method 3
In a zone in which the end portion of the split member is removed, the ignition performed using the split member as the ignition source may be suppressed
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
A combustion burner, wherein there are provided a fuel nozzle (51) through which can be blown a fuel gas that is a mixture of pulverized coal and primary air, and a secondary air nozzle (52) through which can be blown secondary air from the exterior of the fuel nozzle (51). A flame stabilizer (54) is provided toward the axial center at a distal end of the fuel nozzle (51), and a rectification member (55) is provided between an inner wall surface of the fuel nozzle (51) and the flame stabilizer (54), thereby making it possible to achieve an optimal flow of fuel gas that is a mixture of solid fuel and air.