Combustion Burner Fuel Nozzle Flame Stabilization
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Solution Overview
Problem
Conventional combustion burners for pulverized coal boilers face challenges in achieving stable ignition and reducing NOx generation due to the slower combustion rate of solid fuels like pulverized coal, which can lead to flame blow-off and high NOx production.
Innovation Solution
The combustion burner incorporates a fuel nozzle with a partitioning member that expands the inner flow channel cross-sectional area to reduce fuel gas flow rate, a flame stabilizer on the axial center side, and a secondary air nozzle with a decreasing cross-sectional area to manage the flow rates and promote internal ignition, thereby stabilizing the flame and reducing NOx formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flow rate of fuel gas is reduced to approach the combustion rate for stable ignition, then flame stability is improved, but the combustion efficiency may deteriorate
Solution Approach 1:
The fuel gas flow is segmented into inner and outer flow channels with different flow rates. The inner channel provides low flow rate fuel gas for stable ignition near the combustion rate, while the outer channel provides high flow rate fuel gas for maintaining combustion efficiency. This segmentation allows both stability and efficiency to coexist.
Solution Approach 2:
Different regions of the fuel gas flow are given different flow rate characteristics. The central region (inner channel) has reduced flow rate to match combustion rate for stability, while the peripheral region (outer channel) maintains high flow rate for efficiency. Each region has optimized local quality for its specific function.
2Speed
If external ignition is used to form high-temperature and high-oxygen region for rapid combustion, then combustion speed is improved, but NOx generation increases
Solution Approach 1:
The combustion process is segmented into internal ignition in the inner channel and external ignition in the outer channel. Internal ignition reduces NOx by avoiding high-temperature zones, while external ignition maintains combustion speed. The segmented approach allows both objectives to be achieved simultaneously.
Solution Approach 2:
The inner channel acts as an intermediary that provides a low-flow-rate fuel gas path for internal ignition, mediating between the need for stable ignition and reduced NOx. This intermediary structure enables the system to achieve both flame stability and low emissions.
3Reliability
If the flow channel cross-sectional area is expanded in the flow direction to reduce fuel gas flow rate, then flame blow-off is prevented, but the nozzle length increases
Solution Approach 1:
Instead of expanding the flow channel in the flow direction (length dimension), the invention expands the cross-sectional area in the radial dimension. This dimensional change allows flow rate reduction while maintaining compact nozzle length, solving the contradiction between stability and compactness.
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 design enhances internal flame stabilization, reduces NOx production by minimizing high-temperature, high-oxygen regions, and prevents flame blow-off, resulting in a more stable and efficient combustion process.
Implementation Method 1
the flow channel cross-sectional area of the inner flow channel partitioned by the partitioning member expands in the flow direction of the fuel gas
Implementation Method 2
at least one flame stabilizer provided on an axial center side near a tip end of the fuel nozzle
Implementation Method 3
supplies a mixture of primary air (air) and powdered coal (fuel) formed by pulverizing coal, and supplies high temperature combustion burner air (coal secondary air), and the mixture and combustion burner air are injected into the furnace to form a flame such that combustion is possible
Implementation Method 4
a heat exchanger such as a superheater, reheater, economizer, or the like for recovering heat of exhaust gas is provided in the flue, and heat exchanging is performed between the water and exhaust gas generated by combustion in the furnace
Data Source
AI summary
To provide: a fuel nozzle (51) that can inject fuel gas in which fuel and air are mixed; a flame stabilizer (54) provided on an axial center side near a tip end of the fuel nozzle (51); and a casing member (55) that partitions an inner flow channel in which the flame stabilizer (54) is provided and an outer flow channel on an outer side of the inner flow channel, inside the fuel nozzle (51), where the flow channel cross-sectional area of the inner flow channel partitioned by the casing member (55) expands in the flow direction of the fuel gas.