Solid-Fuel Burner Air Injection for NOx Reduction
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Solution Overview
Problem
Conventional solid-fuel-fired boilers and burners produce high amounts of NOx due to high-temperature oxygen remaining regions at the flame's circumference, which are formed by secondary air injection configurations, leading to inefficient combustion and increased NOx emissions.
Innovation Solution
A solid-fuel-fired burner with internal flame stabilization and secondary-air injection ports that do not perform flame stabilization, featuring an air ratio of 0.85 or more, and splitting members arranged at the flow-path front to enhance air diffusion and ignition, reducing the high-temperature oxygen remaining region and NOx production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If secondary air injection ports are disposed above and below primary air in a tangential firing boiler, then airflow adjustment of secondary air around the boiler is achieved, but fine tuning of the amount of secondary air cannot be performed and high-temperature oxygen remaining regions are formed at the flame outer circumference
Solution Approach 1:
The secondary air injection system is divided into multiple independent injection ports (first, second, third, and fourth secondary air injection ports) positioned at different locations around the burner. Each port can independently inject secondary air, allowing fine-tuned control of the total secondary air amount and distribution, thereby preventing the formation of high-temperature oxygen remaining regions that produce NOx.
Solution Approach 2:
Different secondary air injection ports are positioned at specific locations (above, below, left, right of the burner) to create localized air injection zones. This allows differential control of secondary air distribution in different spatial regions, enabling precise control of combustion conditions and suppression of NOx-forming regions at the flame outer circumference.
2Reliability
If flame stabilizing mechanism is disposed at the outer circumference of the burner with secondary air injection ports immediately next to it, then ignition is brought about at the outer circumference of the flame, but a large amount of air is mixed at the outer circumference causing combustion in a high-oxygen high-temperature state that produces NOx
Solution Approach 1:
Instead of placing secondary air injection ports at the outer circumference of the flame (conventional approach), the invention positions them at the inner region near the burner center. The first and second secondary air injection ports are disposed inside the flame stabilizing mechanism, while the third and fourth ports are positioned at the left and right sides of the burner. This inverted positioning ensures that secondary air mixes with primary air before reaching the flame outer circumference, preventing high-temperature oxygen remaining regions and NOx production while maintaining reliable ignition through the flame stabilizing mechanism.
3Device complexity
If one secondary-air injection port is provided above and below the coal-fired boiler, then the configuration is simple, but fine tuning of secondary air amount cannot be performed leading to high-temperature oxygen remaining region formation
Solution Approach 1:
The single secondary air injection port is segmented into four independent injection ports positioned at different locations (above, below, left, right of the burner). Each port can be controlled independently, providing fine-tuning capability for secondary air amount and distribution. This segmentation allows precise control of combustion conditions to suppress NOx formation while maintaining manageable system complexity through standardized port design.
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 decreases NOx emissions by promoting internal ignition and reducing the high-temperature oxygen remaining region, leading to more efficient combustion and lower NOx production in both the burner section and additional-air injection section.
Implementation Method 1
a fuel burner having internal flame stabilization
Implementation Method 2
secondary-air injection ports that do not perform flame stabilization
Implementation Method 3
splitting members arranged at the flow-path front to enhance air diffusion
Implementation Method 4
promoting internal ignition and reducing the high-temperature oxygen remaining region
Data Source
AI summary
A solid-fuel-fired burner that suppresses a high-temperature oxygen remaining region formed at the outer circumference of a flame and that can decrease the amount of NOx eventually produced is provided. A solid-fuel-fired burner that is used in a burner section of a solid-fuel-fired boiler for performing low-NOx combustion separately in the burner section and in an additional-air injection section and that injects powdered solid-fuel and air into a furnace includes a fuel burner having internal flame stabilization and a secondary-air injection port that does not perform flame stabilization, in which the air ratio in the fuel burner is set to 0.85 or more.