Air Volume Control for Solid Fuel Combustion
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Solution Overview
Problem
Large steam generators burning fossil, solid fuels face challenges with slagging and corrosion on combustion chamber tube walls due to low air ratios, which can lead to undesirable NOx emissions and operational issues, especially when burning slagging-critical fuels.
Innovation Solution
A method for air volume control in combustion systems that adjusts the O2 and NOx setpoints to maintain a high air ratio while ensuring compliance with NOx emission limits, using a NOx controller to correct burner and burnout air quantities and dividing partial air quantities between burnout air levels, thereby reducing slagging and corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the air ratio is reduced to lower NOx emissions, then NOx emissions decrease, but slagging and corrosion on combustion chamber tube walls increase
Solution Approach 1:
The combustion air supply is segmented into multiple burnout air levels (at least two different heights) within the combustion chamber. This segmentation allows different air ratios to be applied at different vertical positions, enabling optimized combustion conditions that reduce both NOx emissions and slagging/corrosion risks simultaneously
Solution Approach 2:
Different air ratios are applied locally at different heights in the combustion chamber. The lower burnout air level operates with one air ratio while the upper level operates with another, creating locally optimized combustion zones that address both harmful effects differently at different positions
2Object-affected harmful factors
If the air ratio is increased to prevent slagging and corrosion, then tube wall protection improves, but NOx emissions increase
Solution Approach 1:
The combustion air supply is segmented into multiple burnout air levels (at least two different heights) within the combustion chamber. This segmentation allows different air ratios to be applied at different vertical positions, enabling optimized combustion conditions that reduce both NOx emissions and slagging/corrosion risks simultaneously
Solution Approach 2:
Different air ratios are applied locally at different heights in the combustion chamber. The lower burnout air level operates with one air ratio while the upper level operates with another, creating locally optimized combustion zones that address both harmful effects differently at different positions
3Device complexity
If a single air ratio is used throughout the combustion chamber, then the control system is simple, but it cannot simultaneously optimize both NOx emissions and tube wall protection
Solution Approach 1:
The combustion air supply is segmented into multiple burnout air levels (at least two different heights) within the combustion chamber. This segmentation allows different air ratios to be applied at different vertical positions, enabling optimized combustion conditions that reduce both NOx emissions and slagging/corrosion risks simultaneously
Solution Approach 2:
The air ratios at different burnout air levels are dynamically adjustable and can be independently controlled. This dynamic control allows the system to adapt to varying combustion conditions and fuel types, optimizing performance for different operating scenarios
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 maintains high air ratios at the burner's upper edge, minimizing slagging and corrosion, ensuring compliance with NOx limits and enhancing the availability and maintenance time of steam generators.
Implementation Method 1
The pilot-controlled burner air quantity is corrected by an O 2 controller, which regulates a specific O 2 content in the flue gas
Implementation Method 2
The O 2 controller can be superordinated by a CO controller, which increases the O 2 setpoint of the O 2 controller if the CO emissions are high
Implementation Method 3
the NOx daily mean value is taken into account by a NOx controller for the correction of the burner air quantity predetermined by the O 2 controller
Implementation Method 4
a combustion system operated with fossil, solid fuels
Data Source
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AI summary
The invention relates to a method for air quantity regulation of a combustion system which is operated with solid fossil fuels, wherein the combustion system has a vertical combustion chamber with at least one powdered coal burner in the lower region of the combustion chamber and with at least one burnout air plane in the upper region of the combustion chamber which is traversed by combustion gases from bottom to top, wherein the method comprises: - supplying a burner air quantity to the powdered coal burner(s) and a burnout air quantity to the burnout air plane(s), wherein the burner air quantity and the burnout air quantity is pilot-controlled as a function of the present firing power, - correcting the pilot-controlled burner air quantity by means of an O2 regulator (21) in the event of the O2 nominal value in the flue gas being exceeded or undershot, - and correcting the burner air quantity which is predetermined by the O2 regulator, or correcting the O2 nominal value of the O2 regulator by means of the NOx regulator (22).