Variable Air Excess Control for Hydrogen Premix Burners
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Solution Overview
Problem
Conventional methods for operating premix gas burners, such as those in central heating boilers, are not optimized for hydrogen fuel gas, leading to increased risks of flashback and inefficient combustion due to hydrogen's higher flame speed, which affects air excess factor control and efficiency.
Innovation Solution
A method and device for controlling the air excess factor in premix gas burners that uses a variable desired air excess factor relation, adjusting the air and fuel gas flow rates based on heat demand, to maintain efficient combustion and reduce the risk of flashback, by storing a desired air excess factor relation in an electronic controller and controlling the fuel gas and air flow rates to converge towards the desired air excess factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant air excess factor is used over the entire range of operating conditions, then the control system is simple, but combustion efficiency decreases and flashback risk increases when using hydrogen fuel gas
Solution Approach 1:
The air excess factor is changed from a constant value to a dynamic variable that changes with burner load. The controller adjusts the air excess factor according to the actual burner load conditions, allowing optimal combustion efficiency across the entire operating range while specifically reducing flashback risk at low loads when using hydrogen fuel gas
Solution Approach 2:
The air excess factor parameter is varied based on burner load conditions. By changing this critical combustion parameter dynamically, the system achieves both high combustion efficiency and flashback prevention, particularly improving performance when operating with hydrogen fuel gas at partial load conditions
2Reliability
If the air excess factor is increased to prevent flashback, then safety improves, but combustion efficiency decreases due to excessive air heating
Solution Approach 1:
The air excess factor is dynamically adjusted based on burner load rather than being held constant at a high safety margin. This allows the system to maintain flashback prevention through appropriate air excess at each load level while avoiding the excessive air heating that causes energy loss, particularly at low to medium loads where hydrogen flashback risk is highest but full air excess is unnecessary
3Loss of energy
If the air excess factor is decreased to improve combustion efficiency, then energy efficiency improves, but flashback risk increases due to insufficient air mixing
Solution Approach 1:
The controller dynamically adjusts the air excess factor to maintain optimal values across different burner loads. At low loads where hydrogen flashback risk is highest, the air excess factor is increased appropriately to prevent flashback while minimizing efficiency impact. At higher loads, the air excess factor is optimized for maximum combustion efficiency, thus resolving the trade-off between safety and efficiency
Solution Approach 2:
The system uses feedback from burner load measurements to continuously adjust the air excess factor. This closed-loop control ensures that the air excess factor remains at optimal values for each operating condition, preventing both flashback and excessive energy loss, particularly when operating with hydrogen fuel 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
This approach allows for efficient heat generation while minimizing the risk of flashback and optimizing combustion efficiency across a wide range of burner loads, improving performance compared to constant air excess factor methods, especially when using hydrogen as a fuel gas.
Implementation Method 1
a fan for supplying air or the combustible mixture to the supply channel
Implementation Method 2
a mixing area for mixing the air and the fuel gas so as to form the combustible mixture
Implementation Method 3
supplying the mixture to the premix gas burner to burn the mixture
Data Source
AI summary
A method for operating a premix gas burner wherein an air flow rate and/or a fuel gas flow rate are controlled so as to generate heat with the premix burner in accordance with a heat demand related value. The fuel gas comprises hydrogen and the method further provides a desired air excess factor relation of the air/fuel gas mixture which defines the relation between a desired air excess factor and an input variable like the heat demand related value, an air flow rate related value, or a fuel gas flow rate related value. The desired air excess factor is not a constant factor but varies for different input variable values. The fuel gas flow rate and/or the air flow rate are controlled such that an actual air excess factor converges towards the desired air excess factor while meeting the heat demand.