Dual-Fuel Combustion System with Staged Oxidant Injection
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Solution Overview
Problem
Current combustion technologies fail to achieve dual-fuel combustion of liquid and gaseous fuels with low NOx emissions while maintaining high efficiency, leading to limitations in the use of liquid fuels, particularly in regions with stringent EPA regulations, such as California, where NOx emissions exceed desired levels and soot formation is a concern.
Innovation Solution
A method and apparatus involving the atomization of pressurized preheated liquid fuel, followed by flash vaporization, creating a fuel-rich mixture that undergoes partial combustion in a first chamber, producing a secondary fuel gas which is then cooled and fully combusted in a second chamber, utilizing staged oxidant introduction and internal flue gas recirculation to minimize NOx formation and prevent soot production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If flue gas recirculation is used to reduce peak flame temperature, then thermal NOx formation is reduced, but fuel-bound NOx formation remains high and combustion efficiency decreases
Solution Approach 1:
The combustion process is divided into two distinct stages: a first combustion chamber where fuel is partially combusted with limited air to produce a secondary fuel gas, and a second combustion chamber where complete combustion occurs. This segmentation allows optimization of each stage for different purposes - the first stage minimizes NOx formation by controlling oxygen availability, while the second stage ensures complete combustion for high efficiency.
Solution Approach 2:
A secondary fuel gas is introduced as an intermediary substance between the two combustion chambers. This secondary fuel gas, produced in the first chamber, serves as a bridge that carries the combustion process from partial to complete combustion, enabling the system to achieve both low NOx emissions and high combustion efficiency.
2Productivity
If liquid fuel is atomized and combusted directly, then combustion efficiency is maintained, but NOx emissions and soot formation exceed EPA standards
Solution Approach 1:
The combustion of liquid fuel is segmented into two stages across two chambers. In the first chamber, atomized liquid fuel undergoes partial combustion with controlled air supply, producing a secondary fuel gas with unburned hydrocarbons and CO. The second chamber completes the combustion process. This segmentation prevents the high-temperature complete combustion that produces excessive NOx and soot, while still achieving high overall efficiency.
Solution Approach 2:
The first combustion chamber performs partial combustion rather than complete combustion, deliberately leaving some fuel unburned to form the secondary fuel gas. This partial action reduces peak temperatures and harmful emissions, while the second chamber completes the combustion to maintain high overall efficiency.
3Adaptability or versatility
If gaseous fuel is mixed with liquid fuel for dual-fuel combustion, then fuel flexibility is improved, but combustion control becomes more complex and emissions may increase
Solution Approach 1:
The combustion system is designed with multi-functionality to handle both liquid fuel and gaseous fuel in various combinations. The first combustion chamber can combust liquid fuel alone or liquid fuel mixed with gaseous fuel, while the second chamber always completes the combustion. This universal design allows the system to adapt to different fuel types and mixing ratios without requiring fundamentally different combustion mechanisms.
Solution Approach 2:
The dual-fuel combustion system is segmented such that the first chamber handles the primary combustion of liquid fuel (with optional gaseous fuel addition) and produces secondary fuel gas, while the second chamber handles complete combustion. This segmentation simplifies the control of dual-fuel combustion by separating the functions of fuel introduction and combustion completion.
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 achieves low-NOx emissions (less than 20 ppmv for liquid fuels and less than 5 ppmv for gaseous fuels) while maintaining high efficiency and significantly reducing soot formation, meeting EPA emission standards.
Implementation Method 1
a pressurized preheated liquid fuel is atomized
Implementation Method 2
at least a portion of the atomized liquid fuel is flash vaporized
Implementation Method 3
the fuel/oxidant mixture is introduced into a first combustion chamber in which, due to the fuel-rich stoichiometry of the mixture, partial combustion of the fuel/oxidant mixture is carried out
Implementation Method 4
The secondary fuel gas is cooled, producing a cooler secondary fuel gas
Implementation Method 5
The secondary fuel gas/oxidant mixture is introduced into a second combustion chamber in which substantially complete combustion of the secondary fuel gas/oxidant mixture is carried out
Implementation Method 6
utilizing staged oxidant introduction and internal flue gas recirculation to minimize NOx formation
Data Source
AI summary
A method and apparatus for combustion in which a pressurized preheated liquid fuel is atomized and a portion thereof flash vaporized, creating a mixture of fuel vapor and liquid droplets. The mixture is mixed with primary combustion oxidant, producing a fuel/primary oxidant mixture which is then injected into a primary combustion chamber in which the fuel/primary oxidant mixture is partially combusted, producing a secondary gaseous fuel containing hydrogen and carbon oxides. The secondary gaseous fuel is mixed with a secondary combustion oxidant and injected into the second combustion chamber wherein complete combustion of the secondary gaseous fuel is carried out. The resulting second stage flue gas containing very low amounts of NOx is then vented from the second combustion chamber.