Staged Combustion Zones with Heat Modules for NOx Reduction
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Solution Overview
Problem
Combustion systems face challenges in achieving efficient combustion while minimizing nitric oxide (NOx) emissions, as increasing combustion temperatures to improve efficiency leads to higher NOx emissions, and conventional methods to reduce NOx emissions, such as quenching or recirculating exhaust gas, can cause pressure drops and affect economic viability.
Innovation Solution
The combustion system distributes fuel across multiple combustion zones spaced along a dimension, allowing for staged combustion and heat absorption via heat modules thermally coupled to each zone. This approach minimizes residence time at high temperatures and reduces NOx emissions while maintaining system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air is preheated to increase combustion efficiency, then combustion efficiency is improved, but combustion temperature increases leading to increased NOx emissions
Solution Approach 1:
The combustion system divides the combustion process into multiple zones (primary combustion zone, secondary combustion zone, and tertiary combustion zone) spaced along the combustion chamber. Each zone operates at different temperatures and receives fuel at different stages, allowing efficient combustion while limiting peak temperatures that generate NOx. The preheated air is distributed across these zones rather than concentrated in a single high-temperature region.
Solution Approach 2:
The system changes the temperature parameter distribution along the combustion path by introducing multiple combustion zones with decreasing temperature gradients. Exhaust gas recirculation (EGR) is used to modify the thermal parameters of the combustion mixture, reducing peak temperatures in each zone while maintaining overall combustion efficiency. The preheat temperature of air is optimized to balance efficiency gains against NOx formation risks.
2Object-generated harmful factors
If conventional methods (quenching or recirculating exhaust gas) are used to reduce NOx emissions, then NOx emissions are reduced, but pressure drop increases affecting system performance
Solution Approach 1:
Instead of applying a single aggressive quenching or high-rate EGR strategy that would cause large pressure drops, the system segments the temperature control function across multiple zones. Each zone uses moderate EGR rates and gentle cooling, distributing the pressure loss across the system rather than concentrating it in one location. This allows NOx reduction while maintaining acceptable overall pressure characteristics.
Solution Approach 2:
Air is preheated before entering the combustion zones, which reduces the temperature differential and the amount of aggressive cooling needed afterward. This preliminary heating action allows for more gradual temperature management through the combustion zones, reducing the need for high-pressure-drop quenching methods while still controlling peak temperatures to limit NOx formation.
3Power
If high heat fluxes are required for heat engine operation in CHP applications, then power generation efficiency is improved, but NOx emissions increase due to higher combustion temperatures
Solution Approach 1:
The heat engine receives thermal energy from multiple combustion zones rather than a single high-temperature source. This distributed heat input maintains the high total heat flux needed for power generation while avoiding concentrated peak temperatures that would generate excessive NOx. Each combustion zone contributes to the overall heat budget at manageable temperature levels.
Solution Approach 2:
The system maintains continuous combustion across multiple zones, ensuring steady heat delivery to the heat engine without requiring extreme temperature spikes. The continuous presence of combustion zones at different stages provides uninterrupted thermal energy conversion, maintaining power generation efficiency while operating within temperature limits that control NOx formation throughout the combustion process.
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 solution effectively mitigates NOx emissions and pressure drops, enabling efficient combustion with reduced environmental impact, particularly in combined heat and power applications where high heat fluxes and low NOx emissions are critical.
Implementation Method 1
combustion of preheated air with fuel at various combustion zones along a dimension of the combustion system
Implementation Method 2
combustion zones configured to combust preheated air with fuel and generate heat
Implementation Method 3
heat modules thermally coupled to the combustion zones and configured to absorb heat from the combustion zones
Implementation Method 4
air preheating capabilities
Data Source
AI summary
Combustion systems and associated methods are disclosed herein. In some embodiments, a combustion system comprises a first combustion zone, a second combustion zone downstream of the first combustion zone, and a heat module thermally coupled to the first combustion zone and/or second combustion zone. The first combustion zone is configured to (i) receive and combust preheated air and a first fuel and (ii) generate a first exhaust gas, and the second combustion zone is configured to (i) receive and combust the first exhaust gas and a second fuel and (ii) generate a second exhaust gas. The first exhaust gas can have a first excess air and the second exhaust gas can have a second excess air less than the first excess air. The heat module can comprise a thermionic converter or another heat-to-electricity converter able to generate a power output.