Pellet Stove Flue Gas Recirculation for Brazier NOx Reduction
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Solution Overview
Problem
Traditional biomass stoves, particularly pellet stoves, face challenges in reducing NOx emissions due to the inherent formation mechanism of nitrogenous pollutants during combustion, and existing solutions for reducing emissions are inefficient and difficult to retrofit on existing systems.
Innovation Solution
The solution involves redirecting unburned flue gases to the primary air inlet of the combustion chamber, where they can undergo pyrolysis at high temperatures without oxidation, and mixing with external air to adjust the stoichiometric ratio, facilitating further combustion and reducing pollutant emissions. This is achieved through a flue gas intercepting branch that connects to the primary air inlet, allowing for a compact and retrofittable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If post-combustion chamber is used for flue gas treatment, then unburned residues are burned, but thermal energy is not combined and process efficiency is reduced
Solution Approach 1:
The invention merges the function of treating unburned residues with the primary combustion process by redirecting flue gases to the brazier area where they enhance pyrolysis. This eliminates the need for a separate post-combustion chamber and allows thermal energy to be combined in a single integrated combustion chamber, improving overall efficiency.
Solution Approach 2:
The combustion chamber is given multi-functionality by allowing it to perform both primary combustion and flue gas treatment functions. The brazier area serves dual purposes: generating combustible gases from biomass and processing recirculated flue gases to burn unburned residues, eliminating the need for dedicated post-combustion equipment.
2Object-generated harmful factors
If complex recirculation system is implemented, then emissions are reduced, but device complexity and retrofitting difficulty increase
Solution Approach 1:
Instead of the conventional approach of recirculating flue gases to the flame area, the invention inverts the approach by directing them to the brazier area. This simple inversion of the recirculation path achieves emission reduction without requiring complex system modifications or additional components.
Solution Approach 2:
The invention recovers the useful components of flue gases (heat and unburned combustible materials) by redirecting them to the brazier area where they can still contribute to the combustion process. This recovery approach simplifies the system by eliminating the need for complex separation and treatment devices while maintaining emission reduction benefits.
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 significantly reduces NOx emissions by enhancing the pyrolytic step of biomass conversion and improving the quality of flue gases released, while being cost-effective and easily applicable to existing stoves through a simple geometric arrangement and adjustable mixing ratios.
Implementation Method 1
redirecting unburned flue gases to the primary air inlet of the combustion chamber, where they can undergo pyrolysis at high temperatures without oxidation
Implementation Method 2
mixing with external air to adjust the stoichiometric ratio, facilitating further combustion
Implementation Method 3
a flame area intended for the combustion of combustible gas coming from the brazier area
Data Source
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AI summary
The invention concerns a biomass stove, particularly a pellet stove, comprising a combustion chamber, an unburned gas storage chamber, a flue gas extractor fan device for extracting unburned gas from the storage chamber and for sending it to an exhaust flue, at least one air intake for feeding air from the outside to the inside of the combustion chamber. The combustion chamber comprises a brazier area adapted to receive the biomass and to generate combustible gas and a flame area intended for the combustion of combustible gas coming from the brazier area. There are a first series of apertures at the brazier area for supplying primary gas and a second series of apertures at the flame area for supplying secondary gas. The stove further comprises a branch intercepting the flue gases directed to the exhaust flue such to at least partially direct said flue gases to the primary gas inlet apertures.