Burner with Concentric Air Supply for Low NOx Combustion
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Solution Overview
Problem
Existing burners struggle to achieve low NOx content in exhaust gases, as NOx formation is exacerbated by high combustion temperatures.
Innovation Solution
The burner design incorporates a unique secondary air supply system with concentric cylindrical pipes, preheating secondary air in a dome-shaped closure, and using adjustable twist plates to ensure even air distribution, along with a fuel nozzle construction that introduces exhaust gas into the fuel flow to lower combustion temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high combustion temperatures are used to ensure efficient energy use, then combustion efficiency is improved, but NOx emissions increase
Solution Approach 1:
The combustion process is divided into two distinct stages with separate air supplies. Primary air (50-80% of total air) supports initial combustion at controlled temperature, while secondary air (20-50% of total air) completes combustion after the fuel has burned. This segmentation allows temperature control during the critical combustion phase to minimize NOx formation while maintaining overall combustion efficiency.
Solution Approach 2:
Exhaust gas is pre-injected into the fuel stream before combustion occurs. This preliminary action of mixing exhaust gas with fuel creates a cooler combustion environment from the start, preventing excessive temperature rise that would lead to NOx formation, while still allowing complete combustion to proceed efficiently.
2Object-generated harmful factors
If exhaust gas is injected into the fuel stream to lower combustion temperatures, then NOx emissions are reduced, but combustion efficiency may decrease
Solution Approach 1:
Exhaust gas is introduced into the fuel stream before combustion occurs, creating a pre-mixed fuel-exhaust gas flow. This preliminary cooling action reduces the peak combustion temperature to minimize NOx formation, while the subsequent introduction of primary and secondary air ensures complete combustion proceeds efficiently.
Solution Approach 2:
The composition and temperature of the combustion atmosphere are dynamically adjusted by controlling the proportion of exhaust gas mixed with fuel (20-50% of total air) and the split between primary and secondary air supplies. This parameter optimization maintains combustion efficiency while suppressing NOx formation through temperature control.
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 design achieves effective combustion with significantly reduced NOx emissions in the exhaust gas, ensuring compliance with strict emission limit values while maintaining efficient energy use.
Implementation Method 1
adjustable swirl plates (1f) at the opening on the hot gas side (21), which have an angle of attack of 15° to 80°
Implementation Method 2
preheating secondary air in a dome-shaped closure
Implementation Method 3
preheating secondary air in a dome-shaped closure
Implementation Method 4
injector suction nozzles (5c), which are in fluid communication with the holes (5b) and which project beyond the outer diameter of the primary air supply line (3) on the suction side
Implementation Method 5
a burner (1, 2, 3) that produces exhaust gas with a low NOx content, and to a method for burning fuel with a low proportion of NOx in the exhaust gas
Data Source
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AI summary
The invention relates to a burner, comprising a lateral hot gas region (21) and an outer region (22), a feed line for primary air (3), a feed line for secondary air (1), and a feed line for fuel (2), wherein the feed line for secondary air (1) comprises three concentric cylindrical tubes, and the feed line for fuel (2) is arranged concentrically around the feed line for secondary air (1); wherein there is a first dead volume (4) within the burner between the feed line for secondary air (1) and the feed line for fuel (2), and wherein the feed line for fuel (2) has a nozzle structure (5) on the hot gas side (21); a second dead volume (9) is located between the feed line for secondary air (1) and the feed line for fuel (2) on the side of the outer region (22); and the feed line for primary air (3) is arranged concentrically around the feed line for fuel (2).