Burner Flame Cooling Layout for Low-NOx Aggregate Drying
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Solution Overview
Problem
Asphalt plant dryers produce high nitrogen oxide and sulfur dioxide emissions due to the combustion of fuels, which are harmful to health and the environment, and existing technologies struggle to control combustion temperature effectively.
Innovation Solution
A burner apparatus that directs a stream of air onto the flame as it emerges from the combustion chamber to reduce flame temperature below 1204°C, using a combustion chamber with a fuel dispenser, airflow modifier device, and secondary air channels to mix and cool the flame, thereby reducing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature combustion is used to efficiently dry and heat aggregates, then drying efficiency is improved, but nitrogen oxide emissions increase
Solution Approach 1:
The combustion process is segmented into two distinct zones: a primary combustion chamber where fuel burns at high temperature to generate hot gases, and a secondary combustion zone where additional air is introduced to cool the flame and reduce NOx formation. This spatial segmentation allows the system to maintain high drying efficiency while controlling harmful emissions.
Solution Approach 2:
The invention changes the temperature parameter in the combustion process by introducing secondary air that cools the flame from temperatures above 1204°C (where NOx forms rapidly) to lower temperatures. This parameter change occurs while maintaining sufficient heat for effective aggregate drying, thus resolving the contradiction between productivity and harmful emissions.
2Object-generated harmful factors
If flame temperature is reduced below 1204°C to reduce NOx formation, then nitrogen oxide emissions decrease, but combustion efficiency may be reduced
Solution Approach 1:
The primary combustion chamber performs preliminary combustion at high temperature to generate sufficient heat for drying aggregates. Then, secondary air is introduced downstream to cool the flame and reduce NOx formation. This preliminary action ensures that combustion efficiency is maintained before the cooling step, avoiding energy loss.
Solution Approach 2:
The invention adds a spatial dimension to the combustion process by introducing secondary air from the sides or rear of the combustion chamber, creating a three-dimensional flow pattern. This allows cooling of the flame without directly interfering with the primary combustion zone, thereby maintaining combustion efficiency while reducing NOx emissions in the exhaust gases.
3Object-generated harmful factors
If secondary air is directed onto the flame to cool it, then flame temperature is reduced and NOx emissions decrease, but burner lifespan may be affected
Solution Approach 1:
The harmful function of secondary air (cooling the flame and potentially causing thermal shock to the burner) is separated from the useful function (reducing NOx emissions). The secondary air is introduced downstream of the primary combustion chamber, allowing flame cooling and NOx reduction while minimizing direct thermal shock to the burner components, thus preserving burner lifespan.
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
The apparatus effectively reduces NOx emissions by cooling the flame and promoting efficient combustion, prolonging the burner's lifespan and minimizing environmental impact.
Implementation Method 1
one or more secondary air channels for directing a cooling secondary air flow onto a stream of combustion products as the stream of combustion products emerges from a downstream end of the combustion chamber
Implementation Method 2
an airflow modifier device, located at an upstream end of the combustion chamber, for controlling a primary air flow into the combustion chamber, the airflow modifier device being configured to facilitate mixing of the air with the fuel to give a mixture for combustion
Implementation Method 3
a combustion chamber; a fuel dispenser arranged to direct a flow of fuel into the combustion chamber
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention provides a burner apparatus comprising: a combustion chamber (8); a fuel dispenser (15,16) arranged to direct a flow of fuel into the combustion chamber (8), the fuel dispenser (15,16) being located at an upstream end of the combustion chamber and being connected or connectable to a fuel supply; an airflow modifier device (10), located at an upstream end of the combustion chamber, for controlling a primary air flow into the combustion chamber (8), the airflow modifier device (10) being configured to facilitate mixing of the air with the fuel to give a mixture for combustion; and one or more secondary air channels (24) for directing a cooling secondary air flow onto a stream of combustion products (e.g. flame) as the stream of combustion products emerges from a downstream end of the combustion chamber. Also provided are a dryer apparatus comprising a burner apparatus as described herein and a method of drying aggregates using a burner apparatus as described herein.