Nanoparticle Production via Autoignition Flame Stabilization
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Solution Overview
Problem
The challenge in scaling up nanoparticle production by flame-spray methods for industrial use is the stabilization of the flame and achieving monodispersity, as turbulent flow conditions lead to inhomogeneous particle size and morphology due to recirculation zones and altered combustion kinetics, making it difficult to maintain stable process conditions for large-scale production.
Innovation Solution
A process involving autoignition to stabilize the flame by precisely controlling the ignition delay time and flow velocity, ensuring a homogeneous ignitable mixture is formed, which allows for the stable production of monodisperse nanoparticles by introducing a precursor-solvent mixture into a reactor with a preheated oxygen-containing gas and fuel, where the mixture autoignites after a controlled ignition delay time to form a stabilized flame for nanoparticle formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laminar spray flames are used to achieve monodisperse nanoparticles, then particle size distribution is narrow, but productivity is limited and cannot meet large-scale industrial production requirements
Solution Approach 1:
The invention transitions from laminar to turbulent flow regime by changing the flow parameters (velocity, Reynolds number). This parameter change allows the system to handle much larger material flows (hundreds of kg per day) while maintaining controlled combustion through autoignition, thus resolving the contradiction between narrow particle size distribution and high productivity
Solution Approach 2:
The fuel is preheated to a temperature above its autoignition temperature before injection into the reactor. This preliminary heating ensures that when the fuel contacts the oxygen-containing gas, spontaneous ignition occurs immediately, stabilizing the flame position and ensuring homogeneous combustion conditions even under turbulent flow, thereby maintaining particle size uniformity at high production rates
2Reliability
If swirl-stabilized flames are used to stabilize combustion at high flow rates, then flame stability is improved, but recirculation zones cause inhomogeneous particle size and morphology
Solution Approach 1:
Instead of using swirl to stabilize the flame (conventional approach), the invention inverts the approach by using autoignition of preheated fuel to stabilize the flame. The fuel is heated above autoignition temperature before injection, so combustion is initiated by temperature rather than by swirl-induced recirculation, eliminating backflow zones while maintaining flame stability at high flow rates
Solution Approach 2:
The fuel undergoes preliminary heating to a temperature above its autoignition point before entering the combustion zone. This preliminary action ensures spontaneous ignition occurs at a controlled location without requiring swirl-stabilized recirculation, thus preventing the formation of inhomogeneous recirculation zones while maintaining reliable flame stabilization for high-productivity production
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 enables the production of nanoparticles with a narrow size distribution and uniform morphology, suitable for large-scale industrial production, by maintaining a stable flame position and controlling the ignition delay time to ensure consistent particle formation, achieving particle diameters with a d95 value of less than 1000 nm and a standard deviation of less than 2.2, suitable for various applications.
Implementation Method 1
autoignition of the ignitable mixture (IM) of oxygen-containing gas and fuel after an ignition delay time tID to form a stabilized flame
Implementation Method 2
evaporating/burning the precursor-solvent mixture in the stabilized flame to form nanoparticles from the precursor
Data Source
AI summary
A process for the production of nanoparticles from a liquid mixture comprising at least one precursor and at least one solvent in a reactor with continuous through-flow comprises the steps of feeding at least one oxygen-containing gas inflow stream having a temperature into the at least one reactor, adding at least one fuel having a temperature to the oxygen-containing gas inflow stream, wherein the fuel and the oxygen-containing gas inflow stream form a homogeneous ignitable mixture having a temperature, wherein the temperature of the homogeneous ignitable mixture is above the autoignition temperature of the homogeneous ignitable mixture, introducing at least one precursor-solvent mixture into the homogeneous ignitable mixture; autoignition of the ignitable mixture of oxygen-containing gas and fuel after an ignition delay time to form a stabilized flame and reacting the precursor-solvent mixture in the stabilized flame to form nanoparticles from the metal salt precursor, removing the formed nanoparticles.