Basics
Flame spray pyrolysis is a promising approach for the production of functional nanoparticles which are expected to lead to major advances in the development of batteries or catalysts, for example. Compared to existing large-scale gas phase processes, spray flame synthesis offers a higher variety of material systems and a good scalability. However, industrial-scale implementation is currently failing due to an insufficient understanding of the process. The DFG priority program SPP1980 aims to overcome these challenges in an interdisciplinary approach and lay the foundations for industrial distribution. In recent years, closely related sub-processes of flame spray pyrolysis have been successfully investigated in the various disciplines and a wealth of experimental, simulative, and theoretical instruments have been developed. In the priority program, these methodologies are brought together to analyze the individual sub-processes and to classify them into an overall model. This is intended to create a comprehensive understanding of the process.
An essential sub-process of the flame spray pyrolysis is the atomization of the precursor solution. The atomization forms the first sub-process in the process chain and provides the droplet phase. Through the evaporation of the droplets, the turbulent mixing with the dispersion gas and the subsequent combustion, the atomization has a direct or indirect influence on the local conditions (e.g. temperature, gas composition, velocity fluctuations). These local conditions significantly influence the particle synthesis mechanisms, so that atomization represents a degree of freedom to control and optimize particle product properties. To make use of this, however, a sufficient understanding of the influence of atomization on particle synthesis is necessary.
Methods
In order to numerically investigate the influence of atomization on particle synthesis, a simulation approach is chosen that covers the entire process chain of flame spray pyrolysis. The methods used are based on the relevant length and time scales of the subprocesses. The nozzle internal flow is characterized by large-eddy simulations while the primary breakup is investigated by interface resolving direct numerical simulations. Further downstream, droplet evaporation, mixing, combustion and particle formation are analyzed with large-eddy simulations using a Lagrange-Spray model, a turbulent combustion model and a statistical particle model.