Effect of particle presence on gas phase temperature in the flame spray pyrolysis

S.R. Engel, Yi Gao, A.F. Koegler, D. Kilian, T. Seeger, W. Peukert, A. Leipertz
Department of Engineering Thermodynamics, DE

Keywords: flame spray pyrolysis, optics, CARS, Mie imaging, SiO2 production

Summary:

For the production of manufactured nanoparticles at a commercial scale flame processes are most frequently used. An important basis for understanding the complexity of this process is the characterization of the combustion process in dependence of the operation conditions. As minor changes of process parameters have huge impact on the product, invasive classic methods would fail. Hence, there is a demand for non-invasive advanced optical measurement tools acquiring data regarding the flame and the particle formation without changing the product by the applied measuring technique. In this work, gas phase temperatures, which have an important impact on the particle size, were acquired by O2 pure rotational CARS during flame spray pyrolysis (FSP) and were compared for a particle-free and a particle-laden flame. Furthermore, the influence of different precursor concentrations on the distribution of the liquid regime was investigated by Mie scattering. The CARS results in the particle regime show significantly decreasing flame temperatures in the presence of particles since energy is dissipated rapidly by radiation heat transfer. Mie scattering results display unchanged droplet distributions for varying precursor concentrations. Therefore, measured temperature differences can be exclusively attributed to the presence of particles.