ID 276

Temperature Distribution in Open and Enclosed Flame Spray Reactor

 

Abstract:

Spray processes involving combustion reactions can be found in several industrial applications. By flame spray pyrolysis (FSP), nanoparticles from metals and metal oxides can be synthesized. This process has huge potentials and advantages regarding the final product purity and operational flexibility. To design advanced nanomaterials and improve their properties, studies have been conducted with application to various precursor formulations and variations of the process and reactor design. Enclosing the spray flame reactor with application of an oxidizer co-flow allows controlling the local fuel-oxygen ratio. The enclosement of the reactor results in higher flame temperatures and increased particle growth, resulting in larger primary particles, since the growth of particles in the flame is controlled by the sintering process, which, in turn, is temperature-dependent. However, enclosed reactors can also enhance the formation of major crystal phases, since the cooling rate can also be controlled, what is particularly important for applications demanding pure phase materials. The present work investigates the influence of geometrical setups (open and enclosed reactor) at different operating conditions on the flame temperature and spray behavior as well as on the temperature and temperature residence time distribution of the gas and the particles. From the open reactor results, the natural mass flow of gas entrainment into the flame is estimated. By supplying an appropriate co-flow rate as “artificial entrainment” in the closed reactor setup results in a quite similar flame behavior as found for the open reactor. By reducing the co-flow gas, strong recirculation zones are observed in the reactor, and the temperature increases considerably, resulting in larger nanoparticle sizes.