Thermal Treatment of Granulated Particles by Induction Thermal Plasma

After the invention of induction plasma torch by [Reed, 1961], tremendous achievements have been earned by the researchers in the field of thermal treatment of micro particles by induction plasma torch. Induction thermal plasma (ITP) has become very popular in material processing due to several of its inherent characteristics: such as contamination free (no electrode), high thermal gradient (between torch and reaction chamber), wide pressure range and high enthalpy. ITP have extensively been used for the synthesis and surface treatment of fine powders since couple of decades as a clean reactive heat source [Fan, 1997], [Watanabe, 2004]. ITP technology may ensure essentially the in-flight one-step melting, short melting time, and less pollution compared with the traditional technologies that have been using in the glass industries for the vitrification of granulated powders. Moreover ITP technology may be very effective in the thermal treatment of porous micro particles and downsizing the particle size. During in-flight treatment of particles, it is rear to have experimental records of thermal history of particles; only some diagnosis of the quenched particles is possible for the characterization. Thus, the numerical analysis is the only tool to have comprehensive characterization of the particle thermal history and energy exchange during in-flight treatment. Thus, for numerical investigation it is the challenge to predict the trajectory and temperature history of the particles injected into the ITP torch. Among others Yoshida et al [Yoshida, 1977] pioneered the modeling of particle heating in induction plasmas; though their work assumed the particle trajectory along the centerline of the torch only. Boulos [Boulos, 1978] developed a model and comprehensively discussed the thermal treatment of alumina powders in the fire ball of argon induction plasma. Later (Proulx et al) [Proulx, 1985] predicted the trajectory and temperature history of alumina and copper particles injected into ITP torch and discussed the particle loading effects in argon induction plasma. In this chapter we shall discuss the in-flight thermal treatment mechanism of soda-limesilica glass powders by ITP and to optimize the plasma discharge parameters, particle size and feed-rate of input powders that affect the quenched powders size, morphology, and compositions. The thermal treatment of injected particles depends mainly on the plasmaparticle heat transfer efficiency, which in turn depends to a large extent on the trajectory and temperature history of the injected particles. To achieve that goal, a plasma-particle interaction model has been developed for argon-oxygen plasma, including a nozzle inserted