Design Factors of a Plasma Reactor with a Swirling Flow Field for Production of Rutile TiO₂ Nanoparticles

This study presents the development of a plasma reactor producing rutile TiO₂ nanoparticles as a white pigment. The effects of reactor design factors are also considered based on experimental data. A Direct current thermal plasma using Ar as the plasma medium was applied to heat the reactor. TiCl₄ and O₂ were the reactants with TiO₂ and Cl₂ as the products. The advantage of this process is the production of titanium dioxide nanoparticles without the co-generation of HCl. The effects of design factors such as the position of the nozzles supplying the reactants, temperatures of the reactor and heater, residence time, and swirl number of the flow field on rutile phase generation were investigated. The collected titanium dioxide nanoparticles were examined using X-ray diffraction (XRD) and Scanning electron microscope (SEM). Although there was no significant effect of nozzle position, the temperatures of the reactor and heater showed strong correlations with the rutile phase contents, with temperatures of 1030 to 1060 °C for the reactor and 750 °C for the heater yielding the maximum rutile content of 79.8% at a residence time of 2.2 s. The gas flow pattern in the furnace also exhibited an effect on rutile content, i.e., as the swirl number in the reactor increased, the rutile phase content in the TiO₂ also increased. From experimental results and Computational fluid dynamics, the optimum swirl number was estimated to be between 0.7 and 0.8.