Effect of H2 addition on the preparation of ZrO2 powder from zircon (ZrSiO4) using a plasma torch

Abstract

In this study, the plasma torch is utilized for the preparation of highly pure ZrO2 from zircon (ZrSiO4). The incorporation of H2 into the discharge gas Ar improves the plasma physical parameters and serves as a reducing agent to promote the irreversibility of the pyrolysis reaction of ZrSiO4. ZrSiO4 powder is fed internally into a DC arc plasma torch through a powder feeder device. The DC torch generates thermal plasma that can fully heat all the ZrSiO4 within a short period for pyrolysis, extraction, and separation, eventually producing high-purity ZrO2. According to the results, the addition of H2 to the working gas increases the material temperature in the flame by increasing the plasma temperature, thereby promoting the pyrolysis of ZrSiO4. The temperature of the material is 2500–2600 °C, which is higher than the boiling point of the pyrolysis product SiO2 while maintaining the high melting points of ZrSiO4 and ZrO2. Furthermore, H2 plasma acts as a reducing agent in the pyrolysis reaction, where it combines with the O of the product to prevent the reversibility of the pyrolysis reaction of ZrSiO4 and retains only ZrO2.