Structural control of Na2TiO3 in pre‐treating natural rutile ore by alkali roasting for TiO2 production

Abstract

To improve the use of natural rutile ore with fine particle size and high contents of MgO and CaO in China, a novel pre‐treatment method of natural rutile ore by NaOH roasting to prepare α‐Na2TiO3 for TiO2 production was proposed. γ‐Na2TiO3 is a stable by‐product that can lead to serious caking in the reactor and low titanium yield. Thus, structural control in alkali roasting is necessary. The influence of particle size of natural rutile ore, NaOH‐to‐ore mass ratio, roasting temperature and roasting time on the crystal forms of Na2TiO3 was systematically investigated. The optimized reaction parameters were as follows: average particle size of natural rutile ore, −9.2 µm; NaOH‐to‐rutile mass ratio, 1.2; roasting temperature, 550 °C; and roasting time, 70 min. In these conditions, the titanium conversion and the fraction of α‐Na2TiO3 exceeded 99.5 % and 98 %, respectively. Moreover, the addition of H2O or as‐prepared partial α‐Na2TiO3 as crystal seeds into the reaction system could prepare the roasting product with α‐Na2TiO3 as its main phase using −45 µm (−325 mesh) natural rutile ore.