Fluidization thermal decomposition of sodium fluosilicate

Abstract

To break through the thermodynamic limitation that sodium fluosilicate only can be completely decomposed at high temperature, the technology of pre-decomposition under SiF4 atmosphere and deep decomposition under air condition at lower temperature was developed. The hydrolysis reaction of sodium fluosilicate can be effectively restrained when drying under vacuum or low temperature. Thermal decomposition results of sodium fluosilicate indicate that temperature has a very significant effect on its decomposition. The decomposition ratio can reach 79.4% at 600 °C for 1 h, and 99.6% at 700 °C for 1 h under air condition, respectively. Gas velocity and the type of inert gas have no significant effect on its decomposition. Fine particles affect its decomposition performance due to agglomeration, while coarse particles have good thermal decomposition performance without significant differences. The decomposition reaction process in fluidized bed satisfies the classical Avrami Erofe'EV model, with the reaction order of 1.5 and the activation energy of 61.35 kJ·mol−1.