Utilization of Silicon Dust to Prepare Si3N4 Used for Steelmaking Additives: Thermodynamics and Kinetics

Abstract

Silicone monomers are the basic raw materials for the preparation of silicone materials. The secondary dust generated during the preparation of silicone monomer by the Rochow–Müller method is a fine particulate waste with high silicon content. In this paper, the physical and chemical properties of silicon powder after pretreatment were analyzed, and an experimental study was conducted on the use of silicon dust in the preparation of Si3N4, a nitrogen enhancer for steelmaking, by direct nitriding method in order to achieve the resourceful use of this silicon dust. Furthermore, the thermodynamics and kinetics of the nitriding process at high temperatures were analysed using FactSage 8.1 software and thermogravimetric experiments. The results indicate that after holding at a temperature range of 1300~1500 °C for 3 h, the optimal nitriding effect occurs at 1350 °C, with a weight gain rate of 26.57%. The nitridation of silicon dust is divided into two stages. The first stage is the chemical reaction control step. The apparent activation energy is 2.36 × 105 kJ·mol−1. The second stage is the diffusion control step. The silicon dust growth process is mainly controlled by vapor–liquid–solid (VLS) and vapor–solid (VS) mechanisms.