Development of a non-autoclave technology for producing liquid glass from microsilica dust of ferroalloy production

Abstract

Microsilica dust generated as a by-product of ferrosilicon smelting is a valuable secondary raw material with a high content of amorphous silicon dioxide (SiO₂). In current industrial practice, sodium silicate solutions (liquid glass) are produced predominantly by autoclave dissolution of siliceous raw materials or by melting of silicate lumps at 1300–1400 °C, both of which are characterised by high energy and capital intensity. In this study the parameters of an energy-saving non-autoclave technology for producing sodium silicate solutions from the microsilica dust captured by the gas-cleaning system of the ferroalloy production of JSC Uzmetkombinat are substantiated. The chemical and phase composition of the raw material was determined by X-ray phase analysis, and the particle morphology was studied by scanning electron microscopy. Synthesis of sodium silicate solutions was carried out in a laboratory reactor at atmospheric pressure and a temperature of 90–95 °C with variation of alkali concentration and process duration. The results confirm the feasibility of obtaining liquid glass with the required silicate modulus and a solution concentration of 30–50 % without the use of autoclave equipment, with a 10–20 % reduction of energy consumption compared with the conventional silicate-lump melting technology.