Co-utilization of ferronickel slag and fly ash cenosphere for production of superior thermal insulation materials

Abstract

To dispose the problem of ferronickel slag for its value-added application, it was used for preparing thermal insulation materials by sintering of the slag in the presence of another waste, fly ash cenosphere (FAC), as pore former. The thermodynamic and experimental analyses revealed that the original phase of the slag, olivine, could be transformed to thermal insulation phases, including enstatite and cordierite, by optimizing sintering temperature in the range 1100–1300 °C. Specifically, after initial decomposition of ferronickel slag, there existed a low-iron olivine phase and cordierite and enstatite became the dominant phases when the sintering temperature increased from 1100 °C to 1300 °C. Except for the phase transformation, the microstructural evolution with proper pore features (porosity and size) contributed to a resulting material with desirable thermal and mechanical properties. It was shown that the ferronickel slag sintered at 1200 °C for 2 h with the addition of 25 wt % FAC exhibited the optimal thermal and mechanical performance. Additionally, it possessed good acid and alkali resistances. The results confirmed the feasibility of co-utilization of ferronickel slag and FAC for producing superior thermal insulation materials at a proper temperature, making efficient utilization of both wastes.