Search

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. [ABSTRACT FROM AUTHOR]

A novel approach for preparing thermal insulation materials by microwave sintering of ferronickel slag (FNS) in the presence of fly ash cenosphere (FAC) was proposed and evaluated. The study showed that during microwave radiation, the contact interface between FNS and FAC would preferentially form magnesium iron chromate spinel and magnesium iron aluminate spinel particles as hot spots by absorbing microwave vigorously, promoting decomposition and transformation of the raw materials into the thermal insulation phases, mainly cordierite and enstatite. After sintering at 900 °C by microwave for only 20 min with the addition of 25 wt% FAC, a thermal insulation material with thermal conductivity of 0.41 W/(m·K), bulk density of 1.46 g/cm3, compressive strength of 30.72 MPa, water absorption of 21.07%, and linear shrinkage of 7.06% was obtained. Compared with the conventional sintering method, the temperature was reduced by 300 °C, with the sintering time shortened by 6 times. This study represents a good example for clean and efficient value-added utilization of FNS, FAC and other relavent solid wastes. [ABSTRACT FROM AUTHOR]