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The viscosity, melting proprieties, and molten structure of the high-Al silicon–manganese slag of SiO2–CaO–25 mass% Al2O3–MgO–MnO–K2O system with a varying MgO and K2O content were studied. The results show that with the increase in MgO content from 4 to 10 mass%, the measured viscosity and flow activation energy decreases, but K2O has an effect on increasing those of slags. However, the melting temperature increases due to the formation of high-melting-point phase spinel. Meanwhile, Fourier transform infrared (FTIR) and X-ray photoelectron spectra (XPS) were conducted to understand the variation of slag structure. The O2− dissociates from MgO can interact with the O0 within Si–O or Al–O network structures, corresponding to the decrease in the trough depth of [SiO4] tetrahedral and [AlO4] tetrahedral. However, when K2O is added into the molten slag, the K+ can accelerate the formation of [AlO4] tetrahedra, resulting in the increase in O0 and O− and the polymerization of the structure.

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To provide theoretical basis for the production of pellets, the effect of BaSO4 in the range of 0 to 5.0% on properties of pellets was studied under experimental conditions. The influence mechanism of BaSO4 on the compressive strength of preheated pellets as well as roasted pellets and reduction behavior of roasted pellets was investigated by means of scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). From the results, it can be observed that the compressive strength of preheated pellets varies slightly whereas roasted pellets has a great change when BaSO4 content increases from 0 to 5%. The compressive strength of roasted pellets initially increases then decreases, which reaches the peak value of 3411 N with BaSO4 content of 1.5%. The reduction degree enhances from 80.7 to 97.9% and FeO content reduces from 2.33 to 1.57% with increasing BaSO4 content from 0 to 5.0%. The degree of polycrystalline of hematite improves and the hole size increases obviously when BaSO4 content varies from 0 to 1.5%. The crystallization of hematite decreases and the holes whose distribution is uneven increases when BaSO4 content is more than 1.5%. In reduction process, the wustite reduces and metallic iron increases with increasing BaSO4 content from 0 to 5.0%.

The present work was carried out to study the evaporation of fluoride from CaF 2 -CaO-Al 2 O 3 -MgO-Li 2 O-(TiO 2 ) slag with different TiO 2 contents. The evaporation ratio is determined by monitoring the weight change of the slag by isothermal thermogravimetric analysis in the temperature range of 1470-1530°C. The results show that the evaporation ratio of fluoride is promoted by increasing temperature and adding TiO 2 content from 0 to 13.28 wt-%. It has a slight effect to enhance the fluoride evaporation ratio when the TiO 2 content exceeds 8.67 wt-%. CaF 2 and AlF 3 are major constituents of the evaporation substances. The evaporation of fluoride is affected by the vapour pressure of AlF 3 and the viscosity of slag. The evaporation process for TiO 2 -containing slags is controlled by a chemical reaction in the beginning, followed by a mixed reaction-mass transfer regime, and the limiting factor is the liquid-phase mass transport in the end.