Investigation of Preparation of Slag Wool from Melting-Separated Red Mud

Abstract

The preparation of high-quality inorganic fibers by centrifugation from modified melting-separated red mud, which is the product of the efficient recovery of pig iron from red mud, is a new approach to achieve large-scale production of high value-added materials from red mud. This method has a wide range of application prospects and could contribute substantially to the comprehensive utilization of bulk industrial solid waste and the development of a circular economy. In this study, melting-separated red mud was modified with water-quenched blast furnace slag, quartz sand, and quicklime. The effect of the CaO/Na2O mass ratio on the viscosity, fluidity, and crystallization performance of the melting-separated red mud was investigated; slag wool was prepared by centrifugation under laboratory conditions; and the effect of the CaO/Na2O mass ratio on the morphology and properties of the slag wool was investigated. The viscosity of modified melting-separated red mud with different CaO/Na2O mass ratios shows a decreasing trend with increasing temperature, and the fluidity increases with increasing temperature, indicating that the melt fluidity is improved. The suitable fiber-forming temperature of the melting-separated red mud shows a trend of increasing–decreasing–increasing with an increasing CaO/Na2O mass ratio, and at a CaO/Na2O ratio of 3.0, the maximum suitable fiber-forming temperature is 81 °C. Considering the feasibility of slag wool preparation from modified melting-separated red mud, the CaO/Na2O of the modified raw material system should not be higher than 3.0. The crystallization temperature of modified melting-separated red mud with different CaO/Na2O mass ratios first increases and then decreases, with a peak of 1450 °C at a CaO/Na2O ratio of 4.0. Slag wool prepared from modified melting-separated red mud with different CaO/Na2O mass ratios exhibits good properties, with a diameter of 5.47–6.67 µm and a slag ball content of 2.7–8.4%.