The viscosity, crystallization behavior and glass-ceramics preparation of blast furnace slag: A review

During the blast furnace (BF) smelting process, the viscosity of BF slag affects greatly the quality of molten iron, slag-iron separation, gas flow distribution, etc. After discharged from BF, the crystallization of molten slag at low cooling rate will decrease the glass content and hydration activity of slag, which occurs more easily in the tempting heat recover system of molten slag for energy saving and emission reduction. The glassy slag at quite cooling rate is the valuable resource to replace virgin raw material to conserve the natural resource for producing the value-added materials, which facilitates the circular economy and sustainable development. This paper firstly describes the generation of BF slag, and discusses the research methods of viscosity-structure of the slag and detailed effects of basic oxides, acidic oxides and amphoteric oxides. Then, the characterization methods for crystallization of slag, determination of critical cooling rate, precipitated phases and the effect of chemical components are summarized. With regard to the preparation of glass-ceramics from BF slag, the effects of heat treatment, nucleation agent, addition amount of the slag and main chemical components are expounded. At last, the future challenges and attentions on the viscosity, crystallization and glass-ceramics preparation of BF slag are scrutinized.