Deep insight into phase transition and crystallization of high temperature molten slag during cooling: A review

Abstract

High temperature molten slags, such as blast furnace slag, mold flux, coal slag, etc., exist widely in the metal manufacturing and energy power industries and play important roles in equipment operation, energy saving and emissions reduction as well as resource reuse. The treatment of high temperature molten slag usually involves a phase change cooling process coupled with crystallization behavior, which is a very challenging process and will significantly affect the high-temperature waste heat recovery, the vitreous content in slag, the quality of the as-cast slab, and the stable operation of the integrated coal gasification combined cycle system. This paper firstly reviews the main methods to explore the crystallization behaviors of molten slag. Then, the crystallization behaviors of molten slag are discussed under different cooling rates and main components. In what follows, the attempts on the prediction of molten slag crystallization behaviors are summarized. The major conclusions and future research priorities are as follows: The critical cooling rate of molten slag decreases gradually when it undergoes the isothermal temperature, continuous cooling and variable cooling condition. Moreover, the variation of the precipitated crystal phase is the essential reason that affects the crystallization behaviors of molten slag. To better guide the practical process, it has a long way to go in predicting the crystallization behavior of molten slag using the easy-to-obtain parameters.