Solidification with crystallization behavior of molten blast furnace slag particle during the cooling process

Abstract

The centrifugal granulation technique has been considered for the recovery of waste heat retained in molten blast furnace slag while simultaneously obtaining high value slag particles for cement auxiliary materials. During granulation the high wind speed is expected to acquire high vitreous slag particles formed by centrifugal force of the atomizer, but result in significant energy consumption and low-grade heat of the cooling air. To address this problem, we established a two-dimensional symmetrical model to describe the crystallization behavior of blast furnace slag droplets by the enthalpy method via self-programming. The radiation heat transfer between slag particle and the wall was considered as well as non-isothermal solidification, including a narrow temperature interval of crystallization. The results display the evolutions of the local cooling rate and crystal phase content distribution. The effects of the diameter, initial temperature of the slag particle, wind initial temperature and wind speed are also discussed. Furthermore, two correlations of the average cooling rate and final crystal phase content with dimensionless parameters were developed respectively, to predict slag quality under various operational conditions.