In situ observation of the dissolution kinetics of Al_(2)O_(3) particles in CaO–Al_(2)O_(3)–SiO_(2) slags using laser confocal scanning microscopy

摘要

The dissolution kinetics of Al_(2)O_(3)in CaO-Al_(2)O_(3)SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3)dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3)particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3)ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3)in slag.Diffusion coefficients of Al_(2)O_(3)in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3)increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3)inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3)in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3)mass ratio;R_(0)is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp)is the melting point of slag,K.