Static layer melt crystallization: Effects of impurities on the growth behaviors of crystal layers

In this work, the effects of impurities on the growth behaviors of crystal layer during static layer melt crystallization (LMC) was studied. The crystal layer structure, growth rates, melt temperature curves and separation efficiency were experimentally investigated at different impurity concentrations and temperatures. With the experimental results, the mass transfer at the solid–liquid interface was discussed through: a) calculating the supercooling of the melt over the crystallization and b) deducing the mass transfer coefficient of impurity in the melt boundary layer. It was verified that the melt kept supercooled during the crystallization and concentration polarization occurred at the solid–liquid interface. A power law model was proposed to correlate the growth rate with the temperature gradient of crystal layer, which indicates that the concentration polarization results in the decrease of the latent heat of crystallization, and the mixture with lower impurity concentration and crystallization temperature would exhibit more serious concentration polarization.