We extend Galenko's nonequilibrium kinetic model of planar interface migration during solidification to non-dilute solution with non-straight liquidus and solidus curves. Using this more complex thermodynamic model for silicon-arsenic we show that the model with significant solute drag is consistent with the available experimental data for Si-9at%As alloy. Comparison with the typical kinetic models shows that the present model provides a better description of the data and the linear phase boundary assumption may lead to a relatively large deviation from reality. (C) 2010 Elsevier B.V. All rights reserved.