Melt crystallization using an annular vessel with two circular cylinders was applied to produce high-quality vegetable oil from waste oil. The inner cylinder was cooled at a constant rate and rotated, and the outer cylinder was heated at a constant temperature. The melt was solidified on the inner cylinder surface. The binary system of triolein and palmitic acid was used as the model waste oil. We measured the distribution coefficient of triolein. Suitable operation conditions were proposed to attain a high yield and a high purity of triolein from waste oil. The distribution coefficient correlated well with the theoretical equation derived on the basis of the "local lever rule" at the interface of the crystal layer and melt [1]. (C) 2012 Elsevier B.V. All rights reserved.