Production of highly dry glycerol by solvent-aided melt layer crystallization

Purification of highly viscous pre-purified glycerol to purities of more than 99.9% was performed by solvent-aided melt layer crystallization. Two different setups were used and suitable assumptions for data evaluation that makes results between the setups comparable are presented. Adding 5-30 wt% of 1-butanol to the melt drastically increased the separation performance of a layer crystallization. Purities of up to 99.95% were reached at growth rates of 10−7 m/s, even without post treatments. At higher growth rates or without 1-butanol, layers of lower purity can be grown and then subjected to a sweating-like post treatment, which is effective but does not compensate the influence of solvent or growth rate. Results suggest an effect of migration of liquid inclusions in the crystal layer.