Crystallization Separation of Binary Eutectic Organic Mixtures Using Liquefied-Gas

Crystal size and filtration behavior

Abstract

Batch crystallization of binary eutectic organic mixtures using liqufied gas as a solvent was carried out. Mean diameter of crystals in a crystallizer and mole ratio of liquid adhering to crystals in wet solid on the filter were determined. Propane or chlorodifluoromethane (HCFC22) was added as a liquefied gas solvent to binary eutectic mixtures : benzene+cyclohexane, p-xylene+m-xylene and p-xylene +o-xylene. Mean diameter of crystals increased with increase in moles of liquefied gas added. It ranges from 100 to 230 μm for benzene, 100 to 120 μm for cyclohexane and 400 to 600 μm for p-xylene. The diameter was represented by an exponentially decreasing curve with concentration ratio. Purity of wet solid increased with increasing moles of liquefied gas added. Ratio of adhering liquid to crystals was found to be well correlated with capillary number, which is calculated from density, surface tension of mother liquor and mean diameter of crystals.