Freeze Crystallization

Abstract

Freeze crystallization is very efficient separation technique for separation of soluble pollutant from industrial waste water as compare to Distillation and Evaporation. Main reason behind that is the latent heat of vaporization is nearly 7th times higher than the latent heat of fusion. In this paper Phenol, Acrylic acid and Phenol acetic acid pharmaceutical intermediate) are separated from their aqueous solution. Phenol-water, Acrylic acid-water and Phenol acetic acid-water are eutectic systems. At eutectic composition, it is possible to separate out pure crystals from melt. Hence fewer stages of freeze crystallization are required for eutectic system to separate out pure products.

Key Words: Eutectic freeze crystallizer, solid-liquid

Eutectic Freeze Crystallization (EFC):

When a solution containing dissolved contaminants is slowly frozen, water ice crystals form on the surface, and the contaminants are concentrated in the remaining solution (the mother liquor). The ice crystals can be separated from the mother liquor, washed and melted to yield a nearly pure water stream. The mother liquor will contain a pure salt, which crystallizes at the eutectic temperature. Theoretically, a 100% yield can be obtained in a binary system, which is one of the advantages of EFC technology. The level of accumulation of impurities can be controlled by means of purge streams.

Eutectic freeze crystallization (EFC) is an alternative technology for the separation of highly concentrated aqueous streams. Eutectic Freeze Crystallization is a technique that is capable of separating aqueous solutions into pure water and pure-solidified solutes and that is highly energy efficient, without the introduction of any solvents. In addition, the simultaneous production of pure ice and inorganic/organic chemical is a major advantage. Use of Freeze crystallization is more advantageous for the separation of heat sensitive components from their aqueous solution.

2.1

Freeze crystallization can be applied in separation processes to either purify or concentrate a material, depending on the desired end product. As the solvent crystallizes, the solute is concentrated in the remaining liquid solvent. The purified crystals are removed from the impurity laden liquid (for example by gravity, filtration or centrifuging) and may be used in the solid phase or melted for use as a refined liquid. In some applications, the concentrated liquid may be the desired end product like Phenol and Acrylic