High purity products by crystallisation

Crystallisation from a melt or solution has the potential to yield a product with a very high purity in a single equilibrium step. Pure crystals have to be separated from the impure mother liquor, which is usually done by standard solid-liquid separation techniques like filtration or centrifugation. For high purity products, additional washing is required to remove residual mother liquor from the crystal cake. An attractive alternative, however, is to use a wash column, which combines continuous solid-liquid separation with efficient counter-current washing using very little or no wash liquid. The hydraulic wash column (HWC) developed by TNO combines a high washing efficiency with a high specific production capacity.