WASHING EFFICIENCY IN FRACTIONAL POST-O-2 WASHING

In fractional washing the countercurrent filtrate overflow is divided into fractions with different physical properties (concentration, pH, temperature), The fractions are used separately in earlier stages of w ashing. The purpose of this paper was to test theoretically the possib le benefits of fractional washing in post-O-2 washing. A diffusion was hing model was used to predict the washing efficiency in relation to d issolved organic material in various fractional process configurations . The process configurations studied had one to three filtrate fractio ns with various chemical concentrations in countercurrent two-stage po st-O-2 washing. Fractional washing improved displacement efficiency si gnificantly for some of the calculated examples, Fractional washing pr oved to be especially beneficial for the removal of quick leaching com ponents, (such as metal ions and small molecules). Slow leaching behav ior reduced the potential benefits of fractional washing. Long retenti on times are also essential in fractional washing in order to achieve good results in washing out dissolved organic material.