Prediction of cake‐washing results with continuous filtration equipment

This paper proposes a theory of filter‐cake washing on continous filtration equipment based upon the assumption that mixing of the strong liquor and wash fluid is controlling. The theory can be conventiently applied to experimental filtration leaf tests for determining wash efficiency and is easily extrapolated to full‐scale results with the normally experienced uneven cake thickness and wash‐fluid distribution taken into account. To obtain the necessary wash‐fluid volume for proper soluble removal, a correlation method of wash time as a function of wash ratio with parameters of cake‐formation time has been derived from commonly accepted filtration theory. Experimental and plant data indicate a close agreement with the theory, and the method can be employed to predict filtration rate as a function of wash ratio. A typical illustration has been given to determine filtration requirements for recovering soluble uranium after leaching of the ore by continuous filtration. Washing rate was proved to be conrolling, and this design based only on cake‐formation rate would yield insufficient wash ratios and excessive soluble uranium loss. Final filter and flow‐sheet design must be based on uranium recovery which can be predicted by the proposed methods.