FILTER CAKE DEWATERING BY FORMATION OF BENTONITE SKIN LAYER ON CAKE SURFACE

摘要

References(16) Cited-By(6) Dewatering of filter cakes can be accomplished by covering the cake surface with bentonite slurry at the end of filtration and applying compressed air. By this method, a skin layer of bentonite with high filtration resistance forms on the cake surface and acts as a mechanical piston which compresses the cake. Cake cracking is also rare compared with the case of non-Newtonian fluids shown in the previous paper.14) It is shown that the final equilibrium water content of compressed cakes is quite close to that obtained in mechanical expression. In the consolidation period, the reciprocal flow rate increases rapidly and the hydraulic pressure in the cake decreases enormously with consolidation time, resulting in a substantial decrease in porosity. Based upon the conventional expression theory of filter cake, a method has been developed for analyzing this operation on the assumption that the amount of permeated water from the bentonite slurry is negligible. The method can be used for evaluating the internal structures of compressed cake. Confirmation of favorable coincidence between theory and experiments is demonstrated.