PERMEABILITY OF FILTER CAKES OF PALM OIL IN RELATION TO MECHANICAL EXPRESSION

Permeability and compressibility data are required for an adequate pro cess model for compressible-cake filtration and mechanical expression. Experimental and modeling results of the permeability of palm-oil fil ter cakes (a highly compressible viscoelastic material) are combined w ith compressibility data, leading to a model for the expression step. Permeability measurements show that permeability depends strongly on t he quantity of fine particles in the cake. Removal of fine particles f rom the slurry before expression significantly increases the solid-pha se content during expression due to higher permeability. Modeling resu lts of the expression step show that for palm-oil filter cakes there i s a pressure above which the attainable mass fraction of solids become s independent of pressure. Decrease in specific cake resistance has tw o effects: a higher mass fraction of solids at the same pressure and a higher pressure at which the mass fraction of solids is not affected further.