[...]... in the medium's pores The fluid discharging from the medium is called the filtrate The operation may An Introduction to Liquid Filtration 9 be performed with either incompressible fluids (liquids) or slightly to highly compressible fluids (gases) The physical mechanisms controlling filtration, although similar, vary with the degree of fluid compressibility Although there are marked similarities in the... cake to effect clean separation of An Introduction to Liquid Filtration 13 solids from the mother liquor or to recover the mother liquor from the solids The operation known as de-watering involves forcing a clean fluid through the cake to recover residual liquid retained in the pores, directly after filtering or washing If the fluid is gas, then liquid is displaced from the pores Also, by preheating... then operated at a constant pressure gradient while experiencing a gradual decrease in process rate The structure of the cake formed and, consequently, its resistance to liquid flow depends on the properties of the solid particles and the liquid phase suspension, as well as on the conditions of filtration Cake structure is first established by hydrodynamic factors (cake porosity, mean particle size, size... size inhomogeneity influences the geometry of the cake structure not only at the moment of its formation, but also during the filtration process During filtration, small particles retained on the outer layers of the cake are often entrained by the liquid flow and transported to layers closer to the filter medium, or even into the pores themselves This results in an increase in the resistances across... this leads to a decrease in effective pore size and consequently an increase in flow resistance This results from particle penetration into the pores of the filter medium 10 Liquid Filtration The separation of solid particles from a liquid via filtration is a complicated process For practical reasons filter medium openings should be larger than the average size of the particles to be filtered The filter... dischargeable cake Filtration for both solids and liquid recovery differs from filtration for solids recovery alone in the cake building, washing and drying stages If the filtrate is a valuable liquor, maximum washing is necessary to prevent its loss; but if it is valueless, excess wash liquor can be applied without regard to quality An Introduction to Liquid Filtration 15 Finally, filtration can be... to the particular operation or specific equipment) If distorting side effects are not important, the filtration process may be designed according to existing empirical correlations In 18 Liquid Filtration practice, filtration, washing and dewatering often deviate substantially from theory This occurs because of the distorting influences of filter features and the unaccounted for properties of the suspension... hydraulic resistance to the filtrate flow, Allow easy discharge of cake, High resistance to chemical attack, Resist swelling when in contact with filtrate and washing liquid, Display good heat-resistance within the temperature ranges of filtration, Have sufficient strength to withstand filtering pressure and mechanical wear, Capable of avoiding wedging of particles into its pores There are many filter... mesh Depth-type filter media are largely used for liquid clarification They are characterized by the fact that the solid particles penetrate into the pores where they are retained The pores of such media are considerably larger than the particles of suspension The suspension's concentration is generally not high enough to promote particle bridging 19 20 Liquid Filtration inside the pores Particles are... natural and artificial media usually are normally distributed The average porosity of a heterogeneous nonuniform medium is the volume-weighted average of the number average: m E E", An Introduction to Liquid Filtration 1 The average nonuniform permeability is spatially dependent For a homogeneous but nonuniform medium, the average permeability is the correct mean (first moment) of the permeability distribution . ix About the Author xi Chapter 1 An Introduction to Liquid Filtration 1 Introduction 1 The Porous Media 2 The Filter Media 9 Liquid Filtration Classification 10 The Formation of . Agency for International Development Boston Oxford Johannesburg Melbourne New Delhi Singapore LIQUID Copyright © 1998 by Butterworth-Heinemann A member of the Reed Elsevier group All . volume has been written as an introductory reference and working guide to the subject of liquid filtration engineering. The book is designed to acquaint the newcomer to industry