GENERAL REFERENCES: Moir, Chem. Eng., 89(15), 46 (1982). Brown, ibid.,
58; also published as McGraw-Hill Repr. A078. Cheremisinoff and Azbel, Liq-
uid Filtration, Ann Arbor Science, Woburn, Mass., 1983. Orr (ed.), Filtration:
Principles and Practice, part I, Marcel Dekker, New York, 1977; part II, 1979.
Purchas (ed.), Solid/Liquid Separation Equipment Scale-Up, Uplands Press,
Croydon, England, 1977. Schweitzer (ed.), Handbook of Separation Tech-
niques for Chemical Engineers, part 4, McGraw-Hill, New York, 1979. Shoe-
maker (ed.), “What the Filter Man Needs to Know about Filtration,” Am. Inst.
Chem. Eng. Symp. Ser., 73(171), (1977). Talcott et al., in Kirk-Othmer Ency-
clopedia of Chemical Technology, 3d ed., vol. 10, Wiley, New York, 1980, p.
284. Tiller et al., Chem. Eng., 81(9), 116–136 (1974); also published as
McGraw-Hill Repr. R203.
DEFINITIONS AND CLASSIFICATION
Filtration is the separation of a fluid-solids mixture involving passage
of most of the fluid through a porous barrier which retains most of the
solid particulates contained in the mixture. This subsection deals only
with the filtration of solids from liquids; gas filtration is treated in Sec.
17. Filtration is the term for the unit operation. A filter is a piece
of unit-operations equipment by which filtration is performed. The
filter medium or septum is the barrier that lets the liquid pass while
retaining most of the solids; it may be a screen, cloth, paper, or bed of
solids. The liquid that passes through the filter medium is called the
Filtration and filters can be classified several ways:
1. By driving force. The filtrate is induced to flow through the
filter medium by hydrostatic head (gravity), pressure applied upstream
of the filter medium, vacuum or reduced pressure applied downstream
of the filter medium, or centrifugal force across the medium. Centrifu-
gal filtration is closely related to centrifugal sedimentation, and both
are discussed later under “Centrifuges.”
2. By filtration mechanism. Although the mechanism for sepa-