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From today on, Waterfiltech is gonna update the chapter and information on the practical filtration guide book named “Filters and Filtration Handbook”, written by Ken Surtherland, for a better understanding of filters and filtration spectrum.

A book entitled Filters and Filtration Handbook is clearly stating its purpose in those words, but the primary topic – fluid purification free of contaminants by means of mechanical separation processes – requires a somewhat broader coverage than those words imply. The title of this chapter suggests that broader coverage, even if it is a little confusing, because filtration is one form of separation. The title is, in fact, shorthand for the more cumbersome phrase: “filtration and other related forms of separation”, and has been used in that way for over 40 years, as the title of a leading magazine in the industry proclaims. Throughout this book the term “filtration” should thus be read as to imply that broader term (unless the context suggests the narrower definition).

So it is perhaps as well to start with some sort of definition of these terms, in the context of this Handbook. Filtration specifically, and separation generally, refer to the act of separating one or more distinct phases from another in a process which uses physical differences in the phases (such as particle size or density or electric charge). The whole of the phase separation spectrum is illustrated in Table 1.1, which covers the separation of distinct phases as well as completely mixed ones. In principle, this book is only concerned with the second half of Table 1.1 – the separation of distinct phases. However, as with any attempt to classify things in the real world, there is some overlap with the first half of the table: some membrane processes normally classified with filtration actually operate by molecular diffusion, while one major filtration mechanism involves adsorption (and many adsorbents act as filters as well).

That said, it is in the lower part of Table 1.1 that the main concern of this book lies, primarily in the separation of solid contaminants from liquid or gas flows, by filtration or sedimentation processes. To a lesser extent, liquid/liquid and liquid/gas systems are considered (for which true filtration is not used), although sedimentation systems are employed, together with filtration-like processes, such as demisting.

A filter is basically a device for separating one substance from another, and to do that it requires the placing of a filter medium in the way of the fluid flow, so as to trap the solids in some way. The filter then becomes any contrivance that is able to hold the filter medium in the best way to achieve the purpose of the filter process.

The most common of the distinct phase separation processes given in Table 1.1 are the solid/fluid ones: solid/gas separations being exemplified by the treatment of process and boiler exhausts in bag houses, and by the panels used in building air conditioning; solid/liquid separations cover the enormous range of filter types from the simple cartridge filter to the complex machines such as the rotary pressure drum filter. Most of the inertial separations (cyclone and centrifuge) and sedimentation systems are also found in this category.

This book aims to cover, in a descriptive fashion, the whole spectrum of filtration and its closely related separation processes. It continues in this section with some general material on filters, their characteristics, specification and testing.

The importance of the filter medium to filtration performance is acknowledged in Section 2, devoted to descriptions of filter media. This is followed by a series of descriptions in Section 3 of all of the relevant filtration equipment.

The equipment descriptions are followed by three sections on filtration applications: Sections 4 and 5 deal with liquid filtration, and Section 6 with gas filtration. The penultimate section looks at types of equipment other than filters that are used for clarification, and the book finishes with some guidance on equipment selection.

For further information, please check here.