TABLE OF CONTENTS Depending on the type and mode of operation of a batch filter, a cycle may comprise up to two filtration phases followed by a number of compression, gas deliquoring and washing phases, essentially in any order, as well as a cake discharge operation (see also Tarleton and Hancock, 1997;, Tarleton and Wakeman, 1994c, 2005b; Wakeman and Tarleton, 1994a,b, 1999).
Vacuum and pressure Nutsche filters are similar in many aspects of the filter cycle and a typical example of the latter is shown schematically in Figure 6.1 (see also Sections 1.4.1.1 and 1.4.2.1). In both variants a single leaf forms part of a fully enclosed cylindrical vessel. An imposed constant pressure gradient across the leaf/medium induces combinations of cake formation, deliquoring and washing to meet process requirements. Cake discharge is by a mechanical plough, reslurrying or, in some smaller units, by separation of the filter base.
The multi-element vacuum filter is characterised by the Moore s filter (see Section 1.4.1.2 for a schematic of the filter cycle). These filters, which can also be considered semi-continuous, comprise series of double-sided vertical leaves that are mechanically dipped into an open-top tank of suspension. Vacuum is applied to draw liquor into the rectangular filter leaves leaving cakes forming on each of the exposed cloth surfaces. If necessary the leaves...
