There are two distinct modes of liquid filtration. In one, the filter medium sits across the fluid flow channel, so that all of the liquid must pass through the medium, leaving any separated solids to be held in or on the medium. This is called through-flow or dead-end filtration, and it separates most or all […]
A screw press is a continuously operating machine used to squeeze liquid from a mass of fibrous solids, such as in the recovery of animal or vegetable oils, or further to dewater a pasty filter cake. It consists of a screw rotating inside a perforated or slotted shell, so that the mass is pressed against […]
A small group of filters is classed together as variable volume devices, so called because the filtration zone containing the collected solids is compressed once filtration is complete, in order to dewater the filter cake further before discharge. The diaphragm filter press, described in the previous chapter, fits that definition, but is more sensibly included […]
Belt presses (or press belts or double belt presses as they are equally usefully known), as their name implies, use the pressure of a belt on a mass of wet solids to dewater the solids. They are not filters, because they work by squeezing liquid out of a sludge, but they can be important adjuncts […]
The great success of the filter press has led to several other designs of filter employing the plate principle, most notably the vertical filter press (or tower press as this type is sometimes called – but so is a type of belt press, discussed in Section 3P), which is basic ally a filter press stood […]
The main development of the filter press from the simpler versions just described has been to include an impervious elastomeric sheet in each plate compartment (one for each plate on the feed side of the filter medium, butting up against the corresponding sheet of the next plate). These flexible sheets can be inflated pneumatically so […]
The first main development from the basic plate and frame structure saw the alternating plate and frame replaced by a single set of plates, each two sided, with a raised collar around its periphery, called a recessed plate. Now, when adjacent plates are closed up together, a chamber is formed from the two facing recesses to […]
Even in its most highly automated form the filter press is a relatively simple machine, comprising a series of flat filter chambers mounted vertically one beside the other, between two end plates, one fixed and the other movable horizontally, so as to close the plates together. In the earliest form of filter press, the chamber […]
Although one of the oldest types of filter, the filter press has, over the last century, been the most important of the process pressure filters, and remains important to this day, despite the appearance of competitive types of filter. It has kept this major role by virtue of a small number of design improvements, and […]
The leaf and plate filters are batch filters, and a critical element in their selection is the capacity of the filter for the amount of cake to be treated in a single batch. Flow through the filter will depend upon the nature of the suspended solids and their concentration, the liquid viscosity, the pressure available, […]
