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Beer Filtration
Powder Filters
There are several types of powder filters: the plate and frame, the horizontal leaf, the vertical leaf, and the candle filter.
Plate and Frame
The plate and frame filter, as shown in Figure 15.1, has been the workhorse in breweries around the world for many decades. It is robust and reliable, consistently filtering beer to the specified standards. Plate and frame filters consist of a series of chambers enclosed within a metal frame. Between adjacent frames is a double-sided porous filter plate covered by either a fine mesh or a sheet. The filter sheet acts as a trap for the filter aid, which otherwise might bleed through, thereby assuring excellent clarity. Filter sheets are generally made with cellulose fiber, diatomaceous earth, perlite, and a resin for bonding to give dry and wet strength. Some are available only with filtration fibers. The average pore size of filter sheets is between 4 and 20 microns; therefore, plate and frame filters are readily precoated and less susceptible to malfunction. Each plate alternates with a frame with the entire system held together by a screw or hydraulic clamp mechanism. This type of filter is very similar in appearance to the sheet filter, except it has sludge frames.
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