Pressure Filter
Pressure filters are popular as they allow for easy cake collection and reuse. A filter cake is the solid or liquid material removed from a process stream and can sometimes include valuable materials, such as oil vapors or metallic dusts, which are easily recycled or reincorporated into the production process to reduce waste and cut costs. Additionally, pressure filters can be used to sort the contaminants extracted from a gas or liquid. Differing pressures and progressively more restrictive filter materials used in succession remove some particulates while allowing others to pass or be contained by later filter panels or cartridges. Continual use or batch pressure filters are commonly used for ease, accuracy and material collection purposes in such varied industries as clean-room environments, biomedical, analytical instrumentation, food processing, marine and aviation, agriculture, manufacturing, food and beverage packaging, fine chemical processing and petrochemical among others.
Although continual operations are attainable, most pressure filters are semi-continuous or batch
filtering systems. Cycles for batch filters may run for as little as five minutes or last up to eight hours and may offer automated or manual processing, depending upon the specific capacities and rate of use required for a given application. As manual processing can be labor-intensive most facilities utilize at least partially automated filtration. The design varies considerably, but in the most basic sense it involves a flow line and a filter panel or cartridge made of variable materials designed to trap and contain particulates and contaminants. Common materials include closed cell foams, fiberglass, nylon and even sand. A surge tank is located upstream from the filter in high pressure applications and a batch collection sight may be found downstream. The pressure needed for these filtering systems to operate varies greatly depending upon
filtration media and stream composition. Easily installed in pre-existing flow lines, often the pressure inherent in the movement of materials throughout the manufacturing process is sufficient to push air or fluids through the system. Flow rate, cake thickness, operating temperatures, porosity, filter efficiency and working and static pressure should all be considered when selecting an application-specific pressure filter. Common types include candle filters, filter presses, horizontal plate pressure filters, polishing filters, nutsche filters and vertical leaf filters.
