Advantages of perlite for filtration

General Considerations

Filtration is the separation of solids from liquids by forcing the liquid to flow through a porous medium and depositing the solids on the medium. A filter aid is a finely divided material which, when added to the liquor to be filtered, helps control flow and solids removal. The septum, usually screen or cloth, serves principally as a support for the cake. The filter aid forms a porous layer on the septum and thus the filter aid is the filtering medium that traps the solids being removed and prevents them from blinding the septum. Filter aid filtration is mechanical, not chemical in nature. Irregularly shaped particles interlace and overlay in a fashion that leaves 85 to 95 % voids or open spaces. These voids forms billions of microscopically fine interstices between the filter aid particles. The size of these openings is so minute that the unwanted solids are strained from the liquid. The vast number of openings compensates for their small size resulting in fast flow rates and brilliant clarity.

Good filter aids are light in weight, chemically inert and form high porosity filter cakes to maintain free flow of the liquid. The structure of the particles must be such that they will not pack too closely. This not only permits high initial liquid flow but also provides pore spaces to trap and contain the filterable solids and leave a high percentage of channels remaining open for flow. Particle size distribution must be tailored to permit pre-coating on coarse wire and yet give the desired flow rate and clarity. Nordisk Perlites Filter aids are available in a variety of grades to suit the solids removal requirement of nearly any application.

Perlite filter aid has a large amount of special properties and advantages:

• High capability of filtration
• High clarity
• High flow rate
• Amorphous material - no crystalline particles
• Low density
• Easy cake release
• Doesn't present a health hazard
• Uniform precoat
• Sterile product
• Listed in US Food chemicals codex
Nordisk Perlite produces a full range of filter aids from the finest- for filtration of small particles to filtration of large particles with following high flow rate.

The Perlite filter aid is available in paper bags, big bags and bulk.

In the picture to the left its possible to see how Perlite filter aid works.


Perlite Filter aid is a filter aid, which over the last 65 years has proven itself being a superb material within a number of industries, i.e.

  • Chemical Industries
  • Food processing- & drink industries
  • Pharmaceutical Industries
  • Water treatment and others


Grade Selection

Clarity is considered by many engineers to be the most important measure of efficiency in filter aid filtration. A high quality filter aid is most important for uniform results day after day. Selection of the particular type and grade of filter aid having the correct particle size and distribution is a major factor. After these come many considerations such as the quantity of filter aid to be used; flow rate needed to meet plant production schedules, equipment limitations and general filtration conditions. All of these can best be resolved by tests using the actual liquid involved.

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