What are Filter Aids in Filtration and How Are They Used?
Many of the products you buy and use every day require filtration. Producers start with an amalgamation of ingredients (solids and liquids) that need to be extracted from one another— usually the liquid formed during production. The process of making fruit juices, vegetable oils, baby formulas, wine and beer, vinegar, and even honey all rely on filter aids for their production.
Simply put, a filter aid is a porous medium placed on a filter septum (usually a cloth or screen) to filter liquids for removal of solids. The liquids are forced through the finely divided filter aid and any solids are deposited on the medium, trapping them and preventing them from clogging the septum and adulterating the end-product. A good filter aid is chemically inert, with irregularly shaped particles that leave microscopic open spaces in between particles to provide excellent filtration combined with fast flow rates.
There are many types of filter aid mediums available. Two of the most common are diatomite filter aids (DE filter aids) that are made of diatomaceous earth, and those made from perlite.
Important Differences Between DE Filter Aid and Perlite Filter Aids
Filter aids made with diatomaceous earth (DE) are common, but OSHA rates uncalcined DE as a Group 1 Carcinogen and amorphous silica, which comprises DE, is rated as a Group 3 Carcinogen. In addition, diatomaceous earth tends to build up where it is deposited, causing additional maintenance issues during the filtration process. Diatomite is a sedimentary rock formed as a silicious fossil remnant of algae. The various grades of diatomite must be calcined in order to be used as filter aids, and, in some cases, flux must be added to agglomerate particles to a size that is suitable for filtration. The problem is that not only do these DE filter aids have a pH of 8 to 10, but the calcination process changes the structure to crystalline, which can pose an inhalation hazard.
Perlite-based filter aids such as our Sil-Kleer product are created by taking naturally occurring volcanic glass and heating it above 1500 F. This process causes the moisture inside the rock to vaporize, and the resulting molten glass to form a multi-celled bubble cluster which is milled to form amorphous-shaped particles. This milling in conjunction with classification processes in production create a “cleaner” product with no sub-micron fines and all non-filtering particles (black obsidian) are removed. This arrangement is ideal for cake filtration because the resulting cloth media can be a more open weave, while comparable DE filter aids contain a larger percentage of sub-micron fines.
In fact, the bulk density of Sil-Kleer is 40% to 60% lower than comparable grades of diatomite, making it a much more manageable product to handle. It is also inert, sterile, and has a neutral pH that will not adulterate any substance with which it comes into contact. It is created from a single ingredient that is non-hazardous and features no additives. Perlite, from which Sil-Kleer is made, is classified as Generally Recognized as Safe (GRAS) by the Federal Department of Agriculture (FDA) and both Silbrico’s process and product are Kosher certified.
More Facts About Sil-Kleer
Sil-Kleer is distinct from even other perlite filtration products for its extremely low density. Typically used on vacuum filters (such as rotary vacuum filters, indexing belt filters, filter presses, and vertical or horizontal leaf filters) and tube filters, it is milled, purified, and classified to strict gradation with no sub-micron fines. In addition, our production runs are “to spec” which means that we produce to create a specific grade. Other perlite filter aids are run then divided into cuts or sometimes just a by-product that is milled and called perlite filter aid. This in production control, allows Silbrico to custom create a product to the necessary specifications with the best possible resulting material. This intensity of processing gives Sil-Kleer the advantage of providing faster filter flow rates without sacrificing clarity. Because it is rigorously classified to remove the coarse heavy fraction, Sil-Kleer provides the lowest density of any diatomite or perlite filter aid available.
As is apparent from the pure white color of the product, all non-filtering particles (the black obsidian) have been removed through an exacting milling and classification process that provides a tight particle distribution and a reliable product consistency. Filter aids are typically used for solids between 1 and 100 microns, where permeability is difficult to maintain because of septum blinding from various substances such as yeast cells, bacteria, pollens, starches, sugars, proteins, latexes, and more. The finest grades of Sil-Kleer can efficiently remove particles in the macro-molecular range, such as dyes and pigments, natural color bodies, metal oxides, proteins, and fine carbon blacks.
It’s important to note that because Sil-Kleer is a single ingredient of expanded rock mineral, there is no expiry on its use. If stored properly in dry conditions, it does not degrade in any way and can be used indefinitely. Plus, with its light weight, Sil-Kleer provides double the filtration, pound for pound, over diatomaceous earth.
When You Need Optimal Purity
Sil-Kleer is the perfect filter aid for a wide variety of applications, from food and industrial fermentation to industrial filtration, chemical processing, metal working, energy, and more. With the added filtration power of Sil-Kleer, your filter downtime and maintenance costs can be greatly reduced and filter septums preserved while achieving higher solid capture. When you need sparkling clarity, optimum flow rates, and a lower maintenance filtration option, Sil-Kleer is the clear choice.