The filter medium is a support material that retains particles in the suspension.
⑴ filter media should have the conditions
① porosity, pore appropriate small, the resistance of the fluid is small, but also to seize the particles to be separated
② physical and chemical properties of stability, heat resistance, chemical corrosion.
③ sufficient mechanical strength, long service life
⑵ common industrial filter media
Fabric media, granular media, porous media
① fabric media: also known as filter cloth, including cotton, wool, silk and other natural fibers, glass fiber and a variety of synthetic fibers made of fabric, and metal wire woven into the net, to retain a wide range of particle size, from Mu] m to 1 [mu] m. There are paper, carpets, asbestos and other non-woven products.
◈ features: thin fabric, low resistance, easy cleaning and updating, the price is cheaper, is the industry's most widely used filter media.
◈ The filtration performance of fabric media is affected by many factors, the most important of which is fiber properties, weave pattern and line type.
② granular media: a diatomaceous earth, perlite powder, fine sand, activated carbon, clay and other amorphous particles. Among them, diatomite is an excellent filter medium, the most commonly used.
◈ the advantages of diatomaceous earth filter media
★ generally does not react with acid-base, chemical stability;
★ irregular shape, the gap is large and porous, with a large adsorption surface;
★ non-toxic and incompressible, the formation of the filter layer resistance does not change with the operating pressure.
③ porous solid medium
Porous metal, porous glass, plastic powder into a porous plastic and so on, can be processed into plate or tube, pore size is very small and corrosion-resistant, commonly used in filtering a small amount of particles containing particles, Lt; / RTI & gt; This type of medium thick, fine pore, resistance, can be retained 1 ~ 3μm particles
⑶ filter media selection
The filter medium acts to retain the particles in the filter slurry or to filter the support. Should have sufficient mechanical strength and flow resistance as small as possible.
◈ Filter media selection basis
The size of the solid particles that can be trapped by the filter medium: usually expressed as the pore size of the filter medium. Commonly used filter medium, the fiber filter cloth can retain the smallest particles of about 10μm, diatomite is lμm, ultrafiltration membrane can be less than 0.5μm.
Filter medium permeability: refers to a certain pressure difference, the unit time unit filter area by filtrate volume, it depends on the filter medium on the size and number of capillary aperture.