All porous materials that can make the fluid in the filter slurry pass through and the solid particles contained in it are intercepted to achieve the purpose of solid-liquid separation are collectively referred to as filter media. It is a key component of the filter, which determines the separation accuracy and efficiency of the filter operation, and also directly affects the production intensity and power consumption of the filter. There are many types of filter media used in industry, which can be divided into three categories according to their structure: flexible media; rigid media and loose filter media: Flexible filter media: o metal filter media o non-metallic filter media: cotton fabrics, wool fabrics , silk fabric, synthetic fiber fabric, glass fiber fabric, non-woven fiber fabric: non-woven filter cloth (, filter paper, filter felt, filter pad) o metal, non-metal mixed media rigid filter media o sintered metal mesh, metal fiber sintered Felt, powder sintered material, porous ceramic, sintered porous plastic, sintered aluminum oxide, glass filter medium, loose filter medium o diatomite, expanded perlite powder, cellulose, sand, charcoal powder, smokeless filter medium. related to the mechanism of filtration operation.
The technical characteristics of the filter media used for filter cake filtration must meet the special requirements of this type of filtration: the structure of the media can ensure that the particles can quickly flow on the surface of the media when the filtration starts."bridge", so that fine particles will not be lost (that is, through filtration); the ratio of particles held in the pores of the medium is low, and the blockage of the medium is minimal; the filter cake can be easily and completely removed; the structure of the medium is convenient for cleaning and regeneration. Commonly used filter cake filter media mainly include filter cloth, filter paper, filter screen, side filter element, etc. For the medium used for deep filtration, its structure is required to meet the specified retention accuracy and be able to block the required particles; the bed layer must be There is enough capacity to slow down the process of being blocked by particles to prolong the operation period. The common requirements for all kinds of filter media are: excellent filtration characteristics (small specific resistance, high retention precision, etc.); good physical and mechanical properties (high strength, creep, rigidity and flexibility, high wear resistance, etc.), in a certain process Under the operating conditions and environment, it has good chemical stability (corrosion resistance, high temperature resistance and microbial resistance, etc.), easy cleaning and regeneration, cheap price and reliable source.
Basic requirements for selecting filter media 1. The ability of the filter media to capture solid particles This is related to the separation sequence of filtration. The so-called capture capacity is the smallest particle size that can be retained. The capture capacity depends on the pore size and distribution of the medium itself.
The table below shows the smallest particles that various filter media can capture. 2. Permeability The permeability of the filter medium reflects its resistance to the flow of filtrate, which affects the production strength and filtration driving force of the filter --- the pressure difference The permeability of the filter medium can be described by the Darcy equation: For particles or For a fiber-filled filter bed, the permeability K can be given by the Kozny-Kalman equation: The permeability of the monofilament textile fiber medium can be given by the following semi-empirical equation: It can be seen that the permeability of the filter medium is related to the medium itself related to porosity. The porosity of commonly used filter media is shown in the following table: Media Name Metal mesh plain weave, twill ceramic porous material thin film paper diatomite Refined porosity \%15~2530~3530~50708060~9580~90 3. Unloading and cleaning regeneration performance The slag capacity refers to the ability to remove the filter cake from the surface of the medium by using the filter cake's own strategy or compressed air blowing off, mechanical scraping and other measures after the filtration. Filters are a prerequisite for maintaining normal operation.
During the filtration process, a small amount of filter residue particles are always blocked in the pores of the medium. After the slag unloading process of each operation cycle, the particles must be cleaned from the surface of the medium and the pores by washing and purging to maintain the filtration efficiency of the medium. and performance. The regeneration performance mainly depends on the constituent materials and textile and processing methods (manufacturing process) of the filter medium. 4. Chemical stability Due to the variety of materials processed in the filtration process, their chemical properties are different.
There are acidic, alkaline, strong oxidizing, organic solvents, etc., and they are all filtered at a certain temperature. This requires the selected filter medium structure material to have good chemical stability in the processed material, chemical corrosion resistance, temperature change resistance, and microbial resistance. In general, polypropylene fibers have good acid resistance.
Alkali resistance and oxidant resistance, polyethylene fibers are stable to acid and alkali solutions at room temperature, and polyester materials have good acid resistance. 5. Physical and mechanical properties of materials Physical and mechanical properties of materials include hygroscopicity, Abrasion resistance, mechanical strength, elongation, etc., all affect the filtration performance and service life of the medium. Different types of filters have different requirements on the physical and mechanical properties of the medium. For example, compared with blade filters and drum filters, plate and frame filters have higher requirements for the mechanical strength of filter cloth. Belt filters have higher requirements for filter cloth. The strength requirement is higher than that of the overturning disc filter, and the elongation under a certain load is required to be as low as possible. Poolking is the best swimming pool equipment manufacturer and supplier in China. Poolking exists to provide the highest quality swimming pool equipment while offering competitive pricing..