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Main types of filters


2022-04-29 14:37

Filters are divided into three categories: gravity filters, vacuum filters and pressure filters according to the method of obtaining the filtration driving force.
With the help of the gravity of the suspension and the pressure formed on the filter medium as the driving force for filtration, it is generally operated intermittently, such as a sander.
A negative pressure is formed at the outlet of the filtrate as a driving force for filtration. The absolute pressure of the industrial vacuum filter operating vacuum is (2.5 ~ 8.0) × 105 Pa. The temperature of the suspension during filtration should be lower than the vaporization temperature of the filtrate under the operating vacuum. This filter is divided into intermittent operation and continuous operation. Intermittently operated vacuum filters can filter suspensions of various concentrations. The vacuum filter is filled with the suspension inside the vessel shell. The filter leaves covered with filter cloth on both sides are immersed in the suspension, and the inner cavity of the filter leaves is communicated with the vacuum system. After the filtrate is sucked out, it is led out by the conduit, and the filter residue accumulated on the surface of the filter leaves is removed after the machine is shut down. Continuously operated vacuum filters are suitable for filtering thick suspensions with high solids content. Drum vacuum filters, inner surface drum vacuum filters, disc vacuum filters and tipping bucket vacuum filters all work similarly. The entire filter surface is divided into a plurality of separated filter chambers, and each rotating filter chamber is sequentially connected with each fixed pipe through a distribution valve to suck out the filtrate, washing liquid in the filter chamber, or send compressed air. Each filter chamber rotates once to complete the whole process of filtration operation, and the operations of multiple filter chambers are connected to form continuous filtration. The structure of the belt vacuum filter is similar to that of the belt conveyor, with a continuous filter belt, which is suitable for the easy-to-filter suspension. The belt vacuum filter, the inner filter surface rotary drum vacuum filter and the tipping bucket vacuum filter are all fed on the upper part of the filter medium (filter cloth), which is especially suitable for the suspension with high density of solid particles and fast sedimentation.
It uses the pressure applied at the inlet of the suspension or the mechanical pressing force applied to the wet material as the filtration driving force, and is suitable for the suspension that requires a large pressure difference to filter. It is also divided into intermittent operation and continuous operation. Intermittently operated tubular filter presses and pressure filters for the filtration of low-concentration suspensions. The filter is also a pressurized filter with intermittent operation, which is divided into three types: plate and frame type, box type and vertical type. The oil filter is a plate and frame filter press unit equipped with accessories such as oil pump and vacuum evaporator. Continuously operated rotary drum pressure filters and disc pressure filters perform pressure filtration in a closed shell, and their structures are similar to rotary drum vacuum filters and disc vacuum filters. Due to the complex structure, the application is less.
The commonly used pressure filtration is to filter by reducing the volume of the filter chamber or applying a mechanical pressing force. The filter residue has a low moisture content and is suitable for suspensions with high solid particle concentration. In the belt press filter, the wet filter residue after preliminary deliquoring by gravity or vacuum is moved between two filter belts, and then squeezed and deliquored by rollers. The screw press filter has a cylinder with pores, in which there are rotating spirals, and the depth of the spiral grooves varies. The pores are discharged, and the filter residue is discharged from the small end.
Precision filter is for filtration precision, generally between sand filtration (coarse filtration) and ultrafiltration. Under the action of pressure, the raw water passes through the filter element, the impurities are trapped on the filter element wall, and the water flows out through the filter element, so as to achieve the purpose of filtration. The scale of manufacturers producing filter equipment in my country is dominated by small and medium-sized enterprises. The products are made of high-quality stainless steel, hard polyvinyl chloride, engineering plastics, plexiglass and other corrosion-resistant materials as the shell, mainly high-quality stainless steel, with built-in filter elements of different media. The built-in filter elements include PE core, honeycomb core, folded core, titanium tube sintered core, activated carbon core, ceramic core, polypropylene fiber filter core, etc. Different filter elements have different filtration effects, so the precision filter can remove suspended solids, some colloidal substances and fine particles in the water according to the requirements of raw water quality, effluent quality and water quantity, and achieve different filtration accuracy. The filtration precision of precision filters on the market is in the range of 0.2-100um. Precision filters are often used as protective filters for electrodialysis, ion exchange, reverse osmosis, ultrafiltration and other devices, and can be used in water treatment in food, wine, pharmaceutical, chemical, electronics and other industries, such as:
Food industry: fine filtration of mineral water, clarification and filtration of beverages and alcohol. Pharmaceutical industry: water treatment of sterile water, oral liquid, infusion, injection, etc.;
Electronics industry: pure water preparation and washing water filtration in production plants such as semiconductors, instruments, and picture tubes;
Chemical industry: purification of organic solvents, esters, alcohols, acids, alkalis and other chemical raw materials and oils;
Environmental protection: treatment of various industrial wastewaters such as electroplating wastewater, printing wastewater, pharmaceutical wastewater, etc. Water quality treatment for seawater and brackish water desalination, water supply treatment for hotels and apartments, etc.;
Gardening and gardening: park courtyards, greenhouses, animal husbandry, industrial places that need to artificially create ultra-fine water mist, and irrigation and maintenance of high-end flowers.

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