The main classification
Filters can be divided into three types according to the methods of obtaining the filter impetus: gravity filter, vacuum filter and pressure filter.
The force of gravity
The filter is driven by the pressure formed on the filter medium by the gravity and potential difference of the suspension. It is usually operated intermittently, such as a sand trap.
vacuum
Negative pressure is formed at the filtrate outlet as the driving force of filtration. The absolute pressure of industrial vacuum filter operation 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 operating vacuum. The filter can be divided into intermittent operation and continuous operation. Intermittently operated vacuum filters can filter suspensions of various concentrations. The vacuum filter fills the container housing with suspension. The filter blade coated with press cloth on both sides is immersed in suspension, and the inner cavity of the filter blade is connected with the vacuum system. The filtrate is drawn out by the pipe and the filtrate residue accumulated on the surface of the filter blade is removed after the machine is shut down. A continuously operated vacuum filter is suitable for filtering thick suspensions containing more solid particles. The operating principles of drum vacuum filter, inner surface drum vacuum filter, disc vacuum filter and bucket vacuum filter are similar. The whole filtration surface is divided into several separate filtration Chambers, and each rotary filtration chamber is connected to each fixed pipe through the distribution valve in order to draw out the filtrate and washing liquid in the filtration chamber or feed into the compressed air. Each filter chamber rotates once to complete the whole process of filtration operation, and the operation of multiple filter Chambers is 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, suitable for easily filtered suspension. Belt type vacuum filter, inner filter surface rotary drum vacuum filter and flip bucket vacuum filter are added on the upper part of the filter medium (press cloth), especially suitable for suspension with high solid particle density and fast settling.
pressurized
It takes the pressure applied at the inlet of the suspension or the mechanical pressure applied to the wet material as the filter driving force. It is suitable for the suspension with large filtration pressure difference. It is also divided into intermittent operation and continuous operation. Intermittently operated strainers and pressure strainers are used for low concentration suspension filtration. Filter is also a kind of intermittent operation of the pressure filter, and divided into plate - frame, box and vertical three kinds, the use is very wide. Oil filter is a plate and frame filter press unit with oil pump, vacuum evaporator and other accessories. The rotary drum pressure filter and disc pressure filter are operated continuously in a closed case for pressure filtration. Their structure is similar to that of rotary drum vacuum filter and disc vacuum filter. Due to the complex structure, the application is less.
The commonly used pressurized filtration is to filter with smaller filter chamber volume or mechanical pressure, and the wet content of filter residue is low, which is suitable for suspension with high solid particle concentration. In the belt press filter, the wet filter residue after initial dewatering by gravity or vacuum is clamped between two filter belts and then the dewatering is extruded by the roller. The spiral press filter machine is provided with a cylinder with a pore, in which there is a rotating spiral, the spiral groove depth is different, the material is added from the deep groove end to the shallow groove end, the filter chamber space is gradually reduced, the material is pressed, the filtrate is discharged from the pore of the cylinder, the filtrate is discharged from the small end.
precision
Precision filter is aimed at filtering precision, generally between sand filter (coarse filter) and ultrafiltration. Under the action of pressure, raw water passes through the filter core, impurities are retained on the wall of the filter core, and water flows out through the filter core, so as to achieve the purpose of filtration. At present, small and medium-sized enterprises are the main manufacturers of filter equipment in China. Products are made of high-quality stainless steel, hard PVC, engineering plastics, plexiglass and other corrosion-resistant materials as the shell, which is mainly made of high-quality stainless steel, with built-in filter elements of different media. There are PE core, honeycomb core, folding core, titanium sintering core, activated carbon core, ceramic core, polypropylene fiber filter core and so on. The filter elements have different filtration effects, so the precision filter can remove suspended matter, some colloidal substances and fine particles in the water according to the requirements of the raw water quality, the effluent water quality and the amount of water, and achieve different filtration accuracy. The range of filtration accuracy of precision filters on the market is 0.2-100um. Precision filter is often used as a protective filter for electrodialysis, ion exchange, reverse osmosis, ultrafiltration and other devices. It can be used for water treatment in food, wine, pharmaceutical, chemical, electronic and other industries, such as:
Food industry: fine filtration of mineral water, clarification and filtration of beverage and liquor. Pharmaceutical industry: water treatment of sterile water, oral liquid, infusion, injection, etc.
Electronic industry: semiconductor, instrument, picture tube and other manufacturers of pure water preparation, washing water filtration;
Chemical industry: purification of organic solvents, esters, alcohols, acids, bases and other chemical raw materials and oils;
Environmental protection: electroplating wastewater, printing wastewater, pharmaceutical wastewater and other industrial wastewater treatment. Water treatment for desalination of sea and brackish water, and water treatment for hotels and apartments;
Garden gardening: gardens and courtyards, greenhouses, animal husbandry, places requiring artificial super-fine water mist, and irrigation and maintenance of high-grade flowers.
