The filter is divided into three types according to the method of obtaining the driving force of the filter, which is divided into a gravity filter, a vacuum filter and a pressure filter.
gravity
The pressure formed on the filter medium by the gravity and the difference of the suspension serves as a driving force for the filtration, generally intermittent operation, such as a sander.
vacuum
A negative pressure is formed at the filtrate outlet as a driving force for filtration. The absolute pressure of the industrial vacuum filter operating vacuum is (2.5 to 8.0) x 105 Pa. The temperature of the suspension during filtration should be lower than the vaporization temperature of the filtrate under operating vacuum. This filter is divided into two types: intermittent operation and continuous operation. An intermittently operated vacuum filter filters various concentrations of the suspension. The vacuum filter is filled with a suspension in the outer casing of the container. The filter leaves on both sides of the filter cloth are immersed in the suspension, and the inner chamber of the filter leaves is connected to the vacuum system. After the filtrate is sucked out, it is taken out by the conduit, and the filter residue accumulated on the surface of the filter leaf is removed after the shutdown. A continuously operated vacuum filter is suitable for filtering thick suspensions containing more solid particles. The drum vacuum filter, inner filter drum vacuum filter, disc vacuum filter and tipping vacuum filter work in a similar manner. The entire filtering surface is divided into a plurality of spaced filter chambers, and each of the rotating filter chambers is sequentially connected to each of the fixed tubes through a dispensing valve to suck out filtrate, washing liquid, or compressed air in the filtering chamber. The entire process of the filtering operation is completed by one revolution of each filter chamber, and the operation of the plurality of filter chambers is connected to form a continuous filtration. The belt vacuum filter has a structure similar to that of a belt conveyor and has a continuous filter belt for easy filtration of the suspension. The belt vacuum filter, the inner filter surface drum vacuum filter and the tipping bucket vacuum filter are all fed on the upper part of the filter medium (filter cloth), and are especially suitable for suspensions with high solid particle density and fast sedimentation.
Pressurize
It is used as a filter driving force by the pressure applied at the inlet of the suspension or the mechanical pressing force applied to the wet material. It is suitable for the suspension which requires a large filtration pressure difference, and is also divided into two types: intermittent operation and continuous operation. Intermittently operated tube and tube pressure filters and pressure filters for low concentration suspension filtration. The filter is also a batch-operated pressure filter, which is divided into three types: plate and frame, box and vertical. It is widely used. The oil filter unit is a plate and frame filter press unit equipped with an oil pump, vacuum evaporator and other accessories. The continuously operated drum pressure filter and the disc pressure filter are pressure-filtered in a sealed casing, and the structure is similar to that of a drum vacuum filter and a disk vacuum filter. Due to the complex structure, there are fewer applications.
The commonly used pressure filtration is to filter by using a small filter chamber volume or applying a mechanical pressing force, and the filter residue has a low moisture content, and is suitable for a suspension having a high concentration of solid particles. In the belt press filter, the wet filter residue after preliminary liquid removal by gravity or vacuum is moved between the two filter belts, and then dehydrated by roller pressing. The screw press filter has a cylinder with pores, wherein there are rotating spirals, the spiral grooves are different in depth, and the material is pushed from the deep groove end to the shallow groove end, the filter chamber space is gradually reduced, the material is pressed, and the filtrate is pressed by the cylinder. The pores are discharged and the filter residue is discharged from the small end.
Precision
Precision filters are generally used for filtration accuracy between sand filtration (coarse filtration) and ultrafiltration. Under the action of pressure, the raw water passes through the filter element, and the impurities are trapped on the wall of the filter element, and the water permeates through the filter core to achieve the purpose of filtration. The scale of manufacturers producing filter equipment in China is mainly for 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, mainly made of high-quality stainless steel, with filter elements with different media. The built-in filter has PE core, honeycomb core, folded core, titanium tube sintered core, activated carbon core, ceramic core, polypropylene fiber filter and so on. The filter has different filtering effects. Therefore, the precision filter can remove suspended solids, some colloidal substances and fine particles according to the raw water quality, effluent quality and water quantity to achieve different filtration precision. The precision of precision filters on the market ranges from 0.2 to 100 um. Precision filters are often used as protective filters for devices such as electrodialysis, ion exchange, reverse osmosis, and ultrafiltration. They can be used in water treatment in food, alcohol, pharmaceutical, chemical, and electronics industries.